Towards the hydrogenation of polybutadiene within a single reactive phase

J.M MILANESIO; PABLO E. HEGEL; A.E. CIOLINO; L.M. QUINZANI; L.J. ROVETTO; M.S. ZABALOY

Eindhoven

Simposio; 27th European Symposium on Applied Thermodynamics (ESAT 2014); 2014

Eindhoven University of Technology

Polybutadiene (PB) is an amorphous homopolymer produced from 1,3-butadiene polymerization.Depending on the catalyst and the solvent used in the polymerization reaction, the relative amount ofdouble bond configurations (cis 1-4, trans 1-4 and vinyl 1-2) can be controlled, and, therefore, the PBphysical properties. The complete hydrogenation of PB yields a copolymer of ethylene and 1-butene(hPB) which highly resembles the structure of linear low-density (LLD) polyethylene (PE) (LLDPE) [1].Furthermore, PB may be synthesized using the anionic polymerization technique that makes possibleto obtain polymers of very narrow molecular weight distribution (MW/MN < ∼1.1). Consequently, thehydrogenation of PBs obtained by anionic polymerization could produce LLDPEs of narrow molecularweight distribution. Milanesio et al. [2,3] measured high pressure liquid-liquid phase equilibrium data(also known as ?cloud points?) in binary, ternary and one quaternary system related to the potentialhydrogenation of PB in a single reactive phase. These data suggest that the use of a solvent mixturemade of a light polar solvent, e.g., DME, and a heavier non polar solvent, e.g., C5, should be aconvenient choice to carry out the single-fluid-phase supercritical hydrogenation of PB at relativelymoderate conditions. This solvent mixture tends to solubilize the reactive polymer, its reaction product(i.e. the LLDPE) and intermediate species. The solvent mixture should have a solvent ratio close to 1:1(DME/C5, weight basis) and the polymer mass fraction in the reactive mixture should be about 3 wt%[2, 3]. At these conditions, the pressure needed to have a single phase for the mixture containing theunsaturated reactive polymer and the saturated product is about 300 bar, in the 30 to 200 oCtemperature range, if the hydrogen is absent.In this work, the conditions suggested in references [2, 3] were tested for the hydrogenation of PB inan experimental setup specially designed and built for this project. The effect of a number of variables,such as reaction time, presence of catalyst and initial concentration of hydrogen in the reactivemixture, was studied. The phase behavior during the evolution of the reactive process was alsoinvestigated.References[1] Morton, M. Anionic Polymerization: Principles And Practice. (Academic Press, 1983).[2] Milanesio, J.M., Mabe, G.D.B., Ciolino, A.E., Quinzani, L.M., Zabaloy, M.S., J Supercrit Fluids 55 (2012),333?339.[3] Milanesio, J.M., Mabe, G.D.B., Ciolino, A.E., Quinzani, L.M., Zabaloy, M.S., J Supercrit Fluids 55 (2010),363?372.