GB2054182A

GB2054182A - Process and Apparatus for Treating a Photographic Fixer

Info

Publication number: GB2054182A
Application number: GB8005405A
Authority: GB
Original assignee: Kodak Ltd
Current assignee: Kodak Ltd
Priority date: 1979-02-19
Filing date: 1980-02-18
Publication date: 1981-02-11
Also published as: GB2054182B

Abstract

A process and apparatus are provided for removing the degradation products of a photographic developer from a photographic fixer contaminated with the developer which contaminated fixer has been electrolyzed to recover dissolved silver. The contaminated fixer is cleansed by contacting it with a basic ion-exchange resin e.g. a polystyrene or phenol formaldehyde matrix having basic functional groups such as trimethylbenzyl ammonium groups or secondary and tertiary amine groups. The resin may be present in the electrolytic cell used to electrolyze the fixer and a combustible tubular cathode holder is described in which the resin is held. Alternatively, a separate resin container may be used (see Fig. 3, not shown). A permeable electrode 22 on supports 14, 16 and 12 with a trough 28 for catching particles falling from the electrode is shown in Fig. 2. Fixer enters at 30 and if the permeable electrode becomes clogged leaves via vent 32. Fixer also passes through support member 16 at vent 34 where it contacts the ion exchange resin, which may be contained in a bag, and leaves via vent 36. <IMAGE>

Description

SPECIFICATION Process and Apparatus for Treating a Photographic Fixer The invention relates to a process and apparatus for removing the degradation products of a photographic developer from a photographic fixer and to a process for developing and fixing a photographic silver halide material.

The invention is particularly applicable to systems in which silver is electrolytically removed from a working fixing bath that recirculates continuously through the processing and electrolytic units to maintain a relatively low concentration of silver. Such a system offers potential advantages over one in which the silver is removed only from effluent because there is less loss of silver to the water used to wash the fixed silver halide material, the fixer is less exhausted on account of the lower silver load, and a lower silver concentration in the fixer facilitates the washing.

On the other hand, the developing agents carried over to the fixing bath on and in the silver halide material become oxidised by the electrolytic process. The oxidation products can degrade until they form coloured compounds which can stain the silver halide material. For example, the gelatin forming part of a silver halide material can be stained in this way. If there is no bath between development and fixation to remove most of the developer, the desilvered, recycled fixer can darken rapidly. Many processing machines exist which, to achieve compactness, have no intermediate bath between the developer and fixing stages, and run at an elevated temperature e.g. an M6 'X-Omat' machine ('X-Omat' is a registered Trade Mark). It is for such machines, in particular, that convenient means are needed to prevent the accumulation of staining solutes when electrolysis is carried out.

It has been found that a basic ion-exchange resin will strongly absorb the coloured component from a fixer darkened by electrolysis in the presence of a developing agent.

In accordance with the invention there is provided a process for removing the degradation products of a photographic developer from a photographic fixer contaminated with the developer which has been electrolyzed to recover dissolved silver, which process comprises contacting the fixer with a basic ion exchange resin.

In accordance with another aspect of the invention there is provided a process for developing and fixing a photographic silver halide material which process comprises i) treating the material with a photographic developer, ii) treating the unwashed developed material with a photographic fixer, iii) electrolyzing the fixer to remove the dissolved silver, and iv) contacting the electrolyzed fixer with a basic ion exchange resin to remove the degradation products of the developer present in the fixer as a result of the electrolysis.

The effectiveness of the resin is surprising in view of the fact that the fixer has high concentrations of anions such as thiosulphate and argentothiosulphuric, the latter being of both treble negative charge and five-fold negative change. It is preferable to select a basic ion exchange resin which is resistant to the presence of reducing sulphur compounds. It is also preferable for the resin to have a low affinity for silver compounds as compared with its affinity for developer degradation products.

Preferably, a strongly basic ion-exchange resin is used.

Preferred resins include a resin comprising a polystyrene matrix having strongly basic functional groups and a phenol-formaldehyde resin having strongly basic functional groups.

