CN100510033C - Additive for lubricating oil and fuel oil, lubricating oil composition and fuel oil composition - Google Patents

Abstract

An additive for lubricating oils and fuel oils, which contains, as a main component, a disulfide compound represented by the general formula (I) or (IV): R ¹ OOC-A ¹ -S _x -A ² -COOR ² (I ) (where R ¹ and R ² each independently represent a C _1-30 hydrocarbon group, which may contain oxygen, sulfur or nitrogen, A ¹ and A ² each independently represent a group represented by CR ³ R ⁴ , R ³ and R ⁴ each independently represents a hydrogen atom or a C _1-20 hydrocarbon group, and x represents 2), R ¹ OOC-A ³ -S _x -A ⁴ -COOR ² (IV) (wherein R ¹ and R ² are as defined above, A ³ and A ⁴ each independently represent a group represented by CR ⁵ R ⁶ -CR ⁷ R ⁸ , R ⁵ to R ⁸ each independently represent a hydrogen atom or a C _1-20 hydrocarbon group, and x represents 2). The additive exhibits excellent functions as an extreme pressure additive or an anti-wear agent and corrodes non-ferrous metals to a small extent, so it can be used as a sulfur-containing extreme pressure additive suitable for lubricating oil and fuel oil.

Description

Additive for lubricating oil and fuel oil, lubricating oil composition and fuel oil composition

technical field

The present invention relates to additives for lubricating oils and fuel oils, lubricating oil compositions and fuel oil compositions. More particularly, the present invention relates to additives for lubricating oils and fuel oils, which include disulfide compounds having specific structures as main components and are shown as friction modifiers, especially extreme pressure additives and antiwear agents excellent function, and relates to a lubricating oil composition and a fuel composition each including the additive.

Background technique

Heretofore, lubricating oils have been used in devices and instruments for driving and devices such as internal combustion engines, automatic transmissions, shock absorbers, and power steering for smooth operation of the devices and instruments. It is well known that lubricated surfaces are worn by friction under conditions of high output power and high load, since the lubricating performance becomes insufficient, and seizure occurs under extreme conditions. Therefore, use lubricants that contain extreme pressure additives and antiwear agents. However, common extreme pressure additives are not always satisfactory in that a sufficient seizing preventing effect is not shown due to interaction with other additives, metals are corroded, and wear resistance is insufficient.

Attempts have been made to prepare metalworking oils for metalworking such as cutting, grinding and plastic working by adding oily additives and extreme pressure additives such as alcohols, esters of fatty acids, and fatty acids to mineral oils and synthetic hydrocarbon oils to improve working characteristics .

However, new metalworking oils that can provide further improved working characteristics are required from the standpoint of improvement in productivity and energy saving. On the other hand, the use of chlorine-type extreme pressure additives widely used as extreme pressure additives tends to be inhibited due to adverse effects on working environments such as the formation of rashes on human bodies and the formation of rust on metals used.

As metalworking oils expected to overcome the above problems, oils prepared by adding active sulfur-containing olefin sulfides and overbased sulfonates to base oils are commercially available.

The above commercially available metalworking oils exhibit excellent melt adhesion resistance and have properties of preventing abnormal tool wear such as cracking and tearing of the working surface. However, in machining where friction occurs repeatedly under small loads, the efficiency of production is often adversely affected, because corrosive wear of the tool with active sulfur occurs and before the tool is replaced with a new tool or the tool is ground and resurfaced. The time will be shortened. Conversely, when there is no problem of abnormal wear in metal processing, the efficiency of production often decreases.

Hydraulic oil is a power transmission fluid used to transmit power, control force, and buffer in hydraulic systems such as hydraulic devices and instruments, and exhibit a lubricating function for sliding parts.

Excellent performance against seizure under load and excellent wear resistance are essential basic properties required of hydraulic oils. These properties are provided by adding extreme pressure additives and antiwear agents to base oils such as mineral and synthetic oils. However, common extreme pressure additives are not always satisfactory due to insufficient wear resistance or the occurrence of corrosive wear, although showing sufficient performance to prevent seizure under load.

As for gear oils, especially, gear oils for automobiles, improvements in wear resistance and oxidation stability are urgently needed because of the increase in the amount of load carried and the long distances brought about by the improved road network. Driving conditions have become more severe due to the increase in transportation and the lengthening of the time interval before the oil is refreshed.

Previously, it was common practice that extreme pressure additives or antiwear agents such as sulfurized oils and fats, olefin sulfides, phosphoric acid compounds, phosphorothioate compounds and zinc dithiophosphates were added to the base oil of lubricating oils, As the main reagent for improvement purposes. Further improvements in wear resistance and oxidation stability and further reductions in the ratio of friction coefficients (at low speed/at high speed) are also required.

On the other hand, with fuel oil, it is well known that the lubricating performance becomes insufficient due to the hydrogenation of the fuel oil to a greater extent. It has been pointed out that fuel pump wear occurs more rapidly when highly refined fuels are used. Excellent lubricating properties are required for high-efficiency fuel oils recently used in turbines. Therefore, it is desired to have an excellent additive for fuel oil which is adsorbed to form an extreme pressure lubricating oil film on metal surfaces in devices and instruments of the fuel system, so that the lubricating performance is improved and the wear is reduced.

Generally, sulfur-type extreme pressure additives are often used as extreme pressure additives for lubricating oils. The sulfur type extreme pressure additive has sulfur atoms in the molecule and is dissolved or uniformly dispersed in the base oil to exhibit an extreme pressure effect. Examples of sulfur-type extreme pressure additives include sulfurized oils and fats, sulfurized fatty acids, ester sulfides, polysulfides, olefin sulfides, thiocarbamates, thioterpenes, and dialkylthiodipropionates ester. However, the above sulfur-type extreme pressure additives are not always satisfactory because these additives have problems that the metal is corroded, the effect of preventing seizure is not sufficiently exhibited due to the interaction with other additives, and the resistance Grinding is not enough.

