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Method for preparing composite polypropylene microporous film by phase conversion method and product and application of composite polypropylene microporous film

A technology of composite polypropylene and phase inversion method is applied in the field of preparing composite polypropylene microporous film by phase inversion method, which can solve the problems of low strength of porous film, complicated process and high porosity of porous film

Active Publication Date: 2019-10-18
BEIJING NORMAL UNIVERSITY
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

The porous membrane prepared by the phase inversion method has high porosity, but the strength of the prepared porous membrane is relatively low, and it cannot be directly used as a lithium-ion battery separator
[0007] At present, the production of composite diaphragm is prepared by coating the surface of the diaphragm after preparing the polyolefin diaphragm. The process is complicated and the qualified rate of the product is reduced.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

preparation example Construction

[0064] [Preparation method of composite polypropylene microporous membrane]

[0065] As previously mentioned, the present invention provides a method for preparing a composite polypropylene microporous membrane by a phase inversion method, the method comprising the following steps:

[0066] (S1) Adding a nucleating agent capable of promoting the formation of the β crystal form to the polypropylene, melting and extruding the polypropylene mixed with the nucleating agent, and molding to obtain a high β crystal film;

[0067] (S2) Prepare a polypropylene longitudinally stretched film comprising at least one side with a microporous structure coating in one of the following ways:

[0068] Method 1) Immersion precipitation phase inversion method:

[0069] Longitudinally stretching the high-beta crystal film to obtain a longitudinally stretched film, and coating a polymer-based coating solution containing a porogen component and a film-forming component on one or both sides of the l...

Embodiment 1

[0145] Preparation of coating solution: make a solution of vinylidene fluoride-hexafluoropropylene copolymer (P(VDF-HFP)) and polymethylpyrrolidone (PVP) with N,N-dimethylformamide (DMF), where P The mass percentages of (VDF-HFP) and PVP were 10wt% and 1.5wt%, respectively.

[0146] Homopolypropylene resin with a melt index of 2.5g / 10min and polypropylene β-crystal nucleating agent N,N-dicyclohexyl-2,6 naphthalene diamide accounting for 0.03wt% of homopolypropylene resin were uniformly mixed, After melt extrusion and casting, a polypropylene film containing β crystal nucleating agent is obtained. The thickness of the polypropylene membrane containing β-crystal nucleating agent is 140 microns.

[0147] The film was longitudinally stretched 4.5 times at 100° C. to obtain a longitudinally stretched film. After the longitudinally stretched film is coated with the above coating solution on both sides by the coating system, it is immersed in a water phase coagulation bath with a t...

Embodiment 2

[0151] Preparation of coating solution: Polymethyl methacrylate (PMMA) and polyoxyethylene ether (PEO) are prepared into a solution with N,N-dimethylformamide (DMAC), wherein the mass percentages of PMMA and PEO are respectively 7.5wt% and 1wt%.

[0152] Homopolypropylene resin with a melt index of 2.5g / 10min and the barium salt of polypropylene beta crystal nucleating agent tetrahydrophthalic anhydride accounting for 0.03wt% of homopolypropylene resin are uniformly mixed, and after melt extrusion and casting, A polypropylene film containing β-crystal nucleating agent was obtained. The thickness of the polypropylene membrane containing β-crystal nucleating agent is 140 microns.

[0153] The film was longitudinally stretched 4.0 times at 100° C. to obtain a longitudinally stretched film. After the longitudinally stretched film is coated with the above coating solution on both sides by the coating system, it is immersed in a water phase coagulation bath with a temperature of 3...

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Abstract

The invention discloses a method for preparing a composite polypropylene microporous film by a phase conversion method and product and application of the composite polypropylene microporous film. According to the preparation method, a coating layer is introduced to surface(s) of one side or two sides of the film by a first mode (immersion precipitant phase conversion method) or a second mode (dryphase conversion method) during the fabrication process of bidirectionally stretching a polypropylene microporous substrate layer, the coating layer is only stretched in a longitudinal direction and atransverse direction or is only stretched in the transverse direction, and the preparation of the composite polypropylene microporous film is achieved. With the adoption of the method, the productionprocess of the composite polypropylene microporous film is simplified, the fabricated coating layer is high in porosity, the microporous structure is uniform, and the performance of the polypropylenemicroporous substrate layer can be improved very well. The composite polypropylene microporous film is applied into a lithium battery, the coating layer is a polymer or a composition capable for forming gel with an electrolyte, and thus, the cycle property and the safety of the lithium battery can be improved. The invention also provides a lithium battery diaphragm, and the lithium battery diaphragm comprises the composite polypropylene microporous film.

Description

technical field [0001] The invention belongs to the technical field of microporous membranes, and in particular relates to a method for preparing composite polypropylene microporous membranes by a phase inversion method, as well as products and uses thereof. Background technique [0002] Polyolefin microporous membrane is a kind of polymer membrane, which is a porous membrane with a pore size between 5nm and 1000nm. It is widely used in breathable materials such as diapers, medical dressings, clothing linings, etc., and materials for liquid separation. , ultrafiltration materials, membrane filtration materials, and supercapacitor and battery diaphragm materials and other fields. [0003] There are mainly two methods for preparing polyolefin microporous membranes, one is melt extrusion stretching method (dry method), and the other is thermally induced phase separation method (TIPS, wet method). Among them, the dry stretching process can also be divided into a uniaxial stretc...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H01M2/16H01M2/14H01M10/0525
CPCH01M10/0525H01M50/403H01M50/411H01M50/449Y02E60/10
Inventor 周建军胡志宇李林方芳
Owner BEIJING NORMAL UNIVERSITY
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