JP6665066B2 - Lubricating oil composition for sliding guide surfaces - Google Patents

Description

  The present invention relates to a lubricating oil composition for a sliding guide surface.

  BACKGROUND ART A machine tool is a machine for cutting and grinding metal, and a sliding guide surface (sliding surface) is often used as a guide surface in a machine structure. This sliding guide surface has a large friction coefficient due to surface contact, and tends to cause stick-slip particularly at a low speed. However, if stick-slip occurs, there is a concern that processing accuracy and tool life may be affected. Therefore, lubricating oil for sliding guide surfaces of machine tools (also referred to as sliding surface oil) has a sufficiently low coefficient of friction, good stick-slip suppression (ie, good friction characteristics), and prevention of metal corrosion. Good properties and storage stability are required.

  As a lubricating oil for a sliding guide surface of a machine tool, which focuses on the above characteristics, a lubricating oil composition comprising a predetermined amount of an acidic phosphate ester having a specific structure and an amine compound having a specific structure in a lubricating base oil has been proposed. (For example, see Patent Documents 1 and 2).

It is also known that the processing accuracy of a machine tool is generally affected by the thermal deformation of the machine due to a change in temperature inside and outside. Therefore, in order to achieve high processing accuracy, the on-site response, such as installing the machine tool in a constant temperature chamber and performing the finishing process in a separate process, and the hardware side and software side, such as countermeasures against thermal deformation of the machine tool itself and displacement compensation technology (For example, see Patent Document 3) .

JP 2009-235266 A JP 2011-68801A JP 2012-240137 A

As described above, on the hardware side and the software side as described in Patent Document 3, countermeasures against thermal displacement due to a change in the temperature of the processing environment are taken. The impact on the has been little studied.
However, the study of the present inventors has confirmed that the coefficient of friction on the sliding guide surface increases in a high humidity environment as compared with a low humidity environment, and may affect processing accuracy.
Further, the lubricating oil compositions described in Patent Literatures 1 and 2 do not focus on friction characteristics under high humidity.

  The present invention has been made in view of overcoming the above problems, and has as its object to provide a lubricating oil composition for a sliding guide surface that exhibits excellent friction characteristics under both low humidity and high humidity.

  The present inventors have conducted intensive studies in order to achieve the above object, and as a result, a mixture of an acidic phosphoric acid monoester and an acidic phosphoric acid diester having a specific structure, and a branched-chain aliphatic monoamine in a lubricating base oil. By blending each in a specific amount, and by setting the molar ratio in the blending within a specific range, it has been found that a lubricating oil composition that exhibits good friction characteristics under low humidity, even under high humidity, The present invention has been completed. That is, the following inventions are provided.

<1> Acidity composed of a lubricating base oil and 0.12 to 0.5% by mass, based on the total amount of the composition, of an acidic phosphoric acid monoester and an acidic phosphoric acid diester having a structure represented by the following general formula (1) A mixture of a phosphate ester mixture and 0.015 to 0.09 mass% of a branched aliphatic monoamine based on the total amount of the composition, wherein the acidic phosphate ester mixture (A) and the branched aliphatic A lubricating oil composition for a sliding guide surface, wherein the molar ratio (A / B) to the monoamine (B) is 1.0 to 6.5.

In the general formula (1), R ¹ and R ² represent a hydrogen atom or a saturated or unsaturated straight-chain aliphatic hydrocarbon group having 1 to 30 carbon atoms, and R ¹ and R ² are simultaneously a hydrogen atom. There is no.

<2> The lubricating oil composition for a sliding guide surface according to <1>, further comprising 0.1 to 15% by mass of a sulfur compound based on the total amount of the composition.

  ADVANTAGE OF THE INVENTION According to this invention, the lubricating oil composition for sliding guide surfaces which shows the outstanding friction characteristics in both low humidity and high humidity can be provided.

