JPH1176774A - Separation membrane for dehydration and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a separation membrane for dehydration having sufficiently high water separating performance to a mixed soln. or a mixed vapor of high concn. water and an org. solvent. SOLUTION: The separation membrane for dehydration is formed using the dialdehyde crosslinked quaternized chitosan obtd. by quaternizing a part of the amino group (-NH2 ) of chitosan as shown by the formula (where R1 -R3 are 1-4C alkyl and X<-> is Cl<-> , Br<-> or I<-> ). When the chitosan is made hydrophilic, the separation membrane has enhanced selective water permeability. It is preferable that 5-49% of the amino groups of the chitosan are quaternized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a separation membrane for dehydration used for separating water from a mixed solution of water and an organic solvent or a mixed vapor to dehydrate water.

[0002]

2. Description of the Related Art A method of separating water from a mixed solution of water and an organic solvent, such as a water-alcohol mixed solution, or a mixed vapor,
That is, a distillation method is mainly used as a dehydration method. The distillation method is a method of separating water by utilizing a difference in boiling points of respective components of a mixed solution, and requires a considerable amount of heat energy to heat the mixed solution. In addition, in order to highly dehydrate and concentrate a mixed solution having an azeotropic point, an azeotropic distillation operation must be performed.

[0003] From such a background, in recent years, a membrane separation method has been proposed as a separation method instead of the distillation method.
In this membrane separation method, for example, a mixed solution or a mixed vapor composed of water and an organic solvent is brought into contact with one surface of the membrane, and the water in the mixed solution or the mixed vapor is selectively permeated into the membrane and allowed to permeate the membrane. This is a method of extracting water from the other side of the membrane to separate the water from the mixed solution or mixed vapor and dewatering. As described above, the membrane separation method has various advantages such as energy saving, easy separation of an azeotrope, and a compact apparatus because the separation mechanism is completely different from that of the distillation method.

[0004] The separation and dehydration performance in such a membrane separation method depends on the performance of the membrane. Accordingly, various separation membranes for dehydrating a mixed solution or a mixed vapor composed of water and an organic solvent by a membrane separation method have been proposed. For example, chitosan is known as a membrane material that transmits water preferentially, and Japanese Patent Publication No. 5-53528 proposed by the present applicant discloses a membrane formed from chitosan derivatives obtained by crosslinking chitosan with dialdehyde. Have been.

[0005]

Problems to be Solved by the Invention
The dialdehyde-crosslinked chitosan provided in Japanese Patent Publication No. 28 is highly capable of dehydrating ethanol by separating water from a mixed solution of water and an organic solvent, for example, a water-ethanol mixed solution, and particularly has an ethanol concentration of 30 to 70% by weight. % Ethanol aqueous solution. However, a high-concentration aqueous ethanol solution having an ethanol concentration of more than 90% does not necessarily have sufficient water separation performance, and has room for improvement.

The present invention has been made in view of the above points, and provides a separation membrane for dehydration having sufficiently high water separation performance with respect to a mixed solution or a mixed vapor of high-concentration water and an organic solvent. The purpose is to do so.

[0007]

Dehydrating the separation membrane according to claim 1 of the present invention solving the problem to means for the], a part of the chitosan amino groups (-NH ₂₎ is a quaternary quaternized as the following structural formula Of chitosan,

[0008]

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It is characterized by being formed of a crosslinked dialdehyde. The invention of claim 2 is characterized in that 5 to 40% of the amino groups of chitosan are quaternized. The invention of claim ₃ is characterized in that R ₁ , R ₂ and R _{3 in} the above structural formula are methyl groups.

[0010] A fourth aspect of the present invention, the above structural formula X ^-
Is Cl ⁻ . The method for producing a separation membrane for dehydration according to claim 5 of the present invention is characterized in that an acid aqueous solution containing the quaternized chitosan, dialdehyde and acid catalyst is heated and dried to form a film. .

Further, in the method for producing a separation membrane for dehydration according to claim 6 of the present invention, the aqueous solution containing the quaternized chitosan, dialdehyde and acid catalyst is heated and dried to form a film. The surface is treated with an aqueous solution containing a dialdehyde and an acid catalyst and dried.

