JP6159107B2 - Lubricating oil composition - Google Patents

Description

  The present invention relates to a lubricating oil composition, and more particularly to a lubricating oil composition that can be suitably used for a gear device used in a manual transmission used in an automobile or the like.

The demand for energy saving such as fuel saving and resource saving is a new issue for the purpose of global environmental conservation. In addition, the lubricating oil composition (gear oil) for gear devices used in manual transmissions and final reduction gears for automobiles, speed increasers and reduction gears for various industrial machines, requires performance for energy saving by reducing friction loss. It has been. However, simple reduction of the viscosity of gear oil (for example, 6 mm ² / s or less at 100 ° C. kinematic viscosity) has a great effect of reducing oil stirring loss in the device, but due to insufficient viscosity at high temperature, gear couch noise There is a problem in that gear wear, reduction in tooth surface fatigue life, and seizure of the gear occur. Therefore, the gear oil achieves low viscosity and reduced friction loss in the normal temperature range (20 ° C. or higher and 80 ° C. or lower) while maintaining the oil film holding performance in the high temperature range (eg, 100 ° C. or higher). In addition, it is required to reduce the load on the prime mover when starting the apparatus by improving the low temperature fluidity.

Such gear oil, for example, kinematic viscosity at 100 ° C. is in the lubricating base oil of 1.5 to 10 mm ² / s, the total amount of the composition, kinematic viscosity at 100 ° C. is 40~500mm ² / s A lubricating oil composition comprising 2 to 40% by mass of a high-viscosity synthetic lubricating oil and 0.01 to 5% by mass of an extreme pressure additive such as a phosphorus extreme pressure agent is disclosed (see Patent Document 1). ). Further, 1 and 1 to 49% by weight kinematic viscosity poly -α- olefin basestocks 40~500mm ² / s at 100 ° C., a kinematic viscosity at 100 ° C. is a lubricating oil base stock 2 to 10 mm ² / s Disclosed is a fluid composition comprising 95% by weight, 1 to 49% by weight of a specific polyol ester, and a functional additive package, wherein the composition has a kinematic viscosity at 100 ° C. of at least 4 mm ² / s. (See Patent Document 2). Further, as a base oil, a mineral oil or synthetic oil having a kinematic viscosity at 100 ° C. of 3.5 to 7 mm ² / s and a mineral oil or synthetic oil having a kinematic viscosity at 100 ° C. of ²⁰ to 52 mm ² / s are mixed. And the gear oil composition whose kinematic viscosity in 40 degreeC is 80 mm < ² > / s or less is disclosed (refer patent document 3). Furthermore, there is also known an example in which the base oil is reduced to a viscosity of 3 to 3.8 mm ² / s and a fuel consumption is reduced by using a polymer having a molecular weight of 10,000 to 35,000 as a viscosity index improver (patent) Reference 4).

International Publication No. 2004/0699967 JP 2004-10894 A JP 2007-39480 A JP 2008-208212 A

  However, even the lubricating oil compositions described in Patent Documents 1 to 3 cannot simultaneously achieve the above characteristics required for gear oil. Further, the gear oil described in Patent Document 4 has insufficient fuel saving in the normal temperature range.

  Therefore, the present invention provides a lubricating oil composition that lowers the viscosity in the normal temperature range (20 ° C. or more and 80 ° C. or less) to ensure fuel economy, has excellent shear stability, and can further reduce friction loss. The purpose is to do.

