JPH0214724A - Complex membrane and its preparation - Google Patents

Abstract

PURPOSE:To obtain a complex membrane having controllable permeability and high strength by impregnating an inorganic porous body having functional groups on the surface with a hydrogel monomer and forming the complex membrane by fixing the hydrogel to the surface of the porous body by a polycondensation reaction. CONSTITUTION:A complex membrane is formed by a polycondensation reaction of a hydrogel monomer impregnated into an inorganic porous body having functional groups on the surface, and fixing the hydrogel on the surface of the inorganic porous body. As a result, a complex membrane having variable permeability depending on the volume change caused by the phase transition of a hydrogel supported on the surface of the inorganic porous body, is obtd. Suitable inorganic porous body is one permitting introduction of functional groups onto the surface, concretely, such as porous glass membrane, several kinds of ceramic porous membrane, carbon fiber bundle, etc.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a composite membrane and a method for manufacturing the same, and more specifically, a composite membrane whose permeability can be controlled and which has excellent mechanical strength, and this composite membrane. Relating to a manufacturing method.

[Prior art and problems to be solved by the invention] Among gels, which are polymers swollen by absorbing a solvent in a three-dimensional network, water is contained between the solid phase framework. It is known that hydrogels have excellent water absorption and water retention properties, and that they undergo a phase transition and undergo a significant change in volume due to slight changes in solution composition, salt concentration in the solution, pH, temperature, voltage, etc. It is being

Various attempts have been made to utilize such properties of hydrogels to create membranes with variable permeability.

For example, if such a membrane is installed in a liquid flow path, it becomes possible to control the fluid flux, solute permeability, etc. with the membrane.

However, when a membrane is formed using hydrogel alone, there is a problem in that the membrane does not have sufficient mechanical strength.

Therefore, as a method for improving the mechanical strength of membranes, for example, a method of combining a hydrogel with a polyoxyethylene/polyacrylic acid interpenetrating network polymer has been proposed. There are problems in that the types of gels that can be produced are limited, and the environment in which the membrane obtained by this method is used is limited by the physical properties of the polymer that is the carrier.

Also, in this method, it is necessary to apply pressure to the hydrogel body or mechanically fix it to support it on other polymers, so the mechanical strength of the hydrogel when supporting it on other polymers is important. Intensity becomes an indignant problem.

Furthermore, in a membrane formed by combining a hydrogel with another polymer, the membrane thickness and membrane area change simultaneously due to the phase transition phenomenon of the hydrogel, making it even more difficult to immobilize the hydrogel.

The present invention has been made based on the above circumstances.

An object of the present invention is to provide a composite membrane that can control permeability and has excellent mechanical strength, and a method for producing a composite membrane that allows easy immobilization of hydrogel and has excellent production efficiency.

[Means for Solving the Problems] In order to solve the problems described above, the present inventor has made extensive studies and found that a specific membrane supports a hydrogel containing water between the solid frameworks of the gel. This composite membrane has controllable permeability and excellent mechanical strength.In addition, this composite membrane utilizes chemical bonds between the functional groups present on the surface of a specific membrane and the hydrogel. The present invention was achieved by discovering that it can be obtained efficiently.

The structure of the invention according to claim 1 is a composite membrane characterized in that a hydrogel is supported on the surface of an inorganic porous body, and the permeability can be changed according to a change in volume due to a phase transition of the hydrogel.

The structure of the invention according to claim 2 is characterized in that the hydrogel is immobilized on the surface of the inorganic porous body by impregnating the inorganic porous body having a functional group on the surface with a hydrogel monomer and performing a polycondensation reaction. This is a method for manufacturing a composite membrane.

The composite membrane of the invention according to claim 1 is formed by supporting a drogel on the surface of an inorganic porous body.

The inorganic porous body has a functional group on its surface or can be introduced with a functional group, and specific examples thereof include a porous glass membrane, a porous membrane made of various ceramics, and a carbon fiber bundle. It will be done.

The porous glass film is made of, for example, silica sand (Si02).
, boric acid (H3BO3) and soda ash (Na2CO3
) as the main raw material to create Na2O-B2O5-5i02-based borosilicate glass, and then heat-treated at 500 to 600°C to form a 5f02 glass phase and Na2Q-820 glass.
3 glass phase undergoes glass-glass phase separation on the order of several tens of amperes to form a phase-separated glass, and then acid treatment is performed to elute the Na2O-8203 glass phase, forming a porous glass consisting of the 5i02 glass phase. A quality glass film can be obtained.

Examples of the various ceramic porous membranes include:
Examples include films made of porcelain porous porcelain, alumina porous porcelain, and the like. These ceramic porous membranes are produced using, for example, thermal evaporation.

It can be formed using a thin film forming method such as a sputtering method, an ion blasting method, a CVD method, a plasma CVD method, or an RF sputter etching method.

Examples of the carbon fiber bundle include those made of carbon fibers obtained by firing precursor fibers (precursor) obtained by dry-wet spinning of a polyacrylonitrile polymer at a temperature of about 1500°C.

