US3808142A - Process for preparing lubricating oil compositions containing anti-wear agents - Google Patents

Abstract

A PROCESS IS PROVIDED FOR PREPARING LUBRICATING OIL COMPOSITIONS COMPRISING (A) AN OIL OF LUBRICATING VISCOSITY (B) AN EFFECTIVE AMOUNT OF A DISPERSING AGENT AND (C) A NITRATE OF A GROUP I OR GROUP II METAL IN AN AMOUNT EFFECTIVE TO SUBSTANTIALLY REDUCE WEAR, WHICH PROCESS COMPRISES CONTACTING A LUBRICATING OIL COMPOSITION CONTAINING A GROUP I OR GROUP II METAL DISPERSING AGENT AND HAVING DISPERSED THEREIN A BASIC REACTING GROUP I OR GROUP II METAL COMPOUND, WITH AN AMOUNT OF NITRIC ACID NOT GREATER THAN THE REQUIRED TO REACT WITH THE GROUP I OR GROUP II METAL PRESENT IN EXCESS OF THE METAL REQUIRED TO STOICHIOMETRICALLY COMBINE WITH THE DISPERSING AGENT. THE LUBRICATING OIL COMPOSITION ARE USEFUL FOR, AMONG OTHER THINGS, REDUCING THE WEAR IN INTERNAL COMBUSTION ENGINES, PARTICULARLY IN HIGH POWER OUTPUT ENGINES SUCH AS LOCOMOTIVE ENGINES AND THE ENGINES USED TO PROPEL OCEAN GOING VESSELES.

Description

"United States Patent 3,808,142 PROCESS FOR PREPARING LUBRICATING OIL COMPOSITIONS CONTAINING ANTI-WEAR AGENTS Richard E. Crocker, Novato, Calif., assignor to Chevron Research Company, San Francisco, Calif. No Drawing. Filed July 3, 1972, Ser. No. 268,278

Int. Cl. C10m 3/18 7 US. Cl. 252-401 4 Claims ABSTRACT OF THE DISCLOSURE A process is provided for preparing lubricating oil compositions comprising (a) an oil of lubricating viscosity, (b) an effective amount of a dispersing agent and (c) a nitrate of a Group I or Group II metal in an amount effective to substantially reduce wear, which process comprises contacting a lubricating oil composition, containing a Group I or Group II metal dispersing agent and having dispersed therein a basic reacting Group I or Group H metal compound, with an amount of nitric acid not greater than that required to react with the Group I or Group II metal present in excess of the metal required to stoichiometrically combine with the dispersing agent. The lubricating oil compositions are useful for, among other things, reducing the wear in internal combustion engines, particularly in high power output engines such as locomotive engines and the engines used to propel ocean going vessels.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to a process for preparing lubricating oil compositions, particularly lubricating oil compositions useful to reduce the wear occurring between relatively moving parts such as in the crankcase and between the piston rings and cylinder walls of internal combustion engines.

Wear always has been a continuing problem associated with relatively moving parts. To effect a reduction in such wear, relatively moving parts have been lubricated by various means throughout recorded history. Various types of lubricants such as animal fats have been used. Later, compounded versions of naturally occurring fats and oils were used. Eventually technology progressed to the point where today highly compounded mineral oil and synthetic compound based lubricants are available for lubricating relatively moving parts. However even with these highly compounded lubricants which provide markedly reduced wear, the problem is far from being solved. Appreciable rates of wear still occur in almost any circumstance where relatively moving parts are found. Examples of high rates of wear are found in the crankcase bearings and on piston ring and cylinder wall surfaces of internal combustion engines. Particularly high rates of wear occur in high output engines such as diesel locomotives and ocean going vessel diesel engines (hereinafter referred to as marine engines) especially when these engines are operated on fuels containing appreciable amounts of sulfur.

Description of the prior art Water-in-oil emulsions suitable for lubricating engines such as low speed diesel engines operating on high sulfur fuels are disclosed in Stillebroer et al. US. Pat. 2,744,870 issued May 8, 1956. These water-in-oil emulsions contain from about five to about forty percent water and a water soluble salt of a divalent material.

A process for reacting ions of an acidic material with basic metal-containing organic complexes whereby the anions are incorporated in the metal-containing complexes 3,808,142 Patented Apr. 30, 1974 is disclosed in Le Suer, US. Pat. 3,496,105, issued Feb. 17, 1970. An example is the reaction of the anions of an inorganic acid with a basic, carbonated Group II metalcontaining complex to incorporate the anions into the reaction product. The process is conducted by contacting the complex with the anions of the acidic material in a suitable medium until at least a portion of the anions react With the metal. The process is conducted in the presence of at least one peptizing agent. The products are useful, inter alia, as additives for lubricating oils.

