JPH0592129A - Composite semipermeable membrane - Google Patents

Abstract

(57) [Abstract] [Purpose] The present invention is to provide a novel composite semipermeable membrane having excellent salt blocking performance, particularly positively charged ion blocking performance. [Structure] A semipermeable ultra-thin film is provided on a porous substrate, and a layer of an organic polymer having a quaternary ammonium group and substantially insoluble in water is further laminated thereon.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an organic polymer which has a semipermeable ultrathin film on a porous substrate and further has a quaternary ammonium group and is substantially insoluble in water. The present invention relates to a novel composite semipermeable membrane that is formed by stacking layers and has excellent salt blocking performance, particularly positively charged ion blocking performance.

[0002]

2. Description of the Related Art In recent years, various composite semipermeable membranes formed by forming a semipermeable ultrathin film on a porous substrate as a reverse osmosis membrane are known, as will be described later. Composite semipermeable membranes equipped with these ultra-thin films are generally superior in reverse osmosis performance such as salt blocking performance and water permeability as compared with cellulose acetate membranes that have been widely used as reverse osmosis membranes. However, it is still unsatisfactory in terms of salt blocking performance when applied to practical desalination. Especially in the manufacture of semiconductors,
The ultra-pure water used for cleaning the SI is required to be highly desalted pure water with the recent increase in the integration density of LSIs. The reverse osmosis membrane used in the above is required to have a higher salt blocking performance than the conventional one.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in order to meet the above-mentioned demands, and is a novel composite semi-permeable membrane having a further improved salt blocking performance as compared with the conventional composite semi-permeable membrane. It is intended to provide a permeable membrane.

[0004]

The composite semipermeable membrane according to the present invention has a semipermeable ultrathin film on a porous substrate, and further has a quaternary ammonium group and substantially water. Is characterized in that layers of an organic polymer insoluble in are laminated.

The semipermeable ultrathin film in the present invention is not particularly limited, but a water-soluble polyfunctional amine compound having at least two primary and / or secondary amino groups in the molecule may react with the above amino groups. A thin film obtained by crosslinking with a functional crosslinking agent is preferable.

The water-soluble polyfunctional amine compound having at least two primary and / or secondary amino groups in the molecule preferably has a molecular weight in the range of 50 to 500,000. Including high molecular weight polymers.
As such a water-soluble polyfunctional amine compound, specifically, for example, polyethyleneimine, amine-modified polyepichlorohydrin, a polymer such as a water-soluble oligo by polymerization of an epoquine compound and an amino compound, phenylenediamine, Diaminopyridine, diaminodiphenyl ether, diaminodiphenyl sulfone, piperazine, 2,5-
Examples thereof include diaminopiperazine, homopiperazine, ethylenediamine and the like.

Further, as the polyfunctional crosslinking agent, at least a functional group capable of reacting with an amino group contained in the water-soluble polyfunctional amine compound, such as an isocyanate group, an acid halide group, or an N-haloformyl group, in the molecule. A compound having two is preferably used. Specific examples include isophthaloyl chloride, terephthaloyl chloride, trimesoyl chloride, tolylene diisocyanate, 4,4′-diphenyl diether diisocyanate, and 4,4′-diphenyl dimethane diisocyanate.

In the present invention, the semipermeable ultrathin film is an aqueous solution containing a water-soluble polyfunctional amine compound having at least two primary and / or secondary amino groups in the molecule as a main component on a porous substrate. Can be formed by contacting a polyfunctional crosslinking agent capable of reacting with the amino group with the polyfunctional amine compound to cause interfacial polymerization and crosslinking. Further, if necessary, it may be heated to form a dry film. Usually, the film thickness is in the range of 50 to 10000 angstrom, preferably 100 to 5000 angstrom.

The above-mentioned porous substrate is not particularly limited,
Usually, for example, polysulfone membrane, polyethersulfone membrane, polyacrylonitrile membrane, cellulose ester membrane,
A polyvinyl chloride film or the like is preferably used.

