US3605224A - Bulking method - Google Patents

Abstract

A process for crimping cellulose acetate/cellulose triacetate conjugate filaments by treatment with reagents which preferentially disrupt the molecular orientation and crystallinity of the cellulose acetate followed by reagent removal and drying under conditions of substrate relaxation.

Description

United States Patent Office.

3,605,224 Patented Sept. 20, 1971 3,605,224 BULKING METHOD Jesse L. Riley, William John Robert, and Walter C.

Zybko, Charlotte, NC, assignors to Celanese Corporation, New York, N.Y. No Drawing. Filed July 28, 1969, Ser. No. 845,503 Int. Cl. D02g 1/00 US. Cl. 28-721 22 Claims ABSTRACT OF THE DISCLOSURE A process for crimping cellulose acetate/ cellulose triacetate conjugate filaments by treatment with reagents which preferentially disrupt the molecular orientation and crystallinity of the cellulose acetate followed by reagent removal and drying under conditions of substrate relaxation.

BACKGROUND OF THE INVENTION The present invention relates to a method for bulking conjugate filaments and/ or textile articles of manufacture produced therefrom. More particularly, this invention relates to a process for spontaneously or latently developing bulk in conjugate filaments and yarns composed of coextensive segments of cellulose acetate and cellulose triacetate.

Methods for producing multicomponent or conjugate filaments are well known inv the art. In US. Pat. 3,039,173, for example, there is described a method involving spinning together two or more cellulosic derivatives, at least one of which is fiber-forming, in such a way that the derivatives are not appreciably blended together but rather form over the cross section of the single composite filament two or more distinct zones which extend where desired throughout the entire length of the filament, whereby only one or, alternatively, part of or all of the components form the surface of the single composite filament. The extrusion may be such that the components are localized and held in a side-by-side arrangement in which both components form part of the composite, or the extrusion may be such that one component forms a core and the other a sheath to form a sheath-core composite. In this latter instance, only the sheath contributes to the surface of the composite. See also US. Pat. 3,209,402, which describes method and apparatus suitable for producing multicomponent filaments and yarns. The contents of each of the foregoing patents are incorporated hereby by reference. Thus, the term multicomponent filaments as used herein refers to filaments formed from two or more fiber-forming masses wherein distinct zones of each mass remain segregated in coextensive relationship throughout at least a significant portion of the fiber as opposed to the homogeneity associated with fibers formed from a blend of two or more fiber-forming components. Multicomponent and conjugate are used interchangeably herein to describe such fibers.

Multicomponent filaments that have proven to be of considerable importance commercially are those made up of cellulose triacetate and secondary cellulose acetate. It has been found desirable in preparing such bicomponent filaments to utilize two separate dope streams, one of cellulose triacetate and the other of secondary cellulose acetate (hereinafter referred to as cellulose acetate). These two dope streams are brought together in surface to surface contact, e.g. as by side-by-side arrangement, sheath-core arrangement, or the like, and the resulting composite dope stream is caused to flow by laminar viscous flow to a jet or spinnerette. The composite dope stream is extruded through the jet so as to form a multicomponent (in this instance a bicomponent) filamentary material made up of cellulose triacetate and cellulose acetate.

Prior to the present invention, it has been necessary to treat either the raw cellulose acetate/cellulose triacetate multicomponent fiber or textile articles constructed therefrom, i.e. knitted and woven textile materials, by a timeconsuming and costly process involving saponification of the secondary cellulose acetate to regenerate cellulose to develop adequate fiber crimp and product bulk therefrom in combination with the dimensional stability required in commercially acceptable fibers. Selective saponification of the cellulose acetate component of the conjugate fiber, generally consisting of a mild alkaline treatment, that is, an alkaline treatment bath sufficiently dilute so as not to appreciably affect the triacetate portion of the fiber, along with required post-saponification process steps such as resin treatment for added dimensional stability through repeated laundering cycles, heat setting, and tumble drying, develops sufiicient crimp in the individual conjugate filaments to give textile materials constructed therefrom adequate hand, bulk, stability, and strength. Obviously, the employment of the conventional saponification treatment is attendant with numerous disadvantages, most notable of which are cost, time, and required equipment.

An additional disadvantage associated with the saponification route for developing bulk is the inherent conversion of cellulose acetate into regenerated cellulose, the latter being highly undesirable in many instances as a conjugate fiber component. For instance, a cellulose acetate/cellulose triacetate multicomponent fiber would be preferable to a regenerated cellulose/ cellulose triacetate fiber because of the superior physical and chemical properties of cellulose acetate with respect to certain endproduct manufacturing operations and resulting fabric uses. As examples of the above, others of which will be obvious to those of skill in the art, there may be mentioned the lower specific gravity of cellulose acetate, permitting a greater covering power and warmth in a lighter weight fabric, solution dyeability, and excellent resistance to mildew.

Additionally, as compared to cellulose acetate, regenerated cellulose acetate is characterized by poor dyeing properties in certain respects, i.e. nonuniform pigmentation from disperse dye baths and general decline in dye substantivity, and lower productivity from an economic standpoint due to the approximately 17% weight loss resulting from saponification. Also, fabrics constructed from regenerated cellulose require resin treatments for dimensional stability with consequential fabric tendering and yellowing.

