JP2019131747A - Porous polyimide film roll, production method thereof, and composition - Google Patents

Abstract

To provide a porous polyimide film roll excellent in tensile strength and bending strength, a production method thereof, and a composition used suitably for production thereof.SOLUTION: In the porous polyimide film roll, the tensile strength defined by ASTM Standard D638 is 45 MPa or more.SELECTED DRAWING: None

Description

  The present invention relates to a porous polyimide film original fabric excellent in tensile strength and bending strength, a production method thereof, and a composition suitably used for the production thereof.

Polyimide resin is a material having excellent properties such as mechanical strength, chemical stability, and heat resistance, and a porous polyimide film having these properties has attracted attention.
For example, Patent Document 1 describes a porous polyimide film in which the occurrence of cracks is suppressed by containing a polyimide resin and a non-crosslinked resin other than a polyimide resin, as compared with a porous polyimide film containing only a polyimide resin. Has been.
However, the porous polyimide film described in Cited Document 1 is brittle to the force applied during production, can be produced only on a single sheet, and has poor production suitability.

JP, 2006-183273, A

  The present invention has been made in view of the above-described problems of the prior art, and aims to provide a porous polyimide film original fabric excellent in tensile strength and bending strength, a production method thereof, and a composition suitably used for the production thereof. And

  The present inventors are excellent in tensile strength and bending strength even when a polyimide film containing a polyimide containing a structural unit having a specific structure is made porous, and by applying force such as tension and winding during the production of the original fabric. The inventors have found that the occurrence of film cracking can be suppressed, and that the raw material can be made into a raw material having a long shape (for example, at least 1 m or more) and excellent in winding property, and the present invention has been completed. That is, the present invention is as follows.

  A first aspect of the present invention is a porous polyimide film original fabric having a tensile strength defined by ASTM standard D638 of 45 MPa or more.

（上記式中、Ａ^１１及びＡ^１２は各々独立に、芳香族テトラカルボン酸無水物を含む酸無水物から誘導される４価の芳香族基を表し、Ｂ^１１及びＢ^１２は各々独立に、芳香族ジアミンから誘導される２価のジアミン残基を表し、Ａ^１２及びＢ^１２よりなる群から選択される少なくとも１つはその構造中に２価のスペーサー基を含む。） The 2nd aspect of this invention is a porous polyimide film original fabric containing the polyimide containing the structural unit represented by following formula (1-1) and (1-2).

(In the above formula, A ¹¹ and A ¹² each independently represents a tetravalent aromatic group derived from an acid anhydride containing an aromatic tetracarboxylic acid anhydride, and B ¹¹ and B ¹² are each independently This represents a divalent diamine residue derived from an aromatic diamine, and at least one selected from the group consisting of A ¹² and B ¹² contains a divalent spacer group in its structure.

（上記式中、Ａ^２１及びＡ^２２は各々独立に、芳香族テトラカルボン酸無水物を含む酸無水物から誘導される４価の芳香族基を表し、Ｂ^２１及びＢ^２２は各々独立に、芳香族ジアミンから誘導される２価のジアミン残基を表し、Ａ^２２及びＢ^２２は、下記（Ｉ）及び（ＩＩ）よりなる群から選択される少なくとも１つの条件を満たす。
（Ｉ）Ａ^２２を誘導する芳香族テトラカルボン酸無水物の電子親和力（Ｅａ）が２．６ｅＶ以下である。
（ＩＩ）Ｂ^２２を誘導する芳香族ジアミンが、Ｂ^２１を誘導する芳香族ジアミンと異なる芳香族ジアミンであって、４０℃の水に対する溶解度が０．１ｇ／Ｌ以上である。） A third aspect of the present invention is a porous polyimide film raw material containing polyimide containing structural units represented by the following formulas (2-1) and (2-2).

(In the above formula, A ²¹ and A ²² each independently represents a tetravalent aromatic group derived from an acid anhydride containing an aromatic tetracarboxylic anhydride, and B ²¹ and B ²² are each independently Represents a divalent diamine residue derived from an aromatic diamine, and A ²² and B ²² satisfy at least one condition selected from the group consisting of (I) and (II) below.
(I) The electron affinity (Ea) of the aromatic tetracarboxylic anhydride that induces A ²² is 2.6 eV or less.
(II) The aromatic diamine for inducing B ²² is an aromatic diamine different from the aromatic diamine for inducing B ²¹ , and the solubility in water at 40 ° C. is 0.1 g / L or more. )

A fourth aspect of the present invention is a method for producing a porous polyimide film original fabric,
A film forming step of forming a coating film containing the polyimide precursor and fine particles by applying a composition containing polyamic acid, which is a polyimide precursor, and fine particles onto a substrate to form a coating film, and then drying the coating film. And a firing step of firing the coating film,
The baking step also serves as a fine particle removal step for removing the fine particles, or further includes the fine particle removal step,
Including a peeling step of peeling the coating film or the produced porous polyimide film raw material from the substrate after the baking step after the coating film forming step, after the baking step, or after the fine particle removing step,
It is a manufacturing method whose tensile strength prescribed | regulated by ASTM standard D638 of the said porous polyimide film original fabric is 45 Mpa or more.

（上記式中、Ａ^１１、Ａ^１２、Ｂ^１１及びＢ^１２は上記式（１−１）及び（１−２）におけるものと同義であり、Ａ^１２及びＢ^１２よりなる群から選択される少なくとも１つはその構造中に２価のスペーサー基を含む。）

（上記式中、Ａ^２１、Ａ^２２、Ｂ^２１及びＢ^２２は上記式（２−１）及び（２−２）におけるものと同義であり、Ａ^２２及びＢ^２２は、上記（Ｉ）及び（ＩＩ）よりなる群から選択される少なくとも１つの条件を満たす。） A fifth aspect of the present invention is represented by polyamic acid containing structural units represented by the following formulas (3-1) and (3-2) or represented by the following formulas (4-1) and (4-2). It is a composition containing a polyamic acid containing a structural unit and containing fine particles.

(In the above formula, A ¹¹ , A ¹² , B ¹¹ and B ¹² are the same as those in the above formulas (1-1) and (1-2), and at least selected from the group consisting of A ¹² and B ¹² One contains a divalent spacer group in its structure.)

(In the above formulas, A ²¹ , A ²² , B ²¹ and B ²² have the same meanings as in the above formulas (2-1) and (2-2), and A ²² and B ²² represent the above (I) and ( II) at least one condition selected from the group consisting of:

The porous polyimide film original fabric of the present invention is excellent in production suitability by being excellent in tensile strength and bending strength, the occurrence of film cracking due to the force of tension, winding, etc. during the production of the original fabric is suppressed, and is long. It can be a raw material excellent in winding property (for example, at least 1 m or more).
The manufacturing method of this invention can manufacture the said porous polyimide film original fabric suitably.
The composition of this invention can be used suitably for manufacture of the said porous polyimide film original fabric, especially the manufacture by a roll to roll manufacturing method.

Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and can be implemented with appropriate modifications within the scope of the object of the present invention. .
Moreover, in this specification, "-" represents the following from the above unless there is particular notice.

≪Porous polyimide film stock≫
The porous polyimide film original fabric according to the first aspect has a tensile strength defined by ASTM standard D638 of 45 MPa or more.
When the tensile strength is 45 MPa or more, the occurrence of film cracking due to an applied force such as tension during the production of the original fabric is suppressed, and a raw material having excellent long winding properties can be obtained.
The tensile strength is preferably 70 MPa or more, more preferably 80 MPa or more, still more preferably 90 MPa or more, and particularly preferably 100 MPa or more.
The upper limit of the tensile strength is not particularly limited as long as the effects of the present invention are not impaired, but is, for example, 300 MPa or less, and typically 200 MPa or less.

The porous polyimide film original fabric preferably has a bending strength of 60 MPa or more as defined by ASTM standard D790.
When the bending strength is 60 MPa or more, the occurrence of film cracking due to an applied force such as tension during the production of the original fabric is suppressed, and a raw material having excellent long winding properties can be obtained.
The bending strength is preferably 70 MPa or more, more preferably 80 MPa or more, still more preferably 90 MPa or more, particularly preferably 100 MPa or more, and most preferably 110 MPa or more.
The upper limit of the bending strength is not particularly limited as long as the effects of the present invention are not impaired, but is, for example, 400 MPa or less, and typically 300 MPa or less.

