JP2000143867A - Preparation of porous film for cell separator - Google Patents
Preparation of porous film for cell separatorInfo
- Publication number
- JP2000143867A JP2000143867A JP10328178A JP32817898A JP2000143867A JP 2000143867 A JP2000143867 A JP 2000143867A JP 10328178 A JP10328178 A JP 10328178A JP 32817898 A JP32817898 A JP 32817898A JP 2000143867 A JP2000143867 A JP 2000143867A
- Authority
- JP
- Japan
- Prior art keywords
- temperature
- resin composition
- molecular weight
- porous film
- battery separator
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
Classifications
-
- 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
【０００１】[0001]
【発明の属する技術分野】本発明は、電池セパレータ用
多孔質フィルムの製造方法に関し、更に詳しくは、リチ
ウム一次・二次電池、リチウムイオン一次・二次電池等
の非水溶媒系の電池セパレータ用多孔質フィルムの製造
方法に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a porous film for a battery separator, and more particularly to a method for producing a non-aqueous solvent battery separator such as a lithium primary / secondary battery and a lithium ion primary / secondary battery. The present invention relates to a method for producing a porous film.
【０００２】[0002]
【従来の技術】非化学反応性、軽量、高強度、微細多孔
質フィルム形成の容易さ等の特性からプラスチック多孔
質フィルムが電池セパレータ用に種々の形態で利用され
ている。特に、リチウムイオン電池用セパレータとして
は、安全性の面からポリエチレン製の微細多孔質フィル
ムが提案されている。2. Description of the Related Art Porous plastic films have been used in various forms for battery separators because of their characteristics such as non-chemical reactivity, light weight, high strength, and ease of forming microporous films. In particular, a polyethylene microporous film has been proposed as a lithium ion battery separator from the viewpoint of safety.
【０００３】例えば、特開平８−１３８６４４号公報に
は、粘度平均分子量３００万の超高分子量ポリエチレン
１２重量％、粘度平均分子量４８万の高分子量ポリエチ
レン２４重量％、重量平均分子量２０万のエチレン−プ
ロピレンラバー４重量％、微粉珪酸２１重量％及びジオ
クチルフタレート（ＤＯＰ）３９重量％からなるポリエ
チレン系樹脂組成物をＴダイ法による押出成形によって
厚さ８０μｍのフィルム状に成形し、１，１，１−トリ
クロロエタン中に浸漬してＤＯＰを抽出し、次いで、苛
性ソーダ水溶液中に浸漬して微粉珪酸を抽出し乾燥した
後、延伸して微多孔質膜からなる電池セパレータを作製
する技術が開示されている。For example, Japanese Patent Application Laid-Open No. 8-138644 discloses that 12% by weight of ultrahigh molecular weight polyethylene having a viscosity average molecular weight of 3,000,000, 24% by weight of high molecular weight polyethylene having a viscosity average molecular weight of 480,000, and ethylene glycol having a weight average molecular weight of 200,000. A polyethylene-based resin composition comprising 4% by weight of propylene rubber, 21% by weight of finely divided silicic acid and 39% by weight of dioctyl phthalate (DOP) was formed into a film having a thickness of 80 μm by extrusion using a T-die method. A technique is disclosed in which DOP is extracted by immersion in trichloroethane, then immersed in an aqueous solution of caustic soda to extract fine silica powder, dried, and then stretched to produce a battery separator composed of a microporous membrane. .
【０００４】超高分子量ポリエチレンとこれより低い分
子量の他のポリエチレン系樹脂とのブレンド品について
は、超高分子量ポリエチレン以外のポリエチレン系樹脂
でシャットダウン性能を持たせ、超高分子量ポリエチレ
ンで過昇温時の電池セパレータの形状保持性を持たせよ
うとする構成である。然るに、超高分子量ポリエチレン
は、これより低い分子量の汎用のポリエチレン系樹脂に
比して溶融粘度が非常に高く成形困難な樹脂であり、こ
れらのポリエチレン系樹脂組成物を薄い多孔質フィルム
状の電池セパレータとするために、上記のように、超高
分子量ポリエチレンとこれより低い分子量の他のポリエ
チレン系樹脂に加えて、可塑剤や微粉珪酸を添加して成
形性を容易にした上でフィルム状に押出成形し、得られ
たフィルム状ポリエチレン系樹脂組成物から可塑剤及び
微粉珪酸を抽出除去しているのである。[0004] For blends of ultra-high molecular weight polyethylene with other polyethylene resins having a lower molecular weight, a polyethylene resin other than ultra-high molecular weight polyethylene is provided with a shut-down performance, and ultra-high molecular weight polyethylene is used when overheating. This is a configuration in which the shape of the battery separator is maintained. However, ultra-high molecular weight polyethylene is a resin having a very high melt viscosity that is difficult to mold as compared with general-purpose polyethylene resins having a lower molecular weight, and these polyethylene resin compositions are used in thin porous film batteries. As described above, in addition to ultra-high molecular weight polyethylene and other polyethylene resins having a lower molecular weight, as described above, a plasticizer or fine silica powder is added to facilitate molding and form a film. The plasticizer and the finely divided silica are extracted and removed from the extruded and obtained film-like polyethylene resin composition.
