HK1195920A - Lubricating grease composition - Google Patents

Description

Grease composition

Technical Field

The present application relates generally to grease compositions for extreme pressure applications requiring extended lubrication intervals.

Background

In recent years, the heavy duty truck market has selected diesel engines as its preferred power source due to their excellent life and their operating economy. Recently, specifications for heavy duty diesel engines have shown that the interval between lubricant replacements is longer than has been customary in the past. Extended lubrication intervals (30,000 miles, 4.8x 10) for users of commercial vehicles, such as cross-country truck (cross-country truck)⁴km, or longer) means more on-the road time and greater return on investment and reduced maintenance costs.

Specialized lubricants have been developed that meet the more stringent performance requirements for heavy duty diesel engines as compared to passenger car engines. Grease is used in a variety of applications where high pressures exist, including wheel bearings, chassis, trailing arms, king pins, transfer cross-axle spring pins, shackle pins, brake camshafts, and fifth wheel panels (fifth wheel faceplates) and pivots that operate under high and low temperature conditions.

The extended lubrication intervals using currently available greases lead to driver complaints about heavy steering. Also, high wear is observed at the kingpin, shackle, and ball and knuckle joints. The cause of the high degree of wear in these areas appears to be due to salt corrosion. This salt corrosion produces deep corrosion marks on the metal surfaces as well as the lubricated pipes being plugged, thus accelerating wear due to lack of lubrication. Currently available greases do not provide the necessary degree of rust protection for long service intervals of lubricated components.

In addition, greases having poor water wash-off or water repellency reduce the life of the grease and increase wear on the lubricated surface. Grease that comes into contact with water often hardens and sometimes separates from the element to be lubricated. In the case of hardening, these greases cannot advance to the elements to be lubricated. Since the grease hardens and separates from the element to be lubricated, it no longer seals out water, dust or salts which can lead to abrasive wear and corrosion.

Another problem encountered with currently available greases is that they are not stable in operation. In other words, they do not stay in place on lubricated elements, thus leaving these elements without lubrication, and only allowing a short service interval before the grease has to be replenished. Currently used greases also tend to migrate under impact loading. Shock loading conditions may occur for the overall steering system, for example, when the wheels impact against bumps in the road. A sudden impact tends to push the lubricated elements together, squeezing the grease out from between them. On commercial vehicles, the point that is subject to impact loading is the fifth wheel. If hitting a sharp bump, shock loading may occur, causing the pivot point to subsequently pivot.

Greases that will meet the requirements of extended lubrication intervals for these vehicles must not only have the above characteristics, but must also have suitable high and low temperature properties. In other words, the grease should not soften and flow under the operating conditions encountered in warm climates, but should also exhibit good low temperature pumpability in colder climates.

As the need for higher performance is increasing, it would be desirable to provide greases that exhibit improved lubricating properties and in particular improved water protection and wear protection properties as well as increased grease life.

SUMMARY

In one aspect, applicants provide a grease composition comprising a major amount of a lubricating base oil; a lithium complex thickener; and a polar compound selected from the group consisting of rust inhibitors, nonionic surfactants, and mixtures thereof; wherein the concentration of the polar compound in the grease composition is no greater than 0.5 wt.%, based on the total weight of the grease composition.

In another aspect, applicants provide a method of making a grease composition comprising blending together: a major amount of a lubricating base oil; a lithium complex thickener; and a polar compound selected from the group consisting of rust inhibitors, nonionic surfactants, and mixtures thereof; wherein the concentration of the polar compound in the grease composition is no greater than 0.5 wt.%, based on the total weight of the grease composition.

In yet another aspect, the present invention provides a method comprising lubricating bearings, surfaces and other lubricated components with a grease composition comprising a major amount of a lubricating base oil; a lithium complex thickener; and a polar compound selected from the group consisting of rust inhibitors, nonionic surfactants, and mixtures thereof; wherein the concentration of the polar compound in the grease composition is no greater than 0.5 wt.%, based on the total weight of the grease composition.

Detailed Description

Oil of lubricating viscosity

The grease composition comprises a major amount of a lubricating base oil. As used herein, the term "major amount" refers to a concentration of base oil in the grease composition of at least about 50 weight percent. The amount of base oil in the grease composition is from 50 to 95 wt.%, typically from 55 to 90 wt.% and often from 60 to 85 wt.%, based on the total weight of the grease composition.

