IL10853A - fibers and filaments having improving crimp characteristics and methods for their production - Google Patents

Description

EWIKIQN PILING -PiDE S AND FILAMENTO IIAVINQ IMPROVED CRIMP- CHARACTERISTICS AND METHOD FOR THEIR PRODUCTION This invention relates to synthetic textile fibers and particularly to improved, crimped composite filaments.

In the course of the development of the synthetic textile fiber industry, much effort has been expended towards the production of fibers which retain the well- known advantages of synthetic fibers such as ease-of-care, durability, and improved mechanical properties, but which, at the same time, possess the properties required to obtain fabrics of outstanding aesthetic appeal such, for example, 0 as that which characterizes wool fabrics. Wool fabrics have good bulk and cover, obtainable at a relatively low finishing shrinkage which is quite desirable from an economic standpoint. In addition, wool fabrics have excellent elastic properties such as stretchability, compressional resil - 5 ience, and liveliness, and display a pleasing surface handle. Finally, the surface of wool fabrics is renewable; even after such severe deformations as crushing or glazing, a new surface can easily be obtained, for example, by wetting, steaming, or mere recovery in humid air. 0 Although different proposals of the prior art have attained one or more characteristics of wool fabrics, in no instance have such synthetic materials been properly considered as being wool-like in other than superficial appearance. For example, good bulk, cover, and surface softness 5 have been obtained by processing into fabrics blends of fibers with high and low residual shrinkage, and by subjecting the. as-knit or as-woven fabrics to a shrinking treatment. Though- the bulk and loft of fabrics prepared by this route are excellent, this improvement is at the expense of an undesirably high finishing shrinkage and resilience loss.

It has also been proposed to improve fabric aesthetics by imparting to the synthetic fibers a spiral crimp. Fibers of this type have been prepared by use of special spinning conditions or after-treatments which bring about differential physical properties over the cross-section of single-component filaments, or by spinning together two or more materials to form a composite filament which contains the components in an eccentric relationship over the cross-section of the filaments; if the two components of a composite filament possess substantially different shrinkage, a crimp is caused by the differential shrinkage of the spun and drawn components. Such spirally crimped fibers, if embodied into fabrics, will Impart a softer surface handle and somewhat improved bulk without, however, providing the other characteristics of wool fabrics such as elastic properties or surface renewability.

Improved elastic properties, such as resilience and liveliness, have been incorporated into fabrics by using blends of various substantially different filament deniers instead of only one more or less uniform denier. The elastic properties can also be improved by application to the fabric of certain finishes.

By use of such i ers and processes of the prior art, or combinations thereof, it has thus been possible to match or even to surpass wool in one or several aesthetic properties* But it has as yet not been possible to prepare synthetic fibers which duplicate wool aesthetics in all respects. lha previously known composite orimped filaments have the d eadvantage that par of the crimp is lost or becomes unavailable in fabrics composed of such filaments* due in the iar&© part to the fact that the filaments become compacted and lose freedom of movemen in the fabricf is results in the production of fabrics of reduced covering powe or "leanness*.

The objects of this invention are effected by producing a crimped composite filament of synthetically formed polymers having the capacity of changing the amount of crimp upon being exposed to theeffec of a swelling agent and of everting to the original crimp upon removal of the swelling agent. $his charaeteri ic is, for convenience* referred to as ^re ersi le" crixapj generally speaking this characteristic of the filaments of this invention is observed by the "squirming" of the filaments upon both application and emo al of the swelling agent. fhe filaiaen s o this invention form helical coils due to the difference in length be wee the components after shrinkage, he components swell longitudinally to different extents so that treatment of a crimped filament with a swelling agent spontaneously causes the helical coils to change their appearance and dimensions, such as the diameter of the helix* the itch of the helix crim fre uenc or both. On a li- cation of the smelling agent, a fiber which is free to stove has a motion like that of a turning eorekscrew whic is simultaneously changing its ow dimension* On removal of the swelling agent, as by drying, the helical coil egai s ( or attempts to regain against fabric restraints) its original configuration* She movements within the individual coiled fibers or the forces developed thereby are called * squirming* of the ibers for the purposes of the present invention* The novel* synthetic, composite fibers or fila~ sients of the present Invention comprise at least two distinct components of fully synthetic polymer© which are arranged in an eccentric relationship if viewed in the cross section and are capable of squirming. They may be crimped or they may be self-crimping, i.e. they contain a potential crimp which can be developed into an actual crimp by a simple treatment . The components reversibly swell in the direction of the fiber axis to a different degree upon a treatment with a suitable liquid. The property of a component of reversibly swelling in the direction of the fiber axis will be called "longitudinal swellability" . In accordance with their mode of manufacture, the new fibers usually possess molecular orientation. A pronounced difference in the degree of hydrophillc properties of the polymers comprising the components may cause a different degree of longitudinal swelling in aqueous liquids . In accordance with this invention, this difference of longitudinal swell-ability is preferably more than 0.05$ by Test A and, often, depending on the composition of the components, more than 0.1$ (more than 0.4$ and 1.02$ by Test B respectively).

In accordance with the invention those fibers and filaments are particularly useful and desirable wherein the longitudinal swellability of at least one component is enhanced by the presence in the polymer structure of ionizable groups which have preferably been introduced by copolymer-ization with a comer containing these groups. The ionizable groups may be either attached to the polymer or copolymer forming the component or the component may be a physical admixture of a neutral polymer with another polymer or copolymer containing such ionizable groups . The effect of the ionizable groups is usually considerably enhanced by the presence of the so-called neutral disperse dye-enhancing modifiers in the chain of the copolymer. If only ionizable groups are responsible for the increased longitudinal swellability, satisfactory properties are usually obtained if at least 50 milliequivalents of ionizable groups are present per kilogram of polymer. If both or all of the components of the composite fibers or filaments contain ionizable groups, it is of advantage that the component with the higher longitudinal swellability contains an amount of the ionizable groups per kilogram of polymer which exceeds that contained in the other component or components by at least 0 milliequivalents , If the copolymers contain also a disperse dye-enhancing modifier, it is usually sufficient if there is a differential of at least 30 milliequivalents of ionizable groups per kilogram of polymer in the components . A pronounced enhancement of the longitudinal swellability usually will be obtained by the presence of at least 1% neutral dye-enhancing modifier based on the total weight of the copolymer or component respectively though amounts of more than 3$ are often desirable. The ionizable groups may be either acid groups or basic groups. With most polymers, and particularly with addition polymers or vinyl polymers respectively, acid groups are preferred. The best properties are found with those composite fibers or filaments which contain the groups of strong acids, such as sulfonic acid groups .

The most desirable properties are found in composite fibers and filaments in accordance with this invention which consist of or contain major amounts of ^,»^-*·»»»·*^^ Though generally both or all components of the composite fibers and filaments are comprised of fiber forming polymers, satisfactory properties can also be found with such structures wherein one or more of the components consist of a synthetic polymer which is not fiber forming, as long as at least one of the components is fiber forming.

The components may be arranged in a side-by-side fashion so that all the components contained in the composite fiber or filament make up at least part of the surface thereof . Another desirable arrangement is the so-called sheath-core arrangement where one or more of the components is completely surrounded by another component.

A preferred and convenient method for the produc-tion of the new fibers and filaments of this ^entioj^ ^ comprises co-spinning two or more streams of different polymers by the dry, wet or melt spinning methods with subsequent drawing or stretching to form an oriented, composite filament whereby care is taken that at least one of the components contains more than 30 and preferably more than 0 milliequivalents of ionizable groups per kilogram of polymer. If more than one of the materials used in the process contain ionizable groups, the materials should be selected and combined such that the difference between the lowest and highest content is at least 30 milliequivalents and preferably 50 milliequivalents of ionizable groups per kilogram of polymer.

