US2417833A - Lubricant - Google Patents

Description

Patented 25, 1947 ENT oFFicE-f nunmcan'r pm 11. Lincoln and impair. nee-aroma City,

. th., assignon to Continental Oil Company,

Ponca City, Okla., a corporation of Delaware No Application April 22, 1944, said NO. 532346 9 Claims. 1 Our invention relates broadly to lubricants and more particularly to the use of the higher aliphatic diacids having terminal carboxyl groups as a base material for introducing into the lubricant chemical elements or groups which have a beneficial eiiect thereon.

Most lubricating oils are deficient in one or more, respects. They may have a low resistance to oxidation, corrosion, foaming or sludge formation or low detergency, oiliness or extreme pressure characteristics. It has become the general practice to add to the oil small amounts of an agent or agents capable of correcting or at least minimizing the deficiency. The additives are chemical compounds but it is usually one element or radical in the compound which produces the desired result. These elements, radicals and compounds, are well recognized in the art and have been generally classified according to the result they produce in the lubricant.

For example, low resistance of a lubricant to corrosion, oxidation and sludge formation is corrected by the use of sulfur, phosphorous and nitrogen compounds. Sulfurized sperm oil, sulfurized wax olefins, organic thiophosphates and thiocarbonates, and aromatic or amino-aromatic phosphates are typical examples. As little as 0.001 per cent of these compounds is usually suflicient. v

Foaming of lubricants can be corrected by the addition of .0001 per cent or less of certain active organic silicon compounds such as aliphatic silicone oils, silicone resins or aryl alkyl silicane derivatives.

. Improvement in detergency is eilected by the addition to the oil of compounds capable of dis- 2 I stearate, sulfurlzed sperm oil, trilauryl phosphite and oleic acid are specific examples.

An important object of our invention is to provide an additive that will materially increase the beneficial effect of these compounds on the lubricant.

Another object of our invention is to provide an additive that combines one or more functional groups of the above compounds in a, single molecule.

Other objects and advantages of our invention will be apparent during the course of the following description.

We have discovered that the efliciency of these compounds or radicals can be increased to an unexpected degree by introducing them as substituents of an aliphatic diacid of from 6 to 12 carbon atoms having terminal carboxyl groups. Although any of the acids included in this group may be used, we prefer azelaic acid,

HOOC (CH2) 'zCOOH The diacids can be prepared commercially by a persing, peptizing, or suspending sludge-forming materials therein. Metal salts of petroleum sulfonic acids, metal salts of alkyl substituted phenols and thiophenols, metal salts of phosphoric or thiophosphoric acid, metal salts of organo substituted fatty acid esters and tin, zinc, barium, calcium, aluminum, sodium, potassium and lithium salts and soaps of various organic acids and hydroxy compounds are classes of compounds commonly used as detergents. Typical specific examples of these classes are calcium sulfonate, calcium phenyl-stearate, zinc thiophosphate esters and calcium dichlorostearate. From 0.1 per cent'to 10 per cent of the detergent additive is generally required depending upon the activity of the specific additive employed.

Oiliness and extreme pressure characteristics of lubricants are improved by the addition of chlorinated or sulfurized fatty acid esters or chlorinated wax, in concentrations ranging from 0.01 per cent to 1.0 per cent. Methyl dichlorocontrolled oxidation of the corresponding unsaturated fatty acid with ozone, peroxides, permanz'anates or nitric acid. For example, azelaic may be prepared by the controlled oxidation of oleic acid with ozone,

terminal carboxyl groups. The molecular structure of the latter acids does not permit orientation of both polar carboxyl groups with respect to a planar surface without molecular strain.

We have found that certain compounds are adsorbed or absorbed on the surface of metals in the form of a plurality of layers. This "built up or compound" film is very tenacious and has the property of very markedly reducing the coeificient of friction. The compounds most readily adsorbed by metals are ones consisting of polar molecules, that is, molecules or unsymmetrical electrical character which contain an atom or group of atoms exhibiting a secondary or residual valence. These polar compounds tend to produce regimentation of the molecules. of hydrocarbon oil when added thereto. Ifa metal is immersed in a strongly polar compound a regime' ntatlcn or cybotaxis of the molecules will take place in the adsorbed film, the molecules being oriented with respect to the surface of the metal by which they are adsorbed.

