US3551271A - Nonwoven fabrics containing heterofilaments - Google Patents

Description

United States Patent U.S. Cl. 161-150 5 Claims ABSTRACT OF THE DISCLOSURE A non-woven fabric is made by forming a web containing at least 5% by weight heterofilaments comprising at least two components at least one of which is an elastomer and at least one of which is potentially adhesive, and subsequently activating the adhesive component to bond the structure at the filament cross-over points. Preferably the elastomeric and potentially adhesive component are the same component.

DISCLOSURE This application is a continuation of Ser. No. 473,824, filed July 21, 1965, and now abandoned.

This invention relates to nonwoven fabrics and to processes for making them.

Nonwoven fabrics as heretofore available have usually suffered from certain property limitations and Weaknesses which have tended to restrict their range of applications. Particularly deleterious properties in regard to the employment of nonwoven fabrics in the making, for example, of articles of apparel, have been their general stiff, board-like character and their poor drapability. A number of proposals have been advanced in an attempt to ameliorate those properties, but, generally speaking, the improvements can be effected only by sacrificing strength in the fabric, and this lack of strength may militate against the acceptance of the fabric for certain end uses.

In applications, Ser. No. 346,752 filed Feb. 24, 1964 and Ser. No. 342,300, filed Feb. 4, 1964, both abandoned, there is described and claimed inter alia nonwoven fabrics which exhibit in combination an adequate drapability and a good tensile strength. In broad and somewhat simplified terms, the advantageous combination of properties possessed by the nonwoven fabrics of the aforementioned applications is owed to our discovery of the eflicacy of incorporating in the fibrous webs, from which the fabrics are devised, at least a proportion of composite filaments, of which heterofilaments, that is to say, unitary filaments, consisting of two or more polymeric components contiguous and adherent to one another continuously along the length of the filament are a particular advantageous type.

This invention is based on our discovery of the utility of a certain type of heterofilament in providing nonwoven fabrics which posses not only tensile strength of the same order of magnitude as the fabrics provided by our previously mentioned applications, but, in addition, have a superior drapability, flexibility, crease-resistance properties and conformability.

Accordingly, the nonwoven fabrics of this invention comprise fibrous webs containing at least five percent heterofilaments consisting, of two or more components, at least one of which is an elastomer, fibres in the fibrous webs being bonded together at points where they crossover and contact one another by the adhesive characteristics of a potentially adhesive component of said heterofilaments.

For convenience of discussion we will consider the heterofilament to consist only of two components although it will be understood that the filaments may, if desired, have more than two components. In the two component heterofilaments one or both of the components may be an elastomer. The heterofilaments containing at least one elastomeric component will be referred to herein as elastomeric heterofilaments. For convenience in this specification the non-elastomeric component will be referred to as a hard component.

By the expression potentially adhesive component as used in this specification and the claiming clauses appended hereto we mean a component the adhesive char acteristics of which can be developed without sensibly affecting the other component of the heterofilament.

In the heterofilaments which contain one hard and one elastomeric component, either may be the potentially adhesive component although in certain respects discussed more fully hereinafter it is desirable that the elastomeric component should be the potentially adhesive component.

The terms filament and fibre are used in this specification and in the claiming clauses appended hereto in the generic sense and include continuous filaments, and staple fibres including flock.

The incorporation in the fibrous web from which the fabrics are derived 0f heterofilaments possessing at least one elastomeric component endows the fabric with resilience and flexibility, properties which are reflected in the good drapability, crease-resistance and conformability of the fabrics.

Drapability is measured by determining the length of fabric (the bending length) which is necessary to cause the fabric to bend from the horizontal plane when under no constraint to such an extent as to contact a declining angle of 415 of slope from the point of departure of contact.

Conformability is largely a subjective property which We find convenient for expressing the ability of the fabric to give and yield in adopting a particular configuration. In relation to the application of the fabrics as articles of apparel, it is important that they should have a good conformability.

