Crosslinked hollow fiber membranes and novel methods of making the hollow fiber membranes

Abstract

The present invention relates to a high performance crosslinked hollow fiber membrane and a method of manufacturing the crosslinked hollow fiber membrane.

Description

Technical Field

[0001] This invention relates to high-performance cross-linked hollow fiber membranes and a novel method for manufacturing such cross-linked hollow fiber membranes. Background Technology

[0002] Multilayer hollow fiber membranes are well known in the art. They typically consist of a support layer and a separator layer, which can be made of different materials (asymmetric composite membranes) or substantially the same material (monolithic asymmetric membranes). In both cases, the support layer and separator layer have different morphologies.

[0003] Polyimide membranes, in particular, are known to have excellent inherent separation properties, but they tend to fail when exposed to high concentrations of CO2, H2S, or higher hydrocarbons. This is especially true in natural gas desulfurization, where CO2 is removed from the product gas CH4, where membranes typically encounter feed streams containing large amounts of higher hydrocarbons (C3+, aromatics, and aliphatic), as well as high concentrations of CO2 and H2S.

[0004] A typical way to make the membrane more robust and resistant to such conditions is to crosslink the polymer chains.

[0005] The most well-known method is chemical crosslinking of membranes. For example, US 2016 / 0310912A1 discloses a method for crosslinking hollow fiber and flat sheet membranes, in which the membrane is treated with diamine in a downstream step of the membrane production process. This method is very complex, environmentally unfriendly, and costly because it requires large amounts of diamine and additional equipment for the crosslinking step.

[0006] WO 2014 / / 202324 A1 discloses a method for producing a gas separation membrane that exhibits good separation performance even after prolonged use under harsh conditions. The membrane is thermally crosslinked at very high temperatures in an atmosphere with very low O2 content. This process consumes a very high amount of energy.

[0007] KKKopec et al.'s "Chemistry in a spinneret – On the interplay of crosslinking and phase inversion during spinning of novel hollow-fibremembranes", J.Membr.Sci., 369(2011), 308-318, and SMDutczak et al.'s "Chemistry in aspinneret to fabricate hollow fibres for organic solvent nanofiltration", Separation and Purification Technology, 86(2012), 183-189, and WO2011l / 108929 disclose a one-step membrane production and crosslinking method. In this method, an organic nucleophilic crosslinking agent is added to the pore liquid used during spinning. Crosslinking occurs sequentially during membrane formation. A separate downstream crosslinking step is not required. According to the publications, if a low molecular weight diamine is used as the organic nucleophilic crosslinking agent, a macroporous membrane suitable only for ultrafiltration can be obtained. To obtain a membrane suitable for gas separation, a high molecular weight amine (e.g., polyethyleneimine or PEI) must be used as the crosslinking agent. However, in that case, it becomes very difficult to reduce the thickness of the separation layer and achieve good gas permeability. The membrane's mechanical stability is also insufficient.

[0008] Therefore, there is a strong need for an effective method to produce hollow fiber membranes that are highly insoluble and retain good mechanical strength. Summary of the Invention

[0009] The object of this invention is to provide a novel method for producing hollow fiber membranes without the disadvantages of prior art methods, which have such disadvantages only to a lesser extent. Another object is to provide a novel hollow fiber membrane.

[0010] The specific object of this invention is to provide a method for producing hollow fiber membranes, thereby allowing the acquisition of hollow fiber membranes with high chemical resistance and good mechanical strength. Preferably, this should be achieved without using a separate post-processing step to crosslink the membrane. Even more preferably, a continuous production method for such hollow fiber membranes should be provided.

[0011] A further objective is to provide a cost-effective method, particularly considering energy consumption and equipment investment costs. Even more preferably, it should be possible to implement the new method in existing plants with lower investment costs.

[0012] Another object of the present invention is to provide a method for producing membranes with high selectivity and good separation performance. These membranes should preferably be usable in a wide range of applications, such as gas separation, organic solvent nanofiltration, and vapor recovery.

[0013] The new method should be preferably applicable to a variety of polymers.

[0014] A particular object of the present invention is to provide a method that allows control of the thickness of the separation layer of the membrane and / or the production of membranes having internal and / or external separation layers (i.e., separation layers inside and / or outside (preferably outside) the membrane).

[0015] Other objects not explicitly stated will be apparent from the entirety of the claims, specification, embodiments, and drawings.

[0016] The inventors were surprised to find that these problems could be solved by the method described in claim 1 and the membrane obtainable by the method. A crosslinking agent having at least two amino groups is added to the pore solution during membrane spinning, followed by a thermal post-treatment of the dried membrane under mild conditions to obtain a highly crosslinked membrane with good chemical resistance, mechanical strength, high selectivity, and good separation performance (permeability).

[0017] Because the new method is an in-line process, it is cost-effective, as it eliminates the need for a separate post-treatment crosslinking step. Compared to existing methods, the method of this invention is less toxic and generates less wastewater. Costs can be reduced by decreasing the amount of crosslinking agent.

[0018] The mild conditions of the heat post-treatment, i.e., the lower temperature compared to existing technologies, offer additional economic benefits. Finally, the new method is advantageous because it can be implemented in existing plant equipment.

[0019] In contrast to the one-step crosslinking methods suggested in the prior art, the fibers obtained by the method of the present invention do not have macropores and are suitable for gas separation even when low molecular weight diamines are used as crosslinking agents.

[0020] Another important advantage of the method of the present invention compared to the one-step crosslinking method of the prior art is that an integral asymmetric membrane with an outer dense layer can be obtained even if the crosslinking agent is part of the pore solution spun through the central hole of the spinning die. Therefore, a membrane with a dense outer layer can be obtained by using a dual-hole spinneret installed in most existing plants. In the prior art, if a crosslinking agent is added to the pore solution, a membrane with an inner dense layer is obtained. However, a dense inner layer is generally undesirable and may pose a risk of hollow fiber failure and delamination.

[0021] Unbound by any theory, the inventors believe that this particular benefit of the invention can be achieved by using an amine-based crosslinker with lower polarity and lower water solubility. Such a crosslinker preferably diffuses more uniformly from the pore solution into the wall pores and further into the polymer, whereas the more polar and water-soluble amine-based crosslinkers used in the prior art are preferably retained in the pore liquid and then diffuse only into the polymer around the pores.

[0022] The method of this invention allows for flexible control over the degree of membrane crosslinking (i.e., 100% insolubility in DMF), the mechanical strength of the dense layer, and / or the thickness. Therefore, membranes can be customized for different applications, such as gas separation, vapor recovery, and organic solvent nanofiltration.

[0023] Different types of polymers can be used in the method of the present invention to further increase its flexibility.

[0024] Other advantages not explicitly stated will be apparent from the entirety of the claims, specification, embodiments, and drawings.

[0025] Before describing the details of the invention, the following general definitions are provided:

[0026] The verb "comprising" and its variations, as used in the specification, embodiments, and claims, are used in their non-limiting sense to indicate that the item following the word is included, but not excluding items not specifically mentioned. As a preferred embodiment, "comprising" includes "consisting of," which refers to the item following the word, but excludes items not specifically mentioned.

[0027] The indefinite article "one" or "a" does not preclude the possibility of more than one element, unless the context explicitly requires the presence of one element and only one of the elements. Therefore, the indefinite article "one" or "a" usually means "one or more".

[0028] The phrase "available by means of" as used in the specification and claims is used in a non-limiting sense, meaning that a product obtainable by means of the method described following the phrase can, but does not necessarily have to, be obtained by the method described. If the same product can be obtained by different methods, those methods will also be included. As a preferred embodiment, "available" includes "obtainable by means of".

[0029] "Phase (a1)" and "phase (a1) composition" refer to a composition comprising a polymer (a1.i) and a solvent (a1.ii) for said polymer. "Phase (a1) composition" is referred to in the art as "spinning composition" or "dope solution" or "casting solution".

[0030] "Phase (a2)" and "phase (a2) composition" refer to compositions comprising a non-solvent for the polymer (a1.i) and one or more aliphatic or aromatic amines (a2.i) having at least two amino groups. Phase (a2) extruded through the central hole of the spinning die is also called "pore liquid," while phase extruded through the external hole is also called "shell liquid."

[0031] A1.ii, meaning "solvent or solvent mixture for polymer (a1.i)," is a liquid or a mixture of liquids in which polymer (a1.i) can be completely dissolved. A solvent mixture (a1.ii) for polymer (a1.i) can be a mixture of different solvents used for polymer (a1.i), but it can also be a mixture of solvent and non-solvent used for polymer (a1.i), wherein the solvent content is high enough that polymer (a1.i) can be completely dissolved.

[0032] "A non-solvent or non-solvent mixture for polymer (a1.i)" is a liquid or liquid mixture in which, in both cases, polymer (a1.i) cannot be completely dissolved, preferably, in which case it cannot be dissolved at all. A non-solvent mixture for polymer (a1.i) can be a mixture of different non-solvents for polymer (a1.i), but it can also be a mixture of solvent and non-solvent for polymer (a1.i) in which the solvent content is too low for polymer (a1.i) to be completely dissolved in the mixture.

[0033] As used in this specification, embodiments and claims, "annealing temperature" refers to the temperature of the atmosphere surrounding the film at a distance of up to 10 cm, preferably 2 to 10 cm, from the outer surface of the film during heat treatment step (d).

