JP6293115B2 - Lubricating oil composition - Google Patents

Description

  The present invention relates to a lubricating oil composition.

In order to cope with global warming from the demand for reducing environmental burden, reduction of CO ₂ is strongly desired worldwide. Improving the fuel efficiency of automobiles to reduce CO ₂ is an important issue, and high-power engines that have been reduced in size and weight are spreading. Therefore, for engine oil, there is a concern about deterioration of piston cleanliness accompanying an increase in heat load.
In addition, further improvement in fuel efficiency is required for engine oil. In order to improve the fuel efficiency of engine oil, the improvement of temperature-viscosity characteristics is effective in reducing friction in the fluid lubrication region, and a viscosity index improver is used to improve this temperature-viscosity characteristics. . As this viscosity index improver, polymethacrylate (PMA), polyolefin copolymer (OCP), and the like are used (Patent Documents 1 to 4). In particular, PMA type viscosity index improvers with excellent temperature-viscosity characteristics are frequently used. Has been. However, with a PMA type viscosity index improver, there are difficulties in piston cleanliness under more severe high temperature conditions, and there is also concern about shear stability. Accordingly, there is a need for a lubricating oil composition that maintains good piston cleanliness and shear stability while having excellent fuel economy.

Japanese Patent Laid-Open No. 2008-184568 JP 2010-280817 A JP 2008-248139 A JP 2010-043250 A

  However, the lubricating oil compositions described in Patent Documents 1 to 4 cannot maintain good piston cleanliness and shear stability while having excellent fuel economy.

  Accordingly, an object of the present invention is to provide a lubricating oil composition capable of maintaining good piston cleanliness and shear stability while having excellent fuel economy.

In order to solve the above problems, the present invention provides the following lubricating oil composition.
(1) The lubricating base oil contains (A) a polymethacrylate having a mass average molecular weight of 30,000 to 600,000 and (B) a 95% weight loss temperature in differential thermal analysis of 500 ° C. or less and SSI (shear stability) A lubricating oil composition comprising an olefin copolymer having a sex index) of 40 or less.
(2) In the above lubricating oil composition, the component (A) is a polymethacrylate having a mass average molecular weight of 200,000 or more and 600,000 or less, and the SSI of the component (B) is 30 or less. A lubricating oil composition.
(3) In the lubricating oil composition described above, the kinematic viscosity at 100 ° C. is is less than 9.3 mm ² / s or more 12.5 mm ² / s, kinematic viscosity at 100 ° C. after shear stability test, 9 A lubricating oil composition characterized by being 3 mm ² / s or more.
(4) The lubricating oil composition described above, wherein the kinematic viscosity at 100 ° C. after the shear stability test is 10 mm ² / s or less.
(5) in the lubricating oil composition described above, the kinematic viscosity at 100 ° C. is is less than 5.6 mm ² / s or more 9.3 mm ² / s, kinematic viscosity at 100 ° C. after shear stability test, 5 A lubricating oil composition characterized by being 6 mm ² / s or more.
(6) The lubricating oil composition described above, wherein the lubricating base oil has a viscosity index of 120 or more.
(7) The lubricating oil composition described above, wherein the phosphorus content is 0.12% by mass or less based on the total amount of the composition.
(8) In the above lubricating oil composition, a metal detergent is further blended, and the blending amount of the metal detergent is 0.05% by mass or more and 0.3% in terms of metal based on the total amount of the composition. Lubricating oil composition characterized by being less than or equal to mass%.
(9) The above lubricating oil composition is characterized by further blending at least one ashless dispersant selected from the group consisting of polybutenyl succinimides and polybutenyl succinimide borides. A lubricating oil composition.
(10) The lubricating oil composition described above, wherein the lubricating oil composition is for an internal combustion engine.

The lubricating oil composition of the present invention comprises a lubricating base oil, (A) a polymethacrylate having a mass average molecular weight of 30,000 to 600,000, and (B) a 95% weight loss temperature in differential thermal analysis of 500 ° C. or lower. And an olefin copolymer having an SSI (shear stability index) of 40 or less.
In the method for producing a lubricating oil composition of the present invention, (A) a polymethacrylate having a mass average molecular weight of 30,000 to 600,000 and (B) a 95% weight loss temperature in differential thermal analysis is 500. A lubricating oil composition is produced by blending an olefin copolymer having an SSI (shear stability index) of 40 or less at a temperature of 0 ° C. or less.

