Recycling of PET waste was studied by employing depolymerization to a lower molecular -weight monomer or oligomer（BHET） in a continuous two stage alcoholysis process. A dissolver of 3.4 l capacity was used for dissolving PET waste in BHET at 235 ℃, a preheater for heating EG, and a 2.75 l tubular reactor, equipped with a perforated plate for good mixing, for depolymerization reaction of dissolved PET waste in BHET with EG.
The effect of reaction temperature, residence time, and recycle ratio on the average degree of polymerization of depolymerized oligomer were experimentally investigated. It was found that the optimum conditions were as follows : reaction temperature of 240∼250 ℃, residence time of 10 min, and recycle ratio of 2 : 1 Under the optimum operating conditions the average degree of polymerization of depolymerized oligomer ranged from 1.5 to 1. 7 which appears low enough to be used in repolymerizing to PET.