As described above, various composite semipermeable membranes formed by forming a semipermeable ultrathin film on a porous substrate are already known. For example, polyethyleneimine on a polysulfone porous substrate is known. A composite semipermeable membrane having an ultrathin film obtained by cross-linking styrene with tolylene diisocyanate
Japanese Patent Publication), a composite semipermeable membrane formed by crosslinking an amine-modified polyepichlorohydrin with a polyfunctional crosslinking agent similar to the above to form an ultrathin film instead of polyethyleneimine (Japanese Patent Publication No.
No. 38164), a water-soluble oligomer obtained by polymerization of an epoxy compound and an amine compound is crosslinked with a polyfunctional crosslinking agent similar to the above to form an ultrathin film (JP-A-53-144855). JP), a water-soluble polymer such as polyethyleneimine and a polyfunctional amine compound monomer having two or more amino groups in the molecule are co-crosslinked with the same polyfunctional crosslinking agent to form an ultrathin film. Composite semipermeable membrane (JP-A-56-139105), wherein an aromatic monomer having at least two primary amino substituents in the molecule is cross-linked with a polyfunctional acyl halide-substituted aromatic monomer. , A composite semipermeable membrane formed with an ultrathin film (JP-A-55-14710)
6), polyvinyl alcohol and a polyfunctional amine compound having two or more secondary amino groups in the molecule are crosslinked with a polyfunctional crosslinking agent to form an ultrathin film (JP-B-6).
1-28703) and the like.

The composite semipermeable membrane of the present invention comprises the above-described composite semipermeable membrane already known as such, and further comprising a portion having a quaternary ammonium group and a hydrophobic portion. And a layer of a substantially water-insoluble organic polymer. Here, the quaternary ammonium group is a quaternary ammonium halide group or a quaternized pyridinium halide group.

The above-mentioned organic polymer having a quaternary ammonium group and substantially insoluble in water according to the present invention is (1) 4
Copolymer obtained mainly from a monomer having a secondary ammonium group and a hydrophobic monomer, (2) Copolymer obtained mainly from a monomer containing a tertiary amine and a hydrophobic monomer The compound obtained by quaternization with an alkyl halogen, or (3) a copolymer obtained by using a halogen-containing monomer and a hydrophobic monomer as main components is converted into a quaternary compound with a tertiary amine compound.
It is selected from the graded ones.

In (1), the monomer having a quaternary ammonium group is a vinyl monomer or an acrylic monomer having a quaternary ammonium group, and for example, hydroxypropyl trimethyl methacrylate. Examples thereof include ammonium chloride and ethyl trimethylammonium chloride methacrylate.

The hydrophobic monomer is selected from vinylic monomers and acrylic monomers, and its homopolymer is insoluble in water. Here, examples of the vinyl-based monomer include styrene-based monomers such as styrene and α-methylstyrene, and vinyl esters such as vinyl acetate and vinyl propionate. Examples of the acrylic monomer include methyl acrylate, ethyl acrylate, isopropyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-hexyl. Methacrylate, lauryl methacrylate, methoxyethyl acrylate, glycidyl methacrylate and the like can be mentioned. These may be used alone or in combination with other monomers depending on the monomer.

The copolymer (1) is prepared by dissolving the above-mentioned quaternary ammonium group-containing monomer, a hydrophobic monomer, and a known radical polymerization initiator in an appropriate solvent, and substituting with nitrogen. Obtained by heating.

As the polymerization solvent used here, dimethylsulfoxide, dimethylformamide, dimethylacetamide, tetrahydrofuran, dioxane, methanol, ethanol, isopropyl alcohol, toluene,
Examples include xylene and the like, or a mixed solvent thereof.
Further, water may be added as long as the synthesized copolymer is not insolubilized, and for example, a mixed solvent of tetrahydrofuran / water, dioxane / water or the like may be used.

In (2), examples of the monomer containing a tertiary amine include 2-vinylpyridine, 4-vinylpyridine, N-vinyl-2-pyrrolidone and N, N-dimethylaminopropylacrylamide. ..

Examples of the alkyl halogen include methyl iodide, methyl chloride, methyl bromide, ethyl chloride, ethyl bromide, propyl chloride, propyl bromide and the like.

The copolymer (2) is obtained by copolymerizing the above-mentioned tertiary amine-containing monomer and the above-mentioned hydrophobic monomer in the solvent system in the same manner as in (1), and further adding this solution to an alkyl group. It can be obtained by adding halogen in an equimolar amount or more to the charged tertiary amine and stirring with heating. The unreacted alkylhalogen which has not been involved in the quaternization reaction can be removed by distillation under reduced pressure or precipitation purification to isolate a copolymer having no impurities.

