US2285147A - Process of manufacturing foils, films, and the like - Google Patents

Description

. M62, 1942. a. @ZAPEK 2,285,147

RROCESS OF MANUFACTURING FOILS, FILMS, AND THE LIKE Filed Dec. 24. 1.937

Fig.1.

' 19 2.. l Q 12 Th i? m A 1 Pl/ i .fzmmwm I Elm Cu K WM ATTORNEY P tented J n 2,1

-umrroi STATES PATENT OFFICE I spasm raocrss or MANUFACTURING FOILS,

mars, rum rim mm Emil (lllpek, New York, N.

' anty Trust company of New N. I, a banking corporation December 24, 19:1, No. 18l,583 l s clchns (c1.1s-51) This invention relates to processes for manu- Application factoring foils, films and the like from solutions oi cellulose in eopperoxide ammonia.

Among the objects of the present invention, it

is aimed to provide an improved process for manufacturing foils, films, film sheets and the like from'solutions of cellulose in copperoxlde ammonia, the product .of which is uniform throughout in tensile strength, is free from striations, streaks-and the likeand tree from weak spots and variations in resulting from an undue sheet "in embryo withthe processes ese and other features, capabilities andadvantages of the improved process constituting the present invention will appear from the acpanyin drawing in which Figurelisaticviewshowingthe respective degrem ofconcentration of lye in the filmsheetinembry ,ascomparedtothedegrees 'of concentration of lye in the baths and also compared to the degrees of concentration of amm'oniainthefilmsheetasthcstepsof the process succeed one another;

Fig. 2 is a tic'view of a series baths constituting graphic projections of the baths ontheshowninFig. 1 andtobe read'in connection with Fig. 1;

Fig. 3 is a diagram showing the 'centration of ammonia and lye in the film sheet as the stepsof the process succeed one another.

The improved process is characterized eisentially by the definite relations of different degrees of concentration of sodium hydroxide in a plurality of successive baths for effecting coagtension or pull ofthe heretofore ulation and treatment of the film stock to be produced. Otherwise, the steps of the process are those well known in the art consisting in spreading the cellulose solution which passes into a coagulation bath and in treating the coagulated strip after the coagulation of the solution and thickness so frequently degrees of con 1., assi nmto Guar- York, New York, of New York,

. a coagulated film that is soft and plastic or hard certain characteristics "leading up to the presentin Stability,

' hardness of the film,

films and to their remaining in and strong. It was further found that the soft film on its way through the coagulation baths and subsequent treatment baths is exposed to changes in itsstructure, especially to stretchand swellings, resulting in a completed article characterized by definite imperfections. During the subsequent treatment just mentioned as an instance, a soft film might be stretched lengthwaysdue to the stretch-of the film sheet, the resistance encountered on the way, and the shrinkage caused by regeneration, in consequence of which it will shrink in a transverse direction more than otherwise necessary. This unequal extension of the film sheet in these directions-will result in a finished product having weak spots and generally lacking uniformity strength and extension qualities. Since the hard film is not subjected to these objectionable influencea'it will shrink only slightly in width in the coagulation and treatment baths; and an appreciable shrinkage only occurs in the regeneration bath. Furthermore, due to the in striations is the casewith soft films; and still is substantiallyequal in the length and transverse directions.

As essential to the vformation of such hard such strong condition, after extensive study. and experiment,

discovery were observed.

It was observed, as an instance, if aprocess is characterized by the formation of a precipitate of copper hydroxide at the beginning of the coagulating'treatment, and augmented in the subsequent treatments, the so formed film structure is soft throughout these treatments, and conse-- quently during the accompanying transportation after effective diffusion of the coagulation liquid the particular combination of coagulating liqul and cellulose solutim selected either to produce 55 ternal directly into the coagulation bathtion treatment, but only in of the film structure and the resulting drawing I action exercised on the film, striations, distortions, deformations and Furthermore, if a copper. hydroxide precipitate did not occur at the beginning of the coagulathe subsequent treatments, the so formed film structure mayhave a tougher surface hardness than aforesaid, but it will not be suflicient to avoid the aforesaid striations, distortions, deformations and the like. On the other hand, if a copper hydroxide precipitate did not occur either in the preliminary coagulatlon or in the subsequent alkaline treatments, there will result a film structure sufficiently hard definitely to resist the ordinary inthis shrinkage is less than the like will result;

stresses, and 'consewntly prevent thev entirely disappears in the final regenei'atiom,

should occur after'the cleaning of the film had progressed to the point that the ammonia had; been practically washed out and the film contained only a small amount of caustic soda S0111, tion, this turbidness no longer would result in the formation ofstriations, streaks and defor mations. For instance, a solution of cellulose in copperoxide ammonia and having a content of 7 per cent cellulose and 4.5 per cent of ammonia and 3.3 percent of copperoxide introduced in a large quantity of a coagulation bath consisting of 8 per cent of sodium hydroxide, 0.6 per cent of ammonia and 91.4 per cent of water would positively prevent the forming of any copper hydroxide in the film during the coagulation. The important point, however, was that the hard coagulated film continued hard throughout the entire process until the regeneration bath was reached and that then during the short state of slight turbidness, which then occurred, it did not lose its strong characteristic.

