US2195405A - Photographic fixative composition - Google Patents

Description

Patented Apr. 2, 1940 UNITED STATES PATENT OFFICE PHOTOGRAPHIC FIXATIVE COMPOSITION Merlin Martin Brubaker, Wilmington, DeL, assignor toDu Pont Film Manufacturing Corporation, New York, N. Y., a corporation of Delaware No Drawing. Application October 11, 1938, Serial No. 234,481

17 Claims.

. ing. A still further object is the provision of an acid hardening fixing composition which may be used for the preparation of photographic fixing baths. A still further object is the preparation of an acid hardening fixing bath which has a long life. A still further object is the preparation of an acid hardening fixing bath which will maintain satisfactory hardening over a Wide range of 7 pH values. A still further object is the preparation of an acid hardening fixing bath which is free from sludging tendencies and has a low rate of sulfurization. Other objects include, new processes of fixing photographic film and a general advancement of the art. Still other objects will be apparent from the hereafter described invention.

The above and other objects are accomplished by the incorporation of the sulfamic acids or their easily hydrolyzable salts in afixative composition. In a more limited sense, they are accomplished by the incorporation of the sulfamic acids or their easily hydrolyzable salts as an acid constituent indry photographic fixing compositions, concentrated photographic fixing solutions and in photographic fixing baths. In a preferred embodiment of the invention they are accomplished by the use of sulfamic acid in dry photographic fixing compositions, concentrated fixing solutions and in photographic fixing baths. l

Photographic fixing baths contain at least three basic ingredients, viz: (1) a silver salt solvent or fixative salt such as sodium thiosulfate, potassium thiosulfate, ammonium thiosulfate and their hydration products, e. g. hypo; (2) an acid to neutralize the alkali of the developer carried over into the fixing bath by the photographi element; and (3) a soluble sulfite to inhibit the d composition of the fixative salt. Such baths are known as acid fixing baths. Photographic fixing baths usually containa fourth asic ingredient, namely, a hardening agent for t eernulsion binder which is usually composed of gelatin, e. g. potassium alum, chrome alum, etc. The last mentioned baths are known as acid hardening fixing baths.

The useful life of an acid hardening fixing bath is usually terminated by any one of three events: (1) exhaustion of the fixing agent with consequent excessive clearing; time for the emulsion layers, (2) sulfurization, rendering the bath unfit for use, and (3) sludging from excess alkalinity, usually caused by the carrying over of developer from the developer bath by the films, plates or papers processed.

1 It has been found that the sulfamic acids and substances which readily yield sulfamic acid by hydrolysis in aqueous photographic baths may be used as the acid ingredient of acid fixing and acid hardening fixing compositions, baths and concentrated solutions. These acids are admirably suited for the purpose and maintain the pH of the resulting bath under optimum conditions in that they inhibit sulfurization and sludging and furthermore render the hardening agent effective over a wide pH range.

It has-also been found that the water-soluble salts of the sulfamic acids also have a beneficial effect in the above-described baths and compositions. Aqueous photographic baths contain in addition to the initially added ingredients the reaction products of the ingredients. In the case of the sulfamic acids, the water-soluble salts are formed in the bath during use. For instance, if sodium sulfite is used in the bath containing sulfamic acid, sodium sulfamate is formed. Because of the beneficial effect of the salts, it is preferable that they be added initially. Among the beneficial effects are the facts that the salts have a buffering action and certain salts have a hard.- ening efiect upon the proteins.

The invention will be further illustrated but is not intended to be limited by the following examples:

nxmm 1 Sodium thiosulfate, 7H2O' grams 240 Sodium sulfite, anhydrous do 15 sulfamic acid do Boric acid d0 7.5 Potassium alum do 15 Water to liters 1 2,195,406 Similar results may be obtained with the fol- Mia: B lowing fixing baths: Grams EXAMPLE 2 Potassium alum 32 Sodium thiosulfate, 71120 grams 350 sulfemm 11 Sodium sulfite, anhydrous do 15 To prepare the working bath, Mix A is dis- Sulfamic acid do 10 solved in 600 ccs. of hot water. When cooled, Boric acid do 40 Mix B is added with constant stirring and when Potassium alum do 32 dissolved, the final volume is brought to 1 liter Water to liters 1 with cold water.