In (3), examples of the halogen-containing monomer include vinyl chloride, vinyl bromide, hydroxypropyl methacrylate chloride, p-vinylbenzyl chloride and the like. Examples of the tertiary amine compound include trimethylamine, triethylamine, triethanolamine, pyridine and the like.

The copolymer (3) is obtained by copolymerizing the above halogen-containing monomer and the above hydrophobic monomer in the solvent system in the same manner as in (1), and further adding a tertiary amine to this solution. It can be obtained by adding the compound in an equimolar amount or more to the charged halogen and stirring with heating. An unreacted tertiary amine compound that has not been involved in the quaternization reaction can be removed by distillation under reduced pressure or purification by precipitation to isolate a copolymer having no impurities.

As described above, the copolymers represented by (1) to (3) are composed of a repeating unit of a portion having a quaternary ammonium group and a repeating unit of a hydrophobic monomer. These copolymers are substantially water-insolubilized by containing a hydrophobic portion in the molecule. The composition ratio of the quaternary ammonium group-containing portion and the hydrophobic portion may be appropriately set within a range in which the copolymer is insoluble in water.

The degree of swelling of the above copolymer in water is 100 times or less, preferably 50 times or less.
If it is more than 100 times, the strength of the water-resistant film when this copolymer is laminated on a semipermeable ultrathin film is poor, and the copolymer tends to be detached from the semipermeable ultrathin film, which is not preferable.

Although these copolymers are water-insoluble by themselves, they further have a crosslinkable functional group such as a hydroxyl group, a carboxyl group, an epoxy group and a blocked isocyanate group for the purpose of reinforcing water resistance. It is also possible to copolymerize a small amount of a monomer and crosslink it on the semipermeable ultrathin film by an appropriate crosslinking method.

Further, these copolymers are coated on a semipermeable ultrathin film and dried, and then irradiated with an electron beam, or benzoyl peroxide, potassium persulfate, t-butyl hydroperoxide and the like are added to the copolymer. It is also possible to generate a radical in the skeleton of the copolymer and crosslink it by a method in which a peroxide is mixed and heated after coating.

In the composite semipermeable membrane of the present invention, the thickness of the layer made of such a copolymer is not particularly limited, but it is usually preferably in the range of 10 angstrom to 10 μm. When the thickness of the copolymer layer is less than 10 Å, the salt blocking performance may not be improved in some cases, while when it exceeds 10 μm, the water permeability of the membrane may deteriorate, which is not preferable.

The method for coating the above-mentioned copolymer on the semipermeable ultrathin film on the porous substrate is not particularly limited.
A method of melt-coating the copolymer, a method of dissolving the copolymer in an appropriate organic solvent that does not adversely affect the porous substrate and the semipermeable ultrathin film on the porous substrate, coating the solution, and then drying. The method of dissolving the copolymer in an appropriate organic solvent, developing the solution on the water surface, and laminating the resulting thin film on the semipermeable ultrathin film can be used.

[0028]

In the composite semipermeable membrane according to the present invention, the copolymer layer having a quaternary ammonium group as a positively charged group is stably laminated on the semipermeable ultrathin film without being dissolved in water. , Such a positively charged group impedes the permeation of cation species such as sodium, potassium and calcium through the membrane in the treatment of water containing salt, and in the membrane, in order to maintain electrical neutrality, chlorine ion and the like are retained. It also has a high salt blocking performance, especially a high cation removal performance, as it also impedes the permeation of anionic species through the matrix.

[0029]

The present invention will be described below with reference to examples.
The present invention is not limited to these examples.

Reference Example 1 In a reaction vessel having a capacity of 500 ml equipped with a cooling reflux tube, 60 g of butyl methacrylate, 40 g of ethyl trimethylammonium methacrylate chloride, 150 g of isopropyl alcohol as a polymerization solvent, and 2,2'-azobis as a polymerization initiator. 0.5 g of isobutyronitrile was charged. After sufficiently substituting the inside of the reaction tank with nitrogen, the reaction tank was heated to 60 ° C. while circulating nitrogen in the reaction tank, and stirred for 8 hours to almost complete the polymerization.

A part of the obtained viscous liquid was collected, applied on a polyester film, and dried by heating to obtain a copolymer layer of about 50 μm. This was immersed in water and left at room temperature for 24 hours. The weight of the water-containing copolymer was measured, and the water-containing swelling degree was calculated to be 6 times.

