JPS6252613B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a composite membrane for gas separation made of a polyquinazolone polymer. In recent years, gas separation using organic polymer membranes, especially oxygen enrichment of air, has been attracting attention from the viewpoint of resource and energy conservation.However, conventional oxygen enrichment membranes have an oxygen permeation rate that is too low or Since the permeability coefficient ratio of oxygen to nitrogen is small, it is not suitable for oxygen enrichment on an industrial scale. For example, polydimethylsiloxane has an oxygen permeability coefficient of 10 ^-8 cm ³
(STP)・cm/cm ²・sec・cmHg, which is the highest among conventionally known polymer membranes, but the permeability coefficient ratio for nitrogen is at most about 2, and the selective permselectivity for oxygen is Alternatively, the separation performance is poor, and if a high concentration of oxygen is to be obtained, multistage membrane treatment is required, which is impractical in terms of both equipment and cost. Furthermore, this membrane has low mechanical strength and requires the use of a relatively thick membrane. Therefore, even if the permeation coefficient is large, the permeation rate cannot be increased. For this reason, Japanese Patent Publication No. 47-51715 proposed an oxygen-enriched membrane made of polyvinyltrimethylsilane, which improved the permeability coefficient ratio of oxygen to nitrogen to about twice that of polydimethylsiloxane, but was chemically resistant. It has the disadvantage of being easily degraded by pollutants in the air, oil from pumps, etc. Additionally, in recent years, in addition to oxygen enrichment membranes, with the development of so-called _C1 chemistry, gas separation membranes from synthesis gas have become necessary. Because it is used at high temperatures, extremely high heat resistance is required. As a result of intensive research in view of the above, the present inventors found that
Membranes made of polyquinazolone polymers have excellent gas permselectivity, permeation rate, chemical resistance, heat resistance, processability,
Although it has been found that it has excellent mechanical strength, it is necessary to further increase the gas permeation rate in order to improve the economic efficiency of the gas separation process. For this purpose, a method has been proposed in which a dilute polymer solution is uniformly dispersed on the water surface to form an ultra-thin film, and this ultra-thin film is bonded to a porous substrate (Japanese Patent Laid-Open No. 51-89564 issue). However, this method requires advanced techniques to handle the ultra-thin film on the water surface, is complicated, and is likely to cause defects in the ultra-thin film. Furthermore, it is difficult to closely bond the ultra-thin film and the porous substrate, and the compression resistance, stress resistance, etc. are insufficient for practical use. On the other hand, in the field of separation membranes for water treatment, the method of directly forming a thin film on a porous substrate is already well known, but there is a limit to the thickness that can be made, and it is difficult to form an ultra-thin film of several microns. It is difficult. The present inventors conducted extensive research to obtain an ultra-thin film of polyquinazolone polymer that allows two or more gases to have substantially different permeation rates. The present invention was achieved by successfully forming a thin film with an anisotropic structure consisting of a dense layer and a porous layer that integrally supports the dense layer. The composite membrane for gas separation of the present invention has the general formula (However, R ¹ is a tetravalent organic group, R ² is each independently an alkyl group or aromatic group, R ³ is a (p+2) valent organic group, Z is -COOH, -SO ₃ H, or a metal salt thereof and p is 0 or 1 to 4 independently for each unit.
indicates an integer. ) A thin film made of a polyquinazolone polymer having the bisquinazolone unit represented by () as a repeating unit is formed on a porous substrate, and the thin film consists of a dense ultra-thin film on the surface and a porous layer that integrally supports it. According to the present invention, such a composite membrane for gas separation is characterized by having the following general formula: (However, R ¹ is a tetravalent organic group, R ² is each independently an alkyl group or aromatic group, R ³ is a (p+2) valent organic group, Z is -COOH, -SO ₃ H, or a metal salt thereof and p is 0 or 1 to 4 independently for each unit.
indicates an integer. ) A film-forming solution containing a polyquinazolone polymer having a bisquinazolone unit as a repeating unit represented by It is manufactured by irradiating the surface of the coating layer of the film-forming solution with far infrared rays to evaporate the solvent of the film-forming solution from substantially only the surface layer of the coating layer, and then contacting it with a coagulating solvent mainly composed of water. Ru. In the polyquinazolone polymer represented by the above general formula (), R ¹ is a tetravalent aromatic group, preferably

