US3197406A - Lubricating compositions containing a metal salt of a sulfated aliphatic sulfonic acid - Google Patents

Description

United States, Patent LUBRIGATiNG CQMPGSHKGNS QQNTAENENG A METAL EALT A SULFATED ALEPHATEC SULFONEC A CED Milton S. Koneciry, South Pinafieid, Arnold .l. Morway, Clark, and Jeffrey H. Bartlett, New Providence, NJ, assignors to Esso Research and Engineering ilompany, a corporation of Delaware No Drawing. Filed Eco. 20, 1962, Ser. No. 246,025

8 (Ilairns. (til. 252-=-33.2)

This invention relates to lubricating compositions containing a metal salt of a sulfated aliphatic sulfonic acid. More particularly, this invention relates to lubricants, especially greases, which contain a grease thickening amount of a metal salt of a C to C fatty acid and a metal salt of a C to C sulfated aliphatic sulfonic acid (the acid being formed by the sulfoxidation of paraihns) wherein the fatty acid salt and the sulfonic acid salt are present in certain mole ratios.

BACKGROUND Mixed-salt lubricants containing, as thiekeners, the alkaline earth metal salts (e.g., calcium) of a C to C fatty acid (e.g., acetic acid) and a C to C fatty acid (e.g., l2-hydroxy stearic acid) have found wide-spread use in comm rcial applications. In general, these mixedsalt lubricants have good anti-wear and load carrying (BF) properties and, as a result, have been commercially successful.

When, in the prior art, aryl sulfonates, i.e., metal salts of aryl sulfonic acid (ArSO H), have been employed, alone, as the thickener in lubricating greases, unstable structures have generally resulted. Greases containing such aryl metal sulfonates (or alkyl substituted aryl sulfonates) usually range from semi-fluid to fluid greases. Even when those aryl sulfonates have been used in the complex greases (those containing mixed salts) only those sulfonates of high crystallinity have given satisfactory structures, and even those are generally not suitable for high temperature operations. More recently, Morway and others have reported (US. 2,854,408) that salts of straight chain aliphatic sulfonic acids having from about 10 to carbon atoms may be advantageously employed in grease formulations. Repeated attempts to make good lubricants, e.g., greases, from aliphatic sulfates, however, have generally proven unsuccessful. As a result, it is generally believed that organic sulfates are not suited for use in grease formulations.

DISCOVERY It has now been surprisingly discovered that excellent lubricating compositions may be prepared from a metal salt of a C to C sulfated aliphatic sulfonic acid formed by the sulfoxidation of parafiins. When compared to the prior art sulfonate greases, e.g., US. 2,854,408, these lubricants have greatly improved structural stability, good EP properties, a long lubricant life, and can be used at relatively high temperatures. The greases of the present invention will usually have dropping points in excess of 400 F. Lubicating compositions prepared according to this invention will find utility in the lubrication of moving metal parts and, in general, wherever lubricants having good structural stability, good EP properties, and low sensitivity to temperature are desired, e.g., gear lubrication, bearing lubrication, etc.

SUITABLE SULFONlC ACIDS AND SALTS THEREOF The particular aliphatic sulfonic acid salts which are suited for use according to the present invention are the alkali metal and alkaline earth metal salts of the sulfated aliphatic sulfonic acids obtained from the sulfoxidation of parafhns. The terms metal sulfonate calcium sulfonate (80), sodium sulfonate (80)," etc., as used in this application will refer to the metal salts of the sulfated aliphatic sulfonic acids prepared via the sulfoxidation technique as contrasted with conventional sulfonic acids (and their salts) prepared by known techniques, e.g., sodium decane sulfonate.