【０００５】上記電池セパレータにあっては、得られた
多孔質フィルム中に可塑剤が残存すると、電池セパレー
タの物性が低下するおそれがあるので、これら可塑剤の
抽出除去のため膨大な設備と面倒な工程を設けなけねば
ならないという問題点を有するものであった。又、フィ
ルム状ポリエチレン系樹脂組成物から抽出された可塑剤
及び微粉珪酸を抽出液から分離する工程も同様に設備と
面倒な工程を要するものである。[0005] In the above battery separator, if a plasticizer remains in the obtained porous film, the physical properties of the battery separator may be degraded. However, there is a problem that a complicated process must be provided. In addition, the step of separating the plasticizer and the fine silica powder extracted from the film-like polyethylene-based resin composition from the extract also requires equipment and complicated steps.
【０００６】更に、リチウムイオン電池用のセパレータ
にあっては、現行の厚さは２５μｍ程度であるが、単位
体積当たりの電池の電気容量を増大させるために、更な
る薄肉化が要望されている。電池セパレータの薄肉化
は、これまで、機械的強度が得に難いことやハンドリン
グ性が悪くなること等が隘路となって実現されていなか
った。Further, the current thickness of a separator for a lithium ion battery is about 25 μm. However, in order to increase the electric capacity of the battery per unit volume, further reduction in thickness is required. . Up to now, the thinning of the battery separator has not been realized because of the difficulty in obtaining the mechanical strength and the poor handling property, etc., as a bottleneck.
【０００７】[0007]
【発明が解決しようとする課題】本発明は、叙上の事実
に鑑みなされたものであって、その目的は、可塑剤の抽
出や回収の厄介な工程を要しない生産性の高い製造方法
であって、微細で均一な多孔質構造を有し、且つ、十分
な強度を有する非水溶媒系の電池セパレータ用多孔質フ
ィルムの製造方法を提供することにある。SUMMARY OF THE INVENTION The present invention has been made in view of the above facts, and has as its object to provide a highly productive production method which does not require a cumbersome step of extracting and recovering a plasticizer. It is another object of the present invention to provide a method for producing a nonaqueous solvent-based porous film for a battery separator having a fine and uniform porous structure and having sufficient strength.
【０００８】[0008]
【課題を解決するための手段】請求項１記載の発明の電
池セパレータ用多孔質フィルムの製造方法は、粘度平均
分子量が１００万以上の超高分子量ポリエチレンと粘度
平均分子量が１０万以上１００万未満のオレフィン系熱
可塑性樹脂からなるオレフィン系樹脂組成物に、常温常
圧のもとで気体状態の非反応性ガスを高圧下で溶解した
発泡性樹脂組成物を、加熱溶融し、該発泡性樹脂組成物
の〔（降温時の結晶化ピーク温度）−３０℃〕〜（降温
時の結晶化ピーク温度）の温度範囲で、押出成形金型か
ら賦形して押出し、該発泡性樹脂組成物の融点未満の温
度で、少なくとも一軸に延伸することを特徴とする。According to the first aspect of the present invention, there is provided a method for producing a porous film for a battery separator, comprising an ultrahigh molecular weight polyethylene having a viscosity average molecular weight of 1,000,000 or more and a viscosity average molecular weight of 100,000 or more and less than 1,000,000. A foamable resin composition obtained by dissolving a non-reactive gas in a gaseous state at normal temperature and pressure under high pressure in an olefin resin composition comprising The composition is extruded in a temperature range of [(crystallization peak temperature at the time of cooling) -30 ° C.] to (crystallization peak temperature at the time of cooling) from an extrusion mold and extruded. It is characterized in that it is stretched at least uniaxially at a temperature lower than the melting point.
【０００９】請求項２記載の発明の電池セパレータ用多
孔質フィルムの製造方法は、請求項１記載の電池セパレ
ータ用多孔質フィルムの製造方法において、常温常圧の
もとで気体状態の非反応性ガスが二酸化炭素であるもの
である。According to a second aspect of the present invention, there is provided a method for producing a porous film for a battery separator according to the first aspect of the present invention, wherein the non-reactive material is a gaseous non-reactive material at normal temperature and normal pressure. The gas is carbon dioxide.
【００１０】本発明で用いられる超高分子量ポリエチレ
ンは、粘度平均分子量が１００万以上のポリエチレンで
あり、電池セパレータ構成上、形状保持のための強度付
与因子であり、就中、電池に過電流が流れ、異常昇温し
た際等の電池セパレータの形状保持に寄与するものであ
る。粘度平均分子量が１００万未満では、上記異常昇温
時等において、機械的強度が低下し、形状保持し得なく
なるおそれがある。又、粘度平均分子量は、１００万を
一桁以上極端に超えれば、成形性が悪化し使用不可とな
るが、かかる超々高分子量ポリエチレンは特定の用途以
外に殆ど市販の商品として存在しないので上限を設けて
いない。The ultra-high molecular weight polyethylene used in the present invention is a polyethylene having a viscosity average molecular weight of 1,000,000 or more, and is a strength-imparting factor for maintaining the shape in terms of the structure of a battery separator. This contributes to maintaining the shape of the battery separator when the flow or abnormal temperature rise occurs. If the viscosity average molecular weight is less than 1,000,000, the mechanical strength may be reduced at the time of the abnormal temperature rise, and the shape may not be maintained. Also, if the viscosity average molecular weight is extremely more than one million or more, the moldability is deteriorated and it becomes impossible to use.However, since such ultra-high molecular weight polyethylene hardly exists as a commercial product except for specific applications, the upper limit is set. Not provided.
