JPH02251232A - Two-layered polyimide hollow yarn membrane and its preparation - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention provides a hollow fiber membrane having a two-layer structure of aromatic polyimides that exhibits extremely excellent gas permeability and has excellent heat resistance, pressure resistance, etc. The present invention also relates to a method for producing a polyimide two-layer hollow fiber membrane, which allows the aforementioned excellent performance polyimide hollow fiber membrane to be easily produced with good reproducibility.

The hollow fiber membrane of the present invention can be suitably used in gas separation operations such as hydrogen separation, carbon dioxide separation, oxygen enrichment, and dehumidification.

[Description of prior art]

Previously, JP-A-49-62380, JP-A-62-1
As described in Japanese Patent Application Laid-open No. 91019 and Japanese Patent Application Laid-Open No. 64-15104, multilayer hollow fiber membranes made of high molecular weight polymers such as cellulose acetate, polyvinyl, and polyamide, and their manufacturing methods, have been known. The multilayer hollow fiber membrane of 2007 was not satisfactory in terms of heat resistance, chemical resistance, pressure resistance, etc.

On the other hand, as a method for manufacturing a gas separation membrane made of biphenyltetracarboxylic acid-based aromatic polyimide, for example, as described in JP-A-61-133106,
Solubility obtained from an aromatic tetracarboxylic acid component whose main component is biphenyltetracarboxylic acids and an aromatic diamine component whose main component is an aromatic diamine compound that has a divalent group of -SO, - in its molecule. Using an aromatic polyimide solution of Disclosed is a method for manufacturing (including

The above-mentioned known gas separation membranes made of aromatic polyimides have excellent heat resistance, chemical resistance, and the like, as well as good carbon dioxide gas permeation performance. .

However, when the above-mentioned known gas separation membranes made of aromatic polyimides are actually used for gas separation as an energy-saving technology, they do not necessarily have sufficient pressure resistance and gas permeation rate, and furthermore, they do not have sufficient pressure resistance or gas permeation rate. Gas separation membranes with high pressure resistance and gas permeation rates were expected.

In addition, in the conventional wet membrane forming method for hollow fiber membranes, a single polyimide solution composition is used to continuously form an extremely thin separation layer (uniform outer layer) and a relatively thick porous support layer. In order to form an integrally constructed asymmetric hollow fiber membrane all at once in a coagulation solution, etc., in order for both layers to have their respective sufficient functions, the type of polyide solution composition, There are many restrictions on membrane production conditions, and the resulting hollow fiber membrane may not be able to fully demonstrate the original gas permeation properties of aromatic polyimide gas separation membranes, or the membrane production may require extremely skilled operations. [Problems to be solved by the present invention] This invention has the problem that it may not be possible to produce hollow fiber membranes with good reproducibility and stable performance due to Hollow fiber membranes made of aromatic polyimides for gas separation, which have not only the high-performance properties of aromatic polyimides such as heat resistance and chemical resistance, but also excellent pressure resistance and gas permeation speed as hollow fiber membranes, and The purpose is to provide a manufacturing method with good reproducibility.

[Means for Solving the Problems] That is, the first invention of this application comprises an aromatic tetracarboxylic acid component containing 70 mol% or more of biphenyltetracarboxylic acids, and a divalent group of SOz- in the molecule. An aromatic diamine component containing 50 mol% or more of aromatic diamines having in the molecule and 2 to 30 mol% of an aromatic diamine having a divalent group of -〇(CFs)*- in the molecule. , an asymmetric outer layer formed of soluble aromatic polyimide A obtained by polymerization, in which a homogeneous outer surface layer and a microporous layer are continuously and integrally formed, and biphenyltetracarboxylic acids. A soluble compound obtained by polymerizing an aromatic tetracarboxylic acid component containing 70 mol% or more of The present invention relates to a two-layer polyimide hollow fiber membrane characterized by comprising a microporous inner layer made of aromatic polyimide B.

