US3539679A

US3539679A - Process for producing polynosic fibers

Info

Publication number: US3539679A
Application number: US569685A
Authority: US
Inventors: Yukio Kimura; Taro Yamamura; Atsushi Kawai; Masamichi Ikeda; Takehiro Katsuyama; Takanori Oda; Sakae Kondo
Original assignee: Mitsubishi Rayon Co Ltd
Current assignee: Mitsubishi Rayon Co Ltd
Priority date: 1965-08-03
Filing date: 1966-08-02
Publication date: 1970-11-10
Anticipated expiration: 1987-11-10
Also published as: CH475377A; DE1669494A1; NL6610893A; DE1669494B2; NL134509C; GB1096509A

Description

YUKIO KIMURA ETAL PROCESS FOR PRODUCING POLYNOSIC FIBERS Nov. 10, 1970 2 Sheets-Sheet 1 Filed Aug. 2, 1966 m 8 2 6 G. H 4 2 0 1 9 tm bmt m RE m 8 w 6 F 4 2 0 0 w 5 3 3 A b\ v \QGbtnw EE I Concenfrafion 0f Concenfraf/on 0f su/fur/c ac/d 9/1) SU/fUr/c 06/0, (9/! az /a Nov. 10, 1970 YUKIQ KfMuRA ETAL 3,539,679

7 PROCESS FOR PRODUCING POLYNOSIC FIBERS Filed Aug. 2, 1966 2 Sheets-Sheet 2 United States Patent 3,539,679 PROCESS FOR PRODUCING POLYNOSIC FIBERS Yukio Kimura, Taro Yamamura, and Atsuslii Kawai,

Ohtake-shi, Masamichi Ikeda, Iwakuni-shi, and Takehiro Katsuyama, Takanori Oda, and Sakae Kondo, Ohtake-shi, Japan, assignors to Mitsubishi Rayon Co., Ltd., Tokyo, Japan, a corporation of Japan Filed Aug. 2, 1966, Ser. No. 569,685 Claims priority, application Japan, Aug. 3, 1965, 40/47,040 Int. Cl. D01f 3/12, 3/28 US. Cl. 264-197 1 Claim ABSTRACT OF THE DISCLOSURE A viscose having 'y-value of above 55 is extruded into a coagulation bath containing from 8 to g./l. of sulfuric acid, from 0.05 to 1.5 g./l. of zinc sulfate and from 10 to 150 g./l. of sodium sulfate and kept at a temperature of below C. Filaments thus formed are withdrawn from the coagulation bath in a state where the value of the filaments is above and then stretched while immersed in a second bath containing less than 3 g./l. sulfuric acid, from 0.05 to 3 g./l. zinc sulfate and sodium sulfate. The stretched filaments are then completely regenerated in the third bath. The resulting fibers have high knot tenacity, high loop tenacity, high fibrillation resistance and excellent dyeability.

The present invention relates to process for producing polynosic fibers having high tenacity, high knot tenacity, high loop tenacity, high wet modulus, high fibrillation resistance and excellent dyeability.

Conventional viscose fibers have such defects as inferior mechanical property in wet state, poor alkali resistance and low dimensional stability. Accordingly, various proposals have been made with a view to improve those defects and to produce viscose fibers having similar characteristics to that of cotton. These proposals can be roughly classified into two processes: one of them is such a process in accordance with Japanese Pat. No. 172,865, which comprises extruding a viscose containing cellulose of high polymerization degree into a coagulation bath of low acid concentration. Viscose fibers produced according to this process are called polynosic fiber. Polynosic fiber shows high wet modulus and high alkali resistance, and subsequently high dimensional stability. On the contrary, however, such fiber tends to be brittle due to its low elongation and low loop tenacity. And this brittleness results in the low processability in spinning and weaving, and flex abrasion resistance of the fabric is not satis factory. Another drawback of the polynosic fiber is the fact that it easily fibrillates. That is, when the fiber is abraded in wet state, twig-like fibrils are formed on the fiber surface. This phenomenon is observed, for example, during the dyeing process of the fabric, which not only results in impairing the shade of the dyed fabric but also produces troubles in wearing. The other is such a process as disclosed in Belgian Pat. No. 625,824, which comprises extruding a viscose containing modifier such as amine or polyalkyleneoxide into a coagulation bath containing comparatively small amounts of salts. Viscose fibers produced in acoordance with this process are called High Wet Modulus Fiber, which are generally distinguished from polynosic fiber. The characteristic features of High Wet Modulus Fiber resides in that they have suitably high elongation and excellent lateral properties of the fiber such as loop tenacity and that they are not brittle and have little tendency to fibrillation, and therefore it is ditferent from polynosic fiber in these points.

