CS220108B1 - Gelatin Substrate for Film Mats - Google Patents

Abstract

The invention belongs to the field of photographic chemistry and raw materials for the production of photographic materials. It solves the problem of stabilization and photochemical inertness of gelatin subtractions used for surface treatment of film substrates, with the aim of ensuring sufficient adhesion between the light-sensitive layer and the film substrate. The essence of the invention lies in the fact that as a stabilizer of the gelatin coacervate, which forms the basis of the subtraction solution, esters of unsaturated dibasic acids are used, for example monomethylmaleate or diethylmarate, in an amount of 0.1 to 1.5 parts by weight per 1 part by weight of gelatin.

Description

The invention relates to gelatin substrates for film substrates providing sufficient adhesion between the film substrate and the light-sensitive emulsion. '

In the manufacture of photographic materials, the DC uses a substrate solution containing a hydrophilic polymer, usually gelatin, in a suitable state, to provide sufficient cohesion between the photosensitive emulsion layer and the film backing, usually made of cellulose triacetate, polyethylene terephthalate, polystyrene, or polycarbonate. The optimum solution would be to use a solvent solution which simultaneously dissolves the gelatin and the film former.

Such solvents have been found, for example, ethylene chlorohydrin, phenol and the like, but are not widely used for their toxicity. Therefore, a technique for the preparation of gelatin coacervate has been gradually developed by dispersing a concentrated aqueous gelatin solution in a mixture of suitable non-toxic or less harmful solvents which causes swelling to dissolution of the film-forming polymer in the mixture.

Such a dispersion itself is a completely unstable formation and already during preparation, the gelatin solution droplets agglomerate and separate into a separate phase. Therefore, the droplets of a concentrated, aqueous gelatin solution must be effectively stabilized. Acetic, salicylic, phthalic, trichloroacetic, acetylsalicylic and many others are commonly used to stabilize them. The decisive factor here is to maintain the pH of the coacarate sufficiently far from the isoelectric point of gelatin.

While this stabilization is versatile and sufficiently effective, it is generally reported that the acidic environment has a negative effect on the photographic emulsion, particularly when using high-sensitivity emulsions. It manifests as surface desensitization and accelerated aging of emulsions. In addition, there is also a tendency towards corrosion of the metal parts of the equipment with which the solution comes into contact and the associated secondary effect of the metal ions on the emulsion, especially in the wet treatment of photomaterials.

Substrates stabilized with basic stabilizers, in particular pyridine and pyroline, have also been tested, but have proven to be insufficiently stable, especially during deposition. Even the slightest hint of sedimentation results in reduced adhesion of the emulsion layer and local washout of the emulsion when processed in solutions.

A common negative element is furthermore the interaction of compounds of both kinds with the saline components of the emulsion, where the pH can be localized and both the photochemical properties of the product and the physical-mechanical properties of the interlayer, in particular the adhesion forces, can be affected.

These drawbacks are overcome by gelatin substrates for gelatin coacervate based film substrates and mixtures of organic solvents, in particular C 1 -C 4 aliphatic alcohols, e.g. characterized in that the substrate comprises a gelatin coacervate stabilizer based on unsaturated dibasic acid esters, for example monomethyl maleate or diethyl fumarate, in an amount of 0.1 to 1.5 parts by weight, based on 1 part by weight of gelatin.

An advantage of the invention is that dibasic unsaturated acid esters are perfectly soluble in lower alcohols and have proven to be excellent stabilizers of coacervates of this type. Their pH ranges from 5.8 to 6.5, they are completely photochemically inert and are not sensitive to the presence of inorganic salts, i.e. up to several times the amount of electrolyte required to induce sedimentation and precipitation of coacervate compared to commonly stabilized substrates. Storage of such stabilized substrate solutions at normal temperature is almost unlimited in time.

In stabilizing gelatin coacervate, either directly pure dibasic acid esters can be used or prepared during the technological process of preparing the substrate solution by interaction of the alcohol used with the anhydride of the acid, for example maleic anhydride.

The actual preparation of the substrate consists of preparing an aqueous gelatin solution by stirring or melting the gelatin at temperatures of 40 to 70 ° C in water and then mixing with the stabilizer solution.

For example, a stabilizer solution is prepared by dissolving maleic anhydride in methanol at 40 ° C with stirring and stirring the solution at this temperature for at least 1 hour. It is then slowly added to the gelatin solution with vigorous stirring. The thus prepared stock solution is slowly metered into the solvent mixture. A highly stable gelatin coacervate is formed which is further treated as necessary with a gelatin hardener, for example formaldehyde.

The process for preparing substrates for film substrates is explained in more detail in the examples.

Example 1

In a mixer, a solution containing 60 ° C is prepared at 60 ° C

8.5 g of gelatin and g of distilled water, to which a warm solution consisting of g of methyl alcohol is slowly added under intensive stirring, and

2.6 g of diethyl fumarate.

The stock solution thus prepared is added to the solvent mixture formed over 220 minutes with vigorous stirring

190 g methyl alcohol,

520 g acetone,

0,6 g of formaldehyde and

105 g of ethyl acetate.

The prepared substrate solution was stirred for 1 hour and used to coat the polycarbonate sheet. The solution is stable in storage and processing and ensures good adhesion of the light-sensitive layer to the substrate.

Example 2

In a mixer at 60 ° C, the kg of gelatin in kg of water is melted and mixed.

At the same time, a solution containing kg of methyl alcohol and kg of monoethyl maleate at 40 ° C is prepared in another mixer. The stabilizer solution is slowly added to the gelatin solution with vigorous stirring. The resulting stock solution is then metered very slowly into the solvent mixture formed with stirring

600 kg of methyl alcohol,

105 kg acetone, kg formaldehyde and kg butyl acetate.

The finished substrate solution was stirred for 1 hour

The mixture was cooled to 25 ° C. It is applied to a polyethylene terephthalate substrate, pre-coated with a vinyl chloride-vinylidene chloride copolymer.

Example 3

Allow to swell in the mixer for 45 minutes

1.5 kg of gelatine in

7.5 kg of distilled water and then heated to 40 ° C and mixed until the gelatin is completely dissolved.

At the same time it dissolves in another mixer

0,7 kg maleic anhydride v

8.8 kg of methanol.

The solution is stirred at 40 ° C for at least 1 hour. It is then metered into the gelatin solution with a slow stream of stirring.

The resulting stock solution is slowly added with vigorous stirring to a solvent mixture of kg methanol,

175 kg acetone and kg dichloromethane.

The finished substrate solution was stirred for 1 hour and cooled to 20 ° C. It is applied on triacetate cellulose foil, where it ensures high adhesion of the light-sensitive emulsion to the substrate. The solution is stable during storage and processing.

Claims (1)

Subject Gelatin substrates for gelatin coacervate film substrates and mixtures of organic solvents, in particular C 1 to C 4 aliphatic alcohols, for example methanol, aliphatic ketones such as acetone, acetic esters such as ethyl acetate and aliphatic hydrocarbon halo derivatives of lyses such as dichloromethane, the gelatin coacervate stabilizer based on unsaturated dibasic acid esters, for example monomethyl maleate or diethyl fumarate, in an amount of 0.1 to 1.5 parts by weight based on 1 part by weight of gelatin.