JPH07114940B2 - Permselective membrane - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a permselective membrane made of a specific copolyamide, which is particularly suitable for desalinating seawater or brackish water to obtain fresh water. Regarding

(Prior Art) A solution of one or more organic substances dissolved in a common solvent is pressure-fed to a permselective membrane at a pressure higher than the osmotic pressure of this solution, or the permeation side is reduced to a low pressure. A dialysis method or pervaporation separation method that can selectively permeate and separate components, and water is selectively passed from an aqueous solution of an inorganic salt,
There is a reverse osmosis method that does not allow inorganic salts to pass through.

In these methods, a selectively permeable membrane or a membrane called a reverse osmosis membrane is used. (Hereinafter, both are collectively referred to as a selective permeation film.) Such a selective permeation film is generally made of an organic polymer substance.

The morphology is a homogeneous film consisting of a dense and homogeneous structure or a composite film in which this is applied to an appropriate support, or a surface polymer layer which is generally only dense with a thickness of 0.1 to 0.3 microns or less There are membranes that have an asymmetric structure consisting of a porous substructure that serves as a thin layer support. This is generally called an asymmetric membrane.

The high water permeability and desalination performance of this asymmetric membrane relies on the thin, dense surface polymer layer described above.

Conventionally, cellulose acetate has been industrially used as a material for a selectively permeable membrane.

However, this membrane has hydrolysis resistance, microbial resistance, heat resistance,
There was a problem in terms of film life.

In the patent, an aromatic polyamide is known as a new separation membrane material replacing cellulose for the purpose of improving these points (Japanese Patent Publication No. 53-43540). As a result, hydrolysis, microbial decomposition, and thermal decomposition deterioration were improved, but there was a problem that it was extremely weak against chlorine (oxidizing chlorine) used as a bactericide for water, that is, it lacked chlorine resistance. .

Also, from film tech, metaphenylenediamine,
A membrane obtained by crosslinking paraphenylenediamine with an aromatic polyacid halide such as trimesic acid chloride has been proposed (JP-A-55-147106). It is disclosed that it has not only very good reverse osmosis membrane performance, but also chlorine resistance.

On the other hand, a reverse osmosis anisotropic membrane composed of a copolyamide obtained by reacting a piperazine-based diamine with a heterocyclic and / or aromatic dicarboxylic acid component and having excellent chlorine resistance and reverse osmosis performance (JP-A-49-109271). No. publication) is known.

The reverse osmosis membrane disclosed in JP-A-55-147106 described above,
Although it has chlorine resistance, it has been found that the chlorine resistance is only short-term and cannot be used for a long time.

Further, the polyamide using the piperazine and the aromatic dicarboxylic acid component is poorly soluble in aprotic organic solvents such as N, N-dimethylastamide and N-methylpyrrolidone which are usually used for film formation, It only dissolves in protic solvents such as formic acid and metacresol, which are dangerous. Therefore, it has been found difficult to industrially produce a permselective membrane using this polyamide.

(Problems to be Solved by the Invention) The present inventors have studied the film-forming properties, selective permeability, and chlorine resistance of copolyamides using piperazine-based compounds and aromatic diamine compounds. The present invention has been found out that it depends on the chemical structure of the aromatic diamine compound of copolyamide.

(Means for Solving Problems) The present invention uses a specific bis (aminophenyl) -based compound and a piperazine-based compound as a main diamine component, and the above molar ratio is 95/5 to 35/65. For the diamine component,
It is a permselective membrane made of copolyamide obtained by reacting an aromatic polycarboxylic acid component.

That is, the present invention comprises an aromatic diamine compound represented by the following general formula (1) and a piperazine-based compound, and a mixed diamine component having a mixing molar ratio of 95/5 to 35/65 with an aromatic polycarboxylic acid. It is a selective permeation film formation excellent in film formation property and reverse osmosis performance, which is made of copolyamide having excellent solubility in an aprotic amide solvent obtained by reacting acid components so as to be substantially equal.

