Film formed from a blend of biodegradable aliphatic-aromatic copolyesters

Abstract

A film that is formed from a biodegradable polymer blend of different aliphatic-aromatic copolyesters is provided. More specifically, the blend contains a first copolyester formed from a terephthalic acid monomer. The use of a terephthalic acid monomer results in a polymer chain containing 1,4-(para-) terephthalate units linked in a generally linear configuration (e.g., ˜180°). The blend also contains a second aliphatic-aromatic copolyester formed from a phthalic acid and/or isophthalic acid monomer. The use of such a monomer results in a polymer chain containing 1,2-(ortho-) and/or 1,3-(meta-) linked units. The inclusion of 1,2-(ortho-) and/or 1,3-(meta-) linked units into the polymer backbone of the second copolyester introduces an angle or “kink” (e.g., ˜120° kink for a 1,3-linkage) into the otherwise linear polymer chain. The “kinks” in the second copolyester backbone reduce its melting point and degree of crystallinity, which have an influence on its physical properties (e.g., toughness, tensile strength, and crystallization rate). Thus, the physical properties of the second copolyester may differ substantially from those of the first copolyester. In this regard, the “kinked” second copolyester can provide flexibility for forming films with a wide range of properties that is superior to that which may be achieved using either of copolyesters alone.

Dependencies are inferred from the claim text.