US3468748A - Nonwoven fabric with machine direction elasticity - Google Patents

Description

Sept. 23, 1969 A. H. BASSETT 3,453,748

NONWOVEN FABRIC WITH MACHINE DIRECTION ELASTICITY Filed April 14, 1965 2 SheetsSheet l INVENTOR 4470 6! 545.2277

WW 7 ATTOR Y Sept. 23, 1969 A. H. BASSETT NONWOVEN FABRIC WITH MACHINE-DIRECTION ELASTICITY Filed April 14, 1965 2 Sheets-Sheet 2 INVENTOR.

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United States Patent 3,468,748 NONWOVEN FABRIC WITH MACHINE DIRECTION ELASTICITY Alton H. Bassett, Princeton, N.J., assignor to Johnson & Johnson, a corporation of New Jersey Filed Apr. 14, 1965, Ser. No. 448,173 Int. Cl. B32b 3/10, 7/14; D04h N00 US. Cl. 161-122 5 Claims ABSTRACT OF THE DISCLOSURE A continuously broadening field of application is in evidence for nonwoven fabrics, such that there is much evidence of the successful competition that exists between woven and nonwoven fabrics.

Nonwovens have certain characteristics which make them desirable for some end uses while not so desirable for others. One such feature, which is to be considered here, is their strength and resistance to extension in the machine direction as opposed to the cross direction of the fabric. It is the purpose of this invention to provide an elastic nonwoven fabric which has overcome this resistance to extension in the machine direction without sacrificing any of the strength of the fabric.

This invention provides a nonwoven fabric comprising a bonded web of individualized fibers, and an elastomeric means secured to said web to provide a plurality of buckled areas therein, said nonwoven fabric being characterized by elastic extensibility.

The phrase elastic extensibility as used herein is intended to define the physical state of the fabric of this invention. The fabric is easily deformed and possesses quick recovery from that deformation when the force or forces causing deformation are removed.

By buckled areas is meant the bunching of the fabric which is caused both by the presence of the elastic means and the method used for securing the elastic to the fabric. Basically, the buckles are elongate and extend transverse of the lengthwise direction of the elastic. The longitudinal direction of the buckles and their entire disposition is dependent on the print pattern used to bond the fabric; however, the arrangement of the elastic means is also controlling but to a lesser degree. Physically, the buckled fabric appears corrugated; although, the wrinkles, furrows or ripples extend at an angle to the direction of force which elfects the buckling and they may be parallel or irregularly parallel to one another. While the buckles exhibit lengthwise interruptions, they do extend the width of the fabric. Each lbuckle has an interior void (see FIG. 5) which is effected by the process of formation of the extensible fabric of this invention, and these voids provide greatly improved bulk and softness in the fabric.

More particularly, the instant invention provides a nonwoven fabric comprising a plurality of webs of individual ized fibers bonded in position by a recurring print pattern, and a plurality of lengths of an elastomeric means secured to said fabric in spaced substantially parallel relationship to provide a multitude of elongate irregularly parallel buckled areas throughout said fabric, said fabric being characterized !by elastic extensibility.

The elastomeric means necessary in this invention may be defined by cords, strings, bands, etc., of an elastic ice material such as rubber or any elastomer. It may also comprise an elastic yarn, i.e. a yarn with a core of natural or synthetic rubber covered with cotton, man-made, or any elastic-containing material that has elasticity, fibers, etc. The covering may be accomplished by wrapping or helical winding methods. It is only necessary that the elastic means provide at least 15% elongation in the nonwoven fabric to which it is secured. However, it may provide 400% to 500%, or more, elongation in the fabric. For simplicity, this elastomeric means will be referred to as an elastic strand throughout.

The layer or web of overlapping, intersecting, i.e. individualized fibers which is processed to form nonwoven fabrics, may be produced by any one of a number of conventional techniques for depositing, arranging or rearranging fibers in a web. These techniques include carding, garnetting, airlaying, papermaking methods and the like. Individual webs or thin layers formed by one or more of these techniques may be laminated to provide a thicker layer for conversion into fabric. In general, the individual fibers extend in a plurality of diverse directions in substantial alignment with the major plane of the fabric, overlapping, intersecting and supporting one another to form an open porous fibrous structure.

