JPH0628707B2 - Membrane for separating liquid mixtures - Google Patents

Description

TECHNICAL FIELD The present invention relates to a novel liquid separation membrane.

[Prior Art] Conventionally, distillation is generally used for separation of a mixed liquid. However, distillation requires a large amount of energy and has a problem that it is difficult to separate an azeotropic mixture, a substance having a close boiling point, and a substance unstable to heat. On the other hand, in recent years, a separation method using a membrane has been studied and developed, and future development is expected as an energy-saving separation method.

Membrane separation methods include permeation evaporation method, reverse osmosis method and dialysis method depending on the separation factor and separation operation. Reverse osmosis method and dialysis method include desalination of seawater and brackish water, production of ultrapure water, treatment of waste liquid, etc. Some have already been put to practical use in the fields of water treatment, food industry, medical care, and the like. Among the membrane separation methods, the pervaporation method is to place the liquid mixture to be separated on one side across the membrane,
In this method, one component of the mixed liquid is selectively permeated by reducing the pressure of the other or by flowing an inert gas to the mixed liquid component. This separation method is not affected by osmotic pressure and has a wide range of applications as a method capable of separating a mixed solution having a wide concentration range. Furthermore, as a separation target by the pervaporation method, water-ethanol separation has been particularly noted in that it concentrates ethanol obtained from biomass as alternative energy for petroleum. As such a pervaporative membrane, Japanese Patent Laid-Open No. 59-203610,
59-203607, 59-203602 and 59-4402, sulfonated ethylene copolymers, 58-84005 and 58-89.
No. 901, etc., proposes a fluoropolymer having an acid functional group. Also, JP-A-60-75
Japanese Patent No. 306 discloses a pervaporation method using a polymer of a specific substituted acetylene. On the other hand, Japanese Patent Application Nos. 60-72542, 60-72543, and 60-
278001, 60-278002, 60-2
Nos. 78003 and 60-278004 filed for membranes composed of polymers of various substituted acetylenes.

Among these separation membranes, typical examples of the ethanol permeable membrane include silicone rubber and poly (1-trimethylsilyl-1-propyne).

However, silicone rubber has a separation coefficient α ^EtOH of about 7, and a permeation rate of about 0.2 kg / m ² · hr.
Since a sufficient permeation rate cannot be obtained and the mechanical strength is small, it is said that there is also a problem in thin film formability. Also, poly (1-trimethylsilyl-1-propyne) has a separation coefficient Of about 10 and a permeation rate of about 0.5 kg / m ² · hr is shown, but there are problems such as poor stability of the polymer itself.

[Problems to be Solved by the Invention] Generally, the pervaporation method has not yet been put to practical use because of problems with the membrane separation coefficient, the permeation rate, and the film-forming property. Especially when a liquid mixture of ethanol-water is to be separated, most of the membranes show water selective permeability in terms of separability, and there are very few ethanol selective membranes, and the membrane performance (separation coefficient, permeation rate, etc.) The current situation is that we are not satisfied with this point.

In order to improve the above problems, the present invention provides a membrane having excellent liquid separation performance, particularly ethanol permselectivity, by using a liquid separation membrane containing a polymer of substituted acetylene as a main component.

[Means for Solving Problems] To achieve the above object, the present invention has the following constitution.

