JPS6354404B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a novel permselective composite membrane and a method for producing the same. More specifically, the present invention relates to a permselective composite membrane with excellent permeation rate, salt rejection rate, compaction resistance, and chemical resistance. Despite its excellent basic performance, the cellulose acetate-based reverse osmosis membrane developed by Loeb and Sourirajan et al. has various problems, such as hydrolyzability, compaction, deterioration due to microorganisms, and drying. Many synthetic polymers have been proposed as membrane materials to compensate for these drawbacks.
However, most of them have advantages and disadvantages, and to date, no membrane material has been found that solves all of the above-mentioned problems and has high water permeability and high exclusion properties. We have already proposed a selectively permeable membrane made by crosslinking a polyadduct of a bisepoxy compound and a polyamino compound as a membrane material that satisfies such purposes (Japanese Patent Application No. 1973-
No. 59930, No. 52-60944), as a result of further studies, they discovered that triglycidyl isocyanurate was used as an epoxy compound alone or in combination with a bis-epoxy compound to react with a polyamino compound, and then this was made into a porous material. The present inventors have discovered that a composite membrane formed by coating and impregnating a supporting substrate and then crosslinking the membrane can become a more useful and promising selectively permeable membrane, and has completed the present invention. That is, the present invention provides the following equation: 1(a) Triglycidyl isocyanurate represented by: 100 to 5 mol% and the following formula [However, R is -CH ₂ -CH ₂ - or

Represents [formula]. ] A bisepoxy compound represented by: a polyepoxy compound consisting of 0 to 95 mol%; (b) an amino group containing at least two amino groups or imino groups, or at least one each of an amino group and an imino group; After coating and/or impregnating a microporous support substrate with an aqueous solution of the water-soluble adduct obtained by reacting the adduct with a compound, the support substrate coated with and/or impregnated with the adduct is treated with (c) an amino group. , a permselective composite membrane obtained by contacting with a solution of a polyfunctional compound capable of reacting with an imino group or a hydroxyl group, followed by heat treatment, 2. The microporous supporting substrate is made of polysulfone and/or cellulose acetate. 3. The permselective composite membrane according to claim 1, wherein the polyfunctional compound is isophthalic acid chloride,
4. The permselective composite membrane according to any one of claims 1 to 2, which is one or more selected from the group consisting of terephthalic acid chloride, trimesic acid chloride, and toluene diisocyanate. After that, a divalent and/or trivalent compound having the ability to form a chelate with any one of an amino group, an imino group, a hydroxyl group, and a carboxyl group is added.
A permselective composite membrane according to any one of claims 1 to 3, characterized in that the membrane is modified by treatment with an aqueous solution of a metal salt, and a method for producing the same. Triglycidyl isocyanurate (e.g. Araldite -TGIC) used in the present invention and the formula (However, R is -CH ₂ -CH ₂ - or

[However, in the above formula, n ₁ and n ₂ represent integers of 1 to 10, and R and R' independently represent a hydrogen atom or an alkyl, alkenyl, aryl, alkanol, aralkyl group having 1 to 20 carbon atoms, or -CH ₂ −CH ₂ −CN. ]

[However, R represents H or _-CH3 . ] [However, _n3 is an integer from 1 to 10. ]

