NL8503430A - Maintaining activity of silver halide photographic processing baths - by addn. of aq. liq. concentrate contg. chemicals consumed - Google Patents

Abstract

The activity of photographic processing baths for photographic material based on Ag halide, is maintained during use of the baths of an aq. liq. concentrate of the chemicals used up. The compensator bath is added continuously or batchwise, using an amt. which is a function of the processed surface of the light-sensitive material. For developer baths, the compensator bath contains hydroquinone and/or other developer, 1, 2, 3-benzotriazole and/or other anti-fogging agent, an alkali metal sulphite and a sequestering agent, in concn. higher than in the developer bath, and KBr and an alkali metal hydroxide; partic. the bath contains hydroquinone, 1-phenylpyrazolidone-3, 1, 2, 3-benzotriazole, tetra-Na-EDTA, Na2SO3, KBr and NaOH. For fixing baths, the compensator bath contains an alkali metal sulphite, NH4OH and H3BO3, in concn. higher than in the fixing bath, and (NH4)2S2O3 and/or (NH4)NCS, an Al salt and acetic acid.

Description

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N.O. 33.31Z

A method for maintaining the activity of photographic processing baths using photographic compensating baths, as well as the photographic compensating baths.

The invention relates to a method for maintaining the activity of photographic processing baths during use by means of photographic compensating baths, as well as to such photographic compensating baths.

When exposing photographic silver halide-based materials, a latent image is formed in the silver halide crystals. This latent image can be converted into a visible photographic image by means of a number of photographic processing baths, such as the developer and fixing bath.

Had this processing of the photosensitive material in the past (and for a number of applications, especially amateur applications still take place) in a bowl or tank, today professional and industrial applications almost exclusively use developing machines. The term developing machine can be misleading for the uninitiated in photography and reprography, because a developing machine generally takes care of the total processing of the photosensitive material, so in addition to developing also fixing, rinsing, drying etc.

The transition from scale development to machine development has also had consequences for the formulation of the photographic processing baths. For example, the actual useful life of a scale developer 25 is only a few hours to at most a day, that of a machine developer can vary from a week to several months.

A fixing bath, used in the dish, generally has a somewhat longer life than that of the developer, yet the conditions of use, and thus the recipe, of a scale fix are different from those of a machine fixative bath solution.

In the book "Photographic Processing Chemistry" by L.F.A. Mason (The Focal Press, London, 2nd ed., 1975) describes on page 138 the changes that occur in a developing solution with continuous use: 35 (a) the consumption of certain components of the developing bath, such as developing agents and sulfite, as a result of the development reaction, (b) the release of certain compounds by the development reaction, such as bromide and hydrogen ions, (c) the occurrence of air oxidation, which consumes developing substances and sul-40 bicycle and forms hydroxyHones, 8353430 * 2 (d) reducing the developing liquid amount by transfer to the next bath through the swollen emulsion layer, (e) dissolving substances from the emulsion layer, such as surfactants and gelatin, (f) (not mentioned in the above-mentioned book, but equally important) to be selectively absorbed from the solution by the silver halide crystal of, inter alia, organic anti-fog substances.

To achieve the same photographic and sensitometric results throughout the life of the developing bath, all these changes would have to be undone. It goes without saying that this is an impossible task. In practice this also appears not to be necessary. A number of techniques are available to us, in which the influence of the changes in the chemical composition of the developer on the photographic and sensitometric results can be reduced to an acceptable level.

The first method is to compensate for the loss of development activity by extending the development time or increasing the development temperature. This method is only applicable to a limited extent, while its reliability for professional use is insufficient.

The second method is to compensate for the loss of developing activity by increasing the pH value of the bath using a so-called activator solution. Of this method, which has been frequently used by the graphic lith developers in scaling, it can be mentioned that its reliability and reproducibility for professional use is also insufficient.

A third method, especially common in the graphics industry, is that of regeneration or replenishment. In this method, the changes in the bath composition are compensated as well as possible by, after having removed part of the developer, replenishing the volume with a so-called regeneration solution that contains no or only a low concentration of bromide ions ( whereby the bromide ion concentration of the bath liquid is brought back to the original level) and which replenishes the consumption-reduced concentrations of chemicals, such as developing agent (s), preservatives, alkalis, etc. The effects of air oxidation of the developing bath are also taken into account when formulating a regeneration solution. The amount of regeneration liquid to be added is usually linked to the total surface area and the average blackening of the developed material (film or paper), a regular check of the bath activity through the development of so-called 8503430 * »3 test or check wedges is a necessity. In summary, it can be stated that the regeneration method is a useful method, but that the accuracy of the method leaves much to be desired.

