JPH08243367A - Production of polyimide composite membrane - Google Patents

Abstract

PURPOSE: To produce a hollow fiber composite membrane having a dense layer by co-extruding simultaneously a polyamic acid or polyisoimide dope forming a dense layer and a polymer dope forming a porous supporting layer into hollow fiber by using a multi-circular nozzle, then heating the obtained hollow fiber membrane or bringing the membrane into contact with a catalyst to convert the polyamic acid and the polyisoimide to polyimide. CONSTITUTION: A polyamic acid or a polyisoimide being a precursor of polyimide is excellent in fabrication property, especially in solubility to various kinds of solvents. Taking notice this property, the hollow fiber composite membrane is produced by co-extruding simultaneously the polyamic acid or polyisoimide dope forming the dense layer and the polymer dope forming the porous supporting layer into hollow fiber having a multilayer structure by using the multi-circular nozzle, coagurating the dope, and heating the obtained hollow fiber membrane or bringing the membrane into contact with the catalyst to convert the polyamic acid and the polyisoimide into polyimide. In such a case, the obtained composite membrane is substantially insoluble in the solvent and excellent in solvent resistance.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a hollow fiber composite membrane having high permeability, high separation performance, solvent resistance, heat resistance and durability as a separation membrane applied to gas-gas and liquid-gas separation and the like. The present invention relates to a manufacturing method of.

The separation of substances by a membrane is more advantageous in terms of energy than other separation methods, and has the features that the device is small and lightweight, the mechanism is simple, and maintenance-free. Therefore, it is actively applied to various industrial fields. The hollow fiber composite membrane obtained by the present invention is, for example, oxygen / nitrogen separation of air, separation and recovery of hydrogen from off-gas of the platforming method,
Separation and recovery of hydrogen during ammonia synthesis, recovery of carbon dioxide from waste gas from thermal power generation and waste incineration, removal of nitrogen oxides and sulfur oxides, recovery of carbon dioxide from off-gas in oil fields, hydrogen sulfide from natural gas, Pervaporation separation of volatile mixed liquids such as removal of acidic gases such as carbon dioxide, separation of helium, dehumidification of air and organic vapors, separation of water and alcohol, removal of water from esterification reaction system, liquid It is used to remove the gas dissolved in the liquid, dissolve a specific gas in the liquid, and so on. Of course, the present invention is not limited to these applications.

[0003]

2. Description of the Related Art The basic required performance of a separation membrane is (1) separation performance between a target substance and other components for separation, (2) substance permeation performance, (3) strength of membrane, heat resistance, durability, solvent resistance. It is sex.
The material permeation performance of the membrane is a characteristic that mainly governs the required membrane area, the size of the membrane module and the device, that is, the initial cost, and the development of materials with high material permeation performance and the separation active layer (sometimes referred to as a dense layer) The industrially practicable performance is realized by thinning the film. On the other hand, the substance separation performance of the membrane is a characteristic inherent to the membrane material in the case of a dense membrane, and is a characteristic that mainly controls the yield of the separated substance, that is, a characteristic that controls the running cost. Generally, the material separation property and the permeation property of a membrane are in a trade-off relationship, and a method for producing a separation film satisfying both these properties has been actively studied. In particular, the so-called composite membrane, in which the dense layer and the porous layer are made of different materials, can share various characteristics required as a separation membrane in a well-balanced manner, and due to its excellent mass productivity, it is currently most actively used. Being researched.

For example, JP-A-49-62380 discloses a method for producing a reverse osmosis membrane having a thin dense layer of the same or different polymers and a porous layer by coextrusion. In addition, the development of gas separation technology (Toray Research Center, Inc.), PP39 (July 25, 1990)
(Published daily) describes the application of this production method to the production of a membrane for gas separation.

JP-A-62-191019 discloses that cellulose ester resins such as cellulose acetate, cellulose triacetate and nitrocellulose, vinyl resins such as polyacrylonitrile, polyvinyl alcohol and polyvinyl acetate, polyamide resins and polyesters. A plurality of resin solutions having various concentrations such as a series resin having a resin concentration of 30 to 60% by weight are used, and the resin solutions having higher concentrations are simultaneously extruded from the inside of the concentric opening spinneret to form a plurality of layers. Disclosed is a method for producing a hollow fiber separation membrane having

JP-A-1-99616 discloses a low-concentration polyimide solution having a concentration of 0.1 to 20% by weight from an outer ring opening of a nozzle for wet spinning having a concentric ring opening, and an inner ring opening. It is disclosed that a polyimide hollow fiber separation membrane is produced with good reproducibility by simultaneously extruding a high-concentration polyimide solution having a concentration of 10 to 50% by weight and a concentration of at least 1% by weight or more higher than that of a low-concentration polyimide solution.

In Japanese Patent Laid-Open No. 2-169019, two kinds of aromatic polyimide solutions, which are different from a wet spinning nozzle having a concentric circular opening, are supplied to an outer circular opening at a concentration of 7 to 25 weight. %, The concentration of the polyimide supplied to the internal circular opening is lower than that of the polyimide supplied to the outside, and the concentration is 5 to 25% by weight. At the same time, the extrusion wet spinning is performed to obtain a uniform skin layer (dense layer) and porosity. Disclosed is a method for easily and reproducibly producing a hollow fiber membrane having a two-layer structure in which an asymmetric outer layer in which a layer is integrally formed and an inner layer made of only a porous layer are integrally formed in a concentric pattern. Has been done.