It is a schematic structure figure showing a friction coefficient measuring test machine and a system used in an example. It is the schematic which showed the partial cross section of the lubrication performance evaluation apparatus in the friction coefficient measuring test machine used in the Example.

Hereinafter, the lubricating oil composition for a sliding guide surface of the present invention will be described in detail. In this specification, “to” representing a numerical range represents a range including the numerical values of the upper limit and the lower limit. When a unit is described only in the upper limit in the numerical range represented by “to”, it means that the lower limit is also the same unit.
In the present specification, the amount of each component in the composition is, if there are a plurality of substances corresponding to each component in the composition, unless otherwise specified, the total amount of the plurality of substances present in the composition Means

  In this specification, “high humidity” means 25 ° C. and 75% RH or more, and “low humidity” means 25 ° C. and 30% RH or less.

  The lubricating oil composition for a sliding guide surface of the present invention comprises a lubricating base oil and 0.12 to 0.5% by mass of an acidic phosphoric acid having a structure represented by the following general formula (1) based on the total amount of the composition. A mixture of a monoester and an acidic phosphoric acid diester (hereinafter may be collectively referred to as "component (A) component" or "acidic phosphoric acid ester mixture") and 0.015 to 0.09 mass% based on the total amount of the composition. (Hereinafter referred to as “component (B)”) in the composition, wherein the phosphate mixture (A) and the branched aliphatic monoamine (B) in the composition are Has a molar ratio (A / B) of 1.0 to 6.5.

In the general formula (1), R ¹ and R ² represent a hydrogen atom or a saturated or unsaturated straight-chain aliphatic hydrocarbon group having 1 to 30 carbon atoms, and R ¹ and R ² are simultaneously a hydrogen atom. There is no.

  In the lubricating oil composition for a sliding guide surface of the present invention, a specific amount of a mixture of an acidic phosphate ester having a specific structure ((A) component) and a branched aliphatic monoamine ((B) component) are blended. Thereby, excellent friction characteristics are exhibited under both low humidity and high humidity. For this reason, according to the present invention, there is provided a lubricating oil for a sliding guide surface which can be used not only under low humidity but also under high humidity (for example, during the rainy season, in summer, etc.) without deteriorating the friction characteristics. be able to.

The mechanism of action of the lubricating oil composition for a sliding guide surface of the present invention to exert the above effects is not clear, but is presumed as follows.
That is, the mixture of the monoester and the diester of the acidic phosphoric acid ester (component (A)) also contained in the lubricating oil composition for a sliding guide surface of the present invention has an effect of significantly lowering the friction coefficient under low humidity. On the other hand, under high humidity, the effect of lowering the coefficient of friction tends to decrease. This is because the film formed by the component (A), which is considered to have contributed to the reduction of the friction coefficient on the sliding surface, is not formed under high humidity, or is not maintained even if formed. Guessed. On the other hand, the branched aliphatic monoamine (component (B)) does not have an effect of reducing the friction coefficient under low humidity, but is contained in the lubricating oil composition in a specific amount together with the component (A). This makes it possible to remarkably promote or maintain the film-forming action of the component (A) on the sliding surface under high humidity. Therefore, the lubricating oil composition for a sliding guide surface of the present invention can be used only at low humidity. It is presumed that they exhibit excellent friction characteristics even under high humidity.
Further, since the branched-chain aliphatic monoamine which is the component (B) has a good solubility in a lubricating base oil, the lubricating oil composition for a sliding guide surface of the present invention can improve storage stability. Can be expected.

<Lubricant base oil>
The lubricating base oil used in the lubricating oil composition for a sliding guide surface of the present invention is not particularly limited, and may be a mineral lubricating base oil or a synthetic lubricating base oil.

  Examples of the mineral oil-based lubricating base oil include solvent refined mineral oil, hydrorefined mineral oil, hydrocracked mineral oil, etc. obtained by appropriately refining a lubricating oil fraction of crude oil by solvent refining, hydrorefining and the like. . Further, a base oil obtained by subjecting a raw material such as slack wax by solvent dewaxing to a hydrocracking treatment and a hydroisomerization treatment is also included.

