Synergistic Lubricating Oil Composition Containing Mixture of Antioxidants

Abstract

Disclosed is a lubricating oil composition comprising an oil of lubricating viscosity and an oil soluble synergistic mixture of antioxidants, said mixture comprising: a) a hindered amine antioxidant according to formula (I)

##STR00001## wherein each R.sup.1 is independently selected from a substituted or unsubstituted, branched or linear, C.sub.1-C.sub.20 hydrocarbyl group; R.sup.2 is selected from the group consisting of a hydrogen atom or a, substituted or unsubstituted, branched or linear, C.sub.1-C.sub.20 hydrocarbyl group; each R.sup.3 is independently selected from the group consisting of a hydrogen atom or a, substituted or unsubstituted, branched or linear, C.sub.1-C.sub.20 hydrocarbyl group; each R.sup.4 is independently selected from the group consisting of a hydrogen atom or a, substituted or unsubstituted, branched or linear, C.sub.1-C.sub.20 hydrocarbyl group; n is an integer from 1 to 4; and m is an integer from 1 to 5; and b) a molybdenum succinimide complex.

Claims

1. A lubricating oil composition comprising an oil of lubricating viscosity and an oil soluble synergistic mixture of antioxidants, said mixture comprising: a) a hindered amine antioxidant according to formula (I): ##STR00012## wherein each R1 is independently selected from a substituted or unsubstituted, branched or linear, C1-C20 hydrocarbyl group; R2 is selected from the group consisting of a hydrogen atom or a, substituted or unsubstituted, branched or linear, C1-C20 hydrocarbyl group; each R3 is independently selected from the group consisting of a hydrogen atom or a, substituted or unsubstituted, branched or linear, C1-C20 hydrocarbyl group; each R4 is independently selected from the group consisting of a hydrogen atom or a, substituted or unsubstituted, branched or linear, C1-C20 hydrocarbyl group; n is an integer from 1 to 4; and m is an integer from 1 to 5; b) a molybdenum succinimide complex; and c) a diphenylamine antioxidant different from that of formula I, wherein antioxidants (a) and (c) are present in a weight ratio from 1:1 to 1:4.

2. (canceled)

3. The lubricating oil composition according to claim 1, wherein the hindered amine antioxidant has the following formula (II): ##STR00013## wherein each R1 is independently selected from a substituted or unsubstituted, branched or linear, C1-C20 hydrocarbyl group; R2 is selected from the group consisting of a hydrogen atom or a, substituted or unsubstituted, branched or linear, C1-C20 hydrocarbyl group; each R3 is independently selected from the group consisting of a hydrogen atom or a, substituted or unsubstituted, branched or linear, C1-C20 hydrocarbyl group; each R4 is independently selected from the group consisting of a hydrogen atom or a, substituted or unsubstituted, branched or linear, C1-C20 hydrocarbyl group; n is an integer from 1 to 4; and m is an integer from 1 to 5.

4. The lubricating oil composition according to claim 1, wherein the hindered amine antioxidant has the following formula (III): ##STR00014## wherein each R1 is independently selected from a substituted or unsubstituted, branched or linear, C1-C20 hydrocarbyl group; R2 is selected from the group consisting of a hydrogen atom or a, substituted or unsubstituted, branched or linear, C1-C20 hydrocarbyl group; and R4 is selected from the group consisting of a hydrogen atom or a, substituted or unsubstituted, branched or linear, C1-C20 hydrocarbyl group.

5. The lubricating oil composition according to claim 1, wherein the hindered amine antioxidant has the following formula (IV): ##STR00015## wherein R2 is selected from the group consisting of a hydrogen atom or a, substituted or unsubstituted, branched or linear, C1-C20 hydrocarbyl group; and R4 is selected from the group consisting of a hydrogen atom or a, substituted or unsubstituted, branched or linear, C1-C20 hydrocarbyl group.

