High density polyethylene film with high biaxial orientation

An imbalanced biaxially oriented high density polyethylene (HDPE) film having a greater degree of orientation in the transverse direction than in the machine direction, comprising a base layer consisting of (i) HDPE and, optionally, (ii) one or more of an antioxidant, filler, particulate, dye, pigment, light stabilizer, heat stabilizer, anti-static agent, slip agent, anti-blocking agent, abrasive, an opacifing agent, and a cavitating agent, a first casting promoter layer on a first side of the base layer, and a second casting promoter layer on a second side of the base layer opposite the first side, wherein

• the HDPE of the base layer has a density of at least 0.940 g/cm3 and a melt index of from about 0.5 to about 10 g/10 minutes,
• the base layer represents from about 70% to about 95% of the thickness of the film,
• the film has been stretched in the solid state to a degree of from about 6:1 to about 8:1 in the machine direction at a temperature of from about 140° F. (60° C.) to about 320° F. (160° C.), and
• the film has been stretched in the solid state to a degree of from about 6:1 to about 15:1 in the transverse direction at a temperature of from about 230° F. (110° C.) to about 320° F. (160° C.).

A method of making an imbalanced biaxially oriented high density polyethylene (HDPE) film having a greater degree of orientation in the transverse direction than in the machine direction, wherein

• the film comprises a base layer consisting of (i) HDPE and, optionally, (ii) one or more of an antioxidant, filler, particulate, dye, pigment, light stabilizer, heat stabilizer, anti-static agent, slip agent, anti-blocking agent, abrasive, an opacifying agent, and a cavitating agent, a first casting promoter layer on a first side of the base layer, and a second casting promoter layer on a second side of the base layer opposite the first side,
• the HDPE of the base layer has a density of at least 0.940 g/cm3 and a melt index of from about 0.5 to about 10 g/10 minutes, and
• the base layer represents from about 70% to about 95% of the thickness of the film, the method comprising the steps of
• coextruding the base layer, first casting promoter layer, and second casting promoter layer to form a coextrudate,
• casting the coextrudate to provide a sheet, and
• biaxially orienting the sheet by stretching the sheet in the solid state to a degree of from about 6:1 to about 8:1 in the machine direction and to a degree of from about 6:1 to about 15:1 in the transverse direction.

An imbalanced biaxially oriented high density polyethylene (HDPE) film having a greater degree of orientation in the transverse direction than in the machine direction, comprising a base layer consisting of (i) HDPE and, optionally, (ii) one or more of an antioxidant, filler, particulate, dye, pigment, light stabilizer, heat stabilizer, anti-static agent, slip agent, anti-blocking agent, abrasive, an opacifying agent, and a cavitating agent, a first casting promoter layer on a first side of the base layer, and a skin layer on a second side of the base layer opposite the first side, wherein

• the HDPE of the base layer has a density of at least 0.940 g/cm3 and a melt index of from about 0.5 to about 10 g/10 minutes,
• the base layer represents from about 70% to about 95% of the thickness of the film,
• the film has been stretched in the solid state to a degree of from about 6:1 to about 8:1 in the machine direction at a temperature of from about 140° F. (60° C.) to about 320° F. (160° C.), and
• the film has been stretched in the solid state to a degree of from about 6:1 to about 15:1 in the transverse direction at a temperature of from about 230° F. (110° C.) to about 320° F. (160° C.).

An imbalanced biaxially oriented high density polyethylene (HDPE) film having a greater degree of orientation in the transverse direction than in the machine direction, comprising:

• a base layer consisting of (i) a blend of HDPE and a polymer selected from the group consisting of low density polyethylene (LDPE), ultra-low density polyethylene (ULDPE), linear low density polyethylene (LLDPE), polystyrene, styrene-butadiene copolymer, and polyvinyl acetate, and, optionally, (ii) one or more of an antioxidant, filler, particulate, dye, pigment, light stabilizer, heat stabilizer, anti-static agent, slip agent, anti-blocking agent, abrasive, an opacifying agent, and a cavitating agent,
• a first casting promoter layer on a first side of the base layer, and
• a second casting promoter layer on a second side of the base layer opposite the first side, wherein
• the HDPE of the base layer has a density of at least 0.940 g/cm3 and a melt index of from about 0.5 to about 10 g/10 minutes,
• the base layer represents from about 70% to about 95% of the thickness of the film,
• the film has been stretched in the solid state to a degree of from about 6:1 to about 8:1 in the machine direction at a temperature of from about 140° F. (60° C.) to about 320° F. (160° C.), and
• the film has been stretched in the solid state to a degree of from about 6:1 to about 15:1 in the transverse direction at a temperature of from about 230° F. (110° C.) to about 320° F. (160° C.).