Patent Grant
6869659
This invention relates to loop material, particularly to material to be engaged with hooking members to form a fastening, to its manufacture and use, and to fasteners comprising such loop material.
In the production of woven and non-woven materials, it is common to form the material as a continuous web that is subsequently spooled. In woven and knit loop materials, loop-forming filaments or yarns are included in the structure of a fabric to form upstanding loops for engaging hooks. As hook-and-loop fasteners find broader ranges of application, especially in inexpensive, disposable products, some forms of non-woven materials have been suggested to serve as a loop material to reduce the cost and weight of the loop product while providing adequate closure performance in terms of peel and shear strength. Nevertheless, cost of the loop component has remained a major factor limiting the extent of use of hook and loop fasteners.
To adequately perform as a loop component for touch fastening, the loops of the material must be exposed for engagement with mating hooks. Unfortunately, compression of loop material during packaging and spooling tends to flatten standing loops. In the case of diapers, for instance, it is desirable that the loops of the loop material provided for diaper closure not remain flattened after the diaper is unfolded and ready for use.
We have realized that non-woven fabrics constructed with certain structural features are capable of functioning well for their intended purpose as hook-engageable loop fabrics, while providing particular advantage in regard to expense of manufacture and other properties.
In general, the invention features loop products for hook and loop fasteners, and method of making such loop products.
In one aspect, the invention features a loop product for hook-and-loop fastening, the loop product comprising a non-woven web of entangled fibers, the fibers forming a sheet-form web body stabilized in a condition of at least about 20 percent areal stretch, in which hook-engageable loops extend in clusters from tightened entanglements within the web body, the entanglements being joined together by straightened fibers, the product having a basis weight of less than about 4 ounces per square yard wherein the fibers comprise a blend of relatively higher denier fibers and relatively lower denier fibers.
In another aspect, the invention features a loop product for hook-and-loop fastening, the loop product comprising a non-woven web of entangled fibers, the fibers forming a sheet-form web body stabilized in a condition of at least about 20 percent areal stretch, in which hook-engageable loops extend in clusters from tightened entanglements within the web body, the entanglements being joined together by straightened fibers, the product having a basis weight of less than about 4 ounces per square yard and at least some of the fibers having a fiber denier of less than 3.
Some implementations of these aspects of the invention include one or more of the following features. The majority of the fibers have a fiber denier of 3 or less. At least some of the fibers have a fiber denier of 1.5 or less. The relatively higher denier fibers have a fiber denier of 6 or greater and the relatively lower denier fibers have a fiber denier of less than 6. The relatively lower denier fibers have a fiber denier of 3 or less, e.g., 1.5 or less. The relatively higher denier fibers have a denier of from 2.5 to 3.5 and the relatively lower denier fibers have a denier of from about 1.0 to 2.0.
The web body is stabilized in a condition of at least 10 percent stretch in each of two perpendicular directions. The web body is stabilized in a condition of at least 25 percent stretch in each of two perpendicular directions. The tightened entanglements are present in a density of between about 50 and 1000 entanglements per square inch of web body. The fibers have a tenacity of at least 2.8 grams per denier, e.g., at least 5 grams per denier, more preferably at least 8 grams per denier. The fibers are of a material selected from the group consisting of polyester, polyurethane, polypropylene polyethylene, nylon, homopolymers, mixtures, copolymers, alloys, or coextrusions thereof, natural fibers, and blends thereof. The fibers are a blend of polyester and polypropylene. The loop product has a Gurley stiffness of less than about 300 milligrams. The loop product has a basis weight of less than about 2 ounces per square yard.
The loop product includes polymer filaments entangled among the fibers, the filaments being at least partially melted to bond the web body. The fibers include bicomponent fibers prior to stabilization of the web, the bicomponent fibers including a first polymer that melts during stabilization to provide a stabilizing binder, and a second polymer that does not melt during stabilization. The nonwoven web is stabilized in its stretched state by material adhered to a back surface of the web, e.g., a solidified binder material. The nonwoven web is stabilized in its the stretched state by solidified fibers of low melt polymer. The binder material includes a backing. The binder material includes an impermeable barrier. The binder includes a fire-retardant material.
The loop product further includes a layer adhered to a surface of the nonwoven web opposite the surface from which the loops extend. The layer includes a supporting fabric. The loop product includes a carrier layer laminated to a surface of the nonwoven web opposite the surface from which the loops extend. The carrier layer includes a film. The nonwoven web is laminated to one side of the carrier layer, and the opposite side of the carrier layer is provided with a layer of pressure-sensitive adhesive for application to a surface. The binder forms a backing that is adapted to be welded to a substrate. The binder forms a water-resistant layer. The loop product further includes a resilient layer of foam disposed on a surface of the non-woven web opposite the surface from which the loops extend. The loop product further includes an optically scannable image printed on the loop-carrying surface of the non-woven web. The loop product further includes a layer of resin disposed on a surface of the non-woven web opposite the surface from which the loops extend. The resin layer includes hook projections shaped to engage the hook-engageable loops.
