Process of hardening a silver halide photographic material with a 1-carbamoyloxypyridinium salt

As quick-acting hardeners for layers which contain protein, in particular gelatin layers for photographic purposes carbamoyl oxypyridinium salts are used.

The invention relates to a process for the hardening of photographic layers 
which contain protein, preferably gelatine. 
Numerous substances have already been described as hardeners for protein 
and particularly for gelatine; for example metal salts such as chromium, 
aluminium or zirconium salts, aldehydes and halogen-containing aldehyde 
compounds, in particular formaldehyde, dialdehydes and mucochloric acid, 
1,2- and 1,4-diketones such as cyclohexane-1,2-dione and quinones, 
chlorides of dibasic organic acids, the anhydrides of tetracarboxylic 
acid, compounds which contain several reactive vinyl groups, such as vinyl 
sulphones, acrylamides, compounds containing at least two heterocyclic 
3-membered rings which can easily be split, such as ethylene oxide and 
ethylene imine, polyfunctional methane sulphonic acid esters and 
bis-.alpha.-chloroacyl amido compounds. 
High-molecular weight hardeners have recently become known, for example 
polyacrolein and its derivatives or copolymers as well as alginic acid 
derivatives. These are used especially as hardeners which are confined to 
the layer into which they are introduced. 
Many of the known compounds, however, are unsuitable for photographic 
purposes. Some of them are photographically active and therefore 
unsuitable for hardening photographic materials while others cannot be 
used because they have a harmful effect on certain of the physical 
properties of gelatine layers such as their brittleness. Other may cause 
discoloration or a change in pH during the hardening reaction. 
Furthermore, it is particularly important for hardening photographic 
layers that maximum hardening should be reached as soon as possible after 
drying so that the material which is being hardened does not continuously 
change its permeability to the developer solution as is the case, for 
example, with mucochloric acid or formaldehyde. 
Some cross-linking agents for gelatine, for example the ethylene imine 
compounds, also have a deleterious effect on the skin so that for 
physiological reasons they are unsuitable. 
It has long been known to use trichlorotriazine and dichloroaminotriazines 
as hardeners. Their disadvantages are their relatively high vapour 
pressure and their physiological action. Water-soluble derivatives which 
contain carboxyl and sulphonic acid groups and which have been obtained by 
the reaction of cyanuric chloride with one mol of dimainoalkyl or 
diaminoacryl sulphonic acid or carboxylic acid do not have these 
disadvantages and have therefore recently been proposed as hardeners. 
Their practical utility is, however, limited by the fact that, owing to 
their high solubility, they decompose when left to stand in aqueous 
solution and therefore rapidly lose their activity. Hydroxy 
dichlorotriazine has also been proposed as hardener. Lastly, in a hardener 
used for photographic layers which contain gelatine it is of the utmost 
importance both for reasons of preparation of the photographic material 
and its processing that the onset of the cross-linking reaction should be 
controllable within certain limits, for example by suitable choice of the 
drying temperature of the pH. 
Compounds which contain two or more acrylic acid amido or vinyl sulphone 
groups in the molecule are also known as hardeners for photographic 
gelatine layers, e.g. divinyl sulphone, arylene-bis-vinyl sulphones, 
N,N',N"-tris-acryloyl-hydrotriazine or methylene-bis-vinyl sulphonamide. 
Although hardening of the compounds is quite satisfactory after some time, 
the compounds are only sparingly soluble in water, with the result that 
the layer may be unevenly hardened. 
The consequences of the undesirable properties of the known hardeners 
described above are extremely important for photographic purposes because 
important photographic properties such as the gradation and sensitivity 
and, in many cases, also the silver covering power depend on the degree of 
cross-linking of the layer-forming colloid and alter during storage. 
Although this disadvantage can be attenuated by brief treatment of the 
solidified layer with ammonia or an amine, it cannot be completely 
overcome by this method and there is the added disadvantage that aliphatic 
disulphones have properties which are damaging to the skin. 
Carbamoyl pyridinium salts are also known as hardeners with a very good 
cross-linking action for gelatine and high-molecular weight compounds or 
mixtures of compounds which contain carboxyl groups and amino groups. The 
disadvantage of these hardeners is that they are liable to split off 
pyridine or pyridine derivatives during their reaction with the binder and 
their commercial applications are therefore limited. 
It is an object of this invention to develop quick-acting hardeners for 
layers which contain protein, in particular gelatine layers for 
photographic purposes, which hardeners will not have the technical 
disadvantages of the known compounds. 
It is a further object to provide hardening which does not result in 
increased fog density nor the production of an offensive odor. 
A process for hardening photographic layers which contain protein, 
preferably gelatine, has now been found which is characterised by the use 
of a carbamoyl oxypyridinium salt as harden. 
