JPH02218423A - Gas separation membrane - Google Patents

Abstract

PURPOSE:To form a thin film and heighten oxygen permeation index and oxygen/nitrogen separation index by graft-copolymerizing a polymer of nitropoly(phenylene sulfide) of which a part of the nitro groups is reduced to amino group and siloxane oligomer having epoxy in both terminals. CONSTITUTION:A part of nitro-groups in a nitropolyphenylene sulfide having a large oxygen/nitrogen separation index and a high mechanical strength is reduced into amino group and then the resulting polyphenylene sulfide is graft- copolymerized with siloxane oligomer having epoxy groups in both terminals and expressed as a formula I [(n) stands for 1-20 integer]. By this, polydimethylsiloxane structure having a large oxygen permeating index is introduced into the graft-copolymer. The graft-copolymer is dissolved in an organic solvent of ketones of cyclohexanes and formed into a thin film. By this method, a membrane having large oxygen permeation index, oxygen/nitrogen separation index, and gas permeation speed is obtained.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a gas separation membrane that selectively permeates oxygen, and in particular to a gas separation membrane that is advantageously applied to a method and apparatus for obtaining oxygen-rich air from air. Regarding separation membranes.

[Conventional technology]

Many polymeric materials have been proposed as membrane materials for gas separation membranes that selectively permeate oxygen in the air.

A practical gas separation membrane is required to have high gas permeability and excellent ability to separate oxygen and nitrogen.

Oxygen permeation rate (etlg"/as" ・aea -51
1g) is the unit area G-) of the gas separation membrane, the amount of oxygen permeating through the membrane per unit time (sea L unit pressure (cmHg)) (5, and p is a value that changes depending on the membrane thickness) .

Therefore, even if the separation membrane is made of the same material, the oxygen permeation rate will be different if the membrane thickness is different. Generally, the gas permeation rate is inversely proportional to the film thickness, so the thinner the film thickness, the higher the gas permeation rate, which is practically advantageous.

On the other hand, the gas permeability coefficient (aI?-1-・sea-
5+Bg) is a value obtained by multiplying the gas permeation rate by the membrane thickness, so it is a value specific to the membrane material regardless of the membrane thickness, and serves as an index for comparing the gas permeability of the membrane materials. Therefore, even if a separation membrane has a large gas permeation coefficient, if it lacks mechanical strength and cannot be formed into a thin membrane, it will be disadvantageous in practice (the gas permeation rate will be low). On the other hand, if an extremely thin separation membrane can be formed even with a small gas permeation coefficient, it becomes practical to achieve a high gas permeation rate.

From the above, a practical gas separation membrane must have a large gas permeability coefficient, be able to be made thin, and have a high tb gas permeation rate.

For membrane materials with high gas permeability, the oxygen permeability coefficient is
P□, : 55 x 10-・am” (8T?)
・m/al・-eo-amHg Polydimethylsiloxane is known, but polydimethylsiloxane alone has an oxygen/nitrogen separation coefficient of ao, /M! :=:1.94
and l) t is not large, and its mechanical strength is low and it is difficult to form a thin film, so it has the disadvantage that it is not possible to increase the gas permeation rate. In order to improve these drawbacks, attempts have been made to create copolymers of polydimethylsiloxane and polymers that have high mechanical strength and high oxygen/nitrogen separability.

For example, polycarbonate) (U.S. Pat. No. 5,980,456)
specification, specification No. 3674986, JP-A-1988-
40868), polyvinylpheno-1 & I (JP 60-71006), polyvinyl triorgano vlan (JP 54-56985), polycarbodiimide (JP 52-91100), steel. A gas separation membrane made of a thin film of a copolymer of polydimethylsiloxane and a V derivative (Japanese Unexamined Patent Publication No. 56-26506) has been disclosed.

