JP5138928B2 - Hydraulic fluid composition for front fork shock absorber of motorcycle - Google Patents

Description

The present invention relates to a full Rontofo click slow衝器hydraulic fluid composition of the two-wheeled vehicle.

There are various types of shock absorbers, but they basically consist of a piston with a valve and a cylinder (also called an outer cylinder or tube). The piston is fixed to the rod, the piston slides on the inner surface of the cylinder, and the rod slides on the seal of the rod guide portion. The shock absorber acts as a buffer by the resistance of the working oil, which encloses the working oil and gas if necessary and passes through the valve.
Conventionally, as a hydraulic fluid for a shock absorber, in order to improve various performances required, for example, in Patent Documents 1 to 7, various additives such as phosphate esters, amine compounds, and viscosity index improvers are used. However, for example, in Patent Documents 8 to 16, it is proposed to use various high performance base oils such as poly α-olefin, ester, silicon oil, or deep dewaxed base oil.
However, the optimization of the base oil composition has not been sufficiently studied, and there is still a strong demand for improving ride comfort. Further, when a stick slip occurs between the seal of the shock absorber and the rod, a smooth buffer action cannot be exhibited, and therefore, a stick slip prevention property is required.

By the way, a shock absorber is used for the front fork of a two-wheeled vehicle, but the burden on the driver (feeling of fatigue, safety, etc.) due to good and bad riding comfort is larger than that of a four-wheeled vehicle, so when starting, accelerating, There is a strong demand for further improvements in ride comfort, such as stability during braking, turning, and high-speed driving, control of sinking and lifting, and vibration prevention.
However, it is difficult to improve the straight running stability and vibration control (feeling of damping and stroke) and to improve the stick-slip prevention performance at a high level, and the examination has not been made sufficiently. Currently.
JP-A-5-255683 JP 7-224293 A JP-A-7-258678 JP-A-6-128581 JP 2000-192067 A JP 2002-194376 A Japanese Patent Laid-Open No. 3-28588 Japanese Patent Laid-Open No. 3-285899 JP-A-5-86390 JP-A-5-247482 Japanese Patent Laid-Open No. 6-220480 JP 2000-119672 A JP 2000-047771 A JP 2000-109876 A JP 2000-119672 A JP-A-2005-314609

An object of the present invention, straight running stability and a significant improvement in drivability according to the vibration control, Ru can achieve both the stick-slip properties at a high level, the hydraulic fluid composition for a front fork loose衝器of motorcycles To provide things.

Ie, according to the present invention, a kinematic viscosity of 20 to 50 mm ² / s at 40 ° C., lubricating base oils the total amount of alkyl naphthalene (A) the total number of carbon atoms in the alkyl group is 8 to 50 A lubricating base oil comprising 10 to 30% by mass and one or more base oils selected from the group consisting of paraffinic mineral oils, naphthenic mineral oils and synthetic base oils other than (A). And succinimide having at least one alkyl group or alkenyl group having a number average molecular weight of 700 to 2500 as an ashless dispersant, 0.0001 to 0.05% by mass based on the total amount of the composition. Provided is a hydraulic fluid composition for a front fork shock absorber of a motorcycle (hereinafter sometimes abbreviated as the composition of the present invention) .

Since the hydraulic fluid composition for a shock absorber according to the present invention employs the above-described configuration, it is possible to achieve both a straight running stability, a drastic improvement in drivability for vibration control, and stick-slip prevention at a high level.
Therefore, the hydraulic fluid composition for a shock absorber according to the present invention can be used in suspension devices for automobiles such as shock absorbers, active suspensions, stay dampers, engine dampers, etc., and is particularly suitable for shock absorbers for front forks of motorcycles. In addition, the hydraulic fluid composition for shock absorbers of the present invention is excellent in stick-slip prevention properties and excellent in oxidation stability and low-temperature viscosity characteristics, and is therefore suitable as a hydraulic fluid for automobiles and industrial machinery / equipment. is there.

Hereinafter, the present invention will be described in detail.
The composition of the present invention is selected from the group consisting of an alkylnaphthalene (A) having a specific kinematic viscosity, a paraffinic mineral oil, a naphthenic mineral oil, and a synthetic base oil other than the above (A) as a lubricating base oil. Use seeds or two or more.
By including the component (A), such a lubricating base oil can greatly improve the stick-slip prevention property of the shock absorber and the ride comfort of an automobile, particularly a two-wheeled vehicle.