Le Suer US. Pat. 3,515,669, issued June 2, 1970 discloses a process for preparing Group I and Group II metal dispersions in essentially inert diluents by contacting a Group I or Group II basically reacting metal compound with an acidic material in the presence of a stabilizing agent and a promoter. Preferred basic reacting compounds include Group I and Group II metal oxides, hydroxides and alkoxides. Promoters include phenols, alcohols and nitroalkanes. Stabilizing agents include esters, amides, imides and amidine derivatives of organic acids. Preferred acidic materials are inorganic acids or inorganic acid gases. The metal-containing dispersions obtained are useful as additives for fuels and lubricants.

A process for the preparation of suspensions of water soluble solids in oleaginous media such as hydrocarbons in which the solids are insoluble is disclosed in Blake, U.S. Pat. 3,013,968, issued Dec. 19, 1961. The process involves forming an emulsion from an aqueous solution of the solid and the oleaginous liquid. The water-in-oil emulsion is obtained by using petroleum wax oxidate as the emulsifier. Emulsion is thereafter dehydrated.

Blake et al. US. Pat. 3,065,173, issued Nov. 20, 1962 describes a process for dispersing water soluble solids in the oleaginous material. In this patent the emulsifying agent is montan wax. Blake et al., US. Pats. 3,065,174; 3,065,175 and 3,065,176, all of the same issued date, disclose the use of other emulsifiers in the same process.

Oil soluble basic metal salts of organic acids which can be obtained by the reaction of such acids with an excess amount of a metal base in the presence of an acidic gas and a promoter under substantially anhydrous conditions are described in Norman et al. US. Pat. 3,595,790, issued July 27, 1971. The promoters are organic hydroxy compounds in which the hydroxy group is bonded to a non-benzenoid carbon atom. The inorganic acidic material can be a strong or weak acid or the anhydride gas of the acid.

Cutting fluids for machining ferrous materials are shown in Compton US. Pat. 3,215,630, issued Nov. 2, 1965. These cutting fluids are aqueous salt solutions. Useful salts are those having specified cation-anion radius ratios. The particular ranges of radius ratios useful depend on the anions of the salt. Salts which have radius ratios falling outside this specified range fail to cover the faces of the alpha iron crystals on the ferrous stock and therefore do not provide suitable cutting fluids.

SUMMARY OF THE INVENTION In accordance with the process of the invention, lubrieating oil compositions containing a Group I or Group II metal nitrate are prepared by contacting a lubricating oil composition containing a Group I or Group II metal containing dispersant, and having dispersed therein a basic reacting Group I or Group H metal compound with an amount of nitric acid not greater than that required to react with the Group I or Group II metal present in excess of the metal required to stoichometrically combine with the dispersant anion. The lubricating oil compositions prepared according to the invention are useful for reducing the wear between relatively moving parts. The compositions are particularly valuable since they provide wear protection for engines operated under severe conditions such as when operated on high sulfur content fuels and/or under conditions of high power output.

DESCRIPTION OF THE INVENTION The Process of Preparing the Lubricating Oil Compositions The process of the invention for preparing the lubricating oil compositions comprises contacting a lubricating oil composition containing a Group I or Group II metal containing dispersant and having dispersed therein a basic reacting Group I or Group II metal compound, with an amount of nitric acid not greater than that required to react with the Group I or Group II metal present in excess of the metal required to stoichiometrically combine with the dispersant anion.

The Group I or Group II metal containing dispersants are described herein below the heading of dispersing agents. The basic reacting Group I or Group H metal compound dispersed in the lubricating oil composition can be any such basic reacting compound. However, for convenience these compounds generally are the type of compound found in overbased dispersants such as the sulfonates and phenates discussed below. Such compounds include oxides, hydroxides and carbonates of the Group I and Group II metals. Preferably the metal of the basic reacting compound is the same as the metal of the dispersant. Preferably the composition to which the nitric acid is added is a concentrate of an overbased dispersant.

The amount of nitric acid used in the process is an amount not greater than that required to react with the Group I or Group II metal present in the composition which is in excess of the metal required to stoichiometrically combine with the dispersant anions. The excess Group I or Group II metal present in the composition is that amount of metal which causes what is known as overbasing of the dispersing agent. It is important that the amount of nitric acid used not be greater than required to react with the excess Group I or Group II metal. If a larger amount of nitric acid should be used, the dispersing agent may be attacked by the acid, converting its Group I or Group II metal into a nitrate, and liberating the anionic portion of the dispersing agent as the corresponding protonated compound. Should this occur the effective amount of dispersing agent in the lubricating oil composition will be correspondingly reduced.

