(DE4309734-A1)      Removal of lumen filler and/or unwanted processing auxiliaries from hollow fibres or hollow fibre membranes is effected by extracting the fibre or membrane with a supercritical gas (I).    (I) is pref. CO2, H2O, N2, NH2, N2O, N2O2, MeOH, CHF3, n-butane, propane, ethylene and/or toluene. (I) is opt. mixed with a liq. or solvent, esp. MeOH or H2O. The fibre/membrane (esp. a hollow fibre bundle) is pref. contacted with (I) for 1-600 (pref. 20-240) min., pref. using CO2 at at least 73 (esp. at least 100) bar and at least 31 (esp. at least 40) deg.C. The sepd. lumen filler and/or additive may be recovered and re-used.    USE/ADVANTAGE -   Useful for removing lumen filler or stabiliser (pref. IPM) and other auxiliaries (e.g. thickeners or precipitants) from hollow fibres or fibre membranes for industrial or medicinal use (e.g. in haemodialysis, haemofiltration, sterile filtration or plasmapheresis). (I) have a good cleaning effect, with no problems of environmental pollution or inflammability. They can be used with a wide range of fibre/membrane materials, e.g. cellulose, regenerated cellulose, cellulose acetate, polyolefin, polysulphone, polyacrylonitrile or polyamide. Necessary additives (e.g. glycerol pore stabiliser; or PVP or PEG hydrophobising agent) are not removed.    (US5470474-A)      A process for removing a lumen filler, undesired auxiliary processing agents, or both from finished hollow fibres or finished hollow fibre membranes, comprising extracting the finished hollow fibres or finished hollow fibre membranes with a supercritical gas.    (EP616838-B1)      Removal of lumen filler and/or unwanted processing auxiliaries from hollow fibres or hollow fibre membranes is effected by extracting the fibre or membrane with a supercritical gas (I). Also claimed are hollow fibres or membranes from which lumen filler has been removed by the above process, where the residual content of isopropyl myristate (IPM) is below 500 ppm, esp. below 300 ppm.    (I) is CO2, H2O, N2, NH2, N2O, N2O2, MeOH, CHF3, n-butane, propane, ethylene and/or toluene. (I) is opt. mixed with a liq. or solvent, esp. MeOH or H2O. The fibre/membrane (esp. a hollow fibre bundle) is contacted with (I) for 1-600 (pref. 20-240) min., pref. using CO2 at at least 73 (esp. at least 100) bar and at least 31 (esp. at least 40) deg.C. The sepd. lumen filler and/or additive may be recovered and re-used.    USE -   The process is useful for removing lumen filler or stabiliser (pref. IPM) and other auxiliaries (e.g. thickeners or precipitants) from hollow fibres or fibre membranes for industrial or medicinal use (e.g. in haemodialysis, haemofiltration, sterile filtration or plasmapheresis).    ADVANTAGE -   (I) have a good cleaning effect, with no problems of environmental pollution or inflammability. They can be used with a wide range of fibre/membrane materials, e.g. cellulose, regenerated cellulose, cellulose acetate, polyolefin, polysulphone, polyacrylonitrile or polyamide. Necessary additives (e.g. glycerol pore stabiliser; or PVP or PEG hydrophobising agent) are not removed.