Gas-permeable composite hollow-fiber membrane with a three-layered structure

Gas-permeable composite hollow-fiber membrane with a three-layered structure composed of a high-density polyethylene (HDPE) porous layer, a MK-2F thin dense layer, and a HDPE porous layer has been successfully developed by melt-spinning and cold/hot stretching. The MK-2F thin dense layer was composed of a poly(ethylenebutylene)-block–polystyrene triblock copolymer (SEBS) phase and a (poly(ethylene-co-ethylacrylate) (EEA)+poly(ethylene-co-propylene) (EPP)) phase. When the stretching ratio was increased, oxygen permeance, image, and nitrogen permeance, image, were linearly increased, while the image was almost constant at 2.95–3.0. The thickness of a no-pinhole thin layer was 2–5 μm and its image was 4.0–8.5×10−6 cm3 (25 °C) cm−2 s−1 cmHg−1. Structural analysis of the thin layer indicated that the SEBS and the (EEA+EPP) formed a 3D-network structure, which restricted elastic recovery of the SEBS matrix and led to the thin thickness. In a pervaporation experiment, the H2O vapor permeation rate of the MK-2F thin layer was about 1/4 that of polydimethyl silicone (PDMS), and the IPA vapor permeation rate was about 1/12 that of PDMS even though the gas permeance of the MK-2F thin layer was almost the same as that of PDMS.