WO2014084186A1

WO2014084186A1 - Gas separation membrane

Info

Publication number: WO2014084186A1
Application number: PCT/JP2013/081699
Authority: WO
Inventors: 山中　一広; 健資須田; 大樹魚山
Original assignee: セントラル硝子株式会社
Priority date: 2012-11-28
Filing date: 2013-11-26
Publication date: 2014-06-05
Also published as: CN104822445A; JP2014128787A; JP6194773B2; CN104822445B

Abstract

[Problem] To provide a gas separation membrane which dissolves in an organic solvent, exhibits excellent formability, and exhibits excellent gas-separation performance when used as a gas separation membrane. [Solution] A gas separation membrane having a polyimide structure containing a repeating unit represented by general formula (1) (In the formula, R¹ represents a bivalent organic group, and R² represents a tetravalent organic group.), wherein R¹ is a bivalent organic group represented by general formula (2) (In the formula, R^aa represents a single bond, a sulfur atom, -SO₂-, -CH₂-, -C(=O)-, -C(CH₃)₂-, -C(CH₃)(CH₂CH₃)- or -C(CF₃)₂-, or a bivalent organic group obtained by separating two arbitrary hydrogen atoms from a C3-12 alicyclic hydrocarbon compound or from a C6-25 aromatic hydrocarbon compound. R^ab is a C1-6 alkyl group. ac and ad each independently represent an integer of 0-2. 1≤ac+ad≤4. HFIP represents a -C(CF₃)₂OH group. The line segments intersecting the wavy lines represent the locations of bonds.)

Description

Gas separation membrane

The present invention relates to a gas separation membrane.

Gas separation by a gas separation membrane has long been attracting attention as a simple technique that can continuously separate a mixed gas in a gaseous state and does not involve phase change. Gas separation is a technique for selectively separating gas by utilizing the difference in permeation speed and the presence or absence of permeation depending on the type of gas that permeates the gas separation membrane (hereinafter, sometimes referred to as “gas”).

As such a gas separation membrane material, polymers such as cellulose acetate, polysulfone or polyimide are known. Among these, polyimide is known as a material that has strength suitable for use as a gas separation membrane, is not easily damaged, has excellent heat resistance, and can be used at high temperatures.

There are many reports on gas separation membranes using polyimide, and details on the influence of monomer structure on gas separation performance, such as permeability to membranes for separating the target gas and high selectivity of the target gas, etc. Has been studied.

For example, a polyimide gas separation membrane having a hexafluoroisopropylidene group (hereinafter sometimes referred to as “—C (CF ₃ ) ₂ —group”) in a repeating structure is represented by helium (hereinafter referred to as “He”). ), Carbon dioxide (hereinafter sometimes referred to as “CO ₂ ”), high permeability to these gases, oxygen of these gases (hereinafter sometimes referred to as “O ₂ ”), methane (Hereinafter, sometimes referred to as “CH ₄ ”) is known to have high selectivity.

In addition, by introducing —C (CF ₃ ) ₂ — groups into the repeating unit in the polyimide in the gas separation membrane, the intermolecular interaction is weakened while the rigidity of the molecular chain is enhanced, and the gas separation according to the type of gas. It is said that a difference in membrane permeation is caused and both high membrane permeability and high selectivity can be achieved. (See Non-Patent Document 1 and Non-Patent Document 2).

However, among the raw materials for the synthesis of polyimides having —C (CF ₃ ) ₂ — groups, the only readily available materials are the following diamines and tetracarboxylic dianhydrides. Therefore, when a gas separation membrane is used, there is a problem that it is difficult to design a chemical structure considering strength and separation performance.

Furthermore, there was a problem that the organic solvent to be dissolved was limited.

In Patent Documents 1 to 3, 2-hydroxy-1,1,1,3,3,3-fluoroisopropyl group (hereinafter referred to as “—C (CF ₃ ) ₂ OH group” for polymerizing a fluorine-containing polyimide is disclosed. Alternatively, a fluorine-containing polymerizable monomer which is a diamine having a “HFIP group” and a method for producing the same is disclosed.

In addition, a method for producing a gas separation membrane obtained from polyimide or the like includes a method in which a polyimide solution is wet-coated and then a solvent is simply evaporated to obtain a homogeneous membrane. A heterogeneous asymmetric membrane comprising a dense layer and a porous layer. There is a way to get it. A method of obtaining an asymmetric membrane is a method in which a polymer solution is discharged from a discharge port, a solvent existing in the vicinity of the surface is evaporated in the air to form a dense layer, and then a solvent that is compatible with the solvent of the polymer solution but does not dissolve the polymer. There is a method of immersing in a coagulation bath filled with a certain coagulation liquid to form a fine porous layer in the coagulation layer. Patent Document 4 discloses a method for producing a composite reverse osmosis membrane by this method.

As described above, the diamine compound and tetracarboxylic dianhydride for obtaining a polyimide having a —C (CF ₃ ) ₂ — group are limited, and the chemical structure is limited when forming a polyimide film. When a gas separation membrane is used, there is a problem that it is difficult to design a chemical structure considering workability, strength, and separation performance.

JP 2007-119503 A JP 2007-119504 A JP 2008-150534 A US Pat. No. 3,133,132

An object of the present invention is to solve such problems, and to provide a gas separation membrane that dissolves in an organic solvent, has excellent moldability, and has excellent gas separation performance when used as a gas separation membrane.

The present inventors have made a soluble in an organic solvent, particularly a polar solvent, by using a polyimide compound having an HFIP group, which is a polar group having an —OH group, as a substituent and an alkyl group as a substituent. The present invention was completed by improving the gas separation performance by using the polyimide compound as a gas separation membrane.

That is, the present invention is as follows.

[Invention 1]
General formula (1)

(In the formula, R ¹ represents a divalent organic group, and R ² represents a tetravalent organic group.)
Wherein R ¹ is represented by the general formula (2)

(Wherein R ^aa is a single bond, oxygen atom, sulfur atom, —SO ₂ — group, —CH ₂ — group, —C (═O) — group, —C (CH ₃ ) ₂ — group, —C ( CH ₃ ) (CH ₂ CH ₃ ) — group or —C (CF ₃ ) ₂ — group, an alicyclic hydrocarbon compound having 3 to 12 carbon atoms, or an aromatic hydrocarbon compound having 6 to 25 carbon atoms R ^ab is an alkyl group having 1 to 6 carbon atoms, ac and ad are each independently an integer of 0 to 2; ≦ ac + ad ≦ 4 HFIP represents a —C (CF ₃ ) ₂ OH group, and a line segment intersecting with a wavy line represents a binding site.)
A gas separation membrane having a polyimide structure, which is a divalent organic group represented by:

[Invention 2]
The divalent organic group represented by the general formula (2) is represented by the general formula (3).

(In the formula (3), R ^ba represents a single bond, oxygen atom, sulfur atom, —SO ₂ — group, —CH ₂ — group, —C (═O) — group, —C (CH ₃ ) ₂ — group, A —C (CH ₃ ) (CH ₂ CH ₃ ) — group or a —C (CF ₃ ) ₂ — group, or an alicyclic hydrocarbon compound having 3 to 12 carbon atoms, an aromatic group having 6 to 25 carbon atoms A divalent organic group formed by removing two arbitrary hydrogen atoms from a hydrocarbon compound, R ^bb is an alkyl group having 1 to 6 carbon atoms, and bc and bd are each independently an integer of 0 to 2 Yes, 1 ≦ bc + bd ≦ 4, HFIP represents a —C (CF ₃ ) ₂ OH group, and a line segment intersecting with a wavy line represents a binding site.)
The gas separation membrane of invention 1 which is a divalent organic group represented by:

[Invention 3]
The divalent organic group represented by the general formula (2) is represented by the general formula (4) or (5).

