JPS6388003A - Separation membrane - Google Patents

Abstract

PURPOSE:To obtain a separation membrane made of a hydrophilic polysulfone resin having high water permeability, by applying a wet film forming method to a solution containing a graft polymer having a hydrophilic copolymer of a specific polymerization degree as a main polymer and a polysulfone polymer of a specific polymerization degree as a branch polymer. CONSTITUTION:An aqueous sodium hydroxide solution is added to a solvent solution containing a polysulfone polymer with a polymerization degree of 30-200 having, for example, a hydroxyl group at the terminal thereof to perform reaction to prepare a solution A of polysulfone polymer wherein terminal is of sodium phenolate-type. As a main polymer, a hydrophilic copolymer wherein a polymerization degree is larger than 100 and the polymerization degree of a hydrophilic component occupies 50.% or more of the total polymerization degree, for example, a random copolymer having a composition represented by formula I is used to prepare a solution B which is, in turn, added to the solution A to be reacted therewith and, after purification, a graft polymer is obtained. This polymer is dissolved in a solvent to be cast onto a polyester nonwoven fabric, and the coated fabric is immersed in water to obtain a separation membrane.

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 selectively permeable M membranes used in such systems, including cellulose,
Polymers such as polyamide, polyacrylonitrile, polycarbonate, polyphenylene oxide, and polysulfone are used.

Among these, hydrophobic polymers such as polysulfone, polycarbonate, polyphenylene oxide, and fluorine-containing polymers are originally used as engineering plastics, but they have excellent heat resistance and mechanical properties. Because of this, it is also being used as a material for separation membranes.

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. - low hyperactivity rate.

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 polyvinylpyrrolidone having a molecular weight of 10,000 or more and a method for producing the same. However, in this method of adding a hydrophilic polymer having a molecular weight of 10,000 or more to a film-forming solution (called a dope), the polymer density of the dope increases, and the polysulfone film formed from such a dope increases. In the system M membrane, the added hydrophilic polymer remains throughout the membrane 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-54-26-283 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, this method uses water as a coagulation bath for membrane formation, and oligomers of polyethylene glycol do not remain in the membrane and are all eluted into the water, which does not substantially increase the hydrophilicity of the polysulfone membrane. Therefore, no significant improvement in water permeation rate can be expected.

Furthermore, in JP-A-57-174104, a reactive functional group was introduced into the benzene ring of a polysulfone polymer, and after wet film formation from this polymer solution, it was treated with a solution of a hydrophilic substance that could react with the functional group. A method for crosslinking modification is disclosed. However, with this method, the separation membranes obtained are mostly limited to reverse osmosis membranes, and it is extremely difficult to produce a wide variety of classification membranes.

In addition, the benzene ring of polysulfone polymers generally has low reactivity, and the types of functional groups that can be introduced are limited, 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 problems, have high water permeation rate, and have heat resistance and 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.

In other words, the present invention is directed to ``a hydrophilic copolymer having a total degree of polymerization of more than 100 (of which the degree of polymerization of the hydrophilic component accounts for 50% or more of the total degree of polymerization) is bound with a backbone polymer, and the degree of polymerization is 30 or more and 200 or more. A separation mold made of polysulfone resin, characterized in that it is wet film-formed from a solution of a water-based polysulfone resin containing a graft polymer using the following polysulfone polymer as a technical polymer.

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

In the present invention, a polysulfone resin containing a graft polymer in which the ends of a polysulfone polymer as described above are chemically bonded to a hydrophilic copolymer is used as a probe 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 polymer having a vinyl group at the end is copolymerized with a vinyl monomer or oligomer. A specific reactive functional group,
Examples of combinations of terminal groups that can react with this are given below from known organic chemical reactions.

(1) When the terminal group is a hydroxyl group or an alkali alcoholade group - Functional groups such as acid halide groups, acid anhydride groups, glycidyl groups, heromethyl groups, and sulfonyl halide groups.

(2) When the terminal group is a halogenated alkyl group or a halogenated aryl group, Ni←CHx→-0M group (M is an alkali metal, n is 0 (
valence bond) or positive integer), amino group (this is the first .
(which 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 amino groups and alcoholade groups.