Therefore, it is an object of the present invention to provide an improved process for bulking cellulose acetate/ cellulose triacetate conjugate fibers and textile materials constructed therefrom. More particularly, it is an object of the present invention to provide a rapid, inexpensive process for developing crimp in cellulose acetate/ cellulose triacetate multicomponent fibers. A further object of the invention is to provide a crimping process for conjugate fibers composed of cellulose acetate and cellulose triacetate which does not involve selective saponification of the celluloes acetate portion of the fiber to regenerated cellulose. Still another object of this invention is to provide a bulking process for cellulose acetate/cellulose triacetate multicomponent fibers which does not alter the chemical identity of either the cellulose acetate or triacetate component. An additional object of the invention is to provide a crimping process for cellulose acetate/ cellulose triacetate conjugate fibers which may be subsequently constructed into fabrics retaining dimensional stability without requiring a resin treatment. Other objects will appear obvious to those of skill in the art from the detailed description of the invention hereinafter.

3 SUMMARY OF THE INVENTION In accordance with the present invention, it has been found that treatment of conjugate yarns or filaments comprising cellulose acetate/cellulose triacetate with a fluid capable of disrupting the molecular orientation and crystallinity of cellulose acetate without deleteriously affecting in a significant manner the degree of crystallinity of said cellulose triacetate, followed by removal of the fluid and drying of the substrate while in a relaxed state, produces a differential shrinkage between the relatively amorphous cellulose acetate and relatively crystalline triacetate, the latter resisting shrinkage because of retention of its structural integrity, thereby producing crimped yarns or filaments. Preferably, the fluid treating agent is selected from the class of compounds which function as sub-sol vents for cellulose acetate and, more particularly, is selected from the group consisting of water under conditions of elevated temperature and superatmospheric pressure; and low molecular weight aliphatic and aromatic al cohols, carboxylic acids including the esters thereof, ethers and ketones including intramolecular condensation products such as lactones and aldehydes. These compounds will cause the conjugate yarns or filaments to develop adequate crimp not requiring selective saponification or other similar further bulking steps to enable the production of fabrics displaying excellent tactile properties, loft, dimensional stability, strength, and other desired characteristics. In preferred aspects of the invention, an aqueous formulation is employed for maximum development of shrinkage differential from a one step treatment, the water through its swelling effect on the substrate further accentuating the shrinkage differential. Other acetate sub-solvents are known to those skilled in the art.

A variety of procedures are applicable for bulking the aforesaid conjugate filaments, which filaments are used to exemplify the invention, involving contact with an appropriate chemical treating agent which upon fiber drying and/or subsequent thereto, i.e. following conversion into fabric form, causes differential length change with respect to the individual fiber-forming components of the cellulose acetate/cellulose triacetate conjugate fiber. The chemical agent can develop dimensional change in either the cellulose acetate or triacetate component or can affect both of said components, one to a lesser degree than the other with the cellulose acetate when dried shrinking to a greater extent than the triacetate. The crimp effect occurs during a subsequent drying operation which activates a latent differential shrinkability of the cellulose acetate vis-a-vis the cellulose triacetate. Regardless of the type of length change, the resultant fiber is characterized by an area of cellulose acetate along the internal portion of the crimp, that is, the cellulose acetate shrinks to a greater degree than the cellulose triacetate fraction of the continuous filament.

In one aspect of the invention, the conjugate filamentary material is pretreated to preferentially increase the degree of crystallization of the cellulose triacetate component or, alternatively, is pretreated to set up a high crystallization potential in the cellulose triacetate which is realized during subsequent fluid treatment. This effect may be accomplished by treatment with cellulose triacetate swelling agents, which materials are well-known in the art, under conditions of exposure which may include a simultaneous or post-treatment stretch. In general, these materials do not produce a corresponding increase in degree of cellulose acetate crystallinity. As a result, the shrinkability of the cellulose acetate fraction is not adversely affected during the subsequent drying operation while the resistance to shrinking of the triacetate is increased, because of the increased structural integrity, during processing. Following pretreatment, the multicomponent fiber is washed and contacted before or after drying with the above-described fluid treatment agent, i.e. cellulose acetate sub-solvent, with the development of an unusually high crimp level per unit relaxed length due to My Ad the relatively stationary configuration of the cellulose triacetate component from the crystallization thereof preventing shrinkage of the cellulose triacetate moiety to the degree possible in the absence of the pretreatment. Where desired, latent bulkability is developed by drying treated fibers under tension.

In another embodiment of the invention, which may also be considered as a preferred embodiment thereof, a textile substrate, i.e. fibers as well as manufactured tex tile articles such as knitted, woven and nonwoven fabrics, may be simultaneously dyed and bulked with precise control of dye uptake with respect to uniformity of shade by contact in a treatment zone containing an appropriate dye and critical concentration of chemical bulking agent. The accurate control of the concentration of the bulking agent enables it to function in two capacities during the dyeing procedure, namely, as a dye levelling agent in addition to its function as a crimp-developing compound. In this connection, it has been found that swollen fibers dye more rapidly.

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a procedure whereby conjugate filaments or yarns comprising cellulose acetate/ cellulose triacetate can be conveniently and inexpensively crimped during continuous operations not involving the disadvantages of prior art selective saponification techniqucs.