Recently, as the sulfur type extreme pressure additive, a compound represented by the general formula (VII)

R ⁹ OOC-A ⁵ -S _x -A ⁶ -COOR ¹⁰ ...(VII)

(In the above general formula, each of ^R9 and ^R10 represents a hydrocarbon group having 1 to 20 carbon atoms, each of ^A5 and ^A6 represents a hydrocarbon group having 0 to 20 carbon atoms, and x represents 1 to 6 integer) are disclosed (for example, Japanese Patent Application Laid-Open No. 2001-288490).

However, according to Japanese Patent Application Laid-Open No. 2001-288490), the compound represented by the general formula (VII) is produced by reacting a chlorinated ester such as an ester of monochloroacetic acid with sodium polysulfide, and it is inevitable that this The product obtained by the reaction is a mixture of monosulfide, disulfide and polysulfide (which is trisulfide or higher). The individual number of carbon atoms is stated for the divalent hydrocarbon group represented by A ⁵ and A ⁶ , and the preferred structure of the group is vague because no description is found for the group structure.

Disclosure of the invention

Under the above circumstances, an object of the present invention is to provide a sulfur-type extreme pressure additive which exhibits superior load-carrying capacity and wear resistance and corrosion resistance to non-ferrous metals than those exhibited by ordinary sulfur-type additives is low and can be used in lubricating oils and fuel oils, and lubricating oil compositions and fuel oil compositions including the additive.

As a result of intensive research conducted by the present inventors to achieve the above object, it has been found that the object can be achieved by an additive for lubricating oil and fuel oil including a disulfide compound having a specific structure as a main component. The present invention has been accomplished based on this knowledge.

The present invention provides:

(1) Additives for lubricating oils comprising, as a main component, a disulfide compound represented by the general formula (I):

R ¹ OOC-A ¹ -S _x -A ² -COOR ² ...(I)

wherein R ¹ and R ² each independently represent a hydrocarbon group having 1 to 30 carbon atoms and may have an oxygen atom, a sulfur atom or a nitrogen atom, and A ¹ and A ² each independently represent a group represented by CR ³ R ⁴ , R ³ and R ⁴ each independently represent a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms, and x represents 2;

(2) An additive for lubricating oils comprising, as a main component, a disulfide compound represented by an ester of mercaptoalkanecarboxylic acid represented by at least one of general formula (II) and general formula (III) The oxidative coupling of to obtain:

R ¹ OOC-A ¹ -SH...(II)

wherein R ¹ represents a hydrocarbon group having 1 to 30 carbon atoms and may have an oxygen atom, a sulfur atom or a nitrogen atom, and A ¹ represents a group represented by CR ³ R ⁴ , and R ³ and R ⁴ each independently represent hydrogen atoms or hydrocarbon groups having 1 to 20 carbon atoms, and

R ² OOC-A ² -SH...(III)

wherein R ² represents a hydrocarbon group having 1 to 30 carbon atoms and may have an oxygen atom, a sulfur atom or a nitrogen atom; and A ² represents a group represented by CR ³ R ⁴ , and R ³ and R ⁴ each independently represent hydrogen atoms or hydrocarbon groups having 1 to 20 carbon atoms;

(3) Additives for lubricating oils comprising, as a main component, a disulfide compound represented by the general formula (IV):

R ¹ OOC-A ³ -S _x -A ⁴ -COOR ² ...(IV)

wherein R ¹ and R ² each independently represent a hydrocarbon group having 1 to 30 carbon atoms and may have an oxygen atom, a sulfur atom or a nitrogen atom, and A ³ and A ⁴ each independently represent a group consisting of CR ⁵ R ⁶ -CR ⁷ R A group represented by ⁸ , R ⁵ to R ⁸ each independently represent a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms, and x represents 2;

(4) An additive for lubricating oils comprising, as a main component, a disulfide compound represented by an ester of a mercaptoalkanecarboxylic acid represented by at least one of the general formula (V) and the general formula (VI) The oxidative coupling of to obtain:

R ¹ OOC-A ³ -SH...(V)

wherein R ¹ represents a hydrocarbon group having 1 to 30 carbon atoms and may have an oxygen atom, a sulfur atom or a nitrogen atom, and A ³ represents a group represented by CR ⁵ R ⁶ -CR ⁷ R ⁸ , R ⁵ to R ⁸ each independently represents a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms, and

R ² OOC-A ⁴ -SH...(VI)

wherein R ² represents a hydrocarbon group having 1 to 30 carbon atoms and may have an oxygen atom, a sulfur atom or a nitrogen atom; and A ⁴ represents a group represented by CR ⁵ R ⁶ -CR ⁷ R ⁸ , R ⁵ to R ⁸ Each independently represents a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms;

(5) The additive for lubricating oil described in the above item (1), wherein the content of the polysulfide compound represented by the general formula (I) in which x represents a value of 3 or more is 30% by mass or 30% Mass below, based on the sum of the amount of disulfide compounds and the amount of polysulfide compounds;

(6) The additive for lubricating oil described in the above item (3), wherein the content of the polysulfide compound represented by the general formula (IV) in which x represents a value of 3 or more is 30% by mass or 30% Mass below, based on the sum of the amount of disulfide compounds and the amount of polysulfide compounds;

(7) An additive for fuel oil comprising, as a main component, a disulfide compound represented by the general formula (I):

R ¹ OOC-A ¹ -S _x -A ² -COOR ² ...(I)

wherein R ¹ and R ² each independently represent a hydrocarbon group having 1 to 30 carbon atoms and may have an oxygen atom, a sulfur atom or a nitrogen atom, and A ¹ and A ² each independently represent a group represented by CR ³ R ⁴ , R ³ and R ⁴ each independently represent a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms, and x represents 2;

(8) An additive for fuel oil comprising, as a main component, a disulfide compound through an ester of mercaptoalkanecarboxylic acid represented by at least one of general formula (II) and general formula (III) The oxidative coupling of to obtain:

R ¹ OOC-A ¹ -SH...(II)

wherein R ¹ represents a hydrocarbon group having 1 to 30 carbon atoms and may have an oxygen atom, a sulfur atom or a nitrogen atom, and A ¹ represents a group represented by CR ³ R ⁴ , and R ³ and R ⁴ each independently represent hydrogen atoms or hydrocarbon groups having 1 to 20 carbon atoms, and

