WO2021164143A1 - 一种聚烯烃多孔膜及其制备方法 - Google Patents

一种聚烯烃多孔膜及其制备方法 Download PDF

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WO2021164143A1
WO2021164143A1 PCT/CN2020/091494 CN2020091494W WO2021164143A1 WO 2021164143 A1 WO2021164143 A1 WO 2021164143A1 CN 2020091494 W CN2020091494 W CN 2020091494W WO 2021164143 A1 WO2021164143 A1 WO 2021164143A1
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polyethylene resin
polyolefin porous
white oil
molecular weight
porous membrane
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PCT/CN2020/091494
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English (en)
French (fr)
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贾培梁
翁星星
刘涛涛
王正丽
孙爱斌
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江苏厚生新能源科技有限公司
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Priority to US17/256,234 priority Critical patent/US11186694B2/en
Priority to KR1020207036849A priority patent/KR102327715B1/ko
Priority to JP2020573413A priority patent/JP2022517293A/ja
Publication of WO2021164143A1 publication Critical patent/WO2021164143A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/411—Organic material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/411—Organic material
    • H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
    • H01M50/417—Polyolefins
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/001—Combinations of extrusion moulding with other shaping operations
    • B29C48/0018—Combinations of extrusion moulding with other shaping operations combined with shaping by orienting, stretching or shrinking, e.g. film blowing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/03—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the shape of the extruded material at extrusion
    • B29C48/07—Flat, e.g. panels
    • B29C48/08—Flat, e.g. panels flexible, e.g. films
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/25—Component parts, details or accessories; Auxiliary operations
    • B29C48/28—Storing of extruded material, e.g. by winding up or stacking
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/25—Component parts, details or accessories; Auxiliary operations
    • B29C48/30—Extrusion nozzles or dies
    • B29C48/305—Extrusion nozzles or dies having a wide opening, e.g. for forming sheets
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/25—Component parts, details or accessories; Auxiliary operations
    • B29C48/88—Thermal treatment of the stream of extruded material, e.g. cooling
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/25—Component parts, details or accessories; Auxiliary operations
    • B29C48/92—Measuring, controlling or regulating
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C67/00—Shaping techniques not covered by groups B29C39/00 - B29C65/00, B29C70/00 or B29C73/00
    • B29C67/20—Shaping techniques not covered by groups B29C39/00 - B29C65/00, B29C70/00 or B29C73/00 for porous or cellular articles, e.g. of foam plastics, coarse-pored
    • B29C67/202—Shaping techniques not covered by groups B29C39/00 - B29C65/00, B29C70/00 or B29C73/00 for porous or cellular articles, e.g. of foam plastics, coarse-pored comprising elimination of a solid or a liquid ingredient
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
    • C08J9/28—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof by elimination of a liquid phase from a macromolecular composition or article, e.g. drying of coagulum
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/403—Manufacturing processes of separators, membranes or diaphragms
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C2948/00—Indexing scheme relating to extrusion moulding
    • B29C2948/92—Measuring, controlling or regulating
    • B29C2948/92504—Controlled parameter
    • B29C2948/92514—Pressure
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C2948/00—Indexing scheme relating to extrusion moulding
    • B29C2948/92—Measuring, controlling or regulating
    • B29C2948/92504—Controlled parameter
    • B29C2948/92704—Temperature
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C2948/00—Indexing scheme relating to extrusion moulding
    • B29C2948/92—Measuring, controlling or regulating
    • B29C2948/92819—Location or phase of control
    • B29C2948/92857—Extrusion unit
    • B29C2948/92904—Die; Nozzle zone
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2023/00—Use of polyalkenes or derivatives thereof as moulding material
    • B29K2023/04—Polymers of ethylene
    • B29K2023/06—PE, i.e. polyethylene
    • B29K2023/0658—PE, i.e. polyethylene characterised by its molecular weight
    • B29K2023/0675—HMWPE, i.e. high molecular weight polyethylene
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2023/00—Use of polyalkenes or derivatives thereof as moulding material
    • B29K2023/04—Polymers of ethylene
    • B29K2023/06—PE, i.e. polyethylene
    • B29K2023/0658—PE, i.e. polyethylene characterised by its molecular weight
    • B29K2023/0683—UHMWPE, i.e. ultra high molecular weight polyethylene
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the invention belongs to the technical field of lithium/ion batteries, and specifically relates to a polyolefin porous membrane and a preparation method thereof.
