| abstract |
(57) [Problem] To provide a purification method which is safe and simple in process and can purify high-purity cyanate ester in high yield. SOLUTION: A poor solvent containing alcohols and water is brought into contact with a solution of a crude cyanate ester product containing a cyanate ester of the formula (1) and an impurity comprising a compound containing an unsubstituted phenol, to thereby obtain cyanic acid. A purification method including a step of crystallizing and precipitating an ester. Embedded image (A 1 to A 3 : H, an alkyl group of C 1 to 6 , X: C 1 to 20 Organic group, carbonyl group, sulfone group, divalent S or O. n: 0 to 3, i 1 to i 3 : integer values of 0 to 4. ) |