GB2363128A - Trinuclear molybdenum containing industrial oil composition - Google Patents

Abstract

An industrial oil composition comprising an industrial oil base stock and an antioxidant comprising an amine and an oil soluble trinuclear organomolybdenum compound of the generic formula:<BR> <BR> <CHE>Mo<SB>3</SB>S<SB>x</SB>-(Q)```(I)</CHE><BR> <BR> wherein x is from 4 to 10, preferably 7, and Q is a core group, which may be a ligand, in an amount of less than 10 ppm based on molybdenum metal content. The composition has high oxidation stability and reduced sludge formation.

Description

2363128 INDUSTRIAL OIL COMPOSITIONS This invention relates to lubricating

oil compositions, especially industrial oils 5 such as those used in turbines, hydraulic systems and circulating systems comprising mineral base stock particularly those which are high in saturates and formulated for oxidation resistance.

The importance of improving the antioxidancy and enhanced life for industrial 10 oils is well recognised. In addition, balanced performance in key attributes of industrial oils is also highly desirable. Specifically, new ways to balance long oxidation life while maintaining excellent sludge/deposit control are always beneficial.

For engine oils, to increase oxidation life, impart antifriction properties and add 15 antiwear and extreme pressure protection, molybdenum dithiocarbamates can be added at typical treat rates of 0.5 to 3.0 wt%. However, at these concentrations, they are unsuitable for the majority of industrial oils. Typically, an ashless dithiocarbamate is used in industrial oils when required at about 0. 1 to 1.0 wt% to enhance antioxidancy. Deposit formation is known to occur with both types of additives.

It has been found that problems associated with dithiocarbamates in industrial oils can be mitigated by using very low treat rates of molybdenum dithiocarbamates in combination with amine antioxidants. Such formulations were tested in a Rotary Bomb Oxidation Test (ASTM D2272) (hereafter RBOT) which is a test typically suited for 25 industrial oils due to the cooler environments in which such oils are used, as opposed to the much more severe tests used for engine oils. In the RBOT test, those formulations containing only a dithiocarbamate (which may be ashless) and a phenolic antioxidant had no significant effect versus a phenolic antioxidant used alone.

30 Accordingly, the present invention is an industrial oil composition comprising an industrial oil base stock and an antioxidant comprising an oil soluble trimeric organomolybdenum compound of the generic formula:

M03S.,-M I I herein x is from 4 to 10, preferably 7, and Q is a core group, which maybe a ligand, in Z- an amount such that the molybdenum metal content of said composition is less than 10 Ppm- 5 According to a further embodiment, the present invention is a method of stabilizing an industrial oil composition comprising an industrial oil base stock as herein I defined against oxidative degradation and foaming said method comprising adding to the basestock an antioxidant comprising an oil soluble trimeric organomolybdenum compound of the generic formula:

M03Sx-(Q) (1) wherein x is from 4 to 10, preferably 7, and Q is a core group, which may be a ligand, in an amount of less than 10 ppm based on the molybdenum metal content 15 thereof The industrial oil base stock in the compositions of the present invention suitably comprise a major amount of the so called API Group 1, Group 11, Group III or Group IV base stock. Of these, hydrocracked base stock high in saturates are preferred. Such base 20 stock are suitably Group 11 or Group III base stock which may be a natural or synthetic oil having a kinematic viscosity at I OO'C (KV 1 oo) from about 2 cSt to 40 cSt (2 x 10-6 to x 10-6 M2 /sec), preferably from 2-12 cSt and a saturates content of at least 85%, preferably at least 88%. Specific examples of Group 11 basestock high in saturates include inter alia Chevron RLOP (e.g. I OOR, 220R, 600R) and Mobil Jurong (e.g. J 150, 25 J500) (with > 97% saturates), and Imperial Oil Group 11 (Sarnia MXT 5, 250X) (with >90% saturates); and examples of Group III basestock include inter alia Yubase 4 and Yubase 6 (with saturate contents >97%). These base stocks may be optionally blended with PIB to achieve the desired viscosity 30 The trimeric molybdenum compounds are of formula (1) WS'-(Q) (1) wherein x is from 4 to 10, preferably 7, and Q is a core group. These compounds are 35 relatively new and are claimed and descr-ibed in our pnor published US- A-5,906,968.

