Composite membranes having intrinsic microporosity

Abstract

The present invention relates to a composite membrane for gas separation and/or nanofiltration of a feed stream solution comprising a solvent and dissolved solutes and showing preferential rejection of the solutes. The composite membrane comprises a separating layer with intrinsic microporosity. The separating layer is suitably formed by interfacial polymerisation on a support membrane. Suitably, at least one of the monomers used in the interfacial polymerisation reaction should possess concavity, resulting in a network polymer with interconnected nanopores and a membrane with enhanced permeability. The support membrane may be optionally impregnated with a conditioning agent and may be optionally stable in organic solvents, particularly in polar aprotic solvents. The top layer of the composite membrane is optionally capped with functional groups to change the surface chemistry. The composite membrane may be cured in the oven to enhance rejection. Finally, the composite membrane may be treated with an activating solvent prior to nanofiltration.

Claims

1. An interfacial polymerisation process for forming a thin film composite membrane for gas separation or liquid filtration, comprising the steps of: (a) impregnating a porous support membrane with a first reactive monomer solution comprising: (i) a first solvent for the said first reactive monomer; (ii) a first reactive monomer; (b) contacting the impregnated support membrane with a second reactive monomer solution comprising: (i) a second solvent for the second reactive monomer; (ii) a second reactive monomer; wherein: the first solvent and the second solvent form a two-phase system; either one or both of the first and second reactive monomers comprises one or more selected from the group consisting of: a spiro-contorted centre, and a bridged ring moiety; and a reaction of the first and second reactive monomers results in the in-situ formation of a covalently cross-linked 3-dimensional polymeric network possessing intrinsic microporosity, said intrinsic microporosity being defined as a continuous network of interconnected intermolecular voids, said voids arising from the structure of the first and second reactive monomers; and the reaction of the first and second reactive monomers results in a separating layer forming on the support membrane to give a composite membrane; (c) after a reaction period, immersing the resulting composite membrane into a quench medium.

2. The process as claimed in claim 1, wherein the support membrane is formed from a material selected from the group consisting of an inorganic material including silicon carbide, silicon oxide, zirconium oxide, titanium oxide, aluminum oxide and a zeolite.

3. The process as claimed in claim 1, wherein the support membrane is formed from a polymer or crosslinked polymer selected from the group consisting of polysulfone, polyethersulfone, poly(ether sulfone ketone), polyacrylonitrile, polypropylene, polyamide, cellulose acetate, cellulose diacetate, cellulose triacetate, poly(ether ethyl ketone), poly(pthalazinone ether sulfone ketone), a perfluoropolymer, polyimide, polybenzimidazole, polyether ether ketone and sulfonated polyether ether ketone.

4. The process as claimed in claim 1, wherein step (a) comprises impregnating the porous support membrane, which comprises a first conditioning agent, with the first reactive monomer solution, wherein the first conditioning agent is one or more selected from the group consisting of synthetic oils, mineral oils, vegetable fats and oils, higher alcohols, glycerols, and glycols.

5. The process as claimed in claim 1, wherein the process further comprises a step of impregnating the resulting thin film composite membrane with a second conditioning agent, wherein the second conditioning agent is one or more selected from the group consisting of synthetic oils, mineral oils, vegetable fats and oils, higher alcohols, glycerols, and glycols.

6. The process as claimed in claim 1, wherein the first reactive monomer solution comprises an aqueous solution of a salt of a polyphenol or polyamine which possesses one or more selected from the group consisting of: a spiro-contorted centre, and a bridged ring moiety.

7. The process as claimed in claim 1, wherein the first reactive monomer is one or more selected from the group consisting of 1,1-spirobisindanes, 9,9-spirobisfluorenes, 1,1-spirobis,2,3,4-tetrahydro-naphthalenes, and 9,10-ethanoanthracene.

8. The process as claimed in claim 1, wherein the first reactive monomer solution comprises an aqueous solution of a salt of 5,5′,6,6′-Tetrahydroxy-3,3,3%3′-tetramethyl-1, spirobisindane.

9. The process as claimed in claim 1, wherein the second reactive monomer is one or more selected from the group consisting of mono-acyl chlorides and polyacyl chlorides.

10. The process as claimed in claim 1, wherein the second reactive monomer is one or more selected from the group consisting of trimesoyl chloride, iso-phthaloyl dichloride, and sebacoyl chloride.

11. The process as claimed in claim 1, wherein after step (b) and before step (c), the unreacted groups of the separating layer are capped with functional groups to modify the surface chemistry.

12. The process as claimed in claim 1, wherein the composite membrane is treated with an activating solvent, said activating solvent being a polar aprotic solvent.

13. The process as claimed in claim 12, wherein the activating solvent is one or more selected from the group consisting of dimethylformamide, N-methyl pyrrolidone, dimethylsulfoxide and dimethylacetamide.

14. The process as claimed in claim 1, wherein the contacting time in step (b) is chosen from between 1 second and 5 hours.

15. The process as claimed in claim 1, wherein the temperature of the contacting step (b) solution is held between 10° C. and 100° C.

16. The process as claimed in claim 1, wherein the composite membrane is cured with temperature or microwaves.

17. The process as claimed in claim 1, wherein the first reactive monomer is one or more selected from the group consisting of 1,1-spirobisindanes, 9,9-spirobisfluorenes, 1,1-spirobis,2,3,4-tetrahydro-naphthalenes, and 9,10-ethanoanthracene; and is one or more selected from the group consisting and the second reactive monomer is one or more selected from the group consisting of trimesoyl chloride, iso-phthaloyl chloride and sebacoyl chloride.