[0012]

Embodiments of the present invention will be described below. Chitosan can be obtained by deacetylating chitin and is a cationic polymer soluble in dilute acid. Here, chitin is a linear polysaccharide that forms a supporting tissue of crustaceans and fungi and is the largest unused organic resource, and the present invention has been evaluated as an effective utilization technology of this chitin. You. The production of a separation membrane for dehydration using this chitosan is already known, as can be seen from the above-mentioned Japanese Patent Publication No. 5-53528. However, a water-organic solvent mixed solution or mixed vapor is used. In order to selectively allow moisture to pass through the membrane, it is necessary to increase the hydrophilicity of the membrane. Therefore, in the present invention, quaternized chitosan having quaternized chitosan to enhance hydrophilicity is used.

That is, chitosan is a polymer having a component represented by the following chemical formula 3 as a main repeating unit.

[0014]

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The quaternized chitosan is obtained by trialkylating a part of the amino group (-NH ₂ ) in the structural formula of Chemical Formula 3 with a halogen ion as a counter ion as in Chemical Formula ₂ above. And a part of the repeating unit has the following structural formula.
In the structural formula of Chemical Formula 4, R ₁ , R ₂ , and R ₃ represent —C
H ₃ , —C ₂ H ₅ , —C ₃ H ₇ , or —C ₄ H ₉ , and R ₁ , R ₂ , and R ₃ may be the same or different. Among them, those in which R ₁ , R ₂ and R ₃ are each —CH ₃ are the most practical. In the structural formula of Chemical Formula 4, X ⁻ is any one of a chloride ion (Cl ⁻ ), a bromine ion (Br ⁻ ), and an iodine ion (I ⁻ ). Among them, X ⁻ is preferably Cl ⁻ in terms of stability of the separation membrane and permeation separation performance.

[0016]

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Therefore, the quaternized chitosan can be represented by the following structural formula (Chemical Formula 5).
The left component and the right component are m: n (m and n are positive integers)
Indicates that they are randomly and linearly linked in the ratio of).

[0018]

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In producing the quaternized chitosan represented by Chemical Formula 5, for example, chitosan is reacted with a quaternizing agent such as alkyl iodide in a suitable solvent,
An iodine-type quaternized chitosan having an iodine ion as a counter ion can be obtained. Further, by reacting the iodine-type quaternized chitosan thus prepared with sodium chloride to convert iodine ion and chloride ion, chlorine-type quaternized chitosan having chloride ion as a counter ion can be obtained. Alternatively, by reacting with iodine-type quaternized chitosan using sodium bromide instead of sodium chloride, brominated quaternized chitosan having a bromine ion as a counter ion can be obtained. Examples of the alkyl iodide used as the quaternizing agent include methyl iodide, ethyl iodide, n-propyl iodide, n-butyl iodide, and mixtures thereof.

In the present invention, the quaternized chitosan has a quaternization degree ((n / (m +
n) × 100) is preferably 5 to 40%, that is, chitosan in which 5 to 40% of amino groups are quaternized, and more preferably 8 to 25%. When the quaternization degree is less than 5%, the hydrophilicity is not sufficient, and it is difficult to obtain practical water selective permeation performance. Conversely, the degree of quaternization is 40%
If it exceeds, the hydrophilicity becomes too high, the membrane absorbs water and swells excessively, and the permeation rate of the membrane becomes high, but the selective separation performance with respect to water may be reduced.

As described above, quaternized chitosan has high hydrophilicity and is water-soluble. Therefore, in order to use this quaternized chitosan as a water-organic solvent mixed solution or a mixed vapor separation membrane, it is necessary to insolubilize it in water.In the present invention, quaternized chitosan reacts with dialdehyde under an acidic catalyst. Then, it is made insoluble in water by crosslinking with dialdehyde. When a dialdehyde is allowed to act on quaternized chitosan under an acidic catalyst, an amino group of the quaternized chitosan and an aldehyde undergo a condensation reaction, as shown in the following structural formula of Chemical Formula 6, as an example of a crosslinked structure, Each molecule of the quaternized chitosan is cross-linked by using a Schiff base (-N = CH-) as a cross-linking point to form a three-dimensional structure and become insoluble in water (hereinafter, "Chemical Formula 6").
Is a model showing the outline of the structure of the molecule, and does not accurately represent the structural formula).

