JP2016128532A - Microporous film and manufacturing method therefor - Google Patents
Microporous film and manufacturing method therefor Download PDFInfo
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- JP2016128532A JP2016128532A JP2015002952A JP2015002952A JP2016128532A JP 2016128532 A JP2016128532 A JP 2016128532A JP 2015002952 A JP2015002952 A JP 2015002952A JP 2015002952 A JP2015002952 A JP 2015002952A JP 2016128532 A JP2016128532 A JP 2016128532A
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- 238000004519 manufacturing process Methods 0.000 title claims abstract description 16
- 238000001125 extrusion Methods 0.000 claims abstract description 30
- -1 polypropylene Polymers 0.000 claims abstract description 29
- 239000004743 Polypropylene Substances 0.000 claims abstract description 27
- 229920001155 polypropylene Polymers 0.000 claims abstract description 27
- 229920000642 polymer Polymers 0.000 claims abstract description 25
- 239000000155 melt Substances 0.000 claims abstract description 13
- 239000012982 microporous membrane Substances 0.000 claims description 68
- 238000000034 method Methods 0.000 claims description 61
- 238000012360 testing method Methods 0.000 claims description 37
- 239000002994 raw material Substances 0.000 claims description 28
- 238000002844 melting Methods 0.000 claims description 13
- 230000008018 melting Effects 0.000 claims description 13
- 239000012528 membrane Substances 0.000 claims description 13
- 230000005611 electricity Effects 0.000 claims description 11
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 claims description 7
- 229910001416 lithium ion Inorganic materials 0.000 claims description 7
- 239000003990 capacitor Substances 0.000 claims description 5
- QQONPFPTGQHPMA-UHFFFAOYSA-N propylene Natural products CC=C QQONPFPTGQHPMA-UHFFFAOYSA-N 0.000 claims description 5
- 125000004805 propylene group Chemical group [H]C([H])([H])C([H])([*:1])C([H])([H])[*:2] 0.000 claims description 5
- 125000004432 carbon atom Chemical group C* 0.000 claims description 4
- 238000005259 measurement Methods 0.000 claims description 4
- VGGSQFUCUMXWEO-UHFFFAOYSA-N Ethene Chemical compound C=C VGGSQFUCUMXWEO-UHFFFAOYSA-N 0.000 claims description 3
- 239000005977 Ethylene Substances 0.000 claims description 3
- 238000010438 heat treatment Methods 0.000 claims description 3
- 239000004711 α-olefin Substances 0.000 claims description 3
- 238000012545 processing Methods 0.000 claims description 2
- 230000002040 relaxant effect Effects 0.000 claims description 2
- 239000000463 material Substances 0.000 abstract description 13
- 229920005672 polyolefin resin Polymers 0.000 description 13
- 230000000052 comparative effect Effects 0.000 description 10
- 239000000203 mixture Substances 0.000 description 6
- 229920005989 resin Polymers 0.000 description 5
- 239000011347 resin Substances 0.000 description 5
- 239000000126 substance Substances 0.000 description 5
- 238000000926 separation method Methods 0.000 description 4
- 239000000654 additive Substances 0.000 description 3
- 229920001384 propylene homopolymer Polymers 0.000 description 3
- WSSSPWUEQFSQQG-UHFFFAOYSA-N 4-methyl-1-pentene Chemical compound CC(C)CC=C WSSSPWUEQFSQQG-UHFFFAOYSA-N 0.000 description 2
- 239000004698 Polyethylene Substances 0.000 description 2
- 230000000996 additive effect Effects 0.000 description 2
- 238000010622 cold drawing Methods 0.000 description 2
- 239000003484 crystal nucleating agent Substances 0.000 description 2
- 150000001993 dienes Chemical class 0.000 description 2
- 238000011156 evaluation Methods 0.000 description 2
- 239000003921 oil Substances 0.000 description 2
- 239000012188 paraffin wax Substances 0.000 description 2
- 230000035699 permeability Effects 0.000 description 2
- 239000004014 plasticizer Substances 0.000 description 2
- 229920000573 polyethylene Polymers 0.000 description 2
- 229920000098 polyolefin Polymers 0.000 description 2
- YHQXBTXEYZIYOV-UHFFFAOYSA-N 3-methylbut-1-ene Chemical compound CC(C)C=C YHQXBTXEYZIYOV-UHFFFAOYSA-N 0.000 description 1
- VQTUBCCKSQIDNK-UHFFFAOYSA-N Isobutene Chemical compound CC(C)=C VQTUBCCKSQIDNK-UHFFFAOYSA-N 0.000 description 1
- 241000446313 Lamella Species 0.000 description 1
- 150000001336 alkenes Chemical class 0.000 description 1
- 229920001577 copolymer Polymers 0.000 description 1
- 239000000945 filler Substances 0.000 description 1
- 230000001771 impaired effect Effects 0.000 description 1
- 239000011244 liquid electrolyte Substances 0.000 description 1
- 229920006254 polymer film Polymers 0.000 description 1
- 229920005653 propylene-ethylene copolymer Polymers 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 150000003440 styrenes Chemical class 0.000 description 1
- 229920003002 synthetic resin Polymers 0.000 description 1
- 239000000057 synthetic resin Substances 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
- H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
- H01G11/52—Separators
-
- 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
-
- 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
- Y02E60/13—Energy storage using capacitors
Abstract
Description
本発明はポリプロピレン系重合体からなる微多孔膜、これから得られる蓄電デバイス、及び上記微多孔膜の製造方法に関する。 The present invention relates to a microporous membrane made of a polypropylene polymer, an electricity storage device obtained therefrom, and a method for producing the microporous membrane.
合成樹脂製微多孔膜は、各種分離膜や、電池セパレータの材料として利用されている。中でもポリオレフィン系樹脂は、耐薬剤性が高く、様々な方法で多孔化が可能である点で、薬剤に接した状態で使用される各種分離膜や、電池セパレータ微多孔膜の原料として有用である。 Synthetic resin microporous membranes are used as materials for various separation membranes and battery separators. Among them, polyolefin resins are useful as raw materials for various separation membranes used in contact with chemicals and battery separator microporous membranes because they have high chemical resistance and can be made porous by various methods. .
ポリオレフィン系樹脂フィルムの多孔化方法は、湿式法と乾式法に大別される。湿式法では、ポリオレフィン系樹脂と、可塑剤、オイル、パラフィンなどとの溶融混合物をフィルム状に展開する。次に、ポリオレフィン以外の成分を抽出し、これら成分が存在した部分を空隙化する。その結果、ポリオレフィン系樹脂が微多孔膜に成形加工される。乾式法では、可塑剤、オイル、パラフィンなどの成分や溶剤を含まない、ポリオレフィン系樹脂を主体とする原料を延伸することによって、ポリオレフィン系樹脂を微多孔膜に成形加工する方法である。乾式法として、ポリオレフィン系樹脂中のラメラ構造の間隙に空隙を発生させる方法と、原料に添加した無機添加剤とポリオレフィン系樹脂との界面に空隙を発生させる方法とが知られている。 The method for making a polyolefin resin film porous is roughly classified into a wet method and a dry method. In the wet method, a molten mixture of a polyolefin-based resin and a plasticizer, oil, paraffin or the like is developed into a film. Next, components other than the polyolefin are extracted, and the portions where these components exist are voided. As a result, the polyolefin resin is molded into a microporous film. The dry method is a method in which a polyolefin resin is molded into a microporous film by stretching a raw material mainly containing a polyolefin resin that does not contain components such as plasticizer, oil, paraffin, and a solvent. As a dry method, there are known a method of generating voids in the gaps of the lamellar structure in the polyolefin resin and a method of generating voids at the interface between the inorganic additive added to the raw material and the polyolefin resin.
