Process for crosslinking hydrophilic colloids using unsaturated aldehydes containing N-heterocyclic rings
United States Patent [191 Kitzing Apr. 15, 1975 PROCESS FOR CROSSLINKING I-IYDROPHILIC COLLOIDS USING UNSATURATED ALDEIIYDES CONTAINING N-HETEROCYCLIC RINGS [75] Inventor: Rainer Kitzing, Villars sur Glane.  
  Switzerland [73] Assignee: Ciba-Geigy AG, Basel, Switzerland [22] Filed: Feb. 26, 1973 211 Appl; No.: 335,604  
 [30] Foreign Application Priority Data Feb. 29, 1972 Switzerland 2867/72 [52] US. Cl 260/73 R; 96/111; 96/114;  
  96/114.8; 260/117 [51] Int. Cl C08f 27/18; C08h l/06; C09h 7/00 [58] Field of Search 260/73 R, 117  
 [56] References Cited UNITED STATES PATENTS 3,792,021 2/1974 Tschopp et al. 260/117 X OTHER PUBLlCATlONS Chem. Abstracts, Vol. 76, 1972, Tschopp et aI,  
 Primary ExaminerHoward E. Schain Attorney, Agent, or Firm.loseph G. Kolodny; Edward McC. Roberts; Prabodh I. Almaula [57] ABSTRACT 9 Claims, No Drawings PROCESS FOR CROSSLINKING HYDROPHILIC COLLOIDS USING UNSATURATED ALDEHYDES CONTAINING N-HETEROCYCLIC RINGS The subject of the invention is a process for crosslinking hydrophilic colloids which contain amino, imino and/or hydroxyl groups. According to this process, the crosslinking agents used are compounds which correspond to the formula X -(&#39;)=CHY (1) wherein R, denotes a hydrogen atom. an alkyl group. a cycloalkyl radical, an aralkyl radical, an aryl radical or a heterocyclic radical, X, denotes a heterocyclic radical bonded to the CR,=CH-- group by means of a ring nitrogen atom and Y denotes an optionally functionally modified aldehyde group.  
  By the compounds of the formula l having a functionally modified aldehyde group there are to be understood those functional derivatives of the aldehydes which can either react directly with the hydrophilic colloid, producing crosslinking, or which liberate the aldehyde in an aqueous medium. Such functional derivatives are, for example, the oximes, semi-acetals, acetals, acylals, azomethines and bisulphite adducts and especially the hydrates. The manufacture and splitting of aldehyde derivatives is described in detail in Houben Weyl, Methoden der organischen Chemie,&#34; 4th edition 1954, volume 7/1, pages 413 to 487.  
  Preferred crosslinking agents correspond to the formula or of the formula wherein X, and Y have the indicated meaning and R denotes a hydrogen atom or an alkyl group with at most 4 carbon atoms, for example an ethyl group.  
  The aldehydes and aldehyde-hydrates of the formulae Particularly advantageous results are also achieved with the aldehydes and aldehyde derivatives of the formula wherein R and Y have the indicated meaning and X denotes a monocyclic pyrazole or imidazole radical bonded by a ring nitrogen atom to the CR,=CH group, and amongst these the compounds of the formula should be singled out.  
  Finally, particularly valuable crosslinking agents to be mentioned are the compounds of the formula wherein Y has the indicated meaning, one Z represents a nitrogen atom and the other Z represents a H R -c c-c (9) onto a nitrogen compound of the formula wherein R, denotes a hydrogen atom, an alkyl group, a cycloalkyl radical, an aralkyl radical, an aryl radical or a heterocyclic radical and X denotes a heterocyclic radical bonded to the hydrogen atom by a ring nitrogen atom, for example n c a H c N N-H HCEC-C N--CH=CHC r I 0 o H50 H36 and thereafter, if appropriate, converting the aldehyde group into a functionally modified aldehyde group.  
  The addition reaction is advantageously carried out in an organic solvent, if appropriate at elevated temperature. As examples of suitable solvents there may be mentioned acetone, tetrahydrofurane, chloroform, methylene chloride, benzene, acetic acid and also water. The course and the end of the reaction can easily be followed by thin layer chromatography. The addition products thus obtained can be purified in the usual manner by recrystallisation, reprecipitation, sublimation, distillation or chromatography.  
