JPH06254366A - Separating membrane - Google Patents

Abstract

(57) [Summary] [Structure] A separation membrane using a polyisoimide having a repeating unit represented by the following general formula (I): [Effect] It is possible to provide a separation membrane having excellent thermal stability, mechanical strength, and good solvent solubility, which facilitates molding, and has high membrane selective permeation performance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel separation membrane using polyisoimide. More specifically,
The present invention is particularly excellent in selective permeability of a gas such as hydrogen, carbon monoxide, carbon dioxide, water vapor or the like, or an organic liquid mixture such as alcohol / water, and has good heat resistance and high mechanical strength, and a solvent. The present invention relates to a separation membrane which is excellent in solubility in water and has a large degree of freedom in molding and is suitable for practical use.

[0002]

2. Description of the Related Art Recently, membrane separation technology using polymer membranes has been
Since it can be made compact and has low energy consumption, it has been put to practical use in many fields such as food industry, electronic industry, pharmaceutical industry, nuclear industry, chemical industry, etc. .

Among them, as a gas separation membrane, a composite membrane in which polysulfone and a silicon-based polymer are complexed is known (US Pat. No. 4,230,463), but this membrane has low heat resistance and gas selectivity. Does not always show sufficient performance. Further, it is known that an aromatic polymer as a gas separation membrane, especially a polyimide separation membrane has excellent gas selectivity (US Pat. No. 4,705,504,
JP-A-56-21602). However, in general, polyimide has low solubility in a solvent, and in order to dissolve it in a solvent, an amide solvent having a high boiling point, a halogen solvent that may cause environmental damage, and a strongly corrosive phenol solvent must be used. This is a major problem during molding.

On the other hand, polyisoimide is known, which has a polyimide-like structure from the viewpoint of heat resistance and exhibits excellent properties such as solvent solubility (PCT Patent Publication No. 9000).
1,522, US Defense Patent H729). However, all of these only show information on solvent solubility, mechanical properties, etc., and have not yet been found to have properties of excellent selective permeability.

[0005]

The present invention overcomes the drawbacks of the conventional polymer separation membranes, has good heat resistance, excellent solvent solubility, easy moldability, and excellent The present invention also provides a novel polyisoimide separation membrane that exhibits selective gas permeability and is also suitable for practical purposes.

[0006]

Means for Solving the Problems As a result of intensive studies to develop a polymer separation membrane having the above-mentioned preferable properties, the present inventors can achieve the object by a separation membrane made of polyisoimide. Based on this finding, the present invention has been completed. That is, the gist of the present invention is the general formula (I)

[0007]

[Chemical 2]

(Wherein R is a tetracarboxylic acid residue and R'is a diamine residue). A polyisoimide having a repeating unit is used. In the above general formula (I), R is a tetravalent organic residue which is a tetracarboxylic acid residue, and specifically,

[0009]

[Chemical 3]

Further, aromatic residues such as isomers and derivatives thereof, or the following general formula (II)

[0011]

[Chemical 4]

(Wherein Q is a single bond, -CO-, -S-,
-O -, - S-S - , - SO 2 -, - CH 2 -, - C
_{(CH 3) 2 -, -} C (CF 3) 2 -, - Si (C
_{H 3) 2 -, - O} (C 2 H 4 O) n - (n is an integer of 1 to 3), a. ) An aromatic residue represented by

[0013]

[Chemical 5]

A non-benzene-based aromatic compound residue having a heterocycle such as

[0015]

[Chemical 6]

