Ether-Based Lubricant Compositions, Methods and Uses

Abstract

##STR00001##

The present invention provides a lubricant composition for an internal combustion engine comprising a base oil of lubricating viscosity, wherein the base oil comprises an ether base stock of formula (A): where: R.sub.a and R.sub.b are aliphatic hydrocarbyl groups and may be the same or different; wherein at least one of R.sub.a and R.sub.b is branched-chain alkyl, alkoxy-substituted-alkyl or cycloalkyl-substituted-alkyl; the lubricant composition further comprising: i) at least one molybdenum compound as a lubricant additive which is present, on a molybdenum element basis, in an amount of at least 0.06% by weight of the lubricant composition; or ii) at least one polymethacrylate compound as a lubricant additive which is present in an amount of from 0.1 to 7.5% by weight of the lubricant composition. The lubricant composition may be used for lubricating a surface in an internal combustion engine as well as for improving the fuel economy performance and/or piston cleanliness performance and/or turbocharger cleanliness performance of an engine and/or a vehicle, such as an automotive vehicle associated with an internal combustion engine.

Claims

1. A lubricant composition for an internal combustion engine comprising a base oil of lubricating viscosity, wherein the base oil comprises an ether base stock of formula (A): ##STR00071## where: R.sub.a and R.sub.b are aliphatic hydrocarbyl groups and may be the same or different; wherein at least one of R.sub.a and R.sub.b is branched-chain alkyl, alkoxy-substituted-alkyl or cycloalkyl-substituted-alkyl; the lubricant composition further comprising: i) at least one molybdenum compound as a lubricant additive which is present, on a molybdenum element basis, in an amount of at least 0.06% by weight of the lubricant composition; or ii) at least one polymethacrylate compound as a lubricant additive which is present in an amount of from 0.1 to 7.5% by weight of the lubricant composition.

2. The lubricant composition of claim 1, wherein R.sub.a and R.sub.b are independently selected from alkyl, alkoxy-substituted-alkyl or cycloalkyl-substituted-alkyl, provided that when R.sub.a and R.sub.b are both alkyl at least one of R.sub.a and R.sub.b is/are branched-chain alkyl.

3. The lubricant composition of claim 1, wherein R.sub.a contains more carbon atoms than R.sub.b.

4. The lubricant composition of claim 1, wherein R.sub.a contains from 12 to 30 carbon atoms, and/or R.sub.b contains from 2 to 20 carbon atoms.

5. The lubricant composition of claim 1, wherein the ether base stock is of formula (1): ##STR00072## where: R.sub.1 and R.sub.2 are alkyl or, together with the carbon atom to which they are attached, cycloalkyl; R.sub.3, R.sub.4 and R.sub.5 are H or alkyl; R.sub.6 is alkyl or ##STR00073## where: R.sub.7 and R.sub.8 are H, alkyl or, together with the carbon atom to which they are attached, cycloalkyl; R.sub.9 is H or alkyl; X is alkylene or is absent; and p is 0, 1, 2 or 3; and m and n are 0, 1, 2 or 3, wherein m is 0 when R.sub.4 and R.sub.5 are H.

6. The lubricant composition of claim 5, wherein R.sub.1 and R.sub.2 are C.sub.1-15 alkyl or, together with the carbon atom to which they are attached, C.sub.5-30 cycloalkyl; and/or wherein R.sub.3, R.sub.4 and R.sub.5 are H or C.sub.1-15 alkyl.

7. The lubricant composition of claim 5, wherein m and n are 0, 1 or 2.

8. The lubricant composition of claim 5, wherein the ether base stock has the formula (4): ##STR00074## where: R.sub.1 and R.sub.4 are alkyl; R.sub.3 and R.sub.5 are H or alkyl.

9. The lubricant composition of claim 5, wherein the ether base stock has the formula (7): ##STR00075## where: R.sub.1 and R.sub.2 are alkyl or, together with the carbon to which they are attached, cycloalkyl; R.sub.3, R.sub.4 and R.sub.5 are H or alkyl; and R.sub.6 is alkyl.

10. The lubricant composition of claim 1, wherein the ether base stock contains a total number of carbons atoms of from 20 to 50.

11. The lubricant composition of claim 1, wherein the ether base stock is prepared from bio-derived feedstock containing greater than 50% by weight of biobased carbon.

12. The lubricant composition of claim 1, wherein the at least one molybdenum compound is present, on a molybdenum element basis, in an amount from 0.06% to 0.25% by weight of the lubricant composition.

13. The lubricant composition of claim 1, wherein the at least one polymethacrylate compound is present in an amount of from 0.25 to 7% by weight of the lubricant composition.

