FIELD OF THE INVENTION

This invention relates in general to photography and in particular to the processing of photographic color print materials. More specifically, this invention relates to a rinse bath which is useful in the final step employed in the processing of photographic color print materials. BACKGROUND OF THE INVENTION

Photographic color print materials are typically processed in a series of processing steps which includes color developing, bleach-fixing and rinsing. The bleach-fix bath typically contains a thiosulfate which functions as a fixing agent and forms a silver thiosulfate complex. Following the bleach-fixing step, the prints are treated with a rinse bath to remove the silver thiosulfate complex, and other unwanted residues of the prior processing steps, and are then conveyed through a dryer where they are contacted with warm dry air.

Many different formulations have been proposed heretofore for use as a rinse bath in this process. Usually, the rinse bath includes a biocide to prevent the formation of unwanted biological growths on the prints. It may also contain any of a variety of sequestering agents to retain calcium in solution and thereby avoid precipitation of calcium salts, which can deposit on the prints or foul the processing apparatus. A typical rinse bath is a dilute aqueous solution of citric acid, an alkali metal citrate, an alkali metal or ammonium hydroxide and a biocide.

One of the problems involved in use of such rinse baths is that precipitates of elemental sulfur and/or silver sulfide can form therein as a result of decomposition of the silver thiosulfate complex

generated in bleach—fixing. Such precipitates are highly undesirable, as they can foul the processing equipment and/or deposit on the prints.

It is known to treat photographic color print materials with a rinse bath that contains a polymer of vinyl pyrrolidone. Both the homopolymer of vinyl pyrrolidone and its copolymers are useful for this purpose. (See, for example, Japanese Patent Publication No. 28945/86 and ϋ. S. Patent No. 4,537,856). Use of such polymers is effective in avoiding precipitation of elemental sulfur and silver sulfide, probably as a result of their excellent dispersing properties. However, rinse baths contain¬ ing a vinyl pyrrolidone polymer have a serious disadvantage associated with their use. In particular, it has been found that use of such baths can render the surface of the print excessively tacky so that jamming tends to occur when the print passes through the dryer. Also, the rinse bath can leach materials from the print which are deposited on the rollers of the dryer so as to cause the prints to stick to the rollers with consequent jamming of the dryer.

It is toward the objective of providing an improved rinse bath, that avoids the formation of unwanted precipitates without causing dryer jamming, that the present invention is directed. SUMMARY OF THE INVENTION

In accordance with this invention, a rinse bath for use in the processing of photographic color print materials comprises an aqueous solution con¬ taining (1) a polymer of vinyl pyrrolidone and (2) a polysiloxane surfactant. Advantageously, the rinse bath also contains an effective amount of a biocide. By use of this rinse bath, deposition of precipitates of elemental sulfur and/or silver sulfide on the

prints and processing equipment is avoided, and the prints are easily conveyed through conventional drying equipment without risk of jamming. DESCRIPTION OF THE PREFERRED EMBODIMENTS The rinse bath of this invention is an aqueous solution having a pH in the range of about 4 to about 9 and more preferably in the range of 6 to 8. It contains an effective amount of both a polymer of vinyl pyrrolidone and a polysiloxane surfactant and, most preferably, also contains an effective amount of a biocide.

Polymers of vinyl pyrrolidone are well known commercially available materials. Useful polymers for the purpose of this invention include the homopolymer of vinyl pyrrolidone and copolymers of vinyl pyrrolidone with copoly erizable monomers such as methyl acrylate, methyl methacrylate, ethyl acrylate, vinyl acetate, 4—vinylpyridine, N—acryloyl- morpholine, N-acryloxylpiperidine, and the like. A preferred polymer for use in the rinse bath of this invention is poly-N-vinyl-2-pyrrolidone.