(Y represents a divalent organic group other than -SO _2-. R ¹ and R ² are hydrocarbon groups having 1 to 12 carbon atoms, R ³ and R ⁴ are monovalent organic groups, and ₁ , n ₂ represents 0 or a natural number of 1 to _3. ) The diamine compound (1), the piperazine compound, and the aromatic polycarboxylic acid component used for producing the copolyamide of the present invention are as follows. Is.

Examples of the compound represented by the general formula (1) include 3,3'-diaminodiphenylmethane, 4,4'-diamino-3,3'-dimethyldiphenylmethane and 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'-diamino Diphenyl ether,
2,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 4,4'-diaminobenzanilide, 4,4'-diaminobenzenesulfoanilide, 3,3'-
Diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfide, etc. can be mentioned, and from the viewpoint of solubility and heat resistance of the obtained copolyamide in an aprotic amide solvent, 4,4'-diamino- is preferable. Benzophenone, 4,4'-diaminobenzenesulfoanilide, 3,3'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfide, 1,3-bis (4-aminophenoxy) benzene, 1,4-bis (4 -Aminophenoxy) benzene, 2,2-bis [4- (4-aminophenoxy) phenyl] propane and the like.

When two or more of the above diamine compounds are used, they can be mixed and used at any ratio.

Examples of the piperazine compound include piperazine, 2-methylpiperazine, t (trans) -2,5-dimethylpiperazine, cis-2,5-dimethylpiperazine, 2,6-dimethylpiperazine, 2,3,5-trimethylpiperazine. , 2,2,3,
3,5,5,6,6-octamethylpiperazine, 2,2,5,5-tetramethylpiperazine, 2,2,3,5,5,6-hexamethylpiperazine, 2-ethylpiperazine, 2,5 -Diethylpiperazine, 2,3,5-triethylpiperazine, 2,2,3,5,5,6-hexaethylpiperazine, 2,3,5,6-tetraethylpiperazine, 2-propylpiperazine, 2,5-di Propylpiperazine, 2,3,5-tripropylpiperazine, 2,3,5,6-tetra-n-propylpiperazine, 2-butylpiperazine,
2,5-di-n-butylpiperazine, 2,5-di-tert-butylpiperazine, 2,3,5-tri-n-butylpiperazine,
2-pentylpiperazine, 2-decylpiperazine, 2,5
-Divinylpiperazine, 2,5-diphenylpiperazine,
2-phenylpiperazine, 2,3,5,6-tetraphenylpiperazine, 2-naphthylpiperazine, 2,5-dinaphthylpiperazine, 2-tolylpiperazine, 2,5-ditolylpiperazine, 2,3,5,6 -Tetratolyl piperazine etc. are mentioned. From the viewpoint of solubility in an aprotic amide solvent and salt removal rate, preferred piperazine compounds are piperazine, 2-methylpiperazine and t-2,5-dimethylpiperazine, and particularly preferred is piperazine.

There is only one type of piperazine compound used mainly,
It is also possible to use a mixture of two or more types depending on the application.

The mixing ratio of the aromatic diamine compound represented by the general formula (1) and the piperazine-based compound has a great influence on the physical properties of the copolyamide produced, and the preferable range is 95/5 by molar ratio.
~ 35/65. If the amount of the piperidine compound is more than 65 mol%, the reaction system tends to be non-uniform, and it is difficult to control the degree of polymerization and it is difficult to obtain a highly viscous copolyamide. Also,
The solubility of the copolyamide in the aprotic amide solvent also deteriorates. More preferable amount of the piperazine compound is in the range of 10 to 60 mol% with respect to the total amount of diamine components,
It is particularly preferably in the range of 10 to 40 mol%.

As the aromatic polycarboxylic acid component in the present invention, 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 acid,
Examples thereof include 2,6-naphthalene dicarboxylic acid, 2,7-naphthalene dicarboxylic acid, and acid halide compounds (chloride, bromide, etc.) thereof. Of these, isophthalic acid dichloride and terephthalic acid dichloride are particularly preferable from the viewpoint of reactivity and solubility in an aprotic amide solvent.

