CA1084035A

CA1084035A - Lubricating oil antioxidant compositions

Info

Publication number: CA1084035A
Application number: CA273,439A
Authority: CA
Inventors: Warren Lowe
Original assignee: Chevron Research and Technology Co
Current assignee: Chevron USA Inc
Priority date: 1976-04-01
Filing date: 1977-03-08
Publication date: 1980-08-19
Also published as: DE2711654A1; GB1581654A; FR2346438B1; NL7703602A; BE853185A; DE2711654C2; JPS6158518B2; GB1581653A; FR2346438A1; BR7701967A; GB1581651A; IT1075302B; JPS52121009A; ES457441A1; GB1581652A

Abstract

ABSTRACT OF THE DISCLOSURE

A lubricating oil additive composition which imparts improved oxidation properties to crankcase lubricants comprises an antioxidant selected from aromatic or alkyl sulfides and polysulfides, sulfurized olefins, sulfurized carboxylic acid esters and sulfurized ester-olefins, and an amine of the formula R-RH2, (R1)2NH, (R2)3N, R-N-(C?)xyNH2, A

R3?N-A1)y" 3-x'N?A2-OH)x' or Het N?R4)y,X
y wherein each R is independently alkyl or alkenyl of at least 6 carbon atoms, each R is independently an aliphatic hydrocarbon group, each R2 is independently C3-C10 alkyl, phenyl, or phenyl substituted by 1 or 2 alkyl groups of 1-12 carbon atoms, R3 is C1-C30 alkyl, R4 is alkylene of at least 2 carbon atoms, each A
is independently hydrogen or C1-C18 alkyl, each A1 and A2 is independently C2-C10 alkylene, X is hydrogen, -OH, or -NA2, Y is hydrogen, C1-C6 alkyl, or A1-OH, Het is a carbon chain forming with the N atom a 5- or 6-membered heterocyclic ring, optionally containing in place of one carbon atom an additional N or O
hetero atom, x is an integer from 2 to 4, x' is 1 or 2, y is an integer from 1 to 4, y' is 0 or 1, and y" is 0, 1 ro 2, with the proviso that when y' is 0, X is hydrogen. Lubricating oil compositions containing this additive composition are also disclosed.

Description

i~84~335 BACKGROUND OF THE INVENTION
This invention relates to an improved lubricating composition, and more particularly, this invention relates to a lubricating composition containing an additive combination having improved antioxidation properties.
Hydrocarbon oils are partially oxidized when contacted with oxygen at elevated temperatures for long periods. The internal combustion engine is a model oxidator, since it contacts a hydrocarbon motor oil with air under agitation at high temperatures. Also, many of the metals (iron, copper, lead, nickel, etc.) used in the manufacture of the engine and in contact with both the oil and air, are effective oxidation catalysts which increase the rate of oxidation. The oxidation in motor oils is particularly acute in the modern internal combustion engine which is designed to operate under heavy work loads and at elevated temperatures.
The oxidation process produces acidic bodies within the motor oil which are corrosive to typical copper, lead, and cadmium engine bearings. It has also been discovered that the oxidation products contribute to piston ring sticking, the formation of sludges within the motor oil and an overall breakdown of viscosity characteristics of the lubricant.
Several effective oxidation inhibitors have been developed and are used in almost all of the conventional motor oils today. Typical of these inhibitors are the sulfurized oil-soluble organic compounds, such as wax sulfides and polysulfides, sulfurized olefins, sulfurized fatty acid esters, and sulfurized olefin esters, as well as zinc dithiophosphates and the oil-soluble phenolic and aromatic amine antioxidants. These inhibitors, while exhibiting good antioxidant properties, are burdened by economic and oil contamination problems. It is - 3 - ~ ~L

