DE2217570A1 - METHOD OF BLADING FIXING OF COLOR PHOTOGRAPHIC MATERIAL - Google Patents

Description

AGFA-GEVAERTAG

PATENT DEPARTMENT

LEVERKUSEN . 2217570

Hs / Al

Method of bleach-fixing color photographic material

The invention relates to a method for bleach-fixing color photographic material, which is particularly useful for use suitable in high-speed processing machines.

For the rapid processing of color photographic materials, where you can shorten the entire processing cycle aims are high bath temperatures, strong agitation of the baths, high concentration of active substances in the baths and shortening of the exposure times of the individual baths characteristic » In particular, the intermediate washings are significantly shortened compared to conventional processing steps or they are omitted entirely. With rapid processing, this is often only replaced by stripping off the adhering bath or squeezing by means of pairs of rollers. It is not possible to carry over one bath to the next avoid completely, which often leads to a deterioration in the image quality. This is especially true for the transition from Color developer for the downstream bleach-fix bath. As is well known, the latter has the task of maintaining the entire layer of the to dissolve the silver present from the photographic material, the image silver formed during color development initially being oxidized by the bleaching agent present will. As a result, the bleach-fix bath builds up in dissolved silver.

However, the oxidizing power of the bleach-fix baths is also sufficient to oxidize the color developer remaining in the layers of the color photographic material and thus to

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wanted to lead color coupling. This becomes a general Produces a color haze that falsifies the image colors and causes poor image whites. The other hand is a high Oxidizing power of the bleach-fix bath required, not only for complete bleaching of the image silver, but also to achieve a sufficient color density, especially of the blue-green dye, which is reduced in the bleach-fix bath by the Stage of the bleaching agent, which is a strong reducing agent, to a more or less high proportion to the leuco form is reduced.

Another problem in the processing of color photographic materials, in particular the bleach fixation, is based on the Fulfillment of the requirements stipulated by the waste water legislation. In many cases, bleach-fix baths are inherently non-toxic. At least this can be done through constant reuse in cyclic processes and a corresponding regeneration, the proportion of bath substances that get into the wastewater or wash water be kept low. But especially when using a circular process, there is a constant accumulation of silver held in the bath, so that even the small amounts of lead fixing bath remaining in the gelatin layers in the limited Amount of the subsequent washing water still leads to a concentration of silver ions that is no longer tolerable can result in wastewater. Compliance with the legal requirements therefore requires very small concentrations of silver ions in the bleach-fix bath, which in turn contradicts the cycle processes mentioned.

So the task is to develop a bleach-fix method for rapid processing of color photographic material to find that with excellent image results to a tolerable wastewater pollution, especially with regard to the Silver concentration, led

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Based on a series of tests it has now been found that in one The bleach-fix processing line contains the bulk of the image silver and the remaining halogen over in the first part of the Bath treatment goes into solution and that towards the end of the treatment time only very small amounts of residual silver are dissolved have to.

If you make, for example, the color-developed material _s instead of the bleach-fixing in a single tank, leaving a number of series-connected tanks containing the beginning all the same Bleichfixierbaö go through, you then place the bulk of the silver in your or the first tank (s ), while the amount of silver in the last tank is so small that after adding the washing water, the silver ion concentration remains below the tolerance limit «,

It has also been found that with such a division of the bleach-fixing bath section, the oxidizing power of the lead-fixing bath at the Änfeng fe SWe ke can be reduced in a simple manner to such an extent that oxidation of entrained color developer and the resulting color fogging no longer takes place without the bleach-fix bath is impaired in its bleaching and fixing effect. The reduction in the oxidative power is effected by lowering the pH value or by adding reducing agents or by a combination of these measures.

The invention relates to a process for bleach-fixing developed color photographic material using bleach-fixing baths, which contain a heavy metal complex of a complex-forming aminopolyacetic acid as a bleaching agent and a silver salt solvent as a fixing agent ₉ whereby the developed color photographic material is passed through a bleach-fixing bath section. The method of the present invention

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dung is characterized in that the bleach-fix bath line is subdivided, that at the end of the bleach-fix bath line is poor in silver Bleach-fix replenisher is supplied that the bleach-fix in countercurrent to the direction of travel of the color photographic Material led to the beginning of the bleach-fix bath line and its oxidative power is reduced there by lowering the pH and / or adding reducing agents, that the formation of a color fog is effectively suppressed.

