JP5391526B2 - Lubricating oil composition for impregnation - Google Patents

Description

The present invention relates to a lubricating oil composition for impregnation . More specifically, the present invention relates to a lubricating oil composition for impregnation that enables a reduction in the coefficient of friction at the start of sliding.

  Sintered oil-impregnated bearings are impregnated with lubricating oil in countless holes made of baked metal powder, and the pressure generated when the shaft rotates causes the lubricating oil in the bearing to ooze out during rotation and the pressure when stopped. One characteristic is that the lubricating oil is retained by a pumping action in which the lubricating oil is reduced and further absorbed by the capillary action into the bearing. Because of this mechanism, sufficient lubricating oil is not supplied to the sliding portion at the time of start-up, and the harsh conditions are likely to cause metal contact.

  In addition, when lubricating oil using a low-viscosity base oil, which is advantageous for reducing rotational torque, is used, a sufficient oil film cannot be obtained on the sliding part, and shaft runout that causes unstable rotation of the shaft occurs. Cheap. On the other hand, when a high-viscosity base oil is blended in order to suppress shaft runout, the rotational torque is increased.

In order to solve such a problem, generally, an oily agent, an antiwear agent, an extreme pressure agent, and the like are blended into the lubricating oil, but at the initial stage of use before these perform their functions. It is difficult to make the effect effective. In addition, these additives may corrode or erode sliding members such as metals and resins, and in contact with metal powder in a very large surface area such as sintered bearings, or resin members There is a problem in developing applications that come into contact with
Japanese Patent Laid-Open No. 2002-180078 Japanese Patent No. 3,433,402

An object of the present invention is to provide a lubricating oil composition for impregnation capable of reducing a friction coefficient at the time of sliding start.

The object of the present invention is to provide at least one base oil comprising a synthetic oil having a composition of 100 to 26.95% by weight of a synthetic hydrocarbon oil and 0 to 73.05% by weight of an ester synthetic oil and a glycol oil . This is achieved by a lubricating oil composition for impregnation comprising metal soap having a hydroxyl group or metal composite soap in a proportion of 0.5 to 3% by weight.

The lubricating oil composition for impregnation of the present invention has an excellent effect of enabling reduction of a friction coefficient at the time of rotation or reciprocating sliding start. This is because the metal (composite) soap is maintained in the sliding portion even when the sliding is stopped, and this can reduce the friction coefficient and the torque at the time of sliding start. By reducing the friction coefficient at the start of sliding, it is possible to achieve a longer life of the applied member. The lubricating oil composition for impregnation of the present invention that exhibits such an effect can exert a desired effect without excessively adding an anti-wear agent or the like, so that it can be applied to any sliding member made of metal or resin. However, it can be effectively applied to these members without adverse effects. In addition, even when using a low-viscosity base oil, the metal (composite) soap maintains the oil film thickness, and has the effect of reducing shaft runout during rotation, for example, when a high-viscosity base oil is blended. Further, there is no increase in rotational torque.

The base oil is used as a synthetic hydrocarbon oil alone or as a mixed oil thereof with at least one of an ester synthetic oil and a glycol oil (including polyoxyethylene oil) . Synthetic hydrocarbon oils include poly α-olefins, ethylene-α-olefin co-oligomers, polybutenes or their hydrides, alkylbenzenes, alkyl naphthalenes, etc., and ester-based synthetic oils include polyol esters, dibasic fatty acid esters, Aromatic polyvalent carboxylic acid ester, phosphoric acid ester, phosphorous acid ester, carbonic acid ester, etc., and examples of glycol oil are polyoxypropylene glycol monoether, poly (oxyethylene-oxypropylene) glycol monoether, etc. Is done. When the synthetic hydrocarbon oil is used as a mixed oil with other base oils, the synthetic hydrocarbon oil in the mixed oil is used in a mixing ratio of at least 26.95% by weight.

These base oils generally have a kinematic viscosity at 40 ° C. (based on JIS K2283) of about 20 to 800 mm ² / sec. Of these, for bearings and bushes, those of about 20 to 250 mm ² / sec, preferably about 20 to 100 mm ² / sec are used, and chain oil, gear oil, etc. do not require low temperature properties, In applications in which heat resistance is important, a material having a temperature of about 100 to 800 mm ² / second, preferably about 100 to 400 mm ² / second is used. Here, if a base oil with a kinematic viscosity higher than this is used for bearings and bushes, the low temperature fluidity deteriorates and the torque increases in the low temperature range, while a base oil with a kinematic viscosity lower than this is used. If used, it is not sufficient in terms of volatility, and a sufficient oil film cannot be maintained under high temperature conditions. Also, for chains and gears that do not require very low temperature and use heat resistance, using a base oil with a kinematic viscosity higher than this is satisfactory in terms of heat resistance, but a wide range From the standpoint of obtaining good sliding characteristics within the operating temperature range, if a base oil having a kinematic viscosity lower than this is used, heat resistance cannot be sufficiently satisfied.

