POLYPROPYLENE COMPOSITION WHICH COMBINES LOW INITIAL WELDING TEMPERATURE AND HIGH MELTING POINT Russian patent published in 2020 - IPC C08L23/14 C08F2/00 C08F210/06 C08F210/08 C08F210/16 C08F4/651 C08J5/18 

FIELD: chemistry.

SUBSTANCE: invention relates to a polypropylene composition, a method of producing a polypropylene composition, use of the polypropylene composition and a film. Polypropylene composition is a binary mixture consisting of a propylene polymer PPF1 fraction and a propylene polymer PPF2 fraction. PPF1 fraction is contained in the composition in amount of 30–50 wt. % and is a propylene copolymer comprising propylene monomers and from 1.50 to 7.00 mol. % of one comonomer selected from C₄-C₁₀ alpha-olefin. PPF2 fraction is contained in the composition in amount of 50–70 wt. % and is a propylene terpolymer comprising propylene monomers, from 3.00 to 12.00 mol. % ethylene comonomer and from 1.50 to 17.0 mol. % of one comonomer selected from C₄-C₁₀ alpha-olefin. Polypropylene composition has a melting point (Tm) in range from 140 to 150 °C, as determined by DSC in accordance with ISO 11357, and satisfies the equation: Delta = Tm - SIT, where Delta is in range from 41 to 46 °C, Tm is melting point of polypropylene composition, in °C, SIT is initial welding temperature of polypropylene composition, in °C, calculated for granules by DSC. Said amounts of PPF1 and PPF2 fractions of propylene polymer are calculated relative to total sum of fractions PPF1 and PPF2 of propylene polymers. Method of producing the polypropylene composition involves polymerisation of propylene and one comonomer selected from C₄-C₁₀ alpha-olefin in a first reactor (R-1) to obtain a propylene polymer fraction (PPF1). Then fraction (PPF1) of propylene polymer and unreacted comonomers are transferred from reactor (R-1) to the second reactor (R-2), which is the first gas-phase reactor-1 (GPR-1). Further, in the first gas-phase reactor-1 (GPR-1), polymerisation of propylene, ethylene and one comonomer selected from C₄-C₁₀ alpha-olefin, in the presence of a propylene polymer fraction (PPF1) to obtain a propylene polymer fraction (PPF2). Further, the polypropylene composition is removed from the reactor. Polypropylene composition is used to produce a film or a multilayer film.

EFFECT: invention enables to obtain a polypropylene composition with improved low welding temperature and high melting point.

12 cl, 2 tbl