JPH01299604A - Osmotic vaporation film - Google Patents

Abstract

PURPOSE:To obtain a osmotic vaporation film having high film forming property, high separation coefft., and high permeation velocity by using bis(3- aminophenyl)sulfone and bis[4-(4-aminophenoxy) phenyl]sulfone as diamine components of a copolymer constituting a material for the film. CONSTITUTION:A film to be used for the separation of water from a water/org. liquid mixture by the osmotic vaporation process is constituted of 20-80mol.% bis(3-aminophenyl) sulfone and 80-20mol.% bis[4-(4-aminophenoxy)phenyl] sulfone, as diamine components. Said diamine components are copolymerized with acid component(s) consisting of isophthalic acid and/or terephthalic acid as primary acid components to obtain thus an aromatic polyamide copolymer. A separation film obtd. by this method has high film forming property as it is without requiring introduction of a crosslinked structure nor transformation to a compound film, having high separation coefft. and high permeation velocity.

Description

DETAILED DESCRIPTION OF THE INVENTION <Field of Application in Industry I> The present invention relates to a method for separating water from an aqueous solution of organic matter. More specifically, the present invention relates to a separation membrane for separating water from a water-aluminium liquid mixture by a pervaporation method.

<Prior Art> Distillation has long been known as a method for separating a water-organic liquid mixture or a two-component or more organic liquid mixture. However, it is extremely difficult to separate azeotropic mixtures, near-boiling point mixtures, and compounds that are easily denatured by heat using distillation, and even for mixtures that can be separated by distillation, a large amount of energy is consumed. Separation technology using membranes is expected to solve these problems. Among separation techniques using membranes, the pervaporation method is considered to be particularly effective for separating water-organic liquid mixtures. This pervaporation method involves supplying a mixed liquid for the purpose of separation to one side of a polymer membrane, making the other side a gas phase, and applying a vacuum, reduced pressure, or flowing a carrier gas.
This is a method of separation by applying a vapor pressure difference to allow specific substances to preferentially permeate through the membrane. In other words, the pervaporation method differs greatly from other membrane separation methods such as reverse osmosis and gas separation in that it causes a phase change through a membrane. Fourth, in this method, since the IF force on the permeation side of the membrane is extremely small, the gradient of the chemical potential, which is the driving force for the permeation of substances through the membrane, becomes extremely large, making it possible to separate in the entire concentration range. This is a feature not found in other membrane separation methods. Therefore, this pervaporation method makes it possible to separate organic liquid mixtures, which is difficult to do with reverse osmosis due to its operating pressure.

Another feature of the pervaporation method is that it is an energy-saving process that can separate, concentrate, and purify azeotropic mixtures, near-boiling point mixtures, and thermally decomposable mixtures that were difficult to separate using conventional distillation methods. . In this way, the pervaporation method
It has many features not found in other separation methods, and is one of the most suitable separation methods for separating organic liquid mixtures.

In recent years, research on pervaporation methods in particular has been actively conducted, and there have been many reports regarding the polymer membranes used. For example, for water-ethanol separation, US Pat.
No. 3,502 proposes an acetyl cellulose homogeneous membrane, and US Pat. No. 3,035,080 proposes a hydrolyzed polyvinyl acetate membrane. Also, JP-A-59
JP-A No. 59-55304 and JP-A No. 59-55 disclose a composite film having a cellulose acetate film or a polyvinyl alcohol film as a skin layer.
No. 305 = r publication proposes a polyethyleneimine-based crosslinked composite membrane, and JP-A-61-281138 proposes an acrylic acid group-containing polymer-based crosslinked composite membrane. Jour
nal or Membrane 5science1
(197G) 271-287, a membrane in which polytetrafluoroethylene is grafted with poly(N-vinylpyrrolidone) was published in the Journal of Membrane
neScience 9 (1981) 191-19
In G, a membrane in which styrene is grafted onto polytetrafluoroethylene has been reported. However, although many polymer membranes for pervaporation have been proposed, this pervaporation method has not been put to practical use.

This is because many of the polymer membranes proposed to date for pervaporation have insufficient separation performance or permeation performance, or have problems with membrane formability or membrane durability. ing.

Moreover, as a general tendency, separation performance and permeation performance are contradictory, and it is said that it is difficult to maintain both at a high level. For practical application of pervaporation membranes,
Solving these problems is inevitable. In other words, if the separation performance is poor, even if it passes through the polymer membrane once, it will not be possible to concentrate or separate it to the desired concentration. There are many problems in practical use, such as the need to combine this method with other methods, the equipment becomes larger, and equipment costs become excessive. In addition, the permeation rate of water and organic compounds through a polymer membrane (unit membrane area, il 1st membrane thickness,
(expressed as clear transmission per unit hour) is small, the membrane area must be made very large, the membrane thickness must be extremely thin, or a composite membrane must be used, which also increases the size of the apparatus. This poses practical problems such as reduced film formability, film strength, and durability.

