US Patent 11299621 Anti-blush and chemical resistant polyester film

Embodiments herein relate to a polymer film comprising an anti-blushing composition in a blend comprising polyethylene terephthalate (PET) and polybutylene terephthalate (PBT); wherein the blend contains at least 50 wt. % of PBT; wherein the anti-blushing composition comprises a phosphorus containing compound but excludes certain phosphorus compounds; and wherein the anti-blushing composition is configured to prevent blushing in the polymer film laminated directly to a metal substrate sheet and exposed to steam at a temperature of 260° F. for 90 minutes.