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Publication numberUS20050049082 A1
Publication typeApplication
Application numberUS 10/950,334
Publication dateMar 3, 2005
Filing dateSep 24, 2004
Priority dateMar 18, 1998
Publication number10950334, 950334, US 2005/0049082 A1, US 2005/049082 A1, US 20050049082 A1, US 20050049082A1, US 2005049082 A1, US 2005049082A1, US-A1-20050049082, US-A1-2005049082, US2005/0049082A1, US2005/049082A1, US20050049082 A1, US20050049082A1, US2005049082 A1, US2005049082A1
InventorsMichael Tzivanis, Thomas Kennedy, David Melanson
Original AssigneeCallaway Golf Company
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Golf ball
US 20050049082 A1
Abstract
A golf ball component, such as a golf ball cover layer, formed from a reaction injection molded polyurethane, polyurea or polyurethane/polyurea is disclosed. The cover layer may be relatively thin (for example, 0.075 or less, preferably 0.050 inches or less, more preferably less than 0.040 inches, even more preferably less than 0.030 inches). The golf ball component is produced from a fast reacting aromatic polyurethane composition that is PTMEG based.
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Claims(27)
1. A golf ball comprising:
a core; and
a cover disposed about said core;
wherein said cover comprises a fast reacting PTMEG-based polyurethane and/or polyurea material, wherein said fast reacting PTMEG-based polyurethane and/or polyurea material has a reaction time of less than two minutes at processing conditions.
2. The golf ball of claim 1, wherein said PTMEG-based polyurethane and/or polyurea material comprises the reaction product of an aromatic diisocyanate prepolymer and a PTMEG-based polyol.
3. The golf ball of claim 2, wherein said aromatic diisocyanate prepolymer is a PTMEG-based aromatic diisocyanate prepolymer.
4. The golf ball of claim 2, wherein the polyol further comprises a fast reacting diamine curative or chain extender.
5. The golf ball of claim 4, wherein the diamine curative or chain extender has a Gardner color of less than 10.
6. The golf ball of claim 2, wherein the polyol further comprises a surfactant.
7. The golf ball of claim 2, wherein the polyol further comprises at least one catalyst.
8. The golf ball of claim 1, wherein said cover thickness is less than 0.075 inches.
9. The golf ball of claim 8, wherein said cover thickness is less than 0.025 inches.
10. The golf ball of claim 2, further comprising a mantle disposed about said core.
11. A golf ball comprising:
a core; and
a cover disposed about said core;
wherein said cover comprises the reaction product of an aromatic diisocyanate prepolymer and a PTMEG-based polyol and at least one of a fast reacting diamine curative, a fast reacting chain extender and a catalyst, wherein the reaction product has a reaction time of less than two minutes at processing conditions.
12. The golf ball of claim 11, wherein said aromatic diisocyanate prepolymer is a PTMEG-based aromatic diisocyanate prepolymer.
13. The golf ball of claim 11, wherein the polyol further comprises a fast reacting diamine curative or a fast reacting chain extender.
14. The golf ball of claim 11, wherein the polyol further comprises a surfactant.
15. The golf ball of claim 11, wherein the polyol further comprises at least one catalyst.
16. The golf ball of claim 15, wherein the at least one catalyst is a tin, zinc or zirconium catalyst.
17. The golf ball of claim 11, wherein the diisocyanate prepolymer comprises 4,4′-diphenyl methane diisocyanate.
18. The golf ball of claim 11, further comprising a mantle disposed about the core.
19. The golf ball of claim 11, wherein said cover thickness is less than 0.075 inches.
20. The golf ball of claim 19, wherein said cover thickness is less than 0.025 inches.
21. A golf ball comprising:
a core; and
a cover disposed about said core;
wherein said cover comprises the reaction product of an aromatic diisocyanate prepolymer and a PTMEG-based polyol, wherein said diisocyanate prepolymer comprises 4,4′-diphenyl methane diisocyanate and said polyol comprises a fast reacting diamine curative or a fast reacting chain extender and at least one catalyst.
22. The golf ball of claim 21, wherein said aromatic diisocyanate prepolymer is a PTMEG-based aromatic diisocyanate prepolymer.
23. The golf ball of claim 21, wherein said cover thickness is less than 0.075 inches.
24. The golf ball of claim 23, wherein said cover thickness is less than 0.025 inches.
25. The golf ball of claim 21, further comprising a mantle disposed about said core.
26. The golf ball of claim 21, wherein the diamine curative is diethyl-2,4-toluene diamine.
27. The golf ball of claim 21, wherein the reaction product has a reaction time of less than two minutes at processing conditions.
Description
    CROSS REFERENCE TO RELATED APPLICATION
  • [0001]
    This application is a continuation-in-part of U.S. application Ser. No. 09/040,798 filed Mar. 18, 1998. This application is also a continuation-in-part of U.S. application Ser. No. 09/877,600 filed Jun. 8, 2001, which is a continuation-in-part of U.S. application Ser. No. 09/411,690, filed Oct. 1, 1999, now U.S. Pat. No. 6,290,614, which is a continuation-in-part of U.S. application Ser. No. 09/040,798 filed Mar. 18, 1998. This application also claims priority from Provisional Application Ser. No. 60/505,694 filed Sept. 24, 2003.
  • FIELD OF THE INVENTION
  • [0002]
    The present invention relates to golf balls, preferably golf balls with a fast reacting polyurethane, polyurea or polyurethane/polyurea component, such as a cover layer, having improved durability for repetitive play and improved, faster processing.
  • BACKGROUND OF THE INVENTION
  • [0003]
    Traditional golf ball covers have been comprised of balata or blends of balata with elastomeric or plastic materials. The traditional balata covers are relatively soft and flexible. Upon impact, the soft balata covers compress against the surface of the club producing high spin. Consequently, the soft and flexible balata covers provide an experienced golfer with the ability to apply a spin to control the ball in flight in order to produce a draw or a fade, or a backspin which causes the ball to “bite” or stop abruptly on contact with the green. Moreover, the soft balata covers produce a soft “feel” to the low handicap player. Such playability properties (workability, feel, and the like) are particularly important in short iron play with low swing speeds and are exploited significantly by relatively skilled players.
  • [0004]
    Despite all the benefits of balata, balata covered golf balls are easily cut and/or damaged if mis-hit. Golf balls produced with balata or balata-containing cover compositions therefore have a relatively short life span.
  • [0005]
    As a result of this negative property, balata and its synthetic substitutes, trans-polybutadiene and transpolyisoprene, have been essentially replaced as the cover materials of choice by other cover materials such as ionomeric resins and polyurethanes.
  • [0006]
    Ionomeric resins are polymers containing interchain ionic bonding. As a result of their toughness, durability and flight characteristics, various ionomeric resins sold by E.l. DuPont de Nemours & Company under the trademark Surlyn® and by the Exxon Corporation (see U.S. Pat. No. 4,911,451) under the trademarks Escor® and lotek®, have become widely utilized for the construction of golf ball covers over the traditional “balata” (transpolyisoprene, natural or synthetic) rubbers. As stated, the softer balata covers, although exhibiting enhanced playability properties, lack the durability (cut and abrasion resistance, fatigue endurance, and the like) properties required for repetitive play.
  • [0007]
    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. Metal ions, such as sodium or zinc, are used to neutralize some portion of the acidic groups in the copolymer resulting in a thermoplastic elastomer exhibiting enhanced properties, such as durability, for golf ball cover construction over balata. A softening comonomer, such as an acrylate, may also be added for a softer material. However, some of the advantages gained in increased durability have been offset to some degree by the decreases produced in playability. This is because although the ionomeric resins are very durable, they tend to be very hard when utilized for golf ball cover construction, and thus lack the degree of softness required to impart the spin necessary to control the ball in flight. Since the ionomeric resins are harder than balata, the ionomeric resin covers do not compress as much against the face of the club upon impact, thereby producing less spin. In addition, the harder and more durable ionomeric resins lack the “feel” characteristic associated with the softer balata related covers.
  • [0008]
    As a result, while there are many different commercial grades of ionomers available both from DuPont and Exxon, with a wide range of properties which vary according to the type and amount of metal cations, molecular weight, composition of the base resin (for example, relative content of ethylene and methacrylic and/or acrylic acid groups) and additive ingredients such as reinforcement agents, etc., a great deal of research continues in order to develop a golf ball cover composition exhibiting not only the improved impact resistance and carrying distance properties produced by the “hard” ionomeric resins, but also the playability (for example, “spin”, “feel”, and the like) characteristics previously associated with the “soft” balata covers, properties which are still desired by the more skilled golfer.
