A kind of multilayer microporous film and preparation method thereof

Abstract

The invention provides a method for preparing a multilayer microporous film, comprising: melting and mixing a first high-boiling point diluent and a first polymer resin to form a first mixture, and the first polymer resin contains more than 90 wt % of Polyethylene resin; melting and mixing the second high boiling point diluent and the second polymer resin to form a second mixture, the second polymer resin contains 5wt%-15wt% polyvinylidene fluoride resin and 85wt%-95wt% polyethylene resin; the first mixture and the second mixture are melt-mixed through an extruder to form a thick sheet with a three-layer structure, the melt of the first mixture serves as the middle layer, and the melt of the second mixture The body is used as the surface layer; the slab is stretched into a film, the diluent is washed out from the film, and a multi-layer microporous film is obtained after heat setting. Compared with the prior art, the multilayer microporous membrane prepared by the invention has the characteristics of good heat resistance, high liquid absorption and retention rate and low-temperature closed-cell property.

Description

technical field [0001] The invention relates to the technical field of microporous membranes, in particular to a multilayer microporous membrane and a preparation method thereof. Background technique [0002] At present, polyolefin microporous membranes are widely used in the manufacture of various separation membranes, capacitor diaphragms and lithium-ion battery diaphragms. Among the existing disclosed technical methods, there are mainly two methods for producing polyolefin microporous membranes: melt extrusion stretching method (MECUS) and thermally induced phase separation method (TIPS). The thermally induced phase separation method, commonly known as the wet method, is a method that melts and mixes polyolefins and high-boiling point pore-forming agents in a high-temperature environment to form a homogeneous system. During the cooling process, the system undergoes phase separation, and finally uses the corresponding volatile solvent The pore-forming agent is washed away...

AI Technical Summary

Problems solved by technology

However, this method tends to cause problems such as deterioration of melt-mixing ability due to addition of inorganic materials, generation of pinholes and non-uniform quality due to deterioration of melt-mixing ability at the time of stretching, and possible problems due to the interaction of inorganic materials and polymers. Lack of compatibility at the interface between resins leads to deterioration of physical properties of the film such as puncture strength, although thermal stability improves with the addition of inorganic materials

Separators using inorganic materials will always have the above disadvantages

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