14. The lubricant composition of claim 1, wherein the at least one polymethacrylate compound is a comb-type polymer.

15. The lubricant composition of claim 1, wherein the base oil of the lubricant composition comprises greater than 10% by weight of the ether base stock and/or wherein the lubricant composition comprises greater than 50% by weight of the base oil.

16. The lubricant composition of claim 15, wherein the base oil of the lubricant composition further comprises a base stock selected from Group I, Group II, Group III, Group IV and Group V base stocks and mixtures thereof.

17. The lubricant composition of claim 1, wherein the lubricant composition has at least one of: a kinematic viscosity at 40 C. of less than 60 cSt; a kinematic viscosity at 100 C. of less than 12 cSt; a viscosity index of greater than 100; a viscosity at 150 C. and a shear rate of 10.sup.6 s.sup.1 of no greater than 3 cP; and a Noack volatility of less than 25% by weight.

18. The lubricant composition of claim 1, wherein the lubricant composition has at least one of: an oxidative stability performance on a CEC-L-088-02 test indicated by an absolute viscosity increase at 40 C. of no more than 45 cSt; an oxidative stability performance on a CEC-L-109-14 test indicated by an increase in kinematic viscosity at 100 C. of less than 200%; a fuel economy performance on a CEC-L-054-96 test of at least 2.5%; a piston cleanliness performance on a CEC-L-088-02 test indicated by an overall piston merit of at least 8.5; and a high temperature stability performance on a KHT test at 280 C. in accordance with JPI-5S-55-99 indicated by an overall deposit merit of at least 7.0.

19. The lubricant composition of claim 1, wherein the composition further comprises a phenate detergent in an amount of 0.1 to 5% by weight actives of the lubricant composition.

20. The lubricant composition of claim 1, wherein the composition further comprises a neutral sulphonate detergent in an amount of 0.01 to 5% by weight of the lubricant composition.

21. A method of preparing a lubricant composition, said method comprising providing a base oil as defined in claim 1 and blending the base oil with: i) at least one molybdenum compound suitable for use as a lubricant additive such that the molybdenum compound is present, on a molybdenum element basis, in an amount of at least 0.06% by weight of the lubricant composition; or ii) at least one polymethacrylate compound suitable for use as a lubricant additive such that the polymethacrylate compound is present in an amount of from 0.1 to 7.5% by weight of the lubricant composition, and optionally also blending one or more additional lubricant additives, in order to prepare the lubricant composition.

22. A method of lubricating a surface, said method comprising supplying a lubricant composition as defined in claim 1 to said surface, such as wherein the lubricant composition is supplied to a surface in an internal combustion engine.

23-26. (canceled)

27. A method of reducing or preventing i) scuffing in the piston system of an engine and/or ii) deposits in the turbochargers of an engine, comprising the step of providing to the engine a lubricant composition according to claim 1.

28. A method of improving the fuel economy performance and/or piston cleanliness performance and/or turbocharger cleanliness performance of an engine and/or a vehicle, comprising the step of providing to the engine a lubricant composition according to claim 1.

Description

[0330] The invention will now be described with reference to the accompanying figures and examples, which are not limiting in nature, in which:

[0331] FIG. 1 is a graph of Maximum Deposit Thickness (MDT) observed in HLPS analysis of blended compositions containing Guerbet-derived base stock (GE3) and/or a Group III base stock (Yubase 4) together with different detergents; and

[0332] FIG. 2 is a graph of deposit volume (cm.sup.310.sup.17) observed in HLPS analysis of blended compositions containing Guerbet-derived base stock (GE3) and/or a Group III base stock (Yubase 4) together with different detergents.

EXAMPLES

Example 1

Properties of Ether Base Stocks

[0333] Guerbet-derived base stock GE3 of formula (1) was prepared, the structure of which is shown in Table 4.

TABLE-US-00004 TABLE 4 Molecular Chemical Weight Formula Structure GE3 522.97 C.sub.36H.sub.74O [00070]
The Following Properties of the Base Stock were Tested:

[0334] Kinematic viscosity at 100 C. (KV100) and kinematic viscosity at 40 C. (KV40) were tested according to ASTM D7279.

[0335] Viscosity index (VI) was calculated according to ASTM D2270.

[0336] Pour point was determined according to ASTM D7346.

[0337] Differential scanning calorimetry (DSC) oxidation onset temperature was tested using a method which was based on ASTM E2009 (method B). According to the method, the base stocks were heated from 50 C. to 300 C., at a rate of 50 C./minute, under a pressure of 500 psi in an aluminium SFI pan. The temperature at which an exotherm was observed was recorded.

