This invention relates to lubricant compositions having utility in numerous applications, including particularly in connection with gear, transmission and/or axle applications in the automotive and machinery industries. In preferred aspects, the present invention is directed to lubricant compositions having particular advantage as axle fluids and more particularly heavy duty axle fluids.

BACKGROUND OF THE INVENTION

An important function of lubricant compositions, and in particular gear and axle lubricant fluids, is to provide a high degree of reliability and durability in the service life of equipment in which it is installed. With the increasing costs of energy, particularly gasoline and diesel fuel, the ability of such lubricants to aid in the overall fuel economy of the vehicles in which they are used has become an increasingly important factor in the selection of gear and axle lubricants. Applicants have come to appreciate that by improving the axle efficiency, particularly in heavy duty applications such as Class 8 line haul trucks or vocational vehicles, the fuel efficiency of the vehicles can be improved.

Lubricating oils in general, and gear and axle lubricants in particular, frequently must satisfy a relatively large number of performance criteria to be commercially successful. For example, a commercially successful axle lubricant will frequently be required to possess a high degree of oxidative stability, compatibility, shear stability, corrosion avoidance or resistance, wear protection, shiftability, and extended drain. These properties represent a difficult to achieve set of performance criteria that is made all the more difficult to achieve if the added requirement of enhancing fuel efficiency is present. SUMMARY

Applicants have developed improved lubricant compositions, and in many embodiments lubricant compositions that satisfy at a relatively high level of performance many, and preferably all, of the criteria mentioned above. As used herein, the term "lubricant composition" is used in its broadest sense to include fluid compositions that are used in applications involving metal to metal contact of parts in which at least one function of the fluid is to inhibit or reduce friction between the parts. As such, the term "lubricant composition" as used herein includes gear oils, axle oils and the like.

Preferably the lubricant compositions of the present invention comprise: (a) basestock;(b) viscosity improver; and (c) at least one additive to inhibit and preferably substantially prevent one or more of wearing, scuffing, micropitting and combinations of these and other deleterious effects. In preferred embodiments, the lubricant compositions of the present invention comprise: (a) basestock comprising polyalphaolefin (hereinafter referred to as "PAO"), preferably relatively low viscosity PAO, and even more preferably a PAO having a viscosity of not greater than about 12 centistokes (cSt) and optionally an ester oil; (b) viscosity improver comprising at least one relatively high viscosity PAO-type viscosity improver, preferably having a viscosity of greater than about 40 centistokes (cSt), and even more preferably from about 40 to about 1000 cSt; and (c) a performance additive package comprising at least one additive effective to improve at least one property of the lubricant and/or the performance of the equipment in which the lubricant is to be used. In certain preferred embodiments the performance additive comprises at least one additive based on sulfur chemistry and at least one additive based on phosphorous chemistry. Applicants have found that preferred lubricant compositions of the present invention exhibit and/or produce one or more, and preferably all, of the following advantageous properties: reduction of viscous drag over the application temperature range; film thickness reduction; and churning loss reduction.

In preferred embodiments, the present lubricant compositions exhibit a horsepower (HP) loss reduction, as described and measured in connection with the examples hereof, of at least about 3%, more preferably at least about 4%, and even more preferably at least about 5%.

In preferred embodiments, the present lubricant compositions exhibit a sump temperature reduction, as described and measured in connection with the examples hereof, of at least about 2%, more preferably at least about 5%, and even more preferably at least about 7%.

The present invention provides also methods of making and using a fully formulated lubricant, including a fully formulated heavy duty axle fluid, and to axle, gear, transmission or drive systems containing such oils.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention is directed in one aspect to lubricant compositions comprising at least one base stock, at least one viscosity enhancer for the base stock, and at least one additive. In general, it is contemplated that these components of the present invention may be present compositions in widely varying amounts depending on the particular needs of each application, and all such variations are considered to be within the broad scope of the invention. Nevertheless, applicants have found that in certain preferred embodiments the present lubricant compositions are formulated according to the following preferred ranges of components, it being understood that all percentage values indicated in the following Table 1 are modified by the word "about:" TABLE 1

