US2319305A - Process of continuously forming cellulose films, staple fibers, and artificial silk - Google Patents

Description

J. c. DE NOOIJ EIAL 2,319,305 PROCESS OF CONTINUQUSLY FORMING CELLULOSE FILMS, ST MI'JE FIBERS, AND ARTIFICIAL SILK I May 18, 1943 [VI/ENTOPS:

Jim Com/ans nE/Voou ERNEST BLEIBLER Atforney.

2 Sheets-Sheet 1 Filed Jan. 3, 1938 b cmeaw 1943 DE NoolJ ETAL 2,319,305

' PROCESS OF CONTINUOUSLY FORMING CELLULOSE FILMS, STAPLE FIBERS, AND ARTIFICIAL SILK Filed Jan. 3, 1938 2 Sheets-Sheet 2 f/v VENTORS: M JhNCom aus DEA/o0 1a RNEST BLE/BLER a, wafidbw I After-n ey.

Patented May 18, 1943 PROCESS OF CONTINUOUSLY FORMING CELLULOSE FILMS, STAPLE FIBERS, AND

ARTIFICIAL SILK Jan Cornelis de Nooij and Ernest Bleibler, Ghent,

Belgium; vested in the Alien Property Custodian Application January 3, 1938, Serial No. 183,202 In the Netherlands January 4, 1937 3 (Balms.

Our invention relates to improvements in a process for continuously forming cellulose films, transparent sheets, staple fibers and artificial silk, and especially from solutions of cellulose in sulphuric acid, by use of a movable conveyer, the surface of which may be perforated.

Heretofore in forming cellulose films and transparent sheets two processes were used,

which are both based upon the coagulation of cellulose solutions.

The first and oldest process uses the'so-called pouring drum. The solution used is poured upon .a rotating drum and fiowed on to the desired thickness. In this process commonly a pouring funnel open at the top is used. The surface of the film is formed on the one side by the surface of the drum, and on the other side by flowing and solidifying without coming into contact with a solid object. This process, therefore, requires that the drum have a perfect surface, this being unfavorable especially because of the expense and the possibility of applying the process in actual practice, especially as the surface is chemically affected; moreover the spinning-speed is very limited in practice due to the diameter of the drum.

The second process consists in forcing the cellulose solution'into a coagulation bath between two lips or through a nozzle in such a way that the layer entering the bath is a vertical or sloping direction is immediately washed by the bath liquid on two sides. In this'process the surface, after the cellulose solution leaves the nozzle, is formed on both sides by flowing and solidification without coming into contact with a solid object. In a continuous process the film formed in thi way must be carried upward from the bath which is generally done by leading the product around a driven roller. This process has the disadvantage that the film, whichis at that time only partially coagulated and which is still very weak, is exposed to strong mechanical stresses, since the whole part which travels in an upward direction carries its own weight without any support and must transport itself further.

The first process is applied ordinarily, but not exclusively, for solutions of cellulose in volatile solvents, and the second process is used when solutions of cellulose are used which must be coagulated in a liquid.

When using the first process the spinning-solution must not be very viscous because only a small pressure can be used for pressing the liquid out of the pouring funnel.

The second.processas has been remarked already-requires that the tensile strength of the film be relatively high even at the beginning. A process is known for dissolving cellulose in sulphuric acid (vide U. S. Patent No. 1,991,141) according to which a relatively thick fiuid solution is formed. When coagulating this solution a strongly swollen gel of relatively small initial strength is obtained.

Both the above mentioned coagulation methods are, therefore, not suitable for producing films from solutions according to the patent mentioned above. Applying a pouring-drum is unsuitable inasmuch as a uniform cellulose layer can be obtained only under high pressure. The second method does not come into consideration because the strongly swollen film has a low strength, especially during the coagulation process.

According to our present invention a new coagulation method is used for continuously forming films and transparent sheets, whereby the two principal difficulties as mentioned aboveare removed. Since, however, in spinning staple fibers and artificial silk according to U. S. Patent 1,991,141 the same difficulties are encountered (which are all to be ascribed to the low strength of the product before it has been thoroughly coagulated) our new process may also be applied for the manufacture of both products, the broad nozzle being replaced by one or more spinning nozzles arranged next to each other, in case artificial silk is to be spun.

According to U. S. Patent 1,837,854 a solution of pyroxylin or of other cellulose ester is brought upon an endless conveyer directly out of a nozzle having an elongated slot. the conveyer transporting the material through a bath which absorbs the solvent, thus provoking a coagulation. This method, however, is not sui able for solutions of cellulose in sulphuric acid as this material would stick to the conveyor.

The process according to our invention is characterized by the feature that the layer or one or more jets of cellulose solution is first superficially coagulated on both sides, whereupon it is immediately taken up by the bearing surface and is carried forward in this supported condition in order to be coagulated further.

Another feature of our invention is that the liquid to be coagulated is pressed through the nozzle in a horizontal or practically horizontal direction.

It is of advantage to force the liquid through the nozzle with a pressure of more than 2 kg. per

The bearing surface may consist of a moving band or conveyer running in a horizontal or practically horizontal direction, made of stainless steel or rubber. v

The bearing surface may also consist of the upper part of a rotating drum.

By applying this combination of conditions it is possible to spin continuously solutions of cellulose in sulphuric acid which heretofore could not immediately, the product according to that patent has no opportunity to coagulate superficially on both sides before coming into contact with the conveyer.

