JP6507648B2 - Microporous membrane and method for producing the same - Google Patents
Microporous membrane and method for producing the same Download PDFInfo
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- JP6507648B2 JP6507648B2 JP2015002952A JP2015002952A JP6507648B2 JP 6507648 B2 JP6507648 B2 JP 6507648B2 JP 2015002952 A JP2015002952 A JP 2015002952A JP 2015002952 A JP2015002952 A JP 2015002952A JP 6507648 B2 JP6507648 B2 JP 6507648B2
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- 239000012982 microporous membrane Substances 0.000 title claims description 63
- 238000004519 manufacturing process Methods 0.000 title claims description 15
- 238000000034 method Methods 0.000 claims description 38
- 238000001125 extrusion Methods 0.000 claims description 29
- -1 polypropylene Polymers 0.000 claims description 29
- 229920001155 polypropylene Polymers 0.000 claims description 28
- 239000004743 Polypropylene Substances 0.000 claims description 27
- 229920000642 polymer Polymers 0.000 claims description 26
- 238000002844 melting Methods 0.000 claims description 14
- 230000008018 melting Effects 0.000 claims description 14
- 239000000155 melt Substances 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
- 239000012528 membrane Substances 0.000 claims description 7
- QQONPFPTGQHPMA-UHFFFAOYSA-N propylene Natural products CC=C QQONPFPTGQHPMA-UHFFFAOYSA-N 0.000 claims description 7
- 125000004805 propylene group Chemical group [H]C([H])([H])C([H])([*:1])C([H])([H])[*:2] 0.000 claims description 7
- 230000005611 electricity Effects 0.000 claims description 6
- 239000003990 capacitor Substances 0.000 claims description 5
- 238000010438 heat treatment 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
- 239000004711 α-olefin Substances 0.000 claims description 3
- 230000002040 relaxant effect Effects 0.000 claims description 2
- 239000002994 raw material Substances 0.000 description 26
- 229920005672 polyolefin resin Polymers 0.000 description 13
- 239000000463 material Substances 0.000 description 12
- 230000000052 comparative effect Effects 0.000 description 10
- 239000000203 mixture Substances 0.000 description 7
- 229920005989 resin Polymers 0.000 description 5
- 239000011347 resin Substances 0.000 description 5
- 238000000926 separation method Methods 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- 239000000654 additive Substances 0.000 description 3
- 125000004432 carbon atom Chemical group C* 0.000 description 3
- 238000005259 measurement Methods 0.000 description 3
- 239000011800 void material Substances 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
- 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
- 229920001384 propylene homopolymer 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
- FFBHFFJDDLITSX-UHFFFAOYSA-N benzyl N-[2-hydroxy-4-(3-oxomorpholin-4-yl)phenyl]carbamate Chemical compound OC1=C(NC(=O)OCC2=CC=CC=C2)C=CC(=C1)N1CCOCC1=O FFBHFFJDDLITSX-UHFFFAOYSA-N 0.000 description 1
- 238000010622 cold drawing Methods 0.000 description 1
- 229920001577 copolymer Polymers 0.000 description 1
- 239000003814 drug Substances 0.000 description 1
- 229940079593 drug Drugs 0.000 description 1
- 239000004744 fabric Substances 0.000 description 1
- 239000000945 filler Substances 0.000 description 1
- 229920001519 homopolymer Polymers 0.000 description 1
- 230000001771 impaired effect Effects 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 239000011244 liquid electrolyte Substances 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 229920006254 polymer film Polymers 0.000 description 1
- 239000011148 porous material Substances 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, LIGHT-SENSITIVE OR TEMPERATURE-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
Landscapes
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Manufacture Of Porous Articles, And Recovery And Treatment Of Waste Products (AREA)
- Electric Double-Layer Capacitors Or The Like (AREA)
- Cell Separators (AREA)
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 comprising a polypropylene-based 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。 The synthetic resin microporous membrane is used as a material for various separation membranes and battery separators. Among them, polyolefin resins are useful as raw materials for various separation membranes used in contact with drugs and battery separator microporous membranes in that 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 of making the 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 resin and a plasticizer, oil, paraffin or the like is spread in the form of a film. Next, components other than the polyolefin are extracted, and the portions where these components are present are made void. As a result, the polyolefin resin is formed into a microporous film. The dry method is a method of forming a polyolefin resin into a microporous film by drawing a raw material mainly composed of a polyolefin resin, which does not contain a component such as a plasticizer, oil, or paraffin or a solvent. As a dry method, a method of generating a void in a gap of a lamellar structure in a polyolefin resin and a method of generating a void in an interface between an inorganic additive added to a raw material and a polyolefin resin are known.
