| 摘要 |
<PICT:0812415/IV (a)/1> <PICT:0812415/IV (a)/2> Film-forming material dissolved in a volatile solvent is deposited on a casting surface, part of the solvent is evaporated to provide a selfsustaining film or sheet, and the latter is stripped from the casting surface, a stream of a gaseous medium being directed during the stripping against the surface of the film or sheet that has been in contact with the casting surface. As shown, film-forming material, e.g. a solution of cellulose acetate, propionate, butyrate, acetate propionate, acetate butyrate or nitrate in acetone, methylene chloride or mixtures of methylene chloride and methanol, ethanol, propanol or butanol, or of vinyl chloride in ethyl methyl ketone, or of ethyl cellulose in a benzene-ethyl alcohol mixture, is deposited from a hopper 12 upon a rotating casting wheel 11 which is partially surrounded by a chamber 14 through which an evaporative medium is circulated. The self-sustaining film or sheet is stripped at 17 while a stream of air from a supply 19 is being directed against that surface of the film previously in contact with the drum 11. The film passes through stripping rollers 18 and a heated drying chamber to remove the residual solvent. Film thus prepared has a matt surface. The air from 19 is directed through a series of nozzles 25 in a flat stream against the film. Valves 26 may isolate certain nozzles to produce a pattern effect. The general pressure of the air and thus the matting effect may be varied by use of a valve 22. The angle between the stripped film and the tangent to the casting surface at the stripping point should be between 80 and 120 degrees. Examples are given in which a matting effect is produced when the amount of residual solvent in the stripped film is of the order 24 per cent by weight.
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