Preparation, Structure And Properties Of Hydrogenated Acrylonitrile-butadiene Rubber

The structure, grade , property , main uses and present state of hydrogenated acrylonitrile-butadiene rubber(HNBR) were summarized . And put emphasis on three kinds of hydrogenation processes containing homogeneous solution by rhodium complex catalyst, homogeneous and non-homogeneous solution by palladium catalysts, acrylonitrile-butadiene rubber(NBR) latex . The advantages and disadvantages of each hydrogenation process were pointed out. The catalytic hydrogenation mechanism was elaborated. And, the removal methods of rhodium catalyst in HNBR solution, coagulation and drying processes were introduced .The properties of processing and application were presented from vulcanization, reinforcement and HNBR blend with other rubber or resins.Tris-(triphenylphosphane)- rhodium(I)-chloride as catalyst was prepared by reaction of rhodium(III)-chloride and triphenylphosphane in alcohol solvent. The influences of the reaction factors (reaction time ,compounding material ratio and solvent amount) on catalyst properties( appearance ,rhodium content and activities of catalyst)were investigated The results show that the yield of tris-(triphenylphosphane)- rhodium( I )-chloride was 90% and its appearance was purple when the compounding material ratio of rhodium(III)-chloride and triphenylphosphane was 1:6(mol),alcohol amount was 55-65ml/mmol rhodium(III)-chloride, reaction time was 4-8 hrs in reflux temperature .The catalyst activity evaluating indicated that this catalyst fit to prepare highly hydrogenation degree HNBR.The bench experiment of hydrogenation NBR was carried out with chlorobenzene as solvent, tris-(triphenylphosphane)- rhodium( I )-chloride as catalyst in 50 L autoclave. And the influences of factors(reaction temperature, time, pressure, NBR solution concentration, catalyst concentration and co-catalyst amount) on hydrogenation reaction process, hydrogenation degree and Mooney viscosity(ML 1+4 (100℃)) of HNBR were studied. The results showed that HNBR with hydrogenation degree more than 95% was got with self-made tris-(triphenylphosphane)- rhodium( I )-chloride as catalyst and adding 1% triphenylphosphane(by NBR) as co-catalyst in NBR solution. The ideal catalyst concentration was 160-200×10⁶(by Rh/NBR), reaction temperature was 80-100℃, time was 8-10hrs, pressure was 6-9.5Mpa;The two grades of HNBR were developed in 500L pilot experiment ,one,s hydrogenation degree was 90%,another was 95%.Phycical -mechanical property and aging -behavior were studied, the results showed that the hydrogenation degree , physical -mechanical property and aging -behavior of two HNBR were similar to that of the same as HNBR made in JAPAN, but Mooney viscosity were higher 30-40 units than that of JAPAN.In order to prepare HNBR with lower Mooney viscosity and different acrylonitrile content ,different NBR were coordinated into base rubber for hydrogenation, in which ,NBR were N21 (AN content40%, ML1+4, 100℃was 80) ,N32 (AN content33%, ML1+4 , 100℃was 46) and liquid NBR(LNBR) produced by LANZHOU petrochemical company . HNBR that Mooney viscosity was less than 70 was obtained, using N32 and 5%-10%LNBR blend as base rubber for hydrogenation, but its hydrogenation degree was lower than 90%; HNBR that Mooney viscosity was not only more than 90 was obtained ,using N21 and 5%-10% LNBR blend as base rubber for hydrogenation, but also its hydrogenation degree was lower than 90%; HNBR with wide relative molecular mass distribution was obtained, using N21/N32(30/70) and 5%-10%LNBR blend as base rubber for hydrogenation, its acrylonitrile content was 36%,hydrogenation degree was 90%, Mooney viscosity was lower than 80;The three methods above could not get HNBR with hydrogenation degree more than 95%,then the experiment scheme that adding radical scavenger in reaction system was decided . It could be found that anti-oxidant with -NH-group was the most effective for getting HNBR with Mooney viscosity 70-90 and hydrogenation degree 90%-99%,when selecting anti-oxidant H, DED, 4010,264,aniline,diethyl hydroxylamine and RD as radical scavenger .In fixed pressure(7Mpa) and temperature(90℃), and other unfixed condition, the two kinds of lower Mooney viscosity HNBR with hydrogenation degree 90% and 95% were got, respectively. The properties of green state rubber and vulcanizate were equal to Zetpol 2010and Zetpol 2020 made in JAPAN.Rhodium in HNBR solution was removed by macroporous ion exchange resin with thiourea group, the rhodium content in HNBR could be removed to less than 60×10^-6 (by HNBR) when removing temperature was 70-80℃, HNBR solution concentration was 3%, and kept a certain retention period.Devolatilization efficiency of concentrator-twin screw extruder for HNBR solution was studied in post-treatment of HNBR. The results showed that the solution could be concentrated to more than 20%,when pressure in concentrator was 0.03～0.06Mpa temperature was 150～170℃and kept a certain feed velocity. Overfall material ratio from vent gate was less than 1%, volatile matter of HNBR was less than 1%, solvent recovery ratio was more than 98% after extruder.The variety of molecular chain micro-structure in hydrogenation process was investigated by IR ,spectra confirmed that vinyl-structure in polybutadiene disappeared preferentialy, next was trans-1,4 structure, cis-1,4 structure was the slowest when increasing of HNBR hydrogenation degree. Vinyl-structure had not existed in HNBR when the hydrogenation degree was 90%.Trans-1,4 structure was about to 0 when the hydrogenation degree was 95%.The -CN group was not hydrogenated during the reaction.the heat-oxygen resistance of NBR and HNBR with different hydrogenation degree was investigated by TGA (thermogravimetric analysis),results showed that heat--oxygen resistance was increased gradually in pace with steady growth of hydrogenation degree.The rheological parameters for NBR and HNBR were measured using HAKKE rheometer,. The rheometer curves suggested that NBR was crosslinked seriously in 280℃and strong shear stress for 4min, whereas HNBR were well during 15 min.NBR and HNBR were cured by peroxide on rheometer. The curing curve proved that the torque of NBR was much lower than that of HNBR. The cure rate of HNBR that hydrogenation degree 95% was less faster than that of HNBR 90% at starting stage, but optimum cure time were 6-7min.The stress-stain relation showed that the stain values of NBR and HNBR were similar before the stress was 5Mpa.The variety tendency of stain values were NBR > hydrogenation degree 90% > hydrogenation degree 95% as stress increasing. The stain value of HNBR was much lower than that of NBR in higher stress, it was probably due to NBR crystallinity produced in tensile state.