18. The process as claimed in claim 1, wherein the first reactive monomer solution comprises an aqueous solution of a salt of 5,5′,6,6′-Tetrahydroxy-3,3,3′,3′-tetramethyl-1,1′-spirobisindane; and the second reactive monomer is one or more selected from the group consisting of trimesoyl chloride, iso-phthaloyl dichloride and sebacoyl chloride.

19. The process as claimed in claim 1, wherein the first reactive monomer has any one or more of the following structures 1, 3 to 9, 11 to 16, 19, 20, and 23 to 26: ##STR00001## ##STR00002## ##STR00003## wherein Z is an electrophilic or nucleophilic group capable of reacting with the second reactive monomer.

20. The process as claimed in claim 19, wherein the second reactive monomer is one or more selected from the group consisting of trimesoyl chloride, iso-phthaloyl dichloride, and sebacoyl chloride.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows the molecular weight cut off (MWCO) curve and flux of a TFC-IP-PIMs membrane prepared on a crosslinked P84 support. The TFC membrane has been cured in the oven at 85° C. for 10 minutes. Nanofiltration of a feed solution comprising polystyrene oligomers dissolved in acetone has been performed at 30 bar and 30° C.

(2) FIG. 2 shows the MWCO curve and flux of a TFC—IP-PIMs membrane prepared on a crosslinked P84 support. The TFC membrane has not been cured in the oven. Nanofiltration of a feed solution comprising polystyrene oligomers dissolved in acetone has been performed at 30 bar and 30° C.

(3) FIG. 3 shows the MWCO curve and flux of TFC—IP-PIMs membrane prepared on a crosslinked P84 support. The TFC membrane has been cured in the oven at 85° C. for 10 minutes. Nanofiltration of a feed solution comprising polystyrene oligomers dissolved in methanol has been performed at 30 bar and 30° C.

(4) FIG. 4 shows the MWCO curve and flux of a TFC—IP-PIMs membrane prepared on a crosslinked P84 support. The TFC membrane has not been cured in the oven. Nanofiltration of a feed solution comprising polystyrene oligomers dissolved in methanol has been performed at 30 bar and 30° C.

(5) FIG. 5 shows the MWCO curve and flux of a TFC—IP-PIMs membrane prepared on a crosslinked P84 support. The TFC membrane has been cured in the oven at 85° C. for 10 minutes. Nanofiltration of a feed solution comprising polystyrene oligomers dissolved in DMF has been performed at 30 bar and 30° C.

(6) FIG. 6 shows the MWCO curve and flux of a TFC—IP-PIMs membrane prepared on a crosslinked P84 support. The TFC membrane has not been cured in the oven. Nanofiltration of a feed solution comprising polystyrene oligomers dissolved in DMF has been performed at 30 bar and 30° C.

(7) FIG. 7 shows the MWCO curve and flux of a TFC—IP-PIMs membrane prepared on a crosslinked P84 support. The TFC membrane has been cured in the oven at 85° C. for 10 minutes. Nanofiltration of a feed solution comprising polystyrene oligomers dissolved in THF has been performed at 30 bar and 30° C.

(8) FIG. 8 shows the MWCO curve and flux of a TFC—IP-PIMs membrane prepared on a crosslinked P84 support. The TFC membrane has not been cured in the oven. Nanofiltration of a feed solution comprising polystyrene oligomers dissolved in THF has been performed at 30 bar and 30° C.

(9) FIG. 9 shows the MWCO curve and flux of a TFC—IP-PIMs membrane prepared on a crosslinked P84 support. The TFC membrane has been cured in the oven at 85° C. for 10 minutes. Nanofiltration of a feed solution comprising polystyrene oligomers dissolved in toluene has been performed at 30 bar and 30° C.

(10) FIG. 10 shows the MWCO curve and flux of TFC—IP-PIMs membranes prepared on a crosslinked P84 support. The TFC membrane has not been cured in the oven. Nanofiltration of a feed solution comprising polystyrene oligomers dissolved in toluene has been performed at 30 bar and 30° C.

(11) FIG. 11 shows the MWCO curve and flux for a TFC—IP-PIMs membrane prepared on a PEEK support membrane. The TFC membrane has been cured in an oven at 85° C. for 10 minutes. Nanofiltration of a feed solution comprising polystyrene oligomers dissolved in THF has been performed at 30 bar and 30° C.

(12) FIG. 12 shows the MWCO curve and flux for a TFC—IP-PIMs membrane prepared on a PEEK support membrane. The TFC membrane has been cured in an oven at 85° C. for 10 minutes. Nanofiltration of a feed solution comprising polystyrene oligomers dissolved in acetone has been performed at 30 bar and 30° C.

(13) FIG. 13 shows the MWCO curve and flux for a TFC—IP-PIMs membrane prepared on a PEEK support membrane. The TFC membrane has been cured in the oven at 85° C. for 10 minutes. Nanofiltration of a feed solution comprising polystyrene oligomers dissolved in toluene has been performed at 30 bar and 30° C.

(14) FIG. 14 shows the MWCO curve and flux for a TFC—IP-PIMs membrane prepared on a PEEK support membrane. The TFC membrane has been cured in an oven at 85° C. for 10 minutes. Nanofiltration of a feed solution comprising polystyrene oligomers dissolved in heptane has been performed at 30 bar and 30° C.

(15) FIG. 15 shows the MWCO curve and flux for a TFC—IP-PIMs membrane prepared on a PBI support membrane. The TFC membrane has been cured in an oven at 85° C. for 10 minutes. Nanofiltration of a feed solution comprising polystyrene oligomers dissolved in THF has been performed at 30 bar and 30° C.