[0338] Noack volatility was measured using a method which was based on IP 393 and was considered similar to CEC-L-40-A-93. According to the method, reference oils of known Noack volatility were heated from 40 C. to 550 C. to determine the temperature at which the Noack volatility weight loss of each of the reference oils was reached. The base stocks were subjected to the same process as the reference oils. The Noack weight of the base stocks could be determined based on the results obtained from the reference oils.

[0339] The results of the tests are summarized in Table 5, together with results obtained from a conventional base stock (Yubase 4, a Group III base stock).

TABLE-US-00005 TABLE 5 DSC Noack Pour Oxidation volatility KV100 KV40 Point Onset T (% by (cSt) (cSt) VI ( C.) ( C.) weight) GE3 3.9 16.0 143 42 202.89 2.4 Yubase 4 4.2 19.2 126 12 220.00 11.7

[0340] It can be seen that the Guerbet-derived base stock ether has a lower volatility, lower pour point and lower kinematic viscosity as compared to the conventional base oil, although the DSC oxidation onset temperature is lower in Guerbet-derived base stock than the conventional based oil.

Example 2

Properties of Lubricant Compositions Containing Ether Base Stocks

[0341] Guerbet-derived ether base stock GE3 was blended with conventional base oil additives (additive A, a commercially available additive package providing a dispersant level representative of high performance engine oil between 7 and 10 wt % based on the total weight of the lubricant composition; additive B, a cold-flow improver; additive C, an oxidation inhibitor; and additive D, a viscosity index improver) and conventional base oils (Yubase 4, a Group III base oil; and Yubase 6, a Group III base oil) to form a lubricant blend. A Baseline blend was also prepared. Yubase 4 was chosen as the main component of the Baseline blend, since it exhibits a similar KV100 to Guerbet-derived ether base stock, GE3. The Baseline blend was believed to be a stringent baseline for comparison, since it is a 5W-30 formulation which meets certain specifications (ACEA A5/B5, API-SN/GF-4). The details of the blended compositions are shown in Table 6 in % by weight.

TABLE-US-00006 TABLE 6 Baseline blend GE3 blend Additive A 16.4 16.4 Additive B 0.15 0.15 Additive C 0.1 0.1 Additive D 4 4 Yubase 4 67.45 17.45 Yubase 6 11.9 11.9 GE3 0 50

[0342] No problems with miscibility were encountered during preparation of the blended compositions.

[0343] The blended compositions were tested to see whether the advantageous properties of the base stocks would be reflected in a fully formulated lubricant composition. The following properties were tested:

[0344] Kinematic viscosity at 100 C. (KV100) and kinematic viscosity at 40 C. (KV40) were tested according to ASTM D445 (part of SAE J300).

[0345] Viscosity index (VI) was calculated according to ASTM D2270.

[0346] Cold-cranking simulator (CCS) analysis was carried out at 30 C. according to ASTM D5293 (part of SAE J300).

[0347] High temperature high shear (HTHS) analysis was carried out according to CEC-L-36-A-90.

[0348] Total base number (TBN) was determined according to ASTM D2896.

[0349] Noack volatility was tested according to CEC-L-40-A-93.

[0350] Sulphated ash content was measured according to IP 163.

[0351] The results of the tests are summarized in Table 7.

TABLE-US-00007 TABLE 7 Baseline blend GE3 blend KV40 (cSt) 53.59 44.63 KV100 (cSt) 9.542 8.688 VI 164 177 CCS 30 C. (cP) 4656 2702 HTHS (cP) 2.98 2.75 TBN (mg KOH/g) 11.66 11.44 NOACK (% by weight) 11.2 9.7 Sulphated ash (%) 1.22 1.27

[0352] It can be seen that the properties of the Guerbet-derived base stock are also exhibited in the blended composition. In particular, beneficial viscosity, volatility and cold-flow properties are observed. The Guerbet-derived base stock also exhibited similar HTHS measurements, TBNs and sulphated ash contents to the Baseline blend.

Example 3

Komatsu Hot-Tube (KHT) Test

[0353] Fully formulated compositions comprising Guerbet-derived base stock (GE3) and/or a Group III base stock (Yubase 4) together with varying amounts of a molybdenum-sulfur compound and/or a polymethacrylate compound (a comb-type copolymer of alkyl methacrylates in solutionapproximately 1:1 dilution ratio) as well as additional lubricant additives including (non-borated) dispersant, ZDDP, detergents, antioxidants and viscosity modifier (VM) were subjected to the KHT test in accordance with JPI-5S-55-99 and SAE Technical Paper 840262. Results obtained from the KHT testing in the form of deposit merits are shown in Table 8 (compositional data shown in % by weight).

