Polyurea / calcium sulfonate complex grease composition for use in constant velocity joints

Abstract

This application relates to a polyurea / calcium sulfonate complex grease composition for use in constant velocity joints. The present invention discloses a lubricating grease having thixotropic properties and a method for preparing the same. The lubricating grease comprises a polyurea / high based calcium sulfonate complex thickener, colloidally dispersed calcium carbonate solid particles in the form of calcite, calcium borate or calcium borate complex, a calcium soap of a fatty acid having 12 to 24 carbon atoms, an organo-molybdenum compound, and an antioxidant. The above components are uniformly dispersed in an oil phase medium. The content of high based calcium sulfonate in the lubricating grease is less than 22% by weight.

Description

[Technical field]

[0001] This application generally relates to polyurea / calcium sulfonate complex grease compositions for use in constant velocity joints. A high performance thixotropic polyurea / overbased calcium sulfonate complex hybrid grease is provided, which comprises solid particles of colloidally dispersed calcium carbonate essentially in the form of calcite, a calcium soap of a fatty acid having 12 to 24 carbon atoms, calcium borate or calcium borate complex, an organo-molybdenum compound, and an oil vehicle. The grease of the present invention is provided with less than 22 wt. % overbased calcium sulfonate, with a lower concentration of overbased calcium sulfonate per hardness grade than available overbased calcium sulfonate complex greases, e.g., with a worked cone penetration of 295 or less. [Background technology]

[0002] Overbased calcium sulfonate compositions, such as corrosion-inhibiting, thixotropic greases, or grease-like compositions, are well known for use in a variety of demanding applications. Such greases or grease-like compositions can be used alone or in combination with other components and generally exhibit excellent extreme pressure and antiwear properties, high dropping points, mechanical stability, salt spray and water corrosion resistance, thermal stability at high temperatures, and other desirable properties.

[0003] Greases are rated or graded based on their worked penetration range. For purposes of this invention, cone penetration is measured by the ASTM penetration test (D217). Penetration is the depth (in tenths of a millimeter) to which a standard cone penetrates into the grease under specified conditions. A higher penetration value indicates a softer grease with a higher base oil content, since the cone penetrates deeper into the sample. For example, a grease sold under the designation Grade 0 has a penetration value of 355-385, one with a penetration range of 310-340 is designated Grade 1, and the most widely sold grease has a penetration value range of 265-295 and is designated Grade 2.

[0004] US Patent No. 6,919,301 discloses a grease composition containing a calcium sulfonate complex thickener and a second thickener component in a base oil. The composition of the grease with the second thickener is a polyurea thickener component and a complex metal soap. The calcium sulfonate complex used as a thickener in this invention contains calcium sulfonate as an essential component, and contains a calcium salt (calcium soap) selected from the group consisting of (a) calcium carbonate, (b) calcium dibehenate, calcium distearate, calcium dihydroxystearate, and other higher fatty acid calcium salts, (c) calcium acetate, and other lower fatty acid calcium salts, and (d) calcium borate. The polyurea used as the second thickener is diurea.

[0005] The calcium sulfonate complex in U.S. Patent No. 6,919,301 was synthesized in a base oil as follows. An overbased calcium sulfonate having a high base number was added to a dialkyl diphenyl ether, and the mixture was thoroughly stirred at 50°C. To this was added boric acid, acetic acid, behenic acid, stearic acid, water, and calcium hydroxide, and the mixture was heated to 80-95°C to evaporate and remove the water. Carbon dioxide was then introduced into the mixture to produce calcium carbonate. The resulting mixture was analyzed by an infrared spectrometer to obtain a peak at 882-886 cm. -1 The introduction of carbon dioxide was terminated when it was confirmed that calcium carbonate had stabilized at the peak of . Furthermore, diurea was synthesized in the base oil. The mixture obtained by the above operation was cooled to 60 ° C, and 4,4'-diphenylmethane diisocyanate was added to the mixture and completely dissolved. Then, cyclohexylamine and dialkyl diphenyl ether were added and stirred. Then, the mixture was held at 100 ° C for 60 minutes, and then the mixture was heated to 150 ° C to stop the diurea production reaction. Then, an amine antioxidant and a sulfonic acid-based rust inhibitor were added to the mixture, and the mixture was pulverized and degassed to obtain a grease composition.