電池セパレータ用のポリオレフィン系樹脂製微多孔膜については、特許文献１、２、３に記載されたような、様々な製造方法が知られている。 Various manufacturing methods as described in Patent Literatures 1, 2, and 3 are known for polyolefin resin microporous membranes for battery separators.
特許文献１には、ポリオレフィン系樹脂と共役ジエンポリマーとの混合物からなる原料を、湿式法により微多孔フィルムに加工し、得られた微多孔膜を電池セパレータ材として用いることが記載されている。 Patent Document 1 describes that a raw material composed of a mixture of a polyolefin resin and a conjugated diene polymer is processed into a microporous film by a wet method, and the resulting microporous film is used as a battery separator material.
特許文献２には、ポリプロピレンとポリエチレンとの混合物を、乾式法により２段階で延伸することによって微多孔フィルムに加工し、得られた微多孔膜を電池セパレータ材として用いることが記載されている。 Patent Document 2 describes that a mixture of polypropylene and polyethylene is processed into a microporous film by stretching in two stages by a dry method, and the resulting microporous film is used as a battery separator material.
特許文献３には、ポリオレフィンに低分子量物質を配合した混合物を、乾式法により２段階で延伸することによって微多孔フィルムに加工し、得られた微多孔膜を電池セパレータ材として用いることが記載されている。 Patent Document 3 describes that a mixture in which a low molecular weight substance is blended with polyolefin is processed into a microporous film by stretching in two stages by a dry method, and the obtained microporous film is used as a battery separator material. ing.
ところで、最近の電池性能に対する要求は、ますます高度化、多様化している。特に、車両や携帯端末などの屋外で使用される工業製品に搭載されるリチウムイオン電池には、優れた充放電特性に加え、高い安全性と強度が求められる。リチウムイオン電池セパレータは、電池筺体内に配置されている部材ではあるが、液状電解質に浸漬された状態で幾層にも捲回されて電池筺体空間を満たしているから、セパレータの強度は電池の強度に大きく寄与する。そのため、強度の高いリチウムイオン電池本体を製造するために、強度の高いセパレータが求められている。 By the way, recent demands for battery performance are becoming increasingly sophisticated and diversified. In particular, lithium ion batteries mounted on industrial products used outdoors such as vehicles and portable terminals are required to have high safety and strength in addition to excellent charge / discharge characteristics. Although the lithium ion battery separator is a member arranged in the battery case, it is wound in layers in a state immersed in the liquid electrolyte and fills the battery case space. Significantly contributes to strength. Therefore, in order to manufacture a high-strength lithium ion battery body, a high-strength separator is required.
強度の高いセパレータを製造するためには、セパレータの材料として強度の高い微多孔膜を用いることが求められる。微多孔膜の強度の指標としては、微多孔膜の引張強度と突刺強度が一般的に用いられている。 In order to manufacture a separator having high strength, it is required to use a microporous membrane having high strength as a material for the separator. As an index of the strength of the microporous membrane, the tensile strength and puncture strength of the microporous membrane are generally used.
引張強度と突刺強度が高い、電池セパレータ用のポリオレフィン系樹脂製微多孔膜については、特許文献４、５に記載されている。 Patent Documents 4 and 5 describe polyolefin resin microporous membranes for battery separators that have high tensile strength and high puncture strength.
特許文献４には、ポリプリピレンにβ結晶核剤を配合したポリプロピレン組成物を原料とした、引張強度と突刺強度の高い微多孔膜が記載されている。 Patent Document 4 describes a microporous membrane having a high tensile strength and high puncture strength using a polypropylene composition in which a β crystal nucleating agent is blended with polypropylene.
特許文献５には、ポリプロピレンにポリエチレンを配合したポリプロピレン組成物を原料とした、引張強度と突刺強度の高い微多孔膜が記載されている。 Patent Document 5 describes a microporous film having a high tensile strength and high puncture strength using a polypropylene composition in which polyethylene is blended with polypropylene as a raw material.
しかしながら、セパレータのイオン電導性を発現するための微多孔膜の空孔率と、微多孔膜の強度とはいわゆるトレードオフの関係を示す傾向があり、空孔率と強度とのバランスに優れる電池セパレータ用ポリオレフィン樹脂製微多孔膜には、未だ改善の余地がある。 However, the porosity of the microporous film for expressing the ionic conductivity of the separator and the strength of the microporous film tend to show a so-called trade-off relationship, and the battery has an excellent balance between the porosity and the strength. There is still room for improvement in polyolefin resin microporous membranes for separators.
そこで本発明の発明者は、引張強度や突刺強度などの強度が高く、しかも高い空孔率を有する、電池セパレータ材として有用なポリオレフィン系樹脂製微多孔膜を探求した。 Therefore, the inventors of the present invention have sought a polyolefin resin microporous membrane useful as a battery separator material having high strength such as tensile strength and pin puncture strength and high porosity.
その結果、特定のメルトマスフローレイトを有するポリプロピレン系樹脂を原料として用い、乾式法によって、引張強度や突刺強度などの強度が高く、しかも高い空孔率を有する、電池セパレータ材として有用な微多孔膜を製造することに成功した。 As a result, a microporous membrane useful as a battery separator material that uses a polypropylene resin having a specific melt mass flow rate as a raw material, has high strength such as tensile strength and puncture strength, and high porosity by a dry method. Succeeded in manufacturing.
すなわち本発明は以下のものである。 That is, the present invention is as follows.
（発明１）メルトマスフローレイト（ＭＦＲ、ＪＩＳ Ｋ６７５８に準拠して２３０℃、荷重２１．１８Ｎで測定）が１．０〜１０．０ｇ／１０分であるポリプロピレン系重合体からなり、以下の方法（Ａ）で求めた押出方向（ＭＤ）の引張強度が２００ＭＰａ以上、幅方向（ＴＤ）の引張強度が１０ＭＰａ以上であり、かつ、以下の方法（Ｂ）で測定された突刺強度が４．９Ｎ以上である、微多孔膜。
方法（Ａ）：微多孔膜から押出方向（ＭＤ）と、幅方向（ＴＤ）の２方向に試験片を切り出し、それぞれの試験片（ＭＤ方向の試験片、ＴＤ方向の試験片）の破断荷重（Ｎ）を引張速度５００ｍｍ／分の条件で測定する。以下の式により押出方向（ＭＤ）の引張強度、幅方向（ＴＤ）の引張強度を算出する。
押出方向（ＭＤ）の引張強度（ＭＰａ）＝［押出方向（ＭＤ）の破断荷重（Ｎ）］／［試験片の断面積（ｍｍ２）］
幅方向（ＴＤ）の引張強度（ＭＰａ）=［幅方向（ＴＤ）の破断荷重（Ｎ）］／［試験片の断面積（ｍｍ２）］
方法（Ｂ）：微多孔膜表面に先端が直径１ｍｍの球面形状の針で、１００ｍｍ／分の速度で突刺して針に掛る荷重を測定する。このときの最大荷重（Ｎ）を突刺強度の値とする。
(Invention 1) A melt mass flow rate (MFR, measured at 230 ° C. under a load of 21.18 N in accordance with JIS K6758) is a polypropylene polymer having 1.0 to 10.0 g / 10 min. The tensile strength in the extrusion direction (MD) determined in A) is 200 MPa or more, the tensile strength in the width direction (TD) is 10 MPa or more, and the puncture strength measured by the following method (B) is 4.9 N or more. A microporous membrane.
