| abstract |
The melt-kneading of the polyethylene-based resin and the film-forming solvent is carried out, and the solution A of the resin concentration of 25 to 50% by mass and the solution B of the resin concentration of 10 to 30% by mass, and the resin concentration of the solution A is the resin concentration of the solution B. (A) The resin solutions A and B are simultaneously extruded from a die, the resin solutions A and B are laminated and cooled to form a gel sheet, and the film forming solvent is removed from the obtained gel sheet. Alternatively, (b) the resin solutions A and B are separately extruded from a die, and the film forming solvent is removed from the obtained gel-like sheets A and B to form polyethylene microporous membranes A and B, thereby obtaining the polyethylene microporous membrane A And by alternately joining B, the average pore diameter is changed in the film thickness direction, and the permeability, mechanical properties, heat shrinkage resistance, compression resistance, electrolyte absorption, shutdown characteristic and meltdown characteristic The polyethylene microporous membrane excellent in the balance of can be produced while easily controlling the distribution of the average pore diameter in the film thickness direction. |