US 3485695 A
Description (OCR text may contain errors)
l. s. Nass 3,485,695
METHOD OF MAKING A BONDED PORIFEROUS NON-WOVEN TEXTILE FABRIC Dec. 23, 1969 2 Sheets-Sheet l Original Filed July 31, 1964 .mmf
Dec. 23, 1969 l. s. Ness 3,485,695
METHOD OF MAKING A BONDED PORIFEROUS NON-WOVEN TEXTILE FABRIC Original Filed July 3l,LA 1964 2 Sheets-Sheet 2 ZM/,Mba T- ma# ATTORNEY United States Patent O 3,485,695 METHUD OlF MAKING A BONDED PORTFEROUS NON-WOVEN TEXTILE FABRIC llrving S. Ness, Princeton, NJ., assignor to Johnson & Johnson, a corporation of New Jersey Continuation of abandoned application Ser. No. 386,713, July 31, 1964. This application Jan. 26, 1968, Ser. No.
rut. ci. non; 1/64 U.S. Cl. 156-229 2 Claims ABSTRACT OF THE DISCLOSURE A method of making a bonded, poriferous non-woven textile fabric is disclosed, said fabric having no significant extensibility in the long direction and having undirectional cross elasticity.
This is a continuation of application Ser. No. 386,713, filed July 31, 1964 now abandoned.
This invention relates to nonwoven fabrics, i.e., fabrics produced from textile fibers without the use of conventional weaving and knitting operations, and more particularly to nonwoven fabrics having unidirectional elasticity.
Nonwoven fabrics of various types have become increasingly important in the textile field during the past decade, primarily because of their low cost of manufacture compared to fabrics formed by weaving or knitting spun fibers. Nonwoven fabrics are particularly suitable for applications where launderability is not a prerequisite, or low cost is an important consideration, especially in the case of finished products that are used once and then discarded as, for example, in the manufacture of sanitary napkins, surgical dressings, hospital caps, casket liners, disposable table napkins, hand towels, diapers, drapery fabrics, disposable garments and the like.
The' instant invention provides a poriferous nonwoven fabric of bonded textile fibers, said fabric having unidirectional elasticity.
A nonwoven textile fabric is usually thought of as having two directions, i.e., the machine direction and the cross direction; the machine direction being the direction that the web of textile fibers travel, i.e., from machine station to machine station, as it is manufactured. It is defined by being parallel to the longitudinal axis of the fabric during manufacture. The cross direction is at right angles to the machine direction and defines the width of the fabric or its lateral axis.
More particularly the instant invention provides a poriferous nonwoven textile fabric of bonded textile fibers, the perimeter of each of said pores being defined by bundles of rearranged textile fibers, said pores being arranged columnwise in staggered relationship to corresponding pores defining immediately adjacent columns, said fabric having unidirectional elasticity.
The fabric of this invention is said to have unidirectional elasticity since it possesses elasticity, i.e. elongation and rapid recovery, in either the machine or the cross direction, depending on its method of manufacture; however, this is its major component of elasticity since it is understood that it will have elasticity in the bias.
The fabric of the invention is produced by a process comprising (l) forming a laminate of a plurality of tenuous webs of loosely associated textile fibers dispersed in sheet form, (2) subjecting said laminate to fiber rearrangement to provide systematically staggered pores therethrough, (3) bonding said poriferous or foraminous fabric to provide integrity, (4) drying fabric, (5) drafting said fabric to cause unidirectional extension, (6) ap- "ice plying an elastomeric binder to said extended fabric, and (7) drying said fabric while it is held in said extended position.
The textile fibers used in the production of this fabric may be either individualized fibers, tow, monofilaments or continuous filaments; however, individualized fibers are preferred and these vary from approximately 1/2" to 2" in length. The fibers may be either natural or manmade, i.e. polymers synthesized by man, modied or transformed natural polymers and glasses. They may be elastomeric, in and of themselves, thereby contributing to the elasticity of the final fabric; however, the initial elasticity produced in the fabric by re'ason of this invention is not in any manner dependent upon the fibers possessing inherent elasticity.
Webs of textile fibers are formed by processing the fibers through any suitable machinery to form a sheet of loosely associated fibers. In this web-forming process it is preferred that the fibers be first carde'd; however, this is only a preference and no unsatisfactory results appear if this step is deleted.
