JPS6391122A - Separation of steam - Google Patents

Abstract

PURPOSE:To favorably separate steam from gas by using a membrane of an unsymmetrical structure having specified aromatic copolyimide and/or specified aromatic copolyamidimide as a main constitutional material. CONSTITUTION:A membrane of an unsymmetrical structure having aromatic copolyimide obtained by allowing 3,4,3',4'-benzophenone-tetracarboxylic acid dianhydride to react with the mixture of tolylene diisocyanate and methylenebisphenyl isocyanate and/or aromatic copolyamidimide obtained by allowing 4,4'-methylenebisphenyl isocyanate to react with the mixture of trimellitic acid anhydride and isophthalic acid as a main constitutional material is used. On other words, the membrane of the unsymmetrical structure having copolyimide shown in a formula I and/or copolyamidimide shown in formulas II, III as the main constitutional structure is used. This method is widely expected in applications in industrial fields such as removal of steam incorporated in associated gas of petroleum.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention comprises 3. Aromatic copolyimide and/or 4', 4'' obtained by reacting ≠, 3', ≠'-benzophenone tetracarboxylic dianhydride with a mixture of tolylene diisocyanate and methylene bisphenyl isocyanate.
- Separation of water vapor by separating water vapor from gas using a membrane with an asymmetric structure mainly composed of an aromatic copolyamideimide obtained by reacting methylene pisphenyl isocyanate with a mixture of trimellitic anhydride and isophthalic acid. It is about the method.

[Conventional technology and its problems]

Separation of water vapor from gas is important in connection with, for example, humidification of air and dehumidification of natural gas, and methods such as adsorption, cooling, and wet absorption are widely used.

However, these methods require complicated equipment systems, occupy a large area, and consume even more energy in the case of cooling methods, so none of these methods can be said to be advantageous.

[Means for solving problems]

In view of the above circumstances, the inventors of the present invention have conducted intensive studies and have found that 3. μ, J',! Aromatic copolyimide obtained by reacting '-benzophenone tetracarboxylic dianhydride with a mixture of tolylene diisocyanate and methylene bisphenyl isocyanate and/or φ, 44'
- Advantageous separation of water vapor from gases by using an asymmetrically structured membrane whose main constituent is an aromatic copolyamideimide obtained by reacting methylene bisphenyl isocyanate with a mixture of trimellitic anhydride and isophthalic acid. We discovered what we could do and arrived at the present invention.

In other words, the gist of the present invention is a copolyimide having a structure represented by repeating units of general formula (I), wherein 10 to 30 moles of the above repeating units have R +CH2-Q.
- represents 2θ to riθ of the above repeating unit.
A copolyimide which is molti and/or has a structure in which 9θ to 70 molti of the repeating unit is represented by formula (II), and 10 to 3 of the repeating unit is
A method for separating water vapor is characterized in that water vapor is separated from a gas by using a membrane with an asymmetric structure mainly composed of copolyamideimide having a structure represented by formula (III).

The present invention will be explained in detail below.

The aromatic copolyimide used in the present invention is a copolyimide characterized by the presence of a repeating unit of general formula (1),
Here, in the above repeating unit /Q~30molti, R is +OH
It represents t<Σ, and the above repeating unit glue O
~70 molti is R.

For example, copolyimides with USP 3,7tM, 1As
3.3', II, ≠ mebenzophenone tetracarboxylic dianhydride in an appropriate molar ratio (7) 4'+4''-methylene bisphenyl isocyanate (''+≠) as described in No. I-diphenylmethane diisocyanate) and tolylene diisocyanate (,2,4 monoisomer,
2. ≦-isomer, or a mixture thereof) in the presence of a polar solvent.

Further, the aromatic copolyamideimide used in the present invention has a structure in which 70 to 90 moles of repeating units are represented by the formula (n), and 30 to 1 mole of repeating units
0 molti is a copolyamideimide having a structure represented by formula (III).

This copolyamideimide is described in U.S. Patent No. 3.922. Go9
It is easily manufactured by the method taught in No. 7. Such copolyamideimides can be prepared using the procedures described in the above-mentioned patents from about 20 molar to about θ molar to about 30 molar to about 1 molar.
It can be easily obtained from the reaction of a mixture of trimellitic anhydride and isophthalic acid in a 0 molar ratio and approximately equal amounts of ≠,≠'-methylene bisphenyl isocyanate in a /θθ molar ratio.

