JPS6029742B2 - Method for producing porous polyvinylidene fluoride membrane - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for manufacturing a porous polymer membrane.

Specifically, the present invention relates to a method for producing a porous polymer membrane with excellent corrosion resistance and weather resistance. More specifically, the present invention relates to a method for producing a porous polyvinylidene fluoride membrane. Porous polymer membranes consisting of linear through-holes with uniform pore diameters include polycarbonate, polyethylene terephthalate, cellulose nitrate,
Porous membranes such as cellulose acetate are known, but none of them have sufficient corrosion resistance or membrane resistance. In addition, porous fluororesin membranes have excellent corrosion resistance and weather resistance, but they are made by agglomeration of fluororesin particles or entanglement of fluororesin structures, and the pores have a complicated shape and the pore diameter is not uniform. , and it is not easy to adjust the pore density and pore diameter. The object of the present invention is to provide a method for producing a porous polymer membrane having an arbitrarily selected number and diameter of pores and having excellent corrosion resistance and weather resistance without such drawbacks.

The object of the present invention is thus achieved by the method for producing a porous polymer membrane of the present invention, which comprises irradiating the polyvinylidene fluoride membrane with charged particles in an active gas atmosphere and then etching it with chemicals. Ru. The present invention involves irradiating polyvinylidene fluoride membranes with charged particles, e.g., fission fragments, in an atmosphere of a gas, e.g., oxygen, ozone, to create a linear path for the charged particles, which is then exposed to a chemical, e.g., an aqueous solution of sodium hydroxide. This method forms a through hole centered on the charged particle passage. Charged particles in the present invention have enough energy to penetrate the waist, including fission fragments obtained by fission of fissile materials, various high-energy particles obtained from accelerators,
Q particles obtained by decay of radioactive isotopes can be used.

The distance through which these charged particles penetrate through a material is determined by the type of the particle, its energy, and the target material to be irradiated. Therefore, it is necessary to make the charged particles penetrate the membrane by adjusting the thickness of the membrane, the pressure of the active gas, etc., depending on the charged particles. The number of pores in the resulting porous membrane is equal to the number of irradiated charged particles and can be arbitrarily selected depending on the irradiation conditions. Further, the pore diameter can be arbitrarily adjusted by adjusting etching conditions. The irradiation with charged particles is performed in an active gas atmosphere, and an oxidizing gas such as oxygen, ozone, or nitrogen oxide is used as the active gas. The active gas reacts with the chemical species generated by the interaction between the charged particles and the polymeric material and quickly converts them into compounds that can be etched. Polyvinylidene fluoride has high corrosion resistance against chemicals, but by irradiating it with charged particles in an active gas atmosphere, rapid etching around the charged particle passages becomes possible. As the etching agent, an alkaline solution such as sodium hydroxide, an oxidizing solution such as a sulfuric solution of potassium dichromate, or a mixture thereof with an alcohol or a surfactant can be used.

Next, the present invention will be explained with reference to examples. Example 1 As shown in the drawing, a polyvinylidene fluoride film 3 with a thickness of 9.4 mm and an aluminum foil 1 coated with natural uranium 4 with a thickness of 1000 A were placed facing each other with a collimator 2 in between and exposed to 125 tons of oxygen. was placed in a quartz tube filled with 300 ml of silica, and irradiated with the JRR-4 nuclear reactor at the Japan Atomic Energy Research Institute.

U-2 contained in natural uranium by thermal neutrons in a nuclear reactor
35 atoms undergo nuclear fission, and the fission fragments pass through the collimator in the direction of the arrow and enter the membrane.

Because the collimator is provided, the fission fragments are incident on the membrane surface at an angle close to perpendicular. The above-mentioned membrane thickness, uranium thickness, and oxygen pressure are values such that all fission fragments incident on the membrane penetrate the membrane. After irradiation in a nuclear reactor, the film was immersed in a sodium hydroxide solution at 65° C. and etched while it was exposed.

When the nuclear power output is 1000 KW and the irradiation time is 10 minutes, the pore density calculated from the irradiation conditions is 2 × 1 pike/me, and when the etching time is 6 etching hours, the pore diameter calculated from the gas permeability coefficient of the sample film is 300 A. However, the results of measuring the pore density and pore diameter by electron microscopy were also found to be equal to these, and the pore diameters were found to be uniform. When the obtained porous polyvinylidene fluoride membrane was immersed in 70 qo concentrated nitric acid for 7 days, the weight change was the same as that of the original polyvinylidene fluoride membrane, confirming that it maintained excellent corrosion resistance. .

It was also confirmed that polyvinylidene fluoride's characteristic of low liquid/solid interfacial tension did not change due to nuclear irradiation and butting treatment. Porous polyvinylidene fluoride membranes with excellent corrosion resistance and weather resistance are expected to have wide applications in fields such as industry, medicine, and biochemistry.

The pores are linear in shape, the pore diameter is highly uniform, and the pore density and pore diameter can be easily adjusted depending on the purpose, making it suitable for advanced applications that cannot be achieved with existing porous fluororesin membranes. Conceivable.

[Brief explanation of the drawing]

The figure is an explanatory diagram of irradiation with fission fragments of a polyvinylidene fluoride film.

Claims (1)

[Claims] 1. A method for producing a porous polyvinylidene fluoride film, which comprises irradiating the polyvinylidene fluoride film with charged particles in an active gas atmosphere and then chemically etching it.