[0022]

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Here, the dialdehyde includes glyoxal, malondialdehyde, succindialdehyde,
Glutaraldehyde, adipindialdehyde, maledialdehyde, phthaldialdehyde, isophthaldialdehyde, terephthaldialdehyde, dialdehyde starch and the like can be used. As the acidic catalyst,
Inorganic acids such as hydrochloric acid, sulfuric acid and nitric acid, and organic acids such as formic acid, acetic acid, propionic acid, butyric acid, oxalic acid, malonic acid, succinic acid, glutaric acid and adipic acid can be used.

Next, the production of a separation membrane formed by the crosslinked dialdehyde of quaternized chitosan will be described. First, while dissolving quaternized chitosan in water,
An acid aqueous solution of quaternized chitosan and dialdehyde is prepared by adding an acid catalyst and dialdehyde thereto. Next, the quaternized chitosan and dialdehyde acid aqueous solution are cast into a film by casting or the like, and then dried by heating.
A separation membrane for dehydration comprising quaternized chitosan cross-linked with dialdehyde can be obtained.

In this way, a separation membrane for dehydration comprising quaternized chitosan crosslinked with dialdehyde can be obtained. The surface of this membrane is further treated with an aqueous solution of dialdehyde and an acid solution of dialdehyde containing an acid catalyst. Preferably, by treating and drying, the quaternized chitosan on the membrane surface is further crosslinked with dialdehyde to increase the degree of crosslinking on the membrane surface. At this time, if an organic solvent such as alcohol is mixed with the aqueous acid solution of dialdehyde, the degree of cross-linking on the surface of this film is increased while suppressing the swelling of the quaternized chitosan film cross-linked with dialdehyde. You can do so. As described above, by increasing the degree of cross-linking on the surface of the separation membrane for dehydration, the permselectivity to water can be dramatically improved. In addition, when used as a composite film as described below, the stability of the film can be improved, and peeling and swelling can be suppressed.

In order to improve the processing capacity of the separation membrane for dehydration, it is desirable to form the film with a small thickness. However, if the membrane is made thin, the mechanical strength is impaired. In this case, the mechanical strength is high. It is preferable to form a separation membrane for dehydration on the surface of a support such as a porous film, a tube, or a hollow fiber, and use it as a composite membrane. The separation membrane for dehydration according to the present invention obtained as described above includes water-methanol, water-ethanol, water-n-propyl alcohol, water-iso.
Propyl alcohol, water-n-butyl alcohol, water-i
so-butyl alcohol, water-tert-butyl alcohol, water-pentyl alcohol, water-acetone, water-methyl ethyl ketone, water-methyl isobutyl ketone, water-diethyl ether, water-1,4 dioxane, water-tetrahydrofuran, water-methyl acetate, Water-ethyl acetate, water-
N, N dimethylformamide, water-N, N-dimethylacetamide, water-dimethylsulfoxide, water-ethylene glycol, water-glycerin, etc. to separate and dehydrate water from a mixed solution or mixed vapor of water and an organic solvent What is used.

[0027]

Next, the present invention will be described specifically with reference to examples. Example 1 33 g of chitosan (manufactured by Koyo Chemical Co., Ltd., average molecular weight: 350,000, degree of deacetylation: 100%) was stirred and dispersed in 2300 mL of a 60% by volume aqueous methanol solution,
66 mL of methyl iodide was added thereto, and the mixture was reacted at 50 ° C. for 8 hours to prepare trimethyl-type quaternized chitosan having iodine ions as counter ions. Next, 93 g of sodium chloride was added thereto, and the mixture was further stirred for 30 minutes to cause a reaction. The reaction solution was poured into 12 L of acetone, and trimethyl-type quaternized chitosan having chloride ion as a counter ion (“Chemical Formula 4”) In the structural formula of R ₁ , R ₂ , R
The crude product ( ₃ was a methyl group) was precipitated. After the precipitate was dried under reduced pressure at room temperature, it was dissolved in water at a concentration of 2.5% by weight, and the solution was poured into 7 times the volume of acetone.
Reprecipitation was performed. By repeating this reprecipitation operation twice, a purified product of trimethyl-type quaternized chitosan having a chloride ion as a counter ion was obtained. As a result of analyzing the obtained quaternized chitosan by ¹ H-NMR, the degree of quaternization was 15%. From the calculation of the weight of the obtained quaternized chitosan, the yield was 75%.