Examples thereof include alicyclic organic residues and aliphatic organic residues. Generally, the introduction of the tetravalent organic group into the polyisoimide main chain skeleton is carried out by the reaction of the tetracarboxylic dianhydride and diamine. Specific examples of such tetracarboxylic dianhydride include pyromellitic dianhydride, 3,6-ditrifluoromethylpyromellitic dianhydride, and 1,4,5,8-naphthalenetetracarboxylic dianhydride. 2,3,6,7-naphthalenetetracarboxylic dianhydride, 3,4,3 ', 4'-biphenyltetracarboxylic dianhydride, 3,4,3', 4'-benzophenonetetracarboxylic dianhydride Anhydrous, 3,4,3 ',
4'-diphenylsulfone tetracarboxylic acid dianhydride,
3,4,3 ', 4'-diphenylhexafluoroisopropylidenetetracarboxylic dianhydride, 3,4,3',
4'-diphenylisopropylidenetetracarboxylic dianhydride, diphenyldimethylsilanetetracarboxylic dianhydride, pyrazinetetracarboxylic dianhydride, 3,4
9,10-perylenetetracarboxylic dianhydride, 1,
2,3,4-cyclopentanetetracarboxylic dianhydride, bicyclo [2,2,2] oct-7-ene-2,
3,5,6-tetracarboxylic dianhydride, 5- (2,5
-Dioxotetrahydrofuryl) -3-methyl-3-cyclohexene-1,2-dicarboxylic acid dianhydride, 1,
2,3,4-butanetetracarboxylic dianhydride and the like can be mentioned. These may be used alone or in combination of two or more.

R'in the general formula (I) of the present invention is a divalent organic residue which is a diamine residue, specifically, the following general formulas (III), (IV) and (V).

[0018]

[Chemical 7]

(R "in the general formulas (III) to (V) are respectively
The same or different, hydrogen atom,
Halogen atom such as elemental, chlorine and iodine, nitro group and carbon
The organic groups of 1 to 12 are shown, and as the organic group, methyl,
Tyl, propyl, butyl, i-propyl, i-butyl,
Alkyl groups such as t-butyl, allyl, vinyl, buteni
And alkenyl groups such as acetylene, 2-propynyl, etc.
Alkynyl group, cyclopropyl, cyclopentyl,
Cycloalkyl groups such as chlorhexyl, phenyl, naphthyl
Aryl group such as benzyl, aralkyl group such as benzyl, methoxy group
Alkoxy groups such as Si, ethoxy and propoxy, phenoxy
Aryloxy groups such as naphthoxy and carboxy, and carboxyl groups
And its metal salts, carbonyl groups such as acetyl, acetoxy
Ester-containing organic groups such as ci, carbomethyl, carboethyl, etc.
, N is an integer of 1 to 4, X is -CO-, -S-,-.
O-, -S-S-, -SO₂-, -CH₂-, -C (C
H₃)₂-, -C (CF₃)₂-, -Si (CH₃)₂
-Etc., Y and Z are single bonds, -CO-, -S-, -O.
-, -S-S-, -SO₂-, -CH₂-, -C (CH
₃) ₂-, -C (CF₃)₂-, -Si (CH₃)
₂-, Etc.) and aromatics of derivatives and isomers
Organic residues, and

[0020]

[Chemical 8]

A non-benzene-based aromatic compound residue having a heterocycle such as

[0022]

[Chemical 9]

