高黏微观混合表征新方法及其在双螺杆挤出机中的应用

在双螺杆反应挤出过程中微观混合程度是重要的操作参数。一些特别设计的经典小分子竞争反应体系常用于表征微观混合,但其用于大分子反应的高黏物系时由于大小分子扩散不同容易引起偏差。今建立了一种由苯乙烯-(3-异丙烯基-α,α′-二甲基苄基-异氰酸酯)共聚物(PSt-co-TMI)与9-(甲胺基-甲基)蒽(MAMA)为快反应、PSt-co-TMI与己内酰胺(ε-CL)为慢反应的大分子竞争反应体系,并应用于TSE-20可开启式自啮合双螺杆挤出机中微观混合状况的表征。考察了不同螺杆位置处产物的分离指数和转化率;研究了螺杆转速、喂料速率等对微观混合质量的影响。结果表明:该大分子竞争体系可很好地用于双螺杆挤出机中高黏物系微观混合表征;微观混合在物料熔融后相当短的流程内即完成,微观混合质量在挤出过程稳定后保持不变;对于推进式元件,在相同的喂料速率下随着螺杆转速的增加微观混合质量下降;填充度是影响推进元件中微观混合质量的重要因素,在特定的实验条件随喂料量增大微观混合质量反而改善的原因在于填充度的提高有利于微观混合。

A Method for Assessing Micromixing in TSE and its Application

Micromixing quality is one of the most important parameters in twin-screw extruder (TSE) operation. A new parallel competitive reaction system of macromolecules composed by the reaction between PSt-co-TMI (copolymer of styrene and α,α-dimethyl meta-isopropenyl benzyl isocyanate) and MAMA (9-(methylamino-methyl) anthracene) as the fast reaction and the reaction between PSt-co-TMI and ε-caprolactam as the slow reaction was designed and used to assess the micromixing quality of high-viscous system formed by macromolecular reaction in the TSE. The segregation index and conversion ratio of the competitive reactions in different positions of the TSE were examined. Furthermore, the influences of feed rate and screw speed were studied. It indicates that the proposed macromolecular competitive system can be used to well assess the micromixing quality of the high-viscous materials in TSE; the micromixing is accomplished very quickly after polymer melting, and then the micromixing quality keeps unchanging. As to the impellent type elements of the TSE, under the same feed rate, the micromixing quality decreases with the increase of the screw rotation speed. It was found that the filling degree of the TSE is an important parameter which controls the micromixing quality of the TSE operation. Under some special conditions, with the increase of feed rate the micromixing performance of the TSE is improved instead, which is due to the rise of filling degree of the TSE.