Production of flame-retardant linear polyesters

Claim 1

IN THE PRODUCTION OF POLYETHYLENE TEREPHTHALATE FILAMENTS BY A CONTINUOUS PROCESS OF FEEDING DIMETHYL TEREPHTHALATE AND ETHYLENE GLYCOL COMPONENTS WITH CATALYST TO ESTER INERCHARGE MEANS AND REACTING THE COMPONENTS TO FORM DI-B-HYDROXVETHYL TEREPHTHALATE MONOMER, FEEDING THE MONOMER TO A PREPOLYMERIZING AND POLYMERIZING THE MONOMER TO FORM LOW MOLECULAR WEIGHT PREPOLYMER, FEEDING THE PREPOLYMER TO A FINISH POLYMERIZERE AND COMPLETING THE POLYMERIZATION TO FORM FIBER-FORMING POLYMER, AND FEEDING THE POLYMER TO A SPINNING MACHINE AND MELTSPINNING THE POLYMER INTO FILAMENTS, THE IMPROVEMENT FOR PRODUCING FLAME-RETARDANT FILAMENTS OF EXCELLENT WHITENESS, WHEREIN THE IMPROVEMENT COMPRISES CONTINUOUSLY ADDING TO SAID DI-B-HYDROXYETHYL TEREPHTHALATE MONOMER A MOLTEN STREAM OF 2,I-BIS-(4-NI-HYDROXYETHOXY)-3,5-DIBROMOPHENYL) PROPANE IN AN AMOUNT WHICH PROVIDES FROM ABOUT 4 TO ABOUT 5 MOLE PERCENT BASED ON GLYCOL TEREPHTHALATE STRUCTUAL UNITS PERCENT IN THE COPOLYESTER PRODUCED, AND UP TO 400 PARTS PER MILLION OF AN OPTICAL BRIGHTENER, CONDUCTING THE POLYMERIZATION WITHIN A HOLDUP TIME OF 2.5 HOURS TEMPERATURES FROM ABOUT 273* TO ABOUT 290*C. TO FORM FIBER-FORMING COPOLYESTER, AND MELT-SPINNING THE COPOLYESTER INTO FILAMENTS.