US2572936A - Process for making crimped artificial filaments - Google Patents

Description

Oct. 30, 1951 MVP. KULP ET AL k PROCESS FOR MAKING CRIMPED ARTIFICIAL FILAMENTS Filed Feb. 27, 1947 INVENTOR. MAL RICE 1. KULP WAYNE A. SlSSON Patentcd Oct. 30, 1951 PROCESS FOR MAKING CRIM'PED ARTIFICIAL FILAMENTS Maurice P. Kulp, Linwood, Pa., and Wayne A. Sisson, Silverside Heights, Del., assignors to American Viscose Corporation, Wilmington, Del., a corporation of Delaware Application February 27, 1947, Serial No. 731,374

6 Claims.

This invention relates to the production of artificial filaments and fibers having a pronounced wool-like crimp or curl.

It is the object of the present invention to provide an improved process for producing regenerated cellulose fibers or filaments which are reversibly convertible between a straight condition and a crimped condition, which process is particularly efiective when operating at spinning speeds ranging from the conventional spinning speeds of 30 to 90 meters per minute all the way up to 150 to 200 meters per minute. It is particularly an object of the invention to provide a process of spinning such reversibly crimpable filaments or fibers adapted to continuous production at high spinning speeds.

In the drawing, which is illustrative of the invention,

Figure 1 is a side view of a fiber, greatly enlarged, made by the process of the present invention, and

Figure 2 is an end view of a group of fibers according to the invention, after cutting and dyeing to show up the skin in the manner described hereinbelow.

In accordance with the present invention, crimped filaments of special structure are produced by spinning a viscose having a high content of cellulose, of caustic soda, and of carbon disfulfide into a specially correlated spinning bath under conditions hereinafter described if the filaments are sufiiciently small in diameter, being not larger than ten denier per filament. This can be accomplished by extruding the viscose into an aqueous acid coagulating and regenerating bath which has, because of a high total salt content, a rapid dehydrating effect upon the extruded xanthate filaments and sets up thereon an at least partially regenerated skin of substantial thickness about a still substantially liquid or exceedingly soft and plastic core. This skin is set up rapidly and, having a strong tendency to shrink as the result of the dehydrating action of the coagulating bath, it apparently expends its circumferential shrinkage component, which is prevented by the incompressible core from exerting a mere reduction in diameter of the filaments, by splitting or rupturing longitudinally at numerous places along, or sometimes throughout the length of, the filaments and then compressing the core, thereby causing part of the core to flow through the rupture, in which state the filaments are finally set up. The portion of the resulting filaments that is forced out of the core responds to the subsequent stretching (which is preferably high to obtain the greatest crimpiness) differently than the remainder of the filaments, and because of the eccentric disposition of the two portions relative to the cross-section of the filament, a high degree of crimpiness is obtained.

The cross-section at many points along the filaments and in some cases throughout the length thereof, as shown in the drawing, exhibit a structure in which one portion A has a thick skin showing a break along the juncture with the other portion B which has a thin skin or none at all. As is shown in Figure 1 in that part of the length of the crimped filaments which have the peculiar structure just noted, the portion A hav ing the thick skin generally takes the inside 0! the bends of the crimp, because of a stronger tendency to shrink. The only exception to this generally occurs when the filaments are produced under relatively low or negligible tension, in which event, the thick-skinned portion frequently takes the outside position at the bends in the crimp. The skin apparently is composed of slenderer micelles which are more highly oriented than those of the body or core of the filament. It may be difierentially dyed by the following procedure: A microtome section of one or more of the filaments mounted in a wax block is taken and mounted on a slide with Meyer's albumin fixative. After dewaxing in xylene, the sect-ion is placed in successive baths of and 30% alcohol for a few moments each, and it is then stained in 2% aqueous solution 01 Victoria Blue BS conc. (General Dyestuffs Corp.) for 1 to 2 hours. At this point, the entire section is blue. By rinsing the section first in distilled water and then in one or more baths composed of 10% water and dioxane for a period varying from 5 to 30 minutes depending on the particular filament, the dye is entirely removed from the core, leaving it restricted to the skin areas.

In accordance with the present invention, viscoses having a content of 9 to 10% cellulose and 9 to 10% caustic soda and a correspondingly high content of carbon disulfide, viz. 29 to 45% CS2 (preferably 38 to 42%) based on the alphacellulose content of the pulp are ripened to a salt test of about 3 to 6 (preferably 4 to 5). The ball fall viscosity of the resulting viscoses may be between 20 and depending upon the particular source of cellulose (wood, cotton or other) and the particular procedure of making the viscose. Depending upon the efiiciency of the particular equipment used for blending and ageing, it may be desirable'to reduce the viscosity of certain of the viscoses that would otherwise normally have a viscosity above 80 (ball fall) by increasing the alkali cellulose ageing time.

