JP5199637B2 - Lubricating oil composition for full-time four-wheel drive transfer - Google Patents

Description

  The present invention relates to a gear oil composition, and more particularly to a lubricating oil composition for a full-time four-wheel drive transfer.

  Applicants have proposed that (a) a sulfurized olefin, (b) an alkyl phosphate compound, an alkyl thiophosphate compound, an alkyl as a gear oil for a transmission gear unit that uses a synchronizer ring and a gear cone. A phosphorus compound selected from dithiophosphoric acid compounds, and (c1) metallic detergents, (c2) metal salts of dialkyldithiophosphoric acids, (c3) metal salts of dialkyldithiocarbamates, (c4) zinc naphthenates or lead naphthenates ( It has been provided with a combination of at least one compound selected from c1) to (c4), and has achieved great effects. (Patent Document 1)

In recent years, four-wheel drive vehicles have rapidly become popular in order to obtain stable driving performance of automobiles. Especially in full-time four-wheel drive vehicles, the ratio of the driving force between the front wheels and the rear wheels depends on the driving conditions. Transfer is used so that it can be distributed automatically. Furthermore, while driving, the gear ratio of High and Low can be changed, and the lock and unlock of the center differential (Torsen LSD: registered trademark) can be changed, and the gear mechanism is complicated. The load due to higher engine output is also increasing.
JP 63-61091 A

  The present invention further improves the gear oil previously provided by the applicant, improves the lubrication performance for the latest gear mechanism, and maintains excellent durability, seizure resistance and stability at the level of API-GL-5. However, an object is to obtain a lubricating oil composition for a full-time four-wheel drive transfer that can realize energy saving.

（式１中、ＲはCnH2n+1で表わせる基であり、n＝1〜6である。）
硫黄−リン系極圧剤を５〜２０質量％含有する組成物によってフルタイム四輪駆動トランスファ用の潤滑油組成物とするものである。 The present invention contains a base oil belonging to Group 3 in the base oil category of API (American Petroleum Institute), 5 to 20% by mass of trimethylolpropane ester, and a carboxylic acid ester represented by the following general formula (1) 0.5-5% by mass of dialkyldithiophosphate ester,

(In Formula 1, R is a group that can be represented by CnH2n + 1, and n = 1 to 6.)
The composition containing 5 to 20% by mass of a sulfur-phosphorus extreme pressure agent is used as a lubricating oil composition for full-time four-wheel drive transfer.

  According to the lubricating oil composition of the present invention, the extreme pressure performance is high, the wear resistance and the synchro friction characteristics are excellent, the oxidation stability is high, the influence on the sealing material is small, and the durability of the seal is increased. In addition, it is excellent as a lubricating oil composition having a low overall viscosity and good energy saving, particularly as a lubricating oil composition for a full-time four-wheel drive transfer.

Since it is necessary for the gear oil for automobiles to have good extreme pressure properties, sulfur-phosphorus extreme pressure agents have been mainly used. However, since such gear oils are inferior in synchro friction and wear characteristics in transmissions, in order to solve this problem, zinc dialkyldithiophosphate (ZnDTP) is further added and the viscosity of the lubricating oil is increased. It was.
Although such lubricating oil has been used for a long time, the full-time four-wheel drive transfer as a gear mechanism has a complicated mechanism and places a heavy load on the lubricating oil. On the other hand, improvement in fuel efficiency is required. It is like that. If the viscosity of the lubricating oil is lowered to improve fuel efficiency, it is necessary to increase the amount of extreme pressure agent, which tends to affect the oxidation stability and sealability.

  For this reason, in the present invention, the dialkyldithiophosphate ester containing a carboxylic acid ester is basically used without using the zinc dialkyldithiophosphate (ZnDTP) that has been used for a long period of time. The inventors have found that oxidation stability and oil seal resistance, which have been problems, can be improved, and excellent extreme pressure properties can be maintained while having low viscosity, and the present invention has been achieved based on this.