  As starting for the addition reaction it is possible to use, for example, on the one hand (9) propinal, 3- ethylpropinal or 3-phenylpropinal and on the other l) aziridine, piperidine, morpholine, piperazine, pyrrolidine, imidazoles such as unsubstituted imidazole,  
 Z-methylimidazole, 4-methylimidazole, 2- ethylimidazole, 2,4-dimethylimidazole, 2-ethyl-4- methylimidazole, 4,5-dimethylimidazole, 2,4,5-  
 trimethylimidazole and benzimidazole, pyrazoles such as unsubstituted pyrazole, 2,5-dimethylpyrazole, 2-methyl-5-phenylpyrazole, S-phenylpyrazole or 2- hydroxymethylpyrazole and also triazoles such as 1,2.4-triazole and benzotriazole, and tetrazoles such as unsubstituted tetrazole and S-methyltetrazole, 5- ethyltetrazole, 5-propyltetrazole, 5-phenyltetrazole and 5-cyclohexyltetrazole.  
  The crosslinking agents of the formulae (1) to (8) can be used in the textile and leather industry, the manufacture of paper and the plastics, glue and gelatine industry. Above all, their use as hardeners for watersoluble polymers such as polyvinyl alcohol, gelatine or gelatine derivatives, especially in the form of layers, containing such colloids. in photographic materials. The reaction of these colloids with these compounds in general takes place easily and in the usual manner. The compounds are as a rule sufficiently water-soluble.  
  In most cases it suffices to add the products to be used according to the invention, as an aqueous solution or in a solid form which is as finely divided as possible, to an aqueous solution of the hydrophilic colloid, whilst stirring well.  
  It is thus possible, for example, to bring together a solution of the crosslinking agent in water, or in a mixture with, for example, ethanol, methanol or acetone, and the colloids, at normal or slightly elevated temperature. Hereupon, the crosslinking takes place rapidly and progressively. Gelatine, which optionally contains silver halide and/or other materials for the production of photographic images has here proved particularly suitable. It is possible in the usual manner to cast the gelatine onto a base to form a layer, and to dry it. The layer can then be left at elevated temperature for a certain time, for example up to 24 hours, or at room temperature. Hereupon, hardening takes place rapidly and progressively; the melting point of the gelatine is raised substantially, for example by 25 to 60C, and the reciprocal swelling factor increases correspondingly (compare Table II).  
  The amount of the hardener used depends on the desired degree of hardening but is appropriately 0.1 to per cent by weight relative to the weight of dry gelatine.  
  A particular advantage of the present crosslinking agents is that even when used in low concentration they impart a sufficient degree of hardness to the gelatine layers rapidly, for example after 3 hours, so that the castings can be tested, by processing of samples, immediately following manufacture,even at elevated temperature or in chemically aggressive processing baths.  
  It is furthermore an advantage that during hardening according. to the invention with the compounds of the formula (I), no significant change in pH in the emulsion layer occurs.  
  The hardening effect itself is very stable; even after prolonged storage at temperatures of about 40C and a relative atmospheric humidity of about percent the reciprocal swelling factor remains above 0.2.  
  The degree of hardening is also not changed substantially by acids or bases even on prolonged exposure,  
  which indicates that the hardener-gelatine bond is very resistant, to hydrolysis. Furthermore, the crosslinking agents to be used according to the invention cause no yellowing of the gelatine.  
  The compounds of the formulae (1) to (8) are furthermore generally sufficiently easily soluble in water and are stable in aqueous solution. The sufficient stability and solubility are both important properties which, for example, decisively influence the utilisability in photographic technology. Thus, for example, it is particularly desirable for the continuous manufacture of photographic materials that batches of crosslinking agents should remain stable at room temperature for several hours or days and that the concentration of the hardener for gelatine, and hence its ability to produce crosslinking, should not decline or only decline insignificantly. On the other hand it is equally important that, for the same reason, the hardener should not decompose or only decompose to an insignificant extent, in the casting solution at about 40C during the requisite stand time and dwell time, so as to maintain its full crosslinking action for several hours when casting, drying and storing the photographic material.  
  Furthermore, the viscosity of the casting solution should not increase significantly during the stand time as a result of the addition of the hardener. It is furthermore particularly important that even on prolonged treatment of the cast layer at elevated temperature and atmospheric humidity the hardener should not cause any&#39;yellowing or fogging or influence the gradation.  