In order to produce a permanent crimp in the composite structures of the present invention, the polymers used for the production should have a differential in shrinkage as determined on the extruded and drawn polymer of at least 1% which permits the production of a pronounced crimp by subjecting the oriented, composite fibers or filaments to a shrinkage treatment, e.g. a boil-off or a heat treatment .

If the component having the higher longitudinal swellability is an addition polymer, particularly an acrylonitrile polymer which has more than 85$ acrylonitrile, it is of advantage to use a copolymer which contains in addition a neutral disperse dye-enhancing modifier in combined form. One or more components may consist of a I physical admixture of a copolymer containing the ionizable groups and/or the disperse dye-enhancing modifier with a neutral iber-forming polymer or copolymer.

In the case of addition polymers, and particularly polyacrylonitrile containing more than 8$ acrylonitrile, outstanding properties may be obtained in accordance with the present invention if polymers are selected such that the disperse dye-enhancing modifier (comer) is present in the component having the higher swellability in amounts of at Another method for producing the fibers and filaments of this invention comprises spinning together two or more critically selected synthetic polymeric materials, at least one of which is fiber-forming, in such a way that the materials form over the cross-section of the single composite filament two or more distinct zones which extend through the entire length of the filament in eccentric fashion, whereby only one, or alternatively, part or all the components form the surface of the single composite filament . The crimp may be produced by a shrinkage treatment if one component of the composite, drawn filaments has a substantially greater shrinkability than the other component . In this process at least one component must display a reversible length change, due to longitudinal swelling of the filament, to a substantially greater degree than the other component . By virtue of this characteristic, the crimp of composite filaments of this invention, upon exposure of the filament to a swelling agent, is, at least in part, altered but is regained upon removal of the swelling agent .

The value of this crimp reversibility is evidenced by the ability of the filaments in yarns of this invention, when embodied in a fabric, to squirm or twist around in the fabric under the influence of a swelling agent such as water (and also on removal of the swelling agent), but, nevertheless, to regain the original crimp in the fabric with removal of the swelling agent, as by drying. Fabrics containing these novel filaments acquire a high degree of fullness or covering power as a result of the swelling treatment and to such treatments repeatedly. It will be understood that fabrics composed of the novel filaments can beneficially also be subjected to a physical working of the fabric to develop fullness and covering power to the greatest degree. Since the finishing shrinkage is lo , the yarns of fabrics containing such filaments have a relatively open structure so that the fabrics exhibit unusual elastic properties .

This reversible squirming crimp is also of particular advantage in pile fabrics such as those used in carpets and upholstery where the compacting of the fibers under compression incident to use may be overcome by treatment with water, other swelling agents, or merely exposure to humid air the fibers will squirm or work out of the compressed state but, upon drying, will again squirm and revert to their highly crimped and voluminous state which they had prior to being compressed.

In order to develop the crimp reversibility characteristic of filaments of this invention, one component of the crimped filament should have a reversible length change by Test A after shrinkage of at least 0.05$ and preferably at least 0.10$ more than that of the other component, that is, said component has at least 0.05$ greater change in length of the original length upon swelling than the other component .

The reversible length change of a component may be determined by measuring the increase in length of a mono-component filament of the component polymer (spun and subjected to after-treatments under the same conditions as the composite filament) upon being immersed in the aqueous medium used for the testing of the crimp reversibility of the com .v For all reversible length changes denoted "by Test A1' the tests are executed with strands of approximately 100 denier and approximately 15 inches long as follows . The samples (previously relaxed by a boiloff) are clamped in a tensile tester with a small amount of slack and held in the proper medium (air, cold water, or hot water) for about 2 minutes . The mechanically driven clamp is then started at a low rate of elongation (0 .3 inches per minute); it is stopped and reversed immediately when the stress-strain curve starts to depart from the zero line . The true length of the sample is then calculated from the clamp distance in the starting position and the chart distance between the start of the test and the point where the stress-strain curve began .

After wet tests the samples are dried (while clamped) by means of a hair dryer, and the length of dry strand at room temperature determined as above. Wet-to-dry cycles are repeated until the length change becomes constant . As a rule some shrinkage occurs during the irst cycle . Por most samples, satisfactory results are obtained with three cycles .

The reversible length change is calculated in per cent, based on the final dry length of the sample. Reversible !engt, change . * 100' Results from at least four different strands are averaged to obtain a representative value.

A second test for equilibrium reversible length change whose data are designated "by Test B was devised which gives results more reproducible than Test A above but which in general agrees with those results. In this test strands denier and 6 inches long are then suspended vertically from a a rubber-tooth clamp and weighted with/1.2-gram clamp. The sample is mounted vertically in a stoppered glass tube containing a desiccant in the bottom. The tube is stored vertically overnight (18-24 hours) at 70°C. After the 70°C. conditioning to dry the sample, the 70°C. dry length, i.e., the distance between clamps, is determined with a cathe-tometer. The desiccant is then removed from the tube, the tube filled with water and stored vertically at 70°C . for 6 hours . The length of the wet sample la determined at 70°C . The cycles are repeated as required to obtain reproducible results .

One component of the crimped filament should have a reversible length change by Test B after shrinkage of at least 0. $ and preferably at least 0.6$ more than the other component in order to develop crimp reversibility.

If a component cannot be spun into a monocomponent filament because its molecular weight is too low, its swellabillty is determined by extrapolation from the swellabilities of monocomponent filaments of the same polymer (in different spinnable molecular weights).

In the processing of textile fibers and in the aesthetics of fabrics made from them, the level of crimp in the fiber is important . The proper level of crimp must be maintained in the fibers so that the fibers, in the form of staple fibers, will exhibit sufficient coherence, at least during the early stages of yarn spinning operations, to permit their processing, e.g., combing, carding, and drafting, in existing textile equipment as used in the trade for c t w w Likewise, by adjusting the crimp, usually over the range of crimp which is processable, it is possible to vary fabric aesthetics. High crimp will produce bulky, lofty fabrics. Low crimp will produce consolidated, slick fabrics. This crimp, which is important to fabric aesthetics and fiber processabillty can be obtained easily if the two components of the fiber, in addition to the reversible length change difference discussed above, also exhibit a shrinkage differential.

To develop adequate crimp in the composite is preferably filaments, the shrinkabillty of one component/ at least 1$ greater than the shrinkability of the other component, that is, said component has at least 1% greater loss of the original length upon shrinkage than the other component. The shrinkability of a component is determined by measuring the shrinkage, upon immersion in boiling water under no tension, of a monocomponent filament made from the component polymer (spun and otherwise processed under substantially the same conditions as the composite filament). If a component cannot be spun into a monocomponent filament, e.g., because its molecular weight is too low, its shrinkability is determined by extrapolation from a graph of the shrinkage characteristics of monocomponent filaments of the same polymer (in different, spinnable molecular weights).

The filaments spun in accordance with this invention may be drawn, cross-linked, or subjected to other after-treatments which may be desirable to improve the general properties of the fibers. When testing filaments of the individual components for reversible length change or shrinkage, it is, of course, necessary that these are prepared under the same spinning and after-treatment conditions as those used for the composite filaments.

The crimped fibers of this invention may contain helices which reverse direction at irregular Intervals.

Accurate measurements of crimp reversibility require sam- pies without these reversals. Preparation of such filament samples was accomplished by a pretwisting of the filament (prior to exposure to the crimping medium) to the same degree as the crimp frequency found by examination of similar filaments crimped without pretwisting.