In the base oil, metal soap or metal composite soap, preferably lithium soap or lithium composite soap is used in a proportion of 0.5 to 3% by weight. If metal (composite) soap is used in a smaller proportion, the soap will not entangle and self-aggregate, so a uniform dispersion cannot be obtained and the friction coefficient at the start of sliding is reduced. The purpose cannot be achieved. On the other hand, if it is used in a proportion larger than this, the apparent viscosity of the composition becomes too high, so that it becomes difficult to impregnate, for example, a porous bearing .

Lithium soap is a lithium salt of an aliphatic monocarboxylic acid having 12 to 24 carbon atoms containing at least one hydroxyl group, and lithium composite soap is (a) a carbon having at least one hydroxyl group. the number 12-24 of the lithium salt of an aliphatic monocarboxylic acid and (b) and at least one aliphatic dicarboxylic acid or its diester having 2 to 12 carbon atoms and aromatic monocarboxylic acids or esters thereof having 7 to 24 carbon atoms Is used. As the metal soap, in addition to lithium soap, barium soap, barium composite soap, calcium soap, calcium composite soap, aluminum soap, aluminum composite soap and the like are used.

Antioxidants, rust inhibitors, corrosion inhibitors, extreme pressure agents, oiliness agents, solid lubricants, and viscosity index improvements that have been added to the lubricating oil in the composition and added to the conventional lubricating oil. Other additives such as an agent can be added as necessary to form a lubricant. Examples of the antioxidant include phenolic antioxidants such as 2,6-ditertiarybutyl-4-methylphenol and 4,4′-methylenebis (2,6-ditertiarybutylphenol), alkyldiphenylamine, Examples include amine-based antioxidants such as phenylamine, phenyl-α-naphthylamine, phenothiazine, alkylated phenyl-α-naphthylamine , and alkylated phenothiazine , and phosphoric acid-based antioxidants and sulfur-based antioxidants.

  Examples of the rust preventive agent include fatty acids, fatty acid amines, alkyl sulfonic acid metal salts, alkyl sulfonic acid amine salts, oxidized paraffins, polyoxyethylene alkyl ethers, and the like, and corrosion inhibitors include, for example, benzotriazole and benzimidazole. , Thiadiazole and the like.

  Examples of extreme pressure agents include phosphorous compounds such as phosphate esters, phosphite esters, phosphate ester amine salts, sulfur compounds such as sulfides and disulfides, dialkyldithiophosphate metal salts, and dialkyldithiocarbamic acid metal salts. And sulfur-based compound metal salts, chlorinated paraffin, chlorinated diphenyl and other chlorinated compounds.

  Examples of the oily agent include fatty acids or esters thereof, higher alcohols, polyhydric alcohols or esters thereof, aliphatic amines, fatty acid monoglycerides, montan waxes, amide waxes, and the like. Examples of the solid lubricant include molybdenum disulfide, graphite, boron nitride, and silane nitride.

  Examples of the viscosity index improver include polymethacrylate, ethylene-propylene copolymer, polyisobutylene, polyalkylstyrene, styrene-isoprene copolymer hydride, and the like.

  Preparation of the composition is a method in which a predetermined amount of metal (composite) soap is added to a lubricating oil composition in which other necessary additives have been added to the base oil in advance, and the mixture is sufficiently kneaded with a homomixer, three-roll or high-pressure homogenizer, etc. Is done by.

  Next, the present invention will be described with reference to examples.

Comparative Example 1
Synthetic hydrocarbon oil (Inobean product PAO 2, 40 ° C kinematic viscosity; 5mm ² / sec) 45.1% by weight
Synthetic hydrocarbon oil (manufactured by PAO 4, 40 ° C kinematic viscosity; 19mm ² / sec) 53.8〃
Amine-based antioxidants (Ciba Specialty Chemicals product 1.0 製品
(Irganox L57)
Synthetic Ca sulfonate 0.1 〃
The above components were blended with a homomixer to prepare a lubricating oil composition.

