EP0131970B1 - Process for the production of sulfuric-acid adducts of urea - Google Patents

Description

The present invention relates to a method for producing sulfuric acid adducts of urea.

• (A) Entwicklung des latenten Silberbildes,
• (B) Farbbleichung an den metallisches Silber enthaltenden Bildstellen
• (C) Silberbleichung: Umwandlung des Rest-Silberbildes in komplex lösliche Silberverbindungen
• (D) Fixierung: Berauslösen und Entfernen aller in Form von Komplexen löslichen Silberrerbindungen,

In general, four processing steps are required to process silver color bleaching materials:

• (A) development of the latent silver image,
• (B) Color bleaching at the image areas containing metallic silver
• (C) Silver bleaching: conversion of the residual silver image into complex soluble silver compounds
• (D) fixation: removal and removal of all silver bonds that are soluble in the form of complexes,

wherein steps (B) and (C) and (B), (C) and (D) can be carried out simultaneously in a single bath.

The preparations (baths) used for the color and / or silver bleaching or the combined bleach-fixation are strongly acidic, i.e. have a pH of less than 2, especially less than 1. This pH is generally set using strong acids, primarily mineral acids, such as hydrochloric acid, sulfuric acid, nitric or phosphoric acid, and also sulfanic acid. Good results are also obtained with certain strong organic acids, such as p-toluenesulfonic acid.

The mineral acids most commonly used for bleaching baths so far have some important disadvantages that can have an adverse effect on general use. For example, Hydrochloric acid highly volatile and therefore has a particularly corrosive effect on e.g. Apparatus and devices in which the processing of the photographic material is carried out. Most mineral acids, with the exception of sulfamic acid, are also liquid. Their use, especially in the amateur sector, can therefore pose certain dangers, e.g. by spilling or breaking vessels.

For this reason, the use of solid instead of liquid acids is particularly advantageous because it facilitates the preparation, transport and storage of preparations for color and / or silver bleaching. The sulfamic acid, which is suitable per se and can easily be produced in free-flowing powder form, can in many cases be used as a substitute for liquid mineral acids. One disadvantage, however, is their relatively poor solubility in water. It has also been shown that it reacts with tertiary phosphines, which are used as bleach accelerators, and leads to unstable bleach baths. p-Toluenesulfonic acid, which can also be used in free-flowing powder form, has a high water solubility and provides stable bleaching baths. Disadvantages are the significantly higher price compared to mineral acids, and the high molecular weight, which requires the use of large amounts of weight. The high carbon ballast of p-toluenesulfonic acid also has an adverse ecological impact due to the high oxygen demand in the waste water.

The object of the present invention is to provide strong mineral acids, as are required in the processing of photographic silver color bleaching materials, in a suitable form in order to overcome the disadvantages mentioned above.

It has now been found that in bleaching baths for the silver color bleaching process, sulfuric acid adducts of urea can be used instead of mineral acids. These adducts are solid, of good stability, high solubility in water and they dissociate easily in their original components in aqueous solution.

The present invention thus relates to a process for the preparation of sulfuric acid adducts of urea with a urea-sulfuric acid ratio of 2: 1 or 1: 1, characterized in that the solid urea is entered in the stated ratio in 100 percent sulfuric acid, where Entry speed and external cooling are coordinated so that the temperature during the mixing time is between 70 and 100 ° C, and that the neutral or acid urea sulfate obtained in this way is converted into solid form by cooling and, if necessary, comminuted.

The adducts of one mole of urea with 0.5 or 1 mole of sulfuric acid are particularly well known. The melting points of these adducts are 80 and 70 ° C, respectively. Information about the properties of these adducts, their stability, the reaction kinetics in the melt and in aqueous solutions can be found, among others. at L.H. Dalman, J.Am.Chem.Soc. 56, 549 (1934) P. Baumgarten, Chem. Ber. 69 1929 (1936), E. Cherbuliez & F. Landolt, Helv. 29, 1438 (1946) and G.M. Schwab & E. Schwab-Agallidis, Angew. Chemie, 65, 418 (1953).

The sulfuric acid adducts of urea are prepared either directly from the components or their solutions or also by the action of mineral acid on cyanamide, the latter decomposing to urea, which then forms the addition compound with the acid.