With respect to certain preferred embodiments, the base stock comprises at least one relatively low viscosity PAO and at least one adipate ester. While it is contemplated that a large range of relative concentrations of such components may be present, in general it is preferred that the base stock of the present invention comprise in certain embodiments a PAO:ester weight ratio of from about 0.5 to about 12:1, and more preferably of from about 0.5 to about 12:1. In certain embodiments it is also preferred that the viscosity improver comprise a high viscosity PAO (hereinafter HVPAO) and an additional additive selected from the group consisting of PIB (polyisobutylene), PMA (polymethacrylate), or OCP (olefin co-polymer), and combinations of two or more of these. While it is contemplated that a large range of relative concentrations of such components may be present, in general it is preferred that the viscosity enhancer of the present invention comprise in certain embodiments a additional additive:MN/PAO weight ratio of from about 0 to about 4: 1 , and more preferably of from about 0.2 to about 4: 1.

Applicants have found that in certain preferred embodiments the present lubricant compositions are formulated according to the following preferred ranges of components, it being understood that all percentage values indicated in the following Table 2 are modified by the word "about:" Although it is contemplated that the PAO used in connection with the base stock component of the present invention may vary widely in particular properties and/or structures, in certain embodiments the PAO component is a PAO having a viscosity of from about 4 to about 12 cSt. In preferred embodiments the PAO is selected from group consisting of PAOs having a viscosity of 4, 6, 8, 10, 12 or combinations of two or more of these. In certain preferred embodiments, the PAO used in connection with the base stock component of the present invention is comprised are oligimeric compounds having from 2 to about 3 units, preferably units of 1-decene.

Although it is also contemplated that the PAO used in connection with the viscosity enhancer component of the present invention may vary widely in particular properties and/or structures, in certain embodiments the PAO component of the viscosity enhancer comprises, and preferably in certain embodiments consists essentially of a PAO having a viscosity of from about 40 to about 1000 cSt, and even more preferably from about 40 to about 1000 cSt. In preferred embodiments the PAO component of the viscosity enhancer component is comprised of polymeric compounds having greater than about 50 units, more preferably having greater than from 75 units and even more preferably having greater than from 100 units, preferably units of 1-decene.

TABLE 2

Applicants believe that, in general, numerous particular compounds or combinations of compounds are available for use in connection with each of the ingredients as describe herein. With respect to the optional adipate ester, it is preferred in certain embodiments that the adipate ester comprises a decyl adipate, and even more particularly of one or more adipate esters selected from the group consisting of di-isodecyl adipate, di-isodecyl azelate, and di-tridecyl adipate. In certain preferred embodiments, the present lubricant compositions are formulated in accordance with Tables 3 or 4 below, it being understood that the amounts are weight percentages and the each value is understood to be preceded by the word "about:"

TABLE 3

Basestock ad i pate 5-20%

Basestock Low Viscosity PAO (4-12cSt) 20-60%

Thickener PAO 40-1000 5-40%

Thickener PIP, PMA or OCP 0-20%

Adpack GL-4 Gear Oil Package 5-15%

PPD PMA Polymer 0-2.0%

Defoamer Silicone based 0-2.0%

TABLE 4

Basestock di-isodecyl adipatee 5-20%

Basestock Low Viscosity PAO (6-8cSt) 10-40%

Thickener PAO 40-100 5-40%

Thickener PIP or OCP 0-20%

Adpack Angamol 6004J 5-15%

PPD PMA Polymer 0-1.0%

Defoamer Silicone based 0-1.0%

EXAMPLES

The following examples are provided for the purpose of illustrating the present invention but without limiting the scope thereof.

AVERAGE HORSEPOWER LOSS

COMPARATIVE EXAMPLES Cl - C5 and EXAMPLES 1 - 4

The average horsepower loss ("AHPL") is one measure that can be used to represent the performance of a lubricant composition, particularly an axle or gear oil, with respect to the fuel economy impact on the vehicle in which it will be used. In order to obtain information regarding the relative performance of certain preferred lubricants in accordance with the present invention, testing protocol is used in which a commercial axle is attached to a dynamometer which measures the input the output torque on the axle. This test is run for comparison purposes with several commercially available lubricants and also with two formulations in accordance with the preferred embodiments of the present invention. In order to help assess the relative performance of the different lubricant formulations, a commercially available product sold under the trade designation EMGARD 2986 is tested several times (identified with row headings CIA - CIF) in order to establish an average value for comparison purposes, which values are reported at the end of the table. The results of the test done in connection with the commercially available products are identified across the row headings CI C4 in the Table 5 below. The results of the tests performed in connection with four lubricant compositions of the present invention are reported across the row headings El E4.