Further, a second invention of this application uses a spinning device equipped with a spinning nozzle having concentric circular openings consisting of an external circular opening and an internal circular opening, and (a) the above-mentioned soluble aromatic compound. A low concentration polyimide solution in which polyimide A is uniformly dissolved in an organic polar solvent at a polyimide concentration of 1 to 25% by weight is supplied to the external circular opening, and (b) the soluble aromatic polyimide B is , a high concentration polyimide solution uniformly dissolved in an organic polar solvent with a polyimide concentration of 5 to 35% by weight and 0.5 to 10% by weight higher than the low concentration polyimide solution is poured into the inner circular opening. The two types of polyimide solutions are simultaneously extruded into a two-layered hollow fiber from the two concentric openings of the spinning nozzle, and the two-layered hollow fiber is solidified. The present invention relates to a method for producing a polyimide two-layer hollow fiber membrane, which is characterized in that it is brought into contact with a liquid to form a two-layer hollow fiber membrane.

The hollow fiber membrane of the present invention, for example, as shown in FIG.
It is formed of the above-mentioned aromatic polyimide A, and consists of an extremely thin homogeneous outer surface layer 1 (sometimes referred to as a gas separation layer) and a relatively thick microporous layer 2 having a network structure. The asymmetric outer layer integrally formed with the aromatic polyimide BT; the thick microporous inner layer 3 having a network structure formed integrally forms a hollow fiber membrane. Any polyimide two-layer hollow fiber membrane 4 may be used.

The outer surface layer of the outer layer preferably has a thickness of 0.01 to 1 μm, and the outer surface layer of the outer layer preferably has a thickness of about 0.01 to 1 μm. , thickness 3
~200μm, especially about 5~100μm,
Furthermore, the porous inner layer has a thickness of 10 to 500 μm.
In particular, the two-layer hollow fiber membrane of the present invention preferably has a thickness ratio of 1:0.5 to 1:10, particularly 1:1 to 1:1. Preferably, the ratio is 1:8.

The outer diameter of the hollow fiber membrane of this invention is 50 to 2000.
The thickness is preferably about 100 to 1500 μm, more preferably about 150 to 1000 μm.

The two-layer hollow fiber membrane of this invention has a porosity of its outer layer (100
- polymer fraction) from 55 to 80%, especially from 60 to 75%
The inner layer has a porosity of 45 to 70%, especially 50%.
It is preferable that the porosity of the inner layer is about 64% and larger than the porosity of the outer layer, since this allows high permeability to be maintained and high pressure resistance.

In addition, the polymer fractions (PI and p
g) is the capacity of each aromatic polyimide (A
I and A2), the length of the two-layer hollow fiber membrane manufactured in that unit time (L), and the difference between the outer diameter and inner diameter of the outer layer and inner layer of the two-layer hollow fiber membrane (a+ and aX) It can be calculated using the following formula.

The aromatic polyimide A forming the outer layer of the hollow fiber membrane includes, for example, (a) 10 mol% of biphenyltetracarboxylic acids;
or more, preferably 80 mol% or more, particularly preferably 90 mol% or more
``-100 mol% aromatic tetracarboxylic acid component and (6) aromatic diamines having a -3Oz- divalent group in the molecule at 50 mol% or more, preferably 60 mol%. As mentioned above, the aromatic diamine is particularly preferably contained in a proportion of 70 mol % or more and further has a C(CFs)t- divalent group in the molecule from 2 to 30 mol %, preferably from 3 to 25 mol %.
"Aroma soluble in organic polar solvent" obtained by polymerizing and imidizing approximately equimolar amount of aromatic diamine component containing mol%, particularly preferably 5 to 20 mol%, in an organic polar solvent. Group polyimide 1 may be used.

The biphenyltetracarboxylic acids used in the production of polyimide A include 2.3.3'.

4′-biphenyltetracarboxylic acid, 3.3′, 4.4
Examples include '-biphenyltetracarboxylic acid, acid dianhydrides thereof, and lower alcohol esters thereof.