  • the technical solution adopted by the present invention to solve its technical problem is to provide a polyolefin porous membrane, comprising a first surface and a second surface corresponding to the first surface, and the surface of the polyolefin porous membrane contains dendrites. Crystals and micropores, the dendrites and micropores are interlaced on the first surface or/and the second surface, and the dendrites penetrate the second surface from the first surface.
  • the width of the dendrites is between 0.25-0.5 ⁇ m.
  • the average number of dendrites contained in the polyolefin porous membrane per square micrometer is between 2-8.
  • Another technical solution adopted by the present invention to solve its technical problem is to provide a method for preparing a polyolefin porous membrane, which includes the steps:
  • the mixing and melting of polyethylene resin and white oil the polyethylene resin and white oil are added to the twin-screw extruder through two feeding ports, and the white oil is put in the first feeding port, and the second feeding port Put a mixture of white oil and polyethylene resin into the mouth, and set the temperature to be greater than the melting temperature of the polyethylene resin to form a white oil/polyethylene resin molten mixture;
  • the polyethylene resin in step (1) is a mixed resin of an ultra-high molecular weight polyethylene resin and a high molecular weight polyethylene resin, and the molecular weight of the ultra-high molecular weight polyethylene resin is more than 1,800,000 The molecular weight of the high molecular weight polyethylene resin is between 600,000 and 700,000.
  • the mass percentages of the ultra-high molecular weight polyethylene resin, high molecular weight polyethylene resin and white oil are respectively: 15%-20%, 5%-10%, 70%-80%
  • the total mass percentage of the ultra-high molecular weight polyethylene resin, high molecular weight polyethylene resin and white oil is 100%.
  • the extrusion temperature in step (2) is 10-15°C lower than the melting temperature.
  • the pressure of the T-die in step (2) is between 0.1-0.3Mpa.
  • the solvent in step (5) is dichloromethane.
  • the beneficial effects of the present invention are: the mechanical properties of the polyolefin porous film can be improved, such as tensile strength, puncture strength, etc.; the preparation method provided by the present invention can be used to prepare a polyolefin porous film with excellent tensile properties.
  • the present invention mainly adjusts the raw material formula and improves the processing technology during the preparation of the diaphragm, so that the prepared diaphragm has a specific crystal structure in the microscopic view, which is expressed as a dendritic crystal structure.
  • the microstructure of this lithium-ion battery separator contains a structure in which dendrites and micropores are interlaced on a plane, and the dendrites can also penetrate both sides of the entire membrane with a width between 0.25-0.5 ⁇ m.
  • the number of crystalline structure in a unit area of the diaphragm can be observed by scanning electron microscopy, and the average number of dendrites per square micrometer of the film is between 2-8.
  • the raw materials used in the present invention are polyethylene and white oil.
  • polyethylene adopts a mixed resin of ultra-high molecular weight polyethylene resin (UHMWPE) and high molecular weight polyethylene resin (HDPE). Between 600000-700000.
  • UHMWPE ultra-high molecular weight polyethylene resin
  • HDPE high molecular weight polyethylene resin
  • the present invention has no special requirements for white oil, and any industrial-grade white oil or paraffin oil can be used.
  • the mass ratios of UHMWPE, HDPE and white oil are respectively: 15%-20%, 5%-10%, 70%-80 %.
  • the preparation method adopts a wet stretching process, and the preparation steps are as follows:
  • the polyethylene resin and white oil are fed into the twin-screw extruder through two feeding ports respectively.
  • the first feeding port only puts white oil into the second feeding port. Put the mixture of white oil and polyethylene resin into the mouth, and set the temperature above the melting temperature of polyethylene.
  • the specific temperature varies according to different raw materials, and this patent does not make specific requirements;
  • the stretched film is subjected to heat setting treatment and then wound up.
