JPH01123607A - Production of composite separation membrane - Google Patents

Abstract

PURPOSE:To improve the separation performance of the above membrane by applying a soln. of aromatic polyimide or amido-imide in dioxane as the main solvent on a porous membrane obtained by forming the membrane of the aromatic copolyimide or amido-imide having a specified composition by a wet process, drying the soln., and heat-treating the obtained material. CONSTITUTION:The aromatic copolyimide consisting of the materials shown by formulas I and II in 90-70/10-30 molar ratio or the aromatic copolyamido- imide consisting of the materials shown by formulas III and IV in 70-90/30-10 molar ratio is formed into a membrane by a wet process. A soln. of 0.05-10pts. wt. of the copolyimide or amido-imide in the mixed solvent consisting of 100pts. wt. of dioxane and 5-50pts.wt. of the other polar solvents such as DMF and DMSO is applied on the obtained porous membrane, dried, and heat-treated. By this method, a more stable composite membrane having excellent separation performance and permeability than the conventional one not added with dioxane can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing a composite separation membrane having good separation performance. Specifically, the present invention relates to a method for manufacturing a composite separation membrane that is easy to manufacture, has excellent heat resistance and chemical resistance, has a high permeation rate, and has high separation performance.

[Conventional technology]

Composite membranes made of polysulfone and silicone polymers are known as gas separation membranes (Japanese Unexamined Patent Application Publication No. 2002-120011 and 7-7).
gAAzada). The silicone-based polymer used in this membrane has low heat resistance and its separation performance decreases significantly at high temperatures.
Furthermore, it has poor chemical resistance to aromatic hydrocarbons such as toluene (applicable only in limited applications).

Therefore, aromatic polyimide-based separation membranes, aromatic polyamide-based separation membranes, and the like have been proposed as separation membranes with excellent heat resistance, chemical resistance, and compaction resistance.

In particular, aromatic polyimide separation membranes have very good heat resistance, as well as excellent mechanical properties and chemical resistance, so they are highly expected to be used as separation membranes.

However, in a known method for producing porous polyimide membranes, a solution of polyamic acid obtained by a polymerization reaction of tetracarboxylic dianhydride and aromatic diamine is used to imidize the thin membrane in a coagulating solution. The method of producing aromatic polyimide membranes by coagulation requires operations such as film formation from a solution of polyamic acid, coagulation, and imidization, making it a complicated method that is extremely difficult to control. However, the disadvantage is that it is not possible to stably produce polyimide separation membranes with excellent performance.

In addition, in a method of manufacturing a separation membrane by coagulating aromatic polyimide obtained by a polymerization reaction of biphenyltetracarboxylic dianhydride and aromatic diamine dissolved in a melt of a phenol compound such as p-chlorophenol, The operation is extremely difficult because the aromatic polyimide dissolved in the phenolic compound melt must be coagulated with a coagulating liquid to form a coagulated film that simultaneously forms a dense phase and a porous layer.
If it is difficult to create a separation membrane with stable performance that is reproducible, or if a solvent whose main component is water, which is non-polluting, is used as the coagulation liquid, the coagulation rate is slow and the porous layer cannot be formed sufficiently. There is a tendency for the compact layer to develop without developing.
In extreme cases, coagulation itself may take a long time, or the resulting polyimide separation membrane may not have sufficient permeability.

Therefore, a polyimide-based composite membrane has been proposed, which is a porous polyimide membrane that has a high gas permeation rate and is further coated with polyimide (Japanese Patent Application Laid-Open No. 3-1-2012).

3rd edition/1006).

However, this method for producing a composite membrane has significant environmental problems because it uses a mixed solvent of halogen hydrocarbon/phenol compound. In addition, since the polyimide porous membrane is manufactured using a dry membrane forming method, manufacturing a hollow fiber-like porous membrane requires complicated operations, and it is difficult to obtain a stable hollow fiber shape and permeation performance with good reproducibility. Ta.

[Purpose of the invention]

The present inventors conducted intensive studies on a method for easily manufacturing a separation membrane having even better separation performance while maintaining the good properties of the polyimide, and found that the porous Specific aromatic copolyimide or aromatic cobo I with specific anti-solvent added to the membrane
The present inventors have discovered that a composite separation membrane coated with a dilute solution of J7 midimide, dried, and further heat-treated has significantly improved separation performance while maintaining good heat resistance, chemical resistance, and film formability.

