US2872417A

US2872417A - High dropping point lithium base greases

Info

Publication number: US2872417A
Application number: US462606A
Authority: US
Inventors: Terence B Jordan; John P Dilworth; James R Roach
Original assignee: Texaco Inc
Current assignee: Texaco Inc
Priority date: 1954-10-15
Filing date: 1954-10-15
Publication date: 1959-02-03
Anticipated expiration: 1976-02-03

Description

HIGH DROPPING POINT LITHIUM BASE GREASES Terence B. Jordan and John P. Dilworth, Fishirill, .and James R. Roach, Beacon, N. Y., assignors to The Texas Company, New York, N. Y., a corporation of Delaware No Drawing. Application October 15, 1954 Serial No. 462,606

13 Claims. ,(Cl. 25242.1)

This invention relates to lithium greases characterized l by high dropping points. More particularly, it involves the discovery that a particular class of additives are very eflective in raising the dropping point of lithium greases.

Lithium base greases have met with wide acceptance as general purpose greases. They are water resistant, have high dropping points in the neighborhood of 350 to 400 F. and provide lubrication over a wide temperature range. The instant invention provides means whereby the dropping points of lithium greases are raised 30 to 130 units. Lithium base greases having dropping points over 500 F. are products of this invention.

The high dropping point greases of this invention comprise an oleaginous liquid lubricating base, a lithium salt of a soap-forming fatty acid as the sole thickening agent, an excess of lithium hydroxide over the stoichiometric required to react with the soap-forming material and an ester of a phosphorus acid which may be either a phosphite or a phosphate ester.

The unusual action of phosphite and phosphate esters on dropping points is limited to greases containing a lithium soap as the sole thickening agent. Phosphite and phosphate esters have no significant effect on the dropping points of alkali metal or alkaline earth metal greases or on lithium mixed base greases containing a substantial amount of other alkali metal or of an alkaline earth metal soap. Phosphite and phosphate esters do not raise the dropping points of the following greases: sodium stearate and sodium oleate greases; calcium stearate and calcium 12-hydr0xy stearate greases; 3:1 lithium-calcium 12-hydroxy stearate grease; 1:1 lithium-lead 12-hydroxy stearate grease; 4:1 lithium-sodium 2:1 l2-hydroxy stearate: stearate greases.

The soap-forming component of the high dropping point greases of this invention is a fatty acid, a fatty acid ester such as a glyceride or mono-ester, a hydroxy fatty acid, a hydroxy fatty acid glyceride or ester, or a mixture of one or more of the foregoing. A partial list of soapforming materials is as follows: stearic acid, oleic acid, myristic acid, tallow, menhaden oil, soya bean oil, methyl stearate, hydrogenated castor oil, methyl 12-hydroxy stearate and 12-hydroxy stearic acid. The soap-forming fatty acid or hydroxy fatty acid contains at least 12 and generally less than 24 carbon atoms. Hydroxy fatty acids containing at least 12 carbon atoms and 1 or more carbon atoms separating the hydroxyl group from the carboxyl group, their glycerides and esters are the preferred soapforrning components used in the greases of this invention. Mixtures comprising a hydroxy fatty acid and a conventional fatty acid or glyceride such as stearic acid or tallow constitute preferred soap-forming components; usually the hydroxy fatty acid comprises 50 percent or more of mixtures of this type.

An additional requirement of the high dropping point greases of the invention is that they have an excess of lithium hydroxide over the stoichiometric amount required to neutralize the soap-forming components of the grease mixture. in order for the phosphite or phosphate ester Patented Feb. 3, i959 to effectively raise the dropping point of the lithium base grease, at least 0.05 weight percent excess lithium hydroxide must be present. The excess lithium hydroxide concen tration is between 0.05 and 0.8 percent with the preferred concentration of excess lithium hydroxide falling between 0.15 and 0.5 weight percent of the total grease composition. In the absence of the prescribed excess of lithium hydroxide,'the addition of a phosphite ester does not raise the dropping point of the lithium grease.

