| 摘要 |
<p>A process for producing a multilayer microporous membrane. The process includes the steps of combining a first polyolefin composition and a solvent or diluent to prepare a first polyolefin solution, the polyolefin composition comprising at least a first polyethylene having a crystal dispersion temperature (T cd ) and polypropylene, combining a second polyolefin composition and a solvent to prepare a second polyolefin solution, the second polyolefin composition comprising at least a first polyethylene having a crystal dispersion temperature (T cd ) and polypropylene, extruding the first polyolefin solution and the second polyolefin solution to form a first extrudate and a second extrudate, cooling each extrudate to form a first cooled extrudate and a second cooled extrudate, orienting each cooled extrudate in at least a first direction by about one to about ten fold at a temperature of about T cd +/- 15° C.. and further orienting each cooled extrudate in at least a second direction by about one to about five fold at a temperature about 10° C. to about 40° C. higher than the temperature employed in the first orienting step. A process and system for reducing transverse direction film thickness fluctuation in a cocxtrudcd multilayer film or sheet produced from a polyolefin solution is also provided.</p> |