In the present invention, the H permeation rate is defined as the C1i volume, the 11th film thickness, and the amount of permeated mixture per medium time, N kg・F/l/
- Expressed in units of hr. On the other hand, the separation coefficient (α) is the mixing ratio of water and organic matter in the permeate gas to the ratio of water and organic matter in the feed liquid. That is, αs = (X/Y)1+
/ (X/Y). Here, X and Y represent the respective compositions of water and organic matter in a two-component system, and P and f represent the permeate gas and the feed liquid.

<Problem to be solved by the invention> The purpose of the present invention is to solve the problem of water by pervaporation method.
The present invention solves the problem that conventional membranes cannot simultaneously increase the permeation rate and separation coefficient when separating water from an organic liquid mixture, and provides a polymer membrane with excellent film formability.

<Means for Solving the Problems> As a result of intensive research into pervaporation separation membranes that have high separation performance and permeability while maintaining good film formability and membrane strength, the present inventors have developed the following solutions. separation membranes were found to achieve this objective.

That is, the present invention comprises 20 mol% to 80 mol% of bis(3-aminophenyl)sulfone and 80 mol% to 20 mol% of bis[4-(4-aminophenoxy)phenyl]sulfone.
This is a separation membrane for pervaporation characterized by being made of an aromatic polyamide copolymer having a diamine component and an sulfuric acid component.

Here, in order to explain the content of the present invention in more detail, a liquid separation mechanism using a pervaporation method will be explained. That is,
The liquid separation mechanism by pervaporation is explained as being based on the dissolution and diffusion of the liquid into the membrane.

In general, the separation coefficient αn, which is calculated by dividing the weight ratio of component A to component B after permeation by the weight ratio of component A to component B before permeation, is determined by the ratio of the solubility of component A and component B in the membrane and the membrane It is expressed as the product of the ratio of internal diffusion rates. In order to increase the separation coefficient α, it is necessary to increase either or both of the solubility ratio and diffusion rate ratio of component A and component B.

Solubility is mainly in the intermolecular phase between permeable molecules and the membrane! It is determined by the f effect (chemical compatibility). A solubility parameter is used as a measure of chemical compatibility between a membrane material and an object to be separated. When selecting a membrane material, it is best to choose a substance that has high chemical compatibility with the membrane material and the permeating molecules, or a membrane material with similar polarity. It is said that a highly polar membrane material with a large solubility parameter is suitable, while the opposite membrane material is suitable for hydrophobic membranes. In other words, water-
The former membrane material is suitable for separating ethanol.

However, many of these materials dissolve or swell in the supply liquid, and when such materials are used as intermediate materials, problems arise in terms of membrane durability and the like.

Therefore, after film formation, durability is often imparted by introducing a crosslinked structure through ionic bonding, electric gamma rays, or plasma irradiation, creating a block structure with non-polar materials, or forming a composite film.

The rate of diffusion is determined by the shape, size, aggregation state of the permeating molecules and the free volume of the membrane. In order to reduce the separation factor [alpha]a, the shape of the permeating molecules in the feed liquid must be significantly different. −・Generally speaking, molecules with smaller shapes have a higher diffusion rate. On the other hand, the free volume of a membrane is not defined by macroscopic pores, but by molecular gaps on a molecular scale. In a membrane with a large free volume, the difference in diffusion rate due to the difference in the size of the permeated fraction Y. is small, and in a membrane with a small free volume, the difference in the diffusion rate due to the difference in the size of the permeated molecules is large.

In order to increase the separation coefficient by 1 - by utilizing the size of permeable molecules, it is necessary to reduce the free volume of the membrane.

In order to reduce the free volume of a film, methods have been used to introduce a cross-linked structure or a crystal structure to form a fine three-dimensional network structure.

The present inventors investigated the separation performance of various polymer membranes for aqueous solutions containing water-soluble organic substances, especially alcohols, using the pervaporation method, and found that bis(3-aminophenyl)sulfone and bis[4-( A copolymer of aromatic polyamide containing 4-aminophenoxy)phenyl]sulfone as a diamine component and isophthalic acid component as the main acid component can form a good film using rr+- membrane material without introducing a crosslinked structure or forming a composite film. It was found that it has high separation coefficient and permeation rate.

The present invention will be explained in more detail below.

