US2318552A

US2318552A - Process for the manufacture of films, foils, bands, and the like from cellulose solutions

Info

Publication number: US2318552A
Application number: US116290A
Authority: US
Inventors: Czapek Emil
Original assignee: Individual
Current assignee: Individual
Priority date: 1935-12-18
Filing date: 1936-12-17
Publication date: 1943-05-04
Anticipated expiration: 1960-05-04
Also published as: GB492370A; DE705111C

Description

y 1943- v E. C-ZAPEKI- 2,318,552

PROCESS FOR THE MANUFACTURE OF FILMS, FOILS; BANDS,

AND THE LIKE FROM CELLULOSE SOLUTIONS Filed Dec. 17, 1956 Inventor:

Patented May' l, I943 uiNirEo STATES PATEN T OFFICE PROCESS FOR THE MANUFACTURE OF FILMS, FOILS, BANDS, AND THE LIKE FROM CELLULOSE SOLUTIONS Emil Czapek, New York, N. Y.

Application December 17, 1936, Serial No. 116,290 In Germany December 17, 1935 4 Claims. This invention relates to a process for the manufacture of films, membranes, bands, sheets and the like from solutions of cum-ammonium cellulose.

The principle underlying the manufacture of film-like bands from cellulose solutions by known processes, such as aredescribed in German Patent,

, Nos. 237,152,249356, 421,383 and elsewhere, is

that the coagulation of the solution, the shaping of the film and the consolidation thereof, are carried out in the same working stage. When working in accordance with the first two of the afore-- said processes, the conversion of the cellulose solution into the film is carried out-while freely suspended in' the coagulation bath or only lightly supported by guide rollers, which merely serve to protect delicate membranes from breaking. When the last of the aforesaid processes is em- O, .ployed, the film is left on the moulding drum from the time of its formation until the complete penetration of the precipitation liquid.

The progress of the reactions occurring in ternally in any way except by alterations in the chemical reagents or alteration -of their concentratio'n.-

The present invention on the other hand,- opens up the possibility of influencing the film during-its formation. This is ell'ected in accordance with the invention by dealing separately .with the'processes occurring during its formation, by means of a method which difiers fundaprocess and of the embodiments of the machine for carrying out the process illustrated in the accompanying drawing, in which Figure 1 is a diagrammatic elevation of apparatus made according to one embodiment for carrying out the process; and

Fig. 2 is a similar diagrammatic elevation of an apparatus made according to another em bodiment.

According to the invention, the cuprammonium cellulose solution is applied in known these processes can scarcely be controlled ex mentally from the previously known processes.

Among the objects of the present invention it is aimed to provide an improved process which will permit dividing one of the main reactions thereof into 'a succession of steps instead of combining them in one sole step, with a view to increasing the output of machines for carrying out this process and thereby-to speed up or expedite the operation of such machines for carrying out such processes. I It is still another object of the present. in vention to provide an improved process whereby cert in of the reactions may be divided into successive steps to increasethe flexibility of the process to facilitate regulating-the same according to the thickness of film to be produced with a certain predetermined uniformity and consistency and according to the ingredients used.

, These. and other features, capabilities and advantages of the machines for carrying out the -process constituting the invention will appear from the sub-joined detail description of the This film, which is still soft and plasticinternally and can be made to redissolve, for example by moistening-with water, is thenpassed on further supports, such as .conveyor belts or rollers, through a supplementary coagulation bath, in which it can then be subjected toa .second precipitating action varying from the preliminary coagulation.

Theptreatment with dilute acids for the purpose of the further consolidation of the film and removal of the copper therefrom, which otherwise takes place inknown processes immediately after the coagulation, 'follows only after this treatment.

The purpose of this separate and regulable treatment is manifold. In. the manufacture of cellulose films and the. like from cuprammonium cellulose solutions the removal of the ammonia atthe correct timeiand to an extensive degree from the coagulated structure plays an important role. If for example the ammonia be entirely removed immediately after pouring out on tov the support, i. e.,before the. f

coagulation, the film is extremely difficult to detach from the support. The same thing occurs if the coagulation be effected with bath concentrations of dilute liquor, when the required removal of ammonia from, the film occurs too rapidly. 1 In both cases the coagulatedproduct becomes brittle in addition, so that whe'n'li'fte'd off from the support it breaks and splinters like glass.

If on the other hand the ammonia be removed I the ing approximately 6% to an inadequate extent from the solution, the

the film can be detached from the support. The

subsequent second coagulation proper is then adjusted to the ammonia concentration still present in the film in such a way that the ammonia can escape or is removed from the coagulated structure to the desired degree. For this purpose, for the second" coagulation a liquor is preferably selected of lower concentration than for the preliminary coagulation, in order to facilitate the diffusion of the ammonia out of the film. With this treatment it is now also possible to interpose short or long intermediate stretches of the web where .the ammonia can escape into the air. The use of the word "coagulation" is here to be definitely distinguished from the word. regen-' eration" which latter is used to characterize only the treatment in which the previously coagulated film is being transformed into a cellulose hydrate.

