Patent ID: 8198391

Claim:
A method for producing an aqueous polymer to be used in a pigment dispersion that essentially contains water, the aqueous polymer and a pigment, the method comprising: reacting a diol compound (A) having one or two carboxyl groups within each molecule with a diisocyanate compound (B), thereby producing a reaction product which has a reaction index as calculated by Formula 1 and Formula 2 within a range from 0.95 to 1.10, and comprises a compound represented by [chemical formula (1)]; followed by reacting the reaction product and a diol compound (C), or the reaction product, the diol compound (C) and a diisocyanate group (D); wherein [Chemical Formula 1] is: wherein R 1 and R 3 represent structures of the diisocyanate compound (B) from which the isocyanate group has been excluded, and R 1 and R 3 may be the same or may be different; and R 2 represents a structure of the diol compound (A) having one or two carboxyl groups within each molecule and from which the hydroxyl group has been excluded; wherein Formula 1 is: Reaction index=(reaction rate of isocyanate group)×[(number of moles of diisocyanate compound (B))/(number of moles of diol compound (A))]; and wherein Formula 2 is: (the reaction rate of the isocyanate group)=1−(quantitative value of the isocyanate group in the reaction product)/(quantitative value of the isocyanate group prior to the reaction), and wherein the quantitative value of the isocyanate group is determined by the method described in ISO014896.