r those sold under the names Miglyol 810, 812 and 818 by the company Dynamit Nobel; synthetic oils or esters of formula R5COOR6 in which R5 represents a linear or branched higher fatty acid residue containing from 1 to 40 carbon atoms, including from 7 to 19 carbon atoms, and R6 represents a branched hydrocarbon-based chain containing from 1 to 40 carbon atoms, including from 3 to 20 carbon atoms,