Polyethylene film
Polyethylene films having a good balance of optical and mechanical properties are disclosed. The films are derived from ethylene copolymer compositions made with a suitably substituted phosphinimine catalyst. The ethylene copolymers have very narrow molecular weight distributions and broadened comonomer distributions.
1. A film comprising a copolymer of ethylene and 1-hexene wherein the film has a haze of ≦12%, a dart impact of ≧500 g/mil, an MD tear of ≧200 g/mil and wherein the copolymer has a density of from 0.916 g/cc to 0.930 g/cc, a melt index (I 2 ) of from 0.3 to 3 g/10 min, a melt flow ratio (I 21 /I 2 )<20, a molecular weight distribution (M w /M n )≦2.5, and satisfies the condition:
CDBI≦(β+25)/a-parameter; where β is the amount in weight % of the copolymer that elutes at 90° C. and above as determined by TREF, CDBI is the comonomer distribution breadth index determined by TREF, and the a-parameter is the Carreau-Yasuda shear exponent as determined by DMA at 190° C.
2. The film of claim 1 wherein the copolymer satisfies the condition Tm≦(112.7+0.4×β) where Tm is the peak melting temperature in ° C. as determined by DSC, and β is the amount in wt % of the copolymer that elutes at 90° C. and above as determined by TREF.
3. The film of claim 1 wherein the copolymer has a density of from 0.917 g/cc to 0.920 g/cc.
4. The film of claim 1 wherein the copolymer has a melt flow ratio (I 21 /I 2 ) of from 14 to 19.
5. The film of claim 1 wherein the copolymer has a CDBI of from 50% to 65%.
6. The film of claim 1 wherein the copolymer has a molecular weight distribution (M w /M n ) of from 1.8 to 2.3.
7. The film of claim 1 wherein the copolymer has a hexane extractables of ≦0.5 wt %.
8. The film of claim 1 wherein the film has an MD tear >250 g/mil and a TD tear >380 g/mil.
9. The film of claim 1 wherein the film has a ratio of MD tear to TD tear (MD tear/TD tear) of from 0.50 to 0.85.
10. The film of claim 1 wherein the film has an MD secant modulus at 1% strain ≧130 Mpa and a TD secant modulus at 1% strain ≧135 Mpa.
11. The film of claim 1 wherein the film has a dart impact of ≧600 g/mil.
12. The film of claim 1 wherein the copolymer has a molecular weight distribution (M w /M n ) of ≦2.1.
13. The film of claim 1 wherein the copolymer is made in a single gas phase reactor with a single polymerization catalyst comprising: an organometallic compound having a phosphinimine ligand; an alkylaluminoxane cocatalyst; and an inert support.
14. The film of claim 13 wherein the organometallic compound has the formula:
(1,2-(R 2 )(Ar—F)Cp)Ti(N═P(t-Bu) 3 )X 2 , where R 2 is an alkyl group, Ar—F is a perfluorinated aryl group, a 2,6 fluoro substituted phenyl group, a 2,4,6 fluoro substituted phenyl group or a 2,3,5,6 fluoro substituted phenyl group and X is an activatable ligand.
15. The film of claim 14 wherein the organometallic compound has the formula:
(1,2-(R 2 )(C 6 F 5 )Cp)Ti(N═P(t-Bu) 3 )X 2 , where R 2 is n-propyl, n-butyl or n-hexyl; and where X is an activatable ligand.
16. A film exhibiting a haze of ≦12%, a dart impact of ≧500 g/mil, an MD tear of ≧200 g/mil wherein said film comprises a copolymer of ethylene and 1-hexene and which has a density of from 0.916 g/cc to 0.930 g/cc, an I 21 /I 2 <20, a Mw/Mn of ≦2.5 and which has a TREF profile comprising i) less than 5 wt % of the copolymer represented at a temperature at or below 40° C., ii) a primary peak at a temperature T1, iii) a secondary peak at a temperature T2, and iv) from 10 to 30 wt % of the copolymer is represented at a temperature of from 90° C. to 105 C.°; wherein T2>T1 and the temperature difference between T1 and T2 is less than 20° C.
17. The film of claim 16 wherein the temperature difference between T1 and T2 is less than 15° C.
18. The film of claim 16 wherein from 12 to 25 wt % of the copolymer is represented at a temperature from 90° C. to 105 C.°.
