JPH082414B2 - Water vapor selective permeable membrane - Google Patents

Description

TECHNICAL FIELD The present invention relates to a separation membrane for permeating and separating a specific component from a mixed fluid using a membrane.

More specifically, air conditioning in buildings, production of air with reduced humidity such as instrumentation compressed air, removal of water in natural gas, chemical industry, electrical / electronic industry, precision machinery industry, food industry, The present invention relates to a method for selectively permeating and separating water and water vapor from a water-containing gas by using an ion exchange membrane in the production of a humidity-controlled gas used in a wide range of fields such as textile industry.

[Prior Art] As a method for removing water vapor in a gas, it is roughly classified,
There are four known methods: (1) compression method, (2) cooling method, (3) adsorption method, and (4) membrane separation method.

The membrane separation method is a method in which a gas containing water vapor is brought into contact with one surface of the diaphragm and the water vapor is selectively permeated and separated from the other surface. In principle, the running cost is lower than that of the other three methods, and the device structure is low. However, it has an advantage that it can obtain a dry gas continuously without contaminating the gas, but it has hardly been put into practical use because there is no diaphragm having excellent water vapor permeability.

For example, JP-A-53-97246, JP-A-54-11481, and JP-A-54-54
-152679, JP 60-183025, JP 61-195117, JP 6
2-42723 describes a water-absorbing polymer membrane and a dehumidifying membrane made of a membrane material with large gas permeability used for oxygen separation and hydrogen separation, but it has a low water vapor transmission rate and separation from water vapor and gas. The coefficient is not enough.

Further, for the purpose of improving the amount of water vapor permeation and the film strength, a composite film of a polysulfone porous film, a polypropylene porous film, and a polytetrafluoroethylene porous film is used as a thin film, and the composite film is disclosed in JP-A-53-86684 and JP-A-60. -257819, JP-A-60-261
503, JP-A-62-42772 and the like, although these have improved the membrane strength, they do not have a sufficient amount of water vapor permeation and have a small water vapor selective permeation coefficient.

On the other hand, perfluoroion exchange membranes containing sulfonic acid groups in their side chains, which are used in fuel cell membranes and electrolysis membranes, have high water absorption and a high water permeation rate in the polymer. considered effective as a material, a dehumidifier using a hollow tube of perfluorosulfonic acid polymers, are described in USP3735558, perm pure dry ^R
Available as. However, it has a low water vapor transmission rate, so in industrial applications that process large amounts of gas,
It has the drawback that it cannot replace the conventional freezing method or adsorption method.

Further, Japanese Patent Laid-Open No. 62-7417 describes a dehumidifying membrane which produces a gas having a low dew point temperature by heat-treating a hollow fiber made of a perfluorosulfonic acid polymer. However, there is a drawback that the water vapor permeation rate is significantly reduced due to the removal of

[Problems to be solved by Honmei]

The present invention is intended to solve the above-mentioned drawbacks of the prior art, and an object thereof is to provide a novel dehumidifying membrane having a large water vapor transmission rate and a large water vapor selective permeation coefficient.

It is an object of the present invention to provide a dehumidifying film that can be used for dehumidification of natural gas, dehumidification of corrosive gas that cannot be used in the prior art, and the like, in addition to the production of compressed air for instrumentation and instrumentation according to the prior art. To do.

[Means for Solving the Problems] The above object of the present invention is to provide a multilayer film comprising at least two layers of a resin layer substantially free of ion-exchange groups and an ion-exchanger layer. The water absorption rate is achieved by a water vapor selective permeable membrane composed of a super absorbent resin that is larger than the ion exchanger layer.

The water vapor selective permeable membrane of the present invention is basically a combination of a water-absorbing membrane containing no ion-exchange group and a water-absorbing membrane containing an ion-exchange group, which is a novel feature that has never been seen before. It is based on various ideas and knowledge.

The present inventor has proposed a membrane having excellent water vapor selective permeability,
As a result of diligent research, water-absorbent polymer membranes represented by vinylon films and polyacrylamide gel membranes have lower water vapor permeability than ion-exchange membranes, but have low water vapor permeability. It has been found that when the water absorption rate is increased, the water vapor permeability is improved up to a certain range, but when the water absorption rate is excessively increased, the water vapor permeability is rather decreased. As a result of further studying the water vapor permeability, the unexpected fact that the laminated film of the highly water-absorbing membrane containing no ion exchange group and the ion exchange membrane as described above is higher than the water vapor transmission rate of each single membrane is found. They have found the present invention and completed the present invention.

The reason why the multilayer film of the present invention enhances the water vapor permeability has not been clarified, but it is considered to be probably due to the following reason.

That is, when water vapor permeates the membrane, it is subject to the following three steps of rate limiting. The first step is the dissolution and absorption of water vapor on the membrane surface, the second step is the diffusivity of water vapor in the membrane, and
The third step is water vapor desorption on the permeate side of the membrane.

