JPS5892406A - Selective permeable membrane - Google Patents

Abstract

PURPOSE:To attain to enhance the chemical resistance, the heat resistance and the pressure resistance of a selective permeable membrane, in solution separation due to a reverse osmosis method, by using a methylolated polyhydroxystyrene oxide crosslinked membrane. CONSTITUTION:A selective permeable membrane formed from crosslinked methylolated polyhydroxystyrene oxide has a zore size of 10-300Angstrom and excellent in chemical resistance, heat resistance, pressure resistance and film forming property as a reverse osmosis membrane. The M.W. of the polymer is pref. 300-several ten thousands and crosslinking is pref. carried out in the presence of a catalyst. The formation of the membrane is pref. carried out by a method wherein methylolated polyhydroxystyrene oxide is dissolved in a solvent and the resulting solution is cast into a film on a porous support and, as the porous support, one with a pore size of 5,000Angstrom or less comprising a polysulfone resin is preferred.

Description

Detailed Description of the Invention The present invention provides a selective permeable membrane, more specifically, a selective permeable membrane that has excellent water permeability and selectivity, as well as excellent chemical resistance, heat resistance, 4-consolidation resistance, and film formability. Regarding a sexually permeable membrane.

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. For this reason, it is currently used in many fields for separating inorganic and organic substances in media, including desalination of seawater and brine, and is expected to find even wider applications in the future.

Conventionally, as examples of reverse osmosis membranes, Loeb and Sowr
I Rajan's cellulose acetate membrane (U.S. Pat. No. 3,133,132, No. 3,133,137) and Richte's
Typical examples include aromatic polyamides of R.R. and Hoehu, or polyamide hydrazide M (US Pat. No. 3,567,632). However, these membranes are not always fully satisfactory in terms of water permeability and selectivity (salt removal rate), and furthermore, they have poor chemical resistance, heat resistance, compaction resistance, film formability, etc. also had various problems.

The present inventor conducted research to solve the various problems of conventional selectively permeable membranes, and found that a selectively permeable membrane formed by crosslinking methylolated polyhydroxystyrene oxide having repeated Φ positions, It has been found that this purpose can be fully satisfied. In addition, in the above,
p is 1 or 2, and xly is selected such that the ratio of methylol groups/phenol groups in the polymer is 0.01 to 2.0.

The selectively permeable membrane 9 of the present invention not only has excellent water permeability and selectivity, but also has chemical resistance, heat resistance, compaction resistance, and chlorine resistance shown in the usable pH range of 1 to 12. It is a well-balanced membrane with excellent bacterial resistance. 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 properties.

The methylolated polyhydroxystyrene oxide having the above general formula used in the present invention can be easily obtained by methylolating polyhydroxystyrene oxide in the ortho, meta or para position using known means, for example formaldehyde. The ratio of methylolation in methylolated polyhydroxystyrene oxide is also related to the crosslinking property and water permeability of the selectively permeable membrane obtained, and if it is too small, the above-mentioned desired properties cannot be obtained. The ratio of X and y indicating the methylolation ratio must be selected so that the ratio of methylol groups/phenol groups in the polymer satisfies 001 to 2.0. Among them, the ratio of methylol group/phenol group is 1, and the ratio is 0.1 to 1 for reasons such as the stability of methylolated polyhydroxystyrene oxide in a solution and film forming properties.
The molecular weight of methylol-S-modified polyhydroxystyrene oxide is preferably 300 to several 100,000, especially 1.0 because it is related to the film formability and mechanical properties of the membrane. It is preferable that it is from OOO to about 50,000.

Crosslinking of methylolated polyhydroxystyrene oxide is preferably carried out using a catalyst and dissolved in a suitable medium. As the catalyst, inorganic acids such as sulfuric acid, hydrochloric acid, and phosphoric acid, organic acids such as acetic acid and para+luenesulfonic acid, or bases such as caustic alkali, ammonia, amines, and quaternary ammonium salts are used. Among them, as a catalyst, 0
．． It is particularly preferable to use 1 to 3% sulfuric acid 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, relative to the methylolated polyhydroquinostyrene oxide.