R ² OOC-A ² -SH...(III)

wherein R ² represents a hydrocarbon group having 1 to 30 carbon atoms and may have an oxygen atom, a sulfur atom or a nitrogen atom; and A ² represents a group represented by CR ³ R ⁴ , and R ³ and R ⁴ each independently represent hydrogen atoms or hydrocarbon groups having 1 to 20 carbon atoms;

(9) An additive for fuel oil comprising, as a main component, a disulfide compound represented by the general formula (IV):

R ¹ OOC-A ³ -S _x -A ⁴ -COOR ² ...(IV)

wherein R ¹ and R ² each independently represent a hydrocarbon group having 1 to 30 carbon atoms and may have an oxygen atom, a sulfur atom or a nitrogen atom, and A ³ and A ⁴ each independently represent a group consisting of CR ⁵ R ⁶ -CR ⁷ R A group represented by ⁸ , R ⁵ to R ⁸ each independently represent a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms, and x represents 2;

(10) An additive for fuel oil comprising, as a main component, a disulfide compound through an ester of mercaptoalkanecarboxylic acid represented by at least one of general formula (V) and general formula (VI) The oxidative coupling of to obtain:

R ¹ OOC-A ³ -SH...(V)

wherein R ¹ represents a hydrocarbon group having 1 to 30 carbon atoms and may have an oxygen atom, a sulfur atom or a nitrogen atom, and A ³ represents a group represented by CR ⁵ R ⁶ -CR ⁷ R ⁸ , R ⁵ to R ⁸ each independently represents a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms, and

R ² OOC-A ⁴ -SH...(VI)

wherein R ² represents a hydrocarbon group having 1 to 30 carbon atoms and may have an oxygen atom, a sulfur atom or a nitrogen atom; and A ⁴ represents a group represented by CR ⁵ R ⁶ -CR ⁷ R ⁸ , R ⁵ to R ⁸ Each independently represents a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms;

(11) The additive for fuel oil described in the above item (7), wherein the content of the polysulfide compound represented by the general formula (I) in which x represents a value of 3 or more is 30% by mass or 30% Mass below, based on the sum of the amount of disulfide compounds and the amount of polysulfide compounds;

(12) The additive for fuel oil described in the above item (9), wherein the content of the polysulfide compound represented by the general formula (IV) in which x represents a value of 3 or more is 30% by mass or 30% Mass below, based on the sum of the amount of disulfide compounds and the amount of polysulfide compounds;

(13) A lubricating oil composition comprising component (A): a base oil for lubricating oil; and component (B): the lubricating oil described in any one of the above items (1) to (6). additives;

(14) The lubricating oil composition described in the above item (13), wherein the content of component (B) is in the range of 0.01 to 50% by mass;

(15) A fuel oil composition comprising component (X): fuel oil, and component (Y): the additive for fuel oil described in any one of the above items (7) to (12); and

(16) The fuel oil composition described in the above item (15), wherein the content of component (Y) is in the range of 0.01 to 1,000 ppm by mass.

The most preferred embodiment for carrying out the invention

The compound of the present invention represented by the general formula (I) used as an additive for lubricating oil and fuel oil is a disulfide compound having the following structure:

R ¹ OOC-A ¹ -S _x -A ² -COOR ² ...(I)

In the above general formula (I), R ¹ and R ² each independently represent 1 to 30 carbon atoms, preferably 1 to 20 carbon atoms, more preferably 2 to 18 carbon atoms and most preferably 2 to 18 carbon atoms Atoms of hydrocarbon groups. The hydrocarbon group may be linear, branched or cyclic and may have oxygen, sulfur or nitrogen atoms. R ¹ and R ² may represent the same group or different groups. From the viewpoint of preparation, it is preferred that R ¹ and R ² represent the same group.

A ¹ and A ² each independently represent a group represented by CR ³ R ⁴ . R ³ and R ⁴ each independently represent a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms. As the hydrocarbon group, a hydrocarbon group having 1 to 12 carbon atoms is preferable, and a hydrocarbon group having 1 to 8 carbon atoms is more preferable. Examples of the groups represented by ^A1 and ^A2 include methylene groups, ethylidene groups and propylidene groups. Among these groups, methylene is preferred. The atoms or groups represented by A ¹ and A ² may be the same as or different from each other. From the viewpoint of preparation, it is preferable that atoms and groups represented by R ¹ and R ² are the same as each other. x means 2.

In the additive for lubricating oil and fuel oil of the present invention, it is preferable that the content of the polysulfide compound represented by the general formula (I) in which x represents a value of 3 or more is 30% by mass or 30% by mass Below, based on the sum of the amount of the compound represented by the general formula (I) in which x represents 2 and the amount of the above polysulfide compound. When the above content is 30% or less, corrosion to non-ferrous metals can be sufficiently suppressed. More preferably, the content of the polysulfide compound represented by the general formula (I) in which x represents 3 or more is 10% by mass or less and still more preferably 5% by mass or less.

Therefore, it is important that in the production of the disulfide compound represented by the general formula (I), a method can be used which can obtain as a by-product the disulfide compound represented by the general formula (I), wherein x represents 3 or 3 A polysulfide compound represented by the above general formula (I). In the present invention, it is preferred to produce disulfide compounds, for example according to the method given below.

The oxidative coupling is carried out by using esters of mercaptoalkanecarboxylic acids represented by general formula (II) and/or general formula (III) as raw materials:

R ¹ OOC-A ¹ -SH...(II)

R ² OOC-A ² -SH...(III)

wherein R ¹ , R ² , A ¹ and A ² are as defined above. When the above process is carried out, the formation of polysulfide compounds, ie, trisulfides and higher sulfides, as by-products is substantially absent.

Specifically, R ¹ OOC-A ¹ -S ₂ -A ² -COOR ² , R ¹ OOC-A ¹ -S 2 -A ₁ ^{-COOR 1} and R ² OOC-A ² -S ₂ -A ² - Compounds represented by COOR ² .