TABLE-US-00008 TABLE 8 Lubricant Composition 1 2 3 4 5 6 Yubase 4 83.683 33.683 81.925 31.925 83.685 33.685 GE3 ether 50 50 50 Phenolic AO 0.5 0.5 0.5 0.5 0.5 0.5 Aminic AO 0.1 0.1 0.1 0.1 0.1 0.1 Detergents 2.18 2.18 2.18 2.18 2.18 2.18 Dispersant 6 6 6 6 6 6 ZDDP 0.535 0.535 0.535 0.535 0.535 0.535 VM 7 7 7 7 Antifoam 0.002 0.002 PMA 7 7 MoS 1.76 1.76 compound Mo (elemental, 0.08 0.08 wt. %) KHT 3 7.5 6.5 6.5 6.5 7.5 rating

[0354] According to the results of the KHT testing, the ether containing lubricant composition 2 exhibits a significantly higher KHT merit rating (7.5) compared to that of the non-ether containing lubricant composition 1. These results indicate that the presence of the ether confers a benefit in reducing high temperature induced deposit formation which would otherwise lead to scuffing. In addition, the ether-containing lubricant composition 4, containing an amount of 0.08 wt. % of molybdenum, exhibits the same KHT deposit merit rating (6.5) as the corresponding non-ether containing composition 3. This is particularly advantageous since the ether composition exhibits a lower viscosity profile than the non-ether composition and yet exhibits equivalent high temperature stability. This means that a benefit may be seen in terms of fuel economy through the use of the ether composition of the invention over a conventional non-ether containing composition without any accompanying increase in turbocharger deposits and piston scuffing. As discussed in more detail below, the results in the TEOST 33C testing also demonstrate that the presence of molybdenum impacts deposit formation in ether-containing compositions to no more of a degree than the non-ether containing compositions despite the DSC oxidation onset temperature of the ether base stock being lower than that of the conventional Group III base stock as demonstrated in Example 1.

[0355] The results of the KHT testing also demonstrate a significant advantage in the presence of the at least one polymethacrylate compound, particular in the case of the ether-containing compositions. For instance, the ether-containing lubricant composition 6 also containing a polymethacrylate compound exhibits a substantially higher deposit merit rating (7.5) in the KHT test compared to the non-ether containing composition 5. Thus, when the at least one polymethacrylate compound is present, the ether composition is able to out-perform the corresponding non-ether composition in terms of high temperature stability. This is of particular benefit since the ether composition exhibits a lower viscosity profile than the non-ether composition and so the present invention is able to benefit from increased fuel economy without increasing deposits in hot regions of the engine, such as in turbochargers, or causing piston scuffing which would otherwise shorten engine lifetime.

Example 4

TEOST 33C Test

[0356] Fully formulated compositions comprising Guerbet-derived base stock (GE3) and/or a Group III base stock (Yubase 4) together with varying amounts of a molybdenum-sulfur compound and/or a polymethacrylate (a comb-type copolymer of alkyl methacrylates in solutionapproximately 1:1 dilution ratio) as well as additional lubricant additives including (non-borated) dispersant, ZDDP, detergents, antioxidants and viscosity index modifier (VIM) were subjected to the TEOST 33C test in accordance with standard method ASTM D6335. Results obtained from the TEOST 33C testing in the form of total deposits (in turbochargers) are shown in Table 9 (compositional data shown in % by weight).

