Cross-linked polyolefin separator and method for producing same

A method for manufacturing a crosslinked polyolefin separator, comprising:

• (S1) introducing a polyolefin, a diluting agent, an alkoxysilane containing a carbon-carbon double bonded group, an initiator and a crosslinking catalyst to an extruder, followed by mixing, and carrying out a reactive extrusion;
• (S2) molding and orienting a reactive extruded silane-grafted polyolefin composition in the form of an oriented sheet;
• (S3) extracting the diluting agent from the oriented sheet to obtain a porous membrane;
• (S4) thermally fixing the porous membrane to obtain a thermally fixed porous membrane;
• and
• (S5) crosslinking the thermally fixed porous membrane in the presence of water,
• wherein, in (S1), at least one of the initiator or the alkoxysilane containing a carbon-carbon double bonded group is introduced to the extruder in divided doses at a predetermined time interval and mixed in the extruder, and
• if the initiator is introduced and mixed in divided doses, then a weight ratio (A/B) of a total content (A) of the alkoxysilane containing the carbon-carbon double bonded group to a total content (B) of the initiator is 80-600, and
• if the alkoxysilane containing the carbon-carbon double bonded group is introduced and mixed in divided doses, then a first alkoxysilane containing the carbon-carbon double bonded group introduced initially to the extruder has a higher boiling point, as compared to a second alkoxysilane containing the carbon-carbon double bonded group introduced subsequently to the extruder.