  • [0009]
    Furthermore, a number of different golf ball constructions, such as one-piece, two-piece (a solid resilient center or core with a molded cover), three-piece (a liquid or solid center, elastomeric winding about the center, and a molded cover), and multi-piece golf balls, have been developed to produce golf balls exhibiting enhanced playability and durability. The different types of materials utilized to formulate the cores, mantles, windings, covers, and other layers of these balls dramatically alters the balls' overall characteristics. In addition, multi-layered covers containing one or more ionomer resins or other materials have also been formulated in an attempt to produce a golf ball having the overall distance, playability and durability characteristics desired.
  • [0010]
    For example, in various attempts to produce a durable, high spin golf ball, the golfing industry has blended the hard ionomer resins with a number of softer ionomeric resins and applied these blends to two-piece and three-piece golf balls. U.S. Pat. Nos. 4,884,814 and 5,120,791 are directed to cover compositions containing blends of hard and soft ionomeric resins. However, it has been found that golf ball covers formed from hard-soft ionomer blends tend to become scuffed more readily than covers made of hard ionomer alone. Consequently, it would be useful to develop a golf ball having a combination of softness and durability which is better than the softness-durability combination of a golf ball cover made from a hard-soft ionomer blend.
  • [0011]
    Additionally, thermoset and thermoplastic polyurethanes have recently become popular materials of choice for golf ball cover construction. However, these polyurethanes are difficult and time consuming to process. Moreover, the molding of relatively thin wall cover layer(s) (for example, cover layers 0.075 inches or less in cross-sectional thickness) is difficult to accomplish. This limits the desired performance achieved by thin wall cover molding, such as improved distance. Furthermore, golf balls produced utilizing these materials tend to be soft and readily susceptible to scuffing and cutting.
  • [0012]
    As a result, it would be desirable to produce a polyurethane covered golf ball having a thin wall cover construction which exhibits enhanced durability, namely improved cut and scuff (groove shear) resistance, while maintaining and/or improving such characteristics as playability and distance, as well as improving processing time.
  • SUMMARY OF THE INVENTION
  • [0013]
    An object of the invention is to provide a golf ball with a soft, fast reacting polyurethane, polyurea or polyurethane/polyurea golf ball component having improved durability for repetitive play. Another object of the invention is to provide a method of making such a golf ball.
  • [0014]
    A further object of the invention is to provide a golf ball with a soft, fast reacting polyurethane, polyurea or polyurethane/polyurea outer cover component having enhanced durability while maintaining or improving the playability properties of the ball, as well as a method of making the same.
  • [0015]
    An additional object of the invention is to provide a golf ball with a thin, soft, fast reacting polyurethane, polyurea or polyurethane/polyurea outer cover layer having improved playability, distance and cut resistance. Also included is an improved, faster process for producing such a golf ball.
  • [0016]
    A still further object is to produce a fast reacting polytetramethylene ether glycol (PTMEG) based polyurethane, polyurea or polyurethane/polyurea golf ball component, such as the outer cover layer of a golf ball. Preferably, the cover is of thin wall (for example, 0.075 inches or less, preferably 0.040 inches or less, more preferably 0.030 inches or less and most preferably 0.025 inches or less) construction. A process for producing such a polyurethane cover is also included in the present invention.
  • [0017]
    Another object of the invention is to produce a golf ball having a core with a relatively thin cover layer molded thereon. The cover layer is produced from a PTMEG based polyurethane, polyurea or polyurethane/polyurea material. The polyurethane cover composition is a reaction product of an aromatic diisocyanate prepolymer and a polyol system containing a PTMEG-based polyol, and preferably, in combination with a diamine curative or chain extender, preferably a fast reacting diamine curative or fast reacting chain extender. The resulting product exhibits enhanced playability and durability characteristics. In one embodiment, the aromatic diisocyanate prepolymer is preferably a PTMEG-based diisocyanate prepolymer. A blend of polyols and/or diisocyanates may also be used.
  • [0018]
    Other objects will be in part obvious and in part pointed out in more detail hereafter.
  • [0019]
    In this regard, the invention is directed, in part, to a golf ball component produced from a fast reacting polyurethane, polyurea or polyurethane/polyurea material that is a reaction product of an aromatic diisocyanate prepolymer and a polyol system containing a PTMEG-based polyol, and preferably, in combination with a diamine curative or chain extender, preferably a fast reacting diamine curative or fast reacting chain extender. In one embodiment, the aromatic diisocyanate prepolymer is preferably a PTMEG-based diisocyanate prepolymer. The polyol may optionally comprise a surfactant to promote mixing of the polyol and diisocyanate. Preferably, the component is the outer cover layer of a golf ball, such as a two-piece, three-piece or multi-piece golf ball. A blend of polyols and/or diisocyanates may also be used.
  • [0020]
    In another aspect, the present invention is directed to the process of producing a fast reacting polyurethane, polyurea or polyurethane/polyurea golf ball component, the processes comprising the steps of obtaining or producing a fast reacting PTMEG-based polyurethane, polyurea or polyurethane/polyurea material. The present invention is also directed to the golf ball component produced using such a process.
  • [0021]
    The invention accordingly comprises the several steps and the relation of one or more of such steps with respect to each of the others and the articles possessing the features, properties, and the relation of elements exemplified in the following detailed disclosure.
  • BRIEF DESCRIPTION OF THE DRAWINGS
  • [0022]
    The following is a brief description of the drawings, which are presented for the purposes of illustrating the invention and not for the purposes of limiting the same.
  • [0023]
    FIG. 1 is a cross-sectional view of a golf ball 8 embodying the invention illustrating a core 10 and a cover 12 consisting of an inner layer 14 and an outer layer 16;
  • [0024]
    FIG. 2 is a diametrical cross-sectional view of a golf ball 8 of the invention having a core 10 and a cover 12 made of an inner layer 14 and an outer layer 16; and
  • [0025]
    FIG. 3 is a cross-sectional view of a golf ball 8 embodying the invention illustrating a dual core having an inner core 20 and a core layer 22, and a cover 12 consisting of an inner layer 14 and an outer layer 16.
  • DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
  • [0026]
    The present invention is directed to a molded golf ball component, such as a golf ball cover layer that is comprised of a soft, fast reacting polyurethane, polyurea or polyurethane/polyurea material. Preferably, the golf ball component comprises a thin (for example, 0.075 inches or less, preferably 0.050 inches or less, more preferably 0.040 inches or less, even more preferably 0.030 inches or less, and most preferably 0.025 inches or less) outer cover layer.
  • [0027]
    Along these lines, the present invention concerns the production of a soft, fast reacting polyurethane, polyurea or polyurethane/polyurea golf ball component by reacting an aromatic diisocyanate prepolymer and a polyol system containing a PTMEG-based polyol. In one embodiment, the aromatic diisocyanate prepolymer is preferably a PTMEG-based diisocyanate prepolymer. Preferably a diamine curative or chain extender, and more preferably a fast reacting diamine curative or fast reacting chain extender, is included in the polyol. The polyol may optionally comprise a surfactant, such as an anionic, cationic or non-ionic surfactant, to promote mixing of the polyol and diisocyanate, and one or more catalysts. A blend of polyols and/or diisocyanates may also be used.
  • [0028]
    In a particularly preferred aspect of the present invention, the cover layer is thin (for example, 0.075 inches or less, preferably 0.050 inches or less, more preferably 0.040 inches or less, and most preferably 0.025 inches or less) and is formed from a reaction product of an aromatic diisocyanate prepolymer and a polyol system containing a PTMEG-based polyol. In one embodiment, the aromatic diisocyanate prepolymer is preferably a PTMEG-based diisocyanate prepolymer. Preferably, an amine-based curative or chain extender, and more preferably a fast reacting diamine curative or fast reacting chain extender, is included in the polyol. A blend of polyols and/or diisocyanates may also be used.
  • [0029]
    In another aspect, the present invention provides a golf ball comprising a core, a hard inner cover layer formed over the core, and a softer outer cover layer formed over the inner cover layer. The inner cover layer preferably has a Shore D hardness of at least 60 (or at least about 80 Shore C) as measured on the curved surface thereof and is formed of a composition including at least one material selected from the group of consisting of ionomers, polyamides, polyurethanes, polyureas, polyester elastomers, polyester amides, metallocene catalyzed polyolefins, and blends thereof. The outer cover layer preferably has a Shore D hardness of less than 60, more preferably a Shore D hardness of 55 or less, even more preferably 50 or less, and most preferably 45 or less as measured on the curved surface thereof, the golf ball cover having improved scuff and cut resistance. The outer cover layer is formed from a composition comprising at least one soft, fast reacting polyurethane, polyurea or polyurethane/polyurea material based on PTMEG. The golf ball cover has improved scuff and cut resistance as well as a very fast cure rate. The fast cure rate allows for rapid demolding of the golf ball and improves the process efficiency. The cover may optionally comprise additional layers. In such a golf ball, the present invention is directed, in part, to the process of producing the soft, outer cover layers.
  • [0030]
    The method of forming the soft outer cover layer of the golf balls of the invention is preferably a reaction injection molding (RIM) process because the method can be performed at relatively low temperatures and pressures. The preferred temperature range for the method is from about 90 to about 180° F., and the preferred pressures for the reaction injection molding process are 200 psi or less and more preferably 100 psi or less.
