JPS5892405A - Separation of liquid mixture - Google Patents

Abstract

PURPOSE:To carry out efficient operation, in separating or concentrating an org. liquid mixture by pervaporization, by using a fluorinated olefinic copolymer membrane. CONSTITUTION:In separating or concentrating a mixture of org. liquids or a mixture of water and an org. liquid by pervaporization, a high molecular membrane comprising a copolymer of a fluorovinyl compound containing a carboxylic acid derivative group and having ion exchange capacity of 0.01-3 miliequivalent/g is used to carry out separation or concn. excellent in efficiency and a speed. An operation temp. is pref. 0-200 deg.C, operation pressure is pref. 0- 100kg/cm<2>, the thickness of the membrane is 1-250mu and the membrane may be laminated on a porous support.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for separating or separating a liquid mixture containing at least an organic liquid as one of its components (hereinafter abbreviated as an organic liquid mixture) by pervaporation using a specific polymer membrane. Concerning the method of concentrating.

A process for separating organic liquid mixtures using non-porous, uniform polymeric membranes has been previously described in U.S. Pat.
Numbers are shown in Specification No. 2, 4Ir, etc. This separation process generally involves a pervaporation process using a membrane, in which the liquid to be treated is supplied to the primary side (high pressure side) of a polymer membrane, and substances that are easily permeable are transferred to the secondary side (low pressure side). This is a method of preferentially transmitting it as vapor. This membrane separation method can separate liquid mixtures that could not be separated using conventional simple methods.
For example, it is attracting attention as a new method for separating or concentrating azeotropic mixtures, mixtures with close boiling points and low specific volatility, and mixtures containing substances that polymerize or modify when heated.

Conventionally, the polymer membranes used in such separation methods are polyethylene and polypropylene.

Cellulose polymer materials, polyacrylonitrile, polyamide, polyester, polystyrene.

Membranes made of polytetrafluoroethylene or copolymers thereof are known. However, when such a membrane is used to separate an organic liquid mixture by pervaporation, the following practical difficulties are observed. That is, (1) Since the concentration ratio (separation coefficient "AB") caused by an organic liquid mixture passing through a polymer membrane once is small, it is necessary to use a very large number of membranes in order to concentrate or separate the organic liquid mixture to the desired concentration. must be passed.The general K and the separation factor "AB" are as follows.

(2) Since the amount of permeation of an organic liquid mixture through a polymer membrane (generally expressed as the permeation amount per unit membrane surface area, unit membrane thickness, and unit time) is small, the membrane surface area must be made very large or The thickness of the molecular membrane must be made extremely thin. Therefore, in the former case, the equipment cost becomes excessive, and in the latter case, problems arise in the strength and durability of the membrane.

As the above-mentioned improved process, a method using a polymer membrane in which sulfonic acid groups etc. are bonded to a polymer base, a method using a specific polyamide membrane, a method using an ionomer polymer membrane, etc. are disclosed in Japanese Patent Application Publication No. It is disclosed in Japanese Patent No. 52-111888, Japanese Publication No. 52-111889, Japanese Publication No. 54-33278, Japanese Publication No. 54-33279, etc.

The present inventor has conducted various studies on means of separating or concentrating various organic liquid mixtures by pervaporation.
As a result of repeated studies, it was found that a polymer film made of a fluorocarbon resin having a carboxylic acid type functional group, such as a copolymer of tetrafluoroethylene and a specific fluorovinyl compound having a carboxylic acid type functional group, can overcome the above-mentioned difficulties. We have found that this can be solved advantageously.

The present invention has been completed based on the above findings, and a liquid mixture having a small amount of organic liquid as one of its constituents can be prepared using the general formula CF, = CF-(○&)n-A (however, n is 1 to 10, X and Ma are a fluorine atom or a perfluoroalkyl group having 1 to 10 carbon atoms, and A is -
CN, -COF.

