JPS62114611A - Method for producing separation membrane - Google Patents

Abstract

PURPOSE:To produce a separation membrane having excellent separation performance, heat-resisting property, chemical resistance, and mechanical characteristics with good reproducibility, by dissolving specific aromatic copoly (amide)-imide into an organic polar solvent, forming a thin membrane from a resultant dope liquid. CONSTITUTION:Copolyimide represented by (A) formula I (R, wherein 10-30mol% of its cyclic units is formula II and 90-70mol% thereof being a group of formula III, IV) or copolyamide imide wherein cyclic units of (B) formula V being 90-70mol% and those of formula VI being 10-30mol% is dissolved into an organic polar solvent such as N,N-dimethylformamide, etc., and a thin membrane is solidified in a solidifying liquid using resultant solution as a doping liquid; thereafter a separation membrane is obtained by heating and drying said thin membrane. The separation membrane obtained in a manner as stated above will keep its characteristics of membrane even after the thermal history, for example, of 100-250 deg.C and can perform separation of high temperature gas of 60-180 deg.C over a long period of time.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention is directed to the use of an m-liquid dope solution obtained by dissolving a specific aromatic copolyimide or aromatic copolyamideimide in a polar organic solvent. This method involves forming a liquid thin film, solidifying the thin film, and then heating and drying it to produce a copolyimide or copolyamide-imide separation membrane.

[Conventional technology]

Conventionally, a membrane with an asymmetrical structure of cellulose acetate threads has been well known as a separation membrane, and its manufacturing method involves using an acetone-formamide mixed solution or a solution in which a metal field is dissolved in that solution as a solvent. A method of preparing a dope solution by dissolving cellulose acetate in it, forming a thin film of the dope, partially evaporating the solvent from one side of the thin film, and then immersing the film in cold water. was known.

However, such cellulose acetate-based separation membranes have been unsatisfactory as they have insufficient properties in terms of heat resistance, chemical resistance, microbial resistance, PH resistance, consolidation resistance, resistance to n, etc. .

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

In particular, aromatic polyimide thread membranes have excellent heat resistance, mechanical properties and chemical resistance, and are therefore expected to be useful as separation membranes.

However, the thin film is imidized in a coagulation liquid using a known method for producing a porous polyimide film, which involves dissolving polyamic acid obtained by a polymerization reaction of tetracarboxylic dianhydride and aromatic diamine. However, the method of producing an aromatic polyimide film by solidifying it requires operations such as film formation from a polyamic acid solution, coagulation, and imidization, making it a complicated method that is extremely difficult to control. There was a drawback that it was not possible to stably produce a polyimide film with stable quality and 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 phenolic compound such as P-chlorophenol, The aromatic polyimide dissolved in the phenol compound melt must be coagulated with a coagulating liquid to form a dense phase and a porous layer at the same time to form a coagulated film, which is extremely difficult to operate, and provides stable performance with good reproducibility. If it is difficult to make a separation membrane, or if a solvent whose main component is water, which is non-polluting, is used as the coagulation liquid, the porous layer will not develop sufficiently due to the slow coagulation rate. There is a tendency for dense 1 to develop, and in extreme cases, coagulation itself may take a long time or the obtained polyimide separation membrane may not have sufficient permeation performance.

[Purpose of the invention]

In view of the above points, the present inventors have developed a separation membrane that does not require complicated methods such as imidization in the steps of membrane formation, coagulation, drying, and heat treatment, and has stable and good separation performance. As a result of intensive discussions, a copolyimide or copolyamideimide solution obtained by dissolving a specific aromatic copolyimide or aromatic copolyamideimide in a polar organic solvent and an aromatic hydrocarbon solvent was used as a total dope solution. By coagulating a thin film of the dope solution in a coagulation solution, followed by heating and drying, it was possible to stably produce a separation membrane with excellent separation performance, heat resistance, chemical resistance, and mechanical properties with good reproducibility. Heading The present invention has been arrived at.

That is, the gist of the present invention is a copolyimide having a structure represented by the repeating unit of the general formula (1), in which 10 to 30 mol% of the repeating unit is one in which R represents 0C40; qo~70 mole copolyimide or repeating unit? θ ~ ri O mol S has a structure represented by formula (11), and 70 to 3 of the repeating unit
A copolyamide-imide having a structure in which the molar ratio of , then heating the thin film 1. The present invention resides in a method for producing a separation membrane characterized by drying.

[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 10 to 30 mol% of the above repeating units, R is -0
-C--0-, and the molar ratio of 90 to 70 of the repeating units is R.