Gas separation membranes made of these copolymers have an oxygen/nitrogen separation coefficient of '0JH2'2~3 and an oxygen permeability coefficient of ?□, = 1
．． OX 10-・~2.0X10-easy 51' (8T?
)・aI/−・sea-mug, or oxygen/nitrogen separation coefficient 'OB7M2 = 3~5, oxygen permeability coefficient P
Q, = 1, OX 10-1・~aox1 o-'i(
sτP)ea+/-・5Lea*a+111g However, the oxygen/nitrogen separation coefficient was α=3 or more,
and the oxygen permeability coefficient is P□, = 1. o X 1 ""
Err? (IITF) ・am/a+l@sea
A gas separation membrane having excellent oxygen/nitrogen separation properties and oxygen permeability of 11 g or more has not yet been obtained.

KJd to obtain oxygen-enriched air with an oxygen concentration of 404 or higher
, the oxygen/nitrogen separation coefficient of the gas separation membrane is required to be 3 or more, and the method using the gas separation membrane is advantageous when compared with the method of obtaining oxygen-enriched air using the cryogenic separation method or the PBA method. has an oxygen permeability coefficient of 1'0. = 1.0X
10-" d (8?!') ・5I/4-1Il・
It is desirable that it is 8ec-cm11Ig or more.

[Problem to be solved by the invention]

Copolymer membranes of polydimethylsiloxane and other polymeric materials improve mechanical strength and oxygen/nitrogen separation, but
At the same time, it tends to significantly reduce gas permeability. Therefore, it has been difficult to obtain a highly permeable, highly selective gas separation membrane with a large oxygen permeability ratio and a large oxygen/N separation coefficient.

In view of the above state of the art, the present invention aims to provide a gas permeable membrane that can be made thin, has a large oxygen permeability coefficient, and has a high oxygen/nitrogen separation coefficient.

[Means to solve the problem]

The present invention is a gas separation membrane made of a graft copolymer of a polymer obtained by partially reductively aminating the nitro groups of nitrated poly7-ethylene sulfide and a siloxane oligomer having epoxy groups at both ends.

That is, the present invention produces a siloxane oligomer having epoxy groups at both ends after partially aminating the nitro groups of nitrated $9 phenylene sulfide, which has a large oxygen/'11 elemental separation coefficient and high mechanical strength. This is a gas separation membrane formed by copolymerizing the above and the like, which has significantly improved oxygen permeability, excellent oxygen/nitrogen separation properties, and can be made into a thin film.

Nitrated polyphenylene 4F-rufai) Ha, smoking glass!
10 parts by weight of polyphenylene sulfide A/7 ide was added to the part by weight of Non while cooling to below 10°C, and after the reaction, the reaction solution was gradually added to 3000 parts by weight of water to precipitate the nitrated polyphenylene sulfide. It is obtained by drying nitrated polyphenylene sulfide, pulverizing it, washing it with a large amount of water to remove the acid, and drying it again.

Nitration of polyphenylene sulfide is also possible using a sulfur/nitric acid mixed acid. In this case, 12 parts by weight of nibolifeni V sulfide in a mixed acid of 34 parts by weight of 67 nitric acid and 85 parts by weight of 96 sulfuric acid was added while cooling, and then the temperature was gradually raised and the reaction was carried out at 85 to 90°C for 2.5 hours. Just let it go.

After the reaction, the product is obtained by washing with a large amount of water to remove the acid and drying, as in the case of using fuming nitric acid.

By the above method, about one nitro group is introduced per aromatic nucleus of polyphenylene sulfide. At this time, sulfide is simultaneously oxidized to sulfoxide and sulfone.

Reductive amination of nitrated polyphenylene sulfide is carried out by a hydrogenation reaction using 54 palladium-attached activated carbon as a catalyst.

This is carried out by dissolving 20 parts by weight of nitrated polyphenylene sulfide in 400 parts by weight of dimethyl-homamide, adding 1 part by weight of activated carbon with 54 palladium, and then bringing the mixture into contact with hydrogen at room temperature. At this time, the conversion rate from j9, 2) four groups to amino groups is adjusted by adjusting the amount of hydrogen absorption. The conversion rate is preferably such that about 30 to 80 nitro groups become amino groups. This is because if it is less than 504, it is difficult to form crosslinks between polymer chains due to the terminal epoxy group of the siloxane component, and if it is more than 80, it is difficult to produce the effect of the nitro group.

