CA1156868A - Photographic processing concentrates containing a discontinuous phase of finely divided solid in a continuous phase - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
Photographic processing compositions, such as developing compositions, fixing compositions, bleacning compositions, bleach-fixing compositions, stabilizing compositions, and the like, are prepared in the form of a stable paste that is adapted to be diluted with water or other liquid medium to form a working processing solution. The paste composition utilizes the association of finely-divided solid par-ticles in a stable three-dimensional network to provide advantageous characteristics of both a physical and chemical nature. It provides major economic advantages as compared to liquid concentrates with regard to pack-aging, transporting, and storage considerations and, in view of the convenience in handling and the ease with which it can be converted to a working solution, is substantially superior to a dry powder mix.

Description

PHOTOGRAPHIC PROCESSING CONCENTRATES
BACKGROUND OF THE INVENTION
. _ _ Field of the Inv tion This invention relates in general to photo-5 graphy and in particular to photographic processing compositions such as developing compositions, fixing compositions, bleaching compositions, bleach-fixing compositions, stabilizing compositions, and the llke.
More specifically, this invention relates to photogra~
10 phic processing compositions in a highly concentrated form which is advantageous for packaging, transporting and storage and is adapted to be readily diluted with water or other liquid medium to form a workingsolution.
Descri~tion of the Prior Art The processing of photo~raphic elements 5 ~
such as elements comprising one or more silver halide emulsion layers, is typically carried out with aqueous processing solutions comprising one or more processing agents. In the form in which they are employed, these solutions are relatively dilute and thus it is not generally feasible, from an economic standpoint~ to package, transport and store processing solutions of working strength since this would involve the packag-ing, transporting and storage of large amounts ofwater.
Heretofore, there have been two distihctly different approaches taken to the problem of packaging photogra-phic processing compositions in a form that is suitable for transporting and storage. One approach involves the preparation of dry powder mixes which must be dis-solved in water and then diluted to the proper volumebefore use. The other approach involves the prepara-tion of liquid concentrates, that is~ concentrated solutions which merely have to be diluted with water to obtain a working strength solution. Examples of such packaged processing formulations are described in numerous patents and publications, for example, the dry powder developer mixes of U. S. patents

2,843,484 and 2,846,308~ the black-and-white developer t~
liquid concentrates of U. S. patents 3~467,521, ~.

3~532,49~, 3,854,948 and 4,046,571, and the color developer liquid concentrates of U. S. patents 3~574,619, 3S647,461~ 3,814,606, and published British patent application No. 2,016,723.
Each of the prior art procedures possesses both advantages and disadvantages. For example~ khe use of dry powder mixes avoids the expense involved in shipping and storing of water and enables the prepara-tion of compact light~weight packages that require little storage space. However, dry powder mixes are highly disadvantageous in that they are difficult to handle, create a hazard as a result of the generatlon of dust, require highly accurate weighing and dispens ing techniques which are difficult to control, and often require difficult and time-consuming procedures to bring about dissolution in water during preparation of the working strength solution. On the other hand, liquid concentrates are very convenient to use and much less hazardous, since they eliminate the dust problem, and they can be very readily diluted to working strength without the need for laborious mixing procedures.
However, even though these solutions are concentrated3 they still contain a considerable amount of water, and it is very expensive to have to transport and store this water. Thus, for example, typical liquid concen-trates used in photographic processing are of a concen-tration such that as much as about two-thirds of the total weight is water. Moreover, there is a severe problem involved with liquid concentrates in that, with many photographic processing compositions, there is a tendency for chemlcal interactions to take place between certain of the components, and this frequently prevents the compounding of all of the components in a single liquid concentrate, and necessitates the separa-tion of the components lnto two or more parts which aresubsequently combined to form the working solution.
Often~ as many as three or four different parts are required, and this greatly complicates the packaging operation and adds to the expense of manufacture~

transport, and storage. For example, black-and-white developers of the hydroquinone/pyrazolidone type are typically packaged as a two-part liquid concentrate system3 as described in United States patents 3,532,498 and 3,854,948. However, with developers of this type which contain an aldehydic hardening agent, as is typical in machine processing of X-ray films, it is the usual practice to package as a three-part liquid concentrate system as illustrated, for example, by 10 U. S. patent 4,046,571. Color developers containing primary aromatic amino color developing agents are typically packaged as a liquid concentrate system com-prising at least two parts, and sometimes three or four parts, as illustrated, for example, by UO S. patents 3,647,461 and 3,814,606.
It is known to formulate photographic process-ing agents in tablet form. Such tablets are described, for example, in Canadian patent 831,928. This has many advantages but is not, in general, a feasible commer-cial alternative to the use of dry powder mixes orliquid concentrates. In particular, the preparation of tablets is a complex and expensive procedure, and many photographic processing compositions are of a nature such that they are not amenable to tablet forma-tion. Moreover, tablets usually require the use oflarge amounts of binding agents, and these agents can make dissolution of the tablet quite difficult and/or cause adverse sensitometric ef~ects in processing.
One approach to the problem of promoting prompt dis-solution of photographic processing tablets is to incorporate effervescing agents therein. However, use of these materials is generally not very effective and introduces additional costs and complexity in the manufacturing operationO
Proposals have been made in the past to for-mulate photographic processing concentrates as paste~
like compositions For example, British patent No. 4689 -- A. Do 1894 describes black-and-white developer concentrates having the consistency of a

-4~
paste or cream, Italian patent No. 427,967 describes black-and-white developer concentrates which are pre-pared in paste ~orm, U. S. patent 2,735~774 describes fixer concentrates of paste-like consistency~ and U. SO

5 patent 2g784,0~6 describes black-and-white developer concentrates that are formulated in the form of a smooth gel. However, prior art processing concentrates of paste-like consistency have typically depended on the use of suspending, thickening, binding or gelling agents to maintain solid constituents in a uniform suspension, and have lacked the properties necessary to meet high quality performance specifications. Thus, for example, they have suffered from such problems as poor flow characteristics which render them very dif-~icult to handle, lack of chemical stability, atendency to separate, cake or crystallize, and poor solubility characteristics, such that they have been difficult to dissolve. Use of the suspending, thicken-ing, binding or gelling agents adds substantially to the cost and complexity of the manufacturing operation and can create problems of microbiological growth formation and the formation of scums and residues in processing operations. Moreover, there are very few3 if any~ agents that will function effectively under conditions of high pH and/or high salt concentration.
In some instances, paste like processing concentrates have been prepared without the use of suspending, thickening, binding or gelling agents, but these compo-sitions have exhibited similar disadvantageous characteristics~
It is toward the objective of providing photographic processing concentrates of paste-like consistency in a form that overcomes the problems of prior art pastes and provides many of the advantages of dry powder mixes, while~ at the same time, provid-ing many of the advantages of liquid concentrates3 that the present invention is directed.

