EP0151859B1

EP0151859B1 - Grease composition

Info

Publication number: EP0151859B1
Application number: EP84306857A
Authority: EP
Inventors: John Phillips Doner; Andrew Gene Horodysky; John Antone Keller, Jr.
Original assignee: Mobil Oil Corp
Current assignee: ExxonMobil Oil Corp
Priority date: 1984-02-06
Filing date: 1984-10-09
Publication date: 1992-06-24
Anticipated expiration: 2004-10-09
Also published as: NZ209963A; EP0151859A3; JPS60166399A; DE3485789D1; AU575596B2; JPH0694557B2; BR8406567A; CA1231703A; EP0151859A2; AU3483484A; DE3485789T2

Description

This invention relates to grease compositions. More particularly, it relates to grease compositions comprising oils, hydroxy-containing soap thickener and borated hydroxy-containing esters; and optionally containing phosphorus and sulfur moities.
U.S. Patent 2943054 discloses a lubricating grease consisting essentially of mineral lubricating oil thickened with about 3% to about 30% by weight of barium 12-hydroxystearate and containing a small amount, sufficient to impart good mechanical stability and reversibility characteristics to said grease, of the reaction product, obtained by heating to a temperature between about 215°F and about 425°F, of orthoboric acid and an ester selected from the class consisting of glycol and polyglycol, mono and di-esters of hydroxy fatty acids having 8 to 50 carbon atoms and glycerol mono, di and tri-esters of hydroxy fatty acids having 8 to 50 carbon atoms.
The present invention seeks to provide a grease composition having improved dropping point characteristics.
In accordance with one aspect of the invention, there is provided an improved grease composition containing a major proportion of a grease, from 0.01% to 10% by weight of a reaction product made by reacting an ester of the formula:

R(COOR¹)_n

wherein is 1 to 5; and R and R¹ represent, respectively, an n- or univalent hydrocarbyl or hydroxyhydrocarbyl group containing from 1 to 40 carbon atoms, preferably 8 to 20 carbon atoms, at least one of R or R¹ being a hydroxyhydrocarbyl group
with a boron compound which may be a metaborate or similar boron source, boric acid, boric oxide or an alkyl borate of the formula:

(R²O)_xB(OH)_y

wherein:
R² represents an alkyl group containing from 1 to 6 carbon atoms; and
x is 1 to 3, y is 0 to 2, their sum being 3, and a thickener containing at least 15% by weight of lithium soap of a hydroxy-containing fatty acid,
fatty glyceride or fatty ester containing 12 to 30 carbon atoms whereby the dropping point of the grease composition is at least 240°C.
This invention also provides the use of a thickener containing at least 15% by weight of a lithium soap of a hydroxy-containing fatty acid, fatty glyceride or fatty ester containing 12 to 30 carbon atoms to improve the dropping point of a grease composition comprising a major proportion of a grease and from 0.01% to 10% by weight of a reaction product made by reacting and ester of the formula.