The hardeners of the present invention correspond to the general formula 
##STR1## 
in which 
R.sub.1 represents an alkyl group with preferably 1 to 3 carbon atoms or an 
aryl group such as a phenyl group, 
R.sub.2 represents an alkyl group with preferably 1 to 3 carbon atoms or 
the groups 
##STR2## 
in which 
R.sub.6 represents hydrogen, an alkyl group such as a methyl or ethyl group 
or an aryl group, 
R.sub.7 represents an alkyl group such as a methyl or ethyl group and 
R.sub.8 represents an alkyl group with preferably 1 to 4 carbon atoms; or 
R.sub.1 and R.sub.2 may together represent the atoms required to complete a 
heterocyclic ring system such as a pyrrolidine-, morpholine-, piperidine-, 
perhydroazepine-, 1,2,3,4-tetrahydroquinoline- or imidazolidine-2-one-ring 
or 
R.sub.1 and R.sub.2 may together represent the atoms required to complete a 
piperazine ring in which the second nitrogen atom establishes the 
connection to a second, similar, molecular residue of the general formula, 
R.sub.3 represents hydrogen, a halogen atom such as chlorine or bromine, an 
alkyl group such as a methyl or ethyl group, an oxalkyl group with 
preferably 1 to 3 carbon atoms, a cyano group or a --CONH.sub.2 or 
##STR3## 
alkyl group (such as a methyl or ethyl group) 
R.sub.4 represents hydrogen or an alkyl group such as a methyl or ethyl 
group and 
R.sub.5 represents hyrdrogen or a methyl group; 
X represents an anion such as a Cl--, BF.sub.4 -- or ClO.sub.4 -- im. 
The following compounds have been found to be particularly advantageous. 
The list is given purely by way of example and is not intended to restrict 
the scope of the invention. 
__________________________________________________________________________ 
Subst. Nr. 
##STR4## 
##STR5## X.sup..crclbar. 
Fp.Zers. 
Herstellungs- verfahren 
Ausbeute 
__________________________________________________________________________ 
##STR6## 
##STR7## Cl.sup..crclbar. 
163-67.degree. 
A 89 % 
2 " 
##STR8## Cl.sup..crclbar. 
168-70.degree. 
A 85 % 
3 " 
Cl.sup..sym. 86.degree. 
A 89 % 
4 " 
##STR10## Cl.sup..crclbar. 
90.degree. 
A 80 % 
5 " 
##STR11## ClO.sub.4 .sup..crclbar. 
100-102.degree. 
B 50 % 
6 " 
##STR12## ClO.sub.4 .sup..crclbar. 
95-100.degree. 
B 60 % 
7 " 
##STR13## ClO.sub.4 .sup..crclbar. 
100-102.degree. 
C 40 % 
8 
##STR14## 
##STR15## ClO.sub.4 .sup..crclbar. 
150.degree. 
D 45 % 
9 
##STR16## 
##STR17## Cl.sup..crclbar. 
108-110.degree. 
A 70 % 
10 " 
##STR18## ClO.sub.4 .sup..crclbar. 
64-65.degree. 
B 75 % 
11 " 
##STR19## ClO.sub.4 .sup..crclbar. 
130-32.degree. 
B 65 % 
12 " 
##STR20## Cl.sup.- 
95-100.degree. 
A 72 % 
13 
##STR21## 
##STR22## Cl.sup.- 
114-116.degree. 
A 85 % 
14 
##STR23## 
##STR24## Cl.sup..crclbar. 
90-92.degree. C 
A 82 % 
15 
##STR25## 
##STR26## Cl.sup..crclbar. 
132.degree. C 
A 92 % 
16 " " BF.sub.4 .sup..crclbar. 
138-40.degree. C 
C 85 % 
17 " " ClO.sub.4 .sup..crclbar. 
150-52.degree. C 
C 88 % 
18 " 
##STR27## Cl.sup..crclbar. 
110-13.degree. C 
A 85 % 
19 " " ClO.sub.4 .sup..crclbar. 
140-42.degree. C 
C 85 % 
20 " 
##STR28## Cl.sup..crclbar. 
130-32.degree. C 
A 80 % 
21 " 
##STR29## ClO.sub.4.sup..crclbar. 
144-46.degree. 
C 82 % 
22 " 
##STR30## Cl.sup..crclbar. 
&gt;90.degree. 
A 90 % 
23 " 
##STR31## Cl.sup..crclbar. 
100-102.degree. 
A 81 % 
24 " 
##STR32## Cl.sup..crclbar. 
102-104.degree. 
A 87 % 
25 " 
##STR33## Cl.sup..crclbar. 
100-102.degree. 
A 90 % 
26 " 
##STR34## Cl.sup..crclbar. 
113-115.degree. 
A 80 % 
27 " 
##STR35## Cl.sup.- 
115.degree. 
A 60 % 
28 
##STR36## " ClO.sub.4 .sup..crclbar. 
112-14.degree. 
C 57 % 
29 " 
##STR37## Cl.sup..crclbar. 
93-95.degree. 
A 72 % 
30 " 
##STR38## Cl.sup..crclbar. 
65-70.degree. 
A 90 % 
31 " " BF.sub.4 .sup..crclbar. 
144-48.degree. 
C 83 % 
32 " 
##STR39## Cl.sup..crclbar. 
80-82.degree. 
A 50 % 
33 " 
##STR40## ClO.sub.4 .sup..crclbar. 
150.degree. 
D 60 % 
34 " 
##STR41## ClO.sub.4 .sup..crclbar. 
162-63.degree. 
D 60 % 
35 " 
##STR42## ClO.sub.4 .sup..crclbar. 
200.degree. 
D 50 % 
36 
##STR43## 
##STR44## Cl.sup..crclbar. 
158.degree. 
A 75 % 
37 " 
##STR45## Cl.sup..crclbar. 
138.degree. 
A 80 % 
38 " 
##STR46## Cl.sup..crclbar. 
