Method for preparing thermoelastomeric three-block copolymers

Claim 1

A process for the preparation of three-block copolymers of the ABA or the ABC type wherein the blocks A and C are of a plastomeric nature and the block B is of an elastomeric nature, comprising the steps of effecting the sequential polymerization of the monomers relative to the first plastomeric block, the elastomeric block and the second plastomeric block in the order given, in the presence of a catalytic system comprised of: (a) a compound of aluminum having the formula AlR 2 X', wherein both the radicals R are hydrogen atoms, or alkyl radicals, equal or different, containing up to 8 carbon atoms, and X' is an atom of fluorine, chlorine, bromine or iodine, or a radical containing up to 8 carbon atoms, and (b) a compound selected from the group consisting of: (1) X 2 " wherein X" is a halogen equal to, or different from, X'; (2) X"X"' wherein X" is a halogen as defined above and X"' is a halogen other than X", and (3) a group ##STR3## wherein X" is a halogen, R 1 is a member selected from the group consisting of hydrogen, an alkyl radical containing from 1 to 8 carbon atoms, an aromatic radical, an alkenyl radical containing from 2 to 8 carbon atoms, R 3 is a member selected from the group consisting of hydrogen, an alkyl radical containing from 1 to 8 carbon atoms, an aromatic radical, an alkenyl radical containing from 2 to 8 carbon atoms, and an aralkyl radical, and R 2 is a member selected from the group consisting of an alkyl radical containing from 1 to 8 carbon atoms, an alkenyl radical containing from 2 to 8 carbon atoms, an aromatic radical, an aralkyl radical, an alkaryl radical, a cycloalkyl radical containing from 3 to 10 carbon atoms, and a group ##STR4## wherein R 1 , R 3 and X" are as hereinbefore defined and R 4 is a member selected from the group consisting of an aromatic radical, an aralkyl radical and a methylene chain --(CH 2 ) n -- wherein n is an integer comprised between 1 and 10.