JPH02222424A - Cation selective adsorptive cellular membrane and production thereof - Google Patents

Abstract

PURPOSE:To obtain the subject cellular membrane useful for adsorbing and removing specific cationic components from liquids, such as normal industrial water, by grafting vinyl acetate onto a substrate membrane, saponifying the grafted polyvinyl acetate and reacting the resultant polyvinyl alcohol with a specified aliphatic carboxylic acid. CONSTITUTION:The objective cellular membrane, obtained by exposing a substrate membrane consisting of a polyolefin or a copolymer of the polyolefin and a halogenated olefin to ionizing radiation, then grafting vinyl acetate onto the resultant substrate membrane in the vapor phase, saponifying the grafted polyvinyl acetate, modifying the saponified polyvinyl acetate to polyvinyl alcohol and subsequently reacting the obtained polyvinyl alcohol with an aliphatic carboxylic acid having at least one or more halogen groups as substituent groups and having neutral hydroxyl groups in an amount of >=0.1 mequiv. based on 1g cellular membrane and carboxyl groups in an amount of >=0.1 mequiv. based on 1g cellular membrane chemically bound through ether bonds and methylene chains to the surfaces of the above-mentioned substrate membrane and pores, 0.01-5mu average pore diameter and 20-90% porosity.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is suitable for adsorption and purification of specific cation components (including organic components such as proteins and amino acids) useful 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 cations, 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. be.

In order to solve this problem, it has been proposed to use a membrane that can adsorb and purify these specific cation components.

The expected advantages of membrane properties include better adsorption efficiency, higher purification and removal efficiency, and shorter processing time.

On the other hand, these specific cation components are generally purified by adsorption.
It is known that treatment with a porous membrane made of a polymer containing a cation exchange functional group such as a carboxyl group in its side chain is suitable for removal. However, due to the non-specific adsorption properties of the membrane itself, other components are also adsorbed in addition to the specific cation component to be purified, resulting in poor purification efficiency.

In particular, when used on an industrial scale, the skeleton of the porous membrane itself must be strong, and a hydrophobic one is naturally preferable, but due to its hydrophobicity, non-specific adsorption of proteins etc. occurs. Purification efficiency will deteriorate.

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 a cation 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 above-mentioned specific cations, and a method for producing the same.

[Means to solve the problem]

This invention provides: (1) neutral hydroxyl groups of 0.1 milliequivalent or more per 1 g of porous membrane on the membrane surface and pore surface of a base membrane made of polyolefin or a copolymer of olefin and halogenated olefin; An average pore diameter of 0.01 to 5μ with which more than 0.1 milliequivalent carboxyl groups are chemically bonded per gram of porous membrane through ether bonds and methylene chains.
, a cation-selective adsorption porous membrane with a porosity of 20 to 90%, and (2) a base membrane made of a polyolefin or a copolymer of an olefin and a halogenated olefin, which are irradiated with ionizing radiation and then exposed to a gas phase. grafted vinyl acetate with
A neutral hydroxyl group characterized by saponifying the grafted polyvinyl acetate to modify it into polyvinyl alcohol, and then reacting it with an aliphatic carboxylic acid having at least 1 or more halogen groups as a substituent; The present invention relates to a method for producing a cation-selective adsorption porous membrane having an ether bond and a carboxyl group via a methylene chain.

The material of the porous base membrane used in this invention is composed of polyolefin or a copolymer of olefin and halogenated olefin, and must have hydrophobicity. 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 techniques. 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 carboxyl groups chemically bonded to the surface of the base membrane and the surfaces of the pores. In the present invention, the term "selective adsorption porous membrane in which neutral hydroxyl groups and carboxyl groups are chemically bonded to the surface of the membrane and the surfaces of the pores" refers to the porous membrane.
point to

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. The neutral hydroxyl group is necessary to prevent non-specific adsorption of organic proteins to the porous membrane without denaturing the feed liquid, and the amount of the neutral hydroxyl group bound to the base membrane is determined by its suppressive effect. However, the number of neutral hydroxyl groups per gram of porous membrane is 0.
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, 0.1 to 1 g of porous membrane
20 milliequivalents, more preferably 0.0 per gram of porous membrane.
It is selected from the range of 1 to 10 milliequivalents.

The carboxyl group is always chemically bonded to the polymer skeleton of the base film 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.