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High Wet Modulus Fiber, however, are not satisfied insofar as wet modulus and alkali resistance are concerned.

As regards polynosic fiber, a number of improved methods have been thereafter proposed, and as a result, polynosic fibers of fairly good properties are presently being marketed. However, the polynosic fibers are still found unsatisfactory insofar as the lateral properties of the fiber such as loop tenacity and fibrillation resistance are concerned.

An object of the present invention is to provide fibers having high knot tenacity, high loop tenacity, high fibrillation resistance and excellent dyeability without spoiling the characteristic features of polynosic fiber, and a process for producing such fibers. More particularly the object of the present invention is to provide polynosic fibers having wet tenacity of 3.4 to 5.0 g./d., wet modulus of 1.0 to 2.0 g./d. at 5% elongation, loop tenacity of 2.0 to 4.0 g./d., fibrillation degree of below 20, and solubility of less than 70% in 2 N sodium hydroxide solution at 20 C. after ethanolysis. Still further object of the present invention is to provide a process for producing these polynosic fibers.

The above-mentioned objects of the present invention can be achieved by extruding a viscose having 'y-value of more than 55 into a coagulation bath containing from 8 to 25 g./l. of sulfuric acid, from 0.05 to 1.5 g./l. of zinc sulfate and from 10 to 150 g./l. of sodium sulfate and kept at a temperature of below 35 C., withdrawing the filaments thus formed, in a state where *y-Vtilllfi of the filaments is above 40, introducing the filaments in an state where -value of the filaments is above 30 into the second bath containing sulfuric acid, zinc sulfate and sodium sulfate, the concentration of said sulfuric acid being less than 3 g./l., that of zinc sulfate being from 0.05 to 3 g./l. and the sum of the concentrations of the zinc sulfate and the sodium sulfate being from 0.5 to 60 g./l., introducing the resultant filaments into the third bath to complete regeneration and then subjecting the filaments of aftertreatment by usual method.

It is considered that the brittleness and fibrillation properties of polynosic fiber are attributed to high molecular orientation, high crystallinity and high fibrillar structure which are formed through slow coagulation and regeneration of the viscose extruded into a coagulation bath and subsequent high stretch of the filament. It can be considered, however, that according to the present invention the filaments withdrawn from the coagulation bath are introduced into the second bath containing limited concentration of zinc sulfate, sodium sulfate and very low concentration of sulfuric acid, so that the outer layer of the filaments are subjected to swelling treatment with alkali contained in the interior of said filaments to relieve their excessively orientated structure, thereby producing filaments having excellent properties, for example, high fibrillation resistance and non-brittleness without spoiling the characteristic features of polynosic fiber.

The fibers in accordance with the present invention are excellent not only in mechanical property and fibrillation resistance but also in alkali resistance and dyeability. These are great characteristic features of the present invention.

In accordance with the present invention, either high grade or common pulp can be used. Ageing of alkali cellulose is carried out according to a desired polymerization degree of cellulose. The polymerization degree of cellulose in viscose is preferably above 350, more preferably from 400 to 650.