The polymerization of copolyimides or copolyamideimides and the solvents used to dissolve them are polar organic solvents such as dimethylformamide, dimethylacetamide,
Examples include N-methylpyrrolidone, dimethylsulfoxide, dimethylsulfone, hexamethylphosphoramide, tetramethylurea, and pyridine, but there are no particular limitations. Moreover, these may be used in combination. For the copolyimide in the present invention, preferably dimethylformamide and N-methylpyrrolidone are used, more preferably dimethylformamide.

For the copolyamideimide, preferably dimethylformamide, dimethylacetamide, N-methylpyrrolidone is used, more preferably dimethylformamide is used.

Preferably, the amount of polar organic solvent used in the above polymerization is at least sufficient to initially dissolve all reactants. The amount of solvent used is adjusted depending on the desired viscosity of the copolyimide or copolyamideimide, and the weight percentage of the copolyimide or copolyamideimide is not very important, but it is usually about 5% by weight to about 3% by weight.
Up to 5% by weight is preferred.

The logarithmic viscosity (ηinh) of the copolyimide or copolyamide-imide used in the present invention is θ, /dl/l or more, preferably 0.3 to 100% (measured at 30°C in O1S% in N-methylpyrrolidone) selected from the range.

The above-mentioned membrane with an asymmetric structure using copolyimide and/or copolyamide-imide is a membrane that has a non-uniform structure in the cross-sectional direction of the membrane, for example, a dense and thin skin layer on the surface, and a thin skin layer below it. Examples include those in which a porous sponge layer is present, and these are integrally formed of the same material. The sponge layer may have finger-like pores formed therein.

In a membrane with such an asymmetric structure, the part having the separation function is the skin layer part. The porous layer does not have a separation function, but supports the skin layer, which is flimsy and has insufficient mechanical strength. In a so-called homogeneous membrane that does not have an asymmetric structure, defects such as pinholes are more likely to occur as the membrane becomes thinner, so it is difficult to form a membrane with a practical level of permeation rate, and it cannot be said to be advantageous.

Various membrane shapes can be adopted, such as sheet, spiral, tubular, and hollow fiber shapes.Hollow fiber membranes can increase the effective membrane area per unit volume, and the outer peripheral side of the hollow fiber In the case of pressurizing from the inside, there are advantages such as high mechanical strength against high pressure despite the small thickness of the tube wall.

Methods for producing such a diaphragm include a method of casting a dope solution of the above-mentioned copolyimide and/or copolyamide-imide and a polar organic solvent as its polymerization solvent onto a flat plate such as a glass plate, and a roll method. This can be carried out by a known method such as a coating method, a spin-coding method, or a method of forming a hollow fiber, which is usually employed to increase the surface area.

Further, it is also possible to further provide a support for the MK by casting on a suitable porous (including porous hollow fiber) backing material. The porous support may be any inert porous material that does not block the passage of permeate gas through the membrane and is susceptible to attack by the membrane material, solvent, and coagulation liquid.

Typical examples of this type of support are metal mesh,
Porous ceramics, sintered glass, porous glass, sintered metals, paper, porous non-dissolving plastics, etc. are preferably used, and examples include nonwoven fabrics such as rayon, asbestos, porous polyimide, etc. These materials do not participate in the separation and merely act as a support. It is preferable that the thickness of the thin film of the dope liquid be below the normal/pharyngeal thickness.

Once a thin film is formed, it is immediately immersed in a coagulation solution.
In this case, 1.2 seconds after forming the thin film or after forming the thin film.
0 to /jθ℃, preferably ≠θ to 7.2θ℃ in the atmosphere for 2 to 300 seconds, preferably /θ to / for 0 seconds, more preferably 20 to 7.20 seconds to remove the A portion of the solvent may be removed by evaporation before solidification. Alternatively, hot air may be blown within the above range. Thereby, the thickness of the surface dense layer in the structure of the asymmetric membrane can be changed, and the separation performance of the resulting membrane can be easily controlled.

The coagulating liquid can be appropriately selected from those having good compatibility with the dope liquid and having low solubility with the copolyimide or copolyamide-imide (poor solvent). For example, water, lower alcohols such as gropanol, ketones such as acetone, ethers such as ethylene glycol,
Aromatic compounds such as toluene or a mixture thereof may be used, but water is preferably used from the viewpoint of economic efficiency and pollution.

The temperature of the coagulating liquid is preferably in the range of 0 to 100°C, preferably θ to sO°C.

Any known method may be used to solidify the thin film in liquid form or in which a portion of the solvent has been evaporated. for example,
Examples include a method in which the thin film is immersed together with the substrate on which the thin film is formed into the coagulating liquid, or a method in which only the hollow fiber thin film is immersed in the coagulating liquid.

