CA2105132A1 - Substituted 1, 2, 4-triazole containing lubricants having improved oxidation stability - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

The addition of substituted 1,2,4-triazole compounds to a lubricant imparts improved oxidation stability to the lubricant. The oxidation stability is particularly enhanced when the substituent contains an aromatic moiety such as benzene or a substituted benzene ring.

Description

21~3~1 32 BACKGROUND OF THE INVENTION

1. Field of the Invention Thi0 invention concerns lubricating compo~itions having improved oxidation stability due to the presence of a substituted 1,2,4-triazole compound.

2. Description of Related Art Oxidation stability is an important requirement for all lubricants, including automotive lubricating oils, indu~trial oils, and grea~es. The major cause of oxidative instability is the auto-oxidative breakdown of hydrocarbons in the lubricant~ and the concomi-tant formation of acids and other undesirable oxygenated species, including sludge. Auto-oxidative breakdown i9 strongly catalyzed by traces of metal ions (especially copper and iron) which become solu-bilized when the lubricant contaat~ a metal surface. One way to control auto-oxidation is to add one or more metal deactivators to the lubricant. In general, these deactivators prevent such undesirable catalytLc reactions from occurring in two different way~: The metal deactivators form impervious films on the metal surface, thereby preventing dissolution of the metal ions (these are called "film forming metal passivators~ or the metal deactivators form complexe~
with solublized metal ions, thus rendering them inactive as catalysts ~these are called "301uble metal deactivators~
: ' The use of substituted 1,2,4-triazoles in various composi-tions i~ known. For example, U.S. Patent 4,734,209 disclo3ec the use of certain N-substituted 1,2,4-triazoles as metal deactivators in functional fluids. See al~o V.S. Patents 3,647,814 and 3,663,436.
~ .
However, these patents (the di~clo~ures all of which are incorporated herein by reference) do not disclose the particular sub~tituted 1,2,4-tria~ole containing lubriaant compositions described hereafter.

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2 ~ 2 SUMMARY OF T~E INVENTION

This invention concerns lubricant compositions containing oxidation reducing amounts of certain triazoles. More specifically, we have discovered that the oxidation stability of a lubricant can be improved when the lubricant contains a minor amount of a substituted 1,2,4-triazole having structure I shown below:
N C
Il 11 . ..
C N
N / R1 (I) wherein R1 is ~ and R2 is an aromatic moiety. Preferably, R2 is an aromatic moiety such as benzene or a substituted benzene ring.

DETAILED DESCRIPTION OF THE INVENTION

In general, the lubricants of this invention will comprise a major amount of a lubricating oil basestock (or base oil or oil of lubricating vi3cosity) and a minor amount of the substituted 1,2,4-triazole additive~ having istructure I above.

The lubricating oil basestock can be derived from natural lubricating oils, synthetic lubricating oils, or mi~tures thereof. In general, the lubricating oil basestock will have a kinematic viscosity ranging from about 5 to about 10,000 cSt at 40C, although typical applications will reguire an oil having a viscosity ranging from ahout 10 to about 1,000 cSt at 40C.

Natural lubricating oils include animal oils, vegetable oils (e.g., castor oil and lard oil), petroleum oils, mineral oil~, and oils derived from coal or shale.

2 ~ 2 Synthetic oils include hydrocarbon oils and halo-substituted hydrocarbon oils ~uch as polym~rized and interpolymerized olefins ~e.~. polybutylenes, polypropylene~, propylene-isobutylene copolymers, chlorinated polybutylenes, poly(1-hexenes), poly(1-octene~)~ poly(l-decenes), etc., and mixture~ thereof); alkylbenzenes (e.~. dodecyl-benzene~, tetradecylbenzeneq, dinonylbenzenes, di(2-ethylhexyl)-benzene, etc.); polyphenyls (e.q. biphenyls, terphenyls, alkylated polyphenyls, etc.); alkylated diphenyl ethers, alkylated diphenyl sulfides, a~ well as their derivativ~s, analogs, and homolog~ thereof;
and the like.