As the solvent for the methylolated polyhydroxystyrene oxide, any appropriate solvent such as alcohols, ketones, ethers, etc. can be used as long as it is a solvent for the substance. Among these, preferably lower alcohols having 8 or less carbon atoms, such as methanol, ethanol, n-propatool, and isopropatool;
It is preferable to use a mixed solvent of alcoholic water to which not more than % by weight of water is added. When a solvent is used, the content of methylolated polyhydroxystyrene oxide in the solvent is
It is appropriate to select preferably 0.01 to 5%, particularly 0.1 to 3%.

In the presence of the above catalyst, the methylolated polyhydroxystyrene oxide dissolved in an appropriate solvent preferably has a
By maintaining the temperature at 180°C, particularly 100 to 155°C, preferably from 10 seconds to 6 hours, particularly from 0.5 minutes to 1 hour, crosslinking occurs and a crosslinked product of methylolated polyhydroxystyrene oxide is obtained.

The crosslinked product may be obtained and subsequently formed into a film, but preferably, the crosslinking of the methylolated poly-1-hydroxystyrene oxide is carried out concurrently with the film formation.

In the case of forming a loose film, it is preferable to use an appropriate porous support and form the film on the porous support.

Such porous supports include cellulose esters such as cellulose nitrate and cellulose acetate, folysulfone, polyethersulfone, folystyrene, 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. The pore diameter is desirably 1.oOoA or less, preferably 1.oOoA or less in order to provide particularly high selectivity (exclusion rate).

The shape of the porous support is not a flat membrane, but can be tubular or hollow, and the selectively permeable membrane of the present invention can have any shape according to the shape.

A 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 cast onto a plate and then immersed in water. Thickness 10-5 obtained by
00μ.

The means for crosslinking methylolated polyhydroxystyrene oxide on a porous support to form a film is to use a solution of methylolated polyhydroxystyrene oxide containing the above catalyst,
A method of casting on a porous support, a method of spraying or coating, or a method of floating a porous support on the above solution,
Any method can be employed, such as a method of immersing the porous support in the above solution. During film formation, preferably 0.01% of a surfactant such as sodium lauryl sulfate, sodium alkylbenzenesulfonate, or polyethylene oxide is added to the methylolated polyhydroxystyrene oxide solution.
By adding up to 1%, the stability of the resulting film can be improved.

A thin layer of methylolated polyhydroxystyrene oxide solution is preferably applied to one or both sides of the porous support by evaporating part or all of the solvent and then heat-treating for a predetermined period of time as described above. A crosslinking treatment is performed.

It is estimated that the selectively permeable membrane of methylolated polyhydroxystyrene oxide obtained by oxidation usually has a pore size of 10 to 600 pores, which is an extremely appropriate range for use as a reverse osmosis membrane. The membrane formed on the transparent support is extremely excellent in practical use.

Note that the methylolated polyhydroxystyrene oxide film may be immersed in an aqueous solution of a water-soluble polyvalent metal compound such as barium hydroxide, aluminum hydroxide, calcium chloride, etc., preferably in a range of 0.001 to 20% heavy weight, if necessary. By doing so, the characteristics as a selectively permeable membrane can be further improved.

Furthermore, when obtaining the selectively permeable membrane of the present invention from polyhydroxystyrene oxide, methylolization and crosslinking treatment as well as membrane formation can be carried out simultaneously. In this case, an alcohol aqueous solution of polyhydroxystyrene oxide, formaldehyde, and an acid is preferably heat-treated to methylolate and partially crosslink, and then coated or immersed onto the porous body to complete the crosslinking. will be adopted.

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

Synthesis of reference device poly(p-hydroxystyrene oxide) [Synthesis of p-acetoxystyrene oxide] After dissolving 46.7 parts of m-chloroperbenzoic acid (overlapping parts, same hereinafter) in 880 parts of dichloromethane, While stirring at <0>C, 37.3 parts of p-acetoxystyrene was added dropwise. After the dropwise addition was completed, the mixture was allowed to react at the same temperature for 24 hours. After removing m-chlorobenzoic acid precipitated in the reaction system, the dichloromethane solution is washed several times with a 5% aqueous sodium hydroxide solution to remove dissolved m-chlorobenzoic acid. After removing the caustic soda by washing with water, the mixture was dried through a layer of anhydrous sodium sulfate.

After dichloromethane was distilled off at normal pressure, 35.2 parts of p-acetoxystyrene oxide (86
%), boiling point 83-84° C./1.7 μHf, as a clear liquid.

