Effects of Reaction Temperature and Time on the Convcrsion of a Vulcanizcd EPDM Rubber into Oily Materials by Water Containing Alkalin at High Temperature and High Pressure.

The present study attempts to reduce the abundance of the shredder dust from usedcars and to use it as resources effectively by converting the scrap automotive weatherstrips, which arecomposed of vulcanized ethylene-propylene-diene terpolymer (EPDM) rubbers, into reusable oily materials as softeners for the rubber manufacturing for recycling. The application of hydrothermal solution containing NaOH under supercritical conditions to this conversion was verified through batch processing experiments using a microautoclave. In this paper, the conversion of a vulcanized EPDM rubber by hydrothermal treatment was compared with that by pyrolysis at various temperature (350-450°C) and time (5-30 min). This comparison made clear differences between the cracking reactivity in hydrothermal treatment and that in pyrolysis and led to the followings:(1) Cracking was accelerated above 400°C by hydrothermal treatment, (2) Thepeak of molecular weight distribution in the high molecular weight region which originated in the crackingof the EPDM polymer shifted clearly without broadening, accompanied with the reaction time change at 420°C, (3) The milder cracking occurred in hydrothermal treatment in comparison with pyrolysis, (4) It was conceivable that hydrothermal cracking depressed the radical reaction and retained particular molecular units, (5) Carbon-sulfur linkage correlated with the cracking of the EPDM polymer, (6) Various conditions in hydrothermal treatment enables us to crack the polymer without decomposition of the softener, (7) The control of temperature and time in hydrothermal treatment can make the conversion of the rubber to oily resources with various viscosities and molecular weight distributions.