【摘要】 提出了添加液氮以促进芳纶1414合成体系换热的方法,即将溶液的最高温度控制在2.5℃以下,同时在反应初期(2～11min)使温度下降速率为1.3℃/min.与冰水浴间接换热相比,本法可获得更低的反应温度与更快的移热速率,有利于抑制缩聚反应初期的暴聚现象.分析结果显示,液氮的加入与相变还可促进反应物剧烈混合,传质效果的改善也有利于显著提高产品质量,最终得到了比浓对数粘度高达6.9dL/g的产品.更多还原

【Abstract】 A method to enhance the heat removal in the synthesis system of poly(p-phenylene terephthalamide) (PPTA) by adding liquid nitrogen was proposed. The phase transition of liquid nitrogen is effective to control the maximal temperature of the system below 2.5℃. The decreasing rate of temperature in the initial polymerization stage (2-11 min) is 1.3℃/min. Compared with the indirect heat removal by water-ice bath, this absorbs reaction heat in large amount and quickly, which is crucial to the temperature control for this highly exothermic reaction, especially for the scale up. In addition, the phase transition of liquid nitrogen provides the turbulent mixing of the reactants in the system, which improve the mass transfer and favors the increase in the quality of the product, evidenced by thermogravimetry, XRD and Raman spectroscopy. The viscosity of final product is up to 6.9 dL/g, suggesting its high quality.更多还原