The method finds its preferred application using the usual bleach-fix baths, their bleaching agents from the cobalt (III), copper (II) or preferably the iron (III) complex a complex-forming aminopolyacetic acid, preferably ethylenediaminetetraacetic acid, and its fixing agent is preferably sodium thiosulfate.

When leaving the bleach-fix bath line, the color photographic drags A certain amount of bleach-fix solution. In addition, losses can occur through splashing or evaporation, especially when the individual tracts of the bleach-fix bath section are open and when for acceleration The process is carried out at an elevated temperature. ”These losses are compensated for by adding silver-free or low-silver bleach-fix bath regenerator to the last section of the bleach-fix bath line. The regenerator will even added in excess so that there is a flow direction of the 3Ieichfixierbad that is opposite to the direction of travel of the color photographic material. Through overflow or by means of pumps, the bleach-fix bath comes from the last section against the direction of travel of the color photographic material into the preceding tracts and from there to the beginning of the bleach-fix bath section. When working continuously there is a high silver concentration at the beginning of the route

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one (up to 10g / l), which is considerable in the following tracts decreases and becomes tolerably small at the end of the bleach-fix bath line.

The decrease in concentration essentially depends on the V @ r-.

['o I -

ml / m j to which is countercurrent

flowing replenisher volume b ml / ® * "but neglect in the following tracts of the bleaching bath silver dissolved from your color material is the reduction the silver concentration from tract to tract as a first approximation b. Since the badaieage carried away in the color material is a given

is the number of consecutively 'connected tracts and / or · Regeneratoraienge can be te so that in ge.vjähjt _ΰ What is = serungswasser achieved with the amount Limi w / ii j © a tolerated © ~ Siiber concentration "Bie Ag löazeatratiosi In the last tract c _n dari then be

^c n ^{= c} -i.-. * »

if c ^. = the tolerance coefficient in the water is ₀

Under tracts in the sense of the present © ?! Erfiadtisg means individual sections of the entire Bl © i.chfisi © rbaastr' © ck ©. It can feaside around individual tanks, olle cascaded one behind the other, SiMj and Ia in which the color photographic material is passed through the bleach-fixer in the dew point, and also around spray chambers connected in series in which the lead fixative bath is sprayed onto the Material is brought in ₀ Bi © Tr files can be dimensioned in such a way that the Yerwell sides of the golor material are the same in the individual tracts. Prove to be advantageous, the individual tracts different sizes zi: *. give so that the distribution times of the color material in the different tracts of different lengths

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The division of the bleach-fix bath section into several wings also enables the oxidizing power of the bleach-fix bath to be lowered in the first tract following color development. The reduction in the oxidizing power is achieved according to the invention in that either the bleach-fix bath is used An acid is added to lower the pH value or a reducing agent is added to lower the redox potential will. A combination of the two measures is also possible, compliance with the most favorable conditions in the first tract of the The bleach-fixing bath section can advantageously be monitored and controlled with the aid of electrometric electrodes.

In the case of the usual bleach-fixing baths with the highest possible oxidizing power, the pH is generally between 6 and 8. It has been shown that the pH can be lowered to about 5 without the bleach-fixing effect being impaired, and that at pH about 5.5 even a particularly rapid bleaching takes place. At the same time, however, the oxidation of entrained color developer is suppressed. The lowering of the pH value in the first section of the bleach-fix bath line can be achieved by adding inorganic or organic acids, e.g. B. with phosphoric acid or acetic acid. The control of the pH is expediently fully automatic continuously or discontinuously with the aid of a pH measuring chain, which consists for example of a glass electrode and a calomel electrode and whose potential controls the acid inflow via a small regulator and a solenoid valve.

As already stated, the lowering of the oxidizing power of the bleach-fix bath can also be achieved by metering in a reducing agent to the first tract of the bleach-fix bath line ^ Suitable reducing agents are, for example Hydrazine, hydroxylamine, dithionite, formaldehyde sulfoxylate and their water-soluble salts. In this case, too,

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in the first tract of the bleaching fluid bath line by means of fully automatic Controlling constant conditions, e.g. a constant rl value (redox value), can be maintained by the changes, those of the bleach-fix bath on the one hand by color developer entrained with the color material and on the other hand is subject to the counter-flow of the regenerator, balanced by appropriate metering in of reducing agent will. A measurement and control arrangement similar to that described for pH control is also suitable for this purpose, with but this time, for example, a glass electrode as the measuring chain. electrode and a platinum electrode can be used.