  • [0031]
    Reaction injection molding covers for golf balls offers numerous advantages over conventional slow-reactive processes for producing golf ball covers. The RIM process produces molded covers in a mold release or demold time of 10 minutes or less, preferably 2 minutes or less, and most preferably in 1 minute or less. The RIM process also results in the formation of a reaction product, formed by mixing two or more reactants together, that exhibits a reaction time of about 2 minutes or less, preferably 1 minute or less, and most preferably about 30 seconds or less. An excellent finish can also be produced on the ball.
  • [0032]
    The term “demold time” generally refers to the mold release time, which is the time span from the mixing of the components until the earliest possible time at which the part may be removed from the mold. At that time of removal, the part is said to exhibit sufficient “green strength.” The term “reaction time” generally refers to the setting time or curing time, which is the time span from the beginning of mixing until the time at which the product no longer flows. Further description of the terms setting time and mold release time are provided in the “Polyurethane Handbook,” edited by Gunter Oertel, Second Edition, ISBN 1-56990-157-0, herein incorporated by reference.
  • [0033]
    The RIM process is particularly effective when recycled polyurethane or other polymer resin, or materials derived by recycling polyurethane or other polymer resin, are incorporated into the product. The process may include the step of recycling at least a portion of the reaction product, preferably by glycolysis. From about 5% to about 100% of the polyurethane/polyurea formed from the reactants used to form particular components can be obtained from recycled polyurethane/polyurea.
  • [0034]
    Referring to the FIGS. 1 to 3, the present invention relates to improved multi-layer golf balls, particularly a golf ball 8 comprising a multi-layered cover 12 over a solid core 10, and method for making same. The golf balls of the invention can be of a standard or enlarged size, and the outer cover layer has improved scuff resistance. The core may have multiple layers, such as a dual core as shown in FIG. 3 having a spherical center or inner core 20 and a core layer 22 surrounding the inner core. Additional core layers may also be present. The cover layer is preferably a multi-layer cover comprising at least an inner cover layer and an outer cover, although any number of cover layers, such as 2, 3, 4, 5 or more is possible.
  • [0035]
    The core 10, or the dual core 20, 22, of the golf ball can be formed of a solid, a liquid, or any other substance that will result in an inner ball (core and inner cover layer), having the desired coefficient of restitution (C.O.R.), compression and hardness. The multi-layered cover 12 comprises two layers: a first or inner layer or ply 14 and a second or outer layer or ply 16. The inner layer 14 can be ionomer, ionomer blends, non-ionomer, non-ionomer blends, or blends of ionomer and non-ionomer. The outer layer 16 is preferably softer than the inner layer and is preferably a material comprising polyurethane, polyurea and/or polyurethane/polyurea blends.
  • [0036]
    In a further embodiment, the inner layer 14 is comprised of a hard, high acid (i.e. greater than 16 weight percent acid) ionomer resin or high acid ionomer blend. Preferably, the inner layer is comprised of a blend of two or more high acid (i.e. at least 16 weight percent acid) ionomer resins neutralized to various extents by different metal cations. The inner cover layer may or may not include a metal stearate (e.g., zinc stearate) or other metal fatty acid salt. The purpose of the metal stearate or other metal fatty acid salt is to lower the cost of production without affecting the overall performance of the finished golf ball. In an additional embodiment, the inner layer 14 is comprised of a hard, low acid (i.e. 16 weight percent acid or less) ionomer blend. Preferably, the inner layer is comprised of a blend of two or more low acid (i.e. 16 weight percent acid or less) ionomer resins neutralized to various extents by different metal cations. The inner cover layer may or may not include a metal stearate (e.g., zinc stearate) or other metal fatty acid salt.
  • [0037]
    It has been found that a hard inner layer provides for a substantial increase in resilience (such as enhanced distance) over known multi-layer covered balls. The softer outer layer provides for desirable “feel” and high spin rate while maintaining respectable resiliency. The soft outer layer allows the cover to deform more during impact and increases the area of contact between the clubface and the cover, thereby imparting more spin on the ball. As a result, the soft cover provides the ball with a balata-like feel and playability characteristics with improved distance and durability. Consequently, the overall combination of the inner and outer cover layers results in a golf ball having enhanced resilience (improved travel distance) and durability (for example, scuff and cut resistance, and the like) characteristics while maintaining and in many instances, improving, the playability properties of the ball.
  • [0038]
    The combination of a hard inner cover layer or layers with a soft, relatively low modulus polyurethane, polyurea or polyurethane/polyurea outer cover layer provides for excellent overall coefficient of restitution (for example, excellent resilience) because of the improved resiliency produced by the inner cover layer. While some improvement in resiliency is also produced by the outer cover layer, the outer cover layer generally provides for a more desirable feel and high spin, particularly at lower swing speeds with highly lofted clubs such as half wedge shots.
  • [0039]
    A wide array of materials may be used for the cores and mantle layer(s) of the present invention golf balls. For instance, the core and mantle or interior layer materials disclosed in U.S. Pat. Nos. 5,833,553; 5,830,087; 5,820,489; 5,820,488; 6,277,920; and 6,394,915; all of which are hereby incorporated by reference, may be employed.
  • [0040]
    A variety of conventional materials may be used for one or more cover layers. The cover layer(s) may employ materials disclosed in U.S. Pat. Nos. 6,309,314; 6,277,921; 6,220,972; 6,150,470; 6,126,559; 6,117,025; 5,902,855; 5,895,105; 5,688,869; 5,591,803; and 5,542,677; hereby incorporated by reference. The particular parameters of the various components of the golf balls, as well as the methods for making the same are more specifically set forth below.
  • [heading-0041]
    Inner Cover Laver(s)
  • [0042]
    Preferably, the inner cover layer is harder than the outer cover layer and generally has a thickness in the range of 0.010 to 0.150 inches, preferably 0.010-0.100 inches, more preferably 0.020 to 0.060 inches for a 1.68 inch ball and 0.030 to 0.100 inches for a 1.72 inch (or more) ball. The core and inner cover layer together form an inner ball having a coefficient of restitution of 0.780 or more and more preferably 0.790 or more, and a diameter in the range of 1.48 to 1.67 inches for a 1.68 inch ball and 1.50 to 1.71 inches for a 1.72 inch (or more) ball. The inner cover layer has a Shore D hardness of 60 or more (or at least about 80 Shore C). It is particularly advantageous if the golf balls of the invention have an inner layer with a Shore D hardness of 65 or more (or at least about 100 Shore C). If the inner layer is too thin, it is very difficult to accurately measure the Shore D, and sometimes the Shore C, of the inner layer as the layer may puncture. Additionally, if the core is harder, this will sometimes influence the reading. If the Shore C or Shore D is measured on a plaque of material, different values will result. The above-described characteristics of the inner cover layer provide an inner ball having a PGA compression of 100 or less. It is found that when the inner ball has a PGA compression of 90 or less, excellent playability results.
  • [0043]
    The inner layer compositions of the embodiments described herein may include the high acid ionomers such as those developed by E.l. DuPont de Nemours & Company under the trademark Surlyn® and by Exxon Corporation under the trademarks Escor® or lotek®, or blends thereof.
  • [0044]
    The high acid ionomers which may be suitable for use in formulating the inner layer compositions of various embodiments of the invention are ionic copolymers which are the metal, (such as sodium, zinc, magnesium, and the like), 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 (for example, iso- or n-butylacrylate, and the like) can also be included to produce a softer terpolymer. The carboxylic acid groups of the copolymer are partially neutralized (for example, approximately 10 to 100%, preferably 30 to 70%) by the metal ions. Each of the high acid ionomer resins which may be included in the inner layer 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.
  • [0045]
    The high acid ionomeric resins available from Exxon under the designation Escor® or lotek®, are somewhat similar to the high acid ionomeric resins available under the Surlyn® trademark. However, since the Escor®/lotek® ionomeric resins are sodium or zinc salts of poly(ethylene-acrylic acid) and the Surlyn® resins are zinc, sodium, and magnesium salts of poly(ethylene-methacrylic acid), distinct differences in properties exist. High acid ionomers are well known in the golf ball art.
  • [0046]
    When utilized in the construction of the inner layer of a multi-layered golf ball, it has been found that acrylic acid based high acid ionomers extend the range of hardness beyond that previously obtainable while maintaining the beneficial properties (for example, durability, click, feel, and the like) of 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. By using these high acid ionomer resins, harder, stiffer inner cover layers having higher C.O.R.s, and thus longer distance, can be obtained.
  • [0047]
    More preferably, it has been found that when two or more high acid ionomers, particularly blends of sodium and zinc high acid ionomers, are processed to produce the covers of multi-layered golf balls, (for example, the inner cover layer or layers herein) the resulting golf balls will travel further than previously known multi-layered golf balls produced with low acid ionomer resin covers due to the balls' enhanced coefficient of restitution values.
