| 摘要 |
A microporous membrane is produced by cooling a solution comprising a vinylidene fluoride homopolymer or copolymer having a weight average molecular weight of 1 x 10<5> or more and a solvent therefor, to form a two-phase gel, said microporous membrane comprising a polymer phase comprising said vinylidene fluoride homopolymer or copolymer, and intercommunicating voids which have an average pore size measured by the half-dry method of 0.005 to 5 mu m and range from one side of the membrane to the other side, and said microporous membrane having as its internal structure a percolation structure in which the polymer phase forms an isotropic network structure by three-dimensional branching in arbitrary directions, the voids are formed by surrounding by said polymer phase of the network structure and intercommunicate with one another, and the ratio of the maximum pore size measured by the bubble point method to the average pore size measured by the half-dry method is 2.0 or less. <IMAGE> |
