GB2062265A - A method to process silver halide photosensitive material - Google Patents

Abstract

A method of washing a silver halide photographic material which has undergone an operation comprising fixing, which comprises washing the fixed material successively in a series of compartments of a preliminary aqueous washing bath, arranged so that washing water is flowed from each compartment to its predecessor countercurrent to passage of the silver halide material through the compartments, replenishing the washing water in the second or a subsequent compartment in the series (reckoning in the direction of passage of the material) and, after, the preliminary washing, washing the material in a separate aqueous bath.

Description

SPECIFICATION A method to process silver halide photosensitive material The present invention relates to a processing method for exposed silver halide photosensitive materials, particularly to such method that some ingredient and soluble silver salt, which are brought into washing water with the silver halide photosensitive material, are sharply reduced, and that said ingredient is condensedly recovered.

Generally in the processing of silver halide photosensitive material, the problems of environmental conservation and saving of silver resources are regarded as of major importance nowadays and therefore there are the serious requirements to reduce the environmental pollution produced by waste washing solution and to recover silver from washing water.

To meet said requirements, a variety of the silver recovering processes not only from waste processed solution but from waste washing water. For example, the technical disclosures have been made in the West German OLS No. 2,532,018 and others in relation to electrolyzing process, in the Japanese Patent Publication Open-to-Public Publication No. 1 8318/1 975 and others in relation to metal substitution process, in the Japanese Patent Open-to-Public Publication No. 76029/1978 and others in relation to precipitating process made by chemicals, and in the Japanese Patent Open-to Public Publication No. 59254/1 978 in relation to precipitating process made by microorganism.

However, there has still been the defect in said processes that the silver recovering efficiency is poor because of the fact that the density of soluble silver salt is diluted and attenuated in waste washing water.

Heretofore, in addition to the above, an activated sludge process, process making use of activated charcoal or other adsorbing materials, trickling filtering process, electrolyzing process and so on have been known for the purpose of reducing the pollution of waste washing water, that is, for the purpose of reducing biochemical oxygen demands (BOD)#nd chemical oxygen demands (COD). But these processes have a disadvantage that the financial burden is heavy thereon and that the site required therefor must have a considerable size of land because a large quantity of water is used therefor.

Studies of washing efficiency have been practised. An example of the studies is disclosed in Journal of the SMPTE P248, 64 1 955, in which multiple washing baths are disclosed. It has also been known to furnish a single bath for preliminary washing process with a small quantity of water further to the washing bath to improve the washing method.But, when the photographic material is processed continuously with the process during which the ingredients being carried by the silver halide photosensitive material into the preliminary washing bath have a considerable high degree of density, the eluting speed of soluble silver salt eluted from the sensitive material into the preliminary washing becomes slower, and the eluted solution being carried into the washing bath when the photographic material transfers and thus there has been a serious disadvantage that the recovering efficiency is greatly lowered in said process.

It is an object of the invention to provide a process suitable for economical and continuous processing of photographic material, which reduces BOD or COD amount of waste washing water.

Another object of the invention is to provide a process to improve the efficiency of silver recovery from waste washing water, particularly in a continuous processing.

A further object of the invention is to provide a process of sensitive material reducing ingredients of processing solution which remains in photographic material after processing was made.

By present invention a preliminary washing bath containing more than two of compartments is furnished between a bath containing soluble silver salt from which the photographic material is carried out and a washing bath and washing water is flowed from the rear compartment to the front one of said preliminary washing bath contrary to transportation of photographic material being processed.

The bath containing a soluble silver salt in the invention means the one in which soluble sillver salt is contained as a result that photosensitive material is desilvered in the bath, namely a bath having a function of fixation. The bath containing silver salts of the present invention include fixing bath, bleachfixing bath, fixing bath for monobath development, emulsion hardening fixing bath, bleach-fixing bath for monobath development use, etc.; and said soluble silver salts include complex salt of silver thio-sulfate, complex salt of silver halide, complex salts of silver alkyl sulfide, complex salt of silver thiocyanate, complex salt of silver amine, and silver acetate, etc.

