JP2016210941A - Lubricant oil additive and lubricant oil composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an environmentally gentle lubrication oil additive and a lubrication oil composition excellent in friction reduction effect, even in the sliding conditions of a high load and a low shear speed, capable of suppressing the reduction of the film thickness of lubrication oil at the boundary face of material, having the reduced number of blending components, easily treatable and capable of reducing phosphorous and sulfur.SOLUTION: In such a manner that a lubrication part 12 made of a linear polymer is held, a pair of adsorption parts 11 are respectively coupled to both the edges of the polymer of the lubrication part 12. The lubrication part 12 can be dissolved into base oil, and, e.g., includes a polymethacrylate chain, an olefin copolymer chain and a polyisobutylene chain. Each absorption part 11 is made of a functional group adsorbable in a material of metal or the like. Each adsorption part 11, e.g., includes a carboxyl group, a phosphoric acid group, an amino group, a thiol group or the like.SELECTED DRAWING: Figure 1

Description

  The present invention relates to lubricating oil additives and lubricating oil compositions.

  In recent years, lubricating oils for reducing friction between materials such as engines and general machines tend to lower the viscosity of the base oil of the lubricating oil in order to reduce friction and improve fuel efficiency. This tendency is particularly remarkable in engine lubricating oil and the like. Therefore, in order to reduce friction and wear, oiliness improvers such as higher fatty acids and higher alcohols, reactive antiwear agents such as phosphate esters and zinc dithiophosphate, organic sulfur compounds, etc. It is blended. In addition, polymers such as polymethacrylates, olefin copolymers, and polyisobutylene are separately blended in base oils as viscosity index improvers in order to suppress viscosity changes due to temperature and optimize viscosity characteristics (for example, patents) References 1 to 3).

JP 2010-95664 A JP 2011-57758 A Japanese Patent Laid-Open No. 2001-19990

  However, the low-viscosity lubricating oils described in Patent Documents 1 to 3 are easily discharged from the interface between the materials under sliding conditions at a high load and a low shear rate. As a result, there is a problem that friction increases. In order to prevent contact between the surfaces of the material, it is necessary to increase the thickness of the lubricating oil at the interface between the materials, but in order to increase the thickness of the lubricating oil, the viscosity of the lubricating oil must be increased. However, there was still a problem that the friction increased.

  In addition, the lubricating oils described in Patent Documents 1 to 3 have a problem that the formulation is complicated due to the large number of blending components. Moreover, since reactive additives, such as phosphate ester and zinc dithiophosphate, are difficult to react under low temperature conditions, there is also a problem that the friction reducing effect becomes insufficient. Moreover, since phosphorus and sulfur contained in the additive cause environmental destruction, there is a problem that it is necessary to reduce them.

  The present invention has been made paying attention to such problems, and is excellent in the friction reduction effect. Even under slip conditions at a high load and a low shear rate, the film thickness of the lubricating oil at the interface of the material is improved. An object of the present invention is to provide a lubricating oil additive and a lubricating oil composition that can suppress the decrease, can be easily formulated with a small number of components, can reduce phosphorus and sulfur, and are environmentally friendly.

  In order to achieve the above object, the lubricating oil additive according to the present invention is a lubricating oil additive used by being added to a lubricating oil for reducing friction between materials, wherein the base oil of the lubricating oil is used. A high-molecular-weight lubricating portion that can be dissolved in the material, and a pair of adsorbing portions that have a functional group that can be adsorbed to the material and are coupled to the lubricating portion so as to sandwich the lubricating portion. .

  The lubricating oil additive according to the present invention is a high molecular weight lubricating oil additive (polymer), which is used by being added to the base oil of the lubricating oil. When the lubricating oil is used between the materials, a pair of adsorbing portions are adsorbed on the material, and a high molecular weight lubricating portion which is sandwiched between the adsorbing portions and is soluble in the base oil remains between the materials. Since the lubrication part and each adsorption part between these materials play a role as an oiliness improver, the effect of reducing friction and wear can be exhibited. At the same time, since the non-adsorbed lubricating part is dissolved in the base oil, the viscosity index improvement effect of suppressing the viscosity change due to temperature and optimizing the viscosity characteristics can be sufficiently exhibited. Thus, according to the lubricating oil additive of the present invention, an excellent friction reducing effect can be obtained.

