JPS5892404A - Separation of liquid mixture - Google Patents

Abstract

PURPOSE:To enhance separation efficiency, in separating an org. liquid by pervaporization, by using a high molecular membrane comprising a fluorine contained resin having an acidic functional group wherein the part of the acid type functional group in the surface layer thereof is converted to a non-functional group. CONSTITUTION:As a high molecular membrane, a resin comprising a fluorine contained polymer having an acid type functional group such as a carboxylic acid group, a sulfonic acid group, a phosphoric acid group or a phenolic hydroxyl group is used and the surface layer of the membrane is modified by oxidizing treatment, reducing treatment, alkali treatment, discharge treatment, ionizable irradiation treatment or flame treatment. The degree of modification is appropriately selected corresponding to an org. liquid to be separated. As an org. mixture, a mixture in which an azeotropic substance is present, a mixture comprising org. liquids of which boiling points are mutually close or an isomer mixture are designated and the org. liquid can be separated in high separation coefficient and a permeation amount under such a condition that a temp. is about a room temp. -100 deg.C and pressure is vacuum -30kg/cm<2>.

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.
This is taught in Specification No. 2, etc. This separation process is generally called a pervaporation process using a membrane, in which the liquid to be treated is supplied to the primary side (high pressure side) of the polymer membrane, and substances that are easily permeable are supplied to the secondary side (low pressure side). This is a method of preferentially transmitting it as vapor. This membrane separation method separates or concentrates liquid mixtures that could not be separated using conventional simple methods, such as azeotropic mixtures, mixtures with close boiling points and low relative volatility, and mixtures containing substances that polymerize or modify when heated. It is attracting attention as a new way to do so.

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 recognized. That is, (1) Since the concentration ratio (separation coefficient AB) of an organic liquid mixture passing through a polymer membrane once is small, a very large number of membranes must be passed in order to concentrate or separate the organic liquid mixture to the desired concentration. must be passed. In general, the separation factor α
AB is 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 for separating or concentrating various organic liquid mixtures by pervaporation.
As a result of repeated studies, it has been found that an acid type fluororesin film in which the acid type functional groups in the surface layer are made non-functional can smoothly and advantageously solve the above-mentioned problems.

The present invention has been completed based on the above-mentioned findings, and it is possible to apply a liquid mixture containing at least an organic liquid as one of its constituent components to the surface layer of a polymer membrane made of a fluororesin having acid-type functional groups. The present invention provides a novel method for separating a liquid mixture, which is characterized by separation by pervaporation using a polymer membrane in which at least some of the functional groups are non-functional.

In the present invention, examples of the fluororesin having an acid type functional group (hereinafter abbreviated as acid type fluororesin) include a carboxylic acid group, a sulfonic acid group, and a phosphoric acid group.

A resin made of a fluorine-containing polymer having an acid type functional group such as a phenolic hydroxyl group is preferred. As a resin,
For example, those having a copolymer structure of a fluorinated olefin compound such as tetrafluoroethylene and a fluorovinyl compound containing an acid type functional group such as a sulfonic acid group, a carboxylic acid group, or a phosphoric acid group are preferable.

In particular, it is preferable to use polymers having the following structures (a) and (b).

(a) +aF2-OXX'+-, (b) +0F2-c
x-)-here or? , 01. H or -CF3,
X' is X or CF3 (CF2), m is 1-5, and Y is selected from the following:

Z Rf Z Rfx, y, z are
Both are 0 to 10, and Z+% is -F or carbon number 1 to 1
selected from 0 perfluoroalkyl groups. Also, A is PeOOH, -00081M.

-3o H, -8o ・YU M, etc., or -3o F, -ON, - which can be converted into 531 these groups by hydrolysis.
G! OF.

-COOR', -8o, R1, -0ONR2R"
, -8o2N'R2'R' is an acid type functional group,
M is an alkali metal.

metal atom such as alkaline earth metal or -NRRRR, l is the valence number of M, R1 is an alkyl group having 1 to 20 carbon atoms, R2p (5, R4 ° R5, R6 and R7 are hydrogen Indicates an atom or R1.