Japanese Unexamined Patent Publication (Kokai) No. 4-277019 discloses a gas separation composite membrane having a separation layer of a specific polyamide resin or a specific polyimide resin produced by a known coextrusion method as a method for producing a composite membrane. .

[0009]

In recent years, as described above, for separating gases, polyimide, which is a material excellent in balance between gas separation and permeability and also excellent in strength, durability and heat resistance, is applied to a dense layer. Research on composite membranes is being actively conducted.
However, it is essential that the polyimide applicable to the above-mentioned composite film of the prior art is soluble in a solvent, and therefore, there is a large limitation on the applicable polyimide. Further, as a matter of course, there was a limit to the solvent resistance of the produced composite film.

[0010]

Means for Solving the Problems The present invention has been earnestly studied to solve the above-mentioned drawbacks in the conventional known method for producing a hollow fiber composite membrane, and as a result, a polyamic acid or polyisoimide which is a precursor of polyimide was molded. Focusing on the fact that it is extremely excellent in processability, particularly in solubility in various solvents, a spinning dope for forming a dense layer is prepared from the precursor, and a specific polymer suitable for forming a porous layer is prepared. It was found that an excellent hollow fiber composite membrane can be produced by simultaneously co-extruding with the dope, coagulating, coagulating, heat-treating, etc. to polyimid the precursor to form a dense layer of polyimide. Has been completed. That is, the present invention uses a multi-ring nozzle to simultaneously form a polyamic acid or polyisoimide dope (a) forming a dense layer and a polymer dope (b) forming a porous support layer into a hollow fiber having a multilayer structure. Coextrusion, after contacting with a coagulating liquid to coagulate, the resulting hollow fiber membrane is heated or contacted with a catalyst to polyimidize the polyamic acid or polyisoimide, having a dense layer made of polyimide. The present invention relates to a method for manufacturing a hollow fiber composite membrane.

The polyimide hollow fiber composite membrane produced by the present invention is a composite membrane comprising a polymer layer having a dense layer and a porous support layer supporting the polymer layer, and the polymer layer is formed of a polyimide resin. Has been done. The polymer layer is preferably an asymmetric membrane structure having a dense layer having substantially no communication holes and a porous structure portion, which serves as a separation active layer of the substance to be separated, from the viewpoint that the dense layer can be manufactured thinner. However, by appropriately adjusting the polymer concentration of the spinning dope, the solvent composition, the spinning conditions, etc., a so-called homogeneous membrane structure in which the polymer layer is formed only from a dense layer can be produced. In the present invention, in particular, a composite membrane having a dense layer substantially insoluble in a solvent and comprising a polymer layer having an asymmetric membrane structure and a porous support layer and having excellent solvent resistance can be efficiently produced. . The manufacturing method of the present invention will be described in detail below.

Known multi-annular nozzles can be used in the present invention. Examples thereof include nozzles described in JP-A-1-99616 and JP-A-62-191019. A schematic diagram of a preferred nozzle is shown in FIG. "1" in the figure
Is a slit (core material discharge port) that mainly discharges a gas or liquid (hereinafter referred to as a core material) for maintaining the shape of the hollow fiber,
In the figure, “2” and “3” are slits (dope discharge ports) for flowing out the dope (a) or (b).

The dope (a) used in the production method of the present invention is a polyamic acid or polyisoimide (which may be collectively referred to as a polyimide precursor hereinafter) that produces a polyimide by heating or contact with a catalyst. The dope (a) forms a dense layer. The polyamic acid or polyisoimide has only to be soluble in an organic solvent and can be solidified in a coagulating liquid to form a film, and preferably a substance which is substantially dissolved in various water-soluble organic solvents. Polyamic acid or polyisoimide that produces a solvent-insoluble polyimide by heating in combination with these solvent-soluble properties is more preferable, and polyisoimide that produces a solvent-insoluble polyimide by heating is more preferable.

The polyamic acid which is the polyimide precursor of the present invention generally uses an amide-based solvent such as N, N-dimethylacetamide, N-methylpyrrolidone, N, N-dimethylformamide as a reaction solvent. Dissolve, and then add tetracarboxylic acid dianhydride in an equimolar amount to the diamine component, and add at room temperature or, if necessary, 50
It can be obtained by heating to about 0 ° C. and stirring for several hours, and polycondensing an equimolar amount of a diamine component and a tetracarboxylic dianhydride component. If necessary, a reaction aid such as benzoic acid or pyridine can be added to this reaction solution.

The polyisoimide, which is the polyimide precursor of the present invention, can be formed into a film having substantially a repeating unit represented by the following formula (1) and / or a stereoisomer structure of the following formula (1) as a repeating unit. It is a solvent-soluble polymer having a degree of polymerization.

[0016]

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(In the formula, R and Z are organic groups, preferably aromatic groups.) Polyisoimide is further added to a reaction solution of polyamic acid with triethylamine, trifluoroacetic anhydride, ethyl chloroformate, N, It can be obtained by adding a dehydration ring-closing agent such as N'-dicyclohexylcarbodiimide and stirring the mixture for several hours to dehydrate the polyamide acid.