  In addition, since the lubrication part is sandwiched between the adsorbing parts and joined, even when the sliding condition is high load and low shear rate, it is difficult to drain from the material interface, and the lubricating oil at the material interface Can be suppressed. For this reason, even if it is a sliding condition with a high load and a low shear rate, an increase in friction can be prevented and a friction reduction effect can be maintained.

  Since the lubricating oil additive according to the present invention is an adsorbent additive that is adsorbed to the material and exhibits its effect, it exhibits a sufficient friction reducing effect even at low temperature conditions (near room temperature) where the reaction additive is not effective. can do. In addition, the number of blending components is small compared to the case where conventional oiliness improvers, reaction system additives, viscosity index improvers and the like are separately blended into the base oil, and can be easily formulated. Moreover, the friction reduction effect can be obtained without using phosphorus and sulfur as much as possible, and phosphorus and sulfur can be reduced, which is environmentally friendly.

  In the lubricating oil additive according to the present invention, the lubricating part preferably contains one or more of a polymethacrylate chain, an olefin copolymer chain, and a polyisobutylene chain. In this case, an excellent viscosity index improvement effect can be obtained. Moreover, it is preferable that each adsorption part contains 1 or more types among a carboxyl group, a phosphate group, an amino group, and a thiol group. In this case, each adsorption part plays a role as an oiliness improver, and an excellent friction reducing effect can be obtained.

  In the lubricating oil additive according to the present invention, it is preferable that the lubricating part is made of a chain polymer, and each adsorbing part is bonded to both ends of the polymer. In this case, even under sliding conditions with a high load and a low shear rate, the lubrication part made of a chain polymer can be retained between the materials, and an excellent friction reducing effect can be obtained.

The lubricating oil additive according to the present invention may have a compound represented by the general formula (1) in which the lubricating portion includes a methacrylic acid ester unit and each adsorption portion includes a carboxyl group. In this case, a particularly excellent friction reducing effect can be obtained.
(In the formula, m, n, p and q are integers of 1 or more.)

  M in the general formula (1) is preferably an integer of 100 to 1,000. Moreover, it is preferable that n is an integer of 11-21. Moreover, it is preferable that p is an integer of 2-10. Moreover, it is preferable that q is an integer of 5-18. In these cases, a further excellent friction reducing effect can be obtained.

  The lubricating oil composition according to the present invention is characterized in that the lubricating oil additive according to the present invention is added to the base oil of the lubricating oil.

  Since the lubricating oil composition according to the present invention is added to the lubricating oil composition according to the present invention, it has an excellent friction reducing effect, and even under sliding conditions at high load and low shear rate, the boundary surface of the material It is possible to suppress a decrease in the film thickness of the lubricating oil. In addition, it can be formulated easily and is low in phosphorus and sulfur and is environmentally friendly.

  The lubricating oil composition according to the present invention preferably contains 0.1 to 10 parts by mass of the lubricating oil additive with respect to 100 parts by mass of the base oil of the lubricating oil. In this case, a particularly excellent friction reducing effect can be obtained.

  According to the present invention, the friction reduction effect is excellent, and even under sliding conditions at a high load and a low shear rate, it is possible to suppress a decrease in the film thickness of the lubricating oil at the material interface, Therefore, it is possible to provide a lubricating oil additive and a lubricating oil composition that can be easily formulated with a small amount, can reduce phosphorus and sulfur, and are environmentally friendly.

It is a chemical formula which shows the lubricating oil additive of embodiment of this invention. It is a side view which shows the test method for evaluating the nano friction characteristic between smooth surfaces of the lubricating oil additive of embodiment of this invention. FIG. 2 shows the test results for evaluating the nanofriction characteristics between the smooth surfaces shown in FIG. 2 when (a) the shear rate V = 0.011 μm / s and (b) the shear rate V = 1.1 μm / s. It is a graph. It is a perspective view which shows the test method of the ball-on-disk test for evaluating the macro friction characteristic between the uneven | corrugated surfaces of the lubricating oil additive of embodiment of this invention. It is a graph which shows the test result of the ball on disk test shown in FIG.

1 to 5 show a lubricating oil additive according to an embodiment of the present invention.
Hereinafter, the lubricating oil additive according to the embodiment of the present invention will be described based on the result of the test for evaluating the friction characteristics.