Other suitable resins include weakly basic ionexchange resins. For example, a resin comprising a polystyrene matrix having weakly basic functional groups or a phenol-formaldehyde resin having weakly basic functional groups may be used e.g. Amberlite IRA 68, Amberlite IRA 93 and Duolite S37.

The resins are particularly effective for absorbing the coloured component from a fixer darkened by electrolysis in the presence of Phenidone (1 -phenyl-3-pyrazolidone) and hydroquinone which are the common developing agents in monochrome developers.

Fixer which has been treated in accordance with the invention may be recycled for re-use and the invention is of particular benefit to systems wherein after the fixer has been used it is electrolysed to recover dissolved silver and is then recycled.

The resin may be used in the form of small particles e.g. beads which may be introduced into the system at any point where the volume of the particles, possibly in swollen condition, can be accepted. In general, the resin must be substantially insoluble. It is preferably held in a porous container which prevents the escape of the finer particles. The particles may be incorporated in a filter unit, in a separate vessel or in the processing tank if space allows.

The resin may be introduced into the fixer at any stage e.g. at the start of a fresh bath to delay the onset of colouring or to clean a bath that has become coloured.

In one embodiment of the invention the resin is present in the electrolytic cell. In the electrolytic recovery of silver it is advantageous to use an expendable preferably combustible, electrode as the cathode. In one embodiment of the present invention it is advantageous for the resin to be held within such an electrode so that the resin may be inserted in and removed from the system with the electrode.

According to the present invention there is provided apparatus for performing the process of the invention which apparatus comprises an electrode holder for a tubular porous electrode, comprising a first and a second electrode support, a hollow support member extending therebetween, the electrode holder having fluid passages therein for allowing a proportion of a fixer to be treated to flow inside the support member, the support member having a space therewithin for receiving a container of basic ion exchange resin for treating that proportion of the fixer which flows therethrough, the remainder of the fixer flowing through fluid passages and outside the support member.

Preferably the support member is cylindrical.

The electrode holder is preferably made from a combustible material, such as plastics without incombustible filler material.

The fluid passages are preferably formed in the first and second electrode supports.

The preferred orientation of the electrode holder is with the main axis for fluid flow vertical, and-then the lower of the first and second supports is formed as an annular trough around the electrode holder.

In another embodiment of the invention, the cleaning of the electrolyzed fixer may be effected by flowing it through a separate container holding the resin.

In this embodiment, the process of the invention comprises passing the electrolyzed fixer through a resin container, separate from the electrolytic cell, which container holds a basic ion exchange resin whereby at least a portion of the fixer is brought into contact with the resin.

Further, the invention provides apparatus for performing the process of the invention which apparatus comprises an electrolytic cell for electrolyzing the fixer and, separate from the electroytic cell, a resin container for holding a basic ion exchange resin for cleaning thQ fixer, wherein, when the apparatus is in use, electrolyzed fixer is passed through the container and at least a portion of the fixer is brought into contact with the resin.

This apparatus may form part of apparatus for developing and fixing a photographic silver halide material.

The invention also provides a resin container suitable for use in the process and apparatus of the invention which container comprises means for holding a basic ion exchange resin and means allowing the flow of fixer from a separate electrolytic cell through the container so that, when in use, at least a portion of the fixer is brought into contact with the resin.

It is advantageous to provide the resin container in a circulation line for the fixer. For example, in apparatus for developing and fixing a photographic material such as an M6 'X-Omat' machine, the resin container may be situated in the circulation line between the electrolytic cell and a filter unit.

Preferably, the resin container is situated so that the resin in the container or the container and the resin can be replaced without loss of fixer.

When the fixer is recycled by pumping, the resin container may be situated at an elevation such that, when pumping is not taking place, the container may be replaced or the container may be opened without loss of fixer so that the resin may be inserted or replaced.

The resin container is a vessel of appropriate capacity preferably adapted to be attached to conduit for supplying and removing the fixer. For example, the container may have an inlet pipe and an outline pipe.

The resin container may be provided with a lid.

