JPS63258603A - Aromatic polymer membrane - Google Patents

Abstract

PURPOSE:To obtain hydrophilic polysulphone membrane which is highly heat-and chemical-resistant and also significantly permeable by providing block polymer produced by covalent bonding of the terminal region of polyester sulphone with sulphonated aromatic polysulphone as a constituent element. CONSTITUTION:An active chlomethyl group is introduced to the terminal of polyethersulphone A having an iterative unit of the formula I. In the meantime, aromatic polysulphone B having an active terminal is obtained by allowing 4, 4'-dichlorodiphenyl sulphone to react to aromatic polysulphone having one kind of iterative unit selected by the formulas II-IV and the iterative unit of the formula I. This aromatic polysulphone B is dissolved with a solvent, and allowed to react with polyether sulphone A to obtain a block polymer. This block polymer is dissolved with solvent, and this solution spreads over polyester unwoven fabric. Then it is immersed in water to coagulate, thus obtaining a separation membrane.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a hydrophilized polysulfone membrane,
More specifically, it has a block polymer as a constituent element in which the end portion of polyether sulfone and sulfonated aromatic polysulfone are bonded by covalent bonds, and it has excellent heat resistance, chemical resistance, etc., and has excellent permeability. This relates to a hydrophilized polysulfone membrane with good properties.

(Prior Art and Problems) Polysulfone resins are widely used as separation membrane materials with excellent chemical and thermal durability. Many polyarylethesulfone polymers are known as polysulfone resins, and these resins are characterized by a structure containing repeating units represented by -a. As expected from this structure, polysulfone resin has excellent durability and stability, but on the other hand, it exhibits hydrophobic properties. Typical products are commercially available under the trade names of Victrex from Inverial Chemical Industries (abbreviated as IC1) and Odel from Union Carbide (abbreviated as UCC), but the former has a water absorption rate of 0. 4%, the latter 0.3% (both A, STM D
570), and has a water absorption rate of 1 in 10 or less than that of cellulose acetate, which is known as a hydrophilic membrane material resin. Due to this hydrophobic property, conventional polysulfone membranes are difficult to wet with water once dried, have low water permeability,
There were a number of problems, including ``hydrophobic solutes adhering to the membrane surface and contaminating it easily.''

In order to solve these problems, various methods have been proposed to improve polysulfone membranes.

Examples of methods for providing a hydrophilic polysulfone membrane by introducing hydrophilic groups or hydrophilic polymers into aromatic polysulfone polymers include Japanese Patent Publication No. 13679/1983 and Japanese Patent Application Laid-Open No. 1983-1989.
No. 196322, etc., is a reverse osmosis membrane made from an aromatic polysulfone polymer made hydrophilic by introducing or grafting polyethyleneimine polymers into the polymer main chain. We are proposing a method to provide such. All of these methods are modification methods in which hydrophilic groups or hydrophilic polymers are randomly and uniformly bonded to the aromatic rings of the main chain of aromatic polysulfone polymers through covalent bonds, so they are made of unmodified polymers. It is inevitable that physical properties such as heat resistance will be lower than that of membranes. Furthermore, if the ratio of hydrophilic groups introduced into the polymer is high, the resulting membrane may swell with water, etc.
It can be said that this is a modification method that involves a significant change in the physical properties of the membrane.

On the other hand, various hydrophilized polysulfone membranes made of mixed polymers in which a hydrophilic polymer is blended with an aromatic polysulfone polymer have also been proposed. For example, JP-A-57-5
No. 0507 discloses cellulose derivatives in Japanese Patent Application Laid-open No. 60-20
No. 6404 proposes a hydrophilized polysulfone membrane made of a mixed polymer obtained by blending ethylene-vinyl alcohol copolymers. However, in order to obtain a substantially hydrophilized polysulfone membrane, a significant amount of different polymers must be blended, and it is difficult to obtain a homogeneous blend with polymers with high molecular cohesion, such as aromatic polysulfone polymers. It was difficult. In particular, when attempting to produce the above-mentioned hydrophilized polysulfone membrane by bringing a membrane-forming solution containing a polar organic solvent and a polymer into contact with a non-solvent for a polymer whose main component is water, and coagulating and molding the polymer, In addition to being difficult to obtain a uniform film-forming solution, there are problems with the stability of the solution, such as gelation and phase separation when left standing, and when the polymer coagulates due to contact with non-solvents, different polymers may form. There was also the possibility that the membrane structure would become non-uniform due to separation. In this way, the addition of different polymers was thought to cause deterioration of physical properties such as heat resistance and chemical resistance of the film, not only due to the effect of adding polymers with inferior physical properties, but also due to the formation of a non-uniform film structure. .