Examples thereof include alicyclic organic residues and aliphatic organic residues. As a specific example of such a diamine, metaphenylenediamine, paraphenylenediamine, 4-chlorometaphenylenediamine, 4-fluorometaphenylenediamine, 4-nitrometaphenylenediamine, 2,4-diaminotoluene, 2,6-diaminotoluene, 4,5-diaminometaxylene, diaminomesitylene, 2,3,5,6-tetramethylparaphenylenediamine, 4-phenoxymetaphenylenediamine, 4-naphthoxymetaphenylenediamine, 3,5 −
Diaminobenzoic acid, 3,5-diaminobenzoic acid sodium salt, 3,5-diaminobenzoic acid methyl ester, 3,
5-Diaminobenzoic acid ethyl ester, 3,5-diaminobenzoic acid isopropyl ester, metaphenylenediamine-2-sulfonic acid, metaphenylenediamine-2-
Sulfonic acid sodium salt, 3,5-diaminodiphenylamine, 2,3,5-trimethylbenzidine, 3,
3 ', 5-trimethylbenzidine, 2,2', 6,6 '
-Tetramethylbenzidine, 3,3 ', 5,5'-tetramethylbenzidine, 2,2', 5,5'-tetramethylbenzidine, 2,2 ', 6,6'-tetraethylbenzidine, 3,3' , 5,5'-Tetraethylbenzidine, 5,5'-diethyl-3,3'-dimethylbenzidine, 3,3 ', 5,5'-tetra-n-propylbenzidine, 2,2'-di-i- Propyl-5,5'-dimethylbenzidine, 2,2'-ditrifluoromethylbenzidine, 3,3'-ditrifluoromethylbenzidine,
2,2 ', 6,6'-tetratrifluoromethylbenzidine, 3,3', 5,5'-tetratrifluoromethylbenzidine, 2,2'-dichlorobenzidine, 3,3 '
-Dichlorobenzidine, 3,3 ', 5,5'-tetrabromobenzidine, octafluorobenzidine, 4,4'
-Diamino-5,5'-dimethyl- [1,1'-biphenyl] -3,3'-dicarboxylic acid, 3,3'-diphenyl-5,5'-dimethylbenzidine, 3,3'-dimethoxybenzidine, 3,3'-diethoxybenzidine,
3,3'-diallyl-5,5'-dimethylbenzidine,
3,3'-diaminobenzophenone, 3,3'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfone, bis (3- (3-aminophenoxy) phenyl) sulfone, bis (4- (3-aminophenoxy) Phenyl) sulfone, 2,2-bis (4-aminophenyl) hexafluoropropane, 2,2-bis (3-amino-4,5-dimethylphenyl) hexafluoropropane, 2,2-bis (4- (4 -Aminophenoxy) phenyl) hexafluoropropane, 4,4'-diaminodiphenylmethane, 2,2-bis (4-aminophenyl)
Propane, 2,2-bis (4- (4-aminophenoxy) phenyl) propane, bis (4-amino-3-methylphenyl) methane, bis (4-amino-3-ethylphenyl) methane, bis (4- Amino-3,5-dimethylphenyl) methane, bis (4-amino-3,5-diethylphenyl) methane, bis (4-amino-3,5-di-)
i-propylphenyl) methane, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 1,4-bis (4-aminophenoxy) benzene, 1,4-bis (3-aminophenoxy) benzene,
4,4'-diaminodiphenyl thioether, 4,4 '
-Diaminodiphenylamine, 1,4-diaminoanthraquinone, 1,5-diaminoanthraquinone, 2,7-
Diaminofluorene, orthotolidine sulfone, 2,6
-Diaminopyridine, 2,4-diaminopyridine, 2,
6-diaminopyrazine, bis (p-aminophenoxy)
Aromatic diamines such as dimethylsilane, 1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, 2-methyl-
Aliphatic diamines such as 1,5-diaminopentane, 1,8-diaminooctane, 1,3-bis (3-aminopropyl) tetramethyldisiloxane and 1,3-bis (4-aminobutyl) tetramethyldisiloxane , 1,4-diaminocyclohexane, 1,3-diaminomethylcyclohexane, 1,4-diaminomethylcyclohexane, 4,
4'-diamino-3,3'-dimethyldicyclohexylmethane, 4,4'-diamino-3,3'-diethyldicyclohexylmethane, 4,4'-diamino-3,3'-
Examples thereof include alicyclic diamines such as dimethyldicyclohexane, 1,8-diamino-p-menthane and isophoronediamine. These diamines may be used alone or in combination of two or more.

The polyisoimide separation membrane of the present invention is generally represented by the general formula (VI) obtained by the reaction of the above-mentioned carboxylic acid dianhydride and diamine.

[0025]

[Chemical 10]

It can be obtained by subjecting the polyamic acid precursor of the repeating unit represented by to the presence of a suitable dehydrating agent and / or catalyst and a dehydration ring-closing reaction. Alternatively, it can also be obtained by directly polycondensing a carboxylic acid dianhydride and a diamine in the presence of a dehydrating agent and / or a catalyst.

