JP5542322B2 - Lubricating oil composition for agricultural machinery - Google Patents

Description

  The present invention relates to a lubricating oil composition for agricultural machinery. More specifically, the present invention relates to an agricultural machine having a wet clutch mechanism in a transmission, and relates to a lubricating oil composition for agricultural machines that can maintain good dynamic friction characteristics of a wet clutch over a long period of time and is excellent in wear resistance and demulsibility. .

Agricultural machines include tractors as leveling work machines, rice planting machines as growth management work machines, binders and combiners as harvesting work machines.
In such an agricultural machine, many lubrication points such as a hydraulic pump unit, a transmission unit, a PTO clutch unit, a differential gear unit, and a wet brake unit are often lubricated with one type of agricultural machine lubricant. For this reason, agricultural machinery lubricants are required to have a multi-functional role such as wear resistance, oxidation stability, rust resistance, friction characteristics, and compatibility with organic materials. In order to ensure and further enhance these performances, various additives are currently blended with the selected base oil and supplied as a lubricating oil composition for agricultural machinery (for example, Patent Documents 1 to 3). Etc.).
JP 59-25890 A JP-A-3-20396 JP 2004-59930 A

  By the way, since there are many cases where such a lubricating oil for agricultural machinery is blended with a friction modifier with an emphasis on compatibility with wet brake parts such as prevention of brake squealing, the friction coefficient tends to be low. However, as mentioned above, since the lubricating oil for agricultural machinery usually lubricates a plurality of lubrication points with one type of lubricating oil, it is sufficient for a combine and some tractors that require high control force and power transmission. May not be obtained. This is because a high friction coefficient of the friction material of the wet clutch portion is required for high control force and high power transmission.

  Therefore, it is desirable that the lubricating oil can provide a higher coefficient of friction in the wet clutch part than the suitability to such a wet brake part, particularly from the viewpoint of shortening the shift time and exhibiting good running performance. What can provide a high dynamic friction coefficient is desirable. In addition, it is desirable that a high dynamic friction coefficient can be maintained over a long period, that is, the durability of the dynamic friction coefficient is good.

Furthermore, some agricultural machines are used in paddy fields during the rainy season, and such machines are in an environment where it is unavoidable to mix water into the hydraulic tank. When water is mixed into the oil, rust generation or an emulsion formed by the oil and the water may hinder smooth oil passage in the suction filter portion of the hydraulic pump and lower the filter function. Therefore, it is desirable that emulsion formation is difficult to occur even when moisture is mixed, and that water separation (demulsibility) is high, and that rust prevention is also high.
Moreover, since the load in a gear part etc. is increasing with the high output of a tractor, it is desired that the lubricating oil used for such an agricultural machine has much higher wear prevention property.

  The present invention maintains an initial dynamic friction coefficient over a long period of time, particularly for a friction material of a wet clutch mounted on a transmission of an agricultural machine, has excellent wear resistance, and rusts even when water is mixed into an oil tank. It aims at providing the lubricating oil composition for agricultural machines which can suppress generation | occurrence | production of the emulsion which leads to generation | occurrence | production and hydraulic failure.

As a result of repeated studies aimed at solving the above-mentioned problems, the present inventors have used two types of metal detergents in a specific ratio in a lubricating base oil, and further, a specific zinc dithiophosphate. It has been found that the above-mentioned problems can be solved by blending a specific amount of A, and the present invention has been completed based on this finding.
That is, the present invention provides the following lubricating oil composition for agricultural machinery.

