JPS6274411A - Production process for separating membrane - Google Patents

Abstract

PURPOSE:To produce a separating membrane of high capability of removing vapor out of organic compound gas effectively by coagulating the thin film consisting of the solution of aromatic copolyimide and aromatic copolyamideimide and then heating and drying up. CONSTITUTION:After the aromatic copolyimide or the aromatic copolyamideimide being solved in the polar organic solvent to the extent of 5-35wt% concentration, 1-40wt% of the aromatic hydrocarbon out of which polymer is not separated, is mixed. The thin film 1mm or less is produced by the dope thus provided. The said thin film can be coagulated immediately either in liquid or in gas. Coagulation is carried out either in water at the temperature of 0-50 deg.C or in inert gas containing vapor having relative humidity 10-100% at the temperature of -10-100 deg.C. After that, it is heated up and dried at a temperature of 50-400 deg.C.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention provides a copolyimide single ridge structure in which a specific aromatic copolyimide or aromatic copolyamideimide is dissolved in a polar organic solvent and an aromatic hydrocarbon solvent. Or, it relates to a method of manufacturing a separation membrane of copolyimide or copolyamide-imide by using the copolyamide-imide solution as a dove solution, forming a liquid thin film, solidifying the thin WX, and then drying by heating. be.

[Conventional technology]

Conventionally, cellulose acetate-based membranes with asymmetric structure have been used as separation membranes (known as ``cellulose acetate membranes''). After dissolving cellulose acetate and preparing a dope solution ya', forming a thin film of the dope solution and partially evaporating the solvent from one side of the thin film in step 7,
A known method was to immerse the thin film in cold water.

However, such cellulose acetate-based separation membranes have been unsatisfactory, having insufficient properties in terms of heat resistance, chemical resistance, microbial resistance, PH resistance, compaction resistance, salt accumulation resistance, etc.

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

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

However, using a polyamic acid solution obtained by the polymerization reaction of tetracarboxylic dianhydride and aromatic diamine, which is a known method for producing porous polyimide membranes, the thin film is imide-coated in a coagulation solution. The method of producing an aromatic polyimide film by coagulating while converting 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. This method has the disadvantage that it is not possible to stably produce a polyimide separation membrane with stable quality and excellent performance.

In addition, in the method of creating 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, , it is difficult to coagulate the aromatic polyimide dissolved in the phenolic compound melt using a coagulating liquid to form a dense phase and a porous layer at the same time, and the coagulating liquid is non-polluting water. When using a solvent with a main fraction of In some cases, the process itself took a long time, and the resulting polyimide separation membrane did not have sufficient permeation performance.

[Purpose of the invention]

As a result of intensive studies in view of the above points, the present inventors have found that a specific aromatic copolyimide or aromatic copolyamideimide? By using a polar organic solvent to coagulate a thin film of the dope solution, and then drying it, a separation membrane with excellent separation performance, heat resistance, chemical resistance, and mechanical properties can be produced stably with good reproducibility. We have arrived at the present invention, which we hope can be manufactured.

In other words, the gist of the present invention is the repeating unit? A structure in which O ~ 70 moles or more is represented by formula (I)? and repeating units of 10 to 3
0 mol% is the structure represented by the formula (■)? A copolyimide having 70 to 0 moles of repeating units is represented by the formula Cm)!
A bath liquid in which a copolyamideimide having a structure in which 3θ to /θ mo, 7+/% of the repeating units is represented by the formula (IVJ) is dissolved in a polar organic solvent and an aromatic hydrocarbon solvent. A method for producing a separation membrane is characterized in that a thin film of the dope liquid is coagulated, and then the thin film Y71[++ is heated and dried.

[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, 10 to 30 mol of the above repeating unit is R1/C
>CH2/9 of the above repeating unit
θ~70 mole is R This copolyimide is J, J',
+, , @/-benzophenonetetracarboxylic dianhydride in an appropriate molar ratio, t'-methylene bisphenyl isocyanate (Kihiro'-diphenylmethane diinocyanate) and tolylene diisocyanate (-μm isomer, or their mixture] in the presence of a polar solvent.

Furthermore, in the aromatic coboriatimide used in the present invention, 70 to 90 mol% of the repeating units have a structure represented by the formula (■), and 30 to 1 of the repeating units have a structure represented by the formula (■).
0 mol% is copolyamideimide having the structure represented by formula (■).

This copolyamideimide is disclosed in U.S. Pat.
It is easily manufactured by the method taught in No. Such copolyamide-imides can be prepared using trimellitic anhydride and isophthalate/isophthalate in a ratio of from about 70-1 to about 30 to about 7 theta moles using Procedure Z described in the aforementioned patent.
I
- It can be easily obtained from the reaction of methine bisphenyl isocyanate.

