Example 1
Into a three-neck flask provided with a condenser and a stirrer, 12.51 g of 4,4′-diaminodiphenylmethane (manufactured by Tokyo Chemical Industry Co., Ltd.) and 112.59 g of N-methylpyrrolidone (manufactured by Kanto Chemical Co., Inc.) were put, and by being stirred under ice-cooling to obtain a uniform solution. Next, into a dropping funnel, 5.95 g of methylenediphenyl 4,4′-diisocyanate (manufactured by Tokyo Chemical Industry Co., Ltd.) and 53.5 g of N-methylpyrrolidone (manufactured by Kanto Chemical Co., Inc.) were put, followed by dissolving, and the resulting solution was added dropwise to the reaction solution over a period of 1 hour. The resulting product was stirred at 0° C. to 10° C. for 1 hour, and allowed to react at room temperature for 2 hours. The reaction solution was added dropwise to a mixed solution of 0.5 L of pure water and 0.5 L of methanol, and as a result, a polymer was precipitated. This was collected by filtration, washed, and dried, whereby 14.8 g of a binder polymer (CP-1) having a weight-average molecular weight of 76,000 was obtained. It was confirmed from the NMR spectrum, the IR spectrum, and GPC (polystyrene conversion) that the obtained product was the target substance.