1~4~35 preferred to maintain the sulfur content of the oil, as low as possible, while at the same time receiving the benefits of the antioxidation property. A need, therefore, exists for an improved antioxidant that is stable at elevated temperatures, that can be employed in reduced concentrations, and that is economical and easy to produce.
DESCRIPTION OF THE PRIOR ART
.
United States Patent 2,718,501 discloses a synergistic mixture of a sulfur-containing compound, such as a wax sulfide or dioctadecyl disulfide, and an aromatic amine compound having at least 2 aromatic rings, such as phenyl alpha-naphthyl amine, for use in preventing oxidation in lubricating oils.
United States Patent 2,729,691 discloses a mixture of an arylamine antioxidant and a synergistic amount of an alkylenediamine for protecting organic material from oxidation.
United States Patent 2,958,663 discloses an extreme pressure lubricant composition containing from 0.01 to 5 percent each of sulfurized oleic acid, C18-C22 alkenyl succinic acid, chlorinated paraffin wax containing from 20 to 60 percent chlorine, diphenylamine and N,N-salicylal-1,2-propylenediamine.
United States Patent 3,345,292 discloses stabilized alkyl substituted diaryl sulfides for use as functional fluids where the stabilizer can be diaryl amine or alkylated phenol.
It is an object of this invention to provide additive compositions for crankcase lubricating oils which impart improved antioxidant properties. It is a further object of this invention to provide a synergistic additive composition having antioxidant properties in crankcase lubricating oil compositions.
SUMMARY OF THE INVENTION
A lubricating oil additive composition which imparts improved oxidation properties to lubricants comprises an 1~4~35 antioxidant selected from aromatic or alkyl sulfides and poly-sulfides, sulfurized olefins, sulfurized carboxylic acid esters and sulfurized ester-olefins, and an amine of the formula R-NH2' (R )2NH, ~R )3N, R l I (C 2)~ y 2 ~R ~N-A ~ ,N~A -OH) , or Het N~R ) ,X

wherein each R is independently alkyl or alkenyl of at least 6 carbon atoms, each Rl is independently an aliphatic hydrocarbon group, each R2 is independently C3-C10 alkyl, phenyl, or phenyl substituted by 1 or 2 alkyl groups of 1-12 carbon atoms, R3 is Cl-C30 alkyl, R4 is alkylene of at least 2 carbon atoms, each A
is independently hydrogen or Cl-C18 alkyl, each Al and A2 is independently C2-C10 alkylene, X is hydrogen, -OH, or -NA2, Y is hydrogen, Cl-C6 alkyl, or Al-OH, Het is a carbon chain forming with the N atom a 5- or 6-membered heterocyclic ring, optionally containing in place of one carbon atom an additional N or 0 hetero atom, x is an integer from 2 to 4, x' is 1 or 2, y is an integer from 1 to 4, y' is 0 or 1, and y" is 0, 1 or 2, with the proviso that when y' is 0, X is hydrogen.
As a second embodiment, there is provided a lubricating oil composition comprising an oil or lubricating viscosity and an antioxidant amount of the composition described above.
It has been found that the defined antioxidants in combination with the defined amines complement each other in a synergistic manner, resulting in a combination having antioxidant properties superior to either additive alone. The amine component alone has virtually no antioxidant effect. However, when the defined combination of amine and antioxidant is added to a lubricating oil, less of the antioxidant is needed to obtain oxidation control than when the amine is not present.