The matter disclosed in this prior US patent on the structure, preparation and properties of the trimenc molybdenum compounds is incorporated herein by reference. In these compounds the core group (Q) may be a ligand capable of rendering the organomolybdenum compound of fonnula (1) oil soluble and ensuring that said 5 molybdenum compound is substantially charge neutral. The core group (Q) is generally associated with suitable ligands such as Ly wherein L is the ligand and y is of a sufficient number, type and charge to render the compound of formula (1) oil soluble and to neutralise the charge on the compound of formula (1) as a whole. Thus, more specifically, the trimeric molybdenum compound used in the compositions of the present 10 invention may be represented by the formula (11):

M03S,Ly (II) The ligands "L" are suitably dihydrocarbyl dithiocarbamates of the structure 15 (-S2CNR2) wherein the dihydrocarbyl groups, R2 impart oil solubility to the molybdenum compound. In this instance, the tenn "hydrocarbyl" denotes a substituent having carbon atoms directly attached to the remainder of the ligand and is predominantly hydrocarbyl in character within the context of this invention. Such substituents include the following:

20 (1) hydrocarbon substituents, le, aliphatic (for example alkyl or alkenyl), alicyclic (for example cycloalkyl or cycloalkenyl), aromatic-, aliphatic- and alicyclic substituted aromatic nuclei and the like, as well as cyclic substituents wherein the ring is completed through another portion of the ligand (that is, any two indicated substituents may together form an alicyclic group); (2) substituted hydrocarbon substituents, ie, those containing nonhydrocarbon groups which, in the context of this invention, do not alter the predominantly hydrocarbyl character of the substituent. Those skilled in the art will be aware of suitable groups (eg halo (especially chloro), amino, alkoxyl, mercapto, 30 alkylmercapto, nitro, n1troso, sulphoxy etc.); and (3) hetero substituents, ie, substituents which, while predominantly hydrocarbon in character within the context of this invention, contain atoms other than carbon present in a chain or ring otherwise composed of carbon atoms.

The hydrocarbyl groups are preferably alkyl (e.g, in which the carbon atom attached to the remainder of the ligand 'U' is primary, secondary or tertiary), aryl, Z:1 substituted aryl and/or ether groups.

5 Importantly, the hydrocarbyl groups of the ligands should be such that they have a sufficient number of carbon atoms to render the compound (1) soluble or dispersible in the oil to which the trimeric organomolybdenum compound containing the ligand is added. The total number of carbon atoms present among all of the hydrocarbyl groups of Zl> the organomolybdenum compounds' ligands is suitably at least 21, preferably at least 25, 10 more preferably at least 30 and even more preferably at least 35, typically e.g., 21 to 800.

For instance, the number of carbon atoms in each hydrocarbyl group will generally range from 1 to 100, preferably from 1 to 40 and more preferably from 3 to 20.

The antioxidant in the industrial oil compositions of the present invention suitably 15 also include at least one aminic compound. Suitable aminic compounds for use in the industrial oil compositions of the present invention are suitably diaryl amines, aryl naphthyl amines and alkyl derivatives of diaryl amines and the aryl naphthyl ammes.

Preferred aminic antioxidants are represented by the formulae (VII) and (V111) wherein each of R4 and R5 is a hydrogen atom or represents the same or different alkyl groups 20 from 1 to 20 carbon atoms, preferably 1 to 9 carbon atoms.