The tetracarboxylic dianhydride component and the diamine component that can be used in the polymerization of the polyamic acid or polyisoimide according to the present invention may be selected in an optimum combination depending on the intended use of the membrane, and the following examples are given. . As the tetracarboxylic acid dianhydride, for example, 4,4 ′-(hexafluoroisopropylidene) diphthalic acid dianhydride (hereinafter, referred to as 6
Abbreviated as FDA), pyromellitic dianhydride (hereinafter P
Abbreviated as MDA), 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride, 3,3 ′, 4.
4'-biphenylsulfone tetracarboxylic dianhydride, 3,3 ', 4,4'-diphenyl ether tetracarboxylic dianhydride, naphthalene-1,2,4,5-tetracarboxylic dianhydride, 3,4 , 9,10-Perylenetetracarboxylic dianhydride, bis (dicarboxyphenyl) methanoic dianhydride, bis (dicarboxyphenyl)
Aromatic tetracarboxylic dianhydrides such as ethanoic dianhydride, bis (dicarboxyphenyl) propanoic dianhydride, anthracene tetracarboxylic dianhydride, azobenzene tetracarboxylic dianhydride, and cyclobutane tetracarboxylic dianhydride. Anhydrides, alicyclic tetracarboxylic dianhydrides such as cyclohexanetetracarboxylic dianhydride, and heterocycles such as thiophenetetracarboxylic dianhydride, furantetracarboxylic dianhydride, pyridinetetracarboxylic dianhydride Preferable examples include one or more components selected from the group consisting of group tetracarboxylic dianhydride and the like.

As the diamine component, for example, phenylenediamine such as m-phenylenediamine, or a part of hydrogen of the benzene ring skeleton is substituted with an alkyl group, a hydroxyl group, a carboxyl group, a nitro group, an alkoxy group, a halogen or the like. 4-diaminotoluene, 2,5-dimethyl-
1,4-phenylenediamine, 2,4,6-trimethyl-1,3-phenylenediamine, 3,5-diaminobenzoic acid, 2,4-diaminophenol, 2-chloro-1,
5-phenylenediamine, 2-methoxy-1,4-phenylenediamine, 2-chloro-5-methyl-1,4-phenylenediamine, 3-trifluoromethyl-1,5-
Phenylenediamine, etc. or various isomers of these,
5-naphthalenediamine, 9,9-bis (4-aminophenyl) fluorene, 9,10-bis (4-aminophenyl) anthracene, 2,6-diaminoanthraquinone, 1,5-diaminoanthraquinone, 3,3'- Dimethylnaphthidine or two or more benzene rings with ether group, thioether group, carbonyl group, sulfone group, sulfide group, methylene group, isopropylidene group, hexafluoroisopropylidene group, amino group, amide group, etc. For example, 4,4′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, or 4 in which a part of the bonded diamine component or hydrogen of these benzene rings is substituted with an alkyl group, an aryl group, an alkoxy group, a halogen, a carboxyl group, or the like. , 4'-diaminobenzophenone, 4,4'-diamino Phenyl sulfone,
4,4'-diamino-2,2'-dimethyldiphenyl sulfone, 4,4'-diamino-3,3'-dimethyldiphenyl sulfone, 4,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenylmethane, 4 ，
4'-diamino-3,3'-dimethyldiphenylmethane, 4,4'-diamino-3,3 ', 5,5'-tetramethyldiphenylmethane, 4,4'-diamino-3,
3'-dimethyl-5,5'-diethyldiphenylmethane, 4,4'-diamino-3,3 ', 5,5'-tetraethyldiphenylmethane, 4,4'-diamino-3,
3'-dichlorodiphenylmethane,

2,2-bis (4-aminophenyl) propane, 2,2-bis (4-amino-3,5-diethylphenyl) propane, 2,2-bis (4-amino-3,5)
-Dimethylphenyl) propane, 2,2-bis (4-amino-3-methyl-5-ethylphenyl) propane,
2,2-bis (4-amino-3-methylphenyl) propane, 2,2-bis (4-aminophenyl) hexafluoropropane, 2,2-bis (3-aminophenyl) hexafluoropropane, 4,4 '-Diaminobenzanilide, O-toluidine sulfone, dibenzothiophene-3,7-diamine-5,5'-dioxide, 3,6-
Diaminocarbazole, 2,7-diaminofluorene,
Bis [4- (4-aminophenoxy) phenyl] sulfone, Bis [4- (3-aminophenoxy) phenyl]
Sulfone, 4,4'-bis (4-aminophenoxy)
Biphenyl, 2,2-bis [4- (4-aminophenoxy) phenyl] hexafluoropropane, 1,4-bis (4-aminophenoxy) benzene, 1,3-bis (4
-Aminophenoxy) benzene, 2,2-bis [4-
(4-Aminophenoxy) phenyl] propane, 2,2
-Bis (3-amino-4-hydroxyphenyl) hexafluoropropane, 2,2-bis (3-amino-4-methylphenyl) hexafluoropropane, 2,2-bis [4- (4-aminophenoxy) phenyl ] Hexafluoropropane or the like, or hydrogen in a benzidine or benzidine skeleton substituted with an alkyl group, a halogen, an alkoxy group, a trifluoromethyl group, or the like, for example, 2,2 ′, 6,6′-
Trimethylbenzidine, 3,3'-dimethylbenzidine, 3,3'-dimethoxybenzidine, 2,2'-dichloro-5,5'-dimethoxybenzidine, 3,3 ',
One selected from the group of 5,5'-trimethylbenzidine, 3,3'-dihydroxybenzidine, 3,3-diamino-4,4'-dihydroxybiphenyl, 2,2'-bis (trifluoromethyl) benzidine, etc. The above components can be used.

