JPH1143687A - Friction reducer comprising metal sulfonate and lubricating oil composition containing it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new metal sulfonate having an ability to reduce friction, a friction reducer comprising the metal sulfonate, and various lubricating oil compositions containing it. SOLUTION: This friction reducer comprises a metal sulfonate which consists of a metal and an organosulfonate group containing a hydrocarbon group comprising a linear hydrocarbon group or an aromatic group having at least one linear hydrocarbon group bound thereto and of which the linearity of the alkyl group in the linear hydrocarbon group, as determined by the carbon nuclear magnetic resonance measurement (<13> C-NMR measurement), is at least 20%. The lubricating oil composition is obtained by blending a lube base oil with the friction reducer in an amount, in terms of metal, of 1-10,000 ppm based on the total weight.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a friction reducing agent comprising a metal sulfonate and a lubricating oil composition containing the same, and more particularly, to a metal sulfonate having a specific linear hydrocarbon group. And a lubricating oil composition containing the same.

[0002]

2. Description of the Related Art In recent years, it has become necessary to save resources and save energy in all industrial fields from the viewpoint of environmental protection. As a result, it has become an indispensable means to adjust the desired frictional characteristics by adding additives to the lubricating base oil. Therefore, conventionally, a large number of friction modifiers have been proposed, and oil-based fatty acids, fatty acid metal salts, esters, amines, etc. and extreme pressure agents are used in wet brake oils, automatic transmission oils, sliding surface oils, plastic working oils, and the like. Type phosphoric acid ester, phosphite ester, zinc dithiophosphate, etc. are used.
Extreme pressure agent type phosphoric acid esters, phosphites, acidic phosphite amine salts, molybdenum dithiophosphate, molybdenum dithiocarbamate and the like are used as cutting oils.

Further, magnesium sulfonate used as a metal-based detergent for dispersing sludge formed in lubricating oil, solubilizing a precursor, neutralizing an acid, and the like, in particular, a catalyst having a base number of 300 mg KOH / g or more. An automatic transmission oil obtained by blending a basic magnesium sulfonate with a base oil for the purpose of improving friction characteristics is disclosed (see JP-A-62-84190), and calcium sulfonate, barium sulfonate,
There has been proposed a lubricating oil in which a metal-based detergent such as magnesium sulfonate is used in combination with molybdenum dialkyl dithiocarbamate (see JP-A-62-215697).

[0004] However, these metal sulfonates alone are not yet sufficient in a friction reducing effect, but are merely friction adjusting aids used in combination with friction adjusting agents such as phosphate esters and molybdenum dithiocarbamates. Did not. Therefore, if a metal sulfonate having a higher friction reducing ability is realized, its use area will be expanded over a wide range, and its industrial value will be remarkably increased.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances of the development of friction modifiers, and provides a novel metal sulfonate having a friction reducing ability, a friction reducing agent comprising the metal sulfonate and a friction reducing agent comprising the same. It is an object of the present invention to provide a lubricating oil composition containing

[0006]

Means for Solving the Problems Accordingly, the present inventors have:
As a result of intensive studies to solve the above-mentioned problems, a specific characteristic determined by carbon nuclear magnetic resonance measurement ( ¹³ C-NMR measurement) (hereinafter referred to as “ ¹³ C-NMR measurement” as necessary). It was noted that a metal sulfonate containing an alkyl group having a chain portion has excellent friction reducing ability. Furthermore, the present inventors have found that this metal sulfonate is effective as a friction reducing agent, and provide a lubricating oil composition which has improved friction characteristics by being blended with a lubricating base oil and can be used in various technical fields. They found what they could do, and based on these findings, completed the present invention.

That is, a first aspect of the present invention is a metal sulfonate comprising a hydrocarbon-containing organic sulfonic acid group and a metal, wherein the hydrocarbon group is a chain hydrocarbon group or a chain hydrocarbon group. A friction reducing agent comprising a metal sulfonate having at least one or more bonded aromatic group and having a linear degree of alkyl group in the chain hydrocarbon group of 20% or more as determined by ¹³ C-NMR measurement. It is about.