(16) FIG. 16 shows the MWCO curve and flux for a TFC—IP-PIMs membrane prepared on a PBI support membrane. The TFC membrane has been cured in an oven at 85° C. for 10 minutes. Nanofiltration of a feed solution comprising polystyrene oligomers dissolved in acetone has been performed at 30 bar and 30° C.

(17) FIGS. 17A-17C show the gas separation performance for a TFC—IP-PIMs membrane prepared on a PEEK support membrane. The membrane has been cured in an oven at 85° C. for 10 minutes. Gas permeation experiments were carried out at 40, 50 and 60 psig. FIG. 17A shows CO.sub.2/N.sub.2 selectivity vs. CO.sub.2 permeability;

(18) FIG. 17B shows CO.sub.2/CH.sub.4 selectivity vs. CO.sub.2 permeability, and FIG. 17C shows O.sub.2/N.sub.2 selectivity vs. O.sub.2 permeability.

(19) FIG. 18A shows various concavity-containing monomers.

(20) FIG. 18B shows various concavity-containing monomers.

(21) FIG. 18C shows various concavity-containing monomers.

(22) FIG. 19 shows examples of rigid monomers.

(23) FIG. 20 shows the chemical structures of the monomers used for the interfacial polymerization reaction in Example 1.

DESCRIPTION OF VARIOUS EMBODIMENTS

Definitions

(24) As used herein, the terms “optionally” or “optional” means that the later described event or action may or may not take place, and that the description includes examples where said event or action takes place and examples where it does not.

(25) The term “network polymer” is used herein to refer to a covalently cross-linked 3-dimensional polymeric network. This is in contrast to a “non-network polymer” (or a “linear” polymer) in which the polymers do not have a covalently cross-linked 3-dimensional structure.

(26) The term “microporosity” is used herein to refer to separating layer of the membrane comprising pores of less than or equal to 2 nm in size.

(27) The term “intrinsic microporosity” is used herein to mean the network polymer provides a continuous network of interconnected intermolecular voids (suitably of less than or equal to 2 nM in size), which forms as a direct consequence of the shape and rigidity (or concavity) of at least a proportion of the component monomers of the network polymer. As will be appreciated by a person skilled in the art, intrinsic microporosity arises due to the structure of the monomers used to form the network polymer and, as the term suggests, it is an intrinsic property of a network polymer formed from such monomers. The shape and rigidity of the monomer used to form the network polymer means that polymer possesses an internal molecular free volume (IMFV), which is a measure of the concavity of the monomers and is the difference between the volume of the concave monomer unity compared to that of the corresponding planar shape.

(28) It is understood that the network polymers disclosed herein have a certain property (i.e. intrinsic microporosity). Disclosed herein are certain structural requirements in the monomers used for giving a polymer performing the disclosed function, and it is understood that there are a variety of structures that can perform the same function that are related to the disclosed monomer structures, and that these structures will typically achieve the same result.

(29) Disclosed are the monomers to be used to prepare the network polymers of the invention as well as the polymers themselves to be used within the methods disclosed herein. It is understood that when combinations, subsets, etc. of these monomers are disclosed, that while specific reference of each various individual and collective combinations and permutation of these monomers may not be explicitly disclosed, each is specifically contemplated and described herein. If a particular polymer is disclosed and discussed and a number of modifications that can be made to a number of monomers are discussed, specifically contemplated is each and every combination and permutation of the monomers and the modifications that are possible unless specifically indicated to the contrary. Thus, if a class of monomers A, B, and C are disclosed, as well as a class of monomers D, E and F and an example of a combination polymer A-D is disclosed, then even if each is not individually recited each is individually and collectively contemplated meaning combinations A-E, A-F, B-D, B-E, B-F, C-D, C-E and C-F are considered disclosed. Likewise any subset or combination of these is also disclosed. Thus, for example, the sub-group of A-E, B-F, and C-E would be considered disclosed. This concept applies to all aspects of this application including, but not limited to, steps in methods of making and using compositions of the invention.

(30) By the term “nanofiltration” it is meant a membrane process which will allow the passage of solvents while retarding the passage of larger solute molecules, when a pressure gradient is applied across the membrane. This may be defined in terms of membrane rejection R.sub.i, a common measure known by those skilled in the art and defined as:

(31) $\begin{array}{cc}{R}_i=\left(1-\frac{C_{\mathrm{Pi}}}{C_{\mathrm{ri}}}\right)\times 100\%& \left(1\right)\end{array}$
where C.sub.P,I=concentration of species i in the permeate, permeate being the liquid which has passed through the membrane, and C.sub.R,i=concentration of species i in the retentate, retentate being the liquid which has not passed through the membrane. It will be appreciated that a membrane is selectively permeable for a species i if R.sub.i>0. It is well understood by those skilled in the art that nanofiltration is a process in which at least one solute molecule i with a molecular weight in the range 100-2,000 g mol.sup.−1 is retained at the surface of the membrane over at least one solvent, so that R.sub.i>0. Typical applied pressures in nanofiltration range from 5 bar to 50 bar.

(32) The term “solvent” will be well understood by the average skilled reader and includes an organic or aqueous liquid with molecular weight less than 300 Daltons. It is understood that the term solvent also includes a mixture of solvents.

(33) By way of non-limiting example, solvents include aromatics, alkanes, ketones, glycols, chlorinated solvents, esters, ethers, amines, nitriles, aldehydes, phenols, amides, carboxylic acids, alcohols, furans, and polar protic and polar aprotic solvents, water, and mixtures thereof.