Examples of the synthetic lubricating base oil include α-olefin oligomers which are polymers of α-olefins having 3 to 12 carbon atoms, 2-ethylhexyl sebacate, dioctyl sebacate and other sebacates, azelates, adipates and the like. Polyols such as dialkyl diesters of formulas 4 to 12, 1-trimethylolpropane, esters obtained from pentaerythritol and monobasic acids of 3 to 12 carbon atoms, alkylbenzenes having an alkyl group of 9 to 40 carbon atoms Polyglycols obtained by condensing butyl alcohol with propylene oxide; phenyl ethers such as polyphenyl ether having about 2 to 5 ether chains and about 3 to 6 phenyl groups; No. Further, a base oil obtained by hydrocracking and hydroisomerization of a raw material such as a wax obtained by Fischer-Tropsch synthesis is also included.
The mineral oil-based lubricating base oil and the synthetic lubricating base oil can be used alone or in combination of two or more.

Is not particularly limited kinematic viscosity of the base oil is used in the slideway lubricating oil composition of the present invention preferably has a kinematic viscosity at 40 ° C. is 10 to 300 mm ² / s, at 20~250mm ² / s More preferably, it is particularly preferably 30 to 100 mm ² / s.
The kinematic viscosity of the base oil in this specification is a value measured by JIS K 2283: 2000 "Kinematic viscosity test method".

<Acid phosphate mixture>
In the lubricating oil composition for a sliding guide surface of the present invention, an acidic phosphate ester mixture (component (A)) comprising an acidic phosphate monoester and an acidic phosphate diester having a structure represented by the following general formula (1) ) Is contained in an amount of 0.12 to 0.5% by mass based on the total amount of the composition.

The acidic phosphoric ester mixture as the component (A) is a compound represented by the following general formula (1), wherein one of R ¹ and R ² is a saturated or unsaturated straight-chain aliphatic hydrocarbon group having 1 to 30 carbon atoms. And an acidic phosphoric acid monoester in which the other is a hydrogen atom, and in the following general formula (1), both R ¹ and R ² are a saturated or unsaturated linear aliphatic hydrocarbon having 1 to 30 carbon atoms. It is a mixture of acidic phosphoric acid diesters that are groups.

In the general formula (1), R ¹ and R ² represent a hydrogen atom or a saturated or unsaturated straight-chain aliphatic hydrocarbon group having 1 to 30 carbon atoms, and R ¹ and R ² are simultaneously a hydrogen atom. There is no.

The straight-chain aliphatic hydrocarbon group represented by R ¹ or R ² has 1 to 30, preferably 4 to 22, and more preferably 8 to 18 carbon atoms.
The straight-chain aliphatic hydrocarbon group represented by R ¹ or R ² may be saturated or unsaturated, and has a straight-chain alkyl group having 1 to 30 carbon atoms or a straight-chain alkenyl having 2 to 30 carbon atoms. It is preferably a group.

Preferred examples of the linear alkyl group represented by R ¹ or R ² include a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, a tridecyl group, a tetradecyl group, a pentadecyl group, Hexadecyl group, heptadecyl group, octadecyl group and the like can be mentioned.
Preferred examples of the linear alkenyl group represented by R ¹ or R ² include a hexenyl group, a heptenyl group, an octenyl group, a nonenyl group, a decenyl group, an undecenyl group, a dodecenyl group, a tridecenyl group, a tetradecenyl group, a pentadecenyl group, Examples include a hexadecenyl group, a heptadecenyl group, an octadecenyl group, an oleyl group and the like.

Specific examples of the component (A) include a mixture of mono- and diesters of octyl acid phosphate, and a mixture of mono and diesters of oleyl acid phosphate.

The mixing ratio (x / y) of the acidic phosphoric acid monoester (x) and the acidic phosphoric acid diester (y) in the component (A) is from 10/90 to 90/10 in terms of molar ratio from the viewpoint of frictional characteristics. Preferably, 20 / 80-80 / 20 is more preferable, and 30 / 70-70 / 30 is still more preferable.

