US2784086A

US2784086A - Concentrated developers

Info

Publication number: US2784086A
Application number: US370867A
Authority: US
Inventors: Richard W Henn
Original assignee: Eastman Kodak Co
Current assignee: Eastman Kodak Co
Priority date: 1953-07-28
Filing date: 1953-07-28
Publication date: 1957-03-05
Anticipated expiration: 1974-03-05

Description

United States Patent G CONCENTRATED DEVELOPERS Richard W. Henn, Rochester, N. Y., assignor to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey No Drawing. Application July 28, 1953, Serial No. 370,867

4 Claims. (Cl. 96-66) This invention relates to photographic developers and more particularly to concentrated photographic developers and methods for their preparation.

Photographic developers are frequently prepared in a concentrated form to increase the convenience of storage and shipping. The concentrate may be a mixed powder comprising the solid ingredients of the formula. For convenience in preparing the working solution, however, and to facilitate making small volumes of working solution, the concentrate is frequently prepared in liquid form. Unfortunately, the ordinary components of a developer have a limited solubility and it is uncommon to be able to concentrate the working strength developer by more than two or three times. The use of solvents, and of especially soluble developing agents allows rather higher concentration, but the limits are soon reached. In some cases an excess of the salts or developing agents has been left in the developer in the form of a slurry, but this has not proven satisfactory, as the salts settle out and form larger aggregates which are very diificult to dissolve.

Still another attempt to produce concentrated developers has led to the preparation of pastes in which the components are suspended in such materials as glycerine, a dextrose solution, or a viscous amine. These have never proven satisfactory due to a separation of the salts from the liquid and to the slow solubility of the components.

It is an object of the present invention, therefore, to provide a more suitable method of preparing concentrated photographic developers. It is another object to prepare concentrates of particularly low bulk. It is a further object to prepare concentrates which are readily dispersible in water. Yet another object of the invention is to provide a concentrated developer in which the solid developer constituents are held in a uniform suspension in a colloid comprising alginic acid, salts of alginic acid or esters of alginic acid from which they will dissolve rapidly to form the developing solution. Other objects will become apparent from the description.

In accordance with the invention, these objects are attained by suspending the finely ground components of the developer in a highly soluble gel. Colloids suitable for this suspension are found in alginic acid (a. polymer of anhydro-fl-d-mannuronic acid) its salts and esters. These are available commercially under such trade names as Kelacid, Kelgin, Kelcoloid, Superloid, etc. These compounds are highly hydrophilic, and their gels show high salt tolerance and disperse readily on addition of more water to the gel. This is in sharp distinction to the characteristics shown by other commonly used hydrophilic colloids, such as karaya, locust bean gum, tragacanth, acacia, and the like. The invention therefore comprises the suspension of the finely divided solid components of the photographic developer in a gel made with an appropriate concentration of such a compound of alginic acid as is mentioned above. The

I 2,784,086 Patented Mar. 5 1957 concentration needed will depend on both the nature of the developer and the viscosity of the selected colloid, but will lie between V2 and 10% and more commonly between 1 and 5%. The invention is further illus trated in the following examples:

Example 1.-A universal developer The individual components of this developer were first ground to pass through an mesh sieve. They were then added successively to ml. of a 2% solution of Kelgin (sodium derivative of algin).

Grams Sodium sulfite 24.0 Sodium carbonate 45.0 Elon (monomethyl p-aminophenol sulfate) 1.6 Hydnoquinone 4 .8 Potassium bromidee 1.0 Sodium tetraphosphate 2.0

Example 2.Vqrious colloids In preparing a developer of the above composition and by the above procedure, the following colloids were found suitable:

7 Percent Kelcosol, high viscosity sodium derivative of algin- 0.5 Kelcoloid, low viscosity propylene glycol derivative of alg Kelgin, medium viscosity sodium derivative of algin- Kelgin XL, extra low viscosity sodium derivative of alnin 5 Kelacid, alginic acid 2 Example 3.Mixing procedure In the procedure of Example 1 the finely ground ingredients were added successively to a solution of the gel. This results in almost immediate setting of the gel. Alternative procedures which may be employed include:

(a) The developer ingredients are completely mixed. A suitable preservative, such as phthalic anhydride may be added. They are then finely ground, and added to the gel solution. In the case of the formula of Example 1, stirring for 15 minutes was necessary before gelation occurred and a permanent suspension was produced.

