| abstract |
Porous membranes having a micro phase separationnstructure and showing a light transmittance at thenwavelength of 400 nm of not less than 30% are obtained bynthe dry phase conversion method comprising drying a coatingnlayer of a dope containing a polymer, a good solvent fornthe polymer and a poor solvent for the polymer which solventnhas a higher boiling point than the good solvent. Thenpolymer includes cellulose derivatives, vinyl-seriesnpolymers such as acrylonitrile-series polymers andn(meth)acrylic acid ester-series polymers, polysulfone-seriesnpolymers, and the like. The porous polymernmembranes have a porosity of 10 to 60%, a mean pore sizenof about 0.002 to 0.35 µm and a maximum pore size of notngreater than 0.4 µm. These porous membranes shows not onlynexcellent transparency but also high productivity. |