JP6218931B2 - Laminated porous film and method for producing the same - Google Patents

Laminated porous film and method for producing the same Download PDF

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JP6218931B2
JP6218931B2 JP2016512729A JP2016512729A JP6218931B2 JP 6218931 B2 JP6218931 B2 JP 6218931B2 JP 2016512729 A JP2016512729 A JP 2016512729A JP 2016512729 A JP2016512729 A JP 2016512729A JP 6218931 B2 JP6218931 B2 JP 6218931B2
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porous film
solvent
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laminated porous
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JPWO2015156261A1 (en
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健太 柴田
健太 柴田
直史 藤岡
直史 藤岡
山田　宗紀
宗紀 山田
朗 繁田
朗 繁田
雅弘 細田
雅弘 細田
良彰 越後
良彰 越後
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Unitika Ltd
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B5/00—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts
    • B32B5/18—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by features of a layer of foamed material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/411—Organic material
    • H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
    • H01M50/417—Polyolefins
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/06—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material
    • B32B27/065—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material of foam
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/32—Layered products comprising a layer of synthetic resin comprising polyolefins
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/403—Manufacturing processes of separators, membranes or diaphragms
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/411—Organic material
    • H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/411—Organic material
    • H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
    • H01M50/423—Polyamide resins
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
    • H01M50/451—Separators, membranes or diaphragms characterised by the material having a layered structure comprising layers of only organic material and layers containing inorganic material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
    • H01M50/491—Porosity
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2266/00—Composition of foam
    • B32B2266/02—Organic
    • B32B2266/0214—Materials belonging to B32B27/00
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2305/00—Condition, form or state of the layers or laminate
    • B32B2305/02—Cellular or porous
    • B32B2305/026—Porous
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/70—Other properties
    • B32B2307/724—Permeability to gases, adsorption
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2457/00—Electrical equipment
    • B32B2457/10—Batteries
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Inorganic Chemistry (AREA)
  • Cell Separators (AREA)
  • Laminated Bodies (AREA)
  • Manufacture Of Porous Articles, And Recovery And Treatment Of Waste Products (AREA)
  • Paints Or Removers (AREA)

Description

本発明は、積層多孔質フィルムおよびその製造方法に関する。この積層多孔質フィルムは、例えば、リチウム二次電池用セパレータ等、蓄電素子用のセパレータとして好適に用いることができる。   The present invention relates to a laminated porous film and a method for producing the same. This laminated porous film can be suitably used as a separator for a storage element such as a separator for a lithium secondary battery.

リチウム二次電池は、エネルギー密度が高いので電気自動車やパーソナルコンピュータ、携帯電話などの電子機器に用いる電池として広く使用されている。   Lithium secondary batteries are widely used as batteries used in electronic devices such as electric vehicles, personal computers, and mobile phones because of their high energy density.

このリチウム二次電池は、電池の破損等により内部短絡または外部短絡が生じた場合には、大電流が流れて異常発熱することがある。そのため、リチウム二次電池には一定以上の発熱を防止し、高い安全性を確保することが重要である。この安全性確保手段として、異常発熱の際に、セパレータに、電極間のイオンの通過を遮断して、発熱を防止するシャットダウン機能を持たせる方法が広く実用化されている。   In the lithium secondary battery, when an internal short circuit or an external short circuit occurs due to damage of the battery, a large current may flow to cause abnormal heat generation. Therefore, it is important for lithium secondary batteries to prevent heat generation beyond a certain level and to ensure high safety. As a means for ensuring safety, a method in which a separator has a shutdown function for preventing heat generation by blocking the passage of ions between electrodes in the event of abnormal heat generation has been widely put into practical use.

このシャットダウン機能を有するセパレータとしては例えば、ポリオレフィンからなる多孔質フィルムが用いられる。この多孔質フィルムからなるセパレータは、電池の異常発熱時には、１１０〜１６０℃でポリオレフィンが溶融して無孔化するためイオンの通過をシャットダウンすることができる。しかしながら、このポリオレフィン製セパレータは、高温になると収縮や破断が起こりやすいので、場合によっては、正極と負極が直接接触して、短絡を起こすおそれがあり、短絡による異常発熱を抑制できないことがある。   As the separator having the shutdown function, for example, a porous film made of polyolefin is used. The separator made of this porous film can shut down the passage of ions because the polyolefin melts and becomes nonporous at 110 to 160 ° C. during abnormal heat generation of the battery. However, since this polyolefin separator tends to shrink or break at a high temperature, in some cases, the positive electrode and the negative electrode may be in direct contact with each other to cause a short circuit, and abnormal heat generation due to the short circuit may not be suppressed.

このような問題を解決する方法として、前記ポリオレフィンからなる多孔質フィルム層の片面または両面（以下、「表面」と略記することがある）にポリフッ化ビニリデン等のフッ素系樹脂からなる多孔質層を積層することにより、高温での形状安定性を確保する方法が提案されている。この積層セパレータは、耐熱層を構成するフッ素系樹脂そのものの耐熱性が低いので、高温時での収縮による形状安定性は必ずしも充分ではなかった（例えば、特許文献１、２）。そこで、前記ポリオレフィンからなる多孔質フィルム層にポリイミドやアラミド等の耐熱性樹脂からなる多孔質層を積層することにより、高温での形状安定性を確保する方法が提案されている。   As a method for solving such a problem, a porous layer made of a fluorine-based resin such as polyvinylidene fluoride is provided on one side or both sides of the porous film layer made of polyolefin (hereinafter sometimes abbreviated as “surface”). A method for securing shape stability at a high temperature by laminating has been proposed. Since this laminated separator has low heat resistance of the fluororesin itself constituting the heat resistant layer, shape stability due to shrinkage at high temperature is not always sufficient (for example, Patent Documents 1 and 2). Therefore, a method has been proposed in which shape stability at high temperature is ensured by laminating a porous layer made of a heat-resistant resin such as polyimide or aramid on the porous film layer made of polyolefin.

耐熱性多孔質層を形成する方法としては、耐熱性樹脂（例えばアラミド樹脂）とその良溶媒（例えばアミド系溶媒）や貧溶媒（例えばアルコール系溶媒）を含む溶液をポリオレフィンからなる多孔質フィルム層の表面に塗工後、これを前記耐熱性樹脂の貧溶媒（例えば、アルコール系溶媒や水）からなる凝固浴に浸漬して、相分離を起こさせて多孔質化を図る方法が提案されている（例えば、特許文献３〜６）。   As a method for forming a heat resistant porous layer, a porous film layer comprising a polyolefin containing a solution containing a heat resistant resin (for example, an aramid resin) and a good solvent (for example, an amide solvent) or a poor solvent (for example, an alcohol solvent). After the coating on the surface of the resin, a method is proposed in which it is immersed in a coagulation bath made of a poor solvent (for example, an alcohol solvent or water) of the heat-resistant resin to cause phase separation to make it porous. (For example, Patent Documents 3 to 6).

しかしながら、前記したような方法で得られた積層多孔質フィルムは、耐熱性樹脂中に含まれていたアルコール系溶媒や、相分離を起こさせる際用いられたアルコール系溶媒が、形成された耐熱多孔質層に、微量残留することがあった。アルコール系溶媒の水酸基のプロトンは、化学的に活性である。そのため、このような多孔質フィルムを、前記したリチウム二次電池セパレータ等に用いた場合、残留していた微量のアルコール系溶媒が、リチウム二次電池の電解液中に溶出し、通常、電解質として用いられているＬｉＰＦ６のようなフルオロリン酸塩、ＬｉＢＦ４のようなフルオロホウ素酸塩、ＬｉＡｓＦ６のようなフルオロヒ素酸塩等と反応する懸念があった。すなわち、これらの電解質が、活性プロトンを有するアルコール系溶媒と反応すると、分解してフッ化水素が発生するため、電池特性を損なう虞があった（例えば、特許文献７、８およびその引用文献）。また、前記したような製造方法においては、相分離のために用いた凝固浴から、良溶媒および貧溶媒を含む廃液が大量に発生するため、環境適合性の観点から問題があった。However, the laminated porous film obtained by the method as described above has a heat-resistant porous film in which the alcohol-based solvent contained in the heat-resistant resin or the alcohol-based solvent used for causing phase separation is formed. A small amount of residue may remain in the quality layer. The proton of the hydroxyl group of the alcohol solvent is chemically active. Therefore, when such a porous film is used for the above-described lithium secondary battery separator or the like, a small amount of remaining alcohol-based solvent is eluted in the electrolyte solution of the lithium secondary battery, and is usually used as an electrolyte. There was a concern of reacting with a fluorophosphate such as LiPF 6 used, a fluoroborate such as LiBF 4 or a fluoroarsenate such as LiAsF 6 . That is, when these electrolytes react with an alcoholic solvent having active protons, hydrogen fluoride is generated by decomposition, which may impair battery characteristics (for example, Patent Documents 7 and 8 and references cited therein). . In addition, the above-described production method has a problem from the viewpoint of environmental compatibility because a large amount of waste liquid containing a good solvent and a poor solvent is generated from the coagulation bath used for phase separation.

特許第４１２７９８９号公報Japanese Patent No. 4127989 特許第４５８８２８６号公報Japanese Patent No. 4588286 特開２００２−３５５９３８号公報JP 2002-355938 A 特開２００５−２０９５７０号公報JP 2005-209570 A 特開２００６−３２２４６号公報JP 2006-32246 A 特開２０１０−５００２４号公報JP 2010-50024 A 特開２００２−７５４４０号公報JP 2002-75440 A 特開２００５−２４３４５８号公報JP 2005-243458 A

そこで、本発明の課題は、リチウム二次電池用セパレータとして用いた際、電池特性を損なう虞のない耐熱性の積層多孔質フィルムを提供することにある。さらに、環境適合性が良好な積層多孔質フィルムの製造方法を提供することにある。   Then, the subject of this invention is providing the heat resistant laminated porous film which does not have a possibility of impairing a battery characteristic, when it uses as a separator for lithium secondary batteries. Furthermore, it is providing the manufacturing method of a laminated porous film with favorable environmental compatibility.