The component (A) used in the present invention is an alkylnaphthalene having a kinematic viscosity at 40 ° C. of 20 to 50 mm ² / s, and an alkylnaphthalene having the following properties is preferable in order to further improve the desired effects of the present invention. .
(A) The preferable kinematic viscosity in 40 degreeC of a component is 25-45 mm < ² > / s, More preferably, it is 30-40 mm < ² > / s.
(A) a kinematic viscosity at 100 ° C. of the component, typically 1 to 10 mm ² / s, preferably 3 to 8 mm ² / s, more preferably from 4 to 6 mm ² / s.
Although the aniline point of (A) component does not have a restriction | limiting in particular, Usually, it is 65 degrees C or less, Preferably it is 20-50 degreeC, More preferably, it is 30-40 degreeC.
Although there is no restriction | limiting in particular in the viscosity index of (A) component, Usually, it is 0 or more, More preferably, it is 40-100, More preferably, it is 60-90, Most preferably, it is 70-90.
The pour point of the component (A) is not particularly limited, but is usually 0 ° C. or lower, preferably −10 ° C. or lower, more preferably −20 ° C. or lower.

式(１)中、Ｒ¹、Ｒ²、Ｒ³及びＲ⁴は同一でも異なっていても良く、それぞれ水素原子又は炭素数１〜４０のアルキル基を示し、Ｒ¹、Ｒ²、Ｒ³又はＲ⁴の少なくとも１つはアルキル基を示す。 As the component (A), and more specifically need use compounds represented by the formula (1).

In formula (1), R ¹ , R ² , R ³ and R ⁴ may be the same or different and each represents a hydrogen atom or an alkyl group having 1 to 40 carbon atoms, and R ¹ , R ² , R ³ or At least one of R ⁴ represents an alkyl group.

It is preferred that all in the formula ^{(1) R 1, R 2} , R 3 and R ⁴ is an alkyl group.
Carbon number of an alkyl group is 1-40 normally, Preferably it is 8-30, More preferably, it is 10-20.
The total number of carbon atoms in R ^1, R ^2, R ³ and R ^4, 8-50, and more preferably Ru 10-40 der.

Examples of the alkylnaphthalene represented by the formula (1) include decylnaphthalene, undecylnaphthalene, dodecylnaphthalene, tridecylnaphthalene, tetradecylnaphthalene, pentadecylnaphthalene, hexadecylnaphthalene, heptadecylnaphthalene, octadecylnaphthalene, and nonadecyl. Naphthalene, icosylnaphthalene, di (decyl) naphthalene, di (undecyl) naphthalene, di (dodecyl) naphthalene, di (tridecyl) naphthalene, di (tetradecyl) naphthalene, di (pentadecyl) naphthalene, di (hexadecyl) naphthalene, di ( Heptadecyl) naphthalene, di (octadecyl) naphthalene, di (nonadecyl) naphthalene, di (icosyl) naphthalene, and all these isomers.
Among these, alkyl naphthalene having 1 to 4, more preferably 1 to 2 alkyl groups having 8 to 30 carbon atoms, more preferably 10 to 20 carbon atoms is preferable, and further, the total carbon number of the alkyl groups possessed by alkyl naphthalene. Is preferably an alkylnaphthalene having a molecular weight of 8 to 50, more preferably 10 to 40.
The said alkyl naphthalene may be used individually by 1 type, and may be used as a 2 or more types of mixture. When using the mixture of 2 or more types of alkyl naphthalene, it is preferable that the average molecular weight of the said mixture is 200-500.

  The production method of the alkylnaphthalene is arbitrary, and can be produced by various known methods. For example, hydrocarbon halides, olefins, styrenes, etc., mineral acids such as sulfuric acid, phosphoric acid, silicotungstic acid, hydrofluoric acid, solid acidic substances such as acidic clay, activated clay, aluminum chloride, zinc chloride And an addition reaction to naphthalene in the presence of an acid catalyst such as a Friedel-Crafts catalyst that is a metal halide.

