JPS6125622A - Oxygen permselective membrane - Google Patents

Abstract

PURPOSE:To obtain an oxygen permselective membrane of large permeability, high in oxygen selectivity and membrane strength and can be made to very thin membrane by using macromolecule in which a part or whole of hydroxyl group of phenol is substituted by alkyl group. CONSTITUTION:Macromolecule containing hydroxyl group of phenol as principal constituting unit of polyhydroxystyrene, novolak etc. is used. Mixture of macromolecule made by substituting a part of whole of this hydroxyl group of phenol and polydimethyl siloxane of polymerization degree of 3-60 is used as an oxygen permselective membrane. This material has oxygen permeability coefficient of 5.6X10<-9>-5.5X10<-8>cccm/sec.cm<2>.cmHG and oxygen nitrogen permeability coefficient ratio of PO2/PN2=2.2-2.9.

Description

[Detailed description of the invention] Industrial fields of application The present invention is applicable to internal combustion engines, steel industry, combustion equipment, waste treatment,
Medical Device 2 This relates to an oxygen-selective permeable membrane that is expected to make a significant contribution in the food industry and other fields.

Structures of conventional examples and their problems Organic films mainly composed of polymers have been used mainly as gas barriers.

In recent years, gas separation and concentration that take advantage of differences in gas permeability depending on the type of gas, particularly oxygen enrichment membranes that separate and concentrate oxygen or nitrogen gas from air, have been in the spotlight.

Until now, methods for separating air without using polymers include methods that use zeolite or special carbon. This method takes advantage of the difference in the adsorption and desorption properties of 021N2 gas, but these methods have the drawback that not only can the adsorption and desorption process not be carried out continuously, but the equipment is complicated.

On the other hand, there are mainly two methods for air separation using polymers. One is a method using hollow fibers such as polyethylene, polystyrene, polyethylene terephthalate, or polysulfone (see % JP-A-49-10192, Japanese Patent Publication No. 49-81298, etc.).

The other method uses ultra-thin films such as organosiloxane-polycarbonate copolymers (U.S. Pat.
(See specification No. 980456 and specification No. 3874986). The method using hollow fibers increases the membrane surface area per unit area and increases the permeation flow rate, but it is still too large and convenient to obtain a practical permeation amount. On the other hand, in the case of ultra-thin membranes, the amount of permeation is increased by utilizing the fact that the permeation flow rate is inversely proportional to the membrane thickness, and the thinner the membrane thickness, the more compact the separation device becomes possible. This is based on the fact that when gas passes through a homogeneous membrane, the amount is generally expressed as:

F,,,P,JP-A/L F; Permeation flow rate (c#l/5ec) P; Gas permeability coefficient (C-・cm/crl”MX・cMX
H9) JP, pressure difference (ctHF) A; membrane area (cd) L; membrane thickness (α) In the above formula, A, l! :dP is dependent on the external equipment required for gas separation and has certain limitations. After all, in order to increase the permeation flow rate F, it is necessary to introduce a material that has a large P and can make the film thickness as thin as possible. A copolymer of polydimethylnoroxane and polycarbonate was first developed by General Electric Company in the United States. Since then, as energy conservation has been further promoted, research has been progressing on membrane materials that have higher oxygen selective permeability, good membrane strength, and can be made into extremely thin membranes.

At present, various materials with high oxygen permselectivity are being considered, and although some have been put into practical use, they are still insufficient, and it is necessary to develop materials with even higher permselectivity.
This is a major point for future development.

Purpose of the Invention The present invention has been made in order to solve the above-mentioned problems of the conventional art. The purpose is to provide a selectively permeable membrane.

Structure of the Invention In order to achieve this object, the present invention provides an oxygen-selective permeable membrane comprising a polymer containing a phenolic hydroxyl group as a main structural unit, and in which some or all of the phenolic hydroxyl groups are substituted with an alkyl group. It provides:

As the polymer containing phenolic hydroxyl groups of the present invention, polyhydroxystyrene/or novolac, etc. were used. The alkyl group of the substituent is CH3゜CHCH・...C2
2H46, C23H4□.

26I 3 Aj C24H49, C25H51 were used. Further, polydimethylsiloxane, which is the main component of the copolymer having silicon-oxygen bonds as the main constitutional unit, had a degree of polymerization n of 3 to 60. In the case of other polymerization degrees, problems may arise in terms of reactivity and strength. The oxygen selective permeation characteristics of the material according to the present invention obtained using these materials are as follows.

Oxygen permeability coefficient P02=6.6×10~5+6×1O-
8 (CCφ Kushi/shikikan d/pot H, 9) Also, the ratio of nitrogen and oxygen permeability coefficients, Po2/PN2, is P
O2/PN2=2.2-2.9 Description of Examples Examples of the present invention will be described in detail below along with comparative examples.
These are for illustrating the present invention and are not intended to limit it.

