JPS62168503A - Separation membrane - Google Patents

Abstract

PURPOSE:To enhance the hydrophilic property and water transmitting speed of a polysulfone separation membrane excellent in heat resistance, chemical resistance and mechanical strength, by forming a membrane using a polymer obtained by the graft polymerization of polysulfone with a hydrophilic copolymer according to a wet membrane forming process. CONSTITUTION:The terminal of polysulfone is chemically bonded to a hydrophilic copolymer to prepare a graft polymer. In preparing the graft polymer, a method for reacting polysulfone having a reactive terminal functional group with the hydrophilic copolymer having a functional group capable of reacting said functional group in the side chain thereof or a method for reacting polysulfone having a terminal vinyl group and a vinyl monomer is used and the amount of the graft polymer is set at least to 20mol% or more. A separation membrane is prepared using this polymer according to a wet membrane forming process. The obtained membrane can be enhanced in its water transmitting speed while the heat resistance and mechanical strength of polysulfone are kept.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Background) The present invention relates to a novel separation membrane made of a polysulfone resin containing a hydrophilic graft polymer.

Membrane separation technology has attracted attention for its energy saving and compactness, and has made remarkable progress. Many types of polymers have been researched and developed as membrane materials for permselective separation membranes used in such systems, including cellulose,
Polymers such as polyamide, polyacrylonitrile, polycarbonate, polyphenylene oxide, and polysulfone are used.

Among them, polysulfones and polycarbohydrates ($-)
Hydrophobic polymers such as polyphenylene oxide, polyphenylene oxide, and fluorine-containing polymers are originally used as engineering plastics, but because of their excellent heat resistance and mechanical properties, they have become the main material for separation membranes. It is starting to be used.

Among these membrane materials, aromatic polysulfone membranes are attracting attention as they have high mechanical strength, excellent heat resistance, and chemical resistance.

(Prior art and its disadvantages) However, aromatic polysulfone resin has low hydrophilicity and is a material that is difficult to wet with water, so separation membranes made of this resin have a significantly higher water permeation rate than separation membranes made of hydrophilic materials. is low, resulting in poor filtration efficiency.

Therefore, various attempts have been made to improve the water permeability of aromatic polysulfone separation membranes.

For example, JP-A-58-104940 discloses a polysulfone separation membrane containing polyvinylbitetraridone having a molecular weight of 100,000 or more and a method for producing the same. However, this method of adding a hydrophilic polymer with a molecular weight of 100,000 or more to a film-forming solution (called a dope) does not increase the polymer density of the dope. The hydrophilic polymer added to the polysulfone separation membrane remains in the exchange body and is not removed even during subsequent use, resulting in an extremely dense structure and a decrease in water permeation rate.

On the other hand, JP-A-54-26283 discloses a method in which polyethylene glycol having a molecular weight comparable to that of an oligomer is added to a polysulfone solution and used as a dope.

However, in this method, water is used as a coagulation bath for film formation, and oligomer-level polyethylene glycol does not remain in the film but is completely eluted into the water, and the hydrophilicity of the polysulfone film is not substantially increased. Therefore, no significant improvement in water permeation rate can be expected.

In addition, in JP-A-57-174104, a reactive functional group is introduced into the benzene ring of a polysulfone polymer, and after wet film formation from this polymer solution, a solution of a hydrophilic substance that can react with the functional group is added. A method for crosslinking modification by treatment with is disclosed. However, the separation membranes obtained by this method are limited to reverse osmosis membranes, and it is extremely difficult to manufacture a wide variety of separation membranes.

In addition, the benzene rings of polysulfone polymers generally have low reactivity, which limits the types of functional groups that can be introduced, and it is extremely difficult to control the introduction rate. There may be a marked decrease in sexual performance.

(Structure of the present invention) The present inventors have solved the above-mentioned problems, have a high water permeation rate, and have heat resistance peculiar to polysulfone polymers.
As a result of intensive studies on polysulfone-based resin separation membranes that have chemical resistance and high mechanical strength, we have developed a hydrophilic polysulfone-based resin containing a graft polymer in which a hydrophilic copolymer is used as a backbone polymer and a polysulfone-based polymer is used as a branch polymer. Invented a manufactured separation membrane.