For crimp reversal measurements the test "A" was carried out as ollows . The pretwisted ilament was crimped free of tension by immersion in boiling water or other suitable shrinking media. The crimped filament was then suspended in a tube and kept from floating or bending by a small weight (l milligram) attached to the lower (free) end and insufficient to remove crimp, the weight being dial- shaped to permit measuring and counting rotations of the dial during crimping and uncrimping. The filament was treated successively to 5 cycles each consisting of a 5- minute exposure to 25°C. water followed by a 10-minute drying period in 25°C. moving air. The revolutions of the dial (which are equivalent to the crimp changes) for the drying portion only of each cycle, were averaged for the 5 cycles and expressed as revolutions per centimeter of extended (straight) dry filament and are referred to hereinafter as crimp reversibility. Values from at least three filaments tested as above were averaged to obtain the crimp reversibility of a fiber The crimp reversibility values were corrected to a four denier per filament figure which can readily be done since crimp reversibility is inversely proportional to the cube root of denier.

Here again more reproducible crimp reversibility by Test B values were obtained under equilibrium conditions/ than by the above test, although the same general results were obtained. Test B was applied to the measurement of crimp reversibility as follows A single filament is separated from the single end or tow of drawn., unrelaxed fibers , A three -inch length of the filament is attached to opposite sides of a rectangular copper wire frame with 30 slack between the ends. The rack and filament is then boiled off for 15 minutes to develop the crimp The crimped filament is then transferred to a special viewing holder by taping or gluing the ends so that about 10$ slack is present and the filament length between the clamped ends is approximately 2. 5 Inches. The filament and viewing holder is then mounted vertically in a stoppered test tube containing desiccant. The tube is stored vertically overnight (18-24 hours) at 70°C . Following this conditioning period to dry the filament the tube is then brought to room temperature (approximately 25°C . ) . After allowing 30 minutes for cooling the total number of crimps in the filament between the fixed ends are counted. In counting, any crimp reversal points present are ignored The desiccant is then removed from the glass tube, the tube filled with water and stored vertically at 70°C for 6 hours. The number of crimps in the wet fiber are counted as above . The cycles are repeated as required to obtain reproducible results The equilibrium crimp reversibility or change in crimps/inch of crimped length from 25°C . dry to 70°C. wet expressed as cpi is obtained by the following n equation where the siglj of A cpi is ignored.

In the spinning, the polymers are usually not appreciably blended together in the melt or solution but are fed separately to a shaped orifice where they are simultaneously extruded. The orifice is, then, adapted to receive the components separately for simultaneous extrusion to form a filament in which each component is substantially localized but is held to the other component in an eccentric relation. The extrusion can be such that the components are localized and held together in a ·' side-b -side !' structure in which both components form part of the surface of the composite filament The extrusion may also be such that one component forms a core and the other a sheath to form a composite referred to hereinafter as a 'sheath-core' structure. In this structure, only the sheath contributes to the surface of the composite.

The composite filaments are subjected to stretching, where applicable,- and then given a shrinking treatment (to develop crimp) while substantially free of tension.

Referring to the drawings : Figure 1 is a central cross -sectional elevation of a spinneret assembly which can be used to make the composite filaments of this invention; Figure 2 is a transverse cross-sectional plan view of the apparatus of Figure 1 taken at 2-2 thereof and showing details of the top of the back plate; Figure 3 is a transverse cross-sectional plan view taken at 3-3 of Figure 1 showing details of the bottom of the back plate; Figure 1A is an enlarged portion taken from Figure 1 to show details of the spinneret at the spinning orifice; and Figures 4, 5 and 6 show greatly magnified cross-sections, i.e., sections perpendicular to the filament axis, of typical filaments of this invention produced by dry spinning. In these drawings one component is shaded to show the separation between components.

With reference to Figure 1, the bottom spinneret plate (2) which contains a circle of orifices (3) Is held in place against back plate (l) by retaining rings (12) and (14) and by bolt (13). A fine-mesh screen (4) e.g., 200 mesh per inch, is pressed into position between, and serves as a spacer between, spinneret plate (2) and back plate (l) . Back plate (l) contains two annular chambers (8 and 9) which are connected to suitable piping and filtration apparatus (not shown) to receive different spinning compositions. Lead holes (ll) go from annular chamber (9) to annular space(7). Lead holes (10) lead from annular chamber (8) to annular space (6) . Annular spaces (6) and (7) are separated by wall (5) which is disposed above orifices (3) and spaced from contiguous passage of the spinning fluids from annular spaces (6) and (7) through orifices (3)* the mesh of screen (4) being fine enough to permit spinning fluid passage through orifices (3), as shown in detail in Figure 1A.

In Figure 2 are shown four lead holes (10) and four lead holes(11) equally spaced within the concentric chambers (8 and 9) , respectively.

In Figure 3 are shown the concentric inner and outer annular spaces (6 and 7) and the fine-mesh screen (4) partially in section.

Operation of the described apparatus in the practice of this invention is readily understood. Separate spinning materials are supplied to the inner annular chamber (9) and outer annular chamber (8), respectively, of the back plate; the former flows from chamber (9) through the lead holes (ll) into the inner annular space (7) and thence through screen (4) and orifice (3) to form a part of a composite filament, while the latter passes through the lead hole (10) to the outer annular space (6) and thence through screen (4) and the outer side of the orifice (3) to form the other part of the composite filament.

The acidity of a polymer was determined by percolating a dimethyIformamide solution of the polymer through an ion exchange column containing a mixture of a strongly acidic resin and a strongly basic resin followed by passage through a column containing the acidic resin alone. The free acid groups in the polymer solution were then titrated using an alcoholic solution of KOH and a suitable indicator. The polymer concentration was determined by evaporating a portion of the solution to dryness. Analytical results were expressed as milliequivalents of acidic groups per kilogram of dry polymer.

The basicity of polymers was determined by dissolving the sample in cyclic tetramethylene sulfone, passing the polymer solution through a strongly basic ion exchange resin in the hydroxyl form and titrating with a solution of sulphuric acid in tetramethylene sulfone by a potentiometric method using a glass electrode. The polymer concentration was determined as set forth above with respect to the acidic polymer.

In the following examples, parts, proportions and percentages are by weight unless otherwise indicated, (n) is used to designate intrinsic viscosity.

EXAMPLE 1 Copolymer (a) was made from acrylonitrile, methyl acrylate, and sodium styrene sulfonate by " continuous polymerization in water with K2S O8 catalyst, sodium meta bisulfite activator and Na2C03 for stopping the polymerization at the desired point , the monomers being fed to the reactor at relative rates of 93» 63* 6.00, and 0.37$» respectively. The polymer had an (n) of 1.5 and contained 5I4. milliequivalents of acid groups per kilogram of dry polymer. The polymer contained 6% of methyl acrylate. The proportion of methyl acrylate in a polymer has been found to be the same as in the feed monomers.

Copolymer (b) was made in a similar manner from acrylonitrile and sodium styrene sulfonate with relative feed rates of the monomers of 97.0 and 3,0, respectively. The polymer had an (n) of 1,5 and contained 20I4. milliequivalents of acid groups per kilogram of dry polymer.

Copolymer (c) was made in a similar manner from the continuous polymerization of a monomer feed consisting of 91 acrylonitrile and 6$ methyl acrylate. The polymer had an (n) of 2.1 and contained 26 milliequivalents of acid groups per kilogram of dry polymer which is considered to be present as acid end groups from the sodium meta bisulfite activator and the K2S O8 used in the polymerization. The polymer contained .0$ of methyl acrylate.

