JPS5892409A - Selective permeable membrane - Google Patents

Abstract

PURPOSE:To obtain a selective permeable membrane excellent in water permeability and selectivity, good in chemical resistance shown in a usable pH range of 1-14, heat resistance, compressive strength, chlorine resistance and anti-bacterial property and having good balance. CONSTITUTION:Chloromethyl styrene and styrene sulfonic acid are copolymerized in a ratio of 1/19-19 in the presence of a catalyst comprising an acid such as sulfuric acid or a base to obtain a copolymer with M.W. of about 1,000-50,000. As a solvent, a lower alcohol with a carbon number of 8 or less such as methanol or ethanol is used in an amount of 0.1-3wt%. When polymerization is carried out at 80-155 deg.C for 0.5min-one hr, the crosslinked copolymer is obtained. This copolymer is formed into a film on a porous support comprising cellulose nitrate, polysulfone or one obtained by reinforcing them with a nonwoven fabric to obtain a selective permeable membrane. This membrane has a pore size of usually 10-300Angstrom which is a suitable range in using the same as a reverse osmosis membrane.

Description

Detailed Description of the Invention The present invention provides a selectively permeable membrane, more specifically, a selectively permeable membrane that has excellent water permeability and selectivity, as well as excellent chemical resistance, heat resistance, compaction resistance, and film formability. Regarding permeable membranes.

Separation methods using membranes, especially reverse osmosis, have the advantage of low energy costs because solutes in aqueous solutions can be separated without phase change. This tank is currently used in many fields to separate inorganic and organic substances from media, including desalination of seawater and brine.
Moreover, it is expected that it will have even wider applications in the future.

Conventionally, as examples of reverse osmosis membranes, Loeb and Sowr
Irajan's cellulose acetate membrane (U.S. Pat. Nos. 3,133,132 and 3,133,137) and Ricbte
Typical examples include aromatic polyamide and polyamide hydrazide membranes (U.S. Special Law M3567632) manufactured by R.R. and Hoehu. However, these membranes are not always fully satisfactory in terms of water permeability and selectivity (salt removal rate), and also have poor chemical resistance, heat resistance, compaction resistance, and film formability. It had various problems.

The inventor of the present invention has solved the problems of conventional selectively permeable membranes. After conducting research, he found that the following general formula % ((jl, l, , m and n are mole fractions) , m
+n=1.0.05≦m, n≦095 are satisfied.

Further, M' is hydrogen or an alkali metal. It has been found that a selectively permeable membrane formed by crosslinking a polymer having repeating units represented by ) can fully satisfy this purpose.

The selectively permeable membrane of the present invention not only has excellent water permeability and selectivity, but also has chemical resistance, heat resistance, compaction resistance, chlorine resistance, and resistance in the usable pH range of 1 to 14. It is a well-balanced membrane with excellent bacterial properties. and,
The film-forming properties are also excellent, and particularly when the film is formed on a porous support, a selectively permeable membrane can be obtained which is not only easy to process but also has extremely high reproducibility of various properties.

The polymer having the above general formula used in the present invention can be easily obtained by copolymerizing chloromethylstyrene and styrene sulfonic acid or an alkali metal salt thereof by known means, for example, in the presence of a catalyst. C in the above polymer
The ratio of H2Cl/803M is related to 9 stability and film formability in a polymer solution, as well as the degree of crosslinking and water permeability of the resulting selectively permeable membrane, so it must be selected to satisfy 1719 to 19. There is. Preferably 0.5-10
, more preferably in the range of 1.0 to 5.0.

Since the molecular weight of the above polymer is related to the film formability and mechanical properties of the film, it is preferably 300 to several 100,000, particularly,
It is preferably between 1,000 and 50,000.

Crosslinking of the polymer is preferably carried out using a catalyst and dissolving it in a suitable medium. Catalysts include inorganic acids such as sulfuric acid, hydrochloric acid, phosphoric acid, and acetic acid.

