| 摘要 |
Microporous polymer films are made by coating a substrate with a polymer dispersion and heating to gel the polymer and dry the film while maintaining above the film an atmosphere which is more than 90% but less than 100% saturated with the vapour of the dispersion medium. The substrate may form part of the finished product, in which case a tie coat is first applied, or may be such, e.g. a silicone coated paper, that the resulting film can be stripped therefrom. The dispersion medium is preferably water. Pore size may be controlled by the viscosity of the dispersion, by the addition of vapour (other than that arising from the film) and by the temperature. Examples are given of the production of porous films from carboxylated butadiene/acrylonitrile rubber (on a cellulosic substrate impregnated with a styrene/butadiene polymer tie coat), polyvinyl acetate (on a paper substrate), neoprene (on paper), carboxylated butadiene/acrylonitrile rubber (self-supporting film) and vinyl acetate/dibutyl-maleate copolymer (on a cellulosic substrate impregnated with a styrene/butadiene tie coat). Measured pore sizes vary from 0.0125 mm. to 0.075 mm. with the pores occupying a few per cent of the surface area. Film thicknesses specified are 1 to 5 mils.ALSO:Microporous polymer films are made by coating a substrate with a polymer dispersion and heating to gel the polymer and dry the film while maintaining above the film an atmosphere which is more than 90% but less than 100% saturated with the vapour of the dispersion medium. The substrate may form part of the finished product, in which case a tie coat is first applied, or may be such, e.g. a silicone coated paper, that the resulting film can be stripped therefrom. The dispersion medium is preferably water. Pore size may be controlled by the viscosity of the dispersion, by the addition of vapour (other than that arising from the film) and by the temperature. Examples are given of the production of porous films from carboxylated butadiene/acrylonitrile rubber (on a cellulosic substrate impregnated with a styrene/butadiene polymer tie coat), polyvinyl acetate (on a paper substrate), neoprene (on paper), carboxylated butadiene/acrylonitrile rubber (self-supporting film) and vinyl acetate/dibutylmaleate copolymer (on a cellulosic substrate impregnated with a styrene/butadiene tie coat). Measured pore sizes vary from 0.0125 mm to 0.075 mm with the pores occupying a few per cent of the surface area. Film thicknesses specified are 1 to 5 mils. |