152-154.degree. 
A 82 % 
39 
##STR47## 
##STR48## Cl.sup..crclbar. 
85-86.degree. 
A 90 % 
40 " 
##STR49## ClO.sub.4.sup..crclbar. 
100.degree. 
C 80 % 
41 " 
##STR50## ClO.sub.4.sup..crclbar. 
80.degree. 
C 75 % 
42 " 
##STR51## Cl.sup..crclbar. 
104-106.degree. 
A 84 % 
43 
##STR52## 
##STR53## Cl.sup..crclbar. 
76-78.degree. 
A 76 % 
44 
##STR54## " Cl.sup..crclbar. 
140-144.degree. 
A 85 % 
45 
##STR55## " Cl.sup..crclbar. 
160-162.degree. 
A 95 % 
46 " 
##STR56## Cl.sup..crclbar. 
98-100.degree. 
A 80 % 
47 " 
##STR57## Cl.sup..crclbar. 
218-220.degree. 
A 90 % 
48 " 
##STR58## Cl.sup..crclbar. 
116.degree. 
A 85 % 
49 " 
##STR59## Cl.sup..crclbar. 
125-128.degree. 
A 80 % 
50 
##STR60## 
##STR61## 2 Cl.sup..crclbar. 
109-112.degree. 
A 75 % 
51 
##STR62## 
##STR63## Cl.sup..crclbar. 
87-89.degree. 
A 62 % 
52 " 
##STR64## Cl.sup..crclbar. 
105.degree. 
A 80 % 
53 " 
##STR65## Cl.sup..crclbar. 
88-89.degree. 
A 70 % 
54 
##STR66## 
##STR67## Cl.sup..crclbar. 
168-170.degree. 
A 75 % 
55 
##STR68## " Cl.sup..crclbar. 
169-173.degree. 
A 65 % 
56 
##STR69## " Cl.sup..crclbar. 
173-180.degree. 
A 80 % 
57 
##STR70## " Cl.sup..crclbar. 
173-183.degree. 
A 60 % 
58 
##STR71## " Cl.sup..crclbar. 
221-223.degree. 
A 70 % 
59 
##STR72## 
##STR73## Cl.sup..crclbar. 
180-185.degree. 
A 70 % 
60 
##STR74## 
##STR75## Cl.sup..crclbar. 
133-134.degree. 
A 90 % 
__________________________________________________________________________ 
1-carbamoyloxy- and 1-allophanyloxy pyridinium salts are new compounds, the 
preparation of which has not previously been described, but they can be 
obtained by a surprisingly simple method, namely by reacting carbamide 
chlorides or allophanic acid chlorides with pyridine-N-oxides in aprotic 
media, sometimes also in alcoholic solution or even in aqueous systems. 
They are stable for a considerable time at room temperature in the pure 
state and, even in aqueous solution at pH-values between 5 and 7, they 
undergo degradation surprisingly slowly. The stability of the new 
compounds can be even further improved by suitable choice of so-called 
hard anions, e.g. fluoborate or perchlorate. Whereas the chlorides are in 
many cases hygroscopic, the fluoborates or perchlorates which are easily 
obtainable by salt conversion with sodium fluoborate or sodium perchlorate 
do not show this characteristic. 
The N-oxides used as starting materials are known. They are usually 
prepared from the free bases by oxidation with organic peracids or 
mixtures of hydrogen peroxides and organic acids. Special representatives 
of these compounds, e.g. alkoxy pyridine-N-oxides, however, can generally 
be prepared more satisfactorily by nucleophilic exchange reactions from 
the corresponding nitropyridine- or halopyridine-N-oxides. Reference may 
be made in this connection to "Aromatic Amine Oxides" by E. Ochiai, 
Elsevier 1967 and the references given therein as well as to the 
publication "Die Einfuhrung von Substituenten in den Pyridin-Ring" by K. 
Thomas and D. Jerchel in the journal "Angewandte Chemie" vol. 70, pages 
719-746 (1958). 
N,N-disubstituted carbamide chlorides can be obtained from the 
corresponding secondary amines by reaction with phosgene. Generally 
speaking, di- or tri-substituted allophanic acid chlorides are prepared by 
reacting the corresponding alkyl ureas with phosgene (see H. Ulrich, J. N. 
Tilley, A. A. R. Sayigh; J. Org. Chem. 29, 2401 (1964) and German 
Offenlegungsschrift 2 008 116).

Several methods are available for the preparation of the new hardeners 
according to the invention. These methods will now be illustrated with the 
aid of six examples. 
METHOD OF PREATION A 
Compound 1 
22 g of dimethylcarbamide chloride are added dropwise to 19 g (0.2 mol) of 
pyridine-N-oxide in 100 ml of anhydrous acetone at 0.degree. to 15.degree. 
C over a period of 15 minutes. The temperature is kept at 10.degree. to 
15.degree. C for a further 45 minutes until the product crystallises. The 
reaction mixture is then suction-filtered. 
The yield was 35g, which was 89% (of the theoretical yield) and the melting 
point was 163.degree. to 167.degree. C with decomposition. 
