JPS5955304A - Separation of water-organic liquid mixture - Google Patents

Abstract

PURPOSE:To provide a composite membrane for permeation evaporation having mechanical strength and a high sepn. performance by crosslinking polyethyleneimine and an acid halide group, etc. with an arom. crosslinking agent and forming an ultra-thin film layer having a specific structure on a backing film. CONSTITUTION:A polysulfone film having 40-70mu thickness and 30-600Angstrom micropores on the surface is immersed for 5min at room temp. in 2.0wt% aq. soln. of polyethyleneimine of about 10,000mol.wt. and is then air-dried for 10min. The film is immersed for 3min in a hexane soln. contg. 2.0wt% toluene-2,4- diisocyanate, whereafter the film is heat-treated for 10min at 120 deg.C and is thus crosslinked. When the sepn. performance of the azeotropic liquid mixture of water/methanol=4.5/95.5wt. ratio is measured by using the obtained composite membrane, the flux is 0.28kg/m<2>.hr at 20 deg.C operating temp. and the coefft. of sepn. is 17.7, which values increase with an increase in the operating temp.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for membrane separation of a water-organic liquid mixture by pervaporation.

Distillation has long been known as a method for separating organic liquid mixtures and is generally widely used. However, in the distillation method, it is extremely difficult to separate azeotropic mixtures, near-boiling point mixtures, heat-denatured mixtures, and the like.

For example, in order to separate a water-ethanol azeotrope by distillation, it is necessary to add a third component (eg benzene) and carry out azeotropic distillation at a high reflux ratio. Therefore, the amount of energy consumed is large, and it is advisable to avoid mixing the third component into the finished product.

In order to solve these difficulties, research has been conducted for a long time on methods of dividing liquid mixtures in a gas-liquid system using polymer membranes.
For example, U.S. Patent No. 295350 of B Inn lng
It has been proposed in No. 2, etc. This separation method is pervaporation (
This is a method in which a liquid to be treated is supplied to the primary side (high pressure side) of a polymer membrane, and substances that are easily permeable are preferentially permeated as vapor to the secondary side (low pressure II).

The polymer membrane bed material used in this pervaporation method is selected to have an affinity for the components to be permeated in the liquid to be separated.
Conventionally, polyethylene, polypropylene, cellulose acetate, cellulose.

Membranes made from polyester, polyamide, polyurethane, polyacrylonitrile, polytetrafluoroethylene, etc. are known. However, these have a film thickness of 10 to 1
Since it is a homogeneous membrane (film) of 00 μm, the liquid permeation rate is extremely low, and the separation performance is also unsatisfactory. The permeation rate can be improved by making the film thinner than K, but if it is less than 5 μm, the mechanical strength becomes insufficient and it is difficult to put it into practical use.

As a result of intensive study by the present inventors to solve the above-mentioned drawbacks,
The present invention was achieved by discovering that a membrane with mechanical strength and extremely high separation properties can be obtained by forming an ultra-thin membrane layer with a specific structure on a microporous support membrane. .

That is, when separating a water-organic liquid mixture by pervaporation, the present invention provides polyethyleneimine and an aromatic crosslinking agent having bifunctionality for acid-ride groups and/or incyanate groups on a microporous support membrane. This is a method for separating a water-organic liquid mixture, which is characterized by using a composite membrane obtained by a crosslinking reaction.

The composite membrane used in the present invention is produced by a manufacturing method known in the field of reverse osmosis membranes, which perform liquid-liquid separation (for example, in Japanese Patent Application Laid-Open No. 10394-1983).
(Refer to Publication No. 5). That is, a solution of polyethyleneimine (hereinafter abbreviated as PEI) is applied onto a microporous support membrane, and then brought into contact with a solution of the bifunctional crosslinking agent, followed by dry heat treatment to remove water and organic liquid. The desired composite membrane can be obtained by forming an ultra-thin, cross-linked film layer insoluble on a support membrane. The manufacturing method will be described in more detail below.

The polyethyleneimine used in the present invention is highly branched, with the ratio of 1st, 2nd, and tertiary nitrogen atoms being approximately 1:2:1. Any molecular weight between 300 and 100,000 can be used, and these commercially available products can be used without purification.

Water is used as a solvent when preparing a solution of PEI.