[Lubricating oil additive used for testing]
An ABA type block copolymer represented by the formula (2) in FIG. 1 was produced as the lubricating oil additive of the embodiment of the present invention used for the friction characteristic evaluation test. As shown in FIG. 1, the lubricant additive according to the embodiment of the present invention has a pair of adsorbing portions 11 corresponding to “A” and a lubricating portion 12 corresponding to “B”. Each adsorption part 11 consists of the molecule | numerator containing the carboxyl group which can adsorb | suck to the surface of materials, such as a metal. The lubrication part 12 consists of the chain | strand-shaped polymer containing the methacrylic acid ester unit which can be melt | dissolved in base oil. In the lubricating oil additive according to the embodiment of the present invention, a pair of adsorbing portions 11 are coupled to both ends of the lubricating portion 12 so as to sandwich the lubricating portion 12.

  In the test, four types of lubricating oil additives shown in Table 1 were used. Table 1 shows m (the chain length of the lubrication part 12) and n (the chain length of the side chain alkyl group of the lubrication part 12) and the number average molecular weight in the formula (2) of FIG. (Mn) and the polydispersity (Mw / Mn) which is the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) are shown.

  These lubricating oil additives were made by polymerization of a bifunctional macro chain transfer agent (PAaU10) and an alkyl methacrylate. Specifically, using BMAT represented by the formula (3) as a chain transfer agent, using a radical polymerization initiator, 11-acrylamide undecanoic acid is polymerized in methanol at 70 ° C. in an argon atmosphere, PAaU10 was synthesized as an adsorption site. Subsequently, by using this PAaU10 as a chain transfer agent, radical polymerization of a methacrylic acid ester was performed to synthesize the target lubricating oil additive.

For comparison, a homopolymer represented by the formula (4) (hereinafter referred to as “PSMA ₁₇₄ ”) and a random polymer represented by the formula (5) (hereinafter referred to as “p (S / A ₄ ) ₁₈₄ ”). ) Was also tested. Note that PSMA ₁₇₄ is a polymer without the adsorbing portion 11, and Mn = 59,200 and Mw / Mn = 1.86. Further, p (S / A ₄ ) ₁₈₄ is a polymer in which the adsorbing part 11 and the lubricating part 12 are randomly bonded, and Mn = 61,900 and Mw / Mn = 1.79.

[Nano-friction characteristics evaluation between smooth surfaces]
In order to grasp the limit of the friction reduction effect by the lubricating oil additive according to the embodiment of the present invention, a test for measuring the friction force using a surface force measuring device (SFA) was performed. In the test, as shown in FIG. 2, the lubricating oil (lubricating oil composition) of the test sample is sandwiched between a pair of mica 21a and 21b having a smooth surface, and the interval between the mica 21a and 21b is narrowed. The frictional force F applied to the other mica 21b when one mica 21a was slid at the shear rate V with the load L applied was measured. The load L was in the range of 5 to 40 mN, and the shear rate V was two types of 0.011 μm / s and 1.1 μm / s. The area A is about 1200 to 4000 μm ² .

As a lubricant for the test sample, a lubricant obtained by adding A ₅ S ₉₉₂ A ₅ in Table 1 to a base oil composed of polyalphaolefin (PAO) (“PAO + A ₅ S ₉₉₂ A ₅ ”), formula (4) The lubricating oil to which the homopolymer PSMA ₁₇₄ was added ("PAO + PSMA ₁₇₄ ") and the lubricating oil to which palmitic acid (PA), a general-purpose lubricating oil additive, was added ("PAO + PA") were used. These concentrations are 0.5 wt%. A test was also conducted with only the base oil ("PAO").

The test results are shown in FIG. FIG. 3 also shows the friction coefficient μ of each lubricating oil obtained from the test results. As shown in FIG. 3B, when V = 1.1 μm / s, the lubricating oil PAO + A ₅ S ₉₉₂ A ₅ to which the lubricating oil additive A ₅ S ₉₉₂ A ₅ of the embodiment of the present invention is added, and The lubricating oil PAO + PSMA ₁₇₄ added with the homopolymer PSMA ₁₇₄ has a friction coefficient μ smaller than 0.01, and it was confirmed that it has an excellent friction reducing effect. On the other hand, as shown in FIG. 3A, at a low shear rate of V = 0.011 μm / s, the friction coefficient μ is large in PAO + PSMA ₁₇₄ , but in PAO + A ₅ S ₉₉₂ A ₅ , It was confirmed that the coefficient μ hardly increased and was still smaller than 0.01, and an excellent friction reducing effect could be maintained.

