US3389084A

US3389084A - Lubricating grease containing odd and even-numbered fatty acids

Info

Publication number: US3389084A
Application number: US505730A
Authority: US
Inventors: Jeffrey H Bartlett; Arnold J Morway; Jr Joel R Livingston
Original assignee: Exxon Research and Engineering Co
Current assignee: ExxonMobil Technology and Engineering Co
Priority date: 1965-10-29
Filing date: 1965-10-29
Publication date: 1968-06-18
Anticipated expiration: 1985-06-18

Description

United States Patent 3,389,084 LUBRICATENG GREASE CONTAINING ODD AND EVEN-NUMBERED FATTY ACIDS Jeffrey H. Bartlett, New Providence, Arnold J. Morway,

Clark, and Joel R. Livingston, Jr., Berkeley Heights,

N.J., assignors to Esso Research and Engineering Company, a corporation of Delaware No Drawing. Filed Oct. 29, 1965, Ser. No. 505,730

6 Claims. (Cl. 252-39) ABSTRACT OF THE DISCLOSURE Lubricating greases thickened with alkali or alkaline earth metal salts of low molecular weight fatty acid and a mixture of odd and even numbered fatty acids averaging at least 14 carbon atoms wherein 25 to 75 wt. percent of said mixture is acid containing an odd number of carbon atoms.

This invention relates to lubricating greases thickened with alkali or alkaline earth metal salts of low molecular weight fatty acid and soap of high molecular weight fatty acids, wherein the soap of the high molecular fatty acid component is formed from a mixture of C to C rnonocarboxylic fatty acids having even and odd numbers of carbon atoms.

Greases formed by thickening lubricating oil with alkali metal or alkaline earth metal soap-salt combinations are in wide spread commercial use. An example of one such grease comprises mineral oil thickened with lithium or sodium salt of acetic acid and the corresponding metal soap of various higher fatty acids such as stearic acid. Another example comprises mineral oil thickened with calcium salt of acetic acid with calcium soap of stearic acid. In the past, it has been conventional to use naturally occurring fatty acids as the soap-forming component. However, nature, for some unknown reason, provides only even-numbered fatty acids and all of the aforesaid commercial greases known to the instant inventors are made from higher fatty acids of even-numbered carbon chains. It has now been found, that the aforesaid soap-salt greases can be improved in various ways by the use of a mixture of odd and even-numbered saturated fatty acids as the high molecular weight soap-forming acid. In the case of alkali metal, e.g. sodium, soap-salt greases, soaps of this mixture of odd and even-numbered saturated acids materially increases the lubricating life of the grease in ballbearings at elevated temperatures, show no tendency to form crusts or to harden excessively on long storage, and show greater stability with less tendency to separate oil in storage. In the case of the alkaline earth metal soapsalt greases, particularly those made from calcium, the mixture of odd and even-numbered saturated soap-forming fatty acids inhibits crust formation, i.e. surface hardening of the grease, which is common to alkaline earth metal mixed salt greases made from saturated high molecular weight fatty acids of an even number of carbon atoms. The reason for the increased effectiveness of this mixture of odd and even-numbered fatty acids in forming the soap component of soap-salt greases is not known.

In general, soap-salt greases are usually made by neutralizing with metal base about 0.1 to 4, preferably 0.1 to 2.0 parts by weight of low molecular weight fatty acid per part by weight of high molecular weight fatty acid. These systems can also contain salt of 0.1 to .5 part by weight of intermediate molecular weight, aliphatic saturated, dicarboxylic acid per part of weight of the high molecular weight fatty acid. Usually, all the acids are simultaneously coneutralized with metal base, e.g. lime or NaOH, in situ in at least a portion of the oil, and then ice the mixture is usually heated to 225 to 500 F. to effect dehydration. Lubricating greases generally contain 15 to 45 weight percent of the soap-salt. These greases, in turn, can be diluted with additional oil to form fluid or semifiuid cmpositions containing 5 weight percent or more of the s0ap-salt. The preceding weight percents are based on the total weight of the composition.

Suitable low molecular weight acids for forming soapsalt compositions include fatty acids having 1 to 6 carbon atoms such as formic, acetic, propionic, and similar acids including their hydroxy derivatives such as lactic acid, etc. Acetic acid or its anhydride is preferred.

