Non-aqueous lubricant and fuel compositions comprising fatty acid esters of hydroxy-carboxylic acids, and uses thereof

Abstract

The use as an anti-wear additive and/or friction modifier in a non-aqueous lubricant composition and/or in a fuel composition of at least one long chain fatty acid ester of a hydroxy carboxylic acid in which the long chain fatty acid has at least 4 carbon atoms and the ester is an oil-soluble ester of a mono- or poly-hydroxy carboxylic acid having 1 to 4 groups which are independently carboxylic acid groups or lower hydrocarbyl esters thereof and in which, when the hydroxy carboxylic acid is a mono-hydroxy carboxylic acid, the ester has a long chain fatty acid ester moiety of the hydroxy group of the hydroxy carboxylic acid and, when the hydroxy carboxylic acid is a poly-hydroxy carboxylic acid, the ester has independently long chain fatty acid ester moieties of one or two of the hydroxy groups of the poly-hydroxy carboxylic acid. Also, a non-aqueous lubricant composition and a fuel composition for an internal combustion engine which comprises at least one of said long chain fatty acid esters.

Claims

1. A non-aqueous lubricant composition comprising a major amount of an oil of lubricating viscosity and a minor amount of at least one compound, each compound being an oil-soluble long chain fatty acid ester of a mono- or di-hydroxy carboxylic acid selected from citric acid, malic acid and tartaric acid, wherein: (i) when the compound is an oil-soluble long chain fatty acid ester of a mono-hydroxy carboxylic acid, the compound includes a long chain fatty acyl moiety substituted at the hydroxy group of the mono-hydroxy carboxylic acid, the long-chain fatty acyl moiety having 8 to 22 carbon atoms, and each carboxylate of the mono-hydroxy carboxylic acid independently is a lower alkyl carboxylate ester, each lower alkyl carboxylate ester having an alkyl moiety which independently has 1 to 3 carbon atoms; (ii) when the compound is an oil-soluble long chain fatty acid mono-ester of a di-hydroxy carboxylic acid, the compound includes a long chain fatty acyl moiety substituted at the hydroxy groups of the di-hydroxy carboxylic acid, the long-chain fatty acyl moiety having 8 to 22 carbon atoms, and each carboxylate of the di-hydroxy carboxylic acid independently is a lower alkyl carboxylate ester, each lower alkyl carboxylate ester having an alkyl moiety which independently has 1 to 3 carbon atoms; and (iii) when the compound is an oil-soluble long chain fatty acid di-ester of a di-hydroxy carboxylic acid, the compound includes two long chain fatty acyl moieties, each substituted at one of the hydroxy groups of the di-hydroxy carboxylic acid, each long-chain fatty acyl moiety independently having 8 to 22 carbon atoms, and each carboxylate of the di-hydroxy carboxylic acid independently is a lower alkyl carboxylate ester, each lower alkyl carboxylate ester having an alkyl moiety which independently has 1 to 3 carbon atoms.

2. The composition as claimed in claim 1, wherein each compound is an oil-soluble long chain fatty acid ester of citric acid, wherein: each compound includes a long chain fatty acyl moiety substituted at the hydroxy group of the citric acid, the long-chain fatty acyl moiety having 8 to 22 carbon atoms, and each carboxylate of the citric acid independently is a lower alkyl carboxylate ester, each lower alkyl carboxylate ester having an alkyl moiety which independently has 1 to 3 carbon atoms.

3. The composition as claimed in claim 1 in which each compound is a long chain fatty acid di-ester of tartaric acid, wherein each compound includes two long chain fatty acyl moieties, each substituted at one of the hydroxy groups of the tartaric acid, each long-chain fatty acyl moiety independently having 8 to 22 carbon atoms, and each carboxylate of the tartaric acid is independently is a lower alkyl carboxylate ester, each lower alkyl carboxylate ester having an alkyl moiety which independently has 1 to 3 carbon atoms.

4. The composition as claimed in claim 1 in which each of the compounds is a long chain fatty acid mono-ester of tartaric acid, wherein the compound includes a long chain fatty acyl moiety substituted at only one of the hydroxy groups of the tartaric acid, the long-chain fatty acyl moiety having 8 to 22 carbon atoms, and each carboxylate of the tartaric acid independently is a lower alkyl carboxylate ester, each lower alkyl carboxylate ester having an alkyl moiety which independently has 1 to 3 carbon atoms.

5. The composition as claimed in claim 1 in which each of the long chain fatty acyl moieties has 8 to 18 carbon atoms.

6. The composition as claimed in claim 2 in which each of the long chain fatty acyl moieties has 8 to 18 carbon atoms.

7. The composition as claimed in claim 3 in which each of the long chain fatty acyl moieties has 8 to 18 carbon atoms.

8. The composition as claimed in claim 1 in which each of the long chain fatty acyl moieties has 14 to 22 carbon atoms.

9. The composition as claimed in claim 2 in which each of the long chain fatty acyl moieties has 14 to 22 carbon atoms.

10. The composition as claimed in claim 3 in which each of the long chain fatty acyl moieties has 14 to 22 carbon atoms.

11. The composition as claimed in claim 1 in which each of the long chain fatty acyl moieties has 8, 14, 16, 18 or 22 carbon atoms.

