JP2003080538A - Polyimide porous film and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly durable polyimide honeycomb film capable of being formed by a simple technique. SOLUTION: In the polyimide porous film obtained by applying a hydrophobic organic solvent solution of an amphiphatic polymer to a substrate in an atmosphere with a relative humidity of 50% or more and evaporating fine waterdrops generated by evaporating a hydrophobic organic solvent, the porous film comprises polyimide having a repeating unit represented by formula (1), R<1> is a tetracarboxylic acid residue and R<2> is a diamine residue). In the method for manufacturing the polyimide porous film by applying the hydrophobic organic solvent solution of the amphiphatic polymer to the substrate in the atmosphere with a relative humidity of 50% or more and evaporating fine waterdrops generated by evaporating the organic solvent, the porous film is formed using a polyionic complex of a polyamic acid represented by formula (2) (R<1> and R<2> are each as previously defined and Q is an ammonium cation residue having at least one 4C or more organic group) and lipid and subsequently imidated.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a porous material which can be suitably used as a battery diaphragm material such as a separator or an ion exchange membrane, an optical material such as a display or an optical waveguide, and a catalyst support, and which has excellent durability. And a method for manufacturing a honeycomb membrane through a polyion complex of polyamic acid which is a precursor of polyimide.

[0002]

2. Description of the Related Art A porous film having a shape in which fine pores are regularly arranged can be applied to various applications such as a semiconductor low dielectric constant material, a scattering layer for electronic displays, a magnetic recording material, and a cell culture substrate. It is a promising material being studied. As a method for producing this type of porous membrane, a special polymer that has both a part with strong self-cohesion and a part that exhibits flexibility is used, and these polymers are dissolved in a hydrophobic organic solvent and cast. Method (Science 283,373,1999; Nature 36
9,387,1994) are disclosed. On the other hand, the inventors of the present invention have an amphipathic polymer having a hydrophilic acrylamide polymer as a main chain skeleton and a dodecyl group as a hydrophobic side chain and a lactose group or a carboxyl group as a hydrophilic side chain, or heparin or dextran sulfate. It has been reported that a polyionic complex of an anionic polysaccharide and a quaternary long-chain alkylammonium salt gives a thin film having a honeycomb structure in a similar manner (Supra Molecular Science 5,33).
1, 1998; Molecular Cryst. Liq. Cryst. 322, 305, 1998).
This production method of the present inventors is an excellent method that is simple and has an advantage in production cost because it can be prepared by blowing high-humidity air on the coating film of the hydrophobic solution whose concentration is adjusted, or by placing it under high humidity. is there.

However, it has been feared that the honeycomb membranes known so far have poor durability. In particular, when the honeycomb film is exposed to a high temperature, there is a problem that the porous structure is collapsed due to the low heat resistance of the resin composition constituting it, which makes it difficult to expand the applications of the honeycomb film. Was there.

On the other hand, polyimide is known as a highly durable resin composition and is widely used as an engineering plastic, an optical material, an electronic material and the like. Creating a honeycomb membrane using such a highly durable polyimide is very useful in the sense of realizing a porous membrane with durability, but the polyimide itself is generally insoluble in various solvents. In addition, since it is an electrically neutral resin, it does not form an ionic complex and cannot be used as it is for the production of a honeycomb membrane.

[0005]

The object of the present invention is to provide a highly durable polyimide honeycomb membrane which can be prepared by a simple method, and a polyimide which utilizes a polyionic complex of a polyimide precursor polyamic acid and a lipid. It is to provide a method for manufacturing a honeycomb membrane.

[0006]

DISCLOSURE OF THE INVENTION The inventors of the present invention have conducted extensive studies to realize a honeycomb film containing polyimide, which is a highly durable resin, as a constituent resin component, and have found the present invention.

That is, according to the present invention, a solution of an amphipathic polymer in a hydrophobic organic solvent is applied onto a substrate in an atmosphere having a relative humidity of 50% or more, and the minute water droplets generated by evaporating the organic solvent are evaporated. In the porous membrane obtained by the reaction, the porous membrane has the formula (1)

[0008]

[Chemical 3]

(In the formula, R ¹ is a tetracarboxylic acid residue, and R ^{2 is}
Indicates a diamine residue. And a polyimide porous film having a repeating unit represented by the formula (1).