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 production methods as described in Patent Documents 1, 2 and 3 are known for polyolefin resin microporous films 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 obtained 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 drawing in two steps by a dry method, and the obtained 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 obtained by blending a low molecular weight substance with a polyolefin is processed into a microporous film by drawing in two steps by a dry method, and the resulting 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 and discharge characteristics. The lithium ion battery separator is a member disposed in the battery case, but since it is wound into several layers in a state of being immersed in the liquid electrolyte and fills the battery case space, the strength of the separator is It greatly contributes to the strength. Therefore, in order to manufacture a lithium ion battery main body having high strength, a separator having high strength 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 produce a high strength separator, it is required to use a high strength microporous membrane as a material of the separator. As an indicator of the strength of the microporous membrane, the tensile strength and the piercing 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 disclose polyolefin resin microporous films for battery separators that have high tensile strength and 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 film having high tensile strength and piercing strength, using as a raw material a polypropylene composition in which a β-crystal nucleating agent is mixed with poly (propylene).
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 high tensile strength and piercing strength, which is made of a polypropylene composition in which polyethylene is blended with polypropylene.
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 membrane for expressing the ion conductivity of the separator and the strength of the microporous membrane tend to exhibit a so-called trade-off relationship, and the battery is excellent in the balance between the porosity and the strength. There is still room for improvement in the microporous polyolefin resin membrane 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 inventor of the present invention sought a polyolefin resin microporous film having high strength such as tensile strength and piercing strength and high porosity, which is useful as a battery separator material.
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 film useful as a battery separator material having high strength such as tensile strength and piercing strength and high porosity by a dry method using a polypropylene resin having a specific melt mass flow rate as a raw material 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 polypropylene polymer having a melt mass flow rate (MFR, measured at 230 ° C. and a load of 21.18 N according to JIS K 6758) of 1.0 to 10.0 g / 10 min, the following method ( 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 Is a microporous membrane.
Method (A): A test piece is cut out from the microporous membrane in two directions, the extrusion direction (MD) and the width direction (TD), and the breaking load of each test piece (a test piece in the MD direction, a test piece in the TD direction) (N) is measured at 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 in the direction of extrusion (MD) (MPa) = [break force in the direction of extrusion (MD) (N)] / [cross-sectional area of test piece (mm 2 )]
Tensile strength in the width direction (TD) (MPa) = [break force in the width direction (TD) (N)] / [cross-sectional area of the test piece (mm 2 )]
Method (B): The surface of the microporous membrane is pierced at a speed of 100 mm / min with a spherical needle whose tip is 1 mm in diameter, and the load applied to the needle is measured. The maximum load (N) at this time is taken as the value of piercing strength.
（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 film of Invention 1 wherein the porosity is 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) The melting point of the polypropylene polymer is in the range of 150 to 170 ° C., and the melt mass flow rate (MFR, measured under the conditions according to JIS K 6758 (230 ° C., 21.18 N)) is 1.0 to 10 g The microporous membrane of the invention 1 or 2 which is a propylene-based polymer according to the invention, which is a propylene-based polymer optionally in the range of 10 minutes and optionally containing at least one selected from ethylene and an α-olefin having 4 to 8 carbon atoms .
（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 film according to any one of Inventions 1 to 3, which is used as 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 film 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 film 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) A method for producing a microporous membrane according to any of Inventions 1 to 9, which comprises the following steps.
(Step 1) A polypropylene-based polymer having a melt mass flow rate (MFR) of 1.0 to 10.0 g / 10 min measured at 230 ° C. and a load of 21.18 N according to JIS K 6758 is extrusion-molded The process of forming a film.
(Step 2) A step of heat treating the raw film obtained in Step 1.
(Step 3) A step of stretching the heat-treated raw film obtained in Step 2 at 1.0 to 1.1 times in the length direction at -5 to 45 ° C.
(Step 4) A step of stretching the stretched film having finished step 3 by 1.5 to 4.0 times in the length direction at a temperature 5 to 65 ° C. lower than the melting point of the polypropylene polymer.
