EP4457323A1

EP4457323A1 - Polyurea/calcium sulfonate complex grease composition for use in constant velocity joints

Info

Publication number: EP4457323A1
Application number: EP22914489.4A
Authority: EP
Inventors: Dabo LIU; Xiaolong Li; Yan Wang; Lianhui Zhang
Original assignee: Lanxess Specialty Chemicals Co Ltd
Current assignee: Lanxess Specialty Chemicals Co Ltd
Priority date: 2021-12-31
Filing date: 2022-12-22
Publication date: 2024-11-06
Also published as: CA3244201A1; KR20240153553A; US20250059458A1; JP2025501310A; CN116410813A; EP4457323A4; CN118401641A; MX2024008185A; WO2023125235A1

Abstract

The present application relates to polyurea/calcium sulfonate complex grease composition for use in constant velocity joints. The invention discloses a lubricating grease with thixotropy and a preparation method thereof. The lubricating grease comprises a polyurea/high base number calcium sulfonate composite thickener, colloidally dispersed calcium carbonate solid particles in the form of calcite, a calcium borate or calcium borate composite, a calcium soap of fatty acid having 12 to 24 carbon atoms, an organic molybdenum compound, and an antioxidant. The above components are uniformly dispersed in an oil phase medium. The content of high base number calcium sulfonate in the lubricating grease is less than 22 wt%.

Description

Polyurea/Calcium Sulfonate Complex Grease Composition for Use in Constant Velocity Joints

