JP4800635B2 - Lubricating oil composition for automatic transmission - Google Patents

Description

The present invention relates to automatic transmission (AT) oil for passenger cars, large vehicles, chain-type or belt-type continuously variable transmission (CVT) oil, automatic transmission oil for vehicles having other wet clutches, power steering oil, The present invention relates to a lubricating oil composition for an automatic transmission that is suitable for industrial hydraulic fluids, fluid coupling oils, etc., and has low evaporation loss and good low-temperature viscosity characteristics.

In recent years, in the field of lubricating oil, many studies have already been made in consideration of evaporability from the viewpoint of reducing environmental impact (see, for example, Patent Document 1). Although the automatic transmission has a structure with little loss of transpiration of the lubricating oil, some of the published automatic transmission lubricating oil standards stipulate evaporability, and the internal temperature of the automatic transmission is high, and it is constantly stirred. In addition to being placed in an environment that tends to evaporate, in addition to the recent increase in the number of automobiles and the current situation that the domestic automatic transmission rate is over 90%, etc., for environmentally friendly automatic transmissions Attention has been focused on reducing the evaporation loss of lubricating oil.

In addition, parts such as gears, bearings, and hydraulic actuators are used in automatic transmissions. If the viscosity of the lubricating oil is too high at low temperatures, not only will fuel efficiency deteriorate due to increased fluid resistance during cold, Startability and hydraulic operability may be affected. Therefore, the lubricating oil for automatic transmission is generally required to keep the low temperature viscosity low, for example, poly α-olefin having a specific kinematic viscosity, specific kinematic viscosity, pour point and distillation characteristics, A lubricating oil composition based on a mixture of mineral oils having an aromatic hydrocarbon content of 2% or less is described (see Patent Document 2).

Usually, in order to set the viscosity low, a method of using a base oil containing a large amount of light fractions can be considered, but in this case, there is a concern that light components may evaporate into the atmosphere. For this reason, a lubricating oil with low evaporation loss and excellent low-temperature viscosity characteristics is desired.
JP 2004-137317 A JP-A-10-330778

  An object of the present invention is to provide a lubricating oil composition for an automatic transmission that has both low evaporation loss and low-temperature viscosity characteristics.

As a result of diligent research in view of the above situation, the present inventors have combined a lubricating base oil having specific properties with a specific polymethacrylate (hereinafter sometimes referred to as PMA) system viscosity index improver. It was found that a lubricating oil for an automatic transmission satisfying a low evaporation loss and a good low temperature viscosity characteristic can be obtained.
That is, the present invention provides (A) 5% by volume distillation temperature by gas chromatography method of 340 ° C. or higher and 400 ° C. or lower , flash point 200 ° C. or higher, 40 ° C. kinematic viscosity of 15 mm ² / s or higher and 40 mm ² / s or lower , flow A lubricating oil composition comprising a base oil having a point of −10 ° C. or less and (B) a polymethacrylate viscosity index improver having a weight average molecular weight (Mw) of 50,000 to 450,000 , The lubricating oil composition has a kinematic viscosity at 100 ° C. of 6.0 to 8.3 mm ² / s, a BF viscosity at −40 ° C. of 20,000 mPa · s or less, and JIS
Lubricant for automatic transmission characterized in that the amount of oil is 30 g, the temperature is 120 ° C., the test time is 96 hours, and the mass reduction rate after the test compared to before the test is 2.0% by mass or less in accordance with K2540 An oil composition is provided.

The lubricating oil composition for an automatic transmission according to the present invention has low evaporation loss and low temperature viscosity characteristics due to the synergistic effect of the base oil as the component (A) and the PMA viscosity index improver as the component (B). A lubricating oil composition for an automatic transmission can be obtained. The lubricating oil of the present invention an automatic transmission (AT), continuous variable transmission (CVT), the use of such a power steering, which can contribute to reducing environmental impact in a wide range from a low temperature of the high temperature.