【formula】

[Formula] or

[Formula] is. X combines two divalent aromatic groups to form 4
An organic bonding group that forms a valent aromatic group, and specific examples include -CH ₂ -, -C(CH ₃ ) ₂ -, -CO-,
-SO ₂ -, -O-, -S-, -NH-, -COO-, -
CONH-, etc. can be mentioned. R ² is an alkyl group or an aromatic group, preferably an alkyl group having 1 to 4 carbon atoms, particularly preferably a methyl group or a phenyl group. Although two ^R3s are bonded in the above repeating unit, they do not necessarily have to be the same. Next, R ³ is a divalent organic group, specifically an aromatic group,
It is an aliphatic or alicyclic divalent organic group, or a divalent organic group in which these groups are bonded via an organic bonding group Y. Specific examples of the bonding group Y include -CH ₂ -, -C(CH ₃ ) ₂ -, -CO-, -SO ₂ -, -O
-, -NH-, -S-, -CONH-, -COO-,

【formula】

[Formula] (However, R ⁴ and R ⁵ each independently have 1 to 10 carbon atoms.
represents an alkyl group, a cycloalkyl group having 3 to 10 carbon atoms, or a phenyl group. ) etc. R ³ is preferably an aromatic group and when p=0, i.e. the repeating unit is (However, R ¹ , R ² and R ³ are the same as above.) In the case where

【formula】 【formula】

[Formula] (However, Y is the same as above.) etc. can be mentioned. Therefore, as a preferred specific example of unit (a), can be mentioned. A polyquinazolone polymer having unit (a) as a repeating unit has the general formula (However, R ¹ and R ² are the same as above.) Bisoxazinone represented by the general formula H ₂ N-R ³ -NH in an amount of 0.95 to 1.08 mol, preferably approximately 1 mol per mol of this bisoxazinone. ₂ () (However, R ³ is the same as above.) It is obtained by reacting a diamine represented by the following in an organic solvent under heating. In the bisoxazinone represented by the above general formula (), R ₁ and R ² are as described above,
Specific examples of bisoxazinone preferably used in the present invention include: etc. can be mentioned. In addition, R ³ in the diamine represented by the above general formula () is the same as above, and specific examples of the diamine are m-phenylenediamine, p-phenylenediamine, 4,4'-diaminodiphenylmethane, 4. 4'-diaminodiphenyl ether, 3.
4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfone, p-bis(4-aminophenoxy)benzene, m-bis(4-aminophenoxy)benzene, N・N′-piperazine-bis(p
-aminobenzoic acid amide), m-xylylene diamine, p-xylylene diamine, bis(4-aminocyclohexyl)methane, hexamethylene diamine, hepotamethylene diamine, octamethylene diamine, 1,4-diaminocyclohexane, bis( Examples include 4-aminophenyl)diethylsilane, bis(3-aminopropyl)tetramethyldisiloxane, and the like, which may be used alone or as a mixture. The method for producing bisoxazinone includes, for example,
As described in J. Polymer Sci., 60 , S59 (1962), Industrial Chemistry Journal 73 , 1239 (1970), etc.
Already known and usually the general formula (However, R ¹ is the same as above.) An aromatic diaminodicarboxylic acid represented by the general formula (However, R ² is the same as above.) or an aromatic carboxylic acid chloride represented by the general formula R ² -COCl (However, R ² is the same as above.) You can get it. Usually, the above-mentioned aromatic diaminodicarboxylic acids include 4,6-diaminoisophthalic acid, 2,5-diaminoterephthalic acid, 2,3-diaminoterephthalic acid, general formula (However, Y is the same as above.) Diaminodicarboxylic acids represented by the following are used, acetic anhydride and the like are used as acid anhydrides, and benzoyl chloride and the like are used as acid chlorides. The condensation reaction between bisoxazinone and diamine (2) is carried out in a solvent by heating. As a solvent, it is capable of dissolving bisoxazinone and diamine, and is inert to them.
Preferably, one is used that can also dissolve the produced polyquinazolone polymer and further maintains the reaction system in an acidic environment. Specific examples of preferred solvents include cresols such as p-cresol and m-cresol, chlorophenols such as p-chlorophenol and o-chlorophenol, polyphosphoric acid, and sulfuric acid, which may be used alone or in combination. It will be done. If necessary, a mixed solvent of these solvents and a nonpolar hydrocarbon solvent such as benzene, toluene, xylene, chlorobenzene, or naphtha may also be used. The amount of solvent used for the raw materials is not particularly limited, but is usually 60 to 900 parts by weight per 100 parts by weight of the total amount of bisoxazinone and diamine. The reaction temperature and reaction time between bisoxazinone and diamine vary depending on the types of these raw materials and the type of solvent used, but are usually 5 to 50 minutes at a temperature of 100 to 300°C.
Allow time to react. Next, R ³ and Z when p is an integer from 1 to 4
As a preferred example of and p