(5) When the terminal group is a carbonyl group, - N HN H-based functional groups such as 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 necessary to appropriately select whether to carry out the process before or after the copolymerization depending on the type of hydrophilic component, which will be described later. In addition, if the process is carried out after the copolymerization, the functional group of the hydrophilic component is undesirable. It is necessary to set appropriate reaction conditions so as not to change the direction or reduce 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 terminal groups participate in the reaction, a crosslinking reaction will occur, resulting in a gel-like substance insoluble in a solvent, which can no longer 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 amount is at least mol %, preferably at least 40 mol %. If less than 20 mol % of the graft polymer is contained, the hydrophilicity of the polysulfone resin cannot be significantly improved, and therefore separation membranes manufactured from such resin often have a low water permeation rate.

Furthermore, the structure 1 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, a hydrophilic copolymer with a total polymerization degree of more than 100, in which the polymerization degree of the hydrophilic component accounts for 50% or more of the total polymerization degree, is used as the main polymer, and a polysulfone-based polymer with a polymerization degree of 30 to 200 is used as a branch polymer. It must be a graft polymer.

Therefore, for example, when the total polymerization degree of the backbone polymer is 120, the polymerization degree of the hydrophilic component is 60 or more, and the polysulfone polymer is bonded to some or all of the other copolymer components through the terminal group. Further, 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 polysulfone polymers to greater than 200 using current polymerization technology.
On the other hand, controlling the degree of polymerization to 30 or more and 200 or less is technically and economically easy, and has great industrial advantages.

Further, the hydrophilic component in the above-mentioned backbone polymer preferably has one of the following structures or 2t1 or more as a repeating unit.

-CR, -CH, - ■ Here, R1 is hydrogen or a methyl group.

Ra, R? and Ro each have 1 to 2 carbon atoms
It is an aliphatic hydrocarbon group having 0 atoms, and XO is a halogen ion.

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) is 5% by weight or more and less than 30% by weight when the separation membrane to be manufactured is a high fractionation ultrafiltration membrane or precision S filtration membrane. It is preferable that there be. When manufacturing ultrafiltration membranes or reverse osmosis membranes with low fractionation properties, the content is preferably 10% by weight or more and less than 40% by weight.

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. Moreover, a non-solvent, an electrolyte, etc. can also be added to such a polar organic solvent.

In forming the separation membrane of the present invention from the dope described above, a conventional 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 sheet or tube support (e.g. glass temporary or tube, non-woven fabric, cloth, etc.). Casting by an appropriate method,
Thereafter, it is immersed in a coagulant bath to produce a separation membrane by sol-gel phase conversion. Further, 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 non-solvents for polysulfone resins and easily mix with polar organic solvents, such as water, aqueous solutions of electrolytes such as salt and surfactants, aqueous solutions of polar organic solvents, or hydrophilic polysulfone resins. Examples include non-solvents or aqueous solutions thereof, and water is particularly commonly used.

(Effects of the Present Invention) The characteristics of the separation membrane of the present invention are manifested by wet membrane formation 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 traditionally fast, the hydrophilic backbone polymers form a polysulfone polymer matrix. It will be pushed to the surface. 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. Furthermore, since the polymer matrix that essentially determines the structure of the separation membrane is made of polysulfone polymer, the separation membrane's mechanical strength as well as heat resistance and chemical resistance are comparable to those 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.
[, p value after time is t, b, LP value after a time is L3. ) is defined by .

The contact angle of the film was determined by measuring the contact angle with water at 25° C. using an Elma goniometer type contact angle measuring device Model G-1.

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 (to).

MHz or 270MHz).

And the separation membrane? The measurement of hyperadsorbed insects was carried out using 150 ppffl of cytochrome C phosphate buffer solution (25°C).

In other words, the concentration of cytochrome C78eL with S filtration ability is CH
I) I'll The capacity is set to V, m/ (approximately 50 m/), and this is applied with a pressure of 3 kg/cm'' using a separation membrane with an effective membrane area of S cm'' (15, 2 cm''), and the volume is ff1v, I11! (approximately 10 m/), adsorption on the separation membrane surface fftm (μg/cm'') using the concentration of et condensate Czpm, the volume of permeate V3m/, and the concentration C8ppm.
can be calculated using the following formula. However, in this case it is assumed that adsorption occurs over the effective membrane area.

(Examples) Next, the present invention will be explained in more detail with reference to Examples.

