US3125525A

US3125525A - Lubricating greases containing borate

Info

Publication number: US3125525A
Authority: US
Publication date: 1964-03-17
Anticipated expiration: 1981-03-17

Description

United States Patent Office 3,125,525 Patented Mar. 17, 1964 3,125,525 LUBRICATIN G GREASES CONTAINING BORATE ESTER-AMINE COMPLEXES William R. Siegart, Wappingers Falls, Clemence J. Henry, Newburgh, and Norman R. Odell and Fred C. Toettcher, Fishkill, N.Y., assignors to Texaco Inc., New York, N.Y., a corporation of Delaware No Drawing. Filed Jan. 17, 1961, Ser. No. 83,183

14 Claims. (Cl. 252-3345) This invention relates to lubricating greases and to a novel class of additives therefor. More particularly, it relates to hydroxy fatty acid soap thickened greases containing compounds formed between borate esters and high molecular weight aliphatic amines.

The compounds which are employed as grease additives in accordance with this invention are association complexes which are formed by reacting aliphatic amines of the class consisting of monoamines containing at least 6 carbon atoms per molecule and diamines, with boric acid esters containing 13 --OR or SR groups attached to a' boron atom, where R is a hydrocarbon group or substituted hydrocarbon group. These borate esteramine complexes are disclosed and claimed in copending co-owned application Serial No. 59,180, of E. L. Kay and E. C. Knowles, filed September 29, 1960, as additives for liquid lubricants such as a combination transmission-rear axle automotive lubricant, wherein they impart improved anti-wear properties under the conditions of hypoid gear lubrication as well as detergency and other improved properties for this type of service.

We have found, in accordance with the present invention, that increased dropping points and other advantages, including improved water resistance properties, are obtained in hydroxy fatty acid soap thickened greases by employing therein minor amounts of compounds of the above class. A particularly valuable application of this invention is found in the production of hydroxy fatty acid soap thickened greases containing fatty type extreme pressure agents, which ordinarily strongly degrade the water absorption properties of such greases. Lubricating greases representing a preferred embodiment of this invention, having a combination of high dropping points, good extreme pressure properties and very satisfactory water resistance properties, are obtained by employing borate ester-amine complexes in lithium hydroxy fatty acid soap thickened greases containing sulfurized fatty oils.

The above advantages obtained by employing the borate ester-amine complexes in hydroxy fatty acid soap thickened greases were entirely unexpected on the basis of the experience with these compounds employed in conventional fatty acid soap thickened greases, wherein no advantages were obtained. While we do not intend to be limited by any particular theory, it appears on the basis of infrared analyses and other evidence that a stable coordinated compound is formed by electron sharing between the boron atom of the borate ester compound and the hydroxy group of the hydroxy fatty acid soap, which accounts for the diiference in the effect of the borate ester compounds in hydroxy fatty acid soap thickened greases and in conventional fatty acid soap thickened greases.

The borate esters which are employed for forming these complexes are compounds of the class represented by the formulas:

wherein R is a hydrocarbon or substituted hydrocarbon group, R is hydrogen, a hydrocarbon group or substituted hydrocarbon group, X is oxygen or sulfur, n is a whole number from 0 to 2, inclusive, m is a whole number from 1 to 3, inclusive, the sum of n and in being 3, n is a whole number from O to 3, inclusive, m is a whole number from 1 to 4, inclusive, the sum of n and m being 4, the compound containing at least one hydrocarbon or substituted hydrocarbon group represented by R or R. Hydrocarbon groups represented by R and R include alkyl, aryl, alkaryl and aralkyl groups, and substituted derivatives thereof containing substituents such as hydroxy, alkoxy, phenoxy, nitro and amine groups, halogens, etc. The preferred compounds are those wherein n and 12' equal zero, in being 3 and m being 4, and wherein all of the groups represented by R are hydrocarbon or substituted hydrocarbon groups, preferably containing at least 3 carbon atoms. Particularly preferred compounds are those wherein at least one group represented by R is a phenyl group having an electronegative substituent such as a halogen atom or nitro group in a position para to the ester linkage.