It has now been found that certain fluids, particularly cellulose acetate sub-solvents, characterized by the ability to disorient and break down the weak crystallite ties of cellulose acetate without disrupting, but in many instances improving, the crystallinity of cellulose triacetate, differentially affect the dimensional stability of the individual components of cellulose acetate/cellulose triacetate multicomponent fibers to such a degree that upon drying under relaxed conditions spontaneous crimping of the fibrous material occurs. The treating agents can preferentially operate on one of the yarn components, i.e. the acetate or differentially affect both the acetate and triacetate. Preferably, the treating agent is also a triacetate swelling agent and it should be noted that swelling agents for triacetate which are not species Within the above general description are applicable although not preferred in some instances.

In one aspect of the invention the fluids, particularly liquids, employed in the practice of the invention are oxygen-containing compounds. The oxygen-containing compounds suitable for treating the conjugate filamentary material are low molecular weight aliphatic and aromatic carboxylic acids and esters thereof, alcohols, ketones, ethers, aldehydes, and lactones. The particular compounds employed may contain an aromatic moiety with the proviso that the chemical compound does not contain more than 10 carbon atoms in its structure. Preferably, the bulking agent will contain from 2 to 7 carbon atoms and will be characterized by a phenyl group or two-carbon aliphatic chain within its structural formula and will be considered a sub-solvent for cellulose acetate. As representative compounds within the purview of the present invention, there may be mentioned water under elevated temperature and superatmospheric pressure conditions, acetic acid, amyl acetate, butyl acetate, benzyl alcohol, phenol, butyrolactone, dioxane, acetone, nitromethane, formic acid, isopropyl alcohol, propionic acid, allyl acetate, vinyl acetate, caprolactarn, urea, benzoic acid, sali cylic acid, diethylene glycol diacetate, glycerol diacetate, glycerol triacetate, acetamide and ethylene glycol monomethyl ether. As is known to those skilled in the art, as a general rule, organic sub-solvent agents having hydroxyl functional groups may be employed as such while those deficient in hydroxyl functional groups are generally but not exclusively employed in a medium having such functional groups, ex, in aqueous solutions such as 2040% acetic or propionic acid in water by volume, 3070% by weight aqueous solution of urea and the like, but it should be noted that glycerol triacetate is operable in benzene solution and vinyl acetate may be used undiluted. For optimum effect, the organics are used in combination with water in one-step treatments at preferred temperatures and concentrations with, in general, concentration of organic reagent decreasing as temperature is increased.

Many different treatment procedures may be employed as disclosed hereinafter as well as other contacting procedures, whether or not of a continuous nature, which will be obvious to those of skill in the art. The essential requirements to be borne in mind are adequate contact time with a treatment medium containing sufiicient concentration of chemical agent to differentially affect the dimensional stability of the conjugate fiber and subsequent drying in an unrestrained condition or at least with tension reduced sufficiently to allow the degree of crimp development desired. Preferably, the substrate material is washed to remove excess treatment agent prior to drying. Generally, the water wash is also of benefit in enhancing the crimp effect because of its swelling action on the conjugate fiber, that is, a higher percent crimp per unit length is developed where the fibrous substrate is treated with one of the aforesaid chemical agents followed by a separate water treatment because of a cumulative preferential dimensional instability resulting therefrom.

As stated hereinbefore, the chemical reagents employed as bulking agents herein disrupt the molecular orientation and weak crystallite tire of the cellulose acetate component, without freeing individual molecules of the point of complete solvation, i.e. structural integrity is lessened but still present, thereby allowing the cellulose acetate to appreciably shrink following bulking agent removal and drying. This type of fluid action is designated herein as sub-solvent action and the compounds useable are therefore sub-solvents for cellulose acetate. Simultaneously with sub-solvent action on the acetate, the treatment formulation must not significantly disrupt the crystallinity of the triacetate. Surprisingly, it has been found that in many instances cellulose acetate sub-solvents not only do not lower the structural cohesiveness of the triacetate but actually increase the crystallinity of the triacetate because the increased mobility of molecular segments permits the fuller realization of the potential for crystallization of the triacetate. The swelling action, by permitting segmental rotation and relaxation of stored stresses, removes some of the restriction on crystallite growth and results in an improvement in triacetate crystallinity. The triacetate, because of its retention of a high degree of crystallinity, exhibits minimal if any shrinkage during the subsequent drying operation.

It is to be understood that the present invention is applicable to textile substrates of any type comprising cellulose acetate/cellulose triacetate conjugate fibers or yarns including, but not limited thereto, staple fibers, spun yarns, continuous monoand multifilaments and textile fabrics made therefrom, i.e. by various methods of interlacing such as weaving, braiding, knitting, twisting and the like, as well as nonwoven fabricating techniques. The terms fiber, filament and the like, are used interchangeably throughout the specification.

Likewise the invention is equally applicable to other cellulose esters wherein the ester group contains up to 4 carbon atoms, i.e. cellulose propionate, cellulose butyrate and mixed esters thereof such as cellulose acetate-butyrate, cellulose propionate-butyrate and the like as long the components of the conjugate filament have a degree of esterification difference of at least about -15 percent based on percent hydroxyl radicals esterified, generally with the triester having a degree of esterification of about 2.9 to 3.0 and the diester about 2.0 to 2.6. At times, the inclusion of priopionate and higher ester group substituents in the bicomponent i.e. cellulose acetate/cellulose propionate, will yield sufficient differential shrinkability under the disclosed process conditions.

