US3729318A - Process for cross-linking silver halide gelatino emulsion layer containing non-diffusible compound having epoxide and isocyanate groups - Google Patents

Abstract

PHOTOGRAPHIC GELATINE LAYERS HAVE TO BE HARDENED IN ORDER TO IMPROVE THE MECHANICAL PROPERTIES AND TO RAISE THE MELTING POINT OF THE LAYER. EXCELLENT HARDENING IS OBTAINED BY MEANS OF LOW MOLECULAR COMPOUNDS HAVING A HARDENY EPOXIDE AND A HARDENING ISOCYANATE GROUP.

Description

United States Patent Office 3,729,318 Patented Apr. 24, 1973 3,729,318 PROCESS FOR CROSS-LINKING SILVER HALIDE GELATINO EMULSION LAYER CONTAINING NON-DIFFUSIBLE COMPOUND HAVING EPOX- IDE AND ISOCYANATE GROUPS Wolfgang Himmelmann, Opladen, Peter Bergthaller,

Cologne, and Bernd Quiring and Kuno Wagner, Leverkusen, Germany, assiguors to Agfa-Gevaert Aktiengesellschaft, Leverkuseu, Germany No Drawing. Filed July 21, 1971, Ser. No. 164,811 Claims priority, application Germany, July 25, 1970, P 20 36 998.6 Int. Cl. G030 1/30 US. Cl. 96--111 4 Claims ABSTRACT OF THE DISCLOSURE Photographic gelatine layers have to be hardened in order to improve the mechanical properties and to raise the melting point of the layer. Excellent hardening is obtained by means of low molecular compounds having a hardeny epoxide and a hardening isocyanate group.

The invention relates to a process for hardening layers which contain gelatin using a hardener which is fast to diffusion.

The irreversible cross-linking of the binder of photographic layers is of considerable importance because these layers are treated with various aqueous baths in the course of processing and they must therefore be highly resistant to aqueous solutions, and particularly to alkaline solutions. This is achieved by adding to the proteins which commonly are used to form the layer substances which are capable of undergoing a cross-linking reaction with the protein chains thus raising the melting point of the proteins. This reaction, however, must not reduce the permeability of the proteins to water and in many cases, e.g. in the silver salt diffusion process, it is in fact desirable that the hardened layers should be capable of rapidly taking up a large quantity of water in order to ensure rapid and complete processing.

Numerous compounds and types of compounds which may be used as hardeners for proteins have already become known. The following are given as examples:

Metal salts, such as salts of chromium, aluminium and zirconium; aldehydes and aldehyde compounds which contain halogen, e.g. formaldehydes, dialdehydes and mucochloric acid; 1,2- and 1,4-diketones such as cyclohexane-l,2-dione, quinones, chlorides of dibasic organic acids, dianhydrides of tetracarboxylic acids, and compounds which contain several reactive vinyl g-roups,' e.g. vinyl sulfones, and arylamides; compounds which have at least two heterocyclic rings which are easily cleaved, e.g. ethylene oxide and ethylene imine, polyfunctional methane sulfonic acid esters, bis-a-chloroacylamido compounds and heterocyclic compounds which have active halogen atoms, e.g. halogeno-1,3,5-triazine compounds.

These hardeners are low molecular weight compounds. Some of them are photographically active and therefore cannot be used for certain photographic emulsions. Others, such as the metal salts, increase the brittleness of the layers. Dialdehydes and diketones discolor the layers in various ways and are therefore unusable. Furthermore, acid chlorides and acid anhydrides in many cases alter the pH of the casting solutions so that the pH would have to be readjusted with alkali, which is undesirable or may be impossible because it would impair other photographic properties. It is also known that many hardeners cause fogging or a reduction in the sensitivity of the emulsion after prolonged storage.

Other hardeners again have the disadvantage that the hardening process starts only after some time in storage so that the properties of the layers undergo uncontrollable changes. Lastly, all hardeners which are nonditfusion-fast have the disadvantage that when used in multilayered materials it is difficult to confine their activity to a particular layer.