6. The lubricating oil composition according to claim 1, wherein the hindered amine antioxidant has the following formula (V): ##STR00016## wherein R4 is selected from the group consisting of a hydrogen atom or a, substituted or unsubstituted, branched or linear, C1-C20 hydrocarbyl group.

7. The lubricating oil composition according to claim 1, wherein the total wt. % of the mixture of antioxidants in the composition is less than 5 wt. %.

8. The lubricating oil composition according to claim 1, wherein the total wt. % of the mixture of antioxidants in the composition is less than 2 wt. %.

9. The lubricating oil composition according to claim 1, wherein the diphenylamine antioxidant is diphenylamine, monoalkylated diphenylamine, dialkylated diphenylamine, trialkylated diphenylamine, or mixtures thereof.

10. The lubricating oil composition according to claim 9, wherein the diphenylamine antioxidant is selected from the group consisting of butyldiphenylamine, di-butyldiphenylamine, octytdiphenylamine, di-octyldiphenylamine, nonyldiphenylamine, di-nonyldiphenylamine, t-butyl-t-octyldiphenylamine, and mixtures thereof.

11. The lubricating oil composition according to claim 1, further comprising an oil-soluble, phosphorus-containing, anti-wear compound selected from the group consisting of metal dithiophosphates, phosphorus esters, amine phosphates and amine phosphinates, sulfur-containing phosphorus esters, phosphoramides and phosphonamides.

12. The lubricating oil composition according to claim 11, wherein said phosphorus esters are selected from the group consisting of phosphates, phosphonates, phosphinates, phosphine oxides, phosphites, phosphorites, phosphinites, and phosphines.

13. The lubricating oil composition according to claim 11, wherein the oil-soluble, phosphorus-containing, anti-wear compound is a metal dithiophosphate.

14. The lubricating oil composition according to claim 13, wherein the metal dithiophosphate is a zinc dialkyldithiophosphate.

15. The lubricating oil composition according to claim 1, further comprising supplemental antioxidant selected from the group consisting of hindered phenols, hindered bisphenols, sulfurized phenols, sulfurized olefins, alkyl sulfides, polysulfides, dialkyl dithiocarbamates and phenothiazines.

16. A method for improving oxidation and reducing deposit formation in an engine comprising the steps of: first lubricating said engine with the lubricating oil composition according to claim 1, and then operating said engine.

17. A lubricating oil composition comprising an oil of lubricating viscosity and an oil soluble synergistic mixture of antioxidants, said mixture comprising: a) a hindered amine antioxidant according to formula (I): ##STR00017## wherein each R1 is independently selected from a substituted or unsubstituted, branched or linear, C1-C20 hydrocarbyl group; R2 is selected from the group consisting of a hydrogen atom or a, substituted or unsubstituted, branched or linear, C1-C20 hydrocarbyl group; each R3 is independently selected from the group consisting of a hydrogen atom or a, substituted or unsubstituted, branched or linear, C1-C20 hydrocarbyl group; each R4 is independently selected from the group consisting of a hydrogen atom or a, substituted or unsubstituted, branched or linear, C1-C20 hydrocarbyl group; n is an integer from 1 to 4; and m is an integer from 1 to 5; b) a molybdenum succinimide complex; and c) a diphenylamine antioxidant different from that of formula I, wherein antioxidants (a) and (c) are present in a weight ratio to yield an oxidation inhibition of at least 10%, according to the Oxidator Bx test, over a lubricating oil composition comprising either antioxidant (a) or (c) alone.

18. The lubricating oil composition according to claim 17, wherein the total wt. % of the mixture of antioxidants in the composition is less than 5 wt. %.

19. The lubricating oil composition according to claim 17, wherein the diphenylamine antioxidant is diphenylamine, monoalkylated diphenylamine, dialkylated diphenylamine, trialkylated diphenylamine, or mixtures thereof.

20. The lubricating oil composition according to claim 17, further comprising an oil-soluble, phosphorus-containing, anti-wear compound selected from the group consisting of metal dithiophosphates, phosphorus esters, amine phosphates and amine phosphinates, sulfur-containing phosphorus esters, phosphoramides and phosphonamides.