Certain treatment procedures are of particular utility in the bulking of certain types of substrate materials such as fabrics while other techniques will lend themselves more to the crimping of continuous filaments during multistep processes which impart additional desired properties to the substrate during an integral process.

For example, in one method in accordance with the invention, a continuous strand of material comprising cellulose acetate/cellulose triacetate in co-extensive relationship is passed sequentially through an aqueous treatment bath containing a chemical bulking agent as disclosed which causes latent differential shrinkage of the conjugate fiber and a second bath of cold water wherein no significant shrinkage occurs. Subsequently, the strand, which could be a spun yarn, monofilament, or one member of a multifilament, tow and the like, is dried, such as by single or multiple simultaneous passage through an elongated oven, under relaxed conditions to allow maximum crimp development. At times, if a crimp level below that obtainable under the above conditions is desired, the strand can be dried under a tension suflicient to prevent the cellulose acetate from shrinking to the degree possible under unrestrained operating conditions. However, unless blocked by subsequent treatment, water washing and drying at a later time will develop additional bulk due to a memory effect produced in the fiber. A latent crimp development is desired at times since the yarn is thereby in a straight configuration during the conversion operation, i.e. weaving.

One of the particular advantages of this invention is that it provides a rapid procedure for producing bulky fabric materials. Many fabric finishing operations involve treatment in baths of various formulations followed by drying in unrestrained condition. In such instance, the chemical bulking agent can most often be added in sufficient concentration directly to such baths eliminating the necessity of additional treating units, time, etc. Alternatively, the fabric may be immersed in a separate bulking bath prior to dyeing. As an example of the former and obviously preferred procedures, the chemical treating agent can be incorporated into a suitable dye bath during a simultaneous dyeing and bulking operation.

It is preferred that an inexpensive bath medium be em ployed. In most instances, the treating medium will be predominantly water. To assure adequate fiber swelling, it is desirable to employ a hydrophilic treating medium containing hydroxyl groups to disrupt internal hydrogenbonding of the secondary acetate.

As disclosed hereinbefore, one of the preferred embodiments of the invention resides in a prebulk or two-step treatment involving a pretreatment to preferentially affect in a positive manner the crystallinity of the cellulose triacetate component. This can be accomplished by contact with a first, preferably mild, cellulose triacetate swelling agent. The multicomponent material is then treated with a bulking agent as disclosed, that is, a material as described above which imparts a different shrinkability potential to cellulose acetate and cellulose triacetate so as to preferentially shrink the cellulose acetate component upon drying.

It has been found that the sequential treatment imparts a greater relative degree of crimp in the conjugate fiber than would be expected from a consideration of the activity produced by the separate application of each treatment agent on comparable material. This synergistic effect is particularly evident Where, as preferred, the first treatment agent is one which has a relatively low degree of activity on cellulose triacetate crystallinity. In fact, in the absence of a concomitant stretch being imparted to the textile substrate, no increase in triacetate crystallinity is observed in most instances by the usual testing methods. Any increase in crimp development upon solvent removal and drying would be negligible since the pretreatment agent is preferably also a poor sub-solvent for cellulose acetate. It is postulated that the initial swelling agent treatment allows triacetate molecules to move freely into a more natural molecular alignment conducive to subsequent crystallization upon latter solvent treatment; that is, a high crystallization potential is set up in the triacetate portion of the material which potential is realized upon subsequent treatment. Additionally, the number of small crystallites in the triacetate is increased. Where desired, for maximum effect, the substrate is axially stretched up to its elastic limit simultaneously with swelling agent treatment for molecular orientation along the longitudinal fiber axis. As a result, further triacetate crystallization is accomplished, increasing the degree of crimp developed following subsequent treatments as described. The simultaneous stretching of the cellulose acetate when this embodiment of the invention is employed also increases the shrinkage potential thereof.

The pretreatment agent may be selected from two broad categories of triacetate swelling agents. On the one hand, swelling agents for cellulose triacetate which produce a small increase in triacetate crystallization, even in combination with fiber stretching, may be used. As examples of this former type of swelling agent, there may be mentioned the lower monohydric alcohols containing 1-4 carbon atoms in the molecule, ex. methanol, ethanol, n-propanol, n-butanol, and the like. The other general classification would include triacetate swelling agents having, in certain concentrations and formulations, a sutficient effect on acetate to allow their use as the sole bulking agents in other embodiments of the invention. However, for good synergism, this second group of reagents, Where used as the pretreatment crystallization potentiator, are preferably employed in concentration and/ or formulations which are not useable per se as sole treatment agents. Indeed, at times the identical swelling agent may be employed in both steps of the sequential process with a non preferred formulation being employed in the first phase and optimum parameters being employed in the final acetate sub-solvent treatment. As examples of this latter type of agent, other examples of which are stated throughout the specificaion, there may be mentioned methyl acetate, ethyl acetate, methylene chloride, gamma-butyrolactone, phenol and the like. For many of these reagents, optimum concentrations and/or formulations for use as triacetate swelling agents are disclosed herein and in the patent and literature arts. Where such data is not known precisely, routine experimentation capable of those of ordinary skill in the art will suffice once the principles as described herein are known.