The base oil may be of mineral, synthetic, vegetable, animal origin, or a combination thereof. The base oil of mineral origin may be a mineral oil, such as produced by solvent refining or hydroprocessing. Base oils of synthetic origin may generally include C₁₀-C₅₀Mixtures of hydrocarbon polymers, ester polymers, ether polymers, and combinations thereof. Suitable examples of synthetic oils include polyolefins such as alpha-olefin oligomers and polybutenes; polyalkylene glycols such as polyethylene glycol and polypropylene glycol; diesters such as di-2-ethylhexyl sebacate, di-2-ethylhexyl adipate or the diesters disclosed in U.S. Pat. No. 7,871,967; triesters such as those disclosed in U.S. patent No. 7,544,645; polyol esters, such as trimethylolPropane esters and pentaerythritol esters; a perfluoroalkyl ether; a silicone oil; polyphenylene ether; either alone or as a mixed oil. The base oil may also comprise a fischer-tropsch derived base oil.

In one embodiment, the base oil is a mineral oil. Examples of suitable mineral oils include heavy neutral oils, bright stock oils, naphthenic oils, and mixtures thereof.

In one embodiment, the base oil is a blend having greater than 100m at 40 ℃²A high viscosity base oil of kinematic viscosity/s. In another embodiment, the base oils are a blend of different high viscosity base oils, wherein the different base oils all have greater than 100m at 40 ℃²Kinematic viscosity in/s.

In one embodiment, the base oil has a viscosity of 30m at 40 ℃²/s-600m²Kinematic viscosity in/s; in another embodiment, the base oil has 100m at 40 ℃²/s-300m²Kinematic viscosity in/s; and in yet another embodiment, the base oil has 175m at 40 ℃²/s-275m²Kinematic viscosity in/s.

Composite soap thickener

In addition to the base oil, the grease composition comprises a thickener system comprising C₁₂-C₂₄Lithium soaps of hydroxycarboxylic acids and C₂-C₁₂Lithium soaps of dicarboxylic acids.

Suitable C₁₂-C₂₄The hydroxycarboxylic acids may include 12-hydroxystearic acid, 12-hydroxyricinoleic acid, 12-hydroxybehenic acid, and 10-hydroxypalmitic acid. In one embodiment, said C₁₂-C₂₄The hydroxy fatty acid is 12-hydroxystearic acid.

Said C is₂-C₁₂The dicarboxylic acid may be C₄-C₁₂Or C₆-C₁₀An aliphatic dicarboxylic acid. Suitable C₂-C₁₂The dicarboxylic acid comprisesOxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, suberic acid, pimelic acid, azelaic acid, dodecanedioic acid, and sebacic acid. In one embodiment, azelaic acid or sebacic acid is used.

In one embodiment, the amount of lithium complex thickener in the grease composition is from 2 to 30 wt.%, from 5 to 20 wt.%, or from 10 to 15 wt.%, based on the total weight of the grease composition.

Polar compounds

The grease composition further comprises a polar compound selected from the group consisting of rust inhibitors, nonionic surfactants, and mixtures thereof. Rust inhibitors and nonionic surfactants can be highly polar compounds, and thus can exhibit strong affinity for water in the grease. By removing or reducing the content of at least one of these polar compounds from the formulation, the water resistance of the grease can be significantly improved. Improved water resistance can result in improved product adhesion.

Examples of rust inhibitors include stearic acid and other fatty acids; a dicarboxylic acid; a metal soap; fatty acid amine salts; metal salts of heavy sulfonic acids; a phosphorus ester; an amine phosphate; (lower) alkenyl succinic acids, their partial esters and their nitrogen-containing derivatives; synthetic alkaryl sulfonates (e.g., metal dinonyl naphthalene sulfonate); and the like and mixtures thereof.

Examples of the nonionic surfactant include polyoxyalkylene agents (e.g., polyoxyethylene lauryl ether, polyoxyethylene higher alcohol ether, polyoxyethylene nonylphenyl ether, polyoxyethylene octylphenyl ether, polyoxyethylene octylstearyl ether, polyoxyethylene oleyl ether, polyoxyethylene sorbitol monostearate, polyoxyethylene sorbitol monooleate, and polyethylene glycol monooleate), partial carboxylic acid esters of polyhydric alcohols (e.g., fatty acid glycerides, sorbitan fatty acid esters, pentaerythritol fatty acid esters), and the like, and mixtures thereof.

