Patent GB-999300-A (GB)
Title: Improvements in or relating to the sulphonation of fatty acids and their esters
IPC: C11C3/00
Filed: 1962-08-02
Abstract: Fatty acids of 6 to 28, preferably 8 to 18, carbon atoms, and their esters, which apart from a labile a -hydrogen atom, have no sulphonatable or sulphatable groups, and an iodine value of below 5, are treated with excess gaseous sulphur trioxide, not in adduct form, in which all of the sulphur trioxide needed for the sulphonation is dissolved in the starting materials to be sulphonated at temperatures which are not sufficient for a complete sulphonation; and the reaction is completed at above 70 DEG  C. after at least half, preferably 60-80%, of the starting material has been sulphonated at temperatures lower than 70 DEG  C. Starting materials which contain fatty acid residues with 10 to 14 carbon atoms, especially those from the lauric acid group, per residue give products which are soluble at 20-45 DEG  C. and products of use at 50-100 DEG  C. are obtained from fatty acids of 16 or more carbon atoms, e.g. those derived from vegetable fats, tallow or whale or fish oils.  The esters may be derived from monohydric alcohols of at most 28 carbon atoms, or di- or tri-hydric alcohols, e.g. methyl to nonyl alcohols, or alcohols obtained by reducing the above fatty acids or mixtures thereof, e.g. the hydrogenation products of sperm oil or natural or synthetic wax esters.  The starting materials preferably have an iodine value of below 2 and especially below 1.  Preferably impurities, e.g. proteins and mucins, are removed from the oils to be sulphonated, e.g. by separation during their refining and deacidification. Fatty acids to be used are preferably purified by e.g. redistillation; and esters, if distillable without decomposition, may be purified in a similar way. Preferably solvents are not used but when viscous solutions result a solvent, e.g. perchlorethylene, may be present.  1.1 to 1.8, especially 1.2 to 1.6, mols. of sulphur trioxide per mol. of fatty acid residue, are preferably employed.  The sulphur trioxide is preferably admixed with an inert gas, e.g. air, nitrogen or-carbon dioxide.  Preferably the gas mixture contains 2-40%, especially 3-20%, by weight of sulphur trioxide.  By mixing the reactants at below 30 DEG  C. sulphonation is avoided.  However, it is not necessary to avoid sulphonation during the mixing stage and this step may be effected at 25-45 DEG  C., e.g. 20-35 DEG  C.  Cooling may be required during the mixing.  The initial sulphonation is preferably effected at 45-65 DEG  C. and the final at 75-95 DEG  C., especially 80-90 DEG  C. The product should not be at above 70 DEG  C. for more than one-third of the total reaction time measured from the time the reaction exceeds 30 DEG  C. until it is stopped by cooling or by adding an alkali, or other substance, to react with the sulphur trioxide.  The product may be bleached with hydrogen peroxide preferably 1-4% of the latter, based on the weight of the product, being used as a 30-50% by weight solution, at 40-80 DEG  C. Sulpho-fatty acids, obtained as products, may be esterified with alcohols, preferably monohydric, of 1-6 carbon atoms, the esterification being effected before or after bleaching.  Examples illustrate the sulphonation of methyl laurate, hardened coconut oil fatty acids and their ethyl and sec.-butyl esters, hardened palm kernel oil fatty acids and their ethyl esters, and caprylic acid optionally mixed with methyl esters of hardened palm kernel oil fatty acids.