Information on the production of urea-sulfuric acid adducts can be found, among others, in German patent specification 239,309, American patent specification 3,330,864 or in 'English patent specifications 196,601 and 1,109,619.

The adducts produced according to the invention are stable in solid form and can easily be prepared in the form of free-flowing water-soluble powders or granules.

The adducts of urea with sulfuric acid exist in two stable forms: urea sulfate, the adduct of two moles of urea with one mole of sulfuric acid, and urea hydrogen sulfate, the adduct of one mole of urea with one mole of sulfuric acid. According to the invention, both forms can be produced directly in an anhydrous solid form using a simple production process;

According to this process, urea is introduced directly into solid form in 100% sulfuric acid (monohydrate) with cooling, the temperature not being allowed to rise above about 100 ° C. (preferably 70 ° C. to 100 ° C.) during the reaction. In this way, a melt of urea Hydrogen sulfate or urea sulfate, depending on whether one or two moles of urea have been added per mole of sulfuric acid. The compounds are converted into the solid form by cooling and optionally comminuted.

When producing the urea-sulfuric acid adducts mentioned, it is essential that exactly 100 percent sulfuric acid is used; If the melt contains free water or sulfur trioxide, the stability of the melt is significantly reduced. The melt can be removed by suitable methods, e.g. used in the production of alkali metal hydroxides (cf. Ullmanns Encyklopadie der Technische Chemie, 4th edition, Verlag Chemie, Weinheim, Vol. 17 (1979), p. 204 f), are converted into a solid form suitable for the application. In particular, it can be crystallized in the form of free-flowing pearls, pills, flakes or flakes that are immediately soluble in water. The sulfuric acid adducts can be brought into the form of beads if they are e.g. sprayed in a cooling tower.

In the following example, parts and percentages are by weight unless otherwise stated.

example 1

• Auf einen weissopakem Träger werden in der angegebenen Reihenfolge die folgenden Schichteh aufgetragen:
• Ein rotsensibilisiertes Schichtpaar, bestehend aus
  • 1. einer rotempfindlichen Gelatine-Silberbromidjodid-emulsionsschicht mit einem bleichbarem blaugrünen Azofarbstoff der Formel (101) mit einem Silbergehalt vom 0,144 g Ag/m²
    
  • 2. einer von Bildfarbstoff freien Schicht aus einer rotempfindlichem Gelatine-Silberbromidjodid-Emulsion mit einem Silbergehalt vom 0,300 g Ag/m2;
  • 3. eine erste Gelatine-Zwischenschicht;
  • 4. einer grünempfindlichen Gelatine-Silberbromidjodid-Emulsionsschicht mit einem purpurfarbigen bleichbaren Azofarbstoff der Formel (102) und einem Silbergehalt von 0,212 g Ag/m²;
    
  • 5. einer von Bildfarbstoff freien Schicht aus einer grünempfindlichem Gelatine-Silberbromidjodid-Emulsion mit einem Silbergehalt von 0,300 g Ag/m²;
  • 6. eine zweite Zwischenschicht, bestehend aus Gelatime mit einem Zusatz von kolloidalem Silber in einer Menge von 0,007 g Ag/m² und einer nicht spektral sensibilisiertem unempfindlichem Silberbromidemulsion mit einem Silbergehalt vom 0,2 g Ag/m² ein blauempfindliches Schichtpaar, bestehend aus
  • 7. einer hochempfindlichen jodidfreien Gelatine-Silberbromidschicht mit einem gelben bleichbaren Azofarbstoff der Formel (103) und einem Silbergehalt von 0,360 g Ag/m²:
    
  • 8. einer farbstofffreien hochempfindlichen Gelatine-Silberbromidjodidschicht mit niedrigem Jodidanteil mit einem Silbergehalt vom 0,530 g Ag/m²;
  • 9. eine Gelatine-Schutzschicht.