Method (A): A test piece is cut out from the microporous membrane in two directions of extrusion direction (MD) and width direction (TD), and the breaking load of each test piece (test piece in MD direction, test piece in TD direction). (N) is measured under the condition of a tensile speed of 500 mm / min. The tensile strength in the extrusion direction (MD) and the tensile strength in the width direction (TD) are calculated by the following equations.
Tensile strength (MPa) in extrusion direction (MD) = [Breaking load in extrusion direction (MD) (N)] / [Cross sectional area of test piece (mm 2 )]
Tensile strength (MPa) in width direction (TD) = [Breaking load (N) in width direction (TD)] / [Cross sectional area of test piece (mm 2 )]
Method (B): The load applied to the needle is measured by piercing at a speed of 100 mm / min with a spherical needle having a diameter of 1 mm on the surface of the microporous membrane. The maximum load (N) at this time is defined as the puncture strength value.
（発明２）空孔率が４５〜５５％の範囲にある、発明１の微多孔膜。 (Invention 2) The microporous membrane of Invention 1 having a porosity in the range of 45 to 55%.
（発明３）ポリプロピレン系重合体が、融点が１５０〜１７０℃の範囲にあり、メルトマスフローレイト（ＭＦＲ、ＪＩＳ Ｋ６７５８（２３０℃、２１．１８Ｎ）に準拠した条件で測定）が１．０〜１０ｇ／１０分の範囲にある、任意にエチレン、炭素数４〜８のα−オレフィンから選ばれる少なくとも１種を含んでいてもよい、プロピレン主体の重合体である、発明１または２の微多孔膜。 (Invention 3) Polypropylene polymer has a melting point in the range of 150 to 170 ° C., and a melt mass flow rate (measured in accordance with MFR, JIS K6758 (230 ° C., 21.18 N)) of 1.0 to 10 g. The microporous membrane of Invention 1 or 2, which is a propylene-based polymer, optionally containing at least one selected from ethylene and an α-olefin having 4 to 8 carbon atoms, in the range of / 10 minutes .
（発明４）蓄電デバイスのセパレータに用いられることを特徴とする発明１〜３のいずれかの微多孔膜。 (Invention 4) The microporous membrane according to any one of Inventions 1 to 3, which is used for a separator of an electricity storage device.
（発明５）蓄電デバイスがリチウムイオン電池である、発明４の微多孔膜。 (Invention 5) The microporous membrane of Invention 4, wherein the electricity storage device is a lithium ion battery.
（発明６）蓄電デバイスがキャパシタである、発明４の微多孔膜。 (Invention 6) The microporous membrane of Invention 4, wherein the electricity storage device is a capacitor.
（発明７）発明４の微多孔膜を備える蓄電デバイス。 (Invention 7) An electricity storage device comprising the microporous membrane of Invention 4.
（発明８）発明５の微多孔膜を備えるリチウムイオン電池。 (Invention 8) A lithium ion battery comprising the microporous membrane of Invention 5.
（発明９）発明６の微多孔膜を備えるキャパシタ。 (Invention 9) A capacitor comprising the microporous membrane of Invention 6.
（発明１０）以下の工程を含む、発明１〜９のいずれかの記載の微多孔膜の製造方法。
（工程１）ＪＩＳ Ｋ６７５８に準拠して２３０℃、荷重２１．１８Ｎで測定したメルトマスフローレイト（ＭＦＲ）が１．０〜１０．０ｇ／１０分であるポリプロピレン系重合体を押出成形して原反フィルムを製膜する工程。
（工程２）工程１で得られた原反フィルムを熱処理する工程。
（工程３）工程２で得られた熱処理後の原反フィルムを、−５〜４５℃で、長さ方向に１．０〜１．１倍に延伸する工程。
（工程４）工程３を終えた延伸フィルムを、ポリプロピレン系重合体の融点よりも５〜６５℃低い温度で、長さ方向に１．５〜４．０倍に延伸する工程。
（工程５）工程４で得られた温延伸後のフィルムを、加熱下、長さが０．７〜１．０倍になるように弛緩させる工程。
(Invention 10) The method for producing a microporous membrane according to any one of Inventions 1 to 9, comprising the following steps.
(Step 1) A polypropylene polymer having a melt mass flow rate (MFR) of 1.0 to 10.0 g / 10 minutes measured at 230 ° C. and a load of 21.18 N in accordance with JIS K6758 is extruded to be a raw material The process of forming a film.
(Step 2) A step of heat-treating the raw film obtained in Step 1.
(Process 3) The process of extending | stretching the raw film after the heat processing obtained at the process 2 by 1.0-1.1 times in the length direction at -5-45 degreeC.
(Process 4) The process of extending | stretching the stretched film which finished the process 3 1.5 to 4.0 times in the length direction at the temperature lower than the melting point of a polypropylene-type polymer 5 to 65 degreeC.
(Step 5) A step of relaxing the film after warm stretching obtained in Step 4 so that the length becomes 0.7 to 1.0 times under heating.
本発明の微多孔膜は高い強度と高い空孔率を兼ね備える。したがって本発明の微多孔膜は、優れた物質透過性という化学的機能と、高い強度という構造的機能とを兼ね備える素材である。このような本発明の微多孔膜は、分離膜、蓄電デバイスのセパレータなどの部材に適している。 The microporous membrane of the present invention has both high strength and high porosity. Therefore, the microporous membrane of the present invention is a material having both a chemical function of excellent material permeability and a structural function of high strength. Such a microporous membrane of the present invention is suitable for members such as a separation membrane and a separator of an electricity storage device.
（微多孔膜）
本発明の微多孔膜は、メルトマスフローレイト（ＭＦＲ、ＪＩＳ Ｋ６７５８に準拠して２３０℃、荷重２１．１８Ｎで測定）が１．０〜１０．０ｇ／１０分であるポリプロピレン系重合体からなり、以下の方法（Ａ）で求めた押出方向（ＭＤ）の引張強度が２００ＭＰａ以上、幅方向（ＴＤ）の引張強度が１０ＭＰａ以上であり、かつ、以下の方法（Ｂ）で測定された突刺強度が４．９Ｎ以上である。
方法（Ａ）：微多孔膜から押出方向（ＭＤ）と、幅方向（ＴＤ）の２方向に試験片を切り出し、それぞれの試験片（ＭＤ方向の試験片、ＴＤ方向の試験片）の破断荷重（Ｎ）を引張速度５００ｍｍ／分の条件で測定する。以下の式により押出方向（ＭＤ）の引張強度、幅方向（ＴＤ）の引張強度を算出する。
押出方向（ＭＤ）の引張強度（ＭＰａ）＝［押出方向（ＭＤ）の破断荷重（Ｎ）］／［試験片の断面積（ｍｍ２）］
幅方向（ＴＤ）の引張強度（ＭＰａ）=［幅方向（ＴＤ）の破断荷重（Ｎ）］／［試験片の断面積（ｍｍ２）］
方法（Ｂ）：微多孔膜表面に先端が直径１ｍｍの球面形状の針で、１００ｍｍ／分の速度で突刺して針に掛る荷重を測定する。このときの最大荷重（Ｎ）を突刺強度の値とする。
(Microporous membrane)
The microporous membrane of the present invention is composed of a polypropylene polymer having a melt mass flow rate (MFR, measured at 230 ° C. according to JIS K6758 at a load of 21.18 N) of 1.0 to 10.0 g / 10 min. The tensile strength in the extrusion direction (MD) determined by the following method (A) is 200 MPa or more, the tensile strength in the width direction (TD) is 10 MPa or more, and the puncture strength measured by the following method (B) is It is 4.9N or more.