【００１１】オレフィン系熱可塑性樹脂は、粘度平均分
子量が１０万以上１００万未満のオレフィン系熱可塑性
樹脂であり、電池セパレータ構成上、比較的低温におけ
るシャットダウン機能付与因子である。粘度平均分子量
が１０万未満では、得られる電池セパレータ用多孔質フ
ィルムの機械的強度が低下し、１００万以上では、シャ
ットダウン機能が低下するので上記範囲に限定される。
これらのオレフィン系熱可塑性樹脂としては、上記範囲
の粘度平均分子量を有するものであれば特に限定される
ものではないが、例えば、エチレン、プロピレン、１−
ブテン、４−メチル−１−ペンテン、１−ヘキセン等の
エチレン及びα−オレフィンの単独重合体もしくは共重
合体からなる結晶性熱可塑性樹脂が挙げられる。これら
は単独で用いられてもよいが、２種以上が併用されても
よい。中でも、高密度ポリエチレンは、上記するシャッ
トダウン機能と機械的強度とをバランスよく付与するこ
とができるので、好適に用いられる。The olefin-based thermoplastic resin is an olefin-based thermoplastic resin having a viscosity average molecular weight of 100,000 or more and less than 1,000,000, and is a factor for imparting a shutdown function at a relatively low temperature in terms of the structure of a battery separator. If the viscosity average molecular weight is less than 100,000, the mechanical strength of the resulting porous film for a battery separator is reduced. If the viscosity average molecular weight is 1,000,000 or more, the shutdown function is reduced.
The olefin-based thermoplastic resin is not particularly limited as long as it has a viscosity average molecular weight in the above range. For example, ethylene, propylene, 1-
A crystalline thermoplastic resin comprising a homopolymer or a copolymer of ethylene and an α-olefin such as butene, 4-methyl-1-pentene and 1-hexene is exemplified. These may be used alone or in combination of two or more. Among them, high-density polyethylene is preferably used because it can provide the above-mentioned shutdown function and mechanical strength in a well-balanced manner.
【００１２】粘度平均分子量が１００万以上の超高分子
量ポリエチレンと粘度平均分子量が１０万以上１００万
未満のオレフィン系熱可塑性樹脂の配合比率は、電池の
種類や電池セパレータのサイズ、用いられる超高分子量
ポリエチレン及びオレフィン系熱可塑性樹脂の性状によ
って、決定されるものであって特に限定されるものでは
ないが、好ましくは、粘度平均分子量が１００万以上の
超高分子量ポリエチレンが１０〜６０重量％である。上
記配合比率が１０重量％未満では、得られる電池セパレ
ータ用多孔質フィルムの機械的強度が低下し、就中、過
昇温時の形状保持性が悪くなる。又、６０重量％を超え
ると、シャットダウン機能が低下する。The mixing ratio of the ultrahigh molecular weight polyethylene having a viscosity average molecular weight of 1,000,000 or more and the olefinic thermoplastic resin having a viscosity average molecular weight of 100,000 or more and less than 1,000,000 depends on the type of the battery, the size of the battery separator, and the ultrahigh molecular weight used. It is determined by the properties of the high molecular weight polyethylene and the olefinic thermoplastic resin and is not particularly limited, but preferably, the ultrahigh molecular weight polyethylene having a viscosity average molecular weight of 1,000,000 or more is 10 to 60% by weight. is there. If the mixing ratio is less than 10% by weight, the mechanical strength of the obtained porous film for a battery separator decreases, and in particular, the shape retention at the time of excessive temperature rise deteriorates. On the other hand, if it exceeds 60% by weight, the shutdown function deteriorates.
【００１３】本発明で用いられる常温常圧のもとで気体
状態の非反応性ガスとは、電池セパレータ用多孔質フィ
ルムの製造工程中において、超高分子量ポリエチレンや
オレフィン系熱可塑性樹脂と実質的に反応を起こさず、
これら樹脂を著しく劣化させないものであれば、特に限
定されるものではないが、例えば、窒素、二酸化炭素等
の無機ガス、フロンガス、低分子量の炭化水素等の有機
ガスが挙げられる。これらは単独で用いられてもよい
が、２種以上が併用されてもよい。中でも、二酸化炭素
は、超高分子量ポリエチレン及びオレフィン系熱可塑性
樹脂からなる上記オレフィン系樹脂組成物に対する溶解
度が高く、該オレフィン系樹脂組成物の溶融粘度を大幅
に低下させることができるので好適に用いられる。The non-reactive gas in a gaseous state at normal temperature and normal pressure used in the present invention is substantially mixed with ultra-high molecular weight polyethylene or olefinic thermoplastic resin during the production process of the porous film for a battery separator. Does not react to
The resin is not particularly limited as long as it does not significantly deteriorate the resin, and examples thereof include an inorganic gas such as nitrogen and carbon dioxide, and an organic gas such as a fluorocarbon gas and a low molecular weight hydrocarbon. These may be used alone or in combination of two or more. Among them, carbon dioxide is preferably used because it has a high solubility in the olefin resin composition comprising the ultrahigh molecular weight polyethylene and the olefin thermoplastic resin and can greatly reduce the melt viscosity of the olefin resin composition. Can be
【００１４】上記オレフィン系樹脂組成物に溶解させる
上記非反応性ガスの添加比率は、電池の種類や電池セパ
レータのサイズ、用いられるオレフィン系樹脂組成物及
び非反応性ガスの性状によって、決定されるものであっ
て特に限定されるものではないが、上記非反応性ガスが
二酸化炭素である場合、好ましくは、３〜５０重量％、
より好ましくは５〜３０重量％である。上記非反応性ガ
スの添加比率が３重量％未満では、上記オレフィン系樹
脂組成物をフィブリル化し、均一な多孔質構造を形成す
ることが難しくなり、５０重量％を超えると、添加した
非反応性ガスを上記オレフィン系樹脂組成物中に溶解さ
せるために、溶解圧力を高くする必要があり、大がかり
な設備を要し、経済性を低下させる。The ratio of the non-reactive gas to be dissolved in the olefin resin composition is determined by the type of the battery, the size of the battery separator, the properties of the olefin resin composition and the non-reactive gas used. Although it is not particularly limited, when the non-reactive gas is carbon dioxide, preferably 3 to 50% by weight,
More preferably, it is 5 to 30% by weight. If the addition ratio of the non-reactive gas is less than 3% by weight, it becomes difficult to fibrillate the olefin-based resin composition to form a uniform porous structure. In order to dissolve the gas in the olefin-based resin composition, it is necessary to increase the dissolving pressure, which requires large-scale equipment and lowers economic efficiency.