Logarithmic viscosity (ηinh) &t O, / d6/f of the copolyimide or copolyamideimide used in the present invention
i or more, more preferably θ, 3~u chi/fj (
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 dimethylacetamide, N-methylpyrrolidone, dimethylphorphogide, dimethylsulfone, hexamethylphosphoramide, tetramethylurea, pyridine, etc., but are not particularly limited. Dimethylformamide, dimethylacetamide, N-methylpyrrolidone, and more preferably dimethylformamide are preferably used.

The amount of polar organic solvent used in the above polymerization is preferably small (but sufficient) to initially dissolve all reactants. It is adjusted by the viscosity of

The weight percent of the obtained copolyimide or copolyamideimide is only 1! Although not necessary, it is typically preferred to have a range of from about 5 folds to about 33 folds.

The copolyimide or copolyamide-imide thus obtained is used as a dope solution using a mixed solvent of the aforementioned polar organic solvent, which is a good solvent, and an aromatic hydrocarbon, which is a poor solvent.

The method for dissolving is not particularly limited, but since the copolyimide or copolyamideimide is obtained as a solution dissolved in a polar organic solvent after the above-mentioned polymerization reaction,5 usually this solution is added with a poor solvent for aromatic hydrocarbons. Mix to the extent that copolyimide or copolyamideimide does not precipitate.

A poor solvent is a solvent that has compatibility Y with the solvent in the solution and has low solubility with the solute. The poor solvent for aromatic hydrocarbons referred to in the present invention is one in which a hydrogen atom, an A-P/l/ group, an alkoxyl group, an aralkyl group, a halogen atom, etc. are bonded to six carbon atoms of a benzene ring, such as Benzene, toluene, 0-xylene, m-4'ren,
Examples include p-xylene, mesitylene, turene, ethylbenzene, isopropylbenzene, chlorobenzene, and the like. Preferably benzene, toluene, 0-
Xylene, m-xylene.

p-xylene is preferably used. Furthermore, it is also possible to use mixtures of the substances mentioned.

The concentration of the aromatic hydrocarbon mixed as a poor solvent should be selected appropriately depending on the type of substance. For example, in the case of toluene, the content is /-'10% by weight, preferably in the range of 70 to 30% by weight. By mixing in this concentration range, it is possible to form a sieve film of 1 strength. This concentration range? If the amount is exceeded, the copolyamide-imide composition will precipitate, which is undesirable.

In this way, the aromatic hydrocarbon mixture is conveniently used as a dope solution.

To obtain a thin film from the polyimide or polyamide-imide dope solution, a method of casting on a flat plate such as a glass plate, a method of roll coating, a method of spin-coating, or a hollow coating method that is usually adopted to increase the surface area. This can be done by a known method such as a method of making thread.

Alternatively, the membrane can be further provided with a support by casting onto a suitable porous (including porous hollow fiber) backing material. The porous support can be any inert porous material that does not block the passage of permeate gas through the membrane and is not immersed in the membrane material, solvent, or 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. It is preferable that the thickness of the thin film of the dope solution is usually less than 1/ml.

After 20-/! 0°C, preferably UO~/koθ
1 to 300 seconds in the atmosphere at ℃, preferably /θ~igo
The thin film may be solidified after being heated at zero power for 20 to 20 seconds, preferably 20 to 20 seconds, to evaporate and remove a portion of the solvent in the thin film. Alternatively, hot air may be blown 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.

Coagulation can be carried out in either liquid or gas (for example, the liquid coagulation bath should be one that has good compatibility with the dope solution and has low solubility with the polyimide or polyamide-imide composition (poor solvent)). For example, water, lower alcohols such as propano-I, ketones such as acetone, ethers such as ethylene glycol, aromatic compounds such as toluene, or a mixture thereof. However, water is preferably used from the viewpoint of economy, pollution, etc.

The temperature of the water used is preferably in the range of 0 to 50°C, preferably 0 to 30°C.

Further, as the gas bath, vapor of the poor solvent mentioned above can be used, but water vapor is preferably used from the viewpoint of economic efficiency, pollution, etc.

Water vapor is usually used in a mixture with an inert gas because its vapor pressure is lower than atmospheric pressure.

The content of water vapor is selected from the range of 10 to 100%, preferably 1 Io-ioo% relative humidity.

Inert gases must be polyimide or polyamideimide, solvents, water vapor used for coagulation, and gases that have no substantial effect on the atmospheric atmosphere during film formation. preferable. The temperature of these inert gases containing water vapor is preferably in the range of -100 to 700°C, preferably 0 to 0°C, and the pressure may be normal pressure.