The above aromatic polycarboxylic acid components can be mixed and used in any proportion.

The copolyamide of the present invention can be synthesized by the following solution polymerization method.

As the solvent used in the solution polymerization method, various kinds of organic solvents can be used, but an aprotic amide solvent is preferably used.

Preferred solvents include N-methyl-2-pyrrolidone,
Hexamethylphosphoramide, N, N'-dimethylacetamide, N, N'-dimethylformamide and mixtures thereof can be mentioned. Most preferred is N-methyl-2-pyrrolidone.

In the amide solvent, methylene chloride, chloroform, 1,2-dichloroethane, 1,1,2-trichloroethane,
It is also possible to mix a chlorine-based solvent such as 1,1,2,2-tetrachloroethane or chlorobenzene.

The above solvents used for solution polymerization must be sufficiently dehydrated in advance by a dehydrating agent such as distillation or molecular sieve.

The water content of the solvent used in the solution polymerization reaction of the present invention is 200 ppm or less, preferably 100 ppm or less, and particularly preferably 50 ppm or less.

It is possible to use various kinds of amine compounds as reagents for trapping hydrogen chloride generated during the polymerization, and aliphatic tertiary amine compounds such as triethylenediamine, triethylamine and N-methylmorpholine, pyridine, α-picoline, β -Picoline, γ-picoline, 2-ethylpyridine, 3-ethylpyridine, 4-ethylpyridine, 2-propylpyridine, 4-propylpyridine, and other pyridine-based compounds, N, N-dimethylaniline, N, N-diethylaniline And N, N-dialkylaniline compounds such as
Of these, pyridine, N, N-dimethylaniline, and N, N-diethylaniline are preferable, and pyridine is particularly preferable in terms of increasing the viscosity of the polymer and easiness of purification.

The water content of the acid scavenger used in the polymerization reaction of the present invention is 200 p
pm or less, preferably 100 ppm or less, particularly preferably 50 ppm
It is the following. The acid scavenger to be used is preferably purified in advance by distillation and further sufficiently dehydrated by molecular sieve or the like.

A general polymerization method of solution polymerization will be described. A mixture of the diamine compound (1) and the piperazine compound is dissolved in the amide solvent or the mixed solvent under a nitrogen stream.
The concentration of the charged monomer in the solvent is 10 to 50% (wt monomer / vol solvent), preferably 20 to 40%. Further, a predetermined amount of the scavenger for hydrogen chloride produced during the reaction described above is added to the mixed system. The addition amount of the acid scavenger is not particularly limited, but basically it is preferably 1.0 to 3.0 times mol, and more preferably 1.0 to 2.0 times mol of the theoretically generated hydrogen chloride amount generated during the reaction. The amount of the acid scavenger added depends on the type of the acid scavenger, and therefore the amount cannot be limited. For example: Although the addition amount of pyridine and / or its derivative as an acid scavenger is 1 times mol or more of the theoretically generated hydrogen chloride amount, the viscosity of the produced polymer is not lowered, but the addition amount of pyridine is the reaction solvent used. On the other hand, if the amount is large, pyridine acts as a poor solvent for the polymer, the solution during the reaction becomes non-uniform, and the viscosity is increased and the purification step is hindered. Therefore, the ratio of the amount of pyridine to the amount of the reaction solvent should be 1/2 or less, preferably 1/3 or less.

With respect to the amount of the N, N-dialkylaniline compound added, it is preferably 1.0 to 1.2 times the molar amount of theoretically generated hydrogen chloride. If the amount added is 1.0 or less, the effect as a hydrogen chloride scavenger is reduced, and the viscosity of the resulting copolyamide is also reduced. On the other hand, when it is 1.2 or more, the produced polymer becomes insoluble in the reaction solvent, and the reaction system becomes non-uniform. As a result, it becomes difficult to purify the polymer. Furthermore, the viscosity of the obtained polymer tends to decrease with the addition amount.

