Abstract: Disclosed is a biaxially oriented polyester film, wherein the polyester comprises a linear polyester comprising a dicarbocyclic acid and a diol, and further including from about 3 to 20 mole percent of the dicarboxylic acid of a phosphorus-containing chain member having structural units of the formula ##STR1## wherein R is a saturated, open-chain or cyclic alkylene radical, an arylene radical or an aralkylene radical, andR.sub.1 is an alkyl group containing up to 6 carbon atoms, an aryl or an aralkyl group.Also disclosed is the use of this film as an electrical insulator.

Abstract: Permanently flame-resistant synthetic linear polyesters are obtained by irporating by condensation into the polyester composed of the usual dicarboxylic acid and diol units an alkylphosphine oxide of the formula ##SPC1##Wherein the radicals R to R.sub.4 represent organic radicals of which R.sub.2, R.sub.3 and Z may be substituted by 2 hydroxyl groups altogether, R.sub.2, R.sub.3 and R.sub.4 may also represent hydrogen and a is zero or a whole number of from 1 to 4. The flame-resistant polyesters are processed into shaped structures such as fibers, filaments, sheets, injection and compression molded articles characterized by good flameproofness and dyeing properties.

Abstract: In an improvement of the process of U.S. patent No. 3,941,752, according to which flame retarding linear polyesters are manufactured by reaction of dicarboxylic acids capable of forming high molecular weight linear polyesters or the esters thereof with lower aliphatic alcohols, with diols, and phosphorous compounds of the formula ##STR1## or the esters thereof with lower aliphatic alcohols or also the cyclic anhydrides thereof, the cyclic anhydrides are used after having been dissolved previously at elevated temperature in a diol suitable for the polyester manufacture, preferably in the diol used as main component. The symbols of the formula have the following meanings: R = saturated open-chain or cyclic alkylene, arylene or aralkylene, R.sub.1 = alkyl having up to 6 carbon atoms, aryl or aralkyl; R as well as R.sub.1 optionally containing 1 or more hetero atoms, preferably F, Cl, Br, O or S.

Abstract: Permanently flame resistant filaments and fibers are produced from synthetic linear polyesters in which about 5 to 15 mol% of the acid component of the polyester consist of phosphinic acid structural units of the formula ##EQU1## in which R, R.sub.1 and R.sub.2 stand for organic radicals which may contain hetero atoms, preferably halogen, oxygen or sulfur. The filaments and fibers can be well dyed deep shades and are suitable in all fields of application where textiles which are hard to inflame are desired.

Abstract: Flame-repellant linear polyesters are obtained by incorporating by condensation phosphorus-compounds having the formula ##EQU1## wherein R and R.sub.1 are organic radicals which may also contain hereto atoms into the linear polyesters, preferably those from terephthalic acid and ethylene glycol. These polyesters are materials of which flame-repellent filaments, fibers, sheets, press-moulded and injection-moulded articles may be made. Products of the invention can be used whereever especially acute risks of ignition and fire exist.

Abstract: Flame-repellant linear polyesters are obtained by incorporating by condensation phosphorus-compounds having the formula ##STR1## wherein R and R.sub.1 are organic radicals which may also contain hereto atoms into the linear polyesters, preferably those from terephthalic acid and ethylene glycol. These polyesters are materials of which flame-repellent filaments, fibers, sheets, press-moulded and injection-moulded articles may be made. Products of the invention can be used whereever especially acute risks of ignition and fire exist.