US2515834A

US2515834A - Cellulose filaments and method of producing same

Info

Publication number: US2515834A
Application number: US465414A
Authority: US
Inventors: William D Nicoll
Original assignee: EI Du Pont de Nemours and Co
Current assignee: EIDP Inc
Priority date: 1942-11-13
Filing date: 1942-11-13
Publication date: 1950-07-18
Anticipated expiration: 1967-07-18

Description

W. D. NICOLL July 18, 1950 CELLULOSE FILAMENTS AND METHOD OF PRODUCING SAME Filed Nov. 13, 1942 2 Sheets-Sheet 1 Vlilliam DJVicoll 3mm y 1950 w. D. NICOLL 2,515,834

CELLULOSE FILAMENTS AND METHOD OF PRODUCING SAME Filed Nov. 13, 1942 2 Sheets-Sheet 2 Gil JWfLL/IYG 54670,? m w k 0. s Q1 0 I l I I l l [III II 123466768101/12/6/4 34/91 50 w co/zoumr/zvo 54m mlliamfllvicollgmmm Patented July 18, 1950 UNITED STATES PATENT OFFICE CELLULOSE FILAMENTS AND METHOD OF PRODUCING SAME Application November 13, 1942, Serial No. 465,414

43 Claims.

This invention relates to the production of new and unique crimped, wool-like, regenerated cellulose filaments and fibers, and a new and improved process for obtaining such products.

This application is a continuation-in-part of my copending applications Serial No. 318,326 and Serial No. 318,327 filed February 10, 1940, both now abandoned.

crimp, after being removed mechanica lly for example by stretching, combing or 'the like, may b'fETiltSs an completely resto d by susp'ri'tling the same, f .119 l e It is another object of the present invention to provide a new and improved process for the spinning of regenerated cellulose filaments and fibers from viscose solutions and subjecting said filaments and fibers to a relaxing treatment whereby to impart an intense crimp to said filaments and fibers, which process comprises the substantially complete regeneration of the filaments or fibers prior to the relaxing treatment thereof.

Other objects of the invention will appear here inafter.

It is well known that the viscose process for spinning regenerated cellulose filaments is a highly critical process. comparatively slight variations in the composition of the viscose or in the composition of the spinning bath will prevent satisfactory spinning. This is clearly evidenced by the fact that in commercially useful processes, the art has found it imperative to stay within narrow limits with respect to the cellulose and alkali contents of the viscose and the constituents of the spinning bath.

One of the most important considerations in the critical balance between viscose composition and the composition of the spinning bath is what will here be called the gel swelling factor. To constitute a commercially useful viscose rayon process, the viscose composition and the sulfuric acid coagulating bath composition employed must be so balanced as to permit the production of regenerated cellulose filaments having a gel swelling factor of 6.5 or less and in most instances actual commercial spinning processes will employ conditions which yield filaments exhibiting a gel 2 swelling factor which is less than 6.5. The gel swelling factor of regenerated cellulose filaments is determined in the following manner:

A viscose of known composition is extruded through a spinneret into a sulfuric acid coagulating bath of known composition. The coagulated' filaments, after leaving the bath, are wound in a single layer on to a bobbin with a helical wind of narrow pitch in such a manner that successive windings are very closely spaced. When the bobbin contains 2 to 6 grams of wet gel yarn, the bobbin is removed and rotated on a chuck to centrifuge off the bath carried with the filaments on to the bobbin. The acid-wet gel yarn is then cut from the bobbin and weighed. The whole operation should be carried outwithin four minutes. The acid-wet gel yarn is washed and then dried to remove all the water therefrom and the dry yarn reweighed. The ratio of the weight of acid-wet gel yarn to the weight of the dry yarn is termed its gel swelling factor.

It is possible for this gel swelling factor to range from about 3 to about 12, depending upon the composition of the viscose and of the coagulating bath. For a given viscose composition, a high concentration of sulfuric acid in the coagulating bath will result in the production of a regenerated cellulose having a high gel swelling factor. If the acidity is gradually decreased (with the composition of the viscose and coagulating bath otherwise remaining the same) the gel swelling factor falls to a minimum and then rises again with a further decrease in the acidity. The gel swelling factor at the minimum will be termed the minimum gel swelling factor, and the acidity at this point will be termed the minimum gel swelling factor acidity.

Heretofore the art has arrived at spinning conditions by empirical, trial and error methods. It is now recognized that the minimum gel swelling factor and the minimum gel swelling factor acidity actually play important roles in defining spinning condition. Thus, for example, for a given viscose, yarn properties such as tenacity, elongation, softness, etc., are, as a rule, best when spinning is done at or near the point of minimum gel swelling. In accordance with the present invention, in order to produce high strength, unique, intensely crimped regenerated cellulose filaments departure must be made from conventional spinning conditions. The definition and establishment of the new conditions required for the practice of this invention constitutes essential elements in the provision of a new spinning process and the products resulting therefrom.

Viscose-sulfuric acid-salt systems in which the minimum gel swelling factor of the regenerated cellulose filaments obtainable therefrom is less than 6.5 will hereinafter be referred to as balanced viscose-sulfuric acid-salt spinning bath systems.

It has now been discovered that high strength, unique, intensely crimped regenerated cellulose filaments can be produced by observing the following highly critical combination of conditions: Spinning filaments in a balanced viscose-sulfuric acid-salt spinning bath system in which the spinning bath contains zinc sulfate and the sulfuric acid content of the bath is in accord with the formula:

K(C.N) 100 wherein A is the percentage content by weight of sulfuric acid in the spinning bath,

K is a factor which may have any value from 1.9

C is the percentage content by weight of cellulose in the viscose,

N is the percentage content by weight of caustic alkali (calculated as sodium hydroxide) in the viscose,

a: is the percentage content by weight of sulfuric acid in the coagulating bath which will produce a regenerated cellulose filament having the minimum gel swelling factor with the viscose specified by C and N;

imposing on said filament during the spinning thereof a tension of at least 0.5 gram per denier and a stretch of at least 40%; and, after substantially complete regeneration of said filaments, relaxing the same completely free of all tension in a liquid which will swell the same. [By stretch of at least 40% is meant a stretch (as measured between the point where the spun filaments are first converged in the bath, and collecting device) of at least 40% based on its unstretched length.] For practical purposes, it is generally desirable that the coagulating bath have a temperature of between 40 C. and 75 C. and preferably that the zinc sulfate content of the bath be from 0.1% to 3%.

The present invention may be more readily understood by reference to the following detailed description when taken in connection with the accompanying illustrations, in which:

Figure 1 is a diagrammatic side elevational view, with parts shown in perspective, of one embodiment of apparatus suitable for use in accordance with the invention;

Figure 2 is a similar diagrammatic view showing another embodiment of apparatus for use in accordance with the invention;

Figure 3 is a typical gel swelling factor curve.

Referring to Figure 1 of the drawings, reference numeral ll designates a conduit line for a viscose filament-forming composition which is connected to any suitable source of supply, the conduit II is connected to a candle filter I2 and the candle filter I2 is connected to a spinneret M by means of gooseneck l3. The viscose solution is extruded through the spinneret M to form filaments l5. A bundle of filaments is passed over the fixed convergence guide l6, and thence about roller guides l1 and take-off guide l8. From guide IS, the yarn is passed about feedwheel 19 which feeds the yarn through two vertically spaced sleeve guides 2| and 23. If desired, a liquid may be passed through the two sleeve guides,

thereby to continuously force the yarn through said guides. A rotatable cutter knife 25 may be positioned rotatably between the two sleeve guides 2| and 23, thereby cutting the yarn into small staple lengths. The cutter knife is mounted on a stub shaft 21 and is adapted to be rotated by means of a driven belt, as shown. The staple fibers 28 drop into a relaxing fluid 29 where they are completely free from all tension and will be quickly crimped along the length thereof.

Referring to Figure 2 of the drawings, the yarn I5 composed of freshly spun filaments is passed from the spinneret [4 about fixed convergence guide l6, then through a long bath tank I! to a take-off guide I8. The yarn is then passed about draw-off rollers 30 and 32 which are of sufficient size to provide a surface area of sufficient extent to eliminate any material slippage of the yarn. The yarn is then passed from draw-off roller 32 about guide roller 33 and then about stretching rollers 35 and 31. The yarn passes about rollers 35 and 31 a number of times to eliminate any possibility of slippage of the yarn. Between drawoif roller 32 and guide roller 33, the yarn is subjected to treatment with a stretching bath 42, passed on to the yarn by means of conduit 40. The stretching bath will be described with particularity hereinafter. The draw-off rollers and stretching rollers are positively driven to impart a portion of the tension and stretch on the yarn between the guide l6 and the roller 30, and a portion between the roller 30 and the roller 35.

