VERY THIN MICROPOROUS MATERIAL

摘要

PURPOSE: Very thin microporous material comprises a matrix of substantially linear polyolefin, finely divided substantially water-insoluble filler particles distributed throughout the matrix, and a network of interconnecting pores communicating substantially throughout said microporous material. The very thin microporous material can be produced by the blown film process. The material is used as a separator in a battery. CONSTITUTION: Provided is a microporous material in the form of a sheet, film, tube having an internal diameter of at least 8 centimeters, or layer thereof, having a thickness in the range of from 5 to 26 micrometers which on a coating-free, printing ink-free, impregnant-free basis and pre-bonding basis comprises: (a) a matrix which comprises: (1) from 0 to 100 wt.% high molecular weight substantially linear polyolefin which is high molecular weight substantially linear polyethylene having an ASTM D 1238-86 Condition E melt index of less than 50 grams/10 minutes, an ASTM D 1238-86 Condition F melt index of at least 0.1 gram/10 minutes, and a density in the range of from 0.910 to 0.965 gram/cubic centimeter; high molecular weight substantially linear polypropylene having an ASTM D 1238-86 Condition L melt index in the range of from 0.2 to 50 grams/10 minutes and a density greater than 0.89 gram/cubic centimeter; or a mixture thereof; and (2) from 0 to 100 wt.% ultrahigh molecular weight substantially linear polyolefin which is ultrahigh molecular weight substantially linear polyethylene having an intrinsic viscosity of at least 18 deciliters/gram; ultrahigh molecular weight substantially linear polypropylene having an intrinsic viscosity of at least 6 deciliters/gram; or a mixture thereof; wherein the high molecular weight substantially linear polyolefin and the ultrahigh molecular weight substantially linear polyolefin collectively constitute from 90 to 100 wt.% of the matrix; (b) finely divided substantially water-insoluble filler particles distributed throughout said matrix and constituting from 20 to 85 wt.% of the microporous material, and (c) a network of interconnecting pores communicating substantially throughout said microporous material, the pores constituting at least 25 percent vol.% of the microporous material.