Dissolving the diamine compound in a solution consisting of the solvent and the acid scavenger, in the case of a uniform solution, for the purpose of improving the solubility of the diamine compound, by adding a suitable solvent, or heating the solution It is also possible to do so. The solvent for promoting the solubility needs to be sufficiently dehydrated in advance by distillation or a desiccant. The heating temperature may be any temperature as long as it does not decompose the solvent used and the amine compound, but the most preferable temperature is room temperature.

The solution is then cooled to -10 ° C to 20 ° C, preferably -50 ° C to 10 ° C with a suitable refrigerant. As the refrigerant, water and / or ethylene glycol is generally and preferably used, but the method is not particularly limited.

Next, the aromatic polycarboxylic acid halide is added to the cooled solution of the diamine compound, the acid scavenger and the reaction solvent with stirring, and the stirring is continued for an appropriate time. The form of the aromatic polycarboxylic acid halide at the time of addition may be any form such as a solid state (powder form, flake form or pellet form), a solution state dissolved in a suitable solvent, or a state melted by heating. Is possible, but
The solid state is preferred.

The rate of addition of the aromatic polycarboxylic acid halide to the solution may be any rate as long as it does not continuously exceed 70 ° C, but it is preferable to add it as soon as possible from the viewpoint of formation of a high polymer. . It is preferable to add at least 90 mol% or more of the aromatic polycarboxylic acid halide compound to all diamine components within 5 minutes. Otherwise, the viscosity of the copolyamide obtained is very low. In addition, the stirring speed at the time of adding the aromatic polycarboxylic acid halide affects the degree of polymerization of the produced polymer,
The higher the stirring speed, the higher the degree of polymerization of the obtained polymer, which is preferable from the viewpoint of the physical properties of the polymer.

After the addition of the aromatic polycarboxylic acid halide, stirring is continued for about 30 minutes to 1 hour under the above cooling. The stirring speed at this time may be any speed, but it is preferably as high as possible.

After the reaction under cooling as described above, subsequently, at room temperature, about 1
The polymerization reaction is continued for 2 hours. The stirring speed at this time may be any speed, but it is preferable that the stirring speed is as high as possible in order to obtain a highly viscous polymer.

The aspect of the polymerization reaction system generally depends on the type and concentration of the acid scavenger. For example, when a pyridine compound and an N, N-dialkylaniline compound are used as an acid scavenger, the reaction system is characterized by being a transparent homogeneous solution during and after the polymerization. Therefore, there is an advantage that the viscosity of the produced copolyamide can be estimated from the viscosity of the polymerization reaction solution.

Further, the polymerization reaction solution can be continuously poured into the poor solvent of the polymer to solidify and purify the polymer,
Very convenient. Further, since the reaction system is constantly homogeneous during the polymerization, a polymer having a high degree of polymerization can be obtained.

Addition of a suitable substance to the reaction system before, during, and after the polymerization to neutralize hydrogen halide generated during the polymerization and / or to facilitate the dissolution of the polymer in the reaction solvent. Is also possible.

Examples of such inorganic compounds include lithium chloride,
Preferred examples include calcium chloride, potassium chloride, lithium carbonate, lithium oxide, lithium hydroxide, calcium hydroxide, calcium carbonate and the like. Lithium chloride, calcium chloride, potassium chloride and the like can be added before the polymerization for the purpose of accelerating the dissolution of the polymer, but others are preferably added after the polymerization for the purpose of neutralizing generated hydrogen halide. . Further, as an organic compound having such an effect, propylene oxide is mentioned as a preferable example. The substance can be added before and / or after the polymerization.

If necessary, a terminal terminating agent can be used as the other additive, and as the terminal terminating agent, a compound having only one group that reacts with an amino group and an acid halide group is suitable.

After the polymerization reaction, the obtained solution is mixed with a poor solvent for the polymer such as methanol and water to take out the polymer as a solid. Further, filtration of solid polymer and washing with water and methanol should be repeated to remove the solvent, acid scavenger, hydrochloric acid and oligomer adsorbed on the polymer as much as possible. Thoroughly washed polymer at 130 ℃ -150
The copolyamide of the present invention can be obtained by vacuum drying at ° C.