The diamines used in the aromatic polyamide polymer of the present invention include bis(3-aminophenyl)sulfone and bis[
:4-(4-aminophenoxy)phenylcosulfone. The amount of bis[4-(4-aminophenoxy)phenyl]sulfone used is 20 to 8
It is 0 mol%.

When it is more than 80 mol%, the separation coefficient decreases significantly,
When the amount is less than 20 mol%, the permeation rate decreases significantly. Bis[:4-(4-aminophenoxy)phenyl]
Separation coefficient in the range of 20 to 80 mol% of sulfone,
Shows excellent performance in terms of permeation rate. Preferably, bis[4
-(4-aminophenoxy)phenyl]sulfone is 30
A range of 70 mol % is particularly good.

As the acid component, an isophthalic acid component is mainly used, but a terephthalic acid component or a mixture of both may also be used. In addition, an aromatic dicarboxylic acid component can be used, but the amount used is preferably 20 mol % or less based on the total acid components.

The polymer is obtained by reacting a diamine with a dicarboxylic acid chloride. A solution polymerization method or an interfacial polymerization method is used for the reaction. The shape of the separation membrane made from the polymer is not particularly limited, such as flat membrane, spiral type, or hollow fiber type, but in order to improve separation performance, especially permeation rate,
It is desirable that the membrane has an asymmetric structure.

The polymer is dissolved in a suitable polar solvent such as N-methylpyrrolidone, N,N-dimethylformamide or N,N-dimethylacetamide. It is also dissolved in a mixed solvent of the above-mentioned solvent and glycols, etc., which are slow solidifying agents when forming an asymmetric structure. Therefore, in order to obtain an asymmetric membrane, for example, the polymer is dissolved in a mixture of N-methylpyrrolidone and glycols, which are slow-coagulating agents, and then cast onto a glass plate, and after being left for a certain period of time, water etc. P into the solvent
You only need to pickle it twice.

The membranes prepared in this way are mainly composed of water/organic substances, such as methanol, ethanol, 1-propanol,
Alcohols such as 2-propanol, n-butanol,
One or more of the following: ketones such as acetone and methyl ethyl ketone, ethers such as tetrahydrofuran and dioxane, organic acids such as formic acid and acetic acid, aldehydes such as formaldehyde, acetaldehyde and propionaldehyde, and amines such as pyridine and pyricone. -1- It is used for the separation of aqueous solutions containing compounds by pervaporation,
It can also be used to separate a vapor mixture of water and the organic substance by vapor permeation.

Effects> Since the film obtained from the polymer of the present invention is an aromatic polyamide, it has excellent thermal stability and also has good film formability. The reasons for the high separation coefficient and permeation rate of the protective film are not clear, but due to the moderate flexibility and hydrogen bonding in the aromatic polyamide molecular structure, the molecular gap (free volume) is ) is formed, it is determined if&. Furthermore, the aromatic polyamide contains hydrophilic amide bonds, carboxylic acid groups, amino groups, etc., and has a high affinity for water in the feed solution, so the water permeation rate is higher than that of 41 organisms. This is thought to be because it is larger than the speed.

<Examples> The present invention will be specifically explained below using Examples, but the present invention is not limited thereto.

(1) Film forming method 3 g of polymer was mixed with 12 g of dimethylacetamide (DMA).
C) and cast onto a glass plate using a doctor knife, and after heating and drying at 80°C, the film was peeled off from the glass plate to obtain a homogeneous film. The protective film was sandwiched between filter papers, and heat treatment was performed by heating and drying under reduced pressure at 160° C. for 16 hours.

■Measurement method of pervaporation performance The permeation vaporization performance was measured using a Seikagakuken type pervaporation measuring device.

The effective area of the membrane was 19.6- when the feed side of the water/water-soluble organic compound mixture was under atmospheric pressure and the permeate side was under reduced pressure of Q, 3n+I1 g or less. Water and organic compounds that passed through the membrane were condensed with liquid nitrogen and collected. n-propatool was added to the permeate as an internal standard, and the permeation rate and separation coefficient were determined by TEL)-gas chromatography. The separation coefficient α of water with respect to ethanol is defined as E and Oil as follows.

However, in the above formula, XELOH and Xl120 represent the weight percent of ethanol and water in the feed liquid, and YEtOH and yn2o represent the weight percent of ethanol and water in the permeate.

Example 1 22.8 g (0,09 J) of bis(3-aminophenyl)sulfone and bis[4-(4-
aminophenoxy)phenyl]sulfone 39.8g (
0.99 J) and introduced nitrogen gas. Dehydrated N
-Methylpyrrolidone 500- is added and stirred. After completely dissolving, cool in a water bath until the internal temperature reaches 4°C. 37.4 g of isophthalic acid dichloride powder (0
, 18 ml) and stirred for 1 hour while cooling in a water bath.

