This invention relates to a method of preparing magnesium and calcium dihydrocarbyl dithiophosphates.
The metal dialkyl dithiophosphate family of compounds has been used for some time as additives for lubricating oil compositions to provide improved properties such as antioxidant and antiwear properties. Typically, such dithiophosphate compounds have been prepared by reacting the esters of dithiophosphoric acid with a metal compound such as the oxide, hydroxide or salt. However, there has been considerable difficulty in preparing the magnesium and calcium derivatives because of the relative low reactivity and insolubility of the metal compounds used as starting materials.
Therefore, although the metal dialkyl dithiophosphates and particularly the zinc derivatives have been commercially available and used for many years, there still is the need for a method by which the magnesium and calcium dithiophosphates can be conveniently and economically prepared.