The present application generally relates to polyurea/calcium sulfonate complex grease composition for use in constant velocity joints. High performance, thixotropic polyurea/overbased calcium sulfonate complex hybrid greases comprising solid particles of colloidally dispersed calcium carbonate essentially in the form of calcite, calcium soap of a fatty acid of 12 to 24 carbon atoms, calcium borate or calcium borate complex, an organic molybdenum compound, and oleaginous medium are provided, which have lower concentrations of overbased calcium sulfonate for each thickness grade than available overbased calcium sulfonate complex greases, for example, greases of the invention are provided comprising less than 22 wt%overbased calcium sulfonate complex that have a worked cone penetration rating of 295 or less.
Corrosion-inhibiting, thixotropic greases or grease-like overbased calcium sulfonate compositions are well known, as is their use in a variety of demanding applications. Such greases or grease-like compositions can be used alone, or in combination with other components, and in general exhibit good 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.
Greases are rated or graded on the basis of their worked cone penetration range. For the purposes of this invention, cone penetration is measured by the ASTM cone penetration test (D217) . Penetration is the depth, in tenths of millimeters, to which a standard cone sinks into the grease under prescribed conditions. Higher penetration numbers indicate softer greases with a higher base oil content, since the cone has sunk deeper into the sample. For example, greases sold under the designation grade zero have a cone penetration number from 355 to 385, those having a cone penetration range of 310 to 340 are designated grade one and the most widely sold greases have a cone penetration range of 265 to 295 and are designated grade two.
U.S. Pat. No. 6,919,301 discloses a grease composition with a thickener of a calcium sulfonate complex and a second thickener component in a base oil. A grease composition of a second thickener is a thickener component of polyurea and a complex metallic soap. A calcium sulfate complex used as a thickener in the invention comprises calcium sulfonate as an essential component, and also comprises a calcium salt (acalcium soap) selected from a group of (a) calcium carbonate, (b) a higher fatty acid calcium salt such as calcium dibehenate, calcium distearate and calcium dihydroxystearate, (c) a lower fatty acid calcium salt such as calcium acetate, and (d) calcium borate. The polyurea used as a second thickener is a diurea.
A calcium sulfonate complex in U.S. Pat. No. 6,919,301 was synthesized in a base oil as follows. Overbased calcium sulfonate, having a high base number, was added to dialkyl diphenyl ether, and then the mixture was fully stirred at 50℃. Boric acid, acetic acid, behenic acid, stearic acid, water and calcium hydroxide were added thereto, and water was evaporated and removed by heating the mixture up to 80 to 95℃. Carbon dioxide was then introduced into this mixture to generate calcium carbonate. The obtained mixture was analyzed with an infrared spectrometer, and when the stabilization of calcium carbonate was confirmed at a peak of 882 to 886 cm ^-1, the introduction of carbon dioxide was terminated. Further, diurea was synthesized in a base oil. The mixture, obtained by the above operations, was cooled to 60℃, and 4, 4 ‘-diphenylmethane diisocyanate was added to the mixture and completely dissolved. Thereafter, cyclohexylamine and dialkyl diphenyl ether were added thereto and stirred. After, the mixture was retained at 100℃ for 60 minutes, then the mixture was heated up to 150℃ and the generation reaction of diurea was terminated. Thereafter, amine antioxidant and sulfonate anticorrosive were added to the mixture, and milling and degassing processes were carried out to obtain a grease composition.
The invention disclosed in U.S. Pat. No. 6,919,301 relates to a grease composition having excellent heat resistance, water resistance, lubricating life, oxidation stability, and biodegradability. The invention relates to a rolling apparatus which is preferably used in cars, rolling stocks, electric motors, iron manufacturing machines and others. However, in order for the grease composition to have excellent performance under a high-speed and high-temperature environment, it is preferable that the thickener comprises 25 to 75%by mass of polyurea and 75 to 25%by mass of the complex metallic soap. High polyurea content in this invention is hard to ensure excellent load carrying capacity, high temperature performance, and excellent mechanical stability of the prepared grease without the addition of proper additives. As such, research focuses on lowering the total thickener content in the prepared polyurea/calcium sulfonate complex grease while having excellent performance without high amount of additives. There is continuous interest in research about reducing the ratio of the second thickener polyurea below 5%by mass of the total thickener without lowering the grease grade and required application properties used on a rolling apparatus.
U.S. Pat. No. 4,560,489 discloses a calcium borate modified overbased calcium sulfonate complex grease broadly defined as a combination of (1) an overbased calcium sulfonate in an oil, particularly a mineral oil, containing finely divided 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) , presumably calcium borate or calcium borate intermingled or in some kind of complex in the grease or grease composition as a whole; and (3) a product formed from calcium hydroxide/calcium carbonate and a soap-forming aliphatic monocarboxylic or fatty acid, preferably a soap-forming hydroxy-fatty acid, such as 12-hydroxystearic acid. The greases of U.S. Pat. No. 4,560,489 have excellent properties, but the grease must contain about 40 to 45%by weight overbased calcium sulfonate to obtain a worked cone penetration of 265 to 295. If the content of overbased calcium sulfonate is 38%by weight or less, a relatively soft, generally undesired grease is obtained.
