Process for preparing 3-alkylthiopropionic acid esters

A process for preparing a polyhydric alcohol 3-alkylthiopropionate polyolefin stabilizer capable of enhancing the resistance to deterioration and minimizing the formation of undesirable color and odor of a polyolefin resin when heated at 150.degree. C., comprising the step of heating a reaction mixture containing at least one polyhydric alcohol having 3 to 6 alcoholic hydroxyl groups and 3 to 20 carbon atoms, provided that the number of carbon atoms is at least equal to the number of alcoholic hydroxyl groups, and for each mole of alcoholic hydroxyl group supplied by the polyhydric alcohol from 0.6 to 1.5 moles of a betamercaptopropionic acid compound selected from the group consisting of betamercaptopropionic acid and a lower alkyl ester thereof and from 0.6 to 2 moles of at least one alpha-olefin having 6 to 40 carbon atoms, and an amount effective to initiate reaction of a reaction initiator selected from the group consisting of azonitriles and organic peroxides having 4 to 40 carbon atoms, and subsequently recovering the polyhydric alcohol 3-alkylthiopropionate polyolefin resin stabilizer from the mixture.