R(COOR¹)_n

wherein n is 1 to 5 and R and R¹ are hydrocarbyl or hydroxyhydrocarbyl groups containing 1 to 40 carbon atoms at least one of R and R¹ being a hydroxyhydrocarbyl group with a boron compound.
The presence of phosphorus and sulfur moieties provides and even higher dropping point. Hydrocarbyl and hydroxyhydrocarbyl include alkyl, aryl, aralkyl, alkaryl and cycloalkyl groups. Preferably the ester is overborated, meaning the presence in the product of more than stoichiometric amount of boron.
The esters may contain from 1 to 5 hydroxy groups in the molecule. They may all be attached to either R or R¹ or they may be attached to R and R¹ in varying proportions. Further, the hydroxy groups can be at any position or positions along the chain of R or R¹. It will be understood that the esters contain at least one free hydroxy group prior to reaction with the boron compound.
The disclosed esters can be made by methods well known in the art. In general, they are made by reacting the desired acid or acyl halide and alcohol at temperatures and for times one skilled in the art can easily select. To give an ester having a free hydroxy group either in R or R¹, reactant proportions are chosen accordingly, as one skilled in the art will understand. Suitable hydroxy-containing esters prior to boration include trimethylolpropane monooleate, trimethylolpropane dioleate, trimethylolpropane monostearate, trimethylolpropane distearate, trimethylolpropane monopelargonate, trimethylolpropane monooleate monopelargonate, pentaerylthritol monooleate, pentaerythritol dioleate, pentaerythritol trioleate, pentaerythritol monoisostearate, pentaerythritol monooleate monopelargonate, pentaerythritol monoisostearate, monopelargonate or monohexanoate, pentaerythritol tripelargonate, glycerol monooleate, glycerol dioleate, glycerol monostearate, glycerol monoricinoleate, glycerol monoisostearate, glycerol monopelargonate, glycerol monohexadecanoate, sorbitan monooleate, sorbitan dioleate, sorbitan monostearate, sorbitan distearate, sorbitan monopelargonate, dipentaerythritol monooleate, dipentaerythritol dioleate, dipentaerythritol trileate, ethyleneglycol monooleate, ethyleneglycol monostearate, ethyleneglycol monoisostearate, diethyleneglycol monooleate, diethyleneglycol monopelargonate, diethyleneglycol monoisostearate and triethyleneglycol monooleate, methyl hydroxystearate and ethyl hydroxystearate, or mixtures of the above.
The borated esters of the invention can be made by reacting an ester as defined above with a boron compound, such as boric oxide, a metaborate, boric acid, an alkyl borate or mixtures thereof. The resulting products are primarily borate esters, but other possible products present are the products of reaction between ester dimers, or higher oligomers, and a boron compound to form the corresponding borate esters.
As noted hereinabove, the boron compound used is boric acid, boric oxide or an alkyl borate, preferably boric acid. The alkyl borates include the mono-, di and trialkyl borates, such as the mono-, di- and trimethyl borates, mono-, di- and triethyl borates, mono-, di and tripropyl borates, mono-, di- and tributyl borates, mono-, di and tripentyl borates and mono-, di- and trihexyl borates.
The reaction to form the borate ester can be carried out at a temperature from 80°C to 260°C, preferably from 110°C to 180°C. The temperature chosen will depend for the most part on the particular reactants and on whether or not a solvent is used. Reaction pressures can be vacuum, atmospheric, or positive pressure. In carrying out this reaction, it is preferably that quantities of reactants be chosen such the molar ratio of ester to boron compound be from 1 to 4, preferably from 1 to 2, or more preferably, of about 1. The ester may be reacted with an excess of the borating species to form a borate ester containing from 0.1% by weight of boron to more than 10% of boron.
