Patent ID: 9505899
Filing Date: 2016-11-29
CPC Classification: B29C,B29K,B29L,C08J,C08L

Claim Text:
1. A method for preparing a microporous polyolefin film comprising: (a) a step of injecting a composition comprising polyolefin 30 to 60 wt % and a diluent 40 to 70 wt %, which can make liquid-liquid phase separation with the polyolefin thermodynamically, into an extruding machine, and melting and kneading thereof to prepare a single phase melt; (b) a step of extruding the melt while conducting liquid-liquid phase separation by passing through a section having the temperature below the liquid-liquid phase separation temperature and forming thereof in the form of a sheet; preparing a film by stretching the formed sheet to prepare a film; extracting the diluent from the stretched film by using an organic solvent; drying the film; and heat-setting the dried film to prepare a microporous polyolefin film, wherein Total Hansen solubility parameter of the diluent is higher than Total Hansen solubility parameter of the polyolefin, wherein Total Hansen solubility parameter of the diluent is higher than Total Hansen solubility parameter of the polyolefin by 0.1 to 3.0 (J/cm wherein the diluent comprises an ester of trimethylolpropane or an ester of triethyleneglycol.