JPH0628713B2 - Hydrophilized polysulfone membrane - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a hydrophilic polysulfone membrane,
More specifically, it has a block polymer in which the end portion of the aromatic polysulfone polymer and a hydrophilic compound are covalently bonded to each other as one of the constituent elements, and has excellent heat resistance, chemical resistance, etc., and good permeation performance. And a hydrophilic polysulfone membrane.

[Conventional technology]

Polysulfone resin is widely used as a separation membrane material having excellent chemical and thermal durability. Many polyaryl ether sulfone polymers are known as polysulfone resins, and these resins are generally Is characterized by a structure containing a repeating unit represented by As expected from this structure, the polysulfone resin has excellent durability and stability, but exhibits a hydrophobic property. Typical examples are Victrex from Imperial Chemical Industries and Udel from Union Carbide.
The water absorption rate is 0.4% for the former and 0.3% for the latter (both ASTM D57
0), which is a water absorption rate of 1/10 or less of 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" and "poor water permeability" once dried.
There were many problems such as "hydrophobic solutes tend to adhere to the surface of the film and cause contamination."

In order to solve such problems, various methods for improving the polysulfone membrane have been proposed. As a method for providing a hydrophilized polysulfone membrane by introducing a hydrophilic group or a hydrophilic polymer into an aromatic polysulfone polymer, for example, Japanese Patent Publication No. 53-13679 and Japanese Patent Laid-Open No. 59-196322 disclose sulfone in the polymer main chain. The acid group is described in JP-A-57-17.
No. 4104 proposes a method for providing a reverse osmosis membrane or the like from a hydrophilic polysulfone polymer which is hydrophilized by introducing or grafting polyethyleneimine polymers into the polymer main chain. Since all of these methods are modification means for directly bonding a hydrophilic group or a hydrophilic polymer to the aromatic ring of the aromatic polysulfone polymer main chain through a covalent bond, compared with a membrane composed of an unmodified polymer. It is unavoidable that physical properties such as heat resistance deteriorate. Further, it can be said that this is a modification method involving a remarkable change in the physical properties of the film, such as the film obtained is swollen with water when the ratio of the hydrophilic groups introduced into the polymer is large.

On the other hand, various hydrophilized polysulfone membranes made of a mixed polymer obtained by blending a hydrophilic polymer with an aromatic polysulfone polymer have been proposed. For example, JP-A-57-5
No. 0507 describes a cellulose derivative as disclosed in JP-A-60-20.
No. 6404 proposes a hydrophilized polysulfone membrane composed of a mixed polymer in which ethylene-vinyl alcohol copolymers are blended. However, in order to obtain a substantially hydrophilized polysulfone membrane, it is necessary to blend a considerable amount of different polymers, and to obtain a homogeneous blend with a polymer having a large molecular cohesive force such as an aromatic polysulfone polymer. Was difficult. In particular, when a film-forming solvent containing a polar organic solvent and a polymer is brought into contact with a non-solvent of a polymer containing water as a main component, and the polymer is coagulated and molded to form the hydrophilic polysulfone film, It is difficult to obtain a uniform film forming solvent, and there is a problem in the stability of the solution such as gelation or phase separation during standing, or when the polymer coagulates by contact with a non-solvent There was also a possibility that the separation of the film would occur and the structure of the film would become non-uniform. It was considered that the addition of a different polymer to this sheath causes deterioration of physical properties such as heat resistance and chemical resistance of the film due to the formation of a heterogeneous film structure in addition to the effect of adding the polymer having poor physical properties. .

In contrast to the above proposal, as a method of making the membrane surface hydrophilic without impairing the physical properties of the polysulfone polymer, for example, JP-A-61-87803 discloses a polysulfone membrane which is then formed into a chlorosulfonic acid in the form of a membrane. JP-A-59-186604 discloses a method of sulfonating a polymer by
Each method of positive column plasma treatment of polysulfone film is proposed. However, such a method is a general method, which is only a product or a semi-finished product for which film formation has been completed, requires a special method and apparatus, and is not general.