The dispersing agent is present in the finished lubricating oil composition to maintain the nitrate in a dispersed state in the lubricating oil. If the amount of dispersing agent is reduced the quantity of nitrate which can be maintained satisfactorily dispersed in the lubricating oil composition is reduced. This can lead to sedimentation of the nitrate, particularly when the composition contains high concentrations of the nitrate. Such sedimentation can cause difiiculties when the concentrates are blended with a lubricating oil. Among other problems sedimentation can cause the plugging of pumps, lines, filters and the formation of deposits in storage tanks. Furthermore, quality control of the finished product becomes an extremely difiicult, if not impossible task. Also the finished product is quite likely to be hazy rather than clear and bright.

The nitric acid added to the lubricating oil composition containing the dispersing agent and the basic reacting Group I or Group II metal compound will be an aqueous solution, preferably concentrated, of the nitric acid. Addition to the oleaginous composition is accompanied by vigorous stirring. The addition can be accomplished at temperatures ranging from ambient temperature up to about 175 C. or greater. If the nitric acid is added to the reaction mass at lower temperatures the water from the nitric acid itself as well as the water formed during the reaction are removed by later heating the reaction mass to a temperature great enough to evaporate off the water (conveniently about 150 C.) while maintaining vigorous agitation. If the reaction mass is maintained above the boiling point of water during acid addition, the water will be removed from the reaction mass as it is introduced and formed.

While not necessary, it is preferred the nitric acid addition to the lubricating oil composition be carried out in the presence of an inert diluent. The inert diluent promotes contact between the nitric acid and the basic reacting metal compound. Although any inert diluent can be used, low boiling hydrocarbon fractions are preferred because of the ease with which they may be removed from the lubricating oil composition upon completion of the preparation. Examples of useful diluents include hexane, heptane, naphtha and the like.

The amount of diluent used can vary widely. The lower limit is of course zero when no diluent is used up to any convenient factor of dilution such as 10 or 20 parts of diluent per part of overbased lubricating oil composition. Generally there will be from 1 to 5 parts of diluent per part of oil composition.

Generally subsequent to acid addition and water removal, the oil composition is filtered to remove any nondispersed materials prior to the removal of all of the diluent. Filter aids such as the diatomaceous earths have been found useful in producing a clear, bright finished product.

The quantity of basic reacting Group I or Group II metal compound present in the composition containing a dispersing agent contributes to the alkalinity value (discussed and defined below) of the lubricating oil composition. It will be obvious that the greater the alkalinity value of the composition prior to being contacted with the nitric acid, the larger is the amount of basic reacting Group I or Group II metal compound present. The larger the amount of such compound that is present in the composition the greater is the amount of nitrate that can be formed in situ. The capability to form large amounts of nitrate in situ is particularly advantageous when it is desired to prepare concentrates for blending with other lubricating oils. Therefore, while lubricating oil compositions having alkalinity values of from about 5 to 10 prior to being contacted with nitric acid are suitable for use in the processes of this invention, lubricating oil compositions having alkalinity values of from about 50 to about 600 are preferred when concentrates of the nitrate are to be prepared in situ in the lubricating oil composition.

Starting materials and components of the lubricating oil compositions As described above the lubricating oil compositions prepared by the process of the invention comprise an oil of lubricating viscosity, an effective amount of a dispersing agent and a nitrate of Group I or Group II metal.

The dispersant component: The dispersants are present to, among other things, maintain the nitrate dispersed throughout the lubricating oil. A variety of dispersants are suitable for use in this invention. Excellent results are obtained from Group I and Group II metal-containing dispersants and mixtures thereof.

The Group I and Group II metal containing dispersants are well known in the art. These dispersants are salts of Group I and Group II metals in which the anionic portion of the salt contains an oil solubilizing group.

