US2136463A - Method of preparing tubular artificial textile threads - Google Patents

Description

Patented Nov. 15, 1938 UNITED STATES METHOD OF PREPARING TUBULAR ARTI- FICIAL TEXTILE THREADS Ren Picard, Lyon, and Ren Fays, Villcurbanne, France, assignors to Societe Alsa in Basle, a

corporation of Switzerland No Drawing. Application May 21, 1935, Serial No. 22,518. In France May 25, 1934 '7 Claims.

This invention relates to the manufacture of artificial threads and more particularly to a process of producing artificial textile threads in which each filament is less than 2 deniers and also is 5 tubular, i. e., has a continuous canal.

The regular production of an artificial silk or thread from viscose and of the type wherein each filament is provided with a continuous canal presents, as will be understood, very great difliculties, even when dealing with filaments of an ordinary denier, i. e., of at least 2 deniers. Prior to this invention, the production of a hollow filament having a continuous canal and a denier less than 2 was considered impossible.

The present invention relates to the manufacture of an artificial viscose silk in which each filament is provided with a continuous canal and is of a denier lower than 2 and, in an accessory way, to varying or modifying the feel of the product 0 thus obtained.

In copending application filed May2l, 1935, Serial No. 22,517, there is disclosed a process of producing from viscose an artificial silk or thread wherein each of the filaments is tubular. If the filament denier is to be smaller than 2, then the process described in the copending application must be supplemented by the instant invention, which contemplates the utilization of a spinning bath, the concentration of which depends on filament denier desired. Specifically, the higher the concentration of the bath, the smaller will be the filament produced.

In other words, we have found that by utilizing the principles of the process described in the oopending application, previously referred to, in

conjunction with a spinning bath of higher concentration than set forth in said application, we can produce threads of the same filament count,

each of the filaments, however, being of a denier less than 2.

British Patent No. 163,817, of February 27, 1920, which was filed before the invention of artificial threads with tubular filaments had been made, laid down in principle that the higher the acid concentration employed in the coagulating bath, the finer will be the filaments produced, and that the proportion of acid which is necessary with various thread sizes has been found to be approximately inversely proportional to the square root of the thread size. Related patents mention the possibility of replacing in this general formula a portion of the sulphuric acid by a suitable proportion of ammonium sulphate.

, On the other hand, the British patent specification No. 255,527 shows in a diagram the zones in which the concentration of the spinning bath should remain a function of the degree of ripening of the viscose, for the special case of a thread having tubular fibers of a beautiful brilliancy. The concentration is expressed in this specification by the specific gravity of the bath, or for a given content of sulphuric acid, bythe quantity of sodium sulphate which must be dissolved therein. Since the specification contains no reference to the titer of the elementary fiber, however,it is only logical to conclude that its subject matter relates to an elementary titer of more than 2 deniers, which was the most usual custom at that period.

The principle of the British patent specification No. 163,817 and the indications of the British patent specification No. 255,527 are no longer applicable when it is a matter of obtaining a thread having tubular fibers of a titer less than 2 deniers.

We have found that in this case the acidity of the bath should be increased but in a proportion other than that fixed by the British patent specification No. 163,817, and that the essential factor is the concentration of the bath and not its acidity. By concentration, we mean the weight of dissolved matter per liter, including the acid. According to our invention, the concentrations indicated in the British patent specification No. 255,527 being considered as applied to a thread having tubular fibers of 2 deniers, the said concentrations of sulphuric acid and sodium sulphate are to be increased by 20% at least, and preferably by between 25% and 30%, the saturation point being the sole limit, when the titer of the elementary fiber is 1 denier. The increase for the titers included between 1 and 2 deniers will be obtained by simple interpolation. It is evident that in all these cases, the ratio of the sulphuric acid to the dissolved sulphates remains constant, 1. e., approximately 1:15. This rule may, in this case, be extended to the filament of a half denier, although in practice it is already very difficult to go below one denier, in View of the fact that a filament of this titer represents a continuous tube of 9,000 meters in length and weighing only 1 gram.

In accordance with the principles of this invention, a viscose solution of the type which is employed in the manufacture of hollow filaments is spun into a spinning bath, hereafter more fully described. The coagulated and regenerated cellulose thread is then given a bath travel of not exceeding and preferably less than 25 centimeters. After withdrawal from the spinning bath the thread is given a travel in air of not less than centimeters to ensure substantially complete fixation before engaging the delivery roller. The thread is then wound up in any suitable manner as in a centrifugal spinning bucket.

It is to be noted that during the bath travel it is of advantage if the thread does not engage with any devices which impede the free travel of the thread. If the thread is to be stretched, this is preferably effected by suitable devices imposing the desired tension on the thread between the spinning bath and the delivery roller or beyond the latter.

The spinning bath contains sulphuric acid, sodium sulphate, and preferably also zinc sulphate. The concentration of the bath depends upon the filament-denier desired, 1. e. the higher the concentration of the bath, the smaller will be the filament produced. When a filament-denier of, for example, 1 is desired, the concentration of the bath is at least approximately 20% and preferably approximately 25% to 30% higher than the concentration of the bath employed in the production of filaments having a denier of 2. The bath concentration indicated in British patent specification No. 255,527 is considered as applied to a thread having tubular fibers of 2 deniers. The concentration of the bath which is to be used in the production of filaments having a denier other than 1 and less than 2 can be secured by interpolation from the concentrations herein given. For example, when a filament of 1.5 denier is desired, this can be secured by increasing the sodium sulphate-sulphuric acid concentration approximately 13.8%. In all cases the ratio of approximately 1 part of sulphuric acid to approximately 1.5 parts of sodium sulphate is maintained.