[0034] This invention relates to a method for manufacturing hollow fiber membranes, comprising the following steps:

[0035] (a) Spinning a hollow fiber membrane, the spinning process including

[0036] (a1) A composition comprising phase (a1), preferably a solution, is extruded through the holes of a hollow fiber die, preferably an annular hole:

[0037] (a1.i) polymers selected from the group consisting of optionally functionalized polyimides, copolyimides, block-copolyimides, polyetherimides, polyamide-based imides, or mixtures or blends thereof, and

[0038] (a1.ii) A solvent or solvent mixture used for said polymer (a1.i);

[0039] (a2) A composition comprising phase (a2) is co-extruded through the central hole, preferably an annular hole, and / or through the external hole of the hollow fiber die, preferably an annular hole:

[0040] (a2.i) An amine crosslinking agent having at least two amino groups, preferably an aliphatic or aromatic amine.

[0041] (a2.ii) For polymers (a1.i) that are used in non-solvent or non-solvent mixtures.

[0042] (b) Pass the hollow fiber membrane through a coagulation bath.

[0043] (c) Dry the hollow fiber membrane to a total water and / or residual solvent content of 0 to 5% by weight.

[0044] (d) The hollow fiber membrane is heat-treated at an annealing temperature of 150 to 280°C, preferably 160 to 270°C, more preferably 160 to 260°C, even more preferably 170 to 250°C, particularly preferably 170 to 240°C, and most preferably 180 to 230°C for 15 to 180 minutes, more preferably 30 to 150 minutes, even more preferably 45 to 120 minutes, and most preferably 50 to 100 minutes.

[0045] When the method of the present invention is combined with the polymer used as polymer (a1.i) in step (a), a membrane with good separation performance, good mechanical strength, and chemical resistance can be obtained. Polyimide, copolyimide, or block-copolyimide is preferred as polymer (a1.i). Polymer (a1.i) can be a homopolymer, random polymer, or copolymer, or it can be a mixture or blend of different polymers.

[0046] In principle, all polyimides, copolyimides, block-copolyimides, polyetherimides, and polyamide-based imides that are soluble in solvents or solvent mixtures (a1.ii) can be used in the method of the present invention. In a preferred embodiment of the present invention, the polyimide is used as a polymer that can be obtained by polycondensation of the following substances (a1.i):

[0047] Selected from one or more of the following dianhydrides: BTDA (3,3′,4,4′-benzophenone tetracarboxylic dianhydride), PMDA (pyromellitic dianhydride), BPDA (3,3',4,4'-biphenyltetracarboxylic dianhydride), ODPA (4,4'-oxydiphthalic anhydride), BPADA (4,4'-bisphenol A dianhydride, CAS No. 38103-06-9), 6FDA (4,4'-(hexafluoroisopropylidene)diphthalic anhydride), 3,3′,4,4′-diphenyl sulfone tetracarboxylic dianhydride (DSDA).

[0048] and

[0049] The diisocyanate is selected from one or more of the following: 2,4-TDI (2,4-toluene diisocyanate), 2,6-TDI (2,6-toluene diisocyanate), 4,4'-MDI (4,4'-methylene diphenyl diisocyanate), MesDI (trimethylbenzene diisocyanate, 2,4,6-trimethyl-1,3-phenylene diisocyanate), 2,3,5,6-tetramethyl-1,4-phenylene diisocyanate, diethylmethylphenyl diisocyanate, phenylindenium-based diisocyanates, and 4,4′-methylene 2,2′,6,6′-di-dimethylphenyl diisocyanate.

[0050] Instead of diisocyanates, corresponding diamines can be used. In that case, a polyamic acid is formed as an intermediate, which is converted into a soluble polyimide in a second step, for example, by chemical or thermal imidization. Such imidization methods are known to those skilled in the art.

[0051] Particularly preferred is that the polymer (a1.i) is a polyimide having a structure according to formula (1):

[0052]

[0053] Where 0 ≤ x ≤ 0.5 and 1 ≥ y ≥ 0.5, the sum of x and y = 1, and R represents one or more identical or different parts selected from L1, L2, L3 and L4.

[0054]

[0055] The polyimide is particularly preferred to be a polymer according to formula (1), wherein x = 0, y = 1 and R consists of 64 mol% L2, 16 mol% L3 and 20 mol% L4. This polymer is commercially available under the name P84 or P84 type 70 and has the following CAS number: 9046-51-9.

[0056] Similarly, very particularly preferably, the polyimide of formula (1) is a polymer having the following composition: x = 0.4, y = 0.6, and R consists of 80 mol% L2 and 20 mol% L3. This polymer is commercially available under the name P84HT or P84 HT325 and has the following CAS number: 134119-41-8.

[0057] Details regarding the preparation of these and other similar polyimides can be extracted from WO 2011 / 009919, the contents of which are expressly incorporated herein by reference. Particularly preferred are all polymers described in the examples of WO 2011 / 009919 as polymers (a1.i) in step (a1) of the method of the present invention.

[0058] DE 21 43 080 describes the preparation of a solvent-soluble polyimide from a mixture of toluene-2,4-diisocyanate, toluene-2,6-diisocyanate, and 4,4′-methylenediphenyldiisocyanate and BTDA. It also describes the preparation of a solvent-soluble polyamic acid from a mixture of toluene-2,4-diamine, toluene-2,6-diamine, and 4,4′-methylenediphenyldiamine with BTDA, followed by imidization to the corresponding polyimide. Details regarding the production of these and other similar polyimides and polyamic acids can be extracted from DE 21 43 080, the entire contents of which are expressly incorporated herein by reference. All polymers described in the examples of DE 21 43 080 are particularly preferred for use in the methods of the present invention.

[0059] In another preferred embodiment of the invention, the polymer (a1.i) is a block-copolyimide, i.e., a copolymer comprising blocks (A) and (B) according to the following formulas (2) and (3), preferably consisting of blocks (A) and (B) according to the following formulas (2) and (3):

[0060]

[0061] The segments A and B have different compositions, that is, the R1 and R3 pairs on one side and the R2 and R4 pairs on the other side cannot be the same at the same time.

[0062] The block-copolyimide of this preferred embodiment comprises a continuous phase of block A, wherein functional group R1 comprises one or two of the following functional groups:

[0063]

[0064] R2 contains at least one, two, or three of the following functional groups:

[0065]

[0066] In the most preferred embodiment, segment A has the following composition:

[0067] AF1: 100 mol% R1b and 64 mol% R2a, 16 mol% R2b and 20 mol% R2c;

[0068] AF2: 40 mol% R1a, 60 mol% R1b, 80 mol% R2a, and 20 mol% R2b.

[0069] The listed molar percentages relate to functional groups R1 and R2, such that the amount of each unit is chosen such that the sum is 100 moles for each of these groups.

[0070] Block B was selected as a polymer that is significantly more permeable than block A. R3 in block B contains at least one or more of the following functional groups:

[0071]

[0072] Where X =

[0073]

[0074] R4 contains at least one or more of the following functional groups:

[0075]

[0076] Where X1, X2, X3 and X4 are H or CH3 or alkyl groups having 2 to 4 carbon atoms, and Y = –CH2–, –(CH3)2C–, –SO2–, –(CF3)2C–, –CO–, –COO–, –CONH–, –O–.

[0077] The group X1 to X4 contains at least one of the following groups: preferably at least two of the following groups; more preferably at least three of the following groups; and most preferably all of the following groups X1 to X4 are equal to CH3 or C2 to C4 alkyl.

[0078] R 4c Y in the form is preferably –CH2–, –(CH3)2C–, –(CF3)2C–, or –O–, more preferably Y = –CH2– or –(CH3)2C–. 4c The following composition is particularly preferred: X1, X2, and X3 = H, X4 = CH3 or C2 to C4 alkyl, and Y = –CH2– or –(CH3)2C–, or X1 and X3 = CH3 or C2 to C4 alkyl, X2 and X4 = H or CH3, and Y = –CH2– or –(CH3)2C–, respectively. 4cThe following composition is most preferred: X1, X2, X3, and X4 = CH3 or C2 to C4 alkyl, and Y = –CH2– or -(CH3)2C–, preferably -CH2–. If the groups X1 to X4 in the above preferred embodiments are not H, then they are most preferably CH3.

[0079] In a particularly preferred embodiment, the block (B) has the following composition:

[0080] AF3: 40 to 60 mol% R 3a 0 to 10 mol% R 3b 60 to 30 mol% R 3c and 90 to 100 mol% R 4a 0 to 10 mol% R 4b and 0 to 10 mol% R 4c .

[0081] AF4: 50 mol% R3a, 50 mol% R3c and 100 mol% R4a.

[0082] The molar percentages described for AF3 and AF4 generally relate to functional groups R3 and R4, respectively, and therefore the amounts of each unit are chosen such that their sum for each of these groups is 100 moles.

[0083] Very particularly preferred are the combinations of AF1 and / or AF2 with AF3 and / or AF4. The combination of AF1 or AF2 with AF4 is the most preferred.

[0084] The block lengths n and m of blocks A and B are preferably 1 to 1000, more preferably 1 to 500, even more preferably 1 to 200, still more preferably 5 to 150, even more preferably 10 to 100, even more preferably 10 to 50, and most preferably 10 to 40. The block lengths of blocks A and B can be the same or different. The block-copolyimide can further exhibit some distribution relative to the specific block lengths of blocks A and B; that is, not all blocks A or all blocks B need to have the same length. Therefore, the ratio between blocks A and B can vary over a wide range. For block B, the proportion in the block-copolyimide of the present invention can be 5 to 90%, and for block A, it can be 10 to 95%. Particularly preferred is an A:B ratio of 80:20, 70:30, 60:40, or 50:50, or most preferably 45:55.

[0085] Details regarding the production of block-copolyimides and other similar polyimides of the second preferred embodiment can be extracted from WO 2015 / 091122, the contents of which are expressly incorporated herein by reference. Particularly preferred are all polymers described in the examples of WO 2015 / 091122 used as polymers (a1.i) in step (a1) of the method of the invention.