[Object of the Invention]

As a result of earnest studies in view of the above, the present inventors have found that a block polymer obtained by covalently bonding a terminal portion of an aromatic polysulfone polymer and a hydrophilic compound is used as an element of the membrane material, thereby making the hydrophilic polysulfone. The inventors have found that a film can be obtained, and completed the present invention. The object of the present invention is to provide a hydrophilized polysulfone membrane as a separation membrane having excellent physical properties with almost no loss of physical properties such as excellent heat resistance and chemical resistance of the polysulfone membrane, and having good permeation performance. To do.

[Structure of Invention]

 The hydrophilic polysulfone membrane of the present invention has the following constitution.

A general formula in which a terminal portion of an aromatic polysulfone polymer (denoted by A) and a hydrophilic compound (denoted by B) are bound by a covalent bond, Or (Here, 1 is 0 or 1, and m and n are integers of 1 or more). A hydrophilized polysulfone membrane is characterized by containing a block polymer.

Here, the aromatic polysulfone polymer is a polymer having a repeating unit represented by the following general formula [III] or [IV].

(However, M represents the same or different aromatic groups, R represents a divalent organic group, and a, b, and c each represent 0 or 1.) As a specific example, one of the following repetitions: unit An aromatic polysulfone polymer having a is preferably used, and an aromatic polysulfone polymer having the repeating units (1) and (2) is particularly preferable.

These aromatic polysulfone polymers are prepared by known means of polycondensing monomers such as dichlorodiphenyl sulfone, dichlorophenyl sulfone and bisphenol, or aromatic disulfonyl chloride and bisphenol using alkali such as potassium hydroxide. Can be synthesized, but as a polymer with repeating units of formula (1) U
It is also possible to obtain and use an aromatic polysulfone polymer having a sufficient degree of polymerization from Union Carbide under the trade name of del, and from Imperial Chemical Industries under the trade name of Victrex as a polymer having the repeating unit of formula (2). it can. Furthermore, unless a polymerization terminator is used in the synthesis of the polymer, the terminal portion of the polymer can be a monochlorophenyl group or a monohydroxyphenyl group depending on the monomer used in excess, and it is commercially available. From the aromatic polysulfone polymer, a polymer having any end group can be selected.

The block polymer constituting the present invention is a block polymer having a structure in which a hydrophilic compound is covalently bonded to the end of the aromatic polysulfone polymer by utilizing the chemical reactivity of the end groups of the aromatic polysulfone polymer. Yes, it can be obtained by the means described below.

The above block polymer is, for example, by introducing a polymerizable group moiety into the terminal part by reacting the terminal group of the aromatic polysulfone polymer with a polymerizable compound having an active group capable of reacting with this to form a chemical bond, and then hydrophilic. It can be synthesized by a known method in which a polymerizable monomer or a precursor monomer which can be easily hydrophilized after polymerization is subjected to a polymerization reaction. The most common method for introducing a vinyl-polymerizable functional group is Makromol. Chem. 185 , 1867 (1984) and the introduction of a styryl group by reacting an aromatic polysulfone polymer having a repeating unit of the formula (3) with chloromethylstyrene. However, in order to avoid the formation of a crosslinked structure in the polymerization reaction and the difficulty of controlling the polymerization, a hydrophilic compound is added to the end portion of the aromatic polysulfone polymer by a polymer reaction suitable for the end group of the aromatic polysulfone polymer. It is desirable to introduce it.