The preferred pretreatment agent, recommended for ease of handling as well as accessability, is ethanol. Pure,

i.e. about 9599% ethanol, need not be employed, but an aqueous mixture containing at least about 60% by volume ethanol, preferably over 65% by volume, and most preferably about 80% ethanol, will function satisfactorily. Ambient temperature conditions may be employed and preferably the temperature of treatment will be about 20 C. although temperatures within the range of about C. up to about the boiling point of the mixture are applicable with reduction in concentration at elevated temperatures. Concommitant with such a pretreatment, the textile substrate is desirably placed under tension to effectuate a longitudinal stretch of the conjugate filaments, usually up to about a 20% increase in length and preferably about l5%. Although, as described hereinbefore, fiber extension is not essential to achieve the enhanced percent crimp obtainable through pretreatment where a reagent such as ethanol is employed which preferentially crystallizes cellulose triacetate during stretching, it is highly desirable to stretch the conjugate filament for the additional molecular alignment associated with the orientation process. Depending upon degree of activity and water miscibility, effective concentrations of other pretreatment agents may not coincide with that of ethanol as disclosed above, and routine experimentation within the skill of those knowledgeable in the art may be neces- 8 sary to optimize processing conditions within the general parameter stated herein.

Concentration of the primary treatment agent will depend upon a number of interrelated factors, the most important being the particular bulking reagent selected. In general, considering an aqueous treating bath with percent being either weight/volume or volume/volume reagent/dispersion medium, according to the physical state of the chemical compound, concentration may range from 0.1 to about 100, i.e. no treatment medium, but most often will range from about 0.5 to percent with optimum concentrations for most reagents being in the range of about 1 to 25 percent. Thus, a relatively low concentration of chemical compound is generally required with no appreciable benefit and in many instances very poor results being observed with the use of higher concentrations.

As disclosed hereinbefore, the dispersion medium is preferably of a hydrophilic nature containing hydroxyl functional groups. Most often, where employed the dispersion medium is selected from acetate swelling agents and acetate sub-solvents and where applicable will preferably be water. Thus, a binary system is desirable consisting of an optimum concentration of water-soluble or miscible reagent in combination with water. Of course, ternary and the like systems wherein two or more organic solvents or subsolvent agents for acetate are dissolved in, for example, an acetate swelling agent treatment medium, are operable. In one aspect of the invention, an acetate solvent, e.g. acetone, is used in combination with an acetate swelling agent, i.e. water, to yield a sub-solvent mixture. Concerning selection and proportions, one of the most critical factors to be borne in mind is to avoid complete dissolution of triacetate (or other substrate components). Thus, triacetate solvents are employed under conditions such that they function only as sub-solvents, i.e. 100% methylene chloride is preferably applied as a vapor for rapid dissipation.

Considering the cellulose acetate/cellulose triacetate multicomponent material in greater detail, the conjugate fiber may be of any desired cross-sectional configuration, i.e. sheathcore as well as side-by-side type, and preferably the components are in eccentric relationship. Assuming a bicomponent fiber, ratio by weight may range from about 2: 11:2 with 1:1 being preferred.

Treatment temperature can fluctuate widely and where treatment baths are employed will usually be within the range of about room temperature up to the boiling point of the bath. Temperatures within the range of about 30 C. to 70 C. are usually adequate with a shorter residence time and lower concentration generally being associated with increased temperatures. Temperatures above the designated range can be employed where autoclaves and other similar devices are used during substrate treatment. Residence time is normally about /2 minute to minutes to be correlated with bath concentration, bath temperature, type of substrate, degree of crimp desired and the like. No specific advantages other than the stated use of lower reagent concentrations are known from practicing the invention at higher temperatures, under applied pressures (except where water is the sole treating agent) or for longer residence times. Water washing temperature can range from below room temperature up to temperatures which do not adversely affect the substrate, but the water wash will generally be under ambient conditions. Immersion baths, spraying booths and similar washing arrangements may be employed. The bulking agent should be substantially removed from the substrate material to eliminate any residual swelling effect after crimp development. This could seriously impair yarn and fabric strength. Since water is readily evaporated during the drying operation, it is the preferred washing or solvent removal medium. Of course, other washing agents, such as ethanol, may be employed. Also solvent removal may be accomplished during drying without a previous wash where treating agents of high vapor pressure are employed.

The drying cycle, being essential for adequate bulk development, should be accurately controlled. It is recommended that temperatures from ambient to below about 195 C., preferably 140l60 C., be employed for planar substrates to allow diiferentail shrinkage of the conjugate material. Thus, drying time and temperature should be regulated so that the particular substrate, and of course considering the gross amount of material being dried where tumble drying units are used, will not be too rapidly dried with only a small number of crimps being formed. The substrate must either be in a relaxed state, that is, under conditions allowing freedom to contract, or under reduced tension during drying. If constrained, the conjugate fibers can not shrink to develop adequate bulk. For maximum crimp development, elevated temperatures are usually required.

The following examples illustrate the invention. It is, of course, understood that the invention is not to be limited to certain of the preferred embodiments of the invention as exemplified by the examples.

EXAMPLE 1 This example concerns one of the preferred embodiments of the invention wherein triacetate/acetate conjugate filaments are pretreated prior to actual bulking. Upon immersion in the bath of the primary bulk developing chemical treating agent, the cellulose acetate swells somewhat and relaxes while the cellulose triacetate component swells but remains relatively intractable.