FIG. 1 shows such a measuring and control arrangement in schematic form Depiction. Here 11 means the wing Ί the Bleach-fix bath line. The two measuring electrodes 12 and 13 of the electrometric measuring chain are immersed in the bleach-fixing bath. 12 is a glass electrode; 13 is a calomel electrode with pH control or a platinum electrode with rH control. That measured potential is in the measuring amplifier 14 (e.g. "measuring amplifier Type 70 from the company U.Knick, Berlin) amplifies and operates Via the controller 15 (e.g. Pantam controller Z1 from Gossen, Erlangen) and the relay 16, a solenoid valve 17. The storage vessel 18 contains acid (with pH control) or a reducing solution (with rH control). The inlet 19 in the tract 1 is controlled by the solenoid valve 17.

In the first wing there is an overflow of silver-rich bleach-fix bath deducted, the amount of which depends on the amount of bleach-fixer regenerator added in the last section Overflow can be desilvered according to the known method, e.g. by electrolysis, by precipitation with sulfide or cementation with iron, and then to lead fixer bath regenerator be worked up. The work-up can be carried out batchwise or continuously. There at the

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Most desilvering methods inevitably include the bleach is reduced, it proves to be advantageous in terms of a higher yield if the overflowing bleach-fix bath is already pre-reduced by adding reducing agents to the first tract.

The inventive method of dividing a bleach-fix bath line in two or more separate wings with regeneration and reduction running in the opposite direction to the direction of the material the oxidizing power in the first tract has compared to the previous procedure of a single bleach-fix bath or several subsequent ones with non-cascade regeneration Advantages:

1. The silver concentration in the last tract before the watering can be kept so low that the tolerance limits. are not exceeded in the wastewater.

2. The amounts of water required to avoid exceeding the tolerance of silver ions in wastewater can be small being held.

3. The enrichment of silver in excessively high concentrations in the first tract enables an efficient one. Desilvering with small volumes.

4. The lowering of the redox potential and / or the pH value in the first tract effectively prevents the oxidation of the color developer that has been introduced and thus the production of color veil. Excellent image results are obtained.

5. The reduction of the redox potential in the first tract of the The bleach-fix bath section facilitates silver recovery from the overflow.

6. The possibility of a high oxidizing power in the second and

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secures the following tracts of the bleach-fix bath line adequate bleaching and complete reoxidation the dyes of the color material.

7. Total silver recovery and the possibility of constant rejuvenation of the bleach-fix bath in one Circular process leads to a particularly economical mode of operation.

The method according to the invention can be used in tank systems and tank baths, be used in spray processes or also in roller flushing processes. It is feasible with bleach-fix baths, e.g. as a reversible redox system for the oxidation of silver, copper, cobalt or iron chelates of an aminopolyacetic acid Quinone or iron (Dll) cyanide, as a fixative for halogen silver Use thiosulfates, thiocyanates, thioureas, thioethers or organic diols.

The following examples illustrate the invention.

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example 1

Color paper with a width of 9 cm and a total area of 6 m was imagewise exposed, developed normally in a color developer and then in a bleach-fix bath at 20 ° C the following composition bleach-fixed:

Ethylenediaminetetraacetic acid 3.0 g

Na ₂ HPO ₄ 20 g

Na ₃ PO ₄ '4g

Na-iron-III-EDTA 30 g

Na ₂ SO, 8 g

Ammonium thiosulfate 120 g

Na ₂ CO, 6.0 g

Water _ . 1000 ml glacial acetic acid up to pH I ₁ I.

The bleach-fix bath was in six separate tanks which were successively traversed by the ribbon-shaped developed color material within 4 minutes. That When it left the last tank, Colormaterial no longer contained any silver. For the silver content in the individual tanks the following values.

Tank 1 1.12 g / l = 42 % of Total silver 2 0.97 ti = 36 Il 3 0.38 ft = 14 π / Il ' 4th 0.13 it 5 / Ο It VJl 0.06 It 2, 25% It 6th 0.02 It 0, 75% ti

This result shows that the first third of the bleach-fix bath route already 78%, and in the first half already 92% of the silver in the bathroom were dissolved.

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Example 2

This example uses a bleach-fix bath section divided into three sections and the silver concentrations that are established in the equilibrium state in continuous operation calculated. .

