US2045348A - Manufacture of films, foils, and the like containing cellulose derivatives - Google Patents

Description

June 2 3 ,1936. H; R YFQ 2,45,348

MANUFACTURE OF- FILMS, FOILS AND THE LIKE CONTAINING CELLULOSE DERIVATIVES I I Filed Aug. 25, 1955 HENRY DREY'FUS \NVENTDR Patented June 23, 1936 I l UNITED STATESPATENT OFFICE MANUFACTUREOF FILMS, Fons, AND THE LIKIVESCONTAINING OELLULOSE DERIVA- 'r a .7 Henry Dreyfus London, England Application August 25, 1933, Serial No. 686,739

In Great Britain September 9, 1932 9 Claims. o1. 18-15) I This invention relates to improvements in celludium may tendto set up liquid currents which lose derivative products and particularly to the also disturb the relatively fragile film, it' is admanufacture of films, sheets, foils, for example, vantageous inthe case" when the film'passes those used for wrapping purposes, and like ma through the liquid medium before contacting with terials from solutions of cellulose acetate or other the supporting surface to surround it in this me- '5' cellulose ester or ether by wet coagulation procdium'with a protecting shield. Such shield may esses. if desired be a continuation of the casing sur- I have discovered that particularly good results rounding the film in its passage fromthe' shapare obtained in the manufacture of films, which ing orifice to the surface of the coagulating 10 term is to be understood as includingfoils, sheets medium and may be formed in one piece with it. 10 and the like, from solutions of cellulose acetate When such a shield is employed means will of V or other cellulose derivative when the extrusion course be adopted to ensure that the medium in orifice or other shaping deviceis situated outside the neighbourhood of the film is maintained in the coagulating medium, and according to the such a condition that satisfactory coagulation is present invention, therefore, films having a basis obtained, e. g.'by maintaining a slow circulation 15 of cellulose derivatives are produced by causing of the medium in the vicinity of the product. a solution of a cellulose derivative to issue from In order'to prevent a too rapidi evaporation of a suitable shaping device which is outside the any volatile'solvent from the film after issuing coagulating medium, and then passing the film from'the shaping o'rificeand before its entry into such medium. I into the coagulating bath, itmaybe desirable to 2' Any suitable means of shaping the film-formmaintain a relatively high concentration of soling solution may be employed. Thus it may be vent in the atmosphere surrounding the film. passed through an elongated slit or between roll- Thus when the shaping orifice is contained in' a ers, and the distance of such shaping device from casing as described in the preceding paragraph,

the coagulating medium may be quite small, for the atmosphere in such casing may be maintained Q5 example 1 or 2 inches or'it may be greater, for substantially saturated with solvent vapour, for example, 6 to 8 inches or even more; After issuexample, by the presence inside the casing of a ing from the orifice the film is preferablyreceived vessel containing solvent and/ or a fabric or other upon a suitable supporting surface, for example fibrous material or a porous material as for ex-.

39 a band or drum, and this surface may be wholly ample, pumice,- saturated or substantially satu- 0 or partially immersed inthe coagulating liquid. ratedwith solvent. Suitable means may be pro- By causing the film to enter the coagulating mevided for maintaining the fabric or other exdium before contacting'with the supportingsun tended surface in a saturated state, as for exface the advantages, described in British Patent ample, by immersing a portion of it ina bath con- No. 405,692, resulting from contact of the coagutaining solvent or by allowing solvent to drip onto 3 lating medium with both surfaces of the product it through suitable orifices. If, however, it is may be obtained. i Y. desired that at least a partial coagulation of the Since the films produced according to theprocfilm shall take place before its entry into the ess of the present invention are in general very coagulating medium, means may be provided by 40 thin and fragile, and arethus-liable to be diswhich a current of air or other evaporative me:- 40 turbed in their passage from the shaping orifice dium is passed in contact withthe film during its to the supporting surface or liquid medium by passage from the shaping orifice to the coagulatair currents, it is advantageous to surround the ing medium, for example by passinga currentof shaping orifice with a shield in order to isolate air through the casing surrounding the film, or

