JPH0587119B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a lubricating oil composition for sliding bearings, and more specifically, it has excellent oxidation stability, conformability, seizure resistance, wear resistance, etc., and thus increases the stability and durability of bearings. The present invention relates to a lubricating oil composition that can be used as a lubricating oil composition. [Prior art and problems to be solved by the invention] Generally, sliding bearings used under fluid lubrication conditions reduce fluid resistance and save energy, so the lubricating oil used tends to be of lower viscosity grade. be. In addition, the miniaturization and higher performance of various devices have led to stricter bearing conditions and a reduction in bearing oil film.As a result, the chances of contact between the shaft and the bearing have increased, increasing the risk of abnormal bearing wear and seizure. It is increasing. Therefore, in recent years, the miniaturization of such devices,
With the rapid advancement in performance, there is a strong desire to develop a superior lubricating oil that can maintain good lubrication even under severe bearing conditions. Up to now, attempts have been made to apply lubricating oils containing extreme pressure agents (gear oils, wear-resistant hydraulic oils, etc.), but such lubricating oils are not effective against steel-to-steel contact. Although it is effective to some extent, it is hardly expected to be effective against contact between a sliding bearing (non-ferrous) and a shaft (steel), and it also causes corrosion of the bearing. Additionally, lubricating oils containing alcohol compounds (Japanese Patent Laid-open No. 161486/1986) and lubricating oils containing graphite (Japanese Patent Laid-Open No. 23491/1982) are also known, but none of these In some cases, the effect of improving lubrication performance was small, or even acted as a foreign substance, leading to increased wear. Furthermore, lubricating oils containing fatty acid compounds have the problem of causing bearing corrosion. The present inventors have solved the above-mentioned problems of conventional plain bearings, and are able to maintain sufficiently high lubricity even under severe bearing conditions, achieve energy savings, and increase the stability and durability of the bearing. We conducted extensive research to develop an excellent lubricant. [Means for solving the problem] As a result, we discovered that the use of a base oil that has oxidation stability above a certain value and blending a specific ester with this base oil is suitable for the above purpose. Ta. The present invention was completed based on this knowledge. That is, the present invention has (A) a kinematic viscosity of 5 at 40°C.
~500 cSt, aromatic content of 2% or less, sulfur content of 100 ppm or less, (B) 0.5 to 10 esters of fatty acids with 12 to 22 carbon atoms and monohydric alcohols with 1 to 18 carbon atoms. The present invention provides a lubricating oil composition for sliding bearings, characterized in that the lubricating oil composition is blended in a proportion by weight (based on the entire composition). The lubricating oil composition of the present invention has component (A) as described above.
Component (B) is blended here, and the base oil as component (A) is required to have excellent antioxidant properties in order to ensure the safety and durability of various devices. As a guideline for this antioxidant property, it is desirable that the finished oil (i.e., lubricating oil composition) be tested in a rotating bomb oxidation test (RBOT) for 200 minutes or more (measurement temperature 150°C), and as a base oil that satisfies these conditions, ,
As an oil containing 0.5% by weight of 2,6-di-t-butyl-p-cresol (DBPC), RBOT
It is sufficient if the period is 400 minutes or more (measurement temperature 150°C). The specific properties of a base oil that satisfies these requirements include a kinematic viscosity of 5 to 500 cSt at 40°C, an aromatic content of 2% or less, and a sulfur content.
It must be 100ppm or less. As mentioned above, the base oil as component (A) may have a kinematic viscosity of 5 to 500 cSt at 40°C, but preferably
It is 10~350cSt. If the kinematic viscosity is less than 5 cSt, there will be a problem that the ability to form an oil film will be reduced, and if it exceeds 500 cSt, there will be a problem that bearing loss will become excessively large. Aromatic content of the above base oil (%C _A ; n-d-M
The ring analysis value based on the method) may be 2% or less, preferably 1% or less. This %C _A is 2
There is a problem that the antioxidant property decreases when the amount exceeds 100%. Furthermore, regarding the sulfur content of the base oil,
It should be 100ppm or less, but preferably 50ppm
It is as follows. Here, there is a problem that when the sulfur content exceeds 100 ppm, the antioxidant property decreases. In the present invention, any base oil having such properties can be used regardless of whether it is a mineral oil or a synthetic oil, and these may be used alone or in combination. Examples of mineral oils used as base oils include distillate oils obtained by atmospheric distillation of paraffin base crude oil or intermediate base crude oil, or vacuum distillation of residual oil from atmospheric distillation, or Refined oils obtained by refining according to methods such as solvent-refined oils, hydrogenated refined oils, dewaxed oils, clay-treated oils, and the like can be mentioned. Note that the dewaxed oil is particularly preferably a deeply dewaxed oil that has been highly dewaxed by hydrogenation dewaxing using a zeolite catalyst or the like. There are no particular restrictions on the synthetic oil, and various types can be used, such as poly-α-olefin,