The component (A) which is the base oil in the present invention has a 5% by volume distillation temperature by a gas chromatograph (hereinafter referred to as GC) method of 340 ° C. or higher and 400 ° C. or lower . The GC method in the present invention is measured according to JIS-K2254 (gas chromatograph method). By setting the 5% by volume distillation temperature to 340 ° C. or higher, the desired evaporability can be obtained, and by setting it to 400 ° C. or lower, the fluid resistance to the components in the automatic transmission, such as the hydraulic actuator, etc. It can be avoided that it becomes too large. 5 volume% distillation temperature by GC method (A) component is approximately 400 ° C. or less 340 ° C. or higher, further preferably 400 ° C. or less 345 ° C. or higher.

The component (A) has a flash point of 200 ° C. or higher, preferably 210 ° C. or higher. The flash point in the present invention is measured according to JIS K2265. By using a base oil that satisfies the above-described properties and has a flash point of 200 ° C. or higher, it is possible to achieve the target evaporability. The upper limit of the flash point is not particularly limited, but 350 ° C. or lower is generally used as the lubricating oil.

In addition to the above, the component (A) has a kinematic viscosity at 40 ° C. of 15 mm ² / s to 40 mm ² / s. By setting the kinematic viscosity at 40 ° C. of the component (A) to 15 mm ² / s or more and 40 mm ² / s or less, it is possible to set a viscosity suitable as a lubricating oil for an automatic transmission.
Although there is no particular limitation on the pour point of the base oil, a base oil having a pour point of −30.0 ° C. or lower can give better low temperature fluidity, and particularly a base oil having a pour point of −32.5 ° C. or lower. In the present invention, even if the base oil has a pour point exceeding −30.0 ° C., the base oil having a pour point exceeding −27.5 ° C. Even if it exists, a favorable low-temperature flow characteristic can be exhibited. Incidentally, from the viewpoint of adjusting ease the pour point of the base oil is no more than -10.0 ° C., and more preferably not more than -12.5 ° C., more preferably be less -15.0 ° C. The most preferable temperature is -17.5 ° C or lower.

The base oil of the component (A) of the present invention may be one base oil or a mixed base oil of two or more base oils as long as the above properties are satisfied, and a mineral oil base oil is also a synthetic oil base. Although a base oil can be used, it is desirable to use a mineral oil base oil from the viewpoint of cost and solubility of additives. In the case of a mixed base oil of mineral oil base oil and synthetic oil base oil, the content of mineral oil base oil is preferably 50% by mass or more, more preferably 70% by mass or more, and further preferably 75% by mass. % Or more, most preferably 80% by mass or more.

As long as the properties of the component (A) of the present invention can be satisfied, the production method and properties of the base oil as a raw material are not limited. As the mineral oil base oil, for example, highly refined paraffinic mineral oil obtained by subjecting hydrorefined oil, catalytic isomerized oil or the like to treatment such as solvent dewaxing or hydrodewaxing is preferably used. In addition to the above, mineral base oils obtained by various production methods can be used. For example, raffinate obtained by solvent purification using an aromatic extraction solvent such as phenol or furfural as a lubricating oil raw material, silica-alumina And hydrotreated oil obtained by hydrotreating using a hydrotreating catalyst such as cobalt or molybdenum using bismuth as a carrier. As the synthetic base oil, for example, base oil synthesized by Fischer-Tropsch reaction using a gas such as methane as a raw material, poly-α-olefin oligomer, polybutene, alkylbenzene, polyol ester, polyglycol ester, polyethylene propylene, Examples include hindered esters, dibasic acid esters, phosphate esters, and silicone oils.

In the present invention, a PMA viscosity index improver having a weight average molecular weight (Mw) of 50,000 or more and 450,000 or less is used as the component (B). The weight average molecular weight (Mw) in the present invention is a standard polystyrene conversion for molecular weight calculation measured by gel permeation chromatography (GPC).