Part of the liquid or solvent! Any known method may be used to solidify the evaporated thin film. For example, the thin film may be immersed together with the base material on which it is formed into the coagulating solution, or the thin film may be coagulated only with a hollow fiber thin film.
Examples include a method of immersing it in a liquid.

The coagulated wet film is preferably air-dried or immersed in alcohols/hydrocarbons to reduce the concentration of the solvent and coagulating liquid.

Next, in the case of a copolyimide film, it is heated and dried at a temperature of 30 to 00°C, preferably 100 to 350°C, and in the case of a copolyamide-imide film, it is heated and dried at a temperature of 30 to 350°C, preferably 100 to 300°C. The solvent and the impregnated coagulating liquid are removed by, for example, increasing the temperature gradually from room temperature, or increasing the temperature in multiple steps within each temperature range. If the cutting edge heat drying is carried out too rapidly, foaming may occur, which is undesirable.

The drying time and the coagulation film thickness of the coagulated wet film described above will vary depending on the type of solvent, the amount of evaporated components in the coagulated wet film, etc., and should be determined as appropriate for each specific example. That's fine.

Although it is possible to use the above-mentioned membrane without heating and drying as a separation membrane, drying the above-mentioned DfP and drying improves the separation performance of various gases, tensile strength, tensile elongation at break, etc. The film strength is significantly improved.

In the method of this invention, the shape and density of the pores and pores are determined depending on 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. Layer filling 2 can be easily changed.

However, it is soluble in polar organic solvents such as N,N-dimethylformamide, dimethylacetamide, and N-methylpyrrolidone at room temperature; polyimide or copolyamide-imide compositions can be dissolved in coagulants such as water without the addition of swelling agents. Since a porous structure can be easily obtained, no swelling agent may be added.

The thickness of the copolyimide or copolyamideimide separation membrane is preferably about 1 to 300μ, more typically an overall thickness of 20μ to iooμ.

It maintains its membrane properties even after a long history, and exhibits high heat resistance, such as being able to separate gases at temperatures as high as 0 to 10 degrees Celsius over a long period of time, and is also excellent in chemical resistance.

In addition, the separation performance of the gas permeation nut described later is also extremely excellent.
is about 20 or more, and the methane permeation performance (methane permeation rate QcH4) is /X / 0-7cr/l/crIt
- Sec-anHg or more. In addition, the tensile strength and tensile elongation at break have been significantly improved, making it extremely advantageous in practical use.

〔Example〕

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

For evaluation of gas permeability characteristics, the unit of gas permeability coefficient is P=crllcIIL/c! It is expressed using IIIBecjmouthHgt, which is converted into material/crrL thickness.

-1. In a separation membrane, the permeation rate is due to the thickness of the material itself Q = d/cr71・sec・mH
It is expressed in units of g, and even if the permeability coefficient is the same for film thicknesses of 70μ and /μ, the permeation rate is i.

There will be a difference of twice as much.

Therefore, the required characteristic is the permeation rate, including the effect of membrane flotation.

The water vapor permeation rate was measured in accordance with R.Szrogvc.

Reference Example: J, J? a, q'-benzophenonetetracarphonic anhydride and tolylene diisonanate with a 0 molar coefficient and =θ molar coefficient <z, <<'
A copolyimide was polymerized from a mixture containing -diphenylmethane diisonanate.

The polymerization solvent used was N, N/-dimethylformamide Yf, and the resin concentration was co/i! [Amount%.

Relative viscosity of this copolyimide at 30°C ('7in
hJ (0.3% in dimethylformamide) is o, t,
cLl/g.

Production reference example 61μg and 2g (3,2
0 mol) of trimellitic anhydride and /3 co, 2θi
cO, gO mol of isophthalic acid was charged. The reactor was equipped with a thermometer, condenser, stirrer and nitrogen inlet.

Weigh out 1000.96 g ('1.0 moA/) of Shimari'-methylenebisphenylinone ananate (hereinafter abbreviated as MDI) into a dry bottle of 51, and then add Hiroshi, 3!1.
ml of N-methylpyrrolidone (hereinafter abbreviated as NMP) was weighed out and dissolved in MD. This MI) solution was added to the reactor and then 3 Oml of NMPy was added to the MD weighed bottle for rinsing.

This solution was heated from 3°C to 70' for 3 hours UO min under a stirring speed of 20 rpm and a nitrogen atmosphere.
Heat to C for further hours / minutes / 6 degrees Celsius to /7 / degrees Celsius
heated to. In this way, a 25M mass % solution of IMF of a random copolyamideimide having a structure with about g0 moles of repeating units and a structure with about 20 moles of repeating units was obtained.

The logarithmic viscosity (7
1nh J (o, j% in N-methylpyrrolidone) is 0.
A OJ cil/g.