(In the formula (4), R ^ca is a single bond, oxygen atom, sulfur atom, —SO ₂ — group, —CH ₂ — group, —C (═O) — group, —C (CH ₃ ) ₂ — group, A —C (CH ₃ ) (CH ₂ CH ₃ ) — group or a —C (CF ₃ ) ₂ — group, or an alicyclic hydrocarbon compound having 3 to 12 carbon atoms, an aromatic group having 6 to 25 carbon atoms A divalent organic group formed by removing two arbitrary hydrogen atoms from a hydrocarbon compound, R ^cb is an alkyl group having 1 to 6 carbon atoms, and HFIP represents a —C (CF ₃ ) ₂ OH group. The line segment that intersects with the wavy line represents the binding site.
In the formula (5), R ^da is a single bond, oxygen atom, sulfur atom, —SO ₂ — group, —CH ₂ — group, —C (═O) — group, —C (CH ₃ ) ₂ — group, — A C (CH ₃ ) (CH ₂ CH ₃ ) — group or —C (CF ₃ ) ₂ — group, or an alicyclic hydrocarbon compound having 3 to 12 carbon atoms, an aromatic carbon atom having 6 to 25 carbon atoms A divalent organic group formed by removing two arbitrary hydrogen atoms of a hydrogen compound, R ^db is an alkyl group having 1 to 6 carbon atoms, HFIP represents a —C (CF ₃ ) ₂ OH group, A line segment intersecting with the wavy line represents a binding site. )
The gas separation membrane of invention 1 which is any one of divalent organic groups represented by:

[Invention 4]
The divalent organic group represented by the general formula (2) is represented by the formulas (6) to (8).

(In the formula, HFIP represents a —C (CF ₃ ) ₂ OH group, and a line segment intersecting with a wavy line represents a binding site.)
The gas separation membrane of invention 1 which is any one of divalent organic groups represented by:

[Invention 5]
R ² represents the formulas (9) to (14)

(In the formula, the line segment intersecting with the wavy line represents the binding site.)
A gas separation membrane containing a polyimide structure according to any one of inventions 1 to 4, which is any one of the tetravalent organic groups represented by the formula:

[Invention 6]
6. A gas separation membrane containing a polyimide structure according to any one of inventions 1 to 5, wherein a hydrogen atom of an —OH group of the HFIP group contained in R ¹ is substituted with a glycidyl group.

[Invention 7]
The gas separation membrane according to invention 6, wherein the cyclic ether moiety of the glycidyl group is opened and crosslinked.

[Invention 8]
Furthermore, the gas separation membrane according to any one of inventions 1 to 7, obtained by mixing with an epoxy compound and heating.

[Invention 9]
The epoxy compound has the general formula (15)

(In the formula, R ^e is an f-valent organic group in which any number of hydrogen atoms have been removed from an alkane, aromatic ring or alicyclic ring, and the structure may contain an oxygen atom, a sulfur atom or a nitrogen atom, (Part of the hydrogen atoms may be substituted with a fluorine atom, a chlorine atom, an alkyl group, or a fluoroalkyl group, and f is an integer of 1 to 4.)
The gas separation membrane of the invention 8 represented by these.

The polyimide gas separation membrane having an HFIP group and an alkyl group according to the present invention has a good separation performance due to the HFIP group and the alkyl group. Further, since the HFIP group has an —OH group, it is soluble in a specific organic solvent, particularly a polar solvent, and it is easy to prepare a polyimide solution, and it can be formed into a desired film shape.

Further, in the polyimide gas separation membrane having an HFIP group and an alkyl group according to the present invention, it is easy to introduce the HFIP group into the alkyl group-containing aromatic diamine as a raw material. Compared to a membrane, in addition to gas separation performance, it is possible to design a structure for improving membrane properties such as membrane strength or resistance to swelling in a solvent.

In addition, a gas separation membrane having a —C (CF ₃ ) ₂ — group in addition to an HFIP group and an alkyl group exhibits even better gas separation performance.

Hereinafter, the present invention will be described, but the present invention is not limited to the following embodiments.

The monomer compound used as the raw material of the polyimide having an HFIP group and an alkyl group for producing the gas separation membrane of the present invention includes a diamine having an HFIP group and tetracarboxylic dianhydride. In order to adjust the strength and separation performance of the membrane in addition to the aromatic diamine having an HFIP group and an alkyl group, it is preferable to employ an aromatic diamine for strength as a gas separation membrane. Diamine may be added. Similarly, in addition to tetracarboxylic dianhydride, other dicarboxylic acids and derivatives thereof may be added in order to adjust the strength and separation performance of the membrane.

1. Aromatic diamine having HFIP group and alkyl group Aromatic compound having HFIP group and alkyl group as monomer compound for synthesizing polyimide having HFIP group and alkyl group for producing gas separation membrane of the present invention Diamine is represented by the general formula (2-A)

(Wherein R ^aa is a single bond, oxygen atom, sulfur atom, —SO ₂ — group, —CH ₂ — group, —C (═O) — group, —C (CH ₃ ) ₂ — group, —C ( CH ₃ ) (CH ₂ CH ₃ ) — group or —C (CF ₃ ) ₂ — group, an alicyclic hydrocarbon compound having 3 to 12 carbon atoms, or an aromatic hydrocarbon compound having 6 to 25 carbon atoms R ^ab is an alkyl group having 1 to 6 carbon atoms, ac and ad are each independently an integer of 0 to 2; ≦ ac + ad ≦ 4 HFIP represents a —C (CF ₃ ) ₂ OH group.
It is represented by

In the aromatic diamine (2-A) having an HFIP group and an alkyl group, the divalent organic group formed by removing two hydrogen atoms from an alicyclic hydrocarbon compound having 3 to 12 carbon atoms includes cyclohexane, A divalent organic group formed by leaving two hydrogen atoms of cyclohexane, adamantane or norbornane is preferable. The divalent organic group formed by removing two hydrogen atoms of an aromatic hydrocarbon compound having 6 to 25 carbon atoms is a divalent organic group formed by removing two hydrogen atoms of benzene, biphenyl, naphthalene or fluorene. Groups. Examples of the alkyl group having 1 to 6 carbon atoms include methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, sec-butyl group, and tert-butyl group.