The acid bath must have a regenerating capacity equivalent to that of 9 to 14% of sulfuric acid mixed with a small proportion of a zinc salt and a large proportion of sodium sulfate to fulfill the requirements of the present invention. The zinc salt may be zinc sulfate, the coagulating bath containing at least about 20.5% but not more than about 3% thereof. higher proportion has the advantage of increasing the thickness of skin initially formed, which in turn causes an increase in the differential shrinkage between the two portions of the filaments and results in greater crimpiness. However, it has the disadvantage of increasing the toughness of the skin and making more critical the spinning conditions which will cause rupture to occur consistently. For most purposes it has been found that the most favorable proportion of zinc sulfate is about 1 to 1.5%. The higher proportions between 1.5 to 3% zinc sulfate may be used with entire satisfaction when the higher range of sulfuric acid between and 14% is used, the swelling tendency of the acid on the filaments compensating for the tendency of the zinc sulfate to form a tough skin.

To assure that the bath exerts a strong dehydration on the filaments, a, high proportion of salts, such as sodium sulfate or potassium sulfate between about 15 to should be used.

As a general rule it has been found that the optimum results are obtained for any given viscose by spinning into coagulating baths having from about 9 to about 10% sulfuric acid, about 1 to 1.5% zinc sulfate, and about 19 to 22% sodium sulfate.

The coagulating baths should have a temperature between C. and 60 C., preferably to C. The immersion depends on the speed of spinning, and by way of illustration may be between 10 and 90 inches. The immersion should preferably be sufiicient to substantially completely coagulate the filaments before stretching is performed thereon, so that the maximum difierential in shrinkage is obtained, the longer immersions resulting in more extensive crimping. Preferably the draw-oif speed of the filaments from the spinneret is greater than the velocity of extrusion.

The size of the finished filaments after stretching must be not larger than 10 deniers per filament and preferably is between one and six deniers per filament. For a given set of conditions, the smaller the denier, the greater the crimp. Above about 10 deniers per filament, the crimping is negligible, although the longitudinal rupturing appears to take place.

The longitudinally ruptured filaments are preferably stretched by at least about 40% (as measured by differential in godet speeds) or its equivalent obtained by tension guides, either of a rotary or a stationary type, and the stretching must be followed by relaxation in order to obtain effective crimping. The stage of filament production at which the stretching is effected is not critical, though the most satisfactory results are obtained where the stretching is performed shortly after coagulation while the filaments are still in plastic condition. For example, the filaments after leaving the coagulating bath may proceed in succession about two or more godets, each of which has a greater peripheral speed than that preceding it. The filaments may then proceed through the conventional wet-processing, drying The use of theand collecting stages. As they proceed through these stages, they may be manipulated so as to be substantially free of tension, in which event the finished filaments obtained are inherently 5 crimpy. They may, however, proceed through the treatment stages under tension, in which event the final filaments are substantially free of crimp. However, in this latter case they may be readily crimped at any time before or after shipment merely by plasticizing them, such as by wetting them with cold or hot water, relaxing them while still wet, and drying them while substantially free of tension. If desired, this wetting or plasticizing may be preceded or accompanied by further stretching.

The actual spinning of the filaments may not involve any stretching, such as between godets, in which event the relatively uncrimped filaments collected may be stretched at any subsequent period before or after shipment and then relaxed. Such stretching may be followed by or accompanied by plasticization. After stretching, the filaments are relaxed in plasticized condition and dried in relaxed condition to produce the crimped condition.

The stretching may be performed upon the filaments at any stage of the wet-processing, but the maximum crimping is obtained by applying the stretch shortly after the filaments leave the coagulating medium. At this stage, any degree of stretching may be applied up to the rupture of the filaments, the higher the stretch applied, the greater the crimpiness obtained, thus providing a means of ready control of the crimp. Stretches of 50 to 80% or more yield excellent crimps. Where necessary the stretching may be facilitated by passage of the filaments through a plasticizing bath, such as of hot water, hot acids, and the like.