Compound 15 
30 g of morpholine carbamide chlorine in 50 ml of methylene chloride are 
added dropwise with stirring to 19 g (0.2 mol) of pyridine-N-oxide in 100 
ml of methylene chloride at 0.degree.-15.degree. C. The product is 
suction-filtered after 60 minutes. The yield was 45 g which was 92% of the 
theory with a melting point of 132.degree. C (decomposition). According to 
the analytical results obtained after crystallisation from ethanol/ether, 
compound 15 corresponds to the monohydrate C.sub.10 H.sub.13 N.sub.2 
O.sub.3 Cl.H.sub.2 O. 
Found: C: 45.8 H: 5.7 N: 10.8 Cl: 13.7. Calculated: C: 45.7 H: 5.7 N: 10.7 
Cl: 13.5. 
METHOD OF PREATION B 
Compound 11 
27g (0.2 mol) of diethylcarbamide chloride in 50 ml of ether are added 
dropwise with stirring to a solution of 22 g (0.2 mol) of 
2-methylpyridine-N-oxide in 100 ml of ether at 0.degree.-10.degree. C. 
Stirring is continued for a further two hours at 5.degree. C and the 
reaction mixture is then cooled to 0.degree. C, the supernatant ether is 
decanted from the oil and 36 g of sodium perchlorate in ethanol are added. 
After the reaction mixture has been left to stand overnight, it is 
suction-filtered to remove the precipitated sodium chloride, concentrated 
by evaporation under vacuum at a temperature below 30.degree. C and left 
to stand for crystallization. 
The yield was 40 g which was 65% of the theory the melting point was 
130.degree. to 132.degree. C, with decomposition. 
METHOD OF PREATION C 
Compound 17 
20 g of sodium perchlorate is added with as little water as possible to a 
solution of 24.5 g (0.1 mol) of compound 15 in 60 ml of water. The 
reaction mixture is left to stand for 30 minutes and then 
suction-filtered. 
The yield was 27 g, and the melting point was 150.degree. to 152.degree. C, 
with decomposition. 
Compound 16 
A solution of 24.5 g (0.1 mol) of compound 15 is added to a solution of 14 
g of sodium fluoborate in 25 ml of water. The reaction mixture is 
suction-filtered after 60 minutes. The yield was 25 g, and the melting 
point was 138.degree. to 140.degree. C with decomposition. 
METHOD OF PREATION D 
Compound 34 
30 g (0.2 mol) of morpholine carbamide chloride are added dropwise at room 
temperature to 36.4 g (0.2 mol) of 3-ethoxycarbonyl aminopyridine-N-oxide 
in 150 ml of isopropanol. After 10 hours, 30 g of sodium perchlorate in 
150 ml of ethanol are added and reaction mixture is left to stand 
overnight. The precipitated crystals are suction-filtered. 
The yield was 50 g, with a melting point of 162.degree. to 163.degree. C 
with decomposition. 
The compounds according to the invention may be added as aqueous or 
alcoholic solutions to the protein layers before they are cast. Hardening 
may set in extremely rapidly or moderately soon, depending on the 
structure of the compound and the concentration employed, but even with 
the slowest compounds it is completed within one to two days so that no 
afterhardening effects need be expected. The most rapid hardeners are the 
allophanyl oxypyridinium salts derived from allophanic acid chlorides, 
somewhat slower are those carbamyl oxypyridinium salts which are derived 
from electro-negatively substituted pyridine-N-oxides while the slowest 
are those representatives of the new class of compounds which are derived 
from electropostively substituted pyridine-N-oxides. These, and 
particularly the carbamoyl oxypyridinium salts derived from alkyl 
pyridine-N-oxides, are so stable that they can be kept in aqueous solution 
for many days without any loss of their hardening action and they do not 
increase the viscosity of a gelatine solution at 38.degree. C over several 
hours. 
One particularly advantageous method of applying the hardeners consists of 
casting the protein solutions before they have been treated with hardener 
and then coating the resulting layers, optionally when they are already 
dry, with a solution of the hardening compounds. If desired, however, the 
compounds may also be added as aqueous solutions while the photographic 
material is being processed, for example it may be added to a bath of the 
unhardened or only slightly hardened photographic layers before 
development. 
The compounds described here may be used either singly or as mixtures. They 
may advantageously be used for hardening photographic layers which, in 
addition to containing gelatine, also contain other homopolymers and 
copolymers with carboxyl groups as binders. It is assumed that the 
compounds according to the invention are capable of effecting 
cross-linking of gelatine and polymers which contain carboxyl groups. 
The term `photographic layers` is used here in a quite general sense to 
mean layers which are used in photographic materials, for example 
light-sensitive silver halide emulsion layers, protective layers, filter 
layers, antihalation layers, backing layers or photographic auxiliary 
layers in general. 
Light-sensitive emulsion layers for which the hardening process according 
to the invention is particularly suitable include, for example, those 
layers which are based on unsensitised emulsions, X-ray emulsions and 
other spectrally sensitised emulsions. The hardening process according to 
the invention has also been found satisfactory for hardening the various 
gelatine layers used for black-and-white and colour photographic 
processes. The process according to the invention has been found to be 
particularly suitable for hardening photographic layer combinations which 
are used for carrying out colour photographic processes, e.g. combinations 
which contain emulsion layers with colour couplers or emulsion layers 
which are intended to be treated with solutions which contain colour 
couplers. 
