Ether-Based Lubricant Compositions, Methods and Uses

Abstract

The present invention provides a lubricant composition 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 different; the lubricant composition further comprising from 0.5 to 7% of total dispersant additive, by weight of the lubricant composition. In some embodiments, the ether base stock has the formula (1) where: R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.5 and R.sub.6 are as defined herein. 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 of an engine and/or a vehicle, such as an automotive vehicle associated with an internal combustion engine.

##STR00001##

Claims

1. A lubricant composition comprising a base oil of lubricating viscosity, wherein the base oil comprises an ether base stock of formula (A): ##STR00067## where: R.sub.a and R.sub.b are aliphatic hydrocarbyl groups and may be the same or different; the lubricant composition further comprising from 0.5 to 7% of total dispersant additive, by weight of the lubricant composition.

2. The lubricant composition of claim 1, wherein at least one of R.sub.a and R.sub.b is branched-chain alkyl, alkoxy-substituted-alkyl or cycloalkyl-substituted-alkyl.

3. The lubricant composition of claim 2, wherein R.sub.a and R.sub.b are independently selected from alkyl, alkoxy-substituted-alkyl and cycloalkyl-substituted-alkyl, provided that where 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.

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

5. 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.

6. The lubricant composition of claim 1, wherein the ether base stock is of formula (1): ##STR00068## 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 ##STR00069## 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.

7. The lubricant composition of claim 6, 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.

8. The lubricant composition of claim 6, wherein m and n are 0, 1 or 2.

9. The lubricant composition of claim 6, wherein the ether base stock has the formula (4): ##STR00070## where: R.sub.1 and R.sub.4 are alkyl; R.sub.3 and R.sub.5 are H or alkyl.

10. The lubricant composition of claim 6, wherein the ether base stock has the formula (7): ##STR00071## 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.

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

12. 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.

13. 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.

14. The lubricant composition of claim 13, 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.

15. 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.

16. 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; a fuel economy performance on a CEC-L-054-96 test of at least 2.5%; and a piston cleanliness performance on a CEC-L-088-02 test indicated by an overall piston merit of at least 8.5.

17. The lubricant composition of claim 1, wherein the total amount of dispersant additive present in the lubricant composition is from 1.0 to 7.0% by weight of the lubricant composition.

18. The lubricant composition of claim 1, wherein the dispersant additive is selected from oil soluble salts, esters, amino-esters, amides, imides and oxazolines of long chain hydrocarbon-substituted mono- and polycarboxylic acids or anhydrides thereof; thiocarboxylate derivatives of long chain hydrocarbons; long chain aliphatic hydrocarbons containing polyamine moieties attached directly thereto; Mannich condensation products formed by condensing a long chain substituted phenol with formaldehyde and polyalkylene polyamine; and Koch reaction products.

19. The lubricant composition of claim 1, wherein the dispersant additive is selected from those having a molecular weight of from 500 to 15,000 g/mol.

20. The lubricant composition of claim 18, wherein the dispersant additive is selected from nitrogen-containing dispersants.

21. The lubricant composition of claim 1, wherein the amount of phosphorus contained in the lubricant composition is less than 0.5 wt % based on the total weight of the lubricant composition.

22. 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 0.5 to 7% of total dispersant additive by weight of the lubricant composition, and optionally one or more additional lubricant additives in order to prepare the lubricant composition.

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

24. (canceled)

25. A method of improving the dispersancy properties and/or viscosity profile of a lubricant composition comprising the step of providing or supplying to the lubricant composition at least one of the ether base stocks defined in claim 1.

26. (canceled)

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

28. (canceled)

Description

[0299] The invention will now be described with reference to the accompanying figures and examples, which are not limiting in nature, in which:

[0300] FIG. 1 is a graph of absolute viscosity increase at 100 C. and 5% soot for blended compositions containing Guerbet-derived base stock (GE3) and a Baseline composition;

[0301] FIG. 2 is a graph of kinematic viscosity at 100 C. against soot loading percentage for a blend containing Guerbet-derived base stock and a Baseline composition;

[0302] FIG. 3 is a graph showing engine sludge and varnish merits achieved in a Sequence VG Engine test of blended compositions containing Guerbet-derived base stock (GE3) and a Baseline composition; and

[0303] FIG. 4 is a graph of central spot area of total (%) against dispersant concentration (%) relating to a Soot Blotter Test performed for compositions of the invention and non-ether based lubricant compositions.

EXAMPLES

Example 1Properties of Ether Base Stocks

[0304] 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 [00066]

[0305] The following properties of the base stock were tested:

[0306] Kinematic viscosity at 100 C. (KV100) and kinematic viscosity at 40 C. (KV40) were tested according to ASTM D7279.