Further, the present invention is

[0011]

[Chemical 4]

(Wherein R ¹ is a tetracarboxylic acid residue, R ^{2 is}
Represents a diamine residue, and Q represents an ammonium cation residue having at least one organic group having 4 or more carbon atoms. ) Is a polyionic complex of a polyamic acid and a lipid, and a method for producing a polyimide porous membrane, which comprises forming a porous membrane using the same and then imidizing the same.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Next, the method for producing a polyimide honeycomb film according to the present invention will be described in detail. The reaction scheme in the method for producing a polyimide porous membrane of the present invention is shown below.

[0014]

[Chemical 5]

(In the formula, R ¹ , R ² and Q have the same meanings as described above.) That is, the polyionic complex (2) of the polyamic acid (3) which is the precursor of the polyimide represented by the formula (1). Then, it can be dehydrated and imidized to obtain a novel polyimide honeycomb film.

According to the method for producing a honeycomb membrane of the present inventors, a solution obtained by dissolving an amphipathic polymer in a hydrophobic organic solvent is applied onto a substrate, and the organic solvent is gradually added in air having a relative humidity of 50% or more. It is a method of making it evaporate into.

As the organic solvent evaporates, minute water droplets formed by dew condensation on the surface of the organic solvent due to latent heat of vaporization close-packs in the cast film. By evaporating these small water droplets,
This is a method of forming a thin film having a structure in which micropores having a diameter of 5 μm or less are most closely packed.

However, as described above, the polyimide resin is generally hardly soluble in various organic solvents and is not an amphipathic polymer, so that it cannot be directly applied to the above-mentioned method for producing a honeycomb membrane. Therefore, the present inventors
We paid attention to the fact that polyamic acid, which is a precursor of polyimide, is soluble in an organic solvent, can form a polyionic complex with a lipid, and is suitable for manufacturing a honeycomb membrane.

The polyamic acid used in the present invention is a resin composition obtained by polymerizing a tetracarboxylic dianhydride and a diamine compound in a polar solvent. Although any composition of the polyamic acid can be used in the present invention, considering the durability against hydrolysis when the polyamic acid is saponified with an aqueous alkaline solution, it is preferable to use 3,3'4 per tetracarboxylic dianhydride. 4'-biphenyltetracarboxylic acid, 3,3'4,4'-biphenylethertetracarboxylic acid, 3,3'4,4'-biphenylsulfonetetracarboxylic acid, 3,3'4,4'- Benzophenonetetracarboxylic acid, 2,2-bis (3,4-dicarboxyphenyl) propane, 1,1,1,3,3,3-hexafluoro-2,2-bis (3,4dicarboxyphenyl) propane , Bis (3,4 dialboxoxyphenyl) tetramethyldisiloxa, and other tetracarboxylic acids having a biphenyl structure and their dianhydrides, cyclobutane Tetracarboxylic acid, 1,2,3,4-cyclopentanetetracarboxylic acid, 2,3,4,5-tetrahydrofuran tetracarboxylic acid, 1,2,4,5-cyclohexanetetracarboxylic acid, 3,4-dicarboxylic acid Carboxy-1-cyclohexylsuccinic acid, 3,4-dicarboxy-1,2,3,4
Alicyclic tetracarboxylic acids such as tetrahydro-1-naphthalene succinic acid and dianhydrides thereof, pyromellitic acid, 2,3,6,7-naphthalene tetracarboxylic acid,
1,2,5,6-naphthalene tetracarboxylic acid, 1,
4,5,8-naphthalenetetracarboxylic acid, 2,3,
6,7-anthracene tetracarboxylic acid, 1, 2, 5,
6-anthracene tetracarboxylic acid, 2, 3, 4, 5,
-Pyridinetetracarboxylic acid, 2,6-bis (3,4-
Aromatic tetracarboxylic acids such as dicarboxyphenyl) pyridine and their dianhydrides, which can be used alone or in combination of two or more.