The nonionic surfactant can help the lithium complex thickener precursor dissolve, increasing the thickener formation rate. The applicant has found that the rate of formation of the lithium complex thickener in the grease composition is sufficient in the case where the amount of surfactant is not more than about 0.5 wt.%, or even in the absence of any surfactant.

The amount of the polar compound in the grease composition is not more than 0.5 wt.%, for example 0.01-0.5 wt.%, based on the total weight of the grease composition. In other embodiments, the amount of the polar compound in the grease composition ranges from 0.01 to 0.45 wt.%, based on the total weight of the grease composition; or in the range of 0.01 to 0.4 wt.%; or in the range of 0.01 to 0.35 wt.%; or in the range of 0.01 to 0.3 wt.%; or in the range of 0.01 to 0.25 wt.%; in the range of 0.01-0.2 wt%.

Extreme pressure agent

In one embodiment, the grease composition further comprises at least one extreme pressure agent.

Examples of extreme pressure agents include sulfurized animal or vegetable fats or oils; sulfurized animal or vegetable fatty acid esters; fully or partially esterified esters of phosphorous containing trivalent or pentavalent acids; a sulfurized olefin; a dihydrocarbyl polysulfide; sulfurized Diels-Alder reaction adducts (Diels-Alder adducts); a sulfurized dicyclopentadiene; sulfurized or co-sulfurized mixtures of fatty acid esters and monounsaturated olefins; a co-vulcanized blend of fatty acids, fatty acid esters, and alpha-olefins; dihydrocarbyl polysulfides substituted with functional groups; thial; a thiaketone; an episulfide compound; a sulfur-containing acetal derivative; co-sulfurized blends of terpenes and non-cyclic olefins and polysulfide olefin products; amine salts of phosphoric or thiophosphoric acid esters, and the like, and combinations thereof.

When used, the amount of the extreme pressure agent in the grease composition may be in the range of 0.25-5.0 wt.%, or in the range of 0.5-2.5 wt.%, based on the total weight of the grease composition.

Optional additives

Various other grease additives may be added to the grease composition in amounts sufficient to impart the desired effects (e.g., oxidation stability, tackiness, etc.). Suitable additives include fungicides and antibacterials; a colorant; a shear stability additive; anti-wear/anti-flux agents; flame retardants such as calcium oxide; an oily additive; preservatives such as alkali metal nitrites, for example sodium nitrite; oil barriers such as polybutene; suds suppressors such as alkyl methacrylate polymers and dimethyl siloxane polymers; oxidation inhibitors such as sterically hindered phenols or amines, for example phenyl-alpha-naphthylamine; metal deactivators such as bisalicylidene propylene diamine, triazole derivatives, thiadiazole derivatives, mercaptobenzimidazole; complex organic nitrogen and amine; a friction modifier; a thermally conductive additive; a conductive agent; an elastomer compatibilizer; viscosity modifiers such as polymethacrylate-type polymers, ethylene-propylene copolymers, styrene-isoprene copolymers, hydrated styrene-isoprene copolymers, polyisobutylene, and dispersant-type viscosity modifiers; pour point depressants such as polymethyl methacrylate; pleiotropic additives such as sulfurized oxymolybdenum dithiocarbamate, sulfurized oxymolybdenum dithiophosphate, oxymolybdenum monoglyceride, oxymolybdenum diethylamide, amine-molybdenum complexes, sulfur-containing molybdenum complexes, and the like. Solid materials such as graphite, finely divided molybdenum disulfide, talc, metal powders, and various polymers such as polyethylene wax may also be added to impart special properties.

