JP3021692B2 - Composite semipermeable membrane - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite semipermeable membrane, and more particularly, to a composite semipermeable membrane having a semipermeable ultrathin film on a porous substrate and further having a quaternary ammonium group as a positively charged group thereon. The present invention relates to a novel composite semipermeable membrane which is excellent in salt removal performance obtained by forming a crosslinked polymer layer formed by cross-linking a coalescence, particularly excellent in positive charge ion removal performance.

[0002]

2. Description of the Related Art In recent years, various types of composite semipermeable membranes formed by forming a semipermeable ultrathin film on a porous substrate as a reverse osmosis membrane have been known as described later. Composite semipermeable membranes provided with these ultrathin films are generally superior in reverse osmosis performance such as salt removal performance and water permeability performance to cellulose acetate membranes which have been widely used as reverse osmosis membranes. However, for practical desalination, it is still not satisfactory in terms of salt removal performance. In particular, in the manufacture of semiconductors, ultrapure water used for cleaning LSIs includes recent L.P.
As the integration density of SI further increases, highly desalinated pure water has been required. Thus, the reverse osmosis membrane used in the production of ultrapure water has a higher concentration than before. There is a need for one having even higher salt removal performance.

[0003]

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

[0004]

The composite semipermeable membrane according to the present invention has a semipermeable ultrathin film on a porous substrate, and a polymer having a quaternary ammonium group thereon further crosslinked. It has a crosslinked polymer layer. In the present invention, the semipermeable ultrathin film is crosslinked with a polyfunctional crosslinking agent capable of reacting a water-soluble polyfunctional amine compound having at least two primary and / or secondary amino groups in the molecule with the amino group. It is a film consisting of

[0005] Here, the water-soluble polyfunctional amine compound having at least two primary and / or secondary amino groups in the molecule has a molecular weight in the range of 50 to 500,000, and is therefore Contains high molecular weight polymers. Specific examples of such a water-soluble polyfunctional amine compound include, for example, polyethyleneimine, amine-modified polyepichlorohydrin, polymers such as water-soluble oligomers obtained by polymerization of an epoxy compound and an amino compound, and phenylenediamine. , Diaminopyridine, diaminodiphenyl ether, diaminodiphenylsulfone, piherazine, 2,5-dimethylpiherazine, pomopiherazine, ethylenediamine and the like.

As the polyfunctional crosslinking agent, at least a functional group capable of reacting with the amino group of the water-soluble polyfunctional amine compound, such as an isocyanate group, an acid halide group, and an N-haloformyl group, is provided in the molecule. A compound having two is preferably used. As such a polyfunctional crosslinking agent,
Specifically, for example, isophthaloyl chloride, terephthaloyl chloride, trimesoyl chloride, tolylene diisocyanate, 4,4′-diphenyl diether dissocyanate, 4,4′-diphenyl dimethane dissocyanate, and the like can be given. .

In the present invention, the semipermeable ultrathin film is formed on a porous substrate by using an aqueous solution mainly composed of a water-soluble polyfunctional amine compound having at least two primary and / or secondary amino groups in a molecule. After coating, the polyfunctional amine compound can be formed by contacting with a polyfunctional crosslinking agent capable of reacting with the amino group to cause interfacial polymerization and crosslinking. Usually, the film thickness ranges from 50 to 10,000 Angstroms, preferably from 100 to 5000 Angstroms.

More specifically, usually, an aqueous solution of a water-soluble polyfunctional amine compound as described above is applied on a porous substrate, and then the resulting solution is brought into contact with a polyfunctional crosslinking agent to cause interfacial polymerization. By heating and curing, a dried film can be obtained. The porous substrate is not particularly limited, but usually, for example, a polysulfone film, a polyethersulfone film, a polyacrylonitrile film, a cellulose ester film, a polyvinyl chloride film and the like are preferably used.

