US3038237A - Novel crimped and crimpable filaments and their preparation - Google Patents

Description

June 12, 1962 R. B. TAYLOR, JR NOVEL CRIMPED AND CRIMPABLE FILAMENTS AND THEIR PREPARATION 2 Sheets-Sheet 1 Filed NOV. 5, 1958 FIG.

1N VENTOR ROBERT BURNS TAYLOR, JR.

June 12, 1962 R. B. TAYLOR, JR 3,038,237

NOVEL CRIMPED AND CRIMPABLE FILAMENTS AND THEIR PREPARATION 2 Sheets-Sheet 2 Filed NOV. 3, 1958 FIG.1A

I INVENTOR ROBERT BURNS TAYLOR, JR

BY GflM 014;

ATTORNEY Patented June 12, 1962 3,038,237 NOVEL CRHVIPED AND CRIIVHABLE FHA- MENTS AND 'rrmm PREPARATION Robert Burns Taylor, Jr., Wilmington, DeL, assignor to E. I. du Pont de Nemours and Company, Wilmington,

Del., a corporation of Delaware Filed Nov. 3, 1958, Ser. No. 771,677 Claims. (Cl. 28-$2) This invention relates to synthetic textile fibers and particularly to improved, crimped composite filaments.

This application is a continuation-in-part of application Serial No. 640,722, filed February 18, 1957, and now abandoned.

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 wellknown 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, 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 resilience, 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.

Although different proposals of the prior art have at tained 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 have been obtained by processing into fabric 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 spining 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 fibers 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.

It is, therefore, an object of this invention to provide crimped filaments having improved response to textile finishing operations by virtue of reversible spontaneous crimp changes. It is a further object of the invention to provide filaments and yarns composed of such filaments which, when embodied into fabrics and subjected to finishing treatments, will develop bulk and cover at a low level of fabric shrinkage. A further object of the invention is to provide filaments and yarns of such filaments which, after processing into fabrics and finishing, will provide a yarn and fabric structure exhibiting improved stretchability, compressional resilience, and liveliness. A further object of the invention is to provide fibers which, when embodied in a fabric, will display a renewable surface. Further objects will appear hereinafter.

The objects of this invention have been attained by producing a crimped or crimpable composite filament of synthetically-formed polymers in which at least one polymeric component has a substantial content of ionizable groups which content, in its preferred form, is in substantial excess of the ionizable group content of the other filament component, said filament having the capacity of spontaneously and reversibly changing its degree of crimp upon being exposed to the effect of a swelling agent and reverting to the original crimp upon removal of the swelling agent. This characteristic is, for convenience, referred to as crimp reversibility; generally speaking, this characteristic of the filaments of this invention is observed by the squirming of the filaments upon both application and removal of the swelling agent.

The new improved filaments of this invention may be obtained by 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 of or all the components form the surface of the single composite filament. (For convenience, the following discussion will refer to twocomponent filaments although the filaments may, if desired, have more than two components.)

One component of the crimped filaments of the pres ent invention displays 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 filament-s 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 fulness or covering power as a result of the swelling treatment and retain or even increase this fullness after being subjected 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 low, 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 treat 3 ment 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 is determined by measuring the increase in length of a monocomponent 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 composite filament. For all reversible length changes denoted by Test A the tests are executed with strands of approximately 100 denier and approximately inches long as follows. The samples (previously relaxed by a boil-off) 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 inch 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 first cycle. For most samples, satisfactory results are obtained with three cycles.

The reversible length change is calculated in percent, based on the final dry length of the sample.

length wet length dry X 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 is 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 of the drawn, unrelaxed continuous filaments are boiled in water for 15 minutes. Strands of approximately 300 total denier and 6 inches long are then suspended vertically from a rubber-tooth clamp and weighted with a 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 cathetometer. The desiccant is then removed from the tube, the tube filled with water and stored vertically at 70 C. for 6 hours. It has been determined that all samples reach an equilibrium wet length at 70% C. in this period. The length of the wet sample is 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 0.4% 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 swellability is determined by extrapolation from the swell- 4 abilities 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 cotton, woolen and worsted spinning processes. 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 processability 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 filaments, the shrinkability of one component should be 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 aftertreatments 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 samples 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 pretwisted filament 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 (1 milligram) attached to the lower (free) end and insufiicient to remove crimp, the weight being pointer shaped to permit measuring and counting rotations of the pointer during crimping and uncrimping. 'llhe 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 pointer (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.

Crimp reversibility values by the above method are hereafter designated test A.

Again it was found that more reproducible crimp reversibility values were obtained under equilibrium conditions (corresponding to the reversible length changes by test B) than by the above test, although the same general results were obtained. Data measured by such an equilibrium test will be designated hereafter as by test B. In this test a single filament is separated from the single end or tow of drawn, unrelaxed fibers. A three-inch length or 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 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 firorn 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 cn'mps/inch of crimped length from 25 C. dry to 70 C. wet expressed as Ac.p.i. is obtained by the following equation where the sign of Ac.p.i. is ignored.

number of crimps (25 0. dry) -number of crimps (70 C. wet) total filament length erimped (25 C. dry) In the spinning, the polymers are 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 sideby-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 33 of FIGURE 1 showing details of the bottom of the back plate;

FIGURE 1A is an enlarged portion taken from FIG- URE 1 to show details of the spinneret at the spinning orifice; and

FIGURES 4, 5, and 6 show greatly magnified crosssections, 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 1 by retaining rings 12 and 14 and by bolt 13. A fine-meshscreen 4 e.g., 200 mesh per inch, is pressed into position between, and serves as a spacer between, spinneret plate 2 and back plate ll. Back plate 1 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 11 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 spinneret plate 2 by screen 4 to permit free and 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 lluid passage through orifices 3, as shown in detail in FIGURE 1A.

