JP2016108491A - Lubricant composition for slide guide surface - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lubricant composition for a slide guide surface having excellent low frictional property and extreme pressure property for achieving accurate processing on a machine tool.SOLUTION: A lubricant composition for a slide guide surface is characterized in that; one kind of base oil or mixture of base oils of group I, group II, group III and group IV in a base oil category of API, are based as a base oil, then, a phosphonate (phosphonic acid ester) expressed by the formula 1, and a saturated or unsaturated fatty acid having C7-17 are combined and added thereto.(Ris a saturated or unsaturated alkyl group having C12-22, Ris a saturated or unsaturated alkyl group having C1-18)SELECTED DRAWING: None

Description

  The present invention relates to a lubricating oil composition suitably used for lubricating a sliding guide surface of a machine tool or the like.

  In order to perform high-accuracy machining with a machine tool, it is necessary that the positioning accuracy of the feed axis of the machine tool is excellent, and depending on the object, an accuracy in units of microns is required. However, in a machine tool having a sliding guide surface, a lubricating oil is used because the positioning accuracy may be reduced due to a frictional resistance generated on the guide surface. Is required to have low friction.

  In addition, the lubricating oil used for machine tools is sometimes used not only for the guide surfaces as described above but also for lubricating gears and the like. In such a case, load resistance is also required as an important performance.

  As described above, since smooth movement and high accuracy in the guide surface are required, various friction reducing agents are blended in the lubricating oil used here in order to reduce friction. For example, it is known that a combination of an acidic ester of phosphoric acid and a phosphonic acid ester is used to achieve low friction and to obtain good slipperiness. (Patent Document 1)

Japanese National Patent Publication No. 11-505283

  However, conventional lubricating oil compositions have not yet achieved sufficient lubricity for machine tools that require high-precision processing, and the present invention has been made in view of such circumstances. Therefore, an object of the present invention is to obtain a lubricating oil composition having improved frictional characteristics and extreme pressure characteristics.

  As described above, when various studies and research were repeated for the purpose of reducing friction and obtaining excellent extreme pressure properties, when each phosphonate ester and fatty acid were combined, each additive was used alone. The present inventors have found that a lower friction coefficient and higher load resistance can be obtained than when blended, and the present invention has been completed based on these findings.

The present invention is based on any of Group I base oils, Group II base oils, Group III base oils, Group IV base oils or mixtures thereof in API (American Petroleum Institute) base oil category, A lubricating oil composition for a sliding guide surface is obtained by adding a combination of phosphonate (phosphonic acid ester) and intermediate or higher fatty acid thereto.
Further, as the base oil, it is more preferable to use a highly refined group III base oil of the API base oil category, a base oil of a group IV synthetic oil, or a mixture thereof.

  The lubricating oil composition in the present invention can exhibit excellent friction characteristics and load resistance on a sliding guide surface of a machine tool or the like, and can be effectively used as a lubricating oil composition for a sliding guide surface. .

  As the base oil of the grease of the present invention, Group I to Group IV base oils in the API base oil category, or mixtures thereof are used.

For Group I base oils, for example, paraffin obtained by applying a suitable combination of solvent refining, hydrorefining, dewaxing, etc., to lubricating oil fractions obtained by atmospheric distillation of crude oil There are mineral oils.
The viscosity index is 80 to 120, preferably 95 to 110. The kinematic viscosity at 40 ° C. is preferably ² to 680 mm ² / s, more preferably 8 to 220 mm ² / s. The total sulfur content is more than 300 ppm and less than 700 ppm, preferably less than 500 ppm. The total nitrogen content is also less than 50 ppm, preferably less than 25 ppm. Furthermore, it is good to use an aniline point of 80-150 degreeC, Preferably it is 90-120 degreeC.

For Group II base oils, for example, paraffinic oils obtained by applying a suitable combination of hydrocracking, dewaxing and other refining means to lubricating oil fractions obtained by atmospheric distillation of crude oil There is mineral oil.
The viscosity of these base oils is not particularly limited, but the viscosity index is 80 to less than 120, preferably 100 to less than 120. The kinematic viscosity at 40 ° C. is preferably ² to 680 mm ² / s, more preferably 8 to 220 mm ² / s.
Further, the total sulfur content is 300 ppm or less, preferably 200 ppm or less, more preferably 10 ppm or less. The total nitrogen content is also less than 10 ppm, preferably less than 1 ppm. Furthermore, the aniline point should be 80 to 150 ° C, preferably 100 to 135 ° C.
Group II base oils refined by a hydrorefining method such as the Gulf Company method have a total sulfur content of less than 10 ppm and an aroma content of 5% or less, and can be suitably used in the present invention.

