Process for preparing an overbased detergent

Abstract

The invention relates to a process for preparing an overbased metal detergent in an oil medium comprising the steps of: (1) providing a metal salt selected from the group consisting of a hydrocarbyl-substituted organic acid; a hydrocarbyl-substituted phenol, a phenate, a hydrocarbyl-substituted carboxylate and mixtures thereof; (2) further providing methanol and a mixture of alcohols containing 2 to about 7 carbon atoms, wherein the mole ratio of methanol to the mixture of alcohols is about 2.2 or less, to form a mixture; (3) further providing a basic metal compound; (4) reacting the mixture of step (3) with carbon dioxide to form a carbonated overbased metal sulphonate; (5) performing steps (3) and (4) at least three additional times upon the product of step (4); (6) thereafter removing at least a portion of the water produced in steps (1)-(5) and of the alcohols introduced in step (2); (7) performing step (2) again, upon the product of step (6); (8) performing steps (3) and (4) at least two additional times upon the product of step (7); and (9) thereafter removing a substantial portion of the water and of the alcohols from the composition; wherein the oil medium is present in an amount such that the weight ratio of the acid corresponding to the metal salt of (1) to the oil medium is 0.3 to 1.4; and wherein step (6) is required when the hydrocarbyl-substituted organic acid is a hydrocarbyl-substituted sulphonic acid. The invention further relates to its use in internal combustion engines.