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Publication numberUS20020086746 A1
Publication typeApplication
Application numberUS 09/932,771
Publication dateJul 4, 2002
Filing dateAug 17, 2001
Priority dateJun 1, 1993
Publication number09932771, 932771, US 2002/0086746 A1, US 2002/086746 A1, US 20020086746 A1, US 20020086746A1, US 2002086746 A1, US 2002086746A1, US-A1-20020086746, US-A1-2002086746, US2002/0086746A1, US2002/086746A1, US20020086746 A1, US20020086746A1, US2002086746 A1, US2002086746A1
InventorsMichelle Bellinger, Gary Tavares
Original AssigneeBellinger Michelle A., Gary Tavares
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Methods for manufacturing golf balls with protuberant interior interfaces
US 20020086746 A1
Abstract
A golf ball is disclosed comprising a core having a unique surface configuration and a cover disposed about the core. The unique surface configuration is preferably a protuberant surface. Protuberant surface configurations are preferably provided by a plurality of geometrical shaped projections, which extend outwardly from the surface. A protuberant surface provides a protuberant interface between the layer, i.e., the core, having the protuberant surface and a layer disposed immediately thereon. A protuberant interface is more efficient in terms of energy transfer compared to traditional smooth spherical golf ball layers. Additionally, a golf ball having desired performance characteristics may be formed by the incorporation of a unique protuberant interface.
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Claims(21)
What is claimed is:
1. A method of forming a multi-layered golf ball comprising (i) a core having a protuberant surface defined by a plurality of projections that extend outwardly from the core; and (ii) a cover layer disposed around said core, said method comprising the steps of:
providing a thermoplastic polymeric material;
forming a tube of said thermoplastic polymeric material;
sealing one end of said tube, thereby providing a sealed end;
inserting said tube into a mold defining an interior molding chamber having protuberant interior walls such that the sealed end of said tube is generally disposed within said molding chamber;
inserting an injection component into said tube;
introducing an inflating medium through said injection component to the portion of said tube within said molding chamber such that said inflating medium causes said tube to expand outwardly to said protuberant interior walls of said molding chamber to form a golf ball layer having a protuberant surface;
hardening said golf ball layer; and
removing said golf ball layer from said mold.
2. The method of claim 1 wherein said sealing step is performed by crimping said one end of said tube.
3. The method of claim 1 wherein said injection component is a pin, needle or syringe.
4. The method of claim 1 wherein said inflating medium is pressurized or compressed air.
5. The method of claim 1 wherein said thermoplastic polymeric material is selected from the group consisting of metallocenes, metallocene polyolefins, polyurethanes, silicones, polyamides, polyureas, polyvinyl chlorides, acrylonitrile-butadiene-styrenes, acrylics, stryrene-acrylonitriles, styrene-maleic anhydrides, polycarbonates, polybutylene terephthalates, polyethylene terephthalates, polyphenylene ethers/polyphenylene oxides, reinforced polypropylenes, high-impact polystyrenes and combinations thereof.
6. The method of claim 1 further comprising:
removing excess thermoplastic polymeric material from an outer surface of said golf ball layer.
7. The method of claim 1 wherein said step of sealing said one end of said tube is performed to provide an unsealed end opposite from said sealed end and said step of inserting said tube into said mold is performed such that said unsealed end is disposed outside of said molding chamber.
8. A method of forming a multi-layered golf ball comprising a core having (i) a protuberant surface defined by a plurality of projections that extend outwardly from the core and (ii) a cover layer disposed around said core, said method comprising the steps of:
providing a longitudinal hollow member defining a first end and a second end and an interior channel extending between said first end and said second end;
providing a mold defining an interior molding chamber having protuberant interior walls;
placing a thermoplastic polymeric material onto said first end of said longitudinal member;
positioning said first end of said longitudinal member and said thermoplastic material into said molding chamber;
introducing an inflating medium to said second end of said longitudinal member such that said inflating medium causes said thermoplastic material disposed on said first end of said longitudinal member to expand outwardly to said protuberant interior walls of said molding chamber to thereby form a golf ball layer;
removing said layer from said mold;
removing said longitudinal member from said layer thereby forming an opening in said layer; and
filling said opening.
9. The method of claim 8 wherein said inflating medium is pressurized or compressed air.
10. The method of claim 8 wherein said thermoplastic polymeric material is selected from the group consisting of metallocenes, metallocene polyolefins, polyurethanes, silicones, polyamides, polyureas, polyvinyl chlorides, acrylonitrile-butadiene-styrenes, acrylics, stryrene-acrylonitriles, styrene-maleic anhydrides, polycarbonates, polybutylene terephthalates, polyethylene terephthalates, polyphenylene ethers/polyphenylene oxides, reinforced polypropylenes, high-impact polystyrenes and combinations thereof.
11. The method of claim 8 wherein said step of filling said opening is performed by depositing an effective amount of an agent in said opening, said agent selected from the group consisting of a thermally curable adhesive, an ultra-violet curable adhesive, a paint, a hot melt adhesive, a polymeric material, and combinations thereof.
12. The polymeric material of claim 11 selected from the group consisting of thermoplastic polymeric materials including metallocenes, metallocene polyolefins, polyurethanes, silicones, polyamides, polyureas, polyvinyl chlorides, acrylonitrile-butadiene-styrenes, acrylics, stryrene-acrylonitriles, styrene-maleic anhydrides, polycarbonates, polybutylene terephthalates, polyethylene terephthalates, polyphenylene ethers/polyphenylene oxides, reinforced polypropylenes, high-impact polystyrenes and combinations thereof.
13. The method of claim 8 wherein said step of filling said opening is performed by:
placing a sufficient amount of a resin within a syringe or needle to fill said opening;
injecting said resin into said opening;
cauterizing said layer surrounding said opening by contacting said layer with a heated element;
allowing said resin to soften and flow into said opening such that the resulting surface between said opening and said layer is uniform; and
heating said layer and said resin such that crosslinking between said resin and said layer is promoted.
14. The method of claim 13 wherein said resin is selected from the group consisting of a thermally curable adhesive, an ultra-violet curable adhesive, a solvent or water-based paint, a hot melt adhesive, a polymeric material, and combinations thereof.
15. The method of claim 13 wherein said thermoplastic polymeric material is selected from the group consisting of metallocenes, metallocene polyolefins, polyurethanes, silicones, polyamides, polyureas, polyvinyl chlorides, acrylonitrile-butadiene-styrenes, acrylics, stryrene-acrylonitriles, styrene-maleic anhydrides, polycarbonates, polybutylene terephthalates, polyethylene terephthalates, polyphenylene ethers/polyphenylene oxides, reinforced polypropylenes, high-impact polystyrenes and combinations thereof.
16. The method of claim 8 wherein said opening is filled using spin bonding.
17. A multi-layered golf ball comprising:
a core having a protuberant surface defined by a plurality of projections of the same geometrical shape and base diameter that extend outwardly from said core; and
a cover layer disposed around said core, wherein the base diameter of each projection as measured along the surface of the core is from about 0.0375 inches to about 0.420 inches.
18. The golf ball of claim 17 wherein the geometrical shape is selected from the group consisting of hemispherical, elliptical, conical, pyramidal, rectangular, hexagonal, pentagonal, trapezoidal, and cylindrical.
19. The golf ball of claim 17 wherein the geometrical shape is hemispherical.
20. The golf ball of claim 17 wherein each projection of the protuberant surface of the core extends outwardly a distance of from about 0.0125 inches to about 0.140 inches as measured from the surface of the core.
21. The golf ball of claim 17 further comprising:
one or more mantle layers disposed between said core and said cover layer.
Description
CROSS REFERENCES TO RELATED APPLICATIONS

[0001] This is a continuation-in-part application of U.S. application Ser. No. 08/998,243, filed Dec. 24, 1997, which is a divisional of U.S. application Ser. No. 08/920,070, filed Aug. 26, 1997, which in turn is a continuation of U.S. application Ser. No. 08/542,793, filed Oct. 13, 1995, now abandoned, which is a continuation-in-part of U.S. application Ser. No. 08/070,510, filed Jun. 1, 1993, now abandoned. This application also claims priority from U.S. Provisional Application Ser. No. 60/226,449, filed on Aug. 17, 2000.

FIELD OF THE INVENTION

[0002] The present invention relates to methods for manufacturing golf balls. In particular, the present invention relates to forming a golf ball core having a plurality of protrusions using blow-molding techniques. More particularly, the present invention provides blow-molding techniques to form particular types of golf ball cores that exhibit desirable performance properties.

BACKGROUND OF THE INVENTION

[0003] Golf balls have typically been divided into various types based on the construction of the balls. The first type of ball is a one-piece, or unitary, golf ball. It is essentially constructed of the same material throughout the entire ball. Many range balls and very low cost balls are of this construction.

[0004] A second type of golf ball is a two-piece ball. It consists of a solid core (usually polybutadiene rubber based) and various types of cover material surrounding the core. By utilizing various combinations of core and cover components, golf balls exhibiting a wide range of characteristics can be produced.

[0005] To improve certain performance characteristics, a third type of golf ball has also been developed. This is a wound golf ball, sometimes referenced as a three-piece ball. This ball has typically consisted of an elastomeric core around which an elastomeric thread is wound and a tough, yet resilient, cover over the core and thread.

[0006] The quest to continue to improve the performance of the golf ball led to the development of a fourth type of ball, the multi-layered ball. This type of ball typically includes an elastomeric core surrounded by one or more intermediate layers and a tough cover. Traditionally, each component has had a different composition from the others. In addition, the outer surface of the core and the inner and outer surfaces of the intermediate layers are usually smooth. However, it has been discovered that such a smooth interface between spherical surfaces results in an inefficient transfer of energy between the layers.

[0007] This inefficiency of energy transfer results in problems with several of the main characteristics of a golf ball, such as distance and playability. When a golf club strikes the outer surface of the golf ball cover, only a portion of the entire sphere is contacted in receiving energy. This energy is transferred to each layer of the ball to the core. Because only a portion of the outer cover initially receives energy, portions of each intermediate layer and the core that are linearly related to the portion of the cover receiving the direct contact are critical to the transfer of energy. The smooth interfaces often poorly transfer this energy, resulting in a lower total energy transfer to the entire golf ball from the club. This lower energy transfer may result in a shorter travel distance for the ball, less spin or reduction of other similar playability characteristics.

[0008] A way to eliminate this problem is to change the smooth interfaces of the golf ball components in a manner which allows for a more efficient energy transfer. Some attempts at such a solution have been made. For example, U.S. Pat. No. 5,984,807 issued to Ywai et al. and U.S. Pat. No. 5, 836,834 issued to Masutani et al. disclose the use of solid, geometrically symmetrical projections on the core of a golf ball to improve the interface between the core and its adjacent layer. U.S. Pat. No. 5,820,485 issued to Hwang teaches the use of solid, geometrically symmetrical solid protrusion projections on the inner surface of the cover layer of the golf ball to improve playability characteristics. The developments of the prior art, however, do not provide the optimum energy transfer leading to the best playability characteristics. Furthermore, the prior art has not provided a suitable technique by which to readily and economically manufacture a golf ball with the noted protrusions or projections.

[0009] Accordingly, it is desirable to develop a new golf ball which would overcome the foregoing difficulties by providing a more efficient transfer of energy throughout the ball. In addition, it would be particularly desirable to provide a new technique for manufacturing such a golf ball.

SUMMARY OF THE INVENTION

[0010] A primary object of the present invention is to provide one or more techniques for readily and economically manufacturing a multi-layered golf ball that comprises a core having a protuberant surface defined by a plurality of projections of the same geometrical shape that extend outwardly from the core, one or more optional mantle layers disposed about the core, and a cover layer disposed around the core and the optional mantle layers.

[0011] In this regard, the present invention relates to a process for producing a golf ball having a blow molded protoberant core in order to achieve an improved energy transfer between the core and the cover layer, as well as any mantle layers therebetween. Furthermore, the blow molding process is advantageous in that it provides, in one embodiment, a seamless core. This adds to the stability of the core and avoids balancing problems in forming the core.

[0012] In one aspect of the present invention, a method is provided for forming a multi-layered golf ball with a textured or protuberant core and one or more optional mantle layers. The method comprises the steps of forming a continuous tube of a thermoplastic polymeric material, followed by sealing one end of the continuous tube. The tube is then inserted into a preformed mold with protuberant or textural interior walls, with the sealed end within the mold and the open end of the tube outside of the mold. An injection means or mechanism is then inserted into the unsealed end of the continuous tube. An inflating medium is then introduced through the injection means to the portion of the tube within the mold such that the inflating medium causes the tube to expand outwardly to the protuberant interior walls of the mold to form a golf ball layer. The golf ball layer can vary in thickness and in one embodiment is fully solid. Upon setting, the golf ball layer is removed from the mold and any excess thermoplastic polymeric material is removed from the surface of the layer. The ball can then be finished, including adding one or more mantle layers and a cover layer.

[0013] In another aspect of the present invention, a method is provided for forming a multi-layered golf ball with a protuberant core and one or more optional mantle layers. The method comprises the steps of molding or otherwise positioning a thermoplastic polymeric material onto a hollow longitudinal member such as a core pin or needle. Next, the pin covered with thermoplastic polymeric material is placed into a mold having protuberant or textured interior walls. An inflating medium is then introduced such that the inflating medium causes the thermoplastic material covering the pin to expand outwardly to the protuberant interior walls to form a golf ball core layer. The golf ball core layer can also vary in thickness and/or can be solid. The formed layer is then removed from the mold following setting or curing and the pin is removed from the layer forming a gap in the surface of the layer. The gap is filled and any excess thermoplastic polymeric material is removed from the surface of the layer. The ball can then be finished, including encapsulating the proturberant core layer with one or more mantle layers and a cover layer.

[0014] By producing a blow molded protuberant core encapsulated by at least one intermediate layer and/or an external cover layer, a more optimum surface configuration at the interfaces between the core and the subsequent layers is produced. The interfacial surface pattern that exists optimizes various ball performance characteristics through energy transfer.

[0015] Additional objects and advantages of the present invention will be set forth in part in the description which follows and in part will become apparent upon a reading and understanding of the preferred embodiments or may be learned by practicing the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The present invention will become more fully understood from the detailed description given below and the accompanying drawings. The description and drawings are given by the way of illustration only, and thus do not limit the present invention.

[0017]FIG. 1 is a cross section of three-piece, i.e., multi-layer, non-wound golf ball;

[0018]FIG. 2 is a cross section of a second multi-layer non-wound golf ball;

[0019]FIG. 3 is a block cross section of a cover layer and a core in a conventional golf ball having a smooth interface therebetween;

[0020]FIG. 4 is a diagram showing the energy transfer occurring between the layers of a conventional golf ball having a smooth interface therebetween;

[0021]FIG. 5 is a block cross section of a cover layer and a core in a golf ball having a protuberant interface therebetween in accordance with the present invention;

[0022]FIG. 6 is a diagram showing the energy transfer occurring between the layers of a golf ball having a protuberant interface therebetween in accordance with the present invention;

[0023]FIG. 7 is a perspective of a protuberant core according to a first preferred embodiment;

[0024]FIG. 8 is a cross section of the protuberant core depicted in FIG. 7;

[0025]FIG. 9 is a cross sectional view of a two-piece, non-wound golf ball employing a core according to the first preferred embodiment;

[0026]FIG. 10 is a cross sectional view of a three-piece, non-wound golf ball employing a core according to the first preferred embodiment;

[0027]FIG. 11 is a perspective of a protuberant core according to a second preferred embodiment;

[0028]FIG. 12 is a cross section of the protuberant core depicted in FIG. 11;

[0029]FIG. 13 is a cross sectional view according to a two-piece, non-wound golf ball employing a core structure according to the second preferred embodiment;

[0030]FIG. 14 is a cross sectional view of a three-piece, non-wound golf employing a core structure according to the second preferred embodiment;

[0031]FIG. 15 is a cross sectional view of a multi-layer protuberant core according to a third preferred embodiment;

[0032]FIG. 16 is a cross sectional view of a golf ball employing a core according to the third preferred embodiment;

[0033] FIGS. 17A-E illustrate steps utilized in the manufacture or fabrication of a preferred embodiment of the present invention, with FIG. 17E being an elevational view showing a protuberant golf ball core made in accordance with the process illustrated in FIGS. 17A through 17D;

[0034]FIG. 18 represents a flow chart diagram illustrating the steps involved with extrusion blow molding of a golf ball core in accordance with an aspect of the present invention;

[0035]FIG. 19A-C illustrate steps utilized in the manufacture or fabrication of a preferred embodiment of the present invention; and

[0036]FIG. 20 represents a flow chart diagram illustrating the steps involved with injection blow molding of a golf ball core in accordance with an aspect of the present invention.

[0037] The above-referenced figures are not to scale, but are merely illustrative of the present invention. Specifically, the figures are for the purposes of illustrating the present invention and not to be construed as limiting the invention described herein.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0038] The present invention is based on the discovery that by incorporating a particular surface configuration between a core and either a cover layer or an intermediate layer of a golf ball, desired performance properties may be obtained. In accordance with the present invention, techniques are provided for manufacturing a golf ball that utilizes a surface topography between layers or components of the ball allowing energy to be transferred between regions of the ball efficiently and in a manner such that desirable performance characteristics are achieved.

[0039] Before turning attention to the methods of the present invention, it is instructive to consider various aspects of golf balls having protuberant interior configurations.

[0040] Conventional non-wound golf balls having two or more layers are typically constructed from uniform spherical layers, i.e., layers having a smooth, rounded surface. A smooth surface, as used herein refers to a continuous even surface, i.e., a surface generally free from any disturbances or protrusions in the surface topography. Referring now to FIGS. 1 and 2, respectively, the inner layers of golf ball 10 and golf ball 20, i.e., the core and mantle layers, are smooth-surface, spherical layers.