From the standpoint of spinnabili-ty, preferable viscosity of viscose on spinning is from to 1000 poises at 20 C., more preferably from 200 to 600 poises. The

concentration of cellulose in viscose is determined in accordance with the polymerization degree of the cellulose, and it is usually from 4 to 8%. The alkali concentration in viscose is preferably from 2 to When the alkali concentration is above 5%, the desirable concentration of sulfuric acid in the coagulation bath becomes higher, thereby reducing swelling of the filaments in the second bath. The 'y-value of viscose on spinning must be above 55. When the 'y-value is below 55, that of the filaments introduced into the second bath becomes too W, that is, an amount of cellulose xanthate in the filaments decreases, and on this count swelling of the filaments becomes insufficient, and the 'y-value of viscose is preferably above 65.

In order to carry out spinning operation more easily and improve the fiber properties, surface active agent soluble in viscose and insoluble in coagulation bath, may be added to viscose. As surface active agents, those having the following general formulas are preferably employed:

wherein R is an alkyl group having more than 8 carbon atoms, M is hydrogen, alkali metal or organic base, m is an integer of 1 or 2, n is an integer not greater than 2 and x is 1 in case m=1 and 0 in case m==2,

wherein X is an alkylene group having from 1 to 3 carbon atoms, at least one member of the group consisting of Y, Y and Y" is a (CH ),,COOM group and the remainder is hydrogen atoms. R and R are alkyl groups having more than 7 carbon atoms, acyl groups or hydrogen atoms, but there is no case where R and R are simultaneously hydrogen atoms. M is hydrogen or alkali metal, In is 0 or a positive integer and n is an integer not greater than 2, and

RCONX (CH CO OM wherein R is a saturated or unsaturated hydrocarbon radical having from 7 to 17 carbon atoms, X is a hydrogen or lower alkyl group, M is a hydrogen or alkali metal and n is an integer of 1 or 2.

The amount of surface active agent to be added is from 0.05 to 0.3% based on the weight of viscose.

The concentration of the sulfuric acid in the coagulation bath must be from 8 to 25 g./l. When the concentration of sulfuric acid is below 8 g./l., the spinning becomes difiicult, on the contrary when the concentration of sulfuric acid is above 25 g./l., the concentration of acid adhered to the filaments withdrawn from the coagulation bath becomes excessively high and on this account swelling of the filaments in the second bath becomes insufiicient. The concentration of zinc sulfate in the coagulation bath is one of the most important factors of the present invention. Said concentration must be from 0.05 to 1.5 g./l.

It is presumed that the action of the zinc sulfate is to form a thin film of zinc xanthate on the surfaces of the filaments formed in the coagulation bath and the resultant thin film is to control the diffusion of acid into the interior of the filaments, thereby promoting the swelling of the filaments in the second bath with alkali present in the interior of said filaments. When the concentration of zinc sulfate is below 0.05 g./l., the formation of zinc Xanthate film is insufficient and thereby the effect of the second bath cannot be exhibited. On the contrary, when said concentration is above 1.5 g./ 1., the Youngs modulus of the fibers to be obtained decreases.

Suitable concentration of sodium sulfate is from 10 to 150 g./l. and the concentration below 10 g./l. is economically undesirable. On the contrary, when said concentration is above 150 g./l., the fiber properties become inferior.

Optimum temperature of coagulation bath is below 35 C., preferably below 25 C. When the temperature is elevated above 35 C., the value of filaments in coagulation bath excessively falls. The immersion length of the coagulation bath is determined in connection with composition and temperature of the coagulation bath, spinning speed and the like, hence it cannot be indiscriminately defined. But it is preferred to be as short as possible.

The filaments formed in a coagulation bath are withdrawn from the coagulation bath in such a state where the 'y-value of said filaments is above 40, and then they are introduced into the second bath containing sulfuric acid, zinc sulfate and sodium sulfate in a state where said filaments have a 'y-value of above 30. The concentration of the sulfuric acid in the second bath must be below 3 g./l., that of the zinc sulfate must be from 0.005 to 3 g./l. and the sum of the concentrations of the zinc sulfate and the sodium sulfate must be from 0.5 to 60 g./l. When the concentrations of sulfuric acid, zinc sulfate and sodium sulfate in the second bath deviate respectively from the above-mentioned ranges, swelling effect of the second bath cannot be sufficiently exhibited and thereby the object of the present invention cannot be accomplished.