[0006] The invention disclosed in U.S. Patent No. 6,919,301 relates to a grease composition having excellent heat resistance, water resistance, lubrication life, oxidation stability, and biodegradability. The invention relates to a rolling device preferably used in automobiles, railway vehicles, electric motors, iron-making machines, etc. However, in order for the grease composition to exhibit excellent performance in a high-speed, high-temperature environment, it is preferable that the thickener contains 25-75% by mass of polyurea and 75-25% by mass of a complex metal soap. The high polyurea content in this invention makes it difficult to ensure the excellent load-bearing, high-temperature performance, and excellent mechanical stability of the prepared grease without adding appropriate additives. Therefore, research has focused on reducing the total thickener content of the prepared polyurea / calcium sulfonate complex grease while maintaining excellent performance without a large amount of additives. There is ongoing interest in research on reducing the proportion of the second thickener polyurea to less than 5% by mass of the total thickener without reducing the grade of the grease and the required application properties used in rolling devices.

[0007] No. 4,560,489 discloses calcium borate modified overbased calcium sulfonate complex greases, broadly defined as the combination of (1) an overbased calcium sulfonate in an oil, particularly a mineral oil, containing fine particles of calcium carbonate in the form of calcite; (2) a product formed by the reaction of boric acid with a calcium compound (e.g., calcium hydroxide or calcium carbonate), possibly calcium borate, or mixed or some complex calcium borate, in the overall grease or grease composition; and (3) a product formed from calcium hydroxide / calcium carbonate and a soap-forming aliphatic monocarboxylic acid or fatty acid, preferably a soap-forming hydroxy fatty acid, such as 12-hydroxystearic acid. The greases of US Pat. No. 4,560,489 have excellent properties, but to obtain a worked penetration of 265-295, the grease must contain about 40-45% by weight of overbased calcium sulfonate. Overbased calcium sulfonate contents below 38% by weight result in relatively soft, generally undesirable greases.

[0008] In addition to the above, research has focused on reducing the ash content and cost in the preparation of these greases. Hence, there has been great interest in reducing the overbased calcium sulfonate content without downgrading the grease grade.

[0009] US Patent No. 5,308,514 discloses high performance overbased calcium sulfonate complex greases containing overbased calcium sulfonate, solid particles of colloidally dispersed calcium carbonate in the form of calcite, calcium borate, and calcium soap of fatty acid having 12 to 24 carbon atoms dispersed in an oily medium, similar to the grease components in US Patent No. 4,560,489, but with a lower concentration of overbased calcium sulfonate in each grade of grease. Although it provides greases with a fairly low concentration of overbased calcium sulfonate, it still requires 23 to 28 weight percent overbased calcium sulfonate to obtain a grease with a worked penetration of 265 to 295. Therefore, there is still a need for greases with a lower concentration of overbased calcium sulfonate. Polyurea greases are known to have a much lower ash content and better overall performance, but polyurea greases tend to have poorer mechanical stability. Polyurea composited with overbased calcium sulfonate is a good option to increase mechanical stability, reduce ash content and provide excellent overall performance without a large amount of extraneous additives.

[0010] U.S. Patent No. 6,037,314 describes a lubricating oil composition comprising (a) a base oil, (b) a urea thickener, and certain additives required to improve performance, namely, (c) at least one organo-molybdenum compound, and (d) at least one calcium salt selected from the group consisting of calcium salts of petroleum sulfonates, calcium salts of alkylaryl sulfonates, calcium salts of salicylates, calcium salts of phenates, calcium salts of oxidized waxes, overbased calcium salts of petroleum sulfonates, overbased calcium salts of alkylaryl sulfonates, overbased calcium salts of salicylates, overbased calcium salts of phenates, and overbased calcium salts of oxidized waxes, (e) a thiophosphate. These polyurea greases require additional additives to be suitable for lubrication applications for constant velocity joints.

[0011] US Patent 4,902,435 discloses a grease with a hybrid thickener system using both polyurea thickener and calcium soap thickener with an additive package containing tricalcium phosphate and calcium carbonate to improve performance. The calcium soap thickeners used in this specification are simple calcium soaps or calcium complex soaps, but they are not the calcium sulfonate complex soaps of US Patent 5,308,514 and US Patent 4,560,489, which are prepared from overbased calcium sulfonates in which amorphous calcium carbonate is converted to a form of calcite. Overbased calcium sulfonates are mentioned in US Patent 4,902,435 as a possible source of the calcium carbonate component of the additive package. A similar grease is disclosed in US Patent 5,084,193.