As the diamine compound, p-phenylenediamine, m-phenylenediamine, 2,5-diaminotoluene, 2,6-diaminotoluene, 4,4-diaminobiphenyl, 3,3'-dimethyl-4,4. ′ -Diaminobiphenyl, 3,3′-dimethoxy-4,4′-
Diaminobiphenyl, diaminodiphenylmethane, diaminodiphenylether, 2,2'-diaminodiphenylpropane, bis (3,5-diethyl4-aminophenyl) methane, diaminodiphenylsulfone, diaminobenzophenone, diaminonaphthalene, 1,4-bis (4
-Aminophenoxy) benzene, 1,4-bis (4-aminophenyl) benzene, 9,10-bis (4-aminophenyl) anthracene, 1,3-bis (4-aminophenoxy) benzene, 4,4'- Bis (4-aminophenoxy) diphenyl sulfone, 2,2-bis [4- (4
-Aminophenoxy) phenyl] propane, 2,2'-
Trifluoromethyl-4,4'-diaminobiphenyl,
Aromatic diamines such as 4,4′-bis (4-diaminophenoxy) octafluorobiphenyl, alicyclic diamines such as bis (4-aminocyclohexyl) methane and bis (4-amino-3-methylcyclohexyl) methane, and tetra Aliphatic diamines such as methylenediamine and hexamethylenediamine, diaminosiloxanes and the like can be mentioned. or,
It is also possible to use one kind or a mixture of two or more kinds of these diamines.

The lipid used in the present invention is a group of substances capable of forming a polyionic complex with a polyamic acid, and examples thereof include an aliphatic ammonium salt compound having 4 or more carbon atoms or an alicyclic ammonium salt compound. Although not limited to these ammonium salt compounds, the range of carbon number is usually 4 to
34 and the alicyclic ammonium salt has 5 to 6 carbon atoms. Examples include salts of primary amines such as octylamine, decylamine, tetradecylamine, hexadecylamine, stearylamine, docosylamine, cyclohexylamine, dipentylamine, dihexylamine, dioctylamine, didecylamine, ditetradecylamine, dihexaamine. Decylamine, distearylamine, didocosylamine, N-methyloctylamine, N-methyl-n-decylamine, N-methyl-n-tetradecylamine, N-methyl-n-hexadecylamine, N-methyl-n-octadecyl Amine, salts of secondary amines such as N-methyl-n-eicosylamine, N-methyl-n-docosylamine, N-methyl-n-cyclohexylamine, N, N-dimethyloctylamine, N, N-dimethyl -N-decylamine, N N- dimethyl -n- tetradecylamine, N, N- dimethyl -n- hexadecylamine, N, N- dimethyl -n- octadecylamine,
N, N-dimethyl-n-eicosylamine, N, N-dimethyl-n-docosylamine, N, N-dimethyl-n-
Salts of tertiary amines such as cyclohexylamine, dimethyldioctylamine, dimethyldidecylamine, dimethylditetradecylamine, dimethyldihexadecylamine, dimethyldioctadecylamine, dimethyldiaicosylamine, dimethyldidocosylamine, dimethyldicyclohexylamine And salts of quaternary amines such as The above aliphatic ammonium salts may be used alone or in combination of 2
More than one species can be used. Of these, quaternary ammonium salts are preferred. The counter anion of the quaternary ammonium salt may be an organic anion such as a carboxylate anion, an alkyl sulfonate anion, an alkyl phosphate anion, or an inorganic acid anion. A halide salt such as chloride or bromide is preferably used.

The polyionic complex according to the present invention is prepared by mixing the above lipid as it is with a solution containing a polyamic acid neutralized with a base, or by mixing a solution of the lipid dissolved in an organic solvent which can be used for the polymerization of the polyamic acid. It can be done by doing. This reaction is usually
It can be carried out at 0 to 60 ° C., preferably room temperature. In this reaction, the amount of the lipid compound used is usually 0.5 to 5 mol, preferably 0.5 to 3 mol, per 1 mol of the repeating unit in the polyamic acid molecule. If the amount of the lipid used is too small or too large with respect to the repeating unit in the polyamic acid molecule, the pore size regularity and the shape of the honeycomb membrane of the polyion complex deteriorate.

Although a honeycomb membrane is manufactured using a polyion complex, it is poor in durability because it is not a polyimide as it is. Therefore, the polyamic acid ion complex must be imidized into polyimide while maintaining the honeycomb structure constructed. The polyamic acid ion complex has poor durability to heating and organic solvents, and it is necessary to carefully carry out the imidization reaction.