Description

EXAMPLES

Example 1

[0098] ##STR00008##

[0099] Synthesis of N.sup.1-phenyl-N.sup.4-(2,2,6,6-tetramethylpiperidin-4-yl)benzene-1,4-diamine

[0100] To a solution 1,1,6,6-tetramethyl-4-piperidone (24.4 g, 0.157 mol, 1.0 equiv) and N-phenyl-p-phenylenediamine (28.9 g, 0.157 mol, 1.0 equiv) in 1,2-dichloroethane (300 mLs) was added sodium triacetoxyborohydride (46.6 g, 0.220 mol, 1.4 equiv) and acetic acid (9.43 g, 0.157 mol, 1 equiv). The reaction mixture was stirred at ambient temperature for 48 h under N.sub.2. The reaction mixture was neutralized with 1N sodium hydroxide (150 mLs), the layers were separated, and the aqueous layer was extracted with 3150 mLs of EtOAc. The organic layers were combined, dried over Na.sub.2SO.sub.4, filtered, and concentrated under reduced pressure. Purification by silica gel chromatography (100:0.fwdarw.50:50 hexanes-EtOAc, 3-5 wt % NEt.sub.3) afforded the desired product in 67% yield (34 g): .sup.1H NMR (CDCl.sub.3) 7.21 (t, J=8.4 Hz, 2H), 7.04 (d, J=8.6 Hz, 2H), 6.87 (d, J=8.4 Hz, 2H), 6.81 (t, J=7.3 Hz, 1H), 6.63 (d, J=8.7 Hz, 2H), 5.42 (br s, 1H), 3.74 (tt, J=11.7, 3.4 Hz, 1H), 2.09 (dd, J=12.7, 3.4 Hz, 2H), 1.32 (s, 6H), 1.18 (s, 6H), 0.94 (t, J=12 Hz, 2H). TBN: 272, N wt. %=12.99%

[0101] Example 2

##STR00009##

[0102] Synthesis of N.sup.1-(4-butylphenyl)-N.sup.4-(2,2,6,6-tetramethylpiperidin-4-yl)benzene-1,4-diamine

[0103] To a solution 1,1,6,6-tetramethyl-4-piperidone (1.03 g, 0.007 mol, 1.0 equiv) and N-(4-butylphenyl)benzene,1,4-diamine (1.6 g, 0.007 mol, 1.0 equiv) in 1,2-dichloroethane (35 mL) was added sodium triacetoxyborohydride (2.15 g, 0.009 mol, 1.4 equiv) and acetic acid (0.4 g, 0.007 mol, 1 equiv). The reaction mixture was stirred at ambient temperature for 24 h under N.sub.2. The reaction mixture was neutralized with 1N sodium hydroxide (70 mL), the layers were separated, and the aqueous layer was extracted with 335 mLs of EtOAc. The organic layers were combined, dried over Na.sub.2SO.sub.4, filtered, and concentrated under reduced pressure. Purification by silica gel chromatography (0.fwdarw.100 hexanes-EtOAc, 3-5 wt % NEt.sub.3) afforded the desired product in 40% yield (1 g): .sup.1H NMR (CDCl.sub.3) 7.02 (m, 4H), 6.82 (d, J=8.4 Hz, 2H), 6.61 (d, J=8.7 Hz, 2 H), 5.33 (br s, 1H), 3.73 (tt, J=11.9, 3.5Hz, 1H), 2.54 (t, J=7.7 Hz, 2H), 2.08 (dd, J=12.9, 3.4 Hz, 2H), 1.58 (quint, 2H), 1.58 (m, 2H), 1.36 (m, 2H), 1.33 (s, 6H1.27 (s, 1H), 1.21 (s, 6H), 0.94 (m, 5H).

