JPH0822374B2 - Method for producing graft membrane - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention produces a novel composite graft membrane excellent in over-performance in a selective permeation membrane for simultaneously removing fine particles and, if necessary, ions from an aqueous mixture. Regarding the method.

More specifically, the present invention relates to a method for producing a composite membrane having extremely high capacity and low elution property in a membrane capable of simultaneously removing fine particles in water for general industrial use and ions if necessary.

[Conventional technology]

A highly efficient functional film capable of simultaneously removing fine particles and, if necessary, ions from an aqueous mixture is disclosed in, for example, JP-A-61-220705.
And the method described in JP-A-62-179540.

These novel multi-functional membranes have an excellent function in their over-characteristics, but on the other hand, when an anion group, a cation group or a neutral hydroxyl group is grafted, they have a higher ability (flux) than the substrate membrane. Tended to decrease.

For this reason, the selection of the base material film is important, but the excess capacity of the graft film obtained after designing the base material film is often
It may not be what you expect.

[Means for solving problems]

As a result of earnest research on means for solving the above problems, the present inventor has found that the means can be achieved by the following means.

That is, the present invention is a polyolefin, an olefin and a halogenated olefin copolymer, a porous substrate film made of polyvinylidene fluoride or polysulfone, an anion group, containing a cationic group or a neutral hydroxyl group, or to a monomer that can be introduced, Copolymerizable with this monomer 2
An average pore diameter of 0, which is characterized in that a monomer having a co-reactive group is coexisted and grafted to finally obtain a porous membrane containing an anion group, a cation group or a neutral hydroxyl group.
A method for producing a microporous graft membrane having a porosity of 20% to 80% and a porosity of 001 μm to 5 μm.

 The present invention will be described in more detail below.

The base film used in the present invention is required to be a hydrophobic porous film such as polyolefin, olefin and halogenated olefin copolymer, polyvinylidene fluoride, polysulfone, etc. Useful for maintaining properties.

Specific examples of polyolefins, olefins and halogenated olefin copolymers include polyolefin resins such as polyethylene, polypropylene, polybutylene or mixtures of two or more of the foregoing or ethylene, propylene, butene, hexene, tetrafluoroethylene, chlorotrifluoroethylene. And a copolymer composed of a mixture of two or more of the above.

Next, as an example of an anion group to be grafted to the base material film, a sulfonic acid group and a carboxyl group are preferable, and styrenesulfonic acid, vinylsulfonic acid, acrylic acid, and methacrylic acid are used as monomers containing these.

Preferred examples of the cation group to be grafted on the base material film are quaternary amine, tertiary amine, pyridine group and the like,
Examples of monomers containing them include vinyl pyridine.

An example of the monomer having a neutral hydroxyl group that is grafted to the base material film is allyl alcohol. Further, for example, the present invention can also be applied to a method for producing a graft film in which a vinyl acetate monomer is grafted and then saponified to obtain a neutral hydroxyl group.

Further, as a method for finally obtaining a graft film having a sulfo group, a method in which styrene is first grafted to a base material film and then chemically sulfonated with fuming sulfuric acid or the like is also adopted.

Examples of the monomer having two or more reactivities capable of copolymerizing with the above-mentioned monomer containing an anion group, a cation group or a neutral hydroxyl group include polyalkylene oxides such as divinylbenzene and ethylene glycol dimethacrylate, and dimethacryl. Acid esters, N, N'-methylenebisacrylamide, etc. are used depending on the final application and the kind of the functional monomer.

The addition amount of these two or more reactive monomers is preferably in the range of 0.01 to 20% by weight with respect to the total amount of the monomers, but it is not limited to this, and 90% in special cases. % To add and crosslink.

The graft film can be appropriately produced according to the base film, but specifically, the base film is irradiated with various kinds of radiation (cobalt gamma ray, electron beam) or the like, and the monomer is allowed to exist at the same time as the irradiation. It can be soaked in a monomer and grafted later.

After the grafting, the unreacted monomer is washed off.

Further, additional irradiation of radiation may be performed to modify the graft membrane after or without removing the unreacted monomer by washing.

