US3494995A - Method for spinning viscose - Google Patents

Description

FelxlO, 1970 1'. RMNER ETAL 3,424,

METHOD FOR SPINNING VISCOSE Original Filed Aug. 1. 1966 INVENTOR r :2:

United States Patent 3,494,995 METHOD FOR SPINNING VISCOSE Rainer Thomas, Wilfred Keiler, and Paul Weber, Siegburg,

Germany, assignors to PhIix-Werke Aktiengesellschaft, Hamburg, Germany Original application Aug. 1, 1966, Ser. No. 569,382.

Divided and this application Apr. 8, 1969, Ser.

No. 814,414 Claims priority, application Germany, Aug. 19, 1965,

Int. Cl. D0111 5/ l4; Dtllf 3/12 US. Cl. 264196 6 Claims ABSTRACT OF THE DISCLOSURE CROSS-REFERENCE TO RELATED APPLICATION The present application is a divisional application of the copending application Ser. No. 569,382, filed Aug. 1,

BACKGROUND OF THE INVENTION The present invention relates to a method for spinning viscose and, more particularly, the present invention is concerned with producing fibers, filaments, threads and yarns of regenerated cellulose.

It is known to use formaldehyde for stabilizing by methylolation, the cellulose xanthogenic acid which is formed by spinning viscose into an acidic, zinc-free spinning bath. By using highly substituted cellulose xanthogenates having gamma values higher than 80, it is possible in this manner to obtain threads which can be stretched in hot baths by between 300 and 500% and which possess great strength and extremely low extensibility. The methylolation will cause an improvement in the extensibility of the threads, however it will also cause several different problems during the regeneration of the cellulose.

The degree of substitution of the cellulose after stretching is considerably higher than if the spinning is carried out in the absence of formaldehyde. If one does not cause substantial splitting off of the residual xanthate groups while the spinning rope is still under tension, regeneration will take place only after cutting the rope or after spinning the endless filaments in a centrifuge, i.e., in untensioned condition. The decomposition of the residual xanthate in untensioned condition will cause a reduction in the orientation of the cellulose crystallites, which orientation had been caused previously by the stretching of the fiber, and this reduction of orientation will reduce the strength of the fibers and threads. Furthermore, fibers with an excessive residual substitution during decomposition in tensioned condition tend to form adhesions of the single capillaries into clogged fibers of relatively high titre.

Thus, the requirements made on the bath in which the stretching of the spun fibers is carried out are somewhat contradictory and difficult to comply with. On the one hand, the degree of decomposition of the xanthate should be low in order to permit maximum stretching of the rope, on the other hand, after the stretching, the xanthate should be decomposed as completely as possible while the rope is still under tension.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to overcome the above-discussed difficulties and disadvan tages connected with spinning and subsequent stretching of regenerated cellulose with utilization of a formaldehyde-containing spinning bath.

It is another object of the present invention to provide a method which will permit stretching of the yarn combined with decomposition of the xanthate while the yarn is still in tensioned condition, and which will permit carrying out the process in a simple and economical manner.

Other objects and advantages of the present invention will become apparent from a further reading of the description and of the appended claims.

With the above and other objects in view, the present invention provides in a method of producing spun bodies of regenerated cellulose, the steps of spinning viscose into a formaldehyde-containing precipitating bath so as to form a multiple of coagulated filaments, contacting the thus-formed coagulated filaments first with steam having a temperature of between 95 and 110 C., and thereafter with hot water of between about and C., and stretching the filaments, while the same are contacted by the steam and water, by between about 300 and 500% of their original length.

The present invention permits in a simple and effective manner to obtain maximum stretching of the filaments combined with decomposition of the xanthates while the filaments are still under tension.

The coagulated threads may be stretched in steam preferably having a temperature between about 95 and C., and in water preferably having a temperature of between 70 and 95 C. Stretching preferably may be by between 300 and 500% of the original length of the thread. Thereby it is preferred to pass the threads from contact with steam directly into contact with the hot water bath.