We have found that oil soluble polar molecules having more than one polar group show exceptionally good or poor adsorption properties depending upon the nature and position 01' the polar groups. It is in this connection that the azelalc acid derivatives are particularly eflectlve, since polarity developed in azelalc esters or salts due to the halogen substitution on the alpha carbon (the carbon atom adjacent the carboxyl group) is enhanced by the concomitant polar group substituted on the sixth carbon atom in the molecule, which spacing i ideally suited for synergistic action in accord with the concept of carbon-carbon valence angles and the known ease of formation of six carbon ring systems.

Conversely, dicarboxylic acids having nonterminal carboxyl groups have an opposite effect due to the steric hindrance of its asymmetric molecule just as diacids of less than six carbon atoms have'noncomplimentary polar groups due to the strain inherent in forming an adsorbed ring of less than four carbon atoms.

While the above theory oifers a logical explanation for the superiority of the substituted compound embodyingthe invention, it is to be understood that we are not bound by it. 'Our claims are based upon the superior results observed and not upon any theory to support it.

Another important characteristic .of the acid molecule is its ability to form a stable compound with a number of difierent f nctional radicals substituted thereon. ,These radicals can be substituted on both the terminal carboxyl groups and the connecting aliphatic chain. The, molecule is thus able to bring all of the substituted radicals into intimate association with the lubricant and the lubricated surface. This is important since a radical which has a beneficial efiect upon one characteristic of the lubricant may impair some other desirable characteristic. The adverse effect can be obviated by substituting another element or group on the acid molecule that will enhance the impaired characteristic. In a sense the two radicals complement each other. It is further interesting to note that the complementary radicals are more efiective when introduced into the lubricant as part of the same diacid molecule than when introduced as sepauzess arate compounds according to conventional prac- I tice. Under different circumstances it is, of course, necessary to substitute various radicals or combinations of radicals on the diacid molecule.

The amount of the substituted diacid that must be mixed with a lubricant to obtain maximum correction of its deficiencies will depend upon the particular characteristics that are deficient and upon the particular radical or combination of radicals with which the acid is substituted. We have found that amounts in the order of from 0.0001% to 10% are usually suflicient. In every instance amounts less or more than the optimum amount can be used with less satisfactory results. If the additives are used in relatively high concentrations of from 0.1% to 10%, compounds should be selected that are readily miscible with the lubricant. If lower concentrations of from 0.0001% to 0.1% are used, less soluble compounds may be used since high oil solubility is not such a critical factor.

We have found that the following classes of substituted diacids have high utility.

' I. Monoor diacid salts c-o-o- M Hm M-OOCR,

o-o- M, MR, M-Ih,

M-O-B, or

In the above formula M is a salt forming element such as the metals calcium, barium, strontium, tin, zinc, chromium, cobalt, aluminum, sodium, potassium, lithium, magnesium, bismuth, copper, nickel, manganese, cadmium or silver, or a salt forming group such as ammonium or an amine; and "R" and R2 are organic radicals, there being one or more such It groups as shown by the subscript numerals. As shown, one or both of the terminal carboxyl groups may be neutralized by a salt forming element or radical.

When a monovalent element or radical is used in the above formula, compounds of the following type are obtained.

1. Lithium alpha-dichlor-methyl azelate.

2. Sodium 8-chloro-8-ethylxanthyl ethyl azelate.

3. Ammonium phenyl chloro-azelayl thiocarbonate.

4. Diethyl-ammonium azelayl diphenyl silicol.

5. Sodium anilino-8-chloro-8-diethyl thiophosphato-azelate.

6. Diphenyl-ammonium 8,8-dicresyl ethyl azelate.

7. Lithium anhydro-diazelayl anilide.

-When a polyvalent element or radical is used any of the following types of compounds may be obtained depending upon the particular element or radical selected and conditions under which the substitution takes place.

