Transparent polypropylene copolymer composition having impact resistance
Polypropylene polymer compositions are disclosed that can be formulated to have excellent transparency properties in conjunction with excellent impact resistance properties. The polypropylene polymer compositions are heterophasic compositions containing a first phase polymer combined with a second phase polymer. The first phase polymer is a polypropylene and alpha-olefin copolymer while the second phase polymer is also a polypropylene and alpha-olefin random copolymer. The first phase polymer contains ethylene in an amount less than 5% by weight and is present in an amount greater than the second phase polymer. The second phase polymer has elastomeric properties.
1. A polypropylene composition comprising:
a first polymer phase comprising a polypropylene random copolymer, the polypropylene random copolymer containing ethylene in an amount of less than about 4% by weight;
a second polymer phase combined with the first polymer phase, the second polymer phase comprising a propylene ethylene copolymer containing ethylene in an amount from about 10% to about 20% by weight; and
wherein the polypropylene composition has a melt flow rate of 15 g/10 min or greater at a temperature of 230° C. and at a load of 2.16 kg, the composition having a Gardner drop impact strength at 0° C. of from about 300 inch-lbs to about 500 inch-lbs.
2. The polypropylene composition of claim 1 , wherein the composition further contains a clarifier in an amount less than about 1% by weight and wherein the polypropylene composition has a haze at 1 mm of less than about 15%.
3. The polypropylene composition of claim 1 , wherein the composition has a flexural modulus of from about 400 MPa to about 1000 MPa.
4. The polypropylene composition of claim 1 , wherein the composition has an IZOD impact strength at 23° C. of greater than about 200 J/m and at 0° C. of greater than about 80 J/m.
5. The polypropylene composition of claim 1 , wherein the polypropylene composition has a total cold xylene solubles content of from about 15% to about 30%.
6. The polypropylene composition of claim 1 , wherein the polypropylene random copolymer in the first polymer phase has an intrinsic viscosity and the propylene ethylene copolymer in the second polymer phase has an intrinsic viscosity and wherein a ratio of intrinsic viscosity of the second phase polymer to the first phase polymer is from about 1.1 to about 2.
7. The polypropylene composition of claim 1 , wherein the polypropylene random copolymer in the first polymer phase contains ethylene in an amount from about 2% to about 3.5% by weight.
8. The polypropylene composition of claim 1 , wherein the propylene ethylene copolymer in the second polymer phase contains ethylene in an amount from about 14% to about 17% by weight.
9. The polypropylene composition of claim 1 , wherein the second polymer phase is present in the polypropylene composition in an amount from about 20% to about 40% by weight.
10. The polypropylene composition of claim 1 , wherein the polypropylene composition has a haze at 1 mm of less than about 10%, has a notched IZOD impact strength at 23° C. of from about 300 J/m to about 900 J/m and has a notched IZOD impact strength of 0° C. of from about 100 J/m to about 600 J/m.
11. The polypropylene composition of claim 1 , wherein the polypropylene composition has a melt flow rate of from about 17 g/10 min to about 30 g/10 min.
12. The polypropylene composition of claim 1 , wherein the polypropylene random copolymer in the first polymer phase has been Ziegler-Natta catalyzed and wherein the propylene ethylene copolymer in the second polymer phase has also been Ziegler-Natta catalyzed.
13. The polypropylene composition of claim 12 , wherein the Ziegler-Natta catalysts used for producing the polypropylene random copolymer of the first polymer phase and the propylene ethylene copolymer of the second polymer phase both include an internal electron donor comprising a substituted phenylene aromatic diester.
14. The polypropylene composition of claim 13 , wherein the composition has a xylene soluble portion and wherein the xylene soluble portion has a Koenig B value of from 0.75 to less than 1.
15. The polypropylene composition of claim 13 , wherein the composition has a xylene insoluble portion and wherein the xylene insoluble portion has a Koenig B value of from 0.75 to less than 1.
16. The polypropylene composition of claim 1 , wherein the polypropylene random copolymer of the first polymer phase has a xylene soluble fraction of less than about 10%.
17. The polypropylene composition of claim 1 , wherein the composition further contains an antacid and an antioxidant.
18. An injection molded article formed from the polypropylene composition of claim 1 .
19. A storage container formed from the polypropylene composition of claim 1 .
20. The storage container of claim 19 , wherein the storage container comprises food packaging.