| 摘要 |
1,248,214. Porous films. KANEGAFUCHI BOSEKI K.K. 18 Nov., 1968 [18 Nov., 1967], No. 54710/68. Heading B5B. [Also in Division B2] A porous film is produced by coating a solution, in a hygroscopic organic solvent, of a polyurethane containing from 1 to 30% by weight of the polyurethane, of at least one acid selected from stearic, myristic, palmitic, lauric and oleic acids, on to at at least one surface of a plate, coagulating the polymer with an aqueous solution of an inorganic salt, and removing the porous film from the plate. The inorganic salt may be sodium sulphate, sodium chloride, ammonium sulphate or a mixture thereof, and may be in the range of less than 2/3 saturation concentration. The acid may be present from 5 to 20% by wt. of the polyurethane. The temperature of the coagulating medium may be from 5‹ to 50‹ C. The polyurethane may be present from 10 to 40% by wt. of the solvent. The coating solution may also contain at least one another film forming polymer, e.g. vinyl polymers such as polyvinyl chloride, polyvinyl alcohol, polyacrylonitrile, polyacrylic esters, polyacrylic acid, and copolymers thereof. The plate may be of glass or metal. The coating may be applied by knife, roller, or spray coating. |
