DE2218189C2 - "Aqueous bleaching bath for developed silver and its use" - Google Patents

Description

R ¹

N-CO-N = N-CO-N

contains, in which mean:

R ¹ to R ⁴ each independently represent a hydrogen atom, an alkyl, cycloalkyl, alkoxyalkyl, hydroxyalkyl, aralkyl, AHyI, aryl, hatogenaryl, alkaryl, alkoxyaryl or heterocyclic group, or in pairs R ¹ with R ² and / or R ³ with R ⁴ to complete a heterocyclic

CH,

R ³

R ⁴

Ringes required atoms, whereby not all of the groups R ¹ to R ⁴ may be hydrogen atoms.
3. bleaching bath according to claim 1, characterized in that it contains a compound of the following special formulas as the ionized azodecarbonamide:

CHj

HJC-N-CH ₂ -CH ₂ -NH-CO-N = N-CO-NH-CH ₂ -CH ₂ -N-Ch ₃ CHj CHj

CH ₃

CH ₃

HjC-N-CH ₂ -CH ₂ -NH-CO-N = N-CO-NH-CH ₂ -CH ₂ -N-CH ₃

I I

CH ₃ CHj

2 J °

4. bleaching bath according to claim 1 to 3, characterized in that it contains a sodium acetate / acetic acid buffer to maintain the pH range.

5. bleach bath according to claim 1 to 4, characterized -o characterized in that it additionally contains potassium bromide in a concentration of 0.1 to 1.0 mol per liter contains.

6. bleaching bath according to claim 1 to 5, characterized in that it also contains sodium thiocyanate in a concentration of 1 to IO moles per liter contains.

7. Use of a bleach bath according to claim 1 to 6 for bleaching the developed silver in photographic silver halide emulsion layers.

Dte invention relates to an aqueous bleach bath for developed silver in photographic silver halide emulsion layers and its use.

From DE-OS 19 44 745 it is known to use in photographic silver halide emulsions Azodicarbonamide and / or its derivatives to prevent both fog and staining.

It is often necessary to remove developed silver from silver halide photographic emulsion layers. A method of making black and white Positive images consist e.g. B. in the development of the exposed emulsion layers, in the fading of the developed silver and in the repeated exposure, through which the remaining, not yet exposed Silver halide can be developed, which then, after development and fixing, produces the desired positive image results. A bleaching process is also used in the treatment of color reversal and color negative films

-, Ι required because the developed silver from the

Emulsion layer must be removed before the

different colors in their correct coordination and intensity become visible.

The required fading is usually

by treating the photographic material in a cyanoferrate (III) such as potassium cyanoferrate (III), containing bleach bath carried out. Although these bleach containers give good results, they do but has the disadvantage that the cyanoferrate (III)

6> is highly toxic. These bleaches must therefore be used with great caution and can be used after Use not just thrown away. In practice, their use poses even with the most careful

Handling poses a serious risk of harmful toxicity The possible risk of accumulation due to the great stability of the cyanoferrate (IH) should be taken particularly seriously. It would therefore be a great risk Advantage if that from photographisehep. Silver halide emulsion layers developed silver bleached without the use of highly toxic materials could be.

The object of the invention is therefore an aqueous one To indicate bleaching bath for developed silver in photographic silver halide emulsion layers which contains bleaching agents whose toxic effect is insignificant without impairing the bleaching effect

This problem is solved in that there is a Azodicarbonamide, which has ionized character due to the content of quaternary ammonium groups can, in a concentration of at least 0.01 mol per liter and a pH value in the range of 4 to 7

Such a Bisichbad is when the fading of the photographic silver halide emulsion layers developed silver of great efficiency and efficiency at the same time non-toxic. Azodicarbonamide and its derivatives are non-toxic and must be therefore no special precautions are taken during their application or removal. In addition, they have the advantage that they disintegrate very quickly in solution and therefore into the drain can be discharged without causing dangerous pollution of flowing water. The course of the decay is complicated but it seems that it leads to nitrogen, a urea and Hydrazine derivatives decompose / which in the low concentration in which they are discharged into flowing water are relatively harmless. ind.

Azodicarbonamide and its derivatives are electron acceptors and therefore act as an oxidizing agent in relation to developed silver oxidize developed metallic silver. During the oxidation of the developed metallic silver Azodicarbonamide and its derivatives reduce the double bond between the two nitrogen atoms the azo group opens and becomes saturated.

Azodicarbonamide has a low solubility in water and can therefore not be used in sufficient quantities in Solution can be brought to enable a really fast fading. It will be therefore preferably its derivatives are used.

