|Publication number||US20060148359 A1|
|Application number||US 11/027,390|
|Publication date||Jul 6, 2006|
|Filing date||Dec 30, 2004|
|Priority date||Dec 30, 2004|
|Also published as||WO2006073617A1|
|Publication number||027390, 11027390, US 2006/0148359 A1, US 2006/148359 A1, US 20060148359 A1, US 20060148359A1, US 2006148359 A1, US 2006148359A1, US-A1-20060148359, US-A1-2006148359, US2006/0148359A1, US2006/148359A1, US20060148359 A1, US20060148359A1, US2006148359 A1, US2006148359A1|
|Inventors||Paul Van Gompel, Yung Huang|
|Original Assignee||Kimberly-Clark Worldwide, Inc.|
|Export Citation||BiBTeX, EndNote, RefMan|
|Referenced by (6), Classifications (13), Legal Events (1)|
|External Links: USPTO, USPTO Assignment, Espacenet|
Many of the medical care products, protective wear garments, mortuary and veterinary products, and personal care products in use today are available as disposable products. By disposable, it is meant that the product is used only a few times, or even only once, before being discarded. Examples of such products include, but are not limited to, medical and health care products such as surgical drapes, gowns and bandages, protective workwear garments such as coveralls and lab coats, and infant, child and adult personal care absorbent products such as diapers, training pants, incontinence garments and pads, sanitary napkins, wipes and the like. These products need to be manufactured at a cost which is consistent with single- or limited-use disposability.
Products such as the above mentioned medical, veterinary, protective and personal care products often utilize mechanical fastening systems such as hook-and-loop fastening systems, for purposes of closure or attachment. Fibrous nonwoven webs formed by extrusion processes such as spunbonding and meltblowing, and by mechanical dry-forming process such as air-laying and carding, are ideal candidates to be utilized in or as part of fibrous loop components of the hook and loop fastening system of disposable products, since the manufacture of nonwovens is often inexpensive relative to the cost of woven or knitted loop components.
Therefore, in order to provide loop materials consistent with use in limited- or single-use disposable products, there remains a need for new nonwoven loop material and processes for producing the nonwoven loop materials.
The present invention provides a process for producing composite nonwoven loop materials that are highly suited for use in hook and loop fastening systems. In one aspect, the process for producing the composite loop materials produces a laminate composite loop material and includes the steps of providing a sheet-form elastic substrate layer and at least a first fibrous nonwoven web, the fibrous nonwoven web including fibers which are less elastic than the elastic substrate layer, interposing the elastic substrate layer and the fibrous nonwoven web in a face-to-face relation, bonding the elastic substrate layer and the fibrous nonwoven web together at spaced-apart locations to form a laminate composite material, and then extending the laminate composite in at least one direction, such as, for example, the machine direction or the cross machine direction, in an extension amount sufficient to permanently elongate at least a number of the less elastic fibers along at least a portion of the lengths of the fibers, and then retracting the laminate. In embodiments, the elastic substrate layer may be such as elastic meltblowns, elastic spunbonds or elastic films. A second fibrous nonwoven web may desirably be bonded to the elastic substrate layer on the side opposite the first fibrous nonwoven web.
In another aspect, the process for producing the composite loop materials produces a coform composite loop material and includes the steps of providing a plurality of first, elastic fibers and a plurality of second fibers which are less elastic than the first, elastic fibers, coforming the first elastic fibers and the second fibers together to form a composite nonwoven web, bonding the composite nonwoven web at spaced-apart locations to form a bonded composite nonwoven web, and then extending the bonded composite nonwoven web in at least one direction, such as, for example, the machine direction or the cross machine direction, in an extension amount sufficient to permanently elongate at least a number of the second fibers along at least a portion of the lengths of the second fibers, and then retracting the composite. In embodiments, the first and second fibers may be coformed in spunbond processes, meltblown processes, combinations of spunbond and meltblown processes, or in meltblown-and-staple fiber coforming processes.
The present invention further provides composite nonwoven loop materials such as may be made by the process embodiments described above. The composite loop material includes at least one elastic component and at least one loop-forming component. The loop-forming component includes fibers which form loops extending above the plane of the composite loop material, and the loops have loop ends secured or anchored in bond points. The loop-forming component fibers are less elastic than the elastic component, and at least a plurality of the loop-forming component fibers include first length portions along the fiber having a fiber cross sectional diameter which is at least 5 percent smaller than the cross sectional diameter along a second length portion of the same fiber. In embodiments, the diameter at the first length portions on at least some of the loop-forming fibers may be 10 percent smaller, 15 percent smaller, or even 20 percent or more smaller than the diameter at the second length portions. In embodiments, the elastic component may desirably be such as elastic meltblown, elastic spunbond and elastic films, and the loop-forming component may be spunbond fibers or staple fibers. The composite loop material may desirably be a laminate composite material or a coform composite material.
As used herein and in the claims, the term “comprising” is inclusive or open-ended and does not exclude additional unrecited elements, compositional components, or method steps. Accordingly, the term “comprising” encompasses the more restrictive terms “consisting essentially of” and “consisting of”.
As used herein the term “polymer” generally includes but is not limited to, homopolymers, copolymers, such as for example, block, graft, random and alternating copolymers, terpolymers, etc. and blends and modifications thereof. Furthermore, unless otherwise specifically limited, the term “polymer” shall include all possible geometrical configurations of the material. These configurations include, but are not limited to isotactic, syndiotactic and random symmetries. As used herein the term “thermoplastic” or “thermoplastic polymer” refers to polymers that will soften and flow or melt when heat and/or pressure are applied, the changes being reversible.
As used herein, the terms “elastic” and “elastomeric” are generally used to refer to a material that, upon application of a force, is stretchable to a stretched, biased length which is at least about 133 percent, or one and a third times, its relaxed, unstretched length, and which upon release of the stretching, biasing force will recover at least about 50 percent of its elongation. By way of example only, an elastic material having a relaxed, unstretched length of 10 centimeters may be elongated to at least about 13.3 centimeters by the application of a stretching or biasing force. Upon release of the stretching or biasing force the elastic material will recover to a length of not more than 11.65 centimeters.
