CA1304384C - Mercapto-thiadiazole reaction products as multifunctional lubricant additives and compositions thereof - Google Patents

Abstract

MERCAPTO-THIADIAZOLE REACTION PRODUCTS AS
MULTIFUNCTIONAL LUBRICANT ADDITIVES AND
COMPOSITIONS THEREOF
ABSTRACT
Zinc/phosphorus-free antiwear agents and antioxidants are provided by reaction products of 2,5-dimercapto-1,3,4-thiadiazole with mercaptans and thionyl chloride.

Description

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MERCAPTO-THIADIAZOLE REACTION PRODUCTS AS
MULTIFUNCTIONAL LUBRICANT ADDITIVES AND
COMPOSITIONS THEREOF

This invention is directed to reaction products of mercapto-thiadiazoles, mercaptans and thionyl chloride as zinc/phosphorus-free antiwear agents and antioxidants.
Replacement of zinc phosphorodithioates by zinc/phosphorus-free antiwear additives in circulating oils, gear oils and various other lubrlcating systems is considered highly deslrable because of environmental considerations and the potential electrolytic corrosivity of zinc salts. An additive system whlch in addition to antiwear activity exhibits antioxidant activity and copper passivation is highly desirable. The condensates of the present invention provide outstanding FZG gear performance, low Four-ball wear and antioxidant activity. Furthermore, they contain no corrosive sulfur.
Various reaction products of mercapto and dimercapto-thiadiazoles (DMTD) are known in the art. For example, reactionproducts of 2,5-dimercapto-1,3,4-thiadiazole are disclosed in U.S.
Patent 4,128,510 as being useful as cross-linking agents ~or halogen-containin~ polymers. ~.S. P~`lten~ ~,382,869 dL.sclos~s r~ac~.ion products of mercaptothiadiazoles with hydroxyl-containing compounds as friction reducing and corrosion-inhibiting additives for lubrlcant oils. Although reaction products containing the mercapto-1,3,4-thiadiazole structure has found widespread use as lubricant antioxidants and metal passivators, the compositions and the utility of the reaction products described in this patent application are believed to be unknown heretofore in the art.
This invention provides a product of reaction having multifunctional antiwear/extreme pressure (EP) and antioxidation ., 3~

~.;3~J~ 8 characteristics prepared by reacting a mercapto or dimercapto thiadiazole with a mercaptan and thionyl chloride.
This invention further provides a process of making the above-described product.
This invention also provides lubricant compositions comprising a lubricant and an antiwear/extreme pressure (EP) and/or antioxidant amount of the product of reaction made by reacting a mercapto-thiadiazole with a mercaptan and thionyl chloride. The reaction may take place in the presence of a suitable stabilizing or dispersing agent or said agent may be contacted at the conclusion of the reaction.
rhe synthesis and evaluation of derivatives of mercapto thiadiazoles, particularly 2,5-dimercapto-1,3,4 thiadiazole (DMTD) as potential no-phosphorus multifunctional additives and replacement for Zn phosphorodithioates in circulating oils, gear oils, and other lubricating systems is an attractive and novel route for obtaining these goals.
In general, the additive products of the invention are synthesized by the condensation of a mercapto-thiadiazole, for example, 2,5-dimercapto-1,3,4-thiadiazole with mercaptans and thionyl chloride (SOC12).
Any appropriate mercapto-thiadiazole may be used herein.
Some suitable examples include but are not limited to 3,4-dimercapto-1,2,5-thiadiazole, 3,5-dimercapto- 1,2,4-thiadiazole, 4,5-dimercapto-1,2,5-thiadiazole, 4,5-dimercaptobenzo 1,2,3-thiadiazole, 4,7-dimercaptobenzo 1,2,3-thiadiazole, 4,6-dimercaptobenzo 1,2,3-thiadiazole, 5,6-dimercaptobenzo 1,2,3-thiadiazole, 5,7-dimercaptobenzo 1,2,3-thiadiazole, 6,7-dimercaptobenzo 1,2,3-thiadiazole, 4,5~dimercaptobenzo 2,1,3-thiadiazole, 4,6-dimercaptobenzo 2,1,3-thiadiazole, 5,6-dimercaptobenzo 2,1,3-thiadiazole, 5,7-dimercaptobenzo 2,1,3-thiadiazole, 6,7-dimercaptobenzo 2,1,3-thiadiazole.
Especially preferred is 2,5-dimercapto- 1,3,4-thiadiazole.