Such azodicarbonamide derivatives which can preferably be used have the following general formula

R ¹

\ Il W /

N-C-N = N-C-N

R ³

in which:

R ¹ to R ⁴ each independently represent a hydrogen atom, an alkyl, cycloalkyl, alkoxyalkyl, hydroxyalkyl, aralkyl, allyl, aryl, haloaryl, alkaryl, alkoxyaryl or heterocyclic group, or in pairs R ¹ mi ·. R ² and / or R ¹ with R ^{4 are} the atoms required to complete a heterocyclic ring, w ^ not all of the groups R ¹ to R ⁴ may be hydrogen atoms at the same time.

In order to achieve the best possible results, however, the azodicarbonamide derivatives listed in claim 3 are preferably used, since these are used Derivatives are very soluble in water and therefore can be added in large amounts to a bleaching solution in these azodicarbonamide derivatives at least on one of the amido nitrogen atoms a group with an electrically positively charged center

covalently bound, e.g. B. a quaternary ammonium group, the derivative having at least one negative charged part of the molecule to neutralize the positive Contains charge of the center The bleach bath according to the invention contains the azodi carboxamide and / or its derivatives, preferably in a concentration of 0.03 moles per liter to saturation.

It has also been found that the bleaching effect of azodicarbonamide and / or at least one of its Derivatives can be accelerated by adding free halide ions to the bleach bath. That can go through Addition of a water-soluble halide, such as. B. of potassium bromide, to the bleach bath can be achieved. A such a bleach bath with added potassium bromide is in its bleaching effect is comparable to that of a cyanoferrate (HI) bleach bath.

The bleaching solution expediently contains the water-soluble potassium bromide in a concentration of 0.1 to 1.0 Moles per liter.

ίο Often times, bleach is also used along with a silver halide solvent used so that the bleaching process and the removal of it obtained silver halide can be carried out in a single step. This procedure will

J5 called the bleach-fix method. It was found that the fixing can be carried out at the same time as the bleaching, provided the silver halide solvent reacts with the azodicarbonamide and / or one of its derivatives

Such a bleach-fix bath for a developed silver halide emulsion is made using the bleach bath according to the invention from an aqueous solution of azodicarbonamide and / or at least one of its derivatives, one compatible with it

4> Silver halide solvent, and preferably potassium bromide in the solution. This bleach-fix bath contains preferably 1.0 to 10 moles per liter of the silver halide solvent. A suitable one, also a preferred one Silver halide solvent is sodium thiocyanate, but not sodium thiosulphate, because it reacts with azodicarbonamide and so has the bleaching effect. of azodicarbonamide cancels. However, this can turn into an advantage if bleaching and fixing are not done at the same time. if

Yi namely bleaching with azodicarbonamide before Fixing is done with sodium thiosulfate

no soaking of the photographic material between required for bleaching and fixing.

The aqueous bleach bath according to the invention has

a pH in the range of 4 to 7, with a lower pH resulting in faster bleaching Has.

In order to maintain the desired pH value in the bleach bath, a suitable buffer can be added to the bleach bath

f> i are added. Suitable are e.g. B. a sodium acetate / acetic acid buffer, a potassium hydrogen phihalate / Hydrochloric acid buffer and a disodium hydrogen phosphate / citric acid buffer.

Pie invention can be used to fade developed Silver from all types of photographic silver halide emulsion layers from e.g., black and white and color films, with the developed silver in one or more silver halide emulsion layers grain size and type of silver halide obviously do not play a role Role.

The examples illustrate the invention.

A bleach bath
manufactured:

Example 5 of the following composition is used

IO

15th

r>

example 1

Azodicarbonamide is shaken with a 6 g of sodium acetate trihydrate and glacial acetic acid at 20 ⁰ C to pH buffered 437 1 molar potassium bromide The Azodicarbonamidüberschuß is abfillriert. After 12 minutes, a developed fine-grain emulsion in this solution shows a substantial reduction in optical density, namely from 2.36 to 2.00, measured on a logarithmic scale. The silver salts are then removed by soaking in a sodium thiosulfate solution.

B ice ρ ie 1 2 ² '

A bleach bath with the following composition is prepared: 150 ml of water, 3 g of N, N'-di- (ethyl-2-trimethylammonium) -azodicarbonamide-di-toluo! -P-sulfonate, 3 g potassium bromide and acetic acid to adjust the pH value to 4.0 to 213 ° C.

The rate of bleaching of developed silver in a fine grain silver halide emulsion layer is measured by observing the change in density over various bleaching times. The middle Bleaching speed over the first minute is 0.35 density units per minute. Between One minute and four minutes, the density increases at a constant rate of 0.12 density units per minute.