As used herein the term “fibers” refers to both staple length fibers and substantially continuous filaments, unless otherwise indicated. As used herein the term “substantially continuous” with respect to a filament or fiber means a filament or fiber having a length much greater than its diameter, for example having a length to diameter ratio in excess of about 15,000 to 1, and desirably in excess of 50,000 to 1.
As used herein the term “monocomponent” fiber refers to a fiber formed from one or more extruders using only one polymer composition. This is not meant to exclude fibers or filaments formed from one polymeric extrudate to which small amounts of additives have been added for color, anti-static properties, lubrication, hydrophilicity, etc.
As used herein the term “multicomponent fibers” refers to fibers or filaments that have been formed from at least two component polymers, or the same polymer with different properties or additives, extruded from separate extruders but spun together to form one fiber or filament. Multicomponent fibers are also sometimes referred to as conjugate fibers or bicomponent fibers, although more than two components may be used. The polymers are arranged in substantially constantly positioned distinct zones across the cross-section of the multicomponent fibers and extend continuously along the length of the multicomponent fibers. The configuration of such a multicomponent fiber may be, for example, a concentric or eccentric sheath/core arrangement wherein one polymer is surrounded by another, or may be a side by side arrangement, an “islands-in-the-sea” arrangement, or arranged as pie-wedge shapes or as stripes on a round, oval or rectangular cross-section fiber, or other configurations. Multicomponent fibers are taught in U.S. Pat. No. 5,108,820 to Kaneko et al. and U.S. Pat. No. 5,336,552 to Strack et al. Conjugate fibers are also taught in U.S. Pat. No. 5,382,400 to Pike et al. and may be used to produced crimp in the fibers by using the differential rates of expansion and contraction of the two (or more) polymers. For two component fibers, the polymers may be present in ratios of 75/25, 50/50, 25/75 or any other desired ratios. In addition, any given component of a multicomponent fiber may desirably comprise two or more polymers as a multiconstituent blend component.
As used herein the terms “biconstituent fiber” or “multiconstituent fiber” refer to a fiber or filament formed from at least two polymers, or the same polymer with different properties or additives, extruded from the same extruder as a blend. Multiconstituent fibers do not have the polymer components arranged in substantially constantly positioned distinct zones across the cross-section of the multicomponent fibers; the polymer components may form fibrils or protofibrils that start and end at random.
As used herein the terms “nonwoven web” or “nonwoven fabric” refer to a web having a structure of individual fibers or filaments that are interlaid, but not in an identifiable manner as in a knitted or woven fabric. Nonwoven fabrics or webs have been formed from many processes such as for example, meltblowing processes, spunbonding processes, airlaying processes, and carded web processes. The basis weight of nonwoven fabrics is usually expressed in grams per square meter (gsm) or ounces of material per square yard (osy) and the filament diameters useful are usually expressed in microns. (Note that to convert from osy to gsm, multiply osy by 33.91).
The terms “spunbond” or “spunbond nonwoven web” refer to a nonwoven fiber or filament material of small diameter fibers that are formed by extruding molten thermoplastic polymer as fibers from a plurality of capillaries of a spinneret. The extruded fibers are cooled while being drawn by an eductive or other well known drawing mechanism. The drawn fibers are deposited or laid onto a forming surface in a generally random manner to form a loosely entangled fiber web, and then the laid fiber web is subjected to a bonding process to impart physical integrity and dimensional stability. The production of spunbond fabrics is disclosed, for example, in U.S. Pat. No. 4,340,563 to Appel et al., U.S. Pat. No. 3,692,618 to Dorschner et al., and U.S. Pat. No. 3,802,817 to Matsuki et al., all incorporated herein by reference in their entireties. Typically, spunbond fibers or filaments have a weight-per-unit-length in excess of about 1 denier and up to about 6 denier or higher, although both finer and heavier spunbond fibers can be produced. In terms of fiber diameter, spunbond fibers often have an average diameter of larger than 7 microns, and more particularly between about 10 and about 25 microns, and up to about 30 microns or more.
As used herein the term “meltblown fibers” means fibers or microfibers formed by extruding a molten thermoplastic material through a plurality of fine, usually circular, die capillaries as molten threads or filaments or fibers into converging high velocity gas (e.g. air) streams that attenuate the fibers of molten thermoplastic material to reduce their diameter. Thereafter, the meltblown fibers are carried by the high velocity gas stream and are deposited on a collecting surface to form a web of randomly dispersed meltblown fibers. Such a process is disclosed, for example, in U.S. Pat. No. 3,849,241 to Buntin. Meltblown fibers may be continuous or discontinuous, are often smaller than 10 microns in average diameter and are frequently smaller than 7 or even 5 microns in average diameter, and are generally tacky when deposited onto a collecting surface.
As used herein “carded webs” refers to nonwoven webs formed by carding processes as are known to those skilled in the art and further described, for example, in U.S. Pat. No. 4,488,928 to Alikhan and Schmidt which is incorporated herein in its entirety by reference. Briefly, carding processes involve starting with staple fibers in a bulky batt that is combed or otherwise treated to provide a web of generally uniform basis weight. Typically, the webs are thereafter bonded by such means as through-air bonding, thermal point bonding, adhesive bonding, and the like.
As used herein “coform” or “coformed web” refers to composite nonwoven webs formed by processes in which two or more fiber types are intermingled into a heterogeneous composite web, rather than having the different fiber types supplied as separate or distinct web layers, as is the case in a laminate composite material. Certain well-known coform processes are described in U.S. Pat. Nos. 4,818,464 to Lau and 4,100,324 to Anderson et al., the disclosures of which are incorporated herein by reference in their entireties, wherein at least one meltblown diehead is arranged near a chute or other delivery device through which other materials or fiber types are added while the web is being formed. Such other materials or fiber types disclosed in these patents include staple fibers, cellulosic fibers, and/or superabsorbent materials and the like.