The apparatus shown in Figure 2 is particularly useful in such instances where the requisite tension and stretch cannot be imposed on the filaments solely in their travel through the spinning bath. It has been found that when such filaments are passed into contact with a stretching bath, the requisite tension and stretch can be imposed on the yarn during the spinning thereof.

Figure 3 of the drawings discloses a typical gel swelling factor curve for a viscose of a given composition. From this curve, it will be noted that when the acidity of the bath in per cent by weight of sulfuric acid is 12%, the gel swelling factor of the yarn will be slightly under 9.0. When the acidity of the bath is reduced to 11%, the gel swelling factor lies between 5.0 and 6.0. When the acidity is further reduced to 10%, the gel swelling factor drops between 3.0 and 4.0. With an acidity between 8% and 9%, the gel swelling factor has dropped to a minimum value of 3.0. Further reduction in the acidity of the coagulation bath will cause the gel swelling factor of the yarn to rise again in accordance with the contour of the curve shown in the drawing.

In its broad scope the process of the present invention is operative and. useful with any balanced viscose-sulfuric acid-salt spinning bath system. A number of specific, detailed processes have been operated to good effect.

By way of illustration there will now be discussed three subgeneric embodiments of the broad concept which describe conditions particularly applicable when filaments are to be spun from the more common commercial viscose compositions. The first one has reference to the spinnin of viscose having an alkali content of at least 5%, with or without the use of a secondary stretching bath. The second is concerned with systems using viscose of less than 5% alkali content in which a secondary stretching bath is used followin the initial, substantially complete, coagulation and regeneration in a primary sulfuric acid-salt bath. The third is concerned also with the use of viscose having less than 5% alkali, and

spun in a single coagulating and regenerating regenerated cellulose filaments may be obtained by observing the following relationship factors:

1. The viscose composition must have a salt index (as determined by Reinthaler-Rowe, Artificial Silk, 1928, page 69) of between 1.5 and 6.

. The coagulating and regenerating bath must have a sulfuric acid content of between 6.5% and 9.5%,

. The coagulating and regenerating bath must have a sodium sulfate content of between 15% and 30%.

. The coagulating and regenerating bath must have a zinc sulfate content of between 0.1% and 3%.

. The filaments must travel at least 50 inches in the coagulating and regenerating bath.

. The temperature of the coagulating and regenerating bath must be between 40 C. and 75 C.

. The temperature of the relaxing bath must be between 20 C. and 120 C.

. Imposing on the filaments, during the spinning thereof, a tension of at least 0.5 gram per denier and a stretch of at least 40%, and after substantially complete regeneration of the fil aments, relaxin the same completely free of all tension in a liquid which will swell the same.

In addition to the above-mentioned ingredients of the coagulating bath, it is permissible to have present as much as 6% or 7% glucose or similar organic substances well known in the art. The presence of glucose in the spinning bath is not an essential feature of this process, but may be desirable, particularly when continuous filament yarn is produced. As a guide to the proportion of glucose used, it may be said that 2% of glucose can replace approximately 1% of sodium sulfate.

In accordance with the above detailed process the specifically enumerated factors are all interdependent and must be adjusted in relation to one another in order to obtain the desired result, i. e., a satisfactory crimp.

It is, of course, understood that relaxing of the filaments in an aqueous medium completely free of all tension is absolutely essential, no matter what variations may be introduced in "the other conditions. It is also essential that the tension on the filaments during the spinning (including stretching) be at least 0.5 gram per denier, and that a stretch of at least 40% be placed on the filaments. For each of the factors enumerated above, the range within which the process may be successfully operated has been indi-.

cated but it will be apparent at once, to one skilled in the art, that, if any one of the factors is set at or near the extreme lower or upper limit to restore the balance of the conditions; i. e.,

in the case illustrated, neither the sodium sulfate nor the zinc sulfate contents of the coagulating bath can be the lowest permissible but are preferably increased to, for example, 19% and 2.5% respectively, and likewise the bath temperature should be raised to about 55 C.

For all the important variables, the range within which the process is operable has been indicated above. In view of the present detailed disclosure anyone skilled in the art will readily be able to adjust the conditions in relationship to one another so as to obtain excellent results.

For the purpose of making this process more readily understandable, the following table will be useful to show both the operable ranges and the median ranges. The median ranges comprise those range within which any one factor can be varied at will without necessitating a change in the other factors.

Operable Range Median Range Spinning tension Over0.5g. p. d Temperature of coagulating 4075 Over 0.5 g. p. d. 5060 C.

a Temperature of relaxing bath 20l20 C 60100 C.

Although no definite rules can be given for making all necessary adjustments permitting one to use conditions outside the median ranges but still within the operable range, it can be said, in general, that except for the alkali content of the viscose, the selection of one relationship factor outside the median range requires that all other factors be within this range. In the case of a change in the alkali content of the viscose, I have found that the most important other variable requiring adjustment is the acid content of the coagulating and regenerating bath. This can be done readily by using the general formula discussed above. rule that, over the operable range shown, a 1% increase in alkali content of the viscose is approximately compensated for by a l increase in the acid content of the coagulating and regenerating bath.

As above stated, it is essential in accordance with this invention that a tension of at least 0.5 gram per denier and a stretch of at least 40% be. imposed on the filament during the spinning thereof. The tension and stretch imposed on the filaments may, of course, greatly exceed that above specified. Any tension or stretch under that which will break the filaments may be used in accordance with the present invention. This tension and stretch must be imposed on the filaments during the coagulation and regeneration thereof when operating without a stretching bath as shown diagrammatically in Figure 1 of the drawings. In some instances, however, it may be impossible to impose that amount of stretch and tension without the use of a stretching bath. Under such circumstances, an arrangement as shown in Figure 2 of the drawings may be used. In the latter case, the requisite stretch and tension are partially imposed on the filaments during their passage through the coagulation and regeneration both and partially imposed thereon during their passage through the stretching bath.

I have found as an empirical The path of the filaments through the coagulating and regenerating bath liquor must be sufficiently long to substantially complete the regeneration thereof while in said bath. However, if the stretching bath is capable of regeneration due to heat or content of acid, the regeneration of the filaments may be completed in this bath. For the purposes of the present specification and claims the spinning of the filaments shall include the passage of the filaments through the stretching bath if a stretching bath is employed.

When a stretching bath is used in accordance with the present invention, it must follow the coagulating bath and the yarn must be passed through the same with a continuation of tension and stretching begun in the coagulating bath. The degree to which the filaments are stretched or tensioned in the coagulating bath may be approximately the same as the degree to which they are stretched or tensioned in the stretching bath. Under some circumstances, it may be desirable to stretch and tension the filaments to a greater degree in the coagulating bath than in the stretching bath. Under other circumstances, it may be desirable to impose a greater degree of stretch and tension on the filaments in the stretching bath than in the coagulating bath. The stretching bath should preferably have a temperature of between about 50 C. and the boiling point thereof. The stretching bath should be composed of a non-alkaline, aqueous liquid preferably containing not to exceed that acidity equivalent to 3% sulfuric acid. This bath is preferably composed of water.

The relaxing bath may be composed of any liquid which is capable of swelling the cellulose filaments. Since the filaments will be substantially regenerated by the time they are subjected to relaxation in the relaxing bath, the latter will have substantially no regenerating action on the filaments. The relaxing bath preferably comprises water and it may be acidic, neutral, or alkaline. The relaxing bath may contain an acid or a salt such as calcium chloride, sodium thiocyanate, calcium thiocyanate or the like. Such salts will often impart a particularly desired swelling action to the filaments whereby crimping takes place in a particularly desirable manner. Such relaxing baths may also contain purification agents such as sodium carbonate, caustic soda and the like, which may, similarly to the above-mentioned salts, also have a desirable swelling action on the filaments. A particularly desirable relaxing bath comprises 3.5% aqueous solution of caustic soda. The temperature of the relaxing bath may vary widely as this is not critical. Particularly good results, however, are obtained with a 3.5% caustic soda relaxing bath having a temperature of about 35 C. The relaxing bath may comprise or consist of organic liquids such as glycerol if the latter is used at a temperature of the order of 120 C., at which temperature glycerol is found to. swell regenerated cellulose filaments. Regenerated cellulose fila-, ments may be relaxed in a bath consisting of anhydrous liquid ammonia since the latter is capable of swelling cellulose. Whatever the composition and temperature of the relaxing bath may be, the filaments must be allowed to rest in the relaxing bath free of all tension so that they may swell as completely as possible in the liquid medium. The greater the swelling action on the filaments during relaxation, the more desirable the relaxing bath. The filaments may be passed directly to the relaxing bath from the stretching bath in the form of continuous filaments or staple fibers. Alternatively, the filaments passing from the stretching bath may be collected in any desired manner, for example on a bobbin in accordance with the bobbin spinning process, in a bucket cake in accordance with the bucket spinning process. or loosely in a container therefor. The product may be washed acid free, desulfured and/or bleached prior to the time it is immersed in the relaxing bath or it may be relaxed while in the acid state and then washed, desulfured and/or bleached after crimping has been accomplished. If the product is crimped before the acid is removed, hot water must be used as a relaxing agent and such agents as 3.5% caustic cannot be used. However, if the acid is removed before crimping, then either hot water or a caustic relaxing bath may be used.

