JPS61429A - gas separation membrane - Google Patents

Abstract

PURPOSE:To obtain a gas separation membrane enhanced in the transmission coefficient of oxygen, by coating a porous thin walled holding aid material with a sililated phenoxy resin. CONSTITUTION:A sililated phenoxy resin having a structural unit represented by formula in the main chain thereof, which is obtained by reacting a phenoxy resin and trialkylsilyl halaide, is formed into an extremely thin membrane or applied to a porous thin walled support to form a gas separation membrane. In the formula R<1>-R<8> are a hydrogen atom, a lower alkyl group or a halogen atom and may be respectively same or different. R<9> is a hydrogen atom or a methyl group and R<10>-R<12> is an 1-4C alkyl group and may be, respectively the same or different. The preparation of the extremely thin membrane and the coating of the porous thin walled support are usually performed by using a solution of the sililated phenoxy resin in a solvent. When the porous thin walled support is coated, a solution prepared by dissolving said resin in a solvent not dissolving said porous thin walled support is cast on the support or the support is impregnated or coated with said solution and the solvent is removed by drying.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a gas separation membrane made of a silylated phenoxy resin, and particularly to a separation membrane suitable for oxygen separation.

[Conventional technology]

From the viewpoint of resource and energy conservation, methods of separating substances using membranes are attracting attention. There are various substances that can be separated, and gas separation membranes that separate oxygen, hydrogen, etc. are one of them. If a particular gas in the gas mixture is not concentrated, various effects will be achieved depending on the gas.

For example, in the case of oxygen, it is said that if oxygen-enriched air can be used as boiler combustion air, more than 10% of fuel can be saved, and if oxygen-enriched air is used for medical purposes,
Oxygen separation membranes have many uses, as they are safe and do not have to worry about oxygen poisoning as is the case when using pure oxygen.

The requirements for materials that can be used in oxygen separation membranes include (1) a high oxygen permeability coefficient, (2) a high oxygen permselectivity, and (3) the ability to form membranes. . It seems that no known material has been found that satisfies conditions (1) and (2) at the same time. Therefore, depending on the application, either condition (1) or (2) is usually given priority when selecting the material to be used.

Materials that satisfy the condition of having a large oxygen permeability coefficient include:
polycarbonate/polyorganosiloxane copolymer,
Poly-4-methylpentene-1, fluoropolymer/polyorganosiloxane graft copolymer, phenolic or phenol ether addition polymer/α lll-
1st official”I i@’6fl)y.□A, o,
7□□818□ have been found.

[Problem that the invention seeks to solve]

The inventors of the present invention conducted intensive studies to find useful materials for gas separation membranes, especially oxygen enrichment membranes, and found that the oxygen permeability coefficient was improved by introducing an organic silyl group into the molecular chain of phenoxy resin. This discovery led to the completion of the present invention.

[Means for solving problems]

The present invention is based on the general formula % (%) () (in the formula, R1 to R8 represent a hydrogen atom, a lower alkyl group, or a halogen atom, and each is the same) and is obtained by reacting a phenoxy resin and a trialkylsilyl halide. may also be different, R9 represents a hydrogen atom or a methyl group,
RIO to R12 represent an alkyl group having 1 to 4 carbon atoms, and may be the same or different. ) A gas separation membrane made of a silylated phenoxy resin having a structural unit represented by It is a separation membrane.

The silylated phenoxy resin used in the present invention is obtained by silylating a known phenoxy resin with a trialkylsilyl halide. or its polycondensate with a nuclear substituted product, and is represented by the following general formula (+1+).

...■ (In the formula, R1 to R9 are the same as above, and n is a positive integer of 20 or more.) The phenoxy resin preferably used in the present invention has rl in the formula (fl) of 70 Among the above polymers, the more preferred phenoxy resin is a polymer derived from epichlorohydrin and bisphenol A, and in which n in formula (11) is 70 or more.

Such a phenoxy resin can be produced by condensing bisphenol A or its nuclear substituted product with epihalohydrin or β-methylepihalohydrin in the presence of an alkali such as caustic soda. Regarding this production method, for example, US Pat. No. 2,602,075 and US Pat. No. 3,505,528 are taught and are incorporated by reference. Practically speaking, phenoxy resin is commercially available from Union Carbide Company under the trade name r UCAR Phenoxy Resin, and is divided into five grades, r PEG (CJ, r PIG (HJ and r PKHJ J), according to the difference in molecular weight. There are and these can be used.