TABLE 5

As can be seen from Table 5 above, the lubricant composition in accordance with the present invention labeled E2 exhibited a 5.4% relative improvement in energy efficiency compared to the average established for EMGARD 2896. The formulation designated as E2 in Table 5 above consisted essentially of (CAS # 770-1 1-11) di-isodecyl adipate (5%), PAO 8 (56.6%), PAO 100 (28%), Angamol 6004J (10%), Hitec 5739 (0.3%), E-9817U (0.1%), with all amounts being reported on the basis of weight percent. Also as can be seen from Table 5 above, the lubricant composition in accordance with the present invention labeled E3 exhibited a 3.7% relative improvement in energy efficiency compared to the average established for EMGARD 2896. The formulation designated as E3 in Table 5 above consisted essentially of (CAS # 770- 39-1) di-isodecyl adipate (5%), PAO 8 (56.6%), PAO 100 (13%), Indopol H-1500 SPA (13%), Angamol 6004J (10%), Hitec 5739 (0.3%), E-9817U (0.1%), with all amounts being reported on the basis of weight percent. And finally, the lubricant composition in accordance with the present invention labeled E4 exhibited a 4.3% relative improvement in energy efficiency compared to the average established for EMGARD 2896. The formulation designated as E4 in Table 5 consisted essentially of (CAS # 770-42-1) di-isodecyl adipate (5%), PAO 8 (51.6%), PAO 100 (33%), Angamol 6004J (10%), Hitec 5739 (0.3%), and E-9817U (0.1%), with all amounts being reported on the basis of weight percent.

PHYSICAL PROPERTIES

COMPARATIVE EXAMPLES Cl, C5, C6 and C7 and EXAMPLES 1 and 2

Several properties exist which, at least in certain applications, are considered relevant to the effectiveness of lubricant compositions. Tests are performed for the purpose of obtaining information regarding the relative performance of certain preferred lubricants in accordance with the present invention relative to several commercially available lubricants. The results of the test done for comparison purposes in connection with the commercially available products are identified under column headings Emgard 4209, Emgard 2986, Comp Q and Comp S in Table 6 attached hereto. The results of the tests performed in connection with two lubricant compositions of the present invention are based on the same formulation reported in Table 5 as El and E2, but labeled in Table 6 with row headings Cognis #2 and Cognis #3, respectively.

Based upon the results reported in Table 6, it is seen that the lubricant compositions in accordance with the present invention exhibit excellent shear stability and low temperature properties relative to leading commercially available axle lubricants.

CORROSION AND ANTI-WEAR PROPERTIES

COMPARATIVE EXAMPLES Cl, C5, C6 and C7 and EXAMPLES 1 and 2

Several properties exist which, at least in certain applications, are considered relevant to the anti-corrosion and anti-wear abilities of lubricant compositions. Several tests are performed for the purpose of obtaining information regarding the relative performance of certain preferred lubricants in accordance with the present invention relative to several commercially available lubricants. The results of the test done for comparison purposes in connection with the commercially available products are identified under column headings Emgard 4209, Emgard 2986, Comp Q and Comp S in Table 7 attached hereto. The results of the tests performed in connection with two lubricant compositions of the present invention are based on the same formulation reported in Table 5 as El and E2, but labeled in Table 7 with row headings Cognis #2 and Cognis #3, respectively. Based upon the results reported in Table 7, it is seen that the lubricant compositions in accordance with the present invention exhibit excellent corrosion resistance and wear resistance properties.

STABILITY

COMPARATIVE EXAMPLES CI, C5, C6 and C7 and EXAMPLES 1 and 2

Several properties exist which, at least in certain applications, are considered relevant to the stability of lubricant compositions in the environment of use. Several tests are performed for the purpose of obtaining information regarding the relative performance of certain preferred lubricants in accordance with the present invention relative to several commercially available lubricants. The results of the test done for comparison purposes in connection with the commercially available products are identified under column headings Emgard 4209, Emgard 2986, Comp Q and Comp S in the Table 8 attached hereto. The results of the tests performed in connection with two lubricant compositions of the present invention are based on the same formulation reported in Table 5 as El and E2, but labeled in Table 8 with row headings Cognis #2 and Cognis #3, respectively.