Compared with the ion exchange membrane, the superabsorbent polymer membrane has a low solubility of water vapor in the first step, even though it has a high dissolving and absorbing ability on the membrane surface. On the other hand, in the ion exchange membrane, if the water absorption rate is excessively increased, that is, if the fixed ion concentration in the membrane decreases, the permeability of water vapor decreases. It is explained that the properties, especially the diffusivity in the second step or the water vapor desorption property in the third step, are enhanced.

Thus, by contacting water vapor with the super absorbent resin layer to enhance the dissolution and absorption of water vapor on the membrane surface, while desorbing water vapor from the ion exchanger layer, the permeation of water vapor from each single layer membrane It is described that a high speed membrane is obtained. However, such description is provided for the purpose of understanding the present invention and does not limit the present invention in any way.

The present invention will be described in more detail below. The ion exchanger layer constituting the present invention has a fixed ion concentration of 1 to 6 meq / g H ₂ O, a water absorption rate of 30% by volume or more, and a film thickness of 0.1 to 250 μm.
It is preferably m. Here, the fixed ion concentration is indicated by the ion exchange capacity per 1000 g of water absorbed by the membrane, and the water absorption rate is indicated by% of the volume adsorbed with pure water at 25 ° C with respect to the volume of the dry resin. It is a thing.

When the fixed ion concentration is out of the above range, the water vapor permeability is lowered, so 2 to 5 N is particularly preferably used.
When the water absorption rate is less than 30% by volume, the amount of dissolved and absorbed water vapor in the film is small, so the water vapor permeation rate decreases, and when it exceeds 500% by volume, the mechanical strength of the film decreases remarkably.
0% by volume, preferably 40-250% by volume of ion exchanger layer is used.

Thus, the ion exchanger layer constituting the present invention can be used without any limitation as long as the fixed ion concentration and the water absorption rate have the above-mentioned specific ranges.

Examples of the type of ion-exchange group include cation-exchange groups such as sulfonic acid, sulfonate, carboxylic acid, carboxylate, phosphoric acid, phosphate, acidic hydroxyl group and acidic hydroxide, and 1 to 3
Anion exchange groups such as a secondary amino group and a quaternary ammonium group can be exemplified, but among them, sulfonic acid has high water absorption and also has a high permeation rate in the membrane, so that it is particularly preferable as the first ion exchange layer. Ion exchange capacity 0.8-5.0
A sulfonic acid membrane of milliequivalent / g resin is used.

As the material of the sulfonic acid-containing film, cellulose-based, polyolefin-based, acrylic-based, vinyl acetate-based, polystyrene-based, polysulfone-based, and fluorine-containing polymerization-based materials are used without any limitation. As a method for introducing a sulfonic acid group into these materials, a sulfonic acid group or a monomer that can be converted into a sulfonic acid group is copolymerized, impregnated or graft polymerized, or concentrated sulfuric acid, chlorosulfonic acid,
A method of directly introducing a sulfonic acid group with a sulfonating agent such as sulfuric anhydride / triethyl phosphate complex can be used. Of these, a fluorinated sulfonic acid membrane and a sulfonated polysulfone membrane, which have good mechanical strength, heat resistance, chemical resistance, moldability, especially thin film forming ability and multi-layer forming ability, are preferable.

Fluorine-containing sulfonic acid membrane has a general formula The perfluorosulfonic acid membrane having an ion exchange capacity of 0.65 to 2.5 meq / g resin, and more preferably 1.0 to 2.0 meq / g resin has excellent chemical resistance and moisture in a corrosive fluid. It is preferably used because it can be removed.

As the sulfonated polysulfone-based membrane, one having an ion exchange capacity of 1.0 to 3.5 meq / g resin is used. (However, Ar in the formula is Y represents a single bond, -O -, - S -, - SO 2 -, Or R _{1 to} R ₉ are the same or different hydrocarbon groups having 1 to 8 carbon atoms, a to d are 0 to 4, e is 0 to 3, f + g is 0 to 7,
h + i is 0 to 5, R ₁₀ and R ₁₁ are hydrogen, or 1 to 6 carbon atoms
Hydrocarbon group, X is halogen or --SH, m / n = 100/1 to 1 /
Indicates 10. The sulfonated product of the aromatic polysulfone / polythioether sulfone copolymer represented by) is particularly excellent in solvent resistance since it can give a cured film having a cross-linked structure, and can remove water in an organic solvent. It is preferably used.

Next, as the highly water-absorbent resin layer constituting the present invention, if the water absorption rate is larger than the ion-exchanger layer,
It is used without any restrictions, and preferably has a water absorption of 100 to 300.
Membranes having a thickness of 0.1 to 250 μm of 0% by volume of resin substantially free of ion-exchange groups can be used.

