Influence of Methanol on the Structure and Performance of Overbased Calcium Alkyl-Salicylate

The influence of methanol on overbased calcium alkyl-salicylates was studied with freeze-etching electron-microscope, FT-IR, and calcium distribution test. Although chemical structures of products produced with different methanol amounts are similar, the colloidal structures are different. With increasing dosage of methanol, the size of colloidal particles decreases at first, and then increases. Similar changing tendency is found in the total basicity number of the product. The relative contents of calcium hydroxide in the colloid are inversely proportional to the colloidal particle size. The products with smaller particles exhibits better anti-wear properties, and thermal detergency. The primary mechanism of methanol is also discussed according to the above results.