[0307] Viscosity index (VI) was calculated according to ASTM D2270.

[0308] Pour point was determined according to ASTM D7346.

[0309] 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.

[0310] 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.

[0311] 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 Oxidation volatility KV100 KV40 Pour Point Onset (% by (cSt) (cSt) VI ( C.) T ( 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

[0312] 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.

Example 2: Properties of Lubricant Compositions Containing Ether Base Stocks

[0313] 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

[0314] No problems with miscibility were encountered during preparation of the blended compositions.

[0315] 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:

[0316] Kinematic viscosity at 100 C. (KV100) and kinematic viscosity at 40 C. (KV40) were tested according to ASTM D445 (part of SAE J300).

[0317] Viscosity index (VI) was calculated according to ASTM D2270.

[0318] Cold-cranking simulator (CCS) analysis was carried out at 30 C. according to ASTM D5293 (part of SAE J300).

[0319] High temperature high shear (HTHS) analysis was carried out according to CEC-L-36-A-90.

[0320] Total base number (TBN) was determined according to ASTM D2896.

[0321] Noack volatility was tested according to CEC-L-40-A-93.

[0322] Sulphated ash content was measured according to IP 163.

[0323] 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

[0324] 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: DV-4 Soot Handling Test

[0325] The blended compositions from Example 2 were subjected to a DV-4 soot handling test in accordance with CEC-L-93-04 in order to determine the ability of the compositions to handle an increase in soot loading. Results for absolute viscosity increase at 100 C. and 5% soot, as well as kinematic viscosity increase at 100 C. with increasing soot level from 0 to 6%, obtained from the DV-4 testing are shown in Table 8. The pass limit for a particular sample is set in accordance with a reference oil RL223, tested shortly prior to the sample. As will be appreciated, experimental variation between reference runs may therefore influence the pass limit, so in order to ensure consistency over time, a passing limit is less than or equal to 60% of the KV100 viscosity increase of reference oil RL223 at 6% soot loading.

TABLE-US-00008 TABLE 8 Baseline blend GE3 blend Limits Absolute viscosity increase 9.72 3.83 8.6 at 100 C. and 5% soot (GE3) (mm.sup.2/s) 10.3 (baseline) Soot content/ .sup.0/9.39 .sup.0/8.53 Kinematic Viscosity at 100 C. (mm.sup.2/s) - 0 hours Soot content/ 1.07/9.96 1.12/9.29 Kinematic Viscosity at 100 C. (mm.sup.2/s) - 24 hours Soot content/ 2.19/10.55 2.63/9.93 Kinematic Viscosity at 100 C. (mm.sup.2/s) - 48 hours Soot content/ 3.31/12.03 3.59/10.84 Kinematic Viscosity at 100 C. (mm.sup.2/s) 72 hours Soot content/ 4.56/14.89 4.86/11.31 Kinematic Viscosity at 100 C. (mm.sup.2/s) - 96 hours Soot content/ 5.68/18.17 6.13/12.48 Kinematic Viscosity at 100 C. (mm.sup.2/s) - 120 hours

[0326] The lubricant composition containing the Guerbet-derived base stock passed all aspects of the DV-4 test.

[0327] A graph of the results from Table 8 of absolute viscosity increase at 100 C. and 5% soot for the blended compositions tested is shown in FIG. 1, illustrating the substantially lower viscosity increase observed with the blend containing Guerbet-derived base stock (GE3) as opposed to the Baseline composition.

[0328] Similarly, a graph of the results of kinematic viscosity at 100 C. against soot loading percentage from Table 8 is shown in FIG. 2 for the blend compositions, illustrating a substantially lower rate of viscosity increase in the blend containing Guerbet-derived base stock with increasing soot loading compared with the Baseline composition.

[0329] The graphs of FIGS. 1 and 2 demonstrate that a blend containing an ether base stock, preferably a Guerbet-derived base stock, is more resilient to viscosity increase when subjected to soot than a blend formulated with a conventional base stock.

Example 4: Sequence VG Engine Test

[0330] The blended compositions from Example 2 were subjected to a Sequence VG Engine Test according to ASTM D6593. This test method is used to evaluate an automotive engine oil's control of engine sludge and deposits under operating conditions deliberately selected to accelerate sludge and deposit formation. Cleanliness of the engine is measured via sludge and varnish merits, whereby a higher score demonstrates increased engine cleanliness. Results for the different blended compositions are provided in Table 9.

