US2070027A - Recovery of cellulose organic ester plastic materials - Google Patents

Description

Feb. 9, 1937. M. J. REID 2,070,027

RECOVERY OF CELLULOSE ORGANIC ESTER PLASTIC MATERIALS Filed Sept. 11, 1934 FILM SCRAP mvme CELLULOSE ORGANIC ESTERSUPPORTAND mmocnwwsr SUB CHOPPERS mssowen HOT WATER SALTS TO SILVER By WATER RECOVERY COLORING SUPPORT amcnco HYPOCHLORITE MATTER TO REMOVE BLEACHING REMOVED COLORING MATTER soumou ccLLosoLvz NITROCELLULOSE CELLOSOLVE SOLUTION OF AND PLASTICIZER (HONOETHVL ETHER NITROCELLULOSE LEACHED OUT of ETHYLENECLYCOL AND PLASTICIZER OF SUPPORT T T NITROCELLULOSE NITROCELLULOSE PRECIPITATED BY N'TROCELLULOSE AND PLASTICIZER REMOVED WATER AND FREE SUPPORT FILTERED orr PLASTICIZER FURTHER AMOUNTS PRECIPITATED FROM PLASTICIZER or WATER ADDED cnwsowz soumon REMOVED m0 FILTERED orr AQUEOUS WATER cmosowc REMOVED RECTIFIED CELLOSOLVE RECOVERED gwventon Maz'viuJReid,

EDM.

Patented Feb. 9, 1937 PATENT OFFICE RECOVERY OF CELLULOSE ORGANIC ESTER PLASTIC MATERIALS Marvin J. Reid, Rochester, N. Y., assignor, by

mesne assignments, to Eastman Kodak Company, Jersey City, N. J., a corporation of New Jersey Application September 11, 1934, Serial No. 743,612

'7 Claims.

This invention relates to. the recovery of cellulose organic ester material and more particularly to a process for therecovery of photographic film scrap and like sheet materials which have one or more coatings of another cellulose derivative thereon.

In the manufacture and use of photographic film and like products, there is produced a very considerable amount of waste which, if not reclaimed, would represent a very serious economic loss. A number of different processes have been devised for the reclamation of such material, the

. more important of which relate to the recovery of the valuable silver or silver salts contained 5 in the photographic emulsion. In recent years,

however, considerable attention has been directed, not only to recovering the silver, but also to recovering the other valuable ingredients in the scrap, such as the plasticizers and the cellulose derivative base itself;

As it well known, photographic film generally comprises a cellulose derivative support having coated thereon a gelatino-silver halide emulsion.

In some cases the support is provided with coatings or layers of a different cellulose derivative material, either on the underside of the support or between the support and the emulsion, and the presence of these layers or coatings oftentimes present considerable difilculty in reclaiming the scrap because of the fact that different solvents are required to remove them than those employed for dissolving the material of the support itself. Furthermore, in order to reuse thebase material in the manufacture of further photographic film support, it is necessary to separate the material of the coating layers or subs, as they are sometimes called. Qne of the better known types of photographic materials of this kind is that comprising a support made of cellulose acetate, cellulose acetate-propionate, or some other cellulose organic ester, coated with a thinlayer of nitrocellulose and having the light-sensitive gelatin layer superimposed on the nitrocellulose.

While removal of the gelatin coating is in it- 'self a relatively simple matter, the extraction of the plasticizing materials contained in the support and the removal of the nitrocellulose coating is a matter which presents severe difllculties, especially when it is desired to obtain the material of the support in a condition in which it may be reused in the manufacture of photographic film support, lacquers, or similar to this problem, but until the perfection of the Considerable study has been given,

provide a process whereby the valuable ingredients of a photographic film or other sheet material may be recovered in reusable condition. A further object is to provide such a process which is applicable to the recovery of cellulose organic derivative film support, particularly support formed of cellulose acetate and cellulose acetate propionate containing not more than about 13% propionyl, coated with thin layers of other cellulose derivatives, such as cellulose nitrate. A still further object is to provide a process whereby the plasticizing materials employed in the manufacture of the support may be removed therefrom at the same time as the nitrocellulose coatings without dissolving the principal material of the support. Another object is to provide a process of recovering the valuable constituents of a cellulose derivative scrap material containing a plasticizer. Other objects will appear hereinafter.

After considerable work along the above indicated lines, I have found that if certain types of photographic film scrap is leached with Cellosolve (the monoethyl ether of ethylene glycol) in the manner to be more fully set forth below, all of the above objectsmay be successfully accomplished, I shall, for convenience, describe my invention by reference to photographic film scrap composed of a cellulose acetate support plasticized with triphenyl phosphate and coated with a. thin layer of nitrocellulose and also having a gelatinc-silver halide emulsion thereon, as this is the most common form of scrap material of the nature I have described and serves very well to illustrate the principles of the invention. My invention is not, however, limited to the treatment of coated cellulose acetate products as it may be applied to the treatment of other organic derivatives of cellulose, such as certain of the mixed esters.