Accordingly, in the present invention, the acid type fluororesin can be a copolymer of a fluorinated ethylenically unsaturated monomer (I) and an acid type functional monomer (6). . Examples of (I) include tetrafluoroethylene, chlorotrifluoroethylene, 7'-pyrene hexafluoride, ethylene trifluoride, vinylidene fluoride, and vinyl fluoride, with the general formula 0F2-cxx' ( x and X' are a fluorinated olefin compound represented by (as described above). Among these, perfluoroolefin compounds are preferred, and tetrafluoroethylene is particularly preferred. (2) is preferably a fluorovinyl compound of the general formula aF,,=cxxr (x and Y are as described above), and a preferable example is aF2=cx-(OOF20FR,) p-(o )
, -(eFR/f'')r-A (where p is O-3,,
q is 0 to 1. r is an integer from 0 to 12, X, Rf, A
is as described above, and R'f is 0). From the viewpoint of performance and availability, X is a fluorine atom, and R4 is -0F3. R;
is a fluorine atom, p is 0 to 1. q is 0 to 1. It is preferable that r is 0-8. A preferred representative example of the fluorovinyl compound is CF'2=CFo (CF
2), 4000R9CF2-OFO(CF2)1N80
OF.

CF2-=-OF (1!F outside, 8C+0OR-〇F,
-cyoap2aF(EF,) oaF2aF2aoo
R1゜OF, CFOOF20F (EF,) 0OF2
0F200F, OF, CFO'(E%),, 5
o2F.

CF-FOC! F20F (CF5) 0OF2G! F
Examples include 2SO2F.

In addition, in the present invention, functional groups other than carboxylic acid type,
For example, reduction treatment of a fluorinated copolymer having a sulfonic acid type functional group (JP-A No. 52-24175, No. 7, No. 52-241)
76,, JP-A-52-24177, etc.), oxidation treatment (JP-A-53-132094, JP-A-53-1320)
A b-polymer obtained by converting a sulfonic acid type functional group into a carboxylic acid type functional group may be used as a specific acid type fluororesin. Of course, the acid type functional monomer ( It may be used as 2).

Furthermore, in the present invention, the above-mentioned (I) and (6) or (A) and (
(b) can be used in combination of two or more, and in addition to these, other components such as olefin compounds such as ethylene, propylene, and isobutylene, CF2=O
Fluorovinyl ethers such as FOQ (Q represents a perfluoroalkyl group having 1 to 10 carbon atoms), 0F2=OF
-cp-=cy2゜CF2=OFO(OF2), ~4
Divinyl monomers such as 00F-CF2 and others can also be used alone or in combination of two or more.

In the present invention, the content of acid type functional groups in the acid type fluororesin can be adopted over a wide range, and is selected from a wide range of 0.01 to 3 milliequivalents/g dry resin in terms of ion exchange capacity.

The ion exchange capacity is preferably 0.1 to 2.2 milliequivalents/gram dry resin coverage. In addition, from the viewpoint of mechanical strength as a polymer membrane, the molecular weight of a specific acid type fluororesin is 50°C or higher when expressed as the value of T, which will be described later.
The temperature is preferably about 70 to 300°C.

In this specification, the term "TQj" is defined as follows. That is, the temperature at which a volume flow rate of 100 mm1/sec, which is related to the molecular weight of the polymer, is defined as TQ. The volumetric flow rate is determined by using a polymer with an acid type functional group of methyl ester type such as 10000H3 group, and applying the polymer to 30 to 9/cI! under pressure at a constant temperature for a length of 1 m. The amount of polymer melted and flowed out from two orifices is shown in units of rRj/sec.The "ion exchange capacity" was determined as follows. That is, a specific acid-type fluororesin whose acid-type functional group is H-type, such as 1000H, is left in 1N HCl at 60°C for 5 hours, completely converted to H-type, and HCl remains. Wash thoroughly with water to prevent stains. After that, this H-type resin 0.5
9 was left standing at room temperature for 2 days in a solution prepared by adding 25 ml of water to 25 ml of 0.1N NaOH. The resin was then taken out and the amount of NaOH in the solution was adjusted to 0.1N HOI.
It is determined by back titration.

