GB1001286A - Process for the sulphonation of fatty acids or their esters - Google Patents

Abstract

In the sulphonation of essentially saturated fatty acids of 6-28 C atoms per molecule, or their esters, by the addition of 1.1 to 1.8 mols of sulphur trioxide per mol of fatty acid residue, in the absence of solvents which form adducts with sulphur trioxide, 65 to 90% of the total sulphur trioxide is added at a temperature of not above 70 DEG C. and the remainder at above 70 DEG C. No sulphatable or sulphonatable groups should be present in the fatty acids to allow of sulphonation ether than at the a -hydrogen atom. The trioxide is preferably added continuously at steadily increasing temperatures the first portion at 30 DEG to 70 DEG C., preferably 40 DEG to 65 DEG C., and the residue at 75 DEG to 95 DEG C., preferably 80 DEG to 90 DEG C. The fatty acids preferably have 8-18 C atoms per molecule and an iodine value of below 5, especially below 2. Preferred fatty acids are those derived from plants and animals, e.g. lauric acid, hydrogenated vegetable fats, hydrogenated tallow, whale and fish oils. Their esters may be derived from mono- or polyhydric alcohols, e.g. hydrogenation products of oleyl oleate occurring in sperm oil or natural or synthetic wax esters. Preferably 1.2 to 1.6 moles of trioxide are used per mol of fatty acid residue. The sulphur trioxide is used in the presence of inert gases, e.g. air, N2 and CO2, the gas mixture containing 2-40%, preferably 3-20% by volume, of sulphur trioxide. The addition of the trioxide, and the variation in temperature, are adjusted so that the trioxide reacts as completely as possible. The first stage should take 2/3 to 3/4 of the total reaction time and the second stage not less than 5, preferably 10-15 minutes. The products are bleached preferably as in Specification 1,001,283. The fatty acid products, before or after bleaching, may be esterified with alcohols of 1-6 C atoms, especially monohydric alcohols. Examples are provided in which methyl laurate (made from hardened coconut oil) an ethyl ester derived from hardened coconut oil, an ethyl ester of a hardened and distilled tallow fatty acid, a sec-butyl ester of hardened coconut fatty acid, a mixture of an ethyl ester of a hardened palm kernel fatty acid and hardened palm kernel fatty acid, a mixture of hardened coconut fatty acid ethyl ester and the free acid, hardened palm kernel fatty acid ethyl ester, and hydrogenated palm kernel fatty acid, are sulphonated.