Lubricant composition comprising hydroxycarboxylic acid derived friction modifier

Abstract

The present invention relates to a lubricant composition containing a base stock and at least 0.01 wt % of a friction reducing additive which is a compound of the Formula (I):
R.sup.1[(AO).sub.n—R.sup.2].sub.m  (I)
wherein R.sup.1 is the residue of a group having at least 2 active hydrogen atoms; m is at least 2; AO is an alkylene oxide residue; each n is independently from 0 to 100; and each R.sup.2 is independently H or R.sup.3, where each R.sup.3 is independently a residue of a polyhydroxyalkyl or polyhydroxyalkenyl carboxylic acid, a residue of a hydroxyalkyl or hydroxyalkenyl carboxylic acid and/or a residue of an oligomer of the hydroxyalkyl or hydroxyalkenyl carboxylic acid; and on average at least 0.5 of R.sup.2 groups are R.sup.3. The lubricant composition is suitable for use in an engine oil, a hydraulic oil or fluid, a gear oil and/or a metal-working fluid.

Claims

1. A lubricant composition comprising a base stock and at least 0.10 wt % of a friction reducing additive which comprises a compound of Formula (I):
R.sup.1[(AO).sub.n—R.sup.2].sub.m  (I) wherein: R.sup.1 is a residue of a monosaccharide or a disaccharide; m is 4 to 10; AO is an alkylene oxide residue, where A is —(C.sub.rH.sub.2rO)— and r is 2, 3 or 4; each n is independently from 2 to 20; each R.sup.2 is independently H or R.sup.3, where each R.sup.3 is independently a residue of a polyhydroxyalkyl or polyhydroxyalkenyl carboxylic acid, a residue of a hydroxyalkyl or hydroxyalkenyl carboxylic acid and/or a residue of an oligomer of the hydroxyalkyl or hydroxyalkenyl carboxylic acid; and on average at least 0.5 of R.sup.2 groups are R.sup.3, wherein the lubricant composition is non-aqueous, wherein the product of indices n×m is 10 to 100, and wherein the friction reducing additive has a molecular weight (Mn) between 3,000 to 10,000, and is capable of reducing a coefficient of friction of the lubricant composition by at least 20% when measured using a mini-traction machine (MTM).

2. The lubricant composition according to claim 1 wherein R.sup.1 is a residue of a monosaccharide selected from the group consisting of glucose, fructose and sorbitol or a residue of a disaccharide selected from the group consisting of maltose, palitose, lactitol and lactose.

3. The lubricant composition according to claim 1 wherein m is 5 to 6.

4. The lubricant composition according to claim 1 wherein n×m is 25 to 100.

5. The lubricant composition according to claim 1 wherein at least 2.0 of the R.sup.2 groups are R.sup.3.

6. The lubricant composition according to claim 1 wherein R.sup.3 is a residue of a polyhydroxyalkyl carboxylic acid.

7. The lubricant composition according to claim 6 wherein the number of hydroxyalkyl monomers in the polyhydroxyalkyl carboxylic acid residue is 3 to 10.

8. The lubricant composition according to claim 1 wherein at least 2.0 of the R.sup.2 groups are H.

9. The lubricant composition according to claim 1 wherein the friction reducing additive is an ethoxylated sorbitol ester of a polyhydroxyalkyl carboxylic acid.

10. The lubricant composition according to claim 1 wherein the base stock is selected from the group consisting of an API Group I, II, III, IV, V base oil or mixtures thereof.