A fourth form of activity retention of the bath liquid derived from the above method is that of rejuvenation, a method which has found wide acceptance in the development of color developers. In this method, the developer is passed through an ion-exchanger-filled column. The task of this ion exchanger is to remove the bromide ions from the developer. The substances consumed in the developer are also replenished. This rejuvenation method is not useful for hydroquinone-containing developers, since hydroquinone hinders the proper functioning of the ion exchanger. Most industrial black and white developers are based on hydroquinone.

The fifth method is to mention a method, which has gained a lot of popularity in the 15 graphic industry in recent years, the so-called rapid access process. Fresh developer liquid is added to the developer as a regeneration bath in an amount that is more than theoretically necessary to compensate for the use due to the chemical reactions that have taken place.

In some cases, the developer 's output is slightly reduced by the addition of a so - called starter solution, being an aqueous solution of acetic acid and potassium bromide, among others. This method works well for systems that are not too critical, the disadvantage of which must be mentioned is the wastefulness of the developer, whereby, on the one hand, higher costs are made than necessary, and on the other hand, an environmental burden occurs.

Surprisingly, it has been found that it is quite possible to maintain the activity of developing baths by adding in a concentrated liquid form only those chemicals which were consumed during the development process (and by air oxidation during normal use), the important advantage of achieving a reduction in chemical consumption. Such a concentrated liquid solution is referred to as a "compensator bath". The advantages of such a bath are: 35 - the chemical consumption is reasonably in accordance with the theoretical consumption (consumption as a result of the development reactions occurring, as well as as a result of the transfer of liquid to the next bath), resulting in a substantial saving of chemicals are reached; 40 - from wastage of chemicals by the "necessary" over-regeneration in the method of adding fresh bath liquid, or by draining some of the bath liquid, such as with the lith regeneration method, is no longer the case. The concentrated liquid form makes an important contribution to this.

5 - In those cases where the excess bath liquid is discharged into surface water via a waste water purification plant or not, a significant reduction in the environmentally harmful effect of the waste water will be obtained; for example, chemical oxygen consumption will drop sharply.

10 It has also been shown that, contrary to current opinion in this area (see, for example, the previously quoted book by LFA Mason, p. 138), in this way of maintaining the activity of the bath, it is in no way necessary is to remove the reaction products formed during the processing from the bath liquid. For example, this is essential in the rejuvenation of color developers.

Practical tests have shown that the activity of the processing bath can be maintained for a very long time (months) by dosing the compensating liquid.

It does appear to be advisable in certain cases, during use, to bring the developer into contact with pretreated activated carbon, as described in Dutch patent application 85.01671. This active carbon can, for example, be present in a filter cartridge, which is built into the rotary pump system of the developing machine. As described in the previously cited patent application, this prevents silver contamination of the developer, developing machine and the photographic materials to be processed.

A photographic compensator bath for developing baths will therefore contain developing agents such as hydroquinone and / or 1-phenyl-pyrazolidinone-3, alkali substances such as potassium and / or sodium carbonate, oxygen-binding substances such as sodium and / or potassium sulfite, anti-fog agents such as 1,2 3-benzotriazole, 5-nitrobenzimidazole or 5-nitroindazole and a sequestrant such as ethylenediamine tetraacetic acid tetrasodium salt, in a concentration increased with respect to the respective developing bath, for example by a factor of 1.5-5.

In the foregoing, only the developing liquid was discussed. Depending on the nature of the desired end result, a number of other baths are used in the processing of photographic materials, such as the stop bath, fixer 40 bath, bleach bath, bleach fix bath, booster, attenuator and stabilizer. 8503430 5. ...... '^ •' Τ bath. For each of these baths, a consideration, as mentioned above, can be given, and therefore photographic compensator baths can be formulated, which maintain the activity of the baths in question during use, and whereby chemical consumption and environmental impact are reduced. turn into. For example, a photographic compensator bath for fixer baths will include substances such as an alkali metal sulfite, ammonia, and boric acid or other aluminum salt complexing agent in an increased concentration with respect to the particular fixer in use, for example, by a factor of 1.5-5, as well as ammonium thio -10 sulfate and / or ammonium thiocyanate, an aluminum salt such as aluminum chloride 6-water, aluminum sulfate or aluminum nitrate as the curing agent and a pH adjusting agent such as acetic acid. In this connection it is noted that it is advantageous to electrolytically desalinate the fixing baths in use (and in fact this applies to any silver-containing processing bath) on-line 15 to a level of 0.5 to 2 grams of silver thiosulfate complex ( calculated as silver) per liter. Namely, in this way the dragging out of silver salts from this bath to the rinsing bath section can be reduced, which can be regarded as favorable on environmental grounds. However, a full electrolytic desalination ring is not recommended, as side reactions can cause instability of the fixing bath.

The following examples, not limiting the invention, further illustrate the invention.

