JPS5976504A - Production of reverse osmotic membrane - Google Patents

Abstract

PURPOSE:To produce easily a reverse osmotic membrane in one stage by impregnating a mixture of a unifunctional monomer and a bifunctional monomer in a porous backing membrane and subjecting the same to photopolymn. CONSTITUTION:A mixture of a unifunctional monomer (e.g.; 2-dimethylaminoethyl methacrylate) contg. a photopolymn. initiator and a bifunctional monomer (e.g.; ethylene glycol dimethacrylate) is impregnated in a porous backing membrane. A high pressure mercury vapor lamp is advantageously used for irradiation of said mixture; for example, in the case of a 100W high pressure mercury vapor lamp, the material is irradiated from a transparent film side at 10-15cm distance to initiate immediately polymn. whereby the monomers in the porous backing membrane is easily polymerized and the intended reverse osmotic membrane is obtd. A photosensitizer such as, for example, 2,2-diethoxy acetophenone or the like is used as the photopolymn initiator and a porous high polymer film such as, for example, a porous PP film is used as the porous backing membrane, respectively.

Description

Detailed Description of the Invention The invention relates to a method for producing a reverse osmosis membrane, more specifically, a method for producing a reverse osmosis membrane in one step by impregnating a monomer into a porous support membrane and photopolymerizing it. It is.

Conventionally, composite membranes for reverse osmosis have generally been manufactured by a method of manufacturing a polymer exhibiting reverse osmosis properties and casting the polymer into a porous membrane. In this method, monomers are once polymerized to synthesize a polymer with reverse osmosis properties, reprecipitated and purified, then dissolved in a solvent to prepare a casting solution, coated on a support membrane, and dried. This provides peace of mind during many complicated processes.

As a result of repeated research into a simple manufacturing method for reverse osmosis membranes that does not require such conventional complicated steps, the present inventor has discovered that
It has been found that it can be easily produced by impregnating a porous support membrane with a monomer for forming a reverse osmotic polymer and photopolymerizing it.

That is, in the present invention, a porous support membrane is impregnated with a mixture of a functional monomer and a difunctional monomer containing a photocoagulation initiator, and the monomers are polymerized by irradiating the porous support membrane with light. The present invention provides a method for manufacturing a reverse osmosis membrane, characterized in that:

Preferred monofunctional monomers used in the inventive method include, for example, 2-dimethylamine ethyl methacrylate, acrylic acid, methacrylic acid, N,N-dimethylacrylamide, 2-hydroxyethyl methacrylate,
Acrylic monomers having a hydrophilic group such as -acrylamide-2-methylpropanesulfonic acid can be mentioned, but of course difunctional monomers exhibiting photopolymerizability can also be used. -1: Examples of difunctional monomers include ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, 4-methacrylate, lJ loyloxychalcone, N,N-(2-hydroxy-3-
Examples include methacryloyloxyglopyl) piperazine.

These-functional monomer and difunctional monomer f-historical ratio Q
It is selected as appropriate depending on the type and concentration of salts to be removed by reverse osmosis, but if the amount of bifunctional monomer is too large, the membrane permeation flux will be small, and if it is too small, the removal rate of dissolved salts will be low. This is undesirable because it reduces the performance of the reverse osmosis membrane.
Generally, difunctional monomers are monofunctional monomers f(ζ, 0.
Amounts ranging from 5 to 15 inches are advantageously used. Moreover, the -functional monomer can be used as a single component or in combination of two or more components, and the difunctional monomer can similarly be used in combination of one type of VC or two or more components.

Preferred photopolymerization initiators to be included in these monomers include, for example, 2,2-diethoxyacetophenone, benzoin, benzophenone, benzoin isopropyl ether, and 2,2-dimethoxy-2-phenylacetophenone. Examples include sensitizers. Of these, 2,2-die I xyacetophenone, which is soluble in the liquid monomers mentioned above, is particularly advantageous.

The porous support membrane used in the inventive method is a porous membrane-like material, and for example, a porous polymer film such as a porous polypropylene film is advantageously used. In the present invention, such a porous support membrane is first impregnated with a monomer mixture containing a photopolymerization initiator, and the monomers are polymerized by irradiation with light, preferably under air-free conditions. However, for example, a porous polymer film is placed on a fluororesin plate, impregnated with a monomer mixture, and then covered with a transparent film, and then the air is squeezed out from above using a roller or the like. It is then placed in close contact with the other parts and subjected to light irradiation treatment. The transparent film for blocking air is not preferably a material that dissolves or swells in monomers, but suitable materials include transparent polypropylene film, polyethylene film, and fluorinated ethylene-propylene copolymer film.

