Particle size control of metallocene catalyst systems in loop slurry polymerization reactors
Catalyst compositions containing a metallocene compound, a solid activator, and a co-catalyst, in which the solid activator or the supported metallocene catalyst has a d50 average particle size of 15 to 50 μm and a particle size distribution of 0.5 to 1.5, can be contacted with an olefin in a loop slurry reactor to produce an olefin polymer. A representative ethylene-based polymer produced using the catalyst composition has excellent dart impact strength and low gels, and can be characterized by a HLMI from 4 to 10 g/10 min, a density from 0.944 to 0.955 g/cm 3 , a higher molecular weight component with a Mn from 280,000 to 440,000 g/mol, and a lower molecular weight component with a Mw from 30,000 to 45,000 g/mol and a ratio of Mz/Mw ranging from 2.3 to 3.4.
1. An ethylene polymer having:
a high load melt index (HLMI) in a range from 4 to 10 g/10 min;
a density in a range from 0.944 to 0.955 g/cm 3 ; and
a higher molecular weight component and a lower molecular weight component, wherein:
the higher molecular weight component has a Mn in a range from 280,000 to 440,000 g/mol; and
the lower molecular weight component has a Mw in a range from 30,000 to 45,000 g/mol and a ratio of Mz/Mw in a range from 2.3 to 3.4.
2. An article comprising the ethylene polymer of claim 1 .
3. The article of claim 2 , wherein the ethylene polymer comprises an ethylene/1-butene copolymer, an ethylene/1-hexene copolymer, and/or an ethylene/1-octene copolymer.
4. The ethylene polymer of claim 1 , wherein:
the HLMI is from 5 to 9 g/10 min;
the density is from 0.945 to 0.953 g/cm 3 ;
the Mn is from 290,000 to 410,000 g/mol;
the Mw is from 31,000 to 42,000 g/mol; and
the ratio of Mz/Mw is from 2.4 to 3.3.
5. The ethylene polymer of claim 1 , wherein:
an amount of the lower molecular weight component, based on the total polymer, is in a range from 56 to 72 wt %; and
the ethylene polymer comprises an ethylene/1-butene copolymer, an ethylene/1-hexene copolymer, and/or an ethylene/1-octene copolymer.
6. The ethylene polymer of claim 5 , wherein the ethylene polymer is characterized by a film gel count of less than 50 gels per ft 2 of 25 micron film.
7. A film comprising the ethylene polymer of claim 5 .
8. The film of claim 7 , wherein the film has:
a dart impact from 150 to 750 g/mil; and
a gel count of less than 50 gels per ft 2 of film.
9. The ethylene polymer of claim 1 , wherein the ethylene polymer has:
a CY-a parameter from 0.45 to 0.65;
a relaxation time from 1.5 to 4 sec;
a viscosity at 100 sec −1 from 2000 to 3600 Pa-sec; and
a ratio of viscosity at 0.1 sec −1 to viscosity at 100 sec −1 from 38 to 72.
10. The ethylene polymer of claim 1 , wherein the ethylene polymer comprises an ethylene/1-butene copolymer, an ethylene/1-hexene copolymer, and/or an ethylene/1-octene copolymer.
11. The ethylene polymer of claim 10 , wherein the ethylene polymer contains less than 0.1 ppm by weight, independently, of Mg, V, Ti, and Cr.
12. The ethylene polymer of claim 10 , wherein:
a Mw of the ethylene polymer is in a range from 230,000 to 330,000 g/mol; and
a ratio of Mw/Mn of the ethylene polymer is in a range from 20 to 45.
13. An article comprising the ethylene polymer of claim 12 .
14. A film comprising the ethylene polymer of claim 12 , wherein the film has:
a dart impact from 150 to 750 g/mil; and
a gel count of less than 50 gels per ft 2 of film.
15. The ethylene polymer of claim 12 , wherein a Mz of the lower molecular weight component is in a range from 75,000 to 120,000 g/mol.
16. The ethylene polymer of claim 4 , wherein the ethylene polymer comprises an ethylene/α-olefin copolymer.
17. The ethylene polymer of claim 16 , wherein the ethylene polymer is characterized by a film gel count of less than 50 gels per ft 2 of 25 micron film.
18. The ethylene polymer of claim 4 , wherein an amount of the lower molecular weight component, based on the total polymer, is in a range from 56 to 72 wt %.
19. The ethylene polymer of claim 4 , wherein the ethylene polymer has:
a CY-a parameter from 0.45 to 0.65;
a relaxation time from 1.5 to 4 sec;
a viscosity at 100 sec −1 from 2000 to 3600 Pa-sec; and
a ratio of viscosity at 0.1 sec −1 to viscosity at 100 sec −1 from 38 to 72.
20. An article comprising the ethylene polymer of claim 19 .
21. The ethylene polymer of claim 19 , wherein the ethylene polymer comprises an ethylene/1-butene copolymer, an ethylene/1-hexene copolymer, and/or an ethylene/1-octene copolymer.
22. The ethylene polymer of claim 21 , wherein a Mz of the lower molecular weight component is in a range from 75,000 to 120,000 g/mol.