JPH0235921A - Pervaporation process for organic substance water solution - Google Patents

Abstract

PURPOSE:To separate water efficiently and selectively from organic substance water solution by using an unsymmetrical separation membrane formed with tetracarboxylic acid component and aromatic polyimide made from aromatic diamine component. CONSTITUTION:Tetracarboxylic acid component composed of biphenyl tetracarboxylic acid group as main component and aromatic diamine component containing an aromatic diamine compound, 80% or more of the whole diamine component, represented by the formula II and III (R1, R2=H or CH3), are used. Said components are polymerized and imdated in organic solvent in the presence of an imidating agent at the high or low temperature, to prepare aromatic polyimide in the formula I (a bivalent residual radical of R = diamine compound after removing amino). Said polyimide is included in the ratio of 80% or more at repeating unit. An unsymmerical separation membrane thus manufactured permeation vaporizes water out of organic water solution.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to a tetracarboxylic acid component containing biphenyltetracarboxylic acids as a main component and an aromatic diamine component containing a specific aromatic diamine compound. Asymmetric separation membranes made of aromatic polyimide (e.g.
Water is removed from the organic aqueous solution using a pervaporation method (pervaporation method) in which the organic aqueous solution is brought into direct contact with the asymmetric separation membrane and permeabilized using a flat membrane or hollow fiber membrane. It relates to separation methods for concentrating and separating organic substances.

[Description of Prior Art] Distillation is conventionally known as a method for separating an organic matter aqueous solution into organic matter and water. However, with the distillation method, it is extremely difficult to separate azeotropic mixtures, near-boiling point mixtures, and organic substances that are susceptible to chemical changes due to heat.

In order to solve these problems, separation methods using separation membranes are being researched. In the method of concentrating and separating organic substance aqueous solutions using a separation membrane, for concentrating some low-concentration organic substance aqueous solutions, the organic substance aqueous solution is brought into contact with the separation membrane and specific liquid components are selected by the difference in osmotic pressure. Reverse osmosis has been used to penetrate the membrane. However, the reverse osmosis method cannot be applied to high-concentration aqueous organic matter solutions where the osmotic pressure is high because it is necessary to apply a pressure higher than the osmotic pressure of the separation liquid.Therefore, there is a limit to the concentration range of organic matter aqueous solutions that can be separated. be.

On the other hand, as a separation method that is not affected by osmotic pressure,
The pervaporation method is attracting attention as a new separation method using separation membranes. In this pervaporation method, the organic aqueous solution to be separated is supplied in liquid form to one side of the separation membrane, and brought into contact with the supply side of the separation membrane.
The other side of the separation membrane is placed in a vacuum or reduced pressure state, and as a result, the substances (such as water) that selectively permeate from the supply side of the separation membrane to the other side (permeation side) are extracted in gaseous form, and the aqueous organic matter solution is extracted. This is a method of concentrating or separating organic matter from moisture.

Regarding the above-mentioned pervaporation method, many proposals have been made in the past.

For example, regarding the separation of an aqueous ethanol solution by pervaporation, an example of using a uniform membrane made of cellulose acetate, which has low heat resistance, is disclosed in US Pat. No. 2,953,502.

[Problems to be solved]

However, the known methods have problems such as low permeation rate for water, insufficient selective separation performance between organic matter and water, and insufficient heat resistance and water resistance of the separation membrane. (Due to insufficient durability, it has been extremely difficult to industrially implement the pervaporation method of various organic substance aqueous solutions.

The purpose of the present invention is to provide an industrial method for pervaporating an aqueous solution of organic matter using an asymmetric separation membrane, which is capable of efficiently and selectively separating water from an aqueous solution of an organic matter, without the drawbacks of known pervaporation methods. The purpose of this invention is to provide a pervaporative separation method.

[Means for solving problems]

The present invention provides a pervaporation separation method in which an aqueous solution of an organic substance is brought into contact with an asymmetric separation membrane made of a heat-resistant polymer to mainly pervaporate water from the aqueous solution of an organic substance. It integrates an extremely thin homogeneous layer made of aromatic polyimide with a relatively high ratio of aromatic polyimide, which is directly related to selective separation performance, and a relatively thick porous layer that supports the homogeneous layer. It is an asymmetric separation membrane having a flat membrane shape, a hollow fiber shape, etc., and having the ability to selectively permeate water in an organic substance aqueous solution.

