Catalytic Hydrogenation And Functional Modification Of Nitrile-butadiene Rubber

Hydrogenated nitrile butadiene rubber?HNBR?is an elastomer material with excellent comprehensive properties.The HNBR not only retains the good oil resistance of nitrile butadiene rubber?NBR?,but also has better ozone aging resistance,high temperature resistance and mechanical strength.Due to its excellent properties,HNBR is widely used in automotive industry,petrochemical industry,aerospace and other fields.In this paper,different ruthenium/rhodium catalysts were used to catalyse hydrogenation of NBR under low H₂ pressure.In addition,the functional groups were introduced into the rubber molecular chain innovatively in the hydrogenation process to synthesize ester-end functionalized hydrogenated nitrile butadiene rubber?EF-HNBR?by one-step method.1.Firstly,we synthesize RhCl?PPh₃?₃ and RhCl?PPh₃?₃/RuCl₂?PPh₃?₃ bimetallic catalysts in ethanol solution,and be used for selective catalytic hydrogenation of NBR.Results showed that the RhCl?PPh₃?₃ catalyst has high catalytic activity,and the hydrogenation degree of HNBR can reach more than 98%.It was found that the catalytic activity was increased due to the synergistic effect between ruthenium and rhodium when using bimetal catalysts selective hydrogenation of NBR.The use of relatively cheap ruthenium-based catalysts reduced production costs,and the products did not cross–link.The structure and performance of hydrogenation product were analyzed.The results show that the hydrogenation catalysts selective reduction of the carbon-carbon unsaturated double bond without the reduction of the nitrile group,the glass transition temperature of the product is unchanged,and the thermal stability of the product is improved.2.In view of the poor air stability of RhCl?PPh₃?₃ and RhCl?PPh₃?₃/RuCl₂?PPh₃?₃,and the increase of molecular weight of hydrogenation products leads to processing difficulties.The selective catalyzed hydrogenation of NBR was used Grubbs II,the hydrogenation degree of HNBR above 95%.Comparing the air stability of RhCl?PPh₃?₃ and Grubbs II,it was found that the Grubbs II catalyst with carbin ligand had better air stability,and the hydrogenation degree could still reach 93.5%after being placed in the air for 20 days.Fourier transforming infrared spectrum?FT-IR?,nuclear magnetic resonance spectroscopy?¹H-NMR?and gel permeation chromatography?GPC?of hydrogenation product were analyzed.The results showed that the olefins metathesis catalyst had high activity and selectivity,the hydrogenated products with high hydrogenation degree and good thermal stability,and the weight average molecular weight decreased from 245,000 to 155,000,the poly-dispersity index?PDI?decreased,which greatly improved the processing performance of HNBR.3.On the basis of olefin metathesis hydrogenation,we synthesis the ester end-functional hydrogenated nitrile butadiene rubber?EF-HNBR?in the presence of Grubbs II catalyst and methyl methacrylate?MMA?as chain transfer agent?CTA?by one-step process.Fourier transforming infrared spectrum?FT-IR?,nuclear magnetic resonance spectroscopy?¹H-NMR?,Differential Scanning Calorimetry?DSC?and thermos-gravimetric analysis?TGA?of hydrogenation product were analyzed.The results showed that the selective hydrogenation and functional modification of NBR were simultaneously achieved with Grubbs II catalyst.