In any case, the average pore diameter of the inorganic porous material is preferably within the range of 1,000λ to oooA. However, this average pore diameter can be arbitrarily set to m. For example, the average pore diameter of the inorganic porous body may be set in the range of several λ to several 100X, or several mm depending on the case.

Further, the pore surface area of the inorganic porous material is not particularly limited as long as it has sufficient strength as a support, and can be appropriately determined depending on the use of the composite membrane of the present invention.

The porosity of the inorganic porous body is usually 0.4 cc/g
That's about it.

Furthermore, there is no particular restriction on the shape of the inorganic porous body, and it can be any shape such as a rectangle, square, or circle.

Furthermore, there is no particular restriction on the thickness of the inorganic porous body.

One of the important points in the invention of claim 1 is that the inorganic porous body has a functional group on its surface or can introduce a functional group.

Here, the surface of the inorganic porous body is a concept that includes the surface inside the pores.

The functional group is not particularly limited as long as it can be used for chemical bonding with the hydrogel. For example, a silanol group is present on the surface of the porous glass membrane,
Oxygen or hydroxyl groups derived from metal oxides generally exist on the surface of the various ceramic porous membranes. Also,
Oxygen-containing functional groups generally exist on the surface of the carbon fiber bundle that comes into contact with air, and even if oxygen-containing functional groups do not exist, oxygen-containing functional groups are added to the surface of the carbon fiber bundle by oxidation treatment. It is possible to introduce

One of the important points in the invention of claim 1 is that the surface of the inorganic porous body supports a hydrogel.

Preferred examples of the hydrogel include vinyl-based synthetic polymer gels.

Specifically, acrylic acid, acrylic acid derivatives, vinyl alcohol, ethylene oxide, hydroxyethyl methacrylate, styrene sulfonic acid and its salts, etc., are generally vinyl group-containing, water-soluble heptad homopolymers or copolymers. Alternatively, copolymers of these and, for example, maleic anhydride may be mentioned.

The volume of the hydrogel changes due to phase transition.

Therefore, in the composite membrane of the first aspect of the invention, the pore diameter of the inorganic porous body changes due to a change in the volume of the hydrogel, and the permeability of the composite membrane changes.

Moreover, since the stress applied to the hydrogel is dispersed in the inorganic porous material that is the carrier, the composite membrane has excellent mechanical strength.

The composite membrane of the invention of claim 1 having such characteristics can be efficiently obtained by the manufacturing method of claim 2 which will be described in detail below.

That is, in the method for producing a composite membrane according to the invention of claim 2, an inorganic porous material having a functional group on the surface is impregnated with a hydrogel monomer, and then a single polycondensation reaction is performed to coat the surface of the inorganic porous material. Immobilize the hydrogel.

The inorganic porous body having a functional group on the surface has the above-mentioned claim 1.
The same materials as can be used in the composite membrane of the invention can be used.

When the inorganic porous body does not have a functional group on its surface, the functional group can be introduced by surface treatment of the inorganic porous body.

Examples of surface treatment methods include air oxidation,
After introducing an oxygen-containing group by reagent oxidation, oxygen plasma oxidation, etc., or introducing an amino group by nitrification with a mixed acid and its reduction, it is possible to carry out conversion treatment of functional groups as necessary. can. Esterification may be carried out by dehydration condensation of a dehydrating agent (such as DCC) and an amide or carboxylic acid having a vinyl group in the hydroxyl group on the surface. When the functional group is a hydroxyl group, a coupling agent having a vinyl group (dimethylchlorosilane,
A vinyl group can also be introduced by using diphenylvinylchlorosilane, etc.).

In the method of the present invention, the inorganic porous body is impregnated with a hydrogel monomer after the inorganic porous body has been subjected to the above-described surface treatment or without performing the above-described surface treatment.

Specifically, the inorganic porous body is impregnated with a hydrogel-forming solution.

The hydrogel-forming solution to be used includes, for example, a heptamer solution containing a heptamer such as acrylic acid, acrylamide, N,N'methylenebisacrylamide, and an initiator solution containing an initiator such as potassium persulfate. and can be obtained by mixing them immediately before impregnating the porous body.

In the method of the present invention, the functional group and the hydrogel monomer are then subjected to a polymerization reaction to immobilize the hydrogel on the surface of the inorganic porous body.

The polymerization reaction conditions vary depending on the type of polymer to be immobilized and therefore cannot be determined unconditionally, but for example, when N-isopropylacrylamide is used, the polymerization may be carried out at 0° C. for about 1 hour.

After the reaction is completed, washing is performed using, for example, distilled water to obtain a composite membrane.

[Example] Next, the present invention will be described in more detail by showing examples of the present invention. Note that the present invention is not limited to this embodiment.

