Abstract: Provided is a method for producing high purity cyanate derived from a phenol compound represented by the following formula (I): in the formula, each of A independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, X represents a single bond, an organic group having 1 to 20 carbon atoms, a carbonyl group, a sulfone group, a divalent sulfur atom or an oxygen atom, i and n represent an integer from 0 to 4. The cyanate contains low amount of impurities such as unreacted phenols and imidecarbonate, and is preferably used as a thermosetting resin for a sealing, laminate, composite material, molding material and adhesive for electric parts.

Abstract: Provided is a method for purifying a cyanate at high yield from a cyanate crude product solution comprising a cyanate represented by the general formula (1), unsubstituted phenol and non-alcoholic solvent by contacting with a poor solvent containing an alcohol and water, to crystallize the cyanate: in the formula (1), A1 to A3 each independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms; X represents a single bond, an organic group having 1 to 20 carbon atoms, a carbonyl group, a sulfone group, a divalent sulfur atom or oxygen atom; n represents an integer of 0 to 3; and i1 to i3 each independently represents an integer of 0 to 4. And also provided is a method for separating alcohol from non-alcoholic solvent effectively.

Abstract: A cyanate resin composition comprising as essential components a cyanate compound represented by formula (1) or its prepolymer and a curing agent: ##STR1## wherein each of R.sub.1 and R.sub.2 represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms; A represents an alkyl group having 1 to 3 carbon atoms; i represents an integer of 0 to 3 alone or together with a brominated epoxy compound or a maleimide compound or its prepolymer, said cyanate resin composition giving a cured product having a low-dielectric constant, and a copper-clad laminate composed of a prepreg of said cyanate resin composition and a copper foil.

Abstract: A cyanate resin composition suitable for a copper-clad laminate comprises components (A) and (B).(A) a cyanate compound of the formula: ##STR1## wherein R and Q each represents halogen, C.sub.1-10 alkyl, C.sub.5-7 cycloalkyl or C.sub.6-20 hydrocarbon; i and j each represents 0-4 and M is (2): ##STR2## wherein T represents halogen, C.sub.1-10 alkyl, C.sub.5-7 cycloalkyl or C.sub.6-20 hydrocarbon; k represents 0-10 and m represents 0-8, and(B) a hardener.