JPS61220703A - Separation membrane for liquid mixture - Google Patents

Abstract

PURPOSE:To increase permeation velocity and to improve separation factor in the stage for separating a mixture of water with org. liquid by pervaporation method, by using a membrane comprising polysilarylene siloxane. CONSTITUTION:Polysilarylene siloxane membrane consisting of silicone polymer comprising principal chain consisting of -[Si(CH3)2-R-Si(CH3)2]- as recurrent unit is used. R in the formula is 2-8C hydrocarbon group. The membrane is prepd. easily by casting soln. of the polymer in org. solvent such as toluene added with a crosslinking agent, on a plate made of polypropylene, etc. The liquid mixture which is separated with the membrane is one contg. at least one org. liquid as the component of the mixture and conventional pervaporation device is usable for the separation.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a membrane for separating liquid mixtures made of silicone polymers.

[Conventional technology]

Conventionally, the liquid mixture to be separated is supplied to the feed liquid side (minus side) of two chambers separated by a separation membrane, and the pressure is reduced on the permeate side (secondary side), or an inert gas is supplied. A method of separating a water-organic liquid mixture using the pervaporation method (pervaporation method), which maintains a low vapor pressure by flowing water and preferentially transmits components with high affinity with the membrane as vapor to the secondary side, has been proposed. Various experimental examples have been reported in which a water-organic liquid mixture is separated by such a pervaporation method. Specifically, U.S. Patent No. 2,953,502
In the issue, there is an example of an experiment in which an azeotropic mixture is separated using a cellulose acetate membrane or a polyvinyl alcohol membrane, -Jo
Urrsal of Applied Polymer
Scierkce vol, 26 (1981) no.3
On page 223, nine experimental examples are reported in which a water-methanol mixed liquid is separated using a grafted polyvinyl alcohol membrane.

[Problem that the invention seeks to solve]

The pervaporation method does not have concentration limitations due to osmotic pressure like traditional reverse osmosis methods, so it is not limited to separating liquid mixtures with low concentrations, but can separate liquid mixtures with a whole range of concentrations. Also, it is difficult to separate using conventional distillation methods! It is considered to be a very useful separation method because it has the characteristics of being able to separate azeotropic mixtures and secondary isomers with close boiling points (for example, ortho and para isomers, cis and trans isomers). It is being

However, it is possible to separate a mixed liquid by the pervaporation method using a membrane made of polydimethylsilane, polyolefin, etc., which is conventionally known as a membrane that selectively permeates more nonpolar components from a liquid mixture. Even if the mixed liquid passes through the polymer membrane once, the separation rate, that is, the separation coefficient, is small. It is necessary to transmit the film through the membrane, and in particular, the permeation rate through the polymer membrane [generally expressed as the amount of permeation per unit membrane surface area and unit time, that is, Q (IQ/rthr)] is important for practicality. When it reaches a certain high value, the separation coefficient α becomes extremely low, making it difficult to put it into practical use.

The separation coefficient α3 is defined as a ratio value obtained by dividing the weight ratio WA/WB of component A to component B after permeation through the membrane by the weight ratio WA/WB of component A to component B before permeation through the membrane. The purpose of this invention is to obtain a membrane with a high separation coefficient at a high permeation rate when separating a water-organic liquid mixture by the total pervaporation method.

[Means for solving problems]

The inventors of the present invention have made extensive studies and have discovered that a film made of polysylallylene siloxane is a film that achieves the above object, and has arrived at the present invention. In other words, it is a membrane for separating mixed liquids made of a silicone-based polymer in which the main chain is entirely composed of repeating units.

The silicon-based polymer used in the present invention is difficult to synthesize if R has 1 or 9 or more carbon atoms.
It is preferable that it is 2-8. Here, the hydrocarbon group is (-CH2+n (n = 2 to 8), ΣH1-cη
Examples include CΣCH2-.

The film of the present invention can be easily obtained by dissolving the silicone-based polymer in an organic solvent such as toluene, adding a crosslinking agent such as Siα4, and casting the solution onto a polypropylene plate or the like. This membrane is a membrane with a non-porous, homogeneous skinless structure, and is usually used in the form of a flat plate (flat membrane shape).
It may be used in the form of a thin cylinder or hollow fiber to increase the membrane area per unit volume. However, the film thickness can also be reduced by coating it on a porous base film.

The liquid mixtures that can be separated by the membrane of the present invention are those having at least an organic liquid as one of its M acid components; specific examples of such liquid mixtures include water/methanol, water/ethanol, water/gropanol,
Water/organic liquid mixtures such as water/butanol, water/acetate, water/ethylmethylchthone, water/dioxa/, water/tetrahydro7ran, water/formic acid, water/acetic acid, water/butyushun, and methanol/benzene. , methanol/methyl acetate, ethanol/ethyl acetate, ethyl acetate/hexane.

Examples include organic/organic liquid mixtures such as methanol/chloroform. Furthermore, the liquid mixture that can be separated by the membrane of the present invention is not limited to the two-component system described above, but may also be a multi-component system.

The pervaporation device used in the present invention is not particularly limited; any conventionally known device can be used, and such a device can be operated under conventional conditions to separate a liquid mixture. When performing pervaporation, the larger the pressure difference between the feed liquid side and the permeate side, the more effective it is.
It is preferable to provide an atmospheric pressure difference. The pressure on the feed liquid side is preferably at or near atmospheric pressure, and the pressure on the permeate side is preferably maintained at a reduced pressure below the vapor pressure of the permeate component. Methods for maintaining the permeate side at reduced pressure include drawing a vacuum to reduce the pressure, or flowing a gas that does not react with the constituent components to maintain a low vapor pressure. The appropriate separation temperature is below the azeotropic temperature of the organic liquid mixture to be separated.

