CA1152975A - Lubricant compositions containing antioxidant mixtures of thiazoles and thiadiazoles - Google Patents

Abstract

Lubricant compositions contain an adduct of a benzotriazole compound and an alkyl vinyl ether or a vinyl ester of a carboxylic acid in combination with an alkyl dimercapto thiadiazole as an anti-oxidant and corrosion inhibitor.

Description

llSZ~7~i F-0152 ~UBRICANT COMPOSITIONS CONTAINING ANTIOXIDANT
MIXTURES OF THIAzoLEs AND THIADIAZOLE~

The invention relates to lubricant co~lpositions which are normally susceptible to oxidative deterioration.
Triazoles have been employed in lubricant compositions as metal deactivators. For example U.~.
Patent No. 3,597,353 discloses the use of tetxahydrobenzotxiazole as a metal deactivating additive for natural and synthetic lubricants. Similarly, U.S. Patent No. 3,413,227 describes the use of C2-C20 alkyl-substituted benzotriazole as corxosion or tarnish inhibitors. U.S.
Patent No. 4,060,491 discloses the use of 5-alkyl benzotriazoles, for reducing wear between moving steel-on-steel surfaces.
Reaction products of benzotriazoles are also known. For example, U.S. Patent No. 3,788,993 describes the reaction of benzotriazoles with alkyl or alkenyl succinic anhydrides to form pxoducts which impart corrosion inhibiting properties to lubricating oils.
U.~. Patent No. 4,048,082, discloses the use of esters of adducts of benzotriazole and unsaturated dicarboxylic acids or anhydrides for imparting antirust properties to organic compositions.
~Je now found that combinations of benzotriazole adducts with certain thiadiazoles have extremely valuable properties. In particular, they confer good antioxidation and corrosion-resistant properties on lubricating oils.
In accordance with the present invention, we t therefore provide a lubricating composition containing a major amount of a lubricant and an antioxidant amount of a mixture of (1) an adduct of a benzotriazole compound and a vinyl ether or a vinyl ester of a carboxylic acid and (2) an alkyl dimercapto thiadiazole.
- ;, : .

, 1:~52975 F-0152 The benzotriazole adducts used in the mixtures of the present invention are formed by reacting a benzotxiazole compound with a vinyl ether or a vinyl ester of a carboxylic acid. They are described in our pending European Patent Application No. 79301128 (Publn. No. 6710).
The benzotriazole compounds which may be used to form the adducts have the formula:

R ~ Q
/
N

H

where R is hydrogen or a hydrocarbyl group CDntaining from 1 to 12 carbon atoms, and preferably is hydrogen or an alkyl group containing from 1 to 8 carbon atoms. Particularly preferred are benzotriazole and ~uotriazole.
The vinyl ethers and vinyl esters which may be utilized in forming the adducts of the present invention have the formulae:

O
R'CH=C~aOR" and R'CH=CHOC-R"' respectively, where R' is hydrogen or an alkyl group containing from 1 to 8 carbon atoms in any isomeric arrangement, R" is an alkyl group containing from 1 to 18 carbon atoms in any isomeric arrangement, and R"' may be the same as R" or may be an aryl group, an alkaryl group or an aralkyl group containing from 1 to 18 carbon atoms.
Preferred are those vinyl ethers and vinyl esters wherein R' is hydrogen or an alkyl group containing from 1 to 11 carbon atoms, R" is an alkyl group containing from 1 ;~'' -: '; ,. ` ~` . `