  The hardeners are suitable for hardening (crosslinking) the most diverse layers containing gelatine such as, for example, intermediate layers, emulsion layers, base layers, top layers, backing layers and anti-halation layers. The layers can not only contain the crosslinking agents but also additives of the most diverse kind such as, for example, silver halide, pigments, such as barium sulphate, titanium dioxide, silicon dioxide or pigments of organic nature, such as coloured pigments, as well as image dyestuffs, colour coupling agents, sensitisers, filter dyestuffs, anti-halation dyestuffs and screening dyestuffs, stabilisers, UV-absorbers, optical brighteners and/or other crosslinking agents.  
  In the case of the compounds of relatively small molecular weight it is possible, because of the ease of diffusion in a multi-layer material, to add them only to the auxiliary layers in order to achieve a hardening of the adjacent silver halide layers by diffusion. However, with increasing molecular weight comparable compounds show decreasing diffusion when used in photographic layers. In the manufacture of multi-layer materials, this properly offers decisive advantages in various respects.  
  These new crosslinking agents can also be used mixed with other compounds suitable for crosslinking water-soluble colloids, especially gelatine.  
 Manufacturing Instructions 4.8 g (0.05 mol) of 3,5-dimethylpyrazole and 4.2 g (0.078 mol) of propinal are dissolved in 50 ml of absolute acetone. The solution is warmed and kept for 3 hours under reflux at the boil. After being allowed to cool, the solvent is filtered off and the residue (about 7.6 g) is recrystallised from benzine with addition of active charcoal and is dried. About 4.1 g (55% of theory) of 3-[ 3 ,5 &#39;-pyrazolyl-( 1 )]-propinal of the formula (22). of melting point 73 to 74C, are obtained.  
  in the same manner it is possible to manufacture, from the nitrogen compounds indicated in column 2 of Table l below, and propinal. the other aldehydes of the formulae listed in column 3. The melting points (MP) or boiling points (BP) can be seen from column 4 and the nuclear resonance data (recorded with a VARlAN A 60 A-instrument with tetramethylsilane (TMS) as the internal standard, 8 0 ppm) can be seen from column 5. ln the compounds of the formulae (27). (28) and (3] the position of the CH=CHCHO radical has not been determined.  
 TABLE I 5 Nuclear resonance data (DMSO d 1 2 5 4 Chemical shift 6 Coupling constant No. Startin substance Reaction roduct MP-BP g p ot 8 oc/l Hz 5/&#34;! Hz N MP 66 (21) Pyrazole CH=CHCHO 9.67 6.65 8.55 8 4 (22) 3 5 Dimethyl H3C NCH CH CHQ Isl/[g 1 py o 9.60 6.57 8.1 8 13-5 HEC  (25 Imidazole L/u-cpgct-t-QHO 0 9.60 6.65 8.25 7.5 14.5  
  5 MP (24) Z-Methylimidazole &amp; 12400 9.64 6.65 8.15 8 14 N NCH=CHCHO N i 194 l (25) Benzimidazole TWP-CH CH GH0 o 9.66 6.80 8.52 7.5 14 l I 197 c /N\ MP -cH=0HoH0 47 (26) Benztriazole o 9.85 7.05 9.00 8 14 MP. 7 5 \(cn ore-0:10. 8O 0 2 v (27) Ethyltetrazole I 9.88 6.86 8.85 7.5 14  
 . MP 5 6 N CH CH CHO 109 (28) Phenyltetrazole T E1106 9.88 6.85 8.97 7.5 14  
 TABLE I Continued 5 Nuclear resonance data (DP 1S0 1 1 2 3 4 Chemical shift 6 Coupling constant No. Starting substance Reaction product; MP-BP H a H B H Y a/B Hz 3/7 Hz 29 4,5.fil7-Tetra- L 1 1-CH=CH-0H0 04 5 6 a 2 8 4 hydroindazole Q 5o Indazole N-C1-1=C1-l-Cl-l0 MP 9.85 7.0 8.65 8 4 (Benzpyrazole) 95 1 31 Sodium salt of fi N-CH=CH CHQ MP 9.85 7.0 9.1 8 4 benztriazle-4- HO S 25 sulphonic acid 3 l EXAMPLE 1 Thickness of the dry layer l/SF  6 ml of 6% strength gelatine solution, 1 ml of 1% strength dyestuff solution, 1 ml of 0.025 molar hardener solution and ml of deionised water are mixed and adjusted to pH 6.5. The solution is cast on a tri- Thickness of the swollen layer The values in Table 11 were obtained in such measurements.  