A. Intramolecular diacid salts of the type shown under (1) below if M is a bivalent element or radical, or of the type shown under (2) below if M has a valence greater than two.

oocr. i I)" I 1(0 R) (0H,): M-

H X). N

(R) is an aliphatic group; (R') is an I 7. Alpha-naphthyl-chromium 8-dichloro-az ate.

B. Intermolecular mixed salts of the type shown in the following formula:

where M and M are the same or different metals having valences of two or more and R and R:

are organic radicals, there being one or more such R groups as shown by the subscript numerals. The groups linked through" "11. to the diacid molecule may be aliphatic or aromatic organic acid radicals, inorganic acid radicals or alkyl or aryl hydrocarbon radicals.

Typical examples of compounds included by Formula 113 are:

1. Alpha-chlorostearyl-bismuth 8-di-butylw xanthyl ethyl azelate.

2. Triphenyl-tin ethyl 8-dichloro-azelate.-

3. Calcium di (8,8-dichloro-ethylxanthyl) pchloro-anilino azelate. x

4. Dibutyl-phosphato-zinc alpha naphthylazelat'e. I

5. Zincdi- (8,8' dibutyl thiophosphato) thiophenyl azelate.

II. Monoor diac'id esters azelate. 7. Dithiofurfuryl 8 dithiobutyl thiophenyl azelate.

8. 3,5 diamylphenyl 8 diethylthiophosphatosodium azelate.

III.-Monoor diamz'de of imide derivatives This class of compounds is divided roughly into two groups as shown in Formulas A-and 3/ below.

C-NH2, OM or OR EH91 l H:

N l R: or HR 0 IB. or R N-R, ENHB, Nm or 0N The following compounds are typical examples of the class ot'compounds defined by Formula A:

lidsodium alpha-dithiophenyl azelayl diphenyl am e.

2. Alpha-dichloro methyl azelayl phenyl hydraz ide. 3. Calcium di- (alpha-diphenyl) tributyl-siliconamido azelate.

4. Lauryl alpha-di-h-Mdro YPhenyl azelaylphenyl azide.

5. Stearyl calcium alpha-di-(dibutyl phosphate) tricyclohexyi-silicon azelayl amide.

c. l\ l R Hr)! :-H l/ INHR, NH; or ON In the above formula the amide or imide nitrogen may be unsubstituted or have substituents such as:

a. Organic substituents R or R,

b. Hydrazo radical NHZR.,

' c. Hydrazine radical -NH2,

d. Nitrile +CN.

The following compound is a typicalexample of the class of compounds defined by Formula B.

1. Alpha-diethylzanthyl azelayl imido-silicon triphenyl.

IV. Derivatives of azelaic anhydride.

OM, O R, NHz, ONHl As shown by the above formula the mono, di or polymqlecular acid anhydrides or their derivatives may be formed:

A. The anhydride may be decarboxylated on heating .to produce a cyclic ketone, azelaone, as shown in the following formula:

co in c 0 H2 H: A:

cyclic compound may further be reduced to the cyclic alcohol to form alcoholates, ethers or esters.

B. The anhydride may react with organosilicates, organo-carbonates or thiocarbonates producing an azelaic ester silicate or carbonate as shown in the following formula:

C. The anhydride may react with alcohols,

auaesa phenols or thiophenolsto produce the organic esters. ypical examples of such esters are:

1. Calcium di- (alpha-chloro, alpha-thiophenyl) azelaic anhydride.

2. Zinc dl-(alpha-dicresyl) cyclooctyl thicphosphate.

3. Calcium dl-(alpha diethylxanthyl) cycle-- octyl stearate.

4. Methyl dichloro-azelayl tributyl silicane. 5. Lauryl di-ethylxanthyl ethylxanthyl azelate.

6. Lithium alpha-dithiophenyl thiocresyl aze- A. Azelayl dlthiolic acid forms metal salts,

esters or anhydrides in the same manner as the oxy-acid.

B. The disulflde or the original acid or its derlva.tives maybe further sulfurized with either elemental sulfur or a sulfur compound to formpoly-thio' acids and their derivatives as shown by the following formula:

o=s IM, l 1R. E91 [N31,

Typical examples of poly-thio acid derivatives are:

l. Lithium alpha-diphenyl p.chlorophenyl dithio-azelate.

