JPH0693987B2 - Gas separation membrane and gas separation method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a tetracarbonic acid component containing biphenyltetracarboxylic acids as a main component and 1,4-bis (4-aminophenoxy) benzene (hereinafter abbreviated as TPEQ). And a diamine component containing diaminodiphenyl ether (hereinafter abbreviated as DATE) or 1,3-bis (aminophenoxy) benzene (hereinafter abbreviated as TRER) as a main component. Water vapor permeability comprising the obtained aromatic polyimide, a gas separation membrane having excellent hot water resistance, and the like, and the gas separation membrane is brought into contact with a mixed vapor mainly containing an organic vapor and water vapor to select the water vapor. Permeation of the mixed vapor to separate the vapor, and to produce a high-concentration organic vapor.

[Description of Prior Art]

Aromatic polyimides have recently been attracting attention as a material for separation membranes because they are superior in heat resistance and chemical resistance to polyamide membranes, cellulose membranes, and cellulose acetate membranes. Gas separation membranes are being proposed for water separation.

For example, as disclosed in JP-A-63-247415, gas separation for obtaining a high-concentration organic solvent by removing water (water vapor) from a mixed vapor of an organic solvent containing water vapor. Membrane dehydration process (vapor permeation method)
Is being proposed.

The gas separation membrane used in the vapor permeation method described above is contacted with a water-containing mixed vapor at a high temperature of about 70 ° C or higher for gas separation, and therefore, depending on the material, the gas separation membrane deteriorates due to hydrolysis. Therefore, a gas separation membrane made of a material having high hot water resistance has been required.

However, the known aromatic polyimide gas separation membrane has considerably high heat resistance and durability, but when it comes into contact with the steam-containing mixed vapor at high temperature and gets wet, the separation membrane due to hydrolysis or the like. Since the deterioration of No. 1 started and the deterioration gradually progressed, there was a problem in the durability performance that the permeation performance of the separation membrane and the separation strength were deteriorated, and it was not always satisfactory.

[Problems to be Solved by the Present Invention]

The present invention selectively separates a mixed vapor of an organic vapor containing steam by vapor permeability to obtain a high-concentration organic vapor, and when a high-concentration organic vapor is obtained, the mixed vapor supplied to the gas separation membrane forms a gas separation membrane. Even if the surface gets wet, the gas separation membrane does not deteriorate in gas separation performance and mechanical properties for a long period of time, and it maintains stable separation performance for a long period of time, and is used for gas separation of mixed vapors. To provide a gas separation membrane made of aromatic polyimide capable of achieving the above, and to provide a gas separation method capable of reproducibly performing gas separation of a mixed vapor using such a gas separation membrane for a long period of time. The purpose is.

[Means for solving problems]

The first invention of this application is the general formula I A repeating unit A represented by the general formula II Or the general formula III And an aromatic polyimide having a molar ratio (A: B) of the repeating units of 30:70 to 90:10, and a water vapor transmission rate of 0.5 × 10 ⁻³ cm 2. ³ / cm ² · sec · cmHg or more, the present invention relates to a gas separation membrane, and the second invention of this application is one side of the gas separation membrane made of the aromatic polyimide. The present invention relates to a gas separation method for a steam-mixed gas, wherein a mixed steam mainly containing an organic vapor and steam is contacted at a temperature of 70 ° C. or higher to selectively permeate the steam.

The aromatic polyimide used in the gas separation membrane of the present invention comprises a repeating unit A having a structural formula represented by the general formula I:
Mainly composed of a repeating unit B having a structural formula represented by the general formula II or III (preferably, the content of "the total of repeating units A and B" to "all the repeating units of the aromatic polyimide" is 60 mol). % Or more, particularly preferably 80 to 10
Aroma in which the molar ratio (A: B) of the repeating units A and B is 30:70 to 90:10, preferably 35:65 to 85:15. Group polyimide.

