IL22037A - Composite textile fibers - Google Patents

Description

This invention relates to synthetic multi-component fibers and filaments and more particularly to improved composite textile fibers possessing a permanent non-water reversible crimp.

Many methods have been proposed and used to produce crimped synthetic filaments and fibers. Crimp in textile fibers imparts as aesthetic feel to fabrics knitted or woven. Covering power is improved by the bulking action of crimped fiber. Interfilament adhesion is improved in staple yarns or in non-wovens by crimp. Mechanical crimp is capable of imparting these properties to fibers but is not permanent. Newer proposals involve the conjugate spinning of two or more different synthetic compositions together so that they form a unitary filament which contains the components in an eccentric relation over the cross- section of the filaments. In the case of acrylic fibers, conjugate- spun, crimped, composite or multi-component fibers have heretofore generally been of the water-reversible type which lose their crimp when wet.

It is, therefore, an object of the present invention to provide two- or multi-component, composite filaments having improved crimp properties and improved utility in textile fabrics and other end uses.

An additional object of the invention is to provide composite fibers prepared from acrylonitrile polymers having permanent non-water reversible crimp.

Another object is to provide composite v acrylonitrile polymer containing fibers wherein the two components contain approximately equal numbers of ionizable groups of the same polarity per unit of weight.

Another object is to provide composite components have about the same hydrophillic character.

Other objects and advantages will become apparent from the description which follows hereinaf er.

In general, these and other objects of the invention are attained by producing a composite fiber comprising at least two different components of synthetic polymeric compositions with the components being eccentrically disposed toward each other in distinct zones with adjoining surfaces being in intimate adhering contaot with each other, each of said components extending throughout a substantial length of said filament and the components having an achieved differential shrinkage, as defined herein, of at least 1 percent after exposure to a relaxation medium. The compositions of the invention have several additional characteristics which contribute substantially towards their superior properties and variety of end uses. These are the fact that each of the components contains substantially equal numbers of ionizable groups of the same polarity per unit of weight, thereby permitting equal dyeability of the two components with reactive dyes. Furthermore, both components, usually referred to as the "outer" and "inner" components, have approximately the same tensile recovery and modulus and, therefore, each contributes substantially to the load bearing and recovery properties of the fiber. For acrylonitrie- containing fibers it is preferable to incorporate acid groups as dye receptive sites since a wide range of basic dyes is available for acrylic fibers.

Additionally, the fiber is capable of developing permanent crimp which is not reversible by the action of water or other swelling agents, the non-water reversibility being a feature of the e ual h dro hil ic character of the two com onents with a potassium persulfate catalyst and sodium bisulfite activator, the ionizable groups of the polymer molecules are acidic, coming from fragments of the catalyst and activator components incorporated into the ends of polymer molecules.

Unless acidic monomers, such as sodium vinyl benzene sulfonate are used, the acid content of the polymer per unit weight and subsequent fiber is proportional to the number of polymer chain ends and consequently inversely proportional to the molecular weight of the polymer. Therefore, to insure equal acid group content where acidic monomers are not used, and acid content corcos only from end groups, the polymers should be made to approximately the same molecular weight, as measured by approximately equal values of the specific viscosity of a tenth of one percent solution of polymer in dimethyl formamide .

The use of the term "ionizable group" is intended to refer to a group capable of dissociation with the formation of negatively- and positively- charged ions, the charges on the individual ion being due to the gain or loss of one or more electrons from the outermost orbits of one or more of their atoms.

The use of the expression "hydrophillic character" is meant to express the water sensitivity as reflected in the swelling by water.

The new improved fibers and filaments of this invention may be obtained by spinning together two or more carefully selected polymers, which must be fiber forming, in a manner designed to form over the cross- section of the single composite filament two or more distinct zones which extend over a substantial len th of the filament in eccentric fashion form the surface of the single composite filament. These fibers and filaments will be referred to herein as composite fibers.