The polymer of vinyl pyrrolidone utilized in this invention typically has a molecular weight in the range of from about 2,000 to about 150,000 and more preferably in the range of from 5,000 to 50,000. The most preferred polymer is poly—N-viny1-2— pyrrolidone, with a molecular weight of about 15,000. The polysiloxane surfactants are well known commercially available materials. They are polymers which have a structure comprising repeating -O-Si-0- units. Polysiloxane surfactants have been used heretofore in photographic processing, for example, they have been utilized heretofore in rinse baths employed in the processing of photographic films. As disclosed in U. S. patent 3,545,970 issued

December 8, 1970, in Research Disclosure, Item 13142, "Use Of Ionic Surfactants In Photographic Processing Solutions", March, 1975, in Research Disclosure, Item 17431, "Photographic Processing Baths Containing Surfactants", October, 1978, and in Research Disclosure, Item 22123, "Photographic Processing Baths Containing Surfactants", September, 1982, use of polysiloxane surfactants in such rinse baths is advantageous in preventing "water spotting" of the film. Use of polysiloxane surfactants in the rinse bath of this invention is for a different purpose, which relies on their lubricative properties to prevent jamming of the dryer rather than relying on their surface active properties to prevent water spotting. As disclosed in Canadian Patent No.

991,467 issued June 22, 1976, polysiloxane surfac¬ tants have been used in a variety of photographic processing baths to reduce foam formation. However, use of polysiloxane surfactants in the rinse bath of this invention is for a different purpose which relies on their lubricative properties rather than their anti—foaming properties.

Particularly preferred for use in the rinse bath of this invention are polyalkoxylated dimethyl- polysiloxanes, especially those of the formula described in the aforesaid Research Disclosure Item 17431, which is as follows:

wherein R is lower alkyl, n is an integer with a value of 6 to 10, and X is an integer with a value of 1 to 10. The lower alkyl group represented by R

preferably has 1 to 4 carbon atoms and most preferably is a methyl group.

The most preferred polysiloxane surfactants for the purpose of this invention are polyalkoxylated dimethylpolysiloxanes which contain both ethyleneoxy and propyleneoxy groups in their structure, and are represented by the formula:

wherein R is alkyl of 1 to 4 carbon atoms, m and n are integers with a value of 6 to 10 and X and Y are integers with a value of 1 to 10.

The polyalkoxylated dimethylpolysiloxanes are commercially available materials, for example they are available from Union Carbide Corporation under the trademark SILWET.

Biocides are advantageously incorporated in the rinse bath of this invention to prevent microbial growth. A particularly useful class of biocides for this purpose are the thiazole compounds, especially isothiazolines such as 1,2—benzisothiazolin—3—one, 2-methyl—4-isothiazolin-3-one, 2-octyl-4-isothiazolin- 3-one and 5—chloro-N—methyl—4—isothiazolin-3—one. The ingredients utilized in making up the rinse bath of this invention can be used in any suitable amount, and the optimum amount of each will vary, depending on a number of factors such as the particular compounds employed, the manner of treating the photographic print material with the rinse bath,

and the particular composition of the photographic print material which is to be treated.

Typically, the polymer of vinyl pyrrolidone is used in an amount of from about 0.1 to about 10 grams per liter of rinse bath, and more preferably in an amount of from about 0.15 to about 2 grams per liter; the polysiloxane surfactant is used in an amount of from about 0.005 to about 10 grams per liter of rinse bath, and more preferably in an amount of from about 0.05 to about 2 grams per liter; and the biocide is used in an amount of from about 0.005 to about 1 grams per liter of rinse bath, and more preferably in an amount of from about 0.01 to about 0.2 grams per liter. In addition to a polymer of vinyl pyrrol¬ idone, a polysiloxane surfactant and a biocide, the rinse bath can optionally contain other ingredients such as buffering agents and sequestering agents. The rinse bath of this invention is especially useful in a three—step process for use with photographic color print materials comprising the steps of color developing, bleac'h—fixing and rinsing. The color developing solution used in this process contains a primary aromatic amino color developing agent. 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— hydroxytoluene, 2—amino—3—hydroxytoluene, 2-hydroxy— 3—amino—1,4—dimethylbenzene, and the like.

