FR3092336A1 - Lubricating composition - Google Patents

Abstract

The present invention relates to a lubricating composition comprising a base oil and an antioxidant additive, said antioxidant additive comprising a phenolic antioxidant, an amine-type antioxidant, and a tocopherol supplement comprising at least one element from the list consisting of: beta-tocopherol , delta-tocopherol and gamma-tocopherol. The present invention also relates to a use of a lubricating composition according to the invention, in a heat engine. Abstract figure: Figure n ° 1

Description

Lubricant composition

The present invention is in the field of lubricants. It relates more particularly to a lubricating composition for a heat engine.

Lubricants are commonly used in heat engines. In order to improve their durability, they generally include an antioxidant additive. The composition of the usual antioxidant additive is a mixture of phenolic antioxidant, and amine type antioxidant.

The need to improve the resistance of lubricating compositions against heat degradation has existed since the appearance of heat engines. However, the compositions of antioxidant packages intended for the formulation of lubricants and their performance have changed very little for more than 20 years.

Document WO2014134506 discloses lubricating compositions comprising antioxidants. However, the results obtained in terms of resistance over time are not satisfactory. Furthermore, this document proposes as an antioxidant a combination of phenol and amine, and proposes an alternative list of products, however without giving any technical effect associated with each product proposed, nor any indication to those skilled in the art on the benefits of either product.

An object of the present invention is to provide a lubricating composition having good thermal stability against oxidative degradation.

Another object of the present invention is to provide a lubricating composition whose impact on the environment is reduced.

The object of the present invention is to respond at least in part to the aforementioned objects by proposing a lubricating composition with an improved antioxidant additive. To this end, it proposes a lubricating composition comprising a base oil and an antioxidant additive, said antioxidant additive comprising a phenolic antioxidant, an amine-type antioxidant, and a tocopherol supplement comprising at least one element from the list consisting of: beta -tocopherol, delta-tocopherol and gamma-tocopherol.

Thanks to these provisions, the composition according to the invention has better thermal stability against oxidative degradation, compared to the compositions of the state of the art, while allowing a reduction in the share of amine-type antioxidant , which is an advantage due to the toxicity of this product.

According to other characteristics:

• the sum of the contents by weight of beta-tocopherol, delta-tocopherol and gamma-tocopherol in the tocopherol supplement can be greater than 50%, preferably greater than 70%, improving the thermal stability against oxidative degradation of the lubricating composition,
• the tocopherol supplement can consist of a mixture of several types of tocopherols, at a rate of 0-20% alpha-tocopherol, 0-5% beta-tocopherol, 50-65% gamma-tocopherol and 20-35% delta-tocopherol, which is a product with good results,
• the tocopherol supplement may comprise delta-tocopherol, which allows improved hold over time of the lubricating composition,
• the tocopherol supplement may have a delta-tocopherol content by weight greater than 50%, which further improves the thermal stability against oxidative degradation of the lubricating composition,
• the content by weight of antioxidant additive can be between 0.5 and 1.5%, which is an effective embodiment of the invention,
• the antioxidant additive may have a tocopherol supplement content by weight of between 5 and 30%, which is an effective embodiment of the invention,
• the antioxidant additive may have a ratio of the contents by weight of the amine-type antioxidant to the phenolic antioxidant of less than 0.9, preferably less than 0.8, which makes it possible to improve the toxicological profile of the composition lubricating,
• the base oil can have a sulfur content by weight of less than 0.03% and a viscosity index greater than 120, which is an effective embodiment of the invention.

The present invention also relates to a use of a lubricating composition according to the invention, in a heat engine.

Thanks to these provisions, the heat engine benefits from a composition which has improved resistance over time compared to the compositions of the state of the art thanks to better thermal stability against oxidation degradation, while allowing reduction in the share of amine-type antioxidant, which is an advantage due to the toxicological risk that this product may represent.

The present invention will be better understood on reading the detailed description which follows, with reference to the appended figures in which:

is a graph showing the results of a series of comparative tests of a composition according to the invention,

is a graph showing a second aspect of the results of the series of comparative tests shown in fig. 1.