High molecular weight hardeners have also been described, e.g. periodic oxidation products of starch, and plant gums such as tragacanth, gum arabic, alginic acid, pectins and xylans. These compounds have, however, the disadvantage that they have only a low hardening equivalent. Alginic acid esters and maleic acid half esters of high molecular weight alcohols such as polyvinyl alcohol have similar disadvantages.

Lastly, macromolecular polymerization products of acrolein have also been proposed as hardeners, but they can only be used in the form of their water-soluble bisulfite addition compounds. This is a disadvantage because after preparing the polyacrolein it is necessary to carry out a second operation to obtain the bisulfite addition compound, and the removal of excess sulfurous acid or sulfite can only be achieved by complicated operations.

Now, as before, there is a need for ditfusion-fast hardeners which can be used for producing photographic materials which contain an unhardened layer adjacent to a highly cross-linked layer. Such systems are very important for so-called stripping films. Hardeners which are not diffusion-fast naturally cannot be used for these films because the hardener become distributed throughout the whole stack of layers and all the layers would be crosslinked. Low molecular weight hardeners could in principle be rendered diffusion-fast by known methods. Thus, for example, longer al kyl radicals having more than 10 carbon atoms could be introduced. This method, however, generally leads to complete or partial loss of the hardening activity of the hardeners. Although high molecular weight hardeners are diffusion-fast, they have various other disadvantages, as already mentioned above. For example, the viscosity of their aqueous solutions is relatively high, which makes processing more difiicult. Moreover, it is diflicult to free high molecular weight compounds from unwanted impurities.

It is among the objects of the invention to provide low molecular weight diffusion-fast hardeners for protein layers, by means of which the hardening process can be confined to one layer within a multilayered photographic material.

A process for hardening photographic gelatin layers by the addition of low molecular weight hardeners has now been found in Which the hardeners used are compounds which contain an isocyanate group and an epoxide group.

The hardening compounds correspond, for example, to the folloming formula:

wherein Z represents a bivalent organic linking member, preferably a branched or unbranched, saturated or ethylenically unsaturated aliphatic radical containing up to 10 carbon atoms, arylene, especially phenylene, or cycloal-kylene, preferably cyclohexylene, which may be interrupted by ether (O), carbamoyl (CONH) or urethane (OCONH-) groups.

More particularly suitable are compounds of the following formula:

wherein n represents the integer 1, 2 or 3, preferably 1 or 2, each of X and X represents a bivalent hydrocarbon group with up to 18 carbon atoms, preferably with 2 to carbon atoms. More particularly X and X represent a bivalent straight-chain or branched aliphatic group, which may be saturated or olefinically unsaturated, a bivalent cycloaliphatic group such as cyclohexylene, a bivalent aromatic group such as phenylene or naphthylene. Also included are mixed hydrocarbon groups, for example combinations of aliphatic groups with aromatic or cycloaliphatic groups such as tolylene or xylylene or methylenecyclohexylene. Particularly preferred are compounds in which X stands for an aliphatic group having up to 10 carbon atoms.

The compounds for use according to the invention are characterized by the isocyanate group and the epoxide ring. Both groups react with amino groups of the protein binder, e.g. gelatin, but the isocyanate group reacts much more rapidly than the epoxide group, in fact it reacts immediately when these compounds are added to the solu tion of protein. The hardener is thus combined in a diffusion-fast manner with the film forming agent. The epoxide group which reacts much more slowly reacts only after the layer has been produced, in the course of drying or storage of the photographic material. Herein lies the advantage of the compounds used according to the invention. The cross-linking agent is fixed by the one reactive group, but the viscosity of the protein solution is not increased. The compounds therefore behave quite differently from those which contain two isocyanate groups or two epoxide groups. Those which contain two isocyanate groups react so rapidly in aqueous solution that cross-linking and a high increase in the viscosity is even observed in the casting solutions. Compounds which have two epoxide groups react only slowly in the course of drying or storage and they are therefore not present in a diffusion-fast form in the layers.

