Patent GB-705159-A (GB)
Title: Anti-static treating composition for photographic film supports and finished films
IPC: C08J7/046
Filed: 1950-06-16
Abstract: An anti-static cellulose acetate composition suitable for treating films of cellulose derivatives is prepared by mixing a solution of cellulose acetate containing a solvent or swelling agent for the film with a dispersion containing poly-(methylene salicylic acid) and calcium silicate dispersed in an aralkyl alcohol of the benzene series.  The cellulose acetate solution may be a 5-15 per cent. solution of a cellulose acetate, containing 45-56 per cent. of combined acetic acid, in a solvent such as methanol, ethanol, benzyl alcohol, acetone or ethylene dichloride or a mixture of such solvents.  The cellulose derivative film base may be cellulose nitrate, acetate, propionate, butyrate, acetatepropionate or acetatebutyrate.  The aralkyl alcohol may be benzyl, phenylethyl, phenylpropyl or cinnamic alcohol or saligenin.  The dispersion of calcium silicate in the alcohol may be prepared by grinding a mixture of 5-30 per cent. by weight of powdered calcium silicate (based on the alcohol) with the alcohol for eight hours in a ball mill.  From 1-10 parts by volume of a 20 per cent. dispersion of calcium silicate in the alcohol may be incorporated in a sufficient volume of cellulose acetate solution to make 1,000 parts of the mixture.  The proportion of poly-(methylene salicylic acid) incorporated into the mixture may be 0.05-1 and preferably 0.1-0.5 per cent. by weight.  In an example, a strip of cellulose nitrate film support is coated with a mixture of 5 parts of a 20 per cent. dispersion of calcium silicate in benzyl alcohol, 1 part of poly-(methylene salicylic acid), 50 parts of a 10 per cent. solution of cellulose acetate in 30 parts of methanol and 70 parts of ethylene dichloride, 400 parts of methanol, 500 parts of ethylene dichloride and 44 parts of benzyl alcohol.  In another example, a strip of cellulose acetate film support is coated with a mixture of 5 parts of a 20 per cent. dispersion of calcium silicate in benzyl alcohol, 2 parts of poly-(methylene salicylic acid), 15 parts of a 10 per cent. solution of cellulose acetate in acetone, and 978 parts of a 50/50 mixture of acetone and ethyl alcohol.  Data are furnished for the static susceptibilities of strips of treated and untreated film, and the treatment of photographic film is referred to (see Group XX).  The poly-(methylene salicylic acid) is prepared by heating together under a reflux condenser for two hours a mixture of salicylic acid and 40 per cent. formaldehyde solution in the presence of a minor proportion of concentrated hydrochloric acid. After standing, the plastic mass formed is separated from the supernatant liquor, washed with water, dissolved in concentrated ammonia, and diluted with water.  The solution is then strongly acidified with hydrochloric acid and agitated with live steam to flocculate the precipitated resin.  The mixture is cooled and the resin is filtered off, washed and dissolved in concentrated caustic soda solution.  The solution is diluted and the resin is reprecipitated with hydrochloric acid, steamed, cooled, filtered, washed and dried first in air and then at 80 DEG -90 DEG C. The steaming operation is said to be important to facilitate filtration.