, R+ is an alkyl group having 1 to 20 carbon atoms, M is a metal atom or -Nta'n''π, m is the valence number of M, R2, R3, R4, B:, R6 and π is a hydrogen atom or W), and is composed of at least a two-component copolymer of a fluorovinyl compound and a fluorinated olefin compound, and has an ion exchange capacity of 0.01 to 3 milliequivalents/g dry resin. The present invention provides a novel method for separating liquid mixtures using a molecular membrane, which is characterized by separation by pervaporation.

In the present invention, the fluorovinyl compound constituting the specific polymer membrane has the general formula CF, = cp, as described above.
-(c, d), represented by n-A, where n in the formula.

X, Ma and A are as described above. In this case, it is important to select n as described above from the viewpoint of film formation and performance of the polymer membrane of the present invention. For example, when n is O, copolymerizability with the fluorinated olefin compound is too thick, it is difficult to obtain a copolymer in which the carboxylic acid type functional groups are uniformly dispersed, and the polymer membrane obtained from the copolymer has poor flexibility. On the other hand, if n is too large, the copolymerizability with the fluorinated olefin compound will decrease, making it difficult to obtain a polymer membrane with sufficient ion exchange capacity. From this point of view, it is particularly preferable that n is 2 to 5. Further, A is a carboxylic acid type functional group, namely -COOH.

-CN, -COP, -COC, -coN
It is important that it is a functional group such as aa3. M is a metal atom such as an alkali metal or alkaline earth metal or -Nt
R”it, m is the valence number of M, and lv is the number of carbon atoms from 1 to
20 alkyl groups, R2, R3, R4a'', R
6 and R7 are hydrogen atoms or R1.

In the present invention, from the viewpoint of copolymerization reaction with the fluorinated olefin compound, A is preferably 100F or -Cool"('. From this viewpoint, preferred representative examples of the fluorovinyl compound include CF , = CFCF, COO
CH3't CF, = CFCF2COF.

Examples include CF, :CP(CF, )3COF, and the like.

In the above, preferred functional groups in a specific fluorovinyl compound were exemplified from the viewpoint of availability and copolymerization reactivity, but of course, the functional groups in the polymer membrane during pervaporation are It may be converted into an appropriate type. Such conversion of functional groups is usually carried out after forming a polymer membrane, and it is desirable to select the form of the functional groups as appropriate depending on the organic liquid mixture to be subjected to pervaporation.

On the other hand, the fluorinated olefin compound used in the present invention is preferably represented by the general formula (% is -CF3), and representative examples thereof include tetrafluoroethylene, trifluoroethylene chloride, , fluoropyrene hexafluoride, nithirei trifluoride, vinylidene fluoride, vinyl fluoride, and the like. Usually, perfluoro compounds are preferred, and tetrafluoroethylene is particularly preferred.

In the present invention, two or more of the above can be used as constituent units of the fluororesin having a carboxylic acid type functional group (hereinafter referred to as carboxylic acid type fluororesin), and as described above, these Besides, other copolymerizable components such as olefin compounds such as ethylene, propylene, imbutylene, CF2=ci;'OQ (Q
represents a perfluoroalkyl group having 1 to 10 carbon atoms, such as fluorovinyl ether, CF2-CF-CF =
CF2. CF, = CPo(CF2)−,0CF
One or more types of divinyl monomers such as = CF2 and other functional monomers having sulfonic acid type functional groups can also be used in combination. Of course, a carboxylic acid type functional monomer having a different form from the fluorovinyl compound having a carboxylic acid type functional group in the present invention, such as perfluorovinyl ether having a carboxylic acid type functional group, may be used in combination. .

In the present invention, the content of the specific fluorovinyl compound is related to the ion exchange capacity described below, and may be about 1 to 50 molti, preferably about 2 to 40 molti in the polymer.

