Gear oil composition

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention relates to a gear oil composition, and more specifically, has excellent oxidation stability at a high temperature (150 ° C or higher), copper corrosion resistance at a high temperature (150 ° C or higher), extreme pressure resistance, wear resistance, and resistance to abrasion. The present invention relates to a dual-purpose gear oil composition for automobiles, which has pitching properties and synchro characteristics and can lubricate a manual transmission and a final reduction gear.

【0002】

[Conventional technology]

Since automobile gears are used under high speed and high load conditions, the gear oil used for them must have excellent seizure resistance and wear resistance. Therefore, in order to improve the seizure prevention property, there is a gear oil to which a sulfur-based additive typified by an olefin sulfide, a sulfide oil or fat, etc. is added. In addition, there are gear oils (sulfur-phosphorus gear oils) to which phosphorus-based additives such as phosphoric acid esters or amine salts of phosphoric acid esters have been added to enhance wear resistance, and gear oils to which zinc alkyl dithiophosphate has been added. .. The manual transmission uses gear oil with an extreme pressure level of API GL-3 or GL-4 containing a mild sulfur-phosphorus extreme pressure agent or zinc alkyl dithiophosphate, and the final reduction gear has a high level. API containing highly active sulfur-phosphorus extreme pressure agent because extreme pressure is required Gear oil of GL-5 or higher is used. Therefore, since the gear oils used for the manual transmission and the final reduction gear have different required performances, the manual transmission oil is used for the manual transmission and the final reduction gear oil is used for the final reduction gear. However, there is a strong demand in the market for maintenance-free operation and simplification of oil management, and there is a growing demand for a combined oil that can lubricate a manual transmission and a final reduction gear with one type of gear oil.

【0003】

Gear oil compositions that can lubricate both manual transmissions and final speed reducers have been known so far, and in particular, in the pre-printed edition of the Academic Lecture Meeting of the Society of Automotive Engineers of Japan, 1992, Vol. 2, No. 924, p. 65. A composition combining the described sulfur-phosphorus-based extreme pressure agent, antioxidant and cleaning agent, the sulfur-phosphorus-based extreme pressure agent described in JP-A-9-132790, and alkali metal borate hydration. A composition combining a product and zinc alkyl dithiophosphate, a sulfur compound such as hydrogen sulfide sulfide, terpen sulfide or oil sulfide described in JP-A-10-316987, and an acidic phosphoric acid ester and an amine salt thereof. Combined compositions are known.

【0004】

In recent years, due to the development of expressways, the nationwide expansion of TA-Q-BIN, and the rapid increase in demand for high-speed transportation, the ratio of high-speed operation has increased, and the gear unit has become smaller in terms of higher engine output and improved aerodynamic characteristics. As a result, the gear oil temperature of the manual transmission and the final reduction gear has increased remarkably. The gear oil composition that can be lubricated for both the conventional manual transmission and the final reduction gear has insufficient stability of the sulfur compound used at a high temperature (150 ° C or higher), and decomposes at a high temperature. The oxidative stability of the lubricating oil composition is significantly reduced, causing problems such as corrosion and sludge formation on metals, especially copper, and as a result, wear and seizure of the gear tooth surface are promoted. Furthermore, in a manual transmission, the synchronizer ring and gear cone in the synchromesh mechanism cause problems such as a decrease in friction coefficient or abnormal wear, which causes troubles such as poor synchronization, increased shift force, and forced shifting. Sometimes.

【0005】

[Problems to be Solved by the Invention]

From the above background, an object of the present invention is to have excellent oxidation stability at high temperature (150 ° C or higher), copper corrosion resistance, extreme pressure resistance, wear resistance, synchro characteristics, and manual speed change. The point is to provide a gear oil composition for automobiles that can lubricate the machine and the final reduction gear in common.

【0006】

[Means for Solving the Invention]

As a result of repeated studies to solve the above problems, the present inventors have added dialkyltrisulfide, dithiophosphate ester, acidic phosphate ester and its alkylamine salt to a specific base oil, and alkenyl succinic acid as required. By combining with an imide derivative, oxidation stability and resistance at high temperatures (150 ° C or higher) are achieved while maintaining the same extreme pressure resistance and abrasion resistance as when a conventional sulfur-phosphorus extreme pressure agent is used. It was found that the copper corrosiveness was significantly improved. Furthermore, it was also found that good synchro characteristics can be obtained by using this combination.