The aromatic diamine (2-A) having a HFIP group and an alkyl group is represented by the formula (3-A)

(Wherein R ^ba is a single bond, oxygen atom, sulfur atom, —SO ₂ — group, —CH ₂ — group, —C (═O) — group, —C (CH ₃ ) ₂ — group, —C ( CH ₃ ) (CH ₂ CH ₃ ) — group or —C (CF ₃ ) ₂ — group, an alicyclic hydrocarbon compound having 3 to 12 carbon atoms, or an aromatic hydrocarbon compound having 6 to 25 carbon atoms R ^bb is an alkyl group having 1 to 6 carbon atoms, bc and bd are each independently an integer of 0 to 2, ≦ bc + bd ≦ 4 HFIP represents a —C (CF ₃ ) ₂ OH group.
And a compound represented by the formula (4-A) or (5-A):

(In the formula (4-A), R ^ca is a single bond, oxygen atom, sulfur atom, —SO ₂ — group, —CH ₂ — group, —C (═O) — group, —C (CH ₃ ) ₂ — A —C (CH ₃ ) (CH ₂ CH ₃ ) — group or —C (CF ₃ ) ₂ — group, or an alicyclic hydrocarbon compound having 3 to 12 carbon atoms, or 6 to 25 carbon atoms, A divalent organic group formed by removing two arbitrary hydrogen atoms from an aromatic hydrocarbon compound, R ^cb is an alkyl group having 1 to 6 carbon atoms, and HFIP is a —C (CF ₃ ) ₂ OH group. Represents.
In the formula (5-A), R ^da is a single bond, oxygen atom, sulfur atom, —SO ₂ — group, —CH ₂ — group, —C (═O) — group, —C (CH ₃ ) ₂ — group , —C (CH ₃ ) (CH ₂ CH ₃ ) — group or —C (CF ₃ ) ₂ — group, or an alicyclic hydrocarbon compound having 3 to 12 carbon atoms, aromatic having 6 to 25 carbon atoms It is a divalent organic group formed by leaving two arbitrary hydrogen atoms of a group hydrocarbon compound. R ^db is an alkyl group having 1 to 6 carbon atoms. HFIP represents a —C (CF ₃ ) ₂ OH group. )
Is particularly preferred.

In formula (4-A), the alkyl group having 1 to 6 carbon atoms of R ^cb is a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, a tert-butyl group, or a pentyl group. And a hexyl group.

Specifically, the compounds represented by formula (4-A) are represented by formulas (4-1-A) to (4-22-A).

(Wherein R ^cb is an alkyl group having 1 to 6 carbon atoms. HFIP represents a —C (CF ₃ ) ₂ OH group.)
Among them, the formulas (4-1-A), (4-10-A), (4-13-A), (4-17-A), (4- 21-A) is preferred.

In the formula (5-A), the alkyl group having 1 to 6 carbon atoms of R ^db is a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, a tert-butyl group, or a pentyl group. And a hexyl group.

Specifically, the compounds represented by the formula (5-A) are represented by the formulas (5-1-A) to (5-22-A).

(In the formula, R ^db is an alkyl group having 1 to 6 carbon atoms. HFIP represents a —C (CF ₃ ) ₂ OH group.)
Among them, the formulas (5-10-A) and (5-21-A) are preferable because of easy availability of the raw material diamine.

These aromatic diamines having an HFIP group and an alkyl group may be used in combination of two or more.

The diamine can be obtained by a reaction between an alkyl group-containing aromatic diamine and hexafluoroacetone or hexafluoroacetone trihydrate. Regarding the production method, the reaction of an aromatic diamine having no alkyl group described in Patent Documents 1 to 3 with hexafluoroacetone or hexafluoroacetone trihydrate can be applied.

2. Other diamines In order to adjust membrane properties such as gas separation performance, solubility in polar solvents, membrane strength, etc. in the synthesis of polyimides having HFIP groups and alkyl groups, aromatics having HFIP groups and alkyl groups In addition to the group diamine, other diamines and dihydroxyamines may be used. The amount used is 10 mol% or more and 80 mol% or less, preferably 30 mol% or more and 60 mol% or less with respect to the tetracarboxylic dianhydride.

Examples of the diamine include 3,5-diaminobenzotrifluoride, 2,5-diaminobenzotrifluoride, 3,3′-bistrifluoromethyl-4,4′-diaminobiphenyl, 2,2′-bistrifluoromethyl-4, 4'-diaminobiphenyl, 3,3'-bistrifluoromethyl-5,5'-diaminobiphenyl, bis (trifluoromethyl) -4,4'-diaminobiphenyl, bis (fluorinated alkyl) -4,4'- Diaminobiphenyl, dichloro-4,4′-diaminobiphenyl, dibromo-4,4′-diaminobiphenyl, bis (fluorinated alkoxy) -4,4′-diaminobiphenyl, diphenyl-4,4′-diaminobiphenyl, 4, 4′-bis (4-aminotetrafluorophenoxy) tetrafluorobenzene, 4,4′-bis (4-aminote Rafluorophenoxy) octafluorobiphenyl, 4,4'-binaphthylamine, o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, 2,4-diaminotoluene, 2,5-diaminotoluene, 2,4-diamino Xylene, 2,4-diaminodurene, 1,4-xylylenediamine, dimethyl-4,4'-diaminobiphenyl, dialkyl-4,4'-diaminobiphenyl, 2,2'-dimethyl-4,4'- Diaminobiphenyl, 3,3′-dimethyl-4,4′-diaminobiphenyl, dimethoxy-4,4′-diaminobiphenyl, diethoxy-4,4′-diaminobiphenyl, 4,4′-diaminodiphenylmethane, 3,4 ′ -Diaminodiphenylmethane, 2,4'-diaminodiphenylmethane, 3,3'-dimethyldiamino Phenylmethane, 3,3′-diethyl-diaminodiphenylmethane, 9,9-bis (4-aminophenyl) fluorene, 4,4′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, 2,4′-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfide, 3,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone, 4,4'-diaminobenzophenone, 3,3'-diamino Benzophenone, 1,3-bis (3-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, 4,4′-bis (4- Aminophenoxy) biphenyl, bis (4- (3-aminophenoxy) phenyl) Hong, bis (4- (4-aminophenoxy) phenyl) sulfone, 2,2-bis (4- (4-aminophenoxy) phenyl) propane, 2,2-bis (4- (4-aminophenoxy) phenyl) Hexafluoropropane, 2,2-bis (4- (3-aminophenoxy) phenyl) propane, 2,2-bis (4- (3-aminophenoxy) phenyl) hexafluoropropane, 2,2-bis (4- (4-Amino-2-trifluoromethylphenoxy) phenyl) hexafluoropropane, 2,2-bis (4- (3-amino-5-trifluoromethylphenoxy) phenyl) hexafluoropropane, 2,2-bis ( 4-Aminophenyl) hexafluoropropane, 2,2-bis (3-aminophenyl) hexafluoropropane, 2,2-bis 3-amino-4-hydroxyphenyl) hexafluoropropane, 2,2-bis (3-amino-4-methylphenyl) hexafluoropropane, 4,4′-bis (4-aminophenoxy) octafluorobiphenyl or 4, 4'-diaminobenzanilide can be mentioned, and two or more of these can be used in combination. Among them, it is preferable to use a diamine represented by the following structural formula having a —C (CF ₃ ) ₂ — group, which gives high permeability to the obtained gas separation membrane.