The phosphite and phosphate esters, which, in conjunction with the use of a prescribed excess of lithium hydroxide, raised the dropping points of greases containing lithium soap as the sole thickening agent, have aliphatic, cycloaliphatic, aryl, aralkyl or alkaryl hydrocarbon substituents. Esters in which the hydrocarbon substituents comprise a mixture of aliphatic, cycloaliphatic, aryl, aralkyl or alkaryl radicals may also be used. The general formulas of the phosphite and phosphate esters are as follows:

/0 R /O R PO R 0=P0 R 0 RI! 0 RI! Phosphite esters Phosphate esters wherein the R, R and R represent aliphatic, cycloaliphatic, aryl, alkaryl or aralkyl radicals. The R, R and R" radicals may be different in a particular ester but usually are the same. In general, the hydrocarbon radical may contain 1 to 15 carbon atoms. If aliphatic esters are used, the preferred chain length for the hydrocarbon radical is 3 to 6 carbon atoms, while with aryl esters the preferred chain length is 6 to 9 carbon atoms. Examples of phosphite esters used in the formulation of high dropping point lithium base greases are the following: aliphatic phosphites such as tributyl phosphite, tri-Z-amyl phosphite and tri-Z-pentenyl phosphite; cycloaliphatic phosphites such as tricyclohexyl phosphite, tri-o-methylcyclohexyl phosphite; aryl phosphites such as triphenyl phosphite, tricresyl phosphite, tri-p-t-butylphenyl phospite and trinaphthyl phosphite. The corresponding phosphate esters are also useable, but in the phosphate series the aryl and alkaryl esters such as triphenyl phosphate and tricresyl phosphate are preferred.

The action of phosphite and phosphate esters on lithium base greases containing an excess of lithium hydroxide is limited to hydrocarbon-substituted esters and phosphoric acid. Halo-hydrocarbon esters such as tris-chloroethyl phosphite and tris-dichlopropyl phosphate are not effective in raising the dropping point of lithium base greases having the prescribed excess of lithium hydroxide.

The phosphite or phosphate ester constitutes 0.5 to 5 percent of the total grease composition with concentrations of 1 to 4 percent ester normally being employed. With particularly preferred phosphite and phosphate esters such as triamyl phosphite, tributyl phosphite, triphenyl phosphite, tricresyl phosphate and triphenyl phosphate, lithium base greases having dropping points over 500 F. are obtained with i to 3 percent ester.

Thelithium soap thickening agent consisting of a lithium soap constitutes 5 to 25 weight percent of the total grease composition and usually 6 to 18 weight percent of the total grease.

The oil component of the subject grease composition may be broadly described as an oleaginous vehicle, which includes the conventional mineral lubricating oils, the synthetic lubricating oils prepared by cracking and polymerizing products of the Fischer-Tropsch process and the like, or a synthetic oleaginous compound within the lubricating oil viscosity range. The synthetic oleaginous compounds are those organic compounds which possess lubricating characteristics and may be substituted in whole or in part for the conventional mineral lubricating oils.

Examples of these compounds are the polyethers such as polypropylene glycol, the aliphatic dicarboxylic acid esters, such as the alkyl esters of sebacic acid, the high molecular weight aliphatic ethers, such as normal octyl ether,

phosphate esters in combination with excess alkali in raising the dropping points is limited to greases containing lithium soap as the sole thickening agent. The dropping points of calcium 12-hydroxy stearate grease, a

polyesters of a glycol and dicarboxylic acid such as the 9 lithium lead 12-hydroxy stearate and a mixed lithiumpolyester of propylene glycol and adipic acid and the calcium soap grease were lowered by the addition of an aromatic acid esters, such as the alkyl esters of benzoic or ester of phosphorus. Although not shown in Table 1, phthalic acids. The choice of the oil component bears phosphite and phosphate esters are not effective in raising directly upon the type of lubricating required of the O the dropping points of sodium base greases containing finished product. For example, in a low temperature 1 excess alkali. In contrast, the addition of a number of TABLE 1 Dropping Points, "F.