Properties of

In one embodiment, the grease composition exhibits excellent water protection properties. In one sub-embodiment, the Water protection performance is determined according to ASTM D1264-11 ("Test Method for Determining the Water wash-off of a Grease of Lubricating Grease". The Grease composition has an average Grease wash-off (wash out) of less than 4.0 wt.% in one embodiment, and less than 3.5 wt.% in another embodiment. in another sub-embodiment, the Water protection performance is determined according to ASTM D4049-06 ("Standard Test Method for Determining the Water Spray-off of a Grease at 40 psi)," wherein the adhesion of metal to a surface of a Grease such as a metal surface at 38 kPa is evaluated when subjected to a Water Spray-off Test at 40 kPa "and the adhesion of metal to a surface of a Grease such as a metal surface at 38 kPa is evaluated The wagon wheels are subjected to water mist. In one embodiment, the grease composition has an average water mist removal rate (water spray off) of less than 20 wt.%, in another embodiment, the grease composition has an average water mist removal rate of less than 18 wt.%; and in yet another embodiment, the grease composition has an average water mist removal of less than 15 weight percent.

In one embodiment, the Grease composition exhibits excellent Extreme Pressure Properties as measured using ASTM D2596-10 ("Standard test Method for measuring Extreme Pressure Properties of greases (Four-Ball Method)"), in this test, the load bearing Properties of the Grease are evaluated the applied wear index (LWI) is a measure of the ability of a lubricant to prevent wear under the applied load, the greater this index, the better the potential load bearing Properties of the Grease, this test roughly estimates the impact loading resistance of components such as fifth wheels and chassis, in one embodiment, the Grease composition has an applied wear index value of at least 65, in another embodiment, the Grease composition has an applied wear index value of at least 70, in yet another embodiment, the grease composition has an applied wear index value of at least 75; in yet another embodiment, the grease composition has a loaded wear index value of at least 80.

In one embodiment, the grease composition exhibits excellent bearing life, i.e., is capable of operating longer at high temperatures/speeds than currently available extended service heavy duty greases. In one embodiment, the high temperature stability of a Grease in an Automotive Wheel Bearing and in an improved Automotive front Wheel axle roller-Bearing assembly is simulated (ASTM D3527-07 "Standard Test method for Life Performance of Automotive Wheel Bearing greases" which Grease composition has a Bearing Life of at least 150 hours; in another embodiment, the Grease composition has a Bearing Life of at least 175 hours; and in yet another embodiment, the Grease composition has a Bearing Life of at least 200 hours.

In one embodiment, the Grease composition exhibits excellent low Temperature Torque properties as measured according to ASTM D4693-07 ("Standard test Method for Low-Temperature Torque of Grease Lubricated axle Bearing". The test determines how well the test Grease retards rotation of a specially manufactured sprung automobile-type axle Bearing assembly when subjected to low temperatures. the Torque value calculated from the binding force determination is a measure of the viscous resistance of the grease.in this test, a lower Torque value corresponds to better performance of the Grease at low temperatures.in one embodiment, the Grease composition has a maximum Torque of 30N-m at-40 deg.C, in another embodiment, the Grease composition has a maximum Torque of 28N-m at-40 deg.C, in yet another embodiment, the grease composition has a maximum torque of 26N-m at-40 ℃.

Pumpability of The grease composition at low temperatures (-22 ° f) was evaluated using The Lincoln Central Lubrication System simulator (Lincoln ventometer) test method described in "lubricating Engineers Manual", third edition, Association for Iron & Steel Technology, pp 156-157, 2007. This test evaluates the ability of greases to flow through centralized lubrication systems at lower temperatures.

Example (b):the following examples are given to illustrate the invention. It should be understood, however, that the invention is not limited to the details and arrangement of the embodiments described.

Example 1

Various greases listed in table 1 were prepared and tested. Grease A, which exhibits good adhesion characteristics necessary to provide extended service intervals, has a viscosity of 383m²High base oil viscosity per second, resulting in poor low temperature pumpability. The inventive grease 1 is designed to a) improve water resistance by removing a nonionic surfactant that is commonly used for formulation of a lithium complex thickener and reducing the amount of a rust inhibitor and b) improve low-temperature workability by reducing viscosity of a base oil. Both greases were prepared from highly refined high viscosity mineral oil base oils.

