JPH02222717A - Gas separating membrane and separation of gas - Google Patents

Abstract

PURPOSE:To obtain a gas separating membrane having high separating performance over a long period of time by using arom. polyimide consisting of a specified tetracarboxylic acid component and a specified diamine component in a certain ratio. CONSTITUTION:A gas separating membrane is made of arom. polyimide obtd. by copolymerizing repeating units (A) of a tetracarboxylic acid component based on biphenyltetracarboxylic acids represented by formula I with repeating units (B) of a diamine component based on 1,4-bis(4-aminophenoxy)benzenes and diaminodiphenyl ethers or 1,3-bis(aminophenoxy)benzenes represented by formula II or III. The molar ratio between the repeating units A:B is 30:70-90:10 and the arom. polyimide has >=0.5X10<-3>cm<3>/cm<2>.sec.cmHg velocity of permeation of steam. When the gas separating membrane is used, mixed vapor of water and org. matter is easily and efficiently separated over a long period of time and highly concd. vapor of the org. matter is produced.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention is directed to the use of a tetracarboxylic acid component mainly composed of biphenyltetracarboxylic acids and 1,4-bis(4-aminophenoxy)benzene (hereinafter referred to as TPEQ). abbreviated)
and diaminodiphenyl ether (hereinafter referred to as DA
Water vapor permeability made of aromatic polyimide obtained by copolymerizing with a diamine component whose main component is 1,3-bis(aminophenoxy)benzene (abbreviated as DE) or 1,3-bis(aminophenoxy)benzene (hereinafter abbreviated as TPER). , a gas separation membrane that has excellent hot water resistance, etc., and a mixed vapor mainly containing organic vapor and water vapor that is brought into contact with the gas separation membrane, and the water vapor selectively permeates through the gas separation membrane, and the mixed vapor is gas separated. The present invention relates to a method for producing high-concentration organic vapor.

[Description of prior art]

Recently, aromatic polyimide has been attracting attention as a material for separation membranes because it has better heat resistance and chemical resistance than polyamide membranes, cellulose membranes, cellulose acetate membranes, etc. Gas separation membranes are being proposed for water separation.

For example, as shown in Japanese Patent Application Laid-Open No. 63-247415, gas separation is performed to obtain a highly concentrated organic solvent by removing water (water vapor) from a mixed vapor of an organic solvent containing water vapor. Membrane dehydration processes (vapor permeation methods) are being proposed.

The gas separation membrane used in the vapor permeation method described above is approximately 70°
Gas separation occurs when it comes into contact with a water-containing mixed steam at a high temperature of C or higher, so depending on the material, the gas separation membrane may deteriorate due to hydrolysis, so a gas separation membrane made of a material with high resistance to hot water is required. It was said that

However, although gas separation membranes made of known aromatic polyimides have fairly high heat resistance and durability, when they come into contact with mixed steam containing water vapor at high temperatures and get wet, the separation membranes deteriorate due to hydrolysis, etc. Since the deterioration of the separation membrane begins and gradually progresses, there is a problem in the durability performance of the separation membrane in that the permeation performance and physical strength of the separation membrane decrease, and it has not always been completely satisfactory.

[Problems to be solved by the present invention]

This invention provides a method for selectively separating water vapor from a mixed vapor of organic substances containing water vapor by a vapor permeation method to obtain high-concentration organic vapor. Even if the surface gets wet, the gas separation performance and mechanical properties of the gas separation membrane do not substantially deteriorate over a long period of time, and the membrane maintains stable separation performance over a long period of time, so that it can be used for gas separation of mixed vapors. To provide a gas separation membrane made of aromatic polyimides that can perform the following steps, and to provide a gas separation method that can perform gas separation of a mixed vapor with good reproducibility over a long period of time using such a gas separation membrane. The purpose is to

[Means to solve the problem]

The first invention of this application mainly consists of a repeating unit A represented by the general formula I and a repeating unit B represented by the formula I, and the molar ratio (A:B) of the repeating units is 30; 10, and has a water vapor transmission rate of 0.
5 X 10-'cffl/aj-sec・cmHg
The second invention of this application relates to a gas separation membrane characterized by the above characteristics, and the second invention of this application is to mainly contain organic vapor and water vapor on one side of the aromatic polyimide gas separation membrane. The present invention relates to a gas separation method for a water vapor mixed gas, characterized in that the mixed vapor containing the mixed vapor is brought into contact at a temperature of 70'C or higher, and the water vapor is selectively permeated.