Reference Example 2 In a reaction vessel having a capacity of 500 ml equipped with a cooling reflux tube, 50 g of butyl methacrylate, 25 g of N, N-dimethylaminopropyl acrylamide and 100 dimethylformamide as a polymerization solvent.
g, and 0.5 g of 2,2'-azobisisobutyronitrile as a polymerization initiator. After sufficiently substituting the inside of the reaction tank with nitrogen, the reaction tank was heated to 60 ° C. while flowing nitrogen into the reaction tank, and stirred for 10 hours to almost complete the polymerization.

Further, 30 g of ethyl bromide was added to this solution, and the mixture was further stirred at 50 ° C. for 10 hours. The resulting viscous liquid was added dropwise to a large amount of toluene to precipitate and purify the copolymer, which was then vacuum dried to completely distill off the solvent and unreacted ethyl bromide. When the purified copolymer was analyzed by an infrared spectrophotometer, it was found that the tertiary amine moiety was almost quaternized.

The purified copolymer was dissolved in a mixed solvent of methoxyethanol / water (weight ratio 1/1), coated and dried to obtain a copolymer layer of about 50 μm. This is reference example 1
The degree of swelling obtained by the same method as in was 13 times.

Reference Example 3 In a reaction vessel of 500 ml capacity equipped with a cooling reflux tube, 50 g of methyl methacrylate, 35 g of p-vinylbenzyl chloride, 130 g of dimethylformamide as a polymerization solvent, and 2,2'-azobisiso as a polymerization initiator. 0.4 g of butyronitrile was charged. After sufficiently substituting the inside of the reaction tank with nitrogen, the reaction tank was heated to 60 ° C. while circulating nitrogen in the reaction tank, and stirred for 8 hours to almost complete the polymerization.

Further, 28% of trimethylamine was added to this solution.
60 g of an aqueous solution was added, and the mixture was stirred at 25 ° C for 24 hours. The resulting viscous liquid was added dropwise to a large amount of toluene to precipitate and purify the copolymer, which was then vacuum dried to completely distill off the solvent and unreacted trimethylamine. When the purified copolymer was analyzed by an infrared spectrophotometer, it was confirmed that trimethylamine was added to the halogen portion to form a quaternary ammonium salt.

The purified copolymer was dissolved in a mixed solvent of methoxyethanol / water (weight ratio 1/1), coated and dried to obtain a copolymer layer of about 50 μm. This is reference example 1
The degree of swelling determined by the same method as that of was 18 times.

Reference Example 4 In a reaction vessel of 500 ml capacity equipped with a cooling reflux tube, styrene 80 was added.
g, 4-vinylpyridine 20 g, toluene 1 as a polymerization solvent
50 g and 1 g of 2,2'-azobisisobutyronitrile as a polymerization initiator were charged. After sufficiently substituting the inside of the reaction tank with nitrogen, the reaction tank was heated to 60 ° C. while flowing nitrogen into the reaction tank, and stirred for 8 hours for polymerization. The polymerization rate was 63%. Proton NMR (magnetic nuclear resonance) analysis of the purified copolymer confirmed that the composition ratio [weight / weight] of styrene / 4-vinylpyridine was 79/21, which was almost the same as the charge ratio. did.

Next, 10 g of the obtained copolymer and 40 g of dimethylformamide were charged into a 200 ml reaction tank equipped with a cooling reflux tube, and after the copolymer was dissolved, ethyl bromide 80
g was added. While introducing nitrogen into the reaction tank, the mixture was heated to 60 ° C. and stirred for 5 hours to carry out a quaternization reaction. When this purified product was analyzed by an infrared spectrophotometer, it was confirmed that the nitrogen atom in the pyridine ring was almost quaternized.

The purified copolymer was dissolved in ethanol, coated and dried to obtain a copolymer layer of about 50 μm.
The degree of swelling obtained by the same method as in Reference Example 1 was 2.2 times.

Comparative Example 1 According to Example 1 of JP-A-55-147106, a porous polysulfone membrane was immersed in a 2% m-phenylenediamine aqueous solution. Then, after removing the excess m-phenylenediamine aqueous solution, it was contacted with a trichlorotrifluoroethane solution of 0.1% trimesoyl chloride for 10 seconds and air-dried to obtain a composite semipermeable membrane.