[0104] Example 3

##STR00010##

[0105] Synthesis of N.sup.1-(4-octylphenyl)-N.sup.4-(2,2,6,6-tetramethylpiperidin-4-yl)benzene- 1,4-diamine

[0106] To a solution 1,1,6,6-tetramethyl-4-piperidone (1.3 g, 0.0081 mol, 1.0 equiv) and N-(4-octylphenyl)benzene,1,4-diamine (2.4 g, 0.0081 mol, 1.0 equiv) in 1,2-dichloroethane (60 mL) was added sodium triacetoxyborohydride (2.4 g, 0.011 mol, 1.4 equiv) and acetic acid (0.48 g, 0.0081 mol, 1 equiv). The reaction mixture was stirred at ambient temperature for 24 h under N.sub.2. The reaction mixture was neutralized with 1N sodium hydroxide (60 mLs), and the layers were separated, and the aqueous layer was extracted with 360 mLs of EtOAc. The organic layers were combined, dried over Na.sub.2SO.sub.4, filtered, and concentrated under reduced pressure. Purification by silica gel chromatography (0.fwdarw.100 hexanes-EtOAc, 3-5 wt % NEt.sub.3) afforded the desired product in 50% yield (1.6 g): .sup.1H NMR (CDCl.sub.3) 6.98 (t, J=9.1 Hz, 4H), 6.79 (d, J=8.5 Hz, 2H), 6.59 (d, J=8.7 Hz, 2H), 5.30 (s, 1H), 3.68 (m, J=, Hz, 1H), 3.70 (tt, J=11.5, 3.4 Hz, 1H),_2.50 (t, J=7.7 Hz, 2H), 2.06 (dd, J=13.0, 3.5 Hz, 2H), 1.56 (quint, J=7.4 Hz, 2H), 1.31 (s, 6H), 1.29 (m, 12H), 1.19 (s, 6H), 0.87 (t, J=6.9 Hz, 3H).

Example 4

[0107] ##STR00011##

[0108] Synthesis of N1-(1,2,2,6,6-pentamethylpiperidin-4-yl)-N4-phenylbenzene-1,4-diamine

[0109] To a solution 1,2,2,6,6-pentamethyl-4-piperidone (2.07 g, 0.0122 mol, 1.0 equiv) and N-phenyl-p-phenylenediamine (2.259 g, 0.0122 mol, 1.0 equiv) in 1,2-dichloroethane (85 mL) was added sodium triacetoxyborohydride (3.62 g, 0.0.171 mol, 1.4 equiv) and acetic acid (0.73 g, 0.0122 mol, 1 equiv). The reaction mixture was stirred at ambient temperature for 16 h under N.sub.2. The reaction mixture was neutralized with 1N sodium hydroxide (150 mL), the layers were separated, and the aqueous layer was extracted with 3150 mL of CH.sub.2Cl.sub.2. The organic layers were combined, dried over Na.sub.2SO.sub.4, filtered, and concentrated under reduced pressure. Purified by silica gel chromatography (hexanes/EtOAc: 70:30-0:100) afforded the desired product in 10% yield (0.39 g): .sup.1H NMR (CDCl.sub.3) 7.17 (t, J=7.9 Hz, 2H), 6.99 (d, J=8.7 Hz, 2H), 6.83 (d, J=7.7 Hz, 2H), 6.76 (t, J=7.3 Hz, 1H), 6.58 (d, J=8.7 Hz, 2H), 5.37 (br s,1H), 3.58 (tt=11.6, 3.4 Hz, 1H), 2.27 (s, 3H), 1.95 (m, 2H), 1.24 (t, J=11.9 Hz, 2H) 1.16 (s, 6H), 1.1 (s, 6H).

[0110] Baseline Formulation

[0111] The base line formulation contained a Group 2 base oil, dialkyl zinc dithiophosphate, mixture of polyisobutenyl succinimide dispersants, calcium sulfonate and phenate detergents, a borated friction modifier, a pour point depressant, and an olefin copolymer viscosity index improver.

Example 5

[0112] A lubricating oil composition was prepared by adding 1.0 wt. % of the lubricating oil additive of Example 1 and 0.4 wt. % of moly succinimide according to that described herein to the formulation baseline.