In addition, in the production of polyimide A, other tetracarboxylic acid components that can be used in combination with biphenyltetracarboxylic acids include, for example, pyromellitic acid or its acid dianhydride, benzophenonetetracarboxylic acid or its acid dianhydride. Aromatic tetracarboxylic acids such as biphenyl ether tetracarboxylic acid or its acid dianhydride can be mentioned.

r-so used in the production of polyimide A
The aromatic diamines 1 having a divalent O group in the molecule include at least one aromatic ring (such as a benzene ring) directly on both sides of the -SO□- divalent group. Any aromatic diamine compound may be used, such as 4.4''-diamino-diphenylsulfone, 4.
4'-diamino-3,3°-dimethyl-diphenyl sulfone, 3.3'-diamino-diphenyl sulfone, 3.
Diaminodiphenylsulfones such as 4'-diamino-diphenylsulfone; bis(aminophenoxyphenyl) such as bis(4-(4°-aminophenoxy)phenyl)sulfone and bis(4-(3'-aminophenoxy)phenyl)sulfone; Sulfones, 3.7-Diami2-2,8-dimethyl-diphenylene sulfone, 3.7-Diami-2,8-diethyl-diphenylene sulfone, 3.7-Diami-2,8-dipropyl-diphenylene sulfone, 2. 8-diamino-3,7
Diaminodiphenylene sulfones such as -simethyl-diphenylene sulfone, 3,7-cyamitsu-2°8-dimethoxy-diphenylene sulfone, and 3,7-cyamitsu-thioxanthin-5,5-dioxide, 2.8-
Diamino-thioxanthine-5,5-dioxide, 3.
7-cyamitsu-thioxanthone-5,5-dioxide,
Diamino-thioxanthins such as 2,8-diamino-thioxanthone-5,5-dioxide or derivatives thereof can be mentioned.

'C used in the above manufacturing method for polyimide
(CF,)! As aromatic diamines j having a divalent group of - in the molecule, the above-mentioned C(CF3)! - An aromatic diamine compound in which at least one aromatic ring (such as a benzene ring) is directly bonded to both sides of a divalent group,
For example, 2,2-bis(4-aminophenyl)hexafluoropropane, 2,2-bis(3-aminophenyl)
Hexafluoropropane, 2,2-bis(4-amino-
3-methylphenyl)hexafluoropropane, 2.2
-2.2-bis(aminophenyl)hexafluoropropanes such as -bis(3-amino-4-methylphenyl)hexafluoropropane, to 2.2-bis(4-(4-aminophenoxy)phenyl) Hexafluoropropane, 2,2-bis(4-(3-
Examples include 2,2-bis(aminophenoxyphenyl)hexafluoropropanes such as aminophenoxy)phenyl]hexafluoropropane.

Furthermore, in the method for producing polyimide A described above, r-3O
, -cJ: and -C(CF,) - Other diamine components that can be used in combination with the aromatic diamine compound j having a - divalent group in the molecule include, for example, 4,4°-diamino -diphenyl ether, 3.3'-dimethyl-4,
4'-diamino-diphenyl ether, 13'-jethoxy-4,4'-diamino-diphenyl ether, 3.
Diaminodiphenyl ethers such as 3''-diamino-diphenyl ether, diaminodiphenylmethanes such as 4.4''-diamino-diphenylmethane, 3.3''-diamino-diphenylmethane, 2.2-bis(3-aminophenyl)propane, 2. 2
2,2- such as -bis(4-aminophenyl)propane
Bis(aminophenyl)propanes, 2,2-bis(4-(4'-aminophenoxy)phenyl)propane, 2,2-bis(4-(3°-aminophenoxy)phenyl)propane, etc. -bis(aminophenoxyphenyl)propanes, diaminobenzophenones such as 4.4′-diamino-benzophenone, 3.3″-diamino-benzophenone, Osm- or p-phenylenediamine, 3°5-diaminobenzoic acid, 2 , 6-cyamitubiridine, 〇-tolidine, and the like.

