HK1169075B

HK1169075B - Polyimide membranes made of polymerization solutions

Info

Publication number: HK1169075B
Application number: HK12109706.2A
Authority: HK
Inventors: M．安格兰克; G．鲍姆加藤
Original assignee: 赢创运营有限公司
Priority date: 2009-07-23
Filing date: 2010-07-22
Publication date: 2015-12-24

Description

Polyimide film made from polymeric solution

Technical Field

The present invention relates to polyimide membranes prepared directly from polyimide polymerization solutions without isolating and then redissolving the polyimide in the form of a solid substance, particularly not in the form of a dry solid substance, more particularly not in the form of a dry powder. The polyimide film according to the present invention may be a flat sheet film or a hollow fiber film. The polyimide membrane can be a porous membrane in the form of a microfiltration, ultrafiltration or nanofiltration membrane, and can also be a non-porous membrane for separating gases. All membranes were globally asymmetric membranes and were prepared by the phase inversion method.

Purpose(s) to

The object of the present invention was to find a process for the preparation of polyimides which does not use any substances which have an interfering effect in the subsequent membrane preparation. In addition, it should be possible to produce films with sufficient mechanical properties using the process of the invention.

Other objects not explicitly mentioned will be apparent from the entire context of the following specification, examples and claims.

Background

The preparation of phase inversion films generally requires polymers that are soluble in conventional water-miscible solvents. Several thousand tons of polyethersulfone membranes are currently prepared according to this method. Possible solvents include, but are not limited to, Dimethylformamide (DMF), dimethylacetamide or N-methylpyrrolidone, among others. Many additives, such as co-solvents, non-solvents, pore formers, hydrophilizing agents, etc., are incorporated to affect the properties of the film. The starting materials are usually pellets here, and the casting solutions are prepared by pasting with solvents and additives. Decisive for the success of the membrane preparation here is also the molar mass and the distribution of the polymers used. Generally, polymers with high molar masses and narrow distributions are desired.

P84 is a polymer well known in the literature and used for the preparation of flat sheet and hollow fibre membranes (US2006/0156920, WO 04050223, US 7018445, US 5635067, EP 1457253, US 7169885, US 20040177753, US 7025804). P84 is sold in powder form in two variants (P84 type 70 and P84HT) of the HP Polymer company of Lenzing/Austria. The user then re-dissolves this powder in the aprotic dipolar solvent and blends it with the additive. From which films can subsequently be produced. However, here, each user (e.g. Air liquidmed, US 2006/156920) reports that films and membranes made therefrom are very brittle and that only blends with other polymers lead to stable films and hollow fiber membranes. The powder must be specially treated so that it has a sufficiently high molar mass (Air liquide wo 2006/092677). Here, the processing time and method are very critical. The result is a powder with slightly different properties but yielding casting solutions with different viscosities. Thus, uniform preparation of polymer films can only be achieved with great difficulty.

P84 is also processed in blends with other polymers (US 2006/156920) so that films made therefrom have sufficiently high stability. However, the disadvantage here is the very good gas separation performance, towards CO₂The plasticizing stability and the chemical stability to many solvents can in some cases be disturbed or even destroyed by the incorporation of other polymers.

The reason for the low molar mass lies in the preparation of the P84 powder. Here, the polymer loses molar mass. The molar masses just after polymerization and after powder preparation are described in Table 1.

Table 1: molar masses after polymerization and after powder preparation of P84 type 70 and P84HAT

It is clear that the polymer loses molar mass during the conversion from the polymerization solution to powder by precipitation.

P84 powder is also used for the preparation of flat films (WO 2007/125367, WO 2000/06293). The same problems apply here as in the preparation of hollow fiber membranes.

Disclosure of Invention

Measurement technique

Viscosity measurement

The dynamic viscosity η is determined by shearing the polymer solution once in a cylindrical gap at a constant temperature of 25 ℃ by prescribing various rotation speeds Ω (or shear gradients γ) and subsequently by prescribing various shear stresses τ.

The measuring instrument used was a HAAKE RS 600 with a liquid temperature-adjustable measuring cup container TEF/Z28, a cylindrical rotor Z25DIN53019/ISO3219 and a disposable aluminium measuring cup Z25E/D ═ 28 mm.

The shear stress τ is measured at a specific shear gradient. The dynamic viscosity eta was calculated from the following equation and was found to be 10s^-1Reported in pa.s under shear gradient of (a).

Function of viscosity

Shear gradient γ ═ M Ω

Shear stress

Eta

Shear factor of the rotor: 12350rad/s

Angular velocity

Determination of molar mass

The molar mass was determined using gel permeation chromatography. Calibration was done with polystyrene standards. The reported molar masses are therefore to be understood as relative molar masses.

The following components and settings were used:

permeability of

For thin films, the gas permeability is given by Barrer (10)^-10cm^3.cm^-2.cm.s^-1.cmHg^-1) Is reported in units. Gas permeability of hollow fiber or flat sheet membrane was measured by GPU (gas permeation Unit, 10)^-6cm^3.cm^-2.s^-1.cmHg^-1) Is reported in units. Flux of nanofiltration and ultrafiltration membranes is in l.m^-2.h^-1Bar^-1Is reported in units.

Gas permeability

Gas permeability was measured by the pressure rise method. Here, a gas or gas mixture is applied to one side of a flat film having a thickness of 10 to 70 μ. On the other side, the permeate side, there was a vacuum (about 10) at the start of the experiment^-2Millibar). Subsequently, the pressure rise on the permeate side over time was recorded.

The permeability of the polymer can be calculated by the following formula:

p. by Barrer (10)^-10cm^3.cm^-2.cm.s^-1.cmHg^-1) Permeability in units of

V_{Dead volume}.. in cm³Volume per unit of permeate side

MW_{Gas (es)}.. in g.mol^-1Molar mass of gas in units

Film layer thickness in cm

In g.cm^-3Density of gas in unit

In cm³.cmHg.K^-1.mol^-1Gas constant in units

Temperature in kelvin

In cm²Area of film as unit

Pressure difference between feed and permeate side in cmHg dp/dt. In cmHg.s^-1The pressure rise per unit time on the permeate side is a unit.

If the permeability of the hollow fiber is measured, the same pressure rise method is used.

The permeation amount was calculated by the following formula:

p. with GPU (gas permeation unit 10)^-6cm^3.cm^-2.s^-1.cmHg^-1) Permeability in units

V_{Dead volume}.. in cm³Volume per unit of permeate side

MW_{Gas (es)}.. in g.mol^-1Molar mass of gas in units

In g.cm^-3Density of gas in unit

In cm³.cmHg.K^-1.mol^-1Gas constant in units

Temperature in kelvin

In cm²Hollow fiber outer surface area in units

The selectivity for each pair of gases is a pure gas selectivity. The selectivity between the two gases was calculated from the quotient of the permeabilities:

s. ideal gas selectivity

P₁.. permeability or transmission of gas 1

P₂.. permeability or transmission of gas 2

Amount of liquid permeation

The permeation of the flat sheet membrane was determined using a Milipore stirring unit loaded with 5 to 6 bar of nitrogen. The permeation flux per unit time at the indicated pressure was measured. The permeation is given by:

p. in l.m^-2.h^-1Bar^-1Permeability in units

At l.h^-1Volume flow rate in unit

Pressure difference between feed side and permeate side in bar

In m²Filtration area in units

The retention R is obtained from the following formula:

retention in%

C_P.. concentration of dissolved substance in permeate

C_F.. concentration of dissolved substances in feed

If the retention is 100%, all the material is retained by the membrane. If the retention is 0%, the membrane allows all dissolved species to pass through.

Solution to the problem

The problem of molar mass degradation in the preparation of P84 powder is solved by: the polymer after polymerization in the aprotic dipolar solvent is not isolated in the form of a solid substance, in particular not in the form of a dry solid substance, more particularly not in the form of a dry powder, but the polymerization solution is directly used for preparing a membrane.