The sulfoxidation reaction can be described as follows:

R-H+SO +O RSO Na+RNaSO (treated with 'y-radiation and sodium hydroxide) wherein R-H represents the paraffin feed material. Thus it can be seen that the ultimate product of the sulfoxidation reaction will contain sulfur present in at least two forms-sulfate sulfur and sulfonate sulfur. This sulfoxidation reaction, although not a part of the present invention, per se, is generally carried out at pressures of from atmospheric to 200 p.s.i.g. and at temperatures of from 70 F. to F. The dose rate of the gamma radiation is generally less than 600,000 roentgens/hr. If desired, the radiation source may be removed after the reaction begins and the reaction will run on a self-sustaining basis. The reaction is most conveniently run in a continuous fashion with reactor residence times of from 8 to 60 minutes. The paraffin feed range will vary from about C to C However, the preferred feed range for use in the unique lubricating compositions of the present invention is from C to C with C to C representing the most preferred feed material. The average number of sulfur-containing groups in the sulfoxidation product, per molecule of product, will generally be from 0.9 to 3.2. The preferred range for use in a lubricating grease composition, such as that contemplated by the present invention, will be from 1.1 to 1.8 sulfur groups per molecule.

Part of the sulfur in the sulfoxidation product can be accounted for as sulfur in the form of sulfate sulfur while the remaining sulfur is present as sulfonate sulfur. The preferred amount of sulfate sulfur (based on total sulfur content) in the sulfoxidation products used in the lubricating compositions of the present invention is from 10 to 35%, e.g., 15 to 30%. For example, suitable sulfoxidation products possessing these desired characteristics have been obtained using a C to C mixed paraffin feed and the following conditions:

The presence of the sulfate sulfur creates a grease having improved extreme pressure properties and improved structural stability. Moreover, the presence of the sulfate sulfur appears to give the sulfonate (SO) an increased thickening power. At the present time, it is not known, with any degree of certainty, why the presence of allryl sulfate sulfur in the aliphatic sulfonates (S0) of the present invention should be so beneficial, i.e., form good grease structures when compared to similar aryl and aliphatic sulfonates containing no such sulfate sulfur. However, it is believed that this can be partially attributed to the inorganic nature of the sulfate radical and its inherent stability.

600 F., a pronounced thickening effect occurs.

3 FATTY ACID SALTS The other metal salt to be used in the lubricating compositions of this invention will be the alkali metal or alkaline earth metal salt of a C to C fatty acid. Acetic acid is the preferred fatty acid. Optically, the lubricant may also contain the metal salts of C to C fatty acids. In such a case, the molar proportion of C to C fatty acid will generally be from 10 to 100% of the molar proportion of sulfonic acid (SO) used. At times, however, it may be desirable to use more or less of the C to C fatty acid.

SUITABLE METALS LUBRICAT ING COMPOSITIONS The lubricating compositions of the present invention will comprise a major proportion of a lubricating oil, e.g., mineral lubricating oil, and generally from 2 to 40 wt.

percent, preferably 5 to 30 wt. percent, of the sulfonates (S) or mixed salts. The mixed salts, in turn, will comprise a mixture of the metal salts of a C to C fatty acid and an aliphatic sulfonic acid (SO). Generally from 1 to.70, usually from 5 to about .40 and preferably more than moles of the salt of thelow molecular weight fatty acid, e.g., calcium acetate, Will be employed per mole of the metal sulfonate (S0).

The lubricating compositionsof this invention may be I prepared by several different methods. In one method,

the various acids are dispersed in a lubricating oil menstruum and coneutralized with a metal base (e.g., barium hydroxide). The water of reaction may be left in the lubricant (by not applying heat) to thereby form a coldsett lubricant. However, the lubricant will generally be heated to from 225 to 600 F, to cause dehydration. If the low molecular weight fatty acid salt is calcium acetate and the lubricant is dehydrated at from 225 to 400 F.", the resulting composition will be less viscous than if a higher dehydration temperature is used. This relatively low temperature dehydration technique is ada ventageously used in making semi-fluid or soft greases containing calcium acetate. If the same lubricating composition is heated above 400 F, say from about 430 to This high temperature techniques is used to advantage'when a more solid or a harder product is desired. Once dehydrated, the lubricant may then be cooled to from about 200 to 250 F., where conventional additives, if any, may be added. Alternatively, these additives may be added nearer the upper temperature limit. The lubricant is then preferably cooled to below 150 P. where it can be homogenized, as by passing through aGaulin homogenizer or a Charlotte mill, followed by subsequent cooling to room temperature. If desired, grease concentrates can be made by the above techniques and then diluted 7 with additional lubricating oil to form the final grease composition or even further diluted to form a fluid type lubricant.