The gist of the present invention is that 90 to 70 mol% of the repeating units are of the formula (
I) has a structure represented by and has 10 to 30 repeating units
An aromatic copolyimide in which mol% has a structure represented by formula (n) (I[), or 70-90 mol% of repeating units has a structure represented by formula (I[T)]. and 30% to 10 mol% of the repeating units were formed by a wet film forming method from an aromatic copolyamideimide having a structure represented by the formula (IV). Composite separation characterized by applying a solution of 0.03 to IO parts by weight of the aromatic copolyimide or copolyamideimide dissolved in a mixed solvent containing 3 to 50 parts by weight of an organic polar solvent, followed by drying and heat treatment. This is a method for manufacturing a membrane.

[Structure of the invention]

The method of the present invention will be explained in more detail below.

The aromatic copolyimide used in the present invention is a copolyimide characterized by the presence of repeating units of the general formula,
Here, in 70 to 30 mol% of the above repeating units, R is -Q
-CH2-o-, and this copolyimide is U
As stated in E3F3.7θPe No. 14, j
, J', lI, 4/-benzophenonetetracarboxylic dianhydride in an appropriate molar ratio of p, lI'-methylenebisphenyl incyanate (lI, lI'-diphenylmethane diisocyanate) and tolylene diisocyanate (2, Hiroshi- It can be easily obtained by reacting with the isomer (or the isomer, or a mixture thereof) in the presence of a polar solvent.

Further, in the aromatic copolyamideimide used in the present invention, 70 to 90 mol% of the repeating units have a structure represented by formula (III), and 30-1 of the repeating units are
0 mol % is a copolyamideimide having a structure represented by formula (IV).

This copolyamideimide is described in US Pat. No. 3,929! A
It is easily produced by the method taught in No. 9/. Such copolyamideimides can be prepared with a mixture of trimellitic anhydride and isophthalic acid in proportions of about 70 mole % to about 90 mole % to about 30 mole % to about 70 mole % using the procedures described in the aforementioned patents. Approximately equal amounts of /θθ mol% of p, 4
It can be easily obtained from the reaction of t'-methylenebisphenyl isocyanate.

In order to produce a porous membrane from the aromatic copolyimide or copolyamideimide by a wet film forming method, a solution of the copolyimide or copolyamideimide dissolved in a polar organic solvent such as dimethylformamide is used as a dope solution. It is produced by forming a thin film of liquid, coagulating it in a poor solvent such as water, and then heating and drying the thin film.

Regarding wet film formation of porous membranes of copolyimide and copolyamideimide, patent application No. A/-6qlI7 filed by the present applicant
It can be manufactured according to the method for manufacturing separation membranes such as A2-231IO, A2-231IO, and A62-isot.

Porous membranes can be in the form of flat membranes or hollow fibers, but in gas separation, hollow fibers are preferred from the viewpoint of pressure resistance. Although the membrane thickness and hollow fiber diameter are determined by the pressure used, it is preferable that the membrane thickness is io to SOOμ and the hollow fiber outer diameter is about 100 to 2000μ.

The permeation performance of a porous membrane is determined by the ratio of the permeation rate Q of hydrogen and nitrogen (
QH2/QN2) is about 3 to 100, and the hydrogen permeation rate is /x10-6 to /xIO""1ari"/c
rrr', sec, crnHg 1 preferably /×1
0-'~/X/θ-2(crrr3/d, S 13
C-ellHg).

The dilute solution to be applied onto the porous membrane of aromatic copolyimide or copolyamideimide is (a) dioxane 1
00 parts by weight (b) Polar organic solvent 5 to 30 parts by weight (C) Aromatic copolyimide or aromatic copolyamideimide
It is a dilute solution consisting of 0.05 to 10 parts by weight.

The polar organic solvent may be any solvent as long as it can dissolve the copolyimide or copolyamideimide, but in particular dimethylformamide, dimethylacetamide, N-methylpyrrolidone,
An appropriate amount of a solvent such as an aromatic hydrocarbon, ether, etc. may be added to the dilute solution as long as the copolyimide or copolyamideimide, preferably dimethyl sulfoxide, does not precipitate.

In the dilute solution for coating according to the present invention, if the dioxane content is low, the copolyimide or copolyamideimide porous membrane will be attacked by the polar solvent, making it impossible to obtain high separation performance. This is not preferred because copolyimide and copolyamideimide precipitate. Preferably, the ratio of dioxane and polar solvent is &-, 2& parts by weight of the organic polar solvent per 100 parts by weight of dioxane.

If the content of copolyimide or copolyamide-imide in the dilute solution is low, a composite membrane with high separation performance cannot be obtained, whereas if the content is high, the permeation rate will decrease, which is not preferable. A particularly preferable content of copolyimide and copolyamideimide is 0.00 parts by weight per 100 parts by weight of dioxane. /-1 part by weight.