Thereafter, the mixture was reacted at room temperature for 2 hours, and then poured into 3Q methanol to obtain a solid polymer. The polymer was repeatedly pulverized using a mixer, washed with water, and then dried under reduced pressure. The obtained polymer was formed into a film according to the film forming method described in L, and the permeation vaporization performance was measured. Separation coefficient (α) of water and ethanol is 950, permeation rate is 0.1
4 (kgtOH μm/Ih).

Example 2 In the same manner as in Example 1, 37.2 g of bis(3-aminophenyl)sulfone (0,15soQ) and bis[4-
(4-aminophenoxy)phenyl]sulfone 21.8
Polymerization was carried out using 40.6 g (0.2 mQ) of isophthalic acid dichloride as the diamine component and 40.6 g (0.2 mQ) of isophthalic acid dichloride as the acid component. The obtained polymer was formed into a film according to the above method, and 9.9 g (0.04 J) of bis(3-aminophenyl)sulfone and bis[4-(4-aminophenoxy)phenyl ] Sulfone 58.2g (0,13J) as diamine component, isophthalic acid dichloride 34.5g (0,171 [10)
Polymerization was carried out using as an acid component. The obtained polymer was formed into a film according to the method described above, and its pervaporation performance was measured. The separation coefficient (α) between water and ethanol was 415, and the permeation rate was 0.34 (kg·tOHP/1·hr).

Example 4 The membrane obtained in Example 1 was dried under reduced pressure at 180° C. for 16 hours. As a result of measuring the pervaporation performance, the separation coefficient (α) between water and ethanol was 6618, E, 011, and the permeation rate was 0.18 (kg·μm/♂·h).

Comparative Example 1 In the same manner as in Example 1, 55.0 g (0,22oQ) of bis(3-aminophenyl)sulfone was used as the diamine component, and 45.0 g (0,22J) of isophthalic acid dichloride was added.
Polymerization was carried out using as an acid component.

The obtained polymer was formed into a film according to the method described in L, and the permeation vaporization performance was measured. Separation coefficient of water and ethanol (α
) was 193, and the permeation rate was 0.08E, OH (kg・μm/♂・h).

Comparative Example 2 88.1 g (0.18 J) of bis[:4-(4-aminophenoxy)phenylcosulfone] was prepared in the same manner as in Example 1.
is the diamine component, isophthalic acid dichloride 31.9
Polymerization was carried out using g (0.16 J) as the acid component. The obtained polymer was formed into a film according to the method described above, and its pervaporation performance was measured.

The separation coefficient (α) between water and ethanol is 50, permeation tO
H overspeed was 0.72 (kg·μ h/male·h).

Comparative Example 3 88.1 g (0,18azQ) of bisC4-(3-aminophenoxy)phenyl]sulfone was prepared in the same manner as in Example 1.
is the diamine component, isophthalic acid dichloride 31.9
Polymerization was carried out using g (0,16oQ) as an acid component. The obtained polymer was formed into a film according to the method described above, and its pervaporation performance was measured.

The separation coefficient (α) of water and ethanol is 376, E, O
The H 2 permeation rate was 0.05 (kg·μIII/I41 h).

As is clear from Table 1, the aromatic polyamides using bis(3-aminophenyl)sulfone and bis[4-(4-aminophenoxy)phenyl]sulfone as the diamine component are bis(3-aminophenyl)sulfone, respectively. ) or bis[4-(4-aminophenoxy)phenyl]sulfone as the diamine component.

Table 1 <Effects of the Invention> By using the membrane of the present invention, it is possible to maintain a higher separation coefficient than separation methods using conventional membranes and to achieve f
The T-machine liquid mixture can be efficiently separated by pervaporation. In addition, without crosslinking reaction or forming a composite film, 9
It is possible to make a film using German materials. Therefore, the separation system can be made more compact, rationalized, processing capacity can be increased, and costs can be reduced. It is effective in shortening the It purification process and in practical application of membrane separation methods for energy saving, and has extremely great industrial utility.

Claims (1)

[Claims] Bis(3-aminophenyl)sulfone 20 mol% ~ 80
Consisting of an aromatic polyamide copolymer containing 80 mol% to 20 mol% of bis[4-(4-aminophenoxy)phenyl]sulfone as a diamine component and an isophthalic acid component and/or terephthalic acid as the main acid component. A separation membrane for pervaporation characterized by the following.