Synthetic lubricating oil~ also include alkylene oxide polymers, inter~olymers, copolymers and derivatives thereof wherein the terminal hydroxyl groups have been modified by e~terification, etherification, etc. Thi~ class of synthetic oils is exemplified by polyoxyalkylene polymers prepared by polymerization of ethylene oxide or propylene oxide; the alkyl and aryl ethers of these polyoxyalkylene polymers (e.g., methyl-polyiqopropylene glycol ether having an average molecular weight of 1000, diphenyl ether of polyethylene glycol having a molecular weight of 500-1000, diethyl ether of polypropylene glycol having a molecular weight of 1000-1500); and mono- and polycarboxylic ssters thereof (e.~., the acetic acid esters, mixed C3-Cg fatty acid e~ters, and C13 oxo acid diester of tetraethylene glycol).

Another suitable class of synthetic lubricating oils com-prise~ the ester~ of dicarboxylic acids (e.g., phthalic acid, succinic acid, alkyl succinic acids and alkenyl succinic acid~, maleic acid, azelaic acid, quberic acid, sebasic acid, fumaric acid, adipic acid, linoleic acld dlmer, malonic acid, alkylmalonic acids, alkenyl malonic acids, etc.j with a variety of alcohols (e.~., butyl alcohol, hexyl alcohol, dodecyl alcohol, 2-ethylhexyl alcohol, ethylene glycol, di-ethylene glycol monoether, propyl ne glycol, etc.). Specific examples of thesa esters include dibutyl adipate, di(2-ethylhexyl) sebacate, di-n-hexyl fumarate, dioctyl sebacate, diisooctyl azelate, dilsodecyl azelate, dioctyl phthalate, didecyl phthalate, dieicosyl sebacate, the 2-ethylhexyl diester of linoleic acid dimer, and the complex e~ter ~ : ' `- 2 ~ 3 ~
_ 4 _ formed by reacting one mole of sebacic acid with two moles of tetra-ethylene glycol and two moles of 2-ethylhexanoic acid, and the like.

Esters useful as synthetic oils also include those ~ade from Cs to C12 monocarboxylic acids and polyols and polyol ethers such as neopentyl glycol, trimethylolpropane, pentaerythritol, dipentaerythri-tol, tripentaerythritol, and the like.

Silicon-based oils (such as the polyakyl-, polyaryl~, poly-alkoxy-, or polyaryloxy-siloxane oils and silicate oils) comprise another useful class of synthetic lubricating oils. These oils include tetraethyl silicate, tetraisopropyl silicate, tetra-~2-ethyl-hexyl) silicate, tetra-(4-methyl-2-ethylhexyl) silicate, tetra(p-tert-butylphenyl) silicate, hexa-(4-methyl-2-pentoxy)-disiloxane, poly-(methyl)-siloxanes and poly(methylphenyl) siloxanes, and the like.
Other synthetic lubricating oils include liguid esters of phosphorus-containing acids (e.~., tricresyl phosphate, trioctyl phosphate, diethyl ester of decylphosphonic acid), polymeric tetrahydrofurans, polyalphaolefins, and the like.
:' The lubricating base oil may be derived from unrefined, refined, rerefined oils, or mixtures thereof. Unrefined oils are obtained directly from a natural source or synthetic source (e.~., coal, shale, or tar sands bitumen) without further purification or treatment. Examples of unrefined oil3 include a shale oil ob-tained directly rom a retorting operation, a petroleum oil obtained directly from distillation, or an ester oil obtained directly from an esteri-fication procss~, each of which is then used without further treat-ment. Refined oil~ are similar to the unrefined oils except that refined oils have been treated in one or more purification steps to improve ona or more propertie3. Suitable purification techniques include distillation, hydrotreating, dewaxing, solvent extraction, acid or ba~ extraction, filtration, and percolation, all of which are known to those skilled in the art. Rerefined oils are obtained by treating refined oils in processes similar to those used to obtain the refined oils. These rerefined oils are also known as reclaimed or :, ' - : :~. -. - ., , , , ,' : .

2 1 ~ 2 reprocessed oils and often are additionally processed by techniques for removal of spent additives and oil breakdown products.

