(Synthesis of Water-Insoluble Polymer Dispersant P-1) 88 g of methyl ethyl ketone was added to a 1000 ml three-necked flask equipped with an agitator and a condenser, and was heated to 72° C. under a nitrogen atmosphere. To this, a solution of 0.85 g of dimethyl 2,2′-azobisisobutyrate, 50 g of phenoxy ethylmethacrylate, 13 g of methacrylic acid and 37 g of methyl methacrylate dissolved in 50 g of methyl ethyl ketone was added dropwise over 3 hours. Once the dropwise addition was completed, the mixture was reacted for one more hour, and then a solution of 0.42 g of dimethyl 2,2′-azobisisobutyrate dissolved in 2 g of methyl ethyl ketone was added. The temperature was raised to 78° C., and the mixture was heated for 4 hours. The obtained reaction solution was precipitated two times in large excess of hexane, and the precipitated resin was dried to obtain 96.5 g of phenoxy ethylmethacrylate/methylmethacrylate/methacrylate (copolymerization ratio [% by mass ratio]=50/37/13) copolymer (resin dispersant P-1).