(Step 5) A step of relaxing the warm-stretched film 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 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 a member such as a separation membrane or a separator of a 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 comprises a polypropylene-based polymer having a melt mass flow rate (MFR, measured at 230 ° C. and a load of 21.18 N according to JIS K 6758) 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, the extrusion direction (MD) and the width direction (TD), and the breaking load of each test piece (a test piece in the MD direction, a test piece in the TD direction) (N) is measured at 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 in the direction of extrusion (MD) (MPa) = [break force in the direction of extrusion (MD) (N)] / [cross-sectional area of test piece (mm 2 )]
Tensile strength in the width direction (TD) (MPa) = [break force in the width direction (TD) (N)] / [cross-sectional area of the test piece (mm 2 )]
Method (B): The surface of the microporous membrane is pierced at a speed of 100 mm / min with a spherical needle whose tip is 1 mm in diameter, and the load applied to the needle is measured. The maximum load (N) at this time is taken as the value of piercing strength.
（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 of microporous membrane)
The raw material of the microporous membrane of the present invention is a polypropylene polymer, and a homopolymer of propylene or a copolymer obtained by copolymerizing a comonomer corresponds to this. As a polypropylene polymer used by this invention, what has comparatively high crystallinity and whose melting | fusing point is in the range of 150-170 degreeC is preferable, and what has melting | fusing point in the range of 155-168 degreeC is more preferable. The above comonomer is generally at least one selected from ethylene and an α-olefin having 4 to 8 carbon atoms. In addition to these, even if they are 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 content of the comonomer may be in any range as long as the microporous membrane exhibits the desired properties. Preferably, the amount is 5 parts by weight or less, and particularly preferably 2 parts by weight or less, with respect to 100 parts by weight of the polymer, which is a range to give 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 melt mass flow rate (MFR, measured under the conditions according to JIS K 6758 (230 ° C., 21.18 N)) of the polypropylene polymer is 1.0 to 10 g / 10 min, preferably 1.0 to 5.0 g / l. 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。 In the raw material of the microporous membrane of the present invention, additives such as a crystal nucleating agent and a filler can be blended. 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 of manufacturing microporous membrane)
The microporous membrane of the present invention is produced by the so-called dry method using the above-mentioned 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)
In this step, the raw material is extruded to form a raw film. A polypropylene-based polymer having a melt mass flow rate (MFR) of 1.0 to 10.0 g / 10 min measured at 230 ° C. and a load of 21.18 N according to JIS K 6758 is supplied to an extruder, and the polypropylene-based polymer The mixture is melt-kneaded at a temperature above its melting point, and a polypropylene polymer film is extruded from a die attached to the tip of an extruder. The extruder used is not limited. As an extruder, for example, any of a single screw extruder, a twin screw extruder, and a tandem extruder can be used. Any die may be used as long as it is used for film forming. As the dice, for example, various T-shaped dice can be used. The thickness and shape of the raw film are not particularly limited. Preferably, the ratio (draft ratio) of die slip clearance to 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。
(Step 2: heat treatment step)
It is a process of heat-treating the original fabric film which finished the process 1. A constant tension in the longitudinal 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 is more than 1.0 times and not more than 1.1 times.
（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。
(Step 3: Cold Stretching 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 stretching ratio is 1.0 to 1.1, preferably 1.00 to 1.08, and more preferably 1.02 or more and less than 1.05 in the longitudinal direction. However, the draw ratio is greater than 1.0. The stretching means is not limited. Known means such as roll stretching and tenter stretching can be used. The number of stages of stretching can be set arbitrarily. It may be one-stage stretching, or 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, it is possible to obtain a stretched film having a lamellar part in which the molecular chains are dense and a region (claze) in which the molecular chains between the lamellas are sparse.
（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。
(Step 4: warm drawing step)
This is a step of stretching the stretched film after the step 3 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 stretching ratio is 1.5 to 4.5 times, preferably 2.0 to 4.0 times, and more preferably 3.0 to 3.2 times in the longitudinal direction. The stretching means is not limited. Known means such as roll stretching and tenter stretching can be used. The number of stages of stretching can be set arbitrarily. It may be one-stage stretching, or two or more stages of stretching may be performed through a plurality of rolls. In the warm drawing step, the craze formed in step 3 is stretched to generate pores.
（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。
(Step 5: relaxation step)
In this step, the film is relaxed in order to prevent the shrinkage of the warm-drawn film which has finished step 4. The relaxation temperature is a temperature slightly higher than the temperature of warm drawing, and a temperature higher by 0 to 20 ° C. is general. The degree of relaxation is adjusted so that the length of the stretched film after step 4 is finally 0.7 to 1.0.