The copolymerization in the present invention can be carried out using or without the use of an inert organic solvent or an aqueous medium, under the action of a polymerization initiator such as a peroxy compound, an azo compound, ultraviolet light, or ionizing radiation, using well-known or known means. It can be done by For example, Japanese Patent Publication No. 48-2223, Japanese Patent Publication No. 48-207
Copolymerization can be carried out by methods such as those described in Japanese Patent Publication No. 88, Japanese Patent Publication No. 48-41942, and the like. As the polymerization method, various methods such as bulk polymerization, solution polymerization, suspension polymerization, and emulsion polymerization can be adopted.

The fluorine-containing copolymer of the present invention may be a graft copolymer or a block copolymer, but the carboxylic acid type functional group is uniformly dispersed in the copolymer, and the polymer film has a uniform ion exchange capacity. A copolymer obtained by directly copolymerizing each of the above-mentioned monomer compounds is particularly preferred in that it provides the following.

Further, the means for forming a polymer film from a specific carboxylic acid type fluororesin can be carried out by any known means, such as press molding, roll molding, extrusion molding, solution casting, dispersion molding, or powder molding.

The carboxylic acid-type fluororesin of the present invention may be made of a fluorine-containing copolymer such as an olefin polymer such as polyethylene or polypropylene, preferably polytetrafluoroethylene or a copolymer of ethylene and tetrafluoroethylene, if necessary during film formation. The copolymer can be blended and molded, or the membrane can be reinforced by supporting the copolymer with a support made of cloth, net, or other woven fabric, nonwoven fabric, or porous film made of these polymers. . Note that the weight of the resin forming the blend or support is not included in the ion exchange capacity below.

In the present invention, the content of the carboxylic acid type functional group in the carboxylic acid type fluororesin can be adopted over a wide range;
In a preferred embodiment, the ion exchange capacity described below is o, oi
Selected from a wide range of ~3 mils to 3 mg dry resin. The ion exchange capacity is preferably about 01 to 22 meq/g dry resin. In addition, from the viewpoint of mechanical strength as a polymer membrane, the molecular weight of the carboxylic acid type fluororesin is 50' when expressed by the TQ value described below.
C or higher, preferably about 70 to 300°C.

In this specification, the term rTqJ is defined as follows. That is, the temperature at which the volumetric flow rate 1 ooml'Il/sec associated with the molecular groups of the polymer is defined as TQ. In the roof tile, a polymer with -COOCH8 carboxylic acid type functional groups was used, and the capacity flow rate of the polymer was 30 kg/cr! Under pressure and at constant temperature 1
The amount of polymer melted and flowed out from an orifice with a length of 111 m and a length of 2 mm is expressed in units of mf/sec.

In addition, "ion exchange capacity" was determined as follows. That is, a carboxylic acid-type fluororesin whose carboxylic acid-type functional group is a -COOH group is left in IN HCI at 60°C for 5 hours to completely convert to H-type, and then it is thoroughly diluted with water so that no HCI remains. Washed.

After that, this H-type resin 0.5. ! i! , 0. In a solution prepared by adding 25 ml of water to 25 ml of IN NaOH,
It was left standing at room temperature for 2 days. Next, the resin is taken out and the amount of Nap in the bath liquid is determined by back titration with 0.IN HCl.

The polymer film made of carboxylic acid type fluororesin used in the present invention is a non-porous uniform film, and the film thickness is 1 to 25 mm.
0 micron, preferably about 5 to 180 micron. If the film thickness becomes too thin, the strength of the film will be insufficient, but the durability will be insufficient. Furthermore, if the membrane is too thick, the amount of permeation of the liquid mixture becomes small, making it impractical. The shape of the polymer membrane is normally used as a flat membrane, but it can also be used in other shapes such as a cylindrical shape or a hollow fiber shape to increase the surface area. Various reinforcing means may be applied, such as embedding a material or laminating a membrane on a porous reinforcing body.

The method of the present invention uses the above-mentioned carboxylic acid type fluororesin membrane, -
It is carried out using a device divided into a firebox and a secondary chamber.

