Study On The Characterization And Control Of Oligomers In PET

In this thesis, a frequently concerned oligomer problem in BOPET production was studied. And effective method for oligomers analysis was developed by analyzing the structure and forming theory of polyester oligomers. Rheology and crystalline property as well as spinning and filming property of polyester with different oligomer content were studied. The influence of polymerization technology on oligomer content was studied. The influence of different oligomer content on BOPET was tested on industrial production line. Melting filming technology was developed based on the research of oligomers. A decompose catalyst TDO was developed and tested on BOPET production line. An effective solvent for fast removing the oligomers on the film roller was developed as well.Based on a systemic study on oligomers, it is identified that oligomers were the main reason for the break of BOPET. Under a whole round control of the content of oligomers, a novel melting filming technology was developed. The main task of this thesis were presented as below:1. This thesis studied the theory of secondary reaction of polyester and structure and theory of oligomers2、In this thesis, supersonic extraction was used as the qualitative analysis method for quick estimate the oligomer content of polyester, soxhlet extraction was adopted as the quantitative analysis method for oligomer content. Based on the selecting of extraction technology and confirming of extraction time, the oligomers were completely separated and the content were calculated.3、TLC and chromatographic column were used to separate the oligomes, IR、NMR were used to analysis the oligomers structure. DSC and TG were used to analysis thermal properties of the oligomers.4、Crystallization property and rheologic behavior were analyzed, the results show that oligomers have little influence on rheologic behavior of PET but both influence on the formation of nuclei and the growth of crystallites of PET matrix. Film and spinning were tested on PET with different oligomer contents, the results show that oligomer would cause high film rupture rate and low film property in film drawing and bad spinning ability in spinning.5、PTA route was adopted in PET polymerization, methods for reducing oligomer content were tested through adjustment of technical reference of polymerization. The influence of temperature, viscosity, catalyst and stabilizer to oligomer content were studied. The results show that based on a reasonable polymerization degree a moderate polymerization environment would benefit for low oligomer content in polyester.6、The influence of oligoemrs on PET film was studied on BOPET production line. It is proved that linear oligomer with low melting point and cycle oligomers with aether bond were the main reason for the break of film. Melting film technology was developed by optimizing four kettle polymerization technology and ensuring a minimum content of oligomers.7、Break time decreased and film property was improved by using a novel decomposition catalyst NM-12 in TDO section. Oligomers deposited on the film roller can be quickly removed by adopting tetrahydrofuran(THF) as solvent.