Polymerization process, hdpe polyethylene composition and rotomolded article

A solution phase polymerization process to make a polyethylene composition:

• wherein the solution phase polymerization process comprises:
• polymerizing ethylene and an alpha-olefin in a first reactor with a metallocene catalyst;
• and
• polymerizing ethylene and an alpha-olefin in a second reactor with a Zielger-Natta catalyst;
• wherein the first and second reactor are configured in series with one another;
• wherein the polyethylene composition comprises:
• i) from 10 to 60 weight percent of a first ethylene copolymer having a density of from 0.880 to 0.930 g/cm3, a molecular weight distribution, Mw/Mn of from 1.7 to 2.7, and a weight average molecular weight, Mw of from 75,000 to 250,000 g/mol;
• (ii) from 90 to 40 weight percent of a second ethylene copolymer having a density of from 0.945 to 0.965 g/cm3, a molecular weight distribution, Mw/Mn of from 2.0 to 3.5, and a weight average molecular weight, Mw of from 15,000 to 75,000 g/mol;
• wherein the ratio of the number of short chain branches per thousand carbon atoms in the first ethylene copolymer to the number of short chain branches per thousand carbon atoms in the second ethylene copolymer, SCB1/SCB2 is at least 5.0;
• and
• wherein the polyethylene composition has a density of ≥0.942 g/cm3;
• a melt index, I2>5.0 g/10 min, a melt flow ratio, I21/I2 of ≤50, and a long chain branching factor, LCBF≥0.0010.

A rotomolded article prepared from a polyethylene composition, the polyethylene composition comprising:

• (i) from 10 to 60 weight percent of a first ethylene copolymer having a density of from 0.880 to 0.930 g/cm3, a molecular weight distribution, Mw/Mn of from 1.7 to 2.7, and a weight average molecular weight, Mw of from 75,000 to 250,000 g/mol;
• (ii) from 90 to 40 weight percent of a second ethylene copolymer having a density of from 0.945 to 0.965 g/cm3, a molecular weight distribution, Mw/Mn of from 2.0 to 3.5, and a weight average molecular weight, Mw of from 15,000 to 75,000 g/mol;
• wherein the ratio of the number of short chain branches per thousand carbon atoms in the first ethylene copolymer to the number of short chain branches per thousand carbon atoms in the second ethylene copolymer, SCB1/SCB2 is at least 5.0;
• and
• wherein the polyethylene composition has a density of >0.942 g/cm3;
• a melt index, I2>5.0 g/10 min, a melt flow ratio, I21/I2 of ≤50, and a long chain branching factor, LCBF≥0.0010.