Foamed plastic moldings, which are featured in their lightness in weight, elasticity, cushioning property, heat insulating property and moldability, are recently used in large amounts mainly as packing receptacles and cushioning materials. These foamed plastic moldings, however, pose a problem of pollution of natural environment by disposal thereof. To cope with this problem, biodegradable foamed moldings are proposed. EP-A-569143 discloses a method for obtaining a molded article in which biodegradable aliphatic polyester beads are impregnated with a blowing agent, followed by heat molding in a mold cavity. The foamed molding obtained with this method, however, undergoes considerable shrinkage during the molding step and has poor dimensional stability.
The present invention has been made in view of the problem of the above conventional technique and has as its prime object the provision of expanded beads of an aliphatic polyester which can afford foamed articles of the aliphatic polyester having excellent dimensional stability, heat resistance, cushioning property and mechanical property as well as biodegradability.
USPTO Backgrounds
USPTO Backgrounds