The aromatic polyimide used in the gas separation membrane of the present invention mainly consists of repeating units A consisting of the structural formula represented by the general formula (■) and repeating units B consisting of the structural formula represented by the general formula ■ or ■. (Preferably, the content of "the sum of repeating units A and B" with respect to all the repeating units j of the aromatic polyimide is 60 mol % or more, particularly preferably 80-1
00 mol%), and the repeating units A and B tend to have a no molar ratio (A:B) of 3o near 0 to 90
: 10, preferably 35:65 to 85:15.

The above-mentioned aromatic polyimide (a) contains biphenyltetracarboxylic acids as a main component (preferably 80 mol% or more, particularly preferably 90-
(c) "1,4-bis(4-aminophenoxy)benzene (1'PEQ) J" related to general formula I, and "diaminodiphenyl ether related to general formula H" (DADE)
or rl, 3-bis(aminophenoxy)benzene (TPER) ilJ according to the general formula (2) as the main component (preferably, "r of the above TPEQ, DADEs and TPERs relative to 1 of the total diamine component"). A soluble aromatic polyimide (copolymer) produced by polymerizing and imidizing a diamine component whose total content is 80 mol% or more, especially 90 to 100 mol%, in an organic solvent such as a phenolic compound. combination)
and the molar ratio of the repeating units A and B (
A:B) is an aromatic polyimide having a ratio of 30 to 90:10.

The above biphenyltetracarboxylic acids include 3.3
'', 4.4'-biphenyltetracarboxylic acid, its acid dianhydride, or its acid ester, or 2.
Examples include 3.3°, 4′-biphenyltetracarboxylic acid, its acid dianhydride, and its acid ester.

The tetracarboxylic acid component used in the production of the aromatic polyimide is particularly preferably the above-mentioned 3.3'', 4.4'-biphenyltetracarboxylic acids, and in addition to the above-mentioned biphenyltetracarboxylic acids, Mellitic acid, benzophenonetetracarboxylic acid, diphenylethertetracarboxylic acid, 2,2-bis[4-dicarboxyphenoxy)phenyl]propane, or their acid dianhydrides, acid esters, etc., in small proportions (
20 mol% or less, particularly 10 mol% or less).

In this invention, DADEll, which is one of the diamine components used in the production of aromatic polyimide, includes 4.
Examples include 4'-diaminodiphenyl ether, 3'-4'-diaminodiphenyl ether, and 3,3'-diaminodiphenyl ether.

In addition, as TPER, which is one of the diamine components,
1.3-bis(4-aminophenoxy)benzene, 1.
Examples include 3-bis(3-aminophenoxy)benzene.

In this invention, the diamine component used in the production of the aromatic polyimide is the TPEQ, D
In addition to ADEs and TPERs, e.g.
-diaminodiphenylmethane, 3.4''-diaminodiphenylmethane, 4.41-diaminodiphenylsulfone, 414''-diaminobenzophenone, 2,2-bis(
4-aminophenyl)propane, 2-(4-aminophenyl)-2-(3-aminophenyl)propane, 2.
2-(4-(4-aminophenoxy)phenyl)propane, 0-tolidine, olm- or p-phenylenediamine, 3,5-diaminobenzoic acid, 2゜6-diamitubiridine, 1,4-bis(4 -aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene,
Bis[4-(4-aminophenoxy)phenyl]sulfone and the like can be used in combination in a considerable proportion (20 mol% or less, particularly 10 mol% or less).

In the gas separation membrane of this invention, the water vapor permeation rate is 0.
．． 5 X 10-3cd/d・sec-cm)1
g or more, preferably 0.6X10-3 to 2.5X1
0-3al! /c/sec/c+aHg (and, for example, the ratio of the water vapor permeation rate to the methanol vapor permeation rate (P HzO/P EtOH,
Gas separation performance) is preferably 20 or more, particularly 45 or more.

In the gas separation membrane of the present invention, the aromatic polyimide gas separation membrane is composed of a repeating unit A having a structural formula represented by the general formula (1) and a repeating unit B1 having a structural formula represented by the general formula (2). The molar ratio of units A and B (
An aromatic polyimide in which the ratio A:B, It is suitable because it is particularly excellent in physical property retention performance (hot water resistance), and repeating unit A consisting of the structural formula represented by the general formula ■ and repeating unit Bz consisting of the structural formula represented by the general formula ■. In the gas separation membrane made of aromatic polyimide, the molar ratio (A:BZ) of the repeating units A and B2 is 50:50 to 90:10, particularly preferably 60:40 to 85:15. Aromatic polyimide improves water vapor permeability and retention of physical properties of separation membranes (
It is preferable because it has high hot water resistance) and particularly excellent basic physical properties of the separation membrane.