2. Alpha di-ethylxanthyl azelayl disulfide.

3. Dithiophenyl 2, 8-dlchloro 2,8-dithiobutyl azelate.

4. Methyl dichlorostearyl alpha dlchloro-dithio-az'elate.

VI. Derivatives of alpha halogen azelates In the above formula the represents active atom positions for halogenation; X represents any halogen. Mono or dihalide substitutions can be produced on either or both of the active carbons.

a. The halogen atoms may be replaced by alkyl or aryl groups by use of the Friedel-Crafts reaction with aluminum halides, or the Wurtz- Fittig reaction with sodium metal.

b. The halogenated compounds react with active metals to form organo-metallic derivatives.

0. The halogenated compounds react with active metal salt of alcohols, phenols, thiophenols, xanthates, phosphates, and thiophosphates, to produce varied derivatives.

Examples of the above are:

1. Alpha dichloro-dl-p.-chlorophenyi azelate.

2. Zinc di- (alpha chloro-alpha thiophenyl) lauryl azelate.

3. Methyl dichloro-stearyl alpha-dlchloro-triphenyltin azelate.

4. 2, 8-dlchloro-2,8-ethylxanthyl calcium ricinoleyl azelate.

5. 2,8-dibromo-azelayl lithium benzene p.-sulfonate.

6. Alpha-chloro-alpha-isopropylphenyl azelaylzinc distearate. t

7. Alpha-chloro-alpha-dibutyl thlophosphatolauryl naphthyl dithioazelate.

The metal salts of substituted azelaic acid, the halogen-bearing azelates show desirable oiliness or load-carrying properties, the metal salts of substituted acids possess detergent properties, and the sulfur, phosphorous, and nitrogen derivatives have antisludging, anticorroslon, and antioxidant properties.

Over and above these generally recognizable properties, we are able to add distinct and particular values by introducing:

a. Controlled oil solubility through the reactivity of the terminal carboxyl groups and the active carbon chain, through which selected alkyl or aryloil solubilizing groups may be attached to the azelayl group as a substituent in the chain or as a carboxyl derivative, or to thesalt forming metal.

b. Controlled extreme pressure or oiliness properties due to the presence of two active carbons positioned adjacent to the carboxyl groups, by which means alpha-chloro or dichloro azelates may be formed which have been shown to have highly polar adsorptive properties to metals forming multimolecular oriented films of the addend orr lubricated metal surfaces, such that a continuous effective lubricant film is maintained un-' der conditions of boundary lubrication.

"c. Controlled antisludging, anticorrosion, and anti-oxidation activity through the ability to introduce functional elements such as sulfur in optimum ratio in the molecule as, for example, one or more mercapto, sulfide, disulfide, polysul- ,flde, thiocyanate, sulfoxide, sulfone groups, or as sulfur substituted organic radicals such as thiophosphate, xanthate, thiocarbonate or aryl-sulfonate.

The particularly advantageous feature of the combined oiliness and otherwise functional addend appears to lie in the ability of the alphahalogenated oil-soluble addend to be adsorbed and oriented on the lubricated metal surface b which action the additional functional addend is, perforce, retained in the adsorbed film and. due to the normal carbon valence angles, held adjacent to the metal where the conditions for catalytic and thermal breakdown of the lubricant are at an optimum and precisely where the detergent, antioxidant, anticorrosive, or antisludging agent is needed to solutize, Deptize, or disperse such nonlubricant products of oil or fuel dissociation as may be formed, or inhibit the formation of oxidation and corrosion catalysts. Through the regulated synthesis of the preferred additive, the optimum ratio of detergency-olliness-antioxidati'on-antifoaming and other selected properties may be instituted, or any preferred particular function or functions may be emphasized to the exclusion of others.