The greater efficiency can be obtained by increasing the number of the compartments from two to siz. In practical view point two compartments are most desirable. And, replenishing water to the preliminary washing bath may be supplied to any compartment, and it is preferable, to supply whole washing water into a rear bath to make flow of over-flow (including such as case that a pipe is connected between baths underneath of liquid level therein and liquid passes through the pipe) into a compartment in front of said rear one.More preferably, water is supplied in the component just before the washing bath, an wasted washing water whose amount is substantially same as that of supplied water is discharged form the compartment next to the bath containing soluble silver salt and the discharged water is utilized for the silver recovery purpose, because higher condensation of the soluble silver salt and other ingredients is obtained and also less amount of soluble silver salt flow out into the washing water bath and then the most highest effect can be obtained. And, if occasion demands, a part or whole of discharged water may be supplied in the bath containing soluble silver salt. As for the processes to recover silver from the discharged water, metal substitution process, electrolyzing process, absorption process, and other publicly known processes may be used.

A fresh water is used for supplying into the preliminary washing bath of the invention, and a part of water in washing bath or of discharged flow therefrom may also be used. Quality of such water may be that suitable for washing use. Temperature of the water is in a range of 20--500C, preferably 30--450C. It is preferable that the amount of replenishing water into preliminary washing bath is the amount of the order of 1/200-1/10 of that into washing bath, and from other point of view, is 1-20 times of the amount of liquid being carried together with photographic material into the preliminary washing bath from the bath containing a soluble silver salt. More preferably, 2--10 times of amount of such water being brought with photographic material is desirable.

In the conventionally well known processes of a preliminary washing bath having a single compartment, when the convergent level of the concentration of ingredient reaches in the preliminary washing bath, elution speed of soluble silver salt which is contained in photographic material becomes slower, and there is not much of effectiveness of elution even if preliminary washing time is prolonged, and an amount thereof carried over into washing bath abounds therein. Also when replenishing amount of water into the preliminary washing bath is increased, the carried amount into washing bath may be reduced but the degree of condensation is lowered and the degree of silver recovery is also lowered, that is not desirable.On the contrary, in the present invention, a very favorable and unexpected result has been obtained as that almost all amounts of soluble silver salt in the photographic materials are brought into the preliminary washing bath, with bringing little of them into the washing baths, in condensed state thereof in comparatively small amount of water, and are separable for silver recovery use, by the preliminary washing bath having multiple compartments and the water is flowed from a rear compartment to a respective front compartment of the preliminary washing bath.

The process according to the invention has the greater effectiveness on application to a continuous process (i.e., a continuous process keeping constant processability and preventing processing liquid from exhausting in process by replenishing a processing liquid). An automatic processing machine (hereinafter called as automatic processor) is normally used for continuous processing, and as for such automatic processor, those of automatic hanger processor, automatic roll processor, automatic roller transport type processor, automatic cine processor are included therein, and particularly, the process according to the invention can be favorably applied to the continuous processes using automatic processors.In addition, when using such automatic processor, it is preferable to set up squeezers to squeeze out the liquid brought out with photographic material at the respective positions between each of a bath containing soluble silver salt, a preliminary washing bath and a washing bath.

Further, the process of the invention can be applied to any silver halide photographic materials such as color papers, black an white papers, color reversal papers, color positive films, color negative films, black and white negative films, color reversal film, black and white reversal films, X-ray films, micro films, direct positive films, printing films, sensitive materials for mono-bath developing, bleaching and fixing use.

Next, the effects of the invention are hereby numerated as follows: (1) An amount of BOD or COD of discharged washing water can be reduced to one tenth of that of the conventional processes.

(2) Concentration of soluble silver salt being contained in discharge liquid, which is to subject to silver recovery, can be markedly increased comparing with the concentration obtained in conventional processes and thereby the efficiency of silver recovery can be remarkably improved.

(3) Ingredients of processing liquid, which remain in a photographic material after photographic processing was done, are reduced to less than one half of each of those of conventional processes, when a continuous processing is made by means of a standard automatic processor.

The following are the detailed descriptions of the present invention referring to the examples.

EXAMPLE 1 A picture is exposed to print on Sakura Color Paper (in roll) (made by Konishiroku Photo Ind. Co., Ltd.), and then a continuous replenishing process (hereinafter referred to as running process) is made by making use of an automatic processor (RP-1 180 processor, made by Noritsu Koki Co.) a) Control process 1. Color developing at 330C 3' 308 2. Bleaching and fixing at 330C 1' 308 3. Washing at 30-350C 3' 4.Drying at 75-800C about 2' Further, the washing bath is separated into three parts (they are arranged as the first, second and third part according to the order of processing line), and said parts are of such type that washing water pours into the third part thereof, from which water is flowed into the second bath, from which overflow pours into the first bath, from which over flow pours out to the outside of the processing machine system. (The same type is also applied to the process mentioned hereinafter, that is, washing process of B,CorD.) B) Process according to the present invention 1. Color developing at 330C 3' 30" 2. Bleaching and fixing at 330C 1' 30" 3. Preliminary washing at30-350C 1' 4. Washing at 30-350C 3' 5.Drying at 75-800C about 2' The preliminary washing bath is arranged by two compartments (preliminary washing time: 30" in each compartment), so that washing water is replenished in the rear bath of them from which overflow pours into the front one from which overflow is made then for silver recovery.

