US3428563A - Alkenyl succinimide-antimony dithiophosphate combinations in lubricants - Google Patents

Description

United States Patent 3,428,563 ALKENYL SUCCINIMIDE-ANTIIVIONY DI- THIOPHOSPHATE COMBINATIONS IN LUBRICANTS Warren Lowe, El Cerrito, Calif., assignor to Chevron Research Company, San Francisco, Calif., a corporation of Delaware No Drawing. Filed Oct. 24, 1967, Ser. No. 677,778 US. Cl. 25232.7 9 Claims Int. Cl. C10m 1/54, 3/48, 1/48 ABSTRACT OF THE DISCLOSURE Novel lubricant compositions containing combinations of alkenyl succinimide ashless detergents and antimony dihydrocarbyl dithiophosphates.

Background of invention Lubricant compositions commonly contain detergenttype additives to aid in preventing the deposition of solid materials on engine surfaces. These deposits tend to interfere with circulation of a lubricant and act as abrasives causing excessive Wear of moving engine parts. "It was discovered that in many cases a substantial portion of the deposits were derived from combustion of commonly employed metal-containing detergents. Since it is usually necessary to employ a substantial amount of the detergent in the lubricating composition, usually about 5%, and often as high as weight, the result was that a large amount of metallic ash was deposited upon cylinder walls, pistons, and the like. Recent years have seen the rapid development and introduction of detergent-type additives which contain no metal and thus do not act as precursors for ash.

Among the more successful metal-free detergent-type additives which have been developed are the alkenyl succinimides which are usually prepared by reacting a polyolefin substituted succinic anhydride, such as polyisobutenyl succinic anhydride with a polyamine. Experience has shown that these materials operate very effectively to reduce engine ash. However, it has been discovered by workers in the field that using the succinimide-type detergent additives in place of the previously used metal-containing materials aggravates the problem of controlling bearing corrosion and wear. in the past, materials such as zinc dialkyldithiophosphates have been used to control bearing corrosion. However, it has been found that in the case of the succinimide-type detergents containing a high ratio of basic amino groups, the zinc salts of organic substituted dithiophosphoric acids are relatively ineffective in preventing high engine wear.

Summary of the invention The present invention concerns lubricant compositions which contain a low wear additive combination comprising an alkenyl succinimide detergent and an antimony dithiophosphate. The compositions thus comprise a major portion of an oil of lubricating viscosity, a minor proportion of an alkenyl succinimide sufficient to impart detergency, and a minor proportion, sufiicient to impart anticorrosive and extreme pressure properties of an antimony dithiophosphate.

It has been found that the lubricant compositions thus constituted possess outstanding detergent and corrosion inhibiting properties. Further, it has been found that the problem of high engine wear ordinarily associated with lubricant compositions containing the succinimide detergents in combination with most metal dithiophosphates, such as zinc dithiophosphates, has been avoided. In addition, a substantial improvement in extreme pressure properties is effected.

Description of the preferred embodiments The succinimides which are employed in the additive combination of this invention are generally known as lubricating oil detergents and are reported in a number of domestic and foreign patents, e.g., U .8. Patents Nos. 2,992,708, 3,018,291, 3,024,237, 3,100,673 and French Patent No. 1,265,086. The polyamine used to produce the alkenyl succinimide will generally contain from 2 to 6 amino groups and have a molecular weight in the range of about 60 to 600, preferably about 300. The polyamine may be aliphatic, alicyclic, aromatic, or combinations thereof, preferably aliphatic or heterocyclic with one or more nitrogens present as any other members in the ring, e.g., piperazine. At least two of the amino groups in the polyamine prior to the reaction with the succinic acid or anhydride will have at least one hydrogen, i.e., at least two of the amino groups will be either primary or secondary amines, preferably primary amines.

The preferred groups of amines are the polyalkylene polyamines having the formula:

wherein m is an integer of from 1 to 5 and n is an integer of from 1 to 6. Within the scope of the invention are diethylene triamine, triethylene tetramine, tetraethylene pentamine, trimethylene diamine, di(hexamethylene)triamine, 2,4,2',4'-tetra-amino biphenyl, 1,3,5-triamino benzene, 1,4-di(aminoethyl)cyclohexane, N,N'-bis[N-(2- aminoethyl)piperazine]methane, Z-aminoethyl piperazine, dimethylamino propylene diamine, etc.

