Polymerization of ethylene terephthalate cyclic oligomers with antimony trioxide

Conditions for polymerizing ethylene terephthalate cyclic oligomers (ETCs) with the catalyst antimony trioxide were investigated with the ultimate goa l in mind of using ETCs to produce highperformance poly(ethylene terephthal ate) (PET) composites. The ETCs used were prepared both by a direct synthes is method and by cyclodepolymerization (CDP) in dilute solution. ETCs prepa red exhibited a distribution of oligomeric species displaying a broad melti ng range, the uppermost end of which lies at 290 degrees C. In the case of ETCs prepared by CDP, purified ETCs (p-ETCs) were prepared by eliminating r emaining impurities including linear oligomers and cyclic oligomers contain ing the diethylene glycol (DEG) unit using dichloromethane and tetrahydrofu ran. A homogeneous mixture of ETCs prepared by the direct synthesis method or p-ETCs with antimony trioxide was successfully polymerized to I high mol ecular weight (MW) PET (M-n greater than or equal to 25 000) at 293 degrees C within 15 min. The lower the contents of remaining impurities, the highe r the MW of the resultant PET. The PET of highest: MW (M-n = 32 000) was ob tained from polymerization of p-ETCs with bismuth trioxide at 293 degrees C for 15 min. PET polymerized from p-ETCs showed the same thermal behavior a s did the commercial one. In this research, a useful method of PET recycle by using ETCs was successfully established.