The provision of a short steaming device preceding the hot water bath will assure a favorable sequence of stretching and decomposition of the filaments. Preferably, steaming and hot water bath follow each other immediately so that the filaments leaving the steam atmosphere are directly introduced into the hot water whereby the zone in which predominantly stretching and the zone in which predominantly decomposition takes place will be determined by the deformability or plasticity of the filaments. Due to the fact that the zones of predominantly stretching of the filaments and of decomposition of the same change over into each other and partly overlap it is primarily the deformability of the filaments which determines the zone in which predominantly stretching is carried out. This direct and uninterrupted sequence of steaming and hot water treatment is therefore preferable to a treatment in which there is a clear separation between stretching and decomposition of the filaments, for instance as would be the case by interposition of a Withdrawal means between the steaming zone and the hot water bath.

The method of the present invention gives particularly good results in connection with conventional spinning methods according to which threads of unripened viscose containing between 4 and 7% cellulose, having an alkali factor of between 1.0 and 1.4 and a gamma value greater than 70 are spun into a cold, heavy metal salt-free spinning bath containing per liter between 60 and 90 grams sulfuric acid, between 1.5 and 15 grams formaldehyde, and between 100 and grams sodium sulfate, Particularly good results are obtained by maintaining the cellulose content of the unripened viscose at between 4.5 and 5.5, the alkali factor at between 1.25 and 1.35 and the gamma value higher than 80, and by maintaining the spinning bath at a temperature of between 23 and 27 C., whereby the spinning bath preferably will contain per liter between 68 and 72 grams of sulfuric acid, between and 17 grams formaldehyde and between 130 and 140 grams of sodium sulfate.

The results achieved by following the method of the present invention, including the stretching of the filaments in steam and hot water as well as the decomposition of the xanthogenates will be described in an example further below and by the analytical results given in Tables I and II with respect to the filaments after treating of the same in various stretching devices and prior to stretching.

Prior to introduction into the steam tube (D), the filaments contain considerable proportions of formaldehyde and sulfuric acid. The degree of substitution is high.

After passage through the steam tube (C) in which the filaments are completely stretched, formaldehyde content and acid content are still high and the degree of substitution has dropped to only 55% of its original value.

The formaldehyde and acid content will stabilize the methylolated cellulose xanthogenic acid during stretching in steam of for instance 99 C.

Since saturated steam is preferably used, the actual temperature of the steam will depend on barometric pressure and may be as low as about 95 C. However, it is also possible to use somewhat superheated steam up to a temperature of about 110 C. Thus, generally, the steaming with simultaneous stretching of the filaments will be carried out at a steam temperature of between about 95 and 110 C.

If the filaments are continually decomposed after the steam treatment and in untensioned condition, the previously high degree of orientation of the cellulose molecules will be reduced and thus the quality of the filaments will be impaired.

By stretching in a hot water bath, for instance of 87 C. and containing 3.9 grams per liter of sulfuric acid and 1.5 grams per liter of formaldehyde, without a preceding steaming of the filaments, different results will be obtained as indicated at (B).

The formaldehyde content of the filaments will be greatly reduced, the greater portion of the acid will be washed out and the decomposition of the methylolated cellulose xanthogenic acid will proceed to a considerable extent. Thus, under these conditions, the stabilizing etfect of formaldehyde and acid is not achieved and the decomposing etfect will dominate. For this reason, it is not possible to accomplish in a hot water bath alone stretching to such a high degree as can be achieved by stretching the filaments in a combintion of steam and hot water treatment, or by steam treatment alone, since the decomposition of the methylolated cellulose and xanthogenic acid proceeds much faster in the hot water bath than in the steam tube. The quality of the thus-obtained fibers is not as good as that obtained by the inventive combination of steam and hot water treatment.

By proceeding in accordance with the present invention, i.e., by combining steam treatment and hot water treatment during stretching and tensioning of the filaments complete decomposition of the cellulose xanthogenic acid will be achieved (A). A better fiber quality is obtained which is superior to that obtained by either using steam treatment alone or hot water treatment alone.