In FIGURE 2 are shown four lead holes 1t) 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, sections of bottom spinneret plate 2 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 11 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 holes 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 expression intrinsic viscosity with the symbol n as used herein signifies the value of 1n(n),. at the ordinate axis intercept (i.e., when 0 equals 0) in a graph of as ordinate with 0 values (grams per ml. of solution) as abscissas. (n), is a symbol for relative viscosity, which is the ratio of the flow times in a viscosimeter of a polymer solution and the solvent. In is the logarithm to the base e. All measurements on polymers containing acrylonitrile combined in the polymer molecule were made with dimethylformamide solutions at 25 C.

The acidity of a polymer was determined by percolating a dimethylformamide 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 sulfuric 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, which are illustrative of the invention, parts, proportions and percentages are by 7 7 weight unless otherwise indicated. Also, in all the examples, the polymers were fed to the spinneret, in the form of their solutions, at an equal rate for each polymer so that the filaments contained 50% of each polymer. In addition, in those examples referring to sodium styrene sulfonate, the sulfonate used was 92% sodium p-styrene sulfonate and 8% sodium o-styrene sulfonate.

EXAMPLE I Copolymer a was made from acrylonitrile, methyl acrylate, and sodium styrene sulfonate using the technique of US. Patents 2,628,223 and 2,546,238 (i.e., continuous polymerization in water with K S O catalyst, sodium meta bisulfite activator and Na CO 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 54 milliequivalents of acid groups per ilogram 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 204 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 94% 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 K S O used in the polymerization. The polymer contained 6.0% of methyl acryltae.

EXAMPLE I-A A 25% solution of copolymer a in dimethylformamide and a 25% solution of copolymer b in dimethylformamide 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 18 orifices of 0.006 inch 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 180 C. and wound up at 200 y.p.m. 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., 4 times length before 300% drawing) in 95 C. water and dried.

Morrocomponent 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 25 C. Equilibrium reversible length changes by test B of 3.67% and 6.51% respectively were observed.

EXAMPLE I-B Composite filaments were spun from 22% solutions in dimethylformamide of polyacrylonitrile (the homopolymer) with an intrinsic viscosity of 2.0 containing 26 milliequivalents of acid groups per kilogram of polymer and copolymer through a spinneret similar to that shown in FIGURES 1 to 3 having 140 orifices, 0.0047 inch in diameter, with other conditions as in Example I-A. The spun yarn was drawn 300% (4 times the original length before drawing) in steam. The as-spun filaments had cross-sections similar to FIGURES 4 and 5. Monocomponent filaments of the component polymers, spun and drawn in the sam manner, had reversible length changes according to 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.

Samples of both drawn composite yarns A and B 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 crimp per centimeter respectively for samples A and B. Equilibrium crimp reversibilities by test B of 4.5 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 (g.p.d.) for samples A and B, respectively.

Tufted (pile) fabrics of similar construction were made from the 3-denier per filament unrelaxed (uncrimped) filaments of Example IA, Example LB, 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 of approximately 60% relative humidity for 24 hours. The fabric was then immersed in 60 C. 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 I-A (having reversible crimp) recovered about of its original height after 24 hours and recovered after the wetting and drying cycle. The fabric from the filaments of Example I-B (no reversible crimp) showed no dry recovery and only about 30% recovery after wetting and drying.

Staple fiber (70 parts) was cut from the filaments of Example I-A and blended with wool (30 parts), spun into yarn, woven into a Shetland-type fabric and subjected to the usual finishing and fulling operations em ployed for W001 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 (eg 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 reversible crimp displayed poor bulk and cover despite higher shrinkages, poor elastic properties, and had a less wool-like surface handle.

An additional demonstration of the useful properties of the filaments of this invention was made by measuring the recovery of the fibers from compression. Crimped fibers were cut in 2-inch lengths, hand carded and made into pellets weighing 0.30 gram. The pellets were placed into a cylinder (0.5 inch diameter hole) under a freely sliding piston that exerted 1,000 p.s.i. for two minutes. The height of the pellet under compression was measured. Different compressed pellets of the same fiber were: (1) allowed to recover in dry air 4 hours or (2) placed in 25 C. water for 40 minutes to recover. The heights of the recovered pellets after treatments 1 and 2 were then measured. Results with th composite filaments in Example I-A, LB, and the homocomponent filaments of copolymer 0 are given in the next table as items A, B, and C, respectively.

Pellet Height, in Inches Item Recovered Recovered (3) (2) Compressed ry, cold-wet,

4 hours 40 minutes The ability of the crimped fibers having a reversible crimp to recover from a deformation in the presence of an aqueous medium is plainly seen from the above results.

9 EXAMPLE II The monomers, (AN) acrylonitrile e, (MA) methyl acnylate f, (SSA) sodium styrene sulfon ate g, (MAA) methacrylic acid h, acrylamide i, (V01 vinylidene chlo- 10 All of the above composite filaments displayed equal or superior dry and wet recovery from compression to that of the filaments of Example I-A using the pellet test of Example I.

ride j and (AA) acrylic acid It were used to make poly- EXAMPLE III mers and copolymers in an aqueous continuous polymerization, as in Example I, using monomer feed ratios A copolymer containing acrylonitrile and (VAC) as shown in Table I below. The resulting polymers were vinyl acetate 1 in the proportion 95/5 by weight was preused to make crimped composite filaments, as in Exampared as in Example I, with a n of 2.0. Another copolyple I. Monocomponent filaments were made in a similar mer of acrylonitrile and (MVP) Z-methyl-S-vinyl pyrimanner from the polymer components of the composite dine in in the proportion 50/50 by weight with a n of filaments. 2.0 was made in a similar manner. The two copolymers Examination of the data on items A, B, C and D in were blended in the ratio of 90 parts to 10 parts, respec- Table I, clearly shows the importance of the difference tively. The final analysis of the blended polymer is given in ionizable group content between components as demonin Table l. as component I of item H, and contained 380 strated here by sulfonic acid groups in causing a reversible milliequivalents of basic groups per kilogram of dry polylength change in water and the corresponding effect upon mer. Solutions of this polymer and polyacrylonitrile crimp reversibility in the composite filament. Items E (the homopolymer) of n 2.0 containing 22% polymer in and F demonstrate the beneficial use of an acid modifier dimethylformamide were dry-spun, as in Example I-B, other than styrene sulfonic acid in producing a reversible and the resulting yarn drawn 4 in 95 Water. Boiling crimp in a filament. the unrestrained yarn gave a very excellent crimped The spun yarn of item G was cross-linked before product with 20 crimps per extended inch with properties drawing by treating the spun yarn wound on perforated as shown in Table I.