【００１５】上記オレフィン系樹脂組成物に非反応性ガ
スを高圧下で溶解させる。上記非反応性ガスの溶解は、
非反応性ガスの超臨界状態で行われることが好ましい。
超臨界状態とは、臨界温度及び臨界圧力以上の状態を指
し、例えば、二酸化炭素では、３１℃以上、７．３ＭＰ
ａ以上の状態である。A non-reactive gas is dissolved in the olefin resin composition under high pressure. The dissolution of the non-reactive gas
Preferably, the reaction is performed in a supercritical state of a non-reactive gas.
The supercritical state refers to a state in which the temperature is equal to or higher than a critical temperature and a critical pressure.
a or higher.
【００１６】上記非反応性ガスを超臨界状態で溶解させ
ることによる利点は、上記オレフィン系発泡性樹脂組成
物を脱圧してこれらの非反応性ガスを揮散させて上記オ
レフィン系発泡性樹脂組成物をフィブリル化し、多孔質
化するに際して、上記非反応性ガスをオレフィン系発泡
性樹脂組成物中により均一に溶解し易くし、脱圧によっ
てより均一にして微細なオレフィン系樹脂組成物のフィ
ブリル化構造を形成し得るようにするところにある。The advantage of dissolving the non-reactive gas in a supercritical state is that the olefin-based foamable resin composition is depressurized and the non-reactive gas is volatilized to form the olefin-based foamable resin composition. When fibrillating and making porous, the above-mentioned non-reactive gas is more easily dissolved in the olefin-based foamable resin composition more easily, and the pressure is reduced to make the non-reactive gas more uniform and the fibrillated structure of the fine olefin-based resin composition is reduced. Is to be formed.
【００１７】上記非反応性ガスを溶解したオレフィン系
発泡性樹脂組成物は、押出成形機によって、オレフィン
系発泡性樹脂組成物の融点以上に加熱され、一旦、該樹
脂組成物の結晶構造は融解され、然る後、該発泡性樹脂
組成物の〔（降温時の結晶化ピーク温度）−３０℃〕〜
（降温時の結晶化ピーク温度）の温度範囲で、押出成形
金型から溶融押出され、シート状に賦形され、該樹脂組
成物の融点未満の温度で、少なくとも一軸に延伸され
て、フィブリル化し、均一にして微細なオレフィン系樹
脂組成物の多孔質皮膜からなる電池セパレータが作製さ
れる。尚、降温時の結晶化ピーク温度及び融点は、示差
走査型熱量計（ＤＳＣ）によって測定された値である。The olefinic foamable resin composition in which the non-reactive gas is dissolved is heated by an extruder to a temperature equal to or higher than the melting point of the olefinic foamable resin composition, and once the crystal structure of the resin composition is melted. After that, the foamable resin composition [((crystallization peak temperature at the time of temperature decrease) -30 ° C.])
In a temperature range of (a crystallization peak temperature at the time of temperature decrease), the resin composition is melt-extruded from an extrusion mold, shaped into a sheet, and stretched at least uniaxially at a temperature lower than the melting point of the resin composition to fibrillate. Thus, a battery separator made of a uniform and fine porous film of the olefin resin composition is produced. In addition, the crystallization peak temperature and the melting point at the time of temperature fall are the values measured by the differential scanning calorimeter (DSC).
【００１８】溶融されたオレフィン系発泡性樹脂組成物
は、押出成形金型から降温時の結晶化ピーク温度を超え
る温度で溶融押出される場合には、破泡により巨大な気
泡が混在し、均一にして微細なオレフィン系樹脂組成物
の多孔質体を形成し難くなり、〔（降温時の結晶化ピー
ク温度）−３０℃〕未満の温度で溶融押出される場合に
は、オレフィン系発泡性樹脂組成物の粘度が高くなっ
て、脱圧による体積膨張の度合が低く、気孔率の低い多
孔質体となってしまう。When the melted olefin-based foamable resin composition is melt-extruded from an extrusion mold at a temperature exceeding the crystallization peak temperature at the time of cooling, huge bubbles are mixed due to foam breakage, resulting in uniformity. When it is melt-extruded at a temperature lower than [(crystallization peak temperature at the time of temperature decrease) -30 ° C], the olefin foamable resin is hardly formed. The viscosity of the composition increases, and the degree of volume expansion due to depressurization is low, resulting in a porous body having a low porosity.
