MULTISTAGE COMPOSITION PREPARATION METHOD Russian patent published in 2010 - IPC C08F2/18 C08F210/16 C08F4/654 C08L23/04 

FIELD: chemistry.

SUBSTANCE: present invention relates to a method of preparing an ethylene polymer composition. Described is a method of preparing an ethylene polymer composition in a multistage process. The said method involves polymerisation of only one of ethylene or ethylene with a comonomer to obtain ethylene polymer at the first stage, supply of the polymer obtained at the first stage to the second stage, where at the second stage only one of ethylene or ethylene with a comonomer is polymerised in the presence of the polymer obtained at the first stage, and where the first stage is a suspension polymerisation stage, and polymerisation at the first stage is carried out in the presence of a catalyst system containing: (a) a precursor solid catalyst containing a transition metal selected from titanium and vanadium; magnesium, haloid, electron donor and solid dispersion material containing inorganic oxide, and (b) organoaluminium compound; and where the average diametre of particles of the precursor solid catalyst obtained per total volume of the precursor solid catalyst, D₅₀, ranges from 1 to 13 micrometres. Also described is an ethylene polymer composition obtained using the said method, having density in the range 0.915-0.970 g/cm³ and MI₅ in the range 0.02-3.5 dg/min and less than 6 regions of gel per m² with size greater than 800 micrometres, and less than 100 regions of gel per m² with size ranging from 400 to 800 micrometres, where the amount and size of gel is determined for a 5 m² cast film sample with thickness of 50 micrometres, obtained from the ethylene polymer composition; also described is an industrial product made from the said composition. Described is an ethylene polymer composition obtained using the said method, having density in the range 0.915-0.970 g/cm³ and MI₅ in the range 0.02-3.5 dg/min, where the composition has Young's modulus during bending, measured using an Instron device in accordance with ISO 178, exceeding 1340*{1-exp[-235*(density-0.9451)]}; ethylene polymer composition having density in the range 0.915-0.970 g/cm³ and MI₅ in the range 0.02-3.5 dg/min, where the composition has Young's modulus during bending which exceeds 1355*{1-exp[-235*(density-0.9448)]}. Described is a composition obtained using the said method and containing bimodal polyethylene resin, and where the bimodal polyethylene resin contains high-molecular ethylene polymer and low-molecular ethylene polymer, and where the low-molecular ethylene polymer has MI₂ ranging from 10 g/10 min to 1000 g/10 min and density of at least 0.920 g/cm³, and where the composition has density ranging from 0.915 g/cm³ to 0.970 g/cm³.

EFFECT: improved mechanical properties of products made from the compositions, reduced amount of gel in the compositions.

20 cl, 38 ex, 1 dwg, 4 tbl