JPH01299606A - Separation film for pervaporation - Google Patents

Abstract

PURPOSE:To obtain a separation film having sufficient film forming property, high separation effect, and high permeability by using bis(3-aminophenyl)sulfone and bis(4-aminophenyl)sulfone as diamine components for a copolymer constituting said film. CONSTITUTION:A film for separating water from a water/org. liquid mixture by the pervaporation process is constituted of an aromatic polyamide copolymer consisting of 20-80mol.% bis(3-aminophenyl)sulfone and 80-20mol.% bis(4- aminophenyl)sulfone as diamine components, which are copolymerized with acid components consisting primarily of isophthalic acid and/or terephthalic acid. The separation film obtd. by this process has high separation effect and high permeability, having also sufficient film forming property and high film strength.

Description

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

<Prior Art> Distillation has long been known as a method for separating water-organic liquid mixtures or liquid mixtures of two or more components. 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, a pervaporation method is considered to be particularly effective for separating a water-a-mechanical mixture. This pervaporation method supplies a mixed liquid for 1-1 separation to one side of a polymer membrane, sets the other side to the gas phase, and then generates vapor by applying a vacuum, reduced pressure, or flowing a carrier gas. This is a method in which a specific substance is separated by preferentially passing through the membrane by varying the pressure difference l'j. 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. Historically, in this method, because the J-toca on the permeate side of the membrane is extremely small, the gradient of the chemical potential, which is the driving force for the permeation of the substance through the membrane, becomes extremely large, making it possible to separate 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. . As described above, the pervaporation method has many features not found in other separation methods, and is one of the separation methods most suitable 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. 3,035,060 proposes a hydrolyzed polyvinyl acetate membrane. Also, JP-A-59-
109204 sec'Kl has a composite membrane having a cellulose acetate membrane or a polyvinyl alcohol membrane as a skin layer, as disclosed in JP-A No. 59-55304 and JP-A No. 59-Sho.
No. 55305 proposes a polyethyleneimine-based crosslinked composite membrane, and JP-A No. 81-281138 proposes an acrylic acid group-containing polymer-based crosslinked composite membrane.
Urnal of Membrane 5science
1 (197G) 271-287, poly(N-vinylpyrrolidone) is added to polytetrafluoroethylene.
The membrane grafted with
raneScience 9 (1981) 191-
No. 196 reports a membrane in which styrene is grafted onto polytetrafluoroethylene. 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.

Furthermore, as a tendency within the membrane, separation performance and permeation performance tend to be 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, it will not be possible to concentrate or separate to the desired concentration even after passing through the polymer membrane once, resulting in the need for multi-stage separation operations or problems with other separation methods. There are many practical problems, such as the need for combinations, the large size of the device, and excessive equipment costs. Father, the permeation rate at which water and organic compounds permeate through polymer membranes (111th place)
If the amount of permeation (expressed as the amount of permeation per unit time) is small, the membrane area must be made very large, the membrane thickness extremely thin, or a composite membrane must be used, which also results in an increase in the size of the device. This poses practical problems such as reduced film formability, film strength, and durability.

The permeation rate in the present invention refers to unit area, unit film thickness, 91
kg・μm/r/・hr per hour of permeation mixture immersion
Expressed in units of. 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, α: (X/Y) p/ (X
/Y)r. 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.
In separating water from an organic liquid mixture, the present invention solves the problem that conventional membranes cannot simultaneously increase the permeation rate and separation coefficient, 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 found the following separation membranes. It has been found that the membrane achieves this goal.

That is, the present invention is a patent characterized in that it consists of an aromatic polyamide copolymer containing 20 mol% to 80 mol% of bis(3-aminophenyl)sulfone and a bis(4- or terephthalic acid component) as an acid component. This is a separation membrane for vaporization.