The webs or sheets of fibers are preferably superimposed to provide a laminate of from about 300 grains per square yard to about 1200 grains per square yard. Below about 300 grains per square yard the laminate is too weak or lacks suicient strength to undergo the necessary additional processing. The upper limit is only a practical maximum since it is dictated by the necessity to next bond the laminate to provide integrity and since beyond this limitation, bonding becomes difficult using existing methods and techniques. If the webs or sheets are random lay, i.e., by the air laying of fibrous webs, as for example, by the Rando-Web process, lamination is not necessary since the web has sufiicient substance. The preparation of a laminate, however, is the most preferred embodiment and insures the most desirable results.
Having provided the laminate, it is processed to rearrange the individual fibers which define it and thus to provide a poriferous structure whereby the perimeter of each of the pores is defined by bundles of these rearranged textile fibers and whereby the pores are systematically arranged columnwise' in staggered relationship to corresponding pores defining immediately adjacent columns. This could be accomplished by any feasible method but is preferably accomplished by the method and apparatus disclosed in U.S. 2,862,251.
The laminate is then bonded With adhesive or cementitious materials to provide sufiicient integrity to allow it to be processed further without breaking up. The bondin g operation employed for stabilizing and strengthening nonwoven fabrics has taken on many forms, one popular form being the intermittent bonding of the nonwoven fabric with a predetermined pattern of spaced 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 selfsustaining relationship. The binder areas may also take on any desire'd shape or form including circles, annuli, ovals, elipses, triangles, rectangles, squares, diamonds, parallelograms or other polygons or combinations of such forms either regular or irregular 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 0r irregularly wavy.
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 of the nonwoven fabric should not substantially exceed about 35% 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. The minimum amount of binder can be determined by the minimum amount of binder add-on which is solids add-on.
The binder may also be applied by impregnation, as for example, by passing the fabric through a padder bath and this represents the preferred procedure and results in the most satisfactory product. It is important, in this event, that about at least 5% solids is distributed uniformly throughout the thickness of the fabric. Of course, the binder may be applied using any of the common techniques known to the art. Preferably, if you print bond there should be from about 10 to about 15% binder addon and if you impregnate you would preferably have about 10% binder solids add-on.
The fabric is then dried to develop the bond.
The binder material which is to be used to provide integrity to the laminate or to the poriferous structure is generally defined as any of the common binders available to the textile art provided it has a fair degree of Wet strength; however, if the impregnation technique is utilized the binder used must have a measurable amount of elasticity. Representative examples of some of these binding materials are polyvinyl acetate, polyvinyl chloride, yacrylate, natural or synthetic rubber, and the like. Viscose can be utilized only if the impregnation technique is not employed since it has no elastic properties.
Having bonded the poriferous structure it is now dried to effect the bond. The dried fabric is then drafted, drawn or extended, preferably in the machine direction; this is accomplished by drawing the fabric between two nips or control points running at different speeds. The fabric may be drawn up to any point short of fabric destruction or as little as desired depending upon the amount of elongation and rapid recovery that is desired in the finished fabric.
Retaining the fabric under tension, it is now bonded with an elastomeric binding material and heat is applied to the binder. Throughout the operation, i.e., the application of binder and the drying, the fabric is kept under tension to allow the binder to set and cure and thus retain the fabric in this extended condition. The resultant fabric now has unidirectional elasticity.
The elastomeric binder is generally defined as any binder exhibiting elastomeric properties or any binder that has been termed rubber by the art. Preferably the elastomeric binder is any polymer that has elastic properties and is cross-linked by covalent bonds and will recover, after elongation, with a good power factor. Most preferably a cross-linked acrylic binder is desired since it is defined by chemical stability, resistance to oxidation and to discoloration.
As an alternative to the above-described procedure, the fabric Imay be bonded after fiber rearrangement followed by a combination of drafting to the desired elongation or extension and drying to set the binder and to insure the extended fabric position in the absence of forced extension in the direction of draft. The greatest proportion of extension is given to the fabric if it has been wetted. This wetting can be accomplished by the application of binder or by the utilization of a separate wetting step.
Additionally, a greater degree of elasticity may be supplied if the fiber of the fabric is cotton or rayon or a combination thereof. This would be accomplished by incorporating a cellulose-reactive constituent into the elastomeric binder composition which will provide, after cure, a cross-linking of the cellulosic fibers and an increase in the modulus of the fabric over that fabric elasticity which would have existed in the absence of the cellulose-reactive constituent.