This copolyimide contains j,3',≠,4t'-benzophenonetetracarboxylic dianhydride in an appropriate molar ratio, and di'-methylenebisphenyl isocyanate (y,4t').
-diphenylmethane diisocyanate) and tolylene diisocyanate (1,lI-isomer, or it-co,
6-isomer, or a mixture thereof) in the presence of a polar compound.

Furthermore, in the aromatic copolyamideimide used in the present invention, 70 to 90 mol% of the repeating units have a structure represented by formula (1), and 30-1 of the repeating units are
0 mol S is the formula (IV) 1゛1°0-0'0ONHゝαOH,0... (
It is a copolyamideimide having the structure represented by (b). This copolyamideimide is described in U.S. Patent No. J, 9.2.
9 A 9 / No. 9 A 9 /. Such copolyamideimides can be prepared with a mixture of trimellitic anhydride and inphthalic acid in a ratio of about 70 to about 90 moles 2 to about 30 moles S to about 7Q mole ratio using the procedures described in the aforementioned patents. Approximately equal amounts of ioo mole S can be readily obtained from the reaction of ali'-methylene bisphenyl isocyanate.

The solvents used for polymerizing and dissolving the copolyimide or copolyamideimide are polar organic solvents such as dimethylformamide, dimethylacetamide, N-methylpyrrolidone, dimethylsulfoxide, dimethylsulfone, hexamethylphosphoramide, tetra Methyl original slip,
Examples include pyridine, but are not particularly limited. However, it may be used in combination with these.

For the copolyimide according to the invention, preferably dimethylformamide and N-methylpyrrolidone are used, more preferably dimethylformamide. For the copolyamideimide, preferably dimethylformamide, dimethylacetamide, N-methylpyrrolidone is used, more preferably dimethylformamide is 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 viscosity of the desired copolyimide or copolyamideimide, and is usually about 511% by weight, although the weight of the copolyimide or copolyamideimide is
to about J, tmtX are preferred.

The logarithmic viscosity (ηinh) of the copolyimide or copolyamideimide used in the present invention is θ, /dj or more, more preferably o, J-4Idt7y (O, S% in N-methylpyrrolidone, 1).

A thin film can be obtained from the polyimide or polyamide powder solution by sanding, roll coating, spin-coating on a flat plate such as a glass plate, or by increasing the coating size. This can be carried out by a known method such as a commonly employed hollow fiber method.

However, it is also possible to provide a support for the membrane by casting on a suitable porous (porous hollow fiber) backing material. Any inert porous material that does not block the passage of permeate gas 1 through the membrane and is not attacked by the membrane material, solvent, or coagulation liquid can be used as the porous support.

Typical supports for this shield include metal mesh,
Porous ceramics, sintered glass, porous glass, so-called bonded metals, paper, porous non-phosphorus-injected plastics, etc. are preferably used; for example, nonwoven fabrics such as rayon, asbestos,
Examples include porous polyimide. These materials do not participate in the separation and merely act as supports for the membrane. It is preferable that the thickness of the thin film of the dope liquid is usually less than l-.

Once a thin film is formed, it is immediately immersed in a coagulation solution.
In this case, while forming the thin film or after forming the thin film,
~/! 4 in the atmosphere at θ°C, preferably 1Io to 10°C.
A portion of the solvent in the thin film may be evaporated off by heating for ~300 seconds, preferably 70-110 seconds, more preferably 20 seconds, and then solidified. You may also spray heat lice 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.

The tablet can be appropriately selected from those having good compatibility with the dope solution and having low solubility (poor solubility) in polyimide or polyamideimide. Examples include water, lower alcohols such as propatool, keto/groups such as acetone, ethers such as ethylene glycol, aromatics such as toluene, or mixtures thereof, but there are problems with economic efficiency, pollution, etc. A range from 30 to 30 degrees Fahrenheit is preferably used.

Any known method may be used to coagulate the thin film by evaporating a part of the liquid or solvent. Examples include a method in which the hollow fiber is immersed in a coagulating liquid, and a method in which only a thin film of the hollow fiber is immersed in a coagulating liquid.

After coagulation, the wet film is preferably air-dried or immersed in an alcohol or hydrocarbon to reduce the concentration of the solvent and coagulation liquid.

Next, in the case of a copolyimide film, 5o-eo.

