Process to produce a homogeneous polyethylene material

A process for producing high density polyethylene films, comprising

• producing a polyethylene composition in the presence of an ethylene-polymerizing catalyst system in a multistage reaction sequence of successive polymerization stages, at least one of which is a loop polymerization stage and at least one of which is a gasp polymerization stage, wherein the level of fines produced in said loop polymerization stage is less than 15 wt %, and said loop polymerization stage being operated with an inert diluent selected from linear or branched C4-C6 hydrocarbon(s), said reactor sequence being operated with different amounts of hydrogen and comonomers to produce a high molecular weight portion in one of the polymerization stages and a low molecular weight portion in another so as to provide a bimodal high density polyethylene with a low molecular weight part having a density above 960 kg/m3 and a MFR2 of 250 g/10 min or more, and a high molecular weight part, the composition having a density of 940-965 kg/m3 and MFR21 of 3-50 g/10 min, and blowing said polyethylene composition to a film.

A process for preparing medium density polyethylene films, comprising

• producing a polyethylene composition in the presence of an ethylene-polymerizing catalyst system in a multistage reaction sequence of successive polymerization stages, at least one of which is a loop polymerization stage and at least one of which is a gas phase polymerization stage, wherein the level of fines produced in said loop polymerization stage is less than 15 wt %, and said loop polymerization stage being operated with a diluent selected from linear or branched C4-C6 hydrocarbon(s), said reactor sequence being operated with different amounts of hydrogen and comonomers to produce a high molecular weight portion in one of the polymerization stages and a low molecular weight portion in another so as to provide a bimodal medium density polyethylene with a low molecular weight part having a density of 940-980 kg/m3 and a high molecular weight part, the composition having a density of 925-940 kg/m3 and MFR21 of 7-30 g/10 min, and
• blowing said polyethylene composition to a film.

A process for preparing low density polyethylene films, comprising

• producing a polyethylene composition in the presence of an ethylene-polymerizing catalyst system in a multistage reaction sequence of successive polymerization stages, at least one of which is a loop polymerization stage and at least one of which is a gas phase polymerization stage, wherein the level of fines produced in said loop polymerization stage is less than 15 wt %, and said loop polymerization stage being operated with a diluent selected from linear or branched C4-C6 hydrocarbon(s), said reactor sequence being operated with different amounts of hydrogen and comonomers to produce a high molecular weight portion in one of the polymerization stages and a low molecular weight portion in another so as to provide a bimodal low density polyethylene with a low molecular weight part having a density of 935-960 kg/m3 and a MFR2 of 250 g/10 min or more, and a high molecular weight part, the polyethylene composition having a density of 915-930 kg/m3 and MFR21 of 10-50 g/10 min, and
• blowing said polyethylene composition to a film.

The process according to any one of claims 1922, wherein the film exhibits a number of gels lower than 50 in an area of A4 size.

A method for reducing the level of fine polymer in a process in which ethylene is polymerized in the presence of an ethylene-polymerizing catalyst system in a multistage reaction sequence of successive polymerization stages, at least one of which is a loop polymerization stage and at least one of which is a gas phase polymerization stage, wherein the level of fines produced in said loop polymerization stage is less than 15 wt %, and said loop polymerization stage being operated with an inert diluent, said reactor sequence being operated with different amounts of hydrogen and comonomers to produce a high molecular weight portion in one of the polymerization stages and a low molecular weight portion in another so as to provide a bimodal polyethylene composition having a MFR21 of 3-50 g/10 min, the low molecular weight part having a MFR2 of 250 g/10 min or more, wherein the diluent is selected from the group of linear and branched C4-C6 hydrocarbons and/or mixtures thereof.