Development of a defect-free 6FDA-durene asymmetric hollow fiber and its composite hollow fibers

We have developed 6FDA-durene polyimide and poly(4-vinylpyridine) (PVP)/6FDA-durene composite hollow fibers. The 6FDA-durene fiber was defect-free and had a selectivity of 4.3-5.1 for O₂/N₂. It had an average permeance for O₂ of ≈ 240×10^-6 cm³ (STP)/cm² cmHg and its dense layer thickness was ≈ 2000-3000 μm. The dense layer location was at the outer surface. This fiber was wet-spun directly from an in-situ imidization dope consisting of 14.94 wt% 6FDA-durene in a (70.24/21.5/7.51/0.75) N-methyl-2-pyrrolidone (NMP)/propionic acid (PA)/β-picoline/propionic anhydride solvent mixture. The fiber diameter was ≈500 μm with a wall thickness ≈50-70 μm. The PVP/6FDA-durene composite fiber had a selectivity of 6.9 for O₂/N₂ and a permeance for O₂ of 14.5×10^∂ cm³ (STP)/cm² s cmHg. The newly developed technology suggests, for the first time, that a defect-free hollow fiber can be produced from a modified Lewis acid:base complex dope. Compared to most other conventional hollow fiber fabrication processes, our approach has many advantages because that (1) it is simpler and more economical, (2) spins fibers at low temperatures, (3) employs a dope directly from polymerization, and (4) requires no secondary operations, such as silicone coating and curing.