  • n the number of dendrites per unit area (pieces/ ⁇ m 2 );
  • d represents the average width of dendrites per unit area ( ⁇ m).
  • the polyolefin porous membrane and the preparation method thereof of the present invention can ensure the thickness of the membrane while greatly improving its mechanical tensile properties and puncture resistance.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Health & Medical Sciences (AREA)
  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Manufacture Of Porous Articles, And Recovery And Treatment Of Waste Products (AREA)
  • Cell Separators (AREA)

Abstract

本发明涉及一种聚烯烃多孔膜及其制备方法，在隔膜制备过程中通过原料配方的调整及加工工艺的改进，使所制备的隔膜在微观上具有特定的晶体结构，表现为枝状晶体结构，可以提高聚烯烃多孔膜的机械性能，如拉伸强度、穿刺强度等；使用本发明提供的制备方法可以制备出具有优秀拉伸性能的聚烯烃多孔膜。

Description

一种聚烯烃多孔膜及其制备方法 技术领域
本发明属于锂/离子电池技术领域，具体涉及一种聚烯烃多孔膜及其制备方法。
背景技术
随着锂离子电池在实际中的应用越来越广泛，人们对于锂离子电池的性能要求也随之提高，因此，很多电池企业对高容量的锂离子电池研发投入越来越高。随着新能源汽车的发展，新能源汽车所用的电池是否安全，是否会发生爆炸自燃使得人们对于锂离子电池的安全性有了更高要求。因此，对于应用在电池中的隔膜也提出了新的安全性能的要求，如何最大限度的提高其机械性能，包括拉伸强度、穿刺强度等，是目前隔膜研究者所急需解决的问题。
发明内容
本发明解决其技术问题所采用的技术方案是：提供一种聚烯烃多孔膜，包括第一表面和与所述第一表面相对应的第二表面，在所述聚烯烃多孔膜表面含有枝状晶体与微孔，所述枝状晶体与微孔在所述第一表面或/和第二表面上互相交错，所述枝状晶体自所述第一表面贯穿所述第二表面。
作为本发明的一个优选的实施例，所述枝状晶体的宽度在0.25-0.5μm之间。
作为本发明的一个优选的实施例，平均每平方微米的聚烯烃多孔膜中含有所述枝状晶体的数量在2-8个之间。
本发明解决其技术问题所采用的另一技术方案是：提供一种聚烯烃多孔膜的制备方法，包括步骤：
(1)聚乙烯树脂和白油的混合熔融：将聚乙烯树脂与白油分别通过两个投料口加入到双螺杆挤出机中，在第一个投料口中投入白油，在第二个投料口中投入白油和聚乙烯树脂的混合物，并将温度设置成大于所述聚乙烯树脂的熔融温度，形成白油/聚乙烯树脂熔融混合物；
(2)白油/聚乙烯树脂熔融混合物的挤出：通过所述双螺杆挤出机的T型模头将熔融后的白油/聚乙烯树脂混合物挤出成厚片材；
(3)厚片材的纵向拉伸：将所述厚片材经过6组拉伸辊，温度保持在150℃-170℃之间，前后相邻两个拉伸辊之间的速比控制在1.2-1.8之间，形成隔膜；
(4)隔膜的一次横向拉伸：对所述隔膜进行9-12倍的横向拉伸；
(5)将所述隔膜浸入溶剂中将白油萃取出来；
(6)隔膜的二次横向拉伸：对所述隔膜进行1.2-1.4倍的横向拉伸，使得在隔膜中形成纵向晶体；
(7)将形成纵向晶体后的薄膜进行热定型处理后收卷。