The procedure to be followed in the synthesis of the typical products contemplated by this invention will be made clear to one skilled in the Example I Two parts of azelaic acid dissolved in four parts I of a nonhalogenating solvent such as acetone is halogenated with chlorine gas in the liquid phase until the chlorine content attains thirty per cent of the reaction product (approximately 1.5 parts of chlorine being used). The chlorinated azelaic acid, having approximately the composition of the alpha-dichloride, is freed of the hydrogen chloride produced during halogenation and approximately 80 per cent of the neutral solvent by distillation at either atmospheric or reduced pressure. To this is added 1.0 part of potassium ethyl xanthate prepared by the action of alcoholic potassium hydroxide with carbon disulfide in the ratio of 1 part of potassium hydroxide to 4 parts of ethyl alcohol and 1.4 parts of carbon disulfide. The solution is warmed and refluxed four to five hours, after which the mixture is filtered toremove precipitated salts, and distilled to remove the solvent. The product is heated to 100 C. for one hour with 1 part of phosphorous trichloride and 1.8 parts of p-amylphenol, then poured into water, extracted with ether, recovered, washed, and dried. The product is then heated with 1 part of zinc oxide to 125 C. for one hour with.

stirring. The insoluble solids are removed by filtration, leaving an oil soluble zinc salt of alphachloro-alpha ethylxanthyl p-amylphenyl azelate, which may be dispersed or dissolved in the hydrocarbon lubricant to produce the preferred lubricant composition of our invention- Example If One part of ethyl xanthate and one part of nbutyl acid chloroazelate, prepared as described in Example I, .are dissolved in two parts of acetone (or a, similar aligyl ketone such' as methyl-ethyl ketone) and refluxed for five hours. The solids are filtered ofi, washed with acetone, and the product recovered from the solvent. The mixed calcium salt of the substituted azelaic acid and stearic acid is prepared by the heating of two parts of the substituted azelaic acid with one part of stearic at 120-l50 C. with alcoholic caustic for one hour. The clear solution is treated with a concentrated solution of calcium chloride which precipitates the mixed salt. The dehydrated metal salt is dissolved and/or dispersed in a SAE 50 mineral oil with heating, to serve as a concentrate for the preparation of the lubricant composition of our invention.

Example III Five parts of sodium alpha-dichloro-azelate in ether solution, prepared as described in Example I, are treated with 5.5 parts of p-dichlorobenzene and two parts of finely divided sodium. The reaction proceeds vigorously at room temperature with the precipitation of solid NaCL' After the spontaneous reaction has subsided, the mass is refluxed four to six hours, acidified with dilute sulfuric acid, filtered, the residue washed with ether, the ether solutions united, and heated under. reflux with four parts of sodium laurolate to produce the acid lauryl ester. The resulting products are then treated with 3.5 parts of triphenyl tin hydroxide for three hours under gentle warming. The precipitated salts are filtered off, the product is recovered from ether, dried and suspended in a mineral oil to produce an additive concentrate for the preparation of the. blended lubricant composition.

Example IV Two parts of alpha dichloroazelaic acid, prepared as described in Example I, are boiled with one part'of acetyl chloride to produce azelayl "anhydride. To this is added two parts of diphenyl methyl methoxy silicane (prepared by the action of Grignard reagents on silicon tetrachloride'and the subsequent-treatment with sodium methylate) in ether solution. On gentle heating, the silica-ester is split forming the diphenyl methyl silico-methyl dichloro azelate, which is freed of ether by distillation. The product is dissolved in benzol or naphtha for the preparation of the preferred blended lubricant.

Example V Two parts of alpha-dichloro-azelaic anhydride, prepared as described above, are treated with two parts of diphenyl methyl ammonium hydroxide in alcoholic solution. The mass is heated under reflux for two hours, then two parts of a ten per Example VI Five parts of alpha dichloro azelaic acid, prepared as illustrated in Example I, are treated with six parts of isopropyl-benzene and two parts of anhydrous aluminum chloride. The reaction is completed on heating to l20-l50 C. for two hours. The product is mixed with 5.5 parts of oleic acid and three parts of milled, hydrated, barium oxide; the reaction mass is heated with stirring to 120-150" c. for three hours, after which the. insolubles are removed by filtration and the oilybrown liquid is treated with two parts of phosphorous pentasulfide with stirring for two hours at C. The orange-brown oily product is filtered, clarified by contacting with filtrol clay, and prepared in an oil solution for the preparation of the preferred blended lubricant of our invention.