The procedure may advantageously be applied to the production of staple fiber as well as continuous or broken filament yarns. An illustrative embodiment of its adaptation to staple fiber production is as follows: The filament bundles proceeding from several spinnerets over stretching godets are combined into large bundles of 1200 up to 400,000 deniers. The large bundles while still wet are cut to staple fiber, which is allowed to fall into a liquid bath which may serve mere- 50 ly to effect opening of the fiber clumps and relax the fibers therein, or may also serve the purpose of an additional liquid treatment, such as washing or desulfurizing.

For illustrative purposes, the following specific examples are described:

Example 1 A wood pulp viscose having 9% by weight sodium hydroxide, 10% by weight cellulose, 35%

carbon disulfide (CS2 based on weight of alphacellulose), and a common salt test of 5.3 was spun through a 500 hole spinneret having 2.5 mil holes into a spinning bath at 45 C. containing 9% H2SO4, 1.1% ZnSOl, and 16% NaaSQr. The speed through the bath was about 20 meters per minute and the immersion was 19 inches. After leaving the bath, the filaments passed over two godets in succession having a differential in speed which effected a stretch of the filaments. During this stretching, the filaments were treated with hot water. The filaments were then allowed to fall limply into a receptacle, so that collection was effected with little or no tension. After wet treating and drying without tension, the filaments of 5. two denier per filament size averaged 23 crimps per inch.

Example 2 V A cotton pulp viscose otherwise of the constitution of Example 1 but having a common salt point Example 3 A high alpha-cellulose and wood pulp was converted into a viscose having 10% by weight cellulose, 10% sodium hydroxide, and 33% carbon disulflde (CS: based on weight of alpha-cellulose) and after ageing to a commonsalt point of 4, was spun unto a spinning bath at 50 containing 10% sulfuric acid, 1% zinc sulfate, and 20% sodium sulfate. The speed through the bath was 80 meters per minute andthe immersion was 24 inches. The filaments assembled in the form of a tow were given a 65% godet stretch, during which they were plasticized with hot water. Shortly after stretching and before any substantial drying of 'the filaments, they were cut to staple fiber which were immediately allowed to fall into a water bath for wet opening. .After processing in conventional manner, the fibers were dried without tension. The resulting fibers had a size of 3 denier per filament and averaged about 12 crimps per inch.

Example 4 A wood pulp viscose of the constitution of Example 3, except that the carbon disulfide was about 43%, was'spun at an age of about 5% common salt point into a spinning bath 'at 45 C. containing 14% sulfuric acid, 1.5% zinc sulfate, and 20% sodium sulfate. After leaving the bath, the filaments were given a 62% godet stretch. After wet processing, the filaments were dried in a relaxed condition to give a product having a size of 3 denier per filament and averaging 8 crimps per inch.

Example 5 A cotton pulp viscose having the constitution of that of Example 1 (except that the carbon disulfide was 43%)was spun, after aging to a common salt point of about 4 /2, into a bath at 45 C.

containing 9% sulfuric acid, 0.5% zinc sulfate, and 24% sodium sulfate. The filaments, after leaving the bath, were given a godet stretch of 60%. After wet processing, the filaments were dried in relaxed condition. The product had a size of 3 denier per filament and averaged 13 crimps per inch.

Example 6 crimps per inch. The filaments had a tensile strength of 2.11 grams per denier wet, and had extensibilities of 15.9% dry and 16.3% wet.

Example 7 The procedure of Example 6 was followed, except that no godet stretch was applied, andthe filaments were dried under slight tension, so that no crimp was obtained in the product. Subsequently the filaments were soaked with cold water, stretched 45%, allowed to relax and dried in relaxed condition. The resulting product exhibited an average of 10 crimps per inch.

Example 8 A wood pulp viscose having 10% by weight of sodium hydroxide, 9% cellulose, 33% carbon disulfide (CS: based on alpha-cellulose) and aged to a common salt point of 3.5 was spun into a bath at 45 0., containing 11% sulfuric acid, 1% zinc sulfate, and 20% sodium sulfate. An immersion of 24 inches in the bath and a speed therethrough of meters per minute were used. After leaving the bath, the filaments were plasticized with hot water and given a godet stretch of 65%. Shortly after stretching and before any substantial drying of the filaments, they were cut to staple fibers, which were immediately wet opened and processed in conventional manner, until finally dried without tension. The resulting fibers had a size of 2 denier per filament, and averaged 10 crimps per inch.

Example 9 A viscose of the constitution of Example 5 was spun into a bath at 45 0., containing 12% sulfuric acid, 2% zinc sulfate and 25% sodium sulfate. An immersion of 74 inches and a speed therethrough of meters .per minute were employed. After leaving the bath, the filaments were given a 60% godet stretch. After-wet processing, the filaments were dried in relaxed condition. The resulting product had a size of 2 /2 denier per filament, and averaged 11 crimps per inch.