Examples of suitable compounds of the above clas include the following:

Particularly suitable compounds are di-p-chlorophenylmono-nonylphenyl borate and di-p-chlorophenyl-mono- (alkyl-o-cresyl) borate, wherein the alkyl group contains about 430 carbon atoms.

The aliphatic amines which are employed to form the borate ester adducts or association complexes are compounds of the class comprising monoamines containing at least six aliphatic carbon atoms and diamines, wherein the amine groups may be primary, secondary or tertiary amine groups. Examples of suitable amines include dodecyl amine, tertiary tetradecyl amine, tertiary undecyl amine, secondary dibutyl amine, octylamine, hexadecylamine, ethylene diamine, hexane diamine, etc. The preferred compounds are monoamines containing from about 8 to about 26 aliphatic carbon atoms per molecule, particularly suitable compounds being primary amines wherein the alkyl group is a tertiary alkyl group.

Formation of the borate ester-amine complexes takes place readily over a wide range of conditions. The complex may be prepared by merely mixing together the borate ester and amine in the reacting proportions at room temperature or at moderately increased temperatures in the presence or absence of a solvent. The preparation may also be carried out by reacting together boric acid and alcohol together with the amine in an organic solvent such as benzene, toluene, etc. The borate ester and amine are usually reacted in a 1:1 mol ratio. However, complexes containing reduced amounts of amine, such as borate ester-amine mol ratios of :5 to 10:1 may be employed in some cases, particularly where there are severe copper anti-corrosiveness requirements.

The lubricating greases to which this invention relates are those containing metal soaps of high molecular weight hydroxy fatty acids in sufiicient proportions to provide at least a substantial thickening effect. The metal component may be any metal which is suitable for forming soaps employed as thickening agents in lubricating greases generally, including sodium, potassium, lithium, calcium, barium, strontium, aluminum, manganese, zinc, etc. The alkali metals and alkaline earth metals comprise a preferred class of metals for this purpose. The hydroxy fatty acid soap will usually be present in the composition in amounts from about 3 to about percent by weight, although somewhat smaller or larger amounts are also suitable, such as amounts as low as about 2 percent by weight and as high as about percent by weight of the composition.

The borate ester-amine complexes are ordinarily employed in these lubricating greases in amounts in about the range 01-10 percent by weight, although somewhat larger or smaller amounts may be employed if desired. They are most suitably employed in amounts in about the range 0.5-5 percent by weight of the grease composition.

Suitable soap forming acid materials which may be employed in the production of these greases include hydroxy fatty acids containing from about 12 to about 24 carbon atoms per molecule and one or more hydroxy groups separated from the carboxylic group by at least one carbon atom, and the glycerides and other esters of such acids. The preferred acids are substantially saturated acids containing from about 16 to about 22 carbon atoms and one or two hydroxy groups per molecule. Such materials may be obtained from naturally occurring glycerides, by hydroxylation of fatty acids, by hydrogenation of ricinoleic acid or castor oil, or otherwise by processes such as the catalytic oxidation of hydrocarbon oils and waxes which have been extracted and fractionated to the desired molecular range. Mixtures of hydroxy acids together with unsubstituted fatty acids may be very suitably employed, wherein the hydroxy fatty acid comprises at least about one third of the fatty acid mixture.

