Process for preparing polypropylene composition
AssigneeBorealis AG
InventorsPauli Leskinen, Luca Boragno
Life of this patent
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Abstract
The invention relates to a process for producing a polypropylene composition by sequential polymerization said polypropylene composition having low sealing initiation temperature (SIT) and high melting point (Tm), presenting thus a broad sealing window.
Claims10
1-12. An article comprising a polypropylene composition produced by a sequential polymerization process wherein the polypropylene composition is a binary blend comprising two propylene polymer fractions PPF1 and PPF2 and wherein the process comprises at least two reactors connected in series, said process comprising the steps:
- a) polymerizing in a first reactor (R-1), propylene and one comonomer selected from C4-C10 alpha-olefin to obtain a propylene polymer fraction (PPF1), the first reactor (R-1) being a slurry reactor and the propylene polymer fraction (PPF1) being a propylene copolymer,
- b) transferring the propylene polymer fraction (PPF1) and unreacted comonomers of the reactor (R-1) into a second reactor (R-2), the second reactor (R-2) being a first gas-phase reactor-1 (GPR-1),
- c) polymerizing in the gas-phase reactor-1 (GPR-1) propylene, ethylene and one comonomer selected from C4-C10 alpha-olefin in the presence of the propylene polymer fraction (PPF1) to obtain a propylene polymer fraction (PPF2), being a polypropylene terpolymer,
- d) forming the polypropylene composition from the propylene polymer fraction (PPF2) and the propylene polymer fraction (PPF1), and
- e) recovering the polypropylene composition wherein the mol ratio of C4-C10 alpha-olefin content in the propylene copolymer fraction PPF1 (C4-C10-PPF1)/C4-C10 alpha-olefin content in the polypropylene composition (C4-C10-T) [(C4-C10-PPF1)/(C4-C10-T)] is in the range of 0.10 to 0.95, and
- wherein the polypropylene composition has a melting temperature (Tm) in the range of 135 to 160° C. as determined by DSC according to ISO 11357,
- wherein the polymerization process is carried out in the presence of a Zieqler-Natta catalyst that is free of phthalic compound, wherein the Ziegler-Natta catalyst comprises a transition metal of Group 4 to 6 (TM) and a non-phthalic internal donor (ID).
A film comprising a polypropylene composition produced by a sequential polymerization process wherein the polypropylene composition is a binary blend comprising two propylene polymer fractions PPF1 and PPF2 and wherein the process comprises at least two reactors connected in series, said process comprising the steps:
- a) polymerizing in a first reactor (R-1), propylene and one comonomer selected from C4-C10 alpha-olefin to obtain a propylene polymer fraction (PPF1), the first reactor (R-1) being a slurry reactor and the propylene polymer fraction (PPF1) being a propylene copolymer,
- b) transferring the propylene polymer fraction (PPF1) and unreacted comonomers of the reactor (R-1) into a second reactor (R-2), the second reactor (R-2) being a first gas-phase reactor-1 (GPR-1),
- c) polymerizing in the gas-phase reactor-1 (GPR-1) propylene, ethylene and one comonomer selected from C4-C10 alpha-olefin in the presence of the propylene polymer fraction (PPF1) to obtain a propylene polymer fraction (PPF2), being a polypropylene terpolymer,
- d) forming the polypropylene composition from the propylene polymer fraction (PPF2) and the propylene polymer fraction (PPF1), and
- e) recovering the polypropylene composition wherein the mol ratio of C4-C10 alpha-olefin content in the propylene copolymer fraction PPF1 (C4-C10-PPF1)/Ca-C10 alpha-olefin content in the polypropylene composition (C4-C10-T) [(C4-C10-PPF1)/(C4-C10-T)] is in the range of 0.10 to 0.95, and
- wherein the polypropylene composition has a melting temperature (Tm) in the range of 135 to 160° C. as determined by DSC according to ISO 11357, wherein the polymerization process is carried out in the presence of a Ziegler-Natta catalyst that is free of phthalic compound, wherein the Ziegler-Natta catalyst comprises a transition metal of Group 4 to 6 (TM) and a non-phthalic internal donor (ID).
(canceled)
The article according to claim 13, wherein:
- a) the propylene copolymer fraction (PPF1) obtained in the first reactor (R-1) is produced in an amount of less than or equal to 50 wt %,
- b) the propylene terpolymer fraction (PPF2) obtained in the second reactor (R-2) is produced in an amount of more than or equal to 50 wt %,
- the amount of PPF1 and PPF2 being relative to the total sum of the propylene polymer fractions PPF1 and PPF2.
The article according to claim 13, wherein:
- a) the propylene polymer fraction PPF1 comprises 1.50 to 7.00 mol % of one comonomer selected from C4-C10 alpha-olefin, the amount of C4-Cio alpha-olefin comonomer relative to the total amount of monomers in the propylene copolymer (PPF1), and
- b) the propylene polymer fraction PPF2 comprises 0.30 to 12.00 mol % of ethylene comonomer and 1.50 to 17.00 mol % of one comonomer selected from C4-C10 alpha-olefin, the amount of ethylene and C4-C10 alpha-olefin comonomers relative to the total amount of monomers in the propylene terpolymer (PPF2).
The article according to claim 13, wherein the propylene polymer fraction PPF1 is a propylene copolymer comprising 1-butene (C4) and the propylene polymer fraction PPF2 is a propylene terpolymer comprising ethylene comonomer and 1-butene (C4).
The article according to claim 13, wherein the polypropylene composition satisfies the equation:
- Delta=Tm−SIT
- wherein Delta is in the range of 30 to 50° C., and wherein
- Tm is the melting temperature, in ° C., of the polypropylene composition, and
- SIT is the sealing initiation temperature, in ° C., of the polypropylene composition.
The article according to claim 13, wherein the polypropylene composition has an MFR2 in the range of 1.0 to 50.0 g/10 min, as measured at 230° C. under a load of 2.16 kg according to ISO 1133.
Dependencies are inferred from the claim text.