Abstract: A preparation process of solid polyhydroxycarboxylic acid comprising subjecting an organic solvent solution of polyhydroxycarboxylic acid to cooling.cndot.solidification and grinding. The preparation process can provide high molecular weight solid polyhydroxycarboxylic acid with ease and cheaply, can be converted with ease to a continuous system, and is useful in industry.

Abstract: A purification process for polyhydroxycarboxylic acids which comprises dissolving polyhydroxycarboxylic acid in an water-immiscible phenol or an organic solvent containing said water-immiscible phenol, successively bringing the resulting solution into contact with water which contains an acidic material, separating the organic layer from an aqueous layer, and isolating polyhydroxycarboxylic acid from the organic layer. The process can efficiently remove a catalyst contained in the polyhydroxycarboxylic acid prepared in the presence of the catalyst, does not require polyhydroxycarboxylic acid to be in the form of a solid, and can treat polyhydroxycarboxylic acid in a higher concentration as compared with using chlorinated hydrocarbon as a solvent.

Abstract: A preparation process of polyhydroxycarboxylic acid having an inherent viscosity of 0.3 dl/g or more by dehydrating polycondensation of lactic acid containing hydroxycarboxylic acid in an organic solvent in the presence or absence of a catalyst, comprising using a hydroxycarboxylic acid raw material which comprises one or more impurities selected from the group consisting of methanol, ethanol, acetic acid, pyruvic acid, fumaric acid, methyl lactate, ethyl lactate and butyl lactate in a total amount of 0.3% by mole or less for the amount of said hydroxycarboxylic acid raw material.

Abstract: A preparation process of polyhydroxycarboxylic acid having an inherent viscosity of 0.3 dl/g or more by dehydrating polycondensation of lactic acid containing hydroxycarboxylic acid in an organic solvent in the presence or absence of a catalyst, comprising using a hydroxycarboxylic acid raw material which comprises one or more impurities selected from the group consisting of methanol, ethanol, acetic acid, pyruvic acid, fumaric acid, methyl lactate, ethyl lactate and butyl lactate in a total amount of 0.3% by mole or less for the amount of said hydroxycarboxylic acid raw material.

Abstract: A process for preparing polyhydroxycarboxylic acid by conducting dehydration polycondensation of hydroxycarboxylic acids in the presence or absence of a catalyst and in the presence or absence of an organic solvent, comprising using a vertical high viscosity reactor during all or a portion of the dehydration polycondensation steps and conducting hot polycondensation while separating and removing low boiling components. The process can provide high molecular weight polyhydroxycarboxylic acid with ease and cheaply in industry.

Abstract: A purification process of a polyhydroxycarboxylic acid for efficiently removing a catalyst with a simple method from solid polyhydroxycarboxylic acid by bringing the solid polyhydroxycarboxylic acid which is obtained by a catalytic reaction and has an inherent viscosity of 0.1.about.5.0 dl/g into contact with an acid substance in the presence of a hydrophilic organic solvent. Also disclosed is a polyhydroxycarboxylic acid prepared by direct dehydration polymerization having an extremely reduced content of residual catalyst.

Abstract: A process for producing continuously an aromatic polycarbonate oligomer by reacting an aromatic dihydroxy compound and an alkali metal base or an alkaline earth metal base with a carbonyl halide compound comprises:(1) feeding continuously to a tank reactor an aromatic dihydroxy compound, water, a molecular weight controlling agent, a polymerization catalyst, a carbonyl halide compound, and an organic solvent, and an alkali metal base or an alkaline earth metal base in an amount of 1.15-1.6 equivalents based on the aromatic dihydroxy compound,(2) carrying out the reaction with a residence time as defined by the following formula,log Y<-2.19X+1.84 (0.0005.ltoreq.X<0.84,1.ltoreq.Y<69)where X is an amount of the polymerization catalyst in terms of mole % based on the amount of mole of the aromatic dihydroxy compound fed per unit time, and Y is a residence time (min.

Abstract: A process for stabilizing dibenzylidenesorbitols comprising incorporating 0.05-20 pts. wt. sorbic acid and/or potassium sorbate in 100 pts. wt. dibenzylidenesorbitol represented by the following formula, ##STR1## and a stabilized dibenzylidenesorbitol composition formed thereby. The storage stability of dibenzylidenesorbitols is thus greatly improved.