In the aromatic polyimide A, if the content of structural units based on biphenyltetracarboxylic acids (tetracarboxylic acid component) is too low, such aromatic polyimide will not easily dissolve in organic polar solvents. Or, even when dissolved in a solvent, it tends to precipitate, resulting in an unstable polyimide solution, which is not suitable for film formation.

In the aromatic polyimide A, -SO8 or -C
If the content of the structural unit based on an aromatic diamine compound (diamine component) having a divalent group of F,)z- in the molecule becomes too small, such an aromatic polyimide becomes
When the aromatic polyimide solution is used to form an asymmetric outer layer together with an inner layer by a wet membrane forming method, the final hollow fiber membrane having an asymmetric outer layer made of aromatic polyimide is It is not suitable because the gas permeation rate for hydrogen gas, carbon dioxide gas, etc. becomes slow.

The aromatic polyimide A had a logarithmic viscosity at 30°C (measured concentration: 0.5 g/1oon/! Solvent; solvent; 4 parts by volume of parachlorophenol and 1 part by volume of orthochlorophenol).
(parts by volume of mixed solvent) is 0.1 to 7, especially 0.2 to 5
It is preferable that the degree of

The aromatic polyimide B forming the outer layer of the hollow fiber membrane contains biphenyltetracarboxylic acids in an amount of 70 mol% or more, preferably 80 mol% or more, particularly preferably 90 to 1
00 mol% of an aromatic tetracarboxylic acid component and at least 50 mol% of an aromatic diamine compound having at least two or more aromatic rings, preferably 6O
It is a soluble aromatic polyimide obtained by polymerizing an aromatic diamine component containing -E-le% or more, particularly preferably 70 to 100 mol%, in an organic polar solvent.

The aromatic diamine compounds that can be used in the production of the polyimide B include various aromatic diamine compounds used in the production of the polyimide A, and those having at least 2, especially 2 to 5 aromatic rings ( especially benzene ring)
For example, diaminodiphenyl ethers, diaminobenzoic acid, 2,2-his(aminophenyl)propanes, 2,2-bis(aminophenoxy phenyl)propanes, diaminobiphenyls, diaminodiphenylsulfones, bis(aminophenoxyphenyl)sulfones, diaminodiphenylenesulfones, diamino-thioxanthins or derivatives thereof, 2.2-
Bis(aminophenyl)hexafluoropropanes, 2
．． Preferred examples include 2-bis(aminophenoxyphenyl)hexafluoropropanes and mixtures thereof.

Note that the aromatic diamine component used in the production of polyimide B contains at least 50 mol% or more of the above-mentioned aromatic diamine compound having at least two aromatic rings. Other aromatic diamines that can be used in combination with the diamine compound include o-
Examples include lm- or p-phenylenediamine, 3,5-diaminobenzoic acid, 2,6-cyamitsupyridine, 0-)lysine, and the like.

In the method for manufacturing a polyimide two-layer hollow fiber membrane, which is the second invention of this application, as shown in FIG. (a) The above-mentioned soluble aromatic polyimide A has a polyimide concentration of 1 to 25% by weight, preferably 1.2 to 23% by weight, more preferably 1.2 to 23% by weight. is 1.5-2
A low concentration polyimide solution homogeneously dissolved in an organic polar solvent at 2% by weight is added (preferably at a temperature of about 20 to 150"C, particularly preferably 30 to 120"C and under suitable back pressure) to the outer circular shape. (b) The above-mentioned soluble aromatic polyimide B has a polyimide concentration of 5 to 35% by weight, preferably 6 to 30% by weight, and has a polyimide concentration of 0% to 30% by weight compared to the above-mentioned low concentration polyimide solution. A highly concentrated polyimide solution homogeneously dissolved in an organic polar solvent with a polyimide concentration as high as .5 to 10% by weight, particularly as high as 1 to 8% by weight (preferably about 20 to 150°
C1 (particularly preferably at a temperature between 30 and 120"C and under suitable back pressure) into the internal circular opening 12, from the two concentric openings of the spinning nozzle, the two polyimides are The solution is simultaneously extruded into a two-layered hollow fiber, and the two-layered hollow fiber is soaked in a coagulating liquid (preferably one
(0 to 60°C, especially -5 to 40°C)
For example, a two-layer hollow fiber membrane made of aromatic polyimide is formed by immersing a two-layer hollow fiber in a coagulating liquid.