The polymethacrylate (PMA) -based viscosity index improver, as long as the Mw is 50,000 or more and 450,000 or less, is a dispersion type as shown as an example in the formula (1), as shown as an example in the formula (2). Non-dispersive type may be used, and it is selected without particular limitation. Moreover, what contains polar monomers, such as a nitrogen compound and polyalkylene glycol ester, and the thing containing elemental components other than hydrocarbon may be sufficient. In addition, even if a part of the structure is a polymer compound other than polymethacrylate, a copolymer having a polymethacrylate portion, for example, polymethacrylate copolymerized using at least one of ethylene, propylene, butylene and the like as a raw material Olefin copolymer copolymers, polymethacrylate-polystyrene copolymers and the like can also be used. Good low temperature viscosity characteristics can be obtained by using a polymethacrylate viscosity index improver.

The molecular weight of the PMA based viscosity index improver of the present invention, it is possible to obtain a performance of interest if 50,000 450,000 or less, more preferably 60,000 to 300,000. By setting Mw to 50,000 or more, good low-temperature viscosity characteristics as an object of the present invention can be obtained. Further, by setting Mw to 450,000 or less, the solubility in base oil or lubricating oil for automatic transmission is good. In addition, the content of the component (B) can be selected optimally depending on the presence or absence of other polymer additives, the blending amount, the kinematic viscosity of the target lubricating oil composition, etc., but preferable viscosity index improvement The content of the agent is 0.5% by mass or more and 30% by mass or less, more preferably 1% by mass or more and 25% by mass or less, still more preferably 2% by mass or more and 20% by mass or less, and most preferably 3% by mass. % To 15% by mass.

（式中、Ｒ^１は水素原子又は炭素数１〜２０のアルキル基である。ｌは１以上の整数である。）

(In the formula, R ¹ is a hydrogen atom or an alkyl group having 1 to 20 carbon atoms. L is an integer of 1 or more.)

（Ｒ^１は水素原子又は炭素数１〜２０のアルキル基、Ｒ^２はＨ又はＣＨ_３、Ｘはアミノ基、エステル基又はスルホン酸基である。ｍ及びｎは１以上の整数である。）

(R ¹ is a hydrogen atom or an alkyl group having 1 to 20 carbon atoms, R ² is H or CH ₃ , X is an amino group, an ester group or a sulfonic acid group. M and n are integers of 1 or more.)

Since the above polymethacrylate compounds are usually solid, they are often used as diluted with mineral oil or synthetic oil at about 30 mass% to 70 mass% when blended with base oil. These polymethacrylate viscosity index improvers may be used alone or in combination of two or more. The viscosity index improver used in the present invention is not limited to the above specific examples as long as it has specific properties for achieving the object of the present invention, and generally improves the PMA viscosity index for lubricating oil. Any material used as an agent (polymer) can be used.

Although this invention is characterized by containing (A) component and (B) component, it was further excellent by containing an ashless type dispersant in the ratio of 0.1 mass% or more and 20 mass% or less. Performance can be achieved. When the content of the ashless dispersant is less than 0.1% by mass, the addition effect of the ashless dispersant is often difficult to appear. On the other hand, even when the content exceeds 20% by mass, the content increases. In addition to not being able to obtain a reasonable effect, it is often difficult to satisfy the desired low-temperature viscosity characteristics of the present invention. The content of the ashless dispersant is preferably 0.1% by mass or more and 15% by mass or less, more preferably 0.2% by mass or more and 12% by mass or less, and particularly preferably 0.5% by mass or more. It is 10 mass% or less.

As the ashless dispersant that is component (C), an ashless dispersant that is appropriately used in ordinary lubricating oils can be used without being limited to the following specific examples. Specific examples of the ashless dispersant include boron-free or boron-containing succinimide. As boron-free succinimide, polyalkyl or polyalkenyl succinimide produced by reacting polyalkyl or polyalkenyl succinic anhydride obtained by reacting polyolefin and maleic anhydride with polyalkylene polyamine, etc. Is mentioned. Polybutene is preferred and often used as the polyolefin. Examples of the boron-containing succinimide include those obtained by treating the succinimide with a boron compound. By changing the reaction ratio of the polyalkyl or polyalkenyl succinic anhydride and the polyalkylene polyamine, a mono-form and a bis-form can be obtained. In the present invention, either type may be used.
The molecular weight of the ashless dispersant is preferably 2,000 or more and 18,000 or less, more preferably 2,500 or more and 16,000 or less, and further preferably 2,800 or more and 15,000 or less.
One type of ashless dispersant may be used, or two or more types may be used in combination.