TABLE I It Monomer feed ratios Polymer acidity milliequivalents/kg.

Component I Component II I II I-II e/g (AN/SSA) 91/0. 0 (AN) 575 35 540 e/g (AN/SSA) 95/5 6 (AN 346 28 318 e/g(AN/SSA)97.25/2.75 e/g(AN/SSA)98.75/l.25. 274 141 133 e/ (AN/SSA) 97.5 2. e/g (AN/SSA) 025/15"- 189 132 57 elf/g (AN/MA/SSA) 93.03/0/31- e/h (AN/MAA)95/5 54 550 -405 e/k (AN/AA)9l e AN 1,230 28 1,202 e/g/h/iMAN/SSA/MAA/AC)91.6/.4/ 3 elf/g (AN/MA/SSA)93.6/6/.37 550 54 490 e/l/m (AN/VAC/MVP)90.5/4.5/5.0- e AN) 3B0 20 354 e/j/g (AN/VOla/SSA) 78.7/20/L3 e/j (AN/V012) 80/20 116 28 88 Homocomponent fila- Composite filaments ments reversible S (I-II) Crimp Crimps length change, percent Draw Den./ per ex., per Item ratio fil. Crimp reversibility inch crimped Modulus eh Test A-I Test AII Test A Test B wet Test A Test B 12.0 4x 37.5 0. 71 0.19 .52 4. 3 8X 6 0. 73 13. 2 0.56 0.27 .29 1.8 8X 2 26 0.17 8.2 0.38 0.26 .12 0.0 8X 3 29 0. 09 2.6 0. 0. 90 53 -3. 0 4x 3 10 .5 4. 4 4.5x 3.7 0.1 4x 3 12.5 H 0.30 0.19 .11 4.5x 3 23 013 5? I 4x 15 l (11) At 1.5-all others 2.0 (n). 9 Basicity. 3 Salt. 4 Acid. 5 At pH 3.

tubes in a solution composed of 50 gallons of water, 3 EXAMPLE IV gallons of 40% formaldehyde, and 3 pounds of concentrated sulfuric acid for 18 minutes at 98 C. The cross- A t e 1n MB p y y tn f n linked fiber was then drawn 4X in a 0.3% sodium cara contamlilg 27 mllllequlvfllents 0f acld groups bonate solution at 95 C. The drawn fibers were then P kllogram p lym r as te to annular chamber 9 boiled for one hour on perforated tubes in 0.5% grams/minute) as SlhOWIl FIGURE: e thence NaHCO They were then cut into two-winch lengths 00 t n ul r sp 7 and out me the p g cell and boiled for one hour in distilled Water, which devel- Inches 111 dlametef y feet long) as P of q oped a very excellent spiral cn'mp (designated salt in posite filament so that it faced the center of the spinning Table I below). Another portion of the drawn yarn 6611- rnltan ously, a 27% solution in DME of a was boiled free of tension in 1% hydrochloric acid for P Y acrylonltlllg and Styrene Sulfomc 9 30 minutes followed by boiling in water to obtain the 05 96/4% y welght eempesltlen of n and anelyzmg crimp (designated acid in Table I). 240 milliequivalents of acid per kilogram of polymer was It is considered that cross-linking is merely a means fed to annular Space 8 gums/minute) and n of obtaining the proper balance of physical properties bethrough annular p f 6 to eXtTllded the other mtween the components of the composite filament. ponent of a composite filament so that 1t faced the wall Item I is very useful for use in rugs. It was prepared 70 0f the P g e SPlnneret e talned onfices by dry spinning from a solution in dimethylformamide f 1 nch Im dlameter located on a 5.27 inch di- (DMF). Similar results were also obtained by wet spinameter circle. A mixture of carbon dlOXldC and nitrogen nil-0g a solution in dimethyl acetamide into a 40% aqueous gases were clrculated through the cell at a rate of 57 lbs. solution of dimethyl acetamide. A tufted ile fabric p r' Temperatures of 315, and C- were constructed of these fibers was flame retardent. 75 used for the spinning solutions, head and cell respec- 11 tively. The threadline consisting of 140 composite filaments was wound up at 200 y.p.m.

Three hundred fifty ends of yarn produced as above with a combined denier of 382,000 were combined into a tow and drawn to 4 times their original length (i.e., 4X draw ratio) in baths of water at 95 C. which extracted the residual DMF. The drawn and unrelaxed wet tow was mechanically crimped in a stuffer box similar to that shown in Hitt U.S. 2,747,233 issued May 29, 1956, to an extent of 6-7 herring bone crimps per extended inch using a stuffer box temperature of 50 C. The crimped tow was then cut into 3% length staple. The cut staple, loosely arranged in a tray, was dried for 15 minutes in a circulating air oven at 270-275 F. The dried staple had a weak mechanical crimp of 6 to 7 crimps per inch plus 6 to 8 helical crimps per inch.

The above prepared staple develops 16 helical crimps per inch of extended length when boiled free of restraint in water. The helically crimped fibers thus prepared have a Ac.p.i. of 6.4 crimps per inch. The staple has a tenacity of 2.2 grams per denier (g.p.d.), an elongation at the break of 40%, and a denier per filament of 3 after boiling and drying.

Pilling is a well known phenomenon of fabrics made from staple fiber yarns, and can be described as the tendency to form small clusters, clumps, or balls of interentangled fiber ends on the surface of a fabric. Pilling propensity can be measured by actual Wear-tests or by laboratory tests. The test described in the article Random Tumble Pilling Tester" by E. M. Baird et al. in Textile Research Journal, 26, 731-735 (1956) is used herein. The pilling ratings have the following meanings: (1) no pilling; (5) high pilling, (commercially unacceptable) and (9) saturation pilling with intermediates ratings being assigned.

