Study On Continuous Solution Copolymerization Of Butadiene/Styrene

Solution polymerized styrene-butadiene rubber (SSBR) is one of the most important synthetic rubbers, and is synthesized via anionic solution polymerization process with taking alkyl-lithium as initiator. Tread stock with properties of low rolling resistance and high anti-wet skid, which are the primary features of superior quality automobile tires, can be prepared through the means of molecular design. In the recent years, the demand for SSBR in domestic and overseas market is continuously growing with the development of the automobile industry and construction of highway.Continuous polymerization of 1,3-butadiene and styrene of copolymers by organolithium initiation in solution polymerization systerms offers real production, advantages;such as more economic production, and more uniform compositions Process variables can be.readily adjusted in a continuous operation so as to optimize operations for a given polymerization recipe. Minor adjustments of monomer feed rates, initiator rates, randomizer rates, temperature control, pressure control, solvent usage, all can be readily made in a continuous process, in effect "fine tuning" so as to maintain relatively consistently a product with optimum properties. Continuous polymerization is more suitable for produce random copolymer of butadiene/styrene with relatively broader molecular weight distributionUnfortunately;continuous solution polymerization has the disadvantage of a tendency toward fouling and gel. Having to stop the entire process, clean the equipment, and then start up all over again, means attendant startup problems and necessity to again fine tune the operation. Gel, of course, adversely affects polymer uniformity and quality. Methods of reducing reactor fouling generally involve the addition of a gel inhibitor to the polymerization system.In this thesis, The anionic solution copolymerization of butadiene/styrene with n-butyllithium (n-BuLi),tetrahydrofuran(THF)or(TMEDA) modifier, and cyclohexane solvent was studied experimentally in three agitated tank reactors 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 maximummixednees in three continuous stirred tank reactor(CSTRS) were established. The parameters of the models were evaluated in terms of experimental data and the simulations of the models were carried out. The reaction rate constants(ï¿¡M > k^ ?> kgs ^ kSB) and The apparent reactivityratio(rB ,rs) were obtained in terms of the experimental results and the parameter evaluation.Modeling of dynamic equilibrium of different states of living polymer was studied. The simulated results were good agreeable to the experimental results. The polymerizing technics condition of anionic solution copolymerization SBR is determined by experimental data and the simulations of the models.The experimental results showed that the effects of THF/n-BuLi, comonomer concentration, reaction temperature on the propagation rate constants(ï¿¡BB > kss -. kBS â– > ï¿¡SB)andThe apparent reactivity ratio(rB,rs) of the anionic continuous solution copolymerization ofbutadiene/styrene(includingSSBR-a,SSBR-b, SSBR-c),the content of combined styrene, the micro-structure of the randomized copolymer of butadiene/styrene(includingSSBR-a,SSBR-b, SSBR-c),and the percentage of produce nM, polystyrene chain were significant, The rate of the copolymerization increased obviously with increasing of THF/n-BuLi, comonomer concentration, reaction temperature. 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.