In order to produce a strong film and in order to keep,it in this condition during the subsequent treatment, according to the present invention, the coagulation of the cellulose solution on the pouring base takes place with an alkaline liquid, containing a caustic alkali, for instance sodium hydroxide, and ammonia. The concentration ratio between sodium radicals, Na, and ammonium radicals, NH4, has to be selected, sothat the sodium radicals in the bath liquid exceed the ammonium radicals, contained in the cellulose solution and in the bath liquid in order positively to prevent the forming of copper hydroxide in the film during the coagulation.

Furthermore, the ensuing treatment, in the subsequent baths is started with acomparatively high concentration of sodium radicals, Na, sufiiity substantially The steps of the process now to be described of one c example are, of course, not intended to be all inclusive but merely ypical of the invention. These steps are as follows.

A' solution of cellulose in copper-oxide ammonia is poured ontoa pouring hm bywhich itisintroduced into a coagulation liquid which contains ammonium radicals, NH4,

cient to exceed the ammonia 'radicals'in the film stock being formed and in the bath liquid. Simultaneously with. a progressively diminishing ammonia concentration in the film will the quantity of sodium radicals, Na, bedecreased from bath to bath in the following treatments, to retain a concentration ratio between sodium and ammonium radicals, which is suitable to prevent the forming of copper hydroxide precipitate in the film while passing through the baths having decreasing alkaline contents.

The selection of the concentrations for the treatment baths vary within certain limits according to the composition of the cellulose solu'' tion, according to the thickness of the film to be produced and according to the temperature of the coagulation and the-working speed. As an instance, in the manufacture of films, which in their final condition have a thickness of 0.007 to 0.12 mm., concentrations of caustic soda solution at the start from 4.5 to 11 per cent when the concentration of ammonia at the start is from 0.2 to 1.2 ;per cent have proven to be satisfactory for the'coagulation bath.

If the process just described is followed in the steps preceding the treatment of the film in the acid bath, a comparatively hard, strong film is obtained, which does not depart from its original width and in addition shrinks only slightly in the acid bath.

Films made in, accordance with this process distinguish themselves by a decided regularity or uniformity in their structure, a high stability, strength and a stretching capacity or extensibil- Fig. l where the values on a comparatively large quantityof sodium radicals, Na, and a comparatively small quantity of while supported on this base the solution is coagulated tothe point where the forming strip is entirely penetrated by the coagulation liquid. This stage or condition is reached, it has been observed, when the coagulation liquid penetratesthe inner part of the strip and mo the pouring base.

It may be noted in. this connection that instead of sodium, hydroxide also the lye of an other alkaline metal can be used. Furthermore, it is advisable, to conduct the coagulation in a flow of coagulation liquid in order to avoid the formation of concentration differences in the boundary surface during the coagulation, so that the gradient of potential between cellulose solution and coagulation bath existing and desired at the beginning may remain undistm'bed as much as possible in all parts and throughout the entire width of the film sheet. This object is achieved in a particularly efiective way when causing the coagulation bath liquid to move in an opposite direction to the direction of movement of the film sheet.

base and carriedthrough several treatment baths which also contain sodium radicals, Na, besides ammonium radicals, NR4, concentration as hereinafter to be described.

After leaving these treatment baths, the film manner and dyed respectively.

of concentration have been found the present invention can be conveniently compared with the course of the process generally on a chart, see the ordinate indicate the degrees of concentration of ammonia and alkali lye from 1 to 8 'per cent as indicated and the values on the abscissa indicate the suceesive stages or successive baths from cated through which the film stock passes during its treatment.

As an instance:

Graph A on Fig. 1 represents the degree of concentration of ammonia in the film, graph B the degree of concentration of alkali lye in each 0 represents the concentration the film resulting from the thus charted concentrations in the film and bath. In practice, as shown by the-diagram or chart, the

and cleaning baths are ordistages by an alkali lye of gradconcentrations starting with v on to bath 8. This part of the process of course can also be carried out, starting in the reverse direction by fillin the last bath anew with fresh water and conducting direction of thepath of movement of the film stock. Inbath 9, as an inin various. degrees of.

Assoonasthe bath,itistobel to n asindirapid increase of the lye baths 3 and 2 a greater addition in lye would be made and finally a still greater addition in lye would be made in bath I, so that one would then have to work with a predetermined highest concentration, which in the example just described preferably would be 6.5 per cent.

the lye adhering to the in lye would be made in baths! and 4, while in I In Fig. 3, the values on the abscissa indicate I the degrees of concentrations in percentages of the ammonia in the film, andthe values on the ordinate indicate the degrees of concentrations in percentages of lye in the film. Graph M shows the limit between the clear and the dull film after the coagulation. The'hatched part of the chart, to the right of graph M, indicates the formation of a precipitate of Cu(OH) when the readings of the test appear in that area and the lack of a precipitate when the readings of' the concentrations appear to the left of graph M.