本発明者らは、上記課題を解決すべく鋭意検討した結果、ポリオレフィンからなる多孔質層の表面に、特定の構成としたイミド系高分子からなる多孔質層が形成された積層フィルムとすることにより、前記課題が解決されることを見出し、本発明に到達した。   As a result of intensive studies to solve the above problems, the inventors of the present invention have a laminated film in which a porous layer made of an imide polymer having a specific configuration is formed on the surface of a porous layer made of polyolefin. Thus, the inventors have found that the above-mentioned problems can be solved, and have reached the present invention.

すなわち、本発明は、下記を要旨とするものである。
＜１＞ポリオレフィンからなる多孔質層の表面に、イミド系高分子からなる多孔質層が形成された積層多孔質フィルムであって、以下の特性を有することを特徴とする積層多孔質フィルム：
１） 通気度が、ＪＩＳ規格Ｐ８１１７に基づくガーレ値で、１０秒／１００ｃｃ以上、１０００秒／１００ｃｃ以下である；
２） イミド系高分子からなる多孔質層に、アルコール系溶媒が残留していない；
３） イミド系高分子からなる多孔質層の厚みが、１μｍ以上、２０μｍ以下である。
＜２＞ ＜１＞に記載の積層多孔質フィルムを用いてなるリチウム二次電池用セパレータ。
＜３＞ ポリオレフィンからなる多孔質層の表面に、イミド系高分子と、アミド系溶媒およびエーテル系溶媒を含む混合溶媒とからなる塗液を塗布して塗膜を形成した後、前記塗膜中の溶媒を加熱除去することにより塗膜内で相分離を起こさせて多孔質層を形成せしめることにより、ポリオレフィンからなる多孔質層とイミド系高分子からなる多孔質層とを積層一体化することを特徴とする＜１＞に記載の積層多孔質フィルムの製造方法。That is, the present invention has the following gist.
<1> A laminated porous film in which a porous layer made of an imide polymer is formed on the surface of a porous layer made of polyolefin, and having the following characteristics:
1) The air permeability is a Gurley value based on JIS standard P8117 and is 10 seconds / 100 cc or more and 1000 seconds / 100 cc or less;
2) No alcohol solvent remains in the porous layer made of the imide polymer;
3) The thickness of the porous layer made of an imide polymer is 1 μm or more and 20 μm or less.
<2> A separator for a lithium secondary battery using the laminated porous film according to <1>.
<3> After applying a coating liquid comprising an imide polymer and a mixed solvent containing an amide solvent and an ether solvent to the surface of the porous layer made of polyolefin, a coating film is formed. The porous layer made of polyolefin and the porous layer made of imide-based polymer are laminated and integrated by causing phase separation within the coating film by removing the solvent of the resin by heating to form a porous layer. The method for producing a laminated porous film according to <1>, wherein:

耐熱性に優れたイミド系高分子からなる多孔質層が、ポリオレフィンからなる多孔質層の表面に積層されてなる本発明の積層多孔質フィルムは、通気性が良好であり、かつイミド系高分子からなる多孔質層には、アルコール系溶媒が残留していないので、フィルムは、リチウム二次電池用セパレータとして好適に用いることができる。
また、本発明の製造方法によれば、加熱による溶媒除去という簡単な操作で、積層多孔質フィルムを得ることができる。The laminated porous film of the present invention in which a porous layer made of an imide polymer having excellent heat resistance is laminated on the surface of a porous layer made of polyolefin has good air permeability and an imide polymer. Since the alcohol-based solvent does not remain in the porous layer made of the film, the film can be suitably used as a separator for a lithium secondary battery.
Moreover, according to the manufacturing method of this invention, a lamination | stacking porous film can be obtained by simple operation of the solvent removal by heating.

以下、本発明について詳細に説明する。 Hereinafter, the present invention will be described in detail.

本発明の積層多孔質フィルムは、ポリオレフィンからなる多孔質層の表面に、イミド系高分子からなる多孔質層が形成されたものである。この積層多孔質フィルムは、例えば、ポリオレフィンからなる多孔質層（以下、「Ｓ層」と略記することがある）の表面にイミド系高分子を含む塗液を塗布して塗膜を形成し、しかる後、前記塗膜中の溶媒を加熱除去して、イミド系高分子からなる多孔質層（（以下、「Ｐ層」と略記することがある）をＳ層に積層一体化することにより得ることができる。   The laminated porous film of the present invention is obtained by forming a porous layer made of an imide polymer on the surface of a porous layer made of polyolefin. The laminated porous film is formed by, for example, applying a coating liquid containing an imide polymer to the surface of a porous layer made of polyolefin (hereinafter sometimes abbreviated as “S layer”), Thereafter, the solvent in the coating film is removed by heating, and a porous layer made of an imide polymer (hereinafter sometimes abbreviated as “P layer”) is laminated and integrated with the S layer. be able to.

Ｓ層は、その内部に連結した細孔を有する構造を持ち、一方の面から他方の面に気体や液体が透過可能な、ポリオレフィンからなる多孔質フィルムであり、本発明の積層多孔質フィルムの基材となるものである。   The S layer is a porous film made of polyolefin having a structure having pores connected to the inside thereof and allowing gas and liquid to permeate from one surface to the other surface. It becomes a base material.

Ｓ層におけるポリオレフィン成分の割合は、９０体積％以上であることが好ましく、９５体積％以上であることがより好ましい。ポリオレフィンとしては、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−ヘキセンなどのオレフィンを重合した単独重合体又は共重合体が挙げられる。これらの中でもエチレンを単独重合したポリエチレンが好ましく、重量平均分子量１００万以上の高分子量ポリエチレンがより好ましい。また、プロピレンを単独重合したポリプロピレンもポリオレフィンとして好ましい。   The proportion of the polyolefin component in the S layer is preferably 90% by volume or more, and more preferably 95% by volume or more. Examples of the polyolefin include homopolymers or copolymers obtained by polymerizing olefins such as ethylene, propylene, 1-butene, 4-methyl-1-pentene, and 1-hexene. Among these, polyethylene obtained by homopolymerizing ethylene is preferable, and high molecular weight polyethylene having a weight average molecular weight of 1,000,000 or more is more preferable. Polypropylene obtained by homopolymerizing propylene is also preferable as the polyolefin.

Ｓ層の通気度は、ガーレ値（ＪＩＳ規格Ｐ８１１７）で、１０秒／１００ｃｃ以上、５００秒／１００ｃｃ以下とすることが好ましく、１００秒／１００ｃｃ以上、３００秒／以下とすることがより好ましい。Ｓ層の通気度をこのように設定することにより、Ｐ層を積層した際に、リチウム二次電池用セパレータとして好適な通気性を確保することができる。Ｓ層の気孔率は、電解液の保持量を高めると共に、シャットダウン機能を確保する観点から、２０〜８０体積％が好ましく、３０〜７５体積％がより好ましい。   The air permeability of the S layer is preferably 10 seconds / 100 cc or more and 500 seconds / 100 cc or less, more preferably 100 seconds / 100 cc or more and 300 seconds / less or less in terms of Gurley value (JIS standard P8117). By setting the air permeability of the S layer in this way, air permeability suitable as a separator for a lithium secondary battery can be ensured when the P layer is laminated. The porosity of the S layer is preferably 20 to 80% by volume, more preferably 30 to 75% by volume from the viewpoint of increasing the amount of electrolyte retained and ensuring the shutdown function.

Ｓ層の孔径は、積層多孔質フィルムをリチウム二次電池用セパレータとした際に、十分な通気性が得られ、また、正極や負極への粒子の混入を防止する観点から、３μｍ以下が好ましく、１μｍ以下がより好ましい。Ｓ層の厚みは、シャットダウンによる絶縁性確保の観点から、８〜５０μｍが好ましく、１０〜３０μｍがより好ましい。ここで、Ｓ層の厚みは、前記積層多孔質フィルムの素材としてのＳ層の厚みであり、ＪＩＳ規格（Ｋ７１３０−１９９２）に基づいて測定されるものである。   The pore size of the S layer is preferably 3 μm or less from the viewpoint of obtaining sufficient air permeability when the laminated porous film is used as a separator for a lithium secondary battery and preventing mixing of particles into the positive electrode and the negative electrode. 1 μm or less is more preferable. The thickness of the S layer is preferably 8 to 50 μm, more preferably 10 to 30 μm, from the viewpoint of ensuring insulation by shutdown. Here, the thickness of the S layer is the thickness of the S layer as the material of the laminated porous film, and is measured based on the JIS standard (K7130-1992).

Ｓ層は、ポリオレフィンが主成分であれば特に限定されず、１層のみからなる単層構造であってもよいし、２層以上の層から構成される多層構造であってもよい。多層構造としては、例えば、あるポリオレフィンからなるポリオレフィン層の少なくとも一方の面に、他のポリオレフィンからなるポリオレフィン層が積層された構造などが挙げられる。その中でも、ポリエチレンを主成分とするポリエチレン層の両面に、ポリプロピレンを主成分とするポリプロピレン層が積層された構造（ポリプロピレン層／ポリエチレン層／ポリプロピレン層）が好ましい。   The S layer is not particularly limited as long as polyolefin is a main component, and may have a single layer structure composed of only one layer or a multilayer structure composed of two or more layers. Examples of the multilayer structure include a structure in which a polyolefin layer made of another polyolefin is laminated on at least one surface of a polyolefin layer made of a certain polyolefin. Among them, a structure (polypropylene layer / polyethylene layer / polypropylene layer) in which a polypropylene layer mainly composed of polypropylene is laminated on both surfaces of a polyethylene layer mainly composed of polyethylene is preferable.

