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Preparation method for ultrathin polyolefin microporous membrane, and polyolefin microporous membrane prepared by same

A polyolefin microporous film and polyolefin technology, which is applied in the field of polyolefin microporous film to achieve the effect of improving performance

Active Publication Date: 2013-09-04
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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  • Preparation method for ultrathin polyolefin microporous membrane, and polyolefin microporous membrane prepared by same
  • Preparation method for ultrathin polyolefin microporous membrane, and polyolefin microporous membrane prepared by same
  • Preparation method for ultrathin polyolefin microporous membrane, and polyolefin microporous membrane prepared by same

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Experimental program
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preparation example Construction

[0024] The preparation method of the present application can be used to prepare ultra-thin polyolefin microporous membranes with uniform pores. The polyolefin microporous membranes are particularly suitable for battery separators, thereby reducing the battery qualification rate caused by poor micropore uniformity of the battery separators Low, poor safety and short service life are problems, and at the same time help to increase 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 for the pore formation uniformity of the polyolefin microporous membrane, in addition to being used for battery separators.

[0025] In this application, Tm represents the melting point of polyolefin, which can be measured by the DSC method. The draft ratio is the ratio of the linear speed of the chill roll to the speed of the die head during the process of casting into a base film. Str...

Embodiment 1

[0040] Using polypropylene as raw material, its index is average molecular weight 300,000, density 0.902g / cm 3 , The melting point is 165°C, the melt index is 3.0 g / 10 minutes. The specific process is:

[0041] (1) The base film is prepared by casting. The raw material polypropylene is melted and extruded with a T-shaped casting die under the condition of 240℃, 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 and the annealing treatment time is 2 hours. After the annealing is completed, the base film elastic recovery rate is 80%;

[0043] (3) Multi-point stretching to form holes. The base film annealed in step (2) is cold-drawn at 10°C and a stretching ratio of 2000% / min to form crazing defects, and then at 80-150 Perform multi-point stretching at a temperature of ℃ and a stretching ratio of 400% / min to form a microporous structure, and the num...

Embodiment 2

[0046] Using polypropylene as raw material, its index is average molecular weight 300,000, density 0.902g / cm 3 , The melting point is 165°C, and the melt index is 3.0 g / 10 minutes. The specific process is:

[0047] (1) The base film is prepared by casting. The raw material polypropylene is melted and extruded at 240°C with a T-shaped casting die with a draft ratio of 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, and the annealing time is 20 minutes. After annealing, the base film elastic recovery rate 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 a stretching ratio of 2000% / min to form crazing defects, and then at 80-150 Multi-point stretching at a temperature of ℃ and a stretching ratio of 300% / min to form a microporous structure, and the number of stretching points for multi-point ...

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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] This 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, filter membranes, medical membranes and other fields. At present, there are two methods for manufacturing polyolefin microporous membranes: wet method and dry method: Japanese Asahi-Kasai, Mitsui Chemical and Tonen's related patents JP2004323820 (2004), USPatent6245272 (2001) reported wet process, wet process The process requires the use of a large amount of organic diluent, the equipment is complicated, the cost is high, and it is easy to cause environmental pollution. The advantage is that it can produce ultra-thin films with a thickness of 8-20 microns, but it is also very difficult to produce films with a thickness of less than 14μm; US Patent 3558764 (1971 )...

Claims

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Application Information

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Patent Type & Authority Applications(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
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