Method (A): A test piece is cut out from the microporous membrane in two directions of extrusion direction (MD) and width direction (TD), and the breaking load of each test piece (test piece in MD direction, test piece in TD direction). (N) is measured under the condition of a tensile speed of 500 mm / min. The tensile strength in the extrusion direction (MD) and the tensile strength in the width direction (TD) are calculated by the following equations.
Tensile strength (MPa) in extrusion direction (MD) = [Breaking load in extrusion direction (MD) (N)] / [Cross sectional area of test piece (mm 2 )]
Tensile strength (MPa) in width direction (TD) = [Breaking load (N) in width direction (TD)] / [Cross sectional area of test piece (mm 2 )]
Method (B): The load applied to the needle is measured by piercing at a speed of 100 mm / min with a spherical needle having a diameter of 1 mm on the surface of the microporous membrane. The maximum load (N) at this time is defined as the puncture strength value.
（微多孔膜の原料）
本発明の微多孔膜の原料は、ポリプロピレン系重合体であって、プロピレンの単独重合体あるいはコモノマーを共重合した共重合体がこれに相当する。本発明で使用するポリプロピレン系重合体としては、結晶性が比較的高い、融点が１５０〜１７０℃の範囲にあるものが好ましく、融点が１５５〜１６８℃の範囲にあるものがさらに好ましい。上記コモノマーは、一般的には、エチレンおよび炭素数４〜８のα−オレフィンから選ばれる少なくとも１種である。またこれらと共に、２−メチルプロペン、３−メチル−１−ブテン、４−メチル−１−ペンテンなどの炭素数４〜８の分岐オレフィン類、スチレン類、ジエン類を共重合したものであってもよい。
(Raw material for microporous membrane)
The raw material of the microporous membrane of the present invention is a polypropylene polymer, which corresponds to a propylene homopolymer or a copolymer obtained by copolymerizing a comonomer. The polypropylene polymer used in the present invention preferably has a relatively high crystallinity and a melting point in the range of 150 to 170 ° C, more preferably a melting point in the range of 155 to 168 ° C. The comonomer is generally at least one selected from ethylene and an α-olefin having 4 to 8 carbon atoms. In addition, these may be copolymerized with branched olefins having 4 to 8 carbon atoms such as 2-methylpropene, 3-methyl-1-butene, 4-methyl-1-pentene, styrenes, and dienes. Good.
上記コモノマーの含有量は、微多孔膜が所望の性質を示す限り、いかなる範囲にあってもよい。好ましくは、高結晶性ポリプロピレン系重合体を与える範囲である、重合体１００重量部に対して５重量部以下、特に２重量部以下が好ましい。 The comonomer content may be in any range as long as the microporous membrane exhibits desired properties. Preferably, it is 5 parts by weight or less, particularly 2 parts by weight or less with respect to 100 parts by weight of the polymer, which is a range giving a highly crystalline polypropylene polymer.
また上記ポリプロピレン系重合体のメルトマスフローレイト（ＭＦＲ、ＪＩＳ Ｋ６７５８（２３０℃、２１．１８Ｎ）に準拠した条件で測定）は１．０〜１０ｇ／１０分、好ましくは１．０〜５．０ｇ／１０分である。 The polypropylene polymer has a melt mass flow rate (measured in accordance with MFR, JIS K6758 (230 ° C., 21.18N)) of 1.0 to 10 g / 10 min, preferably 1.0 to 5.0 g / min. 10 minutes.
本発明の微多孔膜の原料には、結晶核剤や充填剤などの添加剤を配合することができる。添加剤の種類や量は、多孔性を損なわない範囲であれば、制限はない。 Additives such as crystal nucleating agents and fillers can be blended in the raw material of the microporous membrane of the present invention. The type and amount of the additive are not limited as long as the porosity is not impaired.
（微多孔膜の製造方法）
本発明の微多孔膜は、上述の原料を用いて、いわゆる乾式法によって製造される。本発明の微多孔膜の製造方法は、以下の工程１〜５を含む。
(Method for producing microporous membrane)
The microporous membrane of the present invention is produced by a so-called dry method using the above-described raw materials. The method for producing a microporous membrane of the present invention includes the following steps 1 to 5.
（工程１：製膜工程）
原料を押出成形して原反フィルムを製膜する工程である。ＪＩＳ Ｋ６７５８に準拠して２３０℃、荷重２１．１８Ｎで測定したメルトマスフローレイト（ＭＦＲ）が１．０〜１０．０ｇ／１０分であるポリプロピレン系重合体を押出機に供給し、ポリプロピレン系重合体をその融点以上の温度で溶融混練し、押出機の先端に取り付けたダイスからポリプロピレン系重合体フィルムを押出す。使用される押出機は限定されない。押出機としては、例えば、単軸押出機、二軸押出機、タンデム型押出機のいずれもが使用可能である。使用されるダイスはフィルム成形に用いられるものであれば、いずれも使用できる。ダイスとしては、例えば、各種Ｔ型ダイス使用することができる。原反フィルムの厚みや形状は特に限定されない。好ましくは、ダイスリップクリアランスと原反フィルム厚さの比（ドラフト比）は１００以上、さらに好ましくは１５０以上である。好ましくは、原反フィルムの厚みは１０〜２００μｍ、さらに好ましくは１５〜１００μｍである。
(Step 1: Film-forming step)
This is a process of forming a raw film by extruding the raw material. A polypropylene polymer having a melt mass flow rate (MFR) measured at 230 ° C. and a load of 21.18 N in accordance with JIS K6758 of 1.0 to 10.0 g / 10 min is supplied to the extruder, and the polypropylene polymer Is melt-kneaded at a temperature equal to or higher than its melting point, and a polypropylene polymer film is extruded from a die attached to the tip of the extruder. The extruder used is not limited. As the extruder, for example, any of a single screw extruder, a twin screw extruder, and a tandem type extruder can be used. Any die can be used as long as it is used for film forming. As the dice, for example, various T-type dice can be used. The thickness and shape of the raw film are not particularly limited. Preferably, the ratio (draft ratio) between the die slip clearance and the raw film thickness is 100 or more, more preferably 150 or more. Preferably, the thickness of the raw film is 10 to 200 μm, more preferably 15 to 100 μm.