The alkenyl succinic anhydrides which are reacted with the amine have the following general formula:

wherein R is alkenyl group, most conveniently obtained by polymerizing an olefin having from about 2 to 5 carbon atoms. The resulting polymer should have a molecular Weight in the range of about 400 to 3,000, more usually in the range of about 900 to 1,200. Useful olefins are illustrated by ethylene, propylene, l-butene, 2-butene, isobutene, l-pentene, and mixtures thereof, preferably isobutene. The methods of polymerizing such olefins to the polymers of the proper molecular weight are Well known in the art and do not require further exemplification. Likewise, the preparation of the alkenyl succinic anhydrides by reaction of the polyolefin and maleic anhydrides has been repeatedly described in numerous patents, e.g., US. Patents Nos. 3,018,250 and 3,024,195, and should not require further detailing. The reaction of the anhydrides with the polyamines to produce the succinimide is carried out at a temperature range of about 200 to about 500 -F., more usually from about 275 to 450 F. The pressure used in the reaction will generally be atmospheric, although, in specific instances, higher or lower pressure may be employed.

The preferred imide from the alkenyl succinic acid with the alkylene polyamine is characterized by the following formula:

where m, n and R are as previously defined. It is preferred that n vary from 2 to 5, preferably 4. However, bissuccinimides containing 2 succinate moieties for each polyamine moiety may also be used.

The bis-succinimides are represented by the following formula:

where m and R are as previously defined and p is an integer from O to 4.

In the formation of the bis materials, two moles of the alkcnyl succinic anhydride are reacted with one mole of the polyamine.

The formation of the imide may be carried out in the presence or in the absence of an inert solvent. The inert solvents or dispersants which may be employed include aromatic hydrocarbons, aliphatic hydrocarbons, specifically mineral oil of lubricating viscosity, aryl halohydrocarbons, ethers, and polyethers, etc.

The reaction time will usually be in excess of 2 hours and will rarely exceed 24 hours. More usually, the reaction time will be in a range of about 3 to hours.

The reaction is usually carried out in an inert atmosphere, such as nitrogen, helium, argon, etc.that is, in the absence of oxygen.

During the reaction it is generally desirable to distill the water from a mixture as it is formed. This can be conveniently accomplished by means of a solvent collector such as a Dean-Stark trap. Desirably the pressure of the system may be reduced below atmospheric to facilitate water removal.

The antimony metal dihydrocarbyl dithiophosphate is an antimony metal salt of a hydrocarbon substituted dithiophosphoric acid, preferably containing from about 8 to about 60 carbon atoms in the hydrocarbon portion. These thiophosphates are also known as phosphorodithioates. They may also be described by the following general formula:

s R10i s sb in which R and R are hydrocarbyl groups containing a total of from about 8 to about 60 carbon atoms, preferably up to about 50 carbon atoms.

In the preferred embodiment, R and R are alkyl radicals of at least 4 carbon atoms, preferably primary alkyl radicals and mixtures thereof, or alkaryl radicals containing at least 12 carbon atoms and mixtures thereof. Most preferably, the alkaryl radicals are derived from alkyl phenols. Alkaryl radicals having at least 6 carbon atoms in the alkyl group are preferred.

Illustrative alkyl, alkaryl, and aralkyl radicals for the thiophosphates in accordance with the above are derived from straight-chain or branched-chain primary, secondary or tertiary alcohols, or from phenols from hydroxy compounds, preferably containing at least 4 carbon atoms, including isobutanol, trimethylcarbinol, 2-ethylbutanol, methyl pentanol, methyl isobutyl carbinol, 2-propy1 ethanol, N-methyl pentanol, methyl isobutyl carbinol, 2-propenyl pentanol, n-decanol, dodecanol, octadecanol, hexylphenol, dodecylphenol, hexadecylphenol, octadecaphenol, etc., and mixtures thereof. The antimony salts of esters of dithiophosphoric acids are prepared by methods known heretofore. For example, a mixture of the desired alcohol or alkyl phenol and phosphorus pentasulfide is reacted at temperatures of about 100 to 200 F., until the dithiophosphoric acid is formed. The reaction may be carried out in the presence of a suitable solvent, for example petroleum naphtha, or may be carried out without dilution. The crude acid mixture is then filtered to remove unreacted phosphorus pentasulfide. The antimony salt may then be produced by reacting antimony oxide (Sb O in proper proportion with the acid. Another suitable group involves neutralization of the acid with a suitable alkali metal or alkaline earth metal base, such as sodium hydroxide, followed by reaction with an antimony salt such as antimony trichloride.

In the finished lubricant composition of the invention, the succinimlde detergent as previously noted is employed in amounts sufficient to improve the detergent characteristics. Ordinarily, amounts of from about 0.1 to about 15 percent by weight are satisfactory for this purpose. Amounts of from about 3 to 8 percent are preferred. However, because of the excellent solubility characteristics of the suceinimide detergent-antimony dithiophosphate combination, lubricating oil concentrates cont-aining higher percentage of the combination, up to about 75 percent by weight, may be prepared.

