JPH0461921A - Composite semipermeable membrane - Google Patents

Abstract

PURPOSE:To obtain a membrane having a high salt removing rate by laminating a semipermeable ultrathin membrane and a membrane composed of a block or graft copolymer having a quarternized polyvinyl pyridine segment to a porous base material. CONSTITUTION:First, an aqueous solution containing a water-soluble polyvalent amino compound, having two or more primary or secondary amino groups in its molecule as a main component, is applied to a porous base material and a polyfunctional crosslinking agent is brought into contact with the coated layer to perform the interfacial polymerization and crosslinking thereof to obtain a composite semipermeable membrane, having a semipermeable ultrathin membrane. Next, a block copolymer, having a quaternized polyvinyl pyridine segment and a monovinyl aromatic polymer segment or a graft copolymer having quaternized polyvinyl pyridine and a water-insoluble polymer, is brought into contact with the composite semipermeable membrane as a membrane according to a water surface developing method to be closely bonded and laminated thereto. By this method, a membrane having a high salt removing rate to treated water containing a slat in low concn. is obtained.

Description

[Detailed Description of the Invention] The present invention relates to a composite semipermeable membrane, and more specifically, it has a semipermeable ultra-thin membrane on a porous base material, and further has a quaternized membrane on it. The present invention relates to a composite semipermeable membrane having excellent salt removal performance, which is formed by laminating membranes made of a block copolymer or a graft copolymer having polyvinylpyridine segments. .

■ Bei Kogi Strain In recent years, various composite semipermeable membranes have been known as reverse osmosis membranes, in which an ultra-thin semipermeable membrane is formed on a porous base material, as described below.

Composite semipermeable membranes with these ultra-thin membranes generally have poorer reverse osmosis performance, such as salt removal performance and water permeability, compared to cellulose acetate membranes, which have traditionally been widely used as reverse osmosis membranes. However, the salt removal rate is still not satisfactory for practical desalting. especially,
In the manufacturing of semiconductors, highly desalinated pure water is required as ultrapure water used for cleaning LSIs, as the integration density of LSIs has become more sophisticated in recent years. Reverse osmosis membranes used for producing pure water are required to have a lower salt removal rate than conventional ones. Moreover, there is a strong demand for something that has a higher salt removal rate even for treated water containing low concentrations of salt.

The present invention was made in response to the above-mentioned needs, and is a composite semipermeable membrane with excellent salt removal performance, especially for treated water containing low concentrations of salt. The purpose is to provide a composite semipermeable membrane having a high salt removal rate.

The composite semipermeable membrane according to the present invention for ``i'' has a semipermeable ultrathin membrane on a porous substrate, and further comprises a block copolymer or graft copolymer having quaternized polyvinylpyridine segments thereon. It is characterized by laminated thin films made of polymers.

In the present invention, the semipermeable ultra-thin film contains primary and/or
Alternatively, it is a membrane in which a polyvalent amino compound having at least two secondary amino groups is crosslinked with a polyfunctional crosslinking agent capable of reacting with the above amino groups. Such an ultra-thin film is produced by coating a porous substrate with an aqueous solution whose main component is a water-soluble polyvalent amine compound having at least two primary and/or secondary amino groups in the molecule, and then applying this polyamine compound as a main component. It can be formed by bringing a polyfunctional amine compound into contact with a polyfunctional crosslinking agent capable of reacting with its amino group to cause interfacial polymerization and crosslinking,
Usually 50 to 10,000 people, preferably 100 to 500 people
It has a thickness of 0 people.

Here, the water-soluble polyvalent amino compound having at least two primary and/or secondary amine groups in the molecule has a molecular weight of 5.
It includes monomer compounds ranging from 0 to 500,000 to high molecular weight polymers, specifically, for example, polyethyleneimine, amine-modified polyepichlorohydrin, water-soluble oligomers obtained by polymerizing epoxy compounds and amino compounds, etc. Polymer, phenylenediamine, diaminopyridine, diaminodiphenyl ether, diaminodiphenylsulfone,
Examples include piperazine, 2,5-dimethylpiperazine, homopiperazine, and ethylenediamine.

Further, as the polyfunctional crosslinking agent, a compound having at least two functional groups capable of reacting with the amino group of the water-soluble amino compound, such as an isocyanate group, an acid halide group, or an N-haloformyl group, is preferably used as the polyfunctional crosslinking agent. Specifically, isophthaloyl chloride, terephthaloyl chloride, trimesoyl chloride, tolylene diisocyanate, 4.
Examples include 4'-diphenyl ether diisocyanate and 4,4'-diphenylmethane diisocyanate.

