Abstract:
Hook-engagable loop materials are provided, which include high bulk yarns. Closure strips employing such materials, and methods of making such materials are also provided.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application is a continuation of PCT/US01/17220, filed May 25, 2001, and also claims priority from U.S. Provisional 60/207,516, filed May 26, 2000. 
     
    
     
       BACKGROUND  
         [0002]    This invention relates generally to touch fasteners and engageable loop members for such fasteners, and more particularly to their application in products such as closure strips for bags and flexible packaging, and to methods and apparatus for their manufacture.  
           [0003]    For many disposable packaging applications, low-cost flexible closures are needed. Some reclosable commercial closures used for bags and the like feature interengaged profile zipper seal technology. Other closures, both single-use and reclosable, can feature various adhesives, twist ties, clip strips or drawstrings. Hook-and-loop closure technology has also been suggested for closures for packaging, such as flexible bags, but to date has not been widely employed.  
           [0004]    Some of the ideal qualities of many high volume, disposable packaging closures include low stiffness, low weight, low bulk and low cost. In many cases, repeated opening and closing is required, but for many disposable applications the anticipated number of repetitive openings and closings of each product is only on the order of two to ten.  
         SUMMARY  
         [0005]    We have realized that for many packaging applications for which hook-and-loop closure technology has generally been considered too bulky or too expensive for practical use, the closure can be arranged such that the hook-and-loop fastening itself is predominantly loaded in shear. Examples include envelope-type and rolled top bag closures, wrap ties, and inner bag face closures incorporating peel-avoiding features. Furthermore, we have realized that for many of these applications, minimal closure strength is required to maintain the opening of the bag or packaging adequately closed against anticipated loads.  
           [0006]    Examples of some of the closure configurations and packaging applications to which this invention is directed and is particularly useful are found in our co-pending U.S. patent application Ser. Nos. 09/187,389, 09/187,936, 09/133,991, provisional U.S. patent application No. 60/159,489, and PCT application US99/26261, filed designating the United States. All of the disclosure of these applications is hereby incorporated by reference.  
           [0007]    With improvements that have occurred over the years in the processes for inexpensively producing very small, molded male fastener elements, such as by the continuous molding methods taught by Fisher (in U.S. Pat. No. 4,794,028, hereby incorporated by reference as if fully set forth), the cost of the loop component of such touch closures has, for many applications, been the limiting factor for the applicability of touch fastener technology.  
           [0008]    We have now found that some commercially available, mass-produced yarns sold for use in, for example, home crafts such as knitting or embroidery, or for use in the production of carpets, can, in conjunction with certain parameters and features, form the basis for inexpensive, effective loop components for hook and loop closure systems. In particular such a loop closure employed in packaging configurations of types constructed to apply loading to the fastener mostly in shear, with low peel loading, is found to provide a low-cost solution for many disposable packaging needs.  
           [0009]    In particular, according to one aspect of the invention, it is discovered that a high bulk yarn, for instance a yarn comprised of multiple, twisted-together plies each formed of fibers or filaments that have been either individually crimped or otherwise textured, can serve admirably to provide a low-cost, hook-engageable component for a hook and loop fastener for flexible disposable packaging such as bags and envelopes. By “bulk” as applied to yarn, we refer to the ratio of area within a cross-section of the yarn occupied by the fibers. In other words, we define a “bulk ratio” as the cross-sectional area of the twisted fiber, determined by the diameter as measured across the twisted plies but ignoring extraneous, loose fiber ends, divided by the fiber area. For yarns consisting of fairly uniform fibers, the fiber area is the cross-sectional area of a single representative fiber, as determined by its nominal diameter, times the total number of fibers in the yarn. We prefer a yarn with a bulk ratio, at rest before lamination, of between about 15 to 50, more preferably between about 18 and 40, and most preferably between about 20 and 25.  
           [0010]    It is generally preferred that the area of the surface of the carrier to which the yarn is applied be substantially planar. By “substantially planar”, we mean that, while the surface may not be completely flat, the surface does not include any continuous raised structures, such as ribs. Other areas of the carrier, spaced from the area to which the yarn is applied, may include hooks or other raised features. Including continuous raised structures will tend to make the fastener material stiffer, and may increase the thickness of the fastener material, which may be undesirable in some applications. It is generally preferred that the carrier sheet be relatively thin, e.g., less than about 0.010 inch, more preferably from about 0.005 to 0.007 inch. Moreover, raised structures may make it impractical to apply the fastener material as a bag closure, due to difficulties in forming a bag side seal around a relatively thick closure strip. In some applications, e.g., when a very thin fastener material is required, it may be desirable for the surface to which the yarn is applied to be free of any raised structures, including discontinuous structures such as posts.  