(34) By way of non-limiting example, specific examples of solvents include toluene, xylene, benzene, styrene, anisole, chlorobenzene, dichlorobenzene, chloroform, dichloromethane, dichloroethane, methyl acetate, ethyl acetate, butyl acetate, methyl ether ketone (MEK), methyl iso butyl ketone (MIBK), acetone, ethylene glycols, ethanol, methanol, propanol, butanol, hexane, cyclohexane, dimethoxyethane, methyl tert butyl ether (MTBE), diethyl ether, adiponitrile, N,N dimethylformamide, dimethylsulfoxide, N,N dimethylacetamide, dioxane, nitromethane, nitrobenzene, pyridine, carbon disulfide, tetrahydrofuran, methyltetrahydrofuran, N-methyl pyrrolidone, acetonitrile, water, and mixtures thereof.

(35) The term “solute” will be well understood by the average skilled reader and includes an organic molecule present in a liquid solution comprising a solvent and at least one solute molecule such that the weight fraction of the solute in the liquid is less than the weight fraction of the solvent, and where the molecular weight of the solute is at least 20 g mol.sup.−1 higher than that of the solvent.

(36) Thin Film Composite Membranes

(37) Thin film composite (also referred to as TFC) membranes will be familiar to one of skill in this art and include an entity composed of a thin film separating layer over a support membrane, where the support membrane is previously formed from a different material. TFC membranes are suitably formed by interfacial polymerisation.

(38) Suitable support membranes can be produced from polymer materials including polysulfone, polyethersulfone, poly(ether sulfone ketone), polyacrylonitrile, polypropylene, polyamide, cellulose acetate, cellulose diacetate, cellulose triacetate, poly(ether ethyl ketone), poly (pthalazinone ether sulfone ketone), a perfluoropolymer, polyimide, polybenzimidazole, perfluropolymers, polyether ether ketone (PEEK), sulfonated polyether ether ketone (S-PEEK), or other polymeric materials known to those skilled in the art. Wherein, the polymer support membrane may be further crosslinked.

(39) Preferably, suitable support membranes may be prepared from an inorganic material such as by way of non-limiting example silicon carbide, silicon oxide, zirconium oxide, titanium oxide, aluminium oxides or zeolites, using any technique known to those skilled in the art such as sintering, leaching or sol-gel processes.

(40) The polymer used to form the support membrane includes but is not limited to polyimide polymer sources. The identities of such polymers are presented in the prior art, U.S. Pat. No. 0038306, the entire contents of which are incorporated herein by reference. More preferably, the support membrane of the invention is prepared from a polyimide polymer described in U.S. Pat. No. 3,708,458, assigned to Upjohn, the entire contents of which are incorporated herein by reference. The polymer, available from HP polymers GmbH, Austria as P84, is a copolymer derived from the condensation of benzophenone 3,3′,4-4′-tetracarboxylic acid dianhydride (BTDA) and a mixture of di(4-aminophenyl) methane and toluene diamine or the corresponding diisocyanates, 4,4′-methylenebis(phenyl isocyanate) and toluene diisocyanate.

(41) Support membranes can be prepared following the methods described in GB 2,437,519, the entire contents of which are incorporated herein by reference, and comprise both nanofiltration and ultrafiltration membranes. More preferably, the membranes of the invention used as supports are within the ultrafiltration range. The membrane supports of the invention may be crosslinked using suitable amine crosslinking agents and the crosslinking method and time may be that described in GB 2,437,519.

(42) The support membrane is optionally impregnated with a conditioning agent. The term “conditioning agent” is used herein to refer to any agent which, when impregnated into the support membrane prior to the interfacial polymerisation reaction, provides a resulting membrane with a higher rate of flux. Any suitable conditioning agent may be used. Suitably, the conditioning agent is a low volatility organic liquid. The conditioning agent may be chosen from synthetic oils (e.g., polyolefinic oils, silicone oils, polyalphaolefinic oils, polyisobutylene oils, synthetic wax isomerate oils, ester oils and alkyl aromatic oils), mineral oils (including solvent refined oils and hydroprocessed mineral oils and petroleum wax isomerate oils), vegetable fats and oils, higher alcohols (such as decanol, dodecanol, heptadecanol), glycerols, and glycols (such as polypropylene glycols, polyethylene glycols, polyalkylene glycols). Suitable solvents for dissolving the conditioning agent include water, alcohols, ketones, aromatics, hydrocarbons, or mixtures thereof. The first and second conditioning agents referred to herein may be the same or different.

(43) In this invention, prior to the interfacial polymerization reaction, the support membrane is optionally treated with a first conditioning agent dissolved in a solvent to impregnate the support membrane. Suitably, the first conditioning agent is a low volatility organic liquid as defined above.

(44) Following treatment with the conditioning agent, the support membrane is typically dried in air at ambient conditions to remove residual solvent.

(45) The interfacial polymerization reaction is generally held to take place at the interface between the first reactive monomer solution, and the second reactive monomer solution, which form two phases. Each phase may include a solution of a dissolved monomer or a combination thereof. Concentrations of the dissolved monomers may vary. Variables in the system may include, but are not limited to, the nature of the solvents, the nature of the monomers, monomer concentrations, the use of additives in any of the phases, reaction temperature and reaction time. Such variables may be controlled to define the properties of the membrane, e.g., membrane selectivity, flux, separating layer thickness. At least one of the monomers used in the reactive monomer solutions should have well-defined concavity (i.e. concave shape). Monomers in the first reactive solution may include, but are not limited to, polyphenols, polyamines, or mixtures thereof. The monomers in the second reactive solution include but are not limited to polyfunctional acyl halides, polyfunctional haloalkylbenzenes, polyfunctional halogenated aromatic species, or mixtures thereof. The resulting reaction may form a network polymer separating layer on top of the support membrane, including but not limited to a network polyester layer, a network polyether layer, a network polyamide layer, or a network layer that includes mixtures of these.

