Experimental Study On Micromixing Process In Viscous Polymer Media

Many polymerization processes proceed in the high viscosity system. The micromixing conditions affect not only the structure of the product but also the molecular weight and distribution. Some chemistry methods (for example, the continuously competing reaction, the parallel competing reaction) were used to research the micromixing process in reactors. At the same time, some models basing on the experimental results were also used to express the corresponding mixing conditions. However, these research methods have focused on small molecular reaction systems. It needs further researchs to test whether these methods are suitable to describe the mixing characteristics of macromolecule in viscous media or not.In the first part of the paper, iodide-iodate parallel competing reaction system is selected to study the influences of the viscosity on the micromixing of the reacting system in beater, and the two kinds of mixing paddles (paddle impeller and fullzone agitator) are carried out. The results indicated that the micromixing effect got worse with the system viscosity increasing but got better with the rotational speed increasing; in the condition of low viscosity, the mixing effect of paddle impeller was better than that of fullzone agitator; while as the viscosity increasing, the mixing effect of fullzone agitator excceded that of paddle impeller.In the second part of the paper, the micromixing of the macromolecule reaction system with high viscosity had also been studied by establishing a new parallel competing reaction. The competing system was constituted by reaction between PS-co-TMI (copolymer of styrene (St) and α,α -Dimethyl meta-Isopropenyl Benzyl Isocyanate (TMI)) and 9-(methylamino-methyl) anthracene (MAMA) and reaction between PS-co-TMI and e-caprolactam (ε-CL), which is known that the former is a rapid reaction and the latter is much slower. The content of ε-CL,MAMA before and after reation can be determined by the infrared,ultra-violet spectrograph. And then the reaction conversion rate can be figured out. And it becomes possible to study themicromixing of the macromolecule reaction system by using this model. Only under the condition that the mixing speed lies between the speed of the rapid reaction and that of the slow one, the aim to study the influences of different factors on the micromixing can be realised.Studing the reaction between PS-co-TMI and ε-CL, the reaction mechanism is that the N=C of the isocyanogen acid radical (-N=C=O) in PS-co-TMI disconnects first, and then reacted with the imido(-NH) in ε-CL to produce a new group (-NH-CO-N-), which is a reversible reaction. The conditions in the range of 76.0℃ ～129.0℃, n(ε-CL)/n(PS-TMI)=2.62～82.7, the reaction activative energy and apparent frequency factor of the positive reaction and the reverse reaction between PS-co-TMI and ε-CL are writed as follows: Ea₊=82.2 kJ/mol, A₊=6.73×10⁸, Ea_-=117.8 kJ/mol,A_-=2.43×10¹². The polar of the solvent can impact on Ea and A of the reaction.