  According to the present invention, it is possible to provide a lubricating oil composition that maintains excellent piston cleanliness and shear stability while having excellent fuel economy.

  The lubricating oil composition of the present invention (hereinafter also simply referred to as “the present composition”) comprises (A) a polymethacrylate having a mass average molecular weight of 30,000 to 600,000 and (B) An olefin copolymer having a 95% weight loss temperature of 500 ° C. or less and a SSI (shear stability index) of 40 or less in a differential thermal analysis is blended. Details will be described below.

[Lubricant base oil]
The lubricating base oil used in the present composition may be a mineral base oil or a synthetic base oil. There is no restriction | limiting in particular about the kind of these lubricating oil base oils, Arbitrary things can be suitably selected and used from the mineral oil and the synthetic oil which were conventionally used as a base oil of the lubricating oil for internal combustion engines. Further, the viscosity index of the lubricating base oil is preferably 120 or more from the viewpoint of temperature-viscosity characteristics and shear stability of the lubricating oil composition.
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, polyol ester, dibasic acid ester, phosphoric acid ester, polyphenyl ether, polyglycol, alkylbenzene, and alkylnaphthalene. Examples of the polyolefin include α-olefin homopolymers and α-olefin copolymers. These base oils may be used individually by 1 type, and may be used in combination of 2 or more type.

[(A) component]
The component (A) in the present composition is polymethacrylate (PMA) having a mass average molecular weight of 30,000 to 600,000. When the mass average molecular weight is less than the lower limit, fuel economy is deteriorated. On the other hand, when the upper limit is exceeded, the shear stability of the lubricating oil composition is lowered. Further, the mass average molecular weight of the component (A) is more preferably from 200,000 to 600,000, even more preferably from 350,000 to 450,000, and from 380,000 to 420, 000 or less is particularly preferable.

The polymethacrylate may be a non-dispersed polymethacrylate or a dispersed polymethacrylate.
The blending amount of the component (A) is preferably 1% by mass or more and 20% by mass or less, and more preferably 2% 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 the lower limit, the effect of improving the viscosity index tends to be insufficient. On the other hand, if the blending amount exceeds the upper limit, the shear stability and piston cleanliness of the lubricating oil composition tend to be lowered.

[Component (B)]
Component (B) in the present composition is an olefin copolymer (OCP) having a 95% weight loss temperature of 500 ° C. or lower and a SSI of 40 or lower in differential thermal analysis. When the 95% weight loss temperature exceeds 500 ° C., the piston cleanliness of the lubricating oil composition decreases. When SSI exceeds 40, the shear stability of a lubricating oil composition will fall. The SSI of the component (B) is more preferably 30 or less, even more preferably 2 or more and 30 or less, particularly preferably 2 or more and 20 or less, and 6 or more and 19 or less. Is most preferred. Furthermore, the 95% weight loss temperature of the component (B) is more preferably 480 ° C. or less, and particularly preferably 461 ° C. or more and 476 ° C. or less.
The 95% weight loss temperature can be measured using a known differential thermal analyzer. The test conditions include, for example, conditions in nitrogen, flow rate: 200 mL / min, heating rate: 10 ° C./min, platinum pan use, sample amount: 6 mg. SSI was measured with the new oil and the kinematic viscosity at 100 ° C. and the base oil kinematic viscosity at 100 ° C. after the shear stability test (ASTM D6278). ) / (New oil kinematic viscosity−base oil kinematic viscosity) × 100.

As the olefin copolymer, for example, an ethylene-propylene copolymer, an ethylene-butylene copolymer, a styrene-isoprene copolymer or a styrene-butadiene copolymer can be used.
The blending amount of the component (B) is preferably 1% by mass or more and 15% by mass or less, more preferably 2% by mass or more and 10% by mass or less based on the total amount of the composition.

[Other additives]
Various additives shown below may be blended with the present composition as long as the effects of the invention are not impaired. Specifically, detergent dispersants, antioxidants, antiwear agents / extreme pressure agents, pour point depressants, friction reducers, metal deactivators, rust inhibitors, surfactants / demulsifiers, antifoaming agents, Corrosion inhibitors, friction modifiers, oiliness agents, acid scavengers, and the like can be appropriately blended and used.