The aromatic polyimide is (a) a tetracarboxylic acid component containing biphenyltetracarboxylic acids as a main component (preferably 80 mol% or more, particularly preferably 90 to 100 mol%), and (b) the general formula I "1,4-bis (4-aminophenoxy) benzene (TPEQ)" relating to the above, and "diaminodiphenyl ether (DAD
E) ”or“ 1,3-bis (aminophenoxy) benzene (TPER) related to the general formula III ”as a main component (preferably,“ all of the diamine components ”above“
The total content of TPEQ, DADEs and TPERs ”is 80 mol%
Soluble aromatic polyimide (copolymer) produced by polymerizing and imidizing a diamine component (above 90% to 100% by mole) with an organic solvent such as a phenolic compound.
The aromatic polyimide has a molar ratio (A: B) of the repeating units A and B of 30:70 to 90:10.

The above-mentioned biphenyltetracarboxylic acids include 3,3 ′,
4,4'-biphenyltetracarboxylic acid, its acid dianhydride, or its acid esterified product, or 2,3,3 ',
4'-biphenyltetracarboxylic acid, its acid dianhydride,
Alternatively, its acid esterified product can be used.

The tetracarboxylic acid component used in the production of the aromatic polyimide is particularly preferably the above 3,3 ′, 4,4′-biphenyltetracarboxylic acid, and in addition to the above biphenyltetracarboxylic acid, a Meritic acid,
Benzophenone tetracarboxylic acid, diphenyl ether tetracarboxylic acid, 2,2-bis [4-dicarboxyphenoxy) phenyl] propane, or their dianhydrides, acid esterified products, etc. in a small proportion (20 mol% or less, especially It can be used at a ratio of 10 mol% or less).

In the present invention, DADEs, which is one of the diamine components used in the production of aromatic polyimide, include 4,4′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, and 3,3′-diaminodiphenyl ether. You can

Also, as TPERs, which is one of the diamine components, 1,3-
Examples thereof include bis (4-aminophenoxy) benzene and 1,3-bis (3-aminophenoxy) benzene.

In the present invention, the diamine component used in the production of the aromatic polyimide is, for example, 4,4′-diaminodiphenylmethane or 3,4′-diaminodiphenylmethane in addition to the TPEQ, DADEs and TPERs. ,Four,
4'-diaminodiphenyl sulfone, 4,4'-diaminobenzophenone, 2,2-bis (4-aminophenyl) propane, 2- (4-aminophenyl) -2- (3-aminophenyl)
Propane, 2,2- [4- (4-aminophenoxy) phenyl]
Propane, o-tolidine, o-, m- or p-phenylenediamine, 3,5-diaminobenzoic acid, 2,6-diaminopyridine, 1,
4-bis (4-aminophenoxy) benzene, 1,3-bis (4-
Aminophenoxy) benzene, bis [4- (4-aminophenoxy) phenyl] sulfone, etc., in a small proportion (20
It can be used in combination at a ratio of not more than mol%, particularly not more than 10 mol%.

In the gas separation membrane of the present invention, the water vapor transmission rate is 0.
5 × 10 ^-3 cm ³ / cm ²・ sec ・ cmHg or more, preferably 0.6 × 10 ^-3
It may be about 2.5 × 10 ⁻³ cm ³ / cm ² · sec · cmHg, and, for example, the ratio of water vapor permeation rate to methanol vapor permeation rate (PH ₂ O / PEtoH, gas separation performance) , 20 or more, particularly 45 or more.

In the gas separation membrane of the present invention, in the aromatic polyimide gas separation membrane composed of the repeating unit A having the structural formula of the general formula I and the repeating unit B ₁ having the structural formula of the general formula II, The molar ratio of repeating units A and B ₁ (A:
B ₁ ) consisting of an aromatic polyimide having a ratio of 30:70 to 70:40, particularly preferably 35:65 to 65:35, has a high water vapor permeability, and further, the physical properties of the separation membrane and the retention of the physical properties thereof. It is preferable because it is particularly excellent in performance (hot water resistance), and the repeating unit A having the structural formula represented by the general formula I and the general formula
In a gas separation membrane made of an aromatic polyimide comprising a repeating unit B ₂ having a structural formula represented by III, the molar ratio (A: B ₂ ) between the repeating units A and B ₂ is 50:50 to 90. Aromatic polyimide with a viscosity ratio of 10, especially 60:40 to 85:15 has high water vapor permeability and high performance of retaining the physical properties of the separation membrane (hot water resistance), and is particularly superior in the basic physical properties of the separation membrane. Therefore, it is preferable.