C) Process according to the present invention The preliminary washing bath Ds tne process B in the invention are arranged by five compartments (preliminary washing time: 12 seconds in each compartment.), so that washing water is replenished in the last compartment of them from which overflow pours into the previous compartment (the fourth compartment), from which overflow pours into the previous (the third) compartment and, in similar way, the overflow from respective rear bath flows in the previously neighbouring compartment thereof and then the overflow pours out from the first compartment (i.e., the bath which is closest to the bleaching and fixing bath).

D) Process for comparison Two of the preliminary washing compartment of the Process B of the present invention are connected with each other by a pipe to make the known mono-bath process, so that the same concentration and composite are obtained in both compartments by circulating liquid therein in the aid of a pump.

The compositions of the process are as follows: [ Color developer ] Benzyl alcohol 15 my Ethylene glycol 15 ml Potassium sulfite 2.0 g Potassium bromide 0.7 g Sodium chloride 0.2 g Potassium carbonate 30.0 g Hydroxylamine 1/2 sulfate 3.0g Polyphosphoric acid (TPPS) 2.0 g Kodak-CD-3 5.5g Fluorescent whitening agent (4,4'-diaminostilbene disulfite derivative) 1.0 g Potassium hydroxide 2.0g Add water to make 1 Itr.

[ Color developer replenisher ] Benzyl alcohol 20 ml Ethylene glycol 20 ml Potassium sulfite 3.0g Hydroxylamine 1/2 sulfate 4.0 g Polyphosphoric acid (TPPS) 3.0 g 3-methyl-4amino-Nethyl-N-(B- methanesulfonamide ethyl)aniline hydrosu!fate 7.0g Fluorescent whitening agent (4,4'-diaminostilbene disulfite derivative) 1.5 g Potassium hydroxide 3.0 g Add water to make 1 it.

[Bleach-fixing] Ethylenediamine iron (III) tetraacetate ammonium 60g Ethylenediamine tetraacetic acid 3 9 Ammonium thiosulfate (70% solution) 100 ml Ammonium sulfite (40% solution) 27.5 ml Adjust to pH 7.10 with potassium carbonate, or acetic acid Add water to make 1 Itr.

[Bleach-fixing replenisher (A) ] Ethylenediamine iron (III) tetraacetate ammonium 260g Potassium carbonate 42 g Add water to make 1 Itr.

The pH value of this solution is 6.70 + 0.1 [Bleach-fixing replenisher (B) ] Ammonium thiosulfate (70% solution) 500 ml Ammonium sulfite (40% solution) 250 ml Ethylenediamine tetraacetic acid 17 9 Glacial acetic acid 85 ml Add water to make 1 Itr.

The pH value of this liquid is 4.60 + 0.1 The running test is performed in such a way that said color developing liquid, bleach-fixing liquid, and washing water are filled up in the respective bath (among which washing water is filled up in the preliminary washing bath), and then color paper is processed with replenishing said color developing replenisher, bleach-fixing replenisher (A) and (B), and water for preliminary washing use at three minutes intervals running through quantitative cups. Each replenisher amount per one square meter of color paper is so determined as 324 ml to the color developing bath, 25 ml each of bleach-fixing replenisher (A) 8 (B), and 200 ml of washing water to the preliminary washing bath, respectively.

Washing water is so replenished continuously, at the rate of 10 Itr. per square meter of color paper, according to the processing volume, with adjusting the flow by a flow-meter.

EXPERIMENT 1 A continuous processing is made in each process of A, B, C, and D, and each overflow of washing water is collected when the replenisher amount reaches convergent (Note 1), and silver density, BOD and COD in each overflow is measured. Further, the overflow from the preliminary washing bath is collected to measure the silver concentration of which results of measurement are shown in Table 1 and Table 2. In addition, the measured values of BOD and COD of city water are also shown wherein for the reference.

(Note 1) Reach of astringency is defined as when total amount of bleach-fixing replenisher solution (i.e., sum of each amount of replenisher solution (A), replenisher solution (B) and color developer solution which is brought in being adhered with sensitive material) to be replenished into bleach-fixing bath becomes double of the capacity of tank.