  Specifically, as the paraffinic mineral oil, a lubricating oil fraction obtained by distillation under reduced pressure of atmospheric residual oil obtained by atmospheric distillation of crude oil is removed from the solvent, solvent extraction, hydrocracking, solvent Mineral oil obtained by appropriately combining one or two or more kinds of purification means of dewaxing, catalytic dewaxing, hydrorefining, sulfuric acid washing, and clay treatment, or wax isomerized mineral oil, GTL WAX (Gas Liquid Wax Another example is a base oil produced by isomerizing Fischer-Tropsch wax).

  The paraffinic mineral oil used in the present invention is a hydraulic fluid for shock absorbers, particularly a hydraulic fluid for shock absorbers used for a front fork of a motorcycle, for the purpose of preventing stick-slip of the shock absorber and improving the ride comfort of automobiles, particularly motorcycles. In order to satisfy various performances required for the above, it is desirable to use a suitable paraffinic mineral oil exhibiting the following properties.

The value of the% C _P /% C _N of paraffinic mineral oils, usually 1 or more, preferably 1 to 20, more preferably from 1.5 to 10, more preferably from 2 to 3.
While% C _P is not particularly limited paraffinic mineral oils, usually 50 or higher, more preferably 55 to 85, more preferably from 60 to 70.
While% C _N is not particularly limited paraffinic mineral oil, preferably 40 or less, more preferably 10 to 35, more preferably from 20 to 30.
While% C _A is not particularly limited paraffinic mineral oil, preferably 0-10, more preferably 1-9, further preferably 3-7.
In the present invention,% C _P ,% C _N and% C _A are percentages of the total number of paraffin carbons determined by a method (ndM ring analysis) based on ASTM D 3238-85, It means the percentage of the total number of naphthene carbons and the percentage of the total number of aromatic carbons.

The kinematic viscosity of the paraffinic mineral oils, at 100 ° C., usually 1 to 20 mm ² / s, preferably 1.5 to 10 mm ² / s, still preferably from 2 to 5 mm ² / s at 40 ° C., usually 3 60 mm ² / s, preferably 4 to 40 mm ² / s, more preferably 5 to 20 mm ² / s, particularly preferably from 6 to 10 mm ² / s.
The viscosity index of the paraffinic mineral oil is usually 80 or more, preferably 80 to 120, more preferably 85 to 110, and still more preferably 85 to 95.
The pour point of the paraffinic mineral oil is usually 0 ° C. or lower, preferably −10 ° C. or lower, more preferably −20 ° C. or lower.
In the present invention, the pour point means a pour point defined in accordance with JIS K 2269 “Pour point of crude oil and petroleum product and cloud point test method of petroleum product”.

The paraffinic mineral oil has, for example, a (P1) aniline point of 96 ° C or higher, preferably 120 or lower, more preferably 100 ° C or lower and / or (P2) an aniline point of 95 ° C or lower, preferably 66 to 95. It is desirable to use paraffinic mineral oil at a temperature of 80C, more preferably 80-90C. Of these, the use of the component (P2) is particularly desirable in the present invention.
In the present invention, the aniline point means an aniline point defined in accordance with JIS K 2256 “Petroleum product aniline point and mixed aniline point test method”.

  As naphthenic mineral oils, solvent removal, solvent extraction, hydrocracking, solvent dewaxing, catalytic desorption are performed on lubricating oil fractions obtained by atmospheric distillation and vacuum distillation of naphthenic crude oils rich in naphthene. Examples thereof include mineral oils obtained by applying a suitable combination of one or more purification means such as wax, hydrorefining, sulfuric acid washing, and clay treatment.

  The naphthenic mineral oil which can be used in the present invention is used for shock absorbers for preventing shock slip and for improving the ride comfort of automobiles, particularly two-wheeled vehicles, or for hydraulic fluids for shock absorbers, particularly for shock absorbers used for front forks of two-wheeled vehicles. In order to satisfy various performances required for a hydraulic fluid, it is desirable to use a suitable naphthenic mineral oil exhibiting the following properties.

The value of the% C _P /% C _N of naphthenic mineral oils, usually less than 1, preferably less than 0.2, more preferably 0.5 to 0.95, more preferably at 0.7 to 0.95 is there.
While% C _P is not particularly limited naphthenic mineral oils, usually less than 50, more preferably 30 to 48, more preferably from 35 to 45.
While% C _N is not particularly limited naphthenic mineral oil, preferably 30 to 80, more preferably 35 to 70, more preferably from 40 to 60.
While% C _A is not particularly limited naphthenic mineral oils, preferably 0 to 25, more preferably 5 to 20, more preferably from 10 to 15.