A 25$ solution of Copolymer (a) in dimethyIformamide and a 25$ solution of Copolymer (b) in dimethyIformamide were simultaneously spun in equal feeds as the two components of side-by-side filaments with a spinneret similar to that shown in Figures 1 to 3 having l8 orifices of 0.006 inches in diameter so as to extrude equal volumes of each component in each filament. The solutions were extruded at 125°C. into an inert gas at l80°C. and wound up at 200 ypm after application of a spinning finish. The arrangement of the components in typical cross-sections resembled those of Figures 4 and 5. The spun yarn was drawn 300$ (4x, i.e., to 4 times the length before drawing) in 95°C . water and dried.

Monocomponent filaments of each component polymer spun and drawn in the same manner as above had reversible length changes by Test A of 0.46 and 0.64$, respectively, after shrinking and subjecting to the action of water at °C . Equilibrium reversible length changes by Test B of 3.67$ and 6.51$ respectively were observed.

EXAMPLE 2.

Composite filaments were spun from 22$ solutions in dimethylformamide of polyacrylonitrile (the homopolymer) with an intrinsic viscosity of 2.0 containing 25 railli-equivalents of acid groups per kilogram of polymer and Copolymer (c) of Example 1 through a spinneret similar to that shown in Figures 1 to 3 having l40 orifices, 0.0047 inches in diameter. The spun yarn was drawn 300$ (to 4 times the original length before drawing), in steam, The as-spun filaments had cross-sections similar to Figures 4 and · onocomponent filaments of the component polymers, spun and drawn in the same manner, had reversible length changes by Test A of 0.19$ and 0.16%, respectively, after shrinking. Equilibrium reversible length changes by Test B of 1.0% and 1.3$ were measured.

EXAMPLE 3 Samples of the drawn composite yarns of Examples 1 and 2 developed approximately 20 helical crimps per inch of extended fiber length (i.e., with the crimps pulled out) respectively, in boiling water. The crimped filaments had crimp reversibilities by Test A of 0.11 and 0.0 crimps per centimeter respectively. Equilibrium crimp reversibilities by Test B of .5 and 0.40 crimps per inch change were obtained.

The value of the wet Initial modulus (Mi) is directly related to the work that the crimped fiber can do in the crimp reversing step between the wet state and the dry state. Initial values (25°C. wet) were 20 and 23 grams per denier (gpd), respectively.

EXAMPLE 4 Tufted (pile) fabrics were made from the 3-denier per filament unrelaxed (uncrimped) filaments of Example 1, Example 2, and homocomponent filaments of Copolymer (a). The fabrics were boiled in water for 30 minutes, air-dried, and brushed up with a hand card. Each pile fabric was then crushed for 24 hours to 10 to 20$ of its initial height by a 1 kilogram weight 2 inches in diameter. After the weight was removed, the fabric was allowed to stand in air fabric was then immersed in 60eC. water for 1 minute without agitation, and air-dried. The fabric from homocomponent filaments showed no recovery after any of the treatments . The fabric from the filaments of Example 1 recovered about 90$ of its original height after 24 hours and recovered 100$ after the wetting and drying cycle. The fabric from the filaments of Example 2 (no crimp reversibility) showed no dry recovery and only about 30$ recovery after wetting and drying .

EXAMPLE 5 Staple fibers (70 parts) were cut from the filaments of Example 1 and blended with wool (30 parts), spun into yarn, woven into a Shetland-type fabric and subjected to the usual finishing and fulling operations employed for wool fabrics of this type. The finished fabric was equivalent to a similar all-wool fabric in bulk and cover in the low shrinkage experienced during the fabric finishing steps (e.g., 25 and 15$ shrinkage in the warp and fill directions, respectively), in elasticity and liveliness, and in the soft, pleasing wool-like surface handle. Similarly constructed fabrics of synthetic filaments not having crimp reversibility displayed poor bulk and cover despite higher shrinkages, poor elastic properties, and had a less wool-like surface handle.

EXAMPLE 6 The monomers, acrylonitrile (e), methyl acrylate (f), sodium styrene sulfonate (g), methacrylic acid (h), and acrylamide (i) were used to make polymers and copolymers in an aqueous continuous polymerization, as in Example 1, using monomer feed ratios as shown in Table I below. The resulting polymers were used to make crimped composite filaments, as in Example 1. Monocomponent filaments were made in a similar TABLE I MONOMER PEED RATIOS Item Component I Component II I e/g/h/i 91.6/ /5/3 e/f/g 93.6/6/.37 55 (AN/SSA/MAA/AC) (AN/MA/SSA) Both ccanponents of all items had (n) of 2.0 * basicity except D and E vhich had (n) of 1.5· A TABLE I (Continued) Homocomponent Fila- COMP ments Reversible length change, % s (1-11) Draw Modulus Test A Test A Test B Ratio Den ./Pil . 25° Wet Item I II A 0.71 0.19 • 52 4.3 8x 6 35 B 0.56 0.27 .29 1.8 8x 2 26 C Ο.38 0.26 .12 0.6 8X 3 29 D 0.46 0 .9 - .53 3.0 4χ 3 19 E 4χ 3 50 P 0.30** 0.19 .11 - 4x 3 23 G 1 .23 0.69 Ο.5 0.8 8x 3 21 ** at pH 3 Examination of the data on items A, B, and C in Table I, clearly shows the importance of the difference in ionizable group content between components as demonstrated here by sulfonic acid groups in causing a reversible length change in water and the corresponding effect upon crimp reversibility in the composite filament. Item D demonstrates the beneficial use of an acid modifier other than styrene-sulfonic acid in producing a reversible crimp in a filament.

The spun yarn of Item E was cross-linked before drawing by treating the spun yarn wound on perforated tubes in a solution composed of 50 gallons of water, 3 gallons of 0$ formaldehyde, and 3 pounds of concentrated sulfuric acid for 18 minutes at 98°C. The cross-linked fiber was then drawn 4x in a 0.3$ sodium carbonate solution at 95°C. The drawn fibers were then boiled for one hour on perforated tubes in 0.5$ NaHCO^. They were then cut into two-inch lengths and boiled for one hour in distilled water, which developed a very excellent spiral crimp (designated "salt" in Table I below). Another portion of the drawn yarn was boiled free of tension in 1% hydrochloric acid for 30 minutes followed by boiling in water to obtain the crimp (designated "acid" in Table I).

It is considered that cross-linking is merely a means of obtaining the proper balance of physical properties between the components of the composite filament.

EXAMPLE 7 A copolymer containing acrylonitrlle and vinyl acetate (j) in the proportion 95/5 by weight was prepared as in Example 1, with a (n) of 2.0. Another copolymer of acrylonitrlle and 2-methyl-5-vlnyl pyridine (k) in the pro-portion 50/50 by weight with a (n) of 2.0 was made in a similar manner. The two copolymers were blended in the ratio of 90 parts to 10 parts, respectively. The final analysis of the blended polymer is given in Table I as component i of item F, and contained 380 milliequivalents of basic groups per kilogram of dry polymer. Solutions of this polymer and polyacrylonitrile (the homopolymer) of (n) 2.0 containing 2$ polymer in dimethylformamide were dry-spun, as in Example 2, and the resulting yarn drawn 4X in 95°C water. Boiling the unrestrained yarn gave a very excellently crimped product with 20 crimps per extended inch with properties as shown in Table I.

