Radiation imagery chemistry: process – composition – or product th – Regenerating image processing composition
Reexamination Certificate
1999-12-15
2001-01-30
Le, Hoa Van (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Regenerating image processing composition
C430S399000, C430S400000
Reexamination Certificate
active
06180326
ABSTRACT:
TECHNICAL FIELD
This invention concerns the decontamination and the regeneration of photographic processing baths and more particularly a method to eliminate organic pollutants contained in photographic baths.
BACKGOUND OF THE INVENTION
Conventionally, silver halide photographic materials, after exposure, pass through successive photographic processing baths. For example, the processing of black-and-white photographic products comprises a black-and-white development step, a fixing step, and a washing step. The processing of color photographic products comprises a color development step, a bleaching step, a fixing step, (or a bleaching-fixing step), and a washing and/or stabilization step.
During the processing of these color photographic materials, the composition of the processing baths changes. In particular, the photographic baths accumulate chemicals such as gelatin, latex, polymers, surfactants, etc., or other organic substances which leak out from the photographic or are the result of reactions during development. All these substances pollute the baths and reduce their efficiency. In addition, the presence of these pollutants in the photographic processing baths causes not only a sensitometric impairment of the photographic products, but also fouling of the processing machine and thereby of the materials being processed. This fouling is especially troublesome because photographic materials are generally processed in automated processing machines. The machines that allow a rapid development of photographic materials are also those most rapidly fouled. In particular, in the photographic processing baths of these automated machines are formed tars derived from the constituents of the photographic materials, which settle on the photographic material during the processing, and foul the machine. The presence of these tars requires frequent cleaning of processing machines, earlier replenishment of the baths, and in extreme cases several washings of the photographic materials.
The prior art has recognized this problem has tried to solve it by adding surfactants to the baths during processing in order to help dissolving the tars formed. However, the large amounts of such surfactants that have to be added impair the stability and efficiency of the processing baths.
The accumulation in the washing and(or) stabilization baths of substances from preceding processing steps impairs the stability of the photographic images developed, adversely affects the sensitometric characteristics, and increases plant maintenance requirements. Because of this, it is difficult to recycle the washing and stabilization baths. It is also unsafe to discard them in sewage, because after processing, the washing and stabilization baths contain compounds that raise the COD values of these baths. For example, effluents can be treated by electrolytic oxidation, dialysis, reverse osmosis (as described in German patent application 3 246 897), flocculation, or oxidation with hydrogen peroxide, possibly combined with UV treatment, as described in the U.S. Pat. No. 5,439,599 of Gehin et al. A non-catalytic oxidation can also be combined with a catalytic oxidation and a biological treatment, as described in European patent application 690 025.
The treatments described in the literature mostly advocate associating two or more methods to achieve satisfactory decontamination of the effluent, so that it can be safely discarded, or to remove species that may hinder re-use of the effluent. Also, some of these methods are costly to implement.
To purify effluents, the use of heat-reversible polymers in the form of hydrogels has also been proposed, as described for example in European patent application 648 521. However, one of the known characteristics of heat-reversible polymers is that their transition temperatures can vary significantly according to the values of several parameters, in particular the presence of surfactants in the effluent, as reported by Y. Q. Zhang et al. in Langmuir 1995, 11, 2493-5. This variability of transition temperature is a drawback for routine use of these polymers to depollute photographic effluents, because these effluents almost always contain surfactants or substances possessing surfactant properties to some degree.
SUMMARY OF THE INVENTION
The object of this invention is to provide a further solution to the problem arising from the presence of organic substances and tars in photographic processing baths. It is desirable to devise a method that allows these substances and tars to be eliminated rapidly and at low cost, without adversely affecting the sensitometric characteristics of the photographic products processed, and without impairing the stability or the efficiency of the photographic processing baths.
Another object of the invention is to reduce the soiling of the automated processing machines, and thereby to reduce the frequency of maintenance operations on these machines.
These and other objects are achieved by the method of this invention, which consists in placing a photographic bath containing organic pollutants and tars in contact with photographically inert heat-reversible polymer particles that are resistant to high pH values.
REFERENCES:
patent: 3497467 (1970-02-01), Coleman
patent: 3691086 (1972-09-01), Lees et al.
patent: 4144373 (1979-03-01), Weiss et al.
patent: 5219717 (1993-06-01), Schmittou et al.
patent: 5840471 (1998-11-01), Fukuwatari et al.
patent: 5972567 (1999-10-01), Poncelet et al.
patent: 1 450 588 (1976-09-01), None
Eastman Kodak Company
Le Hoa Van
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