1~52~7S

F-0152 to 8 carbon atoms, and R"' is an alkyl, axalkyl or alkaryl group containing from about 1 to l4 caxbon ato~s.
Particularly preferred are those vinyl ethers and vinyl esters wherein K' is hydrogen or alkyl of l to 2 carbon ato~s, R" is an alkyl group containing fxom l to 4 carbon atoms, and ~"' is an alkyl ox aryl gxoup containing from l to 6 carbon atoms.
The benzotriazole adducts are foxmed by reacting the benzotriazole compound with the vinyl ether or vinyl ester of a carboxylic acid in proportions, expressed as molar ratios of benzotriazole compound to vinyl ether or vinyl carboxylate, fxom 1:1 to 1:lO, with from l:l to 1:l.5-being preferred.
Temperatures from 25C to 150C, preferably from 80C to l20C are used. In general, the xeactants axe contacted for l to 8 hours, preferably 2 to 4 hours. The particular reaction times used will depend on the temperature and the reactants employed and at higher temperatuxes, the reaction time may be shorter than the time at lower temperatures, for a given pair of reactants.
The reaction often proceeds without the presence of any catalyst. However, catalysts of an acidic natuxe, such as acetic acid, propionic acid, toluenesulfonic acid, phosphonic or polyphosphonic and methanesulfonic acids may be employed. Basic catalysts can also be used. Typical examples include sodium or potassium alkoxides, sodium or potassium metal and their hydxoxides.

`
: . ~. ,. :. .

~529~5 F-015~ The benzotriazole products of the present invention may comprise severa~ isomers, i.e., the vinyl ethers and vinyl esters may connect to the benzotriazole in either the l-H or 2-H position. Also, both Markownikow and anti-Markownikow additions may occur. It has been found that each isomer is individually effective in imparting the improved antioxidant and anti-corrosion properties to the lubricant compositions. Accoxdingly, as used herein the term "adducts" or "benzotriazole products(s)" may refer to " any of the isomers produced, or the mixture of isomers.
The thiadiazoles used in the compositions are the alkyl dimercapto thiadiazoles. The preferred thiadiazoles are the 2,5-dimercapto-1,3,4- thiadiazoles of the formula:
~l - N

C~s/
where X4 and ~5 axe hydrocarbyl groups, either the same or different, containing from 1 to 30 carbon atoms and x is 0 to 8. ~4 and R5 can be, for example, alkyl, aryl, alkaryl o ox axalkyl, prefexably alkyl, and specific examples of which are methyl, butyl, octyl, decyl, dodecyl, octadecyl, phenyl, tolyl, benzyl, and the like. They can be made in accordance with the method descxibed in U.S.Patent 2,719,125 and are commercially available.
The present invention provides improved resistance to oxidation of lubricating media including liquid oils of lubxicating viscosity or gxeases. ~oth mineral (paraffinic or naphthenic) and synthetic oils as well as mixtures of them may be employed as the lubricant or the grease vehicle.
A wide variety of materials may be employed as thickening or gelling agents for greases. These may include the conventional metal salts or soaps and other thickening agents such as the non-soap thickeners, for example, the suxface-modified clays and silicas, axyl ureas and calcium complexes.
Typical synthetic vehicles include polyolefins,polyglycols B
. . . . .. .

. .. ~-- - ~ ~ ~ -. -... . .

F-0152 and esters such as the polybutenes, hydrogenated polydecenes, polypropylene glycol, polyethylene glycol, trimethylol propane esters, neopentyl and pentaerythritol esters, di(2-ethylhexyl) sebacate and di(2-ethylllexyl) adipate.
The antioxidant mixtures of the present invention are unexpectedly effective in mineral oils with a high sulfur content.
The lubricants can also contain other materials, for example, corrosion inhibitors, extreme pressure agents, viscosity index improvers, co-antioxidants and anti-wear agents.
The mixtures of the present invention may be employed in any amount which is effective for imparting the desired degree of oxidation improvement. The mixture is effectively employed in amounts from 0.00l% to 0.~% by weight, ~nd pxeferably from 0.0l% to 0.l% of the total weight of the compoqitlon. When preparing the mixture of the two compounds, from 20% to 80%, preferably 50% to 70% of the benzotriazole adduct and from 80% to 20%, preferably from 30% to 50% of the thiadiazole are used. All percentages are by weight of total mixture.
The following examples will provide specific illustrations of the invention described hereinabove.

