Abstract: The invention relates to the use of thermoplastic polyester molding compounds, containing A) 80 to 100 wt. % of a polyalkylene arylate, especially polybutyleneterephthalate, with a half-width of crystallization heat releases of ≦5° C. and B) 0 to 20 wt. % of other additives, the weight percentages of constituents A) and B) adding up to 100%, for producing molded bodies by blow-molding, profile extrusion and/or pipe extrusion. A preferred use for the inventive molding compounds is the production of light guide sheathing. The invention also relates to a 3-stage method for producing the polyesters as follows: a) esterification or re-esterification of an aromatic dicarboxylic acid or its derivative and a glycol; b) precondensation; and c) polycondensation to a viscosity number of at least 158 ml/g. The reaction is carried out in at least 2 temperature zones in stages a) and b).

Abstract: A process for preparing polyalkylene arylates by esterifying or transesterifying an aromatic dicarboxylic acid or its esters or ester-forming derivatives with a molar excess of an aliphatic dihydroxy compound and polycondensing the resultant esterification or transesterification product comprises polycondensing the prepolymer with a viscosity number (VN) of <30 ml/g in the presence of an oxygen-containing gas.

Abstract: A process for working up residues containing dihydroxy compounds resulting from the preparation of polyesters, where (1) in a first stage there is esterification or transesterification of a dicarboxylic acid or esters thereof or ester-forming derivatives with a molar excess of a dihydroxy compound, (2) in at least one second stage there is polycondensation of the esterification product obtained in (1), (3) the vapors (a) and (b) resulting from the reactions in (1) and (2) respectively are subjected to a treatment to recover the starting materials, wherein the treatment to recover the starting materials is carried out in the presence of an alkali metal or alkaline earth metal compound in an amount of from 0.5 to 10% by weight, calculated as alkali metal or alkaline earth metal, based on the solids content of the vapors.

Abstract: A process for the continuous preparation of thermoplastic polyesters bya) a first step of (trans)esterifying a dicarboxylic acid or its esters or ester-forming derivatives with a molar excess of a dihydroxy compound,b) a second step of precondensing the (trans)esterification product of a), andc) a third step of polycondensing the product of b)comprises carrying out step a) and/or step b) of the process in two or more temperature zones.

Abstract: A process for working up dihydroxy compound residues from the preparation of polyesters bya) a first step of (trans)esterifying a dicarboxylic acid or its esters or ester-forming derivatives with a molar excess of a dihydroxy compound,b) at least one second step of polycondensing the esterification product of a), andc) subjecting the vapors from the reaction of a) and b) to a treatment for recovering the starting materials, comprises1) combining the vapors of step a) and some of the vapors of step b) of the process in at least one column A) and removing the low boiling constituents of the vapors overhead and recycling the bottom product, which predominantly contains the excess dihydroxy compounds and also oligomeric and polymeric reaction products, into step a), and2) transferring the other part of the vapors of step b) of the process into at least one column B) and removing the low boiling constituents of the vapors overhead and discharging the bottom product from the column and subsequently subjecting it to

Abstract: Thermoplastic polyesters are prepared by multistage polycondensation of dihydroxy compounds with dicarboxylic acids or esters or ester-forming derivatives thereof by a process in which, in at least one first stage, an alkali metal compound or an alkaline earth metal compound is added in an amount of from 1 to 10 mmol, calculated as alkali metal or alkaline earth metal, per kg of polyester, and at least one further stage is carried out as a solid-phase condensation.

Abstract: A process for working up residues which contain dihydroxy compounds and are obtained in the preparation of polyesters by reacting dicarboxylic acids or their esters or ester-forming derivatives with dihydroxy compounds,a) in a first stage a diester of a dicarboxylic acid with an alkanol being subjected to transesterification with a molar excess of a dihydroxy compound,b) the vapors which are obtained in the reaction according to a) and contain predominantly the alkanol formed in the transesterification, excess dihydroxy compounds and oligomeric and polymeric reaction products being transferred to a column in which the alkanol is separated off via the top and the other products are separated off as a bottom product, andc) the bottom product being then subjected to a further treatment to recover the dihydroxy compound,wherein a liquid residue containing dihydroxy compounds is added in stage b) of the process, and the bottom product is discharged in substantially liquid form from the column and then subjected to

Abstract: Thermoplastic polyesters are prepared by polycondensation of dihydroxy compounds with dicarboxylic acids or their esters or ester-forming derivatives by a process in which an alkali metal compound or an alkaline earth metal compound is added in an amount of less than 1 mmol, calculated as alkali metal or alkaline earth metal, per kg of polyester.