The aromatic polyimide represented by the above general formula I, for example, contains biphenyltetracarboxylic acids as a main component (preferably at least 80 mol%, particularly preferably 90 to 90% by mole).
At least 80 mol% of at least one diamine compound selected from the group consisting of a tetracarboxylic acid component (containing 100 mol%) and an aromatic diamine compound represented by the general formulas (1) and (2) above, based on the total diamine component. proportion, preferably 85 to 100 mol%, particularly preferably 90
It can be obtained by polymerizing and imidizing an aromatic diamine component containing in a proportion of 100 mol % at a high temperature or at a low temperature in the presence of an imidizing agent.

[However, R is a divalent residue other than the amino group of the diamine compound, and the diamine compound has the following formula: (However, R1 and R2 are hydrogen or a methyl group.)
At least one aromatic diamine compound selected from the group consisting of diamine compounds represented by: This invention relates to a method for pervaporative separation of an aqueous solution of organic matter, characterized in that the aromatic polyimide has 80% or more of repeating units represented by the following.

Each requirement of the present invention will be explained in more detail below.

The asymmetric separation membrane used in the present invention contains repeating units represented by the above-mentioned general formula (1) in an amount of 80% or more, particularly 90 to 100%, of the total main chain bonding units, and the above-mentioned biphenyltetracarboxylic acids having 2 .3.3°, 4°- or 3
．． Examples include 3',4.4°-biphenyltetracarboxylic acid, its acid dianhydride, and lower alcohol esters of the acid. The aromatic polyimide constituting the asymmetric separation membrane used in this invention includes an aromatic tetracarboxylic acid component whose main component is 3.3', 4.4' biphenyltetracarboxylic dianhydride;
The aromatic polyimide represented by the general formula (2) obtained from the above-mentioned diamine component has excellent properties in terms of separation membrane formability, separation performance, water resistance (durability), mechanical strength, heat resistance, etc. preferable.

Examples of tetracarboxylic acid components that can be used together with the above-mentioned biphenyltetracarboxylic acids in the above-mentioned method for producing aromatic polyimide include pyromellitic acid, 3,3"
, 4,4°-biphenyl ether tetracarboxylic acid, 3
．． 3', 4.4°-benzophenonetetracarboxylic acid,
or their acid dianhydrides.

In the above method for producing aromatic polyimide, if the content of biphenyltetracarboxylic acids in the tetracarboxylic acid becomes too low, the resulting aromatic polyimide will no longer be the aromatic polyimide represented by the general formula (2).
As a result, the durability of the asymmetric separation membrane made of aromatic polyimide, which has low water resistance, decreases when it is used for the separation of organic substance aqueous solutions by pervaporation. It's not appropriate.

In addition, as the diamine component, at least one diamine compound selected from the group consisting of diamine compounds represented by general formulas (1) and (2), preferably a mixture of two or more diamine compounds, is added to the total diamine component. , at least 80 mol%, preferably 85 to 100 mol%, particularly preferably 90 to 100 mol%.

When the diamine component contains two or more diamine compounds selected from the group consisting of the diamine compounds represented by the general formulas (1) and (2), the diamine components represented by the general formula (1) or (2) contained therein at least one of the diamine compounds represented by formula (1) is contained in a proportion of about 20 to 80 mol% based on the total diamine components, and
The total amount of diamine compounds represented by
The amount is preferably 00 mol%, more preferably 90 to 100 mol%.

Examples of the aromatic diamine compound represented by the general formula (1) used as the diamine component include diphenylmethane-based diamine compounds such as 3,3°-diaminodiphenylmethane and 4,4''-diaminodiphenylmethane;
2.2-bis[4-aminophenyl]propane, 2.2
-bis[3-aminophenyl]propane, 2.2-bis(3,4-diaminodiphenyl)propane, etc.
Examples include -bisphenylpropane-based diamine compounds.

Furthermore, as the aromatic diamine compound represented by general 2) used as the diamine component, diphenyl ether-based diamines such as 3.3'-diaminodiphenyl ether, 4.4'-diaminodiphenyl ether, 3.4"-diaminodiphenyl ether, etc. Compounds can be mentioned.