A multililament yarn having a 1.2 gram per denier tenacity and 20% elongation at the break, each filament being of about 5.5 denier and composed of 50/50 by weight cellulose acetate/ cellulose triacetate in coextensive side-by-side relationship, is immersed in an ethanol/water solution 80/20 by volume at 20 C. and suflicient tension is applied to elongate the yarn approximately 20% based on initial length. The yarn is dried unrestrained at room temperature with minimal crimp development and samples thereof are immersed in phenol solutions of varying concentrations at 55 C. for minutes. Each sample of yarn is then dipped in a water wash bath for one minute at room temperature and finally air dried under relaxed conditions at 60 C.

Table 1 presents the results obtained.

TABLE 1 Sample: *Degree of bulk AUntreated None. BTreated with 1%% phenol Fair. B Treated with 1%% phenol Do. CTreated with 2 /2 phenol Good. C Treated with 2 /2 phenol Do.

*In all of the examples herein the bulk rating is determined by visible examination in combination with measure ments of length shrinkage and crimp level by one skilled in the art with a fair rating being correlateable to the minimum bulk level acceptable for commercial products. For end products requiring a high degree of texture, i.e. b ulky knits such as sweaters, 13. good to excellent rating would -be required in the yarn.

Further experimentation indicates that optimum process parameters for the phenol treatment are from 1 to 60 minutes in a 1-3% by weight aqueous bath at Example 1 is repeated with the elimination of the ethanol pretreatment. Bulk development following washing and drying is somewhat lower than that shown by Table l but still appreciable.

EXAMPLE 2 This example concerns treating the foregoing bicomponent filaments with aqueous solutions of amyl acetate, butyl acetate, and butyrolactone, by immersing the filaments in a bath thereof.

When amyl acetate or butyl acetate is to be employed, inasmuch as they are each of rather limited solubility in water, it is preferred to employ as the solvent an aqueousalcoholic mixture, or water plus some other appropriate co-solvent.

Suitable alcohols that may be employed include methanol, ethanol, propanol (desirably isopropanol), or any mixtures thereof. The concentration of the alcohol in the water desirably should be from about 10 to 50% by volume. The concentration of the amyl and butyl acetate in the foregoing alcohol-water mixture was advantageously from about 2 to 20% by Weight. Of course, these particular co-solvents are advantageously employed for a cumulative effect since they are within the scope of the invention.

When butyrolactone is utilized rather than amyl or butyl acetate, the alcohol is desirably not employed in combination with the water as the solvent. The concentration of the butyrolactone in the water is from about 5 to 25% by weight.

The temperature of the treating bath should desirably be from about 20 to C., a preferred range being from about 40 to 90 C., the most preferred range being from about 70 to 90 C.

The residence time of the conjugate filaments in the bath may again vary :within considerable limits, generally being form about 1 to 60 minutes. Of course, a residence time in excess of 60 minutes could be employed but would serve no additional advantage. A more preferred time range is from about 2 to 20 minutes, the most preferred range being from about 2 to 10 minutes.

Following the immersion of the conjugate filaments in the aqueous or aqueous-alcoholic treating solution, the filaments are removed and washed with water. Advantageously, this washing is carried out first in cold water and thereafter with boiling water. The washing is desirably carried out for from about 1 to 10 minutes with water at from about 20 to C. Of course, the filaments could be washed with a non-swelling organic solvent and immediately dried with good bulk development. However, this example illustrates the preferred washing method. The foregoing water wash serves to remove the acetate sub-solvent (amyl acetate, butyl acetate, or butyrolactone). Moreover, it will be noted that the water is itself something of a swelling agent for both the cellulose acetate and the triacetate. Of course, because of the presence of more hydroxyl groups in the cellulose acetate, the water tends to exert a greater swelling action thereon than upon the cellulose triacetate. This difierential swelling is further enhanced due to the fact that the triacetate has in a sense been stabilized by virtue of the previous solvent treatment, making it all the more resistant to swelling by the water wash. Thus, water in the absence of pressure (see Example 5 hereinafter) is not considered as useable alone as a bulking reagent but only for its additive elfect in binary and the like formulations. At times it may be employed as a pretreatment agent.

The water wvash is followed by drying of the filaments under relaxed conditions, generally either in air or alternatively in a tumble dryer. The drying results in a differential shrinkage between the acetate and triacetate, the former shrinking markedly more than the latter, so that the drying develops a marked crimping of the multicomponent filaments with a corresponding bulking thereof. Such bulking, of course, greatly improves the covering ability of the filaments, improves the hand, and generally imparts the usual desirable qualities associated with bulking.

Fabric samples knitted from the described conjugate filaments are treated in alcohol-water or water solution of varying concentration of butyrolactone and amyl acetate for 10 minutes at 85 C. and 3 minutes at 50 C l l respectively, as tabulated in Table 2 followed by washing in water at 20 C. for 5 minutes and/or washing in boiling 'water for minutes, and in every case tumble drying at 160 C. for minutes.

TABDE 2 Water Boiling Wash water Degree Sample Bulking agent (20 C wash of bulk 2A. None 10 2O 5% butyrolactonc Yes Fair. 2]) ..do Yes Yes... Do.1 2E 10% butyrolactonc Yes Good 2F do Do. 2G 20% butyrolactone. Very good. 21L do Excellent.

Methanol/watei 50/5 Fair. 15 O O. 5% amyl acetate in nr/w. Yes Good.

50/50. 2L do Yes Yes..." Do. 2M 10%[amyl acetate in m./w. Yes Very good.