The two functional groups of the hardeners according to this invention are connected together by the linking member Z in Formula I. The linking member due to its non-critical nature, can of course be of any structure, and accordingly the hydrocarbon groups can be substituted, for example, with alkyl which would constitute an aliphatic hydrocarbon side chain, or with alkoxy or halogen, especially chlorine. However the substituents should not impair the reaction of the epoxide or isocyanate groups with gelatin.

Compounds of the following formulae have proved to be especially suitable:

CHz-NCO CH3 i C l NCO COMPOUND 4 25 g. of dipheny1methane-4,4-diisocyanate (Desmodur- 44) (0.1 mol) are dissolved in m1. of xylene and heated to 100 C. and 7.4 g. of glycidol (0.1 mol) are added at this temperature. The reaction mixture is cooled and the supernatant layer is decanted from the oil which has separated and the oil is boiled several times with petroleum ether. Yield about 30 g.

COMPOUND 52.2 g. (0.3 mol) of tolylene-2,4-diisocyanate (0.3 mol) in 150 ml. of clean petrol ether are heated to 100 C., 100 mg. of 1,2,4-triazole are added as a catalyst, and 22.2 g. of glycidol (0.3 mol) are the introduced dropwise with stirring. The supernatant layer is decanted while still hot from the bis-glycidyl urethane which has separated. This is then left to get cold and the crystallized product is filtered off. Yield 40-50 g.

COMPOUND 7 67 g. of isophorene diisocyanate (0.3 mol) are heated to 100 C., 22.2 g. of glycidol (0.3 mol) are added drop- Wise with stirring, the reaction mixture is left to get cold and the resulting viscous mass is boiled several times with petroleum ether. Yield 70 g.

COMPOUND 9 (a) A solution of 33.6 g. of hexamethylenediisocyanate in 20 g. of absolute benzene is heated to 80 C. and 7 g. of glycidol are added dropWise with stirring. The solution is then heated for one hour at 80 C. and filtered, and benzene and excess diisocyanate are removed under vacuum. A thick oil remains. Yield 35 g.

(b) 50.4 g. of hexamethylene diisocyanate (0.3 mol) are heated to 100 C., 22.2 g. of glycidol (0.3 mol) are added dropwise with stirring, the reaction mixture is left to cool and the viscous oil is boiled several times With petroleum ether. Yield 60 g.

COMPOUND 10 17.4 g. (0.1 mol) of commercial tolylene diisocyanate (approximately 80% 2,4- and 2,6-tolylene diisocyanate) are heated to 100 C., 11.8 g. of ethylene glycol monoglycidyl ether are added dropwise with stirring, the reaction mixture is left to cool after minutes and the oil is extracted several times With petroleum ether. Yield: 30 g. of an oil which contains substantial quantities of petroleum ether.

For the preparation of compounds for use according to the invention see also German Oifenlegungsschrift No. 1,901,024 or US. application Ser. No. 843.

The term photographic layers includes quite generally any layers used for photographic materials, e.g. light sensitive silver halide emulsion layers, protective layers, filter layers, antihalation layers, backing layers or photographic auxiliary layers in general.

The effect of the compounds used according to the invention is not impaired by the usual photographic additives and the hardeners according to the invention are also inert to photographicaly active substances such as color couplers, stabilizers and sensitizers. Also, they have no influence on the light sensitive silver halide emulsions.