'In a preferred. method, a preformed sulfonate, e.g., calcium sulfonate (SO), is'dispersed in a lubricating oil along with the fatty acid, e.g., acetic acid, and sumcient metal base is added to neutralize the fatty acid. The resulting composition can be processed to form a coldset lubricant, or it can be heated as previously described to dehydrate the composition. Additive, e.g., phenyl al- .41 pha naphthylamine, hydroxy benzophenone, dipyridylamine, 'etc., may then be added andrthe lubricant homogenized.

Various other additives may also be added to the lubricating composition (e.g., 0.1 to 10.0 weight percent each, based on a total formulation weight of 100%). Such additives include oxidation inhibitors such as phenothiazine and dioctyl diphenylamine; corrosion inhibitors such as sodium nitrite and sorbitan monooleate; supple mental grease thickeners such as polyethylene and polypropylene; stabilizers such as aluminum hydroxy stearate, I

and the like.

EXAMPLES V The present invention will be further understood by reference to the following specific examples which inculde a preferred embodiment. All parts are by weight unless otherwise indicatedp v EXAMPLE 1 Part A.6.7 parts of hydrated lime, 77.3 parts of a I mineral oil having a viscosity of 55 SUS at 210 F. and

a VI of 40, and 5 parts of calcium sulfonate (80) were charged to a grease kettle and intimately mixed. Ten parts of acetic acid were added to the mixture and the temperature was raised to 350 F., at which point the heating was terminated. The grease was then cooled to 250 F. and 1 part of phenyl-m-naphthylamine was added.

' The grease was cooled to 100 F. and then homogenized by passage through a Charlotte mill. The formulation and properties of the resulting grease are shown in Table II. Y a

Part B.The calcium sulfonate (SO) used'in this example was prepared by metathesis from a sodium sulfonate (SO) formed in the .sulfoxidation process using the following techniquei Fifty parts by weight of a sodium sulfonate (SO) having a carbon number range of from about C toC (average about C and containing about 1.4 moles of sulfur per mole of sulfonate (ca. 18% of the sulfur was sulfate sulfur) was dispersed in 1000 ml. of distilled water. Ten parts by weight of calcium nitrate (dissolved in 100 ml. of water) was added to the dispersion at F. The resulting dispersion was slowly warmed to F., with mixing. When the mixing was stopped and the dispersion cooled to room temperature, calcium sulfonate (SO) precipitated from the mixture. The supernatant liquid (now containing the newly formed sodium nitrate) was decanted and the calcium sulfonate (SO) precipitate was washed and dried for use in the above-mentioned grease.

EXAMPLE 2 10.8 parts of hydrated lime, 7 0,2 parts of a mineral lubricating oil (Coray 55) having a viscosity of 55 SUS at 210 F. and a VI of 40, and 2.0 parts of a calcium sulfonate (SO) similar to that described with reference to Example 1 were charged to a grease kettle and intimately mixed. Sixteen parts of acetic acid were added to the mixture and the temperature was raised to 440 F., at which point the heating was terminated. The grease was cooled to 250 F. and 1 part of phenyl alpha naphthylamine was added. The resulting grease was then cooled to 100 F. and homogenized by passage through a Charlotte mill. The formulation and properties of this grease are shown in Table II.

EXAMPLE 3 15.0 parts of a sodium sulfonate (SO) similar to that described in Example 1, Part B, 5.0 parts of stearic acid and 71.0 parts of a mineral lubricating oil (Necton 60) added to the mixture in the form of a 48 wt. percent aqueous solution. Four parts of acetic acid were then added, with mixing, and the temperature raised to 420 F.

snot/ ce at which point the heating was discontinued. When the mixture had cooled to 250 F., one part of phenyl alpha naphthylamine was added. After further cooling, the resulting grease was milled in a Morehouse mill. The

a In summary, therefore, it can be seen that the applicants have developed a unique lubricating composition having excellent structure and stability, a high dropping point (over 400 F.), and a long lubrication life at eleformulation and properties of this grease are shown in 5 vated temperatures. Additionally, this unique lubricat- Table II. ing composition has excellent extreme pressure pro- EXAL'IPLE 4: erties Part A. --Pive parts of calcium sulfonat ($0), 6.7 Having described the invention with a certain degree parts of hydrated lime, and 77.3 parts of a mineral of particularity, it should be realized that numerous lubricating oil (Coray 55) having a viscosity of 55 SUS 1g modifications and adaptations can be made to the present at 210 F. were added to a grease kettle and intimately nvention within the spirit and scope of the invention as mixed. Ten parts of glacial acetic acid was then added to mafier clalrned. the mixture with stirring. An excellent, solid grease What is clamied is: formed which was divided into two portions hereinafter 1- A lubricating composition comprising: identified as 4 (I) and 4 (II). Portion 4 (I) was set a major proportion of a lubricating oil, and aside and portion 4 (II) was heated to 320 F. with mixfrom 2 49 P Of metal Salt of C to C ing. Cooling was initiated and 1 part of phenyl alpha aliphatic sulfonic acid, naphthylamine was added at 250 F. After further coolsaid metal being selected from the group consisting ing to 100 F. the product was homogenized. One part of alkali metals and alkaline earth metals, of phenyl alpha naphthylamine was added to portion said aliphatic sulfonic acid being formed by the 4 (I) which was also homogenized. The formulation radio-sulfoxidation of paralhns and containing and properties of those greases, 4 (I) and 4 (11), are an average of from 0.9 to 3.2 sulfur atoms per shown in Table II. molecule, and

Part B.The calcium snlfonate (SO) used in this exfrom 10 to 35% of said sulfur atoms being present ample was obtained as a precipitate from a sodium sulas sulfate sulfur. fonate (S0) by metathesis with aqueous calcium nitrate. 2. lubricating composition as defined in claim 1, The sodium sulfonate was obtained by the sulfoxidation Wherem said aliphatic sulfonic acid contains from 12 to of a mixture of G -C paralfins (average of C 24 carbon atoms. using the conditions set forth in Table 1, Run 1. The so- 3. A lubricating composition comprising: dium sulfonate (SO) contained about 1.4 moles of sulfur (a) a major proportion of a lubricating oil, and per mole of product. Of this sulfur, 21.2% was ac- (b) from 2 to wt. percent of mixed metal salts, counted for as sulfate sulfur. said mixed metal salts comprising metal salt of Table 11 Examples Formulation 1. Mineral lubricating oil 77.3 70.2 71.0 77.3 77.3. 2. Calcium sulfonate (S0) 5 2 5 5. 3. Sodium sulionate (SO) 15 4. Stearic acid 5 s. Acetic acid m 16 4 10 10. 6. Sodium hydroxide 7. Hydrated lime 6.7". 10.8 6.7. 8. Phenyl alpha naphthylaminn 1 1 1 1, 9. Apggcgximate mole ratio of acetic acid to sulfonate 14:1 :1 2:1 14:1.

I PROPERTIES 1. Appearance Excellent Excellent; Excellent; Excellent; Excellent; smooth. homogesmooth. smooth. smooth.

1100115. 2, Droppingpoint,F 500+ 500+ 475 500+ 500+. 3. ASTM penetration at 77 F. (mnL/lfl):

Unworked 285 330 26% 300. 300. Worked strokes 310 3411 285 305 315. Worked 10.000 strokes 315 325 320. 4. Water solubility Insoluble Soluble 5. Luhrieationliie at 250 F. and 10,000r.p.m. (AFBMA- Stillru 1,800 hrs. Still run- NLGI spindle test). nmg at ning at;

2,000 hrs. 2,000 hrs 5. Timlren 13? test, load (lbs) Pass 551bS.. 40+ lbs 45+ lbs. 7. Wheel hearing test: One hr. at 200 F P ss- 0 Fail Pass.

shrink or leak.

As seen by the preceding table, the grease compositions C to C fatty acid and metal salt of C to C of the present invention as represented by Examples 14 60 aliphatic lf i acid in a corresponding molar are good lubricants. Examples 1 and 2, which were ratig of f 1 70; straight calcium greases, were excellent, smooth greases Said metal being Selected from tha group Consist havlflg f PP Polms m excfiss of and long ing of alkali metals, alkaline earth metals, and lubrication lives, i.e., 1800 or more hours. Example 3, mixtures thoreof i ft; g? f i tfg i fi gf said aliphatic sulfonic acid being formed by the ace m P m 9 ma Ion W1 er 5 ecu radio-sulfoxidation of paraffins and containing fatty acid. This grease had a high droppmg point (475 an avera e of from O 9 to 3 Sulfur to A F.) and was somewhat harder. It was water soluble and 1 1 g d a ms should, therefore, be used in applications where water i 6: 3?; f if solubility is not a problem. The greases shown as Exammm o 0 0 Sm m atoms bang Present ples 4 (I) and 4 (II) were also good greases and possessed good EP properties as shown by their performance in the Timken EP Test. These two greases show the effects of changing normal process variables, i.e., degree of dehydration.

as sulfate sulfur. 4. A lubricating composition as defined in claim 3, wherein said lubricating oil is a mineral lubricating oil. 5. A lubricating composition as defined in claim 4, wherein said metal is an alkali metal.

'6. A lubricating composition comprising:

(a) a major proportion of a lubricating oil, and (b) from 5 to 30 wt. percent of mixed metal salts,

said mixed metal salts comprising metal salt of C to C fatty acid and metal salt of C to C aliphatic sulfonic acid in a corresponding molar ratio of 540:l, I v

7 said metal being selected from the group consisting of alkali metals, alkaline earth metals, an

I mixtures thereof,

' said aliphatic sulfonic acid being prepared by the radio-sulfoxidation of parafiins and containing an average of 1.1 to 1.8 sulfur atoms per molecule, and

from 15 to 30% of said sulfur atoms being present as sulfate sulfur.

7. A lubricating composition as defined in claim 6, wherein said metal is calcium and'said C C fatty acid is acetic' acid.

References Cited by the Examiner UNITED STATES PATENTS 11/49 SWenson 252-433 2,507,088 5/50 Bradley ,260513 2,553,422 5/51 OHalloran 25233.2 2,553,423 5/51 Shepard 252-532 2,854,498 9/58 Brugmannet'al. 252,33.2 X 2,856,362 16/58 Morway 25233.2

I FOREIGN PATENTS 6 90,Q46 4/53 Great Britain.

DANIEL E. WYMAN, Primary Examiner.

Claims (1)

1. A LUBRICATING COMPOSITON COMPRISING: (A) A MAJOR PROPORTION OF A LUBRICATING OIL, AND (B) FROM 2 TO 40 WT. PERCENT OF METAL SALT OF C6 TO C30 ALIPHATIC SULFONIC ACID, SAID METAL BEING SELECTED FROM THE GROUP CONSISTING OF ALKALI METALS AND ALKALINE EARTH METALS, SAID ALIPHATIC SULFONIC ACID BEING FORMED BY THE RADIO-SULFOXIDATION OF PARAFFINS AND CONTAINING AN AVERAGE OF FROM 0.9 TO 3.2 SULFUR ATOMS PER MOLECULE, AND FROM 10 TO 35% OF SAID SULFUR ATOMS BEING PRESENT AS SULFATE SULFUR.