JP2522312B2 - Selectively permeable hollow fiber composite membrane and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to desalination of seawater and can water, treatment of domestic wastewater,
The present invention relates to a reverse osmosis membrane used for production of sterile water, production of ultrapure water, recovery of valuable materials from various wastewater, an ultrafiltration membrane, or a dialysis membrane used for blood purification such as artificial kidney. .

(Prior Art) Since a water treatment method using a reverse osmosis membrane is an energy-saving method capable of separating and concentrating water to be treated without a phase change, it has been widely used in many fields as described above in recent years. It came to be implemented. Therefore, with such development, many compounds have been studied so far as a material used as a reverse osmosis membrane. However, the molecular design of reverse osmosis membrane materials still has to rely on empirical ones, and the necessary performance requirements are moderate hydrophilicity and moderate hydrophobicity.

 It has a high degree of crosslinking and a low degree of crystallinity when formed into a film.

It has mechanical strength such as pressure resistance and flexibility necessary for sealing.

The contradictory performance such as above must be balanced appropriately. Among them, cellulose derivatives such as cellulose acetate and cellulose triacetate, and rigid heat-resistant polymers such as aromatic polyamide and polyimide are often used as materials for the reverse osmosis membrane currently used. Among these, comparing cellulose acetate and aromatic polyamide by way of example, in the case of cellulose acetate, there are advantages such as having a high salt exclusion rate and chlorine resistance to oxidizing chlorine used as a bactericide for water, On the other hand, it has weaknesses in bacterial resistance and has a drawback that the pH range of raw water to be treated is limited to a narrow range of about 3 to 8. On the other hand, in the case of conventional aromatic polyamide,
A relatively high salt removal rate is obtained, and the bacteria resistance is good,
Although it has the advantage that the pH range of the raw water to be treated can be wide, it has the drawback of being inferior in oxidation resistance such as chlorine resistance, which is generally said to be the case with synthetic membranes. Therefore, synthetic membrane materials have been developed for the purpose of improving chlorine resistance, but at present, new materials having excellent RO performance such as desalination and water permeability and excellent chlorine resistance have been found. Absent.

In addition, since the reverse osmosis membrane used for desalination of seawater and citrus water in particular is used under high pressure, if used for a long period of time, innumerable micropores distributed in the membrane are gradually compressed. Therefore, the density tends to be high. When this non-recoverable deterioration called compaction occurs, not only does the reverse osmosis membrane make it difficult for water to permeate, but also the exclusion characteristics of dissolved substances change, making it impossible to maintain the initial performance. Various efforts have been made in the past to solve such drawbacks.
One of the ideas is a composite membrane having a two-layer structure in which an ultrathin film corresponding to the surface active layer of the asymmetric membrane is formed on the surface of the porous support membrane by an appropriate method. The asymmetric membrane here means Loeb-Sourirajan.
It is one of the membrane structures typified by membranes, and with the same material,
It is a film having a two-layer structure formed of a semi-permeable thin dense surface active layer and a relatively thick porous layer supporting it.

Generally, what is called reverse osmosis membrane performance can be roughly divided into two types, that is, water permeation flow rate and salt rejection rate. Of these, the latter is not so much affected by the film thickness, but the former is inversely proportional to the effective thickness of the semi-permeable surface active layer, so making the surface active layer extremely thin improves the performance of the reverse osmosis membrane. Leads to. Asymmetric membranes and composite membranes essentially belong to this category and have similar membrane morphology, but differ in that the former are from the same material and the latter are from different materials. Therefore, in the latter case, that is, in the case of the composite membrane, the membrane material for forming the surface active layer and the porous support can be classified by function and selected and optimized separately.

The active layer and the support can be manufactured by suitable manufacturing methods.

 Higher performance and higher durability of the film can be expected.

You can increase the advantages such as.

Polycarbonate, polyphenylene oxide, polysulfone and the like have been conventionally studied as high molecular weight polymers related to the porous support, but they have their respective drawbacks and, at present, aromatic polysulfone is present. Is widely used. This is because amorphous polysulfone is originally a heat-resistant polymer, so it has excellent heat resistance, and also has excellent chemical resistance such as oxidation resistance and acid-alkali, and is also rigid and has excellent pressure resistance. Probably because it is a polymer. However, this aromatic polysulfone also has a drawback that it is inferior in solvent resistance to many solvents such as halogenated hydrocarbons, ketones, ethers esters, and amides. Is a cause of narrowing.