Furthermore, by stretching the filaments in contact with steam, the major portion of the hydrogen sulfide content of the filaments will be expelled. Thus, the undesirable interaction between hydrogen sulfide and formaldehyde which may lead to water insoluble polymers of thioformaldehyde will not take place during hot water treatment and thereby the content of the filaments on water insoluble sulfur compounds will be lower than that achieved by using only the hot Water bath and omitting the steam treatment.

A device for carrying out the process of the present invention preferably includes a steam tube formed of a material which is resistant against acid, formaldehyde and temperatures of up to 110 C., which tube is arranged between the top godet and a hot water bath. Preferably, the steam tube extends downwardly from the top godet to the hot water bath in vertical direction. If the lower end of the steam tube is immersed in the hot water bath, a hydraulically closed system is obtained and it is assured that the filaments will enter the hot water bath directly from the steaming zone.

Furthermore, preferably a direction changing means or roller is located in the hot water bath, which roller or the like, or other guide means, is not driven, so that between the first godet of the spinning device and the final withdrawal means the stretching is carried out in a stepless, continuous manner throughout the steaming and hot water zone. It is achieved thereby that more than of the total stretching of the filaments will take place in the steam tube which, as pointed out above, preferably is fed with saturated or low pressure steam, and the hot water bath will serve predominantly for decomposing the xanthate groups of the filaments.

The novel features which are considered as characteristic for the invention are set forth in particularly in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING The single figure of the drawing shows a schematic elevational view of a spinning device or arrangement in accordance with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to" the drawing, it will be seen that between the top godet 2 of the spinning device and hot water bath 5 a tube 3 is arranged communicating with steam conduit 4, and the filaments are passed through tube 3. For facilitating the initial operation of the device, the steam tube 3 preferably extends vertically between top godet 2 and hot water bath 5, so that the filaments can initially be passed under the force of gravity downwardly through steam tube 3. After passing through steam tube 3, the filaments are guided by non-driven direction changing roller -6 through hot water bath 5, and withdrawn by means of a final conventional withdrawal arrangement 7.

The invention will now be further described in the following example, with reference to the drawing, however, without limiting the invention to the specific details of the example.

Example Viscose containing 5.14% cellulose, and 6.4% sodium hydroxide which had been produced with 64.3% carbon disulfide, is spun at a gamma value of 88.0 and a viscosity of 113 seconds (dropping ball method), through a nozzle containing 3,600 openings of 60 microns diameter. The viscose is spun into an aqueous precipitating bath 10 maintained at a temperature of 24 C. and containing per liter 73.2 grams H 50 129 grams Na SO and 11.8 grams formaldehyde.

The filaments are immersed in the bath for a length of 12 centimeters. The thus-formed multiple filament of 3,600 individual filaments is withdrawn from the bath by means of a first godet 11, at a speed of 7 meters per minute, and passed over the top godet which rotates at 13 meters per minute. From thereon the filaments pass through a vertically arranged glass tube fed with low pressure steam of 99 C. and having an inner diameter duced in accordance with the present invention is immediately apparent.

TABLE IL-FIBER CHARACTERISTICS Breaking elongaof 30 mm. and a length of 800 mm. The lower end portion of the glass tube is immersed for a depth of 20 mm. into the hot water bath 5, the latter containing 3.9 grams per liter sulfuric acid and 1.5 grams per liter formaldehyde. In this manner the filaments pass immediately from the steaming zone 3 into the hot water bath 5 maintained at 87 C., and in bath 5 the direction of the filaments are changed by guide roller 6 by 90 degrees. The filaments pass through bath 5 for a length of 300 mm. The filaments are then passed to a conventional final Withdrawal means 7 which turns at a speed of 34.3 meters per minute.

The thus-obtained filaments are then cut in conventional manner into staple fibers of 40 mm. length and, without being desulfurized, decomposed in water of 79 C. and containing 2 grams of sulfuric acid per liter, and thereafter bleached, further treated in conventional manner and dried. The thus-obtained staple fibers were free of clogged fibers.