In various aspects, the invention features a loop product including a non-woven web of entangled fibers, the fibers forming a sheet-form web body stabilized with binder in a condition of at least about 20 percent areal stretch, in which hook-engageable loops extend in clusters from tightened entanglements within the web body, the entanglements being joined together by straightened fibers, the product having a basis weight of less than about 4 ounces per square yard.
In one such aspect, the fibers include bicomponent fibers prior to stabilization of the web, the bicomponent fibers including a first polymer that melts during stabilization to provide the binder, and a second polymer that does not melt during stabilization.
In another such aspect, the binder includes a stable foam coating.
In a further aspect, the binder includes a polymer film.
In another aspect, the invention features a loop product including a non-woven web of entangled fibers, the fibers forming a sheet-form web body stabilized with binder in a condition of areal stretch, in which hook-engageable loops extend in clusters from tightened entanglements within the web body, the entanglements being joined together by straightened fibers, the product having a basis weight of less than about 4 ounces per square yard, wherein the fibers include a blend of relatively higher denier fibers and relatively lower denier fibers.
The invention also features methods of making loop products.
In one aspect, the invention features a method of forming a loop product from a generally planar non-woven batt of entangled fibers, the fibers including bicomponent fibers that include a first polymer having a first melting temperature and a second polymer having a second melting temperature that is relatively higher than the first melting temperature. The method includes (a) stretching the batt by at least 20 percent in at least one direction in its plane, thereby producing a stretched web of weight less than about 4 ounces per square yard and having a generally planar web body with hook-engageable loops extending therefrom, a substantial number of fibers of the body being regionally taut in the plane of the web body, and extending in different directions radiating from bases of the loops; and (b) stabilizing the web in its stretched condition by heating the web to a temperature that is between the first and second melting temperatures, causing the first polymer to melt and act as a binder.
In another aspect, the invention features a method of forming a loop product from a generally planar non-woven batt of entangled fibers, including (a) stretching the batt by at least 20 percent in at least one direction in its plane, thereby producing a stretched web of weight less than about 4 ounces per square yard and having a generally planar web body with hook-engageable loops extending therefrom, a substantial number of fibers of the body being regionally taut in the plane of the web body, and extending in different directions radiating from bases of the loops; and (b) stabilizing the web in its stretched condition by applying a stable foam to a surface of the web opposite the surface from which the hook-engageable loops extend.
In a further aspect, the invention features a method of forming a loop product from a generally planar non-woven batt of entangled fibers, including (a) stretching the batt by at least 20 percent in at least one direction in its plane, thereby producing a stretched web of weight less than about 4 ounces per square yard and having a generally planar web body with hook-engageable loops extending therefrom, a substantial number of fibers of the body being regionally taut in the plane of the web body, and extending in different directions radiating from bases of the loops; and (b) stabilizing the web in its stretched condition by extruding a polymer film onto a surface of the web opposite the surface from which the hook-engageable loops extend.
Some implementations of these methods may include one or more of the following features. The batt is retained against shrinking in a perpendicular direction within its plane during stretching. The method further includes, after stretching the batt in the one direction, stretching the batt by at least 20% in the perpendicular direction. Stretching increases the area of the batt by at least 50%.
In yet another aspect, the invention features a method of forming a loop product including (a) forming a nonwoven web having hook-engageable loops extending from a first surface; and (b) extruding a polymeric film onto a second surface of the nonwoven web, opposite the first surface.
The invention also features a method of forming a loop fastener product, including (a) forming a nonwoven web having hook-engageable loops extending from a first surface; and (b) applying a layer of a stable foam onto a second surface of the nonwoven web, opposite the first surface.
If desired, an optically scannable image may be printed on the surface of the web from which the loops extend, and/or an adhesive may be applied to the exposed surface of the stable foam.
The invention also features a loop product including (a) a non-woven web of entangled fibers, the fibers forming a sheet-form web body stabilized with binder in a condition of at least about 20 percent areal stretch, in which hook-engageable loops extend in clusters from tightened entanglements within the web body, the entanglements being joined together by straightened fibers, and (b) a foam layer disposed on a surface of the non-woven web opposite the surface from which the hook-engageable loops extend.
Some implementations may include one or more of the following features. The product further includes an optically scannable image printed on the surface from which the hook-engageable loops extend. The stable foam is water resistant. The product further includes a layer of adhesive disposed on an exposed surface of the layer of stable foam.
In a further aspect, the invention features a loop product including (a) a non-woven web of entangled fibers, the fibers forming a sheet-form web body stabilized with binder in a condition of at least about 20 percent areal stretch, in which hook-engageable loops extend in clusters from tightened entanglements within the web body, the entanglements being joined together by straightened fibers, and (b) an optically scannable image printed on a surface of the non-woven web from which the hook-engageable loops extend.
By “hook-engageable” and similar terms used above and throughout this specification, we mean that the loop material defines openings of size adequate to receive the tip or head portion of a male fastener element (such as a hook-shape or mushroom-shape element, for instance) for forming a fastening, and that the openings are exposed and extended for engagement.
By the word “entanglements” we mean that the nodes at which a multiplicity of fibers are intertwined in the non-woven web. These entanglements may be relatively loose, as formed directly by a needling process, for instance, or tightened after formation of the entanglements. By the word “knots” we mean entanglements that have been tightened by applying tension to their intertwined fibers in at least one direction in the plane of the web, and remain in an at least partially tightened state.