Ｓ層に用いられる前記ポリオレフィンからなる多孔質フィルムは、市販品を利用することができる。市販品としては、ＳＫ社やＣｅｌｇａｒｄ社のポリエチレン製多孔質フィルム、Ｃｅｌｇａｒｄ社のポリプロピレン製多孔質フィルム等を例示することができる。これらの市販多孔質フィルムは、厚みが９〜２５μｍでシャットダウン機能を有するものである。   A commercially available product can be used as the porous film made of the polyolefin used for the S layer. Examples of commercially available products include polyethylene porous films from SK and Celgard, polypropylene porous films from Celgard, and the like. These commercially available porous films have a thickness of 9 to 25 μm and have a shutdown function.

Ｐ層を形成するイミド系高分子とは、主鎖にイミド結合を有する高分子もしくはその前駆体のことである。主鎖にイミド結合を有する高分子の代表例としては、ポリイミド、ポリアミドイミド、ポリエステルイミド等が挙げられるがこれらに限定されるものではない。   The imide polymer forming the P layer is a polymer having an imide bond in the main chain or a precursor thereof. Typical examples of the polymer having an imide bond in the main chain include, but are not limited to, polyimide, polyamideimide, and polyesterimide.

前記イミド系高分子の中で、例えば、ポリイミドまたはポリアミドイミドおよびこれらの混合物を好ましく用いることができる。ここで、ポリイミドとしては、可溶性ポリイミド（溶媒に可溶なポリイミド）を好ましく用いることができる。これらイミド系高分子の中でも、力学的特性や耐熱性に優れた芳香族ポリイミドおよび芳香族ポリアミドイミドが好ましい。前記芳香族ポリイミドおよび芳香族ポリアミドイミドは、熱可塑性であっても非熱可塑性であってもよい。これらのイミド系高分子のガラス転移温度は、２００℃以上であることが好ましく、２２０℃以上であることがより好ましい。このようにすることにより、積層多孔質フィルムの良好な耐熱性を確保することができる。ここで、ガラス転移温度（Ｔｇ）は、ＤＳＣ（示差熱分析）により確認することができる。   Among the imide-based polymers, for example, polyimide or polyamideimide and a mixture thereof can be preferably used. Here, as polyimide, soluble polyimide (polyimide soluble in a solvent) can be preferably used. Among these imide polymers, aromatic polyimides and aromatic polyamideimides excellent in mechanical properties and heat resistance are preferable. The aromatic polyimide and aromatic polyamideimide may be thermoplastic or non-thermoplastic. The glass transition temperature of these imide polymers is preferably 200 ° C. or higher, and more preferably 220 ° C. or higher. By doing in this way, the favorable heat resistance of a laminated porous film is securable. Here, the glass transition temperature (Tg) can be confirmed by DSC (differential thermal analysis).

本発明の積層多孔質フィルムを製造するには、例えば、以下のような方法で製造することができる。すなわち、イミド系高分子溶液を、溶媒を用いて製造する際に、イミド系高分子を溶解するアミド系溶媒（良溶媒）と、溶解しないエーテル系溶媒（貧溶媒）とからなる混合溶媒を用いる。ここで、良溶媒とは、イミド系高分子に対し、２５℃で、１質量％以上の溶解度を示す溶媒をいう。また、貧溶媒とは、イミド系高分子に対する溶解度が、１質量％未満である溶媒をいう。イミド系高分子をこの混合溶媒に溶解した溶液（以下、「イミド系塗液」と略記することがある）をＳ層の表面に塗布、乾燥することにより、積層多孔質フィルムを容易に得ることができる。   In order to produce the laminated porous film of the present invention, for example, it can be produced by the following method. That is, when an imide polymer solution is produced using a solvent, a mixed solvent composed of an amide solvent (good solvent) that dissolves the imide polymer and an ether solvent (poor solvent) that does not dissolve is used. . Here, the good solvent refers to a solvent that exhibits a solubility of 1% by mass or more at 25 ° C. with respect to the imide polymer. Moreover, a poor solvent means the solvent whose solubility with respect to an imide type polymer is less than 1 mass%. A laminated porous film can be easily obtained by applying a solution obtained by dissolving an imide polymer in this mixed solvent (hereinafter sometimes abbreviated as “imide coating solution”) to the surface of the S layer and drying. Can do.

イミド系塗液の混合溶媒は、本発明の効果を損なわない範囲において、他の溶媒を含んでもよい。   The mixed solvent of the imide-based coating liquid may contain other solvents as long as the effects of the present invention are not impaired.

このような混合溶媒を用いることにより、アルコール系溶媒を含有しない塗膜が得られるので、この塗膜を乾燥して得られる多孔質層にアルコール系溶媒が残留することはない。   By using such a mixed solvent, a coating film that does not contain an alcohol solvent is obtained, so that the alcohol solvent does not remain in the porous layer obtained by drying the coating film.

このイミド系塗液を、Ｓ層の表面に塗布し、しかる後、塗膜中の溶媒を加熱除去する際、塗膜中に共存しているエーテル系溶媒（貧溶媒）の作用により相分離が起こり、塗膜内に気孔が形成されるので、Ｓ層にＰ層が積層一体化された多孔質フィルムを得ることができる。ここで、溶媒を加熱除去する温度としては、１００〜１５０℃とすることが好ましい。乾燥に際しては、非加湿状態の窒素ガスまたは空気気流中で行うことが好ましい。このようにすることにより、塗膜への水分の混入を防止することができる。なお、エーテル系溶媒は、化学的に活性なプロトンを含有しないので、乾燥後の塗膜には、エーテル系溶媒が、微量残留していても問題はない。   When this imide-based coating liquid is applied to the surface of the S layer and then the solvent in the coating film is removed by heating, phase separation is caused by the action of the ether solvent (poor solvent) coexisting in the coating film. As a result, pores are formed in the coating film, so that a porous film in which the P layer and the S layer are laminated and integrated can be obtained. Here, the temperature at which the solvent is removed by heating is preferably 100 to 150 ° C. The drying is preferably performed in a non-humidified nitrogen gas or air stream. By doing in this way, mixing of the water | moisture content to a coating film can be prevented. Since the ether solvent does not contain chemically active protons, there is no problem even if a small amount of the ether solvent remains in the dried coating film.

前記アミド系溶媒としては、例えば、Ｎ−メチル−２−ピロリドン（ＮＭＰ 沸点：２０２℃）、Ｎ，Ｎ−ジメチルホルムアミド（沸点：１５３℃）、Ｎ，Ｎ−ジメチルアセトアミド（ＤＭＡｃ 沸点：１６６℃）が挙げられる。これらを単独で用いてもよく、２種以上を組み合わせて用いてもよい。これらの中でも、ＮＭＰ、ＤＭＡｃが好ましい。   Examples of the amide solvent include N-methyl-2-pyrrolidone (NMP boiling point: 202 ° C.), N, N-dimethylformamide (boiling point: 153 ° C.), N, N-dimethylacetamide (DMAc boiling point: 166 ° C.). Is mentioned. These may be used alone or in combination of two or more. Among these, NMP and DMAc are preferable.

アミド系溶媒の配合量としては、イミド系高分子の溶解の観点から、全溶媒量に対して１０質量％以上、特に１０〜７０質量％とすることが好ましく、２０〜４０質量％とすることがより好ましい。   The blending amount of the amide solvent is preferably 10% by mass or more, particularly preferably 10 to 70% by mass, and preferably 20 to 40% by mass with respect to the total solvent amount from the viewpoint of dissolution of the imide polymer. Is more preferable.

前記エーテル系溶媒は、前記アミド系溶媒よりも沸点が高いものを用いることが好ましく、その沸点差は、５℃以上が好ましく、２０℃以上がより好ましく、５０℃以上が更に好ましい。具体的には、ジエチレングリコールジメチルエーテル（沸点：１６２℃）、トリエチレングリコールジメチルエーテル（ＴＲＧＭ 沸点：２１６℃）、テトラエチレングリコールジメチルエーテル（ＴＥＧＭ 沸点：２７５℃）等を挙げることができる。これらを単独で用いてもよく、２種以上を組み合わせて用いてもよい。これらの中でも、ＴＥＧＭ、ＴＲＧＭが特に好ましい。   The ether solvent preferably has a boiling point higher than that of the amide solvent, and the difference in boiling point is preferably 5 ° C. or higher, more preferably 20 ° C. or higher, and further preferably 50 ° C. or higher. Specific examples include diethylene glycol dimethyl ether (boiling point: 162 ° C.), triethylene glycol dimethyl ether (TRGM boiling point: 216 ° C.), tetraethylene glycol dimethyl ether (TEGM boiling point: 275 ° C.), and the like. These may be used alone or in combination of two or more. Among these, TEGM and TRGM are particularly preferable.

エーテル系溶媒の配合量としては、通気度の観点から、全溶媒量に対して３０質量％以上、特に３０〜９０質量％とすることが好ましく、６０〜８０質量％とすることがより好ましい。   The blending amount of the ether solvent is preferably 30% by mass or more, particularly preferably 30 to 90% by mass, and more preferably 60 to 80% by mass with respect to the total solvent amount from the viewpoint of air permeability.

