| 摘要 |
1,099,246. Making films of organic or organosilicon polymers. DOW CORNING CORPORATION. Sept. 19, 1966 [Oct. 1, 1965], No. 41773/66. Heading B5B. Films are made from organic or organosilicon polymers which are soluble in volatile organic solvents by forming a 0À2 to 50% by weight solution of the polymer in a volatile organic solvent, placing the solution in contact with a membrane which is permeable to the solvent but not to the polymer, and to which the polymer film to be formed does not adhere, drawing the solvent through the membrane by means of a partial vacuum applied to the other side of the membrane thereby leaving a polymer film in the membrane, and removing the film from the membrane. The polymers used may be infusible at temperatures up to and above 300‹ C. and may be members of the group of organo-polysiloxanes known as phenylsilsesquioxanes, which are infusible at temperatures in excess of 350‹ C. and are readily soluble in solvents such as benzene. The films may be made by means of an apparatus comprising a housing, a support grid in the housing, a silicone rubber membrane supported by the grid and sealed against the housing, and means for producing a partial vacuum in the housing on one side of the silicone rubber membrane whereby solvent may be drawn through the membrane from a solvent-polymer solution. In operation the silicone rubber membrane is first removed from the housing, and swelled by immersion in an organic solvent such as benzene or Stoddard solvent for several hours. The sheet is then replaced on the support grid in the housing and the polymer solution, for example, a 5% by weight solution of a poly (phenylsilsesquioxane), is poured on to the membrane and a partial vacuum (e.g. 7-8 mm. Hg pressure absolute) is applied to the portion of the housing below the membrane and its support grid. When all the solvent has been removed a smooth and wrinkle-free film of the polymer which does not adhere to the membrane remains on the upper surface of the membrane and is stripped from the latter after the pressure in the portion of the housing below the supported membrane is restored to atmospheric. The films may be mass produced by means of an apparatus comprising a drum rotatable about its horizontal axis and having a perforated periphery covered with a membrane permeable to the solvent but not the polymer. The drum is partially immersed in a tank of a solution of the polymer in an organic solvent. A series of heating coils are located around the inner surface of the periphery of the drum and a partial vacuum is applied to the interior of the drum. The polymeric film thereby left on the peripheral surface of the drum as it rotates is continuously stripped from the drum and wound on rolls. |