【0007】

That is, the first aspect of the present invention is that the kinematic viscosity at 100 ° C is 2 to 80 mm.²s^-1In the base oil, (A) General formula: [Chemical 4]

R¹-SSSR¹ ...... (1) (R¹Is a hydrocarbon group), containing one or more dialkyltrisulfides in an amount of 0.1 to 10% by weight based on the total amount of the composition, (B) General formula: [Chemical 5]

(R²O)₂P (= S) SR³ ...... (2) (R²And R³Is a group independently selected from the group consisting of hydrocarbon groups), and one or more dithiophosphates are contained in 0.1 to 5% by weight based on the total amount of the composition, (C) general. formula: [Chemical 6]

(R⁴O)_nP (= O) (OH)_3-n ...... (3) (R⁴Is a hydrocarbon group and n is 1, 2 or 3), one or more phosphorus compounds selected from acidic phosphate esters, phosphoric acid esters and alkylamine salts thereof. The present invention relates to a gear oil composition, which comprises 0.1 to 5% by weight as an essential component based on the total amount of the composition.

【0008】

The second aspect of the present invention further relates to the gear oil composition according to claim 1, wherein (D) alkenyl succinimide or a derivative thereof is contained in an amount of 0.1 to 5% by weight based on the total amount of the composition.

【0009】

The gear oil composition of the present invention composed of the above components has excellent performance that should be provided as a manual transmission oil, that is, excellent oxidation stability at high temperature (150 ° C or higher), and high temperature (150 ° C or higher). Excellent copper corrosion resistance, extreme pressure resistance, wear resistance, pitching resistance, having an appropriate dynamic friction coefficient at the synchronizer ring and gear cone part, long-term dynamic friction coefficient at this synchronizer ring and gear cone part Performance such as maintenance and performance that should be provided as final speed reducer oil, that is, excellent extreme pressure resistance, wear resistance, pitching resistance, oxidation stability, copper corrosion resistance. It has excellent performance and has the characteristic that the manual transmission and the final speed reducer can be lubricated in common.

【0010】

The base oil used in the present invention is a solvent refined base oil, a hydrogenated refined base oil, a highly hydrocracked base oil, or the like alone or as a mixture. Specifically, low temperature fluidity is improved by removing wax from 60 neutral oil, 100 neutral oil, 150 neutral oil, 300 neutral oil, 500 neutral oil and their base oils by solvent refining or hydrogenation refining. Pour point base oil and the like can be mentioned. The highly hydrocracked base oil is made from raw wax (slack wax) separated by solvent dewaxing, which is hydrogenated (contact cracked) in the presence of a catalyst to crack linear paraffin into branched paraffin. A lubricating base oil having a viscosity index of 130 or more (typically 145 to 155) obtained by isomerizing to paraffin, or hydrogen obtained by a cracking process (partial oxidation) of natural gas (methane, etc.). A lubricating oil group having a viscosity index of 130 or more (typically 145 to 155) obtained by using carbon oxide as a raw material to obtain heavy linear paraffin by Fischer-tropus polymerization and catalytically cracking and isomerizing it in the same manner as described above. Oil is mentioned.

【0011】

The properties of the base oil used in the present invention are 2 to 80 mm in kinematic viscosity at 100 ° C.²s^-1, Preferably 4 ~ 50mm²s^-1Is. Here, the kinematic viscosity at 100 ° C is 2 mm.²s^-1If it is less than, the lubricity will be reduced and the seizure resistance will be poor, and 80 mm.²s^-1In the above case, the resistance due to the viscosity becomes large, which is not preferable from the viewpoint of lowering the transmission efficiency due to the gear.

【0012】

The viscosity index of the base oil used in the present invention is 75 or more, preferably 80 or more. If the viscosity index is less than 75, it is not preferable as the base oil of the gear oil composition for automobiles for the present purpose because the startability at low temperature and the deterioration of lubricity due to the decrease in viscosity at high temperature.