In order to solve the above problems, the present invention provides the following lubricating oil composition.
(1) A poly (meth) acrylate having a mass average molecular weight of 3 × 10 ⁴ or more and 5 × 10 ⁴ or less is blended with a base oil having a kinematic viscosity of 100 ° C. of 0.5 mm ² / s to 3.5 mm ² / s. A lubricating oil composition characterized by comprising:
(2) The lubricating oil composition according to the above (1), further comprising an ester having a kinematic viscosity at 100 ° C. of 5 mm ² / s or less as a base oil.
(3) In the lubricating oil composition according to the above (1) or (2), a poly (meth) acrylate having a mass average molecular weight of 1.4 × 10 ⁵ or more and 2 × 10 ⁵ or less is further blended. A lubricating oil composition characterized by that.
(4) The lubricating oil composition according to any one of (1) to (3) above, further comprising a molybdenum compound.
(5) The lubricating oil composition according to any one of (1) to (4) above, further comprising at least one of a cleaning dispersant, an extreme pressure agent, and an oily agent. A lubricating oil composition.
(6) In the lubricating oil composition according to any one of (1) to (5) above, the kinematic viscosity at 100 ° C. of the composition is 13.5 mm ² / s or more and 18.5 mm ² / s or less. A lubricating oil composition, wherein the composition has a kinematic viscosity at 40 ° C. of 65 mm ² / s or less.
(7) The lubricating oil composition according to any one of (1) to (6) above, wherein the composition has a viscosity index of 245 or more.
(8) In the lubricating oil composition according to any one of (1) to (7) above, the rate of decrease in kinematic viscosity at 100 ° C. in a shear stability test (ultrasonic shear test) is 15% or less. A lubricating oil composition characterized by being.
(9) A lubricating oil composition according to any one of (1) to (8), wherein the lubricating oil composition is for a manual transmission.

  According to the present invention, there is provided a lubricating oil composition that lowers the viscosity in the normal temperature range (20 ° C. or more and 80 ° C. or less) to ensure fuel saving, is excellent in shear stability, and can further reduce friction loss. it can.

The lubricating oil composition of the present invention (hereinafter also referred to as “the present composition”) is a base oil having a kinematic viscosity at 100 ° C. of 0.6 mm ² / s to 3.5 mm ² / s and a mass average molecular weight of 3 ×. It is characterized by blending 10 ⁴ or more and 5 × 10 ⁴ or less poly (meth) acrylate. Hereinafter, the composition will be described in detail.

The base oil used in the present composition has a kinematic viscosity at 100 ° C. of 0.5 mm ² / s or more and 3.5 mm ² / s or less, preferably 0.6 mm ² / s or more and 3 mm ² / s or less. If the kinematic viscosity at 100 ° C. is 0.5 mm ² / s or more, the evaporation loss is small. On the other hand, if it is 3.5 mm ² / s or less, the power loss due to viscous resistance is small, and the fuel efficiency improvement effect is obtained. Moreover, when the kinematic viscosity at 100 ° C. of the base oil exceeds 3.5 mm ² / s, it becomes difficult to improve the viscosity index of the composition.

The base oil used in the present composition may be a mineral-type lubricating base oil or a synthetic-type lubricating base oil. There are no particular restrictions on the types of these lubricating base oils, and any appropriate one of mineral oils and synthetic oils conventionally used as base oils for automotive transmission lubricating oils can be used. it can.
Examples of the mineral-based lubricating base oil include paraffin-based mineral oil, intermediate-based mineral oil, and naphthene-based mineral oil. Examples of the synthetic lubricating base oil include polybutene, polyolefin (α-olefin homopolymer and copolymer (eg, ethylene-α-olefin copolymer)), various esters (eg, polyol ester, Dibasic acid ester, phosphoric acid ester and the like), various ethers (for example, polyphenyl ether and the like), polyglycol, alkylbenzene, alkylnaphthalene and the like.
In the present invention, as the base oil, one kind of the mineral-based lubricating base oil may be used, or two or more kinds may be used in combination. Moreover, 1 type of the said synthetic-type lubricating base oil may be used, and may be used in combination of 2 or more type. Furthermore, you may use combining the 1 type or more of the said mineral type lubricating oil base oil, and the 1 type or more of the said synthetic type lubricating oil base oil.

  Further, the viscosity index of the base oil is preferably 70 or more, more preferably 100 or more, and still more preferably 120 or more. Such a base oil having a viscosity index equal to or more than the lower limit has a small change in viscosity due to a change in temperature, and an effect of improving fuel consumption can be obtained even at a low temperature.

The composition contains a poly (meth) acrylate having a mass average molecular weight of 3 × 10 ⁴ or more and 5 × 10 ⁴ or less, preferably 3.2 × 10 ⁴ or more and 4.5 × 10 ⁴ or less. When the mass average molecular weight is within this range, the shear stability is excellent and the viscosity index can be sufficiently increased.
The blending amount of the poly (meth) acrylate is preferably 20% by mass or more and 45% by mass or less, and more preferably 25% by mass or more and 40% by mass or less, based on the total amount of the composition. If the blending amount is less than 20% by mass, the blending effect may not be sufficient. On the other hand, even if the blending amount exceeds 45% by mass, the blending effect is limited.

