Abstract: Disclosed is a high heat resistance and low viscosity polyoxytetramethylene glycol (PTMG) having the following characteristics (1) to (4): (1) a number average molecular weight of from 500 to 3000; (2) a molecular weight distribution of 1.8 or less in terms of the Mw/Mn ratio; (3) a content of high molecular weight PTMG molecules of from 2 to 5% by weight, wherein the high molecular weight PTMG molecules are PTMG molecules having molecular weights which are at least six times as large as the number average molecular weight of all PTMG molecules; and (4) a heteropolyacid content of from 10 to 900 ppb by weight.

Abstract: Provided is a process for producing a tetrahydrofuran polymer using a heteropoly-acid catalyst wherein the content of Al in the heteropoly-acid is 4 ppm or less.

Abstract: A method for controlling the molecular weight distribution of polyether glycol in producing polyether glycol having a specified number average molecular weight by polymerizing tetrahydrofuran as a starting monomer with the use of a heteropoly-acid as a catalyst, which method comprises conducting the polymerization in the presence of an amount of water which can form two phases of the organic phase and a catalyst phase, sampling the polymerization product during the polymerization to determine the molecular weight distribution and, when the molecular weight distribution thus found is narrower than the specified molecular weight distribution, making the residence time distribution of the starting monomer in the catalyst phase wider, while, when the found molecular weight distribution is wider than the specified molecular weight distribution, making the residence time distribution of the starting monomer in the catalyst phase narrower.

Abstract: A method for separation of a liquid mixture wherein a component, intended to be separated, in the liquid mixture is concentrated in the interiors of particles having an average size of 0.1 to 10 .mu.m; the particles are then transported to the surface of a polymeric porous membrane having an average pore size 0.1 to 50 times the average size of the particles under an electrostatic field; and the particles are then separated by a pressure difference loaded on the membrane.