The action of the compounds used according to the invention is not 
deleteriously affected by the usual photographic additives. The hardeners 
are also inert towards photographically active substances such as 
water-soluble and emulsified water insoluble dye components, stabilisers, 
sensitisers and the like. Moreover, they have no influence on the 
light-sensitive silver halide emulsions. Furthermore, the compounds can be 
combined with any compounds from the classes of hardeners previously 
known, for example formalin, mucochloric acid, triacryloformal, bisvinyl 
sulphones, bisvinyl sulphonamides, dialdehydes, bischloroacetamides or 
inorganic salts, e.g. tervalent chromium, tervalent aluminum or zirconium 
salts. 
The layers may contain water-soluble high-polymer compounds in addition to 
gelatine, in particular polyvinyl alcohol, polyacrylic acid sodium and 
other copolymers which contain carboxyl groups, polyvinyl pyrrolidone, 
polyacrylamide or high-molecular weight natural substances such as 
dextranes, dextrines, starch ether, alginic acid or alginic acid 
derivatives. 
The concentrations at which the hardeners according to the invention are 
used may vary within wide limits and depend mainly on the particular 
compound used as hardener. 
Satisfactory results are obtained with quantities of 0.5 to 10% by weight 
and particularly 1 to 5% by weight, based on the dry weight of binder. 
The activity of the hardening compounds is assessed by means of the melting 
point of the layers, which can be determined as follows: 
A layer cast on a support is half dipped into water which is continuously 
heated to a temperature of 100.degree. C. The temperature at which the 
layer begins to run off the support (formation of streaks) is taken as the 
melting point or melting-off point. According to this method of 
measurement, pure protein or gelatine layers which are free from hardener 
in no case show an increase in melting point. The melting-off point under 
these conditions is 30.degree. to 35.degree. C. 
Swelling of the layer is determined gravimetrically in distilled water at 
22.degree. C after 10 minutes' treatment. It is characterised by the 
swelling factor: 
##EQU1## 
To determine the wet scratch resistance, a metal tip of a specified size is 
passed over the wet layer and loaded with an increasing weight. The wet 
scratch resistance is indicated by that weight at which the tip leaves a 
visible scratching trace on the layer. A high weight corresponds to a high 
wet scratch resistance. 
The compounds according to the invention react surprisingly quickly with 
proteins after the drying process and thereby enable materials which 
contain protein to be hardened to an optimum degree within a very short 
time. This unexpected effect of the compounds is particularly important 
for hardening photographic materials which contain proteins and polymers 
with carboxyl groups as binders. The desired degree of hardening can 
easily be adjusted quite accurately at the stage of preparation of the 
materials without prolonged storage times and the attendant uncertainties 
of uncontrollable subsequent hardening. 
The hardening compounds used according to the invention are thus 
distinguished by a hardening reaction which is surprisingly rapid and 
without after-effects or disadvantages. This property of the compounds 
makes them eminently suitable for the preparation of very hard 
photographic layers with a clearly defined and low degree of swelling. 
This result can be obtained simply by treating the dry or slightly swelled 
photographic layer with a solution of the hardening compound for a short 
time and then rapidly drying the layer. Any degree of hardening can easily 
be achieved in this way. The hardening process does not result in 
increased fog density in the photographic material, that is the rise of 
density does not exceed the normal fog density of the unhardened material. 
At the same time, this processing does not yield an offensive odor. Thus 
the hardening process of the present inention involving the application of 
the above-described hardening compounds provides low fogging and an 
absence of offensive odors. 
The following examples serve to explain the invention more fully. 
EXAMPLE 1 
5% aqueous solutions are prepared from compounds 1, 2, 3, 4, 5, 6, 7, 9, 
10, 11, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 25, 26, 27, 29, 30, 
34, 36, 39, 43, 44, 45, 50, 51, 52, 53, 54, 55, 56, 57, 58. Strips of a 
gelatine layer 10 .mu. in thickness which has been cast on a prepared 
cellulose triacetate substrate and which contains 18% by weight of a cyan 
coupler of the formula 
##STR76## 
are half dipped into these solutions for 10 seconds and dried in a blast 
of hot air. The sample strips are then washed with water at 80.degree. C. 
In all the sample strips, the layer adheres to the half which has been 
dipped into solution but is washed off the unhardened half. 
EXAMPLE 2 
Strips of gelatine layers similar to those described in example 1 are 
treated with aqueous solutions of the compounds according to the invention 
indicated in the following table and dried as described in example 1. The 
layer melting points, swelling factor and wet strength are then 
determined. The results are shown in the table. 
For comparison 2 samples in each case of the same unhardened gelatine layer 
were dipped into a 2.5% solution of tris-acryloyl-hexahydro-s-triazine (A) 
and mucochloric acid (B) for 1 minute or 3 minutes and the melting point 
of the layer was determined as already described: 
______________________________________ 
Layer-melting 
point Swelling factor 
Comparison 
after after after Wet strength 
sample drying 1 day 1 day 3 days 1 day 3 days 
______________________________________ 
A 35.degree. C 
B 35.degree. C 
______________________________________ 
The results show that the compounds according to the invention will harden 
unhardened gelatine layers to an extent which is fast to boiling either 
immediately after drying or, at the latest, after one day's storage and 
that no subsequent hardening takes place. 
__________________________________________________________________________ 
Layer Melting 
Swelling factor 
Conc. of point after Wet strength 
Compound 
aqueous 
after 
after 
1 day 
3 days 
1 day 
3 days 
No. solution 
drying 
1 day 
A B A B 
__________________________________________________________________________ 
1 2 % &gt;100.degree. 