Although it is a group represented by a chemical structural formula, in the present invention, a carboxyl group includes a negatively charged 1CO〇-carboxylate group in which a hydrogen atom is removed from a carboxyl group. Generally, these two substances can be easily and reversibly changed into each other by changes in pH, etc., as shown in the example below, and it is not necessary to strictly distinguish between the two substances. (@Tokyo Kagaku Doujin Publishing “Morrison Boyd Organic Chemistry (Middle) 3rd edition JP7
26 (1977)) Carboxylic acid carboxylate carboxyl groups must be present in an amount of 0.1 milliequivalent or more per 1 g of the porous membrane to fully exhibit the intended function. However, if there are too many cation exchange groups specified in this invention, the pores may become clogged, which is not preferable. Preferably, the amount of carboxyl groups is 0.1 to 1 g per 1 g of porous membrane.
20 milliequivalents, more preferably 0.1 per gram of porous membrane.
~10 milliequivalents.

The neutral hydroxyl group and the carboxyl 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.

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. isn't it. In order to maintain the excellent mechanical properties of the base membrane in a porous membrane, it is advantageous to reactively add (graft) the side groups to the surface of the pores as preferentially as possible. Therefore, the meaning of the bonding rate of each group here is:
The values shown are average values measured over the entire membrane, and do not represent the binding rate from a microscopic perspective.

Detection of neutral hydroxyl groups, carboxyl groups, ether bonds, and methylene chains can be performed using infrared spectroscopy (IR), nuclear magnetic resonance spectroscopy (NMR), or the like. (Refer to ``Spectral Identification Method J of Organic Compounds J (1976), published by @Tokyo Kagaku Dojin.) The neutral hydroxyl groups bonded to the base film can be quantified by reacting the membrane with acetic anhydride in a pyridine solvent, It is determined from the amount of acetic anhydride used or the weight increase of the membrane.

In addition, since carboxyl groups are weakly acidic groups, the amount of carboxyl groups bonded to the base membrane can be determined using conventional methods such as ``Augmented Practical Ion Exchange J (1), published by Kagaku Kogyo Co., Ltd.
984) It can be carried out by a titration method in the same manner as the method for quantifying weakly acidic groups (method for quantifying ion exchange capacity of weakly acidic cation exchange resin) described on pages 167 to 174. That is, to give an outline of the process, 1) place the membrane in an aqueous acid solution and change all the carboxyl groups to -COOH type, 2) wash the membrane with pure water to remove excess acid, 2) place the membrane in an aqueous alkaline solution, For example, in a sodium hydroxide aqueous solution, the carboxyl group and COOH+ N ao H → COON a+ Ht O
cause a reaction. The amount of carboxyl groups can be determined by determining the amount of sodium hydroxide in the aqueous sodium hydroxide solution consumed in this reaction by neutralization titration of the aqueous sodium hydroxide solution with an acid.

The cation 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 cation adsorption rate and liquid permeation rate. More preferably 0.01
A range of ~1μ is preferable.

The average pore diameter here refers to the value obtained by the method described in ASTM F 316-70, which is usually called the air flow method, in which the air permeation flux of dry membranes and wet membranes is measured by changing the air pressure. It is determined from that 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 the 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
From the viewpoint of efficiency, it is preferable to use a hollow fiber having a shape of ~lOM and a thickness of 0.05 to 51) Im.

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 polyolefin or a copolymer of olefin and halogenated olefin with ionizing radiation, then graft vinyl acetate in the gas phase, and then use a saponification reaction to graft the grafted side chains. This method is characterized by chemically modifying the compound and then reacting it with an aliphatic carboxylic acid having at least one halogen group as a substituent.

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.

Next, it is reacted with an aliphatic carboxylic acid having at least one halogen group as a substituent.

As the aliphatic carboxylic acid, commercially available reagents such as monochloroacetic acid, dichloroacetic acid, trichloroacetic acid, monobromoacetic acid, monoiodoacetic acid, monobromopropionic acid, dibromopropionic acid, bromosuccinic acid, dibromosuccinic acid, and their alkali metal salts can be used. Can be used.
This reaction can usually be carried out in a solvent that dissolves the aliphatic carboxylic acid used. Further, this reaction tends to proceed in the presence of an alkali, and an alkali such as sodium hydroxide or potassium hydroxide can be added as necessary.

As an example of a preferred reaction, a polyvinyl alcohol grafted porous membrane impregnated with a 10 weight percent to saturated aqueous monochloroacetic acid solution is treated with water in an amount equal to or more than half the total weight of the monochloroacetic acid impregnated into the membrane. Pour into an aqueous solution containing sodium oxide and react at 30 to 100°C for several minutes to 12 hours. By repeating this reaction step, the amount of carboxyl groups introduced into the membrane can be increased.

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

Example 1 Finely powdered silicic acid, Psil VN3LP) 22° 1 part by weight, dioctyl phthalate (DOP) 55.4 parts by weight, polyethylene resin powder [Asahi Kasei 5H-800 grade] 22.
After premixing 5 parts by weight of the composition, 30 mI) 2
After extruding into hollow fibers with an inner diameter of 1.9 mm and a thickness of 0.60 mm in a axial extruder, 1,1.1~trichloroethane [
chlorocene VG (trade name)] for 60 minutes, and then
P 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 fine powder silicic acid, followed by washing with water and drying.

