JP2013057045A - Heat-resistance improved polyolefin microporous membrane and production method therefor - Google Patents
Heat-resistance improved polyolefin microporous membrane and production method therefor Download PDFInfo
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- JP2013057045A JP2013057045A JP2011208058A JP2011208058A JP2013057045A JP 2013057045 A JP2013057045 A JP 2013057045A JP 2011208058 A JP2011208058 A JP 2011208058A JP 2011208058 A JP2011208058 A JP 2011208058A JP 2013057045 A JP2013057045 A JP 2013057045A
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- polyolefin
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Images
Classifications
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- 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
Abstract
Description
本発明は、耐熱性ポリオレフィン微多孔膜及びその製造方法に関する。
具体的には、リチウムイオン二次電池の安全性を高めるセパレータとして有用な高温時の低収縮性、機械的特性、透気度に優れたポリオレフィン微多孔膜とその製造方法に関する。The present invention relates to a heat-resistant polyolefin microporous membrane and a method for producing the same.
Specifically, the present invention relates to a polyolefin microporous membrane that is useful as a separator for enhancing the safety of a lithium ion secondary battery and has excellent low shrinkage at high temperatures, mechanical properties, and air permeability, and a method for producing the same.
ポリオレフィン微多孔膜は、電池用セパレータ、電解コンデンサー用隔膜、各種フィルタ、透湿防水衣料、逆浸透濾過膜、限外濾過膜、精密濾過膜等の各種用途に用いられている。
ポリオレフィン微多孔膜を電池用セパレータ、特にリチウムイオン二次電池用セパレータとして用いる場合、その性能は電池特性、電池生産性及び電池安全性に深く関わっている。そのため優れた透気度、機械的特性、耐熱低収縮性、シャットダウン特性、ノンメルトダウン特性等が要求される。例えば機械的強度が低いと、電池セパレータとして用いた場合に、電極の短絡により電池の電圧が低下してしまうことがある。また金属異物が電池内に混入していると電池セパレータの突き刺し強度が低い場合は電極の短絡を起して電池の異常発熱に至る。
リチウムイオン二次電池は近年、例えばノートブックパソコン、携帯電話、１体型カムコーダー等の携帯用電子機器の主電源として広範に普及している。これらの携帯用電子機器の更なる高性能化と長時間駆動の要求からリチウムイオン二次電池において、さらなる高エネルギー密度化・高容量化・高出力化のための技術開発が進められている。
一方、ハイブリッド車、電気自動車用の電源用では大型リチウムイオン二次電池の安全性の上からはセパレータの収縮更には溶融を起こして破膜による短絡を引き起こし、発煙・発火にいたることを避けなければならない。シャットダウン特性に加え、メルトダウンしない（ノンメルトダウン）特性の観点で十分な耐熱性を有することも要求されている。Polyolefin microporous membranes are used in various applications such as battery separators, electrolytic capacitor membranes, various filters, moisture permeable and waterproof clothing, reverse osmosis filtration membranes, ultrafiltration membranes, and microfiltration membranes.
When the polyolefin microporous membrane is used as a battery separator, particularly as a lithium ion secondary battery separator, the performance is deeply related to battery characteristics, battery productivity, and battery safety. Therefore, excellent air permeability, mechanical properties, heat-resistant and low shrinkage properties, shutdown properties, non-meltdown properties, etc. are required. For example, when the mechanical strength is low, when used as a battery separator, the voltage of the battery may decrease due to a short circuit of the electrode. If metal foreign matter is mixed in the battery, if the puncture strength of the battery separator is low, the electrode is short-circuited, leading to abnormal heat generation of the battery.
In recent years, lithium ion secondary batteries have become widespread as main power sources for portable electronic devices such as notebook personal computers, mobile phones, and single-camcorders. Due to the demand for higher performance and longer driving time of these portable electronic devices, technological development for further increase in energy density, higher capacity, and higher output is being promoted in lithium ion secondary batteries.
On the other hand, in the power supply for hybrid vehicles and electric vehicles, from the viewpoint of safety of large lithium ion secondary batteries, it is necessary to avoid contraction and melting of the separator, causing a short circuit due to film breakage, resulting in smoke and ignition. I must. In addition to shutdown characteristics, it is also required to have sufficient heat resistance from the viewpoint of non-meltdown (non-meltdown) characteristics.
現状のリチウムイオン二次電池のセパレータにはポリエチレンを主体としたポリオレフィン微多孔膜が用いられており、電池の安全性を確保するための機能としてシャットダウン特性は備わっているが、１６０℃以上までメルトダウンしないように工夫することは、ポリエチレンの融点から判断して難しい。一方、ポリオレフィン微多孔膜には、電解液による劣化がほとんどない利点もある。
最近、セパレータの特性についてはリチウムイオン透過性（試験では、空気の透気度で見ることもできる）。機械的強度だけでなく、サイクル特性等の電池寿命に関わる特性や、電解液注入性等の電池生産性に関わる特性も重視される。特にリチウムイオン二次電池の電極は、充放電に伴う膨張／収縮を繰り返す。そのためセパレータに対して、その厚さ方向に加わる力の負荷／解放が繰り返される。近年の電池の高容量化に伴う電極サイズや電極密度の増大等により、電池組み立て時にセパレータに対する圧迫がより強くなる傾向にある。このような状況において電池の特性を維持するには圧迫によるセパレータの透過性変化が小さいことが求められる。セパレータが圧縮されやすいと、電池の容量低下（サイクル特性悪化）を招く恐れが高い。また上記のような電池の高容量化に伴う電極サイズの増大等により、電池への電解液注入性が低下しており、電池生産性の低下を引き起こしている。電解液注入性の改善のためにセパレータを改良することも望まれている。Polyolefin microporous membranes mainly composed of polyethylene are used in current lithium ion secondary battery separators, and they have shutdown characteristics as a function to ensure battery safety. It is difficult to devise not to go down, judging from the melting point of polyethylene. On the other hand, the polyolefin microporous membrane has an advantage that there is almost no deterioration due to the electrolytic solution.
Recently, the separator characteristics are lithium ion permeability (it can also be seen in the air permeability in the test). In addition to mechanical strength, characteristics related to battery life such as cycle characteristics and characteristics related to battery productivity such as electrolyte injection properties are also emphasized. In particular, the electrode of the lithium ion secondary battery repeats expansion / contraction associated with charge / discharge. Therefore, loading / releasing of the force applied to the separator in the thickness direction is repeated. Due to the increase in electrode size and electrode density accompanying the increase in capacity of batteries in recent years, the pressure on the separator tends to become stronger during battery assembly. In order to maintain the characteristics of the battery in such a situation, it is required that the change in permeability of the separator due to compression is small. If the separator is easily compressed, there is a high risk of battery capacity reduction (deterioration of cycle characteristics). Moreover, due to the increase in the electrode size accompanying the increase in capacity of the battery as described above, the electrolyte injection property to the battery is reduced, which causes a decrease in battery productivity. It is also desired to improve the separator in order to improve the electrolyte injection property.
特許文献１には、４−メチル−１−ペンテン重合体樹脂（ＴＰＸ）単独を製膜用の溶剤を選択して液液相分離の方法で耐熱性ポリオレフィン微多孔膜を得ることを提案している。
特許文献２には、耐熱性樹脂を球状又は回転楕円体状の微粒子として溶融させずにポリエチレンに分散するのが好ましいとの耐熱性ポリオレフィン微多孔膜の提案がある。
特許文献３には、４−メチル−１−ペンテン重合体樹脂（ＴＰＸ）単独を多孔化フィルムを製造する方法が提案されている。いずれも本発明の耐熱性微多孔膜を製造するための超高分子量ポリエチレンと高密度ポリエチレンとを含むポリエチレンとの組み合わせについては、言及も示唆もない。
Patent Document 1 proposes to obtain a heat-resistant polyolefin microporous membrane by a liquid-liquid phase separation method by selecting a solvent for film formation of 4-methyl-1-pentene polymer resin (TPX) alone. Yes.
Patent Document 2 proposes a heat-resistant polyolefin microporous membrane that preferably disperses heat-resistant resin in polyethylene without melting as spherical or spheroid fine particles.
Patent Document 3 proposes a method for producing a porous film of 4-methyl-1-pentene polymer resin (TPX) alone. Neither mention nor suggestion about the combination of the ultrahigh molecular weight polyethylene and the polyethylene containing the high-density polyethylene for producing the heat-resistant microporous membrane of the present invention.
リチウムイオン二次電池の安全性を高めるセパレータとして有用な高温時の低収縮性、機械的特性、透過度に優れた耐熱性ポリオレフィン微多孔膜とその製造方法を提供することである。 An object of the present invention is to provide a heat-resistant polyolefin microporous membrane excellent in low shrinkage at high temperatures, mechanical properties, and permeability, which is useful as a separator for enhancing the safety of a lithium ion secondary battery, and a method for producing the same.
本発明者は、ポリオレフィン系エラストマー樹脂を介在させることにより、融点が大きく異なり、相溶性も必ずしも良くない超高分子量ポリエチレンと高密度ポリエチレンとを含むポリエチレンと４−メチル−１−ペンテンと炭素数３以上のα−オレフィンとの共重合体樹脂とを押出内で溶融混練し、均一な樹脂混合物の溶融物を得られることを見出して本発明に到達した。
すなわち、超高分子量ポリエチレンと高密度ポリエチレンとを含むポリエチレン５０−８５重量％、４−メチル−１−ペンテンと炭素数３以上のα−オレフィンとの共重合体樹脂１２．５−３０重量％、ポリオレフィン系エラストマー樹脂１−１０重量％とからなるポリオレフィン混合物及び必要に応じて微粒子の無機フィラ−を加えて製膜用の可塑剤とを二軸押出機にて溶融混練し、ダイより押出し、冷却して得られたゲル状シート成形物を延伸した後に前記製膜用の可塑剤を溶媒により除去し、洗浄し、再び、所定の倍率で延伸し、熱処理することにより得られる耐熱性ポリオレフィン微多孔膜は、表面粗さが比較的大きいことから、耐圧縮性、電解液注入性、機械的特性、透気度及び高温時の低収縮性に優れていることを見出して本発明に到達した。The inventor of the present invention intervenes a polyolefin-based elastomer resin, so that the melting point is greatly different and the compatibility is not necessarily good. Polyethylene including ultrahigh molecular weight polyethylene and high density polyethylene, 4-methyl-1-pentene, and carbon number 3 The present inventors have reached the present invention by discovering that a copolymer resin with the above α-olefin can be melt-kneaded in an extrusion to obtain a uniform resin mixture melt.
That is, 50 to 85% by weight of polyethylene containing ultrahigh molecular weight polyethylene and high density polyethylene, 12.5 to 30% by weight of copolymer resin of 4-methyl-1-pentene and α-olefin having 3 or more carbon atoms, A polyolefin mixture comprising 1-10% by weight of a polyolefin-based elastomer resin and if necessary, a fine inorganic filler is added and melt-kneaded with a plasticizer for film formation in a twin screw extruder, extruded from a die, and cooled. After the gel-like sheet molded product obtained by stretching is stretched, the plasticizer for film formation is removed with a solvent, washed, stretched again at a predetermined magnification, and heat-resistant polyolefin microporous obtained by heat treatment Since the film has a relatively large surface roughness, it was found that the film was excellent in compression resistance, electrolyte injection, mechanical properties, air permeability, and low shrinkage at high temperatures. It has been reached.
本発明の製造方法により得られる耐熱性ポリオレフィン微多孔膜は、融点の大きく異なる超高分子量ポリエチレンと高密度ポリエチレンとを含むポリエチレンと４−メチル−１−ペンテンと炭素数３以上のα−オレフィンとの共重合体樹脂とにポリオレフィン系エラストマー樹脂を介在させることにより、相溶性が必ずしも良くない樹脂同志を二軸押出機にて樹脂混合物と可塑剤を均一に溶融混練出来るようになり、ダイより押出し、冷却して得られたゲル状シート成形物を延伸した後に、前記製膜用の可塑剤を除去することにより得られる。
電池組み立て時に耐熱性ポリオレフィン微多孔膜が、加圧された場合の透気度変化及び膜厚変化が小さく、耐圧縮性、電解液注入性、機械的特性、透気度に優れており、特に長手方向（縦方向）（ＭＤ）及び横方向（ＴＤ）の両方向における高温時の低収縮性に優れている。
そのため本発明の耐熱性ポリオレフィン微多孔膜をリチウムイオン二次電池セパレータとして使用すると、電池の生産性が向上し、かつ優れたサイクル特性により電池が長寿命化する。本発明の均一溶融して得られた耐熱性ポリオレフィン微多孔膜は、単層膜でありながらシャットダウン温度を有し、かつ１８５℃以上まで破膜しないいわゆるノンメルトダウンの特性を有する。The heat-resistant polyolefin microporous membrane obtained by the production method of the present invention is composed of polyethylene containing ultrahigh molecular weight polyethylene and high-density polyethylene having greatly different melting points, 4-methyl-1-pentene, and α-olefin having 3 or more carbon atoms. By interposing a polyolefin-based elastomer resin with the copolymer resin, it becomes possible to uniformly melt and knead the resin mixture and plasticizer with a twin-screw extruder with resins that are not necessarily compatible, and extrude from the die. After the gel-like sheet molded product obtained by cooling is stretched, it is obtained by removing the plasticizer for film formation.
The heat-resistant polyolefin microporous membrane during battery assembly has small changes in air permeability and film thickness when pressurized, and is excellent in compression resistance, electrolyte injection properties, mechanical properties, and air permeability. It is excellent in low shrinkage at high temperatures in both the longitudinal direction (longitudinal direction) (MD) and the transverse direction (TD).
Therefore, when the heat-resistant polyolefin microporous membrane of the present invention is used as a lithium ion secondary battery separator, the productivity of the battery is improved, and the battery has a long life due to excellent cycle characteristics. The heat-resistant polyolefin microporous film obtained by uniform melting of the present invention has a so-called non-melt-down characteristic that has a shutdown temperature and does not break up to 185 ° C. or higher, even though it is a single layer film.
次に本発明の耐熱性ポリオレフィン微多孔膜とその製造方法について説明する。 Next, the heat-resistant polyolefin microporous membrane of the present invention and the production method thereof will be described.
［１］ポリエチレン
本発明のポリオレフィン微多孔膜を構成するポリエチレンは、極限粘度から求めた粘度平均分子量が５０万から１０００万の範囲にある超高分子量ポリエチレンに粘度平均分子量が１５万から５０万未満、好ましくは２０万〜４０万の範囲にある高密度ポリエチレンと併用する。５０万から１０００万の範囲にある超高分子量ポリエチレンを単独、ないし２種以上混合して使用される。エチレンの単独重合体のみならず、他のα−オレフィンを少量含有する共重合体も併用してもよい。エチレン以外の他のα−オレフィンとしてはプロピレン、ブテン−１、ヘキセン−１、ペンテン−１、４−メチルペンテン−１、オクテン等の炭素数３乃至３０のα−オレフィンとの共重合体が挙げられる。
従来は３５０万以上の超高分子量ポリエチレンは、押し出し混練りが難しいとされており使用される事例があまり見られなかったが、本発明では、耐熱性が高く押し出し加工が難しいとされる４−メチル−１−ペンテンと炭素数３以上のα−オレフィンとの共重合体樹脂１２．５−３０重量％を含む系にもかかわらずポリオレフィン系エラストマー樹脂１−１０重量％を添加し、かつ超高分子量ポリエチレンの粘度平均分子量差を３００万以内にとどまるように超高分子量ポリエチレンを可塑剤と共に混合していくことにより市販の粘度平均分子量３５０万を超える５００万以上６４０万までの超高分子量ポリエチレンを使用することも可能にできる。更に粘度平均分子量８００万から１０００万までの超高分子量ポリエチレンでも、特に１５μｍ以下の薄膜にしても引張強度、突き刺し強度を良好に保持できることを見出した。粘度平均分子量が５０万未満である高密度ポリエチレン（ＨＤＰＥ）に加えて中密度ポリエチレン（ＭＤＰＥ）及び低密度ポリエチレン（ＬＤＰＥ、Ｌ−ＬＤＰＥ）を併用することができる。
本発明には、粘度平均分子量が１５万から５０万未満の範囲にある高密度ポリエチレンを併用することがシャットダウン温度を明確に発現する上で好ましい。超高分子量ポリエチレン９０質量％−１５質量％と高密度ポリエチレン８５質量％−１０質量％、好ましくは超高分子量ポリエチレン８５質量％−３０質量％と高密度ポリエチレン１０質量％−７０質量％との混合比率が使用される。シャットダウン温度を顕著に示すようにするには、高密度ポリエチレン混合比率が１０質量％以上、好ましくは２０質量％以上である。[1] Polyethylene The polyethylene constituting the polyolefin microporous membrane of the present invention is an ultrahigh molecular weight polyethylene having a viscosity average molecular weight in the range of 500,000 to 10,000,000 determined from the intrinsic viscosity, and a viscosity average molecular weight of 150,000 to less than 500,000. Preferably, it is used in combination with high density polyethylene in the range of 200,000 to 400,000. Ultra high molecular weight polyethylene in the range of 500,000 to 10 million is used alone or in admixture of two or more. Not only an ethylene homopolymer, but also a copolymer containing a small amount of other α-olefin may be used in combination. Other α-olefins other than ethylene include copolymers with α-olefins having 3 to 30 carbon atoms such as propylene, butene-1, hexene-1, pentene-1, 4-methylpentene-1, and octene. It is done.
Conventionally, ultra-high molecular weight polyethylene of 3.5 million or more is considered to be difficult to extrude and knead, and there have been few cases where it is used. However, in the present invention, it is considered that extrusion processing is difficult because of high heat resistance. 1-10% by weight of a polyolefin-based elastomer resin is added in spite of a system containing 12.5-30% by weight of a copolymer resin of methyl-1-pentene and an α-olefin having 3 or more carbon atoms, By mixing ultra-high molecular weight polyethylene with a plasticizer so that the difference in viscosity average molecular weight of molecular weight polyethylene remains within 3 million, ultra-high molecular weight polyethylene having a viscosity average molecular weight of over 3.5 million and exceeding 6 million is sold. It can also be used. Furthermore, it has been found that even in the case of ultra high molecular weight polyethylene having a viscosity average molecular weight of 8 million to 10 million, the tensile strength and the piercing strength can be satisfactorily maintained even in a thin film of 15 μm or less. In addition to high density polyethylene (HDPE) having a viscosity average molecular weight of less than 500,000, medium density polyethylene (MDPE) and low density polyethylene (LDPE, L-LDPE) can be used in combination.
In the present invention, it is preferable to use a high density polyethylene having a viscosity average molecular weight in the range of 150,000 to less than 500,000 in order to clearly express the shutdown temperature. Ultra high molecular weight polyethylene 90% -15% by weight and high density polyethylene 85% by weight-10% by weight, preferably ultra high molecular weight polyethylene 85% by weight-30% by weight and
粘度平均分子量は、溶剤としてデカリンを使用し、測定温度１３５℃にて極限粘度［η］を測定し、下記の数式により粘度平均分子量（Ｍｖ）を算出する。For the viscosity average molecular weight, decalin is used as a solvent, the intrinsic viscosity [η] is measured at a measurement temperature of 135 ° C., and the viscosity average molecular weight (Mv) is calculated by the following formula.
［２］４−メチル−１−ペンテンと炭素数３以上のα−オレフィンとの共重合体樹脂
本発明で使用されるのはポリ（４−メチル−１−ペンテン）のホモポリマーでなくメチル４−メチル−１−ペンテンと炭素数３以上のα−オレフィンとの共重合体樹脂系重合体樹脂である。４−メチル−１−ペンテンと少なくとも１種類のα−オレフィン、例えば、プロピレン、１−ブテン、１−ヘキセン、１−オクテン、１−デセン、１−ドデセン、１−テトラデセン、１−ヘキサデセン、１−オクタデセン等の炭素数３乃至３０のα−オレフィンとの共重合体である。本発明の超高分子量ポリエチレンとの溶融時の混和性から粉末が好ましく、また混和性と混合後の保持される耐熱性から好ましくは、４−メチル−１−ペンテンを８０モル％以上含む４−メチル−１−ペンテンを主体とした共重合体であり、４−メチル−１−ペンテンとα−オレフィンとの組成比は、ＤＳＣ（示差走査型熱量計）試験に基づいて測定される融点（Ｔｍ）が、２００〜２５０℃、好ましくは２２０〜２４０℃の範囲で調整される。
さらに、ＡＳＴＭ Ｄ１２３８に準じた荷重５ｋｇ、温度２６０℃の条件により測定されるメルトフローレート（ＭＦＲ）は０．０５〜２５０［ｇ／１０分］である。好ましくは１乃至１００ｇ／１０分の範囲のものである。メルトフローレートが０．０５ｇ／１０ｍｉｎ未満のものは溶融粘度が高く成形性に劣り、メルトフローレートが２５０ｇ／１０ｍｉｎを超えるものは溶融粘度が低く成形性に劣り、また機械的強度も低い。[2] Copolymer resin of 4-methyl-1-pentene and α-olefin having 3 or more carbon atoms The present invention uses methyl 4 instead of poly (4-methyl-1-pentene) homopolymer. -Copolymer resin polymer resin of methyl-1-pentene and α-olefin having 3 or more carbon atoms. 4-methyl-1-pentene and at least one α-olefin such as propylene, 1-butene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1- It is a copolymer with an α-olefin having 3 to 30 carbon atoms such as octadecene. From the viewpoint of miscibility with the ultrahigh molecular weight polyethylene of the present invention, a powder is preferable, and from the viewpoint of miscibility and heat resistance retained after mixing, 4-methyl-1-pentene is preferably contained in an amount of 80 mol% or more. It is a copolymer mainly composed of methyl-1-pentene, and the composition ratio of 4-methyl-1-pentene and α-olefin is a melting point (Tm) measured based on a DSC (differential scanning calorimeter) test. ) Is adjusted in the range of 200 to 250 ° C, preferably 220 to 240 ° C.
Further, the melt flow rate (MFR) measured under conditions of a load of 5 kg and a temperature of 260 ° C. according to ASTM D1238 is 0.05 to 250 [g / 10 min]. It is preferably in the range of 1 to 100 g / 10 minutes. When the melt flow rate is less than 0.05 g / 10 min, the melt viscosity is high and the moldability is poor, and when the melt flow rate exceeds 250 g / 10 min, the melt viscosity is low and the moldability is poor, and the mechanical strength is also low.
［３］ポリオレフィン系エラストマー樹脂
本発明で用いられるポリオレフィン系エラストマー樹脂としては、プロピレン由来の構成単位と炭素数２〜３０のα−オレフィン（プロピレンを除く）由来の構成単位とからなる共重合体であり、プロピレン由来の構成単位を１０モル％以上（ここでプロピレン由来の構成単位と炭素数２〜３０のα−オレフィン由来の構成単位の合計を１００モル％とする）含んでおり、共重合成分のα−オレフィンとしては、炭素数２〜３０のα−オレフィン（プロピレンを除く）としては、エチレン、１−ブテン、１−ペンテン、１−ヘキセン、４−メチル−１−ペンテン、１−オクテン、１−デセン、１−ドデセン、１−テトラデセン、１−ヘキサデセン、１−オクタデセン、１−エイコセン等が挙げられる。[3] Polyolefin-based elastomer resin The polyolefin-based elastomer resin used in the present invention is a copolymer comprising a structural unit derived from propylene and a structural unit derived from an α-olefin having 2 to 30 carbon atoms (excluding propylene). Yes, containing 10 mol% or more of a propylene-derived structural unit (here, the total of the propylene-derived structural unit and the C2-C30 α-olefin-derived structural unit is 100 mol%), and a copolymer component As the α-olefin of 2 to 30 carbon atoms (excluding propylene), ethylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene, Examples include 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicocene and the like.
