US2850456A - Grease wherein the thickener comprises metal soaps of hydroxy fatty acid formals - Google Patents

Description

GREASE WEEREIN THE TEHEENER CONERISE METAL SOAPS 9F HYDROXY FATTY ACID FCBRMALS Alfred H. Matuszalr, Westfield, Arnold J. Morway, Clark, and John C. Monday, Cranford, N. 3., assignors to Esso Research and Engineering Company, a corporation of Delaware No Drawing. Application June 15, 1954 Serial No. 437,009

9 Claims. (Cl- 252-39) This invention relates to lubricating grease compositions. Particularly, the invention relates to lubricating grease compositions prepared by thickening a lubricating oil to a grease consistency with metallic soaps of formals of hydroxy fatty acids. The products are excellent grease compositions having outstanding structural stability and long lubricating life.

There have recently become available new hydroxy fatty acids produced from unsaturated fatty acids by treatment with oxidation agents. For example, unsaturated acids having from about 14 to about 22 carbon atoms such as tetradecenoic acids, e. g., myristoleic acid, tsuzuic acid, hexadecenoic acids, e. g., palmitoleic acid, octadecenoic acids, e. g., petroselenic acid, oleic acid, elaidic acid, vaccenic acid, eicosenoic acids, e. g., gadoleic acid, docosenoic acids, e. g., erucic acid, cetoleic acid, mixtures of the above; and thelike; are oxidized with peracetic acid, resulting inpolyhydroxy acids such as di-hydroxy stearic acid, etc. These new hydroxy fatty acids are considerably less expensive than the hydroxy fatty acids available heretofore, which have ordinarily been formed by the hydrogenation of castor oil. Naturally occurring hydroxy fatty acids, and mixtures, such as ricinoleic acid, 12 hydroxy stearic acid, sabi'nic acid (l2-hydroxy lauric acid), juniperic acid (16 hydroxy palmitic acid) are also available commercially.

It has now been found that greases of excellent properties can be prepared using derivatives of these hydroxy fatty acids in the formulation. In these modifications, the monoand polyhydroxy fatty acids are reacted with formaldehyde to form (1) the simple di-acid formal from the monohydn'c acid, (2) the cyclic formal in the case of a dihydroxy fatty acid and (3) the hydroxy cyclic formal in the case of a trihydroxy acid.

These reactions of formaldehyde with mono-, diand tn'hydroxy acids are shown graphically asfollows:

OH:(CH2),(3H(EH-CH(CH2),OOOH ECHO OH O-CHz-O CHACHahGH-GH CH(CH2),,COOH H O (Hydroxy cyclic formal) ice 2. In addition to the above, mixed products could be formed. For example, the dihydroxy fatty acid could react with formaldehyde to form dihydroxy di-acidformals such as while the trihydroxy fatty acid could react with formaldehyde to form formals containing free hydroxy groups and/ or cyclic formal groups such as EXAMPLE I.SIMPLE SOAP GREASE USING A POLYHYDRIC FATTY ACID ALONE Formulation Polyhydroxy stearic acid 12.00 Lithium monohydrate 1.72 Phenyl alpha-naphthylamine 0.50 Mineral oil 85.78

Preparation Charged mineral oil and acid to a fire heated grease kettle and warmed to 150 P. Then added the LiOH H2O as a 20% aqueous solution and heated to 400 F. Added phenyl alpha-naphthylamine and allowed to cool; when cold, homogenized.

Penetrations, 77 F., mm./ 10:

Unworked 290.

Worked 60 strokes 350. Worked 100,000 strokes Fluidized.

No further work, due to poor structural stability of grease.