The membrane preparation method is carried out according to the following substeps:

a) polymerisation

b) Preparation of casting solutions

c) Membrane preparation

Polymerisation

Polyimides are prepared by the polycondensation of aromatic tetracarboxylic anhydrides and aromatic diisocyanates under carbon dioxide releasing conditions. Preferred materials and combinations thereof are described below:

dianhydride:

3,4,3 ', 4' -benzophenonetetracarboxylic dianhydride, 1, 2,4, 5-benzenetetracarboxylic dianhydride, 3,4,3 ', 4' -biphenyltetracarboxylic dianhydride, oxydiphthalic dianhydride, sulfonyldiphthalic dianhydride, 1, 1, 1,3, 3, 3-hexafluoro-2, 2-propylenediphthalic dianhydride

Diisocyanate:

2, 4-tolylene diisocyanate, 2, 6-tolylene diisocyanate, 4' -methylenediphenyl diisocyanate, 2,4, 6-trimethyl-1, 3-phenylene diisocyanate, 2,3, 4, 5-tetramethyl-1, 4-phenylene diisocyanate

The polymerization is carried out in an aprotic dipolar solvent. Preferably, but not limited to, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, N-ethylpyrrolidone and sulfolane are used alone or in combination.

Here, the aromatic dianhydride or the mixture of aromatic dianhydrides is dissolved in an aprotic dipolar solvent at a concentration of 10 to 40 wt. -%, preferably 18 to 32 wt. -%, more preferably 22 to 28 wt. -%, and heated to 50 to 150 ℃, preferably 70 to 120 ℃, more preferably 80 to 100 ℃. To this solution is added 0.01 to 5 wt%, preferably 0.05 to 1 wt%, more preferably 0.1 to 0.3 wt% of a basic catalyst. Useful catalysts include:

● hydroxides, methoxides, ethoxides, carbonates and phosphates of alkali metals and alkaline earth metals, such as, but not limited to, sodium hydroxide, potassium hydroxide, sodium methoxide, potassium methoxide, sodium ethoxide, potassium ethoxide, sodium carbonate, sodium hydrogencarbonate, potassium carbonate, potassium hydrogencarbonate, potassium phosphate, potassium hydrogenphosphate, potassium dihydrogenphosphate

● tertiary amines, such as, but not limited to: trimethylamine, triethylamine, tripropylamine, diazabicycloundecane, diazabicyclooctane, dimethylaminopyridine.

The diisocyanate is then added over a period of 1 to 25 hours, preferably 3 to 15 hours, more preferably 5 to 10 hours.

The following polyimides are particularly preferably prepared:

r is selected from

x, y: 0< x <0.5 and 1> y >0.5

The result is a clear, golden to dark brown polymer solution with a viscosity of 1 to 300pa.s, preferably 20 to 150pa.s, more preferably 40 to 90 pa.s. The molar mass Mp is greater than 100000g.mol^-1And thus is significantly different from polyimide polymer powders, especially P84 polymer powders.

The polyimide polymer of the present invention is obtained in a form dissolved in an aprotic dipolar solvent after the reaction. There are no interfering impurities or by-products in the polymer solution. The viscosity is very high and suitable for the preparation of films. For this reason, it is also economically advantageous not to precipitate and subsequently redissolve the polymer in the same solvent. The solution is therefore used directly for preparing the casting solution without isolation of the polymer and preferably also without further treatment.

Preparation of casting solutions

The polymer solution obtained from polycondensation has a solids content of 22 to 28% by weight and can be used without further treatment for the preparation of casting solutions.

The casting solutions of the present invention are characterized by the following properties:

● which has a sufficiently high viscosity for the production of flat sheet films and hollow fibre films

● which may contain additives that prevent the formation of large cavities (large voids) in the film

● which may contain volatile solvents to produce a surface with a desired pore size.

The casting solution viscosity is ideal when it corresponds to the so-called "entanglement point" in the viscosity curve drawn as a function of the solid matter. This point is the point at which the viscosity versus solids content function transitions from linear to exponential behavior. This point is also very strongly dependent on the molar mass. The higher the molar mass, the lower the solids content at which entanglement occurs.

The casting solutions obtainable by the process of the invention are clearly different from the casting solutions of the prior art in terms of viscosity, molar mass and molar mass distribution. Only with the process according to the invention is it possible to obtain casting solutions which combine a high viscosity with a high molar mass and a narrow molar mass distribution of the polyimide. With the process of the invention it is thus possible to prepare films having outstanding mechanical properties.

With the methods of the prior art, i.e. with dissolution of the pulverulent polyimide and subsequent aftertreatment to increase the molar mass, casting solutions having a comparable combination of properties cannot be obtained.

Additives can also be added in the process of the invention. Different solids contents are obtained by various amounts of additives, which then move the entanglement point. Here, the entanglement point can be moved again by adaptation of the molar mass in the polymerization.

If the composition of the casting solution is very far from the concentration at which the phase separation occurs, the gradient between the solvent and the non-solvent becomes extremely large by the phase inversion in the film production, and a large cavity is obtained in the film. These cavities, also referred to as large voids, result in lower pressure stability of the membrane in applications and limit their use, for example, for natural gas purification. The formation of large voids can be prevented by adding a non-solvent. The following water-miscible solvents or mixtures thereof are suitable for this purpose.

This list is to be regarded as an exemplary list only, and other solvents will also occur to those skilled in the art.

● alcohols, such as methanol, ethanol, isopropanol, propanol, butanol, butanediol, glycerol,

● the water is added into the mixture,

● ketones, such as acetone or butanone.

In order to produce a defined surface of the film, several methods can in principle be used: in addition to the delayed layering process, evaporative removal of volatile cosolvents also results in extremely thin selective layers not only in the field of gas separation membranes, but also in the field of nanofiltration and ultrafiltration membranes. The degree of evaporation removal and hence pore size is affected by the kind of volatile solvent, its concentration, evaporation time, casting solution temperature, amount and temperature of ambient gas in the evaporation removal zone.

Useful volatile solvents include the following. They should be water-miscible, e.g. acetone, tetrahydrofuran, methanol, ethanol, propanol, isopropanol, di-n-propyl alcoholAlkyl, ethyl ether.

The casting solutions are preferably prepared by metering in the additive mixture or by metering in the additives separately from one another one after the other. Here, the additives are metered slowly into the mixture with stirring. The metering is preferably carried out for 10 minutes to 3 hours, particularly preferably for 30 minutes to 2 hours. The addition of the co-solvent causes the partial precipitation of the polyimide at the dropping point. But the solid material dissolves again after a few minutes without residue. The clear solution is then additionally filtered through a 15 μ steel mesh screen to remove interfering impurities that can cause defects in the membrane surface.

After filtration, the solution was left to stand in a closed vessel at 50 ℃ for 2 days to remove bubbles and thus devolatilize.

Preparation of hollow fibers

The devolatilized, filtered and additivated polyimide polymer solution is thermostatted, preferably to 20 to 100 ℃, more preferably to 30 to 70 ℃. The solution was pumped through the outer part of the two-material die with a gear pump. The two-material die had an outer diameter of 600 microns, an inner diameter of 160 microns and a pump power of 1.3 to 13.5 ml/min. A liquid mixture formed from a mixture of water and an aprotic dipolar solvent or solvents is pumped through the inner part of the bi-material die.

Useful solvents include, but are not limited to, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, N-ethylpyrrolidone, sulfolane, or dimethylsulfoxide, among others.

The composition between the solvent and water is 10 to 95 wt% solvent and 90 to 5 wt% water, preferably 30 to 90 wt% solvent and 70 to 10 wt% water, more preferably 50 to 80 wt% solvent and 50 to 20 wt% water. The pump power is 0.2 ml/min to 10 ml/min.

The resulting hollow fibers then enter a tube filled with dry constant temperature gas. Useful gases include: nitrogen, air, argon, helium, carbon dioxide, methane, or other industrial inert gases. The gas temperature is adjusted via a heat exchanger, and it is preferably 20 to 250 ℃, more preferably 30 to 150 ℃, still more preferably 40 to 120 ℃.