EXPERIMENT 2 The results of measuring the amounts of residual hypo in the sensitive materials which were processed with A, B, C and D converged in the experiment 1 are shown in Table 3.

TABLE 1

Process BOD (ppm) COD (ppm) A (Control) 314 401 B (The invention) 1.3.1 162 C (The invention) 1.2 11.5 D (Comparison) 75.4 962 City Water 1.1 1.3 TABLE 2

Silver concentration (ppm) low Preliminary Process \ Washing Bath Washing Bath 450 A (Control) 450 B (The invention) 2.0 2100 C (The invention) O.O 2240 D (Comparison) 12 1690 TABLE 3 r

Amount of Residual Hypo Process (10 2 mg/100 cm2) A (Control) 5.0 B--(The invention) 3.0 C (The invention) 1.0 D D (Comparison) 4.7 As is evident from Table 1, the pollution loading amount of waste washing water in the process D (Comparison) is reduced to the amount being taken the figure down one place only, while that in the process of the invention being used two baths is reduced to the amount being taken the figure down two places.Further, in the process of the invention being used five baths, both BOD and COD thereof are lowered to almost the same amount with that of city water, therefore it is proved to be very effective for reducing the BOD s COD effluent of waste water. And, it is also proved by Table 2 that the process D (Comparison) cannot be in practical use because of the fact that the silver density in the waste washing water is reduced to only the order of one quarter, while in the process B (two-bath process) of the invention, said density is reduced to the order of one thirtieth, and in the process C (five-bath process) of the invention the density is so reduced that silver can hardly be detected therein, therefore the processes of the invention are proved to be very much effective for improving efficiency of silver recovery.

Also, the processes of the invention are proved to be more reasonably effective for reducing amount of residual hypo, in comparison with the conventional processes.

EXAMPLE 2 In the same manner as that of the example 1, Sakura Color Paper is processed and then silver is recovered with the aids of iron-wool process; from overflow of washing water as in the process A; from overflows of preliminary washing bath as in the processes B and C; from overflow of preliminary washing bath and from both of the overflow from the preliminary bath and overflow of washing water as in the process D. The silver recovery ratios corresponding to said processes are shown in Table 4.

Hereupon, the term of silver recovery ratio means the percentage of silver amount actually recovered, against theoretical amount of silver which is contained in sensitive material and/or adhered on the surface of said sensitive material, and then brought from a bath containing soluble silver salt into the next bath.

Process Silver Recovery Ratio A 78 B 94 C 100 D 73 85

(Note) Value of the percentage at the upper row in the silver recovery rate in case of recovery made solely from overflow of the preliminary washing bath, and the value at the lower row is the silver recovery ratio in case of recovery made both from overflow of the preliminary washing bath and from overflow of washing water. As is evident in Table 4, it is proved that the processes B and C of the invention have remarkably superior silver recovery ratios, in comparison with the conventional processes A and D.

Claims (7)

1. In a method for processing a silver halide photographic material, the silver halide photographic material carried out from a bath containing a soluble silver salt is washed in a preliminary washing bath containing two or more compartments and a washing bath being placed after the preliminary washing bath wherein washing water for preliminary washing is supplied to a compartment neighbouring to the washing bath, flowed to the front compartment of the preliminary washing bath, and discharged from the compartment next to the bath containing a soluble silver salt, and the amount of the supplied washing water for preliminary washing bath is 1/200 to 1/10 of that of a supplied washing water for the washing bath and 1 to 20 times of amount of liquid being carried in with the silver halide photographic material from the bath containing a soluble silver halide.

2. A method according to claim 1 wherein the preliminary washing bath contains 2 to 6 compartments.

3. A method according to claim 2 wherein the preliminary washing bath contains two compartments.

4. A method according to claim 1 wherein the bath containing a soluble silver salt is bleach-fixing bath.

5. A method of washing a silver halide photographic material which has undergone an operation comprising fixing, which comprises washing the fixed material successively in a series of compartments of a preliminary aqueous washing bath, arranged so that washing water is flowed from each compartment to its predecessor countercurrent to passage of the silver halide material through the compartments, replenishing the washing water in the second or a subsequent compartment in the series (reckoning in the direction of passage of the material) and, after, the preliminary washing, washing the material in a separate aqueous bath.

6. A method according to claim 5 incorporating any of the features herein described in connection therewith.

7. A method according to claim 5 using the number and arrangement of preliminary washing bath compartments described under B or C of Example 1.