By “stabilized”, we mean that the web is processed to generally maintain its planar dimensions. In other words, a web “stabilized” in a stretched condition will generally maintain its stretched dimensions and not significantly relax or stretch further under conditions of normal use. One way of “stabilizing” the web, for instance, is by solidifying binder at a significant proportion of its entanglements.
Other features and advantages of the invention will be apparent from the description and drawings, and from the claims.
Referring first to
As shown in
The knots themselves are fairly tight, made up of several monofilament fibers, and are interconnected by the taut fibers seen running between them. In between knots, in this embodiment the thin fiber mat is not very dense and is sheer enough to permit images to be readily seen through it. In other embodiments, as will be discussed below, the fiber mat may be relatively dense and opaque. For low cost applications, the fabric preferably weighs less than about 2 ounces per square yard (68 grams per square meter).
In this particular embodiment, the fibers of the mat are held in their taut, straightened condition by a water-based, acrylic binder applied to the side of the mat opposite the loops to bind the mat fibers in their taut condition to stabilize the areal dimensions of the fabric, and to secure the loops at their associated knots. The binder generally ranges between 20 and 40% of the total weight of the fabric and in the presently preferred embodiments accounts for about one third of the total product weight. The resulting fabric is dimensionally stable and strong enough to be suitable for further processing by standard fabric-handling techniques. The fabric also has a slight stiffness, like a starched felt, which can be mitigated by softeners or mechanical working if desired.
The schematic view of
Near the center of
The individual fibers of loop fabric 12 have low denier and substantial tenacity (i.e., tensile strength per unit diameter) to work with very small hooks such as those illustrated in FIG. 1. Fibers with tenacity values of at least 2.8 grams per denier have been found to provide good closure performance, and fibers with a tenacity of at least 5 or more grams per denier (preferably even 8 or more grams per denier) are even more preferred in many instances. In general terms for a loop-limited closure, the higher the loop tenacity, the stronger the closure. The fibers of fabric 12 of
The loop fiber denier may be chosen with the hook size in mind, with lower denier fibers typically selected for use with smaller hooks. However, other performance and aesthetic criteria may also influence the selection of loop fiber denier, as will be discussed below.
As an alternative to round cross-section fibers, fibers of other cross-sections having angular surface aspects, e.g. fibers of pentagon or pentalobal cross-section, can enhance knot tightening for certain applications. Regardless of the particular construction of the individual fibers, they are selected to have a surface character that permits slippage within the knot-forming entanglements during tightening so as to enable stretching the batt without undue fiber breakage.
Referring to
As seen in
Importantly, the density of clusters in the plan view is very low (FIG. 2), leaving sufficient room between the “branches” of neighboring trees to accommodate hooks and deflected loop material during engagement. By leaving adequate room between neighboring loop trees, the heads of many of the hooks of a mating material extend down to the base of the loop material during engagement, without flattening the loop structures. This high penetration rate helps to provide a high engagement rate as the penetrating hooks grab loops as a result of very small relative shear motion between the hooks and the loops while the loop forest is thus penetrated.
Accumulations of solidified binder 21 can be seen in the knots in the highly magnified plan view of FIG. 3A. Applied in liquid form in this example, preferably before the knots are tightened, the binder contributes to securing the loops against being pulled out of the web.
Referring back to
In addition to being advantageously thin, loop fabric formed according to the new principles is particularly flexible. Flexibility can be very important in some fastener applications, especially when the fastener must flex during use, as when used on an article of apparel. In such instances, the loop product of the invention should have a bending stiffness of less than about 300 milligrams, preferably less than about 100 milligrams, as measured with a Gurley stiffness tester. More details on the use of Gurley stiffness testers can be found in Method T 543 OM-94, published in 1984 by the Technical Association of Pulp and Paper (TAPPI).
Various synthetic or natural fibers may be employed in the invention. In some applications, wool and cotton may provide sufficient fiber strength. Presently, thermoplastic staple fibers which have substantial tenacity are preferred for making thin, low-cost loop product that has good closure performance when paired with very small molded hooks. For example, polyolefins (e.g., polypropylene or polyethylene), polyesters (e.g., polyethylene terephthalate), polyamides (e.g., nylon), acrylics and mixtures, alloys, copolymers and coextrusions thereof are suitable. Polyester is presently preferred. Polypropylene is desirable due to its relatively low density, allowing a greater amount of fiber per unit weight, its flexibility, and its weldability to polypropylene products such as the outer covering of diapers. However, polypropylene is incompatible with many binders, so in some cases blends of polypropylene and polyester may be preferable to polypropylene alone.
Relatively low denier fibers, e.g., 3 denier or less, and blends of different denier fibers, may provide advantageous aesthetic and performance properties.
Generally, smaller fiber deniers increase the fiber density per unit weight of the fabric, resulting in greater softness and opacity. Greater opacity improves the aesthetics of the fabric and facilitates printing on the fabric, particularly of detailed information such as optically scannable images, e.g., bar codes (see, e.g., FIG. 8). The reduced porosity of the fabric may also allow the fabric to be moved by vacuum transfer, a technique that is often used in labeling equipment. The higher fiber density also generally results in a more uniform web of fabric, reducing product inconsistency.