イミド系塗液は、例えば、ユニチカ株式会社から多孔質形成用として市販されているＵイミドワニスＳＰ（多孔質形成用ポリイミドワニス）等のポリイミド塗液、およびＵイミドワニスＩＰ（多孔質形成用ポリアミドイミドワニス）等のポリアミドイミド塗液を利用することができる。   Examples of the imide-based coating liquid include polyimide coating liquids such as Uimide varnish SP (polyimide varnish for porous formation) commercially available from Unitika Ltd. for porous formation, and Uimide varnish IP (polyamideimide varnish for porous formation). ) And the like can be used.

ポリイミド塗液は、前記したような市販品を用いてもよいが、原料であるテトラカルボン酸二無水物成分およびジアミン成分を略等モルで配合し、重合反応させて得られる可溶性ポリイミド粉体を、前記混合溶媒に溶解させた溶液も用いることができる。この重合反応は、テトラカルボン酸二無水物成分およびジアミン成分を反応させて得られるポリアミック酸（ポリイミド前駆体）溶液を加熱して行う。この際、ポリアミック酸からポリイミドが生成する際の副生成物である水を、例えば共沸等により除去しながら行うことが好ましい。水を除去しつつイミド化反応を行うポリイミドの重合方法の詳細については、例えば、米国特許３４２２０６１号明細書、特開昭５８−４９７２６号公報等を参照することができる。   Commercially available products such as those described above may be used as the polyimide coating liquid, but soluble polyimide powder obtained by blending the raw material tetracarboxylic dianhydride component and diamine component in approximately equimolar amounts and subjecting them to a polymerization reaction. A solution dissolved in the mixed solvent can also be used. This polymerization reaction is performed by heating a polyamic acid (polyimide precursor) solution obtained by reacting a tetracarboxylic dianhydride component and a diamine component. At this time, it is preferable to carry out while removing water, which is a by-product when the polyimide is produced from the polyamic acid, for example by azeotropic distillation. For details of the polymerization method of polyimide in which the imidization reaction is performed while removing water, reference can be made to, for example, US Pat. No. 3,422,061, JP-A-58-49726, and the like.

テトラカルボン酸二無水物成分は芳香環を有する芳香族テトラカルボン酸二無水物が好ましい。芳香族テトラカルボン酸二無水物成分としては、例えば、ピロメリット酸、３，３’，４，４’−ビフェニルテトラカルボン酸（ＢＰＤＡ）、３，３’，４，４’−ベンゾフェノンテトラカルボン酸、３，３’，４，４’−ジフェニルスルホンテトラカルボン、酸、３，３’，４，４’−ジフェニルエーテルテトラカルボン酸（ＯＤＰＡ）、２，３，３，４−ベンゾフェノンテトラカルボン酸、２，３，６，７−ナフタレンテトラカルボン酸、１，４，５，７−ナフタレンテトラカルボン酸、１，２，５，６−ナフタレンテトラカルボン酸、３，３’，４，４’−ジフェニルメタンテトラカルボン酸、２，２−ビス（３，４−ジカルボキシフェニル）プロパン、２，２−ビス（３，４−ジカルボキシフェニル）ヘキサフルオロプロパン、３，４，９，１０−テトラカルボキシペリレン、２，２−ビス［４−（３，４−ジカルボキシフェノキシ）フェニル］プロパン、２，２−ビス［４−（３，４−ジカルボキシフェノキシ）フェニル］ヘキサフルオロプロパン等の二無水物が用いられる。これらを単独で用いてもよく、２種以上を組み合わせて用いてもよい。これらの中でも、ＢＰＤＡ、ＯＤＰＡが好ましい。   The tetracarboxylic dianhydride component is preferably an aromatic tetracarboxylic dianhydride having an aromatic ring. Examples of the aromatic tetracarboxylic dianhydride component include pyromellitic acid, 3,3 ′, 4,4′-biphenyltetracarboxylic acid (BPDA), and 3,3 ′, 4,4′-benzophenone tetracarboxylic acid. 3,3 ′, 4,4′-diphenylsulfone tetracarboxylic acid, acid, 3,3 ′, 4,4′-diphenyl ether tetracarboxylic acid (ODPA), 2,3,3,4-benzophenone tetracarboxylic acid, 2 , 3,6,7-naphthalenetetracarboxylic acid, 1,4,5,7-naphthalenetetracarboxylic acid, 1,2,5,6-naphthalenetetracarboxylic acid, 3,3 ′, 4,4′-diphenylmethanetetra Carboxylic acid, 2,2-bis (3,4-dicarboxyphenyl) propane, 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane, 3, , 9,10-tetracarboxyperylene, 2,2-bis [4- (3,4-dicarboxyphenoxy) phenyl] propane, 2,2-bis [4- (3,4-dicarboxyphenoxy) phenyl] hexa A dianhydride such as fluoropropane is used. These may be used alone or in combination of two or more. Among these, BPDA and ODPA are preferable.

ポリイミドのジアミン成分は芳香環を有する芳香族ジアミンが好ましい。ポリイミドの芳香族ジアミン成分としては、例えば、ｐ−フェニレンジアミン、ｍ−フェニレンジアミン（ＭＰＤ）、３，４’−ジアミノジフェニルエーテル、４，４’−ジアミノジフェニルエーテル（ＤＡＤＥ）、４，４’−ジアミノジフェニルメタン、３，３’−ジメチル−４，４’−ジアミノジフェニルメタン、２，２−ビス［４−（４−アミノフェノキシ）フェニル］プロパン（ＢＡＰＰ）、１，２−ビス（アニリノ）エタン、ジアミノジフェニルスルホン、ジアミノベンズアニリド、ジアミノベンゾエート、ジアミノジフェニルスルフィド、２，２−ビス（ｐ−アミノフェニル）プロパン、２，２−ビス（ｐ−アミノフェニル）ヘキサフルオロプロパン、１，５−ジアミノナフタレン、ジアミノトルエン、ジアミノベンゾトリフルオライド、１，４−ビス（ｐ−アミノフェノキシ）ベンゼン、４，４’−ビス（ｐ−アミノフェノキシ）ビフェニル、ジアミノアントラキノン、４，４’−ビス（３−アミノフェノキシフェニル）ジフェニルスルホン、１，３−ビス（アニリノ）ヘキサフルオロプロパン、１，４−ビス（アニリノ）オクタフルオロブタン、１，５−ビス（アニリノ）デカフルオロペンタン、１，７−ビス（アニリノ）テトラデカフルオロヘプタンが用いられる。これらを単独で用いてもよく、２種以上を組み合わせて用いてもよい。これらの中でも、ＤＡＤＥ、ＢＡＰＰが好ましい。   The diamine component of the polyimide is preferably an aromatic diamine having an aromatic ring. Examples of the aromatic diamine component of polyimide include p-phenylenediamine, m-phenylenediamine (MPD), 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether (DADE), and 4,4'-diaminodiphenylmethane. 3,3′-dimethyl-4,4′-diaminodiphenylmethane, 2,2-bis [4- (4-aminophenoxy) phenyl] propane (BAPP), 1,2-bis (anilino) ethane, diaminodiphenylsulfone , Diaminobenzanilide, diaminobenzoate, diaminodiphenyl sulfide, 2,2-bis (p-aminophenyl) propane, 2,2-bis (p-aminophenyl) hexafluoropropane, 1,5-diaminonaphthalene, diaminotoluene, Diaminobenzotriflu Ride, 1,4-bis (p-aminophenoxy) benzene, 4,4′-bis (p-aminophenoxy) biphenyl, diaminoanthraquinone, 4,4′-bis (3-aminophenoxyphenyl) diphenylsulfone, 1, 3-bis (anilino) hexafluoropropane, 1,4-bis (anilino) octafluorobutane, 1,5-bis (anilino) decafluoropentane, 1,7-bis (anilino) tetradecafluoroheptane is used. These may be used alone or in combination of two or more. Among these, DADE and BAPP are preferable.

ポリイミド塗液中におけるポリイミドの固形分濃度としては、１〜５０質量％が好ましく、５〜２５質量％がより好ましい。   As solid content concentration of the polyimide in a polyimide coating liquid, 1-50 mass% is preferable and 5-25 mass% is more preferable.

ポリイミド塗液中に含まれるポリイミドは、ポリアミック酸が部分的にイミド化されたものでもよい。ポリイミド塗液の３０℃における粘度は、１〜１５０Ｐａ・ｓが好ましく、１０〜１００Ｐａ・ｓがより好ましい。   The polyimide contained in the polyimide coating solution may be one in which polyamic acid is partially imidized. The viscosity at 30 ° C. of the polyimide coating solution is preferably 1 to 150 Pa · s, and more preferably 10 to 100 Pa · s.

本明細書中、上記のような芳香族テトラカルボン酸二無水物成分および芳香族ジアミン成分を重合反応させてなるポリイミドを「芳香族ポリイミド」と呼ぶものとする。   In the present specification, a polyimide obtained by polymerizing the aromatic tetracarboxylic dianhydride component and the aromatic diamine component as described above is referred to as “aromatic polyimide”.

