POLYETHYLENE COMPOSITIONS, PREPARATION METHODS THEREOF, ARTICLES MADE THEREFROM AND METHOD OF MAKING SAID ARTICLES Russian patent published in 2013 - IPC B29C43/02 C08F10/02 C08F210/16 C08L23/08 

FIELD: chemistry.

SUBSTANCE: group of inventions discloses a polyethylene composition, a method for preparation thereof, articles made therefrom and a method of making said articles. The polyethylene composition contains (1) 100 wt % or less of units derived from ethylene; and (2) less than 15 wt % of units derived from one or more α-olefin comonomers. The polyethylene composition has density of 0.907-0.975 g/cm³, molecular weight distribution (M_w/M_n) of 1.70-3.62, flow melt index (I₂) of 2-1000 g/10 min, molecular weight distribution (M_z/M_w) of less than 2.5 and vinyl unsaturation of less than 0.06 vinyl groups per thousand carbon atoms present in the backbone chain of said composition. The method of producing the polyethylene composition includes the following steps: (1) (co)polymerisation of ethylene and at least one or more α-olefin comonomers in the presence of a hafnium-based metallocene catalyst through a gas-phase (co)polymerisation process in a reactor in a single step; and (2) a polyethylene composition is obtained, where the polyethylene composition has parameter values given according to the invention: density, molecular weight distribution (M_w/M_n), flow melt index (I₂) and vinyl unsaturation. Articles made by pressure moulding contain the polyethylene composition which contains (1) 100 wt % or less of units derived from ethylene and (2) less than 15 wt % of units derived from one or more α-olefin comonomers. The polyethylene composition has the following parameters: density, molecular weight distribution (M_w/M_n), flow melt index (I₂), molecular weight distribution (M_Z/M_w) and vinyl unsaturation in accordance with its parameters given above. The method of making pressure moulded articles includes the following steps: (a) selecting a polyethylene composition which contains (1) 100 wt % or less of units derived from ethylene; and (2) less than 15 wt % of units derived from one or more α-olefin comonomers; (b) pressure moulding said polyethylene composition; and (c) the pressure moulded article is then made.

EFFECT: high efficiency of the method.