US1925564A - Process for the reclamation of film scrap with permanganate solutions - Google Patents

Description

Patented Sept. 5, 1933 UNITED STATES PROCESS FOR THE RECLAMATION OF FILM SCRAP SOLUTIONS WITH PERMANGANATE Thomas F. Murray, Jr., and Cyril J. Staud, Rochester, N. Y., assignors to Eastman Kodak Company, Rochester, New York N. Y., a corporation of No Drawing. Application May 24, 1930. Serial No. 455,450

4 Claims.

This invention relates to a process for the reclamation of photographic film scrap and more particularly to a process for reclaiming film scrap having a base of a cellulose derivative which has been dyed.

In substantially all methods for the recovery of film scrap, the silver halide emulsion is first removed from the film scrapby soaking the scrap in hot water for a short length of time to loosen the emulsion from the scrap. This leaves the film base or support, which may be composed of either cellulose nitrate or cellulose acetate. This film scrap base is then normally either (1) leached with an alcohol solution or (2) bleached and then, leached. The bleaching step has heretofore been accomplished with various compounds which liberate free chlorine, namely, calcium hypochlorite, sodium hypochlorite, hypochlorous acid, or combinations or equivalents thereof. In some instances this treatment is not entirely satisfactory for the reason that the free chlorine, as well as the chloride, must be removed from the scrap before it can be utilized.

We have found that a good many of these seeming complications may be avoided if the film scrap from which the silver halide emulsion has been removed is bleached with a permanganate such as potassium or sodium permanganata-permanganic acid or a mixture of all or any of these.

The greatest'disadvantage in connection with permanganate bleaching is, however, that the permanganates are more costly than the hypochlorites for the same weight of available oxygen. 7

In certain industrial processes there are, however, large quantities of dilute acid permanganate liquors which cannot be longer used nor economically recovered but which, so far as their oxidizing values are concerned, are just as use ful as fresh solutions. These waste permanganate liquors occur, for instance, in the process whereby exposed Cine film is developed and redeveloped by what is known as the reversal process. This liquor has a permanganate content of from about .1% to approximately 1%. When used directly on film scrap base, however, these liquors are ineffective to completely remove the color therefrom even after several hours of treatment; some additional treatment was, therefore, found necessary.

We have discovered that these waste permanganate liquors may be utilized for the bleaching of film scrap base and other scrap if the scrap base is first leached with dilute alcohol, followed by bleaching with the dilute permanganate solutions mentioned above. For instance, 'dyed cellulose acetate film scrap from which the silver halide emulsion has been removed may be treated in a 50% methyl alcohol solution -for about three hours and then washed with water, after which the scrap is subjected to treatment with a waste permanganate solution of the character above described. It was found that after as short a treatment as 15 minutes that the scrap was colorless.

Longer treatments up to one hour or even two hours or more may be desirable where a particularly "deep color has to be removed. The temperature employed may be approximately room temperature, namely, from about 20 to 26 degrees centigrade. After the permanganate treatment, the scrap is removed and washed with water and then cleared in, for instance, an acidified sodium bisulfite solution prepared by dissolving 5 grams of sodium bisulphite in one liter of water and adding 5 cc of 35% hydrochloric acid or an equivalent quantity of sulfuric acid.

It will be understood that in the case of cellulose acetate film scrap base that the leaching so lution may consist of either a methyl or ethyl alcohol mixture, and that the alcohol may be in the proportion of from 70 to 30 per cent alcohol to from 30 to 70 per cent of water. The sodium bisulfite solution is used merely to clarify the film scrap of any permanganate compound and may be a rather dilute solution mildly acidified. The product resulting from the permanganate oxidation may be removed by equivalents of sodium bisulphite such as oxalic acid, sodium nitrite, hydroxylamine, sodium hydrosulphite, sodium metabisulphite or other polythioic' acids or their salts.

In the event that it is desired to reclaim film scrap having a cellulose nitrate base the only precaution necessary is to not employ methyl alcohol in the leaching solution, it being desired, of course, not to employ in the leaching of either the cellulose nitrate or cellulose acetate base any leaching solution which is a solvent for the film base.