ポリアミドイミド塗液としては、前記したような市販品を用いてもよいが、原料であるトリカルボン酸成分（各種トリカルボン酸またはその無水物、酸クロライド誘導体）およびジアミン成分（各種ジアミンまたはそのジイソシアネート誘導体）を略等モルで配合し、重合反応させて得られるポリアミドイミド粉体を前記した混合溶媒に溶解させた溶液も用いることができる。ポリアミドイミドの重合方法としては、無水トリカルボン酸とジイソシアネートとを原料とするイソシアナート法、無水トリカルボン酸クロライドとジアミンとを原料とする酸クロライド法を用いることができるが、重合度の高いポリアミドイミド粉体を得るには酸クロライド法を用いることが好ましい。重合方法の詳細については、特公昭５０−３３１２０号公報（イソシアナート法）、特公昭４２−１５６３７号公報（酸クロライド法）等を参照することができる。   As the polyamide-imide coating solution, commercially available products as described above may be used, but the raw materials are tricarboxylic acid components (various tricarboxylic acids or anhydrides thereof, acid chloride derivatives) and diamine components (various diamines or diisocyanate derivatives thereof). A solution obtained by dissolving the polyamideimide powder obtained by blending at approximately equimolar amounts and carrying out the polymerization reaction in the above mixed solvent can also be used. As a method for polymerizing polyamideimide, an isocyanate method using tricarboxylic anhydride and diisocyanate as raw materials and an acid chloride method using tricarboxylic anhydride chloride and diamine as raw materials can be used. Polyamideimide powder having a high degree of polymerization. In order to obtain a body, it is preferable to use the acid chloride method. For details of the polymerization method, reference can be made to JP-B-50-33120 (isocyanate method), JP-B-42-15637 (acid chloride method) and the like.

トリカルボン酸成分は芳香環を有する芳香族トリカルボン酸が好ましい。芳香族トリカルボン酸成分としては、トリメリット酸クロライド（ＴＭＣ）、無水トリメリット酸（ＴＭＡ）、ヘミメリット酸クロライド、無水ヘミメリット酸が挙げられる。中でもＴＭＣ、ＴＭＡが好ましい。また、芳香族トリカルボン酸成分は、その一部をピロメリット酸、ベンゾフェノンテトラカルボン酸、またはビフェニルテトラカルボン酸等のテトラカルボン酸成分で置換することができる。   The tricarboxylic acid component is preferably an aromatic tricarboxylic acid having an aromatic ring. Examples of the aromatic tricarboxylic acid component include trimellitic acid chloride (TMC), trimellitic anhydride (TMA), hemimellitic acid chloride, and hemimellitic anhydride. Of these, TMC and TMA are preferable. In addition, a part of the aromatic tricarboxylic acid component can be substituted with a tetracarboxylic acid component such as pyromellitic acid, benzophenone tetracarboxylic acid, or biphenyltetracarboxylic acid.

ポリアミドイミドのジアミン成分は芳香環を有する芳香族ジアミンが好ましい。ポリアミドイミドの芳香族ジアミン成分としては、例えば、ｍ−フェニレンジアミン（ＭＰＤ）、ｐ−フェニレンジアミン、４，４’−ジフェニルメタンジアミン、４，４’−ジアミノジフェニルエーテル（ＤＡＤＥ）、ジフェニルスルホン−４，４’−ジアミン、ジフェニルー４，４’−ジアミン、ｏ−トリジン、２，４−トリレンジアミン、２，６−トリレンジアミン、キシリレンジアミン、ナフタレンジアミンまたはこれらのジイソシアネート誘導体を用いることができる。これらを単独で用いてもよく、２種以上を組み合わせて用いてもよい。これらの中でも、ＤＡＤＥ、ＭＰＤが好ましい。   The diamine component of the polyamideimide is preferably an aromatic diamine having an aromatic ring. Examples of the aromatic diamine component of polyamideimide include m-phenylenediamine (MPD), p-phenylenediamine, 4,4′-diphenylmethanediamine, 4,4′-diaminodiphenyl ether (DADE), and diphenylsulfone-4,4. '-Diamine, diphenyl-4,4'-diamine, o-tolidine, 2,4-tolylenediamine, 2,6-tolylenediamine, xylylenediamine, naphthalenediamine or diisocyanate derivatives thereof can be used. These may be used alone or in combination of two or more. Among these, DADE and MPD are preferable.

ポリアミドイミド塗液中におけるポリアミドイミドの固形分濃度は、１〜５０質量％が好ましく、１０〜３０質量％がより好ましい。   1-50 mass% is preferable and, as for the solid content density | concentration of the polyamide-imide in a polyamide-imide coating liquid, 10-30 mass% is more preferable.

ポリアミドイミド塗液の３０℃における粘度は、１〜１５０Ｐａ・ｓが好ましく、５〜１００Ｐａ・ｓがより好ましい。   The viscosity at 30 ° C. of the polyamideimide coating solution is preferably 1 to 150 Pa · s, more preferably 5 to 100 Pa · s.

本明細書中、上記のような芳香族トリカルボン酸成分および芳香族ジアミン成分を重合反応させてなるポリアミドイミドを「芳香族ポリアミドイミド」と呼ぶものとする。   In the present specification, a polyamideimide obtained by polymerizing an aromatic tricarboxylic acid component and an aromatic diamine component as described above is referred to as an “aromatic polyamideimide”.

イミド系塗液には、必要に応じて、各種界面活性剤や有機シランカップリング剤のような公知の添加物を添加してもよい。また、必要に応じて、前記イミド系塗液に、イミド系高分子以外の他のポリマーを添加してもよい。   You may add well-known additives, such as various surfactant and an organic silane coupling agent, to an imide type coating liquid as needed. Moreover, you may add other polymers other than an imide type polymer to the said imide type coating liquid as needed.

イミド系塗液をＳ層の表面に塗布して塗膜を形成するに際しては、ロールツーロールによる連続的に塗布する方法、枚様で塗布する方法が採用でき、いずれの方法でもよい。この時に用いられる塗布装置としては、例えば、ダイコータ、多層ダイコータ、グラビアコータ、コンマコータ、リバースロールコータ、ドクタブレードコータ、バーコータ等を使用することができる。前記したように、得られた塗膜中の溶媒を加熱除去することにより、Ｓ層と積層一体化したＰ層を形成させることができる。ここで、塗布面は、Ｓ層の片面であっても両面であってもよい。   When an imide-based coating liquid is applied to the surface of the S layer to form a coating film, a roll-to-roll continuous coating method or a sheet-by-sheet coating method can be employed, and any method may be used. As a coating apparatus used at this time, for example, a die coater, a multilayer die coater, a gravure coater, a comma coater, a reverse roll coater, a doctor blade coater, a bar coater, or the like can be used. As described above, a P layer laminated and integrated with the S layer can be formed by heating and removing the solvent in the obtained coating film. Here, the application surface may be one side or both sides of the S layer.

本発明の積層多孔質フィルムの通気度は、ガーレ値（ＪＩＳ規格Ｐ８１１７）で、１０秒／１００ｃｃ以上、１０００秒／１００ｃｃ以下であり、１００秒／１００ｃｃ以上、６００秒／以下とすることが好ましく、１００秒／１００ｃｃ以上、５００秒／以下とすることがさらに好ましい。通気度をこのように設定することにより、リチウム二次電池用セパレータとして好適に使用することができる。すなわち、ガーレ値が１０秒／１００ｍｌ未満であるとリチウムイオン二次電池内で負極に析出した金属リチウム等により、正極と短絡することがある。一方、ガーレ値が１０００秒／１００ｍｌを超えると、電池の内部抵抗が高くなり、高い出力密度を得られないことがある。   The laminated porous film of the present invention has a Gurley value (JIS standard P8117) of 10 seconds / 100 cc or more and 1000 seconds / 100 cc or less, preferably 100 seconds / 100 cc or more and 600 seconds / less or less. More preferably, it is 100 seconds / 100 cc or more and 500 seconds / less. By setting the air permeability in this way, it can be suitably used as a separator for a lithium secondary battery. That is, when the Gurley value is less than 10 seconds / 100 ml, there may be a short circuit with the positive electrode due to lithium metal deposited on the negative electrode in the lithium ion secondary battery. On the other hand, if the Gurley value exceeds 1000 seconds / 100 ml, the internal resistance of the battery increases, and a high output density may not be obtained.

本発明の積層多孔質フィルムは、Ｐ層にアルコール系溶媒が残留していない。ここで、「アルコール系溶媒が残留していない」とは、実質的にアルコール系溶媒が残留していないという意味であり、本発明の効果を損なわない範囲であれば、アルコール系溶媒は、微量残留していてもよい。アルコール系溶媒とは、メタノール、エタノール、プロパノール、イソプロピルアルコール、１―ブタノール、エチレングリコール、トリプロピレングリコール、グリセリン等をいう。   In the laminated porous film of the present invention, no alcohol solvent remains in the P layer. Here, “the alcoholic solvent does not remain” means that the alcoholic solvent does not substantially remain, and the alcoholic solvent is in a trace amount as long as the effects of the present invention are not impaired. It may remain. The alcohol solvent means methanol, ethanol, propanol, isopropyl alcohol, 1-butanol, ethylene glycol, tripropylene glycol, glycerin and the like.

本発明の多孔質積層フィルムにおいて、Ｐ層の厚みは、１μｍ以上、２０μｍ以下であり、１．５μｍ以上、１５μｍ以下とすることがより好ましく、２μｍ以上、１０μｍ以下とすることがさらに好ましい。このようにすることによりＰ層の良好な通気性を確保するとともに、Ｐ層が積層された多孔質フィルムの耐熱性を確保することができる。Ｐ層の厚みが薄すぎると、多孔質フィルムの耐熱性を確保できない。一方、Ｐ層の厚みが厚すぎると、通気性を確保できない。ここで、Ｐ層の厚みは、積層多孔質フィルムの厚みから、前記Ｓ層の厚みを減じて算出される厚みであり、積層多孔質フィルムの厚みは、ＪＩＳ規格（Ｋ７１３０−１９９２）に基づいて測定されるものである。   In the porous laminated film of the present invention, the thickness of the P layer is 1 μm or more and 20 μm or less, more preferably 1.5 μm or more and 15 μm or less, and further preferably 2 μm or more and 10 μm or less. By doing in this way, while ensuring favorable air permeability of P layer, the heat resistance of the porous film in which P layer was laminated | stacked can be ensured. If the thickness of the P layer is too thin, the heat resistance of the porous film cannot be ensured. On the other hand, if the P layer is too thick, air permeability cannot be ensured. Here, the thickness of the P layer is a thickness calculated by subtracting the thickness of the S layer from the thickness of the laminated porous film, and the thickness of the laminated porous film is based on the JIS standard (K7130-1992). It is to be measured.