As above set forth, it is essential that the filaments be completely relaxed so that they are free to shrink to the maximum extent. Probably the best method of securing such complete relaxation is to immerse the skeins or staple in the relaxing bath, making sure that there is ample room for the fibers to crimp freely and shrink. If the filaments are not free from all tension, as for example, when they are allowed to relax only partially in a wash and bleach machine by hanging skeins on a rod under the weight of a large amount of liquid, the results are found to be unsatisfactory. This time of immersion of the filaments in the relaxing bath is not critical. Under the proper conditions of relaxation, the crimp will be formed in the fibers in the relaxing bath practically instantaneously. It was considered unexpected and surprising that yarns spun under the above described conditions would develop crimp on relaxing in a swelling medium after the yarn had been subjected to washing treatments and other purification treatments, and even after the yarn had been dried prior to relaxation.

This first embodiment of the invention is specifically illustrated in Examples I-XII inclusive.

In accordance with the second subgeneric embodiment of the invention, which applied more particularly to viscose containing from 3.5% to 5% alkali, the following conditions will produce an excellent grade of crimped fibers having unique characteristics described in detail later on:

1. The viscose solution must have a salt index (as determined by Reinthaler-Rowe, Artificial Silk, 1928, page 69) of between 1.5 and 6.

2. The coagulating and regenerating bath must have a sulfuric acid content of between 3.5% and 6.5%.

3. The coagulating and regenerating bath must have a sodium sulfate content of between 18% and 30%.

4. The coagulating and regenerating bath must have a zinc sulfate content of between 0.1%

and 2.5%.

5. The filaments must have a travel of at least 50 inches in the coagulating and regenerating bath.

6. There must be a total spinning tension on the filaments in the coagulating and regenerating bath and in the secondary stretching bath of at least 0.5 gram per denier and a total stretch of at least 40%.

'7. The temperature of the coagulating bath must be between 40 C. and 75 C.

8. The temperature of the secondary stretching bath must be between 50 C. and C.

9. The temperature of the relaxing bath must between C. and 120 C.

10. The relaxing bath is preferably a liquid having a stronger swelling action on the filaments than water, for example 1%-5% sodium hydroxide solution.

The use of a secondary stretching bath is essential in this second embodiment of the invention. What has been said of the stretching bath in connection with the first embodiment, where its use is optional, applies equally well here. The conditions of relaxation are also the same, except that in this case it is specially desirable that the stretching bath have a positive swelling action on the filaments. The relaxing bath is preferably a dilute (1%5%) solution of caustic alkali.

As in the case of viscose containing more than 5% alkali, the following table will be useful to show both the operable and median ranges in this second embodiment:

Operable Range Median Range Alkali content of viscose 3.5-5% 3.75-4.24%. Salt index of viscose 1.5-6 3.55.5. Acid content of spinning bath- 35-65% 3.75-4.5%. Sodium sulfate in spinning 18-30% l9-25%.

a Zinc sulfate in spinning bath 01-25% O.85-l.5%. Total travel in both baths-.-" Over 50 inches Over 75 inches. Total spinning tension. Over 0.5 g. p. d Over 0.5 g. p. d. Temperature of primary bath. 40-75 C 50-60" 0. Temperature of stretching 50l00 C Gil-100 C.

a Temperature of relaxing bath 0-120 C (SO-100 C.

With regard to the temperature of the relaxing bath, it is generally desirable to employ lower relaxing bath temperatures with dilute caustic relaxing baths than when water is used. For example, a relaxing bath containing 3.5% caustic soda operates particularly well at 35 0.

As in the first subgeneric embodiment, the most important bath variable is the acidity, and this can readily be adjusted by means of the general formula discussed above.

This embodiment of the invention is specifically illustrated in Examples XIII and XIV.

In accordance with the third subgeneric process of the present invention, which is particularly useful where a low alkali (between 3.5% and 5%) viscose is employed and where the use of a single bath is preferred, the following relationship factors, if observed, will produce a particularly desirable crimped yarn:

2. The viscose solution must contain between 0.01% and 1% of a viscose-dispersible salt of a metal whose hydroxide is amphoteric.

3. The coagulating and regenerating bath must have a sulfuric acid content of between 4% 10 during spinning must be stretched at least 40%. 8. The temperature of the coagulating bath must be between 40 C. and C. 9. The temperature of the relaxing bath must be between 20 C. and 120 C.

Water-soluble salts of the following metals, whose hydroxides are amphoteric, are viscosedispersible and have been added to viscose in accordance with the present invention and are known to be operative: zinc, antimony, beryllium, aluminum, cadmium, chromium, lead, iron, copper, cobalt, bismuth, and tin. Water-soluble salts of nickel are also found to be operative for this purpose. Although the amphoteric properties of nickel hydroxide are not clearly established, the latter is considered to be amphoteric in view of its close relationship to iron and cobalt and, therefore, for the purposes of the present invention, it shall be considered as being included in the above-mentioned generic grouping.

The viscose-dispersible salts may be added at any convenient stage before spinning. They are preferably added prior to the final stages of ripening of the viscose. The salt is preferably added in quantities between 0.01% and 1%, based on the weight of the viscose. The word viscose when used herein has its usual meaning of the total solution of cellulose xanthate in aqueous alkali.

The following table will be useful to show both the operable and median ranges when a viscose containing 3.5% to 5% alkali and modified with a salt of an amphoteric metal is used:

Operable Range Median Range Alkali content of viscose 3.5-5% 3.75-4.25%. Salt index of viscose 1 5-6 35-55. Metal salt content of viscose.-- 0.0l-l% 0.10.5%. Acid content of spinning bath 40-60% 40-50%. sOgllllIl sulfate in spinning 18-30% 10-25%.

Zinc sulfate in spinning bath 01-25% 0.85-l.5%. Length of bath traveL. Over 50 inches Over 75 inches. Spinning tension Over 0.5 g. p. d Over 0.5 g. p. d. Temperature of spinning bath 40-75 O 50-00 0. Temperature of relaxing bath 20l20 C (SO- 0.

Here again, the bath acidity may be adjusted according to the general formula previously laid down.

Some of the metals disclosed above and in the Examples are less satisfactor than others, either because they do not produce as high or durable a crimp, or because they impart color to the finished filament. Nevertheless, they are all operable in the process of this invention and they all come within its scope. The salts suitable for this process include salts of inorganic acid (e. g., sulfuric or nitric acids) and organic acids (e. g., acetic or propionic acids). Sulfates are in general preferred since they introduce no extraneous ions in the coagulating bath.

This embodiment of the invention is specifically illustrated in Examples XV and XVI.

Crimped yarns or fibers made in accordance with the present invention may be produced in filament deniers ranging from 1 to 15, or even higher. A decrease in filament denier, other conditions being equal, seems to favor a slight increase in the degree of crimp obtained.

The following examples which are not to be considered limitative of the present invention illustrate in detail specific steps by which the present invention may be carried out.

Example I A commercial type of viscose made from cotton linters and containing 7% cellulose and 6% alkali is spun at a sodium chloride index of 4.0, using a precious metal spinneret and an aqueous regenerating bath comprising 8.00% sulfuric acid, 19% sodium sulfate and 1.5% zinc sulfate at a temperature of 55 C. The thread formed in this manner is made to pass around roller guides in the spinning bath to develop tension and the bath travel used is approximately 130 inches at a spinning speed of approximately 2500 inches per minute. The tension on the thread at the point of its emergence from the bath is approximately 1 gram per denier, and the filaments are of approximately 3.75 denier each. The thread is wound on a bobbin and then cut into length of about 2 inches after which it is dropped into a bath of water heated to 80 C. to 90 C. In the hot water, the staple fiber spontaneously crimps and retains this crimped form substantially unchanged through the steps of washing and drying which follow. If, after repeatedly tensioning the staple fibers to gradually work the crimp out of the same, they are placed in a swelling liquid in a completely relaxed state, the crimp is instantaneously restored.

