JPH02194039A - Selectively anion-adsorptive porous membrane and its production - Google Patents

Abstract

PURPOSE:To obtain a porous membrane desirable for the selective adsorption of an anionic component such as protein by grafting vinyl acetate onto a polyolefin film irradiated with an ionizing radiation, introducing an epoxide into the film after saponification and effecting the addition reaction of ammonia therewith. CONSTITUTION:A base membrane comprising a polyolefin or a copolymer of an olefin with a halogenated olefin is irradiated with an ionizing radiation, and vinyl acetate is grafted onto this membrane in a vapor phase. The grafted polyvinyl acetate is saponified into a polyvinyl alcohol, and an epoxide is introduced thereinto. By the addition reaction of the introduced epoxide with ammonia or an organic amine, the purpose selectively adsorptive porous membrane having neutral hydroxyl groups and anion exchange groups through an ether bond and a methylene chain is obtained. This porous membrane is one in which the neutral hydroxyl groups and the anion exchange groups are chemically bonded to the surfaces of both the base membrane and the pores.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is suitable for adsorption and purification of useful specific anion components (including organic components such as proteins and amino acids) in the pharmaceutical industry and general industry. The present invention relates to a selective adsorption hydrophilic membrane and a method for producing the same.

[Conventional technology]

Conventionally, ion exchange resins, ion chromatography, and the like have been used at the laboratory level to adsorb and purify and remove specific anions, proteins, and the like.

However, when actually used at the industrial standard level, the adsorption efficiency is low, a large amount of liquid is required for desorption purification and removal, the speed is slow, and it is extremely expensive, so it is currently not widely used. .

In order to solve this problem, it has been proposed to use a membrane that can adsorb and purify these specific anion components. Possible advantages of membrane properties include better adsorption efficiency, higher purification and removal, and shorter processing time.

On the other hand, these specific anion components are generally purified by adsorption.
To remove, R=NZ, REN, R=NH, RN)
Treatment with a porous membrane made of a polymer containing an anion exchange functional group such as an organic amine represented by T2 (where R is a hydrocarbon group, N is nitrogen, Z is a halogen, etc.) in the side chain. is known to be suitable. However, due to the non-specific adsorption properties of the membrane itself, in addition to the specific anion component to be purified, other components are also adsorbed.
Purification efficiency also deteriorates.

In particular, when used on an industrial scale, the skeleton of the porous membrane itself must be strong, and a hydrophobic one is necessarily preferred.

In order to improve these problems, it is preferable to make the hydrophobic membrane itself hydrophilic with a functional group having a neutral hydroxyl group.

Recently, a method has been discovered in which a hydrophobic membrane is coated on the one hand with a compound having a neutral hydroxyl group and partially a hydrophilic group, and then an anion exchange functional group is added. Due to physical addition, it does not have the minimum alkali resistance required for industrial use, and repeated use is almost impossible, and partial desorption of the physical adduct occurs, making large-scale or repeated use impossible.

[Problem to be solved by the invention]

An object of the present invention is to provide a novel selectively adsorbent porous membrane suitable for adsorption purification and removal of the specific anions and the like, and a method for producing the same.

[Means to solve the problem]

This invention provides the following features: 1. Neutral hydroxyl groups of 0.1 milliequivalent or more per 1 g of porous membrane, and ether on the membrane surface and pore surface of a base membrane made of polyolefin or a copolymer of olefin and halogenated olefin. An anion-selective adsorption porous membrane having an average pore diameter of 0.01 to 5 μ and a porosity of 20 to 90%, in which 0.1 milliequivalent or more of anion exchange groups per 1 g of pores are chemically bonded via bonds and methylene chains; and 2. A base film made of polyolefin or a copolymer of olefin and halogenated olefin is irradiated with ionizing radiation and then grafted with vinyl acetate in the gas phase, and the grafted polyvinyl acetate is saponified to form polyvinyl acetate. Anion selection having a neutral hydroxyl group and an anion exchange group via an ether bond and a methylene chain, characterized by denaturing to alcohol, then introducing an epoxide, and adding ammonia or an organic amine to the introduced epoxide. The present invention relates to a method for producing an adsorptive porous membrane.

The material of the porous base film used in the second invention is composed of polyolefin, a copolymer of olefin and halogenated olefin, polyvinylidene fluoride, etc., and must be hydrophobic. be. This is necessary to maintain the mechanical properties of the base film.

Specific examples of polyolefins and copolymers of olefins and halogenated olefins include homopolymers of olefins such as polyethylene, polypropylene, and polybutylene, or mixtures of two or more thereof; ethylene, propylene, butene, and pentene. , copolymers of two or more olefins such as hexene, and copolymers of one or more of the above olefins with halogenated olefins such as tetrafluoroethylene and chlorotrifluoroethylene.