[0012] Overbased calcium sulfonate complex greases have excellent properties, but the ash content, due to the amount of calcium sulfonate, calcium soap, and other materials required, is too high for many applications. Polyurea greases are known that have much lower ash contents and many good performance properties, but they tend to have poorer mechanical stability. [Prior art documents] [Patent documents]

[0013] [Patent Document 1] U.S. Patent No. 6,919,301 [Patent Document 2] U.S. Patent No. 4,560,489 [Patent Document 3] U.S. Patent No. 5,308,514 [Patent Document 4] U.S. Patent No. 6,037,314 [Patent Document 5] U.S. Patent No. 4,902,435 [Patent Document 6] U.S. Patent No. 5,084,193 Summary of the Invention [Means for solving the problem]

[0014] It has been found that by replacing a portion of the overbased calcium sulfonate in overbased calcium sulfonate complex greases with polyurea thickeners, it is possible to form thixotropic high performance polyurea / overbased calcium sulfonate complex greases, all of which have the excellent performance and pumping characteristics of the overbased calcium sulfonate complex greases of U.S. Patent No. 5,308,514, but with significantly reduced ash content and significantly improved mechanical stability compared to polyurea greases.

[0015] The high performance thixotropic polyurea / overbased calcium sulfonate complex hybrid grease of the present invention comprises the following components (a)-(d): (a) base oil, (b) thickener, (c) organomolybdenum compound, and (d) antioxidant. For example, the high performance thixotropic polyurea / overbased calcium sulfonate complex hybrid grease of the present invention comprises, in addition to the polyurea / overbased calcium sulfonate complex thickener, solid fine particles of colloidally dispersed calcium carbonate in the form of calcite, calcium borate or a complex of calcium borate, and a calcium soap of a fatty acid having 12 to 24 carbon atoms, preferably a hydroxy fatty acid soap, uniformly dispersed in an oily medium, such as one or more non-volatile oils, such as a mixture of mineral oils and synthetic oils, mineral oils, synthetic oils, or other lubricating oils, and the grease comprises less than 22% by weight, typically not more than 20% by weight, of overbased calcium sulfonate. In a preferred embodiment, the grease has a worked penetration of 295 or less. The grease of the present invention contains less borate and calcium soap and has a lower ash content than the overbased calcium sulfonate complex hybrid greases of the art due to the replacement of a portion of the overbased calcium sulfonate with a polyurea thickener. The grease of the present invention also has excellent antiwear, load carrying, low / high temperature properties, and excellent grease leakage prevention performance.

[0016] For example, in one preferred embodiment, the present invention provides a Grade 2 grease, i.e., a grease having a worked penetration of 265-295, comprising less than 22 wt.% overbased calcium sulfonate and at least 70 wt.% oil, typically at least 75 wt.% or 80 wt.% non-volatile oil.

[0017] The greases of the present invention are made using variations of known methods. For example, one method includes heating a mixture of overbased calcium sulfonate containing amorphous calcium carbonate, water, a converting agent containing a fatty acid, preferably a hydroxy fatty acid having 12 to 24 carbon atoms, at least a portion of which can form calcium soaps, alkylbenzene sulfonic acid, and boric acid in an oil medium to convert the amorphous calcium carbonate to calcite in a manner similar to that of U.S. Pat. No. 5,308,514, and adding a polyisocyanate and one or more amine-containing compounds to form a polyurea, which is then treated to prepare the desired grade of grease, in a manner similar to that of U.S. Pat. No. 4,902,435. Other alternative methods are also described below. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] The high performance, thixotropic polyurea / overbased calcium sulfonate complex hybrid grease of the present invention has the following properties: An oil-based medium of 70% by weight or more, for example, 70 to 90% by weight or 70 to 85% by weight; Uniformly dispersed in said oily medium: less than 22% by weight, e.g., 8 to 21% by weight, of an overbased calcium sulfonate complex thickener comprising fine particles of calcium carbonate in the form of calcite; Polyurea thickener 0.5 to 6.5% by weight, 0.05 to 3% by weight of calcium borate or calcium borate complex, C 12~24 Calcium soap of aliphatic fatty acid 0.05 to 5% by weight, for example 0.5 to 3.5% by weight, 0.1 to 1% by weight of an organic molybdenum compound, 0.5 to 2% by weight of an antioxidant, and 0 to 3% by weight of lime or calcium hydroxide from lime or calcium hydroxide not consumed in the reaction during the preparation of the grease; and all percentages are by weight based on the total weight of the grease.

[0019] In many embodiments, the grease of the present invention comprises: 75 to 85% by weight or 80 to 85% by weight of an oil-based medium, less than 21% by weight, for example 8 to 20% by weight or 10 to 19% by weight, of an overbased calcium sulfonate complex thickener comprising fine particles of calcium carbonate in the form of calcite; 0.8 to 4.8 or 5% by weight of a polyurea thickener; 0.1 to 3% by weight of calcium borate or calcium borate complex, C 12~24 0.8 to 3.5% by weight of calcium soap of aliphatic fatty acid, 0.1 to 1% by weight of an organic molybdenum compound, 0.5 to 2% by weight of an antioxidant, and 0 to 3% by weight of calcium hydroxide not consumed in the reaction during the preparation of lime or calcium hydroxide from lime or grease include.