It is preferable that the coagulated wet film is air-dried or immersed in alcohols/hydrocarbons to maintain a low concentration of the solvent and coagulating liquid.

Next, in the case of a copolyimide film, the solvent and impregnation are removed by heating and drying at a temperature of 100 to 350°C, preferably in the range of 100 to 350°C, and in the case of a copolyamide-imide film, at a temperature of 50 to 350°C, preferably 700 to 300°C. The solidified liquid and the like may be removed by, for example, gradually increasing the temperature from room temperature, or by increasing the temperature in multiple steps within each temperature range. Too rapid heating and drying may cause foaming, which is undesirable.

The heating drying temperature, time, and coagulation film thickness of the coagulated wet film described above vary depending on the type of solvent, the amount of evaporated components in the coagulated wet film, etc., and may be determined as appropriate for each specific example.

Although it is possible to use a strong membrane after the above heating and drying as a separation membrane, by performing the above heating and drying, the separation performance of various gases, tensile strength,
Membrane strength such as tensile elongation at break is significantly improved.

In the method of this invention, the porosity and pore shape are determined by the concentration of copolyimide or copolyamideimide in the dope solution, the type of solvent, the combination of solvents, the addition of a swelling agent, the evaporation conditions, the type of coagulant, the coagulation diameter, etc. , the thickness of the dense layer can be easily changed.

However, copolyimide or copolyamideimide that is dissolved in a polar organic solvent such as N,N-dimethylformamide, dimethylacetamide, or N-methylpyrrolidone at room temperature can be easily dissolved in a coagulating agent such as water without adding a swelling agent. Since a porous structure is obtained, there is no need to add a swelling agent.

The thickness of the copolyimide and/or copolyamide-imide separator membrane is about /~300μ, more typically 20μ~/θOμ
An overall thickness of is preferred.

In the present invention, the term "gas" refers to any type of substance, including, for example,
Oxygen, nitrogen, hydrogen, helium, neon, argon, krypton, xenon, radon, fluorine, chlorine, bromine, -carbon oxide, carbon dioxide, -nitrogen oxide, nitrogen dioxide, ammonia, sulfur dioxide, hydrogen sulfide, hydrogen chloride, paraffin Examples include hydrocarbons, olefin hydrocarbons, and mixtures thereof.

Paraffinic hydrocarbons are also called saturated chain hydrocarbons, alkanes, or methane hydrocarbons, and include methane with carbon numbers /, ethane with carbon atoms, propane with 3 carbon atoms, butane with ≠, pentane with j, hexane with g, and 2 carbon atoms. Preferred examples include hebutane, octane, and the like. In addition to straight-chain normal hydrocarbons, it also includes isomers with side chains when the number of carbon atoms is greater than 1.

Olefinic hydrocarbons have one double bond and are also called unsaturated chain hydrocarbons, alkenes or ethylene hydrocarbons, and include ethylene with a carbon number of 1, propylene with a carbon number of 3, propylene with a carbon number of 3, amylene with a carbon number of J, etc. are preferred.

Separation of water vapor according to the present invention is carried out using the above-mentioned membrane by a conventional method of separation using a gas separation membrane.

〔Example〕

The present invention will be explained in more detail with reference to Examples below.

Manufacturing reference example/Using the procedure followed in the example of U.S. Pat. No. 3,707,1Ajr, 3.3', ≠, ≠! - Benzophenone tetracarboxylic anhydride and rθ molar ratio of tolylene diisocyanate (2, Hiroshi - isomer approximately ♂ 0 mol and 22 g
- a mixture of about 10 mol of isomers) and 2θ mol,
A copolymerized polyimide was polymerized from a mixture containing di-diphenylmethane diisocyanate.

The polymerization solvent used was N,N'-dimethylformamide,
The resin concentration was 27% by weight. This was passed through a concentrator to obtain a 25% by weight copolyimide solution.

copolyimide has a logarithmic viscosity (η1nh
) (θ in dimethylformamide, j%) θ, di/l
was breaking down.

Production reference example /9. d', 2f(3
, 20 mol) of trimellitic anhydride and /37! , p
ot(θ, ro moles) of isophthalic acid was charged. The reactor was equipped with a thermometer, condenser, stirrer and nitrogen inlet.

100 θ, 9 mol (≠, θ mol) of Hiromi'-methylene bisphenyl isocyanate (
MDI (hereinafter abbreviated as MDI) was weighed out, and then 4LJ Hiro-〇N-methylpyrrolidone (hereinafter abbreviated as NMP) was weighed out to dissolve MDI. Add this MDI solution to the reactor, then weigh out the MDI and rinse the bottle.
sOstl! of NMP was added.