Organic acids such as para-toluenesulfonic acid or bases such as caustic, ammonia, amines are used. Among these, it is particularly preferable to use 0.1 to 3% sulfuric acid as the catalyst because the degree of crosslinking and sulfonation of the membrane can be appropriately controlled. The catalyst is used in an amount of 0.05 to 10 times, preferably 0.25 to 2 times, the weight of the polymer.

As the solvent for the polymer, as long as it is a solvent for the substance,
Appropriate substances such as alcohols, ketones, ethers, and water can be used. Among them, methanol, ethanol,
n-Proper Tools.

Lower alcohols preferably having 8 or less carbon atoms, such as isopropanol, and these alcohols preferably include:
It is preferable to use a mixed solvent of alcohol and water to which water is added. When a solvent is used, the content of the polymer in the solvent is preferably selected to be 0.01 to 5%, preferably 0.1 to 3%.

In the presence of the catalyst, the polymer dissolved in an appropriate solvent is maintained at a temperature of preferably 30 to 180°C, particularly 80 to 155°C, preferably 10 seconds to 6 hours, particularly 0.5 minutes to 1 hour. By doing so, a crosslinked polymer is obtained.

The above crosslinked product may be obtained and subsequently formed into a film, but
Preferably, the crosslinking of the polymer is carried out in parallel with film formation. In this film formation, it is preferable to use an appropriate porous support and form the film on the porous support. Examples of such a porous support include cellulose nitrate,
Cellulose esters such as cellulose acetate, polysulfone, polyether sulfone, polystyrene, polyvinyl chloride, chlorinated polyvinyl chloride, polycarbonate, polyacrylonitrile, polyester, or those further reinforced with woven fabric, non-woven fabric, etc. can be used. When the selective permeation membrane is used as a reverse osmosis membrane, the pore diameter of the porous support is preferably 5. Particularly high selectivity below OOOλ (
It is preferable to have a high rejection rate).
The shape of the porous support is not limited to a flat membrane, but can be tubular or hollow, and the shape of the selectively permeable membrane of the present invention is determined according to the shape. 6 The preferred porous support used in the present invention is a polysulfone resin, and preferably a solution of the resin dissolved in a polar solvent such as dimethylformamide is poured onto a plate and then immersed in water. The thickness obtained by dipping 1 is 1o ~
It is 500μ.

The means for crosslinking the above polymer to form a film on the porous support includes a method of casting a polymer solution containing the catalyst on the porous support, a method of spraying or coating it, or a method of spreading the polymer solution containing the catalyst on the porous support. Any method can be adopted, such as a method of floating the porous support in the above solution, or a method of immersing the porous support in the above solution. During film formation, preferably 0.0.0% of a surfactant such as sodium lauryl sulfate, sodium alkylbenzene sulfonate, or polyethylene oxide is added to the polymer solution.
By adding 1 to 1% by weight, the stability of the resulting film can be improved.

applying a thin layer of the polymer solution on one or both sides of the porous support, preferably after evaporating some or all of the solvent;
As described above, crosslinking treatment is performed by performing heat treatment for a predetermined period of time.

It is estimated that the selectively permeable membrane thus obtained usually has a pore size of 10 to 300 pores, which is an extremely appropriate range for use as a reverse osmosis membrane, especially when formed on a porous support. The resulting membrane is extremely superior in practical terms.

In the following examples, the removal rate is expressed by the following formula.

Example 1 Chloromethylstyrene (mixture of meta and para forms) and p
- Copolymer obtained by radical polymerization of sodium styrene sulfonate (CH2Cl/5O3Na-3,O, average molecular weight 6.000) t 0 parts by weight, 1.0 parts by weight of concentrated sulfuric acid, 80 parts by weight of water, Add polysulfone (p-
Thickness 6 obtained by coating a 15% dimethylformamide solution of 3500) on a glass plate and then immersing it in water.
The 0μ porous polysulfone support membrane was soaked for 5 minutes and then air-dried for 1 minute with the membrane vertically at room temperature.

This was heated and dried in an air oven at 160° C. for 15 minutes to carry out a crosslinking reaction. The obtained selectively permeable membrane was
．． When a reverse osmosis test was conducted at room temperature under a pressure of 60:9/J using 5% by weight saline, the salt removal rate after 24 hours was 99.7%, and the water permeation rate at that time was 99.7%. was 0.42 m37 m"-day. Also, 1
Removal rate after ,000 hours is 99.7%, water permeation rate is 0.4
It was 0 m3/m2-day.