[0020] C 12~24 At least a portion of the calcium soaps of aliphatic fatty acids are formed in situ during the conversion of calcium carbonate to calcite, preferably 12~24 All of the calcium soaps of aliphatic fatty acids are formed in situ during the treatment of the overbased calcium sulfonate during the preparation of the grease. More than one type of calcium soap may be present, i.e. calcium soaps of different fatty acids may be present. Preferably, 12~24 Calcium soaps of aliphatic fatty acids are hydroxy C 12 ~C 24 It is preferred to include calcium soaps of fatty acids, particularly 12-hydroxystearic acid. It is also more preferred that the calcium borate species is formed in situ during the treatment of the overbased calcium sulfonate during preparation of the grease. In some embodiments, the grease may also include a calcium salt of a short chain organic acid having 1 to 7 carbon atoms.

[0021] Various common adjunct ingredients, such as the antioxidant phenyl alpha naphthylamine and other additives, are often incorporated into the greases of this invention at levels commonly used.

[0022] The grease is prepared according to a conventional method, which comprises: 1) mixing water, 12-hydroxystearic acid, or other C 12~24 2) heating an overbased calcium sulfonate containing amorphous calcium carbonate starting material in an oily medium, e.g., a base oil, in the presence of a converting agent, typically comprising an alcohol, a lower aliphatic carboxylic acid, a ketone, or the like, useful for converting the amorphous calcium carbonate to calcite calcium carbonate and converting it to calcium carbonate crystalline forms; and 3) heating an overbased calcium sulfonate containing amorphous calcium carbonate starting material in an oily medium, e.g., a base oil, in the presence of a converting agent, typically comprising an alcohol, a lower aliphatic carboxylic acid, a ketone, or the like, useful for converting the amorphous calcium carbonate to calcite calcium carbonate and converting it to calcium carbonate crystalline forms. 12~24 2) converting the isocyanate compound and one or more amine-containing compounds to polyurea; and 3) converting the isocyanate compound and one or more amine-containing compounds to polyurea. In a preferred embodiment, when preparing the grease starting from an overbased calcium sulfonate starting material, all of the calcium borate and C 12~24 Calcium soaps of aliphatic fatty acids are formed in situ.

[0023] Typically, the mixture that is heated during the formation of calcite also contains mono- and / or dialkylbenzene sulfonic acids containing 12 to 40 carbon atoms in the alkyl group, and often the mixture also contains boric acid.

[0024] In some embodiments, after the calcite is formed, additional C is added, optionally along with boric acid and water. 12~24 The resulting mixture is then heated to dissolve the added materials in calcium salts of boric acid and C. 12~24 It is converted into calcium soaps of fatty acids.

[0025] In many cases, the boric acid and / or C used in the method 12~24 It is convenient to introduce all of the fatty acids into the mixture undergoing calcite formation. Boric acid and C 12~24If all of the fatty acids are present, no additional steps are required to prepare calcium borate and calcium salts, and the above products 1) and 2) are formed in a single procedure. Typically, the polyurea is formed after the formation of the products 1) and 2). Additional ingredients such as additional base oil or additives can be added, and other process steps such as milling and grinding the final grease can be used.

[0026] The overbased calcium sulfonates useful in preparing the greases of the present invention can be prepared by any technique used in the art. As described in U.S. Patent No. 4,560,489, typically these materials can be prepared by heating a neutral calcium sulfonate or sulfonic acid, an oily medium, i.e., a base oil, often including a mineral oil, hydrated lime, and a carbonation promoter such as methanol, to a carbonation temperature and adding sufficient carbon dioxide to produce an overbased sulfonate having the desired TBN. A molar ratio of CO2 / Ca(OH)2 of 0.55 to 0.6 produces an excellent starting material for the production of the greases of the present invention.

[0027] The overbased calcium sulfonate may have a metal ratio of about 6 to 40, e.g., 10 to 36. Generally, the base oil is an oil obtained by well-known refining procedures from mineral oil or an oil derivable from mineral oil. The mineral base oil may be of natural or synthetic nature, and the percentage of calcium sulfonate in the mineral oil may vary, e.g., from 15 to 45%. Semi-crude unfiltered mineral oil compositions containing about 10 to 20% naphtha and various percentages of mineral oil and neutral calcium sulfonate may be readily used as charge stock.

[0028] Suitable sulfonic acids useful in the preparation of calcium sulfonates are oil soluble and can be prepared by sulfonating linear or branched alkylbenzenes, such as mixtures of mono- and dialkylbenzenes in which the alkyl groups contain primarily from 12 to 40 carbon atoms, typically mixtures of such alkyl groups. The sulfonic acids are typically converted to calcium sulfonate by reaction with calcium hydroxide.

