JP3098577B2 - Permeation separation membrane - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a permeation separation membrane comprising an ionomer modified with a polyoxyalkylene compound. More specifically, a permeation separation membrane suitable for separating water from a mixture of a water / water-soluble organic compound, comprising a modified ionomer obtained by graft-modifying or cross-linking an ionomer of an alkali metal ion with a polyalkylene compound. About.

[0002]

2. Description of the Related Art As a method for separating azeotropic mixtures, near-boiling mixtures, isomers and the like which are difficult to separate by ordinary separation methods such as distillation, such as a mixture of alcohol and water, they have a hydrophilic segment or group. In recent years, a pervaporation method using a polymer compound membrane (pervaporation) and a vaporization separation method (evaporation) have attracted attention and are being studied. Above all, the separation of water-soluble organic compounds / water such as ethanol / water and N, N'-dimethylformamide / water is considered to be applied to the concentration of biomass alcohol and the recovery of solvent from waste liquid, etc., and has been developed as an energy-saving type separation method. Is being promoted.

As the polymer compound used for the separation membrane, ionized chitosan, ionized alginic acid, acrylic acid-grafted polyethylene, polyvinyl alcohol-based composite membrane, acrylamide-grafted polypropylene, polyimide, poly (1-trimethylsilyl-1-propane) and the like are used. Are known. Although these polymer membranes have excellent separation characteristics, they have the disadvantage that they require complicated steps for forming the membrane due to their poor thermoplasticity and the like, and that the production cost of the membrane is high. On the other hand, an ionomer obtained by crosslinking an ethylene-unsaturated carboxylic acid copolymer with a metal ion, a tetrafluoroethylene-perfluorosulfonated vinyl ether copolymer, or a cross-linking of a tetrafluoroethylene-perfluorocarboxylated vinyl ether copolymer with a metal ion It is known that ionomers also have performance as alcohol / water separation membranes by pervaporation. Each of these ionomers is thermoplastic and has the advantage of being easily formed into a membrane by thermoforming, but has a low separation performance (separation coefficient) and cannot be used practically as a separation membrane.

[0004]

SUMMARY OF THE INVENTION The present inventor has studied an ionomer which has the advantage that the membrane can be easily formed and has improved the low separation performance as a permeation separation membrane which is a disadvantage thereof. The present inventors have found that an ionomer obtained by crosslinking an ethylene-unsaturated carboxylic acid copolymer with an alkali metal ion (hereinafter abbreviated as an alkali metal ionomer) is modified with a polyoxyalkylene compound to achieve the object. Accordingly, an object of the present invention is to provide an ionomer permeation separation membrane having improved separation performance when used as a water-soluble organic compound / water permeation separation membrane.

[0005]

SUMMARY OF THE INVENTION The present invention relates to a permeation separation membrane comprising a modified ionomer obtained by graft-modifying or cross-linking an alkali metal ionomer of an ethylene-unsaturated carboxylic acid copolymer with a polyoxyalkylene compound. It is.

That is, in the permeation separation membrane of the present invention, one part of the unsaturated carboxylic acid unit of the alkali metal ionomer is graft-modified with a polyoxyalkylene compound through an ester bond, or cross-linked with the polyoxyalkylene compound. It is characterized in that an ionomer (hereinafter sometimes simply referred to as a modified ionomer) is used.

Accordingly, the above modified ionomer comprises (A)
A copolymer comprising ethylene, (B) an unsaturated carboxylic acid partially or wholly neutralized with an alkali metal, and (C) an unsaturated carboxylic acid esterified with a polyoxyalkylene compound. In addition, other vinyl monomers may be contained as optional components.

The composition of the above copolymer is such that (A) the ethylene unit is 50 to 99 mol%, particularly 70 to 96 mol%,
(B) 1 to 25 mol%, particularly 4 to 15 mol%, of unsaturated carboxylic acid units partially or wholly neutralized with an alkali metal, (C) unsaturated esterified with a polyoxyalkylene compound Those having a carboxylic acid unit in the range of 0.1 to 10 mol%, particularly 0.2 to 7 mol% are preferred. These monomer units are randomly arranged.
Examples of the unsaturated carboxylic acid unit in the component (B) include acrylic acid, methacrylic acid, maleic anhydride, and monoethyl maleate.

The alkali metal used for neutralizing the unsaturated carboxylic acid in the component (B) includes lithium,
Sodium, potassium, rubidium, cesium and the like can be exemplified, but from the viewpoint of separation performance, sodium, potassium, rubidium, and cesium are preferable, and sodium and potassium are particularly preferable. The degree of neutralization with an alkali metal is from 20 to 100 of the unsaturated carboxylic acid unit of the component (B).
Mole%, especially 30 to 100 mol% is preferred. If the degree of neutralization is lower than this, the separation performance of the obtained permeation separation membrane decreases.