Moreover, it is preferable to mix | blend ester whose 100 degreeC kinematic viscosity is 5 mm < ² > / s or less into this composition as base oil further. By mix | blending such ester with this composition, the solubility of the poly (meth) acrylate mentioned above can increase, and the cloudiness of this composition can be suppressed. However, as a whole mixed base oil, the kinematic viscosity at 100 ° C. should not exceed 3.5 mm ² / s.
The blending amount of such an ester is preferably 5% by mass or more and 20% by mass or less, and more preferably 8% by mass or more and 15% by mass or less based on the total amount of the composition. If the blending amount is less than 5% by mass, the blending effect may not be sufficient. On the other hand, even if the blending amount exceeds 20% by mass, the effect is limited.

  As an above-mentioned ester, as constituent alcohol (unit), n hexanol, n heptanol, n octanol, n nonanol, n decanol, n undecanol, n dodecanol, n tridecanol, n tetradecanol, oleyl alcohol, ethyl hexanol, butyl Octanol, pentylnonanol, hexyldecanol, heptylundecanol, octyldodecanol, methylheptadecanol, oleyl alcohol, benzyl alcohol, 2-phenethyl alcohol, 2-phenoxyethanol, ethylene glycol monobenzyl ether, ethylene glycol monophenyl ether, diethylene glycol Monobenzyl ether, diethylene glycol monophenyl ether, phenol, cresol, xyleno And monools such as alkylphenol, ethylene glycol, diethylene glycol, triethylene glycol, polytetramethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, And polyethylene glycol (both terminal hydroxyl groups), triol such as trimethylolpropane and trimethylolethane, and tetraol such as pentaerythritol.

  Further, as the carboxylic acid (unit) constituting the ester, n butanoic acid, n pentanoic acid, n hexanoic acid, n heptanoic acid, n octanoic acid, n nonanoic acid, n decanoic acid, n undecanoic acid, n dodecanoic acid, n tridecane Acids, n-tetradecanoic acid, ethylhexanoic acid, butyloctanoic acid, pentylnonanoic acid, hexyldecanoic acid, heptylundecanoic acid, octyldodecanoic acid, methylheptadecanoic acid, oleic acid, benzoic acid, toluic acid, phenylacetic acid, and phenoxyacetic acid Examples thereof include dicarboxylic acids such as monocarboxylic acid, adipic acid, azelaic acid, sebacic acid, 1,10-decamethylene dicarboxylic acid, phthalic acid, isophthalic acid, and terephthalic acid. These may be used alone or in combination.

For example, examples of the ester composed of the above-mentioned alcohol and carboxylic acid include polyglycol benzoate such as polyethylene glycol dibenzoate and polypropylene glycol dibenzoate, n-octanoic acid tetraester of pentaerythritol, and n-octanoic acid triester of trimethylolpropane. Linear carboxylic acid hindered esters, long chain diesters such as di-n-octyl azelate and ethylhexyl 1,10-decamethylene dicarboxylate, long-chain monoesters such as dodecyl 16-methylheptadecanoate and n-dodecyl 2-heptylundecanoate Long chain oleyl esters such as esters, oleyl oleate and 16-methylheptadecyl oleate are preferred.
In addition, the said ester mix | blended with this composition does not need to be manufactured from carboxylic acid and alcohol. For example, it may be produced by a transesterification method.

The composition preferably further contains a poly (meth) acrylate having a mass average molecular weight of 1.4 × 10 ⁵ or more and 2 × 10 ⁵ or less. A more preferable mass average molecular weight is 1.6 × 10 ⁵ or more and 1.8 × 10 ⁵ or less. By blending such a high molecular weight poly (meth) acrylate, the viscosity index of the present composition can be further improved. When the mass average molecular weight of the poly (meth) acrylate is less than 1.4 × 10 ⁵ , the effect of improving the viscosity index is limited. On the other hand, when the mass average molecular weight of the poly (meth) acrylate exceeds 2 × 10 ⁵ , the shear stability may be lowered.
A preferable blending amount of the poly (meth) acrylate is 2% by mass or more and 7% by mass or less, and a more preferable blending amount is 3% by mass or more and 6% by mass or less.