[0029] The oil medium content of the finished grease, e.g., non-volatile mineral oil or other non-volatile lubricating oil, includes all non-volatile oils present, i.e., the total amount of oils and base oils introduced as part of the original overbased calcium sulfonate composition. Any base oil useful in the art can be used, and more than one lubricating oil can be used. Examples of useful base oils include mineral oils, naphthenic oils, paraffinic oils, aromatic oils, or synthetic oils such as polyalphaolefins (PAOs), silicone oils, fluorinated or polyfluorinated derivatives of any of these fluids, or combinations thereof. For example, the base oil may be a mixture of mineral oil and synthetic oil. Additionally, refined solvent-extracted hydrotreated degreased base oils and combinations of such base oils are often used. The viscosity of the base oil can range from 50 to 10,000 SUS at 100°F (38°C), e.g., 200 to 2,000 SUS or 300 to 1500 SUS at 100°F (38°C).

[0030] The polyurea thickeners of the present invention include diureas and higher oligomeric ureas. Diurea thickeners are preferred. Diurea compounds include those obtained by the reaction of one or more monoamines and diisocyanate compounds, or one or more diamines and monoisocyanate compounds, with diureas generally prepared from diisocyanates being preferred.

[0031] Representative examples of diisocyanates include phenylene diisocyanate, diphenyl diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate, octadecane diisocyanate, decane diisocyanate, and hexane diisocyanate. Representative examples of monoisocyanates include hexyl isocyanate, decyl isocyanate, dodecyl isocyanate, tetradecyl isocyanate, hexadecyl isocyanate, phenyl isocyanate, cyclohexyl isocyanate, and xylene isocyanate.

[0032] Representative examples of monoamines include pentylamine, hexylamine, cyclohexylamine, heptylamine, octylamine, decylamine, dodecylamine, tetradecylamine, hexadecylamine, octadecylamine, eicosylamine, dodecenylamine, hexadecenylamine, octadecenylamine, octadeccadienylamine, isomers thereof, aniline, substituted anilines, toluidine, naphthylamine, substituted naphthylamines, benzylamine, and substituted benzylamines.

[0033] Higher oligomeric urea compounds include those obtained by reacting a diamine or triamine with a polyisocyanate, typically a diisocyanate compound.

[0034] Representative examples of diamines include ethylenediamine, propanediamine, butanediamine, hexanediamine, octanediamine, dodecanediamine, hexadecanediamine, cyclohexanediamine, cyclooctanediamine, phenylenediamine, tolylenediamine, xylylenediamine, dianilinemethane, and ditoluidinemethane. Representative examples of triamines include aminoethylpiperazine, diethylenetriamine, dipropylenetriamine, and N-methyldiethylenetriamine.

[0035] Examples of preferred urea thickeners include those obtained by the reaction of aliphatic amines such as octylamine, stearylamine, cyclohexylamine, and often mixtures thereof, with diisocyanates such as diphenylmethane diisocyanate.

[0036] Calcium soap-forming fatty acids having 12 to 24 carbon atoms useful in the present invention include dodecanoic acid, palmitic acid, stearic acid, oleic acid, ricinoleic acid, and 12-hydroxystearic acid. Hydroxy fatty acids, particularly hydroxystearic acid, are preferred because they impart greater thickening properties to greases than the unsubstituted fatty acids.

[0037] Calcium soap forming C 12~24 In addition to fatty acids and boric acid, conversion agents useful for the formation of calcite include (among many others): water; alcohols; lower aliphatic carboxylic acids, ketones; aldehydes; amines; phosphoric acids; alkyl and aromatic amines; certain imidazolines; alkanolamines; other boric acids, including tetraboric acid; metaboric acid; and esters of such boric acids; and carbon dioxide, either by itself or in combination with water.

[0038] Suitable salt-forming acids (complex-forming acids) may also be used in preparing the greases of the present invention, including inorganic acids such as sulfonic acid, hydrochloric acid, orthophosphoric acid, pyrophosphoric acid, sulfurous acid, boric acid, etc., and organic acids having 1 to 7 carbon atoms such as formic acid, acetic acid, propionic acid, valeric acid, oxalic acid, malonic acid, succinic acid, and benzenesulfonic acid, etc. However, boric acid and boric acid formers are preferred as they provide the best grease properties.

