Patent EA-000702-B1 (EA)
Title: Films comprising metallocene catalyzed polyethylene
Inventor: SUKHARDIA ASHISH M
IPC: B32B7/02
Filed: 1996-08-08
Abstract: 1. A self-supporting film having one or more layers wherein at least one layer is a low haze layer having a percent haze of less than 10% wherein the polymer consists essentially of polyethylene, optionally containing a fluoroelastomer, a density of at least 0.93 g/cc, and a molecular weight distribution of no more than 4, said polyethylene being further characterized by being substantially free of branches having six or more carbon atoms. 2. A film according to claim 1 wherein said film consists of a single layer. 3. A film according to claim 1 or 2 wherein the polyethylene has a molecular weight distribution of no more than about 3 and, at least about 1,5. 4. A film according to any one of claims 1-3 wherein the polyethylene used to produce said film has a density of at least about 0.94 g/cc, in particular, the density from about 0,94 to about 0,945 g/cc. 5. A film according to any one of the preceding claims which is a blown film. 6. A film according to claim 5 having a thickness in the range of about 6.35 to about 127 mils. 7. A film according to claim 5 or 6 wherein the polyethylene contains ethyl branches and butyl branches. 8. A film according to any one of the preceding claims 9 wherein the polyethylene has a melt index in the range of about 0.2 to about 5 dg/min. 9. A film according to any one of the preceding claims wherein the polyethylene has a shear stress response value in the range of about 16 to about 20. 10. A film according to claim 8 or 9 wherein the polyethylene has a critical shear stress at the onset of melt fracture of less than 4 x 10<6> dyne/cm<2>. 11. A film according to any claim 8, 9 or 10 wherein at least about 20 percent of the polymer chains of the polyethylene contain terminal vinyl groups. 12. A film according to claim 14 wherein the polyethylene is produced by the polymerization of ethylene and in the presence of an alkane liquid diluent under slurry polymerization conditions using a catalyst consisting essentially of the solid catalyst prepared by (a) combining 5-(9-fluorenyl)-5-(cyclopentadienyl)-hexene-l zirconium dichloride and methylaluminoxane in a liquid, (b) prepolymerizing ethylene in the resulting liquid, and (c) separating the resulting solid prepolymerized catalyst system form the liquid. 13. A film according to claim 2 wherein the polyethylene has ethyl branches which are uniformly distributed at the intermolecular level. 14. A film according to claim 14 wherein the polyethylene is produced by the homopolymerization of ethylene and hexene in the presence of an alkane liquid diluent under slurry polymerization conditions using a catalyst consisting essentially of the solid catalyst prepared by (a) combining 5-(9-fluorenyl)-5-(cyclopentadienyl)-hexene-l zirconium dichloride and methylaluminoxane in a liquid, (b) prepolymerizing ethylene in the resulting liquid, and (c) separating the resulting solid prepolymerized catalyst system form the liquid. 15. A film according to claim 1 containing three layers wherein the polymer of each outer layer is a low haze layer having a percent haze of less than 10% wherein the polymer consists essentially of polyethylene, optionally containing a fluoroelastomer, a density of at least 0.925 g/cc, and a molecular weight distribution of no more than 4, said polyethylene being further characterized by being substantially free of branches having six or more carbon atoms.  16. A film according to claim 15 wherein the polyethylene of the inner layer has a density less than that of the two outer layers. 17. A film according to claim 15 or 16 wherein the polyethylene of the inner layer has a molecular weight distribution of at least 10. 18. A film according to claim 17 wherein the polyethylene of the two outer layers is selected from polyethylenes having a density in the range of about 0.94 to about 0.945 g/cc. 19. A film according to claim 17 or 18 wherein the polyethylene of the inner layer has a density in the range of about 0.91 to about 0.929 g/cc and an HLMI in the range of about 12 to 24 dg/min. 20. A film according to. claim 19 wherein the polyethylene of the two outer layers is selected from the same or different polyethylene selected from polyethylenes having a melt index in the range of 0.2 to 5 dg/min. 21. A film according to claim 19 or 20 which is a coextruded blown film having a percent haze of less than 10 percent and a thickness in the range of 6,35 to 127 mil. 22. A film according to claim 20 wherein at least one of the outer layers contains polyethylene having a melt index of less than about 2 dg/min and said polyethylene contains about 0.01 to about 1 weight percent fluoroelastomer. 23. A film according to claim 1 having at least a second layer wherein the polymer of the second layer consists essentially of polyethylene having a density of at least about 0.945 and a molecular weight distribution greater than 6. 24. A film according to claim 1 having at least a first and second layer wherein the polymer of the second layer consists essentially of polyethylene having a density of less than 0.925 g/cc and a molecular weight distribution of less than 4 and wherein the polymer of the first layer has a percent haze of less than 10% and consists essentially of a polyethylene, optionally containing a fluoroelastomer, a density of at least 0.925 g/cc and a molecular weight distribution of no more than 4 and a melt index in the range of about 0.2 to about 10 dg/min, and being further characterized by being substantially free of branches having six or more carbon atoms. 25. A film according to claim 1 wherein the polymer employed in making the low haze layer has a melt index of at least about 2 dg/min and does not contain any fluoroelastomer. 26. A film according to claim 1 wherein the polyethylene used in forming at least one of said at least one low haze layer has a melt index of less than 2 dg/min and contains about 0.01 to about 1 weight percent fluoroelastomer based on the weight of the polyethylene in said layer. 27. A coextruded blown film having a percent haze of less than 17.8% consisting of three layers wherein the polymer of the each outer layers is the same or different polyethylene selected from polyethylenes having a density of at least 0.93 g/cc, and a molecular weight distribution of less than 4 and being further characterized by being substantially free of branches having six or more carbon atoms, and the polymer of the inner layer consists essentially o a copolymer of ethylene and 1-hexene having a density in range of about 0.91 to about 0.929 g/cc, an HLMI in the range of about 12 to 24 dg/min. and a molecular weight distribution greater than 10 produced using a chromium oxide containing catalyst in a particle form polymerization process. 28. A film according to claim 27 having a haze of no more than 10% wherein the polymer of the outer layers is selected from copolymers of ethylene and 1-hexene having a density of at least about 0.93 g/cc, wherein the thickness of each outer layer is in the range of about 5 to about 25 percent of the total thickness of said film, and wherein if the polymer of each of the outer layers was formed into a film 0.0254 mm thick the films would each have a lower haze than a film 0.0254 mm thick produced from the polymer of the inner layer under the same conditions. 29. A low haze self-supporting film wherein the polymer consists essentially of polyethylene, optionally containing a fluoroelastomer, said polyethylene having (i) a density of at least about 0.93 g/cc, (ii) a MWD of no more than 4, and (iii) ethyl branches which are uniformly distributed at the intermolecular level, and optionally (iv) butyl branches, said polyethylene being further characterized by being substantially free of branches having 6 or more carbon atoms.