  • [0048]
    Alternatively, if the inner cover layer comprises a low acid, the low acid ionomers which may be suitable for use in formulating the inner layer compositions of the subject invention are ionic copolymers which are the metal, (sodium, zinc, magnesium, and the like), 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 (for example, iso- or n-butylacrylate, and the like) can also be included to produce a softer terpolymer. The carboxylic acid groups of the copolymer are partially neutralized (for example, approximately 10 to 100%, preferably 30 to 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.
  • [0049]
    The inner layer compositions include the low acid ionomers such as those developed and sold by E.l. DuPont de Nemours & Company under the trademark Surlyn® and by Exxon Corporation under the trademarks Escor® or lotek®, or blends thereof.
  • [0050]
    When utilized in the construction of the inner 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 ionomers, are processed to produce the covers of multi-layered golf balls, (for example, the inner cover layer herein) 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.
  • [0051]
    In one embodiment of the inner cover layer, a blend of high and low acid ionomer resins is used. These can be the ionomer resins described above, combined in a weight ratio which preferably is within the range of 10 to 90 to 90 to 10 high and low acid ionomer resins.
  • [0052]
    Another embodiment of the inner cover layer is primarily or fully non-ionomeric thermoplastic material. Suitable non-ionomeric materials include metallocene catalyzed polyolefins or polyamides, polyamide/ionomer blends, polyphenylene ether/ionomer blends, etc., which have a Shore D hardness of at least 60 (or at least about 80 Shore C) and a flex modulus of greater than about 15,000, more preferably about 30,000 psi, or other hardness and flex modulus values which are comparable to the properties of the ionomers described above. Other suitable materials include but are not limited to thermoplastic or thermosetting polyurethanes, thermoplastic block polyesters, for example, a polyester elastomer such as that marketed by DuPont under the trademark Hytrel®, or thermoplastic block polyamides, for example, a polyether amide such as that marketed by Elf Atochem S.A. under the trademark Pebax®, a blend of two or more non-ionomeric thermoplastic elastomers, or a blend of one or more ionomers and one or more non-ionomeric thermoplastic elastomers. These materials can be blended with the ionomers described above in order to reduce cost relative to the use of higher quantities of ionomer.
  • [0053]
    Another embodiment of the inner cover layer is a cover layer produced using the PTMEG based polyurethane as described below for the outer cover layer. Any other thermoplastic or thermosetting polyurethane material known in the art may also be used for the inner cover layer.
  • [0054]
    A golf ball inner cover layer according to the present invention formed from a polyurethane material typically contains from about 0 to about 60 weight percent of filler material, more preferably from about 1 to about 30 weight percent, and most preferably from about 1 to about 20 weight percent.
  • [heading-0055]
    Outer or Single Cover Laver
  • [0056]
    While the core with the hard inner cover layer formed thereon provides the multi-layer golf ball with power and distance, the outer cover layer 16 is preferably comparatively softer than the inner cover layer. (In an alternative embodiment, if no inner cover layer is desired, a single, soft outer cover layer as described below may be utilized.) The softness provides for the feel and playability characteristics typically associated with balata or balata-blend balls. The outer cover layer or ply is comprised of a relatively soft, low modulus (about 1,000 psi to about 50,000 psi, preferably about 5,000 psi to about 20,000) polyurethane, polyurea or polyurethane/polyurea, or a blend of two or more polyurethanes. The outer layer is 0.005 to about 0.150 inches in thickness, preferably 0.010 to 0.050 inches in thickness, more preferably 0.010 to 0.040 inches in thickness, and even more desirably 0.015 to 0.035 inches in thickness, but thick enough to achieve desired playability characteristics while minimizing expense. Thickness is defined as the average thickness of the non-dimpled areas of the outer cover layer. The outer cover layer 16 preferably has a Shore D hardness of less than 60 (or less than about 90 Shore C), and more preferably 55 or less (or about 85 to 88 Shore C or less). If the outer layer is too thin, it is very difficult to accurately measure the Shore D, and sometimes the Shore C, of the outer layer as the layer may puncture. Additionally, if the inner layer and/or core is harder than the outer layer, this will sometimes influence the reading. If the Shore C or Shore D is measured on a plaque of material, different values may result.
  • [0057]
    The outer cover layer of the invention is formed over a core (or core and mantle or one or more inner cover layers) to result in a golf ball having a coefficient of restitution of at least 0.770, more preferably at least 0.780, and most preferably at least 0.790. The coefficient of restitution of the ball will depend upon the properties of both the core and the cover. The PGA compression of the golf ball is preferably 110 or less, more preferably 100 or less, and even more preferably 90 or less.
  • [0058]
    In a preferred embodiment, the outer cover layer comprises a soft, fast reacting polyurethane, a polyurea or a blend of polyurethanes/polyureas based on polytetramethylene ether glycol (PTMEG). The outer cover layer is preferably formed by RIM. Polyurethanes/ polyureas are polymers that 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, diphenylmethane diisocyanate monomer (MDI) and toluene diisocyanate (TDI) and their derivatives) and a polyol (for example, a polyester polyol or a polyether polyol). Various chain extenders and/or curatives that are well known in the art are also commonly used. A wide range of combinations of polyisocyanates and polyols, and blends 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.
  • [0059]
    Cross-linking of the polyurethane material occurs between the isocyanate groups (—NCO) and the polyol's hydroxyl end-groups (—OH), and/or with already formed urethane groups. 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 of 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-uses.
  • [0060]
    Polyurethanes are typically classified as thermosetting or thermoplastic. Polyurethane becomes irreversibly “set” when polyurethane prepolymer is cross-linked with a polyfunctional curing agent, such as a polyamine or a polyol. The prepolymer typically is made from polyether or polyester. Diisocyanate polyethers are typically preferred because of their hydrolytic properties.
  • [0061]
    The physical properties of thermoset polyurethanes are controlled substantially by the degree of cross-linking. Tightly cross-linked polyurethanes are fairly rigid and strong. A lower amount of cross-linking results in materials that are flexible and resilient. Thermoplastic polyurethanes have some cross-linking, but primarily by physical means. Increasing temperature, as occurs during molding or extrusion can reversibly break the cross-link bonds.
  • [0062]
    Polyurethane/polyurea materials suitable for the present invention are formed by the reaction of a polyisocyanate, a polyol, and optionally one or more curatives or chain extenders, preferably fast reacting curatives or chain extenders. The polyol may be a blend of polyols, such as more than one PTMEG-based polyol, or a PTMEG-based polyol and a PPG-based polyol, and the like. A preferred polyol component is a PTMEG-based polyol.
  • [0063]
    Chain extenders lengthen the main chain of polyurethane/polyurea causing end-to-end attachments. Examples of chain extenders for use in forming polyurethane/polyurea include glycol chain extenders and amine chain extenders, preferably fast reacting chain extenders. Suitable glycol chain extenders include, but are not limited to, ethylene glycol; propylene glycol; butane glycol; pentane glycol; hexane glycol; benzene glycol; xylene glycol; 1,4-butane diol; 1,3-butane diol; 2,3-dimethyl-2,3-butane diol; and dipropylene glycol. Suitable amine chain extenders include, but are not limited to, tetramethyl-ethylenediamine; dimethylbenzylamine; diethylbenzylamine; pentamethyidiethylenetriamine; dimethyl cyclohexylamine; tetramethyl-1,3-butanediamine; 1,2-dimethylimidazole; 2-methylimidazole; pentamethyldipropylenetriamine; and bis-(dimethylaminoethylether). A preferred chain extender for use in the present invention is a fast reacting diamine chain extender such as Ethacure 100LC available from Albermarle. The Ethacure 100LC (low color) is especially desirable due to its low color upon prolonged exposure to air, as in a production environment. Compared to Ethacure 100 that is not low color, the color and color stability is much better when exposed to the same conditions. The low color version is particularly preferred for golf balls that will have a white cover.
  • [0064]
    Any suitable aromatic polyisocyanate or polyisocyanate prepolymer, or blend of polyisocyanates and/or polyisocyanate prepolymers, may be used to form a polyurethane cover or golf ball component according to the present invention. The polyisocyanate is preferably selected from the group of aromatic diisocyanates including, but not limited, to 4,4′-diphenylmethane diisocyanate (MDI); 2,4-toluene diisocyanate (TDI); 1,4-diisocyanate benzene (PPDI); and naphthalene-1,5,-diisocyanate (NDI). Aromatic diisocyanates not only provide improved scuff and cut resistance, they also provide sufficient reactivity of the cover materials for rapid demolding and improved process efficiency, as compared with aliphatic materials. In one embodiment, the polyisocyanate is preferably a PTMEG-based prepolymer. In another embodiment, the polyisocyanate is a MDI polyisocyanate prepolymer. In a further embodiment, the polyisocyanate is a PTMEG-based MDI polyisocyanate.