The fabric of this invention is a nonwoven which is preferably constructed of individualized textile fibers. It has been rearranged to provide pores which are positioned in columns, but in staggered relationship to corresponding pores defining immediately adjacent columns. The fabric has, during manufacture, been extended in one direction, i.e., the machine or cross direction, and bonded in position; therefore, the pores have a longitudinal axis extending in the direction that the fabric was extended or drafted and a shorter lateral axis extending at subtsantially right angles to the former. Regardless of the original configuration of the pores prior to the drafting operation they are elongated in the final product and each possesses one longitudinal axis extending in the same direction as the direction in which the fabric has been extended during manufacture. For the sake of simplicity this direction of extension shall hereinafter be termed the draft direction of the fabric or the draft direction.
The present invention will be more fully understood with reference to the following detailed description and the accompanying drawings in which:
FIGURE l is a schematic illustration of the process for forming the fabric of this invention;
FIGS. 2 and 3 are enlarged idealized representations of an intermediate fabric of the invention;
FIG. 4 is an enlarged idealized representation of one embodiment of the fabric of this invention; and,
FIG. 5 is a diagrammatic representation of the properties exhibited by the fabric of this invention.
More specifically, FIGURE l recites the steps of the process for producing the elastic nonwoven fabric. As is indicated, the webs of textile fibers are first formed and then superimposed to produce a laminate. The laminate is caused to undergo fiber rearrangement to effect the poriferous fabric and then bonded and dried to provide sufficient integrity to permit the fabric to undergo the further processing. This is followed by unidirectional drafting and bonding with an elastomeric binder while the fabric is in extended position. The fabric is then dried in this extended state.
FIGS. 2 and 3 represent embodiments of intermediate fabrics of this invention taken after the fiber rearrangement step of the process but prior to the drafting step. With specific reference to FIG. 2, the machine direction is given by the arrow and the letter M while the cross direction of the fabric runs at right angles to the direction M.
The fabric 1 is poriferous as is evidenced by the pores 2 and is constructed of individual fibers 3 which have been rearranged into bundles defining the perimeters of the pores 2. The pores 2 are shown as extending into columns A, B and C, respectively, which run in the machine direction and in rows E, F, G and H which run in the cross direction. It is essential that the pores of any one column be in staggered relationship to the pores of the immediately adjacent columns as, for example, the pores of column B are staggered with respect to the pores of columns A and C, i.e., the pores of A and C do not occupy a position in rows F and H as do the pores of column B but rather in rows E and G.
The imaginary trapezoid 4 is taken along the'centers of the two pores 2 in columns B and from the center of each of the respective poresn 2 in columns A and C. It is to be noted that the acute angles X of the trapezoid are both positioned along row G and in columns A and C, While the obtuse angles Y are both positioned along column B in rows F and H. The pores 2 are substantially circular and the fabric has been bonded sufficiently to provide the necessary integrity to the poriferous laminate to permit it to undergo the further processing required Without breaking up.
The fabric of FIG. 3 differs from that of FIG. l only insofar as the pores are hexagonal rather than circular and insofar as the fibers of the initial webs were randomly positioned in the fabric of FIG. 2 whereas they were carded and thus oriented in the webs comprising the fabric of FIG. 2. Particular attention is invited to the fact that in FIG. 3 there are two parallel sides 5 and 6 of each pore running in the machine direction for a measurable distance.
FIG. 4 is meant to represent the same section of the fabric shown in FIG. 2 with the sole exception that the fabric depicted is now the finished fabric as opposed to the intermediate fabric of FIG. 2.
The fabric of FIG. 4 has undergone all the processing steps described earlier (see FIG. l) and has therefore been drafted. Unidirectional drafting of the fabric has been accomplished in the machine direction M as is evidenced by the elongated condition of the pores 2. The pores 2 are each now characterized as having a long longitudinal axis 7 extending in the direction in which the fabric has been drafted and a short lateral axis 8 at substantially right angles to the former. The angles X of the trapezoid 4 which were the acute angles in FIG. 2 are now the obtuse angles and angles Y have become the acute angles. Thus a parallel-motion mechanism, or parallelogram-type device familiar as lazy tongs, collapsible gates, or the pantograph device utilized in drafting has been eected and is represented by the imaginary trapezoid of both FIGS. 2 and 4.
In FIG. 4 since this represents one embodiment of the linished fabric of this invention, it has been drafted in the machine direction and bonded in position with an elastomeric bonding material. It has then been processed so that its permanent position is represented by that depicted in FIG. 4. Attempts at fourth extension in the direction of drafting of a fabric will be of no avail and in fact the fabric will exhibit exceptional strength in the direction M; however, extension in the cross direction C in this instance, i.e., in the direction at right angles to the direction of drafting, will be evidenced by elasticity or specifically by fabric extensibility in that direction and fabric recovery to substantially the position shown in FIG. 4. The fabric of FIG. 4 can be extended in direction C to a point just before the rupture of the fabric, i.e to a point just before bers are broken and/or fabric bond sites are ruptured. The degree of recovery is exceptional.
