JPH02273521A - Volatile organic liquid aqueous solution-concentrated film and its manufacture - Google Patents

Abstract

PURPOSE:To manufacture a film to concentrate and separate selectively organic liquid from volatile organic liquid aqueous solution by adding solution of a polymer having fluorine containing alkyl to solution of an acrylonitrile group polymer. CONSTITUTION:Solution of a polymer having fluoroalkyl and whose structure unit is represented by the formula I (representing R1 to R3 =H, alkyl having 1 to 20 carbons, fluoroalkyl, R4= fluoroalkyl having 1 to 20 carbons, X = ester bonding, amide bonding and the like) is added to an acrylonitrile group polymer such as polyacrylonitrile. Then, said mixed solution is manufactured in the form of a porous film of acrylonitrile group polymer. Said film concentrates and separates the organic liquid from the volatile organic liquid aqueous solution with good selectivity.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a separation membrane used in a membrane separation method for concentrating and separating a volatile organic liquid component from an aqueous solution thereof, and a method for manufacturing the same.

(Conventional σ) technology) - In general, from an aqueous solution of an organic liquid that is generated or accumulated in a reaction system or various processes, the organic liquid is concentrated (separated to the outside of the system (7) There are many needs for extraction.Technologies related to membrane separation methods include inverse λ:3 filtration method, ultrafiltration method, diffusion dialysis method9, hemodialysis method, electrodialysis method9.7 Gas separation method, and vapor separation method. In recent years, there has been an awakening (2.
It has been difficult to efficiently separate organic liquid components from an aqueous solution of surfactants in a labor-saving and energy-saving manner.

Even in the pervaporation method, which is currently attracting attention, when attempting to separate f'f liquid from an aqueous solution, almost all membrane materials allow water to permeate selectively. In addition, since it is necessary to maintain a large-capacity device at a high degree of vacuum, there are problems such as an energy-intensive process.

Therefore, we have developed a two-membrane transport membrane separation method using a porous hydrophobic polymer membrane that uses temperature as a driving force to concentrate volatile organic liquid components in a liquid-liquid system. Flowing an inert gas to the secondary side of
TA plan 1 was also published according to the 2'BlB publication.

(Problems to be solved by the invention) However, in the case of the membranes used in the proposals of Japanese Patent Application No. 60-38810 and Japanese Patent Application No. 62-27218, the separation The performance was not fully satisfactory. Also 1, Japanese Patent Application No. 1988-103.5, Japanese Patent Application No. 4036-1982, Japanese Patent Application No. 1988-149
No. 087 discloses that in order to obtain high separation performance, the membrane surface is coated with a polymer such as poly'79, ketone resin, or poly(1-trimethylsilyl-1,-propyne). I proposed a composite membrane 1. However, depending on the polymer used for the coating. The pores on the membrane surface are blocked (5
, the separation performance tends to deteriorate, and 1.: In order to avoid wrinkles, complicated coating operations are required.

(T-th Means for Solving the Problems) The present invention provides a porous film made of an acrylic Yconitrile polymer.
The present invention relates to a method for producing a volatile organic liquid aqueous solution concentrating membrane and a membrane comprising a composition comprising 1'-.

The average pore size of the membrane used in the present invention is 20 son 7.
．． The thickness is preferably 1000 Å or less. If the average pore size is smaller than 208, volatile organic liquid components will not preferentially permeate even in the gaseous state, and if it is larger than 1000, due to the necessarily existing pore size distribution9, the membrane The volatile organic liquid supplied to the primary side passes through the membrane even in liquid state.1. However, in porous membranes, the pores on the surface of the membrane are relatively small9, and the pores expand inside [5, etc.]. Since they are non-uniform throughout, the membrane of the present invention is thought to have greater impermeability to aqueous solutions than the average pore size of the membranes. It is suitable for separating substances that have a diameter of 1/10 or less of the average pore diameter of the membrane and are substantially impermeable to the membrane. <Used. If the ratio of the Stokes radius to the average micropore diameter is greater than 1/10, the volatile organic liquid component, which is a separated substance, will permeate preferentially over water. In addition, in the present invention, "substantially impermeable J
This means that it is impermeable to the membrane in its liquid state, but permeable in its gaseous state. In the present invention, bone vs. τ)
Since the substance is used in the method of permeating through the membrane in a vaporized state, the membrane separates nine substances without getting wet.

In order to advantageously exhibit the separation performance of a membrane, it is necessary to have a larger volume porosity in addition to the average pore diameter, and to have relatively large pores inside the membrane.

