US2371155A - Machine and process for making cfllulose - Google Patents

Description

/ March 13, E CZAPEK MACHINE AND PROCESS FOR MAKING CFLIJULOSE FlL-MS AND THE IJ IKEI Filed Aug. 5, 1940 2 Sheets-Sheet 1 INVENTOR ATTORNEY MACHINE AND PROCESS FOR MAKING CELLULOSE FILMS AND THE LIKE Filed Aug. :5, 1940 2 Sheets-Sheet INVENTOR ATTORNEY Patented Mar. 13,1945 I mourns AND PROCESS FOR MAKING can LULOSE FILMS AND THE LIKE I Emu Czapek, New York, N. Y. Application August 3, 1940, Serial No. 350,291

In G

. 7 Claims. This invention relates to a process for, and to an apparatus for carrying out the process of, the

manufacture of films, foils, membranes, bands, sheets and the like from solutions of cuprammonium cellulose. This application is a continuation in part of my co-pending application, Serial No. 116,290, filed December 17, 1936.

ermany December 17,1935

On the other hand, this method of working has not been adopted for the wet process, according to which-a viscous cellulose solution is caused to precipitate byseveral wet agents such as water, saline solutions, acids and alkalies, for the purpose of forming a film. Since the cellulose solution must be brought into contact with This invention has for an object the manu facture of foils, films, pellicles and the like by pouring a ouprammonium cellulose solution onto a movable support, especially onto a molding belt, and coagulating and solidifying the poured solution, and thereafter continuing the further treatments, mainly the regeneration of the cellulose on said support without detaching the result-'- ing film strip from the support until the chemical .conversion,purification and the like are comstructure was detached from the support as soon pleted, so that after the detachment practically only washing and drying of the filmare still necessary.

These and other features, .capabilitiesandadvantages of the invention will appear from the sub-joined detail descriptioigof specific embodi- -ments illustrative of apparatus for carrying out the processesof the invention illustrated in the accompanying drawings, in which 1 Figures 1 to 6 inclusive illustrate diagrammatically and by wayof example various embodiments of the apparatus in side elevation: and

Fig. 7 is a diagrammatic sketch iilustrative oi the progress of drying of the cellulose pellicle's.

As aforesaid, the present invention has for an: object the manufacture of fella-films, pellicles and the like by the so-called ,wet" process while using a support for the treatments of the film strip as long as possible.

In the so-called dry" process, the advantage of working on a movable support as long as possible, has been recognized for a long time. In such cases the working operation is invariably the same, that is, a viscous solution of a cellulose ester in organic volatile solvents is poured onto the pouring belt and solidifies during the travel of. the belt in its path of movement due to the gradual evaporation of the solvents. 8 ortly before the belt returns to the pouring d ce, the applied coating is dried. so that it ca be detached from the support in the solid condition.

The "dry" casting process there requires only the application of heat and efiluent air for the removal of the solvent vapour, so that the utilisation of the support until the finished film is detached would appear to be more or less compulsory from the outset.

a liquid for the purpose of coagulation, and every further phase of the treatment requires renewed contact of the coating with various other liq-' 'uids,' the support in the wet process, if at all was used for the coagulation only, and the film as formed.

The value of said support in the further stages of the process was imus lost, and the film formed had to be passed, freely suspended and supported at a few points by rollers and feed cylinders, through a large number of treatment baths. In such a process the film is exposed to all mechanical influences which may give rise to breakage, folding up, and the like. In addition the tension, caused bymotion of the machine, would effect an elongation in the longitudinal direction,

whereby of course a shrinkage in the transverse direction necessarily :ollows. This shrinking in the transverse direction in turn would cause the original film to shrink to a greater extent in the transverse direction than in the longitudinal direction, and thus, despite the pouring out of very wide film layers and accordingly wide molding devices, the finished product would turn out in the end to be a relatively narrow film. v

The present invention also avoids all these,

drawbacks, attendant on the one hand on freely suspended lengths of film, and on'the other hand on premature detachment of the still unconsolidated film, by utilizing the pouring support until the 'filrn has been passed through all the necessary chemical treatment phases.

In order more clearly to understand the invention, reference is made to the accompanying drawings, which illustrate diagrammatically and by way of example, in Flgs'l to 6, various em bodiments thereof.