Preferably, an acid dianhydride component selected from 4,4 '-(hexafluoroisopropylidene) diphthalic acid dianhydride (6FDA) and / or pyromellitic dianhydride (PMDA) and 3,6 -Diaminocarbazole, 2,7-diaminofluorene, metaphenylenediamine, 1,5-naphthalenediamine, 2,2-bis (3
-Amino-4-hydroxyphenyl) hexafluoropropane, 3,3'-diamino-4,4'-dihydroxybiphenyl, 2,4-diaminotoluene, 2,6-diaminotoluene, 2,2-bis [4- ( 4-aminophenoxy) phenyl] propane, 2,2-bis [3,5-dibromo-4- (4-aminophenoxy) phenyl] propane, 2,4-diaminophenol, 3,5-diaminobenzoic acid It is a polyamic acid or polyisoimide polymerized from one or more diamine components selected from the above, which produces a solvent-insoluble polyimide upon heating. Particularly preferably, the polymer is a polyisoimide body capable of forming a dense layer of polyimide which is particularly excellent in gas selectivity by heating, but this is a low molecular weight substance such as water during isomerization of the polyisoimide body to an imide body. Is not generated, but this does not limit the present invention.

The polyamic acid or polyisoimide spinning dope (a) may be prepared by directly polymerizing a solution of polyamic acid or polyisoimide obtained by polymerizing tetracarboxylic acid anhydride and diamine in a suitable solvent, or once using polyamide. The acid or polyisoimide may be prepared by dropping the acid or polyisoimide as a solid from the reaction solvent and re-dissolving it in an appropriate organic solvent. The concentration of the polymer solid of the dope (a) is preferably 5% by weight to 35% by weight, and more preferably 1
It is 5% by weight to 30% by weight. The solution viscosity of the dope (a) is not particularly limited as long as wet spinning is possible.

The dope (b) used in the production method of the present invention is a spinning dope for forming a porous support layer of a hollow fiber composite membrane, and is a porous support having pores that are substantially in communication with each other. A layer that can be formed and that sufficiently adheres to a polymer layer having a dense layer of polyimide formed by heating or contacting a polyimide precursor with a catalyst, and having sufficient mechanical strength and heating or a catalyst of the polyimide precursor. Sufficient heat resistance to withstand polyimidization by contact with
A resin having chemical resistance is dissolved in a solvent.

As such a resin, a polyamide resin, a polyetherimide resin, which is soluble in a solvent for preparing a dope,
One or more resins of polysulfone resin, polyamide-imide resin, polyheterocyclic compound such as polybenzimidazole, polybenzoxazole, polyimide resin, or a precursor thereof can be used. Among them, one or more resins selected from polyetherimide resins, polysulfone resins, polyimide resins, and polybenzimidazole resins are particularly preferred because the dope can be easily adjusted. Among them, polyetherimide and / or polysulfone resins and polyimide A mixture with a resin forms a porous support layer with various properties required for a porous support layer, particularly heat resistance and excellent adhesiveness with a polymer layer having a dense layer, in addition to easy dope preparation. It is possible and more preferable.

The polyetherimide resin as used herein is a substantially non-crystalline polymer having a molecular weight capable of forming a film and composed of repeating units having an ether bond and an imide bond. Further, the polysulfone resin as used herein is a substantially non-polymerizable molecular weight having a paraphenylene unit and / or parabiphenylene unit composed of a repeating unit in which a sulfone group and an ether group and / or an isopropylidene group are bonded. It is a crystalline polymer and is generally marketed as polysulfone, polyether sulfone, polyallyl sulfone or polyphenyl sulfone.

The polyimide resin forming the porous support layer according to the present invention may be solvent-soluble or solvent-insoluble. The formation of the solvent-insoluble polyimide porous support layer, the dope of the solvent-soluble polyimide precursor, for example, polyisoimide, using a polyamic acid or polyimide dope,
After coextrusion and solidification film formation, a solvent-insoluble polyimide porous support layer can be formed by heat treatment, contact with a catalyst, irradiation with ultraviolet rays, or the like. The concentration of the polymer solid of the dope (b) is preferably 10% by weight to 35% by weight, more preferably 20% by weight to 30% by weight. The solution viscosity of the dope (b) is not particularly limited as long as wet spinning is possible.

In the method for producing a hollow fiber composite membrane of the present invention, the solvent that can be used for the spinning dopes (a) and (b) is soluble in the polyamic acid, polyisoimide, or each resin forming the porous support layer. Moreover, a solvent having compatibility with the coagulation liquid described below can be appropriately selected and used. These solvents may be the same as or different from the dopes (a) and (b). Since polyamic acid or polyisoimide is excellent in solvent solubility, there is an advantage that an optimum solvent system for forming a dense layer of a hollow fiber composite membrane can be selected from a wide range of solvents.

Examples of the organic solvent which can be used in the dope (a) and / or (b) of the present invention include alkyl halides such as dichloromethane, chloroform and trichloroethane, phenols such as m-chlorophenol and m-cresol, Ketones such as acetone and methyl ethyl ketone, N, N-dimethylacetamide, N-methylacetamide, N, N-dimethylformamide, N, N-diethylformamide, 2-pyrrolidone, N-methylpyrrolidone, hexamethylphosphorotriamide, etc. The amide-based solvent, the sulfur-based solvent such as dimethyl sulfoxide and sulfolane, and one or more solvents such as pyridine, dioxane, tetrahydrofuran, γ-butyl lactone, polyphosphoric acid, and acetonitrile are preferable. Preferred are water-soluble solvents such as N, N-dimethylacetamide, N-methylacetamide, N, N-dimethylformamide, N, N-diethylformamide, 2-pyrrolidone, N-methylpyrrolidone and hexamethylphosphorotriamide. .