[Polymerization and hydrolysis]

After replacing the inside of the reactor with 9 elements, 0.13 part of boron trifluoride (gestyl ether) as a catalyst was added, and the temperature was heated to 60°C.
Then, 8.02 parts of p-acetoxystyrene oxide was added dropwise. 60°C for 4 hours followed by 90°C for 6 hours.
Polymerization was carried out by heating for a period of time until the contents solidified.

After dissolving the obtained polymer in 20 parts of dioxane, caustic soda! Add 10 parts of an aqueous solution containing 1.6 parts of
Hydrolysis was carried out by heating for hours. Poly(p-hydroxystyrene oxide) 4 was obtained by acidifying the reaction solution with hydrochloric acid, filtering the precipitate, washing with water, and drying under reduced pressure.
．． Got 9 copies.

Example 1 Methylolated poly(p-hydroxystyrene oxide) [methylol group/
Phenol group = 0, 30'30.5 weight 1 part, concentrated sulfuric acid 0
．． 5 electric switches, 0.05 weight 1 part sodium lauryl sulfate,
In a solution of 60 parts by weight of water and 40 parts by weight of isopropyl alcohol, polysulfone (p
A porous polysulfone support membrane with a thickness of 60μ obtained by applying a 15% dimethylformamide solution of 5500) on a glass plate and then dipping it in water was immersed for 5 minutes, then the membrane was held vertically at room temperature for 1 hour. Air dried for a minute. This is 150
-°C (7) Heating and drying for 15 minutes in an open air environment to carry out a crosslinking reaction.

When the obtained selectively permeable composite membrane was subjected to a reverse osmosis test at room temperature using 3.5% by weight saline under a pressure of 60 Kp/-, the salt removal rate after 24 hours was 96. .0
%, and the water permeability at that time is 0.28 m3/, m”
-day.

Example 2 Methylolated poly(p-hydroxystyrene oxide)
The same procedure as in Example 1 was carried out, except that the proportions of water and isopropyl alcohol were changed and 1.0 parts by weight of methylolated poly(p-hydroxystyrene oxide), 40 parts by weight of water, and 6 oii parts of isopropyl alcohol were used. The resulting selectively permeable membrane had a salt removal rate of 99.6% and a water permeation rate of 0.25 m3/IHn-day.

Example 3 A selectively permeable membrane obtained in the same manner as in Example 2 except that 5 parts by weight of sodium lauryl sulfate α05 was not used had a salt removal rate of 992% and water permeability 1 of 0.50 m"/m2
It was -day.

Example 4 Poly(p-hydroxystyrene oxide) obtained in Reference Example
1.0 parts by weight, 0.24 parts by weight of 35% formalin aqueous solution, 0.10 parts by weight of sodium lauryl sulfate, and 1 part by weight of sulfuric acid.
．． 0 parts by weight of water and 6 parts by weight of isopropyl alcohol.
After dissolving in a mixed solution of 0 weight and 1 part, and stirring at 60° C. for 3 hours, the reaction solution was cooled to room temperature. Add a thickness of 6 to this solution.
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 150° C. for 15 minutes to carry out a crosslinking reaction. The obtained selectively permeable membrane was mixed with 55% saline solution at 60Kl/? When a reverse osmosis test was conducted at room temperature under the pressure of
” / Mll'-day.

Procedural amendment form) Haruki Shimada, Commissioner of the Japan Patent Office, dated May 1, 19801, Indication of the case, Patent Application No. 189255, filed in 19892, Name of the invention, Selective Permeable Membrane 3, Name of the person making the amendment. Related Patent originator address: 2-1-2 Marunouchi, Chiyoda-ku, Tokyo Name (
004) Asahi Glass Co., Ltd. 4, Agent 105 Address No. 2 Okada Building, 24-11 Toranomon-chome, Minato-ku, Tokyo

Claims (5)

[Claims] (1) A selectively permeable membrane formed by crosslinking methylolated polyhydroxystyrene oxide having repeating units to form a film (in the above, p is 1 or 2, and X and y are methylol groups/ phenol group is selected to be from 0.01 to 2.0). (2) The selectively permeable membrane according to claim (1), which is crosslinked by heat treatment using an acid or a base as a catalyst. (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.