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Polyethylene microporous membrane as well as preparation method and application thereof

A polyethylene microporous membrane and polyethylene technology, applied in electrical components, circuits, battery pack components, etc., can solve problems such as unsuitable for industrial applications, limited diaphragm performance, wide liquid-liquid phase separation area, etc., and achieve good industrial Effect of application prospect, excellent air permeability and mechanical strength

Active Publication Date: 2021-03-26
CHINA PETROLEUM & CHEM CORP +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, the above diluent mixed with polyethylene cannot obtain a wider liquid-liquid phase separation zone, that is, during the phase separation process, as the temperature decreases, the high molecular weight polyethylene in the system can only When the concentration is low, liquid-liquid phase separation occurs, and it is impossible to obtain a microporous membrane with good permeability through the bicontinuous structure, which also cannot ensure that the separator has good mechanical strength and porosity at the same time, which limits the improvement of the performance of the separator.
In addition, the above diluents are usually liquid or viscous at room temperature, and some have a pungent odor, which is not environmentally friendly
Some oil diluents are not easily soluble in the common extractant ethanol, and toxic n-hexane is used as the extractant, which is not suitable for industrial applications

Method used

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  • Polyethylene microporous membrane as well as preparation method and application thereof
  • Polyethylene microporous membrane as well as preparation method and application thereof
  • Polyethylene microporous membrane as well as preparation method and application thereof

Examples

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preparation example Construction

[0030] The invention provides a preparation method of a polyethylene microporous membrane, comprising: mixing polyethylene with a composite diluent to obtain a premix, wherein the polyethylene accounts for 20% to 60% by mass of the premix, and the composite diluent accounts for The mass percentage of the premix is ​​40% to 80%; the premix is ​​melt-extruded and cooled to form a primary film; the diluent in the primary film is removed by an extractant, and then heat-treated to obtain a polyethylene microporous film; wherein the composite diluent includes a high-temperature solvent and a non-solvent, and the high-temperature solvent is selected from myristic acid, palmitic acid, octadecanoic acid, eicosic acid, behenic acid, myristyl alcohol, cetyl alcohol, stearyl alcohol and One or more of eicosanol, preferably myristyl alcohol, cetyl alcohol, stearyl alcohol or eicosanol; the non-solvent is selected from benzophenone, diphenyl carbonate and dimethyl sulfone One or more of the...

Embodiment 1

[0052] Mix polyethylene (viscosity-average molecular weight 1,500,000Da, average particle size 150μm) with composite diluent cetyl alcohol and benzophenone to form a premix, wherein polyethylene mass percent is 35%, cetyl alcohol mass percent is 50 %, the mass percentage of benzophenone is 15%. The premixed material was added into a screw extruder, melted and mixed uniformly to form a film-forming liquid, wherein the melting temperature was 130°C. The film-making solution is molded by an extruder and poured into cooling water to solidify to obtain a nascent film. The cooling temperature is 25°C. The obtained nascent film is stretched horizontally and vertically, and then immersed in ethanol for extraction to remove cetyl alcohol and benzophenone. The extracted film was heat-treated in water at 90° C. for 60 min to obtain a polyethylene microporous film.

[0053] figure 2 It is the scanning electron micrograph of the polyethylene microporous membrane of embodiment 1. like ...

Embodiment 2

[0055] The polyethylene microporous membrane is prepared according to the method of Example 1, the difference is that the composite diluent is cetyl alcohol and diphenyl carbonate, wherein the polyethylene mass percentage is 35%, the cetyl alcohol mass percentage is 50%, and diphenyl carbonate The mass percentage of ester is 15%. There is a phenomenon of liquid-liquid phase separation in this system. The microporous membrane was tested for mechanical properties, air permeability and porosity. The results and the maximum polymer mass concentration corresponding to the liquid-liquid phase separation zone are shown in Table 1.

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Abstract

The invention provides a preparation method of a polyethylene microporous membrane. The method comprises the following steps: mixing 20-60wt% of polyethylene and 40-80wt% of a composite diluent to obtain a premix; carrying out melt extrusion and cooling molding on the premix to obtain a primary membrane; and removing the composite diluent in the primary membrane by adopting an extracting agent, and then carrying out heat treatment to obtain a polyethylene microporous membrane. The composite diluent comprises a high-temperature solvent and a non-solvent, the high-temperature solvent is selectedfrom one or more of tetradecanoic acid, hexadecanoic acid, octadecanoic acid, eicosanoic acid, docosanoic acid, tetradecanol, hexadecanol, octadecanol and eicosanol, the non-solvent is selected fromone or more of benzophenone, diphenyl carbonate and dimethyl sulfone, and the high-temperature solvent accounts for no less than 60 wt%. By adopting the specific composite diluent, liquid-liquid phaseseparation can still occur when the polymer concentration is high in the phase separation process, and the obtained polyethylene microporous membrane has excellent air permeability and mechanical strength and is suitable for being used as a lithium battery diaphragm material.

Description

technical field [0001] The invention belongs to the technical field of polymer material preparation, and in particular relates to a polyethylene microporous membrane and its preparation method and application. Background technique [0002] Lithium battery separator is one of the core materials in lithium-ion batteries. Its main function is to separate the positive and negative electrodes of the battery, while ensuring that lithium ions can pass freely between the positive and negative electrodes. [0003] The currently marketed lithium-ion battery separators mainly include dry-process uniaxially stretched separators, dry-process biaxially stretched separators and wet-process separators. The main difference between these membrane preparation methods lies in the different pore-forming mechanisms of the micropores. In our country, the dry process diaphragm is almost self-sufficient. The dry process is to mix the polymer and additive raw materials, form a uniform melt at high ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H01M50/403H01M50/417H01M50/414
CPCY02E60/10
Inventor 庞博杜泽学
Owner CHINA PETROLEUM & CHEM CORP
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