As described above, various types of composite semipermeable membranes formed by forming a semipermeable ultrathin film on a porous substrate are already known. For example, polyethyleneimine can be used on a polysulfone porous substrate. Semi-permeable membrane having an ultra-thin film obtained by cross-linking a polymer with tolylene diisocyanate (JP-A-49-133282)
Publication), a composite semipermeable membrane formed by crosslinking an amine-modified polyepichlorohydrin with a polyfunctional crosslinking agent similar to the above in place of polyethyleneimine to form an ultrathin film (Japanese Patent Publication No. 55-1979)
No. 38164), a composite semipermeable membrane formed by crosslinking a water-soluble oligomer obtained by polymerization of an epoxy compound and an amine compound with a polyfunctional crosslinking agent similar to the above to form an ultrathin film (JP-A-53-144855). Publication), a water-soluble polymer such as polyethyleneimine and a polyfunctional amine compound monomer having two or more amino groups in a molecule were co-crosslinked with the same polyfunctional crosslinking agent to form an ultrathin film. Composite semipermeable membrane (JP-A-56-139105), which is obtained by crosslinking an aromatic monomer having at least two primary amino substituents in a molecule with a polyfunctional acyl halide-substituted aromatic monomer. A composite semipermeable membrane having a thin film formed thereon (Japanese Patent Application Laid-Open No. 55-147106), an ultrathin film formed by crosslinking a polyvinyl alcohol and a polyfunctional amine compound having two or more secondary amino groups in a molecule with a polyfunctional crosslinking agent. Form Composite semipermeable membrane was (JP-B-61-2
No. 7083).

[0010] The composite semipermeable membrane according to the present invention is formed on a composite semipermeable membrane as described above, which is already known per se.
Further, together with a quaternary ammonium group, at least 2
Polymer having two hydroxyl groups (hereinafter referred to as polymer A)
Or a cross-linked polymer layer obtained by cross-linking a polymer having at least two hydroxyl groups and at least two protected isocyanate groups in a molecule (hereinafter referred to as polymer B). is there.

Here, the quaternary ammonium group is a quaternary ammonium halide group, preferably a quaternary ammonium chloride group or a quaternized pyridinium halide group. Further, the protected isocyanate group means an isocyanate group blocked with a blocking agent or an isocyanate group protected in the form of an amine imide group.

Examples of the polymer A include a homopolymer of hydroxypropyltrimethylammonium methacrylate, a copolymer of ethyltrimethylammonium methacrylate and hydroxyethyl methacrylate, and a copolymer of 4-vinylpyridine and hydroxyethyl methacrylate. Examples include quaternized copolymers.

Further, as the polymer B, for example, 2
A copolymer of an isocyanate monomer obtained by blocking methacryloyloxyethyl isocyanate with an appropriate blocking agent and hydroxypropyltrimethylammonium methacrylate, and a copolymer of the blocked isocyanate with 4-vinylpyridine and hydroxyethyl methacrylate. Unified quaternary compound, 1,1-dimethyl-
Examples thereof include a copolymer of a vinyl monomer having an amine imide group such as 1- (2-hydroxypropyl) amine methacrylimide and hydroxypropyltrimethylammonium methacrylate chloride.

Various blocking agents for blocking isocyanate groups are already known, for example, phenols such as phenol and cresol, alcohols such as methanol, ethanol and methyl cellosolve, methyl ethyl ketoxime and acetaldehyde. Oximes such as oximes can be mentioned. The above-mentioned polymers A and B are both soluble in water and alcohols. Therefore, in the present invention, the crosslinked polymer layer can be formed on the semipermeable ultrathin film by, for example, the following various methods.

In order to form a crosslinked polymer layer formed by crosslinking the polymer A, a water or alcohol solution of the polymer A is applied to the composite semipermeable membrane, and then a polyisocyanate compound as a polyfunctional crosslinking agent is dissolved. The polymer A may be brought into contact with the solution, preferably a hydrocarbon solution, and heated if necessary to crosslink the polymer A between the molecules. Further, as another method, a polyfunctional polyisocyanate compound blocked with a blocking agent as described above is added to a water or alcohol solution of the polymer A, and the obtained solution is applied to a composite semipermeable membrane. The polyisocyanate compound may be liberated by heating to a temperature equal to or higher than the dissociation temperature of the blocked polyisocyanate to cause a crosslinking reaction with the polymer A.