The solution was stirred from 53°C to 70'C for 3 hours at a stirring rate of 1 s rpm and under a nitrogen atmosphere.
The mixture was heated at 1° C. and further heated to 6° C. to 2° C./hour SS min/6° C. In this way, 2f% by weight of NMP, a random copolyamide-imide having a structure of approximately 0 θmolti of the repeating unit and a structure of about 0 molti of the repeating unit.
A solution was obtained.

J (logarithmic viscosity W at 7'C) of this copolyamideimide
(ηtnh) (in N-methylpyrrolidone, o, s%) was θ, Oj di/P.

This solution was added to methanol to precipitate a polymer, which was then dried at 750° C. for 3 hours to obtain a copolyamide-imide powder. The obtained copolyamideimide powder is N,N'-
It was dissolved in dimethylformamide to make a 77% by weight solution.

The copolyimide solution obtained in Example/Manufacturing Reference Example/ was diluted with N,N'-dimethylformamide to prepare a 72w/i% copolyimide solution, and filtered with a 78m Millipore filter.
Purified. This dope solution was cast on a glass plate at room temperature,
Make it evenly thick with a doctor knife /≠mit, / m
A thin film of 11=2 j μm) was formed, and the glass plate was immediately immersed in water at θ°C. After being left for 10 minutes, the peeled film was fixed on a metal rod and left in SO°C water for 30 minutes. After being left at room temperature for about 1 hour, it was heated and dried at 00C for 20 minutes to remove the solvent, producing a copolyimide film with a thickness of about 000C.

When gas permeation performance was measured using a copolyimide membrane with

Table 7 Example C Manufacture Reference Example A copolyamide-imide membrane was manufactured in the same manner as in Example C, except that the copolyamide-imide solution obtained in Reference Example C was used, and the gas permeation performance was measured. /, ≦×/θ−3cdi (S T P )/1
-sec ・craHy, what is the nitrogen permeation rate? ×／θ
cd (S T P )/crIl@sea @cm
Hy, and the ratio of water vapor permeation rate to nitrogen permeation rate was 23j.

Example 3 A copolyimide solution was produced according to Production Reference Example. The above copolyimide solution was extruded at a constant flow rate from a hollow fiber manufacturing nozzle, and at the same time, a liquid mixture of water and dimethylformamide at a ratio of jθ/jθ (weight ratio) was extruded as a core liquid at a constant flow rate.

The hollow filament formed/! After an air gap of σ was taken, the material was introduced from the water into a coagulating bath, immersed for 70 seconds, and then wound up at a constant speed of 1 ml and 1 minute.

After this, it was immersed in water for 5 minutes and air-dried day and night.

Furthermore, after this, both ends of the hollow fiber were fixed to metal rods, and the 3θ
Heat treatment was performed at θ°C for 30 minutes. A permeation test of methane containing water vapor was conducted using this hollow fiber. High pressure side
Oky / 7 G, low pressure side is open to atmospheric pressure, temperature is 7
0℃. The gas compositions on the high-pressure side and the low-pressure side were measured using a gas chromatograph.

The results of the permeation test are the water vapor permeation temperature g, s, s×/θ
crIi(8TP)/crl-sec-cInHf
l Methane permeation rate? ×/θ−'crA(STP)
/'crl·sea @6HHy, and the ratio of the water vapor permeation rate to the methane permeation rate was st.

〔Effect of the invention〕

The present invention is applicable to, for example, removing water vapor from petroleum-associated gas, etc.
It is expected that it will be widely applied in the industrial field.

Claims (2)

[Claims] (1) General formula (I) ▲There are mathematical formulas, chemical formulas, tables, etc.▼・・・・・・(I
) is a copolyimide having a structure represented by repeating units, in which R represents ▲numerical formula, chemical formula, table, etc.▼ in 10 to 30 mol% of the above repeating units, and 90 to 30 mol% of the above repeating units 70 mol% is a copolyimide in which R represents ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ and/or ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ and/or 90 to 7 repeating units
0 mol% is formula (II) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼
...(II) has a structure represented by: and 10 to 3 repeating units
0 mol% is the formula (III) ▲There are mathematical formulas, chemical formulas, tables, etc.▼... (III) Using an asymmetric membrane whose main constituent material is copolyamideimide, which has the structure represented by A water vapor separation method characterized by separating. (2) The separation method according to claim 1, wherein the main component of the gas is air, paraffinic hydrocarbons, olefinic hydrocarbons, or a mixture thereof.