Ethylene-alpha olefin block copolymers and methods for production thereof

A block copolymer comprising an A block and a B block, wherein the A block consists of ethylene optionally containing about 0.03 to about 2 mole percent of a non-conjugated diene, based on the total moles of monomer in said block copolymer, said B block having at least one first polymer segment comprising an ethylene, .alpha.-olefin copolymer, and said B block further comprising a tip segment of ethylene and an .alpha.-olefin,

• said tip segment being a furthest of said segments from an A B junction;
• said block copolymer having a n-hexane soluble portion, not exceeding about 30 weight percent based on the total weight of the block copolymer;
• wherein said block copolymer is made by a process utilizing a vanadium catalyst system, wherein said vanadium catalyst system includes a vanadium compound premixed with an organoaluminum compound, said premixing being for a sufficient time to produce an adequate quantity of active catalyst;
• wherein said vanadium compound is selected from one of the general formulas:
• ##STR6## where x=0 to 3 and R=a hydrocarbon radical;
• ##STR7## where AcAc=acetyl acetonate;
• ##STR8## where x=1 or 2;
• or
• VCl.sub.3.nB;
• where n=2 to 3 and B=Lewis base capable of making hydrocarbon-soluble complexes with VCl.sub.3, where B is selected from the group consisting of tetrahydrofuran, 2-methyl-tetrahydrofuran and dimethyl pyridine, where R represents a C.sub.1 to C.sub.10 aliphatic, acylic, or aromatic hydrocarbon radical;
• wherein the organoaluminum compound is represented one of the general formulas:
• ______________________________________ AlR.sub.3, Al(OR')R.sub.2 AlR.sub.2 X R.sub.2 Al--O--AlR.sub.2 AlR'RX Al.sub.2 R.sub.3 X.sub.3 ;
• or AlRX.sub.2, ______________________________________
• where R and R' represent hydrocarbon radicals, said R and R' being the same or different, wherein X is a halogen selected from the group consisting of bromine, chlorine, and iodine;
• wherein said non-conjugated diene is present in said A block up to about 2 mole percent, based on the total moles of the monomers of said block copolymer;
• wherein said B block has an intra-molecular-composition distribution, wherein at least 2 portions of said B block each portion comprising at least 5 weight percent of said B block, said 2 portions differing in ethylene content by at least about 5 weight percent;
• wherein said alpha-olefin in said B block is propylene;
• wherein said block copolymer is present at greater than about 50 weight percent based on the total weight of polymer, as polymerized;
• wherein said A B block copolymer has a M.sub.w /M.sub.n of less than about 2.5;
• wherein said A block is present in said block copolymer in the range of from about 10 to about 60 weight percent;
• and
• wherein said block copolymer has a number average molecular weight in the range of from about 750 to about 20,000,000.