SUMMARY OF THE INVENTION
~ . . _ In accordance with this invention, photogra-phic processing compositions are packaged, transported, and stored in the form of a stable paste that is adap-ted to be readily dissolved in water or other liquidmedium to form a working processing solution. The paste is comprised of a discontinuous solid phase, comprising ~inely~divided solid particles associated in a stable three-dimensional network, distributed throughout a continuous liquid phase; with the liquid phase being present in an amount which is much less than the amount that would be needed to form a solution of the solid phase, and is just sufficient to impart a paste-like consistency. One or more photographic pro-cessing agents is present in either or both of theliquid and solid phases. The three-dimensional network formed by the association of the finely-divided solid particles provides a high degree of stability to the concentrate, while still permitting it to be readily dissolved in a liquid medium. It also imparts shear-thinning characteristics which greatly facilitate dis-pensing of the concentrate.
The continuous liquid phase can consist o~ a single liquid or of two or more miscible liquids. It can be comprised of water, or of one or more organic liquids, or it can be a mixed aqueous-organic system. The solid phase typically comprises one or more of the ingredients of the processing com~
position which are normally solid materials. While 30 liquid or solid ingredients which are not necessary components of the working processing solution can be incorporated in the paste when needed, it is frequently the case that the paste can be prepared solely ~rom the necessary components of the processing solution, with-35 out the need to delete any ingredients that would beused in the prior art system of liquid concentrates nor to add any additional ingredients. In other words, formulation of the stable paste is achieved by appro-priate selection of the relative proportions of the ~ L 5 ~
ingredients, appropriate control of the particle sizes Or the ingredients, and appropriate control of the pro-cedures whereby they are combinecl.
Most surprisingly, it has been found that in 5 using the paste form o~ concentrate which is described herein, problems of chemical interaction between in-gredients, which cornplicate the use of liquid concen-trates, are frequently much less severe. Thus, in many instances, all of the necessary ingredients can be combined together to form a single paste, or the number of separate parts which is needed in Q system can be reduced, for example, from three to two or from four to three. Typically, the paste will have excellent shelf-life properties, and will be capable of being readily diluted with water or other liquid medium to form a working strength solution that performs in a manner indistinguishable from a working strength solution prepared from liquid concentrates. Also, the pastes described herein are readily adaptable to use in auto-20 matic or semi-automatic procedures for delivery to the processing system, and thus are ~ust as convenient to use as liquid concentrates and much more convenient than dry powder mixes.
The photographic processing concentrates des-cribed herein are stable, non-separating, non-caking, non-crystallizing and readily dissolvable in a liquid medium to form a working processing solution. Con-sidering the complexity and inherent sensitivity to deterioration of modern day photographic processing 30 compositions, particularly such highly complex compo-sitions as color developers and X-ray developers, it was unexpected and surprising to find that a processing concentrate could be formulated in paste form -- to thereby obtain important advantages in regard to packag-35 ing, transport and storage resulting from its excellentstability and low bulk -- and yet could be easily con-verted from the paste form to a working solution that will perform equally as well as a working solution prepared from liquid concentrates. It was even more -7- Pl~ 5~
unexpected and surprising to find that preparation of processing concentrates in paste form can greatly simplify packaging by enabling all components to be incorporated together, or at least reducing the number of component parts into which they must be separated.
DESC~IPTION OF THE PREFERRED E~BODIMENTS
With photographic processing compositions in which all processing agents are normally solid materials, it is ordinarily feasible to prepare the paste of the present invention by combining these solid materials in finely-divided form in the correct proportion and appropriate order with the appropriate amount of water, or other liquid medium, and thoroughly blending them together, taking due care to ensure that the finely-divided solid particles are associated in a stable three-dimensional network, as hereinafter des-cribed in full detail. Similarily, with processing compositions in which some of the processing agents are normally solid materials and others are normally liquid materials, it is ordinarily feasible to prepare the paste of the present invention by combining the solid materials, the liquid materials and water, all in the appropriate proportions, and thoroughly blending them together. In instances where several of the processing agents are liquids, little or no water may be required.
In some instances, it may be advantageous in forming the paste to utilize either liquid or solid iner~
materials which do not have any processing function, i.e ~ which are not processing agents, but which pro-3 mote the desired formation of the paste. Thus, eitheror both of the solid phase and the liquid phase can be composed solely of active agents~ and the use of inert materials is optional, depending on the characteristics of the active agents and the properties desired in the concentrate. Most preferably, the paste-like concen~
trates of this invention are prepared without the use of any suspending, thickening, binding or gelling agents, as these agents typically exhibit many charac-teristics which render their use undesirable in photographic processing compositions.
The term "photographic processing agent" is used herein to refer to a material used to develop or otherwise process a photographic element, for example, ko develop, fix, bleach, harden, stabilize, and the like. Thus, the processing solutions prepared ~rom the pastes described herein can be any of the solutions used in processing photographic materials such as, for example, black-and-white developing solutions, color developing solutions, fixing bathsg bleaching baths, stabilizing baths, stop baths, nucleating baths, mono-baths, bleach-fixes, prehardeners, activators, condi-tioning baths, toners, neutralizers, and the like.
Developing agents of both organic and inor-15 ganic types are well known in the photographic art.Useful classes of organic developing agents include hydroquinones, catechols, aminophenols, pyrazolidones, phenylenediamines, tetrahydroquinolines, bis(pyridone) amines, cycloalkenones, pyrimidines, reductones and coumarins. Useful inorganic developing agents include compounds of a metal, having at least two distinct valence states~ which are capable of reducing ionic sil~er to metallic silver. Such metals include iron, titanium, vanadium, and chromium ~nd the metal com-25 pounds employed are typically complexes with organiccompounds such as polycarboxylic acids or aminopoly-carboxylic acids.
A particularly important class of black-and-white developing a~ents are the dihydroxybenzenes such 30 as~ for example~
hydroquinone, chlorohydroquinone, bromohydroquinone, isopropylhydroquinone, toluhydroquinone, methylhydroquinoneg 2,3-dichlorohydroquinoneg 2,5-dimethylhydroquinone, 2,3-dibromohydroquinoneg 1,4-dihydroxy 2-acetophenone-2,5-dimethylhy-droquinone, 2,5-diethylhydroquinone~
2,5-di-p-phenethylhydroquinone, 2,5-dibenzoylaminohydroquinone, 2,5-diacetaminohydroquinsne, and the like.
A further particularly important class of black-and-white developing agents are the 3-pyrazoli-dones. Useful compounds of this class include those substituted in the l-position by a monocyclic aryl group of the benzene series, including phenyl and sub-stituted phenyl such as p-tolyl, p-chlorophenyl, etc.
A typical compound of this type is l-phenyl-3-pyra-zolidone. In addition to this substitutlon in thel-position, the pyrazolidone nucleus can be substitu-ted in the 4-position~ particularly by lower alkyl and substituted lower alkyl groups such as methyl and hydroxymethyl. Representative compounds of this class are 1-phenyl-4-methyl-3-pyrazolidoneg l^phenyl 4-hydroxymethyl-3-pyrazolidone, 1-phenyl-4,4-dimethyl-3-pyrazolidone, and l-phenyl-4,4-di(hydroxymethyl)-3-pyrazolidone.
Color developers typically contain primary aromatic amino color developing agents. These color developing agents are well known and widely used in a variety of color photographic processes. They include aminophenols and p-phenylenediamines Examples of aminophenol developing agents include o aminophenol, p-aminophenol, 5-amino-2-hydroxy-toluene, 2-amino-3-hydroxy-toluene, 2-hydroxy-3-amino-1,4-dimethylbenzene, and the like.
Particularly useful primary arsmatic amino color developing agents are the p-phenylenedia~ines and especially the N-N-dialkyl-p-phenylenediamines in which the alkyl groups or the aromatic nucleus can be substituted or unsubstituted. Examples of useful p-phenylenediamine color developing agents include:

N-N-diethyl-p-phenylenediamine monohydro chloride, 4-N,N-diethyl-2-methylphenylenediamine monohydrochloride, 4-(N-ethyl-N-2-methanesulfonylaminoethyl)-2-methylphenylenediamine sesquisulfate monohydrate, 4-(N-ethyl-N-2-hydroxyethyl 3 -2-methylpheny-lenediamine sulfate, 4-N~N-diethyl-2,2'-methanesulfonylamino-ethylphenylenediamine hydrochloride, and the like.
An especially preferred class of p~phenylene-di~mine developing agents are those containing at least one alkylsulfonamidoalkyl substituent attached to the aromatic nucleus or to an amino nitrogen. Other es-pecially preferred classes of p-phenylenediamines are the 3-alkyl-N-alkyl-N-alkoxyalkyl-p-phenylenediamines and the 3-alkoxy-N-alkyl-N-alkoxyalkyl-p-phenylene-diamines. These developing agents are descrlbed in United States Patents 3,656,950 and 3,65~,525 and can be represented by the formula:
CH3 - CH2 - N ~ (CH2)n I~J