最も好ましいプロピレンとα−オレフィンからなる共重合体は、１０ｎｍ〜５０ｎｍのナノオーダーレベルのらせん状の結晶部である「島」が互いに連結して網状の構造をとり非晶部全体を覆うミクロ構造を有するものである。この「網」の構造により優れた耐久性、耐熱性、柔軟性を持つことになる。一旦溶融し固形化する際も「網」の構造が残り均一に固形化すると考えられる。特に上記の網状構造を有する三井化学（株）製のノティオシリーズ（例示として「ノティオＰＮ３５６０」、「ノティオＰＮ２０６０」、「ノティオＰＮ２０７０」）を４−メチル−１−ペンテンとα−オレフィンとの共重合体樹脂に組み合わせて使用するのが最適であり２３０℃のメルトフローレートが４−１０ｇ／分、密度が８６５−８７０ｋｇ／ｍ３で低温脆化温度が−２５℃から−３０℃であり荷重２ｋｇ／ｃｍ２における１ｍｍφの５００μｍ進入時の温度（ＴＭＡ）が１００−１４０℃の範囲にあるものが良い。 また、通常結晶化度を高めて耐熱性を上げると柔軟性は下がるのが一般的であるが、当該プロピレン系エラストマー樹脂を混合した場合、結晶部の内部に非晶部をナノレベルで組み込み、それが周りを取り囲む非晶部と連結する構造をとるため耐熱性を上げても柔軟性は下がらない。The most preferable copolymer of propylene and α-olefin has a microstructure in which “islands”, which are nano-order level helical crystal parts of 10 nm to 50 nm, are connected to each other to form a network structure and cover the entire amorphous part. It is what has. This “net” structure provides excellent durability, heat resistance and flexibility. Even when it is once melted and solidified, it is considered that the “net” structure remains and solidifies uniformly. In particular, the Notio series (for example, “Notio PN3560”, “Notio PN2060”, and “Notio PN2070”) manufactured by Mitsui Chemicals, Inc. having the above-described network structure is obtained by combining 4-methyl-1-pentene and α-olefin. It is optimal to use in combination with a polymer resin, the melt flow rate at 230 ° C is 4-10 g / min, the density is 865-870 kg / m3, the low temperature embrittlement temperature is -25 ° C to -30 ° C, and the load is 2 kg. It is preferable that the temperature (TMA) at the time of entering 500 μm of 1 mmφ at / cm 2 is in the range of 100 to 140 ° C. In addition, the flexibility generally decreases when the crystallinity is increased to increase the heat resistance, but when the propylene-based elastomer resin is mixed, the amorphous part is incorporated at the nano level inside the crystal part, Even if the heat resistance is increased, the flexibility does not decrease because it is connected to the surrounding amorphous part.
本発明に使用されるポリオレフィン系エラストマー樹脂としてプロピレン由来の構成単位とエチレン由来の構成単位と炭素数４〜３０のα−オレフィン由来の構成単位とからなる共重合体があり、プロピレン由来の構成単位と炭素数２〜３０のα−オレフィン（プロピレンを除く）由来の構成単位との合計を１００モル％とした場合に、プロピレン由来の構成が１５モル％以上である。
プロピレン・α−オレフィンランダム共重合体（例示として三井化学（株）製の「タフマーＸＭ−５０７０」）、ブテン−α−オレフィンランダム共重合体（例示として三井化学（株）製の「タフマーＢＬ３４５０」、「タフマーＢＬ３１１０」、「タフマーＢＬ２４８１」、「タフマーＢＬ４０００」等があげられる。）、エチレン・α−オレフィンランダム共重合体も使用される。市販品として住友化学（株）製のタフセレンシリーズ（例示として「タフセレンＨ３５２２Ａ」）、エクソンモービルケミカル社製のＶＩＳＴＡＭＡＸＸシリーズ、ザ・ダウ・ケミカル・カンパニー製のＶＥＲＳＩＦＹシリーズがある。As a polyolefin-based elastomer resin used in the present invention, there is a copolymer comprising a propylene-derived structural unit, an ethylene-derived structural unit, and a C 4-30 α-olefin-derived structural unit, and a propylene-derived structural unit. And the sum of the structural units derived from C 2-30 α-olefin (excluding propylene) being 100 mol%, the composition derived from propylene is 15 mol% or more.
Propylene / α-olefin random copolymer (“Tuffmer XM-5070” manufactured by Mitsui Chemicals, Inc.), butene-α-olefin random copolymer (“Tuffmer BL3450” manufactured by Mitsui Chemicals, Inc.) , “Tuffmer BL3110”, “Tuffmer BL2481”, “Tuffmer BL4000”, etc.), and ethylene / α-olefin random copolymers are also used. Commercially available products include Tough Selenium Series (manufactured by “Tough Selenium H3522A”) manufactured by Sumitomo Chemical Co., Ltd., VISAMAXX Series manufactured by ExxonMobil Chemical, and VERSIFY Series manufactured by The Dow Chemical Company.
また、完全非晶ポリプロピレン樹脂と結晶性ポリプロピレン樹脂の混合物からなるか、あるいは、上記のプロピレン・α−オレフィンランダム共重合体をポリプロピレン等に対して３重量％以上３０重量％以下混合したとき、プロピレン・エチレンランダムコポリマのように非晶部を海とし、結晶部を島とした海島状に樹脂が分散した構造でもよい。Further, it is composed of a mixture of a completely amorphous polypropylene resin and a crystalline polypropylene resin, or when propylene / α-olefin random copolymer is mixed in an amount of 3% by weight to 30% by weight with respect to polypropylene, A structure in which the resin is dispersed in a sea-island shape in which the amorphous part is the sea and the crystal part is the island, such as an ethylene random copolymer, may be used.
一方、本発明の超高分子ポリエチレン並びに高密度ポリエチレン等のポリエチレンに相溶するエチレンとブテンとの共重合体の三井化学（株）製のタフマーシリーズ（例示として「タフマーＤＦ８１０」、「タフマーＤＦ７１０」、「タフマーＤＦ６１０」、「タフマーＤＦ６０５」）を混合することにより、４−メチル−１−ペンテンとα−オレフィンとの共重合体樹脂の分散性をより高めることができる。４−メチル−１−ペンテンとα−オレフィンとの共重合体樹脂との樹脂混合系において、樹脂溶融均一性が保持されて優れた耐久性、耐熱性、柔軟性を持つ耐熱性ポリオレフィン微多孔膜になると思われる。またこのことにより当該ポリオレフィン樹脂混合物は、Ｔ−ダイ出のメルトフラクチャーも全く発生することなく溶融特性の安定な均一な組成のシートを得ることができる。On the other hand, a copolymer of ethylene and butene, which is compatible with polyethylene such as ultrahigh molecular polyethylene and high density polyethylene of the present invention, is manufactured by Mitsui Chemicals Co., Ltd. Tuffmer series (for example, “Tuffmer DF810”, “Tuffmer DF710”). ”,“ Tuffmer DF610 ”,“ Tuffmer DF605 ”), the dispersibility of the copolymer resin of 4-methyl-1-pentene and α-olefin can be further increased. Heat resistant polyolefin microporous membrane having excellent durability, heat resistance and flexibility while maintaining resin melt uniformity in a resin mixed system of 4-methyl-1-pentene and α-olefin copolymer resin It seems to become. This also makes it possible for the polyolefin resin mixture to obtain a sheet having a uniform composition with stable melting characteristics without causing any melt fracture of T-die.
［４］ポリプロピレン樹脂
本発明で使用されるポリプロピレンの分子量は特に限定されるものではないが、粘度平均分子量１０万以上粘度平均分子量３０万程度の高分子量ポリプロピレンを用いると耐熱破膜性に優れた微多孔膜を得ることができる。本発明におけるポリプロピレン樹脂としては、ホモポリプロピレン（プロピレン単独重合体）、またはプロピレンとエチレン、１−ブテン、１−ペンテン、１−ヘキセン、１−ヘプテン、１−オクテン、１−ノネンもしくは１−デセンなどαオレフィンとのランダム共重合体またはブロック共重合体などが挙げられる。これらは単独で用いても混合物として用いてもよい。この中でも、機械的強度の観点からホモポリプロピレンがより好ましい。また、ポリプロピレン樹脂のメルトフローレート（ＭＦＲ）は特に制限されるものではないが、通常、ＪＩＳ Ｋ７２１０に準拠して温度２３０℃、荷重２．１６ｋｇの条件で測定してＭＦＲは０．１〜１５ｇ／１０分であることが好ましく、０．５〜１０ｇ／１０分であることがより好ましい。ＭＦＲが０．１ｇ／１０分未満では、成形加工時の樹脂の溶融粘度が高く生産性が低下する。一方、１５ｇ／１０分を超えると得られる微多孔膜の機械的強度が不足するなどの実用上の問題が生じやすい。ポリプロピレン樹脂は高温時の孔径維持、並びに熱破膜温度向上のために前記ポリエチレンの１質量％以上−３０質量％を置換することもできる。ポリプロピレン樹脂含量率が増えると機械的強度が低下するため２０質量％以下が好ましい。[4] Polypropylene resin The molecular weight of the polypropylene used in the present invention is not particularly limited. However, when a high molecular weight polypropylene having a viscosity average molecular weight of 100,000 or more and a viscosity average molecular weight of about 300,000 is used, the film has excellent heat-resistant film breaking property. A microporous membrane can be obtained. As the polypropylene resin in the present invention, homopolypropylene (propylene homopolymer), propylene and ethylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, etc. Examples thereof include random copolymers with α-olefins and block copolymers. These may be used alone or as a mixture. Among these, homopolypropylene is more preferable from the viewpoint of mechanical strength. In addition, the melt flow rate (MFR) of the polypropylene resin is not particularly limited. Usually, the MFR is 0.1 to 15 g as measured according to JIS K7210 at a temperature of 230 ° C. and a load of 2.16 kg. / 10 minutes is preferable, and 0.5 to 10 g / 10 minutes is more preferable. When the MFR is less than 0.1 g / 10 minutes, the melt viscosity of the resin during the molding process is high, and the productivity is lowered. On the other hand, when it exceeds 15 g / 10 min, practical problems such as insufficient mechanical strength of the obtained microporous membrane tend to occur. The polypropylene resin can also replace 1% by mass to -30% by mass of the polyethylene in order to maintain the pore diameter at high temperature and improve the thermal film breaking temperature. When the polypropylene resin content increases, the mechanical strength decreases, so 20% by mass or less is preferable.
［５］低分子量のポリエチレン系ワックス
本発明に使用出来る低分子量のポリエチレン系ワックスとしては、エチレンの単独重合体またはエチレンとα−オレフィンとの共重合体、またはそれらのブレンド物をいう。好ましくは、エチレン・プロピレンランダム共重合体、エチレン・１−ブテンランダム共重合体、エチレン・プロピレン・１−ブテン共重合体であり、ゲルパーミエーションクロマトグラフィーで測定した場合の分子量分布がきわめて狭く、ポリエチレン換算の分子量が２０，０００以上となる成分を出来るだけ少なくなるように、メタロセン触媒を用いて調製される。溶融温度は、８５−１１０℃の範囲にあり、好ましくは８９−１０２℃の融点を有するものである。溶融温度が８９−１０２℃の範囲にある低分子量のエチレン・プロピレンランダム共重合体、エチレン・１−ブテンランダム共重合体、エチレン・プロピレン・１−ブテン共重合体から選ばれた１種以上のエチレン・α−オレフィンランダム共重合体を超高分子量ポリエチレンと高密度ポリエチレンとを含むポリエチレン５０−８５重量％、４−メチル−１−ペンテンと炭素数３以上のα−オレフィンとの共重合体樹脂１０−３０重量％、ポリオレフィン系エラストマー樹脂２．０−１０重量％とからなるポリオレフィン樹脂混合物に対して０．２−５重量％添加するのが良い。好ましくは０．２−２．５重量％である。
融点の大きく異なる４−メチル−１−ペンテンとα−オレフィンとの共重合体樹脂と超高分子量ポリエチレン粉末との二軸押出機への食い込みを良好にする目的とともに出来上がった耐熱性ポリオレフィン微多孔膜の温度に対する感応性が無添加の場合と比較して鋭敏にシャットダウン時、インピーダンスが上昇して１８５℃まで電池が温度上昇し電解液が熱分解するまで微多孔膜はメルトダウンすることなく保持できる。[5] Low molecular weight polyethylene wax The low molecular weight polyethylene wax that can be used in the present invention refers to a homopolymer of ethylene, a copolymer of ethylene and an α-olefin, or a blend thereof. Preferably, an ethylene / propylene random copolymer, an ethylene / 1-butene random copolymer, an ethylene / propylene / 1-butene copolymer, and the molecular weight distribution measured by gel permeation chromatography is extremely narrow, It is prepared using a metallocene catalyst so that the component having a molecular weight in terms of polyethylene of 20,000 or more is minimized. The melting temperature is in the range of 85-110 ° C, preferably having a melting point of 89-102 ° C. One or more kinds selected from a low molecular weight ethylene / propylene random copolymer, an ethylene / 1-butene random copolymer, an ethylene / propylene / 1-butene copolymer having a melting temperature in the range of 89 to 102 ° C. Ethylene / α-olefin random copolymer 50-85 wt% polyethylene containing ultrahigh molecular weight polyethylene and high density polyethylene, copolymer resin of 4-methyl-1-pentene and α-olefin having 3 or more carbon atoms It is preferable to add 0.2-5% by weight to a polyolefin resin mixture comprising 10-30% by weight and polyolefin-based elastomer resin 2.0-10% by weight. Preferably it is 0.2-2.5 weight%.
Heat-resistant polyolefin microporous membrane completed for the purpose of good biting into a twin-screw extruder of a copolymer resin of 4-methyl-1-pentene and α-olefin having greatly different melting points and ultrahigh molecular weight polyethylene powder Compared with the case where the sensitivity to the temperature is not added, the microporous membrane can be maintained without being melted down until the impedance is increased and the temperature of the battery is increased to 185 ° C. and the electrolyte is thermally decomposed. .
例えば融点の異なるポリオレフィン樹脂をｎ（ここではｎは３以上の整数を表す）種類以上使用する場合、高分子量ポリエチレンの融点Ｔ１℃と使用されるポリオレフィン樹脂の融点Ｔ２℃、Ｔ３℃・・・Ｔｎ℃からなる樹脂混合物の平均融点Ｔを下記の式のように定義する。For example, when n or more types of polyolefin resins having different melting points are used (here, n represents an integer of 3 or more), the melting point T 1 ° C. of the high molecular weight polyethylene and the melting point T 2 ° C. of the polyolefin resin used, T 3 ° C. .. The average melting point T of the resin mixture composed of Tn.degree. C. is defined as the following formula.
［６］無機フィラ−
本発明に使用される無機フィラ−としては、例えば、アルミナ、水酸化アルミニウムのアスペクト比を有するナノサイズのベーマイト・アルミナ、シリカ（珪素酸化物）、ナトリウムアルミノシリケート、ナトリウムカルシウムアルミノシリケートチタニア、ジルコニア、マグネシア、セリア、イットリア、酸化亜鉛、酸化鉄などの酸化物系、シリコンカーバイド、窒化ケイ素、窒化チタン、窒化ホウ素等の窒化物系、炭酸カルシウム、硫酸アルミニウム、水酸化アルミニウム、チタン酸カリウム、タルク、カオリンクレー、カオリナイト、ハロイサイト、パイロフィライト、モンモリロナイト、セリサイト、マイカ、アメサイト、ベントナイト、アスベスト、ゼオライト、ケイ酸カルシウム、ケイ酸マグネシウム、ケイ藻土、ケイ砂等のセラミックス、ガラス繊維などが挙げられる。これらの１種を単独で、あるいは２種以上を併用することができる。好ましいのは、電気化学的に安定な、シリカ、アルミナ、チタニウムであり、特にシリカ、アルミノシリケートが好ましい。
前記無機フィラ−粉末粒子の平均粒径としては、好ましくは１ｎｍ以上、より好ましくは１０ｎｍ以上であり、上限として好ましくは１００ｎｍ以下である。
平均粒径を１００ｎｍ以下とすることは、延伸等を施した場合でもポリオレフィン樹脂と無機フィラ−間での剥離が生じにくい傾向となり、マクロボイドの発生を抑制する観点から好ましい。
一方、平均粒径を１ｎｍ以上とすることは、溶融時の無機フィラ−粒子の分散性を確保する上で好ましい。
前記ポリオレフィン樹脂と無機フィラ−粒子との総量中に占める無機フィラ−粒子の割合が５質量％以上４０質量％以下、押出機のバレル、スクリューの耐摩耗の観点から好ましくは５質量％以上２０質量％以下である。無機フィラ−粒子の熱重量分析による１００℃までの重量減少率が５％以下のものであることが好ましい。無機フィラ−粒子の添加により、微多孔膜の引張強度を高めたり、熱収縮率を低くすることができる。[6] Inorganic filler
Examples of the inorganic filler used in the present invention include alumina, nano-sized boehmite / alumina having an aspect ratio of aluminum hydroxide, silica (silicon oxide), sodium aluminosilicate, sodium calcium aluminosilicate titania, zirconia, Oxides such as magnesia, ceria, yttria, zinc oxide, iron oxide, nitrides such as silicon carbide, silicon nitride, titanium nitride, boron nitride, calcium carbonate, aluminum sulfate, aluminum hydroxide, potassium titanate, talc, Kaolin clay, kaolinite, halloysite, pyrophyllite, montmorillonite, sericite, mica, amicite, bentonite, asbestos, zeolite, calcium silicate, magnesium silicate, diatomaceous earth, silica sand, etc. Mix, such as glass fiber and the like. One of these can be used alone, or two or more can be used in combination. Preferred are electrochemically stable silica, alumina and titanium, and silica and aluminosilicate are particularly preferred.
The average particle size of the inorganic filler powder particles is preferably 1 nm or more, more preferably 10 nm or more, and the upper limit is preferably 100 nm or less.
When the average particle size is 100 nm or less, peeling between the polyolefin resin and the inorganic filler tends not to occur even when stretching or the like is performed, which is preferable from the viewpoint of suppressing the generation of macrovoids.
On the other hand, setting the average particle size to 1 nm or more is preferable for ensuring the dispersibility of the inorganic filler particles during melting.
The proportion of the inorganic filler particles in the total amount of the polyolefin resin and the inorganic filler particles is 5% by mass or more and 40% by mass or less, preferably 5% by mass or more and 20% by mass from the viewpoint of wear resistance of the barrel and screw of the extruder. % Or less. It is preferable that the weight loss rate up to 100 ° C. by the thermogravimetric analysis of the inorganic filler particles is 5% or less. By adding inorganic filler particles, the tensile strength of the microporous membrane can be increased and the thermal shrinkage rate can be decreased.
［７］可塑剤
本発明の微多孔膜を製造する際に使用可能な可塑剤としては、液状可塑剤及び固体可塑剤のいずれも使用できる。液状可塑剤としてはノナン、デカン、デカリン、パラキシレン、ウンデカン、ドデカン、流動パラフィン等の脂肪族又は環式の炭化水素、及び沸点がこれらに対応する鉱油留分が挙げられる。溶剤含有量が安定したゲル状成形物を得るためには、流動パラフィン、ミネラルオイルのような不揮発性の液体可塑剤を用いるのが好ましい。液体可塑剤の粘度は２５℃において３０〜５００ｃＳｔの範囲内であるのが好ましく、５０〜２００ｃＳｔの範囲内であるのがより好ましい。液体可塑剤の２５℃における粘度が３０ｃＳｔ未満ではポリオレフィン混合物の溶融物のダイリップからの吐出が不均一であり、かつ混練が困難である。一方５００ｃＳｔ超では可塑剤の除去が困難である。[7] Plasticizer As the plasticizer that can be used in producing the microporous membrane of the present invention, either a liquid plasticizer or a solid plasticizer can be used. Examples of the liquid plasticizer include aliphatic or cyclic hydrocarbons such as nonane, decane, decalin, paraxylene, undecane, dodecane, and liquid paraffin, and mineral oil fractions having boiling points corresponding to these. In order to obtain a gel-like molded article having a stable solvent content, it is preferable to use a non-volatile liquid plasticizer such as liquid paraffin or mineral oil. The viscosity of the liquid plasticizer is preferably in the range of 30 to 500 cSt at 25 ° C., and more preferably in the range of 50 to 200 cSt. When the viscosity of the liquid plasticizer at 25 ° C. is less than 30 cSt, the discharge of the melt of the polyolefin mixture from the die lip is non-uniform and kneading is difficult. On the other hand, if it exceeds 500 cSt, it is difficult to remove the plasticizer.
固体可塑剤は融点が８０℃以下のものが好ましく、このような固体可塑剤としてパラフィンワックス、マイクロクリスタリンワックス等のワックス類、セリルアルコール、ステアリルアルコール等の高級アルコール類、ポリオキシエチレンステアリルエーテル、ポリオキシエチレンイソステアリルエーテル等のポリオキシエチレンアルキルエーテル類、ポリオキシプロピレンステアリルエーテル、ポリオキシプロピルイソステアリルエーテル等のポリオキシプロピレンアルキルエーテル、ポリオキシエチレンステアリルエステル等のポリオキシエチレンアルキルエステル類、ポリオキシプロピレンステアリルエステル等のポリオキシプロピレンアルキルエステル類が挙げられる。液体溶剤と固体溶剤を適宜混合した上で使用してもよい。
特に、ポリオキシエチレンステリルエーテル、ポリオキシエチレンイソステアリルエーテル等のポリオキシエチレンアルキルエーテルを流動パラフィンと混合することにより室温で混合物が固化するので有用である。流動パラフィン９５−７５重量％とポリオキシアルキレンアルキルエーテル５−２５重量％、好ましくは流動パラフィン９０−８０重量％とポリオキシアルキレンアルキルエーテル１０−２０重量％の範囲で使用される。樹脂と可塑剤を両者の融点以上の温度において均一に溶融混練した後、当該混練物を任意の冷却速度にて当該混合樹脂の固化温度以下まで冷却したときに延伸可能な軟質のゲル状シート成形物を得ることが出来る。The solid plasticizer preferably has a melting point of 80 ° C. or lower. As such a solid plasticizer, waxes such as paraffin wax and microcrystalline wax, higher alcohols such as seryl alcohol and stearyl alcohol, polyoxyethylene stearyl ether, poly Polyoxyethylene alkyl ethers such as oxyethylene isostearyl ether, polyoxypropylene stearyl ether, polyoxypropylene alkyl ether such as polyoxypropylisostearyl ether, polyoxyethylene alkyl esters such as polyoxyethylene stearyl ester, polyoxy And polyoxypropylene alkyl esters such as propylene stearyl ester. You may use it, mixing a liquid solvent and a solid solvent suitably.
In particular, it is useful because the mixture is solidified at room temperature by mixing polyoxyethylene alkyl ether such as polyoxyethylene steryl ether and polyoxyethylene isostearyl ether with liquid paraffin. It is used in the range of 95-75% by weight of liquid paraffin and 5-25% by weight of polyoxyalkylene alkyl ether, preferably 90-80% by weight of liquid paraffin and 10-20% by weight of polyoxyalkylene alkyl ether. Forming a soft gel-like sheet that can be stretched when the resin and plasticizer are uniformly melt-kneaded at a temperature equal to or higher than their melting points, and then the kneaded product is cooled to below the solidification temperature of the mixed resin at an arbitrary cooling rate. You can get things.
