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

An additive for lubricating oils which comprises as a main component a disulfide compound which is obtained by oxidative coupling of an ester of a mercaptoalkanecarboxylic acid represented by at least one of general formula (II):

• R1OOC-A1-SH (II)
• wherein R1 represents a hydrocarbyl group which has 1 to 30 carbon atoms and may have oxygen atom, sulfur atom or nitrogen atom, and A1 represents a group represented by CR3R4, R3 and R4 each independently representing hydrogen atom or a hydrocarbyl group having 1 to 20 carbon atoms, and
• general formula (III):
• R2OOC-A2-SH (III)
• wherein R2 represents a hydrocarbyl group which has 1 to 30 carbon atoms and may have oxygen atom, sulfur atom or nitrogen atom, and A2 represent a group represented by CR3R4, R3 and R4 each independently representing hydrogen atom or a hydrocarbyl group having 1 to 20 carbon atoms.

An additive for lubricating oils which comprises as a main component a disulfide compound which is obtained by oxidative coupling of an ester of a mercaptoalkanecarboxylic acid represented by at least one of general formula (V):

• R1OOC-A3-SH (V)
• wherein R1 represents a hydrocarbyl group which has 1 to 30 carbon atoms and may have oxygen atom, sulfur atom or nitrogen atom, and A3 represents 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
• general formula (VI):
• R2OOC-A4-SH (VI)
• wherein R2 represents a hydrocarbyl group which has 1 to 30 carbon atoms and may have oxygen atom, sulfur atom or nitrogen atom, and A4 represents a group represented by CR5R6—CR7R8, R5 to R8 each independently representing hydrogen atom or a hydrocarbyl group having 1 to 20 carbon atoms.

An additive for fuel oils which comprises as a main component a disulfide compound which is obtained by oxidative coupling of an ester of a mercaptoalkanecarboxylic acid represented by at least one of general formula (II):

• R1OOC-A1-SH (II)
• wherein R1 represents a hydrocarbyl group which has 1 to 30 carbon atoms and may have oxygen atom, sulfur atom or nitrogen atom, and A1 represents a group represented by CR3R4, R3 and R4 each independently representing hydrogen atom or a hydrocarbyl group having 1 to 20 carbon atoms, and
• general formula (III):
• R2OOC-A2-SH (III)
• wherein R2 represents a hydrocarbyl group which has 1 to 30 carbon atoms and may have oxygen atom, sulfur atom or nitrogen atom, and A2 represent a group represented by CR3R4, R3 and R4 each independently representing hydrogen atom or a hydrocarbyl group having 1 to 20 carbon atoms.

An additive for fuel oils which comprises as a main component a disulfide compound which is obtained by oxidative coupling of an ester of a mercaptoalkanecarboxylic acid represented by at least one of general formula (V):

• R1OOC-A3-SH (V)
• wherein R1 represents a hydrocarbyl group which has 1 to 30 carbon atoms and may have oxygen atom, sulfur atom or nitrogen atom, and A3 represents 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
• general formula (VI):
• R2OOC-A4-SH (VI)
• wherein R2 represents a hydrocarbyl group which has 1 to 30 carbon atoms and may have oxygen atom, sulfur atom or nitrogen atom, and A4 represents a group represented by CR5R6—CR7R8, R5 to R8 each independently representing hydrogen atom or a hydrocarbyl group having 1 to 20 carbon atoms.