The oil solubilizing group generally has at least 9 and usually 12 to 18 or more carbon atoms, preferably from about 12 to 200 carbon atoms. The oil solubilizing groups are usually but not necessarily hydrocarbyl groups. The hydrocarbyl groups are organic radicals composed of carbon and hydrogen except for minor, sometimes adventitious, amounts of other elements, such as oxygen, chlorine, etc. The term denotes an aliphatic or aromatic radical, or a radical which is a combination thereof, e.g. aralkyl. Preferably, the hydrocarbyl group will be relatively free of aliphatic unsaturation, i.e. ethylenic and acetylenic, particularly acetylenic. The hydrocarbyl substituents will contain 30 carbon atoms and preferably 200 carbon atoms. When the hydrocarbyl groups are of lower molecular weight, the average number of hydrocarbyl sustituents in a given dispersant may be greater than one. The hydrocarbyl groups are preferably aliphatic, having preferably from O to 2 such sites of ethylenic unsaturation and most preferably from O to 1 such site. Hydrocarbyl groups derived from a polyolefin, itself derived from olefins (normally l-olefins) from 2 to 6 carbon atoms (ethylene being co-polymerized with an olefin of at least 3 carbon atoms), or from a high molecular weight petroleum derived hydrocarbon, are preferred and of these, polyisobutylene is most preferred.

Illustrative sources for the high molecular weight hydrocarbyl substituents are petroleum mineral oils such as naphthenic bright stocks, polypropylene, polyisobutylene, poly 1 butene, copolymers of ethylene and isobutylene, polypropylene, and isobutylene, poly-l-pentene, poly 4 methyl 1 pentene, poly 1 hexene, and poly- 3-methylbutene-1, etc.

The acid reacting functional group can be a variety of well known groups which include the sulfonic acid group, the hydroxy group (usually in the form of a phenol) and the carboxylic acid group. These groups, when in the form of the metal salts are known as sulfonates, alcoholates (phenates), and carboxylates, respectively.

These Group I and Group II metal containing dispersants can be used alone or in mixtures. Particularly good results are obtained from sulfonates, phenates and mixtures thereof.

The term sulfonates is intended to encompass the salts of sulfonic acids derived from petroleum products. Such acids are well known in the art. They are prepared by treating petroleum products with sulfuric acid or S0 The compounds in the petroleum product which become sulfonated contain an oil solubilizing group as discussed above. The acids thus obtained are known as petroleum sulfonic acids and the salts as petroleum sulfonates. Also included within the meaning of sulfonates are the salts of sulfonic acids of synthetic alkylaryl compounds. These acids are prepared by treating an alkylaryl compound with sulfuric acid or S0 At least one alkyl substituent of the aryl compound is an oil solubilizing group as discussed above. The acids thus obtained are known as alkylaryl sulfonic acids and the salts as alkylaryl sulfonates. The sulfonates wherein the alkyl is a straight-chain alkyl are the well known linear alkyl sulfonates (LAS). The acids are then converted to the metal salts thereof by neutralization with a bisic reacting alkali or alkaline earth metal compound to yield the Group I or Group II metal sulfonate. Generally the acids are neutralized with an alkali metal base. If an alkaline earth metal salt is desired, it is prepared from the alkali earth metal salt by metathesis. Alternatively, the sulfonic acid may be neutralized by direct reaction with an alkaline earth metal base.

The sulfonates to which the nitric acid is added are overbased. Overbased materials are characterized by a metal content in excess of that which would be present according to the stoichiometry of the metal cation and the particular organic compound said to be overbased. Thus an oil soluble monosulfonic acid wnen neutralized with a Group II basic metal compound, e.g. a calcium compound, will produce a normal sulfonate containing one equivalent of calcium for each equivalent of acid. In other words the normal metal sulfonate will contain one mol of calcium for each two mols of the monosulfonic acid.

By applying well-known procedures overbased or basic complexes of the sulfonic acids can be obtained. These overbased materials can contain amounts of metal many times in excess of that required to neutralize the acid. These stoichiometric excesses can vary considerably, e.g. from about 0.1 to about 30 or more equivalents depending upon the reactants, the process conditions, etc.

The degree of overbasing can be expressed several Ways. One method is to describe the metal ratio. This method describes the ratio of the total chemical equivalents of metal in the product to the chemical equivalents of the compound said to be overbased, based on the known chemical reactivity and stoichiometry of the two reactants. Thus in a normal (neutral) calcium sulfonate, the metal ratio is one (1) and in overbased sulfonate the metal ratio can range from about 1.1 to 30 or more, generally from about 5 to 25.

Another method of expressing the degree of overbasing is to describe the base ratio. This method describes the ratio of chemical equivalents of basic metal to the chemical equivalents of neutral metal. The neutral metal is the metal which would be expected to react with the compound to be overbased, i.e. the metal required to neutralize the sulfonate, phenate or carboxylate. The basic metal is the metal in excess of the neutral metal, i.e. it is the metal available to neutralize acidic combustion products. Thus a normal (neutral) calcium sulfonate has a metal ratio of zero (0) and an overbase sulfonate can have a metal ratio ranging from about 0.1 up to about 30 or more, generally from about 4 to about 24.