wherein n is an integer having a value o~ from 2 to 4, R is an alkyl group of from 1 to 4 carbon atoms, and Rl is an alkyl group of from 1 to 4 carbon atoms or an alkoxy group of from 1 to 4 carbon atoms. Illustra-tive examples of these developing agents inclu~e the following compounds:
N-ethyl-N-methoxybutyl-3-methyl-p-pheny-lenediamine, N-ethyl-N-ethoxyethyl-3-methyl-p-pheny-lenediamine, 5 ~ ~ i6 8 N-ethyl-N methoxyethyl 3-n-propyl-p-pheny-lenediamine, N-ethyl-N-methoxyethyl-3-methoxy-p-pheny-lenediamine, N-ethyl-N-butoxyethyl 3-methyl-p-phenylene-diamine, and the like.
In addition to the primary aromatic amino color developing agent~ color developer compositions typically contain a variety o~ other agents such as alkalies to control pH, bromides, iodides, benzyl alcohol, anti-oxidants, solubilizing agentsg sequester-ing agents~ brightening agents, and so forth.
In the production of color photographic images, it is necessary to remove the silver image which is formed coincident with the dye imagel This can be done by oxidizing the silver by means o~ a suit-able oxidizing agent, commonly referred to as a bleach ing agent, in the presence of halide ion followed by dissolving the silver halide so formed in a silver halide solvent, commonly referred to as a fixing agent.
Alternatively, the bleaching agent and fixing agent can be combined in a bleach-fixing solution and the silver removed in one step by use of such solution. A variety of bleaching agents are known for use in photographic processing~ for example, ferricyanide bleaching agents, persul~ate bleaching agents, dichromate bleaching agents~ permanganate bleaching agents, ferric chloride and water-soluble quinones.
A particularly important group of photogra-phic bleaching agents are the aminopolycarboxylic acid bleaching agents. They are typically utilized in the form of water-soluble salts, such as ammonium or alkali metal salts, of a ferric aminopolycarboxylic acid com-plex. A typical example is the ammonium salt of ferric ethylenediaminetetraacetic acid (NH4FeEDTA), which is also known as ammoni~ ethylenedinitrilotetraacetato ferrate (III)~ Many other aminopolycarboxylic acids in addition to ethylenediamine tetraacetic acid are also useful such as, for example:
nitrilotriacetic acid~
diethylenetriamine pentaacetic acid, ortho-diamine cyclohexane tetraacetic acidg ethylene glycol bis(aminoethyl) ether) tetraacetic acid, diaminopropanol tetraacetic acid~
N-(2-hydroxyethyl)ethylenediamitle triacetic acid 3 ethyliminodipropionic acid, and the like.
The aminopolyacetic acids are preferred, as they are readily available and provide particularly good bleaching action~
Fixing agents used in photographic processing include thioureas, thiocyanates, thiosulfates, mercapto-containing compounds such as mercapto acetic acid, quaternary ammonium salts, polyamines such as tetra-ethylene pent~nine, and the like. In bleach-fix com-20 positions, it is common to employ thiosulfates as fixing agents, typically ammonium thiosulfate or alkali metal thiosulfates such as sodium thiosulfate and potassium thiosulfate.
Bleach and bleach-fix compositions can con-25 tain a wide variety Qf addenda known to the art to be useful in such formulations, including amines, sulfites, mercaptotriazoles~ alkali metal bromides, alkali metal iodides, and the like~
Agents for hardening of gelatin or other 30 hydrophilic colloids employed in photographic elements are often used in processing. For example, they can be incorporated in fixing baths, or in developing baths or utilized in the form of prehardener solutions. In hardening fix baths~ it is common to utilize an alumi~
35 num or zirconium salt as the hardening agent. In developers and prehardeners~ any of a very wide variety of hardening agents can be employed. Such hardening agents include aldehydes such as formaldehyde~ dialde-hydes such as succinaldehyde and glutaraldehyde, -13~
~- diketones~ sulfonate estersg active halogen compounds, and the like.
In color reversal processing of photographic elements~ it is common to utilize nucleating agents to take the place of reversal re-exposure. Nucleating agents can be incorporated in a color developing solu-tion or in a separate bath which is used between first development and color development. Useful classes of nucleat~ng agents include alkali metal borohydrides, ionic boron ~ydrides containing two or more boron atoms per molecule, amine boranes, polyamine boranes, phosphine boranes, arsine boranes, stibine boranes borazines, chelated stannous salts, and the like.
A final step in many color photo~raphic pro-cesses involves treatment of the element with a sta-bilizing bath, which serves to stabilize the dye images.
Such baths frequently include a wetting agent, for example, a polyoxyalkylene compound, and an aliphatic aldehyde, for example, ~ormaldehyde, paraformaldehyde, acetaldehyde, aldol, crotonaldehyde, and the like.
While certain common photographic processing agents that can be used in the paste formulations of this invention have been described in some detail above, it should be understood that the present invention is not limited to these particular processing agents, but is broadly applicable to any of the wide diversity of compositions used in the processing of photographic elements.
Processing of black-and-white photographic elements is generally quite simple, involving only the steps of developing and fixing. Color processing can involve a two-step process, such as a process employ-ing the steps of color developing and bleach~fixing, or more complicated processes such as a process employ-ing a prehardener, a neutralizer, a first developerg acolor developer, a bleach, a fix and a stabilizer.
The present invention can be advantageously utilized with simple processés or with those employing a compiicated series of steps. It is usefu~ in black-; ~ 5 and-white processing (including X-ray processing and processing of lithographic films), in the processing of photographic elements designed for reversal color processing, in the processing of negative color ele-ments~ and in the processing of color print materials.It can be employed with photographic elements which are processed in color developers containing couplers or with photographic elements which contain the coupler in the silver halide emulsion layers or in layers con-tiguous thereto. The photosensitive layers present inthe photographic elements processed according to the method o~ this in~ention can contain any of the conven-tional silver halides as the photosensitive material, for example, silver chloride, silver bromide, silver bromoiodide, silver chlorobromide, silver chloroiodide, silver chlorobromoiodide, and mixtures thereof. These la~ers can contain conventional addenda and be coated on any of the photographic supports, such as, for example~ cellulose nitrate film, cellulose acetate film~ polyvinyl acetal film, polycarbonate film, poly-styrene film, polyethylene terephthalate film, paper, polymer-coated paper, and the like.
The solid material used in preparing the paste-like concentrates of this invention is typically comprised of one or more normally solid processing agents, e.g., such solid processing agents as the salts of p-phenylenediamines which are commonly used as color developing agents. However, where the desired process-ing composition does not require any processing agents which are normally SOlidg or requires an insufficient proportion o~ such agents to render the formation of a paste feasible, inert particulate components which do not perform a processing function, but are added solely to facilitate formation of the paste, can be 35 utilizedO Useful materials for this purpose include a wide ~ariety of finely-divided inert solid materials such as silicon dioxide, sodium sulfate, and diatoma-ceous earth.
Formation of the paste-like photographic processing concentrates of this invention requires the use of solid particles in vcry finely-divided form.
Because the solid particles are very finely-divided, they provide a very large surface area per unit of weight. The amount of surface area is an important factor in determining the physical characteristics of the paste-like concentrateg especially its rheological properties. The desired small particle size and high surface area can be achieved by grinding which takes 10 place during blending of the materials in forming the concentrate, or by grinding individual ingredients prior to blending. The actual particle size employed can vary widely, depending on the particular processing formulation involved. Xowever3 the photographic pro-cessing concentrates of this invention are typicallycharacterized by the presence of particles of very small size. Generally speaking, it is desirable that the finely-divided solid particles have a size below about 100 microns, preferably below about 25 microns, and most preferably below about 3 microns.
The liquid phase of the paste-like concen-trates of this invention can take a variety of forms.
In appropriate situations, e.g., those where the pro-cessing formulation does not employ any processing agents which are liquids, water can be used as the sole liquid ingredient forming the liquid phase. In other instancesJ one or more l~quid processing agents, or a combination of water plus one or more liquid processing agents can be utilized. Inerk organic liquids, i.e~, those which do r,ot have a processing function, can be added in order to promote formation of the paste, if desired.
The photographic processing concentrates described herein are made up of a discontinuous solid 35 phase that is distributed throughout a continuous liquid phase. Thus, the two phases are in intimate association with one another and interact to provide the properties exhibited by the paste. The liquld phase must not be present in either too great or too small an amount in relation to the solid phase or the resulting product will not have the desired paste-like consistency. The actual ratio of liquid to solid in the concentrate can vary widely, depending on the par-5 ticular processing formulation involved, and suchfactors as particle size. Generally speaking, it is desirable khat the liquid phase be present in an amount of from about 0.05 to about o.8 parts per part of solid phase by weight, and more pre~erably in an amount of 10 from about 0.1 to about o.6 parts per part of solid phase by weight.
The photographic processing concentrates of this invention are characterized by a very low ratio of liquid to solid in comparison to prior art photogra-15 phic processing concentrates. A typical example of acolor developer liquid concentrate of the prior art is that described in Example 1 of U. S. patent 3,~47,461.
This developer concentrate contains 2 grams of sodium sulfite and 6.4 grams of 4-amino-N-ethyl-N-(~-methane-20 sulfonamidoethyl)-m-toluidine sesquisulfate monohydrate dissolved in 11 grams of water. This is a weight ratio of liquid to solid of 1.3 to 1. In comparison, the same formulation prepared in the form of a paste-like con centrate in accordance with this invention would typi-25 cally have a ratio of liquid to so:lid of about o.6 to 1.A typical example of a black-and-white developer liquid concentrate of the prior art is that described in Example 1 of U. S. patent 3~467,521. This developer concentrate contains 312 grams of potassium sulfite3 30 15 grams of potassium hydroxide, 90 grams of potassium carbonate~ 45 grams of hydroquinone, 1.5 grams of 1-phenyl-3-pyrazolidone, 10 grams of potassium bromide and 8 grams of ethylenediaminetetraacetic acid dissolved in sufficient distilled water to give a volume of 1 35 liter. This is a weight ratio of liquid to solid of approximately 1 to 1. In comparison, the same for~u-lation prepared in the form of a paste-like concentrate in accordance with this invention would typically have a ratio of liquid to solid of about 0.25 to 1. A typical -17~
example of a prior art developer paste is that des-cribed in Example 1 of U S. patent 2,784,o86. This developer paste is prepared by adding 24.0 grams of sodium sulfite, 45.0 grams of sodium carbonate3 1.6 grams of monomethyl p-aminophenol sulfate, 4.8 grams of hydroquinone~ 1.0 grams of potassium bromide and 2.0 grams of sodium tetraphosphate to 90 milliliters of a 2% solution of the sodium derivative of algin.
This is a weight ratio of liquid to solid o~ approxi~
mately 1 1 to 1. In comparison, a comparable devel-oper prepared in the form of a paste-like concentrate in accordance with this invention would omit the algin derivative and would typically have a ratio of liquid to solid of about 0.25 to 1.
Photographic processing agents present in the paste-like concentrates of this invention can be present in either or both phases. Frequently, a processing agent which is a solid material will be distributed between the solid and liquid phases, with the amount present in each being determined, ln part, by its solubility characteristics. For example, the p-phenylenediamines that are used in color developers will typically be distributed between both phases with a major proportion, e~g., 90~, being in the liquid phase, and a minor proportion~ e.g., 10%, being in the solid phase.
Typically, the photographic processing con-centrates of this invention are prepared in the form of a stiff paste, but the degree of fluidity of these compositions can be varied to a very considerable ex-tent, as desired, so that pastes with either a pourable or non-pourable consistency are within the contemplated scope of this inventionO Thickening or suspending agents are not usually needed in the processing concen-trates of this invention, but their use is optional,and they can be employed3 if desired. Generally speaking, the paste-llke concentrates are readily dis-solved in water, even with the use of only very simple stirring equipment such as a hand-held paddle. Improved results, however, are usually obtained when they are dissolved with the aid of mechanical stirring devices that provide much higher mixing speeds than can be achieved by hand. While the concentrates disclosed herein can be characterized as being stable, non-separating, non-caking~ non-crystallizing and readily dissolvable in a liquid medium to form a working processing solution, such terms are, of course, rela-tive terms, and it is intended by use of these terms only to indicate that the concentrate possesses these characteristics to a degree sufficient to be useful for its intended purpose.
It should be noted that processing concentra-tes prepared in the paste form described herein are not intended to be used, as such, in processing photo-graphic materials, but only after being dissolved in the appropriate amount of water or other liquid medium to form a working strength solutionO Thus, the ob-jectives and purposes of this invention are clearly different than in the case of prior art inventions where photographic processing compositions have been converted to forms other than true solutions with the intention that they be used in such form in the pro-cessing of phokographic elements, for example, the ~5 processing compositions in the form of a foam as described in U. S. patent 2,860,977, the solid fusible processing compositions of U. S. patents 3,347,675 and 3,438,776, and the viscous processing composi`tions of U. S. patent 3,392,019. The concentrates of this invention are designed to facilitate packaging, trans-port and storage, a~d this involves dlstinctly differ-ent considerations and problems than were involved in the aforesaid prior art inventions that were seeking to simplify processing operations per se.
It should also be noted that the paste-like concentrates of this invention are characterized by a very low ratio of liquid to solid. It is this feature that provides the desired low bulk characteristics that provide substantial cost savings in packaging, \~
- 1~
transport and storage. In this regard, the concentra-tes of this invention are clearly distinct from photo-graphic processing concentrates of the prior art~ which have utilized relatively large proportions of w~ter, 5 but have had high viscosity in spite of the high water content because of the presence of large amounts of colloidal thickening, binding, gelling, or suspending agents.
The paste-like photographic processi~g con-1~ centrates of this invention are characterized by the presence of ~inely-divided solid particles associated in a stable three-dimensional network. A variety of mechanisms can result, separately or in combination, in the creation of such a networkO For example, with certain processing formulations, the finely-divided solid particles are present in the form of aggregates or clusters of particles, and such systems can, there-fore, be described as flocculated. In such a floccu-lated suspension, particles associate, through 20 electrical forces, to other particles, and it is this attraction into a network which imparts stability.
With other formulations, network formation is dependent upon morphological association; for example, particles of needle-like structure are generated in blending and 25 grinding of the ingredients, and such particles asso-ciate in a stable three-dimensional network as a con-sequence of their shape. In still other formulations, certain of the components are present in the form of intermolecular association products which create a stable three-dimensional network through physical and chemical interaction, but readily dissociate when the paste is diluted with water.
The term "stable" is used herein in reference to the three-dimensional network in the sense of being descriptive of its capability of functioning to maintain the desired even distribution o~ materials throughout the paste-like concentrate during a shelf life of adequate duration to meet the requirements o~ the photographic art ~L