使用可能な可塑剤量は、相分離構造が樹脂と可塑剤の相溶性、および樹脂と可塑剤の合計重量に対する樹脂の重量比（ポリマー重量分率）によって変化させることができる。
例えば当該ポリオレフィン樹脂混合物と可塑剤との配合割合は、両者の合計を１００重量部として、当該ポリオレフィン樹脂混合物が１０〜４６重量部、当該可塑剤９０〜５４重量部であり、好ましくは当該ポリオレフィン樹脂混合物が３０〜４４重量部である。ポリオレフィン樹脂混合物の割合が１０重量部未満とすると、ポリオレフィン混合物溶融物を押し出す際にダイス出口でスウェルやネックインが大きくなり、ゲル状成形物の成形性及び自己支持性が低下する。一方ポリオレフィン混合物の割合が４６質量部を超えるとゲル状シート成形物の成形性が低下し、また気孔が小さく透過性に劣る。The amount of the plasticizer that can be used can be changed according to the compatibility of the resin and the plasticizer in the phase separation structure and the weight ratio of the resin to the total weight of the resin and the plasticizer (polymer weight fraction).
For example, the blending ratio of the polyolefin resin mixture and the plasticizer is 10 to 46 parts by weight of the polyolefin resin mixture and 90 to 54 parts by weight of the plasticizer, preferably 100 parts by weight of the total of both, preferably the polyolefin resin The mixture is 30 to 44 parts by weight. If the proportion of the polyolefin resin mixture is less than 10 parts by weight, swell and neck-in will increase at the die outlet when extruding the polyolefin mixture melt, and the moldability and self-supporting property of the gel-like molded product will be reduced. On the other hand, when the proportion of the polyolefin mixture exceeds 46 parts by mass, the moldability of the gel-like sheet molding is lowered, and the pores are small and the permeability is poor.
本発明の耐熱性ポリオレフィン微多孔膜の製造方法は、二軸押出機にて超高分子量ポリエチレンと高密度ポリエチレンとを含むポリエチレン５０−８５重量％、４−メチル−１−ペンテンと炭素数３以上のα−オレフィンとの共重合体樹脂１２．５−３０重量％、ポリオレフィン系エラストマー樹脂１−１０重量％とからなるポリオレフィン樹脂混合物、必要に応じて無機フィラーを添加して、製膜用の可塑剤を注入し、溶融混練し、ダイより押出し、冷却して得られたゲル状シート成形物を延伸した後に前記製膜用の溶剤を除去することからなる。
本発明の耐熱性ポリオレフィン微多孔膜は、下記の工程を含む製造方法により好適に製造される。以下各工程を順次詳しく説明する。
（工程１）超高分子量ポリエチレンと高密度ポリエチレンとを含むポリエチレン５０−８５重量％、４−メチル−１−ペンテンと炭素数３以上のα−オレフィンとの共重合体樹脂１０−３０重量％、ポリオレフィン系エラストマー樹脂１−１０重量％からなるポリオレフィン樹脂混合物と酸化防止剤、必要に応じて無機フィラー粉末を２軸押出機に供給し、可塑剤の加熱混合液を注入し、溶融混練りする工程；
（工程２）工程１で作成した溶融混練物をＴダイから押出し、ロールで冷却・圧延しゲル状シート成形物に成形する工程；
（工程３）工程２で得られたゲル状シート成形物を２軸方向（ＭＤ方向，ＴＤ方向）に延伸しながら引き取り速度を上げて厚みを薄く調製する３次元の延伸を行う工程；
（工程４）工程３で得られた薄膜から可塑剤を溶剤で抽出除去、並びに乾燥する工程；
（工程５）工程４で得られた微多孔膜を必要に応じて熱処理、再延伸、熱固定する工程；The method for producing the heat-resistant polyolefin microporous membrane of the present invention comprises 50 to 85% by weight of polyethylene containing ultrahigh molecular weight polyethylene and high density polyethylene in a twin-screw extruder, 4-methyl-1-pentene and 3 or more carbon atoms. A polyolefin resin mixture comprising 12.5-30% by weight of a copolymer resin with an α-olefin and 1-10% by weight of a polyolefin-based elastomer resin, and if necessary, an inorganic filler is added to form a plastic for film formation. It is composed of removing the film-forming solvent after injecting the agent, melt-kneading, extruding from a die, and stretching the gel-like sheet molding obtained.
The heat-resistant polyolefin microporous membrane of the present invention is preferably produced by a production method including the following steps. Each process will be described in detail below.
(Step 1) 50-85% by weight of polyethylene containing ultra high molecular weight polyethylene and high density polyethylene, 10-30% by weight of copolymer resin of 4-methyl-1-pentene and α-olefin having 3 or more carbon atoms, A process of supplying a polyolefin resin mixture comprising 1-10% by weight of a polyolefin-based elastomer resin, an antioxidant, and if necessary, an inorganic filler powder to a twin-screw extruder, injecting a heated plasticizer mixture, and melt-kneading. ;
(Step 2) A step of extruding the melt-kneaded material prepared in Step 1 from a T-die, cooling and rolling with a roll, and forming it into a gel-like sheet molded product;
(Step 3) A step of performing three-dimensional stretching in which the gel-like sheet molded product obtained in Step 2 is stretched in the biaxial direction (MD direction, TD direction) while increasing the take-up speed to prepare a thin thickness;
(Step 4) Step of extracting and removing the plasticizer from the thin film obtained in Step 3 with a solvent, and drying;
(Step 5) A step of heat-treating, re-stretching and heat-setting the microporous membrane obtained in Step 4 as necessary;
上記ポリオレフィン樹脂混合物の溶融混練物には必要に応じて酸化防止剤、紫外線吸収剤、アンチブロッキング剤、核剤、顔料、染料、無機充填材等の各種添加剤を本発明の効果を損なわない範囲で添加することができる。例えば孔形成剤として微粉珪酸を添加することもできる。 Various additives such as an antioxidant, an ultraviolet absorber, an antiblocking agent, a nucleating agent, a pigment, a dye, and an inorganic filler are added to the melt-kneaded product of the polyolefin resin mixture as necessary, so long as the effects of the present invention are not impaired. Can be added. For example, finely divided silicic acid can be added as a pore forming agent.
溶融混練の方法は特に限定されないが、通常は二軸押出機中で均一に混練することにより行う。この方法は当該ポリオレフィン混合物の溶融物を調製するのに適する。溶融温度はポリオレフィン樹脂の平均融点＋７０℃〜＋１２０℃の範囲内であるのが好ましい。
具体的に溶融温度は、押出温度ゾーンを２００〜３００℃の範囲で設定するのが好ましく、２００〜２６０℃の範囲内であるのがより好ましい。可塑剤は混練開始前に添加しても、混練中に二軸押出機の途中から分割添加してもよい。
溶融混練にあたってはポリオレフィン樹脂混合物の酸化を防止するために酸化防止剤を添加するのが好ましい。Although the method of melt kneading is not particularly limited, it is usually carried out by uniformly kneading in a twin screw extruder. This method is suitable for preparing a melt of the polyolefin mixture. The melting temperature is preferably within the range of the average melting point of the polyolefin resin + 70 ° C. to + 120 ° C.
Specifically, the melting temperature is preferably set in the extrusion temperature zone in the range of 200 to 300 ° C, more preferably in the range of 200 to 260 ° C. The plasticizer may be added before the start of kneading or may be added in the middle of the twin screw extruder during kneading.
In melt kneading, it is preferable to add an antioxidant in order to prevent oxidation of the polyolefin resin mixture.
また二軸押出機のスクリュの長さ（Ｌ）と直径（Ｄ）の比（Ｌ／Ｄ）は４５〜１００の範囲が好ましく、５０〜７０の範囲がより好ましい。Ｌ／Ｄを４５未満にすると、溶融混練が不十分となる。特に超高分子量ポリエチレンの完全溶融が困難となる。Ｌ／Ｄを１００超にすると、ポリオレフィン混合物溶融物と可塑剤の押出機内の滞留時間が増大し過ぎ熱劣化を招く。スクリュの形状は特に制限されないが、樹脂融点の大きく異なる成分を溶融・混練りする観点でのスクリュを選択するのが良い。二軸押出機のシリンダ内径は２６〜１５０ｍｍであるのが好ましい。ポリオレフィン樹脂混合物を二軸押出機に入れる際、スクリュ回転数Ｎｓ（ｒｐｍ）に対するポリオレフィン樹脂混合物と可塑剤との投入量Ｑ（ｋｇ／ｈ）の比Ｑ／Ｎｓを０．１〜０．５５ｋｇ／ｈ／ｒｐｍにするのが好ましい。Ｑ／Ｎｓを０．１ｋｇ／ｈ／ｒｐｍ未満にすると、ポリオレフィン樹脂樹脂が過度にせん断破壊されてしまい、強度やシャットダウン温度の低下につながる。一方Ｑ／Ｎｓを０．５５ｋｇ／ｈ／ｒｐｍ超にすると、均一に混練できない。比Ｑ／Ｎｓは０．２〜０．５ｋｇ／ｈ／ｒｐｍであるのがより好ましい。スクリュ回転数Ｎｓは１２０ｒｐｍ以上にするのが好ましい。スクリュ回転数Ｎｓの上限は特に制限されないが、１５０−５００ｒｐｍが好ましい範囲である。 Further, the ratio (L / D) of the screw length (L) to the diameter (D) of the twin screw extruder is preferably in the range of 45 to 100, more preferably in the range of 50 to 70. When L / D is less than 45, melt kneading becomes insufficient. In particular, it becomes difficult to completely melt ultrahigh molecular weight polyethylene. When L / D is more than 100, the residence time in the extruder of the polyolefin mixture melt and the plasticizer is excessively increased, leading to thermal deterioration. The shape of the screw is not particularly limited, but it is preferable to select a screw from the viewpoint of melting and kneading components having greatly different resin melting points. The cylinder inner diameter of the twin screw extruder is preferably 26 to 150 mm. When the polyolefin resin mixture is put into the twin screw extruder, the ratio Q / Ns of the input amount Q (kg / h) of the polyolefin resin mixture and the plasticizer to the screw rotation speed Ns (rpm) is 0.1 to 0.55 kg / h / rpm is preferred. When Q / Ns is less than 0.1 kg / h / rpm, the polyolefin resin resin is excessively sheared, leading to a decrease in strength and shutdown temperature. On the other hand, when Q / Ns exceeds 0.55 kg / h / rpm, uniform mixing cannot be achieved. The ratio Q / Ns is more preferably 0.2 to 0.5 kg / h / rpm. The screw rotation speed Ns is preferably 120 rpm or more. The upper limit of the screw rotation speed Ns is not particularly limited, but 150 to 500 rpm is a preferable range.
ゲル状シート成形物を形成する方法としては、二軸押出機で樹脂と可塑剤を溶融混練し、ポリオレフィン樹脂混合物の溶融物を二軸押出機から直接に又は別の押出機、ギアーポンプを介してＴダイより押出し、冷却することにより得る。
冷却は少なくともゲル化温度以下までは５０℃／分以上の速度で行うのが好ましい。冷却は４０℃以下まで行うのが好ましい。ゲル化温度以下まで５０℃／分以上の速度で冷却することによりポリオレフィン樹脂混合物相が可塑剤によりミクロ相分離された相分離構造を固定化することができる。一般に冷却速度が遅いと得られるゲル状成形物の高次構造が粗くなり、それを形成する擬似細胞単位も大きなものとなるが、冷却速度が速いと密な細胞単位となる。冷却速度が５０℃／分未満では結晶化度が上昇し、延伸に適したゲル状成形物となりにくい。冷却方法としては冷風、冷却水、その他の冷却媒体に直接接触させる方法、冷媒で冷却したロールに接触させる方法等を用いることができる。他にバッチ式混練機で樹脂と可塑剤を溶融混練した後、圧縮成型機を用いてシート・フィルム状にし、冷却する方法が利用できる。As a method of forming a gel-like sheet molding, a resin and a plasticizer are melt-kneaded with a twin-screw extruder, and the melt of the polyolefin resin mixture is directly from the twin-screw extruder or via another extruder or gear pump. It is obtained by extruding from a T-die and cooling.
Cooling is preferably performed at a rate of 50 ° C./min or more at least up to the gelation temperature or less. Cooling is preferably performed to 40 ° C. or lower. By cooling at a rate of 50 ° C./min or higher to the gelling temperature or lower, the phase separation structure in which the polyolefin resin mixture phase is microphase-separated by the plasticizer can be fixed. In general, when the cooling rate is low, the higher order structure of the gel-like molded product becomes coarse, and the pseudo cell unit forming it becomes large, but when the cooling rate is high, it becomes a dense cell unit. When the cooling rate is less than 50 ° C./min, the degree of crystallinity increases, and it is difficult to obtain a gel-like product suitable for stretching. As a cooling method, a method of directly contacting cold air, cooling water, or other cooling medium, a method of contacting a roll cooled by a refrigerant, or the like can be used. In addition, after melt-kneading the resin and the plasticizer with a batch-type kneader, a method of cooling into a sheet / film using a compression molding machine can be used.
ダイリップとしては、通常は長方形の口金形状をしたシート用ダイリップを用いるが、二重円筒状の中空状ダイリップ、インフレーションダイリップ等も用いることができる。シート用ダイリップの場合、ダイリップのギャップは通常０．２〜８ｍｍの範囲内であり、押出し時には１８０〜２５０℃の温度に加熱する。加熱溶液の押し出し速度は０．２〜５０ｍ／分の範囲内であるのが好ましい。 As the die lip, a sheet die lip having a rectangular base shape is usually used, but a double cylindrical hollow die lip, an inflation die lip, or the like can also be used. In the case of a sheet die lip, the die lip gap is usually in the range of 0.2 to 8 mm, and is heated to a temperature of 180 to 250 ° C. during extrusion. The extrusion rate of the heated solution is preferably in the range of 0.2 to 50 m / min.
延伸方法としては、フラット延伸、チューブラ延伸、ロール圧延などが利用可能である。
これらのうち、延伸均一性の観点からフラット延伸が好ましい。
延伸温度は、概ね１２０℃〜ポリオレフィン混合物平均融点の範囲内において選択することが好ましい。延伸温度を１１０℃未満とすると、過大な延伸応力による破膜を招き、また耐溶融収縮性が悪化する。延伸温度の上限は、微多孔膜を構成するポリオレフィン樹脂混合物の平均融点以下であるのが好ましい。当該樹脂混合物の平均融点温度以下であれば樹脂の融解による破膜を防ぐことが可能となる。
延伸温度が結晶融点を超えるとポリオレフィン樹脂混合物が溶融し、延伸による分子鎖の配向ができない。延伸温度は微多孔膜の熱収縮を低減させるために可能な限り高温にすることが望ましい。As the stretching method, flat stretching, tubular stretching, roll rolling and the like can be used.
Of these, flat stretching is preferred from the viewpoint of stretching uniformity.
The stretching temperature is preferably selected within the range of about 120 ° C. to the average melting point of the polyolefin mixture. When the stretching temperature is less than 110 ° C., film breakage due to excessive stretching stress is caused and the melt shrinkage resistance is deteriorated. The upper limit of the stretching temperature is preferably not more than the average melting point of the polyolefin resin mixture constituting the microporous membrane. If it is below the average melting point temperature of the resin mixture, it becomes possible to prevent film breakage due to melting of the resin.
When the stretching temperature exceeds the crystalline melting point, the polyolefin resin mixture melts and molecular chains cannot be oriented by stretching. The stretching temperature is desirably as high as possible in order to reduce the thermal shrinkage of the microporous membrane.
二軸延伸は、ゲル状シート成形物を加熱後、通常のテンター法、ロール法、インフレーション法、圧延法又はこれらの方法の組合せにより行う。同時二軸延伸、逐次延伸又は多段延伸（例えば同時二軸延伸及び逐次延伸の組合せ）のいずれでもよい。二軸延伸と可塑剤除去の順は任意に設定できるが、ゲル状シート成形物を二軸延伸した後可塑剤を除去するのが好ましい。但しこの順に限定する趣旨ではなく、例えばゲル状シート成形物から可塑剤を除去した後、二軸延伸したり、ゲル状シート成形物を二軸延伸した後可塑剤を除去しさらに二軸延伸したり、ゲル状シートを逐次二軸延伸する際の各一軸延伸の間に可塑剤を除去したりしてもよい。
可塑剤除去前の膜に少なくとも１回、少なくとも１方向に延伸し（可塑剤除去前延伸と称す）、更に可塑剤除去後の膜を少なくとも１回、少なくとも１方向に延伸する方法（可塑剤除去後延伸と称す）が実施可能である。少なくとも１回の延伸とは、一段延伸、多段延伸、多数回延伸を行うことを意味する。少なくとも１方向の延伸とは、縦方向１軸延伸、横方向２軸延伸、同時２軸延伸、逐次２軸延伸のことを意味する。Biaxial stretching is performed by heating a gel-like sheet molded article and then using a normal tenter method, roll method, inflation method, rolling method, or a combination of these methods. Any of simultaneous biaxial stretching, sequential stretching or multistage stretching (for example, a combination of simultaneous biaxial stretching and sequential stretching) may be used. Although the order of biaxial stretching and plasticizer removal can be arbitrarily set, it is preferable to remove the plasticizer after biaxially stretching the gel-like sheet molding. However, it is not intended to limit in this order. For example, after removing the plasticizer from the gel-like sheet molding, it is biaxially stretched, or after biaxially stretching the gel-like sheet molding, the plasticizer is removed and further biaxially stretched. Alternatively, the plasticizer may be removed during each uniaxial stretching when the gel sheet is successively biaxially stretched.
Stretching the film before removing the plasticizer at least once in at least one direction (referred to as stretching before removing the plasticizer), and further stretching the film after removing the plasticizer at least once in at least one direction (plasticizer removal) (Referred to as post-stretching). The stretching at least once means that one-stage stretching, multi-stage stretching, or multi-stage stretching is performed. The stretching in at least one direction means longitudinal uniaxial stretching, transverse biaxial stretching, simultaneous biaxial stretching, and sequential biaxial stretching.
ゲル状シート成形物を形成した後、二軸延伸する場合、長手方向（ＭＤ）及び横方向（ＴＤ）における延伸速度は、未延伸シートが延伸される領域において未延伸時の長手方向及び横方向の長さをそれぞれ１とし、１分間当りに伸ばされる長さの割合と定義すると、二軸延伸の長手方向及び横方向の各延伸速度をともに２０倍／分以下する。長手方向又は横方向の延伸速度を２０倍／分超とすると、耐溶融収縮性が悪化したりする。各方向の延伸速度を１５倍／分以下とするのが好ましく、１０倍／分以下とするのがより好ましい。 When biaxial stretching is performed after forming a gel-like sheet molded product, the stretching speed in the longitudinal direction (MD) and the transverse direction (TD) is the longitudinal direction and transverse direction when unstretched in the region where the unstretched sheet is stretched. When the length of each is defined as the ratio of the length stretched per minute, the respective stretching speeds in the longitudinal direction and the transverse direction of biaxial stretching are both 20 times / min or less. When the stretching speed in the longitudinal direction or the transverse direction is more than 20 times / minute, the melt shrinkage resistance is deteriorated. The stretching speed in each direction is preferably 15 times / minute or less, and more preferably 10 times / minute or less.
延伸倍率は、総面積倍率で５０倍以下とする。総面積倍率とはにおける合計延伸倍率と、ＴＤにおける合計延伸倍率との積である。延伸倍率を総面積倍率で５０倍超とすると、耐溶融収縮性が悪化したりする。延伸倍率は総面積倍率で４０倍以下とするのが好ましい。長手方向（ＭＤ）及び横方向（ＴＤ）における１軸方向の倍率で３〜２０倍であることが好ましく、より好ましくは４〜１５倍、さらに好ましくは６〜１０倍である。延伸倍率が４倍以上であれば、十分な延伸配向が与えられるために微多孔膜の強度向上が可能であり、延伸倍率が２０倍以下であれば、過剰な延伸による微多孔膜の構造破壊を防ぐことが可能である。各方向の延伸下限に特に制限はないが、生産性の観点から３倍以上であるのが好ましい。機械的強度向上の観点から、ＭＤ及びＴＤに３倍以上とすることにより総面積倍率で９倍以上とするのが好ましく、ＭＤ及びＴＤに４倍以上とすることにより総面積倍率で１６倍以上とするのがより好ましい。ＭＤにおける合計延伸倍率とＴＤにおける合計延伸倍率の比（ＭＤにおける合計延伸倍率）／（ＴＤにおける合計延伸倍率）は、特に制限されないが、同時二軸延伸、逐次延伸又は段延伸のいずれの場合でも、０．５〜２であるのが好ましく、０．７〜１．３であるのがより好ましく、１であるのが最も好ましい。各方向の延伸速度は２０倍以下である限り、ＭＤとＴＤで互いに異なってもよいが、同じであるのが好ましい。The stretch ratio is 50 times or less in terms of the total area ratio. The total area magnification is the product of the total draw ratio in TD and the total draw ratio in TD. If the draw ratio is more than 50 times in terms of total area, the melt shrinkage resistance may be deteriorated. The stretching ratio is preferably 40 times or less in terms of the total area ratio. The magnification in the uniaxial direction in the longitudinal direction (MD) and the transverse direction (TD) is preferably 3 to 20 times, more preferably 4 to 15 times, still more preferably 6 to 10 times. If the stretching ratio is 4 times or more, sufficient stretching orientation is provided, so that the strength of the microporous film can be improved. If the stretching ratio is 20 times or less, the structure of the microporous film is destroyed due to excessive stretching. It is possible to prevent. Although there is no restriction | limiting in particular in the extending | stretching minimum of each direction, It is preferable that it is 3 times or more from a viewpoint of productivity. From the viewpoint of improving mechanical strength, it is preferable that the total area magnification is 9 times or more by making it 3 times or more in MD and TD, and it is 16 times or more in total area magnification by making it 4 times or more in MD and TD. Is more preferable. The ratio of the total stretch ratio in MD and the total stretch ratio in TD (total stretch ratio in MD) / (total stretch ratio in TD) is not particularly limited, but in any case of simultaneous biaxial stretching, sequential stretching or step stretching. 0.5 to 2 is preferable, 0.7 to 1.3 is more preferable, and 1 is most preferable. As long as the stretching speed in each direction is 20 times or less, MD and TD may be different from each other, but are preferably the same.
所望の物性に応じて、膜厚方向に温度分布を設けて延伸してもよい。膜厚方向に温度分布を設けて延伸することにより一般的に機械的強度に優れた微多孔膜が得られる。洗浄前の延伸ゲル状成形物の少なくとも一面に熱ロールを接触させる処理（熱ロール処理）を施してもよい。加熱ロールに、延伸ゲル状成形物を接触させる。加熱ロールと延伸ゲル状成形物との接触時間は０．５秒〜１分間で良い。ロール表面に加熱オイルを保持した状態で接触させてもよい。加熱ロールとしては、平滑ロール又は吸引機能を有してもよい凹凸ロールのいずれでもよい。 Depending on the desired physical properties, the film may be stretched by providing a temperature distribution in the film thickness direction. By providing a temperature distribution in the film thickness direction and stretching, a microporous film generally excellent in mechanical strength can be obtained. You may perform the process (hot roll process) which makes a hot roll contact at least one surface of the stretched gel-like molding before washing | cleaning. The stretched gel-like molded product is brought into contact with the heating roll. The contact time between the heating roll and the stretched gel-like molded product may be 0.5 seconds to 1 minute. You may make it contact in the state which hold | maintained heating oil on the roll surface. The heating roll may be either a smooth roll or an uneven roll that may have a suction function.