Another method of specifying the degree of overbasing of dispersants such as the sulfonates is by stating the alkalinity value (AV) of the composition. The method for determining the alkalinity value of an overbased composition is set forth in ASTM Method D-2896. Briefly, the alkalinity value is stated as the number of milligrams of potassium hydroxide per gram of composition to which the overbasing is equal. For example if the composition is overbased to the extent that it has the same acid neutralizing capacity per gram as 10 milligrams of potassium hydroxide, the composition is given an alkalinity value of 10. Alkalinity values can range up to about 600. Of course the lower limit is zero for a neutral sulfonate, with values of 10 to 50 being common for slightly overbased sulfonates. Highly overbased sulfonates have values ranging from about 275 to about 450.

A discussion of the general method of preparing overbased sulfonates and other overbased products is disclosed in Le Suer U.S. Pat. No. 3,496,105, issued Feb. 17, 1970 particularly at columns 3 and 4.

The term phenates encompasses Group I and Group II metal salts of phenolic compounds which are substituted with an oil solubilizing group.

The phenates to which nitric acid is added are overbased also. Techniques for producing these overbased complexes are well known, many of which are set forth in the above-mentioned Le Suer patent.

The term carboxylates encompasses the salts of car' boxylic acids. Acids which are useful in the instant invention generally contain at least 12 carbon atoms, e.g. palmitic, stearic, myristic, oleic, linoleic, etc. acids. Other carboxylic acids include the cyclic acids. Among these are acids containing an aryl group, i.e. benzene, naphthalene, etc. substituted with an oil solubilizing radical or radicals having a total of at least 15 to 18 carbon atoms or more, e.g. alkylbenzoic acid, alkylnaphthanoic acid, alkylsalicylic acid, etc. Preferably the cyclic acids are those which contain a cycloaliphatic group substituted with an oil solubilizing group. Examples of such acids are the petroleum naphthenic acids, e.g. cetylcyclohexane carboxylic acid, dilauryldecahydronaphthalene carboxylic acid, etc. Of the above acids, the petroleum naphthenic acids are preferred. The salts of this preferred class of cycloaliphatic acids are commonly known as naphthenates. The carboxylates to which the nitric acid is added are also overbased.

The sulfonates, phenates and carboxylates are present in the lubricating oil composition in the form of their Group I and Group II metal salts. Group I metals useful in forming the dispersing agent include lithium, sodium and potassium. Group II metals useful in forming the dispersing agent include magnesium, calcium and barium of which calcium is preferred.

The various above-described dispersing agents can be used alone or in mixtures. In particular, mixtures of sulfonates and phenates have been found to be useful in the invention.

The dispersing agent will be present in amounts ranging from about 0.001 to 10.0 percent in compositions of the invention prepared for use as the actual lubricating oil composition. Concentrates of lubricating oil additives are often prepared. These concentrates are then later blended with an oil of lubricating viscosity to yield the final lubricating oil composition which will ultimately be used to lubricate relatively moving parts. The amount of dispersing agent contained in concentrates of the compositions of this invention can be quite high; for example, up to about 50 percent or more, generally from about to about 30 percent.

Since the compositions prepared by the process of this invention will in most cases be used in combination with other lubricating oil additives such as overbased dispersants it is generally not necessary that the compositions be highly overbased. The overbased dispersants with which the compositions of this invention will be used will normally supply the necessary reserve alkalinity of the oil. However, for convenience the dispersing agents used in the preparation of the compositions can contain a high degree of overbasing (i.e. more than necessary to form the desired amount of nitrate) thereby avoiding the necessity of further compounding the lubricating oil composition to give it the desired properties.

The nitrate component: In addition to the dispersing agent discussed above the lubricating oil compositions prepared by this invention contain a nitrate of a Group I or Group II metal in an amount effective to substantially reduce wear. The Group I or Group II metals of the nitrate are the same as discussed above for the dispersing agent namely lithium, sodium, potassium, magnesium, calcium and barium. Preferably the Group I and Group II metals are sodium and calcium, respectively.