Flexural rigidity is a measure of the fabric stiffness or flexibility and is related to the quality of stiffness that is appreciated on handling the fabric, and its measurement involves determining the length of fabric which is necessary to cause the fabric to bend from the horizontal plane when under no constraint to such an extent as to contact a plane surface inclined at an angle of 41.5 to the horizontal. The procedure is fully described in British standard specification No. 3,356/ 1961. Briefly stated, it comprises placing a one inch wide strip of the fabric upon a horizontal surface, one end of which abuts against the top end of a 41.5 inclined plane. The test sample is placed with its narrow edge at the juncture of the horizontal and inclined surfaces. It is then moved forward over the edge between the two surfaces until the free end bends over and contacts the inclined surface. The length of the arc (cantilever length) between the point of departure from the horizontal surface and the point of contact with the inclined surface is measured and this is the bending length (in abbreviated form represented by B.L.). The flexural rigidity can then be evaluated from the formula:

Flexural rigidity=weight per unit length x B.L. x k

The advantageous properties discussed above are most manifest when the potentially adhesive component is an elastomeric component of the heterofilament, for then,

3 the bonds formed at points of contact and cross-over of fibres in the fibrous web are elastomeric in character and consequently the fabric has a maximum degree of lateral freedom and flexibility in three dimensions.

Although we have discussed the advantageous properties of the nonwoven fabrics of this invention in relation to the use of a particular type of heterofilament (elastomeric heterofilament), the fact that the heterofilaments provide the fibrous web with a built-in-binding action which is owed to the potentially adhesive component thereof, is also of significance in the development of those properties, and, perhaps more importantly, provides the fabric with good dimensional stability and adequate tensile strength without any sacrifice of the desirable low fabric density.

The nonwoven fabrics of this invention combine together the properties of drapability, flexibility, and conformability with good dimensional stability and tensile strength.

The introduction of resilience and flexibility in the fabrics by using heterofilaments which contain only one elastomeric component successfully overcomes difiiculties which we have experienced in attempting to import those properties into fabrics by using elastic homofilaments. Among the difiiculties which we have found associated with this latter method are, the diificulties of web formation, the tendency of the elastic fibres to migrate through out the web during and subsequent to processing, and the trouble experienced in attempting to form a coherent structure by needle-punching. That these ditficulties are largely obviated when the elastic fibre is incorporated in the web and resulting fabric as one component of a hetertofilament can be attributed to the presence of the other component and its role in, for example, restraining the elastomeric component which is held along its length in association with that component.

In selecting the components for the heterofilaments attention should be paid to their compatibility one with another and also to their ability to adhere together to form a unitary filament.

The heterofilaments may be prepared by any of the well-known processes. Thus melts, or solutions, of the polymeric components may be extruded simultaneously through an orifice in sheath and core or side-by-side relationship, or the components may be extruded through separate orifices using known apparatus and subsequently brought into adhering contact with one another whilst they are still in a tacky condition to form a unitary filament,

As the hard component which may be present in the heterofilaments there are called into question synthetic condensation polymers such, for example, as polyesters, polyamides, polyurethanes, polyureas, and polycarbonates, addition type polymers such as the polyhydrocarbons, and those made from ethylenically unsaturated monomers such, for example, as vinyl chloride, vinylidine chloride, vinyl acetate, acrylonitrile and their copolymers.

The term elastomer as used herein has the meaning conventionally given to the term in the art.

Suitable elastomers for use in this invention may be found in many classes of fibre-forming polymer. The elastomer may, for example, be a segmented (block copolymer) elastomer, of which, as examples, there may be mentioned the following:

N-substituted copolyamides containing from 1534 percent of N-substitution and prepared by the reaction of a lactam of an omega-amino carboxylic acid with N-substituted amino-carboxylic acid containing more than 7 carbon atoms; N-substituted polyamides containing from 15-38 percent of N-substitution and prepared by the reaction of an N,N'-disubstituted aliphatic secondary diamine, a dibasic carboxylic acid containing at least 5 carbon atoms in the chain and a lactam of an omegaamino carboxylic acid containing 720 ring members or by the reaction of an N mono substituted aliphatic diamine, a dibasic carboxylic acid containing at least 5 carbon atoms in the chain and a lactam of an omega-amino carboxylic acid containing 7-20 ring members.