The selection of components is of necessity limited by the fact that the fibers of this invention must be capable of developing self-crimp which is non-reversible by the action of water or other swelling agents in contrast to those disclosed in U. S. Patents 2,988,420 and 3,038,236-2.39. A wide variety of polymer compositions which provide self-crimping, conjugate fibers when co-spun with acrylonitrile polymers is available. Such polymer compositions include copolymers, terpolymers, interpolymers and blends of acrylonitrile with various copolyraerizable mono-olefinic monomers and with other vinyl monomers such as allylidene diacetate, butyl acrylate, bis- ( β-chloroethyl) vinyl phosphonate, diethyl maleate, ethyl acrylate, 2-ethylhexyl acrylate, hexyl meth-acrylate, hydroxyethyl methacrylate, hydroxypropyl me h-acrylate, methyl acrylate, methyl methacrylate, methacrylonitrile a-methylstyrene, methallyl salicylate, methyl vinyl ketone, styrene, t-butylacrylate, trimethanolpropane monoallyl ether, vinyl acetate, vinyl benzoate, vinyl chloride, vinylidene chloride, vinyl formate, vinyl salicylate, vinyl stearate, vinyl succinimide and the like.

Certain other monomers such as acrylaraide, cinnamic acid, methyl vinyl pyridine, N-vinylpyrrolidone, sodium methallyl sulfonate, sodium p- sulfophenyl methallyl ether and sodium styrene sulfonate have, at least to some degree, water sensitive or ionizable groups or both. If these are used in one component, an equivalent amount of the same (or a similar) monomer must be incorporated in the other o o a a e w h r s ec t e action Suitable acrylonitrile polymers which may be used to fo 'm one of the components include any fiber-forming acrylonit: ile compositions known in the prior art, for example as disclosed in U. S. Patents 3 , 053 , 789l 3, 088, 793 and 3 , 088 ,93 :. These polymers may be prepared and spun by any of the well! known prior art polymerization and conjugate spinning techniques.

Preferable and particularly desirable bicomponent compositions are those where one component is a copolymer con-taining 85 to 95 percent by weight of acrylonitrile and 5 to 1 percent vinyl acetate and a second component which is a copolymer of at least 80 percent by weight of acrylonitrile and up to 20 percent styrene and a terpolymer of at least 80 percent by weight of a crylonitrile, from 5 to 15 percent vinyl acetate and from 1 to 10 percent styrene. Other especially useful combinations include those where one component is a terpolymer of acrylonitrile, vinyl acetate and R, wherein R is a dye receptor such as cinnamic acid, itaconic acid or sodium p- sulfophenyl methallyl ether, etc., and the other component is a polymer containing acrylonitrile, vinyl acetate, R and X wherein X is a copolymerizable monomer such as styrene, vinylidene chloride, an acrylate or any other monomer previously mentioned.

The two components are preferably employed in about equal parts although satisfactory performance is possible with composite fibers containing at least 10 percent by weight of one component and up to 90 percent by weight of the other component.

The bicomponent fibers of the invention are sub-jecte.d to crimp development immediately after spinning and fibers depends on the production of assymmetry between adjacent portions of the fiber cross- section and that the two portions have different shrinkage properties under relaxation conditions. The variation in shrinkage need not be great.

Theoretical considerations indicate that differential shrinkage of 1 to 10 percent, when achieved, are sufficient to produce useful crimp levels for various applications. In practice, only a portion of the shrinkage potential as predicted from the shrinkage of fibers of the individual components is realized and potentially higher differential shrinkages are usually required to permit achievement of differentials in the desired range.

The shrinkage of the individual components the relaxation medium can be obtained from fibers of the in-dividual components. The difference in shrinkage of the two components has heretofore been taken as a measure of the crimp level that is developed in the composite fiber. The crimp frequency is taken as proportional to this difference. However, in practice this is only an upper limit. Normally only a portion of this limiting value can be achieved. The shrinkage of the two components and the differential shrinkage (difference in shrinkage of the two components) depend on the temperature of the relaxing medium, the nature of the relaxing medium, and the presence of external restraints. As a consequence, the achieved differential shrinkage in the presence of these factors is used to define the self-crimp potential of these fibers. The achieved crimp level is proportional to the achieved differential shrinkage (-^ S) which is defined by the following equation; S1 - Actual shrinkage of the inner component in the composite fiber - Actual shrinkage of the outer component in the composite f ber LQ - is length of original fiber before shrinking - is length of inner component of composite fiber after shrinking is length of outer component of composite fiber after shrinking The differential shrinkage may range from 1 percent to 10 percent or higher, depending upon crimp level desired.