The quantity of nitrate present in the lubricating oil composition can vary widely. For example, the quantity of nitrate can be as little as 135 parts per million or less (based on nitrate) in the finished compounded lubricating oil composition. In general finished lubricating oil compositions will contain from about 135 parts per million to about 3000 parts per million (based on nitrate) of the Group I or Group II metal nitrates. Preferably the finished lubricating oil compositions will contain from about 180 to about 1100 parts per million (based on nitrate) of the Group I or Group II metal nitrates. Concentrates of a Group I or Group II metal nitrate can contain from 1 to about 55 weight percent of the nitrate. Preferably the concentrates contain from about 2 to about 50 weight percent of the nitrate. Concentrates containing greater amounts of the nitrate have the advantages of reduced transportation costs, reduced storage requirements, etc. since less of it will be required to be blended into a lubricating oil to produce the finished composition. For these reasons concentrates preferably contain. about 20 to about 50 percent of the nitrate.

In most cases the higher concentrations of the nitrate are preferred. However, combinations of certain nitrates with certain dispersing agents produce somewhat unstable dispersions and a certain amount of the nitrate will settle out in the form of sediment during prolonged storage thereby making compounding more difiicult. This problem seems to occur most often with Group I metal nitrates. In these cases it is often desirable to limit the concentration of the nitrate to the lower end of the ranges specified above.

The lubricating oil: The lubricating oil compositions prepared by the invention contains an oil of lubricating viscosity. This oil can be any oil suitable for lubricating purposes. It is generally a lubricating oil fraction of petroleum, either naphthenic or parafiinic base, unrefined, acid refined, or solvent refined as required in the particular lubricating need. Also synthetic oil meeting the necessary viscosity requirements, either with or without a viscosity index improver may be used as the base stock.

The viscosity of the lubricating oil will vary greatly depending upon the use to which it is to be put. It is well within the skill of those in the art to tailor the lubricating oil composition to the desired viscosity specifications by choosing the appropriate base stock, mixing various base oils, and/or compounding these oils or mixtures thereof with various viscosity index improving agents commercially available.

In addition to the dispersing agent and the Group I or Group II metal nitrate the lubricating oil compositions of the invention can contain a variety of other compounding agents such as dispersants, detergents, extreme pressure agents, viscosity index improvers, and other materials known to be useful in compounding lubricating oils to meet the various exacting specification demanded by the particular use to which the lubricating oil is to be put.

The following examples are incorporated for a further understanding of the invention.

EXAMPLE I A dispersion of calcium nitrate in a lubricating oil containing a dispersant was prepared as follows. To a mixture of ml. of naphtha and 800 grams of a lubricating oil composition containing an overbased calcium sulfonate having an alkalinity value of about 290 (calcium content 11.4% w., about 4.13 equivalents of a basic reacting calcium compound as the overbasing material), in a three liter flask was added dropwise, With agitation, 335 grams of concentrated nitric acid (70% w. 'HNO =3.72 equivalents of HN 0 over a one hour period. External cooling wasnot provided and the temperature rose from 74 F. (23 C.) to 104 F. (40 C.). Carbon dioxide and nitrogen oxides were evolved. After acid addition, the flask was fitted with a distillation apparatus and the temperature was raised to 280 F. 0138" C.) to distill over the water and part of the naphtha solvent. The dehydrated mixture was filtered through Standard Supercell (a diatomaceous earth filter aid available from lohns Mansville). The naphtha solvent was then removed by the heating under vacuum to yield 843 grams of a clear, bright composition containing 27% w. calcium nitrate. These concentrates were then compounded with lubricating oils and tested 'as shown in the following examples.

By the same procedure calcium nitrate was prepared dispersed in a lubricating oil containing carbonated, sulfurized calcium polypropylenephenate by adding nitric acid to a calcium overbased lubricating oil containing the dispersant. Prior to addition of the nitric acid, the overbased oil had an alkalinity value of about 2 60. By varying the quantity of acid added to the overbased oil, finished products containing calcium nitrate and having alkalinity values ranging from neutral up to about 100 were prepared.

EXAMPLE II Two series of test oils were prepared using a SAESO oil as the base oil. The oils of both series contained sufficient amounts of an overbased calcium dispersant (calcium as the overbasing metal) to give the finished oil an alkalinity value of about 70. In addition the finished oils of both series contained calcium nitrate at the levels shown in Table I below. The disperant in Series I was a carbonated calcium sulfonate and Series I[ was a carbonated, sulfurized calcium polypropylenephenate.

The oils were analyzed for sediment content (expressed as volume percent of the total composition) using a test procedure similar to that described in ASTM method D2273. Briefly this method involves mixing 25 ml. of the test material with 75 m1. of precipitation naphtha solvent by shaking well. The resulting mixture is then centrifuged at about 12,000 r.p.m. for 15 minutes after which the sediment is rated. The results are shown in Table I.