From the viewpoint of tensile strength and bending strength, the porous polyimide film original fabric according to the first aspect may include polyimide containing structural units represented by the following formulas (1-1) and (1-2). preferable.
From the viewpoint of tensile strength and bending strength, the porous polyimide film original fabric according to the first aspect may also contain polyimide containing structural units represented by the following formulas (2-1) and (2-2). preferable.

（上記式中、Ａ^１１及びＡ^１２は各々独立に、芳香族テトラカルボン酸無水物を含む酸無水物から誘導される４価の芳香族基を表し、Ｂ^１１及びＢ^１２は各々独立に、芳香族ジアミンから誘導される２価のジアミン残基を表し、Ａ^１２及びＢ^１２よりなる群から選択される少なくとも１つはその構造中に２価のスペーサー基を含む。） The porous polyimide film raw material which concerns on a 2nd aspect contains the polyimide containing the structural unit represented by following formula (1-1) and (1-2).

(In the above formula, A ¹¹ and A ¹² each independently represents a tetravalent aromatic group derived from an acid anhydride containing an aromatic tetracarboxylic acid anhydride, and B ¹¹ and B ¹² are each independently This represents a divalent diamine residue derived from an aromatic diamine, and at least one selected from the group consisting of A ¹² and B ¹² contains a divalent spacer group in its structure.

When at least one selected from the group consisting of A ¹² and B ¹² contains a divalent spacer group in the structure, tensile strength (for example, 45 MPa or more) and bending strength (for example, 60 MPa) suitable for raw fabric production The above can be achieved.
From the viewpoint of more reliably achieving the tensile strength and the bending strength, it is preferable that A ¹² contains a divalent spacer group in the structure.

The aromatic tetracarboxylic dianhydride for deriving the tetravalent aromatic group according to A ¹¹ and A ¹² is a divalent spacer in the structure, at least one selected from the group consisting of A ¹² and B ¹² Any aromatic tetracarboxylic dianhydride conventionally used as a raw material for synthesizing polyamic acid can be selected as long as it contains a group.

  Preferred specific examples of aromatic tetracarboxylic dianhydride include 1,1-bis (2,3-dicarboxyphenyl) ethane dianhydride, bis (2,3-dicarboxyphenyl) methane dianhydride, Bis (3,4-dicarboxyphenyl) methane dianhydride, 9,9-bis phthalic anhydride fluorene, 3,3 ′, 4,4′-diphenylsulfonetetracarboxylic dianhydride, 2,2-bis ( 3,4-dicarboxyphenyl) propane dianhydride, 2,2-bis (2,3-dicarboxyphenyl) propane dianhydride, 2,2-bis (3,4-dicarboxyphenyl) -1,1 , 1,3,3,3-hexafluoropropane dianhydride, 2,2-bis (2,3-dicarboxyphenyl) -1,1,1,3,3,3-hexafluoropropane dianhydride, 3, 3 ', 4, 4'- Nzophenone tetracarboxylic dianhydride, bis (3,4-dicarboxyphenyl) ether dianhydride, bis (2,3-dicarboxyphenyl) ether dianhydride, 2,2 ′, 3,3′- Benzophenone tetracarboxylic dianhydride, 4,4- (p-phenylenedioxy) diphthalic dianhydride, 4,4- (m-phenylenedioxy) diphthalic dianhydride, pyromellitic dianhydride (PMDA) ), 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride (BPDA), 2,3,3 ′, 4′-biphenyltetracarboxylic dianhydride, 2,2,6,6-biphenyl Tetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 2,3,6,7-naphthalenetetracar Acid dianhydride, 1,2,3,4-benzenetetracarboxylic dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, 2,3,6,7-anthracenetetracarboxylic acid A dianhydride, 1,2,7,8-phenanthrenetetracarboxylic dianhydride etc. are mentioned. These tetracarboxylic dianhydrides may be used alone or in combination of two or more.

In addition, the aromatic diamine for deriving the divalent diamine residue according to B ¹¹ and B ¹² includes at least one selected from the group consisting of A ¹² and B ¹² including a divalent spacer group in its structure. As long as the aromatic diamine is conventionally used as a raw material for synthesizing polyamic acid, it can be appropriately selected.

  Examples of the aromatic diamine include diamino compounds in which one or two or more and ten phenyl groups are bonded. Specifically, phenylenediamine and derivatives thereof, diaminobiphenyl compounds and derivatives thereof, diaminodiphenyl compounds and derivatives thereof, diaminotriphenyl compounds and derivatives thereof, diaminonaphthalene and derivatives thereof, aminophenylaminoindane and derivatives thereof, diaminotetraphenyl Compounds and derivatives thereof, diaminohexaphenyl compounds and derivatives thereof, and cardo-type fluorenediamine derivatives.

  Phenylenediamine is m-phenylenediamine (MDA), p-phenylenediamine (PDA), etc., and phenylenediamine derivatives include diamines to which alkyl groups such as methyl group and ethyl group are bonded, such as 2,4-diaminotoluene. 2,4-triphenylenediamine and the like.

  The diaminobiphenyl compound is a compound in which two aminophenyl groups are bonded to each other. For example, 4,4'-diaminobiphenyl, 4,4'-diamino-2,2'-bis (trifluoromethyl) biphenyl, and the like.

  The diaminodiphenyl compound is a compound in which two aminophenyl groups are bonded to each other via other groups. The bond is an ether bond, a sulfonyl bond, a thioether bond, a bond by alkylene or a derivative group thereof, an imino bond, an azo bond, a phosphine oxide bond, an amide bond, a ureylene bond, or the like. The alkylene bond has 1 to 6 carbon atoms, and the derivative group has one or more hydrogen atoms in the alkylene group substituted with halogen atoms or the like.

  Examples of diaminodiphenyl compounds include 3,3′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, 4,4′-diaminodiphenyl ether, 3,3′-diaminodiphenyl sulfone, 3,4′-diaminodiphenyl sulfone, 4,4'-diaminodiphenylsulfone, 3,3'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl ketone 3,4′-diaminodiphenyl ketone, 2,2-bis (p-aminophenyl) propane, 2,2′-bis (p-aminophenyl) hexafluoropropane, 4-methyl-2,4-bis (p -Aminophenyl) -1-pentene, 4-methyl-2 4-bis (p-aminophenyl) -2-pentene, iminodianiline, 4-methyl-2,4-bis (p-aminophenyl) pentane, bis (p-aminophenyl) phosphine oxide, 4,4′- Diaminoazobenzene, 4,4′-diaminodiphenylurea, 4,4′-diaminodiphenylamide, 1,4-bis (4-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,3 -Bis (3-aminophenoxy) benzene, 4,4'-bis (4-aminophenoxy) biphenyl, bis [4- (4-aminophenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] Sulfone, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 2,2-bis [4- (4-aminophene) ) Phenyl] hexafluoropropane, and the like.

  The diaminotriphenyl compound is obtained by bonding two aminophenyl groups and one phenylene group via other groups, and the other groups are the same as those of the diaminodiphenyl compounds. Examples of diaminotriphenyl compounds include 1,3-bis (m-aminophenoxy) benzene, 1,3-bis (p-aminophenoxy) benzene, 1,4-bis (p-aminophenoxy) benzene, and the like. be able to.

  Examples of diaminonaphthalene include 1,5-diaminonaphthalene and 2,6-diaminonaphthalene.

  Examples of aminophenylaminoindane include 5 or 6-amino-1- (p-aminophenyl) -1,3,3-trimethylindane.

  Examples of diaminotetraphenyl compounds include 4,4′-bis (p-aminophenoxy) biphenyl, 2,2′-bis [p- (p′-aminophenoxy) phenyl] propane, 2,2′-bis [ p- (p′-aminophenoxy) biphenyl] propane, 2,2′-bis [p- (m-aminophenoxy) phenyl] benzophenone, and the like.

  Examples of the cardo type fluorenediamine derivative include 9,9-bisaniline fluorene.

  A compound in which the hydrogen atom of these diamines is substituted with at least one substituent selected from the group such as a halogen atom, a methyl group, a methoxy group, a cyano group, and a phenyl group may be used.