The lubricating composition according to the invention comprises a base oil and an antioxidant additive. The lubricating composition may have an antioxidant additive content by weight of between 0.5 and 1.5%.

The base oil is preferably a Group III oil, but can also be a Group I, Group II, Group III+, Group IV or Group V oil.

The antioxidant additive includes a phenolic antioxidant, an amine antioxidant, and a tocopherol supplement.

The antioxidant additive may have a tocopherol supplement content by weight of between 5 and 30%, preferably between 5 and 20%.

The phenolic antioxidant can be any phenolic compound, i.e. a compound that has a free OH group attached to a phenyl ring, capable of being an antioxidant. As used herein, the term "phenolic antioxidant" also includes compounds where the OH group is attached to a phenyl ring, wherein the phenyl ring is part of a fused ring structure, for example, the phenyl ring is part of a benzothiophene ring, a naphthalene ring, an indole ring, a benzofuran ring or the like. Preferred phenolic antioxidants are hindered phenols (e.g., with at least one of the two ortho positions of the OH phenolic group substituted, for example, by an alkyl group such as methyl, ethyl, propyl, cyclopropyl, isopropyl, butyl, isobutyl or tert-butyl) and dimer phenols.

The phenolic antioxidant can therefore consist of a hindered phenol or a mixture of several hindered phenols, chosen from 2,6-di-tert-butyl-4-methylphenol, 2-butyl-4,6-dimethylphenol , 2,6-di-tert-butyl-4-ethylphenol, 2,6-di-tert-butyl-4-n-butylphenol, 2,6-di-tert-butyl-4-isobutylphenol, 2 ,6-dicyclopentyl-4-methylphenol, 2-(α-methylcyclohexyl)-4,6-dimethylphenol, 2,6-dioctadecyl-4-methylphenol, 2,4,6-tricyclohexylphenol, 2,6-di -tert-butyl-4-methoxymethylphenol, 2,6-dinonyl-4-methylphenol, 2,4-dimethyl-6-(1'-methyl-undec-1'-yl)-phenol, 2,4- dimethyl-6-(1'-methylheptadec-1'-yl)-phenol, 2,4-dimethyl-6-(1'-methyltridec-1'-yl)-phenol, 2,4-diotylthiomethyl-6- tert-butylphenol, 2,4-diotylthiomethyl-6-methylphenol, 2,4-diotylthiomethyl-6-ethylphenol, and 2,6-didodecylthiomethyl-4-nonylphenol.

The amine antioxidant can be an aliphatic or aromatic amine.

Aromatic amine is a compound that has an amine group, either a free amine group (eg, NH2), or a substituted amine group (eg, NR ¹ R ² , where R ¹ and R ² are independently hydrogen , alkyl, arylalkyl, heteroarylalkyl, cycloalkylalkyl, hétérocyclocycloalkyle, hétérocyclocycloalkyle, arylcycloalkyl, arylcycloalkyl, heteroarylcycloalkyl, arylhétérocycloalkyle, hétéroarylhétérocycloalkyle, hétéroarylhétérocycloalkyle, cycloalkyl, arylcycloalkyl, heteroarylcycloalkyl, heteroarylcycloalkyl, heterocycloalkyl, arylhétérocycloalkyle, alkenyl, arylalkenyl, cycloalkenyl, arylcycloalcène, heteroarylcycloalkenyl, heterocycloalkenyl, heterocycloalkenyl , arylheterocycloalkenyl, heteroarylheterocycloalkenyl, heteroarylheteroalkenyl, alkynyl, arylalkynyl, aryl, cycloalkylaryl, heterocycloalkylaryl, cycloalkenylaryl, heterocycloalkenyl, heteroaryl, cycloalkylheteroaryl, heteroalkylheteroaryl, cycloalkenylheteroaryl or heterocycloalkenylheteroary le), directly attached to an aromatic ring, such as a monocyclic aromatic ring (for example a phenyl ring, or a monocyclic heteroaromatic ring such as a thiophene ring, a pyridine ring, a pyrimidine ring, a furan ring, a pyrazine, a pyridazine ring, a triazine ring), or a polycyclic aromatic ring (for example a bicyclic aromatic ring such as a naphthalene ring, or a bicyclic heteroaromatic ring such as an indole ring, a benzofuran ring, a benzoimidazole ring or a benzothiophene ring, etc. or a tricyclic aromatic ring such as a carbazole).

