JP3358340B2 - Hydrophilic membrane and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydrophilic membrane obtained by retaining a polyoxyethylene glycerin fatty acid ester on a hydrophobic porous membrane.

[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 solution, treatment, and medical fields. . However, if it is used as it is, it has a poor affinity for water, so that it needs to be hydrophilized in advance when 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 surface of the fine pores are wet-treated with an organic solvent such as ketone, and then the organic solvent is replaced with water. There is also a method of hydrophilization by retaining a hydrophilic agent such as a water-soluble hydrophilic polymer or a surfactant on the surface of the hydrophobic porous membrane.

[0003]

However, in the method for hydrophilizing with an organic solvent, it is necessary to keep the hydrophobic porous membrane in a wet state at all times, and the maintenance and management thereof are complicated. In addition, in the method of hydrophilization using a water-soluble hydrophilic polymer, the hydrophilic agent held on the surface of the micropores begins to dissolve in water, and the porous membrane in such a state loses its hydrophilicity once it is dried. Such a use is not preferable. The method of hydrophilizing with a surfactant also has a problem that it is liable to be eluted into water and is susceptible to assimilation by various bacteria. The present invention aims to solve these problems.

[0004]

As a method of solving these problems, the present inventor has proposed a method of improving the hydrophobic porous property of a polymer having a hydrophilic portion and having an affinity for a membrane component resin. Compounds that hardly dissolve into the water to be treated when retained on the porous membrane were selected in consideration of the balance between hydrophilicity and hydrophobicity, and a method for adhering and retaining them on the surface of the porous membrane micropores was studied diligently. As a result, the present invention has been completed.

According to the present invention, there is provided a film made of a thermoplastic resin having at least a part of micropores communicating from one surface to another surface, wherein a polyoxyethylene glycerin fatty acid ester having a polyoxyethylene chain length of 1 to 20 is used. The present invention relates to a hydrophilized film characterized in that hydrophilicity is imparted by adhering to and holding at least a part of the film having micropores. Also,
The thermoplastic resin is a hydrophobic thermoplastic polyethylene resin,
Polypropylene, polyfluoroethylene, polyacrylonitrile, polyethylene terephthalate, polysulfone,
A polyoxyethylene chain length of the polyoxyethylene glycerin fatty acid ester is at least one substance selected from polyamide and polyimide, or two or more copolymers or a mixture of two or more kinds thereof; The present invention relates to a method for producing a hydrophilized film having 12 to 18 carbon atoms.

The hydrophobic porous membrane in the present invention includes:
Arbitrary forms such as a hollow fiber membrane, a flat membrane, and a tubular membrane can be used. The material of the hydrophobic porous membrane is the above-described monomer or copolymer such as polyethylene. The polyoxyethylene glycerin fatty acid ester used in the present invention is represented by the following general formula, and may be a compound of formulas 1 and 2 alone or a mixture of formulas 1 and 2.

[0007]

Embedded image

[0008]

Embedded image

In the formula, m + n = 1 to 20, especially 5 to
20 is preferred. If it exceeds 20, it becomes water-soluble and is not preferred. R = a C ₁₁ -C _17.

The method for producing a hydrophilized membrane of the present invention is characterized in that a polyoxyethylene glycerin fatty acid ester is used alone or in a mixed solvent of an alcohol-based, acetone-based, aromatic-based solvent or the like, or an aqueous solvent thereof, preferably methyl alcohol,
It is dissolved in one or a mixture of two or more of ethyl alcohol, isopropyl alcohol and acetone, or a hydrate thereof to prepare an immersion liquid. The concentration of the immersion liquid is
It is preferable that 1 to 8 parts by weight of polyoxyethylene glycerin fatty acid ester is dissolved in 100 parts by volume of a solvent. Next, the hydrophobic porous membrane is immersed, the solution is sufficiently spread even in the through-holes of the membrane, and then the solvent is removed by drying. Drying means, air drying, vacuum drying,
A usual method such as heating and drying can be appropriately used. The loading rate indicating the amount of the hydrophilic agent on the membrane is represented by the following formula, and the loading rate of the hydrophilic agent in the present invention is preferably 5 to 40% by weight. Loading ratio (% by weight) = amount of hydrophilic agent (g) / weight of hydrophobic yarn (g) × 100

[0011]

The present invention will be described in more detail with reference to the following Examples and Comparative Examples.