In the gas separation method of the present invention, the above-mentioned aromatic polyimide gas separation membrane (for example, a uniform layer having a thickness of about 0.01 to 5 μm and a porous layer having a thickness of about 10 to 200 μm are continuously provided). On one side of the asymmetric separation membrane (flat membrane, hollow fiber membrane, etc.), a mixed vapor mainly containing an organic vapor and steam is 70 ° C. or higher, preferably 80 to 200 ° C., more preferably 100 to 160 ° C. By contacting at temperature, the water vapor is selectively permeated to obtain "vapor rich in water vapor" from the permeate side of the gas separation membrane, while "non-permeate side of the gas separation membrane (source gas supply side)" The organic substance vapor from which the water vapor is substantially removed is obtained, and the mixed vapor is separated into gases.

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 under pressure, particularly preferably 1 to 20 kg / cm ² G, more preferably 1 to 10 kg / cm ² G. It is preferable to carry out under reduced pressure, and the pressure on the permeate side of the gas separation membrane is under increased pressure, normal pressure or reduced pressure, particularly preferably under reduced pressure of 1 to 500 mmHg.

In carrying out the gas separation method of the present invention, by keeping the permeate side of the gas separation membrane at a reduced pressure to ensure a water vapor partial pressure difference between the supply side and the permeate side of the gas separation membrane, the water vapor is selectively and as fast as possible. The water vapor is permeated, whereby the water vapor is selectively removed from the mixed vapor of the raw materials supplied to the supply side of the gas separation membrane. In that case, the higher the degree of pressure reduction, the higher the vapor permeation rate.

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

The mixed vapor may be produced by any method, but generally, 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 be evaporated. Can be obtained by

The concentration of the organic substance in the mixed vapor is not particularly limited, but in the present invention, the concentration of the organic substance is preferably 50% by weight or more, and more preferably about 70 to 99.8% by weight.

The organic substance has a boiling point of 200 ° C. or lower, preferably a boiling point of 150 ° C. or lower, and particularly preferably at room temperature (25
Any organic substance that is liquid at (° C) may be used. Examples of such organic substances include methanol, ethanol, n-propanol, isopropanol, n-butanol, sec-butanol, tert-butanol, aliphatic alcohols such as ethylene glycol, alicyclic alcohols such as cyclohexanol, and benzyl alcohol. Aromatic alcohols such as, 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 dibutylamine , Organic amines such as aniline.

The gas separation method of the present invention is suitably used as a mixed vapor, particularly when dehydrating a "mixed vapor composed of water vapor and alcohol vapor" obtained by evaporating an aqueous alcohol solution such as methanol, ethanol, and isopropanol. be able to.

〔Example〕

Example 1 [Preparation of Aromatic Polyimide Solution] 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride 100
Tetracarboxylic acid component consisting of mol% and 1,4-bis (4-
Aminophenoxy) benzene (TPEQ) 85 mol% and 4,
A PCP solution of an aromatic polyimide obtained by polymerizing a diamine component consisting of 15 mol% of 4'-diaminodiphenyl ether in parachlorophenol (hereinafter abbreviated as PCP) at a temperature of 180 ° C for 20 hours (concentration: 17% by weight) was prepared.

[Spinning of hollow fiber membrane made of aromatic polyimide]

The aromatic polyimide solution is supplied to a spinning device equipped with a hollow fiber spinning nozzle, and the aromatic polyimide asymmetry is produced by a wet film-forming method using a coagulating liquid (temperature: 5 ° C or lower, ethanol-water). A hollow fiber membrane composed of a separation membrane was manufactured.