The composition preferably further contains a molybdenum compound. By incorporating a molybdenum compound, the wear resistance of the composition can be further improved. For example, the wear of the synchronizer ring can be suppressed without lowering the coefficient of friction between the synchronizer ring and the gear cone in the manual transmission.
Examples of such molybdenum compounds include MoDTC (molybdenum dialkyldithiocarbamate) and MoDTP (molybdenum dialkyldithiophosphate). MoDTC is more preferable from the viewpoint of effect.
The blending amount of the above-mentioned molybdenum compound is preferably 30 ppm to 300 ppm by mass, more preferably 50 ppm to 150 ppm, in terms of the total amount of the composition and in terms of Mo element. If the blending amount of the molybdenum compound is less than 30 ppm by mass, the effect of improving the wear resistance may not be sufficient. On the other hand, even if the compounding quantity of a molybdenum compound exceeds 300 mass ppm, the effect is limited.

The composition preferably further contains at least one of a detergent dispersant, an extreme pressure agent, and an oily agent.
As the cleaning dispersant, there are a metal-based detergent and an ashless dispersant. Preferred examples of the metallic detergent include sulfonates, phenates, salicylates and naphthenates of alkaline earth metals (calcium (Ca), magnesium (Mg), etc.). Moreover, the thing whose total base number is 300 mg / KOH or more is preferable. The total base number referred to here is JIS K 2501 “Petroleum products and lubricants—Test method for neutralization number”. Means the total base number by potentiometric titration method (base number / perchloric acid method) measured according to the above. The preferable compounding amount of the metal detergent is in the range of 1% by mass to 2.5% by mass based on the total amount of the composition from the viewpoint of the effect.
Moreover, as an ashless type | system | group dispersing agent, derivatives, such as polybutenyl succinimide, polybutenyl benzylamine, polybutenyl amine, or these boric acid modified substances, are mentioned preferably. A preferable blending amount of the ashless dispersant is in the range of 0.5% by mass or more and 1.5% by mass or less based on the total amount of the composition from the viewpoint of the effect.

Examples of the extreme pressure agent include sulfur-based, phosphorus-based, and boron-based extreme pressure agents. Examples of sulfur-based extreme pressure agents include sulfurized olefins, sulfurized fats and oils, sulfurized esters, thiocarbonates, dithiocarbamates, polysulfides, and the like. Examples of the phosphorus-based extreme pressure agent include zinc dithiophosphate, phosphite, alkyl or aryl acid phosphate, amine salts thereof, trialkyl or triaryl phosphate, and the like.
A preferable blending amount of the extreme pressure agent is in the range of about 0.1% by mass or more and 5% by mass or less, and more preferably in the range of 0.5% by mass or more and 3% by mass or less, based on the total composition.

Examples of the oily agent include aliphatic monocarboxylic acids, polymerized fatty acids, hydroxy fatty acids, aliphatic monoalcohols, aliphatic monoamines, aliphatic monocarboxylic amides, partial esters of polyhydric alcohols and aliphatic monocarboxylic acids (sorbitan). And a partial ester thereof. These may be used individually by 1 type and may be used in combination of 2 or more type.
Although the compounding quantity of an oiliness agent is not specifically limited, It is preferable that it is the range of 0.01 mass% or more and 5 mass% or less on the basis of the composition whole quantity.

The composition may further contain an additive for imparting characteristics necessary as a lubricating oil composition. For example, an antioxidant, a rust inhibitor, a corrosion inhibitor, an antifoaming agent, and the like can be given.
Examples of the rust preventive include fatty acid, alkenyl succinic acid half ester, fatty acid soap, alkyl sulfonate, polyhydric alcohol fatty acid ester, fatty acid amide, oxidized paraffin, alkyl polyoxyethylene ether, and the like. Although the preferable compounding quantity of a rust preventive agent is not specifically limited, It is the range of 0.01 mass% or more and 3 mass% or less on the basis of the composition whole quantity.