By way of example and not by way of limitation, the following examples of preferred lubricant additives are given, Additives inhibiting corrosion, oxidation and sludge formation in lubricants: I

1. Sodium anilino-S-chloro 8-diethyl-thiophos.

' phato-azelate,

2. Zinc di-(8,8-dibutylthiophosphat0) phenyl azelate.

3. Dithiofurfuryl 8-dithiobutyl thiophenyl azelate.

4. Thiophenyl 8-diethylthiophosphato-3,5-diamylphenyl azelate.

5.'Di-alpha-ethylxanthyl azelayl triphenylthiosilicon imide,

6. Lauryl diethylxanthyl thio-oleyl azelate.

'7. Di-alphaethylxanthyl azelayl disulfide.

8. Di-alpha-thiophenyl di-thio-octadecyl azelate.

Additives inhibiting foaming in lubricants:

1. Diphenyl lauryl-azelayl-silicol or its condensation product.

.2. Diisobutyl di-phenylazelayl silicane or its condensation product.

3. Hexyl alpha-dibutylphosphato-methyl aceiayl silicon diol or its silicone condensation products.

4. Butyl di-phenyl tetramethylammonium alpha dichloroazelayl silicane or its condensation products.

Additives imparting detergent properties to a lubricant:

1. Zinc di (al ha-chloro alpha ethylxanthyl) -amylphenyl azelate.

2. Stearyl-calcium di-ethylxanthyl butyl azelate.

3. Triphenyl-tin di-p-chlorophenyl lauryl azelate.

4. Lithium diphenyl methyl ammonium alpha dichloro azelate.

5. Barium diisopropylphenyl azelate thiophosphato-oleate.

6. Lithium alpha-chloro alpha-ethylxanthyl butyl azelate.

7. Bismuth 8,8 butylxanthyl ethyl azelate alpha dichloro-stearate.

8. Zinc di (8,8'-dibutyl thiophosphato) thiophenyl azelate.

9. Calcium di (dibenzvl) azelate.

10. Methyl lauryl alpha diphenyl p-calcium sulfonate.

11. Calcium di (alpha di-cresyl) triamyl-silicon amido-azelate.

12. Barium di (di-alpha ethylxanthyl) stearyl azelate.

13. Lithium alpha dithiophenyl thiocresyl azelate.

14. Cadmium (di-alphasuli'onate) azelate.

15. Lithium alpha-diphenyl dithio-azelate.

Metals other than those illustrated above may be used in salt formation such, for example, as:

phenyl-p-cadrnium p-chlorophenyl Sodium Cobalt Lithium Zinc Potassium Nickel Magnesium Manganese Calcium Aluminum Strontium Chromium Lead Tin Copper Cadmium Bismuth Silver Mercury Tellurium Barium Additives imparting extreme pressure characteristics to the lubricant:

1. Di-p-chlorophenyl alpha dichloro-azelate.

2. Lauryl alpha dichloro methyl azelate.

3. Diphenyl-ammonium alpha-dichloro alphanaphthyl azelate.

4. Alpha-dichloro-stearyl bismuth alpha-dichloro thiophenyl azelate.

5. Cyclohexyl 8-chloro B-ethylxanthyl phenyl azelate.

6. Alpha dichloro methyl azelayl phenyl hydrazide.

7. Calcium di-(alpha-chloro alpha-thiophenyl) lauryl azelate.

8. Zinc di-(alpha-chloro alpha-ethylxanthyl) p-amylphenyl azelate.

Additives imparting oiliness characteristics to the lubricant:

1. Methyl 2,2 dichioro 8,8-thiophenyl lauryl azelate.

2. Methyl 2,2-dichloro 8,8-ethylxanthyl thicphenyl azelate.

3. Methyl alpha-dithiophenyl thiocresyl azelate.

4. Diamylphenyl 2,8-dichloro 2,8-di-diethylthiophosphate-lauryl azelate.

5. Butyl 2-dichloro 8-dithiophenyl methyl azelate.

If the compounded lubricant is to be used under high temperature conditions the addition agent should be nonvolatile and stable at elevated temperatures. For example, if the lubricant is to be used in the crankcase of an internal combustion engine the additive must have a boiling point above 150 F. and must not dissociate from the lubricant at temperatures as high as 250 F.