In the present invention, the acid type fluororesin as described above is formed into a polymer film. The polymer membrane does not necessarily need to be formed from one type of polymer, nor does it need to have only one type of acid type functional group. For example, (for ion exchange capacity, two types of polymers may be used in combination, or a blend membrane may be used in which a weakly acidic functional group such as a carboxylic acid group and a strongly acidic functional group such as a sulfonic acid group are used in combination. , the specific acid-type fluororesin may be a graft copolymer or a block copolymer, but the acid-type functional groups are uniformly dispersed in the copolymer, resulting in a polymer membrane with uniform ion exchange capacity. From this viewpoint, a copolymer obtained by directly copolymerizing each of the monomerized architraves is preferable.

Furthermore, in the present invention, the method for forming a polymer film from the acid type fluororesin may be performed by any known method, such as press molding, roll molding, extrusion molding, solution casting, dispersion molding, or powder molding. It will be done.

The specific polymer membrane in the present invention may be made of an olefin polymer such as polyethylene or polypropylene, preferably a fluorine-containing polymer such as polytetrafluoroethylene or a copolymer of ethylene and tetrafluoroethylene, depending on the requirements. Fabrics such as cloth and nets made of copolymerized polymers,
The membrane can be reinforced by supporting the copolymer with a support made of nonwoven fabric or porous film. In addition, the weight of the resin forming the blend or support is:
It is not included in the above ion exchange capacity value.

In the present invention, in the non-polymer film made of the acid type fluororesin as described above, at least a portion of the acid type functional groups in the surface layer portion thereof are non-functional.

Such modification of acid-type functional groups may be carried out on both sides of the polymer membrane, or may be carried out on only one side.

It is sufficient that the acid-type functional groups to be modified are present only in the surface layer of the membrane. In the present invention, the acid-type functional groups in the surface layer 1 to 10 A below the surface of the membrane or the thickness of the membrane, preferably n or less, and in some cases, n or less, may be partially or partially modified, although they can be entirely modified if desired. It is sufficient to modify the functional groups of. Of course, if necessary, functional groups may be modified not only in the surface layer of the membrane but also in the deeper layer.

As such modification means, one or more treatments such as oxidation treatment, reduction treatment/alkali treatment, discharge treatment, ionizing radiation treatment, flame treatment, etc. can be appropriately employed. In the case of these treatments, it is sufficient to modify at least part of the acid-type functional groups as necessary in a thin area on the surface of the polymer membrane within a range that does not impede the purpose of the present invention, and it is sufficient to modify the acid-type functional groups in a thin range on the surface of the polymer membrane as necessary. If treated, the resin of the polymer membrane itself will collapse, so
To prevent this, it is preferable to carry out the process in a short period of time.

When the polymer membrane of the present invention is subjected to oxidation treatment, the oxidizing agent is preferably chlorine or a strong oxidizing agent such as hydrogen peroxide, perchlorate, permanganate, or dichromate. Gas or aqueous solutions are used. The treatment temperature is preferably 1000 to 200°C. This treatment can also be carried out under pressure if necessary. If the treatment temperature exceeds 200°C, the acid-type functional groups will be modified in excess of what is necessary, which is undesirable, and if the treatment temperature is below 130°C, the modification of the ion exchange groups will hardly proceed, resulting in little effect.

The reducing agent, the alkali, and the oxidizing agent may be used individually, or may be used as a mixture of an alkali and a reducing agent or an alkali and an oxidized jK/).