In FIG. 5 the percent recovery of the fabric of this invention is plotted against the specific elongation which the fabric is made to undergo and the results are plotted.
The fabric is that made via Example l and the results show the excellent elongation and companion recovery exhibited by the fabric.
Referring, after the above explanation, to the fabric depicited in FIG. 3, it is now pointed out that any side to the pores such as sides S and 6 which have measurable distance in one parallel or substantially parallel direction will act to diminish the degree of elasticity which the fabric exhibits since they become rigid members of the pores 2 which hamper or lessen the functioning of the lazy tong principle of the invention.
Each of the pores of the fabric must have a diameter within the range of from about 0.020 to about 1A taken across its longest axis, since below about 0.020 the amount of extensibility exhibited by the fabric is negligible and the pores or holes are of insufficient dimensions to effect the desired lazy tong result and since above about 1A" in diameter the requisite bundles of textile fibers cannot be formed during the fiber rearrangement or in other words the desired pores cannot be produced.
The sum total of the open area per square inch of the fabric must be within the range of from about to about 50% open area or in terms of the number of pores per square inch, from 400 to 10 per square inch. Below the minimum open area the amount of extensibility or elasticity exhibited by the invention is negligible and with an open area above 5 0%, the pore formation is poor and the fabric loses its integrity.
The pores may be of any configuration although as mentioned earlier straight line sides of a pore as for example in any polygon configuration, Where these straight line sides extend at substantially right angles to the direction of the unidirectional elasticity of the fabric and where the straight sides do have some measurable dimension will hamper the invention and will act to lessen the elasticity. The pores should also be ofthe same or very similar configuration and of approximately the same size to avoid discontinuities in the fabric and to contribute to the maximum functional efliciency of the elastic nonwoven fabric.
The pores are positioned systematically in columns in the fabric and in rows extending at right angles to the columns and in staggered relationship thereto. They are positioned systematically in columns to provide a regular reoccuring sequence =which will contribute to the uniform unidirectional elasticity throughout the fabric. Randomized positioning would severely lessen the elasticity. The individual pores of any one column must be arranged in staggered relationship to the corresponding pores defining immediately adjacent columns in order to allow the perfection of the lazy tong principle on which the unidirectional elasticity of the fabric depends. Thus the line drawn through the centers of the pores of any one row will not bisect the center of any pore or pores defining two adjacent columns of pores. As can be realized, a pattern effect can be imparted to the fabric by the pores and still not impair the fabric elasticity, as long as the same pattern of pores reoccurs throughout the fabric systematically in regular occuring sequence and so long as the pores comprising each individual pattern are arranged in the same column row-staggered relationship defined above.
In providing the required relationship between the pores of the column and those of the rows such that the pores arranged columnwise are in staggered relationship to the corresponding pores defining immediately adjacent column, it is only necessary to insure that the centers of any three pores, each in an immediately adjacent column, do not coincide such that they, i.e., the three pores, lie in `a single row running at right angles to the columns. Of course, the ideal arrangement to provide maximum unidirectional elasticity in the fabric would be to position the pores of any one row with respect to the pores of any one column such that lines drawn from the centers of two successive pores in one column to the center of an adjacent pore interposed in a row between them, will produce an angle approaching 0 at their juncture at the center of the pore in the row.
The unidirectional elasticity of the fabric lis provided by the utilization of the lazy tong principle which is realized by the essential pore and hole positioning and configuration in the fabric and by the drafting or extending of the rearranged fabric in one direction followed by the bonding with an elastomeric binder while the fabric is held in an extended position so that the hinder is permitted to set while the fabric is in that extended state. Since the fabric has then been extended and bonded s0 that this extension is retained, the fabric does then exhibit excellent strength but no significant elongation in the draft direction. It does, however, exhibit excellent extensibility and recoverability in the direction substantially at right angles to the draft direction of the fabric. The percent elongation that the fabric will possess will range from about 15% to about 200% and it will be uniform. The elongation may be termed cross extensibility since it is in a direction substantially at right angles to the draft direction of the fabric. The fabric, having been extended to just below its rupture elongation, i.e., to of break, will have at least a 50% recovery which is, in most instances, followed by an elastic aftereffect (following the initial rapid retraction of the extended article) which will slowly cause the total recovery to approach The invention will be more fully described in the following example Which is illustrative and in which parts and percentages are by weight unless otherwise specified.