EXAMPLE 8 A copolymer (component l) containing 4.7 of methyl acrylate and 176 milliequivalents per kilogram of acid groups with a (n) of 2.0 was made from acrylonitrlle, methyl acrylate, and sodium styrene sulfonate using the technique of Example 1 , A second copolymer of (n) 2.0 containing l80 milliequivalents of acid groups per kilogram and no methyl acry-late groups was made from acrylonitrlle and sodium styrene sulfonate using the polymerization technique of Example 1. The two polymers were co-spun as in Example 7 and the resulting composite filaments drawn X in 95°C. water.

Relaxation in boiling water gave an excellent crimped product with properties as described under item G in Table I.

It was very surprising that the presence of the methyl acrylate in the polymer component having the lesser acidity, so enhanced the effect of the ionizable groups present in component A that it had a greater reversible length change than the other component and hence caused a reversible crimp.

EXAMPLE 9 This example illustrates how suitable components may be selected for use in the composite filaments of this Invention.

Various copolymers of acrylonitrile were prepared, as in Example 1, spun into homocomponent filaments and the pertinent properties measured. These results are given in Table II. Reversible length changes were determined in 25°C water. In general, it will be noted that or neutral modifier content as the ionic group contenl of a polymer increases, the reversible length change of yarn prepared from it increases.

Items 14 and 15 show the reversible length change obtained with basic groups in an acid swelling medium.

The data of this example show a process variable that changes the reversible length change of the filaments namely, the draw ratio. As the draw ratio is increased for a given polymer, the reversible length change is decreased. These data indicated the importance of examining homofilaments of prospective polymer candidates for the composite filaments of this invention, under the same conditions that they are to be spun, drawn or otherwise treated in the resulting composite fiber.

Items 9 and 11 of Table II, particularly illustrate the effect of a disperse dye enhancing monomer such as methyl acrylate in the polymer.

TABLE II Monomers AN B acrylonitrile # miliequivalents of acid groups per kilogram of dry poly * miliequivalents of basic groups per kilogram of dry poA ** measured at pH 3 EXAMPLE 10 Another means of evaluating polymer candidates for use in the composite filaments of this invention is by means of cast films using known techniques. Polymers can be quickly and readily cast into films, cut and then carefully drawn, relaxed and shrinkage measurements, and thereafter differential length change measurements made thereon.

Composite films can be made by casting one polymer solution upon another.

Various polymers and copolymers were made from acrylonitrile, sodium styrene sulfonate, methyl acrylate and 2-vinyl pyridine using the polymerization techniques of Example 1. These polymers were then blended as desired to give the required content of icnizable groups and of methyl acrylate. The component polymers for items A, B and C, as acrylonitrile shown in Table III, were all/copoly ers as made. The polymers for items D, E and F of Table III were made by blending a copolymer with either the homopolymer of acrylonitrile or with a copolymer of acrylonitrile and methyl acrylate (94/6 weight ratio). The Tn7 of a11 polymers and blends were 2.0 with the exception of the parent acrylonitrile/vinyl pyridine polymer which had an 7 o 1 .35.

The various polymers and blends were each dissolved in dimethylformamide to make a 1 $ solution of the polymer. A film was cast from a polymer solution on a glass plate by means of a doctor's knife having a clearance of 0.010 inches. This film was dried for 30 minutes at 95°C. in a forced draft oven. An equal amount of a second solution was then cast over this film in a similar manner to yield a final film having 50$ of each polymer and the composite film was then dried under the same conditions as the first film except that it was dried for one hour.

The composite films were stripped from the plate, cut into 1/8 inch wide strips and drawn 4X over a pin heated to 105°C.

The total crimp obtainable was demonstrated by boiling the drawn film strips in water in a tensionless condition, so that they were crimped when wet and even more intensely crimped when dry. This crimp was reversible with changes of moisture.

Samples of drawn films with a small weight attached sufficient to keep the film from crimping but insufficient to elongate the film were then suspended in boiling water for 3 minutes . This treatment length stabilized the film towards shrinkage. The boned-off strips were then suspended free of weights over a hot plate to dry. During the drying process the films formed a spiral crimp. This crimp was completely reversible in that when the crimped, dried, composite films were placed in water and allowed to come to equilibrium they straightened out spontaneously and upon drying again reverted to the crimped condition. It is considered that this crimp represents the crimp reversibility that is due to the differential length change of the two components. It was surprising that a crimped product could be made in the absence of a differential shrinkage between the two components.

The results with various combinations are shown in Table III below. Items A and B of Table III have been included to demonstrate the validity of this method of testing for components inasmuch as these types of pairs of components had already been evaluated in fiber form and gave the same results.

The data indicate that when there is no difference in ionic ionizable group content between the two components at levels as low as 50 milliequivalents per kilogram the presence of ^ methyl acrylate in one component makes that component have a sufficiently higher reversible length change, so that a composite fiber with reversible crimp can be made from that pair of components.

Item P indicates the effect of methyl acrylate on a basic-modified polymer.

Tahle III Component I Component II Item $> Methyl Acidity $ Methyl Acidity Acrylate meg/Kg Acrylate meq/Kg A 0 170 0 170 B 0 I70 0 105 C 0 150 5 150 on D 0 95 3 95 E 0 50 5 50 F 0 2¾0# 3 # "basicity * at pH 3 EXAMPLE 11.

A copolymer of vinyl chloride and of p-styrene sulfonic acid containing 400 milliequivalents of acid groups per kilogram of polymer is made.

A 25$ solution of this polymer in tetrahydrofurane is co-spun, as in Example 2 above with a 25 solution of the homopolymer of polyvinyl chloride in tetrahydrofurane and then drawn 4X in 98°C . water. The composite fibers display a satisfactory crimp reversibility after shrinking in boiling water. A similar copolymer, however containing also $ vinylacetate resulted in composite fibers with a crimp reversibility superior to that made without the vinyl acetate but containing the same p^sulfonic acid content.

EXAMPLE 12.

A copolyamide, namely, poly (hexamethylene adipamide/terephthalamide) 70/30 by weight with a relative viscosity of 11 was made by melt polymerization of the salts of adlpic and terephthalic acid with hexamethylene diamine. Poly(hexamethylene adipamide) of relative viscosity 41 was spun with the above-mentioned copolyamide as sheath and core, respectively, eccentrically to each other.

The pump speeds were adjusted to give a sheath/core ratio by volume 55/^5> the two polymers being co-spun at 290°C. into air at 25°C . , and the resulting yarn wound up at 800 ypm (yards per minute). The wound yarn had a core of kidney-shaped cross section being thus eccentric to the sheath. The yarn was drawn 290$ (3.9 times the original length) over a hot draw pin at 83°C . and thence in contact with a hot plate at l60°C . and collected on a bobbin. The yarn developed an excellent crimp in 95° water The crimped yarn had a crimp reversibility by Test A of 0.09 and had an initial modulus (M^) in 25° water of about 15. Model monocomponent filaments of the copolyamide and the polyamide had longitudinal swellability (i.e.., reversible length change by Test A) of 2.6l$ and 3·13$> respectivel , and had shrinkages of $ and 8.3$, respectively. The differential equilibrium reversible length changes of the copolyamide and the polyamide by Test B was 0.4l.

The equilibrium crimp reversibility by Test B of the crimped composite fiber was 0.90 change in crimps/inch of crimped length.

EXAMPLE 13 Pol (ethylene terephthalate ) flakes having an intrinsic viscosity of Ο. 67 in a solvent mixture of 58. 8 parts "by weight phenol and 41.2 by weight of trlchlorophenol and poly(hexamethylene adipamide) flakes having an instrinsic viscosity of 1.02 in m-cresol are melted separately and extruded at 235°C. through a multi-hole spinneret assembly similar to that shown in Figure 5 of French Patent 1,124, 921. The extruded filament is air quenched. The polyester melt is . extruded through the inner tube of the spinneret and the polyamide through the outer space surrounding the tubes. The eccentric sheath-core filaments are attenuated by pulling them as they are spun away from the spinneret holes with a speed which is about 100 times as high as the speed of the extruded melt.