For Group III base oils, for example, a paraffinic mineral oil produced by advanced hydrorefining or a wax produced by a dewaxing process is isoparaffinized from a lubricating oil fraction obtained by atmospheric distillation of crude oil. There are base oils refined by the ISODEWAX process that converts and dewaxes into base oils, and base oils refined by the mobile WAX isomerization process.
The viscosity of these group III base oils is not particularly limited, but the viscosity index is 120 to 180, preferably 130 to 150. The kinematic viscosity at 40 ° C. is preferably ² to 680 mm ² / s, more preferably 8 to 220 mm ² / s. The total sulfur content is 300 ppm or less, preferably 10 ppm or less. The total nitrogen content is also 10 ppm or less, preferably 1 ppm or less. Furthermore, it is good to use an aniline point of 80-150 degreeC, Preferably it is 110-135 degreeC.

Also, as belonging to Group III, GTL (Gas Liquid) synthesized by the Fischer-Tropsch method, which is a natural gas liquid fuel technology, has a sulfur content and aroma as compared with mineral oil base oil refined from crude oil. Since the group content is extremely low and the paraffin composition ratio is extremely high, the oxidation stability is excellent and the evaporation loss is very small. Therefore, it can be suitably used as the base oil of the present invention.
The viscosity property of the GTL base oil is not particularly limited, but usually the viscosity index is 130 to 180, more preferably 140 to 175. Moreover, kinematic viscosity in 40 degreeC is 2-680 mm < ² > / s, More preferably, it is 5-120 mm < ² > / s. Also, typically, the total sulfur content is less than 10 ppm and the total nitrogen content is less than 1 ppm. An example of such a GTL base oil product is SHELL XHVI®.

Polyolefins belong to Group IV base oils and include polymers of various olefins or hydrides thereof. Any olefin may be used, and examples thereof include ethylene, propylene, butene, and α-olefins having 5 or more carbon atoms. In the production of polyolefin, one of the above olefins may be used alone, or two or more may be used in combination. Particularly preferred is a polyolefin called poly α-olefin (PAO).
These viscosities are not particularly limited, but the kinematic viscosity at 40 ° C. is preferably ² to 680 mm ² / s, more preferably 8 to 220 mm ² / s.

The above-mentioned phosphonate is shown in the following formula 1.

In the above formula 1, R ₁ is a saturated or unsaturated alkyl group having 12 to 22 carbon atoms, preferably 12 to 18 carbon atoms. R ₂ is a saturated or unsaturated alkyl group having 1 to 18 carbon atoms. The alkyl group is usually a straight chain, but may be a branched chain.
Examples of such phosphonates include dimethyl dodecyl phosphonate, dimethyl tridecyl phosphonate, dimethyl tetradecyl phosphonate, dimethyl pentadecyl phosphonate, dimethyl hexadecyl phosphonate, dimethyl heptadecyl phosphonate, dimethyl octadecyl phosphonate, dimethyl nonadecyl phosphonate, dimethyl eicosyl phosphonate, trie Examples include dodecyl phosphonate, tritridecyl phosphonate, tritetradecyl phosphonate, tripentadecyl phosphonate, trihexadecyl phosphonate, triheptadecyl phosphonate, trioctadecyl phosphonate (tristearyl phosphite: tautomer), and trioleyl phosphonate.

  Such a phosphonate is used in an amount of about 0.2% by mass to less than 2% by mass, preferably about 0.5% by mass to about 1.5% by mass with respect to the total amount of the lubricating oil composition.

The fatty acid described above is shown in the following formula 2.

Among the above formula 2, R ₃ is a saturated or unsaturated alkyl group of 7 to 17 carbon atoms.
Examples of such fatty acids include caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, isostearic acid, oleic acid, linoleic acid, linolenic acid, and the like.

  Such a fatty acid is used in an amount of about 0.03% by mass or more and less than about 1% by mass, preferably about 0.1% by mass or more and about 0.7% by mass or less based on the total amount of the lubricating oil composition.

