HYDROFORMYLATION OF NITRILE RUBBER AND ITS CHARACTERIZATION

Selective homogeneous catalytic hydroformylation of nitrile rubber (NBR) has been carried out in presence of trans-chlorocarbonylbis(triphenylphosphine)rhodium(I) [trans-RhCl(CO)(PPh3)2] and hydridocarbonyltris(triphenylphosphine)rhodium(I) [RhH (CO)(PPh3)3] as catalysts. At 363 K, under 5.6 MPa pressure (CO: H2 = 1 : 1) in presence of 0.43 mmol/l catalyst, the amount of hydroformylation is 25% in the case of trans-RhCl (CO)(PPh3)2 and 30% in the case of RhH (CO)(PPh3)3 for NBR with 40 mol-% acrylonitrile. Reaction kinetics suggest that both the reactions are pseudo-first order with respect to olefinic substrate and catalyst concentration. The rate of the reaction is higher in the case of RhH(CO)(PPh3)3. The characterization of the products by IR and NMR spectroscopy shows the formation of internal aldehyde groups from 1,4-units and terminal branched aldehyde groups from 1,2-units of the copolymer. Measurements on intrinsic viscosity [eta] and glass transition temperature (T(g)) suggest a decrease in [eta] and an increase in T(g) with the degree of formyl functionalization. Gel formation has been observed at higher degree of hydroformylation.