作为本发明的一个优选的实施例，步骤(1)中所述聚乙烯树脂为超高分子量聚乙烯树脂和高分子量聚乙烯树脂的混合树脂，所述超高分子量聚乙烯树脂的分子量为1800000以上，所述高分子量聚乙烯树脂的分子量在600000-700000之间。
作为本发明的一个优选的实施例，所述超高分子量聚乙烯树脂、高分子量聚乙烯树脂和白油的质量百分比分别为：15％—20％、5％-10％、70％-80％，所述超高分子量聚乙烯树脂、高分子量聚乙烯树脂和白油的质量百分比合计为100％。
作为本发明的一个优选的实施例，步骤(2)中所述挤出温度低于熔融温度10-15℃。
作为本发明的一个优选的实施例，步骤(2)中所述T型模头的压力在0.1-0.3Mpa之间。
作为本发明的一个优选的实施例，步骤(5)中所述溶剂为二氯甲烷。
本发明的有益效果是：可以提高聚烯烃多孔膜的机械性能，如拉伸强度、穿刺强度等；使用本发明提供的制备方法可以制备出具有优秀拉伸性能的聚烯烃多孔膜。
具体实施方式
本发明主要是在隔膜制备过程中通过原料配方的调整及加工工艺的改进，使所制备的隔膜在微观上具有特定的晶体结构，表现为枝状晶体结构。
这种锂离子电池隔膜的微观结构中含有枝状晶体与微孔在平面上互相交错的结构，且该枝状晶体还可贯穿整个膜的两面，宽度在0.25-0.5μm之间，这种枝状晶体结构在单位面积的隔膜中的数量可以通过扫描电镜观察到，平均每平方微米的膜中所含枝状晶体的数量在2-8个之间。
本发明所用的原料均为聚乙烯和白油，其中聚乙烯采用超高分子量聚乙烯树脂(UHMWPE)和高分子量聚乙烯树脂(HDPE)的混合树脂，UHMWPE的 分子量选用1800000以上，HDPE的分子量选用600000-700000之间。本发明对白油没有特殊的要求，可以采用任意工业级白油或石蜡油，其中UHMWPE、HDPE和白油的质量比比例分别为：15％—20％、5％-10％、70％-80％。
制备方法采用湿法拉伸工艺，制备步骤有：
(1)聚乙烯树脂和白油的混合熔融阶段，将聚乙烯树脂与白油分别通过两个投料口加入到双螺杆挤出机中，第一个投料口只投入白油，第二个投料口投入白油和聚乙烯树脂的混合物，并将温度设置为聚乙烯熔融温度以上，具体的温度根据原料的不同而不同，本专利不做具体要求；
(2)白油/聚乙烯树脂熔融混合物的挤出过程，通过挤出机的T型模头将熔融后的混合物挤出成厚片材，挤出温度低于熔融温度10-15℃之间，模头的压力控制在0.1-0.3Mpa之间；
(3)流延片材的纵向拉伸(MD)过程，其中共有6组拉伸辊，在此过程中需要控制拉伸温度和拉伸辊之间的速比，温度保持在150℃-170℃之间，前后相邻两个拉伸辊之间的速比控制在1.2-1.8之间；
(4)一次横向(TD1)拉伸过程，该步对隔膜进行9-12倍的横向拉伸；
(5)浸入二氯甲烷的溶剂中将白油萃取出来；
(6)二次横向拉伸(TD2)：该步骤对膜进行1.2-1.4倍的拉伸，保证膜中形成纵向晶体；
(7)将拉伸后的薄膜进行热定型处理后收卷。
为使本发明的上述目的、特征和优点能够更加明显易懂，下面结合具体实施方式对本发明作进一步详细的说明。
实施例1
Figure PCTCN2020091494-appb-000001
Figure PCTCN2020091494-appb-000002
注：
n表示单位面积内枝晶数量(个/μm 2)；
d表示单位面积内枝晶平均宽度(μm)。
实施例2
Figure PCTCN2020091494-appb-000003
实施例3
Figure PCTCN2020091494-appb-000004
Figure PCTCN2020091494-appb-000005
实施例4：
Figure PCTCN2020091494-appb-000006
实施例5：
Figure PCTCN2020091494-appb-000007
Figure PCTCN2020091494-appb-000008
