GB691833A - Preparation of translucent sheeting - Google Patents

Abstract

<PICT:0691833/IV (a)/1> A sheet having a ground glass appearance translucent surface is prepared by coating one or both sides of the sheet with a liquid composition comprising a solvent capable of softening or partially dissolving the surface of the sheet and also a particulate substance which is capable of decomposing or subliming to a gaseous product, subjecting the coated sheet to an elevated temperature for a sufficient period to cause decomposition or sublimation of a substantial proportion of the substance, whereby gas holes are formed in the surface and immediately adjacent sub-layers of the sheet to produce a regular roughness on the surface giving translucency, and then subjecting the translucent surface to partial clearing by applying a solvent for the sheet so that some of the gas holes are collapsed. The sheet may be films or foils of cellulose acetate, propionate, butyrate, or acetate butyrate, cellulose ether, or copolymer of vinyl chloride and vinyl acetate ("Vinylite" Registered Trade Mark), and may be pigmented, e.g. with titanium dioxide. The substance may be substantially solvent insoluble ammonium carbonate, bicarbonate, carbamate, benzoate, salicylate, or hydrosulphide decomposing or subliming between 140 DEG and 250 DEG F. and 50 per cent should have a particle size not greater than 0.003 inch. Sheet of film is drawn from roll 2 over idler rolls to coating mechanism 8 for application of the substance dispersed in a liquid containing a small amount of the base film material, which liquid by softening the surface of the sheet causes penetration of the substance below the surface. A suitable liquid is methanol, glycol monomethyl ether and ethylene dichloride mixture, and an alternative mixture contains ground glass, acetic acid, water and acetone in addition. The coated sheet is partly dried and passes to heating chamber 12 at above 150 DEG F. The coated sheet then passes round idler rolls to coating device 31 where methanol, acetone, hydrocarbon, or ethyl acetate or mixtures thereof clearing solvent, which may be diluted with water, is applied; the mixture or dilution of the solvent is selected depending on the amount of clearing required.