Grease composition

Abstract

The invention provides a grease composition for bearings, the grease composition comprising: (i) a mineral-based oil comprising one or more of the ammonium salts of aliphatic carboxylic acids of formula (I) R1X-(R2)-NH3 + n (-OOCR3) wherein R1 is selected from C12 to C20 saturated or unsaturated, branched or linear hydrocarbyl groups; x is selected from NH, + NH2 and N-(R4)-NH3 +; r2 and R4 are independently selected from a C2 to C8 saturated or unsaturated, branched or linear hydrocarbyl group, and can be the same or different; r3 is selected from a C12 to C26 saturated or unsaturated, branched or linear hydrocarbyl group; and n is 1 or 2; and (ii) a simple lithium soap thickener.

Description

Technical Field

[0001] The present invention relates to a grease composition for extending the life of a bearing. Background Art

[0002] Bearings are used to support rotating shafts of wheels, gears, turbines, rotors, etc. in almost all industrial fields. In order to keep bearings running smoothly, they must be properly lubricated to reduce friction, minimize wear on moving parts, and help maintain low operating temperatures. Providing the right lubricant composition for bearings helps machines keep running optimally and prolongs their service life.

[0003] The lubrication of the bearing creates a barrier between the softer material of the bearing and the other parts of the machine. This keeps the bearing moving smoothly and prevents wear. However, over time, the bearing will inevitably wear out and need to be replaced. This requires taking the machine out of service while maintenance is performed. It is important to extend the service life of the bearing without the need for replacement or major maintenance.

[0004] Greases are almost universally considered first for lubricating ball and roller bearings due to their simple design, reduced sealing requirements and less maintenance requirements. Grease compositions mainly contain a base oil and a thickener, with suitable additives depending on the application and conditions of use.

[0005] Many greases are thickened with soaps, and these generally fall into two categories. So-called "simple" soaps are formed by the reaction of a metal hydroxide (usually lithium hydroxide) with a single fatty acid. To form a complex-thickened grease, the fatty acid is combined with a short-chain complexing acid. The acid mixture is then combined with a metal hydroxide to form a complex thickener. Similar to simple soaps, "complex" soaps generally require a single metal hydroxide, such as lithium hydroxide.

[0006] Lithium complex greases such as those disclosed in WO2020139333 and US2010298187 are known to have excellent performance and provide excellent service life when used to lubricate bearings. It is reported that the use of certain synthetic base oils and base oil blends can also provide greases that extend the expected life of bearings.

[0007] How to extend the life of bearings lubricated with simple lithium soap-based greases without using synthetic base oils remains a challenge. Summary of the invention

[0008] The present invention provides a grease composition for a bearing, the grease composition comprising:

[0009] (i) a mineral-based oil containing one or more of the ammonium salts of fatty carboxylates of formula (I):

[0010] R1 X-(R 2 )-NH3 + n( - OOCR 3 ) (I)

[0011] Where R 1 Selected from C 12 To C 20 Saturated or unsaturated, branched or straight chain hydrocarbon group; X is selected from NH, + NH2 and N-(R 4 )-NH3 + ; R 2 and R 4 R is independently selected from C2 to C8 saturated or unsaturated, branched or linear hydrocarbon groups, and can be the same or different; 3 Selected from C 12 To C 26 a saturated or unsaturated, branched or straight chain hydrocarbon group; and n is 1 or 2; and

[0012] (ii) simple lithium soap thickener,

[0013] The grease composition is prepared by a process comprising the steps of combining a mineral base oil with one or more ammonium salts of fatty carboxylates of formula (I), and then thickening the base oil fatty carboxylic acid ammonium salt mixture with a simple lithium soap thickener.

