JPH08131794A - Film for donating hydrophilic effects and manufacture thereof - Google Patents

Abstract

PURPOSE: To obtain a durably porous film which does not show a deterioration of water permeability, if dried by adhering and causing a mixture of vinylacetal copolymer and any other additive to be held by a part of the film with fine pores, and thereby donating hydrophilic effects. CONSTITUTION: In a film comprising a thermoplastic resin with fine pores communicating from one side to the other provided at least, a part of the film, a mixture of a vinylacetal copolymer and at least, one type of any other additive is caused to adhere to and to be held by, at least, a part of the film with fine pores to donate hydrophilic effects. In addition, the thermoplastic resin is at least, one type of material selected from amonghydrophobic thermoplastic resins, a copolymer of two or more different types of the selected resin or a blend of two or more different types of the selected resin. The additive is a nonionic surfactant or a hydrophilic polymer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydrophilization membrane obtained by allowing a hydrophobic porous membrane to hold a mixture of a vinyl acetal copolymer containing a vinyl acetal unit and a hydrophilic monomer unit and an additive component. .

[0002]

2. Description of the Related Art Hydrophobic porous membranes represented by polyolefins have advantages such as high chemical stability and are used in fields such as separation and purification of water or aqueous solutions, treatment, and medical fields. . However, since it has a poor affinity with water as it is, it must be hydrophilized in advance when it is used for treating water or an aqueous solution. As a method for hydrophilizing the hydrophobic porous membrane, for example, alcohol,
There is a method in which the outer surface of the hydrophobic porous membrane and the inner surfaces of the fine pores are wet-treated with an organic solvent such as a ketone, and then the organic solvent is replaced with water. In addition, there is also a method of hydrophilization by holding a hydrophilizing agent such as a water-soluble hydrophilic polymer or a surfactant on the surface of the hydrophobic porous membrane.

[0003]

However, in the method of hydrophilizing with an organic solvent, it is necessary to keep the hydrophobic porous membrane in a wet state at all times, and the maintenance thereof is complicated. Further, in the hydrophilization method using a water-soluble hydrophilic polymer, the hydrophilizing agent held on the surface of the pores begins to dissolve in water, and the porous membrane in such a state loses hydrophilicity once dried, It is not preferable for such applications. The hydrophilic method using a surfactant has a problem that it is likely to be eluted into water and is easily assimilated by various bacteria. The present invention aims to solve these problems.

[0004]

As a method for improving these problems, the present inventors have found that a polymer having a hydrophilic portion and having an affinity for a membrane component resin, and having a hydrophobic porosity. A compound that is less likely to be eluted into the water to be treated when retained on the porous membrane was selected in consideration of the hydrophilicity-hydrophobicity balance, and earnestly studied the method of adhering and retaining it on the surface of the micropores of the porous membrane. As a result, the present invention has been completed.

According to the present invention, in a film made of a thermoplastic resin having at least a part of fine pores communicating from one surface to the other surface, a vinyl acetal copolymer and one or more other additive components are added. The hydrophilic film is characterized in that the mixture of (1) is attached to at least a part of the film having the fine pores to impart hydrophilicity. Further, the thermoplastic resin is a hydrophobic thermoplastic resin such as polyethylene, polypropylene,
At least one substance selected from the group consisting of polyfluoroethylene, polyacrylonitrile, polyethylene terephthalate, polysulfone, polyamide and polyimide, a copolymer of two or more types, or a mixture of two or more types, wherein vinyl of the vinyl acetal-based copolymer is used. The number of carbon atoms in the alkyl group of the acetal ring is 1 to 6, and the vinyl acetal-based copolymer is used alone or in a mixture of two or more kinds. In particular, the alkyl group of the vinyl acetal-based ring of the vinyl acetal-based copolymer is Methyl group, ethyl group, normal propyl group,
An isopropyl group and a phenyl group. The vinyl acetal copolymer used in the present invention is represented by the following general formula,

[0006]

Embedded image

Wherein R = C ₁ -C ₆ alkyl group and phenyl group, preferably CH ₃ , C ₂ H ₅ , C ₃ H ₇ and C ₅ H ₆ and 1 + m = 10-70 mol%, n = 30
~ 90 mol% is preferred. If the hydrophilic monomer unit is less than 30 mol%, sufficient hydrophilicity cannot be imparted, and if it exceeds 90 mol%, it becomes water-soluble and cannot be used.