"General formula (In the formula, R ₁ has hydrogen, an alkyl group, a substituted alkyl group, a phenyl group, a substituted phenyl group, a halogen atom, and R ₂ has a C ₆ or more long-chain alkyl group and a C ₆ or more long-chain alkyl group as a substituent. A phenyl group, and at least one hydrogen on these alkyl groups may be substituted with one or more kinds of halogen atoms or phenyl groups). And a membrane for separating a liquid mixture, which has a property of selectively permeating and separating ethanol from water-ethanol. In the present invention, the general formula (In the formula, R ₁ has hydrogen, an alkyl group, a substituted alkyl group, a phenyl group, a substituted phenyl group, a halogen atom, and R ₂ has a C ₆ or more long-chain alkyl group and a C ₆ or more long-chain alkyl group as a substituent. A phenyl group, in which at least one hydrogen on these alkyl groups may be substituted with one or more kinds of halogen atoms or phenyl groups), a substituted acetylene polymer mainly composed of a structural unit represented by R _As the alkyl group of _1, a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, etc., a substituted alkyl group such as a benzyl group, a phenylethyl group, a phenylpropyl group, a phenylbutyl group, a phenylpentyl group, Phenylhexyl group, naphthylmethyl group, naphthylethyl group, naphthylpropyl group, naphthylbutyl group, naphthyl Pentyl group, naphthoquinone ethylhexyl group,
Diphenylmethyl group, diphenylpropyl group, diphenylethyl group, diphenylbutyl group, diphenylpentyl group, diphenylhexyl group, triphenylmethyl group, triphenylethyl group, triphenylpropyl group, triphenylbutyl group, triphenylpentyl group, triphenylpentyl group As the aromatic such as phenylhexyl group, phenyl group, naphthyl group, anthracenyl group, pyrenyl group and the like, and as the substituted aromatic group, 4-methylphenyl group, 3-methylphenyl group, 2-methylphenyl group, 2, 4 -Dimethylphenyl group, 2,3-dimethylphenyl group, 2,5-dimethylphenyl group, 2,6-dimethylphenyl group, 3,4-dimethylphenyl group, 3,5-dimethylphenyl group, 2,
3,4-trimethylphenyl group, 2,3,5-trimethylphenyl group, 2,3,6-trimethylphenyl group,
2,4,6-trimethylphenyl group, 2-chlorophenyl group, 3-chlorophenyl group, 4-chlorophenyl group,
2,4-dichlorophenyl group, 2,3-dichlorophenyl group, 2,5-dichlorophenyl group, 2,6-dichlorophenyl group, 3,4-dichlorophenyl group, 3,5-dichlorophenyl group, 2,3,4-trichlorophenyl group Group 2,3,5-trichlorophenyl group 2,3,6-
Trichlorophenyl group, 2,4,6-trichlorophenyl group, 2-fluorophenyl group, 3-fluorophenyl group,
4-fluorophenyl group, 2,4-difluorophenyl group,
2,3-difluorophenyl group, 2,5-difluorophenyl group, 2,6-difluorophenyl group, 3,4-difluorophenyl group, 3,5-difluorophenyl group, 2,3,4
-Trifluorophenyl group, 2,3,5-trifluorophenyl group, 2,3,6-trifluorophenyl group, 2,4,
6-trifluorophenyl group, perfluorophenyl group, 2
-Bromophenyl group, 3-bromophenyl group, 4-bromophenyl group, 2,4-dibromophenyl group, 2,3-
Dibromophenyl group, 2,5-dibromophenyl group,
2,6-dibromophenyl group, 3,4-dibromophenyl group, 3,5-dibromophenyl group, 2,3,4-tribromophenyl group, 2,3,5-tribromophenyl group, 2,3, 6-tribromophenyl group, 2,4,6-
Tribromophenyl group, chloronaphthyl group, dichloronaphthyl group, trichloronaphthyl group, bromonaphthyl group,
Examples of the halogen atom include a dibromonaphthyl group, a tribromonaphthyl group, a fluoronaphthyl group, a difluoronaphthyl group, a trifluoronaphthyl group and a perfluoronaphthyl group. Examples of the halogen atom include chlorine, bromine and fluorine. The C ₆ or more long-chain alkyl group for R ₂ is a hexyl group, a heptyl group,
Octyl group, nonyl group, decyl group, undecyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group, nonadecyl group, eicosyl group, etc. Hen'aikoshiru group, C ₆ or longer chain alkyl The phenyl group having a group as a substituent, a hexylphenyl group, a heptylphenyl group, an octylphenyl group, a nonylphenyl group, a decylphenyl group, an undecylphenyl group, a dodecylphenyl group, a tridecylphenyl group, a tetradecylphenyl group, Examples thereof include a pentadecylphenyl group, a hexadecylphenyl group, a heptadecylphenyl group, an octadecylphenyl group, a nonadecylphenyl group, an aicosylphenyl group, and a henaicosylphenyl group.

As to why the polymer of the substituted acetylene having a C ₆ or longer long-chain alkyl group as a side chain of the present invention is excellent as a pervaporative membrane having ethanol permselectivity, it is difficult to establish a clear theoretical proof so far. However, it is considered that since one end of the lipophilic alkyl group is not fixed, the mobility of the alkyl group is increased, which makes ethanol easier to permeate.

Furthermore, the polymer of the present invention is a homopolymer or copolymer having the above-mentioned substituents, and these polymers can be used alone or in a blend with each other. Alternatively, another monomer of the repeating unit may be copolymerized or another polymer may be blended within a range not impairing the present invention.

As a method for obtaining the polymer in the present invention, Japanese Patent Publication No.
No. 1-37312, No. 52-20511, No. 54-43037, No. 55-23565,
No. 55-30722, No. 57-31911, No. 57-36106, and No. 58-32608.
No. 59-78218 and No. 59-1974.
The method disclosed in Japanese Patent No. 10 or the like can be given. Specifically, each substituted acetylene monomer is used with a tungsten-based, molybdenum-based, tantalum-based, or niobium-based catalyst, and if necessary, an organometallic compound such as tin, silicon, bismuth, or aluminum is used as a cocatalyst. make use of,
It is obtained by polymerizing a hydrocarbon or a halogenated hydrocarbon as a solvent.