Comparative Example 2
In Comparative Example 1, instead of synthetic hydrocarbon oil (PAO 2, PAO 4), synthetic hydrocarbon oil (Inobean product PAO 6, 40 ° C kinematic viscosity: 31mm ² / sec) 74.2% by weight and synthetic hydrocarbon oil (the company's product) PAO 40, 40 ° C. kinematic viscosity; 390 mm ² / sec) 24.7% by weight was used.

Comparative Example 3
In Comparative Example 1, 98.9% by weight of bis (2-ethylhexyl) sebacate (Daihachi Chemical Products DOS, 40 ° C. kinematic viscosity; 12 mm ² / sec) was used instead of the synthetic hydrocarbon oil (PAO 2, PAO 4). It was.

Comparative Example 4
In Comparative Example 1, instead of synthetic hydrocarbon oil (PAO 2, PAO 4), synthetic hydrocarbon oil (Inobean product PAO 6, kinematic viscosity at 40 ° C; 31 mm ² / sec) 18.8 wt%, synthetic hydrocarbon oil (the company's product) PAO 40, 40 ° C. kinematic viscosity; 390 mm ² / sec) 5.7 wt% and trimethylolpropane C _{8 to} C ₁₂ carboxylic acid ester (Cognis product, 40 ° C. kinematic viscosity; 18 mm ² / sec) 66.4 wt% were used, and A PMA viscosity index improver (Mw = 250,000) 8.0% by weight synthesized in pentaerythritol C ₆ -C ₉ carboxylic acid ester was used.

Comparative Example 5
In Comparative Example 1, instead of synthetic hydrocarbon oil (PAO 2 and PAO 4), poly (oxyethylene oxypropylene) glycol monoether (Sanyo Chemicals, 40 ° C. kinematic viscosity; 135 mm ² / sec) 98.9 wt% Was used.

The lubricating oil compositions obtained in the above comparative examples were subjected to kinematic viscosity, viscosity index, pour point measurement, and SRV friction test (starting under micro-vibration conditions and measurement of the coefficient of friction when stable). .
Kinematic viscosity: Measured at 40 ° C and 100 ° C according to JIS K2283 Viscosity index: Calculated from kinematic viscosity at 40 ° C and 100 ° C according to JIS K2283 Pour point: According to JIS K2269
SRV friction test: Using a SRV friction tester, the lower test piece is a SUJ2 disk, the upper test piece is a 10 mm diameter SUJ2 ball, and these are point-contacted, with a frequency of 50 Hz, amplitude of 2 mm, load of 100 N, temperature of 80 Measure the coefficient of friction at start-up and stability under the condition of ℃ (The test temperature was set to 80 ℃ to make it difficult to hold the oil film)

The results obtained in Comparative Examples 1 to 5 are shown in Table 1 below.
Table 1
Comparative example
Measurement item 1 2 3 4 5
Kinematic viscosity
40 ° C (mm ² / s) 10 56 12 60 136
100 ° C (mm ² / s) 3 9 3 13 25
Viscosity index 105 140 130 201 219
Pour point (° C) -60.0 -55.0 -70.0 -55.0 -35.0
SRV friction test Coefficient of friction at start-up 0.405 0.415 0.205 0.290 0.181
Coefficient of friction at stability 0.170 0.175 0.115 0.150 0.135

Example 1
To 99.0 wt% of the lubricating oil composition prepared in Comparative Example 1 (base oil: 100 wt% of synthetic hydrocarbon oil) , 1.0 wt% of 12-hydroxystearic acid lithium salt was added.

Example 2
The lubricating oil composition prepared in Comparative Example 2 (base oil: synthetic hydrocarbon oil 100% by weight) 97.0% by weight and Ba composite soap (composite soap of 12-hydroxybarium stearate and sebacic acid) 3.0% by weight Added.

Example 3
To 99.0% by weight of the lubricating oil composition prepared in Comparative Example 2, 1.0% by weight of lithium 12-hydroxystearate was added.

Example 4
To 98.0% by weight of the lubricating oil composition prepared in Comparative Example 2, 2.0% by weight of 12-hydroxystearic acid lithium salt was added.

Example 5
Li complex soap (complex soap of lithium 12-hydroxystearate and azelaic acid) 2.0% by weight was added to 98.0% by weight of the lubricating oil composition prepared in Comparative Example 2.

Example 6 (Reference Example)
To 99.2% by weight of the lubricating oil composition prepared in Comparative Example 3 (base oil: ester-based synthetic oil 100% by weight) , 0.8% by weight of 12-hydroxystearic acid lithium salt was added.