EXAMPLE IL-FORMAL OEPOLYHYDROXY ACID IN SIMPLE SOAP GREASE The polyhydroxy acid used to prepare the formal of this example was obtained by the peroxidation of oleic acid. The polyhydroxy fatty acid had the following physical and chemical properties:

Gardner color l6 Volatile matter percent 0.7 Melting point C 60-64 Acid value 170' Iodine value 4 Sap. value 181 Hydroxyl value 270 Formulation and preparation 7 Same as above, employing CHa(CHz)=CH-CH w 7 H 'fCHP Penetration (77 F.--mm./l0):

Unworked 255 Worked 60 str g 265 Worked 10,000 strokes 285 EXAMPLE III.FORMAL MONOHYDROXY FATTY ACID IN A ,COMPLEX GREASE Charged'formal, hydrated lime and mineral oil to a fire heated kettle and warmed to 150 F. Then added acetic acid and continued heating to- 500 F. Discontinued heating and cooled .to 250-F. Added phenyl alpha-naphthylamine and cooled further to 200 F. Gaulin homogenized the product at 3000 p. s. i. pressure,

filtered and packaged.

XAMPLE IV v Formulation.

I Percent weight Formal of mono hydroxy stearic acid 2.0 Hydrofol acid 51 2.0 Glacial acetic acid 8.0 Hydrated lime 6.0 Phenyl alpha-naphthylamine 0.5

' Mineral oil (55 SUS/210 F.) 81.5

H 7 Preparation Similar to Example I.

Properties Example III ExampleIV Appearance Frnellrmt Excellent, Penetrations (7 7 F. min/10): I

' Unworked 256 250.

Worked, 60 stroke 330 271.

Worked, 100,000 strokes Semi-fluid... 368. Dropping point, F one None. Phase changes (70500 F.) do Do. wlleez bf [aring test 6 hours at 220 F., 660 Pass Pass. Ngrma-Hoiiman oxidation, hours to'5 p. st. 302 302.

rop. Water solubility (boiling water) None None.

EXAMPLE V.--FORMAL OF DI-HYDRQXY STEARIC ACLD IN COMPLEX GREASE The di-hydroxy stearic acid used in this-example had cc.). This material consisting of a mixture of simple and the following properties: Gardner color a a 10 Volatile matter (percent) 0.8 Melting point, C -83 Acid value 168 Iodine value 3 Sap. value 182 Hydroxyl value 257 r The hydroxy stearic acid g., 0.3 m.) was heated During this time 6.2 cc.- of water was azeotroped from the reaction mixture (theory is about 6 cc.). The material was then cooled, filtered to remove the catalyst and stripped to remove theheptane 1'20 The mineral oil, lime and high molecular weight acids were charged me fire heated kettle and warmed to 135 F. The acetic acid was added andheating continued to 500 F. Shut 0E heat and while continuing to agitate,

cooled to 250 F. when the phenyl alpha-naphthylamine was added. Cooled to 200 F., then hon1'0genized,,filtered and packaged.

Properties: 7 7

Appearance Excellent, 5 h o r t fibre grease. Dropping point, "F None. Penetrations 77 F. mm./ 10: Unworked 210. Worked 60 strokes 265.

Worked 100,000 strokes 205 F.), 277 a f t e r cooling a n d working additional 60 strokes. Water solubility Nil.

Norma-Hoffman oxidation, hours to 5 p. s. i. drop in oxyge pressure; Wheel bearing test (6 hours at 250 F.) Pass, no leakage. Phase changes None, up to 450 EXAMPLE VI.--FORMAL= OF .POLYHYDROXY STEARIC ACID IN COMPLEX GREASE Polyhydroxy 'stearic acid, 165.5 g. (0.5 m.), was formalized with 8.2 g. parafo'rmaldehyde in the presence of 0.5 NaHSO catalyst and 100 g. heptane for 2 hours at 107 C. The water collected was 7.4 cc. (theory is 9 cyclic formals was-filtered while hot and then stripped free of heptane C. at 15 mm.). It had some free hydroxyl groups still remaining and was a mushy material which on standing solidified. It was used to prepare a grease as follows.

Formulation Ingredients: Percent weight Hydrogenated fish oil acids 2.0 Polyhydroxystearic acid mono formal 2.0 Glacial acetic acid 8.0 Hydrated lime 6.0 Phenyl alpha-naphthylamine 0.5 Mineral oil (55 SSU/210 F.) 81.5

Preparation 5 Same as Example V.

