JPS59203606A - Permselective membrane - Google Patents

Abstract

PURPOSE:To provide an Si-containing permselective membrane for gas or liquid enhanced in heat resistance and chemical resistance, comprising a polymer with a specific structure based on a structural unit having a perfluorophenyl group on its side chain. CONSTITUTION:A polymer in which a repeating unit represented by the formula (wherein p is 1-2, q is 0 or 1, RO is a lower alkylene group and R is a hydrogen atom, an alkyl group, a halogenated alkyl group or a phenyl group) is contained in an amount of 10% or more is formed into a membrane by a usual method. The obtained permselective membrane comprising an Si-containing polymer having a perfluorophenyl group on its side chain has especially excellent permselectivity in concentrating oxygen in air and has excellent film forming property.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a selectively permeable membrane for gas or liquid mixtures. In particular, the present invention relates to a permselective membrane having excellent permselectivity and film formability for concentrating oxygen gas in the air.

Conventionally, as methods for separating and concentrating oxygen gas and nitrogen gas from air, cryogenic separation methods that utilize the difference in the boiling points of the two gases, and adsorption methods that utilize the difference in adsorption amounts, have generally been used.

In recent years, separation methods using polymer membrane permeation have been attracting attention as a separation method that consumes less energy than these methods. If air richer in oxygen or air richer in nitrogen than air could be easily and economically produced, it would make a significant contribution to fields such as various combustion engines, medical equipment, the food industry, and waste treatment.

The desired characteristics of a polymer membrane used for such purposes are high selectivity between oxygen gas and nitrogen gas and a large amount of oxygen gas permeation. In particular, the latter is extremely important in downsizing the separation device and increasing the amount of gas that can be processed. - In order to obtain a large amount of oxygen gas permeation, it is sufficient to select a membrane material with a large oxygen gas permeability coefficient Po2 and to make the membrane thickness as thin as possible.

Among the known polymer membranes of this size, the gas permeability coefficient P (hereinafter, unless otherwise specified, the unit of permeability coefficient is 4 (STP)・mβ'See・cmHg
shall be. ) is made of polydimethylsiloxane, and its oxygen gas permeability coefficient Po2 is /1X10-8.
The separation coefficient α between oxygen gas and nitrogen gas (α−permeability coefficient of oxygen gas/permeability coefficient of nitrogen gas) is 2.0. However, since polydimethylsiloxane has a low mechanical strength, it is difficult to form a film that can withstand practical use at a thickness of several tens of micrometers or less, and it is difficult to obtain a film that has a sufficient amount of gas permeation.

In order to improve the film forming properties of polydimethylsiloxane, a polydimethylsiloxane-polycarbonate copolymer was developed, and it is said that it is possible to form a thin film of 1 μm or less, but the separation coefficient α between oxygen gas and nitrogen gas is 2. 0 to z4, which is still small, and there is a limit to the oxygen concentration of the oxygen-enriched air that can be obtained.

As a result of intensive research in search of a membrane material that has excellent permselectivity for oxygen gas and sufficient mechanical strength to allow thinning, the present inventors discovered a silicon-containing polymer having perfluorophenyl groups in the side chain. The present invention was completed based on the discovery that the membrane has excellent properties as a selectively permeable membrane. That is, the measurement results of the gas permeability of such a polymer membrane showed that the permeability coefficient Po2 of oxygen gas was 8 x 10-9 or more, and the separation coefficient α between oxygen gas and nitrogen gas was 2.5 to 52, which were very excellent. It has permselectivity and [1,05 to 10μ
It is possible to make the film as thin as m.

Furthermore, polymer membranes have excellent heat resistance, chemical resistance, etc., and can be used as selectively permeable membranes under various environments.

That is, the present invention provides a repeating unit expressed by the following general formula] r, where p-1 or 2. q-0 or 1. ) in an amount of at least 10% by weight of the entire polymer.

The silicon-containing polymer used in the present invention has the general formula C
This is a polymer containing a structural unit represented by D having a perfluorophenyl group in its side chain. An example of a typical structural formula thereof is CH, CH-OH.

