Abstract: A process for the preparation of high molecular weight linear saturated polyesters derived from dicarboxylic acids or their ester-forming derivatives and aliphatic and/or cycloaliphatic diols, comprising the condensation of polyester precondensates having a relative viscosity of from 1.05 to 1.15 at from 220.degree. to 280.degree. C. under reduced pressure, wherein(a) the condensation is first started with from 70 to 95 percent by weight of the polyester precondensate and(b) after from 10 to 50% of the total condensation time the remaining 5 to 30 percent by weight of the polyester precondensate are added to the polyester melt undergoing condensation in accordance with (a), and the condensation is taken to completion.

Abstract: A process for the manufacture of high molecular weight linear polyesters which are derived from dicarboxylic acids or their ester-forming derivatives and from diols, by condensing polyester precondensates, having a relative viscosity of at least 1.05, at from 270.degree. to 340.degree. C. under reduced pressure, the condensation being started at from 290.degree. to 340.degree. C. and the temperature being lowered as the condensation progresses, the final temperature being at least 10.degree. C. above the melting point of the particular polyester produced, and an apparatus for carrying out the process.

Abstract: A process for the manufacture of high molecular weight linear polyesters which are derived from dicarboxylic acids or their ester-forming derivatives and from diols, by condensing polyester precondensates, having a relative viscosity of at least 1.05, at from 270.degree. to 340.degree. C. under reduced pressure, the condensation being started at from 290.degree. to 340.degree. C. and the temperature being lowered as the condensation progresses, the final temperature being at least 10.degree. C. above the melting point of the particular polyester produced, and an apparatus for carrying out the process.

Abstract: A process for achieving a uniform flow profile of very viscous liquids when flowing through tubes or reaction chambers, wherein the very viscous liquid is passed through annular spaces extending concentrically with increasing diameter over the entire cross-section of the tubes or reaction chambers and having the same depth in the direction of flow, and this procedure is repeated once or several times, the annular spaces being staggered with respect to each other as viewed in the direction of flow, and an apparatus consisting of a combination of two or more discs arranged at axial intervals within a tube transversely to the direction of flow, each disc consisting of a plurality of ring-shaped bands of increasing diameter, the bands being arranged freely of one another and concentrically at intervals on a grid supporting means to provide correspondingly concentric open spaces between the bands over the entire cross-section of the tube, with the walls of the bands running parallel to the direction of flow, and t