[0014] The present invention also provides a method for preparing a grease composition, the method comprising the following steps:

[0015] (i) combining a mineral base oil with one or more ammonium salts of fatty carboxylates of formula (I),

[0016] R 1 X-(R 2 )-NH3 + n( - OOCR 3 )(I)

[0017] Where R 1 Selected from C 12 To C 20 Saturated or unsaturated, branched or straight chain hydrocarbon group; X is selected from NH, + NH2 and N-(R 4 )-NH3 + , R 2 and R 4 R is independently selected from C2 to C8 saturated or unsaturated, branched or linear hydrocarbon groups, and can be the same or different; 3 Selected from C 12 To C 26saturated or unsaturated, branched or straight chain hydrocarbon groups; and n is 1 or 2 to form a base oil / fatty carboxylic acid ammonium salt mixture; and

[0018] (ii) thickening the base oil / ammonium salt of fatty carboxylic acid mixture with simple lithium soap.

[0019] The present invention also provides use of the grease composition of the present invention for extending the life of a bearing. DETAILED DESCRIPTION

[0020] The inventors have developed a grease composition which has been shown to significantly improve bearing life according to the FE09 bearing life test (DIN 51821). The grease of the invention is prepared by adding a carboxylic acid ammonium salt to a mineral base oil during the grease manufacturing process. The base oil is then thickened using a simple lithium soap. Advantageously, the grease composition of the invention requires only a simple mineral base oil and a simple lithium soap.

[0021] Base oil used herein is mineral base oil.Mineral base oil includes liquid petroleum and solvent treated or acid treated paraffin, cycloparaffin or mixed paraffin / cycloparaffin type mineral lubricating oil, which can be further refined by hydrofining process and / or dewaxing.According to the definition of American Petroleum Institute (API) category I, II and III, mineral base oil is Class I, Class II and / or Class III base oil.This type of API category is defined in API Publication 1509, 15th edition, Appendix E in April 2002.

[0022] Suitable base oils have a kinematic viscosity at 40°C in the range of 50 cSt to 250 cSt, preferably in the range of 70 cSt to 220 cSt, even more preferably in the range of 80 cSt to 120 cSt.

[0023] Typically, the amount of base oil (excluding the amount of ammonium salt of fatty carboxylic acid) in the grease composition of the present invention is at least 70% by weight, preferably at least 75% by weight, based on the total weight of the grease composition. Typically, the amount of base oil (excluding the amount of ammonium salt of fatty carboxylic acid) in the grease composition is at most 90% by weight, preferably at most 85% by weight, based on the total weight of the grease composition.

[0024] In the grease composition of the present invention, one or more ammonium salts of fatty carboxylates of formula (I)

[0025] R 1 X-(R 2 )-NH3 + n( - OOCR 3 )(I)

[0026] Combine with base oil.

[0027] R 1 Selected from C 12 To C 20 Saturated or unsaturated, branched or straight chain hydrocarbon group.

[0028] X is selected from NH, + NH2 and N-(R 4 )-NH3 + , where R 2 and R 4 Each is independently selected from a C2 to C8 saturated or unsaturated, branched or straight chain hydrocarbon group. 2 and R 4 Independently selected from (CH2) m , wherein m is selected from 2, 3 or 4. Most preferably R 2 and R 4 It is (CH2)3.

[0029] R 3 Selected from C 12 To C 26 Saturated or unsaturated, branched or straight chain hydrocarbon group. 3 Selected from C 16 To C 24 , even more preferably C 18 To C 24 Saturated or unsaturated, branched or straight chain hydrocarbon group.

[0030] In the grease composition used, the fatty acid carboxylic acid ammonium salt may be present as the original salt, or it may also be present as the corresponding amide (eg amide of the general formula (II)).

[0031] R 1 X-(R 2 )-NC(=O)R 3 (II)

[0032] That is, where, due to the conditions for preparing or using the grease, the parent amine R 1 X-(R 2 )-NH2 with the parent acid R 3 The COOH groups react with each other. In some embodiments, further intermolecular and intramolecular reactions may also occur. In practice, a mixture of fatty acid carboxylic acid ammonium salts, amides and any other reaction products is likely to be present in the grease composition.

[0033] In the process of the present invention, the base oil is combined with the fatty carboxylic acid ammonium salt. Typically, this can be done by melting the fatty acid carboxylic acid ammonium salt (if solid) and mixing it with the base oil. This must be done before thickening the base oil with a simple lithium soap.

