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1. (WO1991017479) IMPROVEMENTS RELATING TO A PHOTOGRAPHIC PROCESS
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IMPROVEMENTS RELATING TO A PHOTOGRAPHIC PROCESS

The invention relates to a photographic process of the kind in which silver halide materials carried on a photographic carrier material is treated with a developer to develop an image and is then passed to an amplification bath. Subsequent to the amplification bath, the material is passed to a fixing and washing stage.

During a process of this kind the amplification bath itself has developer carried over into it which is transported on the material being processed and the presence of this developer builds up and shortens the life of the amplifier bath. In order to keep the bath up to the right strength it has to be replenished periodically to compensate for this build-up of developer.

If developer is retained on the material and is not removed completely by the end of the photographic process there is the risk that the final print material obtained will be liable to subsequent staining as the retained developer in the gelatine or its carrier will, under certain conditions, such as exposure to heat and light, cause further action by the developer which reacts with the constituents of the material to give an effect known as staining or a deeper intensity of certain colours. This is clearly not desirable since any photographic print is needed to remain stable over a long period and over a reasonable range of temperature and light conditions .

It is an object of the present invention to provide an improvement in a photographic process of the above kind which uses an amplification bath in which the problems associated with the build-up of developing agent are substantially reduced.

According to the present invention in a photographic process in which photographic material is treated in a developer is subsequently passed to an in-line amplification bath, the step is included of treating the amplification bath with an absorbing agent to remove or substantially reduce the amount of developer retained in the bath.

The absorbing agent is preferably an ionic exchange resin, which may be either cationic, anionic or neutral. In certain circumstances, a mixture of anionic and cationic resins may operate successfully.

As an alternative, the agent may comprise an activated carbon such as activated charcoal.

It has been known to use these absorbing agents for the treatment of waste solutions and to remove the colour developing agent from these waste solutions.

For example, in U.S. Patent Specification No. 4606827 the use of a cation exchange resin is disclosed with a solution which has a pH value not exceeding 8.0 for selective operation of a phenylenediamine colour developing agent to prevent the pollution of discharged waters into public sewers.

In British Patent Specification No. 2054182A the use of an ion exchange resin is disclosed to remove the degradation products of a developer in a fixer after the fixer has been subject to electrolysis to remove the dissolved silver in it.

None of the prior art shows the use of absorbing agents in the tail-end of a photographic process which includes an amplification bath. The following example illustrates the effect of different absorbing materials when used to remove the colour-developing agent when used in an amplification bath:

EXAMPLE

A simulated seasoned amplification bath was made by adding lOOmls. of an 'RX' developer to 500mls of an amplifier suitable for use with low silver materials. The formulae are as follows :

Developer : potassium carbonate 30. Og
sodium sulphite 2. Og
disodium EDTA O.lg
CD3 8. Og
water to 1.0 litre pH adjusted to 10.3 with potassium hydroxide solution Amplifier : hydrogen peroxide ( 100 vol) 30mls
water to 1.0 litre

50mls samples of the amplifier/developer mixture were stirred with 5g of different resins or charcoal for 10 minutes. The residual CD3 in the fixer mixture was determined by HPLC.

The results are tabulated below:

Addition Residual CD3 Resin Type

None 2.0+0.2g/l
Amberlite XAD-2 0.0+0.2g/l Neutral Amberlite XAD-7 0.0+0.2g/l Neutral

Amberlite IRA-400 1.0+0.2g/l Anionic

Duolite C225 1.2+0.2g/l Cationic

Duolite MB5113 0.0+0.2g/l Mixed bed

Zerolit NIP 1.0+0.2g/l Anionic Zerolit 236 0.0+0.2g/l Cationic

Activated charcoal 0.0+0.2g/l It will be seen from the above example that the absorbing agents all had an effect to a greater or lesser degree in reducing the amount of agent in the amplification bath. Clearly a selection of suitable agent has to be made depending on the nature of the developer in each bath. For the ' X'developer selected for this example there are five absorbing agents including both active charcoal and ion exchange resins which are wholly successful in removing all the developing agent.

This enables the amplification bath to have a much longer life than would otherwise be the case and reduces the amount of replenishment which is necessary for it, thus increasing the economics of the process. Furthermore, there will be no staining caused by a build-up of any developing agent in the material.