Effect of alkylaluminum structure on Ziegler-Natta catalyst systems based on neodymium for producing high-cis polybutadiene

摘要

In this work,a laboratory scale process for producing polybutadiene with high content of cis-1,4 repeating units was studied.A Ziegler-Natta catalyst system constituted of neodymium versatate(catalyst),an alkylaluminum compound(alkylating agent and cocatalyst)and tert-butyl chloride(chlorinating agent)was used.The solvent employed was a mixture of hexane and cyclohexane(80/20 v/v).The objective of this work was to evaluate the effect of alkylaluminum structure and the influence of Al/Nd(5 to 15)molar ratio of long chain alkylaluminium compound(tri(n-hexyl)aluminum)on catalyst activity and polybutadiene characteristics.The alkylaluminum compounds employed in this study were tri(i-butyl)aluminum,tri(n-hexyl)aluminum,tri(n-octyl)aluminum and di(i-butyl)aluminum hydride.The polybutadienes molar masses obtained were strongly influenced by the alkylaluminum structure.Polymers with the highest molar masses were obtained when tri(i-butyl)aluminum,tri(n-hexyl)aluminum and tri(n-octyl)aluminum were employed.However,polymers with the highest contents of cis-1,4 units and the lowest molar masses were produced when di(i-butyl)aluminum hydride was employed.