The gas velocity in the tube is preferably 0.1 to 10 m/min, more preferably 0.5 to 5 m/min, still more preferably 1 to 3 m/min. The distance and thus the tube length is preferably 5 cm to 1 meter, more preferably 10 to 50 cm. The thus conditioned filaments are then immersed in a water bath to coagulate the polymer mass and thereby form a film. The bath temperature is preferably 1 to 60 ℃, more preferably 5 to 30 ℃, more preferably 8 to 16 ℃.

Aprotic dipolar solvents and other solvents, such as, but not limited to, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, N-ethylpyrrolidone, sulfolane, dimethylsulfoxide, tetrahydrofuran, and dioxaneThe concentration of alkane, isopropanol, ethanol or glycerol in the precipitation bath is 0.01 to 20 wt.%, preferably 0.1 to 10 wt.%, more preferably 0.2 to 1 wt.%.

The drawing speed of the hollow fiber is 2 to 100 m/min, preferably 10 to 50 m/min, more preferably 20 to 40 m/min. The fiber was wound onto a spool and washed in water until the residual solvent content was below 1%. Followed by treatment in ethanol and hexane. The fiber is then dried, preferably between room temperature and 150 ℃, more preferably between 50 and 100 ℃. Fibers having an outer diameter of 100 to 1000 microns, preferably 200 to 700 microns, more preferably 250 to 400 microns are obtained.

The hollow fiber membrane made of polyimide exhibiting high separation efficiency for various gases is thus obtained by the method of the present invention. An excerpt of the various polymers and gases is summarized in table 2.

Table 2: the transmission of various polyimide hollow fibers of the present invention in a single gas measurement

It is also noteworthy that the membrane is even at high CO₂Also at partial pressure hardly any increase in the methane permeability is exhibited, maintaining their selectivity and therefore hardly plasticizing. This property is that the aftertreatment has a high CO content₂This is the case, for example, when working up crude natural gas or crude biogas, which is necessary for the content and high pressure of acid gas.

The hollow fiber membranes may also be cross-linked with amines. If the hollow fibers are crosslinked, this is done after the washing step. For this purpose, the hollow fibers are guided through a bath containing an amine having at least 2 amino groups per molecule, for example a diamine, triamine, tetraamine or polyamine. The amine may be a primary or secondary amine, or may be composed of a mixture of primary, secondary and tertiary amines in the molecule. Useful amines include aliphatic amines, aromatic amines, and mixed aliphatic-aromatic amines. Silicone-based amines are also possible. Examples of aliphatic diamines include, but are not limited to: diaminoethane, diaminopropane, diaminobutane, diaminopentane, diaminohexane, diaminoheptane, diaminooctane, diaminodecane or diamino compounds of branched or cyclic aliphatic compounds (e.g. cis-and trans-1, 4-cyclohexane) with longer chain compounds.

Useful aromatic compounds include, but are not limited to: p-phenylenediamine, m-phenylenediamine, 2, 4-toluenediamine, 2, 6-toluenediamine and 4, 4' -diaminodiphenyl ether.

Examples of aliphatic-aromatic mixed amines include, but are not limited to: aminoalkyl-substituted aromatic compounds, such as p-bis (aminomethyl) benzene.

Useful silicone-based amines include, but are not limited to: bis (aminoalkyl) siloxanes having various chain lengths.

Representative of useful polyfunctional amines include, but are not limited to, among others, the following compounds: oligo-or polyethyleneimines, N' -trimethylbis (hexamethylene) triamine, bis (6-aminohexyl) amine with various molar masses (400 to 200000 g/mol).

Crosslinking is carried out by placing or continuously drawing the entire hollow fiber through a solution of the particular diamine in water or in a mixture of water and a water-miscible solvent or other solvent that does not affect the membrane structure and dissolves the particular amine. Suitable for this are, for example, but not limited to:

● alcohols, e.g. methanol, ethanol, isopropanol, propanol, butanol, butanediol, glycerol

● ethers, e.g. diethyl ether, tetrahydrofuran, diAlkanes or polyethylene glycols or polyethylene glycol ethers

● aprotic dipolar solvents, e.g. dimethylformamide, dimethylacetamide, N-methylpyrrolidone, N-ethylpyrrolidone, tetramethylurea, dimethyl sulfoxide or sulfolane

● ketones, e.g. acetone or methyl ethyl ketone

● others, such as ethyl acetate, dichloromethane, chloroform, toluene, xylene, aliphatic compounds and alicyclic compounds, such as hexane, heptane or cyclohexane.

The concentration of the diamine is 0.01 to 10% by weight, but is preferably 0.05 to 5% by weight, more preferably 0.1 to 1% by weight.

The crosslinking solution temperature is 1 to 100 ℃, preferably 10 to 70 ℃, more preferably 20 to 50 ℃.

The residence time is from 10 seconds to 10 hours, preferably from 1 minute to 60 minutes, more preferably from 2 to 10 minutes.

To remove residual amine, the film was washed with water. The wash bath temperature is 10 to 90 deg.C, preferably 20 to 60 deg.C. The residence time in the wash bath is from 1 to 200 minutes, preferably from 2 to 50 minutes, more preferably from 3 to 10 minutes.

Obtaining hollow fibers that are no longer soluble in traditional organic solvents such as, but not limited to, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, N-ethylpyrrolidone, tetramethylurea, dimethylsulfoxide or sulfolane, acetone, methyl ethyl ketone, diethyl ether, tetrahydrofuran, di-N-methyl pyrrolidone, ethyl methyl ketone, N-methyl pyrrolidoneAn alkane, ethyl acetate, dichloromethane, chloroform, toluene, xylene, hexane, heptane, or cyclohexane. They are therefore useful for nanofiltration, ultrafiltration and microfiltration in organic solvents.

Preparation of Flat sheet film

The solution to which the additive was added and devolatilized was cast into a blade of a flat sheet film casting apparatus without bubbles. The width of the screed may be up to 1.2 metres. A calendered backed nonwoven made of plastic fibers, preferably but not limited to polyimide, polypropylene, polyamide, polyester or polyphenylene sulfide, is passed under the blade at a speed of 0.1 to 10 meters per minute, preferably 1 to 5 meters per minute. The thickness of the nonwoven is 30 to 300. mu.m, preferably 100 to 200. mu.m. The basis weight is from 20 to 300 g/m, preferably from 50 to 150 g/m. The gap width between the blade and the nonwoven fabric is 100 to 800 micrometers, preferably 200 to 400 micrometers. The coated nonwoven enters a channel filled with a counter-current air flow. Useful gases include, but are not limited to, dry air, nitrogen, argon or helium, among others. The gas velocity flowing over the coated nonwoven moves here in the range from 100 to 5000 m/h, preferably from 200 to 1000 m/h, and the gas temperature can be from 10 to 150 ℃, preferably from 15 to 90 ℃. The coated nonwoven then enters a precipitation bath where the polymer coagulates and forms the desired film. The precipitation bath consists of water or a mixture of water and one or more water-miscible solvents.

Suitable for this include:

● ethers, e.g. diethyl ether, tetrahydrofuran, bisAlkanes or polyethylene glycols or polyethylene glycol ethers

● ketones, for example acetone or methyl ethyl ketone.

The precipitation bath temperature is 1 to 90 ℃, preferably 10 to 50 ℃. After a short residence time of 10 seconds to 10 minutes, preferably 1 to 5 minutes, the film is wound up in the wet state.

To remove residual solvent, the membrane was washed with water. The wash bath temperature is 10 to 90 deg.C, preferably 20 to 60 deg.C. The residence time in the wash bath is from 1 to 200 minutes, preferably from 2 to 50 minutes, more preferably from 3 to 10 minutes.

If the membrane is crosslinked, this is done after the washing step. For this purpose, the film is guided through a bath containing an amine having at least 2 amino groups per molecule, for example a diamine, triamine, tetraamine or polyamine. The amine may be a primary or secondary amine, or may be composed of a mixture of primary, secondary and tertiary amines in the molecule. Useful amines include aliphatic amines, aromatic amines, and mixed aliphatic-aromatic amines. Silicone-based amines are also possible.