[0086] In a third preferred embodiment, a polyimide according to US 3,856,752, particularly a BTDA / DAPI (diaminophenylindene) based polyimide commercially available under CAS No. 104983-64-4 and Matrimid 5128, is used as the polymer (a1.i).

[0087] In step (a), a phase (a2) is used, comprising one or more crosslinking agents (a2.i) having at least two amino groups. The crosslinking agent is preferably selected from one or more aliphatic or aromatic amines having at least two amino groups and mixtures thereof.

[0088] In a preferred embodiment of the invention, an aliphatic or aromatic amine having at least two amino groups is used as a crosslinking agent (a2.i), which is selected from the group consisting of:

[0089] - A substituted or unsubstituted straight-chain or branched aliphatic amine having 6 to 30 carbon atoms, preferably 6 to 24 carbon atoms, more preferably 6 to 20 carbon atoms, and most preferably 6 to 18 carbon atoms, comprising

[0090] o has a carbon chain having 5 to 24 carbon atoms, preferably 5 to 20 carbon atoms, more preferably 6 to 18 carbon atoms, and most preferably 6 to 15 carbon atoms.

[0091] o 2 to 5, preferably 2 to 4, more preferably 2 to 3, and most preferably 2 amino groups, preferably primary amino groups.

[0092] - A substituted or unsubstituted cyclic aliphatic amine having 6 to 24 carbon atoms, preferably excluding 1,3-diaminocyclohexane and 1,4-diaminocyclohexane. The substituted or unsubstituted cyclic aliphatic amine preferably has 7 to 20 carbon atoms, more preferably 8 to 18 carbon atoms, most preferably 8 to 15 carbon atoms, and 2 to 5, preferably 2 to 4, more preferably 2 to 3, and most preferably 2 primary amino groups, optionally containing heteroatoms in the alkyl chain or in the form of bonds between aliphatic rings.

[0093] - A substituted or unsubstituted aromatic or alkyl aromatic amine having 6 to 24 carbon atoms, preferably 7 to 20 carbon atoms, more preferably 8 to 18 carbon atoms, most preferably 8 to 15 carbon atoms, and 2 to 5, preferably 2 to 4, more preferably 2 to 3 and most preferably 2 primary amines, optionally containing heteroatoms.

[0094] and its mixtures.

[0095] Straight-chain or branched aliphatic amines can be substituted. For example, they may contain one or more functional groups other than an amino group, such as hydroxyl, carbonyl, thiol, ester, or amide groups. One or more carbon atoms in the aliphatic carbon chain may be replaced by heteroatoms such as N, O, or S; however, at least one segment of the carbon chain with 5 to 24 carbon atoms (as defined above) that are not broken by heteroatoms must be included.

[0096] Alicyclic amines can be substituted or unsubstituted. For example, they may contain one or more functional groups in addition to an amino group, such as hydroxyl, carbonyl, thiol, ester, or amide groups. Other possible substituents are preferably selected from:

[0097] - A straight-chain or branched alkyl group having 1 to 6 carbon atoms, preferably 1 to 4, more preferably 1 to 3, even more preferably 1 or 2, and most preferably 1 carbon atom, which optionally contains one or more functional groups, preferably amino or hydroxyl, and most preferably amino.

[0098] - A cycloalkyl or alkyl-cycloalkyl group having 3 to 18 carbon atoms, preferably 4 to 15, more preferably 5 to 12, and even more preferably 6 or 12 carbon atoms, optionally containing one or more functional groups, preferably amino or hydroxyl, most preferably amino.

[0099] - Divalent alkyl or cycloalkyl groups that form fused ring systems with two or three alkyl rings.

[0100] One or more carbon atoms in an alicyclic ring can be replaced by heteroatoms such as N, O, or S. Preferably, the alicyclic amine contains at most one heteroatom, or particularly preferably no heteroatom.

[0101] Aromatic or alkyl aromatic amines can be substituted or unsubstituted, meaning they can contain one or more functional groups other than an amino group, such as hydroxyl, carbonyl, thiol, ester, or amide. Other substituents are preferably straight-chain or branched alkyl or cycloalkyl or alkyl-cycloalkyl groups having 1 to 6 carbon atoms, more preferably 1 to 4, more preferably 1 to 3, even more preferably 1 or 2, and most preferably 1 carbon atom, optionally containing one or more functional groups, preferably amino or hydroxyl, and most preferably amino.

[0102] One or more carbon atoms of the aromatic ring or one of its substituents may be replaced by heteroatoms such as N, O, or S. Preferably, the aromatic ring contains at most one heteroatom, or particularly preferably, no heteroatom is present in the aromatic amine.

[0103] As further explained above, it is preferred to use an amine-based crosslinking agent with low polarity and low water solubility as the crosslinking agent (a2.i). The use of such a crosslinking agent (a2.i) results in the advantages described above and further shown in the following examples.

[0104] In another preferred embodiment of the invention, an aliphatic or aromatic amine having at least two amino groups is used as a crosslinking agent with an octanol-water partition coefficient log P equal to or greater than -0.5 (a2.i).

[0105] The P-value represents the concentration ratio of one substance in a two-phase system consisting of 1-octanol and water, and is reported as log P in base 10 (J. Sangster, Octanol-Water Partition Coefficients: Fundamentals and Physical Chemistry, Vol. 2 of Wiley Series in Solution Chemistry, John Wiley & Sons, Chichester, 1997). The octanol-water partition coefficient increases with increasing fat solubility and decreasing water solubility. Particularly preferred are amine crosslinking agents with an octanol-water partition coefficient log P equal to or greater than -0.4, more preferably equal to or greater than -0.3, even more preferably equal to or greater than -0.2, and most preferably equal to or greater than -0.2 to 3 (a2.i). The upper limit of the log P value depends on the solubility of the crosslinking agent in the pore liquid, and on the non-solvent or non-solvent mixture used, the crosslinking agent used, and the concentration of the crosslinking agent. Preferably, combinations in which the crosslinking agent is completely dissolved in the pore solution are used.

[0106] In the specification, embodiments, and claims of this invention, Log P represents the version of the program Chem Draw Prime (version 15.1.0.144). The partition coefficients were calculated by inputting the structural formula of the corresponding compound into PerkinElmer Informatics, Inc. (1998-2016). Chem Draw Prime version 15.1.0.144 calculated three different log P values. The log P values ​​mentioned in this specification, examples, and claims were calculated using Crippen's fragmentation: J. Chem. Inf. Comput. Sci., 27, 21 (1987) with Chem Draw Prime version 15.1.0.144. The log P ranges given above and claimed in the claims are defined for log P values ​​calculated using Chem Draw Prime version 15.1.0.144, ignoring standard deviations.

[0107] Table 1 below provides a non-limiting list of preferred crosslinking agents (a2.i) with an octanol-water partition coefficient log P equal to or greater than -0.5. This table should not be construed as limiting the scope of this application to the listed crosslinking agents. Other amine-based crosslinking agents with calculated log P values ​​within the above-defined range may also be used. This can be achieved using ChemDraw Prime version 15.1.0.144. (1998-2016 PerkinElmer Informatics, Inc.) After inputting the structural formula of the corresponding compound, the value of log P is given in Table 1.

[0108] Table 1:

[0109]

[0110]

[0111] Particularly preferred are the following embodiments, wherein the crosslinking agent (a2.i) has an octanol-water partition coefficient log P equal to or greater than -0.5, more preferably equal to or greater than -0.4, more preferably equal to or greater than -0.3, even more preferably equal to or greater than -0.2, and most preferably equal to or greater than -0.2 to 3, and is selected from the group defined in the above "Preferred Embodiments of the Invention".

[0112] With even more preferred crosslinking agents (a2.i), selected from 1,6-hexylene diamine, 1,7-heptylene diamine, 1,8-octylene diamine, 1,9-nonylene diamine, 1,10-decylene diamine, 1,11-undecylene diamine, 1,12-dodecylene diamine, 1,3-cyclohexanebis(methylamine), 2,2,4-trimethylhexane-1,6-diamine, 2,4,4-trimethylhexane-1,6-diamine, 2-methylpentanediamine, isophorone diamine (3,5,5-trimethyl-3-aminomethyl-cyclohexylamine), 4,4'-diaminodicyclohexane Methane, 2,4'-diaminodicyclohexylmethane, 2,2'-diaminodicyclohexyl, individual isomers or mixtures of isomers, 3,3'-dimethyl-4,4'-diaminodicyclohexylmethane, N-cyclohexyl-1,3-propanediamine, 1,2-diaminocyclohexane, TCD-diamine (3(4),8(9)-bis(aminomethyl)tricyclo[5.2.1.02,6]decane), xylenediamine, aromatic amines, o-phenylenediamine, m-phenylenediamine or p-phenylenediamine, trimethylphenylenediamine, 4,4'-diaminodiphenylmethane, and mixtures of the diamines are also possible.

[0113] The most preferred crosslinking agent (a2.i) is selected from 1,6-hexylene diamine, 1,7-heptylene diamine, 1,8-octylene diamine, 1,9-nonylene diamine, 2,2,4-trimethylhexane-1,6-diamine, 2,4,4-trimethylhexane-1,6-diamine, decane-1,10-diamine, dodecane-1,12-diamine, 2-methylpentanediamine, and 1,3-cyclohexanebis(methylamine), and mixtures of the diamines are also possible.

[0114] The crosslinking agent (a2.i) contains at least two amino groups. They may contain primary, secondary, or tertiary amino groups, or mixtures thereof. Primary and secondary amino groups are preferred. Most preferably, at least one primary amino group is contained.