The amount of residual hydrochloric acid in the polymer thus purified is 50
It should be 0 ppm or less, preferably 200 ppm or less.

Next, a general method of interfacial polymerization will be described. As the organic solvent for the organic phase used in the interfacial polymerization, methylene chloride, chloroform, carbon tetrachloride, chlorobenzene, chlorine-based hydrocarbon solvents such as 1,1,2,2-tetrachloroethane, n-hexane, n-octane, cyclohexanone, etc. And aliphatic hydrocarbons, aromatic hydrocarbons such as xylene, benzene, and toluene, or a mixture thereof.

As a substance that traps hydrogen chloride generated during interfacial polymerization, sodium hydroxide, sodium carbonate, lithium hydroxide, lithium carbonate, potassium hydroxide, etc. are used, and sodium hydroxide and sodium carbonate are particularly preferable. The amount of the additive is 0.5 to 1.5 times the molar amount of hydrogen chloride to be generated, and is determined according to the metal species.

If a general polymerization operation is shown, a solution in which a diamine compound (1) and a piperazine compound and a hydrogen chloride trapping agent are dissolved in water is mechanically mixed with a solution in which a polycarboxylic acid halide compound is dissolved in the above organic solvent. Then, the polymer of the present invention is obtained.

At this time, a part of the organic phase not containing the polycarboxylic acid halide is mechanically mixed with the aqueous phase containing the diamine compound, and the solution of the organic solvent containing the polycarboxylic acid halide is added to the mixture while stirring. Is preferred.

In order to promote the dissolution or dispersion of the diamine compound (1) and the piperazine compound used in the present invention in the aqueous phase,
It is also possible to heat the aqueous phase or add a surfactant to the aqueous phase. The concentration of the polycarboxylic acid halide and the diamine compound in the organic phase and the aqueous phase is generally 0.3.
~ 10 wt% is preferred. An appropriate concentration should be selected depending on the solubility of the diamine compound (1) and the piperazine compound in water. The solution obtained after the polymerization reaction is mixed with methanol, water and the like to form a precipitate, and then filtration and washing with water are repeated several times, and then dried at a predetermined temperature for about 24 hours to obtain the co-precipitate of the present invention. A polyamide can be obtained.

The copolyamide obtained by the present invention is dissolved in an appropriate organic solvent, and the solution is applied to an appropriate plate (glass, metal plate).
An asymmetric membrane can be obtained by immersing it in a poor solvent for the copolyamide after coating on it.

At this time, as a micropore-forming agent, an organic compound such as ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, glycerin and / or lithium chloride, sodium chloride, potassium chloride, magnesium chloride, calcium chloride, strontium chloride,
It is also possible to add an inorganic compound such as magnesium perchlorate to the organic solvent to prepare an asymmetric membrane. It is also possible to obtain a homogeneous film by evaporating the organic solvent from the plate coated with the solution containing no micropore-forming agent. Further, by spinning the solution to form a hollow fiber morphology, also, on a suitable porous membrane, the solution of the copolyamide obtained in the present invention is applied,
It is also possible to take the form of a composite membrane. As the porous membrane used, a porous membrane obtained from a polymer compound, for example, an organic porous membrane such as polyethylene, polysulfone, polypropylene, or polyimide, silica gel, alumina,
Porous substances made of inorganic substances such as silica-alumina and zeolite are suitable. As the coating method, a dipping method,
Any method such as a roll coating method or a quick coating method may be used. The thickness of the applied polymer is 0.05 ~
The coating conditions should be controlled to be 1.0 micron, preferably 0.1-0.5 micron.

At the time of forming the active layer of the film as described above, for the purpose of improving the solubility of the copolyamide in the organic solvent in the organic solvent and adjusting the pore size of the film, an organic compound such as ethylene glycol or glycerin in the organic solvent. And / or it is possible to add an inorganic compound such as lithium chloride, lithium bromide, magnesium chloride, magnesium bromide. Besides applying the polymer, it is also possible to form a thin film on the support as follows.