ポリオレフィン混合物樹脂相は成膜用可塑剤と相分離しているので、洗浄溶剤を用いて成膜用可塑剤を除去すると多孔質の膜が得られる。洗浄溶剤及びこれを用いた成膜用可塑剤の除去方法は公知の方法を利用することができる。 Since the polyolefin mixture resin phase is phase-separated from the plasticizer for film formation, a porous film can be obtained by removing the plasticizer for film formation using a cleaning solvent. As a method for removing the cleaning solvent and the plasticizer for film formation using the cleaning solvent, known methods can be used.
［８］溶剤
可塑剤を除くための溶剤は、使用する樹脂に対して貧溶媒であること、かつ可塑剤に対して良溶媒であること、さらには沸点が膜の融点よりも低いことが好ましい。例えば、ｎ−ヘキサンやシクロヘキサン等の炭化水素類、塩化メチレンや１，１−トリクロロエタン等のハロゲン化炭化水素類、エタノールやイソプロパノール等のアルコール類、ジエチルエーテルやテトラヒドロフラン等のエーテル類、アセトンや２−ブタノン等のケトン類、Ｃ６Ｆ１４，Ｃ７Ｆ１６等の鎖状フルオロカーボン、Ｃ４Ｆ９ＯＣＨ３、Ｃ４Ｆ９ＯＣ２Ｈ５等のハイドロフルオロエーテル、Ｃ４Ｆ９ＯＣＦ３、Ｃ４Ｆ９ＯＣ２Ｆ５のパーフルオロエーテル等の使用が可能である。
可塑剤・溶剤の除去時に膜の収縮を防ぐために、膜を少なくとも１方向に拘束しながら、溶剤に浸漬し、可塑剤除去後に溶剤を膜の融点以下で加熱乾燥法、風乾法等により乾燥除去する方法が好適に利用可能である。[8] The solvent for removing the solvent plasticizer is preferably a poor solvent for the resin used, a good solvent for the plasticizer, and a boiling point lower than the melting point of the film. . For example, hydrocarbons such as n-hexane and cyclohexane, halogenated hydrocarbons such as methylene chloride and 1,1-trichloroethane, alcohols such as ethanol and isopropanol, ethers such as diethyl ether and tetrahydrofuran, acetone and 2- Ketones such as butanone, chain fluorocarbons such as C 6 F 14 and C 7 F 16, hydrofluoroethers such as C 4 F 9 OCH 3 and C 4 F 9 OC 2 H 5 , C 4 F 9 OCF 3 and C 4 F 9 OC 2 F 5 perfluoroether or the like can be used.
In order to prevent shrinkage of the film during removal of the plasticizer / solvent, the film is immersed in a solvent while constraining the film in at least one direction, and after removal of the plasticizer, the solvent is dried and removed by a heat drying method, an air drying method or the like below the melting point of the film. This method can be suitably used.
延伸工程後または可塑剤除去後において少なくとも１回、熱処理（熱延伸処理及び／あるいは熱固定処理及び／あるいは熱収縮処理）を行うとよい。熱処理温度は、熱処理による強度変化、透気度変化等に考慮して行う。Heat treatment (heat drawing treatment and / or heat setting treatment and / or heat shrinking treatment) may be performed at least once after the drawing step or after removal of the plasticizer. The heat treatment temperature is determined in consideration of a change in strength, a change in air permeability and the like due to the heat treatment.
熱延伸処理工程において気孔率等の物性を調整するために、通常用いられるテンター方式、ロール方式又は圧延方式により行い、少なくとも一回、少なくとも一軸方向に、一方向における延伸倍率が１．０１〜２．０倍の延伸倍率で行うのが好ましく、１．０２〜１．５倍の延伸倍率で行うのがより好ましい。
また、熱固定処理は、テンター方式、ロール方式又は圧延方式により行い、耐熱性ポリオレフィン微多孔膜中のポリオレフィン樹脂の結晶化を安定させる。
熱収縮処理は、テンター方式、ロール方式若しくは圧延方式により行うか、又はベルトコンベア若しくはフローティングロールを用いて行ってもよい。熱収縮処理は、少なくとも一方向に５０％以下の範囲で行うのが好ましく、３０％以下、更に好ましくは２０％以下の範囲で行う。In order to adjust the physical properties such as porosity in the hot stretching process, the tenter method, roll method or rolling method that is usually used is used, and the draw ratio in one direction is at least once and at least uniaxial direction is 1.01-2. It is preferable to carry out at a draw ratio of 0.0, more preferably at a draw ratio of 1.02 to 1.5.
The heat setting treatment is performed by a tenter method, a roll method, or a rolling method to stabilize the crystallization of the polyolefin resin in the heat-resistant polyolefin microporous film.
The heat shrinking treatment may be performed by a tenter method, a roll method or a rolling method, or may be performed using a belt conveyor or a floating roll. The heat shrink treatment is preferably performed in a range of 50% or less in at least one direction, 30% or less, and more preferably 20% or less.
上述の熱延伸処理、熱固定処理及び熱収縮処理を多数組み合せて行ってもよい。熱ロール処理は洗浄前の延伸ゲル状成形物の少なくとも一面に熱ロールを接触させる処理（熱ロール処理）を施してもよい。ポリオレフィン樹脂混合物の結晶温度＋１０℃以上〜ポリオレフィン樹脂混合物の平均融点未満に温調した加熱ロールに、延伸ゲル状成形物を接触させる。
加熱ロールと延伸ゲル状成形物との接触時間は０．５秒〜１分間が好ましい。ロール表面に加熱オイルを保持した状態で接触させてもよい。加熱ロールとしては、平滑ロール又は吸引機能を有してもよい凹凸ロールのいずれでもよい。
特に熱延伸処理後に熱収縮処理を行うと、低収縮率で高強度の微多孔膜が得られるため好ましいYou may perform combining the above-mentioned heat | fever extending process, heat setting process, and heat shrink process many. In the hot roll treatment, a treatment (hot roll treatment) in which a hot roll is brought into contact with at least one surface of the stretched gel-like molded product before washing may be performed. The stretched gel-like molded product is brought into contact with a heating roll whose temperature is adjusted to a crystal temperature of the polyolefin resin mixture + 10 ° C. or higher and lower than the average melting point of the polyolefin resin mixture.
The contact time between the heating roll and the stretched gel-like molded product is preferably 0.5 seconds to 1 minute. You may make it contact in the state which hold | maintained heating oil on the roll surface. The heating roll may be either a smooth roll or an uneven roll that may have a suction function.
In particular, it is preferable to perform a heat shrink treatment after the heat stretching treatment because a microporous film having a low shrinkage rate and a high strength can be obtained.
本発明の好ましい実施態様による耐熱性ポリオレフィン微多孔膜の膜厚は５〜１００μｍであり、好ましくは６〜４０μｍ、より好ましくは１０〜２５μｍである。膜厚は、５μｍ以上であれば微多孔膜として十分な強度を有し、１００μｍ以下であれば十分な透過性を有し、高い電解液含浸性を有する膜となる。
なお微多孔膜の厚さは用途に応じて適宜選択できるが、例えばリチウムイオン二次電池用セパレータとして使用する場合は７〜２４μｍが好ましく、１０−１８μｍがより好ましい。
膜厚、ＪＩＳ規格Ｋ７１３０に準じて測定する。The film thickness of the heat-resistant polyolefin microporous membrane according to a preferred embodiment of the present invention is 5 to 100 μm, preferably 6 to 40 μm, more preferably 10 to 25 μm. If the film thickness is 5 μm or more, the film has sufficient strength as a microporous film, and if it is 100 μm or less, the film has sufficient permeability and has a high electrolyte solution impregnation property.
In addition, although the thickness of a microporous film can be suitably selected according to a use, when using as a separator for lithium ion secondary batteries, for example, 7-24 micrometers is preferable and 10-18 micrometers is more preferable.
The film thickness is measured according to JIS standard K7130.
微小孔構造領域と粗大孔構造領域の分布は特に制限されない。通常は、微多孔膜のＭＤ方向及びＴＤ方向のいずれの断面においても、微小孔構造領域及び粗大孔構造領域が不規則に入り組んでおり、個々の領域の大きさも不規則である。このような構造は、例えば透過型電子顕微鏡（ＴＥＭ）等により観察することができ、原子間力顕微鏡（ＡＦＭ）により最大高低差として測定することができる。The distribution of the micropore structure region and the coarse pore structure region is not particularly limited. Usually, in any cross section in the MD direction and TD direction of the microporous film, the micropore structure region and the coarse pore structure region are irregularly arranged, and the sizes of the individual regions are also irregular. Such a structure can be observed, for example, with a transmission electron microscope (TEM) or the like, and can be measured as a maximum height difference with an atomic force microscope (AFM).
上記のような粗大孔構造による比較的大きな空間と比較的大きな表面粗さとを有するので、透気度及び電解液吸収性に優れており、しかも加圧された場合の透気度変化が小さい。そのためリチウムイオン二次電池用セパレータとして用いた場合に、各々優れた電池生産性と電池サイクル特性を実現することができる。Since it has a relatively large space and a relatively large surface roughness due to the coarse pore structure as described above, it has excellent air permeability and electrolyte absorption, and changes in air permeability when pressurized are small. Therefore, when used as a separator for a lithium ion secondary battery, excellent battery productivity and battery cycle characteristics can be realized.
本発明の好ましい実施態様による耐熱性ポリオレフィン微多孔膜は、次の物性を有する。
（１）透気度（ガーレー値）は２０〜３５０秒／１００ｍｌである。透気度がこの範囲であると、微多孔膜を電池セパレータとして用いた場合に電池容量が大きく、電池のサイクル特性も良好である。透気度が２０秒／１００ｍｌ／２０μｍ未満では電池内部の温度上昇時にシャットダウンが十分に行われない。透気度は、ＪＩＳ Ｐ８１１７に準拠のガーレー式透気度計を使用して測定する。
（２）気孔率は３５〜７５％であり、好ましくは４０〜５５％である。気孔率が３５％以上であれば十分な透気度を有し、６０％以下であれば十分な機械的強度を有し、電池セパレータとして用いた場合電極が短絡する危険性が小さい。気孔率は重量法により測定する。試料を５．０ｃｍ角の正方形に切り出して体積（ｃｍ３）、重量（ｇ）を測定する。使用した樹脂密度（ｇ／ｃｍ３）をＡＳＴＭ Ｄ１５０５に準拠して測定する。次式により計算して求める。The heat-resistant polyolefin microporous membrane according to a preferred embodiment of the present invention has the following physical properties.
(1) Air permeability (Gurley value) is 20 to 350 seconds / 100 ml. When the air permeability is within this range, the battery capacity is large when the microporous membrane is used as a battery separator, and the cycle characteristics of the battery are also good. When the air permeability is less than 20 seconds / 100 ml / 20 μm, shutdown is not sufficiently performed when the temperature inside the battery rises. The air permeability is measured using a Gurley type air permeability meter according to JIS P8117.
(2) The porosity is 35 to 75%, preferably 40 to 55%. If the porosity is 35% or more, it has sufficient air permeability, and if it is 60% or less, it has sufficient mechanical strength. When used as a battery separator, the risk of short-circuiting the electrodes is small. The porosity is measured by a gravimetric method. A sample is cut into a square of 5.0 cm square, and the volume (cm 3) and weight (g) are measured. The resin density (g / cm3) used is measured according to ASTM D1505. Calculate by the following formula.
本発明の微多孔膜の最大孔径は、好ましくは０．１〜５μｍ、より好ましくは０．３〜３μｍ、さらに好ましくは０．３〜１．５μｍである。最大孔径が、０．１μ以上であればセパレータとして必要な透過性を有し、５μｍ以下であれば電極脱離成分による短絡を防ぐことが可能である。当該耐熱性ポリオレフィン微多孔膜の表面を走査型電子顕微鏡（ＳＥＭ）で観察する。任意に孔を２０点選び、これら孔の孔径を求め平均することで孔径を算出する。
（４）突刺し強度は、針先端の曲率半径０．５ｍｍ、突き刺し速度２ｍｍ／ｓｅｃで突刺し試験を行い、最大突刺荷重ｇから突刺し強度をＮで表示する。
２Ｎ以上であることが望ましい。突刺し強度が２Ｎ未満では、微多孔膜を電池用セパレータとして電池に組み込んだ場合に、電極の短絡が発生する恐れがある。突刺強度は３Ｎ以上、さらに好ましくは５以上である。電極からの脱離成分によるショートが発生せず、セパレータとして十分な強度を有する。
（５）引張破断強度は、幅１０ｍｍの短冊状試験片を用いてＡＳＴＭ Ｄ８８２により測定する。引張破断強度はＭＤ方向及びＴＤ方向のいずれにおいても４０ＭＰａ以上であることが破膜しない上で好ましい。
（６）引張破断伸度は、幅１０ｍｍの短冊状試験片を用いてＡＳＴＭ Ｄ８８２により測定する。引張破断伸度はＭＤ方向及びＴＤ方向のいずれにおいても２０％以上であることが破膜の心配がなく好ましい。
（７）１３０℃の温度で１時間暴露後の熱収縮率が５０ｍｍ ｘ ５０ｍｍに切り出した試料にＭＤ方向及びＴＤ方向を印する。１３０℃に保持した熱風乾燥機内の微粉珪藻土上に１時間入れる。１時間目に、室温に冷却して縦方向、横方向の寸法変化を測定し、最初の試料片距離に対する百分率で表す熱収縮率を求める。なお、縦（ＭＤ）方向とは、微多孔膜の製造時における押出方向とし、横（ＴＤ）方向とは、微多孔膜の製造時における押出方向に直交する方向とする。熱収縮率はＭＤ方向及びＴＤ方向ともに２５％以下であることが良い。好ましくは２０％、更に好ましくはＭＤ方向及びＴＤ方向ともに１５％以下である。熱収縮率は、当該微多孔膜を１３０℃で１時間暴露したときのＭＤ方向及びＴＤ方向の収縮率をそれぞれ３回ずつ測定し、平均値を算出することにより求める。
熱収縮率が２５％を超えると、当該微多孔膜をリチウムイオン二次電池用セパレータとして用いた場合、異常発熱時にセパレータ端部が収縮し、電極の短絡が発生する可能性が高くなる。
（８）高平滑面を有する一対のステンレス板の間に膜を挟み、これをプレス機により、２．２ＭＰａ（２２ｋｇｆ／ｃｍ２）の圧力下、９０℃で５分間加熱圧縮した後の膜厚変化率は、圧縮前の膜厚を１００％として２０％以下であることが望ましい。膜厚変化率が２０％以下であると、当該微多孔膜をリチウムイオン二次電池セパレータとして用いた場合に、電池容量が大きく、電池のサイクル特性も良好である。膜厚は接触厚さ計（株式会社ミツトヨ製）により測定する。上記条件で加熱圧縮した後の到達透気度（ガーレー値）は６００秒／１００ｍｌ／２０μｍ以下である。到達透気度が５００秒／１００ｍｌ／２０μｍ以下であると、加圧された場合でも透気度変化及び膜厚変化が小さく、リチウムイオン二次電池セパレータとして用いた場合に、電池容量が大きく、透過性、機械的特性及び耐熱収縮性にも優れている。
（９）表面粗さは原子間力顕微鏡（ＡＦＭ）により測定する。最大高低差で好ましい範囲は、２５０ｎｍ以上６００ｎｍである。更に好ましくは３００ｎｍから６００ｎｍの範囲である。２５０ｎｍ未満では、電解液の濡れも悪くなり、セパレータ巻き取りロールからのセパレータ離脱しにくくなる。６００ｎｍを超えるとセパレータの機械的強度が低下して好ましくない。電池用セパレータとして用いた場合の電解液との接触面積が大きく、電解液注入性に優れている。
（１０）耐メルトダウン特性の評価は、４５ｍｍ ｘ ４５ｍｍの寸法に切り出したセパレータ試料に電解液（１Ｍ ＬｉＢＦ４／ポリプロピレンカーボネート（ＰＣ）：ガンマーブチロラクトン（γ−ＢＬ）（１／１容積比））を含浸させ、２０ｍｍ ｘ ２０ｍｍのステンレス板に挟み、これを電池評価用電池容器に封入する。この電池容器を５℃／分昇温速度で加熱する電気炉内に置き、スクリュー電池容器の温度とインピーダンス値を測定する。インピーダンス値は交流法にて振幅１０ｍＶ、周波数１ｋＨｚの交流を１０ｍＡの範囲内で印加し、温度に対しインピーダンス値をプロットし、インピーダンス値が上昇していく過程で１０００ｏｈｍ以上になる温度をシャットダウン温度とする。更に電池容器を５℃／分昇温速度で加熱を続けて、電池容器の温度とインピーダンス値を測定し、インピーダンス値が再度３００ｏｈｍ未満なる時の温度をメルトダウン温度とする。耐メルトダウン特性の評価は、１８５℃に到達しても、１分後でも破膜せず高インピーダンス値を保持している時を１８５℃＜と表示し、優れた耐メルトダウン特性を有することを意味する。
（１１）電池評価は、当該耐熱性ポリオレフィン微多孔膜からなるセパレータは、これを用いる電池の種類に特に制限はないが、特にリチウムイオン二次電池用途に好適である。本発明の微多孔膜からなるセパレータを用いたリチウムイオン二次電池には、公知の電極及び電解液を使用すればよい。また本発明の微多孔膜からなるセパレータを使用するリチウムイオン二次電池の構造も公知のものでよい。
例えば、正極活物質としてコバルト酸リチウム（ＬｉＣｏＯ２；１０ミクロン）粉末９２重量部とアセチレンブラック（電気化学工業社製）粉末２重量部、微粉黒鉛（日本黒鉛社製）２重量部、ポリフッ化ビニリデン（クレハ化学工業株式会社製）の乾燥重量が４重量部となるように６重量％のポリフッ化ビニリデンのＮ−メチルピロリドン溶液を用い、正極剤ペーストを作製する。得られたペーストを厚さ１５μｍのアルミ箔上へ塗工し、乾燥後プ負極活物質の黒鉛化カーボン（日立化成製）粉末９７とＣＭＣ（カルボキシメチルセルロース）（第一工業製薬社製）１部とカルボキシ変性ブタジエン系ラテックス（日本ゼオン社製）の固形分２部とからなる水溶液を用い、負極剤ペーストを作製する。得られたペーストを厚さ１２μｍの銅箔上へ塗工し、乾燥後プレスして負極を作製する。
上記正極を２０ｍｍ×５０ｍｍのサイズに切り出しタブを付けた。また上記負極は２２ｍｍ×５２ｍｍのサイズに切り出しタブを付けた。セパレータは２６ｍｍ×５６ｍｍのサイズに切り出した。これら正極／セパレータ／負極と接合し、電解液を注入してアルミラミネートフィルム内に封入することでアルミラミネート外装セルを作製した。ここで電解液には１ＭでＬｉＰＦ６をエチレンカーボネート／エチルメチルカーボネート（３／７重量比）に溶解したものを用いる。
該セルにおいて０．２Ｃと２Ｃにおける放電電気量を測定し、（２Ｃにおける放電電気量）／（０．２Ｃにおける放電電気量）×１００を電池性能とした。９５％以上を良好な電池性能とする。ここで、充電条件は０．２Ｃ ４．２Ｖ ＣＣ／ＣＶ８時間とし、放電条件は２．７５ＶカットオフのＣＣ放電とする。The maximum pore size of the microporous membrane of the present invention is preferably 0.1 to 5 μm, more preferably 0.3 to 3 μm, and still more preferably 0.3 to 1.5 μm. If the maximum pore diameter is 0.1 μm or more, the required permeability as a separator is obtained, and if it is 5 μm or less, it is possible to prevent a short circuit due to an electrode desorption component. The surface of the heat-resistant polyolefin microporous film is observed with a scanning electron microscope (SEM). Arbitrarily 20 holes are selected, and the diameters of these holes are calculated and averaged.
(4) As for the piercing strength, a piercing test is performed with a radius of curvature of the needle tip of 0.5 mm and a piercing speed of 2 mm / sec, and the piercing strength is indicated by N from the maximum piercing load g.
It is desirable that it is 2N or more. If the piercing strength is less than 2N, there is a possibility that an electrode short circuit may occur when the microporous membrane is incorporated in a battery as a battery separator. The puncture strength is 3N or more, more preferably 5 or more. A short circuit due to a desorbed component from the electrode does not occur, and the separator has sufficient strength.
(5) The tensile strength at break is measured by ASTM D882 using a strip-shaped test piece having a width of 10 mm. The tensile breaking strength is preferably 40 MPa or more in both the MD direction and the TD direction in order not to break the film.
(6) The tensile breaking elongation is measured by ASTM D882 using a strip-shaped test piece having a width of 10 mm. The tensile elongation at break is preferably 20% or more in both the MD direction and the TD direction because there is no fear of film breakage.
(7) The MD direction and the TD direction are marked on a sample cut out at a temperature of 130 ° C. and having a thermal shrinkage rate of 50 mm × 50 mm after 1 hour exposure. Place on fine diatomaceous earth in a hot air dryer maintained at 130 ° C. for 1 hour. At the first hour, the sample is cooled to room temperature and the dimensional changes in the vertical and horizontal directions are measured, and the thermal shrinkage expressed as a percentage of the initial sample piece distance is determined. The longitudinal (MD) direction is the extrusion direction during the production of the microporous membrane, and the transverse (TD) direction is the direction orthogonal to the extrusion direction during the production of the microporous membrane. The thermal shrinkage rate is preferably 25% or less in both the MD direction and the TD direction. It is preferably 20%, more preferably 15% or less in both the MD direction and the TD direction. The thermal shrinkage rate is obtained by measuring the shrinkage rate in the MD direction and the TD direction three times each when the microporous membrane is exposed at 130 ° C. for 1 hour, and calculating an average value.
When the thermal shrinkage rate exceeds 25%, when the microporous membrane is used as a separator for a lithium ion secondary battery, the end of the separator contracts during abnormal heat generation, and the possibility of short-circuiting of the electrodes increases.
(8) Film thickness change rate after a film is sandwiched between a pair of stainless steel plates having a high smooth surface and heated and compressed at 90 ° C. for 5 minutes under a pressure of 2.2 MPa (22 kgf / cm 2 ) using a press machine. Is preferably 20% or less, assuming that the film thickness before compression is 100%. When the film thickness change rate is 20% or less, when the microporous membrane is used as a lithium ion secondary battery separator, the battery capacity is large and the cycle characteristics of the battery are also good. The film thickness is measured with a contact thickness meter (manufactured by Mitutoyo Corporation). The ultimate air permeability (Gurley value) after heat compression under the above conditions is 600 seconds / 100 ml / 20 μm or less. When the ultimate air permeability is 500 seconds / 100 ml / 20 μm or less, the air permeability change and the film thickness change are small even when pressurized, and the battery capacity is large when used as a lithium ion secondary battery separator, Excellent permeability, mechanical properties and heat shrinkage.
(9) The surface roughness is measured with an atomic force microscope (AFM). A preferable range of the maximum height difference is 250 nm or more and 600 nm. More preferably, it is the range of 300 nm to 600 nm. When the thickness is less than 250 nm, the wetness of the electrolytic solution is also deteriorated, and the separator is hardly detached from the separator winding roll. If it exceeds 600 nm, the mechanical strength of the separator is lowered, which is not preferable. When used as a battery separator, the contact area with the electrolyte is large, and the electrolyte injection property is excellent.
