Study On Anionic Continuous Solution Copolymerization Of Butadiene/Styrene

The anionic solution copolymerization of butadiene/styrene with n-butyllithium(n-BuLi) initiator, tetrahydrofuran(THF) modifier, and cyclohexane solvent was studied experimentally in an agitated tank reactor of 2 liters employing the continuous operation mode. The reaction conversion of comonomers, the molecular weight and molecular weight distribution of butadiene/styrene copolymer, and the micro-structure of the copolymer were analyzed by gas chromatograph, gel permeation chromatograph, and nuclear magnetic resonance, respectively. The effects of the mean residence time, the ratio of THF to n-BuLi(THF/n-BuLi), and the reaction temperature on the conversion, the molecular weight and molecular weight distribution, and the micro-structure of the copolymer were investigated. On the basis of the information of experimental study, models of comonomer conversion, and the molecular weight distribution under the condition of the maximum mixednees in a continuous stirred tank reactor(CSTR) were established. The parameters of the models were evaluated in terms of experimental data and the simulations of the models were carried out. Modeling of dynamic equilibrium of different states of living polymer was studied. The effects of dynamic equilibrium performance on the molecular weight distribution were simulated. In this thesis, the effects of the reactant level perturbation in CSTR on the anionic continuous polymerization, the analysis of parametric sensitivity of CSTR, and its dynamic performance were also studied.The experimental results showed that the effects of THF/n-BuLi on the rate of the anionic continuous solution copolymerization of butadiene/styrene, the content of combined styrene, and the micro-structure of the randomized copolymer of butadiene/styrene were significant, and that the effects of the mean residence time on the micro-structure and the molecular weight distribution of the copolymer were not remarkable, and that the effects of the mean residence time and the reaction temperature on the copolymerization rate were significant. The rate of the copolymerization increased obviously with increasing of THF/n-BuLi. The reasonable THF/n-BuLi was found to be 70. The content of combined styrene and the 1,2-structure of the copolymer increased and 1,4-structure decreased with increasing of THF/n-BuLi. This changes become slow when THF/n-BuLi reached about 35. The conversions of comonomer and the average molecular weight increased with increase of the mean residence time. The dispersion index of molecular weight distribution was close to 2.On the basis of the hypotheses of maximum mixedness and one active species, a mathematical model of the anionic solution copolymerization of butadiene/styrene in a CSTR, which included the conversion of the copolymerization and the moments of molecular weight distribution of the copolymer, was established. The reaction rate constants were obtained in terms of the experimental results and the parameter evaluation. The simulation of the conversions of the comonomers and the molecular weight and molecular weight distribution were carried out. The simulated results were good agreeable to the experimental results.The simulated results of the effects of the reactant level perturbation in CSTR on the anionic polymerization showed that for the anionic continuous polymerization the perturbation of reactant level in CSTR would lead to the oscillations of the monomer concentration and the polymer chain length and its distribution in the outlet steam with the same frequency as that of the reactant level perturbation. However, the differences betweenthe average values of the monomer concentration, the polymer chain length, its distribution, and the corresponding values of steady state were very small. The ratios of their amplitudes to the average values were much smaller than that of the reactant level perturbation. The anionic continuous copolymerization of butadiene/styrene is insensitive to the reactant level perturbation. The longer the mean residence time is, the more...