Additive for Lubricating Oil and Fuel Oil, Lubricating Oil Composition, and Fuel Oil Composition

Abstract

An additive for lubricating oils and fuel oils comprising a disulfide compound, as the main component, represented by the general formula (I)

Description

EXAMPLES

The present invention will now be described in further detail by way of examples but should not be limited to these examples.

The friction coefficient wear scar width, and corrosiveness of the lubricating oil composition were determined by the following procedures:

(1) Friction Coefficient and Wear Scar Width

Soda's Four-Ball Testing was carried out under the following conditions:

A hydraulic pressure load was gradually increased for 1080 seconds while each load [0.5, 0.7 0.9, 1.1, 3, or 1.5 kgf/cm² (×0.09807 MPa)] was maintained for 180 seconds at a number of rotations of 500 rpm and an oil temperature of 80° C. The friction coefficient was determined for each load, and the wear scar width was measured after the testing was completed.

(2) Corrosiveness

According to JIS K-2513 “Petroleum Products—Corrosiveness to Copper—Copper Strip Test” at a testing temperature of 100° C. and a testing time of 3 hours and a test tube method, corrosiveness was measured. The tarnish of a copper strip was observed with reference to “Copper Strip Corrosion Standard”, and corrosiveness was evaluated as Subdivision Codes 1a to 4c. A smaller number in Subdivision Codes represents less corrosive and corrosiveness increases in alphabetical order.

Preparative Example 1

Production of tetra-1-octyl dithiomalate

Di-1-octyl thiomalate was oxidized with a dimethyl sulfoxide by the following procedure to produce tetra-1-octyl dithiomalate.

Into a 200 mL pear-shaped flask, 36.4 g of 1-octyl thiomalate and 39 g of dimethyl sulfoxide were placed the mixture was heated in an oil bath at 100° C. for 8 hours. Water and dimethyl sulfoxide were distilled out under reduced pressure. After cooling, the residue was dissolved in toluene, and was washed with an aqueous 5% sodium hydroxide solution and then with water. Toluene was distilled out under reduced pressure to recover 34.1 g of tetra-1-octyl dithiomalate.

Preparative Example 2

Production of tetra-1-(2-ethyl)hexyl dithiomalate

Tetra-1-(2-ethyl)hexyl dithiomalate was prepared as in Preparative Example 1 except that di-1-(2-ethyl)hexyl thiomalate was used instead of di-1-octyl thiomalate.

Preparative Example 3

Production of tetramethyl dithiomalate

Tetramethyl dithiomalate was prepared as in Preparative Example 1 except that distillation-purified dimethyl thiomalate was used instead of di-1-octyl thiomalate.

Preparative Example 4

Production of tetra-1-hexyl dithiomalate

Into a 200 mL pear-shaped flask, 30.0 g of tetramethyl dithiomalate which was prepared in Preparative Example 3, 69.2 g of 1-hexanol, and 1.2 g of p-toluenesulfonic acid monohydrate were placed and methanol was distilled out by spending 12 hours. After cooling, the residue was dissolved in toluene, and was washed with an aqueous 5% sodium hydroxide solution and then with water. Toluene and 1-hexanol were distilled out under reduced pressure to recover 108 g of tetra-1-hexyl dithiomalate.

Preparative Example 5

Production of tetra-1-(2-ethoxy)ethyl dithomalate

Tetra-1-(2-ethoxy)ethyl dithomalate was prepared as in Preparative Example 4 except that 2-ethoxyethanol was used instead of 1-butanol.

Preparative Example 6

Production of tetra-1-butyl dithiomalate

Into a 2 L four-necked flask with a stirring device, 200 g of thiomalic acid and 900 mL of water were added, and 61.0 g of 35% hydrogen peroxide solution was gradually added by spending 2 hours with stirring at a temperature of 25° C. to 35° C. The temperature was raised to 60° C. and the mixture was stirred for 1 hour. The solution was transferred to a 2 L pear-shaped flask and water was distilled out under reduced pressure. To the residue, 600 mL of toluene, 237 g of 1-butanol and 8 g of p-toluenesulfonic acid monohydrate were added. After a Dean-Stark trap was attached, the solution was heated and refluxed for 10 hours. After cooling, the product was washed with an aqueous 5% sodium hydroxide solution and then water. Toluene and 1-butanol were distilled out under reduced pressure to recover 317 g of tetra-t-butyl dithiomalate.