That is, the present invention uses a hydrophilic copolymer having a total polymerization degree of 4 or more and 100 or less, of which the polymerization degree of the hydrophilic component accounts for 50 or more of the total polymerization degree, as a backbone polymer, and a polymerization degree of 30.
A separation membrane made of a polysulfone resin, characterized in that it is wet-formed from a solution of a hydrophilic polysulfone resin containing a graft polymer having polysulfone polymers having a molecular weight of 100 or less as branch polymers. ”.

The polysulfone polymer referred to in the present invention has the following formula (
Aromatic polysulfone polymers having structures I) to (m) are representative.

In the present invention, a polysulfone resin containing a graft polymer in which the terminal end of a polysulfone polymer as described above is chemically bonded to a hydrophilic copolymer is used as a membrane material. In order to produce a polysulfone resin containing a graft polymer, a copolymer having a reactive functional group in its side chain is reacted with a polysulfone polymer having a functional group at its end that can react with the functional group. Alternatively, a polysulfone-based polymer having a vinyl group at the end is copolymerized with a vinyl yarn yarn or oligomer. A specific reactive functional group,
Examples of combinations of end groups that can react with this are listed below from known organic chemical reactions.

(1) When the terminal group is a hydroxyl group or an alkali alcoholade group: A functional group such as an acid hashide group, an acid anhydride group, a glycidyl group, a halomethyl group, or a sulfonyl halide group.

(2) When the terminal group is a halogenated alkyl group or a halogenated aryl group: +C ± i0M group (M is an alkali metal, n is O (valent bond) or a positive integer), an amino group (this is the first . may be secondary or tertiary).

(3) When the terminal group is an amino group: Functional groups such as halogenated alkyl groups and acid halide groups.

(4) When the terminal group is an epoxy group: Functional groups such as amine groups and alcoholade groups.

(5) When the terminal group is a carbonyl group, -Functional groups such as NHNH, groups, and hydroxyl groups.

(6) When the terminal group is a carboxyl group: a functional group such as a hydroxyl group.

In addition, the method for introducing terminal groups into polysulfone-based polymers and functional groups into copolymers may be carried out using known organic chemical reactions, and is not particularly limited. It is necessary to conduct the reaction under conditions that do not cause In the latter case, it is carried out before the copolymerization, but whether to carry out the process after the copolymerization must be selected depending on the hydrophilic component, which will be described later. Appropriate reaction conditions must be set to avoid undesirable changes or decreases in the degree of polymerization.

Of course, commercially available monomers, oligomers, or polysulfone polymers that already have reactive functional groups or terminal groups may be used as they are.

The monomer or copolymer described above is reacted with a terminally reactive polysulfone polymer to produce a graft polymer or a polysulfone resin containing the graft polymer, which is a material for the separation membrane of the present invention.

In this case, care must be taken to set reaction conditions such that only one side of the terminal group of the polysulfone polymer can react.

If both end groups participate in the reaction, a crosslinking reaction will occur, resulting in a gel-like substance insoluble in a solvent, which cannot be used in the wet membrane forming method for producing the separation membrane of the present invention. Therefore, either a method is applied in which a reactive end group is introduced in advance on only one side of the polysulfone polymer, or only one of both end groups is activated.

Also, as with known grafting reactions, the polymer products produced by the above method are not always 100-grafted polymers.

In other words, both the unreacted polysulfone polymer and the graft polymer may coexist in the polymer product after the remaining monomer or remaining copolymer is removed by a reprecipitation method or the like. In the present invention, the proportion of the graft polymer in the polymer product, i.e., the hydrophilic polysulfone resin, is at least 20%.
It is necessary to adjust the grafting reaction conditions so that the molarity is at least 40 molti, preferably 40 molti or more. If less than a 20 mol droplet of the graft polymer is contained, the hydrophilicity of the polysulfone resin cannot be improved to any significant degree, and therefore, the water permeation rate of the II membranes manufactured from such resins is often low. .