【００１９】押出成形金型から溶融押出されてシート状
に賦形されたオレフィン系樹脂多孔質体は、該樹脂組成
物の融点未満の温度で、少なくとも一軸に延伸されるこ
とによって、スキン層が形成された場合であっても、表
面層まで均一に連通化した多孔質構造となり、且つ、高
強度化される。上記延伸温度が、樹脂組成物の融点以上
の温度であると、上記オレフィン系発泡性樹脂組成物が
脱圧されて形成された多孔質構造が損なわれるおそれが
あり、又、延伸時の延伸皮膜の破断が起こり易くなるの
で、融点未満の温度で延伸される。しかし、延伸温度が
余り低いと、延伸倍率の自由度が低下し、就中、薄肉の
電池セパレータ用多孔質フィルムの作製が困難となる。
例えば、厚さ５０μｍ以下の電池セパレータ用多孔質フ
ィルムを作製する場合には、８０℃又はこれ以上の温度
で延伸される。The olefin resin porous body melt-extruded from the extrusion mold and shaped into a sheet is stretched at least uniaxially at a temperature lower than the melting point of the resin composition, whereby the skin layer is formed. Even if it is formed, it becomes a porous structure uniformly connected to the surface layer, and the strength is increased. If the stretching temperature is a temperature equal to or higher than the melting point of the resin composition, the porous structure formed by depressurizing the olefin-based foamable resin composition may be damaged, and the stretched film during stretching may be damaged. Since the glass is easily broken, the film is stretched at a temperature lower than the melting point. However, when the stretching temperature is too low, the degree of freedom of the stretching ratio is reduced, and it is particularly difficult to produce a thin porous film for a battery separator.
For example, when producing a porous film for a battery separator having a thickness of 50 μm or less, the film is stretched at a temperature of 80 ° C. or higher.
【００２０】上記延伸手段は、特に限定されるものでは
ないが、例えば、縦もしくは横一軸延伸法であってもよ
く、逐次もしくは同時二軸延伸法であってもよい。又、
これらに用いられる延伸装置としては、例えば、ロール
延伸方式、テンター延伸方式等の延伸装置が挙げられ、
これらは単独で用いられてもよいが、適宜組み合わせて
用いられてもよい。The stretching means is not particularly limited, but may be, for example, a longitudinal or transverse uniaxial stretching method, or may be a sequential or simultaneous biaxial stretching method. or,
Examples of the stretching apparatus used for these include, for example, a stretching apparatus such as a roll stretching method and a tenter stretching method.
These may be used alone or in combination as appropriate.
【００２１】上記延伸倍率は、電池セパレータのサイ
ズ、用途及び用いられるオレフィン系発泡性樹脂組成物
の種類によって決められるものであって特に限定される
ものではないが、一軸延伸の場合、好ましくは２倍以上
であり、より好ましくは３倍以上であり、二軸延伸され
る場合には、各方向に２倍以上、面積倍率で４倍以上ガ
好ましい。The stretching ratio is determined according to the size and use of the battery separator and the type of the olefin-based foamable resin composition to be used, and is not particularly limited. When it is biaxially stretched, it is preferably at least two times in each direction and at least four times the area magnification.
【００２２】得られる電池セパレータ用多孔質フィルム
における、フィブリル化された平均ファイバー径は、
０．０１〜２μｍφであり、これらのフィブリル化され
たファイバーは三次元網目状構造からなり、気孔率２０
〜８０％程度の多孔質体を構成している。電池セパレー
タ用多孔質フィルムの気孔率は、オレフィン系樹脂組成
物に溶解させる非反応性ガス量、脱圧時の温度・圧力プ
ロファイル、延伸条件等によって制御することができ、
電池の種類や用途によって適宜設定されるが、リチウム
イオン電池用セパレータ用多孔質フィルムとしては、２
０〜８０％の範囲が好ましい。この場合、気孔率が２０
％未満であると、電気抵抗値が大きくなり、８０％を超
えると、引張強さや突刺強度等の機械的強度が低下し、
いずれも好ましくない。The average fibrillated fiber diameter in the obtained porous film for battery separator is as follows:
0.01 to 2 μmφ, and these fibrillated fibers have a three-dimensional network structure and a porosity of 20 μm.
It constitutes about 80% of the porous body. The porosity of the porous film for a battery separator can be controlled by the amount of a non-reactive gas to be dissolved in the olefin resin composition, the temperature / pressure profile at the time of depressurization, stretching conditions, and the like.
Depending on the type and use of the battery, it is appropriately set.
A range from 0 to 80% is preferred. In this case, the porosity is 20
%, The electrical resistance increases, and if it exceeds 80%, the mechanical strength such as tensile strength and puncture strength decreases,
Neither is preferred.
【００２３】得られる電池セパレータ用多孔質フィルム
の厚さは、電池セパレータのサイズ、用途及び用いられ
るオレフィン系発泡性樹脂組成物の種類によって決めら
れるものであって特に限定されるものではないが、例え
ば、リチウムイオン電池用セパレータとしては、好まし
くは５〜５０μｍである。The thickness of the obtained porous film for a battery separator is determined by the size and use of the battery separator and the type of the olefin-based foamable resin composition to be used, and is not particularly limited. For example, the thickness of the separator for a lithium ion battery is preferably 5 to 50 μm.
【００２４】又、得られる電池セパレータ用多孔質フィ
ルムの引張強さは、例えば、リチウムイオン電池用セパ
レータの場合、一軸延伸されたもので１５０ＭＰａ以
上、二軸延伸されたもので８０ＭＰａ以上であり、通常
の電池セパレータに比して高強度、高剛性となってお
り、且つ、従来の電池セパレータ用多孔質フィルムに比
して大幅な薄肉化が実現される。The tensile strength of the resulting porous film for a battery separator is, for example, 150 MPa or more for uniaxially stretched and 80 MPa or more for biaxially stretched lithium ion battery separators. It has high strength and high rigidity as compared with a normal battery separator, and can achieve a significant reduction in thickness as compared with a conventional porous film for a battery separator.