As is clear from the general formula (1), the benzene ring derived from bisphenol A or its derivatives and the hydroxyl group derived from epihalohydrin are considered as sites that can be silylated in the +1i position of the repeating structure of the phenoxy resin.However, The reactivity towards silylation reactions differs between the two sites, with the hydroxyl group being superior to the benzene ring.

Therefore, when alkylsilyl halides are reacted using a basic substance such as pyridine as a catalyst, only the hydroxyl groups react.

When an alkyl cybaride is reacted using an alkali metal alkyl represented by Ikegata and butyl lithium as a catalyst, it is thought that the hydroxyl group is silylated and then the benzene ring is silylated. However, in reality, when silylation is performed using butyllithium, silylation of hydroxyl groups is easy, but benzene?
If you try to silylate the ring, phenoxy 1
Cutting of the molecular chain of M fat occurs. When molecular chains are cut, the molecular stability is lowered, resulting in deterioration of the phenoxy resin, and the film is likely to be damaged during film formation of the silylated phenoxy resin. Therefore, the silylated phenoxy resin suitable for gas separation membranes is one in which the hydroxyl group is silylated, but if the flexibility of the membrane is not impaired to the extent that it hinders membrane formation, it is preferable to use a silylated phenoxy resin in which the benzene ring is not silylated. I don't mind.

All known methods can be applied to silylate the hydroxyl group; for example, 1) after metalating the hydroxyl group with an alkali metal alkyl or an alkali metal aryl,
Method of reacting trialkylsilyl halide, 11)
Preferred methods include a method in which trialkylsilyl halide is reacted in the presence of another basic substance. These methods will be explained below.

1) Method of using alkali metal alkyl or alkali metal aryl The alkyl group and aryl group of alkali metal alkyl or alkali metal aryl do not become part of the phenoxy resin after the silylation reaction, so any group may be selected; Examples of the alkali metal include lithium, potassium, rubidium, and cesium. From the viewpoint of operability, alkyllithium and aryllithium are preferred.

The amount of alkali metal alkyl or alkali metal aryl to be used may be appropriately selected depending on the desired silicon group to be introduced into the phenoxy resin, and is usually 0.3 to 3.0 per repeating unit of the phenoxy resin. equivalent, preferably 0.
Amounts ranging from 5 to 1.5 per cent are used. If the amount is less than the lower limit, the introduction of silicon atoms will be insufficient, and if the amount is more than the upper limit, undesirable side reactions such as molecular chain scission will occur.

The solvent is preferably one that has substantially no reactivity with alkali metal alkyls or alkali metal aryls and can dissolve the phenoxy resin, and examples thereof include benzene, toluene, xylene, and tetrahydrofuran. The reaction temperature ranges from above the freezing point of the phenoxy resin solution to 80°C, preferably from -80°C to 60°C, particularly from -50°C to 30°C.

The alkali metal-added phenoxy resin thus obtained is reacted with a silylating agent to obtain the desired silylated phenoxy resin, but since the alkali metal-added phenoxy resin is extremely reactive, the reaction with the silylating agent is alkali-based. The reaction is carried out by adding a silylating agent without isolating the alkali metal-added phenoxy resin from the metal addition reaction solution.

The silylating agent is 2X-5i(RjO)(Rt+)(R1
2) An alkylsilyl halide compound represented by (in the formula, R10, R11 and R12 are the same as above).

RIO, R11 and R42 preferably have 1 to 1 carbon atoms.
4, and X includes chlorine, bromine or iodine. Specifically, trimethylchlorosilane,
triethylchlorosilane, tripropylchlorosilane,
Examples include tributylchlorosilane, trimethylbromosilane, triethylbromosilane, tripropylbromosilane, tributylbromosilane, trimethyliodosilane, and trimethyliodosilane.

Among these, chlorosilanes in which X is chlorine are preferred.

11) Method using other basic substances The basic substance used in this reaction may be any basic substance other than alkali metal alkyl and alkali metal aryl that act as a base under anhydrous conditions. is also used.

Specifically, aliphatic tertiary amines such as trimethylamine, triethylamine, tripropylamine, and tributylamine; aromatic tertiary amines such as pyridine and picoline; sodium methoxide, sodium ethoxide, sodium propoxide, sodium butoxide, and potassium methoxy. Do, nonolium ethoxide, potassium propoxide, potassium butoxide, lithium methoxide, lithium ethoxide, lithium propoxide,
Typical examples include alkali metal amides such as lithium diisopropylamide, lithium diisobutylamide, sodium diisopropylamide, sodium diisobutylamide, potassium diisopropylamide, potassium diisobutylamide, etc. Examples include, but are not limited to, basic substances.