The presence in a photographic processing concentrate of the stable three-dimensional network described herein is evidenced by a yield point and by rheological behaviour that can be characterized as shear-thinning orpseudoplastic~ The network results from the association of finely-divided particulates through mechanisms such as those outlined above. The dimensions of the network are perhaps best characteri-zed by the ~;stances over which a disruption of one point has an effect at another point. These dimensions are dependent on the materials and methods of formula-tion and can range from a few tens of microns up to many centimeters.
A processing concentrate in the form of a flocculated colloidal suspension is illustrated by a p-phenylenediamine color developer formulation contain-ing both benzyl alcohol and triethanolamine. Color developers containing these two ingredients are des-cribed in U0 S. patent 4,170,478. In this systemg two immiscible solvents, benzyl alcohol and water, are made miscible by the addition of a third solvent, triethanolamine~ which is completely miscible with both of the other solvents. Thus, benzyl alcohol and water are immiscible in any quantity of benzyl alcohol greater than one gram in twenty-five milliliters of water, and of more than one milliliter of water in ten grams of benzyl alcohol. The addition of triethanola-mine increases the solubility of benzyl alcohol in water and vice versa. In this system, flocculation is dependent upon maintaining a low water concentration.
This can be explained, in part, by the fact that with a low concentration of water~ there is a low ionic strength, since salts present in the formulation will not ionize to a high degree in an organic medium.
Under these conditions, flocculation is favored. The result of flocculation is the association of the finely-divided particles in a stable three-dimensional network that is characteristic of the paste-like concentrates of this invention~

-21~
The photographic processing concentrates of this invention exhibit good stability characteristics from the standpoint of both chemical and physical stability~ For example, they are resistant to aerial oxidation and to deleterious changes resulting from chemical reactions between components thereofO They are also highly advantageous in that they are non-separating, non-caking, and non crystallizing. These advantageous characteristics are believed to be impar-ted to the concentrate by the presence of the aforesaidstable three-dimensional network. Thus, for example~
association of the finely-divided particles in a stable three-dimensional network maintains larger particles in suspension, and avoids settling or stratification~
Numerous factors relating to the characteris-tics of the starting materials and the manner in which they are combined to form a paste-like concentrate are believed to interact together to influence the formation of the stable network of associated particles. Such factors include the following:
(1) The order in which the ingredients are combined to form the paste.

(2~ The temperature during formation of the paste.

(3) The type of mixing equipment used in forming the paste and the parameters of mixing such as the degree to which shearing takes place.

(4) The particle size.

(5) The effects of additives which a~e not processing agents, such as dispersing agents or thickenersO

(6) The effect of p~ and the chemical en-vironment during paste for~ation.

(7) The effect of the ratio of aqueous to or~anic liquids when both are present.