【0013】

The base oil of the present invention includes mineral oil, hydrocarbon-based synthetic base oil, alkylbenzene, alkylnaphthalene, ethylene-propylene copolymer polymer, fatty acid ester-based synthetic oil, and aromatic ester-based oil as long as it has the above-mentioned properties. It can be used regardless of synthetic oil or the like, and a mixture of two or more of these can be used. Further, a mixture of the above-mentioned mineral oil and the above-mentioned synthetic oil in an appropriate ratio may be used.

【0014】

The component (A) in the present invention has the following general formula (1). [Chemical 7]

R¹-SSSR¹ ...... (1) (In the formula, R¹Is a hydrocarbon group), and the amount of the dialkyltrisulfide added is 0.1 to 10% by weight, preferably 0.5 to 7% by weight, more preferably 1 to 5% by weight based on the total amount of the composition. is there.

【0015】

The R¹Is a hydrocarbon group, preferably a linear or branched saturated or unsaturated aliphatic hydrocarbon group having 2 to 20 carbon atoms, for example, an alkyl group or an alkenyl group, an aromatic hydrocarbon group having 6 to 26 carbon atoms, and the like. Specific examples include ethyl group, 1-propyl group, 2-propyl group, n-butyl group, t-butyl group, 2-ethylhexyl group, nonyl group, dodecyl group, propenyl group, butenyl group and benzyl group. , A phenyl group, a hexyl phenyl group and the like.

【0016】

The component (B) in the present invention has the following general formula (2). [Chemical 8]

(R²O)₂P (= S) SR³ ...... (2) (In the formula, R²And R³Is a dithiophosphate ester that can be indicated by (a group independently selected from the group consisting of hydrocarbon groups), and the amount of the dithiophosphate added is 0.1 to 5% by weight, preferably 0.2 to 2.5, based on the total amount of the composition. By weight%, more preferably 0.3 to 1%.

【0017】

The R²And R³Is a hydrocarbon group, preferably a linear or branched saturated or unsaturated aliphatic hydrocarbon group having 2 to 20 carbon atoms, such as an alkyl group, an alkenyl group, a cycloalkyl group, a cycloalkenyl group, and 6 to 6 carbon atoms. There are 26 aromatic hydrocarbon groups, such as ethyl group, 1-propyl group, 2-propyl group, n-butyl group, t-butyl group, 2-ethylhexyl group, nonyl group, dodecyl group, etc. Examples thereof include a propenyl group, a butenyl group, a cyclopentadienyl group, a benzyl group, a phenyl group and a hexylphenyl group.

【0018】

The component (C) in the present invention has the following general formula (3). [Chemical 9]

(R⁴O)_nP (= O) (OH)_3-n ...... (3) (In the formula, R⁴Is a hydrocarbon group and n is 1, 2 or 3), which is an acidic phosphate ester, a phosphite ester, and an alkylamine salt thereof, and the amount added thereof is 0.1 to 5 based on the total amount of the composition. By weight%, preferably 0.5 to 4% by weight, more preferably 1 to 3% by weight.

【0019】

The R⁴Is a hydrocarbon group, preferably a linear or branched saturated or unsaturated aliphatic hydrocarbon group having 4 to 20 carbon atoms, that is, an alkyl group, an alkenyl group, a cycloalkyl group, a cycloalkenyl group, and 6 to 26 carbon atoms. Examples include aromatic hydrocarbon groups. Specific examples of these ester compounds include monobutyl phosphate, dibutyl phosphate, tributyl phosphate, monooctyl phosphate, dioctyl phosphate, trioctyl phosphate, dioctyl phosphate, trioctyl phosphate, monophosphate (trioctyl phosphate). 2-Ethylhexyl), Di (2-ethylhexyl) Phosphate, Tri-Phosphate (2-Ethylhexyl), Di-Phosphate (2-Ethylhexyl), Tri-Phosphate (2-Eethylhexyl), Didecyl Phosphate, Phosphate Didecyl, didodecyl phosphate, tridodecyl phosphate, didodecyl phosphite, tridodecyl phosphite, tridecyl thiophosphate, trihexadecil phosphate, trihexadecil phosphite, trioctadecyl phosphate, trioctadecyl phosphite, phosphate Examples thereof include tri (octylphenyl) and tri (octylcyclohexyl) phosphate.

