POLYETHYLENE COMPOSITION WITH RESISTANCE TO ENVIRONMENTAL CRACKING Russian patent published in 2021 - IPC C08L23/06 C08F10/00 C08F2/00 

FIELD: chemistry.

SUBSTANCE: invention relates to a polyethylene composition suitable for the production of various types of molded articles. Described is a polyethylene composition for the production of shaped hollow bodies, containing A) 30-70 wt.% of a homopolymer or copolymer of ethylene with a density equal to or greater than 0.960 g / cm³, and a MIE melt flow index of 2 to 20 g / 10 min, measured according to ISO 1133 at 190°C and with a weight of 2.16 kg, B) 30-70 wt.% of an ethylene copolymer having an MIE index lower than the MIE index from point A). The composition has the following characteristics: 1) density of 0.940 to 0.955 g / cm³, preferably 0.940 to 0.951 g / cm³ determined in accordance with ISO 1183 at 23°C; 2) a MIF / MIP ratio of 12 to 40, in particular 15 to 38 or 17 to 35, where MIF is the melt flow index at 190°C and with a weight of 21.60 kg, and MIP is the melt flow index at 190°C and with a load mass of 5 kg, determined according to ISO 1133-1; 3) a Mz value ranging from 500,000 to 3,500,000 g / mol, preferably from 800,000 to 3,300,000 g / mol, in particular from 800,000 to 3,000,000 g / mol, where Mz is the z-average molecular weight measured by GPC; 4) viscosity η_0.02, ranging from 80,000 to 300,000 Pa⋅s or from 85,000 to 250,000 Pa⋅s, where η_0.02 is the complex dynamic viscosity at an angular frequency of 0.02 rad / s, measured with a rotary conical viscometer at 190°C; 5) an HMWcopo index ranging from 1 to 15, preferably from 1 to 14, in particular from 1 to 10 or from 1 to 9, where the HMWcopo is defined according to the following formula: HMWcopo = (η_0,02 x t_maxDSC)/(10^5), where η_0.02 is the complex dynamic viscosity of the melt in Pa⋅s, measured in a rotary conical viscometer at 190°C under shear conditions with an applied angular frequency of 0.02 rad / s, t_maxDSC is the time in minutes required to achieve the maximum value of the heat flux of crystallization at a temperature of 124°C in a quiescent state, measured in isothermal mode with a differential scanning calorimetry device; 6) an Mz / Mw * ratio of ILCB of less than 6.4, preferably equal to or less than 6.0, in particular equal to or less than 5.9, where ILCB is the ratio of the measured root-mean-square radius of gyration of the macromolecule Rg as measured by the GPC-MALLS method , to the root-mean-square radius of gyration of the macromolecule for linear PE having the same molecular weight of 1,000,000 g / mol. Also proposed are a manufactured article made by blow molding from a polyethylene composition, and a method for producing a polyethylene composition.

EFFECT: improved resistance to environmental cracking and impact resistance, improved surface quality and dimensional stability of the final product, the proposed composition is suitable for the extrusion of hollow products by blow molding, such as drums, containers and storage tanks for gasoline.

8 cl, 1 tbl, 1 ex, 1 dwg