[0115] According to the invention, the solvent or solvent mixture (a1.ii) used for the polymer (a1.i) preferably comprises a polar aprotic solvent. Suitable polar aprotic solvents are well known in the art and are preferably selected from dimethyl sulfoxide (DMSO), dimethylformamide (DMF), dimethylacetamide (DMA), N-methylpyrrolidone (NMP), N-ethylpyrrolidone, sulfolane, and tetrahydrofuran (THF). The solvent used for the polymer can be a mixture of these polar aprotic solvents.

[0116] Preferably, the solvent or solvent mixture (a1.ii) for the polymer (a1.i) comprises 60 to 100% by weight, more preferably 70 to 100% by weight, of a polar aprotic solvent based on the total weight of the solvent mixture. Based on the total weight of the mixture, the polar aprotic solvent may be mixed with 0 to 40% by weight, more preferably 0 to 30% by weight or less of a non-solvent for the polymer (a1.i), but still retain its ability to dissolve the polymer (a1.i).

[0117] According to the invention, the non-solvent or non-solvent mixture (a2.ii) used for the polymer (a1.i) preferably contains a protic solvent. Such solvents are well known in the art and are preferably selected from water, C1-C6 alkanols (e.g., ethanol), C2-C6 alkyldiols (e.g., ethylene glycol), C3-C12 alkyltriols (e.g., glycerol), C4-C20 polyols (e.g., pentaerythritol, bis(trimethylolpropane), diglycerol, bis(trimethylolethane), trimethylolethane, trimethylolpropane, trimethylolpropane, trimethylolbutane, pentaerythritol, dipentaerythritol, tripentaerythritol, and sorbitol), and hydrophilic, preferably water-soluble polymers or copolymers such as polyalkylene polyols and polyvinylpyrrolidone. The non-solvent can be a mixture of non-solvents. Most preferably, it is water or a mixture of a non-solvent and water.

[0118] Preferred polyalkylene polyols are derived from C2-C4 alkylene glycols, and they are selected from polyethylene glycol (PEG), polypropylene glycol (PPO), EO-PO diblock polymers, EO-PO triblock polymers, mixed poly(ethylene-propylene glycol) polymers, and mixed poly(ethylene-butene glycol) polymers. More preferably, hydrophilic polymers or copolymers of C2-C4 alkylene glycols are hydrophilic polymers with a number average molecular weight of 200 to 5000, more preferably 400 to 3000, and particularly 400 to 2000. Most preferably, the hydrophilic block is PEG. Exemplary hydrophilic blocks are PEG200, PEG400, and PEG600.

[0119] Preferably, the non-solvent or non-solvent mixture (a2.ii) contains 60 to 100% by weight, more preferably 70 to 100% by weight, of a proton solvent based on the total weight of the non-solvent mixture. Based on the total weight of the non-solvent mixture, the proton solvent may be mixed with 0 to 40% by weight, more preferably 0 to 30% by weight, or less of a solvent for the polymer (a1.i), but still retains its ability not to dissolve the polymer (a1.i).

[0120] According to the present invention, it is preferred that the non-solvent used for the polymer is miscible with the solvent used for the polymer.

[0121] The method according to the invention is based on liquid-induced phase separation. Typically, in such a method, a polymer solution and a non-solvent, preferably a non-solvent miscible with the solvent used for the polymer, are co-extruded through a multi-hole die, and the solvent is displaced from the polymer phase upon contact between the polymer solution and the non-solvent, and then the polymer becomes a solid at a certain concentration of non-solvent.

[0122] The method according to the invention can be carried out using different spinnerets, such as dual-hole, triple-hole, or quadruple-hole spinnerets. These spinnerets are known in the art and disclosed, for example, in WO 93 / 12868 and WO2007 / 007051, which are incorporated herein by reference. In a dual-hole spinneret, phase a1 is typically extruded through an outer annular orifice, while phase a2 is extruded through a central annular orifice. In a triple-hole spinneret, phase a1 is extruded through a central orifice, while phase a2 is extruded through a central annular orifice and / or through an outer annular orifice, preferably through the outer annular orifice. A quadruple-hole spinneret similarly enables the production of three-layer hollow fiber membranes.

[0123] According to a preferred embodiment of the invention, phase (a1) composition comprises a polymer (a1.i) and a solvent (a1.ii) for the polymer, while phase (a2) composition comprises an amine crosslinking agent (a2.i) having at least two amino groups, preferably an aliphatic or aromatic amine having at least two amino groups, and a non-solvent (a2.ii) for the polymer (a1.i).

[0124] According to another preferred embodiment of the invention, phase (a1) composition comprises a polymer (a1.i) and a solvent mixture (a1.ii) for the polymer, while phase (a2) composition comprises an amine crosslinking agent (a2.i) having at least two amino groups, preferably an aliphatic or aromatic amine having at least two amino groups, and a non-solvent (a2.ii) for the polymer (a1.i). In this second embodiment of the invention, the solvent mixture (a1.ii) for the polymer (a1.i) comprises 60-100% by weight, more preferably 70-99.9% by weight of a solvent for the polymer (a1.i) based on the total weight of the solvent mixture, and 0-40% by weight, more preferably 0.1-30% by weight of a non-solvent for the polymer (a1.i) based on the total weight of the solvent mixture.

[0125] According to a further preferred embodiment of the invention, phase (a1) composition comprises a polymer (a1.i) and a solvent mixture (a1.ii) for the polymer, while phase (a2) composition comprises an amine crosslinking agent (a2.i) having at least two amino groups, preferably an aliphatic or aromatic amine having at least two amino groups, and a non-solvent mixture (a2.ii) for the polymer (a1.i). In this preferred embodiment of the invention, the solvent mixture (a1.ii) in phase (a1) preferably comprises 60-100% by weight, more preferably 70-99.9% by weight, of a solvent for the polymer (a1.i) based on the total weight of the solvent mixture, and 0-40% by weight, more preferably 0.1-30% by weight, of a non-solvent for the polymer (a1.i) based on the total weight of the solvent mixture. The non-solvent mixture (a2.ii) for the phase (a2) composition preferably comprises 60-100% by weight, more preferably 70-99.9% by weight of a non-solvent for the polymer (a1.i) based on the total weight of the non-solvent mixture, and 0-40% by weight, more preferably 0.1-30% by weight of a solvent for the polymer (a1.i) based on the total weight of the non-solvent mixture.

[0126] According to another preferred embodiment of the invention, phase (a1) composition comprises a polymer (a1.i) and a solvent (a1.ii) for the polymer, while phase (a2) composition comprises an amine crosslinking agent (a2.i) having at least two amino groups, preferably an aliphatic or aromatic amine having at least two amino groups, and a non-solvent mixture (a2.ii) for the polymer (a1.i). The non-solvent mixture (a2.ii) for phase (a2) composition preferably comprises 60-99.9% by weight, more preferably 70-99.9% by weight, of a non-solvent for the polymer (a1.i) based on the total weight of the non-solvent mixture, and 0.1-40% by weight, more preferably 0.1-30% by weight, of a solvent for the polymer (a1.i) based on the total weight of the non-solvent mixture.

[0127] Therefore, the present invention includes the following options:

[0128] • Phase (a1) composition: polymer (a1.i) + solvent for polymer (a1.i); Phase (a2) composition: amine crosslinking agent (a2.i) having at least two amino groups, preferably aliphatic or aromatic amine having at least two amino groups + non-solvent for polymer (a1.i).

[0129] • Phase (a1) composition: polymer (a1.i) + solvent for polymer (a1.i) + non-solvent for polymer (a1.i); Phase (a2) composition: amine crosslinking agent (a2.i) having at least two amino groups, preferably aliphatic or aromatic amine having at least two amino groups + non-solvent for polymer (a1.i).

[0130] • Phase (a1) composition: polymer (a1.i) + solvent for polymer (a1.i); Phase (a2) composition: amine crosslinking agent (a2.i) having at least two amino groups, preferably aliphatic or aromatic amine having at least two amino groups + solvent for polymer (a1.i) + non-solvent for polymer (a1.i).

[0131] • Phase (a1) composition: polymer (a1.i) + solvent for polymer (a1.i) + non-solvent for polymer (a1.i); Phase (a2) composition: amine crosslinking agent (a2.i) having at least two amino groups, preferably aliphatic or aromatic amine having at least two amino groups + solvent for polymer (a1.i) + non-solvent for polymer (a1.i). Attached Figure Description

[0132] Figure 1 The diagram schematically shows a dual-orifice spinneret. When the method of the present invention is performed using the dual-orifice spinneret, phase (a1) is extruded through the outer annular orifice (1), while phase (a2) is co-extruded through the central annular orifice (2). The outer diameter of the two material dies is preferably 500 to 800 μm, more preferably 550 to 750 μm, and the inner diameter is preferably 200 to 400 μm, more preferably 250 to 350 μm, and the pump speed is preferably between 0.1 and 13.5 ml / min.

[0133] Figure 2 A three-hole spinneret is schematically shown. When using the method of the present invention with a three-hole spinneret, the following options are preferred:

[0134] Phase (a1) is extruded through the middle annular hole (1) + Phase (a2) is co-extruded through the outer annular hole (3) + Non-solvent is co-extruded through the central annular hole (2).

[0135] Phase (a1) is extruded through the middle annular hole (1) + Phase (a2) is co-extruded through the central annular hole (2) + Non-solvent is co-extruded through the outer annular hole (3).

[0136] Phase (a1) is extruded through the middle annular hole (1) and phase (a2) is co-extruded through the central annular hole (2) and the outer annular hole (3).

[0137] Phase (a1) is extruded through the middle annular hole (1) + Phase (a2) is co-extruded through the outer annular hole (3) + Inert gas, vapor or inert liquid is co-extruded through the central annular hole (2).