Conjugate spinning as developed and as revealed in U. S. Patents 2,l|28,0i6 and 2,1+39,813-8l£ is suitable for the preparation of the composite fibers of this invention.

Conjugate spinning is a means of getting a fiber with asymmetric regions of two different components.

Another simpler method of spinning composite fiber utilizing a fluid blending device is taught by ^ft^wT °i « s In its simplest use composite fiber produced by this method has a distribution of components between filaments which is potentially of lower crimp level when compared to fiber of the same components as prepared by the methods revealed in U. S. Patents 2,.4.28,0.4.6 and 2,.4.39,813-815.

Normal spinning operations such as wet spinning involve at least one stage in which the fiber is stretched at least 1.1 times to develop molecular orientation. The conjugate fiber develops its crimp when subjected to a relaxing environment such as boiling water, hot air or a steam chamber the extent of strain removal depends on the degree of softening of the fiber. Under ideal conditions the crimp frequency, Cf (No. of crimps per inch in the extended fiber), is approximately proportional to the achieved differential shrinkage of the two components and inversely proportional to the square root of the denier. The crimp frequency also depends on the geometry of the fiber cross- section and the relative amounts of the two components making up the conjugate fiber. The level of achieved crimp in bicomponent fibers depends on amount of restraint imposed during crimp development and the extent of relaxation of the components, which is dependent on relaxation conditions. Best results are obtained when the restraints are minimized. Crimp frequency and crimp amplitude cannot be varied independently in bicomponent systems. An optimum balance in appearance and bulk for many textile uses of 3. dpf fiber is achieved at about 15 to 25 crimps per inch. Higher or lower crimp levels may be required for other end uses.

Crimp in conjugate fibers once developed is as permanent as the fiber itself and represents the minimum energy state for the fiber. As taught in the previously mentioned prior art patents, it is possible to select components such that the fiber may appear to have permanent crimp under standard conditions and yet lose its crimp in water or other selected environments. If, for example, the high shrinking component of the filament is hydrophillic and the low shrinking component is hydrophobic in character, the crimped filament may lose or even reverse its crimp when placed in water and recover its original crimp only when dried. While this t e of fiber behavior reduces the ossibilit each time the fabric is dried. The crimp recovery forces developed in such fiber during drying are low. If any external restraint is imposed, crimp development is impaired and nonuniform bulking results. Since the crimp is lost each time the fiber is wetted, handling of fabrics during drying becomes a problem not only to the manufacturer but also to the end-use customer. It has now been found possible according to this invention to select components such that the fiber may have permanent crimp under standard conditions and also retain this crimp in the same environments which promote crimp reversal in prior art fibers. That is, the fibers of this invention have permanent non- ater reversible crimp.

This non-water reversible crimp is achieved by eliminating the hydrophillic, hydrophobic contrast in the filament components. The fibers are spun and then crimped by exposure to a relaxing environment. Such crimp is permanent and elastic when subjected to distortion. The recovery force is high enough that when the distorting influence is removed, the fiber can easily overcome small environmental restraints to achieve its original configuration. This resilient elastic behavior is observed in both compression and tension. The crimp character is unaffected by water, even prolonged exposure to boiling water has no effect on crimp properties if the sample is not cooled under excessive restraints.

The invention is further illustrated by the following examples in which all parts and percentages are by weight unless otherwise indicated. The polymers were prepared with potassium persulfate catalyst and sodium bisulfite activator under condition to give a specific viscosity of about .1 for a one ercent solution in dimeth l forma ide solving the polymers in dimethyl acetamide to make a twenty-five percent solution. The solution of the polymer was accomplished with agitation and heating to 70°C.

Two modes of spinning were used in preparing composite fiber. The first method was conjugate spinning as revealed in U. S. Patents 2,128,0-4.6 and 2,139,8l3-8l5. This method utilizes a knife edge arrangement separating the two components up to a. point just behind the spinnerette holes. The second method of spinning composite fiber utilizes a fluid blending device to supply mixed dope streams to a standard spinnerette as described in the aforementioned " -¾ ¾.^¾ v_\ appiioobiott v c\ . The fiber produced by this method is comprised of filaments which are mostly bicomponent with components in different ratios, in different filaments, in a side by side arrangement with a few mono-component filaments and a few multi- (more than two) layered filaments.