[0041] Interfaces occur at surface boundaries where immediately adjacent layers adhere to or are in intimate contact with one another. Inner layers of golf balls 10 and 20 of FIGS. 1 and 2, respectively, have smooth spherical surfaces. Consequently, a smooth surface interface is formed between adjacent layers in each of the respective golf balls. A smooth interface 17 is formed between spherical core 12 and dimpled cover layer 16 in the golf ball of FIG. 1. Similarly, in FIG. 2, smooth interfaces 26 and 27 are formed between core layer 22 and mantle layer 23, and between mantle layer 23 and cover layer 24, respectively. Referring further to FIG. 2, a smooth interface 25 is formed between core 21 and core layer 22.

[0042] When a golf ball is struck with a golf club, energy is transferred from the face of the club to the cover of the ball and then subsequently transferred from the cover to each layer there beneath. The cover layer material, the core material and/or intermediate layer materials typically differ in both their compositions and physical properties. The energy transfer occurring throughout a golf ball must therefore propagate through different materials. Additionally, different layers of a golf ball typically have different thicknesses, which also affects the transfer of energy within a golf ball.

[0043] The physical arrangement or configuration of the interface between adjacent layers also affects the transfer of energy between respective layers. FIG. 3 represents a block cross section of a golf ball having a cover layer 30 of a given thickness and modulus (in terms of a given type of material) and a core 32 of a different thickness and modulus. A smooth interface 34 is defined between the two layers. FIG. 4 illustrates the transfer of energy occurring between adjacent layers of a golf ball having a smooth interface therebetween, as represented in FIG. 3. The transfer of energy from one layer to another in a ball having a smooth interface between the respective layers is very sudden and rather abrupt. It is believed that significant inefficiencies result from such energy transfers across smooth interfaces.

[0044] As noted, FIG. 3 represents a portion of a non-wound multi-layer golf ball having a smooth interface between a core and a cover layer. And, FIG. 4 is a representation of the transfer of energy that occurs between such a cover and core. FIG. 3 is also considered to represent any adjacent layers of a golf ball having a smooth interface between the respective layers. For example, FIG. 3 may also represent the smooth interface between a cover and a mantle layer, a core and a mantle layer and/or between two mantle layers. FIG. 4, therefore, is also representative of the typical transfer of energy that occurs through any adjacent layers in a golf ball having a smooth interface therebetween, i.e., such as between a core and a mantle layer or between adjacent mantle layers, etc.

[0045] It is desirable therefore to incorporate a structural feature in a golf ball, specifically along the interface between adjacent layers of a golf ball, such as between a cover and a core layer, that allows for an efficient and less abrupt transfer of energy to occur between adjacent golf ball layers or interior regions.

[0046] In a golf ball, a core having a protuberant surface, referred to herein as a protuberant core, contains outwardly extending, and preferably radially extending bulges, protrusions, projections, or protuberances that impart contours or other irregularities to the surface. A protuberant surface provides an alternative to a smooth surface. A protuberant surface contains outwardly extending bulges or projections creating a surface with a unique contour or topography. It has been discovered that changing the surface configuration of a core, such that the core no longer has a uniformly smooth surface, alters the manner in which energy is transferred between adjacent layers.

[0047] When a golf ball layer is molded over or otherwise formed about a protuberant core, such as a cover or another mantle layer, the resulting interface between the two layers is not smooth, but rather conforms to the topography of the surface of the protuberant mantle layer. An interface occurring between a protuberant core and a golf ball layer molded immediately thereon is referred to herein as a protuberant interface.

[0048] Projections may be arranged in any manner to form a protuberant surface. Patterns and arrangements of projections are selected as desired to yield various properties and/or characteristics in a final golf ball product. The outwardly extending bulges on a protuberant core according to the present invention are preferably formed by a plurality of projections. Projections are preferably in the form of geometrical shapes selected from the group including, but not limited to, hemispherical, elliptical, conical, pyramidal, rectangular, hexagonal, pentagonal, trapezoidal, and cylindrical. Projections are most preferably hemispherical.

[0049] A protuberant core preferably comprises projections of the same shape and having equal dimensions, i.e., having equal size. When projections of equal dimensions are employed, the apex, i.e., the top most point, of the projections are considered to be co-planar with each other. However, the present invention encompasses the use of projections having different dimension in terms of the height, base diameter, and/or base length and width of the projection.

[0050] The present invention encompasses protuberant cores having a protuberant surface formed by projections of different geometric shapes. Protuberant cores optionally comprise combinations of two or more geometrical shaped projections. Multiple geometric shapes are arranged in any pattern as desired to provide a mantle layer and/or assembly with a protuberant surface. A non-limiting example of such an embodiment is a protuberant core formed by hemispherical and elliptical projections. The projections could be arranged in any manner such that spherical and/or elliptical projections were repeating, i.e., a projection of a given shape would be immediately adjacent to a projection of the same shape. Additionally the projections could be arranged in an alternating or generally non-repeating fashion. Another non-limiting example of utilizing multiple geometric shapes in accordance with the present invention is a protuberant core formed by a pyramidal, hexagonal, and trapezoidal projections. Accordingly, the projections may be arranged in a repeating or non-repeating manner, such that desired properties are achieved.

[0051]FIG. 5 illustrates a representative embodiment of a protuberant surface in accordance with the present invention. In FIG. 5, core 42 has a protuberant surface topography created by projections 44. Projections 44, shown in cross section of FIG. 5 are representative of cylindrical and/or rectangular projections. A protuberant interface, as illustrated in FIG. 5, is formed where the cover 40 is in intimate contact with the protuberant surface of mantle layer 42. A space is formed between the projections in FIG. 5, and is defined by the distance adjacent projections are spaced apart from one another. A smooth surface area 46, therefore, exists in the region of space between the base of a given projection and any next nearest projection. Unless otherwise noted, the distance between projections is defined in terms of the distance between the bases of a given projection and the base of a next nearest projection.

[0052]FIG. 6 demonstrates the transfer of energy that occurs across the interface between a cover and a core, in which the core has a protuberant surface topography thereby providing a protuberant interface between the cover and the core, such as the interface of FIG. 5. Energy transfer between adjacent layers having a protuberant interface therebetween is gradual and more efficient over the total thickness of the respective layers than the energy transfer occurring across a smooth interface. FIG. 6 is representative of the typical transfer of energy that occurs between adjacent layers having a protuberant surface therebetween. FIG. 6 is merely illustrative, and not to be considered a limiting example of energy transfer across a protuberant interface. Energy transfer between adjacent layers of a golf ball having a protuberant interface therebetween is a function of the thickness of the respective layers, the material used to construct the respective layers, and the surface topography which gives rise to the protuberant interface. A change to any of the above parameters, including the surface topography, which is typically accomplished by utilizing differently shaped projections, will affect how energy transfer occurs between adjacent layers.

[0053] A protuberant interface occurs at the surface boundary where immediately adjacent layers adhere to and/or are in intimate contact with one another and is created by the “lower” layer having a protuberant surface. A protuberant surface, as previously described herein, is preferably formed by a plurality of projections.

[0054] Energy transfer within a golf ball is a function of the thickness of the respective layers, the size, shape and placement of projections, and the materials used to form the respective layers. Physical properties of a golf ball utilizing the present invention may be adjusted and optimized by varying the compositions and thickness of individual layers and also by variations in the surface topography of one or more mantle layers.

[0055] Projection size is defined in terms of the dimensions of the base of the projection and also the height from the base of the projection to the apex or top most point of the projection. For hemispherical, cylindrical, elliptical and conical projections, base size refers to the diameter of the base of individual projections. In the case of pyramidal, rectangular, pentagonal, hexagonal, and trapezoidal projections, base size refers to length and/or width of the base of individual projections. The diameter, or in the alternative, length and/or widths of projections is preferably between about 0.0375 inches to about 0.420 inches, more preferably between about 0.075 inches to about 0.210 inches, and most preferably between about 0.100 inches to about 0.160 inches. Projection heights are preferably between about 0.0125 inches to about 0.140 inches, more preferably between about 0.0250 inches to about 0.070 inches, and most preferably from about 0.0335 inches to about 0.0525 inches.

[0056] Additionally, projections may be arranged such that the bases of adjacent projections are in contact with one another or such that the bases of adjacent projections are not in contact with another. For example, in FIG. 5, the base of a given projection does not make contact with the base of any next nearest projection. Subsequently, a region of the given mantle layer is exposed. The exposed region is considered to be a smooth surface region, as would be found in a mantle construction having a smooth surface. Arrangement of projections is more fully described in accordance with the preferred embodiments. Preferably the distance between the base of adjacent projections is from about 0.010 inches to about 0.250 inches, and more preferably between about 0.020 inches to about 0.200 inches.

[0057] A protuberant core according to the invention is preferably spherical. While a protuberant core does not have a uniformly smooth or even surface topography, in a most preferred form, the overall shape of the layer is spherical and/or circular.

[0058] In a preferred form, a golf ball employing a protuberant core according to the present invention is a two-piece golf ball, having a cover layer molded immediately over the protuberant core. FIGS. 7 and 8 display a protuberant core 50 of a first preferred embodiment in accordance with the present invention. FIG. 7 is a perspective view of protuberant core 50. FIG. 8 is a cross-section of FIG. 7. Hemispherical projections 52 provide the core with a protuberant surface. A flat or smooth surface area 54 is formed on the surface of protuberant core 50, and is defined within the region between adjacent projections. With reference to FIG. 8, projections 52 and smooth surface 54 generally extending between the projections 52 provide core 50 with a protuberant surface.

[0059]FIG. 9 is a cross section of a two piece, non-wound golf ball 60 employing a protuberant core of a first preferred embodiment. A cover layer 62 is molded or otherwise formed over core 50. A protuberant interface is provided where the cover layer adheres to and is in intimate contact with the protuberant surface of the core. The protuberant core of the first preferred embodiment comprises a plurality of hemispherical projections having equal dimensions. That is, the projections each have the same base diameter and the same height. Therefore, the apex of the hemispherical is constant across the core. The core is also to be considered spherical.

[0060]FIG. 10 represents a cross section of a three-piece, multi-layer, non-wound golf ball 70 employing a protuberant core of the first preferred embodiment, wherein a mantle layer 72 is disposed between core 50 and a cover layer 74. A protuberant interface is provided where mantle layer 72 adheres to and makes intimate contact with the protuberant surface of core 50.

[0061] A golf ball employing a mantle assembly of the first preferred embodiment is not limited to the above-described golf balls. It is contemplated that any number of mantle layers may be disposed between a cover layer and the protuberant core.

[0062] A second preferred embodiment of a protuberant core 80 is illustrated in FIGS. 11 and 12. A protuberant surface is provided by a plurality of hemispherical projections 82. In the second preferred embodiment, the base of any selected projection makes contact with the base of each projection to which it is immediately adjacent. Therefore, no smooth surfaces exist on the outer surface of the core of the second preferred embodiment.

[0063]FIG. 13 is a cross section of a two piece, non-wound golf ball 90 having a protuberant core of the second preferred embodiment. A cover layer 92 is disposed over core 80. The ball comprises textured core 80 and cover layer 92. A protuberant interface is provided by the protuberant surface formed by projections 82, where the cover layer adheres to and is in intimate contact with the surface of core 80.

[0064] A cross section of a three piece, multi-layer, non-wound golf ball 100 employing a protuberant core of the second preferred embodiment is shown in FIG. 14, wherein a mantle layer 102 is disposed between core 80 and a cover layer 104. A protuberant interface is provided where mantle layer 102 adheres to and makes intimate contact with the protuberant surface of core 82.

[0065] A golf ball employing a core according to the second preferred embodiment is not limited to the above-described golf balls. It is contemplated that any number of mantle layers may be disposed between a cover layer and a core according to the present invention.

[0066]FIG. 15 shows a third preferred embodiment of a core according to the present invention. The core, a dual (multi-layer) core, comprises an interior spherical center component 112, and a core layer 114 disposed about the center component. Projections 116 and a smooth surface generally extend between the projections 116 to provide core layer 114, and subsequently core 112, with a protuberant surface.

[0067]FIG. 16 is a cross section of a golf ball having a dual core according to the third preferred embodiment. A cover layer 124 is disposed over core layer 114. An optional inner cover layer or mantle layer 122 may be provided. Core layer 114 and interior spherical component 112 comprise a core, as described in accordance with FIG. 15. A protuberant interface is provided where the cover or mantle layer adheres to and is in intimate contact with the protuberant surface of core layer 114.

[0068] A protuberant core according to the present invention is not limited to the particular shapes and/or arrangements of projections described in the first, second, or third preferred embodiments. Additionally, in regards to multi-layer cores, any of the one or more core layers may have a protuberant surface.

[0069] In all of the foregoing noted embodiments, the golf ball comprises a cover layer disposed about the core. The cover may be a single cover layer or optionally a multi-layer cover. The cover layer is constructed from any suitable cover material, known in the golf ball art. Furthermore, the mantle layers may contain a plurality of protuberances. Suitable cover materials are more fully described herein.

[0070] Additionally, it is contemplated that golf balls employing a core according to the present invention may have one or more mantle layers disposed between the core and the cover. Suitable mantle layer materials are more fully described herein.

[0071] Golf balls according to the invention typically have a coefficient of restitution of at least 0.780 and more preferably at least 0.800, and a PGA compression of from about 85 to about 117, more preferably from about 90 to about 105, and most preferably from about 90 to about 97. High spin golf balls according to the invention typically have a PGA compression of from about 70 to about 100, more preferably from about 75 to about 95, and most preferably from about 75 to about 85.

[0072] Cores

[0073] Protuberant cores described heretofore have been solid, one piece cores. It is contemplated that cores according to the present invention may have a multi-layer construction. Multi-layer cores comprise an interior spherical center component, a core layer disposed about the center component, and optionally an outer core layer disposed about the core layer. In accordance with the present invention, at least one of the interior center component, the core layer, and optionally the outer core layer has a protuberant surface as described herein. In a most preferred form, the outermost core layer of a multi-layer core comprises a protuberant surface, however, it is contemplated that inner core layers may be protuberant as well as outer core layers.

[0074] Protuberant cores according to the present invention may be formed from any suitable core material known in the golf ball art. The core may be formed from a thermoset material, a thermoplastic material, or combinations thereof.

[0075] The cores have a weight of about 25 to 40 grams and preferably about 30 to 40 grams. The cores can be molded from a variety of materials. For example the core can be molded from a slug of uncured or lightly cured elastomer composition comprising a high cis content polybutadiene and a metal salt of an ethylenically unsaturated carboxylic acid such as zinc mono- or diacrylate or methacrylate. To achieve higher coefficients of restitution and/or to increase hardness in the core, the manufacturer may increase the amount of zinc diacrylate co-agent. In addition, larger amounts of metal oxide such as zinc oxide may be included in order to increase the core weight so that the finished ball more closely approaches the U.S.G.A. upper weight limit of 1.620 ounces. Non-limiting examples of other materials which may be used in the core composition include compatible rubbers or ionomers, and low molecular weight fatty acids such as stearic acid. Free radical initiator catalysts such as peroxides are mixed with the core composition so that on the application of heat and pressure, a curing or cross-linking reaction takes place.

[0076] A wide array of thermoset materials can be utilized in a core of the present invention. Examples of suitable thermoset materials include butadiene or any natural or synthetic elastomer, including metallocene polyolefins, polyurethanes, silicones, polyamides, polyureas, or virtually any irreversibly cross-linked resin system. Similarly a polybutadiene elastomer could be further used. It is also contemplated that epoxy, phenolic, and an array of unsaturated polyester resins could be utilized.

[0077] The thermoplastic material used in the present invention cores include a wide assortment of thermoplastic materials. Examples of typical thermoplastic materials for incorporation in the golf balls of the present invention include, but are not limited to, ionomers, polyurethane thermoplastic elastomers, and combinations thereof. It is also contemplated that a wide array of other thermoplastic materials could be utilized, such as polysulfones, fluoropolymers, polyamide-imides, polyarylates, polyaryletherketones, polyaryl sulfones/polyether sulfones, polybenzimidazoles, polyether-imides, polyimides, liquid crystal polymers, polyphenylene sulfides; and specialty high-performance resins, which would include fluoropolymers, polybenzimidazole, and ultrahigh molecular weight polyethylenes.

[0078] Additional examples of suitable thermoplastics include metallocenes, polyvinyl chlorides, acrylonitrile-butadiene-styrenes, acrylics, styrene-acrylonitriles, styrene-maleic anhydrides, polyamides (nylons), polycarbonates, polybutylene terephthalates, polyethylene terephthalates, polyphenylene ethers/polyphenylene oxides, reinforced polypropylenes, and high-impact polystyrenes.

[0079] Preferably, the thermoplastic materials have relatively high melting points, such as a melting point of at least about 300° F. The polymers or resin system may be cross-linked by a variety of means such as by peroxide agents, sulphur agents, radiation or other cross-linking techniques. Several examples of these preferred thermoplastic materials and which are commercially available include, but are not limited to, CAPRON® (trademarked by Allied Signal Plastics for a blend of nylon and ionomer), LEXAN® (trademarked by General Electric for polycarbonate), PEBAX® (trademarked by Elf Atochem for a polyether block amide), and HYTREL® (trademarked by Dupont for a series of polyester elastomers). Properties of these four preferred thermoplastics are set forth below in Tables 1-4. When forming a golf ball in accordance with the present invention, if the core is to comprise a thermoplastic material, it is most preferred to utilize PEBAX® thermoplastic resin.

TABLE 1
CAPRON ® 8351
Mechanical DAM 50% RH ASTM Test
Tensile Strength, Yield, 7,800 (54) D-638
psi (MPa)
Flexural Strength, 9,500 (65) D-790
psi (MPa)
Flexural Modulus, 230,000 (1,585) D-790
psi (MPa)
Ultimate Elongation, % 200 D-638
Notched Izod Impact, No Break D-256
ft-lbs/in (J/M)
Drop Weight Impact, 150 (200) D-3029
ft-lbs (J)
Drop Weight Impact, 150 (200) D-3029
@ −40° F., ft-lbs (J)
Physical
Specific Gravity 1.07 D-792
Thermal
Melting Point, ° F. (° C.) 420 (215)
Heat Deflection @ 264 psi 140 (60) D-648
° F. (° C.)