A metal inert agent, an antiwear agent, etc. can further be added to this lubricating oil composition.
As metal deactivators, 2,5-bis (heptyldithio) -1,3,4-thiadiazole, 2,5-bis (nonyldithio) -1,3,4-thiadiazole, 2,5-bis (dodecyldithio) 2,5-bis (alkyldithio) -1,3,4-thiadiazoles such as 1,3,4-thiadiazole, 2,5-bis (octadecyldithio) -1,3,4-thiadiazole, 2,5 -Bis (N, N-diethyldithiocarbamyl) -1,3,4-thiadiazole, 2,5-bis (N, N-dibutyldithiocarbamyl) -1,3,4-thiadiazole, 2,5-bis 2,5-bis (N, N-dialkyldithiocarbamyl) -1,3,4-thiadiazoles such as (N, N-dioctyldithiocarbamyl) -1,3,4-thiadiazole, 2-N, N - 2-N, N-dialkyldithiocarbamides such as tildithiocarbamyl-5-mercapto-1,3,4-thiadiazole, 2-N, N-dioctyldithiocarbamyl-5-mercapto-1,3,4-thiadiazole There are thiadiazole derivatives such as mil-5-mercapto-1,3,4-thiadiazoles.

Depending on the case, benzotriazole, benzotriazole derivatives, benzimidazole, benzimidazole derivatives, indazole, indazole derivatives, benzothiazole, benzothiazole derivatives, benzoxazole derivatives, triazole derivatives, and the like can be used.
These metal deactivators can be used alone or in combination in the lubricating oil composition in the range of about 0.01 to 0.5 mass%.

  Examples of the antiwear agent include diisobutyl disulfide, diisobutyl trisulfide, ditertiary butyl trisulfide, dioctyl trisulfide, ditertiary nonyl trisulfide, ditertiary benzyl trisulfide, and other polysulfides. Also, sulfurized olefins, sulfurized fats and oils, etc. can be used.

These sulfur-based antiwear agents can be used alone or in combination within the range of about 0.1 to 3% by mass in the lubricating oil composition.
The metal deactivator and antiwear agent can be used alone or in appropriate combination. When both are used in combination, a low coefficient of friction is obtained, and the wear resistance is further improved. Extreme pressure performance can be obtained, and it is effective for lubricating the sliding guide surface under severe conditions.

In the lubricating oil composition of the present invention, an amine-based or phenol-based antioxidant, a rust inhibitor, a structural stabilizer, a viscosity modifier, a dispersant, a pour point depressant, an antifoaming agent, if necessary. Other known various additives can be blended.
The viscosity of the lubricating oil composition for sliding guide surfaces described above may be about VG22 to VG220 in the ISO viscosity grade, and preferably VG32 to VG68.

Hereinafter, although the lubricating oil composition for sliding guide surfaces of the present invention will be specifically described with reference to Examples and Comparative Examples, the present invention is not limited thereto.
In order to produce Examples and Comparative Examples, the following materials were prepared.

[1] Base oil Base oil 1: GTL (Gas Liquid) belonging to Group III (Properties: Kinematic viscosity at 100 ° C is 7.579 mm ² / s, Kinematic viscosity at 40 ° C is 43.69 mm ² / s, Viscosity index (VI) is 141, and the density at 15 ° C. is 0.8284. (Royal Dutch Shell, Shell XHVI-8)
Base oil 2: refined mineral oil belonging to Group III (property: kinematic viscosity at 100 ° C. is 7.545 mm ² / s, kinematic viscosity at 40 ° C. is 45.50 mm ² / s, viscosity index (VI) is 132, 15 ° C. Density is 0.8453. (SK Innovations Yu-Base8)
Base oil 3: PAO (polyalphaolefin) belonging to group IV (property: kinetic viscosity at 100 ° C. is 7.741 mm ² / s, kinematic viscosity at 40 ° C. is 46.25 mm ² / s, and viscosity index (VI) is 136) The density at 15 ° C. is 0.8322.) (Ineos Oligomers, Durasyn 168)
Base oil 4: refined mineral oil belonging to group II (property: kinematic viscosity at 100 ° C. is 5.352 mm ² / s, kinematic viscosity at 40 ° C. is 31.10 mm ² / s, viscosity index (VI) is 105, 15 ° C. Density is 0.8627.)
Base oil 5: Refined mineral oil belonging to Group II (properties: kinematic viscosity at 100 ° C. is 9.490 mm ² / s, kinematic viscosity at 40 ° C. is 73.66 mm ² / s, viscosity index (VI) is 106, 15 ° C. The density is 0.8683.)
Base oil 6: Refined mineral oil belonging to Group I (properties: kinematic viscosity at 100 ° C. is 4.628 mm ² / s, kinematic viscosity at 40 ° C. is 24.32 mm ² / s, viscosity index (VI) is 106, 15 ° C. The density is 0.8625.)
Base oil 7: Refined mineral oil belonging to Group I (property: kinematic viscosity at 100 ° C. 7.446 mm ² / s, kinematic viscosity at 40 ° C. 51.37 mm ² / s, viscosity index (VI) 106, 15 ° C. Density 0.88736.)