  • [0065]
    The polyurethane, polyurea or polyurethane/polyurea which is selected for use as a golf ball cover preferably has a Shore D hardness of from about 10 to about 70, more preferably from about 25 to about 60, and most preferably from about 30 to about 55 for a soft cover layer. The polyurethane, polyurea or polyurethane/polyurea which is to be used for a cover layer preferably has a flex modulus from about 1 to about 310 Kpsi, more preferably from about 5 to about 100 Kpsi, and most preferably from about 5 to about 20 Kpsi for a soft cover layer and 30 to 70 Kpsi for a hard cover layer. Accordingly, covers comprising these materials exhibit similar properties.
  • [0066]
    Non-limiting examples of a polyurethane, polyurea or polyurethane/ polyurea suitable for use in the outer cover layer include materials from Uniroyal/Crompton, BASF, Invista and ITWC (such as, for example, Uniroyal/Crompton OP491-59 and VibraRim 831, BASF NB#98113-1-192-4R/WUC 3236T ISO, Terathane® Polyether glycols (Terathane® 250, 650, 1000, 1400, 1800, 2000 and 2900) and ITWC HPM-1A/B). Optionally, the polyurethane material may also be blended with a soft ionomer or other ionomeric and non-ionomeric polymeric fillers or additive materials.
  • [0067]
    Aromatic polyurethanes are preferred because they typically have better scuff resistance characteristics than aliphatic polyurethanes, and the aromatic polyurethanes are typically lower cost than aliphatic polyurethanes.
  • [0068]
    Other suitable polyurethane materials for use in the present invention golf balls include reaction injection molded (RIM) polyurethanes. RIM is a process by which highly reactive liquids are injected into a closed mold, mixed usually by impingement and/or mechanical mixing in an in-line device such as a “peanut mixer,” where they polymerize primarily in the mold to form a coherent, one-piece molded article. The RIM process usually involves a rapid reaction between one or more reactive components such as polyether—or polyester—polyol, polyamine, or other material with an active hydrogen, and one or more isocyanate—containing constituents, often in the presence of a catalyst. The constituents are stored in separate tanks prior to molding and may be first mixed in a mix head upstream of a mold and then injected into the mold. The liquid streams are metered in the desired weight to weight ratio and fed into an impingement mix head, with mixing occurring under high pressure, for example, 1,500 to 3,000 psi. The liquid streams impinge upon each other in the mixing chamber of the mix head and the mixture is injected into the mold. One of the liquid streams typically contains a catalyst for the reaction. The constituents react rapidly after mixing to gel and form polyurethane polymers. Polyureas, epoxies, and various unsaturated polyesters also can be molded by RIM.
  • [0069]
    One or more catalysts may also be included. Examples of catalysts are those well known in the art of polyurethanes, such as tin, zinc and zirconium catalysts, as well as amine catalysts. The tin, zinc or zirconium catalyst preferably comprises at least one member selected from the group consisting of a zirconium complex, dibutyl tin dilaurate, dibutyl acetylacetonate, dibutyl tin dibutoxide, dibutyl tin sulphide, dibutyl tin di-2-ethylhexanoate, dibutyl tin (IV) diacetate, dialkyltin (IV) oxide, tributyl tin laurylmercaptate, dibutyl tin dichloride, organo lead, tetrabutyl titanate, tertiary amines, mercaptides, stannous octoate, potassium octoate, zinc octoate, diaza compounds, and potassium acetate. Examples of amine catalysts include, but are not limited to, N,N,N′-trimethyl-N-hydroxyethyl-bisaminoethyl ether; N,N-bis (3-dimethylaminopropyl)-N-isopropanol amine; N-(3-dimethylaminopropyl)-N,N-diisopropanolamine; N,N-dimethylethanolamine; and 2-(2-dimethylaminoethoxy) ethanol. The quantity of catalyst will depend upon the type of catalyst, polyol, and polyisocyanate used, as well as the curing temperature and desired curing time and other factors. Generally, the amount of catalyst used is from about 0.005 to 0.5 weight percent. Two or more different catalysts may also be used if desired.
  • [0070]
    The polyol component typically contains additives, such as stabilizers, flow modifiers, catalysts, combustion modifiers, blowing agents, fillers, pigments, optical brighteners, surfactants and release agents to modify physical characteristics of the cover. Polyurethane/polyurea constituent molecules that were derived from recycled polyurethane can be added in the polyol component. In a preferred embodiment, the polyol used in the covers of the golf balls of the invention additionally comprises a surfactant. The surfactant may be any desirable anionic, cationic or non-ionic surfactant. When a surfactant is used with the polyol, it promotes mixing of the polyol and isocyanate materials.
  • [0071]
    A golf ball outer cover layer according to the present invention formed from a polyurethane material typically contains from about 0 to about 20 weight percent of filler material, more preferably from about 1 to about 10 weight percent, and most preferably from about 1 to about 5 weight percent.
  • [0072]
    Moreover, in alternative embodiments, either the inner and/or the outer cover layer may also additionally comprise up to 100 weight percent of a soft, low modulus, non-ionomeric thermoplastic or thermoset material. Non-ionomeric materials are suitable so long as they produce the playability and durability characteristics desired without adversely affecting the enhanced travel distance characteristic produced by the high acid ionomer resin composition. These include but are not limited to styrene-butadiene-styrene block copolymers, including functionalized styrene-butadiene-styrene block copolymers, styrene-ethylene-butadiene-styrene (SEBS) block copolymers such as Kraton® materials from Shell Chem. Co., and functionalized SEBS block copolymers; metallocene catalyzed polyolefins; ionomer/rubber blends such as those in U.S. Pat. Nos. 4,986,545; 5,098,105 and 5,187,013; silicones; and, Hytrel® polyester elastomers from DuPont and Pebaxe polyetheramides from Elf Atochem S.A. A preferred non-ionomeric material suitable for the inner and/or outer cover layer includes polyurethane.
  • [0073]
    Additional materials may also be added to the inner and outer cover layer of the present invention as long as they do not substantially reduce the playability properties of the ball. Such materials include dyes (for example, Ultramarine Blue™ sold by Whittaker, Clark, and Daniels of South Plainsfield, N.J.) (see, for example, U.S. Pat. No. 4,679,795); pigments such as titanium dioxide, zinc oxide, barium sulfate and zinc sulfate; UV absorbers; antioxidants; antistatic agents; and stabilizers. Moreover, the cover compositions of the present invention may also contain softening agents such as those disclosed in U.S. Pat. Nos. 5,312,857 and 5,306,760, including plasticizers, metal stearates, processing acids, and the like, 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.
  • [0074]
    If desired, the outer cover layer may additionally comprise one or more isocyanates that may possibly improve the scuff resistance of the outer cover layer. For thermoplastic polyurethane covers, the isocyanate further cross-links the cover material to provide additional scuff resistance while maintaining the other desirable features of the cover, such as softness and feel. The golf balls of the invention that were produced using a PTMEG-based RIM material showed no improvement when dipped in isocyanate. The isocyanate is added to the outer cover layer by any suitable method known in the art, although dipping, wiping, soaking, brushing or spraying the golf ball in or with the isocyanate is preferred. The method of adding the isocyanate, or mixtures thereof, to the cover layer is discussed in more detail below.
  • [0075]
    The isocyanate that may be added to the cover layer to improve scuff resistance can be any aliphatic or aromatic isocyanate or diisocyanate or blends thereof known in the art. Examples of suitable isocyanates include, but are not limited to, 4,4′-diphenylmethane diisocyanate (MDI); 2,4-toluene diisocyanate (TDI); m-xylylene diisocyanate (XDI); methylene bis-(4-cyclohexyl isocyanate) (“HMDI”); hexamethylene diisocyanate (HDI); naphthalene-1,5,-diisocyanate (NDI); 3,3′-dimethyl-4,4′-biphenyl diisocyanate (TODI); 1,4-diisocyanate benzene (PPDI); phenylene-1,4-diisocyanate; and 2,2,4- or 2,4,4-trimethyl hexamethylene diisocyanate (TMDI). Other less preferred diisocyanates include, but are not limited to, isophorone diisocyanate (IPDI); 1,4-cyclohexyl diisocyanate (CHDI); diphenylether-4,4′-diisocyanate; p,p′-diphenyl diisocyanate; lysine diisocyanate (LDI); 1,3-bis (isocyanato methyl) cyclohexane; polymethylene polyphenyl isocyanate (PMDI); and meta-tetramethylxylylene diisocyanate (TMXDI). Preferably, the diisocyanate is an aromatic diisocyanate, and more preferably, MDI. The term “isocyanate” as used herein includes all of these compounds and other isocyanates.