  As the base oil of the present invention, a group 3 base oil is used in the API base oil category. This Group 3 base oil includes, for example, paraffinic mineral oil produced by advanced hydrorefining and wax produced by a dewaxing process for a lubricating oil fraction obtained by atmospheric distillation of crude oil. There are base oils refined by the ISODEWAX process for converting and dewaxing into isoparaffins, and base oils refined by the mobile WAX isomerization process.

  GTL (Gas Liquid) synthesized by the Fischer-Tropsch method, which is a natural gas liquid fuel technology, has extremely low sulfur and aromatic content compared to mineral oil base oil refined from crude oil. Since the composition ratio is extremely high, the oxidation stability is excellent and the evaporation loss is very small. An example of such a GTL base oil product is SHELL XHVI®.

In this lubricating oil composition, trimethylolpropane ester is added as a synthetic base oil. Examples of the carboxylic acid used in the ester include a linear or branched monocarboxylic acid having 2 to 16 carbon atoms. Specifically, for example, acetic acid (2 carbon atoms), propionic acid (3 carbon atoms), Butyric acid (4 carbon atoms), valeric acid (pentanoic acid, 5 carbon atoms), caproic acid (hexanoic acid, 6 carbon atoms), enanthic acid (heptanoic acid, 7 carbon atoms), caprylic acid (octanoic acid, 8 carbon atoms) , Pelargonic acid (nonanoic acid, carbon number 9), capric acid (decanoic acid, carbon number 10), undecanoic acid (carbon number 11), lauric acid (dodecanoic acid, carbon number 12), tridecanoic acid (carbon number 13), There are myristic acid (tetradecanoic acid, carbon number 14), pentadecanoic acid (carbon number 15), palmitic acid (hexadecanoic acid, carbon number 16) and isoforms thereof (having 4 or more carbon atoms).
Among these trimethylolpropane esters, those having 8 to 10 carbon atoms of carboxylic acid are particularly preferred, and usually about 5 to 20% by mass, preferably about 7 to 14% by mass, based on the entire composition. Used to a degree.

この一般式（１）中のＲは、ＣｎＨ２ｎ＋１で表わすことができる直鎖または分岐の飽和炭化水素基であり、ｎで示す数は１〜６の整数である。
このＲは、具体的には、例えば、メチル基、エチル基、プロピル基、イソプロピル基、ブチル基、イソブチル基、ペンチル基、イソペンチル基、ヘキシル基、イソヘキシル基、メチルエチルプロピル基などがある。
こうしたカルボン酸エステルを含有するジアルキルジチオリン酸エステルは、組成物全量に対して、約０．５〜５質量％程度が使用され、好ましくは、約１〜３質量％程度使用される。 Further, a dialkyldithiophosphate ester containing a carboxylic acid ester represented by the following general formula (1) is used in the composition.

R in the general formula (1) is a linear or branched saturated hydrocarbon group that can be represented by CnH2n + 1, and the number represented by n is an integer of 1 to 6.
Specific examples of R include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a pentyl group, an isopentyl group, a hexyl group, an isohexyl group, and a methylethylpropyl group.
About 0.5-5 mass% is used about the dialkyl dithiophosphate ester containing such carboxylic acid ester with respect to the composition whole quantity, Preferably, about 1-3 mass% is used.

The sulfur-phosphorus extreme pressure agent is for obtaining extreme pressure as described above, and is a mixture of a sulfur extreme pressure agent and a phosphorus extreme pressure agent as appropriate.

As the sulfur-based extreme pressure agent , hydrocarbon sulfides represented by the following general formula (2), sulfurized terpenes, sulfurized fats and oils that are reaction products of fats and oils, and the like are used.
(Chemical formula 3)
_{R 1 -Sy- (R 3 -Sy)} n-R 2 (2)

