JPH03217219A - Method for manufacturing porous polymer membrane - Google Patents

Abstract

PURPOSE:To obtain a porous polymer film having large separation efficiency by irradiating both sides of the polymer film with ions so that the porous layer side having fine holes has larger irradiation damages than the other side having cylindrical holes to chemically etch the film. CONSTITUTION:The one side of a polymer film (polycarbonate, etc.) is subjected to ion irradiation (accelerated ions such as argon ions, etc., are convenient for use) which is necessary to form a porous layer (B) having cylindrical holes. Then the other side of the film is irradiated with ion kind and irradiation quantity which satisfy the requirement to form a fine-porous supporting body layer (A), and preferably, this layer is formed in such a manner that the holes penetrate into the layer (A). Thereby, irradiation quantity in the porous layer (A) is larger than that for formation of the porous layer (B). Moreover, it is preferable that the porous layer (A) is easily etched than the porous layer (B). By irradiating both sides of the polymer film to give irradiation damage and to chemically etch the film as above described, the porous film having large separation efficiency and excellent strength is obtained.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to improvements in methods for producing porous polymer membranes.

Furthermore, the present invention relates to an improvement in a method for producing a porous polymer membrane suitable for a separation membrane that can be used as a microfiltration membrane, an ultrafiltration membrane, or the like.

(Conventional techniques and issues) Conventionally, microporous membranes used for separation membranes, etc. have been produced by mechanically stretching a polymer membrane (film) or fibrous material (incompletely), or by chemically Conventionally known porous means include techniques that utilize the solubility difference between the two, techniques that involve mixing and eluting solvent-soluble solid particles, techniques that create a porous membrane by sintering, and techniques that involve pressing a bubble-filled polymer sheet. Manufactured by.

The pore forms vary widely, including those with irregular pores such as three-dimensional network, closed cell type, and open-cell type, as well as those with continuously changing pore diameters.

Moreover, the apparent pore diameter in the porous membrane is also non-uniform, and there is a limit to the separation efficiency for purifying or removing the object to be separated.

Tetrafluoroethylene resin is known as a mechanically (incompletely) stretched film, but this membrane has a limit in separation efficiency because the apparent pore diameter is controlled by stretching.

In addition, chemically treated membranes include cellulose ester, polyamide, polysulfone, etc., and these resins are dissolved in a good solvent and then brought into contact with a poor solvent to obtain a porous membrane using the difference in solubility. be. This structure has a dense layer or a porous skin layer on top of the porous layer. The pore size of this membrane is controlled by controlling the type, concentration, temperature, etc. of the solvent, and the apparent pore size is nonuniform, which limits the separation efficiency.

In recent years, it has become clear that a porous film can be obtained by irradiating a dense polymer film with ions and then chemically etching the damaged areas.
Japanese Patent Publication No. 52-3987, Japanese Patent Publication No. 54-11971
The techniques described in Japanese Patent Application Laid-open No. 59117546 and the like are known. The separation membrane obtained in this way has a uniform pore size and has good separation efficiency.

However, such a membrane requires a film thickness for ions to penetrate, and when using a commercially available ion accelerator for industrial use, the ion energy is at most 10 MeV or less, and the membrane cannot be penetrated. There is a limit to the thickness.

In addition, when used as a separation membrane, in order to maintain membrane strength, the minimum thickness is preferably 10 lIm or more; in the case of such a film, ions either do not penetrate, or even if they do, the perforations are uniform in the direction of the film. In addition, because the length of the hole is long, the resistance during separation becomes large and the time required for separation becomes long. (Means for Solving the Problems) The present inventors have focused on combining a microporous membrane (A) and a porous membrane having cylindrical perforations (B), and have also focused on the method of ion irradiation treatment. It was discovered that by devising techniques, it was possible to produce a porous polymer membrane that had both a microporous membrane (A) and a porous membrane with cylindrical perforations (B) on the front and back surfaces, respectively, and solved the problems of the conventional method. This problem was solved and the present invention was completed.

That is, the present invention provides: A method for producing a porous polymer membrane comprising a microporous layer (A) and a layer (B) having cylindrical perforations,
It is characterized by ion irradiation from both sides of the polymer membrane so that the microporous layer (A) side suffers more irradiation damage than the layer with cylindrical perforations (B), and then chemically etched. This is a method for producing a porous polymer membrane.

Furthermore, the present invention will be specifically explained.

Examples of the polymer film used in the method of the present invention include various polymer films to which irradiation damage and chemical etching treatments can be applied, including polycarbonate, polyarylate, polyphenylene ether, polyester, and nitric acid. Examples include polymer films such as cellulose, cellulose acetate, polyvinylidene fluoride, polytetrafluoroethylene, and polyacrylonitrile.

The high-energy ions (particles) used in the present invention refer to various known charged and uncharged particles that can penetrate a polymer membrane (film) and form desired irradiation damage, and specifically, Fission fragments obtained by fission of fissile material, radioactive isotopes;
Examples include accelerated ions obtained by 2-chapter 1 uyf + m binary 5 box I▼, but it is industrially convenient to use accelerated ions produced by this accelerator. The appropriate energy range is I M e V or higher.

In particular, examples of accelerated ions include argon ions, oxygen ions, nitrogen ions, and nickel ions.

Further, the atmosphere for ion irradiation is not particularly limited, but may be performed in air, under vacuum, or under an active gas such as ozone or oxygen.

Generally, so-called wet etching treatment, which is performed by immersing a polymer membrane (film) in a chemical etching agent for a predetermined period of time, can be suitably applied to the chemical etching treatment used in the present invention.

