Process parameter optimization through Design of Experiments in synthesis of high cis-polybutadiene rubber

POLAR ADDITIVES IN 1,3-BUTADIENE POLYMERIZATION

Butadiene rubbers are frequently produced through solution polymerizations using Ziegler–Natta catalysts based on neodymium. Particularly, there is great interest in developing rubbers that present enhanced processability during the formulation step. For this reason, the present work investigated the production of butadiene rubbers in the presence of polar additives, such as methyl methacrylate, methacrylic acid, and water, through solution polymerizations, using neodymium versatate as catalyst. The obtained results confirmed the possibility of producing butadiene rubbers with polar character that presented improved processability properties during the vulcanization stage. In addition, a new use for water and the manufacture of copolymers of butadiene and oxygenated monomers in polymerization processes that make use of neodymium catalysts are reported for the first time.

BUTADIENE RUBBER: SYNTHESIS, MICROSTRUCTURE, AND ROLE OF CATALYSTS

Butadiene rubber (BR) is one of the most useful and second most produced rubber worldwide. Polymerization of 1,3-butadiene (BD) is a highly stereospecific reaction that offers a wide variety of BR with different microstructures and influences the fundamental properties of the rubber. Since the first successful polymerization of conjugated diene using the Ziegler–Natta–based catalyst (TiCl4 or TiCl3 with aluminum alkyls) in 1954, the research on producing synthetic rubber with an appropriate catalyst system has been accelerated. Subsequently, various research groups are actively engaged in designing active catalyst systems based on a suitable combination of transition metal complexes with alkyl-aluminum and successfully using them in BD polymerization. Although various scientific inventions have proven their significance for the production of high-quality BR, with the rising demands in improving the quality of the product, research on developing new catalyst systems with enhanced catalytic activity and high stereoselectivity is still in progress. The present review focuses on the synthesis of BR using various transition metal catalysts and discusses their microstructures. The catalysts based on new-generation metal complexes with phosphorus, nitrogen, and oxygen donor ligands (e.g., phosphines, imines, 1,10-phenanthroline, and imino-pyridines) have been introduced. The role that catalysts play in the production of BR with different microstructures (i.e., high-cis, high-trans or low-cis, low-trans polybutadiene) has also been described. The combination of catalyst (transition metal complex) and suitable co-catalyst (alkyl-aluminum) is the major factor influencing the reaction and microstructure of the resulting polymer. This report focuses on the effect of transition metal catalysts (i.e., lithium [Li], titanium [Ti], zirconium [Zr], iron [Fe], cobalt [Co], nickel [Ni], and neodymium [Nd]) on the activity and stereoselectivity of polymers such as 1,4-cis-, 1,4-trans-, and 1,2-vinyl-polybutadiene.

Adsorption of an emerging contaminant (primidone) onto activated carbon: kinetic, equilibrium, thermodynamic, and optimization studies

The current study addresses the removal of an emerging environmental contaminant (primidone) in batch adsorption experiments using commercial-grade powdered activated charcoal (PAC). The experiments for the removal of primidone were performed to identify the effect of various adsorption parameters. The second-order rate expression best represented the adsorption kinetics data. The Freundlich isotherm equation was best fitted to the experimental adsorption data at equilibrium for removal of primidone using PAC. The values for change in entropy (ΔS^o) were positive, which indicates that the degree of freedom of the process increases. The negative values of change in enthalpy (ΔH^o) and change in Gibb's free energy (ΔG^o) indicate that the physical adsorption is a dominant phenomenon, and the process is feasible and spontaneous. The negative value of ΔH^o also represented the exothermicity of the adsorption process. The Taguchi optimization technique calculated the influence of variation of different process parameters, viz., initial pH (pH₀), PAC dosage (m), initial adsorbate concentration (C₀), solution temperature (T), and process contact time (t), on the removal of primidone by adsorption from aqueous solution. Each of the above parameters was examined at three levels to study their effects on the adsorptive uptake of primidone using PAC (q_e, mg g^-1), and the optimum value necessary to maximize q_e was determined. The findings from the ANOVA indicate that the PAC dose (m) is the most notable parameter contributing 62.16% to q_e and a 71.96% to the signal to noise (S/N) ratio data, respectively. The confirmation experiments performed at the optimum parameter condition validated the applicability of the Taguchi design of experiments. The percent removal and adsorptive uptake at the optimal condition were 86.11% and 0.258 mg g^-1, respectively.

Synthesis of Highcis-1,4-BR with Neodymium for the Manufacture of Tires

The salt of neodymium has been widely used in industrial polymerization of 1,3-butadiene. We used the ternary catalytic system neodymium versatate/diethylaluminum chloride/triisobutylaluminum (NdV3/DEAC/TIBA) with 0.5 mM NdV3/100 g Bd, NdV3 : DEAC = 1 : 9 mol : mol, and TIBA = 25, 50, 100, and 200 mM. The number-average molecular weight (Mn), weight-average molecular weight (Mw), and polydispersity index (PDI) were analyzed by GPC; the rheological properties were analyzed by DMA. The formulations were prepared with carbon black (IRB6) as reinforcing filler and the mechanical properties were compared to behavior of the different elastomeric compounds. The elastomeric compounds were characterized by their rheological properties, tensile strength, abrasion resistance, tear strength, permanent set, resilience, and fatigue properties. The highcis-1,4 polybutadiene (highcis-1,4-BR) was obtained with a percentage ofcis-1,4 ≥97%. The weight-average molecular weight (Mw) was from 150 × 103to 900 × 103 g/mol and polydispersity index (PDI) was from 3.1 to 5.1. This work is based on evaluation of the effect of the catalyst system on the final properties of the synthesized polybutadiene.