In addition to the above, research focuses on reducing ash content and cost in preparing these greases. Thus, there is great interest in research in reducing the overbased calcium sulfonate content without lowering the grease grade.
U.S. Pat. No. 5,308,514 discloses high performance overbased calcium sulfonate complex greases comprising overbased calcium sulfonate, solid particles of colloidally dispersed calcium carbonate in the form of calcite, calcium borate, and a calcium soap of a fatty acid of 12 to 24 carbon atoms, dispersed in an oleaginous medium, similar to the grease components of U.S. Pat. No. 4,560,489, but the concentrations of overbased calcium sulfonate for each grade of the grease are lower. Even though it provides grease with a considerably low concentration of overbased calcium sulfonate, it still requires 23 to 28%by weight of overbased calcium sulfonate to obtain a grease having a worked penetration of 265 to 295. As such, greases with lower concentrations of overbased calcium sulfonate are still desired. Polyurea greases are known to have a much lower ash content and good comprehensive performance, however, polyurea greases tend to show poor mechanical stability. Polyurea complexed with overbased calcium sulfonate is a better choice to increase the mechanical stability, decrease the ash content, and present good comprehensive performance without high amount of extra additives.
U.S. Pat. No. 6,037,314 discloses a polyurea grease composition for constant velocity joints comprising (a) a base oil and (b) a urea thickener, and certain additives needed to improve performance, i.e., (c) at least one organic molybdenum compound, (d) at least one calcium salt selected from the group consisting of calcium salts of petroleum sulfonates, calcium salts of alkyl aryl sulfonates, calcium salts of salicylate, calcium salts of phenates, calcium salts of oxidized waxes, overbasic calcium salts of petroleum sulfonates, overbasic calcium salts of alkyl aryl sulfonates, overbasic calcium salts of salicylate, overbasic calcium salts of phenates, and overbasic calcium salts of oxidized waxes; and (e) a thiophosphate. These polyurea greases need additional additives to meet the lubricating application for constant velocity joints.
U.S. Pat. No. 4,902,435 discloses greases with a hybrid thickener system, which uses both polyurea and calcium soap thickeners, and an additive package containing tricalcium phosphate and calcium carbonate to improve performance. The calcium soap thickeners used therein are simple calcium soaps or calcium complex soaps, but these are not the calcium sulfonate complex soaps of U.S. Pat. Nos. 5,308,514 and 4,560,489 that are prepared from overbased calcium sulfonate wherein the amorphous calcium carbonate is converted into calcite form. Overbased calcium sulfonate is mentioned in U.S. Pat. No. 4,902,435 as a possible source of the calcium carbonate portion of the additive package. Similar greases are disclosed in U.S. Pat. No. 5,084,193.
Overbased calcium sulfate complex greases have excellent properties, but the ash content due to the amount of calcium sulfonate, calcium soaps and other materials required is too high for many applications. Polyurea greases having a much lower ash content and many good performance characteristics are known, but tend to show poor mechanical stability.
SUMMARY OF THE INVENTION
It has been found that by replacing a portion of the overbased calcium sulfonate in overbased calcium sulfonate complex greases with a polyurea thickener, thixotropic high performance polyurea/overbased calcium sulfonate complex greases can be formed. These thixotropic high performance polyurea/overbased calcium sulfonate complex greases all have excellent performance and pumping characteristics of the overbased calcium sulfonate complex greases of U.S. Pat. No. 5,308,514 while having a significantly reduced ash content, and vastly improved mechanical stability when compared with polyurea greases.
The high performance, thixotropic polyurea/overbased calcium sulfonate complex hybrid greases of the invention comprise the following components (a) to (d) : (a) a base oil, (b) a thickener, (c) an organic molybdenum compound, and (d) an antioxidant. For example, the high performance, thixotropic polyurea/overbased calcium sulfonate complex hybrid greases of the invention comprise, in addition to the polyurea/overbased calcium sulfonate complex thickener, solid, finely divided particles of colloidally dispersed calcium carbonate in the form of calcite, calcium borate or complex of calcium borate, and a calcium soap of a fatty acid of 12 to 24 carbon atoms, preferably a soap of a hydroxy fatty acid, evenly dispersed in an oleaginous medium, e.g., one or more non-volatile oils, such as a mixture of mineral and synthetic oils, a mineral oil, a synthetic oil, or other lubricating oil, wherein the greases contain less than 22%by weight, typically 20%by weight or less, of overbased calcium sulfonate. In preferred embodiments, the grease has a worked cone penetration rating of 295 or less. The present greases contain less borate salts and calcium soaps than overbased calcium sulfonate complex hybrid greases in the art, due to replacing a portion of the overbased calcium sulfonate with the polyurea thickener, thus further lowering the ash content. The present greases also have outstanding wear resistance, load bearing capacity, low/high temperature properties, and excellent grease leakage preventing performance.