Next, a procedure for implementing the present invention will be described. In carrying out the present invention, the polyamic acid to be prepared is produced and purified by a known method. Specifically, it can be obtained by reacting and polymerizing the tetracarboxylic dianhydride and its derivative with the diamine. The ratio between the number of moles of tetracarboxylic dianhydride used and the total number of moles of diamine and general diamine is preferably 0.8 to 1.2. As in the usual polycondensation reaction, the closer the molar ratio is to 1, the higher the degree of polymerization of the polymer produced. At this time, the molecular weight of the polyamic acid should be noted, and when the molecular weight is too large, the honeycomb film may be brittle or colored when manufactured, which may cause difficulty in forming the honeycomb film. is there. If the molecular weight is too small, the manufactured honeycomb membrane may have poor durability or the honeycomb membrane may be difficult to manufacture. Therefore, the molecular weight of the polyamic acid to be used needs to be controlled to a number average molecular weight of 3,000 to 300,000, and more preferably 10,000 to 200,000.

Maleic anhydride, cyclohexanedicarboxylic acid anhydride, norbornene dicarboxylic acid anhydride or the like anhydride is used as the amine terminal blocking agent, and monoamine such as aniline is used as the polyimide precursor as the acid dianhydride terminal blocking agent. During the polymerization of the body or after the completion of the polymerization, the reaction may be performed depending on the terminal concentration.

The method of reacting and polymerizing the tetracarboxylic dianhydride and the above diamine is not particularly limited, but N-
The diamine is dissolved in a polar solvent such as methylpyrrolidone, and the tetracarboxylic dianhydride is added to the solution.
The reaction is performed to synthesize polyamic acid. The reaction temperature at that time is preferably −20 ° C. to 150 ° C., preferably −5.
Any temperature between 0 ° C and 100 ° C can be selected.

Further, as a method for polymerizing the polyamic acid, an ordinary solution method is suitable. Specific examples of the solvent used in the solution polymerization method include N, N-dimethylformamide, N,
N-dimethylacetamide, N-methyl-2-pyrrolidone, N-methylcaprolactam, dimethyl sulfoxide, tetramethylurea, pyridine, dimethyl sulfone,
Hexamethylphosphoramide, butyl lactone, etc. can be mentioned. These may be used alone or in combination.

The obtained polyamic acid solution can be precipitated and isolated in a poor solvent such as methanol or ethanol to use the polyamic acid as a powder.

This polyamic acid is dissolved in a hot alkaline aqueous solution. The alkaline aqueous solution may be applied to the present invention with either an inorganic substance or an organic substance, but it should be noted that if the pH of the alkaline aqueous solution is too high, the polyamic acid may hydrolyze and the molecular weight may decrease, and if the pH is too low, the polyamic acid may be reduced. It takes a very long time to dissolve. Further, if the temperature of the alkaline aqueous solution is too high or too low, the same problem may occur. Therefore, it is preferable to add an aqueous solution of sodium hydroxide from pH 7.5 to pH
Prepared to H9 and used at 50 ° C to 90 ° C. Here, it is also useful to use lipids for dissolution or to perform ultrasonic treatment or other dissolution promoting effect.

To this solution, a solution prepared by dispersing lipids in water by sonication or the like is added, the temperature is returned to room temperature, and the solution is left standing for several hours. An organic solvent is added here, and the organic phase is separated using a separatory funnel or the like. The organic solvent used here must be a solvent that is well separated from water and that is capable of dissolving a polyionic complex of a polyamic acid and a lipid. For example, aromatic solvents such as benzene, halides such as chloroform, esters such as ethyl acetate, ethers such as tetrahydrofuran are used.

Next, the organic phase is concentrated with an evaporator or the like and reprecipitated with an organic solvent. In order to improve the efficiency of reprecipitation, the organic solvent used here dissolves well the organic solvent in the separated organic phase and water, and is further formed by hydrolysis of lipids and polymers that do not form ionic complexes. The one that dissolves the monomer well is applied. For example, alcohols such as methanol, ketones such as acetone, and nitriles such as acetonitrile are suitable.