【００２５】本発明の電池セパレータ用多孔質フィルム
の製造方法は、上述のように構成されており、得られる
電池セパレータ用多孔質フィルムは、均一にして微細な
多孔質体からなり、十分な強度を有し、更に薄肉化の可
能性を有するものである。こうした優れた性能を発現す
る理由については明確ではないが、高圧下でオレフィン
系樹脂組成物に溶解された非反応性ガスが、押出成形
時、オレフィン系樹脂組成物に対して可塑剤的に作用す
ると共に、脱圧時に発泡剤としてオレフィン系樹脂組成
物のフィブリル化を促進して三次元網目状構造の多孔質
体を構成するものと推定される。更に、非反応性ガスの
溶解を超臨界状態で行うことによって、より均一にして
微細な多孔質体とすることができるものであり、生産性
の高い電池セパレータ用多孔質フィルムの製造方法であ
る。The method for producing a porous film for a battery separator of the present invention is constituted as described above. The obtained porous film for a battery separator is made of a uniform and fine porous body and has a sufficient strength. And the possibility of further thinning. It is not clear why such excellent performance is exhibited, but the non-reactive gas dissolved in the olefin resin composition under high pressure acts as a plasticizer on the olefin resin composition during extrusion molding. At the same time, it is presumed that fibrillation of the olefin resin composition is promoted as a foaming agent at the time of depressurization to form a porous body having a three-dimensional network structure. Furthermore, by performing the dissolution of the non-reactive gas in a supercritical state, it is possible to obtain a more uniform and fine porous body, which is a method for producing a porous film for a battery separator with high productivity. .
【００２６】[0026]
【発明の実施の形態】以下に実施例を挙げて本発明を更
に詳しく説明するが、本発明はこれら実施例に限定され
るものではない。DESCRIPTION OF THE PREFERRED EMBODIMENTS 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.
【００２７】図１は、本発明を実施するための製造装置
の一部、押出成形機の概念図であり、押出機のバレル内
の左側フィーディングゾーン及び中央部付近のベントゾ
ーンに各々開口する非反応性ガス供給ラインが設けられ
ている。１及び１’は、ガスボンベであり、各々加圧ポ
ンプ２及び２’によって非反応性ガスをガス供給口（フ
ィーディングゾーン）３及びガス供給口（ベントゾー
ン）３’に圧入される。FIG. 1 is a conceptual view of an extruder, which is a part of a manufacturing apparatus for carrying out the present invention, and is opened to a left feeding zone in a barrel of the extruder and a vent zone near a central portion. A non-reactive gas supply line is provided. Reference numerals 1 and 1 'denote gas cylinders, and pressurized pumps 2 and 2' press non-reactive gases into a gas supply port (feeding zone) 3 and a gas supply port (vent zone) 3 '.
【００２８】４はホッパーであり、オレフィン系樹脂組
成物が押出機のバレル内に供給され、加熱されながらバ
レル内を連続して移送され、超臨界状態においてバレル
内に圧入された非反応性ガスを溶解して金型５に到り、
シート状に賦形されて常圧の大気中に脱圧されて発泡
し、多孔質フィルム６を形成する。Reference numeral 4 denotes a hopper, in which an olefin resin composition is supplied into a barrel of an extruder, is continuously transferred through the barrel while being heated, and is injected into the barrel in a supercritical state by a non-reactive gas. To reach the mold 5,
It is shaped into a sheet, depressurized into atmospheric air at normal pressure and foamed, forming a porous film 6.
【００２９】（実施例）超高分子量ポリエチレン（三井
石油化学社製、商品名「ハイゼックス・ミリオン２４９
Ｍ」、粘度平均分子量２３０万、融点１３６℃、降温時
の結晶化ピーク温度１１８℃）２０重量部と高密度ポリ
エチレン（三井石油化学社製、商品名「ハイゼックス８
０００ＦＰ」、粘度平均分子量４０万、融点１３０℃、
降温時の結晶化ピーク温度１１４℃）８０重量部からな
るオレフィン系樹脂組成物及び非反応性ガスとして二酸
化炭素を、図１に示す構成の押出成形機を用いて厚さ
０．４ｍｍ、直径７０ｍｍの環状フィルムを成形した。(Example) Ultra high molecular weight polyethylene (trade name "HIZEX MILLION 249" manufactured by Mitsui Petrochemical Co., Ltd.)
M ", a viscosity average molecular weight of 2.3 million, a melting point of 136 ° C., a crystallization peak temperature of 118 ° C. upon cooling, 20 parts by weight, and a high-density polyethylene (manufactured by Mitsui Petrochemical Co., Ltd., trade name“ HIZEX8
000FP ", viscosity average molecular weight 400,000, melting point 130 ° C,
(Crystalization peak temperature at the time of cooling: 114 ° C.) An olefin-based resin composition consisting of 80 parts by weight and carbon dioxide as a non-reactive gas were 0.4 mm thick and 70 mm in diameter using an extruder having the structure shown in FIG. Was formed.
【００３０】押出成形機は、単軸スクリュー（Ｌ／Ｄ＝
３０）、バレル設定温度２００℃、スクリュー回転数３
０ｒｐｍ、金型先端樹脂温度１１０℃で、押出量２ｋｇ
／時で押出し、非反応性ガスは、ガス供給口（フィーデ
ィングゾーン）３及びガス供給口（ベントゾーン）３’
より３００ｋｇ／ｃｍ2 の圧力で圧入した。The extruder is a single screw (L / D =
30), barrel setting temperature 200 ° C, screw rotation speed 3
0 rpm, resin temperature at the tip of the mold is 110 ° C, and the extrusion rate is 2 kg
Per hour, the non-reactive gas is supplied to the gas supply port (feeding zone) 3 and the gas supply port (vent zone) 3 ′.