(10) Melt-down resistance was evaluated by applying an electrolyte solution (1M LiBF 4 / polypropylene carbonate (PC): gamma-butyrolactone (γ-BL) (1/1 volume ratio)) to a separator sample cut to a size of 45 mm × 45 mm. Is impregnated and sandwiched between 20 mm × 20 mm stainless steel plates and sealed in a battery container for battery evaluation. The battery container is placed in an electric furnace heated at a rate of 5 ° C./min, and the temperature and impedance value of the screw battery container are measured. For the impedance value, an alternating current method with an amplitude of 10 mV and a frequency of 1 kHz is applied within a range of 10 mA, the impedance value is plotted against the temperature, and the temperature that becomes 1000 ohms or higher in the process of increasing the impedance value is the shutdown temperature. To do. Further, the battery container is continuously heated at a temperature rising rate of 5 ° C./minute, the temperature of the battery container and the impedance value are measured, and the temperature when the impedance value becomes less than 300 ohms again is defined as the meltdown temperature. The evaluation of the meltdown resistance indicates that when it reaches 185 ° C, it does not break even after 1 minute and maintains a high impedance value as 185 ° C <and has excellent meltdown resistance Means.
(11) In battery evaluation, the separator made of the heat-resistant polyolefin microporous membrane is not particularly limited in the type of battery using the separator, but is particularly suitable for lithium ion secondary battery applications. For the lithium ion secondary battery using the separator made of the microporous membrane of the present invention, a known electrode and electrolyte may be used. The structure of the lithium ion secondary battery using the separator made of the microporous membrane of the present invention may also be a known one.
For example, as a positive electrode active material, 92 parts by weight of lithium cobalt oxide (LiCoO 2 ; 10 micron) powder, 2 parts by weight of acetylene black (manufactured by Denki Kagaku Kogyo), 2 parts by weight of fine graphite (manufactured by Nippon Graphite), polyvinylidene fluoride A positive electrode paste is prepared using a 6 wt% polyvinylidene fluoride N-methylpyrrolidone solution so that the dry weight of Kureha Chemical Industry Co., Ltd. is 4 parts by weight. The obtained paste was coated on an aluminum foil having a thickness of 15 μm, and after drying, graphitized carbon (manufactured by Hitachi Chemical) powder 97 and CMC (carboxymethylcellulose) (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) as a negative electrode active material A negative electrode agent paste is prepared using an aqueous solution comprising 2 parts of a solid content of carboxy-modified butadiene latex (manufactured by Zeon Corporation). The obtained paste is applied onto a copper foil having a thickness of 12 μm, dried and pressed to produce a negative electrode.
The positive electrode was cut into a size of 20 mm × 50 mm and attached with a tab. The negative electrode was cut into a size of 22 mm × 52 mm and attached with a tab. The separator was cut into a size of 26 mm × 56 mm. These positive electrode / separator / negative electrode were joined, an electrolytic solution was injected, and sealed in an aluminum laminate film to produce an aluminum laminate exterior cell. Here, a 1M solution of LiPF 6 dissolved in ethylene carbonate / ethyl methyl carbonate (3/7 weight ratio) is used as the electrolytic solution.
The amount of electricity discharged at 0.2C and 2C in the cell was measured, and the amount of electricity discharged at 2C / (amount of electricity discharged at 0.2C) × 100 was defined as the battery performance. 95% or more is regarded as good battery performance. Here, the charging condition is 0.2 C 4.2 V CC / CV 8 hours, and the discharging condition is CC discharge with a 2.75 V cutoff.
このように、本発明の耐熱性ポリオレフィン微多孔膜は、電池用セパレータ、コンデンサー用セパレータ、フィルター等として好適に使用できる。特にリチウムイオン二次電池用セパレータとして最適である。本発明の耐熱性ポリオレフィン微多孔膜の優れた耐メルトダウン特性を生かしてシャットダウン温度が１２５−１４２℃の範囲の中のいずれかの温度を有するポリエチレン系微多孔膜との貼り合せを施し、電池用多層セパレータとして使用したり、電池組み立て時に前述のポリエチレン系微多孔膜と併用することも可能である。Thus, the heat-resistant polyolefin microporous membrane of the present invention can be suitably used as a battery separator, a capacitor separator, a filter, and the like. In particular, it is optimal as a separator for lithium ion secondary batteries. The battery is bonded to a polyethylene microporous membrane having a shutdown temperature in the range of 125 to 142 ° C. by taking advantage of the excellent meltdown resistance of the heat resistant polyolefin microporous membrane of the present invention. It can be used as a multilayer separator for a battery, or can be used in combination with the above-mentioned polyethylene microporous membrane at the time of battery assembly.
本発明を以下の実施例によりさらに詳細に説明するが、本発明はこれらの例に限定されるものではない。 The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.
粘度平均分子量が１１５万の超高分子量ポリエチレン３．３重量％、粘度平均分子量が３９５万の超高分子量ポリエチレン３．３重量％、粘度平均分子量が５８０万の超高分子量ポリエチレン１３．２重量％、粘度平均分子量が６３０万の超高分子量ポリエチレン１６．５重量％、粘度平均分子量が３３．４万の高密度ポリエチレン２７．７重量％、粘度平均分子量が１８．５万の中密度ポリエチレン１３．７重量％、融点ピーク２３２℃を持つ４−メチル−１−ペンテン−１−デセン−１共重合体（ＭＦＲ ２６０℃ ５ｋｇ荷重 ９ｇ／１０分）１３．０重量％と融点ピーク２２８℃を持つ４−メチル−１−ペンテン−１−ヘキサデセン−１−オクタデセン共重合体（ＭＦＲ ２６０℃ ５ｋｇ荷重 ２５ｇ／１０分）３．３重量％とポリオレフィン系エラストマー樹脂として三井化学（株）社製のノティオ［グレード名ＰＮ３５６０］２．５重量％、タフマー［グレード名ＤＦ８１０］１．９重量％、タフマー［グレード名ＢＬ３４５０］０．８重量％、低分子量エチレン・ブテン共重合物として三井化学（株）社製のエクセレックス［グレード名４８０７０Ｂ］０．８重量％とからなるポリオレフィン樹脂混合物１００．０重量部に対して酸化防止剤としてテトラキス［メチレン−３−（３，５−ジターシャリーブチル−４−ヒドロキシフェニル）−プロピオネート］メタン２．５重量部と３，９−ビス（２，６−ジターシャリーブチル−４−メチルフェノキシ）−２，４，８，１０−テトラオキサ−３，９−ジホスファピ［５，５］ウンデカンロニルヒドロキシフェニル）−プロピオネート］メタン０．２５重量部とを、ドライブレンドし、計算による平均融点が１４９．５℃のポリオレフィン樹脂混合物を調製した。当該樹脂混合物３７重量部を二軸押出機（シリンダ径：６９ｍｍ、スクリュの長さ（Ｌ）と直径（Ｄ）の比Ｌ／Ｄ：５２．５、強混練タイプスクリュ使用）に投入し、この二軸押出機のサイドフィーダーから６３重量部の流動パラフィン［６８ｃｓｔ（４０℃）］９０重量％とポリオキシエチレンステアリルエーテル（ＨＬＢ２）７重量％、ポリオキシエチレンイソステアリルエーテル（ＨＬＢ２）３重量％からなる可塑剤を加熱しながら供給し、２４０−２１０℃及び２００ｒｐｍの条件でポリオレフィン・可塑剤混合溶融物を調製する。これを二軸押出機の先端に設置されたギアーポンプを介してＴダイから押し出し、冷却ロールで引き取りながら、ゲル状シート成形物を形成する。得らるゲル状シート成形物に対して、テンター延伸機を用いて、二軸延伸を施す。次いでステンレス製の枠板［サイズ：２０ｃｍ×３０ｃｍ、（以下の実施例および比較例は同じ）］に固定し、室温の塩化メチレンの洗浄槽中に浸漬し、３分間揺動させながら洗浄する。枠ごと取り出し垂直において塩化メチレンを取り除き、再度室温の塩化メチレンの洗浄槽中に浸漬し、３分間揺動させながら洗浄する。枠ごと取り出し垂直において塩化メチレンを取り除き、室温の塩化メチレンの洗浄槽中に浸漬し、３分間揺動させながら三度目の洗浄をする。洗浄し・徐液した膜を室温で風乾する。乾燥した延伸膜を加熱しながら、テンター延伸機により１１０℃−８０℃でＴＤ方向、ＭＤ方向に延伸（第二の延伸）し、テンター内で３０秒間保持しながら熱固定処理し、熱収縮処理を施して耐熱性ポリオレフィン微多孔膜を得る。その特性を表１に示す。
耐メルトダウン特性の評価試験結果、シャットダウン温度は、１３０℃付近で急激なインピーダンス値の上昇を示し５０００オーム以上を示し、１８５℃に到達してもインピーダンス値がの低下はなく、１８５℃＜であった。3.3% by weight of ultra high molecular weight polyethylene having a viscosity average molecular weight of 1.15 million, 3.3% by weight of ultra high molecular weight polyethylene having a viscosity average molecular weight of 39.95 million, and 13.2% by weight of ultra high molecular weight polyethylene having a viscosity average molecular weight of 5.8 million 16.5% by weight of ultrahigh molecular weight polyethylene having a viscosity average molecular weight of 63,000,000, 27.7% by weight of high density polyethylene having a viscosity average molecular weight of 334,000, and medium density polyethylene having a viscosity average molecular weight of 185,000. 4-methyl-1-pentene-1-decene-1 copolymer (MFR 260 ° C., 5 kg load, 9 g / 10 min) having 7% by weight and a melting point peak of 232 ° C. and 4 having a melting point peak of 228 ° C. 4 -Methyl-1-pentene-1-hexadecene-1-octadecene copolymer (MFR 260 ° C., 5 kg load, 25 g / 10 minutes) 3.3 wt% and polyolefin As rubber-based elastomeric resin, Mitsui Chemicals, Inc., Notio [grade name PN3560] 2.5 wt%, Tuffmer [grade name DF810] 1.9 wt%, Tuffmer [grade name BL3450] 0.8 wt%, low As an antioxidant, tetrakis [methylene- (methylene-) is used as a molecular weight ethylene / butene copolymer with 100.0 parts by weight of polyolefin resin mixture consisting of 0.8% by weight of EXELEX [grade name 48070B] manufactured by Mitsui Chemicals, Inc. 3- (3,5-ditertiarybutyl-4-hydroxyphenyl) -propionate] methane 2.5 parts by weight and 3,9-bis (2,6-ditertiarybutyl-4-methylphenoxy) -2,4 8,10-tetraoxa-3,9-diphosphapi [5,5] undecanlonylhydroxyphenyl) -pro And onato] methane 0.25 part by weight, were dry-blended, the average melting point by calculation to prepare a polyolefin resin mixture 149.5 ° C.. 37 parts by weight of the resin mixture was charged into a twin-screw extruder (cylinder diameter: 69 mm, screw length (L) to diameter (D) ratio L / D: 52.5, using a strong kneading type screw). From 63 parts by weight of liquid paraffin [68 cst (40 ° C.)], 7% by weight of polyoxyethylene stearyl ether (HLB2), 3% by weight of polyoxyethylene isostearyl ether (HLB2) from the side feeder of the twin screw extruder The resulting plasticizer is supplied while heating, and a polyolefin / plasticizer mixed melt is prepared under the conditions of 240 to 210 ° C. and 200 rpm. This is extruded from a T-die through a gear pump installed at the tip of a twin-screw extruder, and is taken out with a cooling roll to form a gel-like sheet molding. The resulting gel-like sheet molding is biaxially stretched using a tenter stretching machine. Next, it is fixed to a stainless steel frame plate [size: 20 cm × 30 cm (the following examples and comparative examples are the same)], immersed in a methylene chloride washing bath at room temperature, and washed with rocking for 3 minutes. Take out the entire frame, remove methylene chloride in the vertical direction, immerse it again in a methylene chloride washing bath at room temperature, and wash it while shaking for 3 minutes. Take out the entire frame, remove methylene chloride in the vertical direction, immerse it in a methylene chloride washing bath at room temperature, and wash it for the third time while shaking for 3 minutes. Air-dry the washed and slow-dried membrane at room temperature. While heating the dried stretched film, it is stretched in the TD direction and MD direction (second stretching) at 110 ° C. to 80 ° C. with a tenter stretching machine, and heat-fixed while being held in the tenter for 30 seconds, and heat shrinkage treatment To obtain a heat-resistant polyolefin microporous membrane. The characteristics are shown in Table 1.
As a result of the evaluation test of the meltdown resistance, the shutdown temperature showed a sudden increase in impedance value at around 130 ° C., showed 5000 ohms or more, and even when it reached 185 ° C., the impedance value did not decrease, and 185 ° C. < there were.
粘度平均分子量が１１５万の超高分子量ポリエチレン３．３重量％、粘度平均分子量が２００万の超高分子量ポリエチレン３．３重量％、粘度平均分子量が３１０万の超高分子量ポリエチレン４．０重量％、粘度平均分子量が３９５万の超高分子量ポリエチレン６．７重量％、粘度平均分子量が５８０万の超高分子量ポリエチレン１６．９重量％、粘度平均分子量が６３０万の超高分子量ポリエチレン４．０重量％、粘度平均分子量が３３．４万の高密度ポリエチレン１９．５重量％、粘度平均分子量が１８．５万の中密度ポリエチレン１９．５重量％、融点ピーク２３２℃を持つ４−メチル−１ペンテン−１−デセン−１共重合体（ＭＦＲ ２６０℃ ５ｋｇ荷重 ９ｇ／１０分）１２．４重量％と融点ピーク２２８℃を持つ４−メチル−１−ペンテン−１−ヘキサデセン−１−オクタデセン共重合体（ＭＦＲ ２６０℃ ５ｋｇ荷重 ２５ｇ／１０分）６．２重量％とポリオレフィン系エラストマー樹脂として三井化学（株）社製のノティオ［グレード名ＰＮ３５６０］２．５重量％、タフマー［グレード名ＤＦ８１０］０．９重量％、低分子量エチレン・ブテン共重合物として三井化学（株）社製のエクセレックス［グレード名４８０７０Ｂ］０．８重量％とからなるポリオレフィン樹脂混合物１００．０重量部に対して酸化防止剤としてテトラキス［メチレン−３−（３，５−ジターシャリーブチル−４−ヒドロキシフェニル）−プロピオネート］メタン２．５重量部と３，９−ビス（２，６−ジターシャリーブチル−４−メチルフェノキシ）−２，４，８，１０−テトラオキサ−３，９−ジホスファピ［５，５］ウンデカンロニルヒドロキシフェニル）−プロピオネート］メタン０．２５重量部とを、ドライブレンドし、計算による平均融点が１５１℃のポリオレフィン樹脂混合物を調製した。当該樹脂混合物３２重量部を二軸押出機（シリンダ径：６９ｍｍ、スクリュの長さ（Ｌ）と直径（Ｄ）の比Ｌ／Ｄ：５２．５、強混練タイプスクリュ使用）に投入し、この二軸押出機のサイドフィーダーから６８重量部の流動パラフィン［６８ｃｓｔ（４０℃）］９０重量％とポリオキシエチレンステアリルエーテル（ＨＬＢ２）７重量％、ポリオキシエチレンイソステアリルエーテル（ＨＬＢ２）３重量％からなる可塑剤を加熱しながら供給し、２４０−２１０℃及び２００ｒｐｍの条件でポリオレフィン・可塑剤混合溶融物を調製する。これを二軸押出機の先端に設置されたギアーポンプを介してＴダイから押し出し、冷却ロールで引き取りながら、ゲル状シート成形物を形成する。得らるゲル状シート成形物に対して、テンター延伸機を用いて、二軸延伸を施す。次いでステンレス製の枠板［サイズ：２０ｃｍ×３０ｃｍ、（以下の実施例および比較例は同じ）］に固定し、室温の塩化メチレンの洗浄槽中に浸漬し、３分間揺動させながら洗浄する。枠ごと取り出し垂直において塩化メチレンを取り除き、再度室温の塩化メチレンの洗浄槽中に浸漬し、３分間揺動させながら洗浄する。枠ごと取り出し垂直において塩化メチレンを取り除き、室温の塩化メチレンの洗浄槽中に浸漬し、３分間揺動させながら三度目の洗浄をする。洗浄し・徐液した膜を室温で風乾する。乾燥した延伸膜を加熱しながら、テンター延伸機により１１０℃−８０℃でＴＤ方向、ＭＤ方向に延伸（第二の延伸）し、テンター内で３０秒間保持しながら熱固定処理し、熱収縮処理を施して耐熱性ポリオレフィン微多孔膜を得る。その特性を表１に示す。耐メルトダウン特性の評価試験結果、シャットダウン温度は、１３０℃付近で急激なインピーダンス値の上昇を示し５０００オーム以上を示し、１８５℃に到達してもインピーダンス値がの低下はなく、１８５℃＜であった。3.3% by weight of ultra high molecular weight polyethylene having a viscosity average molecular weight of 1.15 million, 3.3% by weight of ultra high molecular weight polyethylene having a viscosity average molecular weight of 2 million, and 4.0% by weight of ultra high molecular weight polyethylene having a viscosity average molecular weight of 3.1 million 6.7% by weight of ultra high molecular weight polyethylene having a viscosity average molecular weight of 39.55 million, 16.9% by weight of ultra high molecular weight polyethylene having a viscosity average molecular weight of 5.8 million, and 4.0% by weight of ultra high molecular weight polyethylene having a viscosity average molecular weight of 6.3 million 4-methyl-1-pentene having 19.5% by weight of high density polyethylene having a viscosity average molecular weight of 334,000, 19.5% by weight of medium density polyethylene having a viscosity average molecular weight of 18,000 and a melting point peak of 232 ° C. -1-decene-1 copolymer (MFR 260 ° C. 5 kg load 9 g / 10 min) 4-methyl-1 having 12.4% by weight and melting point peak 228 ° C. Penten-1-hexadecene-1-octadecene copolymer (MFR 260 ° C., 5 kg load, 25 g / 10 minutes) 6.2% by weight and polyolefin elastomer resin Notio [grade name PN3560] manufactured by Mitsui Chemicals, Inc. Polyolefin resin comprising 5% by weight, Tuffmer [grade name DF810] 0.9% by weight, and Excellex [grade name 48070B] 0.8% by weight as a low molecular weight ethylene / butene copolymer manufactured by Mitsui Chemicals, Inc. Tetrakis [methylene-3- (3,5-ditertiarybutyl-4-hydroxyphenyl) -propionate] methane 2.5 parts by weight and 3,9-bis (2) as an antioxidant with respect to 100.0 parts by weight of the mixture , 6-ditertiarybutyl-4-methylphenoxy) -2,4,8,10-tetraoxy 3,9 Jihosufapi [5,5] undecane B sulfonyl hydroxyphenyl) - and propionate] methane 0.25 part by weight, were dry-blended, the average melting point by calculation to prepare a polyolefin resin mixture 151 ° C.. 32 parts by weight of the resin mixture was charged into a twin screw extruder (cylinder diameter: 69 mm, screw length (L) to diameter (D) ratio L / D: 52.5, using a strong kneading type screw). From 68 parts by weight of liquid paraffin [68 cst (40 ° C.)], 7% by weight of polyoxyethylene stearyl ether (HLB2), 3% by weight of polyoxyethylene isostearyl ether (HLB2) from the side feeder of the twin screw extruder The resulting plasticizer is supplied while heating, and a polyolefin / plasticizer mixed melt is prepared under the conditions of 240 to 210 ° C. and 200 rpm. This is extruded from a T-die through a gear pump installed at the tip of a twin-screw extruder, and is taken out with a cooling roll to form a gel-like sheet molding. The resulting gel-like sheet molding is biaxially stretched using a tenter stretching machine. Next, it is fixed to a stainless steel frame plate [size: 20 cm × 30 cm (the following examples and comparative examples are the same)], immersed in a methylene chloride washing bath at room temperature, and washed with rocking for 3 minutes. Take out the entire frame, remove methylene chloride in the vertical direction, immerse it again in a methylene chloride washing bath at room temperature, and wash it while shaking for 3 minutes. Take out the entire frame, remove methylene chloride in the vertical direction, immerse it in a methylene chloride washing bath at room temperature, and wash it for the third time while shaking for 3 minutes. Air-dry the washed and slow-dried membrane at room temperature. While heating the dried stretched film, it is stretched in the TD direction and MD direction (second stretching) at 110 ° C. to 80 ° C. with a tenter stretching machine, and heat-fixed while being held in the tenter for 30 seconds, and heat shrinkage treatment To obtain a heat-resistant polyolefin microporous membrane. The characteristics are shown in Table 1. As a result of the evaluation test of the meltdown resistance, the shutdown temperature showed a sudden increase in impedance value at around 130 ° C. and showed 5000 ohms or more. there were.
