JPH0411932A - Production of composite membrane - Google Patents

Abstract

PURPOSE:To stably obtain a composite membrane having large separation factor by forming a thin layer comprising natural polysaccharide or its derv. containing a glucoside group in the main chain and containing ionic groups on a polymerized polymer porous film the surface of which is treated for hydrophilicity impartation. CONSTITUTION:In the production process of he composite membrane, first, at least one surface of a polymerized polymer porous film is preliminarily treated for hydrophilicity impartation or roughened. Then on this surface, a thin layer comprising natural polysaccharide or its derv. containing a glucoside group in the main chain and containing ionic groups is formed. The natural polysaccharide or its derv. is, for example, chitosan, alginic acid or derv. of these.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a method for manufacturing a novel composite membrane, and more specifically, the present invention relates to a method for producing a novel composite membrane, and more specifically, the present invention relates to a method for manufacturing a novel composite membrane, and more specifically, it relates to a method for producing a novel composite membrane, and more specifically, it relates to a method for producing a novel composite membrane, and more specifically, it relates to a method for producing a novel composite membrane, and more specifically, it relates to a method for producing a novel composite membrane. The present invention provides a method for manufacturing a composite membrane suitable for separation.

[Prior Art] A pervaporation method is generally known as an effective method for separating a specific liquid component from a mixture of water and an organic liquid or an organic liquid-organic liquid mixture.

The pervaporation method is a method in which a liquid mixture is supplied to one processing chamber divided by a separation membrane, the other permeation vapor chamber is reduced in pressure, and specific liquid components are extracted from the liquid mixture as vapor into the permeation vapor chamber. It is.

Separation membranes used in such pervaporation methods have excellent permselectivity (hereinafter also referred to as separation coefficient) for specific substances in the liquid mixture to be treated, unit membrane area, and permeation amount per unit time (hereinafter referred to as Two properties are required: a large permeation flux (also called permeation flux). These two characteristics are
Although it is not necessarily clear what kind of action mechanism this is achieved, it may be due to differences in the polarity of the constituent components in the liquid mixture to be processed, molecular weight or molecular structure, strength of polarity present in the separation membrane, difference in charge, distribution, or microscopic presence. It is thought that it is determined by the pore size and the pore diameter.

Conventionally, separation membranes used in this pervaporation method include, for example, cellulose, polyethylene, polypropylene, polyacrylonitrile, polyvinyl alcohol,
Polymer membranes made of polystyrene, polyester, polyamide, polytetrafluoroethylene, or copolymers similar to these are known. In particular, there are reports as follows regarding separation of water-organic liquid mixtures. For example, J, Polym, Sci, Symp
osium, no.

41.145 (19731 describes an example of separating a water-methanol mixture using a Shichilof 7y membrane; J, Appl.
, Polym.

Sci., Vol. 26.3223 (1981) discloses an example in which a water-methanol mixture was separated using the same grafted polyvinyl alcohol membrane.

Recently, chitosan, which is a natural product cationic polymer, has been used to separate a water-alcohol mixture, and a water-ethanol mixture was separated using a chitosan-vinyl monomer polymer membrane (Japanese Patent Laid-Open No. 62 -4407), an example of water-alcohol separation using chitosan-based or cellulose-based derivatives (JP-A No. 62-74)
No. 03) has been reported.

[Problems to be Solved by the Invention] The above polymer membranes all have a relatively large permeation flux, but a small separation coefficient. Therefore, the present inventors have already filed the patent application No. 63-289195 with the main purpose of selectively separating water from a water-organic liquid mixture.
In this issue, we proposed a chitosan-based polymer membrane with a dramatically improved separation coefficient. However, this polymer membrane also had a somewhat insufficient permeation flux, and for industrial use it was necessary to increase the membrane area.

Generally, in order to improve permeation flux, a method has been proposed in which a thin polymer film is formed on a reinforcing support for a porous membrane. For example, Japanese Patent Application Laid-open No. 61-54205 describes a method of coating a microporous support crotch with a thin layer of a specific polymer;
JP-A-7404 describes a method for attaching a cationic multi-PR membrane onto a support membrane such as a microporous membrane, and JP-A-2-43929 describes a method of attaching a cationic polyPR membrane onto a support membrane such as a microporous membrane. A method of coating outer filtration hollow fibers with chitosan or alginate is disclosed.