For the purpose of adjusting the stability and viscosity of the dope for spinning and improving the gas selective permeability of the produced composite membrane, the above solvent may be added to the above-mentioned solvent, if necessary, such as polyethylene glycol, polypropylene glycol, polyvinyl alcohol or polyvinylpyrrolidone. Low molecular weight substances soluble in the solvent, poor solvents for polymers such as xylene and acetic acid, ethylene glycol,
Water-soluble polyhydric alcohols such as glycerin, inorganic salts such as lithium chloride, lithium bromide, potassium chloride and the like can be appropriately added.

In the first step of the production method of the present invention, the dopes (a) and (b) are discharged from the dope discharge port of the multiple ring nozzle while flowing the core material from the core material discharge port of the multiple ring nozzle. They are simultaneously extruded into hollow fibers (co-extrusion), and the extruded hollow fibers having a multilayer structure are brought into contact with a coagulating liquid to coagulate.

In the production method of the present invention, the dense layer is formed on the inner surface of the hollow fiber by appropriately selecting the composition, concentration, and temperature of the dope solution, the composition of the coagulating solution, the composition of the inner tube fluid, the spinning draft, and the like. It can also be formed on the outer surface. It is also possible to obtain a multi-layered hollow fiber membrane by extruding a plurality of dopes (a) and (b) depending on the multiplicity of the multi-annular nozzle. Will be described.

For example, in the case of a composite membrane having a dense layer on the outer surface of the hollow fiber, the dope (a) is discharged from the dope discharge port of the outermost layer of the nozzle shown in FIG. 1 and the dope (b) is discharged from the inner dope discharge port. At the same time, it is extruded into the gas phase at the same time, then immersed in a coagulating liquid to solidify to form a film, so-called known dry-wet method (JP-A-62-191019, JP-A-1-9961).
6 etc.) can be applied. Such a membrane is preferable because of its excellent mass productivity and high gas permeation selectivity of the obtained composite membrane. Further, the dimensions of the hollow fiber composite membrane can be appropriately adjusted to the outer diameter, the inner diameter and the like suitable for practical use by appropriately adjusting the dimensions of the nozzle, the dope extrusion amount, the spinning draft and the like.

The fluid discharged as the core material may be a gas or a liquid, and for example, a gas such as nitrogen or air, or one or more liquids such as water, ethanol, normal propanol, isopropanol, glycerin or the like can be used.

The atmosphere for extruding the dope may be, for example, a gas phase atmosphere of air, nitrogen or the like, or a liquid phase atmosphere of a solvent or the like. In the case of the gas phase atmosphere, air flow, temperature,
In the case of a liquid phase atmosphere, control of humidity and the like can be appropriately performed as necessary, such as control of temperature and the like.

The coagulation liquid is a poor solvent sufficient to coagulate the polymer soluble in the dope solvent, that is, the polyamic acid, polyisoimide, and various polymers forming the porous support layer of the hollow fiber composite membrane. Any liquid may be used, and for example, one or more liquids of water, methanol, ethanol, normal propanol, and isopropanol can be used. Preferred is water or a mixed liquid of water and another organic solvent.

Further, as a second step of the production method of the present invention, a hollow fiber composite membrane comprising a porous support layer and a polymer layer having a dense layer of a polyimide precursor obtained by solidification is heat treated. Alternatively, the precursor is brought into contact with a catalyst to be polyimidized to change the dense layer made of the polyimide precursor into a dense layer made of polyimide. Here, the dense layer of the precursor may show the features of the dense layer of polyimide described below after imidization of the precursor, and the density is generally improved by thermal polyimidization of the precursor described in the present invention. .

The heat treatment conditions for the hollow fiber composite membrane are such that the dense layer made of the polyimide precursor, which is polyamic acid or polyisoimide, is substantially converted into polyimide, and the porous structure of the polymer forming the porous layer is used. It suffices if the condition is not destroyed by heating. The heat treatment is preferably under reduced pressure or in an inert gas atmosphere at 150 ° C. to 400 ° C., more preferably 200 ° C. to 350 ° C., for 10 minutes to 360 minutes, more preferably 30 minutes to 300 minutes. The term "under reduced pressure" as used herein means that each resin forming the hollow fiber composite membrane does not cause oxidative deterioration, and is preferably 200.
A vacuum atmosphere of not more than torr, more preferably not more than 5 torr. Suitable examples of the inert gas usable in the present invention include nitrogen, helium and argon.

In the heat treatment, the hollow fiber composite membrane obtained by coagulation of the spinning dope can be continuously heat treated as it is, or a bundle of hollow fiber composite membranes having an appropriate length can be used. Alternatively, it may be performed after modularization.

The isomerization of the polyisoimide to the corresponding polyimide is not limited to heating but may be a catalyst such as triethylamine, trifluoroacetic acid, 1,8-diazabicyclo [5,4,0] -7-undecene, if necessary. Can also be carried out by a method of bringing the precursor into contact with The method of contacting the catalyst is not particularly limited, and for example, a hollow fiber membrane is formed so that a dense layer made of polyisoimide is brought into contact with the solution in a solution in which a catalytic amount of triethylamine is dissolved in an appropriate solvent such as acetone or methyl ethyl ketone. The polyisoimide can be polyimidized by a method of immersing it for several hours to several tens of hours. In such a treatment, the hollow fiber composite membrane obtained by coagulation of the spinning dope may be continuously treated as it is, or may be in the state of a bundle of hollow fiber composite membranes having an appropriate length. It may be done after modularization.