As the cleaning and dispersing agent, an ashless dispersant and a metal-based cleaning agent can be used.
Examples of the ashless dispersant include succinimide compounds, boron imide compounds, Mannich dispersants, and acid amide compounds. Among these, polybutenyl succinimide and polybutenyl succinimide borate are preferable. These may be used individually by 1 type and may be used in combination of 2 or more type.
The blending amount of the ashless dispersant is not particularly limited, but is preferably 0.1% by mass or more and 10% by mass or less based on the total amount of the composition.

Examples of the metal detergent include alkali metal sulfonate, alkali metal phenate, alkali metal salicylate, alkali metal naphthenate, alkaline earth metal sulfonate, alkaline earth metal phenate, alkaline earth metal salicylate, and alkaline earth metal naphthenate. It is done. Among these, alkaline earth metal salicylates are preferable. Of the alkaline earth metals, calcium and magnesium are preferable. These metal detergents may be used alone or in combination of two or more.
The compounding amount of the metal detergent is preferably 0.05% by mass or more and 0.3% by mass or less in terms of metal based on the total amount of the composition.

Examples of the antioxidant include amine-based antioxidants, phenol-based antioxidants, and sulfur-based antioxidants. These may be used individually by 1 type and may be used in combination of 2 or more type.
Although the compounding quantity of antioxidant is not specifically limited, It is preferable that they are 0.05 mass% or more and 7 mass% or less on the basis of the composition whole quantity.

Examples of the antiwear / extreme pressure agent include phosphorus-based extreme pressure agents and sulfur-based extreme pressure agents. Examples of phosphorus extreme pressure agents include phosphites, phosphates, thiophosphates, and amine salts or metal salts thereof. Examples of sulfur-based extreme pressure agents include sulfurized olefins, sulfurized fats and oils, sulfurized esters, thiocarbonates, dithiocarbamates, and polysulfides. These may be used individually by 1 type and may be used in combination of 2 or more type.
The blending amount of the antiwear agent / extreme pressure agent is not particularly limited, but is preferably 0.1% by mass or more and 10% by mass or less based on the total amount of the composition.

In addition, although this composition contains what was normally mix | blended, depending on the case, at least one part of what was mix | blended may react and become another compound.
The method for producing a lubricating oil composition of the present invention is a method for producing a lubricating oil composition by blending a component (A) and a component (B) with a lubricating base oil. In this production method, the above-described various additives may be further blended into the lubricating base oil as necessary.

[Lubricating oil composition]
Although this composition prepared by the above mixing | blending is not specifically limited, It is preferable that the following conditions are satisfy | filled.
The kinematic viscosity at 100 ° C. is preferably ² mm ² / s or more and 20 mm ² / s or less, and more preferably 5.6 mm ² / s or more and less than 12.5 mm ² / s. The kinematic viscosity can be measured by the method of JIS K 2283.
When the kinematic viscosity at 100 ° C. is 9.3 mm ² / s or more and less than 12.5 mm ² / s, the kinematic viscosity at 100 ° C. after the shear stability test is 9.3 mm ² / s or more. preferably, more preferably not more than 9.3 mm ² / s or more 10 mm ² / s.
Kinematic viscosity at 100 ° C. is is less than 5.6 mm ² / s or more 9.3 mm ² / s, kinematic viscosity at 100 ° C. after shear stability test is preferably 5.6 mm ² / s or more .
If the kinematic viscosity at 100 ° C. after the shear stability test is less than the lower limit, the shear stability tends to be insufficient. For example, in the case of the viscosity grade 5W-30, the stay-in grade cannot be achieved. On the other hand, when this kinematic viscosity exceeds the upper limit, fuel economy tends to deteriorate. The shear stability test can be performed according to the test method described in ASTM D6278.

The viscosity index is preferably 150 or more, and more preferably 170 or more. When the viscosity index is less than the lower limit, the temperature dependency of the viscosity increases, which is not preferable. The viscosity index can be measured by the method of JIS K 2283.
The phosphorus content in the present composition is preferably 0.12% by mass or less based on the total amount of the composition from the viewpoint of reducing the phosphorus content of the lubricating oil composition.

EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by the following examples.
[Examples 1 to 3, Comparative Examples 1 to 6]
In each Example and Comparative Example, a lubricating oil composition (hereinafter, also referred to as “sample oil”) having the composition shown in Table 1 was prepared using the base oils and additives shown below. The experiment was conducted with the viscosity grade of the test oil adjusted to 5W-30.

(1) Lubricating base oil: hydrorefined base oil, 40 ° C. kinematic viscosity 19.6 mm ² / s, 100 ° C. kinematic viscosity 4.2 mm ² / s, viscosity index 122,% CA 0.0, sulfur content 10 mass (2) Viscosity index improver PMA1: polymethacrylate, weight average molecular weight 380,000
(3) Viscosity index improver PMA2: polymethacrylate, mass average molecular weight 420,000
(4) Viscosity index improver PMA3: polymethacrylate, weight average molecular weight 25,000
(5) Viscosity index improver OCP1: Olefin copolymer, shear stability index 6, differential heat 95% weight loss temperature 464 ° C.
(6) Viscosity index improver OCP2: olefin copolymer, shear stability index 15, differential heat 95% weight loss temperature 476 ° C.
(7) Viscosity index improver OCP3: olefin copolymer, shear stability index 19, differential heat 95% weight loss temperature 461 ° C.
(8) Viscosity index improver OCP4: olefin copolymer, shear stability index 50, differential heat 95% weight loss temperature 480 ° C
(9) Viscosity index improver OCP5: olefin copolymer, shear stability index 20, differential heat 95% weight loss temperature 520 ° C
(10) Zinc dialkyldithiophosphate A: zinc content 8.9% by mass, phosphorus content 7.4% by mass, primary alkyl type zinc dialkyldithiophosphate (11) zinc dialkyldithiophosphate B: zinc content 9. 0% by mass, phosphorus content 8.2% by mass, secondary alkyl zinc dialkyldithiophosphate
(12) Antioxidant A: Amine-based antioxidant (13) Antioxidant B: Phenol-based antioxidant (14) Metal-based detergent A: Overbased calcium salicylate, base number (perchloric acid method) 350 mgKOH / G, calcium content 12.1% by mass
(15) Metal-based detergent B: overbased calcium salicylate, base number (perchloric acid method) 225 mgKOH / g, calcium content 7.8% by mass
(16) Polybutenyl succinic acid bisimide: number average molecular weight 2000 of polybutenyl group, base number (perchloric acid method) 11.9 mgKOH / g, nitrogen content 0.99% by mass
(17) Polybutenyl succinic acid monoimide borate: number average molecular weight of polybutenyl group 1000, base number (perchloric acid method) 25 mg KOH / g, nitrogen content 1.23 mass%, boron content 1.3 mass%
(18) Other additives: pour point depressant, rust inhibitor, etc.

Next, each property and characteristic was measured or calculated for each sample oil. Each measurement method or calculation method is as follows. The results are shown in Table 1.
(1) Kinematic viscosity (40 ° C., 100 ° C.) and viscosity index Measured according to “Petroleum product kinematic viscosity test method” defined in JIS K 2283.
(2) High temperature high shear viscosity (150 ° C HTHS viscosity)
It was measured by the method of ASTM D4683 using a TBS high temperature viscometer (Tapered Bearing Simulator).
(3) Kinematic viscosity after shear stability test (100 ° C)
A shear stability test (30 cycles) was performed according to the test method described in ASTM D6278, and the subsequent kinematic viscosity at 100 ° C. was measured in accordance with the “petroleum product kinematic viscosity test method” defined in JIS K 2283.
(4) Motoring torque A test apparatus such as the following was filled with test oil, a motoring torque test was performed, and the motoring torque was measured. Test conditions are shown below. Note that the lower the motoring torque, the better the fuel economy.
Test equipment: Engine motoring drive torque measuring machine Test engine: Inline 4-cylinder gasoline engine (displacement 2 liters, roller valve)
Test conditions: Oil temperature 60 ° C and 100 ° C, rotation speed 1500rpm
Evaluation item: Torque during engine drive (unit: Nm)
(5) Panel coking test The deposit adhesion amount was measured using the following test apparatus. Test conditions are shown below. In addition, the smaller the deposit adhesion amount in the panel caulking test, the better the piston cleanliness.
Test equipment: Panel caulking (panel control) tester Test conditions: Panel temperature 300 ° C., oil temperature 100 ° C., time 3 hours (operation of splashing 15 seconds / stop 45 seconds)
Evaluation item: Deposit amount on panel after test