Example 1 Polyoxyethylene (5) glycerin monostearate [trade name: TMGS-5, manufactured by Nikko Chemicals Co., Ltd.] 2
Part by weight is dissolved in 100 parts by volume of acetone to prepare an immersion liquid, into which a polypropylene porous hollow fiber membrane [Ube Industries, Ltd.
Manufactured, average pore diameter 0.3 μm, porosity 70%] for 30 seconds. Thereafter, the solvent was removed by air drying to obtain a hydrophilic film having a loading of 20%. One hundred hollow fiber membranes subjected to the hydrophilic treatment were bundled and the ends were solidified with a urethane resin to prepare a membrane module having an effective area of 100 cm ² . Water was filtered at a pressure of 1 kg / cm ² on this membrane module, and the water permeability was 65 cc / m ² · min, indicating excellent water permeability. Further, after 5 liters of water were filtered at a water pressure of 1 kg / cm ² and completely dried, no decrease in water permeability was observed.

Comparative Example 1 Using the same polypropylene porous hollow fiber membrane as used in Example 1, a membrane module similar to that of Example 1 was prepared without hydrophilizing the same, and water was filtered. Attempted, but no water permeated.

Example 2 Polyoxyethylene (20) glycerin monostearate (trade name: Riquemar S-120, manufactured by Riken Vitamin Co., Ltd.) was used except that an immersion liquid obtained by dissolving 6 parts by weight in 100 parts by volume of acetone was used. The same hydrophilic treatment as in Example 1 was performed. As a result of the water permeability evaluation using the same membrane module as in Example 1, a water permeability of 75 cc / m ² · min was obtained.

[0015]

The porous polyolefin membrane of the present invention is a porous membrane having a durable hydrophilic property without a decrease in water permeability even when the porous membrane is dried after filtration.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-64-11605 (JP, A) JP-A-61-71803 (JP, A) JP-A-61-191365 (JP, A) 119802 (JP, A) JP-A-4-118033 (JP, A) JP-A-5-64727 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B01D 61/00-71 / 82 510 C02F 1/44

Claims (6)

(57) [Claims] 1. A film made of a thermoplastic resin having at least a part of a fine hole communicating from one surface to another surface, wherein a polyoxyethylene glycerin fatty acid ester is attached to at least a part of the film having the fine hole. A hydrophilized film characterized in that the film is retained to impart hydrophilicity. 2. The thermoplastic resin is a hydrophobic resin of at least one substance selected from polyethylene, polypropylene, polyfluoroethylene, polyacrylonitrile, polyethylene terephthalate, polysulfone, polyamide and polyimide, or a copolymer of two or more kinds thereof. The hydrophilic film according to claim 1, wherein the film is a mixture of two or more kinds. 3. The polyoxyethylene glycerin fatty acid ester having a polyoxyethylene chain length of 1 to 20 and a fatty acid carbon number of 12 to 18 is used.
The hydrophilic membrane according to any one of the above. 4. An immersion liquid obtained by dissolving a polyoxyethylene glycerin fatty acid ester in an alcohol-based, ketone-based, aromatic-based solvent, or a mixed solvent thereof, or a water-containing solvent, and communicating from one side to the other side. A method for producing a hydrophilized film, characterized by immersing a film made of a thermoplastic resin having at least a part of micropores and adhering and holding a polyoxyethylene glycerin fatty acid ester in at least a part of the micropores. 5. The method according to claim 1, wherein the solvent is one of methyl alcohol, ethyl alcohol, isopropyl alcohol and acetone.
5. The method for producing a hydrophilized film according to claim 4, wherein the method is a species or a mixture of two or more species, or a hydrated solvent thereof. 6. A polyoxyethylene glycerin fatty acid ester having a polyoxyethylene chain length of 1 to 20 and a fatty acid carbon number of 12 to 18 is used.
A method for producing the hydrophilized membrane according to any one of the above.