(46) Although water is a preferred solvent for the first reactive monomer solution, non-aqueous solvents may be utilized, such as acetyl nitrile and dimethylformamide (DMF). Although no specific order of addition is necessarily required, the first reactive monomer solution is typically coated on or impregnated into the support membrane first, followed by the second reactive monomer solution being brought into contact with the support membrane. Although one or both of the first monomer and the second monomer may be applied to the porous support from a solution, they may alternatively be applied by other means such as by vapour deposition, or neat.

(47) A residue of a chemical species refers to the moiety that is the resulting product of the chemical species in a particular reaction or subsequent chemical product, regardless of whether the moiety is actually obtained from the chemical species. Thus, an ethylene glycol residue in a polyester refers to one or more —OCH.sub.2CH.sub.2O-units in the polyester, regardless of whether the residue is obtained by reacting ethylene glycol to obtain the polyester.

(48) In this invention, the polymer matrix of the separating layer can comprise any three-dimensional polymer network possessing intrinsic microporosity. In one aspect, the separating layer comprises at least one of an aliphatic or aromatic polyamide, aromatic polyhydrazide, poly-benzimidazolone, polyepiamine/amide, polyepiamine/urea, poly-ethyleneimine/urea, sulfonated polyfurane, polyether, a polyether-amide, a polyether-urea, a polyester, a polyester-amide, polybenzimidazole, polypiperazine isophtalamide, or a polyimide or a copolymer thereof or a mixture thereof. The polymer selected to form the separating layer can be formed by an interfacial polymerization reaction.

(49) It is an important feature of the present invention that at least one of the monomers participating in the interfacial polymerisation reaction is a molecule with a concave shape (i.e. concavity), preferably rigid and linked to another monomer or monomers to form a polymer network within which molecular rotation is preferably hindered. Concavity-containing monomers include but are not limited to molecules containing a spiro-contorted centre, bridged ring moieties and sterically congested single covalent bonds around which there is restricted rotation. These molecules are also known as molecules with awkward shapes (i.e. those that pose packing problems due to their concavities). Structural units with well-defined cavities include but are not limited to 1,1-spirobisindanes (e.g. 1, 3, 4-7, 19 in FIGS. 18A-18C), 9,9-spirobisfluorenes (e.g. 16, 20 in FIGS. 18A-18C), bisnaphthalenes (e.g. 2, 17 in FIGS. 18A-18C) 1,1-spirobis,2,3,4-tetrahydro-naphthalenes (e.g. 11-14 in FIGS. 18A-18C), and 9,10-ethanoanthracene (e.g. 8,9 in FIGS. 18A-18C). Generally, the polymer network of the invention is prepared by reaction of two or more monomers, wherein at least one of the monomers possesses concavity. In one aspect the first monomer is a dinucleophilic or polynucleophilic monomer and the second monomer is a dielectrophilic or a polyelectrophilic monomer. Wherein, each monomer can have two or more reactive groups. Both electrophiles and nucleophiles are well known in the art, and one of skill in the art can choose suitable monomers for the interfacial polymerisation reaction. The first and second monomers can be chosen so as to be able to undergo an interfacial polymerisation reaction to form a three-dimensional polymer network when brought into contact.

(50) In FIGS. 18A-18C, the reactive groups are shown as Z. Here Z may be any suitable nucelophilic group such as hydroxyl or amine groups, and specifically Z=—OH, —NH.sub.2. Alternatively, Z may be any electrophilic group such as an acyl halide, specifically an acyl chloride, or an electron withdrawing group that renders the monomer electrophilic. Suitable electron withdrawing groups include halogenated species F, Cl, Br, or I. 3, 4, 9 and 13 in FIGS. 18A-18C show monomers where Z could be a halogen. FIG. 19 shows examples of rigid monomers, which are optional monomers for the interfacial polymerization reaction. Such monomers may be used individually or as mixtures with other monomers. Reactive groups in FIG. 19 are assigned as Y. Here Y may be any suitable nucelophilic group such as hydroxyl or amine groups, and specifically Z=—OH, —NH.sub.2. Alternatively, Z may be any electrophilic group such as an acyl halide, specifically an acyl chloride, or an electron withdrawing group that renders the monomer electrophilic. Suitable electron withdrawing groups include halogenated species F, Cl, Br, or I. Species 2,5,8,9,11-22 in FIG. 19 show monomers where Y could be a halogen. For the purposes of the current invention, when Z is an electrophile or a leaving group that makes the monomer an electrophile, then Y is a nucleophile, and, when Z is a nucleophile, then Y is an electrophile or a leaving group that makes the monomer an electrophile. When Y is an electrophile, or an electron withdrawing group that makes the monomer electrophilic, including F, Cl, Br, or I, then it may be particularly advantageous to combine a rigid monomer from Chart 2 present in the second reactive monomer solution with any of the monomers described above in Chart 1 which are suitable for use in the first reactive monomer solution, such as polyamines, or polyphenols, to form the separating layer.