以下通过实施例4与现有技术进行对比：
隔膜性质 实施例4 对比例1 对比例2 对比例3 对比例4
n(个/μm 2) 3.7 7.4 6.1 5.4 4.7
d(μm) 0.28 0.04 0.11 0.21 0.34
MD拉伸强度(Kgf/cm 2) 3209 2416 1937 2739 3128
TD拉伸强度(Kgf/cm 2) 3567 2601 2483 2941 3309
MD伸长率(％) 216 239 223 169 143
TD伸长率(％) 246 240 249 184 169
正面穿刺强度(gf) 514 386 409 372 412
反面穿刺强度(gf) 536 361 394 393 429
综上所述，本发明所述的一种聚烯烃多孔膜及其制备方法，能够保证膜的厚度的同时，极大的提高了其机械拉伸性能和防刺穿性能。
以上述依据本发明的理想实施例为启示，通过上述的说明内容，相关工作人员完全可以在不偏离本项发明技术思想的范围内，进行多样的变更以及修改。本项发明的技术性范围并不局限于说明书上的内容，必须要根据权利要求范围来确定其技术性范围。

Claims (9)

  1. 一种聚烯烃多孔膜，其特征在于：聚烯烃多孔膜包括第一表面和与所述第一表面相对应的第二表面，在所述聚烯烃多孔膜表面含有枝状晶体与微孔，所述枝状晶体与微孔在所述第一表面或/和第二表面上互相交错，所述枝状晶体自所述第一表面贯穿所述第二表面。
  2. 根据权利要求1所述的一种聚烯烃多孔膜，其特征在于：所述枝状晶体的宽度在0.25-0.5μm之间。
  3. 根据权利要求1所述的一种聚烯烃多孔膜，其特征在于：平均每平方微米的聚烯烃多孔膜中含有所述枝状晶体的数量在2-8个之间。
  4. 一种聚烯烃多孔膜的制备方法，其特征在于，包括步骤：
    (1)聚乙烯树脂和白油的混合熔融：将聚乙烯树脂与白油分别通过两个投料口加入到双螺杆挤出机中，在第一个投料口中投入白油，在第二个投料口中投入白油和聚乙烯树脂的混合物，并将温度设置成大于所述聚乙烯树脂的熔融温度，形成白油/聚乙烯树脂熔融混合物；
    (2)白油/聚乙烯树脂熔融混合物的挤出：通过所述双螺杆挤出机的T型模头将熔融后的白油/聚乙烯树脂混合物挤出成厚片材；
    (3)厚片材的纵向拉伸：将所述厚片材经过6组拉伸辊，温度保持在150℃-170℃之间，前后相邻两个拉伸辊之间的速比控制在1.2-1.8之间，形成隔膜；
    (4)隔膜的一次横向拉伸：对所述隔膜进行9-12倍的横向拉伸；
    (5)将所述隔膜浸入溶剂中将白油萃取出来；
    (6)隔膜的二次横向拉伸：对所述隔膜进行1.2-1.4倍的横向拉伸，使得在隔膜中形成纵向晶体；
    (7)将形成纵向晶体后的薄膜进行热定型处理后收卷。
  5. 根据权利要求4所述的一种聚烯烃多孔膜的制备方法，其特征在于：步骤(1)中所述聚乙烯树脂为超高分子量聚乙烯树脂和高分子量聚乙烯树脂的混合树脂，所述超高分子量聚乙烯树脂的分子量为1800000以上，所述高分子量聚乙烯树脂的分子量在600000-700000之间。
  6. 根据权利要求5所述的一种聚烯烃多孔膜的制备方法，其特征在于：所述超高分子量聚乙烯树脂、高分子量聚乙烯树脂和白油的质量百分比分别为：15％—20％、5％-10％、70％-80％，所述超高分子量聚乙烯树脂、高分子量聚乙烯树脂和白油的质量百分比合计为100％。
  7. 根据权利要求4所述的一种聚烯烃多孔膜的制备方法，其特征在于：步骤(2)中所述挤出温度低于熔融温度10-15℃。
  8. 根据权利要求4所述的一种聚烯烃多孔膜的制备方法，其特征在于：步骤(2)中所述T型模头的压力在0.1-0.3Mpa之间。
  9. 根据权利要求4所述的一种聚烯烃多孔膜的制备方法，其特征在于：步骤(5)中所述溶剂为二氯甲烷。
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