 TABLE 11 Crosslinking agent, see  
  Table l, l/SF on normal storage after: l/SF on climatically controlled Formula No. storage after:  
  3 2 7 14 28 2 7 14 28 hours days days days days days days days days (21) 0.208 0.223 0.261 0.236 0.269 0.275 0.280 0.267 0.296 (22) 0.141 0.212 0.253 0.220 0.221 0.296 0.282 0.297 0.292 (23) 0.186 0.224 0.231 0.225 0.251 0.238 0.244 0.270 0.269 (24) 0.187 0.212 0.234 0.227 0.210 0.297 0.293 0.292 0.268 (25)* 0.244 0.258 0.223 0.273 0.276 (26)** 0.085 0.122 0.126 0.121 0.134 0.175 0.172 0.185 0.195 *Dissolved in dimethylformamide/water. 1:1 Dissolved in ethanol/water, 1:1  
 Dissolved in dimcthylformnmidc/wntcr. 1:1  
 acetate film of size 13 cm X 18 cm. After solidification EXAMPLE 2 at 10C, the material is dried at 20C over the course of 1 hour. The dyestuff mainly serves to make the samples more easily visible during the swelling measurements. Storage takes place under ambient conditions (NS: 20C, relative atmospheric humidity) or climatic conditions (CS: 43C, 69% relative atmospheric humidity).  
  To determine the reciprocal swelling factor. a 20 [L thick section is prepared from the samples and measured under the microscope. First. the thickness of the dry layer is determined, then deionised water is added and after 4 minutes the thickness of the swollen layer is measured. The reciprocal swelling factor 1/SF corresponds to the ratio 6 g of a water-soluble polyvinyl alcohol are dissolved in 100 m1 of deionised water by stirring at 50C for 1 hour. 680 mg (0.5 millimol) of aldehyde of the formula (24) (see Table l) are dissolved in 10 ml of deionised water. 6 ml of the polyvinyl alcohol solution, 4 ml of the aldehyde solution and 2 ml of deionised water are mixed, the pH value is adjusted to 6.5 and the mixture is cast at room temperature onto a substrated glass plate of 13 cm 18 cm surface area. It is then dried whilst extracting the air from above the layer.  
  A layer obtained in this manner showed, after storage for 7 days at 43C and 69% relative atmospheric humidity, a melting range of 61 to C measured in water; a layer which was otherwise identical but manufactured without addition of the crosslinking agent showed a melting range of 20 to 28C.  
 EXAMPLE 3 60 ml of 6% strength aqueous gelatine solution are diluted with ml of deionised water. 1 ml of a 25 x 10 molar solution of the hardener is added thereto. The solution is adjusted to pH 6.5 and cast on a triacetate film (13 cm X 18 cm). The film is dried by means of circulating air and is measured in a spectrophotometer (Car after climatically controlled storage (43C. 69% relative atmospheric humidity). The optical density at 400 nm is determined, a sample without added hardener serving as the reference. High densities denote a higher yellow fogging.  
  3. Process according to claim 2, which comprises using a crosslinking agent of the formula X,CH=CHY wherein X, and Y have the indicated meaning.  
  4. Process according to claim 3, which comprises using a crosslinking agent of the formula X CH=CHY- 1 wherein X has the indicated meaning and Y denotes an aldehyde group or aldehyde-hydrate group.  
  5. Process according to claim 4, which comprises using a crosslinking agent of the formula X- ,CH=CH-Y wherein Y has the indicated meaning and X; denotes a heterocyclic radical which is bonded to the -CH=CH group by a nitrogen atom ofa five-membere hetero-ring containing 2 to 4 ring nitrogen atoms and 3 to 1 carbon atoms.  
 Hardener Storage conditions Optical density at g N 7 days climatically controlled 3 conditions 0 .005  
 KEN-ciFcrr-ciw H C H I 7 days climatically controlled 6 conditions 0 .019  
  J, C H -I t CH-CH-CHO C10 7 days climatically controlled )cc conditions 0.021 H H Cl Cl 7 days climatically controlled )3=C conditions 0.016 HOOC CHO Compound 22 shows a considerably lesser yellow fogging than the comparison compounds.  
 We claim:  
 6. Process according to claim 1, which comprises 1. Process for crosslinking a hydrophilic colloid 45 usingacrosslinking agent of the formula which contains amino, imino and/or hydroxyl groups, which process comprises using a crosslinking agent of the formula wherein X and Y, have the indicated meaning and R denotes a hydrogen atom or an alkyl group with at most 4 carbon atoms.  
 wherein Y has the indicated meaning, one Z represents a nitrogen atom and the other Z represents a crosslinking polyvinyl alcohol or gelatine.