Example 1 Polysulfone-based polyv- of the formula (1) whose terminal is a hydroxyl group
(V 1ctrex 5003 p, manufactured by Imperial Chemical Industries, Inc. 1 polymerization degree 52) was dissolved at room temperature in a mixed solvent of 400 m/dimethyl sulfoxide (DMSO) and 200 m/benzene chloride (PhC/) at room temperature. .5N ・NaOH
Aqueous solution A solution A of a polysulfone polymer having a sodium ferulate terminal was obtained by preparing an aqueous solution.

On the other hand, a random copolymer having the following composition (degree of polymerization 149) as a backbone polymer was synthesized by a known radical copolymerization method, and 50 g of this was mixed with DMSO2001m/ and PhC/I
Solution B was obtained by dissolving Q (1 m/ml) in a mixed solvent. This solution was slowly added to the above solution A at room temperature, and the mixture was heated to Ihr.
After reacting at 70°C for 2 hours, 0.5 m/ml of concentrated sulfuric acid was added to stop the reaction.

The reaction mixture was reprecipitated in methanol/water - 80/20 (volume ratio), and then centrifuged to methanol/water - 80/2.
The remaining unreacted hydrophilic backbone polymer was completely removed by repeated washing with 0. Analysis of the purified polymer product revealed that it was a graft polymer with the following composition.

This graft polymer was dissolved in DMSO at a concentration of 15-fold monomorphic polymer, and the solution was spread onto a glass plate in a 400μ
After casting, DMSO was slowly evaporated at 90° C. to produce a non-porous film.

Remove the film from the glass plate (after removal ethanol/water = 5
After completely removing DMSO by immersing it in 0/50 (volume ratio) for 24 hours, it was dried at 50°C for 24 hours and the contact angle was measured, which showed a low value of 57°, indicating that the graft polymer is hydrophilic. I understand.

After dissolving 15 parts by weight of this hydrophilic graft polymer in 85 parts by weight of a mixed solvent mainly containing N-methyl-2-pyrrolidone, it was cast onto a polyester nonwoven fabric to a thickness of 150 μm, and immersed in water at 10°C. A separation membrane was obtained. The O filtration adsorption amount m of this separation membrane was measured and found to be 22 μg/cm'', and no staining of the membrane surface by cytochrome C was observed with the naked eye.

Also, LA is 101I13/1111・day・kg/cm'
, β was 3%, indicating high water permeation rate and stability over time.

Comparative Example 1 Polysulfone-based polymer (Vict-rex
A film and a separation membrane were produced in the same manner as in Example 1, except that 5003p) was used.

The film had a contact angle of 76° and was extremely hydrophobic. Also, the separation membrane l11 = 74μg/cI! The adsorption amount was as high as 1'', and the membrane surface was stained red by cytochrome C. On the other hand, L^ was low at 7.1 m'/a+''・day・kg/c+a'', and β was also 20%, indicating a water permeation rate. The decrease over time was significant.

Patent applicant Daicel Chemical Industries, Ltd. agent Patent attorney Takashi Koshiba Procedural amendment (voluntary)

Claims (3)

[Claims] (1) The main polymer is a hydrophilic copolymer with a total polymerization degree of more than 100, 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 to 200 is used as a branch polymer. 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 as a 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. ▼, ■OOM (M is hydrogen or an alkali metal or basic substance that ionically bonds with a carboxylic acid ion.), ■OOR_3 ( R_3 is an aliphatic hydrocarbon group having 1 to 20 carbon atoms.), ■ONR_4R_5 (R_4 and R_5 are each hydrogen or an aliphatic hydrocarbon group having 1 to 20 carbon atoms.), ▲Formula , chemical formulas, tables, etc. ▼ or ▲ Numerical formulas, chemical formulas, tables, etc. (It is a substance.) ▲There are mathematical formulas, chemical formulas, tables, etc.▼ R_6, R_7 and R_8 are aliphatic hydrocarbon groups each having 1 to 20 carbon atoms, and X^■ is a halogen ion. Or ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (R_9 is an aliphatic hydrocarbon group having 1 to 20 carbon atoms, n is an integer of 4 to 6, and X^■ is a halogen ion.) (3) The polysulfone polymer is one of the following (I) to (
The separation membrane made of polysulfone resin 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)