  • [0076]
    As mentioned generally above, the isocyanate or diisocyanate used may have a solids content in the range of about 1 to about 100 weight %, preferably about 5 to about 50 weight %, most preferably about 10 to about 30 weight %. If it is necessary to adjust the solids content, any suitable solvent (such as ketone and acetate) that will allow penetration of the isocyanate into the polyurethane cover material without causing distortion may be used.
  • [heading-0077]
    Core
  • [0078]
    The cores of the inventive golf balls typically have a coefficient of restitution of about 0.750 or more, more preferably 0.770 or more and a PGA compression of about 90 or less, and more preferably 70 or less. Furthermore, in some applications it may be desirable to provide a core with a coefficient of restitution of about 0.780 to 0.790 or more. The core used in the golf ball of the invention preferably is a solid. The term “solid cores” as used herein refers not only to one piece cores but also to those cores having a separate solid layer beneath the covers and over the central core. The cores have a weight of 25 to 40 grams and preferably 30 to 40 grams. When the golf ball of the invention has a solid core, this core can be compression molded from a slug of uncured or lightly cured elastomer composition comprising a high cis content polybutadiene and a metal salt of an α, β, 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 include a small amount of a metal oxide such as zinc oxide. In addition, larger amounts of metal oxide than are needed to achieve the desired coefficient 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 including compatible rubbers or ionomers, and low molecular weight fatty acids such as stearic acid. Free radical initiator catalysts such as peroxides are admixed with the core composition so that on the application of heat and pressure, a curing or cross-linking reaction takes place.
  • [0079]
    A thread wound core may comprise a liquid, solid, gel or multi-piece center. The thread wound core is typically obtained by winding a thread of natural or synthetic rubber, or thermoplastic or thermosetting elastomer such as polyurethane, polyester, polyamide, etc. on a solid, liquid, gel or gas filled center to form a thread rubber layer that is then covered with one or more mantle or cover layers. Additionally, prior to applying the cover layers, the thread wound core may be further treated or coated with an adhesive layer, protective layer, or any substance that may improve the integrity of the wound core during application of the cover layers and ultimately in usage as a golf ball.
  • [heading-0080]
    Method of Making Golf Ball
  • [0081]
    In preparing golf balls in accordance with the present invention, an inner cover layer, preferably a hard inner cover layer, is molded (for example, by injection molding or by compression molding) about a core (preferably a solid core). A comparatively softer outer layer is molded over the inner layer, preferably by reaction injection molding.
  • [0082]
    The RIM process used in forming a cover layer of a golf ball disclosed herein is substantially different from, and advantageous over, the conventional injection and compression molding techniques.
  • [0083]
    First, during the RIM process of the present application, the chemical reaction, i.e., the mixture of isocyanate from the isocyanate tank and polyol from the polyol tank, occurs during the molding process. Specifically, the mixing of the reactants occurs in the recirculation mix head and the after mixer, both of which are connected directly to the injection mold. The reactants are simultaneously mixed and injected into the mold, forming the desired component.
  • [0084]
    Typically, prior art techniques utilize mixing of reactants to occur before the molding process. Mixing under either compression or injection molding occurs in a mixer that is not connected to the molding apparatus. Thus, the reactants must first be mixed in a mixer separate from the molding apparatus, then added into the apparatus. Such a process causes the mixed reactants to first solidify, then later melt in order to properly mold.
  • [0085]
    Second, the RIM process requires lower temperatures and pressures during molding than does injection or compression molding. Under the RIM process, the molding temperature is maintained at about 100-120° F. in order to ensure proper injection viscosity. Compression molding is typically completed at a higher molding temperature of about 320° F. Injection molding is completed at even a higher temperature range of 392-482° F. At this elevated temperature, the viscosity of the molten resin usually is in the range of 50,000 to about 1,000,000 centipoise, and is typically around 200,000 centipoise. In an injection molding process, the solidification of the resins occurs after about 10 to about 90 seconds, depending upon the size of the molded product, the temperature and heat transfer conditions, and the hardness of the injection molded material. Molding at a lower temperature is beneficial when, for example, the cover is molded over a very soft core so that the very soft core does not melt or decompose during the molding process.
  • [0086]
    Third, the RIM process creates more favorable durability properties in a golf ball than does conventional injection or compression molding. The preferred process of the present invention provides improved durability for a golf ball cover by providing a uniform or “seamless” cover in which the properties of the cover material in the region along the parting line are generally the same as the properties of the cover material at other locations on the cover, including at the poles. The improvement in durability is due to the fact that the reaction mixture is distributed uniformly into a closed mold. This uniform distribution of the injected materials reduces or eliminates knit-lines and other molding deficiencies which can be caused by temperature difference and/or reaction difference in the injected materials. The RIM process of the present invention results in generally uniform molecular structure, density and stress distribution as compared to conventional injection molding processes, where failure along the parting line or seam of the mold can occur because the interfacial region is intrinsically different from the remainder of the cover layer and, thus, can be weaker or more stressed.
  • [0087]
    Fourth, the RIM process is relatively faster than the conventional injection and compression molding techniques. In the RIM process, the chemical reaction takes place in under 5 minutes, typically in less than two minutes, preferably in under one minute and, in many cases, in about 30 seconds or less. The demolding time of the present application is 10 minutes or less. The molding process alone for the conventional methods typically take about 15 minutes. Thus, the overall speed of the RIM process makes it advantageous over the injection and compression molding methods.
  • [0088]
    The solid core for the multi-layer ball is about 1.2 to 1.6 inches in diameter, although it may be possible to use cores in the range of about 1.0 to 2.0 inches. Conventional solid cores are typically compression or injection molded from a slug or ribbon of uncured or lightly cured elastomer composition comprising a high cis content polybutadiene and a metal salt of an α, β, ethylenically unsaturated carboxylic acid such as zinc mono or diacrylate or methacrylate. To achieve higher coefficients of restitution in the core, the manufacturer may include fillers such as small amounts of a metal oxide such as zinc oxide. In addition, larger amounts of metal oxide than those that are needed to achieve the desired coefficient are often included in conventional cores 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. Other materials may be used in the core composition including compatible rubbers or ionomers, and low molecular weight fatty acids such as stearic acid. Free radical initiators such as peroxides are admixed with the core composition so that on the application of heat and pressure, a complex curing cross-linking reaction takes place.
  • [0089]
    In some embodiments, the inner cover layer(s) that is molded over the core is about 0.010 inches to about 0.150 inches in thickness, more preferably about 0.020 to about 0.10 inches thick. The inner ball that includes the core and inner cover layer(s) preferably has a diameter in the range of 1.25 to 1.64 inches. The outer cover layer is 0.005 inches to 0.075 inches in thickness, preferably 0.010 to 0.050 inches thick, more preferably 0.010 to 0.040 inches thick, and most preferably 0.010 to 0.030 inches thick. In one preferred embodiment, the outer cover layer is less than 0.025 inches, and in another preferred embodiment the outer cover layer is less than 0.020 inches. Together, the core, the inner cover layer(s) and the outer cover layer combine to form a ball having a diameter of 1.680 inches or more, the minimum diameter permitted by the rules of the United States Golf Association and weighing no more than 1.62 ounces.
  • [0090]
    In a particularly preferred embodiment of the invention, the golf ball has a dimple pattern that provides dimple coverage of 65% or more, preferably 75% or more, and more preferably 85% or more, although any number of dimples and amount of dimple coverage desired may be used. In a preferred embodiment of the invention, there are greater than 300 dimples, preferably from about 300 to about 500 dimples.
  • [0091]
    In a preferred embodiment, the golf ball typically is coated with a durable, abrasion-resistant, relatively non-yellowing finish coat or coats if necessary. The finish coat or coats may have some optical brightener added to improve the brightness of the finished golf ball. In a preferred embodiment, from 0.001 to about 10% optical brightener may be added to one or more of the finish coatings. Preferred finish coatings are solvent based urethane coatings known in the art.
  • [0092]
    The golf balls of the present invention can be produced by molding processes, which include but are not limited to those that are currently well known in the golf ball art. For example, the golf balls can be produced by injection molding or compression molding the novel cover compositions around a wound or solid molded core to produce an inner ball, which typically has a diameter of about 1.50 to 1.67 inches. The outer layer is subsequently molded via reaction injection molding over the inner layer to produce a golf ball having a diameter of about 1.680 inches or more. Although either solid cores or wound cores can be used in the present invention, as a result of their lower cost and superior performance, solid molded cores are preferred over wound cores. The standards for both the minimum diameter and maximum weight of the balls are established by the United States Golf Association (U.S.G.A.).
