US2735774A

US2735774A - Concentrated photographic fixing

Info

Publication number: US2735774A
Authority: US
Priority date: 1954-07-26
Publication date: 1956-02-21
Anticipated expiration: 1973-02-21

Description

United States Patent CONCENTRATED. PHQTOGRAPHIG FIXING SOLUTIONS Richard W. Henri, Rochester, N. .assignor to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey No Drawing. Application Jul 26, 1954, Serial No. 445,933

Claims. (or. 95am) This invention relates to photographic fixing agents and more particularly to concentrated photographic fixing solutions and methods for their preparation.

Heretofore concentrated fixing solutions have been prepared which employed only those ingredients which would conveniently dissolve, or allowed sorne excess of crystals to accumulate in thesolution. These excess crystals required vigorous application of shaking and stirring to r'esuspend before dilution and, due to coarseness, are slow to dissolve.

An object of the present invention is therefore to provide novel methods of obtaining highly concentrated fixing solutions. Another object is to provide methods of preparing stable, readily soluble suspensions of the ingredients of photographic fixing baths. Another object is to provide fixing solution concentrates which provide rapid solution and obviate dusting. Other objects will appear hereinafter.

In accordance with one feature of the present invention these objects are by suspending finely ground or finely divided crystalline elements of the fixing solution in a highly soluble colloid. Colloids particularly suitable for this purpose are esters of alginic acid. These are available commercially under the trade names Kelcoloid LV, Kelcoloid LVF, Kelcoloid HV, and Kelcoloid HVF.

In accordance with another feature of this invention, in case of fixing solutions containing sodium thiosulfate, no extraneous colloid need be added, the stability being apparently achieved through the hydrating action of the anhydrous form of sodium thiosulfate.

It is proposed as a mechanism, the correctness of which, of course, in no way limits my invention, that the stable suspension is formed in the first instance through a weak gelation or cross-linking of the polymeric alginic acid ester, and the concentration of the solid ingredients has not been found to be critical. In the second instance, it is presumed that the formation of a stable suspension occurs through the hydrating action of the sodium thiosulfate which takes up most of the excess water, but this hydrating action is not sufficient to remove entirely all fluidity. In this instance the proportion of water included is more critical than when the algin colloid is employed.

It is considered desirable, when preparing these gels, to obtain a stifily fiuid state, rather than a complete rigidity. Suitable particle size for the suspended solid particles lies between 40 mesh and 100 mesh, although there would be no objection to finer particles. The optimum concentration of the colloid protectant will vary with its molecular weight (viscosity) and with the composition of the fixing bath. In the case of the low viscosity form of the propylene glycol ester of polymeric alginic acid (marketed under the trade name of Kelcoloid LV), a concentration of 2 to 4 per cent is appropriate, if little assistance is obtained from the hydrating action of the ingredients. A concentration of chemical ingredients in the order of 1 gram per cc. is common.

i vaiitageous in some instances, particularly where the 2- The incorporation of an antifoaming material 'is adcolloidal algin is employed, and a silicone preparation;

Dow-Corning .D. C. Antifoam Emulsion has been found suitable.

The invention is further illustrated in the following examples:

Example 1.--S0dium thiosulfate fixer A mixture containing:

Grams Sodium thiosu'lfa'te, anhydrousm 70.0 Potassium aluminum sulfate l2H2O 12:0 Boric acid- 1 1 7.4 Sodium bis lfite s z i 6.0 Sodium acetate 7.2

was added to 60' cc. of a 0.1% solution of Kelcoloid LV; The mixture was finely ground and produced a stifiiy fluid solution of about cc. volume. It dissolved rapidly and without diificulty to produce a solution of normal fixing properties.

