JPH02277530A - Production of porous polyester separating membrane - Google Patents

Abstract

PURPOSE:To improve the heat and weather resistances of a porous polyester separating membrane by forming an irradiation-damaged region in a polymer membrane by irradiation with high energy ions and by chemically etching the damaged region to form the separating membrane. CONSTITUTION:A polymer membrane is formed with arom. polyester synthesized from dihydric phenol and arom. dicarboxylic acid or a deriv. thereof. An irradiation-damaged region is formed in the polymer membrane by irradiating the membrane with high energy ions and a porous polyester separating membrane having straight pores is produced by chemically etching the damaged region. The arom. polyester is preferably synthesized from bisphenol A and phthalic acid or a deriv. thereof. The produced separating membrane is uniform in pore diameter and enables separation with higher efficiency as compared with the conventional three-dimensional network separating membrane.

Description

[Detailed Description of the Invention] [Industrial Field of Application] [Prior Art and Problems] Conventionally, porous separation membranes have been mechanically separated into polymer membranes (films).
Or technology to (incompletely) stretch a fibrous material, technology to chemically utilize the solubility difference of polymers, technology to elute after mixing solvent-soluble solid particles, technology to form a porous membrane by sintering, It is manufactured by conventionally known porous means such as the technique of crushing a cellular polymer sheet.

These separation membranes have a three-dimensional network structure,
The apparent pore size is also non-uniform, which limits the separation efficiency for purification or removal of target separation products.

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

In addition, chemically treated membranes include cellulose ester, polyamide, polysulfone, etc. These resins are dissolved in a good solvent and then brought into contact with a poor solvent to obtain a porous membrane by utilizing the difference in solubility. . The pore size control of this membrane is
This is done by controlling the type, concentration, temperature, etc. of the solvent, and the apparent pore size is non-uniform, which limits the separation efficiency.

In recent years, it has become clear that a porous film can be obtained by irradiating a polymer film with ions and then chemically etching the damaged areas. As such examples, techniques described in Japanese Patent Publication No. 52-3987, Japanese Patent Application Laid-Open No. 59-117546, etc. are known.

The membranes used in these are porous membranes obtained by irradiating a dense polymer film with ions and then etching it. The separation membrane thus obtained has a uniform pore size and has good separation efficiency.

However, although polycarbonate and the like are commercially available as such films, they have poor heat resistance, have low surface hardness and are easily damaged, and are also susceptible to deterioration by radiation such as electron beams and T-rays.

Furthermore, polyethylene terephthalate has a glass transition temperature lower than that of polycarbonate, making it unsuitable for use at high temperatures.

[Means to solve the problem]

The present inventors targeted an aromatic polyester (hereinafter referred to as polyarylate) obtained from a dihydric phenol and an aromatic dicarboxylic acid or a derivative thereof, formed a damaged area by ion irradiation, and then chemically removed the damaged area. By etching the film, it is extremely easy to obtain straight holes, and it also has better heat resistance, radiation resistance, high hardness, and weather resistance compared to conventional porous films of this type made of polycarbonate. It was discovered that an excellent porous polymer film could be obtained, and the present invention was completed.

That is, the present invention includes; a polymer membrane made of an aromatic polyester obtained from a dihydric phenol and an aromatic dicarboxylic acid or a derivative thereof;
Production of a porous polyester separation membrane having straight pores, which comprises irradiating high-energy ions to form an irradiation-damaged region on the polymer membrane, and then chemically etching the damaged region. It's a method.

The present invention will be explained in detail below.

The aromatic polyester used in the method of the present invention can be easily produced from a dihydric phenol compound and an aromatic dicarboxylic acid or a derivative thereof by a method such as an interfacial polycondensation method, a solution polymerization method, or a melt polymerization method.

The dihydric phenol compound, which is one of the raw materials for producing the aromatic polyester, specifically includes bisphenol A, 2.2-bis-(4-hydroxy-35-dibromophenyl)-propane, and 2.2- Bis-(4-hydroxy-3,5-dimethylphenyl)-propane, bis=(
4-Hydroquinphenyl)-methane, bis-(4-hydroxyphenyl)-sulfide, hydroquinone, pp
Examples include o-diphenyl.

Further, specific examples of aromatic dicarboxylic acids or derivatives thereof include phthalic acid, terephthalic acid, isophthalic acid, and dichlorides and esters of these dicarboxylic acids.

The polymer membrane used in the method of the present invention may be made of the above-mentioned aromatic polyester alone, or may be blended or copolymerized with other polyester materials such as polyethylene terephthalate and polycarbonate within the range that meets the purpose of the present invention. It's okay to do that.

Furthermore, the polymer membrane used in the method of the present invention may contain known additives such as stabilizers, fillers, nucleating agents, and the like.

The high-energy ions (particles) used in the method of the present invention refer to various known charged and uncharged particles that can penetrate a polymer membrane (film) and form desired irradiation damage.
Specifically, examples include fission fragments obtained by fission of fissile materials, alpha particles obtained by decay of radioactive isotopes, and accelerated ions obtained by accelerators, but from an industrial perspective it is best to use accelerated ions produced by accelerators. It is a flight. The energy range is l? IeV or higher is appropriate.

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

Chemical etching agents used include alkaline solutions such as sodium hydroxide and potassium hydroxide, mixed solutions of the alkali and alcohol, chromium mixed acid, potassium permanganate, sodium hypochlorite, and sodium perchlorate. Oxidizing agent solutions and acidic solutions such as nitric acid, sulfuric acid, and hydrofluoric acid are used.

The porous separation membrane produced by the method of the present invention has heat resistance,
Since it has radiation resistance and high hardness, the pore density is equal to the ion irradiation density and can be easily controlled.