Example 2 The selectively permeable membrane obtained in Example 1 was subjected to a reverse osmosis test at room temperature under a pressure of AOKg/- using 0.5% saline, and after 24 hours. The removal rate of salt is 9
9.9%, and the water permeability at that time is 0.63 m3/
It was m2-day.

Example 3 The selectively permeable membrane obtained in Example 1 was subjected to a reverse osmosis test at room temperature using a 0.5% by weight aqueous ethyl alcohol solution under a pressure of AOKg/i. The removal rate of ethyl alcohol was 70%.

Example 4 The salt removal rate of a permselective membrane obtained in the same manner as in Example 1 except that it was heated and dried for 15 minutes in an air open environment at 150°C to perform a crosslinking reaction was 99.9%. The water permeability was 0.24 m3/m2-day.

Practical Example 5 The selectively permeable membrane obtained in Example 1 was coated with 1.0 weight silk% D
-(+)-Using lactose aqueous solution, A OKg/ol
A reverse osmosis test was conducted at room temperature under a pressure of 24
The lactose removal rate after hours was more than 9995%.

Example 6 In a solution of 1.0 parts by weight of chloromethylstyrene-sodium styrene sulfonate copolymer (CH2Cl/5O3N&=2.0, average molecular weight 4000), 1.0 parts by weight of concentrated sulfuric acid, and 100 parts by weight of water, A 100 micron thick porous polysulfone support membrane was soaked for 5 minutes and then air-dried for 1 minute with the membrane vertically at room temperature. This was heated and dried for 15 minutes in an open air environment at 130°C to carry out a crosslinking reaction. The obtained selectively permeable membrane was mixed with 3.5% saline solution for 6 hours.
When a reverse osmosis test was conducted at room temperature under a pressure of 0 to 9/J, the removal rate of salt after 24 hours was 99.2%, and the water permeation rate at that time was 0.46 m3//m2 -d
It was ay. In addition, the removal rate after 72 hours was 992%,
The water permeability was 0.46 m37 m2-day.゛Examples 7 to 10 The membranes obtained in Example 6 were as follows.

Table 1 shows the results of a reverse osmosis test conducted at room temperature under a pressure of 60 kg/- using 35 strands of saline solution after immersion in various solutions under different conditions.

Table 1 These results show that the selectively permeable membrane obtained by the present invention is a membrane with excellent heat resistance, pH resistance, and chlorine resistance.

Procedural amendment (signed as of January 1982) Haruki Shimada, Commissioner of the Japan Patent Office1, Indication of the case, Patent Application No. 189261 filed in 19892, Title of the invention, Selective Permeable Membrane 3, Person making the amendment, Relationship with the case Patent applicant address: 2-1-2 Marunouchi, Chiyoda-ku, Tokyo Name (
004) Asahi Glass Co., Ltd. 4, Agent 105 Address No. 2 Okada Building 6, 24-11 Toranomon-chome, Minato-ku, Tokyo Number of inventions increased by amendment None 7 Target of amendment Description 8 Contents of amendment Details Calligraphic engraving X No changes) and above

Claims (1)

[Claims] (1) General formula (where m and n are mole fractions, m+n=1.
The relationships 0.05≦m and n≦0.95 are satisfied. Also, M
is hydrogen or an alkali metal. ) A selectively permeable membrane formed by crosslinking a polymer having repeating units represented by (2) A selectively permeable membrane formed by crosslinking a polymer having repeating units represented by (2) A selectively permeable membrane formed by crosslinking by heat treatment using an acid or base as a catalyst Selection of claim (1) Sexually permeable membrane. (3) The selectively permeable membrane according to claim (2), which is crosslinked using sulfuric acid as a catalyst. (4) The selectively permeable membrane according to claim (1), (2) or (3), which is formed by crosslinking and forming a membrane on a porous support. (5) The selectively permeable membrane according to claim (4), wherein the porous support is polysulfone.