After spinning and cooling, they are drawn over a pin at room temperature (20°C.) to 3.3 times their original length. About 100 yards of the stretched filaments were tightly wound on a bobbin, and the bobbin was heated for minutes in an electric ove , the temperature of which was 115°C . The cooled filaments were then unwound from the bobbin and showed upon inspection no distinct crimp.

However, they possess a potential crimp which can be developed Immediately after the heat treatment or at any time after the fiber is processed into woven textile materials or into knitted goods or after cutting the fibers into staple lengths.

The continuous filaments containing the potential crimp were skeined and hung in boiling water for one minute without applying any tension to the filaments. A very As determined by Test "A" from model monocomponent filaments, the polyamide sheath and the polyester core had longitudinal swellabilities, respectively, of 3.13$ and 0.08 and shrinkabilities, respectively, of 8.3$ and 4.5$. The crimp reversibility of these filaments was 0.48 by Test MA". The reversible length change by Test "B" for the polyamide and the polyester were 2.70 and 0.0 respectively. The composite filament had an equilibrium crimp reversibility by Test "B" of 8.1 changes in crimps/inch of crimped length.

Either component of the composite, crimp reversible filaments of this invention can be found in many groups of synthetic polymer materials. The term "synthetic polymer materials signifies addition polymers as well as condensation polymers which are prepared synthetically from monomeric materials, either as homopolymers or as copolymers.

The polymers may be those spun either according to melt spinning processes or dry spinning processes or by other types of spinning processes. Because of their commercial availability, ease of processing, and excellent properties, condensation polymers like polyamides and polyesters may be used with advantage in the practice of the invention. Specific polyamides which can be used are poly(hexamethylene adipamide), poly(hexamethylene sebacamide), poly (epsilon-caproamide), and their copolymers . Among the polyesters which may be used are poly (ethylene terephthalate) and other polyesters and their copolymers containing dibasic acids, such as sebacic or adipic acid combined, in recurring units, with glycols having 2 or more carbon atoms in the chain. Other polymers are polyurethanes, polyureas, ol eth lene, pol vin l chloride, polyvinylidene As stated, a surprisingly high degree of control and other advantages are achieved, if, as the longitudinally swelling components of the composite filaments, polymers are used which contain combined therein ionizable groups as modifying elements, for example, in polyamides, polyesters, and acr lonitrile polymers (particularly copolymers); the ionizable groups may be basic or acidic, preferably the latter. The examples illustrate the modification of polymer components by the inclusion, during polymerization, of styrene sulfonic acid, methacrylic acid, itaconic acid, fumaric acid, methallyl sulfonic acid, and similar modifiers containing ionizable groups.

Polymers derived from acrylonitrile and particularly those containing 85 or more of acrylonitrile combined in the polymer molecule are particularly useful in the practice of this invention and permit the production of fibers and filaments with surprising, new properties. Polymers containing 8 $ or more of acrylonitrile combined in the polymer molecule, i.e., both the homopolymers and copolymers, are especially preferred because of the chemical inertness, general water insensitivity, high modulus, high tensile strength, light and weather stability and especially the pleasing handle, etc., that are characteristics of filaments formed from these polymers. In general, both components will be preferably made of polymers of acrylonitrile in order that optimum adhesion be obtained between the two components.

The necessary differential reversible length change between the components is readily obtained by selecting the content of ionizable groups in the two polymers and the amount of neutral modifier. containing acid groups such as carboxylic, sulfonic or phosphonlc in either the salt or free-acid form.

Among the carboxylic monomers suitable for use with the addition polymers of / this invention are: acrylic acid, alpha-chloroacrylic acid, methacrylic acid, itaconic acid, fumaric acid, maleic acid, citraconic acid, crotonic acid, vinyl benzoic acid and the like.

The use of stronger (i.e., more highly ionized) acid groups as sulfonic or phosphonlc acids, as for example, l-propene-2-phosphonic , . J · i or phenylethene-2-phosphonic acids are preferred in this invention since they are, in general, more effective than carboxylic acids in causing a reversible length change and also because their copolymers are substantially more stable to heat discoloration.

In addition to p-styrene sulfonic acid, methallyl sulfonic acid, allyl sulfonic acid and ethylene sulfonic acid disclosed above in this application, the following sulfonated polymer!zable monomers and their salts are eminently suited for use in this invention: o- and m-styrene sulfonic acid, allyloxyethylsulfonic acid, methallyloxyethylsulfonic acid, allyloxypropanolsulfonic allylthiopropanolsulfonic acid, allylthioethylsulfonic acid, ».* · < acid, isopropenylbenzenesulfonic acid, vinylbromobenzene-sulfonic acid, vinylfluorobenzenesulfonlc acid, vinylmethyl enzenesulfonic acid, vinylethyl enzenesulfonic acid, isopropenylisopropylbenzenesulfonic acid, vinylhydroxy-benzenesulfonic acid, vinyldichlorobenzenesulfonic acid, vinyldihydroxybenzenesulfonic acid, vinyltrihydroxy-benzenesulfonic acid, vinylhydroxynaphthalenesulfonic acid, isopropenylnaphthalenesulfonic acid, sulfodichlorovinyl-naphthalene, allylbenzenesulfonic acid, methailylbenzene-sulfonic acid, isopropenylphenyl-n-butanesulfonic acid, vinylchlorophenylethanesulfonic acid, vinylhydroxyphenyl-methanesulfonic acid, vinyltrihydroxyphenylethanesulfonic acid, 1-isopropylethylene-l-sulfonic acid, 1-acetylethylene- 1-sulfonic acid, naphthylethylenesulfonic acid, biphenyl-oxyethylenesulfonic acid, propenesulfonic acid, butenesulfonic acid, hexenesulfonic acid, etc. Salts of di-acids such as of disulfonic acids may also be used, for example, salts of 3, -disulfobutene(l), vinylbenzenedisulfonic acid, vinylsulfophenylmethanesulfonic acid, allylidenesulfonic acid, etc.

The required ionizable groups can also be obtained by the use of basic comonomers, such as 2-vlnyl pyridine, 2-methyl-5-vinyl pyridine and others of that type p-dimethylam no-methyl styrene , vinyl ethers of amino alcohols such as betadiethyl aminoethyl vinyl ether, esters of acrylic and methacrylic acid with amino alcohols such as Ν,Ν-diethylaminoethyl acrylate, . and polymerizable quaternary ammonium compounds, such as allyltriethyl-ammonium chloride, vinyl pyridinium chloride, allylpyridinium bromide, methallylpyridinium chloride, beta-vinyloxyethyl dicarbornethoxyethyl methylammonium chloride . and others.

The use of polymerizable quaternary ammonium compounds as sources of basic ionizable groups in the polymers of the filaments of this invention are preferred over other basic modified polymers due to their higher base strength.

Although the polymers containing basic groups are preferably made by copolymer!zation, it will be obvious to those skilled in the art that such basic groups can arise from the after-treatment of the polymer or of the fiber, as for example, the reduction-amination of polymers containing ketone groups made from such monomers as methyl vinyl ketone, isopropenyl methyl ketone and the like or by 'the quaternization of a nitrogen group in a solution of a copolymer, such as a copolymer of acrylonitrile and 2-vinyl pyridine or by exposure of a copolymer containing a methallyl haloacetate to quaternization conditions in a spinning solution.