  The acidic phosphoric acid monoester and the acidic phosphoric acid diester constituting the acidic phosphoric acid ester mixture as the component (A) may each contain one kind of the acidic phosphoric acid monoester and the acidic phosphoric acid diester. A combination of a plurality of types of acidic phosphoric acid monoesters and acidic phosphoric acid diesters may be used.

The linear aliphatic hydrocarbon group of the acidic phosphoric acid monoester (that is, R ¹ or R ² ) and the ^two linear aliphatic hydrocarbon groups of the acidic phosphoric diester (that is, R ¹ and R ² ) , May be the same or different.
Two linear aliphatic hydrocarbon groups present in one molecule of the acidic phosphoric diester are the same linear aliphatic hydrocarbon group. That is, in the acidic phosphoric acid ester mixture as the component (A), one kind or two or more kinds of acidic phosphoric acid diesters may be contained, but R ¹ and R ² in one molecule of the acidic phosphoric acid diester are the same as each other. It is a chain aliphatic hydrocarbon group.

The component (A) is an acidic phosphoric acid monoester and an acidic phosphoric acid diester having the same linear aliphatic hydrocarbon group as the linear aliphatic hydrocarbon group represented by R ¹ or R ² in the general formula (1). Is preferred. Further, the component (A) may be a mixture containing one or more combinations of acidic phosphoric acid monoesters and acidic phosphoric acid diesters having the same linear aliphatic hydrocarbon group.

  Specific examples of the acidic phosphate mixture as the component (A) include the following embodiments (1) to (3).

(1) R ¹ is any one straight-chain aliphatic hydrocarbon group selected from saturated or unsaturated straight-chain aliphatic hydrocarbon groups having 1 to 30 carbon atoms, and R ² is a hydrogen atom an acidic phosphoric acid monoester is a mixture comprising each one at a time and an acidic phosphoric acid diester, a having the same linear aliphatic hydrocarbon group and R ¹ as R ¹ and R ² in acidic phosphoric acid monoester aspect .
Examples of this embodiment include, but are not limited to, mixtures of mono and diesters of octyl acid phosphate, mixtures of mono and diesters of oleyl acid phosphate.

(2) R ¹ is any one straight-chain aliphatic hydrocarbon group selected from saturated or unsaturated straight-chain aliphatic hydrocarbon groups having 1 to 30 carbon atoms, and R ² is a hydrogen atom an acidic phosphoric acid monoester, a mixture containing respectively one by one and an acidic phosphoric acid diester, a having the same linear aliphatic hydrocarbon group and R ¹ as R ¹ and R ² in acidic phosphoric acid monoester, 2 An embodiment including two or more types.
Examples of this embodiment include, but are not limited to, a combination of a mixture of mono- and diesters of octyl acid phosphate and a mixture of mono and diester of oleyl acid phosphate.

(3) R ¹ is any one straight-chain aliphatic hydrocarbon group selected from saturated or unsaturated straight-chain aliphatic hydrocarbon groups having 1 to 30 carbon atoms, and R ² is a hydrogen atom comprising an acidic phosphoric acid monoester, and an acidic phosphoric acid diesters with different linear aliphatic hydrocarbon group as R ¹ and R ² to R ¹ in the acidic phosphoric acid monoester, respectively one at a time or two or more An embodiment that is a mixture.
Examples of this embodiment include a mixture of octyl acid phosphate monoester and oleyl acid phosphate diester, a mixture of oleyl acid phosphate monoester and octyl acid phosphate diester, and the like. Not limited.

As the component (A), an acidic phosphoric acid monoester and an acidic phosphoric acid diester having the same linear aliphatic hydrocarbon group as the linear aliphatic hydrocarbon group represented by R ¹ or R ² in the general formula (1) (A mixture of the above-described embodiments (1) and (2)).