N-alkyl-substituted copolyamides as described in British Patent No. 692,069; and

Polyester-urethanes generally, but in particular those and made from a hydroxyl-terminated copolyester of molecular weight greater than 1500, a dihydric alcohol and an aliphatic or cycloaliphatic diisocyanate, the diisocyanate not being present in a molar excess at any time during the making of the polyurethane.

Suitable elastomers may also be formed using the fibreforming addition polymers, for example, copolymers of butadiene/acrylonitrile, butadiene/ styrene, and butadiene/ 2-vinyl pyridine, polychlorobutadiene and copolymers of isobutylene with small proportions of butadiene.

Examples of two component heterofilaments, contain- ;ing both a hard and an elastomeric component are those characterised by their ability to crimp spontaneously at drawing. Such heterofilaments are characterised by a crimp frequency of at least 10 crimps per inch.

A variety of methods are available by which the nonwoven fabrics of this invention may be made, and the method chosen will depend to a very large extent upon the particular kind of fabric within the general class desired. Common to all the available methods is the initial step of fabricating a fibrous web.

The fibrous web itself may be formed by any of a number of known techniques for depositing or arranging fibres in a web.

These techniques include carding, garnetting, air-laying and paper-making techniques for the fabrication of staple fibres webs. Continuous filament webs may conveniently be prepared by drawing off the filaments directly from a spinning unit, or they may be formed from a package or other storage device for yarn already spun. Continuous filament yarn webs, that is to say, webs in which the filaments are present as multifilaments may conveniently be prepared in a process wherein freshly spun filaments are subjected to the action of a high velocity turbulent fluid jet which attenuates and orients the filaments and intermingles them to form a twistless yarn, which yarn is forwarded by the fluid jet and deposited on a receiving surface in a random loopy manner.

In one method of making fabrics in accordance with this invention the fibrous Web is subjected to a heat and pressure treatment, for example, by passage between the nip of heated calender rollers, whereby the potentially adhesive component is activated i.e. rendered adhesive.

In another method of making the fabrics at least the heterofilaments in the fibrous web are crimped or, if they are already crimped, further crimped, prior to or during the treatment to which the web is subjected in order to activate the potentially adhesive component of the heterofilaments.

Heterofilaments may be crimped by exposing the fibrous web containing them to a suitable shinking treatment. The shrinkage of the heterofilaments in order to effect crimping may be carried out by the use of any suitable shrinking agent. Shrinking may, for example, be carried out by heating by various means, as by the application of hot aqueous media (for example, hot or boiling water, and steam including pressurised steam), oil, hot air or other hot gaseous or liquid media chemically inert to the polymer components of the heterofilaments. Alternatively, or in addition, the heterofilaments may be crimped, or further crimped, by exposing the fibrous web to the action of a swelling agent for one component of the heterofilaments.

Whether crimp be etfected by a physical or chemical treatment we frequently find it convenient to activate the potentially adhesive component, thereby bonding together fibres of the web where they cross-over or contact one another, in the same treatment. Thus, crimp and activation may be effected by sujecting the fibrous web to a heat treatment in which the temperature exceeds the softening point of the potentially adhesive component. Examples of heterofilaments which can be crimped and activated in this manner and the conditions under which these steps can occur are shown in the table below:

Mzziaranyl L.A. (Indentified in Example A polyester urethane.

When the potentially adhesive component of the heterofilament is such that it can be chemically activated the crimping and activation steps may be accomplished in the same chemical treatment. Such a chemical treatment may conveniently be adopted for heterofilaments consisting, for example, of various proportions by weight for example, equal quantities of Maranyl L.A., which is a polyamide copolymer identified in Example 2, as the hard component, and a polyester urethane as the elastomeric, and also the potentially adhesive, component, the two components being arranged in a side-by-side relationship. Such heterofilaments can be crimped, and the elastomer component rendered adhesive, by treating the fibrous web containing the heterofilament at room temperature in a bath of dimethylformamide which can be considered as a selective solvent for the elastomer component.

