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A kind of preparation method of ultra-thin polyolefin microporous membrane and polyolefin microporous membrane prepared thereof

A polyolefin microporous membrane, polyolefin technology, applied in the field of polyolefin microporous membrane, to achieve the effect of improving performance

Active Publication Date: 2015-11-25
SHENZHEN ZHONGXING NEW MATERIAL TECH CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, the existing technology cannot produce ultra-thin diaphragms with uniform structure and stable quality.

Method used

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  • A kind of preparation method of ultra-thin polyolefin microporous membrane and polyolefin microporous membrane prepared thereof
  • A kind of preparation method of ultra-thin polyolefin microporous membrane and polyolefin microporous membrane prepared thereof
  • A kind of preparation method of ultra-thin polyolefin microporous membrane and polyolefin microporous membrane prepared thereof

Examples

Experimental program
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preparation example Construction

[0024] The preparation method of the present application can prepare an ultra-thin polyolefin microporous membrane with uniform pores, and the polyolefin microporous membrane is especially suitable for battery separators, thereby reducing the qualified rate of batteries caused by the poor uniformity of the micropores of the battery separator low cost, poor safety, and short service life, and it is also conducive to improving battery capacity. It can be understood that the polyolefin microporous membrane of the present application can also be used in other fields that have special requirements on the uniformity of the pores of the polyolefin microporous membrane except for battery separators.

[0025] In the present application, Tm represents the melting point of polyolefin, which can be measured by the DSC method. The draft ratio is the ratio of the chill roll drawing line speed to the die discharge speed in the process of casting the base film. Stretch ratio = (film length a...

Embodiment 1

[0040] Using polypropylene as raw material, its index is average molecular weight 300000, density 0.902g / cm 3 , a melting point of 165°C, and a melt index of 3.0 g / 10 minutes. The specific process is:

[0041] (1) The base film is prepared by casting, and the raw material polypropylene is melted and extruded with a T-shaped casting head under the condition of 240 ° C, and the draft ratio is 50 to make the base film;

[0042] (2) Annealing treatment, put the base film prepared in step (1) into an oven for annealing treatment, the oven temperature is 145°C, the annealing treatment time is 2 hours, after the annealing is completed, the elastic recovery rate of the base film is 80%;

[0043] (3) Multi-point stretching to form holes. The base film annealed in step (2) is first cold-drawn at 10°C and 2000% / min. Under the temperature of ℃ and the stretch ratio of 400% / min, multi-point stretching is carried out to form a microporous structure, and the stretching points of multi-poin...

Embodiment 2

[0046] Using polypropylene as raw material, its index is average molecular weight 300000, density 0.902g / cm 3 , a melting point of 165°C, and a melt index of 3.0 g / 10 minutes. The specific process is:

[0047] (1) The base film is prepared by casting, and the raw material polypropylene is melted and extruded with a T-shaped casting head under the condition of 240 ° C, and the draft ratio is 100 to make the base film;

[0048] (2) Annealing treatment, put the base film prepared in step (1) into an oven for annealing treatment, the oven temperature is 155°C, the annealing treatment time is 20 minutes, after the annealing is completed, the elastic recovery rate of the base film is 93%;

[0049] (3) Multi-point stretching to form holes. The base film annealed in step (2) is first cold-drawn at 10°C and 2000% / min. Under the temperature of ℃ and the stretch ratio of 300% / min, multi-point stretching is carried out to form a microporous structure, and the stretching points of multi-...

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Abstract

The invention discloses a preparation method for an ultrathin polyolefin microporous membrane, and a polyolefin microporous membrane prepared by the same. The preparation method comprises the steps of tape casting a polyolefin melt into a substrate, annealing the substrate, stretching at a drawing ratio of 1.0-2.5, and performing thermosetting treatment to prepare the polyolefin microporous membrane. The stretching step includes cold stretching and stepwise hot stretching, wherein the conditions for the stepwise hot drawing stretching are as follows: a number of stretching points is 10-30; a stretching rate per stretching point is smaller than or equal to 200% / min; and a stretching temperature at each stretching point is from Tm-90 DEG C to Tm-15 DEGC, wherein Tm represents a melting point of the polyolefin. The method is characterized in that the prepared polyolefin microporous membrane has the characteristic of very uniform pore structure by stepwise hot stretching at relatively low stretching rate through a plurality of stretching points. Besides, the method is very suitable for making the ultrathin polyolefin microporous membrane with the thickness of 6-14 [mu]m. The polyolefin microporous membrane can meet applications having relatively high requirements for pore-forming homogeneity of the microporous membrane and the thickness of the membrane, and is particularly suitable for the fields of battery diaphragms.

Description

technical field [0001] The present application relates to the field of battery separators, in particular to a method for preparing an ultra-thin polyolefin microporous membrane and the prepared polyolefin microporous membrane. Background technique [0002] Polyolefin microporous membranes are widely used in battery separators, filtration membranes, medical membranes and other fields. At present, the manufacture method of polyolefin microporous membrane has two kinds of wet method and dry method: Japan's Asahi-Kasai, MitsuiChemical and Tonen's related patent JP2004323820 (2004), U.S.Patent6245272 (2001) have reported wet process, wet method The process needs to use a large amount of organic diluents, complex equipment, high cost, and easy to cause environmental pollution. The advantage is that it can manufacture ultra-thin films of 8-20 microns, but it is also very difficult to produce thin films less than 14 μm in thickness; U.S. Patent 3558764 (1971 ), 5385777 (1995) repor...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): B29C69/00B29C47/00B29C41/24B29C55/02B29C71/02B29L7/00
Inventor 胡达文麻小挺
Owner SHENZHEN ZHONGXING NEW MATERIAL TECH CO LTD