Rust resistant lubricant composition

3,208,945

Patented Sept. 28, 1965

United States Patent Office

3,208,945 RUST RESISTANT LUBRICANT COMPOSITION Frank A. Stuart, Orinda, and Warren Lowe, Berkeley, Calif., assignors to California Research Corporation, San Francisco, Calif., a corporation of Delaware No Drawing. Filed May 31, 1963, Ser. No. 284,390

Claims. (CI. 252—51.5)

This application is a continuation-in-part of Warren Lowe and Frank A. Stuart application Serial No. 863,112 (abandoned), filed December 31, 1959, and Frank A. Stuart and Warren Lowe application Serial No. 863,113, filed December 31, 1959, which is now abandoned.

This invention relates to an improved rust-inhibited lubricant composition. More particularly, the invention concerns a superior new lubricating oil composition containing a unique combination of additives which inhibits rusting of ferrous metal parts under severe service conditions in internal combustion engines.

Serious rusting problems are encountered in the operation of modern internal combustion engines. Due to the stringent conditions imposed on the engines in presentday service, more efficient rust inhibitors are needed. Previously known additives which were adequate in preventing rusting in engines in the past under the milder operating conditions characteristic of the times are not sufficiently effective today. Furthermore, the common use of more efficient detergents in the newer lubricating oils to maintain a higher degree of cleanliness of engine parts has placed a still greater burden on the rust-inhibiting additives. This is particularly so in the case of the typical automobile high compression gasoline engines of complex design and the severe operating conditions of recent years.

It has now been found that internal combustion engine rusting problems of the most difficult kind are successfully overcome in a lubricating oil composition comprising a major proportion of a mineral lubricating oil and a minor proportion sufficient to inhibit rusting of the combination of a monoalkenyl succinic anhydride having 8 to 18 carbon atoms in the alkenyl group and a member of the class ⁴⁰consisting of polymerized linoleic acid consisting essentially of a mixture of dimer and trimer acids and hydrogenated derivatives thereof, said combination containing from about 10 to 90% by weight of the monoalkenyl succinic anhydride and from about 10 to 90% by weight ⁴“ of the polymerized linoleic acid.

In another more particular embodiment of the invention, it has been further found that the above-described rust inhibited composition is surprisingly effective in the form of the more efficient detergent lubricating oil com- ⁵⁰positions of today containing polymeric ashless detergents. Such lubricating oil compositions comprise a major proportion of a mineral lubricating oil, a minor proportion of polymeric ashless detergent sufficient to en- __ hance the detergent characteristics of said oil and a minor ⁶⁵proportion sufficient to inhibit rusting of the combination of monoalkenyl succinic anhydride and polymerized linoleic acid as described above.

The improved lubricating oil compositions of this invention are remarkably effective in preventing rusting ⁰⁰of metal surfaces in internal combustion engines under severe service conditions. The lubricant compositions containing the combination of monoalkenyl succinic anhydride and polymerized linoleic acid inhibit rusting to a surprising degree which would not be expected from the ⁰⁵performance of either of the additives alone in similar lubricant compositions.

The rust-inhibited polymeric ashless detergent lubricating oil compositions in accordance with this invention provide freedom from engine deposits and the accompanying wear of engine parts, and at the same time elim10 inate the aggravated rusting problems which ordinarily arise with the use of such polymeric ashless detergent oils in the operation of internal combustion engines under severe service conditions.

The polymerized linoleic acid of the lubricant composition of the invention is commercially available. It may be produced by heating the linoleic acid in the presence of water at temperatures of about 300 to 400’ C. and superatmospheric pressures, and consists essentially of a mixture of dimer and trimer. A very suitable product of this type consists approximately of 75% by weight dimer acid and 25 % by weight trimer acid. The hydrogenated polymeric linoleic acid is conveniently obtained by contacting the polymerized linoleic acid with hydrogen in the presence of a typical hydrogenation catalyst such as nickel.

The alkenyl succinic anhydride of the lubricating oil composition of this invention is also available commercially. It contains from about 8 to 18 carbon atoms in the alkenyl radical as already mentioned. Suitable alkenyl succinic anhydrides include octenyl succinic acid anhydride, decenyl succinic acid anhydride, undecenyl succinic acid anhydride, pentadecenyl succinic acid anhydride, octadecenyl succinic acid anhydride and isomers thereof having alkenyl groups of varied hydrocarbon structure. For present purposes, the tetrapropenyl succinic acid anhydride and triisobutenyl succinic acid anhydride utilizing propylene tetramer and isobutylene trimer as the alkenyl groups are preferred.

The base oil in the lubricant composition of the invention is any oil of lubricating viscosity. Thus, the base oil can be a refined paraffin-type base oil, a refined naphthenic-type base oil or a synthetic hydrocarbon or synthetic nonhydrocarbon oil of lubricating viscosity. As synthetic oils, suitable examples include the hydrogenated polymers of hydrocarbons such as the polybutenes and the condensation products of chlorinated alkyl hydrocarbons with aromatic compounds such as the alkylated benzenes. Other suitable oils are those obtained by polymerization of lower molecular weight alkylene oxides such as propylene oxide and/or ethylene oxide employing alcohol or acid initiators such as lauryl alcohol or acetic acid. Still other synthetic oils include esters, for example, di(2-ethylhexyl) sebacate, tricresyl phosphate and silicate esters such as tetra (2-ethylhexyl) orthosilicate and hexa(2-ethylbutoxy) disiloxane. For present purposes, the mineral lubricating oils are preferred, since they show the greatest improvement in the inhibition of rusting.

As already mentioned, the lubricating oil composition of this invention contains a minor proportion of the combination of monoalkenyl succinic anhydride and polymerized linoleic acid sufficient to inhibit rusting. Usually, from about 0.05% by weight up to about 5% by weight of the combination will be sufficient to provide excellent rust-inhibiting properties to the lubricating oil composition. The combination contains from about 10 to 90% by weight of each of the monoalkenyl succinic anhydride and the polymerized linoleic acid compound as previously mentioned. In the prefered lubricant compositions, it is found that from about 0.1 to 3% by weight of the combination containing from about 50 to 90% by weight of the monoalkenyl succinic acid anhydride and from about 10 to about 50% by weight of the polymerized linoleic acid is most satisfactory.

The polymeric ashless detergents which are used in the lubricating oil compositions in accordance with a particular embodiment of the present invention are macromolecular materials effective in suspending and stabilizing deposit-forming materials. They are not only capable of providing a high degree of cleanliness in spark ignition automobile engines, but have the further advantage of

3.208,945 forming no objectionable ash deposit when they happen to be consumed in the combustion chamber of the engine, unlike many of the metal salt detergents commonly employed in lubricating oil compositions of recent years. Suitable polymeric ashless detergents for present purposes are copolymers of (A) at least one oil-solubilizing monomer having a single ethylenic linkage and containing a monovalent hydrocarbon group of 4 to 30 aliphatic carbon atoms and (B) at least one polar monomer selected from the group consisting of unsaturated aliphatic monoand di-carboxylic acids of 3 to 6 carbon atoms, hydroxy and aminoalkyl esters, amides and amine salts of the aforesaid unsaturated acids in which the hydroxy and aminoalkyl group contains not more than 8 carbon atoms, esters of such acids and polyalkylene glycols and alkyl ethers thereof and heterocyclic nitrogen-contained monomers such as the N-vinyl pyrrolidones.

The oil-solubilizing monomer portion (A) of the macromolecular polymeric materials as described above is poylmerizable through the ethylenic linkage and the aliphatic hydrocarbon group provides oil solubility. Such oilsolubilizing monomers may be represented by the following general formula:

R₁(G’)_n'CH=(G)_aR₂ in which Ri and R₂ are members of the group consisting of hydrogen and hydrocarbon radicals of from 4 to 30 carbon atoms, at least One of which contains an aliphatic hydrocarbon group of from 4 to 30 carbon atoms as described above, G and G' are members of the class consisting of oxy (-—O—), o o o carbonyl (-^-) and carbonyloxy (—<ϋ—0 orO—/i—>

groups and combinations thereof with not more than two alkylene groups of from 1 to 7 carbon atmos each, and n and n' are 0 or 1. When Rj and R₂ are hydrocarbon radicals, they may be alkyl, cycloalkyl, alkenyl, cycloalkenyl, aryl, alkaryl or aralkyl in structure, as illustrated by radicals suhe as 2-ethylhexyl, cyclohexyl, hexenyl, cyclohexenyl, phenyl, naphthyl, tert.-butylphenyl benzyl, etc., with the preferred radicals being as previously mentioned.

Representative oil-solubilizing monomer compounds which can be employed to form the copolymeric additives of the present invention include the following:

OLEFINS

Hexene-1

2-ethylhexene-l

Di- and triisobutylene

Tripropylene

Dodecene-1

Hexadecene-1

Cyclohexene

Octadecene-1

4-octylcyclohexene-l

3-phenylhexadecene-l p-Octyl styrene

Vinyl cyclohexane

2-hexadecylbutadiene-1,3 p-Tert.butyl styrene

ESTERS

Vinyl n-butyl ether

Vinyl 2-ethylhexy ether

Allyl n-butyl ether

Allyl isobutyl ether

Allyl cyclohexyl ether

Allyl 4,4,8,8-tetramethyldocosyl ether

Methallyl n-hexyl ether

Methallyl n-decyl ether

Methallyl 2-ethylhexyl ether

Vinyl caproate

Vinyl palmitate

Vinyl oleate

Allyl caprylate

Allyl laurate

Allyl oleate

Allyl palmitate

Allyl stearate

Allyl 2-ethyl hexanoate

Allyl ricinoleate

Allyl esters of babassu acids

Allyl esters of lard acids

Allyl naphthenate

Methallyl caproate

Methallyl naphthenate

Methallyl ricinoleate

Methallyl p-octyl benzoate

Methallyl oleate ; · . .

Methallyl cyclohexane carboxylate

Methallyl palmitate

Crotyl oleate

Croytl naphthenate α-Methylcrotyl palmitate

1-propenyl naphthenate

1-propenyl elsidate

Dodecyl acrylate

Hexadecyl methacrylate

Ispbutyl α-decyl acrylate

Vinyl p-n-octyl benzoate

Allyl 3,5-diisobutyl benzoate

Cyclohexyl methacrylate

Methallyl octadecyl ether

Propenyl 2-ethylhexyl ether

Crotyl n-octyl ether

Isopropenyl dodecyl ether

1-decenyl butyl ether

1-eicosenyl decyl ether.

Vinyl p-octylphenyl ether

Methallyl p-tert.butylphenyl ether

1-decenyl p-cetylphenyl ether

1-decenyl 2-phcnylbutyl ether

Cyclohexyl 2-dodecenoate ⁴⁰ Decyl vinyl acetate

Isooctyl a-chloroacrylate p-Isoamylphenyl 2-hexadecenoate

4-p-tolylbutyl 2-octadecenoate

Undecyl cinnamate

Methylcyclohexyl 2-ethyl-2-hexenoate 5-ethyldocosyl crotonate

Octadecyl isocrotonate n-Butyl-2-eicosenoate p-Tert.amylphenyl octadecyl maleate p-Hexadecylphenyl 2-ethylhexyl maleate o-Tolyl 2-octadecylcyclohexyl maleate o-Nonylphenyl hexadecyl maleate Dihexadecyl maleate

Dimethylcyclohexyl maleate

Mono-2-ethylhexyl maleate

Di-2-ethylhexyl maleate

Di-dodecyl maleate

Di-dodecyl mesacronate .

Di-dodecyl citraconate o-Tolyl octadecyl itaconate

Mono-hexa decyl itaconate

Isopropenyl palmitoleate

1-decenyl laurate

1-hexadecenyl myristate 65

Although any of the oil-solubilizing compounds described above will give effective copolymer composition for lubricant compositions in accordance with the present invention, higher alkyl esters of ο,β-unsaturated mono70 carboxylic acids of from 3 to 6 carbon atoms having alkyl groups of from 4 to 30 carbon atoms are most prefcred, both for availability and effectiveness of copolymers prepared from them. Representative acids of this type are the acrylic, methacrylic, crotonic, tiglic, angelic, 75 α-ethylacrylic, a-methylcrotonic, α-ethylcrotonic, 0-ethyl3,208,948 crotonic, /3-propylcrotonic, and hydrosorbic acids and the like. Even more desirable are the alkyl esters of acrylic and methacrylic acids containing from 8 to 18 carbon atoms in the alkyl groups, since they are found to provide highly superior polymers for the lubricant composi- 5 tions of the invention and are obtainable in commercial quantities.

The polar acting (B) monomers of the above description include such unsaturated carboxylic acids as acrylic acid, methacrylic acid, tiglic acid, maleic acid, itaconic 10 acid, mesaconic acid, and the like. For present purposes, acrylic acid and methacrylic acid are preferred for their availability and effectiveness.

The polyalkylene glycols and alkyl ethers thereof employed to form the corresponding esters of the unsaturated 15 mono- and dicarboxylic acid as (B) monomers in accordance with the above description range in molecular weight from about 150 to about 30,000, and preferably from about 200 to 10,000. Each polyglycol is preferably linked by a single ester group to the acid. Polyethylene glycols 20 and poly-1,2-propylene glycols and their alkyl ethers are preferred for present purposes. Such polyalkylene glycol materials are produced in accordance with methods known in the art.

Suitable materials within the scope of the (B) mono- 25 mers as mentioned above include two different types of materials, namely, the unsaturated heterocyclic compounds such as the N-vinyl pyrrolidones and the aliphatic hydroxyand aminoalkyl esters and the hydroxy- and aminoalkyl amides and amine salts Of the Unsaturated carboxylic 30 acids. Suitable N-vinyl pyrrolidones are, for instance, 3-methyl-l-vinyl pyrrolidone, 3,3,5-trimethyl-l-vinyl pyrrolidone, etc. Suitable hydroxy- and aminoalkyl ester, amide and amine salt groups include those having the formulae 35 —RNR'R and —ROH in which R is the alkylene group attached to the oxygen or nitrogen of the ester, amide or amine salt and R' 40 and R are alkyl or hydrogen groups, the total number of carbon atoms in the alkylene and alkyl groups is not more than 8. Illustrative monomers of the aforementioned types include 2-hydroxyethyl, methacrylate, N, N-diethylaminoethyl methacrylate, 2-aminoethyl acrylate, 45 di-2-aminoethyl maleate, Ν,Ν-dimethylaminohexyl acrylate, 2-aminoethyl methacrylamide, the octyl ester of 2-aminoethyl maleamic acid, 2-hydroxyethyl methacrylamide, di(2-hydroxyethyl) maleamide, 2-hydroxyethylamine methacrylate, the di(2-hydroxyethylamine) maleate 50 formed when ethanolamine is reacted with methacrylic acid and maleic acid to form the corresponding amine salt.

Another particular version of the compositions of the invention lies in a lubricating oil composition comprising 55 a major proportion of a mineral lubricating oil, a minor proportion sufficient to enhance the detergent characteristics of said oil of the copolymer of (A) alkyl esters of unsaturated monocarboxylic acids of 3 to 6 carbon atoms containing 4 to 18 carbon atoms in the akyl group, and (B) an N-vinyl pyrrolidone, said copolymer having a molecular weight of at least about 20,000 and containing from about 40 to about 97 mole percent of (A) monomer and from about 3 to about 60 mole percent of (B) monomer, and a minor proportion sufficient to inhibit rusting of the combination of a monoalkenyl succinic anhydride having 8 to 18 carbon atoms in the alkenyl group and a member of the class consisting of polymerized linoleic acid consisting essentially of a mixture of dimer and trimer acids and hydrogenated derivatives thereof, said combination containing from about 10 to 90% by weight of the monoalkenyl succinic anhydride and from about 10 to 90% by weight of the polymerized linoleic acid.

The ashless polymeric detergents of the compositions according to the invention have apparent molecular weights in the range from about 2,000 to as high as about 1,000,000 as determined by the standard light scattering methods (see, for example, D’Alelio in “Fundamental Principles of Polymerization,” Wiley & Sons, 1952, pp. 356-267). For practical purposes, molecular weights of from about 100,000 to about 1,000,000 are most suitable.

The preparation of the ashless polymeric detergents is entirely straightforward and is carried out by conventional polymerization reactions of the aforementioned (A) and (B) monomers. Suitable procedures include bulk and solution or emulsion polymerizations with the aid of suitable polymerization initiators or catalysts. Preferably, the polymerization is effected in an inert organic solvent medium such as benzene, using a free radical type initiator in amounts which may range from 0.1 to 10% by weight. Suitable free radical initiators include benzoyl peroxide, α,α'-azodiisobutyronitrile, and and similar known catalysts. Polymerization temperatures may range from about 200 to 400° F.

In further illustration of the invention, the following examples are submitted showing a number of suitable lubricating oil compositions. The proportions are on a weight basis, unless otherwise specified.

In the examples, a variety of suitable base oils is shown. Oil A is a solvent-refined, wax-free SAE 30 grade mineral oil lubricating oil having a viscosity index of 85, which is derived from California waxy crude. Oil B is a 140 neutral mineral lubricating oil from solvent-refined waxy California crude. Oil C is a monolauryl ether of polyethylene glycol having a molecular weight of about 400, and Oil D is di(2-ethylhexyl) sebacate, the latter two being typical synthetic base oils. For convenience, the various compositions are listed in tabular form.

Table/

<td> Ex. No.</td><td> Base on</td><td> Polymeric Detergent</td><td> Ratio (1) Monomer to (2) Monomer to (3) Monomer, Etc.</td><td> Alkenyl Succinic Anhydride, percent</td><td> Linoleic Acid Polymer, percent</td>

<td> 1______</td><td> A.__ .</td><td> 2.8% (1) Dodecyl methacrylate ____</td><td rowspan="11"> 20/1 20/1/1 7/1 10/0/1 5/5/2 f 15/1</td><td rowspan="11"> »0.5 ^b0.1 «1.0 N).5 M1.1 »0.5</td><td rowspan="11"> »0.1 »0.1 «0.5 •0.1 »0.1 •0.5</td>

<td> 2______</td><td> A_____</td><td> (2) N,N'-di-2-hydroxyethyl maleamide— 2.8% (1) Dodecvl methacrylate_______</td>

<td rowspan="3"> 3______</td><td rowspan="3"> A_____</td><td> (2) Allyl stearate..— ______________</td>

<td> (3) Maleic anhydride___________________</td>

<td> 1.5% (1) Dodecyl methacrylate</td>

<td> 4......</td><td> B.....</td><td> (2) N-(2-hydroxycthyl) methacrylamide. 3.0% (1) Tridecyl methazrylate. .·</td>

<td rowspan="2"> 6____—</td><td rowspan="2"> A_____</td><td> (2) Octadecyl methacrylate_____________</td>

<td> (3) Monododecyl ether of hcxadecaethylene glycol methacrylate; 2.5% (1) Allyl stearate______________</td>

<td rowspan="2"> 6......</td><td rowspan="2"> A_____</td><td> (2) Didodecyl maleate................</td>

<td> (3) Di-(hydfoxyethyl)-cthylenediamine salt of monododecyl maleate. 2.8% (1) Vinyl ethylhexoate</td>

<td></td><td></td><td> (2) Itaconic acid_________________________</td>

3,208,045

Table II—Continued

Ex. Base

No. Oil

Polymeric Detergent

Ratio (1) Monomer to( 2) Monomer to (3) Monomer, Etc.

Alkenyl Succinic Anliydrid percent

Linoleic

Acid: Polymer, percent ,7.....-.

8...,— fl——

10—

1Ϊ.—

12-....

13_____

14_____

15...-.

10.....

<img file="US3208945A_D0001.tif" />

2.8% (1) Vinyl stearate...,-------------------- (2) Maleic anhydride----—------------- (3) Monododecyl ether of pentacthylene glycol methacrylate.

(4) Methacrylamide_____:.---------------

2.5% (1) Ally stearate_________________________ .(2) Ethylene glycol mono-oleate monomaleate.

(3) :Mono-N,N'-di(2-hydr0xy-ethyl) ethylene-diamine inaleate (salt).

2.8% (1) Octadecene._____...--------------(2) .Monododecyl maleate_____— (3) Monopentaerythritol maleate

2.8% (1) Hexene-l...-----------—------------ (2) Dodecyl methacrylate..—-— (3) Methacrylic acid--...--.------------- (4) Monododecyl ether ot eicosaethylene glycol methacrylate.

2.8% (1) Di-2-ethylhexyl fumurato------------ (2) Octadecene-1___________— (3) Crotonic acid-------------- (4) Monotridecyl ether of decaethyleno glycol methacry late.

2.8% (1) Allyl ethyl ether..-----,.—— (2) Vinyl stearate____—* *---------------- (3) Itaconic acid.—·---------------- (4) Monododecyl ether of decacthylene glycolcrotonate.

3.0% (1) Vinyl 2-ethylhexyI ether..----------(2) Tetradecylphenyl maleate.—------(3) Dodecyl maleate—.,-------------(4) Maleic acid....-----1.5% (1) Dodecyl acrylate....—-----(2) Monododecyl ether of decaethylene glycol acrylate.

(3) Acrylic acid________________—

1.5% (I) Hexadeeyl styrene—-----------(2) Methacrylic acid————————— 1.5% (1) Butyl methacrylate-----——— (2) Tridecyl methacrylate...————— (3) Octadecyl methacrylate.-------'-----(4) 3-methyl-l-vinyl pyrrolidone..—

30/1/2/1

5/4/1

2/1/1

25/25/1/4

25/25/8/2

14/50/7/3

6/3/1/2

780/9/1 , 5.8/1

3/5/12/1 •1.0 •0.1 m.i •2.0 •3.0 •0.1 •1.0 •0.5

50.5 •0.5 •0.6

80.1 &gt;0.05 «0.1 «0.1 •O.1 &gt;0.5 »0.05 &gt;0.2 •0.1 «0,3 «0.1 •0.1 »0.1 • Tetrapropenyl succinic anhdride. « Linoleic acid dimer. .

b Triisobutenyl succinic anhydride. &gt; Dimerized linoleic acid (85:15 dimer: trimer).

• Octenyl succinic anhydride. · Hydrogenated dimerized linoleic acid.

The polymeric detergents which are employed in an embodiment in the invention as illustrated by the above examples are characterized by sufficient (A) monomer content to provide oil solubility, that is, at least about 0.1% by weight of the polymer in oil and sufficient (B) polar monomer content to give surface-active properties to the polymer macromolecule as a whole. Excellent detergent characteristics are provided by from about 40 to about 97 mole percent of the (A), monomers and from about 3 to about 60 mole percent of the (B) monomers in copolymers of the above-mentioned types. In general, satisfactory detergent properties are imparted to lubricating oils by amounts from about 0.1 to about 10% by weight of the polymers.

Lubricant compositions within the scope, of the present invention may also contain still other additives of conventional types such as pour point depressants, oiliness and extreme pressure agents, anti-oxidants, blooming agents, viscosity index improvers, and the like. Other types of detergents, such as metal salts, may also be employed where ash formation is not a problem.

Illustrative lubricant compositions of the aforementioned types containing additives other than the polymeric detergents with the combination rust inhibitor may include, for example, from about 0.1 to about 10% by weight of alkaline earth metal higher alkyl phenate detergent and wear reducing agents such as the calcium alkyl phenate having mixed alkyl groups of 12 to 15 carbon atoms. They may also include from about 0.1 to 10% by weight of organic thiophosphate corrosion and high temperature oxidation inhibitors such as the reaction product of pinene and P₂S₅, the reaction product of polybutene and P₂S₅and the bivalent metal dihydrocarbon dithiophosphates, zinc butyl amyl dithiophosphate and zinc tetradecylphenyl dithiophosphate. Viscosity index improving agents which may be employed, usually in amounts of from about .l 1 to 10% by weight, include by way of example the ⁴⁵ homopolymers of alkyl methacrylate such as the dodecyl methacrylate polymer known to the trade as Acryloid 710 and Acryloid 763, products of Rohm &amp; Haas Company, and high molecular weight butane polymer such as .. Paratone ENJ 15P, a product of Enjay Company. Metal salt detergents in amounts from about 0.1% to 10% which may also be used are the calcium petroleum sulfonates of the oil-soluble mahogany type and the calcium naphthenates.

₅₅ The lubricant compositions of the invention also take the form of lubricating oil concentrates suitable for blending operations in the production of composition of the aforementioned types. Such concentrates contain as much as 20% of the combination rust inhibitor and up to 60% 00 Of the polymeric ashless detergents or other additives when they are present.

Typical lubricating oil compositions in accordance with the present invention are tested in the standard LS-5 Test Procedure, which has also been termed the “Power65 glide Rust Test.” In this test, a 6-cylinder Chevrolet (1957) engine is operated on the lubricating oil composition. The jacket temperature of the engine varies from 85 to 95° F., the oil sump temperature is 120° F·, and the engine is operated at 1500 r.p.m. for 12 hours. At the 70 end of the test period, the hydraulic valve lifters in the engine, which are extremely sensitive to rusting, are rated on a scale of from 0 to 10, in which 0 is perfectly clean and 10 is heavy rust.

The results of a number of tests are given in the follow⁷⁵ ing table.

3,208,945

Table II

Ex.

No.

Oil

Tetrapropenyl succinic anhydride, Wt. Percent

Triisobutenyl succinic anhydride, Wt. Percent

Dilinoleic acid, Wt. Percent

Hydrogenated dilinoleic acid, Wt. Percent

Powerglide Rust Rating

17.

18.

19.

20.

21.

22.

23.

24.

25.

26.

27.

28.

29.

30.

31.

32.

Ashless detergent polymer compounded oil (E).

_____do___________________________

.....do...........................

_____do___________________________ _____do...._______________________ _____do............._.............

_____do_..........................

.....do.........._________________

.....do___________________________ 150 neutral mineral lubricating .___.do___________________________ _____do___________________________ _____do___________________________

Ashless detergent polymer compounded oil (F).

.__..do___________________________

Ashless detergent polymer compounded oil (G).

0.5

0.5

0.1

0.25

0.25

0.25

0.05 0.05

0.125

0.'0G25

0.125 0.125

0.05

0.025

2.5

3.75 3.5 3

o.25 1.0 1.0

10.0

4.5 6

3.5 7

0.05

0.05

0.5

0.1

In the oils listed in the above table, compounded ashless detergent polymer lubricating oil (E) contains 3.2% of a copolymer of (1) butyl methacrylate, (2) dodecyl methacrylate, (3) octadecyl methacrylate and, (4) Nvinyl pyrrolidone having a ratio of alkyl methacrylate to pyrrolidone of about 10:1 and a molecular weight of approximately 250,000. The oil also contains 18 mM./kg. of zinc butylhexyl dithiophosphate and 0.001% of silicone polymer foam inhibitor. Oil (F) contains 2.5% of a copolymer of (1) dodecyl methacrylate, (2) tridecyl methacrylate, (3) octadecyl methacrylate and (4) polyethylene glycol monomethacrylate (1800 mol. wt.) having a ratio of alkyl methacrylate to poiyglycol methacrylate of about 100:1 and a molecular weight of about 350,000. Oil (G) contains 2% by weight of an approximately 350,000 molecular weight copolymer of dodecyl methacrylate, octadecyl methacrylate, polyethylene glycol monomethacrylate (1800 mol. wt.) and glycidyl methacrylate in 37/17/1/1 mole ratio in which the glycidyl methacrylate is reacted with N-methyl piperazine. The oil also contains the thiophosphate inhibitor (15 mM./kg.) as mentioned above and polylauryl methacrylate and polybutene (Paratone N) viscosity index improvers. The base oils are solvent refined SAE 10 grade mineral lubricating oils.

It will be seen from the test results in the above table that the lubricating oil compositions according to the invention are effectively inhibited against rusting Under severe service conditions. The test results also show that the combination of alkenyl succinic anhydride and polymerized linoleic acid is remarkably more effective than large amounts of either of the additives alone.