The resulting filaments which have dry tensile strengths up to about 2% to 2 /2 or more grams per denier, wet tensiles up to about 1 to 1% or more grams per denier and dry extensibilities down to as low as about 15%, may have from about 5 up to 30 or more crimps per inch.

The individual filaments produced in accordance with this invention have a structure having a cross-section at numerous, or sometimes at all, points of the filament length which comprises two more or less distinct component areas side by side, each of which appears to have a diilerent cbmposition or state of physical aggregation than that of the other. The distinct areas exhibit therein differences in shrinkage, swelling, extensibilities, strength, orientations, dye absorptions, chemical reactivity, crenulation, and they show different skin thicknesses which is readily observable as a differential dye absorption phenomenon when they arestained with certain dyes, such as by the procedure described hereinabove.

The crimped filament takes the form of a regular or irregular helical coil which may reverse itself in direction at more or less frequent intervals of regular or irregular occurrence, the eccentric components of the filament having different skin-thickness following a random helical path about the longitudinal axis of the filament, which path may reverse itself at more or less frequent irregular or regular intervals. Thus, the crimps I of the filament are disposed out of phase and at random in three dimensions.-

The individual filaments produced in accordance with this invention, in their state of normalcy are characterized by a. stabilized condition having an inherent distortion which imparts a permanently recoverable crimp. The only condltion under which it loses its crimp (and in this case the loss is temporary) is that prevailing when the crimped filament is wetted and caused to dry while under tension. It can be repeatedly wet and dried without an appreciable loss in crimpiness, as long as it is permitted to dry in a relaxed condition. If dried under tension the crimp can be recovered merely by wetting and drying while relaxed.

No completely satisfactory, tests have been devised to evaluate the degree of permanency of a crimp. However, the crimped filaments of this invention have been found to possess a crimp 'retentivi ranging from about 60% up to a value approaching 100% when tested in accordance with the procedure outlined in the Hardy et al. Patent 2,287,099. when subjected to that test, not merely after a single immersion but after as many as 20 or more immersions have been found to show crimp retentivities as high as substantially 100%, and relatively few of the filaments made in accordance with this invention have been found to have crimp retentivities as low as 60%. The crimp retentivity test as outlined in Patent 2,287,099 is performed in water at 60 C. It has been found that for the filaments of this invention, crimp retentivity is fully as high when cold or boiling water is used in the test. Thus, the filaments of the present invention show up just as well (that is, from about 60 to 100%), when measured by the crimp recovery from stretc test outlined in the above mentioned Patent 2,287,099, as they ;do when they are evaluated by the crimp retentivity test.

The filaments and staple fibers of the present invention do not appreciably lose their crimp during the ordinary conditions of wear, in either of which temperatures ranging from the neighborhood of the freezing point and the boiling point of water are encountered. Fabricated products made from these filaments and fibers thus have properties which may be made to approach those of natural wool in some respects.

The crimped filaments and fibers of this invention show improved carding and improved spinning quality, increased bulk resilience, and a fabric appearance and feel that approaches that of wool.

The filaments or fibers in straight or crimped condition, may be formed into yarns and thread of all types, and are particularly advantageous for spinning on the woolen system. The yarns or threads may then be woven, knitted, knotted or braided into fabrics. The filaments in such yarns may be rendered crimpy before or after conversion of the yarn into fabrics. Particularly advantageous results are obtained by spinning the fibers in a crimpy condition to improve their coherence during the drafting stages. In many cases, the draftingreduces the crimp because of the high tensions applied. This is favorable to the subsequent fabrication in which a compact condition of the yarns is generally desirable. The yarns in the resulting fabric can then be rendered bulky by soaking in an aqueous medium, preferably hot, while allowing the yarns therein to relax, and subsequently drying in relaxed condi- Individual filaments 8 tion. The more open and loose the mesh of the fabric, the more bulky the fabric becomes. The aqueous medium may be any that are ordinarily used in finishing the fabric, such as rinsing, dyeing, bleaching, softening, soaping, or the like.

The utilization of the special high cellulose content viscose of the present invention makes it possible to spin filaments or fibers having ex-- cellent crimp at extremely high spinning speeds. As compared with prior processes, all of which depend on viscoses having relatively low contents of caustic and cellulose, the present process has an additional advantage in that the viscose-making equipment is used far more efficiently. There is consequently a large saving in the cost of the viscose produced.