The spinning solutions were metered through Zenith pumps to the mixing device or conjugate spinnerette. The solutions were coagulated in a dimethyl acetamide/ water bath at 55°C. The jet stretch was approximately one and the orientation stretch six times. The fibers were washed after the orientation stretch and then dried on steam heated rolls at 135°C Dyeing studies were carried out using a solution containing $ gram liter of Devron Blue 2G(C. I. Basic Blue 22) in water. Dyeing was conducted for 120 minutes at a temperature of 100°C. using I4.O ml. of dye solution per gram of fiber.

Acid groups were determined by titration of re t ene car o a ro platinum electrodes. The solvent for fiber is a mixture of three parts ethylene carbonate and one part propylene carbonate purified with activated carbon. The solution is made up to contain 1 to 2 percent dissolved fiber. The titrant is approximately .02 normal tetramethylammonium hydroxide in a 3 to 1 mixture of ethylene carbonate and propylene carbonate standardized with benzoic acid. The end point was taken as the color change of a phenolphthalein indicator.

Tensile recovery measurements were made accord-ing to the method set forth by A. S. T. M. D I77.4.-6IT.

Crimp development in high pressure steam was accomplished in an autoclave. Exposure time was five minutes. The chamber was evacuated of air before steam was introduced into the autoclave.

EXAMPLE I Polymers of acrylonitrile-vinyl acetate (AN-VA), 9 s ratio, and acrylonitrile-vinyl acetate- styrene (AN-VA-S), 92;6:2 ratio, respectively, were co-spun from a conjugate jet in a 1:1 ratio. The fiber was exposed to high pressures (35 psi) steam to develop crimp. The crimp level of the conjugate fiber was about 35 crimps per extended inch of fiber. Achieved differential shrinkage was 7 percent. The crimp of this fiber was permanent and non-water reversible.

EXAMPLE II The same polymer system as in Example I was spun from a plate mixer standard spinnerette combination of the type disclosed in application \°ι .6&> . The composite fiber developed on the average 20 crimps per extended inch of fiber on exposure to 35 Psi steam. Achieved differential the fiber was uniform in appearance.

EXAMPLE III A terpolymer of acrylonitrile, vinyl acetate, and potassium vinyl benzene sulfonate (AN-VA-KVBS) , 93.5^.0 and 0.5 ratio, respectively, and an interpolymer of acrylonitrile, vinyl acetate, styrene and potassium vinyl benzene sulfonate (AN-VA-S-KVBS) , 91.5-6.0-2.0-0.5 ratio, respectively, were spun as in Example I. The crimp level was comparable to that of Example I. The crimp was permanent and non-water reversible. The samples dyed uniformly and to a much deeper shade than in Example I with Sevron Blue 2Q (C.I. Basic Blue 22).

EXAMPLE IV The same system as in Example III was spun under conditions as in Example II. It developed about 20 crimps per extended inch in 3 psig steam. Crimp was permanent and non-water reversible. The dye produced shades comparable to those of Example III and just as uniform in appearance.

As a measure of the properties of the components as they would be in bicomponent fiber, single components were spoun separately under conditions which attempted to duplicate the conditions the component would undergo during conjugate spinning with respect to jet stretch, orientation stretch, washing, and drying. Properties of these fibers are listed in Table I. Any of the polymer systems listed in Table I can be co- spun with any other to produce a bicomponent fiber. Any pair which can achieve a differential shrinkage of greater than 1 percent will give rise to a self-crimping fiber with thelar-ger the differential shrinkage the higher the crimp level.

When the number of ionizable acid roups er unit wei ht are permanent and the composite fiber will be equally dyeable in both components. Ratios of other than 1.1 and up to 9:1 or higher will give rise to self- crimping structures with the crimp level reduced. In all examples the crimp level can be adjusted by changing the achieved level of differential shrinkage. The higher the steam pressure the higher the crimp level.