When a polymer membrane of an acid type fluororesin is treated by reduction treatment, a strong reducing agent such as hydrogen gas, metallic sodium, or hydrazine is preferably used as the reducing agent. Known means can be applied as a means for causing these reducing agents to act. For example, the specific polymer membrane may be brought into contact with hydrogen gas heated to a temperature of 60 to 180° C. for 1 to 120 minutes.

When treating a polymer membrane of acid-type fluororesin with alkali treatment, a strong alkali aqueous solution of NaOH or KOH with a high concentration of 20 to 60% by weight is used as the alkali. The treatment temperature is preferably in the range of 0 to 200°C. If the treatment temperature is 200° C. or higher, the reaction will proceed rapidly and excessive acid-type functional groups will be modified, which is undesirable. If the treatment temperature is 130° C. or lower, the effect will be less, which is undesirable.

When a specific functional group of the present invention is modified by discharge treatment, corona discharge using unequal electrodes is preferred as the discharge treatment. Any known means can be used for this purpose. As for the discharge voltage, a high voltage of about 100 to 100,000 volts or more can be used, but preferably 500 to 3.00 volts.
It is preferable to perform this at a voltage of 0 volts. The frequency of electricity is also 6
A frequency range of 0 to 500,000 cycles/second can be used, but a frequency of 600,000 to 500,000 cycles/second is particularly preferred. The current flowing between the electrodes can normally be up to 5.5 amperes or more, but is usually between 0.3 and 2.1 amperes to prevent collapse of the electrodes due to excessive current.

It is treated in this way, for example, by discharging for 1 x 10 seconds to 60 seconds, particularly preferably for 0.2 to 5 seconds.

When treating an acid-type fluororesin polymer film with ionizing radiation, the ionizing radiation has an ionizing effect such as α rays, β rays, γ rays, X rays, proton beams, electron beams, and neutron beams. Radiation is used.

Any known means can be used as means for irradiating these radiations. Preferred examples of radiation sources include cobalt-60, electron beam accelerators, and the like. The irradiation time is important because it is related to the degree of modification of the specific acid-type functional groups.If the irradiation is excessive, there is a risk that more specific acid-type functional groups will be modified than necessary, so the irradiation time is important. , preferably for a short period of time ranging from a fraction of a second to a few hundredths of a second.

When treating an acid-type fluororesin polymer membrane by flame treatment, the flame is preferably obtained by burning a mixture of propane, butane, natural gas, acetylene, and oxygen. The temperature of the flame is preferably at least 700°C or higher, more preferably 800 to 900°C. The flame treatment time may be several tenths to several hundredths of a second.

The above-mentioned modification treatment of the acid-type functional groups of the polymer membrane can be carried out continuously, intermittently, or batchwise. In this way, the acid type functional groups on the surface layer of the polymer membrane are modified, but...
It is desirable that the degree of modification be appropriately selected depending on the organic liquid mixture targeted for pervaporation.

In the present invention, the thickness of the polymer membrane made of acid type fluororesin is about 1 to 250 microns, preferably about 5 to 180 microns. If the film thickness becomes too thin, the film will lack strength or durability. 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 usually 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. Furthermore,
Various reinforcing means may be applied, such as embedding a reinforcing material such as a cloth-like material in the membrane, or laminating the membrane on a porous reinforcing body.

The method of the present invention is carried out using an apparatus partitioned into a secondary chamber and a secondary chamber using the above-mentioned specific acid-type fluororesin membrane. −
The next chamber contains the organic liquid mixture to be separated or concentrated in liquid form, while the two fire chambers are evacuated in a suitable manner or circulated with other liquids or gases. In this way,
The organic liquid mixture is passed through a polymer membrane and separated or concentrated by pervaporation. - The liquid inside the next chamber is preferably circulated externally or internally, or - agitated by providing a suitable stirring device inside the next chamber. A specific polymer membrane is held in a suitable manner to partition the primary chamber and the secondary chamber, but it is believed that supporting it with a perforated reinforcing plate, for example, is advantageous in terms of durability. - Substances that permeate the polymer membrane from the next chamber are taken out from the second chamber and collected. It is usually desirable to appropriately heat the secondary chamber and/or the secondary chamber 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 based on a range of degrees.