12. The composition as claimed in claim 1 in which the long chain fatty acyl moieties is oleoyl.

13. The composition as claimed in claim 1 in which the long chain fatty acyl moieties is myristoyl.

14. The composition as claimed in claim 1 in which the alkyl moieties of the lower alkyl carboxylate esters are ethyl.

15. The composition as claimed in claim 2 in which the alkyl moieties of the lower alkyl carboxylate esters are ethyl.

16. The composition as claimed in claim 3 in which the alkyl moieties of the lower alkyl carboxylate esters are ethyl.

17. The composition as claimed in claim 1, wherein each compound is derived from (a) reacting the mono- or di-hydroxy carboxylic acid and the long chain fatty acid or an acyl halide of the long chain fatty acid or (b) reacting a lower hydrocarbyl ester of the hydroxy carboxylic acid and the long chain fatty acid or an acyl halide of the long chain fatty acid.

18. The composition as claimed in claim 1, wherein each compound is an oil-soluble long chain fatty acid ester of citric acid, wherein: each compound includes a long chain fatty acyl moiety substituted at the hydroxy group of the citric acid, the long-chain fatty acyl moiety having 8 to 18 carbon atoms, and each carboxylate of the citric acid independently is a lower alkyl carboxylate ester, each lower alkyl carboxylate ester having an alkyl moiety which is ethyl.

19. The composition as claimed in claim 1, wherein each compound is an oil-soluble long chain fatty acid ester of citric acid, wherein: each compound includes a long chain fatty acyl moiety substituted at the hydroxy group of the citric acid, the long-chain fatty acyl moiety having 14 to 22 carbon atoms, and each carboxylate of the citric acid independently is a lower alkyl carboxylate ester, each lower alkyl carboxylate ester having an alkyl moiety which is ethyl.

20. The composition as claimed in claim 1, wherein each compound is an oil-soluble long chain fatty acid mono- or di-ester of tartaric acid, wherein in which the oil soluble ester has the structural formula: when the compound is an oil-soluble long chain fatty acid mono-ester of tartaric acid, the compound includes a long chain fatty acyl moiety substituted at only one of the hydroxy groups of the tartaric acid, the long-chain fatty acyl moiety having 8 to 22 carbon atoms, and each carboxylate of the tartaric acid independently is a lower alkyl carboxylate ester, each lower alkyl carboxylate ester having an alkyl moiety which independently has 1 to 3 carbon atoms; and when the compound is an oil-soluble long chain fatty acid di-ester of tartaric acid, the compound includes two long chain fatty acyl moieties, each substituted at one of the hydroxy groups of the tartaric acid, each long-chain fatty acyl moiety independently having 8 to 22 carbon atoms, and each carboxylate of the tartaric acid independently is a lower alkyl carboxylate ester, each lower alkyl carboxylate ester having an alkyl moiety which independently has 1 to 3 carbon atoms.

21. The composition as claimed in claim 20, wherein each alkyl moiety of each lower alkyl carboxylate ester is ethyl.

22. The composition as claimed in claim 21, wherein each long chain fatty acyl moiety independently has 8 to 18 carbon atoms.

23. The composition as claimed in claim 21, wherein each long chain fatty acyl moiety independently has 14 to 22 carbon atoms.

24. The composition as claimed in claim 1, wherein each compound is an oil-soluble long chain fatty acid ester of malic acid, wherein each compound includes a long chain fatty acyl moiety substituted at the hydroxy group of the malic acid, the long-chain fatty acyl moiety having 8 to 22 carbon atoms, and each carboxylate of the malic acid independently is a lower alkyl carboxylate ester, each lower alkyl carboxylate ester having an alkyl moiety which independently has 1 to 3 carbon atoms.

Description

FURTHER EXPERIMENTS AND EXAMPLES

(1) Preparation of Triethyl Citrate Butyrate.

(2) To a solution of sodium hydride (0.651 g, 1.5 eq) in THF at 0° C., triethyl citrate (5 g, 1 eq) in THF (50 ml) was added drop wise and stirred for 1 h at 0° C. Then butaryl chloride (2.12 g, 1.1 eq) was added drop wise and stirred for 1 h at 0° C. under nitrogen atmosphere. The stirring was continued for another 12 h at 25-30° C. The reaction was monitored by thin layer chromatography. The reaction was quenched with cold water and extracted with ethyl acetate. Ethyl acetate layer was washed with sodium bicarbonate solution (10%) followed by water and brine solution. The organic layer was dried over sodium sulphate and concentrated to get the crude product. The crude product was purified by column chromatography using 6% ethyl acetate in petroleum ether as eluent. The product was characterized by NMR. Yield was 3 g; 48.6%.