The additive component used in the present invention is sucrose fatty acid ester, glycerin fatty acid ester, polyoxyethylene glycerin fatty acid ester, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester,
Propylene glycol fatty acid ester, polyethylene glycol fatty acid ester, polypropylene glycol fatty acid ester, polyoxyethylene aliphatic alcohol,
And nonionic surfactants such as polyoxypropylene polyoxyethylene block polymer, or polyamide, polyacrylic acid, ethyl cellulose, polyvinylpyrrolidone, polyvinyl alcohol, ethylene-vinyl alcohol copolymer, vinylpyrrolidone-vinyl acetate copolymer , Hydrophilic polymers such as maleic acid resin and polyvinyl acetal diethylaminoacetate. INDUSTRIAL APPLICABILITY The present invention is an effective means when sufficient water permeability is not obtained by homopolymer coating of a polyvinyl acetal copolymer.

As the hydrophobic porous membrane in the present invention,
Any form such as a hollow fiber membrane, a flat membrane, or a tubular membrane can be used. The material of the hydrophobic porous membrane is the above-mentioned monomer or copolymer such as polyethylene.

In the method for hydrophilizing the present invention, the vinyl acetal-based copolymer and the additive are used alone or as a mixed solvent of alcohol-based, acetone-based and aromatic-based solvents, or a water-containing solvent thereof, preferably methyl alcohol, A dipping solution is prepared by dissolving in ethyl alcohol, isopropyl alcohol, or a mixture of two or more kinds of acetone, or a water-containing material thereof. The concentration of the dipping solution is preferably one in which 1 to 5 parts by weight of the vinyl acetal copolymer and the additional components are dissolved in 100 parts by volume of the solvent. When the immersion liquid has a high viscosity at room temperature, the immersion treatment can be performed by appropriately heating to reduce the viscosity of the immersion liquid. Next, the hydrophobic porous membrane is dipped, and the solution is sufficiently spread also in the through-hole fine pores of the membrane, followed by drying to remove the solvent. As a drying means, a usual method such as air drying, reduced pressure drying, and heat drying can be appropriately used depending on the type of solvent. In addition, a solution of the vinyl acetal-based copolymer and the additive component is separately prepared, and the hydrophobic porous membrane is dried each time it is dipped in one type of solution, and a multi-step dipping treatment is performed in which dipping treatment is performed one after another. May be. The solvent species and the order of immersion may be appropriately selected. The carrying rate showing the amount of the hydrophilizing agent on the membrane is represented by the following formula, and the carrying rate of the hydrophilizing agent in the present invention is preferably 5 to 40% by weight. Carrying rate (% by weight) = hydrophilizing agent amount (g) / hydrophobic yarn weight (g) × 100

[0011]

EXAMPLES The present invention will be described in more detail below with reference to examples and comparative examples.

Example 1 Polyvinyl butyral [trade name: S-REC BL-1,
Sekisui Chemical Co., Ltd., hydrophilic monomer part 30 mol%]
1 part by weight and 1 part by weight of polyoxyethylene (20) glycerin monostearate [trade name: Rikemar S-120, manufactured by Riken Vitamin Co., Ltd.] are dissolved in 100 parts by volume of acetone to obtain an immersion liquid, and polypropylene porosity is added therein. Quality hollow fiber membrane [manufactured by Ube Industries, Ltd., average pore size 0.3 μm, porosity 7
0%] was soaked for 30 seconds. Then, the solvent was removed by air drying to obtain a hydrophilic film having a supporting rate of 25%. 100 of the hydrophilically treated hollow fiber membranes were bundled and the ends were fixed with urethane resin to prepare a membrane module having an effective area of 100 cm ² . When water was filtered by applying a water pressure of 1 kg / cm ² to this membrane module, the water permeation rate was 60 cc / m ² · min, showing excellent water permeation. Also, the water pressure is 1 kg / cm
After filtering 5 liters of water in ² and completely drying, no decrease in water permeability was observed.

Comparative Example 1 Polyvinyl butyral [trade name: S-REC BL-1,
Sekisui Chemical Co., Ltd., hydrophilic monomer part 30 mol%]
The performance of the membrane module was evaluated by performing the same operation as in Example 1 except that an immersion liquid prepared by dissolving 1 part by weight in 100 parts by volume of acetone was used, but no water permeated.

Example 2 Polyvinyl butyral [trade name: S-REC BL-1,
Sekisui Chemical Co., Ltd., hydrophilic monomer part 30 mol%]
1 part by weight dissolved in 100 parts by volume of acetone is first
The same polypropylene hollow fiber membrane as that used in Example 1 was immersed in the immersion liquid for 30 seconds. Then, air-dry for 5 minutes, and after applying hot air at 80 ° C. for 5 minutes, polyoxyethylene (20) glycerin monostearate [trade name:
Rikemar S-120, manufactured by Riken Vitamin Co., Ltd.] 1 part by weight was immersed for 30 seconds in a second immersion liquid dissolved in acetone. Then, it was air-dried, and as a result of water permeability evaluation by the same membrane module as in Example 1, a water permeability of 75 cc / m ² · min was obtained.

