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A preparing method of a polyolefin microporous separating membrane

A microporous membrane, polyolefin technology, applied in flat products, applications, electrical components, etc., can solve the problem of low lateral mechanical strength of polyolefin microporous membranes, large differences in lateral and longitudinal thermal shrinkage, and easy sliding of the lamellar cluster skeleton. and other problems, to achieve the effect of small longitudinal thermal shrinkage, reducing the difference between transverse and longitudinal thermal shrinkage, and improving mechanical strength

Active Publication Date: 2015-08-12
UNIV OF SCI & TECH OF CHINA
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0004] The technology of the invention solves the problems: improving the existing dry-process uniaxial stretching preparation of polyolefin microporous diaphragms with low transverse mechanical strength, large difference in transverse and longitudinal thermal shrinkage rates, and easy slipping of the lamella cluster skeleton, etc., and provides a new type of polyolefin membrane. The preparation method of the olefin microporous membrane, the porosity of the microporous membrane prepared by the limited uniaxial stretching is increased, the transverse tensile strength is obviously improved, the arrangement structure of the skeleton lamella clusters is better maintained, the pore size distribution is more uniform, and the formation of The through-hole ratio is significantly increased, and the difference in heat yield between the transverse and longitudinal directions is significantly reduced

Method used

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  • A preparing method of a polyolefin microporous separating membrane
  • A preparing method of a polyolefin microporous separating membrane
  • A preparing method of a polyolefin microporous separating membrane

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Experimental program
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Embodiment 1

[0034] Select iPP with a melt flow index of 2g / 10min as the raw material, and set the temperature of each section of the single-screw extruder from the hopper to the die to 160°C, 190°C, 215°C, 235°C, 215°C, 215°C, Extrude the iPP melt sheet from the slit die at a screw extrusion rate of 140mm / min at 205°C, adjust the air volume of the air knife, blow cold air to cool the surface of the melt sheet at the die, and cool the melt at 90°C The casting roll is used for traction, the 80°C cooling roll is used for cooling, the distance between the die and the first casting roll is 21mm, the stretching ratio of the casting roll is 42, and it is wound by the winding roll to obtain a row-arranged lamellar structure iPP prefabricated membrane. The prefabricated film was annealed in an oven at 130° C. for 120 minutes to obtain an iPP hard elastomer prefabricated film. After the annealed prefabricated film is stretched 30% at room temperature with a stretching rate of 0.2mm / s by a stretchi...

Embodiment 2

[0037] Select iPP with a melt flow index of 2g / 10min as the raw material, and set the temperature of each section of the single-screw extruder from the hopper to the die to 160°C, 190°C, 215°C, 235°C, 215°C, 215°C, Extrude the iPP melt sheet from the slit die at a screw extrusion rate of 140mm / min at 205°C, adjust the air volume of the air knife, blow cold air to cool the surface of the melt sheet at the die, and cool the melt at 90°C Casting roll for traction, 100°C cooling roll for cooling, the distance between the die and the first casting roll is 15mm, the stretching ratio of the casting roll is 84, and it is wound by the winding roll to obtain a row-arranged lamellar structure iPP prefabricated membrane. The prefabricated film was annealed in an oven at 130° C. for 120 minutes to obtain an iPP hard elastomer prefabricated film. After the annealed prefabricated film is stretched 30% at room temperature with a stretching rate of 0.2mm / s by a stretching device, it is furthe...

Embodiment 3

[0040] Select high-density polyethylene (HDPE) with a melt flow index of 0.07g / 10min as the raw material, and set the temperature of each section of the single-screw extruder from the hopper to the die to 150°C, 195°C, 220°C, and 230°C , 220°C, 230°C, 210°C, extrude the HDPE melt sheet from the slit die at a screw extrusion rate of 140rpm, adjust the air volume of the air knife, blow cold air to the die to cool the surface of the melt sheet, and the cooled The melt is pulled by a casting roll at 110°C, the distance between the die and the first casting roll is 15mm, the stretching ratio of the casting roll is 170, and the HDPE with a row-arranged lamellar structure is obtained by winding up the winding roll Prefabricated film. The prefabricated film was annealed in an oven at 120° C. for 120 min to obtain a HDPE hard elastomer prefabricated film. After the annealed prefabricated film is stretched 30% at room temperature with a stretching rate of 1mm / s, it is raised to 120°C a...

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Abstract

A preparing method of a novel polyolefin microporous separating membrane is provided. The method includes steps of preparing polyolefin into a prefabricated membrane with a row-arranged lamellar crystal structure by melting, extruding, casting and drawing; annealing the prefabricated membrane; and performing limited uniaxial cold drawing, limited uniaxial hot drawing and heat setting in order by adoption of a banner wide uniaxial drawing device to obtain the microporous separating membrane. The polyolefin microporous separating membrane prepared by the limited uniaxial drawing is characterized in that porosity is high; the ratio of through holes is high, namely air permeability is good; skeleton lamellar crystal clusters and rows are neatly arranged; transverse mechanical strength is enhanced; and the difference between transverse and longitudinal hot-shrinkage rates is reduced. By adjusting the casting and drawing ratio, the limited uniaxial cold drawing speed and the limited uniaxial cold drawing ratio, regulation and control of the porosity of the microporous separating membrane can be achieved. The disadvantages of polyolefin microporous separating membranes prepared by dry uniaxial drawing methods at present, namely low transverse mechanical strength, large difference between transverse and longitudinal hot-shrinkage rates, easily slidable lamellar crystal cluster skeletons, and the like, can be overcome.

Description

technical field [0001] The invention relates to a preparation method of a lithium battery diaphragm, in particular to a preparation method of a polyolefin microporous film with uniform pore size distribution, neatly arranged skeletons, high transverse tensile strength, and small difference in longitudinal and transverse thermal shrinkage rates. Background technique [0002] The separator is an important part of the lithium-ion battery and an important component that supports the lithium-ion battery to complete the electrochemical process of charging and discharging. According to different physical and chemical properties, lithium battery separator materials can be divided into: woven membrane, nonwoven membrane (non-woven fabric), microporous membrane, composite membrane, separator paper, laminated membrane, etc. Polyolefin materials have excellent mechanical properties, chemical stability and relatively cheap characteristics. Therefore, polyolefin microporous membranes such...

Claims

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Application Information

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IPC IPC(8): H01M2/14B29D7/01H01M50/403H01M50/406H01M50/494
CPCB29D7/01B29K2105/041B29K2023/00H01M50/403Y02E60/10
Inventor 李良彬李薛宇林元菲孟令蒲陈晓伟张瑞张前磊
Owner UNIV OF SCI & TECH OF CHINA
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