The volume porosity is usually 20% or more, preferably 40% or more, and it is advantageous to have a higher volume porosity within a range that does not impair the mechanical properties of the membrane. In addition, the amount of permeated water is 5L-500111ml1h-'m
mtig-”rn 2, nitrogen penetration eye is 0.005=1
．． Ocm' (STP) cr-2s-'cmll(
It is preferable that it is in the range of -'.

Examples of the acrylonitrile-based polymer used in the present invention include polyacrylonitrile homobo+17, acrylonitrile-tetrafluoroethynone copolymer, acrylonitrile-propylene hexafluoride I/N'4 (polymer, or Examples include mixtures, but preferably it is necessary to contain at least 50% by weight of polyacrylonitrile.

As the average molecular weight of the acrylonitrile polymer, the molecular weight of commonly available polymers is sufficient, and the weight average molecular weight is preferably in the range of 50,000 to 500,000, preferably 100,000 to 300,000.

There are various polymers having a substituent having a fluorine-containing alkyl group, but preferably a polymer having a fluorine-containing alkyl group has the general formula [I, I 83 4C-C-) [I] R2X Ra [In the formula, R1, R2, and turtle are hydrogen atoms, carbon atoms 1 to
One or more substituents selected from 20 hydrocarbon groups or fluoroalkyl groups, the turtle represents a fluoroalkyl group having 1 to 20 carbon atoms, and X represents any one of an ester bond, an amide bond, an ether bond, and a sulfamide bond. ]in,
Examples include fluorine-based polymers having the structural units shown below. - In the general formula [1,], R1, R2, Rs
may be the same or different, and may be a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms, such as a methyl group, an ethyl group,
Contains alkyl groups such as octyl group and octadecyl group, aryl groups such as phenyl group, silicon-containing organic groups such as trimethylsilyl group and n-octyldimethylsilyl group, halogen atoms such as chlorine atom, and halogen atom such as perfluoroalkyl group. Examples include substituents selected from organic groups. More preferably, 81 in general formula [I],
It is preferable that 1 is a hydrogen atom, OUT is a methyl group, - is a perfluoroalkyl group having 7 carbon atoms, and X is an ester bond.

The content of the fluorine-based polymer is generally suitably in the range of IQQ ppm to 20%, preferably 300 ppm to 5%, based on the acrylonitrile polymer.

Such a porous membrane made of an acrylonitrile-based polymer can be produced using a mixed solution in which a solution of a polymer having a fluorine-containing alkyl group is added to a solution of an acrylonitrile-based polymer.

Examples of solvents for acrylonitrile polymers include N
-Methyl-2-pyrrolidone, dimethylformamide, dimethylacetamide, diethylacetamide, diethylformamide, hexamethylphosphoramide, tetramethylurea, dimethylsulfoxide and the like. The concentration of this solution is preferably 10% by weight to 50% by weight. Examples of solvents for polymers having a fluorine-containing alkyl group include hydrocarbon derivatives having 1 to 4 carbon atoms and at least one hydrogen atom substituted with a fluorine atom, but are particularly suitable for handling because they are in a liquid state at room temperature. Easy 1.2.2
-Trichloro-1.2.2- Trifluoroethane is preferred. Regarding the amount of this solution to be added to the acrylonitrile polymer solution, if the concentration of the solution of the polymer having fluorine-containing alkyl groups is extremely low, a large amount of solution will be required to add a predetermined amount of the polymer having fluorine-containing alkyl groups. It may become necessary to add a solvent, and phase separation may occur between the solvents. On the other hand, if the concentration of a solution of a polymer having a substituent having a fluorine-containing alkyl group is too high, the viscosity will be high (and the amount of solution added will be extremely small), so it will not be possible to distribute the solution uniformly in the solvent of the acrylonitrile polymer. No longer dispersed.

The amount of solvent in the solution of the polymer having a fluorine-containing alkyl group is preferably in the range of 0.1 to 40% with respect to the amount of solvent in the solution after mixing. As mentioned above, in the membrane manufacturing method, the method for adding a polymer having a fluorine-containing alkyl group to an acrylonitrile-based polymer is simply adding a predetermined amount of a polymer having a substituent having a fluorine-containing alkyl group to the stock polymer solution during membrane formation. Since it is only necessary to add a solution of 1 to 2, it is possible to easily form a membrane without clogging the openings or micropores on the surface of the membrane.