While atmospheric pressure is generally preferred, the reaction can be advantageously run at from 1 to 5 atmospheres. Furthermore, where conditions warrant it, a solvent may be used. In general, any relatively non-polar, unreactive solvent can be used, including benzene, toluene, xylene and 1,4-dioxane. other hydrocarbon and alcoholic soluents, which include propanol, butanol, and hexamethyleneglycol can be used. Mixtures of alcoholic and hydrocarbon solvents can be used also.
The reaction time is not critical. Thus, any phase of the process can be carried out in form 1 to 20 hours.
A narrow class of thickening agents is used to make the grease of this invention. The thickening agents contain at least a portion of a lithium soap of a hydroxyl-containing fatty acid, fatty glyceride on fatty ester having from 12 to 30 carbon atoms per molecule. Preferred members among these acids and fatty materials are 12-hydroxystearic acid, 14-hydroxystearic acid, 16-hydroxystearic acid, 6-hydroxystearic acid or a glyceride or ester thereof.
The entire amount of thickener need not be derived from the aforementioned members. Significant benefit can be attained using as little thereof as 15% by weight of the total thickener. A complementary amount, such as up to 85% by weight of a wide variety of thickening agents, can be used in the grease of this invention. Included among the other useful thickening agents are alkali and alkaline earth metal soaps of methyl-12-hydroxystearate, diesters of a C₄ to C₁₂ dicarboxylic acid and tall oil fatty acids. Other alkali or alkaline earth metal fatty acids containing from 12 to 30 carbon atoms and no free hydroxyl may be used. These include soaps of stearic and oleic acids.
Manufacture of the thickening agents can be done in a variety of grease-making equipment such as open kettles at reduced, atmospheric, or positive pressures; higher pressure reaction chambers which may be operated as high as 180 psig; or continuous manufacturing equipment. The temperature range from the bulk grease under manufacture may range from 15°C (60°F) to 238°C (460°F).
Other thickening agents include salt and salt-soap complexes as calcium stearate-acetate (U.S. Patent No. 2,197,263), barium stearate acetate (U.S. Patent No. 2,564,561), calcium stearate-caprylate-acetate complexes (U.S. Patent No. 2,999,066), and calcium salts and soaps of low-, intermediate-and high-molecular weight acids and of nut oil acids.
Another group of thickening agents comprises substituted ureas, phthalocyanines, indanthrene, pigments such as perylimides, pyromellitdiimides, and ammeline, as well as certain hydrophobic clays. These thickening agents can be prepared from clays which are initially hydrophilic in character, but which have been converted into a hydrophobic condition by the introduction of long-chain hydrocarbon radicals into the surface of the clay prior to their use as component of a grease composition, as, for example, by being subjected to a preliminary treatment with an organic cationic surface active agent, such as an onium compound. Typical onium compounds are tetraalkylammonium chlorides, such as dimethyl dioctadecyl ammonium chloride, dimethyl dibenzyl ammonium chloride and mixtures thereof. This method of conversion is well known to those skilled in the art.
The third member(s) that may be present in the grease composition are the phosphorous and sulfur moieties. Both of these can be present in the same molecule, such as in a metal or non-metal phosphorodithioate of the formula