Particularly useful primary aromatic amino color developing agents are the p-phenylenediamines 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-diethy1-p-phenylenediaminemonohydro- chloride, 4-N,N-diethyl-2-methylphenylenediamine monohydrochloride, 4-(N-ethyl-N-2-methanesulfonylaminoethyl)- 2-methylphenylenediamine sesquisulfate monohydrate, 4-(N-ethyl-N-2-hydroxyethyl)-2-methyl- phenylenediamine sulfate, 4-N,N-diethy1-2,2'-methanesulfonylamino- ethylphenylenediamine hydrochloride, and the like. In addition to the primary aromatic amino color developing agent, color developing solutions typically contain a variety of other agents such as alkalies to control pH, bromides, iodides, benzyl alcohol, anti—oxidants, anti-foggants, solubilizing agents, brightening agents, and so forth.

Photographic color developing compositions are employed in the form of aqueous ^" alkaline working solutions having a pH of above 7 and most typically in the range of from about 9 to about 13. To provide the necessary pH, they contain one or more of the well known and widely used pH buffering agents, such as the alkali metal carbonates or phosphates. Potassium carbonate is especially useful as a pH buffering agent. The bleach-fixing solutions used in the aforesaid three-step process contain a suitable oxidizing agent, commonly referred to as a bleaching agent, and a silver halide solvent, commonly referred to as a fixing agent. The bleaching agent can be used in the bleach—fixing solution in any amount that is effective

to provide the desired bleaching action. Typically, amounts of from about 10 to about 400 grams per liter, and more preferably about 20 to about 150 grams per liter, are utilized. The working strength bleach- fixing solution typically has a pH in the range of from about 5 to about 7.

Bleaching agents of the aminopolycarboxylic acid type are most commonly used and can be employed individually or in the form of mixtures of two or more bleaching agents. Exemplary bleaching agents of the aminopolycarboxylic acid type, which can be used alone or in the form of mixtures, include ferric complexes of: nitrilotriacetic acid, ethylenediamine tetraacetic acid, propylenediamine tetraacetic acid, diethylenetriamine pentaacetic acid, ortho-diamine cyclohexane tetraacetic acid, ethylene glycol bis(aminoethyl ether) tetraacetic acid, diaminopropanol tetraacetic acid,

N-(2—hydroxyethyl)ethylenediamine triacetic acid, ethyliminodipropionic acid, iminodiacetic acid, methyliminodiacetic acid, ethyliminodiacetic acid, and the like.

In some instances the use of a mixture of bleaching agents is preferred over the use of individual bleaching agents. Thus, for example, a mixture can provide a desired level of bleaching power intermediate that of the individual bleaching agents of which it is composed; it can improve the

effectiveness of leuco cyan dye recovery, that is, the reoxidation of the leuco form to the colored cyan dye; it can minimize bleach-induced dye formation, that is, the formation of image dye that occurs when color developer carried by the photographic element into the bleach-fix solution is oxidized to form image dye; and it can improve the effectiveness of bleach—fix regeneration carried out by use of aeration.

Examples of particularly useful mixed bleaches include a mixture of the ferric complex of ethylenediaminetetraacetic acid and the ferric complex of propylenediaminetetraacetic acid, a mixture of the ferric complex of ethylenediamine¬ tetraacetic acid and the ferric complex of methyliminodiacetic acid, and a mixture of the ferric complex of iminodiacetic acid and the ferric complex of methyliminodiacetic acid.

The bleach-fixing solutions contain a fixing agent, such as a water—soluble thiosulfate fixing agent, in addition to the bleaching agent. As is well known, thiosulfates which are useful as fixing agents include ammonium thiosulfate and alkali metal thiosul¬ fates such as sodium thiosulfate and potassium thiosulfate. Typically, the fixing agent is used in an amount of from about 10 to about 200 grams per liter of bleach—fixing solution.

The bleach-fixing solutions can contain other addenda known in the art to be useful in such formulations, such as amines, sulfites, mercapto- triazoles, thiocyanates, and non-chelated salts of aminopolycarboxylic acids.