Next, 2 g of the quaternized chitosan was added to 9 parts of distilled water.
Then, 2.5 g of a 1% by weight glutaraldehyde aqueous solution and 2.5 g of a 0.01 N hydrochloric acid aqueous solution were added to the solution, and the mixture was uniformly stirred and mixed, followed by filtration and defoaming. Thus, an aqueous hydrochloric acid solution of quaternized chitosan and glutaraldehyde was prepared. This quaternized chitosan and glutaraldehyde aqueous solution of hydrochloric acid is 14cm x 14c with outer frame.
m, cast 80 g on the surface of a smooth glass plate, cast and dried at 60 ° C.
To obtain a dialdehyde-crosslinked quaternized chitosan membrane.

This dialdehyde crosslinked quaternized chitosan membrane was used as a separation membrane for dehydration in the apparatus shown in FIG. 1 to separate and dehydrate a mixed vapor of water and ethanol. That is, FIG.
In the apparatus described above, the separation tank 2 is separated from the decompression separation membrane 1 by the decompression chamber 4 on the upper side.
And a lower solution chamber 3.
A mixed solution 5 of water and an organic solvent supplied to the solution chamber 3 is prevented from coming into contact with the separation membrane 1 for dehydration. In FIG. 1, 6 is a constant temperature water bath, 7 is a pipe connected to a condenser,
Reference numeral 8 denotes a cold trap, which is a mixed solution 5 in the solution chamber 3.
Is heated in a constant temperature water bath, and the pressure inside the decompression chamber 4 is reduced by a decompression pump connected via a cold trap 8. Then, the mixed solution 5 is heated to generate a mixed vapor of water and an organic solvent, and the mixed vapor is brought into contact with the separation membrane 1 for dehydration and the pressure in the decompression chamber 4 is reduced. This is to selectively permeate and diffuse into the membrane 1 and vaporize the water selectively permeating the dehydration separation membrane 1 from the surface of the dehydration separation membrane 1 on the decompression chamber 4 side. The dewatering can be performed from the mixed solution 5 by allowing the water in the liquid to permeate through the separation membrane 1 for dehydration and separating.

In Example 1, the mixed solution of water and ethanol was heated, and a mixed vapor of water and ethanol at a concentration of 60 ° C. having the concentration shown in Table 1 was supplied to one side of the separation membrane for dehydration under atmospheric pressure. The pressure was reduced to 0.01 mmHg on the opposite side of the separation membrane. Table 1 shows the permeation rate, the separation coefficient, and the ethanol concentration of the permeate during this separation. The permeation rate was expressed as a permeation amount per unit time and per unit membrane area based on the weight of the vapor permeated through a dewatering separation membrane, collected by a trap cooled with liquid nitrogen and liquefied. The larger the value of the permeation rate, the higher the treatment capacity of the separation membrane for dehydration.

The separation coefficient α was calculated from the following equation by measuring the concentration of ethanol in the permeate by quantifying the liquefied vapor trapped in the permeate through the separation membrane for dehydration by gas chromatography. α _{B / A} = (Y _B / Y _A ) / (X _B / X _A ) where X _A and X _B are the same as the mixed vapor supplied to the separation membrane for dehydration or the A component in the mixed solution. It is the weight fraction of component B, and in the case of a water-ethanol mixture system, component A is E
The tOH and B components become H ₂ O. Y _A and Y _B are the weight fractions of the A component and the B component in the permeated liquid obtained by permeating the membrane. In the case of the water-ethanol mixture system, the A component is Et.
OH and B components become H ₂ O. As the value of the separation coefficient α is larger, water is selectively permeated better than ethanol, and water is more efficiently separated.