Ｐ層の気孔率は、３０〜９０体積％とすることが好ましく、４０〜８０体積％とすることがより好ましい。気孔率をこのように設定することにより、より一層良好な力学的特性と通気性を有する積層多孔質フィルムとすることができる。ここで、気孔率の調整は、前記エーテル系溶媒の配合量や溶媒除去条件等を選ぶことにより行うことができる。なお、Ｐ層の気孔率は、Ｐ層の見掛け密度とＰ層構成するイミド系高分子の真密度（比重）とから算出される値である。具体的には、気孔率（体積％）は、Ｐ層の見掛け密度がＡ（ｇ／ｃｍ３）、イミド系高分子の真密度がＢ（ｇ／ｃｍ３）の場合、次式により算出される。The porosity of the P layer is preferably 30 to 90% by volume, and more preferably 40 to 80% by volume. By setting the porosity in this way, a laminated porous film having even better mechanical properties and air permeability can be obtained. Here, the porosity can be adjusted by selecting the blending amount of the ether solvent, solvent removal conditions, and the like. The porosity of the P layer is a value calculated from the apparent density of the P layer and the true density (specific gravity) of the imide polymer constituting the P layer. Specifically, the porosity (volume%) is calculated by the following equation when the apparent density of the P layer is A (g / cm 3 ) and the true density of the imide polymer is B (g / cm 3 ). The

Figure 0006218931
Figure 0006218931

Ｐ層の孔径は、積層多孔質フィルムをリチウム二次電池用セパレータとした際に、十分な通気性が得られ、また、正極や負極への粒子の混入を防止する観点から、３μｍ以下が好ましく、１μｍ以下がより好ましい。   The pore size of the P layer is preferably 3 μm or less from the viewpoint of obtaining sufficient air permeability when the laminated porous film is used as a separator for a lithium secondary battery and preventing mixing of particles into the positive electrode and the negative electrode. 1 μm or less is more preferable.

以上述べた如く、得られた積層多孔質フィルムは、通気性と耐熱性に優れ、かつＰ層にアルコール系溶媒が残留しないので、リチウム二次電池用セパレータとして、好適に使用することができる。また、本発明の積層多孔質フィルム製造方法によれば、凝固浴を使用しない簡単なプロセスで積層多孔質フィルムを容易に製造することができる。   As described above, the obtained laminated porous film is excellent in air permeability and heat resistance, and no alcohol solvent remains in the P layer. Therefore, it can be suitably used as a separator for a lithium secondary battery. Moreover, according to the method for producing a laminated porous film of the present invention, the laminated porous film can be easily produced by a simple process without using a coagulation bath.

以下、実施例に基づき本発明を更に具体的に説明するが、本発明はこれらの実施例のみに限定されるものではない。   EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example, this invention is not limited only to these Examples.

［実施例１］
Ｓ層を形成する多孔質フィルムとして、Ｃｅｌｇａｒｄ社製「Ｃｅｌｇａｒｄ２５００」を用意した。この多孔質フィルムは、ポリプロピレンからなり、厚みは２５μｍ、通気度を示すガーレ値（ＪＩＳ規格Ｐ８１１７）は１８０秒／１００ｃｃであった。次に、イミド系塗液として、ユニチカ株式会社製「ＵイミドワニスＩＰ」を用意した。この塗液は、溶質として、ＤＳＣによるＴｇが２８０℃の芳香族ポリアミドイミド、溶媒として、ＮＭＰとＴＥＧＭとの混合溶媒が用いられ、アルコール系溶媒は含まないものであった。また、固形分濃度としては、１５質量％であった。この塗液を、前記多孔質フィルムの片面に、バーコータを用いて塗布し、１４０℃の非加湿状態の窒素ガス気流中で３０分乾燥することにより、溶媒を加熱除去し、Ｓ層表面に、厚み８μｍの多孔質ポリアミドイミドからなるＰ層が一体化された積層多孔質フィルム（Ｌ−１）を得た。この積層多孔質フィルム特性およびＰ層の特性を評価した結果を表１に示す。[Example 1]
As a porous film for forming the S layer, “Celgard 2500” manufactured by Celgard was prepared. This porous film was made of polypropylene, had a thickness of 25 μm, and had a Gurley value (JIS standard P8117) indicating air permeability of 180 seconds / 100 cc. Next, “Uimide varnish IP” manufactured by Unitika Co., Ltd. was prepared as an imide coating solution. This coating solution used was an aromatic polyamideimide having a Tg of 280 ° C. by DSC as a solute, a mixed solvent of NMP and TEGM as a solvent, and no alcohol solvent. Moreover, as solid content concentration, it was 15 mass%. This coating solution is applied to one side of the porous film using a bar coater, and dried in a non-humidified nitrogen gas stream at 140 ° C. for 30 minutes to remove the solvent by heating, and on the surface of the S layer, A laminated porous film (L-1) in which P layers made of porous polyamideimide having a thickness of 8 μm were integrated was obtained. Table 1 shows the results of evaluating the properties of the laminated porous film and the properties of the P layer.

［実施例２］
Ｐ層の厚みを４μｍとしたこと以外は、実施例１と同様に行い、積層多孔質フィルム（Ｌ−２）を得た。この積層多孔質フィルム特性およびＰ層の特性を評価した結果を表１に示す。[Example 2]
A laminated porous film (L-2) was obtained in the same manner as in Example 1 except that the thickness of the P layer was 4 μm. Table 1 shows the results of evaluating the properties of the laminated porous film and the properties of the P layer.

［実施例３］
Ｐ層の厚みを１５μｍとしたこと以外は、実施例１と同様に行い、積層多孔質フィルム（Ｌ−３）を得た。この積層多孔質フィルムおよびＰ層の特性を評価した結果を表１に示す。[Example 3]
A laminated porous film (L-3) was obtained in the same manner as in Example 1 except that the thickness of the P layer was 15 μm. Table 1 shows the results of evaluating the characteristics of this laminated porous film and P layer.

［実施例４］
乾燥窒素ガス雰囲気下、ガラス製反応容器に、ＤＡＤＥ０．０７モル、ＭＰＤ０．０３モルを入れ、これにＮＭＰとトリエチルアミン０．１モルを加え、撹拌することにより固形分濃度が１５質量％のＮＭＰ溶液を得た。その後、この溶液を１０℃以下に保ちつつ、ＴＭＣ ０．１モルのＮＭＰ溶液（固形分濃度：２０質量％）を、撹拌下、ゆっくりと滴下した。滴下終了後、溶液を室温に戻し、２時間攪拌を続けた。得られた溶液を、大量の水に投入して、ポリアミドイミドの沈殿を生じせしめ、これを濾過、洗浄することにより、黄色の固体を得た後、２００℃で１２時間加熱して、乾燥とイミド化を行うことによりポリアミドイミド粉体（ＡＰ）を得た。ＡＰのＤＳＣによるＴｇは２８５℃であった。次に、ＡＰをＮＭＰとＴＥＧＭとの混合溶媒に溶解し、固形分濃度が１２質量％のポリアミドイミド塗液（Ａ−１）を得た。ここでＮＭＰとＴＥＧＭの混合比率は、ＴＥＧＭ量を混合溶媒質量に対し７０質量％とした。塗液（Ａ−１）を用い、実施例１と同様にして塗布を行い、Ｓ層表面に多孔質ポリアミドイミドからなるＰ層（厚みは３μｍとした）が一体化された積層多孔質フィルム（Ｌ−４）を得た。この積層多孔質フィルム特性およびＰ層の特性を評価した結果を表１に示す。[Example 4]
Under a dry nitrogen gas atmosphere, put 0.07 mol of DADE and 0.03 mol of MPD in a glass reaction vessel, add NMP and 0.1 mol of triethylamine to this, and stir the NMP solution with a solid content concentration of 15% by mass. Got. Thereafter, while maintaining this solution at 10 ° C. or lower, 0.1 mol of TMC (solid content concentration: 20% by mass) was slowly added dropwise with stirring. After completion of the dropwise addition, the solution was returned to room temperature and stirring was continued for 2 hours. The obtained solution was poured into a large amount of water to cause precipitation of polyamideimide, which was filtered and washed to obtain a yellow solid, which was then heated at 200 ° C. for 12 hours, dried and dried. A polyamide-imide powder (AP) was obtained by imidization. The Tg of the AP by DSC was 285 ° C. Next, AP was dissolved in a mixed solvent of NMP and TEGM to obtain a polyamideimide coating liquid (A-1) having a solid content concentration of 12% by mass. Here, the mixing ratio of NMP and TEGM was such that the amount of TEGM was 70% by mass with respect to the mass of the mixed solvent. Using the coating liquid (A-1), coating was performed in the same manner as in Example 1, and a laminated porous film in which a P layer (thickness was 3 μm) made of porous polyamideimide was integrated on the surface of the S layer ( L-4) was obtained. Table 1 shows the results of evaluating the properties of the laminated porous film and the properties of the P layer.