【0020】

The alkylamine for neutralizing these is the following general formula (4). [Chemical 10]

NR⁵R⁶R⁷ ......(Four) (In the formula, R⁵, R⁶, R⁷Is a group independently selected from the group consisting of a hydrocarbon group and a hydrogen atom, and at least one of them is a hydrocarbon group. ). Specific examples of these compounds include dibutylamine, octylamine, dioctylamine, laurylamine, dilaurylamine, oleylamine, diorailamine, coconutamine, beef tallow amine and the like.

【0021】

The alkenyl succinimide or a derivative thereof as the component (D) in the present invention is not particularly limited, and various substances that can be usually used as an ashless dispersant for lubricating oil can be used. Specific examples of the alkenyl succinate imide or a derivative thereof include a polyolefin having a molecular weight of 300 to 3000, such as polybutene, which is reacted with maleic anhydride to obtain monoalkenyl succinic acid, and then ethylenediamine, diethylenetriamine, dipropylenetriamine, and triethylene. Imidized with a polyamine such as tetramine or tetraethylenepentamine, various alkenylsuccinic imides such as monoamide, diimide, and triimide, or the obtained imide is treated with an aromatic polycarboxylic acid to remain. Amino groups of No. 42-7013, No. 42-8014, No. 42-7013, No. 42-8014, No. 42-7013, No. 42-7013, No. 42-8014, No. 42-7013, No. 42-7013, No. 42-8014, No. Japanese Patent Application Laid-Open No. 51-52831, Japanese Patent Application Laid-Open No. 51-130408, etc., or alkenyl succinate imides such as boron compound derivatives and organic phosphonate derivatives described in JP-A-51-130408 Examples thereof include derivatives of alkenyl succinate imide reacted with sulfonic acid, alkylene oxide, sulfur and the like. Of these alkenyl succinimides or derivatives thereof, preferred is alkenyl succinimide monoimide, which is obtained by reacting polybutene having a molecular weight of 600 to 1000 as polybutene with maleic anhydride and then imidizing it with tetraethylene pentaamine. These alkenyl succinimides or derivatives thereof may be used alone or in combination of two or more. The amount added is 0.1 to 5% by weight, preferably 0.2 to 4% by weight, and more preferably 0.5 to 3% by weight based on the total amount of the composition.

【0022】

The base oil of the present invention is mainly composed of mineral oil or synthetic oil as described above, but in order to actually use it as a gear oil, it is preferable to use a known additive for this base oil as necessary. Can be done. Examples of these additives include friction modifiers such as molybdenum dithiophosphate, molybdenum disulfide, aliphatic amines, higher alcohols, higher fatty acids, fatty acid esters, sarcosic acid esters, and fatty acid amides, petroleum sulfonates, alkylbenzene sulfonates, and dialkylnaphthalene. Anticorrosive agents such as sulfonates, metal defoamers such as benzotriazol and benzothiasiazole, metal-based detergents such as alkaline earth metal sulfonates, alkaline earth metal phenates, alkaline earth metal salicylates, and alkaline earth metal phosphonates, silicones. Antifoaming agents such as, polymethacrylate, polyisobutylene, viscosity index improvers such as polystyrene, flow point lowering agents, and various other additives can be added alone or in combination of two or more. The content of the friction modifier is usually 0.01 to 5% by weight, the content of the rust preventive is usually 0.1 to 10% by weight, the content of the metal deactivator is usually 0.001 to 5% by weight, and the viscosity index improver. The content of is usually 0.1 to 20% by weight, the content of defoaming agent is usually 0.00001 to 0.1% by weight, and the content of other additives is usually 0.01 to 10% by weight (all based on the total amount of the composition). ).

【0023】

The gear oil composition of the present invention can be preferably used as a combined gear oil capable of lubricating a manual transmission and a final reduction gear.

【0024】

[Example]

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

【0025】

Examples and Comparative Examples The composition of the gear oil composition used in the examples is shown in Table 1, and the composition of the gear oil composition used in the comparative example is shown in Table 2. Table 3 shows the performance evaluation results of the gear oil composition used in the examples, and Table 4 shows the evaluation results of the gear oil composition used in the comparative example. The viscosity and performance of these gear oil compositions were evaluated by the tests and performance evaluation tests shown below.