As used herein, “thermal point bonding” involves passing a fabric or web of fibers or other sheet layer material to be bonded between a heated calender roll and an anvil roll. The calender roll is usually, though not always, patterned on its surface in some way so that the entire fabric is not bonded across its entire surface. As a result, various patterns for calender rolls have been developed for functional as well as aesthetic reasons. One example of a pattern has points and is the Hansen Pennings or “H&P” pattern with about a 30 percent bond area with about 200 bonds per square inch (about 31 bonds per square centimeter) as taught in U.S. Pat. No. 3,855,046 to Hansen and Pennings. The H&P pattern has square point or pin bonding areas wherein each pin has a side dimension of 0.038 inches (0.965 mm), a spacing of 0.070 inches (1.778 mm) between pins, and a depth of bonding of 0.023 inches (0.584 mm). The resulting pattern has a bonded area of about 29.5 percent. Another typical point bonding pattern is the expanded Hansen and Pennings or “EHP” bond pattern which produces a 15 percent bond area with a square pin having a side dimension of 0.037 inches (0.94 mm), a pin spacing of 0.097 inches (2.464 mm) and a depth of 0.039 inches (0.991 mm). Other common patterns include a high density diamond or “HDD pattern”, which comprises point bonds having about 460 pins per square inch (about 71 pins per square centimeter) for a bond area of about 15 percent to about 23 percent, a “Ramish” diamond pattern with repeating diamonds having a bond area of about 8 percent to about 14 percent and about 52 pins per square inch (about 8 pins per square centimeter) and a wire weave pattern looking as the name suggests, e.g. like a window screen. As still another example, the nonwoven web may be bonded with a point bonding method wherein the arrangement of the bond elements or bonding “pins” are arranged such that the pin elements have a greater dimension in the machine direction than in the cross-machine direction. Linear or rectangular-shaped pin elements with the major axis aligned substantially in the machine direction are examples of this. Alternatively, or in addition, useful bonding patterns may have pin elements arranged so as to leave machine direction running “lanes” or lines of unbonded or substantially unbonded regions running in the machine direction, so that the nonwoven web material has additional give or extensibility in the cross machine direction. Such bonding patterns as are described in U.S. Pat. No. 5,620,779 to Levy et al., incorporated herein by reference in its entirety, may be useful, such as for example the “rib-knit” bonding pattern therein described. Typically, the percent bonding area varies from around 10 percent to around 30 percent or more of the area of the fabric or web. Thermal bonding imparts integrity to individual layers or webs by bonding fibers within the layer and/or for laminates of multiple layers, such thermal bonding holds the layers together to form a cohesive laminate material.
As used herein, “loops” refers to portions of fibers in a nonwoven web material which define an arch, semi-circle or similar configuration extending above the flat length-width plane of the nonwoven web material. Typically, fiber loops will have loop ends which are anchored or secured by bond points.
The present invention provides a process for producing composite nonwoven loop materials suitable for use in hook and loop fastening systems. The present invention further provides nonwoven loop materials. The invention will be described with reference to the following description and Figures which illustrate certain embodiments. It will be apparent to those skilled in the art that these embodiments do not represent the full scope of the invention which is broadly applicable in the form of variations and equivalents as may be embraced by the claims appended hereto. Furthermore, features described or illustrated as part of one embodiment may be used with another embodiment to yield still a further embodiment. It is intended that the scope of the claims extend to all such variations and equivalents.
In one aspect, the process for producing the composite loop materials produces a laminate composite loop material by bonding at least a first nonwoven web layer to a sheet-form elastic substrate layer at spaced-apart locations, to form a precursor composite material which is a laminate of at least the two layers. The nonwoven web layer should include fibers which are inelastic, or at least less elastic than the elastic substrate layer. The inelastic or less elastic fibers are the loop-forming fibers. In another aspect, the process for producing the composite loop materials produces a coform composite loop material by coforming together a first type of fibers, which are elastic, and a second type of fibers, which are either inelastic or at least less elastic than the first fibers, and bonding the coformed web at spaced-apart locations to form a precursor composite material. As mentioned, the inelastic or less elastic fibers are the loop-forming fibers.
In either aspect, the precursor composite is stretched or extended by the application of one or more biasing forces in at least one direction, such as the machine direction or the cross machine direction, or both. During this stretching or extending step, the composite material is extended from its original length or width dimension to a new, extended length which is greater than the original length. The new, longer length should represent an extension distance which is greater than the capability of the loop-forming fibers to elastically recover. In this way, at least some number, and desirably a substantial majority, of the individual loop-forming fibers are permanently deformed or permanently elongated to a new, longer length, at least along a portion of their individual lengths. Then, the biasing or stretching force is relaxed and the composite material is allowed to retract. The composite material retracts or recovers toward its original unextended length due to the elastic stretch and recovery properties of the elastic component, and may, depending on the type of elastic selected and the amount of extension applied, retract substantially to its original unextended length. As the composite retracts to a length less than the extended length, the portions of the loop-forming fibers which were permanently elongated now have additional length or “slack”, which provides for arcs or looped fiber portions capable of extending from the planar surface of the composite material.
An exemplary composite loop material is shown in
In addition, for the purposes of this illustration only a single fiber 130 is shown, and the fiber is shown to lie essentially in a straight line and to be anchored to each adjacent bond point 150. However, one skilled in the art will recognize that due to the random nature of the directional orientation of fibers in nonwoven webs, in practice a given single fiber would be expected to lie along a random path in the x and y plane of the nonwoven web rather than to follow a single straight line as represented in this illustration.
As can be seen in
As mentioned above, due to the random nature of fiber orientation in nonwoven web materials, a given single fiber will typically lie along a random path in the x and y plane of a nonwoven web instead of following a single straight line path as was represented in
As stated above, after the composite has been stretched and retracted at least some number of the individual loop-forming fibers will have been permanently elongated to a new length which is longer than their pre-stretched length. Desirably, in order to provide as many loop elements as possible, a substantial majority of the fibers will have been permanently elongated. However, for a given direction of composite elongation, such as elongation along a line parallel to line MD, there will generally be fibers having substantial portions of their lengths which are largely unaffected by the composite elongation, where, for example, for a given portion along the length of a fiber, the fiber runs between bond points oriented substantially perpendicular to the direction of elongation. As a specific example, in
As mentioned above, the composite nonwoven loop materials may be produced as laminate composite loop materials and coform composite loop materials, and the loop material and the components used in the composite loop material may have a wide range of basis weights. Generally speaking, the basis weight of the loop-forming component fibrous nonwoven web(s) or loop-forming component fibers in a coform composite loop material may suitably be from about 7 gsm or less up to 100 gsm or more, and more particularly may have a basis weight from about 10 gsm or less to about 68 gsm, and still more particularly, from about 14 gsm to about 34 gsm. Other examples are possible. In addition, generally, the basis weight of elastic fibers in the coform composite loop material or of the elastic substrate layer in the laminate composite loop material may be from about 5 gsm or less to about 100 gsm or greater. More desirably, the elastic component of the composite loop material may have a basis weight from about 5 gsm to about 68 gsm, and still more desirably from about 5 gsm to about 34 gsm. Because elastic materials are often expensive to produce, the basis weight of elastic material utilized is desirably of as low a basis weight as is possible while still providing the desired properties of stretch and recovery to the composite loop material.
