JP3283206B2 - Gear oil composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gear oil composition, and more particularly, to a gear oil composition used under high speed, high load and high temperature atmosphere.

[0002]

2. Description of the Related Art With the development of industry, high efficiency and energy saving have been remarkably improved, but there is still a strong demand for them as eternal problems.
High efficiency and low cost are also required for gears used in various industrial machines. In particular, gears used in power transmission units of automobiles and railways have been reduced in size and weight, and the amount of gear oil has been reduced. Therefore, gear oils that can withstand higher temperatures and withstand higher-load operation per unit oil amount, in combination with the trend toward higher speed and higher output, have been eagerly desired.

[0003] Lubricating base oils include conventional mineral oils, alkylbenzenes and polyalphaolefins (hereinafter referred to as PAOs).
Synthetic oils such as polyalkylene glycol (hereinafter sometimes abbreviated as PAG), esters and the like are used. However, conventional gear oils using mineral oil as a base oil have insufficient thermal stability and cannot be used as a base oil for gear oils, particularly at high speeds and high temperatures. Also, in synthetic oils, for example, PAO has poor solubility of additives as compared with mineral oil-based lubricating oils, synthetic oil-based lubricating base oils such as esters or PAGs, etc., and does not dissolve uniformly, resulting in turbidity. Not only impairs the commercial value of the lubricating oil, but also has the disadvantage that the additive is not used effectively. Particularly in gear oils used under high-severity conditions such as high speed, high load and high temperature, additives tend to be used in a relatively large amount, and therefore, affinity with additives is important. On the other hand, almost no ester-based synthetic oils satisfying both suitable viscosity and pour point at the same time as a gear oil are found. Esters having a relatively low molecular weight have a low pour point, and although this point is satisfied, there is a disadvantage that the viscosity is too low. Esters having a relatively high molecular weight have a high viscosity but a high pour point, so that they are difficult to use as gear oils. Some esters with relatively high molecular weight unsaturated carboxylic acids simultaneously satisfy both viscosity and pour point, but such esters have poor oxidative stability, especially at high temperatures. There are bad drawbacks.

[0004]

SUMMARY OF THE INVENTION In view of the above-mentioned problems of the prior art, the present invention satisfies a gear oil composition suitable for gears operated under severe conditions such as high speed and high load. It is intended to provide a gear oil composition having excellent overall performance and excellent stability especially at high temperatures.

[0005]

Means for Solving the Problems The present inventors have intensively studied the characteristics of various lubricating base oils and additives combined with each other, and as a result, selected a specific base oil, and The inventors have found that the combination solves the above problems, and have completed the present invention. That is, the present invention provides (1) the following (A) and (B) in a weight ratio of 5:95 to 95: 5.
And at least one succinimide and / or a derivative thereof as a dispersing agent and gear oil
Containing 0.2 to 2% by weight based on the composition and having a kinematic viscosity at 100 ° C of 7 to 20 cSt. And a gear oil composition having a pour point of −25 ° C. or less; (A) at least one ester represented by the following formula (1):

[0006]

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In the formula (1), R ¹ represents an alkyl group having 1 to 3 carbon atoms, and R ² , R ³ and R ⁴ represent 4 to 10 carbon atoms.
And (B) a kinematic viscosity at 100 ° C. of 8 to 50 cSt. (2) The gear oil composition according to the above (1), wherein the succinimide derivative is borated.

[0008] When an ester is used as a lubricating oil for gears, one having a small molecular weight is generally preferred because of its low pour point, but its viscosity is too low to be used alone. Those having a high molecular weight have too high a pour point and cannot be used alone with such an ester. However, the particular ester used in the present invention is PAO as described below.
By using in combination with the above, a lubricating base oil for gear oil having desired performance can be obtained.