Intermediate molecular weight dicarboxylic acids which may be used include those acids containing 7 to 12 carbon atoms per molecule, e.g. pimelic, suberic, sebacic, pelargonic, etc.

The high molecular weight fatty acids useful in the present invention for forming the grease is a mixture of saturated fatty acids having at least one odd-numbered acid and at least one even-numbered acid in the mixture, said acids having a carbon atom content within the range of 10 to 23, e.g. 10 to 17 carbon atoms per molecule, in which mixture 25 to wt. percent of said mixture contains an odd number of carbon atoms and in which the average number of carbon atoms in the acids is about 14 or more.

The lubricating oil used in the compositions of the invention may be either a mineral lubricating oil or a synthetic lubricating oil. Synthetic lubricating oils which may be used include esters of dibasic acids (e.g. di-2- ethylhexyl sebacate), esters of glycols (eg. C oxo acid diester of tetraethylene glycol), complex esters (e.g. the complex ester formed by reacting one mole of sebacic acid with two moles of tetraethylene glycol and two moles of 2-ethyl-hexanoic acid), halocarbon oils, alkyl silicates, sulfate esters, mercaptals, formals, polyglycol type synthetic oils, etc.

One source of the fatty acid mixture of odd and even acids is from secondary alcohol produced from mixed hydrocarbons which alcohols are fused at high temperatures with caustic alkali, using about 1 to 2 or more moles of alkali per mole of secondary alcohol materials. An alkali salt results from the fusion reaction which can be utilized directly in lubricating oil as part of the thickener, or this alkali salt can be sprung with a strong mineral acid to form the corresponding fatty acid mixture.

The aforementioned secondary alcohols include those represented by the general formula:

where R and R are aliphatic saturated hydrocarbon radicals. R will usually contain about 7 to 21 carbon atoms, while R will usually contain 1 to 15. The total carbon atom content of the molecule will usually range from 11 to 24, preferably 12 to 22, carbon atoms. Specific examples of such secondary alcohols include mixtures of Z-dodecanol, 3-dodecanol, 4-dodecanol, S-dodecanol, 6- dodecanol, Z-tetradecano], 3tetradecanol, 4-tetradecanol, 5-tetradecanol, 6-tetradecanol, 7-tetradecanol, 2-octadecanol, 3-octadecanol, 4-octadecanol, S-Octadecanol, 6-octa decanol, 7-octadecanol, 8-octadecanol, 9-octadecanol 2- eicosanol, 3eicosanol, 4-eicosanol, 5-eicosanol, 6-eicosanol, 7-eicosanol, 8-eicosanol, 9-eicosanol, IO-eicosanol, 2- tricosauol, 3-tricosanol, 4-tricosanol, S-tricosanol, 6-tricosanol, 7-tricosanol, S-tricosanol, 9-tricosanol, 10-trico sanol, ll-tricosanol, 12-tricosanol, etc.

As mentioned above, one source of these secondary alcohols is by reaction of an aliphatic hydrocarbon stream with air using boric acid as a catalyst. The resulting alcohol is a mixture of secondary alcohols wherein the hydroxy group is more or less randomly distributed along the hydrocarbon chain with only a trace of primary alcohols. This boric acid process is described in the article by J. Germain and J. Cognion, Chemie et Industrie 91 In brief, this process is carried out by passing air through n-paratfin mixtures at temperatures above 150 C. in the presence of boric acid. The product of the reaction is hydrolyzed before or after any unreacted parat'fin is removed. The oxygenated products may be purified by distillation.

During the fusion process, the alkali appears to primarily react with the secondary alcohol to break the molecule at the oxygen atom to form an acid of the longer chain hydrocarbon group and a saturated hydrocarbon from the smaller chain group, as typified by the following reaction:

R|R NaOII RCOONa R'll where R and R have the same meanings as previously given. If an alcohol mixture is used, such as that produced by the aforesaid boric acid process from a mixture of linear hydrocarbons, then a mixture results where R will be divided between odd and even numbers of carbon atoms.