[0032]

[Table 1]

(Example 2) A 0.5N aqueous solution of glutaraldehyde was added to 400 mL of a 0.5% by weight aqueous solution of 0.5N sulfuric acid in 100 mL.
Then, the dialdehyde-crosslinked quaternized chitosan film obtained in Example 1 was immersed in the solution at room temperature for 1 minute, washed with water and dried to obtain a surface of the film. Further cross-linked film thickness 20μ
m of dialdehyde crosslinked quaternized chitosan membrane was obtained.

This dialdehyde-crosslinked quaternized chitosan membrane was used as a dehydration separation membrane in the apparatus shown in FIG. 1 in the same manner as in Example 1 to separate and dehydrate a mixed vapor of water and ethanol. Table 2 shows the permeation rate, the separation coefficient, and the ethanol concentration of the permeate during this separation.

[0035]

[Table 2]

From the comparison of the results in Tables 1 and 2, it was confirmed that the separation coefficient was improved by several times by further crosslinking the surface of the dialdehyde-crosslinked quaternized chitosan membrane as in Example 2. Is done. (Comparative Example 1) 200 g of a 1N acetic acid aqueous solution was added to 2.0 g of a powder of chitosan (average molecular weight of 50,000 to 100,000, deacetylation degree of 99.1%), and the mixture was stirred and dissolved at 25 ° C overnight, and this solution was dissolved. After filtering through a G2 glass filter, the mixture was degassed under reduced pressure using an aspirator. 20 g of the obtained chitosan solution was cast on the surface of a siliconized glass plate,
And then dried for 5 hours to form a chitosan acetate membrane. The membrane is peeled off, immersed in a 1N aqueous solution of NaOH overnight to neutralize, washed sufficiently with water and dried at room temperature under reduced pressure. Thus, a chitosan film having a thickness of 20 μm was obtained. The thus obtained chitosan film is immersed in a solution prepared by adding a 0.5N aqueous sulfuric acid solution as a catalyst to a 0.4% by weight glutaraldehyde aqueous solution at room temperature for 15 minutes,
The crosslinked chitosan was washed with water, and dried under reduced pressure at room temperature to obtain a 20 μm-thick dialdehyde crosslinked chitosan film provided in the above-mentioned Japanese Patent Publication No. 5-53528.

This dialdehyde crosslinked chitosan membrane was used as a dehydration separation membrane in the apparatus shown in FIG.
Water / ethanol mixed vapor was separated and dehydrated. Table 3 shows the permeation rate, separation coefficient, and ethanol concentration of the permeate during this separation.

[0038]

[Table 3]

Comparison of the results in Tables 2 and 3 shows that the separation coefficient of the dialdehyde-crosslinked chitosan membrane of Comparative Example 1 is on the order of several thousands, whereas the dialdehyde-crosslinked quaternized chitosan of Example 2 is different. The separation factor of the membrane is 10,000 or more, confirming that the dialdehyde-crosslinked quaternized chitosan membrane has much better separation performance. Example 3 Polyethersulfone (“A-300N” manufactured by Teijin Amoko Engineering Plastics)
T ": 36 g of PES, 144 g of dimethylformamide, polyethylene glycol (molecular weight: 60)
0) A uniform solution consisting of 20 g was prepared, and the solution was filtered and defoamed.
The glass plate is cast into a solid PES film having a thickness of 70 μm by immersing the whole glass plate in water for solidification at 5 ° C. for phase inversion, washing the plate sufficiently with water and air-drying. Was.

The aqueous solution of hydrochloric acid of quaternized chitosan and gluaraldehyde obtained in Example 1 was cast at a thickness of 0.3 mm on the surface of this porous PES film and dried at 60 ° C. to obtain a porous PES film. Dialdehyde cross-linked quaternized chitosan membrane was composited with the film. This composite membrane was used for 0.
A dialdehyde-crosslinked quaternized chitosan is immersed in a glutaraldehyde sulfate aqueous solution prepared by adding 100 mL of a 0.5N sulfuric acid aqueous solution as a catalyst to 400 mL of a 5% by weight glutaraldehyde aqueous solution at room temperature, and then washed and dried with water. The surface of the membrane was further crosslinked.