[0034] Simple lithium soap thickeners are prepared by the reaction of lithium hydroxide with a fatty acid component. Examples of suitable fatty acid components for preparing simple lithium soap thickeners in grease compositions include hydrogenated castor oil (HCO), hydrogenated castor oil fatty acid (HCOFA), and combinations thereof, preferably hydrogenated castor oil fatty acid (HCOFA). Hydrogenated castor oil (HCO) is a triglyceride of 12-hydroxystearic acid. 12-Hydroxystearic acid is a preferred fatty acid for use herein.

[0035] Hydrogenated castor oil fatty acid (referred to herein as HCOFA) typically contains at least 85% by weight of 12-hydroxystearic acid based on the total weight of HCOFA. HCOFA may contain small amounts of additional components. Examples of additional components include palmitic acid (C 16 ), stearic acid (C 18 ), arachidic acid (C 20 ), 12-keto stearic acid, and combinations thereof. As used herein, the term "hydrogenated castor oil fatty acid" ("HCOFA") refers to a composition comprising an amount of 12-hydroxystearic acid, typically comprising at least 85% by weight of 12-hydroxystearic acid based on the total weight of HCOFA, preferably comprising an amount of 12-hydroxystearic acid in the range of 85% to 87% by weight based on the total weight of HCOFA.

[0036] The lithium hydroxide used to prepare the lithium soap is preferably present at a level in the range of 0.5 wt % to 3 wt %, more preferably in the range of 1 wt % to 3 wt %, based on the weight of the metal complex grease composition.

[0037] The total content of simple lithium soap thickener is preferably in the range of 5 to 15 wt %, more preferably in the range of 8 to 13 wt %, based on the total weight of the grease composition.

[0038] Any suitable method may be used to thicken greases with simple lithium soap thickeners.The typical method described herein for preparing lithium soap thickened greases is for illustrative purposes and is not intended to be limiting.

[0039] The slurry is prepared in a dedicated slurry tank. The specific method is to add solids (such as lithium hydroxide) and liquids (water, base oil, additives, etc.) together to prepare a dispersion or "suspension" and then transfer it to the autoclave. The slurry is mixed in a high shear mixer.

[0040] In the present invention, the base oil in the slurry already contains the fatty carboxylic acid ammonium salt.

[0041] After thorough mixing, the slurry is contacted with a fatty acid component to perform a saponification reaction. The saponification reaction is performed at a temperature of at least 80°C, preferably at least 100°C.

[0042] At least a portion of the water, preferably all of the water, is then removed from the product of the saponification reaction. The water is preferably removed by evaporation in a so-called "degassing step". The water is preferably removed by heating the product of the saponification reaction to a temperature of at least 100°C, more preferably at least 130°C, even more preferably at least 150°C.

[0043] The product is then subjected to a heating step wherein it is heated to a temperature of at least 190°C, preferably in the range of 190°C to 230°C, more preferably in the range of 195°C to 225°C, even more preferably in the range of 200°C to 220°C.

[0044] The product of the heating step is then subjected to a cooling step. The cooling step is preferably carried out in a grease kettle. Performance additives may be added to the grease composition. Preferably, such additives may be added to the grease kettle.

[0045] Various conventional grease additives may be incorporated into the grease composition of the present invention in amounts commonly used in this application to impart certain desirable characteristics to the grease, such as oxidation stability, viscosity, extreme pressure properties and corrosion inhibition.

[0046] Suitable additives include one or more extreme pressure / antiwear agents, for example zinc salts such as zinc dialkyl or diaryl dithiophosphates, borates, substituted thiadiazoles, polymeric nitrogen / phosphorus compounds prepared, for example, by reacting dialkoxyamines with substituted organic phosphates, phosphate amines, sulfurized whale oils of natural or synthetic origin, sulfurized lard oils, sulfurized esters, sulfurized fatty acid esters and similar sulfurized materials, organic phosphates (e.g., according to the formula (OR)3P=O (wherein R is an alkyl, aryl or aralkyl group) and triphenyl thiophosphate; one or more overbased metal-containing detergents such as alkyl Calcium or magnesium salicylate or calcium or magnesium alkylaryl sulfonate; one or more ashless dispersant additives, such as the reaction product of polyisobutenyl succinic anhydride with an amine or ester; one or more antioxidants, such as hindered phenols or amines, for example phenyl alpha-naphthylamine; one or more rust inhibitors; one or more friction modifiers; one or more viscosity index improvers; one or more pour point depressants; and one or more tackifiers. Solid materials such as graphite, finely divided molybdenum disulfide, talc, metal powders, calcium carbonate, and various polymers, such as polyethylene wax, may also be added to impart special properties.