A second aspect of the present invention is a metal sulfonate comprising a hydrocarbon-containing organic sulfonic acid group and a metal in a lubricating base oil, wherein the hydrocarbon group is a chain hydrocarbon group or A metal sulfonate which is an aromatic group in which at least one chain hydrocarbon group is bonded and whose alkyl group linearity in the chain hydrocarbon group is 20% or more as determined by ¹³ C-NMR measurement, The present invention relates to a lubricating oil composition comprising 1 to 10,000 ppm of a metal based on the total weight of the product.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.

The metal sulfonate used as the friction reducing agent of the present invention comprises a hydrocarbon group-containing sulfonic acid group and a metal. For example, the following general formula [I] (RSO ₃ ) _x M [I] A compound that can be represented by one kind of the compound or a mixture of two or more kinds of compounds having different hydrocarbon groups. In the general formula [I], R in the organic sulfonic acid group RSO ₃ ^— is a hydrocarbon group, and is a chain hydrocarbon group or an aromatic group in which at least one chain hydrocarbon group is bonded. As the chain hydrocarbon group, the average number of carbon atoms per organic sulfonic acid group measured by ¹³ C-NMR and calculated assuming that the carbon bonded to the sulfonic acid group is 1 to 12 to 4
And an alkyl group of 0. In particular, carbon number 1
It is preferable to contain at least one alkyl group having 2 to 30 alkyl groups. As the alkyl group, specifically, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group, nonadecyl group, eicosyl group, tetracosyl group, pentacosyl group, hexacosyl group, heptacosyl group, octacosyl group Groups, nonacosyl groups and triacontyl groups, pentatriacontyl groups, octatriacontyl groups and the like.

[0011] The metal sulfonate of the present invention is a ¹³ C-NM
Those having an alkyl group linearity of 20% or more, particularly 30% to 80%, as determined by R measurement are suitable.

Here, the linearity of the alkyl group is based on a unique concept established as a result of repeated experiments by the present inventors, and the number of carbon atoms from the terminal of the alkyl group is 5 or more or Means the ratio of the number of carbon atoms in the linear portion four or more away from the branch to the total number of carbon atoms in the alkyl group, the size of which depends on the bonding position of the aromatic group and the branch position of the alkyl group. It is.

In the present invention, the linearity of the alkyl group is specifically determined by the following formula from ¹³ C-NMR measurement.

[0014]

(Equation 1) The ¹³ C-NMR measurement was performed by converting a metal sulfonate to a corresponding sulfonic acid.

The present inventors have recognized that there is an unexpected correlation between such linearity of the alkyl group and the friction reducing effect of the metal sulfonate,
The higher the linearity of the alkyl group, the more excellent the metal sulfonate is in the effect of reducing friction.
In particular, while 30% to 80% has a particularly remarkable effect,
It was found that if the alkyl group linearity was less than 20%, the effect was not sufficient.

Even when the metal sulfonate has two or more chain hydrocarbon groups per one organic sulfonic acid group, or when two or more different compounds (metal sulfonates) are mixed, the metal sulfonate can be obtained by ¹³ C-NMR measurement. If the obtained alkyl group linearity is 20% or more, it exhibits a friction reducing effect and is effective as the metal sulfonate of the present invention. In particular, when the chain hydrocarbon group of the metal sulfonate is an alkyl group having 12 or more carbon atoms and the degree of linearity is 20% or more, it is preferable from the viewpoint that the friction reducing ability can be significantly increased. The aromatic group bonded to the chain hydrocarbon group may be either a monocyclic or polycyclic fused ring, and those represented by the following structural formulas (a) to (g) are effective. Groups and the like are preferred.

[0017]

Embedded image The metal component represented by M in the above metal sulfonate (RSO ₃ ) _x M is an alkali metal or an alkaline earth metal, and a metal having an atomic number of 12 to 56 is preferable. Specific examples include sodium, potassium, lithium, calcium, magnesium, barium, and the like.Also, aluminum, zinc, tin, chromium, copper, cobalt, and the like are also effective. Are preferred. In the above general formula [I], x is a number corresponding to the valence of the metal component M.

A typical compound of the metal sulfonate of the present invention can be represented by the following general formula [II]. General formula [II]

[0019]

Embedded image In the general formula [II], A and B may be the same or different from each other, and are each an alkyl group or an aromatic group in which at least one alkyl group is bonded, and the alkyl group is a ¹³ C-NMR. The average linearity of all alkyl groups obtained by measurement is 20% or more. The aromatic group is at least one selected from the group consisting of the structural formulas (a) to (g). further,
In the formula, M represents the above-mentioned divalent metal, and among these, an alkaline earth metal is preferable.