Mention may be made of methanol, ethanol, etc., although water is most preferred for the purposes of the present invention. The PEI concentration in the solution is 0.05-10.0% by weight, preferably 0.1-5.
It is 0% by weight.

As a method for applying the PEI solution onto the microporous support membrane, conventionally known methods such as a dipping method, a casting method, and a spray method can be employed.

After removing excess solution, the support membrane coated with the PEI solution is dried by removing the solvent at room temperature or under heat, and then brought into contact with the crosslinking agent solution.

The bifunctional crosslinking agent containing an acid halide group and/or isocyanate group used in the present invention is an aliphatic one having 1 to 2 carbon atoms.

Examples include alicyclic and aromatic dicarboxylic acid cybarides having 5 to 2 carbon atoms, disulfonic acid cybaride diisocyanates, and stabilized diisocyanates.

Examples of these are adipine m chloride, cepatic acid chloride, fumaric acid chloride, ophthalic acid chloride, isophthalic acid chloride, terephthalic acid chloride, 24,4-benzophenone dicarboxylic acid chloride, 1,4-naphthalenedicarboxylic acid chloride. , 1,4-cyclohexanedicarboxylic acid chloride, etc., l, 3-benzenedisulfonic acid chloride, 1,4-benzenedisulfonic acid chloride, 1,4-naphthalenedisulfonic acid chloride, etc., ethylene diincyanate, propylene diisocyanate,
Examples include tolylene diisocyanate, naphthalene diisocyanate, methylene bis(4-phenyl incyanate), and the like. Among these, aromatic crosslinking agents are particularly preferred.

Also included in the bifunctional crosslinking agent are those which form a diacid halide by themselves.

Examples of this include oxy->noryl chloride, phosgene, thionyl chloride, etc.

The bifunctional crosslinking agents may be used alone or in a mixture of two or more.

The reaction between pgi and the crosslinking agent is usually carried out by immersion in a solution of the crosslinking agent. The solvent for the crosslinking agent solution is selected from those that do not dissolve PEI and the support film, and preferred are n-hexane, hebutane, octane-2-cyclohexane, etc.
It can be used. The concentration of crosslinking agent in the solution is 0.05
The purpose can be more effectively achieved by setting the amount to 10.0% by weight, preferably 0.1 to 5.0% by weight.

The thickness of the thin film layer thus obtained is from several hundred amps to about 1 μm.

When acid halides are used as crosslinking agents, hydrogen halides are produced by reaction with amines. This substance is accepted by PEI itself, and the reaction proceeds, but a strong alkali is used as a promoter.

Sodium phosphate, sodium acetate, birin, triethylamine, etc. can also be used. The cholera reaction accelerator (hydrogen halide acceptor) can be added directly to the aqueous solution of nil K PEI for crosslinking reaction, or it can be added in a separate step after the crosslinking reaction.

Although the crosslinking reaction proceeds even at low temperatures, it is desirable to carry out a dry heat treatment in order to obtain a suitable crosslinking porosity. The dry heat treatment temperature is 60 to 150°C, preferably 90 to 130°C.
℃ range, and the dry heat treatment time is still in the range of 1 to 60 minutes, preferably 5 to 30 minutes.

The PgI crosslinked composite membrane that has been subjected to the dry heat treatment may be coated with a protective coating such as polyvinyl alcohol or polyvinylpyrrolidone at an appropriate stage in the modularization process, if desired.

The microporous support membrane according to the present invention is not particularly limited as long as it does not dissolve or swell in the solvent of the PEI to be coated or the solvent of the crosslinking agent, but it can easily produce an asymmetrically porous membrane made of cypress, It is also desirable to have excellent chemical resistance and PL resistance.

Suitable examples of such a microporous support membrane include, but are not limited to, polysulfone and polyvinyl chloride. In particular, polysulfone has excellent performance as a material for the microporous support membrane of the present invention. Polysulfone microporous support L4 is a known method, V.11 is a U.S. Department of the Interior Salt Water Bureau research and development report.

It can be manufactured by the method described in Ma 359.

Such membrane materials generally have a surface pore size of about 100 to 1
The size of the surface pores is preferably between 000A and 5000A, but is not limited thereto, and the size of the surface pores may vary between 50 and 5000A depending on the final use of the membrane. These substrates can be used in either asymmetric or symmetric structures. A preferable supporting membrane constant is 1 to lOV/rf! L・Success・
atm.