Further, when the manufacturing method of the composite membrane is mentioned, this can be roughly classified into the following three methods.

B Type of polymer coated on support B Type of polymer coated on support and crosslinked C Type of polymer coated on support with monomer or prepolymer Of these, most of the composite membranes currently in practical use This is due to the type of c, but this method has the disadvantage that the production of these composite membranes and the reaction conditions of the monomers or prepolymers are complicated, and the reproducibility of the produced composite membrane is poor. have. Nevertheless, the reason why the production method of Ha is generally used is that the aromatic polysulfone used as the support is inferior in solvent resistance to a general-purpose solvent as described above. Therefore, when forming a composite membrane, if the solvent of the polymer to be the surface active layer has a solubility for the aromatic polysulfone as the support, the aromatic polysulfone as the support is destroyed and the composite The manufacture of the membrane becomes extremely difficult. Since it is a material with excellent reverse osmosis performance (hereinafter abbreviated as RO performance) and has a proven track record, most of these are N-methylpyrrolidone (NMP) when widely used aromatic polyamide as a solution. It is specifically dissolved in aprotic amide solvents such as dimethylacetamide (DMAC) and imethylformamide (DMF), so an aromatic polyamide solution is applied to the porous membrane of aromatic polysulfone that is not resistant to these solvents. Direct application was impossible. Therefore, after coating the support with a water-soluble polyamine, a polycondensation reaction is carried out on the surface of the support with an aromatic diisocyanate or an aromatic acyl chloride dissolved in hexane to form a composite film (for example, Desalination , 19 .113 (1976) "5t
h Int.Symp.on Fyesh Water from the Sea "vol 4,267
(1976) or the like, or an aqueous solution containing furfuryl alcohol, sulfuric acid, etc. applied to the surface of the support membrane, and heat treated at about 140 ° C. to simultaneously perform cross-linking polymerization and sulfonation to form a composite membrane. Method (eg USPatent3926
798 (1975)), a complicated so-called interfacial polycondensation reaction is widely used, and it is considered that the film formation is most convenient. In this case, it has been difficult to use the polysulfone support membrane due to the problem of solvent resistance between the polysulfone support membrane and the polyamide polymer.

Most of the forms of these composite membranes are sheet-like membranes, and there are few examples using the hollow fiber membrane form. When a hollow fiber membrane is used, the membrane area per unit volume of the module can be made larger when incorporated into the module than when a sheet-like membrane is used, thus increasing the amount of water produced per unit volume of the module and increasing the cost of increasing water. There is an advantage of lowering it. Nevertheless, there is no example of a composite hollow fiber membrane having an aromatic polyamide polymer as an active layer and an aromatic polysulfone porous layer as a support. This is because the above-mentioned conventional method for forming a composite membrane is complicated, and is not suitable for a hollow fiber membrane in terms of operability and productivity during film formation.

(Problems to be Solved by the Invention) The present invention relates to a hollow fiber composite membrane used for a reverse osmosis membrane, which activates an aromatic polyamide polymer having excellent RO performance, chlorine resistance, and heat resistance. As a layer, a hollow fiber composite membrane having a double structure in which it is coated on an aromatic polysulfone porous support is submitted, and in the process for producing this hollow fiber composite membrane, the aromatic polyamide-based polymer polymer is used. A reverse osmosis membrane with excellent pressure resistance and good RO performance can be obtained simply by dissolving the combined product in a solvent that is a non-solvent for aromatic polysulfone, and then uniformly applying this to the aromatic polysulfone porous support. By operating the coverage of the active layer and the porosity of the support, a more loose reverse osmosis membrane or ultrafiltration membrane (having moderate desalting property at low operating pressure and high water permeability),
Alternatively, the present invention provides a hollow fiber composite membrane that can be used as a dialysis membrane and a method for producing the same.

(Means for Solving Problems) As a result of intensive studies to solve the above problems, the present inventors have found that a copolyamide polymer having a specific chemical structure is dissolved and The present invention has been achieved by finding that there is a solvent that does not dissolve the group polysulfone.