  • [0093]
    In compression molding, the inner cover composition is formed via injection molding at about 380° F. to about 450° F. into smooth surfaced hemispherical shells which are then positioned around the core in a mold having the desired inner cover thickness and subjected to compression molding at 200° F. to 300° F. for about 2 to 10 minutes, followed by cooling at 50° F. to 70° F. for about 2 to 7 minutes to fuse the shells together to form a unitary intermediate ball. In addition, the intermediate balls may be produced by injection molding wherein the inner cover layer is injected directly around the core placed at the center of an intermediate ball mold for a period of time in a mold temperature of from 50° F. to about 100° F. Subsequently, the outer cover layer is molded about the core and the inner layer by similar molding techniques to form a dimpled golf ball of a diameter of 1.680 inches or more. Preferably, the outer cover layer is molded using RIM. To improve the adhesion between the inner cover layer and the outer cover layer, an adhesion promoter may be used. Some adhesion promoters, such as abrasion of the surface, corona treatment, and the like, are known in the art. An example of one preferred adhesion promoter is a chemical adhesion promoter, such as a silane or other silicon compound, preferably N-(2-aminoethyl)3-aminopropyltrimethoxysilane. The intermediate golf ball (core and inner cover layer) may be dipped or sprayed with the chemical, and then the outer cover layer is formed over the treated inner cover layer. After molding, the golf balls produced may undergo various further processing steps such as buffing, painting and marking as disclosed in U.S. Pat. No. 4,911,451.
  • [0094]
    Golf balls and, more specifically, cover layers formed by RIM may be formed by the process described in Application Ser. Nos. 09/040,798, filed Mar. 18, 1998; and Ser. No. 09/877,600, filed Jun. 8, 2001; and U.S. Pat. Nos. 6,290,614 and 6,716,954, all of which are incorporated herein by reference, or by a similar RIM process.
  • [0095]
    The golf balls formed according to the present invention can be coated using a conventional two-component spray coating or can be coated during the RIM process, for example, using an in-mold coating process.
  • [0096]
    The present invention is further illustrated by the following examples in which the parts of the specific ingredients are by weight. It is to be understood that the present invention is not limited to the examples, and various changes and modifications may be made in the invention without departing from the spirit and scope thereof.
  • EXAMPLES Example 1
  • [0097]
    A PTMEG based RIM cover material was produced using the following materials (all amounts are in parts by weight):
    Ex. A Ex. B
    Terathane ® 1000 1000.0 1000.0
    Terathane ® 2000 100.0 100.0
    1,4 Butane diol 90.0 90.0
    Dibutyltindilaurate 1.0 0.5
    Isonate ® 181 785.6 785.6

    (According to Dow Plastics, Isonate® 181 is a MDI prepolymer produced by reacting high purity diphenylmethane diisocyanate with sufficient glycol to allow easy handling. According to Invista, Terathane® polyether glycol is a PTMEG material available in different molecular weight grades. Terathane® is a blend of linear diols in which the hydroxyl groups are separated by tetramethylene ether groups.)
  • [0099]
    The reaction in Example A was very fast, so the amount of catalyst was reduced in half to slow the reaction down. The material was run in a RIM machine, and it reacted very slowly with no catalyst in the system. Adding catalyst increased the reaction rate. The material was molded over glebarred cores and tested for scuff and cut resistance. For comparison, the golf balls were tested against a PPG based RIM system and two golf balls having an injection molded thermoplastic polyurethane cover. One of the thermoplastic polyurethane balls was post-treated to improve scuff and cut while the other thermoplastic polyurethane ball was not post-treated. The results are shown in Table 4 below.
  • [0100]
    The scuff resistance test was conducted in the manner described below. The balls that were tested were primed and top coated. A sharp grooved sand wedge (56 degrees loft) was mounted in a mechanical swing machine. The club swing speed used is 60 mph. After each hit, the club face is brushed clean using a nylon bristled brush. A minimum of three samples of each ball was tested. Each ball was hit three times at three different locations so as not to overlap with other strikes. The details of the club face are critical, and are as follows:
      • Groove width—0.025 inches (cut with a mill cutter, leaving a sharp edge to the groove; no sandblasting or post finishing should be done after milling);
      • Groove depth—0.016 inches;
      • Groove spacing (one groove edge to the nearest adjacent edge)—0.1 05 inches.
  • [0104]
    For each strike, a point value should be assigned for the worst two defects according to the following table:
    Point Value Shear Defect
    0 No visible defects
    0.5 Lines
    1 Lifts
    2 Bad Lifts
    2 Tiny (or Paint) Hairs
    3 Bad Hairs
    3 Shears (if land area is removed on “hard” covers
    (65 Shore D+), rank as the only limit
    6 (max value) Bad Shears (dimples are completely removed, rank
    as the only defect)

    Example - a strike having a shear, tiny hairs, bad lifts and a line would be ranked as a 5 (3 points for a shear and 2 points for tiny hairs)

    Note

    The maximum value per strike is 6.
  • [0105]
    After completing all strikes, determine the average point value. This average point value, or rank, can be correlated to the chart below.
    Rank Average Point Value
    Excellent 0.0-1.0
    Very Good 1.1-2.0
    Good 2.1-3.0
    Fair 3.1-4.0
    Borderline 4.1-5.0
    Poor (unacceptable) 5.1-6.0

    The cut test (off center cut) was performed as described below. An off center cut test was used as it more closely represents actual play. The shear component of this blow makes the off-center cut test the most severe and most useful in determining the cut resistance of a cover material.
  • [0107]
    The cut performance test consists of cutting a minimum of three golf balls at least twice. Each cut is in a different location on the ball so as not to overlap other cuts. Cutting the samples directly on the equator should be avoided. The off-center cut test uses a guillotine to strike the ball with a glancing blow and represents a mishit where the ball might be topped or skulled. To perform the test, adjust the sample holder to the appropriate position and place the golf ball in the sample holder. Carefully lift the guillotine to the top of its stroke, making sure not to hit the release switch on the left of the head. The head should stay at the top by means of its clutch mechanism. Tap the release switch on the left of the head to release the guillotine to strike the ball. Rotate the ball for the next blow(s) making sure the subsequent strike(s) will not overlap. Once all the samples have been cut, each strike is ranked according to the guidelines below. The cut ranking for the sample set is represented by the average of all cuts. An overall ranking of 3 or better is necessary for acceptable field durability.
    DEFECT CHARACTER CUT RANK
    No Visible Marks 0
    Barely Visible Lines 1
    Distinct Lines 2
    Lines with few Wrinkles 3
    Wrinkles and Minor Cuts 4
    Deep Cuts or Tearing 5
  • [0108]
    TABLE 4
    PTMEG Cover Comparison
    Sample Cut Scuff Shore C
    TPU - no post-treatment 4 6 Not measured
    TPU - post-treated 3 2.3 Not measured
    PPG based RIM 3 2 83.7
    PTMEG based RIM 5 1.7 82.9
  • [0109]
    The above test showed that the PTMEG based system provides scuff resistance at least as good as the PPG based RIM system as well as the TPU covered balls (that are currently commercially available).
  • Example 2
  • [0110]
    Multiple golf ball samples were produced using two different PTMEG based RIM systems. The first used a PTMEG based diisocyanate prepolymer (MDI) and a PTMEG polyol having a curative (Ethacure 100LC). The second system was a similar, more resilient system with similar properties. For comparison, golf balls were also produced using 3 different PPG based RIM systems. Eight dozen of each type was produced and tested. The cores were standard solid cores made from a polybutadiene blend, and the mantle layers were all high acid ionomer blends. All balls were compared against commercially available golf balls. The results of the tests are shown below in Tables 5, 6 and 7.
    TABLE 5
    Golf Ball Construction (General)
    Core Construction Cover
    Sample (Solid Core) Mantle Material* Desc.