The present inventors also attempted to separate organic liquids by pervaporation using these methods, but as mentioned above, we used a chitosan-based polymer membrane as a thin film on a porous hollow fiber membrane support. The formed composite membrane still had insufficient permeation flux. Especially when used for a long time, the adhesion of the composite layer is poor and peels off, making it difficult to implement on an industrial scale.

Therefore, it is an object of the present invention to have good separation performance and long-term industrial use, especially when separating water-organic liquid mixtures and organic liquid-organic liquid mixtures by the pervaporation method. The objective is to obtain a separation membrane that is also stable.

[Means for Solving the Problems] In view of the above-mentioned problems, the present inventors have conducted intensive research on composite membranes using chitosan-based polymers. the result,
The present inventors have discovered that a desired separation membrane can be obtained by forming a thin film of a chitosan-based polymer on a porous polymeric polymer membrane whose surface has been treated to make the surface of the polymer porous in advance, and have thus come to provide the present invention. It is something that

That is, the present invention provides a porous film made of a monopolymer polymer.
A thin layer of a natural polysaccharide or a derivative thereof having a glucoside group in its main chain and an ionic group is formed on the surface by adding a hydrophilic group or roughening the surface in advance. This is a method for manufacturing a composite membrane, which is characterized by forming a composite membrane.

Examples of polymeric polymers that are materials for the porous membrane used in the present invention include polyethylene, polypropylene, polyacrylonitrile, polyvinyl chloride, polyvinyl chloride, polyvinylidene chloride, polyvinyl fluoride, polyvinylidene fluoride, and Fluorinated ethylene, polytrifluoro-chlorinated ethylene, polytetrafluoroethylene, copolymer of tetrafluoroethylene and hexafluoropropylene, copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether, tetrafluoroethylene Particularly preferred are fluorine-containing polymers or copolymers such as copolymers of and other chlorine-containing or hydrogen-containing fluoromonomers. Furthermore, from the viewpoint of organic solvent resistance, polyolefin polymers or copolymers are generally preferred, and for example, ethylene and propylene copolymers, such as random or block copolymers, are appropriately selected.

The porous membrane of the present invention made of such a polymeric polymer is
Generally, those having a pore size of 0.1 to 10 μm and a porosity of 10 to 90%, particularly 20 to 70% are preferred. Further, the shape of the porous membrane is not particularly limited, and may be appropriately selected such as a flat membrane, a spiral shape, a hollow fiber shape, a tube shape, etc. depending on the mode of use as a separation membrane 1 and the type of processing liquid to be separated. In particular, a porous membrane having a structure in which a dense layer exists on at least one surface portion of the porous membrane is preferable, and the shape is generally 50 to 300 um in thickness.
A hollow fiber-like porous membrane having an inner diameter of 0.1 to 2 mm is preferably used.

A porous membrane made of a polymeric polymer as described above can be obtained according to a conventionally known manufacturing method.

For example, by using a film-forming method in which a solution of a polymeric polymer dissolved in an appropriate solvent undergoes phase transformation into a predetermined shape in a poor solvent, a film having a dense layer on the surface and a porous layer inside is formed. A porous membrane is obtained.

In addition, a method in which a polymeric polymer is filled with fine particles of inorganic material to form a film, and then the inorganic material is eluted either directly or after stretching, and a method in which an organic solvent with a high boiling point is added to the polymeric polymer to form a film. Then, the desired porosity is obtained by extracting and removing the organic solvent, forming a film by mixing different types of linear polymers with the polymeric polymer, and extracting and removing the different types of linear polymers. A membrane is obtained. In addition, there is a method in which a polymeric polymer is mixed with decomposable fine powder fibers to form a membrane, and then the fine powder fibers are decomposed and removed to form a porous membrane. Specifically, for example, a film is formed using fine powder of a cation exchange resin, and then the iron ion form is decomposed with hydrogen peroxide, or a film is formed by adding fine powder of silicon oxide, and then a film is formed using hydrofluoric acid. A porous membrane can be obtained by a method of decomposing and removing it, or a method of forming a membrane using chopped glass fibers and then decomposing it with hydrofluoric acid.

The greatest feature of the present invention is that when forming a thin layer made of a natural polysaccharide or a derivative thereof having a glucoside group in its main chain and an ionic group on the porous membrane made of the polymeric polymer, The purpose of this method is to treat the surface of a porous membrane made of a polymeric polymer to make it woody.

