| 摘要 |
PROBLEM TO BE SOLVED: To obtain an additive which gives simultaneously an excellent scoring resistance, an excellent wear resistance and an excellent surface fatigue life resistance by carrying out a heat treatment on an acidic phosphoric ester, a phosphonic ester and a boron-containing imide dispersant at a specific temperature and for a specific time. SOLUTION: An additive for a lubricating oil is prepared by carrying out a heat treatment on an acidic phosphoric ester and/or a phosphonic ester of the formula and a boron-containing imide dispersant at 120-150 deg.C for at least 5 h. In the formula, A is hydrogen or hydroxide; (m) is 0 or 1; R1 and R2 are each a l-18C hydrocarbon which can contain one or more oxygen and sulfur atoms and R1 and R2 are not hydrogen simultaneously. No restriction is applied for the boron-containing imide dispersant and the one selected from normally used ones can be used. For example, the one obtained by treating a bispolyalkenyl- or polyalkyl-succinmide with a boron compound or the like can be cited.
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