Propylene-ethylene random copolymers with low XS/ET ratio and high MFR
Propylene and alpha olefin random copolymers are disclosed that have excellent flow characteristics. For instance, the copolymers can be formulated so as to have a melt flow rate of greater than about 45 g/10 min. While still retaining the above flow characteristics, the copolymer can also be formulated to have greater stiffness, low xylene soluble content, and excellent transparency characteristics especially when combined with one or more clarifying agents.
1. A propylene-ethylene copolymer having high flow characteristics, wherein the propylene-ethylene copolymer comprises:
a propylene content of greater than 90% by weight, the propylene-ethylene copolymer has an ethylene content (ET) in an amount of from 2.0% to 5.0% by weight, and
wherein the propylene-ethylene copolymer has a xylene solubles fraction (XS) such that the propylene-ethylene copolymer has a xylene solubles to ethylene content ratio (XS/ET) of less than 1.51, and wherein the propylene-ethylene copolymer has a melt flow rate of greater than 45 g/10 min at a temperature of 230° C. and at a load of 2.16 kg, the and wherein propylene-ethylene copolymer has a molecular weight distribution (Mw/Mn) of greater than 2.8.
2. The propylene-ethylene copolymer as defined in claim 1 , wherein the ethylene content is from 3.0% to 5.0% by weight.
3. The propylene-ethylene copolymer as defined in claim 1 , wherein the ethylene content is from 3.1% to 4.7% by weight.
4. The propylene-ethylene copolymer as defined in claim 1 , wherein the xylene solubles to ethylene content ratio (XS/ET) is from 1.2 to 1.5.
5. The propylene-ethylene copolymer as defined in claim 1 , wherein the propylene-ethylene copolymer has a melt flow rate of greater than 45 g/10 min and less than 140 g/10 min.
6. The propylene-ethylene copolymer as defined in claim 1 , wherein the propylene-ethylene copolymer has a melt flow rate of from 80 g/10 min to 100 g/10 min.
7. The propylene-ethylene copolymer as defined in claim 1 , wherein the propylene-ethylene copolymer has a melt flow rate of from 50 g/10 min to 80 g/10 min.
8. The propylene-ethylene copolymer as defined in claim 1 , wherein the copolymer has a xylene solubles fraction of from 4% to 7% by weight.
9. The propylene-ethylene copolymer as defined in claim 1 , wherein the propylene-ethylene copolymer is formed using a Ziegler-Natta catalyst system, wherein the catalyst system includes an internal electron donor comprising a substituted phenylene aromatic diester.
10. The propylene-ethylene copolymer as defined in claim 9 , wherein the catalyst system further includes a dicyclopentyldimethoxysilane based donor.
11. The propylene-ethylene copolymer as defined in claim 9 , wherein the catalyst system further includes a n-propyltrimethoxysilane based donor.
12. The propylene-ethylene copolymer as defined in claim 1 , wherein the propylene-ethylene copolymer is produced without the use of metallocenes.
13. A polymer composition containing the propylene-ethylene copolymer as defined in claim 1 , wherein the propylene-ethylene copolymer is present in the polymer composition in an amount greater than 70% by weight.
14. The polymer composition as defined in claim 13 , wherein the polymer composition further contains an antioxidant, an acid scavenger, or mixtures thereof.
15. The polymer composition as defined in claim 14 , further comprising a clarifying agent.
16. The polymer composition as defined in claim 15 , wherein the clarifying agent comprises a dibenzylidene sorbitol or a nonitol.
17. The polymer composition as defined in claim 15 , wherein the polymer composition displays a haze at 40 mil of less than 15% and wherein after thermal aging for 24 hours at 55° C., the haze decreases by no more than 15%.
18. An injection molded article formed from the polymer composition as defined in claim 13 .
19. A film formed from the polymer composition as defined in claim 13 .
20. A hot fill packaging container made from the polymer composition as defined in claim 13 .