A silver dye bleaching material suitable for making positive overlay copies of a positive original was made in the following manner:

• The following layers are applied to a white opaque support in the order given:
• A pair of layers sensitized to red, consisting of
  • 1. a red-sensitive gelatin-silver bromide iodide emulsion layer with a bleachable blue-green azo dye of the formula (101) with a silver content of 0.144 g Ag / m ²
    
  • 2. an image dye-free layer of a red-sensitive gelatin-silver bromide iodide emulsion with a silver content of 0.300 g Ag / m2;
  • 3. a first intermediate gelatin layer;
  • 4. a green-sensitive gelatin-silver bromide iodide emulsion layer with a purple-colored bleachable azo dye of the formula (102) and a silver content of 0.212 g Ag / m ² ;
    
  • 5. an image dye-free layer of a green-sensitive gelatin-silver bromide iodide emulsion with a silver content of 0.300 g Ag / m ² ;
  • 6. a second intermediate layer consisting of gelatin with the addition of colloidal silver in an amount of 0.007 g Ag / m ² and a non-spectrally sensitized insensitive silver bromide emulsion with a silver content of 0.2 g Ag / m ² a blue-sensitive layer pair consisting of
  • 7. a highly sensitive iodide-free gelatin-silver bromide layer with a yellow bleachable azo dye of the formula (103) and a silver content of 0.360 g Ag / m ² :
    
  • 8. a dye-free, highly sensitive gelatin-silver bromide iodide layer with a low iodide content with a silver content of 0.530 g Ag / m ² ;
  • 9. a gelatin protective layer.

This material is constructed in such a way that, when processed with a developer containing a silver ligand, in particular sodium thiosulfate, and the subsequent process steps of color and silver bleaching necessary for the silver color bleaching process, the latter preferably combined in a single step, and finally the fixation, a masking of the blue secondary color densities the purple and cyan layer is effected.

• Rotbelichtung: 4 Sekunden
• Grünbelichtung: 17 Sekunden
• Blaubelichtung: 4 Sekundem

A sample strip is cut from this photographic material and exposed additively behind a gray wedge as follows:

• Red exposure: 4 seconds
• Green exposure: 17 seconds
• Blue exposure: 4 seconds

• 1. Silberentwicklungsbad 2,5 Minutem Temp. 32°C
  • Natriumpolyphosphat 1 (g/l)
  • Kaliumhydroxid (85%) 27 (g/l)
  • Borsäure 21 (g/l)
  • Kaliummetabisulfit 18 (g/l)
  • Natriunsulfit, wasserfrei 11 (g/l)
  • 1-Phenyl-3-pyrazolidon 0,3 (g/l)
  • Hydrochinon 5 (g/l)
  • Benztriazol 0,6 (g/l)
  • Kaliumbromid 2 (g/l)
  • Natriumthiosulfat, wasserfrei 1,0 (g/l)
• 2. Wässerung 1 Minute
• 3. Bleichbad 2,5 Minutem
  • Addukt A. und B. (siehe nachfolgende Tabelle)
  • m-Nitrobenzolsulfonsäure -Na-Salz 7,5 (g/l)
  • Kaliumjodid 5 (g/l)
  • 2,3,6-Trimethylchinoxalin 1,5 (g/l)
  • Bis-(cyanoäthyl)-sulfobutylphosphin (Na-Salz) 4 (g/l)
    
• 4. Wässerung 1 Minute
• 5. Fixierbad 2,5 Minuten
  • Ammoniumthiosulfat 250 g/1
  • Kaliummetabisuifit 50 g/I
  • Kaliumhydroxid (85%) 20 g/1
• 6. Wässerung 3 Minuten
  • Totale Verarbeitungszeit 12,5 Minutem

The following processing solutions were used in the order given to process the exposed test strip:

• 1. Silver developing bath 2.5 minutes at 32 ° C
  • Sodium polyphosphate 1 (g / l)
  • Potassium hydroxide (85%) 27 (g / l)
  • Boric acid 21 (g / l)
  • Potassium metabisulfite 18 (g / l)
  • Sodium sulfite, anhydrous 11 (g / l)
  • 1-phenyl-3-pyrazolidone 0.3 (g / l)
  • Hydroquinone 5 (g / l)
  • Benzotriazole 0.6 (g / l)
  • Potassium bromide 2 (g / l)
  • Sodium thiosulfate, anhydrous 1.0 (g / l)
• 2. Soak for 1 minute
• 3. Bleaching bath 2.5 minutes
  • Adduct A. and B. (see table below)
  • m-nitrobenzenesulfonic acid Na salt 7.5 (g / l)
  • Potassium iodide 5 (g / l)
  • 2,3,6-trimethylquinoxaline 1.5 (g / l)
  • Bis- (cyanoethyl) sulfobutylphosphine (Na salt) 4 (g / l)
    