<Example 1> (Step 1) Commercially available polyhydroquinestyrene 129 (MOS 70
0.0, 0.1 mol) was added to 200 ml of ethanol-k, and the mixture was heated and stirred to dissolve. Then, an alcoholic solution of sodium hydroxide (0.01 mol to Oo99 mol)
Pour and sodiumize. Next, the alkyl halide (
The alkyl group is CH3~C26H51 and the amount added is 0.1m
o/or less) to partially alkylate the polyhydroquinestyrene.

(Step 2) Alkylated polyhydroxystyrene obtained in Example 1 (alkyl group, C16H33, alkylation rate 60%) 3I and polysulfone (6.000 in Mω) 3.9
Dissolve chlorbenne with stirring at 300°C for 9 hours. Next, pre-synthesized polydimethylsiloxane (degree of polymerization n=1o)
Add 4g of and heat and stir for about 1 hour, and the reaction solution is
The mixture was poured into methanol 21 to obtain a precipitate. It was dissolved in tetrahydrofuran, repeated reprecipitation purification with a water-methanol mixed solvent, and dried to obtain the desired product. When its characteristics were investigated through low vacuum measurement, Po2 was 5.71×1
It was 0PO27/PN2-2.62.

Suitable results were obtained when the degree of polymerization n of polydimethylsiloxane was 3 to 60.

Comparative Example 1> Similarly to Example 1, polyhydroxystyrene was
Example 1 using 700 as it is without alkylating it.
Synthesis was carried out in the same manner.

However, chlorobenzene alone has poor solubility and 100 m
1 of 1,4-dioxane was added. The properties of the obtained material were as follows.

PO2=4 -02
/SeC II Crl ”C1nHjj )P O
2/P N 2-2-24 Therefore, the example using alkylated polyhydroxy/lene has higher P. It is clear from a comparison between Example 1 and Comparative Example 1 that the selection coefficient and selection coefficient are higher.

Comparative Example 2> Synthesis was carried out in the same manner as in Example 1 using polyhydroxystyrene which had been trimethylsilylated in advance (8,700 trimethylsilylation ratio in Mω: 60%). The properties of the obtained material are as follows.

P()2=4.50X10 (CC-crn/S!I
C・ctl-anHg)Po2/PN2=2.31 This is a good result for Comparative Example 1, but again,
The one using the alkylated hydroxystyrene synthesized in Example 1 shows better values.

<Example 2> Similar to polyhydroxystyrene, novolac was then partially alkylated and synthesized in the same manner as in step 1 of Example 1. Next, synthesis was performed as in step 2 using an alkylated novolac, and the following results were obtained.

P()2=5,60X10(CC・cm
/Sec-crl・cmHji)Po2/PN
2=2.7 <Comparative Example 3> Novolak was partially trimethylated to 60% and synthesized in the same manner as in Example 2. Its characteristics are as follows.

P()2=4.0X10 (CC-c1n/SeC・
csf-cmH,9)Po2/'PN222.35 Similarly, when novolac was used in the synthesis, the results were as follows.

P()2=4, OOX10(CC,c
nX/5ec-crl・,H,9)PQ2/PN2−
2.3.

In all cases, the examples showed superior values in both the oxygen permeability coefficient and the ratio of nitrogen and oxygen permeability coefficients.

Effects of the Invention As explained above, the present invention partially or completely alkylates polymers having phenolic hydroxyl groups, such as polyhydroxystyrene and novolac, and has a high oxygen permeability coefficient and selectivity coefficient, and a high membrane strength. An ultra-thin film with strong properties can be obtained.

Claims (6)

[Claims] (1) An oxygen-selective permeable membrane comprising a polymer having phenolic hydroxyl groups as its main constituent units, wherein some or all of the phenolic hydroxyl groups are substituted with alkyl groups. (2) Claim 1, characterized in that the polymer containing phenolic hydroxyl groups is polyhydroxystyrene.
Oxygen-selective permeable membrane as described in . (3) The oxygen selective permeable membrane according to claim 1, wherein the polymer containing a phenolic hydroxyl group is novolac. (4) The oxygen selective permeable membrane according to claim 1, wherein the alkyl group has 1 to 25 carbon atoms. (5) The oxygen-selective permeable membrane according to claim 1, wherein the polymer containing a phenolic hydroxyl group is substituted with a copolymer whose main constituent unit is a silicon-oxygen bond. (6) A copolymer whose main constituent unit is silicon-oxygen bond is
The oxygen selective permeable membrane according to claim 5, characterized in that the main component is polydimethylsiloxane having a degree of polymerization of 3 to 60.