POLYETHYLENE COMPOSITION WITH HIGH DEGREE OF SWELLING OF EXTRUDED MELT, RESISTANCE TO CRACKING UNDER ENVIRONMENTAL INFLUENCE, AND IMPACT STRENGTH Russian patent published in 2021 - IPC C08L23/08 C08L23/06 C08F4/654 C08F110/02 C08F210/16 

FIELD: polymers.

SUBSTANCE: invention relates to a polyethylene composition suitable for extrusion of hollow products by the blow moulding, e.g., of drums and tanks. The polyethylene composition comprises: A) 30 to 70% wt. of an ethylene homopolymer or copolymer with a density equal to or greater than 0.956 g/cm³ and a melt flow index MIE at 190°C and with a loaded weight of 2.16 kg, according to ISO 1133, of 1 to 8 g/10 min, B) 30 to 70% wt. of an ethylene copolymer with an MIE index lower than the MIE index from point A). Said composition therein exhibits the following features: 1) a density of 0.948 to 0.955 g/cm³, determined according to ISO 1183 at 23°C, 2) an MIF/MI10 ratio from 4 to 8, wherein MIF constitutes the melt flow index at 190°C and with a loaded weight of 21.60 kg, and MI10 constitutes the melt flow index at 190°C and with a loaded weight of 10 kg, determined according to ISO 1133, 3) a viscosity η_0.02, from 350,000 to 600,000 PA∙s, wherein η_0.02 constitutes the complex shear viscosity at an angular frequency of 0.02 rad/sec, measured during dynamic oscillatory shear in a rotational conical viscometer at 190°C, 4) a long-chain branching index, LCBI, at the molecular weight of 1,000,000 g/mol, from 0.65 to 0.74, wherein LCBI constitutes the ratio of the measured root mean square radius of gyration of the macromolecule R_g, measured by the GPC-MALLS method, to the root mean square radius of gyration of the macromolecule for linear PE with the same molecular mass, 5) a ratio (η_0.02/1,000)/LCBI, wherein η_0.02 is divided by 1,000 and by the LCBI index, from 380 to 800. Also described are manufacturing products produced by the blow moulding method, containing such polyolefin composition, and a method for producing a polyethylene composition produced in a cascade, consisting of a reactor with a fluidised bed and a multi-zone circulation reactor with two interconnected reaction zones.

EFFECT: provide a composition with a high degree of swelling of the extruded melt and high impact strength, resistance to cracking under the environmental influence, high surface quality and stability of the dimensions of the resulting product.

11 cl, 1 dwg, 1 tbl, 2 ex