Similar woolen system yarns were spun from the staple fiber of this example (item 1) and from staple cut from homocomponent filaments of the copolymer c of Example I as a control (item 2). Similar fabrics were knitted from these yarns and samples submitted to the pilling instrument for various times. Pilling was judged before and after hand washing in 50 C. water. Results are given below.

Pill rating Total exposure time in minutes 5 10 20 30 60 Item 1:

Before we shing 3. 5 4. 6.0 8 9 After washing 3. 3. 5 4. 0 4. 5 5 Item 2 (control):

Before washing 3.0 4. 5 7 9 9 After washing 3.0 4. 5 7 9 9 Boiling the fabrics after pilling instead of hand washing reduced the level of the pill ratings on item 1 one more unit than indicated above. Boiling had no effect on item 2. This clearly indicates the value of the reversible crimp in reducing the pills on fabrics made of fibers of this invention.

Garments of fleece-type fabrics produced from the fiber of this example and homocomponent filaments of the copolymer 0 of Example I displayed glazing on the seams after conventional seam pressing conditions. Subsequent steaming on a Hoffman Press removed the glaze on fabrics made from fibers of this example but did not affect the control item.

EXAMPLE V The procedure of Example IV was followed with the replacement of the acrylonitrile homopolymer with a 94/6 mixture of the acrylonitrile homopolymer and a copolymer of acrylonitrile and styrene snlfonic acid (96/ 4%) to give a total acidity in the blended polymer of 45 meq. of acid groups per kilogram of polymer. The differential ionic content between the blended polymer and the copolymer was 195 meq./kg. The final staple fiber had a denier per filament of 2.9, a tenacity of 2.1 g.p.d., and an elongation of 31 and had 15 helicfl crimps per inch of extended length after boiling off. The crimp reversibility by test B (A c.p.i.) was 5.1.

The physical properties of the fiber of this example and that of Example IV were considered to be essentially equivalent. The fibers were subjectively evaluated in knit tubing and the aesthetics of the fibers were judged to be equivalent and very satisfactory.

Carded two-gram samples of scoured staple were pot boiled for various lengths of time up to 4 hours in the following black dye bath (all percentages based on weight of fiber):

3.06% CI. Basic Yellow 11 5.04% C. I. Basic Red 13 4.32% Basic Orange of Ex. VIII (n) U.S. 2,821,526 1.68% C.I. Basic Green 4 5.0% a long chain alkyl trimethyl ammonium bromide 12.5% sodium sulfate 0.5% sodium acetate/ acetic acid buffer (pl-1:5)

Dye bath-to-fiber ratio was 1 and fiber was added after the bath had been brought to the boil.

After dyeing, the fibers were scoured in a 2% solution of a non-ionic surfactant (condensation product of polypropylene glycol and ethylene oxide) at the boil for 15 min., rinsed, centrifuged, dried, and carded for visual comparisons of dye quality.

The brightness and depth of shade improved steadily with time. Cross sections of these fibers of Example IV showed: that in the first two hours of dyeing, the acid modified component accepts dye very rapidly and the unmodified side (homopolymer) does not accept dye across its skin barrier in this time interval. The dye that is present in the unmodified side enters it across the polymerpolymer interface in the composite filament. After four hours it was noted that the dye had penetrated further into the unmodified side from the polymer-polymer interface and that there was definite evidence of skin dyeing. The fact that the unmodified side obtained any dye whatsoever in this process was quite surprising since its great reluctance to dye is well known. The 4 hour dyeing time gave deep, relatively bright black shades.

The fibers of this example show greater dye penetration across the polymer-polymer interface and a greater tendency to ring dye. At equal lengths of dyeing time, the fiber of this example gives a brighter black than did the fiber of Example IV.

The dyeings were repeated using dyes equivalent to 7.3, 11.0, and 14.6% dye based on the fiber weight. In the case of Example IV fibers the highest level of dye was needed in order to get bright dark acceptable blacks with this dye procedure. Surprisingly enough, the fibers of this example gave bright black shades at levels of 7.3 and 11% dye that were equivalent to the 14.6% dye level on the other fiber. Single component filament made of the polymer blend (45 meq./kg. total acidity) are only dyed to light shades by the above procedures.

A convenient and economical way to produce the fibers of this example consists of blending the acrylonitrile homopolymer with 10% of its Weight of waste stock of the composite filaments obtained in spinning the fibers of this example and then spinning a solution of this blend with a solution of the acidic copolymer as indicated above.

EXAMPLE VI A series of copolyesters containing sulfonic acid side groups were made by copolymerizing sodium 3,5-di(carbomethoxy) benzene sulfonate (DCBS) with dimethyl terephthalate and ethylene glycol by ester exchange. These copolyesters were melt spun as the sheath of a composite filament around eccentrically disposed cores of poly(ethylene terephthalate) containing 25 meq. of carboxyl groups per kg. of polymer with a relative vis- 13 cosity of 24.6 using a spinneret similar to that shown in US. Patent 2,936,482 issued May 17, 1960, to I. Kilian. All yarns (34 filaments) were drawn over a hot pin at about 104 C. Physical properties were determined on dry yarns after boiling in water for 30 minutes in a relaxed condition. The results are shown in Table II.

The above polymers can also be spun into side-by-side types of composite filaments.

Tubing knitted from the above yarns showed a considerable increase in bulking and covering power over control tubing from the polyester homoiilaments. Ribbons made with the sheath-core yarns as filling exhibited a much softer hand after boil-off than did those with all homofilament yarns.

The effect of the acidic group in a component can be enhanced by the incorporation of a neutral modifier in the polymer as by replacing a portion of the ethylene glycol with a poly(ethylene oxide) glycol of molecular weight 6000 in the polymerization.