TABLE 1

		Grease 1	Grease A
				Components
Mineral oil base oil (% by weight)		67.2	64.7
				Lithium composite thickener (% by weight)		12.1	13.7
Antirust agent (weight%)		0.2	1.0
				Nonionic surfactant (% by weight)		-	0.1
EP, antiwear agent and other additives (% by weight)		20.5	20.5
				Properties of	Test method
NLGI grade		2	2
				Viscosity of base oil at 40 ℃ (m 2/s)	ASTM D445	261	383
Dropping Point (. degree.C.)	ASTM D2265	233min	265
				Penetration rate	ASTM D217	275-295	280
Test of
				Water mist removal rate (% by weight)	ASTM D4049	13.2	28.1

As shown, inventive grease 1 has significantly improved water resistance and much lower base oil viscosity relative to grease a.

Example 2

Inventive grease 1 was then compared to a variety of commercial extended service heavy duty greases (grease B and grease C) in a number of standard performance tests. The results are shown in Table 2.

TABLE 2

Compared to other extended service heavy duty greases, inventive grease 1 exhibited superior water protection performance as demonstrated in water wash and mist removal tests; superior wear performance as demonstrated in the loaded wear index test; excellent long life performance as demonstrated in wheel bearing life tests; and comparable or better low temperature performance as demonstrated by the low temperature torque test and the low temperature pumpability test.

The term "comprising" is meant to include the elements or steps identified following that term, but not to exhaust all such elements or steps, and an embodiment may include other elements or steps. For the purposes of this specification and the claims which follow, unless otherwise indicated, it is to be understood that all numbers expressing quantities, percentages or proportions, and other numerical values used in the specification and claims which follow, are to be understood as being modified in all instances by the term "about". Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties to be obtained by the present invention. It should be noted that, as used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless expressly and unequivocally limited to one referent. As used herein, the term "comprise" and grammatical variations thereof are intended to be non-limiting such that recitation of items in a list is not to the exclusion of other like items that may be substituted or added to the list.

This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to make and use the invention. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other embodiments are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims. To the extent not inconsistent herewith, all citations mentioned herein are hereby incorporated by reference.

Claims (13)

1. A grease composition comprising:

a) a major amount of a lubricating base oil;

b) a lithium complex thickener; and

c) a polar compound selected from the group consisting of rust inhibitors, nonionic surfactants, and mixtures thereof;

wherein the concentration of the polar compound in the grease composition is no greater than 0.5 wt.%, based on the total weight of the grease composition.

2. The grease composition of claim 1, wherein the grease has an average grease wash out (wash out) of less than 4 wt.%, as determined by astm d 1264-11.

3. The grease composition of claim 1, wherein the grease has an average water mist removal (water spray off) of less than 20 weight percent as determined by astm d 4049-06.

4. The grease composition of claim 1, wherein the grease has an applied wear index value of at least 65 as determined by astm d 2596-10.

5. The grease composition of claim 1, wherein the grease has a bearing life of at least 150 hours as determined by astm d 3527-07.

6. The grease composition of claim 1, wherein the grease has a maximum torque of 30N-m at-40 ℃ as determined by astm d 4693-07.

7. Grease composition according to claim 1, wherein the base oil is a mineral oil selected from the group consisting of heavy neutral oil, bright stock oil, naphthenic base oil and mixtures thereof.

8. The grease composition of claim 1, wherein the base oil has a viscosity of 175m at 40 ℃²/s-275m²Kinematic viscosity in/s.

9. The grease composition according to claim 1, wherein the concentration of the polar compound in the grease composition is in the range of 0.01 to 0.25 wt.%, based on the total weight of the grease composition.

10. The grease composition according to claim 1, wherein the concentration of the lithium complex thickener in the grease composition is in the range of 2 to 30 wt.%, based on the total weight of the grease composition.

11. The grease composition of claim 1, further comprising at least one extreme pressure agent.

12. A method of making a grease composition comprising blending together:

a) a major amount of a lubricating base oil;

b) a lithium complex thickener; and

c) a polar compound selected from the group consisting of rust inhibitors, nonionic surfactants, and mixtures thereof;

wherein the concentration of the polar compound in the grease composition is no greater than 0.5 wt.%, based on the total weight of the grease composition.

13. A method of lubricating bearings, surfaces and other lubricated components comprising using a grease composition comprising:

a) a major amount of a lubricating base oil;

b) a lithium complex thickener; and

c) a polar compound selected from the group consisting of rust inhibitors, nonionic surfactants, and mixtures thereof;

wherein the concentration of the polar compound in the grease composition is no greater than 0.5 wt.%, based on the total weight of the grease composition.