JPH0531340A - Heterocycle-containing polyimide gas separation membrane - Google Patents

Abstract

PURPOSE:To obtain the subject separation membrane made excellent not only in selective separability but also in heat resistance and mechanical strength while holding high gas diffusibility by introducing a heterocycle having high electron density into a fluorene skeleton and a polyimide skeleton to control the interval between polymer chains. CONSTITUTION:A membrane is formed using polyimide obtained by reacting aromatic diamine represented by formula I [wherein R is H, an alkyl group represented by CnH2n+1 ((n) is integer of 1-4), an alkoxy group represented by OCnH2n+1 ((n) is integer of 1-4) or halogen], heterocycle-containing diamine other than the formula I represented by formula II H2N-X-NH2 (wherein X is a heterocycle-containing aromatic residue) and tetracarboxylic dianhydride. The mol ratio of the aromatic diamine component represented by the formula I and the aromatic diamine component represented by the formula II is set to the range of 90/10 to 10/90. As a result, a separation membrane excellent not only in both characteristics of gas diffusibility and selectivity but also in heat resistance and mechanical strength is obtained.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a gas separation membrane made of polyimide used for separating one or more gas components from a mixed gas.

[0002]

2. Description of the Related Art In recent years, it has been actively studied to separate and purify a gas mixture using a gas selective permeable membrane. For example, attempts have been made to selectively permeate oxygen from air to prepare oxygen-enriched air, which is then used in medical treatment and combustion systems. And, for gas selective permeable membranes used for these applications, both gas selectivity and gas permeability are large, and further, depending on the use environment, high heat resistance, chemical resistance, high strength, etc. are required. To be done.

Japanese Patent Publication No. 55-41,802 describes a polyimide gas separation membrane in which a substituent is introduced into a rigid polyimide skeleton in order to restrain free rotation around the main chain skeleton. Furthermore, JP-A-1-310,715
In the gazette, a two-component material having a high gas selectivity and a high gas permeability is considered.

[0004]

An object of the present invention is to provide a heterocyclic polyimide gas separation membrane having excellent gas permeability and selectivity as well as heat resistance and mechanical strength. To provide. Another object of the present invention is to provide a heterocyclic polyimide gas separation membrane having excellent properties in separating oxygen / nitrogen, which can be used for separating and concentrating various mixed gases. It is in.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies to develop a separation membrane having a selective separation performance higher than that of a conventionally known polyimide gas separation membrane. In addition, by introducing a heterocycle having a higher electron density than the aromatic ring of a normal aromatic diamine, the spacing of the polymer chains is controlled, and the selectivity and separability are improved while maintaining high gas permeability. ,
We have succeeded in finding a separation membrane material that is also excellent in heat resistance and mechanical strength, and reached the present invention. Hereinafter, the present invention will be described in detail.

The present invention has the following general formula (1):

[Chemical 2] [Wherein R is _{-H, -C n H 2n + 1} ( where n =. 1 to
An alkyl group represented by 4), an alkoxy group represented by —OC _n H _{2n + 1} (where n = 1 to 4 is an integer, and halogen), and an aromatic diamine represented by the following: A heterocyclic diamine other than the general formula (1) represented by the general formula (2) H ₂ N—X—NH ₂ (2) (wherein X represents a heterocyclic aromatic residue-containing residue); Is a heterocyclic ring-containing polyimide gas separation membrane formed by using polyimide obtained by reacting with a tetracarboxylic dianhydride.

As the aromatic diamine used in the present invention,
9,9-bis (3-methyl-4-aminophenyl) fluorene represented by the general formula (1), 9,9-bis (3-ethyl-4-aminophenyl) fluorene, 9,9-bis (3-ethyl-4-aminophenyl) fluorene
9-bis (3,5-dimethoxy-4-aminophenyl)
Fluorene, 9,9-bis (3,5-diethoxy-4-)
Aminophenyl) fluorene, 9,9-bis (3-methoxy-4-aminophenyl) fluorene, 9,9-bis (3-ethoxy-4-aminophenyl) fluorene,
9,9-bis (3,5-dimethoxy-4-aminophenyl) fluorene, 9,9-bis (3,5-diethoxy-)
4-aminophenyl) fluorene, 9,9-bis (3-
Bromo-4-aminophenyl) fluorene, 9,9-bis (3,5-dibromo-4-aminophenyl) fluorene, 9,9-bis (4-aminophenyl) fluorene and the like. The aromatic diamine represented by the general formula (1) may be used alone or in combination of two or more.