For example, in one preferred embodiment the invention provides a grade 2 grease, i.e., a grease having a worked cone penetration rating 265-295, comprising less than 22 wt%overbased calcium sulfonate and at least 70%by weight oil, and typically at least 75%or 80%by weight, of a non-volatile oil.
The greases of the invention are made using variations of known methods. For example, one process comprises a step wherein a mixture of overbased calcium sulfonate comprising amorphous calcium carbonate, water, a converting agent at least a portion of which comprises a fatty acid, preferably a hydroxy fatty acid, of 12 to 24 carbon atoms capable of forming a calcium soap, alkylbenzene sulfonic acid and boric acid in an oleaginous medium is heated to convert the amorphous calcium carbonate to calcite in a manner similar to that of U.S. Pat. No. 5,308,514; a further step wherein a poly isocyanate and one or more amine containing compounds is added to form a polyurea in a manner similar to that of U.S. Pat. No. 4,902,435, followed by processing to prepare a grease of the desired rating. Other alternative processes are also discussed below.
DESCRIPTION OF THE INVENTION
The high performance, thixotropic, polyurea/overbased calcium sulfonate complex hybrid greases of the invention comprise:
70 wt%or more, e.g., 70 to 90 wt%or 70 to 85 wt%, oleaginous medium in which there is homogeneously dispersed:
less than 22 wt%, e.g., 8 to 21 wt%, overbased calcium sulfonate complex thickener comprising fine particles of calcium carbonate in calcite form;
0.5 to 6.5 wt%polyurea thickener;
0.05 to 3 wt%, calcium borate or a calcium borate complex;
0.05 to 5 wt%, e.g., 0.5 to 3.5 wt%, calcium soaps of C _12-24 aliphatic fatty acids;
0.1 to 1 wt%organic molybdenum compound;
0.5 to 2 wt%antioxidant; and
0 to 3 wt%lime or calcium hydroxide from lime or calcium hydroxide not consumed in the reactions during preparation of the grease;
wherein all percentages are weight %based on the total weight of the grease.
In many embodiments, the grease of the invention comprises:
75 to 85 wt%, or 80 to 85 wt%, oleaginous medium;
less than 21 wt%, e.g., 8 to 20 wt%or 10 to 19 wt%, overbased calcium sulfonate complex thickener comprising fine particles of calcium carbonate in calcite form;
0.8 to 4.8 or 5 wt%polyurea thickener;
0.1 to 3 wt%calcium borate or a calcium borate complex;
0.8 to 3.5 wt%calcium soap of C _12-24 aliphatic fatty acids;
0.1 to 1 wt%organic molybdenum compound;
0.5 to 2 wt%antioxidant; and
0 to 3 wt%lime or calcium hydroxide from lime or calcium hydroxide not consumed in the reactions during preparation of the grease.
At least a portion of the calcium soap of C _12-24 aliphatic fatty acids is formed in situ during conversion of the calcium carbonate to calcite, and preferably all of the calcium soap of C _12-24 aliphatic fatty acids are formed in situ during the processing of the overbased calcium sulfonate during 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 the calcium soaps of C _12-24 aliphatic fatty acids comprise calcium soaps of hydroxy C ₁₂-C ₂₄ fatty acids, in particular 12-hydroxystearic acid. It is also more preferred that the calcium borate species is formed in situ during the processing of the overbased calcium sulfonate during preparation of the grease. In some embodiments, the grease may also comprise calcium salts of short chain organic acids having from one to seven carbon atoms.
Various common supplemental ingredients, e.g., antioxidants phenyl alpha naphthylamine and other additives, are often incorporated into the greases of the invention at commonly used levels.
The grease is prepared according to a general process wherein 1) an overbased calcium sulfonate comprising amorphous calcium carbonate starting material in an oleaginous medium, e.g., base oil, is heated in the presence of water, a conversion agent comprising a C _12-24 fatty acid such as 12-hydroxylstearic acid and typically other compounds useful in converting amorphous calcium carbonate to calcite calcium carbonate, such as alcohols, lower aliphatic carboxylic acids, ketones, etc., to convert the calcium carbonate crystal form; 2) calcium salts of boric acid and C _12-24 fatty acids are formed; and 3) an isocyanate compound and one or more amine containing compounds are converted into a polyurea. In preferred embodiments, all of the calcium borates and the calcium soap of C _12-24 aliphatic fatty acids are formed in situ during preparation of the grease starting from an overbased calcium sulfonate starting material.
Typically, the mixture heated during calcite formation also comprises mono-and/or di-alkyl benzene sulfonic acid in which the alkyl groups contain 12 to 40 carbon atoms, and often the mixture of also comprises boric acid.
In some embodiments, additional C _12-24 fatty acids are added, optionally with boric acid and water, after the calcite has been formed, in which case the resulting mixture is heated to effect conversion of the added materials to calcium salts of boric acid and calcium soaps of C _12-24 fatty acids.
It is often convenient to introduce all of the boric acid and/or C _12-24 fatty acids used in the process to the mixture subjected to calcite formation. Where all the boric acid and C _12-24 fatty acids are present during calcite formation step, there is no need for an additional step to prepare the calcium borate and calcium salts, and the product of 1) and 2) above are formed during a single procedure. Typically, the polyurea is formed after the formation of the products of 1) and 2) . Additional components, e.g., additional base oil or additives, may be added and other process steps, e.g., kneading or milling the final grease, may be used.