Many of the filaments of this invention are so highly crimped that novel textiles can be made from them. However, it has been found that filaments having more than about 20 crimps per inch cause difiiculty in the preparation of spun yarns, such as the frequent occurrence of small tangled clumps of fibers (termed neps) during the carding operation. This is particularly true of the cotton system.

Accordingly, it has been found that a temporary weak, mechanical crimp of 9 to 15 crimps per inch can be placed on the drawn but uncrimped filaments of this invention by suitable means that will permit the fibers to be spun into yarns before shrinkage and development of the high helical crimp.

The as-spun filaments of Example I-A were drawn 300% (4X) in 95 C. water as a continuous tow. The drawn and unrelaxed wet tow was mechanically crimped in a stufier box similar to that in Hitt, US. Patent 2,747,233 issued May 29, 1956, to an extent of 12 herringbone crimps per extended inch, using a low temperature in the stutter box of between 55 to 60 C. in order to keep the stability of the crimp reasonably low. The crimped tow was cut into l /z-inch staple and dried at 70 C. for one-half hour. The staple was opened, and spun into yarn on the cotton system. At this stage almost all of the mechanical crimp had been lost and the yarn had the lean appearance of a cotton yarn. A boil-off of the yarn caused the potential crimp of the filaments to develop, so that the yarn had a wool-like bulk and handle.

When a similar Wet drawn tow was cut, opened and dried at 130 C. so that the potential crimp had an opportunity to develop, the staple had approximately 20 crimps per extended inch and could not be spun on the cotton system.

Either component of the composite, crimp reversible filaments of this invention can be found in the class of polymers consisting of synthetic addition polymers and linear polyesters.

Among the polyesters that may be mentioned, besides poly(ethylene terephthalate), are. the corresponding copolymers containing sebacic acid, adipic acid, isophthalic acid as well as the polyesters containing recurring units derived from glycols with more than two carbons in the chain, e.g., diethylene glycol, butylene glycol, decamethylene glycol and trans-bis-l,4-(hydroxymethyl)- cyclohexane. Polymers derived from acrylonitrile and particularly those containing or more of acrylonitrile combined in the polymer molecule are particularly useful in the practice of this invention. Polymers containing 80% or more of acrylonitrile combined in the polymer molecule, i.e., both the homopolymers and copolymers, are especially preferred in the practice of this invention 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 similar polymers (e.g., both acrylonitrile polymers) in order that optimum adhesion be obtained between the two components. The necessary diiferential reversible length change between the components is readily obtained by altering the content of ionizable groups in the two polymers.

Such ionizable groups are readily obtained by copolymerizing acrylonitrile, for example, with monomers containing acid groups such as carboxylic, sulfonic or phosphonic in either the salt or free-acid form.

Among the carboxylic monomers suitable for use in 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 sultonic or phosphonic acids as, for example, l-propene-Z-phosphonic (see US. Patent No. 2,439,214) or phenylethene-Z-phosphonic acids are preferred in this invention since they are, in general, more eifective 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 sulfona-ted polymerizable monomers and their salts are eminently suited for use in this invention: 0- and mstyrene sulfonic acid, allyloxyethylsulfonic acid, methallyloxyethylsulfonic acid, allyloxypropanolsulfonic acid, allylthioethylsulfonic acid, allylthiopropanolsulfonic acid, isopropenylbenzenesulfonic acid, vinylbromobenzenesulfonic acid, vinylfiuorobenzenesulfonic acid, vinylmethylbenzenesulfonic acid, vinylethylbenzenesulfonic acid, isopropenylisopropylbenzenesulfonic acid, .vinylhydroxyben- 'zenesulfonic acid, vinyldichlorobenzenesulfonic acid,

vinyldihydroxybenzenesulfonic acid, vinyltrihydroxybenzenesulfonic acid, vinyl-11ydroxynaphth-alenesulfonic acid, isopropenylnaphthalenesulfonic acid, sulfodichlorovinylnaphthalene, allylbenzenesulfonic acid, methallylbenzenesulfonic acid, isopropenylphenyl-n-butanesulfonic acid, vinylchlorophenylethanesulfonic acid, vinylhydroxyphenylmethanesulfonic acid, vinyltrihydroxyphenylethanesulfonic acid, l-isopropylethylene-l-sulfonic acid, l-acetylethylene-l-sulfonic acid, naphthylethylenesulfonic acid, biphenyloxyethylenesulfonic acid, propenesulfonic acid, butenesulfonic acid, hexenesulfonic acid, etc. Salts of diacids such as of disulfonic acids may also be used, for example, salts of 3,4-disulfobutene(1), vinylbenzenedisulfonic acid, vinylsulfophenylmethanesulfonic acid, allylidinesulfonic acid, etc.

Sul-fonic acid groups can be introduced as end groups in polyesters by using metallic salts of sulfomonocarboxylic esters such as sodium p-carbomethoxy benzene sulfonate and dipotassium S-carbomethoxy benzene1,3-

35 disulfonate and sulfomonohydric alcohols, such as sodium- 3-hydroxy propane-l-sulfonate as chain terminators.

Sulfonate acid groups can be placed in mid-chain units of a polyester by using as a monomer, a dicarboxylic acid compound or its derivative containing a metallic salt of a sulfonate, such as sodium 1,8-di(carbomethoxy)naphthalene 3-sulfonate, potassium 2,5-di(carbomethoxy) benzene sulfonate, and sodium 4,4-dicarbomethoxy butane-l-sulfonate.

Carboxy groups and their salts in a polyester are also useful in this invention although sulfonic acid is preferred. They can be introduced as end groups by using an excess of a dibasic acid or by degrading a polymer by various means. Chain terminators such as potassium monomethyl terephthalate, potassium hydroxybutyrate, or potassium monomethyl sebacate can be used in ester exchange polymerizations.