To aid in the separation of liquid mixtures, if the desired concentration cannot be obtained by passing the membrane through the membrane once, a similar pervaporation device may be installed in series and the membrane may pass through the membrane multiple times, or a distillation method may be used. It can be concentrated and separated to the desired concentration by combining with

[For production]

By the pervaporation method using the membrane of the present invention,
By separating a liquid mixture having at least an organic liquid as one of its components, while maintaining a high separation coefficient,
Although efficient treatment can be achieved with a high permeation rate, such an effect is completely unpredictable from conventional knowledge. Although the reason for this effect is not necessarily clear, the hydrocarbon group R sandwiched between silicon atoms increases the affinity with less polar molecules in the mixed liquid, and polydimethyl This is thought to be because the molecular movement of the polymer is suppressed compared to siloxane and the like.

〔Example〕

EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples, but the present invention is not limited to these in any way.

Examples 1 to 3 100 f of a toluene solution of 1.2-bis(dimethylchlorosilyl)ethane (30 wt. After stirring for an hour, the toluene layer was separated, washed with water, and dried over magnesium sulfate. Next, toluene was evaporated and distilled off to obtain viscous colorless and transparent oily polysilethylene diaxane fC.

Thus obtained the following polysilethylene siloxane 1
After adding 0.01 parts by weight of Siα4 to the polymer as a crosslinking agent to a toluene solution of silicone polymer dissolved in 90 μm of toluene, the mixture was cast onto a polypropylene/board to form a homogeneous layer with a thickness of 100 μm. Obtain a membrane using a pervaporation device (inJ11 area 7,
Aqueous acetic acid solution (Example 1), aqueous ethanol solution (Example 2), and aqueous acetone solution (Example 3) with an organic liquid concentration of 50% by weight were supplied at 25°C, and the permeate side was connected to a vacuum pump. Separation is performed by suction and pervaporation method. The concentration of the next component of the organic liquid that passed through the membrane (the organic liquid permeated preferentially) was analyzed using a gas chromatograph, and the amount of permeation was determined by condensing the gas. The results are shown in Table 1.

"2' Grignard reagent was prepared. Trimethylsilyl chloride 114117't was added dropwise to this, and after 6 hours of reaction, extraction was performed with hexane. Then, the hexane was evaporated and distilled to produce 1,6-bis(trimethylsilyl). Hexane (b
, P, 111℃, 16■Hg) 34f was obtained as follows. 1, 6
- His(trimethylsilyl)hexane 342 was added to a large excess of concentrated sulfuric acid 2002, stirred at room temperature for 72 hours, extracted with hexane, and then the hexane was evaporated to obtain polysilhexylene siloxane 301 with trimethyl terminals. 7
2:o Next, this polyff-tlJ fluoroborane ethyl ether complex 22.7f is reacted and distilled to obtain 1.
6-bis(dimethylfluorosilyl)hexane (b, P
115℃.

28■Hg) 23 ft- was obtained. This 7tsilylhexane was added to 200f of a 40% by weight potassium hydroxide aqueous solution.
1,6-bis(dimethylhydroxysilyl)hexane was obtained as white crystals by washing the floating white solid with water and recrystallizing it with hexane. f/-o A benzene solution of the hydroxysilylhexane 10 (ljKo, 5R of trifluoroacetic acid is added, and dehydration polymerization is performed under reflux to form an oily polysilhexylene siloxane with terminal human mixtures 14 f t4
Next.

The polysylhexylene siloxane thus obtained was treated in the same manner as in Example 1 to obtain a film having a thickness of 100 μm.

The layer was prepared in the same manner as in Examples 1 to 3, and the organic liquid concentration was 50.
weight of acetic acid aqueous solution (Example 4), ethanol aqueous solution (
Example 5) and acetone aqueous solution (Example 6) were supplied at 25°C and the membrane performance was measured. The results are shown in Table 1.

Comparative Examples 1 to 3 Aqueous acetic acid solution (Comparative Example 1) and aqueous ethanol solution (Comparative Example 2) were prepared using a conventional dimethyl silicone film (thickness 100 μm).
) and acetone aqueous solution (Comparative Example 3) were supplied at 25°C,
Membrane performance was measured in the same manner as in Example 1. Table 1 shows the results.
Shown below.

From the above results, the effects of the present invention are clear.

$ 1 From the above results, it is clear that the membrane of the present invention is a membrane that exhibits superior membrane performance compared to conventional membranes.

〔Effect of the invention〕

By using the membrane of the present invention, organic liquid mixtures can be efficiently processed at a high permeation rate while maintaining a higher separation coefficient than in separation methods using conventional membranes. For this reason, separation systems can be made more compact, processing capacity can be increased,
Cost reduction is achieved, and the present invention is effective in practical application of membrane separation methods for shortening separation and purification processes in the chemical industry and saving energy, and has extremely great industrial utility.

Percentage applicant: Director of the Agency of Industrial Science and Technology

Claims (2)

[Claims] (1) ▲There are mathematical formulas, chemical formulas, tables, etc.▼ A membrane for separating mixed liquids made of a silicone polymer whose main chain is a repeating unit of (R: hydrocarbon group). (2) The separation membrane according to claim (1), wherein the hydrocarbon group R has 2 to 8 carbon atoms.