In the above method for producing a two-layer hollow fiber membrane, the external circular opening 1
The discharge amount ratio ((b)/(a)) of the polyimide A solution (a) supplied to the inner circular opening 12 and the polyimide B solution (b) supplied to the inner circular opening 12 is 1.5 to 60. In particular, it is particularly preferable that the molecular weight is about 2 to 40 in order to stably produce a two-layer hollow fiber membrane.

The size of the opening of the spinning nozzle for spinning the above-mentioned two-layer hollow fiber can be appropriately determined depending on the shape of the two-layer hollow fiber to be spun, but the opening interval of the external circular openings It is preferable that the ratio of the opening interval of the internal circular openings to the inner circular opening is about 5:1 to 1:10, particularly about 1:1 to 1:5.

The organic polar solvent used in the production by polymerizing and imidizing polyimide can be used as it is, and can uniformly dissolve the aromatic polyimide A or B. , and is compatible with the coagulating liquid used for spinning described below,
Further, those having a melting point of 200°C or lower, particularly 150°C or lower are preferable, such as phenols such as phenol, cresol, xylenol, catechols, 3-
Chlorphenol, 4-chlorophenol (hereinafter referred to as PC
P), 4-bromophenol, 2-chloro-5
- Phenolic solvents such as halogenated phenols such as hydroxytoluene, or N-methyl-2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, N,N-diethylformamide, N
Preferred examples include amide solvents such as , N-diethylacetamide and dimethyl sulfoxide, and mixed solvents thereof.

The coagulating liquid may be any polar solvent that does not substantially dissolve the polyimides A and B forming the two-layer hollow fiber membrane and is compatible with the solvent of the aromatic polyimide solution. For example, water, methanol, ethanol,
Lower alcohols such as propatool and isoproptool, acetone, methyl ethyl ketone, diethyl ketone,
Examples include ketones such as ethylpropyl ketone, or mixed solvents of water and organic polar solvents such as lower alcohols and ketones.

The polyimide solution in which polyimide A forming the outer layer is dissolved in an organic polar solvent has a solution viscosity (rotational viscosity) of 1 to 20,000 voids, particularly 5 to 10 voids at the spinning temperature.
000 poise, more preferably about 10 to 8000 poise, is preferable for spinning, and the polyimide solution in which polyimide B forming the inner layer is dissolved in an organic polar solvent has a solution viscosity (rotational viscosity) of 100°C. is 1 of the rotational viscosity (100°C) of the polyimide A solution,
01---1.0 times, especially about 1.05 to 5 times, in the embodiment of the method for producing the two-layer hollow fiber membrane of the invention, in which the polyimide solution is transferred from the spinning nozzle to the two-layer hollow fiber membrane for spinning. The two-layer hollow fiber body formed of the two kinds of aromatic polyimide solutions 1 extruded from the nozzle is extruded into the atmosphere, and the coagulation liquid (approximately -10 to 6
After the surface of the hollow fiber is solidified to the extent that it can maintain its hollow fiber shape in 0''C), it is wound around a guide roll, a take-up roll, etc. It is preferable to reciprocate to fully solidify the inside of the hollow filament, and the speed at which the hollow filament is taken up by the take-up roll is preferably about 2 to 80 m/min.

It is more preferable to extract and substantially remove the organic polar solvent that has dissolved the aromatic polyimide remaining inside the two-layer hollow fiber membrane spun as described above.