More fiber per unit weight also generally translates to more loops available for engagement with hooks, which tends to improve the performance of the product, allowing more closure cycles to be obtained without excessive damage to the fabric, and providing better peel strength. Fiber deniers of from 1 to 3 will generally provide these benefits.
Smaller fiber deniers may also result in a higher knot density, providing stronger anchoring of the loops. Moreover, at smaller fiber deniers the loop trees will tend to contain more fibers per tree, resulting in bushier trees and better surface coverage with hook engageable loops.
Blends of fibers of different deniers also provide improved properties. Fabrics containing blends of 3 denier and 1.5 denier fibers, for example, have been found to provide significantly better peel strength, shear strength and opacity than fabrics containing all 6 denier fiber or all 3 denier fiber. Fabrics made with these blends also have a “plushier”, softer feel. Many other different blends of fiber deniers may be used, including blends of relatively high (6 or greater) denier fibers with relatively low denier fibers. The preferred ratio of the different denier fibers can be determined empirically, depending on the properties that are required for a particular application. Ratios of 3 denier fibers to 1.5 denier fibers of from 1:3 to 3:1 have been found to provide good properties.
The fiber density generally is inversely proportional to the fiber denier, in a linear relationship. Thus, a loop product containing all 1.5 denier fibers would have about twice the fiber density of a loop product containing all 3 denier fibers, and about four times the fiber density of a loop product containing all 6 denier fibers. The approximate fiber density of blends of different denier fibers can be calculated based on this relationship.
For a product having some electrical conductivity, a small percentage of metal fibers may be added. For instance, loop products of up to about 5 to 10 percent fine metal fiber, for example, may be advantageously employed for grounding or other electrical applications.
Various binders may be employed to stabilize the fabric. By “binder” we mean a material within the mat (other than the fibers forming the main fastener loops) that secures the loop fibers at associated knots. In some applications, the binder is an adhesive.
In other applications, the binder is in the form of fibers of low-melt polymer dispersed throughout and entangled within the fabric. These low-melt fibers are melted to wet the knot-forming entanglements and then cooled and solidified to secure the loops and stabilize the fabric.
Similarly, the fibers used in the fabric may be bicomponent fibers, including both a high-melt and a low-melt polymer, the low-melt polymer being melted to secure the loops and stabilize the fabric. In this case, the low-melt polymer is generally provided as an outer sheath, surrounding a core of high-melt polymer that remains intact after the low-melt polymer has melted to act as a binder. Preferably the inner core makes up about 60 to 80% of the total volume of the bicomponent fiber. The low-melt and high-melt polymers may be different grades of the same polymer, or different types of polymers. Suitable bicomponent fibers are commercially available, for example from KoSa, Charlotte, N.C., under the tradename “CELBOND.” It is generally preferred that the low-melt polymer have a melting temperature of less than 120° C., and that the high-melt polymer have a melting temperature of greater than 23° C., but these temperatures will vary depending on the processing temperatures used to stabilize the web.
In some embodiments, the binder may be a stable foam, as will be discussed below.
The binder preferably fully penetrates and permeates the interstices between individual fibers in the entanglements of the mat. When employing a liquid binder, the binder is preferably selected to have a sufficiently low viscosity and surface tension to enable it to flow into the untightened (or tightening) entanglements. In the embodiments in which the entanglements are subsequently tightened (such as the loop product shown in FIG. 2), this selected distribution of the fluid binder helps to secure the knots with minimal stiffening of the overall product and without requiring substantial amounts of binder.
In any event, the amount and penetration of the binder should be selected to avoid substantial interference with the desired hook-engaging function of the loops while adequately stabilizing the mat and securing the loops against being pulled from their associated entanglements. For use in applications in which the loop product may come in direct contact with sensitive skin, such as in diapers, the amount and type of binder should also be selected to be biocompatible to avoid skin irritation. Formaldehyde-free binders, for instance, are preferred. As irritation can be aggravated by stiffness, preferably only enough binder to perform the above functions is applied. In some applications, for instance those in which the loop product is directly adhered to a supporting fabric and which does not require substantial fastener strength, the loop product may be provided without a binder.
In important instances, the binder also includes an organic or inorganic fire-retardant, such as antimony oxide, zinc borate, aluminum trihydrate or decabromobiphenyl oxide.
The specific loop product 12 of
For instance, a hook-and-loop product may be formed by ultrasonically welding a piece of the loop material 12 of
Suitable methods for forming such a laminated product are described, e.g., in WO 99/11452, published Mar. 11, 1999.
One of the underlying principles embodied in the formation of self-erecting loop trees is that pulling on a tangled bunch of fibers will form knots. This phenomenon is true with regard to continuous fibers (as any fisherman knows) as well as to bunches of short fibers tangled sufficiently to form a coherent mass. Simply stretching a tangled mass of fibers is insufficient to form an adequate number of erect loop trees, however. The formation of an erect structure of the proper height involves the tightening of adjacent fibers within the plane of the base of the mat about multiple tree-forming fibers at two spaced-apart points along each tree-forming fiber, which themselves remain untightened between such spaced-apart points.