- - It will be obvious to those skilled in the art that the required ionizable groups can be incorporated into a polymeric component by blending of 2 or more polymers.

The polymers should preferably be compatible.

The use of acidic modifiers in a copolymer is preferred. Such polymers , their spinning solutions and spun fibers containing acid groups (especially sulfonic) are resistant to discoloration. The acidic modified polymers also permit cross-dyeing with wool fibers since the wool takes acid dyes and the acidic modifying groups take basic dyes.

Although the above description refers to the use of sodium salts of ionic group -containing acids which are preferred, the invention broadly comprehends salts other than sodium salts, e.g., salts of potassium and lithium, ammonium salts and amine salts, and particularly water-soluble salts of the above or other metal or non-metal cations .

It will be apparent to those skilled in the art that vinyl polymers other than acrylonitrile polymers can be used in this invention which, although not having the required reversible length change per se, can be modified by acidic or basic modifiers and neutral modifiers as suggested above, so that the copolymers do have the required reversible length change. In this manner such vinyl monomers as vinyl chloride, vinylidene chloride, vinyl acetate, vinyl ketones, vinyl ethers and various acrylic esters and their copolymers, can be used in the form of their copolymers with the acidic or basic modifiers, as components of the filaments of this It was surprising that the inclusion of from the so-called disperse 1-15% of certain non-ionic modifiers,/ dye-enhancing modifiers in copolymers of acrylonitrile enhanced the effect of any ionizable groups present in the final polymer. It is considered that these neutral monomers which enhanced the effect of the ionizable groups can be considered as belonging to one of two classes: (1) hydrophobic - polar monomers, i.e., water- insoluble monomers which contain a carbonyl group such as esters, ketones or amides. (2) hydrophylic monomers, i.e., those that are water-soluble such as acrylamide and meth- acrylamide .

In general, it has been found that the monomers that are effective in this connection are also the same monomers which, when incorporated into an acrylonitrile polymer increase the dyeability of fibers made therefrom with disperse dyes.

Dyeability with acid or basic dyes may also increased, be/ but the effect of the neutral monomers is more readily seen by the use of a disperse dye alone.

Among the more desirable monomers from the point of view of enhancing the effect of ionizable group content are methyl acrylate, methyl methacrylate, methyl vinyl ketone, acrylamide, N-tertiary butyl acrylamide, vinyl methoxyethyl ether, methoxyethyl acrylate, vinyl acetate, bis(2-chloroethyl ) vinyl phosphonate and N-vinylpyrrolidone.

They may also be found among ethyl methacrylate, butyl methacrylate, octyl methacrylate, methoxyethyl methacrylate, phenyl methacrylate, cyclohexyl methacrylate, dimethyl amidoethyl methacrylate, and the corresponding esters amides of acrylic acid; aery1/and methacrylamides or alkyl substitution products thereof; unsaturated ketones such as phenyl vinyl ketone, methyl isopropenyl ketone and the like; vinyl carboxylates such as vinyl formate, vinyl propionate, vinyl butyrate, vinyl thiolacetate, vinyl benzoate, esters of ethylene alpha, beta-carboxylic acids such as maleic, fumaric, citraconic, mesaconlc, aconic acids, N-vinyl succlnimide,, vinyl ethers, etc.

While the inclusion of as little as 1$ of one of the above monomers enhances the reversible length change effect of the ionizable groups contained in that polymer, generally from 3 to 10$ is desired. Although a further slight enhancement Is obtained as the concentration is increased above 10$, usually the mechanical properties of the fibers suffer at undue heights of polymer modification so that in any event for the case of the acrylonltrile polymers no more than 15$ of the neutral modifier should be used.

The non-ionic or neutral disperse dye enhancing monomers disclosed herein increase the effect of the ionizable groups in said component in proportion to the concentration of the non-ionic modifier. The following equation provides for the effect of the non-ionic modifier as well as the ionizable group content: n¾ IonsA - mK2 IonsB = 50(preferably = 100) in which IonsA and IonsB represent the concentration of ionizable groups in Components A and B respectively of the composite filament, in meq/Kg (milliequivalents per kilogram of polymer), n and m are enhancement factors having the value of one or more with values increasing with the amount of non-ionic modifier present in the respective components, and K2 are the activity coefficients for the ionizable groups contained in Components A and B, respectively.

The enhancement factors n and m may be measured empirically as a function of the amount of any non-ionic modifier contained in the polymer. For methyl acrylate in acrylonitrile copolymers, the values of m and n are as follows: Methyl Acrylate Enhancement in Polymer Factor 0 1 2 l.l 4 1.3 6 1.8 8 2.4 3.0 with the values for intermediate points, not given in the above table, varying according to concentration.

Typical values for the activity coefficients and K2 are as follows as measured by plotting ionizable group content against reversible length change of mono-component filaments: Monomer Activity Coefficient p-styrene sulfonic acid 1.0 methacrylic acid 1.0 methallyl sulfonic acid 0.5 ethylene sulfonic acid 0.4 itaconic acid 0.3 fumaric acid 0,4 -methyl-2-vinyl pyridine 0.4 2-vinyl pyridine 0.5 When two components are selected so that the above equation is satisfied, the two components will then have the desired differential reversible length change such that the resulting composite filament has crimp reversibility.

It is to be understood that any convenient level of modification by monomers having ionizable groups and by non-ionic disperse dye enhancing monomers can be selected in view of other desired attributes of such modification such as, for example, dyeability.

The selection of the components to be incorporated into the composite fibers will depend on the physical properties desired of the filaments and yarns, e.g., the optimum residual shrinkage, tensile recovery, elongation, such as desired for textile filaments, and the like, that is, properties being readily determined by known methods. Physical properties of the desired components, taken alone, can be relied upon for the selection of the components to be used in any given combination. In view of the fact that - 7 composite filaments of this invention are normally subjected to aqueous treatment, ' it is preferred that the wet modulus at 25°C. of both components be at least 10 gpd. A selection of a high reversible length change difference together with high wet modulus for both components contributes greatly to the impelling force responsible for the high crimp reversibility characteristics of the filaments of this invention. The product of the difference of rever- by Test A sible length change/(in ) between the components multiplied by the 25°C. wet initial modulus (in gpd) of the composite filament is preferably at least 2.0.

Composite filaments prepared for use in accordance with the present invention may be subjected to a drawing (permanent stretching) operation in order to impart to the filaments the desired physical properties as tenacity, elongation and initial modulus. Although drawing may affect shrinkability and the reversible length change of a filament, crimped filaments with a reversible crimp have been made from dry-spun filaments without a drawing treatment. The conditions applied to drawing the spun multicomponent filaments may vary in wide limits. The drawing characteristics of the components can readily be determined from those of monocomponent filaments of each of the component polymers of the composite filaments. The drawing can be accomplished in accordance with known principles applicable to the particular polymers of the composite filaments and, in general, the composite filaments are drawn at least 50$ (i.e., to 150$ of original undrawn length) and preferably about 2-8 times the original lengths. The extent of drawing will, of course, also depend somewhat upon the nature of the particular polymer used in the composite filaments and upon the type of eccentric relationship between those polymers in the composite filament.

In considering the extent of drawing, one should take into consideration the amount of draw which may be effected during the spinning of the filaments, and, in fact, the desired amount of drawing may be effected during spin-ning rather than as a separate drawing step following the windup of the filaments from the spinning operation.

