DE2830917A1 - Incorporation of hydrophobic organic additives - into hydrophilic colloidal dispersions, using liq. prepolymers of conjugated diene(s) or vinyl monomers as solvent - Google Patents

Abstract

Organic additives, esp. hydrophobic colour couplers, are introduced into hydrophilic colloidal layers by dispersion in colour photographic Ag halide materials contg. aq. gelatine or other hydrophilic binders. The high boiling solvent used to introduce the organic additive is a prepolymer of a conjugated diene and/or a vinyl monomer having a molecular wt. of 250-25000 (500-5000). The high molecular solvent is used in an amt. of 5-50 (5-30) wt. % on the hydrophilic binder. The solvents are useful for incorporating organic additives such as colour couplers, dyes, stabilizers, UV absorbers, optical brighteners, etc., into colloidal hydrophilic layers such as photographic emulsions. The solvents have good solvent power for the additives and prevent diffusion of the materials into neighbouring layers, thus giving e.g. good colour sepn. in the photographic image. Recrystallisation of the additives is avoided, so that they retain their activity.

Description

Process for the introduction of organic

Additions in hydrophilic colloid layers Field of application of the invention The invention relates to a method for introducing organic additives into hydrophilic colloid layers, especially the incorporation of hydrophobic color couplers by dispersing it in gelatin or other hydrophilic binders for color photography Silver halide materials.

Characteristics of the known technical solutions During manufacture of color photographic silver halide materials must have numerous additives in effective relationship with one or more hydrophilic colloid layers of the material to be brought. Such additives include color couplers, colorless couplers, mask compounds, Dyes, stabilizers, ultraviolet absorbing agents, optical brighteners, etc. To ensure good color separation, z.3. the color couplers fail the photosensitive silver halide emulsion diffuse and not agglomerate. A commonly used method for making such additives diffusible is the combination of such additives with long straight-chain or branched, aliphatic Groups with 5-20 hydrocarbon atoms.

The presence of these diffusion-proofing groups gives the Molecules have a hydrophobic character, which leads to difficulties in their introduction leads to aqueous, hydrophilic holloid compositions. Well-known procedures, such as they are described e.g. in DT-OS 2 136 492, use high-speed agitators for dispersing the hydrophobic color couplers. According to this Dispelgiertechnik the couplers dissolved in water-immiscible, high-boiling solvent and added to the aqueous, hydrophilic phase. The mixture is then homogenized using a homogenizer converted into a dispersion. Examples of solvents used are alkyl phosphates such as tricresyl phosphate, Di-n-butyl phthalate, cyclic hydrocarbons, oils, natural fat or formamide derivatives used. Often the coupler dissolves in the high-boiling solvent by adding a low-boiling co-solvent such as ethyl acetate. These cosolvents are removed from the solvent by washing or by distillation Dispersion removed. To ensure adequate stability of the dispersions and to achieve a sufficiently small particle size, the aqueous, hydrophilic Phase, which is preferably gelatin, also added wetting agent.

However, a number of difficulties arise with the known dispersion techniques such as recrystallization of the coupler due to the limited solubility in the known high-boiling solvents. This recrystallization leads alongside a reduced Re activity in the color-forming. Reaction to decreased Color formation and cloudiness. This means that there is storage time as well as coupler concentration limited in the dispersion.

Object of the invention The object of the invention is an improved method for introducing organic additives into hydrophilic colloid layers, preferably of hydrophobic color couplers in gelatine or other hydrophilic binders, the disadvantages of known processes such as recrystallization of organic additives, Reduced storage time of the dispersions as well as cloudiness in the photographs Layers, eliminated.

Statement of the essence of the invention The object of the invention is to be found based on finding new high-boiling solvents for organic additives in which these have improved solubility and in which the tendency to crystallize of organic additives is reduced.

Surprisingly, it has been found that when using prepolymers based on conjugated dienes and / or vinyl monomers as high-boiling solvents, especially when introducing hydrophobic color couplers into aqueous gelatine, whose tendency to crystallize is prevented.

According to the invention, e.g. low molecular weight prepolymers are suitable as prepolymers Polybutadiene, polyisoprene, polyacrylic acid esters, polymethacrylic acid esters and their Mixtures with or without functional groups with a molecular weight of 250-25 000, preferably 500-5000. Functional groups that can be, for example, hydroxyl, carboxyl or halogen end groups. Preferably liquid, carboxyl groups containing. Polybutadiene used.

In the photographic layers can be 50 (, preferably 5-30 % of the dry weight of the gelatin that polymers of the invention can be introduced without any photographic disadvantages.

