US1979929A - Process of treating artificial threads - Google Patents

Description

Patented Nov. 6, 19 34 UNITED PROCESS OF TREATING ARTIFICIAL CilHREADS Thomas F. Banigan, Buffalo, N. Y., assignor to Du Pont Rayon Company, New York, N. Y., a corporation of Delaware No Drawing. Application February 12, 1930, Serial No. 427,962

4 Claims.

This invention relates to a process of treating artificial threads. More particularly, it relates to purifying, such as desulphuring and bleaching, artificial threads produced by the viscose,

1 5" method.

In the manufacture of artificial silk by the viscose method it is the practice to spin the viscose solution through fine orifices into a coagulating bath and receive the thread on a collection device, such as a bobbin or rapidly rotating bucket. The freshly spun thread is then treated for the removal of the adhering coagulating bath liquor and subsequently with a desulphuring solution, whereby the sulphur impurities produced in the spinning operation are eliminated. The thread is finally washed and dried. If the thread is to be bleached, this operation is carried out on skeins of the previously dried thread.

The washing and desulphuring treatments are commonly carried outwhile the thread is on the bobbin by the drip method wherein water or other suitable solutions are permitted to drip over the thread, until the desired result has been effected. Processes have already been proposed for the ::treatment of the thread on perforated bobbins wherein the washing and desulphuring operations are effected by pressure or vacuum treatment. In

such processes the cleansing or purifying liquid is forced through the layers of the wound thread. In addition to being slow and tedious, none of 'the drip purifying processes are practical when the spinning is carried out under considerable tension and wherein a very compact and tightly wound cake of thread is formed on the bobbin. -The pressure method of desulphuring artificial thread wound on bobbins, particularly if the artificial thread has been wound under considerable tension, has many serious disadvantages. To obtain good desulphuring it is necessary to 40 flow a considerable amount of the desulphuring liquid through the cake of artificial thread on the bobbin. Artificial thread wound on bobbins forms an exceedingly effective filter. Thus, unless the desulphuring liquid is perfectly clean, and this is exceedingly difficult in actual practice, the ar- 'tificial thread becomes contaminated by the filtering out and depositing on itself of the impurities suspended in the treating liquid. This danger of contamination is true in the case of either .low or high tension spun artificial thread but much more so in the latter case. The treatment of the artificial thread tightly wound on bobbins has also been rendered very difficult by the inability to obtain sufiloient fiow through the cake 554 :to maintain the uniformity of temperature throughout the cake necessary for uniform desulphuring of all parts of the cake. In addition, these processes necessitate the use of comparatively high liquid pressure as, for instance, 15-50 pounds per square inch, and the provision of equipment for producing and withstanding these pressures. The equipment must therefore be made elaborate and at the same time be constructed of special materials capable of withstanding the chemical action of the desulpuring liquid. The use of pressure or vacuum desulphuring therefore becomes very costly and uneconornioal.

I have found that I can eliminate the above disadvantages and provide a very effective method of desulphuring artificial thread, particularly that tightly wound on a bobbin, by the simple process of immersing the thread in a suitable purifying solution for a sufficient time to insure the complete purification of the thread.

It is therefore an object of this invention to provide a simple process of purifying artificial thread produced by the viscose process and which consists in immersing the thread in a purifying solution.

Another object of this invention is to provide a method of desulphuring artificial thread produced by the viscose process which consists in immersing the thread tightly wound on bobbins in a desulphuring solution for a sufficient time to insure a complete removal of the sulphur impurities.

Additional objects will appear from the following description and appended claims.

According to one mode of practicing this invention, the viscose solution is spun in the usual manner and, after coagulation and regeneration of the cellulose, the freshly spun thread is received on a bobbin. The thread on the bobbin is then washed with water in any suitable manner to remove the adhering coagulating bath and/or regenerated bath liquors. The thus washed thread, while it is on the bobbin, is immersed in a desulphuring solution and maintained therein for a sufficient length of time until the desired result is obtained without employing any additional operations to induce fiow of said solution through said cake. In treating thread produced in a method of utilizing considerable tension, it is preferable to dry the thread prior to desulphuring and subsequent to washing. By such treatment the swollen cellulose hydrate is converted into a more compact thread of cellulose and a large number of voids are provided in the cake. This condition of the thread permits a more ready penetration of the desulphuring solution. Furthermore, since the cake is dried, the concentradetails of manipulation and treatment, the intion of the desulphuring solution in contact with the thread is not diluted and the operation is permitted to be more expeditiously performed.

Any of the common and well known solutions may be used as a desulphuring solution. In case aluminum bobbins or other apparatus made of aluminum are employed, it is preferable to use a desulphuring solution comprising 0.1% to 0.5% of sodium sulphide and sodium silicate in such proportions as to produce 0.05% to 0.5% of silica.

The process may be operated at any convenient temperature such as, for instance, approximately 40 0., although it is clear that the temperature and/or the concentration of the solution maybe varied to suit different purposes.

It is apparent that the method previously described is simple in operation and. very economical. In addition to desulphuring tightly wound artificial thread without the necessity of incur-V ring the expense of converting the thread into skeins before treatment, the herein-described method produces a much improved thread. The presence of small amounts of insoluble impurities in the purifying liquid does not affect the process. Only a small amount of treating liquid enters the cake; hence a comparatively small amount of impurity is introduced and. capable of being deposited on the rayon.

While this invention has been described with particular regard to desulphuring of tightly wound artificial thread on bobbins, it is clear that the principles of this invention may also be applied in the bleaching process in a similar manner or to any of the purification or finishing opera- Itions that may be desired. Furthermore, the invention may be successfully used in the treatment of threads in the form of bucket cakes or any other form of freshly spun artificial thread.

Since it is obvious that various modifications and changes may be made in the above specific vention is not restricted thereto except as set forth in the appended claims.

I claim:

1. In a method of producing artificial thread by the Viscose process, the steps of washing a cake of thread, drying said cake, immersing said cake in a purifying solution and maintaining the cake in said solution until the desired results have been obtained without employing any additional operations to induce the flow of said solution through said cake.

2. In a method of producing artificial thread by the viscose process, the steps which consist in washing a cake of tightly wound thread, drying said cake, immersing said cake in a desulphuring solution and maintaining the cake in said solution until the desired results have been obtained without employing any additional operations to induce the flow of said solution through said cake.

3. In a method of producing artificial thread by the viscose process, the steps of winding freshly produced thread on to a bobbin, subjecting the thread on the bobbin to a Washingtreatment, drying the thus washed thread, immersing the dried thread and the bobbin on which it is wound in a purifying solution and maintaining the cake in said solution until the desired results have been obtained Without employing any additional operations to induce the flow of said solution THOMAS F. BANIGAN.