Suitable laminate composite loop material constructions include one or more sheet-form elastic substrate layers with one or more fibrous layers, the fibrous layer or layers including the loop-forming fibers. As mentioned above, the loop-forming fibers should be either inelastic, or at least less elastic than the elastic substrate layer. The two types of layers are placed in face-to-face relation as a composite and then bonded together at spaced-apart locations to form a bonded laminate composite. Suitable elastic substrate layers include elastic spunbond layers, elastic film layers, and/or elastic meltblown layers. Suitable fibrous layers to provide loop-forming fibers include nonwoven layers as are known in the art, such as carded and airlaid staple fiber webs, and spunbond and meltblown meltspun fiber webs.
The production of each of these types of individual elastic substrate layers and fibrous/loop-forming fiber containing layers is mentioned briefly hereinabove, and well known in the art and therefore will not be discussed here in detail. However, it should be noted that in addition to laminating dissimilar sheet types (such as for example an elastic film/inelastic nonwoven laminate, or elastic meltblown/inelastic spunbond), similar types may also beneficially be laminated together to form the laminate composite. As a specific example, spunbonding processes as are known in the art often employ multiple spinpack and fiber drawing unit (“FDU”) assemblies on the same spunbond machine, wherein a first spinpack/FDU assembly deposits its fibers as a web directly onto the collecting surface, and the second spinpack/FDU assembly deposits its fibers onto the web deposited by the first assembly, thereby producing a spunbond web which is formed as two layers. Such a multi-spinpack spunbonding machine may be beneficially used to produce the composite laminate by extruding elastic fibers for the elastic substrate layer from one spinning assembly and extruding the loop-forming spunbond fibers from another spinning assembly.
It should be noted that for the laminate composite loop material, either or both of the sheet-form elastic substrate layer or the loop-forming fibrous nonwoven web may themselves be multi-layer structures. Particular examples of multilayer laminate construction for the loop-forming fibrous nonwoven web include spunbond-meltblown laminates, spunbond-spunbond laminates, spunbond-carded web laminates, and the like. Examples of laminate construction for an elastic substrate layer include spunbond-elastic layer laminates and carded web-elastic layer laminate. Because elastic layers such as an elastic film layer or elastic meltblown layer may feel tacky to the touch, such “faced” elastic layers may be desirable where the loop material laminate is to be used with the elastic substrate layer in skin contact, so that the nonwoven facing over the elastic layer provides more of a cloth-like feel against the skin.
Where the sheet-form elastic substrate layer for the laminate composite loop material is an elastic film layer, it may be desirable for the film to be breathable. Meltblown and spunbond layers are inherently breathable; that is, meltblown and spunbond layers are capable of transmitting gases and water vapors. Film layers however, generally act as a barrier to the passage of liquids, vapors and gases. An elastic layer which is breathable may provide increased in-use comfort to a wearer by allowing passage of water vapor and assist in reducing excessive skin hydration, and help to provide a more cool feeling. Therefore, where a film is used as the elastic component but a breathable composite loop material is desired, the elastic material used may be a breathable monolithic or microporous barrier film.
Monolithic breathable films can exhibit breathability when they comprise polymers which inherently have good water vapor transmission or diffusion rates such as, for example, polyurethanes, polyether esters, polyether amides, EMA, EEA, EVA and the like. Examples of elastic breathable monolithic films are described in U.S. Pat. No. 6,245,401 to Ying et al., incorporated herein by reference in its entirety, and include those comprising polymers such as thermoplastic (ether or ester) polyurethane, polyether block amides, and polyether esters. Microporous breathable films contain a filler material, such as for example calcium carbonate particles, in an amount usually from about 30 percent to 70 percent by weight of the film. The filler-containing film (or “filled film”) opens micro-voids around the filler particles when the film is stretched, which micro-voids allow for the passage of air and water vapor through the film. Breathable microporous elastic films containing fillers are described in, for example, U.S. Pat. Nos. 6,015,764 and 6,111,163 to McCormack and Haffner, U.S. Pat. No. 5,932,497 to Morman and Milicevic, and in U.S. Pat. No. 6,461,457 to Taylor and Martin, all incorporated herein by reference in their entireties. In addition, multilayer breathable films as are disclosed in U.S. Pat. No. 5,997,981 to McCormack et al., incorporated herein by reference in its entirety, may be useful. Another example of a film which can exhibit breathability is a cellular elastic film, such as may be produced by mixing an elastic polymer resin with a cell opening agent which decomposes or reacts to release a gas that forms cells in the elastic film. The cell opening agent can be an azodicarbonamide, fluorocarbons, low boiling point solvents such as for example methylene chloride, water, or other agents such as are known to those skilled in the art to be cell opening or blowing agents which will create a vapor at the temperature experienced in the film die extrusion process. Cellular elastic films are described in PCT App. No. PCT/US99/31045 (WO 00/39201 published Jul. 06, 2000) to Thomas et al., incorporated herein by reference in its entirety.
As another example, if an elastic film layer is the selected elastic substrate layer but liquid barrier properties are not particularly important or are not desired, the elastic film itself (prior to lamination) or the composite laminated with the nonwoven loop-forming fibers may be apertured or perforated to provide a laminate capable of allowing the passage of vapors or gases. Such perforations or apertures may be performed by methods known in the art such as for example slit aperturing or pin aperturing with heated or ambient temperature pins.