- The firebox contains the organic liquid mixture to be separated or concentrated in liquid form, while the second firebox is depressurized by an appropriate method, or
or circulating other liquids or gases. In this way, the organic liquid mixture is permeated through the polymer membrane and separated or concentrated by pervaporation. - The liquid inside the firebox is preferably circulated externally or internally, or - is agitated by providing a suitable stirring device inside the firebox. The specific polymer membrane is held in a suitable manner to partition the primary chamber and the secondary chamber, but it is advantageous in terms of durability if it is supported by, for example, a perforated reinforcing plate. - Substances that permeate the polymer membrane from the firebox are removed from the secondary chamber and collected. It is usually desirable to heat the firebox and/or the secondary chamber appropriately using a suitable heating device, such as a heating jacket.

The separation method of the present invention is carried out over a wide range of temperatures, typically from 0 to 200'C, preferably from room temperature to 100'C.
Selected from a range of approximately ℃.

If the temperature is too high, problems will arise in maintaining the shape of the polymer membrane, and if the temperature is too low, the amount of liquid permeated will be small. Generally, the amount of permeation can be reduced at high temperatures, but the concentration ratio (separation coefficient) due to membrane permeation becomes smaller. In addition, the pressure range that can be adopted is usually from vacuum to 100kli/cr.
/l, preferably about vacuum to 30 kg/7; if the pressure is too high, it becomes difficult to maintain the shape of the polymer membrane.

The organic liquid mixtures that can be separated by the method of the present invention include various combinations, such as mixtures of organic substances that cannot be separated by normal distillation methods because of the presence of azeotropic points, and mixtures of organic substances that cannot be separated by ordinary distillation methods because their boiling points are close to each other. This method is particularly effective in the case of mixtures of organic substances that are difficult to separate by distillation. Further, the organic liquid mixture may be entirely dissolved in each other uniformly, or a part of the organic liquid mixture may exceed the solubility and precipitate into a suspended state.

However, when mixing an organic liquid, it is necessary that the mixed state is liquid within the above-mentioned implementation temperature range and normal pressure or employed pressure range.

Examples of such organic liquid mixtures include benzene/cyclohexane and benzene/n as mixtures having an azeotropic point.
- Mixtures of organic substances such as hexane, methanol/acetone, benzene/methanol, acetone/chloroform; water/isopropanol, water/ethanol, water/n
-Glopanol, water allylalyl, water/2-methoxyethanol, water/isobutanol, -water/n-butanol, water/2-7 linol, water/furfuryl alcohol, water/n-pentanol, water Examples include water/alcohol mixtures such as 2-pentanol 1 water/4-methyl-1-butanol; water/organic solvent mixtures such as water/tetrahydrofuran, water/dioxane, and water/methyl ethyl ketone.

In addition, mixtures whose boiling points are close to each other are Teha, ethylpenze//styrene, p-chloroethylbenzene/p
-Chlorstyrene, toluene/methylcyclohexane,
Examples include butadiene/butenes, butadiene/butanes, n-butene/mebutene, and the like. Other examples include water/glycerin, water/glycols, water/propylene chlorohydrin, water/propylene dichlorohydrin, water/epichlorohydrin, water/hydrazine, and isomer mixtures.

Furthermore, the method of the present invention can be applied to these mixtures not only in the two-component system as described above but also in a multi-component system of three or more components. Of course, the method of the invention can also be applied to mixtures containing organic and inorganic substances, such as wastewater containing organic liquids.

The mixing ratio of the liquid mixture to be treated can be changed within an arbitrary range, but in general, the closer the ratio is to the equivalent situation, the higher the concentration ratio will be. If the desired purity cannot be obtained by passing through a polymer membrane once (-membrane concentration), pass it through a similar device multiple times (multi-stage concentration).
It is also possible to 'concentrate or separate the organic liquid mixture to the desired degree.