[0080]

TABLE 2
LEXAN ® ML5776
Typical
Property Data Unit Method
Mechanical
Tensile Strength, Yield, 8500 psi ASTM D-638
Type 1, 0.125″
Tensile Strength, Break, 9500 psi ASTM D-638
Type 1, 0.125″
Tensile Elongation, Yield, 110.0 % ASTM D-638
Type 1, 0.125″
Flexural Strength, Yield, 12000 psi ASTM D-790
Type 1, 0.125″
Flexural Modulus, 0.125″ 310000 psi ASTM D-790
Impact
Izod Impact, Unnotched, 60.0 ft-lbs/ins ASTM D-4812
73 F.
Izod Impact, Notched, 73 F. 15.5 ft-lbs/ins ASTM D-256
Izod Impact, Notches, 73 F., 12.0 ft-lbs/ins ASTM D-256
0.250″
Instrumented Impact Energy 48.0 ft-lbs ASTM D-3763
@ Peak, 73 F.
Thermal
HDT, 264 psi, 0.250″, 257 deg F. ASTM D-648
Unannealed
Thermal Index, Elec Prop 80 deg C. UL 7468
Thermal Index, Mech Prop 80 deg C. UL 7468
with Impact
Thermal Index, Mech Prop 80 deg C. UL 7468
without Impact
Physical
Specific Gravity, Solid 1.19 ASTM D-792
Water Absorption, 0.150 % ASTM D-570
24 hours @ 73 F.
Mold Shrinkage, Flow, 0.125″ 5.7 in/in E-3 ASTM D-955
Melt Flow Rate, Nom'l, 7.5 g/10 min ASTM D-1238
300 C./1.2 kgf (0)
Flame Characteristics
UL File Number, USA E121562
94HB Rated (tested thickness) 0.060 inch UL 94

[0081]

TABLE 3
PEBAX ® 3533 Resin
ASTM
Property Test Method Units 3533
Specific Gravity D792 1.01
Water Absorption D570 0.5
Equilibrium (20° C., 50% R.H.>) 1.2
24 Hr. Immersion
Hardness D2240 35D
Tensile Strength, Utlimate D638 psi 5600
Elongation, Ultimate D638 % 580
Flexural Modulus D790 psi 2800
Izod Impact, Notched D256 ft
  20° C. lb/in NB
−40° C. NB
Abrasion Resistance H18/1000 g D1044 Mg/100 104
Cycles
Tear Resistance Notched D624C lb/in 260
Melting Point D3418 ° F. 306
Vicat Softening Point ° F. 165
HDT 66 psi D648 ° F. 115
Compression Set (24 hr., 160° F.) D395A % 54

[0082]

TABLE 4
HYTREL ® G4074
Thermoplastic Elastomer
ASTM
Test Method
Physical
Dens/Sp Gr ASTM D792 1.1800 sp gr
23/23 C.
Melt Flow ASTM D1238 5.20 @ E-190 g/10/min
C./2.16 kg
Wat Abs ASTM D570 2.100%
Mechanical
Elong @ Brk ASTM D638 230.0%
Flex Mod ASTM D790 9500 psi
TnStr @ Brk ASTM D638 2000 psi
Notch Izod ASTM D256 No Break @ 73.0 F @ 0.250 inft-lb/in
0.50 @ @ −40.0 F @ 0.2500 inft-lb/in
Hardness
Shore ASTM D2240 40 Shore D
DTUL @ 66 ASTM D648 122 F.  
Melt Point 338.0 F.
Vicat Soft ASTM D1525 248 F.  
Melt Point

[0083] The core compositions of the invention may be based on polybutadiene, natural rubber, metallocene catalyzed polyolefins such as EXACT® (Exxon Chem. Co.) and ENGAGE® (Dow Chem. Co.), polyurethanes, other thermoplastic or thermoset elastomers, and mixtures of one or more of the above materials with each other and/or with other elastomers.

[0084] It is preferred that the base elastomer have a relatively high molecular weight. Polybutadiene has been found to be particularly useful because it imparts to the golf balls a relatively high coefficient of restitution. Polybutadiene can be cured using a free radical initiator such as a peroxide, or can be sulfur cured. A broad range for the molecular weight of preferred base elastomers is from about 50,000 to about 500,000. A more preferred range for the molecular weight of the base elastomer is from about 100,000 to about 500,000. As a base elastomer for the core composition, cis-1-4-polybutadiene is preferably employed, or a blend of cis-1-4 polybutadiene with other elastomers may also be utilized. Most preferably, cis-1-4 polybutadiene having a weight-average molecular weight of from about 100,000 to about 500,000 is employed. Along this line, it has been found that the high cis-1-4 polybutadienes manufactured and sold by Bayer Corporation, Germany, under the trade name TAKTENE® 220 or 1220 are particularly preferred. Furthermore, the core may be comprised of a crosslinked natural rubber, EPDM, metallocene catalyzed polyolefin, or another crosslinkable elastomer.

[0085] When polybutadiene is used for golf ball cores, it commonly is crosslinked with an unsaturated carboxylic acid co-crosslinking agent. The unsaturated carboxylic acid component of the core composition typically is the reaction product of the selected carboxylic acid or acids and an oxide or carbonate of a metal such as zinc, magnesium, barium, calcium, lithium, sodium, potassium, cadmium, lead, tin, and the like. Preferably, the oxides of polyvalent metals such as zinc, magnesium and cadmium are used, and most preferably, the oxide is zinc oxide.

[0086] Exemplary of the unsaturated carboxylic acids which find utility in the core compositions are acrylic acid, methacrylic acid, itaconic acid, crotonic acid, sorbic acid, and the like, and mixtures thereof. Preferably, the acid component is either acrylic or methacrylic acid. Usually, from about 5 to about 40, and preferably from about 15 to about 30 parts by weight of the carboxylic acid salt, such as zinc diacrylate, is included in the core composition. The unsaturated carboxylic acids and metal salts thereof are generally soluble in the elastomeric base, or are readily dispersible.

[0087] The free radical initiator included in the core composition is any known polymerization initiator (a co-crosslinking agent) which decomposes during the cure cycle. The term “free radical initiator” as used herein refers to a chemical which, when added to a mixture of the elastomeric blend and a metal salt of an unsaturated, carboxylic acid, promotes crosslinking of the elastomers by the metal salt of the unsaturated carboxylic acid. The amount of the selected initiator present is dictated only by the requirements of catalytic activity as a polymerization initiator. Suitable initiators include peroxides, persulfates, azo compounds and hydrazides. Peroxides, which are readily commercially available, are conveniently used in the present invention, generally in amounts of from about 0.1 to about 10.0 and preferably in amounts of from about 0.3 to about 3.0 parts by weight per each 100 parts of elastomer.

[0088] Exemplary of suitable peroxides for the purposes of the present invention are dicumyl peroxide, n-butyl 4,4′-bis (butylperoxy) valerate, 1,1-bis(t-butylperoxy)-3,3,5-trimethyl cyclohexane, di-t-butyl peroxide and 2,5-di-(t-butylperoxy)-2,5 dimethyl hexane and the like, as well as mixtures thereof. It will be understood that the total amount of initiators used will vary depending on the specific end product desired and the particular initiators employed.

[0089] Any or all of the previously described components in the cores of the preferred embodiment golf balls of the present invention may be formed in such a manner, or have suitable fillers added, so that their resulting density is decreased or increased. For example, any of the components in the cores could be formed or otherwise produced to be light in weight. For instance, the components could be foamed, either separately or in-situ. Related to this, a foamed light weight filler agent may be added. In contrast, any of these components could be mixed with, or otherwise receive, various high density filler agents or other weighting components such as relatively high density fibers or particulate agents in order to increase their mass or weight.

[0090] The core compositions of the present invention may additionally contain any other suitable and compatible modifying ingredients including, but not limited to, metal oxides, fatty acids, and diisocyanates and polypropylene powder resin. For example, PAPI® 94, a polymeric diisocyanate, commonly available from Dow Chemical Co., Midland, Mich., is an optional component in the rubber compositions. It can range from about 0 to 5 parts by weight per 100 parts by weight rubber (phr) component, and acts as a moisture scavenger. In addition, it has been found that the addition of a polypropylene powder resin results in a core which is hard (i.e., exhibits high PGA compression) and thus allows for a reduction in the amount of crosslinking co-agent utilized to soften the core to a normal or below normal compression.

[0091] Furthermore, because polypropylene powder resin can be added to a core composition without an increase in weight of the molded core upon curing, the addition of the polypropylene powder allows for the addition of higher specific gravity fillers, such as mineral fillers. Since the crosslinking agents utilized in the polybutadiene core compositions are expensive and/or the higher specific gravity fillers are relatively inexpensive, the addition of the polypropylene powder resin substantially lowers the cost of the golf ball cores while maintaining, or lowering, weight and compression.

[0092] Various activators may also be included in the compositions of the present invention. For example, zinc oxide and/or magnesium oxide are activators for the polybutadiene. The activator can range from about 2 to about 30 parts by weight per 100 parts by weight of the rubbers (phr) component.

[0093] Moreover, reinforcement agents may be added to the core compositions of the present invention. Since the specific gravity of polypropylene powder is very low, and when compounded, the polypropylene powder produces a lighter molded core, when polypropylene is incorporated in the core compositions, relatively large amounts of higher specific gravity fillers may be added so long as the specific core weight limitations are met. As indicated above, additional benefits may be obtained by the incorporation of relatively large amounts of higher specific gravity, inexpensive mineral fillers such as calcium carbonate. Such fillers as are incorporated into the core compositions should be in finely divided form, as for example, in a size generally less than about 30 mesh and preferably less than about 100 mesh U.S. standard size. The amount of additional filler included in the core composition is primarily dictated by weight restrictions and preferably is included in amounts of from about 10 to about 100 parts by weight per 100 parts rubber.

[0094] The preferred fillers are relatively inexpensive and heavy and serve to lower the cost of the ball and to increase the weight of the ball to closely approach the U.S.G.A. weight limit of 1.620 ounces. However, if thicker cover compositions are to be applied to the core to produce larger than normal (i.e., greater than 1.680 inches in diameter) balls, use of such fillers and modifying agents will be limited in order to meet the U.S.G.A. maximum weight limitations of 1.620 ounces. Limestone is ground calcium/magnesium carbonate and is used because it is an inexpensive, heavy filler. Ground flash filler may be incorporated and is preferably 20 mesh ground up center stock from the excess flash from compression molding. It lowers the cost and may increase the hardness of the ball.

[0095] Fatty acids or metallic salts of fatty acids may also be included in the compositions, functioning to improve moldability and processing. Generally, free fatty acids having from about 10 to about 40 carbon atoms, and preferably having from about 15 to about 10 carbon atoms, are used. Exemplary of suitable fatty acids are stearic acid and linoleic acids, as well as mixtures thereof. An example of a suitable metallic salt of a fatty acid is zinc stearate. When included in the core compositions, the metallic salts of fatty acids are present in amounts of from about 1 to about 25, preferably in amounts from about 2 to about 15 parts by weight based on 100 parts rubber (elastomer). It is preferred that the core compositions include stearic acid as the fatty acid adjunct in an amount of from about 2 to about 5 parts by weight per 100 parts of rubber.

[0096] Diisocyanates may also be optionally included in the core compositions. When utilized, the diisocyanates are included in amounts of from about 0.2 to about 5.0 parts by weight based on 100 parts rubber. Exemplary of suitable diisocyanates is 4,4′-diphenylmethane diisocyanate and other polyfunctional isocyanates known in the art.

[0097] Furthermore, the dialkyl tin difatty acids set forth in U.S. Pat. No. 4,844,471, the dispersing agents disclosed in U.S. Pat. No. 4,838,556, and the dithiocarbamates set forth in U.S. Pat. No. 4,852,884 may also be incorporated into the polybutadiene compositions of the present invention. The specific types and amounts of such additives are set forth in the above identified patents, which are incorporated herein by reference.

[0098] Cores according to the present invention are preferably manufactured as described below. “Textured” cores according to the present invention may also be formed by methods described in co-pending application, “Method of Making Golf Balls Having a Protrusion Center,” U.S. Ser. No. 09/737,067, filed on Dec. 14, 2000 incorporated herein by reference.

[0099] Cover and Mantle Layers

[0100] The cover and mantle layers of golf balls according to the present invention may comprise any material suitable for use as a golf ball mantle. Examples of preferred materials include, but are not limited to, ionomer resins, nylon compositions, and polyurethane materials.

[0101] Mantle layer materials for a golf ball according to the present invention are selected to produce desired performance characteristics when used in combination with a protuberant core according to the present invention. The surface topography of the protuberant core, along with the core material, the cover material, and the cover construction contribute to the performance characteristics of a golf ball and, thus, are important factors to consider when selecting mantle layer materials.

[0102] It is appreciated that the following described materials are suitable to form any layer within a multi-layer golf ball in a golf ball in accordance with the present invention. Thus, the following materials may be used as an outer core layer, an intermediate mantle layer, an inner cover layer, an outer cover layer, or any other layer within a multi-layer golf ball.

[0103] A. Ionomer Resins

[0104] With respect to a preferred ionomeric cover or mantle layer composition of the invention, ionomeric resins are polymers containing interchain ionic bonding. As a result of their toughness, durability, and flight characteristics, various ionomeric resins sold by E.I. DuPont de Nemours & Company under the trademark “SURLYN®” and more recently, by the Exxon Corporation (see U.S. Pat. No. 4,911,451, incorporated herein by reference) under the trademark “ESCOR®” and the tradename “IOTEK®”, have become the materials of choice for the construction of golf ball layers over the traditional “balata” (transpolyisoprene, natural or synthetic) rubbers.

[0105] Ionomeric resins are generally ionic copolymers of an olefin, such as ethylene, and a metal salt of an unsaturated carboxylic acid, such as acrylic acid, methacrylic acid or maleic acid. In some instances, an additional softening comonomer such as an acrylate can also be included to form a terpolymer. The pendent ionic groups in the ionomeric resins interact to form ion-rich aggregates contained in a non-polar polymer matrix. The metal ions, such as sodium, zinc, magnesium, lithium, potassium, calcium, etc. are used to neutralize some portion of the acid groups in the copolymer resulting in a thermoplastic elastomer exhibiting enhanced properties, i.e., improved durability, etc., for golf ball construction over balata.

[0106] The ionomeric resins utilized to produce cover and mantle compositions can be formulated according to known procedures such as those set forth in U.S. Pat. No. 3,421,766 or British Patent No. 963,380, with neutralization effected according to procedures disclosed in Canadian Patent Nos. 674,595 and 713,631, all of which are hereby incorporated by reference, wherein the ionomer is produced by copolymerizing the olefin and carboxylic acid to produce a copolymer having the acid units randomly distributed along the polymer chain. Broadly, the ionic copolymer generally comprises one or more α-olefins and from about 9 to about 20 weight percent of α, β-ethylenically unsaturated mono- or dicarboxylic acid, the basic copolymer neutralized with metal ions to the extent desired.

[0107] At least about 20% of the carboxylic acid groups of the copolymer are neutralized by the metal ions (such as sodium, potassium, zinc, calcium, magnesium, and the like) and exist in the ionic state. Suitable olefins for use in preparing the ionomeric resins include ethylene, propylene, butene-1, hexene-1 and the like. Unsaturated carboxylic acids include acrylic, methacrylic, ethacrylic, α-chloroacrylic, crotonic, maleic, fumaric, itaconic acids, and the like. The ionomeric resins utilized in the golf ball industry are generally copolymers of ethylene with acrylic (i.e., ESCOR®) and/or methacrylic (i.e., SURLYN®) acid. In addition, two or more types of ionomeric resins may be blended in to the mantle layer compositions in order to produce the desired properties of the resulting golf balls.

[0108] The high acid ionomers; suitable for use in the preferred embodiment golf balls are ionic copolymers which are the metal, i.e., sodium, zinc, magnesium, etc., salts of the reaction product of an olefin having from about 2 to 8 carbon atoms and an unsaturated monocarboxylic acid having from about 3 to 8 carbon atoms. Preferably, the ionomeric resins are copolymers of ethylene and either acrylic or methacrylic acid. In some circumstances, an additional comonomer such as an acrylate ester (i.e., iso- or n-butylacrylate, etc.) can also be included to produce a softer terpolymer. The carboxylic acid groups of the copolymer are partially neutralized (i.e., approximately 10-75%, preferably 30-70%) by the metal ions. Each of the high acid ionomer resins included in the cover compositions of the invention contains greater than about 16% by weight of a carboxylic acid, preferably from about 17% to about 25% by weight of a carboxylic acid, more preferably from about 18.5% to about 21.5% by weight of a carboxylic acid.

[0109] Although an ionomeric composition preferably includes a high acid ionomeric resin and it is contemplated that all known high acid ionomeric resins falling within the parameters set forth above may be used in the present invention, only a relatively limited number of these high acid ionomeric resins are currently available. In this regard, the high acid ionomeric resins available from E.I. DuPont de Nemours Company under the trademark “SURLYN®”, and the high acid ionomer resins available from Exxon Corporation under the trademarks “ESCOR®” or “Iotek®” are examples of available high acid ionomeric resins which may be utilized in the present invention.

[0110] The high acid ionomeric resins available from Exxon under the designation “ESCOR®” and or “IOTEK®”, are somewhat similar to the high acid ionomeric resins available under the “SURLYN®” trademark. However, since the ESCOR® and IOTEK® ionomeric resins are sodium or zinc salts of poly(ethylene acrylic acid) and the “SURLYN®” resins are zinc, sodium, magnesium, etc., salts of poly(ethylene methacrylic acid), distinct differences in properties exist.