A semipermeable ultra-thin film using a polyvalent amine compound and a polyfunctional cross-linking agent as described above is usually produced by applying an aqueous solution of the above-mentioned water-soluble polyvalent amine compound onto a porous substrate, and then applying the polyfunctional cross-linking agent. A dry film can be obtained by contacting them to cause interfacial polymerization and then heating and curing them. The porous base material is not particularly limited, but for example, polysulfone membranes, polyethersulfone membranes, polyacrylonitrile membranes, cellulose ester membranes, polyvinyl chloride membranes, etc. can be suitably used.

As described above, various types of composite semipermeable membranes formed by forming semipermeable ultra-thin membranes on porous substrates are already known. A composite semipermeable membrane having an ultra-thin film cross-linked with (Japanese Unexamined Patent Publication No. 133282/1982), amine-modified polyepichlorohydrin is cross-linked with the same polyfunctional cross-linking agent as above in place of polyethyleneimine. Composite semipermeable membrane formed by forming an ultra-thin film (Special Publication No. 55-38164
(Japanese Unexamined Patent Publication No. 53-14), a composite semipermeable membrane in which an ultra-thin film was formed by crosslinking a water-soluble oligomer obtained by polymerizing an epoxy compound and an amine compound with the same crosslinking agent as above (Japanese Patent Application Laid-Open No. 53-14
4844), a water-soluble polymer such as polyethyleneimine and a polyvalent amino compound monomer having two or more amino groups in the molecule are co-crosslinked using the same polyfunctional crosslinking agent as above to form an ultra-thin film. The composite semipermeable membrane formed (Japanese Patent Application Laid-Open No. 56-13910
5), etc.

In addition to the above, composite semipermeable membranes (specially Japanese Patent Publication No. 147106/1983), a composite semipermeable membrane in which an ultra-thin film was formed by crosslinking polyvinyl alcohol and an amino compound having two or more secondary amino groups in the molecule with a polyfunctional crosslinking agent (Japanese Patent Publication No. 1983-1471- 27083), etc.

The composite semipermeable membrane according to the present invention further comprises a block copolymer or graft copolymer having a quaternized polyvinylpyridine segment on top of the semipermeable ultra-thin membrane of such a conventional composite semipermeable membrane. Laminated thin films.

As the block copolymer, one consisting of a quaternized polyvinylpyridine segment A and a monovinyl aromatic polymer segment B having a glass transition point of 50° C. or higher is preferably used. Such a copolymer may be a diblock represented by AB, a triblock represented by B-A-B, or a mixture thereof.

In the block copolymer, the molecular weight of the quaternized polyvinylpyridine segment is suitably in the range of 1000 to 2ooooo, preferably in the range of 1000 to 100000, as the polyvinylpyridine segment before quaternization. When the molecular weight of the polyvinylpyridine segment before quaternization exceeds 2oooooo, it is not preferable because the solubility in solvents decreases.

Moreover, in the block copolymer, the polyvinylpyridine component before quaternization is preferably in the range of 10 to 90 mol%.

Examples of the monovinyl aromatic polymer segment B include styrene, α-methylstyrene, vinyltoluene,
It is preferable to use a block formed by polymerizing a styrene monomer such as vinyl xylene, and a floc formed from polystyrene is particularly preferable. Its molecular weight is 3000-1
A range of 00000 is appropriate.

Next, the graft copolymer preferably consists of quaternized polyvinylpyridine A and water-insoluble polymer C,
In this case, either may be a trunk component or a branch component.

The water-insoluble polymer C preferably consists of a homopolymer or copolymer of at least one radically polymerizable monomer selected from vinyl monomers and acrylic monomers.

Examples of the vinyl monomer include styrene, α-
Examples include styrenic monomers such as methylstyrene, vinyl esters such as vinyl acetate and vinyl propionate, and vinyl chloride. In addition, examples of the acrylic monomer include methyl acrylate, ethyl acrylate,
t-butyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, methacrylic flit
-butylphenyl, naphthyl acrylate, 4-cyanophenyl acrylate, acrylamide, acrylonitrile, methacrylonitrile and the like. Depending on the monomer, these may be used alone, or depending on the monomer, they may be used in combination with other monomers.

The molecular weight of the branch component in the graft copolymer is in the range of 500 to 100,000, preferably 1,000 to 50,000 when component A is a branch component, and also in the range of 500 to 1ooooo, preferably when component C is a branch component. is 10
The range is from 00 to 50,000. The molecular weight of the branch component is 10
When it exceeds 0,000, the concentration of terminal functional groups during polymerization decreases, polymerization reactivity is impaired, and it becomes difficult to obtain the desired graft copolymer. On the other hand, when the molecular weight of the branch component is less than 1000, it is difficult to achieve the desired effects of the present invention.