【formula】

【formula】

[Formula] etc. can be mentioned. The unit (a) and the unit (b) represented by the following general formula (However, R ¹ , R ² , R ³ and Z are the same as above, and p is an integer of 1 to 4.) It can be similarly obtained by substituting with a diamine having a group Z. That is, the bisoxazinone represented by the general formula (), the diamine represented by the general formula (), and the general formula (However, R ³ is the same as above, and P represents an integer of 1 to 4.) The molar ratio of the total amount of these diamines to 1 mole of bisoxazinone is 0.95 to 1.08, and Preferably, the reaction is carried out under conditions of approximately 1 in the organic solvent with heating. The reaction conditions may be the same. Specific examples of the aromatic diamine represented by the above general formula () include 3,5-diaminobenzoic acid,
4,4'-diaminodiphenylmethane-3,3'-dicarboxylic acid, 3,5-diaminobenzenesulfonic acid, 3,3'-benzidinecarboxylic acid, N/N'-bis(p-aminobenzoyl)-3・5-diaminobenzoic acid, isophthal-3-amino-5-carboxyanilide, 3,3'-benzidinesulfonic acid,
Examples include 4,4'-diaminodiphenylmethane-3,3'-disulfonic acid. Furthermore, advantageously, the polyquinazolone polymer used in the present invention includes bisoxazinone, the diamine component (), and optionally ( ), preferably using a Lewis acid catalyst and a phosphorus-containing dehydrating agent, and by heating and reacting in an aprotic polar organic solvent. Examples of the aprotic polar organic solvent include N-methyl-
2-pyrrolidone, dimethylacetamide, dimethylformamide, dimethylsulfoxide, etc. are used. The amount of solvent used is not particularly limited, but the total amount of bisoxazinone and diamine components is 10 to 50.
It is used in an amount of 20 to 30% by weight, preferably 20 to 30% by weight. As the Lewis acid catalyst, metal halides, particularly chlorides, such as anhydrous stannous chloride, anhydrous cupric chloride, anhydrous cobalt chloride, anhydrous ferric chloride, and anhydrous nickel chloride are preferably used. The amount of catalyst used is per mole of bisoxazinone or diamine.
The amount is 0.002 to 0.2 mol, preferably 0.01 to 0.1 mol. If the amount of catalyst is too large, gelation will occur, which is not preferable. Phosphorus-containing dehydrating agents include phosphorus pentoxide, phosphoric acid, metaphosphoric acid, phosphorous acid, hypophosphoric acid,
Examples include hypophosphorous acid, pyrophosphoric acid, polyphosphoric acid, etc., but phosphorus pentoxide is preferably used. The amount of the dehydrating agent used is 0.001 to 0.4 mol, preferably 0.01 to 0.2 mol, per 1 mol of bisoxazinone. Dehydrating agents effectively prevent gelation. Note that the diamine having an acidic group itself has a catalytic effect in the polymerization reaction between bisoxazinone and diamine. Therefore, when at least a portion of the diamine component has an acidic group, a high molecular weight polyquinazolone polymer can be obtained without particularly using a Lewis acid catalyst. The polymerization reaction is preferably carried out by adding a hydrocarbon solvent capable of azeotroping with water, such as benzene, xylene, toluene, etc., to the solvent, and removing reaction water produced by the polymerization from the system by azeotropy. The temperature of the polymerization reaction is 150 to 200°C, and the time is from several hours to several tens of hours, and usually within 100 hours is sufficient. In the present invention, all polyquinazolone polymers having unit ( ) as a repeating unit have an intrinsic viscosity.
It is preferably in the range of 0.30 to 1.50, preferably 0.4 to 1.0. If the intrinsic viscosity is too small, the self-supporting properties will be poor when used as a gas separation membrane, and the mechanical strength will not be sufficient. On the other hand, if the intrinsic viscosity is too large, it will be difficult to obtain a uniform dope (film-forming liquid). This is because film formation is not easy. In the present invention, the unit (b) may account for 0 to 70 mol% of the total units.
