Abstract: A powder separation apparatus and method are provided so as to be able to accurately separate a raw powder material. This apparatus has a container into which a raw powder material containing a heavy powder and a light powder, and medium particles having a larger particle size than the raw powder material, are supplied; a container shaker for shaking the container; and a gas blower unit for blowing a gas into an interior of a medium particle layer in the container to discharge the light powder with the gas to the outside of the medium particle layer.

Abstract: There is provided a powderizing apparatus and a method capable of powderizing target objects effectively. The powderizing apparatus includes a cylindrical container extending in a horizontal direction, a rotary shaft disposed along the axis of the cylindrical container, a plurality of rods disposed in parallel with respect to the rotary shaft in a position close to an inner wall of the cylindrical container and away from the rotary shaft, rod-fixing members for fixing the rods to the rotary shaft and hammering members provided on the respective rods.

Abstract: A biodegradable optically active copolymer is disclosed, which is represented by the general formula (I): ##STR1## wherein R.sup.1, R.sup.2, R.sup.3 and R.sup.4 each represents a hydrogen atom or a methyl group; m and n each represents a natural number wherein the sum thereof gives 10 to 5,000; and C* represents an asymmetric carbon atom, and a process for producing the copolymer by ring-opening copolymerization of optically active .beta.-butyrolactone with a cyclic carbonate in the presence of catalyst. The biodegradable optically active copolymer of the present invention provides excellent biodegradability (enzyme degradability) and hydrolyzability.

Abstract: A process for producing poly(3-hydroxybutyric acid) comprising ring-opening polymerization of .beta.-butyrolactone is disclosed, wherein the ring-opening polymerization is carried out in the presence of at least one tin compound selected from the group consisting of a distannoxane derivative (e.g., 1-chloro-3-ethoxy-1,1,3,3-tetrabutyldistannoxane), a tin carboxylate compound (e.g., tin dioctanoate), and a di-lower alkyltin oxide (e.g., dibutyltin oxide). Poly(3-hydroxybutyric acid) can be produced in high yield at low cost through simple production steps. The resulting polymer has an increased molecular weight to a degree not heretofore attained.