50 50. 2N do Yes... Yes Excellent. 2

1 Also 3 minutes at 50 C.

Equally good results are obtained with butyl acetate. Of interest is the bulk developed by the methanol/water solvent treatment illustrating another composition com- 25 ing within the scope of the invention but more desirably employed only as a pretreatment agent.

EXAMPLE 3 This example illustrates another of the preferred embodiments of the invention wherein simultaneous dyeing and bulking of fabric are accomplished.

Two-inch squares of a double knit fabric knitted from 180 denier 50/50 by weight acetate (acetyl value of 55)/ triacetate conjugate filament yarn as described are immersed in dioxane/water solutions of varying dioxane concentration at about 25 C. for about 10 minutes. Also included in the bulking chemical bath is 3% (w/w.) of Blue BGLF acetate disperse dye (available from Eastman Chemical Corp. of Kingsport, Tennessee) which produces visible dye streaks of different shades if the acetate substrate does not take up a uniform level of dye across its surface. This dye is the most senitive known for developing streaks because of uneven dyeing. The squares are then washed in cold water (20 C.) for 10 minutes and tumble dried at 160 C. The results are tabulated below in Table 3.

EXAM PLE 4 Example 3 is repeated in the absence of the dye with acetic acid/water solutions of varying acetic acid concentration. Optimum bulking is observed at the 35-40% acetic acid level.

EXAMPLE 5 Fabric samples as in Example 3 are immersed in a water bath at 25 C. for 15 minutes, after which the samples are steam autoclaved for 30 minutes at 15 p.s.i.g. The double knit fabric exhibits a bulk rating of good. Increasing the pressure by 5 p.s.i.g. increments up to p.s.i.g. does not improve the degree of bulk developed.

EXAMPLE 6 Example 3 is repeated with varying levels of benzyl alcohol in water at l25 C. With concentrations of 2 to 2 /2% of benzyl alcohol, good bulking accompanied by level dyeing is observed.

1 2 EXAMPLE 7 This example illustrates the use of the teachings herein to produce latent bulkable fabrics.

A 60 denier, l7 filament multifilament conjugate yarn comprising bilateral filaments of 50/50 bright acetate/ bright triacetate as described is immersed in an aqueous solution of 40% volume/volume acetic acid/water at 25 C. under slack conditions, that is, without tension. The yarn is then wound loosely arounnd a metal frame after which it is immersed in a water bath having a temperature of about 25 C. for a period of about five minutes. The yarn is observed to become taut on the metal frame. The metal frame and yarn are taken from the water bath and the yarn is allowed to dry in air at room temperature. After drying, the yarn is cut off the frame and observed to be straight and to have shrunk l to l /2%.

A fabric knitted from the above yarn, although displaying no bulk or other texture, becomes highly bulked due to latent crimping of the yarn when immersed in cold water (25 C.) for one minute followed by drying at C. in a tumble dryer.

Obviously, this example can be the basis of a continuous operation for providing latently texturable yarn to the trade, which yarn, upon washing and drying, will latently bulk. Thus, in accordance with this aspect of the present invention, conjugate filaments may be extruded to form a conjugate filament yarn. The yarn is then supplied in a plurality of packages on a creel and is then beamed on a tricot beam. Between the creel and the beam the yarn ends are passed through a vessel containing the solvent treating material, e.g. 40% acetic acid/ water (volume/volume) followed by washing and drying under a tension of say one sixtieth of a gram per denier. The yarn is then taken up on the beam in a straight manner, that is, without having been bulked. The yarn from the tricot beam is then knitted into the desired fabric or garment. Upon wetting, as in the scour operation, followed by drying, crimps are formed and the yarn becomes bulky, thereby producing an end product having a decreased air permeability, lofty hand, and the various other desirable attributes associated with bulky yarns.

Various modifications may be made within the scope of the invention which will appear obvious to those of skill in the art. For example, conjugate filament material of cellulose acetate/triacetate bulked as described herein may be selectively saponified in accordance with prior art techniques to produce a product which has a better dimensional stability than comparable saponified yarns which have not been pretreated in accordance with the invention. Further, the present invention is equally applicable to conjugate or more precisely combination yarns per se, as opposed to conjugate filaments, composed of coextensive filamentary components which are differentially shrinkable or elongatable under the conditions of treatment, i.e. crepe fabrics may be prepared from tricot fabrics knitted from a metier plied yarn of nylon/acetate or nylon/acetate/triacetate conjugate filaments when treated, for example, with acetic acid/water solution according to the examples hereinbefore because of the differential shrinkage developed between the nylon and acetate or conjugate filament. At times it may be desirable to preshrink one of the yarn components if the degree of shrinkability therebetween is less than about 5% under treatment conditions, i.e. a yarn composed of preshrunken nylon/acetate-triacetate conjugate filament may be bulked by treatment with benzyl alcohol in accordance with the invention. In other modifications of the invention, one of the components of the cellulose acetate/ cellulose triacetate, conjugate substrate i.e. the acetate, may be blended with a third polymeric fiber-forming material miscible therewith such as an acrylic polymer to affect fiber strength and other properties as desired. Of course, the conjugate components may contain normally acceptable modifiers, i.e. TiO filler, be preferentially dyed and the like or the treating agent may be applied intermittently in random or predetermined fash ion for novelty effects. Further modifications, such as constructing a. fabric from bulkable and non-bulkable fibers according to a preselected pattern for latent bulk development will appear obvious to those of skill in the art.