Example 3

3.16 g (0.1 mol) of N, N'-di (ethyl-2-trimethylammonium) azodicarbonamide-di-toluene-p-sulfonate are dissolved in 50 ml of a molar aqueous potassium bromide solution. To set a pH of 436 at 20 ^° C., 3 g of sodium acetate trihydrate and glacial acetic acid are added. This solution is used to bleach developed silver from a developed photographic X-ray emulsion layer with an average grain diameter of about 1.5 μm. The initial density of 1.7 decreases to 0.61 after one minute.

Example 4

2.84 g (0.1 mol) of N, N'-di- (ethyl-2-trimethylammonium) -azodicarbonamide-di-iodide are dissolved in 50 ml of an aqueous molar potassium bromide solution. To set a pH of 4.96 at 20 ^° C., 3 g of sodium acetate trihydrate and glacial acetic acid are added.

This solution is used to fade developed silver from a developed photographic X-ray emulsion layer with an average grain diameter of 1.5 μm is used. The initial one Density of 1.7 decreases after one minute 0.8.

N, N'-Pi- (Sthyl-2-trimethyl- 38 g ammonium) -azodic8rbonamide- 38 g di-toluene-p-sulfonate 38 g Potassium bromide Sodium Acetate Tribydral 5.0 Acetic acid for adjustment 600 ml a pH of topped up with water

This bleach bath replaces a conventional cyanoferrate (III) bleach bath in treating an exposed commercial color reversal film with the following Treatment baths according to the following treatment sequence.

-r>

First developer 3.0 g Hydroquinone 0.48 g 1-phenyl-3-pyrazolidone Ug Sodium hexametaphosphate anhydrous sodium sulfite 3.0 g borax 1.5g Potassium bromide 0.48 g I potassium thiocyanate 0.48 g Sodium hydroxide 600 ml topped up with water Breaker hardness bath 18.0 g anhydrous sodium acetate 3.0 g Sodium metabisulfite 18.0 g Potassium alum 15.0 g Sodium bisulfate 600 ml topped up with water Color developer 1.68 g Diethyl p-phenylenediamine sulfate Ug Sodium hexametaphosphate 39.0 g anhydrous sodium carbonate 1.5g anhydrous sodium sulfite 0.72 g Potassium bromide 0.6 g Sodium hydroxide 0.6 g Hydroxylamine hydrochloride 600 ml topped up with water

Fixer

anhydrous sodium sulfate 75.0 g

made up to 600 ml with water

Treatment at 20 ° C
is carried out as follows:

Initial development 13 minutes

Soak for 1 minute

Interrupt 5 minutes

Soaking 5 minutes reverse exposure,

Color development 11 minutes

Soak for 1 minute

Interrupt 5 minutes

Soak for 5 minutes

Bleach 10 minutes

Soak for 5 minutes

Fixate 5 minutes

Soak for 15 minutes

Drying 15 minutes

The slides so treated are those treated with a conventional cyanoferrate (MI) bleach bath Slides quite comparable.

Example 6

A bleach-fix bath is made to that described in Example 3 by adding 4.7 g of sodium thiocyanate Bleach bath made. It is found that with this solution both the developed silver and the not developed silver halide can be removed from a photographic film.

Example 7

A bleach bath is made from 250 ml of water, 31.6 g (0.2 mol) N.N'-Di-iäthyl ^ -trimethylammonium / azodicarbonamide-di-toluene-p-sulfonate. 12 grams (0.4 moles) of potassium bromide. 5 g of anhydrous sodium acetate and glacial acetic acid were prepared to adjust the pH to 4.1.

An i-.är, dc! Süb! Ichcr color reversal film - is lighted and then conventionally developed using Kodak's standard E-4 process (see, e.g., The British Journal of Photography Annual "1972, p. 209). with

with the exception that the bleach bath of the present invention described above is used to bleach the silver. Complete bleaching of the silver is achieved at 20 ^° C. in 2 minutes. When the resulting treated film was compared with an identical film treated according to Kodak Standard E-4, no difference in color balance was observed.

The stability of the above-described bleach bath stored in a tightly closed bottle is observed over a period of 4 months. The bleaching effect is recorded by measuring the rate of bleaching of developed silver from a fully developed X-ray photographic film at regular intervals. In the course of the first two months of storage, no change in the bleaching properties is observed; however, only after four months of storage will it be determined «*« "" «. that the sight speed has decreased by about 10 percent of the initial speed. The bleach bath of the invention thus has good storage properties.

Claims (2)

Patent claims: 1. Aqueous bleaching bath for developed silver in photographic superhalide emulsion layers, characterized in that it is a Azodicarbonamide, which has ionized character due to the content of quaternary ammonium groups can, in a concentration of at least 0.01 Contains moles per liter and has a pH in the range from 4 to 7. 2. bleaching bath according to claim 1, characterized in that it is a compound of the following general formula as azodicar'ocnamide