US1920118A - Apparatus for making flowed films and sheets - Google Patents

Description

' July 25, 1933. J..F. WALSH ET AL 1,920,118

APPARATUS FOR MAKING FLOWED FILMS AND SHEETS Filed July 19, 1928 IIIIIIIIIIIIIIIA w 1\\\ JAMES F. WALSH JOHN H. STEVENS KI RTLAND F LYNN AMERIGO F. CAPRIO THOMAS E. AISORN INVENTORS BY f ATTORNEYS Patented July 25, 1933 UNITED STATES JAMES F. WALSH, OF EAST ORANGE, JOHN H. STEVENS, OF SOUTH ORANGE, KIRTLAND FLYNN, 0F ORANGE, AMERIGO F. CAPRIO, OF NEWARK, AND THOMAS E. ALCOBIN, OF MAPLEWOOID, NEW JERSEY, ASSIGNOBS T0 CELLULOID CORPORATION, A 003- PORATION OF NEW JERSEY APPARATUS FOR MAKING FLOWED rims AND sum-rs Application filedJuly 19,

rivatives, the latter being either organic or.

inorganic in nature. I

Heretofore it has been customary to produce films or sheets of cellulosic materials by pouring more or less viscous solutions of the cellulosic materials upon a polished surface of glass or other suitable material. Also such films and sheets have been made by pouring the cellulosic solution upon a belt or wheel with a high finished surface, preferably of metal. In all of these processes the surface upon which the dope solution is formed are rigid and subject to much Wear and tend torbecome corroded and/or pitted. In view gof this fact they must be renewed or refinished frequen'tly in order to yield satisfactory films. These frequent renewals of the film forming surfaces together with the limitations imposed by the use of a rigid and fixed surfacehave greatly curtailed the output of films and sheets with the consequent increase in their cost.

-An object of our invention is to provide a process for the continuous production of sheets or, films. Another object of our invention is to provide a new medium for use as a film forming surface. Still another object of our invention is to devise a process wherein a moving liquid medium, specifically metallic mercury, can be utilized as a film forming surface. Other objects and advantages of our invention will appear hereinafter in the description and claims.

We have found that improvedfilms and sheets of celluloid like materials can be.produced from more or less viscous solutions of cellulose or cellulose derivatives if the solution is poured or delivered onto a moving PATENT orFics 1928. Serial N0. 293,893.

position will not be changed by the solvent present in the cellulosic solution in order 'to Insure a film which will be uniform in composition and in physical appearance and also to enable the liquid to be continuously recirculated through the system.

Metallic mercury has been found by us to meet all these requirements and to yield excellent films or sheets when used as the film forming surface. Its great mobility and its smooth, high-glossed surface, together with its inertness towards the solvents usually employed in the manufacture of films and sheets of cellulosic materials make it especially suitable for the process at hand.

Instead of mercury a low melting alloy can be used, particularly when it is desired to effect a rapid evaporation of a solvent. For example such an alloy could be em- I ployed where the resulting film or sheet, containing some residual solvent, is rolled or piled up into a chase and consolidated into a block under heat and pressure, as is I often done in the cellulose plastic art. Alsosuch a low melting alloy "could be utilized when solvents of high boiling points or low volatility are employed. 7 As an example of such an alloy the folv lowing may be given:

Per cent 30 Lead 25.0 Tin I s 12.5 I Bismuth 50.0 Cadmium 12. 5 I

This alloy has a melting point of about 55. C. and was found to give good results when employed in the place of mercury. Other suitable low melting alloys can also be used.

The process is carried out by depositing the ribbon or sheet of cellulosic solution on a moving body of metallic mercury. The dope is preferably deposited on to the mercury as the solution issues from a hopper and, due to the smoothness of the'mercury surface and the fact that the mercury is continuously moving away from point-at which it receives the sheet or film, a sheet or film of uniform thiclmess and high glo$ is obtained. The thickness of the sheet or film can be varied as desired by increasing or finished product. In the drawing, forming a part of this specification, 1 represents a trough with bafile plates 2, 2 arranged along its base and sides to insure a uniform flow of mercury, 3, in the trough. The mercury is fed into the i trough through inlet 4 and due to the fact that the trough is elevated at the inlet end, the mercur will flow through the trough over the ba es .2, 2=toward the outlet or outlets 5, in the end plate 6. The mercury is.

- drawn oil through an overflow pipe or pipes 7 andis fed to overflow tank 8. The mercury is then recirculated through conduit 9 and mercury pump 10, the latter delivering the mercury to the inlet 4.