[0039] In one embodiment of the present invention, the polyurea / overbased calcium sulfonate complex grease comprises: 1) In a sealed high-pressure reactor, a mixture of overbased calcium sulfonate, base oil, 12-hydroxystearic acid, and other C-type components is heated at a temperature of, for example, above 250°F (121°C), for example, 270-300°F (132-148°C), under high pressure, for example, at 20-25 psi (140-170 kPa). 12~24 mixing a fatty acid, water, a surfactant dodecylbenzenesulfonic acid, boric acid, and a carboxylic acid having 1 to 7 carbon atoms, such as acetic acid; 2) evacuating and heating the reactor to remove water and volatiles; 3) then adding additional base oil, diisocyanate, and one or more amines and heating to react and remove volatiles; 4) then adjusting the final properties of the grease by adding extra base oil and / or additives followed by any additional processing steps; The method is prepared according to the procedure comprising:

[0040] For example, a Grade 2 grease containing less than 22% by weight overbased calcium sulfonate can be formed by the following method: To a mixture of overbased calcium sulfonate (400 TBN) containing 34 parts by weight of amorphous calcium carbonate and 66 parts of mixed mineral and synthetic oils is added 1-6 parts, e.g., 2-2.5 parts of the surfactant dodecylbenzenesulfonic acid; 0.5-5 parts, e.g., 1-3.5 parts of 12-hydroxystearic acid; 1-7 parts, e.g., 2.5-5 parts of water; and 0.05-3.5 parts, e.g., 0.1-3 parts of boric acid. After mixing in a pressure reactor, 0.1-1 parts, e.g., 0.4-0.7 parts of acetic acid is added and the resulting mixture is heated to a temperature of 250-270°F (121-132°C) generating a pressure of 20-25 psi (140-170 kPa) to convert the amorphous calcium carbonate to calcite. Calcite formation occurs at 880 and 705 cm -1 The formation of calcite is monitored by the appearance of a calcite peak in the IR at 100°C. Once the formation of calcite is complete, additional oil blend is usually added. The oil blend is a base oil that is a mixture of mineral and synthetic oils. In this case, from about 35-45 parts oil, a thick reaction mixture is added, followed by 8-15 parts, e.g., 9-12 parts, of 4,4-diphenylmethane diisocyanate, 4-8 parts, e.g., 5.5-6.4 parts of cyclohexaneamine, and 3.7-7, e.g., 4.4-5.4 parts of octodecylamine. Heating is performed to about 280°F (138°C), water and volatiles are removed, and then cooling is performed to below 250°F (121°C). Additional ingredients such as antioxidants phenyl alpha naphthylamine and molybdenum di-thiophosphate are added as needed, and additional oil is added to adjust the grease to the desired NLGI grade. The product can be kneaded or milled to obtain a smooth, homogeneous grease. "Parts" refers to relative amounts by weight of ingredients.

[0041] It is within the ability of the average practitioner in the art to adjust the levels of the various components in the above manner to obtain greases containing various levels of calcium sulfonate, calcium borate, calcium fatty acid soaps, and polyurea thickeners.

[0042] Alternatively, the greases of the present invention can be prepared by a method similar to that described above, except that after formation of the calcite and prior to addition of the polyurea-forming ingredients, additional hydroxystearic acid and optionally lime are added and mixed at a temperature of about 280° F. (138° C.). Additional boric acid and / or water can be added during this alternative step. In a less preferred method, the conversion to calcite is carried out without boric acid, and all of the boric acid used in the grease is added during this alternative step.

[0043] In certain cases, lime or Ca(OH)2 can be added to the reaction mixture at any stage prior to polyurea formation, but in many cases this is not done. Often, free dispersed lime or calcium hydroxide may be present after carbonation of the starting overbased calcium sulfonate or after conversion of amorphous calcium carbonate to calcite.

[0044] The above percentages are expressed as weight % based on the total weight of the grease, reactive mixture or composition to which the reference is made.

[0045] Like many commercially available calcium sulfonate greases, the greases of the present invention are characterized, without additives, by good extreme pressure and antiwear properties, high dropping points, good mechanical stability, salt spray and water resistance, thermal stability at high temperatures, and other desirable properties. Importantly, the greases of the present invention have a much lower ash content than commercial calcium sulfonate greases, making them useful in a wide range of applications, including high speed applications in automotive and other industries where low ash grease products are desired.

[0046] The greases of the present invention are highly suitable for general use as lubricants between metals and / or elastomeric plastics in contact. They are multi-purpose greases that perform as well as, or in many cases even better than, other high-temperature greases, such as polyurea greases, and are particularly effective in high-load environments. A limited selection of possible applications includes CV joints, front-wheel drive joints, universal joints, and bearings that are subject to heavy shock loads, fretting, vibratory motion, and high temperatures, such as in steel mills. The greases of the present invention have outstanding anti-wear, load-bearing, low-temperature / high-temperature properties, and excellent grease leakage prevention. Furthermore, the greases of the present invention are conveniently prepared from non-toxic, low-cost materials. EXAMPLES