When the static film thickness D before sliding at the shear rate V was measured at a load L = 5 mN, it was 20 nm or less with PAO + A ₅ S ₉₉₂ A ₅ , ₅ nm or less with PAO + PSMA ₁₇₄ , and 1.4 nm with PAO alone. It was the following. As described above, the lubricant additive PAO + A ₅ S ₉₉₂ A _{5 according to} the embodiment of the present invention is less likely to be discharged from the interface of the material, and suppresses a decrease in the film thickness of the lubricant at the interface of the material. Can be said. Thus, PAO + A ₅ S ₉₉₂ A ₅ is considered to exhibit an excellent friction reducing effect even under sliding conditions at high load and low shear rate.

[Evaluation of macro friction characteristics between practical surfaces with irregularities]
In order to evaluate the friction characteristics of the lubricant additive according to the embodiment of the present invention with materials and conditions close to practical use, a ball-on-disk test was performed using a tribometer. In the test, as shown in FIG. 4, a lubricating oil (lubricating oil composition) as a test sample is placed on a steel (SUJ2) disk 22, and a steel (SUJ2) ball 23 is loaded thereon with a load L. In the pressed state, the measurement was performed by reciprocating at a shear rate V. The load L was 5 mN. This load is a load at which the pressure becomes 119 MPa, which is similar to the pressure applied to the piston ring of the engine. Further, the shear velocity ^{V, 3 × 10 -3, 10 -2} , 3 × 10 -2, 10 -1, 3 × 10 -1, and the seven 1,3mm / s.

The lubricating oil of the test sample was a lubricating oil ("PAO + A ₅ L ₂₁₆ A ₅ ", "PAO + A ₅ ", which is a base oil composed of polyalphaolefin (PAO) with the four lubricating oil additives listed in Table 1. L ₉₄₆ A ₅ ”,“ PAO + A ₅ S ₁₇₀ A ₅ ”,“ PAO + A ₅ S ₉₉₂ A ₅ ”), lubricating oil added with homopolymer PSMA _{174 of} formula (4) (“ PAO + PSMA ₁₇₄ ”), and The lubricating oil ("PAO + p (S / A ₄ ) ₁₈₄ ") added with the random polymer p (S / A ₄ ) ₁₈₄ of the formula (5) was used. These concentrations are 0.5 wt% (0.5 parts by mass). A test was also conducted for the case of base oil only ("PAO").

FIG. 5 shows the speed dependence of the friction coefficient as a test result. As shown in FIG. 5, four types of lubricating oils PAO + A ₅ L ₂₁₆ A ₅ , PAO + A ₅ L ₉₄₆ A ₅ , PAO + A ₅ S ₁₇₀ A ₅ , to which the lubricating oil additive of the embodiment of the present invention is added, And PAO + A ₅ S ₉₉₂ A ₅ are lubricating oils PAO + PSMA ₁₇₄ and PAO + p (S / A ₄ ) having a shear rate V in the range of 3 × 10 ^{−3 to 3} mm / s and containing a homopolymer or a random polymer. It was confirmed that the friction coefficient was smaller than ₁₈₄ . Further, in the case of only the base oil, the friction coefficient is reduced to about 25 to 70% as compared with PAO, and it was confirmed that the base oil has an excellent friction reducing effect. From this result, it is considered that the friction reducing effect is remarkably improved by the fact that the adsorbing portion 11 is coupled to both ends of the lubricating portion 12.

Further, as shown in FIG. 5, among the four types of lubricating oils to which the lubricating oil additive according to the embodiment of the present invention is added, PAO + A ₅ L ₂₁₆ A ₅ is more preferable than PAO + A ₅ L ₉₄₆ A _5. , also towards the PAO + a ₅ S ₁₇₀ a ₅ than PAO + a ₅ S ₉₉₂ a _5, it was confirmed that the friction coefficient is small. From this, it can be said that the shorter the chain length of the lubrication part 12, the higher the friction reduction effect. Further, towards the PAO + A ₅ S ₉₉₂ A ₅ than PAO + A ₅ L ₉₄₆ A ₅ is also towards the PAO + A ₅ S ₁₇₀ A ₅ than PAO + A ₅ L ₂₁₆ A ₅ is, the friction coefficient is small It was confirmed. From this, it can be said that the friction reducing effect is higher when the chain length of the side chain alkyl group of the lubricating portion 12 is longer.