In response to the above proposal, as a method for making the membrane surface hydrophilic without impairing the physical properties of the polysulfone polymer, for example, JP-A-60-87803 proposes forming a polysulfone membrane and then adding chlorosulfonic acid to the membrane while maintaining the membrane shape. JP-A-59-186604 describes a method for sulfonating polymers by
We have proposed methods for treating polysulfone films with positive column plasma. However, such a method is a complicated method that applies only to products or semi-finished products on which film formation has been completed and requires special methods and equipment, and is therefore not common.

(Means for Solving the Problems) In view of the above, as a result of intensive research, the present inventors have discovered a block polymer in which the end portion of polyether sulfone and a sulfonated aromatic polysulfone are bonded through covalent bonds. The present inventors have discovered that a hydrophilized polysulfone membrane can be obtained by using this as an element of the membrane material, and have completed the present invention. The purpose of the present invention is to develop a hydrophilic polysulfone membrane as a separation membrane with excellent physical properties and good permeability without impairing the excellent physical properties of polysulfone membranes such as heat resistance and chemical resistance. The goal is to provide a membrane.

That is, the present invention provides a repeating unit, and a terminal portion of a polyethersulfone having the following formula (
A block polymer in which a terminal portion of an aromatic polysulfone B having at least one repeating unit selected from n) to (IV) or a sulfonated repeating unit thereof together with a repeating unit of formula (1) is bonded by a covalent bond. This is an aromatic polymer membrane characterized by containing.

Here, the repeating unit of (1) has already been published in JP-A-59-7412.
As shown by grade 8, it is difficult to be chemically modified. For example, in sulfonation, it is not substantially sulfonated by concentrated sulfuric acid, but is sulfonated only by using a strong sulfonating agent such as fuming sulfuric acid or chlorosulfonic acid. On the other hand, (II) to (IV) are more easily modified chemically than (1); for example, (III) and (IV) are
In sulfonation, it is rapidly sulfonated by concentrated sulfuric acid.

Furthermore, for (II), a strong sulfonating agent such as chlorosulfonic acid is generally used, but in the copolymer with (1), it is the repeating unit (It) that undergoes substantial sulfonation. It is known that (for example, Jour
nal of PolymerScience, 22
．． 721-737 (1984)).

In the present invention, chemically stable polyether sulfone A consisting of (1) and (II) to (■
It is important that aromatic polysulfone B containing ) is bonded in a block form. Aromatic polysulfone of random copolymer type consisting of chemically stable repeating units and repeating units susceptible to chemical changes is disclosed in JP-A-59-74128.
For example, when such a copolymer is sulfonated, the sulfonation occurs randomly and evenly over the entire polymer, so a separation membrane made of such a polymer has a Mechanical strength and heat resistance will be significantly reduced. However, with the block polymer of the present invention, even in the case of sulfonation, the sulfonated B component and the non-sulfonated A component cause microphase separation, so the mechanical strength of the entire separation membrane is substantially reduced. Strength and heat resistance hardly decrease.

The method for synthesizing the block polymer, which is a component of the membrane of the present invention, is as follows: (1) Polyether sulfone A is synthesized according to a conventional method (for example, the method disclosed in Japanese Patent Publication No. 47-617 and Japanese Patent Publication No. 42-7799). (II) to (TV) by a known method (for example, Canadian Patent No. 847963) using the active end as a polymerization initiation point without stopping the reaction.
A method of copolymerizing the monomer of (1) with the monomer of (1).