The divalent spacer group includes an ether bond, a thioether bond, a carbonyl group, an alkylene group, a fluorinated alkylene group, a sulfonyl group, a fluorenylene group (two hydrogen atoms bonded to the 9th carbon atom of fluorene). And divalent groups that can be removed).
The alkylene group is preferably a linear or branched alkylene group having 1 to 5 carbon atoms, and examples thereof include a methylene group, an ethylene group, a propylene group, and a dimethylmethylene group.
The fluorinated alkylene group is preferably a linear or branched fluorinated alkylene group having 1 to 5 carbon atoms, such as a difluoromethylene group, a tetrafluoroethylene group, or a bis (trifluoromethyl) methylene group. Is mentioned.

When A ¹² contains a divalent spacer group in its structure, A ¹² can be represented by the following formula (1-2-1).
^{Further, B 12} is, if it contains divalent spacer group in its ^{structure, B 12} can be represented by the following formula (1-2-2).

（上記式中、Ａ^１２１及びＡ^１２２は各々独立に、３価の芳香族基を表し、Ｂ^１２１及びＢ^１２２は各々独立に、２価の芳香族基を表し、Ｘ^１及びＸ^２は各々独立に、２価のスペーサー基を表し、＊は結合手を表す。）
３価の芳香族基としては、ベンゼントリイル基、ナフタレントリイル基等が挙げられ、ベンゼントリイル基が好ましい。ベンゼントリイル基としては、ベンゼン−１，２，４−トリイル基が好ましい。
２価の芳香族基としては、フェニレン基、ナフチレン基等が挙げられ、フェニレン基が好ましい。フェニレン基としては、ｐ−フェニレン基又はｍ−フェニレン基が好ましく、ｐ−フェニレン基がより好ましい。

(In the above formula, A ¹²¹ and A ¹²² each independently represent a trivalent aromatic group, B ¹²¹ and B ¹²² each independently represent a divalent aromatic group, and X ¹ and X ² each represent Independently, it represents a divalent spacer group, and * represents a bond.)
Examples of the trivalent aromatic group include a benzenetriyl group and a naphthalenetriyl group, and a benzenetriyl group is preferable. As the benzenetriyl group, a benzene-1,2,4-triyl group is preferable.
Examples of the divalent aromatic group include a phenylene group and a naphthylene group, and a phenylene group is preferable. As the phenylene group, a p-phenylene group or an m-phenylene group is preferable, and a p-phenylene group is more preferable.

When A ¹² contains a divalent spacer group in its structure, specific examples of the aromatic tetracarboxylic acid anhydride that derives the tetravalent aromatic group according to A ¹² include 1,1-bis (2 , 3-Dicarboxyphenyl) ethane dianhydride, bis (2,3-dicarboxyphenyl) methane dianhydride, bis (3,4-dicarboxyphenyl) methane dianhydride, 9,9-bisphthalic anhydride Fluorene (BPAF), 3,3 ′, 4,4′-diphenylsulfonetetracarboxylic dianhydride (DSDA), 2,2-bis (3,4-dicarboxyphenyl) propane dianhydride, 2,2- Bis (2,3-dicarboxyphenyl) propane dianhydride, 2,2-bis (3,4-dicarboxyphenyl) -1,1,1,3,3,3-hexafluoropropane dianhydride (6FDA ), 2,2- Bis (2,3-dicarboxyphenyl) -1,1,1,3,3,3-hexafluoropropane dianhydride, 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride (BTDA) Bis (3,4-dicarboxyphenyl) ether dianhydride (ODPA), bis (2,3-dicarboxyphenyl) ether dianhydride, 2,2 ′, 3,3′-benzophenonetetracarboxylic dianhydride Products, 4,4- (p-phenylenedioxy) diphthalic dianhydride, 4,4- (m-phenylenedioxy) diphthalic dianhydride, and the like.

When B ¹² contains a divalent spacer group in its structure, specific examples of the aromatic diamine for deriving the divalent diamine residue according to B ¹² include 3,3′-diaminodiphenyl ether, 3,4 '-Diaminodiphenyl ether, 4,4'-diaminodiphenyl ether (ODA), 3,3'-diaminodiphenyl sulfone, 3,4'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfone (DDS), 3,3' -Diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane (DDM), 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl ketone, 3,4'-diaminodiphenyl ketone, 2,2-bis (p-aminophenyl) propane, 2,2′-bis (p-aminophenyl) Xafluoropropane, 4-methyl-2,4-bis (p-aminophenyl) -1-pentene, 4-methyl-2,4-bis (p-aminophenyl) -2-pentene, iminodianiline, 4- Methyl-2,4-bis (p-aminophenyl) pentane, bis (p-aminophenyl) phosphine oxide, 4,4′-diaminoazobenzene, 4,4′-diaminodiphenylurea, 4,4′-diaminodiphenylamide 1,4-bis (4-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,3-bis (3-aminophenoxy) benzene, 4,4′-bis (4-amino) Phenoxy) biphenyl, bis [4- (4-aminophenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] sulfone, 2 2- bis [4- (4-aminophenoxy) phenyl] propane, 2,2-bis [4- (4-aminophenoxy) phenyl] hexafluoropropane, and the like.

As content of the structural unit represented by the said Formula (1-1) in the said polyimide, it is preferable that it is 40 mol% or more from a viewpoint of tensile strength and bending strength, and it is more preferably 50 mol% or more. Preferably, it is 60 mol% or more.
Although there is no restriction | limiting in particular as long as the effect of this invention is not impaired as content value of the structural unit represented by the said Formula (1-1), For example, 99 mol% or less, 95 mol% or less, Is 90 mol% or less.

As content of the structural unit represented by the said Formula (1-2) in the said polyimide, it is preferable that it is 60 mol% or less from a viewpoint of tensile strength and bending strength, and it is more preferably 50 mol% or less. Preferably, it is 40 mol% or less.
The lower limit of the content of the structural unit represented by the above formula (1-2) is not particularly limited as long as the effects of the present invention are not impaired, but typically, for example, 1 mol% or more, 5 mol% or more, Is 10 mol% or more.

（上記式中、Ａ^２１及びＡ^２２は各々独立に、芳香族テトラカルボン酸無水物を含む酸無水物から誘導される４価の芳香族基を表し、Ｂ^２１及びＢ^２２は各々独立に、芳香族ジアミンから誘導される２価のジアミン残基を表し、Ａ^２２及びＢ^２２は、下記（Ｉ）及び（ＩＩ）よりなる群から選択される少なくとも１つの条件を満たす。
（Ｉ）Ａ^２２を誘導する芳香族テトラカルボン酸無水物の電子親和力（Ｅａ）が２．６ｅＶ以下である。
（ＩＩ）Ｂ^２２を誘導する芳香族ジアミンが、Ｂ^２１を誘導する芳香族ジアミンと異なる芳香族ジアミンであって、４０℃の水に対する溶解度が０．１ｇ／Ｌ以上である。）
Ａ^２２及びＢ^２２が、上記（Ｉ）及び（ＩＩ）よりなる群から選択される少なくとも１つの条件を満たすことにより、原反製造に好適な引張強度（例えば、４５ＭＰａ以上）及び曲げ強度（例えば６０ＭＰａ以上）を達成することができる。
引張強度及び曲げ強度をより確実に達成する観点から、上記（Ｉ）の条件を満たすことが好ましい。 The porous polyimide film raw material which concerns on a 3rd aspect contains the polyimide containing the structural unit represented by following formula (2-1) and (2-2).

(In the above formula, A ²¹ and A ²² each independently represents a tetravalent aromatic group derived from an acid anhydride containing an aromatic tetracarboxylic anhydride, and B ²¹ and B ²² are each independently Represents a divalent diamine residue derived from an aromatic diamine, and A ²² and B ²² satisfy at least one condition selected from the group consisting of (I) and (II) below.
(I) The electron affinity (Ea) of the aromatic tetracarboxylic anhydride that induces A ²² is 2.6 eV or less.
(II) The aromatic diamine for inducing B ²² is an aromatic diamine different from the aromatic diamine for inducing B ²¹ , and the solubility in water at 40 ° C. is 0.1 g / L or more. )
When A ²² and B ²² satisfy at least one condition selected from the group consisting of (I) and (II) above, a tensile strength (for example, 45 MPa or more) and a bending strength (for example, 45 MPa or more) suitable for raw material production 60 MPa or more) can be achieved.
From the viewpoint of more reliably achieving the tensile strength and the bending strength, it is preferable that the condition (I) is satisfied.