【formula】

【formula】

【formula】

【formula】

[Formula] The water-soluble adduct in the present invention comprises the above-mentioned polyepoxy compound and the above-mentioned compound containing two or more amino groups and/or imino groups per equivalent of the epoxy group. and preferably at a ratio of 1 to 2 equivalents. In this case, in the case of a compound containing two or more amino groups, calculation is made using only the amino group, and when the compound has one amino group and the others are imino groups, calculation is made using the sum of the amino group and the imino group. In the case of only imino groups, it is naturally calculated using only imino groups. If the equivalent weight of the amino group or imino group is less than 1, a water-insoluble hydrogel tends to form, which is not preferable. Since amino groups and imino groups have significantly different reactivities, reaction conditions may be fairly mild for amino groups, but must be somewhat stricter for imino groups. For example, the above reaction can be carried out at a temperature range of -30°C to 100°C, but most preferably at room temperature (25°C to 100°C).
It is best to do this at around 30℃. At a reaction temperature of -30°C to 5°C, the reaction of amino groups proceeds, but the reaction of imino groups is very slow.
As the reaction temperature increases, the reactivity of the imino group increases, but the particularly preferred range in the present invention is 25°C.
At around ~30℃, most of the amino groups react,
A considerable amount of imino groups remains, and a film crosslinked and heat-treated using an adduct with such a structure is particularly excellent in stability and other aspects. Further, the concentration of the polyepoxy compound and amino compound to be charged is 5 to 50%, preferably 20 to 50%.
It is 40%. The degree of polymerization of the adduct thus obtained varies depending on the charging ratio. For example, in the case of an epoxy compound and a diamino compound, if 2 equivalents of amino group are added to 1 equivalent of epoxy group, on average, the corresponding number of diamino compounds will be added to each epoxy group of the polyepoxy compound, and the reaction will not proceed. However, as the amount becomes lower than 2 equivalents, the degree of polymerization increases. In the present invention, the adduct thus obtained,
In other words, the degree of polymerization of the prepolymer is not so important; in short, it is water-soluble and can be coated and/or impregnated onto a microporous support substrate to form at least a cohesive film-like material as described below. It is sufficient if the film is formed by the crosslinking reaction and heat treatment described later. Of course, it may also be one that is heated to form a hydrogel when forming an aggregated film-like material. Therefore, if the addition polymerization reaction proceeds too much, it may become water-insoluble, and it is difficult to obtain a uniform film before the crosslinking reaction, which is undesirable. In the present invention, the formation of such a water-soluble adduct is mainly controlled by the charging ratio of the epoxy compound and the amino compound, but also by the reaction temperature. In addition, when using two or more types of raw materials, it is possible to mix them from the beginning to create a random composition, but by adding each at each reaction stage, a more regular composition can be created. It is possible to obtain. Just a few examples of the above-mentioned adducts of the present invention obtained in this way include:

【table】

[Table] etc. are given as non-limiting examples of the present invention, but the present invention further includes various combinations. The adduct-containing aqueous solution thus obtained is filtered, diluted or concentrated as required, and then applied to and/or impregnated onto a microporous support substrate. The microporous support substrate has many fine pores, and polysulfone and/or cellulose acetate are preferably used. Methods for producing such microporous support substrates are well known to those skilled in the art, and one example of such methods is as follows, using polysulfone as an example. A microporous support substrate for polysulfone can be obtained by casting a dimethylformamide solution containing 10 to 20% by weight of polysulfone onto a glass plate or reinforcing woven or nonwoven fabric, and then immersing it in water to gel the film. is formed. The microporous membrane thus obtained has an anisotropic structure, and a large number of micropores of usually 100 Å or less are distributed on the so-called front surface. coated or impregnated on the face. The microporous support substrate can have various thicknesses, but is usually 10 to 300μ, preferably 30 to 150μ, and has a membrane constant of 1×10 ^-3 to 1×10 ^-1 g/cm ² .
sec/atm is preferable. The concentration of the adduct in the adduct aqueous solution to be coated and/or impregnated varies depending on the degree of polymerization of the adduct, the structure of the microporous support substrate, the degree of impregnation, etc., but is usually 0.1 to 10% by weight, and is preferably is 0.5 to 5% by weight. It is also possible to raise the temperature during coating and impregnation, or to further add an organic solvent. Examples of such organic solvents include lower alkyl alcohols having 1 to 5 carbon atoms. The aggregated film-like material of the adduct obtained by coating and/or impregnating onto a microporous support substrate has a fairly high water content as it is, so water is removed by evaporation etc. as necessary. . The aggregated film-like substance of the adduct before cross-linking is usually coated with a film thickness of
10 to 10000 Å, preferably 100 to 1000 Å, and the water content is 0 to 50% by weight (wet basis),
Preferably it is 0 to 30% by weight (wet basis). The thus obtained composite of the adduct-like film and the microporous support substrate is further brought into contact with a solution of a polyfunctional compound capable of reacting with amino groups, imino groups, or hydroxyl groups to undergo crosslinking treatment. be done. As such a polyfunctional compound, one containing at least two functional groups of one or more types selected from the following functional group group [A] is used. Functional group group [A]:

[Formula]-SO ₂ X, -N=C=O,

【formula】 [However, in the formula, X represents a halogen atom. ]

Among these, acid chlorides and isocyanates are preferred. Examples of such polyfunctional compounds include aromatic compounds having two or more of the above functional groups and low molecular weight aliphatic compounds which may have an ether bond. As an aromatic group

【formula】 【formula】

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【formula】 【formula】

【formula】

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_{[ Formula : _ _ _} etc. Examples of suitable compounds include:

【formula】

【formula】

【formula】

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【formula】

【formula】

【formula】

【formula】

【formula】

【formula】

【formula】

[Formula] etc. are mentioned as non-limiting examples of the present invention, and among these, particularly preferred are isophthalic acid chloride, terephthalic acid chloride, trimesic acid chloride, and toluene diisocyanate. These crosslinking agents may be used alone or in combination, and in some cases, the water permeability and rejection rate can be improved to some extent by combining them. Just a few examples of the adducts of the present invention crosslinked using such crosslinking agents include:

【table】

[Table] Of course, in the present invention, various structures can be obtained by combining the polyepoxy compound (a), the amino compound (b), and the polyfunctional compound (c). It will be done. In the above examples, all the crosslinking agents are bonded to amino groups and imino groups, but in the present invention, they can also be bonded to hydroxyl groups. In addition, in the above examples, all the amino groups and imino groups are bonded to the crosslinking agent, but in the present invention, the crosslinking agent does not necessarily need to be bonded to all crosslinkable points, and a wide range of crosslinking may be performed depending on the purpose. You can get the degree. The crosslinking reaction of the present invention is achieved by dissolving the above-mentioned crosslinking agent in a suitable organic solvent to form a solution, bringing the solution into contact with the above-mentioned composite, and then heat-treating the solution. In this operation, the crosslinking agent diffuses into the aggregated membrane from the contact surface between the adduct-like membrane of the composite and the crosslinking agent solvent, and at this time the crosslinking reaction proceeds to some extent. By further heat-treating, the unreacted portions of the diffused crosslinking agent can be crosslinked to a desired degree, and the portions where no crosslinking agent is present can also be transformed into a stable structure. In the present invention, as the crosslinking agent diffuses through the aggregated film-like material as described above, a distribution of crosslinking agent concentration occurs within the film, and the areas where no crosslinking agent is present due to heat treatment also have a unique three-dimensional stability. It is believed that these structures further increase the effects of the present invention. The concentration of the crosslinking agent in the crosslinking agent solution is usually 0.05 to 5% by weight, and the temperature of contact with the aggregated film is usually 10 to 100°C.
This is done for 5 seconds to 10 minutes. As the solvent for the crosslinking agent, n having 5 to 10 carbon atoms may be used.
-Alkanes are preferred, particularly preferred are n-hexane and n-heptane. In order to promote the crosslinking reaction, a crosslinking promoter may be included in advance in the aqueous solution of the adduct or in the crosslinking agent solution. As such a promoter, caustic alkali, sodium phosphate, pyridine, surfactant, sodium acetate, etc. are suitably used. The heat treatment to complete the above crosslinking reaction is 50~
It is preferable to carry out the reaction at 150°C, preferably 90-120°C, for 5-20 minutes. The crosslinked composite membrane obtained in this way can be used as is as a permselective membrane, but in the present invention, depending on the raw materials, crosslinking ratio, reaction conditions, etc., the crosslinked composite membrane may remain or be intentionally left. Amino group, imino group, carboxyl group,
By treating with an aqueous solution of a divalent or trivalent metal salt that has the ability to form a chelate with any of the hydroxyl groups, the water permeability and consolidation resistance of the resulting composite membrane may be improved. Processing is also encompassed by the invention. Non-limiting examples of metal salts used in the chelation treatment of the present invention include calcium chloride, barium chloride, iron chloride, magnesium chloride, aluminum chloride, mercuric chloride, strontium chloride, and the like. The chelation treatment is carried out by immersing the above-mentioned crosslinked composite membrane in an aqueous solution of 1 to 50% by weight, preferably 5 to 30% by weight, of the above metal salt at room temperature for 10 to 60 minutes. As shown in the Examples below, the composite membrane obtained by the present invention not only has excellent salt exclusion properties and water permeability, but also has excellent hydrolysis resistance and compaction resistance, and also has a crosslinked structure. Because it is insoluble in organic solvents, it is an extremely useful permselective membrane that can be applied not only to the desalination of seawater and can water, but also to the separation of organic mixtures and the higher-level treatment of industrial wastewater and food industry wastewater. . Hereinafter, the present invention will be explained in more detail with reference to Examples. In the examples, the desalination rate in the reverse osmosis test is a value determined by the following formula. RO removal rate = (1 - NaCl concentration in permeate / Na in feed stock solution