When the composite film of the porous PES film thus obtained and the dialdehyde-crosslinked quaternized chitosan film was observed with a scanning electron microscope, it was found that the porous PES film had a uniform thickness of 2 μm on its surface. It was confirmed that an aldehyde-crosslinked quaternized chitosan film was formed. This dialdehyde cross-linked quaternized chitosan composite membrane was used as a dehydration separation membrane in the apparatus shown in FIG. 1 in the same manner as in Example 1 to separate and dehydrate a mixed vapor of water and ethanol. Table 4 shows the permeation rate, separation coefficient, and ethanol concentration of the permeate during this separation.

[0042]

[Table 4]

Comparing the results in Table 4 with those in Table 2, it was confirmed that the separation coefficients were almost the same, and that the separation performance was high even if the dialdehyde-crosslinked quaternized chitosan membrane was compounded. Is done. (Example 4) The dialdehyde-crosslinked quaternized chitosan composite membrane obtained in the same manner as in Example 3 was used as a separation membrane for dehydration of the apparatus shown in FIG. 1 to separate and dehydrate water-isopropyl alcohol mixed vapor. Was. Separation conditions were the same as in Example 1, and water-isopropyl alcohol mixtures having various concentrations were used. Table 5 shows the permeation rate, the separation coefficient and the isopropyl alcohol concentration of the permeate during this separation.

[0044]

[Table 5]

As shown in Table 5, it is confirmed that the dialdehyde-crosslinked quaternized chitosan membrane has a high separation performance even with a water-isopropyl alcohol mixed system. (Example 5) Porous PE produced in the same manner as in Example 3
On the surface of the S film, quaternized chitosan obtained in the same manner as in Example 1 and an aqueous hydrochloric acid solution of gluaraldehyde were added in an amount of 0.1 mL.
By casting at a thickness of 1 mm and drying at 60 ° C., a dialdehyde-crosslinked quaternized chitosan membrane was composited with the porous PES film. This composite membrane was used as a catalyst in 400 mL of a 0.5% by weight aqueous glutaraldehyde solution as a catalyst.
The surface of the dialdehyde-crosslinked quaternized chitosan film was further cross-linked by immersing in a glutaraldehyde sulfuric acid aqueous solution prepared by adding 100 mL of a 5N sulfuric acid aqueous solution at room temperature for 1 minute, followed by washing and drying.

When the composite film of the porous PES film thus obtained and the dialdehyde-crosslinked quaternized chitosan film was observed with a scanning electron microscope, a uniform thickness of 0.8 μm was formed on the surface of the porous PES film. As a result, it was confirmed that a dialdehyde crosslinked quaternized chitosan film was formed.
FIG. 4 is an electron micrograph of a cross section of a composite film of a porous PES film and a dialdehyde-crosslinked quaternized chitosan film at a magnification of 15,000.

The dialdehyde crosslinked quaternized chitosan composite membrane was used as a separation membrane for dehydration in a pervaporation method of the apparatus shown in FIG. 2 to separate and dehydrate a mixed solution of water and ethanol. That is, the apparatus shown in FIG. 2 is formed by separating the separation tank 2 into an upper solution chamber 3 and a lower decompression chamber 4 with a dewatering separation membrane 1, and is connected via a cold trap 8. The inside of the decompression chamber 4 is depressurized by a decompression pump. Then, a mixed solution 5 of water and an organic solvent is placed in the solution chamber 3.
Is introduced, and the pressure in the decompression chamber 4 is reduced while the mixed solution 5 is in contact with the separation membrane 1 for dehydration.
And selectively permeates and diffuses water therein to the dehydration separation membrane 1 and vaporizes water selectively permeating the dehydration separation membrane 1 from the surface of the dehydration separation membrane 1 on the side of the decompression chamber 4.
As described above, the water in the mixed solution 5 is permeated through the separation membrane for dehydration 1 to be separated, whereby the mixed solution 5 can be dehydrated.