3 substantially the surrounding atmosphere. Such the film may be sprayed with a coagulating mea shield may consist merely of metal or other dium. Moreover, the use of both these means sheets surrounding the shaping orifice and exin conjunction is of course not excluded.v tending downwards towards the supporting sur- If desired, a stretch may be imparted to the face or the surface of the liquid, but preferably films during their production. Thus the film may a casing isemployed in which the shaping orifice be taken up on a drum or other support travel- 50 is situated, the bottom of this casing either dipling at a speed greater than that at-whi'ch'the ping into the coagulating medium or making close film issues from the shaping device, or, alternacontact with the surface of the supporting band, tively, the films may be stretched laterally and/or drum or the like. Further, since the rotation of transversely by means of the apparatus described t supp t g surface in the coagulating-mein U S. Patent No. 2,034,716.. r 55 Any suitable solvent may be employed for forming the solution of the cellulose acetate or other cellulose derivative, as, for example, relatively low boiling solvents or solvent mixtures such as acetone, acetone and alcohol, methylene-ethylene-ether and mixtures of methylene or ethylene chloride with ethyl or methyl alcohol, or of methyl or ethyl acetate with .methyl or ethyl alcohol. Higher*boiling'solventsmayalso be used, for example, methyl ethyl ketone, dioxane, diglycerol tri-ether, diacetone alcohol, esters or ether-esters of olefine and .poly-olefinelglycols, for example, glycol mono-acetate I01 :methyl glycol mono-acetate, ethyl lactate, and homolo-gues and substitution products of methylene ethylene oxide and dioxane, as for example the esters and ether-esters of dioxane-dicarbinol. .Mixturesof solvents, e. g. a mixture of a low and higher boil-- ing solvent, may also be employed. The filmforming solutionsmay also contain diluents, for example water, glycol, glycerol .or other hydroxy compound, benzene, toluene, kerosene,rhexahy- .dro-benzene or other aromatic-aliphatic or alicyclic hydrocarbon, and halogenated hydrocarbons, for example, tetrachlorethane and dichlorethylene. High boiling solvents or plasticizers .for the cellulose derivative .may also be incorporated in the film-forming solutions, and examples of such substances are the aoetins, alkyl phthalates, for example :diethyl :phthalates, and arylsulphonamides, :as for example the monomethylated or .ethylated xylene :sulphonamides.

and 1380;819. .Coagulating baths containing the same solventzas that present in the film-forming solution, as is described in British Patent No. 405,=6.'Z6,maybeadvantageously employed. Again, the coagulating bath may be one in which the solvent :of the film-forming solution is immiscible or is miscible only in certain proportions as described in British Patent No. 407,673. Thus, for example, :an :acetone solution of cellulose acetate maybe coagulated in a bath consisting of orcontaining benzine, kerosene or other para'flin hydrocarbon. Again, coagulating media containing glycerine, sugars or other polyhydroxycompoun'ds may be employed, see for example British Patent No. 406,986. The =use of solutions 'of inorganic salts, for example, sodium chloride or calcium chloride, :as is described in British Patent No. 406,337, has, however, been found to be of particular value in connection with the present process.

The period of contact of the film with the coagula-ting media may be such that when they issue therefrom they contain substantially no residual solvent, in which case they may be directly dried, with or without previous washing or other treatment to remove any adherent coagulating media. If, however, on issuing from the coagulating bath, the films contain residual solvent,theymay be washed, for example with a salt solution or with dilute solutions of solvents in order to remove such solvent and may then be dried. Preferably however, residual solvent, or at least a small percentage of solvent, for example the last 5 to 10% based on the weight of the material, is removed by evaporation, for example by passing the films through drying chamhers or over heated surfaces.

The drying of the films may take place on the drum or other support on which they are produced or in a separate drying apparatus. In the former case the upper part of the ascending side of the drum may be provided with an enclosing heating segment, which may be heated by steam pipes or in any other suitable manner so that the V films are practically completely dried, and they may then be passed to suitable take-up rollers. When-drying takes place in a separate apparatus, the .afi-lms :may pass from the drum or other support to the drying apparatus, for example a steam heated drum.

Examples of apparatus which may be employed according to the present invention are illustrated in {the accompanying drawing, wherein Figure 1 shows a cross-sectional elevation of one form of apparatus comprising a drum which is partially immersed in the coagulating medium,

Figure 2 is a cross-sectional elevation of another form of apparatus wherein the drum is completely immersed in the coagulating medium, and

Figure 3 .isza cross-sectional elevation of a portion of a similar apparatus.