EXAMPLE 3 EXAMPLE 8 Sodium thiosulfate, 'ZHzO grams 350 Mm A Sodium sulfite, anhydrous do 15 Grams Sodium citrate 30 Sodium thiosulfate, anhydrous 350 Borax 10 Sodium sulfite, anhydrous 15 Sulfamic acid 10 Sodium acetate, crystals 30 Potassium alum do 32 3 Water to liters 1 Grams EXAMPLE Potassium sulfamate 30 Sodium thiosulfate, 71-120 grams 350 sodium t anhydrous 18 For pr mg a ry p w ph phw fi sodium acetate 13 tive composition, Mix B is contained in a small Sulfa i 3 m 10 carton within the large bulk, Mix A, which can Boric acid then be stored until required. For use, Mix A Potassium alum 32 is dissolved in 750 ccs. of hot water and then Water to m; 1 the contents of the inner carton, Mix 13, are

added with constant stirring. When all ingre- EXAMPLE 5 clients are dissolved, the final volumeis brought Sodium thiosulfate, crystals -grams 350 to 1 hter cold water- Sodium sulfite, anhydrous do 15 EXAMPLE 9 Potassium tartrate do 30 Sulfami acid L 8 Sodium thiosulfate, crystals g rams- 300 Potassium alum 30 Sodium sulfite, anhydrous do 15 Water to "liters" 1 Glycol bori-borate do 10 N-methylol sulfamate do 30 Th s bath showed excellent resistancetowards Sulfamic acid, 5 sludgmg and sulfurization. water o "liters" 1 I The Sulfamic acids lend themselves remarkably wellto the preparation of dry powder mixtures comprising the active ingredients or fixing baths.

These photographic fixative compositions when dissolved in water, yield acid fixing baths having exceptional long fixation life and are resistant to sludging and sulfurization. The following examples represent dry powder which, when dissolved in water yields ready-to-use fixing baths. If a hardening fixing bath is desired, alums can be added after the bulk of other ingredients are dissolved.

ExAmLE 6 Grams Sodium thiosulfate, anhydrous 225 Sodium sulfite 15 Sulfamic acid 1-0 Sodium citrate 30 Boric acid 10 Dissolve in '750 ccs. of hot water, then add 32 grams of potassium alum with constant stirring and add cold water to make the final volume 1 li er.

EXAMPLE 7' A complete, dry powder fixative composition, comprising all the necessary basic ingredients and requiring only to be dissolved in a given amount of water, which can be prepared in advance of use and stored over long periods of time,

An exposed and developed film when treated in the above bath fixed rapidly and completely and led to a clean negative. The bath furthermore had good gelatin hardening properties.

EXAMPLE 10 Concentrated bath Due to its high solubility in water, in comparison with other dry acids suitable for fixing baths, sulfamic acid lends itself particularly well to the preparation of concentrated stock solutions of fixing baths, a suitable formula being:

The sodium sulfite is first dissolved in 200 ccs.

EXAMPLE 11 Sodium thiosulfate, 7H2O grams 240 Sodium sulfite, anhydrous do 6 Sulfamic acid 1 do 6 Aluminum sulfamate do 8 Water to liters 1 This bath in addition to its good fixing properties has, by reason of its aluminum sulfamate content, an excellent tanning effect on the protein carrier layers used in photographic emulsions.