The pores in the base membrane can be obtained by various shaping methods. For example, Japanese Patent Publication No. 40-957, Japanese Patent Publication No. 47-1982,
Pores having a three-dimensional network structure formed by the microphase separation method or mixed extraction method disclosed in Japanese Patent Publication No. 17460 and Japanese Patent Publication No. 59-37292 are preferred. In addition, the pore size and porosity of the base membrane are slightly larger than those of the target selectively adsorbent porous membrane.

The shape and size of the base membrane are appropriately selected from among flat membranes, tubes, and hollow fiber membranes, depending on the requirements of the desired selective adsorption porous membrane.

The selective adsorption porous membrane of the present invention has neutral hydroxyl groups and anion exchange groups chemically bonded to the surface of the base membrane and the surfaces of the pores. In the present invention, the porous membrane refers to this selective adsorption porous membrane.

Here, "the surface of the membrane and the surface of the pores" refers to the surface of the membrane,
Refers to the surface of the pores inside the membrane.

The neutral hydroxyl groups are bonded in an amount of 0.1 milliequivalent or more per gram of the porous membrane. Specifically, the neutral hydroxyl group refers to a hydroxyl group directly bonded to an aliphatic hydrocarbon or the like, excluding those directly bonded to a benzene nucleus. Neutral hydroxyl groups are necessary to prevent nonspecific adsorption of organic proteins to the porous membrane without denaturing the feed liquid, and the amount of binding to the base membrane is determined by its suppressive effect. Ru.

However, the neutral hydroxyl group is 0 per gram of porous membrane.
．． If less than 1 milliequivalent is bound, nonspecific adsorption of protein cannot be sufficiently prevented.

On the other hand, if there are too many neutral hydroxyl groups, the pores may be blocked, which is not preferable.

Preferably, the amount is selected from the range of 0.1 to 20 milliequivalents, more preferably 0.1 to 10 milliequivalents, per gram of porous membrane.

The anion exchange group is always chemically bonded to the polymer backbone of the base membrane via an ether bond and a methylene chain. Ether bonds and methylene chains are chemically stable and have better acid resistance, alkali resistance, etc. than ester bonds. The anion exchange group is 0.00% per gram of porous membrane.
If the amount is not 1 equivalent or more, the intended function will not be achieved sufficiently.

However, if the amount of anion exchange groups specified in this invention is too large, the pores may be blocked, which is not preferable. Preferably, the amount of anion exchange groups is 0.1 per gram of porous membrane.
-20 milliequivalents, more preferably from 0.1 to 10 milliequivalents.

The neutral hydroxyl group and the anion exchange group via an ether bond and a methylene chain may be contained in the same side chain and bonded to the base film, or may be bonded to the base film through separate side chains. You can leave it there.

Here, the bonding rate of each group is a value based on the fairly macroscopic weight of the membrane, for example, a value that targets only a part of the membrane surface or a part of the inside of the membrane. In order to maintain the excellent mechanical properties of the base membrane in a porous membrane, it is advantageous to react and attach (graft) the above-mentioned groups to the surface of the pores as preferentially as possible. Therefore, the meaning of the bonding rate of each group here is:
The value shown is an average value measured over the entire film, and does not mean the binding rate from a very microscopic viewpoint.

The anion selective adsorption porous membrane of the present invention has an average pore diameter of 0.
It is preferable that the particle diameter is in the range of 0.01 to 5.mu. from the viewpoint of anion adsorption rate and liquid permeation rate. More preferably 0.01
A range of ~1μ is preferable.

Here, the average pore diameter is defined as ASTM F 316-7.
0, which is usually called the air flow method, is a method in which the air permeation flux through a dry membrane and a wet membrane is measured by varying the air pressure, and is calculated from the ratio.

The porosity is preferably in the range of 20 to 90%, and 5
A range of 0 to 90% is more preferred. Here, the porosity is measured by immersing a porous membrane in a liquid such as water in advance, then drying it, and measuring the weight change before and after that.

If the porosity is outside the range of the present invention, it is not preferable in terms of permeation rate, mechanical properties, etc.

The shape of the porous membrane may be a flat membrane, a tube, or a hollow fiber membrane, but particularly for the purpose of the present invention, an inner diameter of 0.05
In terms of efficiency, it is preferable to use a hollow fiber having a shape of ~10 mm and a thickness of 0.05 to 5 tnrn.

The selective adsorption porous membrane of the present invention can be produced by various methods, but one method is advantageous in terms of reaction control and economical efficiency.
One method is to irradiate a base film made of a polyolefin or a copolymer of an olefin and a halogenated olefin with ionizing radiation, and then graft vinyl acetate in the gas phase.
This method is characterized in that the grafted side chains are then chemically modified by a saponification reaction, then an epoxide is introduced, and then ammonia or an organic amine is added to the introduced epoxide.