Examples of aliphatic diamines include, but are not limited to: diaminoethane, diaminopropane, diaminobutane, diaminopentane, diaminohexane, diaminoheptane, diaminooctane, diaminodecane or diamino compounds of branched or cyclic aliphatic compounds (e.g. cis-and trans-1, 4-cyclohexane) with longer chain compounds.

Useful silicone-based amines include, but are not limited to: bis (aminoalkyl) siloxanes of various chain lengths. Representative of useful polyfunctional amines include, but are not limited to, among others, the following compounds: oligo-or polyethyleneimines, N' -trimethylbis (hexamethylene) triamine, bis (6-aminohexyl) amine with various molar masses (400 to 200000 g/mol).

Crosslinking is carried out by placing the entire membrane in a solution of the particular diamine in water or in a mixture of water and a solvent miscible with water or other solvent that does not affect the membrane structure and dissolves the particular amine.

Examples of suitable for this purpose include, but are not limited to:

● ketones, e.g. acetone or methyl ethyl ketone

The concentration of diamine, the temperature of the crosslinking solution, the residence time and the manner in which the washing step is carried out correspond to the values or modes of operation indicated above for the crosslinking of the hollow fibres.

After the washing or crosslinking operation, the membrane is impregnated to ensure pore preservation during subsequent drying. This is done by immersing the membrane in a mixture of water and a water-miscible high boiling compound.

Suitable for use herein are, for example and without limitation: glycerol, polyethylene glycols of various chain lengths, mixed or individual, polyethylene glycol dialkyl ethers of various chain lengths, mixed or individual, as methyl ether or ethyl ether, mono-or diols having boiling points above 200 ℃, for example decanol, 1, 4-butanediol, 1, 6-hexanediol.

The concentration of the high boilers in water is from 5% to 95%, but preferably from 25% to 75% by weight. The impregnation solution temperature is from 1 to 100 ℃, preferably from 10 to 70 ℃, more preferably from 20 to 50 ℃.

After impregnation, the film is dried. Drying can be carried out in ambient air or continuously in a convection dryer. The drying temperature is from 20 to 200 ℃ and preferably from 50 to 120 ℃. The drying time is 10 seconds to 10 hours, preferably 1 minute to 60 minutes, more preferably 2 to 10 minutes. After drying, the final film is wound and may be further processed into spiral wound elements or bag shaped modules.

The flat sheet membranes and hollow fiber membranes according to the invention are therefore distinguished in that they comprise Mp > 100000g.mol^-1Preferably 110000 to 200000g.mol^-1More preferably 120000 to 170000g.mol^-1And a PDI of 1.7 to 2.3, preferably 1.8 to 2.1. Mp here corresponds to the peak maximum of the molar mass distribution under calibration conditions for a control polystyrene standard in 0.01 mol/l lithium bromide in dimethylformamide.

The high molar mass achieves an improvement in the mechanical properties of the film in terms of strength and toughness. This is required especially at high pressures in these applications. For example, flat sheet membranes must withstand at least 40 bar in operation, and some hollow fiber membranes withstand more than 100 bar in natural gas after-treatment.

A high molar mass is also advantageous for setting a sufficiently high viscosity even at moderate solids contents. The casting solution needs a certain viscosity in order to be able to process stably into films and hollow fibers and to be able to use it to prepare dense and selective layers on surfaces.

Detailed Description

Preparation examples

The following examples serve to illustrate and better understand the invention in more detail, but without restricting it in any way.

Preparation of polyimide solution

Example 1: preparation of a solution of P84 type 70 polyimide in dimethylacetamide

A 3 liter glass reactor equipped with a stirrer and a reflux condenser was initially charged with 1622 grams of anhydrous dimethylacetamide. 456.4 g of 3,3 ', 4, 4' -benzophenonetetracarboxylic dianhydride were dissolved therein and the solution was heated to 90 ℃. To this solution was added 0.45 g of sodium hydroxide. 266.8 g of a mixture of 64% of 2, 4-tolylene diisocyanate, 16% of 2, 6-tolylene diisocyanate and 20% of 4, 4' -diisocyanatodiphenylmethane are metered in over a period of several hours under a nitrogen load. In the process, CO2 escapes as a by-product and polyimide is produced directly in solution.

A gold-colored high-viscosity solution having a solids content of 25% and a viscosity of 49pa.s is obtained.

The molar mass was determined by gel permeation chromatography to give the following values: mn 80600g.mol^-1、Mp＝139600g.mol^-1、Mw＝170000g.mol^-1PDI＝2.11

Example 2: preparation of a solution of P84 type 70 polyimide in dimethylformamide

A 3 liter glass reactor equipped with a stirrer and a reflux condenser was initially charged with 1622 grams of anhydrous dimethylformamide. 456.4 g of 3,3 ', 4, 4' -benzophenonetetracarboxylic dianhydride were dissolved therein and the solution was heated to 90 ℃. To this solution was added 0.45 g of sodium hydroxide. 266.8 g of a mixture of 64% of 2, 4-tolylene diisocyanate, 16% of 2, 6-tolylene diisocyanate and 20% of 4, 4' -diisocyanatodiphenylmethane are metered in over a period of several hours under a nitrogen load. In the process, CO2 escapes as a by-product and polyimide is produced directly in solution.

A gold-colored high-viscosity solution having a solids content of 27% and a viscosity of 48pa.s is obtained.

The molar masses were determined by gel permeation chromatography to give the following values: 76600g.mol Mn^-1、Mp＝130500g.mol^-1、Mw＝146200g.mol^-1PDI＝1.91

Example 3: preparation of a solution of P84 type 70 polyimide in N-methylpyrrolidone

A3 liter glass reactor equipped with a stirrer and a reflux condenser was initially charged with 1800 grams of anhydrous N-methylpyrrolidone. 456.4 g of 3,3 ', 4, 4' -benzophenonetetracarboxylic dianhydride were dissolved therein and the solution was heated to 90 ℃. To this solution was added 0.45 g of sodium hydroxide. 266.8 g of a mixture of 64% of 2, 4-tolylene diisocyanate, 16% of 2, 6-tolylene diisocyanate and 20% of 4, 4' -diisocyanatodiphenylmethane are metered in over a period of several hours under a nitrogen load. In this process, CO2 escapes as a by-product and the polyimide is produced directly in solution.

A gold-colored high-viscosity solution having a solids content of 25% and a viscosity of 45pa.s is obtained.

The molar masses were determined by gel permeation chromatography to give the following values: 65700g.mol Mn^-1、Mp＝107200g.mol^-1、Mw＝147000g.mol^-1PDI＝2.24

Example 4: preparation of a solution of P84 type 70 polyimide in N-ethylpyrrolidone

A3 l glass reactor equipped with a stirrer and a reflux condenser was initially charged with 1622 g of anhydrous N-ethylpyrrolidone. 456.4 g of 3,3 ', 4, 4' -benzophenonetetracarboxylic dianhydride were dissolved therein and the solution was heated to 90 ℃. To this solution was added 0.45 g of sodium hydroxide. 266.8 g of a mixture of 64% of 2, 4-tolylene diisocyanate, 16% of 2, 6-tolylene diisocyanate and 20% of 4, 4' -diisocyanatodiphenylmethane are metered in over a period of several hours under a nitrogen load. In this process, CO2 escapes as a by-product and the polyimide is produced directly in solution.

A gold-colored high-viscosity solution having a solids content of 27% and a viscosity of 87pa.s is obtained.

The molar masses were determined by gel permeation chromatography to give the following values: mn 64600g.mol^-1、Mp＝105200g.mol^-1、Mw＝144700g.mol^-1PDI＝2.24

Example 5: preparation of a solution of P84T100 polyimide in dimethylformamide

A 3 liter glass reactor equipped with a stirrer and a reflux condenser was initially charged with 1800 grams of anhydrous dimethylformamide. 473.6 g of 3,3 ', 4, 4' -benzophenonetetracarboxylic dianhydride were dissolved therein and the solution was heated to 90 ℃. To this solution was added 1.8 g of diazabicyclooctane. 254.4 g of 2, 4-tolylene diisocyanate were metered in during a few hours under nitrogen loading. In this process, CO2 escapes as a by-product and the polyimide is produced directly in solution.

