GB540530A - Improvements in the production of sheets from transparent water-resistant organic film-forming substances - Google Patents

Abstract

540,530. Artificial sheets. ROONEY, J. H., HAWTIN, P. R., and SHAW, B. April 18, 1940, No. 7017. [Class 2 (ii)] A sheet is formed from transparent waterresistant organic film-forming substance by depositing a solution of the substance in a volatile solvent on the surface of a solid support to which the substance adheres, removing volatile solvent from the solution and stripping the sheet so formed from the support, the stripping being facilitated by soaking the sheet, while still attached to its support, in a bath containing liquid adapted to change the dimensions of the sheet ; the process may be applied to the production of sheets from esters, ethers, mixed esters, mixed ethers and ester-ethers of cellulose, polyvinyl derivatives, ethers of polyvinyl alcohol, poly-methyl methacrylate, resins of the polystyrene series and co-polymers of two or more polymerized vinyl derivatives or similar polymers of unsaturated substances. A cellulose acetate sheet may be stripped from its glass support by soaking it in water which has a slight swelling action on the cellulose acetate and the evaporation of the volatile solvent of the dope may be carried much further than usual before the stripping treatment thus shortening the time required for seasoning. The sheet may be built up to a thickness of at least 0.05inch by the successive formation of a number of layers one upon another, each layer being deprived of the bulk of its volatile solvent before the formation of the next layer ; the sheet may be loosened from its support by immersing it in an aqueous bath while it contains about 10-15 per cent of water-soluble volatile solvent, stripped from the support and dried, while held flat, in a current of warm air. Specifications 483,242, 533,788, 533,789 and 538,024 are referred to.