The porous membrane of the present invention preferably has an average pore size of 0.001 μm to 5 μm, preferably 0.01 μm to 1 μm. Here, the average pore diameter refers to a value obtained by the method described in ASTM F316-70 when the average pore diameter is 0.01 μm or more, and is usually called an air flow method, which is a dry film or a wet film by changing the air pressure. The air permeation flux is measured and the ratio is determined. The size of 0.01 μm or less is determined by an electron microscope method, a molecular weight cut-off method or the like.

The range of the average pore diameter in the present invention is set from the viewpoint of practical performance, and in the range other than this range, it is unsuitable in terms of the transmission rate or the effect of removing fine particles.

Next, the porosity of the porous film obtained according to the present invention is preferably in the range of 20 to 80%. Here, the porosity is measured by previously immersing the membrane in a liquid such as water, drying the membrane, and measuring the weight change before and after the drying.

When the porosity is outside the range of the present invention, it is not preferable in terms of permeation rate, mechanical properties and the like.

The pore structure of the base film, which is the base of the porous film obtained in the present invention, can be obtained by various molding processes.

Specifically, a so-called stretching method or an etching method made by chemical treatment after electron beam irradiation can be applied, but as a pore structure, a straight-hole through-type void obtained by a stretching method or an etching method is used. Rather than the pore structure, for example, a three-dimensional network structure formed by the micro phase separation method or the mixed extraction method disclosed in Japanese Patent Publication No. 59-37292, Japanese Patent Publication No. 40-957 and Japanese Patent Publication No. 47-17460. Those having are preferred. In particular,
With the establishment of the manufacturing technology for the structure shown in Japanese Patent Laid-Open No. 55-131028, the significance of the present invention has been clarified, and a method for manufacturing a material having excellent performance that cannot be obtained by the conventional technology has been developed. I was able to achieve it.

The shape of the porous membrane may be any of a flat membrane shape, a tube shape, and a hollow fiber membrane shape, but for the purpose of the present invention, an inner diameter of 0.
A hollow fiber type having a shape of 1 to 10 mm and a thickness of 0.05 to 5 mm is preferable.

Next, the effects of the present invention will be specifically shown by examples, but the examples of the present invention do not limit the invention.

Example 1 and Comparative Example 1 22.1 parts by weight of fine silicate (Nipsyl VN3LP), 55.0 parts by weight of dioctyl phthalate (DOP), 23.0 parts by weight of polyethylene resin powder [Asahi Kasei S-360 grade] were premixed, and then 30 Millimeter twin-screw extruder, inner diameter 0.7mm, thickness 0.25mm
After being extruded into a hollow fiber, the product was immersed in 1,1,1-trichloroethane [chlorocene VG (trade name)] for 60 minutes to extract DOP. In addition, about 40% caustic soda solution at a temperature of 60 ℃
After immersing for 20 minutes to extract fine powder of silicic acid, it was washed with water and dried.

The obtained porous membrane was irradiated with an electron beam at 100KGy in a nitrogen atmosphere using an electron accelerator (pressurization voltage: 1.5MeV, electron beam current: 1mA), and then immersed in styrene with dissolved oxygen of 0.1ppm or less in advance and grafted. After washing, drying and sulfonation using fuming sulfuric acid, average pore diameter 0.15μm, porosity 62
%, Sulfonic acid group 1.5 meq / g film (comparative example film (A)) was obtained.

On the other hand, grafting was performed using a mixed monomer of styrene and divinylbenzene (weight ratio 95: 5) instead of the above styrene, and then sulfonation was performed under almost the same conditions to obtain an average pore size of 0.16μ, a porosity of 63%, and a sulfonation. Acid group 1.5 meq / 1
A gram membrane example membrane (A) was obtained.

 Here, the quantification of the sulfone group of the example membrane was as follows.

[Quantification of sulfone group]

The sulfonated porous membrane was dipped in 1N HClag. To form H type, washed with water, and then dipped in 1N CaCl ₂ ag.
Using 0.1N NaOH, titration was performed with phenolphthalein as an indicator.