(~) The effect of the liquid to solid ratio.

Various exothermic and gas~evolving phenomena can take place during mixing to form the paste. These may be explainable in terms of acid-base reactions or other exothermic chemical reactions. An increase in temperature occurs during mixing, in part as a result of chemical reactions, but primarily as a result of the grinding action of the mixer. Care must be taken to prevent the temperature from rising to too high a level~ as this can result in depletion of essential components of the formulation.
Characteristic features of paste-like photo-graphic processing concentrates comprising finely-divided solid particles associated in a stable three-dimensional network include their shear-thinning properties and high sedimentation volumes. (A shear-thinning material is one which has a high viscosity under low shear conditions, and a low viscosity under high shear conditions). The shear-thinning properties possessed by these concentrates are especially signi-ficant in that they greatly facilitate dispensing of the concentrates from the containers in which they are packaged. The particular viscosity and degree of shear-~hinning exhibited varies greatly among the very wide range of different processing compositions coming with-in the scope of the present inventionO For example, typical concentrates have an apparent viscosity in the range of from about 250 to about 1300 centipoises at a hear rate of 800 reciprocal seconds. At a shear rate of 4500 reciprocal seconds, an apparent viscosity in the range of from about 100 to about 50p centipoises is typical. These values re~er to viscosity measurements made in a HERCULES HI-SHEAR VISCOMETER (rotational concentric cylinder type) at ambient temperature. The - _,3_ rotor or inner cylinder (radius 1.95 cm., height 5.0 cm.) is rotated at a constant angular acceleration of approximately 5.~9 rad/sec2 to a maximum angular velocity o~ 115 rad/sec. This rotation imparts an 5 increasing rate of shear (maximum 4549 sec 1) to the sample which is contained in the annulus between the inner and outer cylinders (annulus width 0.5 cm.).
The torque which is transmitted through the sample to the outer cylinder is measured and used in calculation 10 of apparent viscosity as a function of rate of shear;
The stable three-dimensional network formed by association of finely-divided solid particles also imparts a high sedimentation volume to the concentrate.
Unlike a stable suspension of solid particles, in which 15 the particles act independently, in the concentrates des-cribed herein, particles exist in a state of association.
As a consequence, the sedimentation volume is large, whereas the sediment from a stable suspension tends to pack closely, i.e., to approximate closest packing be-20 havior, so as to exhibit a considerably smaller sedimen-tation volume for particles o~ the same dimensions.
Brownian motion can be observed in a stable suspension, but not in a flocculated system~
The flocculated suspensions have been ~ound to 25 exhibit pronounced thixotropic behavior. In particular, they tend to become quite fluid when agitated~ butreturn to a sti~f paste form when at rest. In being mixed~
they are subJect to extreme shearing which prevents ex-tensive association and in consequence, are ~ree-flowing, 30 while upon standing they become quite viscous and"paste-like." In terms of flocculation, it is apparent that standing for a sufficîent time allows further associa-tion of particles into a network. Given enough time, the system will proceed to its point of equilibrium, 35 i.e., optimal degree of association. The optimum condi-tion is dependent upon the particular formulation invol-ved, that is, the particular ingredients and their proportions. Once in its equilibrium state, the material will not readlly dissolve in water. With the application of shearing energy, the network asso-ciations, that is, interparticle attractions, are broken, the viscosity decreases, and the material can be readily dissolved in waterO
The paste-like photographic processing con-centrates of this invention are especially advantageous in the packaging of color developing compositions comprising primary aromatic amino color developing agents. Typically, color developers are packaged and sold in liquid concentrate form, with the chemical formulation for a given process being divided into the least possible number of concentrated parts that will provide good shelf life. Often, the color developer formulation will contain numerous lngredients~ some-times as many as fifteen or more, and it will benecessary to separate it into three or four parts in order to package it in the form of liquid concentrates.
Formation of stable paste-like concentrates, in accor-dance with the teachings herein, will often permit packaging of complex color developers containing as many as fifteen or more ingredients in the form o~ a single paste or, perhaps, two different pastes. It was particularly surprising to ~Lnd that problems of chemical interaction between components of complex color developer formulations which complicate the use of liquid concentrates, and necessitate packaging of as many as four separate liquid concentrates, are frequently much less severe with the paste-like concentrates of this invention.
The primary aromatic amino color developing agents are solid materials which will distribute themselves between the liquid and solid phases of the concentrate. In these concentrates, the liquid phase will typically be comprised of water and at least one organic liquid, since organic liquids, eOg., benzyl alcohol, are necessary components of many currently used photographic color developing compositions.
The starting ingredients for forming the paste-like concentrates can be liquids, powders, or A~ 6~
slurries. Typically, the slurries are saturated solutions with excess solut~s present as undissolved solids. The ingredients are blended in a high shear mixing vessel and can be conveyed to this vessel by any of several methods. Liquids and slurries are usually pumped, while powders are handled with a screw conveyor or other powder transport system~ Agitated storage tanks can be used with the slurries in order to keep the solids in suspension. For uniformity and proper consistency, it is necessary to thoroughly disperse the solids and homogenize the product. This is best accomplished with hydraulic and mechanical shear pro-vided by high speed agitators.
Once the paste has been mixed to the desired consistency, the next step is to convey it to the package-filling apparatus. If mixing is done directly above the filling process, the concentrate can be con-veyed by gravity through a vibrated chute. Alterna-tivelya the concentrate can be conveyed by pumping, typically by pumps of the positive-displacement type.
Package filling can be carried out with the use of an auger system or a piston system~ Packages of a wide variety of types can be utilized and inexpensive pack-aging materials, for example, thermoplastics such as polyethylene, can be employed.
Dispensing of the paste and combining it with water or other liquid medium to form a working process-ing solution can be carried out by any suitable method.
There are two basic approaches which are feasible.
The first of these is to dispense and dissolve the entire contents at one time, i.e., a batch-dispensing approach. In this instance, it is not necessary that the paste be entirely homogeneous, since all of the contents of the package are utilized to form a single batch of processing æolution. The second approach is to dispense a portion of the contents o~ the package intermlttently as needed. In this case, the paste must be completely homogeneous, since each portion dispensed must be like every other to give a consistent working -26- ~5~
solution.
Photographic processing chemicals must be dissolved in water or other liquid medium in very precise amounts in order to prepare working processing 5 solutions. Thus, to be commercially useful, a photo-graphic concentrate must not only possess features facilitating packaging, transport and storage, but must be capable of being dispensed in such a way as to ensure the necessary precision in the preparation of 10 working processing solutions. It is particularly advantageous for the photographic processing concentrate to be "volumetrically dispensable." By the term "volumetrically dispensable," as used herein, is meant a composition which has flow properties such that it 15 can be dispensed from a package in a metered amount on a volumetric basisg and which has a high degree of uni-formity such that each unit volume dispensed contains essentially the same amount of active agents on a weight basis. With such a concentrate, it is possible 20 to combine a predetermined volume of concentrate with a predetermined volume of liquid, e.g., 100 cubic cen-timeters of concentrate combined with one liter of water, and consistently obtain the same weight of active agents in the resulting working solution.
The dilution ratio employed with the process-ing concentrate, that is, the amount of water or other liquid used to convert the paste to a working processing solution, will vary greatly depending on the nature of the photographic element being processed, the processing 30 procedure, and the particular processing formulation involved. In general, the dilution ratio will be in the range from about 1 part of paste to about 8 parts by weight of liquid to about 1 part o~ paste to about 100 parts by weight of liquidO
The term "a photographic processing concen-trate" is used herein to refer to a composition comprising one or more processing agents~ such as developing agents, bleaching agents, ~ixing agents, !,`' i~, ~6~