Next, the polyion complex is separated from this dispersion by using a technique such as centrifugation or filtration. The purified polyion complex is dissolved again in an organic solvent,
A honeycomb film is prepared in high humidity air according to a standard method. It is necessary to use a solvent that is well separated from water and that dissolves the polyionic complex of the polyamic acid and the lipid well. For example, aromatic solvents such as benzene, halides such as chloroform, esters such as ethyl acetate, ethers such as tetrahydrofuran are used.

The formed honeycomb membrane is still a polyion complex with a lipid of polyamic acid, and cannot be said to have high durability as it is. Therefore, this honeycomb film is imidized to complete the invention as a polyimide honeycomb film. Known methods can be applied to the imidization method,
A preferred method is to immerse the honeycomb membrane in a mixed solution of an organic solvent, acetic anhydride and pyridine. The organic solvent used here is preferably one that does not dissolve the polyion complex but dissolves acetic anhydride and pyridine well. Examples include aromatic solvents such as benzene.

After the imidization treatment, it is desirable to remove the residual lipid from the honeycomb membrane. For this purpose, the prepared polyimide honeycomb membrane is washed with an organic solvent. The organic solvent used here does not dissolve the polyimide honeycomb membrane, and it is desirable that it dissolves the lipid well,
For example, solvents such as benzene and other aromatic compounds, chloroform and other halogen compounds, ethyl acetate and other esters, tetrahydrofuran and other ethers, and ethanol and other alcohols can be used.

[0035]

The present invention will be described in more detail with reference to the following examples, which are merely illustrative and do not limit the present invention. Example 1 Biphenyl tetracarboxylic acid anhydride (BPDA) 29.4
g (0.1 mol) and diaminodiphenyl ether (D
A polyamic acid solution was prepared by reacting 20.0 g (0.1 mol) of DE) in 278 g of NMP at 23 ° C. for 24 hours. At this time, a part of the solution was sampled and the number average molecular weight was measured by GPC (Senshu Scientific Co., Ltd., SSC-7200, using RI detector) to obtain 156,0.
It turned out to be 00. 2 L of this solution is ethyl acetate
Was slowly charged to reprecipitate, filtered and dried to obtain 35.0 g of polyamic acid powder. 100 mg of this polyamic acid was dissolved in water having a pH of 8 by heating.
Meanwhile, dimethyldioctadecyl ammonium bromide
200 mg was dispersed in 200 mL of water by applying ultrasonic waves.

The above two liquids were mixed, the temperature was returned to room temperature, and the mixture was stirred overnight. After this, chloroform was added and the chloroform phase was separated using a separatory funnel. Chloroform was concentrated with an evaporator and reprecipitated with acetone. 260 in centrifuge
Centrifuge at 0 rpm for 30 minutes to dry the solvent (5
2.5 mg, yield 22.5%). This polyion complex solution was diluted to prepare a chloroform solution having a concentration of 5 g / L. 5 mL of this solution was dropped on a glass petri dish, and saturated steam was sprayed at a flow rate of 2 L / min to form a honeycomb film. 2 μm diameter from observation with optical microscope
It was confirmed that a honeycomb membrane having a structure in which the fine pores of a certain degree were densely packed was formed (FIG. 1).

This honeycomb film was immersed in a solution of benzene: acetic anhydride: pyridine = 3: 1: 1 overnight to imidize the polyion complex to prepare a polyimide honeycomb film. Lipids were removed by rinsing with ethanol. From observation with an optical microscope, it was confirmed that the honeycomb membrane structure was retained even after the imidization treatment (FIG. 2). The heat resistance test was carried out by peeling the honeycomb film from the glass substrate in ethanol, placing it on a cover glass, heating it on a hot stage at a temperature rise of 10 ° C. per minute, and observing with a microscope. As a result, it was confirmed that the polyimide honeycomb film produced maintained its honeycomb structure up to about 300 ° C.

Example 2 In the same manner as the above, the substrate was changed to glass with ITO electrodes sputtered with gold ions to form a polyimide honeycomb film. Using this sample, the polyion complex and the polyimide honeycomb film were measured and compared by FT-IR (FIG. 3).

