Hollow fiber and a process for preparation thereof

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.