PROCESS FOR THE MANUFACTURE OF SALT MIXTURES OF ALKALI METAL SALTS OF 0,0-DIALKYLDITHIOPHOSPHORIC ACIDS AND THE CORRESPONDING ALKALI METAL CARBONATES

1275364 Sodium and potassium O O-dialkyldithiophosphates KNAPSACK AG 30 Sept 1970 [24 Oct 1969] 46518/70 Heading C2P A mixture of compounds of the formula (RO) 2 PS(SMe) and the corresponding carbonates Me 2 CO 3 , where Me is sodium or potassium and R is C 1-18 alkyl (the Rs are the same or different) is produced by introducing into an acid (RO) 2 PS(SH) an excess of at least one of the carbonates Me 2 CO 3 so as to produce a mixture with an overall alkali metal carbonate content of 10 to 30 weight per cent, and if desired, blending this mixture, while still in the same mixing apparatus with solid diluent whereby the alkali metal O,O dialkyldithiophosphate content in the product is reduced to the requisite value. Preferably the 0,0-dialkyldithiophosphoric acid is prepared by reacting phosphorus pentasulphide with a 5 to 15 weight per cent excess of an alcohol ROH and heating the crude produce under reduced pressure. The solid diluent may be crystalline alkali metal carbonate or sodium chloride, and may be added to the mixture in order to produce mixtures containing less than 70% by weight of the phosphorus compound.