In said drawings, the following are denoted: the pouring device i, the pouring belt 2,'the guide drums 3, 4, 5, 6 and 'i, the spraying devices 8 and 9, the receptacles ill for coagulation liquid,

.a detaching or stripping roller ii, a transferring roller I! for the treatment liquid, couch roller or rollers It for draining of the treatment liquid, a transferring belt it, the detachment at it of the solid film strip from the support, the

perizedandregenerated into cellulose hydrate. The regeneratioiii liquid may be also brought into contact with-the film structure by means of a spraying device I, as shown in Fig. l', a spreading solid film leaves the belt on the detaching out this last wet phase oi treatment on the 1 pouring support also, and in passing the washed from said supportdlrectly to the drying apthe no"opportunity oi'evaporating arrows i8 and II to indicate the direction of W movement of the pouring belt.

In the embodiment shown in Fig. 4, provision is made for enclosing the bath container and for exhausting and recovering the evolved vapours 5 through pipe l8 and fan IS.

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

A solution of cuprammonium cellulose containing approximately seven per cent of cellu- 10 lose and five percent oiamm'o'nia, isspreadfout' by means of a slot'feeder ijorother suitablespreading device, see Fig. 1 on an endless mold-. ing belt 2. The belt moves by rotation 01' the- I drums 3, 4 and 5 inthe'direction oi'the arrows 16 i6 and I1. The spread out cellulose solution, by

travelling with the moving belts, reaches the downwardly disposed part of the path or movement between the drums 3 and 4, where the cel lulose solution is first wetted with a coagulation 20 liquid consisting of a six per cent aqueous caustic soda solution initially to coagulate the solution, and subsequently wetted with water or with a similar alkaline solution but preferably of a lower concentration efiectively to solidify the solution. The wetting operation is effected in Fig. 1 by spraying the coagulation liquid onto the cellulose solution by means of a spraying device 8, although the application can also be eiiected otherwise, for instance by means of ap- 80 plying rollers l2, as illustrated as an instance in Figs. 3 and 6, wetted'with the desired liquid.

Excess of this liquid is received in the receptacle ill, see Fig. l, or is removed by means or couch rollers is, see Figs. 2 and 6. as

The direction of motion of the supporting belt changes at the drum 4, see Fig. 1. The cellulose solution is thus now coagulated on the belt.

Shortly afterwards, and during its passage through the zone between the drums 4 and 5, the 1 film structure previously coagulated and thereby transformed into a film, is treated with a tour per cent aqueous solution of sulphuric acid by mean'sof which saidfilm structure is decopdevice,- s renting roller i2, as shown in Figs.

3 -and; -.a*iel tjbelt, H as shownin Figs. 2 andg5 r glily soakedmith the regeneration ,liich, roller and belt press against turfejromthe outside.

Thereupbn tha'regenerated and ,decopperized ing or stripping roller II, as shown in Figs. 1

" ted, to besubiected to'iurthe'r treatments, in-

cluding rinsing and-drying treatment.

'Aftercompletion oi the chemical treatment, the film consisting of regenerated cellulose has already sufiicient strengthto preclude all fear or breakagelin the freely suspended portion'during. the, washing and drying treatment. Moreover, thereis no objection in princip'letov carry- The improved drying. pr cess or the present invention proceeds from the iact that the cellu- 7 lose'film, since itis nota porous material, be-

haves in a-manner iundainentally' diner-ent than that of paper or -textileiabric. during the mine process. '1'he"watet present in the interior 01 through any pores or intention, but must esca e during heating through thewhomogeneous surface of the film structure. 1

' It is known that with cellulose films the surface dries more quickly than the inner layers.

Furthermore, the drier that the surface is, the

' greater is the resistance that it ofiers to the diffusion of the water included in the interior.

The initial drying process accordingly counteracts the subsequent evaporation or the water present in the interior of the film, which naturally also retards the dryingprocess and also gives rise to undesirable difierences in tension between the surface and the inner layers of the I film, the result being the known irregularities in Y shrinking, deformations, creases and'stresses'in the finished film.

It has now been ascertained in'accordance with the present invention'that the described dimculties can be avoided and the drying eflected more rapidly and economically by conducting the dry- .ing process in such a manner as to avoid hardening or the-surface by said drying. The present invention achieves this by commencing the dryingin a moist atmosphere saturated with water vapour and only reducing the vapour content of this atmosphere as the drying progresses. The warming or the film structure and the moisture contained therein to the necessary evaporating temperature is efiected according to the present and the temperature or the vapour atmosphere on the other hand, should be adjusted in relation to each other and both should be adjusted relatively to the vapour content of theheating atmosphere in such a manner that the foregoing favorable difiusion process may take place.

