Preparation Of Hydrogenated Nitrile Rubber By Controlled Emulsion Hydrogenation And Reaction Kinetic

Hydrogenated nitrile rubber(HNBR)is a rubber with excellent overall performance.Compared with emulsion hydrogenation,solution hydrogenation has shortcomings such as cumbersome production process and environmental impact due to the involvement of organic solvents.The existing methods for the preparation of HNBR by emulsion hydrogenation suffer from high material costs due to excessive catalyst additions,high operating costs due to long reaction times and uncontrolled gel formation.At the same time,the process parameters of NBR lotion hydrogenation pilot plant in this project need to be determined,and the heat removal capacity needs data reference.In this study,we investigated the emulsion hydrogenation of HNBR based on the above problems:(1)the synthesis of a new catalyst and the hydrogenation of NBR emulsions to produce high performance HNBR;(2)the comprehensive analysis of the kinetics of the hydrogenation of NBR emulsions and the calculation of the reaction rate constants for each reaction condition.The specific studies surrounding the above are as follows.1.Firstly,a new ruthenium-based catalyst(tricyclohexylphosphino[2,4-dihydro-2,4,5-triphenyl-3H-1,2,4-triazol-3-ylidene][2-thienylmethylene]ruthenium(II),dichloro)was synthesised for the direct hydrogenation of NBR latex provided by NANTEX Inc,which was tested by FT-IR and ~1H NMR on the product,and the catalyst could be used for the hydrogenation of carbon The catalyst was tested by FT-IR and ~1H NMR for the selective hydrogenation of carbon double bonds(-C=C-)and retention of cyano(-CN).By exploring the effects of each experimental condition(catalyst dosage,stabilization time,hydrogenation temperature,hydrogen pressure,stirring speed and rubber concentration based on carbon-carbon double bond concentration)on the hydrogenation reaction,the catalytic mechanism of this catalyst and the mass transfer process of the hydrogenation reaction were explained,and the optimum experimental conditions for the preparation of HNBR by NBR emulsion hydrogenation were also obtained.The results showed that a double bond conversion of 95 mol%could be achieved within 5 h without gel formation at a catalyst/NBR mass ratio of 0.02 wt%,a carbon-carbon double bond concentration of 150 m M,a reaction temperature of 120°C,a hydrogen pressure of 8.28 MPa and a stabilization time of 30 min.Dynamic light scattering(DLS)tests showed that the particle size of the NBR latex was essentially the same before and after hydrogenation,indicating that the catalyst had almost no effect on the stability of the latex.The catalyst has potential applications in the hydrogenation of other diene-based polymer emulsions,such as SBR and BR.2.The kinetics of the hydrogenation of NBR emulsions was analyzed:(1)Using hydrogen gas flowmeter instantaneous of hydrogen consumption and total consumption were statistically analyzed,at the same time for 2 min interval continuous sampling to test the reaction process of carbon carbon double bond conversion,the conversion rate of hydrogen consumption and sampling samples separately on reaction time curve plotting and comparative analysis,it is found that the two basic consistent.The two curves were found to be in general agreement,and they both basically conformed to the first-order kinetic reaction model in the early stage of the reaction,but deviated from the first-order reaction model in the late stage of the reaction.2)The NBR hydrogenation reaction was decomposed into two parallel reactions,hydrogenation of 1,4-carbon-carbon double bond and hydrogenation of 1,2-vinyl,and by dissecting the hydrogenation kinetic curves,it was found that the hydrogenation rate of 1,2-vinyl was faster than that of 1,4-carbon double bond,and then the derivation of the reaction rate constant equation for the hydrogenation reaction was carried out to calculate the reaction rate constants of the two parallel reactions;(3)The effect of catalyst concentration and hydrogen pressure on the reaction rate constant was studied by using a two-factor design and a single variable kinetic experiment.The results show that the reaction rate constant has a linear relationship to both of them.3.The kinetic profiles of NBR emulsion hydrogenation were analyzed to explore:(1)In the late stages of the hydrogenation reaction,as the conversion of carbon-carbon double bonds continued to increase,the contact probability between the active center of the catalyst and the unconverted double bonds gradually decreased,and the hydrogenation rate gradually decreased.At the same time,the conditions of operation at high temperature also caused some catalysts to be deactivated,resulting in the kinetic data in the late stage of the reaction deviating from the primary reaction model;(2)Since the NBR molecular chains showed free coiling in the micelle particles,the active centre of the catalyst was more likely to contact with the carbon-carbon double bond in the 1,4-vinyl unit,so the hydrogenation rate of 1,2-vinyl was faster than that of 1,4-carbon double bond.4.The self-made HNBR was benchmarked against a competing product Therban3406.The two were processed using a standard HNBR blending formula and their curing characteristics,mechanical properties,oil resistance and heat and air ageing resistance were compared.The experimental results show that the home-made HNBR has excellent performance and is basically comparable to the competing product Therban 3406.