When alcohol is employed for leaching cellu lose acetate before bleaching, it performs a diversity of functions, among which may be mentioned: 1) removal of a portion of the dye present, if the same be alcohol soluble; (2) removal of any other alcohol soluble component of the material; (3) increasing the permeability of the surface layers of the material resulting in more ready penetrability of the cellulose acetate for bleaching solutions.

Also there are instances where it may be advantageous to employ alcohol for leaching cellulose acetate after bleaching. By so doing we have the advantage of (l) removal of the products of reaction; (2) removal of alcohol soluble components of the material; (3) removal of residual dye which was not acted upon during bleaching if such dyes be alcohol soluble. This leaching after bleaching need not be more fully set forth here as approximately the same procedure is followed as when leaching before bleaching except that the time of treatment need not be quite as long. i

What has been stated above concerning alcohol is to be construed as equally applicable to other non-solvents which are suitable for this purpose and apparent to those skilled in the art.

It will thus be apparent that our invention is in fact two fold, namely, (1) the bleaching of dyed cellulosic derivative scrap and (2) the leaching of ing preceded by leaching as it may well be employed without previous leaching althof the latter is to be preferred. Also those claims directed more or less broadlyto leaching and bl'eaching are not limited (unless so stated) to a bleaching step including the use of a permanganate as-it will be quite apparent that previous leaching will make more easy the majority of bleaching pf'oc'' esses such as those disclosed in applications of Charles E. Allen filed i of even date, or even the v usual hypochlorite or chlorine bleach as disclosed in the Middleton Pater'it #1,743,155. r

of the invention will occur to those skilled in the this invention and the scope of the claims a'ppended hereto. For

tive waste, such as dyed artificial silk waste which has a base of cellulose nitrateor acetate.

What we claim as our invention and desire to Patent No. L925, 5641.

instance, the process isequally applicable to any dyed cellulose deriva-,

be secured by Letters Patent of the United States from the scrap.

2. The process of reclaiming dyed photographic cellulose acetate film scrap which comprises pretreating the scrap to remove alcohol soluble components and to increase the permeability of the surface layers thereof by leaching with a 30-70% aqueous ethyl alcohol solution, washing the leached scrap with water to remove residual alcohol, decolorizing the washed scrap by subjecting it to the oxidizing action of a .1-1.% solution of potassium permanganate, washing the bleached scrap with water and thereafter clearing the scrap from traces of unused permanganate by subjecting it to the reducing action of an acidified solution of sodium bisulphite.

3, The process of reclaiming dyed cellulose derivative scrap which comprises removing the alcoholsoluble components of the scrap by leaching it. with an alcohol which is non-solvent of the film scrap, whereby the alcohol soluble componcuts of the scrap are removed and the scrap is rendered porous, swollen and readily susceptible "to furthefprocessing, decolorizing the scrap by subjecting it to the oxidizing action of a bleach 'f-ingsolution and thereafter removing from the scrap the products of the oxidation.

'4. The process of reclaiming dyed cellulose derivative scrap which comprises removing the alcohol soluble components of the scrap by leach- Numerous other variations and modifications ing. it with an aqueous alcohol which is nonsolvent of the film scrap, whereby the alcohol art, and it is intended that all modifications indlcated above and which would occur to those skilled,- in the art shall be included within the spirit of.

,soluble components of the scrap are removed and the scrap is rendered porous, swollen and readily susceptible to further processing, de-

colorizing the scrap by subjecting it to the oxidizing. action of a permanganate solution and thereafter removing from the scrap the products of the oxidation,

THOMAS P. MURRAY, JR. CYRIL J. STAUD.

September 5, loss.

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lit is hereby certiiied that erroraners in the printed specification oi the shove numbered parent requiring correction as iiollowsz' Page 2, time 79, claim 11, strike one the word "iilm"; and that the said Letters Patent should he read with this correction therein that the some may conform to the record oi the case in the Parent @iiica (Moi) ii. iii. iiophino Acting (Coiooioner ,oi lPerenro.