Specific examples of such a dehydrating agent or catalyst include acetic anhydride, propionic anhydride, butyric anhydride, trifluoroacetic anhydride, chloroacetic anhydride, dichloroacetic anhydride, thionyl chloride, acetic chloride, N, N'-. Examples thereof include dehydrating agents such as dicyclohexylcarbodiimide, and catalysts such as triethylamine, dicyclohexylamine, pyridine, quinoline, isoquinoline, dimethylaminopyridine, piperazine, piperidine and phosphorus trichloride. These may be used alone or in combination of two or more. Among these, carbodiimide compounds such as trifluoroacetic anhydride, thionyl chloride, phosphorus trichloride and N, N-dicyclohexylcarbodiimide are particularly effective.

The polyisoimide separation membrane of the present invention preferably has at least 20 mol% of its precursor amic acid units.
As described above, more preferably 50 mol% or more, particularly preferably 70 mol% or more, dehydrated and ring-closed, and further 50 mol% or more, preferably 60 mol% or more, more preferably 70 mol% or more of the ring-closing portion is isoimidated. ing. The polyisoimide separation membrane of the present invention can be used as a homogeneous membrane or a porous membrane, and can also be used as an asymmetric membrane having a dense layer and a porous layer at the same time. Furthermore, a mixed film of an organic material or an inorganic material containing other polyisoimide,
It can also be used as a composite membrane with a porous base membrane.

The method for producing the polyisoimide separation membrane of the present invention is not particularly limited, and any known method can be used. Examples of the method include (1) a method of spreading the solution of the polyisoimide on the water surface, (2) a method of coating the polyisoimide solution on a support base film, and (3) a casting of the polyisoimide solution on a support base. And then peeling from the substrate after evaporating the solvent,
(4) A method in which the solution of the polyisoimide is cast on a support base or extruded from a hollow nozzle and then immersed in a coagulation bath to make it asymmetrical, and the like. The shape of the separation membrane is not particularly limited, and any shape such as a flat membrane shape, a hollow fiber shape, or a tube shape can be used. Further, it is possible not only to use it as the polyisoimide solution, but also to obtain a polyisoimide separation membrane by forming a film in a predetermined shape in the polyamic acid state of the precursor represented by the general formula (VI) and then isoimidizing it.

Next, an example of a suitable method for producing a homogeneous membrane and an asymmetric membrane in the polyisoimide separation membrane of the present invention will be described. The homogeneous film uses a solution of a polyisoimide having a structure represented by the general formula (I) in an organic polar solvent as a dope solution, and uses this as a glass plate having a smooth surface, a Teflon plate,
After casting on a metal plate or the like using a doctor blade or the like to form a thin film having a thickness of about 50 to 1000 μm, and then gradually evaporating the solvent under normal pressure or reduced pressure to make it self-supporting, Further, it can be produced by sufficiently drying. On the other hand, in order to obtain an asymmetric membrane, after casting the dope solution, only the surface is dried for a certain time, and then a solvent that is compatible with the solvent of the dope solution but is a poor solvent for polyisoimide is used. The method of immersing in a coagulation bath that has been used is used. The polymer concentration in the dope used in these cases varies depending on the molecular weight of the polyisoimide used, but is usually adjusted to 2 to 50% by weight.

As another manufacturing method, the general formula (VI) is used.
A solution of a polyamic acid precursor having a structure represented by an organic polar solvent is used as a dope solution, which is then formed into a homogeneous film and an asymmetric film in the same manner as in the above polyisoimide, and then a dehydrating agent such as trifluoroacetic anhydride. Alternatively, a dehydration ring closure reaction can be carried out by contacting with a catalyst to obtain a polyisoimide separation membrane.

The polyisoimide or polyamic acid precursor of the present invention used for the production of these separation membranes uses N-methylpyrrolidone as a solvent and has a polymer concentration of 0.5 g /
dl and logarithmic viscosity of 0.1d when measured at 30 ° C
Those of 1 / g or more, preferably 0.3 to 5 dl / g are suitably used. The logarithmic viscosity is calculated according to the formula defined below.