Aromatic tetracarboxylic acid dianhydride to induce a tetravalent aromatic group of the A ²¹ and ^{A 22 are, A 22} and ^{B 22} is the (I) and at least one selected from the group consisting of (II) As long as the condition is satisfied, it can be appropriately selected from aromatic tetracarboxylic dianhydrides conventionally used as raw materials for synthesizing polyamic acid.
Specific examples of the aromatic tetracarboxylic dianhydride for deriving the tetravalent aromatic group according to A ²¹ and A ²² include an aromatic tetracarboxylic group for deriving the tetravalent aromatic group according to A ¹¹ and A ¹² Specific examples of the acid dianhydride include those described above.

Aromatic diamines which induces a divalent diamine residue of the B ¹¹ and ^{B 12,} at least one condition is satisfied as ^long as ^{A 22} and ^{B 22} is selected from the group consisting of (I) and (II) It can be appropriately selected from aromatic diamines conventionally used as a raw material for synthesizing polyamic acid.
Specific examples of the aromatic diamine to induce divalent diamine residue of the B ¹¹ and B ^12, described above as specific examples of the aromatic diamine to induce divalent diamine residue of the B ¹¹ and B ¹² The thing similar to a thing is mentioned.

Regarding (I) above, Ea of the aromatic tetracarboxylic anhydride that derives A ²² is described in the document CONSULTANTS BUREAU POLYIMIDES Thermally Stable Polymers (M. I. Bessonov, M. M. Koton, V. V. Kudryav. A. Laius), V. M.M. Svetlicnyi, K .; K. Kalnin'sh, V.A. V. Kudryavtsev, and M.M. M.M. Botton, Dokl. Akad. Nauk. , 237, 612-615 (1977) and the like.
The electron affinity of the aromatic tetracarboxylic acid anhydride to induce A ²² (Ea) is preferably not more than 2.3 eV.
Although there is no restriction | limiting in particular as a lower limit of Ea, For example, it is 1.0 eV or more, and is 1.3 eV or more typically.

It illustrates the structure and the electron affinity of the aromatic tetracarboxylic acid anhydride to induce A ²² are shown below, but the invention is not limited thereto.
In the following examples, the numerical value in parentheses is the electron affinity.

Regarding the above (II), “the solubility in water at 40 ° C. is 0.1 g / L or more” means the limit amount (g) at which the aromatic diamine for inducing B ²² dissolves in 1 L (liter) of water at 40 ° C. To do. This value can be easily searched by SciFinder (registered trademark) known as a search service based on a database such as a chemical abstract. Here, among the solubility under various conditions, a value at pH 7 calculated by Advanced Chemistry Development (ACD / Labs) Software V11.02 (Copyright 1994-2011 ACD / Labs) can be adopted.
The solubility of the aromatic diamine to induce B ²² is preferably at 0.5 g / L or more, more preferably 1.0 g / L or more.
Although there is no restriction | limiting in particular as an upper limit of solubility, For example, it is 500 g / L or less, and is typically 400 g / L or less.

The structure of the aromatic diamine for inducing B ²² and its solubility in water at 40 ° C. are exemplified below, but the present invention is not limited thereto.
In addition, in the following illustration, the numerical value in a parenthesis is the solubility with respect to 40 degreeC water.

As content of the structural unit represented by the said Formula (2-1) in the said polyimide, it is preferable that it is 40 mol% or more from a viewpoint of tensile strength and bending strength, and it is more preferably 50 mol% or more. Preferably, it is 60 mol% or more.
Although there is no restriction | limiting in particular as long as the effect of this invention is not impaired as content value of the structural unit represented by the said Formula (2-1), For example, 99 mol% or less, 95 mol% or less, Is 90 mol% or less.

The content of the structural unit represented by the above formula (2-2) in the polyimide is preferably 60 mol% or less and more preferably 50 mol% or less from the viewpoint of tensile strength and bending strength. Preferably, it is 40 mol% or less.
The lower limit of the content of the structural unit represented by the above formula (2-2) is not particularly limited as long as the effects of the present invention are not impaired, but typically, for example, 1 mol% or more, 5 mol% or more, Is 10 mol% or more.

The mass average molecular weight (Mw) of the polyimide contained in the porous polyimide film original fabric according to the first to third embodiments is not particularly limited as long as the effects of the present invention are not impaired, but from the viewpoint of tensile strength and bending strength. It is preferably 5000 or more, more preferably 8000 or more, still more preferably 10,000 or more, and particularly preferably 15,000 or more.
Moreover, when the polyimide precursor solution described later contains an organic solvent, the Mw of the polyimide is not particularly limited as long as the effects of the present invention are not impaired, but even if it is 30,000 or more from the viewpoint of tensile strength and bending strength. It is preferably 50,000 or more.
Although there is no restriction | limiting in particular as long as the upper limit of Mw of a polyimide does not impair the effect of this invention, 100,000 or less are preferable and 80,000 or less are more preferable.
In the present specification, the mass average molecular weight (Mw) is a value measured by gel permeation chromatography (GPC) in terms of polystyrene.

The porous polyimide film original fabric according to the first to third aspects has a plurality of openings irregularly formed on the surface of the original fabric and a plurality of openings irregularly formed on the back surface of the original fabric. It is preferable that it is quality.
The porous polyimide film original fabric according to the first to third aspects includes at least a part of the plurality of openings formed on the surface of the original fabric and at least a part of the plurality of openings formed on the back surface of the original fabric. It is preferable that the material is porous with a communication hole that communicates with the inside of the film and that communicates the original surface and the original surface.

From the viewpoint of the connectivity that allows liquid and / or ionic molecules to pass through or collects a specific substance, for example, filter applications for the purpose of separation of substances and retention of electrolytes, and separator applications. It is preferable that the porous polyimide film raw material which concerns on the aspect of ~ 3 has a porosity of 50% or more, It is more preferable that a porosity is 55% or more, It is further that a porosity is 60% or more. The porosity is particularly preferably 65% or more.
Although there is no restriction | limiting in particular as an upper limit of a porosity, From a viewpoint of intensity | strength, it is preferable that it is 90% or less, and it is more preferable that it is 80% or less.

The porosity indicates, for example, the ratio of voids per unit volume of the original fabric. The porosity can be calculated by, for example, the following formula (A).
Porosity (%) = {Volume of test piece (cm ³ ) − [Weight of test piece (g) / Specific gravity of polyimide (g / cm ³ )]} / Volume of test piece (cm ³ ) × 100 (A)
As will be described later, a desired porosity can be obtained by appropriately adjusting the particle size and content of the fine particles used in producing the raw fabric.

The porous polyimide film original fabric according to the first to third embodiments is excellent in tensile strength and bending strength, so that the occurrence of film cracking due to the force of tension, winding, etc. during the production of the original fabric is suppressed. It can be a raw material. Although there is no restriction | limiting in particular as the film length of the porous polyimide film original fabric which concerns on the 1st-3rd aspect, It is preferable that it is 1 m or more, It is more preferable that it is 5 m or more, It is still more preferable that it is 10 m or more. 30 m or more, particularly preferably 40 m or more.
Although there is no restriction | limiting in particular as an upper limit of film length, For example, it is 2000 m or less, and is typically 1000 m or less.
There is no restriction | limiting in particular as the film width of an original fabric, It can set suitably.
There is no restriction | limiting in particular as thickness of an original fabric, 1 micrometer or more and 500 micrometers or less are preferable, 3 micrometers or more and 200 micrometers or less are more preferable, 5 micrometers or more and 100 micrometers or less are further more preferable, and 7 micrometers or more and 80 micrometers or less are especially preferable.

The porous polyimide film original fabric according to the first to third embodiments has excellent tensile strength and bending strength, and is excellent in winding property, so that it has a diameter of 2.5 cm (1 inch) or more and 25 cm (10 inches) or less. It can be formed by winding around a core, and is preferably formed by winding around a core having a diameter of 5 cm (2 inches) or more and 10 cm (4 inches) or less. As a result, the winding length per roll of raw material becomes longer, and the transportation and storage cost can be suppressed.
Although there is no restriction | limiting in particular as a material of a winding core, The product made from stainless steel (for example, product made from SUS), the product made from a polyethylene terephthalate (PET), etc. are mentioned.