In preparation for needling, batt 124 is gradually compressed in a tapered nip between floor apron 122 and a moving overhead apron 138 to reduce its thickness to about one inch. A relatively thin, low density batt can thus be produced.
Needling of batt 124 is performed in multiple, sequential needling stages in order to provide a very high density of needle penetrations without destroying the low density batt. In the presently preferred method felting needles are employed having fiber-engaging barbs on their sides. Needle punching gives the batt cohesion. The needle barbs pull fibers from one layer of the batt through other layers, entangling the fibers from different layers that are oriented in different directions. The resulting entanglements hold the batt together.
From floor apron 122, the batt is passed to a first needle loom 140 with two needling stations 142 and 144 having rows of notched (i.e., barbed) needles. Needling station 142 needles the batt of staple fibers from its upper surface at a density in the range of 100 to 160 punches per square inch (15 to 25 per square cm). In this embodiment, the batt was needled at a density of 134 punches per square inch (21 per square cm). Subsequently, needling station 144 needles the once-needled batt a second time, with needles that penetrate the batt from its upper surface at a density in the range of 500 to 900 punches per square inch (78 to 140 per square cm) to produce a needled batt 146. In this example, the second needling is at a density of 716 punches per square inch (111 per square cm). We refer to the operation of loom 140 as the first needling stage. Additional information on needling processes can be obtained from the Association of the Nonwoven Fabrics Industry (INDA) of Cary, N.C., which publishes the INDA
Nonwovens Handbook
After the first needling stage, needled batt 146 is passed between drive rolls 148 and into a J-box accumulator 150 which, besides holding a bank of batt to accommodate variations in processing rates, allows the needled batt to relax and cool before entering the second needling stage. Alternatively, the needled batt 146 may be spooled after the first needling stage, with subsequent operations performed on a second line. If materials and conditions allow, the needled batt may be passed directly from the first needling stage to the second needling stage without accumulation, but care should be taken to ensure that the batt is sufficiently cool and relaxed to withstand the second needling stage.
As a result of the needle punching, the fibers of the batt become highly randomized and chaotic. However, the underlying pattern of alternating diagonals remains unchanged, although obscured.
From J-box accumulator 150, needled batt 146 is pulled through a guider/spreader 152 (of, e.g., the one-over-two configuration) to properly apply light tension to the batt as is customary for needling, without significant stretching of the batt. It then passes through a second needle loom 154 for a second needling stage. The operation of this second stage is referred to “super needling”, as it is a very dense secondary needling operation and produces many loops of substantial loft. Loom 154 has a single needling station 156 in which needled batt 146 is needled from the lower side to produce high-loft loops extending from the upper side. To produce such loops, the sharp tips of the notched needles of loom 154 are extended a substantial distance (e.g., about ¼ inch or 6.3 mm) beyond the thickness of the batt in the opposite direction as the needles of the first needling station, pushing individual fibers away from the bulk of the batt to form upstanding loops. When the needles retract, the loops remain. The loops may be formed of fibers that originally lay on the opposite side of the batt, or from fibers drawn from the middle of the batt. In either case, the needles drag fibers out of the batt and leave them extending from the bulk of the batt as loops which give one side of the super-needled batt a fuzzy appearance.
This super-needling process does not require special needling bedplates or supporting brushes into which the needles extend, such as are employed in structured or random velour looms, although such techniques may be employed to advantage, e.g., where large loops are desired for use with large hooks. The super-needling is primarily characterized as an extremely dense needling, on the order of about 1000 to 2000 punches per square inch (155 to 310 per square cm), or preferably about 1400 punches per square inch (217 per square cm). Standard barbed needles are employed, such as triangular section 15×18×42×3 C222 G3017 felting needles from Groz-Beckert. During this secondary needling operation, individual fibers of the batt are pushed through the loop side of the batt to produce loose, relatively lofty loops. Together, these loops give the loop side of the super-needled batt a fuzzy appearance and feel. Too much extension of the individual loop fibers at this point can cause them to break during subsequent stretching, so the distance the needles extend through the batt is selected in consideration of the denier and tenacity of the fibers used. We have found that extending the needles about ¼ inch (6.3 mm) beyond the batt works well for 6 denier fibers with a tenacity of about 3.5 grams per denier.
Needle loom 154 may include an additional, second needling station (not shown). After producing high-loft loops extending from one surface, the batt is super needled in the other direction to produce loops extending from its other surface, such that both sides have extended loops.
After leaving loom 154, super-needled batt 160 is split into two running 45 inch (114 cm) widths and spooled on rolls 162. As shown in
Other suitable needling techniques are described in WO 99/11452.
The batt following super needling has a fair amount of loft and resiliency, with the loops and other fibers of the batt forming loose, gentle arches between entanglements. At this point the batt is very flexible, and the density of fibers gradually decreases away from either side of the material. At first glance, it can be difficult to tell which side has been super-needled, if only one side has been subjected to that action. Batt 160, in this example, has an overall thickness, including loops, of about {fraction (3/16)} inch (4.8 mm) and a weight of between about 2 and 4 ounces per square yard (68 and 135 grams per square meter).
