Process for preparing a high density polyethylene of low n-paraffin content and high melt index ratio

In a process for producing high density polyethylene comprising the steps of:

• (a) polymerizing ethylene in the presence of a vanadium catalyst and an organoaluminum co-catalyst, said vanadium catalyst obtained by;
• (b) treating an inert support in an inert solvent with a vanadium compound, an organoaluminum compound, and an organophosphorus compound to produce a treated support, said vanadium compound being selected from the group of compounds represented by one of the formulas:
• ##STR17## wherein x is a number from 0 to 3 and R' is a hydrocarbon radical;
• ##STR18## wherein z is a number from 2 to 3 and (AcAc) is an acetyl acetonate group;
• ##STR19## wherein (AcAc) is an acetyl acetonate group;
• and
• VCl.sub.3.nB
• wherein n is a number from 2 to 3 and B is a Lewis base which can form hydrocarbon-soluble complexes with VCl.sub.3 to form a vanadium catalyst system;
• the improvement comprising:
• prepolymerizing the treated support of step (b) with a small amount of ethylene and an aliphatic diene, said diene being present in the range of from about 0.1 to about 100 moles of said diene per gram of vanadium, wherein said polyethylene has C.sub.10 -C.sub.32 n-paraffin content of about 0.2 weight percent or less, and a melt index ratio of at least 75.

A process for producing high density polyethylene comprising the steps of:

• (a) polymerizing an .alpha.-olefin monomer, and a minor amount of an aliphatic diene having at least four carbon atoms, in the presence of an organoaluminum co-catalyst and a vanadium catalyst system, said vanadium catalyst system obtained by:
• (b) treating an inert support in an inert solvent with a vanadium compound, an organoaluminum compound, and an organo phosphorus compound, a halogenating agent, said vanadium compound being selected from the group of compounds represented by one of the formulas:
• ##STR20## where x is a number from 0 to 3 and R' is a hydrocarbon radical;
• ##STR21## where z is a number from 2 to 3 and (AcAc) is an acetyl acetonate group;
• ##STR22## where (AcAc) is an acetyl acetonate group;
• and
• VCl.sub.3.nB
• where n is a number from 2 to 3 and B is a Lewis base which can form hydrocarbon-soluble complexes with VCl.sub.3 to form said vanadium catalyst system, and
• (c) recovering polyethylene having a C.sub.10 -C.sub.32 n-paraffin content of about 0.2 weight percent or less and a melt index ratio of at least 75.