    Control 1 1.570″ (93 R) 70 D (.032″) PPG 1 80 PGA Control
    (.023″)
    Control 2 1.570″ (81 R) 70 D (.032″) PPG 1 90 PGA Control
    (.023″)
    0.023″ 0.042″
    COVERS MANTLES
     3 1.550″ (86R) 70 D PPG 1 85 PGA w/.023″ 80B Cover
     4 1.550″ (86R) 70 D PPG 2 85 PGA w/.023″ 82B Cover
     5 1.550″ (86R) 70 D PPG 3 85 PGA w/.023″ 84B Cover
     6 1.550″ (86R) 70 D PTMEG 1 85 PGA w/.023″ 85B Cover
     7 1.550″ (86R) 70 D PTMEG 2 85 PGA w/.023″ 80B Cover
     8 1.550″ (72R) 70 D PPG 1 95 PGA w/.023″ 80B Cover
     9 1.550″ (72R) 70 D PPG 2 95 PGA w/.023″ 84B Cover
     10 1.550″ (72R) 70 D PPG 3 95 PGA w/.023″ 86B Cover
    10A 1.550″ (95R) 70 D PTMEG 1 80 PGA w/.023″ 85B Cover
    .016″ 0.042″
    COVERS MANTLES
    11 1.565″ (88R) 70 D PPG 1 85 PGA w/.016″ 80B Cover
    12 1.565″ (88R) 70 D PPG 2 85 PGA w/.016″ 82B Cover
    13 1.565″ (88R) 70 D PPG 3 85 PGA w/.016″ 84B Cover
    14 1.565″ (88R) 70 D PTMEG 1 85 PGA w/.016″ 85B Cover
    15 1.565″ (88R) 70 D PTMEG 2 85 PGA w/.016″ 80B Cover
    16 1.565″ (74R) 70 D PPG 1 95 PGA w/.016″ 80B Cover
    17 1.565″ (74R) 70 D PPG 2 95 PGA w/.016″ 84B Cover
    18 1.565″ (74R) 70 D PPG 3 95 PGA w/.016″ 86B Cover
    18A 1.565″ (97R) 70 D PTMEG 1 80 PGA w/.016″ 85B Cover

    *PPG 1 - Bayer MP-5000;

    PPG 2 - Bayer MP-15000;

    PPG 3 - Bayer MP-25000

    PTMEG 1 - PTMEG diisocyanate prepolymer (MDI) and PTMEG polyol with curative;

    PTMEG 2 - similar to PTMEG 1 but more resilient
  • [0111]
    TABLE 6
    Ball Static Results
    Core Statics (Size, Wt, Mantle Statics (Size, Wt, Ball Statics (Size, Wt,
    Sample Riehle, Instron, CoR) Riehle, Instron, CoR) PGA Instron, CoR)
     1 1.571″, 38.48 g, 91 R, 1.638″, 42.69 g, 84 R, 1.678″, 45.62 g, 80 PGA,
    .104 I, .802 CoR .0969 I, .814 CoR .0939 I, .817 CoR
     2 1.571″, 38.44 g, 80 R, 1.637″, 42.66 g, 74 R, 1.679″, 45.66 g, 90 PGA,
    .0939 I, .810 CoR .0896 I, .820 CoR .0869 I, .819 CoR
     3 1.549″, 37.20 g, 77 R, 1.636″, 42.64 g, 75 R, 1.680″, 45.72 g, 87 PGA,
    .0978 I, .794 CoR .0918 I, .818 CoR .0895 I, .815 CoR
     4 1.549″, 37.20 g, 77 R, 1.636″, 42.64 g, 75 R, 1.678″, 45.61 g, 86 PGA,
    .0978 I, .794 CoR .0918 I, .818 CoR .0896 I, .816 CoR
     5 1.549″, 37.20 g, 77 R, 1.636″, 42.64 g, 75 R, 1.678″, 45.60 g, 87 PGA,
    .0978 I, .794 CoR .0918 I, .818 CoR .0891 I, .816 CoR
     6 1.549″, 37.20 g, 77 R, 1.636″, 42.64 g, 75 R, 1.680″, 45.67 g, 87 PGA,
    .0978 I, .794 CoR .0918 I, .818 CoR .0891 I, .815 CoR
     7 1.549″, 37.20 g, 77 R, 1.636″, 42.64 g, 75 R, 1.678″, 45.54 g, 86 PGA,
    .0978 I, .794 CoR .0918 I, .818 CoR .0898 I, .814 CoR
     8 1.550″, 37.2 g, 72 R, 1.637″, 42.61 g, 66 R, 1.678″, 45.51 g, 96 PGA,
    .0897 I, .806 CoR .0841 I, .823 CoR .0827 I, .822 CoR
     9 1.550″, 37.2 g, 72 R, 1.637″, 42.61 g, 66 R, 1.678″, 45.59 g, 96 PGA,
    .0897 I, .806 CoR .0841 I, .823 CoR .0829 I, .823 CoR
    10 1.550″, 37.2 g, 72 R, 1.637″, 42.61 g, 66 R, 1.677″, 45.56 g, 97 PGA,
    .0897 I, .806 CoR .0841 I, .823 CoR .0818 I, .824 CoR
    10A 1.550″, 37.25 g, 88 R, 1.636″, 42.63 g, 84 R, 1.679″, 45.60 g, 80 PGA,
    .104 I, .800 CoR .0982 I, .813 CoR .0940 I, .812 CoR
    11 1.566″, 38.15 g, 86 R, 1.650″, 43.53 g, 77 R, 1.679″, 45.55 g, 84 PGA,
    .0995 I, .801 CoR .0927 I, .819 CoR .0908 I, .821 CoR
    12 1.566″, 38.15 g, 86 R, 1.650″, 43.53 g, 77 R, 1.681″, 45.62 g, 85 PGA,
    .0995 I, .801 CoR .0927 I, .819 CoR .0907 I, .821 CoR
    13 1.566″, 38.15 g, 86 R, 1.650″, 43.53 g, 77 R, 1.679″, 45.55 g, 85 PGA,
    .0995 I, .801 CoR .0927 I, .819 CoR .0905 I, .821 CoR
    14 1.566″, 38.15 g, 86 R, 1.650″, 43.53 g, 77 R, 1.679″, 45.47 g, 85 PGA,
    .0995 I, .801 CoR .0927 I, .819 CoR .0906 I, .821 CoR
    15 1.566″, 38.15 g, 86 R, 1.650″, 43.53 g, 77 R, 1.688″, 45.45 g, 85 PGA,
    .0995 I, .801 CoR .0927 I, .819 CoR .0904 I, .821 CoR
    16 1.564″, 38.02 g, 72 R, 1.650″, 43.48 g, 68 R, 1.679″, 45.46 g, 95 PGA,
    .0889 I, .814 CoR .0858 I, .825 CoR .0835 I, .827 CoR
    17 1.564″, 38.02 g, 72 R, 1.650″, 43.48 g, 68 R, 1.678″, 45.44 g, 95 PGA,
    .0889 I, .814 CoR .0858 I, .825 CoR .0835 I, .826 CoR
    18 NA NA Not molded —Defects
    18A 1.566″, 38.17 g, 94 R, 1.650″, 43.57 g, 85 R, 1.681″, 45.65 g, 80 PGA,
    .106 I, .797 CoR .0986 I, .814 CoR .0945 I, .818 CoR
    Commercially Available
    Balls Ball Statics (Size, Wt, PGA Instron, CoR)
    Hogan Apex Tour 1.684″, 45.68 g, 80 PGA, .0939 I, .795 CoR
    Strata Tour Ace 1.683″, 45.63 g, 90 PGA, .0869 I, .802 CoR
    CTU 30 Red 1.681″, 45.72 g, 91 PGA, .0902 I, .798 CoR
    HX Red 1.681″, 45.83 g, 93 PGA, .0888 I, .796 CoR
    Pro V1 1.685″, 45.60 g, 80 PGA, .0967 I, .805 CoR
    Pro V1X 1.684″, 45.67 g, 90 PGA, .0913 I, .807 CoR
  • [0112]
    TABLE 7
    Ball Scuff and Cut Results
    Sample Cold Crack OC Cut Scuff
     1 No Failures 5 3.7
     2 No Failures 5 4.0
     3 No Failures 5 4.6
     4 No Failures 5 4.2
     5 No Failures 5 4.6
     6** No Failures 3 1.8
     7** No Failures 2 1.8
     8 No Failures 5 4.7
     9 No Failures 5 4.4
    10 No Failures 5 5.8
    10A** No Failures 2 1.7
    11 No Failures 5 5.0
    12 No Failures 5 5.2
    13 No Failures 5 5.9
    14** No Failures 3 2.0
    15** No Failures 2 1.4
    16 No Failures 5 4.8
    17 No Failures 5 5.8
    18 NA NA NA
    18A** No Failures 2 1.8
    PRO V1X Not tested 4 1.9
    HOGAN Not tested 4 2.3
    ACE Not tested 4 2.3

    **Samples of the invention
  • [0113]
    The golf ball samples of the invention (Sample numbers 6, 7, 10A, 14, 15, and 18A) comprising a PTMEG based polyurethane material formed by the reaction of a PTMEG based diisocyanate prepolymer and a PTMEG based polyol performed as well as, if not better than, the commercially available golf balls, and better than the PPG based RIM covered golf balls.
  • [0114]
    The foregoing description is, at present, considered to be the preferred embodiments of the present invention. However, it is contemplated that various changes and modifications apparent to those skilled in the art, may be made without departing from the present invention. Therefore, the foregoing description is intended to cover all such changes and modifications encompassed within the spirit and scope of the present invention, including all equivalent aspects.
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Classifications
U.S. Classification473/378
International ClassificationA63B37/12, A63B45/00, A63B37/06, A63B37/00, C08L75/04
Cooperative ClassificationA63B37/12, A63B37/0027, C08L75/04, A63B37/0033, A63B37/0075, C08G2120/00, A63B37/0003
European ClassificationA63B37/12, A63B37/00G, C08L75/04
Legal Events
DateCodeEventDescription
Sep 24, 2004ASAssignment
Owner name: CALLAWAY GOLF COMPANY, CALIFORNIA
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:TZIVANIS, MICHAEL J.;KENNEDY, III THOMAS J.;MELANSON, DAVID M.;REEL/FRAME:015858/0462
Effective date: 20040924