The antimony dithiophosphate is present in the finished compositions in amounts suflicient to inhibit corrosion. Usually amounts from about 0.1 to about 10 percent by weight are satisfactory. Stated in another manner, the amount of phosphate may be expressed as millimoles per kilogram of finished oil, based upon phosphorus content. That is, the amount of antimony dithiophosphate expressed as millimoles of phosphorus per kilogram of oil (i.e., mM./kg.). Expressed in this manner, the amount of antimony salt used in a lubricating oil can be be from about 1 millimole to about millimoles of phosphorus per kilogram of lubricating oil, preferably from about 4 to about 50 millimoles.

Lubricating oils which can be used as base oils include a Wide variety of oils, such as naphthenic base, parafiin base, and mixed base lubricating oils, other hydrocarbon lubricants, e.g., lubricating oils derived from coal products, and synthetic oils, e.g., alkylene polymers (such as polymers of propylene, butylene, etc., and the mixtures thereof), alkylene oxide-type polymers (e.g., propylene oxide polymers) and derivatives, including alkylene oxide polymers prepared by polymerizing the alkylene oxide in the presence of water of alcohols, e.g., ethyl alcohol, dicarboxylic acid esters (such as those which are prepared by esterifying such dicarboxylic acids as adipic acid, azeleic acid, subaric acid, sebacic acid, alkenyl succinic acid, fumaric acid, maleic acid, etc., with alcohol such as butyl alcohols, hexyl alcohol, 2-ethylhexy1 alcohol, dodecyl alcohol, etc.), liquid esters of acids of phosphorus, alkylbenzenes (e.g., monoalkylbenzenes such as dodecyl benzene, tetradecyl benzene, etc.), and dialkylbenzenes (e.g., n-nonyl-Z-ethylhexyl benzene); polyphenyls (e.g., diphenyls and terphenyls), alkyl diphenyl ethers, polymers of silicon (e.g., tetraethyl silicate, tetrraisopropyl silicate, tetra (4 methyl-Z-tetraethyl) silicate, hexyl (4- methyl-2-pentoxy) disiloxane, poly (methyl) siloxane, poly (methylphenyl) siloxane, etc.). Synthetic oils of the alkylene oxide-type polymers which may be used include those exemplified by the alkylene oxide polymers.

In addition to the additive combination of the invention, the lubricating oil compositions may also contain other deteregnts, viscosity index improving agents, rust inhibitors, oiliness agents, grease thickening agents, antioxidants, dyes, foaming agents, etc.

Illustrative lubricant compositions of the above-mentioned types containing additives other than the present ashless detergent antimony dithiophosphate combination may include, for example, from about 0.1 to about 10 percent by weight of alkaline earth metal higher alkyl phenate detergent and wear reducing agent, such as the calcium alkyl phenate having mixed alkyl groups of 12 to 15 carbon atoms. They may also include about 0.1 to 10 percent by Weight of organic thiophosphate corro sion and high temperature oxidation inhibitors such as the reaction product of pinene and P 8 the reaction product of polybutene and P 8 and the bivalent metal dihydrocarbon dithiophosphates such as zinc butylhexyl dithiophosphate. Metal salt detergents in amounts from about 0.1 to 10 percent by weight which may also be used are calcium petroleum sulfonates of the oil-soluble mahogany type and the calcium naphthenates.

The following examples illustrate the improved lubricant compositions in accordance with the present invention. Proportions given are on a weight basis unless otherwise indicated.

Example 1.-Preparation of antimony dialkylphenyl dithiophosphate 500 g. (0.5 mol) of 0,0-dialkylphenyl dithiophosphoric acid (derived from dodecyl phenol) .and 21.0 g. (0.5 mol) of sodium hydroxide (97.3 percent) were placed into a 2-liter, 3-necked flask equipped with stirring unit, heating unit, thermometer, water condenser, and a solvent collector (Dan-Stark trap). The mixture was stirred at 180 to 200 F. for 'four hours (until all sodium 'hydroxide had reacted); a solution containing 38.5 g. of antimony trichloride and 220 cc. of alcohol was added. The mixture was then stirred at reflux temperature for 8 hours. The solvents were withdrawn through the Dean- Stark trap. The material was then filtered through a cake of diatomaceous earth and the filtrate was topped to 200 F. under 0.5 mm. Hg pressure. The product was a viscous liquid containing 4.17 percent by weight antimony.

Example 2.Falex wear and Falex extreme pressure shear test. Comparisons of antimony and zinc dithiophosphates In order to demonstrate the improved wear resistance and extreme pressure properties of oils containing the succinimide, antimony dithiophosphate additive combination, Falex extreme pressure shear test and Falex wear tests were performed on oils containing the succinimide detergent alone, one containing the antimony dithiophosphate of the previous example, and one containing a zinc dithiophosphate prepared from the same acid employed in Example 1.