Examples of the corrosion inhibitor include benzotriazole corrosion inhibitors, benzimidazole corrosion inhibitors, benzothiazole corrosion inhibitors, thiadiazole corrosion inhibitors, and the like. Although the preferable compounding quantity of a corrosion inhibitor is not specifically limited, It is the range of 0.01 mass% or more and 1 mass% or less on the basis of the composition whole quantity.
Examples of antifoaming agents include silicone compounds and ester compounds. Although the preferable compounding quantity of an antifoamer is not specifically limited, It is the range of 1 mass ppm or more and 5000 mass ppm or less on the composition whole quantity basis.

100 ° C. kinematic viscosity of the composition is preferably no greater than 13.5 mm ² / s or more 18.5 mm ² / s, more preferably at most 14 mm ² / s or more 16 mm ² / s. A viscosity index | exponent can be effectively improved as 100 degreeC kinematic viscosity is 13.5 mm < ² > / s or more. On the other hand, if the 100 ° C. kinematic viscosity exceeds 18.5 mm ² / s, fuel economy may be reduced.
It is preferable that 40 ° C. kinematic viscosity of the composition is less than 65 mm ² / s, and more preferably 60 mm ² / s or less. When the 40 ° C. kinematic viscosity is 65 mm ² / s or less, fuel economy is excellent.
The viscosity index of the present composition is preferably 245 or more, and more preferably 250 or more. When the viscosity index is 245 or more, fuel consumption in the normal temperature range is improved due to reduction of stirring loss or the like.

  In the composition, the rate of decrease in the 100 ° C. kinematic viscosity in a shear stability test (ultrasonic shear test) is preferably 15% or less, and more preferably 10% or less. When the rate of decrease in the kinematic viscosity at 100 ° C. is 15% or less, the fatigue life of gears and bearings can be extended, so that the reliability of the apparatus to which the present composition is applied becomes excellent.

  This composition lowers the viscosity in the normal temperature range to ensure fuel economy, is excellent in shear stability, and can also reduce friction loss. Therefore, manual transmissions and final reduction gears for automobiles, and industrial machinery It is suitably used as a lubricating oil composition for a gear device used for a speed increaser, a reduction gear, and the like.

EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples. The performance of the lubricating oil composition (sample oil) in each example (kinematic viscosity at 40 ° C. and 100 ° C., viscosity index, flash point, shear stability, wear characteristics, and appearance) was determined by the following method. .
(1) Kinematic viscosity at 40 ° C. and 100 ° C. Based on the method described in JIS K2283, the kinematic viscosity at 40 ° C. and 100 ° C. (unit: mm ² / s) was measured.
(2) Viscosity index The viscosity index was calculated based on the method described in JIS K2283.
(3) Flash point Measured according to JIS K 2265. Practically preferred is 150 ° C. or higher.

(4) Shear stability (ultrasonic shear stability test)
A test was conducted in accordance with JPI-5S-29-88 (Method A, 60 minutes, 30 mL), and the rate of decrease in dynamic viscosity (%) was calculated from the 100 ° C. kinematic viscosity after the test. The rate of decrease in kinematic viscosity at 100 ° C. is preferably 15% or less.

(5) Wear characteristics (wear of the synchronizer ring)
Using a synchro unit tester, the wear length after 100,000 cycles was measured under the following conditions. The wear length refers to the amount of change (unit: mm) in the gap between the synchronizer ring and the gear cone, and is indicated by a value obtained by subtracting the gap width before the test from the gap width after the test. . It is practically preferable that the wear length is 0.3 mm or less.
Synchronizer ring (SNR) material: high-strength brass SNR cone angle (θ): 6.5 °
Effective radius of SNR (R): 26.5mm
Gear material: Carbon steel Gear rotation speed: 1200rpm
SNR pressing force: 400N
SNR pressing time and rest time: pressing time 0.5 seconds, rest time 1 second Oil temperature: 80 ° C
Oil amount: Fills up to the shaft center of the drive shaft and pressing shaft (approx. 4L)

(6) Appearance After cooling the sample oil at −5 ° C. for 24 hours, the appearance was visually observed to check for cloudiness and precipitation.
The case where there was no cloudiness or precipitation was defined as “good”.