TABLE I Tensile Polymer Composition % Shrinkage A eqStrong Acid .Recovery and Ratio ( 35 psig steam) (1 gr polym. ) 2% $% 10% AN-VC12 (87-13 ) 18 30 65 1*2.k 31.6 AN-VA (¾- 6 ) 23.2 32 66 3k 20.8 AN-VA-MA (92-6-2) 61.8 29 67 21.6 AN-VA-HM ( 92-6-2) 1+7.6 33 68 3 .8 19 AN-VA-EA ( 92-6-2) 56.6 29 65 3k 19 AN-MM (90-10) 37.7 35 66 36. 8 22 AN-MA (90-10) 57. 1 33 58 36.8 20 AN-VA- VBS (93.5- 6.0-0.5) 18 50 66 37.2 23.6 AN-VA-S-KVBS (91.5-6.0-2.0-0.5) Lj.8.6 3 59 35.6 19.2 AN-VA-S (92- 6-2) k 31 65 33 21.8 vci2 = vinylidene chloride MA = methyl acrylate HM = hexylmethacrylate EA = ethyl acrylate MM = methylmethacrylate S = styrene EXAMPLE V A terpolymer of acrylonitrile, vinyl acetate and t-butyl acrylate, 90- 6-I. ratio, and a copolymer of 'V- exposed to high pressure ( 35 psig) to develop crimp. The crimp level of the fiber was I.7 crimps per extended inch. A similar sample was crimped in 5 psig steam, and the crimp developed in this sample was 17 crimps per extended inch. The crimp in both samples was permanent and non- ater reversible.

EXAMPLE VI A terpolymer of acrylonitrile, vinyl acetate and styrene (91-6-3 ratio) and a copolymer of acrylonitrile and vinyl acetate (9lj.-6 ratio) were co-spun from a plate mixer arrangement in various ratios. The fiber samples were crimped in 35 psi steam. When the components were in a 1 to 1 ratio, the crimp level was I.7 crimps per extended inch. For a ratio (acrylonitrile vinyl acetate styrene/acrylonitrile vinyl acetate) of 2/1 the crimp level was 27 crimps per extended inch. For .a ratio (acrylonitrile-vinyl acetate- styrene/ acrylonitrile-vinyl acetate) of 3/1 the crimp level was 22 crimps per extended inch. The crimp in all samples was permanent and non-water reversible.

EXAMPLE VII A copolymer of acrylonitrile and styrene (88-12 ratio) and a copolymer of acrylonitrile and vinyl acetate (9/4.-6 ratio) were co-spun with a conjugate jet in a 1 to 1 ratio. The crimp developed in a sample in 35 psig steam was excessive, being greater than 100 crimps per extended inch. A similar sample developed 25 crimps per extended inch in boiling water. The crimp in these samples was permanent and non-water reversible.

EXAMPLE VIII A terpolymer of acrylonitrile, vinyl acetate and styrene ( 90-6.5-3.5 ratio) was blended 1 to 2 with a This blend was co-spun in a 1 to 1 ratio with a copolymer of acrylonitrile vinyl acetate (94-6 ratio) in a plate mixer. The sample developed 15 crimps per extended inch when exposed to 35 psig steam.

The same blend when co-spun in a plate mixer arrangement in a 1 to 2 ratio with an acrylonitrile- inyl acetate (94-6 ratio) copolymer developed 8 crimps per extended inch of fiber in 35 psig steam.

The crimp in both samples was permanent and non-water reversible.

EXAMPLE IX In this example various composite fibers were tested for crimp frequency using examples crimped for minutes in 35 psig steam unless otherwise noted. The results are shown in Table II.

TABLE II Component 1 Component 2 Crimp frequency ( crimp/extended inch) AN-VA (9 - 6) AN-VA-MA (90-6-4) 6/1 12 AN-VA (94- 6 ) AN-VA (91-9) 1/1 45 AN-VA ( 94- 6 ) AN-VC12 (78-22) 1/1 15 AN-VA (94-6) AN-VA-EA (92-6-2) 1/1 50 AN-VA (94- 6) AN-EA (90-10) 1/1 50 AN-VA ( 9 -6 ) AN-VA-VC12 ( 85.2- 8.0-6.8) 1/1 12* AN-VA-S (94-4-2) AN-VA-S (92-6-2) 1/1 29 3/1 9 1/3 19 AN-VClp (60-40) AN-VA-S (92-6-2) 1/1 24 The foregoing detailed description has been given for clearness of understanding only, and unnecessary limitations are not to be construed therefrom. The invention is not to be limited to the exact details shown and described since obvious modifications will occur to those skilled in the art, and any departure from the description herein that conforms to the invention is intended to be included within the scope of the claims.