That is, the present invention is mainly composed of the structural units represented by the following general formulas (1) and (2), and the molar ratio of the structural units (1) and (2) is
High molecular weight polymer (A) of copolyamide having 95/5 to 35/65
Is coated on a porous hollow fiber support containing aromatic polysulfone as a main component with a thickness of 0.03 to 10 μm (However, R is a divalent aromatic group having 6 to 15 carbon atoms, Y
Represents a divalent organic group. R ₁ , R ₂ , R ₅ and R ₆ represent a hydrogen atom or a hydrocarbon group having 1 to 12 carbon atoms, R ₃ and R ₄ represent a monovalent organic group, and n ₁ and n ₂ represent 0 or 1 Indicates a natural number of ~ 3.
Z represents a carbonyl group or a sulfonyl group, M represents a hydrogen atom, a hydrocarbon group having 1 to 12 carbon atoms, an alkali metal, an alkaline earth metal or a quaternary ammonium group, and Ar represents 6 to 15 carbon atoms. And (n ₃ +2) -valent aromatic hydrocarbon group, n ₃ is 1 or 2. And 2. After coating a solution (B) consisting of a high molecular polymer (A) and a solvent in which aromatic polysulfone is not substantially dissolved on the surface of a porous hollow fiber support containing aromatic polysulfone as a main component, The method for producing a permselective hollow fiber composite membrane as described above, characterized in that the solvent is removed from the solution.

The copolyamide as referred to in the present invention means that, in addition to the diamine component represented by the general formula (1) as an amine component, a diamine compound having appropriate hydrophilicity is appropriately copolymerized,
A compound having a hydrophilic group such as a carbonyl group or a sulfonyl group is more preferable as the diamine component having suitable hydrophilicity for the purpose of the present invention. Of these diamine components, the general formula (1)
In the compound shown therein, Y is —CH ₂ —, —O—, —N
HCO -, - CO -, - SO 2 NH -, - SO 2 -, - S -, - CH 2 CH
_{2 -, - NH -, -} N (CH 3) -, - CH = CH -, - C (C
H ₃ ) _{2− is} an organic group, and R ₁ and R ₂ are hydrogen atoms,
A lower alkyl group (eg, methyl, ethyl, isopropyl, n-propyl group, etc.), an aromatic group (phenyl group, benzyl group, etc.), a cyano group, an acetyl group, a nitro group can be mentioned, and for R ₃ and R ₄ Is a hydrogen atom, a halogen group (eg chlorine, bromine, fluorine), a lower alkyl group (eg methyl, ethyl, isopropyl, n-propyl group), a lower alkoxy group (methoxy group, ethoxy group), an aromatic group (phenyl Group, benzyl group, etc.), cyano group, acetyl group, nitro group.

Further, in the compound represented by the general formula (2), R ₅ , R ₆
Are hydrogen atoms, lower alkyl groups, (methyl, ethyl, isopropyl, n-propyl groups) and the like.