The permeation rate and separation performance of a composite separation membrane can be changed by the permeation performance of a porous membrane manufactured by a wet membrane forming method and the concentration of copolyimide or copolyamide-imide coated thereon.

Next, methods for coating the surface of the porous membrane include dipping,
Methods such as a doctor blade, bar coater, roll transfer method, and spray method are used.

A dipping method is particularly preferred for coating the hollow fibers. It can be applied to the inner surface, outer surface, both or one side of the hollow fiber.

Next, the coating layer is preferably heat-treated at 110-330°C after evaporating the majority of the solvent at 10°C to 100°C.

If the heat treatment temperature is too low, a large amount of solvent will remain, resulting in poor stability of permeation performance in the gas separation membrane.On the other hand, if the heat treatment temperature is too high, the permeation rate will decrease. The permeation performance is high, for example, with a hydrogen and methane separation performance of 30 or higher, and a hydrogen gas permeation rate of tX/0-'crrr''/d, sec.

cm) Ig or higher.

The method of the present invention makes it easy to manufacture a composite separation membrane, and the composite separation membrane has high separation performance (and has excellent permeation performance and permeation rate. Also, the entire composite membrane is made of copolyimide or copolyamide-imide). Therefore, it is particularly suitable for fields such as hydrogen separation in the chemical industry, dehumidification of natural gas, and dehydration of aqueous organic substances, which require heat resistance and chemical resistance.

In the present invention, even if a dilute solution of the solvent is applied to a soluble aromatic copolyimide or copolyamide-imide porous membrane, high separation performance cannot be obtained. This results in an improvement in separation performance.

The cause of this is that when a dilute solution of copolyimide or copolyamideimide dissolved in a highly soluble polar solvent is applied to a soluble porous membrane, the porous membrane swells and deforms, and the confidential layer on the surface is dissolved, causing pinholes etc. On the other hand, in a dilute solution containing a specific amount of the specific dioxane discovered in this invention among the poor solvents found in the present invention, porous It is thought that a composite separation membrane with excellent separation performance, although stable, was obtained because the membrane was less susceptible to attack.

〔Example〕

The present invention will be specifically described below with reference to Examples.

Manufacturing Reference Example-7 US Patent No. 370g'l! ;J, j', ! , 4('
Benzophenone tetracarboxylic anhydride IOθ mol% and tolulene diisocyanate 0 mol%, and +, l
A copolyimide was polymerized from a mixture containing 20 mol% of I'diphenylmethane diisocyanate.

N, N' dimethylformamide was used as the polymerization solvent, and the resin concentration was adjusted to 43 wt%.

Production Reference Example - Production Reference Example - The copolyimide solution obtained in Production Example 7 was extruded at a constant flow rate from a nozzle for manufacturing hollow fibers, and at the same time air was extruded into the hollow at a constant flow rate, and the copolyimide solution was directly placed in a coagulation bath consisting of water (, y0°C).
After being immersed in water for about 70 seconds, it was wound up in water at a speed of 100 g/min. After that, it was washed in water and air-dried for a day and night, and then the ioo℃-
Drying and heat treatment were performed for 30 minutes at 300°C and for 717 minutes.

Hollow fiber outer diameter beam! θμ and inner diameter were 350μ.

The N2 permeation rate of the obtained porous membrane was ko×/θ″″5ar
The ratio of N2 to N2 permeation rates (QHz/QNz) was it at t''/ari', sec, mHg.

Production Reference Example 3 Dioxane,
A suitable amount of N,N dimethylformamide was added to prepare a dilute solution consisting of 10 parts by weight of dioxane, 1 part by weight of N,N dimethylformamide, and 1 part by weight of polyimide.

Example-1 The copolyimide hollow fiber porous membrane of Reference Production Example- was immersed in the dilute copolyimide solution prepared in Reference Example (3) for about 30 seconds, applied to the porous membrane, air-dried overnight, and then
A composite separation membrane was produced by drying at ℃ for 30 minutes and further heating at -30 ℃ for 30 minutes.

The results of the gas permeation test for the composite separation membrane are shown in Table 1.Reference production example - Copolyimide porous hollow fibers were prepared under the same conditions as in Reference production example - except that the film was formed in a coagulation bath consisting of water at dAj℃. Manufactured.

Gas permeation performance and water and ethanol (/0/90wt%) permeation performance by pervaporation method (10℃) -7
Shown below.

Example 2 Manufacture Reference Example - Hiro's copolyimide hollow fiber porous membrane was coated by immersing it in the dilute copolyimide solution prepared in Reference Example 3 for about 7 minutes, air-dried overnight, and then dried at IOO°C for 3Q minutes. Further, a composite separation membrane was produced by heat treatment at 300° C. for 30 minutes.