In the general formula (2), R ₁ and R ₂ are monovalent hydrocarbon groups, which may be the same or different, R ₃ is a divalent hydrocarbon group, and y is an integer of 1 or more, Are 1 to 8, and each y in the repeating unit may be the same or different, and n is 0 or an integer of 1 or more.
Examples of the monovalent hydrocarbon group for R ₁ and R ₂ include 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), and 6 carbon atoms. -26 aromatic hydrocarbon groups, specifically, ethyl group, propyl group, butyl group, nonyl group, dodecyl group, propenyl group, butenyl group, benzyl group, phenyl group, tolyl group, hexylphenyl group Etc.
Examples of the divalent hydrocarbon group represented by R ₃ include linear or branched saturated or unsaturated aliphatic hydrocarbon groups having 2 to 20 carbon atoms and aromatic hydrocarbon groups having 6 to 26 carbon atoms, Specific examples include an ethylene group, a propylene group, a butylene group, and a phenylene group.

Typical hydrocarbon sulfides represented by the general formula (2) are sulfurized olefins and polysulfide compounds represented by the general formula (3).
(Chemical formula 4)
R ₁ -Sy-R ₂ (3)

In the general formula (3), R ₁ and R ₂ are the same as those in the general formula (2), and y is an integer of 2 or more.
Specifically, for example, diisobutyl disulfide, dioctyl polysulfide, ditertiary nonyl polysulfide, ditertiary butyl polysulfide, ditertiary benzyl polysulfide, or sulfurized olefin obtained by sulfurizing olefins such as polyisobutylene and terpenes with a sulfurizing agent such as sulfur. And the like.

As the phosphorus-based extreme pressure agent, phosphoric acid esters, acidic phosphoric acid esters, amine salts of acidic phosphoric acid esters, chlorinated phosphoric acid esters, phosphorous acid esters, phosphorothionate.

  Examples of the phosphate ester include tributyl phosphate, tripentyl phosphate, trihexyl phosphate, triheptyl phosphate, trioctyl phosphate, trinonyl phosphate, tridecyl phosphate, triundecyl phosphate, tridodecyl phosphate, tritridecyl phosphate, Tetradecyl phosphate, tripentadecyl phosphate, trihexadecyl phosphate, triheptadecyl phosphate, trioctadecyl phosphate, trioleyl phosphate, triphenyl phosphate, tris (iso-propylphenyl) phosphate, triallyl phosphate, tricresyl phosphate, Trixylenyl phosphate, cresyl diphenyl phosphate, and xylene Such as Le diphenyl phosphate.

  Specific examples of the acidic phosphate ester include monobutyl acid phosphate, monopentyl acid phosphate, monohexyl acid phosphate, monoheptyl acid phosphate, monooctyl acid phosphate, monononyl acid phosphate, monodecyl acid phosphate, monoundecyl acid Phosphate, monododecyl acid phosphate, monotridecyl acid phosphate, monotetradecyl acid phosphate, monopentadecyl acid phosphate, monohexadecyl acid phosphate, monoheptadecyl acid phosphate, monooctadecyl acid phosphate, monooleyl acid phosphate, dibutyl acid Dipentyl acid phosphate Xyl acid phosphate, diheptyl acid phosphate, dioctyl acid phosphate, dinonyl acid phosphate, didecyl acid phosphate, diundecyl acid phosphate, didodecyl acid phosphate, ditridecyl acid phosphate, ditetradecyl acid phosphate, dipentadecate Examples include dihexadecyl acid phosphate, diheptadecyl acid phosphate, dioctadecyl acid phosphate, and dioleyl acid phosphate.

  Examples of the amine salt of the acidic phosphate ester include methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, heptylamine, octylamine, dimethylamine, diethylamine, dipropylamine, and dibutylamine. , Salts with amines such as, dipentylamine, dihexylamine, diheptylamine, dioctylamine, trimethylamine, triethylamine, tripropylamine, tributylamine, tripentylamine, trihexylamine, triheptylamine, and trioctylamine .