Cl concentration) ×100 Example 1 43.8 g (0.30 mol) of triethylenetetramine and 350 ml of distilled water were placed in a three-necked flask equipped with a stirrer and a thermometer, and triglycidyl isocyanate was added while stirring the system at 30°C. Nurate (Araldite TGIG Nagase/Ciba Co., Ltd.) 29.7g (0.10mol)
is gradually added to the system over 10 minutes. When the system was stirred for 5 hours, triglycidyl isocyanurate was uniformly dissolved in the system. The reaction mixture was filtered and further diluted with water to give a 2% by weight aqueous solution. (This is abbreviated as PEPA-IC _4. ) Polysulfone [Udel 3500 (manufactured by UCC)]
was dissolved in dimethylformamide:N-methylpyrrolidone:methylcellosolve (70:17:14 weight ratio) to make a 15% by weight solution, and the solution was mixed into a polyethylene terephthalate nonwoven fabric [Remay (EI
A microporous polysulfone membrane was obtained by immediately immersing it in water to gel it. The total film thickness was 160μ, and the thickness of the polysulfone on the nonwoven fabric was 60μ. The polysulfone membrane was immersed in the above PEPA-IC ₄ aqueous solution for 5 minutes, and then stood vertically for 10 minutes to air dry.
The membrane was then treated with 1.5 ml of a mixture of isophthalic chloride:trimesic chloride (5:1 weight ratio).
After being immersed in a wt% n-hexane solution for 5 minutes, it was immediately placed in a hot air dryer and heat-treated at 110 to 115°C for 10 minutes. The composite membrane obtained in this way is
As a result of reverse osmosis test under the following conditions, water permeability
110.9/m ²・hr (66.5GFD) and desalination rate 95.6
An initial performance of % was obtained. When this product was continuously tested for 100 hours under the same conditions, the water permeability was 103.7.
/m ² ·hr (62.2GFD) and a salt removal rate of 96.5%. Reverse osmosis test conditions: Stock solution: 1% by weight NaCl aqueous solution Operating pressure: 40Kg/cm ² Stock solution flow rate: 1.80/min Stock solution temperature: 25℃ Stock solution PH: 7.0 Example 2 Tetraethylenepentamine was added at 0.30% instead of triethylenetetramine. A composite membrane was prepared in exactly the same manner as in Example 1 except that the molar ratio was used. The reverse osmosis performance (test conditions were exactly the same as in Example 1) of this product was water permeability of 115.0/m ² ·hr (69.0GFD) and salt removal rate of 95.1%. After the reverse osmosis test, the above composite membrane was immersed in a 20wt% aqueous solution of ferric chloride for 1 hour, and then the membrane was tested again for reverse osmosis, and the water permeability was 138.0/ ^m2 .
hr (82.8GFD) and a desalination rate of 95.2% was obtained. It can be seen that this chelation treatment increased water permeability by approximately 20% (without causing a decrease in desalination rate). Example 3 Instead of triethylenetetramine, ω,ω′-dicyanopentaethylenetetramine [NC(-
A composite membrane was prepared in exactly the same manner as in Example 1, except that 0.30 mol of CH ₂ CH ₂ NH-) ₄ CH ₂ CH ₂ CN] was used. The reverse osmosis performance of this product is water permeability of 72.3/m ²・hr
(43.4GFD) The desalination rate was 96.7%. the membrane
Chlorine resistance was tested by soaking in 5ppm chlorinated water (PH5.0) for 24 hours. Membrane performance after immersion is water permeability of 85.7
/m ² ·hr (51.4GFD) and the desalination rate was 95.5%.
In addition, when the composite membrane of Example 1 (after 100 hours of reverse osmosis test) was immersed in chlorine water under the same conditions,
Water permeability 119.3/ ^m2・hr (71.6GFD) Desalination rate 93.4
A value of % was obtained. Example 4 A composite membrane was obtained in exactly the same manner as in Example 1, except that a mixture of toluene diisocyanate:trimesic acid chloride (1:1 weight ratio) was used instead of isophthalic acid chloride as a crosslinking agent. The reverse osmosis performance of this product is water permeability of 106.0/ ^m2 .
hr (63.6GFD) desalination rate was 95.9%. Example 5 A composite membrane was obtained in exactly the same manner as in Example 1, except that a 1:1 (molar ratio) mixture of ethylene glycol diglycidyl ether and triglycidyl isocyanurate was used instead of using only triglycidyl isocyanurate. The reverse osmosis performance of this product is water permeability of 112.8/ ^m2 .
hr (67.7GFD) and desalination rate was 93.2%. Example 6 A composite membrane was obtained in exactly the same manner as in Example 5, except that glycerin diglycidyl ether was used instead of ethylene glycol diglycidyl ether. The reverse osmosis performance of this product is water permeability of 73.3/m ²・hr
(44.0GFD) The desalination rate was 95.6%. Example 7 1.5 wt% n of isophthaloyl chloride instead of using isophthaloyl chloride:trimesoyl chloride (5:1 weight ratio) mixture as crosslinking agent
A composite membrane was obtained in exactly the same manner as in Example 1 except that -hexane solution was used. The reverse osmosis performance of this product is water permeability of 47.8/ ^m2 .
hr, and the desalination rate was 97.8%.