Examples of the oxidizing agent include oxygen, hydrogen peroxide, halogens such as iodine and bromine, hypohalous acids, hypohalites, sulfoxides such as dimethylsulfoxide and diisopropylsulfoxide and manganese(IV) oxide. Among these oxidizing agents, oxygen, hydrogen peroxide and dimethyl sulfoxide are preferred because of low cost and easy production of disulfides.

Examples of the disulfide compound represented by the general formula (I) include bis(methoxycarbonylmethyl)disulfide, bis(ethoxycarbonylmethyl)disulfide, bis(n-propoxycarbonylmethyl) ) disulfide, bis(isopropoxycarbonylmethyl) disulfide, bis(cyclopropoxy-carbonylmethyl) disulfide, 1,1-bis(1-methoxycarbonylethyl) disulfide Sulfide, 1,1-bis(1-methoxycarbonyl-n-propyl) disulfide, 1,1-bis(1-methoxy-carbonyl-n-butyl) disulfide, 1,1- Bis(1-methoxycarbonyl-n-hexyl) disulfide, 1,1-bis(1-methoxycarbonyl-n-octyl) disulfide, 2,2-bis(2-methoxycarbonyl- n-propyl) disulfide and α,α-bis(α-methoxycarbonylbenzyl) disulfide.

The compound represented by the general formula (IV) of the present invention used for lubricating oil and fuel oil is a disulfide compound having the following structure:

R ¹ OOC-A ³ -S _x -A ⁴ -COOR ² ...(IV)

In the above general formula (IV), R ¹ and R ² are the same as defined for R ¹ and R ² in the general formula (I). R ¹ and R ² may represent the same group or different groups. From the viewpoint of preparation, it is preferred that R ¹ and R ² represent the same group.

A ³ and A ⁴ each independently represent a group represented by CR ⁵ R ⁶ -CR ⁷ R ⁸ . R ⁵ to R ⁸ each independently represent a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms. As the hydrocarbon group, a hydrocarbon group having 1 to 12 carbon atoms is preferable, and a hydrocarbon group having 1 to 8 carbon atoms is more preferable. From the viewpoint of preparation, it is preferable that atoms and groups represented by R ¹ and R ² are the same as each other. x means 2.

In the additive for lubricating oil and fuel oil of the present invention, it is preferable that the content of the polysulfide compound represented by the general formula (IV) in which x represents a value of 3 or more is 30% by mass or 30% by mass Below, based on the sum of the amount of the compound represented by the general formula (IV) in which x represents 2 and the amount of the above polysulfide compound. When the above content is 30% or less, corrosion to non-ferrous metals can be sufficiently suppressed. More preferably, the content of the polysulfide compound represented by the general formula (IV) in which x represents 3 or more is 10% by mass or less and still more preferably 5% by mass or less.

Therefore, it is important that in the production of the disulfide compound represented by the general formula (IV), a method can be used which can obtain the compound represented by the general formula wherein x represents 3 or more in an amount within the above range (IV) The polysulfide compound represented. In the present invention, it is preferred to produce disulfide compounds, for example according to the method given below.

The oxidative coupling is carried out by using esters of mercaptoalkanecarboxylic acids represented by general formula (V) and/or general formula (VI) as raw materials:

R ¹ OOC-A ³ -SH...(V)

R ² OOC-A ⁴ -SH...(VI)

wherein R ¹ , R ² , A ³ and A ⁴ are as defined above. According to the above method, the formation of polysulfide compounds, ie, trisulfides and higher sulfides, as by-products is substantially absent.

Specifically, R ¹ OOC-A ³ -S ₂ -A ⁴ -COOR ² , R ¹ OOC-A ³ -S ₂ -A ³ -COOR ¹ and R ² OOC-A ⁴ -S ₂ -A A compound represented by ⁴ -COOR ² .

As the oxidizing agent used in the oxidation of the ester of α-mercaptocarboxylic acid to produce the corresponding disulfide, an oxidizing agent used in the process of producing disulfide from mercaptan can be used. Examples of the oxidizing agent include oxygen, hydrogen peroxide, halogens such as iodine and bromine, hypohalous acids, hypohalites, sulfoxides such as dimethylsulfoxide and diisopropylsulfoxide and manganese(IV) oxide. Among these oxidizing agents, oxygen, hydrogen peroxide and dimethyl sulfoxide are preferred because of low cost and easy production of disulfides.

Examples of the disulfide compound represented by the above general formula (IV) include 1,1-bis(2-methoxycarbonylethyl)disulfide, 1,1-bis(2-ethoxycarbonylethyl) Disulfide, 1,1-bis(2-n-propoxycarbonylethyl)disulfide, 1,1-bis(2-isopropoxycarbonylethyl)disulfide, 1,1-bis( 2-cyclopropoxycarbonylethyl) disulfide, 1,1-bis(2-methoxycarbonyl-n-propyl)disulfide, 1,1-bis(2-methoxycarbonyl-n-butyl base) disulfide, 1,1-bis(2-methoxycarbonyl-n-hexyl) disulfide, 1,1-bis(2-methoxycarbonyl-n-propyl) disulfide, 2,2 - bis(3-methoxycarbonyl-n-pentyl) disulfide and 1,1-bis(2-methoxycarbonyl-1-phenylethyl) disulfide.

These disulfide compounds exhibit excellent load carrying capacity and wear resistance when they are used as the sulfur type extreme pressure additive and as additives for lubricating oils and fuel oils.

The additives for lubricating oils and fuel oils used in the present invention may include, alone or as a combination of two or more, the above-mentioned disulfide compounds represented by the general formula (I) and/or the above-mentioned disulfide compounds represented by the general formula (IV) Represents the above disulfide compound.

The lubricating oil composition of the present invention comprises component (A): a base oil for lubricating oil and component (B): an additive for lubricating oil including the above disulfide compound. The lubricating oil composition in the present invention includes automotive lubricating oils for driving devices and instruments and gears such as built-in engines, automatic transmission systems, shock absorbers and power steering devices, and for metal processing such as cutting, grinding and deformation treatment Metalworking oil, as well as hydraulic oil, is also a type of power transmission fluid used in hydraulic systems such as hydraulic devices and instruments for power transmission, power control and shock absorption.