Suitable coform composite loop material constructions include elastic meltblown fibers for the elastic component which are coformed with inelastic (or less elastic) staple fibers, such as may be produced according to the above-mentioned U.S. Pat. No. 4,818,464 to Lau and U.S. Pat. No. 4,100,324 to Anderson et al. by introducing staple fibers into the just-extruded meltblown fibers, by delivering the staple fibers down a chute as the meltblown fibers are being extruded and attenuated. Another exemplary coforming process is described in U.S. Pat. No. 5,350,624 to Georger et al., incorporated herein by reference in its entirety. In U.S. Pat. No. 5,350,624, the coforming process uses multiple meltblown dieheads arranged on either side of the delivery chute. Such a process could be utilized by coforming elastic meltblown fibers with a second (loop-forming) inelastic or less elastic meltblown fibers, and/or by adding loop-forming staple fibers via the delivery chute, and/or by meltblowing elastic fibers from both dieheads while adding loop-forming staple fibers via the delivery chute.
As stated above, other nonwoven web production methods capable of producing a heterogeneous mixture or composite of differing fiber types should also be considered to be coforming production methods. For example, a coformed composite web may be produced by orienting one or more meltblown dieheads at a slight angle to extrude elastic meltblown fibers near the exit of a spunbonding fiber drawing unit (or “FDU”) such that the elastic meltblown fibers intermingle into the loop-forming spunbond fibers just prior to the loop-forming spunbond fibers being deposited onto a collection surface. Alternatively, the spunbond fiber drawing unit may be angled into the extrusion path of meltblown fibers, or spunbond fibers may be deflected into the meltblown fibers after the spunbond fibers exit the FDU. In addition, for the purposes of this disclosure, other known processes as may be used to produce intermingled or heterogeneous fiber type composite webs may be considered coforming processes, for example airlaying and carding where two or more fiber types are used, and hydraulic or mechanical needling where two or more staple fiber types are needled together into a composite or where one or more staple fiber types are needled into a previously formed nonwoven web such as a spunbond, meltblown or carded webs, for example.
Also within this usage of a “coformed” web are composite webs formed by such processes as spunbonding, wherein two types of spunbond fibers are spun and intermingled. Such spunbond intermingled webs may be produced from a single spunbond spinpack and spinneret assembly which is capable of spinning two or more distinct polymers or fiber types separately, such as is disclosed in U.S. Pat. No. 6,164,950 to Barbier et al. Using the method and apparatus disclosed in U.S. Pat. No. 6,164,950, a coform composite loop material may be produced by spinning from the one spinneret a first spunbond fiber type which is elastic for the elastic component, and a second spunbond fiber type for the loop-forming fibers which is inelastic or less elastic than the elastic component fibers. Alternatively, a coformed spunbond web may be spun from multiple spinnerets where the fibers are intermingled at some point prior to being deposited on the collecting surface. For example, the elastic component fibers may be produced by one spunbond spinpack and the loop-forming fibers by a second spinpack, but the fibers from both spinpacks are drawn in the same fiber drawing unit. Alternatively, the separate fiber types may be drawn in separate fiber drawing units, where the fiber drawing units are arranged to have the drawing unit exits close enough together to allow fiber intermingling as the fibers exit the drawing unit and are deposited on the collecting surface. Processes for making coformed spunbond webs are more fully described in U.S. Pat. No. 5,853,635 to Morell et al., and U.S. Pat. No. 5,935,512 to Haynes et al., the disclosures of which are incorporated herein by reference in their entireties.
Polymers suitable for making the fibrous nonwoven webs to be used in the embodiments described herein include those polymers known to be generally suitable for making nonwoven webs such as spunbond, meltblown, carded webs and the like, and include for example polyolefins, polyesters, polyamides, polycarbonates and copolymers and blends thereof. It should be noted that the polymer or polymers may desirably contain other additives such as processing aids or treatment compositions to impart desired properties to the fibers, residual amounts of solvents, pigments or colorants and the like.
Suitable polyolefins include polyethylene, e.g., high density polyethylene, medium density polyethylene, low density polyethylene and linear low density polyethylene; polypropylene, e.g., isotactic polypropylene, syndiotactic polypropylene, blends of isotactic polypropylene and atactic polypropylene; polybutylene, e.g., poly(1-butene) and poly(2-butene); polypentene, e.g., poly(1-pentene) and poly(2-pentene); poly(3-methyl-1-pentene); poly(4-methyl-1-pentene); and copolymers and blends thereof. Suitable copolymers include random and block copolymers prepared from two or more different unsaturated olefin monomers, such as ethylene/propylene and ethylene/butylene copolymers. Suitable polyamides include nylon 6, nylon 6/6, nylon 4/6, nylon 11, nylon 12, nylon 6/10, nylon 6/12, nylon 12/12, copolymers of caprolactam and alkylene oxide diamine, and the like, as well as blends and copolymers thereof. Suitable polyesters include poly(lactide) and poly(lactic acid) polymers as well as polyethylene terephthalate, polybutylene terephthalate, polytetramethylene terephthalate, polycyclohexylene-1,4-dimethylene terephthalate, and isophthalate copolymers thereof, as well as blends thereof.
Many elastomeric polymers are known to be suitable for forming the elastic component of the laminate composite loop material, such as elastic fibers and elastic fibrous web layers and elastic films. As stated above, elastic polymers may also suitably be used for forming the loop-forming fibers. However, if an elastic polymer is used for the loop-forming fibers care should be taken to select the polymer for the loop-forming fibers and the elastic component of the composite loop material such that the loop-forming fibers are less elastic than the elastic component. Thermoplastic polymer compositions may desirably comprise any elastic polymer or polymers known to be suitable elastomeric fiber or film forming resins including, for example, elastic polyesters, elastic polyurethanes, elastic polyamides, elastic co-polymers of ethylene and at least one vinyl monomer, block copolymers, and elastic polyolefins. Examples of elastic block copolymers include those having the general formula A-B-A′ or A-B, where A and A′ are each a thermoplastic polymer endblock that contains a styrenic moiety such as a poly (vinyl arene) and where B is an elastomeric polymer midblock such as a conjugated diene or a lower alkene polymer such as for example polystyrene-poly(ethylene-butylene)-polystyrene block copolymers. Also included are polymers composed of an A-B-A-B tetrablock copolymer, as discussed in U.S. Pat. No. 5,332,613 to Taylor et al. An example of such a tetrablock copolymer is a styrene-poly(ethylene-propylene)-styrene-poly(ethylene-propylene) or SEPSEP block copolymer. These A-B-A′ and A-B-A-B copolymers are available in several different formulations from the Kraton Polymers of Houston, Tex. under the trade designation KRATON®. Other commercially available block copolymers include the SEPS or styrene-poly(ethylene-propylene)-styrene elastic copolymer available from Kuraray Company, Ltd. of Okayama, Japan, under the trade name SEPTON®.