It is sometimes desirable to provide the addition agents in the form of a concentrate in a suitable oil. Such concentrates may be employed for fur-' ther blending with a blended lubricating oil in the proportion desired for the particular conditions of use.

The additive may be blended with mineral lubricating oils or with other oils of lubricating viscosity such as vegetable oils, animal oils, synthetic oils or light oil distillates. Furthermore, it is not essential that the additive be the only ingredient in the lubricant; it being understood, of course, that no additional ingredient should be present which is incompatible with the addition agent. Other additives such as those commonly used to improveviscosity index or cold test may be used also.

When used with a blended hydrocarbon oil, only such amounts of the additive should be incorporated as are soluble in the specified amount of oil. By the term soluble," it is intended to indicate the ability to form not only true solutions but also any form of substantially permanently homogeneous composition when incorporated in a blended mineral oil base. Since quite small percentages often give remarkably improved results, it is seldom of extreme importance that the addition agent be oil soluble in all proportions.

It will be understood that certain features and sub-combinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of our claims. Various changes in details may be made without departing from the spirit of our invention.

Having thus described our invention,.we claim:

1. A lubricant comprising a major proportion of an oil of lubricating viscosity having a minor proportion, sufficient to improve the lubricating characteristics of the oil, of an aliphatic diacid of from 6 to 12 carbon atoms, said acid having terminal carboxyl groups which are substituted with a silicon containing radical.

2. A lubricant comprising a major proportion of an oil of lubricating viscosity having a minor proportion, suflicient to improve the lubricating characteristics of the oil, of halogen substituted aliphatic diacid of from 6 to 12 carbon atoms having terminal carboxyl groups which are substituted with a silicon containing radical.

3. A lubricant comprising a major proportion of an oil of lubricating viscosity and a minor proportion, sufficient to improve the lubricating characteristics of the oil, of azelaic acid, the terminal carboxyl groups of which are substituted with at least one chemical group which contains silicon.

4. A lubricant comprising a major proportion of an oil of lubricating viscosity and a minor proportion, suflicient to improve the lubricating characteristics of the oil, of a salt of azelaic acid, the terminal carboxyl groups of which are substituted with at least one silicon-containing chemical group.

5. A lubricant comprising a major proportion l3 of an oil of lubricating viscosity and a minor proportion, suflicient to improve the lubricating characteristics of the oil, of a metal salt of azelaic acid, the terminal carboxyl groups of which are substituted with at least one silicon-containing chemical group,

6. A lubricant comprising a major proportion of an oil of lubricating viscosity and a minor proportion, sufiicient to improve the lubricating characteristics of the oil, of an amine salt of azelaic acid, the terminal carboxyl groups of which are substituted with at least one siliconcontaining chemical group.

7. A lubricant comprising a major proportion Y of an oil of lubricating viscosity and a minor proportion, suflicient to' improve the lubricating characteristics of the oil, of an ammonium salt of azelaic acid, the terminal carboxyl groups of which are substituted with at least one siliconcontaining chemical group. 7

8. A lubricant comprising a major proportion of an oil of lubricating viscosity and a minor proportion, sufiicient to improve the lubricating characteristics of the oil, of an ester of azelaic acid, the terminal carboxyl groups of which are substituted with at least one silicon-containing chemical group.

9. A lubricant comprising a major proportion of an oil of lubricating viscosity and a minor pro- BERT H. LINCOLN. Y JOSEPH M. HERSH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PA'I'EN'I'S Date Number Name 2,349,817 Farrington et al. May 30, 1934 2,334,158 Fuchs et al. Nov. 9, 1943 2,330,239 Prutton Sept. 28, 1943 2,280,474 Byrkit et a1 Apr. 21, 1942 2,262,773 Lincoln et al. Nov. 18, 1941 2,329,474 Lazar et al Sept. 14, 1943 FOREIGN PATENTS Number Country Date British Feb. 6, 1939