Examples of dihydroxyamines include 3,3′-dihydroxybenzidine, 3,3′-diamino-4,4′-dihydroxybiphenyl, 4,4′-diamino-3,3′-dihydroxybiphenyl, 3′-diamino-4,4′-dihydroxydiphenylsulfone, 4,4′-diamino-3,3′-dihydroxydiphenylsulfone, bis (3-amino-4-hydroxyphenyl) methane, 2,2-bis- ( 3-amino-4-hydroxyphenyl) propane, 2,2-bis (3-amino-4-hydroxyphenyl) hexafluoropropane, 2,2-bis (4-amino-3-hydroxyphenyl) hexafluoropropane, bis (4-amino-3-hydroxyphenyl) methane, 2,2-bis (4-amino-3-hydroxyphenyl) propane, , 4'-diamino-3,3'-dihydroxybenzophenone, 3,3'-diamino-4,4'-dihydroxybenzophenone, 4,4'-diamino-3,3'-dihydroxydiphenyl ether, 3,3'-diamino -4,4'-dihydroxydiphenyl ether, 1,4-diamino-2,5-dihydroxybenzene, 1,3-diamino-2,4-dihydroxybenzene, and 1,3-diamino-4,6-dihydroxybenzene Two or more of these may be used in combination. Among them, it is preferable to use dihydroxyamine represented by the following structural formula having a —C (CF ₃ ) ₂ — group, which gives high permeability to the obtained gas separation membrane.

3. Tetracarboxylic dianhydride The tetracarboxylic dianhydride used for synthesizing a polyimide having an HFIP group and an alkyl group according to the present invention is represented by the general formula (16).

(In the formula, R ² represents a tetravalent organic group.)
It is represented by

In the general formula (16), R ² is preferably a tetravalent organic group in which four hydrogen atoms are separated from an alkane, alicyclic ring or aromatic ring, and has a fluorine atom, chlorine atom, oxygen atom, sulfur in the structure. An atom or a nitrogen atom may be contained, and a part of the hydrogen atom may be substituted with an alkyl group, a fluoroalkyl group, a carboxyl group, a hydroxy group or a cyano group.

Specific examples of such tetracarboxylic dianhydrides include pyromellitic dianhydride (hereinafter sometimes referred to as “PMDA”), trifluoromethylbenzenetetracarboxylic dianhydride, bistrifluoro. Methylbenzenetetracarboxylic dianhydride, difluorobenzenetetracarboxylic dianhydride, naphthalenetetracarboxylic dianhydride, biphenyltetracarboxylic dianhydride (hereinafter sometimes referred to as “BPDA”), terphenyltetra Carboxylic dianhydride, 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride (hereinafter sometimes referred to as “BTDA”), oxydiphthalic dianhydride (hereinafter referred to as “ODPA”) Bicyclo (2,2,2) oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, 2 2-bis (3,4-dicarboxyphenyl) hexafluoropropanoic dianhydride (hereinafter sometimes referred to as “6FDA”), 2,3,4,5-thiophenetetracarboxylic dianhydride, 2 , 5,6,2 ′, 5 ′, 6′- hexafluoro-3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, bis (3,4-dicarboxyphenyl) sulfonic acid dianhydride (Hereinafter sometimes referred to as “DSDA”) or 3,4,9,10-perylenetetracarboxylic dianhydride, and these tetracarboxylic dianhydrides may be used alone, Two or more kinds may be used in combination.

Among these, PMDA, BPDA, BTDA, DSDA, ODPA and 6FDA are particularly preferable from the viewpoint of availability, and 6FDA is more preferable from the viewpoint of good gas separation performance (permeability and selectivity).

4). Dicarboxylic acid and dicarboxylic acid derivative In addition to the tetracarboxylic dianhydride, in order to adjust the membrane properties such as separation performance and strength when used as a gas separation membrane, it is represented by the general formulas (17) and (18) Dicarboxylic acids or dicarboxylic acid derivatives may be used. The amount used is 10 mol% or more and 80 mol% or less, preferably 30 mol% or more and 60 mol%, relative to the tetracarboxylic dianhydride. Within the range of this molar ratio, gas separation performance, solubility in polar solvents, and membrane strength can be adjusted.

Formula (17):

(In Formula (17), A is an organic group, preferably a divalent organic group in which two hydrogen atoms are removed from an alkane, alicyclic ring, or aromatic ring, and contains an oxygen atom or a sulfur atom in the structure. Some of the hydrogen atoms may be substituted with an alkyl group, fluorine, chlorine, fluoroalkyl group, carboxyl group, hydroxy group or cyano group, and R ³ is independently a hydrogen atom, having 1 to 10 alkyl groups or a benzyl group.

General formula (18):

(In the formula (18), A is an organic group, preferably an alkane, or a divalent organic group in which one hydrogen atom is removed from an alicyclic ring or aromatic ring, and an oxygen atom, a sulfur atom or a nitrogen atom in the structure. And a part of the hydrogen atoms may be substituted with an alkyl group, fluorine, chlorine, fluoroalkyl group, carboxyl group, hydroxy group or cyano group, and X is independently a chlorine atom, fluorine An atom, a bromine atom or an iodine atom.

In addition, after the condensation reaction, the general formula (19)

(In the formula, A is an organic group, preferably an alkane, or a divalent organic group in which one hydrogen atom is removed from an alicyclic ring or aromatic ring, and contains an oxygen atom, a sulfur atom or a nitrogen atom in the structure. And a part of hydrogen atoms may be substituted with an alkyl group, fluorine, chlorine, fluoroalkyl group, carboxyl group, hydroxy group or cyano group)) The contained structural unit.

When the dicarboxylic acid or the dicarboxylic acid derivative represented by the general formulas (17) and (18) for synthesizing the fluorine-containing polyimide used for the gas separation membrane of the present invention is exemplified in the form of the raw dicarboxylic acid, Oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid or sebacic acid, aromatic carboxylic acid phthalic acid, isophthalic acid, terephthalic acid, 4, 4'-dicarboxybiphenyl, 3,3'-dicarboxybiphenyl, 3,3'-dicarboxyldiphenyl ether, 3,4'-dicarboxyldiphenyl ether, 4,4'-dicarboxyldiphenyl ether, 3,3'-dicarboxyl Diphenylmethane, 3,4'-dicarboxyldiphenylmethane, 4,4'-di Ruboxyl diphenylmethane, 3,3′-dicarboxyldiphenyldifluoromethane, 3,4′-dicarboxyldiphenyldifluoromethane, 4,4′-dicarboxyldiphenyldifluoromethane, 3,3′-dicarboxyldiphenylsulfone, 3,4 ′ -Dicarboxyl diphenyl sulfone, 4,4'-dicarboxyl diphenyl sulfone, 3,3'-dicarboxyl diphenyl sulfide, 3,4'-dicarboxyl diphenyl sulfide, 4,4'-dicarboxyl diphenyl sulfide, 3,3 ' -Dicarboxyl diphenyl ketone, 3,4'-dicarboxyl diphenyl ketone, 4,4'-dicarboxyl diphenyl ketone, 2,2-bis (3-carboxyphenyl) propane, 2,2-bis (3,4'- Dicarboxy Enyl) propane, 2,2-bis (4-carboxyphenyl) propane, 2,2-bis (3-carboxyphenyl) hexafluoropropane, 2,2-bis (3,4'-dicarboxyphenyl) hexafluoropropane 2,2-bis (4-carboxyphenyl) hexafluoropropane, 1,3-bis (3-carboxyphenoxy) benzene, 1,4-bis (3-carboxyphenoxy) benzene, 1,4-bis (4- Carboxyphenoxy) benzene, 3,3 ′-(1,4-phenylenebis (1-methylethylidene)) bisbenzoic acid, 3,4 ′-(1,4-phenylenebis (1-methylethylidene)) bisbenzoic acid 4,4 ′-(1,4-phenylenebis (1-methylethylidene)) bisbenzoic acid, 2,2-bis (4- (3-carboxy Phenoxy) phenyl) propane, 2,2-bis (4- (4-carboxyphenoxy) phenyl) propane, 2,2-bis (4- (3-carboxyphenoxy) phenyl) hexafluoropropane, 2,2-bis ( 4- (4-carboxyphenoxy) phenyl) hexafluoropropane, bis (4- (3-carboxyphenoxy) phenyl) sulfide, bis (4- (4-carboxyphenoxy) phenyl) sulfide, bis (4- (3-carboxy Phenoxy) phenyl) sulfone or bis (4- (4-carboxyphenoxy) phenyl) sulfone, 5- (perfluorononenyloxy) isophthalic acid, a dicarboxylic acid containing a perfluorononenyloxy group, 4- (perfluoronone) Nyloxy) phthalic acid, 2- (perfluorononeni Oxy) terephthalic acid or 4-methoxy-5- (perfluorononenyloxy) isophthalic acid, a dicarboxylic acid containing a perfluorohexenyloxy group, 5- (perfluorohexenyloxy) isophthalic acid, 4- (perfluorohexenyl) Oxy) phthalic acid, 2- (perfluorohexenyloxy) terephthalic acid or 4-methoxy-5- (perfluorohexenyloxy) isophthalic acid, 2,2'-ditrifluoromethyl-4,4'-dicarboxybiphenyl It is done. Two or more of these may be used in combination.

