Figure Molecular structure of 1,3-butadiene.
BR is used in four major areas: tire manufacturing (70%); impact alteration of thermoplastics (25%) such as high impact polystyrene (HIPS) and acrylonitrile butadiene styrene terpolymer, more commonly known as ABS; and everyday products like shoe soles and golf balls (5%) .
As there is a high demand for improvements of the mechanical properties of rubbers used by the tire industry, the production of high-cis polybutadiene has been the subject of several scientific studies in recent years.
Proβ et al. (1993) presented a mathematical model for 1,3-butadiene polymerizations with a neodymium-based catalyst and were able to predict the MWD of the final product, the evolution of 1,3-butadiene concentrations and the dependence of the reaction rate constant on the Cl/Nd molar ratio. The authors showed that distinct catalytic systems presented distinct kinetic constants and produced rubbers with distinct properties .
Ling et al. (2000) proposed a Monte Carlo procedure to simulate the gas phase polymerization of 1,3-butadiene and were able to predict the MWD of the obtained products.
Aminova et al. (2002) developed a mathematical model to describe 1,3-butadiene polymerizations using a cobalt-based catalyst. The author’s proposed model was able to simulate Mn and Mw, branching factors and sedimentation-average degrees of polymerization. It was observed the occurrence of branching reactions, chain transfer to polymer, and chain cross-linking. In another work, Aminova et al. improved the same model in order to describe a continuous process and used the model to simulate the average molecular weights of the obtained products .
Manuiko et al. (2010) proposed a model for 1,3-butadiene solution polymerizations that considers the presence of two types of active sites in the system and the presence of hexachlorop-xylene as a chlorinating agent. Particularly, their model was able to calculate average molecular weights and branching frequencies .
Vasconcelos et al. (2019) developed a mathematical model for the polymerization of 1,3-butadiene using neodymium versatate as a catalyst. The model, in addition to being able to predict final properties of the polybutadiene polymer as average molecular weights and cis-content, was also able to predict the evolution of operation conditions that are used at plant site to monitor the course of the reaction like temperature and pressure .
As far as we have knowledge, given the described scenario, there are not many theorical studies on the number of active catalytic sites in polymerization and their influence on the polymer molar mass distribution profile, as well as temperature and pressure profiles during the process. Thus, the objective of this work is to evaluate this influence by comparing such profiles using Aspen Plus 10 software considering the proposed kinetic mechanism that includes initiation, chain propagation, and monomer transfer steps.