Preferably, the resin container is provided with an internal or external by-pass for the fixer so that the body of resin does not substantially impede the flow of fixer. The by-pass may be achieved by mechanically defining-an unobstructed path for the fixer. Alternatively, a bag of resin may be used the cross-section of which is smaller than the cross-section of the container.

The invention also provides apparatus for developing and fixing a photographic silver halide material-which apparatus comprises i) means for treating the material with a photographic developer, ii) means for treating the unwashed developed material with a photographic fixer, iii) means for electrolyzing the fixer to remove dissolved silver, iv) means for contacting the electrolyzed fixer with a basic ion-exchange resin to remove the degradation products of the developer present in the fixer as a result of the electrolysis, and; v) means for recycling the fixer, wherein (iii) and (iv) comprise either a) an electrolytic cell comprising an electrode holder of the invention, or b) an electrolytic cell and a separate resin container of the invention.

The means for treating the material with developer and with fixer are any of those conventionally employed e.g. processing tanks.

The invention will now be described, by way of example, with reference to the accompanying drawings, in which~ Fig. 1 is a perspective view of an electrode holder according to the present invention with an electrode fitted; Fig. 2 is a vertical section through the electrode and electrode holder shown in Fig. 1; and, Fig. 3 is a schematic cross-sectional view of a resin container of the invention.

In Figs. 1 and 2, the electrode holder 10 has an upper electrode support 12, a lower electrode support 14, and a tubular support member 16 extending between the supports 12, 14.

The support member 16 fits over circular portions 18, 20 on the supports 12, 14 respectively.

A radially permeable cylindrical electrode 22 fits over further circular portions 24,26 on the supports 12, 14 respectively spaced from the support member 16. A suitable electrode is described in U.K. Patent Application No.

51022/76; and Research Disclosure, May 1978, Item No.16950. Alternatively, the electrode may be in the form of a wire grid.

An electrical connection of the appropriate polarity is made at some convenient point.

The lower electrode support 14- also has an annular trough 28 around it which will catch particles of material which fall from the electrode 22. The circular portion 26-and the trough 28 will, in use, engage with a disc-shaped member in an electrolytic cell (not shown), the engagement being maintained, by means such as a bayonet coupling, or by downwards pressure applied to the electrode holder from the top of the electrolytic cell. The disc-shaped member closes the open and of-the lower support 14 to form an entry manifold for the fluid.

When the apparatus is in use, recycled fixer containing developer degradation products is pumped through the disc-shaped member and passes into the space between the electrode 22 and the support member 16 through holes 30 in the lower support 14. It may then pass through the electrode 22. Should the electrode 22 become clogged e.g. due to prolonged electrolysis, then the fixer may leave the space between the electrode 22 and the support member 1 6 through relief vents 32 in the upper support 12.

Some of the fixer from the manifold also passes into the space within the support member 1 6 through a hole 34 where it contacts the ionexchange resin for treating the fixer. The resin may be contained in a porous bag. The fixer then leaves the support member 16 through a hole 36 in the upper support 12. The hole 34 would typically be about 20 mm in diameter to allow rapid flooding of the support member 16, or emptying when the electrode holder -10 is removed from the electrolytic cell.

The hole 36 is smaller, say 3 mm diameter, as it is required only to vent air from within the support member 16 and to pass the fixer slowly, so as not to short circuit the flow of the fixer through the space between the electrode 22 and the support member 16, or to deplete the flow seriously.

Holes 38 are provided in the trough 28, so that the fixer may drain from the trough 28 when the electrode holder 1 3 is removed from an electrolytic cell.

The upper support 12 may be fitted with a handle to ease lifting of the electrode holder 10 from an electrolytic cell.

The electrode holder 10 is preferably made from plastics, any filler used being combustible so that the non-silver part of the electrode 22 and the electrode holder 10 may be removed by burning Advantages in the construction of an electrolytic cell arise in having the fluid entry and exit apertures at-the same end of the cell. As a result the situation will occur where, say, the entry is on the axis of the cell, but the exit is offset from the axis. Then, preferably, the trough 28 would have a diameter only slightly smaller than the internal diameter of the electrolytic cell, so that when the electrode holder 10 is in place a chamber is formed below the trough 28. This serves to equalise the flow of solution past the outer edge of the trough 28 to the off-centre exit aperture below the trough 28.

