Patent ID: 6958409

Claim:
A process for the manufacture of a low sediment overbased metal dialkyl dithiophosphate composition comprising: a) reacting a phosphorous sulfide reactant with at least one C 3 to C 12 primary alcohol to form a dialkyl dithiophosphoric acid; b) neutralizing the dialkyl dithiophosphoric acid with a full charge of metal oxide for a sufficient amount of time, to form an intermediate product comprising basic and neutral dialkyl dithiophosphate salts, said intermediate product characterized as having a ratio of basic salt to neutral salt of about 0.075 to about 0.75, wherein said ratio is determined by 31 P-NMR analysis; c) adding to the intermediate product from 1.5 to 5 weight percent based upon the metal oxide charge, of at least one aliphatic mono-carboxylic acid promoter having 1 to 5 carbon atoms to form a reaction mass; and d) reacting the reaction mass under suitable temperature and time to form an overbased metal dialkyl dithiophosphate product characterized as having a crude sediment before filtration of 0.01 weight percent or less.