Method to produce very stiff polypropylene
AssigneeBorealis AG
InventorsPauli Leskinen, Michiel Bergstra
Life of this patent
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Abstract
The present invention relates to a process for the preparation of a propylene homo- or copolymer, comprising the following steps: (i) feeding propylene and hydrogen, and optionally one or more comonomers, to a reactor R1, wherein the hydrogen is fed to the reactor R1 in a periodically varying amount, (ii) preparing a first fraction of the propylene homo- or copolymer in the reactor R1 in the presence of a catalyst, (iii) transferring the first fraction to a reactor R2, and (iv) preparing a second fraction of the propylene homo- or copolymer in the reactor R2, wherein the melt flow rate MFR (2.16 kg, 230° C.) of the propylene homo- or copolymer is higher than the melt flow rate MFR (2.16 kg, 230° C.) of the first fraction.
Claims25
A process for the preparation of a propylene homo- or copolymer, comprising the following steps:
- (i) feeding propylene and hydrogen, and optionally one or more comonomers, to a reactor R1, wherein the hydrogen is fed to the reactor R1 in a periodically varying amount,
- (ii) preparing a first fraction of the propylene homo- or copolymer in the reactor R1 in the presence of a catalyst,
- (iii) transferring the first fraction to a reactor R2, and
- (iv) preparing a second fraction of the propylene homo- or copolymer in the reactor R2,
- wherein the melt flow rate MFR (2.16 kg, 230° C.) of the propylene homo- or copolymer is higher than the melt flow rate MFR (2.16 kg, 230° C.) of the first fraction,
- wherein a prepolymerisation step in a prepolymerisation reactor, preferably a loop reactor, is carried out before step (i), which includes feeding propylene and hydrogen to the prepolymerisation reactor, wherein the hydrogen feed is provided in a periodically varying amount.
Dependencies are inferred from the claim text.