[0138] Phase (a1) is extruded through the middle annular hole (1) + Phase (a2) is co-extruded through the central annular hole (2) + Inert gas, vapor or inert liquid is co-extruded through the outer annular hole (3).

[0139] Figure 3a The diagram shows a heterogeneous inner layer structure; and Figure 3b An example of the membrane of the present invention having a homogeneous support layer is shown. Detailed Implementation

[0140] According to a preferred embodiment of the invention, based on the total weight of the phase (a1) composition, the phase (a1) composition comprises a total of about 15% to 35% by weight, preferably 20% to 30% by weight, more preferably 22% to 30% by weight, and even more preferably 22% to 29% by weight of polymer (a1.i). The remaining mass of the phase (a1) is preferably a solvent / solvent mixture (a1.ii) for the polymer (a1.i) and other components, such as non-solvents, which may be present to accelerate coagulation. It has been found that increasing the content of polymer (a1.i) in the phase (a1) is beneficial for obtaining membranes with higher selectivity. However, if the content is too high, the viscosity becomes too high and may cause filtration problems.

[0141] According to a preferred embodiment of the invention, based on the total weight of the amine crosslinking agent (a2.i) in phase (a2) plus the mixture of non-solvent or non-solvent mixture (a2.ii), the phase (a2) composition comprises a total of about 0.1 wt% to 30 wt%, preferably 0.5 wt% to 20 wt%, more preferably 1 wt% to 10 wt%, and even more preferably 2 wt% to 8 wt% of an amine crosslinking agent (a2.i) having at least two amino groups, more preferably an aliphatic or aromatic amine, and 70 wt% to 99.9 wt%, preferably 80 wt% to 99.5 wt%, more preferably 90 wt% to 99 wt%, and even more preferably 92 wt% to 98 wt% of a non-solvent or non-solvent mixture (a2.ii). Based on the total weight of the non-solvent mixture (a2.ii), which comprises 1% to 99% by weight, preferably 10% to 95% by weight, more preferably 30% to 90% by weight, and even more preferably 50% to 80% by weight of a solvent for the polymer (a1.i), and 1% to 99% by weight, preferably 5% to 90% by weight, more preferably 10% to 70% by weight, and even more preferably 20% to 50% by weight of a non-solvent for the polymer (a1.i). The amounts of solvent and non-solvent are selected from the ranges given above, such that the sum of solvent and non-solvent is 100% of the weight of the non-solvent mixture. Phase (a2) may consist of an amine crosslinking agent (a2.i) having at least two amino groups plus a non-solvent or a non-solvent mixture (a2.ii), or it may contain other components such as additives.

[0142] Preferably, the phase (a1) is devolatilized before spinning, filtered, and optionally additives are added to the phase (a1). More preferably, the phase (a1) is also isothermated – preferably to 20-100°C, more preferably 30-70°C. The solution is then gear-pumped, for example, through a die. Specifically, devolatilization is important for obtaining a defect-free membrane.

[0143] The preferred distance between the spinning die and the precipitation bath is 1 cm to 1 m, preferably 5 to 60 cm, wherein the hollow fiber is spun into the precipitation bath in step (b) and a hollow fiber membrane is formed by precipitating polymers therein.

[0144] As the solvent evaporates on the outer surface of the membrane during the journey between the spinning die and the precipitation bath, the layer is densified in step (b) to form a separation layer upon precipitation in the precipitation bath. The thickness of the separation layer can be adjusted by the distance from the spinning die to the precipitation bath and by the atmosphere of the membrane during the journey from the spinning die to the precipitation bath.

[0145] In a preferred embodiment, the membrane obtained by the method according to the invention has high permeability, i.e., high permeability. Therefore, the membrane should not have an excessively thick and / or excessively dense separation layer. Thus, it is preferred that, during the spinning process, after step (a) and before entering the precipitation bath in step (b), the hollow yarn is subjected to a flow of a drying isothermal stream of gas or air and / or through a corresponding gas or air atmosphere. Passing the membrane through the gas or air stream is particularly preferred. Drying should be understood as meaning that the gas or air stream is capable of absorbing water. Therefore, at a specific air / gas temperature, the air or gas stream preferably has a relative humidity of 0 to 90%, more preferably 0 to 50%, and more preferably 0 to 30%.

[0146] It is particularly preferred that the hollow fibers exiting the die after step (a) enter a shaft (pipe, chimney) filled with dry, temperature-controlled gas. Useful gases include nitrogen, air, argon, helium, carbon dioxide, methane, or other industrial inert gases. The gas temperature is regulated via a heat exchanger and is preferably between 20 and 250°C, more preferably between 25 and 120°C, and most preferably between 30 and 80°C.

[0147] The gas velocity in the tube is preferably between 0.1 and 10 m / min, more preferably between 0.3 and 5 m / min, even more preferably between 0.5 and 3 m / min, and most preferably between 0.5 and 2 m / min. The tube length is preferably between 1 cm and 1 m, more preferably between 2 and 50 cm, even more preferably between 5 and 40 cm, and most preferably between 5 and 30 cm. The shaft length, gas velocity, and temperature all affect the actual thickness of the membrane separation layer.

[0148] As previously mentioned, the choice of amine crosslinking agent (a2.i) affects the membrane structure and layer structure. For the production of a completely asymmetric membrane with an external separation layer, it is particularly preferred to use an amine crosslinking agent (a2.ii) that is less polar and less water-soluble, as defined above as the preferred crosslinking agent. This crosslinking agent preferably diffuses more uniformly from the pore solution into the wall pores of the hollow fiber membrane and further into the polymer, whereas the more polar and water-soluble amine crosslinking agents used in the prior art are preferably retained in the pore liquid and then diffuse only into the polymer near the pores.

[0149] The fibers spun and preferably conditioned in step (a) are then immersed in a precipitation bath in step (b) to allow the polymer material to coagulate and thus form a film. The bath temperature is preferably between 1 and 80°C, more preferably between 20 and 70°C, and most preferably between 40 and 65°C.

[0150] The concentration of the aprotic dipolar solvent and other solvents (e.g., but not limited to dimethylformamide, dimethylacetamide, N-methylpyrrolidone, N-ethylpyrrolidone, sulfolane, dimethyl sulfoxide, tetrahydrofuran, dioxane, isopropanol, ethanol, or glycerol) in the precipitation bath is preferably between 0.01 wt% and 20 wt%, more preferably between 0.1 wt% and 10 wt%, and most preferably between 0.2 wt% and 1 wt%, with the remainder being water. It is also preferred to use purified water in the water bath.

[0151] The traction speed of the hollow fibers is preferably between 2 and 100 m / min, more preferably between 10 and 80 m / min, and most preferably between 30 and 70 m / min. It has been found that excessively high traction speeds lead to a loss of permeability. However, compared to the prior art, the preferred method according to the present invention can be operated at a higher traction speed, thereby achieving improved productivity.

[0152] The fibers are preferably washed downstream of the settling bath until the residual solvent content is less than 1% by weight, preferably not exceeding 0.5% by weight. Various washing techniques can be used for this purpose. A continuous method in which the fibers pass through one or more consecutive water baths is preferred. It is particularly preferred to heat the water bath to 40 to 90°C, preferably 50 to 80°C, for more effective washing.

[0153] However, fibers obtained from the settling bath may also be entangled and washed offline in water. Washing can be performed at any temperature. However, it is preferable to use a relatively high temperature for washing, as described above. It is preferable to guide the water in a transverse flow along the fibers, i.e., to force it to flow from the inner surface to the outside.

[0154] This is followed by solvent exchange, more preferably in isopropanol and / or hexane, to remove water and DMF. Solvent exchange can be performed as a continuous operation (online) or offline as washing. For online solvent exchange, the fibers are guided through one or more solvent baths, preferably downstream of the washing bath.

[0155] Then, in step (c), the fibers are dried, preferably at a temperature of room temperature to 150°C, more preferably 50 to 100°C, to remove isopropanol and hexane. The total water and / or residual solvent content after drying is 0% to 5% by weight, preferably <3% by weight, more preferably 0.1% to 3% by weight, and preferably consists of water, isopropanol, and hexane fractions.

[0156] Excessive water can lead to hydrolysis and thus chain breakage, resulting in a mechanically unstable film. Although some water and some solvent evaporate during annealing, it has been determined that the maximum content before the start of annealing is advantageously less than 5% by weight, preferably less than 3% by weight.

[0157] In step (d), the hollow fiber membrane obtained from step (c) is subjected to heat treatment at an annealing temperature of 150 to 280°C, preferably 160 to 270°C, more preferably 160 to 260°C, even more preferably 170 to 250°C, particularly preferably 170 to 240°C, and most preferably 180 to 230°C.

[0158] The conditions during heat treatment can vary depending on the desired properties of the membrane. If the annealing temperature is too low or too high, the degree of crosslinking, i.e., the insolubility in the DMF, will be too low. It has been found that if a very high degree of crosslinking is required and therefore chemical stability is necessary, the optimal annealing temperature for step (d) in the method of the present invention is in the range of 180 to 230°C.

[0159] Further investigation revealed that if the annealing temperature during step (d) is too high, the mechanical stability of the film, especially the elongation at break, deteriorates.

[0160] The gas selectivity and permeability of the membrane can also be influenced and controlled by selecting an appropriate annealing temperature in step (d). While a higher annealing temperature results in better selectivity, permeability decreases.

[0161] The embodiments provided below make it clear to those skilled in the art what changes are made, how they affect the properties of the product, and how he or she determines which properties.