Kinematic viscosity naphthenic mineral oil at 100 ° C., usually 1 to 20 mm ² / s, preferably 2 to 15 mm ² / s, still preferably from 3 to 15 mm ² / s at 40 ° C., usually 3～500Mm ² / S, preferably 10 to 300 mm ² / s, more preferably 15 to 250 mm ² / s.
The viscosity index of naphthenic mineral oil is usually 120 or less, preferably 50 or less, more preferably 10 or less, still more preferably 5 or less, preferably −50 or more, more preferably −30 or more.
The pour point of naphthenic mineral oil is usually 0 ° C. or lower, preferably −10 ° C. or lower, more preferably −20 ° C. or lower, and further preferably −30 ° C. or lower.

As the naphthenic mineral oil, for example, a naphthenic mineral oil having an aniline point of 20 ° C or higher can be used. Specifically, (N1) naphthenic mineral oil having an aniline point of 96 ° C or higher and / or (N2) naphthene having an aniline point of 95 ° C or lower is used. Mineral oil.
As the component (N2), for example, (N2-1) naphthenic mineral oil having an aniline point of 66 to 95 ° C., preferably 70 to 85 ° C. and / or (N2-2) aniline point of 65 ° C. or lower, 20 ° C. or higher, More preferably, a naphthenic mineral oil of 50 ° C. or higher is used. Of these, it is more preferable to contain the component (N2). Moreover, it is preferable to contain (N2-1) component among the (N2) component at the point which can raise the viscosity index of a composition more.

  Synthetic base oils other than the component (A) include polybutene or hydrides thereof; poly-α-olefins such as 1-octene oligomers and 1-decene oligomers or hydrides thereof; ditridecyl glutarate, di-2- Diesters such as ethylhexyl adipate, diisodecyl adipate, ditridecyl adipate, di-2-ethylhexyl sebacate; neopentyl glycol ester, trimethylolpropane caprylate, trimethylolpropane pelargonate, pentaerythritol-2-ethylhexanoate, pentaerythritol Examples include polyol esters such as pelargonate; aromatic synthetic oils such as alkylnaphthalenes, alkylbenzenes and aromatic esters other than the component (A); and mixtures of two or more of these.

  The synthetic base oil that can be used in the present invention is a buffer used to improve the stick slip prevention performance of the shock absorber and the ride comfort of automobiles, particularly two-wheeled vehicles, or further to hydraulic fluid for shock absorbers, particularly, front forks of two-wheeled vehicles. In order to satisfy various performances required for the hydraulic fluid for industrial use, it is desirable to use a suitable synthetic base oil having the following properties.

The kinematic viscosity of the synthetic base oils, in 100 ° C., usually 1 to 500 mm ² / s, preferably 2 to 100 mm ² / s, still preferably from 3 to 50 mm ² / s at 40 ° C., usually 3~2000mm ² / s, preferably from 10 to 500 mm ² / s, more preferably 20 to 50 mm ² / s, particularly preferably 25 to 40 mm ² / s.
The viscosity index of the synthetic base oil is usually -50 to 300, preferably 0 to 150, more preferably 50 to 120, and still more preferably 70 to 95.
The pour point of synthetic mineral oil is usually 0 ° C. or lower, preferably −10 ° C. or lower, more preferably −20 ° C. or lower.

Examples of the synthetic base oil include (S1) a synthetic base oil having an aniline point of 96 ° C or higher and / or (S2) a synthetic base oil having an aniline point of 95 ° C or lower.
As the component (S2), for example, (S2-1) a synthetic base oil having an aniline point of 66 to 95 ° C, preferably 70 to 90 ° C and / or (S2-2) an aniline point of 20 ° C or higher and 65 ° C or lower, A synthetic base oil having a temperature of 50 ° C. or lower is preferable.

In the present invention, the content of the component (A) constituting the lubricating base oil is 10 to 30% by mass, particularly preferably 12 to 20% by mass. When the content ratio of the component (A) exceeds 70% by mass, it affects the sealing material or bushing material of the shock absorber and tends to make it difficult to maintain the stick-slip prevention property and the riding comfort improvement effect for a long period of time.
On the other hand, the content ratio of one or more base oils selected from the group consisting of the above-mentioned paraffinic mineral oil, naphthenic mineral oil and synthetic base oil other than the component (A) is preferably based on the total amount of the lubricating base oil. Is 70 to 90% by mass, particularly preferably 80 to 88% by mass.