In all circumstances in which crimping and activation are achieved in separate treatments, the fibrous web, after crimp has been developed in fibres therein, is subjected to a further treatment to activate the potentially adhesive component thereby bonding together fibres of the web where they cross-over or contact one another. Bonding in this manner can be accomplished in a variety of ways and in any particular instance the method used is, to a large extent, dependent on the nature of the potentially adhesive component and also that of the other component of the heterofilament. Where the potentially adhesive component has a lower softening point than the other, it may conveniently be made adhesive by subjecting the web to a heat treatment which may, for example, be achieved by dry heat, as by passing hot air through the web or by heating it in an electric oven, or by treating the web with moist heat as by the use of moist air, hot water or steam. Other possible methods of heat activation include exposing the web to radiation, for example, infra red radiation of a suitable intensity and duration. When the potentially adhesive component is capable of being activated chemically, activation may be achieved by an appropriate chemical treatment.

Whenever crimp is developed in the heterofilaments of the fibrous web, the resulting fabric has a superior bulk or loft, a better developed resiliency and a more open structure than a fabric made from the fibrous web under conditions, for example subjecting the web to a simultaneous heat and pressure treatment, wherein no crimp is developed.

A fabric possessing a compact porous structure and suitable for use in the making of a synthetic leather material may be obtained from the bulky resilient fabric by applying a pressure to the latter within a short interval of time after the fibre bonds have been formed i.e. while they are still in an adhesive condition. Under the applied pressure the crimped fibres are deformed in a manner somewhat analogous to the depression of a helical spring and a myriad of small pores which confer breathability on the resulting fabric are preserved therein.

It is only necessary that the fibrous web contain five percent heterofilaments, although we prefer that they be present in an amount of twenty percent or more, and other fibres which are inert or substantially so to the activation treatment to which the Web is subjected may be employed as a blend with the heterofilaments. Although those other fibres must be inert to the activation treatment they may be potentially crimpable, in which event they may be crimped in any treatment to which the web is subjected to crimp, or further crimp, the heterofilaments therein. Depending upon the particular desiderata sought in the fabric, the percentage of heterofilaments present in the fibrous web may be varied widely.

The nonwoven fabrics find applications in many diverse fields, but they are particularly well adapted for end uses which demand a fabric possessing a good drape, flexibility, crease-resistance and conformability combined with an adequate tensile strength and air-permeability, uses Wherein the advantageous properties of the present fabrics are utilised to the full. The fabrics are, for example, suitable for a number of applications as articles of apparel.

By way of illustration, but not by way of limiting the invention there will now be given the following specific examples.

Example 1 In the heterofilament used in this example, the elastomeric component was an N-substituted polyamide of the type prepared by heating toegther 192 gms. of N,N-diisobutyl hexamethylene diamine, 162 gms. of sebacic acid, and 814 gms. of caprolactam in the presence of 16 gms. omega-amino-undecanoic acid, 1 gm. of orthophosphoric acid and 50 mls, of water as polymerisation catalysts. The resulting polyamide in which approximately 25 percent of the nitrogen atoms carried isobutyl substituents had an inherent viscosity of 0.6, and a softening point of 160 C. The hard component of the heterofilament was nylon 11 having a softening point of 190 C. and an inherent viscosity of 0.63.

A monofilament comprising the above two components arranged in a side-by-side relationship was made by melting under pressure in a spinning machine a sintered rod consisting of equal parts of the two components the spinning machine being adapted to force the molten polymers at a temperature of 240 C. through an undivided filter pack and then extruding the polymers through an orifice contained in a spinneret plate. The extruded monofilament was dusted with talc and then wound onto a bobbin at a rate of 400 feet per minute.

The monofilament was subsequently cold drawn at ambient temperature at a draw ratio of 4:1. The filament crimped spontaneously on relaxing from the drawing tension and had a denier of 15 and a crimp frequently of 2 per inch.