• 4. Soak 1 minute
• 5. Fixer bath 2.5 minutes
  • Ammonium thiosulfate 250 g / 1
  • Potassium metabisuifit 50 g / I
  • Potassium hydroxide (85%) 20 g / 1
• 6. Soak 3 minutes
  • Total processing time 12.5 minutes

After the subsequent drying, positive gray wedges are obtained which have a uniform neutral gray shade over the entire density range, with Dmax values of 1.77 (gray) and D _min values of 0.03 (gray).

An impairment of the image quality when using the adducts A. and B. according to the invention instead of the previously customary free sulfuric acid is not found.

Example 2

In this example, using the same dyes as in Example 1, a six-layer material is used which in the first layer contains the cyan dye and the associated red-sensitized silver halide emulsion, and in the second layer a thin, pure gelatin-containing intermediate layer in the third layer contains the purple dye with the associated green-sensitized silver halide emulsion, the fourth layer is an intermediate layer consisting of gelatin, the fifth layer contains a silver halide layer containing a yellow dye and finally the sixth layer contains a protective layer of pure gelatin.

• Silberentwicklung 6 Minuten
• Na-Polyphosphat 1 (g/l)
• Na Sulfit, wasserfrei 50 (g/l)
• Hydrochinon 5 (g/l)
• Na-Metaborat 15 (g/l)
• 1-Phenyl-3-pyrazolidon 0,3 (g/I)
• Kaliumbromid 3 (g/l)
• Benztriazol 0,2 (g/l)
• Das kombinierte Bleich- und Fixierbad besitzt folgende Zusammensetzung:
• Kombiniertes Bleich- und Fixierbad
• Thioharnstoff-Schwefelsäure-Addukt (1:1) 16 g/l
• Thioharnstoff 7 g/l
• m-Nitrobenzolsulfonsäure, (Natriumsalz) 0,8 g/l
• 1-Phenyl-2-methyl-6,7-dimethoxy-chinoxalin 0,5 g/l
• Kaliumjodid 3 g/l

For the processing of this material, a so-called two-bath process is selected, consisting of a developer bath and a subsequent combined bath, in which the dye and silver bleaching and the fixing take place practically simultaneously. The silver development bath has the following composition:

• Silver development 6 minutes
• Na polyphosphate 1 (g / l)
• Na sulfite, anhydrous 50 (g / l)
• Hydroquinone 5 (g / l)
• Na metaborate 15 (g / l)
• 1-phenyl-3-pyrazolidone 0.3 (g / l)
• Potassium bromide 3 (g / l)
• Benzotriazole 0.2 (g / l)
• The combined bleaching and fixing bath has the following composition:
• Combined bleaching and fixing bath
• Thiourea-sulfuric acid adduct (1: 1) 16 g / l
• Thiourea 7 g / l
• m-nitrobenzenesulfonic acid, (sodium salt) 0.8 g / l
• 1-phenyl-2-methyl-6,7-dimethoxy-quinoxaline 0.5 g / l
• Potassium iodide 3 g / l

A second sample strip is exposed and processed in an identical manner, but using a combined bleaching and fixing bath which contains 9.5 g / l of 96% sulfuric acid.

• D_max ^Dmin
• Rot 1,75 0,05
• Grün 1,91 0,02
• Blau 1,97 0,02

The finished and dried test strips each result in a positive gray wedge with identical sensitometric values. The measured densities (reflectance values) are:

• D _ma x ^D min
• Red 1.75 0.05
• Green 1.91 0.02
• Blue 1.97 0.02

Claims (1)

1. A process for the preparation of an adduct of sulfuric acid and urea, with a urea/sulfuric acid ratio of 2:1 or 1:1, which process comprises introducing the solid urea in the indicated ratio into 100% sulfuric acid, the rate at which the urea is introduced and the external cooling being so matched that during the mixing period the temperature is in the range from 70° to 100° C, and converting the resultant neutral or acid urea-sulfate into the solid form by cooling, and, if desired, comminuting the solid.