Claims (1)

[Claims] 1 (a) The following formula Triglycidyl isocyanurate represented by: 100 to 5 mol% and the following formula [However, R represents -CH ₂ -CH ₂ - or [Formula]. ] Bisepoxy compound represented by: a polyepoxy compound consisting of 0 to 95 mol%; (b) an amino group containing at least two amino groups or imino groups, or at least one each of an amino group and an imino group; After coating and/or impregnating a microporous support substrate with an aqueous solution of the water-soluble adduct obtained by reacting the adduct with a compound, the support coated and/or impregnated with the adduct is treated with (c) an amino group. , a permselective composite membrane obtained by contacting with a solution of a polyfunctional compound capable of reacting with an imino group or a hydroxyl group, followed by heat treatment. 2. The selectively permeable membrane according to claim 1, wherein the microporous support substrate is made of polysulfone and/or cellulose acetate. 3 The polyfunctional compound is isophthalic acid chloride,
The selectively permeable membrane according to any one of claims 1 to 2, which is one or more selected from the group consisting of terephthalic acid chloride, trimesic acid chloride, and toluene diisocyanate. 4 (a) The following formula Triglycidyl isocyanurate represented by: 100 to 5 mol% and the following formula [However, R represents -CH ₂ -CH ₂ - or [Formula]. ] Bisepoxy compound represented by: a polyepoxy compound consisting of 0 to 95 mol%; (b) at least 2 amino groups or imino groups, or at least 1 amino group and imino group each;
After coating and/or impregnating a microporous support substrate with an aqueous solution of the water-soluble adduct obtained by reacting the adduct with an amino compound containing (c) contact with a solution of a polyfunctional compound capable of reacting with amino groups, imino groups or hydroxyl groups, followed by heat treatment; 1. A permselective composite membrane characterized in that it has been modified by being treated with an aqueous solution of a divalent and/or trivalent metal salt having chelate-forming ability.