Polyolefin film and preparation method thereof

Abstract

The invention provides a polyolefin film prepared by a wet multi-step stretching process as well as a preparation method and a device thereof. The prepared film has the thickness of 10-100 mu m, permeability of 10-150 S / in<2>.100 cc.1.22 kPa, average pore diameter of 100-1000 nm, film breaking temperature of 110-160 DEG C, tensile strength of 50-250 MPa, puncture strength of 200-500 g / mu m and porosity of 25-45%. The polyolefin film is prepared by melting polyolefin resins and a pore-forming agent at a higher temperature for uniformly mixing, extruding a melt by an extruder die head 1, and cooling the extruded melt with a vertical cooling roll and a horizontal cooling roll to obtain a solid thick slice; and extracting and heating and drying the cooled thick slice, passing the thick slice through the resins treated by first-step vertical stretching orientation, second-step bidirectional synchronous stretching and third-step lateral expansion stretching as well as sintering and sizing at the sintering temperature of 120-200 DEG C to obtain the polyolefin film.

Description

[0001] Field [0002] The present invention relates to widely used microporous membranes, such as separation membranes used for the separation of substances, selective permeation, etc., as isolation materials for electrochemical reaction devices such as alkaline, lithium ion or fuel cells, etc. The invention relates to a polyolefin microporous film used for separators of non-aqueous electrolyte batteries such as batteries, and also relates to a preparation method of the olefin microporous film. Background technique [0003] The lithium-ion battery separator is one of the most important and indispensable components in the lithium-ion battery. At present, the wet production process for the production of lithium-ion battery separators in the world is to mix hydrocarbons or low-molecular-weight substances with polyolefin resins at relatively high temperatures, melt the cast sheets, and then perform orientation treatment on the sheets in the longitudinal or biaxial direction, and f...

AI Technical Summary

Problems solved by technology

The post-extraction treatment is carried out after the end of stretching. The main material film network and the pore-forming agent have phase separation, but the pore-forming agent is still distributed between the molecular chains that have been bidirectionally oriented and stretched. At this time, the pore-forming agent After the extraction process, the pore diameter of the displaced hole is large, and the contact between the two electrodes cannot be well protected when it is applied to the lithium battery, resulting in a short circuit of the battery; Once the raw material is fixed, the performance of the product will also be fixed. It is not used to adjust the product according to different needs and form a series of products; in addition, because the equipment design is based on a specific raw material, due to Only one step of stretching, the adaptability of the equipment to different raw materials is greatly reduced

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