The above-mentioned paraffinic mineral oil may not be contained in the lubricating base oil, but it is preferably contained because it can easily improve the anti-stick-slip property and increase the viscosity index of the composition. In this case, the content of the paraffinic mineral oils are not particularly limited, with lubricating base oils the total amount, good Mashiku 10-70% by weight, particularly preferably from 25 to 40 wt%.
The above-mentioned naphthenic mineral oil may not be contained in the lubricating base oil, but it is desirable to contain it in particular because it can improve the riding comfort of the two-wheeled vehicle and can be easily adjusted to preferable properties of the lubricating base oil described later. In this case, the content of the naphthenic mineral oil is not particularly limited, with lubricating base oils the total amount, good Mashiku 30-90% by weight, particularly preferably from 50 to 70 wt%.
Synthetic base oils other than the above component (A) may not be included in the lubricating base oil, but to improve stick slip prevention, riding comfort, and other performances required for hydraulic fluid compositions for shock absorbers. As long as these performances are not significantly deteriorated, an arbitrary amount can be contained. In this case, the content of the synthetic mineral oil is not particularly limited, but is usually 70% by mass or less, more preferably 55% by mass or less, and particularly preferably 40% based on the total amount of the lubricating base oil.
It is below mass%.

As the lubricating base oil used in the present invention, for example, a mixed oil comprising the component (A), one or more paraffinic mineral oils, one or more naphthenic mineral oils and one or more synthetic base oils, or Preferred is a mixed oil comprising the component (A), one or more mineral base oils and one or more synthetic base oils.
The lubricating base oil used in the present invention is used to improve the anti-stick-slip performance of the shock absorber and to improve the riding comfort of automobiles, particularly two-wheeled vehicles. In order to satisfy various performances required for hydraulic oil, it is desirable to make adjustments so as to exhibit the following properties.

The kinematic viscosity of the lubricating base oil, at 100 ° C., usually 1 to 20 mm ² / s, preferably 2 to 10 mm ² / s, still preferably from 3 to 5 mm ² / s at 40 ° C., usually 3~60mm ² / s, preferably 5 to 40 mm ² / s, more preferably 10~28mm ² / s, particularly preferably it is desirable that the was adjusted to 15 to 25 mm ² / s.
The viscosity index of the lubricating base oil is not particularly limited, but is preferably 0 or more, more preferably 10 or more, still more preferably 20 or more, preferably 120 or less, more preferably 95 or less, still more preferably 80 or less, Further, it is desirable to adjust to 60 or less, particularly preferably 40 or less.
The pour point of the lubricating base oil is usually 0 ° C. or lower, preferably −10 ° C. or lower, more preferably −20 ° C. or lower, and still more preferably −30 ° C. or lower.
The aniline point of the lubricating base oil is not particularly limited, and is usually adjusted to 120 ° C or lower, preferably 95 ° C or lower, more preferably 50 to 95 ° C, still more preferably 60 to 90 ° C, and particularly preferably 65 to 85 ° C. It is desirable that

The lubricating base oil may contain one or more aniline points selected from base oils having an aniline point of 96 ° C. or higher, but the aniline point is 95 ° C. or lower in that the ride comfort can be further improved. It is preferable to contain one or more selected from base oils. In this case, the content of the base oil having an aniline point of 95 ° C. or lower is not particularly limited, but is preferably 1% by mass or more, more preferably 30% by mass or more, and still more preferably 50% by mass based on the total amount of the lubricating oil base oil. % Or more, more preferably 70% by mass or more, and particularly preferably 100% by mass (including the component (A)).
Here, examples of the base oil having an aniline point of 96 ° C. or higher include the above-described component (P1), the component (N1) and the component (S1), and the base oil having an aniline point of 95 ° C. or lower is the above-mentioned (P2 ) Component, (N2) component, (S2) component, and (A) component.
The base oil having an aniline point of 95 ° C. or lower includes a base oil having an aniline point of 66 to 95 ° C. and a base oil having an aniline point of 65 ° C. or lower. Either one or a mixture of both may be preferably used. it can.

