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 compositing 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 polyester ingredients , such as polyethylene terephthalate , copolymerized with an alkali metal or alkaline earth metal 4 - sulfophthalic acid derivative , and other ingredients , such as polyethylene ether glycols and / or non - aromatic diacids , such as adipic and glutaric acids .