<1> A lubricating oil composition for agricultural machinery,
Mineral oil base oil,
(A) Zinc dialkyldithiophosphate having a secondary alkyl group having 3 to 6 carbon atoms represented by the following general formula (1) is 0.1 to 0 in terms of zinc amount relative to the total amount of the lubricating oil composition. .4 mass%,

(In General Formula (1), R ¹ , R ² , R ³ , and R ⁴ each independently represent a secondary alkyl group having 3 to 6 carbon atoms.)
(B) One or more kinds selected from calcium sulfonate having a base number of 150 mgKOH / g or more and calcium phenate having a base number of 150 mgKOH / g or more, 0.1 to 0 in terms of calcium amount relative to the total amount of the lubricating oil composition. .5% by mass,
(C) Calcium sulfonate having a base number of 50 mgKOH / g or less, 0.05 to 0.3% by mass in terms of calcium amount relative to the total amount of the lubricating oil composition,
A lubricating oil composition for agricultural machinery, comprising:

  According to the present invention, especially when the friction coefficient of the wet clutch mounted on the transmission of an agricultural machine is maintained for a long period of time, the initial dynamic friction coefficient is excellent, and the water is mixed into the oil tank. However, there is provided a lubricating oil composition for agricultural machinery that can suppress the formation of emulsion that leads to the occurrence of rust and poor hydraulic pressure.

<Base oil>
The lubricating oil composition for agricultural machinery of the present invention contains, as a base oil, a mineral lubricating base oil, a synthetic lubricating base oil, or a mixture thereof.
As the mineral oil base oil, those obtained by various production methods can be used. For example, hydrorefined oil, catalyst isomerized oil, etc. are subjected to treatment such as solvent dewaxing or hydrodewaxing. Highly refined paraffinic mineral oil and the like are preferably used. In addition to the above, mineral base oils obtained by various production methods can be used. For example, by using a hydrotreating process using a hydrotreating catalyst such as a raffinate obtained by solvent purification using an aromatic extraction solvent such as phenol or furfural as a lubricant base oil raw material, cobalt or molybdenum using silica-alumina as a carrier. Examples thereof include hydrotreated oil obtained. In particular, a high viscosity index mineral oil obtained by a hydrocracking process or an isomerization process can be mentioned as a suitable one.

  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 thereof include hindered esters and dibasic acid esters. In addition, if it is a small amount, phosphate ester and silicone oil can be used. Each of these base oils may be used alone or in combination of two or more. Further, a mineral oil base oil and a synthetic base oil may be mixed and used.

These base oils preferably have a kinematic viscosity at 100 ° C. according to the JIS K2283 kinematic viscosity test method of 2.0 to 9.0 mm ² / s.

<(A) component>
The lubricating oil composition for agricultural machinery of the present invention is a zinc dialkyldithiophosphate having a secondary alkyl group having 3 to 6 carbon atoms represented by the following general formula (1) as the component (A) (hereinafter, "May be abbreviated as" ZnDTP ").

In the general formula (1), R ¹ , R ² , R ³ , and R ⁴ each independently represent a secondary alkyl group having 3 to 6 carbon atoms. Any one of R ¹ , R ² , R ³ , and R ⁴ is inferior in wear resistance in the case of a primary alkyl group, but all of them are secondary alkyl groups having 3 to 6 carbon atoms. Thus, the wear resistance can be effectively improved.

  The amount of component (A) added is 0.1 to 0.4% by mass, preferably 0.15 to 0.3% by mass, more preferably 0.2 to 0.3% by mass in terms of zinc relative to the total amount of the lubricating oil composition. It is 0.25% by mass. When the addition amount of component (A) is less than 0.1% by mass, the anti-wear property becomes insufficient, and even if added over 0.40% by mass, the effect of improving the anti-wear property corresponding to the addition amount cannot be obtained. , The cost will increase.

<(B) component>
The lubricating oil composition for agricultural machinery of the present invention contains at least one selected from calcium sulfonate having a base number of 150 mgKOH / g and calcium phenate having a base number of 150 mgKOH / g as component (B).
As the structure of the calcium sulfonate and the calcium phenate, for example, the compounds represented by the following general formulas (2) to (4) can be reacted by reacting calcium carbonate or borate in the presence of carbon dioxide. Examples include basic ones.

