Abstract: A method for making hollow fibers having a selective permeability, wherein a majority of the hollow fibers each has on the periphery thereof 1 to 10 fins extending in the longitudinal direction, and the occupancy ratio y of the sections, defined by the peripheries, of all the hollow fibers exclusive of the fin portions in the hollow fiber bundle to the section, vertical to the axial direction of the hollow fiber bundle, of the inner wall of the shell is within a range defined by the following formula (I):41-3.1.sqroot..alpha.x.ltoreq.y.ltoreq.61-3.1.sqroot..alpha.x (I)wherein x stands for the average fin number per hollow fiber in the hollow fiber bundle, and .alpha. indicates the ratio H/d of the average fin height H (.mu.)in the hollow fiber bundle to the average outer diameter d (.mu.) of the hollow fibers exclusive of the fin portions.

Abstract: A process for the preparation of a porous hollow filament composed mainly of an organic polymer, which comprises separately feeding a powder of the organic polymer and a liquid additive to a feed zone of twin-screw extruder, mixing the polymer with the additive in a kneading zone of the extruder to form a substantially liquid mixture, further kneading and compressing the liquid in a kneading and compressing zone of the extruder, feeding the liquid to an extruding zone of the extruder, and extruding the liquid from the extruding zone.

Abstract: Disclosed is a fluid separator comprising a shell filled with a bundle of hollow fibers having a selective permeability, wherein a majority of the hollow fibers each has on the periphery thereof 1 to 10 fins extending in the longitudinal direction, and the occupancy ratio y of the sections, defined by the peripheries, of all the hollow fibers exclusive of the fin portions in the hollow fiber bundle to the section, vertical to the axial direction of the hollow fiber bundle, of the inner wall of the shell is within a range defined by the following formula (I): ##EQU1## wherein x stands for the average fin number per hollow fiber in the hollow fiber bundle, and .alpha. indicates the ratio H/d of the average fin height H(.mu.) in the hollow fiber bundle to the average outer diameter d (.mu.) of the hollow fibers exclusive of the fin portions.

Abstract: A method for heat sterilizing an artificial kidney comprising a receptacle having accommodated therein permselective hollow filaments and including inlet and outlet ports for the blood and inlet and outlet ports for a dialyzate, which comprises(a) filling a primer consisting of water or a water solution into the artificial kidney,(b) connecting a pressure buffer tank to at least one of the inlet and outlet ports,(c) sealing the remaining ports by stopper means,(d) heating the artificial kidney to a temperature of 80.degree. to 130.degree. C. to heat sterilize it, and moving the gas and a part of the primer in the artificial kidney which have been expanded by heating to the pressure buffer tank,(e) cooling the artificial kidney to return the primer in the buffer tank to the artificial kidney, and(f) aseptically sealing the port connected to the pressure buffer tank; and artificial kidneys of specified constituent elements suitable for use in heat sterilization by this method.

Abstract: In a method of obtaining purified 2,6-naphthalenedicarboxylic acid dimethyl ester by vacuum distilling crude 2,6-naphthalenedicarboxylic acid dimethyl ester under conditions of application of heat, the improvement which comprises vacuum distilling a crude 2,6-naphthalenedicarboxylic acid dimethyl ester having an acid value (A.sub.f), as expressed in milligrams of KOH required for neutralizing the carboxyl groups contained in one gram of said crude 2,6-naphthalenedicarboxylic acid dimethyl ester, of from 1.0 to 50.

Abstract: A process for preparing dimethyl 2,6-naphthalenedicarboxylate, which comprises continuously esterifying 2,6-naphthalenedicarboxylic acid with methanol at a temperature of about 140.degree. to about 350.degree. C. in the presence or absence of an esterifying catalyst, said 2,6-naphthalenedicarboxylic acid being fed into an esterification reaction zone in the form of solid particles having a specific surface area of about 4,000 cm.sup.2 /g.