（工程２：熱処理工程）
工程１を終えた原反フィルムを熱処理する工程である。ポリプロピレン系重合体の融点よりも５〜６５℃、好ましくは１０〜２５℃低い温度で、原反フィルムに長さ方向の一定の張力を加える。張力は、好ましくは、原反フィルムの長さが１．０倍を超え１．１倍以下となる大きさである。
(Process 2: Heat treatment process)
This is a step of heat-treating the raw film after step 1 is completed. A constant tension in the length direction is applied to the raw film at a temperature 5 to 65 ° C., preferably 10 to 25 ° C. lower than the melting point of the polypropylene polymer. The tension is preferably such that the length of the raw film exceeds 1.0 and is 1.1 times or less.
（工程３：冷延伸工程）
工程２を終えた熱処理後の原反フィルムを比較的低い温度で延伸する工程である。延伸温度は−５〜４５℃、好ましくは５〜３０℃である。延伸倍率は、長さ方向に１．０〜１．１、好ましくは１．００〜１．０８、さらに好ましくは１．０２以上１．０５未満である。ただし、延伸倍率は１．０倍より大きい。延伸手段は制限されない。ロール延伸法、テンター延伸法などの公知の手段が使用できる。延伸の段数は任意に設定できる。１段延伸でもよく、複数のロールを経て２段以上の延伸を行ってもよい。冷延伸工程で、原反フィルムを構成するポリプロピレン系重合体の分子が配向する。その結果、分子鎖が密なラメラ部と、ラメラ間の分子鎖が疎な領域（クレーズ）とを有する延伸フィルムが得られる。
(Process 3: Cold drawing process)
This is a step of stretching the heat-treated raw film after step 2 at a relatively low temperature. The stretching temperature is −5 to 45 ° C., preferably 5 to 30 ° C. The draw ratio is 1.0 to 1.1, preferably 1.00 to 1.08, more preferably 1.02 or more and less than 1.05 in the length direction. However, the draw ratio is greater than 1.0. The stretching means is not limited. Known means such as a roll stretching method and a tenter stretching method can be used. The number of stretching stages can be set arbitrarily. One-stage stretching may be performed, and two or more stages of stretching may be performed through a plurality of rolls. In the cold drawing step, the molecules of the polypropylene polymer constituting the raw film are oriented. As a result, a stretched film having a lamellar portion with a dense molecular chain and a region (craze) with a loose molecular chain between lamellas is obtained.
（工程４：温延伸工程）
工程３を終えた延伸フィルムを比較的高い温度で延伸する工程である。延伸温度はポリプロピレン系重合体の融点よりも５〜６５℃低い温度、好ましくはポリプロピレン系重合体の融点よりも１０〜４５℃低い温度である。延伸倍率は、長さ方向に１．５〜４．５倍、好ましくは２．０〜４．０倍、さらに好ましくは３．０〜３．２倍である。延伸手段は制限されない。ロール延伸法、テンター延伸法などの公知の手段が使用できる。延伸の段数は任意に設定できる。１段延伸でもよく、複数のロールを経て２段以上の延伸を行ってもよい。温延伸工程で工程３で生じたクレーズが引き延ばされ、空孔が発生する。
(Process 4: Warm stretching process)
In this step, the stretched film after Step 3 is stretched at a relatively high temperature. The stretching temperature is 5 to 65 ° C. lower than the melting point of the polypropylene polymer, preferably 10 to 45 ° C. lower than the melting point of the polypropylene polymer. The draw ratio is 1.5 to 4.5 times in the length direction, preferably 2.0 to 4.0 times, and more preferably 3.0 to 3.2 times. The stretching means is not limited. Known means such as a roll stretching method and a tenter stretching method can be used. The number of stretching stages can be set arbitrarily. One-stage stretching may be performed, and two or more stages of stretching may be performed through a plurality of rolls. In the warm drawing step, the craze produced in step 3 is stretched and voids are generated.
（工程５：弛緩工程）
工程４を終えた温延伸後のフィルムの収縮を防ぐためにフィルムを弛緩させる工程である。弛緩温度は、温延伸の温度よりもやや高い温度であり、０〜２０℃高い温度が一般的である。弛緩の度合いは、工程４を終えた延伸フィルムの長さが最終的に０．７〜１．０倍になるように調整される。
(Process 5: Relaxation process)
In this step, the film is relaxed in order to prevent shrinkage of the film after hot stretching after Step 4 is completed. The relaxation temperature is slightly higher than the temperature of warm stretching, and is generally 0 to 20 ° C higher. The degree of relaxation is adjusted so that the length of the stretched film after Step 4 is finally 0.7 to 1.0 times.
本発明の微多孔膜を特徴づける引張強度は以下の方法（Ａ）により求められる。
方法（Ａ）：微多孔膜から押出方向（ＭＤ）と、幅方向（ＴＤ）の２方向に試験片を切り出し、それぞれの試験片（ＭＤ方向の試験片、ＴＤ方向の試験片）の破断荷重（Ｎ）を引張速度５００ｍｍ／分の条件で測定する。以下の式により押出方向（ＭＤ）の引張強度、幅方向（ＴＤ）の引張強度を算出する。
押出方向（ＭＤ）の引張強度（ＭＰａ）＝［押出方向（ＭＤ）の破断荷重（Ｎ）］／［試験片の断面積（ｍｍ２）］
幅方向（ＴＤ）の引張強度（ＭＰａ）=［幅方向（ＴＤ）の破断荷重（Ｎ）］／［試験片の断面積（ｍｍ２）］
The tensile strength characterizing the microporous membrane of the present invention is determined by the following method (A).
Method (A): A test piece is cut out from the microporous membrane in two directions of extrusion direction (MD) and width direction (TD), and the breaking load of each test piece (test piece in MD direction, test piece in TD direction). (N) is measured under the condition of a tensile speed of 500 mm / min. The tensile strength in the extrusion direction (MD) and the tensile strength in the width direction (TD) are calculated by the following equations.
Tensile strength (MPa) in extrusion direction (MD) = [Breaking load in extrusion direction (MD) (N)] / [Cross sectional area of test piece (mm 2 )]
Tensile strength (MPa) in width direction (TD) = [Breaking load (N) in width direction (TD)] / [Cross sectional area of test piece (mm 2 )]
本発明の微多孔膜を特徴づける突刺強度以下の方法（Ｂ）により求められる。
方法（Ｂ）：微多孔膜表面に直径１ｍｍの先端が球面形状の針で、１００ｍｍ／分の速度で突刺して針に掛る荷重を測定する。このときの最大荷重（Ｎ）を突刺強度の値とする。
It is calculated | required by the method (B) below the puncture strength which characterizes the microporous film of this invention.
Method (B): The load applied to the needle is measured by piercing at a speed of 100 mm / min with a needle having a spherical shape with a tip of 1 mm in diameter on the surface of the microporous membrane. The maximum load (N) at this time is defined as the puncture strength value.
また本発明の微多孔膜の空孔率は以下の関係式を用いて求めた値である。
（空孔率）
幅５０ｍｍ×長さ１２０ｍｍの微多孔膜切片について、以下の計算式により算出した値である。
空孔率（％）＝［１−（切片重量）／（切片面積Ｘ樹脂密度×切片厚み）］×１００
The porosity of the microporous membrane of the present invention is a value determined using the following relational expression.
(Porosity)
It is a value calculated by the following formula for a microporous membrane slice having a width of 50 mm and a length of 120 mm.