(51) In a further embodiment of this invention, the separating layer comprises a network comprised of but not limited to, a polyester, a polyether, a polyamide, a polyimide or a mixture thereof. The polyester, polyamide, polyether or polyimide can be aromatic or non-aromatic. For example, the polyester can comprise residues of a phthaloyl (e.g. terephthaloyl or isophthaloyl) halide, a trimesoyl halide, or a mixture thereof. In another example, the polyester can comprise residues of a polyphenol containing a spiro-contorted centre, or bridged ring moieties or sterically congested single covalent bonds around which there is restricted rotation, or a mixture thereof. Wherein, a concave monomer may include but is not limited to small oligomers (n=0-10) of a polymer with intrinsic microporosity (PIM) containing nucleophilic or electrophilic reactive groups. One of skill in the art can choose suitable PIMs oligomers with reactive groups able to undergo an interfacial polymerisation reaction, which include but are not limited to polyphenols or polyamines (e.g. 25 and 26 in FIGS. 18A-18C). In a further embodiment, the separating layer comprises residues of a trimesoyl halide and residues of a tetraphenol with a spiro-contorted centre. In a further embodiment, the film comprises residues of trimesoyl chloride and 5,5′,6,6′-Tetrahydroxy-3,3,3′,3′-tetramethyl-1,1′-spirobisindane (TTSBI, monomer 1 in FIGS. 18A-18C). In a further aspect, the film comprises the reaction product of trimesoyl chloride and the sodium salt of 5,5′,6,6′-Tetrahydroxy-3,3,3′,3′-tetramethyl-1,1′-spirobisindane (TTSBI). The first reactive monomer solution may comprise an aqueous solution of monomer, and or a rigid monomer (see FIG. 19 for examples), and or a concave monomer (see FIGS. 18A-18C for examples), including, but not limited to a polyphenol with concave shape. This aqueous polyphenol solution may also contain other components, such as polyhydric compounds as disclosed in U.S. Pat. No. 4,830,885. Examples of such compounds include ethylene glycol, propylene glycol, glycerine, polyethylene glycol, polypropylene glycol, and copolymers of ethylene glycol and propylene glycol. The aqueous polyphenol solution may also contain polar aprotic solvents.

(52) Aqueous monomer solutions may include, but are not limited to, an aqueous solution containing a salt of 5,5′,6,6′-Tetrahydroxy-3,3,3′,3′-tetramethyl-1,1′-spirobisindane (TTSBI), an alternative aqueous monomer solution, and/or combinations thereof. Concentrations of solutions used in the interfacial polymerzation may be in a range from about 0.01 weight % to about 30 weight %. Preferably, concentrations of the interfacial polymerization solutions may be in a range from about 0.1% weight % to about 5 weight %. Further, aqueous monomer solutions may be rendered acidic or basic by addition of appropriate reagents, so that the monomers are rendered soluble as acidic or basic salts.

(53) The second reactive monomer solution may contain monomers with or without concavity (see FIGS. 18A-18C for examples), or/and oligomers of PIMs, and or a rigid monomer (see FIG. 19 for examples). Monomers in the second solution, include, but are not limited to polyfunctional acyl halides such as trimesoyl chloride, or/and other monomers including but not limited to polyfunctional haloalkylbenzenes, such as 1,3,5-tris(bromomethyl)benzene, or/and rigid monomers with electrophilic or nucleopihilic reactive groups (assigned as Y) which can undergo interfacial polymerization (see FIG. 19 for examples of rigid monomers) including but not limited to polyfuncional halobenzenes, such as 2,3,5,6-tetrafluoroterephthalonitrile, or a mixture thereof dissolved in a nonpolar solvent such as hexane, heptane, toluene or xylene. Further, the second reactive monomer solution may include, but is not limited to, a xylene solution of iso-phthaloyl dichloride, sebacoyl chloride, an alternative organic monomer solution, and/or combinations thereof.

(54) The disclosed interfacial polymerization reaction time in step (b) may vary. For example, an interfacial polymerization reaction time may be in a range from about 5 seconds to about 48 hours.

(55) Optionally, a capping step (c) may be carried out, in which unreacted groups in the polymer network are capped to modify the surface chemistry of the composite membrane. It comprises contacting the membrane with a solution containing capping monomers, which may include alcohols, including but not limited to R—OH, Ar—OH, alcohols with siloxane-substituents, alcohols with halo-substituents including fluorine R.sub.FOH, where R includes but is not limited to alkyl, alkene, R.sub.F, H, Si—O—Si. Amines may also be used as capping monomers and may include but are not limited to R—NH.sub.2, Ar—NH.sub.2, amines with siloxane-substituents, amines with halo-substituents including fluorine R.sub.FNH.sub.2, where R includes but is not limited to alkyl, alkene, R.sub.F, H, Si—O—Si. The capping medium may comprise a solution containing R-acyl halides or Ar-acyl halides, where R includes but is not limited to alkyl, alkene, R.sub.F, H, Si—O—Si.

(56) A quenching step (d) includes contacting or treating the membrane after the interfacial polymerisation reaction with a quenching medium which may include but is not limited to water.

(57) Optionally, a post treatment step (e) comprises curing the membrane with temperature or with microwaves. Optionally, a post treatment step (f) comprises contacting the composite membranes prior to use for nanofiltration with an activating solvent, including, but not limited to, polar aprotic solvents. In particular, activating solvents include DMAc, NMP, DMF and DMSO. The activating solvent in this art is defined as a liquid that enhances the composite membrane flux after treatment. The choice of activating solvent depends on the separating layer and membrane support stability. Contacting may be effected through any practical means, including passing the composite membrane through a bath of the activating solvent, or filtering the activating solvent through the composite membrane.

(58) The second conditioning agent applied in step (g) is optionally impregnated into the membrane by immersing the TFC membrane in a water or organic solvent bath or baths comprising the second conditioning agent.

