Abstract: Disclosed is a process for manufacturing polyarylene sulfide comprising pre-polymerizing a dihalogeno-aromatic compound with a liquid or gaseous sulfur compound in the presence of a lithium compound in an aprotic organic solvent followed by further polymerizing the resulting pre-polymerized system; which is characterized in that sufficient water is added to the pre-polymerized solution (I) to separate it into a tick polymer phase and a solvent phase, then a solvent is added to the thus-separated, thick polymer phase and the resulting polymer phase is further polymerized, for efficiently manufacturing high-purity polyarylene sulfide. The process does not require any complicated steps of washing the polymer with a multi-stage washing system and is free from the increase in the production costs of the polymer. In the process, the lithium salt used can be recovered efficiently.

Abstract: Polyester polymers consisting essentially of repeating units having the formula ##STR1## repeating units having the formula--O--Ar.sup.1 --CO-- [II],repeating units having the formula--O--Ar.sup.2 --O-- [III],and repeating units having the formula ##STR2## wherein Ar.sup.1 is selected from ##STR3## Ar.sup.2 is selected from ##STR4## halogen substituted radicals of these radicals, and ##STR5## wherein X is selected from --O--, --S--, --SO.sub.2 --, --CO--, --O(CH.sub.2).sub.n O--.--CH.sub.2).sub.n, and ##STR6## wherein each n independently represents a member having a value of from 1 to 10, and each R.sup.4 is independently selected from alkyl radicals of 1 to 5 carbon atoms, andR.sup.2 and R.sup.3 are independently selected from hydrogen atom, halogen radicals, alkyl radicals of 1 to 5 carbon atoms, and phenyl radical, and R.sup.2 and R.sup.3 may be identical or different from each other, andR.sup.