Grease+3% Grease Mixture Grease Tri-2- Tri- Tri- Tri- Trl-2- per se Triamyl Tributyl ethylphenyl eyclocresyl ethyl Phos- Phoshexyl Phoshexyl Phoshexylphite phite Phosphite Phosphate phosphite phite photo Li Myristate (17%), Base oil, 0.2 LiOH 413 484 486 Li Soap from Methyl 12-OH Stearate (6.8%),

Base on, 0.2 LiOH 358 1 500+ 500+ 406 500+ 410 Li 12-OH Stearate (15%), Base oil, 0.2 LiOH. 375 Ca Soap from Methyl 12-OH Stearate (18.9),

Base oil, 0.5 (more): 286 275 1:1 Li-Pb Soap from Methyl 12-011 Stearate (7.8), Base oil, 0.1 LiOH 372 349 6:4 LizCa Soap of 3:1 H002: Stearie acid (17.5%), 0.2 LiOH, Base oil (3:1 mixture of di-2-ethylhexylsebaeate and lube oil) 346 332 1 H0O designates hydrogenated caster oil.

lithium base grease, a mineral lubricating oil within the viscosity range of 40-70 SUS at 100 F, a low pour point, and a viscosity index of 60 or more is preferred.

Additives to impart anti-oxidant and extreme pressure properties may be incorporated in the high dropping point lithium greases of the invention. Aromatic amine type inhibitors have been found particularly efiective antioxidants for lithium base greases; aromatic amines such as tetramethyl diamino diphenyl methane, diphenyl amine and phenyl alphanaphthyl amine are preferred. Extreme pressure additives which may be incorporated in the greases are sulfurized fats, sulfurized oils, chlorinated organic compounds such as chlorosubstituted waxes, chlorosubstituted aromatic compounds and chlorinated olefin polymers and sulfo-chlorinated compounds such as sulfochlorinated olefin polymers and olefins derived from waxes. Another EP agent that can be incorporated in the lithium base greases of the invention is lead naphthenate, which although properly termed a soap, is not a thickening agent.

The high dropping point lithium base greases are prepared by any of the standard procedures employed for lithium base greases. Either the so-called high heat procedure or the low temperature method may be used with the former being preferred. The high heat procedure involves saponification and dehydration at a temperature above the melting point of the soap base followed by controlled cooling with agitation through the transition temperature range. The low temperature procedure is more particularly described in U. S. 2,450,219 and 2,45 0,- 220.

The phosphorus acid ester is incorporated in the grease mixture after dehydration and during the stirred cooling of the grease. Usually it is added with the remainder of the oleaginous vehicle and at a temperature between 200 and 250 F.

The effect of phosphite and phosphate esters on the dropping points of lithium greases are shown in the following tables.

Table 1 demonstrates that the action of phosphite and phosphate esters on dropping points is specific to greases containing a lithium soap as the sole thickening agent. This data clearly proves that the action of phosphite or different phosphite and phosphate esters to greases containing lithium soap as a sole thickening agent and an excess of lithium hydroxide resulted in a remarkable increase in the grease dropping point.

On line 2 of Table 1 there are shown the effects of adding different phosphite and phosphate esters to a grease comprising a lithium soap prepared from methyl 12-hydroxy stearate, a parafiin base oil and 0.2 percent excess lithium hydroxide. This data shows that aliphatic phosphites in which the hydrocarbon group contains 3 to 6 carbon atoms are more effective than hydrocarbon phosphite in which the hydrocarbon radical contains a larger number of carbon atoms. It also shows that aryl phosphates are equivalent in effectiveness to the preferred aliphatic phoshpites in which the hydrocarbon radical contains 3 to 6 carbon atoms.

