||||||||||||||| b USOO526612A United States Patent (19) 11) Patent Number: 5,266,121 Cioletti (45) Date of Patent: Nov. 30, 1993 (54) METHOD OF CLEANING PHOTOGRAPHIC Primary Examiner-Theodore Morris PROCESSING EQUIPMENT Assistant Examiner-Thomas G. Dunn, Jr. 75) Inventor: Kenneth R. Cioletti, Wayne, N.J. sing, Agent, or Firm-Wegner, Cantor, Mueller & 73) Assignee: Helion Industries, Inc., Belleville, N.J. 57) ABSTRACT 21) Appl. No.: 928,354 Three aqueous cleaning solutions are disclosed, which lar. may be used individually or as part of a two-solution 22 Filed: Aug. 12, 1992 cleaning method for silver halide-based photographic 5ll Int. Cl................................................. B08B 9/08 processing systems. One solution comprises water, an 52 U.S. C. ..................................... 134/3; 134/22.19; organic or inorganic iron salt wherein the iron is in the 134/26; 134/42; 252/94; 252/100; 252/102 +3 oxidation state, a chelating agent, and an organic or (58) Field of Search ................... 423/32; 134/3, 22.19, inorganic silver complexing agent. A second solution 134/42, 26; 252/94, 100, 102 comprises water, an organic or inorganic acid or acid (56) References Cited anhydride, a surfactant, and a water soluble solvent. A third solution comprises water, a chelating agent, an U.S. PATENT DOCUMENTS alkali metal silicate salt, a surfactant, and a water soluble 3,625,908 6/1968 Magin ..................................... 134/3 solvent. 3,945,828 3/1976 Iwano ................ ... 430/.464 4,021,264 5/1977 Knorre et al. ........................ 134/42 4,678,597 7/1987 Keiner .............................. 134/22.19 21 Claims, No Drawings 5,266,121 1. 2 However, chlorine bleach does not effectively dissolve METHOD OF CLEANING PHOTOGRAPHC alkaline metal salts. PROCESSING EQUIPMENT DETAILED DESCRIPTION OF THE FIELD OF THE INVENTION INVENTION The present invention is directed to aqueous chemical The object of the present invention is to provide an solutions useful in the cleaning of photographic process effective system for cleaning photographic processor ing tanks and trays. tanks, while eliminating caustic solutions and chronium compounds and reducing cleaning time to around 30 BACKGROUND OF THE INVENTION 10 minutes. Utilizing a three-part system, the invention Traditionally, manual photographic processing in provides versatility in cleaning depending on the degree volved the use of at least four separate solutions: a de to which deposits have built up in the tanks. The present veloper to reduce the silver in the latent image to metal invention effectively removes silver, silver residues, and lic silver, a stop bath to arrest the developer, a fixer to organic deposits from all portions of the processor. The remove undeveloped silverhalide salts, and a wash bath 15 three-part system comprises three aqueous solutions, to remove residual fixer. The need for high speed devel oping has led to automatic processors which develop which may be stored separately to promote storage life, photographic film and paper. and which are useful in the cleaning of processor tanks. A typical automatic processor comprises three tanks: One embodiment of the present invention is a clean a developer tank, a fixer tank, and a wash tank. To 20 ing solution, referred to as solution A, which comprises increase production speed, the stop bath is eliminated. water, an organic or inorganic iron salt wherein the iron However, this requires that the fixer solution be formu is in the +3 oxidation state, a chelating agent, and an lated with high buffering capacity to neutralize the organic or inorganic silver complexing agent. Solution alkaline developer carried over with the photographic A has a pH in the range of about 5.0 to about 8.5 and can film or paper. 25 be used to clean developer or fixer tanks. After prolonged use, deposits can form on the sur A second embodiment of the present invention is a faces of the various tanks and also on the mechanical cleaning solution, referred to as solution B, which com roller/belt systems used to transport the photographic prises water, an organic or inorganic acid or acid anhy materials through the processor. In the developer tank, dride, a surfactant, and a water soluble solvent. The pH the deposits can be metallic silver, silver salts, and alkali 30 of solution B ranges from about 1.0 to about 5.0, de metal salts. In the fixer tank, the deposits can be silver pending on the particular acid, and may be used to clean salts, alkali metal salts, and elemental sulfur. Finally, in developer or fixer tanks. the wash tank, the deposits can be alkali metal salts, A third embodiment of the present invention is a gelatin, and gelatin by-products. cleaning solution, referred to as solution C, which com The prior art discloses the use of separate cleaning 35 prises water, a chelating agent, an alkali metal silicate compositions for the developer and fixer tanks. A salt, a surfactant, and