Single polymer film structures for use in stand-up-pouches
The present invention relates to film structure suitable for use in stand up pouches comprising all polyethylene material. The film structure can be a monolayer film or a multilayer film structure having specific requirements for each layer. The combination results in a film structure having adequate stiffness to function as a stand-up pouch while also providing acceptable water vapor transmission rates and good tear resistance. Such films have improved sustainability characteristics as they should permit down-gauging of the films and, can more easily be recycled, at least for the preferred embodiment comprising only polyethylene resins.
1. A monofilm suitable for use in stand up pouches comprising:
a) a first surface layer (X) comprising from 50 to 100 percent (by weight of the layer (X)) of a linear low density polyethylene having a density from 0.89 to 0.91 g/cm 3 and a melt index of less than 1.3 dg/min, and a peak melting point in a range of from 85° C. to 105° C., and a molecular weight distribution, M w /M n range of 2.0 to 3.0; and
b) a core layer (Y) comprising from 60 to 100 percent (by weight of the layer (Y)) of a first multimodal polyethylene polymer having a multimodal distribution in terms of molecular weight, wherein said first multimodal polyethylene comprises units derived from ethylene and at least one C 3 -C 10 alpha-olefin (preferably C 6 -C 8 ), and wherein the first multimodal polyethylene polymer has a density in the range of 0.950-0.965 g/cm 3 , a melt index of less than 1.20 dg/min, a peak melting point greater than 120° C., and a molecular weight distribution, M w /M n ratio greater than 5.0; and
c) a second surface layer (Z) which comprises:
i) from 50 to 100 percent (by weight of the layer (Z)) of a second multimodal polyethylene polymer having a multimodal distribution in terms of molecular weight, wherein said second multimodal polyethylene comprises units derived from ethylene and at least one C 3 -C 10 alpha-olefin (preferably C 6 -C 8 ), said second multimodal polyethylene polymer having a density in the range of 0.950-0.965 g/cm 3 , a melt index of less than 1.20 dg/min, and a peak melting point in the range of from 120° C. to 135° C., and a molecular weight distribution, M w /M n ratio greater than 5.0; and
ii) from 0 to 50 percent (by weight of the layer (Z)) of a copolymer comprising units derived from ethylene and at least one C 3 -C 10 alpha-olefin (preferably C 6 -C 8 ), and wherein the polyethylene polymer has a density in the range of 0.91- to 0.95 g/cm 3 , a melt index of less than 1.2 dg/min, a peak melting point greater than 110° C., and a molecular weight distribution, M w /M n ratio greater than 3.0.
2. The monofilm of claim 1 , wherein the second surface layer (Z) includes component ii) and component ii) is a multimodal polyethylene polymer.
3. The monofilm of claim 1 , wherein the second surface layer (Z) includes component ii) and component ii) is a monomodal polyethylene polymer.
4. The monofilm of claim 1 , wherein the monofilm is a coextruded film.