The degree of fiber orientation in any particular direction will depend primarily upon the method of formation of the web. Webs formed by air-laying techniques normally have very little orientation in any particular direction and are basically isotropic. On the other hand, webs formed by carding and garnetting techniques are more or less predominantly oriented in the machine or the long direction of the web. Each type of web has its own properties and characteristics and each is capable of use in conjunction with the instant invention.

The fibrous web may contain natural or synthetic, vegetable, animal fibers such as cotton, silk, wool, vicuna, mohair, alpaca, flax, ramie, jute, etc.; synthetic or manmade fibers such as the cellulosic fibers, notably cuprammonium, viscose or regenerated cellulose fibers; cross linked cellulosic fibers such as Corval and Topel; cellulose ester fibers such as cellulose acetate and cellulose triacetate; the saponified cellulose ester fibers; the polyamide fibers; protein fibers; halogenated hydrocarbon fibers; hydrocarbon polyolefin fibers such as polypropylene and polyethylene; polyester fibers; vinyl fibers; acrylic fibers; modacrylic fibers; mineral fibers such as glass and metal; and others.

It is preferred that the individualized textile fibers be of textile staple or equivalent length, or at least cardable, that is to say, from about /2 inch in average length up to about 3 inches or more in average length. Shorter fibers, down to about $1 inch average length, may be added in various proportions to comprise about 50% by weight of the web, or even may comprise the entire web, particularly where the original method of web formation involved a fluid deposition of fibers, such as in a papermaking process, or in air deposition techniques. In such fluid deposition processes, average fiber lengths down to about inch are preferred to the extremely short fiber lengths of down to about A inch and even below used in papermaking processes for making paper. Additionally, when the fluid deposition process is a papermaking process, the fibers should be in a relatively unbeaten form, in contrast to the beaten fibers used for promoting the hydration bonding of the very short fibers in paper.

The denier of the individual synthetic fibers referred to above is preferably in the range of the approximate thickness of the natural fibers mentioned and consequently deniers in the range of from about 1 to about 5 are preferred. Where greater opacity or greater covering power is desired, special fiber deniers of down to about or even about /2 may be employed. Where desired,

deniers of up to about 8, 10, or higher, may be used. The minimum and maximum denier are naturally dictated by the desires or requirements for producing a particular fibrous web, by the machines and methods for producing the same, and so forth.

The weight of the fiborus web of starting material may be varied within relatively wide limits above a predetermined minimum value, depending upon the requirements of the intermediate or the final products. A single, thin web of fibers, such as produced by a card, may have a weight of from about to about 250 or more grains per square yard and may to used in the application of the principles of the present invention. Within the more commercial aspects of the present invention, however, web weights of from about 90 grains per square yard to about 800 grains per square yard are contemplated. If heavier web weights are desired, such as up to 2,000 grains, for example, several of the individual webs may be combined into a laminated structure to obtain the desired Weight. The product of one card may be folded, doubled, tripled, etc., on itself to reach the heavier Weight, or a plurality of cards may be used and the individual products stacked or laminated for a similar purpose.

Fabric stability and strength are usually created in such nonwoven fabrics by bonding with adhesive or cementitios materials. The bonding operation employed for stabilizing and strenghtening nonwoven fabrics in this invention is one of intermittent bonding using a spaced repeating pattern of bonding sites defining discrete binder areas or lines extending across the width of the nonwoven fabric. The individual fibers passing through these binder areas or lines are adhered into a stable, self-sustaining relationship. The binders areas may also take on any desired shape or form including circles, annuli, ovals, ellipses, triangles, rectangles, squares, diamonds, parallelograms, or other polygons, or combinations of such forms, either regularly or irregularly shaped. The binder lines may extend across the nonwoven fabric at any desired angle to the long axis; the binder lines may be parallel, or they may cross each other to form diamond or irregular polygonic figures; the binder lines may be continuous or discontinuous; or they may be straight, curved, sinuous, or irregularly wavy. Examples of some of these patterns and shapes may be found in the above-mentioned US. Patents 2,705,687 and 2,705,688 or in US. Patent 2,880,111.