From the above, among the compounds used for producing the copolyamide of the present invention, an example of a diamine-based compound that induces the diamine component contained in the structural units of the general formulas (1) and (2) is more preferable. The general formula (1) is given in detail.
Examples of the diamine-based compound that induces the diamine component contained in the structural unit of 3,3'-diaminodiphenylmethane, 4,4'-diamino-3,3'-dimethyldiphenylmethane, 4,4'-diamino-3, 3 ', 5,5'-tetramethyldiphenylmethane, 4,4'-diamino-3-ethyldiphenylmethane, 4,4'-diamino-3,3'-diethyldiphenylmethane, 4,4'-diamino-5,5' , 6,6'-Tetramethyldiphenylmethane, 2,2'-bis (3-aminophenyl) propane, 2,2'-bis (4-aminophenyl) propane, 4,4'-diaminodiphenylmethane, 4,4 ' -Diaminodibenzyl, 4,4'-methylenebis (2-chloroaniline), 4,4'-diamino-benzophenone, 3,4 '
-Diaminodiphenyl ether, 2,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 4,4'-diaminobenzanilide, 4,4'-diaminobenzenesulfoanilide, 3,3'-diaminodiphenyl sulfide, 4, 4'-diaminodiphenyl sulfide,
3,3'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfone, 3,4'-diaminodiphenyl sulfone, 3,3'-dinitro-4,4'-diaminodiphenyl sulfone and the like can be mentioned, and preferably Is 4,4'-diamino-benzophenone, 4,4'-diaminobenzenesulfoanilide, 3,3'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfone, 4, 4'-diaminodiphenyl sulfone, 3,4'-diaminodiphenyl sulfone, particularly preferably 3,3'-diaminodiphenyl sulfone,
It is 4,4'-diaminodiphenyl sulfone. Further, as the diamine compound for inducing the diamine component contained in the constitutional unit of the general formula (2), 3,5-diaminobenzoic acid,
3,5-Diaminobenzoic acid methyl ester, 3,5-diaminobenzoic acid ethyl ester, 3,5-diaminobenzoic acid lithium, sodium 3,5-diaminobenzoate, potassium 3,5-diaminobenzoate, N, N ′ -Dimethyl-3,5-diaminobenzoic acid, 3,4-diaminobenzoic acid, 3,4-diaminobenzoic acid methyl ester, 3,4-diaminobenzoic acid ethyl ester, 3,4-diaminobenzoic acid lithium, 3 Sodium 4-diaminobenzoate, potassium 3,4-diaminobenzoate, N, N'-dimethyl-3,4-diaminobenzoic acid, 2,5-
Diaminobenzoic acid, 2,5-diaminobenzoic acid methyl ester, 2,5-diaminobenzoic acid ethyl ester, 2,5-diaminobenzoic acid lithium, 2,5-diaminobenzoic acid sodium salt, 2,5-diaminobenzoic acid potassium salt , N, N'-dimethyl-2,5-diaminobenzoic acid, 2,5-diaminoterephthalic acid, 2,5-diaminoterephthalic acid dimethyl ester,
2,5-diaminoterephthalic acid diethyl ester, 2,5-diaminoterephthalic acid lithium, 2,5-diaminoterephthalic acid potassium salt, 2,5-diaminoterephthalic acid sodium salt, bis (3-carboxy-4-aminophenyl) methane, Bis (3-carbomethoxy-4-aminophenyl)
Methane, bis (3-carboethoxy-4-aminophenyl) methane or m-phenylenediamine-4-sulfonic acid, 1,4-phenylenediamine-2-sulfonic acid, 4,4'-diaminophenylamine-2- Sulfonic acid, 4,4'-diaminostilbene-2,2'-disulfonic acid, p-aminodiphenylamine-2-sulfonic acid, 4
-Amino-4'-methyldiphenylamine-2-sulfonic acid, and their alkali metal salts, alkaline earth metal salts, ammonium salts, esters and the like, and particularly preferably 3,5-diaminobenzoic acid or m -Phenylenediamine-4-sulfonic acid and its alkali metal salts and alkaline earth metal salts.

In the copolyamide of the present invention, the diamine compound that induces the diamine component contained in the structural units of the general formulas (1) and (2) is substantially equal to the aromatic dicarboxylic acid halide compound, and the former diamine. It can be produced by reacting the system compound and the latter diamine compound in a molar ratio of 95/5 to 40/60. At this time, examples of the aromatic dicarboxylic acid halide used include phthalic acid, isophthalic acid, terephthalic acid,
4,4'-diphenyldicarboxylic acid, 1,2-naphthalene dicarboxylic acid, 1,3-naphthalene dicarboxylic acid, 1,4-naphthalene dicarboxylic acid, 1,5-naphthalene dicarboxylic acid, 1,6
-Naphthalene dicarboxylic acid, 1,7-naphthalene dicarboxylic acid, 1,8-naphthalene dicarboxylic acid, 2,3-naphthalene dicarboxylic acid, 2,6-naphthalene dicarboxylic acid, 2,7-naphthalene dicarboxylic acid, halide compounds such as ( chloride,
Bromide), of which isophthalic acid dichloride and terephthalic acid dichloride are particularly preferable.

Further, the copolyamide of the present invention is a diaminodiphenyl compound which is a diamine component contained in the constitutional unit of the general formula (1) and a diamine containing a hydrophilic group contained in the constitutional unit of the general formula (2). The copolymerization ratio with compound is in molar ratio
Although it is 95/5 to 35/65, it is more preferable to copolymerize at a molar ratio of 90/10 to 60/40. This is because the copolymerization ratio of the latter diamine compound is 60% of the total amount of diamine in terms of molar ratio.
If it exceeds%, a copolyamide having a high degree of polymerization cannot be obtained, and further, the salt removal rate decreases and the film strength also decreases.
Therefore, the high molecular polymer (A) referred to in the present invention is, for example, And so on.

The aromatic polysulfone used in the present invention is a polymer having a repeating unit represented by the following general formula (5) or (6), and specific examples thereof include (7) and (8).
An aromatic polysulfone having the repeating unit shown in (9) is more preferably used.

