BIMODAL POLYETHYLENE Russian patent published in 2023 - IPC C08L23/08 C08F2/34 C08F210/06 F16L9/12 C08F4/659 

FIELD: chemical industry.

SUBSTANCE: invention relates to bimodal polyethylene compositions for the manufacture of products such as pipes, films, sheets, extruded products and products obtained by injection molding. The bimodal polyethylene composition contains a polyethylene component with a lower molecular weight (LMW) and a polyethylene component with a higher molecular weight (HMW), in which each of the polyethylene components, LMW and HMW, contains monomeric units derived from ethylene and sonomeric units derived from (C₃-C₂₀)alpha-olefins. At the same time, the bimodal low-density polyethylene composition is characterized by each of the limitations (a)-(g): (a) bimodality (molecular weight distribution) shown on the chromatogram of gel-penetrating chromatography (GPC) of the bimodal low-density polyethylene composition, where the chromatogram shows a peak representing the polyethylene component HMW, a peak representing the polyethylene component LMW, and the local minimum in the range of Log (molecular weight) (“Log(MW)”)) from 3.0 to 7.0 between the peak representing the polyethylene component HMW and the peak, representing the polyethylene component LMW, measured in accordance with the Bimodality Test Method, (b) density from 0.9310 to 0.9450 g/cm³, measured in accordance with ASTM D792-13, Method B; (c) melt index measured in accordance with ASTM D1238-13 at 190°C under a load of 2.16 kg (“I₂” or “MI2”) from 0.010 to less than 0.20 g/10 min, (d) flow index measured in accordance with ASTM D1238-13 at 190°C under a load of 21.6 kg (“I21” or “FI21”) from 8.0 to 15 g/10 min, (e) the ratio of melt flow index (FRR) to the flow index (“I₂₁/I₂”) from 100.0 to 800.0, (f) from more than 0 to 14, wt. %, of ethylene-containing chains having a molecular weight (M_W) of more than 0 to 10000 grams per mol (g/mol), based on the total mass of ethylene-containing components in a bimodal PE composition, and (g) the dispersion of molecular weights (Mw/Mn), ĐM is from 7 to 25, measured in accordance with The gel-penetrating chromatography (GPC) test method. A method for obtaining a bimodal polyethylene composition, a product containing a molded form from a bimodal polyethylene composition, a pipe from a bimodal polyethylene composition and a method for transporting a substance through the internal volume of such a pipe are also described.

EFFECT: bimodal PE composition according to the present invention is characterized by at least one improved property, such as greater resistance to slow crack growth (PENT test method), reduced hydrostatic fracture and/or increased manufacturability.

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