Referring to
From guider 168 the batt passes through a tension controller 176 that maintains a desired tension in the batt through the subsequent binder application process. Controlling the difference between the speed of tension controller 176 and downstream drive rolls 202 applies a desired amount of machine direction stretch to the batt prior to cross-machine stretching. In some cases, no substantial machine direction stretch is purposefully applied, any noted machine direction lengthening being due only to minimal web processing tension in the supply batt. In other cases, machine direction stretch is purposefully induced by running drive rolls 202 faster than tension controller 176.
In the embodiment in which batt 160 has been super-needled to produce loops extending from only its front side 188, batt 160 is next passed through a coating station 190 in which a foamed, water-based adhesive 192 (i.e., a water-based adhesive, whipped to entrain air) is applied to the back side 194 of the batt across its width.
Referring also to
Alternatively, the foam may have a thicker consistency, more like shaving cream, to further reduce the penetration into the batt and form more of a distinct resinous backing. A non-collapsible (i.e., stable) foam of urethane or acrylic, for instance, is useful to produce a radio frequency-weldable backing which functions as a water barrier. Such a product has particular application to disposable garments and diapers.
The stable foam backing also reduces the air permeability of the web, which facilitates vacuum transfer. Vacuum transfer may be used advantageously to apply the closure to a finished product, e.g., a diaper tab to a diaper.
Also, because the stable foam layer reduces the permeability of the web, the web generally has a more substantial appearance, and greater opacity. If desired, the stable foam coating can include a colorant, to provide the finished product with an aesthetic color. The stable foam layer also enhances the printability of the loop material, by providing a more opaque background and a relatively continuous ink-receptive surface. Printing may be performed on either the loop-carrying side of the loop material or the back of the stable foam layer, with good results. Thus, the loop material may be printed with decorative designs, product information, or an optically scannable image such as a bar code.
In addition, the stable foam layer provides a surface to which adhesive can be applied, to adhere the finished product to a desired substrate or object. If desired, the permeability of the stable foam layer can be adjusted so that there will be minimal or no penetration of adhesive through the stable foam layer into the loop-carrying portion of the finished product. In applications in which a purchaser of the loop material will apply an adhesive to the material, the presence of a stable foam layer facilitates application of the adhesive by minimizing the need for the purchaser to adjust his process to prevent adhesive strike-through.
A suitable applicator for applying a stable foam to the web is commercially available from Gaston County Environmental Systems, Stanley, N.C., under the tradename “GASTON COUNTY CFS”. Suitable polymers for use as stable foams include textile polymers such as those commercially available from B. F. Goodrich under the tradenames HYCAR, HYSTRETCH, VYCAR and SANCURE. The use of a stable foam in such an applicator allows a very thin layer of a coating to be applied with a uniform, consistent thickness.
Generally, the wet (as applied) thickness of the foam is from about 0.015 inch to 0.250 inch, and the dry (final) thickness of the foam is from about 0.125 inch to 0.315 inch. The amount that the thickness will change during drying will depend on the wet thickness, with thicker coatings experiencing greater changes in thickness. The shrinkage in the coating is predominantly caused by breaking of the foam bubbles. The degree to which the bubbles break during drying will depend on a number of factors, including surface tension and the size and number of bubbles. If thicker coatings are desired, a bubble stabilizer can be added, to reduce breakage of the bubbles.
It is important that the binder (e.g., adhesive 192) not interfere with the loop-forming portions of the fibers on the front side 188 of the batt. It is not necessary that the knot bases be completely covered by binder; it is sufficient that they be secured by the binder in the finished product to stabilize the fabric against significant further stretching and to strengthen the bases of the loops. Preferably, the binder is at least partially in liquid form to wick into the entanglements before and while they are subsequently tightened during stretching. The capillary action of the liquid binder is such that examination of the finished product shows that the binder is almost exclusively at the knots of the web (at the base of the loops, for instance), and therefore does not tend to adversely affect either the functionality of the free-standing loops or the flexibility of the web.
After leaving coating station 190, the material is subjected to stretching in the plane of the web. In the presently preferred case the web is wound through variable speed drive rolls 202 and onto a tenter frame 204 for cross-machine stretching (i.e., stretching in the cross-machine direction). The speed of drive rolls 202 is adjustable, with respect to both tension control 176 and the rails 206 of the tenter frame, to cause a predetermined amount of machine direction stretch in the batt, either between tension control 176 and drive rolls 202, or between drive rolls 202 and frame rails 206, or both. In some embodiments no permanent machine direction stretch is applied, but the batt is nevertheless held in tension to control adhesive penetration and maintain proper frame rail pin spacing. In other embodiments the batt is generally stretched, in total, between about 20 percent and 50 percent in the machine direction before tentering.
As it enters tenter frame 204, the 45 inch wide batt 160 is engaged along its edges by pins of frame rails 206 that maintain the machine-direction dimension of the material as it is stretched in the cross-machine direction. The spacing (of, e.g., about {fraction (3/16)} inch or 4.8 mm) between adjacent pins is maintained throughout the length of the tenter frame, such that no additional machine-direction stretch is applied. Due to the needling, batt 160 should have enough tensile strength to be properly engaged by the rail pins and withstand the subsequent cross-machine stretching.