19. The film of claim 16 wherein T2 is greater than 90° C.
20. The film of claim 16 wherein T1 is in the range of from 75 to 90° C. and T2 is in the range of 85 to 100° C.
21. The film of claim 16 wherein T1 is in the range of from 80 to 90° C. and T2 is in the range of 90 to 100° C.
22. The film of claim 16 wherein the copolymer has a CDBI of from 50% to 65%.
23. The film of claim 16 wherein the copolymer has a density of from 0.917 g/cc to 0.920 g/cc.
24. The film of claim 16 wherein the copolymer has a molecular weight distribution (Mw/Mn) of ≦2.3.
25. The film of claim 16 wherein the film has a MD tear >250 g/mil and a TD tear >380 g/mil.
26. The film of claim 16 wherein the film has a ratio of MD tear to TD tear (MD tear/TD tear) of from 0.50 to 0.85.
27. The film of claim 16 wherein the film has a dart impact of ≧600 g/mil.
28. The film of claim 16 wherein the film has an MD secant modulus at 1% strain ≧130 Mpa and a TD secant modulus at 1% strain ≧135 Mpa.
29. The film of claim 16 wherein the copolymer is made in a single gas phase reactor with a single polymerization catalyst comprising: an organometallic compound having a phosphinimine ligand; an alkylaluminoxane cocatalyst; and an inert support.
30. The film of claim 29 wherein the organometallic compound has the formula:
(1,2-(R 2 )(Ar—F)Cp)Ti(N═P(t-Bu) 3 )X 2 , where R 2 is an alkyl group, Ar—F is a perfluorinated aryl group, a 2,6 fluoro substituted phenyl group, a 2,4,6 fluoro substituted phenyl group, or a 2,3,5,6 fluoro substituted phenyl group, and X is an activatable ligand.
31. The film of claim 30 wherein the organometallic compound has the formula:
(1,2-(R 2 )(C 6 F 5 )Cp)Ti(N═P(t-Bu) 3 )X 2 , where R 2 is n-propyl, n-butyl or n-hexyl; and where X is an activatable ligand.
32. A film comprising a copolymer of ethylene and 1-hexene wherein the film has a haze of ≦12%, a dart impact of ≧500 g/mil, an MD tear of ≧200 g/mil and wherein the copolymer has a density of from 0.916 g/cc to 0.930 g/cc, a melt index (I 2 ) of from 0.3 to 3 g/10 min, a melt flow ratio (I 21 /I 2 )<20, a molecular weight distribution (M w /M n )≦2.5, and satisfies the condition:
Tm≦(112.7+0.4×β) where Tm is the peak melting temperature in ° C. as determined by DSC, and β is the amount in wt % of the copolymer that elutes at 90° C. and above as determined by TREF.
33. The film of claim 32 wherein the copolymer has a density of from 0.917 g/cc to 0.920 g/cc.
34. The film of claim 32 wherein the copolymer has a melt flow ratio (I 21 /I 2 ) of from 14 to 19.
35. The film of claim 32 wherein the copolymer has a CDBI of from 50% to 65%.
36. The film of claim 32 wherein the copolymer has a molecular weight distribution (M w /M n ) of from 1.8 to 2.3.
37. The film of claim 32 wherein the copolymer has a hexane extractables of ≦0.5 wt %.
38. The film of claim 32 wherein the film has an MD tear >250 g/mil and a TD tear >380 g/mil.
39. The film of claim 32 wherein the film has a ratio of MD tear to TD tear (MD tear/TD tear) of from 0.50 to 0.85.
40. The film of claim 32 wherein the film has an MD secant modulus at 1% strain ≧130 Mpa and a TD secant modulus at 1% strain ≧135 Mpa.
41. The film of claim 32 wherein the film has a dart impact of ≧600 g/mil.
42. The film of claim 32 wherein the copolymer has a molecular weight distribution (M w /M n ) of ≦2.1.
43. The film of claim 32 wherein the copolymer is made in a single gas phase reactor with a single polymerization catalyst comprising: an organometallic compound having a phosphinimine ligand; an alkylaluminoxane cocatalyst; and an inert support.
44. The film of claim 43 wherein the organometallic compound has the formula:
(1,2-(R 2 )(Ar—F)Cp)Ti(N═P(t-Bu) 3 )X 2 , where R 2 is an alkyl group, Ar—F is a perfluorinated aryl group, a 2,6 fluoro substituted phenyl group, a 2,4,6 fluoro substituted phenyl group, or a 2,3,5,6 fluoro substituted phenyl group and X is an activatable ligand.