Esters are compounds obtained by an esterification reaction between an alcohol and an acid, and there are many types of compounds. For example, an ester of an alcohol having no neopentyl skeleton and a carboxylic acid, an ester of a neoacid having a neopentyl skeleton and an alcohol, or a complex of a polyhydric alcohol, a polyhydric carboxylic acid and a monohydric carboxylic acid (or a monoalcohol) There are also esters,
Such esters cannot be preferably used in the present invention because they have poor hydrolytic stability and chemical stability at high temperatures, are expensive in raw materials, or require cumbersome and complicated control during production. Esters with unsaturated fatty acids are also not preferred because of their poor chemical stability at high temperatures. Compared to these esters, neopentyl polyols such as neopentyl glycol, trimethylolethane, trimethylolpropane (hereinafter sometimes abbreviated as TMP), trimethylolbutane, and pentaerythritol (hereinafter sometimes abbreviated as PE) Esters composed of polyhydric alcohols are preferable in that they have excellent hydrolysis stability and chemical stability, are easily available, and can be easily produced. However, among these esters, neopentyl glycol esters having low viscosity and pentaerythritol esters having low solubility in additives are not suitable for achieving the object of the present invention.

After all, the ester used in the present invention is an ester comprising the specific polyhydric alcohol represented by the above general formula (1) and the specific saturated monocarboxylic acid. The polyhydric alcohol component is at least one of the above-mentioned trimethylolethane, trimethylolpropane, and trimethylolbutane. Particularly, esters of trimethylolpropane are preferred. The viscosity of the ester at 100 ° C. is preferably about 3 to 7 cSt, more preferably 3 to 7 cSt.
5 cSt. Further, the pour point is preferably about -10 to -50C or lower, more preferably -30 to -50C or lower. Further, as shown by the formula (1), the ester used in the present invention is a full ester in which all the hydroxyl groups of the polyhydric alcohol are esterified with the carboxylic acid. It is needless to say that it is preferable that unreacted substances and impurities contained in the ester are small, but this also relates to the industrial efficiency in the reactive esterification reaction step and the purification step after the reaction. As the degree of purification of the whole ester including the purified full ester, values of an acid value and a hydroxyl value can be used as a guide. The acid value is preferably 1 mgKOH / g or less, more preferably 0.5 mgKOH / g or less, and the hydroxyl value is preferably 10 mgKOH / g or less.

In the formula (1), -C (O) R ² , -C
As the carboxylic acid corresponding to (O) R ³ and —C (O) R ⁴ , a saturated monovalent carboxylic acid in which R ² , R ³ and R ⁴ correspond to an alkyl group having 4 to 10 carbon atoms, that is, a carbon number 5-1
1 saturated monovalent carboxylic acid. More preferably, it is a carboxylic acid having 6 to 10 carbon atoms. Specifically, linear saturated monovalent carboxylic acids such as valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, and capric acid, or branched saturated monovalent carboxylic acids which are isomers of these acids. Acids. In the esterification, one or two or more of these acids are reacted with each other. Esters synthesized with a mixed acid obtained by mixing two or more of these acids have a viscosity characteristic, Particularly, the fluidity at a low temperature is improved, which is more preferable.

The polyalphaolefin (PAO) used in the present invention has a viscosity at 100 ° C. of 8 to 50 cS.
t. As long as the pour point is −25 ° C. or lower, various types can be used. Therefore, a commercially available one may be appropriately selected and used.

In the gear oil composition of the present invention, the above P
The viscosity of AO is important, and the viscosity at 100 ° C. is 4c.
St. If it is less than 50 cSt., It has the disadvantage of a large evaporation loss. If it exceeds, it is too viscous and handling of the base oil becomes troublesome, so that it cannot be used preferably.

PAO is a polymer obtained by polymerizing one or more alpha-olefins, and alpha-olefins having 2 to 16 carbon atoms, preferably 8 to 12 carbon atoms, can be preferably used. Although PAO is originally a mixture (aggregate) of components (PAO compounds) having a molecular weight distribution, a plurality of mixtures having different viscosities (average molecular weights) may be mixed and used.