Further, in the two-layer hollow fiber membrane, the coagulation liquid is sufficiently replaced by using an inert solvent, for example, an aliphatic hydrocarbon compound such as isopencune, n-hexane, isooctane, or n-heptane. After that, the two-layer hollow fiber membrane swollen with the substituted solvent is dried, and the substituted solvent is evaporated to obtain a dry hollow fiber membrane, and the aroma constituting the dried hollow fiber membrane is It is preferable to perform the heat treatment at a temperature lower than the softening point (or secondary transition point) of the group polyimide.

〔Example〕

EXAMPLES Hereinafter, this invention will be explained in more detail with reference to Examples, but this invention is not limited by these Examples.

Reference Example 1 99 mmol of 3.3',4.4'-biphenyltetracarboxylic dianhydride, 100 mmol of 3,7-cyamidimethyldiphenylene sulfone, 302 g of phenol, a stirrer and a nitrogen gas inlet pipe were used. Place the monomers in an attached separable flask and polymerize both monomers at 180°C for 13 hours while flowing nitrogen gas and stirring the reaction solution to obtain an aromatic polyimide solution with a polyimide concentration of 15%. was prepared.

This aromatic polyimide solution has a solution viscosity at 100°C (
The solution viscosity at 90°C (rotational viscosity) was 1,004 poise and 1,432 poise.

Further, the concentration of the polymer in the aromatic polyimide solution measured by logarithmic viscosity: 0.5 g/100+oj! Solvent, solvent (mixed solvent of 4 parts by volume of parachlorophenol and 1 part by volume of orthochlorophenol) was 1.1.

Reference Examples 2 to 8 The tetracarboxylic acid component shown in Table 1 and the aromatic diamine component were polymerized in the same manner as in Reference Example 1 to prepare various aromatic polyimide solutions.

The concentration of these aromatic polyimide solutions and 1.

The solution viscosity (rotational viscosity) of OoC is shown in Table 1.

The logarithmic viscosity of the polymer in the aromatic polyimide solutions obtained in Reference Examples 2 to 7 (measurement conditions are the same as Reference Example 1) was 1.1, and the logarithmic viscosity of the polymer in the aromatic polyimide solutions obtained in Reference Example 8 was 1.1. The logarithmic viscosity of the polymer in polyimide solution is 1
．． It was 0.

The abbreviations in Table 1 represent the following compounds, respectively.

5-BPDA: 3,3'. 4.4'-biphenyltetracarboxylic dianhydride TSN: 3+7-cyamitdimethyldiphenylene sulfone DADE: 4.4'-diaminodiphenyl ether DA
BA: 3.5-diaminobenzoic acid HFIP: 2.2-bis(4-aminophenyl)hexafluoropropane HFPP: 2.2-bis(4-(4-aminophenoxy)phenyl)hexafluoropropane 1st Table reference examples Acid anhydride Diamine Polymer concentration Solution viscosity mmol] [mmol] [wt%] [Poise] 5-BPDA 99 S-BPDA 99 5N100 5N90 HFIP 10 Comparative examples 1 to 3 Reference examples 1.2.3 and The aromatic polyimide solutions prepared in 8 were used in the combinations shown in Table 2, and each pair of aromatic polyimide solutions was filtered through a 400-mesh stainless wire mesh to prepare a dope solution for spinning.

As shown in Fig. 2, the outer diameter of the outer circular opening of the spinning nozzle of the same two-layer hollow fiber membrane is 1700 μm.
Slit width: 150μm Outer diameter of internal circular opening
・Slit width of 1200 μm; 30
0°C 1m Core opening outer diameter: 400μ
After the hollow fibers are discharged from the spinning nozzle and passed through a nitrogen atmosphere, a coagulating liquid consisting of a 65% by weight aqueous solution of Ek and Nol is prepared. (0°C) respectively,
Furthermore, the guide rolls are reciprocated in a second coagulation liquid in a coagulation device equipped with a pair of guide rolls to complete the coagulation of the hollow fibers, and the two-layer hollow fiber membranes made of each aromatic polyimide are formed. Spinning was carried out at a take-up speed of 15 m/min.