The aforesaid alkali fusion can be carried out at as follows: alkali metal oxide, or alkali metal hydroxide such as sodium hydroxide or potassium hydroxide, preferably in flake or pellet form, is dispersed in an inert mineral oil menstruum. The mixture can then be heated to about 450 to 700 F., e.g., 525 to 625 F., and the secondary alcohodl slowly added, either in increments or continuously, over a period of about /2 to hours, e.g. 1 to 5 hours, While vigorously stirring and maintaining a reaction temperature of about 450 to 700 F., e.g. 525 to 625 F. Or, all of the components can be charged to the reactor at the same time and then heat is applied, etc. In any event, the resulting reaction product includes oil containing alkali metal salt of mixed odd and even-numbered fatty acids.

The acid mixture per se can be prepared from this reaction product as follows: the reaction product is cooled and water is added. The resulting mixture can then be extracted with a light hydrocarbon solvent, such as heptane or the like, in order to remove the oil and unreacted secondary alcohol material to thereby leave an aqueous phase. The remaining aqueous phase is acidified with a mineral acid, e.g. hydrochloric acid, to form monocarboxylic acid. The carboxylic acid can then be removed from the aqueous phase by extraction with a light solvent, e.g. heptane or diethyl ether, and finally crude carboxylic acid is obtained by evaporation of the solvent. While the crude acid may be directly utilized without further purification, it can be purified by vacuum distillation or other known procedures. This acid can then be used for various purposes as previously indicated.

Greases can be prepared directly by carrying out the fusion in lubricating oil in the presence of other acids to form the alkali metal soap-salt system. This in situ greasemaking process is preferably carried out by dispersing the other acid and the secondary alcohol material in the lubricating oil, adding the alkali, preferably in the form of an aqueous solution containing to wt. percent alkali, heating to about 250 to 300 F., until the other acid is converted to its salt, and all the water of reaction is volatilized. The alkali fusion is then carried out by further heating to about 450 to 700 F., e.g. 500 to 600 F., until hydrogen and light hydrocarbon evolution sub stantially ceases, e.g. about A to 5 hours. The grease may then be cooled and finished by conventional means.

Various other additives may also be added to the lubricating composition (e.g. 0.1 to 10.0 weight percent), e.g. detergents such as calcium petroleum sulfonate; oxidation inhibitors such as phenyl-alpha-naphthylamine; corrosion inhibitors, such as sorbitan monooleate; dyes; other grease thickeners, and the like.

The invention will be further understood by the following examples, wherein all parts are by weight and which include preferred embodiments of the invention.

Example I A one gallon nickel reactor equipped with a stirrer, condenser, thermometer and feed line was charged with 370 grns. NQOH pellets, 330 gms. of KOH pellets and 500 gms. of a mineral white oil. This mixture was then heated to 320 C. and maintained at 320 to 340 C. for 95 minutes while 779 grams of a mixture of C secondary alcohols, prepared by the aforesaid boric acid catalysis method, were slowly added over said 95 minute period. The temperature was then allowed to drop to 280 C. during the next 30 minutes. During this total time of 2 hours and 5 minutes, 5.6 standard cubic feet of gas were evolved. At the end of this period, the mixture was further cooled by a slow addition of water. It was then removed from the reactor and given 2 extractions with petroleum ether. The aqueous layer was acidified but no acids separated. Evaporation of the petroleum ether left a residue of 1113 g. This was then dispersed in isopropyl alcohol (60 vol. percent alcohol and 40 vol. percent water) and extracted with petroleum ether to remove the white oil and other hydrocarbon soluble material. The aqueous alcohol phase was acidified with HCl to spring the fatty acids which amounted to 338 g. 302 g. of the resulting crude fusion acid was then distilled in a short path still under reduced pressure to remove any remaining petroleum ether and isopropyl alcohol. Then the distillation was continued under reduced pressure to obtain the cuts shown in the following table:

DISTILLATION OF CRUDE FUSION ACID Cut Vapor Temp., Pressure, mm. Amount, g.