The aromatic substituted triazole additives of this invention have structure ~I) shown above where R1 and R2 are defined as above.
Suitable aromatic moieties include anthrancenyl, naphthyl, phenan-thryl, phenyl, their substituted analogs, and the like. Substituted analogs of naphthyl and phenyl are preferred, with substituted phenyl having the structure ~ being more preferred, wherein R3 i9 hydrogen, an alkyl group having from 1 to 10 carbon atoms, or a radical selected from the group consisting of -OR4 or -NR5R6, where R4, R5, and R6 are hydrogen or an alkyl group containing from 1 to 4 carbon atoms. R4, R5, and R6 may be the same or different, and preferably are all methyl. Pref~rably, R3 i9 hydrogen or an alkyl group of from 1 to 4 carbon atoms, with the alkyl group in the meta or para position relative to the nitrogen atom. Most preferably, R3 i9 methyl. The triazole additives of this invention should be oil soluble.

Compounds having structure I can be prepared, for eiiample, by reactlng 1,2,4-triazole, formaldehyde, and an amine in an aqueous medium or in various solvents (e.~. ethanol, methanol, benzene, or toluene). Approximately equimolar amounts of 1,2,4-triazole and aromatic amine are mixed in a solvent provided that care i9 taken to avoid an excess of the 1,2,4-triazole. Formaldehyd~ (commercially available in aqueous solution with a polymerization inhibltor) i5 then added to the triazole/amine mixture. After completion of the reac-t$on, solvent is removed leaving a substituted 1,2,4-triazole of the structure (I). It is important to follow the sequence of mixing reactants set forth above. I~ these precautions are not taken, a N,N-bis 1,2,4-triazolyl derivative will result. Furthermore, if an alkyl amine i9 used a~ a reactant in place of an aromatic amine, the N,N-bis 1,2,4-triazolyl compound will be obtained without regard to the order of addition oi reactants, e.g., ;:, .-.

:, . , .. . : . , , . . , , .; . .. ... . , . . . , ., , ., : , .:, .. . .
. , : : .. : .: : . :. .: . : .: . . . . ... : ; : : :,: . . .: . : . :

2 1 ~ 2 HC - N
Il 11 . ' N - CH NCH N CH
ll il HCHO 11 ¦¦ \ /
2 HC N + C2H5NH2 --------> HC N N
\

H

The amount of substituted 1,2,4-triazoles added to the lubricant compositions of this invention need only be an amount 3ufficient to increaqe the auto-oxidative stability of the lubricant relative that obtained in the absence of the additive. In general, the amount of additive can range from about 0.01 up to about 5 weight~
or more ~based on the total weight of the composition), depending upon the specific application of the lubricant. Typically, however, from about 0.01 to about 2 wt.% of the additive will be used to ensure solubility of the additive and for economic consideration~. Prefera-bly, the amount of additive used will range from about 0.01 to abcut 1, more preferably from about 0.02 to about 0.2, wt~.

Other additives may be present in the lubricant compositions of this invention a3 well, depending upon the intended use of the composition. Examples of other additives include ash-free detergents, disper~ants, corrosion preventing agcnts, other antioxidants, pour-point depreasants, extreme pressure agents, viscosity improvers, ~colosants, anti~oamer~, and the li~e.

Lubricants containing the substituted 1,2,4-triazol'e addi-tives of this Lnvention can be used in essentially any application requiring a lubricant having good oxidation stability. Thus, as u~ed herein, "lubricant" (or "lubricant compo3ition") i meant to include automotive lubrlcating oils, industrial oils, grea3es, and the like.
For example, the lubricant compositiona of this invention can be u~ed in the lubrication ~ystem of essentially any internal combustion engine, including automobile and truck engines, two-~ycle~ engine~, aviation piston engines, marine and railroad engine~, and the like.

,."' ' ~lso contemplated are lubricants for gas-fired engines, alcohol (e.g.
methanol) powered engines, stationary powered engine~, turbines, and the like.

