US1997753A - Manufacture of artificial threads from cellulose esters or cellulose ethers - Google Patents

Description

Patented Apr. 16, 1935 UNITED STATES PATENT OFFICE ETHER-S Paul Schlack, Berlin-Karlshorst, Germany, as

signor to Aceta G. in.

b. H., Lichtenberg, Germany, a corporation of Germany N Drawing. Application April 27, 1929, Serial No. 358,762. In Germany May 1, 1928 7 Claims.

This invention relates to a process for the manufacture of artificial threads from a solution of cellulose esters and ethers, according to the wet spinning process, and to the threads obtainable thereby. A further object of the present invention is to provide an artificial silk of the class mentioned above, having a dry tensile strength of 2 to 2.5 grams per denier and more.

It is known in the manufacture of threads from cellulose esters or ethers, according to the wet spinning process, to use a precipitating bath which contains a salt having a swelling action upon the thread formed and which causes a retarding of the coagulation of the threads. Such salts are, for instance, sulfo cyanides, zinc halogenides, alkali metal, salicylates and other salts with highly hydrated ions.

Fine threads spun in such a bath by the stretching-spinning process have a tensile strength of about 1.3 to 1.8 grams per denier, which exceeds that of the threads usually obtainable by the dry spinning process to the extent of about 25 to 30%.

However, when using a known precipitating bath of the kind mentioned in the second paragraph of this specification, it easily occurs that the produced fibers having originally a fine titer stick fast together and show after drying a hard and brittle feel contrary to threads obtained by the dry spinning process.

When operating according to my invention, threads are obtainable in which the individual fine fibers are completely separated from one another; after drying, they show an excellent soft feel and an agreeable luster. The latter may be modified by varying the spinning conditions by suitable additions to the spinning bath. Furthermore, the tensile strength of the threads is essentially increased up to 2.5 grams per denier and more.

According to my invention a precipitating bath is used which contains besides such a salt as retards the coagulation of the threads an organic polymerized substance of high molecular weight, which is colloidly dispersed by water. As such a colloid I use, for instance, molasses, sulfite cellulose waste liquor, tanning substances, carbohydrates, such as starch, dextrin, mucilage, gum, or protein-substances, such as gelatin, glue, casein, degraded glutin and the like; furthermore natural resins, soluble synthetic resins, as for instance, the products obtainable from aromatic sulionic acids and aldehydes. The quantity of these substances which I add to the precipitating bath may be varied within wide limits. Good results are obtainable, for instance, when adding only 5 grams of the colloid compound per liter of the precipitating bath. It is obvious that the result varies according to the quantity and to the specific compound used, but the best result may be easily determined by a simpleexperiment in each specific case. I prefer to use as a particularly suitable colloid sulfite cellulose waste liquor or a solution of a slightly degraded protein substance, for instance, that of slightly degraded glutin (see Berichte der Deutschen Chemischen Gesellschaft, vol. 35, page 2195).

The action of the spinning bath may be further modified by adding another salt or other salts which have no or no considerable swelling action upon the substance to be spun, for instance, calcium chloride, magnesium chloride, sodium acetate, ammonium nitrate, or mixtures thereof, or by adding a non-volatile or diflicultly volatile organic substance which has a swelling or dissolving action upon the cellulose product to be spun, for instance, a chlorohydrine, an ester or" a polyvalent alcohol, such as glycol monoacetate, monoacetine, triacetine, an ether of a polyvalent alcohol, such as glycol monomethyl-ether, glycol monoethylether and the like, a monoor polyvalent phenol, a ketone, such as diacetone alcohol, cyclohexanone and its homologues. Instead of adding the swelling agent to the precipitating bath, I can add it also partly or wholly to the solution of the cellulose ester or ether which is pressed into the precipitating bath. In this case, of course, the quantity of the swelling agent in the precipitating bath may be considerably diminished.

The effect of my precipitating bath is not diminished by the fact that a certain amount of the solvent which is used in precipitating the spinning solution is introduced during the spinning process into the precipitating bath, care must be taken, however, that the amount of the solvent present in the precipitating bath does not become too large, and does not exceed about 9%. The maximum quantity depends on the quality of the dissolving agent and on the composition of the precipitating bath and will be easily ascertained from time to time by simple experiments. The manufacture of a uniform product on a large scale is, therefore, connected with no difficulties. Recovery of the solvent and the preparation of the precipitating bath is particularly simple if the acetyl cellulose is dissolved in a single solvent, for instance, acetone.

I prefer to carry out my process in such a way that the length of the threads immersed in the precipitating bath is about 30 cm., but it may be shortened, for example to 15 cm. or extended to 60 cm., or more. The threads are then collected on a bobbin or in a spinning centrifuge in the usual manner.

The threads may be subjected to a stretching procedure in any known manner during. the precipitating step or after their removal from the bath, that is, between the coagulating bath and the collecting device. The stretching may be accomplished either by providing a substantial distance between the bath and the collecting device or by leading the threads over rods or rolls arranged in the bath or between the bath and the collecting device.