R4 H 1 N H (IV 0 30 8- Specific examples of the aminic compounds that may be used in the compositions 35 of the present invention include inter alia:

Monoalkyldiphenyl amines such as eg monooctyIdiphenyl amine and monononyl diphenyl amine; dialkyldiphenyl amines such as eg 4,4'-dibutyldiphenyl amine, 4,4' dipentyldiphenyl amine, 4,4'-dihexyIdiphenyl amine, 4,4'-diheptyldiphenyl amine, 4,4, dioctyldiphenyl amine and 4,4'-dinonyIdiphenyl amine; polyalkyldiphenyl amines such as 5 eg tetra-butyldiphenyl amine, tetra-hexyIdiphenyl amine, tetra- octyidiphenyl amine and tetra-nonyIdiphenyl amine; the naphthylamines such as eg (x-naphthylamine and phenyl (x-naphthylamine; butylpheny-(x-naphthylamine, pentylphenyl-(X- naphthylamine, hexylphenyl-cc-naphthylamine, heptylphenyl-cc-naphthylamine, octylphenyl- (x naphthylamine and nonylphenyl-(x-naphthylamine. Of these, dialkyldiphenyl amine and 10 naphthylamines are preferable.

The industrial oil compositions of the present invention may contain in addition to the trimeric organomolybdenum compounds and the amine a phenolic compound.

Amongst the phenolic compounds, hindered phenols are preferred.

Examples of such phenolic compounds include inter alia:

4,4'-methylene bis(2,6-di-tertbutylphenol) 4,4'-bis(2,6-di-tert-butylphenol) 4,4'-bi s(2 -methyl -6-tert-butylphenol) 20 2,2'-methylene bis(4-ethyl-6-tert-butylphenol) 2,2'-methylene bis(4-methyl-6-tert-butylphenol) 4,4'-butylidene bis(3-methyl-6-tert-butylphenol) 4,4'-isopropylidene bis(2,6-di-tert-butylphenol) 2,2'-methylene bis(4-methyl-6-nonylphenol) 25 2j-isobutylidene bis(4,6-dimethyl phenol) 2,2'-methylene bis(4-methyl-6-eyclohexylphenol) 2,6-di-tert-butyl-4-methylphenol 2,6-di-tert-butyl-4-ethylphenol and 2,4-dimethyl-6-tert-butylphenol Specific hindered phenols which are preferred as the antioxidants may be represented by the generic formulae (V) - (VIII) below in which R,, R2, and R3 are the same or different alkyl. groups from 1 to 20 carbon atoms, preferably 3-9 carbon atoms and x and y are integers from 1 to 4.

R, 0 11 (V) HO -(CH2)X--U-R3 5 7,0 R2 R, 0 11 10 (V1) HO - -(C H-,)x-S-(CH2)y-C -0 -R3 0 R2 R1 15 (Vii) 1 1A0 o- (CH.))X-C-0-(CH2) Y14 C R2 R, 0 11 20 (V111) HO (CH2)X-C-O-(CH2)yS 1 IL -0 2 R2 25 In general, the antioxidant which comprises the trimeric organomolybdenum compound in combination with an aminic and a phenolic compound will form a minor component of the total industrial oil composition. The trimeric organomolybdenum compound is used in an amount in the range from 10 to 200 ppm such that the molybdenum metal content thereof is less than 10 ppm,, preferably less than 5 ppm and 30 typically about 2.5 ppm based on the total oil composition.

The combination of trimenc organomolybdenum compound and an aminic antioxidant in particular has been found to show remarkable synergies in the industrial oil compositions of the present invention.

The phenolic and/or aminic compounds are suitably present in an amount ranging from 0.01 to about 3 wt % of the total oil composition.

It has also been found that if the weight ratio of trimenc organomolybdenum 5 compound to the phenolic and/or aminic compound in the antioxidant is in the range of about 1: 1 to about 1: 600, optimum oxidative sludge control can be achieved by these combined antioxidants of the present invention.

It is particularly preferred that the antioxidant comprises in addition to the trimenc 10 organomolybdenum compound the diaryl amines (III)-QV).

Optionally, the antioxidants may be combined with a carrier liquid in the form of a concentrate. The concentration of the combined antioxidants in the concentrate may vary from 0. 1 to 30 % by weight, and will preferably be in the range of to 0. 1 to 10% by 15 weight.