It should be noted that my process is, in general, applicable only to the leaching of cellulose crganic ester material which is insoluble or substantially insoluble in the leaching solvent (monoethyl ether of ethylene glycol). The invention is, therefore, applicable to the treatment of scrap, having a basis of a mixed cellulose organic ester', said ester containing a rather considerable amount of acetyl groups and a minor amount of higher acyl groups in the molecule. For example, I can successfully leach scrap material composed of a hydrolyzed or unhydrolyzed cellulose acetate propionate containing not over 13% propionyl or butyryl. On

the other hand, my process is not, generally speaking, applicable to the leaching of scrap material composed of the higher mixed organic of photographic film scrap, as it will be evident that it can be applied to any of the above-mentioned types of cellulose organic ester sheeting coated with nitrocellulose, as well as to the recovery of uncoated cellulose derivative sheeting scrap. Likewise, although I have found it convenient to describe my process with particular reference to film scrap plasticized with triphenyl phosphate, my invention is applicable to the recovery of many other plasticizers, such as orthocresyl paratoluene sulphonate, butyl sulphone, ethyl acetanilide, monochlornaphthalene, ethyl benzoate, tricresyl phosphate phthalate.

The accompanying drawing is a schematic diagram or flow sheet of the various steps involved in treating film scrap according to my invention.

- In carrying out my process the film scrap material which may be waste produced in manufacture of coated photographic support itself, or that produced in manufacturing the emulsion coated product, or punchings, or used moving picture film, is chopped into small pieces, preferably of not more than a few square inches or less in area. This operation may be carried out in any suitable type of machinery well known to those skilled in the art, due precautions generally being taken to prevent the accumulation of heat from friction by keeping the material wet with water.

The emulsion coating, if any is present, is then removed by soaking in hot water, a temperature of 120 F. being generally suflicient for this purpose. The washing can be carried out in almost any convenient type of washing apparatus, such as that commonly employed in the ordinary commercial laundry and consisting of a revoluble iron cage which is oscillated while immersed in hot water. I

After removal of the emulsion coating, the

material comprises the cellulose acetate or other cellulose organic ester support or sheeting containing its original plasticizer content and with the above-mentioned, nitrocellulose coating still adhering thereto, the material, of course, still retaining its original physical form. If the original product has been dyed, the dye is in many instances retained by the scrap even after the emulsion coating has 'been removed and it is oftentimes desirable to decolorize it by means of a.

bleaching operation. This may be carried out by subjecting the scrap to the action of a weak calcium hypochlorite solution at approximately -140 F. A suitable bleaching solution may be prepared by dissolving a mixture containing 65% calcium hypochlorite and 35% chlorite in water and diluting the solution until it contains approximately .17% available chlorine. Before the solution is actually used as a and diethyl traction.

sodium hypo chlorine.

The bleached scrap with the nitrocellulose coating still adhering thereto is then placed in another agitating tank and leached, according to the countercurrent principle, with several changes of Cellosolve. The first leaching step is carried out at approximately F. followed by a second leaching at F. and a third at F. In some cases the temperature of the leaching bath may run as high as F.

I have found that the Cellosolve, not only dissolves ofi all of the nitrocellulose coating from the scrap, but also has the remarkable effect of swelling the cellulose organic ,derivative material of the support and simultaneously leaching out the plasticizer, for example, triphenyl phosphate,

contained therein, together with any remaining traces of dye which may have escaped the action of the hypochlorite bleach. The swelled and plasticizer-free cellulose organic derivative material is then mechanically separated from the leach liquor, dried, and is then in a condition in which it may be reused without other treatment in the production of further batches of photographic film support, lacquers, or allied products. With regard to the leaching temperature, it may be said that, in general, the higher the, temperature, the greater will be the swelling action of .the leaching agent upon the support.

The Cellosolve solution of plasticizer and nitrocellulose is then subjected to further treatment to remove the dissolved nitrocellulose and plasticizer. This treatment may be carried out by diluting the solution with sufficient water to precipitate out both the nitrocellulose and plasticizer which are filtered off together. The impure material may be subjected to further treatment to recover the plasticizer in pure form, for example, as described in my eo-pending application Serial No. 743,611 filed September 11, 1934, which includes dissolving the impure plasticizer in ethylene chloride followed by subjecting the resulting solution'to the action of centrifugal force in a supercentrifuge.