≪Use of porous polyimide film stock≫
The porous polyimide film source described above provides various separators (for example, separators for secondary batteries such as nickel cadmium, nickel metal hydride batteries, lithium ion batteries), various filters, fuel cell electrolyte membranes, and low dielectric constant materials. be able to.
The porous polyimide film raw material described above is excellent in tensile strength and bending strength, so that the occurrence of film cracking due to the force of tension, winding, etc. during the production of the raw material is suppressed. 1m or more), it is suitable for manufacturing batteries and filter devices.

≪Method of manufacturing porous polyimide film raw material≫
The method for producing a porous polyimide film raw material according to the fourth aspect is as follows:
A composition containing polyamic acid as a polyimide precursor and fine particles (hereinafter also simply referred to as “polyimide precursor solution”) is applied onto a substrate to form a coating film, and then the coating film is dried and the coating composition is dried. Including a film forming step of forming a film containing a polyimide precursor and fine particles, and a baking step of baking the film,
The baking step also serves as a fine particle removal step for removing the fine particles, or further includes the fine particle removal step,
Including a peeling step of peeling the coating film or the produced porous polyimide film raw material from the substrate after the baking step after the coating film forming step, after the baking step, or after the fine particle removing step,
The tensile strength prescribed | regulated by ASTM standard D638 of the said porous polyimide film original fabric is 45 Mpa or more.

A preferable range of the tensile strength is the same as the range described above for the porous polyimide film original fabric according to the first aspect.
Moreover, the said porous polyimide film original fabric is the same as the range mentioned above about the porous polyimide film original fabric which concerns on a 1st aspect also about the preferable range of the bending strength prescribed | regulated by ASTM specification D790.
It is preferable that the manufacturing method of the porous polyimide film raw material is performed by roll-to-roll from the viewpoint of productivity.

（上記式中、Ａ^１１、Ａ^１２、Ｂ^１１及びＢ^１２は上記式（１−１）及び（１−２）におけるものと同義であり、Ａ^１２及びＢ^１２よりなる群から選択される少なくとも１つはその構造中に２価のスペーサー基を含む。） <Film formation process>
(Polyamide acid)
The polyimide precursor includes a polyamic acid containing structural units represented by the following formulas (3-1) and (3-2), or structural units represented by the following formulas (4-1) and (4-2). It is preferable that it is a polyamic acid containing.

(In the above formula, A ¹¹ , A ¹² , B ¹¹ and B ¹² are the same as those in the above formulas (1-1) and (1-2), and at least selected from the group consisting of A ¹² and B ¹² One contains a divalent spacer group in its structure.)

（上記式中、Ａ^２１、Ａ^２２、Ｂ^２１及びＢ^２２は上記式（２−１）及び（２−２）におけるものと同義であり、Ａ^２２及びＢ^２２は、上記（Ｉ）及び（ＩＩ）よりなる群から選択される少なくとも１つの条件を満たす。）

(In the above formulas, A ²¹ , A ²² , B ²¹ and B ²² have the same meanings as in the above formulas (2-1) and (2-2), and A ²² and B ²² represent the above (I) and ( II) at least one condition selected from the group consisting of:

The composition which concerns on a 5th aspect is represented by the polyamic acid containing the structural unit represented by the said Formula (3-1) and (3-2), or said Formula (4-1) and (4-2). The polyamic acid containing the structural unit is contained, and the fine particle mentioned later is included.
The composition according to the fifth aspect can be suitably used as a polyimide precursor solution in the production method according to the fourth aspect. As a result, a porous polyimide film original fabric having a tensile strength defined by ASTM standard D638 of 45 MPa or more can be suitably produced.

As content of the structural unit represented by the said Formula (3-1) or (4-1) in the said polyamic acid, it is preferable that it is 40 mol% or more, and it is more preferable that it is 50 mol% or more, More preferably, it is 60 mol% or more.
Although there is no restriction | limiting in particular as long as the upper limit of content of the structural unit represented by the said Formula (3-1) or (4-1) is not impaired, for example, 99 mol% or less, 95 mol % Or less, typically 90 mol% or less.

The content of the structural unit represented by the formula (3-2) or (4-2) in the polyamic acid is preferably 60 mol% or less, more preferably 50 mol% or less, More preferably, it is 40 mol% or less.
Although there is no restriction | limiting in particular as long as the effect of this invention is not impaired as content value of the structural unit represented by the said Formula (3-2) or (4-2), For example, 1 mol% or more, 5 mol % Or more, typically 10 mol% or more.

  The polyamic acid which is a polyimide precursor can be obtained by polymerizing an aromatic tetracarboxylic dianhydride and an aromatic diamine. Although the usage-amount of aromatic tetracarboxylic dianhydride and aromatic diamine is not specifically limited, 0.50 mol or more and 1.50 mol or less of aromatic diamine are used with respect to 1 mol of aromatic tetracarboxylic dianhydride. It is preferable to use 0.60 mol or more and 1.30 mol or less, and it is particularly preferable to use 0.70 mol or more and 1.20 mol or less.

The aromatic tetracarboxylic dianhydride can be appropriately selected from aromatic tetracarboxylic dianhydrides conventionally used as raw materials for synthesizing polyamic acid. Aromatic tetracarboxylic dianhydrides may be used in combination of two or more.
Specific examples of the aromatic tetracarboxylic dianhydride include those described above as specific examples of the aromatic tetracarboxylic dianhydride for deriving the tetravalent aromatic group according to A ¹¹ and A ^12. Can be mentioned.

The aromatic diamine can be appropriately selected from aromatic diamines conventionally used as a raw material for synthesizing polyamic acid. Aromatic diamines may be used in combination of two or more.
Specific examples of the aromatic diamine include the same as those described above as specific examples of the aromatic diamine for deriving the divalent diamine residue according to B ¹¹ and B ¹² .

  There is no restriction | limiting in particular in the means to manufacture the polyamic acid used by this invention, For example, well-known methods, such as the method of making aromatic tetracarboxylic dianhydride and aromatic diamine react in an organic solvent, can be used. .

  The reaction between the aromatic tetracarboxylic dianhydride and the aromatic diamine is usually performed in an organic solvent. The organic solvent used for the reaction of aromatic tetracarboxylic dianhydride and aromatic diamine can dissolve aromatic tetracarboxylic dianhydride and aromatic diamine, and aromatic tetracarboxylic dianhydride And if it does not react with aromatic diamine, it will not specifically limit. An organic solvent can be used individually or in mixture of 2 or more types.

  Examples of organic solvents used in the reaction of aromatic tetracarboxylic dianhydride and aromatic diamine include N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-diethylacetamide, N, N- Nitrogen-containing polar solvents such as dimethylformamide, N, N-diethylformamide, N-methylcaprolactam, N, N, N ′, N′-tetramethylurea; β-propiolactone, γ-butyrolactone, γ-valerolactone, Lactone polar solvents such as δ-valerolactone, γ-caprolactone and ε-caprolactone; dimethyl sulfoxide; acetonitrile; fatty acid esters such as ethyl lactate and butyl lactate; diethylene glycol dimethyl ether, diethylene glycol diethyl ether, dioxane, tetrahydrofuran, methyl cellosolve acetate Over DOO, ethers such as ethyl cellosolve acetate; include phenolic solvents cresols, and the like. These organic solvents can be used alone or in admixture of two or more. Among these, a combination of the nitrogen-containing polar solvent and the lactone polar solvent is preferable. Although there is no restriction | limiting in particular in the usage-amount of an organic solvent, It is desirable for content of the polyamic acid to produce | generate to be 5 to 50 mass%.

  Among these organic solvents, N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-diethylacetamide, N, N-dimethylformamide, N, N- Nitrogen-containing polar solvents such as diethylformamide, N-methylcaprolactam, N, N, N ′, N′-tetramethylurea are preferred. From the viewpoint of film formability and the like, it may be a mixed solvent to which a lactone polar solvent such as γ-butyrolactone is added, and is preferably added in an amount of 1 to 20% by mass based on the whole organic solvent. More preferably, it is at least 15% by mass.

  The polymerization temperature is generally from -10 ° C to 120 ° C, preferably from 5 ° C to 30 ° C. The polymerization time varies depending on the raw material composition used, but is usually 3 hours or more and 24 hours or less. The intrinsic viscosity of the polyamic acid solution obtained under such conditions is preferably in the range of 1000 cP (centipoise) to 100,000 cP, and more preferably in the range of 5000 cP to 70000 cP.