°C, preferably in the range of ioo to 3SO °C, in the case of copolyamide-imide membranes, in the range of 0 to 310 °C, preferably in the range of ioθ to
The solvent and the impregnated coagulating liquid are removed by heating and drying in the JOO℃ range.For example, the temperature If may be gradually raised from room temperature, or within each temperature range. The temperature may be increased in multiple steps. If drying is carried out too rapidly, foaming may occur, which is not preferable.

The above-mentioned heating drying temperature and time of the coagulated wet film, and i (coagulated film) vary depending on the type of cup, the amount of evaporated components in the coagulated wet film, etc., so they can be determined as appropriate for each specific example. good.

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

In the method of this invention, the concentration of polyimide or polyamideimide in the dope solution, the dissolved dOAL, the combination of solvents, the addition of swelling agents, the evaporation conditions, the type of coagulant, the coagulation conditions, etc. The layer thickness can be easily changed.

However, copolyimide or copolyamide-imide compounds dissolved in polar organic solvents such as N,N-dimethylformamide, dimethylacetamide, and N-methylpyrrolidone at normal humidity can be dissolved in a coagulating agent such as water without the addition of a swelling agent. In particular, it is not necessary to add a swelling agent because a porous structure can be easily obtained.

The thickness of the copolyimide or copolyamide-imide separator membrane is preferably about 7 to Jθ0μ, more typically an overall thickness of part μ to 100μ.

The copolyimide or V-copolyamide-imide film obtained in the present invention maintains its film properties even when subjected to a thermal history of, for example, 100-U to 0°C, and Gas separation? Can be carried out over a long period41
- Shows high heat resistance and excellent chemical resistance. Also,
The separation performance in the gas permeation test described below is also extremely excellent. SOθ degree, and the n-th methane permeability (methane permeation rate Q, +jH&) is /X/0-7cn! /cur ・l3ea -c
mlJ Above, under certain conditions, 5xiozu style/(
It reaches yIa sec・anHg degree. In addition, the tensile strength, tensile strength, and elongation at break have been significantly improved, so that it can be used in practical applications with great advantage.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to examples.

Evaluation regarding gas permeability characteristics is expressed using the unit of gas permeability coefficient P=cm·cm/crl·eec'cmk1g, which is converted to the thickness of material 1 (7).

On the other hand, in the case of a separation membrane, the permeation rate depends on the thickness of the material itself: 1.11 Q = crtt/crtl ・s
It is expressed in units of ec OcmHg, and lθμ and 7
For a film thickness of μ, the permeation rate is 10 even though the permeability coefficient is the same.
There will be a difference of twice as much.

Therefore, the essential property is the permeation rate, which is a function of the membrane thickness.

The water vapor transmission rate was determined by adding 1 to 0 according to JIS Z-OR.Manufacturing Example 3/Using the procedure described in Example q of U.S. Pat. A copolyimide was polymerized from a mixture containing J', Q, tI'-benzophene+, and lI'-diphenylmethane diisocyanate.

Polymerized horse mackerel uses N,N'-dimethylformamide and the resin concentration? 'i-/weight S.

The relative viscosity (η1n
h) (in dimethylformamide, o,zx) was O,rudtljl.

Production reference example Pre-dried fc/OL reactor VC&/(1, g2
Jl (3,20 mol) of trimellit 1 anhydride and 1
3 bottles of 90 Jl (0.10 mol) of isophthalic acid were charged. The reactor was equipped with a temperature If meter, condenser, stirrer and nitrogen inlet.

VC1000 in sto dry bottle,t&/(tl
, 0%) of +,+'-methylene bisphenyl isocyanate (hereinafter abbreviated as MDI) was weighed, and then 1
1 J'I rnl N-methylpyrrolidone (hereinafter referred to as N
We measured the MDI (abbreviated as MP) and understood it in layman's terms. This M
The D process was added to the reactor and then 1ilDI was weighed out and 74jo Biao of NMP was added to rinse.

A! The bath was heated from 53 DEG C. to 170 DEG C. over a period of 3 hours to 170 DEG C. and from 1.9 DEG C. to 1 DEG C. over a period of 1 hour under a stirring speed of r rpm and a nitrogen atmosphere. In this way, the random copolyamide-imide NMP has a structure of about 0 moles S of repeating units and fJ 20 moles of repeating units.
jt specific stasis was obtained.

The logarithmic viscosity (η
1nh) (0.3% in N-methylpyrrolidone)
, Le 0 ,? dt7g.

This solution was added to methanol to precipitate a polymer, which was then dried at 130° C. for 3 hours to obtain a copolyamide-imide powder.

