JPS6274410A - Production process for separating membrane - Google Patents

Abstract

PURPOSE:To produce a separating membrane of high heat resistance and of high chemical resistance effective in removing vapor contained in gas by coagulating a thin film of copolyimide and copolyamideimide solution in the inert gas containing water and organic solvent vapor. CONSTITUTION:The aromatic copolyimide or the aromatic copolyamideimide is solved in the polar organic solvent into a dope. The logarithmic viscosity of polymer is preferably 0.1dl/g or more. A thin film of 1mm or less is produced by the dope having 5-35wt% concentration. Immediately then the said thin film is coagulated in the inert gas containing solvent vapor carrying coagulating power, and heated and containing solvent vapor carrying coagulating power, and heated and dried in the temperature of 50-400 deg.C. The vapor concentration of inert gas is 10-100% of amount of saturated vapor. The temperature of inert gas is -10-100 deg.C, and a normal pressure can be applied.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a copolyimide rainbow #mari or copolyamideimide solution obtained by dissolving a specific aromatic copolyimide or aromatic copolyamideimide in a polar organic solvent. using,
This method involves forming a liquid thin film, coagulating the thin film in an inert gas containing water vapor, and then heating and drying it to produce a copolyimide or copolyamide-imide separation membrane.

[Conventional technology]

Conventionally, cellulose acetate-based asymmetric membranes have been well known as separation membranes, and the method for manufacturing them is to use an acetone-formamide mixed solution or a solution of a metal salt dissolved in that solution as a solvent, and to add cellulose acetate to the solution. A known method is to prepare a dope solution by dissolving the dope solution, form a thin film of the dope solution, partially evaporate the solvent from one side of the thin film, and then immerse the thin film in cold water. However, such cellulose acetate-based separation membranes have poor heat resistance and
It was unsatisfactory as it had insufficient properties in terms of chemical resistance, microbial resistance, PH resistance, compaction resistance, chlorine resistance, etc.

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, and are also excellent in mechanical properties and chemical resistance, so they are highly expected 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 manufacturing an aromatic polyimide film by coagulating it involves forming a film from a solution of polyamic acid, coagulating it, and imidizing it!
This method is complicated and requires a lot of control, and has the disadvantage that it is not possible to stably produce polyimide separation membranes with stable quality and excellent performance.

In addition, an aromatic polyimide obtained by a polymerization reaction of biphenyltetracarboxylic dianhydride and aromatic diamine dissolved in a melt of a heptanoyl compound such as p-chlorophenol is coagulated to produce a 1i1f # membrane. In this method, the aromatic polyimide dissolved in the phenolic compound melt must be coagulated with a coagulating liquid to create a coagulated film that forms a dense phase and a multi-pentate layer at once, which is extremely difficult to operate and difficult to reproduce. If it is difficult to create a separation membrane with good and stable performance, or if a solvent mainly composed of water, which is non-polluting, is used as the coagulation liquid, the coagulation rate is slow and the porous layer may not fully develop. There is a tendency for a dense layer to develop without solidification, and in extreme cases, solidification itself may take a long time, or
In some cases, the obtained polyimide separation membrane did not have sufficient permeability.

[Purpose of the invention]

As a result of intensive studies in view of the above points, the present inventors have discovered a copolyimide or copolyimide obtained by dissolving a specific aromatic polyimide or aromatic copolyamideimide in a solvent whose main component is a polar organic solvent. By forming a liquid thin film using a polyimide solution, coagulating the thin film in an inert gas containing water vapor, etc., and then heating and drying it, we can improve separation performance, heat resistance, chemical resistance, and mechanical properties. The present invention was achieved by discovering that excellent separation membranes can be produced stably with good reproducibility.