Accordingly, the metal sulfonates of the present invention are more specifically exemplified by the following general formulas [III] to [V].
II]. General formula [III]

[0021]

Embedded image General formula [IV]

[0022]

Embedded image General formula [V]

[0023]

Embedded image General formula [VI]

[0024]

Embedded image General formula [VII]

[0025]

Embedded image In the above general formulas [III] to [VII], R ^{1 to} R
¹⁰ is an alkyl group, and as described above, R ¹ , R ² , and R correspond to the number of carbon atoms per organic sulfonic acid group.
Total ³ and R ^4, the sum of R ^5, a total of R ^6, a total of R ^7, the sum of R ^8, the total of R ^9, the average number of carbon atoms in the sum of R ¹⁰ is preferably 12 to 40, and ¹³ The alkyl group linearity determined by C-NMR measurement is 20% or more.

In the above formulas [III] to [VII], n represents the number of substitution of an alkyl group with an aromatic group.
5 is preferably an integer of 1 to 3, and in each formula, each may be the same or different.

Further, M of the general formulas [III] to [VII]
Is preferably an alkaline earth metal, but may be another divalent metal as described above.

The process for producing a metal sulfonate having an alkyl group having a long chain and a high degree of linearity according to the present invention can be carried out, for example, by using an alkyl group-substituted aromatic hydrocarbon or an olefin-based aromatic hydrocarbon obtained from a petroleum fraction. A sulfonic acid obtained by sulfonation of an alkyl group-substituted aromatic hydrocarbon as an alkylation product to an alkali metal oxide,
After neutralization with a hydroxide, an alkoxide, or the like, a method of producing by adjusting the amount of metal can be employed.

Further, the metal sulfonate having a specific alkyl group linearity of the present invention can be produced by controlling the metal sulfonate having different alkyl group linearity within the above-mentioned specific range by mixing.

In the present invention, the metal sulfonate may be a basic salt or an overbased salt in addition to a normal salt, and the type of the salt may be appropriately selected according to its use. The basic salt may be one produced by a usual method, for example, by dispersing M (OH) ₂ and MCO ₃ (where M represents an alkaline earth metal or the like) in a metal sulfonate in a colloidal form. It can be prepared and can be according to a conventionally employed manufacturing method.

According to the present invention, there is provided a friction reducing agent comprising a specific metal sulfonate as described above, particularly a friction reducing agent for lubricating oil. The friction reducing agent is oil-soluble and can be dissolved in a hydrocarbon or other solvent to form a concentrate, diluted appropriately, or used as a component of another additive and additive package.

Next, the lubricating oil composition of the present invention will be described. The base oil used in the lubricating oil composition of the present invention is not particularly limited, and may be any one of a mineral base oil, a synthetic base oil, and a plant base oil, or a mixed base oil thereof. Can be mentioned.

As the mineral base oil, for example, a lubricating oil fraction obtained by vacuum distillation of a normal distillation residue of a paraffinic, intermediate or naphthenic crude oil is subjected to solvent purification, hydrocracking, hydrotreating, hydrogenation, Mineral oil obtained by various purification processes such as refining, catalytic dewaxing, solvent dewaxing, clay treatment,
After subjecting the vacuum distillation residue to solvent deasphalting, a mineral oil obtained by treating the deasphalted oil by the above-described refining process, or a mineral oil obtained by isomerization of wax, or a mixed oil thereof can be used. . In the above solvent purification,
Aromatic extraction solvents such as phenol, furfural and N-methyl-pyrrolidone are used, and liquefied propane, MEK / toluene and the like are used as solvents for solvent dewaxing. Among the above mineral base oils, hydrotreated oils are preferred from the viewpoint of oxidation stability and the like, and for example, those having an aromatic hydrocarbon content of 2% by weight or less and a saturated hydrocarbon content of 90% by weight or more are used.

On the other hand, synthetic base oils include, for example, poly-α-olefin oligomers having lubricating viscosity, polyol esters such as polybutene, alkylbenzene, trimethylolpropane ester and pentaerythritol ester, polyoxyalkylene glycol, polyoxyalkylene glycol. Examples include esters, polyoxyalkylene glycol ethers, dibasic acid esters, phosphoric acid esters, and silicone oils. Each of these base oils may be used alone, or two or more may be used in combination. As the vegetable oil base oil, rapeseed oil, soybean oil, coconut oil, olive oil, sunflower oil, and the like are used.