TABLE-US-00009 TABLE 9 Lubricant Composition A B C D E F G H I J K Yubase 4 83.593 89.273 87.793 84.193 84.873 86.533 85.823 83.783 82.993 33.87 32.99 GE3 ether 50 50 Phenolic AO 0.5 0 0 0 0 0 0 0.5 0.5 0.5 0.5 Aminic AO 0.2 0.1 0.5 0.1 0.5 0.3 1 1 1 1 1 Sulphonate (400BN) 0.86 0.43 0.86 0.86 0.43 0.64 0.65 0.43 0.43 0.43 0.43 Sulphonate (neutral) 0.34 0.17 0.34 0.34 0.17 0.26 0.26 0.17 0.17 0.17 0.17 Phenate (150BN) 0.97 0.49 0.97 0.97 0.49 0.73 0.73 0.49 0.49 0.49 0.49 Dispersant 6 2 2 6 6 4 4 6 6 6 6 ZDDP 0.535 0.535 0.535 0.535 0.535 0.535 0.535 0.535 0.535 0.535 0.535 VIM 7 7 7 7 7 7 7 Antifoam 0.002 0.002 0.002 0.002 0.002 0.002 0.002 0.002 0.002 0.002 0.002 PMA 7 7 7 7 MoS compound 0.88 0.88 Mo (elemental, wt. %) 0.04 0.04 Total deposits (mg) 17.3 14.2 15.5 7.4 18.2 12.9 15.7 36.6 49.3 33.8 47.4 TEOST 33C
The results of the TEOST 33C generally demonstrate the benefit of increasing dispersant and detergent levels while decreasing antioxidant levels, particularly aminic antioxidant, for reducing deposit formation in turbochargers in non-ether containing compositions, in line with expectations (for instance, compare results for compositions F and G or compare composition D with A-C and E to G). In addition, the results demonstrate that the presence of the at least one polymethacrylate compound, alone or also in combination with the at least one molybdenum compound, is tolerated better by the ether composition than the corresponding non-ether composition (compare results of compositions H and J as well as I and K) in the TEOST 33C test. This is surprising when the DSC oxidation onset stability of the ether base stock is lower than that of the conventional Group III base stock as demonstrated in Example 1 (on the basis of which poorer TEOST 33C performance would be expected). This is particularly advantageous since the ether composition exhibits a lower viscosity profile than the corresponding non-ether composition whilst exhibiting greater high temperature stability in the TEOST 33C test than the corresponding non-ether composition. This means that a benefit may be seen in terms of fuel economy through the use of the ether composition of the invention in comparison to a conventional Group III base oil composition containing no ether base stock, yet without any accompanying increase in turbocharger deposits and piston scuffing.

Example 5

Hot Liquid Process Simulator (HLPS) Testing

[0357] Blended compositions comprising Guerbet-derived base stock (GE3) and/or a

[0358] Group III base stock (Yubase 4) together with varying amounts of sulphonate (400BN), neutral sulphonate, and phenate (150BN) detergents were subjected to HLPS testing. The HLPS testing corresponds to a hot-tube test in which all oil compositions were subjected to the same heating stress, for the same period of time. HLPS testing is used as a means for characterising the propensity of an oil to create deposits in a hotregion of the engine by simulating pressurized oil lines. Results of the HLPS testing in the form of Maximum Deposit Thickness (MDT) (nm), which corresponds to the maximum thickness of deposit measured along the HLPS tube, and total deposit volume (cm.sup.310.sup.17) are provided in Table 10 (compositional data shown in % by weight).

TABLE-US-00010 TABLE 10 Lubricant Composition a b c d e f g h i j k l Yubase 4 100 99.35 97.9 98.57 99.14 99.403 50 49.35 47.9 48.57 49.14 49.403 GE3 ether 50 50 50 50 50 50 Sulphonate (400BN) 0.65 1.43 0.65 1.43 Sulphonate (neutral) 0.86 0.86 Phenate 2.1 0.597 2.1 0.597 HLPS deposit vol. 4.08 5.97 6.76 No result 5.13 2.95 4.28 3.90 2.73 3.98 3.86 3.42 (cm.sup.3, 10.sup.17) MDT nm 252 178 249 232 98 192 249 110 250 199 75

[0359] The results of the HLPS tests demonstrate that, for a given TBN value, the ether based compositions comprising a phenate detergent exhibit significantly lower deposit levels than the corresponding non-ether based compositions. The ether compositions comprising a typical level of neutral sulphonate also perform markedly better than the corresponding non-ether based compositions. The results shown in Table 10 are also shown in the graphs of FIGS. 1 and 2 which show Maximum Deposit Thickness and deposit volume for each of the compositions tested respectively. These data show the advantages that may be derived by employing particular detergents, for instance phenate or neutral sulphonate, in an ether-based lubricant composition for reducing the propensity for deposit formation. This means that other lubricant additives that are known to increase deposits, for example antioxidants, may be used at higher levels without resulting in unacceptable level of deposit formation.

[0360] The dimensions and values disclosed herein are not to be understood as being strictly limited to the exact numerical values recited. Instead, unless otherwise specified, each such dimension is intended to mean both the recited value and a functionally equivalent range surrounding that value. For example, a dimension disclosed as 40 mm is intended to mean about 40 mm.

[0361] Every document cited herein, including any cross referenced or related patent or application, is hereby incorporated herein by reference in its entirety unless expressly excluded or otherwise limited. The citation of any document is not an admission that it is prior art with respect to any invention disclosed or claimed herein or that it alone, or in any combination with any other reference or references, teaches, suggests or discloses any such invention. Further, to the extent that any meaning or definition of a term in this document conflicts with any meaning or definition of the same term in a document incorporated by reference, the meaning or definition assigned to that term in this document shall govern.

[0362] While particular embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope and spirit of this invention.