General formula (2) and general formula (3) are basic calcium sulfonates, and general formula (4) is basic calcium phenate. In the above formulas (2) to (4), R ^{5 to} R ⁸ each independently represents a hydrogen atom or an alkyl group having 1 to 30 carbon atoms, preferably an alkyl group having 6 to 18 carbon atoms. When present, they may be the same or different. n is an integer of 1 to 4, and x of Sx is 1 or 2, preferably 1.

The calcium sulfonate and calcium phenate added as the component (B) have a base number measured by the perchloric acid method of JIS K2501 of 150 mgKOH / g or more. When the base number is less than 150 mgKOH / g, the durability of the dynamic friction coefficient decreases. On the other hand, the upper limit of the base number is not particularly limited, but those that are usually readily available are those up to about 500 mgKOH / g.
Component (B) is added in an amount of 0.1 to 0.5 mass%, preferably 0.1 to 0.3 mass%, more preferably 0.1 to 0, in terms of calcium relative to the total amount of the lubricating oil composition. .2% by mass. When the amount of component (B) added is less than 0.1% by mass, the durability of the dynamic friction coefficient decreases, and when it exceeds 0.5% by mass, an effect commensurate with the blending amount cannot be obtained, and the cost increases. End up.

  If there is a small amount of sulfonates or phenates of alkali metals or alkaline earth metals other than calcium, such as magnesium, barium, sodium, etc., they can be mixed with the above calcium sulfonates or calcium phenates. Since it becomes easy to form an emulsion, it is not desirable to use sulfonates and phenates other than calcium based in the present invention. In addition, although a small amount of alkali metal or alkaline earth metal salicylate can be mixed and used, it is also undesirable to use this because it easily forms an emulsion when mixed with water.

<(C) component>
The lubricating oil composition for agricultural machinery of the present invention contains calcium sulfonate having a base number of 50 mgKOH / g or less as the component (C).
Examples of the structure of calcium sulfonate include those having the same structure as that of the component (B) (represented by the general formula (2) or the general formula (3)). Even if it goes, the base number does not exceed 50 mgKOH / g.

When the base number of the calcium sulfonate as the component (C) exceeds 50 mgKOH / g, it becomes easy to form an emulsion when mixed with water, and sufficient rust prevention properties cannot be obtained.
Component (C) is added in an amount of 0.05 to 0.3% by mass, preferably 0.05 to 0.2% by mass in terms of calcium relative to the total amount of the lubricating oil composition. When the amount of component (C) added is less than 0.05% by mass, an emulsion is likely to be formed when mixed with water, and sufficient rust resistance cannot be obtained. On the other hand, if it exceeds 0.3% by mass, not only an effect commensurate with the amount added is obtained but also the cost increases.

  In the lubricating oil composition for agricultural machinery of the present invention, it is necessary that both the component (B) and the component (C) are added in the predetermined amounts. Component (B) alone has insufficient emulsion formation inhibition and rust prevention properties, and component (C) alone decreases the durability of the dynamic friction coefficient.

<Other ingredients>
In addition to the lubricating base oil and the three essential components (A) to (C) above, the lubricating oil composition for agricultural machinery of the present invention, if necessary, known additives such as an oily agent, Antiwear agent, extreme pressure agent, rust inhibitor, friction modifier, antioxidant, metal deactivator, viscosity index improver, pour point depressant, antifoaming agent, colorant, package additive for tractor hydraulic oil Alternatively, various lubricating oil package additives containing at least one of them can be added. However, since the lubricating oil composition of the present invention emphasizes a high friction coefficient in the wet clutch part rather than suitability for wet brakes, do not mix oiliness agents and friction modifiers that lead to a reduction in the friction coefficient. Is preferred. In addition, although there is a concern about wear of the lubrication part when a friction modifier is not blended, in the present invention, the component (A) contains zinc dialkyldithiophosphate having a secondary alkyl group having 3 to 6 carbon atoms. Therefore, a sufficient antiwear agent can be secured.