That is, the gist of the present invention is that 90 to 70 moles of the repeating unit have a structure represented by formula (1), and /θ to 3 of the repeating unit
A copolyimide having a structure in which 0 mol th is represented by the formula (n) (It), or a copolyimide in which 70 to 90 thy mol of the repeating unit has a structure represented by the formula (DT), and a repeating unit has a structure represented by the formula (DT). The return unit 3θ~70molti is expressed by the formula (
IV) Using a copolyimide or a copolyamide-imide solution in which a copolyamide-imide having the structure represented by is dissolved in a polar organic solvent as a dope liquid, a thin film of the dope liquid is formed.
It is coagulated in an inert gas containing ~100% selected from the group consisting of water, alcohols, ketones, ethers, aromatic hydrocarbons, or mixtures thereof, and then the thin film is heated and dried. A method of manufacturing a separation membrane is provided.

[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, for 10 to 30 moles of the above repeating unit, R is <ΣC
H, -1-Σ, and 9Q to 20 molti of the above repeating unit is R. This copolyimide is 3.3',
Ayu St'-benzophenonetetracarboxylic dianhydride in appropriate molar ratios of %, %'-methylenebisphenyl incyanate (g, a'-diphenylmethane diisocyanate) and tolylene diinocyanate (2,9 as monoisomer, or a mixture thereof) in the presence of a polar solvent.

Further, the aromatic copolyamideimide used in the present invention has a structure in which 70 to 90 moles of repeating units are represented by the formula (m), and 30 to 7 moles of repeating units
0 molti is a copolyamideimide having a structure represented by the formula (■).

This copolyamide-imide is disclosed in U.S. Patent No. 3.9, No. 9
It is easily produced by the method taught in No. Such copolyamideimides can be prepared from about 7θ molti to about 30 molti to about 7θ molti using the procedures described in the aforementioned patents.
It can be easily obtained from the reaction of a mixture of trimellitic anhydride and inphthalic acid in a proportion of Q molty and a substantially equal amount of ski'-methylenebisphenyl isocyanate in a proportion of ioo molty.

The logarithmic viscosity (ηinh) of the copolyimide or copolyamideimide used in the present invention is o, idt/? Above, more preferably 0.3~', tdl/? (0.5% in N-methylpyrrolidone, measured at 30°C).

The solvent used in the polymerization of copolyimide or copolyamideimide is a polar organic solvent such as dimethylformamide,
Examples include, but are not limited to, dimethylacetamide, N-methylpyrrolidone, dimethylsulfoxide, dimethylsulfone, hexamethylphosphoramide, tetramethylurea, and pyridine. Dimethylformamide, dimethylacetamide, N-methylpyrrolidone, and more preferably dimethylformamide are preferably used. Preferably, the amount of polar organic solvent used in the above polymerization is at least sufficient to initially dissolve all reactants. The amount of solvent used is adjusted depending on the desired viscosity of the copolyimide or copolyamideimide, and although the weight percentage of the resulting copolyimide or copolyamideimide is not very important, it is typically about 5% by weight. % to about 3j% by weight are preferred.

To obtain a thin film from the dope solution of the polyimide or polyamide-imide composition, a method of casting on a flat plate such as a glass plate, a method of roll coating, a method of spin coding, or a conventional method to increase the surface area. This can be carried out by a known method such as the currently employed method of forming hollow fibers.

The membrane can also be further provided with support by casting onto a suitable porous (including porous hollow fiber) backing material. As this porous support, any inert porous material that does not block the passage of permeate through the membrane and is eroded by the membrane material, solvent, and coagulation liquid can be used.

Typical examples of this type of support are metal mesh,
Porous ceramics, sintered glass, porous glass, sintered metals, paper, porous non-dissolving plastics, etc. are preferably used, and examples include nonwoven fabrics such as rayon, asbestos, porous polyimide, etc. These materials do not participate in the separation and merely act as supports for the membrane. The thickness of the dope film is usually /rrr! It is preferably n or less.

Once the thin film is formed, it is immediately coagulated in an inert gas containing water vapor or the like. In this case, while forming the thin film or after forming the thin film, θ~/! θ℃, preferably 0 to 72
2 to 30 θ seconds in the atmosphere at 0°C, preferably 70 to ♂
The thin film may be solidified after being heated for 0 seconds, more preferably for 0 to 10 seconds to evaporate and remove a portion of the solvent in the thin film. You may still blow hot air within the above range. Thereby, the thickness of the surface dense layer in the structure of the asymmetric membrane can be changed, and the separation performance of the resulting membrane can be easily controlled. Water vapor dissolves into the film from the surface of the thin film, but water has good compatibility with the dope solution and has low (poor) solubility with the present copolyimide or copolyamide-imide composition. solvent), it has the effect of coagulating the present copolyimide or copolyamide-imide composition.