45. The film of claim 44 wherein the organometallic compound has the formula:
(1,2-(R 2 )(C 6 F 5 )Cp)Ti(N═P(t-Bu) 3 )X 2 , where R 2 is n-propyl, n-butyl or n-hexyl; and where X is an activatable ligand.
46. A film comprising a copolymer of ethylene and an alpha-olefin having from 3-10 carbon atoms wherein the film has a haze of ≦12%, a dart impact of ≧500 g/mil, an MD tear of ≧200 g/mil and wherein the copolymer is selected from a group consisting of copolymer (a), copolymer (b), and copolymer (c);
wherein copolymer (a) has a density of from 0.917 g/cc to 0.920 g/cc, a melt index (I 2 ) of from 0.3 to 3 g/10 min, a melt flow ratio (I 21 /I 2 )<20, a molecular weight distribution (M w /M n )≦2.5, and satisfies the condition: CDBI≦(β+25)/a-parameter;
where β is the amount in weight % of the copolymer that elutes at 90° C. and above as determined by TREF, CDBI is the comonomer distribution breadth index determined by TREF, and the a-parameter is the Carreau-Yasuda shear exponent as determined by DMA at 190° C.;
copolymer (b) has a density from 0.917 g/cc to 0.920 g/cc, an I 21 /I 2 <20, a Mw/Mn of ≦2.5 and which has a TREF profile comprising i) less than 5 wt % of the copolymer represented at a temperature at or below 40° C., ii) a primary peak at a temperature T1, iii) a secondary peak at a temperature T2, and iv) from 10 to 30 wt % of the copolymer is represented at a temperature of from 90° C. to 105 C.°;
wherein T2>T1 and the temperature difference between T1 and T2 is less than 20° C.;
and copolymer (c) has a density of from 0.917 g/cc to 0.920 g/cc, a melt index (I 2 ) of from 0.3 to 3 g/10 min, a melt flow ratio (I 21 /I 2 )<20, a molecular weight distribution (M w /M n )≦2.5, and satisfies the condition: Tm≦(112.7+0.4×β) where Tm is the peak melting temperature in ° C. as determined by DSC, and β is the amount in wt % of the copolymer that elutes at 90° C. and above as determined by TREF.
47. A film comprising a copolymer of ethylene and an alpha-olefin having from 3-10 carbon atoms wherein the film has a haze of ≦12%, a dart impact of ≧500 g/mil, an MD tear >250 g/mil, a TD tear >380 g/mil, and wherein the copolymer is selected from a group consisting of copolymer (a), copolymer (b), and copolymer (c);
wherein copolymer (a) has a density of from 0.916 g/cc to 0.930 g/cc, a melt index (I 2 ) of from 0.3 to 3 g/10 min, a melt flow ratio (I 21 /I 2 )<20, a molecular weight distribution (M w /M n )≦2.5, and satisfies the condition: CDBI≦(β+25)/a-parameter;
where β is the amount in weight % of the copolymer that elutes at 90° C. and above as determined by TREF, CDBI is the comonomer distribution breadth index determined by TREF, and the a-parameter is the Carreau-Yasuda shear exponent as determined by DMA at 190° C.;
copolymer (b) has a density of from 0.916 g/cc to 0.930 g/cc, an I 21 /I 2 <20, a Mw/Mn of ≦2.5 and which has a TREF profile comprising i) less than 5 wt % of the copolymer represented at a temperature at or below 40° C., ii) a primary peak at a temperature T1, iii) a secondary peak at a temperature T2, and iv) from 10 to 30 wt % of the copolymer is represented at a temperature of from 90° C. to 105 C.°;
wherein T2>T1 and the temperature difference between T1 and T2 is less than 20° C.;
and copolymer (c) has a density of from 0.916 g/cc to 0.930 g/cc, a melt index (I 2 ) of from 0.3 to 3 g/10 min, a melt flow ratio (I 21 /I 2 )<20, a molecular weight distribution (M w /M n )≦2.5, and satisfies the condition: Tm≦(112.7+0.4×β) where Tm is the peak melting temperature in ° C. as determined by DSC, and β is the amount in wt % of the copolymer that elutes at 90° C. and above as determined by TREF.