  Examples of the phosphites include dibutyl phosphite, dipentyl phosphite, dihexyl phosphite, diheptyl phosphite, dioctyl phosphite, dinonyl phosphite, didecyl phosphite, diundecyl phosphite, didodecyl phosphite, geode Rail phosphite, diphenyl phosphite, dicresyl phosphite, tributyl phosphite, tripentyl phosphite, trihexyl phosphite, triheptyl phosphite, trioctyl phosphite, trinonyl phosphite, tridecyl phosphite, triundecyl Examples thereof include phosphite, tridodecyl phosphite, trioleyl phosphite, triphenyl phosphite, and tricresyl phosphite.

As the phosphorothionate, specifically, tributyl phosphorothionate, tripentyl phosphorothionate, trihexyl phosphorothionate, triheptyl phosphorothionate, trioctyl phosphorothionate, Torinoniruhosu Phorothionate, tridecyl phosphorothionate, triundecyl phosphorothionate, tridodecyl phosphorothionate, tritridecyl phosphorothionate, tritetradecyl phosphorothionate, tripentadecyl phosphorothionate, tri Hexadecyl phosphorothioate, triheptadecyl phosphorothionate, trioctadecyl phosphorothionate, trioleyl phosphorothionate, triphenyl phosphorothionate, tricresyl phosphorothioate , Trixylenyl phosphorothionate, cresyl diphenyl phosphorothionate, xylenyl diphenyl phosphorothionate, tris (n-propylphenyl) phosphorothionate, tris (isopropylphenyl) phosphorothionate, tris (N-Butylphenyl) phosphorothionate, Tris (isobutylphenyl) phosphorothionate, Tris (s-butylphenyl) phosphorothionate, Tris (t-butylphenyl) phosphorothionate, and the like can be given.

The sulfur-based extreme pressure agent and the phosphorus-based extreme pressure agent are appropriately mixed and used. The sulfur-phosphorus extreme pressure agent may be used in an amount of about 5 to 20% by mass, preferably about 7 to 15% by mass, based on the total amount of the composition.
Further, an extreme pressure additive package which is a mixture of a sulfur-based compound and a phosphorus-based compound is suitable for product quality control. For example, Lubrizol's Angramol 99, 98A and 6043, Afton's H340 , H380 series and the like.

The dialkyldithiophosphate ester containing the carboxylic acid ester of the general formula (1) is a so-called ashless compound that is not a metal salt, but together with this, a small amount of zinc dialkyldithiophosphate (ZnDTP) should be used. You can also.
Specific examples of the zinc dialkyldithiophosphate include zinc dipropyldithiophosphate, zinc dibutyldithiophosphate, zinc dipentyldithiophosphate, zinc dihexyldithiophosphate, zinc diisopentyldithiophosphate, zinc diethylhexyldithiophosphate, zinc dioctyldithiophosphate, Zinc dinonyl dithiophosphate, zinc didecyl dithiophosphate, zinc didodecyl dithiophosphate, zinc dipropylphenyl dithiophosphate, zinc dipentylphenyl dithiophosphate, zinc dipropylmethylphenyl dithiophosphate, zinc dinonylphenyl dithiophosphate, didodecylphenyl dithiophosphorus Zinc acid, zinc dodecylphenyl dithiophosphate, etc. are mentioned. In the present invention, secondary types having 3 to 6 carbon atoms are particularly effective.
The amount of ZnDTP used is preferably such that (Zn amount of ZnDTP) / (amount of dialkyldithiophosphate ester containing a carboxylic acid ester represented by Formula 1) is about 0 to 0.1. .

  In addition to the above-described components, various additives can be appropriately used as necessary in order to further improve the performance. These include viscosity index improvers, antioxidants, metal deactivators, oiliness improvers, antifoaming agents, pour point depressants, cleaning dispersants, corrosion inhibitors, demulsifiers, and other known Mention may be made of lubricant additives.

