GB437431A - A process for the preparation of xanthates - Google Patents

Abstract

Xanthates are prepared by reacting an alcohol, carbon disulphide, and an alkali metal hydroxide at a temperature and pressure at which water is distilled from the mixture. The hydroxide may be dissolved or suspended in substantially anhydrous alcohol present in molecular excess and the carbon disulphide introduced below the surface, in some cases as a solution in the alcohol reacting. The water may distil as a minimum constant boiling mixture with the excess alcohol and/or carbon disulphide. The reaction vessel may be connected to a distilling or fractionating apparatus and the temperature raised to give a very rapid reaction, 25--125 DEG C., being generally suitable. The pressure may be atmospheric, or above or below atmospheric. If water is present in substantial amount it may be distilled off prior to the introduction of carbon disulphide. The heat of reaction is usually sufficient to maintain the required temperature. Rapid removal of water prevents the formation of hydrated xanthates. Inert organic liquids such as hydrocarbons e.g. benzene, toluene, kerosene, gasoline, ethers or esters may be present and may form azeotropic mixtures with the water or water and alcohol. Carbon disulphide may be admitted intermittently or continuously. The process may be continuous, intermittent, or a batch one. Thus the reactants may be continuously introduced in stoichiometrical proportions, the alcohol always being present in excess of that consumed and removed with the water, and the reacted mixture continuously withdrawn, the xanthate in solution and/or suspension being separated and the remainder returned. Alternative modes of operation may be employed, for example the solution or suspension of alkali hydroxide may be introduced into an excess of carbon disulphide. The process is particularly adapted for the production of sodium and potassium xanthates of monohydric alcohols such as ethyl, propyl, isopropyl, prim and sec butyl, isobutyl, amyl, isoamyl and furfuryl alcohols, used as promotors for froth flotation, as insecticides and vulcanizing accelerators. Other alcohols which can be used are polyhydric alcohols such as ethylene, propylene, butylene, and amylene glycols, polyglycols, glycerol and its homologues in which one or more of the hydroxyl groups may be taken up by ether and ester groups. Unsaturated alcohols such as allyl, crotyl methyl allyl, propargyl, cinnamyl, prim and sec butenols, pentenols, and terpineols may also be reacted. Other cyclic alcohols are benzyl and phenyl propyl, and cyclohexanol. In an example anhydrous sec butyl alcohol saturated with KOH at the boiling point (13 per cent by weight KOH) is heated in an insulated vessel attached to a cooled condenser ending in a receiver attached to a vacuum pump. The pressure is reduced to 110 mm. and heat-supplied till the solution just boils. Heating is discontinued and carbon disulphide diluted with an equal weight of the alcohol slowly introduced from a tube beneath the surface. The rate is regulated to give active distillation of water and alcohol. Slightly more than 1 mol. CS2 for each mol of KOH is used. Heat is supplied if necessary. The solid xanthate is separated, washed, and dried.ALSO:Sodium and potassium xanthates of monohydric alcohols such as ethyl, propyl, isopropyl, prim and sec butyl, isobutyl, amyl, isoamyl, and furfuryl alcohols are used as vulcanization accelerators.ALSO:Sodium and potassium xanthates of monohydric alcohols such as ethyl, propyl, isopropyl, prim and sec butyl, isobutyl, amyl, isoamyl and furfuryl alcohols are used as promotors in froth flotation processes.