PREPARATION METHOD OF WATER-SOLUBLE RESIN FOR PAINT BY REACTING POLYVALENT ACID HAVING RESONANCE STRUCTURE WITH PHOSPHORIC ACID OR SULFURIC ACID, ALKALI HYDROXIDE AND ALCOHOL IN TURN

摘要

PURPOSE: Provided is a method for preparing a water-soluble resin for a paint to allow a polyester resin or an alkyd resin to contain many water-soluble polar groups in addition to a carboxyl group for improving the width of water-solubility and for allowing the resin to be air dried and heat cured. CONSTITUTION: The method comprises the steps of treating a polyvalent acid having a resonance structure with phosphoric acid or sulfuric acid; reacting the obtained one with an alkali hydroxide for substitution; and condensation reacting the obtained one with an alcohol to prepare a water-soluble resin for a paint. Preferably the water-soluble resin has a molecular weight of 2,000-10,000, an oil length of solid part of 5-70 %, a OH number of 30-140 mg KOH/g and an acid number of 0-60 mg KOH/g.