&gt;100.degree. 
3.7 3.6 550 p 
600 p 
2 2 % 44.degree. 
&gt;100.degree. 
4.2 4.2 560 p 
560 p 
3 2 % 43.degree. 
&gt;100.degree. 
4.5 4.6 450 450 
5 3 % 50.degree. 
&gt;100.degree. 
4.0 3.9 400 450 
13 2 % 52.degree. 
&gt;100.degree. 
4.5 550 
15 2 % &gt;100.degree. 
&gt;100.degree. 
3.7 3.8 560 600 
16 3 % &gt;100.degree. 
&gt;100.degree. 
3.6 3.8 550 500 
18 2 % 63.degree. 
&gt;100.degree. 
5.6 4.5 350 450 
20 2 % &gt;100.degree. 
&gt;100.degree. 
5.4 4.8 400 450 
21 3 % 50.degree. 
&gt;100.degree. 
4.0 4.0 550 500 
22 2 % 47.degree. 
&gt;100.degree. 
4.8 4.7 450 500 
24 3 % 45.degree. 
&gt;100.degree. 
4.7 450 
25 2 % &gt;100.degree. 
&gt;100.degree. 
4.2 4.3 550 600 
26 3 % 47.degree. 
&gt;100.degree. 
4.8 4.6 450 650 
27 3 % 53.degree. 
&gt;100.degree. 
4.5 4.8 250 350 
39 2 % 59.degree. 
&gt;100.degree. 
3.9 3.6 500 650 
44 3 % &gt;100.degree. 
&gt;100.degree. 
3.8 3.6 450 450 
47 3 % 74.degree. 
&gt;100.degree. 
4.6 3.8 
48 3 % 45.degree. 
&gt;100.degree. 
5.0 5.2 
51 2 % &gt;100.degree. 
&gt;100.degree. 
4.8 5.2 350 300 
52 2.6 % 
&gt;100.degree. 
&gt;100.degree. 
3.0 3.2 600 500 
53 2.6 % 
&gt;100.degree. 
&gt;100.degree. 
3.6 4.2 450 350 
55 2.9 % 
59.degree. 
&gt;100.degree. 
3.7 3.9 400 400 
58 2.5 % 
&gt;100.degree. 
&gt;100.degree. 
3.3 3.8 500 500 
59 2.5 % 
&gt;100.degree. 
&gt;100.degree. 
3.0 3.4 750 800 
__________________________________________________________________________ 
EXAMPLE 3 
Aqueous solutions of the compounds according to the invention are used as 
described in example 2 in the freshly dissolved state and after 3 hours' 
storage and 24 hours' storage of the solutions at room temperature for 
bathing strips of an unhardened gelatine layer similar to that described 
in example 1. The layers are dried and their properties are determined 
after 1 day's storage at room temperature. The results are shown in the 
following table, in which SF = swelling factor and WS = wet strength. 
__________________________________________________________________________ 
Properties after storage time of the solution 
__________________________________________________________________________ 
fresh (30 min) 
3 hours 24 hours 
__________________________________________________________________________ 
Conc. of 
Compound 
solution 
m.pt. 
SF 
WS m.pt. 
SF 
WS m.pg. 
SF 
WS 
__________________________________________________________________________ 
1 2 % &gt;100 .degree. 
3.7 
500 
&gt;100 
3.7 
500 
&gt;100 
3.5 
600 
2 2 % &gt;100 .degree. 
4.2 
500 
&gt;100 
4.4 
500 
&gt;100 
4.4 
500 
3 2 % &gt;100 .degree. 
4.5 
450 
&gt;100 
4.8 
450 
&gt;100 
4.7 
400 
5 3 % &gt;100 .degree. 
4.0 
400 
&gt;100 
4.4 
400 
&gt;100 
4.8 
400 
13 2 % &gt;100 .degree. 
4.4 
550 
&gt;100 
4.7 
550 
&gt;100 
4.7 
550 
15 2 % &gt;100 .degree. 
3.7 
500 
&gt;100 
3.7 
500 
&gt;100 
3.8 
500 
16 3 % &gt;100 .degree. 
3.6 
550 
&gt;100 
3.5 
550 
&gt;100 
3.9 
450 
18 2 % &gt;100 .degree. 
5.6 
350 
&gt;100 
5.6 
350 
&gt;100 
5.1 
350 
20 2 % &gt;100 .degree. 
5.4 
400 
&gt;100 
5.5 
400 
&gt;100 
5.3 
350 
22 2 % &gt;100 .degree. 
4.8 
450 
&gt;100 
4.8 
400 
&gt;100 
4.8 
400 
25 2 % &gt;100 .degree. 
4.2 
550 
&gt;100 
4.9 
500 
&gt;100 
5.6 
450 
26 3 % &gt;100 .degree. 
4.8 
450 
&gt;100 
4.9 
450 
&gt;100 
5.7 
450 
27 3 % &gt;100 .degree. 
4.5 
250 
&gt;100 
4.8 
250 
&gt;100 
4.9 
200 
39 2 % &gt;100 .degree. 
3.9 
500 
&gt;100 
4.0 
500 
&gt;100 
4.0 
500 
44 3 % &gt;100 .degree. 
3.8 
450 
&gt;100 
3.8 
450 
&gt;100 
3.9 
400 
48 3 % &gt;100 .degree. 