  The content of the component (A) in the lubricating oil composition for a sliding guide surface of the present invention is 0.12 to 0.5% by mass based on the total amount of the composition from the viewpoint of friction characteristics and corrosion prevention. It is preferably 0.15 to 0.35% by mass based on the total amount of the composition.

<Branched aliphatic monoamine>
The lubricating oil composition for a sliding guide surface of the present invention contains 0.015 to 0.09 mass% of the branched aliphatic monoamine (component (B)) based on the total amount of the composition.

  The branched aliphatic monoamine as the component (B) is an aliphatic monoamine having one, two or three saturated or unsaturated branched aliphatic hydrocarbon groups in the molecule, and has the following general formula (2) It is preferably an alkylamine represented by

In the general formula (2), R ³ , R ⁴ and R ⁵ each independently represent a hydrogen atom or a branched alkyl group having ³ to 22 carbon atoms, and at least one of R ³ , R ⁴ and R ⁵ is It is a branched alkyl group having 3 to 22 carbon atoms.

From the viewpoint of friction characteristics, the branched alkyl group represented by R ³ , R ⁴ or R ⁵ preferably has 4 to 18 carbon atoms. Preferred examples of the branched alkyl group represented by R ³ , R ⁴ or R ⁵ include isopropyl, isobutyl, isopentyl, isohexyl, isooctyl, isononyl, isodecyl, isoundecyl, isododecyl, Examples include an isotridecyl group, an isotetradecyl group, an isopentadecyl group, an isohexadecyl group, an isoheptadecyl group, and an isooctadecyl group.
As the component (B), R ³ and R ⁴ are each independently a branched alkyl group having 3 to 22 carbon atoms, and R ⁵ is preferably an aliphatic monoamine having a hydrogen atom, and from the viewpoint of cost, Preferably, R ³ and R ⁴ are secondary monoamines, each of which is the same branched alkyl group selected from branched alkyl groups having 3 to 22 carbon atoms.

  Preferred examples of the branched aliphatic monoamine as the component (B) include 2-ethylhexylamine, di-2-ethylhexylamine, and the like.

  The content of the component (B) in the lubricating oil composition for a sliding guide surface of the present invention is 0.015 with respect to the total amount of the composition from the viewpoint of achieving both the friction characteristics under low humidity and the friction characteristics under high humidity. To 0.09% by mass, and preferably 0.02 to 0.08% by mass based on the total amount of the composition. When the content of the component (B) is 0.015% by mass or more, excellent friction characteristics under high humidity are obtained, and when the content is 0.09% by mass or less, a decrease in friction characteristics under low humidity is suppressed. You.

  Further, from the viewpoint of achieving both the friction characteristics under low humidity and the friction characteristics under high humidity, the molar ratio of the acid phosphate mixture (A) to the branched aliphatic monoamine (B) (acid phosphate mixture / branch). (Chain aliphatic monoamine = A / B) is preferably from 1.0 to 6.5, more preferably from 1.2 to 5.2.

In the lubricating oil composition for a sliding guide surface of the present invention, the content ratio (molar ratio) between the acidic phosphoric ester mixture and the branched aliphatic monoamine is confirmed as follows.
When the acidic phosphoric acid ester mixture is in the above-described embodiment (1), the mole (A) indicates the average content of the acidic phosphoric acid monoester and the acidic phosphoric acid diester contained in the mixture. Calculated by dividing by molecular weight.
When the acidic phosphate mixture is in the above-described embodiment (2) (that is, when two or more acidic phosphate mixtures having the same R ¹ and R ² are included), the mole (A) is Calculated as the sum of moles of the acidic phosphate mixture.
When the acidic phosphoric acid ester mixture is in the above-mentioned embodiment (3), the mole (A) indicates the content of one kind of acidic phosphoric acid monoester contained in the mixture by the molecular weight of the corresponding acidic phosphoric acid monoester. And the content of one kind of acidic phosphoric diester contained in the mixture divided by the molecular weight of the corresponding acidic phosphoric diester is calculated as the sum of one or two or more kinds. .
The mole (B) of the branched aliphatic monoamine is calculated by dividing the content of the branched aliphatic monoamine by the molecular weight of the branched aliphatic monoamine. Therefore, the molar ratio (A / B) between the acidic phosphoric ester mixture and the branched aliphatic monoamine is calculated by dividing the molar (A) of the acidic phosphoric ester mixture by the molar (B) of the branched aliphatic monoamine. Is done.
When two or more kinds of branched-chain aliphatic monoamines are contained, the mole (B) is calculated as the sum of moles of each branched-chain aliphatic monoamine.