For example, when the terminal group of the aromatic polysulfone polymer is a monochlorophenyl group, a nucleophilic substitution reaction at the aromatic ring at the polymer terminal end with a hydrophilic compound having a nucleophilic active group such as an alcoholate results in a terminal group. Is a monohydroxyphenyl group, the terminal group is activated to a phenolate ion, and then the hydrophilic compound having an active leaving group such as halogen is subjected to a nucleophilic substitution reaction to give hydrophilicity to each terminal site. The above block polymer can be obtained by the method of introducing a volatile compound. Furthermore, the introduction of the above-mentioned polymerizable group and the subsequent polymerization reaction with hydrophilic monomers, or the introduction of the hydrophilic compound by a polymer reaction is carried out by the aromatic polysulfone immediately after the synthesis and the end portion of which remains activated. It can be carried out subsequently using a polymer, or can be carried out by activating the end of a commercially available aromatic polysulfone polymer. Generally, the chemical reaction of the polymer end group is carried out in a state where the polymer is dissolved in a polar organic solvent, etc., so the polymer solution after the reaction is left as it is, or after adding additives or adjusting the polymer concentration, the stock solution for film formation is used. It is also possible to use

An end portion of the desired aromatic polysulfone polymer,
As means for obtaining a block polymer covalently bonded to a hydrophilic compound, a hydrophilic compound is bonded to the main chain of an aromatic polysulfone polymer, or means for giving a block polymer having extremely poor processability by cross-linking or the like Unless otherwise specified, the method for introducing the polymerizable group or the polymer reaction method is not limited.

Further, in the case of a polymerization reaction with the above-mentioned hydrophilic monomer or a polymer reaction using a hydrophilic compound having a plurality of functional groups capable of becoming an active group, a plurality of each can be obtained by appropriately selecting reaction conditions. It is possible to obtain a block polymer in which an aromatic polysulfone polymer and a hydrophilic compound are alternately bonded in a block shape. Generally, a block polymer in which a hydrophilic compound is bonded to both ends or only one end of an aromatic polysulfone polymer is desirable,
Use of a block polymer in which a plurality of aromatic polysulfone polymers and hydrophilic compounds are alternately bonded in a block shape does not hinder the object of the present invention.

The hydrophilic block polymer used in the present invention has an aromatic polysulfone polymer having an average molecular weight M _A and a hydrophilic compound having an average molecular weight M _B : A block polymer having a block ratio defined by the formula of 0.1% or more and 30% or less is desirable.

A membrane having a block polymer with a block ratio of less than 0.1% as one component cannot sufficiently hydrophilize the membrane surface and the surface in contact with water, and the ratio of the hydrophilic compound to the polysulfone chain. When the ratio becomes high, it becomes difficult to generate a microscopic heterogeneous structure of hydrophilic / hydrophobic parts due to phase separation.

Therefore, the hydrophilic compound that constitutes the present invention refers to a substance that generally has an affinity for water molecules through a hydrogen-bonding functional group or electrolytic group, but is preferably a water-soluble oligomer or polymer, or an intramolecular compound. A compound having one or more hydroxyl groups is used. Specifically, as water-soluble oligomers or polymers, natural polymers and oligomers such as gelatin, casein, pectin, dextran, starch and sodium alginate, semi-synthetic polymers or oligomers such as methylcellulose, carboxymethylcellulose, hydroxylethylcellulose and carboxymethylstarch. Polyvinyl alcohol, polyvinyl methyl ether, polyvinyl pyrrolidone, sodium polyacrylate, polyethyleneimine, polyacrylamide, polyethylene glycol and the like, and synthetic polymers or oligomers and their copolymers or oligomers are preferably used, but corresponding block polymers From the viewpoint of the physical properties of (1), the number of repeating units of these polymers or oligomers is preferably 1 or more and 30 or less.

Specific examples of the compound having one or more hydroxyl groups include formaldehyde, ethylene glycol, glycerin, sorbitol, pentaerythritol, polyols such as inositol, glucose, lactose, and the like.
Examples include monosaccharides such as saccharose and raffinose, polysaccharides and derivatives thereof. However, it is a hydrophilizing compound that can obtain a block polymer in which a target aromatic polysulfone polymer site and a hydrophilic compound are covalently bonded, and the heat resistance and chemical resistance of the hydrophilized polysulfone film The compound is not limited to the above hydrophilic compounds as long as the compound does not significantly deteriorate the physical properties.