The present invention therefore provides a process for drying cellulose pellicles and the like, in which the drying process, is commenced by heating the wet cellulose structure by means of a heated vapour or heated atmosphere and for a heated drying support for the cellulose structore. up to the particular temperature oi drying desired, which vapour atmosphere in relation to the filmtemperature at the time is at least saturated with vapour, and than continuing the drying process, if the film structure is heated to thepredetermined drying temperature by graduv ally allowingthe vapour content to fall in accordance with'the progress of the drying oi the film structure, that is in accordance with the progress of the. diffusion or the water vapour from the interior to the surface of the film structure. The

drying temperature will during this time remain practically constant.

The surprising result'ot this process is shown in the diagrammatic sketch, Fig. 'I, attached hereto, in which diagram the drying time and the degree oi drying out at any time are plotted as '"'o'rdiiia'te'and abscissa respectively. The two curves show the progress oi'the drying in accordance with the former principle (a) and the prin; ci'ple underlyingthe-inv'ention- (b) Whereas" in the case of theiormer drying principle the 'amountof water evaporated is initially many times larger than that in accordance with the ini vention, nevertheless in'the new method 0! workas'rniss in: as the curve shows. the drying process is completed considerably earlier than hitherto. The progress of the curve (in, which is almost a straight-line, shows how uniform is the drying. and investigation of the thus dried product confirms that it is also free from tension, it does not split when out, and is-more resistant to tearing than the hitherto known products.

The present invention, owing to the resultant economy in heat and shortening of the drying time. unites the advantage ofan economical working withgthatpi products'ioi improved quality. Thepresentprocess can in general be car-' ried out on anymachine or apparatus, which enables the pouring supportto be passed through clined direction for the first portion at least and for themaior portion of its travel through the precipitatingbaths. v

This arrangement also affords the advantage that the film precipitated on the surface of the belt does not sag downwards in along horizontal 1 stretch, but receives better support on the drums. It therefore does not possess any tendency to detachitself from the support orto tear owing to' its dead-weight, but lies against the belt. Moreover this arrangement permits a compact and comp'endious construction particularly in belts of the various -treatment liquids necessary for the formation of the film, or to allow said liquids to act ina suitable manner on. the film engaging, and 'formingon, said support for example by g. The ordinarily used type of belt pouring machine, such' as is used for the manufacture of acetate foils and photographic films by the dry" method, cannot be used for the "wet process of the present invention owing to. the necessity for treating the film with several wet reagents, as mentioned-above. These belt pouring machines p with two guiding drums for the pouring belt have not'hitherto been used in practice for the wet process,- because it is not easy to solve the problem of installing, the drums and the lower half of the pouring belt with respect to the usual construction of the apparatus. More- 50 and 100 yards in length. Finally it is possible with this-arrangement to enclose the liquid container in a simple and ingenious manner so that y it is possible to exhaust and recover the vapours.

The pouring belt and/or the drums may be heated or cooled in a manner known per so. For

the supporting belt and the drums also nonover, the fiat elongated shape of the aforesaid apparatus is not favourable for running a belt with a film coating thereon through a precipitating bath'because the him has at the underside and can therefore readily peel'ofl or fall of! from the support oi its ownaccord. A film coating so loosened or peeled off fromthe support gives difficult to avoid on account of the principle of the aforesaid pouring machine type.

A belt pouring machine, however, can therefore be used for this process, according to the present invention. Such machine fulfills the requirements. to-wit; that the poured cellulose solution coming into contact with the treating liquids must not run oi! the belt and, when it subsequently solidifies, that the resulting film structure should not become detached from the belt prematurely. To this end and in accordance with said requirements, the apparatus of the present invention comprises not two guide drums for the belt as hitherto customary, but three or more guide drums some of which, generally two, are mountedoutside of the liquid, while the others are accommodated completely or partially within corrosive kinds of steel are preferably employed, or the'supporting belt and the drums are protected from the varying actions of the treatment baths .bymeans of non-corrosive coatings. I

In accordance with this invention, the drying may be carried out in "practice with any drying machine suitable for drying this product, hn-

proved by modifications of individual parts and by supplementary. mechanical devices. ample, a" cylinder drying machine heated with steam, hot water, oil, and the like, is supplemented by a system of pipes through which there is blown onto or between each pair of the several cylinders, air at the appropriate temperature, and of the requisite water vapour content or else the drying machine is enclosed in surrounding walls in the manner customary in these drying machines. Partition walls 'are disposed at suitable places inside the surrounding walls I which enable different vapour contents of the :4 rise to producing the 'sametroubles asaceompany an unsupported film, and'which also are j surrounding atmosphere to be maintained. The necessary adjustment, regulation and maintenance of this vapour atmosphere is effected onv the one hand, by supplying varying quantities of dry air to the separate'chambers, and on the other hand, by conducting away varying quanti ties of the vapours evolved during drying.