The lubricating base oil used in the lubricating oil composition of the present invention can be produced by appropriately preparing a mixed base material so as to have desired properties according to the use of the lubricating oil composition. For example, regarding the viscosity, as a lubricating oil for an internal combustion engine, the kinematic viscosity at 100 ° C. is 2 mm ² / s to 3 mm.
0 mm ² / s, a range especially of 3mm ² / s~10mm ² / s, As the automatic transmission oil, 100 ° C. kinematic viscosity 2mm ² / s~30mm ² / s, in particular, 3 mm ² / s to
In the range of 15mm ² / s, and 40 ° C as gear oil
Kinematic viscosity of 10mm ² / s~1000mm ² / s in particular, 2
It is preferably adjusted to a range of 0mm ² / s~500mm ² / s.

The metal sulfonate of the present invention is used in an amount of 0.01 to 10% by weight, preferably 0.05 to 5% by weight, based on the total weight of the lubricating oil composition, based on the lubricating oil base oil.
1 ppm to 10,000 pp by weight in terms of metal
m, preferably 50 to 5,000 ppm, a sufficient friction reducing effect can be obtained.

The lubricating oil composition of the present invention may further contain a viscosity index improver, an ashless dispersant, an antioxidant, an extreme pressure agent, an antiwear agent, a metal deactivator, Other additives such as a point depressant, a corrosion inhibitor, and other friction modifiers can be appropriately selected and blended.

Examples of the viscosity index improver include polymethacrylates, polyisobutylenes, ethylene-propylene copolymers, styrene-butadiene hydrogenated copolymers, and the like. % To 35% by weight.

Examples of the ashless dispersant include polybutenyl succinimide type, polybutenyl succinamide type, and the like.
There are benzylamine type and succinate type,
These are usually used in a proportion of 0.05% by weight to 7% by weight.

Examples of the antioxidant include amine antioxidants such as alkylated diphenylamine, phenyl-α-naphthylamine, and alkylated phenyl-α-naphthylamine; 2,6-di-tert-butylphenol;
Examples include phenolic antioxidants such as 4,4'-methylenebis- (2,6-di-tert-butylphenol), and zinc dithiophosphate. These are usually 0.05% by weight to 5% by weight. Used in percentages.

The extreme pressure agent includes, for example, dibenzyl sulfide, dibutyl disulfide and the like, and these are usually used at a ratio of 0.05% by weight to 3% by weight.

Examples of the metal deactivator include benzotriazole, benzotriazole derivatives, thiadiazole and the like, and these are usually used at a ratio of 0.01% by weight to 3% by weight.

Examples of the pour point depressant include ethylene-vinyl acetate copolymer, condensate of chlorinated paraffin and naphthalene, condensate of chlorinated paraffin and phenol, polymethacrylate, polyalkylstyrene and the like. These are usually used at a ratio of 0.1% by weight to 10% by weight.

Examples of the antiwear agent include phosphate esters, zinc thiophosphate, sulfur compounds and the like, and these are usually used at a ratio of 0.01% by weight to 5% by weight.