粘度平均分子量が１０９万の超高分子量ポリエチレン５．５重量％、粘度平均分子量が３６０万の超高分子量ポリエチレン１１．５重量％、粘度平均分子量が５８０万の超高分子量ポリエチレン１６．１重量％、粘度平均分子量が６３０万の超高分子量ポリエチレン４．６重量％、粘度平均分子量が３３．４万の高密度ポリエチレン２１．９重量％、粘度平均分子量が１８．５万の中密度ポリエチレン２１．９重量％、融点ピーク２３２℃を持つ４−メチル−１ペンテン−１−デセン−１共重合体（ＭＦＲ ２６０℃ ５ｋｇ荷重 ９ｇ／１０分）７．５重量％と融点ピーク２２４℃を持つ４−メチル−１−ペンテン−１−ヘキサデセン−１−オクタデセン共重合体（ＭＦＲ ２６０℃ ５ｋｇ荷重 ２１ｇ／１０分）７．５重量％とポリオレフィン系エラストマー樹脂として三井化学（株）社製のノティオ［グレード名ＰＮ３５６０］２．５重量％、低分子量エチレン・ブテン共重合物として三井化学（株）社製のエクセレックス［グレード名４８０７０Ｂ］１．０重量％とからなるポリオレフィン樹脂混合物１００．０重量部に対して酸化防止剤としてテトラキス［メチレン−３−（３，５−ジターシャリーブチル−４−ヒドロキシフェニル）−プロピオネート］メタン２．５重量部と３，９−ビス（２，６−ジターシャリーブチル−４−メチルフェノキシ）−２，４，８，１０−テトラオキサ−３，９−ジホスファピ［５，５］ウンデカンロニルヒドロキシフェニル）−プロピオネート］メタン０．２５重量部とを、ドライブレンドし、計算による平均融点が１４７℃のポリオレフィン樹脂混合物を調製した。当該樹脂混合物３４重量部を二軸押出機（シリンダ径：６９ｍｍ、スクリュの長さ（Ｌ）と直径（Ｄ）の比Ｌ／Ｄ：５２．５、強混練タイプスクリュ使用）に投入し、この二軸押出機のサイドフィーダーから６６重量部の流動パラフィン［６８ｃｓｔ（４０℃）］８４重量％とポリオキシエチレンステアリルエーテル（ＨＬＢ２）９．６ 重量％、ポリオキシエチレンイソステアリルエーテル（ＨＬＢ２）６．４重量％からなる可塑剤を加熱しながら供給し、２４０−２１０℃及び２００ｒｐｍの条件でポリオレフィン・可塑剤混合溶融物を調製する。これを二軸押出機の先端に設置されたギアーポンプを介してＴダイから押し出し、冷却ロールで引き取りながら、ゲル状シート成形物を形成する。得らるゲル状シート成形物に対して、テンター延伸機を用いて、二軸延伸を施す。次いでステンレス製の枠板［サイズ：２０ｃｍ×３０ｃｍ、（以下の実施例および比較例は同じ）］に固定し、室温の塩化メチレンの洗浄槽中に浸漬し、３分間揺動させながら洗浄する。枠ごと取り出し垂直において塩化メチレンを取り除き、再度室温の塩化メチレンの洗浄槽中に浸漬し、３分間揺動させながら洗浄する。枠ごと取り出し垂直において塩化メチレンを取り除き、室温の塩化メチレンの洗浄槽中に浸漬し、３分間揺動させながら三度目の洗浄をする。洗浄し・徐液した膜を室温で風乾する。乾燥した延伸膜を加熱しながら、テンター延伸機により１０５−８０℃でＴＤ方向、ＭＤ方向に延伸（第二の延伸）し、テンター内で３０秒間保持しながら熱固定処理し、熱収縮処理を施して耐熱性ポリオレフィン微多孔膜を得る。その特性を表１に示す。耐メルトダウン特性の評価試験結果、シャットダウン温度は、１３０℃付近で急激なインピーダンス値の上昇を示し５０００オーム以上を示し、１８５℃に到達してもインピーダンス値がの低下はなく、１８５℃＜であった。5.5% by weight of ultra high molecular weight polyethylene having a viscosity average molecular weight of 1.09 million, 11.5% by weight of ultra high molecular weight polyethylene having a viscosity average molecular weight of 3.6 million, and 16.1% by weight of ultra high molecular weight polyethylene having a viscosity average molecular weight of 5.8 million In addition, 4.6% by weight of ultrahigh molecular weight polyethylene having a viscosity average molecular weight of 63,000,000, 21.9% by weight of high density polyethylene having a viscosity average molecular weight of 334,000, and 21.3% of medium density polyethylene having a viscosity average molecular weight of 18,000. 4-methyl-1-pentene-1-decene-1 copolymer having 9% by weight and a melting point peak of 232 ° C. (MFR 260 ° C., 5 kg load, 9 g / 10 minutes) 7.5% by weight and a melting point peak of 224 ° C. 4- Methyl-1-pentene-1-hexadecene-1-octadecene copolymer (MFR 260 ° C. 5 kg load 21 g / 10 min) 7.5% by weight and polyolefin Notio [grade name PN3560] made by Mitsui Chemicals Co., Ltd. 2.5% by weight as an elastomer resin and Excelex [grade name 48070B] 1 made by Mitsui Chemicals, Inc. as a low molecular weight ethylene / butene copolymer Tetrakis [methylene-3- (3,5-ditertiarybutyl-4-hydroxyphenyl) -propionate] methane 2.5 wt.% As an antioxidant with respect to 100.0 wt.% Of the polyolefin resin mixture comprising 0.0 wt.% Part and 3,9-bis (2,6-ditertiarybutyl-4-methylphenoxy) -2,4,8,10-tetraoxa-3,9-diphosphapi [5,5] undecanlonylhydroxyphenyl) -propionate ] 0.25 parts by weight of methane by dry blending and a calculated average melting point of 147 ° C The fin resin mixture was prepared. 34 parts by weight of the resin mixture was put into a twin screw extruder (cylinder diameter: 69 mm, screw length (L) to diameter (D) ratio L / D: 52.5, using a strong kneading type screw). 66 parts by weight of liquid paraffin [68 cst (40 ° C.)] 84 wt%, polyoxyethylene stearyl ether (HLB2) 9.6 wt%, polyoxyethylene isostearyl ether (HLB2) 6 from the side feeder of the twin screw extruder A plasticizer consisting of 4% by weight is supplied with heating, and a polyolefin / plasticizer mixed melt is prepared under the conditions of 240 to 210 ° C. and 200 rpm. This is extruded from a T-die through a gear pump installed at the tip of a twin-screw extruder, and is taken out with a cooling roll to form a gel-like sheet molding. The resulting gel-like sheet molding is biaxially stretched using a tenter stretching machine. Next, it is fixed to a stainless steel frame plate [size: 20 cm × 30 cm (the following examples and comparative examples are the same)], immersed in a methylene chloride washing bath at room temperature, and washed with rocking for 3 minutes. Take out the entire frame, remove methylene chloride in the vertical direction, immerse it again in a methylene chloride washing bath at room temperature, and wash it while shaking for 3 minutes. Take out the entire frame, remove methylene chloride in the vertical direction, immerse it in a methylene chloride washing bath at room temperature, and wash it for the third time while shaking for 3 minutes. Air-dry the washed and slow-dried membrane at room temperature. While heating the dried stretched film, it is stretched in the TD direction and MD direction (second stretching) at 105-80 ° C. with a tenter stretching machine, and heat-fixed while being held in the tenter for 30 seconds. To obtain a heat-resistant polyolefin microporous membrane. The characteristics are shown in Table 1. As a result of the evaluation test of the meltdown resistance, the shutdown temperature showed a sudden increase in impedance value at around 130 ° C. and showed 5000 ohms or more. there were.
粘度平均分子量が１１５万の超高分子量ポリエチレン３．０重量％、粘度平均分子量が３９５万の超高分子量ポリエチレン３．０重量％、粘度平均分子量が５８０万の超高分子量ポリエチレン１１．９重量％、粘度平均分子量が６３０万の超高分子量ポリエチレン１４．８重量％、粘度平均分子量が３３．４万の高密度ポリエチレン２４．９重量％、粘度平均分子量が１８．５万の中密度ポリエチレン１２．４重量％、融点ピーク２３２℃を持つ４−メチル−１−ペンテン−１−デセン−１共重合体（ＭＦＲ ２６０℃ ５ｋｇ荷重 ９ｇ／１０分）１１．７重量％と融点ピーク２２８℃を持つ４−メチル−１−ペンテン−１−ヘキサデセン−１−オクタデセン共重合体（ＭＦＲ ２６０℃ ５ｋｇ荷重 ２５ｇ／１０分）２．９重量％とポリオレフィン系エラストマー樹脂として三井化学（株）社製のノティオ［グレード名ＰＮ３５６０］２．２５重量％、タフマー［グレード名ＤＦ８１０］１．７５重量％、タフマー［グレード名ＢＬ３４５０］０．７重量％、低分子量エチレン・ブテン共重合物として三井化学（株）社製のエクセレックス［グレード名４８０７０Ｂ］０．８重量％、無機フィラー粒子として水澤化学（株）製のナトリウムカルシュウムアルミノシリケート［グレード名シルトンＪＣ−３０］１０．０重量％とからなるポリオレフィン樹脂と無機フィラーとの混合物１００．０重量部に対して酸化防止剤としてテトラキス［メチレン−３−（３，５−ジターシャリーブチル−４−ヒドロキシフェニル）−プロピオネート］メタン２．０重量部と３，９−ビス（２，６−ジターシャリーブチル−４−メチルフェノキシ）−２，４，８，１０−テトラオキサ−３，９−ジホスファピ［５，５］ウンデカンロニルヒドロキシフェニル）−プロピオネート］メタン０．２０重量部とを、ドライブレンドする。当該樹脂混合物３０重量部を二軸押出機（シリンダ径：６９ｍｍ、スクリュの長さ（Ｌ）と直径（Ｄ）の比Ｌ／Ｄ：５２．５、強混練タイプスクリュ使用）に投入し、この二軸押出機のサイドフィーダーから７０重量部の流動パラフィン［６８ｃｓｔ（４０℃）］９０重量％とポリオキシエチレンステアリルエーテル（ＨＬＢ２）７ 重量％、ポリオキシエチレンイソステアリルエーテル（ＨＬＢ２）３重量％からなる可塑剤を加熱しながら供給し、２４０−２１０℃及び２００ｒｐｍの条件でポリオレフィン・可塑剤混合溶融物を調製する。これを二軸押出機の先端に設置されたギアーポンプを介してＴダイから押し出し、冷却ロールで引き取りながら、ゲル状シート成形物を形成する。得らるゲル状シート成形物に対して、テンター延伸機を用いて、二軸延伸を施す。次いでステンレス製の枠板［サイズ：２０ｃｍ×３０ｃｍ、（以下の実施例および比較例は同じ）］に固定し、室温の塩化メチレンの洗浄槽中に浸漬し、３分間揺動させながら洗浄する。枠ごと取り出し垂直において塩化メチレンを取り除き、再度室温の塩化メチレンの洗浄槽中に浸漬し、３分間揺動させながら洗浄する。枠ごと取り出し垂直において塩化メチレンを取り除き、室温の塩化メチレンの洗浄槽中に浸漬し、３分間揺動させながら三度目の洗浄をする。洗浄し・徐液した膜を室温で風乾する。乾燥した延伸膜を加熱しながら、テンター延伸機により１１５−８０℃でＴＤ方向、ＭＤ方向に延伸（第二の延伸）し、テンター内で３０秒間保持しながら熱固定処理し、熱収縮処理を施して耐熱性ポリオレフィン微多孔膜を得る。その特性を表１に示す。耐メルトダウン特性の評価試験結果、シャットダウン温度は、１３０℃付近で急激なインピーダンス値の上昇を示し５０００オーム以上を示し、１８５℃に到達してもインピーダンス値がの低下はなく、１８５℃＜であった。3.0% by weight of ultra high molecular weight polyethylene having a viscosity average molecular weight of 1.15 million, 3.0% by weight of ultra high molecular weight polyethylene having a viscosity average molecular weight of 39.95 million, 11.9% by weight of ultra high molecular weight polyethylene having a viscosity average molecular weight of 5.8 million 14.8% by weight of ultrahigh molecular weight polyethylene having a viscosity average molecular weight of 63,000,000, 24.9% by weight of high density polyethylene having a viscosity average molecular weight of 334,000, and medium density polyethylene having a viscosity average molecular weight of 18,000. 4-methyl-1-pentene-1-decene-1 copolymer having 4% by weight and a melting point peak of 232 ° C. (MFR 260 ° C., 5 kg load, 9 g / 10 minutes) 11.7% by weight and a melting point peak of 228 ° C. 4 -Methyl-1-pentene-1-hexadecene-1-octadecene copolymer (MFR 260 ° C., 5 kg load, 25 g / 10 min), 2.9% by weight and polio As a fin-based elastomer resin, Notio [grade name PN3560] manufactured by Mitsui Chemicals, Inc. 2.25 wt%, Tuffmer [grade name DF810] 1.75 wt%, Tuffmer [grade name BL3450] 0.7 wt%, low Exelex [grade name 48070B] manufactured by Mitsui Chemicals Co., Ltd. as a molecular weight ethylene / butene copolymer, 0.8% by weight, sodium calcium aluminosilicate manufactured by Mizusawa Chemical Co., Ltd. as graded inorganic filler particles [grade name Shilton JC- 30] Tetrakis [methylene-3- (3,5-ditertiarybutyl-4-hydroxyphenyl) as an antioxidant with respect to 100.0 parts by weight of a mixture of polyolefin resin and inorganic filler composed of 10.0% by weight -Propionate] 2.0 parts by weight of methane and 3,9-bis (2, -Ditertiarybutyl-4-methylphenoxy) -2,4,8,10-tetraoxa-3,9-diphosphapi [5,5] undecanlonylhydroxyphenyl) -propionate] methane 0.20 part by weight of Blend. 30 parts by weight of the resin mixture is put into a twin screw extruder (cylinder diameter: 69 mm, screw length (L) to diameter (D) ratio L / D: 52.5, using a strong kneading type screw). From 70 parts by weight of liquid paraffin [68 cst (40 ° C.)], 7% by weight of polyoxyethylene stearyl ether (HLB2), 3% by weight of polyoxyethylene isostearyl ether (HLB2) from the side feeder of the twin screw extruder The resulting plasticizer is supplied while heating, and a polyolefin / plasticizer mixed melt is prepared under the conditions of 240 to 210 ° C. and 200 rpm. This is extruded from a T-die through a gear pump installed at the tip of a twin-screw extruder, and is taken out with a cooling roll to form a gel-like sheet molding. The resulting gel-like sheet molding is biaxially stretched using a tenter stretching machine. Next, it is fixed to a stainless steel frame plate [size: 20 cm × 30 cm (the following examples and comparative examples are the same)], immersed in a methylene chloride washing bath at room temperature, and washed with rocking for 3 minutes. Take out the entire frame, remove methylene chloride in the vertical direction, immerse it again in a methylene chloride washing bath at room temperature, and wash it while shaking for 3 minutes. Take out the entire frame, remove methylene chloride in the vertical direction, immerse it in a methylene chloride washing bath at room temperature, and wash it for the third time while shaking for 3 minutes. Air-dry the washed and slow-dried membrane at room temperature. While heating the dried stretched film, it was stretched in the TD direction and MD direction (second stretching) at 115-80 ° C. by a tenter stretching machine, and heat-fixed while being held in the tenter for 30 seconds, and subjected to heat shrinkage treatment. To obtain a heat-resistant polyolefin microporous membrane. The characteristics are shown in Table 1. As a result of the evaluation test of the meltdown resistance, the shutdown temperature showed a sudden increase in impedance value at around 130 ° C., showed 5000 ohms or more, and even when it reached 185 ° C., the impedance value did not decrease, and 185 ° C. < there were.
粘度平均分子量が１１５万の超高分子量ポリエチレン２２．５重量％、粘度平均分子量が３１０万の超高分子量ポリエチレン１４．４重量％、粘度平均分子量が５８０万の超高分子量ポリエチレン１２．５重量％、粘度平均分子量が３３．４万の高密度ポリエチレン２５．０重量％、融点ピーク２２４℃を持つ４−メチル−１−ペンテン−１−ヘキサデセン−１−オクタデセン共重合体（ＭＦＲ ２６０℃ ５ｋｇ荷重 ２１ｇ／１０分）２０．０重量％とポリオレフィン系エラストマー樹脂として三井化学（株）社製のノティオ［グレード名ＰＮ３５６０］３．１重量％、低分子量エチレン・ブテン共重合物として三井化学（株）社製のエクセレックス［グレード名４８０７０Ｂ］２．５重量％とからなるポリオレフィン樹脂混合物１００．０重量部に対して酸化防止剤としてテトラキス［メチレン−３−（３，５−ジターシャリーブチル−４−ヒドロキシフェニル）−プロピオネート］メタン２．５重量部と３，９−ビス（２，６−ジターシャリーブチル−４−メチルフェノキシ）−２，４，８，１０−テトラオキサ−３，９−ジホスファピ［５，５］ウンデカンロニルヒドロキシフェニル）−プロピオネート］メタン０．２５重量部とを、ドライブレンドし、計算による平均融点が１５１℃のポリオレフィン樹脂混合物を調製した。当該樹脂混合物３６重量部を二軸押出機（シリンダ径：６９ｍｍ、スクリュの長さ（Ｌ）と直径（Ｄ）の比Ｌ／Ｄ：５２．５、強混練タイプスクリュ使用）に投入し、この二軸押出機のサイドフィーダーから６４重量部の流動パラフィン［６８ｃｓｔ（４０℃）］８４重量％とポリオキシエチレンステアリルエーテル（ＨＬＢ２）１６重量％からなる可塑剤を加熱しながら供給し、２４０−２１０℃及び２００ｒｐｍの条件でポリオレフィン・可塑剤混合溶融物を調製する。これを二軸押出機の先端に設置されたギアーポンプを介してＴダイから押し出し、冷却ロールで引き取りながら、ゲル状シート成形物を形成する。得らるゲル状シート成形物に対して、テンター延伸機を用いて、二軸延伸を施す。次いでステンレス製の枠板［サイズ：２０ｃｍ×３０ｃｍ、（以下の実施例および比較例は同じ）］に固定し、室温の塩化メチレンの洗浄槽中に浸漬し、３分間揺動させながら洗浄する。枠ごと取り出し垂直において塩化メチレンを取り除き、再度室温の塩化メチレンの洗浄槽中に浸漬し、３分間揺動させながら洗浄する。枠ごと取り出し垂直において塩化メチレンを取り除き、室温の塩化メチレンの洗浄槽中に浸漬し、３分間揺動させながら三度目の洗浄をする。洗浄し・徐液した膜を室温で風乾する。乾燥した延伸膜を加熱しながら、テンター延伸機により１１５−８０℃でＴＤ方向、ＭＤ方向に延伸（第二の延伸）し、テンター内で３０秒間保持しながら熱固定処理し、熱収縮処理を施して耐熱性ポリオレフィン微多孔膜を得る。その特性を表１に示す。耐メルトダウン特性の評価試験結果、シャットダウン温度は、１３０℃付近で急激なインピーダンス値の上昇を示し５０００オーム以上を示し、１８５℃に到達してもインピーダンス値がの低下はなく、１８５℃＜であった。22.5% by weight of ultra high molecular weight polyethylene with a viscosity average molecular weight of 1.15 million, 14.4% by weight of ultra high molecular weight polyethylene with a viscosity average molecular weight of 3.1 million, 12.5% by weight of ultra high molecular weight polyethylene with a viscosity average molecular weight of 5.8 million 4-methyl-1-pentene-1-hexadecene-1-octadecene copolymer (MFR 260 ° C., 5 kg load, 21 g), 25.0% by weight of high-density polyethylene having a viscosity average molecular weight of 334,000 and a melting point peak of 224 ° C. / 10 min) 20.0% by weight, 3.1% by weight of Mitsui Chemicals Co., Ltd. [grade name PN3560] as polyolefin elastomer resin, Mitsui Chemicals, Inc. as low molecular weight ethylene butene copolymer 100% polyolefin resin mixture comprising 2.5% by weight of EXELEX [grade name 48070B] manufactured by Tetrakis [methylene-3- (3,5-ditertiarybutyl-4-hydroxyphenyl) -propionate] methane 2.5 parts by weight and 3,9-bis (2,6-diter as an antioxidant with respect to parts by weight Dry blending with 0.25 parts by weight of (salibutyl-4-methylphenoxy) -2,4,8,10-tetraoxa-3,9-diphosphapi [5,5] undecanlonylhydroxyphenyl) -propionate] methane. A polyolefin resin mixture having a calculated average melting point of 151 ° C. was prepared. 36 parts by weight of the resin mixture was put into a twin screw extruder (cylinder diameter: 69 mm, screw length (L) to diameter (D) ratio L / D: 52.5, using a strong kneading type screw). A plasticizer consisting of 84 parts by weight of liquid paraffin [68 cst (40 ° C.)] and 16% by weight of polyoxyethylene stearyl ether (HLB2) is supplied from the side feeder of the twin screw extruder while heating, 240-210 A polyolefin / plasticizer mixed melt is prepared under the conditions of ℃ and 200 rpm. This is extruded from a T-die through a gear pump installed at the tip of a twin-screw extruder, and is taken out with a cooling roll to form a gel-like sheet molding. The resulting gel-like sheet molding is biaxially stretched using a tenter stretching machine. Next, it is fixed to a stainless steel frame plate [size: 20 cm × 30 cm (the following examples and comparative examples are the same)], immersed in a methylene chloride washing bath at room temperature, and washed with rocking for 3 minutes. Take out the entire frame, remove methylene chloride in the vertical direction, immerse it again in a methylene chloride washing bath at room temperature, and wash it while shaking for 3 minutes. Take out the entire frame, remove methylene chloride in the vertical direction, immerse it in a methylene chloride washing bath at room temperature, and wash it for the third time while shaking for 3 minutes. Air-dry the washed and slow-dried membrane at room temperature. While heating the dried stretched film, it was stretched in the TD direction and MD direction (second stretching) at 115-80 ° C. by a tenter stretching machine, and heat-fixed while being held in the tenter for 30 seconds, and subjected to heat shrinkage treatment. To obtain a heat-resistant polyolefin microporous membrane. The characteristics are shown in Table 1. As a result of the evaluation test of the meltdown resistance, the shutdown temperature showed a sudden increase in impedance value at around 130 ° C. and showed 5000 ohms or more. there were.