The Mw of the polyamic acid is not particularly limited as long as the effects of the present invention are not impaired, but it is preferably 5000 or more, and preferably 8000 or more from the viewpoint of the tensile strength and bending strength of the raw fabric to be produced. Is more preferably 10,000 or more, and particularly preferably 15,000 or more.
In addition, when the polyimide precursor solution contains an organic solvent, the Mw of the polyamic acid is not particularly limited as long as the effects of the present invention are not impaired, but from the viewpoint of the tensile strength and bending strength of the raw fabric to be produced, 3 It may be 10,000 or more, and preferably 50,000 or more.
The upper limit of Mw of the polyamic acid is not particularly limited as long as the effect of the present invention is not impaired, but is preferably 100,000 or less, more preferably 80,000 or less.

(Fine particles)
The material of the fine particles contained in the polyimide precursor solution is not particularly limited as long as it is a material that is insoluble in the contained solvent and can be removed from the porous polyimide film raw material in the subsequent fine particle removal step. A well-known thing can be employ | adopted.
When the material of the fine particles is an inorganic material, the material of the inorganic fine particles is not particularly limited as long as the inorganic fine particles can be removed by a method such as chemical treatment or heating. Examples of the material of the inorganic fine particles include metal oxides such as silica (silicon dioxide), calcium carbonate, titanium oxide, and alumina (Al ₂ O ₃ ). Preferable inorganic fine particles include silica fine particles such as calcium carbonate and colloidal silica.

  When the material of the fine particles is an organic material, the material of the organic fine particles includes high molecular weight olefin polymers (polypropylene, polyethylene, polybutadiene, polyisoprene, polytetrafluoroethylene, etc.), aromatic vinyl polymers such as polystyrene, and acrylic resins. (Acrylic acid, methyl acrylate, methyl methacrylate, isobutyl methacrylate, polymethyl methacrylate (PMMA), etc.), organic polymers such as epoxy resin, cellulose, polyvinyl alcohol, polyvinyl butyral, polyester, and polyether. These organic polymers may be a copolymer (for example, a copolymer of methyl methacrylate and styrene, a copolymer of acrylic acid and styrene). Further, organic fine particles of different materials may be used in combination.

The mass of the fine particles is preferably 35% by mass or more and more preferably 40% by mass or more with respect to the total mass of the polyamide and the fine particles in the polyimide precursor solution.
Although there is no restriction | limiting in particular as an upper limit, From a viewpoint of intensity | strength, it is preferable that it is 90 mass% or less, and it is more preferable that it is 85 mass% or less.

The shape of the fine particles is not particularly limited, and may be spherical particles or plate-like particles, but spherical particles are preferable, and those having a high true sphericity are more preferable.
The particle size (average diameter or median diameter) of the fine particles is not particularly limited. For example, the average diameter or median diameter is preferably 10 nm to 2000 nm, more preferably 50 nm to 1500 nm, and more preferably 100 nm to 1000 nm.
The particle size distribution index (d25 / d75) of the fine particles is preferably 1 or more, 6 or less, more preferably 1 or more and 5 or less, and still more preferably 1 or more and 3 or less.
Here, d25 and d75 represent particle diameters with cumulative frequency of particle size distribution of 25% and 75%, respectively, and d25 is the larger particle diameter.

Examples of the solvent that can be included in the polyimide precursor solution include water, an aqueous solution of an organic solvent, and an organic solvent.
Specific examples of the organic solvent include those exemplified as the solvent used for the reaction between the aromatic tetracarboxylic dianhydride and the aromatic diamine. An organic solvent may be used independently and may be used in combination of 2 or more type.
Examples of the organic solvent in the case of an aqueous solution of an organic solvent include polar solvents and water-soluble solvents, such as methyl alcohol, ethyl alcohol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, and 2-methyl-1. Alcohols such as -propanol, 1-pentanol, 2-pentanol, 4-methyl-2-pentanol, 1,1-dimethylethanol, 2,2-dimethyl-1-propanol, tetrahydrofurfuryl alcohol; ethylene glycol Organic solvents such as glycols such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether and diethylene glycol, and alcohols are preferred.
Further, B ²² is, if it meets the above (II), as the solvent, which may comprise a polyimide precursor solution, water or an aqueous solution of the organic solvent is preferred.
When organic fine particles are used as the fine particles, water or an aqueous solution of the above organic solvent is preferable.
When inorganic fine particles are used as the fine particles, the organic solvent that can be contained in the polyimide precursor solution is preferably one that can dissolve polyamic acid, polyimide, and the like but does not dissolve inorganic fine particles.
The solid content concentration of the polyimide precursor solution is preferably 5% by mass or more and 50% by mass or less, and more preferably 10% by mass or more and 40% by mass or less.

(Other ingredients)
The polyimide precursor solution may contain a dispersant. In addition to the components described above, the polyimide precursor solution is used for antistatic, flame retardancy, low-temperature firing, release properties, coating improvement, etc. A known component such as an agent, a condensing agent, a release agent, and a surface conditioner may be appropriately included as necessary.

As said base material, films, such as PET (polyethylene terephthalate) or PEN (polyethylene naphthalate), and a SUS board | substrate are mentioned, for example, It is preferable that it is a PET film.
A method of forming a coating film by applying (for example, applying) a polyimide precursor solution on the substrate and then drying (prebaking) the coating film to form a coating film is 0 under normal pressure or vacuum. And a method of drying and forming the coating film at a temperature of from 120 ° C. to 120 ° C. (preferably from 0 ° C. to 90 ° C.), more preferably from 10 ° C. to 100 ° C. (more preferably from 10 ° C. to 90 ° C.). It is done.
There is no restriction | limiting in particular as thickness of a coating film, 1 micrometer or more and 800 micrometers or less are preferable, 3 micrometers or more and 200 micrometers or less are more preferable, 5 micrometers or more and 100 micrometers or less are further more preferable, and 7 micrometers or more and 80 micrometers or less are especially preferable.

<Baking process>
By the firing step of firing the above-described film containing the polyamic acid that is the polyimide precursor, the polyamic acid can be closed to form a polyimide, whereby a polyimide film can be obtained.
For example, the polyamic acid containing the structural units represented by the above formulas (3-1) and (3-2) is converted into the structural units represented by the above formulas (1-1) and (1-2) by the firing step. The polyamic acid containing a structural unit represented by the above formulas (4-1) and (4-2) can be ring-closed to the containing polyimide, and is represented by the above formulas (2-1) and (2-2). Ring closure can be achieved with polyimide containing structural units.
The firing temperature is preferably 120 ° C. or higher and 500 ° C. or lower, and more preferably 150 ° C. or higher and 450 ° C. or lower.
The firing conditions are, for example, a method in which the temperature is raised from room temperature to 420 ° C. in 3 hours and then held at 420 ° C. for 20 minutes, or the temperature is gradually raised from room temperature to 420 ° C. in increments of 20 ° C. (holding 20 minutes for each step) And a stepwise drying-thermal imidization method such as a final holding at 420 ° C. for 20 minutes can also be used.

(Particle removal process)
The manufacturing method may further include a fine particle removal step.
Inorganic fine particles such as silica can be removed by bringing them into contact with hydrogen fluoride water (HF) or the like to dissolve the inorganic fine particles. Further, when the inorganic fine particles are calcium carbonate, an aqueous hydrochloric acid solution can be used instead of HF.
When the fine particles are organic fine particles and are non-crosslinked resin fine particles, the polyimide film is not dissolved, and the non-crosslinked resin particles can be dissolved and removed with an organic solvent in which the non-crosslinked resin particles are soluble. Examples of such an organic solvent include ethers such as tetrahydrofuran; aromatics such as toluene; ketones such as acetone; esters such as ethyl acetate; Among these, ethers such as tetrahydrofuran are preferable, and tetrahydrofuran is more preferable.

When the firing step also serves as the fine particle removal step, the fine particles are preferably organic fine particles.
If the organic material of organic fine particles decomposes at a lower temperature than polyimide, only the organic fine particles can be lost without causing thermal damage to the polyimide.
For example, resin fine particles made of a linear polymer or a known depolymerizable polymer can be mentioned. A normal linear polymer is a polymer in which a polymer molecular chain is randomly cleaved during thermal decomposition, and a depolymerizable polymer is a polymer in which the polymer is decomposed into monomers during thermal decomposition. Any of them disappears from the polyimide film by decomposing into low molecular weight substances or CO ₂ . The decomposition temperature of the resin fine particles used is preferably 200 ° C. or higher and 400 ° C. or lower, for example.