Finally, this two-layer hollow fiber membrane is wound up on a bobbin, and after thoroughly washing the coagulation solvent with ethanol, the ethanol is replaced with n-hexane, and the n-hexane is evaporated at 50°C to form a two-layer membrane. Dry the hollow fiber membrane and further heat at 300°C.
The two-layer hollow fiber membrane was heat-treated at a temperature of 30 minutes to produce a dried and heat-treated polyimide two-layer hollow fiber membrane.

The permeation performance of was measured by the method shown below.

First, a hollow bundle element for permeation performance evaluation was created using each of the two-layer hollow fiber membranes produced as described above, a stainless steel pipe, and an epoxy resin adhesive.

Then, the permeation performance was measured by installing a hollow fiber bundle element for permeation performance evaluation in a stainless steel container, and measuring a mixed gas of hydrogen and methane, a mixed gas of carbon dioxide and methane, or a mixed gas of oxygen and nitrogen. using a temperature of 50 °C, 10
A gas permeation test was conducted at a pressure of kg/cii, and the gas permeation rate and each gas permeation rate ratio (indicating permselectivity and degree of gas separation) were calculated from the measured values of gas chromatography analysis.

Examples 1 to 4 Two-layer hollow fiber membranes were produced in the same manner as Comparative Example 1, except that the aromatic polyimide solutions prepared in Reference Examples 4 to 8 were used in the combinations shown in Table 2. did.

In the two-layer hollow fiber membrane produced in Example 1, the outer layer had a porosity of 65%, and the inner layer had a porosity of 58%.

In addition, the permeation performance of each two-layer hollow fiber membrane was measured using the same measurement method as in Comparative Example 1.

Table 2 shows the fiber diameter and permeation performance of the obtained polyimide two-layer hollow fiber membrane.

Reference Experiment 1 Regarding the polyimide two-layer hollow fiber membrane produced in Example 2, the pressure resistance of the two-layer hollow fiber membrane was measured using the pressure resistance measuring method shown below.

That is, a fiber bundle element of a two-layer hollow fiber membrane for pressure resistance measurement, in which the hollow part of the polyimide two-layer hollow fiber membrane is open at both ends, was installed in a stainless steel container for pressure resistance evaluation, and the inside of the container was heated to 100°C. After that, nitrogen gas is flowed into the hollow part of the two-layer hollow fiber membrane of the element, and while continuously observing the flow rate, the air gap between the inner wall of the container and the outer wall (outer surface) of the two-layer hollow fiber membrane is Liquid paraffin was injected into the chamber, and the limit value of pressure resistance was measured from the relationship between the normal pressure and the change in nitrogen gas flow rate in the hollow section of the two-layer hollow fiber membrane.

As a result of the pressure resistance measurement, the limit value of the polyimide two-layer hollow fiber membrane obtained in Example 2 was 130 kg/et & 1
0. (The polyimide two-layer hollow fiber membrane obtained in the thρ Example also had similar pressure resistance.

Reference Experiment 2 Furthermore, regarding the polyimide two-layer hollow fiber membrane obtained in Example 2, the hydrogen gas permeation rate and the ratio of the hydrogen gas permeation rate to the methane gas permeation rate (separation degree; P Hz
/ P CHa ) at 80°C1120°C or 1
The hydrogen permeation rate and separation degree (P
Hz /PCH-).

Table 3 Measurement temperature Hydrogen permeation rate Separation degree “C(d
/aLsec-cmHg) (PHz/PCHa)80
58X10-' 63120
90X10"' 41150
120X10-' 30 Comparative Example 4 Using the polyimide solution shown in Engineering Reference Example 2, a spinning nozzle for a -layer hollow fiber membrane (outer diameter of the circular opening; 1200
A single layer of polyimide was produced using the same hollow fiber spinning method as in Comparative Example 1, except that the polyimide solution was extruded into a hollow fiber from a slit width of 300 μm and an outer diameter of the core opening of 400 μm. A hollow fiber membrane (outer diameter: 405 μm, membrane thickness: 75 μm) was formed, and the pressure resistance limit value of this single-layer polyimide hollow fiber membrane was 80 kg/ctll.

