Abstract: A spontaneously degradable fiber excellent in bulkiness, softness, stretchability and feeling, which comprises (A) a low heat-shrinkable fiber component comprising a high crystalline aliphatic polyester and (B) a high heat-shrinkable fiber component comprising an aliphatic polyester, e.g., a low crystalline or non-crystalline aliphatic polyester, and a block copolymer or a mixture the main component of which is an aliphatic polyester and which comprises a high-melting component and a low-melting component. Further, fibers excellent in self-crimpability or self-adhesion property and dividable fibers are obtained by suitably combining the fiber components (A) and (B) to form conjugated fibers or composite yarns.

Abstract: A spontaneously degradable fiber excellent in bulkiness, softness, stretchability and feeling, which comprises (A) a low heat-shrinkable fiber component comprising a high crystalline aliphatic polyester and (B) a high heat-shrinkable fiber component comprising an aliphatic polyester, e.g., a low crystalline or non-crystalline aliphatic polyester, and a block copolymer or a mixture the main component of which is an aliphatic polyester and which comprises a high-melting component and a low-melting component. Further, fibers excellent in self-crimpability or self-adhesion property and dividable fibers are obtained by suitably combining the fiber components (A) and (B) to form conjugated fibers or composite yarns.

Abstract: A crosslinked polycarbonate is obtained by polycondensation of diol (A), trivalent or more polyhydric alcohol (B) whose arbitrary two hydroxy groups are not in the positional relationship of 1,2-disubstitution or 1,3-disubstitution, and carbonyl component (C) such as carbonic acid diesters. In the polycondensation step, no side reaction does not occur.This crosslinked polycarbonate is used as a modifier for polylactic acids. The brittleness of the polylactic acid is improved while maintaining mechanical strength, thermostability, and transparency.

Abstract: Biodegradable polymer blends comprising of a polylactic acid or a copolymer containing lactic acid as the main constituent, and a polyhydroxyalkanoate or a copolymer containing two or more hydroxyalkanoic acids as the constituents; methods for controlling the rate of biodegradation of a polylactic acid or a copolymer containing lactic acid as the main constituent, by blending as above; methods for manufacturing such aliphatic polyester polymer blends; and methods for molding such polymer blends; are provided.The aliphatic polyester polymer blends obtained in the invention are colorless and clear, and have excellent biodegradabilities, as well as excellent mechanical strengths. The blends can be molded similarly as in conventional thermoplastic resins, so that they can be utilized in many industries, without problems in the waste product treatment after the use. Furthermore, molded products with excellent qualities are obtained from the blends, because of their improved moldabilities.

Abstract: A biodegradable or hydrolyzable toner for electrophotography, which permits the easy reclaiming and recycling of used copying paper, permits the easy deinking by an existing deinking system, can decrease environmental pollution caused by a toner waste, and has excellent toner properties owing to the uniform dispersion of additives, the toner containing, as a binder resin, a lactic acid-based resin of the formula (1),H--[--O--CH(CH.sub.3)--CO--].sub.n --OR (1)wherein R is an alkali metal or an alkaline earth metal, and n is an integer of 10 to 20,000.

Abstract: A biodegradable copolyester having an average molecular weight of at least 50,000 produced by copolymerizing a lactic acid component as the main component with PEG, an aliphatic polyester or a sulfo group-containing ester-forming compound, a molded article produced using it, such as a conjugate fiber, and a process for producing the molded article.

Abstract: An oriented film with improved tensile strength and Young's modulus can be produced by melting and extruding poly-L-lactic acid and/or poly-D-lactic acid to form a film and, after the film is cooled rapidly, by subjecting it to a stretching process at a temperature above the glass transition temperature and below the cold-crystallization temperature. The stretching may be effected by a method of uniaxial stretching with constant width, successive biaxial stretching or simultaneous biaxial stretching. A thermal treatment may be effected after the stretching process. Films thus obtained have tensile strength over 6 kgf/mm.sup.2 in the stretching direction, Young's modulus over 220 kgf/mm.sup.2 in the stretching direction and transparency to visible light over 90%.