The amount of these basic substances to be used may be appropriately selected depending on the desired amount of silicon groups to be introduced into the phenoxy resin, and is usually 0.5 to 5 silicon groups per repeating unit of the phenoxy resin.
．． It is used in amounts ranging from 0 equivalents, preferably from 0.5 to 1.5 equivalents.

If the amount is below the lower limit, introduction of silicon atoms into the molecular chain will be insufficient. On the other hand, if the amount exceeds the upper limit, the introduction of silicon atoms reaches saturation, and there is no point in using a large amount of the basic substance.

The solvent is one that has substantially no reactivity with the basic substance and dissolves the phenoxy resin. Specific examples include benzene, toluene, xylene, and tetrahydrofuran.

The reaction temperature is above the freezing point of the phenoxy resin solution to 8
0C1 is preferably at a temperature in the range from -80°C to 60°C, particularly preferably from -50°C to 60°C.

In the case of this method, the basic substance plays a role as an acid scavenger, so unlike the case of alkali metal alkyl or alkali metal aryl, the basic substance and silylating agent are simultaneously added to the reaction solution. and react.

As the silylating agent, the aforementioned alkylsilyl halide compounds are similarly used.

The oxygen permeability coefficient of the silylated phenoxy resin thus obtained is determined by the substituents R1o, Rt+ and R12 of the silicon atom.
The effect varies greatly depending on the type of carbon, and the smaller the number of carbon atoms, the more
The oxygen permeability coefficient increases.

Incidentally, when a phenyl group is introduced as a substituent for a silicon atom, the resulting silylated phenoxy resin becomes rubbery, making it difficult to form a film. Therefore, in the present invention, among the above-mentioned silylating agents, a silylated phenoxy resin obtained using trimethylchlorosilane in which all of the silicon atom substituents R1o, R11 and R12 are methyl groups is most preferred.

The amount of silylating agent used may be independent of the amount of alkali metal alkyl, alkali metal aryl, or other basic substance used, and will vary depending on the desired degree of silicon atom introduction. However, as the degree of silylation increases, the oxygen permeability coefficient also increases, so usually a sufficient amount is used to silylate all the hydroxyl groups.

The silylated phenoxy resin is separated and recovered from the silylated phenoxy resin-containing solution prepared by the above method. but,
Simply adding a non-solvent for the silylated phenoxy resin to the reaction solution recovers the silylated phenoxy resin as a rubbery substance, and furthermore, salts formed during the reaction are not removed, which is not desirable for film formation. do not have.

Therefore, in order to separate and recover the silylated phenoxy resin, for example, 1) remove most of the solvent by distillation, 2) extract with chloroform-water, and 2) extract the chloroform layer with anhydrous sulfuric acid.
It is necessary to carry out a series of operations consisting of drying with Jum or the like and removing chloroform by distillation.

The degree of silylation of the silylated phenoxy resin obtained as described above is usually determined by infrared absorption or nuclear magnetic resonance absorption.

The silylated phenoxy resin obtained as described above is made into an extremely thin film or coated on a porous thin support to form the gas separation membrane of the present invention.

A solution of a silylated phenoxy resin dissolved in a solvent is usually used for producing ultra-thin membranes and coating porous thin supports. When coating a porous thin support, a solution dissolved in a solvent that does not dissolve the porous thin support is cast on the support, or the support is impregnated or coated, and the solvent is dried. By removing by. Examples of the solvent include benzene, toluene, xylene, chloroform, and tetrahydrofuran, and examples of the porous thin support include:
Examples include Japanese paper, nonwoven fabric, synthetic paper, 4-filter paper, cloth, wire mesh, filtration membrane, ultrafiltration membrane, etc., and those in the shape of a plane, cylinder, corrugated plate, honeycomb cell, and other types 4 are used as appropriate.

The gas separation membrane of the present invention thus obtained can be used not only to produce oxygen-enriched air from air, but also to separate methane and helium from natural gas, as well as to separate oxygen, nitrogen, carbon dioxide, -carbon oxide, hydrogen, and argon. It can also be used to separate desired component gases from a gas mixture containing one or more gases such as , helium, methane, etc.

〔Example〕

Hereinafter, the gas separation membrane made of the silylated phenoxy resin of the present invention will be specifically explained using Examples and Comparative Examples.