The hopper 11, containing the dope or solution 12, is arranged with a slit like outlet 13 in proximity to the surface of the.

traveling mercury. The hopper is rovided with a gate 14, manipulated by t e lever arrangement 15 to vary the Width of the o ening 13, through which the curtain or sleet of dope 16 is delivered. The trough 1, is provided with a compartment 17 in which heating means may be installed or through which a heating medium may "be passed to maintain the mercury at elevated temperatures in order to facilitate theevaporation of the solvent in the dope solution. The stripping roll 18 is positioned near the outlet end of the trough 1 and takes up the film from the surface of the mercury. The film thus taken up is passed from the roll 18 to the drying drum 19 and thence to the Winding spool or drum20. One. or more drying rolls may be used as desired and the film or sheet may be passed over several rolls similar to 18 before being passed :to the drying drum or drums.

.In operating in accordance with our in vention we proceed as follows. Upon a su faceof metallic mercuryof sufiicient depth and so arranged that it will flow of its own level-seeking tendency a broad sheet or rib bon of a solution of ccll-ulosic materials is deposited, the supply of dope being regulated in accordance with the thickness of sheet or film desired the rate of travel of the mercury, the volatility of the solvent, employed, etc. lVhere deemed advisable the flow of the mercury can be accelerated by utilizing submerged propelling devices in the mercury bath. In such an event care must. be taken that the smoothness of the mercury surface is not destroyed or. dis- 6 turbed. A natural flow induced solelyby producing the films and for winding up r the inclination of the trough and the draw mercury inthe bath and also because it reduces the possibility of distortion or rippling on the mercury surface.

The uniform forward moving of the mercury is insured by the proper distribution of the bafiles2, 2 for instance, by spacing the same about a foot apart'along thelength of the trough. These ballles, of course, are sufliciently narrow or shallow so as to permit the mercury to com letely cover the same. This arrangement 0 bafiies overcomes or counteracts the usual tendency of li uid steams to move at a greater rate of spec in the centre than at the sides.

The constant forward moving of the mercury bath serves to uniformly draw the dope solution from the hopper outlet and as the sheet or film moves forward the .solvent evaporates. leaving the comparatively dry sheet or film on the surface of the mercury. This evaporation of the solvent can be expedited by maintaining the mercury at ele vat-ed temperatures in any desired manner.

The film or sheet, in more or less dried condition, is removed from its mercur support by -means of the stripping r0 1. If the sheet or film has a sufficiently low per-- centage of solvent remaining therein it may be passed directly to the drying drum or drums, otherwise it should first be passed or containing a cellulosic base, whether the same is cellulose or one or more of its de rivatives, such as, for example, pyroxylln, acetyl cellulose, viscous, ethyl cellulose, etc.

The term cellulose derivatives as used in the description and claimsis used to include the esters and ethers of cellulose as well as cellulose itself, regenrated or otherwise.

The dopcs or solutions of the cellulose derivatives employed can be produced by utilizing any suitable solvents or mixtures of solvents for the specific cellulose derivatives or derivatives employed. 'Where desirablc. depending upon the use to which the final product is to be put, the solvent or solvents employed may be modified by suitable restraining agents in the form of selected organic compounds or they may have incorporated therein plastifiers for the particular cellulose derivative used.- Also inflam-ma Mandi! bility reducing agents or fire retardants can be incorporated in the dope where such addition will not interfere with the flowing or feeding-of the film onto the mercurysurface. The size of the trough '1, or the mercu bath will vary, depending upon the widt and length of the film} or 'sheet desired.

Where a thin sheet or film is desired the length of travel on the mercury bed will not have to be as long as it will be for a thick film or sheet. A suitable length :for the mercury bath has been foundto be 45 'feet, permitting the maintenance of a sheet or film of about 40 feet in length onthe bath. This length gives the sheet or film ample time to dry and set sufiiclently to ena Is it to be stripped from the mercury bed.

The following is given as an example of a suitableembodiment of our invention forthe production ofa celluloseac'etate film-ap- .2 2

proximately 1.005v inches thick.

The cellulose acetate do e, utilizing a rapidly drying solvent me ium, was poured ontoa movm mercury bed of approximately 45 feet in length and 28 inches in width. The rate of travel of the mercury bed was 120 feet per hour and the film in process of deposition and setting was 40 feet long and 22 inches wide. These'conditions allow twenty minutes for the setting and drying of the film from the time of its delivery from the hopper to the point of stripping from the mercury bed.