Staple fibers were also produced under similar conditions. However passage through the steam tube was eliminated and thus the filaments were stretched and decomposed only in hot water bath 5 having the composition and temperature described above. Stretching was carried out by 350% Again, the staple fibers were free of clogged single capillaries.

Again, under the same general operating conditions, staple fibers were produced by proceeding as described above, with passage of the filaments through the steam tube but eliminating the subsequent hot water bath. Stretching was carried out by 390%. The thus-obtained staple fibers did include clogged single capillaries.

Table 1 below gives the results of analytical determinations carried out with filaments which were produced according to the present invention by passing the filaments under tension through the steam tube and hot water bath 5. The analytical results obtained with the filaments produced according to the present invention are described under A.

Corresponding analytical results for filaments which were stretched only in hot water and produced without passage through the steam tube are indicated under B, and analytical results of filaments produced by passage through the steam tube but under elimination of the subsequent water bath are indicated under C. For purpose of comparison there are given also the analytical results obtained with filaments prior to being stretched and these results are indicated under D.

TABLE I.COHPOSITION OF FILAil/IENTS STRETCHED AS INDICATED [In percent by weight of cellulose content] Stretching Total Xanthate Formal- Method CS2 CS2 dehyde HzS H2804 The abbreviation Cond. is meant to denote that the fiber has been conditioned by being kept prior to testing for 24 hours at 22 C. and 65% relative humidity.

The abbreviation Rkm denotes the kilometric length, i.e., the length of the fiber of the same type which must be suspended from the fiber to be tested in order to break the latter.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other methods of spinning differing from the types described above.

While the invention has been illustrated and described as embodied in a spinning method for spinning regenerated cellulose, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing Will so fully reveal the gist of the present invention that others can be applying current knowledge readily adapt it for various applications without omitting features that, from the standpont of prior art, fairly constitute essential characeristics of the generic or specific aspects of this invention.

What is claimed as new and desired to be secured by Letters Patent is:

1. A method of spinning regenerated cellulose comprising the steps of extruding viscose into a formaldehyde containing precipitating bath so as to form a multiple of coagulated filaments; passing the thus-formed coagulated filaments through a steaming zone in which said filaments are contacted with steam having a temperature of between about and 110 (1.; directly passing said filaments from said steaming zone into, and substantially unsupported through, a watering zone in which the steamed filaments are contacted from all sides with hot water having a temperature of between 70 and 95 C.; and stretching said filaments during its passage through said steaming and watering zones to between about 300% and 500% of its original length.

2. A method as defined in claim -1, wherein said filaments pass through the steaming zone in downward direction.

3. A method as defined in claim 2, wherein said filaments pass through said watering zone in substantially horizontal direction.

4. A method of spinning regenerated cellulose as defined in claim 1, wherein said viscose is an unripened viscose having a cellulose content of between 4 and 7%, an alkali factor of between 1.0 and 1.4 and a gamma value greater than 70.

5. A method of spinning regenerated cellulose as defined in claim 4, wherein said precipitating bath is free of heavy metal salts and contains 60-90 grams of sulfuric acid, 5-15 grams of formaldehyde, and -150 grams of sodium sulfate per liter.

6. A method of spinning regenerated cellulose as defined in claim 5, wherein said viscose is an unripened viscose having a cellulose content of between 4.5 and 5.5%, an alkali factor of between 1.25 and 1.35 and a gamma value greater than 80, and 'wherein said precipitating bath is maintained at a temperature of between 25 and 27 C.

acid, between 10 and 13 grams formaldehyde, and between 130 and 140 grams sodium sulfate.

References Cited UNITED STATES PATENTS 8 2,666,976 1/1954 Olmer et a1 264-467 3,432,589 3/1969 Drisch 264-188 X JULIUS FROME, Primary Examiner 5 J. H. WOO, Assistant Examiner US. Cl. X.R.

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