In the lubricating oil composition of the present invention, the base oil for lubricating oil used as component (A) is not particularly limited, and is suitably selected from mineral oils and synthetic oils according to the purpose and conditions of use of the composition . Examples of mineral oils include distillates obtained by atmospheric distillation of paraffin-based crude oils, intermediate-based crude oils, and naphthenic crude oils, distillates obtained by vacuum distillation of residues of atmospheric distillation, and distillates obtained by ordinary methods. Refined oils obtained by refining these oils, such as solvent-refined oils, hydrogen-refined oils, oils treated by dewaxing, and clay-treated oils.

Examples of synthetic oils include low-molecular-weight polybutene, low-molecular-weight polypropylene, oligomers of α-olefins having 8 to 14 carbon atoms, hydrogenated products of these oligomers, ester-type compounds such as polyol esters (such as fatty acid esters with trimethylpropane and esters of fatty acids with pentaerythritol), esters of dibasic acids, esters of aromatic polycarboxylic acids and esters of phosphoric acid, alkylaromatics such as alkylbenzenes and alkylnaphthalenes, polyglycols Oils such as poly(alkylene) glycols, and silicone oils.

The base oil may be used alone or as a combination of two or more.

The content of the lubricating oil additive of component (B) in the lubricating oil composition of the present invention can be appropriately selected depending on the purpose and conditions of use of the composition. Generally, the content is in the range of 0.01-50% by mass. For lubricating oils and hydraulic oils for automobiles, the content is generally selected within the range of 0.01-30% by mass and preferably within the range of 0.01-10% by mass. For metalworking oils, the content is generally selected within the range of 0.1-60% by mass and preferably within the range of 0.1-50% by mass, although the additive can be used alone without being mixed with other components.

The lubricating oil compositions of the present invention suitably include various other additives such as other friction modifiers (oil additives and other extreme pressure additives), antiwear agents, ashless dispersants, metal based detergents, viscosity index improvers, pouring Point reducers, rust inhibitors, metal corrosion inhibitors, defoamers, surfactants and antioxidants, depending on the purpose of use.

Examples of other friction modifiers and antiwear agents include sulfur type compounds such as olefin sulfides, dialkyl polysulfides, diarylalkyl polysulfides and diaryl polysulfides; phosphorus type compounds such as esters of phosphoric acid , esters of phosphorothioate, esters of phosphorous acid, alkyl hydrogen phosphite, amine salts of esters of phosphoric acid and amine salts of esters of phosphorous acid; chlorine type compounds such as chlorinated esters of fatty acids and chlorinated fatty acids; ester type Compounds such as esters of alkyl maleic acid and alkenyl maleic acid and esters of alkyl succinic acid and alkenyl succinic acid; organic acid type compounds such as alkyl maleic acid, alkenyl maleic acid, alkyl and alkenyl succinic acids; and organometallic compounds such as salts of naphthenic acids, zinc dithiophosphate (ZnDTP), zinc dithiocarbamate (ZnDTC), organomolybdenum dithiophosphate sulfide (MoDTP) and oxymolybdenum sulfide dithiocarbamate (MoDTC).

Examples of ashless dispersants include succinimide, boron-containing succinimide, benzylamine, boron-containing benzylamine, esters of succinic acid and mono- and dicarboxylic acids (typical examples of which include fatty acids and succinic acid) amides. Examples of metal type detergents include neutral metal sulfonic acid salt, neutral metal phenate, neutral metal salicylate, neutral metal phosphonate, basic sulfonate, basic phenate, basic salicylic acid salts, basic phosphonates, overbased sulfonates, overbased phenates, overbased salicylates and overbased phosphonates.

Examples of viscosity index improvers include polymethacrylates, dispersion type polymethacrylates and olefin type copolymers such as ethylene-propylene copolymers. Examples of pour point depressants include polymethacrylates.

Examples of rust inhibitors include alkenyl succinic acid and partial esters thereof. Examples of corrosion inhibitors for metals include benzotriazole-type agents, benzimidazole-type agents, benzothiazole-type agents and thiadiazole-type agents. Examples of antifoaming agents include dimethyl polysiloxane and polyacrylates. Examples of surfactants include polyoxyethylene alkylphenyl ethers.

Examples of antioxidants include amine-type antioxidants such as alkylated diphenylamines, phenyl-α-naphthylamines, and alkylated naphthylamines; and phenolic antioxidants such as 2,6-di-tert-butyl-cresol and 4 , 4'-methylenebis(2,6-di-tert-butylphenol).

The lubricating oil composition of the present invention is used as an automotive lubricating oil for driving devices and instruments and gears such as built-in engines, automatic transmission systems, shock absorbers and power steering devices, and for metal processing such as cutting, grinding and deformation treatment Metal processing oil, as well as hydraulic oil, is also a type of power transmission fluid used in hydraulic systems such as hydraulic devices and instruments for power transmission, power control and shock absorption.

The fuel oil composition of the present invention comprises component (X): fuel oil and component (Y): an additive for fuel oil including the above disulfide compound.

In the fuel oil composition of the present invention, fuel oil highly refined by hydrogenation such as high-efficiency fuel oil for turbines is preferably used as the fuel oil of component (X).

The content of the fuel oil additive of component (Y) in the fuel oil composition of the present invention is generally in the range of 0.01 to 1,000 ppm by mass and preferably in the range of 0.01 to 100 ppm by mass.

The fuel oil composition of the present invention may further include various types of additives, if necessary. Examples of additives include general additives for fuel oil, examples of which include antioxidants such as phenylenediamine type antioxidants, diphenylamine type antioxidants, alkylphenol type antioxidants and aminophenol type antioxidants; detergents such as polyetheramine and polyalkylamines; metal deactivators such as Schiff-type compounds and sulfamide-type compounds; agents to prevent surface ignition such as organophosphorus-type compounds; agents to prevent freezing such as polyols; combustion enhancers such as higher alcohol sulfates; antistatic surfactants such as anionic surfactants, cationic surfactants and amphoteric surfactants; rust inhibitors such as alkenyl succinate esters; identification agents such as quinizarin and coumarin; fragrance agents such as natural extracts and synthetic fragrances; and Colorants such as azo dyes.

