PURPOSE: To obtain the titled resin excellent in thermal properties, etc., by reacting a solution of a trialkylammonium salt of novolak, prepared by reacting novolak of a specified MW with a trialkylamine in the presence of an organic solvent, with an excess of a cyanogen halide at a specified temperature.
CONSTITUTION: Novolak of number-average MW 300W1,500, represented by the formula, wherein R1W4 are each H or methyl and a is 1W10, is mixed and reacted with a trialkylamine (e.g., triethylamine) in the presence of an organic solvent (e.g., dichloromethane) in such a ratio that one trialkylamine molecule is present per phenolic hydroxyl group to be converted into a cyanato group of the novolak. Then the titled resin is prepared by reacting the resulting solution of a trialkylammonium salt of novolak with an excess of a cyanogen halide at a temperature of 30W65°C (1W2 cyanogen halide molecules are present per ammonium salt of the hydroxyl group to be converted into a cyanate group).
IGARASHI HIDEO
UEDA YOSHIO
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