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 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, 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, and diols.
Examples of the antioxidant include amine-based, phenol-based, and sulfur-based antioxidants.
Examples of the metal deactivator include benzotriazole, thiadiazole, alkenyl succinate and the like.
Examples of the viscosity index improver include polyalkyl methacrylate, polyisobutylene, ethylene-propylene copolymer, styrene-isoprene copolymer, styrene-butadiene hydrogenated copolymer, or polyisobutylene.
Examples of the pour point depressant include polyalkyl methacrylate, chlorinated paraffin-naphthalene condensate, and alkylated polystyrene.
Examples of the antifoaming agent include silicon compounds such as dimethylpolysiloxane, fluorosilicone compounds, and ester-based compounds.

<Preparation method>
As a method for preparing the lubricating oil composition for agricultural machinery of the present invention, the base oil and the essential components (A) to (C) and various additives may be appropriately mixed as necessary. The mixing order is not particularly limited, and the essential components (A) to (C) may be sequentially mixed with the base oil, or the essential components (A) to (C) may be mixed in advance. . Furthermore, various additives may be added to the base oil in advance, or may be added in advance to any of the essential components (A) to (C).

<Application>
The lubricating oil composition for agricultural machinery of the present invention can be suitably used for agricultural machinery of a type in which a high friction coefficient in a wet clutch is more important than compatibility in a wet brake.

  On the other hand, the lubricating oil composition for agricultural machinery of the present invention can also be used for sintered metal friction materials, but when the load is large with sintered metal friction materials, a sufficient dynamic friction coefficient is obtained. Durability may not be obtained. Therefore, the lubricating oil composition of the present invention is applied to a small agricultural machine having a small load on the transmission, etc., compared to a machine having a friction material made of sintered metal and a large load on the transmission, etc. It can be preferably used.

Next, the present invention will be described more specifically with reference to examples. In addition, this invention is not restrict | limited at all by these examples.
In Examples and Comparative Examples, base oil and additives for each component were blended to prepare a tractor hydraulic oil composition, and the performance of each was evaluated. The components of the base oil and additives used for preparing the compositions in each Example and each Comparative Example are as follows.

(1) Base oil The following base oil A and base oil B are mixed within a range where the base oil B is 1 to 10% by volume, so that the 100 ° C. kinematic viscosity of the composition is about 7.0 mm ² / s. Prepared.
Base oil A: Kinematic viscosity at 100 ° C. is 5.7 mm ² / s, highly refined mineral oil base oil having a viscosity index of 108 Base oil B: Kinematic viscosity at 100 ° C. is 11.1 mm ² / s Highly refined mineral oil base oil with a viscosity index of 97

(2) Zinc dialkyldithiophosphate (ZnDTP)
ZnDTP (secondary)
A zinc dialkyldithiophosphate in which R ^{1 to} R ^{4 in} the general formula (1) are all secondary alkyl groups having 3 or 6 carbon atoms. Zinc content: 9.0% by mass.
ZnDTP (primary) -A
A zinc dialkyldithiophosphate in which R ^{1 to} R ^{4 in} the general formula (1) are all primary alkyl groups having 8 carbon atoms. Zinc content: 9.5% by mass.
ZnDTP (primary) -B
A zinc dialkyldithiophosphate in which R ^{1 to} R ^{4 in} the general formula (1) are all primary alkyl groups having 8 carbon atoms. Zinc content: 8.9% by mass.

(3) Ca sulfonate (base number 330)
Calcium sulfonate, which is a mixture of natural formula (2) and general formula (3) (natural system) and has a base number measured by the perchloric acid method of JIS K2501 of 330 mgKOH / g and a Ca concentration of 12% by mass.

(4) Ca sulfonate (base number 20)
A calcium sulfonate represented by the general formula (3) and having a base number of 20 mgKOH / g and a Ca concentration of 2.7% by mass as measured by the perchloric acid method of JIS K2501.

(5) Viscosity index improver A non-dispersed polyalkyl methacrylate having a weight average molecular weight of 370,000.