Comparative Example 2 Polyvinyl butyral [trade name: S-REC BL-1,
Sekisui Chemical Co., Ltd., hydrophilic monomer part 30 mol%]
The performance of the membrane module was evaluated in the same manner as in Example 1 except that an immersion liquid prepared by dissolving 2 parts by weight in 100 parts by volume of acetone was used, but no water permeated.

Example 3 Polyvinyl acetal copolymer [trade name: S-REC KX-1, manufactured by Sekisui Chemical Co., Ltd., hydrophilic monomer part 7]
8 mol%] 2 parts by weight and 1 part by weight of sorbitan monolaurate [trade name: SML, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.], and an ethanol-water (80:20) mixed solution was added to 100 parts by volume. The same operation as in Example 1 was performed except that a liquid was used,
As a result of evaluating the performance of the membrane module, 55 cc / m ² ·
A water permeability of min was obtained.

Comparative Example 3 Polyvinyl acetal copolymer [trade name: S-REC KX-1, manufactured by Sekisui Chemical Co., Ltd., hydrophilic monomer part 7]
8 mol%] 2 parts by weight of ethanol-water (80:20) mixture was added and dissolved in 100 parts by volume. The same operation as in Example 1 was carried out except that the performance was evaluated. However, water did not permeate at all.

[0018]

EFFECT OF THE INVENTION The hydrophilized polyolefin porous membrane of the present invention is a porous membrane having durable hydrophilicity with no deterioration in water permeability even when the porous membrane is dried after filtration.

Claims (6)

[Claims] 1. A film made of a thermoplastic resin having at least a part of fine pores communicating from one surface to the other surface, wherein a mixture of a vinyl acetal copolymer and one or more other additive components. To impart hydrophilicity by adhering and holding at least a part of the film having the micropores. 2. The hydrophilic membrane according to claim 1, wherein the vinyl acetal-based copolymer is a water-insoluble vinyl acetal-based copolymer containing 30 to 90 mol% of hydrophilic monomer units. 3. An additive component is sucrose fatty acid ester, glycerin fatty acid ester, polyoxyethylene glycerin fatty acid ester, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, propylene glycol fatty acid ester, polyethylene glycol fatty acid ester, polypropylene glycol fatty acid ester,
Nonionic surfactants such as polyoxyethylene aliphatic alcohol and polyoxypropylene polyoxyethylene block polymer, or polyamide, polyacrylic acid, ethyl cellulose, polyvinylpyrrolidone, polyvinyl alcohol, ethylene-vinyl alcohol copolymer, vinyl 2. One or more selected from the group consisting of pyrrolidone-vinyl acetate copolymer, maleic acid resin and polyvinyl acetal diethylaminoacetate.
The hydrophilicized film described. 4. The thermoplastic resin is a hydrophobic resin such as polyethylene, polypropylene, polyfluoroethylene, polyacrylonitrile, polyethylene terephthalate, polysulfone, polyamide, and at least one substance selected from the polyimide, or two or more copolymers or It is a mixture of 2 or more types, The hydrophilization film in any one of Claims 1-2. 5. An immersion liquid is prepared by dissolving a vinyl acetal copolymer and one or more other additive components in an alcohol solvent, a ketone solvent, an aromatic solvent, a mixed solvent thereof, or a water-containing solvent thereof. , Immersing a film made of a thermoplastic resin having at least a part of micropores communicating from one surface to the other surface, and adhering and holding the vinyl acetal-based copolymer and additive components to at least a part of the micropores A method for producing a hydrophilic film, which is characterized in that 6. A solution obtained by dissolving a vinyl acetal copolymer in an alcohol solvent, a ketone solvent, an aromatic solvent, a mixed solvent thereof, or a water-containing solvent thereof is used as a first immersion liquid, and is applied from one surface to the other surface. Immersing a film made of a thermoplastic resin having communicating fine pores in at least a part thereof, and subsequently or after drying, other additive components are alcohol-based, ketone-based, aromatic-based solvents, or mixed solvents thereof. Alternatively, the method for producing a hydrophilized film is characterized by immersing in a second dipping solution dissolved in the water-containing solvent to cause the vinyl acetal-based copolymer and the additional component to adhere to and be held in at least a part of the fine pores.