The nitro group of nitrated polyphenylene sulfide is 30
~ 80 Ghuft copolymerization of a reductively aminated polymer with a siloxane oligomer having epoxy groups at both ends is generally carried out by dissolving the reductively aminated polymer in cyclohexanone to form a swt4 solution, and then A siloxane oligomer having an epoxy group is added in an amount of α5 to 1.0 moles of amino groups present in the polymer, and
This may be carried out by stirring and heating at 100° C. for 3 to 6 hours. After the reaction, the product is precipitated in water, dried, washed with petroleum ether to remove unreacted siloxane oligomers, and dried again to obtain a graft copolymer. At this time, the siloxane oligomer having an epoxy group at both ends can be prepared by forming a film by forming a film in an organic solvent of ketones such as isobutyl ketone, methyl/%/V chlorohexanone, and acetophenone. It will be done.

[Effect]

Nitration of polyphenylene sulfide with nitric acid is
A nido group is introduced into the aromatic nucleus, but at the same time the sulfide is oxidized to become a sulfoxide and a sulfone. Its structure is expressed, for example, as follows.

(However, n represents an integer from 1 to 20) is preferably used.

The graft copolymer obtained by the above method was mixed with cyclohexanone, 2-pentano? , 3-pentanone, 2-hexanone, methyl isobutyl ketone, 2-heptanone, 4
-Heptanone, diHeptanone (n+m) is the same as the degree of polymerization of polyphenylene sulfide, and is about 140 to 200.

The catalytic hydrogenation reaction using activated carbon with buffidium as a catalyst selectively reduces the nitro groups of nitrated polyphenylene sulfide to form the following structure.

A graft copolymer of a polymer in which the nitro groups of nitrated polyphenylene sulfide are partially reduced and aminated and a V-loxane oligomer having epoxy V groups at both ends is a (by reaction with the terminal eboxy V group of the san oligomer) becomes a bonded structure. Its structure is expressed, for example, as follows.

-(0~'0-c-on-cIII) In the above graft copolymer, since the epoxy V group remains at the end of the chloroxane component, when the reaction temperature is further raised and heated for a long time, the They combine to form a cross-linked structure.

The siloxane content of the graft copolymer is 50 to 8
54, when the siloxane content is low, the oxygen permeability coefficient tends to be low.

Example 1 Borifueni V sulfide 1 in 100 parts by weight of fuming nitric acid
0 parts by weight was gradually added while cooling to 10° C. or lower to completely dissolve the solution, and then the solution was gradually added to 4000 parts by weight of water to form a precipitate. After drying the precipitated nitrated polyphenylene sulfide, it was ground, washed with a large amount of water to remove the acid, and then dried again.

After dissolving 10 parts by weight of polyphenylene sulfide dinitrate in 200 parts by weight of dimethylformamide and adding 15 parts by weight of activated carbon with 5 moss palladium, hydrogen was added at room temperature. I let him touch me.

At this time, the supply of hydrogen was stopped when 1100 cc of hydrogen at 25° C. and 1 atm had been absorbed. After the reaction, the 54 palladium-attached activated carbon was removed, added to about 4,000 parts by weight of water to form a precipitate, and dried after suction-filtering.

About 8 nitro groups of nitrated polyphenylene sulfide
After dissolving 10 parts by weight of the above-mentioned polymer subjected to 04 reductive amination in 190 parts by weight of cyclohexanone, it was mixed with sz weight g of a VCL xane oligomer sz having epoxy V groups at both terminals having the following structure, and stirred and heated at 80° C. for 5 hours. After the reaction, about 4000 parts by weight of water was added to form a precipitate, which was dried after passing through suction V, washed with petroleum ether and dried again.

