JP2520923B2 - Lubricating base oil for two-cycle gasoline engine - Google Patents

Description

TECHNICAL FIELD The present invention relates to a lubricating base oil for a two-cycle gasoline engine, and more particularly to a lubricating base oil suitable for a two-cycle gasoline engine, which has excellent cleanliness and seizure resistance. Regarding

[Problems to be Solved by Prior Art and Invention]

Generally, a two-cycle gasoline engine such as a small two-wheeled vehicle, unlike other engines, needs to have a large output per displacement, so that the clearance between the piston and the liner is small. Under these circumstances, the above-mentioned lubricating oil for two-cycle gasoline engines is required to have excellent cleanliness and to have excellent seizure resistance so that the deposit in the ring groove and the dirt around the piston are minimized. Sex is required.

However, the lubricating oils that have been used up to now are not always satisfactory in cleanliness and seizure resistance, and with the recent improvements in the performance of small motorcycles and the like, lubricating oils with better properties are required. ing.

[Means for solving problems]

Therefore, the present inventors have conducted intensive studies to solve the above-mentioned drawbacks of conventional lubricating oils for two-cycle gasoline engines and to develop lubricating oils having excellent cleanliness and seizure resistance. . As a result, they have found that highly refined mineral oil or synthetic oil having specific properties is suitable for the purpose, and completed the present invention.

That is, the present invention has a kinematic viscosity at 100 ° C. of 2 to 20 cS.
A lubricating base oil for a two-cycle gasoline engine, which is mainly composed of a base oil having a t, a viscosity index of 75 or more, an aromatic content of 5% or less and a sulfur content of 0.1% or less.

As described above, the base oil of the present invention has a kinematic viscosity at 100 ° C. of 2 to 20 cSt, preferably 3 to 15 cSt. Where 100 ° C
If the kinematic viscosity is less than 2 cSt, the lubricity is lowered and the seizure resistance is inferior. If the kinematic viscosity exceeds 20 cSt, the detergency is lowered and the exhaust gas concentration is increased. The viscosity index is 75 or more, preferably 80 or more. When the viscosity index is less than 75, there is a problem that the cleanliness is deteriorated, and it is not suitable as a lubricating base oil for a two-cycle gasoline engine which is an object of the present invention. Further, the aromatic content (% C _A ) should be 5% or less, preferably 3% or less. % If C _A is more than 5% can not achieve the purpose of cleanliness is poor present invention. The above is the% C _A is a cyclic analytical value based on the n-d-M method.

The base oil has a sulfur content of 0.1% or less,
It is preferably 0.01% or less. This sulfur content is 0.1%
If it exceeds the range, there is a problem that the cleanability is lowered and the seizure resistance is lowered.

As the base oil of the present invention, any mineral oil or synthetic oil can be used as long as it has the above-mentioned properties. Here, as the mineral oil, those obtained by various methods can be used. For example, a distillation oil obtained by distilling a paraffin-based crude oil or an intermediate-base crude oil under atmospheric pressure or distilling a residual oil of atmospheric distillation under reduced pressure is used. Refined oil obtained by refining the oil according to a conventional method,
Alternatively, a deep dewaxed oil obtained by further subjecting this to a deep dewaxing treatment can be mentioned as a preferable example. The method for refining the distillate oil at this time is not particularly limited, and various methods can be considered. Usually, (a) hydrogenation treatment, (b) dewaxing treatment (solvent dehydrogenation or hydrodewaxing), (c) solvent extraction treatment, (d) alkali distillation or sulfuric acid washing treatment,
(E) The white clay treatment is performed alone or in combination in an appropriate order. It is also effective to repeat the same processing by dividing it into a plurality of stages. For example, a method of hydrotreating a distillate oil, or a method of hydrotreating, followed by an alkali distillation or a sulfuric acid washing treatment, a method of hydrotreating a distillate oil, and a dewaxing treatment, a distillate oil as a solvent After the extraction treatment, there is a method of performing a hydrogenation treatment, a method of subjecting the extracted oil to a two-stage or three-stage hydrotreatment, or a method of subjecting the extracted oil to an alkali distillation or a sulfuric acid washing treatment.

As the mineral oil used in the base oil of the present invention, the refined oil thus obtained, or a deep dewaxed oil obtained by subjecting the refined oil to a dewaxing treatment again as needed is preferably used. The dewaxing treatment performed here is called a deep dewaxing treatment, and is performed by a solvent dewaxing treatment method under severe conditions or a catalytic hydrodewaxing treatment method using a zeolite catalyst.

On the other hand, as the synthetic oil used as the base oil of the present invention, the degree of polymerization of α-olefins having 8 to 12 carbon atoms (octene-1, nonene-1, decene-1, undecene-1, dodecene-1, etc.) is 2
The number of oligomers can be up to about 10. Further, as the base oil of the present invention, a mixture of the above mineral oil and synthetic oil in an appropriate ratio may be used.

The base oil of the present invention is mainly composed of the above-mentioned mineral oil or synthetic oil, but when actually used as a lubricating oil for a two-cycle gasoline engine, this base oil can be used as it is. Preferably, this base oil is mixed with polybutene, kerosene, pour point depressant, detergent dispersant, and other various additives, if necessary, and used.

Here, as the detergent dispersant, metal type detergent dispersants such as sulfonate, finate, salicylate, phosphonate, and naphthenate, and ashless detergent dispersants such as succinimide, benzylamine, succinate, and copolymers. Among these, sulfonate and succinimide are particularly preferably used.

〔Example〕

Next, the present invention will be described in more detail with reference to Examples and Comparative Examples.

Examples 1 to 4 and Comparative Examples 1 to 4 Various base oils were mixed with kerosene and a detergent dispersant to prepare sample oils, and a detergency test and a baking test were conducted. The results are shown in Table 1.

 The test method is as follows.

Detergency test Using a commercially available 50cc two-cycle engine with separated lubrication (gasoline specification) and operating at 5000 rpm (full load), 5
After running for 0 hours, the cleanliness of the piston was evaluated with a merit rating (10: best, 0: worst).

Baking test A Falex test was conducted in accordance with ASTM D 2670. The test condition was a constant load (700 lbs), and the time until the seizure was evaluated in seconds. The test materials were pins (aluminum piston materials) and blocks (standard products), and the sample oil was only applied to these sample materials.

[Effects of the Invention] As described above, when the lubricating base oil of the present invention is used as a lubricating oil for a two-cycle gasoline engine, the cleanliness and seizure resistance are far superior to those of conventional lubricating oils. . Therefore, the lubricating base oil of the present invention has a high output,
It is effectively used as a lubricating oil for various high-performance two-stroke gasoline engines.

Claims (1)

(57) [Claims] 1. A two-cycle gasoline engine whose main component is a base oil having a kinematic viscosity at 100 ° C. of 2 to 20 cSt, a viscosity index of 75 or more, an aromatic content of 5% or less and a sulfur content of 0.1% or less. Lubricating oil base oil.