| 摘要 |
<p>1449644 Porous films MATSUSHITA ELECTRIC INDUSTRIAL CO Ltd 17 Aug 1973 [18 Aug 1972 12 Oct 1972] 39081/73 Heading B5B [Also in Division C3] A porous film is prepared by forming a film from a blend of 100 parts by weight of a first polymer composition I and from 30 to 250 parts by weight of a second polymer composition II, stretching the film to increase its dimension in one direction by at least 1À5 times and to increase its surface area by from 2 to 20 times and then treating the stretched film with a liquid or vaporous solvent to swell polymer composition I but to elute the composition II from the film, so leaving a porous film. The size of the pores in the final film may be adjusted by using a copolymer as either I or II and altering the ratio between the components of the copolymer. Specified polymers I are polyethylene, polypropylene, polystyrene, polyvinyl chloride, polycarbonate, polysulphone, polyamide and an ethylene-vinyl acetate copolymer. Exemplified polymers II are polymethyl methacrylate, polystyrene, ethylene-vinyl acetate copolymer and polyethylene oxide. Specified copolymers for adjusting pore size are, ethylene-vinyl acetate, ethylene-propylene, propylene-vinyl chloride, styrene-acrylonitrile, styrene-butadiene, styrene-methyl acrylate and vinyl acetate-ethyl acrylate copolymers.</p> |