5 parts by weight of the graft copolymer obtained by the above method was added to 3-
Dissolve in 95 parts by weight of pentanone and apply 50 parts by weight on a glass plate.
It was cast to a thickness of 0 μm and dried at 80° C. for 1 hour. The thickness of the obtained graft copolymer film was 1 liter and 4 μm.
, the oxygen permeation rate is 4.8 X 1 G-'cm"/e
ym"-seo-mHg (oxygen permeability coefficient p□, = 1
．． 9 X 1 G---Confucian 151I! ae・C-aI
(g) The oxygen/nitrogen separation coefficient was "ox/*,=".

Example 2 The nitrated polyphenylene sulfide synthesized in Example 1 was catalytically hydrogenated in the same manner as in Example 1 to convert the nitro groups present in the polymer into about 50 amino groups. After 10 parts by weight of this polymer was dissolved in 190 parts by weight of cyclohexanone, it was mixed with 31 parts by weight of the same siloxane oligomer with epoxy groups at both ends as in Example 1, and stirred and heated at 80 DEG C. for 5 hours. After the reaction, the reaction solution was heated to about 4. A precipitate was formed by adding OOd parts by weight of water, dried after filtration with suction, washed with petroleum ether and dried again.

3 parts by weight of the graft copolymer obtained by the above method was added to 3-
Dissolved in 97 parts by weight of pentanone and placed 300 parts by weight on a glass plate.
It was cast to a thickness of μm and dried at 80° C. for 1 hour. The thickness of the obtained graft copolymer membrane was α1 μm, and the oxygen permeation rate was t5 X j O−” csl/d * s+
eo・c++IT1g (oxygen permeability 1, 5 X i
G-Hatakeml-as/d・sea・naHg)
, the oxygen/nitrogen separation coefficient is α0JNz = 5-5
There was f.

Example 3 The nitrated polyphenylene sulfide synthesized in Example 1 was catalytically hydrogenated in the same manner as in Example 1 to convert the nido groups present in the polymer into about 8041 mino groups. After dissolving 10 parts by weight of this polymer in 190 parts by weight of V-clohexanone, it was mixed with 35 parts by weight of a siloxane oligomer with epoxy groups at both ends having the following structure, and the mixture was stirred and heated at 80° C. for 5 hours. After the reaction, the reaction solution was precipitated in about 4,000 parts by weight of water, filtered with suction, dried, washed with petroleum ether, and dried again.

3 parts by weight of the graft copolymer obtained by the above method was added to 3-
Dissolve in 97 parts by weight of pentanone and place on a gaff plate.
It was cast to a thickness of 0 μm and dried at 80° C. for 1 hour. The thickness of the obtained graft copolymer membrane was 11 μm, and the oxygen permeation rate was 1.7 × 1 G-” al/d・see
-311g (Oxygen permeability factor 1,7 x 10-・-
・ays/al ・sea ・cstHg), oxygen/
The nitrogen separation factor was "Os/Nx = 51.

〔Effect of the invention〕

In the present invention, the oxygen/nitrogen separation coefficient is 'C)s/Hz =
11, the highly selective nitrated polyphenylene sulfide has an oxygen permeability coefficient of p□, =55×10−$−・
A highly permeable polydimethylsiloxane structure with a weight of 5I/-・sea・country 111g is introduced by graft copolymerization, and the oxygen/nitrogen separation coefficient is 'On/Hs=IO or more, and the oxygen permeability coefficient is tOXlo-Koichi Hatake/-
・It has become possible to produce a gas separation membrane with high selectivity and high permeability that is more than -ecΦHg. Furthermore, since the graft copolymer has mechanical strength, it can be made into a thin film, and the oxygen permeation rate, which is a practical problem, can be reduced to 1. y x t o-”
d15Il・θθO−ersHg,
It is an excellent gas separation membrane.

Claims (2)

[Claims] (1) A gas separation membrane made of a graft copolymer of a polymer obtained by partially reductively aminating the nitro groups of nitrated polyphenylene sulfide and a siloxane oligomer having epoxy groups at both ends. (2) The gas separation membrane according to claim 1, wherein the siloxane oligomer having epoxy groups at both ends has the following structure. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (However, n represents an integer from 1 to 20.)