[0111] Examples of the high acid methacrylic acid based ionomers found suitable for use in accordance with this invention include SURLYN® AD-8422 (sodium cation), SURLYN® 8162 (zinc cation), SURLYN® SEP-503-1 (zinc cation), and SURLYN® SEP-503-2 (magnesium cation). According to DuPont, all of these ionomers contain from about 18.5 to about 21.5% by weight methacrylic acid.

[0112] More particularly, SURLYN® AD-8422 is currently commercially available from DuPont in a number of different grades (i.e., AD-8422-2, AD-8422-3, AD-8422-5, etc.) based upon differences in melt index. According to DuPont, SURLYN® AD-8422 offers the following general properties when compared to SURLYN® 8920 the stiffest, hardest of all on the low acid grades (referred to as “hard” ionomers in U.S. Pat. No. 4,884,814, incorporated herein by reference):

TABLE 5
Low Acid High Acid
(15 wt % Acid) (>20 wt % Acid)
SURLYN ® SURLYN ® SURLYN ®
8920 8422-2 8422-3
Ionomer
Cation Na Na Na
Melt Index 1.2 2.8 1.0
Sodium, Wt % 213 1.9 2.4
Base Resin MI 60 60 60
MP1 , ° C. 88 86 85
EP1 , ° C. 47 48.5 45
Compression Molding2
Tensile Break, psi 4350 4190 5330
Yield, psi 2280 3670 3590
Elongation, % 315 263 289
Flex Mod, K psi 53.2 76.4 88.3
Shore D hardness 66 67 68

[0113] In comparing SURLYN® 8920 to SURLYN® 8422-2 and SURLYN® 8422-3, it is noted that the high acid SURLYN® yield, lower elongation, slightly higher Shore D hardness and much higher flexural modulus. SURLYN® 8920 contains 15% weight methacrylic acid and is 59% neutralized with sodium.

[0114] In addition, SURLYN® SEP-503-1 (zinc cation) and SURLYN® SEP-503-2 (magnesium cation) are high acid zinc and magnesium versions of the SURLYN® AD 8422 high acid ionomers. When compared to the SURLYN® AD 8422 high acid ionomers, the SURLYN® SEP-503-1 and SEP-503-2 ionomers can be defined as follows:

TABLE 6
SURLYN ® Ionomer Ion Melt index Neutralization %
AD 8422-3 Na 1.0 45
SEP 503-1 Zn 0.8 38
SEP 503-2 Mg 1.8 43

[0115] Furthermore, SURLYN® 8162 is a zinc cation ionomer resin containing approximately 20% by weight (i.e., 18.5-21.5% weight) methacrylic acid copolymer that has been 30-70% neutralized. SURLYN® 8162 is currently commercially available from DuPont.

[0116] Examples of the high acid acrylic acid based ionomers suitable for use in the present invention include the ESCOR® or IOTEK® high acid ethylene acrylic acid ionomers produced by Exxon. In this regard, ESCOR® or IOTEK® 959 is a sodium ion neutralized ethylene-acrylic acid copolymer. According to Exxon, IOTEK® 959 and 960 contain from about 19.0 to about 21.0% by weight acrylic acid with approximately 30 to about 70 percent of the acid groups neutralized with sodium and zinc ions, respectively. The physical properties of these high acid acrylic acid based ionomers are as follows:

TABLE 7
ESCOR ®
Property ESCOR (IOTEK ® 959) (IOTEK ® 960)
Melt Index, g/10 min 2.0 1.8
Cation Sodium Zinc
Melting Point, ° F. 172 174
Vicat Softening Point, ° F. 130 131
Tensile @ Break, psi 4600 3500
Elongation @ Break, % 325 430
Hardness, Shore D 66 57
Flexural Modulus, psi 66,000 27,000

[0117] Furthermore, as a result of the development of a number of new high acid ionomers neutralized to various extents by several different types of metal cations, such as by manganese, lithium, potassium, calcium and nickel cations, several new high acid ionomers and/or high acid ionomer blends besides sodium, zinc and magnesium high acid ionomers or ionomer blends are now available for golf ball cover and mantle production. It has been found that these new cation neutralized high acid ionomer blends produce compositions exhibiting enhanced hardness and resilience due to synergies which occur during processing. Consequently, the metal cation neutralized high acid ionomer resins recently produced can be blended to produce substantially harder golf balls having higher C.O.R.'s than those produced by the low acid ionomer compositions presently commercially available.

[0118] More particularly, several new metal cation neutralized high acid ionomer resins have been produced by neutralizing, to various extents, high acid copolymers of an alpha-olefin and an alpha, beta-unsaturated carboxylic acid with a wide variety of different metal cation salts. It has been found that numerous new metal cation neutralized high acid ionomer resins can be obtained by reacting a high acid copolymer (i.e., a copolymer containing greater than 16% by weight acid, preferably from about 17 to about 25 weight percent acid, and more preferably about 20 weight percent acid), with a metal cation salt capable of ionizing or neutralizing the copolymer to the extent desired (i.e., from about 10% to 90%).

[0119] The base copolymer is made up of greater than 16% by weight of an alpha, beta-unsaturated carboxylic acid and an alpha-olefin. Optionally, a softening comonomer can be included in the copolymer. Generally, the alpha-olefin has from 2 to 10 carbon atoms and is preferably ethylene, and the unsaturated carboxylic acid is a carboxylic acid having from about 3 to 8 carbons. Examples of such acids include acrylic acid, methacrylic acid, ethacrylic acid, chloroacrylic acid, crotonic acid, maleic acid, fumaric acid, and itaconic acid, with acrylic acid being preferred.

[0120] The softening comonomer that can be optionally included in the mantle layers of the preferred embodiment golf balls of the invention may be selected from the group consisting of vinyl esters of aliphatic carboxylic acids wherein the acids have 2 to 10 carbon atoms, vinyl ethers wherein the alkyl groups contains 1 to 10 carbon atoms, and alkyl acrylates or methacrylates wherein the alkyl group contains 1 to 10 carbon atoms. Suitable softening comonomers include vinyl acetate, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, or the like.

[0121] Consequently, examples of a number of copolymers suitable for use to produce the high acid ionomers included in the preferred embodiment balls of the present invention include, but are not limited to, high acid embodiments of an ethylene/acrylic acid copolymer, an ethylene/methacrylic acid copolymer, an ethylene acid copolymer, an ethylene/maleic acid copolymer, an ethylene/methacrylic acid/vinyl acetate copolymer, an ethylene/acrylic acid/vinyl alchol copolymer, etc. The base copolymer broadly contains greater than 16% by weight unsaturated carboxylic acid, from about 30 to about 83% by weight ethylene and from 0 to about 40% by weight of a softening comonomer. Preferably, the copolymer contains about 20% by weight unsaturated carboxylic acid and about 80% by weight ethylene. Most preferably, the copolymer contains about 20% acrylic acid with the remainder being ethylene.

[0122] Along these lines, examples of the preferred high acid base copolymers which fulfill the criteria set forth above, are a series of ethylene-acrylic copolymers which are commercially available from The Dow Chemical Company, Midland, Mich., under the “PRIMACOR®” designation. These high acid base copolymers exhibit the typical properties set forth below:

TABLE 8
Typical Properties of PRIMACOR ® Ethylene-Acrylic
Acid Copolymers
Melt Flexural Vicat
Per- Index, Tensile Mod- Soft Shore D
cent Density, g/ YD. ulus PT Hard-
Grade Acid glcc 10 min. St (psi) (psi) (° C.) ness
ASTM D-792 D-1238 D-638 D-790 D-1525 D-2240
5980 20.0 0.958 300.0 4800 43 50
5990 20.0 0.955 1300.0 650 2600 40 42
5990 20.0 0.955 1300.0 650 3200 40 42
5981 20.0 0.960 300.0 900 3200 46 48
5981 20.0 0.960 300.0 900 3200 46 48
5983 20.0 0.958 500.0 850 3100 44 45
5991 20.0 0.953 2600.0 635 2600 38 40

[0123] Due to the high molecular weight of the PRIMACOR® 5981 grade of the ethylene-acrylic acid copolymer, this copolymer is the more preferred grade utilized in the invention.

[0124] The metal cation salts utilized in the invention are those salts which ethylene the metal cations capable of neutralizing, to various extents, the carboxylic acid groups of the high acid copolymer. These include acetate, oxide or hydroxide salts of lithium, calcium, zinc, sodium, potassium, nickel, magnesium, and manganese.

[0125] Examples of such lithium ion sources are lithium hydroxide monohydrate, lithium hydroxide, lithium oxide and lithium acetate. Sources for the calcium ion include calcium hydroxide, calcium acetate and calcium oxide. Suitable zinc ion sources are zinc acetate dihydrate and zinc acetate, a blend of zinc oxide and acetic acid. Examples of sodium ion sources are sodium hydroxide and sodium acetate. Sources for the potassium ion include potassium hydroxide and potassium acetate. Suitable nickel ion sources are nickel acetate, nickel oxide and nickel hydroxide. Sources of magnesium include magnesium oxide, magnesium hydroxide, magnesium acetate. Sources of manganese include manganese acetate and manganese oxide.

[0126] The new metal cation neutralized high acid ionomer resins are produced by reacting the high acid base copolymer with various amounts of the metal cation salts above the crystalline melting point of the copolymer, such as at a temperature from about 200° F. to about 500° F., preferably from about 250° F. to about 350° F. under high shear conditions at a pressure of from about 10 psi to 10,000 psi. Other well known blending techniques may also be used. The amount of metal cation salt utilized to produce the new metal cation neutralized high acid based ionomer resins is the quantity which provides a sufficient amount of the metal cations to neutralize the desired percentage of the carboxylic acid groups in the high acid copolymer. The extent of neutralization is generally from about 10% to about 90%.

[0127] As indicated below in Table 9, a number of new types of metal cation neutralized high acid ionomers can be obtained from the above indicated process. These include new high acid ionomer resins neutralized to various extents with manganese, lithium, potassium, calcium and nickel cations. In addition, when a high acid ethylene/acrylic acid copolymer is utilized as the base copolymer component of the invention and this component is subsequently neutralized to various extents with the metal cation salts producing acrylic acid based high acid ionomer resins neutralized with cations such as sodium, potassium, lithium, zinc, magnesium, manganese, calcium and nickel, several new cation neutralized acrylic acid based high acid ionomer resins are produced.

TABLE 9
Formulation Wt % Wt % Melt Shore D
No. Cation Salt Neutralization Index C.O.R. Hardness
 1 (NaOH) 6.98 67.5 0.9 .804 71
 2 (NaOH) 5.66 54.0 2.4 .808 73
 3 (NaOH) 3.84 35.9 12.2 .812 69
 4 (NaOH) 2.91 27.0 17.5 .812 (brittle)
 5 (MnAc) 19.6 71.7 7.5 .809 73
 6 (MnAc) 23.1 88.3 3.5 .814 77
 7 (MnAc) 15.3 53.0 7.5 .810 72
 8 (MnAc) 26.5 106 0.7 .813 (brittle)
 9 (LiOH) 4.54 71.3 0.6 .810 74
10 (LiOH) 3.38 52.5 4.2 .818 72
11 (LiOH) 2.34 35.9 18.6 .815 72
12 (KOH) 5.30 36.0 19.3 Broke 70
13 (KOH) 8.26 57.9 7.18 .804 70
14 (KOH) 10.7 77.0 4.3 .801 67
15 (ZnAc) 17.9 71.5 0.2 .806 71
16 (ZnAc) 13.9 53.0 0.9 .797 69
17 (ZnAc) 9.91 36.1 3.4 .793 67
18 (MgAC) 17.4 70.7 2.8 .814 74
19 (MgAC) 20.6 87.1 1.5 .815 76
20 (MgAC) 13.8 53.8 4.1 .814 74
21 (CaAc) 13.2 69.2 1.1 .813 74
22 (CaAc) 7.12 34.9 10.1 .808 70
23 (MgO) 2.91 53.5 2.5 .813
24 (MgO) 3.85 71.5 2.8 .808
25 (MgO) 4.76 89.3 1.1 .809
26 (MgO) 1.96 35.7 7.5 .815
27 (NiAc) 13.04 61.1 0.2 .802 71
28 (NiAc) 10.71 48.9 0.5 .799 72
29 (NiAc) 8.26 36.7 1.8 .796 69
30 (NiAc) 5.66 24.4 7.5 .786 64

[0128] When compared to low acid versions of similar cation neutralized ionomer resins, the new metal cation neutralized high acid ionomer resins exhibit enhanced hardness, modulus and resilience characteristics.

[0129] When utilized in golf ball cover construction, it has been found that the new acrylic acid based high acid ionomers extend the range of hardness beyond that previously obtainable while maintaining the beneficial properties (i.e., durability, click, feel, etc.) of the softer low acid ionomer covered balls, such as balls produced utilizing the low acid ionomers disclosed in U.S. Pat. Nos. 4,884,814 and 4,911,451, and the recently produced high acid blends disclosed in U.S. Pat. No. 5,688,869, all of which, as previously noted, are herein incorporated by reference.

[0130] Moreover, as a result of the development of a number of new acrylic acid based high acid ionomer resins neutralized to various extents by several different types of metal cations, such as manganese, lithium, potassium, calcium and nickel cations, several new ionomers or ionomer blends are now available for golf ball production. By using these high acid ionomer resins harder, stiffer golf balls having higher C.O.R.s, and thus longer distance, can be obtained.

[0131] Other ionomer resins may be used in the mantle layer compositions, such as low acid ionomer resins, preferably such that the molded layer produces a Shore D hardness of 65 or more.

[0132] Suitable low acid ionomers include, but are not limited to, those developed and sold by E.I. DuPont de Nemours & Company under the trademark “SURLYN® and by Exxon Corporation under the trademark “ESCOR®” or tradename “IOTEK®”, or blends thereof.

[0133] The low acid ionomeric resins available from Exxon under the designation “ESCOR®” and or “IOTEK®”, are somewhat similar to the low acid ionomeric resins available under the “SURLYN®” trademark. However, since the ESCOR®/IOTEK® ionomeric resins are sodium or zinc salts of poly (ethylene-acrylic acid) and the “SURLYN®” resins are zinc, sodium, magnesium, etc. salts of poly (ethylene-methacrylic acid), distinct differences in properties exist.

[0134] When utilized in the construction of a mantle layer of a multi-layered golf ball, it has been found that the low acid ionomer blends extend the range of compression and spin rates beyond that previously obtainable. More preferably, it has been found that when two or more low acid ionomers, particularly blends of sodium and zinc high acid ionomers, are processed to produce the mantle layers of multi-layered golf balls, the resulting golf balls will travel further and at an enhanced spin rate than previously known multi-layered golf balls. Such an improvement is particularly noticeable in enlarged or oversized golf balls.

[0135] For example, the normal size, multi-layer golf ball taught in U.S. Pat. No. 4,650,193 does not incorporate blends of low acid ionomeric resins of the present invention in the mantle layer. In addition, the multi-layered ball disclosed in the '193 patent suffers substantially in durability in comparison with the present invention.

[0136] Furthermore, use of a mantle layer formulated from blends of lower acid ionomers produces multi-layer golf balls having enhanced compression and spin rates. These are the properties desired by the more skilled golfer.

[0137] The cover layers are preferably formed from an ionomer resin. In a preferred form of the invention, soft cover layers, i.e. those with a Shore D hardness of 10-55 and more preferably 30-50, comprise an ionomer with an average weight percent acid content of about 15 or less which is at least 10% neutralized. More specifically, the soft cover layers typically constitute a blend of two types of ionomers in which one component of the blend is an ethylene-acrylic acid or ethylene-methacrylic acid copolymer containing at least about 15 wt % acid groups which are at least partially neutralized with a cation, and the other type of ionomer is a terpolymer of ethylene, acrylic acid or methacrylic acid and a softening termonomer such as butyl acrylate or methyl acrylate, resulting in an overall wt % acid content of about 15 or less. Non-limiting examples of suitable blends are described in U.S. Pat. Nos. 4,884,814 and 5,120,791, both of which are incorporated herein by reference. In a particularly preferred form of the invention the soft cover layer is comprised of at least about 75 wt % terpolymer type ionomer.

[0138] The cover layers of intermediate hardness, e.g., those with a Shore D hardness of 50-65, preferably are made from the same types of materials as are used for the soft cover layers. It is particularly preferred to use blends of about 25-75 wt % copolymer ionomer with about 75-25 wt % terpolymer type ionomers.

[0139] The hard ionomeric cover layer or layers can contain a single type of ionomer or a blend of two or more types of ionomers. Furthermore, a hardening and/or softening modifier can be added. In a particularly preferred form of the invention, the hard cover layer or layers contain one or more ionomers having at least 16 weight % acid groups, which are at least partially neutralized.

[0140] Each of the various cover layers can be foamed or unfoamed. Preferably, each layer is unfoamed. A foamed layer has a lower density than an unfoamed layer, thereby affecting the weight distribution and moment of inertia. Typically, the melt index is increased by foaming. The use of a foamed cover layer results in the need to increase the weight of the core of the ball, thereby allowing for easier initiation of spin to a ball, particularly on short shots. This may partially compensate for a low spin rate on a hard covered ball, particularly in the case of a player who does not strike the ball at a fast swing speed. A foamed layer generally has a lower modulus and thus increased flexibility. Typically, a foamed layer is formed by adding a small amount of a chemical blowing agent to the cover material prior to molding. The blowing agent is selected such that it will release gas at the molding temperature for the cover layer.

[0141] Non-limiting examples of materials which are suitable to form the outer cover layer of the golf ball are ionomer, a metallocene catalyzed polyolefin such as EXACT®, INSITE®, AFFINITY®, or ENGAGE® which preferably is crosslinked, polyamids, amide-ester elastomer, or graft copolymer of ionomer and polyamide such as CAPRON®, ZYTEL®, ZYTEL®, PEBAX®, etc., a crosslinked transpolyisoprene blend, a thermoplastic block polyester such as HYTREL®, or a thermoplastic or thermosetting polyurethane, such as ESTANE® X-4517.