  In the lubricating oil composition for an automatic transmission according to the present invention, in addition to the above three components (A), (B), and (C), a known additive such as a metal-type detergent may be used as necessary. , Oiliness agent, antiwear agent, extreme pressure agent, rust inhibitor, friction modifier, antioxidant, corrosion inhibitor, metal deactivator, pour point depressant, antifoaming agent, colorant, for automatic transmission A package additive or a package additive for various lubricating oils containing at least one of them can be added.

  Examples of the metal detergent include neutral, basic, and overbased sulfonates, phenates, salicinates, and phosphonates. Examples of oil agents include oleic acid, stearic acid, higher alcohols, amines, esters, sulfurized fats and oils, acidic phosphate esters, and acidic phosphite esters. Examples of the antiwear agent include dithiophosphate metal salts, thiophosphate metal salts, sulfur compounds, phosphate esters, phosphite esters, acidic phosphate esters and amine salts thereof. Examples of extreme pressure agents include hydrocarbon sulfides, sulfurized fats and oils, zinc dithiophosphate, phosphate esters, phosphite esters, chlorinated paraffins, and chlorinated diphenyls. Examples of the rust inhibitor include carboxylic acid and its amine salt, ester, sulfonate, boron compound and the like. Examples of the friction modifier include organic molybdenum compounds, polyhydric alcohol partial esters, amines, amides, sulfurized esters, phosphate esters, acidic phosphate esters and amine salts thereof. Examples of the antioxidant include amine-based, phenol-based, and sulfur-based antioxidants. Examples of the corrosion inhibitor include benzotriazole and alkenyl succinate. Examples of the pour point depressant include polymethacrylate and polybutene. Examples of the antifoaming agent include silicon compounds, fluorosilicon compounds, ester-based compounds, and the like.

100 ° C. kinematic viscosity of the automatic transmission lubricating oil composition of the present invention is a 6.0~8.3mm ² / s, more preferably 6.3~8.2mm ² / s, 6.5~8. Most preferred is 1 mm ² / s.
The lubricating oil composition for an automatic transmission of the present invention has excellent low temperature viscosity characteristics. The low-temperature viscosity characteristics indicate performance such as low-temperature fluidity, low-temperature startability, and hydraulic operability at low temperatures. Specifically, the low-temperature viscosity characteristic can be evaluated by, for example, the BF viscosity at −40 ° C. BF viscosity at -40 ℃ is less than or equal to 20,000mPa · s.

EXAMPLES Next, although an Example demonstrates in detail, this invention is not specifically limited to these Examples.

(Examples 1-2)
The following base oils and additives were mixed in the blending amounts shown in Table 1 to prepare a lubricating oil composition for an automatic transmission. Table 1 shows the performance characteristics of the obtained lubricating oil composition for automatic transmissions.

<Base oil>
Base oil A: Highly refined mineral base oil with 100 ° C. viscosity of 3 cSt Base oil B: Highly refined mineral oil base oil with 100 ° C. viscosity of 4 cSt Base oil C: Highly refined mineral oil base oil with 100 ° C. viscosity Base oil having a viscosity of 6 cSt D: Hydrogenated refined paraffin mineral oil base oil and 100 ° C. viscosity of 3 cSt E: Hydrogenated refined paraffin mineral oil base oil having a viscosity of 4 cSt at 100 ° C.