Other aromatic diamine compounds that can be used as the diamine component in conjunction with general formula (1) and/or (2) include, for example, (a) 1,4-bis(4-aminophenoxy)benzene, 1,4- Bis(3-aminophenoxy)benzene, 1
．． 3-bis(4-aminophenoxy)benzene, 1.3
- Bis( such as bis(3-aminophenoxy)benzene)
phenoxy) benzene-based diamine compound, ■) bis(
Bis(4-(phenoxy)phenyl)ether-based diamine compounds such as 4-(4-aminophenoxy)phenyl]ether, bis(4-(3-aminophenoxy)phenyl)ether, (C)bis(4-( 4-aminophenoxy)phenyl]methane, 2,2-bis(4-(4-
Bis(4) such as aminophenoxy)phenyl]propane
-(phenoxy)phenyl]alkane-based diamine compounds; (d) o-) lysine, m-) biphenyl-based diamine compounds such as lysine; (e) phenylenediamine-based diamines such as m-phenylenediamine and p-phenylenediamine; Examples include compounds.

In the present invention, in the aromatic polyimide represented by the general formula (1), the diamine compound for forming R in the general formula (I) is selected from 4,4''-diaminodiphenylmethane and 4,4'-diaminodiphenyl ether. It is preferable to use two types of diamine compounds, particularly preferably two types of diamine compounds.

The asymmetric separation membrane made of aromatic polyimide represented by the general formula I used in this invention is formed by casting or extruding a thin film (flat film shape, hollow fiber shape) of a polyimide solution, and then forming the thin film by casting or extrusion. It can be produced by a wet membrane forming method in which a flat membrane or hollow fiber asymmetric separation membrane is formed by contacting with a relatively low temperature coagulation liquid to solidify the thin film. No., Japanese Patent Application Publication No. 1983
It can be manufactured by a conventionally known film forming method such as that described in Japanese Patent No. -157435.

The pervaporation separation method of the present invention includes: (a) An aqueous organic substance solution is introduced into a separation membrane module incorporating an asymmetric separation membrane (flat membrane shape, hollow fiber shape) made of aromatic polyimide represented by the general formula I above. supply,
and (b) bringing the organic substance aqueous solution into direct contact with the supply side of the asymmetric separation membrane in the separation membrane module, and (b) bringing the permeate side of the asymmetric separation membrane into direct contact with the feed side of the asymmetric separation membrane, if necessary. (C) Finally, water is mainly permeated through the asymmetric separation membrane from the supplied organic aqueous solution under reduced pressure by connecting it to a vacuum pump or the like. The concentrated organic liquid is taken out and collected from the permeate side (supply side) to the outside of the separation membrane module, and at the same time, from the permeate side of the asymmetric separation membrane to the outside of the separation membrane module.
The permeated vapor (permeate) with a high moisture content is extracted,
If necessary, the permeated vapor (permeate) is cooled, condensed, and recovered.

In this invention, the organic aqueous solution supplied to the separation membrane module is about 25 to 120°C, particularly preferably 50 to 1
It is preferable that the temperature be heated to about 00°C.

The pressure on the permeate side of the asymmetric separation membrane in the separation membrane module is preferably reduced to 200 torr or less, particularly preferably 100 torr or less, when performing pervaporation separation of the organic aqueous solution.

Examples of organic substances to which the pervaporation method of an aqueous organic substance solution in the separation method of the present invention can be applied include methanol, ethanol, n-propertool, isopropertool, and n-propertool.
Aliphatic alcohols such as butanol, 5ec-butanol, tert-butanol, ethylene glycol, alicyclic alcohols such as cyclohexanol, aromatic alcohols such as benzyl alcohol, organic carboxylic acids such as formic acid, acetic acid, propionic acid, and butyric acid, butyl acetate , organic acid esters such as ethyl acetate and malonic acid ester, ketones such as acetone and methyl ethyl ketone, and cyclic ethers such as tetrahydrofuran and dioxane, and may be a mixture of two or more thereof.

The separation membrane module described above is not particularly limited, but is preferably, for example, a plate-and-frame type module, a spiral type module, a hollow fiber membrane type module, etc., although it is not particularly limited.

〔Example〕

EXAMPLES Hereinafter, examples and comparative examples regarding the pervaporative separation method of the present invention will be shown, and the present invention will be explained in more detail.

In the Examples and Comparative Examples, the permeation rate Q and the separation coefficient α are determined by cooling and condensing the vaporized components that have passed through the membrane, measuring their weight, and adding dehydrated n- Propatool was added, and the weight ratio of water to organic matter was measured by TCD-gas chromatography, and calculated using the formula shown below.