The hydrophilic treatment is carried out by providing a hydrophilic group in advance to at least one surface of the porous membrane, or by roughening the surface. Typical examples of such methods include, for example, a method in which a porous membrane is treated by infiltrating a surfactant solution, and irradiation with ultraviolet rays in an atmosphere of oxygen, ammonia, etc. in the presence of a photosensitizer if necessary. Methods: corona discharge treatment; flame treatment; surface treatment with an erosive reagent such as dichromic acid mixture; etc.

A more specific explanation of these methods is as follows.

In the treatment method using a surfactant, a cationic, anionic or nonionic surfactant is selected and used depending on the polymer material of the porous membrane. For example, if the porous membrane is made of polyolefin material, a nonionic surfactant is preferably used.

Generally 0.0% of surfactant. The porous membrane is immersed in an old to 5% aqueous solution, an organic solvent solution, or a mixed solution of water and an organic solvent, and after the surfactant is sufficiently adsorbed on the surface layer of the porous membrane, it is taken out and soaked as necessary. is washed, then air-dried or force-dried, and then served in a state that contains some moisture depending on the case.

For surface treatment of porous polymers with ultraviolet rays, in the case of flat films, it is necessary to arrange ultraviolet lamps so that the light source can irradiate the film as uniformly as possible, or to use a reflector to ensure that the irradiation is uniform on the film surface. Make it. Further, in the case of a hollow fiber membrane, the device may be devised so that the entire surface can be uniformly irradiated with ultraviolet rays. The atmosphere in which ultraviolet rays are irradiated may be appropriately selected depending on the type of polymer material to be treated, such as air, oxygen, nitrogen, or ammonia gas atmosphere.

Generally, when UV irradiation is applied, hydrogen atoms on polymer chains in a porous membrane are detached to form double bonds, carbonyl bonds, carboxylic acid groups, amino groups, hydroxyl groups, etc., and the surface layer of the porous membrane becomes hydrophilic. will be granted. Therefore, at this time,
If necessary, the generation of radicals can be promoted by irradiating ultraviolet rays in the presence of a photosensitizer. Examples of photosensitizers include benzophenone,
Compounds having a ketone group such as Michler's ketone or a conventionally known photosensitizing group can be used without any restrictions.Such photosensitizers may be selected as appropriate depending on the type of porous polymer used. .The amount of UV irradiation is generally II)
Irradiation in the range of 20 mLh/cm2 to 100 m is preferable.
A range of W-h/cm2 is particularly preferred.

As the treatment method using corona discharge, the means normally used when treating polymeric films can be used as is. In addition, when the hollow fiber membrane is subjected to hydrophilic treatment, the treatment can be carried out continuously or repeatedly using a corona discharge treatment device that matches the shape of the hollow fiber membrane. The conditions for this corona discharge treatment vary depending on the material of the porous membrane polymer, so they are not generally determined, and are generally used in a treatment atmosphere such as air, oxygen, nitrogen, ammonia gas, sulfur dioxide gas, etc., and the purpose of the treatment. Determined accordingly. When corona discharge treatment is carried out industrially, it is desirable to carry out the treatment in air and to select conditions under which many carbonyl groups, carboxylic acid groups, hydroxyl groups, etc. are generated in the surface layer of the porous membrane polymer.

It is also effective to immerse the porous polymer in an corrosive solvent such as dichromic acid to erode the surface layer of the porous polymer to form hydroxyl groups, carboxylic acid groups, and the like.

Specifically, a mixed solution of dichromic acid and sulfuric acid, nitric acid, perchloric acid, and the like are effective for making the surface layer of the porous polymer hydrophilic. Treatments that clearly introduce ion-exchangeable hydrophilic groups, such as surface treatment with concentrated sulfuric acid, chlorosulfonic acid, or organic amines, also bring good results. In particular, when the porous membrane is composed of a fluorine-containing polymer, it is essential to perform a hydrophilic treatment on the surface of the porous membrane.
Specific methods include, for example, etching the surface layer with sodium naphthalene or potassium naphthalene;
Any of the conventionally known chemical treatment methods for fluoropolymer, such as surface treatment with lithium amide and treatment with FISO3C1, can be suitably applied.

Furthermore, as a hydrophilic treatment for a porous membrane.