If the amount of units (b) is too large, the strength of the resulting gas separation will be poor for practical use, which is not preferable. The polyquinazolone polymer consisting of the unit () is insoluble in most organic solvents except for those exemplified as polymerization reaction solvents, and
It has extremely excellent chemical resistance. Furthermore, this polymer shows no weight loss even when heated to 450°C, and has extremely excellent heat resistance. The gas separation membrane according to the present invention is preferably produced by coating a porous support substrate with a membrane-forming solution (hereinafter referred to as dope) in which a polyquinazolone polymer is dissolved in a solvent.
After heating at a temperature of 100℃ or less for several minutes, the surface layer of the dope coating layer is irradiated with far infrared rays to substantially evaporate the solvent only from the surface layer of the dope coating layer, and then water or water is the main component. Obtained by contacting with a coagulating solvent. The concentration of the polyquinazolone polymer in the dope is 5 to 30% by weight, preferably 7 to 20% by weight, and dilute solutions are generally preferred. In the present invention, so that the polyquinazolone film formed on the porous substrate has an anisotropic structure,
It is necessary for the dope to contain additives that are soluble in the dope solvent and in water. Such additives, also commonly called swelling agents, are preferably inorganic salts, usually halides of alkali metals and alkaline earth metals, preferably lithium, sodium, potassium and magnesium, especially chlorides and bromides, Examples include nitrates, sulfates, perchlorates, and mixtures thereof, and preferably lithium nitrate, potassium nitrate, lithium chloride, potassium chloride, calcium chloride, calcium nitrate, calcium sulfate, lithium bromide, potassium bromide, etc. However, it is not limited to these. The above-mentioned inorganic additives are usually used in an amount of 5 to 200 parts by weight, preferably 10 to 120 parts by weight, per 100 parts by weight of the polyquinazolone polymer, although it depends on the type of additive and the polymer concentration in the dope. . If the amount of the additive used is too large, it tends to impair the uniformity of the dope, making it difficult to obtain a uniform permeable membrane, which is not preferable. In order to increase the gas permeation rate, the thinner the film is, the more preferable it is, but on the other hand, from the point of view of mechanical strength, the thicker the better, and from these points of view, the film thickness should be 3 to 30
μ is desirable, and the coating thickness of the dope is usually 20 to 120 μ so that a film of such thickness can be obtained.
The dope solvent is dimethyl sulfoxide, N-methyl-2-pyrrolidone, N.N.
-Aprotic polar organic solvents such as dimethylacetamide and N.N-dimethylformamide are preferred. Further, according to the present invention, by using a water-soluble low-boiling organic solvent as the doping solvent in place of a portion of the aprotic polar organic solvent, it is possible to promote the formation of a dense layer in the anisotropic film. Such a low boiling point water-soluble organic solvent is used within a range that does not impede the uniformity of the dope, and although it depends on the type of solvent, it is usually 20 parts by weight or less, preferably 20 parts by weight or less per 100 parts by weight of the aprotic polar organic solvent. It is used in an amount of 10 parts by weight or less. As the low boiling point water-soluble organic solvent, for example, acetone, tetrahydrofuran, ethanol, ethyl cellosolve, etc. are preferably used. The supporting base material for applying the dope must not swell or dissolve in the dope solvent and must be porous. Specifically, polyester, polypropylene,