[Examples 1-9, Comparative Examples 1-9]
Lubricating oil compositions (sample oils) shown in Tables 1 and 2 were prepared using the base oils and additives shown below. The performance of each sample oil was evaluated by the method described above, and the results are shown in Tables 1 and 2.
Mineral oil-1: Highly refined mineral oil (100 ° C. kinematic viscosity: 0.87 mm ² / s)
Mineral oil-2: Highly refined mineral oil (100 ° C. kinematic viscosity: 1.5 mm ² / s, viscosity index: 83)
Mineral oil-3: Highly refined mineral oil (100 ° C. kinematic viscosity: 2.2 mm ² / s, viscosity index: 109)
Mineral oil-4: Highly refined mineral oil (100 ° C. kinematic viscosity: 2.7 mm ² / s, viscosity index: 114)
Mineral oil-5: Highly refined mineral oil (100 ° C. kinematic viscosity: 3.1 mm ² / s, viscosity index: 109)
Mineral oil-6: Highly refined mineral oil (100 ° C. kinematic viscosity: 4.1 mm ² / s, viscosity index: 131)
Synthetic oil-1: poly-α-olefin (kinematic viscosity at 100 ° C .: 1.8 mm ² / s, viscosity index: 128)
Synthetic oil-2: poly-α-olefin (100 ° C. kinematic viscosity: 3.9 mm ² / s, viscosity index: 120)
Synthetic oil-3: poly-α-olefin (100 ° C. kinematic viscosity: 5.9 mm ² / s, viscosity index: 132)
Ester A: Dibasic acid ester (100 ° C. kinematic viscosity: 4.3 mm ² / s, viscosity index: 139)
PMA-1: Polymethacrylate (Mw = 1.7 × 10 ⁵ )
PMA-2: Polymethacrylate (Mw = 5.5 × 10 ⁵ )
PMA-3: Polymethacrylate (Mw = 3.2 × 10 ⁴ )
ZnDTP: dithiophosphate ester polybutenyl succinimide polysulfide sulfurized oil phosphate ester amine salt sorbitan partial ester Ca sulfonate: total base number 400 mgKOH / g
MoDTC: Mo amount in compound: 4.1% by mass
Antifoaming agent: Silicone

[Evaluation results]
As is clear from the results shown in Table 1, the sample oils of Examples 1 to 9 (lubricating oil compositions of the present invention) ensure the fuel saving by reducing the viscosity in the normal temperature range (40 Viscosity is 65 ° C. or less). In addition, it has excellent shear stability. Furthermore, it is also excellent in wear resistance, and specifically, since the wear of the synchronizer ring is small, it can be seen that the synchro operability can be maintained over a long period of time.
On the other hand, as shown in Table 2, in the sample oils of Comparative Examples 1 to 9, at least one of the 100 ° C. kinematic viscosity of the base oil and the mass average molecular weight of the polymer (PMA) is out of the range defined in the present invention. Therefore, the problem of the present invention cannot be solved.

Claims (5)

To a base oil having a kinematic viscosity at 100 ° C. of 0.5 mm ² / s to 3.5 mm ² / s,
A poly (meth) acrylate having a mass average molecular weight of 3 × 10 ⁴ or more and 5 × 10 ⁴ or less is blended,
The amount of the poly (meth) acrylate is 25% by mass or more based on the total amount of the composition,
Further, as a base oil, 15 mass% or less of an ester having a 100 ° C. kinematic viscosity of 5 mm ² / s or less,
Furthermore, a poly (meth) acrylate having a mass average molecular weight of 1.4 × 10 ⁵ or more and 2 × 10 ⁵ or less is blended,
The composition at 100 ° C. has a kinematic viscosity of 13.5 mm ² / s to 18.5 mm ² / s,
The composition has a 40 ° C. kinematic viscosity of 65 mm ² / s or less,
A lubricating oil composition, wherein the composition has a viscosity index of 245 or more. The lubricating oil composition according to claim 1, wherein
Furthermore, a lubricating oil composition comprising a molybdenum compound. The lubricating oil composition according to claim 1 or 2,
Furthermore, a lubricating oil composition comprising at least one of a cleaning dispersant, an extreme pressure agent, and an oily agent. In the lubricating oil composition according to any one of claims 1 to 3,
A lubricating oil composition characterized in that the rate of decrease in kinematic viscosity at 100 ° C. in a shear stability test (ultrasonic shear test) is 15% or less. The lubricating oil composition according to any one of claims 1 to 4, wherein the lubricating oil composition is for a manual transmission.