Process for the preparation of polypropylene with improved productivity

Patent metadata

Field	Value
Publication number	US-9512246-B2
Application number	US-201314418808-A
Country	US
Kind code	B2
Filing date	Jul 30, 2013
Priority date	Aug 7, 2012
Publication date	Dec 6, 2016
Grant date	Dec 6, 2016

Abstract

A process for the preparation of a polypropylene in a sequential polymerization process including a pre-polymerization reactor and at least two polymerization reactors connected in series. The polymerization in the at least two polymerization reactors takes place in the presence of a Ziegler-Natta catalyst. The Ziegler-Natta catalyst includes (a) a pro-catalyst that has a compound of a transition metal, a compound of a metal which metal is selected from one of the groups 1 to 3 of the periodic table (IUPAC), and an internal electron donor, (b) a co-catalyst, and (c) an external donor. The Ziegler-Natta catalyst is present in the pre-polymerization reactor. Ethylene and propylene are fed to the pre-polymerization reactor in a feed rate ratio of 0.5 to 10.0 g/kg.

First claim

We claim:

1. A process for the preparation of a polypropylene (PP) in a sequential polymerization process comprising a pre-polymerization reactor (PR) and at least two polymerization reactors (R1 and R2) connected in series, wherein
the polymerization in the at least two polymerization reactors (R1 and R2) takes place in the presence of a Ziegler-Natta catalyst (ZN-C), and said Ziegler-Natta catalyst (ZN-C) comprises
(a) a pro-catalyst (PC) comprising
(a1) a compound of a transition metal (TM),
(a2) a compound of a metal (M) which metal is selected from one of the groups 1 to 3 of the periodic table (IUPAC),
(a3) an internal electron donor (ID),

(b) a co-catalyst (Co), and
(c) an external donor (ED),
wherein the mol-ratio of co-catalyst (Co) to external donor (ED) [Co/ED] is in the range of above 10 to below 25, and
said Ziegler-Natta catalyst (ZN-C) is present in the pre-polymerization reactor (PR) and ethylene (C2) in addition to propylene (C3) is fed to said pre-polymerization reactor (PR)
(i) in a C2/C3 feed ratio of 0.5 to 10.0 g/kg;
and/or
(ii) in a manner to accomplish a C2/C3 ratio in the pre-polymerization reactor (PR) of 0.5 to 5.0 mol/kmol.

2. The process according to claim 1 , wherein ethylene is fed to the pre-polymerization reactor (PR) in addition to propylene
(a) in a C2/C3 feed ratio of 1.0 to 8.0 g/kg,
and/or
(b) in a manner to accomplish a C2/C3 ratio in the pre-polymerization reactor (PR) of 0.8 to 3.0 mol/kmol.

3. The process according to claim 1 , wherein further the mol-ratio of co-catalyst (Co) to transition metal (TM) [Co/TM] is in the range of above 100 to below 200.

4. The process according to claim 1 , wherein further
(a) the mol-ratio of co-catalyst (Co) to external donor (ED) [Co/ED] is in the range of above 12 to below 23,
and/or
(b) the mol-ratio of co-catalyst (Co) to transition metal (TM) [Co/TM] is in the range of above 110 to below 195.

5. The process according to claim 1 , wherein the sequential polymerization process comprises at least three polymerization reactors (R1, R2 and R3) connected in series.

6. The process according to claim 1 , wherein
(a) the temperature is at least in one of the at least two polymerization reactors (R1 and R2) in the range of 50° C. to 130° C.,
and/or
(b) the temperature in the pre-polymerization reactor (PR) is 0 to 60° C.

7. The process according to claim 1 , wherein
(a) the weight-ratio of co-catalyst (Co) to propylene (C3) [Co/C3] is in the range of 25 g/t to 40 g/t,
and/or
(b) the weight-ratio of external donor (ED) to propylene (C3) [ED/C3] is in the range of 2.8 g/t to 4.8 g/t.

8. The process according to claim 1 , wherein
(a) the metal of the compound of a transition metal (TM) is selected from one of the groups 4 to 6 of the periodic table (IUPAC),
and/or
(b) the compound of a metal (M) is MgCl 2 ,
and/or
(c) the internal donor (ID) comprises an dialkylphthalate of formula (II)

wherein R 1 and R 2 are independently a C 1 to C 4 alkyl.

9. The process according to claim 1 , wherein
(a) the co-catalyst (Co) is an aluminium compound,
and/or
(b) the external donor (ED) is a hydrocarbyloxy silane.

10. The process according to claim 1 , wherein
(a) the pre-polymerization reactor (PR) is a bulk slurry reactor;
and/or
(b) the first reactor (R1) is a loop reactor (LR) and/or optionally subsequent reactor(s) are gas phase reactors (GRs).