Examples of elastic polyolefins include ultra-low density elastic polypropylenes and polyethylenes, such as those produced by “single-site” or “metallocene” catalysis methods. Such polymers are commercially available from the Dow Chemical Company of Midland, Mich. under the trade name ENGAGE®, and described in U.S. Pat. Nos. 5,278,272 and 5,272,236 to Lai et al. entitled “Elastic Substantially Linear Olefin Polymers”. Also useful are certain elastomeric polypropylenes such as are described, for example, in U.S. Pat. No. 5,539,056 to Yang et al. and U.S. Pat. No. 5,596,052 to Resconi et al., incorporated herein by reference in their entireties, and polyethylenes such as AFFINITY® EG 8200 from Dow Chemical of Midland, Mich. as well as EXACT® 4049, 4011 and 4041 from Exxon of Houston, Tex., as well as blends.
As mentioned, after formation of the elastic component(s) with the loop-forming fiber containing component(s), the laminate composite web or coform composite web should be bonded at spaced-apart locations. Suitable methods for applying spaced-apart bond locations or discrete bond “points” on either the laminate composite loop material or the coform composite loop material include thermal bonding methods as are known in the art, such as the exemplary thermal point bonding methods described herein. Other suitable methods known to those skilled in the art for imparting discrete bonds at spaced-apart locations may also be used, for example by point or drop deposition of adhesive materials, or by ultrasonic bonding. After the laminate composite or coform composite material has been bonded at spaced-apart locations, it should be stretched or extended in one or more directions in order to permanently deform the loop-forming fibers. That is, the loop-forming fibers are permanently deformed by having at least portions of their lengths permanently increased. Then, the composite material is allowed to retract under or due to the elastic recovery force of the elastic component. When the elastic component retracts, the now-elongated loop-forming fibers, which are anchored or secured at the spaced-apart bond locations, can bunch up or flex or bow up away from the flat x-and-y plane of the material, thereby forming loop elements capable of engaging hook members.
Stretching or extending of the composite material may be performed by any method as is known in the art for extending webs. For example, a web may be stretched in the machine direction by passing the web through two or more pairs of driven nipped rollers, wherein an upstream pair of driven rollers is driven at a first velocity, and a downstream pair of driven rollers is driven at a second velocity which is greater than the first velocity. Because the second velocity is greater than the first velocity, the composite material will experience a machine direction tensioning force or biasing force as it travels through the two nips. This machine direction tensioning force will cause the composite material to be stretched or extended in the machine direction. Because the at least one component of the composite material is elastic, when the tension is removed or relaxed the composite will retract toward its original machine direction length.
Machine direction drawing may also be accomplished by a non-nipped roller assembly having multiple driven rollers in a vertical stack, which is referred to as a “machine direction orienter” or MDO unit. The web material travels through the roller stack in an alternating or “S” wrap or “serpentine” wrap fashion, such that the material contacts a first driven roller with one planar material surface, a second driven roller with the opposite planar material surface, a third roller with the first planar material surface again, and so on. Each subsequent driven roller is driven at a speed slightly higher than the previous roller. Still another method for machine direction stretching of a moving web includes passing the web through a nipped pair of rollers having a gear-tooth type surface engraving which creates channels or grooves and high points or teeth in the surfaces of the rollers which run along the longitudinal axis of the rollers. The high points or teeth on one roller fit or match within the grooves of the other roller when the two rollers are nipped.
It may alternatively or also be desirable to stretch/extend the composite material in the cross machine direction, by such methods as tenter frames and grooved rollers. Grooved rollers may be more desirable for cross machine direction extending because nonwoven and film materials may have a tendency to develop longitudinal tears under an applied transverse biasing force. Grooved rollers may be constructed from a series of spaced disks or rings mounted on a mandrel or axle, or may be a series of spaced circumferential peaks and grooves cut into the surface of a roller. A pair of matched grooved rollers is then brought together with the peaks of one roller fitting into the grooves of the other roller, and vice versa, to form a “nip”, although it should be noted that there is no requirement for actual compressive contact as is the case for typical nipped rollers. Grooved rollers as are known in the art are described as imparting an “incremental stretching” because the whole transverse width of a web material may be stretched by what amounts to a large number of small scale stretches (between each peak-to-peak distance) aligned along the transverse or cross machine direction of the web, which are less likely to cause tears than gripping the side edges of a web material and applying a stretching force to the web as a whole.
The overall level of stretching or extending performed on the composite material will depend on a number of factors, including desired amount of permanent loop-forming fiber elongation along the above-mentioned first portions of the fibers, types of polymers selected for the elastic and loop-forming fiber component, and the ability of the components to extend without breaking. Generally, the level of extending should not be so great as to exceed the maximum stretchability of the elastic component, such that its recovery properties are largely diminished. Also, the level of extending should not be so great as to substantially destroy the loop-forming fibers or the fibrous nonwoven web containing the loop-forming fibers, although some fiber breakage is acceptable. In broad terms, the composite may be extended in an amount from about 5 percent of its unstretched dimension to about 300 percent or more of its unstretched dimension. More particularly, the composite may be extended in an amount from about 20 percent of its unstretched dimension to about 200 percent of its unstretched dimension. Still more particularly, the composite may be extended in an amount from about 40 percent of its unstretched dimension to about 150 percent of its unstretched dimension.
The composite loop materials described herein are highly suitable for use as the loop component in a hook and loop fastener system in a wide variety of applications, including uses such as fasteners and closures for medical and health care products such as surgical drapes, gowns and bandages, protective workwear garments such as coveralls and lab coats, and infant, child and adult personal care absorbent products such as diapers, training pants, incontinence garments and pads, sanitary napkins, wipes and the like. Because of the elastic construction components and stretch processing the composite loop materials are inherently extensible and/or elastic, which can provide improved product fit and body conformance attributes. Also, the composite loop material can be provided as a very flexible and drapeable sheet material, compared to typical knitted loops which are often adhered to a stiff backing material to provide anchoring for the knitted loop elements.