［実施例５］
ＮＭＰとＴＥＧＭの混合比率を、ＴＥＧＭ量を混合溶媒質量に対し８０質量％としたこと以外は、実施例４と同様にして、固形分濃度が１２質量％のポリアミドイミド塗液（Ａ−２）を得た。塗液（Ａ−２）を用い、実施例１と同様にして塗布を行い、Ｓ層表面に多孔質ポリアミドイミドからなるＰ層（厚みは３μｍとした）が一体化された積層多孔質フィルム（Ｌ−５）を得た。この積層多孔質フィルム特性およびＰ層の特性を評価した結果を表１に示す。[Example 5]
Polyamideimide coating liquid (A-2) having a solid content concentration of 12% by mass in the same manner as in Example 4 except that the mixing ratio of NMP and TEGM was 80% by mass with respect to the mass of the mixed solvent. Got. Using the coating liquid (A-2), the application was carried out in the same manner as in Example 1, and a laminated porous film in which a P layer (thickness 3 μm) made of porous polyamideimide was integrated on the surface of the S layer ( L-5) was obtained. Table 1 shows the results of evaluating the properties of the laminated porous film and the properties of the P layer.

［実施例６］
イミド系塗液としてユニチカ株式会社製「ＵイミドワニスＳＰ」を用意した。この塗液は、溶質として、ＤＳＣによるＴｇが２２５℃の芳香族ポリイミド、溶媒としては、ＮＭＰとＴＥＧＭとの混合溶媒が用いられ、アルコール系溶媒は含まないものであった。また、固形分濃度としては、１５質量％であった。この塗液を、前記多孔質フィルムの片面に、バーコータを用いて塗布し、１４０℃の非加湿状態の窒素ガス気流中で３０分乾燥することにより、溶媒を加熱除去し、Ｓ層表面に、厚み４μｍの多孔質ポリイミドからなるＰ層が一体化された積層多孔質フィルム（Ｌ−６）を得た。この積層多孔質フィルム特性およびＰ層の特性を評価した結果を表１に示す。[Example 6]
“Uimide varnish SP” manufactured by Unitika Ltd. was prepared as an imide coating solution. This coating liquid used was an aromatic polyimide having a Tg of 225 ° C. by DSC as a solute, and a mixed solvent of NMP and TEGM as a solvent, and did not contain an alcohol solvent. Moreover, as solid content concentration, it was 15 mass%. This coating solution is applied to one side of the porous film using a bar coater, and dried in a non-humidified nitrogen gas stream at 140 ° C. for 30 minutes to remove the solvent by heating, and on the surface of the S layer, A laminated porous film (L-6) in which a P layer made of porous polyimide having a thickness of 4 μm was integrated was obtained. Table 1 shows the results of evaluating the properties of the laminated porous film and the properties of the P layer.

［実施例７］
乾燥窒素ガス雰囲気下、ガラス製反応容器中に、ＢＰＤＡ０．０４モル、ＯＤＰＡ０．０６モルを入れ、ＮＭＰと共に投入し、溶液としたのち、ＤＡＤＥ０．１モルのＮＭＰ溶液を投入し、撹拌下、ＢＰＤＡ０．０４モル、ＯＤＰＡ０．０６モルを徐々に加え、５０℃で４時間反応させて、ポリアミック酸のＮＭＰ溶液（固形分濃度 １５質量％）を得た。このポリアミック酸溶液にトルエンを添加して、固形分濃度を１３質量％の溶液とした。この溶液を２００℃に加熱して、反応の進行に伴ってトルエンと共沸してきた水分を分離しながら３時間イミド化反応を行った。その後、トルエンを留去して得られたポリイミド溶液を大量の水中に投入して、ポリイミドの沈殿を生じせしめ、これを濾過、洗浄、解砕後、１２０℃で５時間加熱することにより、可溶性ポリイミド粉体（ＢＰ）を得た。粉体ＢＰのＤＳＣによるＴｇは２３１℃であった。次に、粉体ＢＰをＤＭＡｃとＴＥＧＭとの混合溶媒に溶解し、固形分濃度が１２質量％のポリイミド塗液（Ｂ−１）を得た。ここでＤＭＡｃとＴＥＧＭの混合比率は、ＴＥＧＭ量を混合溶媒質量に対し７０質量％とした。塗液（Ｂ−１）を用い、実施例６と同様に塗布して、Ｓ層表面に多孔質ポリイミドからなるＰ層（厚みは３μｍとした）が一体化された積層多孔質フィルム（Ｌ−７）を得た。この積層多孔質フィルム特性およびＰ層の特性を評価した結果を表１に示す。[Example 7]
In a dry nitrogen gas atmosphere, 0.04 mol of BPDA and 0.06 mol of ODPA were placed in a glass reaction vessel, and added together with NMP to obtain a solution. Then, 0.1 mol of DADE was added to the NMP solution, and BPDA0 was stirred. 0.04 mol and ODPA 0.06 mol were gradually added and reacted at 50 ° C. for 4 hours to obtain an NMP solution of polyamic acid (solid content concentration 15% by mass). Toluene was added to this polyamic acid solution to obtain a solution having a solid content concentration of 13% by mass. This solution was heated to 200 ° C., and an imidization reaction was performed for 3 hours while separating water azeotroped with toluene as the reaction progressed. Thereafter, the polyimide solution obtained by distilling off toluene was poured into a large amount of water to cause precipitation of polyimide, which was filtered, washed and crushed, and then heated at 120 ° C. for 5 hours, thereby being soluble. A polyimide powder (BP) was obtained. The Tg of the powder BP by DSC was 231 ° C. Next, the powder BP was dissolved in a mixed solvent of DMAc and TEGM to obtain a polyimide coating liquid (B-1) having a solid content concentration of 12% by mass. Here, the mixing ratio of DMAc and TEGM was set so that the amount of TEGM was 70% by mass with respect to the mass of the mixed solvent. Using the coating liquid (B-1), a laminated porous film (L-) coated in the same manner as in Example 6 and integrated with a P layer (thickness 3 μm) made of porous polyimide on the surface of the S layer. 7) was obtained. Table 1 shows the results of evaluating the properties of the laminated porous film and the properties of the P layer.

［実施例８］
ＤＭＡｃとＴＥＧＭの混合比率を、ＴＥＧＭ量を混合溶媒質量に対し６０質量％としたこと以外は、実施例４と同様にして、固形分濃度が１２質量％の塗液（Ｂ−２）を得た。塗液（Ｂ−２）を用い、実施例７と同様にして、Ｓ層表面に、厚み３μｍの多孔質ポリイミドからなるＰ層が一体化された積層多孔質フィルム（Ｌ−８）を得た。この積層多孔質フィルム特性およびＰ層の特性を評価した結果を表１に示す。[Example 8]
A coating liquid (B-2) having a solid content concentration of 12 mass% was obtained in the same manner as in Example 4 except that the mixing ratio of DMAc and TEGM was changed to 60 mass% with respect to the mass of the mixed solvent. It was. Using the coating liquid (B-2), in the same manner as in Example 7, a laminated porous film (L-8) in which a P layer made of porous polyimide having a thickness of 3 μm was integrated on the surface of the S layer was obtained. . Table 1 shows the results of evaluating the properties of the laminated porous film and the properties of the P layer.

［実施例９］
ＴＥＧＭをＴＲＧＭとしたこと以外は、実施例７と同様にして、固形分濃度が１２質量％の塗液（Ｂ−３）を得た。塗液（Ｂ−３）を用い、実施例７と同様にして、Ｓ層表面に、厚み３μｍの多孔質ポリイミドからなるＰ層が一体化された積層多孔質フィルム（Ｌ−９）を得た。この積層多孔質フィルム特性およびＰ層の特性を評価した結果を表１に示す。[Example 9]
A coating liquid (B-3) having a solid content concentration of 12% by mass was obtained in the same manner as in Example 7 except that TEGM was changed to TRGM. Using the coating liquid (B-3), in the same manner as in Example 7, a laminated porous film (L-9) in which the P layer made of porous polyimide having a thickness of 3 μm was integrated on the surface of the S layer was obtained. . Table 1 shows the results of evaluating the properties of the laminated porous film and the properties of the P layer.

［比較例１］
Ｐ層の厚みを２５μｍとしたこと以外は、実施例１と同様に行い、積層多孔質フィルム（Ｍ−１）を得た。この積層多孔質フこの積層多孔質フィルムおよびＰ層の特性を評価した結果を表１に示す。[Comparative Example 1]
A laminated porous film (M-1) was obtained in the same manner as in Example 1 except that the thickness of the P layer was 25 μm. The results of evaluating the characteristics of the laminated porous film and the P layer are shown in Table 1.

［比較例２］
実施例４で用いたポリアミドイミド粉体（ＡＰ）をＮＭＰに溶解し、固形分濃度が１２質量％のポリアミドイミド塗液（Ａ−３）を得た。塗液（Ａ−３）を用い、実施例１と同様にして塗布を行い、Ｓ層表面にポリアミドイミドからなるＰ層（厚みは３μｍとした）が一体化された積層多孔質フィルム（Ｍ−２）を得た。この積層多孔質フィルム特性およびＰ層の特性を評価した結果を表１に示す。[Comparative Example 2]
The polyamideimide powder (AP) used in Example 4 was dissolved in NMP to obtain a polyamideimide coating liquid (A-3) having a solid content concentration of 12% by mass. Using the coating liquid (A-3), coating was performed in the same manner as in Example 1, and a laminated porous film (M-) in which a P layer (thickness 3 μm) made of polyamideimide was integrated on the surface of the S layer. 2) was obtained. Table 1 shows the results of evaluating the properties of the laminated porous film and the properties of the P layer.

