Method for producing agrichemical-containing resin composition

A method for producing an agricultural chemical-containing resin composition, including:

• mixing an agricultural chemical active ingredient A having a water solubility of 100 ppm or higher at 25° C., a styrene-maleic anhydride copolymer or a styrene-maleic anhydride copolymer-mixed resin, and a white carbon, at arbitrary composition ratios, so as to prepare a plurality of types of compositions;
• respectively granulating these compositions to have an average particle diameter from 10 to 25 μm, adding these granulated compositions to 25° C. distilled water, and measuring the release rate Y(t) (% by mass) of the agricultural chemical active ingredient A after t hours from the addition;
• analyzing the content Ac (% by mass) of the agricultural chemical active ingredient A and the content Ca (% by mass) of the white carbon relative to the total mass of the agricultural chemical active ingredient A, the styrene-maleic anhydride copolymer or the styrene-maleic anhydride copolymer-mixed resin, and the white carbon, and the thus measured release rate Y(t), by a linear least-squares method, so as to obtain
• Yev(t)=a(t)×AcS+b(t)×CaS+c(t) Equation (I)
• (provided that, in the Equation (I):
• the symbol Yev(t) represents the estimated release rate (% by mass) of the agricultural chemical active ingredient A after t hours from the addition;
• the symbols a(t), b(t), and c(t) represent coefficients after t hours obtained from the linear least-squares method;
• the parameter t represents the elapsed time (hr) after the addition;
• the symbols AcS and CaS respectively represent the content (% by mass) of the agricultural chemical active ingredient A and the content (% by mass) of the white carbon relative to the total mass of the agricultural chemical active ingredient A, the styrene-maleic anhydride copolymer or the styrene-maleic anhydride copolymer-mixed resin, and the white carbon);
• selecting a content AcS of the agricultural chemical active ingredient A from a range not lower than 5% by mass and not higher than 35% by mass, and a content CaS of the white carbon from a range not lower than 0.1% by mass, so that the estimated release rate Yev(0.25) of the agricultural chemical active ingredient A after 15 minutes from the addition to 25° C. distilled water be not higher than 40% by mass in said Equation (I);
• and
• mixing the agricultural chemical active ingredient A, the styrene-maleic anhydride copolymer or the styrene-maleic anhydride copolymer-mixed resin, and the white carbon, so that the thus selected contents AcS and CaS can be achieved.