Detection of damage to carbonless copying paper - by spraying with soln. of substd. phenol

摘要

Detection of microcapsule damage in pressure- or heat- sensitive carbonless copying papers contg. encapsulated leuco dyes is effected by spraying the surface of the paper with a soln. of a phenol (I) of formula R-Ar-X-Ar'-OH (where Ar and Ar' are phenylene gps.; R is H, OH or 1-6C alkyl; X is a bond, SO2, 3-12C alkylene or 6-12C cycloalkylene) in an inert organic solvent. Specified cpds. (I) include bisphenol A, 2,2'-dihydroxybiphenyl and 4,4'-dihydroxy-cyclohexylidenebisphenol. The soln. is pref. applied as an aerosol spray with a propellant. Suitable solvents are ethers and chlorinated hydrocarbons. The concn. of (I) is pref. 0.1-20 (esp. 0.5-5) wt.%. The solns. are colourless themselves but produce intense colours on contact with leuco dye released from damaged capsules (cf. phenol resins, DS 2160755).