Porous membranes made of polyethylene, polyamide, polytetrafluoroethylene, etc. are preferably used. The membrane pore diameter is preferably about 0.05 to 10 μm, but may be larger than this. In the present invention, it is preferable to coat or impregnate the porous membrane with a good or poor solvent for the polyquinazolone polymer before applying the dope to the porous membrane. This is to prevent the dope from penetrating into the inside of the porous membrane and to form a relatively thin anisotropic membrane on the surface of the membrane. As a good solvent, the same solvent as the above-mentioned dope solvent can be used, and as a poor solvent, a water-soluble organic solvent such as acetone, ethanol, isopropyl alcohol, ethylene glycol, glycerin, etc. can be used. In the present invention, the dope may be heated at a temperature of 60 to 180° C. for about 15 seconds to 5 minutes after being applied to the support substrate and before being irradiated with far infrared rays. This is to increase the polymer concentration of the entire dope coating layer. Specifically, this heat drying may be performed using, for example, a circulating hot air dryer. Next, the surface of the doped coating layer on the supporting substrate is irradiated with far-infrared rays, and the solvent is evaporated only from the extremely thin surface layer of the coating layer, so that the doped coating layer has a high polymer concentration in the extremely thin surface layer. It will be done. The conditions for far-infrared irradiation are not particularly limited, but for example, when a belt conveyor type far-infrared irradiation device is used, it is 100 to 800 W·sec/cm ² , preferably 300 to 700 W·sec/cm ² . After such treatment, the dope coating layer is immersed together with the supporting substrate in water or a coagulating solvent mainly composed of water.
A polymer film having an extremely dense ultra-thin film dense layer on the surface layer and this dense layer integrally supported by a porous layer is formed on a porous support base material. That is, in general, in the case of anisotropic polymer membranes such as those described above, it is substantially only the dense layer that contributes to gas permeability and separation of gas mixtures, and therefore,
The thinner the dense layer, the better the gas permeability and separation properties. However, it is generally difficult to apply a thin layer of dope onto a porous support substrate. Moreover, even if coating is possible, it is more difficult to form this coated layer into an anisotropic film having an ultra-thin dense layer without defects on the surface, and it tends to become a homogeneous film. However, according to the present invention, the thickness of the anisotropic polymer membrane is from several microns to several tens of microns, but from a comparison of gas permeability with a homogeneous film of polyquinazolone polymer,
The dense layer of the anisotropic membrane has a thickness of only a few microns at most, resulting in extremely high gas permeability and separation properties. Furthermore, as mentioned above, polyquinazolone polymers have excellent chemical resistance, heat resistance, and mechanical strength, so they are suitable not only for oxygen enrichment but also for gas separation at high temperatures in _C1 chemistry. Can be used. Although water is used as the coagulating solvent in most cases, a mixed solvent of water and a water-soluble organic solvent such as methanol, ethanol, acetone, or ethylene glycol may be used if necessary. After solidification in this manner, the resulting wet film is dried in a conventional manner. For example, after air drying at room temperature, drying at about 60°C in a vacuum dryer. Alternatively, the wet membrane may be immersed in methanol, water in the membrane may be replaced with methanol, and then air-dried. Examples of the present invention are listed below, but the present invention is not limited thereto. In the following examples, the gas permeability coefficient P is determined by the high vacuum method at 25°C, and the separation coefficient α is the gas permeability coefficient at 25°C/nitrogen permeability coefficient (P _N
