| 摘要 |
961,494. Polytetrafluoroethylene films. SUMITOMO ELECTRIC INDUSTRIES Ltd. Jan. 5, 1962 [Jan. 14, 1961], No. 583/62. Heading B5B. Sintered polytetrafluoroethylene films are made by pouring fine polytetrafluoroethylene powder combined with a lubricant on to a sheet, passing the sheet through compression rollers so as to form a thin and uniform film of lubricant - containing polytetrafluoroethylene, removing the lubricant, sintering and separating the sintered polytetrafluoroethylene film from the sheet. Sintering is preferably effected at a temperature of at least 327 ‹ C. Specified lubricants include solvent naphtha, white oil, toluene, solutions of polyisobutylene in these solvents, and alcohols and esters. Suitably, 10-30 g. of lubricant is mixed with 100 g. of the polytetrafluoroethylene powder. Mixing the powder and lubricant may be effected in a rotating or tumbling vessel. The sheet may be of metal, plastic, paper or fabric, heat-resistant materials being preferred, e.g. stainless steel, aluminium, polyimide resin, polybenzimidazol resin, glass-fibre cloth, carbonized fibre cloth and polyimide resin-coated fabric. The compression rolling causes the formation of a fibrous structure in the polytetrafluoroethylene, orientated in the machine direction. Lubricant is removed by heating or by solvent extraction and the film and sheet are then heated to sinter the polytetrafluoroethylene film, which may then be peeled off the sheet. As shown, the lubricant - containing polytetrafluoroethylene powder 2 is poured on to a sheet 3, and passed through compression rollers 1, 1. Lubricant is removed by passing the sheet through the drying oven 5 and sintering is effected in sintering oven 6. The film 7 is then separated from the sheet 3. |
