Conventionally, the preparation of mineral oil-derived lubricant base oils required drilling of crude oil which is buried underground. From a global environmental point of view, to prepare mineral oil-derived lubricant base oils in such a manner is to add carbon buried underground to the surface circulation system of the earth. Used mineral oil-derived lubricant base oils may be removed by burning or discarded as liquid. During the course of burning, CO2 is added to the surface circulation system which would otherwise not have been. When discarded as liquid, since mineral oil-derived lubricant base oils possess a very low biodegradability of about 10 to about 30% (based on the CEC analysis method), more serious problems are posed. The remainder (i.e. the portion not biodegraded) of the mineral oil-derived lubricant base oils may be absorbed into the ecosystem in the surface circulation system to cause a variety of problems. In addition, from a macroscopic point of view, the problem of serious environmental pollutants, such as sulfur (S), nitrogen (N), heavy metals, etc. present in the crude oil drilled to produce mineral oil-derived lubricant base oils, being included in the surface circulation system and causing troubles cannot be ignored.
In contrast, the problem of adding carbon in the form of CO2 to the surface circulation system does not occur in the case of biomass-derived lubricant base oils, because biomass comes from animals or plants which are already present in the surface circulation system, which is to say that carbon already being circulated in the surface circulation system is utilized in this case. Since the biomass-derived lubricant base oils inherently have a biodegradability of at least about 70% or more and exhibit a biodegradability of nearly 100%, there is little negative impact posed on the ecosystem from burning or discharging into the nature the biomass fat-derived lubricant base oils which are discarded after use. Of course, toxic substances such as S, N, heavy metals, aromatics, etc. are not present throughout the preparation process.
Therefore, in order to overcome the above-described problems which the mineral oil-derived lubricant base oils have, preparation technology for a biomass-derived lubricant base oil has been proposed as a way to make an ecofriendly lubricating oil which has high biodegradability and is free of toxic substances (S, N, aromatics, heavy metals).
In addition, a lubricating oil is a physical mixture of about 80% of a base oil and about 20% of additives. As the substance which most prominently determines lubrication properties—such as viscosity, a viscosity index, a low-temperature fluidity, etc.—of a lubricating oil, a base oil has a hydrocarbon chain structure and can determine major lubrication properties by its structural regularity, molecular weight, etc. However, a lubricating oil may require alterations in the lubrication properties by small extents depending on the application, and, when the lubricating oil does not meet certain standards of lubrication properties, additives may be used to supplement any insufficient lubrication properties. Examples of such additives include a detergent, a dispersant, an antioxidant, a corrosion inhibitor, a viscosity index improver, a pour point depressant, etc. However, most of such additives include aromatic substances, etc. and thus have problems of being poorly miscible with base oils each of which makes up about 80% of a lubricating oil.
An alkyl naphthalene is introduced to the conventional lubricant base oil for improving a low-temperature fluidity and facilitating a mixing of the lubricant base oil with additives. However, alkyl naphthalenes are substances prepared as a result of bonding between alkyl groups and aromatic compounds and thus have problems of having a low biodegradability.
Therefore, the development of a lubricant base oil—which is highly biodegradable and also able to inhibit the production of additional CO2 greenhouse gas and thus is ecofriendly, while also retaining the merits as a dispersant and advantages of an improved low-temperature fluidity, all of which the conventional lubricant base oils have—is immediately required.