etc. It can be, but is not necessarily, a composition that is complete in the sense that it merely needs to be combined with water, or other liquid medium, to ~orm a working strength processing solutionO In some in-5 stances, it will be intended to be combined withanother photographic processing concentrate, as well as water or other liquid medium, to form a working strength processing solution, and this other processing concentrate can be a paste, a powder, or a liquidO
10 For exQmple, a photographic developing solution might comprise ~ive active agents, namely, a developing agent, an alkali, an anti~oggant, an anti-oxidant and a sequestering agent. In utilizing concentrates in accordance with this invention, it may be advantageous 15 to ~orm a ~irst paste containing the developing agent and anti-oxidant, and a second paste containing the alkali, the anti~oggant and the sequestering agent, and then to combine the first and second pastes together, along with an appropriate quantity o~ water, 20 to form a working strength developing solution. In another instance, a photographic processing composition might require several di~erent solid processing agents and one liquid processing agent, and the paste-like concentrate could include only water and the several 25 solid processing agents, while the working strength solution would be prepared by combining the liquid processing agent and the paste, along with an appropriate quantity o~ water.
While the photographic processing concentrates -28- ~ 5~
described herein have been referred to throughout the specification as "pastes," and this term is aptly des-criptive of their characteristics, they could also be re~erred to by a variety of other terms, such as, for 5 example~ the terms "semi solid~" or "semi fluid" or "plastic."
The term "a photographic processing solution, as used herein, is intended to include working solu-tions~ replenisher solutions, starter solutions, and lO so forth.
The paste-like photographic processing concen-trates of this invention can be evaluated by the prepara-tion of rheograms, that is, plots of shear rate versus shear stress. In such plots, the viscosity is inversely 15 proportional to the slope of the curve. For a strictly pseudoplastic or shear-thinning fluid, the values of shear stress obtained during an ascending series of shear rates correspond to those obtained in a descending series of shear rates. In other words, the curve for a 20 descending series retraces the curve for an ascending series. The occurrence of thixotropic loops in a rheo-gram provides rheological evidence that the composition is a structured fluid, that is, one comprising a three-dimensional network~ Thus, with a thixotropic pseudo-25 plastic fluid, the rheogram exhibits what can be termeda thixotropic loop or hysteresis loop in that the des-cending series does not retrace the curve for the ascending series.
A thixotropic fluid is one which exhibits a 30 time-sensitive viscosity. In other words, the viscosity decreases with increasing shear duration. When a thixotropic fluid is sheared at a constant shear rate, the viscosity decreases with time until some equilibrium value is reached. This is interpreted by rheologists as 35 the breakdown of a structure present in the fluid.
When an ascending series of shear rates is imposed on a thixotropic pseudoplastic fluid, and immediately followed by a descending seriesg the curve is not retraced A hysteresis loop is produced,with the curve of the des-40 cending series displaced toward the shear rate axis~

~ . _ .

This loop is also known as a thixotropic loop and is due to the breakdown of structur~ with time.
The photographic processing concentrates of this invention comprise finely~divided soiid particles 5 associated in a stable three~dimensional network which imparts shear-thinning characteristics to the concen-trate. Thus, they can be characterized as thixotropic pseudoplastic fluids.
As previously pointed out, a key feature of 10 the present invention is the low ratio of liquid to solid, which characterizes the paste-like concentrates.
Such low ratio is rendered feasible by proper compound-ing of the ingredients of the formulation to achieve a stable three-dimensional network of associated particles.
15 In prior art attempts to prepare paste-like photographic processing concentrates, commercial success was not achieved because the concentrates prepared without the use of thickening~ gelling, binding or suspending agents would harden to a hard unusable mass in a relatively 20 short time, e.g., a few days, or would separate into two or more phases. On the other hand, when thickening, gelling, binding or suspending agents were employed to alleviate these problems, other difficulties were en-countered, such as poor flow characteristics~ crystalli-25 zation, and limited solubility characteristics. Thepresent invention is predicated on the discovery that thickening, gelling, binding or suspending agents are not necessary in pr~cessing concentrates of paste-like consistency, and that the desired shelf stability can 30 be achieved by careful control of the parameters of the manufacturing process, including, in particular, such important parameters as the particle size, the order in which the ingredients are combined, the degree of mixing and the ratio of liquid to solid components.
The invention is further illustrated by the following examples o~ its practice.
Exalæ~
A photographic processing concentrate intended to be diluted with water to form a color developing 40 solution for developing negative-positive color film . .

was prepared in the following manner:
780 milliliters Or a 47$ by weight aqueous solution of potassium carbonate and 240 grams of pow-dered potassium sulfite were added to a one-gallon 5 stainless steel Waring Blender, equipped with a cooling jacket, and blended for two minutes at low speed. 516 grams of 4-(N ethyl-N-2-methanesulfonylaminoethyl)-2-methylphenylenediamine sesquisulfate monohydrate in the form of a finely-divided powder was then added slowly 10 while stirring with a spatula. 502 grams of powdered potassium carbonate was then added, and the mixture was blended for three minutes at high speed.
The product obtained was a pourable paste having a weight ratio of liquid to solid of 0.16 to 1 15 which exhibited shear-thinning characteristics. It was diluted with water in a ratio of 50 grams of water to one gram of paste and dissolved readily to produce a working color developing solutionc Example 2 A photographic processing concentrate intended to be diluted with water to form a hardening developer for processing X-ray film was prepared as a two-part paste formulation in the following manner:
To prepare the first part, 787.5 grams of 25 potassium hydroxide (45% aqueous solution), 1545.69 grams of potassium sulfite, 157.5 grams of sodium bicar-bonate; 21 grams of boric acid, 35 grams of ethylene-diaminetetraacetic acid, 1.26 gr~ms of 5-methylbenzotri-azole, 5.25 grams o~ 5-nitroindazole, 630 grams of 30 hydroquinone and 175 grams of water were thoroughly blended together. The product obtained was a pourable paste which had a weight ratio of liquid to solid of 0.22 to 1 and exhibited shear-thinning characteristics.
To prepare the second part, 100 grams of 35 glycerol and 150 grams of water were added to a one-quart Osterizer Blender and blended at slow speed.
31.5 grams of powdered 1-phenyl-3-pyrazolidone was added and blending was continued for about 2 minutes. 31701 grams of powdered glutaraldehyde bis bisulfite was added _ _ .

slowly, using a spatula to work it into the mixture as - necessary, and blending was continued for about 3 ~.in-utes. The product obtained was a pourable paste which had a weight ratio of liquid to solid of 0.7 to 1 and exhibited shear-thinning characteristics.
To prepare a working developing solution, 5.6 grams of the first paste and 1.0 grams of the second paste were combined with 30 grams of waterS Both pastes dissolved readily to thereby produce a developing solu tion suitable for the processing of X-ray film.
Example 3 A photographic processing concentrate inten-ded to be diluted with water to form a color developing solution for developlng color prints was prepared from the following ingredients:

Components ~

1. Benzyl alcohol 493 milliliters t 2. l-Hydroxyethylidene-l,l-¦ . diphosphonic acid (60% by weight aqueous solution) 40 milliliters 3. Potassium carbonate (anhydr~us) 1600 grams 4. Potassium sul~ite (anhydrous) 100 grams 5. Potassium bromide 16.7 grams 6. Hydroxylamine sulfate 170 grams 7. 4-(N-ethyl-N-2-methanesulfonyl aminoethyl)-2~methylphenylene-diamine sesqulsulfate monohydrate 215 grams

8. Lithium sul~ate 89 grams These ingredients were added in the order specified to a one-gallon stainless steel Waring Blender equipped with a cooling jacket. Mixing was carried out .,~...... .

. :,.

at a high speed for times of 30 seconds for addition of ingredient 2, 15 seconds for addition of ingredient 3, 2 minutes for addition of ingredient 4, 1 minute for addition of ingredient 5, 2 minutes for addition of in-5 gredient 6, 3 minutes for addition of ingredient 7, and1 minute for addition of ingredient 8.
The product obtained was a pourable paste having a weight ratio of liquid to solld of 0.3 to 1 which exhibited shear-thinning characteristics. It was 10 diluted with water in a ratio of 18 grams of water to one gram of paste and dissolved readily to produce a working color developing solution.
Example 4 A photographic processing concentrate intended 15 to be diluted with water to form a color developing so-lution for developing color prints was prepared from the following ingredients:
Com~onent Wei~ht (grams 1. Triethanolamine 960.0 20 2. Benzyl alcohol 1071.0 3. Sulfonated fatty acid surfactant 2.0 4. Potassium hydroxide (45~ by weight aqueous solution) 291.2 5. Potassium hydroxide (85~ solid)370.0 25 6. l-Hydroxyethylidene~ diphosphonic acid (60~ by weight aqueous solution) 92.8 7. Potassium bromide 11.2 8. Potassium sulfite 40.0 -33- ~ 5 Component Weight (grams~

