Additives for lubricating oils and fuel oils, lubricating oil compositions, and fuel oil compositions

Abstract

Additives for lubricating oils and for fuel oils which comprise as the main component a disulfide represented by the following general formula (I) or (IV): R1OOC-A1-Sx-A2-COOR2  (I) (R1 and R2 each independently represent a hydrocarbyl group which has 1 to 30 carbon atoms and may have oxygen atom, sulfur atom or nitrogen atom, A1 and A2 each independently represent a group represented by CR3R4, R3 and R4 each independently representing hydrogen atom or a hydrocarbyl group having 1 to 20 carbon atoms, and x represents 2.) R1OOC-A3-Sx-A4-COOR2  (IV) (R1 and R2 are as defined above, A3 and A4 each independently represent a group represented by CR5R6—CR7R8, R5 to R8 each independently representing hydrogen atom or a hydrocarbyl group having 1 to 20 carbon atoms, and x represents 2.) The additives exhibit excellent functions as the extreme pressure additive and the antiwear agent and the suppressed corrosive property to nonferrous metals and are advantageously used as the sulfur-based extreme pressure additives for lubricating oils and fuel oils.

Description

TECHNICAL FIELD [0001] 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 comprise a disulfide compound having a specific structure as the main component and exhibit excellent functions as the friction modifier, in particular, as the extreme pressure additive and the antiwear agent, and lubricating oil compositions and fuel compositions each comprising the additive. BACKGROUND ART [0002] Heretofore, lubricating oils are used for apparatuses and instruments used for driving and apparatuses such as internal combustion engines, automatic transmissions, shock absorbers and power steerings to achieve smooth working of the apparatuses and instruments. It is well known that the lubricated surface is worn by friction under conditions of great output powers and great loads since the lubricating property beco...

AI Technical Summary

Benefits of technology

[0015] Under the above circumstances, the present invention has an object of providing a sulfur-based extreme pressure additive which exhibits more excellent load carrying capacity and wear resistance than those exhibited by conventional sulfur-based additives and the suppressed corrosive property to nonferrous metals and can be used for lubricating oils and fuel oils, and a lubricating oil composition and a fuel oil composition comprising the additive.

[0025] Examples of the oxidizing agent include oxygen, hydrogen peroxide, halogens such as iodine and bromine, hypohalous acids, hypohalites, sulfoxides such as dimethyl sulfoxide and diisopropyl sulfoxide and manganese (IV) oxide. Among these oxidizing agents, oxygen, hydrogen peroxide and dimethyl sulfoxide are preferable since the price is low and the production of the disulfide is facilitated.

[0034] As the oxidizing agent used for oxidation of an ester of an α-mercaptocarboxylic acid to produce the corresponding disulfide, oxidizing agent used in the production of a disulfide from a 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 dimethyl sulfoxide and diisopropyl sulfoxide and manganese (IV) oxide. Among these oxidizing agents, oxygen, hydrogen peroxide and dimethyl sulfoxide are preferable since the price is low and the production of the disulfide is facilitated.

[0036] These disulfide compounds exhibit excellent load carrying capacity and wear resistance when they are used as the sulfur-based extreme pressure additive and are used as the additives for lubricating oils and fuel oils.

Problems solved by technology

It is well known that the lubricated surface is worn by friction under conditions of great output powers and great loads since the lubricating property becomes insufficient, and seizure takes placed under extreme conditions.

However, conventional extreme pressure additives are not always satisfactory in that the sufficient effect of preventing the seizure is not exhibited due to interactions with other additives, metals are corroded, and wear resistance is insufficient.

However, in working in which friction takes place repeatedly under a relatively small load, the efficiency of the production is frequently adversely affected since corrosive wear of tools with the active sulfur proceeds and the period of time before exchange of the tool with a new tool or grinding of the tool to refresh its surface decreases.

On the contrary, the efficiency of production is frequently decreased when the problem of the abnormal wear is absent in the metal working.

However, conventional extreme pressure additives are not always satisfactory due to insufficient wear resistance or occurrence of corrosive wear although a sufficient property of preventing the seizure under loads may be exhibited.

On the other hand, as for fuel oil, it is known that the lubricating property becomes insufficient as the fuel oil is hydrogenated to a greater degree.

It is pointed out that the wear of a fuel pump takes place more quickly when a highly refined fuel is used.

However, the above sulfur-based extreme pressure additives are not always satisfactory since these additives have problems in that metals are corroded, the effect of preventing seizure is not sufficiently exhibited due to interactions with other additives, and the wear resistance is insufficient.