In the present invention, as the concentration of sulfuric acid in the second bath is very low, swelling of the filaments becomes excessively large in case salts are not present in the second bath, and thereby the properties of the fibers obtained become inferior. However, an excessively high concentration of salts is not desirable because the swelling effect of alkali is restrained. In the present invention, especially the effect of the zinc sulfate in the second bath is remarkable. This is considered to be attributable to that besides a proper swelling restraining action, zinc sulfate controls the decomposition of the zinc xanthate on the surface of the filaments formed in the coagulation bath to make swelling of the filaments effective.

Temperature of the second bath is normally above 50 C., preferably above C. particularly when formaldehyde is contained in the coagulation bath.

According to the present invention, the filaments withdrawn from the coagulation bath are introduced in a state where its v-value is above 40 into the second bath in which the concentration of sulfuric acid is below 3 g./l., that of zinc sulfate is from 0.05 to 3 g./l. and the sum of the concentrations of the zinc sulfate and the sodium sulfate is from 0.5 to 50 -g./l. and stretched in said bath.

In order to promote the effect of the second bath and to make the prevention of the mutual adhesion of the filaments more easily, the filaments withdrawn from the coagulation bath may be immediately treated with a diluted aqueous solution of heavy metal salt and then introduced into the second bath. As heavy metal salt, cadanium sulfate and nickel sulfate are preferable. The concentration of heavy metal salt is preferably from 0.2 to 1 g./l. Temperature of an aqueous solution of heavy metal salt is preferably below room temperature.

The filaments withdrawn from the second bath, if necessary after cutting, are introduced into the third bath (regeneration bath). In the third bath, the filaments are completely regenerated. As the third bath, an aqueous bath containing from 2 to 15 g./l. of sulfuric acid and kept at a temperature above 80 C. is preferably employed.

In accordance with the present invention, when formaldehyde is not added to the coagulation bath, it is possible to produce polynosic fibers having from 3.4 to 5.0 g./d. of wet tenacity, from 1.0 to 2.0 g./d. of wet modulus at 5% elongation, from 2.0 to 4.0 g./d. of loop tenacity fibrillation degree of below 20 and solubility of lower than 70% in 2 N sodium hydroxide solution at 20 C. after ethanolysis.

FIGS. 1-3 show the relation between concentration of sulfuric acid in the second bath and fiber property.

FIGS. 4-6 show the state of fibrillation of fibers. The present invention is illustrated by referring to the following examples, but the scope of the present inven- 6 FIGS. 46 are photographs showing states of fibrillation of fibers obtained by the procedure for measuring the fibrillation degree. From these photographs, it is seen that the fibers produced according to the present invention are less prone to fibrillation.