Example 1 and Comparative Example 1 Phenoxy resin (manufactured by UCC, grade name r P K HHJ) 1 under a nitrogen stream in a 1-shaped 3-tube flask
0g was dissolved in 500ml dry tetrahydrofuran and 50ml/dry pyridine was added. The mixture was cooled to zero, 8.9 M of trimethylchlorosilane was added thereto, and the temperature was raised to room temperature while stirring (stirred for about 6 hours). After confirming the completion of the reaction by infrared absorption spectrum (O
Most of the solvent was removed using an evaporator (H group equivalent reaction), and this was extracted with chloroform-water. After drying the chloroform layer over anhydrous sodium sulfate, the solvent was evaporated and isolated. The product was dissolved in chloroform to form a thin film by a casting method, and the oxygen permeability coefficient was measured by a vacuum method using a Seikaken gas permeability meter (manufactured by Rika Seiki Kogyo Co., Ltd.). As a result, the oxygen permeability coefficient is 2,6 x 1
ncc(STP)(*/d-5ec-(*Hg), and the separation coefficient between oxygen and nitrogen was 6.55 (Example 1).

On the other hand, when 6g of the phenoxy resin of Example 1 was dissolved in 100ml of chloroform and a thin film was made by a casting method and the oxygen permeability coefficient was measured, the oxygen permeability coefficient was 2.
x 10”cc(STP)G+++/ad-sec
-cmHg (Comparative Example 1).

By comparing the results of Example 1 and Comparative Example 1,
It is clear that by completely trimethylsilylating the hydroxyl groups present in the repeating units of the phenoxy resin, the oxygen permeability coefficient is improved approximately 100 times.

Example 2 Example 1 except that triethylchlorosilane 11.8m was used instead of trimethylchlorosilane in Example 1.
I did it in the same way. The oxygen permeability coefficient of the obtained gas separation membrane was 1.8X10cc (STP)cv/aa
, sec - cmHg, and the separation coefficient between oxygen and nitrogen was 6.50. In addition, when the infrared absorption spectrum of the triethylsilylated phenoxy resin was measured,
Since the absorption based on hydroxyl groups completely disappeared, it was found that the hydroxyl groups were substantially iooo% silylated.

Even with triethylsilylation, the oxygen permeability coefficient is almost 1.
It is clear that the improvement is 00 times.

Example 6 10 g of the phenoxy resin used in Example 1 was dissolved in 50011/dry tetrahydrofuran under a nitrogen stream, cooled on ice, and 1.1 equivalents per 1 equivalent of water and acid group of the phenoxy resin were added. of butyllithium (15% hexane solution, 24 mJ) was added, and the mixture was stirred for about 1 hour while cooling on ice. Then, 1.05 equivalents of trimethylchlorosilane (4
7 ml) was added, the ice bath was removed, and the mixture was stirred for 1.5 hours. The reaction solution was poured into 1 liter of methanol with stirring and left in the apparatus overnight. The supernatant was decanted and the remaining tarry material was dissolved in chloroform. Chloroform was evaporated to obtain trimethylsilylated phenoxy resin. Since the phenoxy resin does not dissolve in hexane, the trimethylsilylation rate was not sufficient, and as a result of quantitative determination by nuclear magnetic resonance absorption, the trimethylsilylation rate was about 50%. When the oxygen permeability coefficient of this was measured in the same manner as in Example 1, the obtained silylated fetoxy resin was 9.
9X10"(°°3°0"゛/crl-sec-c"'
Hg T ly j f:.

〔effect〕

As is clear from the Examples and Comparative Examples, it is known as a resin with adhesive properties and has an oxygen permeability coefficient of 10"c.
c(STP) an/ad-sec, although it is on the order of land, it is 1o-10c due to the silylation of the present invention.
It was found that c(STP) mlcrl-sec, cxHg increases by two digits, and is characterized by a good gas separation membrane.Patent applicant Kazuyoshi Nagano, representative of Mitsubishi Gas Chemical Co., Ltd.

Claims (1)

[Claims] 1 General formula obtained by reacting phenoxy resin and trialkylsilyl halide▲There are mathematical formulas, chemical formulas, tables, etc.▼・・・・・・・・・(
I) (In the formula, R1 to R8 represent a hydrogen atom, a lower alkyl group, or a halogen atom, and may be the same or different, and R9 represents a hydrogen atom or a methyl group,
R10 to R12 represent an alkyl group having 1 to 4 carbon atoms, and may be the same or different. ) A gas separation membrane made of silylated phenoxy resin that has a structural unit represented by the following in its main chain. 2. The gas separation membrane according to claim 1, which is formed by coating a porous thin-walled holding aid with a silylated phenoxy resin.