Isoprene-butadiene Copolymer Using Rare Earth Catalyst System

The rare-earth catalytic system can regulate the relative molecular weight of the isoprene-butadiene copolymer,and the strength of the copolymer has a great relationship with the relative molecular weight.The isoprene-butadiene copolymer can have good mechanical properties and processing properties by the rare earth catalytic system.The copolymer has a single glass transition peak around-80 C.The isoprene and butadiene monomers exhibit a random distribution in the copolymer and the copolymer have good low temperature resistance.The new catalyst of neodymium was a homogeneous catalyst by adding isoprene monomers in the catalyst,and the isoprene-butadiene copolymers were synthesized by the new catalyst.The effects of different aging conditions,polymerization conditions and oil filling on the yield,microstructure,relative molecular mass and molecular weight distribution after oil filling were systematically investigated.The isoprene-butadiene copolymer was synthesized in hexane using Nd(vers)3/Al(i-Bu)3/Al(i-Bu)2Cl catalyst.The catalyst aging at 50?for 5 h.The effects of aging temperature,monomer addition,aging temperature,molar ratio of catalyst components and polymerization time,polymerization temperature and monomer ratio on the copolymerization of butadiene were investigated.The results show that the reaction conditions have little effect on the microstructure of the copolymer.The copolymer was of high cis-1,4 stereoregularity in both polyisoprene unit(cis-1,4=97%)and polybutadiene unit(cis-1,4=98%).The polymerization activity of the catalyst can be improved by adding the monomer Ip;when[Al]/[Nd]=15[Cl]/[Nd]=1.5,[Ip]/[Nd]=10,the polymerization yield of the catalyst is 85%.The molecular weight distribution of the product is 4.2,the average molecular weight is 3.85 x 10~4~4.30 x10~4,and the glass transition temperature of the copolymer is about-80?.When the monomer feed ratio is different,the unimodal GPC curve of the copolymer indicated that thepolymerization proceeds a single active site.The DSC curve of the copolymer showed single glass transition temperature which proved random copolymerization.