The polyisocyanate compound used above is not particularly limited. Examples thereof include tolylene diisocyanate and diphenyl methane diisocyanate, polymers thereof, isophorone diisocyanate, hexamethylene diisocyanate, triphenyl methane triisocyanate, and tris (P-isocyanatophenyl) thiophosphite, an adduct of trimethylolpropane and tolylenediisocyanate, an adduct of trimethylolpropane and xylylenediisocyanate, and the like.

On the other hand, in order to form the crosslinked polymer layer of the polymer B on the composite semipermeable membrane, for example, a water or alcohol solution of the polymer B is applied on the composite semipermeable membrane, and the blocked polyisocyanate is applied. May be heated to a temperature equal to or higher than the dissociation temperature to release the isocyanate group and to crosslink between molecules or within the molecule. A catalyst such as a tertiary amine or an organotin compound may be used, if necessary, at the time of the crosslinking reaction in order to promote the above-mentioned crosslinking reaction between the isocyanate group and the hydroxyl group.

In the present invention, the thickness of the crosslinked polymer layer thus formed is usually in the range of 10 Å to 10 μm. When the thickness is less than 10 angstroms, the salt removing performance of the obtained composite semipermeable membrane is hardly improved. On the other hand, when it exceeds 10 μm, the water permeability of the obtained membrane is remarkably reduced, which is not preferable.

[0019]

As described above, the composite semipermeable membrane according to the present invention is stable in that the crosslinked polymer layer having a quaternary ammonium group as a positively charged group on the semipermeable ultrathin film does not dissolve in water. In the treatment of water containing salt, such positively charged groups prevent cation species such as sodium, potassium and calcium from permeating the membrane, and in the membrane, to maintain electrical neutrality. Also, since it also prevents matrix transmission of anionic species such as chlorine ions, it has high salt removal performance, particularly high cation removal performance.

[0020]

EXAMPLES The present invention will be described below with reference to examples.
The present invention is not limited by these examples. Reference Example 1 29 g of methyl ethyl ketoxime was dissolved in 50 g of benzene, and 51.6 g of 2-methacryloyloxyethyl isocyanate was added dropwise to this solution at a temperature of 25 ° C. over about 40 minutes, followed by stirring at 45 ° C. for 2 hours. The obtained reaction product was analyzed by proton NMR, and it was confirmed that the product was a block product in which methyl ethyl ketoxime was almost quantitatively added to 2-methacryloyloxyethyl isocyanate. Reference Example 2 In the same manner as Reference Example 1, tolylene diisocyanate was reacted with an equal amount of methyl ethyl ketoxime to obtain a blocked diisocyanate. Reference Example 3 40 g of hydroxypropyltrimethylammonium methacrylate chloride was dissolved in 60 g of methanol, and 0.4 g of azobisisobutyronitrile was added thereto. The mixture was stirred at 60 ° C. for 8 hours under a nitrogen gas atmosphere to obtain a quaternary ammonium group. Was obtained. Reference Example 4 32 g of hydroxypropyltrimethylammonium methacrylate chloride and 8 g of the blocked isocyanate compound obtained in Reference Example 1 were dissolved in 60 g of methanol.
0.4 g of azobisisobutyronitrile was added thereto, and the mixture was stirred at 60 ° C. for 6 hours under a nitrogen gas atmosphere to obtain a polymer having a quaternary ammonium group. Reference Example 5 40 g of 4-vinylpyridine, 10 g of hydroxyethyl methacrylate and 21 g of the blocked isocyanate compound obtained in Reference Example 1 were dissolved in 100 g of methanol, and 0.7 g of azobisisobutyronitrile was added thereto. At 60 ° C. for 6 hours to obtain a copolymer. Next, 80 g of ethyl bromide was added thereto, and the mixture was stirred at 45 ° C. for 8 hours.