Clothes pins (claws) of the glands of the well and Haie bunshaku Reference examples 1 to 10 Using approximately equal moles of the acid component and the diamine component consisting of the charging ratio shown in Table 1, parachlorophenol was prepared in an organic polar solvent. Then, polymerization and imidization were carried out at the polymerization temperature and polymerization time shown in Table 1 to produce an aromatic polyimide solution.

Table 1 shows the polymer concentration and solution viscosity (rotational viscosity of loO"c; voids) of each aromatic polyimide solution produced as described above.

Using the aromatic polyimide solution obtained as described above, a wet film forming method was performed using the coagulating liquid and hollow fiber take-up speed shown in Table 2, and the shape (inner diameter and hollow fiber diameter) shown in Table 2 was applied. Asymmetric hollow fiber separation membranes made of aromatic polyimide having different membrane thicknesses were manufactured.

Examples 1 to 8 and Comparative Examples 1 to 2 Four asymmetric hollow fiber separation membranes produced in each reference example were bundled to form a yarn bundle, and one end of the yarn bundle was sealed with epoxy resin. , an inlet for preparing a hollow fiber bundle element having an effective membrane area shown in Table 2 and supplying an aqueous organic substance solution;
A separation membrane module was manufactured by placing the hollow bundle element inside a container having an outlet for unpermeated matter and an outlet for permeated matter.

Example 9 A separation membrane module was manufactured in the same manner as in Example 1, except that the hollow fiber membrane manufactured in Reference Example 1 was further heat-treated at 270°C, and the hollow fiber membrane was used.

To the separation membrane module manufactured in each of the above examples, the second
An aqueous organic matter solution with the composition, supply amount, and temperature shown in the table is supplied, and the inside of the hollow fiber of the hollow fiber membrane element in the separation membrane module is permeated under a reduced pressure of 3 torr or less, and the permeate is cooled and recovered. did.

Table 2 shows the permeation rate Q in pervaporation and the separation coefficient α between water and organic matter.

In addition, the following hot water resistance tests were conducted on the hollow fiber separation membranes manufactured in each reference example, and the results of the tests were used in the second test.
Shown in the table.

After holding the hollow fiber membrane in hot water at 150°C for 20 hours, it was dried under reduced pressure at room temperature, and a mixed solvent of parachlorophenol (PCP) and orthochlorophenol (OCP) (PCP10CP= 4/1 weight ratio) to dissolve the polyimide forming the hollow fiber membrane, and
The logarithmic viscosity was measured at °C, and the retention rate was calculated using the formula shown below.

In addition, the abbreviations in Table 1 have the following meanings.

BPDA; 3,3°, 4,4°-biphenyltetracarboxylic dianhydride ETDA; 3.3°, 4.4”-biphenyl ether tetracarboxylic dianhydride DADE; 4,4'-diaminodiphenyl ether DA
DM; 4,4°-diaminodiphenylmethane 341 P
, 2.2-(3,4-diaminodiphenyl)promain BAPP, 2.2-bis(4-(4-aminophenoxy)phenyl)propane TPE-Q; 1,4-bis(4-aminophenoxy)benzene TSN; o-tolidine sulfone PASN; 4,4'-diaminodiphenylsulfone [Operations and effects of the present invention] The separation method of the present invention is a separation method related to pervaporation using an asymmetric separation membrane made of a specific aromatic polyimide. Therefore, it can be used for the separation and concentration of aqueous solutions of various organic substances, and can be used for aqueous solutions of organic substances with a wide range of concentrations, and has sufficient heat resistance, water resistance, and solvent resistance. Furthermore, it uses a specific asymmetric membrane made of polyimide that has high water permeability and separation performance, so it can perform stable separation by pervaporation for a long time. can.

Patent applicant: Ube Industries Co., Ltd.

Claims (1)

[Claims] In a pervaporation separation method in which an aqueous solution of an organic substance is brought into contact with an asymmetric separation membrane made of a heat-resistant polymer to mainly pervaporate water from the aqueous solution of an organic substance, the heat-resistant polymer has the general formula I ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (I) [However, R is a divalent residue excluding the amino group of the diamine compound, and the diamine compound has the general formula II ▲Mathematical formulas, chemical formulas, tables, etc. ▼ (II) and general formula III ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (III) (However, R^1 and R^2 are hydrogen or methyl groups) Consisting of a diamine compound represented by At least one aromatic diamine compound selected from the group consisting of: A method for pervaporative separation of an aqueous solution of organic matter, characterized in that the aromatic polyimide has 80% or more of repeating units represented by the following.