METHODS FOR CONTROLLING POLYMER PROPERTIES Russian patent published in 2024 - IPC C08F2/34 C08F4/24 C08F210/16 

FIELD: chemistry.

SUBSTANCE: invention relates to methods of controlling polymer properties during polymerisation. Disclosed is a method of producing a polyolefin by contacting a reaction mixture with a reduced chromium oxide catalyst in a gas-phase reactor to produce a polyolefin, where the reaction mixture contains ethylene and a comonomer, wherein the comonomer includes an alpha-olefin containing from 3 carbon atoms to 20 carbon atoms, where the reaction temperature in the gas-phase reactor is increased to reduce the level of comonomer in the polyolefin or where the reaction temperature in the gas-phase reactor is reduced to increase the level of comonomer in the polyolefin, wherein the obtained polyolefin is characterized by (i) a modified Charpy impact strength, measured in accordance with ASTM D6110, of 20 kJ/m² or more; (ii) an equivalent stress cracking resistance measured at an actual pressure of 900 lb/in² (6210 kPa) as determined using a constant stress for the notched thread in accordance with ASTM F2136 of about 50 hours or more; (iii) density from 0.952 g/cc to 0.958 g/cc; and (iv) a melt flow index (I₂₁) in range of 2 g/10 min to 5 g/10 min; and two versions of the composition for use in industrial articles containing a polyolefin obtained using the disclosed method.

EFFECT: achieving a balance between impact viscosity and resistance to cracking under stress in ambient conditions due to control of polymer properties.

15 cl, 9 dwg, 2 tbl, 17 ex