Hollow Fiber Membrane For Use in an Anesthetic Circuit

Abstract

Hydrophobic poly(4-methyl-1-pentene) hollow fiber membrane for retention of anesthetic agents with an inner and an outer surface and between inner and outer surface an essentially isotropic support layer with a sponge-like, open-pored, microporous structure free of macrovoids and adjacent to this support layer on the outer surface a dense separation layer with a thickness between 1.0 and 3.5 μm. The membrane has a porosity in the range of greater than 35% to less than 50% by volume and a permeance for CO2 of 20-60 mol/(h·m2·bar), a gas separation factor α(CO2/N2) of at least 5 and a selectivity CO2/anesthetic agents of at least 150.The process for producing this membrane is based on a thermally induced phase separation process in which process a homogeneous solution of a poly(4-methyl-1-pentene) in a solvent system containing components A and B is formed, wherein component A is a strong solvent and component B a weak non-solvent for the polymer component. After formation of a hollow fiber the hollow fiber is cooled in a liquid cooling medium to form a hollow fiber membrane. The concentration of the polymer component in the solution may be in the range from 42.5 to 45.8 wt.-% and the hollow fiber leaving the die runs through a gap between die and cooling medium with a gap length in the range of 5-30 mm.

1 . A membrane comprising: an integrally asymmetrical hydrophobic hollow fiber membrane for retention of anesthetic agents, which membrane is composed primarily of a poly(4-methyl-1-pentene) and has an inner surface facing towards its lumen, an outer surface facing outwards, a support layer with a sponge-like, open-pored, microporous structure between inner surface and outer surface and adjacent to this support layer on the outer surface a separation layer with denser structure, wherein the support layer is free of macrovoids and the pores in the support layer are on average essentially isotropic,
 wherein
 separation layer has a thickness in the range between 1.0 and 3.5 μm and, 
 the membrane has a permeance for CO2 of 20-60 mol/(h·m 2 ·bar), a gas separation factor α(CO2/N2) of at least 5 and a selectivity CO 2 /Sevoflurane of at least 150 
 the membrane has a porosity in the range of greater than 35% to less than 50% by volume. 
   
     
     
         2 . The membrane according to  claim 1 , wherein the membrane structure changes abruptly in the transition from the separation layer to the support layer. 
     
     
         3 . The membrane according to  claim 1 , wherein the separation layer has a thickness between 1.0 μm and 2.0 μm. 
     
     
         4 . The membrane according to  claim 1 , wherein the membrane has the permeance for CO2 of 25-40 mol/(h·m 2 ·bar). 
     
     
         5 . The membrane according to  claim 1 , wherein the membrane has the permeance for CO2 of 25-40 mol/(h·m 2 ·bar) and an O2 permeance of at least 10 mol/(h·m 2 ·bar). 
     
     
         6 . The membrane according to  claim 1 , wherein the membrane has the selectivity CO2/Sevoflurane of at least 220. 
     
     
         7 . The membrane according to  claim 1 , wherein the membrane has the selectivity CO2/Sevoflurane of at least 400. 
     
     
         8 . The membrane according to  claim 1 , wherein the membrane has the gas separation factor α(CO2/N2) of at least 8.