As is clear from the results shown in Table 1, in the lubricating oil compositions of the present invention (Examples 1 to 3), the kinematic viscosity after the shear stability test was a stay-in grade (9.3 mm ² / s or more). While maintaining (good shear stability), it is confirmed that there is little deposit adhesion in the panel coking test (good piston cleanliness) and low motoring torque (good fuel economy) It was done. On the other hand, in the test oils of Comparative Examples 1 and 2, it was found that the shear stability and the piston cleanliness were deteriorated although the motoring torque was low due to the blending of only polymethacrylate. In addition, it was found that the motoring torque was high in the sample oil of Comparative Example 3 that was formulated with only the olefin copolymer. In the sample oil of Comparative Example 4, since an olefin copolymer having poor shear stability (high SSI) was blended, the kinematic viscosity after the shear stability test satisfied the stay-in grade (9.3 mm ² / s or more). I knew that I would not. In the test oil of Comparative Example 5, since the olefin copolymer having a 95% weight loss temperature of 500 ° C. or higher in the differential thermal analysis was blended, it was found that the piston cleanliness deteriorated. In the test oil of Comparative Example 6, since polymethacrylate lower than the lower limit of the molecular weight range of the present application was blended, it was found that the temperature-viscosity characteristics were deteriorated and the motoring torque was high (fuel economy was poor). .

Claims (11)

(A) polymethacrylate having a mass average molecular weight of 200,000 or more and 600,000 or less, and (B) 95% weight loss temperature in differential thermal analysis is 500 ° C. or less, and SSI (shear stability index) A lubricating oil composition comprising an olefin copolymer having a viscosity of 40 or less,
The blending amount of the component (A) is 1% by mass or more and 20% by mass or less based on the total amount of the lubricating oil composition.
The lubricating oil composition, wherein the blending amount of the component (B) is 2% by mass or more and 6.45% by mass or less based on the total amount of the lubricating oil composition.   The lubricating oil composition according to claim 1, wherein the component (B) is an ethylene-propylene copolymer, an ethylene-butylene copolymer, or a styrene-butadiene copolymer.   The lubricating oil composition according to claim 1 or 2, wherein the blending amount of the component (A) is 10.5% by mass or more and 20% by mass or less based on the total amount of the lubricating oil composition. The kinematic viscosity at 100 ° C. is 9.3 mm ² / s or more and less than 12.5 mm ² / s, and the kinematic viscosity at 100 ° C. after the shear stability test is 9.3 mm ² / s or more. The lubricating oil composition according to any one of to 3 . The lubricating oil composition according to claim 4 , wherein the kinematic viscosity at 100 ° C. after the shear stability test is 10 mm ² / s or less. Kinematic viscosity at 100 ° C. is less than 5.6 mm ² / s or more 9.3 mm ² / s, kinematic viscosity at 100 ° C. after shear stability test is 5.6 mm ² / s or more, according to claim 1 The lubricating oil composition according to any one of to 3 . The lubricating oil composition according to any one of claims 1 to 6 , wherein the lubricating base oil has a viscosity index of 120 or more. The lubricating oil composition according to any one of claims 1 to 7 , wherein a phosphorus content is 0.12% by mass or less based on the total amount of the lubricating oil composition. It is further formulated with a metallic detergent,
The lubricating oil composition according to any one of claims 1 to 8 , wherein the compounding amount of the metal-based detergent is 0.05% by mass or more and 0.3% by mass or less in terms of metal based on the total amount of the composition. object. The lubrication according to any one of claims 1 to 9 , further comprising at least one ashless dispersant selected from the group consisting of polybutenyl succinimides and polybutenyl succinimide borides. Oil composition. The lubricating oil composition according to any one of claims 1 to 10 , which is used for an internal combustion engine.