After the obtained copolymer was purified, it was analyzed by an infrared absorption spectrum to confirm that a pyridine unit was almost completely quaternized. Reference Example 6 32 g of hydroxypropyltrimethylammonium methacrylate chloride and 8 g of 1,1-dimethyl-1- (2-hydroxypropyl) amine methacrylimide were dissolved in 60 g of methanol, and 0.4 g of azobisisobutyronitrile was added thereto. The mixture was stirred at 60 ° C. for 7 hours in a nitrogen gas atmosphere to obtain a copolymer having a quaternary ammonium group. To give the Supporting connexion composite semipermeable membrane with the method described in Example 1 of Comparative Example JP 55-147106 JP. Comparative Example 1
Of the composite semipermeable membrane. Example 1 1 g of the copolymer obtained in Reference Example 3 was dissolved in water, and 1% by weight
An aqueous solution was prepared. To this, 0.2 g of the blocked diisocyanate obtained in Reference Example 2 was added.
0.001 g of diazabicyclo [2.2.2] octane was added.

The solution thus obtained was dried to a dry film thickness of 0.1 μm.
m on the composite semipermeable membrane of the comparative example so that
C. for 10 minutes to crosslink the copolymer to obtain a composite semipermeable membrane according to the present invention. Example 2 1 g of the copolymer obtained in Reference Example 4 was dissolved in water, and 1% by weight
An aqueous solution was prepared. To this, 0.2 g of the blocked diisocyanate obtained in Reference Example 2 was added.
0.005 g of diazabicyclo [2.2.2] octane was added.

The solution thus obtained was dried to a film thickness of 0.05.
μm on the composite semipermeable membrane of the comparative example,
The mixture was heated at 0 ° C. for 10 minutes to crosslink the copolymer to obtain a composite semipermeable membrane according to the present invention. Example 3 In Example 2, instead of the copolymer obtained in Reference Example 4,
A composite semipermeable membrane according to the present invention was obtained in the same manner as in Example 2 except that the copolymer obtained in Reference Example 5 was used. Example 4 1 g of the copolymer obtained in Reference Example 6 was dissolved in water, and 1% by weight
An aqueous solution was prepared. This solution was applied on the composite semipermeable membrane of Comparative Example so as to have a dry film thickness of 0.1 μm, and then heated at 150 ° C. for 30 minutes to crosslink the copolymer, thereby forming the composite semipermeable membrane according to the present invention. Obtained.

Using each of the composite semipermeable membranes obtained as described above, a 1 ppm aqueous sodium chloride solution (pH 6
7) was subjected to desalination by reverse osmosis under the conditions of a temperature of 25 ° C. and a pressure of 15 kg / cm 2, and the salt removal rate was examined. Table 1 shows the results. Here, the removal rate of sodium ion or chloride ion is: removal rate = [1− (concentration of sodium ion or chloride ion in membrane permeated water) / (concentration of sodium ion or chloride ion in treated water)] × 100 (%) Is defined by

[0025]

[Table 1]

As is clear from the results shown in Table 1, according to the composite semipermeable membrane of the present invention, the chlorine ion removal rate was hardly reduced as compared with the composite semipermeable membrane of the comparative example. ,
The removal rate of sodium ions is remarkably improved, and the removal rate of salt is high.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-53-18482 (JP, A) JP-A-63-178805 (JP, A) JP-A-4-7026 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) B01D 69/12 B01D 71/58 B01D 71/82

Claims (3)

(57) [Claims] 1. A composite half comprising a semipermeable ultra-thin film on a porous substrate, and a crosslinked polymer layer formed by crosslinking a polymer having a quaternary ammonium group thereon. Permeable membrane. 2. The composite semipermeable membrane according to claim 1, wherein the crosslinked polymer is obtained by crosslinking a polymer having a quaternary ammonium group and a hydroxyl group between molecules with a polyisocyanate. 3. A crosslinked polymer having a quaternary ammonium group and a hydroxyl group and a polymer having a blocked polyisocyanate or amine imide group crosslinked intramolecularly or intermolecularly. Composite semipermeable membrane.