<Peeling process>
The manufacturing method includes a peeling step of peeling the coating film or the manufactured porous polyimide film raw material from the base material before the baking step after the coating film forming step, after the baking step, or after the fine particle removing step. Including.
Moreover, the said manufacturing method further includes the process wound around the core of diameter 2.5cm or more and 25cm or less from a viewpoint of productivity, when a porous polyimide film original fabric is long (for example, 1 m or more). Is preferred.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the scope of the present invention is not limited to these examples.

(Synthesis example)
Aromatic tetracarboxylic acid anhydrides and aromatic diamines shown in Table 1 below are reacted, and polyamic acids 1 to 3 containing acid anhydride residues and diamine residues at the composition ratio (mol%) in Table 1 below. Comparative polyamide acids 1 and 2 were also obtained.
In Table 1 below, “solubility” indicates solubility in water at 40 ° C.

[Example 1]
Using a homogenizer, 42 g of spherical silica (median average particle size of 280 nm, particle size distribution index (d25 / d75) of 1.5 or less) was uniformly dispersed in 42 g of dimethylacetamide (DMAC) to obtain 84 g of a silica dispersion.
A DMAC solution of polyamic acid 1 obtained above (concentration of polyamic acid 1 of 20% by mass) was prepared, and 52.5 g of the solution, 84 g of the silica dispersion, and 13.5 g of DMAC were mixed, The polyimide precursor solution (composition) of Example 1 was obtained by mixing uniformly using (Sinky Corporation) (the mass ratio is spherical silica: polyamic acid = 80: 20, and the volume ratio is Spherical silica: polyamic acid = 73: 27).

[Comparative Examples 1 and 2]
In place of the DMAC solution of polyamic acid 1, a DMAC solution of comparative polyamic acid 1 (concentration 20% by mass of comparative polyamic acid 1) and a DMAC solution of comparative polyamic acid 2 (concentration of comparative polyamic acid 2 of 20% by mass) Except having used, it carried out similarly to Example 1, and obtained the polyimide precursor solution of the comparative examples 1 and 2.

[Example 2]
A polystyrene particle aqueous dispersion (40 mass%) containing spherical particles of polystyrene (PS) (median average particle size 260 nm, particle size distribution index (d25 / d75) 1.5 or less, hereinafter simply referred to as “polystyrene particles”); The obtained aqueous solution of polyamic acid 1 (concentration of polyamic acid 1 of 15% by mass) was mixed, pure water was further added, and the mixture was uniformly mixed so that the solid content concentration became 23% by mass. The polyimide precursor solution of Example 2 was obtained (the mass ratio is polystyrene particles: polyamic acid = 60: 40, and the volume ratio is polystyrene particles: polyamic acid = 68: 32).

Example 3
Instead of the obtained polyamic acid 1 aqueous solution (polyamic acid 1 concentration 15 mass%), the obtained polyamic acid 1 water / IPA (isopropanol) aqueous solution (polyamic acid 1 concentration 15 mass%, water / A polyimide precursor solution of Example 3 was obtained in the same manner as Example 2 except that IPA = 9/1 (mass ratio) was used.
Example 4
Instead of the obtained aqueous solution of polyamic acid 1 (polyamide acid 1 concentration 15 mass%), the obtained polyamic acid 1 water / NMP (N-methylpyrrolidone) aqueous solution (polyamide acid 1 concentration 15 mass%) The polyimide precursor solution of Example 4 was obtained in the same manner as in Example 2 except that water / NMP = 9/1 (mass ratio) was used.

[Examples 5 and 6 and Comparative Example 3]
Instead of the polyamic acid 1 aqueous solution, the polyamic acid 2 aqueous solution (polyamic acid 2 concentration 15 mass%), the polyamic acid 3 aqueous solution (polyamic acid 3 concentration 15 mass%), and the comparative polyamic acid 2 aqueous solution A polyimide precursor solution of Examples 5 and 6 and a polyimide precursor solution of Comparative Example 3 were obtained in the same manner as in Example 2 except that (concentration 15% by mass of comparative polyamide acid 2) was used.

Example 7
An aqueous dispersion (21% by mass) containing a non-crosslinked styrene / acrylic copolymer (hereinafter simply referred to as “A / St”) having an average particle size of 0.1 μm, and an aqueous solution (polyamide) of the obtained polyamic acid 1 The polyimide precursor solution of Example 7 was obtained by uniformly mixing the acid 1 with a concentration of 21% by mass (for the mass ratio, A / St: polyamic acid = 50: 50, and for the volume ratio). A / St: Polyamic acid = 57: 43).
Example 8
An aqueous dispersion (40% by mass) containing calcium carbonate fine particles (average particle size 700 nm) obtained by the production method described later and an aqueous solution of polyamic acid 1 obtained above (concentration of polyamic acid 1 of 30% by mass) were uniformly formed. To obtain a polyimide precursor solution of Example 8 (the mass ratio is approximately calcium carbonate particles: polyamic acid = 73: 27, and the volume ratio is calcium carbonate particles: polyamic acid = 40: 60.)

[Dispersion of calcium carbonate fine particles]
10 g of calcium carbonate fine particles (batterite type, average particle size 700 nm) unmodified on the surface were added to 50 g of isopropyl alcohol, and stirred for 1 hour using a stirrer while cooling with ice water to prepare an isopropyl alcohol suspension of calcium carbonate fine particles. . On the other hand, 0.2 g of adipic acid was added to 23 g of isopropyl alcohol and stirred for 10 minutes to completely dissolve it to prepare an isopropyl alcohol solution. The isopropyl alcohol suspension and the isopropyl alcohol solution were stirred at room temperature for 2 hours to obtain a slurry containing calcium carbonate fine particles whose surface was modified with adipic acid and isopropyl alcohol. After filtering the slurry using a Kiriyama funnel (manufactured by Kiriyama Seisakusho) and a cellulose filter paper having a collected particle diameter of 1 μm, the filtered product is dried at 120 ° C. for 1 hour, and adipic acid is surface-modified calcium carbonate Fine particles were obtained. 7.2 g of the calcium carbonate fine particles were added to 10.8 g of pure water, and homogenized using a homogenizer for 40 seconds at a grinding power of 20%, and then homogenized for 40 seconds at a grinding power of 30%. Obtained.

(Film formation process and peeling process)
The polyimide precursor solutions (compositions) obtained in Examples 1 to 8 and Comparative Examples 1 to 3 were obtained on a PET film by using a coating apparatus to obtain a final film thickness (film thickness of the porous polyimide film original film). Was applied to form a coating film, and the PET film on which the coating film was formed was placed in a baking furnace and dried at 80 ° C. for 5 minutes to form a coating film.
The resulting coating was peeled from the PET film.

<Film cracking resistance test of coating>
The state of film cracking of the film due to the peeling was visually evaluated according to the following criteria as “film cracking resistance (film)”. The results are shown in Table 2 below.
◯: There was no film cracking.
X: The strength of the film was brittle and film cracking occurred.
XX: The strength of the film was very brittle and many film cracks occurred.

About the film formed from the polyimide precursor solution of Comparative Examples 1-3, the film | membrane crack occurred and the subsequent baking process and fine particle removal process could not be performed.

(Firing process of the film after peeling)
The above film was baked at a furnace temperature of 420 ° C. for 5 minutes using a baking furnace (however, Example 7 was 380 ° C. for 5 minutes) to form a polyimide film.
About the film formed from the polyimide precursor solution of Examples 2-6, the said baking process can serve as a fine particle removal process, and the polystyrene particle | grains can be burned off by the said baking, Thereby, Example 2 with a film thickness of 25 micrometers 6 porous polyimide film raw material was obtained.

(Particle removal process)
For the polyimide film formed from the polyimide precursor solution of Example 1, the porous polyimide of Example 1 having a film thickness of 25 μm was immersed in 10% by mass of hydrogen fluoride water (HF) for 10 minutes to dissolve silica. A film stock was obtained.
The polyimide film formed from the polyimide precursor solution of Example 7 was immersed in the same manner except that tetrahydrofuran (THF) was used instead of 10% by mass of hydrogen fluoride water to dissolve A / St. 7 porous polyimide film raw material was obtained.
The polyimide film formed from the polyimide precursor solution of Example 8 was immersed in the same manner except that 10% by mass hydrochloric acid was used instead of 10% by mass hydrogen fluoride water to dissolve calcium carbonate. 8 porous polyimide film raw material was obtained.
As a result of measuring the porosity of the obtained porous polyimide film raw materials of Examples 1 to 6, all the raw materials were in the range of 60% to 70%. Examples 7 and 8 were in the range of 50% to 60%.