           [0011]    For some closures, the yarn is partially encapsulated in the surface resin of a closure strip on which an array of molded male fastener elements are integrally formed, such that when the closure is closed the male fastener elements engage and retain unencapsulated, lofty segments of individual fibers or filaments of the yarn. In such closures the yarn is preferably permanently encapsulated in the closure strip continuously along the length of the yarn to anchor the yarn firmly against being pulled from the encapsulating resin during loading or opening. The yarn may be laid longitudinally straight along the closure in the machine direction of manufacture, or in a reciprocating pattern to form a broad loop region of the closure. In some cases, the yarn extends across the loop region of the closure, transverse to the machine direction and length of the closure strip and the molded array of fastener elements.  
           [0012]    The encapsulated fibers of the yarn preferably are of a material having a higher melting point than that of the encapsulating resin, such that the fibers may be encapsulated in the resin without losing their integrity as fibers or being melted into the base resin. Preferred base resin materials will be compatible with the resin of the packaging to which they are to be applied and include polyethylene, polypropylene, nylon, PVC and other thermoplastics. Preferred yarn materials include acrylic and nylon (such as those of, for example, knitting yarns for sweaters and such), polyester, polypropylene, natural fibers such as cotton or wool, and bulk continuous fiber yarns used for carpets and such.  
           [0013]    We have found that such yarns can be effectively and inexpensively encapsulated in a resin base under conditions selected to cause only fiber segments on a near side of the yarn to become encapsulated by the resin, leaving the fiber segments on a far side of the yarn in a lofty condition, exposed for engagement by male fastener elements. We have found that, without any post-processing of the yarn fibers or base resin (i.e., as encapsulated), the yarns of such loop products can provide sufficient engagement with suitable male fastener elements to function as reclosable closures for many disposable packaging applications. The encapsulation may be accomplished, for instance, by employing a cooled roll, preferably in a calendar stack, which receives the yarn and the resin with at least one molten surface.  
           [0014]    It has also been found that inexpensive, high loft yarns may be suitably encapsulated in base resin of a closure strip by introducing the yarn directly into the fastener element forming nip of the device taught by Fisher, under nip pressures high enough to force the resin into fastener element cavities, while leaving a sufficient number of fibers of the yarn unencapsulated, exposed and of sufficient loft to define hook-engageable loops. As the yarn is not to provide any structural strength or stiffness to the base of the closure, only enough fibers of the yarn need be encapsulated to resist anticipated pull-out forces at every point along its length. It is found, for example, that with polyethylene as a base resin, extruded into the forming station at temperature above 400 degrees Fahrenheit, a high bulk, twisted, multi-ply, acrylic knitting yarn survives the process conditions, only yarns at one side being matted and encapsulated by the base-forming resin, while the fibers at the opposite side, held adjacent a cold roll during the process, survive intact and spring back after processing to a high bulk condition. Because of the twisting of the plies about each other, a significant number of the exposed fiber segments are at most only as long as a partial revolution of one ply twist, secured at each end in the base resin and thus effectively defining hook-engageable fibers anchored to the base. In other words, the high effective twist of the filaments can create hook-engageable loop segments of less than about ¼ inch in length.  
           [0015]    By appropriately controlling the forming speed and resin temperature and pressure (the optimal values of which are interdependent and will depend on the type of resin employed and the geometry of the product, as will be understood by those of normal skill in the art), the resulting penetration of substrate resin into the loop material may be controlled so as to not completely flood the exposed surface of loops with resin. In many applications, the use of appropriately contoured staking rings to force the yarn into the molten resin can help to form a pattern of lofted regions of yarn that are less penetrated by resin than other areas. Such lofted regions can extend even more loops for ready engagement by fastener elements.  