In the absence of this provision to balance the flow the deposit on the electrode 22 becomes greater where the flow and agitation are greater, at the part of the electrode 22 nearer the exit aperture.

The holes 34, 36 may be in the side of the support member 1 6, so that all the fluid flows through the holes 30 and then splits into the two separate flow paths.

Fig. 3 shows a resin container of the invention which comprises a hollow cylindrical body 10.

The lower end of the body 10 is closed and is provided with an inlet pipe 11. An outlet pipe 12 is provided in the side wall of the body 10 near its upper end. The upper end of the body 10 is closed with a removable lid 13 having a compression or screw closure A gasket 14 ensures a good seal between the lid 13 and the top of the body 10.

Inside the container, a perforated platform 15 is positioned adjacent and spaced apart from the lower end wall of the body 10. A baffle 1 6, adjacent and parallel to the side wall of the body 10, extends from the perforated platform to a point near the top of the container adjacent the outlet pipe 12.

A porous bag 17 containing resin beads 18 is held in the space defined within the side wall of the body 10, the perforated platform 15 and the baffle 16. A free channel 19 exists between the baffle 16 and the side wall of the body 10.

When in use, electrolyzed fixer is passed into the container through the inlet pipe 11. Part of the fixer passes through the perforated platform 15 and through the porous bag of resin beads 18 before leaving the container through the outlet pipe 12, while the remaining fixer flows unimpeded from the inlet pipe to the outlet pipe through the free channel 19.

The resin container shown is suitable for use with, for example, an M6 'X-Omat' machine in which it may be incorporated in the circulation line between the cell and the filter unit at an elevation such that, when the pumps are not running, the container may be open without loss of solution to insert a bag of resin or to replace the resin already there. Preferably, the container is situated so that the level of free fixer solution in the system and the level of the outlet pipe 12 coincide.

Although the resin container shown is a closed container designed to operate under positive pressure conditions, it will be appreciated that for operation under atmospheric pressure an open container may be used.

The invention is further illustrated with reference to the following Examples and the accompanying drawings.

Example 1 The electrolyzed fixing bath of an M6 'X-Omat' machine for processing X-ray film was worked with developed film until the solution had become dark brown. ('X-Omat' is a registered trade mark).

In Figure 4, curve 1 shows the typical spectral absorption of the solution at this stage. 250 g of Zerolit FF (ip) resin beads of 14-52 mesh size with 3 to 5 percent cross-linking were introduced into the outer chamber, that is on the inlet side, of the filter unit. Zerolit FF (ip) resin comprises a matrix of cross-linked polystyrene having trimethylbenzylammonium groups. The colour of the bath progressively lightened and after 48 hours it had become pale to the eye as indicated by curve 2 of Figure 4. Before treatment the fixing bath produced a density to blue light on preprocessed, unexposed film of 0.05, whereas, after blanching the density fell to zero.

Example 2 The degree of darkening of the electrolyzed fixing bath of an M6 'X-Omat' machine was measured over a period of time with and without the presence of Zerolit FF (ip) resin beads in the bath. The results are shown in Figure 5 in which the absorbance of the fixing bath of light having a wavelength of 420 nm is plotted against time in days of operation. In the control run in which no resin was employed, the fixer darkened rapidly and the stain threshold of the film was reached after about 14 days. In the run in which the resin was used the fixer darkened much less rapidly and the stain threshold was not reached until about 39 days. Further, the maximum darkening of the solution was limited by the resin until the run finished after 65 days.

Example 3 The electrolyzed fixing bath of an M6 'X-Omat' machine for processing X-ray film was worked with developed film until the solution had darkened and had an absorbance of 1.77 with respect to light having a wavelength of 420 nm.

('X-Omat' is a registered Trade Mark).

Approximately 200 g of Duolite S37 resin granules were added to the fixer whereupon the colour of the fixer gradually lightened during operation. After a period of 4 hours the absorbance of the fixer had fallen to 0.65.

