Abstract: Polyisobutylene succinimide (PIBSI), an ashless dispersant for lubricating oil, was prepared by using polyisobutylene (PIB) with different molecular weights as raw materials, reacting with amine, maleic anhydride and diluent under different conditions, and its dispersion and oxidation resistance were tested. The effects on PIBSI properties of PIB with different molecular weights and synthesis process of polyisobutylene succinic anhydride (PIBSA) were investigated. The results show that with the increase of the relative molecular weights of PIB, the dispersion and antioxidant properties of PIBSI are improved. Compared with chlorination process, free radical one-step process can not only reduce energy consumption and pollution, but also improve the performance of PIBSI. Among them, PIBSI prepared from PIB raw materials with number average molecular weight of 2 300 by free radical one-step process has the best dispersion performance, and its oil sludge dot dispersion value (SDT) can reach 73.15%.

Key words: polyisobutene, polyisobutylene succinimide, ashless dispersant, dispersibility