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Suitable mercaptans include but are not limited to Cl to about ~2 alkyl mercaptans. Especially preferred are t-nonyl and hexadecyl mercaptans.
Optionally a stabilizing or dispersing agent may be used in the synthesis process. The reaction process in accordance with the lnvention may be carried out in the presence of such agent or the product of reaction thereof may be treated with such agent. Any suitable agent known in the art that would disperse the reaction medium and stabilize the products without having a detrimental effect upon the desired reaction may be used. Particularly qualified are thiadiazoles such as 2,5-bis(t-nonyl-thio)-1,3,4-thiadiazole and non-emulsive amines such as"Primene 81R"amine.
Generally any t-alkylthio-thiadiazole may be used. "Primene 81R"*
amine is a partlcularly preferred non-emulslve amine. It is believed to be a mixture of primary aliphatic amines of predominantly C12 to C14 t-alkyl groups. It is more fully r~ported in U.S. Patent 3,224,957 of E.A. ~t, issl}~ Deo~er 21, 1965 .
The reaction conditions are based primari~ly on the particular reactants. Usually, however, the temperature may vary 20 from about 50 to about 120C, the pressure fr~m ambient to 1030 kPa if desired, and the tLme from about 1 to about 8 hours or more depending on specific reactants.
The molar ratio of reactants DMTD/mercaptan/thlonylchloride varies ~rom about 1:2:1.5 ko about 25 1:12:8. The amount of stablllzing or dispersing agent when used may vary from about 5 to about 60 wt.% based on the weight of the condensation product. Preferably from about 10 to about 50 wt.X is used.
The lubricants which may be used with the additives (reaction products) of thls invention are mineral and synthetic lubricating oils, mixtures thereof and greases made therefrom. The mineral oils will be understood to include not only the paraffinic members, but also the naphthenic members. By synthetic oils are meant synthetic hydrocarbons, polyalkylene oxide oils, polyacetals, ,C ' * Trademark ~ 3~?~ 3~

polysilicones and the like, as well as synthetic ester oils.
Included among the latter type are those esters made from monohydric alcohols and polycarboxylic acids, such as 2-ethyl-hexylazelate and the like. Also included are those esters made from polyhydric alcohols and aliphatic monocarboxylic acids. Those of this group are especially important and in this group are found esters prepared from (1) the trimethylols, such as the ethane, propane and butane derivatives thereof, (2) 2,2-disubstituted propane diols and (3) the pentaerythritols reacted with aliphatic monocarboxylic acids containing from about 4 to 9 carbon atoms. Mixtures of these acids may be used to prepare the esters. Preferred among the esters are those made from pentaerythritol and a mixture of C5-Cg acids.
As has been disclosed hereinabove, the reaction products are useful as antiwear/EP and antioxidant agents. They are added to the lubricating medium in amounts sufficient to impart such properties to the lubricant. More particularly, such properties will be imparted to the lubricant by adding from about 0.01% to about 10% by weight, preferably from about 0.01% to about 3%, of the neat product.
Having discussed the invention in broad and general terms, the following are offered to illustrate it. It is to be understood that the examples are merely illustrative and are not intended to limit the scope of the invention.

DMTD, SOC12 and t-nonylmercaptan condensate (molar ratio 1:2.2:2) in 2,5-bis(t-nonylthio)-1,3,4-thiadiazole dispersing medium ( 50 wt.%).
50 gms of 2,5-bis(t-nonylthio)-1,3,4-thiadiazole, t-nonylmercaptan (32 gms., O.2 mole) and DMTD
(2,3-dimercapto-1,3,4-thiadiazole; 15 gms., 0.1 mole) are placed in a flask equipped with dropping funnel, reflux condenser, thermometer, mechanical stirrer, a nitrogen inlet tube and outlet tube leading from the condenser to scrubbers containing aqueous NaOH

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solution. The reaction system is protected from exposure to moist air by means of drying tubes.
The mixture is heated to 85C with stirring under a dry nitrogen stream. SOC12 (26.18 gms.; 0.22 mole) is cautiously added dropwise over a period of thirty minutes. The reaction is strongly exothermic and is able to retain the temperature of the reaction mixture at 85-88C without external heating throughout most of the addition period. The reaction mixture which is a homogeneous fluid is heated at 85C for two additional hours after completion of lo the SûC12 addition. It is subsequently placed under house vacuum and heated to final temperature of 105C. The mixture is cooled to room temperature and treated with n-hexane (300 ml). The solution is heated at 70C for a few minutes, is cooled and filtered. A
minimal quantity of solids ( 0.69) is collected on the filter. The filtrate is mixed with 200 ml of 5 wt.~ aqueous NaOH solution and warmed to 55C. The organic layer is separated. The aqueous layer is extracted with an additional quantity of n-hexane (50 ml). The combined organic layers are washed with water, dried and stripped of solvent and volatiles under house vacuum and final pot temperature 86C. The residue, a clear purple fluid, weighed 102.87 gms. It was readily soluble in 100 cSt oil, n-hexane, acetone, dimethyl fluoride (DMF) but sparingly soluble in water, acetonitrile and dimethyl sulfoxide (DMSO). Infrared (IR) Spectrum was consistent with anticipated structure of poly dithionyl sulfoxide.