In addition the antiwear properties of the oils were determined by means of the well known 4-ball test. In this test three /2" diameter steel balls are clamped together and immersed in the test lubricant. A fourth ball was then rotated at about 1200 r.p.m. in contact with the other three balls. A 50 kg. load was applied for the time indicated and the temperature was maintained at 135 C. The sizes of the wear scars on the three stationary balls are measured and the average scar size in millimeters reported. In Table I below, the values reported are the average of three runs. The smaller the scar, the greater the antiwear properties of the lubricant. The 4-ball test is described in more detail in the American Association of Lubrication Engineers Standard Handbook for Lubrication Engineers, chapter 17, James J. OConnor, ed., McGrawHill, New York, 1968.

TABLE I.4-BALL WEAR TESTS Nitrate 4-ball wear scar, mm.

Sediment, Oil number Cation P.p.m. percent vol. 1hr. 2hr.

0. 00' 01 0.68 I Tr 0. 402 Tr 0. 380 0.385 Tr 0.402 0.05 0.407 0.07 0. 0. 00s 0. Tr 0.

1 Parts per million of nitrate. 1 Tr=t1'ace.

EXAMPLE III A series of tests were run in a one cylinder high output diesel engine to determine the quantity of deposits which may form on the piston. The base oil used was a solvent refined neutral paraflinic oil having a viscosity of 480 SUS (Saybolt Universal Seconds) at 77 F. The engine is run for 16 hours with each sample of oil, disassembled, and visually rated for deposits. Each of the four ring grooves are rated on a scale from zero to 100 with zero representing no deposits and 100 representing heavy black deposits. Each of the three lands (the space between the ring grooves) are rated on a scale of from 0 to 800 with 0 representing no deposits and 800 representing heavy deposits. Deposits on the underhead of the piston, which is sprayed with crankcase oil for cooling purposes, are on a scale of from 0 to 10 with ten representing no deposits.

The results are shown in Table II below.

TABLE II Run Groove Land Under- No. Base oil plus/kg. of oil deposits deposits head so mMols of suliurized Ca 33-134. 3-05 e7o-95-e5 9.4 5

polypropyienephenate, AV=260. 2 50 AIQIMOZISOOI Ca sulfonate 44-4.61.3-0.5 3360-80-45 9.1

9 3... 50 mMols of Ca sulionate- 54 6. 6-1. 00.5 1365-45-10 9.7

CaNO, as prepared in EX. I. 9 0 4. Same as Run number 2---- -32-1. 10.5 1310-15-35 9. 8

1 In order from top of piston.

I Equivalent to about 5,000 p.p.m. nitrate.

EXAMPLE IV Several test oils were prepared containing overbased calcium sulfonates and sulfurized calcium polypropylenephenates both with and without calcium nitrate as an antiwear agent. The base oil in each case was a high viscosity index oil to which was added sufiicient overbased sulfonate 10 or phenate and nitrate-dispersant (if used) to bring the total alkalinity value of the oil up to about 50.

These oils were used to lubricate the cylinder walls of a 3-cylinder Bolnes engine. The Bolnes 3 engine is a small (relatively speaking) marine propulsion diesel engine hav ing two lubricating systems. One system lubricates the cylinder walls and the other the remainder of the engine. The cylinder walls are lubricated via a circumferential row of small ports in the wall itself. The flow of oil into the cylinder is regulated such that the amount of oil is sufiicient to prevent scoring of the walls and to neutralize the acidic products of combustion. Most of the oil is burned during the combustion cycle but a small amount remains unburned to carry away ash and ash forming components of the oil. During the test runs, this drip oil was sampled periodically and analyzed for iron content which was taken as a measure of wear. Because most of the oil is burned during combustion the iron content of the drip oil is relatively high.

During each run with each test oil, the period from startup to 48 hours was taken as the break-in or stabilizing period for the test oil. Beginning with 48 hours the drip oil from each cylinder was sampled at 6 hour intervals and tested for iron content. Each test run was terminated at 72 hours. The iron content of the drip oil reported in Table HIA below is the average of the five values obtained from the five samples taken during the sample period.

TAB LE IHA Cylinder oil 1 2 2 1 3 4 Wear. percent wt. ironin drip oil: 9

Cylinder 1..-- 87 70 75 66 Cylinder 2. 58 57 97 89 67 Cylinder 3. 26 32 71 92 66 Average 92 55 79 85 66 1 See Table IIIB for composition. 1 In one hundredths of one percent.