Example 2.-S0dii4m-ammonium thiosulfate fixer The following hardener constituents Grams Sodium acetate 30.0 Potassium aluminum sulfate l2HzO 30.0 Boric acid 15.0 Sodium bisulfite 10.0 Sodium citrate 3.0

Example 3.Ammonium thiosulfate fixer To cc. of 76% ammonium thiosulfate solution were added 5.2 grams of Kelcoloid LV, which was allowed to stand for 4 days, until dissolved. Then 4 drops of DC Antifoam Emulsion were added and 60 grams of a hard ener, prepared in the proportions of Example 2. This produced a stable fixer of about cc. volume which dissolved readily and without foam difficulty. A higher thiosulfate ion concentration was achieved, however, without essentially increasing volume, by the further addition of 50 grams of anhydrous sodium thiosulfate. This alternative mixture was also readily soluble and stable, and produced an active fixer when diluted 1 part to 7 parts of water.

Example 4.S0dium-amm0nium thiosulfate fixer To a mixture of the following hardener ingredients Grams Sodium acetate 15.0 Boric acid 7.5 Sodium citrate 1.5 Ammonium aluminum sulfate 5.0 Sodium bisulfite 5.0

60 cc. of a 76% solution of ammonium thiosulfate was added slowly, with grinding and stirring. Then 80 grams of anhydrous sodium thiosulfate were added, and grinding continued. Finally, an additional 5 cc. of the ammonium thiosulfate solution were added. This formed a stiffly fluid mixture, which dissolved readily on dilution with water and proved stable in prolonged incubation tests.

Example 5 The following ingredients were ground together in a mortar:

Sodium acetate grams 15.0 Boric acid do 7.5 Sodium citrate do 1.5 Ammonium alum do 5.0 Sodium bisulfite do 5.0 Ammonium thiosulfate, 76% solution, weight volume cc 65.0 Sodium thiosulfate, anhydrous grams 75.0

This gel was found to be entirely stable in accelerated aging tests including incubation at 110 F. for a period in excess of four months. Added to ten parts of water, it produced a clear solution which actively fixed both negative and positive films.

I have found that the concentrate made in accordance with this invention is quite efiective and provides faster solution and obviates dusting.

I claim:

1. A photographic fixing composition in suspension in a colloidal gel, comprising a water soluble colloidal gel of an ester of alginic acid and suspended therein a thiosulfate selected from an alkali sulfite and an ammonium sulfite, a hardening agent, boric acid and a salt of a solid 4 organic acid selected from the group consisting of acetic acid and citric acid.

2. A photographic fixing composition in suspension in a colloidal gel comprising a water soluble colloidal gel of an ester of alginic acid and suspended therein sodium thiosulfate, potassium aluminum sulfate, boric acid, sodium bisulfite and sodium acetate.

3. A photographic fixing composition in suspension in a colloidal gel comprising a water soluble colloidal gel consisting of propylene glycol alginate and suspended therein sodium thiosulfate, potassium aluminum sulfate, boric acid, sodium bisulfite and sodium acetate.

4. A photographic fixing composition in suspension in a colloidal gel comprising propylene glycol alginate gel, sodium acetate, boric acid, sodium citrate, ammonium alum, sodium bisulfite, ammonium thiosulfate, and sodium thiosulfate.

5. A photographic fixing composition in suspension in a colloidal gel comprising propylene glycol alginate gel, sodium acetate, boric acid, sodium citrate, ammonium alum, sodium bisulfite and sodium thiosulfate.

References Cited in the file of this patent UNITED STATES PATENTS

Claims

1. A PHOTOGRAPHIC FIXING COMPOSITION IN SUSPENSION IN A COLLOIDAL GEL, COMPRISING A WATER SOLUBLE COLLOIDAL GEL OF AN ESTER OF ALGINIC ACID AND SUSPENDED THEREIN A THIOSULFATE SELECTED FROM AN ALKALI SULFITE AND AN AMMONIUM SULFITE, A HARDENING AGENT, BORIC ACID AND A SALT OF A SOLID ORGANIC ACID SELECTED FROM THE GROUP CONSISTING OF ACETIC ACID AND CITRIC ACID.