Improvements in or relating to the manufacture of transparent cellulosic sheets and films

Abstract

Abstract Cellulosic sheets and films having improved resistance to the effects of low humidity and having good surface properties are made by incorporating in the sheet or film such a high proportion of softener as would normally cause surface tackiness and adhesion, and applying to the surface an aqueous suspension or emulsion which comprises predominantly a soap and/or a wax, with or without a smaller proportion of a resin. The proportion of softener, which is preferably glycerol, may be from 15 to 25 per cent of the weight of the sheet or film. In a modification, there is applied to cellulosic sheets to increase their slipperiness one over another, an agent which comprises predominantly a soap, with or without a normally solid wax, and with or without a smaller proportion of a resin. The process is applicable to sheets of regenerated cellulose and to sheets obtained from aqueous cellulosic dispersions including cellulose ethers such as glycol cellulose, lowly substituted methyl and ethyl cellulose, cellulose glycollic acid, cellulose phthalic acid, and lowly esterified cellulose esters and ether-esters. Suitable soaps are sodium and potassium stearates, oleates, laurates, and ricinoleates, triethanolamine soaps, sodium sulphuric acid esters of stearyl, oleyl, lauryl, cetyl and myristyl alcohols, and sodium petroleum sulphonate. Waxes specified are hydrogenated oils, higher fatty acids, wax-like fatty acid esters; higher alcohols, paraffin wax, montan wax, and shellac wax, and suitable resins are natural shellac, cumar resin, rosin, and sodium salts of abietic acid. The anti-sticking agents may be applied together with or after the softening agent. A number of examples are given. Specification 472,265 is referred to.

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