By way of illustration, comparative examples are given merely to indicate the results which the instant process renders it possible to obtain, and without limiting the invention thereto. To a viscose solution containing 7.3% cellulose and 4% caustic soda, sufiicient sodium carbonate is added to increase the total alkalinity to 7%. The viscose solution is then ripened for 73 hours at 13C. and thereafter spun. to produce 100 denier-100 filament threads, into one of the following aqueous bathsl Grams per liter a. Sulphuric acid 140.0 Sodium sulphate 220.0 Zinc sulphate 2.5

b. Sulphuric acid 180.0 Sodium sulphate 280.0

Zinc sulphate 2.5

In each instance, the thread is given a bath travel of 20 centimeters. Also, in each case the thread, on leaving the spinning bath, travels centimeters in the air before arriving at the delivery roller which delivers it at a speed of 60 meters into a centrifugal pot rotating at 5,000 revolutions per minute.

When bath a was used, spinning was difiicult and each of the filaments was not tubular. On the other hand, when bath 5" was employed, there was no difiiculty in spinning and each of the filaments was tubular.

Another illustrative example of the instant invention comprises spinning a viscose solution of the type previously mentioned in the following bath to produce a 100 denier-66 filament thread:

Grams per liter Sulphuric acid 160.0 Sodium sulphate 250.0 Zinc sulphate 2.5

ditlOl'lS.

The bath travel, travel in air, winding, etc. are the same as in the previous example.

In the example next preceding, no spinning difiiculties were encountered and each of the filaments was tubular.

It is to be understood that the invention is not restricted to the foregoing examples. The examples have been set forth to permit comparison of the results secured under three different con- It will be seen that, on this basis, assuming that the titer of the filament is 2 deniers, as stated hereinbefore, by an increase in the concentration (sulphuric acid and sodium sulphate) of 27.6% a diminution of the titer by 1 denier is obtained, while an increase of 13.8% secures a diminution of half a denier.

Using the concentration of Example 1 of British Patent 255,527 as the prior art bath, the following table gives the concentrations at the various percentage increases:

13.8% approximately 424 grams per liter 20.0% "approximately 448 grams per liter 25.0% appro-ximately 466 grams per liter 27.6% approximately 475 grams per liter 30.0% approximately 492 grams per liter These examples clearly show the necessity of adding a new factor to that which is indicated by the British Patent No. 163,817.

The threads obtained according to the present invention are characterized by an extraordinary suppleness, feel and curl. They provide noncreasing fabrics. They have a very particular interest when they are obtained in the form of slivers intended to be cut up into lengths to constitute artificial schappe, the said slivers being preferably obtained on a continuous frame in which the sliver is spun and undergoes all the subsequent treatments as far as final drying. Thus, it is readily possible to produce slivers of 100,000 deniers having fibers or" at most 1 denier, all provided with a continuous central channel. This spun material, having a Wooly appearance which has never before been attained, lends itself to numerous uses in fields into which artificia. silk has only rarely penetrated.

If instead of maintaining the ratio of the sulphuric acid to the sodium sulphate at the value given by British patent specification No. 255,527, the quantity of sodium sulphate which corresponds thereto is caused to vary slightly, for example, 20 grams per liter more or less, the feel of the thread is modified. Starting from the concentration giving average feel, if the proportion is increased, the softness diminishes and the curl increases; if it is lower, the converse takes place.

Since it is obvious that various changes and modifications may be made in the above description without departing from the nature or spirit thereof, this invention is not restricted thereto except as set forth in the appended claims.

We claim:

1. Artificial threads composed of a plurality of tubular regenerated cellulose filaments, each of said filaments being tubular throughout its length and of a denier less than 2.

2. Artificial threads composed of a plurality of tubular regenerated cellulose filaments, each of said filaments being tubular throughout its length and of a denier of l.

3. Artificial threads composed of a plurality of tubular regenerated cellulose filaments, each of said filaments being tubular throughout its length and of a denier of 1.5.

4. In a process of producing threads composed of filaments, each of which is tubular throughout its length and has a denier less than 2, the steps which comprise spinning a viscose solution capable of producing hollow filaments into a bath containing sulphuric acid and sodium sulphate in the ratio of approximately 1 part of sulphuric acid to 1.5 parts of sodium sulphate, the total quantity ofboth the said sulphuric acid and the said sodium sulphate being in excess of approximately 373 grams per liter, causing the thread to travel in said bath for a distance not in excess of centimeters, withdrawing the thread from said bath and causing it to travel in the air for a distance of not less than 150 centimeters.

5. In a process of producing threads composed of filaments, each of which is tubular throughout its length and has a denier less than 2, the steps which comprise spinning a viscose solution capable of producing hollow filaments into a bath containing sulphuric acid and sodium sulphate in the ratio of approximately 1 part of sulphuric acid to 1.5 parts of sodium sulphate, the total quantity of both the said sulphuric acid and the sodium sulphate being from approximately 410 to 492 grams per liter, causing the thread to travel in said bath for a distance not in excess or 25 centimeters, withdrawing the thread from said bath and causing it to travel in the air for a distance of not less than 150 centimeters.

6. In a process of producing threads composed of filaments, each of which is tubular throughout its length and has a denier less than 2, the step which comprises spinning a viscose solution capable of producing hollow filaments into a bath containing the following ingredients in approximately the following proportions:

Grams per liter Sulphuric acid 180.0 Sodium sulphate 280.0 Zinc sulphate 2.5

causing the thread to travel in said bath for a distance not in excess of 25 centimeters, with- Grams per liter Sulphuric acid .i 160.0

Sodium sulphate 250.0 Zinc sulphate 2.5

causing the thread to travel in said bath for a distance not in excess of 25 centimeters, withdrawing the thread from said bath and causing it to travel in the air for a distance of not less than 150 centimeters.

RENE PICARD. RENE FAYS.