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.