11. The lubricant composition according to claim 1 wherein the lubricant composition is a gear oil.

12. The lubricant composition according to claim 1 wherein the lubricant composition is an engine oil.

13. An engine comprising the lubricant composition according to claim 12.

14. A method of reducing friction in an automotive engine which comprises using an engine oil comprising a base stock and at least 0.01 wt % of a friction reducing additive which comprises a compound of the Formula (I):
R.sup.1[(AO).sub.n—R.sup.2].sub.m  (I) wherein: R.sup.1 is a residue of a monosaccharide or a disaccharide; m is 4 to 10; AO is an alkylene oxide residue, where A is —(C.sub.rH.sub.2rO)— and r is 2, 3 or 4; each n is independently from 2 to 20; and each R.sup.2 is independently H or R.sup.3, where each R.sup.3 is independently a residue of a polyhydroxyalkyl or polyhydroxyalkenyl carboxylic acid, a residue of a hydroxyalkyl or hydroxyalkenyl carboxylic acid and/or a residue of an oligomer of the hydroxyalkyl or hydroxyalkenyl carboxylic acid; and on average at least 0.5 of R.sup.2 groups are R.sup.3, wherein the engine oil is non-aqueous, wherein the product of indices n×m, is 10 to 100, and wherein the friction reducing additive has a molecular weight (Mn) between 3,000 to 10,000, and is capable of reducing a coefficient of friction of the lubricant composition by at least 20% when measured using a mini-traction machine (MTM).

15. The lubricant composition according to claim 1 wherein the residue of a polyhydroxyalkyl or polyhydroxyalkenyl carboxylic acid, the residue of a hydroxyalkyl or hydroxyalkenyl carboxylic acid and/or the residue of an oligomer of the hydroxyalkyl or hydroxyalkenyl carboxylic acid is derived from a hydroxyalkyl or hydroxyalkenyl carboxylic acid of formula HO—X—COOH where X is a divalent saturated or unsaturated aliphatic radical containing 8 to 20 carbon atoms.

16. The method according to claim 14 wherein the residue of a polyhydroxyalkyl or polyhydroxyalkenyl carboxylic acid, the residue of a hydroxyalkyl or hydroxyalkenyl carboxylic acid and/or the residue of an oligomer of the hydroxyalkyl or hydroxyalkenyl carboxylic acid is derived from a hydroxyalkyl or hydroxyalkenyl carboxylic acid of formula HO—X—COOH where X is a divalent saturated or unsaturated aliphatic radical containing 8 to 20 carbon atoms.

17. The lubricant composition according to claim 1, where R.sup.1 is a residue of a monosaccharide selected from the group consisting of glucose, fructose and sorbitol.

18. The method according to claim 14, where R.sup.1 is a residue of a monosaccharide selected from the group consisting of glucose, fructose and sorbitol.

19. The lubricant composition according to claim 1, where r is 2.

20. The method according to claim 14, where r is 2.

Description

EXAMPLES

Example 1

(1) 100 g of sorbitol and 0.1 g of NaOH (0.007% by wt) were added to a pressurized stainless-steel reactor. The reaction mixture was heated with vigorous mixing to 120° C. 1,222 g of ethylene oxide was then added in portions and allowed to react, so that the total pressure of the gases did not exceed 35 psi. After addition of the last portion of the ethylene oxide, the reaction mixture was heated to 150° C. and stirred at this temperature for two additional hours to complete the ethoxylation reaction.

(2) 453 g of ethoxylated sorbitol (produced above), 997 g of poly(12-hydroxystearic acid) and 0.3 g of tin oxalate catalyst were mixed together and heated to 230° C. Vacuum and slight nitrogen sparge (0.1 cfm) were applied, and the reaction was carried out until the acid number of the mixture was below 2 mgKOH/g. The reaction was then cooled to 80-90° C., and 4 g phosphoric acid (75 wt %) was added in order to neutralize the catalyst. The product was then filtered to remove solid impurities. If required, a deodorization process was performed by applying live steam to the product at 125-135° C. for about 2 hours. The final product had a saponification value of 143 mgKOH/g, an acid value of 1.1 mgKOH/g, an iodine value of 1.7 gl/100 g, a hydroxyl value of 25.4 mgKOH/g, and a viscosity of 22,000 Cp at 20° C.

Example 2

(3) The procedure of Example 1 was repeated except that 293 g of ethylene oxide and 185 g of the resultant ethoxylated sorbitol were used. The final product had a saponification value of 143 mgKOH/g, an acid value of 1.4 mgKOH/g, an iodine value of 1.7 gl/100 g, and a hydroxyl value of 25.4 mgKOH/g.