Duolite S37 is a weakly basic ion-exchange resin comprising a porous hydrophilous crosslinked phenol formaldehyde matrix having secondary and tertiary amine functional groups.

Claims

1. A process for removing the degradation products of a photographic developer from a photographic fixer contaminated with the developer which has been electrolyzed to recover dissolved silver, which process comprises contacting the fixer with a basic ion-exchange resin.

2. A process as claimed in claim 1 wherein the resin is a strongly basic ion-exchange resin.

3. A process as claimed in claim 2 wherein the resin comprises a polystyrene matrix having strongly basic functional groups or a phenolformaldehyde resin having strongly basic functional groups.

4. A process as claimed in any one of the preceding claims wherein the resin is in the form of particles.

5. A process as claimed in any one of the preceding claims wherein the fixer is contacted with the resin in an electrolytic cell for electrolyzing the fixer.

6. A process as claimed in any one of claims 1 to 4 wherein the electrolyzed fixer is passed through a resin container, separate from the electrolytic cell used to electrolyze the fixer, which container holds the resin whereby at least a portion of the fixer is brought into contact with the resin.

7. A process as claimed in claim 1 substantialily as hereinbefore described with reference to and as illustrated in Figs. 1 and 2 or Fig. 3.

8. A process as claimed in claim 1 substantially as hereinbefore described in any one of Examples 1 to 3.

9. A process for developing and fixing a photographic silver halide material which process comprises i) treating the material with a photographic developer, ii) treating the unwashed developed material with a photographic fixer, iii) electrolyzing the fixer to remove the dissolved silver, and iv) removing the degradation products of the developer from the fixer by a process as claimed in any one of the preceding claims.

10. Apparatus for removing the degradation products of a photographic developer from a photographic fixer contaminated with the developer which has been electrolyzed to recover dissolved silver, which apparatus comprises an electrode holder for a tubular porous electrode, comprising a first and a second electrode support, a hollow support member extending therebetween, the electrode holder having fluid passages therein for allowing a proportion of a fixer to be treated to flow inside the support member, the support member having a space therewithin for receiving a container of basic ion exchange resin for treating that proportion of the fixer which flows therethrough, the remainder of the fixer flowing through fluid passages and outside the support member.

11. Apparatus as claimed in claim 10 wherein the support member is cylindrical.

12. Apparatus as claimed in claim 10 or claim 11 wherein the electrode holder is combustible.

13. Apparatus as claimed in any one of claims 10 to 12 wherein the main axis for fluid flow of the electrode holder, when in use, is vertical and the lower of the first and second supports is formed as an annular trough around the electrode holder.

14. Apparatus as claimed in claim 10 substantially as hereinbefore described with reference to and as illustrated in Figs. 1 and 2.

15. Apparatus for removing the degradation products of a photographic developer from a photographic fixer contaminated with the developer which has been electrolyzed to recover dissolved silver, which apparatus comprises a resin container comprising means for holding a basic ion exchange resin and means allowing the flow of fixer from a separate electrolytic cell through the container so that, when in use, at least a portion of the fixer is brought into contact with the resin.

16. Apparatus as claimed in claim 15 substantially as hereinbefore described with reference to and as illustrated in Fig. 3.

17. Apparatus as claimed in claim 1 5 or claim 16 further comprising an electrolytic cell separate from the resin container.

1 8. Apparatus for developing and fixing a photographic silver halide material which apparatus comprises i) means for treating the material with a photographic developer, ii) means for treating the unwashed developed material with a photographic fixer, iii) means for electrolyzing the fixer to remove dissolved silver, iv) means for contacting the electrolyzed fixer with a basic ion-exchange resin to remove the degradation products of the developer present in the fixer as a result of the electrolysis, and v) means for recycling the fixer, wherein (iii) and (iv) comprise either a) an electrolytic cell comprising an electrode holder as claimed in any one of claims 10 to 14, or b) an electrolytic cell and a separate resin container as claimed in claim 15 or claim 16.