Abstract: Phosphinic acid (also called hypophosphorous acid), when used in very small quantities, is disclosed to act as a catalyst to accelerate the reaction of rosin with an unsaturated dibasic acid to form a modified rosin for subsequent esterification with a polyhydric alcohol. According to the process of the invention, a rosin is reacted with an unsaturated dibasic acid such as maleic anhydride or fumaric acid in the presence of phosphinic acid at a temperature of from about 180.degree. C. to about 220.degree. C. When the modified rosin is subsequently esterified, the rosin ester exhibits improved color, softening point, and viscosity in a specified solution.

Abstract: Phosphinic acid (also called hypophosphorous acid), when used in very small quantities, is disclosed to act as a catalyst to accelerate the reaction rate of esterification of rosin with pentaerythritol. According to the process of the invention, a rosin is reacted with at least an equivalent amount of pentaerythritol in the presence of phosphinic acid at a temperature of from about 180.degree. C. to about 300.degree. C. When tall oil rosin is esterified by the invention process, a rosin ester is produced without appreciable color degradation.

Abstract: Partial hydrogenation and sulfur reduction of tall oil rosin process is disclosed whereby the olefinic double bonds of the tall oil rosin resin acid mixture are selectively hydrogenated without reduction of the dehydroabietic acid aromatic double bonds by contacting the tall oil rosin with hydrogen in the presence of a palladium on carbon catalyst under conditions of pressure and temperature to produce a partially hydrogenated tall oil rosin of reduced sulfur content and an acid number no lower than 160.