Example II Viscose thread is spun exactly as in Example I except that the thread is not cut into staple but washed on the bobbin, twisted (4 turns per inch) while maintained in a wet condition and afterwards relaxed in a bath of hot water in the form of loose skeins. Other modifications based on the production of continuous filament, crimped yarn by this invention include relaxing of the yarn in an untwisted condition, and drying of the yarn on the bobbin before subjecting it to the relaxing treatment.

Example III Viscose similar to that used in Example I is spun into a bath containing 8.5% sulfuric acid, 19% sodium sulfate, 0.85% zinc sulfate and 4% glucose. The temperature of the bath is 45 C. with a tension on the thread of 0.5 gram per denier. Bath travel, spinning speeds and other conditions are similar to those given in Example I. The fiber produced in this way is almost equally as well crimped as that obtained from Example I.

Example IV Viscose similar to that used in Example I is spun as before under tension of about 1 gram per denier into a regenerating bath containing 8.25% sulfuric acid, 19% sodium sulfate and 0.85% zinc sulfate. The crimped fiber produced by relaxing the cut staple in water is exactly the same as that obtained in Example I.

Example V Viscose similar to that used in Example I is spun into fibers of 1.5 denier each at a tension of 0.5 gram per denier per filament using a regenerating bath comprising 8.5% sulfuric acid, 23% sodium sulfate, and 0.85% zinc sulfate at a temperature of 55 C. The resulting crimped fibers are exceedingly soft and have a pleasing, loose, full hand similar to that of Wool.

Example VI Viscose made from a good grade of wood pulp and having approximately the same composition as regards cellulose and alkali content as that 12 used in Example I is spun in a manner similar to that of Example I. The relaxed fibers are equally well crimped as those of Example I.

Example VII Example VIII Viscose similar to that of Example I is spun at a salt index of 5.4 using a regenerating bath containing 8.5% sulfuric acid, 19% sodium sulfate and 1.5% zinc sulfate. The tension, bath travel and method of relaxing the yarn are similar to those of Example I. The product is also similar to that of Example I.

Example IX Viscose similar to that of Example I except that it is not permitted to ripen to the same extent and therefore has an index of 5.4 instead of 4.0 is spun under a tension of 1 gram per denier into a coagulating and regenerating bath containing 9.5% sulfuric acid, 19% sodium sulfate and 2.5% zinc sulfate at a temperature of 55 C. The bath travel, spinning speed and other conditions used are the same as in Example I. The product, after relaxing in hot water, is crimped and wool-like in appearance.

Example X Viscose similar to that of Example I is spun into a bath containing 6.75% sulfuric acid, 15%

sodium sulfate, 1.5% zinc sulfate at a temperature of 45 C. The spinning tension is 0.75 gram per denier, but the other conditions, including bath travel and spinning speed are the same as in Example I. On relaxing the product in hot water, highly crimped fibers similar to those from Example I are obtained.

Example XI Viscose similar to that of Example I is spun under a tension of 1 gram -per denier into a bath containing 9% sulfuric acid, 30% sodium sulfate and 0.85% zinc sulfate. Other details of the spinning procedure and method of relaxing the yarn in water are the same as those in Example I. The product is also similar to that of Example I.

Example XII Viscose similar to that of Example I is spun into a bath containing 8% sulfuric acid, 23% sodium sulfate, 0.85% zinc sulfate and 4% glucose. Other details of the spinning procedure and method of relaxing the yarn are similar to those of Example I. The product is obtained in the form of highly crimped fibers also similar to those of Example I.

Example XIII A commercial type of viscose containing 7% cellulose and 4% alkali, and having a salt index of 4.2 (Reinthaler-Rowe) is spun through a precious metal spinneret in an aqueous coagulating and regenerating bath comprising 4% sulfuric acid, 25% sodium sulfate and 1% zinc sulfate and having a temperature of 52 C. The yarn formed in this manner is made to pass about into an aqueous solution containing 3.5% caustic at a temperature of 35 C. In this relaxing bath, the staple fibers are spontaneously crimped and retain this crimped form substantially una convergence guide located 17 inches from 5 changed through the steps of washing and drythe spinneret and around roller guides in the ing which follow. If, after repeatedly tensioning spinning bath to develop tension. The yarn the staple fibers to work the crimp gradually travels in this bath a total of 240 inches from out of the same, they are placed in a liquid in a the convergence guide to the draw-01f roller. completely relaxed state, the crimp is spontane- The tension on the yarn at the draw-01f roller is ously restored. 0.23 gram per denier, which results in a stretch Example XV 5.51555552255 55355155553 A into a Second bath composed of water at 600 alkali is prepared in a conventional manner from from which it is withdrawn by another draw-01f 15 Wood pulp except e durmg e mlxme of roller. A tension of 0'67 gram per denier is cellulose xanthate with water, prior to ripening, plied to the yarn at this draw-off roller, result- 1 of sulfate (based the welght of t ing in a stretch in the water bath of 24.2%. The Viscose). 1s i f to the 501M101? The resultmg total stretch, therefore, which is applied to the dlsperslen npened to a e Index of and yarn, is 69.8% The yam so produced is then forced through a precious metal spmneret posed of 1200 filaments of 5.5 denier each. The regenemime bath eompnsmg 45% P yarn is Wound on a bobbin and then cut into fur1c acid, sodium sulfate, and 0.85% z nc lengths of about 21/2 inches after which it is sulfate. The precious metal spmneret conta ns dropped into an aqueous solution containing 40 openings of such a size as to form 150 denier 35% caustic Soda at a temperature of In 25 thread. The total bath travel in the coagulatthis relaxing bath, the staple fibers are sponi and regeneratleg P 15 epproxlme'tely 130 taneously crimped and retain this crimped form t W the spmnmg tenslon e the Fhread substantially unchanged through the steps of approxlmately gram demer p long washing and drying which follow. If, after rebath travel W hlgh tenslon f tamed by peatedly tensioning the staple fibers to work the i l' i f g g i g i a l? crimp gradually out of the same, they are placed t fi in a liquid in a completely relaxed state, the a y mcreasmg ensmn e e instantaneousl restored perature of the coagulating bath is 55 C. The cramp 15 thread is collected on a bobbin and, immediately Example XIV after collection, is cut from the bobbin into A commercial type of viscose containing 7% tengths of about 2 Inches and permltfed to fall cellulose and 4% alkali, and having a salt index P g wager fg ig about 90 Upoln of 4.8 (Reinthaler-Rowe) is spun through a z g 2 g i :2 3; 23? 3:222:3 precious metal spmneret in an aqueous coagu' wool in appeara nce. The crimp is durable and lating and regenerating bath comprising 3.98% resistant to Washing sulfuric acid, 25.1% sodium sulfate and 1.48% zinc sulfate and having a temperature of 52 C. Example XVI The yarn formed in this manner is made to pass To viscose similar in cellulose and alkali conabout a convergence guide and around roller tent to that used in Example XV is added 0.1% guides in the spinning bath to develop tension. pper s lf based on the w h f h o l The yarn travels in this bath a total of 215 inches Yiscose soilit-ions Viscose pened o n from the convergence guide to the draw-off roller. Index -9 F spun under tenslon of grains The tension on the yarn at the draw-off roller is per demer 1 coagulatmg e regeneratmg 0.25 gram per denier, which results in a stretch 5O bath contammg f" e' 25% sodnfm in the yarn from the convergence guide to the sulfate and 0 85% zinc sullate. The bath travel, draw-off roller of 21 8% The yarn is then led g f ggg g bath a h g i m O xamp e e yarn pro uce 1s 0 a gr enfggl ifiig g fg f l ifi iy ggig 3253;; ish-brown color. Upon relaxing this yarn in hot 4 of 05 I v I i '3 I 1 no Plied i fi 2; this i b' gl f g g/ r g bodiment of the invention, excellently crimped m a 5 C 111 e Wa a 0 e yarns can be obtained by spinning viscose under total Stretch, therefore, which is applied to the the conditions summarized in the table below, yarn is 64.5%. The yarn pr c d is Composed the bath travel being in all cases approximately of 1800 filaments of 3.0 de e each. The yarn 60 130 inches and the bath temperature 55 C.:

Cellulose Alkali I Salt 4 L s cigrgggzeof cflligi ggeof Metal Salt 1n viscose lrliigggsgf g s g gg fi i g Tension Per cent Percent Percent G.p.d. 7 4 4.4 4.1 25 0.55 1.0 7 4 4.0 4.75 25 0.55 1.1 7 4 4.0 4. 25 0. 1.0 7 4 4.0 4.0 25 0. 1.1 7 3.5 5.5 4.0 50 0. 85 0.8 7 5 4.0 0.0 15 0.55 0.9

is wound on a bobbin and then cut into lengths of about2 inches, after which it is dropped The value of the general formula KaN I: I

will be apparent by consideration of the following table, which indicates the minimum gel swelling acidity and the acidity range within which maximum crimp is obtained for the various viscose compositions used in several of the examples.