The shrinking of the composite filaments in order to effect crimping, may be carried out by the use of any suitable known shrinking agent. Shrinking will ordinarily be carried out by the use of hot aqueous media such as hot or boiling water, steam, or hot highly humid atmosphere, or by the use of hot air or other hot gaseous or liquid media chemically inert to the polymers of the composite filaments.

The shrinking temperature is generally in the neighborhood of 100°C. but may be higher or lower, e.g., 50°C up to o about 150 C. or even up to a temperature not exceeding the melting point of the lowest melting polymeric component of the fiber.

A continuous process for the production of the crimped filaments of this invention is as follows: The tow of spun yarn is washed of residual solvent and simultaneously drawn 4X in 95-98°C water followed by an additional draw of 2X (total draw β3 through a steam cell in 20 psi drawn (gage) of steam. The/ yarn is piddled deposited transversely and lengthwise of a travelling belt from the steam cell and cut into staple lengths with a rotary knife cutter. The cut chips of staple are sprayed with water to a minimum of 5 % water content and then steamed and dried in sequence on a conveyor, which treatment crimps the fibers. The dried chips are then opened and baled.

If a less intense crimp is desired, the cut chips may be dried, e.g., with 90° air, opened and then crimped o by heating with, e.g., 130 C. air for ten minutes.

A preferred process is to saturate the drawn tow with water, piddle it onto a continuous belt, subject to atmospheric steam for 1-4 minutes (which crimps the filaments), remove excess water by passing through rollers, cut into staple lengths and dry with 80-130°C. air for 10-20 minutes.

Although this invention has been illustrated by the use of side-by-side structures, a structure which has a core completely and eccentrically surrounded by a sheath is applicable. For example, a sheath of a copolymer made from acrylonitrile, methyl acrylate and potassium styrene sulfonate with monomer feed ratios of 93.5/5.96/0.5^ was spun around a core of homopolymer of acrylonitrile^sing a apln^ rffTct niinllnr Lu LlidL ahowri In The sheath and eccentrically disposed core comprised 0$ each of the filamentary volume. The 160 filament bundle of yarn was drawn X in 95°C. water. Upon boiling the drawn yarns in water, crimped filaments with a reversible crimp were obtained. With this type of structure the component having the greater reversible length change is preferably spun as the sheath of the filaments.

The filaments and y¾rns of this invention possess the characteristic of crimp reversibility, that is, the ability to return to the original crimp state spontaneously after having been treated with a swelling agent and after removal of the swelling agent following such treatment. The preferred system exhibiting this characteristic of crimp reversibility involves filaments which have been crimped by a suitable shrinking treatment and which, upon being swollen, lose a portion of the crimp. Such filaments may be woven or knitted, either in the potentially crimpable or in the crimped state, as continuous filaments or as staple fibers, and if woven or knitted in the uncrimped or potentially crimpable state, the crimp may be developed in the fabric by treatment with a suitable - - shrinking agent. The crimped filaments of the fabric will, upon treatment with a swelling agent, as by aqueous treatment in the washing, scouring, dyeing, and other treatments normally applied to fabrics, move around or squirm during such treatments and, upon removal of the swelling agent, regain the lost crimp with the imparting of a fullness and highly increased covering power to the fabric . Not only is this of advantage in the type of fabric used for clothing, but it is of great Importance in piled fabrics such as those used in carpets and upholstery, where the compacting of the fibers under compression incident to use, may be overcome by treatment with water, other swelling agent, or merely exposure to humid air to cause the fibers to squirm or work out of the compressed state, but upon drying, the fibers will again revert to their highly crimped and voluminous state prior to their having been compressed. The yarns and fabrics of this invention, therefore, have inproved stretch-ability, compressional resilience and liveliness and display a renewable surface, good bulk and covering power can be developed at a low level of fabric shrinkage.

Although the invention has, in its preferred form, been applied to filaments which lose at least a part of their crimp upon the swelling treatment, it is within the scope of this invention to utilize a reversible crimp wherein the crimped filaments actually gain additional crimp upon treatment with a swelling agent; in this case, also, the filaments squirm and work around with respect to each other upon treatment with a swelling agent and also upon removal of the swelling agent as by drying, thereby, because of the freedom of movement of the filaments even with The invention is particularly directed to filaments and yarns (i.e., bundles of filaments) having deniers of the magnitude used in textiles. It is preferred that the filaments of this invention have a denier of 1 to (inclusive) and that the yarns of this invention have a denier of 30 to 8, 000 (inclusive).

While the invention has been described in its preferred form with respect to filaments made by extrusion from round spinneret orifices, the orifices may be of a different shape, e.g., cruciform, square, triangular or slotted to yield filaments having a cross-section corresponding generally to the shape of such holes, i.e., cross- or star-shaped, square, triangular or elliptical (the shape imparted by a slotted or elongated rectangular spinning orifice).

Figures 4 and 5 of the drawings, referred to above, illustrate typical cross-sections of side-by-side composite filaments of this invention made in accordance with the above Examples. Figure 6 of the drawings also illustrates typical cross-sections of side-by-side filaments of this invention produced when the spinning conditions are varied somewhat from those which tend to produce filaments having the cross-sections of Figures and 5 · The filaments of the present invention can be fabricated into knitted or woven goods, either as continuous filament or as yarns composed of cut staple fibers. The new continuous or staple ilaments of this invention can be crimped before they are further processed or in any state of processing, for instance, after they are spun into yarns or after the woven or knitted goods are made from these yarns . Another important application comprises the processing of the continuous filaments into bulky fabrics which again can be carried out with the continuous filaments in the crimped or uncrimped state. In the latter case, the crimp can be developed after weaving or knitting the yarns obtained therefoi«m or in any stage of the processing. Very interesting applications of the continuous yarns are, for instance, the preparation of worsted fabrics which may be woven from the uncrimped yarns containing the potential crimp and which are crimped after weaving and finishing.

These worsted fabrics have an appearance and hand very similar to those obtained from staple yarns. However, they do not possess the disadvantages in processing and use of these fabrics. Another very important application of the fibers of this invention comprises the use in carpets arid other heavy textile goods where again the fibers containing the potential crimp can be knitted or woven and the crimp is developed in the finished goods.

HAVIMGJNOW particularly described and ascertained the nature of our said invention and in what manner the same is to be performed we declare that what we claim is:-

Claims (1)

1. · Synthetic composite fibersJadP filaments comprising a least two distinct components of synthetic polymer© arranged in an eccentric relationship in such a manner that the fibre as a whole is capable of squirming (as herein defined). 2· Synthetic fibers or filaments in accordance with Claim 1 comprising at least two different synthetic polymers held together in eccentric relationshi if viewed in the cross section whic are capable of self-crimping characterized in that the components revereibly swel to a different degree in the direction of the length axis upon treatment with a suitable liquid* 3» Fibers or filaments in accordance with Claims 1 or 2 characterised in that both components are raolecularly oriented* 4« Fibers or filaments in accordance with Claims 1 to 3 characterized in that they are capable o crimpin due to a differential in shrinkage* 5« libera and filaments in accordance with Claim 4 characterised in that the difference in ahrinkability of the components is at least 1$· 6· Fibers and filaments of Claims 1 to 5 characterized in that they >ossess a pronounced crimp* 7· Fibers and filaments in accordance with Claims 1 to 6 characterized in that at least one component is more hdrophilic than the remaining component o components and possesses a crimp reversibility upon treatment with and subsequent removal of an aqueous liquid. < 8. Fibers and filaments in accordance with Claims 2 to 7 characterized in that the difference in longitudinal swellability is at least 0.05 (Test A) or at ^Least Λ% (Test B), ^ ^—^- ot^