Porosity (%) = [1− (section weight) / (section area × resin density × section thickness)] × 100
本発明の微多孔膜は、高い引張強度と高い突刺し強度を示す。本発明の微多孔膜の、押出方向（ＭＤ）の引張強度（ＭＰａ）は２００ＭＰａ以上、幅方向（ＴＤ）の引張強度（ＭＰａ）は１０ＭＰａ以上である。本発明の微多孔膜の突刺強度は４．９Ｎ以上である。さらに本発明の微多孔膜は４５〜５５％という高い空孔率を備える。 The microporous membrane of the present invention exhibits high tensile strength and high puncture strength. The tensile strength (MPa) in the extrusion direction (MD) of the microporous membrane of the present invention is 200 MPa or more, and the tensile strength (MPa) in the width direction (TD) is 10 MPa or more. The puncture strength of the microporous membrane of the present invention is 4.9 N or more. Furthermore, the microporous membrane of the present invention has a high porosity of 45 to 55%.
本発明の微多孔膜の例を以下に示す。なお、実施例、比較例で製造した微多孔膜の引張強度、突刺強度は、以下の操作で測定、算出した。 Examples of the microporous membrane of the present invention are shown below. The tensile strength and puncture strength of the microporous membranes produced in the examples and comparative examples were measured and calculated by the following operations.
（押出方向（ＭＤ）の引張強度の測定）
プロピレン系樹脂微多孔フィルムから、押出方向（ＭＤ）１２０ｍｍ×幅方向（ＴＤ）１０ｍｍの試験片を切り出す。引張試験機（島津製作所社製オートグラフ ＡＧＳ−Ｘ）を使い、試験片をつかみ間隔５０ｍｍで挟み、５００ｍｍ／分の速度で引張り、押出方向（ＭＤ）の破断荷重（Ｎ）を測定する。次に、試験片の引張方向の断面積（１０ｍｍ×試験片の厚み（ｍｍ））を求める。
以下の式により、押出方向（ＭＤ）の引張強度（ＭＰａ）を算出する。
押出方向（ＭＤ）の引張強度（ＭＰａ）＝［押出方向（ＭＤ）の破断荷重（Ｎ）］／［試験片の断面積（ｍｍ２）］
上述の操作を合計５枚の試験片で行う。得られた５回分の押出方向（ＭＤ）の引張強度（ＭＰａ）の平均値を求める。この平均値を、実施例、比較例の押出方向（ＭＤ）の引張強度（ＭＰａ）とする。
(Measurement of tensile strength in extrusion direction (MD))
A test piece having an extrusion direction (MD) of 120 mm and a width direction (TD) of 10 mm is cut out from the propylene-based resin microporous film. Using a tensile tester (manufactured by Shimadzu Corporation Autograph AGS-X), the test piece is clamped at a spacing of 50 mm, pulled at a speed of 500 mm / min, and the breaking load (N) in the extrusion direction (MD) is measured. Next, the cross-sectional area (10 mm × thickness of the test piece (mm)) in the tensile direction of the test piece is obtained.
The tensile strength (MPa) in the extrusion direction (MD) is calculated by the following formula.
Tensile strength (MPa) in extrusion direction (MD) = [Breaking load in extrusion direction (MD) (N)] / [Cross sectional area of test piece (mm 2 )]
The above operation is performed on a total of five test pieces. The average value of the tensile strength (MPa) of the obtained 5 times of extrusion directions (MD) is calculated | required. Let this average value be the tensile strength (MPa) of the extrusion direction (MD) of an Example and a comparative example.
（幅方向（ＴＤ）の引張強度の測定）
プロピレン系樹脂微多孔フィルムから、幅方向（ＴＤ）１２０ｍｍ×押出方向（ＭＤ）１０ｍｍの試験片を切り出す。引張試験機（島津製作所社製オートグラフ ＡＧＳ−Ｘ）を使い、試験片をつかみ間隔５０ｍｍで挟み、５００ｍｍ／分の速度で引張り、幅方向（ＭＤ）の破断荷重（Ｎ）を測定する。次に、試験片の引張方向の断面積（１０ｍｍ×試験片の厚み（ｍｍ））を求める。
以下の式により、幅方向（ＴＤ）の引張強度（ＭＰａ）を算出する。
幅方向（ＴＤ）の引張強度（ＭＰａ）=［幅方向（ＴＤ）の破断荷重（Ｎ）］／［試験片の断面積（ｍｍ２）］
上述の操作を合計５枚の試験片で行う。得られた５回分の幅方向（ＴＤ）の引張強度（ＭＰａ）の平均値を求める。この平均値を、実施例、比較例の幅方向（ＴＤ）の引張強度（ＭＰａ）とする。
(Measurement of tensile strength in the width direction (TD))
A test piece of width direction (TD) 120 mm × extrusion direction (MD) 10 mm is cut out from the propylene-based resin microporous film. Using a tensile tester (Autograph AGS-X, manufactured by Shimadzu Corporation), the test piece is sandwiched at a spacing of 50 mm, pulled at a speed of 500 mm / min, and the breaking load (N) in the width direction (MD) is measured. Next, the cross-sectional area (10 mm × thickness of the test piece (mm)) in the tensile direction of the test piece is obtained.
The tensile strength (MPa) in the width direction (TD) is calculated by the following formula.
Tensile strength (MPa) in width direction (TD) = [Breaking load (N) in width direction (TD)] / [Cross sectional area of test piece (mm 2 )]
The above operation is performed on a total of five test pieces. The average value of the tensile strength (MPa) of the obtained width direction (TD) for 5 times is calculated | required. Let this average value be the tensile strength (MPa) of the width direction (TD) of an Example and a comparative example.
（突刺強度の測定）
プロピレン系樹脂微多孔フィルムから、幅１０ｃｍ×長さ１０ｃｍの正方形片を切り出す。この試験片に対し、直径１１ｍｍの穴が開いた治具に固定し、その穴の中央に先端が球面（曲率半径Ｒ：０．５ｍｍ）の直径１ｍｍの針で、１００ｍｍ／分の速度で突刺したときの荷重を測定する。この時の最大荷重（Ｎ）を突刺強度とする。
(Measurement of puncture strength)
A square piece having a width of 10 cm and a length of 10 cm is cut out from the propylene-based resin microporous film. The test piece is fixed to a jig having a hole with a diameter of 11 mm, and a 1 mm diameter needle with a spherical tip (curvature radius R: 0.5 mm) at the center of the hole and pierced at a speed of 100 mm / min. Measure the load when The maximum load (N) at this time is defined as the puncture strength.