<Sulfur compound>
The lubricating oil composition for a sliding guide surface of the present invention may also contain a sulfur compound (hereinafter sometimes referred to as “component (C)”). Examples of such sulfur compounds include hydrocarbon sulfides, sulfurized fats and oils, and the like.
Examples of the hydrocarbon sulfide include a hydrocarbon sulfide represented by the following general formula (3) or (4).

In the general formulas (3) and (4), R ⁶ and R ⁸ each independently represent a monovalent hydrocarbon group (for example, a straight chain having 2 to 20 carbon atoms such as an alkyl group or an alkenyl group). Or a branched saturated or unsaturated aliphatic hydrocarbon group or an aromatic hydrocarbon group having 6 to 26 carbon atoms), and R ⁷ , R ⁹ and R ¹⁰ are each independently a divalent hydrocarbon group (E.g., a linear or branched saturated or unsaturated aliphatic hydrocarbon group having 2 to 20 carbon atoms, or an aromatic hydrocarbon group having 6 to 26 carbon atoms).
In the general formula (3), one of the monovalent hydrocarbon groups represented by R ⁶ and R ⁸ is a monovalent hydrocarbon further having a functional group such as a hydroxy group, a carbonyl group, a carboxyl group, and an ester group. It may be a group.

In the general formulas (3) and (4), a is an integer of 1 or more, and each a may be the same or different in a repeating unit, and b represents 0 or an integer of 1 or more. .
Specific examples of the monovalent hydrocarbon group represented by R ⁶ or R ⁸ include an ethyl group, a propyl group, a butyl group, a nonyl group, a dodecyl group, a propenyl group, a butenyl group, a phenyl group, a tolyl group, and a hexylphenyl. Group, benzyl group and the like.
Specific examples of the divalent hydrocarbon group represented by R ⁷ , R ^9, or R ¹⁰ include an ethylene group, a propylene group, a butylene group, and a phenylene group.

  Specific examples of these hydrocarbon sulfide compounds include (i) polysulfide compounds such as diisobutyl disulfide, dioctyl polysulfide, di-tert-butyl polysulfide, di-tert-nonyl polysulfide, dibenzyl polysulfide, and (ii) polysulfide compounds. Sulfurized olefins obtained by sulfided olefins such as isobutylene and terpenes with sulfides such as sulfur, and (iii) reaction products of isobutylene and sulfur, represented by the following general formula (5) or (6). And the like, which are presumed to have the following structure.

  In the general formula (5), a and b are the same as a and b in the general formula (3).

  In the general formula (6), a and b are the same as a and b in the general formula (4).

Examples of the sulfurized fats and oils include reaction products of fats and oils and sulfur.
Here, examples of the fats and oils include animal and vegetable fats and oils such as lard, beef tallow, whale oil, palm oil, coconut oil, and rapeseed oil.
The content of the component (C) in the lubricating oil composition for a sliding guide surface of the present invention is preferably from 0.1 to 15% by mass, more preferably from 0.2 to 15% by mass, based on the total amount of the composition, from the viewpoint of friction characteristics. ~ 5% by mass.