The change of the polyimide precursor into polyimide can be easily confirmed by the change of these infrared absorption spectra. For example, the change from the polyisoimide form to the corresponding polyimide is about 1810 which is characteristic of the polyisoimide form.
cm ^-1 absorption peak near about 920 cm ^-1 vicinity disappeared, characteristic absorption peaks at about 1780 cm ^-1 vicinity of polyimide in place can be easily confirmed by appearance.
The change to a polyimide corresponding polyamide acid product emerges and disappearance of the absorption peak derived from polyamic acid 3250Cm ^-1 vicinity and 1650 cm ^-1 vicinity, instead 1
It can be easily confirmed by the absorption peak characteristic of polyimide near 780 cm ^-1 .

Further, it is preferable that the organic solvent remaining in the obtained composite membrane is substantially removed. For example, the organic solvent is removed by washing with warm water and / or washing with a low-boiling solvent capable of dissolving the residual solvent and replacing with vacuum heating. It can be carried out by a known method such as drying. It is preferable to remove the residual organic solvent, especially the dope solvent, before the heat treatment step for polyimidization.

The polyimide hollow fiber composite membrane produced by the present invention is a composite membrane having a dense layer made of polyimide as described above. The dense layer made of polyimide described in the present invention means that the mechanism of membrane permeation of oxygen, nitrogen, hydrogen, etc., such as oxygen, nitrogen, hydrogen, etc., has at most only the communicating pores having a pore diameter equal to or smaller than the Knudsen flow rate-determining mechanism, and the communication thereof. 1 × 10 ^-3 or less at AnaHiraki porosity area ratio, preferably 1 × 10 ^-4 or less, further preferably 1 × 10 ^-6 or less, and most preferably the communication hole is a gas substantially absent It is a dense thin film layer in which the membrane permeation mechanism is dissolution-diffusion limited, and the thinner the thickness, the more preferable, the thickness is 2 μm or less, the thickness is preferably 1 μm or less, more preferably 0.5 μm or less, and the most preferable. It means a dense thin film layer having a thickness of preferably 0.1 μm or less. The fact that the diameter of the communicating pores existing in the dense layer is at most equal to or smaller than the diameter of the Knudsen flow is easily confirmed by, for example, the ratio of the permeation rates of oxygen and nitrogen passing through the membrane being 0.935 or more within the error range. it can. Further, the open area ratio of the communication holes of the dense layer is 1 × 10 ⁻³ or less means that the surface of the dense layer is covered with a silicone or the like as necessary to seal the communication holes or a thin film having a thickness of 2 μm or less at most. It can be confirmed that the rate-determining rate of the gas permeation mechanism is that of gas diffusion and diffusion into polyimide. This is because when, for example, oxygen and nitrogen are used as the gas, a polyimide dense layer in a practically thin film thickness range where a treatment such as coating is carried out with a material having extremely high gas permeability such as silicone, if necessary. It can be easily confirmed by showing that the oxygen / nitrogen separation coefficient is about 80% or more even if the characteristic value of the polyimide material is low.

The present invention also provides a hollow fiber composite membrane having optimum dimensions for various practical applications by appropriately adjusting the nozzle size, the dope extrusion amount, the spinning draft, and the like.
For example, when the hollow fiber internal pressurization method is used for separation of oxygen and nitrogen in the air, limiting factors such as membrane strength, durability, compressed air pressure loss, and yarn occupied cross-sectional area (module size) The hollow fiber inner diameter is 130 μm to 400 μm, the outer diameter is 200 μm to 800 μm, and the thickness of the porous layer mainly responsible for the physical strength of the hollow fiber membrane is 30 μm to
A preferred hollow fiber composite membrane that is 300 μm is provided.

In the composite film of the present invention, in order to close pinholes (fine holes) slightly generated in the dense layer of the composite film, the surface of the dense layer is coated or coated with a material having a high gas permeability such as silicone or polyacetylene. Stopping treatment may be performed, or the dense layer may be subjected to surface treatment with chlorine or fluorine gas or plasma treatment in order to further enhance gas selectivity.

[0045]

The present invention will be described in more detail with reference to the following examples. Reference Example 1 <Polymerization of Polyamic Acid> At room temperature under a nitrogen atmosphere, 2.
0.3 mol of 2'-bis [3,5-dibromo-4- (4-aminophenoxy) phenyl] propane was dissolved in 1800 g of dimethylacetamide (hereinafter abbreviated as DMAC) dehydrated with molecular sieve 3A, and then P
After adding 0.3 mol of MDA and stirring at room temperature for 3 hours, D
An additional 400 ml of MAC was added and diluted. Then, 0.4 mol of benzoic acid was added and completely dissolved, and then pyridine was added to 0.4 mol.
4 mol was added and further stirred for 3 hours. Isopropanol was added to the obtained viscous liquid, the polyamic acid solid was separated by filtration, and sufficiently dried in a vacuum oven at about 100 ° C. to obtain a polyamic acid solid. A DMAC solution containing about 10% by weight of the obtained solid matter was cast on a glass plate and vacuum dried at 60 ° C. for 3 hours and further at 100 ° C. for 4 hours to obtain a dense film. This film has 3250 cm ^-1 and 16
It had an absorption spectrum derived from a polyamic acid body in the vicinity of 50 cm ^-1, and it was confirmed that this solid substance was a polyamic acid body. Then, this film at 240 ℃ for about 5 hours,
When heat treatment was performed in a vacuum oven, the infrared absorption band disappeared and an absorption band derived from imidecarbonyl near 1780 cm ^-1 appeared. The heat-treated film is D
It was insoluble in various solvents such as MAC and N-methylpyrrolidone (hereinafter abbreviated as NMP).