_{-Ar-SO 2 -Ar-O- (} Ar-Rn-Ar-X) m- (5) -Ar-SO 2 -Ar-SO 2 -Ar-O- (6) ( where, Ar each may be the same or R represents a different aromatic group, R represents a divalent organic group, X represents 0 or SO ₂ , and m and n each represent 0 or 1.) Further, for the porous hollow fiber support containing these aromatic polysulfones as main components, the aromatic polysulfone is dissolved in N, N-dimethylacetamide by applying, for example, the method found in Japanese Patent Application Laid-Open No. 57-7202. It can be easily obtained by dry-wet spinning using a solution containing polyethylene glycol and / or a surfactant as a non-solvent as a dope solution. More preferably, the aromatic polysulfone porous hollow fiber support thus obtained is treated with hot water under pressure to obtain a more stable support.

In order to coat the aromatic polysulfone porous hollow fiber support thus obtained with the copolyamide polymer (A) according to the present invention, first, the copolyamide polymer (A) is supported. It must dissolve in a solvent that is non-solvent to the body. The advantage of the present invention is that such a solvent can be selected first, and alkylene glycol monoalkyl ether, alkylene glycol monoalkyl ester or monoacetin, glycerin derivatives such as diacetin,
Alternatively, a mixed solvent thereof may be mentioned as an example, and these solvents show good solubility in the polymer (A), but do not attack the aromatic polysulfone porous support. Further, since the solvent needs to be evaporated and removed in the film forming step, it is more preferable that the solvent has a boiling point of 200 ° C. or lower. Examples of the solvent include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether,
Examples thereof include ethylene glycol monomethyl ester, ethylene glycol monoethyl ester and monoacetin.

Next, various methods such as a dip coating method, a spray coating method, and a liquid surface spreading method can be considered as the method for applying the solution in which the high molecular polymer (A) is dissolved in the solvent onto the aromatic polysulfone porous support. However, the method is not limited to these coating methods, but the dip coating method or the liquid level expansion method is more preferable in view of the hollow fiber membrane form.
Regarding the concentration of the coating agent used at this time, the concentration of the high molecular polymer (A) is 0.1 to 10% by weight, more preferably
A 1.0 to 5.0% solution is used, and an inorganic substance such as an alkali or alkaline earth metal salt, or a relatively low molecular weight polyol such as glycerin or ethylene glycol is used as a pore-forming agent or a thickener in the coating agent solution. It is also possible to mix a proper amount of the kinds and the like. Here, the concentration of the polymer (A) contained in the coating agent solution is 0.1
When the concentration is lower than the weight concentration, a defect occurs in the surface active layer,
On the other hand, when the concentration is higher than 10% by weight, the thickness of the surface active layer becomes too thick and the permeation flow rate of water may decrease. Further, the thickness of the surface active layer referred to here is required to be 0.03 to 10 μm and uniform, preferably 0.03 to 3.0 μm, and more preferably 0.01 to 1.0 μm. When the thickness exceeds 10 μm, the permeation flow rate of water decreases because the resistance increases as described above.

Now, as a method of coating the high molecular polymer (A) on the aromatic polysulfone porous hollow fiber support, for example, the dip coating method will be described. First, the support was immersed in the coating agent prepared as described above. After that, the solvent can be dried and removed, and the coated hollow fiber can be wound up by a simple method. However, in this case, factors such as the time for immersing the support in the coating agent and the drying temperature or the coating speed affect the reverse osmosis performance of the resulting composite membrane.
It is necessary to select the optimum conditions. The time for dipping the support in the coating agent is about 0.1 to 30 seconds, and the drying temperature is 4
A coating speed of about 0 to 120 ° C. of about 10 to 50 m / min is suitable for the present invention, but since these three factors interact with each other, it is necessary to select the optimum conditions depending on the time. Further, as a drying method, more preferably, drying with hot air is performed.

Thus, according to the present invention, it is possible to coat the aromatic polysulfone porous hollow fiber support with the aromatic copolyamide without attacking the support, and it is possible to easily obtain a permselective composite hollow fiber membrane. .

Action The alkylene glycol monoalkyl ethers or alkylene glycol monoalkyl esters used in the present invention are good solvents for the high molecular weight polymer (A) used in the present invention. It is a non-solvent for aromatic polysulfones. Therefore, these solvents do not attack the aromatic polysulfones.

The present invention will be described below with reference to Examples and Comparative Examples.
It goes without saying that the examples given here do not limit the invention. The reverse osmosis performance evaluation method and the reverse osmosis performance evaluation method in the presence of free chlorine are shown below.

