DE740796C - Process for the production of barite on papers for photographic purposes - Google Patents

Description

Process for the production of barite on papers for photographic purposes Purposes The invention relates to a process for the production of baryta on photographic Papers to which gelatin-free halogen silver emulsions can be applied.

It is known to use simple or mixed cellulose esters as binders to use for the barytage, on which silver halide gelatin ions are layered will.

In the case of gelatin-free halogen silver emulsions, however, it has been found that the sensitizing dyes or other substances in the barvtage or even into the papers or, conversely, harmful substances from the papers into the emulsions hike over.

This' disadvantage is overcome according to the invention in that such simple or mixed cellulose esters can be used, which are produced by extensive hydrolysis sensitive to water but not yet soluble in water.

The barium sulfate is applied to the papers from a dispersion, which is a cell silose ester of the type mentioned and a mixture as a solvent of water with a volatile organic solvent, e.g. B. a lower one Alcohol, it being possible for a plasticizer to be present in the solution.

The esters used are cellulose acetates with an acetyl content between rg and 30 %, as well as mixed esters, such as cellulose acetate propionate or cellulose acetate butyrate, which have a water sensitivity similar to that of the acetates mentioned.

The cellulose esters can have higher or lower viscosity, whereas those with a lower viscosity are to be preferred because barite coatings, Which Contain esters of low viscosity, can be applied with less solvent can.

The new coatings can also be applied several times on top of one another to reinforce them, whereby the solid matter content in the individual layers can change. EXAMPLE 100 parts of ethyl alcohol and 70 parts of water are simultaneously added to 3o parts of a 10% strength solution of a largely hydrolyzed cellulose acetate with an acetyl content of 25 ', l, this cellulose acetate being dispersed in a solvent mixture of 10 parts of ethyl alcohol and 7 parts of water . The mass is well stirred; while stirring, 50 parts of barvt white then become. dispersed in 100 parts of a mixture of equal volume of ethyl alcohol and water, added. After thorough stirring, the hasse is then mixed in with 70 parts of an identical 10% cellulose acetate solution as was used before, and the mixture is stirred well. This mixture contains about 100 parts of 100% acetate solution, 120 parts of water, 150 parts of ethyl alcohol and 50 parts of barite white. This dispersion is then brushed onto a paper with high .Mpha-Celltilose-Gelialt, upon which a gelatin-free halogen silver emulsion # -tuf can be applied. EXAMPLE 2 50 parts of acetone and 50 parts of water are added at the same time to 30 parts of a 10% solution of a largely hydrolyzed cellulose acetate propiotate, 17% acetyl and 9 % propionyl, which is dispersed in a mixture of equal amounts of water and acetone. The mass is stirred and then a dispersion of 50 parts of barley white in 50 parts of acetone and 50 parts of water is added. After thorough stirring, the mass is then added to 70 parts of the same 10% cellulose acetate propionate solution that has already been used, and the mixture is further stirred very well; it is then brushed onto the paper layer, onto which a gelatin-free emulsion can then be poured perfectly.

The production of the cellulose esters used here is described in American patent specification 2 129 05 2, the Hvdrolvse was canceled before the water solubility was reached.

On photographic papers, «- moose using after Paper prepared according to the method according to the invention, can be clear and sharp images achieved «- earth. The sensitizing dyes neither penetrate into the bar floor into the paper. The new bar floor can also contain gelatine Emulsions are used, although the special part of the new baryages themselves especially with gelatin-free emulsions shows which water-sensitive cell silose ester included as a binder.

Claims (2)

PATENT CLAIMS: i. Process for the production of barite on paper for photographic use using simple or mixed cellulose esters as a binder for the Bartagen, characterized in that such simple or mixed cellulose esters are used, which are water-sensitive due to extensive hydrolysis, but have not yet been made water-soluble. 2. The method according to claim i. characterized in that the barium sulfate is applied from a dispersion. which contains a water-sensitive simple or mixed cellulose ester which has been largely hydrolyzed and, as a solvent, a mixture of water with an organic, volatile solvent such as a lower alcohol. To distinguish the subject of the application from the state of the art, the following publications were considered in the granting procedure: German patent specification. 1 r. 677 37 (); Farbe und Lack, Centralblatt 1940, p. 177; Papier-Zeitung, 1938, pp. 664 to 666.