In the present invention, it is particularly preferable to contain a base oil having an aniline point of 65 ° C. or lower. Here, examples of the base oil having an aniline point of 66 to 95 ° C. include the above-described (P2) component, (N2-1) component and (S2-1) component, and the base oil having an aniline point of 65 ° C. or less. Includes the above-mentioned (N2-2) component, (S2-2) component and (A) component. As the base oil having an aniline point of 65 ° C. or lower, either (N2-2) component, (S2-2) component or a mixture of both can be preferably used. The viscosity index of the product can be further increased, and since the effect on the content is high, (S2-2) component, among them, aromatic base oils such as alkylbenzene and alkylnaphthalene are more preferable, the above essential components ( An alkylnaphthalene having a kinematic viscosity at 40 ° C. of the component A) of 20 to 50 mm ² is particularly preferable.

In the lubricating base oil, the content of the base oil having an aniline point of 65 ° C. or lower (including the above component (A)) is not particularly limited, but is preferably 1% by mass or more based on the total amount of the lubricating base oil. Preferably it is 5 mass% or more, More preferably, it is 10 mass% or more, More preferably, it is 15 mass% or more, Preferably it is 70 mass% or less, More preferably, it is 55 mass% or less, Most preferably, it is 40 mass% or less.
In the lubricant base oil, the content ratio of the base oil having an aniline point of 66 ° C. or higher is not particularly limited, but is preferably 30 to 100% by mass, more preferably 45% by mass or more based on the total amount of the lubricant base oil. Preferably it is 60 mass%, Preferably it is 95 mass% or less, More preferably, it is 85 mass% or less. Here, the base oil having an aniline point of 66 ° C. or higher includes the above-mentioned (P1) component, (P2) component, (N1) component, (N2-1) component (S1) component and (S2-1) component. Can be mentioned.

  The composition of the present invention includes the above-described lubricating base oil, so that the stick-slip prevention property of the shock absorber and the riding comfort of an automobile, particularly a two-wheeled vehicle can be achieved. In order to satisfy various performances required for a hydraulic fluid for a shock absorber used in a front fork, for example, at least one additive selected from the group consisting of an antiwear agent, an ashless dispersant, and a friction modifier is used. It is preferable to include.

As the antiwear agent, any compound usually used as an antiwear agent for lubricating oils can be used, and examples thereof include phosphorus and / or sulfur containing antiwear agents. Specifically, for example, phosphorus-containing antiwear agents such as phosphate esters, phosphites, thiophosphates, thiophosphites, derivatives thereof, metal salts thereof or amine salts thereof A sulfur-containing compound such as disulfides, sulfurized olefins, sulfurized fats and oils, dithiocarbamate, zinc dithiocarbamate and the like, and one or a mixture of two or more selected from the group consisting of these antiwear agents. Not.
Among these, zinc dialkyldithiophosphate, phosphite and / or phosphate ester having an alkyl group or alkenyl group having 1 to 30 carbon atoms, preferably 4 to 24 carbon atoms, more preferably 12 to 20 carbon atoms. Desirably, the use of phosphites having an alkyl or alkenyl group having 12 to 20 carbon atoms such as oleyl hydrogen phosphite is particularly desirable.
The ratio in the case of containing an antiwear agent is usually in the range of 0.01 to 5% by mass based on the total amount of the composition. In addition, among these, the ratio in the case of containing a phosphorus containing antiwear agent is 0.005-0.1 mass% normally as phosphorus amount on the basis of the total amount of the composition, preferably 0.01-0.08 mass%. More preferably, it is 0.01-0.04 mass%.

The ashless dispersant contains 0.0001 to 0.5% by mass of a succinimide having at least one alkyl group or alkenyl group having a number average molecular weight of 700 to 2500, preferably 900 to 1500, based on the total amount of the composition. Of these, use of the bis-type succinimide is desirable. Examples of the ashless dispersant other than the ashless dispersant include, for example, succinimide having an alkyl group or alkenyl group having 40 to 400 carbon atoms, benzylamine, polyamine or a boron compound thereof, a phosphorus compound, a sulfur compound, and an oxygen-containing organic compound. include modified derivatives by compounds but have a limitation.
The ratio when the ashless dispersant is contained is generally 0.01 to 20% by mass, preferably 0.01 to 5% by mass, more preferably 1% by mass or less, and particularly preferably 0.5%, based on the total amount of the composition. It is below mass%. The content ratio of the ashless dispersant as the nitrogen amount is usually 0.0001 to 0.2% by mass, preferably 0.05% by mass or less, more preferably 0.01% by mass or less, based on the total amount of the composition. More preferably, it is 0.005 mass% or less.