That is, after coating the solution of the aromatic diamine compound (1) of the present invention and the piperazine-based compound on the porous film, it is immersed in an organic solvent in which an aromatic polycarboxylic acid halide is dissolved for a predetermined time, thereby It is also possible to form a film of the copolyamide of the present invention on the porous film. Examples of the porous membrane material used include polymer compounds such as polyethylene, polypropylene, polysulfone, and polyimide.

It is also possible to form the copolyamide film on a porous film material made of an inorganic compound such as silica gel, alumina, silica-alumina, or zeolite.

In order to increase the strength of the film when forming the composite film, trimesic acid chloride, trimellitic acid chloride, 3-chlorosulfonylisophthalic acid chloride, pyromellitic acid chloride,
A compound having a group reactive with three or more amines such as benzophenonetetracarboxylic acid chloride may be added in any proportion.

(Function) A copolyamide obtained by reacting a mixed diamine component of a specific bis (aminophenyl) -based compound and a piperazine-based compound with an aromatic polycarboxylic acid component is N, N-dimethylacetamide or N-methyl- 2-pyrrolidone, N, N-
Since it is dissolved in an aprotic amide-based organic solvent such as dimethylformamide, the film forming property is good. Furthermore, the permselective membrane obtained from the present copolyamide has excellent permselectivity and chlorine resistance.

The present invention is described in detail below, but the present invention is not limited to the examples.

(Example) Example 1 200 ml of N-methylpyrrolidone and 28 ml of triethylamine were added to 16.02 g (0.08 mol) of 4,4'-diaminodiphenyl ether and 1.72 g (0.02 mol) of piperazine, and a nitrogen introduction tube, a thermometer, and stirring were added. Into a four-necked flask with a capacity of 500 ml equipped with a nitrogen stream under a nitrogen stream, after sufficiently stirring, while cooling the entire reaction system with ice, 20.31 g of isophthalic acid dichloride
(0.1 mol) is added rapidly under a stream of nitrogen. After reacting under ice cooling for about 60 minutes, the temperature is returned to room temperature and the reaction system is stirred for about 1 hour. After the reaction is completed, the above reaction profit is added to 1500 ml of methanol.
Pour in to precipitate the copolyamide. This precipitate is crushed with a household mixer, filtered, washed with water, etc. several times to remove unreacted substances and solvent, and finally washed with methanol, dried at 140 ° C. under vacuum for 48 hours, and purified. A copolyamide was obtained. The yield of the purified product obtained is about 90.
%,Met. An asymmetric membrane was prepared according to the method described above (see page 22 of the present invention) and the reverse osmosis performance was evaluated. The results are shown in Table 1.

(Examples 2 and 3) In Example 1, 4,4'-diaminodiphenylmethane (4c) was used instead of 4,4'-diaminodiphenyl sulfone.
, The mixing molar ratio of piperazine is 20 mol%, 50 mol%
The same procedure as in Example 1 was carried out except that

The reduced viscosities of the obtained polymers were 2.30 and 0.70, respectively. In addition, the polymer showed excellent solubility in NMP, and the production of asymmetric membranes and reverse osmosis experiments were performed according to the method described above. The results are shown in Table 1.

(Examples 4 and 5) The same procedure as in Examples 2 and 3 was repeated except that 4,4'-aminobenzanilide (4am) was used in place of diaminodiphenyl ether in Examples 2 and 3. Using the obtained polymer, asymmetric membrane production and reverse osmosis experiments were carried out according to the method described above. The results are shown in Table 1.

(Example 6) In Example 1, in place of 4,4'-diaminodiphenyl ether, 4,4'-aminobenzsulfoanilide (4s
Example 1 was repeated except that m) was used. Asymmetric membrane production and reverse osmosis experiments were performed according to the method described above.

The results are shown in Table 1.