Example 7
The lubricating oil composition prepared in Comparative Example 4 (base oil: 26.95% by weight of synthetic hydrocarbon oil, 73.05% by weight of ester-based synthetic oil) was added to 99.5% by weight of 0.5% by weight of 12-hydroxystearic acid lithium salt. .

Example 8
To 97.0 wt% of the lubricating oil composition prepared in Comparative Example 4, 3.0 wt% of 12-hydroxystearic acid lithium salt was added.

Example 9 (Reference Example)
To 99.0% by weight of the lubricating oil composition prepared in Comparative Example 5 (base oil: 100% by weight of glycol oil) , 1.0% by weight of lithium 12-hydroxystearate was added.

Example 10 (Reference Example)
To 97.0% by weight of the lubricating oil composition prepared in Comparative Example 5, 3.0% by weight of Ba composite soap (composite soap of 12-hydroxybarium stearate and sebacic acid) was added.

About the lubricating oil composition for impregnation obtained in each Example, examination of fluidity and measurement of SRV friction test were performed. Here, the fluidity is determined by measuring the viscosity under the conditions of 25 ° C. and a shear rate of 300 / sec using a cone plate rheometer, and determining that the fluidity is less than 5,000 mPa · sec. evaluated.

The results obtained are shown in Table 2 below. Here, the fluidity , particularly the coefficient of friction at start-up , was good in all examples. The numerical value in parentheses below the starting friction coefficient value is the starting friction coefficient value in each corresponding comparative example.
Table 2
Example
Measurement item 1 2 3 4 5 6 7
SRV friction test Coefficient of friction at start-up 0.208 0.170 0.203 0.176 0.186 0.133 0.189
(0.405) (0.415) (0.415) (0.415) (0.415) (0.205) (0.290)
Coefficient of friction at stability 0.165 0.178 0.179 0.174 0.177 0.115 0.151

Table 2 (continued)
Example
Measurement item 8 9 10
SRV friction test Start-up friction coefficient 0.150 0.151 0.147
(0.290) (0.181) (0.181)
Coefficient of friction at stability 0.147 0.133 0.135

Comparative Example 6
0.05% by weight of lithium 12-hydroxystearate was added to 99.95% by weight of the lubricating oil composition prepared in Comparative Example 1.

Comparative Example 7
To 99.95% by weight of the lubricating oil composition prepared in Comparative Example 2, 0.05% by weight of Ba composite soap (composite soap of 12-hydroxy barium stearate and sebacic acid) was added.

Comparative Example 8
0.05% by weight of lithium 12-hydroxystearate was added to 99.95% by weight of the lubricating oil composition prepared in Comparative Example 3.

Comparative Example 9
0.05% by weight of 12-hydroxystearic acid lithium salt was added to 99.95% by weight of the lubricating oil composition prepared in Comparative Example 4.

Comparative Example 10
0.05% by weight of lithium 12-hydroxystearate was added to 99.95% by weight of the lubricating oil composition prepared in Comparative Example 5.

Comparative Example 11
To 92.0% by weight of the lubricating oil composition prepared in Comparative Example 1, 8.0% by weight of lithium 12-hydroxystearate was added.

Comparative Example 12
To 92.0% by weight of the lubricating oil composition prepared in Comparative Example 3, 8.0% by weight of Li composite soap (composite soap of lithium 12-hydroxystearate and azelaic acid) was added.

Comparative Example 13
To 92.0% by weight of the lubricating oil composition prepared in Comparative Example 4, 8.0% by weight of Ba complex soap (composite soap of 12-hydroxy barium stearate and sebacic acid) was added.

  Since the lubricating oil compositions obtained in Comparative Examples 6 to 10 could not be homogenized, fluidity studies and SRV tests were not performed, and the lubricating oil compositions obtained in the above 11 to 13 were not fluid. The SRV test was not conducted.

Impregnating lubricating oil composition of the present invention are all porous bearings, bushings, can be effectively used as a lubricating oil applied to a chain or gear.

Claims (3)

Metal soap having at least one hydroxyl group in a base oil composed of 100 to 26.95% by weight of synthetic hydrocarbon oil and 0 to 73.05% by weight of synthetic synthetic oil and glycol oil A lubricating oil composition for impregnation comprising metal composite soap in a proportion of 0.5 to 3% by weight. 2. The lubricating oil composition for impregnation according to claim 1, wherein the metal soap or metal composite soap having at least one hydroxyl group is lithium or barium soap or composite soap . Both porous bearings, bushings, impregnating lubricating oil composition of claim 1, wherein used a chain or gear.