dducts of Benzotriazole nd'n-Butyl'Vinyl Ether A mixture of 59.5 g. of benzotriazole, 100 g. of n-butyl vinyl ethe'r and 100 ml. of benzene was heated at _5_ ' 11~2~75 F-0152 90C (refluxing) for 6 hr. An additional 50 g. of n-butyl vinyl ether was added and refluxing at 90C was continued for about 5 hours after which unreacted n-butyl vinyl ether and the benzene solvent were removed by distillation. 'rO
the residue, petroleum ether (bp 30-60C) was added and precipitated unreacted benzotriazole (9.1 g,) was removed by filtering. Distillation of solvent from the filtrate left 90 g. (97%) of the mixed isomeric addition product.
Gas chromatography showed that the reaction l0 product consisted of two major components (isomers) which could not be separated by distillation. A narrow fraction, having a bp of 100-103C at less than 0.1 mm. H~. was estimated, from gas chromatography, to be a 30:70 mixture of isomeric mono-addition products.
Elemental analysis conformed to a mono-adduct reaction product having the empirical formula C12H17N3O:

Analysis (wt, ) C H N
Calculated for C12H17N3O : 65.73 7.81 19.16 Found : 66.34 7.63 19.9 One isomer (designated Isomer A) was separated by elution from a column packed with"Alcoa F-20"alumina (Alcoa is a trade mark), using petroleum ethex (bp 30-60C) as a solvent. A satisfactory elemental analysis for the mono-adduct was obtained:

Analysis for Isomer A (wt. %) C H N
Calculated for C12H17N3O : 65.73 7.81 19.16 Found : 66.31 8.08 19.0 .

~
.

. . . . . . . . ..
,, `' ' ' ' . . .

; , . . ..

---`` 1152~75 F-0152 The ultra-violet spectxum of Isomer A showed maxima at 284.2, 277.6, 272.5 and a shoulder of 266.0 nm .
The ultra-violet spectrum for the starting benzotriazole was significantly different, having maxima at 276, 259 and 254 nm. The nmr proton spectrum had a quartet, indicating splitting of the proton by an adjacent methyl group showing that the isomer is a Markownikow adduct. Based on these data, it is concluded that Isomer A has the following structure: ¦
!

N CH
N OC4Hg , The second isomer (designated isomer B) was isolated by benzene elution from a neutral alumina column.
A satisfactory elemental analysis for the mono adduct was also obtained:

Analysis for Isomer B (wt. %) C H N
Calculated for C12H12N3O : 65.73 7.81 19.16 Found : 65.607.78 19.4 The ultra-violet spectrum of Isomer B showed maxima at 282, 261, and 254.5 nm. This is similar to the ultra-violet spectrum of the starting benzotriazole which showed maxima at 276, 259, and 254 nm. The infrared spectrum of Isomer B
showed significant differences from that of Isomer A. The .

-7- i 1.

.

;, .
~, ' . ' ~ '. ' ' ' ~ ' ' ' . ' ' ' ' ~ ' ' : ', '' ~ ' ' :

11~2975 F-0152 nmr proton spectrum ofIsomer B also had a quartet, indicating that a methyl group is splitting a single adjacent proton and this isomer is also a Markownikow adduct, Based on these data, it is concluded that Isomer B has the following stxucture:

H

' Toluotriazole and n-Butyl Vinyl Ether Addition Product A mixture of l90 g. of toluotriazole (5-methyl-benzot~iazole), 300 g. of _-butyl vinyl ether and 200 ml. of benzene was heated, while refluxing at 88-92C, for a total of 14 hrs. Unreacted n-butyl vinyl ether and benzene solvent were removed by distillation under reduced pressure and the residue was cooled and filtexed through a bed of Super Cel (trade mark) filter media. There was obtained 306 g. of the addition product, a clean dark amber liquid ~e~resenting a yleld of 92%.

