The present invention relates to tough and ductile biodegradable, aliphatic
polyester blend compositions and methods for preparing such compositions. It relates to products made out of such blend compositions, including, but not limited to, films, fibers, nonwovens, sheets, coatings, binders, foams and molded products for packaging. The products exhibit a desirable combination of high strength,
ductility and
toughness, while maintaining flexibility, biodegradability and compostability. The products are useful for a variety of biodegradable articles, such as diaper topsheets, diaper backsheets, disposable wipes, shopping and
lawn / leaf bags, agricultural films, disposable garments, medical disposables, paper coatings, biodegradable packaging, binders for
cellulose fibers or synthetics, and the like. The
polyester blend of the present invention comprises: (a) a
copolymer comprising two randomly repeating
monomer units wherein the first randomly repeating
monomer unit has the structure: wherein R<1 >is H, or C1 or C2
alkyl, and n is 1 or 2. The second RRMU comprises at least one
monomer selected from the group consisting of the structures (II) and (III): wherein R<2 >is a C3-C19
alkyl or C3-C19 alkenyl, and wherein m is from 2 to about 16; wherein at least about 50 mole % of the
copolymer comprises RRMUs having the structure of the first RRMU of formula (I). and wherein the polyhydroxyalkanoate is present at a level of at least about 20%, by weight, of the total of the polyhydroxyalkanoate and the aliphatic ester polycondensate. wherein R<1 >is H or a C1-2
alkyl and n is 1 or 2; and the second randomly repeating monomer unit has the structure: wherein R<2 >is a C3-19 alkyl or alkenyl; and (b) an aliphatic ester polycondensate synthesized from an aliphatic polyhydric
alcohol and an aliphatic polycarboxylic acid compound.