In FIG. 2 there is one consisting of three chambers 21, 22 and 23 Bleach-fixing bath section and an adjoining wash chamber 24 are shown schematically. The color material ■ is introduced into chamber 21 after color development at 25, passes through the individual chambers of the fixing bath section one after the other and 'arrives from the last chamber 23 of the fixing bath section into the soaking chamber 24. A.

the amount of silver introduced per m of color material; a the per m of color material through uptake in the emula / m ^ is de po Colaeil r u sion layers entrained amount of bath, and b Ll / m J is the pro

The amount of regenerator 26 flowing into the last chamber 23 is the amount of regenerator 26 that flows into the last chamber 23 and is transferred in countercurrent to the direction of flow of the material into the front parts of the fixing bath section and taken as overflow 27 from the first chamber 21. -W {jL / m ^] is the per m ^{2 of} color material. Amount of washing water 28 consumed, which determines the silver concentration of the Ba * - ·. des further reduced by the factor a _e 29 is that the what--

w
chamber 24 leaving wastewater '

The lead times and thus the flow paths through the chambers 21-23 are so dimensioned that are in chamber 21 90%, in chamber 22, the remaining 10% of the layer of silver dissolved out ', and the distance in chamber 23 substantially serves only to re-oxidation of the cyan dye . In the following calculations, e denotes that silver fraction from the IC emulsion layers which is in the. first chamber 21 from the

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Layers is removed, i.e. e = O, 9O.

The following data was used as a basis for the bleach-fix bath range described in this example:

Amount of silver contained in the material per m A = 1.35 g / m

2-2

Carry-over amount per m a = 2.5. 10 "l / m

ρ _A ρ

Amount of regenerator per m b = 2.5. 10 l / m

2?

Watering amount per m w = 10 l / m

Dissolved silver content in the 1st tract e = 0.9 (= 90 %)

From the list of the equilibrium conditions within the processing system, the _{following equations result for the silver concentrations C 1} , Cp, C, in chambers 21-23:

e.A + (1-e) Away - a
a .b
+ b
•
» C ₁ = a + b away
- a + b a + b - away Cp = a.C "+ (1-e) a + b
.A C.
0, = a +
^C 2 b - from
a +
. a b

a + b

and for the silver concentration in the washing water (chamber
24):

With the values given above, the equations yield:
C ₁ = 56/1; Cp = 0.83 g / l, C, = 75 mg / l; C = 0.19 mg / l.

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These values are correct within an error limit of + 10% with the values obtained in a practical experiment. A silver concentration of 0.2 to 1 mg / 1 is found in the wastewater regarded as tolerable

One would do the bleach fixation in the usual way If carried out in a single tract, a silver concentration would be obtained with the ratios used in the example in wastewater from 12.2 mg / 1., i.e. 65 times.

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Claims (4)

Claims Λ) Process for the bleach-fixing of developed color photographic material using bleach-fixing baths which contain a heavy metal complex of a complexing aminopolyacetic acid as a bleaching agent and a silver salt solvent as a fixing agent, the developed photographic material being passed through a bleach-fixing bath line, characterized in that the bleach-fix bath section is subdivided so that at the end of the bleach-fix bath section there is less silver Bleach-fixer regulator is supplied that the bleach-fixer in countercurrent to the direction of travel of the color photographic Material led to the beginning of the bleach-fix bath stretch and there in its oxidative power by lowering the pH and / or the addition of reducing agents is reduced to such an extent that the formation of a color haze is effective is suppressed. 2. The method according to claim 1, characterized in that the amount of added at the end of the bleach-fixing bath Bleach-fix replenisher is sized so that an overflow containing silver at the beginning of the bleach-fix bath section Bleach-fix bath is obtained. 3. The method according to claim 2, characterized in that the overflow is desilvered and converted to a low-silver bleach-fixer regenerator is worked up. 4. The method according to claim 1, characterized in that the reduction in the oxidative power of the bleach-fixer on Start of the bleach-fix bath line by electrometric Measuring chains is controlled. A - G 947 ^ -14- 309 8 42/1055 Method according to claim 1, characterized in that the The bleach-fix bath section is subdivided so that the residence times of a color material passing through the bleach-fix bath section are of different lengths in the individual sections.,. A - G 947 - 15 - 309842/1055>; - Blank page