JPH0148802B2 - - Google Patents

Description

[Detailed description of the invention]

a Technical Field The present invention relates to a separation membrane and a separation method using the same. More specifically, the mixed liquid is placed on one side of the separation membrane, and the other side is evacuated to keep the absolute vapor pressure low, or the partial pressure of the target component is kept low by flowing an inert gas. The present invention relates to a pervaporation membrane that separates a target component from a mixed liquid by permeating the target component liquid due to the pressure difference on both sides of the membrane and evaporating it on the low pressure side, and a method for using the same. b Background Art The pervaporation method is a separation method devised for the purpose of separating liquid mixtures that cannot be separated by ordinary distillation methods. Examples of such liquid mixtures include azeotropic mixtures, near-boiling point mixtures, and mixtures containing compounds that are easily denatured by heat. Such separation methods have already been described.
For example, US Pat. No. 2,953,502 discloses separation of an azeotrope using a polyvinyl alcohol membrane, and US Pat. No. 3,726,934 discloses separation of an organic liquid mixture using a polyacrylonitrile membrane. In addition to the above, membranes made of polyethylene, polypropylene, cellulose acetate, polyamide, polyurethane, and polytetrafluoroethylene have been used as pervaporation separation membranes, but these generally have poor selective separation properties and are difficult to separate liquids. The permeation rate is also low. Therefore, if the membrane thickness is reduced to increase the liquid permeation rate for practical use, the mechanical strength of the membrane decreases, and the equipment structure becomes complicated to strengthen it, and the selective separation is poor, so multi-stage separation is required. However, it has disadvantages such as having to be used as a device. Under such circumstances, the inventors of the present invention have arrived at the present invention as a result of intensive research aimed at obtaining a selectively permeable membrane with high selective separation performance and liquid permeation rate, as well as excellent mechanical strength. c Disclosure of the invention The present invention comprises the following structural units (a), (b) and (c). [However, in the formula, R ₁ and R ₂ are the same or different,
Represents an aliphatic hydrocarbon group having 6 to 18 carbon atoms.
M represents a hydrogen atom or a monovalent or divalent cation. ] The constituent units selected from (a) / ((b) + (c)) = 1 to 3
and a separation membrane having an active layer mainly composed of a polymer having a ratio of (c)/(b) = 0 to 1, and
This is a method for separating water-soluble organic substances using this method. The above structural units (a), (b) and (c) in the present invention
Examples of the polymer having the following include those obtained by reacting the following poly(olefin-maleic anhydride) [] with a long-chain alkylamine, [] and those obtained by imidizing this []. The above polymer [ ] is α- having 8 to 20 carbon atoms.
This is a known product obtained by alternating copolymerization of olefins and maleic anhydride. Polymer []
is obtained by reacting the polymer [] with an aliphatic amine having 6 to 18 carbon atoms. Typical examples of such amines include tridecylamine, stearylamine, and laurylamine. This amine modification reaction can be carried out on the polymer [] in a solvent inert to the above amine. Suitable examples of such solvents include chloroform, methylene chloride, tetrahydrofuran, and toluene. The reaction is completed in several hours at room temperature to 70°C.
The reaction mixture is purified by reprecipitation treatment in methanol or ethanol. It is also possible to convert the carbosyl group in the polymer [] above into a carboxylate, and this is included in the present invention. Such a conversion reaction can be carried out by bringing the carboxyl group-containing polymer into contact with an aqueous solution of an alkali metal salt or alkaline earth metal salt in accordance with a conventional method. Among the above polymers [], ring closure to imide rings is achieved by heating those containing an aboxyl group in acetic anhydride at 50 to 80°C for several hours.
In the present invention, in order to obtain a membrane having good separation performance, the above polymer repeating units (a), (b), (c)
Contains (a) as an essential component and (b) or/and
(c) to (a):(b)+(c)=1:1~3:1 and (c):(b)=
It is important to have a ratio of 0:1 to 1:1. If the units (b) and (c) are contained in an amount greater than equimolar to (a), the selectivity of the membrane obtained will decrease, which is not preferable. Furthermore, if the polymer does not contain any units (b) or (c), the solubility of the polymer generally decreases, making film formation difficult. The polymer obtained as described above can be formed into a film by a conventional coating method. Film-forming solvents generally include non-polar solvents,
For example, chloroform, tetrahydrofuran, methylene chloride, toluene, perchloren, etc. are used. The polymer solution can be formed into a film on a glass plate or a Teflon plate, but in the present invention, it is preferable to form a thin layer coating on a microporous support membrane in order to maintain the strength of the membrane and increase the amount of permeation. As the microporous support membrane in the present invention, a porous membrane having a fine structure with an average pore diameter of 50 to 5000 Å and excellent mechanical strength is selected. Preferred materials for such a porous membrane include polypropylene, polyethylene, polysulfone, polyvinylidene fluoride, polytetrafluoroethylene, and polyvinyl chloride, with polyethylene and polypropylene porous membranes being particularly preferred. The manufacturing method of these porous membranes is known; for example, polypropylene porous membranes are manufactured by British