tion is not limited by these examples. In these examples, 5 EXAMPLE 2 the stretch rate is expressed as percent of the length of the stretched filament to its original length. The same n t Example l rvas extn id d into a coagu ation at containing 4 g. o sul uric EXAMPLE 1 acid, 75 g./l. of sodium sulfate and 0.3 g./l. of zinc sul- Alkali cellulose was prepared from wood pulp ac- 1O fate and kept at 20 C., through a spinneret having 12,000 cording to usual method. After aging, the resultant alkali orifices of 0.06 mm. diameter. cellulose was xanthated with 57% of carbon disulfide The filaments withdrawn from the coagulation bath, based on the weight of cellulose. The Xanthate was disof which the immersion length was 30 cm., were immesolved in dilute aqueous sodium hydroxide solution to diately introduced into the second bath containing 1.5 obtain viscose containing 6.5% of cellulose, the polymg./l. of sulfuric acid, 7 g./l. of sodium sulfate and 0.3 erization degree of the cellulose was 480, and 3.9% of g./l. of zinc sulfate and kept at 90 C., and stretched to total alkali. The viscose was then filtered, deaerated and 240%. The 'y-value of the filaments introduced into the ripened to obtain a viscosity of 320 poises at C. second bath was 53. The spinning speed was 15 m./min. and 'y-value of 81. Through a spinneret having 12,000 20 The stretched filaments were withdrawn from the second orifices of 0.06 mm. diameter, the resultant viscose was bath and then passed through a bath having the same extruded into a coagulation bath containing 15 g/l. of composition and temperature as in the second bath withsulfuric acid, 60 g./l. of sodium sulfate and 0.6 g./l. of out stretching, and thereafter, passed through the third zinc sulfate and kept at 20 C. The filaments withdrawn bath containing 5 g./l. of sulfuric acid and kept at 85 C. from the coagulation bath, of which the immersion length to complete regeneration. The properties of the fibers thus was cm., were immediately introduced into the second obtained (A) are shown in the following table, compared bath containing 1 g./1. of sulfuric acid, 15 g./l. of sodium with those of the fibers (B) obtained in the same manner sulfate and 0.4 g./l. of zinc sulfate and kept at 90 C., as in this example except that zinc sulfate was not conand then stretched to 250%. The 'y-value of the filaments tained in the coagulation bath.

Solubility in 2 N N aOH et solution Dry Wet Dry knot Loop modulus at Dye (20 C.) after tenacity, elongation, tenacity, tenacity, 5% elongaabsorption, Fibrllla ethanolysis, Denier g./d. percent g./d. g. tion g./d. percent tion degree percent (A) 1. 2 4. 3 13 3. 2 2. s 1. 4 83 15 63 (B) 1. 2 4. 0 7 1. 3 0. 9 2.1 56 52 55 introduced into the second bath was 52. The spinning EXAMPLE 3 speed was 15 m./minute. The filaments withdrawn from the second bath were introduced into the third bath con- 40 Alkali Cellulose Was P p from Wood P p r taining 5 g./l. of sulfuric acid and kept at 85 C. to coming to 1131131 method- After aging, the l'fisultant alkali plete regeneration, and then subjected to after-treatment 0611111056 Was Xal'lthated With 60% 0f Carbon dislllfide i accordance i h h 1151131 h d based on the weight of the cellulose. The xanthate was dis- The properties of the fib r (A) thus obtained were solved in aqueous sodium hydroxide solution to obtain vis- Shown in the f ll i table, compared with those f cose containing 5.5% of cellulose, the polymerization depolynosic fibers being marketed and those of fi be 's gree Of the cellulose Was and Of total alkali. represented i (c), as a comparative example, b i d This viscose was filtered, deaerated and ripened to obtain in th Same manner as i thi example except th t th a viscosity of 390 poises and 'y-value of 88. The viscose concentration of the sulfuric acid in the second bath Was was extruded through a spinneret having 18,000 r fi 10 g./l. of 0.06 mm. diameter, into a coagulation bath containing Wet tenacity alter Solubility in Dry treated 2 N NaOH Dry Wet Dry Wet knot Loop Wet modwith 5% solution tenaetenacelongaelongatenactenaculus at NaOH Water Dye ab- (20 C.) after ity, ity, tion, tion, 'y, ity, 5% elongasolution, swelling, sorption, Fibrillation ethanolysis, Denier g./d. g./d. percent percent g./d. g./d. tion, g./d. g./d percent percent degree percent (A) 1.2 4.7 3.9 13 15 3.5 3.2 1.2 3.6 74 87 11(F1o.4) 56 (B)--- 1.2 4.2 3.1 11 13 1.3 1.5 1.2 2.4 69 55. 78 (FIG. 5) 75 (0)... 1.2 4.9 4.0 11 12 1.6 1.3 1.4 3.4 66 4s 70 (FIG. 6) 72 Fibrillation degree: Number of twig-like fibrils ob- 13 g./l. of sulfuric acid, g./l. of sodium sulfate and served for a length of 1.5 mm. of sample fiber obtained 0.4 g./l. of zinc sulfate and kept at 21 C. The filaments by cutting fiber in 5 mm. length and then crushing the 65 withdrawn from the coagulation bath, of which the immercut fiber with a domestic mixer (320W, 3,000 r.-p.m.) for sion length was 35 cm, were immediately introduced into 15 minutes together with water 10,000 times the amount the second bath containing 0.8 g./l. of sulfuric acid, 10 of the fibers at 20 C. g./l. of sodium sulfate and 0.5 g./l. of zinc sulfate and Ethanolysis conditions: 1 g. of sample fiber is sub kept at 90 C., and then stretched to 225%. The y-value jected to depolymerization in 100 cc. of ethanol solution of the filaments introduced into the second bath was 58. containing 5% by volume of 3.5 N HCl aqueous solution The spinning speed was 13 m./minute. The filaments at C. for6hours. withdrawn from the second bath were introduced into FIGS. l-3 show the relation of the properties of the the third bath containing 5 g./l. of sulfuric acid and fiber obtained by the same method as in this example kept at C. to complete regeneration. except that the concentration of sulfuric acid in the s'ec- 75 The properties of the fibers thus obtained (A) are 0nd bath is varied within a range of less than 10 g./l.