The polyimide obtained by using the above general formula (1) as the diamine component exhibits restricted center rotation characteristics, which widens the intervals of the polymer chains, resulting in comprehensive gas fluidity. be able to. However, on the other hand, there is still room for improvement in selective separation.

Therefore, in the heterocycle-containing polyimide of the present invention, a heterocycle having an electron density higher than that of the aromatic ring of a usual aromatic diamine is introduced into the polyimide skeleton together with the fluorene skeleton, whereby the distance between the polymer chains is increased. Is controlled to improve selective separation while maintaining high gas permeability. Here, as the heterocyclic diamine component to be introduced into the polyimide skeleton together with the fluorene skeleton, those which are rigid and have excellent flatness are preferable, and examples thereof include 2,6-diaminopyridine, 2,3-diaminopyridine and 3,4-. Diaminopyridine, 2,4-diaminopyrimidine, 2,4
-Diamino-6-methyl-S-triazine, 2,6-diaminopurine, 3,5-diamino-1,2,4-triazole, 2,6-diaminocarbazole and the like. Further, even if only one kind of these heterocyclic diamines is used, 2
It is possible to use more than one species together.

The tetracarboxylic dianhydride used in the present invention includes 3,3 ', 4,4'-benzophenone tetracarboxylic dianhydride and 3,3', 4,4'-biphenyltetracarboxylic dianhydride. Substance, bis (2,3-dicarboxyphenyl) sulfone dianhydride, 2,2-bis (3,4
-Biscarboxyphenyl) -1,1,1,3,3,3
-Hexafluoropropane dianhydride, pyromellitic dianhydride and the like. Further, this tetracarboxylic dianhydride may be used alone or in combination of two or more thereof, but as the tetracarboxylic dianhydride, 2,2
-Bis (3,4-biscarboxyphenyl) -1,1,
Particularly high gas permeability can be obtained when 1,3,3,3-hexafluoropropane dianhydride is used.

The molar ratio of the aromatic diamine component represented by the general formula (1) and the heterocyclic diamine component represented by the general formula (2) to be introduced into the polyimide skeleton together with the fluorene skeleton is 90/10 to 10/90. The range is 80/20 to 80/80. Outside this range, the separation membrane material having high selective separation and high gas permeability, which is the object of the present invention, cannot be obtained. That is, the aromatic diamine component represented by the general formula (1) and the heterocyclic diamine component represented by the general formula (2) introduced into the polyimide skeleton together with the fluorene skeleton have a molar ratio of more than 90/10. It is not possible to obtain high selective separation,
On the contrary, if this molar ratio is less than 10/90, sufficiently high gas permeability and excellent solvent solubility cannot be obtained.

The heterocyclic ring-containing polyimide used in the present invention contains 0.5 g of this polyimide in 100 m of N-methyl-2-pyrrolidone in order to maintain its mechanical strength at a sufficient level.
The logarithmic viscosity based on the value measured at 30 ° C. of the solution dissolved in 1 is preferably 0.2 dl / g or more, more preferably 0.5 dl / g or more. In particular, when the logarithmic viscosity is 0.5 dl / g or more, any polyimide has a glass transition temperature of 350 ° C. or more and a decomposition initiation temperature of 550 ° C.
In addition to the high heat resistance as described above, the tensile strength of the film also exhibits excellent mechanical strength of 10 kg / mm ² or more.