Figured illustrates an apparatus comprising a vessel 5 for coagulating medium, a. drum 6 which rotates in such medium, and a valve-controlled I inlet FI and. -.an outlet .8 for coagulating medium. Thefihnd is extruded through a suitable shaping device I10 connected by means of a pipe I I with a :supply of film-forming solution, and contacts with the drum 5 from which it passes'to a roller and .thence to suitable washing and drying devices. The shaping device I0 is situated in a casing I'2, .oneside of the casing being formed by an extension :of an end of the vessel 5, while the opposite side of the casing extends downward towards the coagulating drum without actually touching the surface of this drum. A hinged flap -I3 is fitted in the side of the casing to allow of access to the shaping device.

Figure 2 illustrates a similar form of apparatus comprising ra drum 6 rotating in a vessel 5 provided with a valve-controlled inlet I and an outlet 8 for coagulating medium. Both inlet and outlet are formed by a slotted or perforated pipe extending across the Width of the vessel, so as to obtain auniform introduction and withdrawal of coagulating'medium across the Width of the vessel. The film '9 extruded from the shaping device "I11, which is situated Within a casing I2 and which isconnected with the supply of film-forming solution by a pipe II, contacts with the drum 6 and passes from the drum over a roller to washing and drying devices. The drum 6 is entirely immersed in the coagulating medium, and one side of the casing I2 surrounding the film-forming-device is extended downwardly below the surface of the coagulating medium until it almost contacts with the drum. In order to assist circulation of the coagulating medium the portion of this 'side of the casing below the surface of the coagulating medium may be perforated, or maybe formed of metal gauze. Towards the bottom of one side of the casing, but above the level of the coagulating medium, is a shallow vessel I 5 which may be filled with solvent liquid in order to maintain the atmosphere in the casing substantially saturated with solvent, and in order to assist in achieving this object a piece of suitable absorbent fabric or other material I6 is suspended from the top of the casing so that its lower edgev dips in the solvent contained in the vessel l5; Doors I3 and I4 are fittedto the easing to allow of access to the film-forming device and the vessel l5 andfabric I6. Figure 3-illustrates a detail of asimilar-apparatus in which means are provided for effecting evaporation of some of the solvent from the film before its entrance into .the coagulating medium. As inv the other illustrations the apparatus comprises a supply pipe H and a shaping device H), which is situated within a casing I2 and from which the film 9 is extruded, the film contacting with a supporting drum 6. Coagulating medium is withdrawn from the;v'essel 5 by an outlet pipe 8, similar to that described in connection with Fig. 2, An inlet for evaporative medium is provided at I! and an outlet for such medium at .IB, both inlet'and outlet being fitted with valves Example A 25% solution of cellulose acetate in acetone is extruded through a shaping orifice contained in a suitable casing, as illustrated, for example, in Figure 2, and after passing for about three inches through the atmosphere contained in the casing it enters a coagulating bath consisting of a 25% aqueous solution of calcium chloride. After passing for about two to four inches through the coagulating bath the film passes round a rotating drum Where the coagulation of the film is completed. The film is then washed, first with dilute aqueous calcium chloride solution, for example 5-8%, and then with water, is dried on a steam heated drum, and wound.

While the invention is of particular value in relation to the production of films from solutions of acetone-soluble cellulose acetate, yet it is also of value for the manufacture of such products containing other cellulose acetates or other derivatives of cellulose, for example celulose formate, propionate, butyrate, nitroacetate or other organic ester or mixed ester of cellulose, cellulose nitrate, methyl, ethyl, butyl or benzyl cellulose or other cellulose ether or mixed ether, and mixed ether-esters, for example ethyl cellulose acetate and oxy-ethyl-cellulose acetate.

While particular methods of carrying out the present invention have been described above, it is to be understood that the invention broadly covers the production of films, foils, sheets and the like from solutions of cellulose derivatives, by passing the solutions into coagulating baths from shaping devices which are not in contact with such baths, and also includes the apparatus described in connection with the preferred forms of the invention.

The term encompassing gaseous medium as employed hereinafter in the claims is to be construed to means a gaseous medium which contacts with both sides of the shaped product.

