PURPOSE: To obtain a polyester outstanding in the dispersibility of the fine particles contained, suitable for films, by incorporating both specific calcium carbonate fine particles and cadmium carbonate in the form of a glycol slurry in the reaction system followed by polycondensation.
CONSTITUTION: For example, an esterification is carried out between (A) an aromatic dicarboxylic acid (or its ester-forming derivative) (e.g., terephthalic acid) and (B) a glycol (e.g., ethylene glycol). Thence, a slurry prepared by dispersing, e.g., using a homomixer, (C) calcium carbonate fine particles with an average size ≤5μm (e.g., aragonite) and (D) pref. 0.02W40pts.wt., based on 100pts.wt. of the component C, of strontium carbonate in the same glycol as the component B is incorporated in the reaction system so that the amount of the component C falls between 0.01 and 2.0wt% based on the final polyester to carry out a polycondensation, thus obtaining the objective polyester.
SANENOBU KAZUYUKI
YAMAGUCHI HIROBUMI
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