The pressure was increased by 300 kg / cm 2 .
【００３１】得られた環状フィルムを長さ方向にスリッ
トしてシート状に開き、二軸延伸機を用いて、延伸温度
１２０℃で４×４倍に延伸し、厚さ２５μｍの電池セパ
レータ用多孔質フィルムを作製した。得られた電池セパ
レータ用多孔質フィルムの断面を顕微鏡観察し、フィブ
リル化したファイバー径が０．０３〜０．５μｍの三次
元網目状の多孔質構造が認められた。気孔率は４１．３
％、引張強さは１８１ＭＰａであった。又、ガーレー式
デンソメータを用いて通気度を測定した結果、３９０ｓ
ｅｃ／１００ｍｌであった。The obtained annular film is slit in the longitudinal direction, opened in the form of a sheet, stretched 4 × 4 times at a stretching temperature of 120 ° C. using a biaxial stretching machine to form a 25 μm thick porous film for a battery separator. A quality film was prepared. A cross section of the obtained porous film for a battery separator was observed with a microscope, and a three-dimensional mesh-like porous structure having a fibrillated fiber diameter of 0.03 to 0.5 μm was observed. Porosity is 41.3
%, And the tensile strength was 181 MPa. In addition, as a result of measuring the air permeability using a Gurley type densometer, 390 s
ec / 100 ml.
【００３２】（比較例１）金型先端樹脂温度を１２５℃
に変更したこと以外、実施例と同様にして押出成形した
が、脱圧発泡時に、部分的に巨大気泡の発生が多く、電
池セパレータ用多孔質フィルムは得られなかった。(Comparative Example 1) The temperature of the resin at the tip of the mold was 125 ° C.
Extrusion molding was carried out in the same manner as in Example, except that the large amount of large bubbles was generated partially during depressurization foaming, and a porous film for a battery separator could not be obtained.
【００３３】（比較例２）金型先端樹脂温度を７０℃に
変更したこと以外、実施例と同様にして電池セパレータ
用多孔質フィルムを作製した。得られた電池セパレータ
用多孔質フィルムの断面を顕微鏡観察し、フィブリル化
したファイバー径が０．０２〜０．８μｍの三次元網目
状の多孔質構造が認められた。気孔率は１７．３％、引
張強さは１９３ＭＰａであった。又、ガーレー式デンソ
メータを用いて通気度を測定したが、通気しなかった。Comparative Example 2 A porous film for a battery separator was produced in the same manner as in Example except that the temperature of the resin at the tip of the mold was changed to 70 ° C. The cross section of the obtained porous film for a battery separator was observed under a microscope, and a three-dimensional network porous structure having a fibrillated fiber diameter of 0.02 to 0.8 μm was observed. The porosity was 17.3% and the tensile strength was 193 MPa. The air permeability was measured using a Gurley type densometer, but no air was permeated.
【００３４】（比較例２）延伸温度を１５０℃に変更し
たこと以外、実施例と同様にして電池セパレータ用多孔
質フィルムを作製した。しかし、延伸時にしばしばフィ
ルムの切断トラブルが発生し、経済性のある電池セパレ
ータ用多孔質フィルムの製造はできなかった。Comparative Example 2 A porous film for a battery separator was produced in the same manner as in Example except that the stretching temperature was changed to 150 ° C. However, troubles in cutting the film often occurred during stretching, and it was not possible to produce an economical porous film for a battery separator.
【００３５】[0035]
【発明の効果】本発明の電池セパレータ用多孔質フィル
ムの製造方法は、以上のように構成されているので、得
られる電池セパレータ用多孔質フィルムは、均一にして
微細な多孔質体からなり、十分な強度を有し、更に薄肉
化の可能性を有するものである。しかも、通常の気体圧
入式押出発泡機を用いて生産性高く製造することができ
る。According to the method for producing a porous film for a battery separator of the present invention as described above, the obtained porous film for a battery separator is made of a uniform and fine porous body. It has sufficient strength and has a possibility of further thinning. In addition, it can be manufactured with high productivity by using a normal gas injection type extrusion foaming machine.
【図１】本発明を実施するための押出成形機の概念図で
ある。FIG. 1 is a conceptual diagram of an extrusion molding machine for carrying out the present invention.
１、１’：ガスボンベ ２、２’：かあつポンプ ３：ガス供給部（フィーディングゾーン） ３’：ガス供給部（ベントゾーン） ４：ホッパー ５：金型 ６：多孔質フィルム（環状） 1, 1 ': Gas cylinder 2, 2': Gas pump 3: Gas supply unit (feeding zone) 3 ': Gas supply unit (vent zone) 4: Hopper 5: Mold 6: Porous film (annular)
───────────────────────────────────────────────────── フロントページの続き (51)Int.Cl.7 識別記号 ＦＩ テーマコート゛(参考） // Ｂ２９Ｋ 23:00 105:04 Ｆターム(参考） 4F071 AA15 AA20 AA21 AB01 AB17 AB22 AC02 AC03 AE01 AG21 AH15 BA01 BB06 BB07 BC01 BC17 4F074 AA16 AA17 AB01 BA32 CA02 CA03 CA22 CA24 CC02Z CC03X CC04X CC34X DA02 DA49 4J002 BB03W BB03X BB04X BB12X BB14X BB15X BB17X DE016 DF006 EA016 EB066 GQ01 5H021 BB01 BB02 BB05 BB19 CC00 EE04 EE37 HH06 HH07 ──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. 7 Identification symbol FI Theme coat ゛ (Reference) // B29K 23:00 105: 04 F term (Reference) 4F071 AA15 AA20 AA21 AB01 AB17 AB22 AC02 AC03 AE01 AG21 AH15 BA01 BB06 BB07 BC01 BC17 4F074 AA16 AA17 AB01 BA32.