TABLE-US-00009 TABLE 9 Limits Baseline blend GE3 blend (ACEA A1) Final Average Engine Sludge 8.56 9.35 >7.8 (Merits) Final Rocker Cover Sludge 9.44 9.56 >8 (Merits) Final Average Piston Skirt 8.71 8.79 >7.5 Varnish (Merits) Final Average Engine 9.34 9.48 >8.9 Varnish (Merits)

[0331] The results of the Sequence VG Engine Test shown in Table 9, which are also illustrated in FIG. 3, demonstrate that the blended composition comprising the Guerbet-derived base stock provides superior performance in each aspect of the test, particularly in reducing average engine sludge formation, in comparison to the Baseline composition.

[0332] The results of the DV-4 soot handling test and Sequence VG Engine Test highlight the superior performance of the blended composition comprising the Guerbet-derived base stock in comparison to the Baseline composition. In particular, it has been consistently shown that the blended composition comprising the Guerbet-derived base stock exhibits substantially lower viscosity increases in response to increasing levels of soot and performs better in preventing engine sludge formation in comparison with a Baseline composition comprising the same conventional amount of dispersant.

[0333] It therefore follows that blended compositions comprising ether base stocks in accordance with the present invention will exhibit the same or improved performance even where a lower amount of dispersant is contained in the formulation compared to conventional blended compositions, such as the blended Baseline composition utilized in the above examples. Using lower than conventional amounts of dispersant in a lubricant composition is particularly advantageous as it avoids viscosity increases associated with the presence of dispersants which compromises fuel economy. Thus, the same or better fuel economy in an engine is achievable with the lubricant compositions of the invention compared to lubricant compositions comprising conventional base stocks employing greater amounts of dispersant.

[0334] The effects of using lower dispersant amounts in the lubricating compositions in accordance with the invention are further illustrated in the below example.

Example 5: Soot Blotter Test

[0335] Blended compositions comprising Guerbet-derived base stock (GE3) or a Group III base stock (Yubase 4) together with varying amounts of the same dispersant (PIBSA-PAM) were subjected to a Soot Blotter Test according to the following method: [0336] 1. Weigh out 1 g of a standard marine heavy fuel oil (HFO). [0337] 2. Add 99 g of candidate lubricant composition to the 1 g of HFO. [0338] 3. Shear the HFO/lubricant mix at 3400 rpm in a Silverson stirrer for 120 seconds. [0339] 4. Place the sheared oil/HFO mixture into an oven at 60 C. and leave for 24 hours. [0340] 5. Remove oil from oven and spot samples of HFO/lubricant mix on to filter paper. [0341] 6. Place filter paper into the oven at 60 C. for 60 minutes. [0342] 7. Remove filter paper from the oven and measure average diameter of central dark spot and average diameter of the whole spot based on four measurements. [0343] 8. Calculate percentage area of central spot based on total average area of the whole spot, calculated based on the average diameters measured in step 7. [0344] 9. Percentage calculated in step 8 corresponds to the degree of dispersancy.

[0345] HFO contains a significant proportion of asphaltenes and therefore the Soot Blotter Test effectively tests the ability of the candidate lubricant composition to disperse and hold asphaltenes in the oil phase; higher percentages determined in the Soot Blotter Test mean that the asphaltene is better dispersed within the oil phase, indicating that soot and sludge will be better dispersed in the oil in use. Results for the Soot Blotter Test for different compositions comprising different concentrations of dispersant are shown in Table 10.

TABLE-US-00010 TABLE 10 Dispersant Central spot area Base stock concentration (%) of total (%) Yubase 4 0 44.5 1 50.0 2 50.8 4 53.5 6 57.3 GE3 0 50.5 1 53.3 2 55.8 4 60.5 6 60.7

[0346] The results of the Soot Blotter Test shown in Table 10 demonstrate that the blended composition comprising the Guerbet-derived base stock provides superior performance in each aspect of the test, particularly in reducing average engine sludge formation, in comparison to the Baseline composition. These results are also provided in a graph shown in FIG. 4 showing central spot area of total (%) against dispersant concentration (%) which further illustrates the improvement in soot and sludge handling properties of the compositions of the invention in comparison to conventional non-ether based lubricant compositions. For example, it will be appreciated that a composition according to the invention comprising 4% dispersant provides better dispersancy than the Yubase 4 lubricant composition comprising 6% dispersant. Similarly, a composition according to the invention comprising 2% dispersant provides better dispersancy than the Yubase 4 lubricant composition comprising 6% dispersant. These results demonstrate that lubricant compositions comprising ether base-stocks according to the present invention allow for lower amounts of dispersant to used in the formulation whilst maintaining desirable soot and sludge handling properties.

[0347] 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.

[0348] 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.

[0349] 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.