High-efficiency acetaldehyde removal during solid-state polycondensation of poly(ethylene terephthalate) assisted by supercritical carbon dioxide  

作　　者：Zhenhao Xi Tian Liu Wei Si Fenglei Bi Zhimei Xu Ling Zhao 

机构地区：[1]State Key Laboratory of Chemical Engineering,East China University of Science and Technology

出　　处：《Chinese Journal of Chemical Engineering》2018年第6期1285-1291,共7页中国化学工程学报（英文版）

基　　金：Supported by the National Key Research and Development Program of China(2016YFB0302702);the National Natural Science Foundation of China(21676083);the Shanghai Rising-Star Program(16QB140130);the 111 Project(B08021)

摘　　要：The concentration of acetaldehyde(AA) is the main quality index of poly(ethylene terephthalate)(PET) used in food and drink packaging.A new method for AA removal has been developed by using supercritical carbon dioxide(sc CO2) during the solid-state polycondensation of PET.The influence factors of AA removal including the temperature,pressure,reaction time and the size of pre-polymer particles are systematically studied in this work.The results indicate that it is a highly efficient way to obtain high molecular weight PET with relative low concentration of AA.Correspondingly,the polymerization degree of PET could increase from 27.9 to 85.6 while the concentration of AA reduces from 0.229 × 10^(-6) to 0.055 × 10^(-6) under the optimal operation conditions of 230 °C,8 MPa and size of 0.30–0.45 mm.Thermodynamic performance tests show the increasing extent of PET crystallinity due to the fact that the plasticization of sc CO_2 is not obvious with extended reaction time,therefore the increasing crystallinity has no significant influence on AA removal.SEM observations reveal that the effects of sc CO_(2-) induced plasticization and swelling on PET increase significantly with the decrease of prepolymer size,and the surface of PET becomes more loose and porous in favor of the AA removal.The concentration of acetaldehyde（AA） is the main quality index of poly（ethylene terephthalate）（PET） used in food and drink packaging.A new method for AA removal has been developed by using supercritical carbon dioxide（sc CO2） during the solid-state polycondensation of PET.The influence factors of AA removal including the temperature,pressure,reaction time and the size of pre-polymer particles are systematically studied in this work.The results indicate that it is a highly efficient way to obtain high molecular weight PET with relative low concentration of AA.Correspondingly,the polymerization degree of PET could increase from 27.9 to 85.6 while the concentration of AA reduces from 0.229 × 10^（-6） to 0.055 × 10^（-6） under the optimal operation conditions of 230 °C,8 MPa and size of 0.30–0.45 mm.Thermodynamic performance tests show the increasing extent of PET crystallinity due to the fact that the plasticization of sc CO2 is not obvious with extended reaction time,therefore the increasing crystallinity has no significant influence on AA removal.SEM observations reveal that the effects of sc CO（2-） induced plasticization and swelling on PET increase significantly with the decrease of prepolymer size,and the surface of PET becomes more loose and porous in favor of the AA removal.

关 键 词：Supercritical CO2 Solid-state polycondensation Poly（ethylene terephthalate） Removal of acetaldehyde 

分 类 号：TQ323.41[化学工程—合成树脂塑料工业] TS206.4[轻工技术与工程—食品科学]