[0047] The invention will now be further illustrated by reference to the following non-limiting examples.

[0048] Example

[0049] The present invention will now be explained in more detail using working examples and comparative examples, but the present invention is by no means limited to these examples. The raw materials used are as follows. If not explicitly stated, the amounts shown in the working examples and comparative examples are shown in Table 1 below. In addition, the amounts of raw materials disclosed in Table 1 (particularly the amounts of lithium hydroxide and fatty acids) are the amounts of reagents. Therefore, the actual amounts of the components in the composition are calculated based on the values ​​shown in Table 1 and the purity given below.

[0050] Thickener Raw Materials

[0051] Lithium hydroxide: Special grade, purity 56%

[0052] Hydrogenated castor oil (HCO): saponification value 180.5 mg / g KOH

[0053] Base oil A: Paraffinic mineral oil obtained by dewaxing and solvent refining, group 2 base oil, kinematic viscosity at 100°C is 11.74 mm 2 / s, viscosity index is 107

[0054] Base oil B: paraffinic mineral oil obtained by dewaxing and solvent refining, group 2 base oil, kinematic viscosity at 100°C is 31.56 mm 2 / s, viscosity index is 96

[0055] Base oil C: blend of base oil A and 5% m / m fatty carboxylic acid ammonium (I)

[0056] Additive A: Overbased calcium alkyl salicylate. Mineral oil content about 30%

[0057] Additive B: Alkylmercaptothiadiazole, mineral oil content 25.5%

[0058] Additive C: A sulfurized mixture of highly refined natural triglycerides and natural fatty acid esters

[0059] Additive D: Bismuth naphthenate, naphthenic acid, mineral oil content 29% to 31%

[0060] Additive E: 55% zinc naphthenate in naphthenic oil, 45% mineral oil

[0061] Additive F: Butylated / octylated diphenylamine

[0062] Working Example

[0063] Base oil C containing 5% of ammonium fatty carboxylate (I) is added to a grease preparation tank. Hydrogenated castor oil is added and the mixture is heated to 90°C to melt the contents of the container. Then, an appropriate amount of lithium hydroxide dispersed in water is added to the mixture. During further heating of the mixture, ester cleavage of the hydrogenated castor oil occurs, and the grease thickener is continuously formed while the lithium hydroxide and fatty acids undergo saponification reaction. The water is evaporated by continuous heating to 220°C while stirring vigorously. The mixture is cooled to below 100°C and then additives A to F are added to the base grease. After adding the additives, the grease is cooled to room temperature and a uniform grease is obtained after shearing the grease with a high-pressure homogenizer.

[0064] Comparative Example 1

[0065] Add base oil A to the grease preparation tank. Follow the procedure of the working example to obtain a homogeneous grease.

[0066] Comparative Example 2

[0067] Add base oil B to the grease preparation tank. Follow the procedure of the working example to obtain a homogeneous grease.

[0068] Comparative Example 3

[0069] Base Oil A was added to the grease preparation tank. A base grease was prepared according to the procedure described for the working examples. After saponification and heating to 220°C, the resulting base grease was cooled to below 100°C. Before adding additives A to F, ammonium fatty carboxylate (I) was added at a treat rate of 3.89% of the total formulation. The material was then sheared with a high pressure homogenizer to obtain a uniform grease.