When the precipitated nitrocellulose and plasticizer are removed from the diluted aqueous liquid, as indicated in the preceding paragraph, the solvent. may be recovered therefrom by any appropriate means, such as distillation or ex- As previously indicated, my process is not limited to the treatment of photographic film scrap, but may be applied to any cellulose organic ester material coated with nitrocellulose. 'The effectiveness of the process depends primarily upon the used a liquid which has the power of dissolving nitrocellulose and simultaneously swelling j the cellulose organic derivative material and simultaneously leaching out the plasticizer and dye, if any, from the support. I have found that Cellosolve adequately meets all of these requirements, and may be successfully applied in my process, as will be more fully set forth, in the recovery of almost any of the more commonly known cellulose derivative plasticizers.

selected from the group consisting of triphenyl In my co-pending application Serial No. 612,850, I have described a process for recovering film scrap and particularly for recovering the plasticizer contained therein free from nitrocellulose by leaching the scrap with methyl alcohol. My present process is an improvement thereon in that it is particularly applicable to the treatment of cellulose organic ester materials coated with nitrocellulose and has many advantages over the methyl alcohol treatment. Among these may 'be mentioned the fact that Cellosolve is in itself capable of leaching out practically all of the dye-stufis commonly employed in connection with photographic film support. Therefore, I may, if desired, dispense with the bleaching step altogether. I have found that Cellosolve is a much better solvent with respect to nitrocellulose and a solvent for a far wider range of cellulose nitrates than is methyl alcohol. It is a considerably better swelling agent for the cellulose organic ester material of the support and acts at lower temperatures. With regard to its action on dye-stuffs, it is to be noted that even under the most favorable circumstances, a dye, such as nigrosine, may not be completely extracted from the support by means of methyl alcohol, whereas by the use of my process I am enabled to leach out all of this type of dye and obtain a clear, practically water-white dope from the recovered cellulose derivative base.

In addition to these advantages, I have also found that Cellosolve is particularly desirable from the corrosion standpoint and this is of the utmost importance in dealing with large installations of metallic equipment. By corrosion I refer to the efiect on film-forming equipment of the materials which have been recovered by my process and reused as ingredients of dopes or filmforming solutions. I find that dopes prepared from materials recovered by means of the process of my invention as above outlined give no evidence of corrosion of equipment even over long periods of time, whereas with alcohol and certain other types of leaching solvents there is noticeable corrosion. My process is also considerably less hazardous in that Cellosolve has a comparatively high flash point (40 C. as compared to 15 C. for methyl alcohol). My process is especially economical due to the fact that the evaporation rate of Cellosolve is far less than that of methyl alcohol or similar leaching solvents, Cellosolve evaporating at the rate of ap-. proximately .023 pounds per unit time at a given temperature as compared with .234 pounds of methyl alcohol per unit time at the same temperature and under the same conditions.

What I claim as my invention 'and desire to secure by Letters Patent of the United States is:

1. The process of recovering the valuable constituents from a cellulose organic derivative scrap insoluble in monoethyl ether of ethylene glycol and containing a cellulose organic derivative plasticizer, which comprises leaching out the plasticizer with monoethyl ether of ethylene glycol to form a solution thereof, removing the undissolved cellulose organic derivativefrom the solution, and precipitating the plasticizer from the solution. 2. The process of recovering the valuable constituents from a cellulose organic derivative scrap insoluble in monoethyl ether of ethylene glycol and containing a cellulose derivative plasticizer monoethyl ether of ethylene glycol to form a so-- lution thereof, removing the undissolved cellulose derivative from the solution, and precipitating the triphenyl phosphate from the solution.

4. The process of recovering the valuable constituents from a cellulose organic derivative scrap insoluble in monoethyl ether of ethylene glycol and containing triphenyl phosphate which comprises leaching out the triphenyl phosphate with monoethyl ether of ethylene glycol to form a .solution thereof, removing the undissolved cellulose derivative from the solution, and precipitating the triphenyl phosphate from the solution by adding water thereto.

5. The process of recovering the valuable constituents from film scrap comprising a cellulose organic ester support insoluble in monoethyl ether of ethylene glycol and containing a cellulose derivative plasticizer selected from the group consisting oftriphenyl phosphate, orthocresyl paratoluene sulfonate, butyl sulfone, ethyl acetanilide, monochlornaphthalene, ethyl benzoate,

tricresyl phosphate,'and diethyl phthalate, and

having a cellulose nitrate coating thereon, which comprises simultaneously dissolving off the cellulose nitrate coating and leaching out the plasticizer with monoethyl ether of ethylene glycol, removing the undissolved cellulose .organic ester from the solution, and precipitating the plasticizer and cellulose nitrate by adding water to the solution.

6. The process of recovering thevaluable constituents from film scrap comprising a cellulose organic ester support insoluble in monoethyl ether of ethylene glycol and containing triphenyl phosphate and having a cellulose nitrate coating thereon, which comprises simultaneously dissolving off the cellulose nitrate coating and leaching out the triphenyl phosphate with monoethyl ether of ethylene glycol; removing the undissolved cellulose organic ester from the solution,- and precipitating the triphenyl phosphate and cellulose nitrate by adding water to the solution. i

7. The process of recovering'the valuable constituents from film scrap comprising a cellulose acetate support containing triphenyl phosphate and having a cellulose nitrate coating thereon, which comprises simultaneously dissolving off the cellulose nitrate coating and leaching out the triphenyl phosphate with monoethyl ether of ethylene glycol, removing the undissolved cell ulose acetate from the solution, and. precipitating the triphenyl phosphate and cellulose nitrate by adding water to the solution.

MARVIN J. REID.

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