The heterocyclic ring-containing polyimide used in the present invention can be produced by using any of the various conventional general production methods for polyimide. For example, a predetermined amount of 9,9-bis (4-aminophenyl) fluorene,
2,6-diaminopyridine and 2,2-bis (3,4-
Biscarboxyphenyl) -1,1,1,3,3,3-
Hexafluoropropane dianhydride was dissolved in N-methyl-2-pyrrolidone as a solvent, and the mixture was stirred in a nitrogen stream under a nitrogen stream.
By reacting at 0 ° C. for 8 hours, a uniform and transparent polymer solution can be obtained. The polymer thus obtained has excellent solvent solubility and N-methyl-2
10% by weight in various solvents such as -pyrrolidone, N, N-dimethylacetamide, dimethyl sulfoxide, dimethylformamide, tetrachloroethane and m-cresol
It can be dissolved at the above concentrations. The method for synthesizing the heterocycle-containing polyimide used as the separation membrane of the present invention described above is merely an example, and the present invention is not limited thereto.

Further, in these heterocyclic polyimides, oxygen / nitrogen selective separability and gas permeability are controlled by changing the type of heterocyclic diamine other than the general formula (1) and the ratio of copolymerization. can do. Furthermore, since the heterocyclic polyimide-containing polyimide of the present invention has excellent solvent solubility, it also has excellent processability required when used as a gas separation membrane, and can be formed into a thin film using a wet method or can be formed into a hollow fiber. Etc. are possible.

[0015]

The polyimide obtained by using only the compound of the general formula (1) as the diamine component exhibits restricted central rotation characteristics, which widens the intervals of the polymer chains, and as a result, comprehensive gas flow. However, there is still room for improvement in selective separability. The heterocycle-containing polyimide of the present invention, in the polyimide skeleton together with the fluorene skeleton, by introducing a heterocycle having a higher electron density compared to the aromatic ring of a normal aromatic diamine, to control the spacing of the polymer chain, high. It is possible to improve the selective separation while maintaining the gas permeability.

[0016]

EXAMPLES The present invention will be specifically described below based on examples, but the present invention is not limited to these examples. The gas permeation performance is represented by the gas permeation coefficient P determined by the following mathematical formula. The unit of P is indicated by B (barrel).

[Equation 1] The gas permeability was measured using a gas permeability measuring device. In this method, a predetermined test gas is supplied at low pressure to one surface of a test membrane mounted on the cell of the same apparatus, and the amount of gas that permeates from the other surface of the membrane is analyzed by gas chromatography. Further, the selective separability of gases was expressed by the ratio of the measured permeation coefficient of each gas.

Example 1 In a 500 ml four-necked flask equipped with a thermometer, a nitrogen inlet tube, an ester condensation tube and a stirrer, 9,9-bis (4-aminophenyl) fluorene (hereinafter , BAF) 6.729 g (20 mmol),
2.83 g (20 mmol) of 2,6-diaminopyridine (hereinafter abbreviated as 2,6-Py) and 2,2-bis (3,4-biscarboxyphenyl) -1,1,1,
3,3,3-hexafluoropropane dianhydride (hereinafter,
6770 FDA) 17.770 g (40 mmol),
N-methyl-2-pyrrolidone (hereinafter abbreviated as NMP) 1
78 g and were charged and dissolved by stirring. Then, the mixture was reacted at 180 ° C. for 8 hours under stirring to obtain a yellow transparent and uniform reaction solution. The reaction solution was poured into methanol and the precipitated polymer was filtered off and dried to obtain a polyimide powder.

The polyimide obtained had an inherent viscosity of 0.72 in a 30 ° C. NMP solution. In addition, a 15 wt% NMP solution of this polymer was prepared, coated on a glass plate, and dried in an oven at 80 ° C. for 1 hour. Then 23
After heating to 0 ° C and continuing drying for 2 hours, slowly cool to a thickness of 1
A homogeneous film of mil was obtained. A gas permeation test was conducted at 25 ° C. using this homogeneous membrane. The results are shown in Table 1.