[0070] Table 1

[0071]

[0072]

[0073] Test methods used: 1 ASTM D217; 2 IP369; 3 ASTM D4048;

[0074] 4 DIN51805; 5 ASTM D1831; 6 IP 121; 7 ASTM D6138; 8 ASTM D2596;

[0075] 9 ASTM D2266; 10 DIN 51821

[0076] Additional information and test data for the above examples are shown in Table 1. A homogeneous grease was obtained in all examples and the basic test data provided shows similar results for most of the properties evaluated. Only the working example using base oil C containing 5% of ammonium fatty carboxylate (I) showed significant improvements in roller stability according to ASTM D1831 and bearing life at 140°C according to DIN 51821. Compared to Comparative Example 1, the working example showed a 103% increase in bearing life based on the F50 value.

[0077] However, Comparative Example 3, in which the fatty ammonium carboxylate (I) was added near the end of the process in combination with the other additives A to F, did not show the same beneficial effect. Based on the F50 value of Comparative Example 1 without fatty ammonium carboxylate (I), the application pattern described for Comparative Example 3 instead shortened the bearing life by 79%.

Claims

1. A grease composition for a bearing, the grease composition comprising: (i) a mineral base oil containing one or more of the ammonium salts of fatty carboxylates of formula (I): R 1 X-(R 2 )-NH3 + n( - OOCR 3 )(HE) Where R 1 Selected from C 12 To C 20 Saturated or unsaturated, branched or straight chain hydrocarbon group; X is selected from NH, + NH2 and N-(R 4 )-NH3 + ; R 2 and R 4 R is independently selected from C2 to C8 saturated or unsaturated, branched or linear hydrocarbon groups, and can be the same or different; 3 Selected from C 12 To C 26 a saturated or unsaturated, branched or straight chain hydrocarbon group; and n is 1 or 2; and (ii) simple lithium soap thickener, The grease composition is prepared by a process comprising the steps of combining the mineral base oil with the one or more ammonium salts of fatty carboxylates of formula (I), and then thickening the base oil fatty carboxylic acid ammonium salt mixture with the simple lithium soap thickener.

2. The grease composition according to claim 1, wherein R 2 and R 4 Independently selected from (CH2) m , wherein m is selected from 2, 3 or 4.

3. The grease composition according to claim 1 or claim 2, wherein R 3 Selected from C 16 To C 24 Saturated or unsaturated, branched or straight chain hydrocarbon group.

4. The grease composition according to any one of claims 1 to 3, wherein the simple lithium soap thickener is prepared by the reaction of lithium hydroxide with a fatty acid component selected from hydrogenated castor oil (HCO), hydrogenated castor oil fatty acid (HCOFA) and combinations thereof.

5. The grease composition according to any one of claims 1 to 4, wherein the total content of the simple lithium soap thickener is in the range of 5 wt% to 15 wt%.

6. A method for preparing a grease composition, the method comprising the steps of: (i) combining a mineral base oil with one or more ammonium salts of fatty carboxylates of formula (I), R 1 X-(R 2 )-NH3 + n( - OOCR 3 )(HE) Where R 1 Selected from C 12 To C 20 Saturated or unsaturated, branched or straight chain hydrocarbon group; X is selected from NH, + NH2 and N-(R 4 )-NH3 + , R 2 and R 4 R is independently selected from C2 to C8 saturated or unsaturated, branched or linear hydrocarbon groups, and can be the same or different; 3 Selected from C 12 To C 26 a saturated or unsaturated, branched or straight chain hydrocarbon group; and n is 1 or 2; and (ii) thickening the base oil fatty carboxylic acid ammonium salt mixture with simple lithium soap.

7. The method of claim 6, wherein the simple lithium soap thickener is prepared by the reaction of lithium hydroxide with a fatty acid component selected from the group consisting of hydrogenated castor oil (HCO), hydrogenated castor oil fatty acid (HCOFA), and combinations thereof.

8. The method according to claim 6 or claim 7, wherein R 2 and R 4 Independently selected from (CH2) m , wherein m is selected from 2, 3 or 4; and wherein R 3 Selected from C 16 To C 24 Saturated or unsaturated, branched or straight chain hydrocarbon group.

9. Use of the grease composition according to any one of claims 1 to 5 for extending the life of a bearing.

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