The hollow fiber membrane has an outer diameter of 431 μm and an inner diameter of 266 μm.
m is a continuous long hollow fiber.

[Manufacture of separation membrane module]

Ten hollow fiber membranes produced as described above are bundled and cut to form a yarn bundle of hollow fiber membranes, and one end of the yarn bundle is sealed with a curable resin to produce a yarn bundle element, Next, the yarn bundle element is internally provided in a "gas separation container having a raw material mixed vapor supply port, a permeated gas extraction port, and a non-permeated gas extraction port", and an "effective length of hollow fiber membrane: 8.6 cm." , And an effective area of 11.6 cm ² of yarn bundle element ”was built in.

[Gas separation of mixed steam]

A 60% by weight aqueous ethanol solution is vaporized under atmospheric pressure by an evaporator to produce a "mixed vapor containing ethanol vapor and water vapor", and then heated by a heater.
The mixed vapor at 100 ° C. is supplied to the gas separation membrane module, and is brought into contact with the surface of the hollow fiber membrane constituting the fiber bundle element on the supply side (outside of the hollow fiber membrane) to form a hollow fiber membrane. The permeate side (the inside of the hollow fiber side) was maintained at a reduced pressure of 4 mmHg to separate the mixed vapor into gas.

In the gas separation as described above, the "permeate gas having a high concentration of water vapor" obtained from the permeate gas outlet of the gas separation container is condensed with a dry ice-ethanol trap to collect the condensate, On the other hand, the non-permeable gas (dry gas from which steam has been removed) obtained from the non-permeate side (supply side) of the hollow fiber membrane is returned to the evaporator and circulated for use while performing gas separation of mixed vapor. went.

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

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

Further, unused hollow fiber membranes were immersed in a 60% by weight ethanol aqueous solution at 150 ° C. for 20 hours, and the changes in elongation and breaking strength of the hollow fiber membranes before and after the treatment were examined, and the hot water resistance of the hollow fiber membranes was examined. Was evaluated.

Table 1 shows test results such as the above-mentioned permeation performance (water vapor permeation rate, water-ethanol selective permeation rate) and hot water resistance test.

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

Then, in the same manner as in Example 1, hollow fiber membrane yarn bundle elements were formed from the respective aromatic polyimide solutions, and then gas separation membrane modules were formed from the respective hollow fiber membrane yarn bundle elements.

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

A hot water resistance test was conducted on 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: 4,4'-diaminodiphenylmethane [Advantageous Effects of the Present Invention] The gas separation membrane of the present invention can bring mixed vapor mainly containing organic vapor and steam into contact with the vapor to selectively permeate the vapor to perform gas separation of the mixed vapor. It is a gas separation membrane made of aromatic polyimide and has a high level of heat resistance, water resistance, gas separation performance (water vapor permeability, selective permeability of water-organic substances), etc., and especially, a mixed liquid of water and organic substances. It is a gas separation membrane having excellent high temperature durability against.

Since the gas separation method of the present invention uses the above-mentioned excellent aromatic polyimide gas separation membrane, a mixed vapor of water and an organic substance is easily and efficiently gas separated for a long period of time.
It is a gas separation method that can produce a high concentration of organic vapor.

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Claims (2)

[Claims] 1. A general formula I A repeating unit A represented by the general formula II Or the general formula III And an aromatic polyimide having a molar ratio (A: B) of the repeating units of 30:70 to 90:10, and a water vapor transmission rate of 0.5 × 10 ⁻³ cm 2. A gas separation membrane characterized by being ³ / cm ² · sec · cmHg or more. 2. The method according to claim 1 and one side of the gas separation membrane,
A mixed vapor containing mainly organic vapor and water vapor at 70 ° C
A method for gas separation of a steam-mixed gas, which comprises bringing the steam into contact with each other at the above temperature to selectively permeate the steam.