Properties:

Appearance Excellent, smooth homogeneous product. Dropping point, "F None. Penetration 77 F. mm./l0:

Unworked 210. Worked 60 strokes 228. Worked 100,000 strokes; 316. Water solubility Insoluble.

Phase changes None up to 450 F. Wheel bearing test, 6 hours at 220 F Pass, no leakage. Norma-Hoffman oxidation,

hours to 5 p. s. i. drop 375.

Lubrication life hours,

10,000 R. P. M.250 F- 1166.

It will be seen by the data in the examples above that the formals of hydroxy fatty acids make excellent grease soaps, giving lubricating grease compositions having very satisfactory performance characteristics. As is shown in Example I, the polyhydroxy acids alone do not form satisfactory grease compositions in that they tend to overplasticize the grease and give products that are too soft to perform satisfactory lubricating functions.

In addition to the metals used in the example above, the formals of the hydroxy fatty acids may be saponified with any of the commonly known alkali or alkaline earth metals to form satisfactory grease soaps. The choice of the metal component depends to a certain extent on the use for which the soap is contemplated. The alkaline earth metals, particularly calcium, strontium, barium and magnesium, may be used and the alkali metals such as sodium, lithium and potassium may also be used in certain formulations. The alkaline earth metals are particularly advantageous for use in preparing the high acetate complex grease structures. As is pointed out above, in addition to the formal of the hydroxy fatty acids, other soap forming acidic materials may be incorporated into the grease compositions of invention. Any of the commonly known high molecular weight acids having from about 12 to about 30 carbon atoms, preferably those having from 14 to 22 carbon atoms, may be used. These acids may be derived from saturated or unsaturated, naturally occurring or synthetic fatty materials. Examples of operable fatty acids in clude stearic, arachidic, hydrogenated fish oil acids, coconut oil acids, tallow acids, etc.

When it is desired to prepare a complex lubricating grease, the high molecular weight portion of the total soap content is complexed with a low molecular weight acid salt. Such low molecular weight acids include those having from about 1 to about 6 carbon atoms, such as formic, acetic, propionic, and similar acids, including their hydroxy derivatives such as lactic acid, etc. The

, amount of the low molecular weight acid salt that is used to form the complex with the high molecular weight fatty acid will again depend upon the use for which the grease composition is desired. It has recently been found that grease compositions containing a high ratio of low molecular weight acid to high molecular weight acid are particularly outstanding for high temperature use. Especially desirable grease compositions may be prepared by thickening to a grease consistency a lubricating oil with a complex alkaline earth soap grease wherein the complex soap comprises a mixture of high molecular weight acid salt in a mol ratio of salt to soap of between about 7.5:1 to 50:1, preferably 9:1 to 15:1.

The total amount of the soap used in preparing the grease formulations will vary from between about 3 to about 30 weight based on the weight of the total composition. Within this broad range, from about 6% to about 20% will normally be found to be preferable. The choice of the menstruurn used in preparing the lubricating greases of invention may be made from a wide range of lubricating oils, whether naturally occurring or synthetic. Quite generally this oil should have a viscosity within the range of about 35 to about 200 SUS at 210 F. and flash points of about 350 to about 600 F. Among the synthetic lubricants operable may be mentioned diesters of dibasic acids, complex esters, formals, hydrocarbon polymers, silicone oils, polyglycol derivatives, etc. The naturally occurring lubricating oils used 6 may be either of naphthenic or paraflinic origin refined by any of the techniques well known to the art.

When it is desired to utilize the formals of the hydroxy fatty acids in conjunction with another high molecular weight fatty acid, the two soap forming materials may be admixed in any desired proportion. In other words, the soap may consist entirely of the metallic soap of the formal of the hydroxy fatty acid, or relatively minor amounts, that is from about 1% to about 10%, of the total high molecular weight acid.