Further, as shown in FIG. 5, among the lubricating oils to which the lubricating oil additive according to the embodiment of the present invention is added, PAO + A ₅ L ₂₁₆ A ₅ , PAO + A ₅ S ₉₉₂ A ₅ and PAO + A ₅ S ₁₇₀ A _{In 5} , the minimum value of the friction coefficient is about 0.04. In the case of a lubricating oil using an inorganic additive such as conventional MoS ₂ , the minimum value of the friction coefficient is about 0.05 at high temperature and high pressure. By using the agent, it is considered that the friction reducing effect can be enhanced as compared with the inorganic additive. In addition, the inorganic additive contains sulfur and may cause environmental destruction, whereas the lubricant additive according to the embodiment of the present invention is derived from the BMAT used as the chain transfer agent. It contains only three sulfur atoms, does not contain phosphorus, and can be said to be environmentally friendly.

  From the above test results, the operation of the lubricating oil additive according to the embodiment of the present invention will be described. That is, the lubricating oil additive according to the embodiment of the present invention is used by being added to the base oil of the lubricating oil, and when the lubricating oil is used between materials such as metals, the pair of adsorbing portions 11 is used as the material. The lubricating portion 12 that is adsorbed and sandwiched between the adsorbing portions 11 also remains between the materials. For this reason, the lubrication part 12 and each adsorption | suction part 11 can exhibit the effect which reduces friction and abrasion by playing the role as an oil-based improvement agent. At the same time, since the unadsorbed lubricating part 12 is dissolved in the base oil, the viscosity index improvement effect of suppressing the viscosity change due to temperature and optimizing the viscosity characteristic can be sufficiently exhibited. Thus, according to the lubricant additive of the embodiment of the present invention, an excellent friction reducing effect can be obtained. For example, the friction coefficient of the lubricating oil can be reduced to a maximum of 70% compared to the case of the base oil alone and to a maximum of about 50% compared to conventional additives such as higher fatty acids and higher alcohols.

  In addition, since the lubrication part 12 is sandwiched between the adsorbing parts 11 and coupled to each other, it is difficult for the lubrication part 12 to be discharged from the boundary surface of the material such as a metal even under slip conditions at a high load and a low shear rate. A reduction in the film thickness of the lubricating oil on the surface can be suppressed. For this reason, even if it is a sliding condition with a high load and a low shear rate, an increase in friction can be prevented and a friction reduction effect can be maintained.

  The lubricant additive according to the embodiment of the present invention is an adsorbent additive that adsorbs on the material and exhibits its effect, so that friction is sufficiently reduced even at low temperature conditions (near room temperature) where the reaction additive is not effective. The effect can be demonstrated. For this reason, for example, in a hybrid car or the like, the engine temperature rise is small and the reactive additive is hardly effective. However, by using the lubricating oil additive according to the embodiment of the present invention, the friction reducing effect of the lubricating oil is sufficiently obtained. Can be demonstrated.

  In the lubricating oil additive according to the embodiment of the present invention, one component in which two adsorbing portions 11 and one lubricating portion 12 are combined has a plurality of functions such as an oiliness improver and a viscosity index improver. Compared to the case where conventional oiliness improvers, reaction system additives, viscosity index improvers, and the like are separately blended into the base oil, the number of blending components is reduced and can be easily formulated. Moreover, the friction reduction effect can be obtained without using phosphorus and sulfur as much as possible, and phosphorus and sulfur can be reduced, which is environmentally friendly.