In a preferred embodiment of the present invention, there is provided a metal sulfonate comprising a metal and an organic sulfonic acid group containing a hydrocarbon group, wherein the hydrocarbon group has at least a chain hydrocarbon group or a chain hydrocarbon group. Is a single-bonded aromatic group, and the chain hydrocarbon group is a ¹³ C-NMR
A friction reducer for lubricating oil comprising a metal sulfonate having an average carbon number of 12 to 40 per organic sulfonic acid group determined by measurement and having an alkyl group linearity of 20% or more; A metal sulfonate comprising an organic sulfonic acid group and a metal, wherein the hydrocarbon group is a chain hydrocarbon group or an aromatic group in which at least one chain hydrocarbon group is bonded, and the chain hydrocarbon group is Is an alkyl group having an average carbon number of 12 to 40 per organic sulfonic acid group determined by ¹³ C-NMR measurement, and a friction reducer for lubricating oil comprising a metal sulfonate having an alkyl group linearity of 30% or more. A lubricating base oil comprising a metal sulfonate comprising a hydrocarbon group-containing organic sulfonic acid group and a metal, wherein the hydrocarbon group is a chain hydrocarbon group or a chain hydrocarbon group; At least one linked aromatic group, the chain-like hydrocarbon group
^A metal sulfonate which is an alkyl group having an average number of carbon atoms of 12 to 40 per organic sulfonic acid group determined by ¹³ C-NMR measurement and has an alkyl group linearity of 20% or more,
1 ppm to 1 as a metal amount based on the total weight of the lubricating oil composition
A lubricating oil composition comprising 0.00000 ppm, a lubricating base oil comprising a metal sulfonate comprising an organic sulfonic acid group containing a hydrocarbon group and a metal, wherein the hydrocarbon group is a chain hydrocarbon group or An aromatic group in which at least one chain hydrocarbon group is bonded, and the chain hydrocarbon group is
^A metal sulfonate having an average number of carbon atoms of 12 to 40 per organic sulfonic acid group determined by ¹³ C-NMR measurement and having an alkyl group linearity of 20% or more,
1 ppm to 1 as a metal amount based on the total weight of the lubricating oil composition
0,000 ppm, and at least one selected from the group consisting of viscosity index improvers, ashless dispersants, antioxidants, extreme pressure agents, metal deactivators, pour point depressants and antiwear agents. The lubricating oil composition can be provided.

According to a further preferred embodiment of the lubricating oil composition of the present invention, the aromatic hydrocarbon is 2% by weight or less,
A hydrotreated oil containing 90% by weight or more of a saturated hydrocarbon is used as a base oil, which has one to two alkyl groups having 14 to 24 carbon atoms per organic sulfonic acid group, and is determined by ¹³ C-NMR measurement. A lubricating oil composition comprising 50 to 5000 ppm of calcium sulfonate having an alkyl group linearity of 40% or more based on the total weight of the lubricating oil composition.

As described above, the metal sulfonate of the present invention can be used as a friction reducing agent in addition to a lubricating oil for an internal combustion engine, an automatic transmission oil, a gear oil, a hydraulic oil, a wet brake oil,
It can be used for sliding surface oil, plastic working oil, cutting oil, etc., but is not limited thereto, and can be used without limitation as long as the metal sulfonate can exert a friction reducing effect. .

[0048]

EXAMPLES The present invention will now be described in detail with reference to Examples and Comparative Examples. Examples and the like mainly show the effects of the specific alkyl group of the metal sulfonate of the present invention.
The present invention is not limited by these examples and the like. The alkyl group linearity of the metal sulfonate used in the following Examples and the like and the performance evaluation of the lubricating oil composition were measured by the following methods.

Method for Measuring Alkyl Group Linearity The metal sulfonate was converted to sulfonic acid, and the ¹³ C-NMR spectrum was measured under the following measurement conditions. The alkyl group linearity was calculated by the following equation. Measurement conditions Equipment used EX400 (manufactured by JEOL Ltd.) Observation nucleus ¹³ C Observation frequency 100.50 MHz Measurement mode Gated ¹ H decoupling Internal standard TMS (= 0 ppm) Relaxing reagent Cr (acac) ₃ solvent CDCl ₃ Sample amount 300 mg Temperature 30 ° C

[0050]

(Equation 2)

Performance Evaluation Friction Coefficient Measurement Method For a lubricating oil composition containing a predetermined amount of metal sulfonate, the friction coefficient was measured using LFW-1 as a tester under the following conditions. Friction material; steel / steel load; 200 lb oil temperature; 80 ° C. rotation speed; 600 rpm measurement time;

[0052] Was prepared and mixed with 100 N of solvent-refined mineral oil (kinematic viscosity at 100 ° C .: 4.2 mm ² / s) at 140 ppm based on the total weight of the lubricating oil composition to prepare a lubricating oil composition. When the coefficient of friction of the obtained lubricating oil composition was measured by the above method, it was 0.09.

Example 2 A lubricating oil composition was prepared in the same manner as in Example 1 except that the amount of calcium sulfonate 1 was increased from 140 ppm to 560 ppm in terms of calcium. When the obtained lubricating oil composition was subjected to performance evaluation, the friction coefficient was 0.08, and the friction characteristics were improved.

[0054] Was prepared and added to the same lubricating base oil as in Example 1 in terms of calcium content of 1,200 pp based on the total weight of the lubricating oil composition
m to prepare a lubricating oil composition. The obtained lubricating oil composition was subjected to the above-described performance evaluation, and a result having a friction coefficient of 0.10.