Example

The present invention is more specifically described with reference to the following examples. However, the present invention is not limited to these Examples.

The coefficient of friction, diameter of wear marks and corrosion were evaluated according to the following methods.

(1) Friction coefficient and diameter of wear marks

A four-ball test of the Soda type was performed under the following conditions.

The test was carried out at a rotation speed of 500 rpm and an oil temperature of 80°C while the load was gradually increased. The loads in these steps were 0.5, 0.7, 0.9, 1.1, 1.3 and 1.5 kgf/cm ² (×0.09807 MPa), respectively. The load was maintained for 180 seconds in each step, and the total time of the test was 1,080 seconds. The coefficient of friction is obtained at each step and the diameter of the wear scar is measured at the end of the test.

(2) Corrosive

The corrosion test is based on the Japanese Industrial Standard K-2513 method "Test method for copper plate corrosion by petroleum products", and the test time is 3 hours by the test tube method at a test temperature of 100°C. The change in color of the copper plate was observed according to the "Corrosion Standard for Copper Plates" and the corrosivity was evaluated according to the grading from 1a to 4c. The smaller the number, the less corrosive. Corrosivity increases in alphabetical order.

Preparation Example 1 Preparation of two (ethoxycarbonylmethyl) disulfides

Ethyl thioglycolate was oxidized with dimethylsulfoxide according to the following method and bis(ethoxycarbonylmethyl)disulfide was prepared. Trisulfides and higher sulfide polysulfides are absent in the obtained compounds.

20.9 g of methyl thioglycolate and 30.8 g of dimethyl sulfoxide were added to a 100 ml eggplant-shaped flask, and the resulting mixture was heated in an oil bath at 120° C. for 8 hours. After cooling, the obtained reaction mixture was dissolved in 100 ml of toluene and washed with water ten times to remove unreacted dimethyl sulfoxide. Toluene was distilled off under reduced pressure to obtain 16.0 g of bis(ethoxycarbonylmethyl)disulfide.

Preparation Example 2 Preparation of two (n-butoxycarbonylmethyl) disulfides

Oxidation was carried out according to the same procedure as carried out in Preparation 1, except that n-butyl thioglycolate was used to prepare bis(n-butoxycarbonylmethyl)disulfide. Trisulfides and higher sulfide polysulfides are absent in the obtained compounds.

Preparation Example 3 Preparation of two (n-octyloxycarbonylmethyl) disulfides

Oxidation was carried out according to the same procedure as carried out in Preparation 1, except that n-octyl thioglycolate was used to prepare bis(n-octyloxycarbonylmethyl)disulfide. Trisulfides and higher sulfide polysulfides are absent in the obtained compounds.

Preparation Example 4 Preparation of two (2-ethylhexyloxycarbonylmethyl) disulfide

Oxidation was carried out according to the same procedure as carried out in Preparation 1, except that 2-ethylhexyl thioglycolate was used to prepare bis(2-ethylhexyloxycarbonylmethyl)disulfide. Trisulfides and higher sulfide polysulfides are absent in the obtained compounds.

Preparation Example 5 Preparation of two (isooctyloxycarbonylmethyl) disulfides

Oxidation was carried out according to the same procedure as carried out in Preparation 1, except that isooctyl thioglycolate was used to prepare bis(isooctyloxycarbonylmethyl)disulfide. Trisulfides and higher sulfide polysulfides are absent in the obtained compounds.

Preparation Example 6 Preparation of two (n-stearyloxycarbonylmethyl) disulfides

Oxidation was carried out according to the same procedure as carried out in Preparation 1, except that stearyl thioglycolate was used to prepare bis(n-stearyloxycarbonylmethyl)disulfide. Trisulfides and higher sulfide polysulfides are absent in the obtained compounds.

Preparation Example 7 1, the preparation of 1-bis(1-ethoxycarbonylethyl) disulfide

Oxidation was carried out according to the same procedure as carried out in Preparation Example 1, except that ethyl α-mercaptopropionate was used to prepare 1,1-bis(1-ethoxycarbonylethyl)disulfide. Trisulfides and higher sulfide polysulfides are absent in the obtained compounds.

Comparative Preparation Example 1 The preparation of two (n-butoxycarbonylmethyl) polysulfides

Sodium polysulfide is prepared from sodium sulfide and sulfur, and bis(n-butoxycarbonylmethyl)polysulfide is prepared by reacting the obtained sodium polysulfide with n-butyl chloroacetate. In this preparation, the ratio of the molar amounts of sodium sulfide to sulfur is adjusted so as to be able to obtain sodium polysulfide (Na ₂ S _x ) having an average number (x) of sulfur of 2, in contrast to the disulfides of the invention. Sodium polysulfide was used in excess of 5%, so that no n-butyl chloroacetate remained. Specifically, bis(n-butoxycarbonylmethyl)polysulfide was prepared by the reaction according to the following method. In a 500ml four-neck glass flask equipped with a stirrer and a reflux condenser, add 26.4g of sodium sulfide nonahydrate, 3.52g of sulfur and 150ml of 95% ethanol, and the resulting mixture is heated at 80°C under stirring. Heated in the bath for 5 hours. After the reaction mixture had cooled to room temperature, 30.12 g of n-butyl chloroacetate were added in small portions and the resulting mixture was stirred at room temperature for 2 hours. The reaction fluid was transferred to a separatory funnel, dissolved in 500 ml of toluene and washed ten times with water. Toluene was distilled off under reduced pressure to obtain 26.5 g of bis(n-butoxycarbonylmethyl)polysulfide.

The obtained compound was analyzed according to high performance liquid chromatography [column: ODS; solvent: acetonitrile; detector: refractive index (RI) detector]. The results were as follows: monosulfide: 21%; disulfide: 40%; trisulfide: 20%; tetrasulfide: 12%; and pentasulfide: 4%. The values are expressed in % by mass.

