环状对苯二甲酸乙二醇酯低聚体的沉淀分离提纯与开环聚合

Precipitation,Separation,Purification and Ring-Opening Polymerization of Cyclic Ethylene Terephthalate Oligomers

通过低溶液浓度下聚对苯二甲酸乙二醇酯(PET)的解聚成环(CDP)反应可制备环状对苯二甲酸乙二醇酯低聚体(CET),但解聚粗产物组成复杂,影响CET高值化应用。本研究对PET解聚产物进行选择性沉淀分离提纯,研究了沉淀温度、沉淀剂种类等对CET收率的影响,并考察了纯化CET的热性能和开环聚合行为。结果表明:以乙醇为沉淀剂时,选择性沉淀得到的CET中线性低聚物和催化剂残留量随温度降低而减少,沉淀温度为30℃时线性低聚物和催化剂残留量较低;以正己烷等饱和烷烃为沉淀剂,沉淀温度为30℃时,可得到不含线性低聚物组分的CET,且以正己烷为沉淀剂,CET收率最高(72.69%)。纯化CET在不加催化剂或添加1%(质量分数)三氧化二锑催化剂、320℃下开环聚合8 min,可分别制得特性黏数为0.56 dL/g和0.64 dL/g的PET。

Cyclic ethylene terephthalate(CET)can be prepared by the cyclo-depolymerization(CDP)of polyethylene terephthalate(PET)at low solution concentrations,but the composition of crude depolymerization product is complicated and needs further purification for high-valued application.Here,effects of precipitation temperature and type of precipitating agent on the yield of CET,thermal properties and ring-opening polymerization behavior of purified CET were investigated.The results showed that when ethanol was used as the precipitant,the content of linear oligomers and catalyst residues in the selectively precipitated CET decreased with the reduction of temperature,and at a precipitation temperature of 30℃,the content of linear oligomers and catalyst residues was relatively low.When saturated alkanes such as n-hexane were used as precipitants,CET free of linear oligomer components could be obtained at a precipitation temperature of 30℃,and the highest yield of CET(up to 72.69%)was achieved using n-hexane as the precipitant.Purified CET,without the addition of a catalyst and with the addition of 1%(mass fraction)antimony trioxide catalyst,could be ring-opening polymerized at 320℃for 8 min to produce PET with intrinsic viscosities of 0.56 dL/g and 0.64 dL/g,respectively.