[Reference Example 2] <Polyisoimide polymerization> At room temperature under a nitrogen atmosphere,
NMP solution 8 in which 0.15 mol of 3'-diamino-4,4'-dihydroxybiphenyl and 0.15 mol of 2,7-diaminofluorene were dehydrated with molecular sieve 3A
Dissolve in 00 g, then add 0.26 mol of PMDA and 6
FDAWP (0.06 mol) was added and dissolved, and the mixture was stirred at room temperature for 4 hours, and then phthalic anhydride (0.33 mol) was added and the mixture was stirred and dissolved for 2 hours. Next, 800 g of NMP solution was added and diluted. To this solution, 0.4 mol of triethylamine was added and stirred. Then, while cooling the reaction vessel in ice water, 0.6 mol of trifluoroacetic anhydride was slowly added dropwise while stirring the solution, and the mixture was further stirred for 4 hours. The resulting viscous liquid was dropped into a large amount of isopropanol and filtered to separate solids. After sufficiently washing with a large amount of isopropanol, it was thoroughly dried in a vacuum oven at about 100 ° C. to obtain a solid polyisoimide. A 10 wt% NMP solution of the obtained polyisoimide was cast on a glass plate and heated at 60 ° C.
After vacuum drying for 3 hours at 100 ° C. for 4 hours, a dense film was obtained. Approximately 1810 cm in infrared absorption spectrum
^Over it was confirmed isoimide specific absorption peak in the near ^1. Then, when this film was heat-treated at 240 ° C. for about 5 hours in a vacuum oven, the infrared absorption band disappeared, and instead, an absorption band derived from imidecarbonyl near 1780 cm ⁻¹ appeared. Also, the heat-treated film is DMAC,
It was insoluble in various solvents such as NMP.

Reference Example 3 <Synthesis of polybenzimidazole> 16 in a nitrogen atmosphere
1,3Og of polyphosphoric acid heated and kept at 0 ° C for 3,3 ',
0.3 mol of 4,4-tetraaminobiphenyl was dissolved, followed by 0.2 mol of isophthalic acid and 2,2-bis (4
-Carboxyphenyl) hexafluoropropane 0.9
The mol was dissolved, the temperature was raised to 200 ° C., and the mixture was stirred for 15 hours.
The viscous reaction solution obtained was poured into water, and the precipitated polymer was separated by filtration, washed well with water, and then the remaining water in the polymer solid was sufficiently replaced with methanol to perform vacuum drying to obtain the polymer solid. Got Confirmation that this is polybenzimidazole is about 10% by weight of this solid
The DMAC solution of is cast on a glass plate at 60 ° C. for 3 hours,
Further, it was confirmed by the existence of an absorption spectrum derived from imidazole in the vicinity of 1620 cm ^{−1 of} a dense film obtained by vacuum drying at 220 ° C. for 5 hours.

[Example 1] The polyamic acid obtained in Reference Example 1 was dissolved in DMAC in a nitrogen atmosphere at about 70 ° C in an amount of 25% by weight, filtered through a stainless steel filter having a filtration filtration pore size of 20 µm, and defoamed under reduced pressure for spinning. A dope (a) was obtained. Also,
Matriimide 5218 [Ciba Geigy: Soluble Polyimide] / Ultem 1000 [GE Plastics: Polyetherimide] / DMAC = 12/16/72 wt% dissolved in a composition and filtered through a stainless filter having a filtration pore size of 20 μm, and degassed under reduced pressure. Dope for spinning (b)
I got From the outer diameter of the ring, use these dope solutions φ1.8-
Using a multi-annular nozzle of φ1.5-φ1.1-φ0.4-φ0.2 [mm], while allowing water to flow from the central circular tube, the porous support layer of the composite membrane from the inner circular ring At a rate of about 3 g / min for forming dope, and at a rate of about 0.6 g / min for the dope solution (a) of polyamic acid heated to about 50 ° C. from the outer ring. At the same time, after discharging into the air atmosphere, it is continuously introduced into the coagulating liquid of isopropyl alcohol / water of about 50/50 adjusted to 5 ° C. and coagulated, and continuously wound on the bobbin at a winding speed of about 20 m / min. I took it. The obtained hollow fiber was immersed in running water of about 50 ° C., thoroughly washed, lightly dried, further sufficiently replaced with ethanol for washing, and sufficiently vacuum dried at about 120 ° C. Then, heat treatment was performed in vacuum at 250 ° C. for 5 hours to polyimidize the polyamic acid body. The obtained hollow fiber composite membrane had an inner diameter of about 210 μm, an outer diameter of about 440 μm, and a ratio of the hollow fiber inner side porous support layer thickness / hollow fiber outer side porous layer thickness of about 5: 1 by microscopic observation of the hollow fiber cross section. It was a hollow fiber composite membrane having a dense layer on the outer surface of the hollow fiber. The gas permeation characteristics of the obtained hollow fiber composite membrane were measured by ASTM in pure gas using 25 ° C. atmosphere and ΔP = about 2 [kg / cm ² ].
It was measured by the pressure method according to D1434. The results are shown in Table 1.