Lubricating oils employed in the greases include conventional mineral oils and synthetic oils, such as high molecular weight ethers, esters, silicones, etc. mineral oils include both paraflinic and naphthenic oils and blends thereof, having viscosities in the range from about seconds Saybolt Universal at F. to about 225 seconds Saybolt Universal at 210 F. A particularly suitable class of synthetic lubricating oils comprises synthetic dicarboxylic acid esters, such as di-2- ethylhexyl sebacate, (di-secondary amyl) sebacate, di-2- ethylhexyl azelate, etc. and polymers obtained by condensing dicarboxylic acids with glycols as disclosed in U.S. 2,628,974, as well as the sulfur analogs of such esters. Other synthetic oils which may be employed in accordance with this invention include the silicone polymers, including dialkyl silicone polymers such as dimethyl silicone polymer, diethyl silicones and mixed aryl alkyl silicone polymers such as phenyl methyl silicone polymer, having viscosities in the lubricating oil viscosity range.

The sulfurized fatty oils which are employed in the greases representing a preferred embodiment of this invention may be any sulfurized natural or synthetically obtained fatty materials such as have been employed heretofore as extreme pressure additives in lubricating compositions, including, for example, products obtained by sulfurizing castor oil, lard oil, sperm oil, corn oil, fish oil, or the like. A suitable material of this character is Suitable sulfurized lard oil containing from about 5 to 12 percent by weight of sulfur, obtained by heating No. 1 lard oil with about 10 to 15 percent of sulfur at a temperature above 300 F., and preferably in about the range 350- 400 F., for a suflicient time to obtain a homogeneous product. A particularly preferred material of this type is sulfurized sperm oil, containing from about 5 to 15 percent of sulfur. The composition may very suitably contain from about 0.5 to 15 percent, and preferably from about 1 to 10 percent by weight, of the sulfurized fatty oil.

The lubricating greases of this invention may also contain other additives of various types such as are commonly employed in lubricating greases, such as other extreme pressure agents, anti-corrosives, anti-oxidants, etc., as well as different thickening agents, such as other soaps of various types and finely divided solids having grease forming properties.

The grease preparation may be carried out in any suitable manner. The borate ester-amine complex may be added either during the grease preparation or it may be incorporated into the previously prepared grease by heating a mixture of the grease and a borate ester-amine complex at a mildly elevated temperature such as about F. with stirring, preferably followed by milling. It is conveniently added during the grease preparation when the mixture has cooled below about 200 F.

The following examples are given for the purpose of more fully disclosing the invention.

EXAMPLE I A lubricating grease having the following composition in percent by weight:

Lithium 12-hydroxystearate 7.8 Free LiOH 0.2 Borate ester-amine complex 3.0 Lubricating oil Remainder The lubricating oil is a mixture in a 3:1 ratio by weight, respectively, of Z-ethylhexyl sebacate and a highly rcfined paraflinic distillate oil having a Saybolt Universal viscosity of about 100 seconds at 100 F.

The borate ester is an association complex obtained by reacting a borate ester with a high molecular weight amine in a mol ratio of 1:1. The amine employed is suitably a commercial material sold by Rohm & Haas under the trade name of Primene 81-R consisting of tertiary alkyl primary amines in the range from C12H25NH2 to C15H31NH2.

Following is a detailed description of the preparation of one of these borate ester-amine complexes: 257 grams (2 mols) of p-chlorophenol, 61.8 grams (1 mol) of boric acid and 200 ml. of isopropyl benzene were charged to a 1 liter, three-necked flask equipped with stirrer, condenser and Barrett type distilling receiver, and the mixture heated under reflux for 2.16 hours until 36 ml. (2 mols) of water were removed. At this point 220 grams (1 mol) of nonylphenol were added and the solution was refluxed for an additional 26.16 hours until 18 ml. of water were obtained. The solvent was removed under reduced pressure and 191 grams (1 equivalent based on Rohm & Haas data) of Primene 81R were added slowly over a period of 40 minutes, a temperature rise of about 34 C. occurring in the reaction mixture indicative of adduct formation. The product was stirred for an additional 2.16 hours and then removed from the flask; the product was a clear yellow viscous liquid, obtained in a 99+ percent yield.