Particularly preferably 10 to 10 f/cd・sec・at
m range. Furthermore, the membrane constant referred to here is 21
This value represents the amount of pure water permeated under a pressure of \9/cJ.

The support membrane may have any shape such as a hollow fiber, a flat plate, or a tubular shape. In the case of Y plate-like or tubular shape, it is ill'a:
It is best to use it in a woven fabric case or in a strengthened form with cloth. Examples of such woven fabrics and nonwoven fabrics include those made of polyethylene prephthalate, polypropylene, nylon, vinyl chloride, and the like.

The thus obtained logging membrane has a high affinity for water, and therefore allows water to permeate selectively from the water-organic liquid mixture for a long time, thereby increasing the organic temperature in the coating mixture. The thing becomes Ij] ability.

In the present invention, the active layer side of the membrane (PEI crosslinked membrane M
(side) is brought into contact with the supply liquid (- next side), and the substance that has permeated through one tube is taken out from the secondary side in a gaseous state. Therefore, either reduce the pressure on the secondary side or flow an inert gas such as air to lower the chemical potential to a level lower than the primary a11 (!
l: One thing is necessary.

The primary elevation 1 can apply pressure within the range of 1"-100 KyA broom υ:", preferably t L < tJ, 10 Kg/era from atmospheric pressure. When the pressure on the secondary side is σ;
00 birds 11g or less, more preferably 'iJ', 100
It is best to maintain a vacuum of 4 g or less per ml.

The temperature of the application source in the preparative method of the present invention is 0 to 100°C,
The temperature is 0 to 90°C. In the immersion vaporization method, step 7
It has been known from the past that the higher the value of 1□1, the higher the permeation rate, but the lower the separation coefficient. However, in the membrane used in the present invention, it was found that both Ul and the permeation rate of 1 separation < number of pairs became worse depending on the coating 11i [# liquid spread. In such cases, separation at high temperature is considered to be advantageous.

The water-organic liquid mixture that can be separated in the present invention is represented by water/organic liquid mixture.
Isoprobyl alcohol. water/ethyl alcohol, water/n-furobyl alcohol.

Book/allyl alcohol, water/2.3-dichloro-1-furopanol-1 water/2-methoxyethanol, water/isobutyl alcohol 1'e water/x --jpnol, ice/2
-butanol v water/furfuryl alcohol + water/2
-Pentanol t Water/2-Pentanol, Water/4-
Examples include water-alcohol mixtures such as methyl-1-butanol; water-organic solvent systems such as water/tetrahydrofuran, water/dioxane, and water/methyl ethyl ketone. Among these, the present invention can be particularly disadvantageously used for dividing an azeotropic mixture of water and alcohols.

Depending on the form of the initial membrane tj and 6a porous support membrane used in this specification, it can be used in the form of a hollow fiber module, spiral module, plate-in-frame module, or tubular module. It can be advantageously used on bamboo because a large membrane area can be obtained.

Hereinafter, the present invention will be explained in more detail with reference to Examples.

The supply side of the water/state liquid mixture is under atmospheric pressure, and the collection side is at zero pressure.
．． The test was carried out under a reduced pressure of 3 to 1 (g. The area is 11.0cyJ
It is.

The water and the organic 6λ body that passed through Le.2 were condensed and collected, and the permeation 5j (Flux) was determined in units of Kq/ln'·hr.

In addition, the Kasei ratio fJ of the collected fluid was determined by TCD-gas chromatography, and the segmentation coefficient (α) of manliness was determined.

Note that the division 1 coefficient α is defined as follows.

KA/λB However, in the above equation, xA and xB are component A of the supply liquid,
yA and yB represent the pfM% of B, and yA and yB represent the 2 (amount ratio) of components A and H in the collection liquid (permeate), and the A component indicates a component that selectively permeates. water-
Since it selectively permeates water even from organic liquid mixtures, A
Since the component is water, it is called I/C.

Reference Example': +Production method of woven fabric reinforced polysulfone porous membrane A densely woven Dacron nonwoven fabric (fabric weight f180Y/crA) was fixed to a glass plate. Next, 12.5 wt% of polysulfone and 12.5 wt% of methyl cellosolve were added on the nonwoven fabric.
A nonwoven reinforced porous polysulfone layer was obtained by casting a solution containing 1% and the remainder dimethylformamide into a layer with a thickness of about 200 μm, and immediately gelling the polysulfone layer in a water bath at room temperature.