In addition, the composite loop material can be initially produced in an unstretched composite state, and the unstretched composite wound up onto a roll for storage or transport, and only converted into the final composite loop material by stretching or extending at the facility that manufactures the product that the loop material is to be a component of. In this case, the loop material may be stored and shipped in the form of the less lofty precursor composite material, which is more convenient because loftier or bulkier (i.e. thicker) webs require more storage space. Also, performing the extending step at the manufacturing facility, just prior to conversion of the loop material into or onto a product, has the added benefit that the loop elements have not been compressed while being stored and transported in a rolled material form.
As stated, the composite loop materials of the invention are highly suitable for use as the loop component in a hook and loop fastener system in a wide variety of applications. The composite loop materials may be used with any suitable hook-type member which is capable of engaging the loop elements. The term “hook” or “hook member” encompasses various shapes or geometries of protuberances that are suitable for engaging into a loop material in order to place or secure a fastener. Exemplary hook shapes include prongs, stems, trees (such as the shapes connoted by “evergreen” and “palm” trees), mushrooms, J-shaped hooks, bi-directional hooks and studs protruding at various angles. Exemplary hook members are readily available commercially from, for example, Velcro USA, Inc. of Manchester, N.H. and from the 3M Company, St. Paul, Minn.
While not described in detail herein, various additional potential processing and/or finishing steps as are known in the art for processing of nonwoven web and film materials may be performed on the composite loop material without departing from the spirit and scope of the invention. Examples of further processing includes such as slitting, treating, aperturing, printing graphics, or further lamination of the composite with other materials, such as other films or other nonwoven layers. General examples of web material treatments include electret treatment to induce a permanent electrostatic charge in the web, or in the alternative antistatic treatments, or one or more treatments to impart wettability or hydrophilicity to a web comprising hydrophobic thermoplastic material. Wettability treatment additives may be incorporated into the polymer melt as an internal treatment, or may be added topically at some point following fiber or web formation. Still another example of web treatment includes treatment to impart repellency to low surface energy liquids such as alcohols, aldehydes and ketones. Examples of such liquid repellency treatments include fluorocarbon compounds added to the web or fibers of the web either topically or by adding the fluorocarbon compounds internally to the thermoplastic melt from which the fibers are extruded.
As a specific example of an embodiment of the foregoing, a coform composite loop material could be produced in the following manner. The coform composite loop material may be constructed of a meltblown elastic component which is coformed with polyethylene-polypropylene sheath-core type staple fibers as the loop-forming fibers. These two components may be coformed together substantially in accordance with the disclosure of above-mentioned U.S. Pat. No. 4,100,324 to Anderson et al. The two components may each be present in the coform composite loop material at a basis weight of approximately 20 gsm so as to produce a composite material having a basis weight of approximately 40 gsm.
To form the elastic meltblown fibers for the elastic component of the coform composite loop material, a commercially available polyethylene elastic polymer, available from The Dow Chemical Company (Midland, Mich.) under the trade name AFFINITY® EG 8200, may be melted by an extruder at approximately 520° F. (about 270° C.) and supplied to the meltblowing diehead and conveyed therethrough to be extruded as molten polymer threads or filaments. As the elastic polymer is extruded from the meltblown diehead, the just-extruded threads or fibers are entrained in and drawn by converging high velocity air streams heated to about 520° F. (about 270° C.) which attenuate the polymer threads to form elastic meltblown fibers.
At the same time, the sheath-core staple fibers, such as polyethylene/polypropylene bicomponent sheath-and-core fibers available from ES Fibervisions of Athens, Ga., may be introduced into the meltblown fiber flowpath by delivering the staple fibers down a delivery chute, to be entrained into the meltblown fibers as they are being drawn in the converging attenuation air streams. Thereafter, the intermingled elastic meltblown fibers and loop-forming fibers staple fibers are collected onto a moving foraminous forming surface to form an integrated elastic meltblown/staple fiber composite web. The composite web may then be transported by the moving foraminous forming surface to a thermal point bonding calender roll assembly, such as the above-described expanded Hansen and Pennings or “EHP” bond pattern to bond the composite web at spaced-apart locations over about 15 percent of its planar surface area.
After bonding, the coformed composite material is stretched in the machine direction by passing the web through two pairs of driven nipped rollers, wherein the first or upstream pair of driven rollers is driven at a first velocity, and the second or downstream pair of driven rollers is driven at a second velocity which is 150 percent of the first velocity. That is, for a first roller pair velocity of about 300 feet per minute (about 91 meters per minute), the second roller pair velocity is about 450 feet per minute (about 137 meters per minute). Because the second velocity is greater than the first velocity, the composite material will experience a machine direction tensioning force or biasing force as it travels through the two nips and be stretched or extended along its machine direction. This machine direction stretching of the coformed composite causes the spaced-apart locations of the bonds along the machine direction to become farther apart.
Because the spaced-apart locations of these bonds anchor the loop-forming staple fibers, those staple fibers and/or portions of the staple fibers traveling a generally machine direction path from bond location to bond location are thereby elongated past their deformation limit, causing them to become permanently elongated. Then, after stretching or extending, the tension is removed or relaxed by rolling the coformed composite up onto a material winding roller which is turning at a linear velocity that is less than that of the second roller pair, for example at about the same linear velocity as the first pair of rollers, to allow the elastic meltblown component of the composite to retract toward its original machine direction length. Those portions of the loop-forming staple fibers which have been permanently elongated between the spaced-apart bond locations will have additional length available to form arcs or loop elements.
As another specific example of an embodiment of the foregoing, a laminate composite loop material could be produced in the following manner. The laminate composite loop material may be formed in a spunbonding operation, wherein the first bank of spunbond fibers are formed from an elastic polymeric composition, and the second bank of spunbond fibers is formed from an inelastic polymeric composition. As an example, an elastic polymer such as the AFFINITY® EG 8185 brand polyolefin plastomer from Dow Chemical of Midland, Mich. may be supplied to a first extruder to be melted at about 120° C. (about 250° F.) and pumped through a first polymer supply pipe to a first spunbond spinneret/capillary assembly to be extruded as a plurality of molten fibers in a curtain. The molten fibers may be quenched with air from an air blower located adjacent the curtain of fibers and the fibers may then be fed through a pneumatic fiber draw unit or aspirator such as is described in U.S. Pat. No. 3,802,817 to Matsuki et al. to draw or attenuate the fibers, that is, reduce their diameter. An endless foraminous forming surface may be positioned below the fiber draw unit to receive the drawn elastic fibers from the outlet opening of the fiber draw unit and a vacuum apparatus may be positioned below the foraminous forming surface to facilitate the proper placement of the elastic fibers onto the forming surface. The rate of extrusion of the elastic spunbond fibers, combined with the speed of the foraminous forming surface, may desirably make the first (elastic) spunbond layer have a basis weight of about 14 grams per square meter.
