| abstract |
PROBLEM TO BE SOLVED: To provide a crosslinked polyethylene microporous membrane having high strength, low shutdown temperature and high meltdown temperature, high safety as a battery separator, and a method for producing the same. (A) Ultra high molecular weight polyethylene having a weight average molecular weight of 5 × 10 5 or more, or a mixture of ultra high molecular weight polyethylene of 5 × 10 5 or more and high density polyethylene of 1 × 10 4 to less than 5 × 10 5 And (b) a weight average molecular weight of 1 × 10 4 to 5 It comprises a composition having a low density polyethylene of × 10 5 and a weight ratio (a) / (b) of 95/5 to 50/50), and a gel fraction of 10%. It is produced by a process of preparing a polyethylene solution, a process of forming a gel-like molded product, a process of stretching and removing a solvent, a process of drying and cross-linking the film by ionizing radiation with a ~ 80% polyethylene microporous membrane. The solvent may be added before or during kneading, and the solvent is removed before and / or after stretching. |