JPH057748A - Gas separation membrane - Google Patents

Abstract

PURPOSE:To obtain a gas separation membrane excellent in film forming properties, heat resistance, solvent resistance and gas diffusion selectivity by constituting said membrane of a copolymer of copolymerizable monomers based on specific fumaric diester and a specific styrene derivative. CONSTITUTION:A gas separation membrane is obtained from a copolymer obtained by polymerizing polymerizable monomers based on fumaric diester represented by formula I (wherein X and Y are same or different and are a 3 or more C alkyl group, a 4 or more C cycloalkyl group, a 4 or more C cycloalkyl group having a 3 or more C branched alkyl group or an aryl group having a 3 or more C alkyl group or a 4 or more C cycloalkyl group) and a styrene derivative represented by formula II (wherein Z is a 1-12C fluoroalkyl group, a 4-10C cyclofluoroalkyl group, a 4-10C cyclofluoroalkyl group having a 1-12C fluoroalkyl group or an aryl group having a 1-12C fluoroalkyl group or a 4-10C cyclofluoroalkyl group).

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 which is excellent in film forming property and heat resistance and has high selective permeability.

[0002]

2. Description of the Related Art Oxygen-enriched air is continuously supplied to various combustion systems such as industrial boilers, furnaces or internal combustion engines such as automobiles, household heating appliances, etc. to improve combustion efficiency and to reduce fuel consumption. Can save money,
It is also useful for environmental pollution problems because it can prevent incomplete combustion, and also in the medical field, fermentation industry,
It is also useful in other fields such as cultivated fisheries and sewage treatment. Therefore, a gas separation membrane capable of efficiently separating nitrogen and oxygen in the atmosphere to produce oxygen-enriched air has been attracting attention.

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

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

Further, poly (4-methylpentene-1)
Has excellent mechanical strength, chemical stability, and thermal stability with PO _{2 in} the first half of 1.0 × 10 to ⁹ units, but requires high technology for thinning and has a selective oxygen permeability. Not enough, so it's actually only used in part.
Further, natural rubber can be easily formed into a thin film, and although PO ₂ is 1.0 × 10 to ⁹ units, it has disadvantages that it is inferior in chemical stability and durability and has low oxygen selective permeability.

As described above, since a gas separation membrane exhibiting sufficient performance has not been obtained, in order to obtain the required oxygen-enriched air, use oxygen enrichment devices in multiple stages or enlarge the device. The current situation is unavoidable.

[0007]

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

[0008]

According to the present invention, the following general formula 3

[0009]

[Chemical 3]

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

[0011]

[Chemical 4]

(In the formula, 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 and having a fluoroalkyl group having 1 to 12 carbon atoms. Group or an aryl group having a fluoroalkyl group having 1 to 12 carbon atoms or a cyclofluoroalkyl group having 4 to 10 or more carbon atoms, and n represents an integer of 1 to 5) (hereinafter referred to as styrene derivative) And a gas separation membrane made of a copolymer obtained by polymerizing a polymerizable monomer mainly containing (2).

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail below. A 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.
Is. Specific examples of the fumaric acid diester 1 include ditert-butyl fumarate and di (2) fumarate.
-Propyl), di-tert-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, fumaric acid is added with isobutene or 2-methyl-butene-1,2,3-dimethyl-in the presence of an acid catalyst such as sulfuric acid or p-toluenesulfonic acid. Known esterification reaction such as a method of adding a corresponding olefin such as butene-1, a method of reacting a fumaric acid chloride with a corresponding alcohol, a method of reacting a fumaric acid chloride with an alkali metal alkoxide of the corresponding alcohol, and the like Alternatively, it can be easily obtained by a method such as once converting maleic acid into a maleic acid diester by the above-mentioned esterification reaction and then converting into a fumaric acid diester using an isomerization catalyst such as thiourea or amine. Incidentally, at this time, with respect to the acid group of fumaric acid or maleic acid, the charged amount of olefins, alcohols or alkali metal alkoxides is set to ½ equivalent, and then reacted with different olefins or alcohols, Asymmetric fumaric acid diesters can be synthesized.

The styrene derivative used as the essential polymerizable monomer component in the present invention is the styrene derivative 2 represented by the 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, the production is difficult. Specific examples of the styrene derivative 2 include 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',
Preferable examples include 10 ', 10'-heptadecafluorodecyloxymethyl) styrene.

To prepare the styrene derivative 2, it corresponds to chloromethylstyrene (the number of chloromethyl groups is 1 to 5) in the presence of a catalyst such as tetranormal butyl ammonium hydrogensulfate or tetranormal butyl ammonium bromide. It can be easily obtained by dehydrochlorinating a fluoroalkyl alcohol.

The weight ratio of the diesters 1 to the styrene derivative 2 is preferably 1: 0.01 to 1, and more preferably 1: 0.02 to 0.2. If the charging ratio of the styrene derivative 2 is outside the above range, the film forming property to a thin film is deteriorated, which is not preferable.