The overbased calcium sulfonates useful in the preparation of the grease of the invention can be prepared by any technique employed in the art. Typically, these materials can be prepared by heating neutral calcium sulfonate or sulfonic acid, oleaginous medium, i.e., a base oil often comprising a mineral oil, hydrated lime and a carbonation promoter, such as methanol, to the carbonation temperature, and adding sufficient carbon dioxide to produce an overbased sulfonate having the desired TBN as described in U.S. Pat. No. 4,560,489. A molar ratio of 0.55-0.6 CO ₂ /Ca (OH) ₂ produces an excellent starting material for the production of the greases of the present invention.
The overbased calcium sulfonate can have a metal ratio of about 6 to 40, e.g., 10 to 36.
The base oils are, generally speaking, oils obtained by well-known refining procedures from mineral oils or can be derived from mineral oils. The mineral base oils can be of natural or synthetic character, the proportions of calcium sulfonates in the mineral oil can be variable, e.g., 15 to 45 %. A semi-crude, unfiltered mineral oil composition containing about 10 to 20%naphtha and varying proportions of mineral oil and neutral calcium sulfonate is readily usable as a charge stock.
Suitable sulfonic acids useful in the production of the calcium sulfonates are oil-soluble and can be produced by sulfonating a linear or branched chain alkyl benzene, such as a mixture of mono-and di-alkyl benzenes in which the alkyl group contains largely from 12 to 40 carbon atoms, generally mixtures of such alkyl groups. The sulfonic acids are conventionally converted to calcium sulfonates by reaction with calcium hydroxide.
The oleaginous medium content of the finished grease, e.g., non-volatile mineral oil or other non-volatile lubricating oil, includes the total amount of all non-volatile oil present, that is, the oil introduced as part of the original overbased calcium sulfonate composition plus the base oil. Any base oil useful in the art may be used and more than one lubricating oil may be used. Examples of useful base oils include mineral oil, naphthenic oil, paraffinic oil, aromatic oil, or a synthetic oil such as a polyalphaolefin (PAO) , silicon oils, a fluoronated or polyfluoronated derivative of any of these preceding fluids, or combinations thereof. For example, the base oil may be a mixture of mineral oil and synthetic oil. In addition, refined solvent-extracted hydrogenated dewaxed base oil 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, e.g., 200 to 2,000 SUS or 300 to 1500 SUS at 100°F.
The polyurea thickeners of the present invention include diureas and higher oligomeric ureas. Diurea thickeners are preferred. Diurea compounds include those obtained through a reaction of one or more monoamine with a diisocyanate compound or one or more diamine with a mono-isocyanate compound, generally diureas prepared from a diisocyanate are preferred.
Representative examples of diisocyanates include phenylene diisocyanate, diphenyl diisocyanate, tolylenediisocyanate, diphenylmethane diisocyanate, octadecane diisocyanate, decane diisocyanate, and hexane diisocyanate. Representative examples of mono-isocyanates include hexylisocyanate, decylisocyanate, dodecylisocyante, tetradecylisocyanate, hexadecylisocyanate, phenylisocyanate, cyclohexylisocyanate and xyleneisocyanate.
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.
Higher oligomeric urea compounds include those obtained through a reaction of a diamine or triamine with a polyisocyante, typically a diisocyanate compound.
Representative examples of diamines include ethylenediamine, propanediamine, butanediamine, hexanediamine, octanediamine, dodecanediamine, hexadecanediamine, cyclohexanediamine, cyclooctanediamine, phenylenediamine, tolylenediamine, xylylenediamine, dianiline methane, and ditoluidinemethane; representative triamines include aminoethyl piperazine, diethylene triamine, dipropylene triamine and N-methyldiethylene triamine.
Examples of preferred urea thickeners include those obtained through a reaction of aliphatic amine such as octylamine, stearylamine, cyclohexyl amine, and often a mixture thereof, with a diisocyanate, such as diphenylmethane diisocyanate.
Calcium-soap-forming fatty acids of 12 to 24 carbon atoms useful in the invention include dodecanoic acid, palmitic acid, stearic acid, oleic acid, ricinoleic acid, 12-hydroxystearic acid. The hydroxy fatty acids, particularly hydroxystearic acid, are preferred since they provide greater thickening to the greases than the unsubstituted fatty acids.
Conversion agents, in addition to the calcium-soap-forming C12-24 fatty acids and boric acid, useful in the formation of calcite include (among many others) : water; alcohols, lower aliphatic carboxylic acids, ketones; aldehydes; amines; phosphorus acids; alkyl and aromatic amines; certain imidazoilines; alkanolamines; other boron acids including tetraboric acid; metaboric acid; and esters of such boron acids; and, also, carbon dioxide as such or in combination with water.
Suitable salt-forming acids (complex forming acids) may also be used in preparation of the greases of the present invention, including inorganic acids, such as sulfonic acid, hydrochloric acid, orthophosphoric acids, pyrophosphoric acid, sulfurous acid, boric acid; and organic acids of 1 to 7 carbon atoms, such as formic acid, acetic acid, propionic acid, valeric acid, oxalic acid, malonic acid, succinic acid and benzene sulfonic acid. Boric acid and boric acid formers, however, are preferred since they provide the best grease properties.