a water soluble solvent. This solu strong oxidizer plus a solvent for silver salts is used on tion may be used to clean the fixer tank. the developer tank. Typically, such a cleaner includes A fourth embodiment of the present invention is a chromic acid or chromate salts plus sulfuric or sulfamic method of cleaning a photographic processor compris acid. The cleaner can be formulated as a powder or ing the steps of filling the processor with one of solu liquid. In addition, a neutralizer, such as an alkali bisul tions A, B, or C, draining, and rinsing with water. fite solution, is used to remove residual chromate salts. A fifth embodiment of the present invention is a two Other variations include alkaline powders which are solution method of cleaning a photographic processor combinations of alkali thiosulfate and ammonium sulfate comprising the steps of filling the processor with solu or other ammonium salts. More recently, a powdered 45 product consisting of a peroxymonosulfate compound, tion A, draining, rinsing with water, filling the proces sold under the name OXONE (a trademark of E. I. sor with solution B, draining, and rinsing with water. Dupont de Nemours Company), and citric acid has Suitable chelating agents include EDTA; DPTA; been developed. hydroxy(EDTA); sodium, potassium, or ammonium The major problem with non-chromate based clean SO salts of EDTA; sodium or potassium salts of hydroxy ers is the time involved in cleaning. The OXONETM ethyl ethylene diamine triacetic acid; sodium or potas /citric acid cleaner usually requires at least eight to ten sium salts of diethylene triamine pentaacetic acid; Na Fe hours to effectively remove all residues. Even after this EDTA; and ferric ammonium EDTA. time, it does not always remove the organic "tar' resi Suitable silver complexing agents include sodium, dues found in tanks used for processing color film and 55 potassium, or ammonium thiosulfate; sodium, potas paper. sium, or ammonium thiocyanate; sodium dithionate; In cleaning the fixer tank, a strong caustic solution, alkyl alkanolamines; alkyl amines; thiourea; alkyl thio such as sodium or potassium hydroxide, is normally urea; cysteine HCl; ammonium dithiocarbamate; mono employed to dissolve the silver complexes and salts. In ethanolamine oxalate; and alkanolamine oxalates. addition, powdered products are available which typi Suitable silver oxidizing agents include ferric chlo cally consist of trisodium phosphate. Such caustic solu ride; ferric ammonium sulfate; ferric nitrate; potassium tions suffer the disadvantages of being injurious to the or sodium ferricyanide; ferric sulfate; and other com eyes and skin. Also, phosphates are banned in many pounds capable of oxidizing metallic silver to its ionic localities. The wash tanks are normally contaminated State. with alkali metal salts and gelatinous residue resulting 65 Suitable inorganic acids include phosphoric, nitric, from the growth of microorganisms in the tank and and sulfuric acids. gelatin residue from the film or paper. Generally, chlo Suitable organic acids include acetic, oxalic, propi rine bleach is used to clean and disinfect the wash tanks. onic, hydroxyacetic, trichloroacetic, and citric acids. 5,266,121 3 4 Suitable acid anhydrides include acetic and propionic anhydride. -continued Suitable surfactants include ethoxylated nonylphe Composition Silver Clearing Time nols; linear alcohol ethoxylates; alkanolamine; and po 4 ml A6 -- 4 ml X2 -- 92 ml water 17.70 ninutes 6 ml A6 - 6 ml X2 - 88 ml water 4.30 minutes tassium or sodium salt of dodecylbenzene sulfonic acid. 8 ml A6 - 8 ml X2 - 84 m water 11.0 minutes Preferred surfactants are nonylphenol 9-12 mole ethyl 10 in A6 - 10 ml X2 - 80 ml water 9.5 minutes ene oxide and linear alcohol ethoxylate 9-12 mole ethyl ene oxide. Suitable water soluble solvents include glycol ethers, From these results, it was calculated that 6.10 g/l to such as diethylene glycol monobutyl ether, dipropylene O 31.0 g/1 of ferric ammonium EDTA produces the best glycol monomethyl ether, and propylene glycol mono clearing times, although good clearing times can still be methyl ether, and alcohols. obtained at concentrations between 5.0 to 35.0 g/l. The In solution A, it is possible to combine the silver ratio of ammonium thiosulfate to ferric ammonium oxidizing agent and the chelating agent as the Fe3+ salt EDTA was 1.6:1.0, which is suitable for cleaning most of the chelating agent. A preferred range of mole ratio 15 systems where silver halide salts are more prevalent of chelating agent to Fe3+is 1.1-1.2:1. For example, than metallic silver, although the ratio can be adjusted such a combination can be ferric ammonium EDTA. to account for differences in the relative amounts of free The invention is more fully described by, though not silver and silver halide. Thus, a suitable concentration limited to, the following examples. range for ammonium thiosulfate is between 7.5 and 55.0 20 g/l.