PREPARATION OF NEW RUBBER MATERIALS FROM HIGHLY DEPROTEINIZED NATURAL RUBBER

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Highly deproteinized natural rubber (HDPNR) latex was prepared by incubation of commercial high-anmonia latex with a proteolytic enzyme in the presence of a surfactant, followed by centrifugation twice. The nitrogen content of HDPNR was less than 0.02%, suggesting the complete removal of protein in the rubber.Low molecular-weight natural rubber (LNR) and LNR latex were prepared by oxidative degradation of HDPNR latex in the presence of 1 phr of K_2S_2O_8 and 15 phr of propanal, by shaking at 60ﾟC.The intrinsic viscosity [eta] of HDPNR with only K_2S_2O_8 decreased from 7.2 to 5.5 after 2 hr and then increased to 6.5 after 3 hr. By the additaion of propanal, HDPNR showed a significant decrease in[eta]to give 0.5 after 5 hr of the rection, while rubber from high-ammonia nataural rubber latex showed a slight decrease in[eta]. The concentration of latex and the kind of surfactant used for stabilizing latex gave no much effect on the degradation rate of HDPNR latex. The LNR latex is stable as latex form and the dried rubber coagulated from latex is transparent and colorless. The LNR was a telechelic polymer containging aldehyde and ketone groups at both terminals by NMR and molecular weight analyzes.A graft copolymer of natural rubber with stirene was made from HDPNR latex with tert-butyl hydroperoxide/tetra ethylene pentamine (TBHPO-TEPA) as an organic redox initiator, The stirene content, graft efficiency and molecular weight of grafted polystirene were significantly increased by deproteinization. The unber of grafting sites for graft copolymer from HDPNR latex was about three-times larger than that determined for graft copolymer from untreated natural rubber latex. The differences of reactivity between HDPNR and untreated natural rubber were explained to be due to the removal of protein and naturally occurring antioxidant present in untreated natural rubber.