The pore density is determined by considering membrane strength, pore overlap, etc.
lXl010 holes/cd or less is preferred.

Further, the pore diameter can be easily controlled by etching conditions, ie, etching agent, concentration, carbon mixture, time, etc., and any pore diameter of several tens of micrometers or less, preferably 20 micrometers or less, can be uniformly obtained.

Further, when the etching conditions are the same, the pore size obtained varies depending on the ion species used for irradiation, and the larger the mass of ions, the larger the pore diameter obtained, and it is also possible to control the pore diameter depending on the ion species.

The porous polycarbonate separation membrane obtained by the method of the present invention is a straight-pore type porous membrane with uniform pore diameter, so it has high separation efficiency and is inferior to the currently commercially available porous polycarbonate separation membranes. Because it is a polymer with
It has excellent heat resistance and minimal deformation during separation at high temperatures, making it useful as separation membranes such as molecular sieves and precision filtration membranes and ultrafiltration membranes for water purification.

[Effect]

The porous polyalate separation membrane produced by the method of the present invention has uniform pore diameters, and compared to three-dimensional mesh separation membranes produced by conventional methods, it is capable of highly efficient separation based on pore diameter, allowing removal of all but the target material. It becomes possible.

In addition, compared to currently commercially available porous polycarbonate separation membranes with perforations that utilize fission fragments, because they are made of an amorphous polymer, they have superior heat resistance, less deformation during separation at high temperatures, and weather resistance. It has excellent properties and can be separated in an atmosphere exposed to ultraviolet light, etc.

Furthermore, since it is a wholly aromatic polyester, it has excellent radiation resistance and can be used on electron beams and T-rays.

The invention is illustrated by the following examples, which are not intended to limit the scope of the invention.

A 3.5 μm thick film of polyarylate (trade name: Espenok R1 manufactured by Sumitomo Chemical) was prepared and irradiated with N° ions using an ion accelerator. The irradiation conditions were acceleration voltage 3. O
MV, irradiation dose lXl0'' ions/cid.

The film thus produced was etched with a 6N NaOH aqueous solution at room temperature for 5 hours, washed with water for 1 hour, and thoroughly dried.

When the pore diameter of the porous membrane thus prepared was measured using a scanning electron microscope, it was confirmed that the porous membrane had a uniform pore diameter of 0.1 μm.

Mimifl Bolyarylate (Product name: U Polymer U-2030,
A film with a thickness of 4 μm (manufactured by Unitika ■) was prepared and irradiated with N ions using an ion accelerator.

The irradiation conditions were acceleration voltage 3. OMV, irradiation 11×10a ions/C+a.

The film thus produced was etched with a 6N NaOH aqueous solution at room temperature for 5 hours, washed with water for 1 hour, and thoroughly dried.

When the pore diameter of the porous membrane thus prepared was measured using a scanning electron microscope, it was confirmed that the porous membrane had a uniform pore diameter of 0.1 Nm.

Commercially available polycarbonate (product name: Macrohole KG,
A porous film having a pore diameter of 0.1 μm was obtained by irradiating and etching a 3.5 μm thick film (manufactured by Bayer AG) under the same conditions as in Example 1.

Comparison ±1 A 4 μm thick film of polyethylene terephthalate (trade name: Nilmirror, manufactured by Toshi ■) was irradiated with N ions using an ion accelerator. The irradiation conditions were acceleration voltage 3. OMV, irradiation dose 1×10@ions/c++l.

The membrane thus produced was etched with a 6N NaOH aqueous solution at room temperature for 10 hours, washed with water for 1 hour, and thoroughly dried.

When the pore diameter of the porous membrane thus prepared was measured using a scanning electron microscope, it was confirmed that the porous membrane had a uniform pore diameter of 0.1 μm.

Electron beams were applied to the two types of porous membranes prepared as described above at 80%
It was found that when irradiated with M r a d, polyarylate hardly changes, but polycarbonate becomes brittle and deterioration progresses, and only polyarylate has excellent radiation resistance.

Further, as for the weather resistance test, an accelerated deterioration test for 2,000 hours was conducted using a carbon arc 2 sunshine weather meter. As a result, the polycarbonate became brittle, but the polyarylate remained largely unchanged and hardened in terms of weather resistance.

In the heat resistance test, the phase transition temperature was measured by DSC.

Polyarylate has a heat resistance of about 190°C, and compared to polycarbonate's 150°C and polyethylene terephthalate's 70°C, polyarylate has excellent heat resistance, and it can be easily expected that the change in pore size during high-temperature use will be small.

(Effects of the Invention) The porous polyester separation membrane produced by the method of the present invention has uniform pore diameters and can perform separation with higher efficiency than the three-dimensional mesh separation membrane produced by the conventional method.
It can be used in fields that require highly accurate separation, such as the separation of bacteria and viruses.

In addition, compared to currently commercially available porous polycarbonate separation membranes with perforations that utilize fission fragments, they have superior heat resistance, less deformation during separation at high temperatures, and can be used in high-temperature processes without deterioration. It is possible.

Furthermore, it has excellent weather resistance and can be separated in an atmosphere exposed to ultraviolet rays or the like.

Furthermore, it has excellent radiation resistance and is thought to be usable on electron beams and T-rays.

Claims (2)

[Claims] (1) After irradiating a polymer film made of an aromatic polyester obtained from a dihydric phenol and an aromatic dicarboxylic acid or a derivative thereof with high-energy ions to form an irradiation-damaged area on the polymer film, A method for producing a porous polyester separation membrane having straight pores, the method comprising chemically etching damaged areas. (2) The aromatic polyester constituting the polymer membrane is
A method for producing a porous polyester separation membrane having straight pores, characterized in that the membrane is an aromatic polyester obtained from bisphenol A and phthalic acid or a derivative thereof.