v EXAMPLE 12 Sodium thiosulfate, 7H2O grams 350 Sodium sulfite, anhydrous do 15 Sodium citrate do 18 N-methyl sulfamic acid do 12 Potassium alum do 32 Water to liters, 1 In place of the substituted sulfamic acids and .ions, other acidic compounds which yield such ions may be used in place thereof or in admixture therewith. As further-examples of suitable compounds, mention is made of sodium metaborate, potassium tetrahydrodiborate, sodium hexahydrotetraborate as well as other water soluble, particularly alkali metal salts of the oxygen acids of boron. The organic esters and salts of ester of the boron acids, e. g. glycol borate, lycery'l borate, glycol and glycerol boriborate, the aryl-boric acids, including phenyl boric, pcarboxylphenylboric, p-tolyl boric acids and their alkali metal and ammonium salts are very effective when used. in combination with the sulfamic acids'and sulfamates of this invention.

, The addition of small quantities of other acids,

such as tartaric, fumaric, malic, maleic, lactic,

* glycolic, glycerophosphoric, propionic and butyric may be resorted to. The lithium, sodium, potassium salts of these acids, as well as any of the above acids may be used as a source of the acid ions. The water-soluble salts of the sulfamic acids herein described such as the sodium, potassium, lithium, ammonium, aluminum, etc. salts are very useful. It has been found that the sodium and potassium salts of the diand polybasic acids especially the organic acids, are particularly effective in fixing compositions and baths containing sulfamic acids or their substitution derivatives in causing the resulting baths to be highly resistant to sludging and sulfurization. These salts of citric, tartaric, boric, succinic, malic and, maleic acids which have 2 or 3 ionizable sodium or potassium groups are more effective than 1 those acids which yield a single sodium or potassium ion such as sodium acetate.

In place of the specific fixing salts set forth in the preceding examples, any water soluble thiosulfate may be substituted. Suitable thiosulfates including ammonium thiosulfate, potassium thiosulfate, lithium thiosulfate, thiosulfate complexes such as potassium and magnesium thiosulfate.

Fixing baths prepared according to the foregoing invention have a number of distinct advantages. They have a long fixation. hardening and stain preventing life. They are remarkably resistant to sulfurization and sludging and in the latter respect will tolerate exceedingly high concentrations of alkali developers before showing tendencies to sludge.

The sulfamic acids and particularly sulfamic acid, are well suited for dry fixing powders and may be packaged and stored for long periods of time.

As many apparently widely different embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that I do not limit myself to the specific embodiments hereof except as defined in the appended claims.

I claim:

1. A composition containing a photographic fixing agent and at least one compound taken from the group consisting of sulfamic acids, substances which readily yield sulfamic acids by hydrolysis in aqueous baths and water soluble salts of sulfamic acids.

2. A photographic fixative composition containing a photographic fixing agent and a sulfamic acid.

3. A composition containing a photographic fixing agent and sulfamic acid.

4. A photographic fixative composition comprising a soluble thiosulfate and a sulfamic acid.

5. A photographic fixativei composition comprising a soluble thiosulfateand a sulfamic acid salt, and a sulfamic acid.

6. A photographic fixative composition comprising an alkali metal thiosulfate and sulfamic acid.

7. An acid hardening photographic fixing coniposition comprising an alkali metal thiosulfate, sulfamic acid, a water soluble sulfite, and a protein hardening agent.

8. An acid hardening photographic fixing composition comprising an alkali metal thiosulfate, an alkali metal sulfite, sulfamic acid, a protein hardening agent and a substance capable of yielding different acid ions.

9. A dry photographic fixative composition solid substance is sodium 13. A photographic fixing composition comprising a concentrated aqueous solution containing a water-soluble thio sulfate, a water soluble sulflte, a sulfamic acid and a protein hardening agent.

14. An aqueous photographic fixing bath containing a fixing agent and sulfamic acid.

15. A photographic fixing bath comprising an alkali metal thiosulfate, an alkali metal sulfite, sulfamic acid, and a protein hardening agent.

10. The process which comprises fixing a photographic element in the presence of a sulfamic acid.

1'7. The process which comprises fixing a photographic element in the presence of sulfamic acid.

MERLIN MARTIN BRUBAKER.