Use of a diester to improve the anti-wear properties of a lubricant composition

Abstract

The present invention relates to the use of a diester of the following formula (I):
R.sup.a—C(O)—O—([C(R).sub.2].sub.n—O).sub.s—C(O)—R.sup.b  (I),
as an additive to improve the anti-wear properties of a lubricant composition comprising one or more anti-wear additive(s).

Claims

1. A method of improving the anti-wear properties of a lubricant composition comprising one or more anti-wear additives chosen from metal alkylthiophosphates, the method comprising adding to the lubricant composition an amount of a diester sufficient to improve the anti-wear properties of the composition, wherein the diester is represented by the following formula (I):
R.sup.a—C(O)—O—([C(R).sub.2].sub.n—O).sub.s—C(O)—R.sup.b  (I), wherein: R represents, independently of one another, a hydrogen atom, or a linear or branched (C.sub.1-C.sub.5)alkyl group; s has a value of 1 or 2; n has a value of 1, 2 or 3, wherein when s is 2, n may be identical or different from s; and R.sup.a and R.sup.b are independently selected from saturated or unsaturated, linear or branched, hydrocarbon-containing groups having a linear chain of 2 to 11 carbon atoms; with the provisos that: when s and n both have a value of 2, at least one of the R groups represents a linear or branched (C.sub.1-C.sub.5)alkyl group; and when s has a value of 1 and n has a value of 3, at least one of the R groups bound to the carbon in the beta position of the oxygen atoms of the ester functions represents a hydrogen atom, wherein the lubricant composition is of a grade according to the SAEJ300 classification defined by the formula (X)W(Y), wherein X represents 0 or 5; and Y represents an integer from 4 to 30, wherein the total amount of metal alkylthiophosphates in the composition ranges from 0.01 wt. % to 6 wt. %, relative to the total weight of the lubricant composition, wherein the total amount of diesters of formula (I) added to the lubricant composition ranges from 1 wt. % to 20 wt. %, relative to the total weight of the lubricant composition, wherein the anti-wear properties of the lubricant composition, evaluated according to a procedure based on standard ASTM D2670, are improved compared to a composition that is otherwise identical except for not comprising a diester of formula (l′), and wherein the lubricant composition comprises at least 50 wt. % of one or more base oils different from the diesters of formula (I).

2. The method of claim 1, wherein the total amount of diesters of formula (I) added to the lubricant composition ranges from 5 wt. % to 20 wt. %, relative to the total weight of the lubricant composition.

3. The method of claim 1, wherein the one or more anti-wear additives are selected from zinc dialkyldithiophosphates represented by the formula:
Zn((SP(S)(OR)(OR′)).sub.2, wherein, R and R′ are independently selected from linear or branched alkyl groups comprising from 1 to 18 carbon atoms.

4. The method of claim 1, wherein the lubricant composition comprises a total amount of metal alkylthiophosphates ranging from 0.1 wt. % to 2 wt. %, relative to the total weight of the lubricant composition.

5. The method of claim 1, wherein the one or more base oils are oils of group II, Ill, or IV of the API classification.

6. The method of claim 1, wherein the lubricant composition further comprises one or more of friction modifying additives, extreme pressure additives, detergents, antioxidants, viscosity index improvers, pour point depressants, dispersants, antifoaming agents, thickeners, or mixtures thereof.

7. A method of improving the anti-wear properties of a lubricant composition comprising one or more anti-wear additives chosen from metal alkylthiophosphates, the method comprising adding to the lubricant composition an amount of a diester sufficient to improve the anti-wear properties of the composition, wherein the diester is represented by the following formula (I′):
R.sup.a—C(O)—O—([C(R).sub.n—O)—([C(R′).sub.2].sub.m—O).sub.s-1—C(O)—R.sup.b  (I′), wherein: R and R′ are independently selected from a hydrogen atom or a linear or branched (C.sub.1-C.sub.5)alkyl group; s has a value of 1 or 2; n has a value of 2; m has a value of 2; and R.sup.a and R.sup.b are independently selected from saturated or unsaturated, linear or branched, hydrocarbon-containing groups having a linear chain of 2 to 11 carbon atoms; with the proviso that when s has a value of 2, at least one of the R or R′ groups represents a linear or branched (C.sub.1-C.sub.5)alkyl group, wherein the total amount of metal alkylthiophosphates in the composition ranges from 0.05 wt. % to 4 wt. %, relative to the total weight of the lubricant composition, and wherein the total amount of diesters of formula (I′) added to the lubricant composition ranges from 1 wt. % to 20 wt. %, relative to the total weight of the lubricant composition, wherein the anti-wear properties of the lubricant composition, evaluated according to a procedure based on standard ASTM D2670, are improved compared to a composition that is otherwise identical except for not comprising a diester of formula (r), and wherein the lubricant composition comprises at least 50 wt. % of one or more base oils different from the diesters of formula (I).

8. The method of claim 7, wherein: s has a value of 2; one of the R groups represents a linear or branched (C.sub.1-C.sub.5)alkyl group and the other R group represents a hydrogen atom; and one of the R′ groups represents a linear or branched (C.sub.1-C.sub.5)alkyl group and the other R′ group represents a hydrogen atom.

