Method for producing masterbatches

Abstract

The present invention provides a method of producing a masterbatch which can yield a masterbatch that contains a metal salt compound and has an improved moldability with little coloration. The method of producing a masterbatch according to the present invention is a method of producing a masterbatch in which a metal salt compound is incorporated into a polyester resin, the method being characterized by comprising: a first step of obtaining a kneaded product by feeding the polyester resin and the metal salt compound to an extruder and melt-kneading the polyester resin and the metal salt compound; and a second step of, while continuing kneading after the first step, further feeding the polyester resin to the extruder and kneading the resulting mixture, wherein, in the first step, the polyester resin and the metal salt compound are fed at such a mass ratio that the amount of the metal salt compound is not more than twice the amount of the polyester resin; the total amount of the polyester resin fed in the first and second steps and the metal salt compound fed in the first step is, in terms of mass ratio, in the range of 2 to 20 times the total amount of the polyester resin and the metal salt compound that are fed in the first step.

Dependencies are inferred from the claim text.