As the gear oil, a sulfur-based extreme pressure agent or a phosphorus-based extreme pressure agent is used because it is used for smooth sliding between metal members to which a very high surface pressure is applied. It is important to efficiently disperse sludge generated by using these extreme pressure agents and keep the sliding surface clean. Detergent dispersants include benzylamine, Ca-sulfonate, succinimide and derivatives thereof. However, benzylamine is inferior in cleaning dispersibility at high temperatures as compared with Ca-sulfonate, succinimide and the like, and Ca-sulfonate inhibits seizure resistance and abrasion resistance of the extreme pressure agent. On the other hand, succinimide or a derivative thereof exhibits excellent clean dispersibility at high oil temperatures, and is therefore suitable for gears used under high-speed, high-load, and high-temperature atmospheres. However, since PAO generally has a disadvantage that it is difficult to dissolve, in the gear oil composition of the present invention using PAO, the added succinimide or a derivative thereof exerts its role (cleaning / dispersing effect) as a whole. Without waste, it is of concern that the precipitation of the additives will greatly impair the commercial value of the gear oil composition, but the present invention particularly relates to this succinimide or a derivative thereof. The disadvantage that the compound is difficult to dissolve in PAO is solved by using the above-mentioned mixed base oil obtained by mixing PAO with a specific ester.

The succinimide used in the present invention includes those represented by the following general formulas (3) and (4).

[0017]

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In the formula, R ⁵ represents a hydrocarbon group having 1 to 50 carbon atoms; R ⁶ represents an alkylene group having 2 to 5 carbon atoms;
Represents an integer of 1 to 10, and X represents hydrogen, an acyl group, a boron-containing substituent, or the like. In formulas (3) and (4), a plurality of R ⁵ , a plurality of R ⁶ , or a plurality of Xs may be the same or different.

Of the above-mentioned succinimides or derivatives thereof, the use of succinimide containing boron is more preferable because it has little effect on lowering the seizure resistance and abrasion resistance of the extreme pressure agent. Since such compounds are already commercially available, they can be appropriately selected and used. For example, Lubrizol's LZ935 (product model number, the same applies hereinafter), Exxon Chemical's PARANOX106, Olonite's OLOA373, AX-963, and Ethyl's X-X
8788 and the like. It goes without saying that a so-called package type additive in which succinimide or a derivative thereof is previously blended may be used.

The succinimide or a derivative thereof is added in an amount of 0.2 to 2% by weight, preferably 0.4 to 1.0% by weight, based on the gear oil composition. do it. In the case of a boron-containing succinimide derivative, the amount of addition may be blended within the above range, but based on the amount of boron, 0.001 to 0.05 with respect to the entire gear oil composition. % By weight, preferably 0.005 to 0.02% by weight.

In the present invention, the above ester and PA
O is used as an essential component of the lubricating oil of the gear oil. By using the ester and PAO together, the poor solubility of PAO is compensated for by the ester, and the poor balance between the viscosity and the pour point of the ester is compensated for by the PAO. A lubricating oil for gears is obtained. It is preferable that the ester and the PAO be mixed and used in a weight ratio of 5:95 to 95: 5. If the mixing ratio of PAO exceeds 95, the problem of solubility with the above-mentioned additives will occur, and if the mixing ratio of ester exceeds 95, the problems of viscosity and pour point will occur. Not preferred. The mixing ratio of the ester and the PAO is more preferably 60:40 to 10:90, and further preferably 40:60 to 15:85.

The viscosity at 100 ° C. of the gear oil composition obtained as described above is preferably 7 to 2
0cSt. More preferably, 9 to 11 cSt. It is. 7
cSt. If it is less than 1, lubrication problems such as abrasion may be a problem in terms of securing the oil film thickness. On the other hand, 20 cSt. When it exceeds, power loss due to viscous resistance increases, and energy is wasted. The pour point is -25 ° C or lower, preferably -30 ° C or lower. Pour point is -25 ° C
If it is higher, the flow is impaired in winter or in a cold region, and good starting performance cannot be obtained, which may result in gear damage. If the lubricating oil composition for gears of the present invention obtained by mixing the above ester and PAO in the above proportions satisfies the above viscosity and pour point ranges, the respective viscosities of the ester and PAO as base oils and It goes without saying that the pour point need not be in this range.