In Table 2 there is presented data proving the necessity of employing excess lithium hydroxide in conjunction with a phosphite or phosphate ester in order to obtain an increase in dropping point.

Example 1 in Table 2 shows that lithium grease containing 3 percent triamyl phosphite but having no excess lithium hydroxide had a melting point of about 358 P. which is substantially the same dropping point of the lithium soap grease without any phosphite ester. An identical grease mixture containing both 0.2 percent excess lithium hydroxide and 3 percent triamyl phosphite had a dropping point well over 500 F.

TABLE 2 Necessity of excess LiOH Dropping point, F. (1) Li soap from methyl 12-OH stearate base oil,

triamyl phosphite (3%) Example 2 in Table 2 demonstrates that the excess of lithium hydroxide must be above about 0.05 percent in order for the phosphite or phosphate ester to have a substantial effect on the dropping point. A lithium myristate grease containing 2.7 weight percent tricresyl phosphate mixture and only 0.01 excess lithium hydroxide had a melting point of 414 E, which is approximately that of a lithium myristate grease containing no phosphate ester. Increase of the excess lithium hydroxide content to the prescribed 0.05 weight percent minimum raised the dropping point 16 F. to 430 F. When the excess lithium hydroxide level reached 0.18 and 0.32 percent, greases having 500+ F. dropping points were obtained.

Table 3 proves that the dropping point improvement is obtained with relatively small amounts of a phosphite ester as long as the grease contains a lithium soap as the sole thickening agent and an excess of lithium hydroxide. In this table, the base grease comprises about 7 percent lithium soap prepared from methyl 12-hydroxy stearate, about '90 percent paraffin base oil and 0.2 percent excess lithium hydroxide.

TABLE 3 Dropping point, Composition: F.

Base grease 372 Base grease+0.5% triamyl phosphite 392; 396 Base grease+1% triamyl phosphite 500+;500+ Base grease+2% triamyl phosphite" 500+; 500+ Base grease+3% triamyl phosphite 500+; 500-]- This data shows that it is not necessary to use large amounts of phosphorus ester in order to obtain substantial dropping point improvement. The exact concentration giving optimum results will vary with the phosphite or phosphate ester employed, but will usually fall in the range of 1 to 4 percent of the total composition.

The efiectiveness of a mixture of an ester of phosphorus and excess lithium hydroxide in raising the dropping point of a lithium grease containing an EP agent is demonstrated by the following data. A lithium grease was prepared comprising 5.9 percent lithium soap from methyl 12-hydroxy stearate, 5 percent lead napthenate and 7.5 percent of sulfurized fatty oil as an EP agent, 80.9 percent parafiin base oil, 0.5 percent diphenylamine and 0.2 percent excess lithium hydroxide. The base grease, which gave a Timken OK load test of 45 pounds and a Norma-Hofiman oxidation pressure drop of 7 pounds in e100 hours, had a dropping point of 351; addition of 1.5 percent triamyl phosphite to the grease composition raised the dropping point to 410 F. and the resulting grease had a Timken OK load of 40 pounds and showed Norma-Hoifman oxidation pressure drop of 8 pounds in 100 hours.

The inelfectiveness of halohydrocarbon-substituted phosphite and phosphate esters in raising the dropping point of a lithium soap grease containing the prescribed excess of lithium hydroxide is shown by the following data. A grease was prepared comprising 8 percent of lithium soap prepared from methyl l2-hydroxy stearate, 91.3 percent paraffin base oil, 0.5 percent diphenylamine as an anti-oxidant and 0.2 percent excess lithium hydroxide. The resulting grease had a dropping point of 380 F. Two additional grease mixtures were prepared having identical soap, anti-oxidant and excess lithium hydroxide content; in one grease mixture designated A 3 percent tris-dichloropropyl phosphate was incorporated. While in the other designated B 3 percent tris-chloroethyl phosphite was incorporated. Grease A had a dropping point of 369 F., 11 F. lower than the base grease, whereas grease B had a dropping point of 374 F., 6 F. below that of the base grease.

