Abstract: The present invention provides a process of reducing acrolein byproduct from polytrimethylene terephthalate using selected phosphorous compounds to contact the polytrimethylene terephthalate or reactants in the process of producing polytrimethylene terephthalate. The selected phosphorous compounds are retained in the polytrimethylene terephthalate. The present invention also provides polytrimethylene terephthalate compositions containing amounts of phosphorous compounds.

Abstract: A process for the production of polytrimethylene terephthalate (PTT), wherein the process comprises: (i) one or more esterification steps, wherein terephthalic acid (TPA) or an alkyl diester of terephthalic acid is reacted with 1,3-propanediol (PDO); and (ii) one or more subsequent polycondensation steps, wherein the process further comprises the addition of a protic acid, other than terephthalic or isophthalic acid, before and/or during the one or more esterification steps, wherein the protic acid has a dissociation constant of at most 4 (pKa measured in water at 25° C.), and wherein the total amount of protic acid added before and/or during the one or more esterification steps is in the range of from 0.001 to 10 millimole of acid per kilogram of polytrimethylene terephthalate produced.

Abstract: Small amounts of one or more alkali or alkaline earth metal salts, particularly lithium or calcium salts, added to polytrimethylene terephthalate (PTT) have been found to greatly accelerate the crystallization rate of the polymer. Preferably, from about 1 to about 10 ppm of the alkali or alkaline earth metal, based on metal, is effective. For example, 7 ppm of Li+ can produce about 5-20 times faster crystallization, depending on the rate of cooling, compared to PTT without lithium. The rapid-crystallizing PTT compositions are preferably comprised of carboxylate salt endgroups, COOM, wherein M is an alkali or alkaline earth metal cation, preferably lithium or calcium cation. The metal salt is conveniently added to the polymerization process.