Carboxy groups can also be introduced to midchain units of a polyester. Metallic salts of carboxylic acids do not enter into an ester exchange polymerization, so that compounds such as potassium dimethyltrimesate, or the potassium salt of desoxycholic acid (HO) C23H3qCOOK can be copolymerized with, for example, dimethyl terephthalate. Mid-chain carboxy groups can also be introduced by melt blending a polyester having predominately hydroxyl end groups with a dianhydride such as pyromellitic anhydride followed by extrusion of the modified polyester into shaped articles, the holding time at the high temperature of melt-blending and extrusion being of short duration.

The required ionizable groups can also be obtained by the use of basic comonomers, such as 2-vinyl pyridine, 2-methyl-5-vinyl pyridine and others of that type as disclosed in 2,491,471, issued to Arnold, p-dimethylaminomethyl styrene (see U.S. Patent No. 2,691,640), vinyl ethers of amino alcohols such as betadiethyl aminoethyl vinyl ether, esters of acrylic and methacrylic acid with amino alcohols such as N,N-diethylaminoethyl acrylate, and polymerizable quaternary ammonium compounds, such as allyltriethylammonium chloride, vinyl pyridiniurh chloride, allylpyridinium bromide, methallylpyridinium chloride, and others as disclosed in Price U.S. Patent No. 2,723,238 issued November 8, 1955, beta-vinyloxye'thyl dicarbomethoxyethyl methylammonium chloride and others as disclosed in Albisetti and Barney, U.S. Patent No. 2,729,622 issued January 3, 1956, 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 basic strength.

Although the polymers containing basic groups are preferably made by copolymerization, 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 as disclosed in Ham U.S. Patent No. 2,740,763 issued April 3, 1956, or by the quaternization of a nitrogen group in a solution of a copolymer, such as a copolymer of acrylonitrile and 2-vinyl pyridine as shown in Ham U.S. Patent No. 2,676,952 issued April 27, 1954, or by exposure of a copolymer containing a methallyl haloacetate to quaternization conditions in a spinning solution as disclosed in Ham U.S. Patent No. 2,656,326 issued October 20, 1953.

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

The use of acidic modifiers in a copolymer are preferred since in general they afiord better polymerizations, such as less tendency to form insoluble gels than basic modifiers. Polymers, their spinning solutions and spun fibers containing acid groups (especially sulfonic), are more resistant to discoloration by heat than are the basic modified polymers. Such acidic modified polymers also permit cross-dyeing with wool fibers since the wool takes acid dyes and the acidic modifying groups take basic dyes. An additional disadvantage of the polymers containing amine groups is that such amine groups must be in a salt form to ionize, which requires an acid pre-treatment or an aqueous, acidic swelling medium. In this connection, it will be understood that ionizable groups are those which ionize in the swelling medium to which the filaments are subjected. This medium is normally an aqueous medium which is substantially neutral, but in some cases as where amine salt groups represent the ionizable groups, the swelling medium may be an acid-containing aqueous medium.

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 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, vinylacetate, 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 invention. One example of one such modified vinyl polymer having an ionic modifier can be prepared as follows:

A copolymer of vinyl chloride and p-styrene sulfonic acid containing 400 milliequivalents per kilogram of acid groups is made by using the polymerization technique of U.S. Patent No. 2,628,957. A 25% solution of this polymer in tetrahydrofurane is co-spun, as in Example I above, with a 25% solution of the homopolymer of polyvinyl chloride in tetrahydrofurane and then drawn 4 in 98 C. water. The composite fibers display a reversible crimp after shrinking in boiling water.

It was surprising that the inclusion of from 1-15% of certain non-ionic modifiers in copolymers of acrylonitrile enhanced the effect of any ionizable groups present in the final polymer. This discovery, as an effective means of enhancing the efiect of ionic groups on reversible length change or crimp squirm, is not specifically claimed in the present case but is claimed in the patent application of Belck et al. filed of even date herewith. Explanation, however, is believed advisable in view of the fact that certain broad claims are presented herein which Will embrace within their scope at least some of the subject matter of said Belck et al. patent application filed of even date herewith. It is considered that these neutral monomers which enhance the effect of the ionizable groups can be considered as belonging to one of two classes:

(1) Hydrophobicpolar 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 watersoluble such as acrylamide and methacrylamide.

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 a disperse dye, such as the blue-disperse dye Prototype 62. Dyeability with acid or basic dyes may also be affected, 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 methoxethyl ether, methoxyethyl acrylate, and vinyl 17 acetate bis-(Z-chloroethyl) vinyl phosphonate, N-vinyl pyrrolidone, N-vinyl methylformarnide and N,N-dimethyl acrylamide.

Suitable monomers may be found among ethyl methacrylate, butyl methacrylate, octyl methacrylate, methoxyethyl methacrylate, phenyl met-hacrylate, cyclohexyl met-hacrylate, dimethyl amidoethyl methacrylate, and the corresponding esters of acrylic acid; acrylamides 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, betacarboxylic acids such as maleic, fumaric, citraconic, mesaconic, aconic acids, N-vin-yl succinimide, vinyl ethers, etc.

While the inclusion of as little as 1% of one of the above monomers enhances the reversible length change eifect 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 acrylonitrile polymers no more than 15% of the neutral modifier should be used.

The composite filaments of this invention are characterized in that at least one of the components contains at least 50 milliequivalents of an ionizable group per kilogram of polymer. It is preferred that one component, in addition to containing at least 50 milliequivalents, contains a substantial excess of ionizable groups over the other component where both components contain such groups. It is desired to point out, however, that the non-ionic disperse dye enhancing monomers disclosed herein increase the effect of the ionizable groups in said component in proportion to the concentration of the nonionic modifier. It is therefore desired, in order to obtain the substantial effects of this invention, to make allowance, where necessary, for the non-ionic modifier content. The following equation makes due allowance for the effect of the non-ionic modifier:

nK ions mK ionS ZSO (preferably 2100) Percent methyl acrylate in polymer: Enhancement factor 1 2 1.1

with the values for intermediate points, not given in the above table, varying according to concentration.