25 Example 1

A developer and a compensator bath of the following composition were formulated: developer compensator bath hydroquinone 15 g 30 g 30 l-phenylpyrazolidinone-3 1 g 2 g 1,2,3-benzotriazole 0.1 g 0.4 g ethylenediamine tetraacetic acid, tetrasodium salt 1 g 4 g sodium sulfite, anhydrous 20 g 40 g 35 potassium bromide 5 g 5 g sodium carbonate, anhydrous 25 g - sodium hydroxide - pH -> 11.0 water, qs 1 liter 1 liter

A Chemco PowerMatic E-65 developer-40 chine was filled with this developer. The bath temperature was adjusted to 30 ° C, the

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"ί« ί ...... i ---- - - 6 throughput was set to achieve an effective development time of 30 sec. The photosensitive material was Chemco 400 Powertype RC paper. An addition of only 40 ml / m ^ was found to be sufficient to maintain bath activity for more than two months, tenfold required in conventional regeneration systems, noting that potassium bromide concentration is maintained not only by the addition of the compensator bath, but also via the release from the silver halide present in the photographic material The two month period should not be considered as limiting At the end of the two month trial period, the bath activity was found to have lost little value , so that a forecast of the lifespan of the bath of half a year or more can be considered real.

In this test, a filter containing pretreated activated carbon 15 was also incorporated into the developer pump system. As a result, there was no trace of contamination in the developer at the end of the trial period.

Example 2 A fixer bath and compensator bath of the following composition were formulated: fixer bath compensator bath ammonium thiosulfate 200 g 200 g sodium sulfite, anhydrous 20 g 100 g 25 ammonia, 25% 15 g 20 g boric acid 10 g 20 g aluminum chloride-6-water - 20 g acetic acid pH - ^ 4.0 pH - ^ 7.0 water, qs 1 liter 1 liter 30 With this fixing bath, to which 25 ml / 1 Chemco 963 PowerMatic Hard ner was added, a Chemco PowerMatic E-65 (with built-in desalination unit) was filled (fixing bath temperature: 27 ° C; fixing time 30 sec.).

5000 Chemco 400 35 Power type RC paper was fed into this machine for six months. During this time, the activity of the fixing bath was maintained by adding only 15 ml / m @ compensator bath while recovering approximately 5 kg of metallic silver.

40 8503430

Claims (10)

Method for maintaining the activity of photographic processing baths for silver halide-based photographic material during the use of such baths, characterized in that the chemical consumption occurring during the use of these baths is compensated by means of the adding an aqueous liquid concentrate of the spent chemicals, being the compensator bath, to the photographic baths. A method according to claim 1, characterized in that the chemical consumption occurring during the use of the photographic processing baths is continuously or dose-compensated by adding a compensating bath to the photographic baths. 3. Process according to claim 1 or 2, characterized in that the amount of compensator bath is added as a function of the processed surface of the photosensitive material. 4. Process according to one or more of claims 1-3, characterized in that a compensating bath based on hydroquinone and / or other developing substances, 1,2,3-benzotriazole and / or other anti-fog agents is used in the developing baths, an alkali metal sulfite and a sequestrant in an increase in developer baths, as well as potassium bromide and an alkali metal hydroxide. 5. Process according to claim 4, characterized in that in developing baths a compensating bath is used based on hydroquinone, 1-phenylpyrazolidone-3, 1,2,3-benzotriazole, ethylenediamine tetraacetic acid - tetrasodium salt and sodium sulfite in a of developer baths increased concentration, as well as potassium bromide and sodium hydroxide. 6. Process according to one or more of claims 1-3, characterized in that in fixing baths a compensating bath based on an alkali metal sulfite, ammonia and boric acid in an increased concentration with regard to fixing baths, as well as ammonium thiosulfate and / or ammonium thio- apply cyanate, an aluminum salt and acetic acid 7. Compensator bath, suitable for use in developing baths, characterized in that the bath is hydroquinone and / or other developing substances, 1,2,3-benzotriazole and / or other anti-fogging agents, an alkali metal sulfite and a sequestering agent of developing baths contains increased concentration, as well as potassium bromide and an alkali metal hydroxide. Compensator bath according to claim 7, characterized in that the bath 3303430 v 'V hydroquinone and / or other developing substances, 1,2,3-benzotriazole and / or other anti-fogging agents, an alkali metal sulfite and a sequestering agent in respect of developer baths with a factor of 1.5-5 increased concentration, as well as potassium bromide and an alkali metal hydroxide. Compensator bath, suitable for use in fixing baths, characterized in that the bath contains an alkali metal sulfite, ammonia and boric acid in an increased concentration with regard to fixing baths, as well as ammonium thiosulfate and / or ammonium thiocyanate, an aluminum salt and acetic acid. . Compensator bath according to claim 9, characterized in that the bath contains an alkali metal sulfite, ammonia and boric acid in a concentration increased by 1.5-5 with respect to fixing baths, as well as ammonium thiosulfate and / or ammonium thiocyanate, an aluminum salt and vinegar -15 contains acid. *** Λ A -te ί * Λ; Λ Λ li V v 'V' J l V V