It is to be understood thatchanges and variations may be made without departing from the spirit and scope of the invention as defined by the appended claims.

We claim? 1. A process for the production of filaments of not more than denier per filament comprising extruding a viscose containing between 9 and 10% of cellulose, between. 9 and 10% sodium hydroxide and having a sodium chloride salt test of 3 to 6 into a coagulating bath consisting of water, between 9 and 14% sulfuric acid, between 0.5 and 3% zinc sulfate, and between and sodium sulfate, stretching the filaments, relaxing the filaments in a wet condition, and drying them in a relaxed state.

2. A process for the production of filaments of not over 10 denier per filament comprising extruding a viscose containing between 9 and 10% cellulose, between 9 and 10% sodium hydroxide and having a sodium chloride salt test of 3 to 6 into a coagulating bath consisting of water, between 9 and 14% sulfuric acid and between 0.5 and 3% zinc sulfate, and between 15 and 25% sodium sulfate, continuing to pass the filaments through the coagulating bath to effect substantially complete coagulation thereof, subsequently stretching the filaments at least 40%, wetting them, relaxing them while in a wet condition, and drying them in relaxed condition.

3. A process for the production of filaments of not over 10 denier per filament comprising extruding a viscose containing between 9 and 10% cellulose, between 9 and 10% sodium hydroxide and having a sodium chloride salt test of 3 to 6 into a coagulating bath consisting of water, between 9 and 10% sulfuric acid, between 1 and 1 zinc sulfate, and between 15 and 25% sodium sulfate, continuing to pass the filaments through the coagulating bath to effect substantially complete coagulation thereof, shortly thereafter stretching the filaments at least 40%, relaxing them, and-subsequently drying them while in relaxed condition. a

4. A process for the production of filaments of not over 6 denier per filament comprisin extruding a viscose containing between 9 and 10% cellulose, between 9 and 10% sodium hy- 35 droxide and having a. sodium chloride salt test of 4 to 5 into a coagulating bath consisting of water, between 9 and 10% sulfuric acid, between 1 and 1.5% zinc sulfate, and between about 19 and 22% sodium sulfate, continuing to pass the 5. A process for the production of filaments filaments through the coagulating bath to effect,

prising extruding aviscoae containing a small amount of a viscodty reducing agent, between 9 and'10% cellulose. between 9 and 10% sodium hydroxide and having a sodium chloride salt test of 3rto 6 into a coagulating bath consisting of water, between 9 and 14% sulfuric cid, between 0.5 and 2% zine sulfate, and between 15 and 25% sodium sulfate, stretching the lilaments, relaxing the filaments in a.wet condi tion, and drying them in a relaxed state.

6. A process for the production of filaments of not over 6 denier 'per filament comprising extruding a viscose containing between 9 and 10% cellulose. between"9 and 10% sodium hyiii-oxide, between 38 and 45% carbon dtsuliide based on the weight of alpha-cellulose, and havingwa sodium chloride salt test one to 5 into. a

coagulating bath. consisting of water, between 9 and 10% sulfuricacid; between 1 and 1.5% zinc sulfate, and between about 19 and 22% sodium sulfate, continuing to bass the filaments through the coagulating bath to effect nibstantially complete coagulation thereof, shortly thereafter 10 stretching tbe fllaments at least 40%. relaxing them,.and subsequently drying them while in relaxed condition.

. MAURICE P. KULP; WAYNE A. SISSON.

REFERENCES CITED The following references are of record in the- Number Name Date 1,931,239 Picard Oct. 17, 1933 2,267,055 Tippetts Dec. 23, 1941 2,315,560 Btoeckly etal. Apr. 6, 1943 2,340,377 Graumann et ai. Feb. 1, 1944 2,360,273: 00: Dec. 5, 1944. 2,491,938 Schimer et al. Dec. 20, 1949 FOREIGN PATENTS Number Country Date 492,279 Germany Feb. 8. 1930 Certificate of Correction Patent No. 2,572,936

October 30, 1951 MAURICE P. KULP ET AL.

It is hereby certified that error appears in the above numbered patent requiring correction as follows:

Column 3, line 9, for 20.5% read 0.5%

and that the said Letters Patent should be read as corrected above, so that the same may conform to the record 0 f the case in the Patent Oflice. Signed and sealed this 19th day of February, A. D. 1952.

printed specification of the THOMAS F. MURPHY,

Assistant Commissioner of Patenta.

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