Patent ID: 11872531
Assignee: LG CHEM, LTD.
Field: Chemical engineering (Chemistry)
Classification: CPC B | IPC B

Claim 7:
8. A method for preparing the porous fluorine-based resin membrane according to claim 1, comprising the steps of:
preparing a fluorine-based resin sheet by mixing a fluorine-based resin and a lubricant to prepare a fluorine-based resin composition, applying pressure to the fluorine-based resin composition to form a preformed body; extruding the preformed body in a form of a sheet using a die, followed by rolling; and then conducting a heat-treating the sheet at 120° C. to 200° C.;
stretching the fluorine-based resin sheet in a ratio of from 1 to 12 times in the machine direction at a temperature of 200° C. to 340° C.;
stretching the sheet stretched in the machine direction, in a ratio of from 5 to 25 times in the transverse direction at 200° C. to 320° C.; and then
heat setting the sheet stretched in the machine direction and the traverse direction at a temperature of 370° C. to 390° C. for 5 seconds to 9 seconds,
wherein the extrusion step is carried out at a temperature of 25° C. to 50° C. and a pressure of 1 to 40 MPa.