The polyoxyalkylene compound used for modifying the alkali metal ionomer is a compound having a polyoxyalkylene group (-(R'O) _n- ) in the molecule. Where R ′ is methylene, ethylene, propylene,
A lower alkylene group such as butylene is suitable, and n is preferably 2 to 100. Among such polyoxyalkylene compounds, in particular, compounds having a glycidyl group at one end or both ends, for example, a compound of the formula

[0011]

[0012] (Where R is a hydrocarbon group such as an aryl group, a cycloalkyl group, or an alkyl group, or hydrogen), by using a polyoxyalkylene monoglycidyl ether or polyoxyalkylene diglycidyl ether represented by the following formula: It is suitable as a denaturing agent because it can easily react with and bind to the compound. By modifying the alkali metal ionomer with this polyoxyalkylene compound, the water-soluble organic compound /
Water separation efficiency is significantly improved.

Preferred as the optional optional vinyl monomer is an ester or vinyl ester of an unsaturated carboxylic acid. As esters of unsaturated carboxylic acids, methyl (meth) acrylate, ethyl (meth) acrylate, isobutyl (meth) acrylate, n-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, diethyl maleate And vinyl esters such as vinyl acetate and vinyl propionate. (Here, (meth) acrylic acid means acrylic acid or methacrylic acid.) The content of the vinyl monomer is 0 to 25 mol%, preferably 0 to 15 mol%.

The modified ionomer is produced by producing an alkali metal ionomer by a known ionomer production method, and then mixing the alkali metal ionomer and the polyoxyalkylene compound under melting conditions using an extruder or a kneader. And a method in which a polyoxyalkylene compound is added to an aqueous dispersion of an alkali metal ionomer, mixed and then heated to a temperature of 70 ° C. or more to react. Further, by stirring an ethylene-unsaturated carboxylic acid copolymer, an alkali metal compound, and a polyoxyalkylene compound in hot pressurized water, a modified ionomer can be directly produced from the ethylene-unsaturated carboxylic acid copolymer. It is possible.

In the production of the permeation separation membrane of the present invention, the modified ionomer is formed as a film by extrusion molding for a thermoplastic resin such as an inflation film molding method or a T-die film molding method, or as a tubular membrane by hollow molding. can do.

By using these thermoforming methods, the ionomer-modified product can be formed into a film by itself, and the film can be formed from a composition blended with another thermoplastic resin.
It can also be used as a laminate with other resins, papers, nonwoven fabrics and the like.

Further, the modified product is made into a solution with an aqueous dispersion or a suitable solvent, and the resulting solution is cast on a suitable substrate and then dried by heating to form a film, or after coating the solution on the outside of a resin hollow fiber, 70 ° C ~ 200
It can be used as a multilayer hollow fiber-shaped permeation separation membrane by forming the membrane by heating to ° C.

In any of the methods, by forming a laminated film of the modified ionomer and a porous substrate such as another thermoplastic resin, paper, or a nonwoven fabric, the modified ionomer which contributes to the permeation separation function can be obtained. The transmission speed can be improved by reducing the thickness of the layer, and a decrease in film strength due to the reduction in thickness can be compensated for by the strength of the base material layer. Even if blended with other thermoplastic resin, the performance as a permeation separation membrane is maintained, so the balance between membrane strength and heat resistance and separation performance can be controlled by selecting the type of resin to be blended and the mixing ratio. it can. Examples of the thermoplastic resin that can be blended with the modified ionomer include a polyolefin-based resin and a polyamide.

[0019]

EXAMPLES The present invention will be specifically described below with reference to examples. The modified polyoxyalkylene compound ionomer used in the examples, and the composition, physical properties, and permeation vaporization measurement methods of the ionomer, polyoxyalkylene compound, and the like used as raw materials thereof are as follows.

1. As a raw material of the ionomer polyoxyalkylene compound ionomer modified product, and using the six ionomer as the non-modified product for comparison. Table 1 shows the composition, physical properties and the like.

[0021]

[Table 1]

2. Polyoxyalkylene Compound Nagase Kasei Kogyo Co., Ltd. polyoxyethylene epoxy compound (trade name: Dinacol) was used.

(1) Dinacol Ex-145 phenol polyoxyethylene glycidyl ether

(2) Dinacol Ex-832 polyethylene glycol diglycidyl ether

3. Polyoxyalkylene compound modified eye
1. Onomer (1) Ionomer Modified 1 Ionomer 3 with phenol polyoxyethylene glycidyl ether ( Dinacol Ex-145)
7% by weight (0.51 mol% of the total composition) graft modified product (modified by melt mixing in an extruder)

(2) Modified ionomer 2 Crosslinked and modified 10% by weight of ionomer 6 with polyoxyethylene diglycidyl ether (Dinacol Ex-832) (modified in an aqueous dispersion of the ionomer) and cast on a polyester film Film forming)

(3) Ionomer-modified product composition Ionomer-modified product 1 25 parts by weight and low-density polyethylene 75 parts by weight (Mirason-16 MFR 4.0 dg / min (190 ° C.) manufactured by Mitsui Petrochemical Industries, Ltd.) Density 0 .923) and melt blends with

Pervaporation Separation Measurement Method The pervaporation separation measurement apparatus shown in FIGS. 1 and 2 was used to measure the separation performance of an ethanol / water mixed solution by various sample membranes.