Among these, terephthalic acid, isophthalic acid, 4,4'-dicarboxybiphenyl, 2,2'-ditrifluoromethyl-4,4'-dicarboxybiphenyl because of its ease of availability and ease of condensation polymerization. 2,2-bis (4-carboxyphenyl) hexafluoropropane is preferred.

5. Synthesis of polyimide having HFIP group and alkyl group A method for synthesizing a polyimide having an HFIP group and an alkyl group used in the gas separation membrane of the present invention will be described.

Here, the expression “dicarboxylic acid (derivative)” means “dicarboxylic acid or dicarboxylic acid derivative”. The same shall apply hereinafter in the specification.

In order to synthesize a polyimide having an HFIP group and an alkyl group for use in the gas separation membrane of the present invention, the above-mentioned aromatic diamine having an HFIP group and an alkyl group and tetracarboxylic dianhydride are essential, and if necessary , A method of adding other diamines and dicarboxylic acids (derivatives), and then melting them at 150 ° C. or higher and reacting them without solvent, a method of carrying out a polymerization reaction in an organic solvent at a reaction temperature of −20 to 80 ° C. Can be mentioned. In the polymerization reaction, the diamine and the carboxylic dianhydride or dicarboxylic acid (derivative) are reacted in a one-to-one ratio in terms of a molar ratio, so that an aromatic diamine having an HFIP group and an alkyl group, and other The abundance ratio of diamine, tetracarboxylic dianhydride and dicarboxylic acid (derivative) is expressed as a molar ratio, and aromatic diamine and other diamine: tetracarboxylic dianhydride and dicarboxylic acid (derivative) = 1: 1. It is preferable.

The organic solvent that can be used in the polymerization reaction is only required to dissolve the reaction substrate. N, N-dimethylformamide, N, N-dimethylacetamide, hexamethylphosphoric triamide, or N-methyl-2-pyrrolidone, which are amide solvents, are used. Benzene, anisole, diphenyl ether, nitrobenzene or benzonitrile as aromatic solvents, chloroform, dichloromethane, 1,2-dichloroethane or 1,1,2,2-tetrachloroethane as halogen solvents, and γ-as lactones Butyrolactone, γ-valerolactone, δ-valerolactone, γ-caprolactone, ε-caprolactone or α-methyl-γ-butyrolactone, alcohols and glycol ethers such as 2-methoxyethanol, 2-ethoxyethanol, 2-butoxy Ethanol or n- butyl alcohol. Further, the polymerization reaction may be carried out in the presence of these organic solvents and an acid acceptor such as pyridine or triethylamine.

The polyamic acid having an HFIP group and an alkyl group obtained by the polymerization reaction can be further imidized by cyclization by dehydration ring-closing reaction, and converted into a target polyimide having an HFIP group and an alkyl group. .

The dehydration ring closure reaction is performed under conditions that promote cyclization, such as heating and use of an acid catalyst. Generally, the polyamic acid solution having an HFIP group and an alkyl group immediately after the polymerization reaction is imidized at a high temperature of 150 ° C. or more and 250 ° C. or less to prepare a polyimide solution having an HFIP group and an alkyl group. At that time, pyridine, triethylamine, acetic anhydride or the like may be added. The concentration of the polyimide having an HFIP group and an alkyl group in the solution is preferably 5% by mass or more and 50% by mass or less. If it is less than 5% by mass, it is too thin to be industrially practical. If it exceeds 50% by mass, it is difficult to dissolve. Furthermore, it is preferably 10% by mass or more and 40% by mass or less.

The weight average molecular weight (hereinafter sometimes referred to as “Mw”) of the polyimide having an HFIP group and an alkyl group according to the present invention is preferably 10,000 or more, and more preferably 20,000 or more. The upper limit of the weight average molecular weight is preferably 500,000 or less, and more preferably 300,000 or less. When the weight average molecular weight is less than 10,000, the strength of the resulting polymer film is poor. When the weight average molecular weight is more than 500,000, the viscosity of the resulting polymer solution becomes too high and handling becomes difficult. The weight average molecular weight here is determined as a converted value based on standard polystyrene by gel permeation chromatography (hereinafter sometimes referred to as “GPC”) analysis (the same applies hereinafter). Detailed analysis conditions for the analysis are described in the examples of the present application.

6). Preparation of polyimide solution having HFIP group and alkyl group The polyimide solution having HFIP group and alkyl group thus obtained can be used as it is for gas separation membrane production. In addition, a polyimide solution having an HFIP group and an alkyl group is added to a poor solvent such as water or alcohol for the purpose of removing residual monomers and low molecular weight substances contained in the polyimide solution having an HFIP group and an alkyl group. After the polyimide having an HFIP group and an alkyl group is precipitated and isolated and purified, it may be adjusted by dissolving it again in the organic solvent to the above concentration.

The organic solvent that can be used is such that the polyimide having an HFIP group and an alkyl group can be dissolved, and N, N-dimethylformamide, N, N-dimethylacetamide, N, N-dimethylformamide, and hexamethylphosphoric acid are amide solvents. Halogen solvents such as triamide, N-methyl-2-pyrrolidone, aromatic solvents benzene, anisole, diphenyl ether, nitrobenzene, benzonitrile, chloroform, dichloromethane, 1,2-dichloroethane, 1,1,2,2- Tetrachloroethane, lactones γ-butyrolactone, γ-valerolactone, δ-valerolactone, γ-caprolactone, ε-caprolactone or α-methyl-γ-butyrolactone, phenols phenol, cresol, xylenol, catechol or Chlorophenol, are alcohols and glycol ethers 2-methoxyethanol, 2-ethoxyethanol, 2-butoxyethanol or n- butyl alcohol or may be used to select from a mixed solvent thereof.

7). Production of Gas Separation Membrane Gas separation membrane containing polyimide having HFIP group and alkyl group according to the present invention is a wet film-forming method for producing a thin film by using solvent evaporation from a polyimide solution having HFIP group and alkyl group. Or asymmetric membrane having a dense layer and a porous layer obtained by other methods.