[0047] (Example A1) 280 g of overbased calcium sulfonate (400 TBN) in 380 g of semi-synthetic oil, 11 g of the surfactant dodecylbenzenesulfonic acid, 12 g of 12-hydroxystearic acid, 25 g of water, and 2 g of boric acid were mixed in a pressure reactor. After the addition of 3 g of acetic acid, the reactor was sealed and heated to 250-270 °F (121-132 °C) and a pressure of 20-25 psi (140-170 kPa) was developed. After 1 hour, concentration of the amorphous carbonate and conversion to calcite was complete as confirmed by infrared, and the reactor was evacuated and heated to 260 °F (127 °C). The reaction mixture was then cooled to 160°F (127°C) and then 220g of mixed oil and 8g of 4,4-diphenylmethane diisocyanate were added, followed by 4g of cyclohexaneamine and 4.2g of octodecylamine. The resulting mixture was heated to form the diurea thickener, water was removed, and the reactants were stripped at 280°F (138°C), after which the product was cooled to below 250°F (121°C) and 19g of phenyl alpha naphthylamine and 5g of molybdenum di-thiophosphate were added, approximately 130g of mixed base oil was added, and the product was adjusted to a Grade 2 grease containing 20.0% starting overbased calcium sulfonate and having a consistency of 265-295. The mixed base oil was a mixture of mineral and synthetic oils.

[0048] (Example A2) The procedure of Example A1 was repeated except that the amounts of 4,4-diphenylmethane diisocyanate, cyclohexaneamine, and octodecylamine added were each increased by 1.2 times, additional oil was added, and the final grease hardness was adjusted to obtain a Grade 2 grease hardness containing 17.5% starting overbased calcium sulfonate.

[0049] (Example A3) The procedure of Example A1 was repeated, except that the base oil was entirely mineral oil instead of a semi-synthetic oil (e.g., a mixture of mineral and synthetic oils), to obtain a Grade 2 grease containing 19.7% starting overbased calcium sulfonate.

[0050] (Example A4) The procedure of Example A1 was repeated, except that the base oil was entirely mineral oil, the amounts of 4,4-diphenylmethane diisocyanate, cyclohexaneamine, and octodecylamine added were each increased by 1.2 times, and additional oil was added and the final grease consistency was adjusted to obtain a Grade 2 grease consistency containing 17.1% starting overbased calcium sulfonate.

[0051] (Comparative Example) (Comparative Example B1) 280 g of overbased calcium sulfonate (400 TBN), 11 g of the surfactant dodecylbenzenesulfonic acid, 12 g of 12-hydroxystearic acid, and 25 g of water in 380 g of mixed oil were mixed in a pressure reactor. After the addition of 3 g of acetic acid, the reactor was sealed and heated to 250-270°F (121-132°C) and a pressure of 20-25 psi (140-170 kPa) was generated. After 1 hour, concentration of the amorphous carbonates and conversion to calcite was complete as confirmed by infrared, the reactor was evacuated, 105 g of mixed oil was added, and the mixture was cooled to 200°F (93°C). To this mixture, 9.7 g of additional 12-hydroxystearic acid was added, and the resulting mixture was mixed for 15 minutes, after which 10.5 g of lime in 25 g water and 12.1 g of boric acid in 25 g water were added. The reaction mixture was then mixed at 280°F (138°C), adjusted to Grade 2 hardness with about 90 g of a mixed oil, such as a mixture of mineral and synthetic oils, cooled to below 200°F (93°C), and 4.4 g of phenyl alpha naphthylamine and 1.2 g of molybdenum di-thiophosphate were added to yield a Grade 2 grease containing 23.8% of the starting overbased calcium sulfonate.

[0052] (Comparative example B2) A commercial polyurea grease for CVJ applications was used as a comparative example.

[0053] (Comparative Example B3) A commercially available lithium molybdenum disulfide grease for lubricating CVJs was also used as another comparative example.

[0054] The greases from the above examples were subjected to the corresponding tests, the results of which are shown in Table 1.

[0055] [Table 1]

[0056] From the above test data, it can be seen that the polyurea / calcium sulfonate greases of Examples A1 and A2 have similar performance. Both Examples A1 and A2 contain a base oil that is a semi-synthetic oil, which is a mixture of mineral oil and synthetic oil. Example A2 was prepared with a higher grease yield and a lower concentration of overbased calcium sulfonate to improve mobility (and a lower ash content) compared to the concentration of overbased calcium sulfonate in Example A1. A similar trend was observed in Examples A3 and A4. That is, Example A4 was prepared with a higher grease yield and a lower concentration of overbased calcium sulfonate to improve mobility (and a lower ash content) compared to the concentration of overbased calcium sulfonate in Example A3. As shown in Examples A1, A2 and Examples A3, A4, as the polyurea content increases, the concentration of overbased calcium sulfonate tends to decrease. Furthermore, Examples A1 and A2, which contain a mixture of mineral oil and synthetic oil as the base oil, have better low temperature properties than Examples A3 and A4, which contain mineral oil as the base oil.

