Multivalent metal-modified salicylic acid resins, and color-developing agents and copying paper using the resins

摘要

Disclosed herein are novel multivalent metal-modified salicylic acid resins useful as color-developing agents for pressure-sensitive copying paper. They can each be produced by causing a salicylic acid ester and a styrene derivative to undergo a Friedel-Crafts reaction in the presence of a strong acid catalyst, hydrolyzing the resulting salicylic acid ester resin, and then reacting the thus-obtained salicylic acid resin with a multivalent metal salt.