In this case, a solvent which can be washed with water, such as toluene, xylene, methyl isobutyl ketone, methyl ethyl ketone and ethyl acetate is used to carry out the esterification reaction, and washing is continued until acid components and ionic impurities are not detected in waste water. [0285] An esterification rate of the esterified products falls is a range of 10 to 100 mole %, preferably