What I claim and desire to secure by Letters Patent is:-

1. Apparatus for the manufacture of films, comprising a vessel for coagulating liquid, means for circulating coagulating liquid through such vessel and for maintaining a constant level of coagulating liquid therein, a device having a slot formed therein for shaping the film-forming solution disposed above the level of liquid in said vessel and adapted to extrude the'shaped material'first through an encompassing gaseous medium and then into the said liquid, a casing surrounding the shaping device and extending from such'device to the surface of the coagulating liquid adapted substantially toisolate the said encompassing gaseous medium from the surround .ing atmosphere, and means for introducing the vapor of a liquid into the interior of such casing.

2. Apparatus for the manufacture of. films,

comprising" a vessel for coagulating liquid, means for circulating coagulating liquid through such vessel and for maintaining a constant level of coagulating liquid therein, a device having a slot formed therein forshaping the film-forming solution disposed above the level. of liquidin said vessel and adapted to extrude the shaped material first through an encompassing gaseous medium and then intothe said liquid, a casing surrounding the shaping device andextendingfrom such device to the'surface of the coagulating liquid adapted substantially. to isolate the said encompassing gaseous medium from the surrounding atmosphere, means for introducing the vapor of a liquid into the interior of such cas- 2 ing, and a rotatable drum positioned at least partially below the liquid level in the vessel for coagulating liquid and adapted to receive and support the shaped material.

3. Apparatus for the manufacture of films,

comprising a vessel for coagulating liquid, means for circulating coagulating liquid through such vessel and for maintaining a constant level of coagulating liquid therein, a device having a slot formed therein for shaping the film-forming solution disposed above the level of liquid in said vessel and adapted to extrude the shaped mate rial first through an encompassing gaseous medium and then into the said liquid, a casing surrounding the shaping device and extending from such device to the surface of the coagulating liquid adapted substantially to isolate the said encompassing gaseous medium from the surrounding atmosphere, means for introducing the vapor of a liquid into the interior of such casing, a rotatable drum positioned at least partially below the liquid level in the vessel for coagulating liquid adapted to receive and support the shaped material after such material has passed through a portion of the coagulating liquid, and a shield adapted substantially to isolate the portion of the coagulating liquid surrounding the shaped material along its path from the surface of the coagulating liquid tothe surface of the drum from the remainder of the coagulating liquid.

4. Process for the manufacture of films, which comprises forming a solution of an organic derivative of cellulose into the required shape, passing the shaped product through an encompassing gaseous medium while retarding evaporation of solvent from the shaped product by introducing solvent vapor into said gaseous medium from an external source, and thereafter coagulating the shaped product by passing it into a coagulating bath.

5. Process for the manufacture of films, which comprises forming a solution of cellulose acetate into the required shape, passing the shaped product through an encompassing gaseous medium while retarding evaporation of solvent from the shaped product by introducing vapor of said solvent into said gaseous medium from an external source, and thereafter coagulating the bath.

6. Process for the manufacture of films, which comprises forming a solution of cellulose acetate into the required shape, passing the shaped product for a distance of 1 to 8 inches through a confined encompassing gaseous medium while retarding evaporation of solvent .from the shaped product by introducing vapor or said solvent into said gaseous medium from an external source, and therafter coagulating the shaped material by passing it into a coagulating bath.

'7. Process for the manufacture of films, which comprises forming a solution of cellulose acetate into the required shape, passing the shaped product for a distance of 1 to 8 inches through a confined encompassing gaseous medium while retarding evaporation of solvent from the shaped product by introducing vapor of said solvent into said gaseous medium from an external source, thereafter coagulating the shaped material by passing it into a coagulating bath, and receiving it on a moving supporting surface which is at least partially immersed in said bath.

8. Process for the manufacture of films, which comprises forming a solution of cellulose acetate into the required shape, passing the shaped product for a distance of 1 to .8 inches througha confined encompassing gaseous medium while retarding evaporation of solvent from the shaped product by introducing vapor of said solventinto said aseous medium from an external source, and thereafter coagulating the shaped product by passing it into a coagulating bath so that coagulating liquid contacts with both sides of the shaped product and then contacting the shaped product with a moving supporting surface which is at least partially immersed in said bath.

9. Process according to claim 8 wherein the portion of coagulating medium through which the shaped product passes before contacting with the supporting surface is substantially separated from the remainder of the liquid.

HENRY DREYFUS.

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