As a result, in the spectrum of the polyion complex
2900 cm derived from the alkyl chain of the observed lipid^-1
1600 cm characteristic of front and rear peaks and amide^-1Degree of
The peak is no longer observed for the polyimide, instead it is
1720 cm characteristic of Mido ^-1And 1780 cm^-1New to
Since a large peak was observed, polyimide was formed.
It was confirmed that the lipid was washed out.

Example 3 Cyclobutane tetracarboxylic acid anhydride (CBDA) 1
A polyamic acid solution was prepared by reacting 9.6 g (0.1 mol) of diaminodiphenyl ether (DDE) with 20.0 g (0.1 mol) of polyamic acid in 222 g of NMP at 23 ° C. for 24 hours. At this time, a part of the solution was sampled and GPC (Senshu Kagaku, SSC-7200, RI
The number average molecular weight is measured with a detector),
It was found to be 000. This solution is ethyl acetate 2
Slowly charged into L to reprecipitate, filtered and dried to obtain 30.0 g of polyamic acid powder. 470 mg of this polyamic acid was dissolved in water having a pH of 8 by heating. On the other hand, 1.90 g of dioctadecyldimethylammonium bromide was ultrasonically dispersed in 200 mL of water. The above two liquids were mixed, the temperature was returned to room temperature, and the mixture was stirred overnight. After this, chloroform was added and the chloroform phase was separated using a separatory funnel. Chloroform was concentrated with an evaporator and reprecipitated twice with acetonitrile. This was dried (873 mg, yield 77.6%).

A chloroform solution having a concentration of 5 g / L of this polyion complex solution was prepared. 5 mL of this solution was dropped on a glass petri dish, and saturated steam was sprayed at a flow rate of 2 L / min to form a honeycomb film. From observation with an optical microscope, it was confirmed that a honeycomb film having a structure in which micropores having a diameter of about 2 μm were most closely packed was produced. This honeycomb film was treated with benzene: acetic anhydride: pyridine = 3: 1:
It was immersed overnight in the solution of No. 1 and the polyion complex was imidized to form a polyimide honeycomb film. Lipids were removed by rinsing with ethanol. From observation with an optical microscope, it was confirmed that the honeycomb membrane structure was retained even after the imidization treatment.

[0042]

INDUSTRIAL APPLICABILITY The present invention can provide a honeycomb film having excellent durability by forming a polyimide honeycomb film by forming a polyimide film after forming a honeycomb film with a polyamic acid which is a polyimide precursor. .

[Brief description of drawings]

FIG. 1 is a micrograph of a polyamic acid honeycomb film prepared according to Example 1.

FIG. 2 is a micrograph of a polyimide honeycomb film produced according to Example 1.

FIG. 3 is a comparison of a polyamic acid honeycomb film prepared according to Example 2 and a polyimide honeycomb film by FT-IR spectrum.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) B29K 105: 04 B29K 105: 04 F term (reference) 4D006 GA50 MA03 MA12 MA21 MB15 MC58X NA04 NA10 NA16 NA64 PC01 4F205 AA40 AC05 AG20 AM26 GA06 GB01 GE22 GN22 GN24 5H026 AA06 CX05 EE18

Claims (2)

[Claims] 1. Obtained by applying a solution of an amphipathic polymer in a hydrophobic organic solvent onto a substrate in an atmosphere having a relative humidity of 50% or more, and evaporating minute water droplets generated by evaporating the organic solvent. In the porous membrane, the porous membrane has the formula (1): (In the formula, R ¹ represents a tetracarboxylic acid residue, and R ² represents a diamine residue.) A polyimide porous film comprising a polyimide having a repeating unit. 2. Obtained by applying a solution of an amphipathic polymer in a hydrophobic organic solvent onto a substrate in an atmosphere having a relative humidity of 50% or more, and evaporating minute water droplets generated by evaporating the organic solvent. In the method for producing a porous membrane,
The porous membrane has the formula (2): (In the formula, R ¹ represents a tetracarboxylic acid residue, R ² represents a diamine residue, and Q represents an ammonium cation residue having at least one organic group having 4 or more carbon atoms.) A method for producing a polyimide porous membrane, which is a polyion complex of a lipid and a lipid, and which comprises using the same to form a porous membrane and then imidizing the same.