[0162] Compared to the annealing temperature, the duration of the temperature treatment in step (d)—from the time the target temperature is reached—has a smaller impact on membrane performance. However, as shown in the examples, some properties such as gas selectivity, permeability, and insolubility can also be influenced and controlled by the heat treatment time in step (d). Preferably, the heat treatment in step (d) is performed for 15 to 300 minutes, more preferably for 30 to 240 minutes, even more preferably for 30 to 90 minutes, and most preferably for 60 to 90 minutes.

[0163] The heating rate selected to achieve the heat treatment temperature in step (d) is preferably from about 35°C, in the range of 0.1 to 10°C / min, more preferably in the range of 1 to 5°C / min, and most preferably in the range of 1 to 2°C / min, so that annealing can be carried out uniformly throughout the membrane bundle and the final temperature can be reached simultaneously. A relatively slow heating rate is particularly advantageous when annealing a large number of fibers simultaneously, in order to ensure uniform annealing of the fibers.

[0164] The annealing temperature (i.e., the atmosphere at a distance of up to 10 cm, preferably 2 to 10 cm, around the membrane) is measured using three or more sensors, preferably thermocouples. When annealing only one membrane, the specified distance relates to the distance to the outer surface of the membrane. When two or more membranes are annealed simultaneously, for example, in a membrane bundle or a stacked arrangement of membranes, the distance relates to the outer surface of the membrane that is completely on the outside, i.e., the distance to the outer surface of the membrane bundle or other membrane arrangement.

[0165] When the oxygen content of the atmosphere at a distance of up to 10 cm, preferably 2 to 10 cm, around the membrane does not exceed a certain maximum during annealing, the mechanical properties of the membrane and its productivity are found to be particularly good. Therefore, preferably, the heat treatment is carried out at an oxygen content of no more than 0.5 vol%, more preferably no more than 0.25 vol%, even more preferably no more than 0.1 vol%, and even more preferably no more than 0.01 vol%.

[0166] Particularly good results were obtained when annealing the membranes in a gas atmosphere or gas flow with a correspondingly low oxygen content, and not just in a vacuum. Not wanting to be limited to any one theory, the inventors believe that the gas atmosphere and / or gas flow ensures a uniform temperature distribution within the membrane bundle to be annealed, and thus ensures uniform annealing of all membranes.

[0167] Therefore, during annealing and preferably at least in the first stage of cooling, more preferably also during annealing and / or until the end of the cooling step, the membrane is preferably surrounded by an atmosphere with a relatively low oxygen content. It is particularly preferred that the membrane be subjected to a stream or mixture of gases having the aforementioned low oxygen content during the aforementioned stages, more preferably a stream of at least one inert gas (e.g., a rare gas, nitrogen, or sulfur hexafluoride), or even more preferably a stream of nitrogen. The appropriate gas stream is most preferred. During cooling, i.e., once the temperature has permanently dropped below the maximum annealing temperature, a vacuum may also be applied.

[0168] Particularly preferred is that, after cooling to a temperature below 150°C begins, the atmosphere around the membrane at a distance of up to 10 cm, preferably 2 to 10 cm, corresponds to the aforementioned gas atmosphere and / or is evacuated. At lower temperatures, especially below 150°C, the membrane's reactivity is so low that contact with an oxygen-rich atmosphere will generally no longer cause any damage.

[0169] Cooling the membrane after heat treatment stage (d) can be “passive,” i.e., by shutting off the heat source. However, it is particularly preferred that the fully annealed membrane be “actively” cooled, for example, by rinsing the oven or by contacting the membrane with an inert gas at a temperature appropriately regulated to have the specified O2 content. Alternatively, however, cooling is also preferably performed using a heat exchanger and / or a cooling loop. Other technical modifications to achieve proper cooling are known to those skilled in the art and are covered by this invention. Active cooling improves space-time yield and reduces the risk of undesirable degradation of membrane properties still occurring during cooling.

[0170] In the method of the present invention, it is preferable to use a silicone elastomer, for example, after drying. 184. The membrane is treated to repair any possible defects.

[0171] Another embodiment of the present invention is a hollow fiber membrane obtainable by the method according to the present invention. The fibers of the present invention are preferably integrally asymmetrical hollow fiber membranes.

[0172] The degree of crosslinking of the polymer in the fiber can be controlled, but is preferably very high. It can be measured by immersing the membrane in DMF at 25°C for 24 hours under controlled conditions. Insoluble matter is filtered, dried, and weighed. No insoluble matter corresponds to 100% crosslinking, and complete dissolution corresponds to 0% crosslinking. Preferably, the membrane of the present invention has a degree of crosslinking of at least 85%, more preferably 90 to 100%, and even more preferably 95 to 100%.

[0173] The cross-linked hollow fiber membrane of the present invention comprises:

[0174] Polymers selected from polyimides, copolyimides, block-copolyimides, polyetherimides, polyamide-based imides, or mixtures or blends thereof, and

[0175] Amine crosslinking agents having at least two amino groups, preferably aliphatic or aromatic amines.

[0176] It also possesses a dense, cross-linked outer layer and a homogeneous, cross-linked inner support layer. The "homogeneous, cross-linked inner support layer" refers to a single layer visible in a scanning electron microscope image (300x magnification) of the front side of the hollow fiber, between the dense outer layer (not visible in magnified images) and the inner surface of the hollow fiber. Figure 3b An example of the membrane of the present invention having a homogeneous support layer is shown in the figure, while Figure 3a An example of a membrane with a heterogeneous inner layer structure (i.e., having two visible inner layers and a clearly visible boundary between the two layers) is shown. Because the connection between the two layers at the visible boundary is weak, therefore... Figure 3aThe structure of these materials exhibits poor mechanical stability. Considering their mechanical stability, the membrane of the present invention, with its homogeneous structure, is advantageous. Furthermore, the hollow fibers of the present invention, with their cross-linked inner layers—meaning not only the dense outer layer but also the inner layer is cross-linked—are therefore widely insoluble.

[0177] Preferred polymers and amine crosslinking agents that can be included in the crosslinked hollow fiber membrane according to the invention are those defined as preferred embodiments for the above-described method of the invention.

[0178] The cross-linked hollow fiber membranes of the present invention are preferably integrally asymmetric hollow fiber membranes. They can be obtained by the method according to the present invention.

[0179] The hollow fiber membrane according to the present invention is particularly suitable for gas separation processes, vapor separation processes and liquid filtration processes.

[0180] Analytical methods

[0181] Permeability

[0182] With GPU (gas permeation unit, 10) -6 cm 3 .cm -2 .s -1 .cmHg -1 The permeability of hollow fiber membranes to gas is reported in units of 100%.

[0183] The permeability P / l is calculated using the following formula (since the thickness of the separation layer is unknown):

[0184]

[0185] P / l…with GPU (gas permeation unit, 10) -6 cm 3 .cm -2 .s -1 .cmHg -1 Permeability in units of )

[0186] Q…in cm 3 Gas flow rate on the permeate side in units of (STP) / s

[0187] R…in cm 3 .cmHg.K -1 .mol -1 gas constant in units

[0188] T... Kelvin temperature (room temperature, ~23℃)

[0189] A… with cm 2 The external area of ​​a unit hollow fiber (in 60 to 80 cm²) 2between)

[0190] Δp…the pressure difference between the feed side and the permeate side, expressed in cmHg.

[0191] dp / dt in cmHg.s -1 The pressure increase per unit time on the permeable side

[0192] The selectivity of various gas pairs is the pure gas selectivity. The selectivity between two gases is calculated based on permeability:

[0193]

[0194] S…ideal gas selectivity

[0195] P1…permeability or permeability of gas 1

[0196] P2…permeability or permeability of gas 2

[0197] Determination of residual solvent content

[0198] Residual solvents (e.g., isopropanol, hexane) were determined by headspace injection of polymers dissolved / dispersed in 1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone (DMPU) via gas chromatography.

[0199] Weigh 250–300 mg of sample precisely to 0.1 mg (initial weight) and place it in a tare bottle. Then, add 5.00 mL of DMPU using a full-volume pipette or dispenser, and seal the bottle with a septum using a cap crimper. Incubate the sample in a headspace syringe at 120°C for 90 minutes, then inject it headspace onto a GC column.

[0200] Residual DMF in moist hollow fiber samples was determined by Soxhlet extraction in ethanol. Subsequent quantification was performed by direct injection of the extract onto a GC. Residual DMF in dried hollow fiber samples was determined using headspace GC.

[0201] GC: Perkin Elmer AutoSystem XL

[0202] Column: Perkin Elmer WAX ETR, 30m x 0.53mm, df=2.00μm, #N931-6570

[0203] Headspace autosampler: Perkin Elmer TurboMatrix 40

[0204] Carrier gas: 5 ml helium 4.6 (or better)

[0205] FID detector gas: 40 ml / min hydrogen, 400 ml / min synthesis air

[0206] GC temperature program:

[0207] Initial temperature: 175℃ for 3 minutes.

[0208] Heating rate 1: Increase to 230°C at 20°C / min and hold for 3 minutes.

[0209] Run time: 8.75 minutes

[0210] Cycle time: 15 minutes

[0211] After analysis, the residual solvent content is automatically calculated according to the following formula.

[0212]

[0213] It is printed as “concentration [%]”.

[0214] Determination of residual water content

[0215] The residual water content was determined by extraction of the membrane with isopropanol followed by Karl Fischer titration. The membrane was transferred to a pre-dried 250 ml Schott glass container and topped with a weighed amount of dry isopropanol. The container was left to stand at room temperature overnight.