It isobvious that various changes and modifications may be made to the details of construction without departing from the general spirit of the invention as set forth in the appended r m1 s 7 FY a p i V l .i. The process of'manuf mr NH ions. membranes, hands and the like, from cf monium cellulose solution while continuously v supported during coagulation and regeneration, which comprises pouring the cellulose solution onthe outer face of an endless. movable support to form a layer, coagulatingthe layer by a coagulating liquid while still on the outer face of the support, thereupon regenerating the layer so coagulated by a regeneratingliquid while still for the chemical process by the suitable location of the third or also of a fourth or fifth drum.

In accordance therewith, the pouring slit is located over the upper or dry" run of the pourin; belt, while the belt itself is guided in an in on the outer face or the support, and only then removing the layer so regenerated from-the initial support to prevent any interruption in sup porting the layer before being finally removed.

2. The process of manufacturing foils, membranes, bends and the like, from a cuprainmonlum cellulose solution while continuously supported during coagulation and regeneration, which comprises pouring the/cellulose solution on the outer face of an endless movable sup port to term layer, coagulating the layer by a coagulating liquid whilestlll on the outer of the support, thereupon regenerating the layer on the outer face of the support, thereupon washing the layer while still on the outer face or the r awai s so coagulst'ed by a regenerating liquid while still on the outer face of an endless movable support toform-a layer. coagulating the layer by a cosupport, and only'then removing the layer from for a drying on theouter face of an endless movable support to form a layer, coagulating the layer by a coagulating liquid while still on the outer face of the support, thereupon regenerating the layer so coagulated by a regenerating liquid while still on the outer face of the support and the'ntrans ferring the layer so regenerated from the initial support, the coagulating and regenerating liquids being applied by spraying or the like. v

4. The process of'manufacturing films, foils, membranes, bands and the like, from a cuprammonium cellulose solution while I continuously supported during coagulation and regeneration,

which comprisesipouring the cellulose solution on the outer face of an endless movable support to form a layer, coagulating the layer by a coagulating liquid while still on the outer face of the support, thereupon regenerating the layer so coagulated by a regenerating liquid while stillon the outer face of the support and then transferring the layer so regenerated from the initial support, the coagulating and regenerating liq uids being applied by transferring the same onto the layer from wetted transfer rollers or the like. 5. The process of manufacturing films, foils,

agulstingliquid while still on the outer face of the support, thereupon regenerating the layer" so coagulated by a regenerating liquid while still on the outer face of the support and then transierring the layer so regenerated from the initial support, the coagulating and regenerating liquids .being applied to the layer by transferring the same from a wetted transfer belt or the like.

6. In an apparatus for the manufacture of extensive lengths of sheets, films and the like, the

combination of an endless supporting belt, guiding drums solely on the inside-of said endless belt for'movably supporting said belt, a pouring device for pouring a cellulose solution on the belt to form a supported layer, means for successively applying treatment liquids including coagulating and regenerating liquids to the supported layer without in any way interrupting its support on said single supporting belt, and means for finally removing the layer so treated.

'1'. In an apparatus for the manufacture of ex- 'tensive lengths of sheets, films and the like, the

combination of anendless supporting belt and a drying apparatus, guiding drums solely on the inside of said endless belt for movably supportin: said belt, a-pouring device tor'pouring a celmembranes, bands and the like, from a cuprammonium cellulose solution while continuously supported during coagulation and regeneration,

1 which comprises pouring the cellulose solution lulose solution onto the belt to form a supported layer, means for successively applying treatment liquids including coagulating and regenerating liquids to the supported layer without in any way interrupting its support on said single supporting belt, means for washing thelayer while still supported, on said belt, and means for finally removing the layer from said belt and transferring it to the drying apparatus.

EMIL CZAPEK.

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