(Example 1) Average pore size 20QOA, diameter 25++u+, thickness 1m
Inorganic porous body I made of porous glass [manufactured by Asahi Glass ■] with an average pore size of 6900 A, diameter 35 mm, and thickness 0.81 mm [manufactured by Asahi Glass ■] Surface treatment was carried out using (1) according to the procedures shown in (1) to (2) below.

■ To remove impurities on the surface of the inorganic porous body, after immersing the inorganic porous body and the inorganic porous body ■ in nitric acid,
After washing with distilled water, vacuum drying was performed.

(2) Next, inorganic porous body (1) and inorganic porous body (2) were immersed in hydrogen peroxide, washed with distilled water, and then vacuum dried.

(2) An anhydrous benzene solution containing a predetermined amount of acrylic acid and dicyclohexyl carbon diimide is permeated through the inorganic porous body I and the inorganic porous body H that have been subjected to the treatment in (2) above. Double bonds were introduced into the surfaces of inorganic porous material I and inorganic porous material (2) by carrying out a dehydration condensation reaction between the silanol groups present on the surface of material (1) and acrylic acid.

■153Eto5 Upper 1 The inorganic porous body and the inorganic porous body ■ into which double bonds have been introduced into the surface by the treatment described in (■) above are impregnated with a hydrogel-forming solution (aqueous solution) having the following composition. One polycondensation reaction was carried out on a water bath at a temperature of 70° C. for 15 minutes.

Hydrogel solution composition acrylamide BOgl acrylic acid 20g/IN, N'-methylenebisacrylamide 1.7g/potassium persulfate 0.2g/1 After completion of the reaction, take out the inorganic porous body and the inorganic porous body ■ from the mass. By immersing these in running water and washing them, a composite MIC obtained by supporting a hydrogel on an inorganic porous body I is obtained.
Hereinafter, this will be referred to as sample I), and a composite membrane consisting of an inorganic porous body H supporting hydrogel (hereinafter, this will be referred to as sample I).
) was obtained.

Regarding Sample I and Sample ■ thus obtained,
The transmission characteristics were evaluated.

The transmission characteristics were evaluated as follows.

(a) Regarding the sample process, the relationship between the permeation flux of the water/acetone mixed solution and the acetone concentration was investigated at an operating pressure of 15 kg/cm² and a temperature of 25°C.

The results are shown in Figure 1.

(b) For sample ■, the pressure was 15 kg/cm2. temperature 2
The relationship between the permeation flux of a water/acetone mixed solution and the acetone concentration at 5°C was investigated.

The results are shown in Figure 2.

(c) For sample ■, pressure 15 kg/c 2. temperature 2
The permeation characteristics of polyoxyethylene solution at 5°C were investigated.

That is, molecular weights 2,000, 7,000 and 20
, 000 was dissolved in (a) water and (b) in a 40% acetone solution.

The results are shown in FIGS. 3(a) and 3(b).

(Evaluation) As is clear from Figures 1 and 2, the permeation flux changes rapidly at a constant acetone concentration, and this change is reversible. We confirmed that the sex changes reversibly.

Furthermore, as is clear from Figures 3(a) and 3(b), when the acetone concentration is 0%, the polyethylene glycol that permeates through the 8 composite membrane has a molecular weight of only 2,000 and 7,000. Although it is slight [Figure 3 (
a) Reference, 1. When the acetone concentration was 40%, almost all the polyethylene glycol permeated through the composite membrane, so it is presumed that a phase transition occurred in the hydrogel.

[Effects of the Invention] According to the present invention, (1) A hydrogel is supported on an inorganic porous body, and the pore diameter of the inorganic porous body is reversible due to a volume change accompanying a phase transition of the hydrogel. As k changes, a reversible change in permeability can be realized.

(2) Since the stress applied to the hydrogel is dispersed in the inorganic porous material, it has excellent mechanical strength.

(3) A composite that has the advantages of (1) and (2) above, since the hydrogel is immobilized by utilizing the chemical bond between the hydrogel and the functional group present on the surface of the inorganic porous material. A membrane can be obtained efficiently.

It is possible to provide an industrially useful composite membrane having the following advantages and a method for producing the same.

[Brief explanation of the drawing]

FIGS. 1 and 2 are characteristic curves showing the solution permeation characteristics of the composite membrane of the present invention, and FIGS. 3(a) and 3(b) are the permeation characteristics of polyethylene glycol through the composite membrane of the present invention, respectively. This is a characteristic curve showing. 1st figure - 7ton mix 8 bu oki yaku no ryozoto> jidenbu 1000 2nd rice - cho 7ton mixed bank 11 [minute 1000 (a) time open [ Figure 3 (b) 1゜3゜Time [minutes]

Claims (2)

[Claims] (1) A composite membrane characterized in that a hydrogel is supported on the surface of an inorganic porous material, and the permeability can be changed according to a volume change due to a phase transition of the hydrogel. (2) A method for producing a composite membrane, comprising immobilizing a hydrogel on the surface of the inorganic porous material by impregnating a hydrogel monomer into an inorganic porous material having a functional group on the surface and performing a polycondensation reaction. .