JP3132050B2 - Gas separation membrane - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas separation membrane having excellent film-forming properties and heat resistance and having high permselectivity.

[0002]

2. Description of the Related Art Oxygen-enriched air is continuously supplied to various combustion systems, for example, internal combustion engines such as industrial boilers, furnaces or automobiles, household heating appliances, etc., to improve combustion efficiency and improve fuel efficiency. Save money,
In addition, it can prevent incomplete combustion, so it is also useful on environmental pollution problems.
It is also useful in other fields such as aquaculture, sewage treatment and the like. Therefore, a gas separation membrane capable of efficiently separating nitrogen and oxygen in the atmosphere and producing oxygen-enriched air has attracted attention.

As the gas separation membrane, for example, polydimethylsiloxane (Japanese Patent Application Laid-Open No. 54-56985) or poly (trimethylsilylpropyne) as a polymer membrane material having high gas permeability has a relatively high gas permeability. Poly (4-methylpentene-1), natural rubber, and the like are known as polymer membrane materials having excellent oxygen permeability and high oxygen selective permeability.

However, polydimethylsiloxane and poly (trimethylsilylpropyne) have oxygen permeability PO ₂ (hereinafter referred to as PO ₂ ) as high as 1.0 × 10 to ⁸ or more, but PO ₂ and nitrogen permeability PN permeability coefficient ratio of ₂ alpha
(PO ₂ / PN ₂ ) (the permeability coefficient is the same as the gas separation ratio) (hereinafter referred to as α) is about 2, the oxygen concentration of the obtained oxygen-enriched air is as low as about 25%, and Inferior in mechanical strength and difficult to thin. Furthermore, poly (trimethylsilylpropyne) has an unsaturated double bond (C = C) in the main chain, and therefore has a disadvantage of poor durability (oxidation stability), and is not suitable for practical use. Furthermore, the polydimethylsiloxane has a low α, but is excellent in chemical stability and has high gas permeability. Therefore, in order to improve the α, modification by copolymerization with various compounds or the like, for example, dimethylsiloxane- Modifications such as parahydroxystyrene copolymers and dimethylsiloxane-polycarbonate copolymers have been attempted, but α is hardly improved.

[0005] Poly (4-methylpentene-1)
Means that PO ₂ is in the first half of 1.0 × 10 to ⁹ units and has excellent mechanical strength, chemical stability and thermal stability, but requires advanced technology for thinning, and has high oxygen selective permeability. It is not enough and is actually only used in one part.
Further, natural rubber can be easily formed into a thin film, and although PO ₂ is in the order of 1.0 × 10 to ⁹ units, it has disadvantages in that it is inferior in chemical stability and durability and low in oxygen selective permeability.

As described above, since a gas separation membrane exhibiting sufficient performance has not been obtained, in order to obtain necessary oxygen-enriched air, it is necessary to use an oxygen enrichment apparatus in multiple stages or to increase the size of the apparatus. At present it is inevitable.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a gas separation membrane which has excellent gas selectivity, especially α, is easy to form a film, and has practical mechanical strength.

[0008]

According to the present invention, the following general formula 3

[0009]

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(Wherein X and Y are the same or different groups and are each a branched alkyl group having 3 or more carbon atoms, a cycloalkyl group having 4 or more carbon atoms, a carbon atom having a branched alkyl group having 3 or more carbon atoms) An aryl group having a cycloalkyl group having 4 or more atoms, an alkyl group having 3 or more carbon atoms, or an aryl group having a cycloalkyl group having 4 or more carbon atoms, provided that part or all of the hydrogen atoms in the alkyl group or the cycloalkyl group are A fumaric acid diester (which may be substituted by a fluorine atom) (hereinafter referred to as fumaric acid diester 1);

[0011]

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(Wherein Z is a fluoroalkyl group having 1 to 12 carbon atoms, a cyclofluoroalkyl group having 4 to 10 carbon atoms, or a cyclofluoroalkyl group having 4 to 10 carbon atoms having a fluoroalkyl group having 1 to 12 carbon atoms) A styrene derivative (hereinafter referred to as a styrene derivative) represented by a group or a fluoroalkyl group having 1 to 12 carbon atoms or an aryl group having a cyclofluoroalkyl group having 4 to 10 or more carbon atoms, and n is an integer of 1 to 5 2) is provided as a gas separation membrane made of a copolymer obtained by polymerizing a polymerizable monomer having as a main component.