[Homogeneous membrane]
For example, the homogeneous film is formed by wet-coating a polyimide solution having the HFIP group and alkyl group described above on a substrate such as a glass substrate using a spin coater, applicator, etc., and then in a dry gas such as air, nitrogen or argon. After heating and evaporating the solvent, it is obtained by peeling from the glass substrate. In addition, instead of a polyimide solution having an HFIP group and an alkyl group, a polyamic acid solution having an HFIP group and an alkyl group is used to coat the substrate by the above procedure, followed by heating to imidize to form a homogeneous film. You can also get

In order to be used for a gas separation membrane, the thickness of the homogeneous membrane is preferably 5 μm or more and 1 mm or less. A film thinner than 5 μm is difficult to manufacture and easily broken. A film thicker than 1 mm is difficult for gas to permeate. More preferably, it is 10 μm to 200 μm.

[Asymmetric membrane]
An asymmetric film having a dense layer and a porous layer can be formed by the method described above. Moreover, after forming an asymmetric film using a polyamic acid solution instead of a polyimide solution, the asymmetric film can also be obtained by thermal imidization.

In the asymmetric membrane, the dense layer has different permeation speeds depending on the gas type, and has a gas separation function to be selected for the mixed gas. On the other hand, the porous layer has a role as a support for maintaining the membrane shape.

The asymmetric membrane containing polyimide having an HFIP group and an alkyl group used for the gas separation membrane of the present invention may be either a flat membrane shape or a hollow fiber shape.

The thickness of the dense layer is preferably 10 nm or more and 10 μm or less. If it is thinner than 10 nm, it is difficult to form a film and it is not practical. If it is thicker than 10 μm, it is difficult for gas to permeate. Preferably they are 30 nm or more and 1 micrometer or less.

The thickness of the porous layer is preferably 5 μm or more and 2 mm or less for a flat film. If it is thinner than 5 μm, it is difficult to form a film and it is not practical. If it is thicker than 2 mm, it is difficult for gas to permeate. More preferably, they are 10 micrometers or more and 500 micrometers or less. In the hollow fiber shape, the inner diameter is 10 μm or more and 4 mm or less, preferably 20 μm or more and 1 mm or less, and the outer diameter is 30 μm or more and 8 mm or less, preferably 50 μm or more and 1.5 mm or less. In the case of a hollow fiber shape, it is preferable to have a dense layer on the outside.

As the coagulation liquid for producing the asymmetric membrane, water or a mixed solvent of water and an organic solvent is preferably used. The mixed solvent contains 40% by mass or more, preferably 50% by mass or more of water, and examples of the organic solvent include alcohols such as methanol, ethanol or isopropanol, and ketones such as acetone, methyl ethyl ketone, and diethyl ketone. When water or a mixed solvent thereof is used for the coagulation liquid, there is no need to make the film production facility explosion-proof, and the cost can be reduced.

[Coagulation liquid]
The polyimide having an HFIP group and an alkyl group to be used for the gas separation membrane of the present invention has an amide solvent N, N-dimethylacetamide, N, N-dimethylformamide, or It is particularly easy to dissolve in N-methyl-2-pyrrolidone, lactones γ-butyrolactone and γ-valerolactone, and it is easy to produce a homogeneous film having a desired film thickness. It is also easy to produce a film.

In particular, in producing an asymmetric membrane, by changing the distance from the discharge port to the coagulation bath, and when discharging in the form of a hollow fiber, both dry air, aqueous coagulation liquid, etc. are discharged inside the discharge port. A desired dense layer can be formed. A porous layer having a desired pore size, pore size distribution, and thickness can be formed by changing the organic solvent species of the coagulation bath.

The film treated with the coagulating liquid is preferably used after being dried by heat treatment. The heat treatment temperature is preferably not higher than the glass transition temperature of polyimide so as not to melt.

[Silicone resin coating]
For the purpose of repairing the surface defect of the produced gas separation membrane, a silicone resin may be coated on the surface of the separation membrane. As a coating method, a known coating method such as spin coating, coating with an applicator, or dip coating can be used.

Silicone resins include general dimethyl silicone, phenyl group-containing silicone, vinyl group-containing silicone, Si-H group-containing silicone, trifluoropropyl group-containing silicone, silanol group-containing silicone, amino group-containing silicone, epoxy group-containing silicone, A methacryl group containing silicone, an acryl group containing silicone, etc. are mentioned. These are commercially available, such as DMS series, PDV series, VDT series, FMV series, HMS series, DMS series, HPM series, FMS series, SQO series, AMS series, MCR series, ECMS series, RMS series manufactured by Gelest. Is mentioned.

8). Combined use of epoxy compound The polymer compound having a repeating unit represented by the general formula (1) is mixed with an epoxy compound as in the gas separation membranes of Inventions 6 to 9 for the purpose of improving mechanical strength or plastic resistance. And cured by heating or light irradiation to form a cured film. The cured film can also be applied to the homogeneous film and the asymmetric film.

Epoxy compounds include phenol novolac resin, cresol novolac resin, aromatic hydrocarbon formaldehyde resin modified phenol resin, dicyclopentadiene modified phenol resin, phenol aralkyl resin, cresol aralkyl resin, naphthol aralkyl resin, biphenyl modified phenol aralkyl resin, phenol triol. Contacting methylol methane resin, tetraphenylol ethane resin, naphthol novolak resin, naphthol-phenol co-condensed novolak resin, naphthol-cresol co-condensed novolac resin, biphenyl-modified phenol resin or aminotriazine-modified phenol resin compound with epichlorohydrin An epoxy compound modified by epoxy is mentioned.

These are commercially available, bisphenol A type (Dainippon Ink Industries, trade name, Epicron 840), bisphenol F type (Asahi Denka Kogyo, trade name, Adeka Resin EP-4901), cresol novolak type (Dainippon Ink Industries, trade name, Epicron N-600 series), dicyclopentadiene type (Dainippon Ink Industries, trade name, Epicron HP-7200 series), Triazine (Nissan Chemical Industry Co., Ltd.) Manufactured, trade name, TEPIC series) and the like.

General formula (15)

(Wherein R ^e is an f-valent organic group in which f hydrogen atoms have been removed from an alkyl group, an aromatic ring or an alicyclic ring, and the structure may contain an oxygen atom, a sulfur atom or a nitrogen atom; (A part of the atoms may be substituted with a fluorine atom, a chlorine atom, an alkyl group or a fluoroalkyl group. F is an integer of 1 to 4.)
Is synthesized from a corresponding alcohol and epichlorohydrin.