For light irradiation, a high-pressure mercury lamp is usually advantageously used. For example, with a 100W high-pressure mercury lamp, polymerization starts immediately when the light is irradiated from the transparent film side at a distance of 10 to 15z.
The monomers in the porous polymer support readily form polymers. This light irradiation process is completed in a relatively short time of several minutes to several tens of minutes, but preferably, for example, after light irradiation,
It is heat-treated at a temperature of about 0.00-110"C for 3-10 minutes. After the heat treatment, the covered transparent film is peeled off to easily obtain a reverse osmosis composite membrane.

Non-inventive person'! In E:, as mentioned above, a monofunctional monohydric substance having a hydrophilic group is advantageously used. When acrylic acid is used, it is preferable to immerse it in an aqueous solution of hydrochloric acid, and in cases where acrylic acid is used, it is preferable to make it into a polymer salt by immersing it in an aqueous solution of arsenium hydroxide. can improve sex.

The method of the present invention does not involve the complicated steps of the conventional reverse osmosis membrane manufacturing method, is easy to handle and operate, and can significantly reduce the total loss. It is industrially advantageous. In addition, the reverse osmosis membrane obtained by the uninvented method has a dissolved salt rejection rate of 70 to 80 when applied to a sodium chloride solution of 0.3, which is the same as that of conventional reverse osmosis membranes. It is a reverse osmosis composite membrane comparable in degree and can be put to practical use.

The reverse osmosis membrane obtained by the uninvented method can be used for desalination of brine and production of desalinated water from an aqueous inorganic salt solution in the same way as conventional products.
It can also be used as an ion exchange membrane.

Hereinafter, the non-invention will be explained in more detail from Example V i1. lII will explain.

Example 1 1 of 2-dimethylamine ethyl methacrylate-1- (abbreviated as DAM). A predetermined amount of a bifunctional monomer, namely 4-methacryloyloxychalcone (M(1) or ethylene glycol dimecacrylate (EG)) and 2,2-jethoxyacetophenone (EAP) as a photopolymerization initiator, are added to □cc. , 02 CO'!i7 were mixed to prepare a monomer mixture. This solution was spread over a porous polypropylene membrane (
Oelgaad 2400, hydrophobic, diameter 7.5o++
), the entire impregnated film was sandwiched between a Teflon plate and a transparent polypropylene film, and the transparent polypropylene film was squeezed with a roller to expel air and adhere tightly. Then, a 100W high-pressure mercury lamp was used to
Transparent polypropylene 11111 was irradiated with light for 10 minutes from a distance of It was immersed in a solution of concentrated hydrochloric acid 2C (]7, (an aqueous solution of IQcc diluted with water) and left overnight. At this stage, the dimethylamino groups were in the form of hydrochloride, and the membrane swelled and spread out somewhat. After washing the molecules with Abco
r Using RO-3 type reverse osmosis old (1 socc capacity), 0
．． A reverse osmosis experiment was conducted using an aqueous solution of IJium chloride (Section 3). The operating pressure is 70.9/cni and the effective membrane area is 30.2 cni.

The results obtained for various reverse osmosis membranes prepared with varying doses of MC or EG are shown in Table 1. In addition, a membrane without the bifunctional monomer Kuwabata was produced in the same manner, and the measured values are also listed in the table.

Example 2 In Example 1, acrylic acid was used instead of 2-dimethylaminoethyl methacrylate-1, and a difunctional monomer and a photoinitiator (KAP) were mixed and impregnated into a porous membrane. A photopolymerized film was prepared in the same manner as in Example 1. This membrane was immersed in a 5% caustic soda aqueous solution for 30 minutes to form a salt, which caused the membrane to swell and spread. After thorough washing with water, the O membrane was cut and passed through a reverse osmosis membrane to measure the salt rejection rate and flux. The results are shown in Table 2.

In addition, the bifunctional monomers bp, N, N-(2-hydroxy'-3-methacryloyl-xyfilovir)
It is piperazine.

Example 3 2-acrylamido-2-methylpropanesulfone
0.21 &, 'MC! 0.02. ! ? fN,
2ccvc of N-Si)l-f-ruacrylamide was dissolved, a portion thereof was taken, and photopolymerized in a porous polypropylene membrane in the same manner as in Example 1 to create a reverse osmosis membrane. The salt rejection rate for a 0.3 sodium chloride aqueous solution is 7
67 at operating pressure of 0 K9/crl, flux is 0.73
1/hr・7f? Met.

Patent applicant Makoto Ishizaka, Director of the Agency of Industrial Science and Technology - Designated agent
Osaka Industrial Technology Testing Institute Director, Agency of Industrial Science and Technology Osaka Naito

Claims (1)

[Claims] 1. A porous support membrane is impregnated with a mixture of a monofunctional monomer and a difunctional monomer containing a photopolymerization initiator, and the monomers are polymerized by irradiating the membrane with light. A method for manufacturing a reverse osmosis membrane, characterized by: 2. The method according to claim 1, wherein the 2-functional monomer is an acrylic monomer having a hydrophilic group. 3. Method g according to claim 1, wherein the porous support membrane is a porous plastic film.