Example 6

[0113] A lubricating oil composition was prepared by adding 0.2 wt. % of the lubricating oil additive of Example 1, 0.4 wt. % of moly succinimide according to that described herein, and 0.8 wt. % of a dialkylated diphenylamine antioxidant to the formulation baseline.

Example 7

[0114] A lubricating oil composition was prepared by adding 0.3 wt. % of the lubricating oil additive of Example 1, 0.4 wt. % of moly succinimide according to that described herein, and 0.7 wt. % of a dialkylated diphenylamine antioxidant to the formulation baseline.

Example 8

[0115] A lubricating oil composition was prepared by adding 0.5 wt. % of the lubricating oil additive of Example 1, 0.4 wt. % of moly succinimide according to that described herein, and 05 wt. % of a dialkylated diphenylamine antioxidant to the formulation baseline.

Example 9

[0116] A lubricating oil composition was prepared by adding 0.5 wt. % of the lubricating oil additive of Example 2, 0.4 wt. % of moly succinimide according to that described herein, and 0.5 wt. % of a dialkylated diphenylamine antioxidant to the formulation baseline.

Example 10

[0117] A lubricating oil composition was prepared by adding 0.5 wt. % of the lubricating oil additive of Example 3, 0.4 wt. % of moly succinimide according to that described herein, and 0.5 wt. % of a dialkylated diphenylamine antioxidant to the formulation baseline.

Comparative Example 11

[0118] A lubricating oil composition was prepared by adding 0.5 wt. % of the lubricating oil additive of Example 1 and 0.5 wt. % of a dialkylated diphenylamine antioxidant to the formulation baseline.

Comparative Example 12

[0119] A lubricating oil composition was prepared by adding 1.0 wt. % of a dialkylated diphenylamine antioxidant to the formulation baseline.

Comparative Example 13

[0120] A lubricating oil composition was prepared by adding 1.5 wt. % of a dialkylated diphenylamine antioxidant to the formulation baseline.

Comparative Example 14

[0121] A lubricating oil composition was prepared by adding 1.0 wt % of Naugalube APAN (Alkylated phenyl-alpha naphthylamine from Chemtura) to the formulation baseline.

Comparative Example 15

[0122] A lubricating oil composition was prepared by adding 1.0 wt % Naugard PANA (Phenyl-alpha-napthylaylamine from Chemtura) to the formulation baseline.

Comparative Example 16

[0123] A lubricating oil composition was prepared by adding 0.4 wt. % of moly succinimide according to that described herein and 1.0 wt. % of a dialkylated diphenylamine antioxidant to the formulation baseline.

Comparative Example 17

[0124] A lubricating oil composition was prepared by adding 1.0 wt. % of the lubricating oil additive of Example 1 to the formulation baseline.

Comparative Example 18

[0125] A lubricating oil composition was prepared by adding 1.5 wt. % of the lubricating oil additive of Example 1 to the formulation baseline. [0126] Oxidator Bx Test

[0127] Oxidation studies of the products of selected Examples were carried out in a bulk oil oxidation bench test as described by E. S. Yamaguchi et al. in Tribology Transactions, Vol. 42(4), 895-901 (1999). In this test the rate of oxygen uptake at constant pressure by a given weight of oil was monitored. The time required (induction time) for rapid oxygen uptake per 25 grams of sample was measured at 171 C. under 1.0 atmosphere of oxygen pressure. The sample was stirred at 1000 revolutions per minute. The results are reported, however, as time for rapid oxygen uptake per 100 grams of sample. The oil contained a catalyst added as oil soluble naphthenates to provide 26 ppm iron, 45 ppm copper, 512 ppm lead, 2.3 ppm manganese, and 24 ppm tin. [0128] TEOST MHT4 testASTM 7097