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. Further, the usable pressure range is usually vacuum to 100 to 9/d, preferably vacuum to about 30 kg/cnt, and if the pressure is too high, maintaining the shape of the polymer membrane becomes the key.

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. Furthermore, all of the organic liquid mixture may be mutually uniformly dissolved, or some of the organic liquid mixtures may precipitate (exceeding the solubility and become suspended).

However, the organic liquid mixture needs to be in a liquid state in its mixed state within the above-mentioned implementation temperature range and at normal pressure or within the 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
- propatool, water/allylic alcohol, water/2-methoxyethanol, water/isobutanol.

Water/n-butanol, water/2-butanol, water/furfuryl alcohol, water/n-pentanol, water/2-pentanol, water/water such as 4-methyl-1-butanol/
Alcohol mixtures include water/organic solvent mixtures such as water/tetrahydrofuran, water/dioxane, and water/methyl ethyl ketone.

In addition, as mixtures whose boiling points are close to each other, ethylbenzene/styrene, p-chloroethylbenzene/p
-chlorostyrene, toluene/methylcyclohexane, butadiene/butenes, butadiene/butanes, n-
Examples include butene/1-butene. Other examples include water/glycerin, water/glycols □, water/propylene chlorohydrin, water/propylene dichlorohydrin, water/ehyrylohydrin, water/hydrazine, and isomer mixtures.

Furthermore, the method of the present invention can be applied to these mixtures not only in the above two-component systems but also in multi-component systems, such as ternary or more. 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 extent.

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

Example 1 Tetrafluoroethylene and CF2-CFO (CF2),
By copolymerizing C00CH5, the ion exchange capacity is 1.30.
A copolymer 5 (7) was obtained. The copolymer was heated to 200°C.
After press molding to make a 100μ thick film,
Hydrolyzed. Next, one side of the obtained film was
It was immersed in a 40 wt% NaOH aqueous solution at 0°C for 2" hours. Then, it was treated with pure water at 90°C for 16 hours, and then
A membrane was obtained by drying at °C for 24 hours.

A mixed solution of water and isopropanol (isopropanol/water-82/18
, weight ratio) were separated. Temperature 40℃, permeate side pressure 1Q
The separation coefficient 1 of water for isopropanol obtained at mmHg is 22.5, and the permeation amount is 410 f1-
/J*hr.

Example 2 Tetrafluoroethylene and OF CFOCF20F (C
Fri0CF20F2SO2F was copolymerized to obtain a copolymer with an ion exchange capacity of 0.83 rr+e (7Slt-).The copolymer was press-molded at 200°C to a thickness of 1
After forming a film of 0.00 and p, it was hydrolyzed. next,
One side of the obtained film was exposed to 50% N by weight at 140°C.
It was immersed in an aOH aqueous solution for 1 hour. Then, 90% in pure water
C. for 16 hours and then dried at 70.degree. C. for 24 hours to obtain a membrane.

As a result of conducting a separation experiment similar to Example 1 using this membrane, the separation coefficient and permeation amount were 14.6 and 185, respectively.
It was 0 f'/m2s hr.

% formula % 1. Indication of the case Patent Application No. 189253 filed in 1989 2. Name of the invention Separation of liquid mixture 3. Person making the amendment Relationship to the case Patent applicant address Chiyoda, Tokyo 2-1-2 Marunouchi Ward Name (
004) Asahi Glass Co., Ltd. 6. Number of inventions increased by amendment None 7. Subject of amendment Specification

Claims (1)

[Claims] A polymer film made of a liquid mixture containing at least an organic liquid as one of its constituents, in which at least a part of the acid type functional groups in the surface layer of a polymer film made of a fluororesin having acid type functional groups is made non-functional. A method for separating a liquid mixture, which is characterized by separating by pervaporation using a membrane.