A kind of preparation method of polyolefin microporous film and its obtained microporous film

Abstract

The invention discloses a preparation method for a polyolefin micro-porous membrane and a micro-porous membrane prepared by using the same. The preparation method comprises the following steps: melting, extruding, stretching and cooling polyolefin, thereby forming a nonporous membrane; after laterally stretching the nonporous membrane, performing layering and thermal treatment on a lamella; and after longitudinally stretching the nonporous membrane acquired from the step b, performing thermal treatment on the nonporous membrane. The prepared polyolefin micro-porous membrane contains the holes, longitudinal and lateral length-diameter ratio of which is (1.1:1)-(5:1); the longitudinal and lateral tensile strength ratio is (1.2:1)-(4:1); the fluctuation range of thickness is equal to or morethan -2.5% and equal to or less than +2.5%; the longitudinal thermal contraction is equal to or less than 2%; and the lateral thermal contraction is equal to or less than 1%. The preparation method for the polyolefin micro-porous membrane has the advantages that the production facility is simple, the cost is low, the environment is protected, the prepared membrane contains the holes having a shape approaching to ellipse and meanwhile has higher lateral tensile strength, better tearing strength, small contractibility rate and small thickness fluctuation, no crystal form nucleating agent or hole-forming material capable of forming holes is added in the preparation process, and the like.

Description

technical field [0001] The invention relates to a preparation method of a polyolefin microporous membrane and the obtained microporous membrane, belonging to the technical field of polymer material processing. Background technique [0002] Known polyolefin microporous membranes can be manufactured by various methods, and the physical properties of the membranes obtained by different processes have different performances. The current techniques used to manufacture polyolefin microporous membranes are mainly: dry stretching and wet stretching. [0003] In dry stretching, the formation of pores results from the stretching of a non-porous precursor. Conventional dry stretching, the obtained film has disadvantages such as poor transverse strength, poor tear strength, large thermal shrinkage rate and large thickness fluctuation. [0004] The wet process refers to dissolving the polymer in a high-boiling point, low-volatility solvent at high temperature to form a homogeneous liqu...

AI Technical Summary

Problems solved by technology

The pore size of the diaphragm produced by the wet process is well controlled and has good mechanical properties. However, compared with the dry process, the wet process has complex equipment, large investment, high cost, and certain pollution to the environment.

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