NaOH与TEAH催化熔融酯交换合成聚碳酸酯及其重排产物研究

NaOH AND TEAH CATALYZED POLYCARBONATE SYNTHESES THROUGH MELT TRANSESTERIFICATION AND THE REARRANGMENT PRODUCTS IN BOTH PROCESSES

分别以NaOH和氢氧化四乙基铵(TEAH)为催化剂,碳酸二苯酯(DPC)和双酚A(BPA)为原料,采用熔融酯交换法合成聚碳酸酯.当DPC与BPA的摩尔比为1.05∶1,催化剂与BPA的摩尔比为5×10-4∶1时,在所采用的工艺条件下,可分别得到Mn、Mw/Mn为1.69×104、1.97(NaOH催化),1.23×104、1.44(TEAH催化)的聚碳酸酯.对反应体系的特性黏数和体系熔体流动性变化情况进行测定.利用氢核磁共振谱、紫外光谱、高效液相色谱等分析手段对反应过程中Fries、Kolbe-Schmitt、异丙基自由基重排反应进行了研究,探讨了这些重排副产物在不同催化剂反应体系下的产生和变化过程,发现Fries重排是3类重排中最易发生的反应,在氢氧化钠催化体系全过程中都存在,体系的高温高黏对Kolbe-Schmitt重排有较大影响,与氢氧化钠作催化剂相比,氢氧化四乙基铵催化合成聚碳酸酯的分子量较低,分子量分布较窄,两种重排反应程度都远低于前者.在二催化体系中都未发现异丙基自由基结合导致的重排产物.

The synthesis of polycarbonate（PC） was carried out by using the melt transesterification of bisphenol A（BPA） and diphenyl carbonate（DPC） catalyzed respectively by NaOH and tetraethylammonium hydroxide（TEAH）.When the molar ratio of DPC to BPA was 1.05∶ 1 and that of catalysts to BPA was 5 × 10-4∶ 1,under the process conditions selected,polycarbonates with Mn of 1.69 × 104,Mw/Mn of 1.97（catalyzed by NaOH） and M n of 1.23 × 104,M w/M n of 1.44（catalyzed by TEAH） were produced.The variation of intrinsic viscosity of the PC samples and the liquidity of relevant melt flow in different stages of the reaction process were determined.The 1H-NMR spectroscopy,UV spectroscopy and HPLC were employed to analyze the Fries,Kolbe-Schmitt and isopropyl radical combination rearrangement.In different catalytic processes,all these rearrangements have different forming and varying conditions.It is observed that the Fries rearrangement is the one most prone to appear among the three kinds of rearrangement reactions,which exists in the entire NaOH-catalyzed process.Kolbe-Schmitt rearrangement is impacted significantly by the high-temperature and melt viscosity of the reaction system.Compared with NaOH,in the TEAH-catalyzed system,the molecular weight of polycarbonate is lower,the molecular weight distribution is narrower and the degree of Fries and Kolbe-Schmitt rearrangements is much lower.In both catalytic processes,no rearrangement products caused by the combination of isopropyl radicals were found.