Example 2 The composition of the spinning dope (b) was changed to Matriimide 5218 / Ultem 1000 / Radel A-.
100 (Teijin Amoco: Polyethersulfone)
A hollow fiber composite membrane having a dense layer of polyimide on the outer surface of the hollow fiber was obtained by the same method as in Example 1 except that / DMAC = 12/8/8/72% by weight. The gas permeation characteristics of the obtained hollow fiber membrane were measured by using pure gas in an atmosphere of 25 ° C.,
It was measured by the pressure method according to ASTM D1434 at ΔP = about 2 [kg / cm ² ]. The results are shown in Table 1. [Example 3] The polyisoimide obtained in Reference Example 2 was dissolved in NMP at 25% by weight in NMP at about 70 ° C under a nitrogen atmosphere, and filtered with a stainless filter having a filtration and filtration pore size of 20 µm to defoam under reduced pressure. A spinning dope (a) was obtained. Also Matriimide 5
218 / Ultem 1000 / NMP = 12/16/72
The weight% solution was filtered through a stainless steel filter having a filtration and filtration pore size of 20 μm, and defoamed under reduced pressure to obtain a spinning dope (b). A hollow fiber composite membrane having a dense layer of polyimide on the outer surface of the hollow fiber was obtained in the same manner as in Example 1 except that the above spinning dopes (a) and (b) were used. The gas permeation characteristics of the obtained hollow fiber membrane were measured using pure gas.
ASTM in 5 ° C atmosphere, ΔP = about 2 [kg / cm ² ]
It was measured by the pressure method according to D1434. The results are shown in Table 1. [Example 4] Polyisoimide obtained by the same method as in Reference Example 2 was dissolved in NMP at 25% by weight in NMP at about 70 ° C under a nitrogen atmosphere, and filtered with a stainless filter having a filtration pore size of 20 µm. Defoaming under reduced pressure was performed to obtain a dope for spinning (a). Also, Matriimide 5218 / Radel A-100 / NMP =
A 12/15/73 wt% solution was filtered through a stainless filter having a filtration pore size of 20 μm, and defoaming under reduced pressure was carried out to obtain a spinning dope (b). The spinning dope (a),
A hollow fiber composite membrane having a dense layer made of polyimide on the outer surface of the hollow fiber was obtained in the same manner as in Example 1 except that (b) was used. The gas permeation characteristics of the obtained hollow fiber membrane were measured by using pure gas in an atmosphere of 25 ° C. and ΔP = about 2 [kg / c
m ² ] and measured by the pressure method according to ASTM D1434. The results are shown in Table 1. [Example 5] The composition of the spinning dope (b) was Matriimide 5
218 / NMP = 25/75 wt%, and a hollow fiber composite membrane having a dense layer of polyid on the outer surface of the hollow fiber was obtained by the same method as in Example 2 except that the heat treatment temperature was 350 ° C. The gas permeation characteristics of the obtained hollow fiber membrane were measured by using pure gas in an atmosphere of 25 ° C. and ΔP = about 2 [kg / c
m ² ] and measured by the pressure method according to ASTM D1434. The results are shown in Table 1.

Example 6 The composition of the spinning dope (b) was adjusted to the polybenzimidazole / Ultem 1000 / DMAC = 17/8/75 wt% synthesized in Reference Example 3, and the heat treatment temperature for the polyimidization was adjusted. A hollow fiber composite having a dense layer of polyid on the outer surface of the hollow fiber was obtained in the same manner as in Example 2 except that the operation was performed at 290 ° C. The gas permeation characteristics of the obtained hollow fiber membrane were measured according to ASTM D143 using pure gas in an atmosphere of 25 ° C. and ΔP = approximately 2 [kg / cm ² ].
The pressure method was used according to 4. The results are shown in Table 1.

[0051]

[Table 1]

[0052]

According to the present invention, it is possible to produce a composite film which has not been heretofore practically insoluble in a solvent and has excellent solvent resistance. Moreover, since the range of types of polyimide that can be manufactured is widened, it is possible to provide a composite membrane having excellent gas permeation selection characteristics. Further, according to the production method of the present invention, such a hollow fiber composite membrane can be provided at an industrial production level.

[Brief description of drawings]

FIG. 1 is a schematic view of a multi-layer extrusion nozzle for carrying out the present invention, in which A is a sectional view of the nozzle and B is the shape of a nozzle discharge port.

[Explanation of symbols]

 1 Core material discharge port 2 Dope discharge port 3 Dope discharge port

Claims (8)

[Claims] 1. A multifilamentary nozzle is used to simultaneously form a polyamic acid or polyisoimide dope (a) for forming a dense layer and a polymer dope (b) for forming a porous support layer at the same time as a hollow fiber having a multilayer structure. Coextrusion, after contacting with a coagulating liquid to coagulate, the resulting hollow fiber membrane is heated or contacted with a catalyst to polyimidize the polyamic acid or polyisoimide, having a dense layer made of polyimide. Method for producing hollow fiber composite membrane. 2. The manufacturing method according to claim 1, wherein the polyimidization is performed by heat treatment. 3. The method according to claim 2, wherein the dope (a) is a dope of polyisoimide or polyamic acid that produces a solvent-insoluble polyimide by heating. 4. The method for producing a hollow fiber composite membrane according to claim 3, wherein the dope (a) is a polyisoimide dope. 5. The production method according to claim 2, 3 or 4, wherein heating is performed at 150 ° C. to 400 ° C. under reduced pressure or in an atmosphere of an inert gas. 6. The manufacturing method according to claim 5, wherein heating is performed for 10 to 360 minutes. 7. The polymer dope (b) is one or more resins selected from a polyetherimide resin, a polysulfone resin, a polyimide resin, and a polybenzimidazole resin. The manufacturing method according to any one of items. 8. The method according to claim 7, wherein the polymer dope (b) is a dope of a mixture of a polyetherimide resin and / or a polysulfone resin and a polyimide resin.