Based upon the results reported in Table 8, it is seen that the lubricant compositions in accordance with the present invention exhibit excellent stability.

SLUDGE CONTROL

COMPARATIVE EXAMPLES Cl, C5, C6 and C7 and EXAMPLES 1 and 2

Several properties exist which, at least in certain applications, are considered relevant to the ability of lubricant compositions to have a positive effect on the control of sludge creation and/or build up in the environment of use. Several tests are performed for the purpose of obtaining information regarding the relative performance of certain preferred lubricants in accordance with the present invention relative to several commercially available lubricants. The results of the test done for comparison purposes in connection with the commercially available products are identified under column headings Emgard 4209, Emgard 2986, Comp Q and Comp S in the Table 9, and associated pictures, attached hereto. The results of the tests performed in connection with two lubricant compositions of the present are based on the same formulation reported in Table 5 as El and E2, but labeled in Table 9 with row headings Cognis #2 and Cognis #3, respectively.

Based upon the results reported in Table 9, it is seen that the lubricant compositions in accordance with the present invention exhibit excellent sludge control.

WEAR CONTROL

COMPARATIVE EXAMPLES Cl, C5, C6 and C7 and EXAMPLES 1 and 2

Several properties exist which, at least in certain applications, are considered relevant to the ability of lubricant compositions to resist or reduce the rate of wear of the moving metal parts with which it is in contact in the environment of use. Several tests are performed for the purpose of obtaining information regarding the relative performance of certain preferred lubricants in accordance with the present invention relative to several commercially available lubricants. The results of the test done for comparison purposes in connection with the commercially available products are identified under column headings Emgard 4209, Emgard 2986, Comp Q and Comp S in the Table 10, attached hereto. The results of the tests performed in connection with two lubricant compositions of the present invention are based on the same formulation reported in Table 5 as El and E2, but labeled in Table 10 with row headings Cognis #2 and Cognis #3, respectively. Based upon the results reported in Table 10, it is seen that the lubricant compositions in accordance with the present invention exhibit excellent wear resistant properties. FRICTIONAL PROPERTIES COMPARATIVE EXAMPLES CI, C5, C6 and C7 and EXAMPLES 1 and 2

The frictional properties of a lubricant composition are in general considered to be highly relevant to the ability of lubricant compositions to exhibit superior performance in the environment of use. Several tests are performed for the purpose of obtaining information regarding the relative performance of certain preferred lubricants in accordance with the present invention relative to several commercially available lubricants. The results of the test done for comparison purposes in connection with the commercially available products are identified under column headings Emgard 4209, Emgard 2986, Comp Q and Comp S in the Table 1 1, attached hereto. The results of this test in accordance with the present invention are based on the same formulation reported in Table 5 as El and E2, but labeled in Table 1 1 with row headings Cognis #2 and Cognis #3, respectively

One method of testing the frictional properties of lubricant is to utilize a 19.05mm (3/4 inch) steel ball and 46 mm diameter steel desk. The ball is loaded against the face of the disc and the ball and the disc are driven independently to create a mixed rolling/sliding contact. The force between the ball and disk is measured by a force transducer. Additional sensors measure the applied load, the lubricant temperature and (optionally) electrical contact resistance between specimens and the relative wear between them. A schematic diagram of such a test apparatus is provided below.

Such an apparatus is used to test lubricant compositions in accordance with the present invention, using a film thickness of one to 1000 nm (+1-1 nm), speeds of 0.010 - 1.0 m/s, loads of 100 N, a slide/roll ratio (SSR) of 50%, contact pressures of approximately 3.0 to GPa, a temperature range of from 40 to 100 C, a power supply of from 100 to about 240 V, a total weight of 50 kg and dimensions (Wx HxD) of 50X50X30 cm. The results of this test indicate that lubricant compositions in accordance with preferred aspects of the present invention produced exceptional low friction coefficients relative to other commercially available lubricant compositions, as identified in the attached Table 1 1. TRACTION PROPERTIES

COMPARATIVE EXAMPLES Cl, C5, C6 and C7 and EXAMPLES 1 and 2 The traction properties of a fluid in many instances are relevant to the ability of lubricant compositions to exhibit superior performance in the environment of use. Several tests are performed for the purpose of obtaining information regarding the relative performance of certain preferred lubricants in accordance with the present invention relative to several commercially available lubricants. The results of the test done for comparison purposes in connection with the commercially available products are identified under column headings Emgard 4209, Emgard 2986, Comp Q and Comp S in the Table 12, attached hereto. The results of the tests performed in connection with two lubricant compositions of the present invention are based on the same formulation reported in Table 5 as El and E2, but labeled in Table 12 with row headings Cognis #2 and Cognis #3, respectively.