[0033]

## EQU1 ## Logarithmic viscosity = natural logarithm (viscosity of solution / viscosity of solvent) / polymer concentration in solution The polyisoimide separation membrane according to the present invention is used for gas separation membrane, reverse osmosis membrane, ultrafiltration membrane, microfiltration membrane, etc. It can also be used for separation of organic liquid mixture by pervaporation, dehydration of organic liquid, and the like. Among these, the gas separation performance or the selective permeability of the organic liquid mixture by the pervaporation method is particularly excellent.

As the gas separation, separation of hydrogen, helium, nitrogen, argon, carbon monoxide, carbon dioxide, methane, etc. is preferable, and particularly for separation of hydrogen / nitrogen, hydrogen / methane, carbon dioxide / methane, nitrogen / oxygen. It is preferably used.
In the organic solvent / water separation, lower alcohols such as ethanol and isopropanol, acetone, tetrahydrofuran, acetic acid, etc. are preferably used as the organic solvent.
For separation of organic solvent / organic solvent, benzene / cyclohexane or the like can be used.

[0035]

The present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. The gas permeation performance can be represented by the gas permeation coefficient P calculated by the following equation.

[0036]

[Equation 2] The unit of P is represented by cB (centimeter barrel) according to the following equation.

[0037]

[Equation 3]

The gas permeability was measured using a gas permeability measuring device. This is one in which a predetermined test gas is supplied at a constant pressure to one surface of a test membrane attached to the cell of the device, and the amount of gas pressure transmitted from the other surface of the membrane is analyzed by a pressure sensor or a gas chromatograph. Is. Further, the selective separation of gas was expressed by the ratio of the measured gas permeation coefficients.

Reference Example In a 1 liter four-necked flask equipped with a stirrer and a nitrogen inlet tube, under nitrogen atmosphere, at room temperature 3,3 ', 5,5'-
Tetramethylbenzidine 43.7 g (182 mmol)
And 170 ml of N-methyl-2-pyrrolidone (hereinafter abbreviated as NMP) were added and stirred to obtain a uniform solution.
Then, under stirring, 81.3 g (182 mmol) of 3,4,3 ', 4'-diphenylhexafluoroisopropylidenetetracarboxylic dianhydride was added to the diamine solution together with 200 ml of NMP. Stirring was continued at room temperature for 24 hours to obtain a viscous polyamic acid precursor acid solution having a polymer concentration of 25% by weight. Take a portion of this solution and
When it was diluted with MP to a concentration of 0.5 g / dl and the logarithmic viscosity was measured at 30 ° C., it was 1.72 dl / g.

Example The solution obtained in the reference example was stirred and N, N'-dicyclohexylcarbodiimide (hereinafter abbreviated as DCC).
150 g was added with 1.8 l NMP. After the addition of DCC, the solution thickened slightly before solids began to precipitate. 5
After continuing the stirring for a period of time, the reaction solution was filtered using a Teflon filter manufactured by Millipore Co. having a nominal pore diameter of 3 μm to separate solids. A large amount of isopropanol (IP
It was precipitated in A), pulverized, filtered and washed with IPA three times, and then dried at 40 ° C. under reduced pressure to obtain a polyisoimide powder. This powder is used in addition to amide solvents such as NMP and DMSO (dimethyl sulfoxide), as well as THF.
(Tetrahydrofuran), DOX (1,4-dioxane) and other ether solvents, MEK (methyl ethyl ketone), acetone and other ketone solvents, chloroform, DC
It was dissolved in a chlorine-based solvent such as M (methylene chloride).

Proton Nuclear Magnetic Resonance ( ¹ H
-NMR) spectrum analysis confirmed that the residual amide group was 7% or less and the ring closure rate was 93% or more.
In the infrared absorption (IR) spectrum analysis, 181
Absorption of 1,708 cm ^-1 isoimide groups, and 178
From a comparison of absorption of imide groups at 8,723 cm ⁻¹ , it was confirmed that 95% or more were isoimide groups and the rest were imide groups.

