Lubricating oil point depressant

The lubricating oil is mainly modulated with mineral oil as the base oil, which is the base oil obtained by refined processing of petroleum distillates. The oil usually contains a certain amount of wax, and some lubricating oil distillates contain more than 40% wax. At low temperature, the wax in the oil will precipitate to form crystals, and be structured into a loose and disorderly three-dimensional crystal network. The oil is wrapped by this loose and disorderly three-dimensional crystal network, which will hinder its flow and even solidify. When the appropriate point depressant is added to the oil, the molecules of the point depressant will adsorb or form eutectic on the surface of the wax, which will have an effect on the growth direction and shape of the wax crystals, preventing the wax from forming a network structure and eutectic, thus effectively maintaining the fluidity of the oil at low temperatures.

Point depressant, also known as oil pour point improvers, refers to chemicals that can reduce the freezing point of lubricating oil, generally polymer organic compounds. The commonly used depressants in lubricating oil are alkyl naphthalene, polyester and polyolefin. Polyesters are mainly polymethacrylate, polyolefin is mainly polyalpha-olefin.

Alkyl naphthalene is the earliest used lubricating oil point depressant. Alkyl naphthalene used as point depressant is produced by chlorinated paraffin process and is still widely used. Alkyl naphthalene as the main point depressant has good economy, and can get better point depressant effect when used in line with other types of point depressant. As a depressant, alkyl naphthalene also plays the role of antioxidant in lubricating oil, the reason why it plays the role of antioxidant is that the polycyclic aromatic hydrocarbons in the hydrocarbon mixture will protect other hydrocarbons with their own oxidation, so that the oxidation rate of the entire oil system will slow down and play the role of antioxidant. In addition, its oxidation products can also play the role of antioxidants, because alkyl naphthalene is easy to be oxidized to alkyl phenols, and phenols are well-known antioxidants, and the oxidation products of this alkyl naphthalene is still a good effect of point lowering agent, so the use of lubricating oil containing alkyl naphthalene point lowering agent even if the oxidation is deeper, its freezing point is not significantly increased.

Polymethacrylate is a kind of multi-effect lubricating oil additive, as a point depressant, it has a good point depressant effect in various lubricating oil, and also plays the role of viscosity index improver and anti-foam agent in oil. Polymethacrylate is an acrylate non-silicon anti-foam agent, the effect of this kind of anti-foam agent is greatly affected by the lubricating oil system, so the use of polymethacrylate as a point depressant must be coordinated with the anti-foam agent.

Polyα-olefin is a non-surfactant point depressant, and the pour point rebound phenomenon that the pour point of oil increases with the increase of point depressant content does not appear when polyα-olefin is used as point depressant. Because the poly-α-olefin point depressant molecule does not contain polar groups, it is best to combine with alkyl naphthalene point depressant or acrylate point depressant, so that the arrangement and distribution of controlled wax crystals can be more orderly, and better point depressant effect can be obtained.

The above three point depressants basically will not have a negative impact on the performance of the oil system, and in addition to the point reduction function, other functions of the oil can be enhanced to a certain extent. The use of point depressant in lubricating oil can effectively reduce the solidification temperature of mineral lubricating oil, improve the low temperature flow of oil, and significantly improve the performance and economic benefit of oil.