粘度平均分子量が１１５万の超高分子量ポリエチレン６．７重量％、粘度平均分子量が３９５万の超高分子量ポリエチレン６．６重量％、粘度平均分子量が５８０万の超高分子量ポリエチレン６．６重量％、粘度平均分子量が６３０万の超高分子量ポリエチレン８．３重量％、粘度平均分子量が８００万の超高分子量ポリエチレン８．３重量％、粘度平均分子量が３３．４万の高密度ポリエチレン２６．５、融点ピーク２３２℃を持つ４−メチル−１−ペンテン−１−デセン−１共重合体（ＭＦＲ ２６０℃ ５ｋｇ荷重 ９ｇ／１０分）２４．０重量％と融点ピーク２２８℃を持つ４−メチル−１−ペンテン−１−ヘキサデセン−１−オクタデセン共重合体（ＭＦＲ ２６０℃ ５ｋｇ荷重 ２５ｇ／１０分）６．０重量％とポリオレフィン系エラストマー樹脂としてポリオレフィン系エラストマー樹脂として三井化学（株）社製のノティオ［グレード名ＰＮ３５６０〕３．９重量％、タフマー［グレード名ＤＦ８１０］１．６重量％、タフマー［グレード名ＢＬ３４５０］０．８重量％、低分子量エチレン・ブテン共重合物として三井化学（株）社製のエクセレックス［グレード名４８０７０Ｂ］０．７重量％とからなるポリオレフィン樹脂混合物１００．０重量部に対して酸化防止剤としてテトラキス［メチレン−３−（３，５−ジターシャリーブチル−４−ヒドロキシフェニル）−プロピオネート］メタン２．５重量部と３，９−ビス（２，６−ジターシャリーブチル−４−メチルフェノキシ）−２，４，８，１０−テトラオキサ−３，９−ジホスファピ［５，５］ウンデカンロニルヒドロキシフェニル）−プロピオネート］メタン０．２５重量部とを、ドライブレンドし、計算による平均融点が１６２℃のポリオレフィン樹脂混合物を調製する。当該樹脂混合物３０重量部を二軸押出機（シリンダ径：６９ｍｍ、スクリュの長さ（Ｌ）と直径（Ｄ）の比Ｌ／Ｄ：５２．５、強混練タイプスクリュ使用）に投入し、この二軸押出機のサイドフィーダーから７０重量部の流動パラフィン［６８ｃｓｔ（４０℃）］９０重量％とポリオキシエチレンステアリルエーテル（ＨＬＢ２）７ 重量％、ポリオキシエチレンイソステアリルエーテル（ＨＬＢ２）３重量％からなる可塑剤を加熱しながら供給し、２４０−２２０℃及び２００ｒｐｍの条件でポリオレフィン・可塑剤混合溶融物を調製する。これを二軸押出機の先端に設置されたギアーポンプを介してＴダイから押し出し、冷却ロールで引き取りながら、ゲル状シート成形物を形成する。得らるゲル状シート成形物に対して、テンター延伸機を用いて、二軸延伸を施す。次いでステンレス製の枠板［サイズ：２０ｃｍ×３０ｃｍ、（以下の実施例および比較例は同じ）］に固定し、室温の塩化メチレンの洗浄槽中に浸漬し、３分間揺動させながら洗浄する。枠ごと取り出し垂直において塩化メチレンを取り除き、再度室温の塩化メチレンの洗浄槽中に浸漬し、３分間揺動させながら洗浄する。枠ごと取り出し垂直において塩化メチレンを取り除き、室温の塩化メチレンの洗浄槽中に浸漬し、３分間揺動させながら三度目の洗浄をする。洗浄し・徐液した膜を室温で風乾する。乾燥した延伸膜を加熱しながら、テンター延伸機により１２０−８０℃でＴＤ方向、ＭＤ方向に延伸（第二の延伸）し、テンター内で３０秒間保持しながら熱固定処理し、熱収縮処理を施して耐熱性ポリオレフィン微多孔膜を得る。その特性を表１に示す。耐メルトダウン特性の評価試験結果、シャットダウン温度は、１３０℃付近で急激なインピーダンス値の上昇を示し５０００オーム以上を示し、１８５℃に到達してもインピーダンス値がの低下はなく、１８５℃＜であった。6.7% by weight of ultra high molecular weight polyethylene having a viscosity average molecular weight of 1.15 million, 6.6% by weight of ultra high molecular weight polyethylene having a viscosity average molecular weight of 39.95 million, and 6.6% by weight of ultra high molecular weight polyethylene having a viscosity average molecular weight of 5.8 million 85.3% by weight of ultrahigh molecular weight polyethylene having a viscosity average molecular weight of 63,000,000, 83% by weight of ultrahigh molecular weight polyethylene having a viscosity average molecular weight of 8 million, and 26.5% high density polyethylene having a viscosity average molecular weight of 334,000 4-methyl-1-pentene-1-decene-1 copolymer having a melting point peak of 232 ° C. (MFR 260 ° C., 5 kg load, 9 g / 10 minutes) and 24.0% by weight and 4-methyl- having a melting point peak of 228 ° C. 1-pentene-1-hexadecene-1-octadecene copolymer (MFR 260 ° C., 5 kg load, 25 g / 10 minutes) 6.0% by weight and polyolefin type Lastio resin as polyolefin elastomer resin, Mitsui Chemicals Co., Ltd. Notio [grade name PN3560] 3.9 wt%, Tuffmer [grade name DF810] 1.6 wt%, Tuffmer [grade name BL3450] 0.8 wt% Tetrakis as an antioxidant with respect to 100.0 parts by weight of a polyolefin resin mixture consisting of 0.7% by weight of Exelex [grade name 48070B] manufactured by Mitsui Chemicals, Inc. as a low molecular weight ethylene / butene copolymer [Methylene-3- (3,5-ditertiarybutyl-4-hydroxyphenyl) -propionate] 2.5 parts by weight of methane and 3,9-bis (2,6-ditertiarybutyl-4-methylphenoxy) -2 , 4,8,10-tetraoxa-3,9-diphosphapi [5,5] undecane Sulfonyl hydroxyphenyl) - and propionate] methane 0.25 part by weight, were dry-blended, the average melting point by calculation to prepare a polyolefin resin mixture 162 ° C.. 30 parts by weight of the resin mixture is put into a twin screw extruder (cylinder diameter: 69 mm, screw length (L) to diameter (D) ratio L / D: 52.5, using a strong kneading type screw). From 70 parts by weight of liquid paraffin [68 cst (40 ° C.)], 7% by weight of polyoxyethylene stearyl ether (HLB2), 3% by weight of polyoxyethylene isostearyl ether (HLB2) from the side feeder of the twin screw extruder The resulting plasticizer is supplied while heating, and a polyolefin / plasticizer mixed melt is prepared under the conditions of 240 to 220 ° C. and 200 rpm. This is extruded from a T-die through a gear pump installed at the tip of a twin-screw extruder, and is taken out with a cooling roll to form a gel-like sheet molding. The resulting gel-like sheet molding is biaxially stretched using a tenter stretching machine. Next, it is fixed to a stainless steel frame plate [size: 20 cm × 30 cm (the following examples and comparative examples are the same)], immersed in a methylene chloride washing bath at room temperature, and washed with rocking for 3 minutes. Take out the entire frame, remove methylene chloride in the vertical direction, immerse it again in a methylene chloride washing bath at room temperature, and wash it while shaking for 3 minutes. Take out the entire frame, remove methylene chloride in the vertical direction, immerse it in a methylene chloride washing bath at room temperature, and wash it for the third time while shaking for 3 minutes. Air-dry the washed and slow-dried membrane at room temperature. While heating the dried stretched film, it was stretched in the TD direction and MD direction (second stretching) at 120-80 ° C. with a tenter stretching machine, and heat-fixed while being held in the tenter for 30 seconds. To obtain a heat-resistant polyolefin microporous membrane. The characteristics are shown in Table 1. As a result of the evaluation test of the meltdown resistance, the shutdown temperature showed a sudden increase in impedance value at around 130 ° C. and showed 5000 ohms or more. there were.
粘度平均分子量が１１５万の超高分子量ポリエチレン１８．５重量％、粘度平均分子量が３２０万の超高分子量ポリエチレン１５．９重量％、粘度平均分子量が５８０万の超高分子量ポリエチレン１４．８重量％、粘度平均分子量が６３０万の超高分子量ポリエチレン１４．８重量％、粘度平均分子量が３３．４万の高密度ポリエチレン１８．５重量％、融点ピーク２３２℃を持つ４−メチル−１−ペンテン−１−デセン−１共重合体（ＭＦＲ ２６０℃ ５ｋｇ荷重 ９ｇ／１０分）１０．０重量％と融点ピーク２２８℃を持つ４−メチル−１−ペンテン−１−ヘキサデセン−１−オクタデセン共重合体（ＭＦＲ ２６０℃ ５ｋｇ荷重 ２５ｇ／１０分）２．５重量％とポリオレフィン系エラストマー樹脂としてポリオレフィン系エラストマー樹脂として三井化学（株）社製のノティオ［グレード名ＰＮ３５６０］２．５重量％、タフマー［グレード名ＤＦ８１０］１．７重量％、低分子量エチレン・ブテン共重合物として三井化学（株）社製のエクセレックス［グレード名４８０７０Ｂ］０．８重量％とからなるポリオレフィン樹脂混合物１００．０重量部に対して酸化防止剤としてテトラキス［メチレン−３−（３，５−ジターシャリーブチル−４−ヒドロキシフェニル）−プロピオネート］メタン２．５重量部と３，９−ビス（２，６−ジターシャリーブチル−４−メチルフェノキシ）−２，４，８，１０−テトラオキサ−３，９−ジホスファピ［５，５］ウンデカンロニルヒドロキシフェニル）−プロピオネート］メタン０．２５重量部とを、ドライブレンドし、計算による平均融点が１４４℃のポリオレフィン樹脂混合物を調製する。当該樹脂混合物３６重量部を二軸押出機（シリンダ径：６９ｍｍ、スクリュの長さ（Ｌ）と直径（Ｄ）の比Ｌ／Ｄ：５２．５、強混練タイプスクリュ使用）に投入し、この二軸押出機のサイドフィーダーから６４重量部の流動パラフィン［６８ｃｓｔ（４０℃）］９０重量％とポリオキシエチレンステアリルエーテル（ＨＬＢ２）７ 重量％、ポリオキシエチレンイソステアリルエーテル（ＨＬＢ２）３重量％からなる可塑剤を加熱しながら供給し、２４０−２２０℃及び２００ｒｐｍの条件でポリオレフィン・可塑剤混合溶融物を調製する。これを二軸押出機の先端に設置されたギアーポンプを介してＴダイから押し出し、冷却ロールで引き取りながら、ゲル状シート成形物を形成する。得らるゲル状シート成形物に対して、テンター延伸機を用いて、二軸延伸を施す。次いでステンレス製の枠板［サイズ：２０ｃｍ×３０ｃｍ、（以下の実施例および比較例は同じ）］に固定し、室温の塩化メチレンの洗浄槽中に浸漬し、３分間揺動させながら洗浄する。枠ごと取り出し垂直において塩化メチレンを取り除き、再度室温の塩化メチレンの洗浄槽中に浸漬し、３分間揺動させながら洗浄する。枠ごと取り出し垂直において塩化メチレンを取り除き、室温の塩化メチレンの洗浄槽中に浸漬し、３分間揺動させながら三度目の洗浄をする。洗浄し・徐液した膜を室温で風乾する。乾燥した延伸膜を加熱しながら、テンター延伸機により１１５−８０℃でＴＤ方向、ＭＤ方向に延伸（第二の延伸）し、テンター内で３０秒間保持しながら熱固定処理し、熱収縮処理を施して耐熱性ポリオレフィン微多孔膜を得る。その特性を表１に示す。耐メルトダウン特性の評価試験結果、シャットダウン温度は、１３０℃付近で急激なインピーダンス値の上昇を示し５０００オーム以上を示し、１８５℃に到達してもインピーダンス値がの低下はなく、１８５℃＜であった。18.5% by weight of ultra high molecular weight polyethylene having a viscosity average molecular weight of 1.15 million, 15.9% by weight of ultra high molecular weight polyethylene having a viscosity average molecular weight of 3.2 million, and 14.8% by weight of ultra high molecular weight polyethylene having a viscosity average molecular weight of 5.8 million 4-methyl-1-pentene having 14.8% by weight of ultrahigh molecular weight polyethylene having a viscosity average molecular weight of 63,000,000, 18.5% by weight of high density polyethylene having a viscosity average molecular weight of 334,000, and a melting point peak of 232 ° C. 1-decene-1 copolymer (MFR 260 ° C., 5 kg load, 9 g / 10 min) 4-methyl-1-pentene-1-hexadecene-1-octadecene copolymer having 10.0% by weight and a melting point peak of 228 ° C. ( MFR 260 ° C 5 kg load 25 g / 10 min) 2.5 wt% and polyolefin elastomer resin as polyolefin elastomer resin Notio [grade name PN3560] 2.5% by weight made by Mitsui Chemicals Co., Ltd. as a resin, 1.7% by weight Toughmer [grade name DF810], made by Mitsui Chemicals, Inc. as a low molecular weight ethylene / butene copolymer As an antioxidant, tetrakis [methylene-3- (3,5-ditertiarybutyl-4-hydroxyphenyl) was added to 100.0 parts by weight of a polyolefin resin mixture consisting of 0.8% by weight of EXELEX [grade name 48070B]. ) -Propionate] 2.5 parts by weight of methane and 3,9-bis (2,6-ditertiarybutyl-4-methylphenoxy) -2,4,8,10-tetraoxa-3,9-diphosphapi [5,5 ] Undecanlonyl hydroxyphenyl) -propionate] 0.25 part by weight of methane, dry blended and calculated The average melting point to prepare a 144 ° C. of the polyolefin resin mixture. 36 parts by weight of the resin mixture was put into a twin screw extruder (cylinder diameter: 69 mm, screw length (L) to diameter (D) ratio L / D: 52.5, using a strong kneading type screw). From 64 parts by weight of liquid paraffin [68 cst (40 ° C.)] 90 wt%, polyoxyethylene stearyl ether (HLB2) 7 wt%, polyoxyethylene isostearyl ether (HLB2) 3 wt% from the side feeder of the twin screw extruder The resulting plasticizer is supplied while heating, and a polyolefin / plasticizer mixed melt is prepared under the conditions of 240 to 220 ° C. and 200 rpm. This is extruded from a T-die through a gear pump installed at the tip of a twin-screw extruder, and is taken out with a cooling roll to form a gel-like sheet molding. The resulting gel-like sheet molding is biaxially stretched using a tenter stretching machine. Next, it is fixed to a stainless steel frame plate [size: 20 cm × 30 cm (the following examples and comparative examples are the same)], immersed in a methylene chloride washing bath at room temperature, and washed with rocking for 3 minutes. Take out the entire frame, remove methylene chloride in the vertical direction, immerse it again in a methylene chloride washing bath at room temperature, and wash it while shaking for 3 minutes. Take out the entire frame, remove methylene chloride in the vertical direction, immerse it in a methylene chloride washing bath at room temperature, and wash it for the third time while shaking for 3 minutes. Air-dry the washed and slow-dried membrane at room temperature. While heating the dried stretched film, it was stretched in the TD direction and MD direction (second stretching) at 115-80 ° C. by a tenter stretching machine, and heat-fixed while being held in the tenter for 30 seconds, and subjected to heat shrinkage treatment. To obtain a heat-resistant polyolefin microporous membrane. The characteristics are shown in Table 1. As a result of the evaluation test of the meltdown resistance, the shutdown temperature showed a sudden increase in impedance value at around 130 ° C. and showed 5000 ohms or more. there were.
粘度平均分子量が２４．５万のポリプロピレンホモポリマ−１０．３重量％、粘度平均分子量が１１５万の超高分子量ポリエチレン６．６重量％、粘度平均分子量が３９５万の超高分子量ポリエチレン６．６重量％、粘度平均分子量が５８０万の超高分子量ポリエチレン１９．９重量％、粘度平均分子量が６３０万の超高分子量ポリエチレン１３．３重量％、粘度平均分子量が３３．４万の高密度ポリエチレン２２．６％、融点ピーク２３２℃を持つ４−メチル−１−ペンテン−１−デセン−１共重合体（ＭＦＲ ２６０℃ ５ｋｇ荷重 ９ｇ／１０分）１１．１重量％と融点ピーク２２８℃を持つ４−メチル−１−ペンテン−１−ヘキサデセン−１−オクタデセン共重合体（ＭＦＲ ２６０℃ ５ｋｇ荷重 ２５ｇ／１０分）２．８重量％とポリオレフィン系エラストマー樹脂としてポリオレフィン系エラストマー樹脂として三井化学（株）社製のノティオ［グレード名ＰＮ３５６０］３．２重量％、タフマー［グレード名ＤＦ８１０］２．１重量％、タフマー［グレード名ＢＬ３４５０］０．７重量％、低分子量エチレン・ブテン共重合物として三井化学（株）社製のエクセレックス［グレード名４８０７０Ｂ］０．８重量％とからなるポリオレフィン樹脂混合物１００．０重量部に対して酸化防止剤としてテトラキス［メチレン−３−（３，５−ジターシャリーブチル−４−ヒドロキシフェニル）−プロピオネート］メタン２．５重量部と３，９−ビス（２，６−ジターシャリーブチル−４−メチルフェノキシ）−２，４，８，１０−テトラオキサ−３，９−ジホスファピ［５，５］ウンデカンロニルヒドロキシフェニル）−プロピオネート］メタン０．２５重量部とを、ドライブレンドし、計算による平均融点が１５１℃のポリオレフィン樹脂混合物を調製する。当該樹脂混合物３４重量部を二軸押出機（シリンダ径：６９ｍｍ、スクリュの長さ（Ｌ）と直径（Ｄ）の比Ｌ／Ｄ：５２．５、強混練タイプスクリュ使用）に投入し、この二軸押出機のサイドフィーダーから６６重量部の流動パラフィン［６８ｃｓｔ（４０℃）］９０重量％とポリオキシエチレンステアリルエーテル（ＨＬＢ２）７ 重量％、ポリオキシエチレンイソステアリルエーテル（ＨＬＢ２）３重量％からなる可塑剤を加熱しながら供給し、２４０−２２０℃及び２００ｒｐｍの条件でポリオレフィン・可塑剤混合溶融物を調製する。これを二軸押出機の先端に設置されたギアーポンプを介してＴダイから押し出し、冷却ロールで引き取りながら、ゲル状シート成形物を形成する。得らるゲル状シート成形物に対して、テンター延伸機を用いて、二軸延伸を施す。次いでステンレス製の枠板［サイズ：２０ｃｍ×３０ｃｍ、（以下の実施例および比較例は同じ）］に固定し、室温の塩化メチレンの洗浄槽中に浸漬し、３分間揺動させながら洗浄する。枠ごと取り出し垂直において塩化メチレンを取り除き、再度室温の塩化メチレンの洗浄槽中に浸漬し、３分間揺動させながら洗浄する。枠ごと取り出し垂直において塩化メチレンを取り除き、室温の塩化メチレンの洗浄槽中に浸漬し、３分間揺動させながら三度目の洗浄をする。洗浄し・徐液した膜を室温で風乾する。乾燥した延伸膜を加熱しながら、テンター延伸機によりＴＤ方向、ＭＤ方向に延伸（第二の延伸）し、テンター内で２０秒間保持しながら熱固定処理として熱収縮処理を施して耐熱性ポリオレフィン微多孔膜を得る。その特性を表１に示す。
耐メルトダウン特性の評価試験結果、シャットダウン温度は、１３０℃付近で急激なインピーダンス値の上昇を示し５０００オーム以上を示し、１８５℃に到達してもインピーダンス値がの低下はなく、１８５℃＜であった。Polypropylene homopolymer having a viscosity average molecular weight of 245,000 10.3% by weight, 6.6% by weight of ultrahigh molecular weight polyethylene having a viscosity average molecular weight of 1.15 million, and ultrahigh molecular weight polyethylene having a viscosity average molecular weight of 39.55 million 19.9% by weight of ultrahigh molecular weight polyethylene having a weight average molecular weight of 5.8 million, 13.3% by weight of ultra high molecular weight polyethylene having a viscosity average molecular weight of 63,000,000, and high density polyethylene 22 having a viscosity average molecular weight of 334,000 4-methyl-1-pentene-1-decene-1 copolymer (MFR 260 ° C., 5 kg load, 9 g / 10 min) having a melting point peak of 232 ° C. -Methyl-1-pentene-1-hexadecene-1-octadecene copolymer (MFR 260 ° C., 5 kg load, 25 g / 10 min), 2.8% by weight and polio As a fin-based elastomer resin, polyolefin elastomer resin as Mitio Chemical Co., Ltd. Notio [grade name PN3560] 3.2 wt%, Tuffmer [grade name DF810] 2.1 wt%, Tuffmer [grade name BL3450] 0. An antioxidant for 100.0 parts by weight of a polyolefin resin mixture consisting of 7% by weight and 0.8% by weight of EXELEX [grade name 48070B] manufactured by Mitsui Chemicals, Inc. as a low molecular weight ethylene / butene copolymer Tetrakis [methylene-3- (3,5-ditertiarybutyl-4-hydroxyphenyl) -propionate] methane 2.5 parts by weight and 3,9-bis (2,6-ditertiarybutyl-4-methylphenoxy) -2,4,8,10-tetraoxa-3,9-diphosphapi [5,5] Emissions decane b sulfonyl hydroxyphenyl) - and propionate] methane 0.25 part by weight, were dry-blended, the average melting point by calculation to prepare a polyolefin resin mixture 151 ° C.. 34 parts by weight of the resin mixture was put into a twin screw extruder (cylinder diameter: 69 mm, screw length (L) to diameter (D) ratio L / D: 52.5, using a strong kneading type screw). From 66 parts by weight of liquid paraffin [68 cst (40 ° C.)], 7% by weight of polyoxyethylene stearyl ether (HLB2), 3% by weight of polyoxyethylene isostearyl ether (HLB2) from the side feeder of the twin screw extruder The resulting plasticizer is supplied while heating, and a polyolefin / plasticizer mixed melt is prepared under the conditions of 240 to 220 ° C. and 200 rpm. This is extruded from a T-die through a gear pump installed at the tip of a twin-screw extruder, and is taken out with a cooling roll to form a gel-like sheet molding. The resulting gel-like sheet molding is biaxially stretched using a tenter stretching machine. Next, it is fixed to a stainless steel frame plate [size: 20 cm × 30 cm (the following examples and comparative examples are the same)], immersed in a methylene chloride washing bath at room temperature, and washed with rocking for 3 minutes. Take out the entire frame, remove methylene chloride in the vertical direction, immerse it again in a methylene chloride washing bath at room temperature, and wash it while shaking for 3 minutes. Take out the entire frame, remove methylene chloride in the vertical direction, immerse it in a methylene chloride washing bath at room temperature, and wash it for the third time while shaking for 3 minutes. Air-dry the washed and slow-dried membrane at room temperature. While heating the dried stretched film, it is stretched in the TD direction and MD direction (second stretching) by a tenter stretching machine, and heat-shrinking treatment is performed as a heat fixing process while being held in the tenter for 20 seconds. A porous membrane is obtained. The characteristics are shown in Table 1.
As a result of the evaluation test of the meltdown resistance, the shutdown temperature showed a sudden increase in impedance value at around 130 ° C., showed 5000 ohms or more, and even when it reached 185 ° C., the impedance value did not decrease, and 185 ° C. < there were.
粘度平均分子量が１１５万の超高分子量ポリエチレン６．６重量％、粘度平均分子量が３９５万の超高分子量ポリエチレン６．６重量％、粘度平均分子量が５８０万の超高分子量ポリエチレン３．３重量％、粘度平均分子量が６３０万の超高分子量ポリエチレン９．９重量％、粘度平均分子量が８００万の超高分子量ポリエチレン６．６重量％、粘度平均分子量が１０００万の超高分子量ポリエチレン６．６重量％、粘度平均分子量が３３．４万の高密度ポリエチレン２７．７重量％、粘度平均分子量が１８．５万の中密度ポリエチレン１０．５重量％、融点ピーク２３２℃を持つ４−メチル−１−ペンテン−１−デセン−１共重合体（ＭＦＲ ２６０℃ ５ｋｇ荷重 ９ｇ／１０分）１３．０重量％と融点ピーク２２８℃を持つ４−メチル−１−ペンテン−１−ヘキサデセン−１−オクタデセン共重合体（ＭＦＲ ２６０℃ ５ｋｇ荷重 ２５ｇ／１０分）３．３重量％とポリオレフィン系エラストマー樹脂として三井化学（株）社製のノティオ［グレード名ＰＮ３５６０］２．５重量％、タフマー［グレード名ＤＦ８１０］１．９重量％、タフマー［グレード名ＢＬ３４５０］０．８重量％、低分子量エチレン・ブテン共重合物として三井化学（株）社製のエクセレックス［グレード名４８０７０Ｂ］０．７重量％とからなるポリオレフィン樹脂混合物１００．０重量部に対して酸化防止剤としてテトラキス［メチレン−３−（３，５−ジターシャリーブチル−４−ヒドロキシフェニル）−プロピオネート］メタン２．５重量部と３，９−ビス（２，６−ジターシャリーブチル−４−メチルフェノキシ）−２，４，８，１０−テトラオキサ−３，９−ジホスファピ［５，５］ウンデカンロニルヒドロキシフェニル）−プロピオネート］メタン０．２５重量部とを、ドライブレンドし、計算による平均融点が１４９．５℃のポリオレフィン樹脂混合物を調製した。
当該樹脂混合物３４重量部を二軸押出機（シリンダ径：６９ｍｍ、スクリュの長さ（Ｌ）と直径（Ｄ）の比Ｌ／Ｄ：５２．５、強混練タイプスクリュ使用）に投入し、この二軸押出機のサイドフィーダーから６６重量部の流動パラフィン［６８ｃｓｔ（４０℃）］９０重量％とポリオキシエチレンステアリルエーテル（ＨＬＢ２）７重量％、ポリオキシエチレンイソステアリルエーテル（ＨＬＢ２）３重量％からなる可塑剤を加熱しながら供給し、２４０−２２０℃及び２００ｒｐｍの条件でポリオレフィン・可塑剤混合溶融物を調製する。これを二軸押出機の先端に設置されたギアーポンプを介してＴダイから押し出し、冷却ロールで引き取りながら、ゲル状シート成形物を形成する。得らるゲル状シート成形物に対して、テンター延伸機を用いて、二軸延伸を施す。次いでステンレス製の枠板［サイズ：２０ｃｍ×３０ｃｍ、（以下の実施例および比較例は同じ）］に固定し、室温の塩化メチレンの洗浄槽中に浸漬し、３分間揺動させながら洗浄する。枠ごと取り出し垂直において塩化メチレンを取り除き、再度室温の塩化メチレンの洗浄槽中に浸漬し、３分間揺動させながら洗浄する。
枠ごと取り出し垂直において塩化メチレンを取り除き、室温の塩化メテレンの洗浄槽中に浸漬し、３分間揺動させながら三度目の洗浄をする。洗浄・徐液した膜を室温で風乾する。。
乾燥した延伸膜を加熱しながら、テンター延伸機により１１０℃−８０℃でＴＤ方向、ＭＤ方向に延伸（第二の延伸）し、テンター内で３０秒間保持しながら熱固定処理し、熱収縮処理を施して耐熱性ポリオレフィン微多孔膜を得る。その特性を表１に示す。
耐メルトダウン特性の評価試験結果、シャットダウン温度は、１３０℃付近で急激なインピーダンス値の上昇を示し５０００オーム以上を示し、１８５℃に到達してもインピーダンス値がの低下はなく、１８５℃＜であった。6.6% by weight of ultra high molecular weight polyethylene with a viscosity average molecular weight of 1.15 million, 6.6% by weight of ultra high molecular weight polyethylene with a viscosity average molecular weight of 39.55 million, 3.3% by weight of ultra high molecular weight polyethylene with a viscosity average molecular weight of 5.8 million 9.9% by weight of ultra high molecular weight polyethylene having a viscosity average molecular weight of 6.3 million, 6.6% by weight of ultra high molecular weight polyethylene having a viscosity average molecular weight of 8 million, and 6.6% by weight of ultra high molecular weight polyethylene having a viscosity average molecular weight of 10 million 4-methyl-1- having 27.7% by weight of high density polyethylene having a viscosity average molecular weight of 334,000, 10.5% by weight of medium density polyethylene having a viscosity average molecular weight of 18,000 and a melting point peak of 232 ° C. Pentene-1-decene-1 copolymer (MFR 260 ° C., 5 kg load, 9 g / 10 minutes) 13.0% by weight and 4-methyl-1 having a melting point peak of 228 ° C. Penten-1-hexadecene-1-octadecene copolymer (MFR 260 ° C., 5 kg load, 25 g / 10 minutes) 3.3% by weight and Notio [grade name PN3560] manufactured by Mitsui Chemicals, Inc. as polyolefin elastomer resin 5% by weight, Tafmer [Grade Name DF810] 1.9% by weight, Tafmer [Grade Name BL3450] 0.8% by weight, Excelex [Grade Name] manufactured by Mitsui Chemicals, Inc. as a low molecular weight ethylene / butene copolymer 48070B] Tetrakis [methylene-3- (3,5-ditertiarybutyl-4-hydroxyphenyl) -propionate] methane 2 as an antioxidant with respect to 100.0 parts by weight of a polyolefin resin mixture comprising 0.7% by weight .5 parts by weight and 3,9-bis (2,6-ditertiarybutyl-4-methyl Ruphenoxy) -2,4,8,10-tetraoxa-3,9-diphosphapi [5,5] undecanlonylhydroxyphenyl) -propionate] 0.25 part by weight of methane, dry blended and calculated average melting point A polyolefin resin mixture having a temperature of 149.5 ° C. was prepared.
