Color developer for pressure-sensitive recording sheets

Abstract

Herein disclosed is a method for preparing a nuclear-substituted salicylic acid or a metal salt thereof represented by the following general formula (1): ##STR1## [wherein R.sub.1 and R.sub.2 each represents a t-butyl group, a t-amyl group, a t-octyl group, an isononyl group or an isododecyl group, provided that at least one of R.sub.1 and R.sub.2 represents an isononyl group or an isododecyl group; M represents a hydrogen atom or a metal atom; and n is the atomic valency of the metal atom M] which comprises the step of subjecting, to a Kolbe-Schmitt reaction, an alkali metal salt of a nuclear-substituted phenol represented by the following general formula (2): ##STR2## [wherein R.sub.1 and R.sub.2 are the same as those defined above] in which 100 to 50% of the alkali metal salt is potassium salt and 0 to 50% thereof is sodium salt, in a substantially water-insoluble solvent as a reaction medium. The method makes it possible to improve the yield of the specific nuclear-substituted salicylic acid and metal salts thereof and to provide such products having high purity without any post-treatment. The compounds can be used in color developers for pressure-sensitive recording sheets without any additional purification treatment.