Example 4 A lubricating oil composition was prepared in the same manner as in Example 3 except that the amount of calcium sulfonate 2 was increased from 1,200 ppm to 2,400 ppm in terms of calcium, and subjected to performance evaluation. The result was a coefficient of friction of 0.08.

[0056] Was prepared and added to the same lubricating base oil as in Example 1 in terms of calcium amount of 2,400 p based on the total weight of the lubricating oil composition.
pm was blended to prepare a lubricating oil composition. When subjected to performance evaluation, a result having a friction coefficient of 0.09 was obtained.

Example 6 The amount of calcium sulfonate 3 was from 2,400 ppm to 4,80 ppm in terms of calcium.
A lubricating oil composition was prepared in the same manner as in Example 5 except that the amount was increased to 0 ppm. When subjected to performance evaluation,
The result was a coefficient of friction of 0.08.

[0058] Was prepared and added to the same lubricating base oil as in Example 1 in terms of calcium amount based on the total weight of the lubricating oil composition at 2,400 pp
m to prepare a lubricating oil composition. As a result of the performance evaluation, the friction coefficient was 0.13.

[0059] Was prepared and added to the same lubricating base oil as in Example 1 in terms of calcium amount of 2,400 p based on the total weight of the lubricating oil composition.
pm was blended to prepare a lubricating oil composition. The coefficient of friction of the obtained lubricating oil composition was 0.14.

Comparative Example 3 A lubricating oil composition was obtained in the same manner as in Comparative Example 2 except that the amount of calcium sulfonate 5 was increased from 2,400 ppm to 4,800 ppm in terms of calcium. The coefficient of friction was 0.13, and it was found that even if the amount of calcium sulfonate having a small alkyl group linearity was increased, almost no effect on the friction characteristics was obtained.

Comparative Example 4 Solvent-refined mineral oil 10 used in Example 1 as a lubricating base oil
When only 0N (kinematic viscosity at 100 ° C .: 4.2 mm ² / s) was subjected to performance evaluation, a result of a friction coefficient of 0.14 was obtained.

The measurement results of the friction coefficient and the calcium sulfonate used in the above Examples and Comparative Examples are shown in Tables 1 and 2, respectively. From these results, it was found that the alkyl group linearity of the metal sulfonate was 20
% Or more, a low coefficient of friction can be obtained even if the amount of calcium sulfonate is small (Examples 1 and 2), whereas if the alkyl group linearity is low, low friction is obtained even if the amount of calcium sulfonate is increased. No coefficient was obtained (Comparative Example 3). Even when a metal sulfonate whose linearity does not reach 20% is used, it is shown by comparison of Comparative Examples 2 and 4 that the friction coefficient of the lubricating oil composition is the same as that of the base oil alone. It became clear that chain degree was the main factor affecting the friction characteristics.

[0063]

[Table 1]

[0064]

[Table 2]

[0065]

The metal sulfonate having an alkyl group linearity of 20% or more has a large friction reducing effect, is useful as a friction reducing agent for lubricating oil, and can improve the friction characteristics of a lubricating oil composition.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C10N 30:06

Claims (3)

[Claims] 1. A metal sulfonate comprising a hydrocarbon group-containing organic sulfonic acid group and a metal, wherein the hydrocarbon group is a chain hydrocarbon group or an aromatic group in which at least one chain hydrocarbon group is bonded. A friction reducing agent comprising a metal sulfonate having an alkyl group linearity of 20% or more in the chain hydrocarbon group determined by carbon nuclear magnetic resonance measurement ( ^13C -NMR measurement). . 2. The friction reducing agent comprising a metal sulfonate according to claim 1, wherein the chain hydrocarbon group is an alkyl group. 3. A lubricating base oil comprising a metal sulfonate comprising a hydrocarbon group-containing organic sulfonic acid group and a metal, wherein the hydrocarbon group has at least a chain hydrocarbon group or a chain hydrocarbon group. A metal sulfonate, which is an aromatic group having at least one bond and has a linear degree of alkyl group of 20% or more in the chain hydrocarbon group determined by carbon nuclear magnetic resonance measurement ( ¹³ C-NMR measurement), A lubricating oil composition comprising 1 to 10,000 ppm of a metal based on the total weight of the composition.