2 ). Example 1 N-methyl-2- was placed in a flask equipped with a stirrer, a nitrogen gas introduction device, a reflux condenser with a reaction product water extraction device, and a jacket bath capable of heating to a temperature of 250°C.
85 g of pyrrolidone was charged, and 5.7 g of lithium chloride and 0.39 g of phosphorus pentoxide were added and dissolved. Next, the structure below 18.39 g (0.055 mol) of bisoxazinone,
4,4'-diaminodiphenyl ether 8.81g
(0.044 mol) and 3.15 g (0.011 mol) of 4,4'-diaminodiphenylmethane-3,3'-dicarboxylic acid.
was dissolved. 14g xylene as azeotropic dehydration solvent
was added and heated to 180°C under a nitrogen stream to reflux the xylene, and the reaction was carried out for 15 hours while continuously removing the reaction product water by azeotropy to obtain a viscous polymer solution. Ta. This polymer solution was poured into a large amount of water to coagulate and precipitate the polymer, which was then vigorously stirred and pulverized in water using a mixer. After separating this powder, it was vacuum dried at 60℃ for 10 hours, and the logarithmic viscosity was 0.71.
of polyquinazolone was obtained. This polyquinazolone
80 mol% bisquinazolone units and 20 mol% bisquinazolone units It had Next, 10 g of this polyquinazolone and 2 g of lithium chloride were dissolved in 88 g of N-methyl-2-pyrrolidone, and the mixture was pressurized using paper with an average pore size of 10 μm to remove foreign substances. The dope prepared in this manner was cast onto a polypropylene porous membrane ("Jyuragard 2400" manufactured by Polyplastics Co., Ltd.) impregnated with N-methyl-2-pyrrolidone in advance, and then heated at 80°C for 2 minutes. Next, the doped surface was irradiated with far infrared rays for 3 minutes. Thereafter, it was immediately immersed in cold water at 2° C., and N-methyl-2-pyrrolidone in the polymer film formed with the base material was eluted into the water. Similarly, composite membranes were obtained by varying the coating thickness of the dope cast onto the base material. After each composite membrane obtained in this way was air-dried at room temperature for a day and night, it was fixed on a glass plate and heated at 60℃ for 10 minutes.
Vacuum dried for hours. Table 1 shows the thickness and performance of the composite membrane for gas separation thus obtained. For comparison, a homogeneous membrane was prepared from the polyquinazolone obtained above. That is, 10g of polyquinazolone is
- After dissolving in 90 g of methyl-2-pyrrolidone, it was filtered under pressure using paper with an average pore size of 10 μm to remove foreign substances. After coating this polymer solution on a glass plate, it was kept in a vacuum dryer at room temperature for 5 hours, and then for 90 minutes.
The solvent was removed by drying at °C for 10 hours. The polyquinazolone membrane was peeled off by immersion in water and vacuum dried at 80°C to obtain a homogeneous membrane. The gas permeability of this membrane is shown in Table 2. The oxygen permeability coefficient of this homogeneous membrane is 1.5×10 ^-10 cc
Using (STP)·cm/cm ² ·sec·cmHg and assuming that the homogeneous film corresponds to the dense layer of the composite membrane of the present invention, the thickness of the dense layer in the composite membrane was determined by calculation. 1st
Shown in the table. The above results indicate that the anisotropic composite membrane according to the present invention has an extremely high gas permeability, although the separation coefficient is slightly lower than that of the corresponding homogeneous membrane of the same thickness.