Roughening the surface of the porous membrane, that is, providing fine irregularities, also gives favorable results. Specifically, for example, a flat membrane or a hollow fiber is manufactured, and upon winding, an unevenness is created on a guide roll thereof, and the unevenness is obtained by bringing the flat membrane or hollow fiber into contact with this. In addition to the method of bringing a film-like material into contact with an uneven surface to form an uneven surface, there are also methods such as forming an uneven surface on a film-like material and attaching and pressing particles like particles. The method is appropriately selected depending on the purpose.

In addition, techniques generally used for surface treatment of polymers, such as flame treatment, are also effective.

In the present invention, the material forming the thin layer on at least one surface of the porous membrane is a natural polysaccharide or a derivative thereof having a glucoxide group in its main chain and an ionic group.

The above-mentioned ionic group is not particularly limited as long as it is a functional group that generates a positive charge or a negative charge depending on the mode of use, for example, in an aqueous solution or an organic solvent, and known ones can be employed.

To give specific examples of positively charged ones, -class primary, class- and tertiary-amines, quaternary ammonium bases, tertiary sulfonium bases, quaternary phosphonium bases. , cobaltidinium base, etc., and negatively charged ones include sulfonic acid groups, carboxylic acid groups, phosphoric acid groups, phosphorous acid groups, sulfuric ester groups, phosphoric ester groups, thiol groups, phenolic hydroxyl groups, perfluorinated hydroxyl groups, etc. grade alcohol, etc.

The natural polysaccharide or its derivative used in the present invention is not particularly limited as long as it has a glucoside group in its main chain and an ionic group as described above, and known polysaccharides can be used. Typical examples that are generally most suitably used are as follows.

Examples of polymers having glucoside groups and cationic groups include chitosan, which is obtained by hydrolyzing chitin naturally occurring in shrimp, crabs, insects, etc., and removing all or part of the acetyl groups; Its derivatives, such as those crosslinked by chemical reaction using the amino groups of chitosan,
Those into which a negative charge has been introduced, those which have been inactivated, and those into which a parent group such as another hydroxyl group has been introduced are preferably used.

Further, as the polymer having a glucoside group and an anionic group, for example, natural polysaccharides such as alginic acid and pectic acid, and derivatives thereof are preferably used. Furthermore, a polyion complex was formed using chitosan and alginic acid, a multilayer M film in which a thin film of alginic acid was formed on a thin film of chitosan, a film in which a multilayer film was formed on the contrary, and a film in which three or more layers were formed. It is effectively used in various aspects such as things.

The molecular weight of the natural polysaccharide or its derivative used in the present invention is not particularly limited as long as it can form a thin layer on at least one surface of the porous membrane, but it is generally in the range of 3,000 to 1,000,000. Chitosan having a molecular weight of 80,000 to 140,000 is particularly preferred.

The method of forming a thin layer of the natural polysaccharide or its derivative on at least one surface of the porous membrane in the present invention is not particularly limited, but is the most common method. Examples of methods commonly used include: applying a solution in which the natural polysaccharide or its derivative is dissolved on the surface of a porous membrane and removing the solvent; immersing the porous membrane in the solution; A composite film having a desired thickness may be obtained by repeating the method or the like. In general, the preparation of the above solution varies depending on the type of natural polysaccharide, molecular weight, etc., but usually the concentration of the solution is 3 to 12% by weight.
The viscosity should be adjusted within the range suitable for coating or dipping. Furthermore, the thickness of the thin layer formed on the surface layer of the porous membrane varies depending on the purpose and manner of use, but is generally 0. It is preferable to select from a range of 10 μm to 10 μm.

In the present invention, after forming a thin layer of a natural polysaccharide or a derivative thereof having a glucoside group in its main chain and an ionic group on the surface of a porous membrane, if necessary, for example, glutaraldehyde etc. It is preferable to carry out crosslinking treatment using a crosslinking agent.

The composite membrane obtained by the present invention is particularly effective as a separation membrane in a pervaporation method, particularly for dehydrating a mixed solution of water and organic liquid. For example, in the case of a flat membrane, it can be incorporated into something like a filter place type heat exchanger, and if necessary, it can be used by laminating a large number of membranes, or it can be used in a spiral type. In addition, in the case of hollow fibers or tubes, it is possible to put them in a housing and fix them by potting both ends, and to flow the mixture to be separated inside the hollow fibers and apply a vacuum to the outside. The mixed liquid to be separated may be passed through the chamber and the inside pressure may be reduced, or the chamber may be appropriately selected and used depending on the purpose of separation. In particular, in the case of hollow fibers, a membrane is formed by forming a thin layer on the outside of a hollow system that is a porous membrane, using a derivative of natural polyF or 1 having a glucoside group in its main chain and an ionic group bonded to it. However, as a separation membrane in the pervaporation method, good results can be obtained stably over a long period of time.