[0216] Tensile strength and elongation at break

[0217] Tensile strength and elongation at break were tested using a Zwick Z050 static material testing machine. The obtained values ​​are the average of 10 readings from 10 independent hollow fibers. The following are the setup parameters:

[0218] Table 2:

[0219] Clamping length 200 mm Preload force 0.1 N Preload speed 20 mm / min Test speed 50 mm / min Cut-off load threshold 80 %Fmax Fracture load threshold 0.5 N

[0220] Record the tensile strength when the elongation is no longer linearly related to the applied load. Record the elongation at break, which is the change in length of the hollow fiber before it breaks.

[0221] Example

[0222] The following examples are intended to illustrate and describe the invention in more detail, but should not be construed as limiting the invention in any way.

[0223] chemicals used

[0224] Polymer (a1.i)

[0225] PI 1: P84 HT prepared according to Example 7 of WO2011009919

[0226] Co-PI: Block-co-polyimide with the following blocks

[0227] o A segment: BTDA / PMDA–TDI

[0228] o B-block: BTDA / PMDA–MesDA

[0229] The ratio A:B is 80:20

[0230] It was prepared according to Example 40 of WO 2015 / 091122 with a block ratio of 80:20 instead of 75:25.

[0231] Crosslinking agent (A2.i)

[0232] Table 3

[0233]

[0234] solvent

[0235] DMF is derived from dimethylformamide from BASF.

[0236] non-solvent

[0237] water

[0238] Example 1: General Description of the Membrane Production Process

[0239] To prepare phase (a) solution, polymer (a1.i) was dissolved in a solvent. The solution was devolatiled, kept at 50°C, and pumped through a dual-material die gear pump at a flow rate of 324 g / h. While the polymer solution (a1) was being transported in the outer region of the dual-material die, phase (a2), composed of a non-solvent (a2.ii) for polymer (a1.i) and a diamine crosslinking agent (a2.i), was being transported in the inner region as a porous solution to create pores in the hollow fibers. The flow rate of the porous solution was 120 ml / h. After a distance of 13 cm from the die, the hollow fibers entered a coagulation bath containing warm water at 50°C. The hollow fibers traveled through a tube from the die to the precipitation bath. This tube was filled with a nitrogen flow of 0.90 l / min, and the internal temperature of the tube was 35°C. The fibers were drawn through a water bath and finally wound at a speed of 40 m / min. After several hours of water extraction, the hollow fibers were immersed in isopropanol. After solvent exchange, the membrane is guided through a drying zone at 70°C and dried over approximately 50 seconds. The resulting membrane is then heated to the desired annealing temperature under a vacuum of 30 mbar absolute pressure (N2 rinsing, O2 content < 0.001 vol%), and subsequently held at the final temperature for the desired time.

[0240] The materials used as polymer (a1.i), diamine crosslinking agent (a2.i), solvent (a1.ii), non-solvent (a2.ii), composition of phases (a1) and (a2), annealing temperature and annealing time are given in the various examples and comparative examples below.

[0241] Example 2: Effect of the amount of diamine crosslinking agent (a2.i) on the degree of crosslinking of the membrane (insolubility in DMF)

[0242] Hollow fiber membranes were prepared according to the parameters given in Table 4, based on Example 1.

[0243] Table 4

[0244]

[0245]

[0246] The analysis results in Table 4 show that the degree of crosslinking can vary over a wide range using the method of the present invention.

[0247] Example 3: Effects of the polarity of the diamine crosslinking agent (a2.i) and annealing temperature on film structure and properties

[0248] Hollow fiber membranes were prepared according to the parameters given in Table 5, based on Example 1.

[0249] Table 5

[0250]

[0251] The results in Table 5 show that if polyethyleneimine, which has a very low log P value, is used as the crosslinking agent, the degree of crosslinking after annealing is at a comparable level. However, if TMD, which has a high log P value, is used as the crosslinking agent, the method of the present invention allows for flexible adjustment of the degree of crosslinking.

[0252] In addition, such as Figure 3a As shown, using polyethyleneimine as a crosslinking agent results in the formation of an internal dense layer near the surface of the hollow fiber lumen. This structure may pose a risk of failure and could lead to membrane delamination. If the preferred crosslinking agent TMD is used, the formation of an internal dense layer can be avoided, and as... Figure 3b The homogeneous membrane was obtained as shown.

[0253] Table 5 also shows that using a crosslinking agent with a high octanol / water partition coefficient log P, followed by heat treatment of the crosslinked membrane, produces hollow fiber membranes with better mechanical properties. As shown below, heat treatment is necessary to obtain good membrane selectivity.

[0254] Example 4: Effect of annealing temperature in step (d) on the properties, chemical and mechanical stability of the film.

[0255] According to Example 1, hollow fiber membranes were prepared according to the parameters given in Table 6.

[0256] Table 6

[0257]

[0258] The results in Table 6 show the effect of annealing temperature in step (d). While selectivity and tensile strength improve with increasing temperature, penetration and elongation decrease with further increases in annealing temperature. Optimal chemical resistance (insolubility in DMF) is achieved at temperatures between 200 and 250 °C.

[0259] Example 5: Effect of annealing duration in step (d) on the properties, chemical and mechanical stability of the membrane.

[0260] Hollow fiber membranes were prepared according to the parameters given in Table 7, based on Example 1.

[0261] Table 7

[0262] Example 5.3 Example 5.4 Polymer (al.i) PI 1 PI 1 Diamine crosslinking agent (a2.i) TMD TMD solvent DMF DMF non-solvent <![CDATA[H2O]]> <![CDATA[H2O]]> The phase (a1) is composed of a weight ratio of (a1.i):solvent:nonsolvent. 1∶2.63∶0 1∶2.63∶0 The phase (a2) is composed of a solvent: non-solvent: (a2.i) weight ratio. 1∶0.42∶0.07 1∶0.42∶0.07 Annealing temperature [°C] 270 270 Annealing time [min] 60 90 Insoluble percentage in DMF [%) 88 87 Tension [N] 1.6 1.5 Elongation [%) 15.4 15.4 <![CDATA[Permeability O2 [GPU]]]> 11.9 10.6 <![CDATA[Selective O2 / N2]]> 7.1 7.0

[0263] Table 7 shows that the annealing duration in step (d) has little effect on the membrane performance.

[0264] Example 6: Comparison of the effects of different crosslinking agents (a2.i) on the mechanical properties and chemical resistance of the resulting membranes

[0265] According to Example 1, hollow fiber membranes were prepared according to the parameters given in Tables 8.1 to 8.6.

[0266] Table 8.1

[0267]

[0268] Table 8.2

[0269]

[0270] Table 8.3

[0271]

[0272]

[0273] Table 8.4

[0274]

[0275] Table 8.5

[0276]

[0277] Table 8.6

[0278]

[0279] Tables 8.1 to 8.6 show that, according to the method of the present invention, wherein chemical crosslinking occurs during the phase invention process (hollow fiber formation in step (a)), the crosslinking agent can be selected according to the polarity of the crosslinking agent, thereby providing control over the crosslinking process.

[0280] Using amine-based crosslinking agents with low polarity and low water solubility, exhibiting high log P (>-0.5), allows for better control of the crosslinking process. The degree of crosslinking can be further increased through appropriate heat treatment at temperatures of 150–250 °C.

Claims

1. A method for manufacturing a hollow fiber membrane, comprising the following steps: (a) Spinning hollow fiber membranes, including (a1) A composition comprising the following phase (a1) is extruded through the orifice of a hollow fiber die: (a1.i) Polymers selected from polyimides, copolyimides, block-copolyimides, polyetherimides, polyamide-based imides, or mixtures or blends thereof, and (a1.ii) Solvent or solvent mixture used for said polymer (a1.i); (a2) A composition comprising the following phase (a2) is co-extruded through the central hole and / or the outer hole of the hollow fiber die: (a2.i) An amine crosslinking agent having at least two amino groups. (a2.ii) A non-solvent or non-solvent mixture used for the polymer (a1.i), (b) Pass the hollow fiber membrane through a coagulation bath. (c) Dry the hollow fiber membrane to a total water and / or residual solvent content of 0 to 5% by weight. (d) The hollow fiber membrane is heat-treated at an annealing temperature of 150 to 280 °C, wherein the annealing is carried out in a gas atmosphere or gas stream with low oxygen content and not only in a vacuum, wherein the oxygen content of the atmosphere at a distance of up to 10 cm around the membrane does not exceed 0.5% by volume.

2. The method according to claim 1, wherein the hollow fiber die head is a two-hole spinneret, a three-hole spinneret, or a four-hole spinneret.

3. The method according to claim 2, wherein the hollow fiber die is a spinneret with annular holes.

4. The method according to any one of claims 1 to 3, wherein the phase (a1) composition comprises a total of 15% to 35% by weight of the polymer (a1.i) based on the total weight of the phase (a1) composition.

5. The method of claim 4, wherein the phase (a1) composition comprises a total of 20% to 30% by weight of the polymer (a1.i) based on the total weight of the phase (a1) composition.

6. The method of claim 4, wherein the phase (a1) composition comprises a total of 22% to 30% by weight of the polymer (a1.i) based on the total weight of the phase (a1) composition.

7. The method of claim 4, wherein the phase (a1) composition comprises a total of 22% to 29% by weight of the polymer (a1.i) based on the total weight of the phase (a1) composition.

8. The method according to any one of claims 1 to 3, wherein, based on the total weight of the composition (a2), the phase (a2) composition comprises a total of 0.1% to 30% by weight of an amine crosslinking agent having at least two amino groups (a2.i).

9. The method according to claim 8, wherein, based on the total weight of the composition (a2), the phase (a2) composition comprises a total of 0.5% to 20% by weight of an amine crosslinking agent having at least two amino groups (a2.i).