The base oil employed was a California paraflin-based, solvent refined neutral oil having a viscosity of 480 SSU at 210 F. The alkenyl succinimide employed was a polyisobuteny-l succinimide of tetraethylene pentamine in which the polyisobutenyl group had a molecular weight of about 1,000. The succinimide was obtained by reacting about equal molar proportions of polyisobutenyl succinic anhydride and tetr-aethylene pentamine. The polyisobutenyl group contained about 64 to 68 carbon atoms. The detergent additive was employed .at a concentration of 5 percent and the dithiophosphates at 40 millirnoles per kilogram of phosphorus.

The Falex Wear Test is performed using a standard Falex test apparatus fitted with a steel shaft and cast iron jaws. The shaft is allowed to rotate between two screw-loaded jaws. The shaft is allowed to rotate at a speed of 290 r.p.m. between the jaws, both shaft and jaws immersed in the oil sample which is maintained at a temperature of 210 F. Starting from pressure, the screw-loaded jaws are caused to be impinged against the shaft, the pressure being increased in 30-pound increments over a half-minute period, the pressure being allowed to remain at that incremental pressure for 6 minutes, until a pressure of 440 pounds was applied at the end of 30 minutes. The shaft is allowed to rotate for an additional 30 minutes with the loading maintained at 440 pounds by means of adustment every minutes. At the end of the period the total weight loss of the shaft in milligrams is determined.

The Falex E.P. Shear Test is run using the same basic apparatus as the Wear test, except that both shaft and jaws are steel, the temperature is ambient, and from an initial 300-pound loading for one minute for break-in,

TABLE I.FALEX WEAR AND EXTREME PRESSURE SHEAR. TESTS Wear Test Shear Test Antieorrodent Additive Pin Weight Load to (40 mM./kg. P) Loss (mg.) Failure None (Base Oil plus Detergent) 12. 8 850 Zinc Dithiophosphate 7. 3 1, 300 Antimony Dithlophosphate. 5. 1 3, 600

It may be seen from these data that, as compared with the zinc compound, the antimony dithiophosphate was substantially more etfective in wear and almost three times as elfective in increasing the extreme pressure property of the composition.

Example 3.- alex wear test and extreme pressure shear test. Comparisons of antimony dithiophosphate and antimony dithiocarbamate In order to demonstrate the increased effectiveness of the antimony dithiophosphate in producing greater extreme pressure characteristics and low wear in combination with succinimide detergent additives, in comparison with an antimony dithiocarbamate, commercially available materials were subjected to the same tests as described in Example 2. The base oil and succinimide additive were the same and the additive was employed in the same concentration as in Example 2. The antimony dithiophosphate and antimony dithiocarbamate were, respectively, Vanlube 648 and Van lube 73 (6.8% by weight) materials sold by the Vanderbilt Company. The additives were employed at a concentration of 20 mM./ kg. Table II following contains this data.

TABLE IL-FALEX WEAR AND EXTREME PRESSURE SHEAR TESTS It may be seen from these data that the antimony dithiophosphate is substantially more effective in reducing Falex wear and increasing the E.P. shear performance. It may be noted that in comparison with the uninhibited oil, the dithiocarbamate doubled the wear; the dithiophosphate halved it.

I claim:

1. A lubricant composition comprising a major portion of an oil of lubricating viscosity, a minor portion, sufiicient to enhance detergency of the oil, of an alkenyl succinimide detergent additive, and a minor portion, sufficient to impart wear inhibition, of an antimony dihydrocarbyl dithiophosphate wherein the hydrocarbyl groups of the antimony dithiophosphate contain a total of from about 8 to 60 carbon atoms.

2. The lubricant composition of claim 1, wherein the alkenyl succinimide is represented by the formula:

0 RoH- N[CHz(CH2)mNH]nH CHz-C I5 in which m is an integer of from 1 to 5, n is an integer of 1 to 6, and R is an alkenyl group of 400 to 3,000 molecular weight.

3. The lubricant composition of claim 1, wherein the alkenyl succinimide is represented by the formula:

in which m is an integer of 1 to 5, p is an integer of to 4 and R is an alkenyl group of 400 to 3,000 molecular weight.

4. The lubricant composition of claim 2, in which the alkenyl succinimide detergent additive is present in the amount of from 2 to 15 percent by weight.

5. The lubricant composition of claim 2, in which m is 1 and n is 4.

6. The lubricant composition of claim 3, in which in is 1 and p is 4.

7. The lubricant composition of claim 1, in which the antimony dihydrocarbyl dithiophosphate is represented by the formula:

| Re a UNITED STATES PATENTS 2,976,122 3/1961 Ertelt et al. 25232.7 3,018,247 1/1962 Anderson et a1 252-32.7 3,219,666 11/1965 Norman et al. 252-515 3,239,462 3/1966 Bergstrom et al. 252-515 PATRICK P. GARVIN, Primary Examiner.

US. Cl. X.R. 25251.5