Hollow fiber and a process for preparation thereof
A process for preparing a hollow fiber includes the steps of providing a dope solution including polyamide imide (PAI), providing an aqueous bore solution including polyethylene imine (PEI), extruding the dope solution in an cross-sectional annular shape and ejecting the bore solution in the center of the annular shape, allowing the PAI and the PEI to react, thereby forming an internal surface layer including the cross-linked reaction product, and forming a polyamide Thin Film Composite (TFC) layer by interfacial reaction of aqueous di- or triamine compound and organic di- or triacylhalide compound on the internal surface layer including the cross-linked reaction product.
1 . A process for preparing a hollow fiber comprising the steps of:
a) providing a dope solution comprising polyamide imide (PAI),
b) providing an aqueous bore solution comprising polyethylene imine (PEI),
c) extruding the dope solution in a cross-sectional annular shape and ejecting the bore solution in the center of the annular shape,
d) allowing the PAI and the PEI to react, thereby forming an internal surface layer comprising the cross-linked reaction product, and
e) forming a polyamide Thin Film Composite (TFC) layer by interfacial reaction of aqueous di- or triamine compound and organic di- or triacylhalide compound on the internal surface layer comprising the cross-linked reaction product, such that the internal surface layer functions as a primer for attaching the TFC layer to a PAI support layer.
2 . The process according to claim 1 , wherein the dope solution and/or the aqueous bore solution further comprises an aprotic solvent selected from the group consisting of N-methyl pyrrolidone (NMP), dimethylacetamide (DMAC), dimethylsulfoxide (DMSO), and dimethylformamide (DMF), or mixtures thereof.
3 . The process according to claim 1 , wherein the dope solution further comprises a polymer selected from the group consisting of polyphenylsulfone (PPSU), polyethersulfone (PES), Sulfonated polyethersulfone (SPES), polysulfone (PSU), polyetheretherketone (PEEK), high-temperature sulfone resins, self-reinforced polyphenylene, polybenzimidazole (PBI), polyimide (PI), polyetherimide (PEI), polyphenylene sulfide (PPS), or mixtures thereof.
4 . The process according to claim 1 , wherein the solution viscosity of the PAI in 25 wt % NMP and measured at 40° C. is 30,000 cP or less.
5 . The process according to claim 1 , wherein the dope solution further comprises a glycol selected among ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, glycerol or polyethylene glycol (PEG).
6 . The process according to claim 1 , wherein the PEI of the aqueous bore solution has an average molecular weight (Mw) of 100,000 g/mol or above and is optionally branched.
7 . The process according to claim 1 , wherein the nascent hollow fiber after extrusion is moved through an air gap before being coagulated in a non-solvent.
8 . The process according to claim 1 , wherein a plurality of the hollow fibers is assembled in a module before the polyamide TFC layer is formed.
9 . The process according to claim 1 , wherein aquaporin water channels are incorporated into the TFC layer.
10 . The process according to claim 9 , wherein the aquaporin water channel incorporated into the TFC layer is assembled in a nanostructure comprising polyethyleneimine, and is first solubilized in a detergent, the detergent being selected from the group consisting of lauryl dimethylamine N-oxide (LDAO), octyl glucoside (OG), dodecyl maltoside (DDM) or a combination thereof.
11 . The process according to claim 10 , wherein the aquaporin water channel incorporated into the TFC layer is assembled in a nanostructure or vesicle, the nanostructure or vesicle comprising an amphiphilic diblock copolymer of the PMOXA-PDMS type and PDMS comprising a functional end group comprising one or more of amine, carboxylic acid, and/or hydroxy groups.