4~35 Preferably, from 2 to 40 millimols of an oil-soluble zinc salt is present per kilogram of the lubricating oil composition. While this zinc salt is not required to achieve the synergistic effect from the combination of the antioxidant and the amine, an improved lubricating oil composition results from the use of all three additive components.
DETAILED DESCRIPTION OF THE INVENTION
. _ _ _ _ The compositions of this invention are highly stable additives for crankcase lubricating oils and impart excellent antioxidant properties to these oils.
In a preferred embodiment of the lubricating oil composition, 0.25 to 10 weight percent of the antioxidant is present and 0.001 to 5 weight percent of the amil~e is present.
The weight ratio of the antioxidant to amine is ordinarily in the range of 1 to 0.001-21.
More preferably, 0.25 to about 2 weight percent of the antioxidant is present in the lubricating oil. More preferably, the amine is present in the amount of 0.01 to 0.3, preferably 0.05 to 0.3 weight percent.
In a further preferred embodiment, from 9 to 30 mmols per kilogram of the oil-soluble zinc salt is present.
ANTIOXIDANT COMPONENT
The class of antioxidants which may be used are conventional sulfur-containing antioxidants such as wax sulfides and polysulfides, sulfurized olefins, sulfurized carboxylic acid esters and sulfurized ester-olefins.
The sulfi~rized fatty acid esters are prepared by reacting sulfur, sulfur monochloride, and/or sulfur dichloride with an unsaturated fatty ester under elevated temperatures.
Typical esters include Cl-C20 alkyl esters of C8-C24 unsaturated fatty acids, such as palmitoleic, oleic, ricinoleic, -- 1~84~35 petroselinic, vaccenic, linoleic, linolenic, oleostearic, licanic, paranaric, tariric, gadoleic, arachidonic, cetoleic, etc. Particularly good results have been obtained with mixed unsaturated fatty acid esters, such as are obtained from animal fats and vegetable oils, such as tall oil, linseed oil, olive oil, castor oil, peanut oil, rape oil, fish oil, sperm oil, and so forth.
Exemplary fatty esters include lauryl tallate, methyl oleate, ethyl oleate, lauryl oleate, cetyl oleate, cetyl linoleate, lauryl ricinoleate, oleyl linoleate, oleyl stearate, and alkyl glycerides.
Cross-sulfurized ester olefins, such as a sulfurized mixture of C10-C25 olefins with fatty acid esters of C10-C25 fatty acids and Cl-C25 alkyl or alkenyl alcohols, wherein the fatty acid and/or the alcohol is unsaturated may also be used.
Sulfurized olefins which may be used as an antioxidant in the practice of this invention are prepared by the reaction of the C3-C6 olefin or a low-molecular-weight polyolefin derived therefrom with a sulfur-containing compound such as sulfur, sul-fur monochloride, and/or sulfur dichloride.
Another class of organic sulfur-containing compounds which may be used is sulfurized aliphatic esters of an olefinic mono- or dicarboxylic acid, for example aliphatic alcohols of 1-30 carbon atoms, used to esterify monocarboxylic acids such as acrylic acid, methacrylic acid, 2,4-pentadienoic acid and the like, or fumaric acid, maleic acid, muconic acid, and the like.
Sulfurization is carried out by combining these esters with elemental sulfur, sulfur monochloride and/or sulfur dichloride.
The preferred antioxidants are the aromatic and alkyl sulfides, such as dibenzylsulfide, dixylyl sulfide, dicetyl sulfide, diparaffin wax sulfide and polysulfide, cracked wax-1~4~S

olefin sulfides and so forth. They can be prepared by treating the starting materiall e.g., olefinically unsaturated compounds, with sulfur, sulfur monochloride, and sulfur dichloride.
Particularly preferred are the paraffin wax thiomers described in United States Patent 2,346,156.
All of the sulfides and polysulfides included within the scope of this invention are sulfurized sulfides and poly-sulfides. That is, the sulfide or polysulfide has been reacted with additional sulfur, sulfur monochloride or sulfur dichloride after the initial formation of the sulfide. Residual chlorine that may be present in the antioxidant after sulfurization is not detrimental and may be beneficial.
THE AMINE COMPOUNDS
The second component of the additive composition for use in lubricating oils may be a primary, secondary or tertiary amine or a hydroxy amine.
The Primary Amines The primary amines are mainly those compounds defined by the following formulas:

R-NH2 or R ~ N-(CH2) ¦ yNH2 or Het N~R4 ~ X

wherein each A is independently hdyrogen or Cl-C18 alkyl, R is alkyl or alkenyl of at least 6 carbon atoms, R4 is an alkylene of at least 2 carbon atoms, x is an integer from 2 to 4, y is an integer from 1 to 4, and Het is a carbon chain forming with the N
atom a 5- or 6-membered heterocyclic ring optionally containing in place of one carbon atom an additional N or 0 hetero atom, X