18 gms. of three inch staple fibres formed from the crimped heterofilament were carded on a Shirley miniature card and the laps so formed laid on top of one another with successive laps disposed at an angle of with respect to the previous lap so forming a cross-laid web having a weight of 9 ounces per square yard. A 5" x 4 /2 portion of this cross-laid web was placed between the heated plates of a hot press maintained at a temperature of C. and therein subjected to a pressure of 300 p.s.i. for a period of 1% minutes.

The resulting fabric was in the form of a thin sheet.

On examining the fabric under the microscope it was observed that in consequence of the temperature and the applied pressure the adhesive characteristics of the elastomer component of the heterofilament had been developed and refined bonds had formed at the points of contact and cross-over of adjacent fibres. Despite the activation treatment to which the web had been subjected the elastomeric component remained in contiguous association with the poly(amino-undecanoic acid) component which retained its fibrous form. The absence, of any spread of the potentially adhesive, that is to say, the elastomeric component, throughout the structure and the refined nature of the bonds formed resulted in preservation of substantially all the interstitial spaces between fibres, and gave the resulting fabric a porous air-permeable structure.

7 The fabric was a drapable material having a texture simulating to a certain degree that of a woven fabric. It had the physical properties shown in the table which follows:

poly(hexamethylene adipamide) and poly(hexamethylene sebacamide) sold by Imperial Chemical Industries Limited under the name Maranyl LA. 29. It had a Vicat softening point of 190 C. and an inherent viscosity of 0.962. The elastomeric component was a polyester ure- Density, gm./cc. 0.5 a thane. The extruded monofilarnent was passed through Mean bending length, cms. 4.25 an aspirating jet within which it was acted upon by high Flexural rigidity, mgm. cm. 2,350 velocity air supplied through an inlet in the sidewall of the jet. Toroidal vortices having their axes substantially Since the fabric had a homogeneous structure, in the 10 perpendicular t th mean axis of the filament, are sense that, it consisted entirely of fibres all of which were th ht t b f d within the jet thereby creating a selected from the same chemical classification i.e. all the t b l t one around the filament which had the effect fihres had the Same functional groups, it Was readily y of whipping the filament from side to side. The filament Wlth y one dyesthfl- To Produce a leather-like material was forwarded by the blast of air issuing from the jet, to the fabric Could be coated, for p With a p ya foraminous receiving surface where it was laid in a urethane, and dried. A leather-like grain could be imrandom loopy manner in the form of a continuous filaprinted on the coated surface of the dyed fabric by pressment web having a Weight of approximately 1 ounce per ing the surface with a patterned heated embossing plate. square yard. A portion (15.7 cms. X 19.4 cms.) of this The influence of the elastomeric component of the w b w ighing 1.1 .gms. was placed between two brOWn heterofilament in endowing the fabric with resilience and paper h et ea h of which had previously been coated h y, Properties Which find eXPTeSSiOII in the good with poly(tetrafluoroethylene), and the resulting sanddfapablhty, flexibility, Crease-resistance and tensile Wich passed at a rate of 1 foot per minute between the strength which the fabric possesses, can conveniently be nip of two calendar rollers each four inches in diameter Illustrated by a comparison of the measured p y and which exerted a pressure of approximately 100 p.s.i. pr p r i f t ri With a a r r v d f m a The temperature of the calendar rolls was of the order fibrous web consisting of heterofilaments which contain f 178 C. two components, none of which are elastomeric. Such The effect, u on the fibrous web, of the heat and presa fabrlc may be prepared in the following manner: sure applied in the calendar was to activate the .polyester A q y of tWo and a half inch 15 denier pl fibres urethane component of the heterofilaments, which became formed from heterofilam ts Consisting of equal P P tacky and in this condition bonded together fibres in the tlohs y Welght of Poly(hox'dthothylolle adtpamide) and fibrous web at points where they cross-over or contact an 80/20 random copolymer of poly (hexamethylene adipone other, P y( P Capfolaotam) y 66//66/6), The bonds which confer upon the fabric dimensional the two components being arranged in a side-by-side reintegrity and mechanical strength were elastomeric in lp, Was carded in a Shirley mini t re car n 5 character and consequently the fabric possessed a high the t p so formod laid on p of each other h 5116- degree of lateral freedom and flexibility in three dimen- Cesslve o dlsposed at all angle of With pe t to sions. The excellent drapability, crease-resistance and o PIoVlous p 50 forming a Cross-laid Web having a conformability of the fabric can be attributed to the WBlght f 9 Ounces P Square y r The Web s then elastomeric bonds holding the fabric together and to the plaoedhotwoeh the tWo heated Plates of a hot Press t presence in the heterofilaments of an elastomeric commalhtalhed at a tothpefatufo of and Subjected ponent. Moreover, since the polyester-urethane on actitherem to a pressure of 300 p.s.i. for a period of 1% vation formed refined bonds, that is to say, there was an minutes. In consequence of the temperature and pressure absence of blobs, the fibres being cemented together only to which the fibrous web was subjected, the adhesive charat points of contact and the polyester urethane over the acteristics of the lower melting point component, i.e. the greater part of the length of the heterofilaments remained copolymer component, of the heterofilament w re dev lin contiguous association with the hard component, the p that is to y it became adhesive thereby Causing fabric had a porous, air-permeable structure. fibres in contact with one another to stick or fuse together. The properties of the nonwoven fabric discussed The fabric which was strong had a stiff and board-like above find expression in the physical measurementslisted handle. It had the properties listed in the table below: in the table which follows:

Properties Mean Elastic Work bending Flexural Tensile recovery, recovery, Density, length, rigidity, Extension, strength, 10 percent 10 percent Direction gm./cc. cms. mgm.cm. percent kgJgmJcm. extension extension QLQiEPJStIIIII: 8:3 1. '72 39 $5 3%? Density-0.45 gm./ cc. Mean bending length-very much greater than 6 cms. Flexural rigidityvery much greater than 6,500 mg./'cm.

It will be observed that the drape of the novel fabric 65 described in this example was at least some 30 percent better than the drape of the fabric derived from the nonelastomeric heterofilaments.

Example 2 being 300 C. The hard component was a copolymer of To demonstrate the superior drape, flexibility, creaseresistance and conformability of the nonwoven fabric of this example when compared with a fabric derived from heterofilaments which contained no elastomeric component, a continuous filament web having similar basic weight (1.15 ounces per square yard) as the web described hereinbefore was made by the same method from a heterofilament consisting of poly(epsilon caprolactam) as one component and an /20 random copolymer of polytepsilon caprolactam) and poly(hexamethylene adipamide) as the other. The web was then fused by passage through calender rolls, under identical conditions as before except that the temperature was 200 0., thereby forming a sheet fabric weighing 1.5 ounces per square 9 yard and having the properties shown in the table which follows:

1 O This Web was then immersed for a period of 30 minutes in dimethylformamide to activate the elastomer compo- Properties Mean Tensile bending Flexural strength, Density, length, rigidity, Extension, kg./gm./cn1. Direction gnL/ec. cm. mgm./crn. percent Along fabric 0. 3 3. 3 184 11 95 Across fabric 0.3 3. 2 166 11 71 On comparing the values listed in this table with the nent of the heterofilament fibres which, in consequence, values found for the corresponding properties listed in became adhesive and in that condition bonded together the preceding table the superiority of the fabric derived fibres in the web, The ability of the dimethylformfrom heterofilaments containing an elastomeric compo- 15 amide to activate the elastomer component can be exn n i i for i not y had a better p y, plained on the basis that it is a selective solvent for that crease-resistance, flexibility and conformability but it also component, and as such causes swelling and gelation of had a much better tensile strength. The combination of the elastomer. In addition to its swelling action the diall these advantageous properties makes the novel fabric 3 methylforrnamide shrink th lastom component thereeminently suited for numerous apparel applications. by further crimping the heterofilament fibres.