wherein R³ is a hydrocarbyl group containing 3 to 18 carbon atoms, M is preferably a metal, but may be a non-metal, such as one of those mentioned hereinbelow, n is the valence of M and Z is oxygen or sulfur, at least one Z being sulfur.
In this compound, R³ is preferably an alkyl group and may be a propyl, butyl, pentyl, hexyl, octyl, decyl, dodecyl, tetradecyl or octadecyl group, including those derived from isopropanol, propanol, butanol, isobutanol, secbutanol, 4-methyl-2-pentanol, 2-ethylhexanol, oleyl alcohol, and mixtures thereof. Further included are alkaryl groups such as butylphenyl, octylphenyl, nonylphenyl and dodecylphenyl groups.
The metals embraced by M included those in Groups IA, IIA, IIB and VIII of the Periodic Table. Some that may be mentioned are lithium, sodium, calcium, zinc, cadmium, silver, gold and molybdenum. Non-metallic ions include organic groups derived from vinyl esters such as vinyl acetate, vinyl ethers such as butyl vinyl ether and epoxides such as propylene oxide and 1,2-epoxydodecane. The non-metallic ions may also be derived from nitrogenous compounds such as those derived from hydrocarbyl amines and diamines, including oleylamine and N-oleyl-1,3-propylenediamine and such as the imidazolines and oxazolines.
The phosphorous and sulfur can also be supplied from the combination of two separate compounds, such as the combination of (1) a dihydrocarbyl phosphite having 2 to 10 carbon atoms in each hydrocarbyl group or mixtures of phosphites and (2) a sulfide such as sulfurised isobutylene, dibenzyl disulfide, sulfurised terpenes, phosphorodithionyl disulfide and sulfurised jojoba oil. The phosphites include the dibutyl, dihexyl, dioctyl, didecyl and similar phosphites. Phosphate esters containing 4 to 20 carbon atoms in each hydrocarbyl group, such as tributyl phosphate, tridecyl phosphate, tricresyl phosphate and mixtures of such phosphates, can also be used.
In summary, it is essential to the practice of this invention, in which greases having improved dropping points are obtained, that at least the first two of the above-mentioned ingredients be formulated into the composition. Thus, first, with respect to the preparation of the grease, the thickener will have at least 15% by weight of a metal or non-metal hydroxyl-containing soap therein, the total thickener being from 3% to 20% by weight of the grease composition. Secondly, there will be added to the grease from 0.01% to 10% by weight, preferably 0.1% to 2%, of a borated ester, in which such ester has been reacted with preferably at least an equimolar amount of boron compound; and, thirdly, the composition may have therein from 0.01% to 10% by weight, preferably from 0.2% to 2% by weight, of phosphorus and sulfur-containing compounds or a mixture of two or more compounds which separately supply the phosphorus and sulfur moieties. If separate compounds are used, an amount of the mixture equivalent to the above concentration levels is used to supply desired amounts of phosphorus and sulfur.
It was noted that, when the hydroxy-containing thickener was used with the borated ester, the dropping point of the grease was consistently unexpectedly higher than with a grease from the same grease vehicle and the same borated ester, but with a different thickener, such as a non-hydroxy-containing thickener. Thus, the broad invention is to a grease composition comprising the two components mentioned.
In general, the reaction products of the present invention may be employed in any amount which is effective for imparting the desired degree of friction reduction, antiwear activity, antioxidant activity, high temperature stability or antirust activity. In many applications, however, the borated esters and the phosphorus- and/or sulfur-containing compound(s) are effectively employed in combined amounts from 0.02% by weight, and preferably from 0.2% to 4% of the total weight of the composition.
The greases of the present invention can be made from either a mineral oil or a synthetic oil, or mixtures thereof. In general, mineral oils, both paraffinic, naphthenic and mixtures thereof, may be of any suitable lubricating viscosity range, as for example, from 45 SSU at 37.8°C to 6000 SSU at 37.8°C, and preferably from 50 to 250 SSU at 99°C. These oils may have viscosity indexes ranging to 100 or higher. Viscosity indexes from 70 to 95 are preferred. The average molecular weights of these oils may range from 250 to 800. In making the grease, the lubricating oil from which it is prepared is generally employed in an amount sufficient to balance the total grease composition, after accounting for the desired quantity of the thickening agent, and other additive components to be included in the grease formulation.
In instances where synthetic oils are desired, in preference to mineral oils, various compounds of this type may be successfully utilised. typical synthetic vehicles include polyisobutylene, polybutenes, hydrogenated polydecenes, poly propylene glycol, polyethylene glycol, trimethylol propane esters, neopentyl and pentaerythritol esters, di(2-ethylhexy) sebacate, di-(2-ethylhexyl) adipate, dibutyl phthalate, fluorocarbons, silicate esters, silances, esters of phosphorus-containing acids, liquid ureas, ferrocene derivatives, hydrogenated synthetic oils, chain-type polyphenyls, siloxanes and silicones (polysiloxanes), alkyl-substituted diphenyl ethers typified by a butyl-substituted bis(p-phenoxy phenyl) ether, phenoxy phenylethers.
The metallic soap grease compositions containing one or more of the borated hydroxy-containing ester and, optionally, one or more of the sulfur and phosphorus combinations described herein provide advantages in increased dropping point, improved grease consistency properties, antirust characteristics and potential antifatigue, antiwear and antioxidant benefits unavailable in any of the prior greases now known. The grease composition of this invention is unique in that it can be preferably manufactured by the admixture of additive quantities of the alcohol borates to the fully formed soap grease after completion of saponification.
The following Examples will present illustrations of the invention.