(3) Preparation of Triethyl Citrate Octanoate.

(4) The same procedure was used as for preparation of triethyl citrate butyrate but using octyl chloride.

(5) Preparation of Triethyl Citrate Myristate.

(6) The same procedure was used as for preparation of triethyl citrate butyrate but using myristryl chloride.

(7) Preparation of Diethyl Tartrate Dibutyrate

(8) To a solution of sodium hydride (0.8712 g, 1.5 eq) in THF at 0° C., diethyl tartarate (5 g, 1 eq) in THF (50 ml) was added drop wise and stirred for 1 h at 0° C. Then butaryl chloride (7335 g, 3 eq) was added drop wise and stirred for 1 h at 0° C. under nitrogen atmosphere. The stirring was continued for another 12 h at 25-30° C. The reaction was monitored by thin layer chromatography. The reaction was quenched with cold water and extracted with ethyl acetate. Ethyl acetate layer was washed with sodium bicarbonate solution (10%) followed by water and brine solution. The organic layer was dried over sodium sulphate and concentrated to get the crude product. The crude product was purified by the column chromatography using 7% ethyl acetate in petroleum ether as eluent. The product was characterized by NMR. The yield was 3.2 g; 38.5%.

(9) Preparation of Lubricant Compositions.

(10) The esters prepared above, were formulated into lubricating compositions in combination with an additive package (10.21 wt %), which contained a conventional non-borated dispersant, calcium sulfonate and phenate detergents, phenolic and aminic anti oxidants, anti foam and Group III base oil. The lubricant compositions also comprised ZDDP at a treat rate corresponding to 400 ppm phosphorus, a viscosity modifier (4%) and a mixture of Yubase 4 and 6 base oils.

(11) The lubricant compositions were prepared to have the same ester additive concentration (when present) on a molar basis, of 0.036 molL.sup.−1

(12) Wear Testing

(13) The lubricant compositions prepared above were tested in a Cameron Plint wear test using the same procedure as described in section 2 above except that the test duration was 21 hours. The results are set out in Table 9 below.

(14) Friction Coefficient Testing.

(15) The lubricant compositions prepared above were tested in an HFRR test in the same way as described in section 4 above, except that the results were reported as an average of readings taken at the end of each of 15 minute operating periods at each of three testing temperatures of 60, 90 and 120° C. The results are set out in Table 9 below.

(16) The results in Table 9 show that the esters according to the present invention exhibit anti-wear properties.

(17) The results in Table 9 also show that the esters according to the present invention exhibit friction modifying properties. In particular, for the triethyl citrate esters, the friction modifying properties appear to exhibit a peak in performance with increasing chain length of the long chain fatty acid with a peak at or around a carbon chain length of 14 carbon atoms.

(18) The results in Table 9 also show that the friction modifier properties of the diethyl tartrate dibutyrate are superior to diethyl tartrate and diethyl tartrate diacetate

(19) TABLE-US-00009 TABLE 9 Reduction in Reduction of Wear wear volume Average average friction co- volume compared Friction efficient compared Additive (m.sup.3/Nm) to Expt. Q (%) Coefficient to Expt. Q (%) Expt. Q None (400 ppm P) 1.59 × 10.sup.−17 — 0.16 — Expt. R Triethyl citrate (1.00 wt %) 2.75 × 10.sup.−18 82.68 0.15 4.13 Expt. S Triethyl citrate acetate (1.15 wt %) 2.45 × 10.sup.−18 84.57 0.15 4.25 Example 5 Triethyl citrate oleate (1.96 wt %) 2.53 × 10.sup.−18 84.05 0.14 11.39 Example 6 Triethyl citrate butyrate (1.25 wt %) 2.48 × 10.sup.−18 84.36 0.15 3.19 Example 7 Triethyl citrate octanoate (1.46 wt %) 2.89 × 10.sup.−18 81.80 0.14 12.97 Example 8 Triethyl citrate myristate (1.76 wt %) 2.90 × 10.sup.−18 81.70 0.13 19.93 Expt. T Sakuralube 165 @ 1% 2.53 × 10.sup.−18 84.07 0.12 27.38 Expt. U GMO @ 0.5% 0.13 21.58 Expt. V Diethyl tartrate (0.75 wt %) 3.10 × 10.sup.−18 80.46 0.15 5.42 Expt. W Diethyl tartrate diacetate (1.05 wt %) 3.40 × 10.sup.−18 78.58 0.16 2.99 Example 9 Diethyl tartrate dibutyrate (1.25 wt %) 3.53 × 10.sup.−18 77.78 0.15 8.85 Expt. X Blank (285 ppm P) 6.84 × 10.sup.−18 59.16 0.16 2.66 Example 10 Triethyl citrate oleate at 285 ppm P 2.24 × 10.sup.−18 85.87 0.14 15.19