【table】

[Table] Example 2 8 g of polyquinazolone obtained in Example 1 was added to N-methyl-2-pyrrolidone together with 4 g of lithium nitrate.
Dissolve in a mixed solvent of 75g and 1.7g of acetone,
A dope was prepared in the same manner as in Example 1. Using this dope, a composite membrane was formed on a polypropylene porous membrane in exactly the same manner as in Example 1. The oxygen permeability of this membrane is 9.1×10 ^-7 cc (STP)/cm ²・sec・cm
Hg, the separation coefficient was 4.8. Example 3 The same porous polypropylene membrane as in Example 1 was impregnated with acetone, and then immersed in ethylene glycol to replace the acetone, thereby impregnating ethylene glycol into the porous membrane. After applying the same dope as in Example 1 onto this porous membrane, the surface of the dope coating layer was irradiated with far infrared rays for 2.5 minutes. After that, it was immediately immersed in cold water at 2°C to remove the ethylene glycol in the porous membrane and the N in the coagulated polyquinazolone membrane.
-Methyl-2-pyrrolidone was eluted in water and dried in the same manner as in Example 1. The oxygen permeability of this membrane was 3×10 ⁻⁶ cc (STP)/cm ² ·sec·cmHg, and the separation coefficient was 4.0. In addition, after applying the dope directly to the polypropylene porous membrane without pre-impregnating it with a solvent,
The composite membrane obtained by the same treatment as above has an oxygen permeability of 6.7×10 ^-7 cc (STP)/cm ² sec cmHg,
The separation coefficient was 4.9. Example 4 74.8 g of N-methyl-2-pyrrolidone was charged into the same flask as in Example 1, 600 mg (0.003 mol) of anhydrous stannous chloride was added as a polymerization catalyst, and 426 mg (0.003 mol) of phosphorus pentoxide was added as a dehydrating agent. was added and dissolved. Next, 20.1 g (0.06 mol) of bisoxazinone, the same as in Example 1, and 12.0 g (0.06 mol) of 4,4'-diaminodiphenyl ether were added and dissolved, and 15 g of xylene was further added as an azeotropic solvent. The xylene was refluxed by heating to a temperature of 170 to 190° C. under a nitrogen stream, and polymerization was carried out while continuously removing reaction product water by azeotropy. start the reaction
After 10 hours, 15 g of N-methyl-2-pyrrolidone was added to dilute the reaction mixture, and the polymerization was continued for an additional 32 hours. The xylene was distilled off to obtain a viscous polyquinazolone polymer solution. The logarithmic viscosity of this polymer is 0.78
and consists of the following units: 10 g of the obtained polyquinazolone polymer and 2 g of lithium chloride were dissolved in 88 g of N-methyl-2-pyrrolidone, and after removing foreign substances by filtration, Example 1
A composite membrane was obtained using a polypropylene porous membrane in the same manner as above. The oxygen permeability of this membrane is 2.3×10 ^-6
cc(STP)/ ^cm2 ·sec·cmHg, the separation factor was 4.5. Comparative Example The same dope as in Example 1 was applied to a polypropylene porous membrane, and then heated at a temperature of 120° C. for 4 minutes in a circulating hot air dryer. A film obtained by coagulating and forming a film in the same manner as in Example 1 without irradiating with far infrared rays,
Oxygen permeability is 4×10 ^-8 cc (STP)/cm ²・sec・cm
On the other hand, the separation coefficient is 4.6, which is not improved.

Claims (1)

[Claims] 1. General formula (However, R ¹ is a tetravalent organic group, R ² is each independently an alkyl group or aromatic group, R ³ is a (p+2) valent organic group, Z is -COOH, -SO ₃ H, or a metal salt thereof and p is 0 or 1 to 4 independently for each unit.
indicates an integer. ) A thin film made of a polyquinazolone polymer having the bisquinazolone unit represented by () as a repeating unit is formed on a porous substrate, and the thin film consists of a dense ultra-thin film on the surface and a porous layer that integrally supports it. A composite membrane for gas separation characterized by comprising: 2 R ¹ is [Formula], R ² is a methyl group or a phenyl group,
The gas separation composite membrane according to claim 1, wherein p is 0 and R ³ is [Formula] or [Formula]. 3 R ¹ is [Formula], R ² is a methyl group or a phenyl group,
When p is 0, 1 or 2, and p is 0,
For gas separation according to claim 1, wherein R ³ is [Formula] or [Formula], and when p is not 0, R ₃ is [Formula] [Formula] or [Formula] Composite membrane.