US2918431A - Blended grease compositions - Google Patents

Description

United States Patent BLENDED GREASE COMPOSITIONS Arnold J. Morway, Clark, N.J., assignor to Esso Research and Engineering Company, a corporation of Delaware No Drawing. Application May 29, 1956 SerialNo. 587,957

8 Claims. (Cl. 252-40) This invention relates to mixed base lubricating grease compositions having outstanding lubrication life as well as other desirable grease characteristics. More specifically, the invention pertains to compounded grease compositions comprising a sodium base lubricating grease and an alkaline earth metal base lubricating grease.

The present application is a continuationrin-part of .Serial No. 498,739, filed April 1, 1955.

In brief compass, the invention relates to lubricating grease compositions comprising component 1, a sodium soap-salt complex thickened grease, and component 2, an alkaline earth metal mixed salt or amixed salt thickened grease. The two components. may be prepared separately and; then blended, or they may be prepared sequentially in the same grease kettle. 'Ihe grease compositions of the invention are useful, for example, in lubricating antifriction bearings for services operating at elevated temperatures. The greasecompositions are particularly characterized by their outstanding lubricating life, high dropping point, and water resistance.

The use of sodium soap-salt complex as a grease thickener is well known in the art. Suitable sodium soapsalt complexes for the purposes of this invention consist of a sodium soap of a high molecular weight carboxylic acid having from about 12 to 30, preferably about 16 to 22, carbon atoms per molecule, and a sodium salt of a low molecular weight monocarboxylic acid having from about 1 to 3 carbon atoms per molecule. Mol ratios of salt to soap can be in the range from 0.5/1 to 1.25/1, a ratio of about 1/1 being preferred. A preferred sodium soap-salt complex thickened grease for use as component 1 in the grease compositions of the present invention is prepared by the alkali fusion of rapeseed oil, More specifically, this grease can be prepared by saponi- *fying rapeseed oil with an excess of alkali in a lubricating oil base stock to a temperature of about 350 to 380 F. The amount of alkali employed is about 75 to 125%, preferably about 100%, more than that required to saponify the rapeseed oil. The reactants are then heated to at least about 425 F., the temperature at which hydrogen evolution begins. The mixture is then heated to and maintained at a temperature within the range of about 450 to 500 F. for about 1 to 4 hours, preferably about 2 hours, or until hydrogen gas evolution recedes. The grease mixture is cooled to obtain the final lubrieating grease composition.

On saponification of the rapeseed oil, glycerine is released by hydrolysis of the glyceride ester. The glycerine in turn is dehydrated at temperatures above 425 F. and breaks down to produce acrolein, which is converted into thealkali metal salt of a low molecular weight carboxylic acid, by alkali fusion. Thus, the final grease-thickening product comprises sodium soaps of a mixture of C to C fatty acid soapswith sodium acrylate in minor proportions, up to about 1 mol of sodium acrylate per mol of high molecular weight carboxylic acid. Some sodium fol-mate, sodium acetate, sodium propionate and the like may also be present. In general, the sodium soap-salt complex thickened grease employed herein will contain about 18 to 36 wt. percent, preferably about 21 to 3 0wt. percent, based on the total grease composition, of the complex thickener.

Component 2 is an alkaline earth mixed salt or alkaline earth mixed salt thickened grease, as noted above. The mixed salt comprises at least one alkaline earth metal salt of a low molecular weight carboxylic acid having from about 1 to 3 carbon atoms per molecule and at least one alkaline earth metal salt of an intermediate molecular weight carboxylic acid having from about 7 to 10 carbon atoms per molecule, in which the mol ratio of low to intermediate molecular weight carboxylic acid is about 2:1 to 25:1, preferably about 4:1 to 12: 1.

These mixed salts employed as component 2 may be prepared by coneutralization of a mixture of the acids with the desired alkaline earth metal base, particularly the hydroxides and/or carbonates. The coneutralization step may be carried out (1) in situ in component 1, or (2) in a lubricating oil to form a grease which subse quently is blended with component 1. In case (2), the mixed salts of high metal content are incorporated in mineral and/or synthetic lubricating oils in grease-making proportions of about 5 to 50 Wt. percent, preferably about 10 to 30%, based on the total composition. -In either case, it is preferred to first disperse the alkaline earth metal base in the component .1 grease or in lubrieating oil with. mixing, and then to add the low and in,- termediate molecular weight carboxylic acids. The resulting mixture containing coneutralized acids is "then heated to a dehydration temperature such as 300 F. to 350 F. When the coneutralization step is carried out in lubricating oil, forming a grease which is subsequently blended with the component 1 grease, it is generally preferred to heat to a higher temperature such as above about 400 F., preferably about 430 to 510 F.

The lubricating oils useful in preparing the. component greases of the blended grease compositions of the in.- vention may be either mineral, synthetic, vegetable lubricating oils and the like. In general, the lubricating oils should have a viscosity within the range of about 60 to 2500 SUS at 100 F. and 35 to 200 SUS at 210 F., a pour point of about +20 to F., and a flash point of about 350 to 650 F. As mentioned above, synthetic as well as mineral lubricating oils may be employed as part or all of the liquid phase of the greases. Such synthetic lubricating oils include the hydrocarbon, hydrocarbon polymer, ester, complex ester, formal, mereaptal, polyalkylene oxide, silicone or similar types. More particularly, diester synthetic lubricating oils such as di-2-ethylhexyl sebacate, di-C Oxo azelate, diisooctyl azelate and di-C Oxo adipate may be used. Other suitable synthetic oils are complex esters prepared from polybasic carboxylic acids, polyhydric alcohols, monobasic acids and/ or monohydric alcohols, such asthe glycol-centered or dibasic acid-centered complex esters.

The high molecular weight carboxylicacids useful for preparing the sodium soap-salt complex thickeners of component 1 described above are those saturated and unsaturated, grease-making fatty acids that are commonly known to the art. In general, these fatty acids have from about 12 to 30 carbon atoms, preferably about 16 to 22 carbon atoms per molecule, and include such fattty acids as myristic acid, palmitic acid, stearic acid, the various hydroxy stearic acids, oleic acid, arachidic acid, behenic acid, erucic acid, lignoceric acid and the like. Mixtures in any proportions of these high molecular weight fatty acids are also operable. Naturally occur ring high molecular weight acids such as fish oil acids, tallow acids, castor oil acids, coconut oil acids may ,taining minor amounts of C acids may be used. Either saturated or unsaturated fatty acids may be used, though the saturated fatty acids are preferred. Straight chain or substantially straight chain acids are preferred in the preparation of relatively firm greases; while the branched -.chain acids are useful in the preparation of softer greases.

Single or mixed intermediate weight acids having an average saponification value of from about 310 to 440, especially about 320 to 420, are preferred. Suitable acids include:

5-methyl-2-hexanoic Heptanoic (enanthic) Octanoic (caprylic) 2-ethyl hexanoic C Oxo acid Nonanoic (pelargonic) Decanoic (capric) C Oxo acids The OX0 acids are'those formed by the well-known Oxo process of synthesis with carbon monoxide, hydrogen and olefins, the latter being C and C polymers of propylene with or without some butylene, for making C and C 0x0 acids.

The low molecular weight carboxylic acids contemplated in this invention for both component 1 and component 2 include saturated and unsaturated carboxylic acids having from about 1 to 3 carbon atoms, such as formic, acetic, propionic, acrylic and similar acids including their hydroxy derivatives, e.g., lactic acid. Monocarboxylic acids are particularly useful, and acetic acid is especially preferred for preparing the mixed salt complex grease thickeners. In general, the low molecular weight carboxylic acid employed should have a saponification value of above about 600, preferably about 750 to 1300. Mixed low molecular weight carboxylic acids, wherein the acids contain from about 1 to 3 carbon atoms, having saponification values above about 600 may I also be employed. The acetic acid can be either glacial acetic acid or an aqueous solution of acetic acid. When the latteris employed, the concentration of acid in solution may vary from about 60 to 99.9 wt. percent, and is preferably about 80 wt. percent.

' The alkaline earth metal hydroxides or carbonates such as those of calcium, barium and strontium are particularly useful for purposes of this invention. Calcium hydroxide is especially preferred. Metals such as magnesium and zinc may also be utilized in preparing the component 2 mixed salt described above.

In accordance with one aspect of this invention, about 25 to 75 wt. percent of the component 1 grease are blended with about 75 to 25 wt. percent of the component 2 grease. Preferred proportions are, however, about 40 to 60 wt. percent of component 1 and about 60 to 40 wt. percent of component 2. The temperatures at which blending is carried out are within the range of about 80 to 200 F., preferably about 100 to 150 F. It will be understood that the two grease components may advantageously be blended or finished by passage through a Gaulin homogenizer, Morehouse Mill or the like at high rates of shear within the range of about 50,000 to 500,000 reciprocal seconds.

The invention will be more fully understood by reference to the following examples illustrating various modifications of the invention.

4 EXAMPLE I Grease A A grease was prepared from the following ingredients:

Weight percent Rapeseed oil 24.00 Sodium hydroxide 5.00 Phenyl alpha-naphthylamine 1.00 Metal deactivator 1 0.50

Mineral lubricating oil:

55 SUS 210 F 39.50

Condensation product or 1 mol of propylene diamlne and 2 mols of salicylaldehyde.

Solvent refined, propane precipitated Mid-Continent residuum, V.I. of about and a. flash point of about 375.

SUS vls./100 F.:367; 102 V.I.

The rapeseed oil and 55 vis./210 F. mineral oil were charged to a fire-heated kettle and warmed to F. The sodium hydroxide as a 40% aqueous solution was then added and the temperature raised to 360 F. where the mass was dehydrated. The temperature was then raised to 425 F. where hydrogen evolution started as indicated by initiation of foaming in the kettle. The temperature was raised further to 500 F. and held at this temperature until foaming ceased. The additional oil was then added and the grease cooled to 180 F. when the inhibitors (phenyl alpha naphthylamine and Du Pont metal deactivator) were added.

Grease B A grease was prepared from the following ingredients:

Percent weight Glacial acetic acid 12.0

Commercial caprylic acid 1 6.0 Hydrated lime 9.8 Phenyl alpha-naphthylamine 1.0 Metal deactivator 0.5 Mineral lubricating oil 55 SUS 210 F 70.7

Grease C A grease was prepared by blending the following component greases'at a temperature of about 100 F.

- 7 Percent weight Grease A 50 Grease B 50 The ASTM penetration of Greases A, B and C were about 285 mm./ 10 (77 F.) unworked and about 300- 305 mm./ 10 (77 F.) after 60 strokes.

Greases A, B and C were then tested for lubrication life in the NLGI-AFBMA test; the results are as follows:

Lubrication life (hrs.)

Grease: 10,000 r.p.m. 250' F. A 3900 B 2400 C 1 5500 t Grease K 1 9* m1 th e t was discontinued- The above data show that by blending" the two greases dfthe A and B type a finalgrease" composition C unexpectedly has a' lubricating life far in excess of either Grease A or B alone.

While blended Grease C is an excellent grease having an outstanding lubrication life, it involves at least two separate grease kettle manufacturing steps. It would be desirable, therefore, to have a grease-making method involving only one grease kettle manufacturing step. However, previous attempts to prepare mixed base thickened greases (containing soap-salt complexes) by direct or simultaneous neutralization of the saponifiable materials with lime and sodium hydroxide have not been successfill. The resulting products have been soft, fluid, grainy greases.

In accordance with another. aspect of the present invention, a grease-making process has been found whereby excellentmixedbase thickened greases (containing soapsalt complexes) having desirable grease characteristics can be prepared in a single kettle manufacturing step. In general, the process encompasses the preparation of a sodium soap-salt complex thickened grease at elevated complexing temperatures, cooling the resulting grease composition to a temperature of about 180 to 200 F., and then, in situ, preparing the alkaline earth metal mixed salt thickened grease, heating the resulting grease mixture to about 300 to 320 F., and subsequently cooling to obtain said final grease composition.

More specifically, this process involves charging rapeseed oil (or a mixture of low molecular weight and high molecular weight acids) and a dispersing proportion of the lubricating oil base, either one lubricating oil or a mixture of lubricating oils having different viscosity in dices, to a fire heated grease kettle, heating the dispersion to a temperature of about 120 to 150 F., and then adding sodium hydroxide. The heating is continued to a temperature of about 480 to 520 F. The grease mixture is maintained at this temperature until gas evolution recedes. The grease mixture is then cooled to about 160 to 180 F., and the lime added with thorough mixing. A mixture of intermediate molecular weight carboxylic acids having about 7 to 10 carbon atoms per molecule and low molecular weight carboxylic acids having about 1 to 3 carbon atoms per molecule is then added to the cooled grease mixture containing the lime. The entire grease mixture is then heated to a temperature within the range of about 300 to 320 F. for about /2 to 1 hour. The resulting grease is cooled to a temperature of about 180 to 200 F. At this temperature, conventional grease additives may be added if desired. The grease is then cooled to obtain the final grease composition. As noted above, the grease may be finished by being homogenized in a Gaulin homogenizer, Morehouse Mill or the like at high rates of shear.

A grease prepared in accordance with this novel grease manufacturing process is shown in the following example.

EXAMPLE 1r Formulation: Percent weight Rapeseed oil 12.0

Caprylic 24.5%, capric 57.8% and lauric 17.6%. Condensation product of 1 mol of propylene diamine and 2 mole of salicylaldehyde.

v PREPARATION The rapeseed oil, one-third ofithe mineral lubricating oil 55 SUS 210" F.), the se l'sus'lioo E. lubricating oil, and the 2200 SUS/ F; lubricating oil were charged toa fire heated grease kettle-and heated to about.

F. A 40% aqueous solution of the sodium hydroxide was charged, and the resulting mixture then heated to a temperature of about 500 F. After the gas evolution had appreciably receded the balance of the 55 SUS/210 F. mineral oil was added and the grease mixture cooled to about F. The hydrated lime was then thoroughly mixed into the cooled grease mixture, and a mixture of the caprylic acid and acetic acid added-. The resulting mixture was heated to a temperature of about 300 F., and then rapidly cooled 1200 FL At" this temperature, the phenyl alpha-naphthylamine and the metal deactivator were added. The resulting grease composition was finished by: being. passedthrough. d Gaulin homogenizer at 6500 p.s.i.g.'

PROPERTIES AppearanceExcellent, smooth, uniform grease. Penetrations, 77 F. mm./ 10:

Unworked 295 Worked 60 strokes 305 Worked 100,000 strokes 360 Dropping point, 0 F 500+ Water washing, percent loss 15 Water solubilityboiling Water Nil Norma Hoffmann oxidation test (hrs. to 5 p.sli. drop) Lubrication life, hours 10,000 r.p.m. 250 F 1 1500+ Wheel hearing test, 660 r.p.m.220 F Pass 4-ball wear test scar diam. mm. (1800 r.p.m. 75 c. 1 hr.--10 kg. load) 0.2"5' Grease did not fail; the test was discontinued.

EXAMPLE III Formulation: Percent Hydrofol acids 51* 10.50 Glacial acetic acid 8.00 Commercial caprylic acid 3.00 Sodium hydroxide Hydrated lime 4.80 Phenyl alpha naphthylamine 1.00 Metal deactivator 2 0.50 Mineral lubricating oil 55 vis./ 100 F 69.20

1 Hydrogenated fish oil acids having an average molecular. weight about equivalent to stearic acid.

2 Condensation product of 1 mol of propylene diamin and 2 mols of salicylaldehyde.

PREPARATION Charged Hydrofol Acids 51 and mineral oil to kettle and warmed to 150 F., then added 40% aqueous solution of sodium hydroxide followed immediately by of the acetic acid. Continued heating to 500 F; to forni complex, then cooled to 150 F. Added lime and in timately mixed into warm grease. Then added balance of acetic acid mixed with caprylic acid. Reacted and heated to 300 F. Held at this temperature for 10 minutes, then cooled to 180 F. Added the phenyl alpha naphthylamine and metal deactivator. Cooled further to 140 F. and Gaulin homogenized at 5000 p.s.i.

PROPERTIES Appearance Excellent, uniform grease. Dropping point, F ;;.;;:..;;.u Penetration, 77 F., 10:

Unworked 28S Worked 60 strokes 295 Worked 100,000 strokes 320 Water washing test, loss 20% Norma Hotfmann oxidation (hrs. to 5 p.s.i. drop)- 365 4-ball wear test scar spot diam. mm. (1800 r.p.m.-1O kg. load-1 hr.75 C.) 0.28

7 The above data show that an excellent mixed base complex thickened grease can be effectively prepared in {single kettle manufacturing step. The data further show that the resulting grease product has outstanding water resistance, a high dropping point and long lubrication life, as well as other desirable characteristics.

It will be understood that the specific conditions and materials of the foregoing examples may be varied within the limits indicated in the general portions of the specification. Furthermore, the compositions prepared in accordance with the invention may contain various conventional additives such as oxidation inhibitors, metal deactivators, corrosion preventatives, extreme pressure agents, tackiness agents, and the like. j The final grease compositions of the present invention (whether prepared by blending of the two individual greases or by preparation in a single kettle manufacturing step) will generally comprise a major proportion of a lubricating oil and the following concentrations of grease thickeners in accordance with this invention:

Wt. Percent of Total Grease General Preferred 1. Total thickener (sodium soap-salt complex plus alkaline earth metal mixed salts) 7-45 15-35 2. Sodium soap-salt complex -30 8-20 3. Alkaline earth metal mixed salts 2-40 5-20 Generally it will be desirable that the weight ratio of sodium soap-salt complex to alkaline earth metal mixed salts be about 1:3 to 3:1, preferably about 121.5 to 1.511. When two individual greases are prepared initially and then blended together in accordance with the present invention (in proportion of about 1:3 to 3:1, preferably about 121.5 to 1.5 :1), the two individual greases will generally each contain a major proportion of a lubricating oil and the following concentrations of grease thickeners:

What is claimed is:

1. A blended grease composition comprising a mixture of two component greases, one component being from 25 to 75% by weight of a sodium soap-salt complex thickened grease wherein the sodium soap-salt complex comprises a sodium soap of high molecular weight carboxylic acids having from about 12 to 30 carbon atoms per molecule and a sodium salt of low molecular weight carboxylic acids having about 1 to 3 carbon atoms per molecule, said complex being prepared at complexing temperatures of 430 to 510 F. and wherein the mol ratio of the salt to the soap in the complex is in the range of 0.5 to 1.25:1, and the other component being from 7525% by weight of an alkaline earth metal mixed salt thickened grease wherein said alkaline earth metal mixed salt comprises low molecular weight carboxylic acids having from about 1 to 3 carbon atoms per molecule and intermediate molecular weight carboxylic acids having from about 7 to 10 carbon atoms per molecule wherein the mol ratio of the low to intermediate molecular weight carboxylic acids in the mixed salt is in the range of 2:1 to 25:1.

2. The blended grease composition of claim 1 wherein said alkaline earth metal is calcium.

3. The blended grease composition of claim 1 wherein said low molecular weight carboxylic acid is acetic acid and said intermediate molecular Weight carboxylic acid is commercial caprylic acid.

4. A lubricating grease composition comprising a major proportion of a lubricating oil and about 7 to 45% by weight, based on total composition, of a grease thickener consisting of (a) sodium soap-salt complex prepared at temperatures of 430 to 510 F., and (b) alkaline earth metal mixed salt, said sodium soap-salt complex representing about 5 to 30% by weight of the total composition and being a metal complex of C to C fatty acids and C to C monocarboxylic acids, the mol ratio of said C to C monocarboxylic acids to said C to C fatty acids in said complex being in the range of 0.5 :1 to 1.25: 1, said alkaline earth metal mixed salt representing about 2 to 40% by Weight of the total composition and comprising salts of C to C carboxylic acids and C to C carboxylic acids, the mol ratio of said C to C carboxylic acids and said C to C carboxylic acids being in the range of 2:1 to 25:1.

5. A blended grease composition comprising a mixture of 25 to by weight of a sodium soap-salt complex thickened grease prepared by the alkali fusion of rapeseed oil in the presence of mineral lubricating oil and 75 to 25% by weight of an alkaline earth metal mixedsalt thickened grease comprising alkaline earth metal salts of: C to C carboxylic acid and C to C carboxylic acid, and wherein the molratio of the C to C to the C to C carboxylic acid is in the range of 2:1 to 25:1.

6. A process for preparing a lubricating grease composition which comprises admixing rapeseed oil, sodium hydroxide and mineral lubricating oil, heating the mixture to a temperature of about 480 to 520 F. until gas evolution recedes, cooling the mixture to about to F., adding an alkaline earth metal base to the cooled mixture, then adding a mixture of intermediate and low molecular Weight carboxylic acids, the mol ratio of the low to the intermediate molecular weight carboxylic acids being within the range of 2:1 to 25:1, heating the resulting grease mixture to a temperature of about 300 to 320 F., and then cooling to obtain said final lubricating grease composition.

7. The process of claim 6 wherein said alkaline earth metal base is calcium hydroxide.

8. The process of claim 6 wherein said low molecular weight carboxylic acid is acetic acid and said intermediate molecular weight carboxylic acid is commercial caprylic acid.

References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES NLGI Spokesman, vol. 14, No. 12 (March 1951), pages 7-23. 1

Claims (1)

1. A BLENDED GREASE COMPOSITION COMPRISING A MIXTURE OF TWO COMPONENT GREASES, ONE COMPONENT BEING FROM 25 TO 75% BY WEIGHT OF A SODIUM SOAP-SALT COMPLEX THICKENED GREASE WHEREIN THE SODIUM SOAP-SALT COMPLEX COMPRISES A SODIUM SOAP OF HIGH MOLECULAR WEIGHT CARBOXYLIC ACIDS HAVING FROM ABOUT 12 TO 30 CARBON ATOMS PER MOLECULE AND A SODIUM SALT OF LOW MOLECULAR WEIGHT CARBOXYLIC ACIDS HAVING ABOUT 1 TO 3 CARBONS ATOMS PER MOLECULE, SAID COMPLEX BEING PREPARED AT COMPLEXING TEMPERATURES OF 430* TO 510*F. AND WHEREIN THE MOL RATIO OF THE SALT TO THE SOAP IN THE COMPLEX IS IN THE RANGE OF 0.5:1 TO 1.25:1, AND THE OTHER COMPONENT BEING FROM 75-25% BY WEIGHT OF AN ALKALINE EARTH METAL MIXED SALT THICKENED GREASE WHEREIN SAID ALKALINE EARTH METAL MIXED SALT COMPRISES LOW MOLECULAR WEIGHT CARBOXYLIC ACIDS HAVING FROM ABOUT 1 TO 3 CARBON ATOMS PER MOLECULE AND INTERMEDIATE MOLECULAR WEIGHT CARBOXYLIC ACIDS HAVING FROM ABOUT 7 TO 10 CARBON ATOMS PER MOLECULE WHEREIN THE MOL RATIO OF THE LOW TO INTERMEDIATE MOLECULAR WEIGHT CARBOXYLIC ACIDS IN THE MIXED SALT IS IN THE RANGE OF 2:1 TO 25:1.