' lr~ -8-D
- .
.~
~ . : . : - - .
.. .. - . : :

, - . -.

1~2~75 Benzotriazole and Vinyl Acetate Addition Product - Base Catalyzed To benzotriazole ~59.5 g.) and potassium tert-butoxide in toluene (lO0 ml.), heated at l03-ll5C, vinyl acetate (86 g.) was added during about 2.25 hr. The reaction mixture was then heated at 98C while stirring for an additional 5 hr. period. The reaction mixture was washed with water, dried and stripped of solvent by rotary evaporation. The addition product (50.5 g.), m.p. 63-64C
was obtained from the residue by extraction with cyclohexane. Recrystallization from benzene gave a white crystalline solid, m.p. 64-65C. The infrared spectrum was consistent with the adduct structure. Elemental analysis was satisfactory:

C ~ N
Analysis calculated for Cl oHl lO2N3 :58-53 5.40 20.48 Found : 58.8l 5.46 20.4 Evaluation of Products The alkyl dimexcapto thiadiazole used in the blends described below was purchased as Amoco l50. lt is the product of Example VI of U.S. Patent No. 3,7l9,l25.
Three diffexent blends, made up as follows, were evaluated in various tests:
1. A solvent paraffinic neutral mineral oil (viscosity: 35 cSt at 38C) with 0.55% of a standard additive system and comprising (1) 60% of the reaction product of 1 mole of butyl vinyl ether and l mole of toluotriazole and

(2) 40% of the alkyl dimercapto thiadiazole.

_g_ *Trademark ~, ~
~ .

.
., 1~5Z975 F-0152 2. A blend containing highly ~efined base stock (viscosity: 35 cSt at 38C; viscosity index of 111 ) blended with a standard additive system.

3. A blend containing 25% of l and 75% of 2.
These tests included determination of neutralization number (NN) foaming tendency, rusting, coppe~
corrosion and rotary bomb oxidation test (RBOT).
Copper Co _osion Test~- ASTM D-130 A polished copper strip is immersed in the sample and heated at a tempexature and for a time characteristic of the material being tested. At the end of this period the copper strip is removed, washed, and compared with the ASTM
Copper Strip Corrosion Standards. A temperature of 120k and a time of 3 hours were used.
Rotary Bomb Oxidation Test ~BOT) - ASTM D-2272 The test oil, water, and copper catalyst coil, contained in a covexed glass container, are placed in a bomb equipped with a pressure gage. The bomb is charged with oxygen to a pressure of 620 kPa., placed in a constant-temperatuxe oil bath set at 150C, and rotated axially at l00 rpm at an angle of 30 from the horizontal.
The time for the test oil to react with a given volume of oxygen is measured, completion of the time being indicated by a specific drop in pressure, here a pressure drop of 172 kPa.

~' ' . ' .

"~,, ~.

, ., ,.. . . , . .- , ._ , , . .
.. ~ . . , ' . ~ ' ' ' , , .

11~7s F-0152 Rust Test A~TM D-665 The method involves stirring a mixture of 300 ml.
oE the oil under test with 30 ml. of distilled or synthetic sea water, as requiredl at a temperature of 60C with a cylindrical steel specimen completely immersed therein. It is customary to run the test for 24 hours; however, the test period may, at the discretion of the contracting parties, be for a shorter or longer period. The test was run fox 24 hours using synthetic sea water at 60C.
Foam Test - ASTM D-892 The sample, maintained at a temperature of 24C is blown with air at a constant rate for 5 minutes, then allowed to settle for 10 minutes. The volume of foam is measured at the end of both periods. The test is repeated on a second sample at 93C and then, after collapsing the foam, at 24C.
The results are summarized in Table l.