(Example 7) The procedure of Example 1 was repeated, except that 4,4'-diaminodiphenyl sulfide (4sf) was used instead of 4,4'-diaminodiphenyl ether. An asymmetric membrane was produced from the obtained polymer and the reverse osmosis was evaluated. The results are shown in Table 1.

(Examples 8 to 11) In Example 1, 1,4-bis (4-aminophenoxy) benzene (tq) and 1,3-bis (4-aminophenoxy) were used instead of 4,4'-diaminodiphenyl ether. 20 mol% of benzene (tr), 2,2-bis [4- (4-aminophenoxy) phenyl] propane (pp), or 50
All the same as in Example 1 except that the mol% was used.
Got the result. As shown in the table, the permselective membrane obtained from this copolyamide showed excellent reverse osmosis performance and chlorine resistance.

(Examples 12 to 14) In Examples 6, 9 and 10, except that terephthalic acid dichloride (T) was used instead of isophthalic acid dichloride.
Similarly, the results shown in Table 1 were obtained. As shown in the table, the selectively permeable membrane obtained from this copolyamide showed excellent reverse permeation performance and chlorine resistance.

The piperazine-containing copolyamide obtained in the present invention exhibited film-forming properties and reverse osmosis performance not found in conventional piperazine-based polyamides.

Comparative Example 1 Metaphenylenediamine 10.80 g (0.10 mol), and N-
Add 150 ml of methylpyrrolidone to a 500 ml four-necked round-bottomed flask equipped with a nitrogen inlet tube, a thermometer, and a stirring blade, stir to homogenize, then cool to 0 ° C., and powder the mixture while stirring. Isophthalic acid dichloride 20.30g (0.1mol)
Is added at once and the isophthalic acid dichloride adhering to the inner wall of the container is washed off with 10 ml of N-methylpyrrolidone. When isophthalic acid dichloride is added, the temperature of the reaction system is approximately 50 ° C.
After stirring for about 1 hour while cooling, the temperature is returned to room temperature and stirring is continued for 2 hours to complete the reaction. 1500 ml of the obtained solution was poured into methanol to precipitate the polyamide. The precipitate was filtered, ground in a water-mixed home mixer, washed, and dried under reduced pressure for 24 hours to obtain a purified polyamide. The yield of this polyamide was about 85%.

Comparative Example 2 A purified polyamide was obtained in the same manner as Comparative Example 1 except that terephthalic acid dichloride was used instead of isophthalic acid dichloride in Comparative Example 1 above. The yield of this polyamide was about 73%.

Comparative Example 3 A copolyamide was obtained in the same manner as in Comparative Example 1, except that a mixed diamine compound of metaphenylenediamine and 2,4-diaminobenzenesulfonic acid (molar ratio 10 mol%) was used in Comparative Example 1. The yield of this copolyamide was 82%.

Comparative Example 4 Comparative Example 3 except that terephthalic acid dichloride was used instead of isophthalic acid dichloride in Comparative Example 3 above.
A copolyamide was obtained in the same manner as in. The yield of this copolyamide was about 83%.

Comparative Example 5 Piperazine 8.6 g (0.10 mol), sodium hydroxide 8.4 g
(0.21 mol) and 300 cc of water are supplied to a cylinder of 2 and dissolved uniformly, and while stirring this solution with ice cooling, 20.3 g (0.10 mol) of isophthalic acid dichloride dissolved in 300 ml of cyclohexanone is added, Stir for 5 minutes to react. The yield of the purified product obtained by purifying this reaction product in the same manner as in Example 1 was 67%.

Comparative Example 6 A polyamide was obtained in the same manner as in Comparative Example 5 except that terephthalic acid dichloride was used instead of isophthalic acid dichloride in Comparative Example 5. The yield was 68%.

