MULTIMODAL ETHYLENE COPOLYMER, METHOD FOR PRODUCTION THEREOF, TUBES MADE THEREFROM AND USE OF SAID TUBES Russian patent published in 2013 - IPC C08L23/04 C08L23/08 C08F297/08 F16L9/12 

FIELD: chemistry.

SUBSTANCE: multimodal ethylene copolymer has density of 924-960 kg/m³, melt flow index STR₅ of 0.5-6.0 g/10 min, melt flow index STR₂ of 0.1-2.0 g/10 min and shear thinning index IUVS_2.7/210 of 2-50. The multimodal ethylene copolymer contains at most 100 ppm by weight of volatile compounds. The multimodal ethylene copolymer is obtained in two steps by polymerisation in the presence of a catalyst with a single polymerisation centre of ethylene, hydrogen and one or more alpha-olefin having 4-10 carbon atoms. A low-molecular weight component (A) of the ethylene polymer is obtained in a first polymerisation zone and a high-molecular weight component of the ethylene copolymer (B) is obtained in a second polymerisation zone. The first and second polymerisation steps can be carried out in any order and the next step is carried out in the presence of a polymer obtained at the previous step. Components (A) and (B) are present in the multimodal ethylene copolymer in amount of 30-70 wt % and 70-30 wt %, respectively, of the total amount of components (A) and (B). Component (A) has weight-average molecular weight of 5000-100000 g/mol and density of 945-975 kg/m³, and component (B) has weight-average molecular weight of 100000-1000000 g/mol and density of 890-935 kg/m³.

EFFECT: improved properties of the compound.

15 cl, 1 tbl, 3 ex