TABLE l Blend 1 _ 2 3 _ NN 0.07 0.20 0.32 Foam Test l80/0 225/0 l90/0 Rust Test Pass Pass Pass Copper Corrosion Test lB lA lA
.
RBOT, Min. 390/425 260 ll0 ~.: ;, . .
,~

., . _ ~ ~s~i7~ii F-0152 Other blends were made up as follows:
1. A base fluid containing 99.45V/o of a 35 cSt (38C) turbine base oil and a standard additive package.
2. Blend 1 plus 0.05% by weight of a mixture containing (l) 60% by weight of the reaction product of 1 mole of butyl vinyl ether and l mole of tolyltriazole and (2) 40% by weight of the alkyl dimercapto thiadiazole, 3. Blend l plus 0.05% by wéight of the reaction product (l) of Blend 2,

4. Blend l plus 0.05% by weight of the alkyl dimercapto thiadiazole of Blend 2.
These were evaluated in the tests described below.
Total Oxidation Products'Test'(CIGRE) - IP'280 Oxygen is passed for 164 hours through a sample of the oil with the added soluble metal catalyst, ixon and coppex and maintained at 120~. The volatile acid products, the acidity of the oil and the sludge formed are determined.
If the measuxement of the length of time to obtain a pronounced change in the rate of evolution of volatile acid ' is required, an acidity/time curve can be obtained by daily determinations of the volatile acids. The catalyst is a soluble copper salt.

Rotary'Bomb Oxidation Test'(RBOT~ --ASTM'D-2272 - Described above.

: ~ -~ ' : ~' ~;, ' .

.: .
.
~ .

..... . . .
. : :
. , . , ; ~: -,' , . .
. ~ . . . .

~15297S

F-0152 Turbine Oil Stability Test (TOST) - ASTM D-943 The oil sample is subjected to a temperature of 90C in the presence of water, oxygen and an iron-copper catalyst. The test was carried out for 2500 hours.
The results were as follows: j Blend l 2 3 4 CIGRE, Total oxidation Pxoducts 5.53 0.29 l.l5 5.22 t RBOT Min. 3l5 440 400 395 TOST %
~ludge, ~y wt. 0.76 0.l6 0.28 0.~6 .

, ~ , .

.~

.. ': ' ~ .
: ' '' ,' . ~ ,''. ": ~ ''

Claims (9)

1. A lubricating composition comprising a lubricant and from 0.001 to 0.2% of a mixture of (1) from 20 to 80% of an adduct of a benzotriazole compound of the formula wherein R is H or a hydrocarbyl group of from 1 to 12 carbon atoms, a vinyl ether of the formula R'CH=CHOR"

wherein R' is hydrogen or an alkyl group of from 1 to 8 carbon atoms, R" is an alkyl group of from 8 to 18 carbon atoms, or a vinyl ester of the formula wherein R' and R" are the same as above and R''' is the same as R" or an aryl group, an alkaryl group or an aralkyl group containing 1 to 18 carbon atoms, and (2) from 80 to 20% of an alkyl dimercapto thiadiazole.

2. The composition of Claim 1 in which R is an alkyl group containing 1 to 8 carbon atoms.

3. The composition of Claim 2 in which R is tertiary octyl.

4. The composition of Claim 1 wherein the vinyl ether is n-butyl vinyl ether.

5. The composition of Claim 1 in which the vinyl ester is vinyl acetate.

6. The composition of Claim 1 in which the dimercapto thiadiazole has the formula wherein R4 and R5 are hydrocarbyl groups containing from 1 to 30 carbon atoms and x is 0 to 8.

7. The composition of Claim 6 in which the thiadiazole is tertiary butyl 2,5-dimercapto-1,3,4 -thiadiazole.

8. The composition of Claim 1 in which (1) is the adduct of benzotriazole and n-butyl vinyl ether and (2) is tertiary octyl 2,5-dimercapto-1,3,4-thiadiazole.

9. The composition of Claim 1 in which (1) is the adduct of toluotriazole and n-butyl vinyl ether and (2) is tertiary octyl 2,5-dimercapto-1,3,5-thiadiazole.