In one embodiment of the invention, a polyurea/overbased calcium sulfonate complex grease is prepared according to a procedure comprising 1) mixing an overbased calcium sulfonate, a base oil, a C _12-24 fatty acid such as 12-hydroxylstearic acid, water, detergent dodecylbenzene sulfonic acid, boric acid and a carboxylic acid having from 1 to 7 carbon atoms, such as acetic acid in a sealed high pressure reactor while heating, e.g., at temperatures of above 250 °F, e.g., between 270 and 300°F, and elevated pressures, e.g., 20-25 psi; 2) venting the reactor with heating to remove water and volatiles; 3) adding additional base oil, diisocyanate and one or more amines, heating to effect reaction and removal of volatiles; and 4) adjusting the final properties of the grease by adding additional base oil and/or additives, followed by any additional processing steps.
For example, a grade 2 grease comprising less than 22 wt%overbased calcium sulfonate can be formed by the following procedure:
To a mixture of 34 parts by weight overbased calcium sulfonate (400TBN) comprising amorphous calcium carbonate and 66 parts mixed mineral and synthetic oil is added 1 to 6 parts, e.g., 2 to 2.5 parts detergent dodecylbenzene sulfonic acid; 0.5 to 5 parts, e.g., 1 to 3.5 parts 12-hydroxy stearic acid; 1 to 7 parts, e.g., 2.5 to 5 parts water; and 0.05 to 3.5 parts, e.g., 0.1 to 3 parts, boric acid. After mixing in a pressure reactor, 0.1 to 1 part, e.g., 0.4 to 0.7 part, acetic acid is added and the resulting mixture is heated to temperatures of 250 -270 °F developing a pressure of 20 to 25 psi to convert the amorphous calcium carbonate to calcite. Formation of calcite is monitored by the appearance of calcite peaks in the IR at 880 and 705 cm ^-1. When calcite formation is complete, additional mixed oil is generally added. The mixed oil is base oil that is a mixture of mineral oil and synthetic oil. In this case, from about 35 to 45 parts oil, to the now thickened reaction mixture, after which 8 to 15 parts, e.g., 9 to 12 parts, 4, 4-diphenylmethane diisocyanate is added followed by 4 to 8 parts, e.g., 5.5 to 6.4 parts cyclohexanamine and 3.7 to 7, e.g., 4.4 to 5.4 parts, octodecylamine. Heating is performed to about 280°F to remove water and volatiles, then cooling is performed to below 250°F. If desired, additional components, such as the antioxidant phenyl alpha naphthylamine and molybdenum di-thiophosphates, are added and the grease is adjusted to the desired NLGI grade by addition of additional oil. In order to obtain a smooth homogeneous grease, the product may then be kneaded or milled. “Parts” refers to relative amounts by weight of a component.
Adjusting the levels of the various components in the processes above to obtain a grease with various levels of the calcium sulfonate, calcium borate, calcium fatty acid soaps and polyurea thickener is well within the skill of the average practitioner in the art.
Alternatively, the grease of the present invention may be prepared by a process similar to the above process except that after calcite formation and before addition of the polyurea forming components, additional hydroxy stearic acid and optionally lime are added and mixed at temperatures of about 280°F. Additional boric acid and/or water may also be added during this alternative step. In a less preferred process, the conversion to calcite is run without boric acid and all the boric acid used in the grease is added during this alternative step.
In certain cases, lime or Ca (OH) ₂ may be added to the reaction mixture at any stage prior to polyurea formation, but in many cases this is not done. Often after carbonation of the starting overbased calcium sulfonate, or after the conversion of amorphous calcium carbonate to calcite, free dispersed lime or calcium hydroxide may be present.
The foregoing percentages are in terms of wt. %, based on the total weight of the grease, reaction mixture or composition being referred to.
As with many commercial calcium sulfonate greases, the greases of the invention are characterized by good extreme pressure and anti-wear properties, high dropping points, good mechanical stability, salt spray and water resistance, thermal stability at high temperature and other desirable properties, even without additives. Significantly, the greases of the present invention have much lower ash content, making them useful in a wider range of applications, than available calcium sulfonate greases, including high speed applications in automobile and other industries, where lower ash content grease products are desired.
The greases of the present invention are well suited for general use as a lubricant between contacting metals and/or elastomeric plastics. They are multi-purpose greases which equal and, in many cases, outperform other high temperature greases such as polyurea greases and are especially effective in environments with high load situations. A limited selection of possible uses includes CV joints, front-wheel drive joints, universal joints and bearings which are subjected to heavy shock loads, fretting, and oscillating motions and high temperatures such as in steel mills. The greases of the present invention have outstanding wear resistance, load bearing capacity, low/high temperature properties, and excellent grease leakage preventing performance. Furthermore, the greases of the present invention are conveniently prepared from non-toxic and low-cost materials.
EXAMPLES
Example A1