Typical values for the activity coefficients K and K are as follows, as measured by plotting ionizable group content (corrected for non-ionic modifier enhancement) against reversible length change on monocomponent filaments:

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 components to be used in any givencombination. In View of the fact that 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 g.p.d. 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 reversible length change (by test A) (in percent) between the components multiplied by the 25 C. wet initial modulus (in g.p.d.) of the composite filament is preferably at least 2.04

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 polymers 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 spinning 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 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 8x) through a steam cell in 20 p.s.i. (gage) of steam. The drawn yarn is piddled (deposited transversely and lengthwise of a travelling belt as described in US. Patent No. 2,333,279) 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 50% water content and then steamed and dried in sequence on a conveyor, which treatment crirnps 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 by heating with e.g., 130 C. air for ten minutes.

Another continuous 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 primarily with dry spinning, it is, of course, applicable to filaments prepared by wet spinning, plasticized melt spinning, as described in US. Patent No. 2,706,674 issued to Rothrock on April 19, 1955, or melt spinning.

Although this invention has been illustrated primarily 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 93.5/5.96/0.54 was spun around a core of homopolymer of acrylonitrile using a spinneret similar to that shown in US. Patent No. 2,936,482 issued May 17, 1960, to J. Kilian. The sheath and eccentrically disposed core comprised 50% each of the filamentary volume. The 160 filament bundle of yarn was drawn 4X 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 of the above examples, and yarns produced therefrom, possess, in common with all the filaments of this invention, 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 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 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. 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 increased crimp, insuring the imparting of increased fullness, bulk and covering power to the fabric.

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 15 (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 having a substantially round cross-section 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., crossor star-shaped, square, triangular or elliptical (the shape imparted by a. slotted or elongated rectangular spinning orifice).

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 watersoluble salts of the above or other metal or non-metal cations.

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 crosssections 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 4 and 5.

EXAMPLE VIII 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 I, spun into homocomponent filaments and the pertinent properties measured. These results are given in Table III below. In general, it will be noted that as the ionic group content 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.

TABLE III Polymer Filaments Monomers Monomer Draw Reversible Reversible Initial feed ratio ratio length length Shrinkmodu- (n) Acidity 1 change change age lusWet percent percent at 25 0.

test A test B 1. AN/methacrylic acid 95/5 1. 15 550 4X 0.99 6. 56 34 16 2. AN/methyl acrylate/itaconic acid 94/4/2 1. 2 535 4X 0. 425 7. 58 28 20 3. AN/methyl acrylate/tumaric acid 92.7/5/2 3 l. 1 384 4X .42 4.02 26 19 4. AN/methyl acrylate. 94/6. 2.0 27 8X 0. l6 1. 30 17 41 4a. AN 2.0 26 8X 0. 19 0.97 14 53 5. AN [methyl acrylate/sodium p-styrene sulfona e 93.63/6/.37 1. 54 4. 5X 0. 46 3. 57 28 23 6. AN/sodium p-styrene sulfonate /l 2. 0 98 8X 0.22 1. 57 15 41 7. AN/methyl acrylate/ethylene sulfonic acid 1. 5 60 4X 0. 16 2. 62 28 23 8. AN/sodium methallyl sulfonate 1.9 157 4X 0.20 3. 67 22 23 9. AN/sodium p-styrene sulfonate 2.0 204 8X 0.25 3.00 17 27 10. AN/sodium p-styrene sulfonate- 0 204 X 4 6. 51 29 20 11. AN/methyl acrylate/sodium p-styrene sulf0nate 2. 3 176 8X 0. 48 3. 65 21 23 12. AN/methyl acrylate/sodium p-styrene sulfonateu 2. 3 176 4. 5X 1.23 7. 90 32 15 13. AN/sodium p-styrene sulfonate 2. 0 346 8X 0.71 5.05 21 16. 5 14. AN/2-vinyl pyridine 1. 7 2 318 4X 3 0. 32 3 l. 69 24 18 15. AN/2-methyl-5-vinyl pyridine 1.7 2 318 4X 3 0. 25 a 1. 11 23 22 X milliequivalents of acid groups per kilogram of dry polymer.

1 milliequivalents of basic groups per kilogram of dry polymer. 3 measured at pH 3.

The data of this example shows a process variable that changes the swellability of the filaments, namely, the draw ratio. As the draw ratio is increased for a given polymer, the reversible length change is decreased. This data indicates 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.

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 upon another. In this manner a composite film in which one film contained about 6% of sodium methallyl sulfonate and 94% acrylonitrile (based on monomer feed rates) and the other film contained about 0.23% sodium styrene sulfonate, 93.78% acrylonitrile and 5.99% methyl acrylate (based on monomer feed 7 ratios) produced a composite film with an excellent crimp reversibility.

Since the invention is capable of considerable variation and modification, any departure from the above description which conforms to the spirit of the invention, is also intended to be included within the scope of the claims.

I claim:

1. A composite filament crimpable from a straight state upon relaxation by shrinking comprised of at least two polymeric components selected from the group consisting of synthetic addition polymers and polyesters, said polymeric components being eccentrically disposed towards each other in distinct zones with adjoining surfaces being in intimate adhering contact with each other, each of said components extending throughout the length of said filament, one of said components containing at least 50 milliequivalents per kilogram of polymer of ionizable groups, said groups being chemically bonded to the polymer chain of said component and being ionizable in a swelling agent for said component to provide a reversible length change in said component, the number of said ionizable groups being in substantial excess of such groups on any of said other components, one of said components having a shrinkability of at least 1% greater than any of said other components and one of said components having a reversible length change after shrinkage evidenced by an increase in length of at least 0.05% greater than any of said other components when treated with said swelling agent with said component substantially returning to its original length upon removal of said swelling agent, said filament assuming a crimped state upon relaxation by shrinking and exhibiting crimp reversibility characterized by squirming of said filament upon treatment with and upon removal of said swelling agent after said shrinking.

2. The composite filament of claim 1 wherein one of said components contains at least 100 milliequivalents per kilogram of polymer of ionizable groups in excess of those contained by any of said other components.