[2] Additive Additive 1-1: Dimethyloctadecylphosphonate Additive 1-2: Tridodecylphosphonate Additive 1-3: Tristearyl phosphite Additive 2-1: Caprylic acid Additive 2-2: Add lauric acid Agent 2-3: Stearic acid Additive 2-4: Oleic acid

Additive 3: Diethylbenzylphosphonate Additive 4: Behenic acid Additive 5: Thiadiazole Additive 6: Ditercharide decyl trisulfide

(Examples 1-16, Comparative Examples 1-12)
Using the materials described above, the sliding guide surface lubricating oil compositions of Examples 1 to 16 and Comparative Examples 1 to 12 were prepared according to the compositions shown in Tables 1 to 3. The compounding amount of the composition was expressed in mass%.

〔test〕
(Friction coefficient: pendulum friction coefficient test)
About the lubricating oil composition of Examples 1-16 and Comparative Examples 1-12, the coefficient of friction was measured with the Kamata type pendulum type oiliness tester by Shinko Construction Co., Ltd. In this test, test oil is applied to the friction portion of the pendulum fulcrum, the pendulum is vibrated, and the friction coefficient is obtained from the vibration attenuation. The test was performed at room temperature (25 ° C.).
The test was evaluated according to the following criteria.
Coefficient of friction is 0.110 or less.
Friction coefficient exceeds 0.110 .... × (Not possible)

(Flash point)
The flash point is measured five times for each sample of Examples 1 to 16 and Comparative Examples 1 to 12 using the Cleveland open automatic flash point measuring device according to JIS K2265-4. Obtained by rounding off digits.
The thermometer was thermometer number 32 (COC) defined in JIS B7410.
The test was evaluated according to the following criteria.
220 ° C or higher ...... ○ (Good)
Less than 220 ℃ ・ ・ ・ × （Not possible）

(Load resistance characteristics test: Shell four-ball EP test)
In accordance with ASTM D2783, Examples 1, 12 and Comparative Examples 5 and 6 were tested for load bearing capacity.
Condition: Number of revolutions; 1760 ± 40 rpm,
Time; 10 seconds,
Temperature: Room temperature Test items: ISL (Initial Seizure Load, unit kgf) and WL (Weld Load, unit kgf) were determined.
Test method: 50 kgf, 63 kgf, 80 kgf, 100 kgf, 126 kgf, 160 kgf, 200 kgf, 250 kgf, and 315 kgf were applied to obtain numerical values until reaching the WL.

The ISL was evaluated according to the following criteria.
80kgf or more ... (Good)
Less than 80kgf …… ×× (Not possible)
The WL was evaluated according to the following criteria.
126kgf or more ... (Good)
Less than 126kgf ・ ・ ・ ・ ・ ・ × (Not possible)

(Abrasion resistance test: Shell four ball WEAR test)
The test equipment and test method are based on ASTM D4172, applying a load of 40 kgf, rotating at an oil temperature of 75 ° C. for 1 hour at a speed of 1200 rotations / min, and measuring the wear scar diameter generated at the contact point. Tests were performed on Examples 1 and 12 and Comparative Examples 5 and 6.
The test was evaluated according to the following criteria.
Wear scar diameter is 0.50 mm or less.
Wear scar diameter exceeding 0.50mm.

(Storage stability)
About the lubricating oil composition of Examples 1-16 and Comparative Examples 1-12, it left still at 25 degreeC for 1 day (24hr), and observed visually about the presence or absence of turbidity or a deposit.
Those that did not cause turbidity or precipitation.
This was indicated for turbidity and precipitation.
In the storage stability, turbidity and precipitation were not suitable as a sliding guide surface lubricating oil composition, so the other tests described above were not performed.

(Test results)
The test results of Examples and Comparative Examples are shown in Tables 1-3.

[Discussion]
As shown in Table 1, when the base oil 1 of Example 1 contains the additive 1-1 and the additive 2-3, the friction coefficient is as low as 0.093 and the flash point is as high as 270 ° C. It turns out that it is excellent as a lubricating oil composition. On the other hand, it can be seen that the one lacking one additive 2-3 of Comparative Example 1 passes the flash point, but is not preferable because the friction coefficient is as high as 0.114.
Similarly, when Example 2 and Comparative Example 2 are compared, it can be seen that Example 2 is preferable, while that of Comparative Example 2 lacking additive 2-3 from one Example 2 is not preferable. The oil of Example 3 in which the base oil 1 of Example 2 is changed to the base oil 2 is also good.
Moreover, even if the additive 1-2 is included as in Comparative Examples 3 and 4, good results cannot be obtained if the additive 2 is not included.