[0142] The inner and intermediate cover layers can be made of any of the materials previously listed as being useful for forming an outer cover layer. Furthermore, the inner and intermediate cover layers can be formed from a number of other non-ionomeric thermoplastics and thermosets. For example, lower cost polyolefins and thermoplastic elastomers can be used. Non-limiting examples of suitable non-ionomeric polyolefin materials include low density polyethylene, linear low density polyethylene, high density polyethylene, polypropylene, rubber-toughened olefin polymers, acid copolymers which do not become part of an ionomeric copolymer when used in the inner cover layer, such as PRIMACOR®, NUCREL®, ESCOR® and ATX, plastomers and flexomers, thermoplastic elastomers such as styrene/butadiene/styrene (SBS) or styrene/ethylene-butylene/styrene (SEBS) block copolymers, including KRATON® (Shell), dynamically vulcanized elastomers such as SANTOPRENE® (Monsanto), ethylene vinyl acetates such as ELVAX® (DuPont), ethylene methyl acrylates such as OPTEMA® (Exxon), polyvinyl chloride resins, and other elastomeric materials may be used. Mixtures, blends, or alloys involving the materials described above can be used. It is desirable that the polyolefin be a tough, low density material. The non-ionomeric polyolefins can be mixed with ionomers.

[0143] The inner, intermediate and outer cover layers optionally may include processing aids, release agents and/or diluents. Another useful material for the inner and/or intermediate cover layers is a natural rubber latex (prevulcanized) which has a tensile strength of 4,000-5,000 psi, high resilience, good scuff resistance, a Shore D hardness of less than and an elongation of more than 500%.

[0144] As indicated above, the inner, intermediate and outer cover layers may contain plastomer. The plastomer preferably either is crosslinked or is blended with an ionomer or other compatible material. Plastomers are olefin copolymers with a uniform, narrow molecular weight distribution, a high comonomer content, and an even distribution of comonomers. The molecular weight distribution of the plastomers generally is about 1.5-4, preferably 1.5-3.5 and more preferably 1.5-2.4. The density is typically in the range of 0.85-0.97 if unfoamed and 0.10-0.90 if foamed. The comonomer content typically is in the range of 1-32%, and preferably 2-20%. The composition distribution breadth index generally is greater than 30%, preferably is at least 45%, and more preferably is at least 50%.

[0145] The cover compositions which may be used in making the preferred embodiment golf balls of the present invention are set forth in detail but not limited to those in U.S. Pat. No. 5,688,869, incorporated herein by reference. In short, the cover material is comprised of hard, high stiffness ionomer resins, preferably containing relatively high amounts of acid (i.e., greater than 16 weight percent acid, preferably from about 17 to about 25 weight percent acid, and more preferably from about 18.5 to about 21.5 weight percent) and at least partially neutralized with metal ions (such as sodium, zinc, potassium, calcium, magnesium and the like). The high acid resins are blended and melt processed to produce compositions exhibiting hardness and coefficient of restitution values when compared to low acid ionomers, or blends of low acid ionomer resins containing 16 weight percent acid or less.

[0146] The preferred cover compositions may also be prepared from specific blends of two or more high acid ionomers with other cover additives which do not exhibit the processing, playability, distance and/or durability limitations demonstrated by the prior art. However, as more particularly indicated below, the cover composition can also be comprised of one or more low acid ionomers so long as the molded covers exhibit a hardness of 65 or more on the Shore D scale. These include lithium ionomers or blends of ionomers with harder non-ionic polymers such as nylon, polyphenylene oxide and other compatible thermoplastics. Of course, the cover compositions are not limited in any way to those compositions set forth in said co-pending applications.

[0147] The low acid ionomers which may be suitable for use in formulating cover layer compositions are ionic copolymers which are the metal, i.e., sodium, zinc, magnesium, etc., salts of the reaction product of an olefin having from about 2 to 8 carbon atoms and an unsaturated monocarboxylic acid having from about 3 to 8 carbon atoms. Preferably, the ionomeric resins are copolymers of ethylene and either acrylic or methacrylic acid. In some circumstances, an additional comonomer such as an acrylate ester (i.e., iso- or n-butylacrylate, etc.) can also be included to produce a softer terpolymer. The carboxylic acid groups of the copolymer are partially neutralized (i.e., approximately 10-75%, preferably 30-70%) by the metal ions. Each of the low acid ionomer resins which may be included in the inner layer cover compositions of the invention contains 16% by weight or less of a carboxylic acid.

[0148] Regarding multi-layer cover constructions, the outer cover layer is preferably softer than the low acid ionomer blend based inner layer. The softness provides for the enhanced feel and playability characteristics typically associated with balata or balata-blend balls. The outer layer or ply is comprised of a relatively soft, low modulus (about 1,000 psi to about 10,000 psi) and low acid (less than 16 weight percent acid) ionomer, ionomer blend or a non-ionomeric thermoplastic elastomer such as, but not limited to, a polyurethane, a polyester elastomer such as that marketed by DuPont under the trademark HYTREL®, or a polyester amide such as that marketed by Elf Atochem S.A. under the trademark PEBAX®. The outer layer is fairly thin (i.e., from about 0.010 to about 0.070 in thickness, more desirably 0.03 to 0.06 inches in thickness for a 1.680 inch ball and 0.04 to 0.07 inches in thickness for a 1.72 inch ball), but thick enough to achieve desired playability characteristics while minimizing expense

[0149] Preferably, an outer layer includes a blend of hard and soft (low acid) ionomer resins such as those described in U.S. Pat. Nos. 4,884,814 and 5,120,791, both incorporated herein by reference. Specifically, a desirable material for use in molding an outer layer comprises a blend of a high modulus (hard), low acid, ionomer with a low modulus (soft), low acid, ionomer to form a base ionomer mixture.

[0150] A high modulus ionomer herein is one which measures from about 15,000 to about 70,000 psi as measured in accordance with ASTM method D-790. The hardness may be defined as at least 50 on the Shore D scale as measured in accordance with ASTM method D-2240.

[0151] The hard ionomer resins utilized to produce an outer cover layer composition comprised of hard/soft blends include ionic copolymers which are the sodium, zinc, magnesium or lithium salts of the reaction product of an olefin having from 2 to 8 carbon atoms and an unsaturated monocarboxylic acid having from 3 to 8 carbon atoms. The carboxylic acid groups of the copolymer may be totally or partially (i.e., approximately 15-75%) neutralized. The hard ionomeric resins are likely copolymers of ethylene and either acrylic and/or methacrylic acid, with copolymers of ethylene and acrylic acid being the most preferred. Two or more types of hard ionomeric resins may be blended into the outer cover layer compositions in order to produce the desired properties of the resulting golf balls.

[0152] The hard “IOTEK®” resins (i.e., the acrylic acid based hard ionomer resins) are the more preferred hard resins for use in formulating the outer layer blends for use in the present invention. In addition, various blends of “IOTEK®” and SURLYN® hard ionomeric resins, as well as other available ionomeric resins, may be utilized in the present invention in a similar manner.

[0153] Examples of commercially available hard ionomeric resins which may be used in the present invention in formulating the inner and outer cover blends include the hard sodium ionic copolymer sold under the trademark SURLYN® 8940 and the hard zinc ionic copolymer sold under the trademark SURLYN® 9910. SURLYN® 8940 is a copolymer of ethylene with methacrylic acid and about 15 weight percent acid which is about 29% neutralized with sodium ions. This resin has an average melt flow index of about 2.8. SURLYN® 9910 is a copolymer of ethylene and methacrylic acid with about 15 weight percent acid which is about 58 percent neutralized with zinc ions. The average melt flow index of SURLYN® 9910 is about 0.7. The typical properties of SURLYN® 9910 and 8940 are set forth below:

TABLE 10
Typical Properties of Commercially Available Hard
SURLYN ® Resins Suitable for Use in the Inner and Outer Layer
Blends of the Present Invention
ASTMD 8940 9910 8920 8528 9970 9730
Cation Type Sodium Zinc Sodium Sodium Zinc Zinc
Melt flow index, D-1238 2.8 0.7 0.9 1.3 14.0 1.6
gms/10 min.
Specific Gravity, g/cm3 D-792 0.95 0.97 0.95 0.94 0.95 .095
Hardness, Shore D D-2240 66 64 66 60 62 63
Tensile Strength, D-638 (4.8) (3.6) (5.4) (4.2) (3.2) (4.1)
(kpsi), MPa
Elongation, % D-638 470 290 350 450 460 460
Flexural Modulus, D-790 (51) (48) (55) (32) (28) (30)
(kpsi) MPa
Tensile Impact (23° C.) D-18225 1020 1020 865 1160 760 1240
KJ/m2 (ft.-lbs./in) (485) (485) (410) (550) (360) (590)
Vicat Temperature, ° C. D-1525 63 62 58 73 61 73

[0154] Examples of the more pertinent acrylic acid based hard ionomer resin suitable for use as an inner and outer cover composition sold under the “IOTEK®” tradename by the Exxon Corporation include IOTEK® 4000, IOTEK® 4010, IOTEK® 8000, IOTEK® 8020 and IOTEK® 8030. The typical properties of these and other IOTEK® hard ionomers suited for use in formulating an inner and/or outer layer cover compositions are set forth below:

TABLE 11
Typical Properties of IOTEK ® Ionomers
ASTM
Method Units 4000 4010 8000 8020 8030 7010 7020 7030
Resin Properties
Cation type zinc zinc sodium sodium sodium zinc zinc zinc
Melt index D-1238 g/10 min. 2.5 1.5 0.8 1.6 2.8 0.8 0.8 2.5
Density D-1505 kg/m3 963 963 954 960 960 960 960 960
Melting Point D-3417 ° C. 90 90 90 87.5 87.5 90 90 90
Crystallization Point D-3417 ° C. 62 64 56 53 55
Vicat Softening Point D-1525 ° C. 62 63 61 64 67 60 63 62.5
% Weight Acrylic Acid 16 11
% of Acid Groups Cation Neutralized 30 40
Plaque Properties
(3 mm thick, compression molded)
Tensile at Break D-638 MPa 24 26 36 31.5 28 38 38 38
Yield Point D-638 MPa none none 21 21 23 none none none
Elongation at Break D-638 % 420 420 350 410 395 500 420 395
1% Secant Modulus D-638 MPa 160 160 300 350 390
Shore Hardness D D-2240 55 55 61 58 59 57 55 55
Film Properties
(50 Micron Film 2.2.1 Blow-Up Ratio)
Tensile at Break
MD D-882 MPa 41 39 42 52 47.4
TD D-882 MPa 37 38 38 38 40.5
Yield Point
MD D-882 MPa 15 17 17 23 21.6
TD D-882 MPa 14 15 15 21 20.7
Elongation at Break
MD D-882 % 310 270 260 295 305
TD D-882 % 360 240 280 340 345
1% Secant Modulus
MD D-882 MPa 210 215 390 380 380
TD D-882 MPa 200 225 380 350 345
Dart Drop Impact D-1709 g/micron 12.4 12.5 20.3

[0155] Comparatively, soft ionomers are used in formulating the hard/soft blends of inner and outer cover compositions. These ionomers include acrylic acid based soft ionomers. They are generally characterized as comprising sodium or zinc salts of a terpolymer of an olefin having from about 2 to 8 carbon atoms, acrylic acid, and an unsaturated monomer of the acrylate ester class having from 1 to 21 carbon atoms. The soft ionomer is preferably a zinc based ionomer made from an acrylic acid base polymer in an unsaturated monomer of the acrylate ester class. The soft (low modulus) ionomers have a hardness from about 20 to about 40 as measured on the Shore D scale, as measured in accordance with ASTM method D-2240, and a flexural modulus from about 1,000 to about 10,000, as measured in accordance with ASTM method D-790.

[0156] Certain ethylene-acrylic acid based soft ionomer resins developed by the Exxon Corporation under the designation “IOTEK® 7520” (referred to experimentally by differences in neutralization and melt indexes as LDX 195, LDX 196, LDX 218 and LDX 219) may be combined with known hard ionomers such as those indicated above to produce the inner and outer cover layers. The combination produces higher C.O.R.s at equal or softer hardness, higher melt flow (which corresponds to improved, more efficient molding, i.e., fewer rejects) as well as significant cost savings versus the inner and outer layers of multi-layer balls produced by other known hard-soft ionomer blends as a result of the lower overall raw materials costs and improved yields.

[0157] While the exact chemical composition of the resins to be sold by Exxon under the designation IOTEK® 7520 is considered by Exxon to be confidential and proprietary information, Exxon's experimental product data sheet lists the following physical properties of the ethylene acrylic acid zinc ionomer developed by Exxon:

TABLE 12
Physical Properties of IOTEK ® 7520
Property ASTM Method Units Typical Value
Melt index D-1238 g/10 min. 2
Density D-1505 kg/m3 0.962
Cation zinc
Melting Point D-3417 ° C. 66
Crystallization Point D-3417 ° C. 49
Vicat Softening D-1525 ° C. 42
Plaque Properties
(2 mm thick Compression
Molded Plaques)
Tensile at Break D-638 MPa 10
Yield Point D-638 MPa None
Elongation at Break D-638 % 760
1% Secant Modulus D-638 MPa 22
Shore D Hardness D-2240 32
Flexural Modulus D-790 MPa 26
Zwick Rebound ISO 4862 % 52
De Mattia Flex Resistance D-430 Cycles >5000

[0158] In addition, test data collected by the assignee indicates that IOTEK® 7520 resins have Shore D hardnesses of about 32 to 36 (per ASTM D-2240), melt flow indexes of 3□0.5 g/10 min (at 190° C. per ASTM D-1288), and a flexural modulus of about 2500-3500 psi (per ASTM D-790). Furthermore, testing by an independent testing laboratory by pyrolysis mass spectrometry indicates that IOTEK® 7520 resins are generally zinc salts of a terpolymer of ethylene, acrylic acid, and methyl acrylate.

[0159] Furthermore, a newly developed grade of an acrylic acid based soft ionomer available from the Exxon Corporation under the designation IOTEK® 7510, is also effective, when combined with the hard ionomers indicated above in producing golf ball covers exhibiting higher C.O.R. values at equal or softer hardness than those produced by known hard-soft ionomer blends. In this regard, IOTEK® 7510 has the advantages (i.e., improved flow, higher C.O.R. values at equal hardness, increased clarity, etc.) produced by the IOTEK® 7520 resin when compared to the methacrylic acid base soft ionomers known in the art (such as the SURLYN® 8625 and the SURLYN® 8629 combinations disclosed in U.S. Pat. No. 4,884,814).

[0160] In addition, IOTEK® 7510, when compared to IOTEK® 7520, produces slightly higher C.O.R. valves at equal softness/hardness due to the IOTEK® 7510's higher hardness and neutralization. Similarly, IOTEK® 7510 produces better release properties (from the mold cavities) due to its slightly higher stiffness and lower flow rate than IOTEK® 7520. This is important in production where the soft covered balls tend to have lower yields caused by sticking in the molds and subsequent punched pin marks from the knockouts.

[0161] According to Exxon, IOTEK® 7510 is of similar chemical composition as IOTEK® 7520 (i.e., a zinc salt of a terpolymer of ethylene, acrylic acid, and methyl acrylate) but is more highly neutralized. Based upon FTIR analysis IOTEK® 7520 is estimated to be about 30-40 wt.-% neutralized and IOTEK® 7510 is estimated to be about 40-60 wt.-% neutralized. The typical properties of IOTEK® 7510 in comparison of those of IOTEK® 7520 are set forth below:

TABLE 13
Physical Properties of IOTEK ® 7510
in Comparison to IOTEK ® 7520
IOTEK ® 7520 IOTEK ® 7510
MI, g/10 min 2.0 0.8
Density, g/cc 0.96 0.97
Melting Point, ° F. 151 149
Vicat Softening Point, ° F. 108 109
Flex Modulus, psi 3800 5300
Tensile Strength, psi 1450 1750
Elongation, % 760 690
Shore D Hardness 32 35

[0162] It has been determined that when ionomer blends are used for the outer cover layer, good results are achieved when the relative combination is in a range of about 90 to about 10 percent hard ionomer and about 10 to about 90 percent soft ionomer. The results are improved by adjusting the range to about 75 to 25 percent hard ionomer and 25 to 75 percent soft ionomer. Even better results are noted at relative ranges of about 60 to 40 percent hard ionomer resin and about 40 to 60 percent soft ionomer resin.

[0163] Specific formulations which may be used in the cover composition are included in the examples set forth in U. S. Pat. Nos. 5,120,791 and 4,884,814. The present invention is in no way limited to those examples.

[0164] B. Nylon Compositions

[0165] Furthermore, examples of compositions for use as mantle layers include a graft copolymer or blend of a polyamide homopolymer with one or both of an ionomeric terpolymer and an ionomeric copolymer with two types of monomers. Preferred polyamides for use according to the invention are polymers of caprolactam such as polyepsiloncaprolactam (Nylon 6), polyhexamethyleneadipamide (Nylon 66), copolymers of nylon 6 and Nylon 66 and mixtures thereof. The ionomeric component of the invention preferably is a copolymer formed from an alpha-olefin having 2 to 8 carbon atoms and an acid which is selected from the group consisting of alpha, beta-ethylenically unsaturated mono- or dicarboxylic acids and is neutralized with cations which include at least one member selected from the group consisting of zinc, lithium, sodium, manganese, calcium, chromium, nickel, aluminum, potassium, barium, tin, copper, and magnesium ions. Preferred cations are zinc, sodium and lithium, and combinations thereof. The copolymer may further be formed from an unsaturated monomer of the acrylate ester class having from 1 to 21 carbon atoms.

