Ethylene copolymer having enhanced film properties

1. A blown film comprising an ethylene copolymer comprising ethylene and an alpha olefin having 3-8 carbon atoms, the ethylene copolymer having a density of from 0.912 g/cm 3 to 0.925 g/cm 3 , a melt index (I 2 ) of from 0.1 g/10 min to 5.0 g/10 min, a melt flow ratio (I 21 /I 2 ) of from 20 to 30, and a normal comonomer distribution profile in a GPC-FTIR analysis, wherein the normal comonomer distribution profile has a slope of from −3.5 to −7.5, where the slope is defined as the number of short chain branches per 1000 carbons at a molecular weight of 300,000 minus the number of short chain branches per 1000 carbons at a molecular weight of 30,000.

2. The blown film of claim 1 wherein the ethylene copolymer has a characteristic composition distribution parameter, β Tp1 which satisfies the relationship:

β Tp1 ≤22750-1400 (SCB/1000C−2.5×I 2 ); wherein β Tp1 has dimensions of (Daltons/° C.).

3. The blown film of claim 1 wherein the ethylene copolymer has a characteristic composition transition parameter, Φ Tp1→Tp2 which satisfies the relationship: Φ Tp1→Tp2 ≤4230-140 [SCB/1000C+0.5×I 21 /I 2 )−2×I 2 ]; wherein Φ Tp1→Tp2 has dimensions of (Daltons/° C.).

4. The blown film of claim 1 wherein the ethylene copolymer has a molecular weight distribution (M w /M n ) of from 2.5 to 4.0.

5. The blown film of claim 1 wherein the ethylene copolymer has a multimodal profile in a TREF analysis, the multimodal profile comprising two intensity maxima occurring at elution temperatures Tp1 and Tp2, wherein Tp1 is between

80° C. and 90° C. and Tp2 is between 90° C. and 100° C.

6. The blown film of claim 1 wherein less than

0.5 wt % of the ethylene copolymer elutes at a temperature of above 100° C. in a TREF analysis.

7. The blown film of claim 1 wherein the alpha-olefin is 1-hexene.

8. The blown film of claim 1 wherein the ethylene copolymer has a CDBI 50 of from 20 wt % to 40 wt %.

9. The blown film of claim 1 wherein the ethylene copolymer has a melt index (I 2 ) of from 0.2 to 2.0 g/10 min.

10. The blown film of claim 1 , having a 0.8 mil thickness at a die gap of 85 mil and a blow up ratio (BUR) of 2:1, has a dart impact of greater than 350 g/mil.

11. The blown film of claim 1 wherein the ethylene copolymer is made with a Ziegler-Natta catalyst.

12. The blown film of claim 1 , wherein the ethylene copolymer is made in a gas phase polymerization process.

13. The blown film of claim 11 wherein the Ziegler-Natta catalyst comprises:

a) a calcined silica support;

b) a first aluminum compound having the formula Al 1 R b (OR) a X 3−(a+b) , wherein a+b=3 and b≥1,

R is a C 1-10 alkyl radical, and X is a chlorine atom;

c) a magnesium compound having the formula Mg(R 5 ) 2 where each R 5 is independently selected from the group consisting of C 1-8 alkyl radicals;

d) a reactive organic halide selected from the group consisting of CCl 4 and C 3-6 secondary and tertiary alkyl chlorides or a mixture thereof;

e) a titanium compound having the formula Ti(OR 2 ) c X d wherein R 2 is selected from the group consisting of a C 1-4 alkyl radical, and a C 6-10 aromatic radical, X is selected from the group consisting of a chlorine atom and a bromine atom, c is 0 or an integer up to 4 and d is 0 or an integer up to 4 and the sum of c+d is the valence of the Ti atom;

f) an electron donor wherein the electron donor is a trialkylamine compound; and

g) a second aluminum compound having the formula Al 2 R b (OR) a X 3−(a+b) , wherein

a+b=3 and b≥1, R is a C 1-10 alkyl radical, and X is a chlorine atom.

14. The blown film of claim 1 , wherein the ethylene copolymer has a bulk density of greater than 25 lbs/ft 3 .

15. The blown film of claim 1 having a machine direction tear of ≥400 g/mil when the film has a thickness of 0.8 mil and is made at a die gap of 85 mil and a blow up ratio (BUR) of 2:1.