Example 2 Using the same apparatus as in Example 1, BA was used as the diamine component.
F3, 365 g (10 mmol) and 2,6-Py3.2
A homogeneous film having a thickness of 1 mil was obtained in the same manner as in Example 1 except that 74 g (30 mmol) was used and 6FDA 17.770 g (40 mmol) was used as the acid anhydride component. A gas permeation test was conducted at 25 ° C. using this homogeneous membrane. The results are shown in Table 1.

Example 3 Using the same apparatus as in Example 1, BA was used as a diamine component.
F 3.365 g (10 mmol) and 3,5-diamino-
1,2,4-triazole (hereinafter abbreviated as Tri) 2.
Using 973 g (30 mmol), as the acid anhydride component, 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride (hereinafter abbreviated as BTDA) 12.889 g
A homogeneous film having a thickness of 1 mil was obtained in the same manner as in Example 1 except that (40 mmol) was used. 2 using this homogeneous membrane
A gas permeation test was conducted at 5 ° C. The results are shown in Table 1.

Example 4 Using the same apparatus as in Example 1, BA was used as a diamine component.
F 6.729 g (20 mmol) and 2,4-diaminopyrimidine (hereinafter abbreviated as Pym) 2.202 g (20 m)
mol) and BTDA1 as an acid anhydride component.
A homogeneous film having a thickness of 1 mil was obtained in the same manner as in Example 1 except that 2.889 g (40 mmol) was used. A gas permeation test was conducted at 25 ° C. using this homogeneous membrane. The results are shown in Table 1.
Shown in.

Example 5 Using a device similar to that of Example 1, BA was used as a diamine component.
F 3.365 g (10 mmol) and 2,4-diaminopyrimidine (hereinafter abbreviated as Pym) 3.304 g (30 m
mol) and BTDA1 as an acid anhydride component.
A homogeneous film having a thickness of 1 mil was obtained in the same manner as in Example 1 except that 2.889 g (40 mmol) was used. A gas permeation test was conducted at 25 ° C. using this homogeneous membrane. The results are shown in Table 1.
Shown in.

Comparative Example 1 BA was used as a diamine component using the same apparatus as in Example 1.
A homogeneous film having a thickness of 1 mil was obtained in the same manner as in Example 1 except that F13.458 g (40 mmol) was used and 6FDA17.770 g (40 mmol) was used as the acid anhydride component. A gas permeation test was conducted at 25 ° C. using this homogeneous membrane. The results are shown in Table 1.

Comparative Example 2 Using the same apparatus as in Example 1, BA was used as the diamine component.
A homogenous film having a thickness of 1 mil was obtained in the same manner as in Example 1 except that F13.458 g (40 mmol) was used and BTDA12.889 g (40 mmol) was used as the acid anhydride component. A gas permeation test was conducted at 25 ° C. using this homogeneous membrane. The results are shown in Table 1.

[0025]

[Table 1]

[0025]

As described above, the heterocyclic polyimide gas separation membrane of the present invention has both high gas permeability and separation selectivity, and is also excellent in heat resistance and mechanical strength. Therefore, it can be used for separation and concentration of various mixed gases, and in particular, it exhibits excellent performance in separation of oxygen / nitrogen, and has high industrial value.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hironobu Kawasato             1618 Ida, Nakahara-ku, Kawasaki-shi, Kanagawa             Inside the Advanced Technology Research Laboratories

Claims (2)

[Claims] 1. The following general formula (1): [Wherein R is _{-H, -C n H 2n + 1} ( where n =. 1 to
An alkyl group represented by 4), an alkoxy group represented by —OC _n H _{2n + 1} (where n = 1 to 4 is an integer, and halogen), and an aromatic diamine represented by the following: A heterocyclic diamine other than the general formula (1) represented by the general formula (2) H ₂ N—X—NH ₂ (2) (wherein X represents a heterocyclic aromatic residue-containing residue); A heterocyclic ring-containing polyimide gas separation membrane obtained by forming a membrane using a polyimide obtained by reacting with a tetracarboxylic dianhydride. 2. The molar ratio of the aromatic diamine represented by the general formula (1) and the aromatic diamine component represented by the general formula (2) is in the range of 90/10 to 10/90. Heterocyclic polyimide gas separation membrane of.