10 g of this polyisoimide powder was added to THF9.
0 g was added and dissolved to prepare a uniform solution having a polymer concentration of 10% by weight. This polyisoimide solution has a nominal pore size of 3
It filtered using the Teflon filter by the Millipore company of (micrometer). This filtrate was cast on a glass plate with a thickness of 20 mil using a doctor knife and dried in a nitrogen stream at 40 ° C for 3 hours to obtain a self-supporting film, which was then dried under reduced pressure at 40 ° C for 4 hours. To obtain a polyisoimide homogeneous film having a thickness of about 1 mil.

As a result of conducting a gas permeation test at 30 ° C. using this homogeneous membrane, the gas permeation coefficients of hydrogen, carbon dioxide and methane are 8560 cB (centimeter barrel), 7930 cB and 268 cB, respectively. Sex is hydrogen / methane = 32, carbon dioxide / methane = 30
It was found that this separation membrane has high separation performance.

Comparative Example To a polyamic acid precursor solution obtained in the same manner as in the Reference Example, 74 g of acetic anhydride and 1 liter of NMP were added and mixed uniformly, then 74 g of triethylamine was added together with 0.8 liter of NMP, and the mixture was stirred for 24 hours. The solution which started to become slightly cloudy was precipitated with a large amount of IPA, pulverized, and then filtered and washed three times to obtain a powder. This was dried under reduced pressure at 100 ° C. for 1 hour and then at 200 ° C. for 3 hours to obtain a polyimide powder. This powder was dissolved in NMP and methylene chloride,
DMSO, DM in which the polyisoimide of the Example was dissolved
It was insoluble in F, THF, DOX, acetone, MEK, chloroform and the like.

Next, 10 g of the obtained polyimide powder was added with N.
90 g of MP was added and dissolved to prepare a uniform solution having a polymer concentration of 10% by weight. This polyimide solution was filtered using a Teflon filter manufactured by Millipore with a nominal pore size of 3 μm. The filtrate was cast on a glass plate with a doctor knife at a thickness of 20 min and dried in a nitrogen stream at 70 ° C. for 3 hours to give a self-supporting film, which was then dried under reduced pressure at 120 ° C.
It was dried at ℃ for 4 hours to obtain a polyimide homogeneous film having a thickness of about 1 mil. As a result of conducting a gas permeation test at 30 ° C. of this homogeneous membrane, the gas permeation coefficients of hydrogen, carbon dioxide and methane were 7350 cB, 6820 cB and 262 c, respectively.
It was B and the selective separability of gas was hydrogen / methane = 28 and hydrogen dioxide / methane = 26.

[0046]

EFFECTS OF THE INVENTION The separation membrane of the present invention has thermal stability and high mechanical strength, is easy to mold due to the good solvent solubility of isoimide, and has a high permselective performance, which makes it a conventional separation membrane. It can be used more advantageously in comparison. For example, in addition to separation of carbon dioxide used for tertiary recovery of petroleum, separation of water vapor from natural gas, helium, and acidic gases such as carbon dioxide / hydrogen sulfide, further refinement of petroleum, hydrogen recovery process in an ammonia synthesis plant, synthesis Gas, separation of hydrogen and carbon monoxide from ironmaking gas, composition control, production of oxygen-enriched air for combustion and medical purposes, or separation of nitrogen or oxygen from air for production of nitrogen as an inert gas, etc. It can be used as a gas separation membrane. Further, since the polyisoimide separation membrane of the present invention is excellent in organic solvent resistance and water resistance, it is used for treating wastewater containing an organic solvent by using a reverse osmosis membrane, or an ultrafiltration membrane or a microfiltration membrane. You can also Further, it can be advantageously applied as a membrane used for separating an organic liquid mixture by pervaporation or dehydrating the organic liquid.

Claims (1)

[Claims] 1. The following general formula (I): (However, R is a tetracarboxylic acid residue and R'is a diamine residue.) A separation membrane characterized by using a polyisoimide having a repeating unit