Claims (2)
子量ポリエチレンと粘度平均分子量が１０万以上１００
万未満のオレフィン系熱可塑性樹脂からなるオレフィン
系樹脂組成物に、常温常圧のもとで気体状態の非反応性
ガスを高圧下で溶解した発泡性樹脂組成物を、加熱溶融
し、該発泡性樹脂組成物の〔（降温時の結晶化ピーク温
度）−３０℃〕〜（降温時の結晶化ピーク温度）の温度
範囲で、押出成形金型から賦形して押出し、該発泡性樹
脂組成物の融点未満の温度で、少なくとも一軸に延伸す
ることを特徴とする電池セパレータ用多孔質フィルムの
製造方法。An ultrahigh molecular weight polyethylene having a viscosity average molecular weight of 1,000,000 or more and a viscosity average molecular weight of 100,000 or more and 100 or more.
A foamable resin composition obtained by dissolving a non-reactive gas in a gaseous state at normal temperature and pressure under high pressure in an olefin resin composition comprising less than 10,000 olefin thermoplastic resins is heated and melted, and the foaming is performed. The foamable resin composition is extruded in a temperature range of [(crystallization peak temperature at the time of temperature decrease) -30 ° C] to (crystallization peak temperature at the time of temperature decrease) from the extrusion mold. A method for producing a porous film for a battery separator, comprising stretching the film at least uniaxially at a temperature lower than the melting point of the product.
スが二酸化炭素である請求項１記載の電池セパレータ用
多孔質フィルムの製造方法。2. The method for producing a porous film for a battery separator according to claim 1, wherein the non-reactive gas in a gaseous state at normal temperature and normal pressure is carbon dioxide.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP10328178A JP2000143867A (en) | 1998-11-18 | 1998-11-18 | Preparation of porous film for cell separator |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP10328178A JP2000143867A (en) | 1998-11-18 | 1998-11-18 | Preparation of porous film for cell separator |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JP2000143867A true JP2000143867A (en) | 2000-05-26 |
Family
ID=18207354
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP10328178A Withdrawn JP2000143867A (en) | 1998-11-18 | 1998-11-18 | Preparation of porous film for cell separator |
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Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2002338730A (en) * | 2001-05-18 | 2002-11-27 | Asahi Kasei Corp | Microporous film made of polyethylene and cell obtained using the same |
| JP2002367589A (en) * | 2001-06-08 | 2002-12-20 | Asahi Kasei Corp | Polyolefin separator |
| JP2003162991A (en) * | 2001-11-27 | 2003-06-06 | Matsushita Electric Ind Co Ltd | Manufacturing method of separator for battery, separator for battery, and battery using the same |
| JP2006514702A (en) * | 2002-04-26 | 2006-05-11 | アトフイナ・リサーチ | Improved processing of bimodal polymers |
| JP2006169497A (en) * | 2004-11-19 | 2006-06-29 | Tokyo Univ Of Agriculture & Technology | Porous body and manufacturing method thereof |
| JP2007160691A (en) * | 2005-12-13 | 2007-06-28 | Mitsubishi Plastics Ind Ltd | Method for manufacturing porous body and porous body |
| WO2010058789A1 (en) * | 2008-11-19 | 2010-05-27 | 三井化学株式会社 | Polyolefin resin composition and applications thereof |
| JP2011068906A (en) * | 2004-11-19 | 2011-04-07 | Tokyo Univ Of Agriculture & Technology | Porous body |
-
1998
- 1998-11-18 JP JP10328178A patent/JP2000143867A/en not_active Withdrawn
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JP2002338730A (en) * | 2001-05-18 | 2002-11-27 | Asahi Kasei Corp | Microporous film made of polyethylene and cell obtained using the same |
| JP2002367589A (en) * | 2001-06-08 | 2002-12-20 | Asahi Kasei Corp | Polyolefin separator |
| JP2003162991A (en) * | 2001-11-27 | 2003-06-06 | Matsushita Electric Ind Co Ltd | Manufacturing method of separator for battery, separator for battery, and battery using the same |
| JP2006514702A (en) * | 2002-04-26 | 2006-05-11 | アトフイナ・リサーチ | Improved processing of bimodal polymers |
| JP2006169497A (en) * | 2004-11-19 | 2006-06-29 | Tokyo Univ Of Agriculture & Technology | Porous body and manufacturing method thereof |
| JP2011068906A (en) * | 2004-11-19 | 2011-04-07 | Tokyo Univ Of Agriculture & Technology | Porous body |
| JP2007160691A (en) * | 2005-12-13 | 2007-06-28 | Mitsubishi Plastics Ind Ltd | Method for manufacturing porous body and porous body |
| WO2010058789A1 (en) * | 2008-11-19 | 2010-05-27 | 三井化学株式会社 | Polyolefin resin composition and applications thereof |
| JPWO2010058789A1 (en) * | 2008-11-19 | 2012-04-19 | 三井化学株式会社 | Polyolefin resin composition and use thereof |
| US8349957B2 (en) | 2008-11-19 | 2013-01-08 | Mitsui Chemicals, Inc. | Polyolefin resin composition and uses thereof |
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