000			01844nam a2200241Ia 4500
008			220216s9999 xx 000 0 und d
100			_aKodama Soji
245		0	_aPreparation of low molecular weight natural rubber by ozonolysis of high ammonia latex
260			_bJournal of Rubber Research _c2003
300			_a153-163
520			_aDepolymerisation of natural rubber (NR) by bubbling ozone into high ammonia latex was attempted in order to prepare liquid natural rubber. NR was found to depolymerise at a faster rate with increasing ozone generation. Addition of hydrogen peroxide to the latex accelerated the depolymerisation of NR. Regardless of added hydrogen peroxide concentration, when the pH of latex was above 8 at the initial stage of reaction, the rate of depolymerisation was remarkably rapid. However, subsequently, the reaction abruptly slowed when the pH fell below 8. The decreases in pH was due to the formation of levulinic acid during reaction. These results suggested that the main reaction of the depolymerisation in latex was not direct oxidation by ozone through the formation of ozonide, but radical oxidation by hydroxyl and hydroperoxyl radicals formed by reaction between ozone and hydroxyl ion under basic conditions. It seemed that the very slow depolymerisation below pH 8 was due to the formation of levulinic acid from a terminal of a polymer chain, by direct oxidation of ozone. The minimum weight-average molecular-weight of the depolymerised NR achieved was about 50 000.
650			_aDepolymerisation
650			_aHigh ammonia latex
650			_aHydrogen peroxide
650			_aLevulinic acid
650			_aLiquid natural rubber
650			_aMolecular-weight
650			_aOzone
650			_aWeight-average
700			_aFurukawa Mutsuhisa
700			_aNishi Katsushi
942			_cJS
999			_c65604 _d65604