11. The process according to claim 1 , wherein the process does not comprise a washing step for the polypropylene (PP).

12. The process according to claim 1 , wherein
(a) in the pre-polymerization reactor (PR) propylene is reacted in the presence of ethylene and the Ziegler-Natta catalyst (ZN-C) comprising the pro-catalyst (PC), the external donor (ED) and the co-catalyst (Co), obtaining thereby a mixture (MI) of the produced polypropylene (Pre-PP) and the used Ziegler-Natta catalyst (ZN-C),
(b) transferring said mixture (MI) comprising the Ziegler-Natta catalyst (ZN-C) and the polypropylene (Pre-PP) and un-reacted ethylene in the first polymerization reactor (R1),
(c) in the first polymerization reactor (R1) propylene, ethylene and optionally at least one other α-olefin, like optionally a C 4 to C 10 α-olefin, are polymerized in the presence of the Ziegler-Natta catalyst (ZN-C) obtaining a first polypropylene fraction (PP-A) of the polypropylene (PP),
(d) transferring said first polypropylene fraction (PP-A) to the second polymerization reactor (R2),
(e) in the second polymerization reactor (R2) propylene and optionally at least one other α-olefin, like optionally a C 2 to C 10 α-olefin other than propylene, is/are polymerized in the presence of the first polypropylene fraction (PP-A) obtaining a second polypropylene fraction (PP-B) of the polypropylene (PP), said first polypropylene fraction (PP-A) and said second polypropylene fraction (PP-B) form a first mixture (1 st M),
(f) transferring said first mixture (1 st M) to a third polymerization reactor (R3), and
(g) in the third polymerization reactor (R3) propylene and optionally at least one other α-olefin, like optionally a C 2 to C 10 α-olefin other than propylene, is/are polymerized in the presence of the first mixture (1 st M) obtaining a third polypropylene fraction (PP-C) of the polypropylene (PP), said first mixture (1 st M) and said third polypropylene fraction (PP-C) form the polypropylene (PP).

13. The process according to claim 1 , wherein the polypropylene (PP) has
(a) a melt flow rate (MFR 2 ) measured according to ISO 1133 in the range of 0.5 to 7.0 g/10 min;
and/or
(b) an ash content below 45 ppm;
and/or
(c) a shear thinning index (0/100) measured according to ISO 6271-10 (200° C.) of at least 20;
and/or
(d) a polydispersity index (PI) of at least 2.5.

14. The process according to claim 1 , wherein the polypropylene (PP) has
(a) a melting temperature Tm of more than 163° C.;
and/or
(b) a crystallization temperature Tc of more than 110° C.

15. The process according to claim 1 , wherein the polypropylene (PP) is an ethylene-propylene copolymer (E-PP).

16. The process according to claim 1 , wherein the polypropylene (PP) is
(a) a monomodal polypropylene (PP),
or
(b) is a multimodal polypropylene (PP), wherein each polypropylene fraction present has a different melt flow rate MFR 2 .

17. An ethylene-propylene copolymer (E-PP) having
(a) a melt flow rate (MFR 2 ) measured according to ISO 1133 in the range of 0.5 to 7.0 g/10 min,
(b) a melting temperature Tm of more than 163° C.,
(c) an ethylene content of more than 0.05 wt.-% to 0.80 wt.-% based on the total weight of the ethylene-propylene copolymer (E-PP),
(d) optionally a crystalline fraction melting above 170 to 180° C. of at least 14.0 wt.-%, wherein said fraction is determined by the stepwise isothermal segregation technique (SIST), and
(e) an ash content below 45 ppm.

18. The ethylene-propylene copolymer (E-PP) according to claim 17 , wherein said ethylene-propylene copolymer (E-PP) has further
(a) a crystallization temperature Tc of more than 110° C.,
and/or
(b) 2,1 erythro regio-defects of equal or below 0.4 mol determined by 13 C-NMR spectroscopy,
and/or
(c) a crystalline fraction melting above 160 to 170° C. of more than 36.0 wt.-%, wherein said fraction is determined by the stepwise isothermal segregation technique (SIST),
and/or
(d) a shear thinning index (0/100) measu

Assignees

• Borealis Ag

Inventors

• Neissl Wolfgang
• Gloger Dietrich
• Horill Thomas
• Sandholzer Martina
• Potter Gregory

Classifications

• C08F210/06 Primary

  Propene · CPC title

• C08F2500/12

  Melt flow index or melt flow ratio · CPC title

• C08F2500/15

  Isotactic · CPC title

• C08F4/6543

  halides of magnesium · CPC title

• C08F210/16

  Copolymers of ethene with alpha-alkenes, e.g. EP rubbers · CPC title