[Effects of the Invention] According to the present invention, it is possible to obtain a separation membrane for pervaporation that stably has a large separation coefficient and a large permeation flux during long-term industrial use. It is extremely useful.

[Examples] Hereinafter, the contents of the present invention will be specifically explained by examples, but the contents of the present invention are not limited to the following examples.

(In addition, parts in the blending amount in the examples represent parts by weight) Example 1 53.4 parts of polytrifluoro-chlorinated ethylene resin (Daiflon M-300, manufactured by Daikin T Gyo Co., Ltd.), fine powder silicic acid ( Tokuyama Soda Co., Ltd., Trisil) 26.7 parts, chlorotrifluoroethylene oligomer (Daikin Co., Ltd., Daifloyl #20) 60 parts, silicone oil (trade name KF-96)
) were mixed, sufficiently stirred with a homogenizer, and then sufficiently kneaded to form pellets.

Using this pellet, the outer diameter is 2.5 mm and the inner diameter is 1.5 mm.
Hollow fibers were manufactured by extrusion from the outer tube of a double tube nozzle for manufacturing hollow fibers. Next, this hollow fiber was immersed in 1.1.1-trichlorotrifluoroethane for 16 hours to extract and remove the eluted components, and then further immersed in a 50% aqueous solution of caustic soda to remove the fine powdered silicic acid by extraction. Then,
A porous hollow fiber with an average pore diameter of 0.25 μm and a porosity of 75% was obtained.

This porous hollow fiber was made of 1,8-diazabicyclo f5,4.
In a 30% aqueous solution of O1-7-undecene, 90
The surface layer of the porous hollow fiber was made hydrophilic by heat treatment at ℃ for 16 hours. In addition, after pressing the treated porous hollow fibers under pressure, the surface was measured by FTIR, and absorption was observed based on -NH-.

Next, this hydrophilized hollow fiber was immersed in a 3% by weight chitosan aqueous solution prepared by dissolving chitosan (average molecular weight 120,000, degree of deacetylation 90%) in an IM acetic acid aqueous solution to adhere it to the outer surface. After that, excess chitosan liquid was dropped in the air, and the sample was immersed in a neutralization coagulation bath (ethanol:water:sodium hydroxide 6:3:1) for 1 hour. after that,
After thorough washing with water, the chitosan on the outer surface of the hollow fibers was crosslinked using glutaraldehyde in the presence of a sulfuric acid catalyst.

When the surface condition and cross section of the obtained composite hollow fiber membrane were observed using a scanning electron microscope, a uniform chitosan layer of 5 μm in thickness was confirmed on the outer periphery of the porous hollow fiber membrane.

This composite hollow fiber membrane was cut into 15 cm pieces and 10 pieces were bundled together and inserted into a glass tube, and both ends were treated with resin to form a module. Using this modular hollow fiber membrane separation device, an ethanol aqueous solution is passed into the hollow fiber from the bottom end of the module, and the pressure outside the hollow fiber is 2 T.
90wt% by pervaporation method at orr,
The permeation rate (g/Hr·rn2) and selective separation coefficient of a 95 wt% ethanol aqueous solution at 55°C were measured.

Note that the permeation rate (g/Hr·m21) is the weight of the permeate per unit membrane area and unit time, in which the permeate side gas is collected in a dry ice-methanol trap.

Further, the selective separation coefficient is defined as for a water-ethanol mixed liquid.

In the formula, X and xEtOH are the respective H) in the feed solution.
0 is the weight fraction of water and the weight fraction of ethanol in the water-ethanol mixed solution, Y and YELOII are the weight fraction of water and the weight of ethanol in the permeate that permeates through the membrane, respectively. It shows the fraction, and each was quantified using a gas chromatograph.

The results are shown in Table 1.