The structure 9 composition of the graft polymer also affects the hydrophilicity of the resin, that is, the water permeability of the separation membrane. In the present invention, the base polymer is a hydrophilic copolymer with a total polymerization degree of 4 or more and 100 or less, in which the polymerization degree of the hydrophilic component accounts for 50 or more of the total polymerization degree, and a polysulfone-based polymer with a polymerization degree of 30 or more and 100 or less. It must be a graft polymer with a branched polymer.

Therefore, when the total degree of polymerization of the backbone polymer is 4, the degree of polymerization of the hydrophilic component is 2 to 3, and the polysulfone polymer is bonded to other copolymer components through terminal groups. In addition, if the total polymerization degree of the backbone polymer exceeds 100, it is due to excessive hydrophilicity.
That is, it is undesirable because it causes severe swelling of the separation membrane due to water. On the other hand, if the degree of polymerization of the polysulfone-based polymer is less than 30, the heat resistance and mechanical strength of the polysulfone-based polymer cannot be fully exhibited.

Furthermore, it is extremely difficult to increase the degree of polymerization of the polymer to greater than 100 using current polymerization technology;
Controlling the degree of polymerization to 0 or more and 100 or less is technically and economically easy, and has great industrial advantages.

Further, it is preferable that the hydrophilic component in the above-mentioned backbone polymer has one or more of the following structures as a repeating unit.

-CRt　-CH! − book & Here, R1 is hydrogen or a methyl group.

The crow has 720 carbon atoms. It is.

In the present invention, the separation membrane of the present invention is manufactured by a wet membrane forming method using a solution of a polysulfone resin containing a graft polymer as described above.

The resin concentration in the polysulfone resin solution (hereinafter referred to as dope) should be 5 weight or more and less than 30 weight if the separation membrane to be manufactured is a highly fractionated ultrafiltration membrane or a precision filtration membrane. It is preferable that there be. When manufacturing low fractionation ultrafiltration membranes and reverse osmosis membranes, 10% to 40% by weight
It is preferable that it is less than

The solvent used is not particularly limited as long as it is an organic solvent that dissolves the hydrophilic polysulfone resin, but examples include N,N-dimethylacetamide, N,N-dimethylformamide,
N-methyl-2-pyrrolidone, dimethyl sulfoxide,
Examples include 2-pyrrolidone. It is also possible to add a non-solvent, an electrolyte, etc. to such a polar organic solvent.

As explained above, the separation membrane of the present invention can be prepared from rice dope! 1!
For forming a film, a conventionally used wet film forming method can be employed.

To form a separation membrane in the form of a sheet or tube, a dope is applied to a thickness of several tens of microns to several hundred microns on a suitable support (for example, a glass plate or tube, nonwoven fabric, cloth, etc.) in the form of a sheet or tube. Casting by an appropriate method,
Thereafter, it is immersed in a coagulant bath to produce a separation membrane by sol-gel phase conversion. Furthermore, a hollow fiber separation membrane can be manufactured by spinning the dope through a hollow fiber forming nozzle using a known method.

Coagulants used in film formation are polysulfone resin non-solvents that are easily mixed with polar organic solvents, such as water, aqueous solutions of electrolytes such as salt and surfactants, aqueous solutions of polar organic solvents, or hydrophilic solvents. Examples include non-solvents of polysulfone resins or aqueous solutions thereof, but water is particularly commonly used.

(Effects of the Present Invention) The characteristics of the separation membrane of the present invention are manifested by wet film forming of the hydrophilic polysulfone resin solution as described above. In other words, due to the presence of the hydrophilic graft polymer,
During wet film formation, microphase separation occurs into a component rich in hydrophilic backbone polymers and a component rich in polysulfone polymers, and since the aggregation speed of polysulfone polymers in water is extremely fast, the hydrophilic backbone polymers form on the surface of the polysulfone polymer matrix. will be pushed out. As a result,
The microporous surface of the resulting separation membrane is rich in hydrophilic backbone polymer components, resulting in significantly improved hydrophilicity and extremely high water permeation rate of the separation membrane. Moreover, since the polymer matrix that essentially determines the structure of the separation membrane is made of polysulfone polymer, not only the mechanical strength of the separation membrane but also the heat resistance and chemical resistance are comparable to that of polysulfone polymer. level will be reached. Therefore, it can be effectively used in membrane separation operations under harsh conditions that conventional hydrophilic polymer-based separation membranes, such as separation membranes made of cellulose acetate, cannot withstand.