A further feature of the present invention is that in the industrial oil compositions of the present invention the presence of a trimeric organomolybdenum compound facilitates the control of sludge or deposit formation from such compositions. This is 20 totally unexpected since dithiocarbamates are known to be sludge precursors in industrial oils.

In general, these industrial oil compositions may include additives commonly used such as eg antiwear agents, detergents, dispersants, rust inhibitors, viscosity index 25 improvers, extreme-pressure agents, friction modifiers, corrosion inhibitors, demulsifying aids, pour point depressants, anti-foams and the like.

The present invention is further illustrated with reference to the following Examples:

EXAMPLES

General Procedure:

5 A series of Rotary Bomb Oxidation Tests (RBOT, ASTM D2272) were run using several different antioxidants at 0.4 wt% with and without three different dithiocarbamates (DTC). Four different antioxidants were tested. These were a hindered phenol, a diplienylamine, an diphenyldiamine and a phenyl naphthylamine: Irganox@ L (hindered phenol, ex Ciba Chemicals), Irganoxg L57 (alkylated diphenylamine, ex 10 Ciba Chemicals), UOP 225 (alkylated diphenyidiamine, ex UOP) and Irganox@ L06 (alkylated PANA, ex Ciba Chemicals). Molybdenurndithiocarbarnate (MoDTC) dimer (Molyvan(E) 822, is a dinuclear molybdenum dithiocarbamate containing 5 % wt molybdenum (ex R T Vanderbilt Co) and trimer (PDN 5203, an experimental sample containing 5% by wt of Mo, ex Exxon) were added at 50 ppm which represented about 15 2.5 ppni of molybdenum metal in the oils tested. Ashless DTCs (Vanlubeg 7723, ex RT Vanderbilt Co) were added at 50 ppm for one sample, and 500 ppm for the remainder of the testing. In addition, each formulation contained the following components of which W the dimereaptothiadiazole and the benzotriazole derivatives are standard metal passivators which are used in the same concentrations in all formulations tested herein.

TABLE 1

COMPONENT Weight % Dimercaptothiadiazole derivative 0.01 Benzotnazole derivative 0.08 _Succmimide rust inhibitor 0.08 All base stocks were blended at 32 cSt at 40'C. Most of the testing was carried 25 out in a blend of Group 11 basestocks. A small number of tests were carried out with two other basestock blends: borderline GroupIl/11I and Group I base stock.

The results of the tests are shown in Table 2 below:

TABLE2

Sample 1 2 3 4 5 6 7 8 9 Components (Wt%) Group 11 Basestock 99.425 99.425 99.430 99.425 99.425 99.430 99,425 99. 425 99.430 MoDTC dimer 0.005 - 0.005 - - 0 005 - - MoDTC trimer 0.005 0.005 0.005 Irganox@ L06 0.400 0.400 0.400 - - - Irganox@ L57 - - - 0,400 0.400 0.400 - - - UOP 225 - - - - - 0.400 0.400 0.400 Benzotriazole derivative 0.080 0.080 0.080 0.080 0.080 0.080 0.080 0. 080 0.080 Succinimide rust inhibitor 0.080 0.080 0.080 0,080 0.080 0.080 0.080 0. 080 0.080 Dimercaptothiadiazole 0.010 0,010 0.010 0.010 0.010 0.010 0.010 0.010 0. 010 RBOT Life (minutes) 1915 1890 1605 410 645 245 815 1235 750 TABLE 2 (continued) Sample 10 11 12 13 14 15 16 17 Components (Wt'Y(,) Imperial Oil Group 11 - - - Balance Balance Balance Balance b/s blend Petro-Cinada Phoenix Balance Balance GrOLIP 11/111 b/s blend Imperial Oil Group I b/s Balance Balance - - blend Vanlube 7723 0.050 0.050 0.005 0.050 MoDTC trimer 0.005 0.005 Irganox L06 0.400 0,400 - - 0.400 - - Irganox L57 - - 0.400 0,400 - 0.400 0.400 - UOP 225 - - - - - - - 0.400 Benzotriazole derivative 0.080 0.080 0.080 0.080 0.080 0.080 0.080 0,080 Suc cinimide FUSt 0.080 0.080 0.080 0.080 0.080 0.080 0.080 0.080 inhibitor Dimercaptothiadiazole 0.010 0.010 0.010 0.010 0.010 0.010 0.010 0.010 derivative RBOT Life (minutes) 1472 893 675 305 16 620 270 1085 From the above results, it can be seen that all of the amine antioxidants tested showed an increase in oxidation life when a dithiocarbamate was added. However, the only phenol tested (Irganox L135) did not respond to the addition of MoDTCs and no significant change in RBOT life was recorded in the absence of an amine.