EXAMPLE 1

Glycerol monooleate (115 g), consisting of a mixture of about 60% of glycerol monooleate and about 40% of glycerol dioleate, xylene (38 g) and butanol (122 g) were charged to a reactor equipped with a heater, an agitator and a condenser. The reactor contents were heated to 50°C, and boric acid (100 g) was charged to the ester and solvent. The reaction mixture was heated to 204°C and was held there for about 3 hours until water evolution ceased. The reactor contents were cooled to 155°C and vacuum (to less than 2 mm of Hg) was applied to remove the solvents. The crude product was further cooled to 105°C and it was then filtered through diatomaceous earth to yield a viscous, amber liquid.

EXAMPLE 2

Same as Example 1, except that the following ratios by weight were used to give an excess of boron:
7.55 pounds glycerol monooleate/pound boric acid
1.13 pounds butanol/pound boric acid
0.17 pound xylene/pound boric acid

EXAMPLE 3

A lithium hydroxystearate grease thickener was prepared by saponification of a mixture containing 12-hydroxystearic acid (8%) and the glyceride thereof (9%) with lithium hydroxide in a mineral oil vehicle at 177°C in a closed contactor. After depressuring and dehydration of the thickener in an open kettle, sufficient mineral oil was added to reduce the thickener content to 9.0%. After cooling to 99°C, a typical grease additive package, consisting of an amine antioxidant, phenolic antioxidant, metallic dithiophospate, sulfur-containing metal deactivator and nitrogen containing antirust additives, was added. This produced a base grease for evaluating the effect of borated hydroxyl-containing esters on grease dropping point and other properties.

EXAMPLE 4

To the grease of Example 3 was added 2 wt. % of the borated glycerol monooleate of Example 1. The addition was accomplished in a laboratory grease blender from 110°C to 116°C.

EXAMPLE 5

Same as Example 4, except that 2 wt % of the borated glycerol monooleate of Example 2 was used.

EXAMPLE 6

Prepared like the grease of Example 3, except that the mineral oil was thickened with the lithium soap of a 50/50 (wt) mixture of stearic and palmitic acids.

The results, obtained using the ASTM D-2265-78 Test, are summarised in Table I.

Table I

Sample		D2265 Dropping Point, °C.
Base Grease A (Example 3)	(containing amine antioxidant, phenolic antioxidant, 1.5 wt. % of zinc dialkyl phosphorodithioate, (where alkyl is derived from a mixture of C₃ to C₆ primary alcohols), and sulfur-containing metal deactivator and nitrogen containing antirust additives.	202
Example 4 -	Base grease A + 2.0 wt. % borated glycerol monooleate	240
Example 5 -	Base grease A + 2.0 wt. % borated glycerol monooleate (1/3 excess boron)	290
Base Grease B (Example 6)	Base grease thickened with lithium and with lithium soap of a 50/50 (wt) mixture of stearic and palmitic acids	209
Example 7 -	50 wt. % of base grease A used in Examples 4 and 5 and 50 wt. % of base grease B of Example 6	190
Example 8 -	Base grease of Example 6 containing 2 wt. % of the borated glycerol monooleate of Example 1	207

Example 8 clearly shows no dropping point improvement when the borated ester is added to a non-hydroxy-containing carboxylate soap thickened grease.

Claims

A process for preparing an improved grease composition which process comprises formulating a major proportion of a grease, from 0.01% to 10% by weight of a reaction product made by reacting an ester of the formula