Any membrane shape can be used, such as a sheet-like membrane, a hollow fiber-like membrane, etc., but hollow fiber membranes are advantageous from a practical standpoint.

The sheet-like membrane is prepared by applying a mixed solution of the above-mentioned acrylonitrile polymer solution and a fluorine-containing alkyl group-containing polymer solution to a solid surface, a support, or a funerary support membrane.
- Casting, dispensing or coating at a constant thickness (7
, After evaporating the solvent for a certain period of time, the solvent is replaced with a coagulation solvent.1. can be obtained. Here, the inside of the solid surface is dissolved in the solvent of the polymer mixed solution or the substituting solvent! It is a solid, smooth surface without any material 7, and a glass plate, a plate 7 made of polytetrafluoroethylene, a metal plate, etc. can be used. In addition, the support is a membrane strength reinforcing material that does not dissolve in the solvent of the polymer mixed solution or the solvent to be substituted, and has substantially no separation performance, 9, nonwoven fabric 5, cloth, metal mesh, etc.

etc. can be used. Furthermore, the porous support membrane is a porous membrane that does not dissolve in the solvent of the polymer mixed solution or the solvent to be substituted, and an organic porous membrane such as porous glass, porous ceramics, etc. and 1. Porous membranes of various polymers can be used. Here, the polymers of the organic porous support membrane include polyedinone 1, polypropylene, polytetrafluoroedinone, and copolymers of the following polymers, polyvinylidene fluoride, polyacrylic acid, and polyacrylic acid. Ester, polymethacrylic acid7. , polymethacrylic acid ester, polyacrylamide, polyvinyl alcohol, and other vinyl polymers, copolymers thereof, blend polymers thereof, polyesters, polyamides, polysiloxanes, polyphosphazenes 5, cellulose polymers, and the like.

On the other hand, in the case of a hollow fiber membrane, a mixed solution of the above-mentioned acrylonitrile-based polymer solution and a solution of a polymer having a fluorine-containing alkyl group is poured into the hollow fiber while flowing a fluid through the annular 11K gold to the center. Discharging method: After coating the surface of a hollow fiber support membrane and evaporating the solvent for a certain period of time9,
There are methods such as replacing the solvent with a coagulation solvent 3, cyclic 11
When using gold, the fluid flowing into the center may be water, liquid,
Air, nitrogen, argon, etc. can be used as a gas such as a coagulable liquid such as alcohol, an incompatible liquid, and a mixed liquid thereof. A hollow fiber support membrane is a porous membrane that does not dissolve in the solvent of the polymer solution or the solvent to be substituted, and is a porous membrane that does not dissolve in the solvent of the polymer solution or the solvent to be substituted. 7! Porous membranes of various polymers can be used. here,
Polymers for the porous support membrane include polyethylene, polypropylene, polytetrafluoroethylene, tyrene and copolymers of the above polymers, polydinylidene fluoride, polyacrylic acid, polyacrylic ester, polymethacrylic acid,
Vinyl polymers such as polymethacrylic acid ester, polyacrylamide, polyvinyl alcohol, copolymers thereof, and blend polymers thereof, polyesters, polyamides, polysiloxanes, polyphosphazenes,
Examples include cellulose polymers.

The coagulating solvent is a solid content of the mixed solution that is miscible with the solvent of the mixed solution at the time of film formation described in 7. It refers to a solvent that precipitates. Examples of such solvents include alcohols such as methanol, ethanol, and propatool, acetone, water, and mixed solvents of these or other solvents.

In order to prepare a dry porous membrane with a suitable porous structure, it is preferable to replace the non-solvent of the acrylonitrile polymer with a solvent that is miscible with water. 1. However, the aqueous volatile organic liquid solution to which the present invention can be applied may be prepared by drying a water-containing film under mild conditions. Basically, it can be applied to substances whose composition is larger than that in the liquid phase9. Examples of such substances are methanol and ethanol5!]
propatool, is1] - propatool, n-butanol, t-butanol, acetone, tetrahydrofuran, 114-dioquinane, methylamine, ethylamine, acetonitrile, methyl ethyl ketone, methyl acetate,
When applying the present invention, the concentration of the aqueous solution of these substances obtained is preferably in an extremely low concentration range from the viewpoint of taking advantage of the characteristics of the method of the present invention.1. <,0,
A weight percentage of 5 to 20% is suitable. The upper limit of the aqueous solution concentration is mainly 1. The aqueous solution to be separated is determined at a concentration that does not wet the membrane1. This is related to the physicochemical properties of the membrane material boria, the micropore diameter of the membrane, the surface tension of the separation target, etc., and in the case of porous materials, factors such as Difficult to specify within shells as they are intricately related.