Chemical Engineering 9 , (8) 523 (1964)
It can be produced by the method described. The microstructure of the membrane may be asymmetric or symmetric. The membrane constant is preferably 1 to 10 ^-4 g/
cm ² sec atm, particularly preferably 1 to 10 ^-3 g/
^cm2・sec・atm. The membrane constant here is 25
This value represents the amount of pure water permeated under a pressure of 2 Kg/cm ² at ℃. The forms of microporous support membranes include flat membranes,
Any form of membrane such as tubular or hollow fiber membranes can be manufactured, but in the case of flat membranes or tubular membranes, it is preferable from the viewpoint of mechanical strength to have a structure in which the back side of the membrane is reinforced with woven fabric or non-woven fabric. . Preferred examples of such woven and nonwoven fabrics include those made of polyethylene terephthalate, polypropylene, polyamide, polyvinyl chloride, and the like. The thickness of these microporous support membranes is usually 50μ to 5μ.
mm, preferably 100 μm to 1 mm. To obtain the separation membrane of the present invention, the above-mentioned polymer solution is coated on the above-mentioned microporous membrane by a casting method, a spray method, a dipping method, etc., and then the solvent is heated at room temperature to 100°C for 10 to 10 minutes. It is common to dry for 30 minutes. The concentration of the polymer solution depends on the polymer composition and type of solvent, but is generally 0.5 to 20wt.
%, preferably in the range of 1 to 10 wt%. By casting the polymer solution at this concentration, a thin film having a thickness of 1 to 50 μm and a thickness of 5 to 20 wt % is formed on the microporous membrane. The organic liquid selectively permeable membrane of the present invention is suitable for the purpose of highly selectively permeating a water-soluble organic liquid from a water-water-soluble organic liquid mixture. Such mixtures include water/ethyl alcohol, water/isopropyl alcohol, water/n-propyl alcohol, water/allylic alcohol, water/2-methoxyethanol, water/isobutyl alcohol, water/1-
Mixtures of water and alcohol such as butanol, water/2-butanol, water/furfuryl alcohol and water/1-pentanol, water/tetrahydrofuran, water/dioxane, water/ethyl ketone, water/acetic acid, water/propion Mention may be made of acids, mixtures of water/butyric acid, water/valeric acid and the like. Among the aqueous solutions mentioned above, the one most efficiently separated by the membrane of the present invention is an alcohol/water mixture having three or more carbon atoms. The present invention will be further explained below with reference to Examples. Pervaporation experimental method The pressure on the supply side of the organic liquid mixture was atmospheric pressure, and the permeation side (collection side) was conducted under reduced pressure of 0.3 mmHg unless otherwise specified. The above mixed solution was supplied to the active layer surface (ultra-thin film surface) side of the membrane, and the supplied solution was circulated while maintaining the temperature on the membrane surface at a constant temperature. The effective area of the membrane was 11.0 cm ² . The components that permeated the membrane were condensed and collected, and the amount of permeation (Flux) was determined in units of Kg/m ² ·hr. In addition, the composition ratio in the collected liquid was determined by TCD-gas chromatography, and the separation coefficient (α) of the membrane was determined. Note that the separation coefficient α ^A _B is defined by the following equation. α ^A _B = (Y _A / Y _B ) / (X _A / X _B ) However, X _A and X _B are the A component and B component in the feed liquid.
Component weight %, T _A and Y _B indicate the weight % of A component and B component in the collected liquid (permeate side), and the easily permeable component was used as the A component Example 1 Stirrer, reflux device, and temperature 300ml with meter
Octadecene-maleic anhydride copolymer (PA-
18) was dissolved, and then a solution of 8.0 g of stearylamine in 50 ml of chloroform was gradually added dropwise through a dropping funnel. After the dropwise addition was completed, stirring was performed at 50°C for 5 to 7 hours. The reaction mixture was mixed with an equal volume of 1/10N hydrochloric acid and ethanol.
A crude reaction product was obtained by reprecipitation in 500 ml. After filtration and drying, this product was dissolved again in chloroform to make a 10% by weight solution, and the procedure of reprecipitation in ethanol was repeated three times to obtain a purified polymer. The infrared absorption spectrum of this product revealed that all acid anhydride groups had disappeared, and carboxyl groups and amide groups were newly generated. This material was dissolved in chloroform to make a 5% by weight solution, and a porous polypropylene membrane (Jyuragard) was prepared.
2400) and air-dried for 30 minutes.
The thus obtained composite membrane having a film thickness of 55 μm was subjected to a pervaporation test with a 2.5% by weight n-butanol aqueous solution at 30°C and 0.1 mmHg for 6 hours using the method described in the reference example. Permeate n-butanol concentration 51.5% (selectivity coefficient α ^n-BuoH _H2O 41.4), permeate flow rate
A high degree of alcohol selective permeation of 4.25×10 ^-6 Kg・m ^-2・S ^-1 was achieved. Examples 2 to 7 Using the composite membrane obtained in Example 1, methanol,
ethanol, propanol, isopropanol,
A pervaporation test was conducted using aqueous solutions of amyl alcohol and octyl alcohol as stock solutions under the following conditions. The results are shown in Table 1.