(2) Terminal group of commercially available polyether sulfone A (-Cj
2 or -〇) A method of using 1) as it is or changing it to another functional group and reacting it with aromatic polysulfone B having an active end by a known organic chemical reaction.

There are two main methods. The polymers synthesized by these methods contain a block polymer represented by the general formula %() (where l is 0 or l, m and n are integers of 1 or more).

The purity of the block polymer here does not need to be 100% (there is no problem even if unreacted aromatic polysulfone B and unreacted polyether sulfone A are mixed. Since polysulfone B is selectively and almost completely hydrophilized in the hydrophilization reaction (mainly sulfonation reaction), it can be extracted and removed by washing with water or the like.

Furthermore, the above block polymer and conventional aromatic polysulfone (preferably polyether sulfone having the repeating unit (1)) may be mixed in any proportion.

However, the content of aromatic polysulfone component B in the film is 2
% by weight or more and 65% by weight or less, and the ion exchange capacity of the membrane after sulfonation is O, 1 meq/g or more, 2 a+e
It is particularly preferable that it is q/g or less.

When the content of aromatic polysulfone component B is less than 2% and the ion exchange capacity is less than 0.1 meq/g, it is difficult to improve the hydrophilicity of the membrane. On the other hand, if the B content exceeds 65% and the ion exchange capacity exceeds 2 meq/g, the mechanical strength and heat resistance of the membrane will be significantly impaired.

The aromatic polymer membrane of the present invention contains the above-described block polymer, and is finally subjected to a hydrophilic treatment. This hydrophilization treatment, that is, the introduction of parent wood groups, may be carried out at the stage of aromatic polysulfone B or its monomer used when synthesizing the block polymer, or may be carried out subsequent to the synthesis of the block polymer. Of course, after forming into a separation membrane, it may be subjected to hydrophilic treatment.

The most preferred hydrophilic treatment is sulfonation.

The sulfonation reaction can be carried out by a known method, for example, by immersing the aromatic polymer, which is the material of the membrane of the present invention, in concentrated sulfuric acid or by bringing it into contact with vapors of fuming sulfuric acid or chlorosulfonic acid. The aromatic polymer of the present invention sulfonated in this way has a structure in which -3O3H groups are introduced into some or all of the repeating units of aromatic polysulfone B in the block polymer, but of course -S O3-M” group (
M is an alkali metal or NR, (R is an alkyl group)
) may be converted into salts such as

Incidentally, the aromatic polymer film of the present invention is prepared by using the above-mentioned block polymer-containing aromatic polymer in a conventional aromatic polysal polymer solvent, such as N.

N-dimethylacetamide, N,N-dimethylformamide, N-methyl-2-pyrrolidone, 2-pyrrolidone,
Water-soluble solvents such as dimethyl sulfoxide, sulfolane, and tetrahydrofuran (these are the first group of solvents)
It is possible to form a film from this solution by a known phase transformation method by dissolving it in a water-insoluble halogenated hydrocarbon solvent such as dichloromethane, methylene chloride, or chloroform (these are the solvents of group Ⅰ). That is, when using the first group of solvents, the above-mentioned aromatic polymer is dissolved therein, and if necessary, an electrolyte, a water-soluble polymer, or a water-soluble poor solvent (for example, water, alcohols, ketones, etc.) is added. A film-forming solution (this is called a dope) is prepared by simultaneously dissolving and mixing (e.g., dope). In order to form a separation membrane in the form of a sheet or tube, the dope is spread over a suitable sheet or tube support (e.g. glass plate or tube, non-woven fabric, cloth, etc.) to a thickness of several tens of microns to several hundred microns. Casting by an appropriate method within the range of
If necessary, after leaving it in an atmosphere under certain conditions (for example, air containing vapor of a poor solvent) for a certain period of time, remove the poor solvent (mainly water).
Wet or wet-dry film formation is performed by immersing the material in a coagulation bath consisting of sol-gel phase conversion. Further, a hollow fiber membrane can be manufactured by spinning the dope through a hollow fiber forming nozzle using a known method.