(A) Reverse osmosis performance evaluation method: a continuous pump-type reverse osmosis device was used, and the selective permeable hollow fiber composite membrane or
The mini-module prepared from the hollow fiber membranes shown in Comparative Examples 3 and 4 was set, and 2000 ppm of Nacl was fed into this apparatus as a stock solution. Operating temperature 25 ℃ Operating pressure 30kg / cm ² 2
After continuous operation for a period of time, sampling of the permeate was started, and the amount of permeated water and the salt removal rate were measured. Here, the salt removal rate was calculated by the following formula.

Reverse osmosis performance evaluation in the presence of chlorine ions Use the same stock solution (pH 6.5) as above except that chlorine ions are contained at a ratio of 50 ppm, and operate using a continuous pump type reverse osmosis device in the same manner as above. After 10 hours from the start of operation, the amount of permeated water and the salt removal rate were measured.

Reference Example 1 The following is a spinning example of the aromatic polysulfone porous hollow fiber support used in the present invention.

35 parts by weight of aromatic polysulfone (Udel P-3500) was added to a solution of 45.5 parts by weight of N, N-dimethylacetamide in which 0.5 part by weight of sodium laurylbenzenesulfonate was previously dissolved, and the mixture was heated and stirred at 130 ° C. After confirming that the polymer was completely dissolved, PEG-400 19
A part by weight was added, and the mixture was further heated and stirred for 1 hour to obtain a dope solution. Next, after defoaming this dope solution, the dope solution was discharged from a tube-in-orifice nozzle and spun dry and wet at a spinning speed of 30 m / min. At this time, N, N-dimethylacetamide, ethylene glycol and water are respectively used as coagulant.
Using a solution prepared by mixing 21 parts by weight, 9 parts by weight, and 70 parts by weight,
As the inner liquid, a solution prepared by mixing 70 parts by weight and 30 parts by weight of N, N-dimethylacetamide and ethylene glycol, respectively was used. After washing the obtained hollow fiber thoroughly with water, it is heat-treated under pressure at 120 ° C to give an outer diameter of 250 (μm) and an inner diameter of 110.
(Μm) Aromatic polysulfone porous hollow fiber support was obtained. The porosity of this hollow fiber support was 56%, and
When pure water at ℃ is run at an operating pressure of 28 kg / cm ² , the water permeability is 300 / m ² D.
Met.

Reference Example 2 Hereinafter, a synthesis example of a copolyamide having a carboxylic acid group used in the present invention is shown.

3,5-Diaminobenzoic acid 1.9018g (0.0125mol), 3,3 '
-Diaminodiphenyl sulfone 27.9979g (0.1125mol)
Was charged into a 500 ml four flask equipped with a nitrogen introducing tube, a thermometer and a stirrer under a nitrogen stream. Further, 150 ml of N-methyl-2-pyrrolidone was added to this system to dissolve the above monomers. After sufficiently stirring this, while cooling the entire reaction system with ice, 25.3775 g of isophthalic acid chloride (0.125 mol
l) was added rapidly under a nitrogen stream. After reacting for about 60 minutes under ice cooling, the temperature was returned to room temperature, and the reaction system was stirred for about 1 hour. After completion of the reaction, this solution was added to 1500 ml of methanol to precipitate a polymer. A series of purification steps of crushing the polymer with a household mixer, filtering, and washing with water were repeated to remove unreacted substances in the polymer and remove the solvent. Finally, the polymer was washed in methanol and dried under vacuum at about 140 ° C. for about 48 hours to obtain a copolyamide represented by the following formula (10). Of the obtained polymer The yield is about 95% and the reduced specific viscosity is η _SP /C=0.97 (0.5g / dl
N-methyl-2-pyrrolidone 30 ° C).

Reference Example 3 A synthesis example of the copolyamide having a sulfonic acid group used in the present invention is shown below.

(A) Preparation of metaphenylenediamine-4-sulfonic acid sodium salt: sodium hydroxide, 21.37 g (0.5343mo
l) was dissolved in 500 ml of water, and 100.56 g (0.5343 mol) of metaphenylenediamine-4-sulfonic acid was added and dissolved in this homogeneous solution. The solution was evaporated to dryness to obtain crude crystals of sodium salt of metaphenylenediamine-4-sulfonic acid. After thoroughly washing this with special grade n-hexane,
Recrystallized with water. The crude product was dried under reduced pressure at 100 ° C. for 24 hours. The yield of the obtained salt was about 70%.