Also in the graft copolymer, the water-insoluble polymer is preferably polystyrene, and the polyvinylpyridine component before quaternization preferably accounts for 10 to 90 mol%.

In the present invention, the above block copolymers and graft copolymers can be obtained, for example, by the methods described below.

First, as for the block copolymer, it is preferable to use anionic polymerization as described in Japanese Patent Publication No. 56-39648, since the size and arrangement of the segments are extremely constant. In addition, regarding the graft copolymer, firstly, a macromonomer of component A or component B is prepared by the already known lipping anionic polymerization, and then copolymerized with component B or component A by radical polymerization. Obtainable.

As the quaternizing agent for such block copolymers and graft copolymers, alkyl halides having 1 to 20 carbon atoms and alkyl cybarides having 1 to 18 carbon atoms are suitable, and in particular,
From a reactivity standpoint, bromides or iodides are preferred. Therefore, for example, alkyl halides such as methyl bromide, ethyl bromide, n-octyl bromide, and methyl iodide, ethyl tribromide, n-nonyl tribromide, and lauryl tribromide are preferably used.

In the present invention, the quaternization rate in the block copolymer and graft copolymer is preferably 10% or more. When the quaternization rate is less than 10%, the resulting composite semipermeable membrane has poor water permeability and no salt removal effect is observed, which is not preferable.

In the present invention, the method for quaternizing the block copolymer and graft copolymer using the quaternizing agent is to dissolve the copolymer and the quaternizing agent in an appropriate solvent, and add this solution to the water surface as described below. It is preferable to form a thin film by a spreading method, closely stack it on a composite semipermeable membrane, and then heat treat it, but other methods can also be used.

As such a quaternization method, firstly, the copolymer and the quaternization agent are dissolved in a solvent, and then heated and stirred. It is preferable to use a substance that does not cause the reaction or inhibit the reaction, and also dissolves the raw materials and products. Therefore, for example, alcohols such as methanol and ethanol,
Dimethylformamide 1. Dimethylacetamide, N-
Polar solvents such as methylpyrrolidone are preferred. A second method includes forming a thin film made of the copolymer on a composite semipermeable membrane by an appropriate method, and then reacting it with the quaternizing agent under reduced pressure.

In order to coat a thin film of the copolymer on a semi-permeable ultra-thin film, there are two methods: melt-coating the copolymer, dissolving the copolymer in an appropriate organic solvent, coating this solution, and drying it. However, in particular, the water surface development method described below is applicable when the porous base material of the composite semipermeable membrane has poor heat resistance or poor solvent resistance. It is also preferable to use this method because it is possible to obtain a copolymer thin film having a uniform thickness.

In the water surface development method, for example, as shown in FIG. 1, a solution of the copolymer is discharged from a nozzle 1 onto a water surface 3 in a water tank 2 using a metering pump (not shown), and the aqueous solution is spontaneously released. The copolymer is then expanded to form a thin film 4 of the copolymer. The thin film thus obtained is brought into contact with the traveling composite semipermeable membrane 8 using rolls 5, 6 and 7, and laminated in close contact with it.

The developing solvent used in such a water surface development method is preferably an inert solvent that dissolves the copolymer, such as alcohols such as methanol and ethanol, polar solvents such as tetrahydrofuran, dimethylformamide, and dimethylacetamide, water or A mixed solvent of these is used.

Particularly when sufficient water surface developability cannot be obtained even with the use of a single solvent, it is effective to add a second organic solvent to the first developing solvent as a developing aid. Such developing aids include, for example, aliphatic and aromatic ketones, esters, alcohols, amines, aldehydes,
Mention may be made of peroxides and mixtures thereof.

The concentration of the copolymer solution used in the water surface development method is 0.5 to
50% by weight, preferably in the range 1-40% by weight.

If the copolymer concentration is too low, a uniform and continuous thin film cannot be obtained; on the other hand, if the copolymer concentration is too high, the spreadability of the solution on the water surface decreases, which is not preferable.

When laminating a thin film of the block copolymer or graft copolymer on a composite semipermeable membrane, the thin film may be laminated in a single layer, or may be laminated in a multilayer of two or more layers. .

When laminating multiple layers, it is preferable to sufficiently dry the moisture adhering to the previously laminated thin film before laminating.