The hydrophilized polysulfone film of the present invention is a resin containing the above block polymer, which is made into a thin film by a casting method or a method of extruding from a nozzle or the like from a stock solution for film formation which is dissolved in a polar organic solvent, and the solvent is evaporated to homogenize Obtaining a hydrophilized polysulfone membrane by a known method in which phase separation is caused by a method such as forming a membrane or contacting with a non-solvent of a polymer containing water as a main component, and then polymer coagulation molding to form a porous membrane. You can In addition, by appropriately selecting the film forming method, the hydrophilized polysulfone film can be obtained in any shape such as a flat film, a tubular film, and a hollow fiber film. Furthermore, it is also possible to use the hydrophilized polysulfone film as a base film or a thin film, or as a composite film in which different thin films or base films are respectively combined.

The resin containing the above-mentioned block polymer used here was a mixture of a block polymer in which a terminal portion of an aromatic polysulfone polymer and a hydrophilic compound were covalently bonded and an aromatic polysulfone polymer in an arbitrary ratio. As long as the resin is mainly composed of components, it does not hinder the present invention even if it contains an additive depending on the purpose of producing or using the separation membrane.

The hydrophilic polysulfone film of the present invention has a microphase-separated structure in which a hydrophilic part and a hydrophobic part are sea-island-like by selecting film forming conditions, or a hydrophilic part is present only on the surface like a resin structure constituting the film. It is possible to have an extremely microscopic non-uniform structure in which the particles gather. In particular, a film-forming method of contacting a film-forming solution containing a polar organic solvent and a polymer with a non-solvent of a polymer containing water as a main component, and coagulating and molding the polymer is a solution of the film-forming solution caused by the non-solvent. Form a relatively macroscopic heterogeneous membrane structure that results from phase separation. Further, the polymer part of the film structure has a microscopic non-uniform structure of the hydrophilic part and the hydrophobic part. Therefore, the film forming method is
This is a preferred method for producing a separation membrane having highly controlled macro and micro structures. That is, in the case of forming a heterogeneous structure film by the phase conversion method, hydrophilic parts gather on the surface of the polymer phase generated by phase separation, and at the same time, hydrophobic polysulfone chains gather inside, so that all of the film surface and the inside of the film are gathered. It is possible to prepare a polysulfone membrane having a structure in which the surface contacting with water is coated with a hydrophilic compound.

〔The invention's effect〕

The hydrophilic polysulfone membrane of the present invention is a block polymer in which the terminal portion of the aromatic polysulfone polymer, which is a constituent element, and the hydrophilic compound are bound by a covalent bond, while hardly impairing the excellent physical properties of the aromatic polysulfone polymer. Since it has good hydrophilicity, it has excellent heat resistance, chemical resistance, and the like, as well as excellent permeation performance, particularly water permeation performance.

Further, since the membrane of the present invention hardly adsorbs solutes such as proteins and has good stain resistance, it is possible to obtain a stable permeated liquid with little deterioration in permeation performance. Further, since the contaminants adhering to the film surface are weakly adsorbed, there is an advantage that the cleaning and recovery operation can be easily performed.

The membrane of the present invention has good wettability with water, and can be easily re-wet without the need for hydrophilic treatment with a wetting agent or the like.

Hereinafter, the present invention will be specifically described with reference to examples.

The block compound of the hydrophilic compound and the aromatic polysulfone polymer used in the present invention was synthesized according to the reference example.
The structures of the polymer end groups of all the polymers obtained by the reaction were determined by spectral analysis by 270 MHz FT-NMR using deuterated dimethyl sulfoxide as a solvent. Further, the reaction rate of the hydrophilic compound introduced into the terminal group of the aromatic polysulfone polymer was calculated by the following formula.

The abbreviations of the solvents used are as follows.

DMSO: dimethylsulfoxide, DMF: dimethylformamide, NMP: N-methyl-2-pyrrolidone Further, the performance evaluation of the obtained separation membrane was performed by using distilled water and ovalbumin (MW45000, manufactured by Wako Pure Chemical Industries, Ltd.) 1
Using 00 ppm 1/15 M phosphate buffer as a test solution, the pure water permeability (Lp) and the ovalbumin exclusion rate (R ₀ ) were measured.