           [0016]    It is also found that such partially-encapsulated, twisted multi-ply fibers can provide good fiber density for accepting very small male fastener elements, such as hooks of height of 0.015 inch or less, arranged in arrays with a density of between about 500 and 3000 fastener elements per square inch. It has been found that sufficient open space is created between filaments of the exposed segments of each ply, as well as interstices between the twisted plies, to allow for effective penetration by the fastener elements to achieve effective reclosable hook and loop engagement for disposable packaging applications.  
           [0017]    As used in this specification, the general term “hook-engageable” as applied to loops means loops that can be engaged by hooks of one of the various available types, such as J-hooks, palm trees and mushrooms.  
           [0018]    The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims. 
       
    
    
     DESCRIPTION OF THE DRAWINGS  
       [0019]    [0019]FIG. 1 is a perspective view of a composite touch fastener in the form of a closure strip.  
         [0020]    [0020]FIG. 1A is an enlarged view of area  1 A in FIG. 1, showing the structure of the loop component of the closure strip.  
         [0021]    [0021]FIG. 1B is a microphotograph of a cross-sectioned loop component.  
         [0022]    [0022]FIG. 1C is a microphotograph of a four-ply yarn loop component, partially untwisted.  
         [0023]    [0023]FIG. 1D is a microphotograph of one of the plies of the yarn strand of FIG. 1C, removed from the strand.  
         [0024]    [0024]FIG. 1E is a microphotograph of many of the individual filaments making up one ply of the yarn loop component.  
         [0025]    [0025]FIGS. 2 and 2A illustrate several methods for forming the closure strip of FIG. 1.  
         [0026]    [0026]FIGS. 3A and 3B are enlarged transverse views of alternate embodiments of the forming nip of the apparatus of FIG. 2, showing the yarn loop component being partially embedded in resin of the closure strip.  
         [0027]    FIGS.  4 A- 4 C show undulating yarn loop component patterns.  
         [0028]    [0028]FIG. 5 illustrates a method and apparatus for forming the closure strip with a yarn loop component having an undulating pattern and encapsulated in the closure substrate as the closure substrate is formed.  
         [0029]    [0029]FIG. 5A shows a variation of the nip arrangement of the machine of FIG. 5.  
         [0030]    [0030]FIG. 6 is a cross-sectional view taken along line  6 - 6  in FIG. 5.  
         [0031]    [0031]FIG. 7 shows a method and apparatus for applying a yarn loop strip in an undulating pattern to a closure strip after the closure strip fastener elements and base are formed.  
         [0032]    [0032]FIG. 8 is a cross-sectional view taken along line  8 - 8  in FIG. 7.  
         [0033]    [0033]FIG. 9 shows two yarn strands laid in a staggered sinusoidal pattern across a bead of molten resin on a closure strip to form a loop component.  
         [0034]    [0034]FIG. 10 shows a disposable, flexible bag incorporating the closure strip of FIG. 1.  
         [0035]    [0035]FIGS. 11A and 11B are cross-sectional views taken along line  11 A- 11 A of FIG. 10 with the bag as originally sealed, and as reclosed, respectively.  
         [0036]    [0036]FIG. 12 illustrates a method of opening the bag of FIG. 10.  
         [0037]    [0037]FIG. 13 illustrates a wrap tie closure incorporating a yarn loop component.  
         [0038]    [0038]FIG. 13A is a cross-sectional view taken along line  13 A- 13 A in FIG. 13.  
         [0039]    [0039]FIG. 14 shows a disposable bag being secured with the wrap tie closure of FIG. 13.  
         [0040]    [0040]FIG. 15 illustrates a process for making wrap tie closures in a continuous process.  
         [0041]    FIGS.  15 A- 1   5 D show the product being processed at respective points along FIG. 15.  
         [0042]    [0042]FIGS. 16 and 16A are illustrative plan and side views, respectively, of the function and basic structure of the combiner of FIG. 15.  
         [0043]    [0043]FIG. 17 shows a closure strip being attached to an edge of a bag.  
         [0044]    [0044]FIG. 18 shows a twin closure strip configuration.  
         [0045]    [0045]FIG. 19 shows a side view of a fastener product having yarns on one side and hooks on the opposite side. FIG. 19A is a cross-sectional view of the product of FIG. 19, taken along line A-A.  
         [0046]    [0046]FIG. 20 is a perspective view of a fastener product including an alternating arrangement of yarns and rows of hooks.  