<Tensile strength and bending strength test>
About the test piece of the porous polyimide film original fabric of Examples 1-8 obtained above and Comparative Examples 1-3, tensile strength and bending strength were measured based on the following standard methods (measuring device: EZ-TEST). / CE (manufactured by Shimadzu Corporation)).
Tensile strength: ASTM D638
Flexural modulus: ASTM D790
The results are shown in Table 2 below.

As is clear from the results shown in Table 2, the requirement “including the structural units represented by the above formulas (3-1) and (3-2)” and “the above formulas (4-1) and (4) -2) In Comparative Examples 1 to 3 using comparative polyamic acids 1 and 2 that do not satisfy any of the requirements "including the structural unit represented by 2)" A film crack occurred.
In addition, the porous polyimide film original fabrics of Comparative Examples 1 to 3 are not long enough to have a tensile strength of less than 45 MPa, have a bending strength of less than 60 MPa, and can be long (for example, 1 m or more). There wasn't.
On the other hand, the requirement “including structural units represented by the above formulas (3-1) and (3-2)” and “including structural units represented by the above formulas (4-1) and (4-2)” are included. In any of Examples 1 to 8 using any one of the polyamic acids 1 to 3 satisfying at least one of the requirements, the film has a length of 40 m without any film cracking after coating and drying and peeling. We were able to.
Moreover, the porous polyimide film original fabrics of Examples 1 to 8 are all excellent in tensile strength (45 MPa or more) and bending strength (60 MPa or more), wound on a core having a diameter of 3 inches, and roll material having a length of 40 m. And was able to.

  Moreover, Example 1 using the polyamic acid 1 whose content of the structural unit represented by the above formula (3-2) or (4-2) is 60 mol% or less, and the above formula (3-2) or From the comparison with Example 6 using the polyamic acid 3 in which the content of the structural unit represented by (4-2) exceeds 60 mol%, it is represented by the above formula (3-2) or (4-2). It can be seen that when the content of the constituent unit is 60 mol% or less, the tensile strength and the bending strength are excellent.

Claims (16)

  A porous polyimide film original fabric having a tensile strength specified by ASTM standard D638 of 45 MPa or more.   The porous polyimide film original fabric according to claim 1, which has a bending strength of 60 MPa or more as defined by ASTM standard D790. The porous polyimide film original fabric of Claim 1 or 2 containing the polyimide containing the structural unit represented by following formula (1-1) and (1-2).

(In the above formula, A ¹¹ and A ¹² each independently represents a tetravalent aromatic group derived from an acid anhydride containing an aromatic tetracarboxylic acid anhydride, and B ¹¹ and B ¹² are each independently This represents a divalent diamine residue derived from an aromatic diamine, and at least one selected from the group consisting of A ¹² and B ¹² contains a divalent spacer group in its structure. The porous polyimide film original fabric of Claim 1 or 2 containing the polyimide containing the structural unit represented by following formula (2-1) and (2-2).

(In the above formula, A ²¹ and A ²² each independently represents a tetravalent aromatic group derived from an acid anhydride containing an aromatic tetracarboxylic anhydride, and B ²¹ and B ²² are each independently Represents a divalent diamine residue derived from an aromatic diamine, and A ²² and B ²² satisfy at least one condition selected from the group consisting of (I) and (II) below.
(I) The electron affinity of the aromatic tetracarboxylic anhydride that induces A ²² is 2.6 eV or less.
(II) The aromatic diamine for inducing B ²² is an aromatic diamine different from the aromatic diamine for inducing B ²¹ , and the solubility in water at 40 ° C. is 0.1 g / L or more. ) The porous polyimide film original fabric containing the polyimide containing the structural unit represented by following formula (1-1) and (1-2).

(In the above formula, A ¹¹ and A ¹² each independently represents a tetravalent aromatic group derived from an acid anhydride containing an aromatic tetracarboxylic acid anhydride, and B ¹¹ and B ¹² are each independently This represents a divalent diamine residue derived from an aromatic diamine, and at least one selected from the group consisting of A ¹² and B ¹² contains a divalent spacer group in its structure. The porous polyimide film original fabric containing the polyimide containing the structural unit represented by following formula (2-1) and (2-2).

(In the above formula, A ²¹ and A ²² each independently represents a tetravalent aromatic group derived from an acid anhydride containing an aromatic tetracarboxylic anhydride, and B ²¹ and B ²² are each independently This represents a divalent diamine residue derived from an aromatic diamine, and A ²² and B ²² satisfy at least one condition selected from the group consisting of (I) and (II) below.
(I) The electron affinity of the aromatic tetracarboxylic anhydride that induces A ²² is 2.6 eV or less.
(II) The aromatic diamine for inducing B ²² is an aromatic diamine different from the aromatic diamine for inducing B ²¹ , and the solubility in water at 40 ° C. is 0.1 g / L or more. )   The porous polyimide film raw material of Claim 5 or 6 whose content of the structural unit represented by the said Formula (1-2) or (2-2) in the said polyimide is 60 mol% or less.   The porous polyimide film original fabric according to any one of claims 1 to 7, wherein the film length is 1 m or more.   The porous polyimide film original fabric according to any one of claims 1 to 8, which is wound around a core having a diameter of 2.5 cm to 25 cm.   The porous polyimide film raw material of any one of Claims 1-9 whose porosity is 60 mass% or more. A method for producing a porous polyimide film raw material,
A film forming step of forming a coating film containing a polyimide precursor and fine particles by applying a composition containing polyamic acid, which is a polyimide precursor, and fine particles onto a substrate to form a coating film, and then drying the coating film And a firing step of firing the coating film,
The firing step also serves as a fine particle removal step for removing the fine particles, or further includes the fine particle removal step,
Including a peeling step of peeling the coating film or the manufactured porous polyimide film original fabric from the base material before the baking step after the coating film forming step, after the baking step, or after the fine particle removing step,
The manufacturing method whose tensile strength prescribed | regulated by ASTM standard D638 of the said porous polyimide film original fabric is 45 Mpa or more.   The manufacturing method according to claim 11, wherein the porous polyimide film has a bending strength of 70 MPa or more as defined by ASTM standard D790.   The film length of the said porous polyimide film original fabric is 1 m or more, Furthermore, the process of winding the said porous polyimide film original fabric on the winding core of diameter 2.5cm or more and 25cm or less is further included. Production method.   The particle size distribution index (d25 / d75) of the fine particles is 1 or more and 6 or less, d25 and d75 represent particle diameters having a cumulative frequency of particle size distribution of 25% and 75%, respectively, and d25 is the larger particle diameter. The manufacturing method of any one of Claims 11-13 which exists.   The manufacturing method according to claim 11, wherein the fine particles are organic fine particles when the firing step also serves as the fine particle removal step. Including a polyamic acid containing structural units represented by the following formulas (3-1) and (3-2) or a polyamic acid containing structural units represented by the following formulas (4-1) and (4-2), A composition comprising fine particles.

(In the above formula, A ¹¹ and A ¹² each independently represents a tetravalent aromatic group derived from an acid anhydride containing an aromatic tetracarboxylic acid anhydride, and B ¹¹ and B ¹² are each independently This represents a divalent diamine residue derived from an aromatic diamine, and at least one selected from the group consisting of A ¹² and B ¹² contains a divalent spacer group in its structure.

(In the above formula, A ²¹ and A ²² each independently represents a tetravalent aromatic group derived from an acid anhydride containing an aromatic tetracarboxylic anhydride, and B ²¹ and B ²² are each independently This represents a divalent diamine residue derived from an aromatic diamine, and A ²² and B ²² satisfy at least one condition selected from the group consisting of (I) and (II) below.
(I) The electron affinity of the aromatic tetracarboxylic anhydride that induces A ²² is 2.6 eV or less.
(II) The aromatic diamine for inducing B ²² is an aromatic diamine different from the aromatic diamine for inducing B ²¹ , and the solubility in water at 40 ° C. is 0.1 g / L or more. )