C. Hg

1 82 1. 0 39 2 180 O. 5 170 3 220 O. 4 22 B ottoms 10 Cut 1 was mainly petroleum ether and isopropyl alcohol. The main fraction (Cut 2) of 170 g. had a neutralization number of 214.7 mg. KOH/ g. which is equivalent to a molecular weight of 261. Analysis of this fraction by gas chromatography gave the following result:

No. of C-atoms in acid: Wt. percent 10 6.6 10 5.0 11 5.4 12 6.5 13 6.8 14 6.5 15 11.1 16 10.2 17 35.3 17+ 6 6 Example IA 13.8 parts of hydrated lime and 57.2 parts of mineral lubricating oil having a viscosity of SUS at 210 F. were intimately mixed. 10 parts of the acid mixture (Cut 2) prepared above was added. 18.0 parts of glacial acetic or acid was then added. The free alkalinity was adjusted to 0.7 weight percent as NaOH. The mass was heated at 325 F. until dehydrated. Heating Was then discontinued and the reaction mass cooled rapidly to 250 F. where 1 As seen in Table I, the grease of Example I-A, containing Cut 2, i.e. the odd and even carbon atom fatty acid mixture, resulted in a softer grease (as indicated by the ASTM penetrations with better storage stability than part of phenyl-alpha-naphthylamine was added as an oxi- 5 the grease of Example I-B, made from saturated evendation inhibitor. The composition was then further cooled numbered carbon atom fatty acid. to 110 F. where it was homogenized by passing through The grease of Example II illustrates a sodium grease a Morehouse mill having 0.003 clearance. of a type suitable for ball-bearing lubrication made from Exam p16 a mixture of even-numbered fatty acid, i.e. Hydrofol Acid 51, and the mixed odd and even carbon atom fatty acid. Example was repeatedexacflyexcept that 1 8 At least about 29.3 weight percent of the total high of Hydrofol Acid 51 (a hydrogenated fish oil acid having molecular weight fatty acid a Wijs iodine number of 3.0 and having about a C aver- 10 age chain length was used in place of the Cut 2 acid 58.6% mixture. 15

Example II therefore, has an odd-number of carbon atoms. The re 10 parts of flydmfol Acid 51, 10 parts of the Cut 2 sulting grease gave a lubrication life in excess of 2000+ acid mixture and 67 parts of mineral lubricating oil havhours: at 300 Th1s W eyicepuonany good smce ing a viscosity of 55 SUS at 210 F. were added to a fireprcfmum grade Command gr.ease.made by alkah heated kettle. The kettle contents were then stirred while fuslon of rapesd 011 3 a lubncanon Me at i i heating to R Then 80 parts of sodium hydroxide perature of only about s00 to 400 hours. In addition, the (100% was added in the form of an aqueous solution grease of Example a Changeling type Thus consisting of 40 Weight percent of sodium hydroxide and m a 204 ballbeamig rotauzlg at loooo 60 weight percent water. The mixture was then heated packed ii the grease f Exampe h temperiiwre O to a maximum of 640 F. and maintained at this temperathe bfialmg rose. w 130 to lmtwl chummg and mm for about 3 hours 1 part of phenyl wnaphthylamine then after 15 m inutes of operation fell to a steady temas an antioxidant was added at a temperature of about peraltlure of 100 as the channel f 250 F. during the cooling cycle. The product was then grease of Example, In 7 ii imother b finished by homogenizing by passing it through a Morebeanng WW a made i hihlum 1 the mixed house min having about 0003 clearance odd and even acids of the invent on. This grease was also tested in a 204 mm. ball-bearing operating at 10,000 Example III r.p.m. and showed an initial temperature rise from the 15 parts of the Cut 2 acid mixture were mixed with ambient iempemture of 80 to 1,400 after 5 fninutes 719 parts of a mineral lubricating Oil of 60 SUS of operation. At the end of 1 0 minutes of operation, the cosity at 210 F. in a kettle. 3 parts of azelaic acid were temperablmllad fallen to 85 whlch t,empera,ture was added and the kettle contents then were warmed to 0 then maintained as a steady state condition. This grease R 61 parts of lithium hydroxide monohydrate in the was also a channeling grease and is particularly suitable form of an aqueous Solution Containing 20 Weight Pep tor ball-bearing lubr cation. These channeling greases are cent lithium hydroxide monohydrate was next added, folfreqlllenfly ds'slfed u c they provide adequate bearing lowed by the addition of 3.0 parts of glacial acetic acid. lubncatlon i a power 108.5 and i uses The temperature of the mixture was raised to 0 to due to reduction of friction engendered. by churning of dehydrate the grease, after which the grease was allowed the greaseto COOL 1 Part of phenyl wnaphthylamine was added As a further example of the greases of the invention, ft the grease had cooled to 250 The grease was a grease can be prepared by coneutralizing with a neutrafurther cooled to 120 F. and homogenized in a More-, filing amount of lime a mixture Consisting of 10 Parts of house mill. The grease was stirred continuously during a C13 aliphatic s raight chain monocarboxylic acid, 10 the aforesaid cooling. parts of C aliphatic straight chain monocarboxylic acid,

The grease compositions of Example I, II and III and 4 parts of acetic acid in 70 parts of mineral lubriprepared above and their physical properties are sumeating oil of 60 SUS viscosity at 210 F. and heating to marized in Table I which follows: 440 F. to dehydrate the resulting grease.