Preparative Example 7

Production of tetra-1-hexyl dithiomalate

Tetra-1-hexyl dithiomalate was prepared as in Preparative Example 6 except that 1-hexanol was used instead of 1-butanol

Preparative Example 8

Production of tetra-1-octyl dithiomalate

Tetra-1-octyl dithiomalate was prepared as in Preparative Example 6 except that 1-octanol was used instead of 1-butanol.

Example 1

Tetra-1-octyl dithiomalate produced in Preparative Example 1 was added to mineral oil of a 500 neutral fraction (P500N) such that the additive content in the composition was 1% by mass to prepare a lubricating oil composition The observed properties of the composition are shown in Table 1.

Examples 2 to 7

As shown in Table 1, the additives prepared in Preparative Examples 2 and 4 to 8 were each added mineral oil of a 500 neutral fraction (HG500) such that the additive content in the composition was 1% by mass to prepare lubricating oil compositions. The observed properties of the compositions are shown in Table 1.

Comparative Example 1

Mineral oil of a 500 neutral fraction (P500N) was evaluated as in Example 1 with addition of no additive. The results are shown in Table 1.

	TABLE 1
								Comparative
	Example 1	Example 2	Example 3	Example 4	Example 5	Example 6	Example 7	Example 1
Preparation of additive	Preparative	Preparative	Preparative	Preparative	Preparative	Preparative	Preparative	—
	Example 1	Example 2	Example 4	Example 5	Example 6	Example 7	Example 8
Friction	Load × 98.07	0.5	0.031	0.044	0.042	0.034	0.044	0.042	0.038	0.044
Coefficient	(kPa)	0.7	0.048	0.055	0.054	0.049	0.055	0.055	0.051	0.055
		0.9	0.053	0.064	0.059	0.054	0.063	0.061	0.059	0.064
		1.1	0.055	0.065	0.062	0.057	0.065	0.065	0.059	0.070
		1.3	0.057	0.069	0.063	0.058	0.066	0.067	0.060	0.072
		1.5	0.058	0.072	0.066	0.061	0.066	0.069	0.061	0.076
Wear scar width (mm)	0.41	0.47	0.41	0.36	0.36	0.42	0.42	0.52
Corrosiveness to copper strip	1b	1b	1b	1b	1b	1b	1b	1b

Examples and Comparative Example show that the lubricating oil compositions containing the additives of the present invention each has a low friction coefficient and a small wear scar width and thus high load-bearing capacity and wear resistance.

INDUSTRIAL APPLICABILITY

The additive for lubricating oils and fuel oils and the lubricating oil composition and fuel oil composition containing the additive of the present invention show superior load-bearing capacity and wear resistance and are useful in the fields of a variety of lubricating oils and fuel oils.

Claims

1. An additive for lubricating oils comprising a disulfide compound, as the main component, represented by the general formula (I). R1OOC—CR3R4—CR5(COOR2)—S—S—CR10(CCOR7)—CR8R9—COOR6  (I)

2. An additive for lubricating oils comprising a disulfide compound, as the main component, prepared by oxidative coupling of a mercaptoalkanedicarboxylic acid diester represented by the general formula (II) and/or general formula (III) R1OOC—CR3R4—CR5(COOR2)—SH  (II)

3. An additive for lubricating oils comprising a disulfide compound, as the main component, prepared by oxidative coupling of a mercaptoalkanedicarboxylic acid represented by the general formula (IV) and/or general formula (V): HOOC—CR3R4—CR5(COOH)—SH  (IV)

4. An additive for fuel oils comprising a disulfide compound, as the main component represented by the general formula (I): R1OOC—CR3R4—CR5(COOR2)—S—S—CR10(COOR7)—CR8R9—COOR6  (I)

5. An additive for fuel oils comprising a disulfide compound as the main component, prepared by oxidative coupling of a mercaptoalkanedicarboxylic acid diester represented by the general formula (II) and/or general formula (III): R1OOC—CR3R4—CR5(COOR2)—SH  (II)

6. An additive for fuel oils comprising a disulfide compound, as the main component, prepared by oxidative coupling of a mercaptoalkanedicarboxylic acid represented by the general formula (IV) and/or general formula (V): HOOC—CR3R4—CR5(COOH)—SH  (IV)

7. A lubricating oil composition comprising (A) a lubricating base oil and (B) the additive for lubricating oils as claimed in any one of claims 1 to 3.

8. A lubricating oil composition as claimed in claim 7 wherein the content of the component (B) is 0.01 to 50% by mass.

9. A fuel oil composition comprising (X) a fuel oil and (Y), the additive for fuel oils as claimed in any one of claims 4 to 6.

10. A fuel oil composition as claimed in claim 9 wherein the content of the component (Y) is 0.01 to 1000 ppm by mass.