[Example] Next, the present invention will be explained with examples.

The experiment of the method of concentrating a volatile organic liquid aqueous solution of the present invention was conducted as follows:
This was carried out by the method schematically shown in FIG.

That is, a 5% ethanol aqueous solution is heated to 30°C from supply tank 1.
It is adjusted and supplied to the membrane module 4 and circulated.

On the other hand, on the secondary side of the membrane, there is an inlet 12 on the secondary side of the membrane module.
Nitrogen gas was passed through the needle valve 5 as an inert gas, and the permeated components were collected in the cold trap 6 along with the permeated vapor from the same outlet 11. The cold trap 6 is connected to the vacuum pump 1 via a cold trap 7 for equipment maintenance, and via a pressure regulator 8 to maintain a predetermined degree of reduced pressure.
Connected to 9.

The experiment was carried out by assembling the apparatus as shown in Figure 1, circulating the aqueous solution, starting operation under the specified conditions, and using the cock 16, trap 13, and cock 18 to bring the pressure, nitrogen flow rate, and permeation state to a steady state. , the cocks 16 and 18 were closed, the cocks 15 and 17 were opened, and the permeated liquid necessary for measuring the amount of permeation and analyzing the permeated components was collected in the trap 6 cooled with liquid nitrogen and sampled.

The amount of permeation was determined by weighing, and the composition of the amount of permeation was determined by gas chromatography or differential refractometer to determine the solute concentration. The separation coefficient was calculated using the following formula. cl is the solute concentration (weight fraction) of the feed solution and Q is the solute concentration (weight fraction) of the permeate solution.

α6°”'= (C!/ (l C?) ) / (
CI/(1-Q)) Also, the average micropore radius of the membrane was measured by the method described below. That is, the water permeability of the membrane (Lp)
and the diffusive separability (Pn+) of the solute, which is the substance to be separated: methanol, ethanol, propatool, butanol,
It was measured using acetone etc. and calculated using the relationship of the following formula.

Pm・(D/l) (H/ts2)
(2) t, p・(H/L) tRp 2/(llη
(3) Here, D is the diffusion coefficient of the solute, L is the film thickness, H is the water content, $1 is the oil passage ratio of the solute, Rp is the average micropore radius, and η is the viscosity of water. IS was calculated from the following formula.

Isv' = RT/D (4)
ISW = (RT/Pi-Vs/Lll) (H/
L) (5) D = Isw/l5v0 (5) where R is the gas constant, T is the absolute temperature at the time of measurement, and vS is the partial molar volume of the solute.

Example 1 A copolymer with an intrinsic viscosity [η] of 1.2 consisting of 94% acrylonitrile and 6% methyl acrylate was prepared at a polymer concentration of 2.
0%, and the solution viscosity at 50°C was adjusted to 97 poise. Polymer solution using DMSO as a solvent] 00Gg, in the general formula [I], R1 and R2 are hydrogen atoms, T is a methyl group, the peak is a perfluoroalkyl group having 7 carbon atoms, and X is a fluorine-containing alkyl group having an ester bond. 2 of polymers with groups
%1.2.2-trichloro-1°2,2-trifluoroethane solution (10 cc) was added to prepare a spinning stock solution. This spinning stock solution is passed through the hollow part using a circular hollow fiber spinning nozzle into two
Nitrogen was introduced at a pressure of Q+n+nHg, and a spinning dope was spun from the annular part. In this state, it is spun into water at 35°C from a spinneret, coagulated, and then washed with water.
After treatment with hot water at ℃, polyacrylonitrile hollow fibers in a water-containing state were obtained.

This membrane was immersed and replaced in methanol and n-hexane in sequence, and then air-dried. The outer diameter of the obtained hollow fiber membrane was 1614 μm,
The inner diameter was 1025 μm, and the 1-volume porosity was 78%.

This dried hollow fiber membrane was cut into lengths of about 30 cm, and seven pieces were bundled and inserted into an acrylic case. This case is about 20
It has a structure in which two fluid inlets and outlets are provided on the sides of a cm-sized acrylic pipe, with both ends of the pipe serving as the inlet and outlet for the ethanol aqueous solution, and the sidewall serving as the inlet and outlet for the inert gas. After inserting the hollow fibers, both ends of the case were potted with epoxy adhesive, and after curing, both ends were cut to create an opening for the hollow fiber membrane.