Chemical etching agents used include alkaline solutions such as sodium hydroxide and potassium hydroxide, oxidizing agents such as potassium permanganate and sodium hypochlorite, hydrochloric acid, sulfuric acid,
Examples include acidic solutions such as hydrofluoric acid. Furthermore, a substance having an effect as a surfactant may be added.

In the present invention, first, ion irradiation necessary to form a porous layer (B) having cylindrical perforations is performed from one side of a polymer membrane (film).

At this time, it is preferable that the amount of ions to be irradiated is 109 ions/c+I1 or less, taking into consideration the overlap of the perforations.

Next, from the other side, ion species and irradiation amount sufficient to obtain a microporous porous support layer (A) are irradiated, and it is confirmed that the perforations penetrate into the porous layer (^). preferable.

Therefore, in this case, it is necessary that the irradiation amount on the microporous porous layer (A) side is larger than the irradiation amount required to form the porous layer (B) having cylindrical perforations.

Furthermore, the microporous porous layer (A) is preferably etched more easily than the porous layer (B) having cylindrical perforations, and for this reason, the irradiated ions on the side of the microporous porous layer (A) is preferably an ion with a large mass.

By chemically etching the polymer membrane (film) which has been damaged by irradiation by irradiating both sides of the polymer membrane (film) in this way, a microporous porous layer (A) is formed on each side of the polymer membrane (film). Porous layer with cylindrical perforations (B
) can be obtained.

In this case, the chemical etching process may be performed simultaneously with the ion irradiation process.

This porous polymer membrane can be thicker than a perforated membrane obtained by irradiation with the same ion species and energy; Support layer (A) and porous layer with cylindrical perforations (B)
It has stronger mechanical strength than a membrane with a perforated layer alone.

(Function) The porous polymer membrane obtained by the method of the present invention has a microporous support layer (A) and a porous layer (B) having cylindrical perforations in one polymer membrane. (film) and does not have an interface, so problems such as interfacial peeling do not occur.

Furthermore, the porous polymer membrane obtained by the method of the present invention is
The film thickness is 10 μm compared to the porous film made by general ion irradiation.
The separation and removal process speed is faster.

Furthermore, the porous polymer membrane obtained by the method of the present invention is
Since it has a microporous support layer (A) and a porous layer (B) having cylindrical holes, it exhibits excellent separation ability.

(Examples) The present invention will be illustrated by the following examples, which are not intended to limit the scope of the invention.

Example 1 From one side of a 10 μm thick polycarbonate film,
After irradiating IXIO'/c+fi helium ions, argon ions were irradiated from the back side of the film.
10 pieces/Clll were irradiated. This film was washed with 6N Na
By enoching in an OH aqueous solution at 50° C. for 10 hours, a perforated layer with a pore diameter of 0.01 μm was obtained, and a porous support layer with an uneven surface was also formed.

Example 2 As in Example 1, oxygen ions were extracted from one side of a polyarylate film with a thickness of 12 μm at I
After irradiation, argon ions were applied 1x from the back side of the film.
1011 pieces/d were irradiated. This film was coated with 6N NaO
By etching in an H aqueous solution at 50° C. for 6 hours, a perforated layer with a pore size of 0.1 μm was obtained, and a porous support layer was also formed.

Example 3 As in Example 1, one side of a 10 μm thick poly p-phenylene ether film was irradiated with 1×10 s/d of M elementary ions, and then nickel ions were irradiated with IXIO”/ci from the back side of the film. .3(l) of this film
Enotation was carried out in 5N NaOH + 20d ethanol solution at 45°C for 6 hours. As a result, a perforated layer having a pore diameter of 0.1 μm was obtained, and a porous support layer having an uneven surface was also formed.

Comparative Example 1 From one side of a 10 μm thick polycarbonate film,
After irradiating with nitrogen ions at 1×10'1/d, the film was irradiated with 1×108 argon ions/d from the back side of the film. This film was soaked in a 6N NaOH aqueous solution at 50°C for 4 hours.
By etching for a long time, the nitrogen ion irradiation side becomes 0.
．． A porous layer with a pore diameter of 1 μm and a porous layer with a pore diameter of 0.2 μm on the argon ion irradiation side were obtained.

The probability that nitrogen ion perforations penetrate the porous layer of argon ion perforations is very small, so it cannot be used as a separation membrane.

Comparative Example 2 From one side of a polycarbonate film with a thickness of 10 μm,
After irradiating with IXIO' nitrogen ions/d, the film was irradiated with 1×101 helium ions/d from the back side of the film.

By etching this film in a 6N NaOH aqueous solution at 50°C for 3 hours, the nitrogen ion irradiation side became 0.
The perforated layer having a pore diameter of 1 μm and the helium irradiation side having a small mass have little irradiation damage, the degree of surface irregularity is slight, and no porous layer is formed.

(Effects of the Invention) The porous polymer membrane obtained by the production method of the present invention has a cylindrical perforation layer with a uniform pore diameter, so it has a high separation efficiency, and the microporous porous layer supports and supports the membrane. It serves as a reinforcing body and provides a porous membrane with excellent strength.

Furthermore, according to the manufacturing method of the present invention, the thickness of the perforated layer can be arbitrarily changed depending on the irradiation conditions (ion species, energy, etc.), and it is also possible to form a perforated layer as thin as 1 pm or less. Furthermore, according to the manufacturing method of the present invention, even with a commercially available accelerator,
Because the film is irradiated from both sides, it can be applied to films that are thicker than the ion range.

Claims (1)

[Claims] In a method for producing a porous polymer membrane comprising a microporous layer (A) and a layer having cylindrical perforations (B),
It is characterized by ion irradiation from both sides of the polymer membrane so that the microporous layer (A) side suffers more irradiation damage than the layer with cylindrical perforations (B), and then chemically etched. A method for producing a porous polymer membrane.