The rinse bath of this invention is especi¬ ally useful in the processing of reflection print materials having a resin-coated photographic paper support and especially in the rapid access processing of such materials. For a detailed description of

photographic elements, including reflection print materials, and methods for their manufacture, reference can be made to Research Disclosure, Item 17643, Vol. 176, December, 1978, published by Industrial Opportunities Ltd., Homewell, Havant Hampshire, P09 1EF, United Kingdom. Rapid access processing of reflection print materials comprising high chloride emulsions is described in some detail in International Patent Publication No. 087/04534, published July 30, 1987.

The invention is further illustrated by the following examples of its practice.

KODAK EKTACOLOR 2001 Paper was processed in a KODAK SYSTEM 20 paper processor using KODAK EKTACOLOR RA Developer Replenisher, KODAK EKTACOLOR RA Bleach—Fix and Replenisher and a rinse bath as described below. For each variation in the rinse bath, the racks and tanks in the rinsing section of the processing apparatus and the dryer rack rollers were cleaned. Fresh rinse bath was prepared in the processor. Once the processor was up to temperature, 5,000 prints were processed, the racks and dryer rollers were examined, and the seventh roller on the down side of the dryer was removed for evaluation. The rinse bath formulations evaluated and the results obtained are summarized in Table I below. In each case, the polyalkoxylated dimethylpolysiloxane employed was a compound represented by formula II herein.

Table I

Rinse Concentration Roller Comments Regarding

Bath Components (gms/liter) Condition Condition of Prints

Water 994.00 Clean High stain at low

Sodium citrate 1.42 utilization operation

Citric acid 0.93 of processor

Ammonium hydroxide (207» solution) 0.81 5-Chloro-N-methyl—4-isothiazolin-3-one

(1.57. solution) 3.00

Water

Poly—N—viny1-2— yrrolidone 5-Chloro-N-methyl—4-isothiazolin-3-one (177o solution)

Water

Poly— —viny1-2-pyrrolidone

5-Chloro-N-methyl-4-isothiazolin-3-one

(177o solution) Polyalkoxylated dimethylpolysiloxane

Table I (Continued)

Rinse Concentration Roller Comments Regarding

Bath Components (gms/Liter) Condition Condition of Prints

Water 999.00 Excessive Clean prints

Poly-N-vinyl-2-pyrrolidone 0.25 build-up

5-Choro-N-methyl-4-isothiazolin-3-one of deposits

(171 solution) 0.26

Water 999.00 Clean Clean prints

Poly-N-vinyl-2-pyrrolidone 0.25

5-Chloro-N-methyl-4-isothiazolin-3-one

(177o solution 0.26

Polyalkoxylated dimethylpolysiloxane 0.20

Tap water Clean High stain at low utilization operation of processor. Bio¬ logical growths form on prints.

Demineralized water Clean High stain at low utilization operation of processor. Bio¬ logical growths form on prints.

As shown by the data in Table I, with rinse bath No. 1, which contained neither a polymer of vinyl pyrrolidone nor a polysiloxane surfactant, results were unsatisfactory as the prints were stained under low utilization conditions from deposition of sulfur and silver sulfide. Such staining was avoided by the use of polyvinylpyrrol- idone in rinse baths No. 2 and No. 4, but deposits built up on the rollers with a consequent tendency for jamming to occur. Use of water as a rinse bath, as in tests 6 and 7, is unsatisfactory because of stain formation and the formation of biological growths. Only rinse baths No. 3 and No. 5, which contained a polymer of vinyl pyrrolidone, a polysiloxane surfactant and a biocide gave fully acceptable results with clean prints and no problem of jamming in the dryer.

The rinse baths of this invention exhibit many advantageous features for use in processing photographic color print materials. For example, they avoid, or at least substantially reduce, biological growths and precipitation of sulfur or silver sulfide, they have no objectionable odor, they do not adversely affect image-dye stability, and they avoid, or at least substantially reduce, the tendency for jamming of the dryer to occur.