1 etc. can be mentioned.

The silicon-containing polymer used in the present invention contains repeating units represented by the general formula [I] in an amount of 10% by weight or more based on the entire polymer, as exemplified by the following structural formula. There is no problem even if less than 90% by weight of structural units other than (1) is copolymerized with respect to the whole.

CH3HCH3 111 -8i-0-, -3i-0-, -8i-0-.

1 1 1 CH30H3CH=CH2 CH, CB.

1-8i-X-8i-0- (wherein, However, it is preferable that the weight fraction of perfluorophenyl groups in the entire polymer is 0.2 or more; The higher the value, the better the selectivity between oxygen gas and nitrogen gas.Also, a conventional method can be used to polymerize these monomers.

In order to provide a sufficient amount of gas permeation and to have practical strength, the polymer membrane preferably has a thickness of α05 to 100 μm, particularly α1 to 50 μm. For thin films with a thickness of 1 μm or less, it is preferable to use them together with a support. As the support, any porous material having sufficient strength to support the membrane can be used, such as a woven or nonwoven support, a microfilter, or an ultrafiltration membrane.

The method for forming a film of the polymer of the present invention is not particularly limited, and any known or well-known method may be used. For example, a film can be formed by evaporating the solvent from a casting solution on a metal or glass plate or on a water surface. Alternatively, methods such as immersing a porous support in a solution, pulling it up, applying the solution, and drying can be employed.

The membranes obtained in this way are flat membranes and tubular membranes.

It can be used in any form, such as a hollow fiber membrane.

As described above, the present invention uses a membrane made of a silicon-containing polymer having perfluorophenyl groups in its side chains to achieve extremely excellent permselectivity for oxygen gas.

It has achieved properties such as film formability, heat resistance, and chemical resistance.

The present invention will be described in detail below with reference to Examples, but it goes without saying that the present invention is not limited thereto.

In the present invention, the gas permeability coefficient P was measured using a high vacuum pressure method.

Examples 1-3 Pentafluorostyrene 19.49 to chloroplatinic acid 10
After adding 40 mg of a wt% 2-propertool solution under a nitrogen stream and heating to 80°C, methyldichlorosilane 14
．． 4 g was added and reacted at 100°C for 2 hours. The product was fractionally distilled to give methyl-2-(pentafluorophenyl)ethyldichlorosilane 2129+. Methyl-2
-(pentafluorophenyl)ethyldichlorosilane,
Dimethyldichlorosilane, methylvinylcyclosilane oso, 70: 29.5: 0.5, 50, respectively
: 49.5 :05 and 30:69.5:Q, 5
The molar ratio was adjusted, and after hydrolysis in ether, the molecular weight was increased using concentrated sulfuric acid as a catalyst. Each film was formed using benzoyl peroxide as a crosslinking agent and used as a sample for permeation measurement. Table 1 shows the permeability coefficient P○2 of oxygen gas and the separation coefficient α between oxygen gas and nitrogen gas at 25°C for these membranes.
Shown below.

Table 1 Example 4 Jetoxydichlorosilane 9. A 20% by weight ether solution of (pentafluorophenyl)magnesium chloride 2189 was added to a 40% by weight hexane solution of Og, and under reflux,
The reaction was carried out for 3 hours, and 97 pieces of di(pentafluorophenyl)jethoxysilane were obtained by fractional distillation. Using this as a monomer, it was hydrolyzed in toluene and polymerized using hydrochloric acid as a catalyst. The obtained polymer was made into a solution of 4% toluene, and the solvent was removed on a glass plate to obtain a homogeneous film with a thickness of 7 μm. Oxygen gas permeability coefficient P of this membrane at 25°C
02 was &4XlO-', and the separation coefficient α between oxygen gas and nitrogen gas was 3.2.

Claims (1)

[Scope of Claims] A selectively permeable membrane consisting essentially of a polymer containing repeating units represented by the following general formula in an amount of at least 10% by weight or more based on the entire polymer.