Stretch-pillowed bulked laminate useful as an ideal loop...

Details Stretch-pillowed bulked laminate useful as an ideal loop... Stretch-pillowed bulked laminate useful as an ideal loop...

1997-09-15

2003-07-08

Juska, Cheryl A. (Department: 1771)

Stock material or miscellaneous articles

Structurally defined web or sheet

Discontinuous or differential coating, impregnation or bond

C442S394000, C156S290000, C428S099000

Reexamination Certificate

active

06589638

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to composite materials which can be designed to have breathable barrier applications and which may be particularly useful as a component of fasteners of the hook and loop type typified by those extensively marketed by VELCRO INTERNATIONAL and now available from numerous sources for applications from shoe ties to golf gloves and many others where nonpermanent attachment is desired. These fasteners fundamentally include a hook member and a loop member that, when pressed together, entangle in a manner that resists shear forces but can be separated when subjected to a desired level of peel force. The design of these members has become quite sophisticated and provides a wide range of properties obtainable by varying factors such as hook shape, size and flexibility as well as similar loop features. For many low cost applications such as fasteners for disposable garment applications like diapers and adult incontinent wear, it has been necessary to develop inexpensive manufacturing techniques and materials for such fasteners that, nevertheless, meet the performance requirements. Particularly for such applications where the loop component also serves as the backing material, it is highly desirable that it can be breathable for comfort and also that it serve as a barrier to prevent leakage. The present invention provides a composite of film and nonwoven fabric for use as an ideal loop fastener component particularly suited to such disposable product applications.
2. Background
The art is replete with references to hook and loop type fasteners and components for such fasteners intended for use in disposable product applications such as disposable diapers and the like. Just by way of example, reference may be had to coassigned U.S. Pat. No. 5,614,281 to Jackson et al. which, itself, provides much background information and for that purpose is incorporated herein by reference in its entirety. Other loop fastener materials are described in, for example, U.S. Pat. No. 4,761,318 to Ott et al., U.S. Pat. No. 5,032,122 to Noel et al., U.S. Pat. No. 5,326,612 to Goulait, U.S. Pat. No. 5,595,567 to King et al, and U.S. Pat. No. 5,647,864 to Allen et al. Briefly, a particularly economical loop component may be formed using nonwoven manufacturing techniques such as spunbonded processes that result in significant areas of the web between bond points where the filaments are unbonded to each other and available to engage hooks of a complementary hook member. Factors, such as configuration, number and area coverage of the bonds in the nonwoven as well as the selection of a particular hook member, may be varied to achieve a desired level of peel strength and other properties within a designated cost range. In addition, the selection of a polymer or other compositional ingredient for the nonwoven and/or the hook component can affect the performance and/or cost of the fastener in a given application. There remains a need for a loop fastener component that can have tailored properties such as peel strength, shear strength and refastenability as well as barrier and, if desired, breathability functions at a cost consistent with use as a backing component of disposable products. Other uses for breathable barrier materials having clothlike attributes such as surgical gowns and drapes, for example, will be apparent to those skilled in the art.
SUMMARY OF THE INVENTION
The present invention is directed to a nonwoven and film composite material that can include properties making it particularly adapted for use as a loop fastener component that includes a laminate of a film layer and a prebonded nonwoven layer wherein the laminate bonds are separate and independent of the bond sites of the prebonded nonwoven while leaving filaments or fibers between such laminate bond sites both bonded and unbonded. For improved comfort and utility as a backing component of a personal care product such as a disposable diaper, for example, the laminate can be breathable with a moisture vapor transmission rate above about 100 g/m
2
/24 hours and can have a hydrohead value of at least 50 mbar. In use with a complementary hook component, a loop fastener formed from this composite provides capability for fastening anywhere on the backing of the product and consistent refastenability over a period of time and for the number of cycles of opening and closing that is suitable for many disposable and limited use applications. The nonwoven layer contains a bond pattern of either uniform or nonuniform bond impressions that result in an unbonded area of at least 70%, taken over any 100 cm square of nonwoven surface. In addition the bond frequency provides a pattern density in the range of from about 50 to about 200 bonds/in.
2
with an area coverage of from about 5% to about 30%, advantageously from about 10% to about 25%. The film layer is either a multilayer or coextruded structure with an exposed layer of a soft, amorphous polymer, or a monolayer and, in either case, is a predominantly microporous barrier to liquid that is conformable and compatible with the nonwoven. Lamination may be achieved by an application of heat and pressure taking advantage of the amorphous polymer properties either in the multilayer film, or as the separately applied bonding layer in the monolayer film embodiment, for example. The independent laminate bond pattern is selected so that areas between the laminate bonds contain separate nonwoven bonds that further integrate the fibers or filaments of the nonwoven surface. For example, laminate bond patterns may have less than 50% coverage of the laminate surface area, advantageously less than about 30% and may be uniform or nonuniformly shaped and/or configured and will generally be significantly fewer in number than the nonwoven prebonds. To enhance clothlike aesthetics and engagement of hook elements for the loop component applications, a retracted laminate may be formed by stretching the film prior to lamination to the nonwoven and subsequently allowing the laminate to relax or retract, producing a pillowed/highly bulked nonwoven film laminate between bond areas where the film and nonwoven remain securely attached. The invention also includes the method for making the composite.
DETAILED DESCRIPTION
Definitions
As used herein the following terms have the specified meanings, unless the context demands a different meaning, or a different meaning is expressed; also, the singular generally includes the plural, and the plural generally includes the singular unless otherwise indicated.
“Nonwoven” means a web of fibers or filaments that is formed by means other than knitting or weaving and that contains bonds between some or all of the fibers or filaments; such bonds may be formed, for example, by thermal, adhesive or mechanical means such as entanglement.
“Fiber” means an elongated strand of defined length, such as staple fibers formed by cutting a continuous strand into lengths of, for example, 2 to 5 cm. Collections of fibers may have the same or different lengths.
“Filament” means a generally continuous strand that has a very large ratio of length to diameter, for example, 1000 or more.
“Spunbond” means a nonwoven of filaments formed by melt extrusion of a polymer into strands that are quenched and drawn, usually by high velocity air, to strengthen the filaments which are collected on a forming surface and bonded, often by the patterned application of heat and pressure. Spunbonded processes are described, for example, in the following patents to which reference may be made for additional details: U.S. Pat. No. 4,340,563 to Appel et al., U.S. Pat. No. 3,802,817 to Matsuki et al., and U.S. Pat. No. 3,692,618 to Dorschner et al.
“Loop” means an area of separation of at least one fiber or filament from others in a nonwoven and includes but is not limited to configurations where the same fiber or filament intersects itself; i.e. a complete circle or oval, for example, need not be formed.
“Complementary hook” means a structure adapted for u

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