Examples of the present invention will be described in more detail below, but it goes without saying that the present invention is not limited in any way by such explanations.

Example 1 In a 200 ml stainless steel pressure-resistant reaction vessel, 201 trichlorotrifluoroethane and 20 g of CF2: CF
-CF2COOCH3 and 80 μm of azobisisobutyronitrile were charged. After sufficient degassing, tetrafluoroethylene was charged to 18 kliF/d at 70°C to carry out a copolymerization reaction. After 20 hours, 7.5 g of copolymer was obtained. The copolymer was press-molded at 180°C to form a film with a thickness of 100μ.

After hydrolyzing the film in caustic soda,
Treated at 0°C for 16 hours, then dried at 70°C for 24 hours, yielding an ion exchange capacity of 1.30 rreg/! 9 membranes were obtained. A mixed solution of water and isopropanol (impropanol/water = 82
/18, weight ratio) was separated. The separation coefficient of water obtained at a temperature of 40°C and a permeation side pressure of 10: nm for isopropanol is 20.2, and the amount of permeation is 45697.
Ivy at 7Fll-hr.

Example 2 CF', = 2 instead of CF-CF2COOCH3
5g of CF2 = CF(CF, )s coF and 5g
A copolymerization reaction was carried out in the same manner as in Example 1 except that CF2=CFOC,F was charged, and the ion exchange capacity was 1.2.
A copolymer of 0rreg/9 was obtained. 1 of the copolymer
It was press-molded at 800C to form a film with a thickness of 100μ.

After hydrolyzing the film in caustic soda, the functional group was changed to -COOH in hydrochloric acid, treated with pure water at 90°C for 16 hours, and then dried at 70°C for 24 hours. A mixed solution of water and ethanol (ethanol/water = 94/6, weight ratio) was separated by pervaporation using the membrane. 4
0℃.

10-1 mm) (The separation coefficient of water obtained in j9 for ethanol is 5.60, and the amount of permeation is 750j
j/-・h "It was.

Example 3 CF2= CF-CF, Co0cH, tetrafluoride: f-
Ion exchange capacity is 0.91 by copolymerizing f L/7.
A copolymer of rreg/9 was obtained. The copolymer was press-molded into a film with a thickness of 100 μm.

The film was hydrolyzed in lithium hydroxide and diluted with pure water at 9%
After processing at 0°C for 16 hours, it was dried at 70°C for 24 hours to obtain a film with -αηLi type functional groups. Using this model, a separation experiment similar to that in Example 2 was conducted, and as a result, the separation coefficient and permeation amount were 5.59. 53 '19/rrt ・h
It was r.

April 1980, Commissioner of the Patent Office Haruki Shimada1, Indication of the case Patent Application No. 189254 of 19892, Name of the invention Method for separating liquid mixtures3, Person making the amendment Case and Relationship of patent issuer Address: 2-1-2 Marunouchi, Chiyoda-ku, Tokyo Name (
004) Asahi Glass Co., Ltd. 4, Agent No. 2 Okada Building 6, Number of inventions increased by amendment None 7, Subject of amendment Specification

Claims (1)

[Claims] A liquid mixture containing a small amount of an organic liquid as one of its constituents is defined by the general formula CF2=cp-(cM)n-A (where n is 1 to 10, and X and M are A fluorine atom or a perfluoroalkyl group having 1 to 10 carbon atoms, and A is -C
N, -COF, -Cα morphism. -αη+ffi, -coo-! -M or -CONR
"R:, R1 is an alkyl group having 1 to 20 carbon atoms, M is a metal atom or -NR4-R6R7, m is the valence number of M, R2, R3, R4, R5, all
and R7 is a hydrogen atom or R) and a fluorinated olefin compound, and has an ion exchange capacity of 0.
Polymer In2 which is 01-3 milliequivalents/gram dry resin
A method for separating a liquid mixture, characterized in that the separation is performed by pervaporation.