[0166] The Shore D hardness of a hard nylon-containing layer according to the invention is typically in the range of from about 65 to about 85. Shore D hardness is measured in accordance with ASTM D-2240. The Shore D hardness of a soft nylon-containing layer according to the present invention typically is in the range of from about 50 to about 65. Both hard and soft nylon-containing layers preferably are made from resin compositions which have a melt index of from about 0.5 to about 20 g/10 min., more preferably from about 0.5 to about 8 g/10 min., and most preferably from about 1 to about 4 g/10 mins.

[0167] An “ionomeric copolymer” as this term is used herein is a copolymer of alpha-olefin and an alpha, beta-ethylenically unsaturated mono- or dicarboxylic acid with at least 3% and preferably at least 10% of the carboxylic acid groups being neutralized with metal ions. The alpha-olefin preferably has 2-8 carbon atoms, the carboxylic acid preferably is acrylic acid, methacrylic acid, maleic acid, or the like and the metal ions include at least one cation selected from the group consisting of ions of zinc, magnesium, lithium, barium, potassium, calcium, manganese, nickel, chromium, tin, aluminum, sodium, copper, or the like. Preferably the cation is zinc, sodium or lithium or a combination thereof. The term “copolymer” includes (1) copolymers having two types of monomers which are polymerized together, (2) terpolymers (which are formed by the polymerization of three types of monomers), and (3) copolymers which are formed by the polymerization of more than three types of monomers.

[0168] A “polyamide component” as used herein is a polyamide homopolymer, a polyamide copolymer containing two or more types of amide units, e.g., Nylon 6, 12, or a combination of both a polyamide homopolymer and a polyamide copolymer. The polyamide component preferably is a long chain polymer, not an oligomer, which typically is a short chain polymer of about 2 to 10 units. An “ionomeric component” is (a) a non-polyamide-containing ionomeric copolymer which is capable of being mixed or blended with the polyamide component, (b) the ionomeric portion of a polyamide-containing ionomeric copolymer, or a combination of both (a) and (b). If the polyamide component and ionomeric component are bonded to one another, the acid portion of the ionomeric component preferably is neutralized before the reaction of the polyamide and ionomeric components, but could also be neutralized after the reaction of the polyamide and ionomeric components.

[0169] The details of interaction between a polyamide and an ionomeric copolymer are not fully understood. A polyamide and an ionomer could, for example, be intimately mixed without any bonding but with specific intermolecular interactions. Furthermore, it is possible, in combining a specific quantity of polyamide with a specific quantity of ionomeric copolymer that portions of the overall quantities of the polyamide component and ionomeric component could be bonded to each other, as in a graft reaction, while other portions of the polyamide component and ionomeric component could form a blend which may have specific intermolecular interactions. Thus, this application is not intended to be limited by the degree of bonding versus intermolecular interaction of the polyamide component and ionomeric component unless specifically indicated.

[0170] Golf balls of the present invention employ a composition that is the reaction product (“RP”) of a reactive mixture of polyamide, ionomeric copolymer, and an ester copolymer. The RP preferably is formed from a reactive mixture of at least one of polyepsiloncaprolactam (Nylon 6) and polyhexamethyleneadipamide (Nylon 66), zinc neutralized ethylene/methacrylic acid ionomer copolymer, and ethylene (meth)acrylate. As used herein, the term “(meth)acrylate” includes both acrylates and methacrylates. The polyamide preferably is about 50 wt % to about 90 wt % of the reactive mixture, the ionomeric copolymer is about 5 to about 50 wt % of the reactive mixture, and the ester copolymer is about 1 to about 20 wt % of the reactive mixture. More preferably, the polyamide is about 60 to about 72 wt % of the reactive mixture, the ionomeric copolymer is about 26 to about 34 wt % of the reactive mixture, and the ester copolymer, preferably olefin ester copolymer, is about 2 to about 6 wt % of the reactive mixture.

[0171] Typically, the carboxylic acid groups of the terpolymer ionomer are partially (i.e., approximately 5 to 80 percent) neutralized by metal ions such as Li, Na, Zn, Mn, Ni, Ba, Sn, Ca, Mg, Cu and the like, preferably Zn, Na or Li or a combination thereof, and most preferably Zn or Li or a combination thereof. These terpolymer ionomers usually have a relatively high molecular weight, e.g., a melt index of about 0.1 to about 1000 g/10 min., and/or a weight average molecular weight of 5000 up to one million. The ethylene/methyl acrylate/acrylic acid terpolymer ionomer may comprise about 50 to about 98 wt %, preferably about 76 to about 75 wt %, and most preferably about 76 wt % ethylene; about 1 to about 30 wt %, preferably about 15 to about 20 wt %, and most preferably about 18 wt % methyl acrylate; and about 1 to about 20 wt %, preferably about 4 to about 10 wt %, and most preferably about 6 wt % acrylic acid. Useful terpolymer ionomers include, for example, ethylene/methyl acrylate/acrylic acid terpolymer ionomers, such as “IOTEK®”. Specifically, preferred terpolymer ionomers for use in the invention include Zn neutralized ethylene/methyl acrylate/acrylic acid terpolymer ionomers, including IOTEK® 7520 and IOTEK® 7510, and Li neutralized ionomers such as ESCOR® ATX-320-Li-80.

[0172] ESCOR® ATX 320 Li-80 is produced by utilizing a 6.0 wt % acrylic acid/18.0 wt % methyl acrylate 76 wt % ethylene terpolymer produced by Exxon Chemical Co. under the designation ESCOR® ATX 320. The acid groups present in the terpolymer then are neutralized to 80 mol % by using lithium hydroxymonohydrate. Neutralization is performed by adding lithium hydroxymonohydrate and ESCOR® ATX 320 terpolymer to an intensive mixer (BANBURY® type). The Li salt solubilizes in the ATX 320 terpolymer above the melting temperature of the terpolymer, and a vigorous reaction occurs with foaming as the Li cation reacts with the acid groups of the terpolymer, and volatile byproducts are evaporated. The reaction is continued until foaming ceases (i.e., about 30 to about 45 minutes at 250° F. to 350° F.) and the batch is removed from the BANBURY® mixer. Mixing continues on a hot two-roll mill (175° F. to 250° F.) to complete the neutralization reaction. For the purpose of determining the weight percent of neutralization of the acrylic acid groups in the terpolymer ionomer after reacting with the Li salt, it is assumed that one mole of Li neutralizes one mole of acrylic acid. The calculations of neutralization are based upon an acrylic acid molecular weight of 72 g/mol, giving 0.067 moles of Li per 100 grams of the terpolymer.

[0173] Although ESCOR® ATX 320 terpolymer can be 80 mol % neutralized by Li, it is to be understood that other degrees of neutralization with Li, ranging from about 3 mol % to about 90 mol %, may be employed to provide useful ionomers. Thus, for example, ATX 320 that is 20 mol % neutralized by Li, hereinafter referred to as ATX 320-Li-20 may be employed. In addition, various cation salts such as salts of Na, K, Mg, Mn, Ca and Ni may be employed in a manner similar to Li salts to provide various other ESCOR® ATX 320 type terpolymer ionomers.

[0174] Commercially available products which are the reaction products of reactive mixtures of polyamide, ionomeric copolymer, and olefin ester copolymer include CAPRON® 8351, available from Allied Signal. This reactive mixture, and the processing thereof, is believed to be described in U.S. Pat. No. 4,404,325, the teachings of which are incorporated herein by reference in their entirety. As described therein, the preferred polyamide is polyepsiloncaprolactarn or polyhexamethyleneadipamide, and most preferably polyespiloncaprolactam. The preferred olefin ester copolymer is ethylene/ethyl acrylate. The preferred ionic copolymer is a Zn neutralized copolymer of ethylene/methacrylic acid available from DuPont under the trade name SURLYN® 9721 (1801). According to claim 7 of U.S. Pat. No. 4,404,325, the polyamide is present in the reactive mixture in an amount of about 60 to about 72 wt %, the ionomeric copolymer is present in an amount of about 26 wt % to about 34 wt %, and the olefin ester copolymer is present in an amount of about 2 to about 6 wt %, based on the total weight of the reactive mixture. It is believed that CAPRON® 8351 has a nylon backbone with ionomer grafted thereto. Allied Signal indicates that CAPRON® 8351 is a graft copolymer which has the properties set forth below:

TABLE 14
Test Method
Property (ASTM) Value
Specific Gravity D-792 1.07
Yield Tensile Strength, psi (MPa) D-638 7800 (54)
Ultimate Elongation % D-638 200.00
Flexural Strength, psi (MPa) D-790 9500 (65)
Flexural Modulus, psi (MPa) D-790 230,000 (1585)
Notched Izod Impact ft-lbs/in D-256 No Break
Drop Weight Impact ft-lbs/in D-3029 150 (200)
Drop Weight Impact @ @ −4° F., D-3029 150 (200)
ft-lbs (J)
Heat Deflection Temperature D-648 60.00
@ @ 264 psi, C.
Melting Point, C. D-789 215.00

[0175] CAPRON® 8351 is the most preferred RP for use in the invention. Variations of CAPRON® 8351 also may be used. For example, variations of CAPRON® 8351 which may be used include those which employ polyepsiloncaprolactam or polyhexamethyleneadipamide with olefin ester copolymers such as ethylene/methyl acrylate, ethylene/ethyl methacrylate, and ethylene/methyl methacrylate. Ionomeric copolymers which may be used in variations of CAPRON® 8351 include ionomeric copolymers of an alpha olefin of the formula RCH═CH2 where R is H or alkyl radicals having 1 to 8 carbons, and an alpha, beta-ethylenically unsaturated carboxylic acid having from 3 to 8 carbons. The ionic copolymer has at least about 10 wt % of the COOH groups neutralized with metal cations, preferably Zn. Examples of these ionic copolymers include Zn neutralized ethylene/methacrylic acid. In variations of CAPRON® 8351, the reactive mixture neutralized to produce such variations may include about 50 wt % to about 90 wt % polyamide, about 5 wt % to about 50 wt % ionic copolymer, and about 1 wt % to about 20 wt % olefin ester copolymer, all percents based on the weight of the reactive mixture.

[0176] In another preferred embodiment, golf balls of the invention employ preferably as a mantle layer, a composition that includes RP and at least one terpolymer. Terpolymers which may be employed include olefin/alkyl (meth)acrylate/carboxylic acid terpolymers. These terpolymers typically have about 50 to about 98 wt % olefin, about 1 to about 30 wt % alkyl acrylate, and about 1 to about 20 wt % carboxylic acid. The olefin may be any of ethylene, propylene, butene-1, hexene-1 and the like, preferably ethylene. The alkyl (meth)acrylate may be any of methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, butyl vinyl ether, methyl vinyl ether, and the like, preferably methyl acrylate. The carboxylic acid may be any one of acrylic acid, methacrylic acid, maleic acid, and fumaric acid. Monoesters of diacids such as methyl hydrogen maleate, methyl hydrogen fumarate, ethyl hydrogen fumarate, and maleic anhydride which is considered to be a carboxylic acid may also be used. Preferably, the carboxylic acid is acrylic acid. Useful ethylene/methyl acrylate/acrylic acid terpolymers may comprise about 98 to about 50 wt %, preferably about 65 to about 85 wt %, and most preferably about 76 wt % ethylene; about 1 to about 30 wt % preferably about 15 to about 20 wt and most preferably about 18 wt % methyl acrylate; and about 1 to about 20 wt preferably about 4 to about 10 wt %, and most preferably about 6 wt % acrylic acid.

[0177] Olefin/alkyl(meth)acrylate/carboxylic acid terpolymers which are preferred for use in the compositions employed in the invention are ethylene/methyl acrylate/acrylic acid terpolymers such as those marketed by Exxon Chemical Co. under the name ESCOR®. Examples of these terpolymers include ESCOR® ATX 320 and ESCOR® ATX 325. The properties of ESCOR® ATX 320 and ESCOR® ATX 325 as provided by Exxon are set forth below:

TABLE 15
ESCOR ® ESCOR ®
Property/Resin ATX-320 ATX-325
Melt Index1 5.0 g/ 20.0 g/
10 min 10 min
Density1 0.950 g/cc 0.950 g/cc
Melting Point1 69 C. 67 C.
Crystallization Temperature1 51 C. 50 C.
Vicat Softening Temperature 200 g2 66 C. 60 C.
Tensile Strength @@ Yield3 12 MPa 7.8 MPa
Hardness4 34.00 30.00
Elongation @@ Break3 >800% >800%

[0178] Other olefin/alkyl(meth)acrylate/carboxylic acid terpolymers which may be employed with RP in the compositions employed in the invention include but are not limited to:

[0179] ethylene/n-butyl acrylatelacrylic acid,

[0180] ethylene/n-butyl acrylate/methacrylic acid,

[0181] ethylene/2-ethoxyethyl acrylate/acrylic acid,

[0182] ethylene/2-ethoxyethyl acrylate/methacrylic acid,

[0183] ethylene/n-pentyl acrylate/acrylic acid,

[0184] ethylene/n-pentyl acrylate/methacrylic acid,

[0185] ethylene/n-octyl acrylate/acrylic acid,

[0186] ethylene/2-ethyhexyl acrylate/acrylic acid,

[0187] ethylene/n-propyl acrylate/acrylic acid,

[0188] ethylene/n-propyl acrylate/methacrylic acid,

[0189] ethylene/n-heptyl acrylate/acrylic acid,

[0190] ethylene/2-methoxylethyl acrylate/acrylic acid,

[0191] ethylene/3-methoxypropyl acrylate/acrylic acid,

[0192] ethylene/3-ethoxypropyl acrylate/acrylic acid, and

[0193] ethylene/acrylate/acrylic acid.

[0194] Compositions which may be employed to provide golf balls according to this embodiment of the invention include about 1 to about 90 wt %, preferably about 1 to about 30 wt %, and most preferably about 15 wt % RP; and about 99 wt % to about 10 wt % terpolymer, preferably about 99 wt % to about 70 wt and most preferably about 85 wt % terpolymer.

[0195] Other terpolymer ionomers which may be used in the compositions employed in this embodiment of the invention include ethylene/alkyl ester/methacrylic acid terpolymer ionomers; such as those disclosed in U.S. Pat. No. 4,690,981, the teachings of which are incorporated by reference in its entirety herein, and which are available from DuPont Corp. under the trade name SURLYN®. Properties of various SURLYN® terpolymer ionomers which may be used in the invention are set forth in Table 16. The terpolymer ionomer may be about 1 wt % to about 99 wt %, preferably about 50 wt % to about 99 wt %, and most preferably about 85 wt %, all amounts based on the total weight of the RP-terpolymer ionomer composition. RP may be about 1 wt to about 99 wt %, preferably about 1 wt % to about 50 wt %, and most preferably about 15 wt %, all amounts based on the total weight of the composition.

TABLE 16
Resin SURLYN ®
Property ASTM 7390 7940 80201 8528 8660 8680 81201 83201 90201
Cation Li LI Na Na Na Na Na Na Zn
Melt Flow D-1238 1.80 2.60 1.00 1.30 3.90 10.00 0.90 0.90 1.10
Index
(g/10 min)
Density D-792 0.94 0.94 0.95 0.94 0.94 0.94 0.94 0.94 0.96
Notched D-256 NB1 NB1 NB1 11.40 16.00 NB2
Izod
Tensile D-1822S 140.00 220.00 630.00 550.00 795.00 345.00 235.00 213.00 610.00
Impact
(23 C)
ft-lb/in2
Flexural D-790 67.00 61.00 14.00 32.00 31.70 34.00 49.10 19.30 14.00
Mod
(23 C)
kpsi
Yield D-838 2.80 2.20 1.80 1.60 1.90 2.20 2.30
Strength
(kpsi)
Elongation D-838 290.00 285.00 530.00 450.00 419.00 470.00 680.00 770.00 510.00
(%)
Hardness, D-2240 68.00 68.00 56.00 60.00 60.00 62.00 38.00 25.00 55.00
Shore D
Vicat D-1525-70
Tempera- Rate B 62.00 63.00 61.00 73.00 78.00 71.00 51.00 48.00 57.00
ture (C.)
Resin Property ASTM 93201 9520 9650 9720 9730 9910 9950 9970
Cation Zn Zn Zn Zn Zn Zn Zn Zn
Melt Flow Index D-1238 0.60 1.10 5.00 1.00 1.60 0.70 5.50 1.40
(g/10 min)
Density D-792 0.94 0.95 0.96 0.96 0.95 0.97 0.96 0.95
Notched Izod D-256 10.10 14.50 NB1 NB1 6.80 NB1 NB1
Tensile Impact D-1822S 570.00 460.00 600.00 590.00 485.00 485.00 360.00
(23 C)
(ft-lb/in2
Flexural Mod D-790 3.70 38.00 32.00 36.00 30.00 48.00 37.00 28.00
(23 C) kpsi
Yield Strength D-838 3.50 1.80 1.80 1.70 1.60 2.00 1.80 1.60
(kpsi)
Elongation (%) D-838 500.00 410.00 410.00 440.00 460.00 290.00 490.00 480.00
Hardness, D-2240 40.00 60.00 63.00 61.00 63.00 64.00 62.00 62.00
Shore D
Vicat Temperature D-1525-70 454.00 74.00 71.00 71.00 73.00 62.00 66.00 61.00
(C.) Rate B

[0196] Other suitable nylon containing compositions include compositions of olefin/carboxylic acid copolymer ionomers made from two types of monomers and RP. Olefin/carboxylic acid copolymer ionomers which may be employed with RP include those wherein the carboxylic acid groups of the copolymer ionomer are partially (i.e., approximately 5 to 80%) neutralized by metal ions such as but not limited to Li, Na, Zn and Mg, and preferably Zn, Na. Ionic copolymers may be zinc neutralized ethylene/methacrylic acid ionomer copolymer, Na neutralized ethylene/acrylic acid copolymer ionomers, and mixtures thereof. The Zn neutralized ethylene/acrylic acid copolymer ionomer can be the reaction product of Zn neutralization of an ethylene/acrylic acid copolymer having about 15 to about 20 wt % acrylic acid and a melt index of about 37 to about 100. These copolymer ionomers usually have a relatively high molecular weight, e.g., a melt index of about 0.1 to about 1,000 g/10 min., and/or a weight average molecular weight of 5,000 up to one million. Useful copolymer ionomers include, for example, ethylene/acrylic acid copolymer ionomers; sold by Exxon Chemical Co. under the designation “IOTEK®” such as IOTEK® 7030, IOTEK® 7020, IOTEK® 7010, IOTEK® 8030, IOTEK® 8020, and IOTEK® 8000. Non-limiting examples of preferred IOTEK® copolymer ionomers for use in the invention include IOTEK® 7010, IOTEK® 7030 and IOTEK® 8000. Properties of various IOTEK® copolymer ionomers are shown in Tables 17-18.