One common factor, however, is to be particularly noted in all of these patterns, namely, that the total surface coverage of the binder areas or lines on the nonwoven fabric should not substantially exceed about of the total surface of the nonwoven fabric. Preferably, such coverage should be less than about 25% and sometimes down to about 8% of the total surface of the nonwoven fabric. Binder areas occupying greater than about 35% stitfens the fabric and interferes with the elastic properties desired.

The binder used in adhering the individualized fibers in position for simultaneously adhering the plurality of webs together and for bonding the elastic strands in position may be selected from a large group of such binders known to industry. It is necessary, however, that a binder be used which can satisfactorily adhere to and bond the different types of fibers together or at least mechanically interlock the fibers together and that it also binds securely the elastic strands to the fabric at the bond sites. Representative of the binders available for such a purpose are regenerated cellulose; vinyl resins such as plasticized or unplasticized polyvinyl acetate, polyvinyl chloride, polyvinyl alcohol, etc., either as homopolymers or copolymers; acrylic resins such as ethyl acrylate, methyl methacrylate, methyl acrylate, butyl methachylate, etc.; butadiene resins such as butadiene-acrylonitrile, butadiene-styrene, etc.; other synthetic rubbers; natural rubber, urea resins such as urea-formaldehyde, cyclic urea-formaldehyde, etc., aldehyde resins such as melamine-formaldehyde, phenolformaldehyde, resorcinol-formaldehyde, etc.; epoxy resins; cellulose derivatives such as carboxyrnethyl cellulose; hydroxyethyl cellulose, etc.; starches; gums; casein; etc.

These binders may be added, as desired, in the form of emulsions, solutions, dispersions, plastisols, powders, etc. Autogenic bonding, preferably by heat and/or pressure and/or solvents, may also be used when thermoplastic fibers are present.

The percent add-on of such binder materials may be varied within relatively wide limits depending to a large extent upon the specific binder employed and upon the type, Weight and thickness of the nonwoven fabric. For some binders, as low as about 1% by weight up to about 12% by weight, based on the weight of the dry webs being bonded, has been found satisfactory. For other binders, as high as from about 15% to about 50% by weight has been found preferable. Within the more commercial aspects of the present invention, however, from about 2% to about 35% by weight, based on the weight of the dry webs being bonded, has been found desirable.

In producing the fabric of this invention, several webs of nonwoven fabric are laminated together. The elastic means is extended to an amount sutficient to provide at least-15% elongation in the fabric and secured, by an appropriate chemical binder to the fabric using a print bonding technique. It is held in this extended position until the binder has dried. While the composite of the first nonwoven laminate and the elastic means are so positioned, a second nonwoven laminate may be secured to the first laminate to cover the elastic means. In any event, after the chemical bonding agent has dried, the apparatus holding the elastic means in an extended position is removed, and the fabric is caused to deform, creating a series of substantially parallel, irregular buckles.

The buckles so formed are spaced one from the other by troughs but are substantially parallel to one another. They do not extend in their lengthwise direction for any great distance but originate and terminate within the boundaries of the fabric itself, i.e. except for those that originate near a boundary. They are irregular rather than uniform and they vary in magnitude. It should be understood that the magnitude of the buckles is essentially dependent upon the amount of deformation caused by the relaxing of the elastic means which, of course, is itself dependent upon the degree of extension applied to it and upon the print pattern utilized for bonding. Thus, the extent of buckling can be controlled and the degree of bulk which the buckling imparts to the fabric can also be controlled and predicted as desired to conform to its desirability in the end product. The absorbency of the fabric is also enhanced by the degree of buckling.

The placement of the elastic means within or on the fabric will also control the amount and intensity of buckling. For example, thin bands or strings of an elastic material under tension and positioned very close together in parallel relationship in or on the fabric and secured in position will cause a greater number of buckles per square inch than will the same elastic material under the same tension spaced four or five times the distance from its nearest neighbor as it was in the first instance. Also, in the latter case the magnitude of the buckle will be greater. A like result will appear with a significant variance in the dimensions of the elastic material, a variance in the amount of tension or extension placed on a strand or band of elastic material as opposed to another and with the use differing elastic materials.