16 over and produce a crimped effect. For this reason, use is made of the high spinning tensions which are a fundamental feature of the present invention. A proper balance between the above described relationship factors is considered to be essential since only under such selected condi- Viscose Characteristics Spinning Bath Characteristics System Characteristics Example (A) Spin- Cellulose Caustic Ind x Tem H180 NazS04 ZnS04 Glucose (X) MGS nmg acidity Conc. Gone. 9 Couc. Cone. Cone. Conc. Acidity range as calculated Per Cent Per Cent C. Per Cent Per Cent Per Cent Per Cent Per Cent Per Cent 7 6 4.0 55 8. 19 1. 9.0 7.1-9.2 7 6 4. 0 55 8.0 19 1. 5 9. 0 7. 1-9. 2 7 6 4. 0 45 8. 5 19 0.85 4.0 9. 3 7. 5-9. 7 7 6 4.0 55 8. 19 0.85 9. 4 7. 5-9.8 7 6 4.0 55 8. 5 23 0.85 9. 2 7. 4-9. 6 7 6 4.0 55 8.0 19 1. 5 9.0 7. 1-9. 2 7 6 1. 9 55 7. 5 19 1.5 8.3 6. 7-8. 7 7 6 5. 4 55 8.5 19 1. 5 8.75 7. 0-9. 1 7 6 5. 4 55 9. 5 19 2. 5 9. 75 7. 8-10. 2 7 6 4.0 6.75 15 1.5 7. 8 6. 8-8. 2 7 6 4.0 9.0 30 0. 85 10. 8 8. 6-11. 3 7 6 4.0 55 8.0 23 0.85 9. 2 7. 4-9. 6 7 4 4. 2 52 4.0 25 1.0 6.8 3. 6-4. 7 7 4 4. 8 52 3. 98 25. 1 1. 48 6. 6 3. 5-4. 6 7 4 4. 4 0.1% ZnSO; 55 4. 6 25 0.85 6. 6 3. 5-4. 62 7 4 4.0 0.1% C11S04 55 4. 6 25 0.85 6. 2 3. 5-4. 6

2.5 (C) (N) Max. A 1 g (g wn)! Mm. A 100 X The variation in the range is explained by the fact that some systems have very flat minimum gel swelling curves near the minimum gel swelling point.

The crimped fibers produced by this process are entirely new and different in character from previously known crimped fibers. They are characterized by unique and outstanding properties not found in the crimped fibers produced heretofore. One of these entirely new and unexpected properties lies in the fact that the crimp, after being removed through stretching, combing, or other mechanical treatment, is substantially completely restored to the fiber simply by suspending it in water, or other aqueous liquid, in the absence of tension. The crimp regain is practically instantaneous, whether the fiber treated be in the form of staple or of continuous filaments. It can be readily demonstrated by manually stretching, or repeatedly combing a sample of crimped fiber so as to destroy its crimp, then immersing the sample in water, whereupon it at once crinkles and crimps to give the original structure. This surprising property is, of course. of great importance in the industrial processes to which the fibers may be subjected. For example, carding usually destroys, at least partly, the crimp in an ordinary crimped fiber. Fibers made by this process, however, may be carded and afterward immersed in Water, whereby the original crimp is restored completely or substantially so. No previously known crimped regenerated cellulose fibers even remotely possess this remarkable characteristic.

It is theorized that the production of crimped high tenacity fibers according to this invention is possible primarily by reason of the fact that during spinning there is formed in individual filaments a certainljh dfiinoneuniformitnwitb-rep c to th pri n at qnnt the cel ul se. Q E PIiET ing the edges or outside boundary of the filament a .-.s nnrisingthegngmr seetionsh t. when fibers possessing W mphnit emitniniheir..c se he are permitted to shrink freely, the different layers of regenerated cellulose do not shrink to the same extent and the fibers tend spontaneously to fold tions is the rate of penetration of acid into the thread such that s'gata difierefieat'ien"caste obtained between the degree of orient/ation of f l b er yva ll apdfiber,gore. Thi e is a possibility that differences in the fiber structure (density and degree of orientation) occur across the filament which ultimately cause the fiber to crimp when relaxed. The foregoing theoretical discussion is not, however, to be construed as limiting the process of this invention.

The high tenacity crimped fibers which may be obtained as a result of the present invention are characterized by filament strength of from 2.25 to over 3 grams per denier dry tenacity, and from 1.25 to over 2 grams per denier wet tenacity. The dry extensibilities, after straightening the crimp therefrom, for threads formed in accordance with the present invention are of the order of 10% to 20%, depending on the spinning tension used in their formation, and in general, it can be said that the extensibilities of crimped fibers produced in accordance with the present invention are better than those of straight fibers of equal tensile strength but spun without permitting free shrinkage. The curly crimp in the fibers produced in accordance with the present invention is durable and produces a pleasing, wool-like appearance and hand. In the case of fibers which have been cut to staple length before being permitted to relax in water, the crimps obtained are quite irregular, both as to their number per inch and their arrangement around the fiber axis. It is difficult, therefore, to define the degree of crimp obtained in these fibers in a quantitative manner, but in general, it may be said that the number of crimps per unit length along the axis of the unstretched fiber is above 10 crimps per inch. This means that these fibers are easily distinguishable from ordinary regenerated cellulose staple fibers, even those made by the so-called acid-cutting process, since at most the latter do not show more than 5 or 6 crimps per inch. The crimps in the fibers are 17 remarkably resistant to laundering with soap. As has been mentioned previously, even after removing the crimp by stretching the filaments, the crimp can be restored by subjecting the filaments or fibers to another relaxing treatment in a, liquid.

Continuous filament yarn comprising crimped filaments of the type hereinabove described. is particularly desirable for the production of woven and knit goods where more than average yarn strength, together with a wool-like hand, is desired. Th e gri rnped st le fibers of the present invention are yery d jfd'f' tff p fbdiictibh of an ique and sup spun yarn. Fabrics produced from both continuous filament and spun yarn made in accordance with the present invention will have a very desirable hand, due to regain of filament and fiber crimp upon Since it is obvious that many changes and modifications can be made in the above described details without departing from the nature and spirit of the invention, it is to be understood that the invention is not to be limited to the said details except as set forth in the appended claims.

I claim:

1. A process for the production of highly crimped regenerated cellulose filaments and fibers which comprises the steps of spinning filaments from a balanced viscose-sulfuric acid-salt spinning bath system in which the spinning bath contain 0.1% to 3.0% zinc sulfate and a substantial amount of sodium sulfate and in which the sulfuric acid content of the spinning bath is of the order of 11.3% or less and is in accord with the formula:

K(C.N) 100 wherein A is the sulfuric acid content in per cent by weight of the spinning bath and i less than a:,

K is a factor which may have any value from C is the cellulose content in per cent by weight of the viscose and is approximately 7%,

N is the sodium hydroxide content in per cent by weight of the viscose and is at least 3.5% and :r is the percentage content by weight of sulfuric acid in the spinning bath which will produce a regenerated cellulose filament having the minimum gel swelling factor with the viscose specified by C and N, said viscose having a salt index of between 1.5 and 6.0 and said bath having a sodium sulfate content of between 15% and 30% with a filament travel of at least 50 inches in the coagulating and regenerating bath and said bath having a temperature of between 50 and 75 C.

imposing on said filaments, during the spinning thereof, a tension of at least 0.5 gram per denier and a stretch of at least 40%, and, after substantially complete regeneration of said filaments, relaxing the same, completely free from all tension, in a liquid which will swell the same at a temperature of between and 120 C.