The compounds are preferably used in the form of their solutions in aprotic solvents in quantities of 0.5 to 8%, preferably 1 to 5% (based on the dry weight of gelatin). They are added before the gelatin solutions are cast and preferably before digestion. The solutions are then digested for at least /2 hour at to C. to ensure that the isocyanate groups have undergone complete reaction. This is essential to ensure that the hardener is fixed in a diffusion-fast form. The layer binder may contain other water-soluble high molecular Weight compounds in addition to gelatin, e.g. polyvinyl alcohol, polyvinyl pyrrolidone, polyethylene oxide and polyacrylamide and latices of water-insoluble high molecular weight compounds such as polyethyl acrylate, polybutylcryltae and other copolymers which serve as plasticizers or as additives which increase the covering power of silver. Casting may be followed by a prolonged period of drying before a new layer is applied. The technical advance provided by the application of the compounds according to the invention consists in the fact that hardening is strictly confined to layer to which the hardener has been added. When building up an assembly of layers, there is no difiiculty in following a strongly hardened layer with a less hardened or unhardened layer. When using conventional hardeners, the preparation of multilayered assemblies of this kind can generally only be achieved if certain precautions are taken. If, for example, a layer of unhardened gelatin which can be washed off at 36 C. is to be cast onto a layer I which has been hardened with formalin, the excess formalin must either be removed from layer I by storing the layer or tempering it at elevated tempertaures or more preferably an intermediate layer which binds the formalin must be placed between layers I and II.

The melting point of the layers is determined as follows: Half of the layer which has been cast on a support is dipped in cold water which is continuously heated by 5 C. per minute up to C. The temperature at which the layer runs off the support (formation of streaks) is taken as the melting point. In other tests, the layers which had been hardened in accordance with the invention weie first treated for 5 minutes with a 5% aqueous sodium carbonate solution and the melting points were then determined both immediately after drying and after the layers had been stored as indicated above. Under the conditions at which the measurement are carried out, pure gelatin layers which contain no hardener in no case showed an increase in melting point.

Example 1 5 ml. of a 5% aqueous saponin solution are added as wetting agent to cc. of a 10% aqueous gelatin solution and the compounds are added in each case in amounts of 2% based on the gelatin content. The compounds are dissolved in ethyl acetate and dispersed in the gelatin. The pH of the solution is adjusted to 6.2. The casting solutions are poured on a previously prepared cellulose triacetate support. After drying, the layers (layer I) are stored for 36 hours at 57% C. and 34% relative humidity. After determination of the melting point, the cast layer is covered with a conventional silver halide gelatin emulsion without hardener, which emulsion contains 45 g. of silver halide and 60 g. of gelatin per kg. The melting point of the emulsion layer (layer II) is determined after storing for 36 hours at 57 C. and 34% relative humdity.

The figures above show that in contrast to the triazine hardeners, the compound according to the invention are diffusion-fast, and hardening is in each case confined to the layer to which the hardener has been added.

Example 2 1%, 2% and 5%, respectively, of the compounds according to the invention dissolved in ethyl acetate solution (percentage content based on the gelatin) were added in an emulsified form to 1 kg. of a silver halide gelatin emulsion of the type conventionally used for black and white material containing per kg. 80 g. of gelatin. The solutions are left to stand for /2 hour at 36 C. and then cast on a baryta-coated paper support after the addition TABLE II Melting point of the layer in 0.

Swelling Condition I Condition II in percent Compound 1:

l00 495 2 10100 400 Compound 2:

1% 42 45 2% 540 Compound 3:

1% 41 44 2% 590 Compound 4 360 2% 280 Compound 7:

0 50 5100 590 2% 2l00 10100 550 Compound 5:

1% 62 10100 -1 520 2% 10100 10100 390 Compound 9 42 10l00 2% 10100 1or00 430 Compound 10:

1% 38 3100 490 2% 50 l0'l00 420 Compound 11:

17 465 27 390 Compound 1 1% 50 515 2% 2l00 10l00 360 Compound 13:

1 10100" means that the melting point of gelatin is above 100 C. and the a yer dissolves 013 only after 10 minutes boiling in water.

The table shows that the compounds according to the invention are efficient hardeners. They do not influence the photographic properties of the emulsion.

Swelling of the layers is determined gravimetrically after 10 minutes treatment of the layers in distilled water at 22 C. and it is indicated in percent.

