Research On The Hydrogenation Of SBS,SIS And SIBS With Metallocene Catalysts

Catalytic hydrogenation is of great significance for improving the mechanical properties and anti-aging properties.Compared with traditional Ziegler catalysts,titanocene catalysts have the advantages of high hydrogenation activity,moderate hydrogenation conditions,and no need for post-treatment.But the efficiency and reproducibility of hydrogenation of common titanocene catalysts are not satisfactory enough.So we designed various titanocene catalysts of different structures and compositions to catalyze the hydrogenation of SBS,SIS and SIBS,and studied on the performance of hydrogenated products.Firstly,we studied on the effects of ETE and DMTHFA on the micro structures of SBS,and investigated the hydrogenation efficiency of"Cp2TiCl2/lithium hydride/aromatic ester" catalytic system,"Cp2TiCl2 or CpTiCl3/TPM-Li"catalytic system and "Cp2TiCl2/trialkyl aluminum/silicate ester”catalytic system.We found that compared with ETE,DMTHFA has a stronger influence on 1,2-PB%of SBS,and 1,2-PB%mainly depends on the concentration of lewis base in the entire glue system.The hydrogenation degree at 2h of "Cp2TiCl2/trialkyl aluminum/silicate ester"catalytic system reached 99%showing both high stability at high temperature and high hydrogenation activity which is because lithium alkoxides(prepared in situ by the reaction of silicate ester with lithium hydride)tend to insert the locking structure between titanium and aluminum and thereby increasing the chance of exposure of titanium metal center.Therefore,we designed three "Cp2TiCl2/trialkyl aluminum/lithium alkoxide" catalytic system with IPA-Li,BHT-Li and lithium ethoxy of which the hydrogenation degree at 2h reached 99%,it is proved that the hydrogenation mechanism of "Cp2TiCl2/trialkyl aluminum/silicate ester" catalytic system is right.Followings are optimal hydrogenation conditions of "Cp2TiCl2/trialkyl aluminum/lithium alkoxide " catalytic system:hydrogenation temperature is higher than 75 ℃,hydrogen pressure is higher than 1.50MPa,the content of Ti is 0.11mmol/100gSBS,the ratio of Al/Ti is higher than 4.80/1,and the ratio of lithium alkoxide/Ti is higher than 6.0/1.excessive viscosity of glue system and very low hydrogenation temperature,the ratio of Al/Ti and lithium alkoxide/Ti is conducive to hydrogenation.Then,we adopted "Cp2TiCl2/lithium hydride/aromatic ester" catalytic system," Cp2TiCl2/TPM-Li " catalytic system and " Cp2TiCl2/trialkyl aluminum/silicate ester " catalytic system to catalyze the hydrogenation of SIS.We found that titanocene catalysts can hardly catalyze the hydrogenation of SIS due to the steric hindrance of the methyl groups and the σ-π hyperconjuction of 1,4-PI,following is the sequence of hydrogenation reactivity of several structure units:1,2-PB>1,4-PB>3,4-PI>1,4-PI.According to the hydrogenation activity of different structure units,we synthesized SIBS and hydrogenated it with"Cp2TiCl2/trialkyl aluminum/lithium alkoxide”catalytic system in order to prepare HSIBS of which PB and 3,4-PI is selectively hydrogenated.Since the reactivity ratio of Bd is higher than that of Ip and lewis base tends to increase the difference of their reactivity ratio,the random copolymerization of Bd and Ip is achieved by controlling the feed rate of Bd lower than Ip.Through DSC analysis of SIBS,we can found that all SIBS has only one Tg under 0℃ which indicated that there is no PB block in SIBS.Finally,we mainly analyzed crystallization and mechanical properties of SEBS and HSIBS.It was found that the increase of Ip%and the content of pendant groups may decrease the stereoregularity of the polymer chain,and the lower the isotacticity,the more unfavorable the crystallization;and the increase of Ip%and the content of pendant groups may increase the rigidity of the molecular chain,thus deteriorates the movement ability of the polymer’ segment.Hydrogenation modification significantly increased the tensile strength of polymer,and greatly reduced the loss rate of strength(W),significantly improved mechanical and anti-aging properties of polymer.