BEST MODE FOR CARRYING OUT THE INVENTION The gas separation membrane of the present invention comprises a specific fumaric acid diester,
It is characterized by comprising a copolymer obtained by polymerizing a polymerizable monomer having a specific styrene derivative as a main component.

The fumaric acid diester used as an essential polymerizable monomer component in the present invention is the fumaric acid diester 1 represented by the above general formula (3). In this case, the carbon number of the alkyl group of X and Y is preferably 3 to 12, and the carbon number of the cycloalkyl group is preferably 4 to 14
It is. Examples of the fumaric acid diester 1 include, for example, di-tert-butyl fumarate, di (2) fumarate
-Propyl), ditert-amyl fumarate, di (3-pentyl) fumarate, di (2,3-dimethyl-fumarate)
2-butyl), 3-pentyl-tert-amyl fumarate, di (2,3-dimethyl-2-butyl) fumarate, 2-propyl-tert-butyl fumarate, 3-fumarate
Pentyl-tert-butyl, 3-pentyl fumarate-
Preferable examples include tert-amyl and 3-pentyl-2,3-dimethyl-2-butyl fumarate.

To prepare the fumaric acid diester 1, for example, isobutene or 2-methyl-butene-1,2,3-dimethyl-fumarate is added to fumaric acid in the presence of an acid catalyst such as sulfuric acid or p-toluenesulfonic acid. Known esterification reactions such as a method of adding a corresponding olefin such as butene-1, a method of reacting fumaric acid chloride with a corresponding alcohol, and a method of reacting fumaric acid chloride with an alkali metal alkoxide of a corresponding alcohol. Alternatively, maleic acid can be easily obtained by a method of once converting maleic acid into a maleic acid diester by the above-described esterification reaction, and then converting the maleic acid to a fumaric acid diester using an isomerization catalyst such as thiourea or an amine. In this case, the amount of olefins, alcohols or alkali metal alkoxides was reduced to one half equivalent to the acid group of fumaric acid or maleic acid, and then reacted with different olefins or alcohols. Asymmetric fumaric diesters can be synthesized.

The styrene derivative used as an essential polymerizable monomer component in the present invention is a styrene derivative 2 represented by the above general formula (4). At this time, if the fluoroalkyl group of Z has 13 or more carbon atoms or the cycloalkyl group has 11 or more carbon atoms, production is difficult. As the styrene derivative 2, specifically, for example, 4-
(2 ′, 2 ′, 3 ′, 3 ′, 3′-pentafluoropropyloxymethyl) styrene, 4- (2 ′, 2 ′, 3 ′, 3′-tetrafluoropropyloxymethyl) styrene, 4- ( 2 ',
2 ′, 3 ′, 3 ′, 4 ′, 4 ′, 5 ′, 5′-octafluoropentyloxymethyl) styrene, 4- (2 ′, 2 ′, 3 ′, 3 ′,
4 ′, 4 ′, 5 ′, 5 ′, 6 ′, 6 ′, 7 ′, 7′-dodecafluoroheptyloxymethyl) styrene, 4- (3 ′, 3 ′, 4 ′,
4 ', 5', 5 ', 6', 6 ', 7', 7 ', 8', 8 ', 9', 9 ', 10',
10 ', 10'-heptadecafluorodecyloxymethyl) styrene and the like can be preferably mentioned.

The styrene derivative 2 is prepared by, for example, using chloromethylstyrene (the number of chloromethyl groups is 1 to 5) in the presence of a catalyst such as tetra-n-butylammonium hydrogensulfate or tetra-n-butylammonium bromide. It can be easily obtained by a dehydrochlorination reaction with a fluoroalkyl alcohol.

The charge ratio of the diesters 1 to the styrene derivative 2 is preferably from 1: 0.01 to 1 by weight, more preferably from 1: 0.02 to 0.2. When the charging ratio of the styrene derivative 2 is out of the range, the film forming property to a thin film is undesirably reduced.