Comparative Example 2 According to Example 5 of Japanese Patent Publication No. 61-50641, polyethyleneimine (manufactured by Nippon Shokubai Chemical Co., Ltd., trade name Epomin P-1000) 2.5% was added to porous polysulfone, and tr.
An aqueous solution containing 0.25% ans-2,5-dimethylpiperazine was applied. Then, contact with 0.3% hexane solution of tolylene diisocyanate for 1 minute, air dry for 5 minutes, and then
Heat treatment was performed at 10 ° C for 10 minutes to obtain a composite semipermeable membrane.

Example 1 The copolymer obtained in Reference Example 1 was applied as a 3% by weight isopropyl alcohol solution onto the composite semipermeable membrane of Comparative Example 1 so as to have a dry film thickness of 0.2 μm, and at 120 ° C. It was dried by heating for 10 minutes to obtain a composite semipermeable membrane according to the present invention.

Example 2 The copolymer obtained in Reference Example 2 was made into a mixed solution of 3% by weight methoxyethanol / water (weight ratio 2/1) to give a dry film thickness of 0.2.
1 μm to the composite semipermeable membrane of Comparative Example 1,
The composite semipermeable membrane according to the present invention was obtained by heating and drying at 20 ° C for 10 minutes.

Example 3 Instead of the copolymer obtained in Example 2 in Example 2,
A composite semipermeable membrane of the present invention was obtained in the same manner as in Example 2 except that the copolymer obtained in Reference Example 3 was used.

Example 4 The copolymer obtained in Reference Example 4 was applied as a 3 wt% ethanol solution onto the composite semipermeable membrane of Comparative Example 1 so as to have a dry film thickness of 0.2 μm, and the mixture was heated at 150 ° C. for 5 hours. The composite semipermeable membrane according to the present invention was obtained by heating and drying for minutes.

Example 5 The composite semipermeable membrane of the present invention was prepared in the same manner as in Example 1 except that the composite semipermeable membrane of Comparative Example 1 was used instead of the composite semipermeable membrane of Comparative Example 1. Got

Using each of the composite semipermeable membranes obtained as described above, an aqueous sodium chloride solution (pH 6) having a concentration of 1 ppm was used.
Table 1 shows the results of examining the salt rejection by subjecting 7 to 7) to desalting by reverse osmosis under the conditions of a temperature of 25 ° C. and a pressure of 15 kg / cm ² . Here, the inhibition rate of sodium ion or chlorine ion is: inhibition rate = [1- (sodium ion or chloride ion concentration in membrane permeate water) / (sodium ion or chloride ion concentration in water to be treated)] × 100 (%) Defined in. The sodium ion concentration and the chlorine ion concentration were measured by atomic absorption spectrometry and ion chromatography, respectively.

[0049]

[Table 1]

As is clear from the results shown in Table 1, the composite semipermeable membranes of Examples 1 to 4 were compared with the composite semipermeable membrane of Comparative Example 1, and the composite semipermeable membrane of Example 5 was compared. It can be seen that, compared with the composite semipermeable membrane according to Example 2, the blocking rate of chlorine ions is hardly reduced, while the blocking rate of sodium ions is significantly improved, and the salt blocking rate is high.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Kazuo Tanaka 1-2 1-2 Shimohozumi, Ibaraki City, Osaka Prefecture Nitto Denko Corporation

Claims (3)

[Claims] 1. A semipermeable ultrathin film is provided on a porous substrate, and a layer of an organic polymer having a quaternary ammonium group and substantially insoluble in water is further laminated thereon. A composite semipermeable membrane characterized in that 2. An organic polymer having a quaternary ammonium group and being substantially insoluble in water is (1) a copolymer obtained mainly from a monomer having a quaternary ammonium group and a hydrophobic monomer. Polymer, (2) A quaternized product of a copolymer obtained by using a monomer containing a tertiary amine and a hydrophobic monomer as main components with an alkyl halogen, or (3) a halogen-containing unit amount The composite semipermeable membrane according to claim 1, which is selected from a copolymer obtained mainly from a polymer and a hydrophobic monomer, which is quaternized with a tertiary amine compound. 3. The composite semipermeable membrane according to claim 1, wherein the swelling degree in water of the organic polymer having a quaternary ammonium group and substantially insoluble in water is 100 times or less.