LP and Ro are defined by the following formulas.

Reference Example 1 150 ml of DMS was placed in a 300 ml three-necked flask, and 0.27 g of sodium ethoxide was added and stirred under a nitrogen stream. Next, pentaerythritol (Wako Pure Chemical Industries
3.6 g) was added, the temperature was raised to 85 ° C., and stirring was continued for 1.5 hours. Then, the aromatic polysulfone polymer (V
3. Add 20 g of ictrex 4800P, manufactured by Imperial Chemical Industries, Ltd., and keep the reaction solution temperature at 80 ° C.
Stir for 5 hours. After cooling the reaction mixture to room temperature, 5
Transferred to a 00 ml separatory funnel. The reaction solution was added dropwise from the separatory funnel into the saturated saline solution of 3 under vigorous stirring to obtain a suspension containing a white flake-like precipitate. The suspension was centrifuged at 10,000 rpm for 30 minutes to collect the precipitate. The collected precipitate was vigorously stirred in distilled water 2 to suspend it for a while, then suctioned with paper and washed thoroughly with water. The resulting precipitate was placed in a vacuum dryer at 80 ° C for 1
After vacuum drying for 24 hours, 15.8 g of white powder was obtained. The recovery rate of the charged polymer was 79%. The obtained polymer was soluble in polar organic solvents such as DMSO, NMP and DMF.

It was confirmed by NMR spectrum analysis that the obtained polymer was an aromatic polysulfone polymer having a repeating unit of the above formula (2) having a terminal group represented by the following formula (6).

^The reaction rate determined by ¹ H-NMR was 78%.

Example 1 The polymer obtained in Reference Example 1 was dissolved in DMSO at a concentration of 20% by weight.
Was dissolved in to form a uniform solution and then degassed by standing to obtain a solution for film formation. Apply this film-forming solution onto a polyester nonwoven fabric
It is cast at a thickness of 50 μm and left at room temperature for 30 seconds, then 10
The separation membrane produced by coagulating the polymer by immersing in water at ℃ was collected.

The pure water permeability (Lp) of the obtained membrane is 32 m ³ / m ² · day · kg
The ovalbumin rejection (Ro) was 81% at / cm ² .

Comparative Example 1 Instead of the polymer obtained in Example 1 and Reference Example 1, Victrex.
4800P (Made by Imperial Chemical Industries)
A separation membrane was obtained in the same manner except that was used.

The pure water permeability (Lp) of the obtained membrane was 5.2 m ³ / m ² · day · kg / cm ² , and the rejection rate (Ro) of ovalbumin was 81.
%Met.

Claims (5)

[Claims] 1. A terminal portion of an aromatic polysulfone polymer (denoted by A) and a hydrophilic compound (denoted by B).
General formula in which and are linked by a covalent bond Or (Wherein, l is 0 or 1, m and n are integers of 1 or more), a film-forming liquid containing a polymer containing a block polymer and a polar organic solvent is used as a non-solvent for a polymer containing water as a main component. A hydrophilized polysulfone membrane, which is produced by subjecting the polymer to coagulation and molding by contacting with a polymer. 2. When the average molecular weight of the aromatic polysulfone polymer is M _A and the average molecular weight of the hydrophilic compound is M _B , The hydrophilized polysulfone membrane according to claim 1, which is a block polymer having a block ratio defined by the formula of 0.1% or more and 30% or less. 3. A repeating unit of an aromatic polysulfone polymer, Or The hydrophilized polysulfone membrane according to claim 1, represented by: 4. The hydrophilized polysulfone membrane according to claim 1, wherein the block polymer is a block polymer in which a hydrophilic compound is bonded to both ends or one end of an aromatic polysulfone polymer. 5. A hydrophilic compound selected from the group consisting of water-soluble oligomers or polymers consisting of 1 to 30 repeating units and the group consisting of compounds having one or more hydroxyl groups in the molecule. The hydrophilic polysulfone membrane according to claim 1, which is a hydrophilic compound containing two or more species at an arbitrary ratio.