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

Solubility is mainly determined by intermolecular interactions (chemical compatibility) between permeable molecules and the membrane. The solubility parameter is taken up as a measure of chemical compatibility between the membrane material and the separation target. 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. In the case of hydrophobic membrane materials, highly polar membrane materials with large solubility parameters are suitable, and in the case of hydrophobic membrane materials, the opposite membrane material is suitable. In other words, the former membrane material is suitable for water-ethanol separation.

However, many of these materials dissolve or swell in the supply liquid, and when such materials are used alone, 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, electron beam 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 increase the separation coefficient αn, the shapes of the permeating molecules in the feed liquid must be significantly different. - Molecules with small shapes have a high diffusion rate within the membrane. 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 permeating molecules 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 permeating molecules is large.

In order to increase the separation coefficient 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 membrane, methods have been taken to introduce a cross-linked structure or a crystalline structure to form a microscopic ::, dimensional mesh structure.

The present inventors investigated the separation performance of various polymer membranes for aqueous solutions containing zero water-soluble substances, especially alcohol, using the pervaporation method. -A copolymer of aromatic polyamide containing diamine component (aminophenyl) sulfone and isophthalic acid component as the main acid component has good film formability and high separation coefficient as a single material without introducing a cross-linked structure or forming a composite film. 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(3-aminophenyl)sulfone.
4-aminophenyl) sulfone. The amount of bis(4-aminophenyl)sulfone used is 20 to 80 mol% based on the total amount of both acids. If it is more than 80 mol%, the separation coefficient is extremely low, and if it is less than 20 mol%, the permeation rate is significantly reduced.In the range of 20 to 80 mol% bis(4-aminophenyl)sulfone, the separation coefficient is It exhibits excellent performance in both permeation rate.Preferably, the range of 30 to 70 mol% of bis(4-aminophenyl)sulfone is particularly excellent.

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. Other aromatic dicarboxylic acid components 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 obtained 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 soluble in a mixed solvent of a glycol, etc., which is a slow coagulant when forming an asymmetric structure, and a No. 112 solvent. 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. Just immerse it in a solvent.

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. Although it is used to separate an aqueous solution containing the compound of (1) 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. Although the reasons for the high separation coefficient and A permeation rate of the polyamide are not clear, due to the moderate flexibility in the aromatic polyamide molecular structure and the action of water-toxic bonds, molecular gaps (free) suitable for the separation of water and organic matter are created. volume) is estimated to have been formed. In addition, aromatic polyamide contains hydrophilic amide bonds, carboxylic acid groups, amine groups, etc., and has a high affinity for water in the feed solution, so the water permeation rate is higher than the permeation rate of organic matter. It is given a rating of 4 because it is large.

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

(1) Film forming method 3g of polymer to 12g of dimethylacetamide (1)
The mixture was dissolved in MAC) and cast onto a glass plate IZ using a doctor knife, and after drying by heating at 1.80°C, the film was peeled off from the glass plate to obtain a homogeneous film. Furthermore, sandwich the protective membrane between the filter paper, 1
Heat treatment was performed by heating and drying under reduced pressure at 80° C. for 16 hours.

■ All standard methods for pervaporation performance The permeation performance was measured using a Seikagaku-style permeation measurement device.

The supply side of the water/water-soluble organic compound mixture was at atmospheric pressure F1, and the permeation side was Q, and the effective area of the membrane at reduced pressure of 3 wmHg or less was 19.6 ctft. 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 TCD-gas chromatography. The separation coefficient α of water for 20 liters of ethane H is defined as follows.

However, in the above formula, XELOH and XH2O represent the weight percent of ethanol and water in the feed liquid, and YE, OH, and YH20 represent the weight percent of ethanol and water in the permeate.

Example 1 27.5 g (0,11 J) of bis(3-aminophenyl) sulfone and bis(4-aminophenyl) in a flask. Add 27.5g (0.11J) of sulfone,
Introduce nitrogen gas. Dehydrated N-methylpyrrolidone 5
Add 00- and stir. After completely dissolving, cool in a water bath until the internal temperature reaches 4°C. Input 45.0 g (0.22[IQ) of isophthalic acid dichloride powder from Sample Input [1] and stir while cooling in a water bath for 1 hour.