[Actions and effects of the present invention]

The polyimide two-layer hollow fiber membrane of the present invention has a two-layer structure made of biphenyltetracarboxylic acid-based aromatic polyimide, and has the inherent chemical resistance that aromatic polyimide has.
It maintains a high level of heat resistance, durability, mechanical strength (pressure resistance), etc., and the outer layer is a homogeneous layer made of special aromatic polyimide A obtained using aromatic diamine. Since it is formed of an asymmetric layer 1 consisting of a microporous layer, it is an excellent gas separation membrane that has an extremely high permeation rate for gases such as hydrogen, carbon dioxide, and oxygen.

The manufacturing method of this invention uses the above-mentioned polyimide two-layer hollow fiber membrane,
This method allows production with good reproducibility.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view schematically showing a part of the structure of a two-layer hollow fiber membrane created based on a microscopic photograph taken of the cross-sectional structure of the polyimide two-layer hollow fiber membrane of the present invention. It is. FIG. 2 is a sectional view showing an example of a two-layer hollow fiber spinning nozzle. 1; outer surface layer of the outer layer; 2; microporous outer layer. 3; inner layer, 4; two-layer hollow fiber membrane, 11; outer circular opening,
12; Internal circular opening; 13; Core opening; 14; Hollow fiber spinning nozzle. Patent Applicant Ube Industries Co., Ltd. Muf, J

Claims (2)

[Claims] (1) An aromatic tetracarboxylic acid component containing 70 mol% or more of biphenyltetracarboxylic acids, and -SO_2-
and an aromatic diamine component containing 50 mol% or more of aromatic diamines having -C(CF_3)_2- in the molecule and 2 to 30 mol% of aromatic diamines having -C(CF_3)_2- in the molecule. An asymmetric outer layer formed of the obtained soluble aromatic polyimide, in which a homogeneous outer surface layer and a microporous layer are continuously and integrally formed, and a biphenyltetracarboxylic acid of 70 mol% or more. Formed from a soluble aromatic polyimide obtained by polymerizing an aromatic tetracarboxylic acid component and an aromatic diamine component containing at least 50 mol% of an aromatic diamine compound having at least two or more aromatic rings. A polyimide two-layer hollow fiber membrane characterized by comprising a microporous inner layer and a microporous inner layer. (2) Using a spinning device equipped with a spinning nozzle having concentric circular openings consisting of an external circular opening and an internal circular opening, (a) Aromatic tetracarboxylic acids containing 70 mol% or more of biphenyltetracarboxylic acids; Carboxylic acid component and -SO_2-
and an aromatic diamine component containing 50 mol% or more of aromatic diamines having -C(CF_3)_2- in the molecule and 2 to 30 mol% of aromatic diamines having -C(CF_3)_2- in the molecule. A low concentration polyimide solution in which the obtained soluble aromatic polyimide is uniformly dissolved in an organic polar solvent at a polyimide concentration of 1 to 25% by weight is supplied to the external circular opening, and (b) biphenyltetracarboxylic acid is added. an aromatic tetracarboxylic acid component containing 70 mol% or more of acids; and at least 2
A soluble aromatic polyimide obtained by polymerizing an aromatic diamine component containing at least 50 mol% of an aromatic diamine compound having 1 or more aromatic rings has a polyimide concentration of 5 to 35% by weight, and Supplying a high concentration polyimide solution uniformly dissolved in an organic polar solvent with a polyimide concentration 0.5 to 10% higher by weight than the low concentration polyimide solution to the internal circular opening, The above two types of polyimide solutions are extruded simultaneously into a two-layered hollow fiber from the concentric openings, and the two-layered hollow fiber is brought into contact with a coagulation liquid to form a two-layered hollow fiber. A method for producing a polyimide two-layer hollow fiber membrane, characterized by forming.