[0057] Compared with the pure calcium sulfonate grease of Comparative Example B1, Examples A1-A4 have lower calcium sulfonate thickener content, lower wheel bearing leakage, and higher weld points. The greases of Examples A1-A4 are more suitable for automobile constant velocity joint applications. In addition, the greases of Examples A1-A4 exhibit better mechanical stability, friction and wear performance, low temperature and extreme pressure properties than the polyurea grease of Comparative Example B2. Compared with the lithium molybdenum disulfide grease of Comparative Example B3, the greases of Examples A1-A4 are shown to have better mechanical stability, friction and wear performance, extreme pressure properties, and high temperature properties.

[0058] The prepared polyurea / calcium sulfonate complex grease had reduced thickener content compared to pure calcium sulfonate grease. The prepared polyurea / calcium sulfonate complex grease showed superior properties to the leading commercial CVJ greases, making it a suitable choice for lubricating automotive constant velocity joints.

Claims

1. The following ingredients (a) to (d): (a) a base oil, (b) a thickening agent; (c) Organomolybdenum compounds, and (d) Antioxidants Polyurea / calcium sulfonate complex grease for constant velocity joints, comprising:

2. 2. The grease of claim 1, wherein said component (a) is a mixed mineral and synthetic oil.

3. 2. The grease of claim 1, wherein the component (a) is a mineral oil.

4. 2. The grease of claim 1, wherein said component (a) is a synthetic oil.

5. The grease is 70% by weight or more of an oil-based medium; Uniformly dispersed in said oily medium: less than 22% by weight of a calcium sulfonate complex thickener containing fine particles of crystalline calcium carbonate in the form of calcite; Polyurea thickener 0.5 to 6.5% by weight, 0.05 to 3% by weight of calcium borate or calcium borate complex, C 12～24 0.5-3.5% by weight of calcium soap of aliphatic fatty acids, 0.1 to 1% by weight of an organic molybdenum compound, 0.5 to 2% by weight of an antioxidant, and 0 to 3% by weight of lime or calcium hydroxide from lime or calcium hydroxide not consumed in the reaction during the preparation of the grease; Including, 5. A grease according to any one of claims 1 to 4, wherein all percentages are by weight based on the total weight of the grease.

6. 2. The grease of claim 1, wherein said component (b) is a polyurea / calcium sulfonate complex thickener.

7. Said C 12～24 Calcium soap of aliphatic fatty acids is C 12～24 6. The grease of claim 5, comprising calcium soaps of hydroxy fatty acids.

8. Said C 12～24 8. The grease of claim 7, wherein the calcium soap of a hydroxy fatty acid comprises a calcium soap of hydroxystearic acid.

9. 6. The grease of claim 5, wherein the polyurea thickener is obtained by the reaction of a diisocyanate with one or more amine-containing compounds.

10. 10. The grease of claim 9, wherein the diisocyanate comprises 4,4'-diphenylmethane diisocyanate.

11. 10. The grease of claim 9, wherein the one or more amine-containing compounds comprise one or more of octylamine, stearylamine, or cyclohexylamine.

12. 5. A grease according to any one of claims 1 to 4, wherein component (c) is a molybdenum di-thiophosphate.

13. 5. The grease according to claim 1, wherein component (d) is one or a mixture of dialkyldiphenylamines, phenyl-α-naphthylamines, di-tert-butyl-p-cresol, and 2-naphthol.

14. 14. A method for preparing a grease of the polyurea / calcium sulfonate complex according to any one of claims 1 to 13, said method comprising the steps of: In a sealed reactor, overbased calcium sulfonate, base oil, 12-hydroxystearic acid, and other C-type components are mixed under high pressure and heated. 12～24 mixing a fatty acid, water, dodecylbenzenesulfonic acid, boric acid, and a carboxylic acid having 1 to 7 carbon atoms; evacuating and heating the reactor to remove water and volatiles; thereafter, adding additional base oil, diisocyanate, and one or more amines and heating to form the polyurea / calcium sulfonate complex thickener and remove volatiles; thereafter, adjusting the final properties of the grease by adding additional base oil and / or additives, followed by any additional processing. A method comprising:

15. 15. The method of claim 14, wherein additional hydroxystearic acid and / or boric acid, water, and an appropriate amount of lime are optionally added and mixed at a temperature of about 280°F (about 138°C) after formation of the calcite and prior to addition of the polyurea forming components.

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