Examples of such a coagulating liquid include, in addition to water, lower alcohols such as globanol, ketones such as acetone, ethers such as ethylene glycol, aromatic hydrocarbons such as toluene, or mixtures thereof. Naturally, the vapors of these substances also have a coagulating effect in the same way as water vapor, but water vapor is preferably used from the viewpoint of economy, pollution, etc. The value of □'1.100 of these substances contained in the inert gas is selected from the range of /θ to 700% of the saturated vapor content, preferably tpto to 10 to 100%.

The inert gas must be a gas that does not have any substantial effect on the polyimide or the polyamide-imide composition, the solvent, the vapor of the substance used for coagulation, and the atmospheric atmosphere in which the film is formed. , nitrogen is preferred. The temperature of these inert gases containing water vapor is -/θ~100℃,
Preferably, the range is θ to /θ°C, and the pressure may be normal pressure.

Any known method may be used to solidify the thin film in liquid form or in which a portion of the solvent has been evaporated. Examples include a method in which a thin film is coagulated together with a substrate on which the thin film is formed in an inert gas containing water vapor or the like, or a method in which only the hollow fiber thin film is coagulated in an inert gas containing water vapor or the like.

It is preferable that the coagulated wet film is air-dried or immersed in alcohol or hydrocarbons, so that the concentration of the solvent and coagulation liquid is kept low.

Next, in the case of a copolyimide film, the temperature is 50 to 00°C, preferably 100 to 300°C, and in the case of a copolyamide-imide film, the temperature is 50 to 350°C, preferably 700 to 300°C.
Heating and drying is carried out within a range of 0.degree. C., and the method may be, for example, by gradually increasing the temperature from room temperature at any time, or by increasing the temperature in multiple steps within each temperature range. Too rapid heating and drying may cause foaming, which is undesirable.

The heating and drying temperature, time and thickness of the coagulated wet film described above may vary depending on the type of solvent, the amount of evaporated components in the coagulated wet film, etc., and may be determined as appropriate for each specific example.

Although it is possible to use the membrane without heating and drying as described above as a separation membrane, performing the heating and drying described above improves the separation performance of various gases, the tensile strength,
Membrane strength such as tensile elongation at break is significantly improved.

In the method of this invention, the porosity and pore shape are determined by the concentration of polyimide or polyamideimide in the dope solution, the type of solvent, the combination of solvents, the addition of a swelling agent, the evaporation conditions, the type of coagulant, the coagulation conditions, etc. , the thickness of the dense layer can be easily changed.

However, copolyimide or copolyamide-imide compositions dissolved in polar organic solvents such as N,N-dimethylformamide, dimethylacetamide, and N-methylpyrrolidone at room temperature can be dissolved in coagulants such as water without the addition of a blowing agent. Since a porous structure can be easily obtained in the presence of a swelling agent, it is not necessary to add a swelling agent. The thickness of the copolyimide or copolyamide-imide separation membrane is about /~200μ, more typically co-O
A thickness of ~10θμ is preferred.

The copolyimide or copolyamide separation membrane obtained by the present invention maintains its membrane properties even after being subjected to a thermal history of 700 to 260°C, and can maintain the separation of gases at high temperatures of about 10 to 260°C for a long time. It exhibits high heat resistance such that it can be used for a long period of time, and also has excellent chemical resistance. In addition, the separation performance in the gas permeation test described below is also excellent. The permeation performance (methane permeation rate Q, CH,) is /
x 1O-7cl/ca-esc-cm Hy or more. Furthermore, compared to membranes obtained by immersion coagulation in water instead of hygroscopic coagulation in water vapor, the tensile membrane strength and tensile elongation at break have been significantly improved, making it extremely advantageous for practical use. can do.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples.