(59) The resultant high flux semipermeable network TFC membranes with intrinsic microporosity of the invention can be used for gas separation or nanofiltration operations, particularly in nanofiltration in organic solvents, and more particularly nanofiltration operations in polar aprotic solvents.

(60) Gas separations include the separation of binary, ternary and multicomponent mixtures including oxygen, nitrogen, hydrogen, carbon dioxide, methane.

(61) A variety of membrane shapes are useful and can be provided using the present invention. These include but are not limited to spiral wound, hollow fibre, tubular, or flat sheet type membranes. The membrane of the present invention can be configured in accordance with any of the designs known to those skilled in the art, such as spiral wound, plate and frame, shell and tube, and derivative designs thereof.

(62) The following examples illustrate the invention.

EXAMPLES

(63) In the following examples 1-3, nanofiltration performance of the inventive membranes was evaluated according to flux profiles and molecular weight cut off (MWCO) curves. All nanofiltration experiments were carried out at 30 bar using a cross-flow filtration system. Membrane discs, of active area 14 cm.sup.2, were cut out from flat sheets and placed into 4 cross flow cells in series. Permeate samples for flux measurements were collected at intervals of 1 h, and samples for rejection evaluations were taken after steady permeate flux was achieved. The MWCO was determined by interpolating from the plot of rejection against molecular weight of marker compounds. The solute rejection test was carried out using a standard feed solution comprised of a homologous series of styrene oligomers (PS) dissolved in the selected solvent. The styrene oligomer mixture contained 1-2 g L.sup.−1 each of PS 580 and PS 1090 (Polymer Labs, UK), and 0.01 g L.sup.−1 of α-methylstyrene dimer (Sigma-Aldrich, UK). Analysis of the styrene oligomers was done using an Agilent HPLC system with UV/Vis detector set at a wavelength of 264 nm. Separation was achieved using a reverse phase column (C18-300, 250×4.6 mm). The mobile phase consisted of 35 vol % analytical grade water and 65 vol % tetra hydrofuran with 0.1 vol % trifluoroacetic acid.

(64) Solvent flux (J) was determined by measuring permeate volume (V) per unit area (A) per unit time (t) according to the following equation:

(65) $\begin{array}{cc}J=\frac{V}{A.Math.t}& \left(1\right)\end{array}$

(66) The rejection (R.sub.i) of markers was calculated from equation 2, where C.sub.P,i and C.sub.F,i correspond to styrene concentrations in the permeate and the feed respectively.

(67) $\begin{array}{cc}{R}_i=\left(1-\frac{C_{P,i}}{C_{F,i}}\right).Math.100\%& \left(2\right)\end{array}$

(68) In example 4, gas separation performance of the inventive membranes was evaluated according to pure gas permeation measurements with CH.sub.4, N.sub.2, O.sub.2 and CO.sub.2. The gas selectivities were measured for CO.sub.2/N.sub.2, CO.sub.2/CH.sub.4 and O.sub.2/N.sub.2. The gas permeabilities were measured with a soap-bubble meter at feed pressures of 40, 50 and 60 psig. The gas selectivity of the inventive membranes was calculated by:

(69) $\begin{array}{cc}{\alpha }_{{\mathrm{CO}}_2/N_2}=\frac{\left(\mathrm{PG}/l\right){\mathrm{CO}}_2}{\left(\mathrm{Pg}/l\right)N_2}& \left(3\right)\end{array}$

(70) Where α is the selectivity and P.sub.g is the gas permeability.

Example 1

(71) In the following example, membranes of the present invention are formed through interfacial polymerisation to form a polyester on a crosslinked polyimide support membrane, as follows:

(72) Formation of Crosslinked Polyimide Support Membrane

(73) A polymer dope solution was prepared by dissolving 24% (w/w) polyimide (P84 from HP Polymer AG) in DMSO and stirring overnight until complete dissolution. A viscous solution was formed, and allowed to stand for 10 hours to remove air bubbles. The dope solution was then cast on a polyester or polypropylene (Viledon, Germany) non-woven backing material taped to a glass plate using a casting knife (Elcometer 3700) set at a thickness of 250 μm. Immediately after casting, the membrane was immersed in a water bath where phase inversion occurred. After 15 minutes, it was changed to a new water bath and left for an hour. The wet membrane was then immersed in a solvent exchange bath (isopropanol) to remove any residual water and preparation solvents.

(74) The support membrane was then crosslinked using a solution of hexanediamine in isopropanol, by immersing the support membrane in the solution for 16 hours at room temperature. The support membrane was then removed from the crosslinking bath and washed with isopropanol for 1 h to remove any residual hexanediamine (HDA).

(75) The final step for preparing the crosslinked polyimide support membrane involved immersing the membrane overnight into a conditioning agent bath consisting of a volume ratio of 3:2 polyethylene glycol 400/isopropanol. The membrane was then wiped with tissue paper and air dried.

(76) Formation of Thin Film Composite Membranes by Interfacial Polymerisation:

(77) TFC membranes were hand-cast on the crosslinked polyimide support membrane through interfacial polymerization. The support membrane was taped to a glass plate and placed in an aqueous basic NaOH solution (pH=13) of 2% (w/v) 5,5′,6,6′-Tetrahydroxy-3,3,3′,3′-tetramethyl-1,1′-spirobisindane (98%, ABCR GmbH) for approximately 2 min. The phenoxide loaded support membrane was then rolled with a roller to remove excess solution. The saturated membrane support was then immersed in a solution of 0.1% (w/v) trimesoyl chloride (TMC, 98%, Sigma-Aldrich) in hexane. After 2 min of reaction, the resulting membranes were withdrawn from the hexane solution and rinsed with water (which corresponds to step (d) of the process defined herein, i.e. immersing the membrane into a quenching medium). The chemical structures of the monomers used for the interfacial polymerization reaction are shown in FIG. 20.

