Abstract: The invention relates to the conversion of a mixed plastic waste by means of mechanical treatment of the starting material mixture in the presence of a mineral oil. The essence of the invention consists therein that a crushed plastic waste mixture containing about 20% by weight of low density polyethylene with a softening point below 150° C. is heat-treated in an oily medium in an apparatus exerting intense kneading-moulding effect at a temperature between 150° C. and 250° C. under vigorous stirring until the formation of a quasi-homogenous, liquid-phase or meltphase bitumen-like material, then separating the bitumen-like material obtained.