9. Amino-substituted ctilbene brightening agent 240~0

10. Lithium sulfate 224.0 5 11. Hydroxylamine sulfate 504.0 12. 4-(N ethyl-~r-2-methanesulfonyl~
aminoethyl)-2-methylphenylene-diamine sesquisulfate monohydrate 544.0 10 13. Potassium carbonate 2000.0 Components 1 to 5 were added to a 6-literVME-6 mixer manufactured by Fryma-Maschinen AG, and blended while cooling to a temperature of 17C. The mixer was then started and components 6 to 13 were added through 15 the addition port, allowing about ~; to 5 minutes between addltions for thorough mixing. Aft;er addition of the first five components, the dissolver (a rotating disk with a saw tooth type configuration) was started, and allowed to run throughout the mixing procedure. The 20 colloid mill (two rotating conical disks) was started after all components had been added, and allowed to run ~or one hour.
The product obtained was apourable paste hav-ing a weight ratio of liquid to solid of 0.61 to lwhich 25 exhibited shear-thinning characteristics. It was dilu ted with water in a ratio of 11.75 grams of water to one gram of paste, and dissolved readily to produce a working color developing solution.
The paste described above was analyzed by a 30technique involving high speed centrifugation to separ-ate the continuous liquid phase and the discontinuous solid phase, ~ollowed by analysis of the separated phases. The continuous liquid phase was analyzed by ultraviolet spectroscopy~ gas chromatography, Karl -3~-Fischer titration and total alkalinity titrimetry. The discontinuous solid phase wac analyzed by ultraviolet spectroscopy, gas chromatography, Karl Fischer titration, total alkalinity titrimetry, and gravimetric sulfate 5 analysis, It was found that about 85~ of the triethanol-amine, about 95~ of the benzyl alcohol, and about 90% of the 4-(N-ethyl-N-2-methanesulfonylaminoethyl)-2-methyl-phenylenediamine sesquisulfate monohydrate were present in the continuous liquid phase. Potassiurn carbonate was 10 found to be the major constituent of the discontinuous solid phase, with greater t~an 95% of the total potass-ium carbonate being found in this phase. Water, including water that was formed in situg constituted about 4~ of the paste by weighk. Particle sizes of 15 solid materials in the paste were in the range from about 0.5 to about 3 microns.
Example 5 A photographic processing concentrate intended to be diluted with water to form a black-and-white de-20 veloping solution was prepared with the use of a mortarand pestle from the following ingredients:

~ Weight (gramS 2 1. Potassium sulfite, anhydrous220.3 20 Sodium bicarbonate 22.4 25 3. Boric acid 3.0 4. Ethylenediaminetetraacetic acid 5.4 5. 5-Methylbenzotriazole 0.2 6. 1-Phenyl-3-pyrazolidone 4.5 7. Hydroquinone 89.7 30 8~ Potassium hydroxide (45% aqueous solution)138.4 9. Water 25.0 Component 1 was ground for four minutes and set aside. Components 6 and 7 were each ground for -~5-three minutes and were also set aside. Components 1 to 7 were then combined in the mortar and ground ~or two minutes. Component 8 was added slowly with mixing.
Component 9 was then added slowly with mixing. The com-5 position was mixed for three minutes after the finaladdition~
Within five hours, the material had set to a stiff paste. No separation, caking, or crystallization was evident even after two days. Rheograms of both freshly-prepared and two-hour old composition had dis-tinct thixotropic loopsO
Example_6 A photographic processing concentrate intended to be diluted with water to form a color developing solu-tion was prepared with the use of a mortar and pestlefrom the following ingredients:

Compone Weight (~rams 1. Triethanolamine 94.4 2. Benzyl alcohol 93.6 20 3 Potassium hydroxide, anhydrous25.6 4. l-Hydroxyethylidene-191-diphosphonic acid (60% by weight aqueous solution) 8.1 5. Sulronated fatty acid surfactant0.2 25 6. Potassium bromide o.g8 7. Potassium sulfite 3.5 8. Amino-substituted stilbene brightening agent 2100 Component Weight (~rams~

9. Lithium sul~ate 19~6 lOo Hydroxylamine sulfate 44.1

11. 4-(N-ethyl-N-2-methanesulfonyl-aminoethyl)-2~methylphenylene-diamine sesquisulfate monohydrate 47.6

12. Potassium carbonate 175.0 Components 3~ 10, 11, and 12 were ground separ-ately and set aside. Components 1 to 5 were added to the mortar in numerical order with mixing~ Components 6 to 9 were combined together and then added slowly with mixing. Then components 10, 11, and 12 were slowly added in order with mixing. When all additions were com-plete~ the composition was mixed for ~ive minutes. The total time of mixing was about thi;rty-three minutes.
Within twenty-nine hours, the material had set to a stiff paste. A~ter several days, there were no signs o~ separation, crystallization~ or caking. Rheograms for freshly-prepared and four-hour old samples had sig-nificant thixotropic loops.
Example_7 A photographic processing concentrate intendedto be diluted with water to form a fixing solution was prepared with the use of a mortar and pestle from the following ingredients:

Component Weigh 1. Ammonium thiosul~ate (80~ aqueous solution) 423,7 2~ Sodium thiosulfate 9o.o 30 3. Sodium sulfite 16.2 -~7-Component ~Jei~ht (grams 4. Sodium metabisulfite 19.0 5. Sodium acetate 45.0 6. Acetic acid 22.8 5 7. Sodium glyconate 8.1 8. Aluminum sulfate 57.8 Gomponents 2 and 5 were ground separately and set aside. All components were added together, slowly, in order, and with mixing. When all additions were com-plete, the composition was mixed for two more minutes.
Within two and one-half hours, the composition had set to a smooth, stiff paste. No signs of separa-tion, caking, or crystallization were apparent even after four days. Rheograms of fresh and two-hour old sampleshad thixotropic loops. The rheogram of the two-hour old sample had a very distinct loopO
For purposes of comparison with the above examples, a paste-like photographic processing concen-trate was made according to the formula and procedure of British patent No. 4689 -- A. D. 1894. The concen-trate was prepared in a mortar and pestle from the following ingredients:

1. ~ydroquinone 168 grams 2. Potassium metabisulfite168 grams 25 3. Potassium bromide 84 grams 4. Water 108 grams Component 1 was ground in the mortar for eight m~nute.s. Components 2 and 3 were ground together for five minutes and then were comblned with component 1 30 and ground for five more minutes. Component 4 was added slowly with mixing; and when all additions were ~ ~6 -~8-complete, the composition was mixed for three minutes.
Within one day of preparation~ the material had separated into a fluid upper layer and a dense sediment and was not useful for preparation of a working photographic processing solution For purposes of further comparison with the above examplesg a paste-like photographic proc~ssing concentrate was made according to the formula and pro-cedure of Æxample 5 of U. S~ patent 2,735,774. The concentrate was prepared in a mortar and pestle from the following ingredients:

1. Sodiu~ acetate 30 grams 2. Boric acid 15 grams 3. Sodium citrate 3 grams 15 4. Ammonium alum 10 grams 5O Sodium bisulfite 10 grams 6. Ammonium thiosulfate (76% aqueous solution) 100 milliliters 7. Sodium thiosulfate, anhydrous150 grams Components 1 to 5 were ground together in the mortar for five minutes. Component 6 was added slowly with mixing. Component 7 was ground separately before adding it to the mixture. When all additions were com-plete, the composition was mixed for five minutes.
Within 30 minutes, this compositlon had notice-ably stratified, leaving a dense sediment at the bottom of the jar. After three and one-half days, a clear liquid layer had formed at the top of the sample. In addition, rheograms for both freshly prepared and two hour old composition showed no evidence of thixotropy.
The paste-like concentrates of this invention provide many important advantages in the photographîc art. For example, they result in a major reduction in the costs for transport and storage of packaged chemicals, as compared to liquid concentrates. This is because of the much lower content of water that is required as com-pared to liquid concentrates, which results in much less ---" 9 ~68~3 bulk and weight~ and thus much lower costs. Many pro-cessing chemicals are not surficiently soluble in water to ~orm highly concentrated solutions, so liquid concen-trates often require a substantial water content. With 5 the paste-like concentrates of this invention3 a given quantity of processing solution can often be made from a package which has half or less than half of the weight and volume of a corresponding package of liquid concentrate.
A further advantage of paste concentrates, as compared to liquid concentrates, is that they tend to be more chemically stable and to require less separation of ingredients and, accordingly~ fewer separate parts in the total package~ Keeping properties are generally 15 significantly better with pa.stes because o~ such fea-tures as reduced susceptibility to oxidation, reduced susceptibility to deterioration caused by temperature changes, and reduced tendency for crystalllzation to occur.
Formation of working solutions ~rom the paste concentrates o~ this invention is relatively simple, as ccmpared to the difficult and time~consuming dissolution procedures required with dry powder formulations. More-over, the paste concentrates are c~enable to use with 25 processing compositions in wh~ch some of the necessary ingredients are normally liquid, and some are normally solid,-whereas dry powder formulations are useful only with compositions in which all necessary ingredients are normally solid. Paste formulations also e~ectively 30 avoid the problems of caking and dusting that plague the use of dry powder formulations.
As will be evident from the disclosure and examples herein, the paste-like photographic processing concentrates of this invention combine many of the 35 advantages of liquid concentrates with many of the ad-vantages of dry powder formulations to solve longstand-ing problems in the art of packaging photographic processing agents. They dissolve easily and speedily to form working processing solutions3 for example ~o~
replenisher solutions, and can be adapted for use in systems in which replenisher solution is held in a storage tank or for direct use in continuous replenish-ment of processing machines.
The invention has been described in detail with particular reference to preferred embodiments there-of, but it will be understood that variations and modi-fications can be effected within the spirit and scope of the invention.

