Polyolefin microporous film and its preparation method
A technology of microporous membranes and polyolefins, applied in chemical instruments and methods, membranes, membrane technologies, etc., can solve the problems of reduced overcharge characteristics, low transverse thermal shrinkage, battery safety, etc., and achieve permeability and Excellent heat shrinkage properties, excellent thermal stability, high puncture strength and the effects of permeability
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[0039] In addition, the present invention provides a method for preparing a polyolefin-based microporous membrane by a wet method, which is characterized in that the following steps are carried out before the extraction step, which includes: kneading and extruding polyolefin resin and diluent process, sheet forming process, stretching process, etc.; after the extraction process, the following processes are carried out, which include: implementing more than three steps of heat treatment process, including implementing more than two heat stretching steps, and performing more than two steps of heat treatment One or more thermal relaxation steps are included between the thermal stretching steps.
[0040] In addition, the present invention provides a method for producing a polyolefin-based microporous membrane, wherein the first stretching step in the heat treatment process is carried out at [melting temperature of polyolefin-based resin - 30°C] to [melting temperature of polyolefin...
Embodiment 1
[0117] Use a weight average molecular weight of 3.0×10 5 . High-density polyethylene having a melting temperature of 135° C. was used as component I, and paraffin oil having a dynamic viscosity of 160 cSt at 40° C. was used as component II. The proportions of component I and component II were 30% and 70%, respectively.
[0118] Using a twin-screw kneader, the above composition was extruded at 230° C., and a sheet was prepared using a T-shaped die and a casting roll. This sheet was sequentially stretched 7 times in the longitudinal direction at 113°C and 6.5 times in the transverse direction at 128°C. In a state where tension is applied to the stretched film, the dichloromethane at 25 to 30° C. is used to extract the diluent. The heat treatment process is carried out along the transverse direction, and the temperature, heat stretch ratio and heat relaxation ratio in each step of the heat treatment process are shown in Table 1 below, and each step is carried out for 5 seconds....
Embodiment 2
[0120] Use a weight average molecular weight of 3.0×10 5 . High-density polyethylene having a melting temperature of 135° C. was used as component I, and paraffin oil having a dynamic viscosity of 160 cSt at 40° C. was used as component II. The proportions of component I and component II were 30% and 70%, respectively.
[0121] Using a twin-screw kneader, the above composition was extruded at 230° C., and a sheet was prepared using a T-shaped die and a rubber roller. This sheet was sequentially stretched 6 times in the longitudinal direction at 118°C and 6.5 times in the transverse direction at 125°C. In a state where tension is applied to the stretched film, the dichloromethane at 25 to 30° C. is used to extract the diluent. The heat treatment process is carried out along the transverse direction, and the temperature, heat stretch ratio and heat relaxation ratio in each step of the heat treatment process are shown in Table 1 below, and each step is carried out for 5 seconds...
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Abstract
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