Tenter frame 204 has a tapered section where the rails 206 separate at a constant, adjustable range rate over a machine-direction length of about 10 feet (3 meters) to a final width, which can range from 45 inches (114 cm) to about 65 to 69 inches (165 to 175 cm). This equates to a cross-machine stretch, in this particular embodiment, of about 50 percent. In general, to take advantage of the economics that can be realized according to the invention, the batt should be stretched to increase its area by at least about 20 percent (we call this “percent areal stretch”), preferably more than about 60 percent areal stretch and more preferably more than about 100 percent areal stretch, to increase the area of the product while tightening the binder-containing entanglements of the batt that contribute to improvement in the strength of anchorage of the individual loops. We have found that in some cases the super-needled batt can be stretched, by employing the above method, at least 130 areal percent or more and provide very useful hook-engaging properties. The more the stretch, the greater the overall yield and the lighter in weight the final product. Even greater overall cross-machine stretch percentages can be employed, for instance by using multiple tentering stages in situations wherein the batt is constructed to withstand the stretch and still be able to reasonably engage hooks. In one instance, the super-needled batt described above was stretched from an initial width of 45 inches (114 cm) to 65 inches (165 cm), softened (by adding a softener), slit to a 45 inch (114 cm) width, stretched a second time to a 65 inch (165 cm) width before applying a binder, and still had useful, hook-engageable loops. In some cases final product widths of 6 to 8 feet (1.8 to 2.4 meters) or even much more can be achieved.
In one embodiment, the non-woven web starting material used to manufacture the loop component is a fairly dense, needle punched, non-woven web of fibers lying in an apparently chaotic and tangled manner. One side, the “fuzzy side”, has an excess of large, loose loop fibers created during a second needle punching process. The web is first stretched to 130 percent of its initial length in the machine direction. This stretching results in necking—the material narrows to 80 percent of its initial width, from 45 inches (114 cm) to 36 inches (91 cm). It is then coated with a binder. Next, it is stretched to 175% of its necked width, from 36 inches (91 cm) to 63 inches (160 cm). During this process the material becomes much more sparse, with spider-like clusters of fiber (see bases B of
The amount of needling, the starting basis weight, and the stretchability of the batt are all related. Within a range of basis weight and needling density useful for creating a stretchable web, increasing either the basis weight of the starting batt or the needling density will decrease the amount of stretch that can be applied to the needled batt. As is known in the art, there is a minimum basis weight required for effective needling, below which an insufficient number of entanglements will be formed by the needling to produce a coherent web which can be handled without falling apart. At the other end of the spectrum, too high of a basis weight can result in needle breakage and/or fiber breakage during needling. To produce the very light, thin loop material enabled by the invention, the basis weight of the starting batt and the needling density should be selected to permit a fair amount of stretch of the needled material, as it is the stretching that thins the needled product and increases its yield. In other words, if the needled product is to be stretched, the needling process should leave a substantial proportion of the base fibers slack, and their entanglements loose.
The denier of the fibers used may also affect stretchability in the cross-machine direction. Generally, if the variables discussed above are kept constant, as denier decreases stretchability in the cross-machine direction will also tend to decrease. Generally, this tendency may be offset by changing the basis weight and/or needling density as discussed above.
The “loop trees” (see FIG. 3), which do not distinctly appear in the pre-stretched batt, obtain their final form as fibers of the ground portion of the web are pulled and the entanglements beneath them are tightened during stretching to form knots. As the batt is stretched, the tension in the taut fibers of the web forces some of the loop trees to stand erect, such that the overall thickness of the stretched batt (with functional loops) can actually be greater than the unstretched batt. To extend the horticultural analogy, the homogeneous thicket of the loop surface of the unstretched batt becomes the orchard of spaced clusters of the stretched product. Although the loop trees or loop formations correspond to locations where the batt was punched during super-needling, the resulting “orchard” of loop formations does not exhibit the same ordered pattern, after the web is stretched, as might be anticipated by the pattern of punches of the needling process. We believe that the arrangement of loop formations is randomized during the stretching process, as distances between entanglements change as a function of the properties, direction and number of the fibers connecting various nodes. The resulting product has no apparent order to the arrangement of loops extending from its surface.
Despite the relatively wide loop spacing that is achieved, the loops, after curing of the binder, are found to be so strongly anchored and so available for engagement by the hooks, that a web unusually treated according to these techniques can perform in an excellent manner despite having a gossamer appearance.
Referring back to
In another embodiment, hook-engageable loops are formed on both sides of the web by needling, by the super-needling techniques acting on staple fibers that have been described, or by other known techniques. After forming the loops the web is passed through a bath of binder. In some cases, where the loops are relatively stiff and the binder is of suitably low viscosity, after removal from the bath the binder drains from the loops and the loops, by their own resiliency and stiffness resume their free-standing stance while capillary action retain the binder in the center of the fabric. The web is then subjected to stretching and curing as above.