Nonwoven fabrics are normally noted as having no extensibility in the machine direction but this direction does represent the direction of greatest tensile strength in the fabric. Placing the elastic material under tension in parallel relationship running in the machine direction, securing it in position to the nonwoven while it is still under tension. and removing this tension when the chemical bonding material has been dried will cause the buckling which will permit hitherto unobtainable elasticity in the machine direction of the nonwoven fabric. The degree of elasticity can be controlled by the amount of tension applied to the elastic material and the degree of buckling can also be predicted and controlled as mentioned earlier.

The elastic means will, in the usual case, always be positioned under tension in the nonwoven fabric in parallel relationship to the other strips, bands, etc., of elastic material so positioned. Unless unusual effects are desired, the buckles will always be created running at substantially right angles to the lengthwise direction of the elastic bands, etc. This could be varied by using elastic materials having different degrees of elasticity but applying equal tension to all, or by varying the parallel relationship of the elastic strips or bands to produce unusual effects or designs in the fabric.

The present invention will be more fully understood by reference to the following detailed description and the accompanying drawings in which:

FIGURE 1 is a schematic presentation depicting a method of construction of one embodiment of this invention,

FIG. 2 depicts the composite structure of FIG. 1,

FIG. 3 is a schematic perspective view of one embodiment of a nonwoven fabric of this invention,

FIG. 4 depicts the appearance of the fabric of FIG. 3 when opposed force is applied to it at points A and B,

FIG. 5 is a cross section taken through 55 of FIG. 3, and

FIG. 6 is a schematic diagram of a commercial process for making the fabric of this invention.

Referring to FIG. 1, a first ply I consisting of three layers, 1, 2 and 3, each of overlapping, intersecting individualized fibers and a ply II consisting of a layer 9 of a construction similar to that of each of the layers of laminate I is shown. Laying across ply II are a plurality ofbands 4 of elastic, i.e. natural rubber, which are held under tension by means 5 which could easily be a clamp or a similar device. The tension utilized is such as to provide uniform extension of about 100% to each of thebands 4. Each of the layers of individualized fibers in plies I and II is produced follownig the teachings of US. 3,081,514 and US. 3,081,515 to provide a fabric having a repeating pattern of apertures or holes 10, each bounded by bundles ofindividualized fibers 11.

One method of constructing a fabric of this invention would be to sandwich theelastic bands 4 between plies I and II to provide the composite 6 shown in FIG. 2. In this instance a bonding composition has been applied to the fabric via a wavy-line pattern 7. The binder composition is such that it will not only bind the individualized fibers but also of such a composition as will bind the elastic bands securely to the plies I and H and thus require it to maintain the same points of attachment along its length as it has while under tension as shown. This insures that when the tension to thebands 4 is removed, the band will not slip insofar as its bonding sites with thefabric 6 is concerned but rather that they will pull the fabric to a lesser dimension causing a multitude of buckles to form in thefabric 6 as is shown in FIG. 3.

Note should be taken of the fact that thebuckles 8 in FIG. 3 are substantially parallel and at substantially right angles to the lengthwise direction of thebands 4. Thebuckles 8 extend discontinuously to span the length or width of the fabric and their magnitude is that which effects the bulk, and thus the softness and absorbability of thefabric 6. These buckles are separated bytroughs 12.

FIG. 4 depicts thefabric 6 of FIG. 3 with opposed forces being applied along lines A--A and BB. Thefabric 6 will permit elongation in the lengthwise direction of thebands 4 to an extent sufficient to take up the buckled fabric. Beyond that point rupture of fiber bond and fiber length will be encountered. The amount of elongation of the fabric in other than the lengthwise direction of thebands 4 will diminish as an angle of from the line defining the length of anyband 4, is established. There will be very little elasticity at right angles to the line of thebands 4. Of course, interesting features can be established by varying the parallelism of each or several of thebands 4 with respect to its neighbors or by positioningother bands 4 across its neighbors. As shown, however, the fabric has uniform elastic extensibility and the resultant recovery in any planar direction.