         [0047]    [0047]FIG. 21 is a perspective view of a fastener product including a plurality of substantially parallel yarns. FIG. 21A is a highly enlarged perspective view of detail A in FIG. 21.  
     
    
       [0048]    Like reference numbers and designations in the various drawings indicate like elements.  
       DETAILED DESCRIPTION  
       [0049]    [0049]FIG. 1 is a perspective view of a composite touch fastener in the form of a closure strip.  
         [0050]    [0050]FIG. 1A is an enlarged view of area  1 A in FIG. 1, showing the structure of the loop component of the closure strip.  
         [0051]    [0051]FIG. 1B is a microphotograph of a cross-sectioned loop component.  
         [0052]    [0052]FIG. 1C is a microphotograph of a four-ply yarn loop component, partially untwisted.  
         [0053]    [0053]FIG. 1D is a microphotograph of one of the plies of the yarn strand of FIG. 1C, removed from the strand.  
         [0054]    [0054]FIG. 1E is a microphotograph of many of the individual filaments making up one ply of the yarn loop component.  
         [0055]    [0055]FIGS. 2 and 2A illustrate several methods for forming the closure strip of FIG. 1.  
         [0056]    [0056]FIGS. 3A and 3B are enlarged transverse views of alternate embodiments of the forming nip of the apparatus of FIG. 2, showing the yarn loop component being partially embedded in resin of the closure strip.  
         [0057]    FIGS.  4 A- 4 C show undulating yarn loop component patterns.  
         [0058]    [0058]FIG. 5 illustrates a method and apparatus for forming the closure strip with a yarn loop component having an undulating pattern and encapsulated in the closure substrate as the closure substrate is formed.  
         [0059]    [0059]FIG. 5A shows a variation of the nip arrangement of the machine of FIG. 5.  
         [0060]    [0060]FIG. 6 is a cross-sectional view taken along line  6 - 6  in FIG. 5.  
         [0061]    [0061]FIG. 7 shows a method and apparatus for applying a yarn loop strip in an undulating pattern to a closure strip after the closure strip fastener elements and base are formed.  
         [0062]    [0062]FIG. 8 is a cross-sectional view taken along line  8 - 8  in FIG. 7.  
         [0063]    [0063]FIG. 9 shows two yarn strands laid in a staggered sinusoidal pattern across a bead of molten resin on a closure strip to form a loop component.  
         [0064]    [0064]FIG. 10 shows a disposable, flexible bag incorporating the closure strip of FIG. 1.  
         [0065]    [0065]FIGS. 11A and 11B are cross-sectional views taken along line  11 A- 11 A of FIG. 10 with the bag as originally sealed, and as reclosed, respectively.  
         [0066]    [0066]FIG. 12 illustrates a method of opening the bag of FIG. 10.  
         [0067]    [0067]FIG. 13 illustrates a wrap tie closure incorporating a yarn loop component.  
         [0068]    [0068]FIG. 13A is a cross-sectional view taken along line  13 A- 13 A in FIG. 13.  
         [0069]    [0069]FIG. 14 shows a disposable bag being secured with the wrap tie closure of FIG. 13.  
         [0070]    [0070]FIG. 15 illustrates a process for making wrap tie closures in a continuous process.  
         [0071]    FIGS.  15 A- 15 D show the product being processed at respective points along FIG. 15.  
         [0072]    [0072]FIGS. 16 and 16A are illustrative plan and side views, respectively, of the function and basic structure of the combiner of FIG. 15.  
         [0073]    [0073]FIG. 17 shows a closure strip being attached to an edge of a bag.  
         [0074]    [0074]FIG. 18 shows a twin closure strip configuration.  
         [0075]    [0075]FIG. 19 shows a side view of a fastener product having yarns on one side and hooks on the opposite side. FIG. 19A is a cross-sectional view of the product of FIG. 19, taken along line A-A.  
         [0076]    [0076]FIG. 20 is a perspective view of a fastener product including an alternating arrangement of yarns and rows of hooks.  
         [0077]    [0077]FIG. 21 is a perspective view of a fastener product including a plurality of substantially parallel yarns. FIG. 21A is a highly enlarged perspective view of detail A in FIG. 21.  
         [0078]    Like reference numbers and designations in the various drawings indicate like elements.