Study On The Minimizing Of Polyester Oligomer

Poly(ethylene terephthalate) owns excellent properties and is widely used in textile as well as bottle,package material,film,engineer plastics and so on.Recently years,together with the development of super high speed spinning,fine-denier filament and bi-oriented film producing,the requests for the PET properties become more and more strictly.Oligomer is the main factors that influence the quality of PET,which has been focused worldwide day by day.In this respect,decreasing the content of oligomer has the high feasibility to improve the quality of PET now.With respect to the above considerations,the results are as follows:(1) In this thesis,the extraction technique of oligomer from PET chip was studied by soxhlet extraction,the size of PET chips and time of extraction on the extraction quantities of oligomers was investigated.It is identified that extraction end point can be determined by continuous reflux extraction for 15 hours at 80℃as quantitative method for normal PET chips by chloroform as extraction menstrual.The oligomer was characterized by molecular weight distribution,UV and FT-IR spectrum and DSC.The study results showed that the extracted oligomer was mostly cyclic trimer. (2) PET production on industrial production line was studied and it is identified that oligomer was produced on condensation stage of PET synthesis process.Orthogonal design showed that the maximum influencing factor of polymerization process is condensation temperature and condensation time,the second influencing factor is the amount of catalyst and amount of stabilizer.In the polymerizing procedure,the moderate polymerization environment would benefit for low oligomer content in polyester.After the selection and optimize action of the polymerization additive system,it is proved that addition of 1425 was the optimum favor to the reduction of oligomer content of PET.(3) Based on the study of the polymerizing process and optimum additive system,we select different PET with different content of oligomer of different condensitation additive system,the content of oligomer that effect the crystallization and thermal degradation properties was studied; The DSC parameters show that the cyclic oligomer acts as nucleating agent during the process of PET melt crystallization.The results of thermal gravimetric analysis showed additive depressed the thermal degradation and it has good effect.(4) Based on the study of optimum additive system to decrease the oligomer content of PET with mini-type polymerizer,we carried out synthetic experiments in scale-up with additive 1425 and TEPA by optimal synthetic process.Through the 20L polymerizer polymerization date and the analysis of production test result,1425 has outstanding effect on decreasing the content of oligomer,and the higher the amount was,the greater the effect became.