3. The composite filament of claim 1 wherein one of said components contains at least 50 milliequivalents per kilogram of polymer of sulfonic acid groups.

4. The composite filament of claim 1 wherein said increase in length is at least 0.10%.

5. The product of claim 1 in which the ionizable groups are acid groups.

6. The product of claim 1 in which the ionizable groups are basic groups.

7. The product of claim 1 in which at least one of the components comprises an acrylonitrile polymer containing at least acrylonitrile combined in the polymer molecule.

8. The product of claim 1 in which both of said components comprise polymers of acrylonitrile containing at least 85% acrylonitrile combined in the polymer molecule.

9. A composite filament crimpable from a straight state upon relaxation by shrinking comprised of two acrylonitrile polymer components, each of said components having an initial modulus at 25 C. of at least 10 grams per denier, said polymeric components being eccentrically disposed towards each other in distinct zones with adjoining surfaces being in intimate adhering contact with each other, each of said components extending throughout the length of said filament, one of said components containing at least 50 milliequivalents per kilogram of polymer of ionizable groups, said groups being chemically bonded to the polymer chain of said component and being ionizable in a swelling agent for said component to provide a reversible length change in said component, the number of said ionizable groups being in substantial excess of such groups on the other of said components, one of said components having a shrinkability of at least 1% greater than the other of said components and one of said components having a reversible length change after shrinkage evidenced by an increase in length of at least 0.10% greater than the other of said components when treated with said swelling agent with said component substantially returning to its original length upon removal ofsaid 23 swelling agent, said filament assuming a crimped state upon relaxation by shrinking and exhibiting crimp reversi bility characterized by squirming of said filament upon treatment with and upon removal of said swelling agent after said shrinking.

10. A composite filament crimpable from a straight state upon relaxation by shrinking comprised of at least two polyester components, each of said components having an initial modulus at 25 C. of at least 10 grams per denier, said polyester components being eccentrically disposed towards each other in distinct zones with adjoining surfaces being in intimate adhering contact with each other, each of said components extending throughout the length of said filament, one of said components containing at least 50 milliequivalents per kilogram of polymer of ionizable groups, said groups being chemically bonded to the polymer chain of said component and being ionizable in a swelling agent for said component to provide a reversible length change in said component, the number of said ionizable groups being in substantial excess of such groups on any of said other components, one of said components having a shrinkability of at least 1% greater than any of said other components and one of said components having a reversible length change after shrinkage evidenced by an increase in length of at least 0.10% greater than any 25 of said other components when treated with said swelling 24 agent with said component substantially returning to its original length upon removal of said swelling agent, said filament assuming a crimped state upon relaxation by shrinking and exhibiting crimp reversibility characterized by squirming of said filament upon treatment with and upon removal of said swelling agent after said shrinking.

References Cited in the file of this patent UNITED STATES PATENTS 1,993,847 Koch Mar. 12, 1935 2,200,134 Schlack May 7, 1940 2,351,090 Al'les June 13, 1944 2,428,046 Sisson et al. Sept. 30, 1947 2,439,813 Kulp et al Apr. 20, 1948 2,439,814 Sisson Apr. 20, 1948 2,439,815 Sisson Apr. 20, 1948 2,571,457 Ladisch Oct. 16, 1951 2,674,025 Ladisch Apr. 6, 1954 2,931,091 Breen Apr. 5, 1960 2,936,482 Kilian May 17, 1960 FOREIGN PATENTS 514,638 Great Britain Nov. 14, 1939 1,124,921 France July 9, 1956 760,179 Great Britain Oct. 31, 1956

Claims (1)

1. A COMPOSITE FILAMENT CRIMPABLE FROM A STRAIGHT STATE UPON RELAXATION BY SHRINKING COMPRISED OF AT LEAST TWO POLYMERIC COMPONENTS SELECTED FROM THE GROUP CONSISTING OF SYNTHETIC ADDITION POLYMERS AND POLYESTERS, SAID POLYMERIC COMPONENTS BEING ECCENTRICALLY DISPOSED TOWARDS EACH OTHER IN DISTINCT ZONES WITH ADJOINING SURFACES BEING IN INTIMATE ADHERING CONTAC T WITH EACH OTHER, EACH OF SAID COMPONENTS EXTENDING THROUGHOUT THE LENGTH OF SAID FILAMENT, ONE OF SAID COMPONENTS CONTAINING AT LEAST 50 MILLIEQUIVALENTS PER KILOGRAM OF POLYMER OF IONIZABLE GROUPS, SAID GROUPS BEING CHEMICALLY BONDED TO THE POLYMER CHAIN OF SAID COMPONENT AND BEING IONIZABLE IN A SWELLING AGENT FOR SAID COMPONENT TO PROVIDE A REVERSIBLE LENGTH CHANGE IN SAID COMPONENT, THE NUMBER OF SAID IONIZABLE GROUPS BEING IN SUBSTANTIAL EXCESS OF SUCH GROUPS ON ANY OF SAID OTHER COMPONENTS, ONE OF SAID COMPONENTS HAVING A SHRINKABILITY OF AT LEAST 1% GREATER THAN ANY OF SAID OTHER COMPONENTS AND ONE OF SAID COMPONENTS HAVING A REVERSIBLE LENGTH CHANGE AFTER SHRINKAGE EVIDENCED BY AN INCREASE IN LENGTH OF AT LEAST 0.05% GREATER THAN ANY OF SAID OTHER COMPONENTS WHEN TREATED WITH SAID SWELLING AGENT WITH SAID COMPONENT SUBSTANTIALLY RETURNING TO ITS ORIGINAL LENGTH UPON REMOVAL OF SAID SWELLING AGENT, SAID FILAMENT ASSUMING A CRIMPED STATE UPON RELAXATION BY SHRINKING AND EXHIBITING CRIMP REVERISBILITY CHARACTERIZED BY SQUIRMING OF SAID FILAMENT UPON TREATMENT WITH AND UPON REMOVAL OF SAID SWELLING AGENT AFTER SAID SHRINKING.

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