shown in the following table, compared with those of the filaments (B) obtained in the same manner as in this example except that the filaments are withdrawn from the coagulation bath, regenerated in the air until the 7- value of the filaments reaches 29 and then introduced into the second bath to stretch to 210%.

8 acid, 10 g./l. of sodium sulfate and 0.2 g./l. of zinc sulfate and kept at 90 C. and stretched to 240%. The spinning speed was 20 m./minute. The filaments withdrawn from the second bath were introduced into the third bath containing 5 g./l. of sulfuric acid and kept at 80 C. to

Solubility Wet; in 2 N NaQH modulus at solution Vet Wet Dry knot Loop 5% elonga- Dye v (20 C.) after tenacity, elongation, tenacity, tenacity, ation absorption, Fibrillaetlianolysls,

Denier g./d. percent g./d. g./d. g./d. percent tion degree percent EXAMPLE'4 15 complete regeneration and then subjected to after-treat- Alkali cellulose was prepared from wood pulp according to usual method. After ageing, the resultant alkali cellulose was xanthated with 60% of carbon disulfide based on the weight of cellulose. To the xanthate, 0.05% of N,N'-dioctyltriethylenetetramine monoacetate (Na salt) based on the weight of the viscose was added together with aqueous sodium hydroxide solution and water to obtain a viscose containing 6.5% of cellulose, the polymerization degree of the cellulose 'was 490 and 4.1% of total alkali. This viscose was filtered, deaerated and ripened to obtain a viscosity of 310 poises and 'y-value of 87. The viscose was extruded through a spinneret having 12,000 orifices of 0.06 mm. diameter, into a coagulation bath containing 13 g./l. of sulfuric acid, 70 g./l. of sodium sulfate and 0.6 g./l. of zinc sulfate and kept at 22 C. The filaments withdrawn from the coagulation bath were immediately introduced into the second bath containing 0.1 g./l. of sulfuric acid, 2.0 g./l. of sodium sulfate and 0.2 g./l. of Zinc sulfate and kept at 90 C., and stretched to 255%. The 'y-value of the filaments introduced into the second bath was 59. The spinning speed was 23 m./minute. The filaments withdrawn from the second bath were introduced into the third bath containing 3 g./l. of sulfuric acid and kept at 80 C. to complete regeneration and then subjected to after-treatment according to usual method.

The properties of the fibers thus obtained are shown in the following table.

