US3010898A - Barium c20-c22 soap-barium carbonate grease composition and process for forming same - Google Patents

Description

more fully appear.

3,010,898 BARIUM C -C SOAP-B CONATE GREASE CQMPOSITION PROCESS FOR FOG S John W. Wiison, .lr., Redding Ridge, 'Conn., assignor to Socony Mobil Oil Company, Inc, a corporation of New York No Drawing. Filed May 20, 1959, Ser. No. 814,400 10 Claims. (Cl. 252-18) The present invention relates to lubricating greases especially adapted for use under a wide range of operating temperatures and under unusually high bearing loads. More particularly, it relates to such lubricating greases consisting essentially of a petroleum lubricating oil fraction thickened to the desired grease consistency by incorporating therein a thickening or gelling agent comprising a barium soap of a long chain fatty acid produced in situ by reacting the fatty acid, while admixed with the oil fraction, with a substantial excess of colloidal barium carbonate, the excess barium carbonate remaining in the finished grease as reserve base serving to neutralize acidic materials with which it may come in contact during use and, apparently, also serving other useful functions.

The invention provides improved greases of the type described and also provides an improved method for the manufacture of such greases.

Lubricating greases have, for decades, been produced by thickening petroleum lubricating oil fractions with a soda or lime soap of oleic, palmitic or stearic acid, or mixtures thereof, by saponifying the fatty acid in admixture with the mineral oil. Soaps of other metals have also been used in the manufacture of lubricating greases.

It has also been proposed to effect the thickening of lubricating oil by dispersing therein inorganic colloids in expanded form, such as gels or clays, or certain unneutralized oxides or carbonates, carbon black or the like. More recently, it has been proposed to produce lubricating greases by thickening an oil lubricant with colloidal calcium carbonate which has been coated, or in some way complexed by chemical interaction, with a calcium salt of a low molecular weight dibasic aliphatic acid.

To my knowledge, none of the greases so produced have been entirely satisfactory for lubricating parts subject to high temperature operating conditions under extremely high bearing loads. invention, and my improved method of producing such greases, are distinguished from the greases and procedures of the prior art in several important respects as will hereinafter appear.

It is an object of my present invention to produce lubricating greases containing reserve alkalinity and which are stable against separation in storage and against separation or leakage of oil under high temperature operating conditions and which are capable of maintaining efiiciency lubrication under unusually high bearing loads.

It is a more specific object of the invention to produce such greases having A.S.T.M. dropping points of at least 300 F., and preferably in excess of 350 R, which under the A.S.T.M. wheel bearing performance test at 220 F. suffers an oil leakage not exceeding about 10 grams, and preferably less than grams, which by the rolling stability. test at room temperature will show a final micro penetration not exceeding 230, and which passes the four-ball weld test at a load of 200 kgs. These objects are attained by my present invention, aswill hereinafter As indicated above, the process of thelpresent inven- .tion, broadly stated, comprises the reacting of a fatty acid, while admixed with a petroleum lubricating oil The greases of my present I fraction, with a substantial excess of colloidal barium operation as just broadly stated will not result in a lubricating grease meeting the above-noted specifications, unless several important conditions, hereinafter described, are met. Y

I have found that for producing such greases having these desired properties, the characteristics of the colloidal barium carbonate used are of utmost importance. While I cannot describe with certainty the essential characteristics of the carbonate, there has been developed a novel process by which colloidal suspensions of barium carbonate in methanol, having the characteristics essential for my present purpose, may be consistently produced, and which is the subject matter of copending application Ser. No. 814,399, filed concurrently herewith. It is my present belief that the unique qualities of the resultant colloid are in some way related to the particle diameter or structure or surface chemistry of the colloidal particles or some combination of those properties, not fully understood. The particle diameters of such suspensions, which I have used with particular advantage, have been shown by electron microscope examination to be rela-- tively uniform and to fall within the range of 0.02 to 0.2 micron.

According to the process described and claimed in the above-noted copending application, barium oxide in pro-- portions within the range equivalent to about 10% to about 15% barium, preferably about 12.5%, is reacted with anhydrous methyl alcohol to produce a clear solution. Then an amount of water within the range of about 1 mol to about 4 mols, preferably about 2 mols, per mol of barium present in the solution, is added to and thoroughly dispersed in the solution to form a homogeneous mixture. The solution is then carbonated by dissolving carbon dioxide therein in a molar proportion at least equal to the mols of barium present therein. The foregoing steps may be carried out at ambient temperatures and pressures. The resultant mixture is then mildly heated to a temperature of about 153 F. with refluxing for a period of approximately one-quarter hour, until a substantially clear colloidal solution of the carbonate is obtained.

This preformed colloidal suspension of the barium carbonate in methanol is, in accordance with my present invention, mixed in suitable proportions with the petroleum oil fraction and the fatty acid and the mixture heated to evaporate the alcohol, promote reaction of the carbonate with the fatty acid and drive off the water.

A further important condition which must be met in carrying out my process is the rate at which the methanol is expelled from this mixture. Upon evaporation of the methanol, the mixture assumes a semi-fluid consistency. I have found, however, that if the methanol is expelled too rapidly, a grease satisfactory for my present purpose will not result. It is my present belief that this is due to some change in the character of the colloid brought about by too rapid expelling of the methanol. 7

In laboratory size batches, I have found that the desired results are obtained where at least the major portion of the methanol is driven oif by gradually heating the mixture, without mechanical agitation, to a moderate temperature, of the order of -200 F., for a period ofabout one hour. The optimum temperature and extent of this preliminary heating step will vary somewhat with the volumeof the batch and the dimensions of the heating vessel Asa general guide in this respect, I have found that the rateof expelling the methanol should not exceed about-0.6 gallon per square foot of disengaging surface per hour, Substantiallyglower evaporation rates may be used elfectively, Satisfactory results have been i d u n ev p a ion. rate a u as gallon Patented Nov. 28, 1961 of methanol per square foot of disengaging surface per hour. Rates below about 0.4 gallon do not appear to have added advantage and are'usually not recommended because of excessive processing time and cost. Evaporation rates substantially in excess of 0.6 gallon per square foot of surface per hour, for instance evaporation rate of 0.8. gallon, have been found to result in an inferior grease. Usually a methanol evaporation rate within the range of about 0.5 to about 0.6 gallon per square foot of surface per hour is preferred.

After the methanol has been substantially completely expelled, the batch is heated to at least 300 F., with stirring, until substantially all the water present therein has been driven 01f.

A third essential feature of my present process is the character of the fatty acid used. For this fatty constitucut, I use a straight-chain, saturated, unsubstituted fatty acid consisting predominantly of a fatty acid or a mixture of fatty acids containing 20 to 22 carbon atoms per molecule, i.e., arachidic or behenic acid or a mixture thereof. The use of unsaturated or substituted fatty acids, and even straight-chain, saturated, unsubstituted fatty acids of lower molecular weight, has not resulted in greases having the desired properties. A mixture of about equal proportions of arachidic and behenic acids is recommended. Behenic acid alone produces excellent results, but its cost is presently too great to be economically attractive. V

I have, with particular advantage, used a mixture of fatty acids marketed by Arch-er-DanielsMidland Company under their proprietary trade name Hydrofol Acid AB? and having the following analysis and approximate composition:

TABLE 1 of the fatty acid. However, most advantageous results have been obtained where the said molar ratio was about Other conditions remaining constant, I have found that the maximum yield, i.e., the maximum consistency of the finished grease for a given amount of thickener, will vary somewhat with the temperature to which the batch is heated in the final stage of the operation. Maximum yields have usually been obtained where the final temperature is about 450 F. However, most desirable performance of the greaseunder the A.S.T.M. wheel hearing performance test has been obtained byusing a finish ingtemperature of about 350 F. i

For most advantageous results, particularly with respect to oil leakage under conditions of the A.S.T.M. wheel bearing performance test, I have found it necessary to incorporate in the grease a minor proportion of a dispersing agent or stabilizer, such as a high molecular weight sulfonic acid, more particularly a sulfonic acid of a molecular weight of about 400 to about 500.

The optimum propotrion of such sulfonic to be used will vary somewhat depending upon the particular suli fonic acid used, the proportions and identity of the other ingredients and also the desired characteristics of the re- Titer (3.. 60-63 Iodine value max 5 Acid value 178-185 Saponificat-ion value 179-186 Color Lovibond, 5 A" max 25Y/2.5R Calculated molecular weight 302-314 Spec. grav., 100/25 C. 0.828 Approximate composition, percent:

V14 2 C 13 C13 7 V C 30 C22 The nature of the petroleum lubricating oil fraction used is subject to'considerable variation depending upon the intended use of the grease and the specificcharacusing the previously described Hydrofol Acid AB and a'naphthenic oil fraction havinga viscosity of about seconds SSU at 210 F., I have, with particular advan tage, used approximately one part, by weight, of the sultant grease. When used, the stabilizer should be incorporated in the mixture of the fatty acid, petroleum oil and colloidal barium carbonate suspension prior to the evaporation of the methanol therefrom.

I have, with particular advantage, used for this purpose a solution of 39% dinonylnaphthalene sulfonic acid in naphtha, and have found it to promote better dispersion of the soap and colloidal carbonate in the oil and to improve the lubricating characteristics and stability of the resultant grease under operating conditions.

. As previously indicated, the proportion of the sulfonic acid used does not appear to be particularly critical. However, for most satisfactory results, I have used approximately one part of the above-described sulfonic acid, dry weight basis, for each 10 parts of the Hydrofol Acid AB. Where the stabilizer is used as above described, I have, with advantage, increased the finishing temperature of the batch to about 450 -F., thus obtaining maximum yield with a minimum of oil leakage under conditions of the A.S.T.M. wheel bearing performance test.

' The invention and the utility thereof will be further illustrated by the following specific examples in which the variables have been reduced, so far as practical, for comparative purposes. It will be understood, however, that the invention is not restricted to the specific material and operating conditions of these illustrative examples.

Example I ing 12.5% barium and produced as previously described herein. These materials were mixed in the following acid for each 5 or 6 parts of the on; Where a less viscous oil is used, a somewhat larger proportion of fatty 1 acid will be required to produce a grease of eqfialcon- 1 sistency' or dropping point, other conditions remaining constant, i 2' Also using the materialsjustv named, I have, with ad vantage, varied the proportion of barium carbonate used over a range equivalent to2 to5 mols of-barium per mol proportions by weight:

' Parts Fatty acid V 50 Oil fraction i 336 Colloidal suspension 352 Themixture was mildly heated to atemperature within and ten minutes, during which timejthe methyl alcohol mixture.

the range'of F. to 200 F. for a period of one hour s The temperatur'e of the batch was then raised to approximately 300 F., while stirring, and maintained at that temperature for about 20 minutes with continued stirring. The temperature was then increased to approximately 350 F., with continued stirring, and maintained at that temperature for an additional to 30 minutes. The heating and stirring were then discontinued and the batch permitted to cool to room temperature. The resultant grease was of a somewhat crumbly nature but upon milling resulted in a smooth, homogeneous grease having the properties set forth in the subsequent tabulation, Table 2.

Example II In this operation, the fatty acid, the oil and the colloidal suspension of barium carbonate were the same, and were used in the same proportions, as in the preceding example. Unlike Example I, there was incorporated in the mixture, prior to evaporating the methanol therefrom, 13 parts by weight of a 39% dinonylnaphthalene sulfonic acid, of a molecular weight of about 425, in naphtha, as a stabilizing or dispersing agent.

This mixture was preliminarily mildly heated, as described in Example I, for evaporating the methanol and the heating was thereafter continued with stirring at a temperature of 300 F. for approximately minutes. With continued stirring the temperature of the batch was then raised to about 450 F. and maintained at that temperature for approximately 15 minutes. The stirring and heating were then discontinued and the batch permitted to cool to room temperature. The batch was then milled which resulted in a smooth homogeneous grease having the properties set forth in subsequent Table 2.

Example 111 In this operation, the fatty acid, the oil and the colloidal suspension of barium carbonate, and the proportion thereof, were identical with those used in Example I and the procedure was substantially identical therewith except that the maximum final temperature of the batch was approximately 300 F. A serviceable grease resulted. However, under final test, the product was somewhat inferior to that of Example I or Example II, as will appear from the following tabulation:

TABLE 2 Ex. I Ex. II Ex. III

A.S.T.M. Dropping Point, F 301 383 300+ Scale Penetration (unworked) 132 110 181 Equivment A.S.T.M. Penetration 263 225 348 Rolling Stability Test (2 hrs., dry,

Room Temp):

Original Penetration 84 70 136 Final Penetration 102 98 183 Wheel Bearing Performance Test (6 hrs,

220 F., 90 gram pack): Oil Leakage grams 7 2 0.5 10 1 Four-Ball Wear Test, Wear Scar Diameter, mm.:

6 kg. Load, 130 F., 1,800 r.p.m 40 kg. Load, 300 F., 600 r.p.m Four-Ball Weld Test 200 kgs frared analysis any indication of the presence of a complex of the excess barium carbonate with the barium soap.

The herein referred to A.S.T.M. dropping point values and A.S.T.M. wheel bearing performance test, were at; termined and carried out in accordance with the pre with the procedure described in the article beginning on page 1 of National Lubricating Grease Institute Spokesman, vol. VI, No. 12, of March 1943.

I claim:

1. Process for producing lubricating greases comprising the following steps, mixing a petroleum lubricating oil fraction, a fatty acid consisting predominantly of straightchain, saturated, unsubstituted fatty acids containing from- 20 to 22 carbon atoms per molecule and a colloidal suspension of barium carbonate in methanol, the latter in a proportion within the range equivalent to about 2 to about 5 mols of barium carbonate per mol of fatty acid and produced by reacting with anhydrous methyl alcohol, to form a clear solution, an amount of barium oxide equivalent to about 10% to about 15% barium, based on the weight of the alcohol, and adding to the resultant solution and thoroughly dispersing therein, with stirring to form a homogeneous solution, an amount of water within the range from about 1 mol to about 4 mols permol of barium present in the solution, thereafter dissolving carbon dioxide in the resultant solution in a molar proportion at least equal to the mols of barium present therein and heating the resultant mixture with refluxing until a substantially clear colloidal solution is obtained,

mildly heating the mixture of oil, fatty acid and colloidal carbonate suspension to a temperature and at a rate adapted to expel the methanol therefrom at a rate not exceeding about 0.6 gallon of methanol per square foot of disengaging surface per hour until the methanol has been substantially completely evaporated therefrom, increasing the temperature of the mixture to at least 300 F. but not exceeding about 450 F. and continuing the heating, with stirring, until substantially all the water present therein has been driven off, then gradually cooling the mixture to room temperature and milling the resultant cooled mixture to a smooth grease.

2. The process of claim 1 in which the barium carbonate suspension used is one containing 12.5% barium and is used in a proportion equivalent to 3.5 mols of barium per mol of fatty acid.

3. The process of claim 1 in which the colloidal suspension of barium carbonate used is one produced by reacting with the anhydrous methyl alcohol an amount of barium oxide equivalent to about 12.5% barium, adding to the resultant solution and thoroughly dispersing therein, with stirring to form a homogeneous solution, about 2 mols of water, per mol of barium present in the solution, and thereafter saturating the resultant solution with carbon dioxide.

4. The process of claim 1 in which the grease batch is finally heated to a temperature within the range of 350 F. to 450 F.

5. The process of claim 1 in which the petroleum lubricating oil fraction is a solvent refined naphthenic fraction having a viscosity of 50 SSU at 210 F.

6. The process of claim 1 inwhich a sulfonic acid dispersing agent, having a molecular weight within the range of about 400 to about 500, and in a minor proportion efiectiveto promote dispersion of the colloidal carbonate and soap in the mineral oil, is incorporated in the mixture of oil, fatty acid and colloidal carbonate suspension prior to expelling the methanol therefrom.

7. The process of claim 1 in which about 10% of dinonylnaphthalene sulfonic acid, based on the weight of the fatty acid used, is incorporated in the mixture of predominantly of straight-chain, saturated, unsubstituted,

fatty acid containing from 20-22 carbon atoms per molecule, dinonylnaphthalene sulfonic acid and a colloidal suspension of barium carbonate in methanol, the suspension having'been produced by reacting with anhydrous methyl alcohol, to form a clear solution, an amount of barium oxide equivalent to about 12.5% barium, adding to the resultant solution and thoroughly dispersing therein, with stirring to form a homogeneous solution, about 2 mols of water, per mol of barium present in the solution, and thereafter saturating the solution ,with carbon dioxide and heating the resultant mixture with refluxing until a substantially clear colloidal solution is obtained, mildly heating the mixture of oil, fatty acid, carbonate suspension and sulfonic acid to a temperature within a range of 170200 F. until the methanol'has been substantially completely expelled therefrom, then heating the batch to about 300 F., with stirring, until the water present in the batch has been substantially completely eliminated, then increasing the temperature of the batch to about 450 F., with continued stirring, thereafter cooling the batch to room temperature and milling the resultant grease to a smooth homogeneous consistency, the proportions of the respective ingredients used being approximately as follows: 7

Parts by weight 50 Fatty arid Oil 336 Carbonate suspension 352 Sulfonic acid 9. A stable, substantially anhydrous homogeneous lubricating grease having reserve alkalinity and consisting essentially of a petroleum lubricating oil fraction thickenedto the desired consistency with an admixture of 'a barium soap of a straight-chain, saturated, unsubstituted,

fatty acid consisting predominantly of fatty acidscontaining from 20 to 22 carbon atoms per molecule, and colloidal barium carbonate, the proportion of soap, expressed inlterms of the fatty acid content, being about 1 part of fatty acid for each 5-6 parts of oil and the molar proportion of colloidal barium carbonate present in the grease being about 1 to about 4 times the weight of that combined with the fatty acid, said grease having an A.S.T.M. dropping point of at least 300 F., and which under the, A.S.T.M. wheel bearing performance test, 6 hours at 220 F., gram pack, suffers an oil leakage not exceeding about 10 grams. 7

10. A stable,'substantially anhydrous homogeneous lubricating grease having reserve alkalinity and consisting essentially of a solvent refined naphthenic petroleum oil fraction thickened to the desired consistency with an admixture of a barium soap of a straight-chain, saturated, unsubstituted fatty acid consisting predominantly of fatty acids containing from 20 to 22 carbon atoms per molecule, colloidal barium carbonate and a sulfonic acid dispersing agent having a molecular weight of 400-500, the proportion of soap, expressed in terms of the fatty acid content, being about 1 part of fatty acid for each 5-6 parts of oil and the molar proportion of colloidal barium carbonate present in the grease being about 1 to about 4 times the weight of that combined with the fatty acid, said grease having an A.S.T.M. dropping point in excess'of 350 F. and which under the A.S.T.M. wheel bearing performance test, 6 hours at 220 F., 90 gram pack, suffers an O1]. leakage of less than 5 grams.

References Cited in the file of this patent UNITED STATES PATENTS 2,154,383 Ott et a1. Apr. 11, 1939 2,417,433 McLennan Mar. 18, 1947 2,503,749 Langer et a1 Apr. 11, 1950 2,629,692 Liehe Feb. 24, 1953 2,865,956 Ellis et a1. Dec. 23, 1958 2,889,279 Carlyle et al June 2, 1959 FOREIGN PATENTS 507,259 Canada Nov. 9, 1954 507,437 Canada Nov. 16, 1954

Claims (1)

1. PROCESS FOR PRODUCING LUBRICATING GREASE COMPRISING THE FOLLOWING STEPS, MIXING A PETROLEUM LUBRICATING OIL FRACTION, A FATTY ACID CONSISTING PREDOMINANTLY OF STRAIGHTCHAIN, SATURATED, UNSUBSTITUTED FATTY ACIDS CONTAINING FROM 20 TO 22 CARBON ATOMS PER MOLECULE AND A COLLOIDAL SUSPENSION OF BARIUM CARBONATE IN METHANOL, THE LATTER IN A PROPORTION WITHIN THE RANGE EQUIVALENT TO ABOUT 2 TO ABOUT 5 MOLS OF BARIUM CARBONATE PER MOL OF FATTY ACID AND PRODUCED BY REACTING WITH ANHYDROUS METHYL ALCOHOL, TO FORM A CLEAR SOLUTION, AN AMOUNT OF BARIUM OXIDE EQUIVALENT TO ABOUT 10% TO ABOUT 15% BARIUM, BASED ON THE WEIGHT OF THE ALCOHOL, AND ADDING TO THE RESULTANT SOLUTION AND THOROUGHLY DISPERSING THEREIN, WITH STIRRING TO FORM A HOMOGENEOUS SOLUTION, AN AMOUNT OF WATER WITHIN THE RANGE FROM ABOUT 1 MOL TO ABOUT 4 MOLS PER MOL OF BARIUM PRESENT IN THE SOLUTION, THEREAFTER DISSOLVING CARBON DIOXIDE IN THE RESULTANT SOLUTION IN A MOLAR PROPORTION AT LEAST EQUAL TO THE MOLS OF BARIUM PRESENT THEREIN AND HEATING THE RESULTANT MIXTURE WITH REFLUXING UNTIL A SUBSTANTIALLY CLEAR COLLOIDAL SOLUTION IS OBTAINED, MILDLY HEATING THE MIXTURE OF OIL, FATTY ACID AND COLLOIDAL CARBONATE SUSPENSION TO A TEMPERATURE AND AT A RATE ADAPTED TO EXPEL THE METHANOL THEREFROM AT A RATE NOT EXCEEDING ABOUT 0.6 GALLON OF METHANOL PER SQUARE FOOT OF DISENGAGING SURFACE PER HOUR UNTIL THE METHANOL HAS BEEN SUBSTANTIALLY COMPLETELY EVAPORATED THEREFROM, INCREASING THE TEMPERATURE OF THE MIXTURE TO AT LEAST 300* F. BUT NOT EXCEEDING ABOUT 450*F. AND CONTINUING THE HEATING, WITH STIRRING, UNTIL SUBSTANTIALLY ALL THE WATER PRESENT THEREIN HAS BEEN DRIVEN OFF, THEN GRADUALLY COOLING THE MIXTURE TO ROOM TEMPERATURE AND MILLING THE RESULTANT COOLED MIXTURE TO A SMOOTH GREASE.