Comparative Preparation Example 2 Preparation of two (2-ethylhexyloxy-carbonylmethyl) sulfides

Add 45.1 g of 2,2'-thioglycolic acid, 101.6 g of 2-ethylhexanol and 2.0 g of p-toluenesulfonic acid monohydrate to a 500 ml eggplant-shaped glass flask equipped with a Dean Stark trap, The resulting mixture was heated at reflux for 5 hours. After cooling, the reaction fluid was transferred to a separatory funnel and washed twice with an aqueous solution of sodium bicarbonate and five times with water. Toluene was distilled off under reduced pressure to obtain 120.0 g of bis(2-ethylhexyloxycarbonylmethyl)sulfide.

Example 1

To 500 neutral fraction mineral oil P500N (kinematic viscosity at 100°C: 10.9 mm ² /s; % CAO: 0.1% or less) was added bis(ethoxycarbonyl) obtained in Preparation Example 1 Methyl)disulfide was added in an amount such that the content in the entire composition was 1% by mass, and a lubricating oil composition was prepared. The properties of the lubricating oil compositions obtained were evaluated. The results are shown in Table 1.

Examples 2 to 7

To the mineral oil P500N of 500 neutral fractions, the additive obtained in Preparation Example 2-7 was added so that the content in the whole composition was 1% by mass as shown in Table 1, and a lubricating oil composition was prepared . The properties of the lubricating oil compositions obtained were evaluated. The results are shown in Table 1.

Comparative Example 1

The same procedure as in Example 1 was performed except that the bis(2-ethylhexyloxycarbonylmethyl)sulfide obtained in Comparative Preparation Example 1 was used. The results are shown in Table 1.

Comparative Example 2

The same procedure as in Example 1 was carried out except that the bis(n-butoxycarbonylmethylene)polysulfide obtained in Comparative Preparation Example 2 was used. The results are shown in Table 1.

Comparative Example 3

The 500 neutral fraction mineral oil P500N was evaluated without additives according to the same procedure as carried out in Example 1 . The results are shown in Table 1.

Table 1-1

Table 1-2

Preparation Example 8 1, the preparation of 1-bis(2-ethoxycarbonylethyl) disulfide

Ethyl α-mercaptopropionate was oxidized with dimethylsulfoxide according to the following procedure, and 1,1-bis(2-ethoxycarbonylethyl)disulfide was prepared. Trisulfides and higher sulfide polysulfides are absent in the obtained compounds.

20.9 g of ethyl α-mercaptopropionate and 30.8 g of dimethyl sulfoxide were added to a 100 ml eggplant-shaped flask, and the resulting mixture was heated in an oil bath at 120° C. for 8 hours. After cooling, the obtained reaction mixture was dissolved in 100 ml of toluene and washed with water ten times to remove unreacted dimethyl sulfoxide. Toluene was distilled off under reduced pressure to obtain 16.0 g of 1,1-bis(2-ethoxycarbonylethyl)disulfide.

Preparation Example 9 Preparation of 1,1-bis(2,2-ethylhexyloxycarbonyl-ethyl) disulfide

2-Ethylhexyl thioglycolate was oxidized according to the same procedure as in Preparation Example 1 to prepare 1,1-bis(2,2-ethylhexyloxycarbonylethyl)disulfide. Trisulfides and higher sulfide polysulfides are absent in the obtained compounds.

Example 8

The ^1,1 -bis( 2-Ethoxycarbonylethyl) disulfide was added in such an amount that the content in the entire composition was 1% by mass, and a lubricating oil composition was prepared. The properties of the lubricating oil compositions obtained were evaluated. The results are shown in Table 2.

Example 9

The same procedure as in Example 8 was carried out except that the 1,1-bis(2,2-ethylhexyloxycarbonylethyl)disulfide obtained in Preparation Example 8 was used. The results are shown in Table 2.

Table 2

As is clear from the results in Examples and Comparative Examples, the lubricating oil composition using the additive of the present invention obtained wear marks with a small diameter and exhibited very excellent load carrying capacity and wear resistance. As shown in Comparative Example 1, when a lubricating oil composition having a larger content of the polysulfide compound represented by the general formula (I) or (IV) in which x is 3 or more is used, the effect on Corrosiveness of non-ferrous metals. In contrast, the lubricating oil composition of the present invention exhibits very excellent performance with regard to suppressed corrosion.

Industrial Applicability

According to the present invention, it is possible to provide a sulfur type extreme pressure additive which exhibits load carrying capacity and wear resistance which are superior to those exhibited by ordinary sulfur type additives and which is low in corrosion to non-ferrous metals, and It can be used in lubricating oil and fuel oil, and provides lubricating oil composition and fuel oil composition including the additive.

Claims (12)