[0129] TEOST MHT4 is a proposed procedure for performance category GF-5. ASTM

[0130] D7097 is designed to predict the deposit-forming tendencies of engine oil in the piston ring belt and upper piston crown area. Correlation has been shown between the TEOST MHT procedure and the TU3MH Peugeot engine test in deposit formation. This test determines the mass of deposit formed on a specially constructed test rod exposed to repetitive passage of 8.5 g of engine oil over the rod in a thin film under oxidative and catalytic conditions at 285 C. Deposit-forming tendencies of an engine oil under oxidative conditions are determined by circulating an oil-catalyst mixture comprising a small sample (8.4 g) of the oil and a very small (0.1 g) amount of an organometallic catalyst. This mixture is circulated for 24 hours in the TEOST MHT4 instrument over a special wire-wound depositor rod heated by electrical current to a controlled temperature of 285 C. at the hottest location on the rod. The rod is weighed before and after the test. Deposit weight of 35 mg is considered as pass/fail criteria.

[0131] A copy of this test method can be obtained from ASTM International at 100 Barr Harbor Drive, PO Box 0700, West Conshohocken, Pa. 19428-2959 and is herein incorporated for all purposes.

TABLE-US-00001 TABLE 1 Oxidation Inhibition Properties (Ox Bx) TEOST (hr to rapid MHT4 Test Example Description O.sub.2 uptake) (deposit mg) Example 5 1.0 wt % Hindered Amine 45.7 20.1 antioxidant of Example 1 + 0.4 wt % Molybdenum Succinimide Example 6 0.2 wt % Hindered Amine 57.4 34.7 antioxidant of Example 1 + 0.4 wt % Molybdenum Succinimide + 0.8 wt % DPA Example 7 0.3 wt % Hindered Amine 51.4 29.7 antioxidant of Example 1 + 0.4 wt % Molybdenum Succinimide + 0.7 wt % DPA Example 8 0.5 wt % Hindered Amine 58.0 22.5 antioxidant of Example 1 + 0.4 wt % Molybdenum Succinimide + 0.5 wt % DPA Example 9 0.5 wt % Hindered Amine 51.0 35.8 antioxidant of Example 2 + 0.4 wt % Molybdenum Succinimide + 0.5 wt % DPA Example 10 0.5 wt % Hindered Amine 47.9 37.4 antioxidant of Example 3 + 0.4 wt % Molybdenum Succinimide + 0.5 wt % DPA Comparative 0.5 wt % Hindered Amine 33.2 31.7 Example 11 antioxidant of Example 1 + 0.5 wt % DPA Comparative 1.0 wt % DPA 24.2 48.4 Example 12 Comparative 1.5 wt % DPA 27.4 NM Example 13 Comparative 1.0 wt % Naugalube APAN 27.3 43.3 Example 14 (Alkylated phenyl-alpha naphthylamine from Chemtura) Comparative 1.0 wt % Naugard PANA 32.6 47.6 Example 15 (Phenyl-alpha-naphthylamine from Chemtura) Comparative 1.0 wt % DPA + 0.4 wt % 31.6 39.9 Example 16 Molybdenum Succinimide Comparative 1.0 wt % Hindered Amine 35.4 38.9 Example 17 antioxidant of Example 1 Comparative 1.5 wt % Hindered Amine 63.5 30.2 Example 18 antioxidant of Example 1

[0132] The Oxidator Bx test measures oxygen uptaken time. Higher test hours correlate to longer lifetimes of the antioxidant mixture. The synergistic effects described in this invention are found in examples 5-10, and show superior antioxidancy performance by the oxidator Bx test over comparative examples11-17. Comparative Example 18 shows that high treat rates of antioxidants are needed to rival the performance of amines from examples 1-3 in combination of a molybdenum succinimide (Examples 5-10).

[0133] The TEOST MHT4 test (ASTM 7097) is a deposit-forming test, and there is an inverse relationship between the amount of deposits formed and performance of the antioxidant. The beneficial combinations of the amine in Example 1 with a molybdenum succinimide (Example 5), and optionally a DPA (Examples 6-10) generally show lower deposits compared to single amine formulations, either with or without combination of a molybdenum succinimide (Examples 12, 14-17).