Evaluation regarding gas permeability characteristics is expressed using the unit of gas permeability coefficient: p=7-C1n/cn4·θec*cmHy, which is converted into material/G thickness.

On the other hand, in the case of a separation membrane, the permeation temperature of the material itself is Q = crti/ad ・see -cm
It is expressed in units of Hy, and even if the permeability coefficients are the same for film thicknesses of 70μ and /μ, there is a tenfold difference in the permeability coefficients. Therefore, the required characteristic is the permeation rate, including the influence of membrane thickness. The water vapor permeability coefficient was measured according to J Engineering S Z20♂.

Preparation Reference Example: 3.3',4t,a'-benzophenonetetracarboxylic anhydride and 10 moN% Toso 1 / diisocyanate and 20 mole glue J'-
A copolyimide was polymerized from a mixture containing diphenylmethane diisocyanate.

N,N'-dimethylformamide was used as the polymerization solvent, and the resin content was 1/2.

The relative viscosity of this copolyimide at 30°C (η1nh
) (O,j% in dimethylformamide) is 0,6dt
/W.

Production reference example: Into the pre-dried /θt reactor, 2? (3,2
0 mol) of trimellitic anhydride and /3, ? θf
(OJO mol) of inphthalic acid was charged. The reactor was equipped with a thermometer, condenser, stirrer and nitrogen inlet.

7000,9t r (u, 0
Weigh out t, t, 9t/-methylene bisphenyl isocyanate (hereinafter abbreviated as MDI) (mole), and then
13% li of N-methylpyrrolidone (hereinafter abbreviated as NMP) was removed to dissolve MDI.

This MDI solution was added to the reactor and then 36jOwl of NMP was added to weigh out the MDI and rinse the bottle.

The solution was heated in a tube from 53° C. to 77° C. for 3 hours and 0 minutes under a stirring speed of &j rpm and a nitrogen atmosphere and then heated for an additional hour/hour. The mixture was heated to 1/6°C to 7/°C. In this way, NMP of a random copolyamide-imide in which about 0 moles of repeating units have a structure of K and about 20 moles of repeating units have a structure of 12j''
A weight i% solution was obtained.

Logarithmic viscosity It of this copolyamideimide at 30°C
(η1nh) (θ, !% in NMP) is 0. t03d
i/? Met.

This solution was added to methanol to precipitate a polymer, which was then dried at 750° C. for 3 hours to obtain a copolyamide-imide powder.

The polyimide solution obtained in Example/Reference Example/ was diluted with N,N'-dimethylformamide to produce a polyimide solution of 77 layers, which was filtered and purified using a μ Millipore filter. This dope solution was cast on a glass plate at room temperature, and the thickness was uniformized using a doctor knife / 9tmj, L: / m1 = 25
A thin film of the dope solution was formed as μ) and left in an atmosphere of 1.20°C and 50% relative humidity for 20 hours.
The solvent was removed by heating and drying for 2Q minutes, and the membrane was peeled off from a glass plate to produce a polyimide porous membrane with a thickness of about % j II. When a gas permeation test was conducted using this polyimide porous membrane, the water vapor permeation rate QH, O
, methane permeation rate 11 Qcn, , separation performance of water vapor and methane (ratio of permeation rate of water vapor and methane) Q, H, o
/QaH4 was as follows.

QH,O=6. wa×/θ-' cr/l/cr/l
-sec @crrHyQ, C1(,=ko0.2 x
10-” crA/li-sec *cmHyQ,H
, o/QcH, = J' 3 The tensile strength of this film was 2.3 A/-1, and the elongation at break was 2.2%.

The polyamide-imide solution obtained in Examples and Reference Examples was diluted with N,N'-dimethylformamide to produce a polyamide-imide solution having a concentration of 77% by weight and was purified by filtration with a /μ Millipore filter. This dope solution was cast onto a glass plate at room temperature, left for 20 hours with a doctor knife, heated and dried at 200°C for 20 minutes to remove the solvent, and the film was peeled off from the glass plate to a thickness of approximately /jθμ. A porous polyamide-imide membrane was manufactured. When we conducted a gas permeation test using this membrane, we found that Q, H, O% Q, OH,, Q, H, O/Q, OH4
was as follows.