However, the lubricant composition_ of this invention are particularly useful in industrial oils such a3 turbine oils, gear oils, compre_sor oils, hydraulic fluids, spindle oil~, high speed lubricating oils, process oils, heat transfer oils, refrigeration oils, metalworking fluid~, and the like.

This invention will be further understood by referencP to the following examples, which include preferred embodiments of this invention, but which are not intended to restrict the scope of the claim~. In Examples 1-3, various substi~uted 1,2,4-triazole compoundq were added to sampie~ of a lubricating oil. Preparation of the substituted triazole~ is given below. Several different oxidation tests were then performed on the samples to determine their oxidation stability. Unless otherwise stated, the lubricating oil used in Examples 1-2 was a partially formulated lubricating oil consisting of a Solvent 150 Neutral base oil containing 0.04 wt.% of a rust inhibi-tor and 0.2 wt.% of a phenolic antioxidant. The sub~tituted triazole compounds tested included various aromatic sub~tituted 1,2,4-triazole additives having ~tructure I and a commercially available additive, which is believed to have structure II shown below (l-di-2-ethylhe~
aminomethyltriazole):
N C
Il 11 \ / I
N C-C-C-C-C-C (II) C~l2 N l2H5 C--C--C--C--C--C

wherein R1 and R2 are each C-C-C-C-C-C.

2 1 U ~7 ~ 3 ~

Preparative Example A

0.08 mmoles of 1,2,4-triazole and 0.08 mmoles o~ 4-butyl-aniline are added to 30 ml of methanol. 6 ml of a 37% solution of formaldahyde (0.08 moles) is then added and the reaction mixture allowed to stand overnight. Methanol was removed by distillation and product having ~tructure (I) wherein R2 is ~ C4Hg was isolated.

Pre~arative Examole B

0.3 moles of 1,2,4-triazole and 0.3 moles of p-toluidine were added to methanol and stirred until the reactants dissolved. 0.3 moles formaldehyde (as 37% solution) was added and ths reaction mixture ~tirred for several hours. Upon removal of methanol, a product having structure (I) wherein R2 is ~ CH3 waB isolated.

In Examples 1-3, one or more of the following tsst~ were performed to determine the oxidation stability of several lùbricant formulation3 containing the various additives.

CIGRE ~IP 280) OxLdation Test : '~
The CIGRE test measures the ability of an additive to deacti-vate soluble copper and iron. In this tes'c, the oil i9 oxidized at 120C for 164 hours in the presence of a catalyst containing soluble copper naphthenate and soluble iron naphthenate. An oxygen flow rate : .
of 1 liter/hr i3 maintained during the test. The Total Acid Number (TAN) and the weight percent sludge produced during the test were .
determined and used to calcuIate the Total Oxidation Products (TOP~
using the following equation:

TOP = 3 + wt. ~ sludge :
Lower TOP values indicate greater oxidation stability.

-- -- . . .

Rotarv Bomb Oxidation Test ~BOT) This test i~ described in ASTM D2272 and measures the effec-tiveness of an additive to deactivate a solid copper catalyst. In this test, the oil i8 oxidi~ed in the presence of a copper wire catalyst and water. The ~life~ of the test oil is the time requirsd for the oil to r~act with a given amount of oxygen. The longer the "life", the More stable the oil formulation (l.e. the more effective the antioxidant).

Universal Oxidation Test ~UOT) This is a high temperature oxidation test de~igned to deter-mine the effectiveness of additives to deactivate a mixture of solid copper and iron catalysts. Air i3 blown through the oil at a rate of 3.0 liters/hr and at a temperature of 135C. A water condenser is employed to condense volatile products. The effectiveness of the antioxidant is determined by measuring the time required for the acid titre of the oil to increase by 0.5 neutralization number (mg ROH/g oil). The longer the life, the more effective the antioxidant.

E~ample 1 - CIGRE Tests on the Partially Fo~mulated Oil CIGRE tests were performed on several samples of the par-tially formulated oil to which variou3 1,2,4-triazole compounds had been added. The initial concentration of each additive in thi3 example (and in Examples 2 and 3) was about 2 x 10-4 moles/100 g oil to ensure that the additives were tested on a equal molar basis. As such, the wt.~ of the additives in the tables will vary with the molecular weight of the additive. The results of these test~ are shown in Table 1 below.