(6) Dispersant A monosuccinimide having a polybutenyl group having a weight average molecular weight of about 1000 and a nitrogen content of 2.1% by mass.

<Evaluation method>
-Dynamic friction coefficient and endurance test of dynamic friction coefficient-
SAE No. stipulated in the automotive standard JASO M348 “Automatic Transmission Oil Friction Characteristics Test Method” of the Japan Society for Automotive Engineers. 2 Using a test apparatus, the JASO M348 test was conducted to examine the friction characteristics of the paper friction material. Here, the dynamic friction coefficient means that the friction disk is rotated at a constant speed of 3600 rpm, then the drive power of the motor for dynamic friction test is turned off, and at the same time, a pressing load is applied to brake the inertia disk with the friction torque generated by the friction disk and steel plate. The dynamic friction coefficient value (μd) calculated by the following equation (5) from the friction torque Td when the rotation speed reaches 1800 rpm after the start of braking.

μd: Dynamic friction coefficient T: Friction torque (Nm)
n: number of friction discs re: average friction effective radius P: pressing load A: friction area

  A 5000 cycle test was carried out by the JASO method, and the μd value at the time of 500 cycles in the middle and the μd change rate calculated from the following formula (6) were determined. When the μd value at the 500th cycle is low, the wet clutch becomes slippery, and the larger the μd change rate, the poorer the dynamic friction coefficient.

-Water separation test-
The water mixing method shown by the filterability evaluation described in SAE Paper 972788 was performed. Specifically, water was mixed in the test oil, stirred, allowed to stand for 168 hours, and centrifuged (1000 × g, 1 hour), and then the emulsion amount was measured. The smaller the emulsion amount, the better (demulsibility).

-Rust prevention test-
It evaluated by the wet test based on JISK-2246, and the presence or absence of the rust after the test for 100 hours was evaluated.

−Abrasion prevention test−
In accordance with ASTM D4171, a shell four-ball test was performed under the following conditions, and the wear scar diameter after the test was measured. The smaller the numerical value of the wear scar diameter, the higher the wear prevention effect.
Rotation speed: 1800rpm
Test time: 30min
Oil temperature: 80 ° C
Load: 392N

  The formulations and test results in Example 1-3 and Comparative Example 1-6 are shown in Tables 1-3.

  * In the test of the coefficient of friction μd change rate in Comparative Examples 1 and 2, μd was abnormally high at an early stage of the test, and the plate was severely damaged.

  As shown in the results of the above examples, the lubricating oil composition for agricultural machinery of the present invention is excellent in durability of the dynamic friction coefficient, and is good even when used for a long period of time. It can be seen that it is useful as a lubricating oil for agricultural machinery such as a tractor because it is highly effective and also has an excellent emulsion formation inhibiting effect and rust prevention.

Claims (2)

A lubricating oil composition for agricultural machinery,
Mineral oil base oil,
(A) Zinc dialkyldithiophosphate having a secondary alkyl group having 3 to 6 carbon atoms represented by the following general formula (1) is 0.1 to 0 in terms of zinc amount relative to the total amount of the lubricating oil composition. .4 mass%,


(In General Formula (1), R ¹ , R ² , R ³ , and R ⁴ each independently represent a secondary alkyl group having 3 to 6 carbon atoms.)
(B) One or more kinds selected from calcium sulfonate having a base number of 150 mgKOH / g or more and calcium phenate having a base number of 150 mgKOH / g or more, 0.1 to 0 in terms of calcium amount relative to the total amount of the lubricating oil composition. .5% by mass,
(C) Calcium sulfonate having a base number of 50 mgKOH / g or less, 0.05 to 0.3% by mass in terms of calcium amount relative to the total amount of the lubricating oil composition,
A lubricating oil composition for agricultural machinery, comprising:   The lubricating oil composition for agricultural machinery according to claim 1, which is a lubricating oil composition for agricultural machinery having a wet clutch mechanism in a transmission.