As the friction modifier, any compound usually used as a friction modifier for lubricating oils can be used. For example, an alkyl group or alkenyl group having 6 to 30 carbon atoms, particularly a linear alkyl group having 6 to 30 carbon atoms. Or fatty acid containing nitrogen such as aliphatic alcohol, aliphatic ether, aliphatic amine, fatty acid, fatty acid ester, sarcosine, etc. having at least one linear alkenyl group in the molecule, or a derivative thereof. Not. Of these, fatty acids having an alkyl group or alkenyl group having 12 to 20 carbon atoms or derivatives thereof are preferred, and esters of the fatty acids and polyhydric alcohols such as glycerol monooleate, glycerol dioleate, and glycerol trioleate. The use of at least one is particularly desirable.
The ratio in the case of containing a friction modifier is usually 0.01 to 5% by mass, preferably 0.1 to 3% by mass based on the total amount of the composition.

The composition of the present invention is generally used in lubricating oils in order to improve other effects without impairing the desired effects of the present invention in addition to the above-mentioned specific lubricating base oils and specific additives. At least one of the other additives that have been used can be blended.
Examples of such additives include viscosity index improvers, antioxidants, fluidity improvers, metal deactivators, antifoaming agents, metal detergents, corrosion inhibitors, rust preventives, demulsifiers, Various additives, such as a coloring agent, are mentioned.

As the viscosity index improver, any compound usually used as a viscosity index improver for lubricating oils can be used. For example, a polymer or copolymer of one or more monomers selected from various methacrylates So-called non-dispersed viscosity index improvers such as coalesced or hydrogenated products, so-called dispersed viscosity index improvers obtained by copolymerizing various methacrylic esters containing nitrogen compounds, non-dispersed or dispersed ethylene-α-olefins A copolymer is mentioned. Here, examples of the α-olefin include propylene, 1-butene, and 1-pentene.
In addition, a viscosity index improver such as polyisobutylene or a hydrogenated product thereof, a hydride of a styrene-diene copolymer, a styrene-maleic anhydride copolymer, or a polyalkylstyrene can also be used.
The number average molecular weight of the viscosity index improver is, for example, usually 5000 to 1,000,000, preferably 100,000 to 900,000 in the case of dispersed and non-dispersed polymethacrylates, and usually 800 to 5000, preferably in the case of polyisobutylene or a hydride thereof. In the case of 1000 to 4000, an ethylene-α-olefin copolymer or a hydride thereof, it is usually 800 to 500000, preferably 3000 to 200000.
These viscosity index improvers can contain one or two or more arbitrarily selected compounds in any amount, and the content ratio is usually 0.1 to 20 on the basis of the total amount of the composition. % By mass.

As the antioxidant, any compound usually used as an antioxidant for lubricating oils can be used. For example, 2,6-di-tert-butyl-p-cresol, 4,4′-methylenebis (2, 6-di-tert-butylphenol), octyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, 3-methyl-5-tert-butyl-4-hydroxyphenyl substituted fatty acid esters, etc. And amine-based antioxidants such as phenyl-α-naphthylamine, alkylphenyl-α-naphthylamine, and dialkyldiphenylamine.
The ratio in the case of containing an antioxidant is usually 0.01 to 5% by mass based on the total amount of the composition.