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, the extrusion direction (MD) and the width direction (TD), and the breaking load of each test piece (a test piece in the MD direction, a test piece in the TD direction) (N) is measured at 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 in the direction of extrusion (MD) (MPa) = [break force in the direction of extrusion (MD) (N)] / [cross-sectional area of test piece (mm 2 )]
Tensile strength in the width direction (TD) (MPa) = [break force in the width direction (TD) (N)] / [cross-sectional area of the 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。
The puncture strength characterizing the microporous membrane of the present invention is determined by the following method (B).
Method (B): The tip of a 1 mm diameter tip is a spherical needle on the surface of the microporous membrane, and the load applied to the needle is measured by piercing at a speed of 100 mm / min. The maximum load (N) at this time is taken as the value of piercing strength.
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 the value computed by the following formula about the microporous film slice of width 50 mm x length 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 microporous membrane of the present invention has a tensile strength (MPa) in the extrusion direction (MD) of 200 MPa or more, and a tensile strength (MPa) in the width direction (TD) of 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。 An example of the microporous membrane of the present invention is shown below. In addition, the tensile strength and the puncture strength of the microporous film manufactured by the Example and the comparative example were measured and computed 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))
From the propylene-based resin microporous film, a test piece with an extrusion direction (MD) of 120 mm and a width direction (TD) of 10 mm is cut out. Using a tensile tester (Autograph AGS-X manufactured by Shimadzu Corporation), hold the test piece at a grip interval of 50 mm, pull at a speed of 500 mm / min, and measure the breaking load (N) in the extrusion direction (MD). Next, the cross-sectional area (10 mm × thickness of the test piece (mm)) of the test piece in the tensile direction is determined.
The tensile strength (MPa) in the extrusion direction (MD) is calculated by the following equation.
Tensile strength in the direction of extrusion (MD) (MPa) = [break force in the direction of extrusion (MD) (N)] / [cross-sectional area of test piece (mm 2 )]
Perform the above operation with a total of 5 test pieces. The average value of the tensile strength (MPa) in the extrusion direction (MD) of the obtained 5 times is determined. 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))
From the propylene-based resin microporous film, a test piece of 120 mm in width direction (TD) × 10 mm in extrusion direction (MD) is cut out. Using a tensile tester (Autograph AGS-X manufactured by Shimadzu Corporation), hold the test piece at a grip interval of 50 mm, pull at a speed of 500 mm / min, and measure the breaking load (N) in the width direction (MD). Next, the cross-sectional area (10 mm × thickness of the test piece (mm)) of the test piece in the tensile direction is determined.
The tensile strength (MPa) in the width direction (TD) is calculated by the following equation.
Tensile strength in the width direction (TD) (MPa) = [break force in the width direction (TD) (N)] / [cross-sectional area of the test piece (mm 2 )]
Perform the above operation with a total of 5 test pieces. The average value of the obtained tensile strength (MPa) in the width direction (TD) for five times is determined. 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 10 cm wide x 10 cm long is cut out of 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 needle having a spherical surface (curvature radius R: 0.5 mm) and a diameter of 1 mm at the center of the hole and a stab at a speed of 100 mm / min. Measure the load when you The maximum load (N) at this time is taken 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 min and a melting point of 165 ° C. measured according to JIS K 6758 (230 ° C., 21.18 N) was used as a raw material of the microporous membrane. (Step 1) The raw material melt-kneaded by 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 by 1.04 times in the lengthwise direction at 30 ° C. (Step 4) The obtained stretched film is stretched at 145 ° C. in the lengthwise direction, the first stage is 2.4 times, and the second stage is 1.3 times, and the total draw ratio is 3.0 times It was warm stretched. (Step 5) The stretched film was relaxed at 150 ° C. so that the length of the obtained stretched film was 0.88 times. Thus, a microporous membrane of the present invention having a final thickness of 20 μm was obtained. The heat shrinkage 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 materials) The same raw materials as in Example 1 were used. (Step 1) The raw material melt-kneaded by 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 by 1.04 times in the lengthwise direction at 30 ° C. (Step 4) The obtained stretched film is stretched in the lengthwise direction at 145 ° C., the first stage 3.0 times, the second stage 1.0, and the total draw ratio 3.0 times It was warm stretched. (Step 5) The stretched film was relaxed at 150 ° C. so that the length of the obtained stretched film was 0.88 times. Thus, a microporous membrane of the present invention having a final thickness of 20 μm was obtained. The heat