<Additives>
Additive F: Package additive for automatic transmission oil (1) (substantially free of viscosity index improver and ashless dispersant)
Additive G: Package additive for automatic transmission oil (2) (substantially free of viscosity index improver and ashless dispersant)
Additive H: PMA viscosity index improver additive I having a weight average molecular weight (Mw) of 170,000 as a main component and a PMA viscosity index improver additive I: weight average molecular weight ( PMA viscosity index improver additive J based on a mixture of PMA of formula (1) and PMA of formula (2) whose Mw) is 100,000: Weight average molecular weight (Mw) is 20,000 PMA viscosity index improver additive K having a mixture of PMA of formula (1) and PMA of formula (2) as a main component: PMA of formula (1) having a weight average molecular weight (Mw) of 1,000,000 And PMA viscosity index improver additive L comprising a mixture of PMA of formula (2) as a main component: an olefin copolymer (OCP) viscosity index improver additive M having a weight average molecular weight (Mw) of 120,000: Weight average molecular weight (Mw) is 5 100 is a boron-containing type polyalkenylsuccinimide (ashless dispersant)
Additive N: Boron-free polyalkenyl succinimide having a weight average molecular weight (Mw) of 6,200 (ashless dispersant)

In addition, the molecular weights of the additives H, I, J, K, L, M, and N are measured by “TOSOH HLC-8020”, and the weight average molecular weight (Mw) is in terms of standard polystyrene for molecular weight calculation.
The 5 vol% distillation temperature in Table 1 was measured according to JIS K2254 (gas chromatographic method), and the flash point was measured according to JIS K2265. Further, the evaporability test and Brookfield (BF) viscosity were evaluated by the following methods.

(1) Evaporation test: In accordance with JIS K2540, the oil amount is 30 g, the temperature is 120 ° C., the test time is 96 hours, and the mass reduction rate after the test is compared with 2.0% by mass or less. did.
(2) BF viscosity: Measured at −40 ° C. according to ASTM D 2983-80, and the criterion was 20,000 mPa · s or less.

(Comparative Examples 1-5)
The base oil and additives shown in Table 2 were mixed in the blending amounts shown in Table 2 to prepare a lubricating oil composition for an automatic transmission. Table 2 shows performance characteristics of the obtained lubricating oil composition for automatic transmissions.

The lubricating oil composition for an automatic transmission according to the present invention includes an automatic transmission (AT) oil for passenger cars and large vehicles, a chain type or belt type continuously variable transmission (CVT) oil, and other wet clutches. It can be used as a vehicle automatic transmission oil, power steering oil, general industrial hydraulic fluid, fluid coupling oil, etc., and can be used for many other applications.

Claims (2)

(A) 5% by volume distillation temperature by gas chromatography is 340 ° C. or higher and 400 ° C. or lower , flash point 200 ° C. or higher, 40 ° C. kinematic viscosity is 15 mm ² / s or higher and 40 mm ² / s or lower , and pour point is −10 ° C. or lower. (B) a lubricating oil composition containing a polymethacrylate viscosity index improver having a weight average molecular weight (Mw) of 50,000 or more and 450,000 or less , wherein the lubricating oil composition is 100 The kinematic viscosity at 60 ° C. is 6.0 to 8.3 mm ² / s, the BF viscosity at −40 ° C. is 20,000 mPa · s or less, and JIS
Lubricant for automatic transmission characterized in that the amount of oil is 30 g, the temperature is 120 ° C., the test time is 96 hours, and the mass reduction rate after the test compared to before the test is 2.0% by mass or less in accordance with K2540 Oil composition. (A) 5% by volume distillation temperature by gas chromatography is 340 ° C. or higher and 400 ° C. or lower , flash point 200 ° C. or higher, 40 ° C. kinematic viscosity is 15 mm ² / s or higher and 40 mm ² / s or lower , and pour point is −10 ° C. or lower. A lubricating oil composition comprising (B) a polymethacrylate viscosity index improver having a weight average molecular weight (Mw) of 50,000 to 450,000 , and (C) an ashless dispersant . The kinematic viscosity at 100 ° C. is 6.0 to 8.3 mm ² / s, the BF viscosity at −40 ° C. is 20,000 mPa · s or less, and JIS
Lubricant for automatic transmission characterized in that the amount of oil is 30 g, the temperature is 120 ° C., the test time is 96 hours, and the mass reduction rate after the test compared to before the test is 2.0% by mass or less in accordance with K2540 Oil composition.