(B) Synthesis of poly [terephthaloyl- (3,3'-diaminodiphenyl sulfone / sodium metaphenylenediamine-4-sulfonate)]: 7.88 g of sodium metaphenylenediamine-4-sulfonate obtained in (A)
(0.0375 mol) and 21.37 g (0.0875 mol) of 3,3'-diaminodiphenyl sulfone were charged under a nitrogen stream into a 500 ml four-necked flask equipped with a nitrogen introducing tube, a thermometer and a stirring device. Further, 150 ml of N-methyl-2-pyrrolidone was added to this system to almost dissolve the above monomers. At this time, sodium metaphenylenediamine-4-sulfonate was not completely dissolved and was in a dispersed state. After stirring this well, 25.3 g (34.5 ml, 0.25 mol) of triethylamine was added as a hydrogen chloride scavenger, and the temperature of the reaction system was 30
It was ice-cooled until the temperature became below ℃. While stirring the whole reaction system under ice cooling, 25.38 g (0.125 mol) of terephthaloyl chloride was gradually added under a nitrogen stream. At this time, the temperature of the reaction system was kept below about 20 ° C. After reacting for about 60 minutes under ice-cooling, the temperature was returned to room temperature, and the mixture was further stirred for about 1 hour. After completion of the reaction, this reaction solution was added to 1500 ml of methanol to precipitate a polymer. The polymer obtained with a household mixer was pulverized, filtered, and washed with water several times to carry out a purification step to remove unreacted substances and solvent in the polymer. Finally, the polymer is washed with methanol and dried under vacuum at about 140 ° C. After drying for 48 hours, a copolyamide represented by the above formula (11) was obtained. The yield of the obtained polymer was about 95%, and the reduced viscosity of the polymer was η _SP /C=1.06 (0.5 g / dl
N-methyl-2-pyrrolidone, 30 ° C).

Reference Example 4 The thickness of the surface active layer of the selectively permeable hollow fiber composite membrane obtained by the present invention was measured by a transmission electron microscope (TEM), and the surface of the membrane was observed by a scanning electron microscope (SEM). .

Examples 1 to 3 The copolyamide (polymer (A)) obtained in Reference Example 2 was dissolved in a solvent (solvent (C)) that does not dissolve aromatic polysulfone, and this was used as a coating agent. This coating agent was dip-coated on the aromatic polysulfone porous hollow fiber support shown in Reference Example 1, dried and then thoroughly washed with water. Table 1 shows the coating composition and coating conditions, and the reverse osmosis performance of the obtained composite membrane.

Examples 4 to 6 The copolyamide (polymer (A)) obtained in Reference Example 3 was dissolved in a solvent (solvent (C)) that does not dissolve aromatic polysulfone, and this was used as a coating agent. This coating agent was dip-coated on the aromatic polysulfone porous hollow fiber support shown in Reference Example 1, dried and then thoroughly washed with water. Table 1 shows the composition of the coating agent and the coating conditions, and the reverse osmosis performance of the obtained composite membrane.

Comparative Example 1 5 parts by weight of high molecular weight polymers (10) and (11) respectively
94.6 parts by weight of N, N− in which 0.4 parts by weight of lithium chloride was dissolved
It was dissolved in dimethylacetamide (DMAC), and this was used as a coating agent for dip coating on the aromatic polysulfone porous hollow fiber support shown in Reference Example to obtain a hollow fiber composite membrane. DM with polysulfone support
Since it was dissolved in AC, yarn breakage occurred and it was not possible to coat.

Comparative Example 2 NOMEX (Formula (12)), which is a type of aromatic polyamide Was tried to prepare a coating agent solution by dissolving it in methyl cellosolve (ethylene glycol monomethyl ether), but NOMEX was not dissolved in methyl cellosolve.

Comparative Example 3 The high molecular weight polymer (10) was added so that the weight concentration was 12%.
It was dissolved in ethylene glycol monomethyl ester to obtain a coating agent. This coating agent was coated on the aromatic polysulfone porous hollow fiber support shown in Reference Example 1 in the same manner as in Examples 1 to 6, and the reverse osmosis performance of the obtained composite hollow fiber membrane was measured.
It was measured at an operating pressure of 30 kg / cm ² using 0.2% saline solution at 25 ° C as raw water. The results are shown in Table 1.

Comparative Examples 4, 5 40 parts by weight of high molecular weight polymers (10) and (11) were respectively dissolved in 4 parts by weight of lithium chloride.
It was dissolved in DMAC, and 6 parts by weight of propylene glycol was added thereto to form a dope solution, which was then discharged from a tube-in-orifice nozzle to obtain each asymmetric hollow fiber membrane. Furthermore, under the same conditions as in Examples 1 to 3,
The reverse osmosis membrane performance of these hollow fiber membranes was evaluated. Table 2 shows the results.

