JPH05253455A - Cyclodextrine-polyvinyl alcohol composite membrane - Google Patents

Abstract

PURPOSE:To obtain a separation membrane excellent to separate water from ethanol by film-forming a solution containing cyclodextrine oligomer and polyvi nyl alcohol and cross-linking treating the obtained film. CONSTITUTION:Cyclodextrine oligomer and polyvinyl alcohol are dissolved in water, is film-formed by spreading on an adequate plane and vaporizing water and the film is cross-linking treated. As the cross-linking treating, either chemical cross-linking executed by reacting a cross-linking agent such as glutalaldehyde in the presence of an acid catalyst or physical cross-linking executed by irradiating with an active beam such as electron beam is used. In this case, the larger the degree of cross-linking is, the more selectivity and permeable speed to water increase. The mixing ratio of cyclodextrine oligomer and polyvinyl alcohol is preferably 1:1 to 1:4 in weight ratio. The ratio is controlled optionally and the separation membrane according to the purpose is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cyclodextrin-polyvinyl alcohol composite membrane useful as a separation membrane, for example, a separation membrane for separating water and ethanol, and a method for producing the same.

[0002]

2. Description of the Related Art Separation membranes for separating a specific component from a mixture of two or more gases or liquids include
Various types of films such as cellulose acetate film, polyethylene film, polypropylene film, silicone rubber film, maleimide-acrylonitrile copolymer film, nylon film, polyphenylene ether film, Teflon film, and nafion film have been known.

Membranes for preferentially separating water or alcohol from a mixed solution of water and alcohol include, for example, crosslinked polyvinyl alcohol, regenerated cellulose, acetyl cellulose, chitosan, acrylic acid-acrylonitrile copolymer. It is known to use a material having a high affinity with water.

However, since the separation performance of each of these separation membranes is limited by the material thereof, the separation performance cannot be adjusted according to the purpose of separation.
In addition, in order to separate well miscible components such as water and alcohol, there are many points that have to be solved in terms of low efficiency and practical application.

On the other hand, cyclodextrin has small pores in the molecule and is widely used in the fields of inclusion compounds, catalysts, etc., but it is difficult to form a membrane, so it is unsuitable as a material for a separation membrane. Met.

[0006]

The present invention has been made for the purpose of providing a novel separation membrane having good selective separation performance and capable of controlling the separation performance according to the purpose of use. Is.

[0007]

Means for Solving the Problems As a result of intensive studies, the present inventors have conducted extensive studies in order to develop a separation membrane having excellent separation performance and capable of efficiently separating water and ethanol. Focusing on the fact that the dextrin oligomer shows excellent substance separation performance similar to cyclodextrin, and is soluble in water and can be arbitrarily mixed with polyvinyl alcohol,
After forming a film of a mixture of cyclodextrin oligomer and polyvinyl alcohol, and then cross-linking, a composite film with excellent selective separation performance can be obtained, and at that time, the separation can be performed by changing the mixing ratio of the cyclodextrin oligomer and polyvinyl alcohol. It has been found that the performance can be easily controlled, and the present invention has been completed based on this finding.

That is, the present invention provides a composite membrane comprising a cross-linked product of a mixture of a cyclodextrin oligomer and polyvinyl alcohol.

This composite film is formed, for example, by dissolving a cyclodextrin oligomer and polyvinyl alcohol in water, spreading the solution on a suitable flat surface to evaporate the water, and then subjecting the obtained film to a crosslinking treatment. Can be manufactured.

At this time, the cyclodextrin oligomer used as a raw material preferably has a degree of polymerization of 2 to 5. The polyvinyl alcohol has a degree of polymerization of 1000 to 30.
It is preferably about 00 and the saponification degree is 95% or more. The mixing ratio of the cyclodextrin oligomer and polyvinyl alcohol is preferably in the range of 1: 1 to 1: 4 by weight.

The cross-linking treatment after forming a film of a mixture of a cyclodextrin oligomer and polyvinyl alcohol may be chemical cross-linking by reacting a cross-linking agent such as glutaraldehyde in the presence of an acid catalyst, or by using an electron beam. Physical crosslinking may be performed by irradiating with such actinic rays. In this case, the greater the degree of cross-linking, the greater the selectivity towards water and the rate of permeation.

In an ordinary separation membrane, when the hydrophilicity is improved, the selectivity for water increases, but the permeation rate tends to decrease. Therefore, in the case of the present invention, this is a very specific phenomenon. it can.

In the present invention, the cyclodextrin oligomer and water can be mixed at an arbitrary ratio, so that the weight fraction of cyclodextrin in the composite film can be increased to 1/3 or more. Further, the crosslinking treatment described above can almost completely suppress the leakage of cyclodextrin in water.

When the composite membrane of the present invention is used as a separation membrane, it is preferable to form a film having a thickness of about 50 to 300 μm.

[0015]

EXAMPLES Next, the present invention will be described in more detail by way of examples.