Claims (24)

We Claim:

1. A photographic processing concentrate which combines shelf stability and low bulk characteristics that facilitate transport and storage with the ability to readily dissolve in a liquid medium to form a photo-graphic processing solution, said concentrate comprising a discontinuous solid phase distributed throughout a continuous liquid phase, said solid phase comprising finely-divided solid particles associated in a stable three-dimensional network which imparts shear-thinning characteristics to said concentrate, at least one of said liquid phase and said solid phase comprising at least one photographic processing agent, said liquid phase being present in an amount sufficient to impart a paste-like consistency to said concentrate.

2. A photographic processing concentrate which combines shelf stability and low bulk characteristics that facilitate transport and storage with the ability to readily dissolve in a liquid medium to form a photo-graphic processing solution, said concentrate comprising a discontinuous solid phase distributed throughout a continuous liquid phase, said solid phase comprising finely-divided solid particles associated in a stable three-dimensional network which imparts shear-thinning characteristics to said concentrate, at least one of said liquid phase and said solid phase comprising at least one photographic processing agent selected from the group consisting of developing agents, bleaching agents and fixing agents, said liquid phase being pre-sent in an amount sufficient to impart a paste-like consistency to said concentrate.

3. A photographic color developer concentrate which combines shelf stability and low bulk characteris-tics that facilitate transport and storage with the ability to readily dissolve in a liquid medium to form a photographic color developing solution, said concen-trate comprising a discontinuous solid phase distributed throughout a continuous liquid phase, said solid phase comprising finely-divided solid particles associated in a stable three-dimensional network which imparts shear-thinning characteristics to said concentrate, at least one of said liquid phase and said solid phase comprising a primary aromatic amino color developing agent, said liquid phase being present in an amount sufficient to impart a paste-like consistency to said concentrate.

4. A photographic color developer concentrate which combines shelf stability and low bulk characteris-tics that facilitate transport and storage with the ability to readily dissolve in a liquid medium to form a photographic color developing solution, said concen-trate comprising a discontinuous solid phase distributed throughout a continuous liquid phase, said solid phase comprising finely-divided solid particles associated in a stable three-dimensional network which imparts shear-thinning characteristics to said concentrate, at least one of said liquid phase and said solid phase comprising a primary aromatic amino color developing agent, said liquid phase comprising water and a water-miscible or-ganic liquid and being present in an amount sufficient to impart a paste-like consistency to said concentrate.

5. A photographic fixer concentrate which combines shelf stability and low bulk characteristics that facilitate transport and storage with the ability to readily dissolve in a liquid medium to form a photo-graphic fixing solution, said concentrate comprising a discontinuous solid phase distributed throughout a con-tinuous liquid phase, said solid phase comprising finely-divided solid particles associated in a stable three-dimensional network which imparts shear-thinning characteristics to said concentrate, at least one of said liquid phase and said solid phase comprising a thiosulfate fixing agent, said liquid phase being pre-sent in an amount sufficient to impart a paste-like consistency to said concentrate.

6. A photographic bleach concentrate which combines shelf stability and low bulk characteristics that facilitate transport and storage with the ability to readily dissolve in a liquid medium to form a photo-graphic bleaching solution, said concentrate comprising a discontinuous solid phase distributed throughout a continuous liquid phase, said solid phase comprising finely-divided solid particles associated in a stable three-dimensional network which imparts shear-thinning characteristics to said concentrate, at least one of said liquid phase and said solid phase comprising a ferricyanide bleaching agent, said liquid phase being present in an amount sufficient to impart a paste like consistency to said concentrate.

7. A photographic bleach concentrate which combines shelf stability and low bulk characteristics that facilitate transport and storage with the ability to readily dissolve in a liquid medium to form a photo-graphic bleaching solution, said concentrate comprising a discontinuous solid phase distributed throughout a continuous liquid phase, said solid phase comprising finely-divided solid particles associated in a stable three-dimensional network which imparts shear-thinning characteristics to said concentrate, at least one of said liquid phase and said solid phase comprising an aminopolycarboxylic acid bleaching agent, said liquid phase being present in an amount sufficient to impart a paste-like consistency to said concentrate.

8. A photographic processing concentrate as claimed in claim 1 wherein the size of said finely-divided particles is below about 100 microns.

9. A photographic processing concentrate as claimed in claim 1 wherein said liquid phase is present in an amount of from about 0.1 to about 0.6 parts per part of said solid phase by weight.

10. A photographic processing concentrate as claimed in claim 1 wherein said concentrate has a vis-cosity in the range between about 100 and about 500 cen-tipoises at a shear rate of 4500 sec-1.

11. A photographic processing concentrate as claimed in claim 3 wherein said primary aromatic amino color developing agent is 4-(N-ethyl-N-2-methanesulfonyl-aminoethyl)-2-methylphenylenediamine sesquisulfate monohydrate.

12. A photographic processing concentrate as claimed in claim 7 wherein said bleaching agent is an ammonium salt of ferric ethylenediaminetetraacetic acid.

13. In a method of photographic processing in which a processing composition is prepared and packaged in the form of a concentrate that is adapted for packag-ing, transport and storage and said concentrate is subsequently diluted with a liquicl medium to form a working strength processing solution, the improvement wherein said concentrate comprises a discontinuous solid phase distributed throughout a continuous liquid phase, said solid phase comprising finely-divided solid parti-cles associated in a stable three-dimensional network which imparts shear-thinning characteristics to said concentrate, at least one of said liquid phase and said solid phase comprising at least one photographic pro-cessing agent, said liquid phase being present in an amount sufficient to impart a paste-like consistency to said concentrate.

14. A method as claimed in claim 13 wherein said photographic processing agent is selected from the group consisting of developing agents, bleaching agents and fixing agents.

15. A method as claimed in claim 13 wherein said photographic processing agent is a primary arsmatic amino color developing agent.

16. A method as claimed in claim 15 wherein said liquid phase comprises water and a water-miscible organic liquid.

17. A method as claimed in claim 13 wherein said photographic processing agent is a thiosulfate fixing agent.

18. A method as claimed in claim 13 wherein said photographic processing agent is a ferricyanide bleaching agent.

19. A method as claimed in claim 13 wherein said photographic processing agent is an aminopolycar-boxylic acid bleaching agent.

20. A method as claimed in claim 13 wherein the size of said finely-divided particles is below about 100 microns.

21. A method as claimed in claim 13 wherein said liquid phase is present in an amount of from about 0.1 to about 0.6 parts per part of said solid phase by weight.

22. A method as claimed in claim 13 wherein said concentrate has a viscosity in the range between about 100 and about 500 centipoises at a shear rate of 4500 sec-1.

23. A method as claimed in claim 15 wherein said primary aromatic amino color developing agent is 4-(N-ethyl-N-2-methanesulfonylaminoethyl)-2-methylphenyl-enediamine sesquisulfate monohydrate.

24. A method as claimed in claim 19 wherein said bleaching agent is an ammonium salt of ferric ethylenediaminetetraacetic acid.