Claims (1)

1. HAVING NOW particularly described and ascertained the nature of our said invention and in What manner the same is to he performed, we declare that what we claim is 1. A composite fiber comprising (a) at least two different components consisting of compositions containing acrylonitrlle, (b) said components being eccentrically disposed toward each other in distinct zones with adjoining surfaces being in intimate adhering contact with each other, (o) each of said components containing substantially equal number of ionizable groups per unit of weight* (d) each of said components being substantially equal in tensile recovery and modulus, (e) the components having a difference in shrinkage under relaxing conditions which ie sufficient to giv a differential shrinkage of at least 1 percent in the composite fiber* and (f) each of said components havin equal hydrophilic character whereby said fiber is capable of developing crimp which is non-water reversible'* 2· The composite fiber of claim 1 characterized in that one synthetio polymeric component J hsists of a copolymer of from 85 to 95 percent acrylonitrlle and 5 to 15 percent vinyl acetate and a second polymeric component consists of a terpolymer of at least 80 percent acrylonitrile from to 15 percent vinyl acetate and 1 to 10 percent styrene and said components are employed in a ratio of from 1 to 1 and 9 to 1. ' f. The composite fiber of Claim ^ characterized in that one synthetic polymeric component consists of a copolymer of from 80 to 95 percent acrylonitrile and 5 to 20 percent vinyl acetate and a second polymeric component consists of a copolymer of 70 to 99 percent acrylonitrile and 1 to 30 percent styrene, and said components are employed in a ratio of from 1 to 1 and 9 to 1. f. The composite fiber of Claim f> characterized in that one synthetic polymeric component consists of a copolymer of 85 to 95 percent acrylonitrile and 5 to 1 percent vinyl acetate and a second polymeric component consists of at least 80 percent acrylonitrile, up to 1 percent vinyl acetate and from 1 to 10 percent of an acrylate, and said components are employed in a ratio of from 1 to 1 and 9 to 1. tj . The composite fiber of Claim ^ characterized in that one synthetic polymeric component consists of a copolymer of 85 to 95 percent acrylonitrile and 5 to 15 percent vinyl acetate and a second polymeric component consists of at least 80 percent acrylonitrile and up to 20 percent of vinylidene chloride, and said components are employed in a ratio of from 1 to 1 and 9 to 1. 6. The composite fiber of Claim ^ characterized in that one synthetic polymeric component consists of a copolymer of 80 to 95 percent acrylonitrile, 5 to 15 percent a mono-olefinic monomer and a second polymeric component 5 to 15 percent of the mono-Die inic monomer of the first ^τί* component having a difference in percentage level of at least 2 percent, and said components are employed in a ratio of from 1 to 1 and 9 to 1 , 7. The composite fiber of claim 1 characterized in that one synthetic polymeric component consists of a copolymer of 9k percent acrylonitrile and 6 percent vinyl acetate and a second polymeric component consists of a ter-polymer of 92 psrcent acrylonitrile, 6 percent vinyl acetate and 2 percent styrene, and said components are employed in a 1 to 1 ratio, 8* The composite fiber of claim 1 characterized in that one synthetic polymeric component consists of a copolymer of 85 to 95 percent acrylonitrile and 5 to 15 percent vinyl acetate and a second polymeric component consists of at least 80 to 98 percent acrylonitrile, 1 to 15 percent vinyl acetate and from 1 to 12 percent vinylidene chloride, and said components are employed in a 1 to 1 ration. 9· The composite fiber of claim 1 characterized in that one synthetic polymeric component consists of a terpolyme of 80 to 95 percent acrylonitrile, 5 to 15 percent vinyl acetate and 0.1 to 5 percent of a dye receptor and a second polymer component consists of 80 to 92 percent acrylonitrile, 2 to 10 percent vinyl acetate, 1 to 5 percent styrene and 0.1 to percent of a dye receptor, and said components are employed in a 1 to 1 ratio. 10. A composite fiber comprising at least two different components of compositions containing acrylonitrile substantially as described in the herein Examples. Dated this Second day of September 6-+. Agent for Applicants.