Propylene block copolymers

Claim 1

A thermoplastic propylene block copolymer, characterized in that: (1) the limiting viscosity of said copolymer in decalin at 135° C. is 0.3 to 15 dl/gram; (2) said copolymer comprises 2 to 40 percent by weight of hexene-1 and 1 to 50 percent by weight of ethylene, the remainder being substantially propylene, in blocks consisting essentially of (a) a random copolymer block of propylene and hexene-1 and (b) an ethylene polymer block selected from the group consisting of ethylene homopolymer blocks, binary random copolymer blocks of ethylene and hexene-1 and ternary random copolymer blocks of ethylene, propylene and hexene-1; and (3) the quantity, the fusion peak temperature as determined by differential scanning calorimetry (DSC), and the contents of hexene-1 and ethylene of each of the fractions resulting from successive extraction of the copolymer at 40° C. and 80° C. by means of o-dichlorobenzene are as indicated in the table: ______________________________________ Content of [straight- Content chain α- of Quantity Fusion olefin] ethylene (% by peak temp. hexene-1 (% (% by Fraction weight) by DSC (°C.) by weight) weight) ______________________________________ Fraction Substan- soluble at tially no 40° C. or peaks recog- lower 5 to 40 nizable 5 to 80 4 to 50 Fraction soluble above 40° C. up to 80° C. 15 to 45 80 to 150 3 to 60 3 to 45 Fraction at the high- insoluble at er temp. 135 80° C. or to 165 at the lower 15 to 80 lower temp. 0.1 to 11 1 to 35 105 to 135 ______________________________________