9. The method of claim 7, wherein: s has a value of 1, and one of the R groups represents a linear or branched (C.sub.1-C.sub.5)alkyl group and the other R group represents a hydrogen atom.

10. The method of claim 7, wherein the total amount of diesters of formula (I′) added to the lubricant composition ranges from 5 wt. % to 20 wt. %, relative to the total weight of the lubricant composition.

11. The method of claim 7, wherein the one or more anti-wear additives are selected from zinc dialkyldithiophosphates represented by the formula:
Zn((SP(S)(OR)(OR′)).sub.2, wherein R and R′ are independently selected from linear or branched alkyl groups comprising from 1 to 18 carbon atoms.

12. The method of claim 7, wherein the lubricant composition comprises a total amount of metal alkylthiophosphates ranging from 0.1 wt. % to 2 wt. %, relative to the total weight of the lubricant composition.

13. The method of claim 7, wherein the one or more base oils are oils of group II, Ill, or IV of the API classification.

14. The method of claim 7, wherein the lubricant composition is of a grade according to the SAEJ300 classification defined by the formula (X)W(Y), wherein X represents 0 or 5, and Y represents an integer from 4 to 30.

15. The method of claim 7, wherein the lubricant composition further comprises one or more of friction modifying additives, extreme pressure additives, detergents, antioxidants, viscosity index improvers, pour point depressants, dispersants, antifoaming agents, thickeners, or mixtures thereof.

16. The method of claim 1, wherein: the anti-wear additives comprise zinc dialkyldithiophosphate, and the composition further comprises at least one polymethylacrylate polymer.

Description

EXAMPLES

Example 1

Preparation of Lubricant Compositions Comprising a Diester Required According to the Invention and of Comparative Compositions

(1) Lubricant compositions according to the invention (I1 and I2), using a diester of formula (I), and comparative compositions (C.sub.1 and C.sub.2), without a diester of formula (I), were formulated with the components and amounts (expressed in percentage by weight) indicated in Table 1 below.

(2) The lubricant compositions are obtained by simple mixing of the following components at room temperature: Base oil of group III (KV100=4.2 mm.sup.2/s, KV40=19.1 mm.sup.2/s, VI of 126) available commercially for example from the company SK Lubricants under the trade name Yubase® 4, Conventional additive package 1 comprising an anti wear additive (zinc bis(dithiophosphate) and bis[O,O-bis(2-ethylhexyl)], for example marketed under the name OLOA® 269R), antioxidants, a friction modifier, a dispersant and detergents, Conventional additive package 2 comprising an antiwear additive (zinc bis[O-(1,3-dimethylbutyl)] bis[O-(isopropyl)] bis(dithiophosphate)), antioxidants, a friction modifier, a dispersant and detergents, A polymethacrylate comb polymer available commercially from the company Evonik under the trade name Viscoplex® V3-200, and optionally A diester of formula (I) according to the invention, obtained by an esterification reaction between dipropylene glycol and at least two nonanoic fatty acids.

(3) TABLE-US-00002 TABLE 1 Compositions according Comparative to the invention compositions I1 I2 C1 C2 Additive package 1 12.2 12.2 Additive package 2 12.2 12.2 PMA polymer 4.7 4.7 4.7 4.7 Base oil 68.1 68.1 83.1 83.1 Ester of formula (I) of 15 15 0 0 the invention

(4) The characteristics of the compositions thus prepared are presented in the following Table 2.

(5) TABLE-US-00003 TABLE 2 Compositions I1 I2 C1 C2 HTHS.sup.(1) 2.59 2.60 2.58 2.57 KV40 (mm.sup.2/s).sup.(2) 31.14 31.07 32.32 32.09 KV100 (mm.sup.2/s).sup.(3) 7.92 7.92 7.39 7.42 VI.sup.(4) 243 244 206 209 .sup.(1)high-temperature, high-shear (HTHS) viscosity measurement, at shear of 10.sup.6 s.sup.−1 and at 150° C. by the standardized method ASTM D4683; .sup.(2)(3)kinematic viscosity at 40° C. (KV40) and at 100° C. (KV100) measured according to standard ASTM D445-97; .sup.(4)viscosity index (VI), measured according to standard ASTM D2270-93

Example 2

Evaluation of the Antiwear Properties

(6) Method of Evaluation

(7) This evaluation is based on a procedure according to standard ASTM D2670, requiring the use of a FALEX tribometer, in the following test conditions. test specimens: FALEX steel grinding time: 300 s; test duration: 180 min; grinding load: 445 N; test load: 1335 N; speed: 290 rev/min; room temperature.

(8) The test results are presented in Table 3 below, and are expressed more specifically in uni; the lower the value obtained, the better are the antiwear properties of the composition evaluated.

(9) TABLE-US-00004 TABLE 3 Compositions I1 I2 C1 C2 Wear (μm) 24 41 95 97 Pin mass loss vés (mg) 3 18 56 57 Test end temp. (° C.) 80 103 119 134 Mean torque at end of 40 80 105 109 test (Ncm)

(10) The results show that the addition of a diester of formula (I) according to the invention to the lubricant compositions makes it possible to improve their antiwear properties significantly.