Examples of the alcohol include 1,4-cyclohexanediol, 1,3-adamantanediol, catechol, 1,3-benzenediol, 2,2′-dihydroxybiphenyl, 4,4′-dihydroxybiphenyl, and 2,2′-methylene. Diphenol, 4,4'-methylenediphenol, ethylene glycol, propylene glycol, 2,2-bis (4-hydroxyphenyl) -propane, 2,2-bis (4-hydroxyphenyl) -3-methylpropane, 2 , 2-bis (4-hydroxyphenyl) -butane, 3,3-bis (4-hydroxyphenyl) -pentane, 2,2-bis (4-hydroxyphenyl) -4-methylpentane, 3,3-bis ( 4-hydroxyphenyl) -hexane, 2,2-bis (3-chloro-4-hydroxyphenyl) -Propane, 2,2-bis (3,5-dichloro-4-hydroxyphenyl) -propane, 2,2-bis (3-bromo-4-hydroxyphenyl) -propane, 2,2-bis (3,5 -Dibromo-4-hydroxyphenyl) -propane, 2,2-bis (3-methyl-4-hydroxyphenyl) -propane, 2,2-bis (4-hydroxyphenyl) -1,1,1,3,3 , 3-hexafluoropropane, 2,6-dihydroxynaphthalene, 2,3-dihydroxynaphthalene, 2,7-dihydroxynaphthalene, 1,4-dihydroxynaphthalene, 1,5-dihydroxynaphthalene, 2,3-dihydroxypyridine, , 4-dihydroxypyridine, 4,4′-dihydroxydiphenyl ether, 4,4′-dihydroxydiphenyl sulfide, , 4'-dihydroxydiphenyl sulfoxide, 4,4'-dihydroxydiphenyl sulfone, 4,4'-dihydroxybenzophenone, 1,4-dihydroxyhexane, 2,2-bis (4-hydroxycyclohexyl) -propane, 1,1 ' -Methylenedi-2-naphthol, 4,4 ', 4'-trihydroxytriphenylmethane, 1,1,1-tris (4-hydroxyphenyl) ethane or α, α, α'-tris (4-hydroxyphenyl) -1-ethyl-4-isopropylbenzene.

As the alcohol, it is also possible to use an alcohol in the HFIP group contained in the repeating unit represented by the formula (1).

In obtaining the gas separation membranes of Inventions 6 to 9, these epoxy compounds and epoxy resin curing agents may be used in combination. Examples of the curing agent include amine compounds, acid anhydride compounds, amide compounds, phenol compounds, mercaptan compounds, imidazole compounds, polysulfide resin compounds, and phosphorus compounds. Specifically, thermosetting agents diaminodiphenylmethane, diaminodiphenylsulfone, diethylenetriamine, triethylenetetramine, polyalkylene glycol polyamine, phthalic anhydride, trimellitic anhydride, pyromellitic anhydride, maleic anhydride, tetrahydrophthalic anhydride Methyltetrahydrophthalic anhydride, methylnadic anhydride, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, 2-methylimidazole, triphenylphosphine, 2-ethyl-4-methylimidazole, BF ₃ -amine complex or Examples thereof include guanidine derivatives, diphenyliodonium hexafluorophosphate which is an ultraviolet curing agent, and triphenylsulfonium hexafluorophosphate.

The mixing ratio of the polymer compound having the repeating unit represented by the general formula (1) and the epoxy compound is expressed by mass ratio: polymer compound: epoxy compound = 10: 90 to 98: 2, preferably 50: 50-95: 5.

The mixing ratio of the epoxy compound and the curing agent for the epoxy resin is 70:30 to 99.5: 0.5, preferably 90:10 to 99: 1, expressed as a mass ratio.

In the middle step of manufacturing the gas separation membrane, for example, it is applied to a glass or silicon substrate, and then cured by heating or ultraviolet irradiation with an ultraviolet (UV) lamp or the like to form a crosslinked and cured gas separation membrane. Can do. The organic solvent that can be used is particularly limited as long as it dissolves the HFIP group-containing polyimide represented by the general formula (1) and the polyimide having an alkyl group, and the composition mainly composed of the epoxy compound. It can be used without any problems. Specific examples include N, N-dimethylformamide, N, N-dimethylacetamide, N-methylformamide, amide solvents such as hexamethylphosphoric triamide, N-methyl-2-pyrrolidone, cyclohexanone, propylene glycol Examples thereof include monomethyl ether acetate and γ-butyrolactone.

Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to these examples.

[Adjustment of polyimide film]
Preparation of a polyimide membrane having a HFIP group and an alkyl group for a gas separation membrane will be described.

To a 200 mL three-necked flask equipped with a nitrogen inlet tube and a reflux condenser, the following HFA-2DMeBD (2.06 g, 3.78 mmol), 6FDA (1.68 g, 3.78 mmol), N, N-dimethylacetamide (14 g) After stirring at room temperature for 18 hours under a nitrogen atmosphere, pyridine (0.66 g, 8.32 mmol) and acetic anhydride (0.77 g, 7.56 mmol) were added, and the mixture was further stirred at room temperature for 3 hours. . The resulting reaction solution was heated to 200 ° C., further stirred for 6 hours, and then cooled to room temperature. A uniform N, N-dimethylacetamide solution in which polyimide 1 was dissolved was obtained. The Mw of polyimide 1 determined by GPC (gel permeation chromatography) measurement of the solution (the apparatus is HLC-8320 manufactured by Tosoh Corporation, the solvent is tetrahydrofuran, converted to polystyrene, and the same shall apply hereinafter) was 42,000.

(In the formula, Me represents a methyl group. The same shall apply hereinafter in the specification.)
The N, N-dimethylacetamide solution was applied onto a glass substrate, and using a spin coater, rotation speed: 1000 rpm, holding time: 30 sec. Spin coating was performed under the following coating conditions. The obtained glass substrate was heat-treated at 200 ° C. for 1 hour in a nitrogen atmosphere, and then peeled off from the glass substrate to obtain a film obtained from polyimide 1, that is, a polyimide 1 film having an HFIP group and an alkyl group (hereinafter, referred to as “polyimide 1 film”). It may be expressed as “Polyimide film 1”). The film thickness was measured and found to be 25 μm.

Next, a series of diamine compounds (HFA-2DMeBD, HFA-MeFL, HFA-3DMeBD, mHFA-3DMeBD) having the HFIP group and the alkyl group shown below,

And the following tetracarboxylic dianhydrides (PMDA, BPDA, BTDA, DSDA, ODPA, 6FDA),

Were reacted to obtain polyimide films (polyimide films 2 to 17) obtained from polyimides 2 to 17 in the same manner as described above. Table 1 shows the raw material compounds and film thicknesses of the polyimide films 2 to 17, and Table 2 shows Mw of the polyimides 2 to 17.

Next, a series of diamine compounds having an HFIP group and an alkyl group (HFA-2DMeBD, HFA-MeFL, HFA-3DMeBD) and a series of tetracarboxylic dianhydrides (6FDA, BPDA, BTDA, DSDA) are combined and polymerized. A predetermined amount of the following epoxy resin 1 or epoxy resin 2 and triphenylphosphine (1% by mass relative to the epoxy resin) as a curing agent were added to the DMAc solution obtained after the reaction to obtain polyimides. The polyimides were respectively formed to obtain polyimide films 18 to 23. Table 3 shows the raw material compounds of the obtained polyimide films 18 to 23 together with the respective film thicknesses.

Epoxy resin 1: bisphenol A type epoxy resin (JER828 manufactured by Mitsubishi Chemical Corporation)
Epoxy resin 2: Cresol novolac type epoxy resin (manufactured by Aldrich, catalog No. 408042)

[Evaluation of Polyimide 5]
The polyimide 5 was measured for gas permeability coefficient and evaluated for separation performance. The measurement method of the gas permeation performance of the gas separation membrane is shown below.

The gas permeation coefficient was determined by placing a gas separation membrane with a membrane area of 7 cm ^{2 in} a stainless steel cell, and the differential pressure method described in Part 1 of JIS K7126-1: 2006 “Plastics—Film and Sheet—Gas Permeability Test Method”. Measured according to

Specifically, helium (He), carbon dioxide gas (CO ₂ ), oxygen gas (O ₂ ), and methane gas (CH ₄ ) are used as test gases under the condition of a temperature of 23 ° C., and JIS K7126-1: 2006 In conformity, the permeability coefficient and separation performance of each gas (ratio of the permeability coefficient of each gas) were measured.