FIG. 5 represents an enlargement of a cross section taken along 55 of FIG. 3. While an elastic strand cannot be seen in this view, the effect of its presence is readily discernible. The plies I and II have been bonded together by a horizontal wavy-line pattern 7 as seen in FIG. 2 and it is readily apparent that due to the nature of the webs, the layers or plies are only indistinctly in evidence due to the intermingling and intermixing of the individualized fibers of both. Since the elastic bands in FIG. 3 have been relieved of the tension applied during manufacture of thefabric 6, buckles 8 have been forced to develop between the bond sites 7. Thesebuckles 8 may be compound in that several small buckles form between adjacent bond sites 7, or they may be unitary in that but one forms between these two referenced points. In either event, short lengths ofindividualized fibers 13 protrude from the laminate and are quite thick per unit area of the fabric. These protrudingfibers 13 contribute to the improved bulk and softness in thefabric 6 and they offer a capillary effect which enhances fabric absorption.

The degree of buckling and the magnitude of the buckles developed is, of course, principally dependent upon the print pattern used in that the spacing of the lines of binder from one another, if lines are used, the distance between adjacent bond sites and the area of each of these bond sites all bear a direct relationship on the free area left which can buckle. However, the number of plies of fabric in the laminate, the weight of the fabric per unit area and the kind and width of the elastic strand, as well as the tension applied to the latter during fabric production, all contribute to the ultimate characteristics of the buckles.

A schematic diagram of a comercial process for making the fabric of this invention is given via FIG. 6. Twocard webs 26 and 28 are led to a conveyor belt 37 as they immerge from theirrespective carding apparatus 20 and 21. A thinwide band 38 of an elastomer is spliced inapparatus 39 into a plurality of strands 27 each having a corresponding small cross section. The strands 27 are fed through a first set of nip rolls 22 and 23 having a regulated number of revolutions per minute, and then between another pair of nip rolls 24 and 25 each having an increased speed over that exhibited by 22 and 23 to provide sufficient tension on each of the plurality of elastic strands to uniformly impart a lengthwise extension of about 25% in the length of each of these strands 27 over their original untensioned length. It is understood that tension could be applied to the elastic strands 27 by other means, or by using the two sets of nip rolls as outlined and running both sets at uniform speeds but having the diameter of 23 appreciably larger than 24. The minimum tension required is that which will provide an elastic elongation and recovery in the fabric of at least 15%.

The strands are led under tension to positions contiguous to the surface ofweb 26 and they are caused to meetweb 26 to provide a plurality of strands 27 extending parallel to the machine direction of theweb 26 and spaced equidistant one from another (see FIG. 1). Asecond web 28 of individualized fibers is fed, after emerging from the cardingapparatus 21, to a positionadjacent web 26 and in facewise engagement therewith. The composite of twowebs 26 and 27 of individualized fibers having sandwiched therebetween a plurality of strands 27 of an elastomer, is carried on conveyor belt 7 37 either directly to print rolls 29 and 30 or they may be passed through rearranging apparatus K and then to the print rolls. In either instance the tension initially applied to strands 27 via nip rolls 2223 and 24-25 is maintained by nip rolls 34 and 35.

If the composite 40, i.e.webs 26 and 28 plus the plurality of strands 27, is passed through the rearranging apparatus designated K, the individualized fibers of both webs are systematically and simultaneously rearranged to provide a repeating pattern of openings or holes through the composite, with each hole being defined by bundles of rearranged individualized fibers (see FIGS. 1 and 2). This is accomplished in accordance with the teachings of U. S. 3,081,514 and U.S. 3,081,515.