In order to prepare a copolymer by polymerizing the polymerizable monomer, the copolymer can be easily obtained by a commonly used radical polymerization method. Specifically, for example, azo radical polymerization initiators such as azobisisobutyronitrile, azobiscyclohexanecarbonitrile, azobisvaleronitrile; benzoyl peroxide, tert-butylhydroxide, cumene peroxide, diacyl peroxide Various radical polymerization initiators such as inorganic peroxide polymerization initiators such as ammonium persulfate and potassium persulfate, and redox initiators such as hydrogen peroxide-sodium hydroxide. Use
Polymerization can be carried out by a radical polymerization method for general-purpose vinyl monomers such as solution polymerization, bulk polymerization, emulsion polymerization, suspension polymerization, and radiation polymerization. At this time, a bulk polymerization method or a suspension polymerization method capable of sufficiently increasing the concentration of the polymerizable monomer is most preferable because the molecular weight of the copolymer can be increased. When the polymerization temperature is higher than the 10-hour half-life temperature of the radical polymerization initiator to be used, the molecular weight of the obtained copolymer becomes small. Therefore, the polymerization temperature is set to the 10-hour half-life temperature of the radical polymerization initiator to be used. It is preferably performed at a lower temperature.

The average molecular weight of the copolymer is 10,000
The range of 0 to 1,000,000 is preferable, and 50,000
A range of 0 to 500,000 is particularly preferred. When the average molecular weight is less than 10,000, the mechanical strength and long-term stability of the obtained film decrease, and it becomes difficult to make the film thinner,
If it exceeds 1,000,000, the solubility in an organic solvent at the time of film formation decreases, which is not preferable.

In order to use the gas separation membrane of the present invention, the above-mentioned copolymer is used in the form of a membrane unit such as a flat membrane, a composite flat membrane, a spiral membrane unit, or a hollow system. Can be. As the membrane unit, a flat membrane by a solvent casting method, a hollow membrane by a mixed spinning method, and the like can be preferably used. The film thickness varies depending on the application, but is preferably in the range of 1 to 1000 μm.

[0022]

The gas separation membrane of the present invention is composed of a copolymer of a polymerizable monomer containing a specific fumaric acid diester and a specific styrene derivative as main components. , And also have a high oxygen permeability coefficient, have a higher α than conventional gas separation membranes, and have excellent gas selective permeability.

[0023]

EXAMPLES The present invention will be described below in more detail with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0024]

Example 1 Ditert-butyl fumarate (DtBF)
9.5 parts by weight and 4- (2 ′, 2 ′, 3 ′, 3 ′, 3′-pentafluoropropyloxymethyl) styrene (F ₅ POMS
t) 0.5 part by weight was taken in a glass ampule and azobisisobutyronitrile (AIB) was used as a radical polymerization initiator.
N) 0.05 part by weight of purified benzene and further 7 parts by weight of purified benzene were taken out, sufficiently purged with nitrogen, deaerated under reduced pressure, and the ampule was sealed. Next, this ampoule was placed in a shaking thermostat and subjected to radical polymerization at 60 ° C. for 30 hours.
After the polymerization is completed, benzene is charged into the ampoule, and the produced polymer is dissolved to form a solution. The resulting solution is poured into a large amount of methanol to precipitate the polymer, and the benzene-
After re-precipitation was repeated in a methanol system, the solution was dried under reduced pressure and dried.
8.5 g of a copolymer of tBF / F ₅ POMSt was obtained.

Next, 0.5 g of the obtained copolymer is dissolved in 50 ml of benzene, and the obtained solution is poured into a flat petri dish having a smooth bottom and a diameter of about 10 cm to prevent dust and dirt from entering. The benzene was slowly evaporated to form a transparent uniform film. When the film thickness was measured, about 0.06
Mm. The gas permeability of the obtained membrane was measured by a high vacuum method, and each gas permeability coefficient was determined. Further, a 1% by weight benzene solution of the obtained polymer is prepared, dropped into still water using a syringe to form a film, and when the film is transferred to a glass support, it is determined whether the film is broken. The possibility of thinning was examined. Table 1 shows the results.

[0026]

Example 2 In place of F ₅ POMSt, 4- (2 ′, 2 ′,
Polymerization was carried out in the same manner as in Example 1 except that 0.5 parts by weight of 3 ′, 3′-tetrafluoropropyloxymethyl) styrene (F ₄ POMSt) was used, and DtBF / F ₄ POMS was performed.
9.3 g of t copolymer was obtained. Using the obtained polymer,
The film was evaluated in the same manner as in Example 1. Table 1 shows the results.

[0027]

Example 3 In place of F ₅ POMSt, 4- (2 ′, 2 ′,
Polymerization was carried out in the same manner as in Example 1 except that 3 parts by weight of 3 ′, 3 ′, 4 ′, 4 ′, 5 ′, 5′-octafluoropentyloxymethyl) styrene (F ₈ PeOMSt) was used, and DtBF /
8.8 g of F ₈ PeOMSt copolymer was obtained. The film was evaluated in the same manner as in Example 1 using the obtained polymer. Table 1 shows the results.