(78) Membrane identification codes for the TFC membranes prepared in this Example are as follows:

(79) TABLE-US-00001 Entry No. Membrane Membrane code 1 TFC membrane prepared on TFC-PIMs-PI-n crosslinked PI as support 2 Cured TFC membrane prepared on TFC-PIMs-PI-oven-n crosslinked PI as support

(80) Where n identifies membranes made in independent batch n.

(81) Curing of TFC Membranes in the Oven (Step e)

(82) A post-formation treatment step was carried out on the composite membranes in which the membranes were cured in the oven at 85° C. for 10 minutes.

(83) Composite Membrane Performance

(84) The performance of TFC membranes in DMF, THF, acetone, methanol and toluene were evaluated with and without curing with temperature. The rejection curves and fluxes for the TFC membranes in DMF/PS solution, THF/PS solution, acetone/PS solution, methanol/PS solution and toluene/PS solution with and without curing in the oven are shown in FIGS. 1 to 10. It is clear that curing the membranes at 85° C. increases rejection.

Example 2

(85) TFC membranes were prepared on PEEK support membranes, as follows:

(86) Fabrication of Membrane Supports from Polyetheretherketone (PEEK):

(87) A polymer dope solution was prepared by dissolving 12.3% (w/w) PEEK (VICOTE 704, a polyether ether ketone (PEEK) polymer, from Victrex) in 79.4% methane sulfonic acid (MSA) and 8.3% sulfuric acid (H.sub.2500. The solution was stirred overnight until complete dissolution. A viscous solution was formed, and allowed to stand for 10 hours to remove air bubbles. The solution was then cast on a polyester non-woven backing material taped to a glass plate using a casting knife (Elcometer 3700) set at a thickness of 250 μm. Immediately after casting, the membrane was immersed in a water bath where phase inversion occurred. After 15 minutes, it was changed to a new water bath and left for an hour. The wet membrane was then immersed in a water bath to remove any residual preparation solvents.

(88) The final step for preparing the PEEK support membrane involved immersing the membrane overnight into a conditioning agent bath consisting of a volume ratio of 3:2 polyethylene glycol 400/isopropanol. The membrane was then wiped with tissue paper and air dried.

(89) TFC membranes were fabricated as per EXAMPLE 1, on top of the PEEK support membrane. The TFC membranes were cured in the oven at 85° C. for 10 minutes as per EXAMPLE 1.

(90) Membrane identification codes for the TFC membranes prepared in this Example are as follows:

(91) TABLE-US-00002 Entry No. Membrane Membrane code 3 Cured TFC membrane prepared TFC-PIMs-PEEK-oven-n on crosslinked PI as support

(92) Where n identifies membranes made in independent batch n.

(93) Composite Membrane Performance

(94) The performance of TFC membranes cured with temperature was evaluated in acetone, THF, toluene and heptane. The rejection curves and fluxes for the cured TFC membranes in acetone/PS, THF/PS, toluene/PS, and heptane/PS solutions are shown in FIGS. 11, 12, 13 and 14 respectively.

Example 3

(95) In this particular example TFC membranes were prepared on PBI support membranes, as follows: Fabrication of membrane supports from polybenzimidazole (PBI):

(96) A polymer dope solution was prepared by diluting a commercial dope solution of 26 wt % PBI dissolved in DMAc (trade name: Celazole®) to 15 wt % with DMAc. The solution was stirred for 4 h until complete dissolution. A viscous solution was formed, and allowed to stand for 10 hours to remove air bubbles. The solution was then cast on a polypropylene non-woven backing material taped to a glass plate using a casting knife (Elcometer 3700) set at a thickness of 250 μm. Immediately after casting, the membrane was immersed in a water bath where phase inversion occurred. After 15 minutes, it was changed to a new water bath and left for an hour. The wet membrane was then immersed in a water bath to remove any residual preparation solvents.

(97) The final step for preparing the PBI support membrane involved immersing the membrane overnight into a conditioning agent bath consisting of a volume ratio of 3:2 polyethylene glycol 400/isopropanol. The membrane was then wiped with tissue paper and air dried.

(98) TFC membranes were fabricated as per EXAMPLE 1, on top of the PBI support membranes. The TFC membranes were cured in the oven at 85° C. for 10 minutes as per EXAMPLE 1.

(99) Membrane identification codes for the TFC membranes prepared in this Example are as follows:

(100) TABLE-US-00003 Entry No. Membrane Membrane code 4 TFC membrane prepared on TFC-PIMs-PBI-oven-n crosslinked PBI as support

(101) Where n identifies membranes made in independent batch n.

(102) Composite Membrane Performance

(103) The performance of TFC membranes cured with temperature was evaluated in acetone and THF. The rejection curves and fluxes for the cured TFC membranes in acetone/PS and THF/PS solutions are shown in FIGS. 15 and 16 respectively.

Example 4

(104) TFC membranes were fabricated as per EXAMPLE 2 (i.e. with PEEK as support membrane without conditioning with PEG). The TFC membranes were cured in the oven at 85° C. for 10 minutes. Before the gas permeation membranes were immersed in MeOH, followed by hexane and left to dry overnight.

(105) Composite Membrane Performance

(106) The gas separation performance of TFC membranes cured with temperature was evaluated for N.sub.2, CO.sub.2, CH.sub.4 and O.sub.2. The permeabilities vs. selectivities at different pressures are shown in FIGS. 17A-17C.