Thereafter, after reacting at room temperature for 2 hours, a solid polymer was obtained by pouring into 3Q methanol. The polymer was pulverized using a mixer, washed repeatedly with water, and then dried under reduced pressure. The obtained polymer was formed into a film according to the above-mentioned film forming method, and the permeation vaporization performance was measured. The separation coefficient (α) between water and ethanol is 3387. The permeation rate is 0.2
5 (kgE, OH・μfalse/rl・h).

Example 2 In the same manner as in Example 1, 3 g (0,17 J) of bis(3-aminophenyl) sulfone 41 and 13.8 g (0,06 J) of bis(4-aminophenyl) sulfone were used as diamine components, and isophthal Acid dichloride 45.0g (
Polymerization was carried out using 0.22 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 was 579, and the LOH permeation rate was 0.09 (kg·μm/rl·h).

Example 3 In the same manner as in Example 1, 13.8 g (0,06 J) of bis(3-aminophenyl) sulfone and 41.3 g (0,17 J) of bis(4-aminophenyl) sulfone were used as diamine components, and isophthal Acid dichloride 45.0g (0
, 22+J) was used as the acid component. The obtained polymer was formed into a film according to the method described in "-" and its pervaporation performance was measured.

The separation coefficient (α) between water and ethanol is 315, and the tOH permeation rate is 0.42 (kg”, un/1111@hr
)Met.

Comparative Example 1 Polymerization was carried out in the same manner as in Example 1, using 55.0 g (0.22 J) of bis(3-aminophenyl)sulfone as the diamine component and 45.0 g (0.22 J) of isophthalic acid dichloride as the acid component. Ta.

The obtained polymer was formed into a film according to the method described above, and its pervaporation performance was measured. Separation coefficient of water and ethanol (α
) was 193, and the permeation rate was 0.08E, 01l (kg·μrn/11h).

Comparative Example 2 In the same manner as in Example 1, 55.0 g (0.22 J) of bis(4-aminophenyl)sulfone was used as a diamine component,
Polymerization was carried out using 45.0 g (0.22 J) of isophthalic acid dichloride as the acid component. The obtained polymer was formed into a film according to the method described in 1-, and the permeation vaporization performance was measured. The separation H,0 coefficient (α) of water and ethanol is 14, and the permeation rate is 0.20 (kgE,
OR ・μm/n? *h).

Comparative Example 3 In the same manner as in Example 1, 88.1 g (0.16 J) of bis[4-(4-aminophenoxy)phenylcosulfone] was used as the diamine component, and 31.9 g of isophthalic acid dichloride was added.
Polymerization was carried out using (0.16 mQ) 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 50, permeability E, O
H overspeed was 0.72 (kg·μ layer/male·h).

Table 1 As is clear from Table 1, the aromatic polyamides using bis(3-aminophenyl) sulfone and bis(4-aminophenyl) sulfone as diamine components are bis(3-aminophenyl) sulfone, respectively. or bis(4-
Compared to aromatic polyamides containing (aminophenyl) sulfone as the diamine component, it exhibits extremely high pervaporation performance.

[Effects of the Invention] By using the membrane of the present invention, organic liquid mixtures can be efficiently separated (separated by pervaporation) at a higher permeation rate while maintaining a higher separation coefficient than separation methods using conventional membranes. In addition, it is possible to form a membrane using a single material without cross-linking reaction or forming a composite membrane.As a result, separation systems can be made more compact and rational, increasing throughput and reducing costs. Therefore, the present invention is effective in practical application of a membrane separation method for shortening the process and saving energy in the chemical industry, etc., and has extremely large industrial requirements.

Patent applicant: Director-General of Basic Industries Bureau, Ministry of International Trade and Industry

Claims (1)

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