FIG. 1 is a flow sheet of a pervaporation separation measuring apparatus. The permeation cell (1) is maintained at a constant temperature by attaching it to a thermostatic water bath (2). The whole system after the permeation side of the permeation cell is evacuated by the vacuum pump (3), and always 1 mm
A cold trap (6), which is kept at Hg or less and condenses the permeate, is provided on the way.

FIG. 2 is a sectional view of the transmission cell (1) in FIG. 1, and the sample film (11) is mounted on a support (11).

In order to measure the separation performance, first, the permeation cell (1)
Is filled with a supply liquid (ethanol / water), and left for 6 hours or more. After the membrane-solvent system is thus equilibrated, the cold trap (6) is cooled with liquid nitrogen, and the permeate side (low concentration side) is evacuated to high vacuum.
The weight of the permeate was measured over time while alternately switching the cold traps, and the permeation rate was determined. Also,
The composition of the permeate was analyzed by gas chromatography. X
_A, A of the X _B supply side, each of the weight fraction of component B,
Y _A, Y _B of the transmission side A, when the respective weight fractions of the component B, the separation factor of the B component to A component (alpha _BA) is expressed by the following equation. α _BA = (Y _B / Y _A ) / (X _B
/ X _A ) Here, ethanol was used as the A component, and water was used as the B component.

Examples 1 and 2 Films of the modified polyoxyalkylene 1 (Example 1) and the composition of the modified polyoxyalkylene (Example 2) formed by the blown film molding method were used as permeation separation membranes. And a pervaporation separation test of ethanol / water mixtures having various mixing ratios was carried out according to the above-described measurement method. Table 2 shows the results. As is clear from the results in Table 2, the separation of ethanol / water is performed efficiently by using the permeation separation membrane composed of the modified polyoxyalkylene of the present invention or a composition containing the modified polyoxyalkylene. In particular, the separation coefficient was confirmed to be better as the alcohol content in the mixture was higher, and was confirmed to be useful for separating water from the ethanol / water mixture.

Example 3 Dinacol Ex-832 was added to and mixed with the aqueous dispersion of the ionomer 6, cast on a polyester film, and dried by heating at 150 ° C. for 1 minute to form a coating film. The coating is peeled from the polyester film. 1 of the obtained modified ionomer 2
The pervaporation and separation performance of the ethanol / water mixture was measured in the same manner as in Example 1 using a 0-μm thick membrane. As a result, excellent results were obtained in both the permeation amount and the separation coefficient. Table 2 shows the results
Shown in

Comparative Examples 1-4 Unmodified ionomer 1 (Comparative Example 1), ionomer 4 (Comparative Example 2), ionomer 2 (Comparative Example 3) instead of the polyoxyalkylene modified product of Example 1 as a permeation separation membrane And Ionomer 5 (Comparative Example 4) using a film formed by the blown film molding method,
A pervaporation / separation test of an ethanol / water mixture was performed in the same manner as described above. The results are shown in Table 2. When the membrane of the unmodified ionomer is used, it can be seen that the separation coefficient is lower and the separation efficiency is inferior to that of the polyoxyalkylene-modified ionomer.

[0035]

[Table 2]

[0036]

According to the permeation separation membrane of the present invention, the permeation separation performance of a water-soluble organic compound / water by pervaporation is improved by graft modification or cross-linking modification of an alkali metal ionomer with a polyoxyalkylene compound. Similarly to the above, since it can be easily formed as a film or a hollow fiber, it can be used as a separation membrane for alcohol / water or the like.

Further, since it can be easily used as a laminated film with another thermoplastic resin, a porous substrate such as paper or non-woven fabric, or as a blend film with another thermoplastic resin, the thickness of the layer of the modified ionomer can be easily increased. It is possible to improve the permeation speed by reducing the thickness, and to produce a separation membrane having a good balance between the strength and heat resistance of the membrane and the separation performance.

[Brief description of the drawings]

FIG. 1 shows a flow sheet of a pervaporation separation measuring apparatus.

FIG. 2 shows a cross-sectional view of a transmission cell.

[Explanation of symbols]

 (1) Permeation cell (2) Constant temperature bath (3) Vacuum pump (4) Manometer (5) Two-way cock (6a, 6b, 6c) Cold trap (7) Three-way cock (11) Sample membrane support (12) Sample Membrane (13) Cooling tube (14) Stirrer blade (15) Liquid supply side container (16) O-ring (17) Exhaust chamber

Claims (2)

(57) [Claims] 1. A permeation separation membrane comprising a modified ionomer obtained by graft-modifying or crosslinking-modifying an alkali metal ionomer of an ethylene-unsaturated carboxylic acid copolymer with a polyoxyalkylene compound. 2. The permeation separation membrane according to claim 1, wherein the polyoxyalkylene compound is polyoxyalkylene monoglycidyl ether or polyoxyalkylene diglycidyl ether.