Example 3 3 g. of Compound 5 and 3 g. of Compound 9, respec tively, are added to 1 kg. of a silver chlorobromide emulsion which is ready for casting and which contains g. of gelatin, silver halides in an amount which corresponds 50 to 38 g. of silver nitrate and 18 g. of l-hydroxy-4-sulfo- N-octadecyl-2-naphthamide as cyan-forming coupler. The emulsions were cast on a layer support of triacetylcellulose. Determination of the melting points of the layers and of the amount of swelling were carried out after stor- 5 ing the material for 36 hours at 57 C. and 34% relative humidity.

The photographic properties are not affected and the color shade of the dye is not altered.

Example 4 2% of Compound 7 (based on gelatin) are added to a 6% aqueous gelatin solution. The mixture is digested for /2 hour at 40 C. and it is cast on a previously prepared cellulose acetate support after the addition of a Wetting agent. The layer is dried and kept for 36 hours at 34% relative humidity at 57 C. A layer of gelatin which does not contain hardener is then cast on the first layer. After drying, a silver halide gelatin emulsion to which 2% of Compound 7 have been added and which has also been digested for /2 hour at 40 C. is applied. After this has been kept at 34% relative humidity and 57 C. for 36 hours, the melting point of the upper and lower layer has risen to C. The melting point of the middle layer is 42 C., which proves that the hardener is fast to diffusion.

We claim:

1. In a process for the production of a photographic light sensitive element having a plurality of layers including at least one silver halide gelatino emulsion onto a layer support and drying, the improvement consisting or casting a silver halide gelatino emulsion containing an effective amount of a non-diffusible compound having the following formula:

wherein Z represents a bivalent, saturated or ethylenically unsaturated aliphatic radical containing up to 10 carbon atoms, or arylene, drying the cast layer and cross-linking said compound in the dried silver halide gelatino emul sion to yield a hardened layer.

2. The process of claim 1, wherein the hardening agent has the formula wherein n represents 1 or 2 and each of X and X represents a bivalent straight-chain or branched aliphatic group, which may be saturated or olefinically unsaturated, or a bivalent cycloaliphatic group.

3. The process of claim 2, wherein X is an alkylene group having up to 10 carbon atoms and X is (1) an alkylene group having up to 10 carbon atoms, (2) a bi valent cycloaliphatic group, (3) a phenylene group or (4) a bridge member containing alkylene and phenylene or alkylene and a bivalent cycloaliphatic group.

4. A photographic light sensitive element having a plurality of layers including at least one sliver halide gelatino emulsion layer containing an effect amount non-diffusible compound having the following formula:

CHzCI -ICH2OZNCO wherein Z represents a bivalent, saturated or ethylenically unsaturated aliphatic radical containing up to 10 carbon atoms, or arylene, said compound being cross-linkable in the dried silver halide gelatino emulsion to yield a hardened layer.

References Cited UNITED STATES PATENTS 3,220,864 11/1965 Kenyon et al. 96lll X 3,047,394 7/1962 Allen et al. 96l11 3,551,159 12/1970 Froehlich 96-111 3,103,437 9/1963 Henn et al 96l11 NORMAN G. TORCHIN, Primary Examiner W. W. H. LOWIE, Assistant Examiner UNITED STATES PATENT OFFICE CETEFICATE OF CORRECTION Patent No. 729315 Dated April 24. 1973 Inventor(s) 'm] m,ann at al It is certified that: error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below: Column 1, line 21, "hardeny" should read hardening Column 1, line 52, "arylamides" should read acrylamides Column 2, line 29, "hardener" should read hardeners Column 5, line 8, "the" should read then Column 5, line 71, "p-olybutylcryltae" should read polybutylacrylate I Column 6, line 3, before "layer" insert the Column 6, line 13, "tempertaures" should read temperatures Column 8, lines 16 and '17, after "emulsion" insert layer by casting the gelatinoqemulsion after "consisting" the word "or" should read of Signed and Sealed this 20th day of November 1973'.

(SEAL) Attest:

EDWARD M.FI.ETCHER,JR. RENE D. TEGTl [EYER Attesting Officer 7 Acting Commissioner of Patents FORM PO-105O (10-69) US COMM-DC 60376-P69 u.s. GOVERNMENT Pmm'mc QFFICE I969 0-366-334,