US2490068A - Lubricants - Google Patents

Description

Patented D... e, 1949 LUBRICANTS Bert H. Lincoln and Joseph M. Hersh, Ponca City, Okla., assignors to Continental Oil Company, Ponca City, Okla, a corporation of Delaware No Drawing. Original application April 22, 1944,

Serial No. 532,346. Divided and this application March 5, 1946, Serial No. 652,242

3 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 effect thereon.

This application is a division of our copending application Serial No. 532,346, filed April 22, 1944, now Patent No. 2,417,833.

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 sufficient.

Foaming of lubricants can be corrected by the addition of 0.000001 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 effected by the addition to the oil of compounds capable of dispersing, 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.

I 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)1COOH. The diacids can be prepared commercially by a controlled oxidation of the corresponding unsaturated fatty acid with ozone, peroxide, permanganates, or nitric acid. For example, azelaic acid may be prepared by the controlled oxidation of oleic acid with ozone.

The outstanding superiority of the substituted diacid may be attributed to the fact that it is a dipolar molecule. The terminal carboxyl groups are apparently balanced and spaced by the intermediate aliphatic chain, and their presence at each end of the chain permits the molecule to be oriented in relation to a lubricated surface. This theory accounts for the fact that the same results are not observed if the active radicals are substituted on an acid having but one carboxyl group or on a diacid having proximal or nonterminal 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 coefiicient of friction. The compounds most readily adsorbed by metals are ones consisting of polar molecules, that is, molecules of unsymmetrical electrical character which contain an atom or group of atoms exhibiting a secondary or residual valence. duce regimentation of the molecules of hydrocarbon oil when added thereto. If a metal is immersed in a strongly polar compound, a regimentation 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 of the polar groups. It is in this connection that the azelalc acid derivatives are particularly effective, since polarity developed in azelaic esters or salts due to the halogen substitution .on the alpha carbon (the carbon atom adjacent either carboxyl group) is enhanced by the concomitant polar group substituted on the sixth carbon atom in the molecule, which spacing is ideally suited for synergistic action in accord with the concept of carbon-carbon valence angles and the known ease of formation of six membered 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 noncomplementary polar groups due to the strain inherent in forming an adsorbed ring of less than four carbon atoms.

While the above theory offers a logical explanation for the superiority of the substituted compound embodying the 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 functional 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 effect 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 separate compounds according to conventional practice. 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 These polar compounds tend to proare readily miscible with the lubricant. 11 lower concentrations of from 0.0001 per cent to 0.1 per cent are used, less soluble compounds may be used, since high oil solubility is not such a critical factor.

The present invention is concerned primarily with the diester derivatives which have the following characterizing structure:

COOR

coon

Derivatives of azelaic anhydrzde As shown by the above formula the mono-, di-, or polymolecular acid anhydrides or their de- 5 rivatives may be formed:

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

or. O0 (du o -3 Hi). c=o Co,

| heat CH:

\C O CH2 C. The anhydride may react with alcohols, phenols, or thiophenols to produce the organic esters. Typical examples of such esters are:

1. Methyl dichloro-azelayl tributyl silicane.

2. Lauryl di-ethylxanthyl ethylxanthyl azelate.

O-CsHg SE S NASH r H) NA( H01 H:)1 as; i/ 0CeH5 Diphenyl azelate- Dlthiolic acid- Dleulflde A. Azelayl dithiolic acid forms esters or anhydrides in the same manner as the oxy-acid.

B. The disulfide of the original acid or its substituted derivatives may be further sulfurized with either elemental sulfur or a sulfur compound to form poly-thio acids and their derivatives as shown by the following formula:

Typical examples of poly-thio acid derivatives are:

1. Dithiophenyl 2, 8-dichloro 2, 8-d1th1obutyl azelate. 2. Methyl dichlorostearyl alpha dichloro-dithio-azelate.

Derivatives of alpha halogen azelates 0-! R, etc. 0:R, etc. H2 5 X- H i t 1 l H95 E Hm 5 H: i X X i I O-ER, etc. 0-312, etc.

In the above formula, the represents active atom positions for halogenatlon; X represents any halogen. Monoor 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.

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

Examples of the above are:

1. Alpha dichloro-di-p-chlorophenyl azelate.

2. Methyl dichloro-stearyl alpha-dichloro-triphenyl-tin azelate.

3. Alpha-chloro-alpha-dibutyl thiophosphatolauryl naphthyl dithioazelate.

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 aryl oil solubilizing groups may be attached to the azelayl group as a substituent in the chain or as a carboxyl derivative, or to the ester-forming radical.

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 dl-chloro enelates may be formed which have been shown to have highly polar adsorptive properties to metals forming multimolecular oriented films of the addend on lubricated metal surfaces, such that a continuous effective lubricant film is maintained under 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, polysulfide, thiocyanate, sulfoxide, sulfone groups, or as sulfur-substituted organic radicals such as thiophosphate, xanthate, thiocarbonate, or arylsulfonate.

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 by 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, peptize, 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, oiliness, antioxidation, 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 art by the following examples which are presented for the purposes of illustration:

Example I Two parts of azelaic acid dissolved in four parts 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 to remove precipitated salts, and distilled to remove the solvent. The product is heated to 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 C. for one hour with stirring. The insoluble solids are removed by filtration, leaving an oil soluble zinc salt of a1- pha-chloro-alpha ethylxanthyl p.-amyl-phenyl azelate, which may be dispersed or dissolved in the hydrocarbon lubricant to produce the preferred lubricant composition of our invention.

7 Example II 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 silico-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 naptha for the preparation of the preferred blended lubricant.

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:

Anti-oxidants in lubricating oils:

1. Dithiofurfuryl B-dithiobutyl thiophenyl azelate.

2. Thiophenyl 8-diethylthiophosphato-3,5-di- 'amylphenyl azelate.

3. Lauryl diethylxanthyl thio-oleyl azelate.

4. 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 azelayl silicon diol or its silicone condensation products.

Additive imparting detergent properties to a lubricant:

1. Methyl lauryl alpha diphenyl p-calcium sulfonate azelate.

Additives imparting extreme pressure characteristics to the lubricant:

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

2. Lauryl alpha dichloro methyl azelate.

3. Cyclohexyl 8-chloro 8-ethylxanthyl phenyl azelate.

Additives imparting oiliness characteristics to the lubricant:

1. Methyl 2,2'-dichloro 8,8'-thiophenyl lauryl azelate.

2. Methyl 2,2-dich1oro 8,8'-ethylxanthyl thi phenyl 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 further 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 imprOVe viscosity index or cold test may be used also. W

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 subcombinations 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.

Other modes of applying the principle of the invention may be employed, change bein made as regards the details described, provided the features stated in any of the following claims or the equivalent of such be employed.

Having described our invention, we claim:

1. A lubricating oil comprising a major proportion of an oil of lubricating viscosity and 0.0001% to 10% of a di-ester of azelaic acid, the terminal carboxyl groups of which are substituted with at least one diphenyl silicon containing chemical group.

2. A composition in accordance with claim 1 in which said di-ester also includes chlorine.

3. A lubricatin oil comprising a major proportion of an oil of lubricating viscosity and 0.0001% to 10% of diphenyl-methyl silica-methyl dichloro azelate.

BERT H. LINCOLN. JOSEPH M. HERSH.

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

UNITED STATES PATENTS Number Name Date 1,993,737 Graves et a1. Mar. 12, 1935 2,134,736 Renter Nov. 1, 1938 2,334,158 Von Fuchs et a1. Nov. 9, 1943 2,439,817 Farrington et al. May 30, 1944

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