As stated above, the conditions above set out are illustrative only, the dimension of the trough, time of settin rate of travel, etc., being variable depending upon the size and thickness of the sheet desired, the nature of the solvent'employed, the temperature of the bath,'etc. Thus :where a thicker sheet or film is desired therate offfiow of a level position.

the mercury can be lower and/or the length of the bed increased.

It will be seen that our invention makes it possible to form films and sheets on plane or substantially flatsurfaces in place '0 wheels, belts, etc. This offers a great advantage, particularly when comparatively thick sheets or films are desired. Thes thicker sheets or films require more time for setting and drying than is possible to be attained on the curved surface of a wheel. This premature removal of the film support very frequently results in a sagging or distortion of the film or sheet due to insufiicient time having been allowed .it to set. Although thick sheets or films are usually produced on belts of similar surfaces these also have been found objectionable, because of the tendency of the bath to sag or sway from These difiiculties are all overcome by the use of a mercury orother liquid bath in accordance with our invention for the mercury or other liquid is always level or substantially so. The employment higher rate of central flow of the mercurv of 'a liquid or mercury-bath has the further advanta; that its motion is moresmooth and uni orm than that of a belt mechanical- -.ly. vdriven.

The uniform forwardmotion of the mar: cury is-accomplished, as previously stated, by slightly tilting the trough in the direction of its length and further by providing several draw-offs at the lower end of the trough. To. further insure that the liquid or mercury will travel forward uniformly, at least along that part of its surface which .is in contact with the :film or sheet, the mer curv surface should 'be of sufiicient width that there will be at least 3 inches of unused mercury surface on each side of the film. This will minimize the tendency of a and will supplement the efiect of the bafiies The process utilized in accordance with our invention is not limited to moving the mercury bed forward in the manner above set forth. Any means which will not distort or disturb the smooth surface of the mercury can be utilized. For example, the

mercury might be carried forward on a travelmg belt suitably sectioned to hold the mercury level until it passes beyond the strippingpoint and also provided with sides to retain the mercury. Also it is possible to impart the forward motion to the :mercury by installing propelling devices in the body .of the mercury as previously indicated.

Our inventionv .has the further advantage that it not only'ma-kesit possible to pro duce uniform sheets or films of any size butthe products obtained are superior to "sheets or films obtained as a result of present modes of manufacturing.

Also since it does away-with the constant renewal-and refinishing of the highly polished surfaces now necessary for film manufacture, it lowersthe cost of production con siderably. Another decided advantage re f sulting from our invention is the fact that all thicknesses of sheet or film can be produced :by this method, whereas, comparatively thin sheets only can be produced where a wheel is used as the film forming;

surface.

The terms sheets and films are used interchangeably since the production of sheeting of various thicknesses by the present process is; contemplated. The term sheets as used in the claims is therefore to be interpreted as including films as well as sheets. The term spreading as used in the claims embraces within its scope any suitable means of depositing; the sheet forming solu-- tion onto the moving bath, whether the same beby flowing, dropping or spraying.

.Having described our invention, what we claim .and desire to secure by Letters Patent is: I

no. -u

1. Apparatus for the production of sheets which comprises in combination an inclined ":trough, a liquid sheet-supporting surface, a

reservoir adapted to contain the sheetforming solution and a stripping roll adapted to 1 remove the sheet from the sheetsupporting surface. p 4 J 2'. Apparatus for the reduction of sheets which comprises in com ination an inclined trough, a liquid sheet-supporting surface, a

reservoir adapted to contain the sheet forming solution, a stripping roll adapted to recollected.

move the sheet from its" support, drying means to efiect the final drying of the sheet and a roller on which the dried sheet is 1 3. Apparatus for the roduction of sheets which comprises in com ination' an inclined trough provided with an inletand outlets,

a liquid sheet-supporting surface, a reservoir adapted to contain the sheet forming solutionJa-nd a stripping roll adapted to remove the sheet from the sheet-supporting surface,

which comprises in com ination an inclined trough provided with bafiies and aninlet and outlets, a liquid sheet-supporting surface, a reservoir adapted to contain a sheet forming solution and a stripping roll for removing the sheet from the sheet-support.

1 7 JAMES F. WALSH.

JOHN H. STEVENS. KIRTLAND FLYNN. AMERIGO F. CAPRIO. THOMAS E. ALCORN.

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