A gold-colored high-viscosity solution having a solids content of 25% and a viscosity of 59pa.s is obtained.

The molar masses were determined by gel permeation chromatography to give the following values: mn 82100g.mol^-1、Mp＝151500g.mol^-1、Mw＝181900g.mol^-1PDI＝2.21

Example 6: preparation of a solution of P84T80 polyimide in dimethylformamide

A 3 liter glass reactor equipped with a stirrer and a reflux condenser was initially charged with 1622 grams of anhydrous dimethylformamide. 473.6 g of 3,3 ', 4, 4' -benzophenonetetracarboxylic dianhydride were dissolved therein and the solution was heated to 90 ℃. To this solution was added 1.8 g of diazabicyclooctane. 254.4 g of a mixture of 80% of 2, 4-tolylene diisocyanate and 20% of 2, 6-tolylene diisocyanate were metered in over a period of several hours under a nitrogen load. In the process, CO2 escapes as a by-product and polyimide is produced directly in solution.

A gold-colored high-viscosity solution having a solids content of 27% and a viscosity of 108pa.s is obtained.

The molar masses were determined by gel permeation chromatography to give the following values: mn 83800g.mol^-1、Mp＝152300g.mol^-1、Mw＝173800g.mol^-1PDI＝2.07

Example 7: preparation of a solution of P84HT polyimide in dimethylformamide

A 3 liter glass reactor equipped with a stirrer and a reflux condenser was initially charged with 1800 grams of anhydrous dimethylformamide. 316.4 g of 3,3 ', 4, 4' -benzophenonetetracarboxylic dianhydride and 142.8 g of pyromellitic dianhydride were dissolved therein and the solution was heated to 90 ℃. To this solution was added 1.8 g of diazabicyclooctane. 283.4 g of a mixture of 80% of 2, 4-tolylene diisocyanate and 20% of 2, 6-tolylene diisocyanate were metered in over a period of several hours under a nitrogen load. In the process, CO2 escapes as a by-product and polyimide is produced directly in solution.

A gold-colored high-viscosity solution having a solids content of 27% and a viscosity of 70pa.s is obtained.

The molar masses were determined by gel permeation chromatography to give the following values: mn 75500g.mol^-1、Mp＝122200g.mol^-1、Mw＝150900g.mol^-1PDI＝2.00

Example 8: preparation of P84MDI polyimide solution in dimethylformamide

A 3 liter glass reactor equipped with a stirrer and a reflux condenser was initially charged with 1500 grams of anhydrous dimethylformamide. 369.2 g of 3,3 ', 4, 4' -benzophenonetetracarboxylic dianhydride were dissolved therein and the solution was heated to 90 ℃. To this solution 1.5 g of diazabicyclooctane were added. Under a nitrogen load, 222.3 g of 2,4, 6-trimethyl-1, 3-benzenediisocyanate were metered in over a period of several hours. In this process, CO2 escapes as a by-product and the polyimide is produced directly in solution.

A pale yellow viscous solution with a solids content of 25% and a viscosity of 5pa.s was obtained.

The molar masses were determined by gel permeation chromatography to give the following values: mn 55200g.mol^-1、Mp＝95000g.mol^-1、Mw＝112000g.mol^-1PDI＝2.03

Film preparation and intrinsic gas permeability

The polymerization solution was filtered through a 15 μmetal sieve without dilution. The film was prepared using a doctor blade using an instrument from Elcometer corporation (Elcometer 4340). A glass plate was coated with the polymer solution using a squeegee and a gap size of 250 μ. The solvent was subsequently removed by evaporation in a circulating air drying cabinet at 70 ℃ (0.5h), 150 ℃ (2h) and 250 ℃ (12 h). The film is then substantially free of solvent (< 0.1% by weight) and detached from the glass plate. A film having a thickness of about 30 to 40 microns is thus obtained. None of these films was brittle and showed good mechanical properties. Subsequent examination under a microscope finds defect-free locations from these films and cuts circular samples 46 mm in diameter. These samples were then placed in a self-assembled gas permeation device and the permeability of each gas was determined by a vacuum method.

This involves loading the membrane with a single gas (e.g. nitrogen, oxygen, methane or carbon dioxide) at various pressures and recording the pressure increase on the permeate side. Whereby Barrer (10-6 cm) is calculated³.cm^-2.s^-1.cmHg^-1) Permeability in units. Some examples are set forth below.

Example 9: gas permeability of various polymers from the above examples

Adding an additive to the polymerization solution

Example 10: preparation of casting solution for preparing polyimide hollow fiber from P84 type 70

1168 g of a P84 type 70 solution from example 2 in dimethylformamide were mixed at room temperature in a 3l glass stirred tank with a powerful stirrer with a mixture of 94.1 g of tetrahydrofuran and 40.3 g of isopropanol added dropwise. In the process, the polymer precipitated for a short time at the dropping point, but immediately dissolved again. Stir until a homogeneous solution results. This homogeneous solution was then filtered through a sieve having a mesh size of 15 μ and left to stand without stirring for 2 days. A casting solution having a solid content of 23.5%, a dimethylformamide content of 66.5%, a tetrahydrofuran content of 7% and an isopropanol content of 3% was obtained.

Example 11: preparation of casting solution for preparing polyimide hollow fiber from P84 type 70

In a 3l stirred tank with intensive stirrer 1034 g of a solution of P84 type 70 from example 2 in dimethylformamide are mixed at room temperature with a mixture of 58.6 g of tetrahydrofuran and 46.9 g of isopropanol added dropwise. In the process, the polymer precipitated for a short time at the dropping point, but immediately dissolved again. Stir until a homogeneous solution results. This homogeneous solution was then filtered through a sieve having a mesh size of 15 μ and left to stand without stirring for 2 days. A casting solution having a solid content of 23.8%, a dimethylformamide content of 67.2%, a tetrahydrofuran content of 5% and an isopropanol content of 4% was obtained.

Example 12: preparation of casting solution for preparing polyimide hollow fiber from P84HT

In a 3l glass stirred tank with a powerful stirrer, 1034 g of a solution of P84HT from example 7 in dimethylformamide are mixed at room temperature with a mixture of 47 g of tetrahydrofuran and 65g of isopropanol added dropwise. In the process, the polymer precipitated for a short time at the dropping point, but immediately dissolved again. Stir until a homogeneous solution results. This homogeneous solution was then filtered through a sieve having a mesh size of 15 μ and left to stand without stirring for 2 days. A casting solution having a solid content of 23.6%, a dimethylformamide content of 66.9%, a tetrahydrofuran content of 4% and an isopropanol content of 5.5% was obtained.

Example 13: preparation of casting solution for preparing polyimide hollow fiber from P84T100

In a 3l glass stirred tank with a powerful stirrer, 1034 g of a solution of P84T100 from example 5 in dimethylformamide are mixed at room temperature with a mixture of 46.8 g of tetrahydrofuran and 58.5 g of isopropanol added dropwise. In the process, the polymer precipitated for a short time at the dropping point, but immediately dissolved again. Stir until a homogeneous solution results. This homogeneous solution was then filtered through a sieve having a mesh size of 15 μ and left to stand without stirring for 2 days. A casting solution having a solid content of 22.1%, a dimethylformamide content of 68.9%, a tetrahydrofuran content of 5% and an isopropanol content of 4% was obtained.

Example 14: preparation of a casting solution from P84 type 70 for the preparation of flat sheet membranes for organophilic nanofiltration

In a 3l glass stirred tank with intensive stirrer 1034 g of a solution of P84 type 70 from example 2 in dimethylformamide are mixed at room temperature with 258.5 g of tetrahydrofuran added dropwise. Stir until a homogeneous solution results. This homogeneous solution was then filtered through a sieve having a mesh size of 15 μ and left to stand without stirring for 2 days. A casting solution having a solid content of 21.6%, a dimethylformamide content of 58.4% and a tetrahydrofuran content of 20% was obtained.