Based on the above-mentioned JIS K7126-1: 2006, the measurement results of the gas permeability coefficient of the membrane prepared from polyimide 5 are shown in Table 4, and the evaluation results of the separation performance are shown in Table 5.

Similarly, the measurement results of the gas permeability coefficient of the membrane having polyimide 6 and the membrane having polyimide 8 are shown in Table 4, and the evaluation results of the separation performance are shown in Table 5.

Next, the gas separation performance of the polyimide film having the HFIP group and the alkyl group (polyimide films 5, 6 and 8) and the polyimide film not having the HFIP group of the following structural formula not included in the scope of the present invention (comparison) The gas separation performance of Examples 1 and 2) was compared.

[Comparative Example 1]

The CO ₂ permeability coefficient of the polyimide film having no HFIP group of Comparative Example 1 was 5 Barrer. As shown in Table 4, the CO ₂ permeability coefficient of the polyimide film obtained from the polyimide 5 having an HFIP group and an alkyl group of the present invention was 347 Barrer. From these results, it was clarified that the introduction of HFIP group increased the CO ₂ permeability coefficient and showed better performance.

[Comparative Example 2]

The CO ₂ permeability coefficient of the polyimide film having no HFIP group of Comparative Example 2 was 12 Barrer. As shown in Table 5, the CO ₂ permeability coefficient of the polyimide film obtained from the polyimide 8 having an HFIP group and an alkyl group of the present invention was 310 Barrer. From these results, it was clarified that the introduction of HFIP group increased the CO ₂ permeability coefficient and showed better performance.

Furthermore, the permeability coefficients of CO ₂ of the polyimide films 1 to 4, polyimide films 7 and polyimide films 9 to 23 of the present invention are all 50 Barrer or higher, showing a high permeability coefficient, compared with the polyimide films of Comparative Examples 1 and 2. However, it has become clear that it shows better performance.

The gas separation membrane comprising a polyimide membrane having an HFIP group and an alkyl group according to the present invention has a large difference in permeation rate (gas permeation coefficient) depending on the type of gas, and is excellent in gas separation performance. Therefore, it can be suitably used for a separation / fixation technique of carbon dioxide from liquefied natural gas or the like, and a water-ethanol separation membrane for the purpose of recovering ethanol for fuel.

Claims

General formula (1)

(In the formula, R 1 represents a divalent organic group, and R 2 represents a tetravalent organic group.)
Wherein R 1 is represented by the general formula (2)

(Wherein R aa is a single bond, oxygen atom, sulfur atom, —SO 2 — group, —CH 2 — group, —C (═O) — group, —C (CH 3 ) 2 — group, —C ( CH 3 ) (CH 2 CH 3 ) — group or —C (CF 3 ) 2 — group, an alicyclic hydrocarbon compound having 3 to 12 carbon atoms, or an aromatic hydrocarbon compound having 6 to 25 carbon atoms R ab is an alkyl group having 1 to 6 carbon atoms, ac and ad are each independently an integer of 0 to 2; ≦ ac + ad ≦ 4 HFIP represents a —C (CF 3 ) 2 OH group, and a line segment intersecting with a wavy line represents a binding site.)
A gas separation membrane having a polyimide structure, which is a divalent organic group represented by:
The divalent organic group represented by the general formula (2) is represented by the general formula (3).

(In the formula (3), R ba represents a single bond, oxygen atom, sulfur atom, —SO 2 — group, —CH 2 — group, —C (═O) — group, —C (CH 3 ) 2 — group, A —C (CH 3 ) (CH 2 CH 3 ) — group or a —C (CF 3 ) 2 — group, or an alicyclic hydrocarbon compound having 3 to 12 carbon atoms, an aromatic group having 6 to 25 carbon atoms A divalent organic group formed by removing two arbitrary hydrogen atoms from a hydrocarbon compound, R bb is an alkyl group having 1 to 6 carbon atoms, and bc and bd are each independently an integer of 0 to 2 Yes, 1 ≦ bc + bd ≦ 4, HFIP represents a —C (CF 3 ) 2 OH group, and a line segment intersecting with a wavy line represents a binding site.)
The gas separation membrane of Claim 1 which is a bivalent organic group represented by these.
The divalent organic group represented by the general formula (2) is represented by the general formula (4) or (5).

(In the formula (4), R ca is a single bond, oxygen atom, sulfur atom, —SO 2 — group, —CH 2 — group, —C (═O) — group, —C (CH 3 ) 2 — group, A —C (CH 3 ) (CH 2 CH 3 ) — group or a —C (CF 3 ) 2 — group, or an alicyclic hydrocarbon compound having 3 to 12 carbon atoms, an aromatic group having 6 to 25 carbon atoms A divalent organic group formed by removing two arbitrary hydrogen atoms from a hydrocarbon compound, R cb is an alkyl group having 1 to 6 carbon atoms, and HFIP represents a —C (CF 3 ) 2 OH group. The line segment that intersects with the wavy line represents the binding site.
In the formula (5), R da is a single bond, oxygen atom, sulfur atom, —SO 2 — group, —CH 2 — group, —C (═O) — group, —C (CH 3 ) 2 — group, — A C (CH 3 ) (CH 2 CH 3 ) — group or —C (CF 3 ) 2 — group, or an alicyclic hydrocarbon compound having 3 to 12 carbon atoms, an aromatic carbon atom having 6 to 25 carbon atoms A divalent organic group formed by removing two arbitrary hydrogen atoms of a hydrogen compound, R db is an alkyl group having 1 to 6 carbon atoms, HFIP represents a —C (CF 3 ) 2 OH group, A line segment intersecting with the wavy line represents a binding site. )
The gas separation membrane according to claim 1, which is any one of divalent organic groups represented by:
The divalent organic group represented by the general formula (2) is represented by the formulas (6) to (8).

(In the formula, HFIP represents a —C (CF 3 ) 2 OH group, and a line segment intersecting with a wavy line represents a binding site.)
The gas separation membrane according to claim 1, which is any one of divalent organic groups represented by:
R 2 represents the formulas (9) to (14)

(In the formula, the line segment intersecting with the wavy line represents the binding site.)
The gas separation membrane containing a polyimide structure according to any one of claims 1 to 4, which is any one of tetravalent organic groups represented by the formula:
The gas separation membrane containing a polyimide structure according to any one of claims 1 to 5, wherein a hydrogen atom of an -OH group of the HFIP group contained in R 1 is substituted with a glycidyl group.
The gas separation membrane according to claim 6, wherein the cyclic ether moiety of the glycidyl group is opened and crosslinked.
The gas separation membrane according to any one of claims 1 to 7, further obtained by mixing with an epoxy compound and heating.
The epoxy compound has the general formula (15)

(In the formula, R e is an f-valent organic group in which any number of hydrogen atoms have been removed from an alkane, aromatic ring or alicyclic ring, and the structure may contain an oxygen atom, a sulfur atom or a nitrogen atom, A part of hydrogen atoms may be substituted with a fluorine atom, a chlorine atom, an alkyl group or a fluoroalkyl group, and f is an integer of 1 to 4.)
The gas separation membrane of Claim 8 represented by these.