In order to elucidate our invention the following example is given, reference being made to the drawings showing an apparatus according to our invention, alsoby way of example only.

In said drawings,

Fig. 1 is a somewhat diagrammatic view, showing a vertical section through an apparatus having means for feeding the solution into the coagulation bath, and means for supporting the resulting weak film or the like on a conveyor while the coagulation proceeds until the film gains strength, and

Fig. 2 is a fragmentary plan view correspond-- ing thereto, showing the means for feeding the solution into the bath.

The cellulose solution e. g. obtained by the process according to U. S. Patent No. 1,991,141 is supplied from a tank to a channel] which is formed in the interior of a nozzle-piece 2. Said nozzle-piece is pivotally supported by bearings 3 and 4 and may berotated by means of a handwheel 5 acting by means of a worm 6 on teeth on one of the pivots of the nozzle-piece 2.

The channel I in the nozzle-piece is connected by a passage 1 to the nozzle which is formed by a fixed part 8 extending throughout the length of the nozzle-piece and a corresponding movable part 9. Said movable part may be adjusted by means of hand-wheels I 0 which are each fixed on a screw I I engaging a threaded hole in a part 12 of the nozzle-piece 2. The number of adjusting means depends upon the length of the movable nozzle-part 9. In the embodiment shown in the drawings four adjusting devices are shown for a nozzle of a width of e. g. 100-150 cm. but it is evident that the number of these maybe varied in accordance with the circumstances.

The cellulose solution is supplied to the channel i and forced out of the nozzle under a relatively high pressure of e. g. 8 atmospheres. This solu-- tion leaves the nozzle preferably in a horizontal direction, passing into a coagulation liquid which is contained in a bath l3 so that the cellulose solution is first superficially coagulated on both sides. As a coagulation bath it is preferred to use .water or diluted sulphuric acid of about 15% of room temperature. The product thus formed as a film l 4 is immediately taken up and conveyed by a moving surface e. g. a conveyer [5 running through the bath with a speed ofe. g. 30 meters per minute and is further coagulated by the coagulation liquid IS in the bath IS. The conveyer I5 is moved by a roller II which is driven by any suitable known apparatus, e. g. an electric motor and a reduction gear, which are not shown in the drawings. The conveyer, I 5 is further guided by a roller l8 and has a tightener I9.

The distance from the nozzle to the conveyer I5 is only small and may generally be about 2 to 10 cm.

After the coagulation of the surface has been completedor after the film has obtained sumcient strength the film, which now consists of a gel, may be lifted from the conveyer after having passed under a roller 20 and may then be guided by other rollers 2| and 22 or another conveyer in order to be submitted to further treatment.

Our invention may be practiced in various ways in connection with various materials and by means of various forms of apparatus without departing from the scope of our invention.

It is to be remarked, however, that the nozzle or nozzles should preferably be acid-proof and capable of resisting high pressures. When preparing viscose films, pressures are applied from 0.1 to 1 kg. per cm., but in the acid process pressures of 2 to 10 kg. per cm. are applied.

Solutions made by dissolving cellulose directly in sulphuric acid, have two chief properties in common, namely first that such solutions are of extraordinarily high viscosity and second that they can be coagulated only very slowly, and consequently the spinning apparatus according to the present invention presents the only means at present known to us for continuously spinning such solutions. The slowness of coagulation which is characteristic of all these acid solutions, while no doubt due partly to the high viscosity, is caused mainly by the fact that the spinning of such solutions is a physical process (washing out or diffusing of acid into the bath) and not a chemical reaction, in marked contrast to the spinning of viscose, for example.

Favorable results are obtained by using a solution of cellulose in sulphuric acid as obtained according to U. S. Patent 1,991,141, a length of the conveyer of 1 to 5 meters, e. g. 2 meters, a coagulating bath consisting of 15% of sulphuric acid in water and a spinning speed of 30 meters per minute.

What I claim is:

1. The process of continuously forming cellulose sheets, films, staple fibers, artificial silk and the like, from solutions of cellulose in sulphuric acid, which consists in extruding the cellulose solution through at least one nozzle in a substantially horizontal direction into a bath capable of leaching out the acid and thereby coagulating the solution, thus initially merely superficially coagulating it on all sides, and producing a relatively weak product incapable of supporting anymaterial tension, thereupon immediately physically supporting the extruded solution within said bath and carrying it forward within the bath while thus physically supported, to cause it to be coagulated further and thus attain sufiicient strength to become self-supporting.

2. The process of continuously forming cellulose sheets, films, staple fibers, artificial silk and th like, from solutions of cellulose in sulphuric acid, which consists in extruding the cellulose it forward within the bath at a speed corresponding to the rate of formation of the said product while thus physically supported, to cause it to be coagulated further and thus attain sumcien strength to become self-supporting. 3. The process of continuously forming cellulose sheets, films, staple fibers, artificial silk and the like, from coagulable solutions of celluose in'suiphuric acid, which consists in extruding the cellulose solution, through at least one nozzle, in a substantially horizontal direction into a bath capable of leaching out the acid and thereby coagulatlng the solution, under suflicient pressure to cause it to continue to travel substantially horizontally under its own momentum for a short time, suflicient for merely superficially initially coagulating it on all sides, thus producing a product of very low strength not capable of supporting its own weight during the completion of the coagulation, and thereupon immediately physically supporting the extruded solution and carrying it onward in the bath to complete the coagulation while thus supported.

JAN CORNELIS DE NOOIJ. ERNEST BLEIBLER.

Images