Lubricating oil composition for internal combustion engines and method for producing same

Abstract

To provide a lubricating oil composition for internal combustion engines, which is capable of maintaining a high HTHS viscosity with low viscosity, while exhibiting excellent stability of thermal oxidation resistance. A lubricating oil composition for internal combustion engines, which contains a lubricant base oil and 3% by mass or more but less than 40% by mass of a liquid random copolymer of ethylene and an alpha-olefin, said random copolymer being produced using a specific catalyst, and which is configured such that: the kinematic viscosity at 100 degC is 6.9 mm2 / s or more but less than 12.5 mm2 / s; and the lubricant base oil is composed of a mineral oil that has a kinematic viscosity at 100 degC of 2-7 mm2 / s, a viscosity index of 105 or more and a pour point of -10 degC or less and / or a synthetic oil that has a kinematic viscosity at 100 degC of 1-7 mm2 / s, a viscosity index of 120 or more and a pour point of -30 degC or less.

Description

technical field [0001] The present invention relates to a lubricating oil composition for an internal combustion engine and a method for producing the same. Background technique [0002] Petroleum products generally have the so-called temperature dependence of viscosity, that is, when the temperature changes, the viscosity changes greatly. For example, in lubricating oils used in automobiles and the like, it is preferable that the temperature dependence of the viscosity is small. Therefore, in lubricating oil, in order to reduce the temperature dependence of viscosity, a certain polymer soluble in the lubricating oil base can be used as a viscosity modifier (also called a viscosity index improver). In recent years, OCP (olefin copolymer) has been widely used as such a viscosity modifier, and various improvements as exemplified in Patent Document 1 have been made to OCP in order to further improve the performance of lubricating oil. [0003] On the other hand, as the demand...

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Problems solved by technology

[0004] In engine oil, the viscosity modifier is used to maintain the lubricating oil at an appropriate viscosity at high temperature, but the general viscosity index improver has a high molecular weight, and the molecular orientation of the viscosity modifier will occur due to shear stress, which is easy to cause the lubricating oil The viscosity is reduced

Therefore, when a viscosity modifier with a high molecular weight is used to increase the viscosity of HTHS, there is a problem that the 100°C kinematic viscosity of the engine oil itself must be increased.

[0005] On the other hand, low-molecular-weight viscosity modifiers can suppress the decrease in viscosity due to shearing, but are poor in improving the viscosity index. Therefore, compared with the case of using high-molecular-weight viscosity modifiers, low-temperature viscosity characteristics are inferior, and it is difficult to achieve multiple level (multi grade)

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