In the gas separation method of the present invention, the gas separation membrane made of the aromatic polyimide (for example, thickness: about 0.01 to 5 μm) is used.
(flat membrane, hollow fiber membrane, etc. of an asymmetric separation membrane having a continuous homogeneous layer of m and a porous layer of thickness: about 10 to 200 μm)
A mixed vapor mainly containing organic vapor and water vapor is placed on one side of the
More preferably, the water vapor is brought into contact at a temperature of 100 to 160°C, and the water vapor is selectively permeated to obtain "vapor rich in water vapor" from the permeate side of the gas separation membrane, while the non-permeate side of the gas separation membrane "Organic vapor from which water vapor has been substantially removed" is obtained from the raw material gas supply side, and the mixed vapor is subjected to gas separation.

In the gas separation method of the present invention, the pressure of the mixed vapor supplied to the gas separation membrane is normal pressure or pressurized, particularly preferably 1 to 20 kg/aflG, more preferably 1 to 10 kg/aflG.
It is preferable to carry out the reaction under an increased pressure of kg/cfflG, and the pressure on the permeate side of the gas separation membrane is increased, normal pressure or reduced pressure, particularly preferably 1 to 500 mmHg.

In carrying out the gas separation method of this invention, the permeate side of the gas separation membrane is maintained at reduced pressure to ensure a water vapor partial pressure difference between the supply side and the permeate side of the gas separation membrane, thereby selectively removing water vapor as quickly as possible. This selectively removes water vapor from the mixed vapor of the raw materials fed to the feed side of the gas separation membrane. In that case, the higher the degree of pressure reduction, the higher the vapor transmission rate.

Furthermore, in the gas separation method of the present invention, by performing gas separation while circulating dry gas as a carrier gas on the permeation side of the gas separation membrane, it becomes easy to selectively permeate and remove water vapor. Therefore, it is suitable.

The above-mentioned mixed vapor may be produced by any method, but in terms of -m, an aqueous solution of an organic substance is heated to a temperature higher than the boiling point or azeotropic temperature of the organic substance to evaporate it. This can be obtained by

Although the concentration of organic matter in the mixed vapor is not particularly limited, in the present invention, it is preferable that the concentration of organic matter is 50% by weight or more, particularly about 70 to 99.8% by weight.

The above-mentioned organic substance may have a boiling point of 200°C or lower, preferably 150°C or lower, and particularly preferably an organic substance that is liquid at room temperature (25°C). Examples of such organic substances include methanol, ethanol, n
-propanol, isopropanol, n-butanol,
Aliphatic alcohols such as 5ec-butanol, Ler t-butanol, and ethylene glycol, alicyclic alcohols such as cyclohexanol, aromatic alcohols such as benzyl alcohol, and organic carboxylic acids such as formic acid, acetic acid, propionic acid, and butyric acid. , esters such as ethyl acetate and butyl acetate, ketones such as acetone and methyl ethyl ketone, cyclic ethers such as tetrahydrofuran and dioxane, and organic amines such as dibutylamine and aniline.

The gas separation method of the present invention is particularly suitable for dehydrating "mixed vapor consisting of water vapor and alcohol vapor" obtained by evaporating an aqueous alcohol solution such as methanol, ethanol, or isopropanol. Can be adopted.

〔Example〕

Example 1 [Preparation of aromatic polyimide solution] A tetracarboxylic acid component consisting of 100 mol% of 3.3',4.4'-biphenyltetracarboxylic dianhydride;
1.4-bis(4-aminophenoxy)benzene (TP
EQ) and a diamine component consisting of 85 mol% and 15 mol% of 4.4''-diaminodiphenyl ether in parachlorophenol (hereinafter abbreviated as PCP) at 180%
A PCP solution (concentration = 17% by weight) of an aromatic polyimide obtained by polymerization at a temperature of 20°C for 20 hours was prepared.

[Spinning of hollow membrane made of aromatic polyimide] The above aromatic polyimide solution was supplied to a spinning device equipped with a hollow fiber spinning nozzle, and a coagulating solution (temperature: 5°C or less, ethanol-
A hollow fiber membrane consisting of an asymmetric separation membrane made of aromatic polyimide was manufactured by a wet membrane forming method using water).

The hollow fiber membrane has an outer diameter of 431 μm and an inner diameter of 2
It is a continuous long hollow fiber with a diameter of 66 μm.