TABLE IIIB Cylinder oil No. Composition 1 Contains an overbased calcium sulionate, AV of concentrate=410. 2 Same as 1 except contains 540 ppm. nitrate as calcium nitrate prepared in Ex. I. 3 Contains an overbased calcium poiypropylenephenate, AV of concentrate=260. 4 Same as 3 except contains 540 p.p.m. nitrate as calcium nitrate prepared in Ex. I.

As can be seen from the data in Table III-A, the presence of calcium nitrate in the cylinder oil in runs 2 and 3 markedly reduced wear (by an average of 32%) as com pared with runs 1 and 4 which used the same oil without the nitrate. Similarly the presence of nitrate in run 6 reduced wear (by 22%) relative to run 5 which used the same oil without the nitrate.

EXAMPLE V This example demonstrates the desirability of incorporating additional oxidation inhibitors into oils containing the Group I and II metal nitrates. The results shown below in Table IV-A are those obtained from testing the oils in an oxidation test. This test measures the time required for the consumption of one (1) liter of oxygen by 100 grams of test Oil at 340 C.). In addition the total number of liters of oxygen consumed in ten hours is determined as well as the percent viscosity (measured at 100 F. (38 0.)) increase for the ten hour period.

Table IV-B shows the composition of the oils tested, the results of which are shown in Table IV-A.

TABLE IV-A.OXIDATION TESTS Oxygen uptake Total up- Tlmc to 1 take hr., liter, hr. liters Viscosity increase, percent TABLE IV-B.OIL COMPOSITIONS Oil N 0. Composition 1A A commercially available railroad locomotive diesel engine lubricating oil, contains no calcium nitrate.

1B Same as 1A except contains 0.3 wt. percent of calcium nitrate concentrate prepared in Ex. 1.

2A Lubricating oil obtained from Casper, Wyo. oil fields; contains 3.64 wt. percent of an oil solution of the reaction product of a succinic anhydride substituted with a polyisobutenyl radical having a number average molecular weight of 950 and tetraethylenepentamine, approximately 44% active amide; and 80 mMols of Ca/kg. of oil of the calcium nitratecalcium sulionate concentrate prepared in Ex. I.

2B Same as oil 2A plus mMols oi Zn/kg. of zinc bis(polypropylenephenyl) dithiophosphate as an oxidation inhibitor.

20 Same as oil 2A except contains 75 mMols of Ca/kg. of an overbased calcium sulfonate having AV=275.

2D Same as oil 20 except contains 20 mMols of Zn/kg. of the oxidation inhibitor of oil 2B As can be seen from the data presented in Table IV-A, the presence of the calcium nitrate-calcium sulfonate dispersion increases the oxidative susceptibility and viscosity increase of the lubricating oils. However, it will be noted that the presence of small amounts of the oxidation inhibitor in oils 2B and 2D markedly reduced the oxygen uptake and viscosity increase relative to the oils without the oxidation inhibitor.

The lubricating oil compositions prepared by the process of this invention are the invention of William R. Miner and Charles K. Parker, Jr. and are disclosed and claimed in US. patent application Ser. No. 268,257 filed on even date herewith and entitled Lubricating Oil Composition Containing Anti-Wear Agents.

I claim:

1. A process of preparing a lubricating oil composition containing from 135 parts per million to 55 weight percent of a Group I or Group II metal nitrate which comprises contacting a lubricating oil composition containing from 0.001 to weight percent of a dispersing agent selected from the group consisting of Group I or Group II metal-containing sulfonates, phenates, carboxylates, and mixtures thereof, and having dispersed therein a basicreacting Group I or Group II metal compound, with an amount of nitric acid not greater than that required to react with the Group I or Group II metal present in excess of the metal required to stoichiometrically combine with the dispersing agent anions, wherein said lubricating oil composition prior to being contacted with said nitric acid has an alkalinity value of from 5 to 600.

2. A process of claim 1 wherein said Group I or Group II metal-containing carboxylate is a Group I or Group II metal containing naphthenate.

3. A process of claim 2, wherein said Group I and Group II metals are selected from the group consisting of lithium, sodium, potassium, magnesium, calcium and barium.

4. A process of claim 3, wherein said lubricating oil composition prior to being contacted with nitric acid has an alkalinity value of from 50 to 500.

References Cited UNITED STATES PATENTS 2,483,800 10/1949 Zimrncr et a1. 25233.4

FOREIGN PATENTS 793,684 4/1958 Great Britain 25218 PATRICK P. GARVIN, Primary Examiner A. H. METZ, Assistant Examiner US. Cl. X.R.