In the composite semipermeable membrane according to the present invention, the thickness of the membrane made of such a graft copolymer is usually 30 to 10 μm.
The range of m is good. When the membrane thickness of the graft copolymer is less than 30 mm, it is not effective in improving the salt removal performance, while when it exceeds 1011 mm, the water permeability of the membrane is unfavorably reduced.

As described above, the composite semipermeable membrane according to the present invention includes a thin film made of a block copolymer or a graft copolymer having quaternized polyvinylpyridine segments on a semipermeable ultrathin film. The charged nature of this quaternized polyvinylpyridine segment inhibits the permeation of ions such as sodium chloride, but does not inhibit the water permeability of the underlying composite semipermeable membrane. It has a high salt removal rate for treated water containing

EXAMPLES The present invention will be explained below with reference to Examples, but the present invention is not limited to these Examples in any way.

Reference example 1 0゜1 m in a reaction tank made high vacuum by break seal method
ol/j! A solution of 5ec-butyllithium in cyclohexane6. 5 ml and 15 g of styrene were charged, and the reactor was stirred for 30 minutes while being cooled on an ice-water bath to obtain a styrene adhesive polymer.

Next, 25 g of purified 2-vinylpyridine was added to the reactor and stirred for an additional 30 minutes on an ice water bath to obtain a polystyrene-poly(2-vinylpyridine) living polymer.

This die block copolymer was taken out from the reactor, purified, and analyzed by GPC and proton NMR.
The block copolymer had a polystyrene block having a number average molecular weight of 23,000 and a polyvinylpyridine block having a number average molecular weight of 37,000.

Reference Example 2 In the same manner as Reference Example 1, first, polystyrene poly(2
-vinylpyridine) living diblock copolymer was obtained, and then 3.25% of 1,4-dibromobutane was added to this solution.
mmol was added to obtain a triblock copolymer consisting of polystyrene-poly(2-vinylpyridine)-polystyrene. As a result of GPC analysis, this block copolymer had a triblock ratio of 84%.

This triblock copolymer IOg was dissolved in 50ml of dimethylformamide, and then ethyl bromide Log was added thereto, and the mixture was stirred under reflux at a temperature of 60°C for 8 hours to cause a quaternization reaction. Next, dimethylformamide and excess ethyl bromide were removed under reduced pressure to obtain a polystyrene-quaternized polyvinylpyridine-polystyrene triblock copolymer.

Reference example 3 0゜1 m in a reaction tank made into a high vacuum using the break-seal method
24 ml of a cyclohexane solution of 5ec-butyllithium (ol/l) and 15 g of styrene were charged, and the reactor was stirred for 30 minutes while being cooled on an ice-water bath to obtain a stinone sticking polymer.

Next, 2 g of ethylene oxide was added to the reactor,
Furthermore, 3 g of methacrylic acid chloride was added and stirred for 30 minutes to obtain a polystyrene macromonomer.

After purifying this macromonomer, it was analyzed by GPC and proton NMR, and the number average molecular weight was 6500.
The terminal functional group modification rate was 98%.

1 og of this polystyrene macromonomer and 10 g of 2-vinylpyridine were dissolved in 30 ml of benzene, and 0.1 g of abbisisobutyronitrile was added thereto, and the mixture was stirred at 60"C for 24 hours under a nitrogen atmosphere. A graft copolymer of styrene as a part and vinylpyridine as a trunk was obtained.

The obtained graft copolymer was subjected to GPC and proton NMR.
As a result of analysis, the number average molecular weight was 30,000, the weight average molecular weight was 85,000, and the proportion of poly-2-vinylpyridine component was 45%.

Reference example 4 0゜1 m in a reaction tank created with a high vacuum using the break-seal method
25 ml of a cyclohexane solution of 5ec-butyl lithium of 1 ol/1 and 13 g of purified 2-vinylpyridine were charged, and the reactor was stirred for 30 minutes while being cooled on an ice-water bath.
A 2-vinylpyridine pasting polymer was obtained.

Next, p-vinylbenzyl chloride 2 was added to this reactor.
g and stirred for 30 minutes to obtain poly(2vinylpyridine) macromonomer.

After purifying this macromonomer, it was analyzed by GPC and proton NMR, and the number average molecular weight was 5500.
The terminal functional group modification rate was 96%.

This poly(2-vinylpyridine) macromonomer Lo
g and 10 g of styrene were dissolved in 30 ml of Hensen, and further, 0.1 g of azobisisobutyronitrile was added thereto, and the mixture was stirred at 60°C for 24 hours under a nitrogen atmosphere to dissolve vinylpyridine in the branch portions and trunk bones. obtained a styrene graft copolymer.

