the invention provides novel polyesters , fibers and films , nonwovens from the fibers and disposable products of the polyesters such as diapers . the products are degradable under the conditions typically existing in waste composting processes , have low ingredient costs and yet provide strength and toughness properties adequate for end uses such as in disposable diapers . the polyesters are based upon polyethylene terphthalate copolymerized with a cycloaliphatic diacid , preferably hexahydroterephthalic acid , and containing alkali metal or alkaline earth metal sulfo groups , such as a metal 5 - sulfoisophthalic acid derivative .