Preparation of hollow fibers

Example 15: preparation of hollow fibers from the cast solution containing P84 type 70 in dimethylformamide from example 10

The devolatilized, filtered and additivated solution from example 10 formed from P84 type 70 in dimethylformamide was thermostatted to 50 ℃ and pumped through a two-material die with a gear pump. The flux was 162 g/h. While the polymer solution was conveyed in the outer region of the two-material die, a mixture of 70% dimethylformamide and 30% water was conveyed inside to prepare pores in the hollow fiber. The flux was 58 ml/h. After a distance of 40 cm, the hollow fibers were subjected to cold water at 10 ℃. The hollow fibers are here encapsulated with a tube. The tube was filled with a nitrogen flow of 2 l/min and the temperature inside the tube was 41 ℃. The fiber was then drawn through a water wash bath and finally wound up at a speed of 15 meters per minute. After several hours of extraction with water, the hollow fibers were first immersed in ethanol, then in heptane, and then dried in air. A hollow fiber with an outer diameter of 412 μ, a pore diameter of 250 μ and a wall thickness of 81 μ was obtained.

A single gas measurement yields the following permeabilities of the hollow fiber at 5 bar transmembrane pressure:

oxygen: 1.450GPU

Nitrogen gas: 0.165GPU

Carbon dioxide: 6.03GPU

Methane: 0.084GPU

The single gas selectivity was thus 8.8 between oxygen and nitrogen and 71.9 between carbon dioxide and methane.

A single gas measurement yields the following throughputs of the hollow fiber at 40 bar transmembrane pressure:

carbon dioxide: 8.99GPU

Methane: 0.101GPU

The single gas selectivity was 88.5 between carbon dioxide and methane.

Example 16: preparation of hollow fibers from the cast solution containing P84 type 70 in dimethylformamide from example 11

The devolatilized, filtered and additive-added solution of P84 type 70 from example 11 in dimethylformamide was thermostated to 50 ℃ and pumped through a two-material die with a gear pump. The flux was 162 g/h. While the polymer solution was conveyed in the outer region of the bi-material die, a mixture of 70% dimethylformamide and 30% water was conveyed internally to make pores in the hollow fibers. The flux was 58 ml/h. After a distance of 42 cm, the hollow fibers were subjected to cold water at 10 ℃. The hollow fibers are here encapsulated with a tube. The tube was filled with a nitrogen flow of 2 l/min and the temperature inside the tube was 46 ℃. The fiber was then drawn through a water wash bath and finally wound up at a speed of 24 meters/minute. After several hours of extraction with water, the hollow fibers were first immersed in ethanol, then in heptane, and then dried in air. Hollow fibers were obtained with an outer diameter of 310 μ, a pore diameter of 188 μ and a wall thickness of 61 μ.

A single gas measurement yields the following throughputs of the hollow fiber at a transmembrane pressure of 9 bar:

oxygen: 1.463GPU

Nitrogen gas: 0.164GPU

The single gas selectivity is thus 8.9 between oxygen and nitrogen.

Example 17: preparation of hollow fibers from the cast solution containing P84T100 in dimethylformamide from example 13

The devolatilized, filtered and additive-added solution of P84T100 from example 13 in dimethylformamide was thermostated to 50 ℃ and pumped through a double material die with a gear pump. The flux was 162 g/h. While the polymer solution was conveyed in the outer region of the bi-material die, a mixture of 70% dimethylformamide and 30% water was conveyed internally to make pores in the hollow fiber. The flux was 58 ml/h. After a distance of 42 cm, the hollow fibers were subjected to cold water at 10 ℃. The hollow fibers are here encapsulated with a tube. The tube was filled with a nitrogen flow of 2 l/min and the temperature inside the tube was 46 ℃. The fiber was then drawn through a water wash bath and finally wound up at a speed of 20 m/min. After several hours of extraction with water, the hollow fibers were first immersed in ethanol, then in heptane, and then dried in air. Hollow fibers were obtained with an outer diameter 339 μ, a pore diameter 189 μ and a wall thickness of 75 μ.

oxygen: 0.564GPU

Nitrogen gas: 0.072GPU

Carbon dioxide: 1.679

Methane: 0.023

The single gas selectivity was thus 7.8 between oxygen and nitrogen and 71.6 between carbon dioxide and methane.

Example 18: preparation of hollow fibers from cast solution containing P84HT in dimethylformamide

The devolatilized, filtered and additive-added solution of P84HT from example 12 in dimethylformamide was thermostated to 50 ℃ and pumped through a two-material die with a gear pump. The flux was 162 g/h. While the polymer solution was conveyed in the outer region of the bi-material die, a mixture of 70% dimethylformamide and 30% water was conveyed internally to make pores in the hollow fiber. The flux was 58 ml/h. After a distance of 15 cm, the hollow fibers were subjected to cold water at 10 ℃. The hollow fibers are here encapsulated with a tube. The tube was filled with a nitrogen flow of 1 liter/min and the temperature inside the tube was 40 ℃. The fiber was then drawn through a water wash bath and finally wound up at a speed of 24 meters/minute. After several hours of extraction with water, the hollow fibers were first immersed in ethanol, then in heptane, and then dried in air. A hollow fiber with an outer diameter of 306 μ, a pore diameter of 180 μ and a wall thickness of 63 μ was obtained.

A single gas measurement yields the following permeabilities of the hollow fiber at 10 bar transmembrane pressure:

carbon dioxide: 6.0GPU

Methane: 0.2GPU

The single gas selectivity is therefore 30 between carbon dioxide and methane.

Example 19: preparation of hollow fibers from the polymerization solution containing P84HT in dimethylformamide from example 7

The devolatilized, filtered solution of P84HT from example 7 in dimethylformamide was thermostatted to 50 ℃ and pumped through a two-material die with a gear pump. The flux was 162 g/h. While the polymer solution was conveyed in the outer region of the bi-material die, a mixture of 70% dimethylformamide and 30% water was conveyed internally to make pores in the hollow fiber. The flux was 58 ml/h. After a distance of 15 cm, the hollow fibers were subjected to cold water at 10 ℃. The hollow fibers are here encapsulated with a tube. The tube was filled with a nitrogen flow of 1 liter/min and the temperature inside the tube was 70 ℃. The fiber was then drawn through a water wash bath and finally wound up at a speed of 24 meters/minute. After several hours of extraction with water, the hollow fibers were first immersed in ethanol, then in heptane, and then dried in air. A hollow fiber with an outer diameter of 307 μ, a pore diameter of 189 μ and a wall thickness of 59 μ was obtained.

carbon dioxide: 3.37GPU

Methane: 0.051GPU

The single gas selectivity is therefore 66 between carbon dioxide and methane.

The fibers were additionally measured at higher pressures to measure plasticizing behavior and pressure stability.

Preparation of Flat sheet film

Example 20: preparation of Flat films from P84 type 70

A 35 cm wide film was prepared from the casting solution described in example 14 on a flat sheet film apparatus. Here, the casting solution was coated on a calendered polyester nonwoven fabric having a unit area weight of 100 g/square meter and a speed of 5 m/min using a blade and a casting gap of 200 μ. The coated polyester nonwoven was then guided through a well-like configuration through which nitrogen flowed. The flow rate was 339 m/h. The residence time thus achieved was 3 seconds. The coated nonwoven fabric was then immersed in cold water at 10 ℃. The crude membrane was then wet wound.

Subsequently, the membrane was extracted in water at 70 ℃ and impregnated with a conditioner (25% dimethyl ether of polyethylene glycol in water (PGDME 250 from Clariant corporation)). Drying at 60 ℃ in a hanging dryer.

The membrane was characterized in a Milipor stirring unit at a pressure of 5 bar. The solvent used was heptane, in which hexaphenylbenzene was dissolved at a concentration of 12 mg/l. MeasuringThis gave a retention of 94% of 1.7l.m^-2.h^-1Bar^-1The flux of (c).

The membrane was subsequently also tested in toluene at a pressure of 30 bar and 30 ℃. Low polystyrene was used as the test molecule. The flux of toluene in this test was 90l.m^-2.h^-1. The membrane showed very high retention over the whole molar mass range and had a sharp Cut-off (Cut-off) in the range of 200 to 300 daltons (see fig. 3).

