Some polybasic acid derivatives were obtained from substituted benzoic acids such as p- and o-toluic acids, and p-formaldehyde in concentrated sulfuric acid by a method similar to that of Naokawa et al. The structure of these resinous substituted benzoic acid–formaldehyde materials was determined by a paper chromatography and infrared spectrum analysis, and found to be
where n = 0–2; R = H, R′, and R″ = H or CH3, respectively. New glycidyl-ester-type epoxy resins were prepared from these substituted benzoic acid–formaldehyde resins and epichlorohydrin in the presence of sodium hydroxide, using dioxane as a solvent. These resins were considered to have the general structure shown above, where n = 0–2, , and R′ and R″ = H or CH3, respectively.