After this warm face was poured into methanol and polymer 7 was precipitated, /! ; Dry at Q°C for 3 hours to obtain copolyamideimide powder.

Example/Reference Example/Polyimide solution obtained in 7N, N/-dimethylformamide diluted with 77% polyimide solution
Y was produced and filtered and purified using a μmI bore filter. Toluene Y-1 was added to this solution to give a concentration of 7 MIk% and thoroughly mixed to obtain a dope solution. This dope solution was cast onto a glass plate at room temperature and the thickness was uniformed using a doctor knife. /emt1. /mtx=xtμ> thin HY type f
fu, the glass plate was immediately immersed in water at 0°C.

After being left for io minutes, the peeled membrane was fixed on a metal frame and left in water at 50°C for 30 minutes. Further, after being left at room temperature for about an hour, it was heated and dried for -00°C - λθ minutes to remove the solvent and form a polyimide film 'a''M.

Mechanical strength, gas permeation performance and sound were measured using this polyimide Hanyin. The results are shown in Table/.

A polyimide film was prepared in the same manner as in Example except that the temperature of the water used for dipping was 10°C. The results are shown in Table/.

Example 3 A polyimide film was produced in the same manner as in Example 3, except that air containing water vapor at a temperature of 23° C. and a relative humidity of 60% was used instead of water.

Results 2 are shown in Table 1.

The polyamide-imide solution obtained in Examples and Reference Examples was diluted with YN,N'-dimethylformamide to produce a 17% polyamide-imide solution by weight, which was filtered and purified using a /μ Millipore filter. Toluene was added to this solution in an amount of 51% by weight and mixed completely to form a dope solution. This dope solution was cast onto a glass plate at room temperature to form a uniform thickness of 11) using a doctor knife, and the glass plate was immediately immersed in water at 0°C. After being left for 70 minutes, the peeled film was fixed on a metal frame and left in water at SO 0 C for 30 minutes. Further, after being left at room temperature for about an hour, the mixture was dried under low heat for -00C--0 minutes to remove the solvent, thereby producing polyamide-imide Hanyin.

Mechanical strength and gas permeability were measured using this polyamide-imide membrane. The results are shown in Table/.

Example! A polyamide-imide membrane was produced in the same manner as in Example t, except that the temperature of the water used for immersion was 20°C. The results are shown in Table/.

Example 6 A polyamide-imide film was produced in the same manner as in Example 1, except that air (/atmospheric pressure) containing water vapor at a temperature of SS° C. and a relative humidity of 60% was used instead of water. Results Table 7/[Show.

Comparative Example A polyimide film was produced in the same manner as in Example except that the dope solution was prepared without adding toluene. The results are shown in Table 1.

Comparative Example A polyimide film was produced in the same manner as in Example 1, except that the dope solution was not added with cotoluene and the ZJO was not performed. Results table/[show.

Comparative Example 3 Did you implement what you did? A polyimide film tgJ was prepared in the same manner as in 1J3. The results are shown in Table/.

Comparative Example A polyamide-imide membrane was produced in the same manner as in Example q, except that dope solution A was prepared without adding gtoluene. The results are shown in Table/.

HiF! Example 2 A polyamide-imide film was produced in the same manner as in Example f14j except that dope solution 7 was monitored without adding toluene. The results are shown in Table 1.

A polyamide-imide film was prepared in the same manner as flJ6 except that the dope solution was prepared without adding comparative galtoluene. I made a reverse. The results are shown in Table/.

〔Effect of the invention〕

The copolyimide or copolyamide-imide separation membrane of the present invention can be used in industrial fields, such as the removal of water vapor in petroleum-associated gas, the removal of water vapor in gas used for synthesis of chemical processes, and the removal of water vapor in coke oven gas. It is expected that it will be widely applied.

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) which has the structure represented by and has 30 to 1 repeating units.
0 mol% is formula (IV) ▲There are mathematical formulas, chemical formulas, tables, etc.▼・・・・・・(IV) A copolyamide-imide having a structure represented by the formula (IV) is dissolved in a polar organic solvent and an aromatic hydrocarbon solvent. A method for producing a separation membrane, which comprises using a solution as a dope, coagulating a thin film of the dope, and then heating and drying the thin film. (2) While or after forming a thin film of the dope liquid, partially evaporate the polar organic solvent and aromatic hydrocarbon solvent from one side of the thin film, solidify the thin film, and then heat the thin film; The manufacturing method according to claim 1, which comprises drying. (3) The manufacturing method according to claim 1 or 2, characterized in that the thin film of the dope liquid is solidified in water. (4) The manufacturing method according to claim 1 or 2, characterized in that the thin film of the dope liquid is solidified in an inert gas containing water vapor.