Polyolefin three-layer composite microporous membrane and preparation method thereof

A polyolefin three-layer composite microporous membrane and a preparation method thereof are disclosed, aiming at solving the problems of difficult technique control and non-uniform product pores. Raw materials polyethylene and polypropylene are prepared into polypropylene/polyethylene/polypropylene three-layer composite microporous membrane, wherein an adhesive substance is added into the raw material polyethylene; the technique comprises the following steps: a. curtain coating preparation of basement-membrane; b. multistage annealing treatment; c. three-layer basement-membrane composition; d. multipoint stretching pore-forming; and e. thermoforming treatment. The invention has the advantages of undamaged basement-membrane, good safety, simple preparation, small equipment investment, non-blockage of membrane pores during preparation process, high porosity, easy control of porosity and the like, is suitable for making polyolefin microporous membrane of various types used for breathability material, ultrafiltration, membrane filtration, super capacitor and battery diaphragm materials, etc.