Next, the present invention will be specifically explained with reference to Examples.
Let the Lp value after minutes be Lp, and the Lp value after 3 hours be Lp.

) It is defined in .

Further, the contact angle of the film was determined by measuring the contact angle with water at 925° C. using an Elma goniometer complete contact angle measuring device Model G-I.

The degree of polymerization of the polymer was measured using a steam osmometer manufactured by KNAUER, and the structure and composition of the backbone polymer and graft polymer were determined by elemental analysis and NMR (9QME (z or 270
MHz).

The amount of filtration and adsorption of the separation membrane was measured using a 150 ppm cytochrome C phosphate buffer solution (25°C).

In other words, the concentration of the cytochrome C solution before filtration is 0.1 ppm.
Let the +capacity be ■, - (approximately 50-), and pressurize it with a separation membrane with an effective membrane area of 5d (15,2d) on the 3rd floor- to make the capacity V,
When filtered and concentrated to IRt (approximately 10-), the concentration of the concentrated liquid is C1ppm, the volume of the permeated liquid is V, 11t, @ degree C5
The adsorption amount m (μt/cd) on the separation membrane surface is calculated using ppm.
) can be calculated using the following formula. However, in this case it is assumed that adsorption occurs over the effective membrane area.

Example 1 Polysulfone polymer of formula (I) having a hydroxyl group at the terminal (Victrex 5003 P, manufactured by ICI, 9 polymerization degree 52) 30t't dimethyl sulfoxide (hereinafter referred to as DM)
SO) 200 and benzene chloride (hereinafter referred to as PhC1) 10
0- in a mixed solvent at room temperature, and add 0.5N Na to this.
6.5 mL of an OH aqueous solution was added and the reaction was carried out at room temperature for 2 hours to obtain solution A of a polysulfone polymer having sodium ferulate terminals.

On the other hand, fcH-C having the following composition as the backbone polymer
Hm size 1 (H-CH*1- ■ A random copolymer was synthesized by a known radical copolymerization method, and this 14.5t was combined with DMSOloo- and PhC150
A solution Bt- was obtained by dissolving it in a mixed solvent of -. Add the above solution At-Yukushi to this solution at room temperature, and add it for 17 hours at room temperature.
After reacting at 0°C for 2 hr, 0.2-ml of concentrated sulfuric acid was added to stop the reaction.

The reaction mixture was reprecipitated with methanol/water = so/20 (volume ratio), and then subjected to Soxhlet extraction with ethanol for 7 hours to completely remove the remaining hydrophilic backbone polymer. Analysis of the purified polymer product revealed that it was a graft polymer having the following composition.

This gelasto polymer was mixed with dimethylformamide (DMF).
) at a polymer concentration of 15% by weight, this solution was cast onto a glass plate to a thickness of 400 μm, and then slowly D.
The MF was evaporated to produce a non-porous film. After peeling off the film from the glass plate, ethanol/water = 5015
0 (volume ratio) for 24 hours to completely remove DMF, dried at 50°C for 24 hours, and measured the contact angle.6
It was 6°. A film of the polysulfone polymer used in the above-mentioned graft reaction was prepared in a similar manner, and the contact metal content was measured at 73°, indicating that the above-mentioned graft polymer had significantly improved hydrophilicity. .

After dissolving 15 parts by weight of this hydrophilic graft polymer in 85 parts by weight of N-methyl-2-pyrrolidone, it was cast onto a glass plate to a thickness of 250 μm, and after 30 seconds, it was immersed in water at 10°C to separate it. A membrane was obtained. When the amount of adsorption on the surface of this separation membrane was measured, it was 19 .mu..eta.-, and no staining by cytochrome C was observed with the naked eye. In addition, when the Lp of the polyester nonwoven fabric reinforced film obtained by wet film formation using the polyester nonwoven fabric as a substitute for a glass plate during casting was measured, it was found to be 15rrl/lr? , day, Kf/-day, and the decrease rate β was 25 days. On the other hand, the elimination rate R of ovalbumin.

was 100 chi.