Hydrocarbon-based synthetic oils such as polyptene are preferred. Next, in the lubricating oil composition of the present invention, an ester is blended as the component (B) into the base oil, which is the component (A). Must be an ester with a monohydric alcohol. Particularly preferred are fatty acids having 14 to 20 carbon atoms and monohydric alcohols having 1 to 8 carbon atoms. Monohydric alcohol esters of polybasic acids and fatty acid esters of polyhydric alcohols have small effects and are also insufficient in terms of thermal stability, water separation, etc. Also,
If the number of carbon atoms in the fatty acid constituting the ester is less than 11 or more than 23, the solubility will decrease, and if the monohydric alcohol has more than 19 carbon atoms, the solubility will decrease and little improvement in friction properties can be expected. . Preferred esters suitably used in the present invention include isopropyl palmitate, butyl stearate, isopropyl myristate, 2-ethylhexyl stearate, 2-ethylhexyl palmitate, and myristic acid. Butyl ester, 2-ethylhexyl myristate, butyl palmitate, isopropyl stearate, methyl oleate, butyl oleate, 2-oleic acid
-ethylhexyl ester, oleyl oleate, methyl erucate, isopropyl erucate, butyl erucate,
Examples include lauric acid lauryl ester, and these may be used alone or in combination. Further, in the present invention, the blending ratio of the ester is 0.5 to 10% by weight, preferably 1 to 5% by weight, based on the entire composition. Here, if the blending ratio of ester is less than 0.5% by weight, hardly any improvement in friction performance can be expected, and even if it exceeds 10% by weight, no increase in the effect can be expected. The lubricating oil composition of the present invention may be obtained by blending an ester as a component (B) in a predetermined ratio with the base oil as the above component (A), but if necessary, an oxidized Inhibitors (phenolic antioxidants such as DBPC, amine antioxidants, etc.), rust inhibitors (alkenyl succinic acid partial esters, lower fatty acids, etc.), viscosity index improvers (polymethacrylate, olefin copolymers, etc.), It is also effective to blend appropriate amounts of pour point improvers (polymethacrylate, etc.), antifoaming agents (silicone oil, etc.), etc. [Example] Next, the present invention will be explained in more detail with reference to Examples and Comparative Examples. Examples 1 to 5 and Comparative Examples 1 to 6 A lubricating oil composition was prepared by blending the base oil shown in Table 1 with additives such as esters shown in Table 2 at a predetermined ratio. Various performance evaluations were performed on the composition. The results are shown in Table 2. The performance evaluation shown in Table 2 was performed as follows. (1) RBOT (Rotating Bomb Oxidation Test) It was conducted at a temperature of 150°C in accordance with ASTM D 2272. (2) Friction coefficient Using a Chimken friction tester, as a test piece,
WJ-3 (Bavitt alloy; composition Sn80.13wt%,
Sb12.06wt%, Cu4.21wt%, Pb3.59wt%) (partial bearing shape) - SUJ-2 (contact width 13.1mm, HRc62, chimken cup diameter 49.2mm, mirror finish) (ring)
oil temperature 45℃, sliding speed 0.08m/sec x 60
minute, load 363Kgf (surface pressure at this time: 198Kgf/cm ² )
Under these conditions, the friction coefficient immediately after loading (initial friction coefficient) and after 60 minutes were measured. (3) Break-in performance Using the same Chimken friction tester and test piece as in (2) above (but with a ring contact width of 3 mm), at an oil temperature of 40°C and a sliding speed of 2.1 m/sec, a surface pressure of 216 Kgf/
cm ² x 30 minutes, 432Kgf/cm ² x 30 minutes, 648Kgf/cm ² x 30
A stepwise load of 10 millivolts was applied between the rotating ring and the partial bearing, and the continuity state (%) at the time of contact was evaluated by electrical measurement. That is, if there is complete fluid lubrication between the rotating ring and the partial bearing, the electrical resistance will be infinite and the conductivity will be 0% because there are no contact parts. On the other hand, with mixed lubrication, there will be partial contact and the conductivity will be a certain value (0 to
100), and if it is mixed/boundary lubrication, there will be constant contact and the conductivity will be 100%. (4) Seizure resistance A Soda four-ball tester was used, and a cylindrical end face test piece [lead bronze (composition: Cu67.06wt%,
Pb26.00wt%, Sn5.48wt%, Ni0.94wt%)−S45C
(HRc36, mirror finish)], oil temperature 40℃ (200℃)
ml/min), surface pressure 25Kgf at sliding speed 1m/sec
−/cm ² ×Gradual load every 10 minutes up to 300Kgf/
^cm2 , and the seizure (torque suddenly increases) load was evaluated by surface pressure. (5) Wear resistance After the seizure resistance test in (4) above (maximum load surface pressure 300Kg
f/cm ² ×10 minutes)) The lead bronze surface wear depth (μm) was evaluated.

【table】

【table】

〔Effect of the invention〕

As mentioned above, according to the lubricating oil composition of the present invention,
As a sliding bearing oil, it has excellent oxidation stability, conformability, seizure resistance, and wear resistance, and has a small coefficient of friction, increasing the stability and durability of bearings. Furthermore, the lubricating oil composition of the present invention can be used in sliding bearings under severe conditions, and can extend bearing maintenance intervals while reducing power loss. Therefore, the lubricating oil composition of the present invention can be used as a lubricating oil for sliding bearings, especially non-ferrous sliding bearings.
be used effectively.

Claims (1)

[Claims] 1 (A) A base oil with a kinematic viscosity of 5 to 500 cSt at 40°C, an aromatic content of 2% or less, and a sulfur content of 100 ppm or less, (B) a fatty acid with a carbon number of 12 to 22 and a carbon number of 1 to 1.
A lubricating oil composition for sliding bearings, characterized in that it contains 0.5 to 10% by weight (based on the entire composition) of an ester with 18 monohydric alcohols.