| abstract |
Overbased sulfurized alkaline earth metal alkylphenate having excellent water tolerance properties in lubricant formulations is prepared by charging into a reactor a preheated (280-380°F) mixture of alkaline earth metal base and alkylphenol (preferably in oil), while simultaneously, but separately, charging a promoter solvent such as a glycol. Then a controlled amount of molten sulfur is charged at a rate that controls the reaction exotherm and off-gas evolution, while maintaining the 280-380°F temperature. Upon completing the sulfur charge, the reactor contents are allowed to interact at 280-380°F long enough to form the sulfurized alkylphenate. While keeping the temperature at 280-380°F, the sulfurized alkylphenate is overbased by charging the reactor simultaneously with controlled amounts of alkaline earth metal base, promoter solvent, and carbon dioxide gas, at a controlled charge rate not much greater or less than the rate at which the reactants undergo reaction to form the overbased phenate. Upon completing the charging of the alkaline earth metal base and promoter solvent, the carbon dioxide charge is continued until completion of the carbonation reaction. Unreacted alkylphenol and promoter solvent are stripped off under vacuum with inert gas purge at 400-480°F, and the resultant reaction product is filtered and the filtered product recovered. The reaction cycle time is no more than about 6 hours, and the filtered product has water tolerance properties normally associated with a batch preparation of the same product requiring a reaction cycle time of at least 8 hours. |