The foregoing tables and examples demonstrate that the action of hydrocarbon phosphite and phosphate esters on dropping point is specific to greases containing a lith- 6 ium soap as a sole component and containing the prescribed excess of lithium hydroxide. This discovery is particularly important in the formulation of lithium greases to meet the high dropping point requirement specifications of greases used for high temperature operation, for example in steel mill greases.

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

We claim:

1. A high dropping point grease comprising a lithium soap as the sole thickening agent, a liquid oleaginous lubricating base, 0.05 to 0.8 weight percent excess lithium hydroxide over the stoichiometric required for the reaction with the soap-forming component and 0.5-5 weight percent of a tri-C to C hydrocarbon ester of phosphorus.

2. A grease according to claim 1 containing a phosphite ester.

3. A grease according to claim 1 containing a phosphate ester.

4. A grease according to claim 1 containing 0.15 to 0.5 weight percent excess lithium hydroxide.

5. A grease according to claim 1 containing a trialiphatic hydrocarbon phosphite ester in which the hydrocarbon radical contains 3 to 6 carbon atoms.

6. A grease according to claim 1 containing a triaryl hydrocarbon phosphite ester in which the hydrocarbon radical contains 6-9 carbon atoms.

7. A high dropping point grease according to claim 1 containing a triaryl phosphate hydrocarbon ester in which the hydrocarbon radical contains 6-9 carbon atoms.

8. A high dropping point grease comprising a lithium soap of a hydroxy-substituted aliphatic fatty acid containing 12 to 24 carbon atoms as the thickening agent, a liquid oleaginous lubricating base, 0.15 to 0.5 weight percent excess lithium hydroxide over the stoichiometric required for reaction with said hydroxy fatty acid and 0.5 to 5 weight percent tri-C to C hydrocarbon ester of phosphorus.

9. A grease according to claim 8 containing a lithium soap of 12-hydroxy stearic acid and triamyl phosphite.

10. A high dropping point grease comprising lithium myristate as the thickening agent, a liquid oleaginous lubricating base, 0.15 to 0.5 weight percent excess lithium hydroxide, 0.5 to 5 weight percent tri-C to C hydro carbon ester of phosphorus. l

11. A grease according to claim 10 containing tri-cresyl phosphate.

12. A grease according to claim 10 containing tri-2- ethylhexyl Phosphate.

13. A high dropping point grease comprising a lithium soap of 12-hydroxy stearic acid as the thickening agent, a mineral lubricating oil, 5 percent lead naphthenate, 0.2 percent excess lithium hydroxide and 1.5 percent triamyl phosphite.

References Cited in the file of this patent UNITED STATES PATENTS 2,294,804 Ricketts Sept. 1, 1942 2,585,321 Butcosk Feb. 12, 1952 2,626,896 Dilworth et a1 Ian. 27, 1953 2,626,898 Dilworth et a1 Jan. 27, 1953 2,639,266 Dilworth et al May 19, 1953 2,651,616 Matthews et al. Sept. 8, 1953 2,663,691 Dilworth Dec. 22, 1953 2,684,944 Zajac July 27, 1954 OTHER REFERENCES Boner: Lubricating Greases, Rheinhold Pub. C0., 1954, New York, N. Y., pages 446-447.

Claims

1. A HIGH DROPPING POINT GREASE CO PRISING A LITHIUM SOAP AS THE SOLE THICKENING AGENT A LIQUID OLEAGINOUS LUBRICATING BASE 0.05 TO 0.8 WEIGHT PERCENT EXCESS LITHIUM HYDROXIDE OVER THE STOICHIOMETRIC REQUIRED FOR THE REACTION WITH THE SOAP-FORMING COMPONENT AND 0.5-5 WEIGHT PERCENT OF A TRI-C1 TO C15 HYDROCARBON ESTER OF PHOSPHORUS.