Cross-linking membranes with diamines

Example 21: cross-linking flat membranes with amines

The flat film from example 20 was placed in a 0.1% ethanol solution of oligoethyleneimine (#468533, Aldrich, typical molecular weight 423, containing 5-20% tetraethylenepentamine) for 16 hours. The membrane was crosslinked and showed no solubility in hexane, heptane, toluene, xylene, acetone, butanone, methanol, ethanol, isopropanol, tetrahydrofuran, dichloromethane, chloroform, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, dimethylsulfoxide, and ethyl acetate.

The membrane was characterized in a Milipor stirring unit at a pressure of 5 bar. The solvent used was dimethylformamide, in which hexaphenylbenzene was dissolved at a concentration of 2.2 mg/l. The measurement gave a retention of 1.3 l.m.^-2.h^-1Bar^-1The flux of (c).

Example 22: cross-linking hollow fiber membranes with amines

The hollow fiber membrane from example 19 was placed in a 0.1% solution of hexamethylenediamine in ethanol for 16 hours. The membrane was crosslinked and showed no solubility in hexane, heptane, toluene, xylene, acetone, butanone, methanol, ethanol, isopropanol, tetrahydrofuran, dichloromethane, chloroform, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, dimethylsulfoxide, and ethyl acetate.

Drawings

FIG. 1: effect of concentration of P84 type 70 in DMF on solution viscosity: comparison of P84 polymerization solution with P84 solution made from precipitated and redissolved polymer at 25 deg.C

FIG. 2: cross section of hollow fiber membranes with large voids (left drawing) and without large voids (right drawing)

FIG. 3: application test of the film from example 20

Claims

1. A method for producing a polyimide film, characterized in that it comprises the following steps

a) Preparation of polyimide

b) Preparation of casting solutions comprising polyimides

c) A polyimide film was produced from the casting solution,

and the polyimide between said steps a) and b) is not isolated as a solid substance and dissolved again,

and is

The membrane is prepared by a phase inversion method,

wherein for the preparation of the polyimide in stage a), use is made of

An aromatic dianhydride, or a mixture thereof,

and

an aromatic diisocyanate or a mixture thereof,

and

an aprotic dipolar solvent or a mixture thereof.

2. The process according to claim 1, characterized in that the polyimide between the steps a) and b) is not isolated as a dry solid substance and redissolved.

3. The process according to claim 1, characterized in that the polyimide between said steps a) and b) is not isolated in the form of a dry powder and redissolved.

4. The process according to claim 1, characterized in that the aromatic dianhydride is 3,4,3 ', 4' -benzophenonetetracarboxylic dianhydride, pyromellitic dianhydride or 3,4,3 ', 4' -biphenyltetracarboxylic dianhydride.

5. The process according to claim 1, characterized in that the aromatic diisocyanate is 2, 4-toluene diisocyanate, 2, 6-toluene diisocyanate, 4' -methylene diphenyl diisocyanate, 2,4, 6-trimethyl-1, 3-benzene diisocyanate or 2,3,5, 6-tetramethyl-1, 4-benzene diisocyanate.

6. Process according to claim 1, characterized in that the aprotic dipolar solvent is dimethylformamide, dimethylacetamide, N-methylpyrrolidone, N-ethylpyrrolidone, sulfolane, tetrahydrofuran or di-tertAn alkane.

7. The method according to claim 1, characterized in that the polyimide is a polyimide having the following structure:

r is selected from

x, y: 0< x <0.5 and 1> y > 0.5.

8. The method according to claim 1, characterized in that the polyimide is selected from the group consisting of:

p84 type 70 prepared by the reaction of 3,3 ', 4,4 ' -benzophenonetetracarboxylic dianhydride and a mixture of 64% 2, 4-toluene diisocyanate, 16% 2, 6-toluene diisocyanate and 20% 4,4 ' -diisocyanatodiphenylmethane;

P84T80 prepared by the reaction of 3,3 ', 4, 4' -benzophenonetetracarboxylic dianhydride and a mixture of 80% 2, 4-toluene diisocyanate and 20% 2, 6-toluene diisocyanate;

p84HT prepared by reacting 3,3 ', 4, 4' -benzophenonetetracarboxylic dianhydride and pyromellitic dianhydride with a mixture formed from 80% 2, 4-toluene diisocyanate and 20% 2, 6-toluene diisocyanate;

p84MDI, prepared by reaction of 3,3 ', 4, 4' -benzophenonetetracarboxylic dianhydride with 2,4, 6-trimethyl-1, 3-benzenediisocyanate; and

P84T100 prepared by reaction of 3,3 ', 4, 4' -benzophenonetetracarboxylic dianhydride with 2, 4-toluene diisocyanate.

9. Process according to any one of claims 1 to 8, characterized in that the polymerization in step a) is carried out in an aprotic dipolar solvent selected from the group consisting of dimethylformamide, dimethylacetamide, N-methylpyrrolidone, N-ethylpyrrolidone, sulfolane and mixtures thereof, and/or

An aromatic dianhydride or a mixture of aromatic dianhydrides is dissolved in an aprotic dipolar solvent at a concentration of 10 to 40% by weight and the solution is heated to 50 to 150 ℃, to which solution or mixture 0.01 to 5% by weight of a basic catalyst is added.

10. The process according to claim 9, characterized in that the concentration of the aromatic dianhydride or mixture of aromatic dianhydrides is between 22% and 28% by weight; and/or

Heating the solution to 70 ℃ to 120 ℃; and/or

The concentration of the catalyst is 0.1 to 0.3 wt.%.

11. A method according to claim 10, characterized in that the solution is heated to 80 ℃ to 100 ℃.

12. Process according to claim 9, characterized in that the catalyst is selected from the group consisting of hydroxides, methoxides, ethoxides, carbonates and phosphates of alkali metals or alkaline earth metals and tertiary amines.

13. Process according to claim 9, characterized in that a clear golden to dark brown polymer solution with a viscosity of 1 to 300pa.s is obtained, wherein the molar mass Mp of the polyimide polymer is greater than 100000g.mol^-1。

14. The method according to any one of claims 1 to 8, characterized in that a water-soluble additive is added for preparing the casting solution in step b).

15. A process according to claim 14, characterized in that the additive used is

A non-solvent or a mixture thereof,

and/or

A pore-forming agent, a surfactant and a surfactant,

and/or

A water miscible solvent or a mixture thereof.

16. Process according to claim 15, characterized in that the solvent miscible with water is volatile and is diethyl ether, tetrahydrofuran, bisAn alkane or acetone.

17. A process according to claim 15, characterized in that the non-solvent is water, methanol, ethanol, n-propanol, isopropanol, butanol, butanediol, ethylene glycol, glycerol or γ -butyrolactone.

18. The method according to claim 15, characterized in that the pore former is polyvinyl-pyrrolidone.

19. Process according to claim 15, characterized in that the water-miscible solvent is dimethylformamide, dimethylacetamide, N-methylpyrrolidone, N-ethylpyrrolidone, sulfolane or dimethylsulfoxide.

20. The method according to any one of claims 1 to 8, characterized in that in step c) the backing nonwoven is coated with a cast polyimide solution.

21. A method according to claim 20, characterized in that after coating the backing nonwoven with the polymer casting solution, a part of the solvent is evaporated with a dry constant temperature nitrogen or air flow to adjust the separation limit of the membrane.

22. The process according to any one of claims 1 to 8, characterized in that the polyimide film is crosslinked with an aliphatic diamine, bis-4, 4' - (aminomethyl) benzene or a polyethyleneimine or mixtures thereof.

23. The method of claim 22, wherein the step of removing comprises removing the substrate from the substrate

The aliphatic diamine is diaminoethane, diaminopropane, diaminobutane, diaminopentane, diaminohexane, diaminooctane, diaminodecane or diaminododecane

And/or

The crosslinking is carried out at a temperature of from 0 to 90 ℃,

and/or

The crosslinking time is from 10 seconds to 16 hours.

