Novel method for preparation of low molecular weight natural rubber latex

Low molecular-weight natural rubber (LNR) and LNR latex was prepared by oxidative degradation of deproteinized natural rubber (DPNR) latex in the presence of 1 phr of K2S2O8 and 15 phr of propanal, by shaking at 60 degrees C. The intrinsic viscosity [eta] Of DPNR with only K2S2O8 decreased from 7.2 to 5.5 after 2 h and then increased to 6.5 after 3 h. By the addition of propanal, DPNR showed a significant decrease in the [eta] value of LNR with [eta] of about 0.5 after 5 h of the reaction, while rubber from high-ammonia natural rubber (HANR) latex showed a slight decrease in [eta] The concentration of latex and the kind of surfactant used for stabilizing the latex had little effect on the degradation rate of DPNR latex. The LNR latex is stable as the latex form and the dried rubber coagulated from latex is transparent and colorless. The LNR was a telechelic polymer containing aldehyde and ketone groups at both terminals as determined by NMR and molecular weight analyses.