| abstract |
A solution (11) comprising an organic solvent, a polymer, and a plasticizer (TPP, BDP, etc.), the amount of the plasticizer being 0.01-50 wt.% based on the polymer, is cast on an endless belt (51). The solution (11) thus cast becomes a cast film (22). Due to dew condensation, waterdrops are formed on the cast film (22) passing through a first area (46). The waterdrops on the cast film (22) passing through a second area (47) grow and, simultaneously therewith, the organic solvent vaporizes. The waterdrops on the cast film (22) passing through a third area (48) vaporize. The cast film (22) which has passed through the third area (48) is peeled off the endless belt (51) with a stripping roller (57) to obtain a porous film (17) rich in flexibility. |