Polyolefin Microporous Membrane

Inactive Publication Date: 2008-08-14
ASAHI KASEI CHEM CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0009]An object of the present invention is to provide a polyolefin microporous membrane which is excellent in permeability and impregnation with electrolyte, can be thinned to further thin thickness, is high in mechanical strength even when thi

Problems solved by technology

That is, if the temperature of battery further rises after shut-down of separators, fluidization of separator begins to cause decrease of electrical resistance, resulting in restoration of current.
When electrodes are packed, the inside of the battery is in the state of being densely packed, which causes the problem of low impregnation with electrolyte.
However, according to the technology disclosed in this document, the separators can hardly be thinned, and it is difficult to attain increased capacity of battery per unit volume.
According to this method, since agg

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Example

EXAMPLE 1

[0088]32 parts by mass of polypropylene (density: 0.90, viscosity average molecular weight: 300,000) and 8 parts by mass of silica (oil absorption: 200 ml / 100 g) as materials of surface layer, 2 parts by mass of bis(p-ethylbenzylidene)sorbitol as a nucleating agent, 0.3 part by mass of tetrakis-[methylene-(3′,5′-di-t-butyl-4′-hydroxyphenyl)propionate]methane as an antioxidant, and 12 parts by mass of liquid paraffin (kinematic viscosity at 37.78° C.: 75.90 cSt, density: 0.868) as a plasticizer were blended and stirred by a mixer to prepare a raw material. 40 parts by mass of a high density polyethylene (density: 0.95, viscosity average molecular weight: 250,000) as a material of interlayer and 0.3 part by mass of tetrakis-[methylene-(3′,5′-di-t-butyl-4′-hydroxyphenyl)propionate]methane as an antioxidant were blended to prepare a raw material. The respective blends were introduced through feeders of two twin-screw extruders having a bore diameter of 25 mm and L / D=48. Further...

Example

EXAMPLE 2

[0089]A microporous membrane was produced in the same manner as in Example 1, except that a high density polyethylene (density: 0.95, viscosity average molecular weight: 250,000) was used in place of polypropylene as the material of the surface layer. The physical properties of the resulting microporous membrane are shown in Table 1.

Example

EXAMPLE 3

[0090]A microporous membrane was produced in the same manner as in Example 1, except that 36 parts by mass of polypropylene (density: 0.90, viscosity average molecular weight: 300,000) as a material of the surface layer, 4 parts by mass of silica (oil absorption: 200 ml / 100 g) and 6 parts by mass of liquid paraffin as a plasticizer were blended and stirred by a mixer to prepare a raw material, and, furthermore, 54 parts by mass of liquid paraffin was charged in the extruder for the surface layer by side feeding. The physical properties of the resulting microporous membrane are shown in Table 1.

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Abstract

Disclosed is a polyolefin microporous membrane including a multilayer film having two or more layers. In this polyolefin microporous membrane, at least one surface layer has a thickness of not less than 0.2 μm but not more than 5 μm and contains inorganic particles, while at least one layer contains a polyethylene and has an air permeability of not less than 50 second/100 cc but not more than 1000 second/100 cc and a puncture strength of not less than 3.0 N/20 μm.

Description

TECHNICAL FIELD[0001]The present invention relates to a polyolefin microporous membrane, particularly, to a polyolefin microporous membrane suitable as separators for lithium ion batteries, precision filter membranes, separators for capacitors, and materials for fuel cells.BACKGROUND ART[0002]Polyolefin microporous membranes are used as precision filter membranes, separators for batteries, separators for capacitors, materials for fuel cells, etc., and particularly, used as separators for lithium ion batteries. Recently, lithium ion batteries are used for miniature electronic instruments such as portable telephones and notebook type personal computers, and it is further attempted to apply them to electric cars, small motorbikes, etc.[0003]Polyethylene microporous membranes are used as separators for lithium ion batteries because they are high in permeability, and besides they have a function to clog the communicating pores upon melting the polymer at 130-150° C. and to shut-down the ...

Claims

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Application Information

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IPC IPC(8): H01M2/16B32B3/10B32B27/32H01M50/417H01M50/451H01M50/457H01M50/489
CPCB32B27/32H01M2/1686H01M2/1653Y10T428/24998Y10T428/249978Y02E60/10H01M50/417H01M50/457H01M50/451H01M50/489B32B27/08B32B27/18B32B27/205H01M50/411H01M50/449H01M50/491B32B2307/518B32B2457/10B32B2305/026B32B2305/02
Inventor OHASHI, MASAHIROSOGO, HIROSHI
Owner ASAHI KASEI CHEM CORP
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