shrinkage 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) As a raw material of the microporous membrane, a propylene-ethylene copolymer having a melt mass flow rate (MFR) of 1.5 g / 10 min and a melting point of 158 ° C. measured according to JIS K 6758 (230 ° C., 21.18 N) did. (Step 1) The raw material melt-kneaded by a single-screw extruder was extruded from a T-die at a draft ratio 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 at 30 ° C. in the lengthwise direction to 1.07 times. (Step 4) The obtained stretched film is stretched in the lengthwise direction at 128 ° C., the first stage 3.2 times, the second stage 1.0, and the total draw ratio 3.2 times It was warm stretched. (Step 5) The stretched film was relaxed at 150 ° C. so that the length of the obtained stretched film was 0.88 times. Thus, a microporous membrane of the present invention having a final thickness of 20 μm was obtained. The heat shrinkage 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 min and a melting point of 165 ° C. measured according to JIS K 6758 (230 ° C., 21.18 N) was used as a raw material of the microporous membrane. (Step 1) The raw material melt-kneaded by 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) Cold-stretch the raw film at 30 ° C. in the lengthwise direction to 1.03 times in the lengthwise direction (Step 4) The obtained stretched film is stretched at 145 ° C. in the lengthwise direction, and the first step is 1.0 times The second stage was stretched 2.9 times and warm stretched to a total draw ratio of 2.9 times. (Step 5) The stretched film was relaxed at 150 ° C. so that the length of the obtained stretched film was 0.87 times. Thus, a comparative microporous membrane with a final thickness of 20 μm was 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 Comparative Example 1 was used. (Step 1) The raw material melt-kneaded by 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) Cold-stretch the raw film at 30 ° C. in the lengthwise direction to 1.03 times in the lengthwise direction (Step 4) The obtained stretched film is stretched at 145 ° C. in the lengthwise direction, and the first step is 1.0 times The second stage was stretched 2.8 times and warm stretched to a total stretching ratio of 2.8 times. (Step 5) The stretched film was relaxed at 150 ° C. so that the length of the obtained stretched film was 0.85 times. Thus, a comparative microporous membrane with a final thickness of 20 μm was 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 films of the present invention obtained in Examples 1, 2 and 3 have higher tensile strength and piercing strength than Comparative Examples 1 and 2. In addition, the microporous films of the present invention obtained in Examples 1, 2 and 3 are superior to Comparative Examples 1 and 2 also in view of the balance among 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 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 a member such as a separation membrane or a separator of a storage device. The microporous film of the present invention is useful as a material of a vehicle battery separator used in severe environments and a separator of a capacitor 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）：
厚み２０μｍの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。 Melt mass flow rate (MFR, measured at 230 ° C, load 21.18 N according to JIS K 6758) is a polypropylene polymer having a weight of 1.0 to 10.0 g / 10 min, determined by the following method (A) The fineness 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, the test piece in the TD direction) is tensioned. Measure 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 in the direction of extrusion (MD) (MPa) = [break force in the direction of extrusion (MD) (N)] / [cross-sectional area of test piece (mm 2 )]
Tensile strength in the width direction (TD) (MPa) = [break force in the width direction (TD) (N)] / [cross-sectional area of the test piece (mm 2 )]
Method (B):
Using a spherical needle with a tip of 1 mm in diameter on the surface of a microporous membrane with a thickness of 20 μm, the load applied to the needle is measured by piercing at a speed of 100 mm / min. The maximum load (N) at this time is taken as the value of piercing strength.
（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、原反フィルムの長さ方向に、原反フィルムの長さが１．０倍を超え１．１倍以下となる一定の大きさの張力を加え、ポリプロピレン系重合体の融点よりも５〜６５℃低い温度で熱処理する工程。
（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３．０〜３．２倍に２段以上で延伸する工程。
（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-based polymer having a melt mass flow rate (MFR) of 1.0 to 10.0 g / 10 min measured at 230 ° C. and a load of 21.18 N according to JIS K 6758 is extrusion-molded The process of forming a film.
(Step 2) A tension of a certain size such that the length of the raw film is more than 1.0 times and not more than 1.1 times in the length direction of the raw film obtained in the step 1 And heat treatment at a temperature 5 to 65 ° C. lower than the melting point of the polypropylene polymer .
(Step 3) A step of stretching the heat-treated raw film obtained in Step 2 at 1.0 to 1.1 times in the length direction at -5 to 45 ° C.
(Step 4) A step of drawing the stretched film, which has finished Step 3, in two or more steps at 3.0 to 3.2 times in the length direction at a temperature 5 to 65 ° C. lower than the melting point of the polypropylene polymer.
(Step 5) A step of relaxing the warm-stretched film obtained in Step 4 so that the length becomes 0.7 to 1.0 times under heating.
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