is hydrogen or, when y' is 1, NH2, and y' is 0 or 1.
Preferably A is hydrogen, x is 2, R contains at least 12 carbon atoms and R3 is alkyl of 2 to 12, more preferably 2 to -1~84~35 6, carbon atoms. Also, in the polyamine compounds, it is preferred that the R group have from about 30 to about 250, preferably 30 to 120, carbon atoms. R as polyisobutylene is particularly preferred for the polyamine compounds.
When R is alkenyl, the alkenyl portion preferably has 1 to 2 olefinically unsaturated linkages per molecule. If a totally saturated group, is desired, the compound containing, e.g. a polyisobutylene group, can be hydrogenated with hydrogen over a noble metal catalyst, such as platinum, using conventional hydrogenation techniques.
The R group may be either branched or unbranched hydrocarbon. In the monoamine compounds, R is preferably alkyl of 12 to 22 carbon atoms, and more preferably is octadecyl.
The heterocylic primary amines included within the invention have 5- or 6-membered heterocyclic rings containing at least one nitrogen atom and optionally an additional nitrogen or oxygen hetero atom. The heterocyclic ring designated He~__JN- can be saturated or unsaturated and is preferably piperazinyl, piperidinyl, imidazolyl, morpholinyl, pyrazolyl or pyridyl. The heterocyclic ring may be substituted by one or more alkyl groups which do not affect the synergistic activity of the amine.
The compounds included within the scope of the above formula are compounds whose methods of preparation are well known.
The Secondary Amines The secondary amines are primarily those of the formula (R1)2NH or He N-(R4) ,X

In the aliphatic amines each R is independently an aliphatic hydrocarbon group. The total number of carbon atoms in the groups must be sufficient to render the compound oil soluble.

1~84~5 Preferably each R contains from 6 to 30 carbon atoms, and more preferably from 6 to 18 carbon atoms. In preferred compounds, R
and Rl are saturated, straight-chain alkyl radicals.
For the heterocyclic compounds, Het is a carbon chain forming with the N atom a 5- or 6-membered heterocyclic ring optionally containing in place of one carbon atom an additional N
or O hetero atom, and y' is O or 1. When y' is 0, X is hydrogen.
When y' is 1, R4 is alkylene of at least 2 carbon atoms and X is hydrogen or HNA wherein A is Cl-C18 alkyl. When X is hydrogen, the ring Het N- contains an addition nitrogen atom bonded to one hydrogen atom. An example of this type of compound is an alkyl piperazine of the formula ~

The ring may be substituted by one or two alkyl groups that do not affect the synergistic activity of the amine.
The preparation of these compounds is well known in the art. Typical compounds are di-n-decylamine, di-n-hexadecylamine, di-n-octadecylamine, and the like. Other typical compounds are those where the hydrocarbon portion of the compound is derived from mixtures of fatty acids. Preferred are those mixtures derived from coconut oil or soya bean oil. The amine derived from coconut oil (designated "dicocoamine") is particularly preferred. The coconut oil is hydrolyzed to yield an amine wherein each R group contains from 6 to 18 carbon atoms and the majority of the R groups contains 10, 12 or 14 carbon atoms.
The Tertiary Amines The oil-soluble tertiary amines are primarily those of the formula (R2)3N or He N-(R4) ,-X. In the non-heterocyclic compounds, each R2 is independently C3-C10 alkyl, phenyl, or 1~84Q~5 phenyl substituted by 1 or 2 alkyl groups of up to 12 carbon atoms.
Preferably each R is the same and is selected from C3-C6 alkyl or phenyl.
Typical alkyl-substituted phenyl groups include tolyl, xylyl, tetrapropenylphenyl, octylphenyl, and the like.
For the heterocyclic compounds, Het is a carbon chain forming with the N atom a 5- or 6-membered heterocyclic ring optionally containing in place of one carbon atom an additional N
or 0 hetero atom, R4 is alkylene of at least 2 carbon atoms, y' is 1, and X is hydrogen or -NA2 where each A is independently Cl-C18 alkyl. Each N atom has no bonds directly to a hydrogen atom.
The ring may be substituted by one or two alkyl groups that do not affect the synergistic activity of the amine.
The compounds are conventional compounds that can be prepared by well-known methods.
The Hydroxy Amines The oil-soluble hydroxy amines are primarily those of the formula y 3 X-,N~A2-OH)x, or Het N~R4~ ,X

wherein each A and A is independently C2-C10 alkylene, R is Cl-C30 alkyl, Y is H, Cl-C6 alkyl or -Al-OH, y" is 0, 1 or 2, and x' is 1 or 2, Het is a carbon chain forming with the N atom a 5-or 6-membered heterocyclic ring, optionally containing in place of one carbon atom an additional N or 0 hetero atom, R4 is alkyl of at least 2 carbon atoms, y' is 1, and X is OH.
Particularly preferred heterocyclic compounds are those of the formula 1~84~}5 N ~ N-(R4) ,OH

In a preferred non-heterocyclic embodiment, A is ethylene and A is trimethylene, Y is H or -A2-OH, R3 is Cl-C20 alkyl, and most preferably C16-C18 alkyl, x' is 2 and y" is 1.
The preparation of the imidazoline compounds is disclosed in United States Patents 2,974,022, 2,839,371,

2,839,372 and 2,839,373.
The compounds included within the scope of the above formula are compounds whose methods of preparation are well known.
THE OIL-SOLUBLE ZINC SALT
The zinc salts which may be used in this invention are oil-soluble zinc salts. They are used in the lubricating oil to supply from 9 to 40 mmols of zinc per kilogram of oil.
The zinc salt is preferably a zinc dihydrocarbyldithio-phosphate having from 4 to 20 carbon atoms in each hydrocarbyl group. The zinc dihydrocarbyldithiophosphate is formed by reacting the corresponding dihydrocarbyldithiophosphoric acid with a zinc base, such as zinc oxide, zinc hydroxide and zinc carbonate. The hydrocarbyl portions may be all aromatic, all aliphatic, or mix-tures thereof.
Exemplary zinc dihydrocarbyldithiophosphates include:
zinc di~n-octyl~dithiophosphate, zinc butyl isooctyl dithiophosphate, zinc di(4-methyl-2-pentyl)dithiophosphate, zinc di(tetrapropenylphenyl)dithiophosphate, zinc di(2-ethyl-1-hexyl)dithiophosphate, zinc di(isooctyl)dithiophosphate, zinc di(hexyl)dithiophosphate, zinc di(ethylphenyl)dithiophosphate, i~84~35 zinc di(amyl)dithiophosphate, zinc di(alkylphenyl)dithiophosphate, zinc butylphenyldithiophosphate, and zinc di(octadecyl)dithiophosphate.
Preferred compounds are those zinc dihydrocarbyl- -dithiophosphates having from 4 to 18 carbon atoms in each hydrocarbon group. Especially preferred are the zinc dialkyldithiophosphates wherein each alkyl group typically contains from 4 to 8 carbon atoms and the zinc di(alkylaryl)-dithiophosphates wherein each alkylaryl group contains from 15 to 21 carbon atoms.
The lubricating oil composition is prepared by admixing, by conventional mixing techniques, the desired amount of antioxidant and amine in a suitable lubricating oil. The selection of the particular base oil and amine, as well as the amounts and ratios of each, depends upon the contemplated application of the lubricant and the presence of other additives.
Generally, however, the amount of oil-soluble antioxidant employed in the lubricating oil will vary from 0.25 to 10, and usually from 0.25 to 2, weight percent. The primary amine will range from 0.01 to 2, and usually from 0.01 to 0.3, preferably from 0.05 to 0.3, weight percent based on the weight of the final composition. The weight ratio of oragnic oil-soluble antioxidant to amine will generally vary from 5-20 to 1, and usually from 10-20 to 1.
Concentrates of the new additive composition of this invention can be prepared for easier handling and storage of the additive. Usually the concentrate will be 10 to 90% by weight additive composition and from 10 to 90% by weight lubricating oil diluent. Preferably the additive composition comprises 20 to 80%
by weight of the lubricating oil additive concentrate. This concentrate is diluted with additional oil before use.

1~4~35 The lubricating oil which may be used includes a wide variety of hydrocarbon oils such as naphthenic base, paraffin base, and mixed base oils. Other oils include lubricating oils derived from coal products and synthetic oils, e.g., alkylene polymers (such as propylene, butylene, and so forth, and mix-tures thereof), alkylene oxide-type polymers (e.g~ alkylene oxide polymers prepared by polymerizing alkylene oxides, such as ethy-lene oxide, propylene oxide, etc. in the presence of water or alcohol, e.g. ethyl alcohol~, carboxylic acid esters ~e.g. those which are prepared by esterifying carboxylic acids, such as adipic acid, azelaic acid, suberic acid, sebacic acid, alkenyl-succinic acid, fumaric acid, maleic acid and so forth, with an alcohol such as butyl alcohol, hexyl alcohol, 2-ethylhexyl alcohol, pentaerythritol and so forth, liquid esters of phos-phorus-containing acids such as trialkyl phosphate, tricresyl phosphate, etc., alkylbenzenes, polyphenyls (e.g., biphenyls and terphenyls), alkylbiphenyl ethers, esters and polymers of silicon, e.g., tetraethylsilicate, tetraisopropylsilicate, hexyl(4-methyl-2-pentoxy)disilicate, poly(methyl)siloxane, and poly(methylphenylsiloxane) and so forth. The lubricating oils may be used individually or in combinations whenever miscible, or whenever made so by use of mutual solvents. The lubricating oils generally have a viscosity which ranges from 50 to 5000 SUS
(Saybolt Universal Seconds), and usually from 100 to 1500 SUS at 100F.
In addition to the antioxidant, the amine compound and the oil-soluble zinc salt, other additives may be used in the lubricating composition without affecting its high stability and performance over a wide temperature scale. One type of additive which may be used is a rust inhibitor. The rust inhibitor is used in many types of lubricants to suppress the formation of - 1~84035 rust on the surface of metallic parts. Typical rust inhibitors include sodium nitrite, alkenylsuccinic acid and derivatives thereof, alkylthioacetic acid and derivatives thereof, poly-glycols and derivatives thereof, and alkoxylated amines and derivatives thereof. Other types of lubricating additives which may be used are metallic or ashless dispersants and detergents.
Typical of these are the conventional succinimides, succinates, hydrocarbylalkylene polyamines, alkaline earth metal salts of alkylaryl sulfonates, phenates and the like.
Other types of lubricating oil additives which may be used include antifoam agents (e.g., silicones, organic copolymers), stabilizers and antistain agents, tackiness agents, antichatter agents, dropping point improvers and antisquawk agents, lubricant color correctors, extreme-pressure agents, odor control agents, detergents, antiwear agents, thickeners, and so forth.
LUBRICANT PERFORMANCE
The presence of the amine in the lubricant composition increases the antioxidation properties of the oil-soluble, sulfur-containing antioxidant. With this combination, less of the anti-oxidant is necessary in the lubricant to achieve the desired antioxidation properties. If the antioxidant is used at conven-tional levels, increased oxidation protection is obtained.
The following examples are presented to illustrate the practice of specific embodiments of this invention and should not be interpreted as limitations on the scope of this invention.

The combination of the amines with this antioxidant in improving the antioxidation properties of a lubricating oil over the use of either of the components individually is illustrated by the following test. The oxidation test uses the resistance of 1~841D35 the test sample to oxidation using pure oxygen with a Dornte-type oxygen absorption apparatus (R.W. Dornte, "Oxidation of White Oils", Industrial and Engineering Chemistry, Vol. 28, page 26, 1936). The conditions are an atmosphere of pure oxygen exposed to the test oil maintained at a temperature of 340F. The time required for 100 g of test sample to adsorb 1000 ml of oxygen is observed and reported in the following Table I. The test oil in sections A, E, F and G is Midcontinent neutral oil containing 6% of a conventional succinimide dispersant, 0.05% terephthalic acid, 0.4% of a conventional rust inhibitor, and 9 m mols/kg of a zinc dithiophosphate.
The test oil in sections B, C and D is a refined mineral oil.

TABLE I
Oxidation Antioxidant 0.1% Primary Amine Life/Hrs.
_~_________________ __________________________________ _ ______________ __ __ 5.2 A) 1% diparaffin - 6.4 polysulfide 0.5 1% diparaffin dodecylamine 8.6 polysulfide " 2-ethylhexylamine 8.0 " Primene JMT * 7.1 " Duomeen T * 7.5 " oleyl-NH(cH2)3NH2 6.6 " PB12EDA 6.9 24EDA o . 66 1% diparaffin 24 9.8 polysulfide 32EDA5 8.0 - N-(2-aminoethyl)piperazine 5.2 1% diparaffin " 10.1 polysulfide *Trade mark C~.

-1 - bis(aminopro~yl~ethylene di~mine 4.8 2 lh diparaffin ll 10.4

3 polysulfide

4 B)50 mmols/kg diparaf- - 3.18 fin polysulfide 6 (18.0~ S) 7 " 10 ~mols/kg octadecylamine 15.75 8 ~' (l5.9~ S) - 4.80 9 " " 10 mmolsfkg octadecylamine 17.77 50 mmols/kg sulfur- - 2.33 11 ized ester (9.88~ S) 12 " 10 mmols/kg o~tadecylamine 5.17 13 " (14.5~ S) - 1.03 14 " " 10 mmols/kg octadecylamine 4.80 C)50 mmols/kg diparaf- - 5 16 fin polysulfide 17 " 2.5 mmols~kg octaae_ylamine 11 18 " 10 " " 18 19 " 20 " ~' . 18 " 50 " " 21 21 D)32.5 mmols/kg diparaf- - 0.9 22 fin polysulfide 23 " 2.5 mmols/kg octadecylamine 1.3 24 " 10 " " 9.5 " 20 " " 3.0 26 ~ 50 - " 9 5 27 25 " - 0 28 " 2.5 mmols~kg octade_yla~ine 0 29 ~ 10 ~ 0.8 " 50 " " 1.3 31 ~C~3 32 ~R-~ NH2 where the R group has approximately 33 ~ 18 carbon atoms 34 ~H3 1~84~35 C 1 8H37NH (CH2) 3NH2 Reaction product of ethylene diamine (EDA) and polyisobutenyl chloride having a number average molecular weight of 530.
Reaction product of EDA and polyisobutenyl chloride having a number average molecular weight of 950.
5Reaction product of EDA and polyisobutenyl chloride having a number average molecular weight of 1400.
6Base oil contains no zinc dithiophosphate.
Oxidation E) Antioxidant Secondary Amine Life/Hrs.
- 0.1% dicocoamine 0.48 1% diparaffin - 6.1 polysulfide " 0.1% dicocoamine 8.9 " 0.2% di-n-hexylamine 13.8 " 0.1% disoyamine 7.4 " 0.1% dioctylamine 8.6 " 0.1% di(2-ethylhexyl)amine8.6 Base oil without zinc dithiophosphate Average of 3 tests Oxidation F) Antioxidant Tertiary Amine Life/Hrs.
1% diparaffin - 6.4 polysulfide " 0.1% tributylamine 7.5 1~84~35 Oxidation G2 Antioxidant Hydroxy Amine Life/Hrs _ 5.1 _ 0.1% A4 4.6 1% diparaffin - 6.4 polysulfide ,. 0.1% A4 8.6 " 0.1% Ethomeen 18-121* 8.5 " 0.1% Ethoduomeen T-122*9.4 " 0.1% Ethoduomeen T-133*7.2 Cl8H37N~cH2cH2oH)2 2C18H37-~-CH2CH2CH2-N~CH2CH2 )2 H

18H37 7-CH2cH2cH2-N~cH2cH2oH)2 R

4A is N / \ N-CH2CH20H where R is C12 C17 y The resistance to increase in viscosity of lubricating oils containing an antioxidant composition of this invention as compared to antioxidant alone is illustrated by the following engine test. In this test, an Oldsmobile* engine is charged with 10.65 pounds of the oil to be tested. The engine is then started and run for 2 minutes at 850 rpm with no load. The rpm's are then increased to 1500 with a 50-pound load and 450 psi oil pressure, and the engine is run for 8 minutes. The engine is shut down with the oil circulating for 10 minutes. The oil pump is then shut down and the oil sampled after 5 minutes. This procedure is repeated until the viscosity of the oil increases 500%. The number of hours elapsed during the test is recorded.

* Trade mark ' I - 19 -i~841~5 The base oil used in this test is a Midcontinent neutral oil having a viscosity of 350 SUS at 100F, 6% wt of a conventional succinimide dispersant, 0.05% wt of terephthalic acid, and 0.4~ wt of a conventional rust inhibitor. The results of this test are reported in Table II.
TABLE II

Hours to reach Antioxidant Secondary Amine 500% Visc. 100F

2% diparaffin polysulfide - 52 1% diparaffin 232% vis. incre~se polysulfide 0.1% dicocoamine after 142 hours lEngine test was terminated because of electronic problems.

AntioxidantHydroxy Amine Hours 500% Visc. 100F

2% diparaffin polysulfide - 52 2% diparaffin polysulfide 0.2% Al 93 A is as defined at page 19, line 21.
The test procedure of Example 2 was repeated in a formulation containing 6% of a conventional succinimide dispersant, 40 mmols per kg of a calcium phenate and 18 mmols per kg of a zinc dithiophosphate. The results are shown in Table III.

TABLE III
Hours to 500%
AntioxidantSecondary Amine Yisc. Incre~se _ _ 44,56 2% diparaffin polysulfide - 92 2% diparaffin polysulfide 0.2% dicocoamine 123 2% sulfurized cracked wax olefin (13% S) 0.2% dicocoamine 72 2% sulfurized cracked wax olefin ~24% S) 0.2% dicocoamine ~166 The symbol > means "greater than".

~,v

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. An additive composition for use in crankcase lubricating oils comprising:
(1) an oil-soluble antioxidant selected from aromatic or alkyl sulfides and polysulfides, sulfurized olefins, sulfurized carboxylic acid esters, and sulfurized ester-olefins, and (2) an amine of the formula R-NH2, (R1)2NH, (R2)3N, , or , wherein each R is independently alkyl or alkenyl of at least 6 carbon atoms, each R1 is independently an aliphatic hydrocarbon group, each R2 is independently C3-C10 alkyl, phenyl, or phenyl substituted by 1 or 2 alkyl groups of 1-12 carbon atoms, R3 is C1-C30 alkyl, R4 is alkylene of at least 2 carbon atoms, each A is independently hydrogen or C1-C18 alkyl, each Al and A2 is independently C2-C10 alkylene, X is hydrogen, -OH, or -NA2, Y is hydrogen, C1-C6 alkyl, or A1-OH, x is an integer from 2 to 4, x' is 1 or 2, y is an integer from 1 to 4, and y" is 0, 1 or 2 and wherein the weight ratio of said antioxidant to said amine is 1:0.001-21.

2. A lubricating oil concentrate comprising from 90-10% by weight of an oil of lubricating viscosity and from 10-90% by weight of the composition of Claim 1.

3. A lubricating oil composition comprising an oil of lubricating viscosity and an antioxidant amount of the composition of Claim 1.

4. The composition of Claim 3 wherein the amine is a primary amine of the formula R-NH2 or in which R is alkyl of at least 12 carbon atoms, A is hydrogen, and x is 2.

5. The composition of Claim 3 wherein the amine is octadecylamine or N-(2-aminoethyl)piperazine.

6. The composition of Claim 3 wherein the amine is a secondary amine.

7. The composition of Claim 6 wherein the amine is (R1)2NH in which each R1 is C6-C18 alkyl.

8. The composition of Claim 7 wherein the amine is dicocoamine.

9. The composition of Claim 3 wherein the amine is a hydroxyamine.

10. The composition of Claim 9 wherein A2 is ethylene, A1 is trimethylene,Y is hydrogen or A2OH, R is C12-C20 alkyl, x is 2 and y is 0 or 1.

11. The composition of Claim 10 wherein the amine is

12. The composition of Claim 1 wherein the antioxidant is a wax sulfide or polysulfide.

13. The composition of Claim 1 which also contains an antioxidant-antiwear amount of an oil-soluble zinc salt.

14. The composition of Claim 13 wherein the zinc salt is a zinc dihydrocarbyldithiophosphate.

15. A method for preparing a lubricating oil composition of Claims 4-12 which comprises admixing (1) an oil-soluble antioxidant selected from aromatic or alkyl sulfides and polysulfides, sulfurized olefins, sulfurized carboxylic acid esters, and sulfurized ester-olefins, and (2) an amine of the formula R-NH2, (R1)2NH, (R2)3N, , wherein each R is independently alkyl or alkenyl of at least 6 carbon atoms, each R1 is independently an aliphatic hydrocarbon group, each R2 is independently C3-C10 alkyl, phenyl, or phenyl substituted by 1 or 2 alkyl groups of 1-12 carbon atoms, R3 is C1-C30 alkyl, R4 is alkylene of at least 2 carbon atoms, each A is independently hydrogen or C1-C18 alkyl, each A
and A2 is independently C2-C10 alkylene, X is hydrogen, -OH, or -NA2, Y
is hydrogen, C1-C6 alkyl, or A1-OH, x is an integer from 2 to 4, x' is 1 or 2, y is an integer from 1 to 4, and y" is 0, 1 or 2, the oil soluble antioxidant being mixed with the amine in a weight ratio of antioxidant to amine of 1:0.001-21.

16. A method of protecting a lubricating oil from oxidation which comprises adding to the oil the antioxidant additive composition of Claim 1.