Preparation Of Isoprene-pentadiene Copolymer Rubber By Polymerization Of C₅ Fraction

With the development of petrochemical industry,the comprehensive utilization of C₅fraction,a by-product from ethylene production,has received more and more attention.In this paper,the C₅ fraction after preliminary treatment was used to obtain a novel1,3-pentadiene-isoprene random copolymer rubber by catalyst Nd(P₂₀₄)₃/AlⁱBu₃/AlEt₂Cl.The rubber had better performance than polyisoprene rubber after being kneaded and vulcanized,which was of great significance for the effective utilization of the C₅ fraction and the development of high value-added new rubber products.1.The role of each component in the C₅ fraction in the copolymerization was studied in detail using a ternary neodymium-based catalyst.Isoprene and E-1,3-pentadiene were copolymerization monomers;alkane,monoolefin,1,4-pentadiene,Z-1,3-pentadiene acted as a solvent which didn’t change before and after copolymerization,while cyclopentadiene acted as poison in the copolymerization.2.The effects of type and amount of neodymium salts,alkyl aluminums,halogen-containing compounds,copolymerization temperature and monomer dosage on the copolymerization were studied in detail.The results showed that the controlled molecular weight M_n=3.8×10⁴¹4.3×10⁴ g·mol^-1 and medium molecular weight distribution M_w/M_n=2.17².78 of the 1,3-pentadiene-isoprene copolymer obtained under the polymerization conditions of Nd(P₂₀₄)₃/AlⁱBu₃/AlEt₂Cl catalyst at a ratio of 1/2³0/3⁵,polymerization temperature of 25⁷0°C and copolymerization time of 6¹2 h.The isoprene cis-1,4 selectivity in the copolymer was 96%,and the pentylene cis-1,4 selectivity was 60%.The reactivity ratio of isoprene(r_IP)and E-1,3-pentadiene(r_EPD)were 2.45 and 0.41(r_IP×r_EPD=1.00)indicated that the copolymer of C₅ fraction by Nd(P₂₀₄)₃/AlⁱBu₃/AlEt₂Cl was an 1,3-pentadiene-isoprene random copolymer,while having a low glass transition temperature T_g=-60°C.By controlling the ratio of the C₅ fraction to the catalyst,an1,3-pentadiene-isoprene random copolymer having a controlled molecular weight(M_n=3.8×110⁴²1.1×110⁴ g·mol^-1)and medium molecular weight distribution（M_w/M_n=2.17to 2.78）was obtained.3.The obtained 1,3-pentadiene-isoprene copolymer,which having a molecular weight（M_n）of 21.1×10 4 g·mol^-1 and a 1,3-pentadiene content of 22%,was vulcanized at 135°C,and the t₁₀ as 13 min 55 sec and the t₉₀ was 35 min 2 sec.The vulcanized rubber had a crosslink density of 2.11×110^-5 g·mol^-1,a hardness of 53,a tensile strength of 19.3 MPa,an elongation at break of 1175%and a loss factor（tanδ）of 1.32.The tensile strength change rate was-82%,and the elongation at break was changed to-77%after thermal oxygenation at100°C of 3 days.Compared with polyisoprene rubber,the mechanical properties of copolymer rubber were comparable,the tanδpeak was lower,and the processing safety and heat oxidative aging resistance were better than polyisoprene rubber.