Detergent-dispersants of high alkalinity for lubricating oils and process for their preparation

A process of preparing a detergent-dispersant from an alkaline-earth metal alkylbenzene sulfonate, an alkylphenol, an alkaline-earth base, an alkylene glycol, sulfur, and carbon dioxide, which process comprises:

• (1) reacting sulfur at a temperature between about 100.degree. and 190.degree. C., with an alkylphenol bearing one or more C.sub.6 -C.sub.60 alkyl substituents, in the presence of a dilution oil, an alkaline-earth metal alkylbenzene sulfonate of a molecular weight of more than about 300, and a T.B.N. less than or equal to 170, a base derived from an alkaline-earth metal, and an alkylene glycol, the amount of alkylphenol used being between about 5 and 35 parts by weight per 100 parts by weight of alkylphenol/alkylbenzene sulfonate mixture, and the amount of alkylbenzene sulfonate being between 95 and 65 parts by weight to 100 parts by weight of alkylphenol/alkylbenzene sulfonate mixture;
• (2) precarbonating the resultant mixture at a temperature of between about 100.degree. and 250.degree. C., with carbon dioxide;
• (3) superalkalinizing and carbonating the resultant precarbonated mixture by means of a base selected from among the alkaline-earth metal oxides and hydroxides and of carbon dioxide in the presence of an alkylene glycol at a temperature of between about 100.degree. and 250.degree. C.;
• and
• (4) eliminating the excess alkylene glycol and recovering the resultant detergent-dispersant of high alkalinity.