Comparative Example 7 Piperazine 0.86 (0.01 mol), metaphthalenediamine
4.32 g (0.04 mol), sodium hydroxide 4.8 g (0.12 mol) and 160 ml of water were supplied to a cylinder of 1 to dissolve them uniformly, and this solution was ice-cooled and stirred while isophthalic acid dissolved in 75 cc of cyclohexanone. Dichloride 10.15 g (0.
(05 mol) was added, and the mixture was stirred for about 60 minutes to be regenerated, 300 cc of n-hexane was added to this reaction product to cause precipitation, and purification was carried out in the same manner as in Example 1 to obtain a copolyamide. The yield of this copolyamide was 74%.

Comparative Example 8 A copolyamide was obtained in the same manner as in Comparative Example 7 except that terephthalic acid dichloride was used instead of isophthalic acid dichloride in Comparative Example 7. The yield of this copolyamide was 71%.

Table 1 shows the solubility of NMP in Comparative Examples 1 to 8 and the film characteristics.

In Table 1, the acid component I is isophthalic acid dichloride, T
Is terephthalic acid dichloride, m of the diamino component (I) is metaphenylenediamine, pip of the diamine component (2) is piperazine, ms is metaphenylenediamine-4-sulfonic acid, and the molar ratio (%) of the diamino component is Is the molar ratio of the diamine component (2) to the total diamine component (1) + (2). The film forming property ⊚ is very good, ○ is good, Δ is bad, and x is impossible. Permeability and salt removal rate indicate reverse osmosis membrane performance.
Water permeability when provided at a pressure 55 kg / cm ² to normal continuous pump reverse osmosis device saline solution as a stock solution of (/ m ² ·
(Day) and the salt concentration in the stock solution and the salt concentration in the permeated water with respect to the salt concentration in the stock solution were shown as a salt removal rate (%) calculated as a percentage (the larger the number, the better the salt removal performance). “With chlorine” means that 50% of the above 35000 ppm saline solution is used.
A chlorine-containing saline solution containing ppm chlorine is supplied as a stock solution, and the water permeation rate and salt removal rate after 10 hours are shown.

Chlorine absorption is 150 ℃ after freeze pulverizing polyamide,
0.5 g of fine powder of 10 microns or less dried in a vacuum chamber for about 15 hours was used as a chlorine source, sodium hypophosphite, and as a buffer for adjusting PH, phosphoric acid, 1 potassium dihydrogen phosphate, 1 phosphoric acid.
The chlorine concentration obtained by mixing 2 potassium hydrogen is about 220 ppm,
Put into 500cc of PH5 chlorine aqueous solution, and in a constant temperature bath at 40 ° C, calculate the chlorine absorption rate from the change in chlorine concentration in the chlorine aqueous solution over time, and do not mix the polyamide that was previously obtained. The value obtained by subtracting the spontaneous disappearance rate of chlorine in the aqueous chlorine solution was taken as the chlorine absorption rate of the polyamide itself, and was shown by the molar ratio of the chlorine absorption amount to one unit of polyamide one hour after the start of the chlorine absorption rate measurement test. The smaller the chlorine absorption, the better the chlorine resistance of the polyamide.

(Effects of the Invention) The permselective membrane according to the present invention is not only excellent in film-forming property and reverse osmosis performance, but also particularly has chlorine resistance and is suitable for desalination of seawater and brackish water.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Haruhiko Naruzawa 2-1-1 Katata, Otsu City, Shiga Toyobo Co., Ltd. Research Institute (72) Inventor Yasuo Kato 2-1-1 Katata, Otsu City, Shiga Prefecture Koichi Nakano, Examiner, Research Laboratory, Toyobo Co., Ltd. (56) References JP-A-62-244404 (JP, A) JP-A-63-213522 (JP, A)

Claims (1)

[Claims] 1. A mixed diamine component consisting of an aromatic diamine compound represented by the following general formula (1) and a piperazine compound, the mixed molar ratio of which is 95/5 to 35/65, and an aromatic polycarboxylic acid. A permselective membrane made of copolyamide obtained by reacting components. (Y represents a divalent organic group other than -SO _2-. R ¹ and R ² are hydrocarbon groups having 1 to 12 carbon atoms, R ³ and R ⁴ are monovalent organic groups, n ₁ and n ₂ represent 0 or a natural number of 1 to _3. )