While the elastic component fibers are being formed in the first spunbond bank, an inelastic polypropylene polymer such as the polypropylene designated 3155 from the ExxonMobil Chemical Company, Houston, Tex. may be supplied to a second extruder to be melted at about 232° C. (about 450° F.) and pumped through a second polymer supply pipe to a second spunbond spinneret/capillary assembly to be extruded as a plurality of molten fibers in a curtain. The molten fibers may be quenched with air from an air blower located adjacent the curtain of fibers and the fibers may then be fed through a second pneumatic fiber draw unit or aspirator such as the above-mentioned draw unit disclosed in U.S. Pat. No. 3,802,817 to Matsuki et al. The second, inelastic spunbond fibers may then exit the fiber draw unit to be deposited on top of the first elastic spunbond fibers, which are on the endless foraminous forming surface. As mentioned above with respect to spunbond bank 1/elastic fibers, a vacuum apparatus may also be positioned below the foraminous forming surface under spunbond bank 2, to facilitate the proper placement of the inelastic fibers. The rate of extrusion of the second, inelastic spunbond fibers, combined with the speed of the foraminous forming surface, may desirably make the second (inelastic) spunbond layer have a basis weight of about 26 grams per square meter, such that the entire laminate composite material has a basis weight of about 40 grams per square meter, and the laminate composite material therefore contains about 65 weight percent of the loop-forming fibers and about 35 weight percent of the elastic layer.
After the two layers of spunbond (elastic from the first spunbond bank, inelastic from the second spunbond bank) have been formed into a laminate construction (that is, the two layers as formed are already in a face-to-face relation), the two layers may be bonded together by a suitable thermal calendering method, such as by use of the HDD pattern mentioned above. After bonding, the laminate composite material is stretched in the cross machine direction by passing the laminate through a pair of nipped grooved rollers. As mentioned above, the grooved roller nip may be formed between spaced circumferential peaks and grooves cut into the surfaces of each matching roller. Then, the grooved rollers may be brought together with the peaks of one roller fitting into the grooves of the other roller, and vice versa, to form a “nip”, although in this example there is no compressive contact between the top of a peak on one roller and the bottom or nadir of a groove on the other roller. The matching or fitting peaks and grooves may desirably be constructed such that the pitch (peak-to-peak distance) is about 4 millimeters. The laminate material will experience a cross machine direction tensioning force or biasing force as it travels through the grooved roller nip and will be stretched or extended along its cross machine direction or transverse axis. This transverse or cross machine direction stretching of the laminate composite causes the spaced-apart locations of the bonds which are primarily aligned along the cross machine direction to become farther apart. Because the spaced-apart locations of these bonds anchor the loop-forming inelastic spunbond fibers, those inelastic spunbond fibers and/or portions of the inelastic spunbond fibers traveling a generally cross machine direction path from bond location to bond location are thereby elongated past their deformation limit, causing them to become permanently elongated. Then, after the laminate composite exits the grooved rolling nip, it retracts under the power of the elastic spunbond layer toward its original cross machine direction width or dimension. Those portions of the loop-forming inelastic spunbond fibers which have been permanently elongated between the spaced-apart bond locations will have additional length available to form arcs or loop elements.
The composite loop materials disclosed herein are highly suitable for use in medical care products, protective wear garments, personal care products and other products or applications utilizing hook and loop attachment or fastening systems. Examples of such products include, but are not limited to, medical and health care products such as surgical drapes, gowns and bandages, protective workwear garments such as coveralls and lab coats, and infant, child and adult personal care absorbent products such as diapers, training pants, incontinence garments and pads, sanitary napkins, wipes and the like. The composite loop materials provide the benefits of ease of storage and transport prior to conversion into a fastener, potentially improved loop element loft after conversion into a fastener, and have enhanced comfort qualities such as superior material drape and flexibility properties, as well as providing a loop material capable of elastic extensibility.
While various patents have been incorporated herein by reference, to the extent there is any inconsistency between incorporated material and that of the written specification, the written specification shall control. In addition, while the invention has been described in detail with respect to specific embodiments thereof, it will be apparent to those skilled in the art that various alterations, modifications and other changes may be made to the invention without departing from the spirit and scope of the present invention. It is therefore intended that the claims cover all such modifications, alterations and other changes encompassed by the appended claims.
|Citing Patent||Filing date||Publication date||Applicant||Title|
|US7875014||Apr 29, 2005||Jan 25, 2011||Kimberly-Clark Worldwide, Inc.||Absorbent garment having a garment shell|
|US8052666||Dec 30, 2004||Nov 8, 2011||Kimberly-Clark Worldwide, Inc.||Fastening system having elastomeric engaging elements and disposable absorbent article made therewith|
|US8080198||Aug 31, 2007||Dec 20, 2011||Avery Dennison Corporation||Elastic diaper component|
|USRE44842 *||Jul 2, 2012||Apr 15, 2014||Aplix, Inc.||Loop material for loop and hook type fastener used in a disposable article or garment|
|WO2008028106A2 *||Aug 31, 2007||Mar 6, 2008||Avery Dennison Corp||Elastic diaper component|
|WO2008028120A1 *||Aug 31, 2007||Mar 6, 2008||Avery Dennison Corp||Stretchable laminate|
|U.S. Classification||442/328, 442/329|
|International Classification||D04H1/00, D04H13/00, D04H3/00|
|Cooperative Classification||D04H3/163, D04H13/007, D04H13/002, Y10T442/601, Y10T442/602|
|European Classification||D04H13/00B5, D04H13/00B2, D04H3/16B|
|Dec 30, 2004||AS||Assignment|
Owner name: KIMBERLY-CLARK WORLDWIDE, INC., WISCONSIN
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:VAN GOMPEL, PAUL THEODORE;HUANG, YUNG HSIANG;REEL/FRAME:016146/0263
Effective date: 20041216