DMTD, SOC12, t-nonylmercaptan (molar ratio 1:2.2:2) condensate treated with"Primene 81R Amine"(10 wt.~).
DMTD (2,3 dimercapto-1,3,4 thiadiazole; 759, 0.5 mole), t-nonylmercaptan (1609, 1.0 mole) and toluene (500 ml) are placed in a flask equipped with dropping funnel, mechanical stirrer, reflux condenser, thermometer, nitrogen inlet tube and outlet tube leading from the condenser to scrubbers containing aqueous solution of - NaOH. The reaction system is protected from exposure to moist air by means of drying tubes.

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The mixture is heated to 75C (with stirring) under a light stream of dry nitrogen SOC12 (130.9g, l.l mole) diluted with 150 ml of toluene is added dropwise over a period of one hour. The temperature of the reaction mixture is maintained at 75-80C
throughout the SOC12 addition and for two additional hoursO The solvent and any volatiles present are distilled under reduced pressure-house vacuum. the final pot temperature is allowed to reach llO~C. The res~due (278 gms) ls cooled to room temperature and treQt~d wlth ono liter of n-h~x~no ~nd 600 ml Of 5 wt,% aquoous NaOH solution. the organic layer is separated. The aqueous layer ls extracted wlth an addltlonal ~uuntlty of hexane (200 ml). The combined extracts are washed with water and dried. "Primene 81R~*
amine (27.8 gms) is added. the clear solution is stripped of solvent and any volatiles under house vacuum and final pot S temperature is 100C. The residue, a clear purple fluid, we~ghs 288 gms. It is readily soluble in lOO cst oil, n-hexane, acetone, methyl ethyl ketone (MEK) and DMF. IR spectrum ls ln agreement wlth anticipated structure.
The condensation react~on, believed novel, is applicable over a broad spectrum of uses. The polarity of the sulfoxide groups in the vicinlty of the thiadiazole moiety enhances the adhesion to metals through a potential bldentate ligant formation. This arrangement protects metal surfaces through strong adsorption-chemisorption and consequently increases the antiwear-EP
activity of the aggregate Evaluation of Products The examples in accordance with the invention were blended into a zinc/phosphorus-free heavy duty circulating oil formulation deslgnated Test Oil #l and 2 and evaluated as to gear test wear, antiwear/EP characteristics and antioxidation properties. See Tables l and 2.
The formulation was tested for gear wear protection according to the FZG Gear Test (DIN-51.354). In this test, * Trademark - ` ~ 3~?~38~

F-3880 ~ 7 -dip-lubricated gears are weighed and operated at a fixed speed and fixed initial oil temperature (90C) in the gear oil under test.
The load on the teeth is increased in increments. After each load stage, the weight changes are determined and recorded. The results are reported in Table 1 and Table 2. The higher the Fail Stage value the better the material. The lower the wear value the better the product.
The formulation was also tested for its antiwear properties according to the Four-~all Wear Test. The results are set forth in Table 2. The products of the examples and comparative examples were tested in the 4-ball test using a modified 4-ball machine. In this test, three stationary balls are placed in a lubricant cup and a lubricant containing the additive to be tested is added thereto~ A
fourth ball is placed on a chuck mounted on a device which can be used to spin the ball at known speeds and loads. Various percentages by weight of each product was placed in the blend. The samples were tested at 54C (130F) at a load of 20 kg and 1800 rpm for 60 minutes.
The formulation was tested for its antioxidation characteristics in accordance with the Rotary 80mb Test (R80T-ASM
D-2272). The test oil, water, and copper catalyst coil, contained in a covered glass container, are placed in a bomb equipped with a pressure gauge. The bomb ls charged with oxygen to a pressure of 620 kPa (90 psi), placed in a constant temperature oil bath set at 150C, and rotated axially at 100 rpm at an angle of 3û 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.

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ZINC/PHOSPHORUS-FREE HEAVY CIRCULATING OIL FORMULATIONS
FZG
Fail Wear Composition Stage mg Reference Oils A Test Oil #1 - 0.25% Zn (DTP)2 11 125 - 1.00% Zn (DTP)2 11 72 Test Oil #1 less Zn (DTP)2 8 __ + 1% (1) 9 349 + 1% (2) 10 118 Thionyl Chloride Reaction Products + 1% (3) 12 45 + 1% Ex. 1 12 40 ~ 1% Ex. 2 12 37 .
(1) Comparative Example: sulfurized olefin (2) Comparative Example: mercaptobenzothiazole type antiwear agent (3) Reaction prod~ct of SOC12/CgSH/DMTD without dispersing medium.

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ZINC/PHOSPHORUS-FREE CIRCULATING OIL FORMULATIONS

Test Oil #2 less Zn(DTP2 plus:
ATest Oil #2 EXAMPLE EXAMPLE EXAMPLE EXAMPEE
~0.09% 3 2 2 Performancé Tests Zn(OTP)~] o~-o9% 0.09% 0.2% _ 0.2%
FZG Gear Test Fail Stage 8/9 9 9 10 9 Wear, mg 20 30 51 -- 21 4-Ball Wear Scar Diam, mm0.25 0.26 -- 0.27 0.25 RBOT, mlnutes225 365 -- 415 --_ (3) Reaction product of SOC12/CgSH/OMTD without dispersing medium.
A Test Oils #1 and #2 represent typical rust inhibited circulatory oils used to lubricate industrial equipment such as pumps, gears, etc.

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From the above data it is quite clear that the reaction products (additives) of the present invention provide noticably outstanding FZG gear performance and antiwear/EP characteristics but also exhibit significant antioxidation properties.
These additives, in accordance with the invention, prepared by reaction of thionyl chloride with mercapto-thiadiazole and mercaptan, provide outstanding FZG gear performance, low Four-ba wear and a boost in oxidation stability. Accordingly they show promise as replacements for zinc dithiophosphate antiwear agents used in heavy circulating oil formulations.
Although the present invention has been described with preferred embodiments, it is to be understood that modifications and variations may be resorted to, without departing from the spirit and scope of this invention, as those skilled in the art will readily understand. Such modifications and variations are considered to be within the purview and scope of the appended claims.

Claims (18)

1. A product of reaction having multifunctional antiwear/extreme pressure and antioxidation characteristics prepared by reacting a mercapto or dimercapto thiadiazole with a mercaptan and thionyl chloride.

2. The product of claim 1 wherein the mercaptan is a C1 to a C22 alkyl mercaptan.

3. The product of claim 2 wherein the mercaptan is a tertiary alkyl mercaptan.

4. The product of claim 3 wherein the mercaptan is t-nonyl mercaptan.

5. The product of claim 1 wherein the reaction is carried out in the presence of a stabilizing or dispersing agent.

6. The product of claim 5 wherein the stabilizing agent is added to the reaction medium after the reaction is substantially completed.

7. The product of claim 5 wherein the agent is an alkylthio-thiadiazole or a bis alkylthio-thiadiazole.

8. The product of claim 7 wherein the agent is 2,5-bis(t-nonylthio)-1,3,4-thiadiazole.

9. The product of claim 6 wherein the agent is "Primene 81R" amine.

10. The product of claim 5 wherein from 5 to 60 wt.%, based on the weight of the reaction product, of the stabilizing or dispersing agent is used.

11. The product of any one of claims 1 to 10 wherein the molar ratio of mercapto or dimercapto-thiadiazole to thionyl chloride to mercapto is from 1:2:1.5 to 1:12:8.

12. The product of claim 1 wherein the reaction temperature is from 50° to 120°C.

13. The product of claim 1 wherein the pressure is from ambient to 1030 kPa.

14. The product of claim 1 wherein the reaction time is from 1 to 8 hours.

15. A lubricant composition comprising a major amount of an oil of lubricating viscosity or grease prepared therefrom and a minor amount of the product of claim 1.

16. The composition of claim 15 wherein the product of reaction is prepared from 2,5-dimercapto-thiadiazole, thionyl chloride and t- nonylmercaptan in the presence of 2,5-bis(t-nonylthio)-1,3,4-thiadiazole.

17. The composition of claim 15 wherein the product of reaction is prepared from 2,5-dimercapto-thiadiazole, thionyl chloride, t-nonylmercaptan and thereafter treated with "Primene 81R" amine.

18. The composition of claim 15 wherein the oil of lubricating viscosity is selected from mineral, synthetic and mixtures of mineral and synthetic oil.