Any of the commonly known grease additive materials such as stabilizers, oxidation inhibitors, cooling agents, tackiness agents or the like may be blended with the grease compositions of this invention.

To summarize briefly, the instant invention relates to new and improved lubricating grease compositions which are prepared by thickening a lubricating oil base stock to a grease consistency with a minor but grease forming amount of a metal soap of a formal of a hydroxy fatty acid. The hydroxy fatty acid may be a mono hydroxy material or it may be a polyhydroxy fatty acid. Other grease making fatty acid soaps may be combined with the formals and the total grease making soap composiion may be complexed with low molecular weight acids such as formic acid, acetic acid, furoic acid and the like. Normally from 5% to 30% by weight of the total grease thickener will be used, preferably about 6 weight percent to about 20 weight percent. When a complex grease composition is contemplated, the low molecular Weight acid used to form the complex may be present in amounts varying between about 3 to about 20 weight percent of the total composition. Especially preferred are the complex grease compositions comprising a low molecular weight acid having from 1 to 6 carbon atoms with high molecular weight acids having from 12 to 30 carbon atoms in a mol ratio of low molecular weight acid to high molecular weight acid of from 7.5 :1 to 20:1.

What is claimed is:

1. A lubricating grease composition comprising a mineral lubricating oil containing combined therein a minor, but grease thickening, amount of metal soap of a formal of a hydroxy-fatty acid having from about 14 to 22 carbon atoms, said metal constituent being selected from the group consisting of alkali and alkaline earth metals.

2. A lubricating grease composition which comprises alubricating oil base stock thickened to a grease consistency with a complex soap which comprises a metal salt of a low molecular weight acid, a metal soap of a high molecular weight fatty acid and a metal soap of a formal of a hydroxy-stearic acid, said metal constituents being selected from the group consisting of alkali and alkaline earth metals.

3. A lubricating grease composition according to claim 2 wherein said metal soap and wherein said metal salt are of calcium.

4. A lubricating grease composition according to claim 2 wherein said hydroxy-stearic acid is a mono-hydroxystearic acid.

5. A lubricating grease composition according to claim 2 wherein said hydroxy-stearic acid contains more than one hydroxy group.

6. A lubricating grease composition comprising a major proportion of a lubricating oil and a minor, but grease thickening, amount of a soap-salt complex which comprises the alkaline earth metal soap of a mixture of a high molecular weight fatty acid and a formal of a hydroxy-stearic acid and the alkaline earth metal salt of a low molecular weight acid containing from 2 to 6 carbon atoms, the molar ratio of said salt to said mixture of soaps in said complex being between about 7.5 :1 to 20:1, and wherein said mixture consists of about equal weight percentages of said high molecular weight fatty acid and said formal.

7. A lubricating grease composition comprising a lubricating oil thickened to a grease consistency with a metal .7 2,850,456 a t 7 V a s soap-salt complex, which consists of ametal salt of a 9- The lubri g grease Composition of claim 7 low molecular weight fatty acid and a-metal soap of a wherein Said Y Y fatty acid Y O Y Stearic formal of ahydroxy fatty acid having from about 14 a id. a

to 22 carbon atoms, said metal constituents being selected Q p f the group consisting f alkali and alkaline earth 5 References Cited-1n the file of H118 patent metals and wherein the molar ratio of said salt to said UNITED STATES PATENTS soap is about 7.5 :1 to 20:1.

8. The lubricating grease composition of claim 7 2,397,956 Fraser P 7,1946

wherein said metal salt is acetic acid.

Claims (1)

1. A LUBRICATING GREASE COMPOSITION COMPRISING A MINERAL LUBRICATING OIL CONTAINING COMBINED THEREIN A MINOR, BUT GREASE THICKENING, AN AMOUNT OF METAL SOAP OF A FORMAL OF A HYDROXY-FATTY ACID HAVING FROM ABOUT 14 TO 22 CARBON ATOMS, SAID METAL CONSTITUENT BEING SELECTED FROM THE GROUP CONSISTING OF ALKALI AND ALKALINE EARTH METALS.