The PrEpolymers are still known for the purpose of improved dispersibility be diluted with low-boiling solvents such as ethyl acetate, whose Removal from the dispersants after dispersing by distillation or other means suitable separation methods takes place. In addition, anion-active, cation-active or nonionic wetting agents can be used as dispersing aids.

Gelatin is preferably used for all hydrophilic colloids. That However, the process according to the invention is also suitable for dispersing processes in water-soluble synthetic high polymers, such as. Polyvinyl alcohol, polyvinyl pyrrolidone, polyacrylamide or their mixtures with gelatin.

The advantage of the method according to the invention for introducing organic Additions to hydrophilic colloid layers consist in improved incorporation. The result is stable dispersions with an average particle size of less than 0.15 µ. The method also allows the refractive index of the solution of organic additives in the prepolymer to match that of the gelatin, creating a wide variation in particle size the Dispergate is given. Compared to known methods, the tendency to crystallize of the organic additives in the photographic layers are suppressed and thus a improved storage stability with little influence on the viscosity of the casting composition achieved. The prepolymers also ensure improved diffusion resistance of additives, so that certain hydrophobic color couplers with alkyl chain lengths of C-5 up to C-8 can be used. The method also enables manufacture of dispersants with increased concentration of organic additives, in particular of hydrophobic color couplers during manufacture of photographic Silver halide material. Another advantage is that the Prepolymers cause plasticization of the layers. In addition, do not step as when using dibutyl phthalate as a high-boiling solvent, displacement reactions of the sensitizers from the silver grain. Exudation of the prepolymers from the Gelatin layers, as is the case with other substances, e.g.

Dibutyl phosphate, tricresyl phosphate is observed, does not occur.

Working Examples Example 1 6 g of a naphthol color coupler are used in a mixture of 20 ml of ethyl acetate and 3.8 g of liquid polybutadiene with a Dissolved carboxyl content of 2.4% and a molecular weight of 2,800 and 0.2 g of an anion-active wetting agent are added. The solution formed is by means of a High-speed stirrer mixed with 70 ml of 11.5% strength aqueous gelatin solution at 50 ° C. After the mixture has been homogenized for 3 minutes, it is reduced at 50 ° C. under reduced pressure The ethyl acetate is removed under pressure and the dispersion obtained is stored at 5 ° C. Man receives a homogeneous dispersion that does not have any tendency to crystallize after 9 months shows and by gentle stirring with a ready-to-pour gelatin-silver halide emulsion can be mixed. The mean particle diameter (electron microscopic Evaluation of the prepolymer droplets containing the color coupler is 0.12> i.

Example 2 The procedure of Example 1 is repeated, wherein instead of prepolymers, 3.8 g of dibutyl phthalate is used. A homogeneous one is obtained Dispersion with an average particle diameter of 0.1 g.

After 9 months of storage, a considerable part of the crystallized Naphtolfarbkunstlers, so that a material unusable for photographic layers arises.

Example 3 To 550 g of a highly sensitive photographic positive emulsion, the 3.5 g of silver iodobromide (with 2 mol of recent silver iodide) are 80 ml 0.3% methanolic solution of an optical sensitizer, 10 ml of a 1% aqueous solution of a 1,3,4-triazaindolizine, 240 g prepared according to Example 1 Disperse and 2 @ ml of a 2% solution of the sodium salt of 2-p-toluenesulfamido-4,6-dichloro-s-triazine given and mixed at pH 5.5 and a temperature of 40 °. According to conventional Application of the casting composition on a cellulose triacetate carrier and tank development at 20 ° C. the photographic properties summarized in Table 1 are obtained.

Example 4 A photographic material is produced analogously to Example 3, Jednch a dispersate is used in which the high-boiling solvent is dibutyl phthalate was used.

The photographic properties obtained are for comparison in Table 1 listed.

Table 1 material according to example 3 4 relative sensitivity 100% 87% gradation 4.8 3.5 0.06 0.06

Claims (3)

E r f i n d u n g s a n p r ü c h e 1) Method of introduction organic additives in hydrophilic colloid layers, preferably for incorporation of hydrophobic color couplers by dispersing in aqueous gelatin or others hydrophilic binders for color photographic silver halide material, marked in that prepolymers are used as the high-boiling solvent for the organic additives based on conjugated dienes and / or vinyl monomers with a molecular weight from 250-25,000, preferably from 500 to 5000 in an amount from 5 to 50%, preferably from -5 to 30 % of the dry weight of the hydrophilic binder can be used. 2. The method according to item 1, characterized in that in addition low-boiling solvents such as ethyl acetate can be used. 3. The method according to item 1 to 2, characterized in that the prepolymer preferably liquid polybutadiene containing carboxyl groups is used. will.