It can also be seen that the RBOT responses of DTCs with different amine antioxidants are different. Two different phenyl naphthylamines give similar responses although one is more responsive than the other to the addition of MoDTC. It can also be seen that the alkylated diphenylamine and alkylated diphenyldiamine show a greater increase in RBOT life with the trimeric MoDTC than with the dimeric MoDTC. With these amine antioxidants the ashless DTC had to be added at a ten-fold increase in concentration (relative to the MoDTC) in order to achieve an increase in RBOT commensurate with that obtainable with the trimeric organomolybdenum compound.

The results also show that the trimeric organomolybdenum compound is also effective with Imperial Oil Sarnia MCT Group 1, Imperial Oil SarniaGroup 11 and PetroCanada Phoenix (borderline Group II/Group 111) base stocks. The RBOT life in each case increased significantly (synergistically) when the trimeric organomolybdenum compound was used in combination with the alkylated diphenylamine. In each case, the oxidation stability was also improved.

12-

Claims (1)

1. We Claim:

   I An industrial oil composition comprising an industrial oil base stock and an antioxidant Comprising an oil soluble trimeric organomolybdenum compound of the generic formula:

   5 M03Sx-(Q) wherein x is from 4 to 10 and Q is a core group, which may be a ligand, in an amount such that the molybdenum metal content of said composition is less than 10 ppm..

   10 2. A composition according to Claim I wherein the industrial oil base stock comprises a major amount of an oil selected from API Group 1, Group 11, Group III and Group IV base stock.

   3. A composition according to Claim I or 2 wherein the industrial oil base stock is a 15 hydrocracked base stock, high in saturates.

   4. A composition according to any one of the preceding Claims wherein the industrial oil base stock is a natural or synthetic oil having a kinematic viscosity at 100'C (KVI()o) from about 2 cSt to 40 cSt (2 x 10-6 to 40 x 10-6 M2/SCC).

   5. A compositon according to any one of the preceding Claims wherein the industrial oil base stock has a saturates content of at least 85% by weight.

   6. A composition according to any one of the preceding Claims wherein the base 25 stock is optionally blended with a thickener or VI improver to achieve the desired viscosity.

   7. A composition according to any one of the preceding Claims wherein the trimeric molybdenum compounds are of formula (1) M03Sx-(Q) (1) wherein x is 7.

   8. A composition according to any one of the preceding Claims wherein the core group (Q) is a ligand capable of rendering the organomolybdenum compound of formula (1) oil soluble and ensuring that said molybdenum compound is substantially charge neutral.

   9. A composition according to any one of the preceding Claims wherein the core group (Q) is a ligand Ly wherein L is the ligand and y is of a sufficient number, type and charge to render the compound of formula (1) oil soluble and to neutralise the charge on the compound of formula (I) as a whole.

   10. A composition according to any one of the preceding Claims wherein the trimeric organomolybdenum compound is of the formula (II):

   15 M03SLy (I1) wherein the ligands 'U' are dihydrocarbyl dithiocarbamates of the structure (-S2CNR2) wherein the dihydrocarbyl groups, R2 impart oil solubility to the molybdenum compound.

   11. A composition according to Claim 10 wherein the hydrocarbyl groups of the total number of carbon atoms present among all of the hydrocarbyl groups of organomolybdenum compounds' ligands is at least 21.