Two hundred eighty grams overbased calcium sulfonate (400TBN) in 380 grams semi-synthetic oil, 11 grams detergent dodecylbenzene sulfonic acid, 12 grams 12-hydroxystearic acid, 25 grams water and 2 grams boric acid were mixed in a pressure reactor. After addition of 3 grams acetic acid, the reactor was sealed and heated to 250-270°F, developing a pressure of 20 to 25 psi. After 1 hour, thickening and conversion of amorphous carbonate to calcite was complete as determined by infra-red, the reactor was vented and heated to 260°F. Next, after cooling the reaction mixture to 160°F, 220 grams mixed oil and 8 grams 4, 4-diphenylmethane diisocyanate was added, followed by 4 grams cyclohexanamine and 4.2 grams octodecylamine. The resulting mixture was heated to form the diurea thickener, water was removed and the reactants were stripped at 280°F after which the product was cooled to below 250°F, 19 grams phenyl alpha naphthylamine and 5 grams molybdenum di-thiophosphates were added and about 130 grams mixed base oil was added to adjust the product to a grade 2 grease containing 20.0%starting overbased calcium sulfonate and having a penetration rating between 265-295. The mixed base oil was a mixture of mineral oil and synthetic oil.
Example A2
The procedure of Example A1 was repeated except that the amount of 4, 4-diphenylmethane diisocyanate, cyclohexanamine and octodecylamine added was increased 1.2 times respectively and additional oil was added to adjust the final grease thickness, yielding a grade 2 grease thickness containing 17.5%starting overbased calcium sulfonate.
Example A3
The procedure of Example A1 was repeated except that the base oil was completely mineral oil instead of semi-synthetic oil (for example, a mixture of mineral oil and synthetic oil) , yielding a grade 2 grease containing 19.7%starting overbased calcium sulfonate.
Example A4
The procedure of Example A1 was repeated except that the base oil was completely mineral oil, the amount of 4, 4-diphenylmethane diisocyanate, cyclohexanamine and octodecylamine added was increased 1.2 times respectively, and additional oil was added to adjust the final grease thickness, yielding a grade 2 grease thickness containing 17.1%starting overbased calcium sulfonate.
Comparative Examples
Comparative Example B1
Two hundred eighty grams overbased calcium sulfonate (400TBN) in 380 grams mixed oil, 11 grams detergent dodecylbenzene sulfonic acid, 12 grams 12-hydroxystearic acid, and 25 grams of water were mixed in a pressure reactor. After addition of 3 grams acetic acid, the reactor was sealed and heated to 250-270°F developing a pressure of 20 to 25 psi. After 1 hour, thickening and conversion of amorphous carbonate to calcite was complete as determined by infra-red and the reactor was vented and cooled to 200°F with the addition of 105 grams mixed oil. To this mixture, 9.7 grams of additional 12-hydroxylstearic acid was added, the resulting mixture was mixed for 15 minutes, after which 10.5 grams lime in 25 grams water and 12.1 grams boric acid in 25 grams water were added. The reaction mixture was then mixed at 280°F, the thickness adjusted to grade 2 with about 90 grams mixed oil, e.g., mixture of mineral oil and synthetic oil, cooled to below 200°F, and 4.4 grams phenyl alpha naphthylamine and 1.2 grams molybdenum di-thiophosphates were added to yield a grade 2 grease containing 23.8%starting overbased calcium sulfonate.
Comparative Example B2
A commercial polyurea grease for the application of CVJ was used to a comparative example.
Comparative Example B3
A commercial molybdenum disulfide lithium grease for the lubrication of CVJ was also used to another comparative example.
The greases from the above Examples were subjected to the corresponding tests. The results are shown in the following table.
It can be seen from the above testing data, the polyurea/calcium sulfonate greases of Examples A1 and A2 have similar performance. Both Examples A1 and A2 include a base oil that is a semi-synthetic oil, which is a mixture of mineral oil and synthetic oil. Example A2 was prepared in higher yield of grease and had lower concentrations of overbased calcium sulfonate (and lower ash content) to improve mobility when compared to the concentrations of overbased calcium sulfonate in Example A1. The same trend also appeared in Examples A3 and A4. That is, Example A4 was prepared in higher yield of grease and had lower concentrations of overbased calcium sulfonate (and lower ash content) to improve mobility when compared to the concentrations of overbased calcium sulfonate in Example A3. The trend is lower concentration of overbased calcium sulfonate when increased the polyurea content as showed in Examples A1, A2 and Examples A3, A4. Further, Examples A1 and A2, which included a mixture of mineral oil and synthetic oil as the base oil, have more excellent low temperature property than Examples A3 and A4, which included mineral oil as the base oil.
Compared with the pure calcium sulfonate grease of Comparative Example B1, Examples A1 to A4 have lower calcium sulfonate thickener content, lower wheel bearing leakage and higher weld load. The greases of Examples A1 to A4 are more suitable for the application of constant velocity joints in automobiles. Also, the greases of Examples A1 to A4 show better mechanical stability, friction and wear performance, low temperature and extreme pressure properties than the polyurea grease of Comparative Example B2. Compared with the molybdenum disulfide lithium grease of Comparative Example B3, the greases of Examples A1 to A4 are shown to have better mechanical stability, friction and wear performance, extreme pressure and high temperature properties.
The prepared polyurea/calcium sulfonate complex grease decreased the thickener content compared with pure calcium sulfonate grease. The prepared polyurea/calcium sulfonate complex grease shows more excellent properties than main CVJ greases available on the market and provides a suitable option for the lubrication of CVJ in automobiles.