2. A process for the production of highly crimped regenerated cellulose filaments and fibers which comprise the steps of spinning filaments from a balanced viscose-sulfuric acid-salt spinning bath system in which the spinning bath contains 0.1% to 3.0% zinc sulfate and a substantial amount of sodium sulfate and in which the sulfuric acid content of the spinning bath i of the order of 11.3% or less and is in accord with the formula:

K (ON) A--[ 100 .a: wherein A is the sulfuric acid content in per cent by weight of the spinning bath and is less than :r,

K is a factor which may have any value from C is the cellulose content in per cent by weight of the viscose and is approximately 7%;

N is the sodium hydroxide content in per cent by weight of the viscose and is at least 35%; and

x is the percentage content by weight of sulfuric acid in the spinning bath which will produce a regenerated cellulose filament having the minimum gel swelling factor with the viscose specified by C and N, said viscose having a salt index of between 1.5 and 6.0 and said bath having a sodium sulfate content of between and %.with a filament travel of at least 50 inches in the coagulating and regenerating bath and said bath having a temperature of.

between 50 and 75 C.

passing said filaments in the spinning thereof through a non-alkaline stretching bath containing not to exceed that acidity equivalent to 3% sulfuric acid, imposing on said filaments, during the spinning thereof, a, tension of at least 0.5 gram per denier and a tretch of at least and, after substantially complete regeneration of said filaments, relaxing the same, completely free from all tension, in a liquid which will swell the wherein A is the sulfuric acid content in per cent by weight of the spinning bath and is less than :c,

K is a factor which may have any value from 1.9 to 2.5,

C is the cellulose content in per cent by weight of the viscose and is approximately 7%,

N is the sodium hydroxide content in per cent by weight of the viscose and is at least 3.5%, and

a; is the percentage content by weight of sulfuric acid in the spinning bath which will produce a regenerated cellulose filament having the minimum gel swelling factor with the viscose,

specified by C and N, said viscose having a salt index of between 1.5 and 6.0 and said bath having a sodium sulfate content of between 15% and 30% with a filament travel of at least inches in the coagulating and regenerating bath and said bath having a temperature of between 50 and C.

passing said filaments in the spinning thereof through a non-alkaline stretching bath containing not to exceed that acidity equivalent to 3% passing said filaments in the spinning thereof through a non-alkaline, aqueous stretching bath having a temperature between 50 C. and the boiling point thereof, imposing on said filaments during the spinning thereof a tension of at least 0.5 gram per denier and a stretch of at least 40%, and, after substantially complete regeneration of said filaments, relaxing the same, completely free from all tension, in a liquid which will swell the same at a temperature of between nd 120 C.

sulfuric acid and having a temperature between 50 C. and the boiling point thereof, imposing on said filaments during the spinning thereof, a tension of at least 0.5 gram per denier and a stretch of at least 40%, and, after substantially complete regeneration of said filaments, relaxing the same, completely free from all tension, in a liquid which will swell the same at a temperature of between 0 and 120 C.

4. A process for the production of highly crimped regenerated cellulose filaments and fibers which comprises the steps of spinning filaments from a balanced viscose-sulfuric acid-salt spinning bath system in which the spinning bath contains 0.1% to 3.0% zinc sulfate and a substantial amount of sodium sulfate and in which the sulfuric acid content of the spinning bath is of the order of 11.3% or less and is in accord with the formula:

wherein A is the sulfuric acid content in per cent by weight of the spinning bath and is less than 11:,

K is a factor which may have any value from C is the cellulose content in per cent by weight of the viscose and i approximately 7%,

N is the sodium hydroxide content in per cent by weight of the viscose and is at least 3.5%, 1 and is the percentage content by weight of sulfuric acid in the spinning bath which will produce a regenerated cellulose filament having the minimum gel swelling factor with the viscose specified by C and N, said viscose having a salt index of between 1.5 and 6.0 and said bath having a sodium sulfate content of between 15% and 30% with a filament travel of at least inches in the coagulating and. regenerating bath and said bath having a temperature of between 50 and C.

5. A process for the production of highly crimped regenerated cellulose filaments and fibers which comprises the steps of spinning filaments from a balanced viscose-sulfuric acid-salt spinning bath system in which the spinning bath contains 0.1% to 3.0% zinc sulfate and a substantial amount of sodium sulfate and in which the sulfuric acid content of the spinning bath is of the order of 11.3% or less and is in accord with the formula:

K(C.N)

weight of the spinning bath and is les than 0:,

K is a factor which may have any value from C is the cellulose content in per cent by weight of the viscose and is approximately 7%. 75

is the percentage content by weight of sulfuric acid in the pinning bath which will produce a regenerated cellulose filament having the minimum gel swelling factor with the viscose specified by C and N, said viscose having a salt index of between 1.5 and 6.0 and said bath having a sodium sulfate content of between 15% and 30% with a filament travel of at least 50 inches in the coagulating and regenerating bath and said bath having a temperature of between 50 and 75 C.

passing said filaments in the spinning thereof through a non-alkaline stretching bath containing not to exceed that acidity equivalent to 3% sulfuric acid, imposing on said filaments during the spinning thereof a tension of at least 0.5 gram per denier and a stretch of at least 40%, at least a portion of said stretch being imposed on the filaments in the spinning bath and a. portion of aid stretch being imposed on the filaments in the stretching bath, and, after substantially complete regeneration of said filaments, relaxing the same, completely free from all tension, in a liquid which will swell the same at a temperature of between 0 and C.

6. A process for the production of highly crimped regenerated cellulose filaments and fibers which comprises the steps of spinning filaments from a balanced viscose-sulfuric acid-salt spinning bath system in which the spinning bath contains 0.1% to 3.0% zinc sulfate and a substantial amount of sodium sulfate and in which the sulfuric acid content of the spinning bath is of the order of 11.3% or less and is in accord with the formula:

wherein A is the sulfuric acid content in per cent by weight of the spinning bath and is less than :c, K is a factor which may have any value from 1.9 to 2.5, C is the cellulose content in per cent by weight of the viscose and is approximately 7 N is the sodium hydroxide content in per cent by weight of the viscose and is at least 3.5%, and is the percentage by weight of sulfuric acid in the spinning bath which will produce a regenerated cellulose filament having the minimum gel swelling factor with the viscose specified by C and N, said viscose having a salt index of between 1.5 and 6.0 and said bath having a sodium sulfate content of between 15% and 30% with a filament travel of at least 50 inches in the coagulating and regenerating bath and said bath having a temperature of between 50 and 75 C.

passing said filaments in the spinning thereof through a non-alkaline stretching bath containing not to exceed that acidity equivalent to 3% sulfuric acid, imposing on said filaments during the spinning therof a tension of at least 0.5 gram per denier and a stretch of at least 40%, the greater portion of said stretch being imposed on the filaments in the stretching bath and the smaller portion of said stretch being imposed on the filaments in the spinning bath, and, after substantially complete regeneration of said filaments, relaxing the same, completely free from 21 all tension, in a liquid which will swell the same at a temperature of between and 120C.

7. A process for the production of highly crimped regenerated cellulose filaments and fibers which comprises the steps of spinning filaments from a balanced viscose-sulfuric acid-salt spinning bath system in which the spinning bath contains 0.1% to 3.0% zinc sulfate and a substantial amount of sodium sulfate and in which the sulfuric acid content of the spinning bath is of the order of 11.3% or less and is in accord with the formula:

K(C.N) A:

wherein A is the sulfuric acid content in per cent by weight of the spinning bath and i less than x,

a: is the percentage content by weight of sulfuric acid in the spinning bath which will produce a regenerated cellulose filament having the minimum gel swelling factor with the viscose specified by C and N, said viscose having a salt index of between 1.5 and 6.0 and said bath having a sodium sulfate content of between 15% and 30% with a filament travel of at least 50 inches in the coagulating and regenerating bath and said bath having a temperature of between 50 and 75 C.

imposing on said filaments, during the spinning thereof, a tension of at least 0.5 gram per denier and a tretch of at least 40%, and, after substantially complete regeneration of said filaments, relaxing the same, completely free from all tension, in water at a temperature of between 0 and 120 C.

8. A process for the production of highly crimped regenerated cellulose filaments and fibers which comprises the steps of spinning filaments from a balanced viscose-sulfuric acid-salt spinning bath system in which the spinning bath contains 0.1% to 3.0% zinc sulfate and a substantial amount of sodium sulfate and in which the sulfuric acid content of the spinning bath is of the order of 11.3% or less and i in accord with the formula:

wherein A is the sulfuric acid content in per cent by weight of the spinning bath and is less than 2., K is a factor which may have any value from C is the cellulose content in per cent by weigh of the viscose and is approximately 7%,

a: is the percentage content by weight of sulfuric acid in the spinning bath which will produce a regenerated cellulose filament having the minimum gel swelling factor with the viscose specified by C and N, said viscose having a salt index of between 1.5 and 6.0 and said bath having a, sodium sulfate content of between 15% and 30% with a filament travel of at least 50 inches in the coagulating and regenerating bath and aid bath having a temperature of between 50 and 75 C.

passing said filaments in the spinning thereof through a non-alkaline stretching bath containing not to exceed that acidity equivalent to 3% sulfuric acid, imposing on said filaments, during the spinning thereof, a tension of at least 0.5 gram per denier and a stretch of at least 40%, and, after substantially complete regeneration of said filaments, relaxing the same, completely free from all tension, in water at a temperature of between 0 and. 125 C.