   25 12. A composition according to any one of the preceding Claims wherein the industrial oil compositions also include at least one aminic compound.

   13. A composition according to Claim 12 wherein the aminic compounds for use in the industrial oil compositions is selected from diaryl amines, aryl naphthyl amines and 30 alkyl derivatives of diaryl amines and the aryl naphthyl amines.

   14. A composition according to Claim 12 or 13 wherein the aminic antioxidant is represented by the formulae (111) or (IV) wherein each of R-4 and R5 is a hydrogen atom or represents the same or different alkyl groups from 1-8 carbon atoms.

   R4 H Y5 1 (111) 0-N- H R4 1 OV) N-C 15. A composition according to Claim 16 wherein the aminic compound is selected 20 from monooetyldiphenyl amme, monononyl diphenyl amme, 4,4'- dibutyIdiphenyl amine, 4,4'-dipentyldiphenyl amine, 4,4'-dihexyidiphenyl amine, 4,4'diheptyldlphenyl amme, 4,4'-dioctyidiphenyl amme, 4,4'-dinonyldiphenyl amme, tetra-butyldiphenyl amine, tetra hexyIdiphenyl amme, tetra-oetyldiphenyl amme, tetra-nonyldiphenyl amine, a naphthylamine, phenyl-ce-naphthylamine, butylpheny-a-naphthylamine, pentylphenyl-cc 25 naphthylamine, hex ylphenyl -(x-n aphthylamine, heptylphenyl-cenaphthylamine, octylphenyl-a-naphthylamine and nonylphenyl-(x-naphthylamine.

   16. A composition according to any one of the preceding Claims 12 to 16 wherein said composition contains in addition to the tnmeric organomolybdenum compounds and 30 the amine, a phenolic compound.

   17- A composition according to Claim 16 wherein the phenolic compound is a hindered phenol.

   35 18. A composition according to Claim 16- or 17 wherein the phenolic compound is selected from:

   - 15 4,4'-methylene bis(2,6-di-tert-butylphenol) 4,4'-bis(2,6-di-tert-butylphenol) 4,4'-bis(2-methyl-6-tert-butylphenol) 2,2'-methylene bis(4-ethyl-6-tert-butylphenol) 5 2,2'-methylene bis(4-methyl-6-tert-butylphenol) 4,4'-butylidene bis(3-methyl-6-tert-butylphenol) 4,4'-isopropylidene bis(2,6-di-tert-butylpheriol) 2,2'-methylerie bis(4-methyl-6-nonylphenol) 2,2'-isobutylidene bis(4,6-dimethyl phenol) 10 2,2'-methylene bis(4-methyl-6-cyclohexylphenol) 2,6-di-tert-butyl-4-methylphenoI 2,6-di-tert-butyl-4-ethylphenol and 2,4-dimethyl-6-tert-butylphenol 19. A composition according to any one of the preceding Claims wherein the trimeric organomolybdenum compound is present in said composition in an amount from 10 to ppm such that the molybdenum metal content of said composition is less than 10 ppm.

   20. A composition according to any one of the preceding claims wherein the amount of trimeric organomolybdenum compound present in said composition is such that the molybdenum metal content of said composition is about 2.5 ppm.

   21. A composition according to Claim 6 wherein the thickener is a polyisobutene.

   22. A composition according to any one of the preceding Claims wherein said composition includes antiwear agents, detergents, rust inhibitors, viscosity index improvers, extreme-pressure agents, friction modifiers, corrosion inhibitors, demulsifying aids, pour point depressants or anti-foams.

   23. A method of stabilizing against oxidative degradation and foaming an industrial oil composition comprising an industrial oil base stock as claimed in any one of the preceding Claims 1-23 said method comprising adding to the basestock an antioxidant comprising an oil soluble trimeric organomolybdenum compound of the generic fon-nula:

   35 M03Sx-(Q) (1) wherein x is from 4 to 10, preferably 7, and Q is a core group, which may be a ligand, in an amount such that the amount of rnolybdenum metal in said composition is less than ppm.