Table 1 Example 2 Polypropylene (manufactured by Tokuyama Soda Co., Ltd., PN-120, M
After uniformly mixing 57 parts of the pellets of 11.2) and 43 parts of silicon oxide having an average particle size of 1 μm, pellets were made again. This pellet is placed in a mold for extruding a hollow tubular body for 23 minutes.
A tubular body was made by extrusion molding at 0°C, and this was stretched 5 times at 100°C to obtain a porous hollow fiber membrane having an outer diameter of 2.5 mm and an inner diameter of 1.8 mm. The surface of the hollow fiber obtained is
Long pores of 0.1 to 1 μm in the stretching direction were observed using an electron microscope.

This polypropylene hollow fiber was fed at a rate of 10 m/min with a gap between the discharge bar and the roll of 3.5 mm using a corona discharge treatment device manufactured by Kasuga Denki Kikki, and was treated with an applied voltage of 100 μ and an applied current of 6.5 mA. A hydrophilic group consisting of hydrophilic C0OH was added.

Next, the hollow fibers were immersed in a 5% aqueous solution prepared by dissolving chitosan (molecular weight 120,000) in an acetic acid aqueous solution to uniformly adhere the chitosan solution to the surface of the hollow fibers, and then dried. after that,
The acetate of chitosan was made into chitosan by immersion in 0.5 N caustic soda, and then immersed in a 10% aqueous solution of glutaraldehyde at 50° C. for 5 hours to crosslink the surface chitosan layer. Furthermore, this was again immersed in 0.5N hydrochloric acid and then dried.

Using this hollow fiber coated with chitosan, a length of 15 cI
It was made into 11 modules. That is, 20 of these hollow fibers were placed in a glass tube with a diameter of 3 cm, both ends were fixed with epoxy resin, and an outlet for taking out the permeated vapor was provided in the outer part of the glass tube to create a separation device for barbeparation. Configured. In this separation device, a 95% ethanol solution containing 5% water was flowed through the hollow fibers, and a dehydration experiment was conducted continuously at 55° C. with reduced pressure on the outside of the hollow fibers. The degree of vacuum was 3 Torr. As a result, the amount of permeated liquid was 0.9k
g/Hr-m" and the separation factor was 3500.

On the other hand, an identical module was manufactured except that a chitosan thin film was formed on the same polypropylene hollow fiber as described above without corona discharge treatment, and a water-ethanol aqueous solution was dehydrated under the same conditions. As a result, the amount of permeated liquid was 1.3 kg.
/Hr-m2 and the separation factor was 220.

Example 3 Unsintered tetrafluoroethylene resin powder (manufactured by Daikin Industries, Ltd.,
Polyflon TFE, fine powder) 100 parts and 15
20 parts of a petroleum fraction having a boiling point of 0 to 250°C were placed in a closed container and thoroughly stirred to mix and disperse. The resulting mixture was extruded using a ram extruder to form strips with a thickness of 6 mm and a width of 100 mm. This strip was stretched by 300% in the same direction and perpendicular to the extrusion direction using a calendar roll to form a sheet having a thickness of 0.1 mm.

After drying this sheet in an oven at 150 to 200°C, it is stretched at a rate of 25% in the extrusion direction and heated to about 350°C along the surface of a metal drum to form a white opaque polytetrafluoroethylene. Got a sheet. When the membrane surface and cross section were observed using a scanning electron microscope, it was found that continuous pores were present, the specific gravity was 0.55, and the porosity was 7.
It was 5%. Further, this porous membrane was immersed in a sodium-naphthalene tetrahydrofuran solution (manufactured by Junkosha, Tetra Etch) for 10 seconds, and then washed with methanol and water. This treatment imparted OH groups to the membrane surface. The above porous membrane was immersed in a 5% aqueous solution of chitosan acetate with a molecular weight of approximately 100,000, pulled up, and dried. Only one membrane surface was brought into contact with 1.0N caustic soda for 10 minutes, and immediately washed with water. , the thin layer of chitosan on the membrane surface not in contact with caustic soda was dissolved and removed.

The obtained membrane was placed in a flat membrane pervaporation evaluation cell with the side with the thin chitosan layer facing up. That is,
A filter paper is placed on a sintered stainless steel porous plate with a diameter of 70 mm, the membrane of the present invention is placed on top of the filter paper, and after sealing, a 90 mm
% aqueous ethanol or 95% ethanol was placed, the lower part was reduced to 2 mmHg, and pervaporation was performed at 60°C.