OH20= 41% X/Ocrl/cF7! IS
ec TcmHyQ, 0H4 = /, 9 X 10-'' QH, o/Q, aH4 = 3 da Further, the tensile strength of this film was /, !kLi/md, and the tensile elongation at break was 79%.

Comparative Example/Example/A thin film was formed using the same polyimide solution in the same manner as in Example/.
The glass plate was immersed in water at 20°C, and after being left for /θ minutes, the peeled film was fixed on a metal frame and soaked in water at sO°C for 30 minutes.
It was left standing for a minute. After leaving it in the air at room temperature for about 7 hours,
Dry by heating at 200℃ for 20 minutes to remove the solvent, and the
A polyimide porous membrane with a thickness of μ was produced. When a gas permeation test was conducted using this membrane, the following results were obtained.

QH, O=/, 7X/(7ad/d fist 8ec*cmHy
QOH,=l! x 10-” Also, the tensile strength of this film is θ, 7 Ay/md
, the tensile elongation at break was the same.

Comparative Example: A thin film was formed using the same polyamide-imide solution as in Example 2, immersed together with the glass plate in water at -0°C, left for /θ minutes, and the peeled film was fixed on a metal frame. It was placed in water at 0.degree. C. for 3.theta. minutes. Further, the mixture was allowed to stand in the air at room temperature for about 7 hours, and then heated and dried at 200° C. for 20 minutes to remove the solvent, thereby producing a polyamideimide porous membrane with a thickness of about 3 μm. When a gas permeation test was conducted using this membrane, the following results were obtained.

QH! o=/, 2X10 i/cn fist 5ec-(BH
yQcH,= Jj
The tensile elongation at break was 3%.

〔Effect of the invention〕

The copolyimide or copolyamide-imide separation membrane obtained by the present invention can be used, for example, to remove water vapor from petroleum-associated gas,
Removal of water vapor in gases subjected to synthesis of chemical processes,
It is widely expected to be applied in industrial fields, such as removing water vapor from coke oven gas.

Applicant: Mitsubishi Chemical Industries, Ltd. Agent: Patent attorney: Yo Hase - and 7 others Procedural amendment (voluntary) July 75, 1985 1 Indication of case: 1985 Patent Application No. 2/Da/4
t7 No. 3 Person making the amendment

Claims (4)

[Claims] (1) 90 to 70 mol% of repeating units are of the formula (I) ▲
There are mathematical formulas, chemical formulas, tables, etc. ▼・・・・・・It 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) Copolyimide having the structure represented by, or 70 to 90 mol% of the repeating units is formula (III) ▲Mathematical formulas, chemical formulas,
There are tables, etc. ▼・・・・・・(III) It has the structure expressed as 30 to 1 repeating unit.
0 mol% is the formula (IV) ▲There are mathematical formulas, chemical formulas, tables, etc.▼・・・・・・(IV) Copolyimide or copolyamide made by dissolving copolyamideimide having the structure represented by the following in a polar organic solvent. An imide solution is used as a dope solution, and a thin film of the dope solution is heated with one type of vapor selected from the group consisting of water, alcohols, ketones, ethers, aromatic hydrocarbons, or mixtures thereof. A method for producing a separation membrane, comprising coagulating it in an inert gas containing a saturated vapor amount x 100 of 10 to 100%, and then heating and drying the thin film. (2) A separation membrane according to claim 1, characterized in that a thin film of the dope liquid is hygroscopically coagulated in an inert gas having a relative humidity of 10 to 100%, and then the thin film is heated and dried. Production method. (3) A patent claim characterized in that while or after forming a thin film of dope liquid, a portion of the polar organic solvent is evaporated from one side of the thin film, and then solidified, and then the thin film is heated and dried. A method for producing a separation membrane according to item 1 or 2. (4) The method for producing a separation membrane according to any one of claims 1 to 3, wherein the inert gas is air or nitrogen.