  In the lubricating oil additive according to the embodiment of the present invention, the lubricating portion 12 is not limited to a polymethacrylate chain, and may include an olefin copolymer chain or a polyisobutylene chain. Also in these cases, an excellent viscosity index improving effect can be obtained. Moreover, each adsorption part 11 may contain not only a carboxyl group but a phosphoric acid group, an amino group, and a thiol group. Also in these cases, each adsorption | suction part 11 plays the role as an oil improvement agent, and can acquire the outstanding friction reduction effect. Moreover, it is preferable that m in General formula (1) is an integer of 100-1000. Moreover, it is preferable that n is an integer of 11-21. Moreover, it is preferable that p is an integer of 2-10. Moreover, it is preferable that q is an integer of 5-18. In these cases, an excellent friction reducing effect can be obtained.

21a, 21b Mica 22 Disc 23 Ball

To achieve the above object, the lubricating oil additive of the present invention, the lubricating oil for reducing friction between the materials, a lubricating oil additive used is added, the lubricating oil base A lubricating part having a high molecular weight that can be dissolved in oil; and a pair of adsorbing parts that have a functional group that can adsorb to the material and are coupled to the lubricating part so as to sandwich the lubricating part. Has a compound represented by the general formula (1) containing a methacrylic acid ester unit and each adsorbing part containing a carboxyl group .
(In the formula, m, n, p and q are integers of 1 or more.)

The lubricating oil additive of the present invention, since the lubricant portion contains a methacrylic acid ester unit, it is possible to obtain an excellent viscosity index improving effect. Further, each suction part, because it contains a carboxyl group, can each suction portion serves as the oiliness improver, to obtain a good friction reducing effect.

The lubricating oil additive of the present invention comprises the lubricating unit is a chain-like polymer, for each suction unit is coupled to both ends of the polymer, high load, a slip condition at low shear rates However, the lubrication part which consists of chain polymers can be stopped between materials, and the outstanding friction reduction effect can be acquired.

[Lubricating oil additive used for testing]
An ABA type block copolymer represented by the formula (2) in FIG. 1 was produced as the lubricating oil additive of the embodiment of the present invention used for the friction characteristic evaluation test. As shown in FIG. 1, the lubricant additive according to the embodiment of the present invention has a pair of adsorbing portions 11 corresponding to “A” and a lubricating portion 12 corresponding to “B”. Each adsorption part 11 consists of the molecule | numerator containing a carboxyl group which can adsorb | suck to the surface of materials, such as a metal. The lubrication part 12 consists of the chain | strand-shaped polymer containing the methacrylic acid ester unit which can be melt | dissolved in base oil. In the lubricating oil additive according to the embodiment of the present invention, a pair of adsorbing portions 11 are coupled to both ends of the lubricating portion 12 so as to sandwich the lubricating portion 12.

Claims (11)

A lubricating oil additive used in addition to a lubricating oil to reduce friction between materials,
A high molecular weight lubricating part that is soluble in the base oil of the lubricating oil;
A pair of adsorbing portions having functional groups capable of adsorbing to the material and coupled to the lubricating portions so as to sandwich the lubricating portions;
Lubricating oil additive characterized by having.   The lubricating oil additive according to claim 1, wherein the lubricating part contains one or more of a polymethacrylate chain, an olefin copolymer chain, and a polyisobutylene chain.   The lubricating oil additive according to claim 1 or 2, wherein each adsorption part contains one or more of a carboxyl group, a phosphate group, an amino group, and a thiol group. The lubricating part is made of a chain polymer,
The lubricating oil additive according to any one of claims 1 to 3, wherein each adsorbing portion is bonded to both ends of the polymer. The lubricating oil additive according to claim 1, wherein the lubricating part includes a methacrylic acid ester unit, and each adsorbing part includes a compound represented by the general formula (1) including a carboxyl group.
(In the formula, m, n, p and q are integers of 1 or more.)   The lubricating oil additive according to claim 5, wherein m in the general formula (1) is an integer of 100 to 1,000.   The lubricating oil additive according to claim 5 or 6, wherein n in the general formula (1) is an integer of 11 to 21.   The lubricating oil additive according to any one of claims 5 to 7, wherein p in the general formula (1) is an integer of 2 to 10.   The lubricating oil additive according to any one of claims 5 to 8, wherein q in the general formula (1) is an integer of 5 to 18.   A lubricating oil composition, wherein the lubricating oil additive according to any one of claims 1 to 9 is added to a base oil of the lubricating oil.   The lubricating oil composition according to claim 10, wherein the lubricating oil additive is contained in an amount of 0.1 to 10 parts by mass with respect to 100 parts by mass of the base oil of the lubricating oil.