Here, the resin containing substantially no ion-exchange group means that the fixed ion concentration is generally 0.1 meq / g H ₂ O or less or the ion exchange capacity is not more than 0.1 meq / g resin. Resins with extremely low selectivity are also included.

As such a super absorbent polymer, a starch-based, cellulose-based, polyvinyl alcohol-based, acrylic-based single film, or acrylonitrile graft, acrylic acid graft, styrene sulfonic acid graft, vinyl sulfonic acid graft, or water-soluble Examples include cross-linked resins, preferably polyvinyl alcohol acetal cross-linked film, acrylic acid-bikenized film, and acrylamide-bisacrylamide cross-linked film having heat resistance, chemical resistance, and graded water.
It is used because of its excellent hygroscopicity.

Thus, the above-mentioned ion exchanger layer and superabsorbent resin layer are made into a multilayer by an appropriate method. For example, in the case where at least one is a thermoplastic resin, at a decomposition temperature or less, a method of thermocompression bonding, or at least one,
In the case of forming a coating film from a resin solution, a coating method or a method of polymerizing a monomer or a prepolymer on one film to form a coating multilayer is used.

The thickness of such a multilayer film can be made as thin as possible in order to increase the water vapor transmission rate. However, in the multilayer film of the present invention, when the film thickness is reduced, it is recognized that the water vapor selective permeation coefficient is lowered, so that the total film thickness is preferably 0.2 to 500 μm, particularly 2 to 250 μm, and ion exchange. The ratio of the thickness of the body layer and the super absorbent polymer layer is 1/99 ~
It is preferably used from the viewpoint of the balance between water vapor permeability and film strength by forming multiple layers at 99/1, particularly 33/70 to 90/10.

The multi-layer water vapor permeable membrane thus obtained can be used as it is, but when the multi-layer membrane is further used in combination with a porous substrate having an inner pore wall having hydrophilicity, the water vapor permeability is It is preferable for obtaining a film having excellent mechanical strength. The reason why the inner wall of the pores of the porous substrate must have hydrophilicity is not always clear, but when using a porous substrate that does not have hydrophilicity, the water vapor permeation of the multilayer film alone Compared with the speed, when it is reduced to 1/3 to 1/4, on the other hand, when a porous substrate coated with a hydrophilic layer is used, the water vapor transmission rate is further improved in comparison with that of a multilayer film. can do. Further, the porous substrate is laminated on the super absorbent polymer layer and / or the ion exchanger layer, but it is preferable that the porous substrate is laminated on the ion exchanger layer side in order to obtain high water vapor permeability. Many.

The multi-layer water vapor selective permeable membrane thus obtained is preferably contacted with a gas containing water vapor on the highly water-absorbent resin layer side, and contacted with a dry gas on the ion exchanger layer side, or with reduced pressure. By allowing water vapor to permeate, it can be used as a water vapor selective permeable membrane having a further improved water vapor permeability as compared with a single-layer membrane.

Next, the present invention will be described by way of examples, but the present invention is not limited to such examples.

Prior to the examples, various measuring methods used in the following examples will be collectively described.

(1) Measurement of water absorption W A single ion-exchanger layer produced under the same conditions as the multilayer membrane whose permeability is measured is immersed in pure water at 25 ° C. to obtain a membrane weight W ₁ ,
The ion exchange layer is vacuum dried to obtain the weight W ₂ of the dry film and the density ρ of the dry film by the following formula.

W = 100 (W ₁ −W ₂ ) / W ₂ ÷ ρ (2) Calculation of fixed ion concentration A _{W From} the ion exchange capacity (m eq / g resin) A _R and W ₁ and W ₂ above, Ask.

A _W = A _R / (W ₁ −W ₂ ) ÷ W ₂ (3) Measurement of water vapor transmission rate Q (m ³ (STP) / m ² .hr.atm) Calculate the water vapor transmission rate.

(4) Water vapor selective permeation coefficient α The permeation rate Q _A of the gas A is obtained with a Seikaken-type gas permeation measuring instrument and calculated by the following equation.

α _A = Q / Q _A [Example] Example 1 CF ₂ = CFOCF ₂ CF (CF ₃ ) O (CF ₂ ) ₂ SO ₂ F, an ion exchange capacity of 1.1 milliequivalent of a copolymer of tetrafluoroethylene. / g resin was obtained. Next, the copolymer was converted into an acid form and then dissolved in ethanol to obtain an acid type copolymer solution having a solid content concentration of 10% by weight.

The acid-type copolymer solution thus obtained was applied to one side of a vinylon film having a thickness of 65 μm and dried to laminate a perfluorosulfonic acid film having a thickness of 70 μm. The water vapor permeation rate was determined by bringing water vapor into contact with the vinylon film side of the multilayer film. The results are shown in Table 1.