Further, the gear oil composition obtained as described above can contain various additives conventionally added to lubricating oils, as long as the object of the present invention is not impaired. Such additives include, for example, sulfurized olefins, extreme pressure agents such as tricresyl phosphate, antiwear agents, antioxidants such as ditertiary butyl paracresol, zinc dialkyldithiophosphate, and metal deactivators such as benzotriazole. And defoaming agents such as silicone oil. The amount of the additive may be appropriately selected according to the required value of the gear used, the characteristics of the base oil, the characteristics of the additive, and the like. A gear oil additive package in which several kinds of the above additives are combined and premixed can also be used.

The gear oil composition of the present invention, which is excellent in the solubility, detergency, and oxidation stability of additives, can be used for gears used in various industrial machines, and for vehicles for movement and transportation, especially for motor vehicles of railways. It is useful as a lubricating oil for the gears used.

[0025]

The present invention will be described in more detail with reference to examples and comparative examples.

Examples 1 to 4 and Comparative Examples 1 to 6 Mineral oils A and B used as base oils in Examples and Comparative Examples
Table 1 shows the properties of PAO-A to C and ester-A to G. In Table 1, a mixture of saturated monocarboxylic acids having the indicated C number was used for the esters A and C.

[0027]

[Table 1]

The additives include a package additive (additive A) comprising a sulfur-based extreme pressure agent, a phosphorus-based extreme pressure agent, an antioxidant, a metal deactivator and an antifoaming agent. And an additive obtained by mixing Lubrizol LZ935 comprising borated succinimide as a cleaning dispersant (additive B)
And a pour point depressant (additive C) consisting of polymethacrylate having a number average molecular weight of about 40,000. In addition,
About 13% by weight of LZ935 in Additive B
(Approximately 0.25% by weight of boron).

The lubricating oil compositions for gears of Examples 1 to 4 and Comparative Examples 1 to 6 were prepared by blending these base oils and additives in the weight ratios shown in the upper part of Table 2. Physical properties of the obtained lubricating oil composition for gears were measured and evaluated, and the results shown in the lower part of Table 2 were obtained. The physical properties of the base oil and the lubricating oil composition for gears were measured and evaluated by the following methods.

Pour point: Measured according to JIS K 2269.

Kinematic viscosity: Measured according to JIS K 2283.

Viscosity index: Calculated according to JIS K 2283.

Total acid value: JIS K2501-5.
Measured according to the section.

Oxidation stability: JIS K 2514-4.
The measurement was performed according to the method described in the section (ISOT). However, the temperature was 170 ° C. and the test time was 48 hours. The oxidation stability was evaluated based on the degree of lacquer after the test (presence or absence of deposits on the varnish rod), the viscosity ratio of the lubricating oil before and after the test, and the increase in the total acid value. Turbidity: Using a constant temperature bath at a temperature of 60 ° C., a base oil and an additive are charged into a 100 cc beaker at a predetermined ratio (the ratio in Table 2), stirred and mixed for 1 hour, and left at room temperature for 3 days.
The presence or absence of turbidity was visually observed.

[0035]

[Table 2]

From the results shown in Table 2, although the lubricating oil compositions for gears of Examples 1 to 4 contain the succinimide derivative containing boron, no turbidity is observed and the pour point is low. According to the results of the oxidation stability test, the varnish rod has no deposits, is excellent in cleanliness, and has a small increase in viscosity and total acid value.
High oxidation stability.