5.0 &gt;100 
5.0 &gt;100 
5.5 
55 2.9 % 
&gt;100 .degree. 
3.7 
400 
&gt;100 
3.7 
400 
&gt;100 
3.8 
400 
__________________________________________________________________________ 
The results of Example 3 show the excellent stability of the aqueous 
solutions of the compounds according to the invention even after one day's 
storage. There is therefore no doubt that the compounds are sufficiently 
stable for large-scale industrial use. 
EXAMPLE 4 
Compounds 1, 2, 3, 5, 15, 18, 20, 21, 22, 24, 25, 26, 27, 34, 39, 43, 45, 
46, 47, 48, 49, 50 are added to samples of a 10% gelatine solution in 
quantities of 2%, based on the gelatine. 30 minutes after addition of the 
compounds, the gelatine is cast on a transparent cellulose triacetate 
substrate covered with a bonding layer to form gelatine layers 10 .mu. in 
thickness which are then dried. 24 hours after casting, the layer melting 
point, swelling factors and wet strength values were determined. The 
results are shown in the following table: 
______________________________________ 
Compound 
(2 % based 
Layer melting 
Swelling Wet Strength 
on gelatine) 
point factor (in pond) 
______________________________________ 
1 10'100.degree. 
3.4 550 p 
2 10'100.degree. 
3.4 450 p 
3 10'100.degree. 
4.0 350 p 
5 10'100.degree. 
4.4 200 p 
15 10'100.degree. 
3.8 550 p 
18 10'100.degree. 
4.0 750 p 
20 10'100.degree. 
4.8 600 p 
21 10'100.degree. 
4.4 500 p 
22 10'100.degree. 
3.3 450 p 
24 10'100.degree. 
3.8 350 p 
25 10'100.degree. 
5.0 250 p 
26 10'100.degree. 
3.4 400 p 
27 10'100.degree. 
4.2 300 p 
34 10'100.degree. 
4.3 
39 10'100.degree. 
3.5 550 p 
43 10'100.degree. 
4.1 450 p 
45 10'100.degree. 
3.5 450 p 
46 10'100.degree. 
3.1 450 p 
47 10'100.degree. 
4.1 450 p 
48 10'100.degree. 
4.4 250 p 
49 10'100.degree. 
4.2 250 p 
50 10'100.degree. 
3.5 450 p 
______________________________________ 
One part of the casting solution is left to stand at 40.degree. C for 2 
hours or 5 hours after their preparation. The viscosities of the solutions 
are determined in an outflow viscosimeter and the results are compared 
with those of fresh solutions (outflow time in seconds = ") 
______________________________________ 
10% gelatine (+2% hardener) 
Compound 
viscosity fresh 
after 2 hours 
after 5 hours 
______________________________________ 
1 33" 33.5" 34" 
2 26" 26" 26" 
3 27" 27" 28" 
5 28" 28" 28" 
15 45" 54" 75" 
18 41" 45" 45" 
20 42" 48" 59" 
21 27" 31" 36" 
24 26" 26" 27" 
25 31" 40" 41" 
26 28" 31" 35" 
27 28" 29" 29" 
34 25" 26" 27" 
39 32" 32" 34" 
43 35" 36" 41" 
46 27" 29" 29" 
47 29" 34" 37" 
48 30" 38" 46" 
49 32" 41" 41" 
______________________________________ 
For comparison, the following results are obtained with samples which, 
instead of containing a compound according to the invention, contain one 
of the following conventional hardeners: 
______________________________________ 
10% gelatine (+ 2% hardener) 
viscosity 
Compound fresh after 2 hours 
after 5 hours 
______________________________________ 
C 80" 80" cross-linked 
D 178" 222" 268" 
E 149" 156" 189" 
______________________________________ 
C: 1-methyl-3(3'-dimethylaminopropyl)-carbodiimide hydrochloride 
D: 2,4-dichloro-6-(2'-methoxy)-ethoxy-1,3,5-triazine 
E: 2,4-dichloro-6-isopropoxy-1,3,5-triazine. 
As the results show, the hardening action of the compounds according to the 
invention sets in only slowly when they are in a state of solution and it 
only comes fully into effect after the materials have dried. This means 
that the hardeners according to the invention can be added to casting 
solutions even at higher gelatine concentrations without the gelatine 
being cross-linked within 5 hours or undergoing too much increase in its 
viscosity. The hardeners according to the invention therefore do not 
require the use of dosing devices or other technical apparatus designed to 
add the hardener immediately before casting. 
EXAMPLE 5 
An unsensitised silver bromide emulsion layer is applied to a paper 
substrate which has been laminated with polyethylene and covered with a 
bonding layer, and the emulsion layer is dried. Hardening is carried out 
by application of a 3% aqueous solution of compounds 1, 2, 13, 15, 16, 18, 
20, 22, 25, 44 and 55 according to the invention, followed by drying. For 
comparison, another emulsion layer is hardened with 0.5% formaldehyde as 
casting additive and another with 0.5% of 
6-methoxyethoxy-2,4-dichlorotriazine. 
The samples are stored for 1, 3 and 5 days and then exposed under a step 
wedge and processed at 25.degree. C as follows: 
Developer: 
3 g of hydroquinone, 
1 g of p-methylaminophenol, 
13 g of anhydrous sodium sulphite, 23 g of anhydrous sodium carbonate, 
1 g of potassium bromide made up with water to 1000 ml. 