Irradiation of the base film with ionizing radiation is usually performed in vacuum or in an inert gas. As the ionizing radiation, electron beams or gamma rays are preferably used.

Next, vinyl acetate is grafted onto the base film in a gas phase to bond polyvinyl acetate to the surface of the base film and the surfaces of the pores.

The grafted polyvinyl acetate is saponified and modified into polyvinyl alcohol, and the saponification is carried out by a normal saponification reaction.

The amount of neutral hydroxyl groups bound to the base membrane by this method is determined by reacting the membrane with acetic anhydride in a lysine solvent and determining the amount of acetic anhydride consumed or the weight gain of the membrane.

Next, epoxide is introduced, but as epoxide,
Shrimp halohydrin, especially epichlorohydrin, is preferred.
In addition, as a difunctional epoxide, 1,4-bis-(2,
3-epoxypropoxy)-butane and the like can also be used.

Introducing the epoxide can also be carried out in an aprotic polar organic solvent such as dimethyl sulfoxide, if necessary.

In addition, the reaction progresses easily in the presence of an alkali, and an aqueous solution of sodium hydroxide or the like can be added as necessary.

As an example of a preferred reaction, the membrane is immersed in a mixed solution of dimethyl sulfoxide in an amount of 1 to 10 times the amount of the dry membrane and epichlorohydrin in an amount of 1 to 5 times the amount of the dry membrane, and then an alkali is added in an amount of 1 to 100% by weight of the epichlorohydrin.

The reaction temperature is O~100''C1 reaction time is several minutes~12 hours.

To measure the amount of bound epoxy groups, 1 g of the membrane is immersed in an aqueous sodium thiosulfate solution and heated, and the generated OH- ions are measured using phenolphthalein as an indicator.
0. Determined by titration with IN hydrochloric acid.

A membrane with fixed epoxy groups is immersed in an ammonia solution or an organic amine solution to open the epoxy ring and bond the amine.

The concentration of the ammonia solution is preferably about 3 to 40%.As the organic amine, aliphatic amines and aromatic amines such as monoamines such as methylamine, dimethylamine, and trimethylamine, and diamines such as ethylenediamine are also used.

In order to exhibit anion exchange function, the amine needs to be quaternized. Some quaternary amines reversibly become tertiary depending on the pH, so in order to quaternize, the atmosphere of the membrane must be changed to p
It may be necessary to keep the pH lower than Ka.

The anion exchange capacity of the anion exchange group-containing membrane thus obtained is measured by a conventionally known method, for example, as described in "Practical Ion Exchange" co-authored by Miyahara et al. (Kagaku Kogyo Co., Ltd. (1972) pp. 50-58).

On the other hand, regarding neutral hydroxyl groups, new neutral hydroxyl groups are generated in the ring-opened epoxy group when the amine and epoxy group react, so the amount of neutral hydroxyl groups in the entire membrane itself initially and the amount of neutral hydroxyl groups produced through saponification.

At this time, since a neutral hydroxyl group is generated on the side chain adjacent to the position where the amine is added, nonspecific adsorption to the side chain can be sufficiently suppressed.

According to the method of the present invention, the anion exchange group is chemically bonded to the membrane base material, such as polyolefin, via an ether bond and a methylene chain. For example, if glycidyl methacrylate or glycidyl acrylate is directly grafted, it will be through an ester bond, but the method of the present invention is superior in terms of acid resistance and alkalinity. Membranes can be manufactured.

Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples.

Example Fine powder silicic acid, butyl VN3LP) 22.1 parts by weight, dioctyl phthalate (DOP) 55.4 parts by weight, polyethylene resin powder [Asahi Kasei 5H-800 grade 122.
After premixing 5 parts by weight of the composition, it was extruded into a hollow fiber having an inner diameter of 1.9 mm and a thickness of 0.60 mm in a 30 mm twin-screw extruder, and then 1.1.1-trichloroethane [chlorocene VC (commercial product) name)] for 60 minutes, DOP
was extracted. Further, it was immersed in a 40% aqueous solution of caustic soda at a temperature of 60° C. for about 20 minutes to extract the finely divided silicic acid, followed by washing with water and drying.

An electron accelerator (pressure voltage 1.5 Mev) was applied to the obtained porous membrane.
After irradiation with an electron beam of 20 Mrad in a nitrogen atmosphere using an electron beam current of 1 mA), vinyl acetate was grafted in the gas phase.

Next, the grafted porous membrane was treated with IN caustic soda for 80 minutes.
The reaction was carried out for 10 hours at "C", and complete completion of the reaction was confirmed by a decrease in weight.