In order to polymerize the above-mentioned polymerizable monomer to prepare a copolymer, it can be easily obtained by a generally used radical polymerization method. Specifically, for example, azo-based radical polymerization initiators such as azobisisobutyronitrile, azobiscyclohexanecarbonitrile and azobisvaleronitrile; benzoyl peroxide, tert-butylhiddle peroxide, cumene peroxide, diacyl peroxide. Organic peroxide-based radical polymerization initiators such as ammonium persulfate, inorganic radical polymerization initiators such as ammonium persulfate and potassium persulfate, or various radical polymerization initiators such as redox initiators such as hydrogen peroxide-sodium hydroxide Used,
Polymerization can be carried out by a general-purpose radical polymerization method of vinyl monomers such as solution polymerization, bulk polymerization, emulsion polymerization, suspension polymerization and radiation polymerization. At this time, the bulk polymerization method or suspension polymerization method, which can sufficiently increase the concentration of the polymerizable monomer, is most preferable because the molecular weight of the copolymer can be increased. Further, when the polymerization temperature is higher than the 10-hour half-life temperature of the radical polymerization initiator used, the molecular weight of the obtained copolymer becomes small. Therefore, the polymerization temperature is the 10-hour half-life temperature of the radical polymerization initiator used. It is preferable to carry out 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 50000
The range of 0 to 500,000 is particularly preferable. When the average molecular weight is less than 10,000, the mechanical strength and long-term stability of the obtained film are reduced, and it becomes difficult to form a thin film.
When 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 copolymer is used as a membrane unit by flattening the membrane, forming a complex flat membrane, forming a spiral type membrane unit, or making a hollow system. You can 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. Although the film thickness varies depending on the use, it is preferably in the range of 1 to 1000 μm.

[0022]

Industrial Applicability The gas separation membrane of the present invention comprises a copolymer of a polymerizable monomer containing a specific fumaric acid diester and a specific styrene derivative as main components, so that the film forming property, heat resistance and solvent resistance are improved. In addition, it has a high oxygen permeability coefficient, has a higher α than the conventional gas separation membrane, and has excellent gas selective permeability.

[0023]

EXAMPLES The present invention will be specifically described below with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

[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 is placed in a glass ampoule and used as a radical polymerization initiator, azobisisobutyronitrile (AIB).
N) 0.05 parts by weight and further 7 parts by weight of purified benzene were taken out, sufficiently replaced with nitrogen, and then deaeration under reduced pressure was repeated, and then the ampoule was sealed. Next, this ampoule was placed in a shaking type constant temperature bath, and radical polymerization was carried out at 60 ° C. for 30 hours.
After the completion of the polymerization, benzene was charged into the ampoule, the generated polymer was dissolved to form a solution, and the resulting solution was poured into a large amount of methanol to precipitate the polymer, and the benzene-
After reprecipitation was repeated in a methanol system, it was dried under reduced pressure to obtain D
8.5 g of a tBF / F ₅ POMSt copolymer was obtained.

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

[0026]

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

[0027]

Example 3 Instead of F ₅ POMSt, 4- (2 ′, 2 ′,
Polymerization was performed 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. Using the obtained polymer, the film was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[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 performed in the same manner as in Example 1 except that 0.5 part by weight was used, and 7.5 parts of DtBF / F ₁₂ POMSt copolymer was obtained.
g was obtained. Using the obtained polymer, as in Example 1,
The film was evaluated. The results are shown in Table 1.

[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 performed in the same manner as in Example 1 except that 0.5 parts by weight of 0 ′, 10 ′, 10′-heptadecafluorodecyloxymethyl) styrene (F ₁₇ DOMSt) was used, and DtBF / F was used.
8.2 g of ₁₇ POMSt copolymer was obtained. Using the obtained polymer, the film was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0030]

Comparative Example 1 Polymerization was performed in the same manner as in Example 1 except that only 10 parts by weight of DtBF was used as the polymerizable monomer, and the obtained polymer was used to evaluate the film in the same manner as in Example 1. It was The results are shown in Table 1.

[0031]

[Comparative Example 2] F ₅ POMSt10 as a polymerizable monomer
Polymerization was performed in the same manner as in Example 1 except that only parts by weight were used, and the obtained polymer was used to evaluate the film in the same manner as in Example 1. The results are shown in Table 1.

[0032]

[Comparative Example 3] F ₈ POMSt10 as a polymerizable monomer
Polymerization was performed in the same manner as in Example 1 except that only parts by weight were used, and the obtained polymer was used to evaluate the film in the same manner as in Example 1. The results are shown in Table 1.

[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'-octafluoropentyloxy) styrene _{F 12 HOMSt; 4- (2'} , 2 ', 3', 3 ', 4', 4 ', 5',
5 ', 6', 6 ', 7', 7'-dodecafluoroheptyl oxy) styrene _{F 17 DOMSt; 4- (3 '} , 3', 4 ', 4', 5 ', 5', 6 ',
6 ', 7', 7 ', 8', 8 ', 9', 9 ', 10', 10 ', 10'-heptadecafluorodecyloxymethyl) styrene

Claims (1)

What is claimed is: (Claim 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 a carbon number 4 The aryl groups having the above cycloalkyl groups are shown. However, a fumaric acid diester represented by the above-mentioned alkyl group or cycloalkyl group, in which a part or all of hydrogen atoms may be substituted with fluorine atoms, and the following general formula 2 (In the formula, Z is a C1-C12 fluoroalkyl group, a C4-C10 cyclofluoroalkyl group, a C1-C1
A C4 to C10 cyclofluoroalkyl group having a 12 fluoroalkyl group, a C1 to C12 fluoroalkyl group, or an aryl group having a C4 to 10 or more cyclofluoroalkyl group is shown. N is 1
A gas separation membrane made of a copolymer obtained by polymerizing a polymerizable monomer having a styrene derivative represented by the formula (1 to 5) as a main component.