Effect Of Trace Impurities On Isoprene Polymerization

Polyisoprene rubber refers to cis-1,4-polyisoprene rubber,referred to as isoprene rubber?IP?,also known as"synthetic natural rubber",which is the third largest synthetic rubber in the world after SBR and cis-1,4-polyisoprene rubber.Isoprene rubber has many properties similar to natural rubber.Isoprene rubber has wear resistance,elasticity,heat resistance and low temperature flexibility,and its heat resistance even exceeds that of natural rubber.The advantages of isoprene rubber are light color,high purity,good fluidity,uniform quality,greatly reducing the time of plasticization,simple mixing process,small expansion and contraction,and tensile tendency.However,natural rubber is slightly higher than isoprene rubber in terms of raw rubber strength,adhesiveness,processability and tear strength and fatigue resistance of vulcanizates.The CIS-1,4-structure content of isoprene rubber?92%to98%?is lower than that of natural rubber?>98%?;the crystallization property is lower than that of natural rubber;the relative molecular mass is lower than that of natural rubber,and some branched chains and gels are also used.The degree of polymerization of isoprene has always been used as an index to measure the molecular size of isoprene rubber,which is greatly affected by the impurity content.The control range of the impurity content has been a hot topic at home and abroad.In this paper,2-methyl-1-butene-3-alkyne and cis-2-pentene were used as impurities to prepare hexane solutions of 2-methyl-1-butene-3-alkyne and cis-2-pentene in different content range.The prepared impurity solutions were accurately quantified by gas chromatography,and 2-methyl-1-butene-3-alkyne and cis-2-pentene in different concentration were respectively mixed into isoprene,and rare earth alkylaluminum mixed catalyst was added Through the results of isoprene rubber conversion,cis-1,4-structure content,molecular weight and distribution,the effects of 2-methyl-1-butene-3-ethyne,cis-2-pentene on isoprene rubber polymerization were explored.In this paper,isoprene rubber containing 2-methyl-1-butene-3-alkyne and isoprene rubber containing cis-2-pentene were successfully prepared.The content of cis-1,4-structure,molecular weight and distribution of isoprene rubber were affected by the change of the content of 2-methyl-1-butene-3-alkyne and cis-2-pentene,thus the polymerization degree of polyisoprene rubber could be significantly improved.It can be concluded from the experiment that 2-methyl-1-butene-3-alkyne,as an-impurity,has a direct effect on the molecular structure of isoprene rubber,resulting in obvious changes in the properties of isoprene rubber.In isoprene monomer rubber,the content of 2-methyl-1-butene-3-alkyne controlled below 5.3×10^-6?g/ml?has little effect on the degree of polymerization.Through the experiment,we think that in isoprene monomer rubber,cis-2-pentene as impurity,with the increase of its content,the polymerization degree of isoprene monomer rubber decreases.