The results are shown in Table 2. Note that when the cross section of the membrane was observed using a scanning electron microscope, the thickness of the chitosan layer was approximately 3 μm.

Example 4 Polyethylene (manufactured by Sumire Kagaku Co., Ltd. Sumirikisen FA201-
0. 50 parts of pellets of 'MI2) and finely powdered silicon oxide (
140 parts of particles having a particle size of 1 um were added thereto, and 10 parts of dioctyl phthalate were added thereto and mixed uniformly to form pellets. This was extruded from a hollow fiber molding die at 220°C, and then further stretched 5 times at 100°C to obtain a porous hollow fiber having an outer diameter of 31I1 m and an inner diameter of 2.5 mm. Next, the outer surface layer of this porous hollow fiber was treated with an ozone generator (Okano Seisakusho, EO-3).
02 type) was supplied with oxygen and exposed to air containing 1.38 mo1% ozone at room temperature for 8 hours, the contact angle with water was measured and found to have decreased from 100° to approximately 70°. . Through the above treatment, carbonyl groups and carboxylic acid groups were added to the outer surface layer of the hollow fibers.

Next, a composite membrane was obtained using the above-treated porous hollow fibers in the same manner as in Example 1, with a thin layer of chitosan present on the outer surface of the porous hollow fibers. Using this composite membrane, a dehydration experiment of a water-ethanol aqueous solution was conducted using the same method and conditions as in Example 1. The results are shown in Table 3.

Table 3 Example 5 Polyflon paper PA-512 (manufactured by Daikin Industries, Ltd.) was immersed in a 2% aqueous solution of sodium dodecylbenzenesulfonate for 1 hour and then dried. This treatment imparted -303- groups to the paper surface. Next, a 0.01% aqueous solution of sodium alginate was prepared, the Polyflon paper was dipped into it, dried, dipped again and dried, and this process was repeated 10 times. The membrane was placed on a sheet of paper, methyl alcohol was poured onto the membrane surface from above, and the presence or absence of pinholes was confirmed from the wetness of the blue paper. As a result, no pinholes were observed.

Using the composite membrane obtained above, a water-ethanol solution containing 90% ethanol was dehydrated using the separation device for pervaporation measurement used in Example 3. As a result, the amount of permeated liquid was 0.21 kg/Hr-m2
The separation factor was 28,000. The pervaporation measurement conditions were as follows: 90% ethanol solution was circulated at 60° C. and 3 Torr.

On the other hand, the same procedure as above was carried out, except that sodium alginate was attached to Polyflon paper that had not been treated with sodium dodecylbenzenesulfonate and a composite membrane was used.
The amount of permeated liquid was 0.51 kg/)lr·m2, and the separation coefficient was 120.

Example 6 The polypropylene hollow fiber used in Example 2 was treated by immersing it in a solution consisting of 1 part of chlorosulfonic acid and 2 parts of ethylene dichloride at 30° C. for 8 hours, followed by washing with water, washing with methanol, and drying. Elemental analysis of the treated hollow fibers revealed that the CI content was 1.2%. Through this treatment, -5O□C1 groups and -5O3H are added to the surface of the hollow fiber.
group was introduced.

Next, using the above-treated hollow fiber membrane, it was composited with chitosan in the same manner and under the same conditions as in Example 1.

Using this composite membrane, a dehydration experiment of a water-ethanol aqueous solution was conducted in the same manner as in Example 1. The results are shown in Table 4.

Example 7 Both sides of a porous membrane made of polypropylene (manufactured by Celanese, trade name: Duragart 4410) were subjected to corona discharge treatment.

That is, using the same corona discharge treatment apparatus used in Example 2, the gap between the discharge bar and the roll was 1.5 mm, and 10
Feed the porous membrane at a speed of m/min, applied voltage 75V, applied current 6.5A, applied power 4g? , 5 V. Next, this membrane was immersed in a 1% by weight sodium alginate aqueous solution and air-dried to obtain a composite membrane having sodium alginate membranes each having a thickness of 20 U on the front and back sides of the membrane. Separately, membranes were obtained in which sodium alginate was separately composited onto the front and back sides of the membrane to a thickness of 20 μm.

Using these composite membranes, a dehydration experiment using perpaper ration of a water-ethanol aqueous solution was conducted in the same manner as in the previous example. The results are shown in Table 5.