EXAMPLE l A fabric is made by laminating oriented card webs to a Weight of 330 grains per square yard. The fiber comprises 75% extra dull and 25% regular dull viscose rayon Pounds Karamul 142 ST 200 Water 200 Catalyst A 1 The pH of the binder is adjusted to approximately 7 with ammonia. The padded web is dried over steam cans operating at 275 F. The binder picked up is such as to add 35 grains per square yard of dry binder solids so that the total finished weight is 365 grains per square yard.
This base fabric is further processed by passing through another padder containing a solids bath of Karamul 142 (manufactured by Refined Products Company and formulated as above except to 5% solids level). The wet out fabric is dried over steam cans operating at 275 P. The steam cans are operated at a faster line speed than the padder so as to effect a drafting of the wet web between the two units. The resin applied, which is soft and elastomeric, is caused to be set while the fabric is stretched and locks the lazy tongs in a closed position. The dried fabric has substantial widthwise extensibility as the tongs open. This fabric has a resultant cross-extensibility of 170% and substantially 100% recoverability. In this instance, the fabric fed to the padder is 44 inches Wide. Due to the drafting, it is reduced to 28 inches in width at the dry cans. It is to be appreciated that the drafting also affects the fabric weight per unit area. In this instance, the final stretch fabric weighs 750 grains per square yard. This comprises approximately 450 grains per square yard of fiber and 300 grains per square yard of total binder solids.
The fabric can be treated although the softness and hand of the finished article are satisfactory.
The fabric can be treated to be made Waterproof and can be treated to provide additional softness, hand, etc., although the softness and hand of the finished article are satisfactory. It rcan also be dyed or otherwise colored and can, in general, be treated in accordance with those methods and ultimate desires presently practiced with nonwoven fabrics.
What is claimed is:
1. The process for producing a poriferous non-woven fabric having no significant extensibility in the long direction and having unidirectional cross elasticity defined by an elongation in the range of from about to about 200% and an elastic recovery after elongation to 80% of break of at least 50% rapidly and approaching 100% slowly which comprises:
(1) forming a laminate of a plurality of tenuous webs of loosely associated textile fibers dispersed in sheet for-m;
(2) subjecting said laminate to ber rearrangement to provide a poriferous fabric having systematically staggered pores therethrough;
(3) bonding said poriferous fabric to provide integrity;
(5) drafting said fabric in the long direction thereof in an amount short of fabric destruction to cause unidirectional long extension and unidirectional crosswise reduction whereby said pores become elongated and have a long longitudinal axis and a short lateral axis;
(6) applying an elastomer binder to said extended fabric; and
(7) drying said fabric while it is held in said extended position to provide pores having a diameter within the range of from about 0.02" to about 1A" taken across the long axis of said pores, and said fabric having an over-all open area of at least about 20%, whereby said fabric has no significant extensibility in the long direction but has excellent extensibility and recoverability after extension in the cross direction.
2. The process for producing a poriferous non-woven fabric having no significant extensibility in the long direction and having unidirectional cross elasticity defined by an elongation in the range of from about 15 to about 200% and an elastic recovery after elongation to of break of at least 50% rapidly and approaching 100% slowly which comprises:
(1) forming a tenuous web of loosely assoicated textile fibers dispersed in sheet form;
(2) subjecting said web to fiber rearrangement to provide a poriferous fabric having systematically staggered pores therethrough;
(3) bonding said poriferous fabric to provide integrity;
(5) drafting said fabric in the long direction thereof up to about 80% of break to cause unidirectional long extension and unidirectional crosswise reduction whereby said pores become elongated and have a long longtiudinal axis and a short lateral axis;
(6 applying an elastomer binder to said extended fabrics; and
(7) drying said fabric while it is held in said extended position to provide pores having a diameter within the range of from about 0.02 to about 1A taken along the long axis of said pores, and said fabric having an over-all open area of at least about 20%, whereby said fabric has no significant extensibility in the long direction but has excellent extensibility and recoverability after extension in the cross direction.
References Cited UNITED STATES PATENTS 2,697,678 12/1954 Ness et al 161-170 X 2,862,251 12/1958 Kalwaites 161-169 X 2,958,608 11/1960 Barnard 161-138 X 3,081,515 3/1963 `Griswold et al. 161-169 X ROBERT F. BURNETT, Primary Examiner LINDA M. CARLIN, Assistant Examiner Us. C1. XR.