The speed of spinning may be varied within wide limits. It depends on the length of immersion of the thread in the precipitating bath, on the opening of the nozzle, on the concentration of the spinning solution, on the quantity of the spinning solution conveyed by the spinning pump to the nozzle, etc. The temperature of the precipitating bath and of the spinning solution may also be varied within certain limits, as, for instance, from to 40 C. I prefer to keep them at room temperature, that is to say, at about C.

When using a bath according to my invention, it is easy to produce artificial silk threads from acetyl cellulose having a. dry tensile strength of 2 to 2.5 grams per denier and more, that is to say, at least double the strength of the products which are obtainable by spinning in accordance with the usual dry spinning process.

The following examples are given to illustrate my invention without limiting it to the specific details given therein:

Example 1.-A solution of 22 per cent. strength of acetyl cellulose in acetone is forced through spinning nozzles having bores of 0.5 mm. diameter into a precipitating bath which contains per liter 200 grams of ammonium sulfocyanide and 550 grams of purified sulfite cellulose waste liquor of specific gravity 1.25. The temperature of the bath should be about 20 C. and the length of immersion about 30 centimeters. The content of acetone in the bath may vary within wide limits, for example, between 1 and 9 per cent. The thread which is spun at a speed of about 15 to 20 meters per minute is washed with water on its way to the spool or to the spinning box. A silk is obtained with a nearly circular section, with an individual titer of l to 2 deniers and a dry tensile strength from 2 to 3 grams per denier.

Example 2.-The operation is carried out as described in Example 1, but a precipitating bath is used containing instead of the sulfite cellulose waste liquor per liter 400 grams of molasses residue of specific gravity 1.33. By molasses residue the final molasses is meant, that is to say, the product which remains after removing the crystallized portions of sugar.

Example 3.The operation is as described in Example 1, but there are substituted for the sulfite cellulose waste liquor about 500 grams of an aqueous solution of degraded glutin of specific gravity 1.25 per liter of the precipitating bath.

Example 4.-A solution consisting of 20 parts of acetyl cellulose, 2 parts of ammonium sulfocyanide, 4 parts of water and 74 parts of acetone, is spun into a precipitating bath which contains per liter 500 grams of a soluiton of degraded glutin having the specific gravity 1.25 and 40 grams of ammonium sulfocyanide. As mentioned in the preceding examples a silk is obtained with a section approximating to a circular form, the strength of which however is somewhat smaller and amounts to about 2 grams per denier.

Example 5.A spinning solution consisting of 20 parts of an acetyl cellulose, containing chemically bound 54.5% of acetic acid in 80 parts of acetone is spun into a precipitating bath which contains:

1 part of the glutin solution mentioned in Example 4,

1.2 parts of ammonium sulfocyanate,

1 part of sodium acetate,

1 part of calcium chloride and 3.5 parts of water.

The temperature of the precipitating bath should be kept at 20, the length of immersion of the thread is about 30 centimeters and the drawing speed about -30 meters per minute. A silk is obtained with nearly circular section, good luster and a dry tensile strength of 2.5 to 3.5 grams per denier.

Having now particularly described the nature of my said invention and in what manner the same is to be performed, I declare that what I claim is:

1. In the manufacture of artificial silk from organic cellulose derivatives the steps which comprise extruding a solution of an organic cellulose derivative dissolved in an organic solvent into a precipitating bath comprising besides an agent capable of exerting a swelling action on the cellulose derivative an organic colloid soluble in said precipitating bath,-and stretching the freshly precipitated threads.

2. In the manufacture of artificial silk from organic cellulose derivatives the steps which comprise extruding a solution of a cellulose acetate into a precipitating bath comprising besides an agent capable of exerting a swelling action on the cellulose acetate an organic colloid soluble in said precipitating bath, and stretching the freshly precipitated threads.

3. In the manufacture of artificial silk from organic cellulose derivatives the steps which comprise extruding a solution of a. cellulose acetate into an aqueous precipitating bath comprising besides an agent capable of exerting a swelling action on the cellulose acetate a colloid soluble in said precipitating bath, and stretching the freshly precipitated threads.

4. In the manufacture of artificial silk from organic cellulose derivatives the steps which comprise extruding a solution of a cellulose acetate into an aqueous precipitating bath comprising besides an agent capable of exerting a swelling action on the cellulose acetate a polymeric carbohydrate soluble in said precipitating bath, and stretching the freshly precipitated threads.

5. In the manufacture of artificial silk from organic cellulose derivatives the steps which comprise extruding a solution of a cellulose acetate into an aqueous precipitating bath comprising besides an agent capable of exerting a swelling action on the cellulose acetate a protein soluble in said precipitating bath, and stretching the freshly precipitated threads.

6. In the manufacture of artificial silk from organic cellulose derivatives the steps which comprise extruding a solution of a cellulose acetate into an aqueous precipitating bath comprising besides ammonium sulfo cyanide, degraded glutin, and stretching the freshly precipitated threads.

7. In the manufacture of artificial silk from organic cellulose derivatives the steps which comprise extruding a solution of a cellulose acetate into an aqueous precipitating bath comprising besides ammonium sulfo cyanide, sulfite cellulose waste liquor, and stretching the freshly precipitated threads.

PAUL SCHLACK.