（実施例１）
（原料）微多孔膜の原料として、ＪＩＳ Ｋ６７５８（２３０℃、２１．１８Ｎ）に従い測定したメルトマスフローレイト（ＭＦＲ）が２．０ｇ／１０分、融点が１６５℃のプロピレン単独重合体を使用した。（工程１）単軸押出機で溶融混練した原料をドラフト比１５９でＴダイから押出し、厚さ２２μｍの原反フィルムを製造した。（工程２）次いで、原反フィルムを１５０℃で熱処理した。（工程３）原反フィルムを３０℃で長さ方向に１．０４倍に冷延伸した。（工程４）得られた延伸フィルムを１４５℃で長さ方向に、１段目は２．４倍に、２段目は１．３倍に延伸して、総延伸倍率３．０倍となるように温延伸した。（工程５）得られた延伸フィルムの長さが０．８８倍になるように１５０℃で弛緩させた。こうして最終厚みが２０μｍの本発明の微多孔膜が得られた。得られた微多孔膜の熱収縮率と空孔率を上述の方法で測定し、その結果を製造条件と共に表１に示す。
Example 1
(Raw material) A propylene homopolymer having a melt mass flow rate (MFR) of 2.0 g / 10 minutes and a melting point of 165 ° C. measured according to JIS K6758 (230 ° C., 21.18 N) was used as a raw material for the microporous membrane. (Step 1) The raw material melt-kneaded with a single screw extruder was extruded from a T-die at a draft ratio of 159 to produce a raw film having a thickness of 22 μm. (Step 2) Next, the raw film was heat-treated at 150 ° C. (Step 3) The raw film was cold-stretched 1.04 times in the length direction at 30 ° C. (Step 4) The obtained stretched film is stretched in the length direction at 145 ° C., the first step is 2.4 times, the second step is 1.3 times, and the total draw ratio is 3.0 times. So that the film was warm-stretched. (Step 5) It was relaxed at 150 ° C. so that the length of the obtained stretched film was 0.88 times. Thus, the microporous membrane of the present invention having a final thickness of 20 μm was obtained. The heat shrinkage rate and porosity of the obtained microporous membrane were measured by the above-described method, and the results are shown in Table 1 together with the production conditions.
（実施例２）
（原料）実施例１と同じ原料を使用した。（工程１）単軸押出機で溶融混練した原料をドラフト比１５９でＴダイから押出し、厚さ２２μｍの原反フィルムを製造した。（工程２）次いで、原反フィルムを１５０℃で熱処理した。（工程３）原反フィルムを３０℃で長さ方向に１．０４倍に冷延伸した。（工程４）得られた延伸フィルムを１４５℃で長さ方向に、１段目は３．０倍に、２段目は１．０倍に延伸して、総延伸倍率３．０倍となるように温延伸した。（工程５）得られた延伸フィルムの長さが０．８８倍になるように１５０℃で弛緩させた。こうして最終厚みが２０μｍの本発明の微多孔膜が得られた。得られた微多孔膜の熱収縮率と空孔率を上述の方法で測定し、その結果を製造条件と共に表１に示す。
(Example 2)
(Raw material) The same raw material as in Example 1 was used. (Step 1) The raw material melt-kneaded with a single screw extruder was extruded from a T-die at a draft ratio of 159 to produce a raw film having a thickness of 22 μm. (Step 2) Next, the raw film was heat-treated at 150 ° C. (Step 3) The raw film was cold-stretched 1.04 times in the length direction at 30 ° C. (Step 4) The obtained stretched film is stretched in the length direction at 145 ° C., the first stage is 3.0 times, the second stage is 1.0 times, and the total draw ratio is 3.0 times. So that the film was warm-stretched. (Step 5) It was relaxed at 150 ° C. so that the length of the obtained stretched film was 0.88 times. Thus, the microporous membrane of the present invention having a final thickness of 20 μm was obtained. The heat shrinkage rate and porosity of the obtained microporous membrane were measured by the above-described method, and the results are shown in Table 1 together with the production conditions.
（実施例３）
（原料）微多孔膜の原料として、ＪＩＳ Ｋ６７５８（２３０℃、２１．１８Ｎ）に従い測定したメルトマスフローレイト（ＭＦＲ）が１．５ｇ／１０分、融点が１５８℃のプロピレン−エチレン共重合体を使用した。（工程１）単軸押出機で溶融混練した原料をドラフト比２０５でＴダイから押出し、厚さ２２μｍの原反フィルムを製造した。（工程２）次いで、原反フィルムを１５０℃で熱処理した。（工程３）原反フィルムを３０℃で長さ方向に１．０７倍に冷延伸した。（工程４）得られた延伸フィルムを１２８℃で長さ方向に、１段目は３．２倍に、２段目は１．０倍に延伸して、総延伸倍率３．２倍となるように温延伸した。（工程５）得られた延伸フィルムの長さが０．８８倍になるように１５０℃で弛緩させた。こうして最終厚みが２０μｍの本発明の微多孔膜が得られた。得られた微多孔膜の熱収縮率と空孔率を上述の方法で測定し、その結果を製造条件と共に表１に示す。
Example 3
(Raw material) Propylene-ethylene copolymer having a melt mass flow rate (MFR) measured according to JIS K6758 (230 ° C., 21.18N) of 1.5 g / 10 min and a melting point of 158 ° C. is used as a raw material for the microporous membrane. did. (Step 1) The raw material melt-kneaded with a single screw extruder was extruded from a T-die with a draft ratio of 205 to produce a raw film having a thickness of 22 μm. (Step 2) Next, the raw film was heat-treated at 150 ° C. (Step 3) The raw film was cold-stretched 1.07 times in the length direction at 30 ° C. (Step 4) The obtained stretched film is stretched at 128 ° C. in the longitudinal direction, the first stage is stretched 3.2 times, the second stage is stretched 1.0 times, and the total stretch ratio is 3.2 times. So that the film was warm-stretched. (Step 5) It was relaxed at 150 ° C. so that the length of the obtained stretched film was 0.88 times. Thus, the microporous membrane of the present invention having a final thickness of 20 μm was obtained. The heat shrinkage rate and porosity of the obtained microporous membrane were measured by the above-described method, and the results are shown in Table 1 together with the production conditions.
（比較例１）
（原料）微多孔膜の原料として、ＪＩＳ Ｋ６７５８（２３０℃、２１．１８Ｎ）に従い測定したメルトマスフローレイト（ＭＦＲ）が０．５ｇ／１０分、融点が１６５℃のプロピレン単独重合体を使用した。（工程１）単軸押出機で溶融混練した原料をドラフト比１５９でＴダイから押出し、厚さ２２μｍの原反フィルムを製造した。（工程２）次いで、原反フィルムを１５０℃で熱処理した。（工程３）原反フィルムを３０℃で長さ方向に１．０３倍に冷延伸した（工程４）得られた延伸フィルムを１４５℃で長さ方向に、１段目は１．０倍に、２段目は２．９倍に延伸して、総延伸倍率２．９倍となるように温延伸した。（工程５）得られた延伸フィルムの長さが０．８７倍になるように１５０℃で弛緩させた。こうして最終厚みが２０μｍの比較用の微多孔膜が得られた。評価結果を製造条件と共に表１に示す。
(Comparative Example 1)
(Raw material) A propylene homopolymer having a melt mass flow rate (MFR) of 0.5 g / 10 minutes and a melting point of 165 ° C. measured according to JIS K6758 (230 ° C., 21.18 N) was used as a raw material for the microporous membrane. (Step 1) The raw material melt-kneaded with a single screw extruder was extruded from a T-die at a draft ratio of 159 to produce a raw film having a thickness of 22 μm. (Step 2) Next, the raw film was heat-treated at 150 ° C. (Step 3) The raw film was cold-stretched 1.03 times in the length direction at 30 ° C. (Step 4) The obtained stretched film was 145 ° C. in the length direction and the first step was 1.0 times The second stage was stretched 2.9 times and warm-stretched so that the total stretching ratio was 2.9 times. (Step 5) The obtained stretched film was relaxed at 150 ° C. so that the length thereof was 0.87 times. A comparative microporous membrane having a final thickness of 20 μm was thus obtained. The evaluation results are shown in Table 1 together with the production conditions.