（６）金属系清浄分散剤：Ｃａサリシレート（塩基価（ＢＮ）；２２５ｍｇＫＯＨ／ｇ）
（７）流動点降下剤：アクリレート系流動点降下剤
（８）消泡剤：シリコーン系消泡剤 The following samples were prepared for the production of Examples 1-2 and Comparative Examples 1-5.
(1) Base oil (1-1) Base oil A: API group 3 (characteristics: kinematic viscosity at 40 ° C .; 20 mm ² / s, kinematic viscosity at 100 ° C. 4.3 mm ² / s, viscosity index; 125)
(1-2) Base oil B: API group 3 (characteristic: kinematic viscosity at 40 ° C .; 43 mm ² / s, kinematic viscosity at 100 ° C .; 7.5 mm ² / s, viscosity index; 132)
(1-3) Trimethylolpropane ester: (Characteristics: Kinematic viscosity at 40 ° C .; 19 mm ² / s, kinematic viscosity at 100 ° C .; 4.3 mm ² / s, viscosity index; 137)
(2) Sulfur-phosphorus extreme pressure agent: SP-based package additive (3) Zinc dialkyldithiophosphate (secondary in which isopropyl (C3) and 4-methyl-2-pentyl (C6) as an alkyl group are about 4: 6 Stuff)
(4) Dialkyldithiophosphate ester containing carboxylic acid ester: as shown in the above general formula (1), wherein R is an ethyl group.
(5) Dialkyldithiophosphate ester containing carboxylic acid: compound represented by the following chemical formula (4)

(6) Metal-based detergent dispersant: Ca salicylate (base number (BN); 225 mgKOH / g)
(7) Pour point depressant: Acrylate pour point depressant (8) Antifoam agent: Silicone defoamer

The above samples were used and mixed well according to the composition shown in Table 1 to obtain Examples 1 and 2 and lubricating oil compositions of Comparative Examples 1 to 5 for comparison.
In Comparative Example 5, commercially available Toyota genuine transfer oil GL-5 75W90 was used.

(Measurement of properties and composition)
The following numerical values were determined for the lubricating oil compositions of Examples and Comparative Examples and listed in Table 1.
1. Kinematic viscosity at 100 ° C (mm ² / s)
2. Phosphorus content (P amount) (mass%)
3. Zn content (Zn content) (mass%) (calculated amount)

(test)
In order to compare the performance of Examples and Comparative Examples, the following tests were conducted.
(Oxidation performance test)
In the oxidation performance test, a heating test was conducted at 135 ° C. for 96 hours by a test method based on the lubricating oil oxidation stability test specified in JIS K2514, and the following items before and after the test were measured.
1. 100 ° C kinematic viscosity change rate (%)
Evaluation criteria: Acceptance criteria is 10% or less.
2. Insoluble matter after the test (pentane B) (mass%)
Evaluation criteria: Less is better.
3. Acid value (AN) increase (mgKOH / g)
Evaluation criteria: Less is better.
(Oil seal resistance)
The oil seal resistance test was conducted for 70 hours at 120 ° C. in accordance with the following immersion test method, and the following items were measured before and after the test.
1. Change in hardness (JIS K6253)
Evaluation criteria: “−” indicates softening and “+” indicates hardening.
2. Volume change rate (%) (JIS K6258)
3. Tensile strength change rate (%) (JIS K6251)
Evaluation criteria: The acceptance criteria is set to be within -40%.
4). Elongation change rate (%) (JIS K6251)
Evaluation criteria: The acceptance criteria is set to be within -40%.
(Synchronous characteristics test)
The synchro characteristic test was performed using synchro and gear (cone angle 7 °, radius 30.8 mm), gear rotation speed 1200 rpm, synchro pressing force 400 N, pressing time 0.5 sec, pause time 1.0 sec, oil temperature 80 The following items were measured at a temperature of 100,000 ° C. and a cycle number of 100,000.
1. Friction coefficient Evaluation criteria: Acceptance criteria are about 0.09 to 0.14.
2. Amount of wear Amount of change in the gap between the synchro and the gear cone. Amount of wear = Clearance width (mm) due to gap before test-gap after test.
Evaluation criteria: Less is preferable.
(Real machine durability evaluation / Differential durability test)
Tests were performed using Example 1 and Comparative Example 5.
(1) Parts used: Transfer with Torsen mechanism for 2 liter engine (2) Evaluation condition: Step 1 and step 2 below are sequentially repeated (500 cycles) to determine whether or not the differential is smoothly performed.
Step 1: Input speed 500rpm
Input torque 800N ・ m
Output speed 1000rpm (rear side)
Oil temperature 40 ℃
Time 10 minutes Step 2: Stop operation (stand still)
Time 15 minutes (3) Evaluation criteria: “Pass” is the case of smooth operation, and “Fail” if there is damage.
(Evaluation of actual fuel consumption, vehicle fuel consumption test)
Tests were performed using Example 1 and Comparative Example 5.
(1) Vehicle used: 2 liter engine mounted / FR system four-wheel drive vehicle (2) Evaluation condition: EC Cold mode (3) Evaluation: The fuel efficiency effect with Comparative Example 5 is displayed in%.
(Practicality evaluation)
A comprehensive evaluation was made on the practical performance as a lubricant for full-time four-wheel drive transfer. The lubricating oil of Comparative Example 5 was used as the reference oil, and those in the above-mentioned various test items that were equivalent or better were designated as “OK” and those that were inferior in some items were designated as “NG”.

