Patent GB-1063431-A (GB)
Title: Improvements in and relating to the bleaching of sulphonation products
IPC: C07C303/42
Filed: 1965-01-14
Abstract: Acid sulphonation products, which are defined as the esters of a -sulpho fatty acids which may be derived from C1- 4 monohydric aliphatic or polyhydric alcohols and which have been obtained in a continuous process by reacting substantially saturated fatty acid esters, the total fatty acid residues of which comprise at least 70% of fatty acids with 16-22 carbon atoms, or of mixtures of such acids, with gaseous sulphur trioxide diluted with an inert gas, in the absence of solvents or substances forming adducts with sulphur trioxide, using a quantity of sulphur trioxide of from 1.1 to 1.7 mol. SO3 per fatty acid residue, are bleached in a first partial bleaching stage in which there is added to the sulphonation products present in a flowable state at temperatures from 45-70 DEG  C. not more than 4% of the weigut of the sulphonation product of bleaching agent comprising an aqueous solution or suspension of hydrogen peroxide, or a substance that forms hydrogen peroxide under the reaction conditions, chlorites, chlorates or perchlorates, the corresponding free acids or their anhydrides and containing the said bleaching agents in a concentration of 10 to 70% by weight, effecting the bleaching at temperatures not exceeding 100 DEG  C., treating the partially bleached sulphonation product with neutralizing agent in such amount that a 5% aqueous solution of the paste obtained possesses a pH value of at least 4, and completing the bleaching in a second bleaching stage with hydrogen peroxide or hypochlorite at temperatures from 10 DEG  to 100 DEG  C. Before the addition of bleaching agent in the first stage, the temperature of the sulphonic acid paste should not exceed 70 DEG  C., and instead of hydrogen peroxide, substances may be used which form hydrogen peroxide under the reaction conditions, for example salts or peroxy hydrates of hydrogen peroxide or their compounds of addition with organic substances, and the chlorites, chlorates and perchlorates may also be used as the free acids or as their anhydrides.  The neutralizing agent may be an inorganic base, for example the carbonates or bicarbonates derived from ammonia, sodium, potassium or magnesium, or an organic base such as a lower C1- 6 amine or an alkylolamine, for example mono-, di-, or tri-ethanolamine, and they may be used as aqueous solutions in concentrations from 1 to 30% by weight of neutralizing agent or alone where the neutralizing agent is itself a liquid.  In the second bleaching stage, the bleaching agent is preferably hydrogen peroxide or compounds which form hydrogen peroxide under the bleaching conditions, or hypochlorous acid or its salts, and the quantity used is suitably 2 to 8% by weight of bleaching agent.  In one suitable method for carrying out the continuous bleaching operation, the sulphonation product and the bleaching agent of the first stage are charged to storage vessels from which they are conveyed via dosing pumps to a mixer. The sulphonation product mixed with bleaching agent is then passed through a heat exchanger and via a temperature-controllable stock vessel into a second mixer, into which the neutralizing agent and the second stage bleaching agent are introduced by dosing pumps. A portion of the sulphonation product treated with first stage bleaching agent is returned to the first mixer wherein the ratio by weight of partly bleached returned material to unbleached sulphonate may be in the range 1: 1 to 9: 1. The product from the second mixer passes to another storage vessel where the second bleaching stage is effected.  Specified fatty acid starting materials which are sulphonated and then bleached are tallow fatty acid methyl esters and the methyl esters of a hardened coconut fatty acid.