(Advantages of the Invention) Conventionally, aromatic polyamides used for reverse osmosis membranes cannot dissolve in aromatic polysulfone in a solvent which is a non-solvent, and therefore, the amine component and the acid component are used as monomers or prepolymers. After the application in this state, a complicated method of providing an aromatic polyamide surface active layer on the aromatic polysulfone support by a method such as interfacial polymerization has been used. Therefore, it has a drawback that the film forming process is complicated and that the amine component present in the thin film upon polymerization is susceptible to oxidative deterioration such as chlorine. Further, due to the complexity of the membrane-forming process, it has been practically impossible to obtain a permselective hollow fiber composite membrane using an aromatic polysulfone as a support. However, the polymer (A) used in the present invention can be dissolved in a solvent that is a non-solvent for aromatic polysulfones such as alkylene glycol monoalkyl ethers and alkylene glycol monoalkyl esters. The production method of coating a polymer on a support, which is the simplest method for obtaining a composite membrane, has become feasible.

Further, the high molecular polymer (A) used in the present invention is an aromatic copolyamide having high desalination property and excellent chlorine resistance. Therefore, by producing a composite membrane in which this high molecular polymer (A) is coated on a polysulfone porous support, it has a high salt removal rate and a high water permeation rate, and also has high chlorine resistance, pressure tightness and heat resistance. An excellent reverse osmosis membrane can be obtained, and it can also be applied to ultrafiltration membranes and dialysis membranes simply by manipulating the coverage of the surface active layer.

Claims (4)

(57) [Claims] 1. A copolyamide mainly composed of structural units represented by the following general formulas (1) and (2), in which the molar ratio of the structural units (1) and (2) is 95/5 to 35/65. A permselective hollow fiber composite membrane, wherein the high molecular polymer (A) is coated on a porous hollow fiber support containing aromatic polysulfone as a main component to a thickness of 0.03 μm to 10 μm. (However, R is a divalent aromatic group having 6 to 15 carbon atoms, Y
Represents a divalent organic group. R ₁ , R ₂ , R ₅ and R ₆ represent a hydrogen atom or a hydrocarbon group having 1 to 12 carbon atoms, R ₃ and R ₄ represent a monovalent organic group, and n ₁ and n ₂ are 0 or A natural number of 1 to 3 is shown.
Z represents a carbonyl group or a sulfonyl group, M represents a hydrogen atom, a hydrocarbon group having 1 to 12 carbon atoms, an alkali metal, an alkaline earth metal or a quaternary ammonium group, and Ar represents 6 to 15 carbon atoms. And (n ₃ +2) -valent aromatic hydrocarbon group, n ₃ is 1 or 2. ) 2. A copolyamide mainly composed of structural units represented by the following general formulas (1) and (2), in which the molar ratio of the structural units (1) and (2) is 95/5 to 35/65. A solution (B) consisting of a high-molecular polymer (A) and a solvent that does not dissolve aromatic polysulfone is coated on the surface of a porous hollow fiber support containing aromatic polysulfone as a main component, and then the solution is removed from the solution. A method for producing a selectively permeable hollow fiber composite membrane, which comprises removing a solvent. (However, R is a divalent aromatic group having 6 to 15 carbon atoms, Y
Represents a divalent organic group. R ₁ , R ₂ , R ₅ and R ₆ represent a hydrogen atom or a hydrocarbon group having 1 to 12 carbon atoms, R ₃ and R ₄ represent a monovalent organic group, and n ₁ and n ₂ are 0 or A natural number of 1 to 3 is shown.
Z represents a carbonyl group or a sulfonyl group, M represents a hydrogen atom, a hydrocarbon group having 1 to 12 carbon atoms, an alkali metal, an alkaline earth metal or a quaternary ammonium group, and Ar represents 6 to 15 carbon atoms. And (n ₃ +2) -valent aromatic hydrocarbon group, n ₃ is 1 or 2. ) 3. The selective permeability according to claim 2, wherein the solvent for the high molecular weight polymer (A) of the copolyamide in the solution (B) is alkylene glycol monoalkyl ether. Method for producing hollow fiber composite membrane. 4. The selective permeability according to claim 2, wherein in the solution (B), the solvent for the high molecular weight polymer (A) of copolyamide is alkylene glycol monoalkyl ester. Method for producing hollow fiber composite membrane.