34 parts by weight of the resin mixture was put into a twin screw extruder (cylinder diameter: 69 mm, screw length (L) to diameter (D) ratio L / D: 52.5, using a strong kneading type screw). From 66 parts by weight of liquid paraffin [68 cst (40 ° C.)], 7% by weight of polyoxyethylene stearyl ether (HLB2), 3% by weight of polyoxyethylene isostearyl ether (HLB2) from the side feeder of the twin screw extruder The resulting plasticizer is supplied while heating, and a polyolefin / plasticizer mixed melt is prepared under the conditions of 240 to 220 ° C. and 200 rpm. This is extruded from a T-die through a gear pump installed at the tip of a twin-screw extruder, and is taken out with a cooling roll to form a gel-like sheet molding. The resulting gel-like sheet molding is biaxially stretched using a tenter stretching machine. Next, it is fixed to a stainless steel frame plate [size: 20 cm × 30 cm (the following examples and comparative examples are the same)], immersed in a methylene chloride washing bath at room temperature, and washed with rocking for 3 minutes. Take out the entire frame, remove methylene chloride in the vertical direction, immerse it again in a methylene chloride washing bath at room temperature, and wash it while shaking for 3 minutes.
Take out the entire frame, remove methylene chloride in the vertical direction, immerse it in a washing bath of methylene chloride at room temperature, and wash it for the third time while shaking for 3 minutes. Air-dry the washed / slowly-treated membrane at room temperature. .
While heating the dried stretched film, it is stretched in the TD direction and MD direction (second stretching) at 110 ° C. to 80 ° C. with a tenter stretching machine, and heat-fixed while being held in the tenter for 30 seconds, and heat shrinkage treatment To obtain a heat-resistant polyolefin microporous membrane. The characteristics are shown in Table 1.
As a result of the evaluation test of the meltdown resistance, the shutdown temperature showed a sudden increase in impedance value at around 130 ° C., showed 5000 ohms or more, and even when it reached 185 ° C., the impedance value did not decrease, and 185 ° C. < there were.
粘度平均分子量が１１５万の超高分子量ポリエチレン６．７重量％、粘度平均分子量が３９５万の超高分子量ポリエチレン１２．９重量％、粘度平均分子量が５８０万の超高分子量ポリエチレン６．６重量％、粘度平均分子量が６３０万の超高分子量ポリエチレン１６．６重量％、粘度平均分子量が３３．４万の高密度ポリエチレン２６．５、融点ピーク２３２℃を持つ４−メチル−１−ペンテン−１−デセン−１共重合体（ＭＦＲ ２６０℃ ５ｋｇ荷重 ９ｇ／１０分）２４．０重量％と融点ピーク２２８℃を持つ４−メチル−１−ペンテン−１−ヘキサデセン−１−オクタデセン共重合体（ＭＦＲ ２６０℃ ５ｋｇ荷重 ２５ｇ／１０分）６．０重量％低分子量エチレン・ブテン共重合物として三井化学（株）社製のエクセレックス［グレード名４８０７０Ｂ］０．７重量％とからなるポリオレフィン樹脂混合物１００．０重量部に対して酸化防止剤としてテトラキス［メチレン−３−（３，５−ジターシャリーブチル−４−ヒドロキシフェニル）−プロピオネート］メタン２．５重量部と３，９−ビス（２，６−ジターシャリーブチル−４−メチルフェノキシ）−２，４，８，１０−テトラオキサ−３，９−ジホスファピ［５，５］ウンデカンロニルヒドロキシフェニル）−プロピオネート］メタン０．２５重量部とを、ドライブレンドし、ポリオレフィン樹脂混合物を調製する。当該樹脂混合物３０重量部を二軸押出機（シリンダ径：６９ｍｍ、スクリュの長さ（Ｌ）と直径（Ｄ）の比Ｌ／Ｄ：５２．５、強混練タイプスクリュ使用）に投入し、この二軸押出機のサイドフィーダーから７０重量部の流動パラフィン［６８ｃｓｔ（４０℃）］９０重量％とポリオキシエチレンステアリルエーテル（ＨＬＢ２）７ 重量％、ポリオキシエチレンイソステアリルエーテル（ＨＬＢ２）３重量％からなる可塑剤を加熱しながら供給し、２４０−２２０℃及び２００ｒｐｍの条件でポリオレフィン・可塑剤混合溶融物を調製する。これを二軸押出機の先端に設置されたギアーポンプを介してＴダイから押し出し押し出し、冷却ロールで引き取ろうとしたが、切れやすく安定したゲル状シート成形物は、得られず、耐熱性ポリオレフィン微多孔膜とするには至らなかった。6.7% by weight of ultra high molecular weight polyethylene having a viscosity average molecular weight of 1.15 million, 12.9% by weight of ultra high molecular weight polyethylene having a viscosity average molecular weight of 39.95 million, and 6.6% by weight of ultra high molecular weight polyethylene having a viscosity average molecular weight of 5.8 million 16.5% by weight of ultra high molecular weight polyethylene having a viscosity average molecular weight of 63,000,000, 26.5 high density polyethylene having a viscosity average molecular weight of 334,000, and 4-methyl-1-pentene-1- having a melting point peak of 232 ° C. 4-methyl-1-pentene-1-hexadecene-1-octadecene copolymer (MFR 260) having a decene-1 copolymer (MFR 260 ° C., 5 kg load 9 g / 10 min) 24.0% by weight and a melting point peak 228 ° C. ℃ 5kg load 25g / 10min) 6.0 wt% low molecular weight ethylene butene copolymer excelex [G Tetrakis [methylene-3- (3,5-ditertiarybutyl-4-hydroxyphenyl) -propionate as an antioxidant with respect to 100.0 parts by weight of a polyolefin resin mixture comprising 0.7% by weight ] 2.5 parts by weight of methane and 3,9-bis (2,6-ditertiarybutyl-4-methylphenoxy) -2,4,8,10-tetraoxa-3,9-diphosphapi [5,5] undecanlo Nylhydroxyphenyl) -propionate] 0.25 part by weight of methane is dry blended to prepare a polyolefin resin mixture. 30 parts by weight of the resin mixture is put into a twin screw extruder (cylinder diameter: 69 mm, screw length (L) to diameter (D) ratio L / D: 52.5, using a strong kneading type screw). From 70 parts by weight of liquid paraffin [68 cst (40 ° C.)], 7% by weight of polyoxyethylene stearyl ether (HLB2), 3% by weight of polyoxyethylene isostearyl ether (HLB2) from the side feeder of the twin screw extruder The resulting plasticizer is supplied while heating, and a polyolefin / plasticizer mixed melt is prepared under the conditions of 240 to 220 ° C. and 200 rpm. This was extruded from a T-die through a gear pump installed at the tip of a twin-screw extruder, and tried to take it off with a cooling roll. However, a gel-like sheet molded product that was easy to cut was not obtained, and heat-resistant polyolefin microporous It could not be made into a film.
粘度平均分子量が１１５万の超高分子量ポリエチレン２２．５重量％、粘度平均分子量が３１０万の超高分子量ポリエチレン１３．８重量％、粘度平均分子量が５８０万の超高分子量ポリエチレン１５．０重量％、粘度平均分子量が３３．４万の高密度ポリエチレン４０．０重量％、融点ピーク２２４℃を持つ４−メチル−１−ペンテン−１−ヘキサデセン−１−オクタデセン共重合体（ＭＦＲ ２６０℃ ５ｋｇ荷重 ２１ｇ／１０分）５．０重量％とポリオレフィン系エラストマー樹脂として三井化学（株）社製のノティオ［グレード名ＰＮ３５６０］１．２重量％、低分子量エチレン・ブテン共重合物として三井化学（株）社製のエクセレックス［グレード名４８０７０Ｂ］２．５重量％とからなるポリオレフィン樹脂混合物１００．０重量部に対して酸化防止剤としてテトラキス［メチレン−３−（３，５−ジターシャリーブチル−４−ヒドロキシフェニル）−プロピオネート］メタン２．５重量部と３，９−ビス（２，６−ジターシャリーブチル−４−メチルフェノキシ）−２，４，８，１０−テトラオキサ−３，９−ジホスファピ［５，５］ウンデカンロニルヒドロキシフェニル）−プロピオネート］メタン０．２５重量部とを、ドライブレンドし、計算による平均融点が１３７℃のポリオレフィン樹脂混合物を調製する。当該樹脂混合物３４重量部を二軸押出機（シリンダ径：６９ｍｍ、スクリュの長さ（Ｌ）と直径（Ｄ）の比Ｌ／Ｄ：５２．５、強混練タイプスクリュ使用）に投入し、この二軸押出機のサイドフィーダーから６６重量部の流動パラフィン［６８ｃｓｔ（４０℃）］８３重量％とポリオキシエチレンステアリルエーテル（ＨＬＢ２）１７ 重量％、からなる可塑剤を加熱しながら供給し、２２０−２００℃及び１６０ｒｐｍの条件でポリオレフィン・可塑剤混合溶融物を調製する。これを二軸押出機の先端に設置されたギアーポンプを介してＴダイから押し出し、冷却ロールで引き取りながら、ゲル状シート成形物を形成する。得らるゲル状シート成形物に対して、テンター延伸機を用いて、二軸延伸を施す。次いでステンレス製の枠板［サイズ：２０ｃｍ×３０ｃｍ、（以下の実施例および比較例は同じ）］に固定し、室温の塩化メチレンの洗浄槽中に浸漬し、３分間揺動させながら洗浄する。枠ごと取り出し垂直において塩化メチレンを取り除き、再度室温の塩化メチレンの洗浄槽中に浸漬し、３分間揺動させながら洗浄する。枠ごと取り出し垂直において塩化メチレンを取り除き、室温の塩化メチレンの洗浄槽中に浸漬し、３分間揺動させながら三度目の洗浄をする。洗浄・徐液した膜を室温で風乾して耐熱性ポリオレフィン微多孔膜を得る。その特性を表１に示す。
耐メルトダウン特性の評価試験結果、シャットダウン温度は、１３０℃付近で急激なインピーダンス値の上昇を示し３０００オーム以上を示したが、１５５℃付近でインピーダンス値が１００オームまで低下した。22.5% by weight of ultra high molecular weight polyethylene with a viscosity average molecular weight of 1.15 million, 13.8% by weight of ultra high molecular weight polyethylene with a viscosity average molecular weight of 3.1 million, 15.0% by weight of ultra high molecular weight polyethylene with a viscosity average molecular weight of 5.8 million 4-methyl-1-pentene-1-hexadecene-1-octadecene copolymer (MFR 260 ° C., 5 kg load, 21 g, 40.0% by weight of high-density polyethylene having a viscosity average molecular weight of 334,000 and a melting point peak of 224 ° C. / 10 min) 5.0% by weight and 1.2% by weight of Mitsui Chemicals Co., Ltd.'s Notio [grade name PN3560] as polyolefin elastomer resin, Mitsui Chemicals, Inc. as low molecular weight ethylene / butene copolymer Exelex [Grade name 48070B] manufactured by Polyolefin resin mixture consisting of 2.5% by weight 100.0 Tetrakis [methylene-3- (3,5-ditertiarybutyl-4-hydroxyphenyl) -propionate] methane 2.5 parts by weight and 3,9-bis (2,6-ditertiary as an antioxidant with respect to parts Butyl-4-methylphenoxy) -2,4,8,10-tetraoxa-3,9-diphosphapi [5,5] undecanlonylhydroxyphenyl) -propionate] 0.25 part by weight of methane, A polyolefin resin mixture is prepared having a calculated average melting point of 137 ° C. 34 parts by weight of the resin mixture was put into a twin screw extruder (cylinder diameter: 69 mm, screw length (L) to diameter (D) ratio L / D: 52.5, using a strong kneading type screw). A plasticizer comprising 66 parts by weight of liquid paraffin [68 cst (40 ° C.)] 83% by weight and polyoxyethylene stearyl ether (HLB2) 17% by weight is supplied from the side feeder of the twin screw extruder while heating, 220- A polyolefin / plasticizer mixed melt is prepared at 200 ° C. and 160 rpm. This is extruded from a T-die through a gear pump installed at the tip of a twin-screw extruder, and is taken out with a cooling roll to form a gel-like sheet molding. The resulting gel-like sheet molding is biaxially stretched using a tenter stretching machine. Next, it is fixed to a stainless steel frame plate [size: 20 cm × 30 cm (the following examples and comparative examples are the same)], immersed in a methylene chloride washing bath at room temperature, and washed with rocking for 3 minutes. Take out the entire frame, remove methylene chloride in the vertical direction, immerse it again in a methylene chloride washing bath at room temperature, and wash it while shaking for 3 minutes. Take out the entire frame, remove methylene chloride in the vertical direction, immerse it in a methylene chloride washing bath at room temperature, and wash it for the third time while shaking for 3 minutes. The washed and slowly-dried membrane is air-dried at room temperature to obtain a heat-resistant polyolefin microporous membrane. The characteristics are shown in Table 1.
As a result of the evaluation test of the melt-down resistance, the shutdown temperature showed a sudden increase in impedance value at around 130 ° C. and was 3000 ohms or higher, but the impedance value decreased to 100 ohms around 155 ° C.
粘度平均分子量が１１５万の超高分子量ポリエチレン２２．５重量％、粘度平均分子量が３１０万の超高分子量ポリエチレン１５．９重量％、粘度平均分子量が５８０万の超高分子量ポリエチレン１５．０重量％、粘度平均分子量が３３．４万の高密度ポリエチレン３０．０重量％、融点ピーク２２４℃を持つ４−メチル−１−ペンテン−１−ヘキサデセン−１−オクタデセン共重合体（ＭＦＲ ２６０℃ ５ｋｇ荷重 ２１ｇ／１０分）１１．３重量％とポリオレフィン系エラストマー樹脂として三井化学（株）社製のノティオ［グレード名ＰＮ３５６０］２．８重量％、低分子量エチレン・ブテン共重合物として三井化学（株）社製のエクセレックス［グレード名４８０７０Ｂ］２．５重量％とからなるポリオレフィン樹脂混合物１００．０重量部に対して酸化防止剤としてテトラキス［メチレン−３−（３，５−ジターシャリーブチル−４−ヒドロキシフェニル）−プロピオネート］メタン２．５重量部と３，９−ビス（２，６−ジターシャリーブチル−４−メチルフェノキシ）−２，４，８，１０−テトラオキサ−３，９−ジホスファピ［５，５］ウンデカンロニルヒドロキシフェニル）−プロピオネート］メタン０．２５重量部とを、ドライブレンドし、計算による平均融点が１４３℃のポリオレフィン樹脂混合物を調製する。当該樹脂混合物３３重量部を二軸押出機（シリンダ径：６９ｍｍ、スクリュの長さ（Ｌ）と直径（Ｄ）の比Ｌ／Ｄ＝５２．５、強混練タイプスクリュ使用）に投入し、この二軸押出機のサイドフィーダーから６７重量部の流動パラフィン［６８ｃｓｔ（４０℃）］８３重量％とポリオキシエチレンステアリルエーテル（ＨＬＢ２）１７重量％、からなる可塑剤を加熱しながら供給し、２２０−２００℃及び１６０ｒｐｍの条件でポリオレフィン・可塑剤混合溶融物を調製する。これを二軸押出機の先端に設置されたギアーポンプを介してＴダイから押し出し、冷却ロールで引き取りながら、ゲル状シート成形物を形成する。得らるゲル状シート成形物に対して、テンター延伸機を用いて、二軸延伸を施す。次いでステンレス製の枠板［サイズ：２０ｃｍ×３０ｃｍ、（以下の実施例および比較例は同じ）］に固定し、室温の塩化メチレンの洗浄槽中に浸漬し、３分間揺動させながら洗浄する。枠ごと取り出し垂直において塩化メチレンを取り除き、再度室温の塩化メチレンの洗浄槽中に浸漬し、３分間揺動させながら洗浄する。枠ごと取り出し垂直において塩化メチレンを取り除き、室温の塩化メチレンの洗浄槽中に浸漬し、３分間揺動させながら三度目の洗浄をする。洗浄・徐液した膜を室温で風乾して耐熱性ポリオレフィン微多孔膜を得る。その特性を表１に示す。
耐メルトダウン特性の評価試験結果、シャットダウン温度は、１３０℃付近で急激なインピーダンス値の上昇を示し３０００オーム以上を示したが、１６２℃付近でインピーダンス値が３００オームまで低下した。
表１から、実施例１〜９では、透気度、突刺し強度、引張破断強度、引張破断伸度及び耐熱収縮性のバランスに優れ、加熱圧縮後の膜厚変化率が小さい、電解液吸収性にも優れる表面粗度を有する耐熱性ポリオレフィン微多孔膜が得られることが分かる。22.5% by weight of ultra high molecular weight polyethylene with a viscosity average molecular weight of 1.15 million, 15.9% by weight of ultra high molecular weight polyethylene with a viscosity average molecular weight of 3.1 million, 15.0% by weight of ultra high molecular weight polyethylene with a viscosity average molecular weight of 5.8 million 4-methyl-1-pentene-1-hexadecene-1-octadecene copolymer (MFR 260 ° C., 5 kg load, 21 g, 30.0% by weight of high-density polyethylene having a viscosity average molecular weight of 334,000 and a melting point peak of 224 ° C. / 10 minutes) 11.3% by weight, 2.8% by weight of Mitsui Chemicals Co., Ltd. [grade name PN3560] as polyolefin elastomer resin, Mitsui Chemicals, Inc. as low molecular weight ethylene / butene copolymer Exelex [Grade name 48070B] manufactured by Polyolefin resin mixture 100.0 consisting of 2.5% by weight Tetrakis [methylene-3- (3,5-ditertiarybutyl-4-hydroxyphenyl) -propionate] methane 2.5 parts by weight and 3,9-bis (2,6-diter as an antioxidant with respect to parts by weight Dry blending with 0.25 parts by weight of (salibutyl-4-methylphenoxy) -2,4,8,10-tetraoxa-3,9-diphosphapi [5,5] undecanlonylhydroxyphenyl) -propionate] methane. A polyolefin resin mixture having a calculated average melting point of 143 ° C. is prepared. 33 parts by weight of the resin mixture was put into a twin-screw extruder (cylinder diameter: 69 mm, screw length (L) to diameter (D) ratio L / D = 52.5, using a strong kneading type screw). A plasticizer consisting of 67 parts by weight of liquid paraffin [68 cst (40 ° C.)] 83% by weight and polyoxyethylene stearyl ether (HLB2) 17% by weight is supplied while heating from the side feeder of the twin screw extruder. A polyolefin / plasticizer mixed melt is prepared at 200 ° C. and 160 rpm. This is extruded from a T-die through a gear pump installed at the tip of a twin-screw extruder, and is taken out with a cooling roll to form a gel-like sheet molding. The resulting gel-like sheet molding is biaxially stretched using a tenter stretching machine. Next, it is fixed to a stainless steel frame plate [size: 20 cm × 30 cm (the following examples and comparative examples are the same)], immersed in a methylene chloride washing bath at room temperature, and washed with rocking for 3 minutes. Take out the entire frame, remove methylene chloride in the vertical direction, immerse it again in a methylene chloride washing bath at room temperature, and wash it while shaking for 3 minutes. Take out the entire frame, remove methylene chloride in the vertical direction, immerse it in a methylene chloride washing bath at room temperature, and wash it for the third time while shaking for 3 minutes. The washed and slowly-dried membrane is air-dried at room temperature to obtain a heat-resistant polyolefin microporous membrane. The characteristics are shown in Table 1.
As a result of the evaluation test of the meltdown resistance, the shutdown temperature showed a sudden increase in impedance value at around 130 ° C. and was 3000 ohms or more, but the impedance value decreased to 300 ohms at around 162 ° C.
From Table 1, in Examples 1-9, it is excellent in the balance of air permeability, puncture strength, tensile breaking strength, tensile breaking elongation, and heat shrinkage resistance, and the rate of change in film thickness after heat compression is small. It can be seen that a heat-resistant polyolefin microporous membrane having a surface roughness that is also excellent in properties can be obtained.
本発明によれば高エネルギー密度化・高出力化・大型化した高性能なリチウムイオン二次電池に望まれる安全性の高い耐メルトダウン特性と他の良好なセパレータ特性を兼ね備え、セパレータとして取り扱いやすく、優れたリチウムイオン二次電池用セパレータとなる耐熱性ポリオレフィン微多孔膜とその製造方法の提供が可能となる。According to the present invention, the high-performance lithium-ion secondary battery with high energy density, high output, and large size has high safety meltdown resistance and other good separator characteristics, and is easy to handle as a separator. Thus, it becomes possible to provide a heat-resistant polyolefin microporous membrane that is an excellent separator for a lithium ion secondary battery and a method for producing the same.
１、ポリオレフィン混合物の平均融点（℃）
２、耐熱性ポリオレフィン微多孔膜のメルトダウン温度とノンメルトダウン温度（℃）1. Average melting point of polyolefin mixture (℃)
2. Meltdown temperature and non-meltdown temperature (℃) of heat-resistant polyolefin microporous membrane
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