What we claim is:

1. A process for developing crimp in a cellulose acetate/cellulose triacetate conjugate yarn or conjugate filament substrate which includes the steps of:

(l) contacting said substrate with a fluid capable of disrupting the molecular orientation and crystallinity of said cellulose acetate without deleteriously affecting in a significant manner the degree of crystallinity of said cellulose triacetate, said fluid being selected from the group consisting of water and low molecular Weight aliphatic and aromatic alcohols, carboxylic acids, carboxylic acid esters, ethers, ketones, lactones and aldehydes, said water being under conditions of elevated temperature and atmospheric pressure, and mixtures thereof;

(2) substantially removing said fluid from said substrate; and

(3) drying said substrate under conditions of relaxation to differentially shrink said cellulose acetate and said cellulose triacetate, thereby crimping said cellulose acetate, cellulose triacetate yarn or filament.

2. The process of claim 1 wherein said fluid is selected from the group consisting of dioxane, acetic acid, acetone, benzyl alcohol, phenol, amyl acetate, butyl acetate and butyrolactone.

3. The process of claim 1 wherein said substrate is a textile fabric.

4. The process of claim 1 wherein said fluid is a compound containing up to about 10 carbon atoms.

5. The process of claim 1 wherein said fluid is a subsolvent for cellulose acetate.

6. A process for developing crimp in a cellulose acetate/cellulose triacetate conjugate yarn or conjugate filament substrate which comprises increasing the degree of crystallinity of said cellulose triacetate by treating said substrate with a swelling agent for cellulose triacetate and then treating said substrate with the process of claim 5.

7. The process of claim 6 wherein said substrate is stretched along the longitudinal axis of the yarn or fi1ament during said swelling agent treatment.

8. The process of claim 7 wherein said yarn or filament is stretched below its elastic limit.

9. The process of claim 6 wherein said swelling agent is selected from the class consisting of low molecular weight aliphatic monohydric alcohols.

10. The process of claim 9 wherein said alcohol is ethanol.

11. The process of claim wherein steps (2) and (3) thereof are simultaneously accomplished.

12. The process of claim 5 wherein said conjugate filament is one coextensive filamentary component of a conjugate yarn, at least a second component of said 14 conjugate yarn and said conjugate filament having a differential shrinkability of at least about 5 percent when treated by the process of claim 2.

13. The process of claim 5 wherein step (2) is accomplished by washing said substrate with water.

14. The process of claim 5 wherein said sub-solvent is a mixture of two or more cellulose acetate sub-solvents.

15. The process of claim 5 wherein said sub-solvent is applied in an aqueous formulation.

16. The process of claim 5 wherein said substrate is also contacted with a dye during step (1).

17. The process of claim 16 wherein said sub-solvent is employed in a concentration to maintain level dye pick-up by said substrate.

18. The process of claim 17 wherein said sub-solvent is selected from the class consisting of benzyl alcohol and dioxane.

19. A process for developing crimp in a cellulose acetate/cellulose triacetate conjugate yarn or conjugate filament substrate which comprises preferentially setting up a high crystallization potential in said cellulose triacetate and then treating said substrate with the process of claim 2.

20. A process for producing latently bulkable cellulose acetate/cellulose triacetate conjugate yarn or conjugate filament which comprises (1) contacting said yarn or filament with a fluid capable of disrupting the molecular orientation and crystallinity of said cellulose acetate without deleteriously affecting in a significant manner the degree of crystallinity of said cellulose triacetate; (2) substantially removing said fluid from said yarn or filament; and (3) drying said substrate under conditions of constraint to prevent significant shrinkage of said yarn or filament to produce essentially straight yarn or filament suitable for textile conversion operations.

21. The process of claim 20 wherein said fluid is a subsolvent for cellulose acetate.

22. A process for producing bulky textile fabric materials constructed of cellulose acetate/cellulose triacetate conjugate yarns or conjugate filaments treated in accordance with the process of claim 21 which comprises constructing said yarns or filaments into a textile fabric material; wetting said fabric material and drying said fabric material under conditions of relaxation sufficient to differentially shrink said cellulose acetate and said cellulose triacetate, thereby crimping said cellulose acetate/ cellulose triacetate yarns or filaments to produce a bulky fabric material.

References Cited UNITED STATES PATENTS 2,375,864 5/1945 Morgan 8--l31 2,408,381 10/1946 Dodge 8l31 3,039,173 6/1962 Mehler et al. 161173X 3,057,038 10/1962 Soehngen 161173 3,128,148 4/1964 Moore et al. 8131 LOUIS K. RIMRODT, Primary Examiner US. Cl. X.R.

PO-T w UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 05,224 Dated September 20, 1971 fl flesse L. Riley, William John Roberts & Walter C. Zybko It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 3, "Robert" should read "Roberts" Column 4, line 58, the word "atom" should be inserted prior to the word "aliphatic" Column 9, line 7, the word "differentail" should be "differential" Column 10, line 30, the word "form" should read "from" Column 10, line 51, the word "difierential" should read "differential" Column 12, line 9, "arounnd" should read "around" Signed and sealed this 4th day of April 1972 (SEAL) Attest:

EDWARD M.FLETCHER,JR ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents