US2809160A

US2809160A - Lubricant composition

Info

Publication number: US2809160A
Application number: US556087A
Authority: US
Inventors: William T Stewart; Lowe Warren
Original assignee: California Research LLC
Current assignee: California Research LLC
Priority date: 1955-12-29
Filing date: 1955-12-29
Publication date: 1957-10-08
Anticipated expiration: 1974-10-08

Description

2,809,160 Patented Oct. 8, 1957 LUBRICANT co rosrrroN William T. Stewart, El Cerrito, and Warren Lowe, Berkeley, Calif., assignors to California Research Corpora= tion, San Francisco, Calif., a corporation of Delaware 7 N Drawing. Application December 29, 1955,

Serial No. 556,087

11 Claims. (Cl. 25233.4)

This invention relates to a novel lubricant composition; More particularly, the invention is concerned with a new and unusually effective lubricating oil composition having improved corrosion inhibiting properties.

Lubricating oils generally have a tendency to become corrosive to metals during their normal service due to oxidation and the'formation of decomposition products.

alloy metal bearings which, besides their possible catalytic elfect on the decomposition of lubricating oils, are especially subject to' corrosive attack and alteration of their friction characteristics which places a greater burden on the lubricity: of the lubricant composition.

Corrosion'inhibitors which have been added heretofore to lubricating oils in general to improve their resistance to the formation and effect of corrosive products have not been entirely satisfactory. Many of the additives are only partly effective and permit'the bearings and other metal surfaces to be slowly but eventually corroded away. Other additives which are substantially effective at the outset are used up during service and are therefore active only for a limited period. I e

' Another, more specific disadvantage of the corrosion inhibitors employed prior to this has been due to the fact that lubricating oils for internal combustion engines are commonly compounded with additives such as wear inhibitors, pour point depressants, sludge inhibitors, detergents and the like to loosen, suspend and otherwise,

counteract the eifect of decomposition products and provide eflicient lubrication. Unfortunately, many of these agents adversely affect the activity of the corrosion inhibitors, and it is necessary to find inhibitors which will function in combination with them.

Furthermore, many of the most effective corrosion inhibitors known prior to this invention contain active sulfur in some form and are therefore'undesirable for use with silver and similar metal-containing bearings which are subject to attack by active sulfur. These types of bearings, although once not so widely used and therefore considered to constitute only a minor problem, are being increasingly employed today; Particularly in certain important classes of internal combustion engines,

as, for example, marine and railroad diesel engines, silver metal-containing bearings are more and more common, and the problem of providing proper lubrication for them from the standpoint of low corrosivity and improved lubricity is one of major importance.

In accordance with the present invention, a superior new lubricant composition, having improved corrosion inhibiting properties has been found comprising a major portion of an oil of lubricating viscosity corrosive to metal surfaces in normal use and a minor portion, sufficient to inhibit corrosion, of a phthalic acid of the group consisting of isophthalic acid and terephthalic acid and mixtures thereof.

'The novel lubricant composition according to the invention is characterized by remarkable corrosion inhibiting properties for metal surfaces and alloy bearings over extended periods of operation. It also provides a greatly improved quality of lubrication for bearings and other rubbing surfaces. A further outstanding characteristic of the composition lies in the fact that these beneficial properties are obtained without adverse effect from other conventional additives commonly employed in lubricant compositions. Still another advantage of the lubricant composition according to the invention is its ability to provide unusually effective lubrication for particular alloy bearings such as the silver metal-containing bearings more and more commonly found in marine and railroad diesel engines.

In a more specific and preferred embodiment the present invention isconcerned with a lubricant composition comprising an oil of lubricating viscosity in combination with a lubricating oil detergent additive, said combination being corrosive to metal surfaces in normal use, and a minor portion, sufficient to inhibit corrosion, of a phthalic acid of the group consisting of isophthalic acid and terephthalic acid and mixtures thereof, said minor portion of lubricating oil detergent additive being sufficient to suspend said phthalic acid in the oil of lubricating viscosity.

The lubricating oil detergent additive of the composition is a well-known type of additive generally used in lubricant compositions. The term, as employed here in its commonly accepted sense, denotes a recognized class of chemical compounds which are known for their function of enablinga lubricating oil medium to maintain oxidation products, resins, and other types of insoluble materials in suspension or dispersion in the oil. Such detergent compounds in lubricant compositions in actual use may remove naturally formed protective films from metal surfaces, thus rendering the compositions more corrosive. Illustrative lubricating oil detergent additives fall within general classes of types. Examples of the better known classes are the metal salts of naphthenic acids such as aluminum naphthenate; metal salts of fatty acids and substituted fatty. acids such as calcylate; metal salts of petroleum sulfonic acids such as calcium sulfonate and basic calcium sulfonate; metal salts of alkyl phenol sulfides such as barium amyl phenol sulfide; metal salts of alkyl phenols such as aluminum dicetyl phenate and calcium dicetyl phenate; metal salts of thiophosphoric acid esters such as the zinc salt of the p-tert.-amylphenyl ester of dithiophosphoric acid; and metal salts, of wax substituted phenol derivatives such as the wax substituted metal phenates. Presently preferred are the alkaline earth metal petroleum sulfonates and alkaline earth metal phenates such as basic calcium petroleum sulfonate, calcium cetyl phenate and sulfurized calcium cetyl phenate. These particular lubricating oil detergent additives, alone and together, are found to be unusually efiective when combined with the isophthalic and terephthalic acid in lubricant compositions for internal combustion engine use according to this invention.

Nonmetallic lubricating oil detergent additives are also suitable for the lubricant compositions of the invention. This type of lubricating oil detergent additive for present purposes, may be conveniently described as a macromolecular copolymer characterized by oil solubilizing monomer as hexadence-l or octyl styrene; an ester such as allyl stearate or lauryl methacrylate; an ether such as vinyl nbutyl ether; or a ketone such as methallyl isobutyl ketone. The polar type monomer group may be an unsaturated monocarboxylic acid such as methacrylic acid, amides and esters thereof such as n-lauryl acrylamide and pentaerythritol monomethacrylate, unsaturated dicarboxylic acids such as maleic acid and amides and esters thereof such as the half-amides, half-esters, diamides and diesters as illustrated by the N,N-di-tert.bu tyl monoamide of maleic acid, monopentaerythritol ester of maleic acid and similar diamides and diesters.

Other oil-soluble dispersants may be included in the lubricant compositions either in addition to or in lieu of the metallic and nonmetallic lubricating oil detergent additives described above. Such dispersants are illustrated by the phosphatides such as animal lecithin and the partial or complete esters of long-chain car-boxylicacids with polyhydric alcohols such as pentaerythritol mono-oleate and glycerol sorbitan laurate. These materials, like the other dispersants or lubricating oil detergent additives mentioned previously, also serve to maintain the isophthalic or terephthalic acid of the present compositions in stable suspension. Thus, the phthalic acids are circulated freely in the lubricating oil system wherever corrodible metal surface are encountered to effectively inhibit corrosion and promote improved lubrication of rubbing surfaces.

The isophthalic acid and terephthalic acid are commercially available materials. proved lubricant compositions obtained when they are combined with oils of lubricating viscosity, however, a brief review of their more important characteristics may be appropriate here. structurally, the isophthalic acid and terephthalic acid are unique in that the carboxyl groups are separated by the benzene ring as illustrated bythe following formulae:

noooOooorr @COOH Terephthalle acid IsOphthalic acid These particular dicarboxylic acids, it will be noted, are

unlike other dicarboxylic acids in that the carboxyl groups are located where they will be able to function most effec,. tively. Other dicarboxylic acids of both aliphatic and;

aromatic types may cyclize and form their anhydrides which may not be as elfective as. the acids.

The isophthalic acid and terephthalic acid may be ern ployed together in lubricating oil compositions accordingv This may be advantageous where con;

to the invention. ditions of operation are such that the solubility of the isophthalic acid or terephthalic acid becomes critical, In a case of this type, the lubricating oil composition may be saturatedwith one of the acids and still be capable of incorporating a similar amount of the other acid to augment the corrosion inhibiting properties. The compositions of this invention containing the phthalic acid selected from the group consisting of isophthalic and terephthalic acid and mixtures thereof, as described above, are surprisingly more effective in the inhibition of corrosion of metal surfaces such as alloy metal bearings and the like than similar compositions containing their isomer, orthophthalic acid, commonly referred to in the art as phthalic acid.

Still more unexpected is the fact that the terephthalic acid is a much better corrosion inhibitor than the isophthalic.

acid. So far as is known, it has never been suggested heretofore that either of these particular acids might be effective in lubricant compositions as corrosion inhibitors, let

alone that terephthalic acid would be far superior to its isomer, isophthalic acid, in such a capacity.

In accordance with a preferred embodiment of the invention, as already described, a lubricating oil detergent In view of the remarkably imadditive is present in a minor amount, sufficient to suspend the phthalic acid in the oil of lubricating viscosity. Amounts up to 20% by weight of the lubricant composition are generally suitable for this purpose, although concentrates for use in blending operations to prepare the lubricant compositions of the invention may contain up to 50% by weight or more of the detergent. For present purposes, very superior lubricant compositions are obtained with from 0.1 to 10% by weight of the detergent.

The phthalic acid of the group consisting of isophthalic acid and terephthalic acid is present in the lubricant composition in a minor portion, suflicient to inhibit corrosion, as stated above. Generally, amounts up to about 1.0% by weight of the lubricant composition are very satisfactory. For present purposes the preferred lubricant compositions contain from about 0.001 to 0.5% by Weight. Such compositions are unusually stable and provide remarkably effective corrosion inhibition for extended periods.

Any of the Well-known types of oils of lubricating viscosity are suitable base oils for the compositions of the invention. In normal usage these oils are corrosive to metal surfaces. They include hydrocarbon or mineral lubricating oils of naphthenic, paraffinic, and mixed naphthenic and paraffinic types. They may be refined by any of the conventional methods such as solvent refining and acid refining. Synthetic hydrocarbon oils of the alkylene polymer type or those derived from coal and shale may also be employed. Alkylene oxide polymers and their derivatives such as the propylene oxide polymers and their ethyl esters and acetyl derivatives in which the terminal hydroxyl groups have been modified are also suitable. Synthetic oils of the dicarboxylic acid ester type including dibutyl adipate, di-Z-ethylhexyl sebacate, di-n-hexyl fum arate polymer, di-lauryl acylate, and the like may be used; Alkyl benzene types of synthetic oils such as tetradecyl benzene, etc., arev also included. Liquidesters of acids. of phosphorus including tricresyl phosphate, diethyl esters of decane phosphonic acid, and" the. like. may also be employed. Also suitable are the polysiloxane oils of the type of polyalkyl-, polyaryl-, polyalkoxyand polyaryloxysiloxanes such as polymethyl siloxane, polymethylphenyl siloxane, and polymethoxy phenoxy siloxane and silicate.

ester oils such as tetraalkylandtetraaryl silicates of the tetra-Z-ethylhexyl silicate and tetra-p-tert.-butylphenyl silicate types.

As, already mentioned, the corrosion inhibiting compositions ofthis invention are outstanding in; that they are unusually effective in the form of compounded lubricating oilscontaining conventional additives such asoxidation inhibitors, detergents or dispersants, sludge inhibitors, pour depressants, V. I. improvers, antifoaming agents,- rust inhibitors, oiliness orfilm strengthening agents, wearinhibitors, dyes and the like. A greatmanyof thesecornpoundedoils are generally: corrosivetometal surfacesand,

oils as generally compounded for internal combustion,

engine use are unusually corrosive to metal surfaces and are thusmost greatlybenefitted by the addition ofthe particular phthalic acids.

The following examples are submitted asadditionaljllustrations of the inyention. These examples show, the preparation of the various lubricant. compositions and; the v v uation. of heir ff tiv ness a orro ion inhibitors.

5 The proportions given in these examples, unless otherwise specified, are on a Weight basis and include both percent and millimoles per kilogram (mM./kg.) of the various additives.

EXAMPLE I 190.5 parts of mineral oil concentrate containing 'sul-' mM./kg. basic calcium petroleum sulf oriate, i0 mM/kg'.

sulfurized basic calcium alkyl phenate and 0.5% by weight terephthalic acid.

furized calcium alkyl phenate and analyzing 4.4% calcium and-246 parts of basic calcium petroleum sulfonate mineral oil concentrate analyzing 1.67% calcium along with 175 parts of benzene were charged to a reaction vessel equipped with mechanical stirrer, dropping funnel,

thermometer, distillation column and heating means. The mixture was stirred at about 150 F. for 20 minutes. 10.5

parts of isophthalic acid was dissolved in 590 parts of isopropyl alcohol at 165 F. and the resulting solution was basic calcium alkyl phenate, basic calcium petroleum sul- I tomato and isophthalic acid were combined with 95.74 parts of-a solvent refined SAE 40 mineral lubricating oil base having a viscosity index of 60 to yield a composition consisting of 60 V. I. SAE 40 base oil, 20 mM./kg. of sulfurized basic calcium alkyl phenate, '10 mM./kg. of basic calcium petroleum sulfonate and 0.10% by weight of isophthalic acid. a

' EXAMPLE II '350 parts of a'solvent refined SAE 40miner al lubricat ing oil base having a viscosity index of 60 and containing 10 mM./kg. of basic calcium petroleum sulfonate and mM./ kg. of sulfurized basic calcium alkyl phenate was charged to a glass reaction vessel. The oil washeated while stirring to about 150 F. 0.35 part of isophthalic acid were dissolved in about 24 parts of isopropyl alcohol at'165 F. and the hot solution was added to the oil in the reaction vessel with stirring. The isopropyl alcohol was slowly distilled off. The product consisted of a 60 V. I. SAE 40 mineral lubricating oil base, 10 mM./kg. basic calcium petroleum sulfonate, 20 mM./kg. sulfurized basic calcium alkyl phenate and 0.10% isophthalicacid. 7

EXAMPLE III 350 parts of a solvent refined mineral SAE '40 lubricating oil base containing 10 mM./kg. basic calcium petroleum sulfonate and 20 mM./l g. sulfurized basic calcium The oil alkyl phenate was charged to a reaction vessel. was stirred at about 150 F.and 0.0525 part of terephthalic acid was added. The mixture was then stirred at about 200 F. for 20 minutes. The product'was a composition consisting of a 60 V. I. SAE'40 base oil, 10 mM./kg. basic calcium petroleum sulfonate, 20 mM./ kg. sulfurized basic calcium alkyl phenate and 0.015% by weight of terephthalic acid. a

EXAMPLE IV '350 parts of a solvent refined SAE 40 mineral lubricating oil containing 10 mM./kg. basic calcium petroleum sulfonate and 20 mM./ kg. of sulfurized basic alkyl phenate was charged to a reaction vessel. The oil was stirred at about 150 F. for 20 minutes. 0.175 part of terephthalic acid was dissolved in 125 parts of isopropyl alcohol at about 165 F. and the hot solution was then added to the oil. The resulting mixture was stirred at about 160 F. for an additional 20 minutes. The remaining isopropyl alcohol was removed by distilling up to about 305 F. at 2 mm. mercury pressure. The product was a composition co'nsisan ar a. 60 V. IQSAE' 40 lubricating oilbase, 10

- phenate. mineral oil containing 10% by weight of a copolymeric By the same general procedure as outlined in the above examples additional corrosion inhibited lubricant compositions were prepared in illustration of the invention. Th'ey contained both mineral oils and a variety of synthetic oils used either alone with the phthalic acids or in combination with conventional lubricating oil additives to illustrate the overall effectiveness of the compositions in accordance with this invention.

The unusual effectiveness of the lubricant composition according to this invention is illustrated by its performance in standard lubricating oil tests for determining corrosion inhibition. In the Copper-Lead Strip Corrosion Test, a polished copper-lead strip is weighed and immersed in 300 ml. of test oil contained in a 400 ml., lipless Berzelius beaker. The test oil is maintained at 340 F. under a pressure of 1 atmosphere of air and stirred with the mechanical stirrer at 1000 R. P. M. After 2 hours, a synthetic naphthenate catalyst is added to provide the 1501- I lowing catalytic metals:

0.008% by Wei ht Iron 1 0.004% by weight Lead 0.002%' by wei ht Copper 0.0005% byweight Manganese 0.004% by weight Chromium 1 The test iscontinued for 20 hours. The copper-lead strip is then removed, rubbed vigorously with a soft cloth and weighed to determine the net weight loss.

The lubricating oil compositions in the tests include a variety of base oils. Mineral oil (A) is an acid refined White mineral oil. Synthetic oil (B) is a poly-1,2-propylene glycol phenyl methyl diether having a molecular weight of 1200. Synthetic oil (C) is .di-2-ethylhexyl sebacate. compounded oil (D) is a solvent refined SAE 40 mineral lubricating oil having a viscosity index of 60 and containing 10 mM./kg. of basic calcium petroleum sulfonate and 20 mM./kg. of sulfurized basic calciumcetyl phenate. Compounded oil (E) is the same mineral lubricating oil but contains only 10 mM./ kg. basic calcium petroleum sulfonate. Compounded oil (F) is the same mineral lubricating oil but contains 14 mM./kg. lead cetyl Compouridedoil (G) is an acid refined white detergent which is the copolymer of lauryl methacrylate with the diethylaminoethyl ester of acrylic acid sold by Du Pont as Lubricating Oil Additive No. 565. Compounded oil (H) is the same oil, but contains 20 mM./kg. sulfurized basic calcium cetyl phenate;

Illustrative test results are shown in the following table. Concentrations of the phthalic acids employed are given in percent by weight of the composition.

. Table l COPPER-LEAD STRIP CORROSION TEST Copper-Lead 0.3% Phthalic anhydride in fifibiidiih'iiii 0.3% Orthophthalic acid in compounded oil (D) 0.3% Isophthalic acid in compounded oil (D) 1 2% Isophthalic acid in compounded oil (D) 2 Terephthalic acid in compounded oil (D) 2. Phthalic anhydride in compounded oil (D) 300. 75% Orthophthalic acid in compounded oil (D) 207. 75% Isophthalic acid in compounded oil (D) 14.

75% Terephthalic acid in compounded oil (D) Dimcthyl isophthalate in compounded oil (D) Diphenyl isophthalate in compounded oi1.(D) Diphenyl tcrephthalate in compounded oil (D)..

8.875% Isophthalic acid in compounded oil (D) 1.0

1 Crude isophthalic acid containing 15% terephthalic acid.

2 Substantially pure isophthalic acid containing about 3% by weight.

terephthalic acid.

The above testadata show thatallof the various mineral oils and; synthetic: oils alone or in combination with conventionallubricating oilj additives which: are normally corrosive to metal surfaces are benefited. with the addition of isophthalic: acid and/ or terephthalic .acid corrosion inhibitors in accordance with the invention. The effectiveness of oils of lubricating oil viscosity in general which. are normally corrosive to metal surfaces in the corrosion inhibited compositions of the invention is illustrated by a representative group consisting of mineral lubricating oils, alkylene oxide polymer synthetic lubricating oils and dicarboxylic acid diester synthetic lubricating oils. In one particular combination, that employing compounded oil (D), the above test data show that the reference oil containing heavy duty lubricating oil detergent additives and stabilizers when used alone gives a copperlead strip Weight loss of over 300 mg. By way of distinction, compositions in accordance with this invention employing as little as 0.1% terephthalic acid, for example, give a very low corrosion loss of only'2.5 mg. Although the terephthalic acid-containing compositions are distinctly superior as shown by the test results and, therefore, constitute a preferred embodiment of the invention, both isophthalic acid and terephthalic acid-containing lubricant compositions are outstanding in comparison with lubricant compositions containing their isomer orthophthalic acid or their ester derivatives.

The. performance characteristics of the lubricating oil compositions of this invention are also illustrated by their evaluation in a number of engine tests. The engine test procedures and techniques, though conventional and well known inthe lubricating oil art, are briefly described for-the sake of convenience in the following paragraphs along with the test data.

Inthe L-4 engine test the corrosion characteristics of the: oils are determined in a Chevrolet standard 6-cylinder engine in a typical laboratory installation. Weighed copper-lead test bearings and new piston rings are installed. The testis run at a constant engine speed at about 300 R. P. M. under a load of 30 brake horse-power for a. total of 36 hours subsequent to a run-in period of- 8 hours. The outlet temperature of the jacket coolant is. 20.0. F. and the oil sump temperature is 280 F. At the conclusion of the test the engine is disassembled and inspected for varnish and sludge deposits and the various parts parts arerated on a cleanliness-scale of 0 to 10, 10 being perfectly clean. The bearings are weighed to determine the weight loss perwhole bearing due to corrosion. Illustrative test results on the compositions of the invention using a compounded oil (A) as described above containing 10 mM./kg. of neutral calcium petroleum sulfonate and rnM./kg. of calcium alkyl phenate, sulfurized, and a similar compounded oil (B) containing solvent refined 1,401 neutral mineral lubricating oil as the base oil but with 7% of a polymeric. detergent of the lauryl methacrylate-methacrylic acid-lauryl polyethylene glycol methacrylatertype, are given in the following table.

8 Table II:

4-4 ENGINE TEST Weight Loss, Cleanli- Addltive and Oil Mg. Per Whole ness Bearing None-compounded oil (A) alone More than 500- 0.1% 'Ierephthallc'acid in compounded oil 82 0.2(5A7)6 Terephtha1ic acid in compounded oil None compoundcd oil (B) alone 0.1% Isophthalic acid in compoundedoil' (B)- There isvery little viscosity increase in the test oils employing the isophthalic and terephthalic acids, according to the present invention. The engine cleanliness ratings of the compositions of the invention are unusually high. Although the conventional compounded reference oils give unsatisfactorily highcorrosion' losses, in excess of 500 rngs., the isophthalic acid and terephthalic acid containing compositions give unusually low corrosion losses of less than ings. in all instances. From the results of these tests,-it will be seen that the compositions according to this invention not only'provide excellent corrosion inhibition in actual-engine-operation, but also give very high performance ratings so-far as engine cleanliness is concerned,

The L-4 Engine Test referred to above is more fully described in'the CRC Handbook, 1946 edition, Co-ordinating Research Council, New York, New York.

In the Navy Propulsion Load Test described in Mil. P-17269 (Ships) 11 July 1952; the compositions of the invention are evaluated as diesel engine lubricating oils under severe operating conditions. The tests are run in a General Motors 4-cy-li'nder diesel engine using one percent sulfur fuel. Copper-lead bearings are employed. The tests are run at a constant speed of 1800 R. P. M. under aload of' 30 brake. horse-power per cylinder. The crankcase temperature is-250 F. The present test is run continuouslyto simulate railroad diesel engine perform.- ance unlike the. standard Navy test procedure which permits regular 4-hour'shutdown periods. Sea water was also excluded for the same reason. The reference oil is a solvent refined SAE 40 mineral lubricating oil base having a viscosity index of 60 and containing 10 mM./kg. of neutral calcium petroleum sulfonate and 20 mM./kg.

of calcium alkyl phenate, sulfurized. Test results are as" In-theNavy Propulsion LoadTest results shown above, the bearing weight. loss due. tov corrosion by the reference oil, a conventional, heavy duty compounded oil, is extremely high. Such an oil would be impossible to use for any extended period oftimewithout shutdown. By way of distinction, the lubricating oil compositions according to the invention containing isophthalic acid and terephthalic acid give remarkably low corrosion losses after much longer periods of continuous operation.

The improved lubricating ability of the compositions of the invention, aside from their unusualeffectiveness in providing corrosion inhibition and clean engines, is also shownby a kinetic Oiliness test. In, this, test, rubbing. surfaces consisting of 'a steel track rotated beneath loaded buttonsunder a constant pressure and at a constant temperature are employed- The; movement of the buttons due to friction. is, restrained by a: spring, and the relative ,.fi r friction is measuredfor each sample at tracksp eeds of 2,5, 10 and 30 R. P. M. The temperature selected' for these tests is as noted in the following table.

From the above test results carried out under a variety of conditionspit will'be seen that the lubricant composition of the inventionprovides' greatly improvedlubri cation in the overcoming of friction between rubbing surfaces compared'to 'straight'andconventional compounded lubricating oils. This improvement in the so-called oiliness characteristic is obtained not only under ordinary conditions, but also when the surfaces include particular metals such as silver.

The lubricating oil compositions illustrative of the invention are also evaluated for their effectiveness as inhibitors in gasoline-type internal combustion engines. This test is termed the L-4 Strip Corrosion Test because of its correlation with the L-4 Chevrolet Engine Test referred to in the CRC Handbook, 1946 edition, Coordinating Research Council, New York, New York. In the test the same apparatus and conditions as described in the above Copper-Lead Strip Corrosion Test are employed with two essential modifications. The temperature is maintained at 295 F. to simulate lower temper atures encountered in gasoline engines and a synthetic naphthenate catalyst of the following type is used containing lead in further duplication of gasoline engine operation:

0.0095% by weight Copper 0.0056% by weight Iron 0.0005% by weight Manganese 0.11% by weight Lea 0.0049% by weight Tin The reference oils include compounded oils (A) and (B) as already described in the previous tests. Compounded oils (C) and.(D) are the same as compouuded'oil (B) except that they contain 3.75% and 4% by weight, respectively, of the polymeric detergent.

Table V L-4 STRIP CORROSION TEST Copper-Lead Additive and Oil Strip Weight Loss (Mgs.)

None-cornpounded oil (A) alone 250. 0.1% Terephthalic acid in compounded oil (A). 6. 3 0.25% Terephthalic acid in compounded 011 (A). 3. 9 None-140 neutral base oil 92. 5 Nonecompounded oil (B) alone 244. 0 0.1% Isophthalic acid in compounded 011 (B) 2. 5 None-compounded oil (0) alone 121. 5 0.02% Isophtha-lic acid in compounded oil (0 11. 1 None-compounded oil (D) alone h 184. 8 0.02% Isophthalic acid plus 0.5% sulfurlzed dlparatfin sulfide in compounded oil (D) 1. 3

The test results shown in the above table illustrate the effectiveness of the lubricant compositions according to this invention under low temperature operating conditions. Copper-lead corrosion is substantially inhibited in all of the lubricant compositions containing the isophthalic acid or terephthalic acid inhibitors. The test results show further that the corrosivity of compounded lubricating oils, which are much more corrosive than the base oil alone, is efiectively inhibited. As previously mentioned,

mam)

ib in such compounded lubricant preferred embodiment of the the inhibition of corrosion compositions constitutes a invention. i

Although the compositionsofthe invention have been described above primarily as internal combustion engine lubricants, they are also suitable for other applications Such applications include their use as gear lubricants, ice machine oils, instrument oils, constituent oils for grease manufacture, turbine oils, and the like.

This application is a'continuation-in-part of vWilliam T. Stewart and Warren Lowe U. S. patent application Serial No. 478,538 filed December 29, 1954, now abandoned.

Weclaim:

l. A lubricant composition comprising a major portion of an oil of lubricating viscosity selected from the group consisting of mineral lubricating oils, alkylene oxide polymers and esters of dicarboxylic acids, said oil being corrosive to metal surfaces in normal use and a minor portion, suflicient to inhibit corrosion, of a phthalic acid of the group consisting of isophthalic acid and terephthalic acid and mixtures thereof.

2. A lubricant composition comprising a major portion of an ester of a dicarboxylic acid as a lubricating oil corrosive to metal surfaces in normal use and a minor portion, suflicient to inhibit corrosion, of a phthalic acid of the group consisting of isophthalic acid and terephthalic acid and mixtures thereof.

3. A lubricant composition comprising a major portion of an oil of lubricating viscosity in combination with a minor portion of a lubricating oil detergent additive, said combination being corrosive to metal surfaces in normal use and a minor portion, sutficient to inhibit corrosion, of a phthalic acid of the group consisting of isophthalic acid and terephthalic acid and mixtures thereof, said minor viscosity.

4. A lubricant composition comprising a major portion of a mineral lubricating oil in combination with a minor portion of a lubricating oil detergent additive, said combination being corrosive to metal surfaces in normal use and a minor portion, sufiicient to inhibit corrosion, of a phthalic acid of the group consisting of isophthalic acid and terephthalic acid and mixtures thereof, said minor portion of lubricating oil detergent additive being sufficient to suspend said phthalic acid in the mineral lubricating oil.

5. A lubricant composition comprising a major portion of 'a mineral lubricating oil in combination with a minor portion of an alkaline earth metal petroleum sulfonate, said combination being corrosive to metal surfaces in normal use and a minor portion, suflicient to inhibit corrosion, of isophthalic acid, said minor portion of alkaline earth metal petroleum sulfonate being suflicient to suspend said isophthalic acid in the mineral lubricating oil.

6. A lubricant composition comprising a major portion of a mineral lubricating oil in combination with a minor portion of an alkaline earth metal petroleum sulfonate, said combination being corrosive to metal surfaces in normal use and a minor portion, suhicient to inhibit corrosion, of terephthalic acid, said minor portion of alkaline earth metal petroleum sulfonate being suificient to suspend said terep'hthalic acid in the mineral lubricating oil.

7. A lubricant composition comprising a major portion of a mineral lubricating oil in combination with a minor portion of an alkaline earth metal petroleum sulfonate and an alkaline earth metal alkyl phenate, said combination being corrosive to metal surfaces in normal use and a minor portion, sufficient to inhibit corrosion, of isophthalic acid, said minor portion of alkaline earth metal petroleum sulfonate and alkaline earth metal alkyl phenate being suflicient to suspend said isophthalic acid in the mineral lubricating oil.

8. A lubricant composition comprising a major portion of a mineral lubricating oil in combination with a minor portion or analkaline.earthnietalpetrolenm.snltonateand:

anyalkaline earth metal alkylf phenate, :said1conibi1iation being corrosive to metal surfaces in normal usetand a minor portion, sufficient to, inhibit corrosion, of terephphenate being sufiicient to suspendsaidterephthalic acid inthe. mineral lubricating oil.

9. A lubricant composition comprising. a majo, portion of a mineral lubrieatingoil incombination. with a minor portion of a. calciumv petroleumv sulfonate, said combinationtbeingcorrosive to. metal surfaces-in normal use and a minor portion, suflicient to inhibit corrosion, of isophthalic acid, said minor portion of. calciumtpetroleurn sulfonate being suificient.tosuspcndtsaidisophthalic acid in the mineral lubricating oil.

10. A lubricant compositiontvcomprising a major portion of. a mineral lubricating oil" in v combination with a minor portion of a calcium petroleum sulfonate, said combination beingtcorrosive to metal surfaces iirnormal use and a minor portion, sufiicient to inhibit corrosion, of. terephthalic, acid, said minor portion of Falcium petroleum sulfonate being sufficient to suspend said terephthalic acid in the mineral lubricating oil.

11. A lubricant composition comprising a major portion of a mineral lubricating oil in combination with a minor portion of a calcium petroleum sulfonate and a calcium alkyl'phenate, said combination being corrosive to metal surfacesinnormal use and a minor portion, sufficient to inhibit corrosion, of a mixture of isophthalic acid and'terephthalic acid, said minor portion-of calcium petroleum sulfonate and calcium alkyl phenate being sufficient to suspend said mixture of isophthalic acid and terephthalic acid in the mineral lubricating oil.

References Cited in the file of this patent UNITED STATES PATENTS

Claims

1. A LUBRICANT COMPOSITION COMPRISING A MAJOR PORTION OF AN OIL OF LUBRICATING VISCOSITY SELECTED FROM THE GROUP CONSISTING OF MINERAL LUBRICATING OILS, ALKYLENE OXIDE POLYMERS AND ESTERS OF DICARBOXYLIC ACID, SAID OIL BEING CORROSIVE TO METAL SURFACES IN NORMAL USE AND A MINOR PORTION, SUFFICIENT TO INHIBIT CORROSION, OF A PHTHALIC ACID OF THE GROUP CONSISTING OF ISOPHTHALIC ACID AND TEREPHTHALIC ACID AND MIXTURES THEREOF.