[Manufacture of separation membrane module] The 10 hollow fiber membranes produced as described above were bundled and cut to form a fiber bundle of hollow fiber membranes, and one end of the fiber bundle was sealed with a curable resin. The yarn bundle element is manufactured, and then r
The fiber bundle element is installed in a gas separation container having a mixed vapor supply port, a permeated gas outlet, and an unpermeated gas outlet, and the effective length of the hollow fiber membrane is 8.6.
A gas separation membrane module incorporating a yarn bundle element 1 having an effective area of 11.6 CTA was manufactured.

[Gas separation of mixed steam]

A 60% by weight aqueous ethanol solution was vaporized in an evaporator under atmospheric pressure to produce a mixed vapor 1 containing ethanol vapor and water vapor, and the mixed vapor was heated to 100° C. by heating with a heater. supplied to the gas separation membrane module and brought into contact with the supply side (outside of the hollow fiber membrane) surface of the hollow fiber membrane constituting the fiber bundle element,
The mixed vapor was gas-separated by maintaining the permeation side of the hollow fiber membrane (inside the hollow fiber membrane) at a reduced pressure of dma+Hg.

In gas separation as described above, the permeate gas 1 with a high concentration of water vapor obtained from the permeate gas outlet of the gas separation container is condensed in a dry ice-ethanol trap to collect the condensate, - On the other hand, the unpermeated gas (dry gas from which water vapor has been removed) obtained from the unpermeated side (supply side) of the hollow fiber membrane is returned to the evaporator, and while being circulated and used, gas separation of mixed vapor is performed. I did it.

Among the components of the condensate collected in the trap, the ethanol concentration was analyzed by gas chromatography analysis,
The water content was determined by subtracting the ethanol content from the total amount.

From the concentrations of each component obtained as described above, the water vapor permeation rate and the selective permeability of water vapor to ethanol (gas separation performance) were calculated, and the gas separation performance was evaluated.

In addition, unused hollow fiber membranes were immersed in a 60% ethanol aqueous solution at 150°C for 20 hours, and changes in the elongation and breaking strength of the hollow fiber membranes before and after the treatment were investigated. Aqueous properties were evaluated.

Table 1 shows the test results of the above-mentioned permeation performance (water vapor permeation rate, water-ethanol permselectivity), hot water resistance test, etc.

Examples 2 to 6 PCP solutions of aromatic polyimides were prepared in the same manner as in Example 1, except that diamine components having the types and compositions shown in Table 1 were used.

Then, in the same manner as in Example 1, fiber bundle elements of hollow fiber membranes were formed from each aromatic polyimide solution, and gas separation membrane modules were then formed from the fiber bundle elements of each hollow fiber membrane.

Furthermore, gas separation of mixed vapor was performed in the same manner as in Example 1 except that each gas separation membrane module was used.

In addition, a hot water resistance test was conducted for each hollow fiber membrane.

The results are shown in Table 1.

In Table 1, each abbreviation has the following meaning.

TPEQ: 1.4-bis(4-aminophenoxy)benzene 4.4°-DADE: 4.4'-diaminodiphenyl ether 3.4'-DADE: 3.4'-diaminodiphenyl ether TPER: 1,3 -Bis(4-aminophenoxy)benzene DM 74.4''-diaminodiphenylmethane [Effects of the present invention] The gas separation membrane of the present invention brings into contact a mixed vapor mainly containing an organic substance vapor and water vapor to remove the water vapor. It is a gas separation membrane made of aromatic polyimide that can selectively permeate and perform gas separation of mixed vapors, and has excellent heat resistance, water resistance, and gas separation performance (water vapor permeability, water-organic matter selective permeability). This gas separation membrane has a high level of properties such as:

The gas separation method of the present invention uses the above-mentioned excellent gas separation membrane made of aromatic polyimide, so that mixed vapor of water and organic matter can be easily and efficiently separated into gases for a long period of time.
This is a gas separation method that can produce highly concentrated organic vapors.

Patent applicant: Ube Industries Co., Ltd.

Claims (2)

[Claims] (1) General formula I ▲There are mathematical formulas, chemical formulas, tables, etc.▼Repeating unit A shown by (I) General formula II ▲There are mathematical formulas, chemical formulas, tables, etc.▼(II) Or, general formula III ▲Mathematical formula , chemical formulas, tables, etc. ▼ (III) Consisting mainly of repeating unit B shown in The water vapor transmission rate is 0.
5×10^-^3cm^3/cm^2・sec・cmH
1. A gas separation membrane characterized in that it has a molecular weight of at least 100 g. (2) Bringing a mixed vapor mainly containing organic vapor and water vapor into contact with one side of the gas separation membrane according to claim 1 at a temperature of 70°C or higher to selectively permeate the water vapor. Characteristic gas separation method for water vapor mixture.