<Other additives>
In the lubricating oil composition for a sliding guide surface of the present invention, known lubricating oil additives can be used alone or in combination of two or more in order to further enhance various performances.
Such additives include fatty acids, phenolic antioxidants, amine antioxidants, metal deactivators such as benzotriazole derivatives, styrene butadiene water-added polymers, ethylene propylene polymers, polyisobutylene, polymethacrylate, etc. Pour point depressants, defoaming agents such as polyacrylates and polydimethylsiloxanes, demulsifiers such as ethylene oxide-propylene oxide copolymers, and rust inhibitors such as alkenyl succinic acid half esters.

  Next, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

  As examples and comparative examples, lubricating oil compositions for sliding guide surfaces having the compositions shown in Table 1 were prepared. The base oils and additives used in the preparation are as follows.

・ Base oil (solvent refined paraffinic mineral oil, kinematic viscosity at 40 ° C: 68 mm ² / s, viscosity index: 100, flash point: 224 ° C)
Component (A) 1 (mixture of octyl acid phosphate monoester and octyl acid phosphate diester, mixture molar ratio (60 to 50/40 to 50)
(A) Component 2 (mixture of oleyl acid phosphate monoester and oleyl acid phosphate diester, mixture molar ratio (60 to 50/40 to 50)
-(B) component 1 (2-ethylhexylamine)
・ (B) Component 2 (di-2-ethylhexylamine)
Component (C) (sulfide ester, which is included in the hydrocarbon sulfide represented by the aforementioned general formula (3))

  Using a sample for evaluation separated from the lubricating oil composition for a sliding guide surface of each Example and Comparative Example, the dynamic friction coefficient under high and low humidity was measured by a friction characteristic test described below, and the friction was measured. The properties were evaluated. The results are shown in Table 1.

<Friction property test>
FIG. 1 is a schematic configuration diagram showing a friction coefficient measurement system used for a friction characteristic test. The measurement is controlled and automatically operated by the NC controller 10. The frictional force generated in the measurement test is detected by a lubrication performance evaluation device 20 configured using a strain gauge, output to a PC (personal computer) 40 via an A / D converter 30, and the measured value is output to the PC 40. Be recorded.

FIG. 2 is a schematic diagram showing a partial cross section of the lubrication performance evaluation device 20 shown in FIG.
As shown in FIG. 2, the lubrication performance evaluation device 20 includes a base (comprising a movable base 1a, fixed bases 1b and 1c, and columns a and b), and a servomotor 2 fixed to the base. The shaft 3 having the rotating body 3a holding the upper test piece A attached to the other end to which the rotation of the servo motor 2 is transmitted at one end, the coupling 4 attached to the shaft 3, and the friction surface of the upper test specimen A A lower test piece B provided on a movable base 1a provided to be able to move up and down with respect to the base at a position facing the lower test piece B whose friction surface faces the friction surface of the upper test piece A; The servomotor 4 was rotated in a state where the oil supply pipe 5 for supplying the lubricating oil composition (that is, the sample for evaluation) and the oil discharge pipe 6 for discharging, and the upper test piece A and the lower test piece B were in contact with each other. Sometimes detect the frictional force generated between test pieces A and B Made from the force a total of 7.
The lubricating oil composition (evaluation sample) is supplied from the lower part of the lower test piece B by a pump (not shown), and is sent from the central part of the test piece to the friction surface.
The upper test piece A and the lower test piece B rotate while making surface-to-surface contact, and the generated friction force is detected as a friction torque by a dynamometer 7 constituted by a strain gauge.

In the friction characteristic test, using the measurement system shown in FIG. 1, the smoothing operation was performed for 0, ⁴ , 8, and 16 hours at a sliding speed of 0.01 μm / s to 100 mm / s and a surface pressure of 2.0 kg / cm ² . After that was performed. In the test, the temperature was 25 ° C., the humidity in the evaluation under low humidity conditions was controlled to 30% RH or less, and the humidity in the evaluation under high humidity conditions was controlled to 75% RH or more.
The evaluation was performed by measuring the dynamic friction coefficient of each of the lubricating oil compositions of Examples and Comparative Examples at a smoothing operation of 8 or 16 hours and a sliding speed of 0.01 μm / s.