TABLE I Grease Composition (Wt. Percent) I-A LB 11 III Cut2 10.0 10.0 15.0 Hydroiol Acid 51 10. 0 10.0 Glacial Acetic Acid. 18. O 18. 0 4 O 3. 0 Azelaic Acid.. 3.0

Lithium Hydroxide Monohydrate 6. l Phony] a-naphthylamine 1. 0 1. 0 1. 0 1. 0 Mineral lubricating oil, 80 SUS. at

210 F 57.2 57.2 Mineral lubricating oil, 55 SUS. at

21 67. 0 Mineral lubricating oil, SUS. at

Properties:

Appearance Excellent Excellent Excellent Excellent Dropping Point, F None None 500+ 50+ ASTM Penetration, 77 F., mm./10:

Unworked 260 181 210 Worked 6O Strokes 280 200 210 215 Worked 10,000 Strokes. 275 210 220 230 Lubrication Lite 1 (hrs.):

10,000 r.p.m.:

Tirnken e.p. test, lbs 60 Storage Stability- Water Solubility Insoluble Insoluble l Mixture of odd and even number acids. 1 Soft after 6 mos. 3 Forms crust after 24 hrs.

What is claimed is:

1. A soap-salt lubricating grease comprising a major amount of mineral lubricating oil and about 15 to 45 weight percent of a metal soap-salt thickener of C to C fatty acid and a mixture of high molecular weight monocarboxylic fatty acid having carbon atoms contents in the range of about 10 to 23 carbon atoms, wherein said metal is selected from the group consisting of alkali metal and alkaline earth metals, wherein the weight amount of said low molecular weight acid is about .1 to 4 times the amount of said mixture of high molecular weight fatty acid, and wherein said mixture has at least one odd-numbered fatty acid and at least one evennumbered fatty acid, said mixture averaging at least 14 carbon atoms and wherein 25 to 75 weight percent of said mixture is acid containing an odd number of carbon atoms.

2. A lubricating grease according to claim 1, wherein said metal is calcium and said low molecular weight fatty acid is acetic acid.

3. A lubricating grease according to claim 1, wherein said metal is an alkali metal and said low molecular weight fatty acid is acetic acid.

4. A lubricating grease according to claim 1, wherein said thickener also includes metal salt of 0.1 to 0.5 part, of C to C dicarboxylic acid per part of said mixture of high molecular weight fatty acid.

5. A lubricating grease according to claim 1, wherein said high molecular weight fatty acid is the acid reaction product obtained by caustic fusion of a mixture of C secondary aliphatic saturated alcohols wherein the hydroxy group is randomly distributed along the hydrocarbon chain.

6. A lubricating grease comprising a major amount of mineral lubricating oil and about 15 to 45 weight percent of metal soap-salt of about 0.1 to 4.0 parts of acetic acid per one part of higher monocarboxylic fatty acid which consists of about 25 to 75 weight percent of saturated fatty acid having an odd number of carbon atoms in its molecules and 75 to 25 weight percent of higher fatty acid having an even number of carbon atoms in its molecules, said higher fatty acid having carbon atom contents within the range of 10 to 23 carbon atoms and averaging at least 14 carbon atoms, and wherein said metal is selected from the group consisting of alkali metal and alkaline earth metal.

References Cited UNITED STATES PATENTS 2,735,815 2/1956 Morway 25239 2,846,392 8/1958 Morway et a1 25239 2,859,179 11/1958 Lux et al 25239 2,898,296 8/1959 Pattenden et al 25239 2,976,242 3/1961 Morway 25239 3,013,974 12/1961 Morway et al 25239 3,033,787 5/1962 Morway et al. 25239 DANIEL E. WYMAN, Primary Examiner.

I. VAUGHN, Assistant Examiner.