Example 1 Polyvinyl alcohol (trade name "Kuraray Poval 117
H ", average degree of polymerization 1700, degree of saponification 98-99%) and mixture of β-cyclodextrin oligomer (epichlorohydrin crosslinking, degree of polymerization about 3) (weight ratio 2: 1) 10 g
Was dissolved in 100 ml of deionized water at 100 ° C. After stirring at 100 ° C., a clear, homogeneous solution was obtained.

Next, this solution was spread on a glass plate and left in a desiccator at room temperature for 1 week to evaporate the solvent.

The film thus obtained was treated with 0.5% by weight of glutaraldehyde, 0.5 mol of H2SO4, N2.
It was dipped in an aqueous solution containing 20% by weight of a2SO4 and crosslinked for 1 to 8 hours to produce a transparent composite film having a dry film thickness of 100 μm.

Example 2 A transparent composite film having a dry film thickness of 100 μm was prepared in the same manner as in Example 1 except that a mixture of polyvinyl alcohol and β-cyclodextrin oligomer in a weight ratio of 4: 1 was used. ..

Reference Example 1 Using the pervaporation apparatus having the structure shown in FIG. 1, a water-ethanol pervaporation separation experiment was conducted on the composite membrane.

That is, the composite membrane was installed in the permeation cell 3 made of stainless steel, and the temperature of the cell was kept at 30 ° C. in the constant temperature bath 4. Then, a mixed liquid of water and ethanol was circulated from the supply tank 1 by the pump 2 and sucked from the permeate side of the composite membrane by the rotary vacuum pump 7 at a pressure of 0.5 Torr.
The permeate was captured by a glass collection bottle 6.6 cooled with liquid nitrogen and its composition was analyzed by gas chromatography.
Reference numeral 5 in FIG. 1 is a pressure gauge.

Crosslinking time 1 obtained in Examples 1 and 2
FIG. 2 is a graph showing the relationship between the ethanol weight fraction on the feed side and the ethanol weight fraction on the permeate side measured as described above for the time composite membrane.

The black circles in the figure represent the weight ratio of polyvinyl alcohol to cyclodextrin of 2: 1 and the black triangles represent the ratio of 4: 1. The white circles represent the results of the polyvinyl alcohol alone film for comparison. is there.

FIG. 3 is a graph showing the relationship between the ethanol weight fraction on the feed side and the total permeation rate through the composite membrane for the same sample.

As is apparent from these graphs, the composite membrane of the present invention has a higher water selectivity and a higher permeation rate than the polyvinyl alcohol single membrane.

Reference Example 2 The composite membrane obtained by crosslinking for 8 hours in Example 1 was examined in the same manner as in Reference Example 1 to examine the relationship between the ethanol weight fraction on the feed side and the ethanol weight fraction on the permeate side. The result is shown in FIG. 4 as a black circle graph. The white circles in FIG. 4 are the results for the film of polyvinyl alcohol alone for comparison.

As is clear from this figure, the selectivity of water is higher in the one treated for 8 hours than in the one treated for 1 hour.

FIG. 5 is a graph showing the relationship between the ethanol weight fraction on the feed side and the permeation rate for the same sample.

Reference Example 3 In order to investigate the dissociation property of cyclodextrin in the composite film obtained in Example 1, the composite film was immersed in water for 1 to 3 days, and the weight change before and after the immersion was relative to the dry weight after film formation. Calculated as the weight. The results are shown in Table 1.

[0030]

[Table 1]

As is clear from this table, the amount of dissociation of cyclodextrin decreases as the crosslinking treatment time increases.

[0032]

INDUSTRIAL APPLICABILITY When the composite membrane of the present invention is used as a separation membrane for ethanol and water, both the water selectivity and the permeation rate can be increased, so that both can be efficiently separated. In addition, since the cyclodextrin oligomer can be arbitrarily mixed with water, the ratio of cyclodextrin and polyvinyl alcohol can be arbitrarily controlled, and a separation membrane having performance suitable for the intended purpose can be obtained.

[Brief description of drawings]

FIG. 1 is a systematic diagram of an apparatus for conducting a pervaporation separation experiment of a composite membrane of the present invention.

FIG. 2 shows the 1 hour cross-linked composite membranes obtained in Examples 1 and 2.
The graph which shows the separation performance of ethanol and water.

FIG. 3 is a graph showing the permeation rate of a mixed solution of ethanol and water through the 1-hour cross-linked composite membranes obtained in Examples 1 and 2.

FIG. 4 is a graph showing the separation performance between ethanol and water of the 8-hour cross-linked composite membrane obtained in Example 1.

5 is a graph showing the permeation rate of a mixed solution of ethanol and water of the 8-hour cross-linked composite membrane obtained in Example 1. FIG.

[Explanation of symbols]

 1 Supply tank 3 Permeation cell 4 Constant temperature bath 6 Collection bottle 7 Vacuum pump

Claims (2)

[Claims] 1. A composite membrane comprising a crosslinked product of a mixture of a cyclodextrin oligomer and polyvinyl alcohol. 2. A method for producing a composite film, comprising forming a solution containing a cyclodextrin oligomer and polyvinyl alcohol into a film, and then subjecting the obtained film to a crosslinking treatment.