24. The method according to claim 22, characterized in that the polyimide film is crosslinked with an aliphatic diamine or bis-4, 4' - (aminomethyl) benzene, and

the crosslinking is carried out by immersion in a solution of the diamine in water or alcohol or a mixture thereof,

and/or

The diamine is present in a concentration of 0.01 to 50 wt.%.

25. A process according to claim 22, characterised in that the polyethyleneimine is an oligoethyleneimine.

26. Process according to claim 24, characterized in that the alcohol is methanol or ethanol or isopropanol.

27. Process according to claim 23, characterized in that the crosslinking is carried out at a temperature of 10 to 60 ℃.

28. Process according to claim 23, characterized in that the crosslinking is carried out at a temperature of 15 to 30 ℃.

29. The method according to claim 23, characterized in that the crosslinking time is 30 seconds to 30 minutes.

30. The method according to claim 23, characterized in that the crosslinking time is 1 to 5 minutes.

31. The process according to claim 24, characterized in that the diamine concentration is from 0.1% to 10% by weight.

32. The process according to claim 24, characterized in that the diamine concentration is between 0.2% and 1% by weight.

33. The process according to any one of claims 1 to 8, characterized in that an overall asymmetric hollow fiber membrane is produced in step c).

34. The method according to claim 33, characterized in that the hollow fibers are spun in a continuous process from a cast polyimide solution according to claim 14 and a drilling solution by means of a two-material die.

35. The method of claim 34, wherein the step of removing comprises removing the substrate from the substrate

The drilling solution is a mixture of water or alcohol and dimethylformamide, dimethylacetamide, N-methylpyrrolidone, N-ethylpyrrolidone, sulfolane, dimethylsulfoxide, or a combination thereof

And/or

A spinning die head is spaced from 1 to 60 cm from a water spinning bath in which the hollow fiber is spun, and an integrally asymmetric hollow fiber membrane is formed by precipitating the polymer

And/or

During spinning, the hollow thread before entering the spinning bath is flushed with a dry constant temperature nitrogen or air flow to adjust the separation performance of the membrane

And/or

The polyimide polymer is crosslinked with an aliphatic diamine, bis-4, 4' - (aminomethyl) benzene, or a polyethyleneimine, or mixtures thereof.

36. A process according to claim 35, characterised in that the aliphatic diamine is diaminoethane, diaminopropane, diaminobutane, diaminopentane, diaminohexane, diaminooctane, diaminodecane or diaminododecane,

and/or

The crosslinking is carried out at a temperature of 0 to 90 DEG C

And/or

The crosslinking time is from 10 seconds to 16 hours.

37. A method according to claim 35, characterized in that the polyimide polymer is crosslinked with an aliphatic diamine or bis-4, 4' - (aminomethyl) benzene and said crosslinking is carried out by dipping into a solution of said diamine in water or alcohol or a mixture thereof,

and/or

The diamine is present in a concentration of 0.01 to 50 wt.%.

38. A method according to claim 35, characterised in that the polyethyleneimine is an oligoethyleneimine.

39. Process according to claim 37, characterized in that the alcohol is methanol or ethanol or isopropanol.

40. The method according to claim 36, characterized in that the crosslinking is carried out at a temperature of 10 to 60 ℃.

41. The method according to claim 36, characterized in that the crosslinking is carried out at a temperature of 15 to 30 ℃.

42. The method according to claim 36, characterized in that the crosslinking time is 30 seconds to 30 minutes.

43. The method according to claim 36, characterized in that the crosslinking time is 1 to 5 minutes.

44. The process according to claim 37, characterized in that the diamine concentration is from 0.1% to 10% by weight.

45. The process according to claim 37, characterized in that the diamine concentration is from 0.2% to 1% by weight.

46. The method of claim 34, wherein the polyimide polymer solution is thermostated to 20 to 100 ℃ and then pumped through the outer part of the two-material die.

47. A method according to claim 46, characterized in that the polyimide polymer solution is thermostatted to a temperature of 30 to 70 ℃.

48. The method according to claim 35, characterized in that the composition between the solvent and the water of the drilling solution is 10 to 95 wt. -% solvent and 90 to 5 wt. -% water.

49. The method according to claim 35, characterized in that the composition between the solvent and the water of the drilling solution is 30 to 90 wt. -% solvent and 70 to 10 wt. -% water.

50. The method according to claim 35, characterized in that the composition between the solvent and the water of the drilling solution is 50 to 80 wt% solvent and 50 to 20 wt% water.

51. The method according to claim 35, characterized in that the hollow fibers enter a tube filled with dry thermostatic gas before entering the spinning bath.

52. A method according to claim 51, characterized in that

The dry constant temperature gas is selected from nitrogen, air, argon, helium, carbon dioxide, methane or other industrial inert gases; and/or

The temperature of the drying constant-temperature gas is 20 to 250 ℃; and/or

The gas velocity in the tube is 0.1 to 10 m/min; and/or

The tube length is 10 to 50 cm.

53. A method according to claim 52, characterized in that the temperature of the drying thermostatted gas is between 30 and 150 ℃.

54. A method according to claim 52, characterized in that the temperature of the drying thermostatted gas is between 40 and 120 ℃.

55. The process according to claim 34, characterized in that the spinning bath temperature is 5 to 30 ℃.

56. The process according to claim 55, characterized in that the spin bath temperature is 8 to 16 ℃.

57. A method according to claim 34, characterized in that the hollow fibres are drawn at a speed of 2 to 100 m/min.

58. The method according to claim 34, characterized in that the hollow fibers are washed in water until the residual solvent content is below 1%.

59. The method according to claim 34, characterized in that the hollow fibers are dried between room temperature and 150 ℃.

60. The method of claim 59, wherein the hollow fibers are dried at a temperature of between 50 and 100 ℃.

61. Polyimide film obtainable according to the process of any one of claims 1 to 60, wherein the polyimide film comprises Mp>100000g.mol^-1Mp ═ peak maximum of molar mass distribution, calibrated against polystyrene standards in 0.01 moles per liter of lithium bromide in dimethylformamide, and PDI from 1.7 to 2.3.

62. The polyimide membrane of claim 61, wherein the PDI is from 1.8 to 2.1.

63. A polyimide film according to claim 61 or 62, characterised in that the polyimide is a polyimide having the following structure:

r is selected from

x, y: 0< x <0.5 and 1> y > 0.5.

64. A polyimide membrane according to claim 61 or 62, characterised in that the polyimide membrane is a microfiltration, ultrafiltration or nanofiltration membrane useful for separating homogeneously dissolved or particulate matter from organic solvents or from water, or the polyimide membrane is a non-porous membrane useful for gas separation.

65. A polyimide membrane according to claim 61 or 62, characterised in that the polyimide membrane is an integrally asymmetric flat sheet membrane on a backing non-woven fabric or an integrally asymmetric hollow fibre membrane.

66. A polyimide film according to claim 65, characterised in that the backing nonwoven fabric is a backing nonwoven fabric made of polyphenylene sulfide, polyethylene terephthalate or polypropylene.

67. A polyimide membrane in accordance with claim 65, wherein said polyimide membrane is a polyimide hollow fiber membrane, said polyimide hollow fiber membrane being capable of being used to separate various gas mixtures.

68. The polyimide membrane of claim 67, wherein said polyimide hollow fiber membrane is selected from the group consisting of

For separating methane and carbon dioxide

And/or

For separating oxygen and nitrogen

And/or

For separating hydrogen from process gases

And/or

For separating water vapor from various types of gases or gas mixtures.

69. Polyimide membrane according to claim 65, characterised in that the flat sheet membrane or hollow fibre membrane comprises an Mp of 110000 to 200000g.mol^-1The polyimide of (1).

70. The poly according to claim 65Imide membrane, characterized in that the flat sheet membrane or hollow fiber membrane comprises an Mp of 120000 to 170000g.mol^-1The polyimide of (1).

71. A polyimide film according to claim 61, characterised in that the polyimide is selected from:

72. Casting solution obtainable according to the method of any one of claims 1 to 60.