The porous polysulfone layer obtained in this way has a thickness of about 40 to 70 μm, has an asymmetric structure, and has a large number of micropores of about 30 to 600 pores. Observed by electron micrograph. These porous substrates have a high permeability of pure water in 21/'cJG.
Time constant P) is about 3+O~7. OX10? /ca-y
It was y2・atm.

EXAMPLE A 2.0-layer aqueous solution of polyethyleneimine (Nippon Shokubai Kasho Kogyo Co., Ltd. 3.1-200) having a molecular weight of about 10,000 was prepared. The polysulfone microporous support membrane obtained in the above reference example was immersed in this solution for 5 minutes at room temperature, then taken out and air-dried for 10 minutes in a normal state. After soaking the membrane in a hexane solution containing 2.0 g and Q% of toluene-12,4-diisocyanate, which is a crosslinking agent, for 3 minutes (at room temperature), Vessel 12
Dry heat treatment was performed at 0°C for 10 minutes.

Using this 7g mixture, water/ethanol = 4.5/;
@ 5.5 (1%) pif? % was measured under the conditions described earlier in the text, and as shown in Table 1, it was found that as the operating temperature increases, the flux increases and the separation coefficient α also increases.

Table 1 (Feed
:Water/Ethanol=4.5/9 5.5) Example Using the composite t"b obtained in Example 1, the separation characteristics for each of the A and 11 components of water-ethanol mixture 4 and 7α were determined. 11j1
It is made at a temperature of 30℃! II was determined and the results were as shown in Table 2.

Table 2

(30) Example Using the 7y composite film obtained in Example 1, water/isoprohal)-12/8B (heavy fjf-cleavage) molecule, 11 properties of the boiling mixture system were unified. 7, as shown in Table 3, I9
The value shown is shown below.

Example 4 In fact, the characteristics were determined using the same composite membrane as in Example 1. It was as shown in Table 4.

4 Water-inpropanol mixed system (30°C) Examples 1 and 5 In Example 1, isophthalic acid chloride was used instead of toluene-2,4-diisocyanate as the bridging agent 2. Composite film':y:
! ”: 'A・':' L7, water/x Tan-ru 4.5/95.5 (heavy le] ≠) naru 7: n crystal self-thread i J I) i' J at A degree? Blr ke property rI
As shown in ``+, l, and s'', as the temperature rises, both FIIIX and α'! Is the same phenomenon as in Example 1 that lvi increases? ! I was caught.

Table 5 (Feed: Water/
Ethanol-4,5/9 Fi, 5) 4i Example 6 for element 11 Using the vO membrane obtained in Example 5, the separation characteristics at the same temperature were determined for each water-ethanol mixture (:! Creation temperature 30 The results were as shown in Table 6.

Table 6 Water-ethanol system (aO°C) Example 7 Using the composite nyy obtained in Example 5, water/isoprop/
The Naf reactivity of the azeotropic mixture system was measured as shown in Table 7.

Separation ItA・Example 8 Actual %-Example 5
(When measured at 1℃, the results are shown in Table 8.Table 8 Water-Impropanol system (30℃) lKM Showa 57-1632214 No. 2 Name of the invention (Wed)! 111 Separation method 3 of the person making the correction - I-type with G note! 41 I Saka Makoto, Agency of Industrial Science and Technology, 1-3-1 Kure, Ugaseki, Chiyoda-ku, Tokyo (114) −, (i
ff Correct V3 answer + 11 Akira 111) 1 * In the 5th line from the bottom of page 45, “
Correct ``Oxi/acid plido'' to ``sakusin enemy chloride.''

+z+ clear anatomy tl calligraphy 10 'fi gg l 2
Correct the line "100°C, 0-90°C" to "100'c, preferably 0-90°C".

(3) Change the “statement” in the third line from the bottom of page 13 of the specification to “
Revised as "Surface".

that's all

Claims (1)

[Claims] When a water-organic liquid mixture is separated by pervaporation, a crosslinking reaction is performed between polyethyleneimine and a bifunctional aromatic crosslinking agent for acid halide groups and/or insyanide groups on a microporous support membrane. A method for separating a water-organic liquid mixture, characterized by using a composite membrane obtained by cooling the mixture.