Experiments on concentrating volatile organic liquid aqueous solutions were carried out using ethanol 5
! The test was carried out as described above using a 1% aqueous solution.

In this example, as a result of measurement under the conditions of a module inlet temperature of 29.5°C, a degree of vacuum of 640 mmHg, and a carrier gas amount of 25 hl, the permeated water amounts of ethanol and water were 051, D, and 27 kg, respectively. Separation coefficient αl:: + fl 1″(1
Since the polyacrylonitrile membrane selectively permeates ethanol, the polyacrylonitrile membrane selectively permeates ethanol.Example 2 The fluorine-containing alkyl group of Example 1 has a substituent that
) A polyacrylo 0 nitrile hollow fiber membrane was manufactured by I'
5. In the experiment of the similar concentration method, the separation coefficient α1 (i
I+・3.64h,-) 1゜Example: (The mixture of polymers having a substituent that makes the -nitrogen-containing alkyl group of Example 1 ?"J is 1oOcc, and 7 ponds are under the same conditions. Boria ° Kuri 1 Coni I / Lil system hollow fiber 11Q was prepared by 1. =, similar concentration method σ) experiment, ; E was carried out 1
．． The separation coefficient that is missing in the 1′ shoe is α1””=4
．． 47 and the width direction (・(, ta 1, Example 4 Real!i1+i Example IC ha)
4) Instead of a polymer having a substituent, general formula [1]
B1, R2, R3 are Ryo Mizuhara, Yama is IHlIH, 2H
,211~hebuta1cafluoro1-1decyl group, X is
- A polyacrylonitrile hollow fiber membrane was prepared under the same conditions using a polymer with chill bonds (1. A similar concentration method experiment was carried out by Mukoro, ■Yu). Mukai 1-shi 80.

Comparative Example 1 Polyacrylonitrile hollow fiber membranes were prepared with and without the addition of poly(7) having a substituent having a fluorine-containing -1° alkyl group in Example 1, and experiments using the concentration method were conducted in the same manner. As a result, the dry hollow fiber membrane gradually got wet after the experiment started (the undiluted solution leaked out from the membrane surface (3), which was difficult to measure). [Effect of the invention 1] According to the present invention, a volatile organic liquid with improved separation selectivity is obtained for use in a novel membrane separation method for a liquid-gas system that selectively concentrates and separates the liquid from an aqueous volatile organic liquid solution. 1. A method for preparing an aqueous solution concentrating membrane Ris.

[Brief explanation of drawings]

Figure 1 is a schematic diagram showing the lf method for manufacturing FJ membranes according to the present invention.
: ,, H-dol jf: l・wrap 7: cold trap 8 pressure regulator 1-1 ・Output [I] 12
:,,, &D 19 Vacuum pump ゛Special 1 pestle Applicant Figure 1

Claims (5)

[Claims] (1) A porous membrane made of an acrylonitrile polymer, characterized in that it is made of a composition containing a polymer having a fluorine-containing alkyl group. (2) The volatile organic liquid aqueous solution concentration membrane according to claim 1, wherein the porous membrane made of an acrylonitrile polymer contains at least 50% by weight of polyacrylonitrile. (3) The polymer having a fluorine-containing alkyl group has the general formula [
I], ▲There are mathematical formulas, chemical formulas, tables, etc.▼[I] [In the formula, R_1, R_2, R_3 are one or more types selected from a hydrogen atom, a hydrocarbon group having 1 to 20 carbon atoms, or a fluoroalkyl group. Substituent, R_4 has 1 carbon atom
~20 fluoroalkyl groups, X represents any one of an ester bond, an amide bond, an ether bond, and a sulfoamide bond. ] The volatile organic liquid aqueous solution concentration membrane according to claim 1, characterized in that it contains a fluorine-based polymer having a structural unit represented by the following formula. (4) R_1 and R_2 in the general formula [I] are hydrogen atoms,
4. The volatile organic liquid aqueous solution concentration membrane according to claim 3, wherein R_3 is a methyl group, R_4 is a perfluoroalkyl group having 7 carbon atoms, and X is an ester bond. (5) A method for producing a volatile organic liquid aqueous solution concentrated film, which comprises forming a film using a mixed solution obtained by adding a solution of a polymer having a fluorine-containing alkyl group to a solution of an acrylonitrile polymer.