[0028]

Example 4 Instead of F ₅ POMSt, 4- (2 ′, 2 ′,
3 ′, 3 ′, 4 ′, 4 ′, 5 ′, 5 ′, 6 ′, 6 ′, 7 ′, 7′-dodecafluoroheptyloxymethyl) styrene (F ₁₂ HOMS
t) Polymerization was carried out in the same manner as in Example 1 except that 0.5 part by weight was used, and 7.5 parts of the DtBF / F ₁₂ POMSt copolymer was used.
g was obtained. Using the obtained polymer, as in Example 1,
The films were evaluated. Table 1 shows the results.

[0029]

Example 5 Instead of F ₅ POMSt, 4- (3 ′, 3 ′,
4 ', 4', 5 ', 5', 6 ', 6', 7 ', 7', 8 ', 8', 9 ', 9', 1
Polymerization was carried out in the same manner as in Example 1 except that 0.5 part by weight of 0 ′, 10 ′, 10′-heptadecafluorodecyloxymethyl) styrene (F ₁₇ DOMSt) was used, and DtBF / F
8.2 g of ₁₇ POMSt copolymer was obtained. The film was evaluated in the same manner as in Example 1 using the obtained polymer. Table 1 shows the results.

[0030]

Comparative Example 1 Polymerization was carried out in the same manner as in Example 1 except that only 10 parts by weight of DtBF was used as a polymerizable monomer, and a film was evaluated in the same manner as in Example 1 using the obtained polymer. Was. Table 1 shows the results.

[0031]

Comparative Example 2 F ₅ POMSt10 as a polymerizable monomer
Polymerization was carried out in the same manner as in Example 1 except that only parts by weight were used, and the obtained polymer was evaluated in the same manner as in Example 1. Table 1 shows the results.

[0032]

Comparative Example 3 F ₈ POMSt10 as a polymerizable monomer
Polymerization was carried out in the same manner as in Example 1 except that only parts by weight were used, and the obtained polymer was evaluated in the same manner as in Example 1. Table 1 shows the results.

[0033]

[Table 1]

The abbreviations in the table indicate the following compounds, respectively. DtBF; di-tert-butyl fumarate DiPF; di-isopropyl fumarate F ₅ POMSt; 4- (2 ′, 2 ′, 3 ′, 3 ′, 3′-pentafluoropropyloxymethyl) styrene F ₄ POMSt 4- (2 ′, 2 ′, 3 ′, 3′-tetrafluoropropyloxymethyl) styrene F ₈ PeOMSt; 4- (2 ′, 2 ′, 3 ′, 3 ′, 4 ′, 4 ′,
5 ′, 5′-octafluoropentyloxymethyl) styrene F ₁₂ HOMSt; 4- (2 ′, 2 ′, 3 ′, 3 ′, 4 ′, 4 ′, 5 ′,
5 ′, 6 ′, 6 ′, 7 ′, 7′-dodecafluoroheptyloxymethyl) styrene F ₁₇ DOMSt; 4- (3 ′, 3 ′, 4 ′, 4 ′, 5 ′, 5 ′, 6 ′,
6 ', 7', 7 ', 8', 8 ', 9', 9 ', 10', 10 ', 10'-heptadecafluorodecyloxymethyl) styrene

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B01D 71/00-71/82

Claims (1)

(57) [Claims] 1. The following general formula 1 (Wherein X and Y are the same or different groups,
A branched alkyl group having 3 or more carbon atoms, a cycloalkyl group having 4 or more carbon atoms, a cycloalkyl group having 4 or more carbon atoms having a branched alkyl group having 3 or more carbon atoms, an alkyl group having 3 or more carbon atoms, or 4 carbon atoms The aryl group having the above cycloalkyl group is shown. However, a part or all of the hydrogen atoms in the alkyl group or the cycloalkyl group may be substituted with a fluorine atom) and a fumaric acid diester represented by the following general formula 2 (Where Z is a fluoroalkyl group having 1 to 12 carbon atoms, a cyclofluoroalkyl group having 4 to 10 carbon atoms,
It represents a cyclofluoroalkyl group having 4 to 10 carbon atoms having 12 fluoroalkyl groups, a fluoroalkyl group having 1 to 12 carbon atoms, or an aryl group having a cyclofluoroalkyl group having 4 to 10 or more carbon atoms. N is 1
A gas separation membrane comprising a copolymer obtained by polymerizing a polymerizable monomer having a styrene derivative represented by the following formula: