US2720491A - Extreme pressure lubricant - Google Patents

Description

United S sv Patent Helen Sellei Beretvas, Chicago, Ill.,. assigmor to Standard Oil Company, Chicago, 111., a corporation of Indiana No Drawing. Application June 28, 1954, Serial No. 439,868

16 Claims. c1. zs2 37.2

This invention relates to novel lubricant compositions having especial utility under extreme pressure conditions. It is particularly concerned with extreme pressure lubricants containing complex double soaps of naphthenic acid and certain low molecular Weight aliphatic carboxylic acids.

The use of oil soluble lead containing compounds, e. g. lead naphthenate, lead olcate, etc. as components of extreme pressure lubricants is well known. Particularly outstanding extreme pressure lubricants have now been prepared which contain a double lead soap of naphthenic acid and certain low molecular weight aliphatic carboxylic acids including lactic acid, maleic acid, etc. By use of such lead soaps, either alone or in combination with a simple lead soap such as lead naphthena'te, the extreme pressure properties of lubricating oils containing sulfur and usually chlorine containing E. P. additives (extreme pressure additives) may be greatly improved over that obtainable with a simple soap alone. And it has been found that for a given weight of soap the amount of lead introduced to the oil can be increased by using the novel complex soaps instead of a simple soap, e. golead naphthcnate. Moreover, the properties of complex soaps have been found to be substantially more consistent and not subject to the Widevariation experienced with commercial lead naphthenate purchased from several dilferent suppliers.

The lowmolecular weight a-lip'haticcarboxylic acids suitable for use in accordance herewith are those containing from two to about six and preferably three or four carbon atoms. Acids having either a hydroxy group attached to one of the carbons in the chain or those having adouble bond in the linear carbon chain may be used. Such compounds may be monoor di-carboxylic and typical examples thereof are: g'lycolic acid, lactic acid, maleic acid, malic acid, citric acid, 7 hydroxy butyric acid, a hydroxy butyric acid, etc.

Whereas certain low molecular weight carboxylic acids have been enumerated above, these are for purposes of illustration and not of limitation. And it should be undcrstood that those compoundsfalling generally within the broad definition of the useful class of compounds may be employed.

lit accordance herewith, basic lead naphthenate is preferablyreacted with litharge and a low molecular weight acid to produce the complex soap of the present invention. Naphthenic acid may, of course, be used in such reaction instead of the soap. The so-called basic lead napht'henate is an available article of commerce which is incompletely converted to the totally neutralized soap and is therefore usually more expedient to employ since half-the double complexsoapis, in effect, already for-med. The present invention will, accordingly, be described with respect to such preferred method of preparation. Itis theoretically possible that the reaction may begin with n-aphthenic acid and the soap of the low molecular weight acid, e, g. lead lactate, to obtain the resultant complex double soap, but the oilinsolubility of the low moleculat weight soap and consequent inferior contact in the reaction zone make such method less desirable. Saponification resulting in the complex soap may be preferably initiated by a small amount of caustic or potash which may be added in pellet or other form in small amount, e. g. from about 0.05 to about 2% by weight.

The manner in which the double soap is prepared is not of itself a part of the invention and although it has been found as a practical matter that the double soaps are best prepared in accordance with the technique detailed, other methods resulting in the soap may, of course, be employed. Especially, however, in connection with the introduction of more than the theoretical (or stoichiometric) amounts of lead or lactic acid, as will hereinafter be discussed, the technique described herein has been found most satisfactory. The preparation of basic leadnaphthenate'is, of course, well known to those skilled in the art and is in no way a part of the instant invention. The generally greater effectiveness of lead fish oil soaps as extreme'pressure additives as compared to lead naph thenate is believed to be related to the relative oil-insolu bility of the former. Accordingly, efforts to improve the effectiveness of the lead naphthenate have resulted in the discovery that complex soaps embodying a low molecular weight acid radical are substantially less soluble in oil and vastly superior in their extreme pressure properties to lead naphthenate. Thus, it would appear that the least soluble complex soap which may, however, still be dispersed or dissolved in a lubricating oil is the most satisfactory. Because the low molecular weight acids em pl'oyed decrease oil solubility of the complex, the larger the amount of such acid in the complex the lower the solubility of the same for a given weight of soap and the more improved are the extreme pressure properties. However, the desire for a rather insoluble lead soap must be tempered by the necessity of keeping the additive in the oil, i. e. producing a stable lubricant. In this connection, it has been found that oleic acid or an alkyl phenol, e. g. nonyl phenol or other alkyl phenols hav- "ing a total of from about 8 to about 12 and preferably about 9 or 10 carbon atoms in no more than two alkyl side chains and no such side chain containing fewer than fourcarbon atoms, is especially effective in solu'biliz-ing complex double soaps which are ditficultly soluble. The alkyl phenol may be employed in an amount of from abouttlS-to about 10% and preferably from about l'to about 6%. Moreover, solvent extracts, e. g. phenol, furfural, Ghlorex, etc., of lubricating oils and other petroleum fractions are also excellent solubilizers for use in accordance herewith. From about 1 to about 50% by weight or more and preferably from about 2 to about 3 0% of extract solu'bilizer may be used. Lead naph- "theriate is itself a useful solubilizing agent and is especially advantageous from the standpoint of introducin'g still more lead to the lubricant.

As will be apparent from data set forth in Table 1, oleic acid has especial utility in extreme pressure lubricants of the type herein described over and above its more solubili'zing influence upon the complex soap. This higher molecular weight unsaturated carboxylic acid has been shoW-n'to substantially improve the extreme pressure properties of such an oil. And, in accordance with a preferred lubricant composition of the present invention, there is employed in conjunction with the complex soap and a sulfurized and chlorinated E. P. additive, at least about 1% oleic acid, by weight, based upon tot-allubricant and preferably from about 2 to 7%. As much as 10% or more may be used but the resulting improvement, if any, compared to cost is ordinarily not justifiable.

I-n accordance with the preferred embodiment of the present invention, the complex double soaps are prepared by combining litharge and basic lead naphthenate in a ratio of from about 1:1 to about 1:6 parts, by weight, and preferably about 1:4. The low molecular weight acid component of the double soap is employed in an amount of from about 1 to about moles of low molecular weight acid per mole of litharge and preferably from about 1 to about 2. More lactic acid may be used; it is doubtful that the same will combine in a stable manner and is, accordingly, unnecessary.

Thus, for example, 100 parts, by weight, of a commercial basic lead naphthenate (containing 30% lead) are reacted with from about to about 65 parts of litharge, and preferably about 1 part of litharge to every 4 parts of basic lead napthenate, and from 1 to 5 moles of low molecular weight acid, e. g. lactic acid, per mole of litharge. Preferably, about 1 to 2 moles of low molecular weight acid per mole of litharge are employed although larger amounts of litharge may be employed.

It will be apparent that in the event of employment of the large amounts of reactants in the upper ends of the above defined ranges, there will of necessity be substantially more than the theoretical stoichiometric quantity required for the formation of double soaps having the formula RCOOPbOOCR, wherein R represents the radical of naphthenic acid and R represents an acyclic radical of the particular low molecular weight acid. As will appear from data hereinafter presented, soaps containing such an excess have been found especially desirable but it is not understood in just what manner such an excess contributes to the excellent results obtained. For this reason, the double soaps are sometimes referred to herein as complex lead soaps or complex double soaps in order to emphasize the existence in certain instances of a stable excess of lead and/or low molecular weight acid. The theoretical double soap, i. e. containing no excess is, of course, included within the meaning of such terms. These excesses are believed to be held in the double soap inthe form of a chemical complex.

The preparation of the complex double soap is preferably carried out at a temperature in the range of from about 240 F. to 320 F. but a broader range of temperatures, for example, from about 200 F. to about 400 F. may be employed.

-. Complex double soaps of the present invention are primarily useful in heavier mineral lubricating oils of the type employed for extreme pressure use, e. g. lubricating oils having a viscosity at 210 F. of at least about 50 S. S. U. and preferably about 75 to about 115 S. S. U. The soaps are not limited in their. utility to such oils, however, and may be used with oils having lower as well as higher viscosities. Such oils may be acid treated, solvent extracted, etc. without in any way departing from the scope of this invention. Non-solvent extracted, acid treated (sulfuric acid) oils are preferred for use in accordance herewith.

The amount of the novel soaps, described herein, which may be employed in extreme pressure lubricants will vary over a rather wide range depending upon the type of oil, the other additives employed, the intended application of the particular lubricant, etc., but generally an amount of from about 1 to about. 10%, by weight, based on total lubricant and preferably from about 3 to about 7%, by weight, has been found desirable.

For the purpose of illustrating the preparation of the novel complex soaps of the present invention but with- .out any intention of being limited to the specific illustrative examples set forth, the following examples are presented:

Example 1 Three hundred grams of commercial basic lead naphthenate (approximately 30% lead) were reacted with of the active acid) was added (the mole ratio, of PbO to lactic acid being about 1:2) in about 5 minutes and the temperature dropped to 230 F. Reaction was apparently complete in about 7 minutes, but stirring was continued for about an hour during which time the temperature slowly dropped. The resulting product was quite hard and contained about 36% lead.

Example 2 Commercial basic lead naphthenate (30% lead) in an amount of 19.8 pounds was mixed with 5% pounds of lactic acid (80%-technical grade) and heated to 240 F. 68 grams of potassium hydroxide pellets were added along with 4.8 pounds of litharge. These materials were added in about half an hour and the temperature rose to 310 F. The mixture was then stirred for about 3 hours at 300 F. and the heat was then shut ofi. To the hot product (at about 300 F.) was then added 16 pounds of oleic acid and the mixture was then stirred for about one-half hour. The lead content of the product before the addition of oleic acid was 36.2%. The Pb content of the blend was 22%.

Example 3 Three hundred grams of commercial basic lead naphthenate 30% lead) were mixed with 150 grams of lactic acid (80%-technical grade) and heated to about 240 F. A relatively small amount of potassium hydroxide pellets were added to initiate saponification while adding grams of litharge. The ratio of litharge to lactic acid on a mol basis was about 1:4. The reaction was complete in about half an hour and the temperature rose to about 300 F. as in Example 2. Stirring was continued for several hours and the heat was then turned off. The complex soap which comprised 35.5% lead by weight was then blended with oleic acid in a 60% soap- 40% oleic acid ratio in order to prepare a material readily soluble in the lubricating oil.

Example 4 Three hundred grams of commercial lead naphthenate (30% lead) were mixed with grams of maleic acid and heated to about 240 F. 5 potassium hydroxide pellets were added along with 75 grams of litharge and the temperature rose to about 300 F. Reaction was over rather quickly but stirring was continued for approximately two hours. The complex soap contained 40.9% lead and was then blended with oleic acid to give a somewhat ditficultly soluble additive for lubricating oils.

In order to determine, in the laboratory, the effectiveness of the complex double soaps prepared in accordance with theforegoing examples, tests were run in both the Timken and Shell four-ball extreme pressure testing machines. Each of these testing machines is useful in the laboratory evaluation of extreme pressure lubricants, but they are dissimilar in their method of testing and in the results obtainable therefrom. Thus, oils will often show up well on one test but noton the other. However, lubricating engineers, while not entirely in agreement as to the exact meaning of these tests when translated into actual performance, have been able to correlate these tests to a certain extent and, in general, find them most helpful in evaluating new lubricant compositions. Field tests in the rear axle gears of at least one major automobile manufacturer have resulted in adoption of extreme pressure lubricants of the type herein described.

The Timken machine and test are well known to those skilled in the art, and it is, unnecessary here to describe the same in detail since they are fully described in the Journal of the Institute of Petroleum 32, pp. 209-210 and 220-222 (1946). The Shell four-ball testing machine is likewise well known to those skilled in the art for its utility in evaluating hypoid lubricants and is likewise described in detail in the literature National Petroleum News 31, 52 (December 27, 1939) p. R551 and also Journal of the Institute of Petroleum 32, pp.-21-0-21 2 and Set forth in Table 1 are the results of tests in the Timken machine which demonstratet-he improvementobtained by employing the novel soaps of the present inventionincomparisonwith the use of lead naphthenate. .In each of the testsnset forth in Table 1,,alubricant base comprising a non-solvent extracted S. A. E. 50 grade mineral. oil containing 5%, by weight, of sulfurized sperm oil (.10 to 1.3% sulfurr), 3% of a chlorinated hydrocarbon (-73% chlorine wasemployed. The ultimate lubricant in each instance had aviscositywat 2l0 F. of between. about 80 *and'98 S. S. U.

TABLE 1 1 F 1 iimen L'lesdt Percent esu s, on RunNb. Nliiihuieni" 3 23; 3333 Lbs.

F igg Complex Acid Tires Fail 5 it None None 35 40 5 i None 2 451: 50 6 None 4 50 55 4.2 None 13.8 55: 60 None 5 None 65 70 None "3 '4 65 70 None 5 2 75 B 1. b 1. 5 2 70 75 N one =4: 2 15.8 70 '75 None 4; 2 6. :8 75 80 None A 452 6. 8 80 '85 None 4 14.2 6. 8 80 85 I Complex soap employed was made in accordance'with method of ustrative Example 1, supra, no oleic .acid was employed to solubilize th'e'compiex.

Complex soap employed was unade in accordance with method of illustrative Example 1,.supra, and then blended with an equal amount of Pb naphthenate"(30% Pb).

I Sample of complex soap omployedwas that prepared in :ExampleB, supra, 2.8% oleic acid was combined with the soap initially to render the same readily soluble and 4% additional oleic acid was added to final ubricant.

4 Sample of complex soap employed was that prepared in illustrative Example 4, supra, 218% ct oleic acid added tosoaplnitially and 4% additional as in 1 Complex soap employed was made in accordance with method of illustrative Example 2, supra, 2.8% of oleic acid added to soap initially and "4% additional -as in The striking improvement in the Timken results when employing a novel complex of the present invention is demonstratedby the above table. The advantage of the complex soap over the lead naphthenate, either alone or in the presence of oleic acid, is obvious.

Additional tests in the Shell four-ball tester further demonstratethe improvement obtained with the complex as compared to lead naphthenate. In these tests in order to demonstrate the effectiveness of the complex in the absence of sulfurized or chlorinated materials, only those materials noted in the table were present in an acid treated S. A. E. 50 base oil and no sulfur or chlorinated materials were employed.

The above data indicate the improvement obtainable with the complex soap and demonstrate, in a second test, the improved results obtainable with the lead complex soap. Whereas the use of oleic acid results in no apparent improvement as evidenced in the Shell four-ball test, it would appear to merely be further confirmation of lack of correlation between the various extreme pressure tests.

Although the specific materials employed in the tests set carbons and organic materials.

. g I a forth Table l were a sulfurized sperm oil and a chlorinated hydrocarbon, it should be understood that many other known sulfur and/ or chlorine-containing materials may be employed in conjunction with the lead complexes of the present invention. Thus, sulfurized hydrocarbons, sulfurized carboxylic acids, e. g. sulfurized tall oil, sulfurized oleic acid, etc., organic sulfides, sulfurized vegetable oils, polysulfides, e. g. the dialkyl tri-, tetra-, pentaand hexasulfides, and other oil-soluble: sulfur-containing compounds or materials useful in extreme pressure lubricants, may be employed alone or in combination with each other, in accordance herewith. Reference is made to U. S. 2,136,391, 2,202,394, and many other patents disclosing sulfur containing additives for extreme pressure addition; such materials are generally useful in accordance herewith. Such sulfur-containing organic constituents are generally employed in the extreme pressure lubricant in an amount suflicient to afford a lubricant sulfur content of from about 0.3 to about 5.0%. Thus, an amount of sulfur-containing organic E. P. additive of from about 1 to about 20% and preferably from about 3 to about 15% may be employed. Likewise, chlorinated compounds of various types may be employed in lubricants containing the novel complexes. Thus, chlorinated hydrocarbons have been employed which, for example, may be obtained by chlorinating paraffin wax or olefinic hydrocarbons. Individual chlorinated aliphatic compounds such as hexachlorethane, heptachlorpropane, octachlorbut'ane, etc. are useful. Reference is made to U. S. 2,178,513 which sets forth a substantial number of halogenated organic ring compounds which are useful in extreme pressure lubricants. Such materials may be em- .ployedin accordance with the present invention. U. S. 2,276,341 discloses. large numbers of chlorinated hydro- These also may be employed in accordance herewith. The chlorine-containing E. P. agents or additives are employed in the present extreme pressure lubricants in an amount sufficient to afford a lubricant content of from about 0.38.0% preferably from about 1% to about 3% of chlorine. An amount of chlorine-containing organic E. P. additive of from about 1% to about 10% and preferably about 2 to about 8% may be employed.

In addition to the sulfurized, chlorinated and lead-conmin ng materials disclosed hereinabove, it should be understood that lubricants containing the same may also have added thereto typical lubricating oil additives such as antioxidants, oiliness agents, corrosion inhibitors, detergents, etc. In particular, phosphorus-containing compounds often employed in extreme pressure lubricants may be employed. A particularly useful phosphorus-containing material is that resulting from the treatment of a hydrocarbon, e. g. an olefin polymer, with a phosphorus sulfide. Other phosphorus containing compounds, useful in lubricants of this kind, may also be employed.

As indicated above, lead naphthenate may be employed in addition to the lead complexes of the present invention. Likewise, other lead soaps such as lead oleate, lead tallate, and lead soaps of various high molecular weight oilsoluble carboxylic acids which do not substantially affect the viscosity of the lubricant, i. e. do not substantially thicken or gel the lubricant, may be employed in conjunction with the novel complexes of the present invention. Moreover, the lead soaps may themselves be sulfurized lead tallate, sulfurized lead naphthenate, etc. and used in conjunction with the complex soaps of the present invention.

Percentages recited herein and in the appended claims are by weight unless otherwise indicated.

Having thus described my invention what I claim as novel and desire to protect by Letters Patent is set forth in the following claims:

1. A normally liquid extreme pressure lubricant comprising a mineral lubricating oil and a minor amount of a complex double soap having the general formula RCOOPbOOCR wherein R represents a naphthenic acid 'radical and R represents the acyclic radical of a carboxylic acid containing from 2 to about 6 carbon atoms which carboxylic acid is selected from the group consisting of unsaturated carboxylic acids and hydroxy carboxylic acids.

2. The lubricant of claim 1 wherein the low molecular weight carboxylic acid is lactic acid.

3. The lubricant of claim 1 wherein the low molecular weight carboxylic acid is maleic acid.

7. A lubricant comprising a mineral lubricating oil and 1 from about 1 to about 10% of a complex double soap having the general formula RCOOPbOOCR' wherein R represents a naphthenic acid radical and R represents the acyclic radical of a carboxylic acid containing from 2 to about 6 carbon atoms which carboxylic acid is selected from the group consisting of unsaturated carboxylic acids and hydroxy carboxylic acids.

8. A lubricant comprising a mineral lubricating oil, an

amount of sulfur-containing organic material effective to improve extreme pressure properties of said lubricant, and from about 1 to about 10% of a complex double soap having the general formula RCOOPbOOCR' wherein R represents a napthenic acid radical and R represents the acyclic radical of a carboxylic acid containing from 2 to about 6 carbon atoms which carboxylic acid is selected from the group consisting of unsaturated carboxylic acids and hydroxy carboxylic acids.

9. The lubricant of claim 8 wherein the sulfur-containing organic material is a sulfurized sperm oil.

10. The lubricant of claim 8 which includes an amount of chlorine-containing organic constituents effective to improve the extreme pressure properties of said lubricant. 11. The lubricant of claim 8 which includes from 1 to about 10% of oleic acid.

12. The lubricant of claim 8 which contains from about 1.5 to about 50% of a solvent extract of a mineral lubricating oil.

13. The lubricant of claim 8 which contains from about 1.5 to about'50% of a solvent extract of a petroleurn mineral oil and from about 0.5 to about 10% of an alkyl phenol containing a total of from about 8 to about 12 carbon atoms in no more than two alkyl side chains, with no such side chains containing less than four carbon atoms.

14. The lubricant of claim 8 which contains from about 0.5 to 10% of an alkyl phenol containing a total of from about 8 to about 12 carbon atoms in no more than two alkyl side chains, with no such side chains containing less than four carbon atoms.

15. The lubricant of claim 14 wherein the alkyl phenol is nonyl phenol.

16. An extreme pressure lubricant composition comprising essentially a major proportion of a mineral lubricating oil and the followingconstituents in the following approximate weight percentagesz' Per cent Complex double soap 3 to 7 Organic sulfur-containing E. P. additive 3 to 15 Organic chlorine-containing E. P. additive 2to 8 Oleic acid t 2 to 7 Alkyl phenol 1 to 6 References Cited in the file of this patent UNITED STATES PATENTS 1,781,167

Doell Nov. 11, 1930 2,163,622 Neeley et al: June 27, 1939 2,455,892 Fraser Dec. 7, 1948 2,595,566

Worth et a1. May 6, 1952

Claims (1)

1. A NORMALLY LIQUID EXTREME PRESSURE LUBRICANT COMPRISING A MINERAL LUBRICATING OIL AND A MINOR AMOUNT OF A COMPLEX DOUBLE SOAP HAVING THE GENERAL FORMULA RCOOPBOOCR'' WHEREIN R REPRESENTS A NAPHTHENIC ACID RADICAL AND R'' REPRESENTS THE ACYCLIC RADICAL OF A CARBOXYLIC ACID CONTAINING FROM 2 ABOUT 6 CARBON ATOMS WHICH CARBOXYLIC ACID IS SELECTED FROM THE GROUP CONSISTING OF UNSATURATED CARBOXYLIC ACIDS AND HYDROXY CARBOXYLIC ACIDS.