Polyester blends and their use in compostable products such as disposable diapers

Claim 1

A fiber and film forming blend of starch, in amount by weight 1 to 80%, and of a polyester, in amount by weight 99 to 20%, wherein said polyester consists essentially of recurring structural units of the formulae: --[--C(O)--R--C(O)--OGO--].sub.a --[--C(O)--Q--O--].sub.b -- wherein up to about 40 mole % of R is selected from the group consisting of a chemical bond and one or more divalent, non-aromatic, C 1 -C 10 hydrocarbylene radicals, and the remainder of R is at least about 85 mole % p-phenylene radical, wherein G is up to about 30 mole % of a polyethylene ether radical selected from the group consisting of --(CH.sub.2).sub.2 --O--(CH.sub.2).sub.2 -- and --(CH.sub.2).sub.2 --O--(CH.sub.2).sub.2 --O--(CH.sub.2).sub.2 -- and the remainder of G is selected from the group consisting of polyalkylene ether radicals of molecular weight at least about 250, and --(CH 2 ) 2 --, --(CH 2 ) 3 --, and --(CH 2 ) 4 -- radicals, wherein Q is derived from an hydroxy acid of formula HO[--C(O)--Q--O--].sub.x H, where x is an integer, such hydroxy acid having a melting point at least 5° C. below its decomposition temperature, and Q is selected from the group consisting of a chemical bond and hydrocarbylene radicals --(CH 2 ) n --, where n is an integer from 1 to 5, --C(R')H--, and --C(R')HCH 2 --, wherein R' is selected from the group of --CH 3 and --CH 2 CH 3 , and wherein "a" and "b" are mole fractions of the polymer, and the mole fraction "a" may be 0.6 to 1 and, correspondingly, mole fraction "b" may be 0 to 0.4, and wherein about 0.1 to about 15 mole % of the polymer contains alkali metal or alkaline earth metal sulfo groups.