JPH054126B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to porous polyolefin hollow fibers with excellent hydrophilicity.

[Prior art]

Various membranes are known as ultrafiltration membranes and precision filtration membranes used for producing pure water, filtering colloidal substances in water, and the like. In particular, membranes for medical, pharmaceutical, food, and precision industries are required to remove bacteria, and in particular, membranes that can also remove pyrogens are required for medical and pharmaceutical applications. . Although many membranes that can remove bacteria are known, there are no ultrafiltration membranes or microfiltration membranes that can simultaneously remove pyrogens.

Reverse osmosis is known as a method that can also remove pyrogenic substances, but because reverse osmosis requires high pressure, equipment costs are high, the equipment is large, and it is difficult to satisfy economic efficiency unless the throughput is increased. In addition, it is possible to store treated water and use it little by little as needed. Even if various measures are taken to store water, there is a drawback that bacteria and pyrogens can contaminate the treated water.

In particular, porous membranes for water treatment, which have minute pores that can block bacteria, cannot pass through water unless they are hydrophilic. However, membranes made of hydrophilic materials tend to deteriorate when attacked by microorganisms, and they also block bacteria. The problem is that the bacterial concentration increases on the side where the bacteria is exposed.

First, in Japanese Patent Publication No. 56-52123 and Japanese Patent Application Laid-open No. 57-42919, the applicant solved the drawbacks of conventional devices, and developed a device that has low equipment costs and energy costs, is simple in structure, has few failures, and As a highly reliable membrane for precision filtration equipment, we proposed a porous polyolefin hollow fiber in which micropores with a pore diameter of 0.01 to 1 μm communicate between the inner and outer walls of the hollow fiber. However, since this is a hydrophobic porous polyolefin hollow fiber, it is used by temporarily making it hydrophilic with alcohol etc. before use and replacing it with water. If the surface of the porous polyolefin hollow fiber is removed and dried by contacting with air, there is a problem that the freeness decreases, and there has been a strong demand for the development of a porous polyolefin hollow fiber with excellent hydrophilicity.

[Problem to be solved]

An object of the present invention is to provide a hydrophilized porous polyolefin hollow fiber that is safe and has excellent operability.

[Means to solve]

The above object of the present invention is to provide a porous polyolefin in which micropores formed between a large number of fibrils arranged substantially in the longitudinal direction of the hollow fibers communicate between the inner wall surface and the outer wall surface of the hollow fibers. This is achieved by using hydrophilized porous polyolefin hollow fibers, which are characterized by having a membrane made of cellulose formed on the surface of the fibrils.

A porous polyolefin hollow fiber in which micropores formed by a large number of fibrils communicate between the inner wall surface and the outer wall surface of the hollow fiber is disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 57-42919.
It can be manufactured by No. As a method of forming a cellulose membrane on the surface of the fibrils forming such porous polyethylene hollow fibers to obtain permanently hydrophilized porous polyethylene hollow fibers, for example, a solution containing cellulose acetate is added to the porous polyethylene. After the hollow fibers are impregnated, they are immersed in a coagulant solution of the cellulose acetate and subjected to rapid wet coagulation treatment to form a cellulose acetate film on the surface of the fibril, and then dipped in a heated aqueous sodium hydroxide solution to form a cellulose acetate film. It is possible to convert the cellulose into a thin cellulose film by saponifying the cellulose. In this case, any cellulose acetate used in the present invention can be used as long as it has film-forming ability.
It is preferable that the cellulose acetate be as uniform as possible on the surface of the fibril and that the amount of the adhesion be kept to a minimum, so as to minimize the clogging of the pores of the hollow fibers due to the adhesion treatment. Cellulose membranes obtained by saponifying cellulose acetate exhibit excellent hydrophilicity. Therefore, a porous polyolefin hollow fiber having a cellulose membrane fixed to the surface of the fibril exhibits excellent hydrophilicity.

In order to manufacture a module using the hydrophilic porous polyolefin hollow fiber of the present invention, it is sufficient to apply the general known module manufacturing method using porous hollow fiber as it is, from the outer wall side of the porous hollow fiber to the inner wall side. Any form of module may be used as long as it filters liquid or gas from the side or from the inner wall to the outer wall. By using the hydrophilized porous polyolefin hollow fiber of the present invention, it is possible to remove colloidal substances, bacteria, and pyrogenic substances, and while maintaining safe operability at all times, equipment costs and energy costs are lower than conventional equipment. The structure is simple, there are few failures, and it enables highly reliable precision filtration.

〔Example〕

Hereinafter, the present invention will be explained with reference to Examples.

A porous polyethylene hollow fiber (manufactured by Mitsubishi Rayon Co., Ltd., trade name: EHF) was immersed for 30 seconds in a solution at 25°C in which 2 parts by weight of cellulose acetate flakes for producing diacetate fibers were dissolved in 98 parts by weight of dimethylformamide. Porous polyethylene hollow fibers with a porous thin film of cellulose acetate fixed on the surface of the laminated structure of the hollow fibers are taken out and immediately immersed in water at 25°C to make them porous by rapid coagulation of cellulose acetate and to remove solvent. I got it. Subsequently, this hollow fiber was immersed in an aqueous solution containing 0.5% by weight of sodium hydroxide at 60°C for 60 minutes to saponify the cellulose acetate membrane, and then thoroughly washed with water and dried to solidify the cellulose membrane. A hydrophilized porous polyethylene hollow fiber was obtained. 100 of these hydrophilic porous polyethylene hollow fibers were bundled in a U-shape and the openings of the hollow fibers were solidified with resin to produce a module with a length of the resin-embedded portion of 2 cm and an effective length of the hollow fibers of 15 cm.

As a result of measuring the water pressure resistance of the above module using hydrophilized porous polyethylene hollow fibers, the pressure was 0.05Kg/cm ²
Water filtration was initiated at extremely low pressures of G, giving excellent hydrophilicity.

Furthermore, in order to determine whether or not the module using hydrophilized porous polyethylene hollow fibers has permanent hydrophilicity, a pressure of 1 kg/cm ² G was applied, water was allowed to pass for 1 hour, the water was removed, and the module was dried in a vacuum dryer at 40°C for 20 hours. After drying for several hours, the water pressure resistance was measured and showed a G value of 0.06Kg/cm ² , showing almost no decrease in hydrophilicity even after a large amount of water and subsequent drying treatment, demonstrating excellent permanent hydrophilicity. was granted.

Comparative Example 1 A normal module was prepared in the same manner as in Example 1 using the porous polyethylene hollow fibers that had not been subjected to the hydrophilic treatment. The module using this untreated porous polyethylene hollow fiber had a significantly high water pressure resistance, and no water was allowed to pass through even when a pressure of 3 kg/cm ² G was applied.

〔Effect of the invention〕

The hollow fiber module using the hydrophilic porous polyolefin hollow fibers of the present invention can repeat filtration with stable reliability without decreasing the filtration rate even after filtration is interrupted and the hollow fibers are brought into contact with air. can do.

Claims (1)

[Claims] 1. A porous polyolefin hollow fiber in which micropores formed between a large number of fibrils arranged substantially in the longitudinal direction of the hollow fiber communicate between the inner wall surface and the outer wall surface of the hollow fiber, A hydrophilic porous polyolefin hollow fiber characterized by having a membrane made of cellulose formed on the surface of the fibril.