1. An additive for lubricating oil, which comprises, as a main component, a disulfide compound represented by the general formula (I): R ¹ OOC-A ¹ -S _x -A ² -COOR ² ...(I) wherein R ¹ and R ² each independently represent a hydrocarbon group having 1 to 30 carbon atoms, A ¹ and A ² each independently represent a group represented by CR ³ R ⁴ , R ³ and R ⁴ each independently represent hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms, and x represents 2; The condition is that the content of the polysulfide compound represented by the general formula (I) in which x represents a value of 3 or more is 30% by mass or less, based on the amount of the disulfide compound and the polysulfide compound The sum of the quantities. 2. An additive for lubricating oils comprising, as a main component, a disulfide compound obtained by the synthesis of an ester of mercaptoalkanecarboxylic acid represented by at least one of general formula (II) and general formula (III) Oxidative coupling to obtain: R ¹ OOC-A ¹ -SH ...(II) wherein R ¹ represents a hydrocarbon group having 1 to 30 carbon atoms, and A ¹ represents a group represented by CR ³ R ⁴ , and R ³ and R ⁴ each independently represent a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms group, and R ² OOC-A ² -SH ...(III) wherein R ² represents a hydrocarbon group having 1 to 30 carbon atoms; and A ² represents a group represented by CR ³ R ⁴ , and R ³ and R ⁴ each independently represent a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms group; The condition is that the content of the polysulfide compound represented by the general formula (I) in which x represents a value of 3 or more is 30% by mass or less, based on the amount of the disulfide compound and the polysulfide compound The sum of the amount of R ¹ OOC-A ¹ -S _x -A ² -COOR ² ... (I). 3. An additive for lubricating oils comprising, as a main component, a disulfide compound represented by the general formula (IV): R ¹ OOC-A ³ -S _x -A ⁴ -COOR ² ...(IV) wherein R ¹ and R ² each independently represent a hydrocarbon group having 1 to 30 carbon atoms, A ³ and A ⁴ each independently represent a group represented by CR ⁵ R ⁶ -CR ⁷ R ⁸ , R ⁵ to R ⁸ each independently represents a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms, and x represents 2; The condition is that the content of the polysulfide compound represented by the general formula (IV) in which x represents a value of 3 or more is 30% by mass or less, based on the amount of the disulfide compound and the polysulfide compound The sum of the quantities. 4. An additive for lubricating oils comprising, as a main component, a disulfide compound obtained by the synthesis of an ester of a mercaptoalkanecarboxylic acid represented by at least one of the general formula (V) and the general formula (VI). Oxidative coupling to obtain: R ¹ OOC-A ³ -SH ...(V) wherein R ¹ represents a hydrocarbon group having 1 to 30 carbon atoms, and A ³ represents a group represented by CR ⁵ R ⁶ -CR ⁷ R ⁸ , and R ⁵ to R ⁸ each independently represent a hydrogen atom or have 1 to 20 hydrocarbon groups of carbon atoms, and R ² OOC-A ⁴ -SH ...(VI) wherein R ² represents a hydrocarbon group having 1 to 30 carbon atoms; and A ⁴ represents a group represented by CR ⁵ R ⁶ -CR ⁷ R ⁸ , and R ⁵ to R ⁸ each independently represent a hydrogen atom or have 1 to 20 a hydrocarbon group of carbon atoms; The condition is that the content of the polysulfide compound represented by the general formula (IV) in which x represents a value of 3 or more is 30% by mass or less, based on the amount of the disulfide compound and the polysulfide compound The sum of the amount of R ¹ OOC-A ³ -S _x -A ⁴ -COOR ² ... (IV). 5. An additive for fuel oil comprising, as a main component, a disulfide compound represented by the general formula (I): R ¹ OOC-A ¹ -S _x -A ² -COOR ² ...(I) wherein R ¹ and R ² each independently represent a hydrocarbon group having 1 to 30 carbon atoms, A ¹ and A ² each independently represent a group represented by CR ³ R ⁴ , R ³ and R ⁴ each independently represent hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms, and x represents 2; The condition is that the content of the polysulfide compound represented by the general formula (I) in which x represents a value of 3 or more is 30% by mass or less, based on the amount of the disulfide compound and the polysulfide compound The sum of the quantities. 6. An additive for fuel oil comprising, as a main component, a disulfide compound obtained by the synthesis of an ester of mercaptoalkanecarboxylic acid represented by at least one of general formula (II) and general formula (III) Oxidative coupling to obtain: R ¹ OOC-A ¹ -SH...(II) wherein R ¹ represents a hydrocarbon group having 1 to 30 carbon atoms, and A ¹ represents a group represented by CR ³ R ⁴ , and R ³ and R ⁴ each independently represent a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms group, and R ² OOC-A ² -SH ...(III) wherein R ² represents a hydrocarbon group having 1 to 30 carbon atoms; and A ² represents a group represented by CR ³ R ⁴ , and R ³ and R ⁴ each independently represent a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms group; The condition is that the content of the polysulfide compound represented by the general formula (I) in which x represents a value of 3 or more is 30% by mass or less, based on the amount of the disulfide compound and the polysulfide compound the sum of the quantities; R ¹ OOC-A ¹ -S _x -A ² -COOR ² ... (I). 7. An additive for fuel oil comprising, as a main component, a disulfide compound represented by the general formula (IV): R ¹ OOC-A ³ -S _x -A ⁴ -COOR ² ...(IV) wherein R ¹ and R ² each independently represent a hydrocarbon group having 1 to 30 carbon atoms, A ³ and A ⁴ each independently represent a group represented by CR ⁵ R ⁶ -CR ⁷ R ⁸ , R ⁵ to R ⁸ each independently represents a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms, and x represents 2; The condition is that the content of the polysulfide compound represented by the general formula (IV) in which x represents a value of 3 or more is 30% by mass or less, based on the amount of the disulfide compound and the polysulfide compound The sum of the quantities. 8. An additive for fuel oil comprising, as a main component, a disulfide compound obtained by the synthesis of an ester of mercaptoalkanecarboxylic acid represented by at least one of general formula (V) and general formula (VI). Oxidative coupling to obtain: R ¹ OOC-A ³ -SH ...(V) wherein R ¹ represents a hydrocarbon group having 1 to 30 carbon atoms, and A ³ represents a group represented by CR ⁵ R ⁶ -CR ⁷ R ⁸ , and R ⁵ to R ⁸ each independently represent a hydrogen atom or have 1 to 20 hydrocarbon groups of carbon atoms, and R ² OOC-A ⁴ -SH ...(VI) wherein R ² represents a hydrocarbon group having 1 to 30 carbon atoms; and A ⁴ represents a group represented by CR ⁵ R ⁶ -CR ⁷ R ⁸ , and R ⁵ to R ⁸ each independently represent a hydrogen atom or have 1 to 20 a hydrocarbon group of carbon atoms; The condition is that the content of the polysulfide compound represented by the general formula (IV) in which x represents a value of 3 or more is 30% by mass or less, based on the amount of the disulfide compound and the polysulfide compound The sum of the amount of R ¹ OOC-A ³ -S _x -A ⁴ -COOR ² ... (IV). 9. A lubricating oil composition comprising component (A): a base oil for lubricating oil; and component (B): the additive for lubricating oil described in any one of claims 1 to 4. 10. The lubricating oil composition according to claim 9, wherein the content of component (B) is in the range of 0.01 to 50% by mass. 11. A fuel oil composition comprising component (X): fuel oil, and component (Y): the additive for fuel oil described in any one of claims 5 to 8. 12. The fuel oil composition according to claim 11, wherein the content of component (Y) is in the range of 0.01 to 1,000 ppm by mass.