The process of the present invention first of all enables cuprammonium solutions to be employed having a higher ammonia content than usual, also permits a better and more thorough removal of the ammonia from the coagulated solutions, and finally enables the output of the machines tobe considerably increased and the speed of working to be raised, because only a preliminary coagulation now takes place on the same support, on which otherwise the complete coagulation must be carried out in'know'n manner. This takes much less time. The fact that the film is detached from the support in a perfect manner and better than in the known processes is a further advantage which likewise benefits the speed of production.

The invention will now be described with reference to the following example:

A solution of cuprammonium cellulose, containof cellulose and 7% of ammonia, is spread out by means of a slot nozzle or other suitable spreading device a on the cylindrical shell surface of a moulding drum (Fig. 1) or of a moulding belt b .(Fig. 2). Through the rotation of the horizontally mounted drum b, the solution arrives shortly after the spreading in a. coagulation bath 0 consisting of a soda lye of 6% strength, through which it is passed within a few seconds. After leaving this bath the film, now superficially coagulated, is detached from the pouring support and passed on to a take-up dr'um' d or the-like, from where it is passed along on suitable rollers e or suitable supports.

During this movement the film is'first led freely through the air to enable it to give of! a part of the ammonia present in the interior and is then dipped into a bath f of a soda lye of 3% in which it remains until the precipitation is completed. It then passes into a bath phuric acid of 2% strength for the purpose of regeneration and removal of the copper. The premature removal of the film from the support also permits the stretching of the film after such removal-similarly to the stretch spinning process for rayon-for the purpose of increasing its strength, by giving the take-up drum d an advance. Fig. 1 shows the method of working when strength,

g of sula moulding drum is used, and Fig, 2 shows the use of a moulding belt and a special-device for obtaining an open air run after the detachment dr and d2.

Subsequent to the regenerating and de-copperizing step which maytake place in the bath g aforesaid, as is customary, the resulting layer will be subjected to further treatment including washing, softening and drying.

I claim:

l. A process for the manufacture of films, foils.

membranes, bands and the like from solutions of cuprammonium cellulose, which comprises pouring a cellulose solution onto a support, ad-

vancing the solution so supported through a preliminary coagulating bath containing an aqueous alkaline solution, subjecting the solutionso advanced to a preliminary coagulation while-being advanced through such preliminary bath to produce a self-sustaining layer readily detachable from the support, detaching the layer' so produced fromthe support, effecting a final coagulation of the layer so producedin a second bath containing a coagulating fiuid of a similar nature to that in the first bath but of a lower concentration than that in the first bath, and there upon subjecting the layer so produced to further successive treatments including regenerating and de-copperizing, washing and drying.

2. A process for the manufacture of films, foils, membranes, bands and the like'from solutions oi cuprammonium cellulose, which comprises pouring a cellulose solution onto a support, advancing the solution so supported through a preliminary coagulating bath containing an aqueous alkalinesolution and subjecting the solution so advanced to a preliminary coagulation while being advanced through such bath to produce a self-sustaining layer readily detachable from the support, detaching the layer so produced from the support, removing the bulk of the ammonia from the layer so produced and thereby effecting final coagulation of the layer so produced in a second bath containing a coagulating fluid of a similar nature to that in the first bath but of a lower concentration than that in the first bath. and thereupon subjecting the layer so produced to further successive treatments including regenerating and de-copperizing, washing and drying.

3. A process for the manufacture of films, foils, membranes, bands and the like from solutions of cuprammonium cellulose, which comprises pourso produced from the support,effecting final coagulation of the layer so produced in a second bath containing a coagulating fluid of similar nature to that in the first bath but of a lower concentration than that in the first bath, and

, thereupon subjecting the layer so coagulated to further successive treatments including regenerating and de-copperizing, washing and drying.

4. A process for the manufacture of ,fllms, foils, membranes, bands and the like from solutions of cuprammonium cellulose, which comprises pouring a cellulose solution onto a support and spreading it thereon while said support and said solution are substantially free of coagulating 2,318,852 liquids, whereby said spread solution] adheres to said support, advancing the cellulose solution so supported through a preliminary coagulating bath,-and subjecting the cellulose solution so advanced to a preliminary coagulation while advancing through such bath to produce a partly support, moving said surface at a faster rate than said first supportto stretch the'intervening area of the'thus partly coagulated layer disposed between the two supports, thereupon efiecttng final coagulation of the layer so stretched in a second bath, containing a coagulating fluid of a similar nature to that in the first bath and thereupon subjecting the layer so'coagulated to further succes'sive treatments including regenerating and decopperizingjwashing and drying.

' EMIL CZAPEK.