Example 3 The tensile strength and dimensional stability possessed by the resulting nonwoven fabric was owned to the re- A heterofilament having the Same components and inforcement of the binding action attributable to the rangement thereof as the heterofilament used in Example {V t i ll dh i component b h random i l k. 2 Was eXtrlld d as a m fil n n the manner ing, inercurling and/or interlooping resulting from crimp. scribed in Example 1 a Spinning temperature of The fabric possessed an enhanced bulk and resiliency, C. The monofilarnent which was wound up onto a bobbin a more Open appearance, and a loweT density as at 400 feet/minute had an as-spun denier of 104. It was pared with the f b i of Examples 1 to 3 and this may Subsequently cold-drawn at ambient temperature at be attributed, at least in some measure, to the presence dlZlW ratio Of The filament had a denier Of in the fabric of crimped filaments and to thg absence of was cut into flock sing a Diifsfling flock cutting any application of pressure in the bonding together of machine. fibres in the fibrous web.

A quantity of this flock and a quantity of cellulose pulp W l i (Weight ratio Was diSPEISed y Vigfous agitation 1. A nonwoven fabric comprising a fibrous web conover a ten minute period, in three litres of Water containmi i at least fi percent, b d on h i h f ing a small quantity of Dispersol V.L. (the Word Disperfibres in the web, of heterofilaments consisting of at least sol is a registered trademark). The resulting uniform 5118- two components, at least one of which is an elastomer PQIlSiOn was filtered O er an 8 inch square 100 mesh wire and which is potentially adhesive, and at least one other Screen t0 give a uniform coherent Web having a Weight component being a hard, non-elastomeric component of 2 /2 ounces per square yard, and an excellent Wet with fibres in the fibrous Web bonded together at points strength. This Web was placed between two p0ly(tetrawhere they cross-over and contact one another by the fluoroethylene) coated sheets of brown paper so form g adhesive characteristics of said elastomeric, potentially a sandwich which was passed at the rate of 1 foot per adhesive component, said fabric having a bending length minute between the nip of a pair of four inch diameter of from 1.75 cm. to 4.25 cm. and having a ratio of calender rollers maintained at a temperature of 180 C- bending length in centimeters to density in grams per and exerting a pressure of approximately 100 psi cubic centimeter of from 5.8 to 8.5.

As a result of the applied heat and pressure the Web 2. A nonwoven fabric as claimed in claim 1 wherein experienced considerable area shrinkage and the polyester the heterofilaments are crimped. urethane component of the heterofilament flock beca e 3. A nonwoven fabric as claimed in claim 2 wherein adhesive thereby serving to bond together fibres Which the heterofilaments have a crimp frequency of at least came into contact with that component. The fabric, which 10 crimps per inch. was considerably more drapeable and flexible than a 4. A nonwoven fabric as claimed in claim 1 wherein similar fabric derived from a non-elastomer heterofila- 20 to 50 percent, based on the Weight of fibres in the ment, had a weight of four ounces per square yard, an web, of the fibres are heterofilaments and the balance extension of 34 percent and a tensile strength of 83 are non-activatable. k m /cm, 5. A nonwoven fabric as claimed in claim 1 wherein Example 4 50 to 100 percent, based on the weight of fibres in the A heterofilament having the same components and ar- 22%; t fg f g gi and the balance rangement thereof as the heterofilament used in Example 2 was extruded as monofilament in the mamEerOdeScIiIbEd References Cited in Exam le 1 at a spinning temperature of 0 C. e monofilar iient which was wound up onto a bobbin at 400 UNITED STATES PATENTS feet/minute had an as-spun denier of 104. It was sub- 2,774,129 12/1956 Sec i t 1 1 1 9 sequently drawn at ambient temperature at a draw ratio 3,038,235 6/1962 Zimmerman 1611 75X of 4:1. The filament which had a denier of 20 crimped 3,348,993 10/ 1967 Sissons 1 1 4 spontaneously on relaxing from the drawing tension. The crimped 25 denier filament (crimp frequency 12 ROBERT BURNETT, Pflmafy EXamlneI crimps per inch) was cut into two inch staple, a quantity MAY, Assistant Examine,-

of which was carded on a Shirley miniature card so as to form a web having a weight of approximately 3 ounces.

U.S. Cl. X.R. 156306; 16ll73