As the fluidity improver, any compound usually used as a fluidity improver for lubricating oils can be used, and examples thereof include polymethacrylate fluidity improvers.
Examples of metal deactivators include imidazoline, pyrimidine derivatives, alkylthiadiazoles, mercaptobenzothiazoles, benzotriazoles or derivatives thereof, 1,3,4-thiadiazole polysulfide, 1,3,4-thiadiazolyl-2,5-bis. Examples thereof include dialkyldithiocarbamate, 2- (alkyldithio) benzimidazole, and β- (o-carboxybenzylthio) propiononitrile.
Examples of the antifoaming agent include silicone, fluorosilicone, and fluoroalkyl ether.
Examples of metal detergents include alkali metal or alkaline earth metal sulfonates, finates, salicylates, and phosphonates.
Examples of the corrosion inhibitor include benzotriazole, tolyltriazole, thiadiazole, and imidazole compounds.
Examples of the rust preventive include petroleum sulfonate, alkylbenzene sulfonate, dinonylnaphthalene sulfonate, alkenyl succinic acid ester, and polyhydric alcohol ester.
Examples of the demulsifier include polyalkylene glycol nonionic surfactants such as polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, and polyoxyethylene alkyl naphthyl ether.
When these additives are contained, the ratio is usually 0.005 to 5% by mass for the fluidity improver, metal detergent, corrosion inhibitor, rust inhibitor, and demulsifier, based on the total composition. The deactivator is usually 0.005 to 1% by mass, and the antifoaming agent is usually 0.0005 to 1% by mass.

EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further more concretely, this invention is not limited at all by these.
Example 1 and Comparative Examples 1-3
Using various lubricating base oils shown in Table 1, the hydraulic fluid composition for shock absorbers of the present invention was prepared according to the composition of Example 1 shown in Table 2.
The composition was subjected to the following friction test and an actual vehicle riding comfort evaluation test using a two-wheeled vehicle. The results are shown in Table 2. Moreover, the composition of Comparative Examples 1-3 for a comparison was prepared, and the same test was done. The results are shown in Table 2.

(Friction test)
Using a Bowden testing machine, place a nitrile sealant with a thickness of about 2 mm on a holder with a hole with a diameter of 10 mm, and fix it with a steel ball of 1/2 inch pressed from above. And placed on a chrome-plated steel plate to which a few drops of test oil were dropped. A load of 9.8 N was applied to this and reciprocated at a stroke of room temperature and a sliding speed of 4 mm / s and 10 mm, and the friction coefficient μi at the start of sliding and the friction coefficient μd in the middle of the stroke were measured.
The higher the μd, the higher the coefficient of friction between the sealing material and the steel material, and the easier it is to control, and if the μi / μd value, which is an index of stick-slip characteristics, is in the range of 1.05 to 1.10, conventional stick-slip prevention It corresponds to a general hydraulic fluid composition for a shock absorber having a property, and when it exceeds 1.10, stick slip tends to be generated easily, and when it is less than 1.05, particularly when it is 1.00 or less. Is particularly excellent in stick-slip prevention.
(Evaluation of actual ride comfort)
A shock absorber filled with hydraulic fluid for shock absorbers was attached to the front fork of a two-wheeled vehicle (type), and riding comfort was evaluated under the following driving conditions.
The evaluation of ride comfort was evaluated individually for the following items by two or more drivers, and the average score of each driver was compared.
Straight running stability: Score 0-5 (best: 5), damping and stroke feeling: Score 0-5 (best: 5)
Note that the straight running stability indicates a feeling of riding related to the straight running stability, and the feeling of damping and the feeling of stroke indicate a feeling of riding related to the absorption characteristic of vibration due to sinking / lifting in the buffer direction.

  As is apparent from Table 2, the hydraulic fluid composition for shock absorbers according to the present invention (Example 1) has a greatly improved riding comfort evaluation result, and also has excellent anti-stick-slip properties, achieving both performances. I understand that I can do it. On the other hand, it can be seen that the compositions (Comparative Examples 1 to 3) containing no alkylnaphthalene are inferior in any of these performances.

Claims (2)

Alkylnaphthalene (A) having a kinematic viscosity at 40 ° C. of 20 to 50 mm ² / s and a total number of carbon atoms of the alkyl group of 8 to 50 is 10 to 30% by mass based on the total amount of the lubricating base oil. A lubricating base oil containing one or more base oils selected from the group consisting of mineral oils, naphthenic mineral oils and synthetic base oils other than (A) above, and a number average molecular weight of 700 as an ashless dispersant Hydraulic operation for a front fork shock absorber of a motorcycle characterized by containing 0.0001 to 0.05 mass% of succinimide having at least one alkyl group or alkenyl group of ˜2500 as a nitrogen amount based on the total amount of the composition Oil composition. The hydraulic fluid composition for a front fork shock absorber of a motorcycle according to claim 1, comprising at least one additive selected from the group consisting of an antiwear agent and a friction modifier.