Graph-F illustra the concentration'of the lye in the film when theprocess corresponds to the concentrations charted in Fig. l, by the graph C, in which the beginning of the coagulation is represented by the point a while point z corresponds to the degrees of-concentration where the film should be carried into the regeneration bath.

From the course of the graphs in Fig. lit will be understood that in the example you the concentration of ammonia in the at the beginning of the coagulation would amount to 4.5 per cent and during the coagulation would drop to 2.5 percent. This remaining 25 per cent 'will be substantially reduced in the-subsequent baths to the practically insignificant concentration of 0.2 per cent. Graph C represents that at the beginning ofthe coagulation, the. fi m would have a concentrationof 1 per cent of caustic soda solution and that the coagulation in the example given was caused by a great and concentration in the film resulting, in the subsequent baths immediately followin'g'the coagulation, in a concentration of 6.5 per cent. As a result of'the washing then occurring, the lye, NaOH, concentration in them drops gradually to 2 per cent.

The concentration of and the cleaning baths 2 to 5 is charted by graph B. As indicative of an increase of the dye NaOE concentration in the film, graph B appears above graph C. To indicate that the reduction .of lye NaOH, by washing has started, graph 13 crosses graph G and thereupon remains to the end, ac-

.cording to the desired gradient of potential required, beneath graph 0. Furthermore; the chart shows that the Lye content in the film and in the treatment baths has to be considerably greater than the content of ammonia'in the film In Fig. 3, there is charted the same process charted in Fig. 1 but from another point vof 'view mainly from the viewpoint of the relative alkali and ammonia content in the film. Here,

the lye in the treatment sented as at a and endin at b,-whe re the subsequent treatment follows, which is completed with the last washing treatment at z. 3

Ifastraightline were drawn from ato'z it would enter the hatched space representing the formation of a precipitate in the film. even be- ,fore the termination of the coagulation. On the 1 other hand, if thefilm is treated in the indirect course by theuseof the lye, NaOH, con centration, while at the concentration drops gradually, in'this way, which is illustrated by graph spread solution to a coagulation treatment in a preliminary coagulation bath consistlng'o'f an aqueous solution of caustic alkali and ammonia of a concentration with not more than '11 per cent caustic soda solution and exceeding 7 the ammonia'content'in'the film stock and a concentration beginning with not more than 1.2

per cent concentration of ammonia to prevent H the forming of any copper hydroxide precipitale in the film stock while being mu tedl and thereupon subjecting the film stock to a succession of baths of decreasing decreasing ammonia content, thealkali content of each of which exceeds the ammonia content of a bath and the ammonia content of the illm while passing through the baths.

2. The process of manufacturing foils,

stock and the like from .a solution of cellulose in copper oxide ammonia characterized -by spreading the solution by of a pouring device, thereupon subjecting the so spread solu-{ ,tion toa preliminary coagulafloninanaqueous coagulating liquid containing causfie'alkall'and a lesser'amount of ammonia, the caustic alkali content and the ammonia content in thefliquim and in the cellulose solution being so proportioned as to preclude the precipitation of cop-- per hydroxide from. the cellulose solution, and thereupon continuing the coagulation in. a series of coagulating baths of simultaneously decreasing'caustic alkali and ammonia contents, the causticalkalicontentinflieserlofbathsbeing 'les than the caustic alkali content .in. and'exceedingtheammoniacontentmthecellulose solution being coagulated at all times, theammonia content in the coag ting and in theseriesofbathsbeinglessthantheammonia content in the cellulose solution being coagulated atall times, to reduce gradually caustic alkali content and the ammonia content ofrthe series of baths being so proportioned as topreclude'the' the coagulation process in the film isrepreprecipitation of copper hydroxide. from the cellulose solution.

3. The process of manufacturing foils film stock and the like from a solution of in copper oxide ammonia characteri ed by spreading the solution by means of a pouring device, thereupon coagulating the so spread solutioninaseriesof containing caustic alkali and ammonia and of gradually skmetimetheammonia F, the hatched spaoejs not entered until in the verylaststage when alkalLandof' the alkali andammonia content inthe cellulose solution being coagulatedand'-the caustic alkali content in the cellulose solution in the remainder of said baths and exceeding the ammonia content in the cellulose solution being coagulated at all times, the ammonia content in the series of coagulating baths-being less than the content in the cellulose solution being coagulated at all times. to reduce gradually the alkali and ammonia content in the cellulose solution being coagulated during the coagulation thereof in said remainder of said series of baths and the caustic alkaline content and the ammonia content of the series of baths being so proportioned as to preclude the precipitation of copper hydroxide from the cellulo solution at all times; a

EMIL CZAPEK.

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