(result)
The results of the above tests are shown in Table 1.
(Evaluation)
In Example 1, a dialkyldithiophosphate ester (compound of formula 1) containing a carboxylic acid ester is used and ZnDTP is not contained, and the standard of viscosity change rate at 100 ° C. for oxidation stability is −2 It is excellent at .8%, the amount of insoluble matter (pentane B) is as small as 0.06% by mass, the amount of increase in acid value is also small, and good oxidation stability is exhibited. In addition, the oil seal resistance of Example 1 is slightly soft, but the volume change rate is small. The tensile strength change rate and the elongation change rate are both smaller than the acceptance standard value, and excellent results are obtained in oil seal resistance. Furthermore, in the synchro characteristics, the amount of wear is small, which is a preferable state. It has passed the actual machine durability evaluation and differential durability test, and the result of the vehicle fuel consumption test is improved by 0.5% compared to Comparative Example 5, which is because the kinematic viscosity at 100 ° C is particularly low. Although estimated, more favorable results have been obtained.
Although the thing of Example 2 contains the dialkyl dithiophosphate ester containing carboxylic acid ester, and a small amount of ZnDTP, it is somewhat inferior in the tensile strength change rate and elongation change rate of oil seal resistance compared with Example 1. Good results have been obtained.
Thus, Examples 1 and 2 are good in practicality evaluation.
On the other hand, the thing of the comparative example 1 is inferior in oxidation stability by the numerical value of the viscosity change rate of 100 degreeC and the amount of insoluble matter (pentane B), and inferior also in oil-seal resistance. . In Comparative Examples 2 and 3, the viscosity change rate at 100 ° C. and the numerical value of the amount of insoluble matter (pentane B) are poor and the oxidation stability is poor. The thing of the comparative example 4 is unpreferable because the abrasion amount in a synchro characteristic is large. Toyota Genuine Transfer Oil GL-5 75W90 of Comparative Example 5 gives good results as a whole, but Examples 1 and 2 give better results than Comparative Example 5. I understand.

Claims (3)

0.5 to 5% by mass of a base oil belonging to group 3 of the API base oil category, 5 to 20% by mass of trimethylolpropane ester, and dialkyldithiophosphate containing a carboxylic acid ester represented by the following general formula 1 And a lubricating oil composition for full-time four-wheel drive transfer containing 5 to 20% by mass of a sulfur-phosphorus extreme pressure agent.

(In Formula 1, R is a group that can be represented by CnH2n + 1, and n = 1 to 6.) Furthermore , the lubricating oil composition for full-time four-wheel drive transfer of Claim 1 which contains zinc dialkyldithiophosphate 0.05 mass% or less as zinc amount.   3. The full-time four-wheel drive transfer device according to claim 1, wherein the lubricating oil composition satisfies an extreme pressure level GL5 in a gear oil classification of API and has a seal retaining property with respect to a nitrile rubber sealing material. Lubricating oil composition.