TABLE 17
ASTM IOTEK ® IOTEK ® IOTEK ® IOTEK ® IOTEK ® IOTEK ®
Method 4000 4010 7010 7020 7030 8000
Resin Property
Cation Zn Zn Zn Zn Zn Na
Melt Flow Index D-1238 2.50 1.50 0.80 1.50 2.50 0.80
g/10 min
Density Point, C D-792 964.00 966.00 968.00 966.00 964.00 957.00
Melting Point, C D-2240 85.00 84.00 83.50 84.00 85.00 83.00
Crystallization D-638 58.00 56.00 55.00 56.00 58.00 45.00
Point, C
Vicat Softening D-638 60.00 60.00 60.00 60.00 60.00 54.00
Point, C
Flexural Mod, MPa D-790 155.00 175.00 190.00 175.00 155.00 320.00
Tensile Impact at D-1822 480.00 520.00 550.00 520.00 480.00 570.00
23 C, KJ/m2
(Type S Dumbbell,
2 mm Thick
Compression Plaques)
Plaque Properties
(2 mm thick com-
pression molding)
Tensile Strength at D-638 22.60 23.50 24.50 23.50 22.60 33.00
Break MPa
Yield Point MPa D-638 12.00 13.00 14.00 13.00 12.00 18.50
Elongation at Break % D-638 460.00 450.00 440.00 450.00 460.00 370.00
1% Secant Modulus D-638 125.00 135.00 150.00 135.00 125.00 280.00
MPa
Shore D Hardness D-2240 52.00 53.00 54.00 53.00 52.00 60.00
ASTM IOTEK ® IOTEK ® IOTEK ® IOTEK ® IOTEK ®
Method 8020 8030 7520 7510 3110
Cation Na Na Zn Zn Na
Melt Flow Index g/10 min D-1238 1.60 2.80 2.00 0.80 1.30
Density Point, C D-792 0.96 956.00 962.00 970.00 939.00
Melting Point, C D-2240 84.00 87.00 67.00 67.00 95.00
Crystallization Point, C D-638 47.00 49.00 39.00 38.00 58.00
Vicat Softening Point, C D-638 54.50 55.50 40.00 40.00 75.00
Flexural Mod, MPa D-790 340.00 355.00 30.00 35.00 260.00
Tensile Impact at 23 C, KJ/m2 D-1822 550.00 500.00 780.00 950.00 580.00
(Type S Dumbbell, 2 mm Thick
Compression Plaques)
Plaque Properties
(2 mm thick compression
molding)
Tensile Strength at Break MPa D-638 32.50 32.00 12.00 15.00 28.00
Yield Point MPa D-638 18.50 18.00 4.00 4.00 14.00
Elongation at Break % D-638 380.00 410.00 680.00 570.00 510.00
1% Secant Modulus MPa D-638 280.00 280.00 22.00 27.00 210.00
Shore D Hardness D-2240 60.00 60.00 30.00 35.00 55.00

[0197]

TABLE 18
ASTM EX EX EX EX
Method 1001 1004 1006 1007
Resin/Property
Cation Exxon Na Zn Na Zn
Melt Flow Index g/10 D-1238 1.00 2.00 1.30
min
Melting Point (C) D-3417 83.70 82.50 86.00
Crystallization Point (C) D-3417 41.30 52.50 47.50 52.30
Plaque Properties
(2 mm thick compression
molding)
Tensile Strength at D-638 34.40 20.60 33.50 24.10
Break MPa
Yield Point MPa D-638 21.30 14.00 19.30 13.80
Elongation at Break % D-638 341.00 437.00 421.00 472.00
1% Secant Modulus MPa D-638 356.00 128.00 314.00 154.00
1% Secant Modulus MPa D-790 365.00 130.00 290.00 152.00
Shore D Hardness D-2240 63.00 53.00 58.00 51.00
Vicat Softening Point D-1525 51.50 55.00 57.00 60.50

[0198] Compositions of nylon homopolymer and/or copolymer and one or more olefin/alkyl acrylate/carboxylic acid terpolymer ionomers are also suitable compositions in a golf ball according to the present invention. Terpolymer ionomers which may be used with the nylon homopolymers preferably are ethylene/methyl acrylate/acrylic acid terpolymer ionomers. Nylon homopolymers for use in any of the compositions employed in the invention include but are not limited to Nylon 6, Nylon 66, and mixtures or copolymers thereof. Other nylons such as Nylon 11, Nylon 12, Nylon 612, Nylon 66/6 and Nylon 46 also can be used as long as sufficient durability is achieved. In the case of Nylon 6, a polyamide chain of about 140 to about 222 repeating units is typically useful, but lower and higher molecular weight material may be employed. CAPRON® 8202, a Nylon 6 type polymer available from Allied Signal, is preferred. According to Allied Signal, CAPRON® 8202 has the properties set forth below.

TABLE 19
Test Method
Property (ASTM) Value
Specific Gravity D-792 1.13
Yield Tensile Strength, psi (MPa) D-638 11500 (80)
Ultimate Elongation % D-638 70.00
Flexural Strength, psi (MPa) D-790 15700 (110)
Flexural Modulus, psi (MPa) D-790 410,000 (2825)
Notched Izod Impact, ft-labs/in D-256 1.0 (55)
Heat Deflection Temperature @ D-648 65.00
264 psi, C.
Melting Point, C. D-789 215.00
Rockwell Hardness, R Scale D-785 119.00

[0199] Terpolymer ionomers which may be employed include but are not limited to those having from about 50 to about 98 wt %, preferably from about 76 to about 75 wt %, and most preferably about 76 wt % ethylene; from about 1 to about 30 wt %, preferably about 15 to about 20 wt %, and most preferably about 18 wt % methyl acrylate, and about 1 to about 20 wt %, preferably about 4 to about 10 wt %, and most preferably about 6 wt % acrylic acid, wherein the acrylic acid has been neutralized by Zn, Li or Na or combinations thereof. Preferred terpolymer ionomers include IOTEK® 7520, IOTEK® 7510, ESCOR® ATX 320-Li-80, or a mixture thereof. The nylon homopolymer may be present in the compositions in an amount of about 1 wt % to about 99 wt %, preferably about 1 wt % to 50 wt %, and most preferably about 15 wt % of the composition. The terpolymer ionomer may be about 99 wt % to about 1 wt %, preferably about 1 wt % to 50 wt %, and most preferably about 85 wt %, all amounts based on total weight of the composition.

[0200] ZYTEL® 408 is a Nylon 66 modified molding compound containing ionomer. It is believed that ZYTEL® 408 is an intimate mixture of polyamide and an ionomeric terpolymer of an alpha-olefin, an acrylate ester, and an alpha, beta-ethylenically unsaturated mono- or dicarboxylic acid with a portion of the carboxylic acid groups being neutralized with metal ions. The properties of ZYTEL® 408, as provided by DuPont, are shown below:

TABLE 20
Test Method
Property (ASTM) Value1
Specific Gravity D-792 1.09
Tensile Strength (−40° F.) D-638 15100 psi
Tensile Strength (−40° C.) D-638 104.1 MPa
Flexural Modulus (−40° F.) D-790 410,000 psi
Flexural Modulus (−40° C.) D-790 2827 MPa
Izod Impact Strength at −40° F. D-256 1.3 ft. lb./in.
Izod Impact Strength at −40° C. D-256 69 J/m
Gardner Impact at −30° F.  D-3029 >320 ft. lbs.
Heat Deflection temperature @ D-648 75 C.
1.8 · 106 Pa
Melting Point D-789 255 C.

[0201] Other suitable nylon compositions include compositions of polyamide homopolymers or copolymers, and olefin/carboxylic acid copolymer ionomers made from two types of monomers such as IOTEK®. In the case of Nylon 6, a polyamide chain of about 140-222 repeating units is typically useful, but lower and higher molecular weight material may be employed. A preferred polyamide homopolymer is CAPRON® 8202 available from Allied Signal. Useful copolymer ionomers include copolymer ionomers having about 99 wt % to 70 wt %, preferably about 90 wt % to 80 wt %, and most preferably 85 wt % ethylene; and about 1 wt % to about 30 wt %, preferably about 10 wt % to about 20 wt %, and most preferably 15 wt % acrylic acid. A preferred ethylene/acrylic acid copolymer ionomer is IOTEK® 7010 from Exxon Chemical Co. The copolymer ionomer may be present in the composition in an amount of about 99 wt % to about 1 wt %, preferably about 95 wt % to about 70 wt %, and most preferably about 80 wt % of the composition. The polyamide homopolymer may be about 1 wt % to about 99 wt %, preferably about 5 wt % to about 30 wt %, and most preferably about 20 wt %, wherein all amounts are based on the total weight of the composition.

[0202] Two or more copolymer ionomers may be preblended prior to blending with polyamide homopolymers and/or RP to provide compositions which may be used in the invention. Thus, preblends of hard and soft copolymer ionomers, as well as preblends of high carboxylic acid copolymer ionomers and low carboxylic acid copolymer ionomers may be utilized to provide compositions for use in the invention. An example of such a preblend is a mixture of IOTEK® 8000 and IOTEK® 7010.

[0203] Two or more terpolymers may be preblended prior to blending with any of RP or the polyamide homopolymers to provide compositions which may be used in the invention. Thus, preblends of hard and soft terpolymers, as well as preblends of high carboxylic acid terpolymers and low carboxylic acid terpolymers may be utilized to provide compositions for use in the invention.

[0204] C. Polyurethanes

[0205] Polyurethanes are polymers which are used to form a broad range of products. They are generally formed by mixing two primary ingredients during processing. For the most commonly used polyurethanes, the two primary ingredients are a polyisocyanate (for example, diphenyl methane diisocyanate monomer (“MDI”) and toluene diisocyanate (“TDI”) and their derivatives) and a polyol (for example, a polyester polyol or a polyether polyol).

[0206] A wide range of combinations of polyisocyanates and polyols, as well as other ingredients, are available. Furthermore, the end-use properties of polyurethanes can be controlled by the type of polyurethane utilized, i.e., whether the material is thermoset (crosslinked molecular structure) or thermoplastic (linear molecular structure).

[0207] Crosslinking occurs between the isocyanate groups (—NCO) and the polyol's hydroxyl end-groups (—OH). Additionally, the end-use characteristics of polyurethanes can also be controlled by different types of reactive chemicals and processing parameters. For example, catalysts are utilized to control polymerization rates. Depending upon the processing method, reaction rates can be very quick (as in the case for some reaction injection molding systems (“RIM”) or may be on the order of several hours or longer (as in several coating systems). Consequently, a great variety of polyurethanes are suitable for different end-users. A non-limiting example of a suitable polyurethane is ESTANE® X4517 from B.F. Goodrich.

[0208] The physical properties of thermoset polyurethanes are controlled substantially by the degree of crosslinking. Tightly crosslinked polyurethanes are fairly rigid and strong. A lower amount of crosslinking results in materials that are flexible and resilient. Thermoplastic polyurethanes have some crosslinking, but purely by physical means. The crosslinking bonds can be reversibly broken by increasing temperature, as occurs during molding or extrusion. In this regard, thermoplastic polyurethanes can be injection molded, and extruded as sheet and blow film. They can be used up to about 350° F. and are available in a wide range of hardnesses.

[0209] Polyurethane materials suitable for the present invention are formed by the reaction of a polyisocyanate, a polyol, and optionally one or more chain extending diols. The polyisocyanate is selected from the group including diphenyl methane diisocyanate (“MDI”); toluene diisocyanate (“TDI”); xylene diisocyanate (“XDI”); methylene bis-(4-cyclohexyl isocyanate) (“HMDI”); hexamthylene diisocyanate; and naphthalene-1,5,-diisocyanate (“NDI”).

[0210] One polyurethane component which can be used in the present invention incorporates TMXDI (“META”) aliphatic isocyanate (Cytec Industries, West Paterson, N.J.). Polyurethanes based on meta-tetramethylxylylene diisocyanate can provide improved gloss retention UV light stability, thermal stability, and hydrolytic stability. Additionally, TMXDI aliphatic isocyanate has demonstrated favorable toxicological properties. Furthermore, because it has a low viscosity, it is usable with a wider range of diols (to polyurethane) and diamines (to polyureas). If TMXDI is used, it typically, but not necessarily, is added as a direct replacement for some or all of the other aliphatic isocyanates in accordance with the suggestions of the supplier. Because of slow reactivity of TMXDI, it may be useful or necessary to use catalysts to have practical demolding times. Hardness, tensile strength and elongation can be adjusted by adding further materials in accordance with the supplier's instructions.

[0211] Further examples of suitable polyurethanes include polyurethane systems formed via reaction injection molding (RIM). RIM processing to form various layers of a golf ball is described in detail in pending application U.S. Ser. No. 09/411,690, incorporated herein by reference.

[0212] Non-limiting examples of suitable RIM systems for use in the present invention are BAYFLEX® elastomeric polyurethane RIM systems, BAYDUR® GS solid polyurethane RIM systems, PRISM® solid polyurethane RIM systems, all from Bayer Corporation (Pittsburgh, Pa.), SPECTRIM® reaction moldable polyurethane and polyurea systems from Dow Chemical USA (Midland, Mich.), including SPECTRIM® MM 373-A (isocyanate) and 373-B (polyol), and ELASTOLIT® SR systems from BASF® (Parsippany, N.J.). Preferred RIM systems include BAYFLEX® MP-10000 and BAYFLEX® 110-50, filled and unfilled. Further preferred examples are polyols, polyamines and isocyanates formed by processes for recycling polyurethanes and polyureas. Peroxides, such as MEK-peroxide and dicumyl peroxide can be used. Furthermore, catalysts or activators such as cobalt octoate 6% can be used.

[0213] Moreover, in alternative embodiments, the outer cover layer formulation may also comprise a soft, low modulus non-ionomeric thermoplastic elastomer including a polyester polyurethane such as B.F. Goodrich Company's ESTANE® polyester polyurethane X-4517. According to B.F. Goodrich, ESTANE® X-4517 has the following properties:

TABLE 21
Properties of ESTANE ® X-4517
Tensile  143
100%  815
200% 1024
300% 1193
Elongation  641
Youngs Modulus 1826
Hardness A/D 88/39
Dayshore Rebound  59
Solubility in Water Insoluble
Melt Processing Temperature >350° (>177° C.)
Specific Gravity (H2O = 1) 1.1-1.3

[0214] Other Components

[0215] In addition to the above noted ionomers, compatible additive materials may also be added to produce the cover compositions of the present invention. These additive materials include dyes (for example, Ultramarine Blue™ sold by Whitaker, Clark, and Daniels of South Painsfield, N.J.), and pigments, i.e., white pigments such as titanium dioxide (for example Unitane™ 0-110) zinc oxide, and zinc sulfate, as well as fluorescent pigments. As indicated in U.S. Pat. No. 4,884,814, the amount of pigment and/or dye used in conjunction with the polymeric cover composition depends on the particular base ionomer mixture utilized and the particular pigment and/or dye utilized. The concentration of the pigment in the polymeric cover composition can be from about 1% to about 10% as based on the weight of the base ionomer mixture. A more preferred range is from about 1% to about 5% as based on the weight of the base ionomer mixture. The most preferred range is from about 1% to about 3% as based on the weight of the base ionomer mixture. The most preferred pigment for use in accordance with this invention is titanium dioxide.

[0216] Moreover, since there are various hues of white, i.e., blue white, yellow white, etc., trace amounts of blue pigment may be added to the cover stock composition to impart a blue white appearance thereto. However, if different hues of the color white are desired, different pigments can be added to the cover composition at the amounts necessary to produce the color desired.

[0217] In addition, it is within the purview of this invention to add to the cover compositions of this invention compatible materials which do not affect the basic novel characteristics of the composition of this invention. Among such materials are antioxidants (i.e., SANTONOX®), antistatic agents, stabilizers and processing aids. The cover compositions of the present invention may also contain softening agents, such as plasticizers, etc., and reinforcing materials such as glass fibers and inorganic fillers, as long as the desired properties produced by the golf ball covers of the invention are not impaired.

[0218] Furthermore, optical brighteners, such as those disclosed in U.S. Pat. No. 4,679,795, herein incorporated by reference, may also be included in the cover composition of the invention. Examples of suitable optical brighteners which can be used in accordance with this invention are UVITEX® OB as sold by the Ciba-Geigy Chemical Company, Ardsley, N.Y. UVITEX® OB is thought to be 2,5-Bis(5-tert-butyl-2-benzoxazoly)thiophene. Examples of other optical brighteners suitable for use in accordance with this invention are as follows: LEUCOPURE® EGM as sold by Sandoz, East Hanover, N.J. 07936. LEUCOPURE® EGM is thought to be 7-(2n-naphthol(1,2-d)-triazol 2yl)-3phenyl-coumarin. PHORWHITE® K-20G2 is sold by Mobay Chemical Corporation, P.O. Box 385, Union Metro Park, Union, N.J. 07083, and is thought to be a pyrazoline derivative, EASTOBRITE® OB-1 as sold by Eastman Chemical Products, Inc. Kingsport, Tenn., is thought to be 4,4-Bis(-benzoxaczoly)stilbene. The above-mentioned UVITEX® and EASTOBRITE® OB-1 are preferred optical brighteners for use in accordance with this invention.

