Polyethylene rich/polypropylene blends and their uses
The present invention includes a blend composition comprising at least one coupled propylene polymer and at least 55 weight percent of at least one ethylene polymer, based on the total weight of the coupled propylene polymer and the ethylene polymer. The invention also includes methods for making the coupled propylene polymer and methods for making the blend composition. The present invention further includes films made from the blend composition.
1. A blend composition comprising:
(a) at least one propylene polymer having a melt strength of at least 20 cN; and
(b) greater than 55% by weight based on the combined weight of component (a) and (b), of at least one ethylene polymer having a density of from 0.90-0.94 g/cm 3 and having a melt index (as measured in accordance with ASTM D 1238, at a tamperature of 190° C. under a weight of 2.16 KG) of at least 0.1″ g/10, min.
2. The blend composition of claim 1 , wherein: (i) the modulus of a film made from the blend is higher than the modulus of a film made from component (b); and (ii) a film made from the composition has higher film toughness properties, compared with a film formed in approximately the same manner from a comparable ethylene polymer resin having a 2% secant modulus equivalent to the composition and thc same comonomer as (b), of at least one of: tear resistance in either the machine direction (MD) or cross direction (CD) as measured by the Elmendorf Tear method (ASTM D-1922); or dart impact strength as measured by the procedure of ASTM D-1709 or a modified method thereof in which the height from which thc dart is dropped is decreased from 26″ to 10.5″(0.66 m to 0.27 m), or puncture resistance.
3. The blend composition of claim 1 , wherein the at least one propylene polymer has a melt strength of at least 40 cN.
4. The blend composition of claim 1 , wherein the at least one propylene polymer has a molt strength of at least 50 cN.
5. The blend composition of claim 1 , wherein the at least one ethylcnc polymer comprises at least 60% by weight of the blend.
6. The blend composition of claim 1 , wherein the at least one ethylene polymer has a density of from 0.905-0.925 g/cm 3 and a melt index of at least 0.5 g/10 min.
7. The blend composition of claim 1 , wherein a blown film wade from the blend composition exhibits a mechanical properties balance.
8. The blend composition of claim 1 , wherein the at least one propylene polymer is an impact propylene copolymer that has been reacted with a bis(sulfonyl azide) and component (b) is less than 85% by weight of the blend.
9. The blend composition of claim 8 , wherein component (b) is prepared using a Ziegler-Natta type catalyst and is a copolymer of ethylene and a comonomer selected from the group consisting of: 1-octane, 1-hexene, 1-butene, and mixtures thereof.
10. The blend composition of claim 8 , wherein component (b) is prepared using a Ziegler-Natta type catalyst and is a copolymer of ethylene and a comonomer selected from the group consisting of:1-octene, 1-hexene, and mixtures thereof.