US1625562A - Manufacture of artificial silk and the like - Google Patents

Description

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Patented Apr. 19, 1927.

UNITED STATES 1,625,562 PATENT OFFICE.

FREDERICK CARL NIEDERHAU 'SER AND ALFRED ERNEST SUNDERLAND, OF ROANOKE,

VIRGINIA, ASSIGNORS TO THE VISCOSE COMPANY, OF MARCUS HOOK, PENNSYL- VATNIA A CORPORATION OF PENNSYLVANIA.

MANUFACTURE OF ARTIFICIAL SILK AND THE LIKE.

No Drawing.

Our invention relates to an improvement in the process of manufacturing products such as artificial silk from a cellulosic solution, and particularly from solutions of cellulose xanthate or viscose. The object of our invention is to provide a setting bath with an ingredient which not only reduces the stringent action of'the usual acid constituent of the bath, but also has the effectof retarding crystallization of salts carried from the bath by a set product so that subsequent steps in the treatment of the latter may be carried out with greater latitude as regards time sequence, without impairing its quality or strength.

In the manufacture of products such as. artificial silkor the like-from cellulose solutions, e. g. as cellulose xanthate or viscose, the solution is introduced through suitable orifices into a so-called setting bath, which has the effect of converting the solution into products such as filaments having a certain body and tensile strength. Filaments thus formed are commonly led from the setting bat-h to suitable spinning apparatus, where a group of filaments is twisted together to form a thread which is thereafter subjected to subsequent treatment to remove all'traces' pf the bath and leave a thread of pure celluose.

The setting bath for viscose solution comprises a mineral acid, such as sulphuric acid, a salt such as sodium sulphate, and in some cases otheringredients such as zinc, etc. As the filament or strip emerges from the setting bath it carries with it certain of. the ingredients of the solution, e. g. the salt. If the filament be permitted to dry, or to stand for a sufiicient period to partially dry, the salt crystallizes, ruptures the filament walls, and thus weakens the product. It is necessary therefore to wash out the salt romptly in order to maintain the strength 0 thefilament. This requires a fairly rapid sequence of operations, which it is not always convenient or possible to complete in time to insure the best results. Moreover, the acid of the bath has a more or less stringent ac} tion on the cellulose and tends to weaken the filament and to impair the feel or quality of the product.

We have now discovered that by adding to the setting bath a suitable substance or substances, the stringency of the acid action Application filed November 9. 1920. Serial No. 422,783.

upon the filament may be reduced and the crystallization of the salt in the product after its Withdrawal from the setting bath may be greatly retarded, with the advantageous result that the subsequent steps of the process may be carried out with greater latitude as regards time sequence, and without deleterious efiect upon the product. In fact the product of our researches has proved to be of improved quality as regards not only tensile strength, but also flexibility, texture and softness to the touch.

Various substances have been found suitable for the purpose, such as soluble colloids or emulsoids, e. g. gelatine,'glue, gum acacie (tragacanth) gum dragon and agar agar. Particularly serviceable and economical are gelatine or glue. The proportions in which the ingredients may be added is variable, but we have found that about 2% of glue added to the usual bath produces excellent results. Thus, to a setting bath having the usual content of acid (say about 8 parts sulphuric acid) and salt (say about 15 parts sodium sulphate) a small quantity (say 2 parts) of glue is added to produce the desired result. This addition not only raises the specific gravity of the solution, but also increases its viscosity.

The product from such a bath may be kept for several days without crystalliza u tion of its contained salt or injury to its strength. Moreover, our experiments have disclosed that the stringent action of the acid in the bath is lessened, as borne out by the feel of the filaments, and also bystrength tests. Furthermore, a desirable cementing action results, that is to say, where a group of filaments emerging from the bathis spun into a twisted thread, which is subsequently reeled, while partially dry, there is less of the undesirable flufiing of the fibers on the reel, due to the fact that the glue serves to hold the fibers or filaments together during the subsequent treatment of the same after leaving the bath.

No difficulty is experienced in removing this ingredient from the product in the final washing steps to which the latter is subjected. In fact after the usual sulphiding operation not a trace is left in the thread.

Obviously, the proportions of the added ingredient to the usual setting elements of,

the bath may be varied, and wide latitude is possible in the choice of ingredients which will have the desired ell'ect.

\Ve therefore do not limit our invention to the substances mentioned, but claim as our invention 1. In the manufacture of cellulose products from a cellulosic solution, a setting bath into which the solution is projected and from which the set product is withdrawn, said bath comprising a crystalline reagent and a soluble colloid serving to materially retard the crystallization of said reagent in the set product withdrawn from the bath.

2. In the manufacture of cellulose prodducts from a cellulosic solution, a setting bath into which the solution is projected and from which the set product is withdrawn, said bath comprising a crystalline reagent and gelatinous material serving to material- 1y retard the crystallization 01' said reagent in the set product withdrawn from the bath. I

3. In the manufacture of cellulose products from a cellulosic solution, a setting hath into which the solution is projected and from which the set product 'is withdrawn, said bath comprising a salt, an acid, and a soluble colloid.

4. In the manufacture of cellulose products from a cellulosic solution, a setting bath into which the solution is projected and said bath comprising an acid reagent and a soluble colloid serving to reduce the stringent action of the acid upon the prodnot.

In testimony whereof we have signed our names to this specification.

FREDERICK CARL NIEDERHAUSER. ALFRED ERNEST SUNDERLAND.