［比較例３］
ＮＭＰとＴＥＧＭの混合比率を、ＴＥＧＭ量を混合溶媒質量に対し２５質量％としたこと以外は、実施例４と同様にして、固形分濃度が１２質量％のポリアミドイミド塗液（Ａ−４）を得た。塗液（Ａ−４）を用い、実施例１と同様にして塗布を行い、Ｓ層表面に多孔質ポリアミドイミドからなるＰ層（厚みは３μｍとした）が一体化された積層多孔質フィルム（Ｍ−３）を得た。この積層多孔質フィルム特性およびＰ層の特性を評価した結果を表１に示す。[Comparative Example 3]
Polyamideimide coating liquid (A-4) having a solid content concentration of 12% by mass in the same manner as in Example 4 except that the mixing ratio of NMP and TEGM was 25% by mass with respect to the mass of the mixed solvent. Got. Using the coating liquid (A-4), coating was carried out in the same manner as in Example 1, and a laminated porous film in which a P layer (thickness 3 μm) made of porous polyamideimide was integrated on the surface of the S layer ( M-3) was obtained. Table 1 shows the results of evaluating the properties of the laminated porous film and the properties of the P layer.

［比較例４］
実施例４で用いたポリアミドイミド粉体（ＡＰ）を、ＮＭＰとトリプロピレングルコール（ＴＰＧ）との混合溶媒に溶解し、固形分濃度が１２質量％のポリアミドイミド塗液（Ａ−５）を得た。ここでＮＭＰとＴＰＧの混合比率は、ＴＰＧ量を混合溶媒質量に対し２５質量％とした。塗液（Ａ−５）を用い、実施例１と同様にして塗布を行い、Ｓ層表面に多孔質ポリアミドイミドからなるＰ層（厚みは３μｍとした）が一体化された積層多孔質フィルム（Ｍ−４）を得た。この積層多孔質フィルム特性およびＰ層の特性を評価した結果を表１に示す。[Comparative Example 4]
The polyamideimide powder (AP) used in Example 4 was dissolved in a mixed solvent of NMP and tripropylene glycol (TPG), and a polyamideimide coating liquid (A-5) having a solid content concentration of 12% by mass was obtained. Obtained. Here, the mixing ratio of NMP and TPG was such that the amount of TPG was 25% by mass with respect to the mass of the mixed solvent. Using the coating liquid (A-5), the application was carried out in the same manner as in Example 1, and a laminated porous film in which a P layer (thickness 3 μm) made of porous polyamideimide was integrated on the surface of the S layer ( M-4) was obtained. Table 1 shows the results of evaluating the properties of the laminated porous film and the properties of the P layer.

［比較例５］
実施例４で用いたポリアミドイミド粉体（ＡＰ）を、ＮＭＰとＴＰＧとの混合溶媒に溶解させてポリアミドイミド塗液を作成し、積層多孔質フィルム（Ｍ−５）を得ようとしたが、均一な溶液を得ることができなかった。ここでＮＭＰとＴＰＧの混合比率は、ＴＰＧ量を混合溶媒質量に対し７０質量％とした。[Comparative Example 5]
The polyamideimide powder (AP) used in Example 4 was dissolved in a mixed solvent of NMP and TPG to create a polyamideimide coating solution, and an attempt was made to obtain a laminated porous film (M-5). A uniform solution could not be obtained. Here, the mixing ratio of NMP and TPG was such that the amount of TPG was 70% by mass with respect to the mass of the mixed solvent.

［比較例６］
実施例７で用いたポリイミド粉体（ＢＰ）を、ＤＭＡｃとＴＰＧとの混合溶媒に溶解し、固形分濃度が１２質量％のポリイミド塗液（Ｂ−４）を得た。ここでＤＭＡｃとＴＰＧの混合比率は、ＴＰＧ量を混合溶媒質量に対し２５質量％とした。塗液（Ｂ−４）を用い、実施例１と同様にして塗布を行い、Ｓ層表面にポリイミドからなるＰ層（厚みは３μｍとした）が一体化された積層多孔質フィルム（Ｍ−６）を得た。この積層多孔質フィルム特性およびＰ層の特性を評価した結果を表１に示す。[Comparative Example 6]
The polyimide powder (BP) used in Example 7 was dissolved in a mixed solvent of DMAc and TPG to obtain a polyimide coating liquid (B-4) having a solid content concentration of 12% by mass. Here, the mixing ratio of DMAc and TPG was such that the amount of TPG was 25 mass% with respect to the mass of the mixed solvent. Using the coating liquid (B-4), coating was carried out in the same manner as in Example 1, and a laminated porous film (M-6) in which a P layer made of polyimide (thickness 3 μm) was integrated on the surface of the S layer ) Table 1 shows the results of evaluating the properties of the laminated porous film and the properties of the P layer.

［比較例７］
実施例７で用いたポリイミド粉体（ＢＰ）を、ＤＭＡｃとＴＰＧとの混合溶媒に溶解させてポリイミド塗液を作成し、積層多孔質フィルム（Ｍ−７）を得ようとしたが、均一な溶液を得ることができなかった。ここでＤＭＡｃとＴＰＧの混合比率は、ＴＰＧ量を混合溶媒質量に対し７０質量％とした。[Comparative Example 7]
The polyimide powder (BP) used in Example 7 was dissolved in a mixed solvent of DMAc and TPG to prepare a polyimide coating solution, and an attempt was made to obtain a laminated porous film (M-7). A solution could not be obtained. Here, the mixing ratio of DMAc and TPG was such that the amount of TPG was 70% by mass with respect to the mass of the mixed solvent.

実施例で示した様に、ポリオレフィンからなる多孔質層の片面または両面に、イミド系高分子からなる多孔質層が形成されている本発明の積層多孔質フィルムは、耐熱性に優れたイミド系高分子からなる多孔質層がポリオレフィンからなる多孔質層の表面に積層されており、この耐熱多孔質層は、気孔率が高く、通気性が良好であるので、これを積層した積層多孔質フィルムも通気性に優れる。さらに、この耐熱多孔質層は、アルコール系溶媒が残留していないものである。従い、本発明の積層多孔質フィルムは、リチウム二次電池用セパレータとして好適に用いることができる。
また、本発明の製造方法によれば、加熱による溶媒除去という簡単な操作で、積層多孔質フィルムを得ることができる。ここでは、貧溶媒を含む凝固浴を用いないので、凝固浴からの廃液が発生しない。従い、環境適合性が良好である。As shown in the Examples, the laminated porous film of the present invention in which a porous layer made of an imide polymer is formed on one or both sides of a porous layer made of polyolefin is an imide type having excellent heat resistance. A porous layer made of a polymer is laminated on the surface of a porous layer made of polyolefin, and since this heat-resistant porous layer has a high porosity and good air permeability, a laminated porous film in which this is laminated Also excellent in breathability. Further, this heat-resistant porous layer is one in which no alcohol solvent remains. Therefore, the laminated porous film of the present invention can be suitably used as a separator for a lithium secondary battery.
Moreover, according to the manufacturing method of this invention, a lamination | stacking porous film can be obtained by simple operation of the solvent removal by heating. Here, since a coagulation bath containing a poor solvent is not used, waste liquid from the coagulation bath is not generated. Therefore, environmental compatibility is good.

Figure 0006218931
Figure 0006218931

本発明の積層多孔質フィルムは、例えば、リチウム二次電池用セパレータ等、蓄電素子用のセパレータとして有用である。   The laminated porous film of the present invention is useful as a separator for a storage element such as a separator for a lithium secondary battery.

Claims (4)

ポリオレフィンからなる多孔質層の片面または両面に、塗液を塗布して塗膜を形成した後、前記塗膜中の溶媒を加熱除去することにより塗膜内で相分離を起こさせて多孔質層を形成せしめることにより、ポリオレフィンからなる多孔質層とポリアミドイミドからなる多孔質層とを積層一体化する、積層多孔質フィルムを製造するための塗液であって、
前記塗液が、ポリアミドイミドと、アミド系溶媒と、エーテル系溶媒としてのトリエチレングリコールジメチルエーテルおよび／またはテトラエチレングリコールジメチルエーテルと、からなることを特徴とする積層多孔質フィルム製造用塗液。 After applying a coating liquid on one or both sides of a porous layer made of polyolefin to form a coating film, the solvent in the coating film is removed by heating to cause phase separation in the coating film. the by allowed to form, integrally laminated to a porous layer made of a porous layer and a polyamide-imide comprising a polyolefin, a coating liquid for producing a product layer porous film,
A coating liquid for producing a laminated porous film , characterized in that the coating liquid comprises polyamideimide, an amide solvent, and triethylene glycol dimethyl ether and / or tetraethylene glycol dimethyl ether as an ether solvent . 前記エーテル系溶媒の配合量が全溶媒量に対して６０〜８０質量％である、請求項１に記載の積層多孔質フィルム製造用塗液。 The coating liquid for laminated porous film production according to claim 1, wherein the blending amount of the ether solvent is 60 to 80% by mass with respect to the total amount of the solvent. 請求項１または２記載の積層多孔質フィルム製造用塗液を用いた、積層多孔質フィルムの製造方法。 A method for producing a laminated porous film using the coating liquid for producing a laminated porous film according to claim 1 . 請求項３に記載の積層多孔質フィルムの製造方法で得られた積層多孔質フィルムのリチウム二次電池用セパレータへの使用。 Use in a lithium secondary battery separator of the laminated porous fill beam obtained by the method for producing a laminated porous film according to claim 3.
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