Table I shows the gas and water/ethanol permeation performance of the composite separation membrane by the pervaporation method.

Production reference example-3 61 da, 2 g (j,
4 mol) of trimellitic anhydride and /3 co, Ri09
The reactor, charged with (0.10 mol) of isophthalic acid, was equipped with a thermometer, a condenser, a stirrer, and a nitrogen inlet.

7000.96 g (4,0 mol) o in a dry bottle of Sl, 4! 'Diphenylmethane diisocyanate (
(hereinafter abbreviated as MDI), then measure the N of D3 Dago.
-'Methylpyrrolid/(hereinafter abbreviated as NMP) was weighed out and MDI was dissolved. Add this MDI solution to the reactor, then weigh out the MDI and rinse the bottle using step 3b.
Sort of NMP was added.

&! The solution was heated from 33° C. to 170° C. for 3 h tio min under a stirring speed of r rpm and a nitrogen atmosphere.
heated to.

The logarithmic viscosity (η
inh) (o, sg' in NMP) is 0.1.03di/
It was i.

This solution was added to methanol to precipitate a polymer, which was then dried at lSO°C for 3 hours to obtain cobolyamitoimide powder.

A copolyamide-imide solution was prepared by dissolving it in KDMF to a solid content of 1% by weight.

Production Reference Example-6 Production Reference Example-The copolyamide-imide solution obtained in DA is extruded at a constant flow rate through a nozzle for manufacturing hollow fibers, and at the same time, water is extruded into the hollow fibers at a constant flow rate to directly create a coagulation bath consisting of water at 3°C. Lead inside about i.

After being immersed for a second, it was wound up in water at 4'm/min.

After washing in water and air drying for a day and night, 100'C-30
2 minutes and then a dry heat treatment at 2SO° C. for 30 minutes.

The permeation performance of the obtained porous membrane of copolyamideimide is shown below.
Shown in l.

Production Reference Example-7 Appropriate amounts of dioxane and N,N dimethylformamide were added to the copolyamide-imide solution obtained in Production Reference Example-3 to obtain 73 parts by weight of dioxane and N,N dimethylformamide λ.
A dilute solution containing 1 part by weight of polyimide and 1 part by weight of polyimide was prepared.

Example-3 A composite separation membrane was manufactured under the same conditions as Example-7 except that the copolyamide-imide hollow fiber porous membrane of Reference Production Example-6 was used with the copolyamide-imide dilute solution prepared in Reference Example-7. .

Table 1 shows the results of a gas permeation test for the composite separation membrane.

Comparative Example-l A solution obtained by diluting the copolyimide solution obtained in Production Reference Example-/ with N-N dimethylformamide to the solid content/parts by weight on the copolyimide hollow fiber porous membrane of Production Reference Example-2. A composite separation membrane was manufactured in the same manner as in Example-7.

Table 1 shows the results of gas permeation through the composite separation membrane.

Comparative Example - 1 Manufacture The copolyimide solution obtained in Reference Example 1 was added to the copolyimide hollow fiber porous membrane of Reference Example 2 at a solid content of 1 part by weight, parachlorophenol/chloroform =
(/0 heavy ft m/?.

(parts by weight) to prepare a dilute solution and produce a composite separation membrane in the same manner as in Example-7.

Table 1 shows the results of gas permeation through the composite separation membrane.

Comparative Example-3 N-N dimethylformamide/
A composite separation membrane was produced in the same manner as in Comparative Example-1 except that toluene was 70 parts by weight.

Table 1 shows the results of gas permeation through the composite separation membrane.

Claims (2)

[Claims] (1) 90 to 70 mol% of repeating units are of the formula (I) ▲
There are mathematical formulas, chemical formulas, tables, etc. ▼……Has a structure represented by (I) and has 10 to 3 repeating units
0 mol% is formula (II) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ ………(II) An aromatic copolyimide having the structure represented by, or 70 to 90 mol% of the repeating units is formula (III) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼......(III) It has a structure represented by and has a repeating unit of 30 to 1
0 mol% is the formula (IV) ▲There are mathematical formulas, chemical formulas, tables, etc.▼......(IV) , A solution of 0.05 to 10 parts by weight of the aromatic copolyimide or copolyamideimide dissolved in a mixed solvent containing 100 parts by weight of dioxane and 5 to 50 parts by weight of another organic polar solvent is applied, dried, and heat treated. A method for producing a composite separation membrane characterized by the following. (2) Claim 1, wherein the organic polar solvent is a solvent selected from dimethylformamide, dimethylsulfoxide, dimethylacetamide, or N-methylpyrrolidone.
Manufacturing method described in section.