IMPACT-RESISTANT POLYOLEFN COMPOSITIONS Russian patent published in 2009 - IPC C08L23/10 C08L23/12 C08F2/00 

FIELD: chemistry.

SUBSTANCE: invention relates to polyolefin compositions with good balance of hardness and impact-resistance and high elongation rating. A hetero-phase polyolefin composition is described, containing (wt %): (A) from 50 to 80 wt % crystalline propylene polymer with polydispersity index from 5.2 to 10 and isotactic pentad (mmmm) content over 97.5 mol %, determined by ¹³C-NMR spectroscopy in a fraction which is insoluble in xylene at 25°C; wherein the said polymer is chosen from a propylene homopolymer or propylene copolymer and at least a comonomer, chosen from ethylene and α-olefin with formula H₂C=CHR, where R is a linear or branched C_2-6-alkyl radical, containing at least 95 % repeating units derived from propylene; (B) from 5 to 20 % of the first elastomeric ethylene copolymer with at least a comonomer chosen from propylene and another α-olefin with formula H₂C=CHR, where R is a linear or branched C_2-6-alkyl radical; wherein the said first elastomeric copolymer contains from 25 to less than 40% ethylene and is soluble in xylene at room temperature in amount ranging from over 85 wt % to 95 wt %, where characteristic viscosity [η] of the fraction soluble in xylene ranges from 2.5 to 4.5 dl/g; and (C) from 10 to 40% of a second elastomeric ethylene copolymer with at elast a comonomer, chosen from propylene and another α-olefin with formula H₂C=CHR, where R is a linear or branched C_2-6-alkyl radical; wherein the said second elastomeric copolymer contains 50 to 75% ethylene and is soluble in xylene at room temperature in amount ranging from 50 wt % to 85 wt %, where characteristic viscosity [η] of the fraction which is soluble in xylene ranges from 1.8 to 4.0 dl/g; in which total amount of copolymer (B) and copolymer (C) ranges from 20 to 45 % of the total amount of components (A)-(C), total amount of ethylene with respect to total amount of components (A)-(C) is 23 wt %, and the ratio of ethylene content in the fraction which is insoluble in xylene at room temperature, (C₂xif), multiplied by the weight percent content of the fraction which is insoluble in xylene at room temperature, (%XIF), and ethylene content in the fraction which is soluble in xylene at room temperature, (C₂xsf), multiplied by weight percent content of the fraction which is soluble in xylene at room temperature (%SXF), i.e. C₂xif x % XIF)/(C₂xsf x % SXF), satisfies the following relationship (I): (C₂xif x % XIF)/(C₂xsf x % SXF)>0.01 x + 0.261, where x is total amount of ethylene. Described also is a method of polymerisation of the polyolefin composition described above, involving at least three consecutive steps, where components (A), (B) and (C) are obtained on separate consecutive steps, where operations on each step, except the first step, take place in the presence the polymer formed in the previous step and catalyst used in the previous step.

EFFECT: obtaining polyolefin compositions with high hardness, without reducing impact resistance, especially impact resistance at low temperatures and elastic properties.

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