The polyimide solution obtained in Reference Example 1 was diluted with N,N'-dimethylformamide to produce a polyimide ha having a weight of 77 mm, which was filtered and purified using a 7 μm Millipore filter. This dope solution was cast onto a glass plate with the width of the chamber, and the thickness was made uniform using a doctor knife. / emid , /mil = λ!
A thin film of μ) was formed, and the glass plate was immediately immersed in water at -0°C. After leaving for 70 minutes, the peeled film was fixed on a metal frame and allowed to stand in water at SO 0 C for 30%. Further, the mixture was left to stand at room temperature for about 1 hour, dried at -00 DEG C. for 1.theta. minutes, and the bath was removed to produce a polyimide film with a thickness of about 1 da O.mu..

Using this polyimide membrane, the gas permeability was calculated by adding 11 to 9, and the result was 1! ! :Obtained.

QH, Oe /, 7XIQ-1' Shin, Ama sea
Bell yrHgQOH,=3Jx10-”LfCdaeeQ
*mHa.

Example U Using the same polyimide solution as in Example 7 as a dope solution, a thin film was formed on a glass plate in the same manner as in Example 1, and then placed in a hot air drying oven and dried at UO°C for 7 minutes, and then immediately , immersed in water at 2Q°C. After leaving for IQ minutes, the peeled membrane was fixed on a metal frame and left in SO''C water for 30 minutes.

Furthermore, tJ opens at 2 o'clock at room temperature! This was then heated and dried at 200° C. for 20 minutes to produce a polyimide film.

Gas permeation performance was measured using this polyimide membrane. The results are shown in Table 7.

Examples 3 to g A polyimide film was produced in the same manner as in Example 3, except that the hot air drying conditions were changed. Table 1 shows the results of drying conditions and gas permeation performance.

Example 9 The polyamideimide solution obtained in Production Reference Example 2 was diluted with N,N'-
It was dissolved in dimethylformamide to produce a 17% by weight polyamideimide solution, which was filtered and purified through a lμ Millipore filter. Cast this dope solution onto a glass plate at room temperature and use a doctor knife to spread it to a uniform thickness.
A thin film was formed, and the glass plate was immediately immersed in water at -0°C. After being left for 10 minutes, the peeled film was fixed on a metal frame and left in SO°C water for 3θ minutes. Further, after being left at room temperature for about an hour, the film was dried by heating at -00°C for Q minutes to remove the solvent, leaving a polyamideimide film with a thickness of about iaoμ.

Using this polyamide-imide membrane, the gas permeability is increased to 111%.
When I1 was added, the following result was obtained.

QH, O= /, / X / 0-” Crd/C71
sea ecmHgQOH4=Qa7X/0−
'cnl/cd1m see mcmHgQH,O/
Q[]H,: u,? 4 ([Effects of the Invention] The copolyimide or copolyamide-imide separation membrane of the present invention can be used, for example, to remove water vapor from petroleum-associated gas, remove water vapor from gas used in the synthesis of sheep processing, and remove water vapor from coke oven gas. It is widely expected to have applications in the industrial field, such as the removal of water vapor.

Claims (4)

[Claims] (1) General formula (I) ▲There are mathematical formulas, chemical formulas, tables, etc.▼...A copolyimide having a structure represented by repeating units of (I), in which 10 to 30 mol% of the above repeating units are R. ▲There are mathematical formulas, chemical formulas, tables, etc.▼, and 90 to 70 mol% of the above repeating units are R, ▲There are mathematical formulas, chemical formulas, tables, etc.▼ and/or A copolyimide that represents ▼ or 90 to 70 mol% of the repeating units has a structure represented by formula (II) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ ... (II) and repeats Unit 10-3
0 mol% is formula (III) ▲There are mathematical formulas, chemical formulas, tables, etc.▼... (III) A solution in which copolyamideimide having the structure represented by formula (III) is dissolved in a polar organic solvent is used as a dope liquid, and the dope is A method for producing a separation membrane, which comprises immersing a thin film of liquid in a coagulating liquid to solidify it, and then heating and drying the thin film. (2) while forming or following the formation of a thin film of dope liquid, partially evaporating the polar organic solvent from one side of the thin film, and then immersing the thin film of dope liquid in a coagulation liquid to solidify it; 2. The method for producing a separation membrane according to claim 1, wherein the separation membrane is then heated and dried. (3) As a polar organic solvent, N
, N-dimethylformamide and/or N-methylpyrrolidone; for the copolyamideimide, N,N-dimethylformamide, dimethylacetamide and/or N-methylpyrrolidone are used. 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, characterized in that water is used as the coagulating liquid.