As compared with the gear lubricating oil composition of the example, the comparative example has various disadvantages. For example, in Comparative Example 1, since mineral oil is used, no turbidity is observed, but the oxidation stability is poor and the viscosity increase is particularly large.

Comparative Example 2 was pentaerythritol (PE)
And an ester of oleic acid (C18), which also has poor oxidation stability, and particularly has a large increase in viscosity and a large total acid value. Comparative Example 3 is trimethylolpropane (TMP)
And lauric acid (C12) ester,
High pour point. Comparative Example 4 uses an ester of TMP and oleic acid (18 carbon atoms), has poor oxidation stability, and particularly has a large increase in viscosity and a large increase in total acid value. Furthermore, since it does not contain succinimide or a derivative thereof, it adheres to a varnish rod and has poor cleanability. The composition of Comparative Example 5 using an ester of PE and heptanoic acid (carbon number 7) has poor solubility with additives and causes turbidity. Since Comparative Example 6 does not contain a specific ester component as a base oil, the solubility is poor and turbidity occurs.

COMPARATIVE EXAMPLE 7 An additive (additive D) obtained by mixing Lubrisol LZ58B made of overbased Ca sulfonate as a detergent and dispersant with the above additive A (additive D) was used in place of additive B in Example 2. A gear oil composition (Comparative Example 7) was prepared in exactly the same manner as in Example 2 except for the above. LZ blended with additive D
The proportion of 58B was about 13% by weight. The gear oil composition of Comparative Example 7 had almost the same properties as Example 2 as shown below.

Turbidity no pour point -52.5 ° C. kinematic viscosity (40 ° C.) 60.43 mm ² / s (100 ° C.) 9.691 mm ² / s viscosity index 144 total acid number 0.72 mg KOH / g When the load resistance was measured by the Soda Four Ball Method of JIS K2519, Example 2 was 0.59 MPa, whereas Comparative Example 7 was 0.49 MPa, which was considerably inferior to Example 2.

[0041]

The gear oil composition of the present invention is a gear oil composition comprising a specific ester and PAO and further comprising succinimide or a derivative thereof, so that the gear oil composition has excellent solubility with additives. Not only has a high commercial value, but also has excellent oxidation stability and cleanliness, and can be suitably used particularly for gears used under high speed, high load, and high oil temperature.

Continued on the front page (51) Int.Cl. ⁷ Identification code FI C10M 139: 00) C10M 139: 00) C10N 20:00 C10N 20:00 A 20:02 20:02 30:06 30:06 30:08 30 : 08 40:04 40:04 60:14 60:14 (72) Inventor Kazuo Nakamura 2-8-8 Hikaricho, Kokubunji-shi, Tokyo 38 Inside the Railway Technical Research Institute (72) Inventor Kiyoshi Tanaka Kokubunji, Tokyo 2-8-8 Ichimitsucho 38 Within the Railway Technical Research Institute (72) Inventor Yasutomo Sone 2-8-8 Hikaricho Kokubunji-shi, Tokyo 38 Within the Railway Technical Research Institute (58) Fields surveyed (Int .Cl. ⁷ , DB name) C10M 169/04

Claims (2)

(57) [Claims] 1. The following (A) and (B) are in a weight ratio of 5: 9.
A base oil mixed at a ratio of 5 to 95: 5 and at least one succinimide and / or a derivative thereof as a detergent / dispersant in an amount of 0.2 to 2% by weight based on the gear oil composition;
The kinematic viscosity at 100 ° C. is 7 to 20 cSt. And a pour point of -25 ° C or lower. (A) at least one ester represented by the following formula (1): In the formula (1), R ¹ represents an alkyl group having 1 to 3 carbon atoms, and R ² , R ³ and R ⁴ represent an alkyl group having 4 to 10 carbon atoms, which may be the same or different. Good (B) The kinematic viscosity at 100 ° C. is 8 to 50 cSt. At least one polyalphaolefin which is 2. The gear oil composition according to claim 1, wherein the succinimide derivative is borated.