The obtained porous membrane was subjected to an electron accelerator (pressure voltage: 1.5 M).
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 at ℃ for 10 hours, and complete reaction was confirmed by a decrease in weight.

The neutral hydroxyl group content of the polyvinyl alcohol grafted porous membrane thus obtained was 5.2 milliequivalents per tg of the polyvinyl alcohol grafted porous membrane.

50g of this polyvinyl alcohol grafted porous membrane
It was immersed in 700 g of a 5 weight percent monochloroacetic acid aqueous solution at room temperature for about 30 minutes. Next, the membrane was pulled out of the monochloroacetic acid aqueous solution and immediately prepared separately, 9.
50% by weight aqueous sodium hydroxide solution at 0°C 1
000g. After reacting at 90 to 100°C for about 20 minutes, it was washed with water. Porous membrane 1 of the obtained porous membrane
The amount of neutral hydroxyl group bonded per g is 4.6 milliequivalents,
The amount of carboxyl group bonded is 0.4 milliequivalent, the porosity is 70
%, and the average pore size was 0.35 μm.

Example 2 50 g of the porous membrane obtained in Example 1 was again added to 700 g of a 75 weight percent monochloroacetic acid aqueous solution at room temperature for about 30 g.
It was immersed for 0 minutes. Next, this membrane was pulled out of the monochloroacetic acid aqueous solution and immediately added to a separately prepared 50% by weight aqueous sodium hydroxide solution at 90°C. O
It was poured into OOg.

After reacting at 90 to 100°C for about 20 minutes, it was washed with water. The amount of neutral hydroxyl groups bound per 1 g of porous membrane of the obtained porous membrane was 3.9 milliequivalents, the amount of carboxyl groups bound was 0.8 milliequivalents, the porosity was 70%, and the average pore diameter was 0.35.
It was μm.

Using this cation selective adsorption porous membrane, the membrane area is 1rr.
Create a module of r and cytochrome 0600 pp
20f/hr・rr? filtered at a speed of The concentration of cytochrome C in the solution after filtration for 20 minutes was 0.51)I)m.

After filtration in this manner for 1 hour, the liquid in the module was drained. An alkaline aqueous solution with a pH of 14 was supplied to the module, and the furnace liquid was collected. The amount of cytochrome C recovered in the furnace fluid was 96% of the amount calculated to have been adsorbed in the module.

In addition, after washing the above module with an alkaline aqueous solution of pH 14, a cytochrome C solution (p
When H8,4) was filtered, the concentration of cytochrome C in the furnace liquid was 0.6 ppm, indicating that the adsorption effect was effective even after washing with alkaline water.

Note that even after repeating the same operation 1001 times, the adsorption effect remained virtually unchanged.

Comparative Example The polyvinyl alcohol grafted porous membrane obtained during the production of the cation selective adsorption porous membrane of Examples 1 and 2 (the amount of neutral hydroxyl groups bonded is 5.2 ml J equivalent per 1 g of the polyvinyl alcohol grafted porous membrane). , a porosity of 70%, and an average pore diameter of 0.37μ), a module with a membrane area of 1M was produced. ) When a liquid containing cytochrome C was filtered using this module under the same conditions as in Example 2, the concentration of cytochrome C in the furnace liquid was 597 ppm.
Met.

In addition, after washing the membrane with alkaline water under the same conditions as in Example 2,
When the liquid containing cytochrome C was filtered again under the same conditions as in Example 2, the concentration of cytochrome C in the furnace liquid was 595.
It was ppm. The non-adsorption effect of the comparative membrane remained virtually unchanged even after alkaline cleaning.

〔Effect of the invention〕

The porous membrane of the present invention can be used as a specific component adsorption membrane to absorb specific cation components (
Depending on the application, such as adsorption and removal, or adsorption and purification and recovery of organic components (including organic components such as proteins and amino acids), it is possible to exhibit effects not seen in conventional industrial membranes, and the benefits are also immeasurable. do not have.

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 A cation-selective adsorption porous membrane with an average pore diameter of 0.01-5μ and a porosity of 20-90%, in which 0.1 milliequivalent or more carboxyl groups are chemically bonded per gram of porous membrane through 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. After denaturation to alcohol, at least one substituent
A method for producing a cation-selective adsorption porous membrane having a neutral hydroxyl group and a carboxyl group via an ether bond and a methylene chain, the method comprising reacting an aliphatic carboxylic acid having three or more halogen groups. (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.