Next, when an overtest was actually carried out using the water quality liquid shown below, the results shown in Table 1 were obtained.

[Natural liquid properties]

Concentration of fine particles in stock solution ¹⁾ 3 × 10 ⁴ cells / cc Bacterial concentration ²⁾ 10 ³ cells / cc Iron ^{+ 3} ion concentration 0.15 mmol / l Sodium ion concentration 0.50 mmol / l 1) 0.2 μm Directly on a polycarbonate flat membrane Measured value under microscope 2) Value measured directly by microscope after staining with Broca staining method 3) Measured value by atomic absorption method As is apparent from the above table, the inventive example membrane (A) is
The result shows that the initial permeation rate is superior to that of the comparative example membrane (A), and the ion removability is also good.

Example 2 and Comparative Example 2 25.0 parts by weight of ethylene-tetrafluoroethylene copolymer (trade name Aflon COP), 53.6 parts by weight of chlorotrifluoroethylene oligomer (trade name Daifloyl # 20),
Silicone oil) Product name: KF-96) 6.2 parts by weight, 15.1 parts by weight of finely divided silica are premixed, and the inner diameter is 0.7 m with a 30 mm twin screw extruder.
m, extruded into a hollow fiber with a thickness of 0.25 mm, immersed in 1,1,1-trichloroethane [Fluorocene VG (trade name)] for 60 minutes to extrude the moldable agent, and then caustic soda 40 at a temperature of 60 ° C %
After immersing in an aqueous solution for about 20 minutes to extract finely divided silicate, it was washed with water and dried.

An electron accelerator (pressurizing voltage 1.
After irradiation with 100KGY in a nitrogen atmosphere using 5MeV, electron beam current 1mA), it was exposed to allyl alcohol in which dissolved oxygen was adjusted to 0.1ppm or less in advance and grafted, and 2.5 meq / 1
Gram Membrane Comparative Example Membrane (B) (Average Pore Diameter 0.16 μm, Porosity
60%).

Further, instead of the allyl alcohol in the comparative example film (B), a mixed monomer of allyl alcohol and polypropylene dimethacrylate (95: 5) was used, and grafting was carried out under almost the same conditions, and the example film (B) ( Average pore size
0.17 μm, porosity 62%) was obtained.

In addition, here, the quantification of the hydroxyl groups in the example film and the comparative example film was as follows.

[Quantification of hydroxyl group]

The membrane after alkali treatment is thoroughly washed with water and dried, then an appropriate amount of acetic anhydride-pyridine mixed solution (1: 3 volume ratio) is added, and the mixture is heated in a sealed container at 60 ° C for 2.5 hours. After cooling, water was added to change excess acetic anhydride to acetic acid, a mixed indicator of cresol red and thymol blue was added, and titration was performed using standard alkali hydroxide.

 The overperformance of the two membranes is shown in Table 2.

In addition, 1% is added to the above-mentioned Example film (B) and Comparative Example film (B).
Roh γ- aminobutyric acid model solution through overspeed, where the retention was measured after spent 6m ³ / m ^2, 70% respectively, the retention, Atsuta 65%. Then, after washing this with an aqueous solution of caustic soda and steam sterilization and measuring the overspeed, it was recovered to 100% and 95%, respectively.

[Effects of the Invention] According to the present invention, a highly efficient membrane that can be widely used in the semiconductor industry, general industry, nuclear wastewater treatment, pharmaceutical industry, etc.
It is possible to manufacture without deteriorating its performance.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location B01D 71/82 500 9538-4D

Claims (1)

[Claims] 1. A monomer containing an anion group, a cation group or a neutral hydroxyl group or capable of being introduced into a porous base material film comprising polyolefin, olefin and halogenated olefin copolymer, polyvinylidene fluoride or polysulfone, An average pore diameter of 0.001 characterized in that a monomer having two or more reactive groups copolymerizable with this monomer is coexisted and grafted to finally obtain a porous membrane containing an anion group, a cation group or a neutral hydroxyl group. A method for producing a microporous graft membrane having a micrometer to 5 micrometers and a porosity of 20% to 80%.