In Example 5, the concentration of 60 ° C.
Was supplied to one side of the separation membrane for dehydration, and the pressure on the other side of the separation membrane for dehydration was reduced to 0.5 mmHg. Table 6 shows the permeation rate, separation coefficient, and ethanol concentration of the permeate during this separation.

[0049]

[Table 6]

Example 6 A dialdehyde-crosslinked quaternized chitosan composite membrane obtained in the same manner as in Example 5 was used as a separation membrane for dehydration in the apparatus shown in FIG. 3 to separate and dehydrate water-ethanol mixed vapor. Was. The apparatus shown in FIG. 3 is formed by partitioning the inside of the tank 2 with a separation membrane 1 for dehydration into a steam supply chamber 11 and a decompression chamber 4. Is decompressed. On the other hand, the mixed solution 5 of water and the organic solvent is sent from the solution tank 12 to the vaporizer 14 by the liquid sending pump 13,
The gas is vaporized at 4 and supplied to the vapor supply chamber 11 as a mixed vapor. Part of the mixed steam supplied to the steam supply chamber 11 is sent to the condenser 16 through the needle valve 15, condensed and liquefied by the condenser 16, and returned to the solution tank 12. In FIG. 3, reference numeral 17 denotes a constant temperature bath for heating the separation tank 2 and the vaporizer 14. Then, a mixed vapor of water and an organic solvent is introduced into the vapor supply chamber 11, and the pressure in the decompression chamber 4 is reduced while the mixed vapor is in contact with the separation membrane for dehydration 1. And water which selectively permeates and diffuses into the separation membrane 1 for vaporization and vaporizes from the surface of the separation membrane 1 for dehydration on the decompression chamber 4 side. The dewatering can be performed from the mixed solution 5 by allowing the water of the mixed solution 5 to pass through the dewatering separation membrane 1 and separating it.

In Example 5, mixed vapor at a temperature of 110 ° C. was supplied at a pressure of 2280 mmHg to the dialdehyde-crosslinked quaternized chitosan membrane of the composite membrane at a pressure of 2280 mmHg, and the permeate side was 0.5 m
This was performed under reduced pressure to mHg. Table 7 shows the permeation rate, separation coefficient, and ethanol concentration of the permeate during this separation.

[0052]

[Table 7]

Example 7 Polysulfone (“P-350” manufactured by Teijin Amoko Engineering Plastics)
0 ": hereinafter abbreviated as PS) to prepare a uniform solution comprising 46 g, 130 g of dimethylacetamide and 30 g of methylcellosolve, and this solution was filtered and defoamed to obtain a spinning solution.
By discharging the spinning solution from the outer tube of the double tube nozzle and simultaneously discharging water as a core solution from the inner tube and inverting the phase in a coagulation water bath at 5 ° C., a hollow fiber is formed. By thoroughly washing with water and drying, the outer shape 1.2
mm, a porous PS hollow fiber having an inner diameter of 0.8 mm was obtained.

The porous PS hollow fiber was immersed in an aqueous hydrochloric acid solution of the quaternized chitosan and glutaraldehyde obtained in Example 1, taken out, and an excess liquid was dropped. A polyaldehyde crosslinked quaternized chitosan membrane was formed into a composite PS hollow fiber. This composite hollow fiber membrane was treated with a 0.5 wt% glutaraldehyde aqueous solution 400 m
L is immersed in a glutaraldehyde sulfuric acid aqueous solution prepared by adding 100 mL of a 0.5N sulfuric acid aqueous solution as a catalyst at room temperature for 1 minute, washed with water and dried to further crosslink the surface of the dialdehyde crosslinked quaternized chitosan film. did.