R(COOR¹)_n

wherein n is 1 to 5 and R and R¹ are hydrocarbyl or hydroxyhydrocarbyl groups containing from 1 to 40 carbon atoms, at least one of R and R¹ being a hydroxyhydrocarbyl group, with a boron compound, and a thickener containing at least 15% by weight of a lithium soap of a hydroxy-containing fatty acid, fatty glyceride or fatty ester containing from 12 to 30 carbon atoms whereby the dropping point of the grease composition is at least 240°C.
The process of Claim 1 additionally formulating from 0.01% to 10% by weight of a phosphorus and sulfur compound or a mixture of phosphorus-containing and sulfur-containing compounds to supply an equivalent amount of phosphorus and sulfur.
The process of Claim 1 or 2 wherein the thickener is derived from 12-hydroxystearic acid, 14-hydroxystearic acid, 16-hydroxystearic acid, 6-hydroxystearic acid or a glyceride or ester thereof.
The process of claim 1, 2 and 3 wherein R is an alkyl, aryl, aralkyl, alkaryl or cycloalkyl group or a hydroxy-substituted member thereof.
The process of Claim 4 wherein the ester is trimethylolpropane monooleate, trimethylolpropane dioleate, trimethylolpropane monostearate, trimethylolpropane distearate, trimethylolpropane monopelargonate, trimethylolpropane monooleate monopelargonate, pentaerylthritol monooleate, pentaerythritol dioleate, pentaerythritol trioleate, pentaerythritol monoisostearate, pentaerythritol monooleate monopelargonate, pentaerythritol monoisostearate, monopelargonate or monohexanoate, pentaerythritol tripelargonate, glycerol monooleate, glycerol dioleate, glycerol monostearate, glycerol monoricinoleate, glycerol monoisostearate, glycerol monopelargonate, glycerol monohexadecanoate, sorbitan monooleate, sorbitan dioleate, sorbitan monostearate, sorbitan distearate, sorbitan monopelargonate, dipentaerythritol monooleate, dipentaerythritol dioleate, dipentaerythritol trioleate, ethyleneglycol monooleate, ethyleneglycol monostearate, ethyleneglycol monoisostearate, diethyleneglycol monooleate, diethyleneglycol monopelargonate, diethyleneglycol monoisostearate and triethyleneglycol monooleate, methyl hydroxystearate or ethyl hydroxystearate.
The process of Claim 1, 2, 3, 4, or 5 wherein the boron compound is selected from the group consisting of a metaborate, boric acid, mono-, di and trimethyl borate, mono-, di and triethyl borate, mono-, di and tripropyl borate, mono-, di and tributyl borate, mono-, di and tripentyl borate and mono-, di and trihexyl borate.
The process of Claim 2, 3, 4, 5, or 6 wherein the phosphorus and sulfur moieties are supplied by a phosphorothioate of the formula
wherein R³ is a hydrocarbyl group containing 3 to 18 carbon atoms, M is a metal or non-metal, n is a valence of M and Z is oxygen or sulfur, at least one of which is sulfur.
The process of Claim 7 wherein R³ is derived from isopropanol, butanol, isobutanol, sec-butanol, 4-methyl-2-pentanol, 2-ethylhexanol or mixtures thereof.
The process of Claim 7 wherein M is a metal from Group IA, IIA, IIB or VIII of the Periodic Table.
The process of Claim 9 wherein the metal is lithium, sodium, molybdenum, calcium, zinc, cadmium, silver or gold.
The process of Claim 7 wherein M is derived from vinyl acetate, butyl vinyl ether, propylene oxide, 1,2-epoxydodecane or nitrogenous compounds.
The process of Claim 2 wherein the phosphorus and sulfur moieties are supplied by a combination of (1) a dihydrocarbyl phosphite having 2 to 6 carbon atoms in each hydrocarbyl group, mixtures of such phosphites, or a phosphate ester having 4 to 20 carbon atoms in each hydrocarbyl group and (2) a sulfide selected from sulfurised isobutylene, dibenzyl disulfide, sulfurised terpenes, phosphorodithionyl disulfide and sulfurised jojoba oil.
The process of Claim 12 wherein the phosphite is a dibutyl, dihexyl, dioctyl or didecyl phosphite or mixtures thereof.
The process of Claim 12 wherein the phosphate ester is a tributyl, tridecyl or tricresyl phosphate or mixtures thereof.
The process of Claim 1 wherein the esters is glycerol monooleate, the boron compound is boric acid, the thickener is lithium 12-hydroxystearate and the phosphorus and sulfur moieties are from zinc dialkyl phosphorodithioate, where alkyl is a mixture of alkyls containing 3 to 6 carbon atoms.
The process of Claim 1 wherein the grease vehicle is a mineral oil, synthetic oil or a mixture thereof.
The use of a thickener containing at least 15% by weight of a lithium soap of a hydroxy-containing fatty acid, fatty glyceride or fatty ester containing 12 to 30 carbon atoms to improve the dropping point of a grease composition comprising a major proportion of a grease and from 0.01% to 10% by weight of a reaction product made by reacting and ester of the formula.

R(COOR¹)_n

wherein n is 1 to 5 and R and R¹ are hydrocarbyl or hydroxyhydrocarbyl groups containing 1 to 40 carbon atoms at least one of R and R¹ being a hydroxyhydrocarbyl group with a boron compound.