The grease preparation is carried out by saponifying Hydrofol acids 200 with excess lithium hydroxide in the presence of a major proportion of the mineral oil contained in the grease. The saponification is accomplished by heating the mixture for about 1 /2 hours at 317 F. The saponification mixture is then heated up to 400 F. while adding 2-ethylhexyl sebacate and circulating the mixture through a shear valve at 75 lbs. pressure drop while the mixture is maintained at 400 F. The mixture is cooled to 200 F. during about 2 /2 hours While additional amounts of mineral oil and Z-ethylhexyl sebacate are added. The grease is finally drawn and finished by milling in a Premier colloid mill. The borate esteramine complex is incorporated into the base grease thus obtained by heating a mixture of the grease and the borate ester-amine complex in suitable proportions by weight at 150 F. for 30 minutes with stirring and then milling with one pass through a Premier colloid mill at 0.002 inch clearance. The grease thus obtained has a smooth buttery texture and very superior lubricating properties generally.

The following table shows the effect of the borate esteramine complexes in increasing the dropping point of the above grease.

Table I Borate ester/ amine Dropping point complex: ASTM, F. None 367 Tri-(nonylphenyl) borate/amine 480 Mono-nonylphenyl-di-(p-chlorophenyl) borate/ amine 427 Tri-(p-chlorophenyl) borate/amine 411 Di-p-chlorophenyl-mono-l1-(1 carbomethoxy) heptadecyl borate/amine 412 Tri-thiophenyl borate/amine 419 Tri-p-tertiary butyl-thiophenyl borate/amine 440 In addition to the increased dropping points, a moderate extreme pressure improvement was also obtained with the halogenated borate ester-amine complexes in the above grease, as shown by the data given in the following table.

Table II Borate ester/ amine complex: Mean Hertz load, kg. None 21 Tri-(nonylphenyl) borate/amine 22 Mono-nonylphenyl-di-(p chlorophenyl) borate/ amine 26 Tri-(p-chlorophenyl) borate/ amine 28 Di-p-chlorophenyl-mono-l1-(1 carbomethoxy) heptadecyl borate/ amine 31 EXAMPLE II A lubricating grease representing a preferred embodiment of the invention having the following composition in percent by weight:

Lithium 12-hydroxystearate 6.0 Free LiOI-I 0.1 Glycerine 0.6 Diphenylamine 0.6 Sulfurized sperm oil 7.0 Lead naphthenate 1.0 Borate ester-amine complex 0.5-3.0 Lubricating oil Remainder The lubricating oil employed in the above grease is a lend in about a 1:4 weight ratio respectively of a refined parafiinc distillate oil having a Saybolt Universal viscosity at 100 F. of about 180, and a refined residual fraction from a mixed base crude having a Saybolt Universal viscosity at 210 F. of about 105.

The sulfurized sperm oil is a commercial product containing about percent by weight of sulfur, and the lead naphthenate is also a commercial product obtained from petroleum naphthenates.

The grease is prepared substantially as described in Example I, employing hydrogenated castor oil as the saponifiable material and adding the sulfurized sperm oil, lead naphthenate and diphenylamine during cooling of the grease mixture and when the temperature is about 200 F.

Table III below shows the effect of the borate ester- 6 amine complexes in improving the Water absorption properties of the above grease.

Table I I I Concen- Water Penetra- Borate Ester/amine tration, Absorbed, tion of Percent Percent Emulsion None l 220 377 Tri-p-chlorophenyl borate/amine 0. 5 326 Do 1. O 45 324 D0 2.0 25 313 Di-pehlorophenylmonononylph enyl borate/amine 0. 5 150+ 343 D0 1. 0 35 315 D o 2. 0 40 313 Di-para-tort.- butylphenyl-monopnitrophenyl borate/amine 1. 0 150+ 324 D0 2. 0 35 313 D inonylphenyl mono pentachlorophenyl borate/amine 1. 0 150+ 326 Do 2. 0 40 328 Emulsion inversion.