The molecular weight of these polymers used in the present invention is GP
The polystyrene-equivalent number average molecular weight by O (gel permeation chromatography) is 10,000 or more, preferably 10,000 to 5,000,000, and particularly 20,000 to 1,000,000. If the number average molecular weight is less than 10,000, the film forming property is poor.

The film used in the present invention can be obtained as follows, but is not limited thereto. The polymer according to the present invention is dissolved in a solvent and cast on a suitable surface such as a glass plate or "Teflon (registered trademark of DuPont) plate, and then the solvent is evaporated to form a film,
The film can be obtained by peeling by any means. Alternatively, in general, according to a method for obtaining an asymmetric membrane such as a reverse osmosis membrane, evaporation of the solvent is stopped midway, and the solvent is coagulated in an appropriate coagulating medium to obtain an asymmetric membrane. Alternatively,
The film can also be obtained by hot pressing below the decomposition point of the polymer. It is also possible to use a dilute solution of these polymers directly on a porous support and evaporate the solvent to form an ultrathin film on the porous support, which can be used as a composite membrane. Further, a solution of these polymers is spread on a suitable solvent that is incompatible with the solvent (such as water), and the ultrathin film obtained by evaporating the solvent is laminated on the porous support,
It can also be used as a composite membrane.

The film thickness of the film thus obtained has a value of 10 Å to 1 mm, 0.1 μm to 500 μm as a homogeneous film, 0.1 μm to 500 μm as an asymmetric film, and 10 Å to 100 μm as an ultra thin film of a composite film. Can be used in.

The organic solvent used to obtain the solution of the polymer according to the present invention may be any organic solvent as long as it dissolves these polymers or blends well and easily evaporates during film formation, such as benzene and toluene. Hydrocarbon-based solvents such as cyclohexane and n-hexane, oxygen-containing hydrocarbon-based solvents such as tetrahydrofuran, halogenated hydrocarbon-based solvents such as chloroform, dichloromethane and carbon tetrachloride are preferably used.

The membrane thus obtained can be incorporated as a flat membrane in a liquid separation membrane device of spiral type, plate-and-frame type, tubular type or the like. The membrane can also be used in the form of hollow fibers or composite hollow fibers. However, the invention is not dependent on the shape of these membranes.

The liquid mixture to be separated in the present invention is a mixed liquid of a water-soluble organic substance and a stylish liquid, or a mixed liquid of an organic liquid and an organic liquid, and the water-soluble organic substance is a water-soluble alcohol such as methanol, ethanol, n-propanol or i-propanol. , And ethers such as ethyl ether, tetrahydrofuran and dioxane, water-soluble ketones such as acetone and methyl ethyl ketone, and acetic acid, and the mixed liquid of organic liquid and organic liquid is methanol / methyl acetate, ethanol / ethyl acetate. , Ethanol / ethyl acetate, etc. Among them, it is particularly effective for separating a mixed liquid of a water-soluble organic substance and water.

[Examples] The present invention will be described in detail below with reference to Examples, in which the separation coefficient α and the permeation rate Q are calculated by the following equations.

^{_{α ▲ 1 2 ▼ = (C}} 1 / C 2) / (C - 1 / C - 2) C 1: Concentration of the A component in the permeate (%) _{C 2:} Concentration of the B component in the permeate (% ) C ^- ₁ : Concentration (%) of A component in the feed liquid C ^- ₂ : Concentration (%) of B component in the feed liquid Q = W / A W: Permeation amount per hour (Kg / hr) A : Membrane area (m ² ) Example 1 0.4 g of poly (2-henaicosin) was dissolved in 10 ml of cyclohexane to prepare a cast solution. This casting solution was cast on a Teflon plate and the solvent was evaporated at room temperature to obtain a 20 μm film. Separation coefficient was obtained as a result of performing pervaporation separation using a 10% by weight aqueous solution of the feed solution, a feed solution temperature of 30 ° C., and a secondary pressure of 10 torr using this film. It was 8 (Kg / m ² h).

[Advantages of the Invention] Since the present invention has the above-mentioned configuration, it has the following special effects.

 The separation factor is larger than that of the conventional one.

 High transmission speed.

 Good film formability.

 Easy to cast with solvent.

 The morphology of the membrane can be varied.

Claims (1)

[Claims] 1. A general formula (In the formula, R ₁ has hydrogen, an alkyl group, a substituted alkyl group, a phenyl group, a substituted phenyl group, a halogen atom, and R ₂ has a C ₆ or more long-chain alkyl group and a C ₆ or more long-chain alkyl group as a substituent. A phenyl group, and at least one hydrogen on these alkyl groups may be substituted with one or more kinds of halogen atoms or phenyl groups). And a membrane for separating a liquid mixture, which has a property of selectively permeating and separating ethanol from water-ethanol.