[Table] Examples 8 to 14 The alcohol aqueous solution separation performance of a composite membrane having a film thickness of 41 μm obtained by modifying PA-18 in the same manner as in Example 1 using oleylamine instead of stearylamine was investigated. Ta. The results are shown in Table 2.

[Table] Examples 15 to 16 In Example 1, the ethanol aqueous solution separation performance of composite membranes obtained by similarly modifying PA-18 using octylamine or laurylamine instead of using stearylamine was evaluated. Examined. The results are shown in Table 3.

【table】

Claims (1)

[Claims] 1. The following structural units (a), (b) and (c) [However, in the formula, R ₁ and R ₂ are the same or different,
Represents an aliphatic hydrocarbon group having 6 to 18 carbon atoms.
M represents a hydrogen atom or a monovalent or divalent cation. ] The constituent units selected from (a)/((b)+(c))=1~
3 and a ratio of (c)/(b)=0 to 1. 2. Claim 1, wherein R ₁ and R ₂ are groups selected from aliphatic hydrocarbon groups having 12 to 18 carbon atoms.
The organic substance permselective pervaporation separation membrane described in 2. 3. The organic substance permselective pervaporation separation membrane according to claim 1 or 2, wherein (a)/((b)+(c))=1. 4. An organic matter selectively permeable pervaporation separation membrane according to any one of claims 1 to 3, wherein the active layer is supported by a porous support. 5 The following structural units (a), (b) and (c) [However, in the formula, R ₁ and R ₂ are the same or different,
Represents an aliphatic hydrocarbon group having 6 to 18 carbon atoms.
M represents a hydrogen atom or a monovalent or divalent cation. ] The constituent units selected from (a)/((b)+(c))=1~
3 and separating water-soluble organic compounds from an aqueous solution containing a small proportion of water-soluble organic compounds by pervaporation using a separation membrane mainly composed of a polymer having a ratio of (c)/(b) = 0 to 1. A method for separating water-soluble organic compounds consisting of: 6. The separation method according to claim 5, wherein R ₁ and R ₂ are aliphatic hydrocarbon groups having 12 to 18 carbon atoms. 7. The separation method according to claim 5 or 6, wherein (a)/((b)+(c)) is 1. 8. The separation according to any one of claims 5 to 7, wherein the aqueous solution containing a small proportion of a water-soluble organic compound is an aqueous solution containing 0.1 to 20 wt% of an alcohol having 1 to 8 carbon atoms. Method.