Comparative Example 1 The copolymer solution used in Example 1 was applied onto a glass plate and dried to obtain a perfluorosulfonic acid single film.

The water absorption rates of the perfluorosulfonic acid film and the vinylon film used in Example 1 were 64% by volume and 118% by volume, respectively.
Met. The fixed ion concentration of the perfluorosulfonic acid film was 3.3 meq / g H ₂ O.

The water vapor transmission rate of each single film was determined, and the results are shown in Table 1.

Example 2 The perfluorosulfonic acid copolymer solution obtained in Example 1 was applied onto the surface of a PTFE porous membrane having a pore size of 1.7 μ, a porosity of 80% and a film thickness of 150 μm, and dried to obtain an ion exchanger layer having a film thickness of 10 μm. Was formed. Then, a 2 wt% ethanol solution of a perfluorosulfonic acid copolymer was impregnated into the pores of the PTFE porous membrane and dried to make the inner walls of the pores hydrophilic. The hydrophilic layer attached to the inner wall of the hole was 3 g per 1 m ² .

The water vapor transmission rate of the membrane thus obtained is 165 m ³ / m ² .h
It was r.atm.

Next, on the surface of the perfluorosulfonic acid film of the film, 5 parts by weight of acrylamide, 0.25% by weight of bisacrylamide,
A mixed solution of 0.04 part by weight of ammonium persulfate and 100 parts by weight of water was applied and polymerized to form 20 μm of a polyacrylamide gel layer having a water absorption rate of 2000% by volume. The polyacrylamide gel layer of the thus obtained multi-layer membrane was contacted with water vapor and the water vapor transmission rate was determined to be 200 m ³ / m ² .hr.atm.

Example 3 A sulfonated polysulfone-polythioether sulfone copolymer represented by the following formula was obtained.

m / n = 1/1 Ion exchange capacity 1.85 meq / g resin Next, the copolymer was dissolved in N-methylpyrrolidone, and then the solution was cast on a glass plate and dried to form a membrane with a thickness of 70 μm. Obtained.

The film thus obtained was hydrated in pure water at 100 ° C.,
The water absorption rate and water vapor transmission rate were calculated to be 83% at 70% by volume.
It was m ³ / m ² .hr.atm.

Then, on one surface of the film, the water absorption rate was 15 in the same manner as in Example 2.
A 30% volume of 00% polyacrylamide gel was formed. The water vapor transmission rate of the obtained multilayer film is 110 m ³ / m ² .hr.
It was atm.

[Brief description of drawings]

 FIG. 1 shows a schematic view of an apparatus for measuring water vapor transmission rate. 1 ... Water vapor permeation measuring cell 2 ... Water vapor chamber side pressure gauge 3 ... Permeation chamber side pressure gauge 4 ... Moisture aggregation trap 11 ... Porous support 12 ... Measurement sample membrane 13 ... Water vapor 14 …… Pure water

Claims (8)

[Claims] 1. A multi-layer membrane comprising at least two layers of an ion-exchange group and a resin layer which does not substantially contain an ion-exchange group, wherein the resin layer has a higher water absorption rate than that of the ion-exchange layer. A water vapor selective permeable membrane comprising a resin. 2. The ion exchanger layer has a fixed ion concentration of 1 to 6.
Milli-equivalent / g H ₂ O, water absorption 30% by volume or more, film thickness 0.1-250μ
The water vapor selective permeable membrane according to claim 1, wherein m is m. 3. The ion exchange layer has an ion exchange capacity of 0.65 to.
The water vapor selective permeable membrane according to claim 1, which is a fluorinated sulfonic acid membrane of 2.5 meq / g resin. 4. The ion exchange layer has an ion exchange capacity of 1.0 to
The water vapor selective permeable membrane according to claim 1, which is a sulfonated polysulfone membrane of 3.5 meq / g resin. 5. The water vapor selective permeable membrane according to claim 1, wherein the highly water-absorbent resin has a water absorption rate of 100 to 3000% by volume and a film thickness of 0.1 to 250 μm. 6. A water vapor selective permeable membrane according to claim 1, wherein the thickness of the multilayer film of the super absorbent polymer and the ion exchanger layer is 0.2 to 500 μm. 7. A water vapor selective permeable membrane according to claim 1, wherein the multi-layer membrane of the super absorbent polymer and the ion-exchange layer is compounded with a porous base material having hydrophilicity on the inner wall of the pores. . 8. A gas containing water vapor is brought into contact with the super absorbent resin side and a dry gas is brought into contact with the ion exchanger layer side,
Alternatively, the vapor permeation method of the vapor permselective permeable membrane according to any one of claims 1 to 7, wherein vapor is selectively permeated by reducing the pressure.