Example 3

(4) The procedure of Example 1 was repeated except that 997 g of 12-hydroxystearic acid was used instead of poly(12-hydroxystearic acid). The final product had a saponification value of 143 mgKOH/g, an acid value of 1.6 mgKOH/g, an iodine value of 1.7 gl/100 g, and hydroxyl value of 26.1 mgKOH/g.

Example 4

(5) The friction reducing additives (FRA) produced in Examples 1 to 3 were evaluated using the MTM test procedure described above and the results for Group H mineral oil are shown in Tables 2 to 4.

(6) TABLE-US-00002 TABLE 2 Coefficient of Friction at 40° C. Test Composition +0.5 wt % +0.5 wt % +0.5 wt % Speed Control of FRA of FRA of FRA (m/s) Composition of Example 1 of Example 2 of Example 3 0.002 0.100 0.060 0.092 0.037 0.020 0.070 0.057 0.073 0.520 0.200 0.060 0.059 0.063 0.570 2.000 0.052 0.053 0.054 0.540

(7) TABLE-US-00003 TABLE 3 Coefficient of Friction at 100° C. Test Composition +0.5 wt % +0.5 wt % +0.5 wt % Speed Control of FRA of FRA of FRA (m/s) Composition of Example 1 of Example 2 of Example 3 0.002 0.104 0.044 0.101 0.065 0.020 0.081 0.042 0.087 0.061 0.200 0.054 0.039 0.058 0.054 2.000 0.040 0.037 0.041 0.041

(8) TABLE-US-00004 TABLE 4 Coefficient of Friction at 150° C. Test Composition +0.5 wt % +0.5 wt % +0.5 wt % Speed Control of FRA of FRA of FRA (m/s) Composition of Example 1 of Example 2 of Example 3 0.002 0.106 0.016 0.099 0.070 0.020 0.079 0.018 0.079 0.057 0.200 0.041 0.021 0.041 0.038 2.000 0.020 0.016 0.019 0.020

Example 5

(9) The friction reducing additives (FRA) produced in Examples 1 to 3 were evaluated using the MTM test procedure described above except that a commercially available conventional automotive engine oil (GF-5 approved, viscosity grade 10W-30) was used at 135° C., instead of Group II mineral oil. The results are shown in Table 5.

(10) TABLE-US-00005 TABLE 5 Coefficient of Friction at 135° C. Test Composition +0.5 wt % +0.5 wt % +0.5 wt % Speed Control of FRA of FRA of FRA (m/s) Composition of Example 1 of Example 2 of Example 3 0.002 0.132 0.095 0.116 0.106 0.020 0.141 0.094 0.114 0.086 0.200 0.109 0.072 0.105 0.071 2.000 0.042 0.032 0.047 0.061

Example 6

(11) The friction reducing additive (FRA) produced in Example 1 was evaluated for its performance as an additive in a metal working fluid. A Microtap II thread tapping machine supplied by Microtap USA, Inc. is used to measure the tapping torque of metal working fluids. The Microtap II machine cuts threads in pre-drilled holes at a selected set of operating parameters. Tests were performed on 50 mm×200 mm×8 mm mild steel bars containing 3.7 mm diameter holes. They were supplied by the company Robert Speck Ltd.

(12) For this Example, the following parameters were used: 1 ml of metal working fluid is added to the Microtap II machine using a pipette Ambient temperature 6.0 mm depth of hole 4 mm forming tap Maximum torque set at 220 Ncm Cutting speed 1000 rpm

(13) After applying the metal working fluid, the holes were threaded and the amount of torque required was recorded. If the metal working fluid isn't adequate to allow the thread to be formed within the set maximum torque of 220 Ncm then multiple attempts are made by the machine and then declared as a fail. The results are given in Table 6 below.

(14) TABLE-US-00006 TABLE 6 Micro Tap Test Results Control Composition Control Composition + of ISO 22 S/N 100 2 wt % of Metal Working Fluid Group 1 Mineral Oil FRA of Example 1 Torque required (Ncm) 220-FAIL 156

(15) The above examples illustrate the improved properties of a lubricant composition according to the present invention.