Whether or not the individualized fibers of the twoplies 26 and 28 of the composite are jointly rearranged, the composite 40 is led to print rolls 29 and 30 where thebonding material 31 is applied to the laminate 40 in a repeating pattern of spaced binder areas as shown in FIG. 2. The laminate 40 is then fed through a dryer to set the binder and then fed through the tension maintaining apparatus, i.e. nip rolls 34 and 35, and wound up under tension on areceiver 36. The fabric is wound up and stored under tension in order to provide a neat package but also to insure that deformation and ripping of Two carded webs of individualized fibers, i.e. 1 /2 denier, 1% inch staple viscose rayon, are prepared in .accordance with the teachings of U.S. 3,081,514 or U.S. 3,081,515 to provide two layers of rearranged fibers and present a fabric of bundled fibers substantially separated by a uniform recurring pattern of voids. A ribbon of size 40-77 W white rubber (United Elastic Corporation) of 40 gauge is uniformly scored to split it into 23 substantially equal lengths. Each length has a substantially equal gauge.

Each of these lengths is laid in parallel relationship along one of these nonwoven rearranged webs to run in the machine direction of the web. The 23 lengths are positioned such as to provide equidistant spacing between each length and to cover .a 8 /2 inch span of the fabric, measured in the cross direction. Each end of each length is then afiixed to a clamp and the total lengths are uniformly extended by opposed forces to 100% of their original length. The second rearranged web is placed in facewise engagement with the first to cover these parallel lengths of rubber which are still held under tension. A binder, i.e. Tylac, a carboxylated butadiene-acrylonitrile sold by International Latex Corporation, is applied to the composite of two rearranged webs having the extended parallel lengths of rubber sandwiched therebetween. A print pattern of four horizontal wavy lines per inch adds 90 grains per square yard to the initial fabric weight (both webs) of 290 grains per square yard which has received a contribution of 240 grains per square yard by the addition of the rubber. The composite fabric is then dried over steam cans operating at 250 F. and the 8 tension holding the elastic lengths in an extended state is removed.

The resultant fabric is buckled and easily extensible to 100% elongation in the machine direction of the nonwoven laminate. It exhibits unusually improved bulk and softness and it readily conforms to a surface it is placed against, e.g. a portion of the human anatomy, and maintains its position with an adhesive-like force or tenacity.

I claim:

1. A nonwoven fabric comprising 1) a bonded nonwoven web of overlapping, intersecting fibers having an average fiber length of at least about inch, where said fibers are selected from the group consisting of natural fibers, synthetic fibers and mixtures thereof, and where said fibers are bonded in intermittently spaced positions by a recurring print pattern of intermittantly spaced binder areas to form said bonded nonwoven web, and (2) a plurality of elastic means secured, while in an elongated condition, to intermittantly spaced positions of said bonded nonwoven web by means of said intermittantly spaced binder areas, the bonding of said nonwoven web and the securing of the elastic means thereto taking place simultaneously, said plurality of elastic means being secured in a spaced substantially parallel relationship to the machine direction of said fabric to provide, on release of said elastic means, a multitude of elongated, irregularly parallel buckled areas having voids between said bonded nonwoven web and said elastic means throughout said fabric, said fabric being characterized by elastic extensibility in the machine direction, improved bulk and fluid transmission therethrough.

2. The fabric of claim 1 wherein said fabric comprises 1), a plurality of webs of fibers wherein each web is constructed of fibers having an average fiber length of at least about inch, where said fibers are selected from the group consisting of natural fibers, synthetic fibers, and mixtures thereof, and where said fibers are bonded in position by .a recurring print pattern and, (2), a plurality of elastic means secured to said fabric, in a spaced substantially parallel relationship, while in an elongated condition, to the machine direction of said fabric to provide, on release of said elastic means, a multitude of elongated irregularly parallel buckled areas throughout said fabric, said fabric being characterized by elastic extensibility in the machine direction, improved bulk and fluid transmission therethrough.

3. The fabric of claim 1 wherein said fibers have an average length of at least about /2 inch.

4. The fabric of claim 1 wherein said fabric exhibits an elastic elongation in machine direction of at least about 15%.

5. The fabric of claim 1 wherein said binder occupies up to about 35% of the total surface area of the nonwoven fabric.

References Cited UNITED STATES PATENTS 22,038 11/1858 Solis 156161 3,081,515 3/1963 Griswold et al 16l-109 3,316,136 4/1967 Pufahl 16176 X ROBERT F. BURNETT, Primary Examiner R. L. MAY, Assistant Examiner U.S. Cl. X.R.

l6l-14l, 144, 146, 156

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