These aryl groups may contain one or more substituents such as (1) alkyl and substituted alkyl groups as exemplified above, (2) alkoxy groups having alkyl and substituted alkyl groups as exemplified above, (3) halogen atoms such as a fluorine atom, a chlorine atom, a bromine atom and an iodine atom and (4) an amine of the formula --NR19 R20 wherein R19 and R20 independently represent alkyl group a