Comparative Example 1 A film was formed in the same manner as in Example 1, except that the polysulfone polymer t used in the graft reaction of Example 1 was used instead of graft polymer 0. The adsorption amount of the obtained membrane was 74
It was as high as μ9/−, and the membrane surface was stained red by cytochrome C. On the other hand, the Lp of the polyester nonwoven reinforced membrane is 9 days and 6 days.

It was low at V-, and β was also 35).

In addition, the elimination rate Ro of ovalbumin was as low as 87 chi.

Example 2 A random copolymer having the following composition as a backbone polymer was synthesized by a known radical copolymerization method, and 3.3t was mixed with DMSO60ff17! and PhC1
The grafting reaction and N production were carried out in the same manner as in Example 1, except that solution B was prepared by dissolving 40-40% in a mixed solvent. It was found that the obtained graft polymer had the following composition.

When this graft polymer was formed into a film in the same manner as in Example 1 and the contact angle was measured, it showed a low value of 54°, indicating that it was highly hydrophilic.

This hydrophilic graft polymer was molded into a separation membrane in the same manner as in Example 1, and the membrane performance was evaluated; m = 26
pf/cd, Lp = 33η-1 day, V-1β;
It was found that it had extremely excellent performance of 17% and Ro=91%.

Example 3 A random copolymer having the following composition as the backbone polymer was synthesized by a known radical copolymerization method, and 2.9t of this was dissolved in a mixed solvent of DMSO60- and PhC140-, except that it was used as solution B. The graft reaction was carried out in the same manner as in Example 1. After the reaction mixture was reprecipitated twice in acetone/water = 80/20 (volume ratio), the resulting graft polymer was analyzed and found to have the following composition.

26 - This graft polymer was formed into a film in the same manner as in Example 1, and the contact angle was measured, showing a low value of 6f, indicating that it was made hydrophilic.

This hydrophilic graft polymer was formed into a separation membrane using the same method as in Example 1, and the membrane performance was evaluated. m = 60 t
It was found to have extremely excellent performance: tf/ad + Lp = 12 rr/fee'1 day, interval -9β = 11%, and Ro = 98%.

Claims (3)

[Claims] (1) The base polymer is a hydrophilic copolymer with a total polymerization degree of 4 or more and 100 or less, in which the polymerization degree of the hydrophilic component accounts for 50% or more of the total polymerization degree, and a polysulfone-based polymer with a polymerization degree of 30 or more and 100 or less. 1. A separation membrane made of a polysulfone resin, characterized in that it is wet-formed from a solution of a hydrophilic polysulfone resin containing a graft polymer having as a branch polymer. (2) The polysulfone resin separation membrane according to claim 1, wherein the hydrophilic component has one or more of the following structures as repeating units. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ Here, R_1 is hydrogen or a methyl group. Also, R_2 has ▲ mathematical formulas, chemical formulas, tables, etc. ▼, ▲
There are mathematical formulas, chemical formulas, tables, etc. ▼, ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼, ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (M is an alkali metal or basic substance that ionically bonds with hydrogen or carbanion ) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (R_3 is an aliphatic hydrocarbon group having 1 to 20 carbon atoms.) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (R_4 and R_5 are each hydrogen or an aliphatic hydrocarbon group having 1 to 20 carbon atoms.) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ or ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (n is 0 (atomic bond) to 10 Integer. M is an alkali metal or basic substance that ionically bonds with hydrogen or sulfonic acid.) ▲Mathematical formulas, chemical formulas, tables, etc. are available▼ (R_6, R_7, and R_8 are fats each having 1 to 20 carbon atoms. (R_9 is an aliphatic hydrocarbon group having 1 to 20 carbon atoms, and n is 4 to 6. The integer X^■ is a halogen ion.) (3) The polysulfone polymer is one of the following (I) to (
The polysulfone resin separation membrane according to claim 1, characterized in that it has at least one type of repeating unit of III). ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (I) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (II) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (III)