Patent ID: 7361295

Claim:
A process for solvent casting which comprises casting a dope from a casting die onto a casting support, drying the cast dope on the casting support to form a film, stripping off the film from the casting support, and further drying the film while conveying the film with carrying it at both side edges of the film by a tenter, wherein dry thickness (X μm) of the both side edges and mean dry thickness (T μm) of product portion of the film have following relationship: in the case that the tenter is a pin tenter, in the range of T≦60, 40≦ X≦ 200 (1) in the range of 60<T≦120, 40+( T− 60)×0.2≦ X≦ 300 (2) in the range of 120<T, 52+( T− 120)×0.2≦ X≦ 400 (3): in the case that the tenter is a clip tenter, in the range of T≦40, 5≦ X≦T+ 50 (4) in the range of 40<T≦120, 20≦ X≦T+ 100 (5) in the range of T>120, 60 ≦ X≦T+ 200 (6); wherein the temperature of said tenter is lower than the boiling point of residual solvent in the film by 2-50° C.; wherein said tenter is forced to be cooled by a cooling means; and wherein the temperature of the film at both side edges carried by the tenter is lower than the boiling point of residual solvent by 2-50° C., but higher than dew-point of atmospheric gas by 2-50° C.