Blush and chemical resistant polyester film
AssigneeToray Plastics (America), Inc.
InventorJan Moritz
Life of this patent
Estimating the term…
Abstract
A composite includes a multilayer polyethylene terephthalate (PET) film having a base layer and an adjacent skin layer. The PET of the skin layer has inherent viscosity of about 0.70-0.90 and carboxyl endgroup concentration of less than 25 eq/T. The base layer can be affixed to a thin metal sheet. Optionally, the base layer of a second multilayer PET film with a skin layer inherent viscosity of about 0.70-0.90 and carboxyl endgroup concentration of less than 25 eq/T can be affixed to the opposite side of the metal sheet. The composite is suited for making food and chemical containers such as food storage cans that resist blush discoloration from steam contact during container formation and age degradation during extended storage of harsh chemical products.
Claims10
A layered composite, comprising:
- a first multilayer film about 5 μm to about 75 μm thick, the film comprising a base layer and a skin layer coextensively adjacent and in direct contact with a side of the base layer, in which at least 70 wt % of the base layer and the skin layer each independently consists of polyethylene terephthalate (PET), wherein the PET of the base layer has intrinsic viscosity less than about 0.70, and the PET of the skin layer has intrinsic viscosity in the range of about 0.70 to about 0.90 and carboxyl end group concentration less than about 25 eq/T;
- one metal sheet about 50 μm to about 1300 μm thick, in which the first multilayer film is affixed to a first side of the metal sheet positioned such that a side of the base layer opposite the skin layer of the first multilayer film is in direct contact with the first side of the metal sheet;
- and
- a second multilayer film about 5 μm to about 75 μm thick, the second multilayer film comprising a second base layer and a second skin layer coextensively adjacent and in direct contact with a side of the second base layer, in which at least 70 wt % of the second base layer and the second skin layer each independently consists of PET, the PET of the second skin layer having intrinsic viscosity in the range of about 0.70 to about 0.90 and carboxyl end group concentration less than about 25 eqT, and in which the second multilayer film is affixed to a second side of the metal sheet positioned such that a side of the second base layer opposite the second skin layer is in direct contact with the second side of the metal sheet,
- wherein the first multilayer film and the second multilayer film as affixed to the metal sheet remain clear with no hazing or clouding after exposure to steam for 90 minutes or more.
Dependencies are inferred from the claim text.