Comparative Example 5 does not contain one additive 1-1 of Example 1, but passes the coefficient of friction and flash point. However, in Comparative Example 5, the WL of the shell four-ball EP test is 126 kgf as compared with Example 1, but the ISL is 63 kgf lower than that of 80 kgf of Example 1, and the wear scar diameter of the shell four-ball WEAR test is also low. Is lower than 0.71 in Example 1 by 0.73, which is not preferable.
Comparative Example 6 uses the same composition as in Example 1, but the content of additive 1 and additive 2 is small, friction coefficient, shell four ball EP test ISL, WL and shell four ball WEAR test. All of the wear scar diameters were unacceptable and greatly inferior to Example 1.
Comparative Example 7 uses the same composition as in Example 1, but the contents of Additive 1 and Additive 2 are increased, and turbidity occurs in storage stability, which is not preferable. It was. Other tests were not performed due to the occurrence of turbidity as described above.

As shown in Table 2, in Examples 4 to 8, the base oil 1 and the additive 1-1 are common, and the additive 5 is added to both, and the type and content of the additive 2 are included. Although the amount was changed, both passed in the coefficient of friction and the flash point, and it turns out to be preferable.
Example 9 is obtained by changing the additive 1-1 of Example 7 to the additive 1-2, and Example 10 is obtained by changing the base oil 1 of Example 9 to the base oil 2. Both are preferable in that they have passed in terms of friction coefficient and flash point.

In Comparative Example 8, 0.3% by mass of Additive 4 (behenic acid) was used instead of Additive 2 in Examples 4 to 8, and Comparative Example 9 was also used by 1.5% by mass. In both cases, precipitation occurred in storage stability, which was not preferable. In addition, no other test was performed because of the precipitation.
Comparative Example 10 contains additive 5 in base oil 1 but does not contain either additive 1 or additive 2 and has a flash point of 0.146, which is very high, with a coefficient of friction of 0.146. It is very high and not preferable.

Moreover, as shown in Table 3, Example 11 adds Example 6 to Example 1, and has passed in the friction coefficient and flash point.
In Example 12, Additives 5 and 6 were added to Example 1 and passed in the friction coefficient and flash point. Compared to Example 1, the wear scar diameter of the shell four-ball WEAR test was Although it is substantially the same, it turns out that a numerical value is high in any of ISL and WL of the shell four-ball EP test, and it is more preferable when high extreme pressure property is required.
In Examples 13 to 16, the base oil 1 of Example 12 was changed to another base oil, both of which passed in the coefficient of friction, and the flash points were slightly lower in Examples 15 and 16, Both have passed.

Comparative Example 11 does not include both the components of Additive 1 and Additive 2 of Example 11 and has passed the flash point, but as with Comparative Example 10, it has a high coefficient of friction and is not preferred. There wasn't.
In Comparative Example 12, a phosphonic acid ester having a benzene ring of Additive 3 was used instead of Additive 1-1 of Example 12, and both the friction coefficient and the flash point were rejected. It turns out that it is not preferable.

Claims (4)

A base oil that is any of Group I to Group IV base oils in the API base oil category or a mixture thereof, and a phosphonate according to Formula 1 below:

(In Formula 1, R ₁ represents a saturated or unsaturated alkyl group having 12 to 22 carbon atoms, and R ₂ represents a saturated or unsaturated alkyl group having 1 to 18 carbon atoms.)
The fatty acid of formula 2 below and

(In Formula 2, R ₃ represents a saturated or unsaturated alkyl group having 7 to 17 carbon atoms.)
A lubricating oil composition for a sliding guide surface, comprising:   The sliding guide surface according to claim 1, wherein the phosphonate is 0.2% by mass or more and less than 2% by mass with respect to the total amount of the composition, and the fatty acid is contained by 0.03% by mass or more and less than 1% by mass. Lubricating oil composition.   The lubricating oil composition for a sliding guide surface according to claim 1 or 2, wherein the base oil is a group III base oil and / or a group IV base oil in the API base oil category. The lubricating oil composition for a sliding guide surface according to any one of claims 1 to 3, further comprising an antiwear agent and / or a metal deactivator.