Table 5 Examples 8-11 A porous membrane made of the same polytrifluoroethylene chloride resin hollow fibers used in Example 1 and whose surface was similarly treated to make it hydrophilic was used.

On the other hand, chitosan dope powder (average molecular weight 100,000 to 120,000, degree of deacetylation 90%) was added to an IM-acetic acid aqueous solution at a concentration of 1% by weight, 2% by weight, 3% by weight, and 5% by weight, respectively. was prepared and stirred and dissolved overnight at 25°C. After filtering these solutions through a G-2 glass filter, deaeration was performed under reduced pressure using an aspirator to prepare an aqueous chitosan solution. Next, the hollow fibers whose outer surfaces had been subjected to hydrophilic treatment were immersed in chitosan aqueous solutions of various concentrations.
A crosslinking reaction was carried out in the same manner as in Example 1.

A dehydration experiment of a water-ethanol aqueous solution was conducted in the same manner as in Example 1 using hollow fiber membranes composited with these chitosan aqueous solutions of predetermined concentrations.

The results are shown in Table 6.

Example 12 25 parts of polyvinylidene fluoride (manufactured by Pennwalt Co., USA, trade name Kynar) was mixed with 65 parts of dimethylacetamide and 10 parts of polyethylene glycol having an average molecular weight of 3000, and further 5 parts of polyoxyethylene sorbitan monomer. Oleate (manufactured by Kao Atlas Co., Ltd., trade name Tween 80) was added to form a homogeneous solution. This solution was kept at a temperature of 40° C., extruded from a hollow spinning nozzle with a gear pump, and poured into hot water at 70° C. to be molded.

Similarly, 70°C warm water was used as the core liquid. The obtained hollow fiber had an outer diameter of 2.5n+m and an inner diameter of 2.0+nm, had many voids in its cross section, and had a dense skin layer on its inner and outer surfaces. 30 pieces of this hollow fiber
% trimethylamine aqueous solution and heated at 60° C. for 8 hours to partially introduce amino groups into the surface layer of the hollow fiber.

Next, this hollow fiber was immersed in a 2% aqueous solution of chitosan acetate having a molecular weight of about 110,000, and then pulled up and dried. Then 0
．． The sample was immersed in an aqueous solution of 0.01% sodium alginate and dried again. Furthermore, in the same manner, it was repeatedly dipped and dried in an aqueous chitosan acetate solution and a sodium alginate solution five times, and finally dipped in a chitosan acetate solution and dried.

This material, in which chitosan acetate and sodium alginate were present in a layered form on the surface layer, was immersed in a solution containing 5% glutaraldehyde and 5% sulfuric acid to crosslink the chitosanic acid. lastly,
It was equilibrated in 0.5N sodium sulfate to form a composite membrane.

Using this membrane, 80% ethanol, 10% methanol,
A 10% water mixed solution was dehydrated.

Conducted at 60°C and 2 Torr, permeate volume was 0.7 kg.
/Hr-m2, the separation coefficient of water to total alcohol content was 28,000.

On the other hand, when a similar thin film was formed on a hollow fiber of polyvinylidene fluoride that had not been treated with trimethylamine, the permeate amount was 1.2 kg/m2°Hr and the separation coefficient was 400.

Example 13 The porous flat membrane of polytetrafluoroethylene synthesized in Example 3 was placed on a glass plate, and the surface was averagely polished in the transverse and longitudinal directions with 1500-grit sandpaper. When this surface was observed using a scanning electron microscope, irregularities of approximately 0.1 to 0.2 μm were observed uniformly over the entire film.

The surface of this surface-roughened membrane was subjected to exactly the same treatment as in Example 3, such as immersing it in a 5% aqueous solution of chitosan acetate having a molecular weight of about 10,000, pulling it up and drying it.
Ethanol-based pervaporation was performed. The results are shown in Table 7. Note that when the cross section of the membrane was observed using a scanning electron microscope, the thickness of the chitosan layer was approximately 3 μm.

Table 7

Claims (2)

[Claims] (1) At least one surface of a porous membrane made of a polymeric polymer is given a hydrophilic group in advance or the surface is roughened, and then the surface has a glucoside group in the main chain and an ion 1. A method for producing a composite membrane, which comprises forming a thin layer of a natural polysaccharide or a derivative thereof having a functional group. (2) The method for producing a composite membrane according to claim 1, wherein the natural polysaccharide or its derivative is chitosan, alginic acid, or a derivative thereof.