[0219] Moreover, since many optical brighteners are colored, the percentage of optical brighteners utilized must not be excessive in order to prevent the optical brightener from functioning as a pigment or dye in its own right.

[0220] Other soft, relatively low modulus non-ionomeric thermoplastic elastomers may also be utilized to produce the outer cover layer as long as the non-ionomeric thermoplastic elastomers produce the playability and durability characteristics desired without adversely effecting the enhanced spin characteristics produced by the low acid ionomer resin compositions. These include, but are not limited to thermoplastic polyurethanes such as: TEXIN® thermoplastic polyurethanes from Mobay Chemical Co. and the PELLATHANE® thermoplastic polyurethanes from Dow Chemical Co.; ionomer/rubber blends such as those in Spalding U.S. Pat. Nos. 4,986,545; 5,098,105 and 5,187,013; and, HYTREL® polyester elastomers from DuPont and PEBAX® polyesteramides from Elf Atochem S.A.

[0221] Preferably, in a golf ball, according to the invention, at least one layer of the golf ball contains at least one part by weight of a filler. Fillers preferably are used to adjust the density, flex modulus, mold release, and/or melt flow index of a layer. More preferably, at least when the filler is for adjustment of density or flex modulus of a layer, it is present in an amount of at least five parts by weight based upon 100 parts by weight of the layer composition. With some fillers, up to about 200 parts by weight probably can be used.

[0222] A density adjusting filler according to the invention preferably is a filler which has a specific gravity which is at least 0.05 and more preferably at least 0.1 higher or lower than the specific gravity of the layer composition. Particularly preferred density adjusting fillers have specific gravities which are higher than the specific gravity of the resin composition by 0.2 or more, even more preferably by 2.0 or more.

[0223] A flex modulus adjusting filler according to the invention is a filler which, when used in an amount of, e.g., 1 to 100 parts by weight based upon 100 parts by weight of resin composition, will raise or lower the flex modulus (ASTM D-790) of the resin composition by at least 1% and preferably at least 5% as compared to the flex modulus of the resin composition without the inclusion of the flex modulus adjusting filler.

[0224] A mold release adjusting filler is a filler which allows for the easier removal of a part from a mold, and eliminates or reduces the need for external release agents which otherwise could be applied to the mold. A mold release adjusting filler typically is used in an amount of up to about 2 weight percent based upon the total weight of the layer.

[0225] A melt flow index adjusting filler is a filler which increases or decreases the melt flow, or ease of processing of the composition.

[0226] The layers may contain coupling agents that increase adhesion of materials within a particular layer, e.g., to couple a filler to a resin composition, or between adjacent layers. Non-limiting examples of coupling agents include titanates, zirconates and silanes. Coupling agents typically are used in amounts of 0.1 to 2 weight percent based upon the total weight of the composition in which the coupling agent is included.

[0227] A density adjusting filler is used to control the moment of inertia, and thus the initial spin rate of the ball and spin decay. The addition in one or more layers, and particularly in the outer cover layer of a filler with a lower specific gravity than the resin composition results in a decrease in moment of inertia and a higher initial spin rate than would result if no filler were used. The addition in one or more of the cover layers, and particularly in the outer cover layer of a filler with a higher specific gravity than the resin composition, results in an increase in moment of inertia and a lower initial spin rate. High specific gravity fillers are preferred as less volume is used to achieve the desired inner cover total weight. Non-reinforcing fillers are also preferred as they have minimal effect on COR. Preferably, the filler does not chemically react with the resin composition to a substantial degree, although some reaction may occur when, for example, zinc oxide is used in a shell layer which contains some ionomer.

[0228] The density-increasing fillers for use in the invention preferably have a specific gravity in the range of 1.0 to 2.0. The density-reducing fillers for use in the invention preferably have a specific gravity of 0.06 to 1.4, and more preferably 0.06 to 0.90. The flex modulus increasing fillers have a reinforcing or stiffening effect due to their morphology, their interaction with the resin, or their inherent physical properties. The flex modulus reducing fillers have an opposite effect due to their relatively flexible properties compared to the matrix resin. The melt flow index increasing fillers have a flow enhancing effect due to their relatively high melt flow versus the matrix. The melt flow index decreasing fillers have an opposite effect due to their relatively low melt flow index versus the matrix.

[0229] Fillers which may be employed in layers other than the outer cover layer may be or are typically in a finely divided form, for example, in a size generally less than about 20 mesh, preferably less than about 100 mesh U.S. standard size, except for fibers and flock, which are generally elongated. Flock and fiber sizes should be small enough to facilitate processing. Filler particle size will depend upon desired effect, cost, ease of addition, and dusting considerations. The filler preferably is selected from the group consisting of precipitated hydrated silica, clay, talc, asbestos, glass fibers, aramid fibers, mica, calcium metasilicate, barium sulfate, zinc sulfide, lithopone, silicates, silicon carbide, diatomaceous earth, polyvinyl chloride, carbonates, metals, metal alloys, tungsten carbide, metal oxides, metal stearates, particulate carbonaceous materials, micro balloons, and combinations thereof. Non-limiting examples of suitable fillers, their densities, and their preferred uses are as follows:

TABLE 22
FILLER TABLE
Filler Type Spec. Grav. Comments
Precipitated hydrated silica 2.00 1, 2
Clay 2.62 1, 2
Talc 2.85 1, 2
Asbestos 2.50 1, 2
Glass fibers 2.55 1, 2
Aramid fibers (KEVLAR ®) 1.44 1, 2
Mica 2.80 1, 2
Calcium metasilicate 2.90 1, 2
Barium sulfate 4.60 1, 2
Zinc sulfide 4.10 1, 2
Lithopone 4.2-4.3 1, 2
Silicates 2.10 1, 2
Silicon carbide platelets 3.18 1, 2
Silicon carbide whiskers 3.20 1, 2
Tungsten carbide 15.60  1.00
Diatomaceous earth 2.30 1, 2
Polyvinyl chloride 1.41 1, 2
Carbonates
Calcium carbonate 2.71 1, 2
Magnesium carbonate 2.20 1, 2
Metals and Alloys (Powders)
Titanium 4.51 1   
Tungsten 19.35  1   
Aluminum 2.70 1   
Bismuth 9.78 1   
Nickel 8.90 1   
Molybdenum 10.20  1   
Iron 7.86 1   
Steel 7.8-7.9 1   
Lead 11.40  1, 2
Copper 8.94 1   
Brass 8.2-8.4 1   
Boron 2.34 1   
Boron carbide whiskers 2.52 1, 2
Bronze 8.70-8.74 1   
Cobalt 8.92 1   
Beryllium 1.84 1   
Zinc 7.14 1   
Tin 7.31 1   
Metal Oxides
Zinc oxide 5.57 1, 2
Iron oxide 5.10 1, 2
Aluminum oxide 4.00
Titanium oxide 3.9-4.1 1, 2
Magnesium oxide 3.3-3.5 1, 2
Zirconium oxide 5.73 1, 2
Metal Stearates
Zinc stearate 1.09 3, 4
Calcium stearate 1.03 3, 4
Barium stearate 1.23 3, 4
Lithium stearate 1.01 3, 4
Magnesium stearate 1.03 3, 4
Particulate Carbonaceous Materials
Graphite 1.5-1.8 1, 2
Carbon black 1.80 1, 2
Natural bitumen 1.2-1.4 1, 2
Cotton flock 1.3-1.4 1, 2
Cellulose flock 1.15-1.5  1, 2
Leather fiber 1.2-1.4 1, 2
Micro Balloons
Glass 0.15-1.1  1, 2
Ceramic 0.2-0.7 1, 2
Fly ash 0.6-0.8 1, 2
Coupling Agents Adhesion Promoters
Titanates 0.95-1.17
Zirconates 0.92-1.11
Silane 0.95-1.2

[0230] Method of Manufacture

[0231] The golf balls of the present invention generally can be produced by molding a mantle or other layer about a protuberant core or core component to produce an intermediate golf ball having a diameter of about 1.50 to 1.67 inches, preferably about 1.620 inches. The cover layer is subsequently molded over the mantle layer to produce a golf ball having a diameter of 1.680 inches or more.

[0232] The most preferred method of forming golf balls in accordance with the present invention is blow molding. In blow molding a protuberant core in accordance with a preferred aspect of the present invention, a continuous tube or parison of a thermoplastic polymeric material is extruded by a conventional extrusion process, preferably in a downward direction. The thermoplastic polymeric material employed can be any of the materials as described above, which include metallocenes and metallocene polyolefins, polyurethanes, silicones, polyamides (for example, nylons), polyureas, polyvinyl chlorides, acrylonitrile-butadiene-styrenes, acrylics, stryrene-acrylonitriles, styrene-maleic anhydrides, polycarbonates, polybutylene terephthalates, polyethylene terephthalates, polyphenylene ethers/polyphenylene oxides, revinforced polypropylenes, high-impact polystyrenes or virtually any irreversibly cross-linked resin system. The plastication temperature of the thermoplastic materials employed in using this method ranges generally from about 250° F. to about 600° F.

[0233] A preferred process of extrusion blow molding a core in accordance with a preferred embodiment of the present invention is shown in FIG. 17A-E. The continuous tube of the thermoplastic material 148 is introduced into a spherical mold 154 such that one end, preferably the bottom end, is fixed within the mold, with the opposite end exposed above the mold. The end that is fixed within the mold is crimped or pinched off, thereby closing that end of the tube. The other end of the tube remains outside of the mold and open.

[0234] To the open end of the tube, an inflating medium 156 is introduced by an injection component 158, for example, a needle, blow pin or pipe. The inflating medium 156 is preferably pressurized or compressed air. The inflating medium 156 is introduced into the tube using the blow pin or needle to allow inflation of the tube within the mold. The introduction of the inflating medium into the tube forces the thermoplastic polymeric material 148 that makes up the tube outward, pressing up against the interior wall 159 of the spherical mold. This process forms a seamless spherical core shell. The blow pressure of the inflating medium within the tube is about 5 psi to about 200 psi, and that pressure is applied for a period of time of about 1 second to about 15 seconds in order to expand the thermoplastic polymeric material. The pressure exerted to inflate the polymeric material will vary according to a number of factors. Such factors include the type of thermoplastic polymeric material, the desired thickness of the shell wall, the overall diameter of the finished golf ball desired and others.

[0235] Once the thermoplastic polymeric material 148 has been inflated to fit the shape of the mold, it is allowed to set and/or harden. A second medium can then be optionally used to fill the set shell core wall. For example, a thermoplastic polymeric material can be used as the second medium. Using a polymeric material as the inflating medium allows the formation of a seamless and solid spherical core. This is unlike traditional core compression molded technology. As stated above, the amount of pressure and duration of injection of the polymeric material will vary based on a number of factors. A predetermined amount of the thermoplastic polymeric material is injected into the closed preform mold cavity 154 through the blow needle or pin 158 such that the melted thermoplastic material fills the void between the preform cavity and the blow pin or needle. The amount of the polymeric material injected depends on a number of factors which includes the desired diameter of the core and the density of the material.

[0236] Alternatively, co-extrusion blow molding can be used to form a one-piece, seamless center core shell. Co-extrusion blow molding is similar to the process described above, but wherein the continuous tube or parison is extruded comprising two or more layers of either similar materials or dissimilar materials. For example, a combination of two or more of the thermoplastic polymeric materials described above in extrusion blow molding could be used in co-extrusion blow molding to impart differing mechanical properties. After the filled sphere is formed, a finishing process such as die trimming or centerless grinding is employed to remove any excess material from the point of entrance of the parison or tube.

[0237] In addition to extrusion blow molding, injection blow molding could be used in the present invention, as shown in FIGS. 19A-C. Injection blow molding involves a process that is similar to extrusion blow molding. In injection blow molding, a continuous tube of a thermoplastic polymeric material 148 is injection molded onto a generally hollow longitudinal member such as a core pin, or needle. The core pin, covered with the thermoplastic polymeric material, is then placed within the preformed mold 190, which is preferably spherical. The core pin is then inflated so as to allow inflation of the thermoplastic polymeric material within the mold. An inflating medium 156, such as pressurized or compressed air, is then introduced into the core pin 158. The inflation of the core pin forces the thermoplastic polymeric material on the blow pin outward, pressing up against the interior wall 186 of the spherical mold 190. This process forms a seamless spherical core shell.

[0238] The pressure exerted to inflate the core pin to force the thermoplastic polymeric material against the interior walls of the mold will vary according to a number of factors. These factors include the shear and temperature dependent viscosity, the temperature-dependent tensile strength on the pin, tensile elongation during inflation, crystallization kinetics on the core pin and during blowing and cooling, and other factors as described above for extrusion blow molding.

[0239] The amount of thermoplastic polymeric material that is injected into the mold can vary depending on the desired core structure. For example, if a core structure of a single thermoplastic is desired, then enough material may be injected so as to fill the mold. Alternatively, if more than one seamless core layer is desired, the first thermoplastic may be injected and allowed to set, followed by one or more other thermoplastic materials. Once the desired amount of thermoplastic polymeric material is injected, the core pin is removed. As the core pin is removed, thermoplastic material is continuously added so as to displace the volume taken by the core pin and not leave any air voids within the mold.

[0240] The aperture or hole made by the inflating pin or needle can be sealed using a variety of different methods such as the use of a thermally curable adhesive, a UV curable adhesive, a solvent or water-based paint, a hot melt adhesive or a polymeric material. This can be accomplished by using a needle to place a small amount of the thermoplastic resin within the needle pin used to fill the mold. The needle is withdrawn and the area surrounding is washed and then air blown dry. The aperture that has been filled is then cauterized along with the material surrounding the aperture by contacting the material with a heated rod, causing the thermoplastic material to soften and flow into the aperture. A secondary heat source is put into contact with the material surrounding the aperture to enhance bonding of the thermoplastic material placed within the aperture. The secondary heat source also serves the function to promote further crosslinking between the patch of thermoplastic resin and the existing thermoplastic material. Alternatively, any plugs or holes along the surface of the golf ball core can be sealed by spin bonding. Spin bonding conditions are typically around 3150 rpm and 15 seconds dwell.

[0241] After the filled sphere is formed, a finishing process such as die trimming or centerless grinding may be employed to remove any excess material from the point of entrance of the core pin.

[0242] In accordance with one aspect of the present invention method of forming protuberant cores, blow molding is the preferred method. In forming golf balls according to the present invention, a tube of thermoplastic polymeric resin 148 is formed as shown in FIG. 17A. The tube 148 is then fitted into a mold 154 and a hollow needle or pin 158 is inserted into the mold 154 and the tube 148, as depicted in FIG. 17B. As shown in FIG. 17C, a filling medium 156 is then injected into the mold, causing the sides of the tube 148 to press up against the interior protuberant shaped walls of the mold 154. In FIG. 17D, removal of the needle or pin 158 is shown, as well as setting of the thermoplastic polymeric material. The ball is then finished in accordance with conventional finishing process as described above, arid any mantle layers desired and a cover layer is added to form a finished golf ball with a protuberant core as shown in FIG. 17E. FIG. 18 represents a flow chart diagram illustrating the steps involved with extrusion blow molding of a golf ball core in accordance with the steps as described above.

[0243] FIGS. 19A-C illustrate the steps utilized in the manufacture or fabrication of an alternate method of manufacturing protuberant golf ball cores of the present invention. FIG. 19A displays the initial steps to the formation of an injection blow molded protuberant core for a golf ball. A thermoplastic polymeric material is placed on an end of a hollow longitudinal member such as a hollow needle or pin 158. The needle or pin 158 is inserted into a mold 190 having a molding chamber with protuberant interior walls. An inflating medium 156 is introduced into the hollow needle 158 and into the mass of the polymeric material to cause the material to expand or essentially inflate. This operation is continued until the polymeric material is urged against the protuberant interior walls of the molding chamber. The resulting core or layer is then allowed to set, and the needle or pin 158 is removed from the protuberant core. A filler can then be used to patch the opening made by the needle or pin as described above. The ball is then finished in accordance with conventional finishing process as described above, and any mantle layers desired and a cover layer are added to form a finished golf ball with a protuberant core as shown in FIG. 19C. FIG. 20 represents a flow chart diagram illustrating the steps involved with extrusion blow molding of a golf ball core in accordance with the steps as described above.

[0244] The invention has been described with reference to the preferred embodiments. Obviously, modifications and alterations will occur to others upon a reading and understanding of the preceding detailed description. It is intended that the invention be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.

Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US6773364Nov 13, 2002Aug 10, 2004Acushnet CompanyGolf ball having a non-uniform thickness layer
US7022034Nov 13, 2002Apr 4, 2006Acushnet CompanyGolf ball having a non-uniform thickness layer
US7048652 *Dec 22, 2004May 23, 2006Bridgestone Sports Co., Ltd.Golf ball
US7201670 *Jul 30, 2004Apr 10, 2007Mizuno CorporationGolf ball and mold for manufacturing core thereof
US8343406 *Apr 18, 2011Jan 1, 2013Acushnet CompanyProcess for manufacturing golf balls having multi-layered covers
Classifications
U.S. Classification473/374, 473/378
International ClassificationC08L69/00, A63B37/02, C08L23/08, A63B37/00, C08L75/04, C08L53/00
Cooperative ClassificationC08L75/04, A63B37/02, A63B37/0097, A63B37/0003, C08L23/08, A63B37/0024, A63B37/0076, A63B37/0064, C08L69/00, C08L23/0876, A63B37/0096, A63B37/0005, C08L53/00, A63B37/0075
European ClassificationC08L23/08, A63B37/00G12D38, A63B37/00G
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