【0026】

(Kinematic viscosity at 100 ° C) Measured by the test method specified in JIS K 2283.

【0027】

(Oxidation stability test) In accordance with the Oxidation Stability Test (ISOT) method for internal combustion engine lubricating oil specified in JIS K 2514 3.1, the test oil temperature was 150 ° C and the test time was 96 hours and 192 hours. .. The evaluation was performed by measuring the rate of change in kinematic viscosity of the test oil after the test at 100 ° C, the rate of change in total acid value, and the amount of pentane insoluble.

【0028】

(Copper plate corrosiveness test) The test oil temperature was 150 ° C and the test time was 3 hours in accordance with the test method specified in JIS K 2513.

【0029】

(Extreme pressure test) In accordance with the shell 4-ball extreme pressure test method specified in ASTM D 2783, the test oil is initially seized under the conditions of an initial oil temperature of 24 ° C, a shaft rotation speed of 1800 rpm, and a test time of 10 seconds. The load and fusion load were measured.

【0030】

(Abrasion resistance test) Based on the shell 4-ball abrasion resistance test method specified in ASTM D 4172, the test was performed under the conditions of initial oil temperature 80 ° C, shaft rotation speed 1800 rpm, load 40 kgf, and test time 60 minutes. For the evaluation, the diameter of the wear mark generated on the test ball after the test was measured.

【0031】

(Pitching resistance test) Based on the Unisteel bearing rolling fatigue test method specified in IP305, the test oil temperature was 120 ° C, the rotation speed was 1500 rpm, and the load was 1000 kgf, using NSK5110 bearings (6 balls). .. The evaluation was repeated 10 times, and L on the Weibull plot.₁₀And L₅₀Was calculated.

【0032】

(Synchro property test) Evaluation was made by the following method described in JP-A-9-132790. The synchronizer ring and gear cone are installed on the table, and the rotation speed of the gear cone is maintained at 1200 rotations by the motor. Then, the synchronizer ring is pressed with a load of 40 kgf. After that, the load on the synchronizer ring is removed, and the synchronizer ring is disconnected from the gear cone. The pattern consisting of pressing and disconnecting the synchronizer ring is repeated for 10,000 cycles. In this repetition, the torque generated when the synchronizer ring was pressed was measured, and the coefficient of dynamic friction was obtained. This coefficient of dynamic friction was compared between 100 cycles and 10000 cycles, and evaluated by the level of the coefficient of friction. That is, those having a high coefficient of friction and capable of maintaining this coefficient of friction even with durability are considered to have excellent synchro characteristics.

【0033】

[table 1]

<img file="JP2000328084A_D0001.tif" />【0034】

[Table 2]

<img file="JP2000328084A_D0002.tif" />【0035】

[Table 3]

<img file="JP2000328084A_D0003.tif" />【0036】

[Table 4]

<img file="JP2000328084A_D0004.tif" />【0037】

The gear oil composition of the present invention (Examples 1, 2, 3, 4) was evaluated for oxidative stability at 150 ° C., and the viscosity increase, total acid value change, and pentane insoluble matter were found in the conventional gear oil composition. It is significantly reduced as compared with the products (Comparative Examples 1, 2, 3, 4, 5, 6), and it can be seen that the oxidation stability at this temperature is excellent. Moreover, from the copper plate corrosion test at a high temperature (150 ° C), it can be seen that the corrosiveness to copper is significantly reduced. On the other hand, from the extreme pressure test and the wear resistance test, it can be seen that the gear oil composition has wear resistance and pitching resistance equal to or higher than that of the conventional gear oil composition. Furthermore, from the evaluation of the synchro characteristics, it can be seen that the coefficient of dynamic friction between the synchro cone and the synchro ring is higher than that of the conventional one even after 10,000 cycles.

【0038】

[effect]

According to the present invention, a gear oil having excellent oxidation stability at high temperature (150 ° C or higher), copper corrosion resistance at high temperature (150 ° C or higher), extreme pressure resistance, wear resistance, pitching resistance and synchro characteristics. The composition could be provided.