10. The method according to claim 8, wherein, based on the total weight of the composition (a2), the phase (a2) composition comprises a total of 1% to 10% by weight of an amine crosslinking agent having at least two amino groups (a2.i).

11. The method according to claim 8, wherein, based on the total weight of the composition (a2), the phase (a2) composition comprises a total of 2% to 8% by weight of an amine crosslinking agent having at least two amino groups (a2.i).

12. The method according to claim 8, wherein the amine crosslinking agent (a2.i) having at least two amino groups is an aliphatic and / or aromatic amine crosslinking agent.

13. The method according to any one of claims 1 to 3, wherein an amine crosslinking agent (a2.i) having at least two amino groups is used, said crosslinking agent having a partition coefficient of log P equal to or greater than -0.5 octanol-water.

14. The method according to claim 13, wherein the amine crosslinking agent (a2.i) having at least two amino groups is an aliphatic and / or aromatic amine crosslinking agent.

15. The method of claim 13, wherein the amine crosslinking agent (a2.i) having at least two amino groups has an octanol-water partition coefficient log P equal to or greater than -0.

4.

16. The method of claim 13, wherein the amine crosslinking agent (a2.i) having at least two amino groups has an octanol-water partition coefficient log P equal to or greater than -0.

3.

17. The method of claim 13, wherein the amine crosslinking agent (a2.i) having at least two amino groups is equal to or greater than an octanol-water partition coefficient log P of -0.

2.

18. The method of claim 13, wherein the amine crosslinking agent (a2.i) having at least two amino groups has an octanol-water partition coefficient log P of -0.2 to 3.

19. The method according to any one of claims 1 to 3, wherein the amine crosslinking agent (a2.i) is an aliphatic and / or aromatic amine having at least two amino groups.

20. The method of claim 19, wherein the aliphatic and / or aromatic amine having at least two amino groups is selected from: - Substituted or unsubstituted straight-chain or branched aliphatic amines having 6 to 30 carbon atoms, comprising Carbon chains with 5 to 24 carbon atoms, and 2 to 5 amino groups - A substituted or unsubstituted cyclic aliphatic amine having 6 to 24 carbon atoms and 2 to 5 primary amino groups, optionally containing heteroatoms in the alkyl chain or in the form of bonds between aliphatic rings. - A substituted or unsubstituted aromatic amine or alkyl aromatic amine having 6 to 24 carbon atoms and 2 to 5 primary amino groups, optionally containing heteroatoms. and its mixtures.

21. The method of claim 20, wherein the substituted or unsubstituted straight-chain or branched aliphatic amine has 6 to 24 carbon atoms.

22. The method of claim 20, wherein the substituted or unsubstituted straight-chain or branched aliphatic amine has 6 to 20 carbon atoms.

23. The method of claim 20, wherein the substituted or unsubstituted straight-chain or branched aliphatic amine has 6 to 18 carbon atoms.

24. The method of claim 20, wherein the substituted or unsubstituted straight-chain or branched aliphatic amine comprises a carbon chain having 5 to 20 carbon atoms.

25. The method of claim 20, wherein the substituted or unsubstituted straight-chain or branched aliphatic amine comprises a carbon chain having 6 to 18 carbon atoms.

26. The method of claim 20, wherein the substituted or unsubstituted straight-chain or branched aliphatic amine comprises a carbon chain having 6 to 15 carbon atoms.

27. The method of claim 20, wherein the substituted or unsubstituted straight-chain or branched aliphatic amine comprises 2 to 4 amino groups.

28. The method of claim 20, wherein the substituted or unsubstituted straight-chain or branched aliphatic amine comprises 2 to 3 amino groups.

29. The method of claim 20, wherein the substituted or unsubstituted straight-chain or branched aliphatic amine comprises two amino groups.

30. The method according to any one of claims 27 to 29, wherein the amino group is a primary amino group.

31. The method of claim 20, wherein the substituted or unsubstituted cyclic aliphatic amine comprises 7 to 20 carbon atoms.

32. The method of claim 20, wherein the substituted or unsubstituted cyclic aliphatic amine comprises 8 to 18 carbon atoms.

33. The method of claim 20, wherein the substituted or unsubstituted cyclic aliphatic amine comprises 8 to 15 carbon atoms.

34. The method of claim 20, wherein the substituted or unsubstituted cyclic aliphatic amine comprises 2 to 4 primary amino groups.

35. The method of claim 20, wherein the substituted or unsubstituted cyclic aliphatic amine comprises 2 to 3 primary amino groups.

36. The method of claim 20, wherein the substituted or unsubstituted cyclic aliphatic amine comprises two primary amino groups.

37. The method of claim 20, wherein the substituted or unsubstituted aromatic amine or alkyl aromatic amine comprises 7 to 20 carbon atoms.

38. The method of claim 20, wherein the substituted or unsubstituted aromatic amine or alkyl aromatic amine comprises 8 to 18 carbon atoms.

39. The method of claim 20, wherein the substituted or unsubstituted aromatic amine or alkyl aromatic amine comprises 8 to 15 carbon atoms.

40. The method of claim 20, wherein the substituted or unsubstituted cyclic aliphatic amine comprises 2 to 4 primary amino groups.

41. The method of claim 20, wherein the substituted or unsubstituted cyclic aliphatic amine comprises 2 to 3 primary amino groups.

42. The method of claim 20, wherein the substituted or unsubstituted cyclic aliphatic amine comprises two primary amino groups.

43. The method of claim 19, wherein the aliphatic and / or aromatic amine having at least two amino groups is selected from 1,6-hexylene diamine, 1,7-heptylene diamine, 1,8-octylene diamine, 1,9-nonylene diamine, 1,10-decylene diamine, 1,11-undecylene diamine, 1,12-dodecylene diamine, 2,2,4-trimethylhexane-1,6-diamine, 2,4,4-trimethylhexane-1,6-diamine, 2-methylpentanediamine, isophoric acid, etc. Ketodiamine (3,5,5-trimethyl-3-aminomethyl-cyclohexylamine), 4,4'-diaminodicyclohexylmethane, 2,4'-diaminodicyclohexylmethane, 2,2'-diaminodicyclohexylmethane, alone or mixtures of isomers, 3,3'-dimethyl-4,4'-diaminodicyclohexylmethane, N-cyclohexyl-1,3-propanediamine, 1,2-diaminocyclohexane, TCD-diamine (3(4),8(9)-bis(aminomethyl)tricyclo[5.2.1.0] 2,6 [Decane], xylene diamine, aromatic amines, o-phenylenediamine, m-phenylenediamine or p-phenylenediamine, trimethylphenylenediamine, 4,4'-diaminodiphenylmethane, and mixtures of the diamines are also possible.

44. The method according to claim 19, wherein the aliphatic and / or aromatic amine having at least two amino groups is selected from aliphatic amines, 1,6-hexylene diamine, 1,7-heptylene diamine, 1,8-octylene diamine, 1,9-nonylene diamine, 2,2,4-trimethylhexane-1,6-diamine, 2,4,4-trimethylhexane-1,6-diamine, decane-1,10-diamine, dodecane-1,12-diamine, 2-methylpentanediamine, 1,3-cyclohexanebis(methylamine), and mixtures of the diamines are also possible.

45. The method according to any one of claims 1 to 3, wherein the solvent (a1.ii) used for the polymer (a1.i) comprises a polar aprotic solvent.

46. ​​The method according to claim 45, wherein the solvent (a1.ii) used for the polymer (a1.i) is selected from dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, N-ethylpyrrolidone, sulfolane, tetrahydrofuran, and mixtures thereof.

47. The method according to any one of claims 1 to 3, wherein the non-solvent (a2.ii) used for the polymer (a1.i) comprises a proton solvent.

48. The method according to claim 47, wherein the non-solvent (a2.ii) used for the polymer (a1.i) is selected from water, C1-C6 alkanols, C2-C6 alkyldiols, C3-C12 alkyltriols, C4-C20 polyols, and hydrophilic polymers or copolymers.

49. The method of claim 48, wherein the hydrophilic polymer or copolymer is water-soluble.

50. The method of claim 48, wherein the hydrophilic polymer or copolymer is selected from polyalkylene polyols and polyvinylpyrrolidone.

51. The method according to any one of claims 1 to 3, wherein the heat treatment of the hollow fiber membrane in step d) is carried out at an annealing temperature of 160 to 270°C.

52. The method of claim 51, wherein the annealing temperature is 160 to 260°C.

53. The method according to claim 52, wherein the annealing temperature is 170 to 250°C.

54. The method of claim 53, wherein the annealing temperature is 170 to 240°C.

55. The method of claim 54, wherein the annealing temperature is 180 to 230°C.

56. The method of claim 1, wherein the oxygen content of the atmosphere at a distance of up to 10 cm around the membrane is no more than 0.25% by volume.

57. The method of claim 1, wherein the oxygen content of the atmosphere at a distance of up to 10 cm around the membrane is no more than 0.1% by volume.

58. The method of claim 1, wherein the oxygen content of the atmosphere at a distance of up to 10 cm around the membrane is no more than 0.01% by volume.

59. A crosslinked hollow fiber membrane obtainable by the method according to any one of claims 1 to 58, comprising: Polymers selected from polyimides, copolyimides, block-copolyimides, polyetherimides, polyamide-based imides, or mixtures or blends thereof Amine crosslinking agents having at least two amino groups, Its features are, It has a dense, cross-linked outer layer and a homogeneous, cross-linked inner support layer.

60. The cross-linked hollow fiber membrane according to claim 59, characterized in that, It is an integrally asymmetrical hollow fiber membrane.

61. Use of the hollow fiber membrane according to any one of claims 59 to 60 in gas separation methods, vapor separation methods, and liquid filtration methods.

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