In addition, when using the solvent of Group Ⅰ, the dope prepared in the same manner as in Group 1 is cast into a sheet shape, a tube shape, or a hollow fiber shape in the same manner as in the case of Group 1, or A relatively porous separation membrane can be finally obtained by discharging and exposing to an atmosphere under a certain condition for a certain period of time to cause liquid-liquid phase separation and further evaporating the solvent. This method is almost the same as the dry film forming method for cellulose acetate membrane filters.

(Effects of the Invention) The aromatic polymer membrane of the present invention finally has a block polymer of polyether sulfone and sulfonated aromatic polysulfone as a constituent element.

Therefore, the microporous surface of the membrane is highly hydrophilic, but the polymer matrix, which essentially determines the structure of the membrane, is mainly composed of polyether sulfone, resulting in a membrane with a microphase-separated structure. There is. As a result, the membrane of the present invention has a high water permeation rate and is resistant to dirt, while its mechanical strength, heat resistance, chemical resistance, etc. are almost comparable to those of conventional aromatic polysulfone membranes. It has the ability to Therefore, it can be effectively used in membrane separation operations under harsh conditions that conventional separation membranes mainly made of hydrophilic polymers (e.g., cellulose acetate membranes or hydrophilized polysulfone membranes made by conventional methods) cannot withstand. It has advantages.

(Example) Next, the present invention will be specifically explained with reference to an example. (E) x Water permeation time (days) x Filtration pressure (Kg/
cm) (However, the Lp value after 1 hour of filtration is Lp', and the value after 3 hours is Lp3.)

Further, the amount of filtration and adsorption of the separation membrane was measured using 100 pp■ ovalbumin phosphate buffer IT (25°C).

In other words, the concentration of the ovalbumin solution before filtration is Cl1)
Let pHl+capacity be V, d (approximately 50 sffi), and use a separation membrane with an effective membrane area Sc+1 (13,5 c+fl) to apply a pressure of 3 kg/CTM to a capacity ■2- (approximately 10 d
), the concentration of the concentrate Czppra
, the volume of the permeate V3d, and the concentration Capl)In, the amount of adsorption per filtration area m (μg/cJ) can be calculated by the following formula.

Example 1 Polyether sulfone (Victrex 5003p, r(
1, average molecular weight 12.000) was dissolved in a mixed solvent of 400 d of dimethyl sulfoxide (hereinafter referred to as DMSO) and 200 d of benzene chloride (hereinafter referred to as PhCffi) at room temperature, and a 0.5 N NaOH aqueous solution 13 was added to this. The reaction was carried out at room temperature for 2 hours to obtain a solution of polyether sulfone having sodium ferulate terminals. α to this
, 1.5 g of α'-dichloro-P-xylene was added, and the reaction was carried out at room temperature for 1 hour and at 70°C for 2 hours to introduce active chloromethyl groups at the polymer terminals. The solution of this reaction mixture is called Solution A.

On the other hand, an aromatic polysulfone having repeating units of formulas (■) and (1) in a molar ratio of 1:1 and having potassium ferulate terminals was synthesized by a known method. That is, 5.5 g of hydroquinone, 13 g of 43% KOH aqueous solution,
50 DMSO.

and 6 ml of benzene were charged, and N2 gas was blown into the reactor. The mixture was refluxed for 3-4 hr, water was continuously removed as an azeotrope with benzene, and 13
Benzene was sufficiently distilled off at around 0'C. Cool the mixture and 4,4°-dichlorodiphenylsulfone 14.
4 g, &['g water DM 5040d were added under N2 atmosphere. This mixture was heated to 130°C and maintained at 130-140°C for 6 hours with thorough stirring. This reaction mixture was poured into 300 mjt of water, and the white polymer was washed with water in a furnace and dried under reduced pressure to obtain the desired aromatic polysulfone.