, . ,, .-.. . . .

210~132 Wt. ~ CIGRE TOP
Additive Additive Rl R2 (ll None 0 -- -- 4.0 Structure I 0.05 H ~ -C4H9 0.72 Structure II 0.08 (2) (2) 3.6 (1) An average o~ two to four run~.

(2) C-C-C-C-C-C-Example 2 - RBOT and UOT Tests on the Partially Formulated Oil RBOT and UOT tests were performed on ~everal formulations similar to those tested in Example l, except that the additives were tested on a equal weight rather than equal molar basis. The re~ults of these test~ are 3hown in Table 2 below.

Wt. % RBOT Life UOT Life Additive Additive R1 R2 ~Minl (1) ~Hrl (1) Nonç 0 -- -- 127 45 Structure II 0.08 (2) (2) 315 158 Structure I 0.08 ~ - ~ -C4Hg 369 835 Structure I 0.08 H ~ 375 985 Structure I 0.08 H - ~ -CH3 420 920 (1) An average of two to 9iX runs.
f2H5 (2) C-C-C-C-C-C-'. ' ~ '',, ; .~ ' '. ' ' '' , ~. ' -~ 2~i3~

Exam~le 3 - RBOT and UOT Tests on Fully Formulated Oil ~ OBT and UOT Tests were performed on a Eully formulated oil containing (in addition to an additive of thi~ invention) a rust inhibitor, a phenolic antioxidant, a flow improver, an amine anti-oxidant, and a pour depressant. The results of these tests are shown in Table 3 below.

Wt. % RBOT Life U~T Life Additive Additive Rl R2 (Min) tl) IHr) (1 Structure II 0.0~ (~) (2) 730 423 Structure I 0.08 H - ~ -C4Hg 760 799 Structure I 0.08 H ~ 490 670 Structure I 0.08 H - ~ -CH3 -- 738 (1) An average of two runs.
I2H5 ~ : :
(2) C-C-C-C-C~C-~ ' The data in Tables 1 and 2 show that the additives of this invention impart oxidation stability to lubricant formulations that do not contain such additives. The data in Table 1 also show that formulations containing the 1,2,4-triazole compounds of this invention impart equivalent improvement in oxidation stability as a commercially available additive, but at a lower concentration. Further, the data in Tables 2 and 3 show that the formulations containing the 1,2,4-triazole compounds of this invention have greater oxidation stability than formulation~ containing commercially available additives at the same concentration.

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- .. ., :, . . . ,, . ~ , ,: " :. . :. , ;. . :, : :: ~ : . : . :

Claims (10)

1. A lubricant composition comprising a major amount of a lubricating base oil and a minor amount of an additive having the formula:

wherein R1 is hydrogen and R2 is an aromatic moiety.

2. The composition of claim 1 wherein the aromatic moiety is anthrancenyl, naphthyl, phenanthryl, phenyl, or their substituted analogs.

3. The composition of claim 2 wherein the aromatic moiety is a substituted analog of naphthyl or phenyl.

4. A lubricant composition comprising a major amount of a lubricating base oil and a minor amount of an additive having the formula:

wherein R1 is hydrogen and R2 is wherein R3 is hydrogen, an alkyl group containing from 1 to 10 carbon atoms, or a radical selected from the group consisting of -OR4 or NR5R6 in which R4, R5, and R6 are hydrogen or an alkyl group containing from 1 to 4 carbon atoms.

5. The composition of claim 4 wherein R3 is hydrogen.

6. The composition of claim 5 wherein R3 is alkyl group containing from 1 to 4 carbon atoms.

7. The composition of claim 6 wherein R3 is a methyl group.

8. The composition of claim 7 wherein the methyl group is in the para position relative to the nitrogen atom.

9. The composition of claim 7 wherein the methyl group is in the meta position relative to the nitrogen atom.

10. The composition of claim 4 wherein R4, R5, and R6 are each a methyl group.