After thoroughly washing the polyvinyl alcohol grafted porous membrane thus obtained, 500 ml of dimethyl sulfoxide, 300 ml of epichlorohydrin, and 70 ml of 50% caustic soda were added to 50 g of the membrane, and the mixture was reacted at 30°C for 5 hours. . After the reaction, the mixture was thoroughly washed with methanol and then with water.

One gram of this membrane was added to a 1.3M aqueous sodium thiosulfate solution, heated to 70"C, and titrated with N/10 hydrochloric acid using phenolzurein as an indicator to determine the amount of epoxy introduced. N/g polymer.

The membrane was immersed in a 29% ammonia aqueous solution, and after 24 hours, was immersed in N/10 hydrochloric acid to form a quaternary amine.

When the anion exchange group content of the membrane thus obtained was measured by the method described above, it was found to be 0.35% per gram of porous membrane.
It was milliequivalent. Moreover, the amount of bonded neutral hydroxyl groups was 3.0 milliequivalents per 1 g of the porous membrane. The porosity and average pore diameter were 70% and 0.35μ, respectively.

Using this anion selective adsorption porous membrane, the membrane area is 1nl.
A module of 600 p of horse hemoglobin was prepared.
201/hr, rd of a solution containing p+m (pH 8,65)
filtered at a speed of The horse hemoglobin concentration in the filtrate after filtration for 20 minutes was 0.5 ppra.

After filtration in this manner for about 1 hour, the liquid inside the module was drained and washed with water. p) The hydrochloric acid acidic solution of II was supplied to the above module, and the filtrate was collected. The amount of horse hemoglobin recovered in the filtrate was 96% of the amount calculated to be adsorbed in the module.

In addition, when the above module was washed with put4 alkaline aqueous solution and further treated with p1 hydrochloric acid, and then filtered under the same conditions as above, the horse hemoglobin concentration in the filtrate was 0.6 pps+, and the alkaline water washing It was found that the anion selective adsorption effect was maintained even after the addition.

Note that even after repeating the same operation 100 times, the selective adsorption effect remained virtually unchanged.

Comparative Example A polyvinyl alcohol-grafted porous membrane (neutral hydroxyl group bonding amount: 3.0 meq/g polymer, porosity: 70%, average pore diameter: 0.001) obtained during the production of the anion-selective adsorption porous membrane of Example. 37μ), a module with a membrane area of 1 port was fabricated.

When a solution containing horse hemoglobin was filtered using this module under the same conditions as in the example, the horse hemoglobin concentration in the filtrate was 597 pp111.

Further, after the membrane was washed with alkaline water and treated with hydrochloric acid under the same conditions as in the example, the solution containing horse hemoglobin was filtered again under the same conditions as in the example, and the horse hemoglobin concentration in the filtrate was 595 ppa+.

The non-adsorption effect of the comparative membrane was virtually unchanged.

〔Effect of the invention〕

The porous membrane of the present invention can be used as a specific component adsorption membrane for fermentation/pharmaceutical industries and general industrial water; ■ adsorbs and removes specific anion components from liquids; ■ adsorbs and purifies specific anion components from liquids. ■By adjusting the pH of the stock solution, it is possible to adsorb and purify only organic components such as specific proteins, and to develop effects not seen in conventional industrial membranes. The benefits are immeasurable.

Patent applicant: Asahi Kasei Industries, Ltd.

Claims (4)

[Claims] (1) Neutral hydroxyl groups of 0.1 milliequivalent or more per 1 g of porous membrane, ether bonds, and methylene An anion-selective adsorption porous membrane having an average pore diameter of 0.01 to 5μ and a porosity of 20 to 90%, in which 0.1 milliequivalent or more of anion exchange groups per gram of porous membrane are chemically bonded via chains. (2) The porous membrane has an inner diameter of 0.1-10 mm and a thickness of 0.05-10 mm.
The selective adsorption porous membrane according to claim 1, which has a hollow fiber shape of 5 mm. (3) After irradiating a base film made of polyolefin or a copolymer of olefin and halogenated olefin with ionizing radiation, vinyl acetate is grafted in the gas phase, and the grafted polyvinyl acetate is saponified to form polyvinyl acetate. Anion selection having a neutral hydroxyl group and an anion exchange group via an ether bond and a methylene chain, characterized by denaturing to alcohol, then introducing an epoxide, and adding ammonia or an organic amine to the introduced epoxide. Method for manufacturing adsorbent porous membrane (4) The base film has a three-dimensional network structure, and the film shape has an inner diameter of 0.
．． 4. The method for producing a selective adsorption porous membrane according to claim 3, wherein the membrane has a hollow fiber shape of 1 to 10 mm and a thickness of 0.05 to 5 mm.