Table IV below shows the effect of borate ester-amine complexes upon the dropping point of greases containing other metal soaps of hydroxy fatty acids. The borate ester amine complex employed in these greases was that of monononylphenyl-p-chloropheny1 borate with Primene 81-R. The greases were mineral oil base greases containing the thickening agents shown in the table.

In contrast to the above results obtained with hydroxy fatty acid soap thickened greases, no improvement in dropping point or other advantage was found with the borate ester-amine complexes in greases thickened with conventional fatty acid soaps.

Obviously many modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof and only such limitations should be imposed as are indicated in the appended claims.

We claim:

1. A lubricating grease consisting essentially of a lubricating oil thickened to a grease consistency by a metal hydroxy fatty acid soap and containing about 0.1-10 percent by weight of a complex of a borate ester and an aliphatic amine selected from the group consisting of monoamines containing at least 6 aliphatic carbon atoms per molecule and diamines, said borate ester and said amine being in a mol ratio of 10:1 to 1:1, respectively, and said borate ester being a compound of the class represented by the formulas:

wherein R is selected from the class consisting of hydrocarbon groups and substituted hydrocarbon groups, R is selected from the class consisting of hydrogen, hydrocar bon groups and substituted hydrocarbon groups, X is selected from the class consisting of oxygen and sulfur, n is a whole number from 0 to 2, inclusive, m is a whole number from 1 to 3, inclusive, the sum of n and in being 3, n is a whole number from 0 to 3, inclusive, m is a whole number from 1 to 4, inclusive, the sum of n and m being 4, and at least one group represented by R and R Which is present in the compound being selected from 7 the class consisting of hydrocarbon groups and substituted hydrocarbon groups.

2. A lubricating grease according to claim 1 wherein the said aliphatic amine is a tertiary alkyl monoamine containing about 8 to 26 carbon atoms per molecule.

3. A lubricating grease according to claim 1 wherein the said borate ester and said amine are in the mol ratio of about 1:1.

4. A lubricating grease according to claim 1 wherein the said borate ester is a compound represented by the said formulas wherein n and 12' equal 0 and the groups represented by R are chosen from the class consisting of hydrocarbon groups and substituted hydrocarbon groups.

5. A lubricating grease according to claim 4 wherein the said borate ester contains one phenyl group having a para positioned electronegative substituent.

6. A lubricating grease according to claim 1 containing a minor proportion, sufiicient to impart improved extreme pressure properties to the composition, of a sulfurized fatty oil.

7. A lubricating grease according to claim 1 wherein the metal component of the said metal hydroxy fatty acid soap is chosen from the group consisting of alkali metals and alkaline earth metals.

8. A lubricating grease according to claim 1 wherein the said lubricating oil is a mineral oil.

9. A lubricating grease according to claim 1 wherein the said lubricating oil is a dicarboxylic acid ester.

10. A lubricating grease according to claim 1 wherein the said metal fatty acid soap is lithium 12-hydroxystearate.

11. A lubricating grease according to claim 1 wherein the said borate ester is di-p-chlorophenyl-mono-nonylphenyl borate.

12. A lubricating composition according to claim 1 wherein the said borate ester is di-p-chlorophenyl-mono- (alkyl-o-cresyl) borate, said alkyl group containing about 4-30 carbon atoms.

13. A lubricating grease consisting essentially of a lubricating oil selected from the class consisting of mineral oils and ester oils thickened to a grease consistency by a metal hydroxy fatty acid soap and containing about 0.5- 15 percent by weight of a sulfurized fatty oil and about 0.55 percent by weight of a complex of a borate ester and an aliphatic monoamine containing about 8 to 26 carbon atoms per molecule, said borate ester and said monoamine being in a mol ratio of 10:1 to 1:1, respectively, and said borate ester being a compound of the class represented by the formulas:

References Cited in the file of this patent UNITED STATES PATENTS Brunstum et a1. Aug. 5, 1958 Ashby et al Nov. 22, 1960