9. A process for the production of highly crimped regenerated cellulose filaments and fibers which comprises the steps of spinning filaments from a balanced viscose-sulfuric acid-salt spinning bath system in which the spinning bath contains 0.1% to 3.0% zinc sulfate and a substantial amount of sodium sulfate and in which the sulfuric acid content of the spinning bath is of the order of 11.3% or less and is in accord with the formula:

wherein A is the sulfuric acid content in per cent by weight of the spinning bath and is less than 3:,

passing said filaments in the spinning thereof through a non-alkaline stretching bath containing not to exceed that acidity equivalent to 3% sulfuric acid and having a temperature between 50 C. and the boiling point thereof, imposing on said filaments during the spinning thereof a tension of at least 0.5 gram per denier and a stretch of at least 40%, and, after substantially complete regeneration of said filaments, relaxing the same, completely free from all tension, in Water at a temperature of between 0 and 120 C. 10. A process for the production of highly crimped regenerated cellulose filaments and fibers which comprises the steps of spinning filaments from a balanced viscose-sulfuric acid-salt spinning bath system in which the spinning bath contains 0.1% to 3.0% zinc sulfate and a substantial amount of sodium sulfate and in which the sulfuric acid content of the spinning bath is of the order of 11.3% or less and is inaccord with the formula:

[K(C.N) a

wherein A is the sulfuric acid content in per cent by weight of the spinning bath and i less than at,

:c is the percentage content by weight of sulfuric acid in the spinning bath which will produce a regenerated cellulose filament having the minimum gel swelling factor with the viscose specified by C and N, said viscose having a salt index of between 1.5 and 6.0 and said bath having a sodium sulfate'content of between 15% and 30% with a filament travel of at least 50 inches in the coagulating and regenerating bath and said bath having a temperature of between 50 and 75 C.

passing said filaments in the spinning thereof through a non-alkaline, aqueous stretching bath having a temperature between 50 C. and the boiling point thereof, imposing on said filaments during the spinning thereof a tension of at least 0.5 gram per denier and a stretch of at least 40%, and, after substantially complete regeneration of said filaments, relaxing the same, completely free from all tension, in water at a temperature of between and 120 C.

11. A process a defined in claim 1 in which the filaments are relaxed in the relaxing bath immediately after stretching the same.

12. A process as defined in claim 1 in which the filaments are collected on a yarn support and subjected to a washing treatment after stretching and prior to relaxation.

13. A process as defined in claim 1 in which the filaments are collected on a yarn support and subjected to a washing and drying treatment after stretching and prior to relaxation.

14. A process for the production of crimped regenerated cellulose filaments and fibers which comprises the steps of spinning filaments, under tension, from a viscose solution into a coagulating and regenerating bath, and after substantially complete regeneration of said filaments, freely suspending the filaments, in filamentous structure form, in an aqueous liquid bath in complete absence of tension to completely relax the same, said steps being carried out in accordance with the following critical relationship factors:

(a) The viscose solution must have an alkali content (calculated at NaOH) of 5% to The viscose solution must have a salt index (as determined by Reinthaler-Rowe, Artificial Silk, 1928, page 69) of between 1.5

and 6. Y

(c) The coagulating and regenerating bath must have a sulfuric acid content of between 6.5%

and 9.5%.

The coagulating and regenerating bath must have a sodium sulfate content of between and 30%.

The coagulating and regenerating bath must have a zinc sulfate content of between 0.1%

and 3%.

The filaments must have a travel of at least 50 inches in the coagulating and regenerating bath.

The spinning tension on the filaments in the coagulating and regenerating bath must be at least 0.5 gram per denier and the filaments during the spinning thereof must be.

stretched at least 40%.

24 (h) The temperature of the coagulating bath must be between 40 C. and 75 C. (i) The temperature of the relaxing bath must be between 20 C. and 120 C.

and not more than one of said critical factors lie outside of the following range for the indicated factors:

( Salt index of viscose 3.5 to 5.5 (lc) Sulfuric acid content of the bath 7.5% to 8.5% (1) Sodium sulfate content of the bath 19% to 25% (m) Zinc sulfate content of the bath 0.85% to 2.0% (11.) Length of bath travel Over 75 inches (0) Temperature of coagulating bath 50 C. to 60 C. (p) Temperature of relaxing bath 60 C. to C.

15. A process as defined in claim 14 in which the relaxing treatment liquid is water.

16. A process as defined in claim 14 in which the relaxing treatment liquid comprises an aqueous solution of an alkaline material taken from the group consisting of sodium hydroxide and sodium carbonate.

17. A process for the production of crimped regenerated cellulose filaments and fibers which comprises the steps of spinning filaments, under tension, from a viscose solution into a coagulating and regenerating bath, and after substantially complete regeneration of said filaments, freely suspending the filaments, in filamentous structure form, in an aqueous liquid bath in complete absence of tension to completely relax the same, said steps being carried out in accordance with the following critical relationship factors:

The viscose solution must have an alkali content (calculated as NaOH) of between 5.75% and 6.25%.

The viscose solution must have a salt index (as determined by Reinthaler-Rowe, Artificial Silk, 1928, page 69) of between 3.5 and 5.5.

The coagulating and regenerating bath must have a sulfuric acid content of between 7.5% and 8.5%.

The coagulating and regenerating bath must have a sodium sulfate content of between 19% and 25%.

The coagulating and regenerating bath must have a zinc sulfate content of between 0.85% and 2%.

The filaments must have a travel of at least 75 inches in the coagulating and regenerating bath.

The spinning tension on the filaments in the coagulating and regenerating bath must be at least 0.5 gram per denier and the filaments during the spinning thereof must be stretched at least 40%.

The temperature of the coagulating bath must be between 50 C. and 60 C.

(i) The temperature of the relaxing bath must be between 60 C. and 100 C.

20. A process as defined in claim 14 which comprises subjecting the filaments to a liquid washing treatment after coagulation and prior to the relaxing treatment.

21. A process as defined in claim 14 which comprises subjecting the filaments to a liquid washing treatment, and drying, after coagulation and prior to the relaxing treatment, the temperature of the relaxing bath being at least 60 C.

22. A process as defined in claim 14 which comprises subjecting the filaments to a secondary stretching treatment in an aqueous bath having a temperature of at least 60 C. prior to the relaxing treatment.

23. A process as defined in claim 1'7 which comprises subjecting the filaments to a liquid washing treatment after coagulation and prior to the relaxing treatment.

24. A process as defined in claim 1'7 which comprises subjecting the filaments to a liquid washing treatment, and drying, after coagulation and. prior to the relaxing treatment.

25. A process as defined in claim 17 which comprises subjecting the filaments to a secondary stretching treatment in an aqueous bath having a temperature of at least 60 C. prior to the relaxing treatment.

26. A process for the production of crimped regenerated cellulose filaments and fibers which comprises the steps of spinning filaments, under tension, from a viscose solution into a coagulating and regenerating bath passing said filaments through a non-alkaline stretching bath, and. after substantially complete regeneration of said filaments, relaxing the filaments, free from tension, in an aqueous liquid'bath, said steps being carried out in accordance with the following critical relationship factors:

(a) The viscose solution must have an alkali content (calculated as NaOH) of between 3.5% and 5%. The viscose solution must have a salt index (as determined by Reinthaler-Rowe, "Artificial Silk, 1928, page 69) of between 1.5 and 6. The coagulating and regenerating bath must have a sulfuric acid content of between 3.5% and 6.5%. The coagulating and regenerating bath must have a sodium sulfate content of between 18% and 30%. The coagulating and regenerating bath must have a zinc sulfate content of between 0.1% and 2.5%. (f) The filaments must have a travel of at least 50 inches in the coagulating and regenerating bath. i The spinning tension on the filaments in the coagulating and regenerating bath must be at least 0.5 gram per denier and the filaments during the spinning thereof must be stretched at least 40%. The temperature of the coagulating bath must be between 40 C'. and 75 C. (i) The temperature of the secondary stretching bath must be between 50 C. and 100 C. (7') The temperature of the relaxing bath must be between 0 C. and 120 C.