Processing: 
2 minutes at 25.degree. C. 
Short stop bath: 
2% acetic acid solution, 1 minute at 25.degree. C. 
Fixing bath: 
200 g of sodium thiosulphate, 
20 g of potassium metabisulphite, water up to 1000 ml 
Processing: 
5 minutes at 25.degree. C 
Washing: 15 minutes at 20.degree. C. 
The following results are obtained: 
The speed is constant after 1 day when compounds 1, 2, 13, 15, 16, 20, 22, 
25 and 44 are used and after 3 days and when compounds 18 and 55 are used. 
Swelling factor and speed undergo no further changes. 
In samples hardened with formaldehyde or alkoxy dichlorotriazine hardeners, 
some loss in speed could still be observed after 8 days. The final speed 
was practically the same in all of the samples. 
It follows that the compounds according to the invention enable the final 
hardness to be rapidly obtained and give rise to photographic products 
with constant speed over a prolonged storage time. 
EXAMPLE 6 
A colour reversal film is prepared by applying the following layers in 
succession on a cellulose acetate substrate: 
1. A red-sensitive silver iodobromide emulsion (70 g of gelatine, 32 g of 
silver (96% silver bromide, 4% silver iodide) per kg, 6 g of a cyan 
coupler of the formula 
##STR77## 
24 g of cyan coupler of the formula 
##STR78## 
silver application 0.9 g/m.sup.2 ; 
2. An interlayer containing 3 g of polymeric white coupler of the formula 
##STR79## 
per kg of casting solution; 
3. A green-sensitised silver iodobromide emulsion (96% AgBr, 4% AgI) 
containing, per kg of emulsion, 70 g of gelatine, 32 g of silver, 25 g of 
a magenta coupler of the formula 
##STR80## 
silver application 0.9 g/m.sup.2 ; 
4. A silver filter layer containing colloidal silver obtained from 1.8 g of 
silver nitrate in 12 g of gelatine per 1000 ml. Colour density 0.6 
(measured behind blue filter); 
5. A non-sensitised silver iodobromide emulsion with an iodide content of 
2%, containing, per kg, 110 g of gelatine, 70 g of silver and 45 g of a 
yellow coupler of the formula 
##STR81## 
silver application 1.3 g/m.sup.2. 
The material is hardened by bathing it in a 2%-solution of compound 15. 
A second reversal material is built up in a similar manner, with the 
difference that the red-sensitised and the green-sensitised emulsion layer 
and the interlayers contain 0.4% of 
1,3,5-tris-acryloyl-hexahydro-5-triazine, based on gelatine, and the 
non-sensitised layer contains 0.6% of tris-acryloylhexahydro-5-triazine as 
hardener. 
Two lengths of film are obtained, from each of which a sample is exposed 
behind a graduated wedge after 1 day, 8 days and 28 days' storage at room 
temperature and then subjected to reversal processing as described below. 
One further sample from each film length is stored moist at 35.degree. C 
and 80% relative humidity for 3 days. 
Processing: 20.degree. C. 
Black-and-white developer: (7 minutes) 
300 ml of distilled water, 
2g of sodium hexametaphosphate, 
2.3 g of p-methylaminophenol, 
50 g of sodium sulphite anhydrous, 
6.6 g of hydroquinone, 
50 g of sodium carbonate anhydrous, 
3.5 g of potassium thiocyanate, 
1.8 g of potassium bromide, 
0.008 g of potassium iodide, made up with water to 1000 ml: pH 10. 
Short stop bath: (5minutes) 
300 ml of distilled water, 
30 g of sodium acetate crysrallised, 
5 ml of acetic acid made up to 100 ml with water: pH 5. 
Washing: 10 minutes 
Reversal exposure: 2 minutes 
Colour development: 18 minutes 
300 ml of distilled water, 
2 g of nitrilotriacetic acid, 
3.5 g of N,N-diethyl-p-phenylenediamine, 
20 g of trisodium phosphate, 
0.7 g of potassium bromide, 
0.8 g of hydroxylamine hydrochloride, made up to 1000 ml with water: pH 
11.7. 
Washing: 5 minutes, 
Bleaching bath: 5 minutes 
8 g of potassium ferricyanide, 20 g of potassium bromide, 12 g of disodium 
phosphate made up to 1000 ml with water, adjusted to pH 5.2 with acetic 
acid. 
Washing: 5 minutes 
Fixing bath: 5 minutes 150 g of ammonium thiosulphate, 
10 g of sodium sulphite anhydrous, 
2 g of sodium hexametaphosphate made up to 1000 ml with water: pH 7. 
Final washing: 5 minutes. 
The photographic assessment shows that the sample which has been hardened 
with compound 15 according to the invention reaches it final speed after 
only 1 day and has been hardened fast to boiling. No loss of speed by 
subsequent further hardening is observed. 
The sample which has been hardened with conventional hardener has a layer 
melting point of 40.degree. C after 1 day and 8 days, and the sample which 
has been hardened for 28 days shows a distinct loss in speed compared with 
that of the fresh sample. The general speed of the sample when fresh is 
higher than that of the material which has been hardened with the compound 
according to the invention. 
Both film samples have the same final speed after 3 days' storage in a 
moist atmosphere. Reversal fog, maximum density loss and gradation changes 
do not occur.