（比較例２）
（原料）比較例１と同じ原料を使用した。（工程１）単軸押出機で溶融混練した原料をドラフト比１５９でＴダイから押出し、厚さ２２μｍの原反フィルムを製造した。（工程２）次いで、原反フィルムを１５０℃で熱処理した。（工程３）原反フィルムを３０℃で長さ方向に１．０３倍に冷延伸した（工程４）得られた延伸フィルムを１４５℃で長さ方向に、１段目は１．０倍に、２段目は２．８倍に延伸して、総延伸倍率２．８倍となるように温延伸した。（工程５）得られた延伸フィルムの長さが０．８５倍になるように１５０℃で弛緩させた。こうして最終厚みが２０μｍの比較用の微多孔膜が得られた。評価結果を製造条件と共に表１に示す。
(Comparative Example 2)
(Raw material) The same raw material as in Comparative Example 1 was used. (Step 1) The raw material melt-kneaded with a single screw extruder was extruded from a T-die at a draft ratio of 159 to produce a raw film having a thickness of 22 μm. (Step 2) Next, the raw film was heat-treated at 150 ° C. (Step 3) The raw film was cold-stretched 1.03 times in the length direction at 30 ° C. (Step 4) The obtained stretched film was 145 ° C. in the length direction and the first step was 1.0 times The second stage was stretched 2.8 times and warm-stretched so that the total stretching ratio was 2.8 times. (Step 5) The obtained stretched film was relaxed at 150 ° C. so that the length thereof was 0.85 times. A comparative microporous membrane having a final thickness of 20 μm was thus obtained. The evaluation results are shown in Table 1 together with the production conditions.
実施例１、２、３で得られた本発明の微多孔膜は、比較例１、２に比べて引張強度と突刺強度が高い。しかも、実施例１、２、３で得られた本発明の微多孔膜は、引張強度、突刺強度、空孔率とのバランスからみても比較例１、２よりも優れている。 The microporous membranes of the present invention obtained in Examples 1, 2, and 3 have higher tensile strength and puncture strength than Comparative Examples 1 and 2. Moreover, the microporous membranes of the present invention obtained in Examples 1, 2, and 3 are superior to Comparative Examples 1 and 2 in terms of the balance between tensile strength, puncture strength, and porosity.
本発明の微多孔膜は高い強度と高い空孔率を兼ね備える。したがって本発明の微多孔膜は、優れた物質透過性という化学的機能と、高い強度という構造的機能とを兼ね備える素材である。このような本発明の微多孔膜は、分離膜、蓄電デバイスのセパレータなどの部材に適している。本発明の微多孔膜は、過酷な環境下で使用される車両用電池のセパレータ、屋外で使用されるキャパシタのセパレータの材料として有用である。 The microporous membrane of the present invention has both high strength and high porosity. Therefore, the microporous membrane of the present invention is a material having both a chemical function of excellent material permeability and a structural function of high strength. Such a microporous membrane of the present invention is suitable for members such as a separation membrane and a separator of an electricity storage device. The microporous membrane of the present invention is useful as a material for separators for vehicle batteries used in harsh environments and capacitor separators used outdoors.
Claims (10)
方法（Ａ）：
微多孔膜から押出方向（ＭＤ）と、幅方向（ＴＤ）の２方向に試験片を切り出し、それぞれの試験片（ＭＤ方向の試験片、ＴＤ方向の試験片）の破断荷重（Ｎ）を引張速度５００ｍｍ／分の条件で測定する。以下の式により押出方向（ＭＤ）の引張強度、幅方向（ＴＤ）の引張強度を算出する。
押出方向（ＭＤ）の引張強度（ＭＰａ）＝［押出方向（ＭＤ）の破断荷重（Ｎ）］／［試験片の断面積（ｍｍ２）］
幅方向（ＴＤ）の引張強度（ＭＰａ）＝［幅方向（ＴＤ）の破断荷重（Ｎ）］／［試験片の断面積（ｍｍ２）］
方法（Ｂ）：
微多孔膜表面に先端が直径１ｍｍの球面形状の針で、１００ｍｍ／分の速度で突刺して針に掛る荷重を測定する。このときの最大荷重（Ｎ）を突刺強度の値とする。 It consists of a polypropylene polymer having a melt mass flow rate (measured in accordance with MFR, JIS K6758 at 230 ° C. and a load of 21.18 N) of 1.0 to 10.0 g / 10 minutes, and is obtained by the following method (A). The tensile strength in the extrusion direction (MD) is 200 MPa or more, the tensile strength in the width direction (TD) is 10 MPa or more, and the puncture strength measured by the following method (B) is 4.9 N or more. Porous membrane.
Method (A):
Test pieces are cut out from the microporous membrane in two directions, the extrusion direction (MD) and the width direction (TD), and the breaking load (N) of each test piece (the test piece in the MD direction and the test piece in the TD direction) is pulled. The measurement is performed at a speed of 500 mm / min. The tensile strength in the extrusion direction (MD) and the tensile strength in the width direction (TD) are calculated by the following equations.
Tensile strength (MPa) in extrusion direction (MD) = [Breaking load in extrusion direction (MD) (N)] / [Cross sectional area of test piece (mm 2 )]
Tensile strength (MPa) in width direction (TD) = [Breaking load (N) in width direction (TD)] / [Cross sectional area of test piece (mm 2 )]
Method (B):
Using a spherical needle having a 1 mm diameter tip on the surface of the microporous membrane, the load applied to the needle by piercing at a speed of 100 mm / min is measured. The maximum load (N) at this time is defined as the puncture strength value.
（工程１）ＪＩＳ Ｋ６７５８に準拠して２３０℃、荷重２１．１８Ｎで測定したメルトマスフローレイト（ＭＦＲ）が１．０〜１０．０ｇ／１０分であるポリプロピレン系重合体を押出成形して原反フィルムを製膜する工程。
（工程２）工程１で得られた原反フィルムを熱処理する工程。
（工程３）工程２で得られた熱処理後の原反フィルムを、−５〜４５℃で、長さ方向に１．０〜１．１倍に延伸する工程。
（工程４）工程３を終えた延伸フィルムを、ポリプロピレン系重合体の融点よりも５〜６５℃低い温度で、長さ方向に１．５〜４．０倍に延伸する工程。
（工程５）工程４で得られた温延伸後のフィルムを、加熱下、長さが０．７〜１．０倍になるように弛緩させる工程。 The manufacturing method of the microporous film of any one of Claims 1-9 including the following processes.
(Step 1) A polypropylene polymer having a melt mass flow rate (MFR) of 1.0 to 10.0 g / 10 minutes measured at 230 ° C. and a load of 21.18 N in accordance with JIS K6758 is extruded to be a raw material The process of forming a film.
(Step 2) A step of heat-treating the raw film obtained in Step 1.
(Process 3) The process of extending | stretching the raw film after the heat processing obtained at the process 2 by 1.0-1.1 times in the length direction at -5-45 degreeC.
(Process 4) The process of extending | stretching the stretched film which finished the process 3 1.5 to 4.0 times in the length direction at the temperature lower than the melting point of a polypropylene-type polymer 5 to 65 degreeC.
(Step 5) A step of relaxing the film after warm stretching obtained in Step 4 so that the length becomes 0.7 to 1.0 times under heating.
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