2'7. A process as defined in claim 26 in which the relaxing treatment liquid comprises an aqueous solution of an alkaline material taken from the group consisting of sodium hydroxide and sodium carbonate.

28. A process as defined in claim 26 which comprises subjecting the filaments to a liquid washing treatment after coagulation and prior to the relaxing treatment.

29. A process as defined in claim 26 in which the temperature of the relaxing bath is at least 60 C., and which comprises subjectingthe filaments to a liquid washing treatment, and to drying, after coagulation and prior to the relaxing treatment.

30. A regenerated cellulose filament having a non-uniformity of strucfiim'tw''n the exterior and interior portions of the filament and having a difierence of structure occurring across the filament, said filament having the characteristic, when straight, of spontaneously cri nplng upon being s uspended, free of tension, in an aq i 'fj liqu i d. "31. A regenerated cellulose filament having a non-uniformity of structure between the exterior and interior portions of the filament and having a difference of structure occurring across the filament, said filament having al crimp ,which,

ei rse eizletelrsgst filament, free from tensio' 327A" regiirsta tenure non-uniformity of structure between the exterior and interior portions of the filament and having a difference of structure occurring across the filament, said filament having at least ten crimps per inch which, upon being mechanically?? lulose fil nt having fnon-uniformitfiffiifictlifebt n the exterior and interior portions of the filament and having a difference of structure occurring across the filament, said filament having the characteristic of spontaneously crimping, upon being suspended, free of tension, in an aqueous liquid.

35. A substantially straight regenerated cellulose filament having a non-uniformity of structure between the exterior and interior portions of the filament and having a difference of structure occurring across the filament, said filament having the characteristic of spontaneously crimping with at least ten crimps per inch, upon being suspended, free of tension, in an aqueous liquid.

36. A substantially straight regenerated cellulose filament having a non-uniformity of structure between the exterior and interior portions of the filament and having a difference of structure occurring across the filament, said filament having a tenacity of at least 2.25 grams per denier and having the characteristic of spontaneously crimping, upon being suspended, free of tension, in an aqueous liquid.

37. A process for the production of crimped regenerated cellulose filaments and fibers which comprises the steps of spinning filaments under tension from a viscose solution into a coagulating and regenerating bath and, after substantially complete regeneration of said filaments, relaxing the filaments free from tension in an aqueous bath, said steps being carried out in accordance with the following relationship factors:

(a) The viscose solution has an alkali content (calculated as NaOH) of between 3.5% and The viscose solution has a salt index of between 1.5 and 6.0;

The viscose solution contains between 0.01% and 1.0% of a viscose-dispersible salt of a metal, the hydroxide of which is amphoteric; The coagulating and regenerating bath has a sulfuric acid content of between 4% and The coagulating and regenerating bath has a sodium sulfate content of between 18% and 30%;

The coagulating and regenerating bath has a zinc sulfate content of between 0.1 and 2.5%;

The filaments have a travel of at least 50 inches in the coagulating and regenerating bath;

The spinning tension on the filaments in the coagulating and regenerating bath is at least 0.5 gram per denier and the filaments during the spinning thereof are stretched at least 4 (i) The temperature of the coagulating bath is between 40 C. and 75 C.

The temperature ofthe relaxing bath is between C. and 120 C.

38. The process of claim 37 in which a stretch of at least 40% is imposed during coagulation and regeneration.

39. The process of claim 37 in which the relaxing liquid is an aqueous solution of an alkaline material.

40. A process for the production of crimped regenerated cellulose filaments and fibers which comprises the steps of spinning filaments under tension from a viscose solution into a coagulating and regenerating bath and, after substantially complete regeneration of said filaments, relaxin the filaments free from tension in an aqueous bath, said steps being carried out in accordance with the following relationship factors:

(a) The viscose solution has an alkali content (calculated at NaOH) of between 3.75% and 4.25%;

The viscose solution has a salt index of between 3.5 and 5.5;

The viscose solution contains between 0.01%

and 0.5% of a viscose-dispersible salt of a metal, the hydroxide of which is amphoteric; The coagulating and regenerating bath has a sulfuric acid content of between 4% and 5%; The coagulating and regenerating bath has a sodium sulfate content of between 19% and (f) The coagulating and regenerating bath has a zinc sulfate content of between 0.85% and 1.5%; The filaments have a travel of at least 75 inches in the coagulating and regenerating bath; The spinning tension on the filaments in the coagulating and regenerating bath is at least 0.5 gram per denier and the filaments during the spinning thereof are stretched at least 28 (i) The temperature of the coagulating bath is between 50 C. and 60 C.; (:i) The temperature of the relaxing bath is between 60 C. and 100 C.

41. The process of claim 40 in which a stretch of at least 40% is imposed during coagulation and regeneration.

42. The process of claim 40 in which the relaxing treatment liquid is an aqueous solution of an alkaline material.

43. A process for the production of crimped regenerated cellulose filaments and fibers which comprises the steps of spinning filaments,

under tension, from a viscose solution into a coagulating and regenerating bath, passing said filaments through a non-alkaline stretching bath, and after substantially complete regeneration of said filaments, relaxing the filaments, free from tension, in an aqueous liquid bath, said steps being carried out in accordance with the following critical relationship factors:

(a) The viscose solution has an alkali content (calculated as NaOH) of between 3.75% and 4.24%. The viscose solution has a salt index (as determined by Reinthaler-Rowe, Artificial Silk, 1928, page 69) of between 3.5 and 5.5. The coagulating and regenerating bath has a sulfuric acid content of between 3.75% and 4.5%. The coagulating and regenerating bath has a sodium sulfate content of between 19% and 25%. The coagulating and regenerating bath has a zinc sulfate content of between 0.85% and 1.5%. (f) The filaments have a travel of at least inches in the coagulating and regenerating bath. The spinning tension on the filaments in the coagulating and regenerating bath is at least 0.5 gram per denier and the filaments during the spinning thereof are stretched at least 40%. The temperature of the coagulating bath is between 50 C. and 60 C. (i) The temperature of the stretching bath is between 60 C. and C. (7') The temperature of the relaxing bath is between 60 C. and 100 C.

WILLIAM D. NICOLL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,683,199 Lilienfeld Sept. 4, 1928 2,015,201 Stockly et al. Sept. 25, 1935 2,192,074 Givens et al. Feb. 27, 1940 2,238,977 Jackson et al. Apr. 22, 1941 2,249,745 Charch et a1 July 22, 1941 2,249,756 Finzel July 22, 1941 2,267,055 Tippetts Dec. 23, 1941 2,297,613 Fink et al. Sept. 29, 1942 2,297,746 Charch et al. Oct. 6, 1942 2,312,152 Davis Feb. 23, 1943 FOREIGN PATENTS Number Country Date 481,565 Great Britain Mar. 11, 1938 493,288 Great Britain Oct. 3, 1938 Certificate of Correction Patent No. 2,515,834 July 18, 1950 WILLIAM D. N IOOLL It is hereby certified that error appears in the numbered patent requiring correction as follows:

Column 3, line 4, before the syllable balinsert an opening quotation mark; column 6, line 73, for both read bath; column 9, linel, after must insert be; column 13, line 33, for cramp read crimp;

columns

13 and 14, in the table, under the heading Metal Salt in Viscose, line 3 thereof, for 0.1% Pb (OCOCH read 0.1% Pb(OO0OH line 4, for 0.1% AI (SO*) read 0.1% AZ (SO column 14, second line below the table, for that portion of the equation reading (KQN) read K(0.N); column 27, line 50, for at N aOH read as NaOH;

and that the said Letters Patent should be read as corrected above, so that the same may conform to the record of the case in the Patent Ofiice.

Signed and sealed this 17th day of October, A. D. 1950.

[SEAL] THOMAS F. MURPHY,

Assistant Oomrnieszoner of Patents.

printed specification of the above

Claims

30. A REGENERATED CELLULOSE FILAMENT HAVING A NON-UNIFORMITY OF STRUCTURE BETWEEN THE EXTERIOR AND INTERIOR PORTIONS OF THE FILAMENT AND HAVING A DIFFERENCE OF STRUCTURE OCCURRING ACROSS THE FILAMENT, SAID FILAMENT HAVING THE CHARACTERISTIC, WHEN STRAIGHT, OF SPONTANEOUSLY CRIMPING UPON BEING SUSPENDED, FREE OF TENSION, IN AN AQUEOUS LIQUID.