One method of testing the traction properties of a lubricant composition is to measure the thickness and traction properties of elastohydrodynamic lubricant (EHL) films utilizing an apparatus to having at least one bowl or roller loaded against the internal diameter of a transparent ring having a larger radius then the bowl or roller. The lubricant to be tested is placed between the rotating roller and arraying thereby forming an EHL film where the ball and arraying contact. Roller and arraying rotating speeds are controlled to obtain different amounts of relative sliding motion between the respective surfaces. Contact between the surfaces and the resultant film are observed by way of a transparent ring which allows optical measurements of lubricating film thickness. Traction forces generated during contact are also measured. A schematic diagram of such a test apparatus is provided below.

layer

Such an apparatus is used to test lubricant compositions in accordance with the present invention, using a film thickness of one to 1000 nm (+/-1 nm), speeds of 0.010 - 3.5 m/s, loads of 1 to 50 N, a slide/roll ratio (SSR) of 50%, contact pressures of approximately 3.0 to GPa, a temperature range of from 40 to 100 C, a power supply of from 100 to about 240 V, a total weight of 50 kg and dimensions (Wx HxD) of 50X50X30 cm. The results of this test indicate that lubricant compositions in accordance with preferred aspects of the present invention produced acceptable film thicknesses, especially at temperatures of 40 C, relative to other commercially available lubricant compositions, as identified in the attached Table 12.

SEAL COMPATIBILITY

COMPARATIVE EXAMPLES CI, C5, C6 and C7 and EXAMPLES 1 and 2

One property of lubricant compositions which is considered to be important in at least in certain applications is the compatibility of the lubricant with nonmetal parts in the system and environment of use, especially including seals, gaskets and the like. Several tests are performed for the purpose of obtaining information regarding the relative performance of certain preferred lubricants in accordance with the present invention relative to several commercially available lubricants in connection with seal compatibility. The results of the test done for comparison purposes in connection with the commercially available products are identified under column headings Emgard 4209, Emgard 2986, Comp Q and Comp S in Table 13 and the associated graph attached hereto. The results of the tests performed in connection with two lubricant compositions of the present invention are based on the same formulation reported in Table 5 as El and E2, but labeled in Table 13 with row headings Cognis #2 and Cognis #3, respectively.

Based upon the results reported in Tables 13 and the associated graph, it is seen that the lubricant compositions in accordance with the present invention exhibit or would be expected to exhibit excellent compatibility with the seals, gaskets and the light used in connection with the systems and devices in which the present lubricant compositions are intended to be included. TABLE 6 - PHYSICAL PROPERTIES

TABLE 7 - CORROSION AND ANTI- WEAR PROPERTIES

TABLE 8 - STABILITY PROPERTIES

TABLE 9 - SLUDGE CONTROL PROPERTIES

COGNIS 2 COMPS COMPQ

TABLE 10 - WEAR CONTROL

TABLE 11 - FRICTIONAL PROPERTIES

Emgard 4209 Emgard 2986 Cognis #2 Cognis #3 CompQ CompS

TABLE 12 - TRACTION PROPERTIES

0 070

D Traction Coefficient (20 mm/s) @40 D Traction Coefficient (200 mm/s) @40

0 060 DTraction Coefficient (1000 mm/s) @40

0 050

0 040

0 030 κ>

0 020

0 010

0 000

Emgard 4209 Emgard 2986 Cognis #2 Cognis #3 Comp Q Comp S

TABLE 13 - SEAL COMPATIBILITY

Emgard Emgard Cognis Cognis Comp Q Comp S 4209 2986 #2 #3

Thickness @ 40 (1.133 m/s), nm 419 480 380 419 441 435 Thickness @ 100 (1.133 m/s), nm 105 103 111 100 103 122 κ 4->

Emgard 4209 Emgard 2986 Cognis #2 Cognis #3 Comp Q Comp S