Denier 1.1 Dry tenacity, g./d. 4.3 Wet tenacity, g./d. 3.5 Dry elongation, percent 12 Wet elongation, percent 16 Dry knot tenacity, g./d. 3.6 Loop tenacity, g./d. 3.7 Wet modulus at 5% elongation, g./d 1.3 Wet tenacity after treated with 5% NaOH solution,

g./d. 3.2 Dye absorption, percent 92 Fibrillation degree 5 Solubility in 2 N NaOH solution C.) after ethanolysis, percent 54 EXAMPLE 5 The alkali cellulose obtained in the same manner as in the Example 1 was xanthated without ageing, with 65% of carbon disulfide based on the weight of the cellulose. The resultant alkali cellulose was xanthatized. To the xanthate, 0.1% of sodium N-lauryl B-iminopropionic acid based on the weight of the cellulose was added together with aqueous sodium hydroxide solution and water to obtain a viscose containing 5.5% of cellulose, and 3.3% of total alkali. The viscosity of the viscose was 280 poises, the 'y-value was 86, and the polymerization degree of the cellulose was 520 on spinning. The viscose was extruded into a coagulation bath containing 13 g./l. of sulfuric acid, 70 g./l. of sodium sulfate and 0.5 g./l. of zinc sulfate and kept at 20 C., and the resultant filaments were withdrawn from the coagulation bath, immediately introduced into the second bath containing 0.3 g./l. of sulfuric Inent according to usual method.

The properties of the fibers thus obtained are shown as follows:

Denier 1.1 Dry tenacity, g./d. 4.7 Wet tenacity, g./d. 4.0 Dry elongation, percent 13 Wet elongation, percent 15 Dry knot tenacity, g./d. 3.9 Loop tenacity, g./d. 3.6 Wet modulus, at 5% elongation, g./d. 1.3 Dye absorption, percent Fibrillation degree 6 Solubility in 2 N NaOH solution (20 C.) after ethanolysis, percent 56 What is claimed is:

1. A process for producing polynosic fibers characterized by extruding a viscous having 'y-value of above 55 into a coagulation bath substantially free of formaldehyde containing from 8 to 25 g./l. of sulfuric acid, from 0.05 to 1.5 g./l. of zinc sulfate and from 10 to g./l.

of sodium sulfate and kept at a temperature below 35 C., Withdrawing the filaments thus formed from the coagulation bath in a state where the 'y-value of the filaments is above 40, treating said filaments With a dilute aqueous solution containing about 0.2 to 1.0 g./l. of a heavy metal salt selected from the group consisting of cadmium sulfate and nickel sulfate maintained at a temperature below room temperature, immediately introducing the resulting filaments into a second bath containing less than 3 g./l. sulfuric acid, from 0.05 to 3 g./l. zinc sulfate and sodium sulfate, the sum of the concentrations of the Zinc sulfate and the sodium sulfate being from 0.5 to 50 g./l. in a state where 'y-value of the filaments is above 30, stretching the filaments more than 150% while immersed in said second bath, withdrawing the stretched filaments and then introducing the filaments into a third bath to complete regeneration.

References Cited UNITED STATES PATENTS 2,860,480 11/1958 Cox 264-197 X 3,038,778 6/1962 Daimler et al.

3,084,021 4/1963 Movimoto 264-197 X 3,139,467 6/1964 Drisch.

3,226,461 12/1965 Wise et al 264-197 X 3,324,216 6/1967 Imoshita et al.

3,341,645 9/1967 Horiuchi et al. 264-197X 3,351,696 11/1967 Drisch 264-197 X 3,352,957 11/1967 Drisch 264-197 X 3,381,075 4/1968 Tonami et al 264-193 3,388,117 6/1'968 Roberts et a1 264-191 3,320,117 9/1967 Aok, et al. 162-157 3,419,652 12/1968 Kubota et a1 264-168 JULIUS FROME, Primary Examiner J. H. WOO, Assistant Examiner U.S. Cl. X.R. 264- UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 79 Dated NOV. 7

Yukio Kimura et al Inventor(s) It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In the heading to the printed specification line 10 after "40/47 ,040 insert August 23 1965 40/51 ,359

and November 5 1965 +O/67 ,863

Signed and sealed this 11th day of April 1972 (SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Paten' 1 FORM PO-IOSO (10-69)