(b) The developer components are ground in water, rather than dry, and the gel is added from a thicker solution. In the case of the formula of Example 1, 48 cc. of water were employed and 28 cc. of a 2% solution of Kelgin. The mixture set rapidly.

(c) The powders are ground directly in the gel. Again using the formula of Example 1, setting was found to occur rapidly if the powders were added successively in the order named, grinding after each addition, but if added as a mixed unit, and then ground, the slurry required stirring for 90 minutes before setting occurred.

Example 4.-Negative developer The following ingredients, ground to pass a 60-mesh sieve, were added successively to 30 cc. of a 2% solution of sodium alginate, The sodium alginate employed was the Kelgin" of Examples 1 and 3.

Grams Sodium sulfi "19.2 Sodium "rnetaborate, -otahydrate 614 Elon -(monomethyl 'p-taminophenol sulfate 116 Hydroquinone 1.6 Potassium bromide 0.3

This yielded a permanent gel of moderate viscosity which was found to be readily dispersible in water. Used in the proportion of 1 part of :gel to '15 :PaItS'Of water it produced a developer'entirely suitable :for-the processing of high speed negative emulsions.

was added to 400 cc. of a 2% solution of Kelgin and 100 cc. of water and ball milled-for "20 hours. The resulting suspension dissolved rapidly in water, to produce a developer suitable for X-ray materials when diluted in the proportions of 1 part of gel to 15 parts of Water.

As indicated above Kelg in is a medium viscosity so dium alginate; Kelcoloid is a propylene glycol derivative of algin; Kelcosol is a high viscosity sodium alginate; and Superloid is a high viscosity ammonium alginate.

The particular advantage of the present invention is that when the concentrate is diluted to form the working developer, it does not have a viscosity appreciably greater than the same developer without the colloid. The sole purpose of the alginate is to hold the solid developer constituents in a uniform suspension from which they will dissolve rapidly to form the working solution.

I claim:

1. A photographic developer comprising a silver halide developer and an alkali both of which are in finely ground solid form suspended as a thick paste in a colloidal gel consisting of a compound selected from the group consisting-of alginic acid, a salt of 'al'ginic acid, and an ester of alginic acid, said compound *being in to 40% concentration in Water.

2. A photographic developer comprising a silver halide developer and an alkali both of which are in finely ground solid form suspended as a thick paste in a colloidal gel consisting of sodium alginate colloid, said colloid being in /2% to 10% concentration in Water.

3. A photographic developer comprising monomethyl p-aminophenol sulfate, hydroquinone, potassium bromide, sodium sulfite, sodium carbonate, and sodium tetraphosphate all of which are in finely ground solid form suspended as a thick paste in a colloidal gel consisting of sodium alginate colloid, said colloid bein'g in /2'% to 10% concentration 'in water.

"4.- A photographic developer comprising monomethyl p-aminophenol sulfate, hydroquinone, potassium bromide, sodium s'ulfit'e, sodium carbonate, sodium tetraphosphate and phthalic anhydr-ide all of which are in finely ground solid form suspended as a thick paste "in a colloidal gel consisting of sodium alginate colloid, said colloid being in to 10% concentration in water.

References oitedinthe fileof this patent UNITED STATES PATENTS

Claims

1. A PHOTOGRAPHIC DEVELOPER COMPRISING A SILVER HALIDE DEVELOPER AND AN ALKALI BOTH OF WHICH ARE IN FINELY GROUND SOLID FORM SUSPENDED AS A THICK PASTE IN A COLLOIDAL GEL CONSISTING OF A COMPOUND SELECTED FROM THE GROUP CONSISTING OF ALGINIC ACID, A SALT OF ALGINIC ACID, AND AN ESTER OF ALGINIC ACID, AND COMPOUND BEING IN 1/2% TO 10% CONCENTRATION IN WATER.