JPH0225652B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a separation membrane for separating a water-organic acid mixture formed by blending a silicone polymer with a trisubstituted phosphine oxide. [Prior Art] Conventionally, a liquid mixture to be separated is supplied to the feed liquid side (primary side) of two chambers separated by a separation membrane, and the pressure is reduced on the permeate side (secondary side), or The water-organic liquid is maintained at a low vapor pressure by flowing an inert gas, and the pervaporation method allows components with high affinity with the membrane to preferentially permeate as vapor to the secondary side. Methods for separating mixtures have been implemented, and various examples have been reported in which water-organic liquid mixtures were separated by such pervaporation methods. Specifically, U.S. Patent No.
No. 2953502 includes an experimental example of separating azeotropic liquids using cellulose acetate membranes and polyvinyl alcohol membranes, Journal of Applied Polymer
Science Vol. 26 (1981), page 3223, reports on an experimental example in which a water-methanol mixed liquid was separated using a grafted polyvinyl alcohol membrane. [Problems to be solved by the invention] Since the pervaporation method does not have concentration limitations due to osmotic pressure like conventional reverse osmosis methods, it is not limited to the separation of low-concentration liquid mixtures; It is possible to separate liquid mixtures with concentrations in the range of , as well as azeotropes and solvent isomers with close boiling points (e.g. ortho and para isomers, cis and trans isomers) that are difficult to separate by conventional distillation methods. It is considered to be a very useful separation method because of its characteristics such as the ability to separate. However, it is practically difficult to use conventional pervaporation membranes to separate water-organic acid mixtures due to deterioration of the membrane due to acid. Furthermore, even if a material with excellent chemical resistance such as silicone, polyolefin, or polytetrafluoroethylene is used for the membrane, if the mixed liquid is separated by passing through the polymer membrane once, that is, the separation coefficient is small. To separate or concentrate to the desired concentration, it is necessary to pass through a large number of membranes.
In addition, especially when the permeation rate through a polymer membrane (generally expressed as the amount of permeation per unit membrane surface area and unit time, that is, Q (Kg/m ² hr)) reaches a high value that is practical. , the separation coefficient α becomes very low, so it is still difficult to put it into practical use. Separation coefficient α ^A _B is the weight ratio WA/WB of component A to component B after permeation through the membrane.
The value divided by the weight ratio WA/WB of the components, α ^A _B = WA/WB in permeate/WA/WB in permeate, is defined as α A B = WA/WB in permeate liquid; The purpose of separation by vaporization is to obtain a membrane with a high separation coefficient at a high permeation rate. [Means for Solving the Problems] The present inventors have made extensive studies and found that a film obtained by blending a silicon-based polymer with a trisubstituted phosphine oxide that has an affinity for organic acids is a film that achieves the above objectives. We have discovered that this is the case, and have arrived at the present invention.
That is, the present invention

This is a membrane for separating mixed liquids made by blending 1 to 50% by weight of trisubstituted phosphine oxide with a silicone polymer having a repeating unit of the formula (R ₁ : hydrocarbon group). The silicone polymer used in the present invention is

[Effect]

By separating a water-organic acid mixture by the pervaporation method using the membrane of the present invention, it is possible to efficiently treat the water-organic acid mixture at a high permeation rate while maintaining a high separation coefficient. This is completely unpredictable based on knowledge. Although the reasons for this effect are not necessarily clear,
It is presumed that the trisubstituted phosphine oxide in the film forms a complex with the organic acid. [Examples] Hereinafter, the present invention will be specifically explained with reference to Examples, but the present invention is not limited by these in any way. Examples 1 to 3 100 g of a 30% by weight toluene solution of 1,2-bis(dimethylchlorosilyl)ethane (manufactured by Shin-Etsu Chemical) was dropped into 300 g of water/toluene (weight ratio 1/1),
After stirring at 80° C. for 20 hours, the toluene layer was separated, washed with water, and dried over magnesium sulfate. Next, toluene was evaporated and distilled off to obtain a viscous, colorless, transparent oily polysilethylene siloxane. Trioctylphosphine oxide was added in the amount shown in Table 1 to a toluene solution of silicone polymer in which 10 g of the polysylethylene siloxane thus obtained was dissolved in 90 g of toluene to form a homogeneous solution. 0.01 to polymer with _SiCl4 as crosslinker
After adding parts by weight, it was cast onto a polypropylene plate to obtain a homogeneous blend film. The membrane was attached to a pervaporation device (effective membrane area 7.0 cm ² ), and water-acetic acid mixtures with various concentrations shown in Table 1 were heated at 25°C.
The permeate side was suctioned to 1 mmHg using a vacuum pump, and separation was performed by the pervaporation method. The acetic acid concentration of the components that permeated the membrane (acetic acid permeated preferentially) was analyzed using a gas chromatograph, and the amount of permeated components was determined by condensing the permeated components.
Table 1 shows the separation coefficient and permeation rate 6 hours after starting pervaporation.

[Table] Comparative Examples 1 and 2 The same operations as in Examples 1 and 2 were performed except that a membrane obtained without blending trioctylphosphine oxide with polysylethylene siloxane was used. Table 2 shows the membrane performance at various acetic acid concentrations.

〔Effect of the invention〕

By using the membrane of the present invention, it is possible to efficiently treat a water-organic acid mixture at a high permeation rate while maintaining a higher separation coefficient than separation methods using conventional membranes without causing deterioration due to acid. Can be done. Therefore, the separation system can be made more compact, its processing capacity can be increased, and costs can be reduced, 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.
It has extremely great industrial utility.

Claims (1)

[Scope of Claims] 1. A membrane for separating mixed liquids, which is prepared by blending 1 to 50% by weight of trisubstituted phosphine oxide with a silicone polymer having a repeating unit of the formula (R ₁ : hydrocarbon group). 2. The separation membrane according to claim 1, wherein the hydrocarbon group R ₁ has 2 to 6 carbon atoms. 3. The separation membrane according to claim 1, wherein the silicone polymer is polysilethylene siloxane. 4 The trisubstituted phosphine oxide is (R ₂ ) ₃ P=O
( _R2 : a hydrocarbon group having 4 to 18 carbon atoms), the separation membrane according to claim 1, 2, or 3. 5 The trisubstituted phosphine oxide is (R ₂ ) ₃ P=O
( _R2 : a hydrocarbon group having 6 to 12 carbon atoms), the separation membrane according to claim 1, 2, or 3.