| 摘要 |
PURPOSE: Provided are a porous polyolefin film for battery diaphragm which prevents heat deflection of the diaphragm and enhance the strength of battery, such as tensile strength, and so on, and which substantially enhance electric resistance and shutdown properties of battery, and a method for producing the same. CONSTITUTION: The porous polyolefin film consists of porous insulating ceramic film with a thickness of 5-20 micrometers laminated on the surface of porous polyolefin film, in which pores with diameter of 0.5-1 micrometer are formed with porosity of 30-75%. Pores with diameter of 1 micrometer or less are formed in the insulating ceramic film with porosity of 30-75%. The porous polyolefin film is produced by the steps of (i) homogeneously mixing and dispersing the insulating ceramics with binder to prepare ceramic coating, applying the coating to the polyester film, and drying the applied film to form a laminated film; (ii) mixing a polyolefin resin with paraffin wax or process oil to obtain a mixture, and sequentially melt-roll mixing milling, injecting, compression drying and stretching the mixture to form polyolefin film; (iii) contacting the porous ceramic film part of the laminated film obtained from the step(i) with polyolefin film obtained from the step(ii), laminating them together in the speed of 30-70 m/minute, and then isolating the polyester film part from the laminated film.
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