In other instances, as where the loop material is less stiff, auxiliary means are employed to remove excess binder after passing through the bath, as by passing the fabric through a nip of squeeze rolls, or by subjecting both sides of the fabric to an air knife, or by blotting followed, in each case for instance by blowing air or otherwise loosening the loops and causing them to stand upright.
Other embodiments carrying hook-engageable loops on one or both sides, and incorporating heat-fusible binder fibers or other heat-fusible binding constituents, are bonded by non-contact means such as by blasts of hot air directed at both sides of the fabric at temperatures sufficient to melt the heat-fusible binding material and lock the fabric structure in its stretched condition.
Heat fusible fibers or other material colored black or otherwise adapted to absorb radiant heat, may be activated by radiant heaters to bind the ground portion of the fabric following stretching. Care must be taken, in such instances, to avoid mitigation of the engagement properties of the free-standing loops.
Referring back to
Alternatively, heated rolls, “hot cans” or platens may be employed to stabilize the back side of the fabric in its stretched condition. This embodiment does not require a coating or adhesive when using thermoplastic fibers, as the fibers are locally fused together by heat. Cooled rolls engage the loop side of the fabric during stabilization, to prevent damage to the hook-engageable loops.
It will be understood that the above-described stretching technique can be employed to advantage on other stretchable, loop-defining non-woven webs. Thus, in its broadest aspects, the invention is not to be limited to the use of needled webs. Webs formed by hydro or air current entanglement can, for instance, be employed.
In most cases where significant strength performance is desired, it is preferable to employ non-woven materials formed of staple fibers to take advantage of their drawn, molecular oriented structure, or other fibers of the substantial tenacity. We have found that loops formed of crimped staple fibers work particularly well, as the crimps of the fibers help to hold the loops apart from each other and exposed for engagement, as well as permitting greater hook penetration of the “forest” of loop structures. The crimps can also assist in the formation of the loop structures, as they form snag points for enhancing the entangling of the base fibers.
Inter-fiber friction is known to be important for efficient needling. Because of its higher friction, polyester is considered to be a better fiber material for needling than polyethylene, even though polyethylene can provide a better hand for some applications. For products tightened by stretching rather than hyper-needling, however, lower needling efficiencies can be tolerated, enabling the use of low-friction, good hand materials like polyethylene.
Besides being useful for loop-forming fibers, crimped or variable thickness fibers are also useful for forming the stretched base web. The crimps or thickness variations help to entangle base fibers as they slide against one another during tightening. As known in the art of needling, crimps can also improve needling efficiency. A spun fiber can be effectively “crimped” by subjecting the spun fiber as it leaves its nozzle to a series of transverse air blasts from one or more directions. An hourglass thickness variation can be produced in spun fibers by modulating the ambient air pressure just outside the opening of the nozzle.
As mentioned above, in certain applications the stretched is advantageously secured to a supporting material in its stretched condition.
The complete disclosures of U.S. patent application Ser. No. 09/262,159, filed Mar. 3, 1999, and U.S. patent application Ser. No. 08/922,292, filed Sep. 3, 1997 are incorporated herein by reference.
Other embodiments are within the scope of the following claims. For example, rather than using a liquid adhesive or foam as a binder, as discussed above, the web may be stabilized by applying a polymer film to the web, e.g., by lamination or extrusion.
A standard packaging film extruding process (slot die process) can easily be adapted so that the film-extruding die directly coats a surface of the web to stabilize the web. For example, as shown in
A suitable lamination process includes directing a pre-formed resin film along side and parallel to the back side (the non-loop-carrying side) of a web of loop material. The film and web are then run through a hot can nip process which melts the resin film directly onto the back surface of the loop material.
In addition to stabilizing the web, the polymer film can be selected to also act as a bonding layer, allowing the loop material to be easily bonded to a substrate. Thus, the film may be used as a tie layer, which enhances the adhesion between two dissimilar surfaces, for example adhesion of nylon or polyester fibers in the non-woven web to a polyethylene substrate, e.g., a polyethylene bag.
The film may be non-porous, to facilitate vacuum transfer and/or provide barrier properties, or can be porous if desired. The film may be printed or embossed after it is applied, and may be used to provide features such as tagging or anti-theft circuitry. The film may be as thin as 0.001″ if desired. This process can also be used to apply a polymer film to other types of nonwoven loop materials, as well as the loop materials described above.
| Number | Date | Country | Kind |
|---|---|---|---|
| PCTUS98/18401 | Sep 1998 | WO | international |
This application is a continuation-in-part of U.S. patent application Ser. No. 09/996,618, filed Nov. 27, 2001, now U.S. Pat No. 6,783,834 which is a continuation of U.S. patent application Ser. No. 09/262,159, filed Mar. 3, 1999, now U.S. Pat. No. 6,329,016, which is a continuation-in-part of U.S. patent application Ser. No. 08/922,292, filed Sep. 3, 1997, now U.S. Pat. No. 6,342,285, and which also claims the benefit of PCT Patent Application US98/18401, filed Sep. 3, 1998 and designating the United States.
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| Number | Date | Country | |
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| Child | 09996618 | US |
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| Child | 10125679 | US | |
| Parent | 08922292 | Sep 1997 | US |
| Child | 09262159 | US |