  Table 1 shows the kinetic friction coefficients obtained for the lubricating oil compositions of Examples and Comparative Examples under the above-mentioned friction coefficient measurement tester and test conditions.

  When the kinetic friction coefficient is 0.010 to 0.040 at both low humidity and high humidity, the lubricating oil composition having excellent friction characteristics without practical problems is evaluated.

The following can be seen from the evaluation results shown in Table 1.
A specific content (mass%) and a specific molar ratio (hereinafter, referred to as A / B ratio) of an acidic phosphoric ester mixture as the component (A) and a branched aliphatic monoamine as the component (B) are added to the lubricating base oil. ), The lubricating oil compositions of Examples 1 to 5 are all excellent in friction characteristics at low humidity and high humidity, and are most suitable as lubricating oils for sliding guide surfaces which are less affected by changes in the humidity of the processing environment. You can see that there is.
On the other hand, it can be seen that Comparative Example 1, which does not contain the branched aliphatic monoamine as the component (B), has poor friction characteristics at high humidity.
In Comparative Example 2, the content of the branched aliphatic monoamine as the component (B) is lower than the lower limit of 0.015% by mass in the present invention, and the A / B ratio exceeds 6.5. It can be seen that the friction characteristics at high humidity were inferior.
Comparative Example in which the content of the branched aliphatic monoamine as the component (B) is slightly higher than the upper limit of 0.09% by mass in the present invention and the A / B ratio is smaller than 1.0. In the case of No. 3, the friction characteristics at low humidity and high humidity are inferior.
Further, in Comparative Example 4 in which the content of the acidic phosphoric acid ester mixture as the component (A) and the content of the branched aliphatic monoamine as the component (B) are higher than the upper limit in the present invention, low humidity and high humidity were observed. It can be seen that the friction characteristics at humidity are inferior.
In Comparative Example 5 in which the content of the acidic phosphate mixture as the component (A) is lower than the lower limit of 0.12% by mass in the present invention and the A / B ratio is lower than 1.0. It can be seen that the friction characteristics are inferior at both low humidity and high humidity.
Further, in Comparative Example 6, in which only the A / B ratio is smaller than 1.0 and out of the range of the present invention, it can be seen that the friction characteristics are inferior at both low humidity and high humidity.

  Thus, in the present invention, blending the component (A) and the component (B) at an appropriate content (% by mass) and molar ratio achieves both low-humidity and high-humidity friction characteristics. Shows that it is indispensable.

Reference Signs List 10 NC control device 20 Lubrication performance evaluation device 30 A / D converter 40 PC (personal computer)
1a movable base,
1b, 1c Fixed bases a, b Column 2 Servo motor A Upper test piece B Lower test piece 3 Shaft 3a Rotating body 3a
4 Coupling 5 Oil supply pipe 6 Drainage pipe 7 Dynamometer

Claims (2)

Acidic phosphoric acid ester comprising a lubricating base oil and 0.12 to 0.5% by mass, based on the total amount of the composition, of an acidic phosphoric acid monoester and an acidic phosphoric acid diester having a structure represented by the following general formula (1): A mixture of the acidic phosphate ester mixture (A) and the branched-chain aliphatic monoamine (B) in the composition, containing 0.015 to 0.09 mass% of a branched-chain aliphatic monoamine based on the total amount of the composition; ), Wherein the molar ratio (A / B) to the lubricating oil composition for sliding guide surfaces is 1.0 to 6.5.


In the general formula (1), R ¹ and R ² represent a hydrogen atom or a saturated or unsaturated straight-chain aliphatic hydrocarbon group having 1 to 30 carbon atoms, and R ¹ and R ² are simultaneously a hydrogen atom. There is no.   The lubricating oil composition for a sliding guide surface according to claim 1, further comprising 0.1 to 15% by mass of a sulfur compound based on the total amount of the composition.