Claims

The polyurea/calcium sulfonate complex grease for constant velocity joints comprising the following components (a) to (d) :

(a) a base oil;

(b) a thickener;

(c) an organic molybdenum compound; and

(d) an antioxidant.
The grease as claimed in claim 1, wherein the component (a) is a mixed mineral and synthetic oil.
The grease as claimed in claim 1, wherein the component (a) is a mineral oil.
The grease as claimed in claim 1, wherein the component (a) is a synthetic oil.
The grease as claimed in any one of claims 1 to 4, wherein the grease comprises: 70 wt%or more oleaginous medium in which there is homogeneously dispersed:

less than 22 wt%calcium sulfonate complex thickener comprising fine particles of crystalline calcium carbonate in calcite form;

0.5 to 6.5 wt%polyurea thickener;

0.05 to 3 wt%calcium borate or a calcium borate complex;

0.5 to 3.5 wt%calcium soap of C _12-24 aliphatic fatty acids;

0.1 to 1 wt%organic molybdenum compound;

0.5 to 2 wt%antioxidant; and

0 to 3 wt%lime or calcium hydroxide from lime or calcium hydroxide not consumed in the reactions during the preparation of grease,

wherein all percentages are weight %based on the total weight of the grease.
The grease as claimed in claim 1, wherein the component (b) is a polyurea/calcium sulfonate complex thickener.
The grease as claimed in claim 5, wherein the calcium soap of C _12-24 aliphatic fatty acids comprises a calcium soap of C _12-24 hydroxy fatty acids.
The grease as claimed in claim 7, wherein the calcium soap of C _12-24 hydroxy fatty acids comprises a calcium soap of hydroxystearic acid.
The grease as claimed in claim 5, wherein the polyurea thickener is obtained by reaction of a diisocyanate and one or more amine containing compounds.
The grease as claimed in claim 9, wherein the diisocyanate comprises 4, 4’-diphenylmethane diisocyanate.
The grease as claimed in claim 9, wherein the one or more amine containing compounds comprises one or more of octylamine, stearyl amine, or cyclohexyl amine.
The grease as claimed in any one of claims 1 to 4, wherein the component (c) is molybdenum di-thiophosphates.
The grease as claimed in any one of claims 1 to 4, wherein the component (d) is one or a mixture of dialkyldiphenylamine, phenyl-α-naphthylamine, di-tert-butyl-p-cresol, and 2-naphthol.
A process for preparing the polyurea/calcium sulfonate complex grease of any one of claims 1 to 13, the process comprising mixing an overbased calcium sulfonate, a base oil, a C _12-24 fatty acid such as 12-hydroxylstearic acid, water, dodecylbenzene sulfonic acid, boric acid and a carboxylic acids having from 1 to 7 carbon atoms, in a sealed reactor while heating under elevated pressure; venting the reactor and then heating to remove water and volatiles; then adding additional base oil, diisocyanate and one or more amines, heating to effect reaction to form a polyurea/calcium sulfonate complex thickener and removal of volatiles; and then adjusting the final properties of the grease by adding extra base oil and/or additives, followed by any additional processing steps.
The process as claimed in claim 14, wherein after calcite formation and before addition of the polyurea forming components, additional hydroxy stearic acid and/or boric acid, water, and an appropriate amount of lime are optionally added and mixed at temperatures of about 280 °F.