When the composite hollow fiber membrane of the porous PS hollow fiber thus obtained and the dialdehyde-crosslinked quaternized chitosan membrane was observed with a scanning electron microscope, the surface of the porous PS hollow fiber was 0.2 μm thick. It was confirmed that a dialdehyde-crosslinked quaternized chitosan film was formed with a uniform thickness. This composite hollow fiber membrane is cut into a length of 18 cm and bundled into 10 bundles.
This was placed in a stainless steel pipe, and the end of the composite hollow fiber membrane was solidified with resin to form a module. The module was replaced with the separation tank 2 in FIG. 3 to separate and dehydrate water / ethanol mixed steam. Here, a mixed vapor at a temperature of 110 ° C. was supplied to the outside of the composite hollow fiber membrane at a pressure of 2280 mmHg, and the inside of the composite hollow fiber membrane was reduced to 0.5 mmHg for separation. Table 8 shows the permeation rate, separation coefficient, and ethanol concentration of the permeate during this separation.

[0056]

[Table 8]

As can be seen from Table 8, it is confirmed that even if the dialdehyde-crosslinked quaternized chitosan membrane is combined with the hollow fiber, high separation performance is obtained.

[0058]

Dehydrating the separation membrane according to claim 1 of the present invention as described above according to the present invention, the part of the chitosan amino groups (-NH _2), quaternized quaternized as the following structural formula Chitosan,

[0059]

Embedded image

Since it is formed by dialdehyde cross-linking, the performance of selectively permeating water can be enhanced by hydrophilizing chitosan, and it can be used for a mixed solution or a mixed vapor of high-concentration water and an organic solvent. Thus, a separation membrane for dehydration having sufficiently high water separation performance can be obtained. In the invention of claim 2, since 5 to 40% of the amino groups of chitosan are quaternized, it is possible to obtain appropriate hydrophilicity.
It is possible to obtain a separation membrane for dehydration having high water separation performance.

In the method for producing a separation membrane for dehydration according to a fifth aspect of the present invention, the aqueous solution of quaternized chitosan and dialdehyde is heated and dried to form a film. The graded chitosan can be crosslinked with dialdehyde, and a water-insoluble separation membrane for dehydration can be easily produced. In the method for producing a separation membrane for dehydration according to claim 6 of the present invention, the aqueous solution containing the quaternized chitosan, dialdehyde and acid catalyst is heated and dried to form a film. Since it is treated with an aqueous solution containing an aldehyde and an acid catalyst and dried by heating, the surface of the film formed by aldehyde cross-linking can be further cross-linked with aldehyde to increase the cross-linking density of the surface and separate water. The performance can be further enhanced.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an example of a separation device.

FIG. 2 is a schematic sectional view showing another example of the separation device.

FIG. 3 is a schematic sectional view showing still another example of the separation device.

FIG. 4 shows a cross section of the composite membrane of the porous PES film obtained in Example 5 and the dialdehyde-crosslinked quaternized chitosan membrane cut by 150
It is an electron micrograph enlarged to 00 times.

[Explanation of symbols]

 1 Separation membrane for dehydration

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Kenji Uchiyama 1-46-504, Aowamatanishi, Minoh-shi, Osaka (72) Inventor Kiyoko Tsutsui 8-73-23, Nishitomikagaoka

Claims (6)

[Claims] 1. A quaternized chitosan in which a part of the amino group (—NH ₂ ) of chitosan is quaternized according to the following structural formula: A separation membrane for dehydration, comprising a crosslinked dialdehyde. 2. The separation membrane for dehydration according to claim 1, wherein 5 to 40% of the amino groups of chitosan are quaternized. 3. The separation membrane for dehydration according to claim ₁ , wherein R ₁ , R ₂ , and R _{3 in the} structural formula are methyl groups. 4. The separation membrane for dehydration according to claim 1, wherein X ^{− in the} structural formula is Cl ⁻ . 5. A method for producing a separation membrane for dehydration, comprising heating and drying an aqueous solution containing the quaternized chitosan, dialdehyde and an acid catalyst according to claim 1 to form a film. . 6. An aqueous solution containing the quaternized chitosan according to claim 1 and a dialdehyde and an acid catalyst is heated and dried to form a film, and the surface of the dried film is coated with a dialdehyde and an acid catalyst. A method for producing a separation membrane for dehydration, comprising treating with an aqueous solution containing the compound and drying.