The obtained graft copolymer was subjected to GPC and proton NFi
As a result of analysis using R, the number average molecular weight was 40,000, the weight average molecular weight was 150,000, and poly-2
- The proportion of vinylpyridine component was 48%.

Comparative Example 1 A composite semipermeable membrane was prepared as Comparative Example 1 according to the method described in JP-A-55-147106.

Example 1 The block copolymer prepared in Reference Example 1 and n-lauryl tribromide in an equal amount to its vinylpyridine component were dissolved in a mixed solvent of tetrahydrofuran/water in equal amounts, and this solution was prepared as shown in FIG. A thin film having a thickness of 0.05 μm was developed by the water surface development method as shown in 1. The composite semipermeable membrane according to the present invention was obtained by laminating it on the composite semipermeable membrane shown as the comparative example.

The copolymer concentration of the block copolymer solution was 10% by weight, the amount of copolymer solution supplied to the water surface was 0.07 m1/min, and the film forming speed was 7 m/min.

Thereafter, the composite semipermeable membrane was heated at 110° C. for 40 minutes to quaternize and crosslink the block copolymer.

Example 2 The block copolymer prepared in Reference Example 2 was dissolved in a mixed solvent of tetrahydrofuran/water in equal amounts, and this solution was spread into a thin film with a thickness of 0.05 μm using the water surface spreading method in the same manner as above. A composite semipermeable membrane according to the present invention was obtained by laminating it on the composite semipermeable membrane shown as the comparative example.

The copolymer concentration of the block copolymer solution was 10% by weight, the amount of the copolymer solution supplied to the water surface was 0.07 ml/Z, and the film forming speed was 7 m/min.

Example 3 The graft copolymer prepared in Reference Example 3 and n-lauryl tribromide in an equal amount to its vinylpyridine component were dissolved in a mixed solvent of tetrahydrofuran/water in equal amounts, and this solution was dissolved in the same manner as above. The membrane was developed into a thin film with a thickness of 0.05 μm using a water surface spreading method, and laminated on the composite semipermeable membrane shown as the comparative example, to obtain a composite semipermeable membrane according to the present invention.

The copolymer concentration of the graft copolymer solution was 10% by weight, the amount of copolymer solution supplied to the water surface was 0.07 ml/min, and the film forming speed was 7 m/min.

Thereafter, the composite semipermeable membrane was heated at 110° C. for 40 minutes to quaternize and crosslink the graft copolymer.

Example 4 The graft copolymer prepared in Reference Example 4 and n-lauryl tribromide in an equal amount to its vinylpyridine component were dissolved in a mixed solvent of tetrahydrofuran/water in equal amounts, and this solution was mixed with the above solution. Similarly, it was developed into a thin film with a thickness of 0.05 μm using the water surface spreading method, and laminated on the composite semipermeable membrane shown as the comparative example, to obtain a composite semipermeable membrane according to the present invention.

The copolymer concentration of the graft copolymer solution was 10% by weight, the amount of copolymer solution supplied to the water surface was 0.07 m1/min, and the film forming speed was 7 m/min.

Thereafter, the composite semipermeable membrane was heated at 110° C. for 40 minutes to quaternize and crosslink the graft copolymer.

Regarding each composite semipermeable membrane obtained as above,
As treated water, 1 pp111 of sodium chloride aqueous solution
Aqueous solution pH 6-7, temperature 25℃, pressure 15kg/cn
A reverse osmosis test was conducted by contacting the composite semipermeable membrane under the conditions of f and measuring its ion permeability.

The results are shown in Table 1. Here, the ion permeability is given by the following formula: Defined by

Note that the concentration values of sodium ions and chloride ions were determined based on respective calibration curves prepared in advance by ion chromatography analysis.

Table 1 As is clear from the results shown in Table 1, the composite semipermeable membranes according to Examples 1 to 4 had lower performance compared to the composite semipermeable membrane according to the comparative example.
The permeability of each ion is reduced without impairing the water permeability, thus improving the salt removal rate.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a method of laminating a thin film on a composite semipermeable membrane using a water surface spreading method. ■...Nozzle, 2...Aquarium, 3...Water surface, 4...
・Copolymer thin film, composite semipermeable membrane.

Claims (1)

[Claims] (1) A semi-permeable ultra-thin film is provided on a porous substrate, and a segment or branch portion made of a water-insoluble polymer is further provided on top of the semi-permeable ultra-thin film.
1. A composite semipermeable membrane characterized in that thin films made of a block copolymer or a graft copolymer having graded polyvinylpyridine segments are laminated.