This aromatic polysulfone 15g-1-DMS05M and P
hCj! This solution was added to the above-mentioned solution A and reacted at room temperature for 1 hour and at 70°C for 2 hours, and then concentrated sulfuric acid was added to stop the reaction.

The reaction mixture was diluted with methanol/water (8/2 (volume ratio)).
After reprecipitation, the polymer was washed with water in a separate furnace and then dried under reduced pressure. From the 270 MHz 'H-NMR analysis and the measurement of molecular weight distribution by organic solvent-based gel permeation chromatography, this polymer has a repeating unit (1) and ( IV
) was confirmed to be a block polymer in which the aromatic polysulfone B having equimolar amounts of polysulfone B was bonded in blocks through benzyl ether bonds. Also, B of this polymer
The content of the components was 20%.

20 g of this block polymer was shaken for 18 hours with 100 rnl of concentrated sulfuric acid, further 50 d of concentrated sulfuric acid was added, and shaking was continued for 18 hours. Next, add this solution to 50% W/
The white precipitate was washed with water in a furnace and then dried under reduced pressure. This precipitate is essentially a block polymer in which the repeating unit (IV) in the block polymer of Example 1 is monosulfonated.
Confirmed by MR analysis.

20 parts by weight of this block polymer was dissolved in a mixed solvent containing 70 parts by weight of DMS and 10 parts by weight of acetone to obtain a dope. This was cast onto a polyester nonwoven fabric to a thickness of 150 μm, and after 30 seconds, it was immersed in water at 10'C to solidify, thereby obtaining a separation membrane.

The ion exchange capacity of this membrane is 0.6 meq/g, and L
P' = 15 Bo/Bo, Day, Temple/Cm1. β=0%1RO=
100% and m = 10 μg/cd, and the film performance was significantly improved by converting it into sulfur/[/phon. Moreover,
There was no change in performance of this membrane even after it was immersed in hot water at 80°C for one month.

Comparative Example 1 A N membrane was produced in the same manner as in Example 1, except that polyether sulfone (Victrex 5003p) used in the synthesis of Example 1 was used instead of the block polymer. This membrane has no ion exchange function and Lp' = 8 po/
Bo・day・kg/cd, β=10%.

Ro=100%, m=70 μg/C11l, and the film was easily stained.

Claims (5)

[Claims] (1) Repeating unit▲There are mathematical formulas, chemical formulas, tables, etc.▼・・・・・・( I
) and at least one repeating unit selected from the following formulas (II) to (IV) or a repeating unit obtained by sulfonating the terminal part of a polyethersulfone (hereinafter referred to as A) having the formula (I) An aromatic polymer membrane comprising a block polymer in which a repeating unit of and a terminal portion of an aromatic polysulfone (hereinafter referred to as B) are bonded by covalent bonds. ▲There are mathematical formulas, chemical formulas, tables, etc.▼・・・・・・(II) ▲There are mathematical formulas, chemical formulas, tables, etc.▼・・・・・・(III
) ▲There are mathematical formulas, chemical formulas, tables, etc.▼・・・・・・(IV) (2) Homopolymer of repeating units of formula (I) or formula (II)
The aromatic polymer membrane according to claim 1, comprising a mixture of the block polymer and a copolymer having at least one repeating unit selected from ) to (IV) together with the repeating unit of formula (I). . (3) The content of aromatic polysulfone component B in the aromatic polymer membrane is 2% by weight or more and 65% by weight or less, and the ion exchange capacity of the membrane is 0.1 meq/g or more and 2 meq/g.
The aromatic polymer membrane according to claim 1, wherein the aromatic polymer membrane has a molecular weight of less than g. (4) The block polymer has the general formula, Bl-(A-B)m...(V) or Al-(B-A)n...(VI) (where l The aromatic polymer membrane according to claim 1, wherein m and n are integers of 1 or more. (5) The aromatic polymer membrane according to claim 1, which is produced using a dry, dry-wet, or wet phase conversion film forming method.