The amine-type antioxidant can be an aromatic amine, in which the amine group is attached to two aromatic rings, such as two monocyclic aromatic rings (for example, as described here) which are the same or different, two polycyclic aromatic rings (for example, as described herein) which are the same or different, or a monocyclic aromatic ring (eg, as described here) and a polycyclic aromatic ring (eg, as described here). The amine antioxidant may be a diphenylamine. The amine antioxidant can further be an aromatic amine having the amine group attached to a monocyclic aromatic ring (eg, a phenyl ring) and a polycyclic aromatic ring (eg, a naphthalene ring). The amine antioxidant can be selected from the group consisting of dinonyl diphenylamine, butylated, octylated diphenylamine, dioctyl diphenylamine, Ν,Ν'-diisopropyl-p-phenylenediamine, N,N'-di-sec-butyl-p-phenylenediamine , N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine, N,N'-bis(1-ethyl-3-methylpentyl)-p-phenylenediamine, N,N'-bis(1-methylheptyl) -p-phenylenediamine, N,N'-dicyclohexyl-p-phenylenediamine, N,N'-diphenyl-p-phenylenediamine, N,N'-di(naphth-2-yl)-p-phenylenediamine, N-isopropyl-N '-phenyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, N-(1-methylheptyl)-N'-phenyl-p-phenylenediamine, N-cyclohexyl-N' -phenyl-N'-phenyl-p-phenylenediamine, 4-(p-toluenesulfonamido)-diphenylamine, N,N'-dimethyl-N,N'-di-sec-butyl-p-phenylenediamine, diphenylamine, diphenyl amine styrene ( CAS No. 68442-68-2), N-allyldiphenylamine, 4-isopropoxydiphenylamine, di(4-methoxyphenyl)amine, 2,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, N,N,N',N'- tetramethyl-4,4'-dia minodiphenylmethane, 1,2-di[(2-methylphenyl)amino]-ethane, 1,2-di(phenylamino)propane, (o-tolyl)biguanide, di[4-(1',3'-dimethylbutyl)phenyl] amine, N-phenyl-1-naphthylamine tert-octylated, phenyl-1- naphthylamine amine p,p'-dioctyldiphenyl, mixture of tert-butyl-diphenylamines tert-butylated/tert-octylated mono- and di-alkylated, mixture of nonyldiphenylamines mono- and di-alkylated, mixture of mono- and di-alkylated dodecyldiphenylamines, mixture of mono- and di-alkylated isopropyl/isohexyl-diphenylamines, mixtures of mono- and di-alkylated tert-butyldiphenylamines, 2,3-dihydro-3 ,3-dimethyl-4H-1,4-benzothiazine, phenothiazine, mixture of mono- and di-alkylated tert-butyl/tert-octyl-phenothiazines, mixtures of mono- and di-alkylated tert-octylphenothiazines, N-allylphenothiazine and Ν ,Ν,Ν',Ν'-tetraphenyl-1,4-diaminobut-2-ene.

The tocopherol supplement includes at least one of beta-tocopherol, delta-tocopherol and gamma-tocopherol.

The sum of the contents by weight of beta-tocopherol, gamma-tocopherol and delta-tocopherol in the tocopherol supplement may be greater than 50%, preferably greater than 70%.

Example of composition of the tocopherol supplement according to the invention:

• 0 to 20% alpha-tocopherol,
• 0 to 5% beta-tocopherol,
• 50 to 65% gamma-tocopherol,
• 20 to 35% delta-tocopherol.

In a preferred embodiment of the invention, the tocopherol supplement comprises delta-tocopherol, preferably the content by weight of the tocopherol supplement in delta-tocopherol is greater than 50%.

The antioxidant additive may have a ratio of the contents by weight of the antioxidant of the amine type to the phenolic antioxidant of between 0.6 and 1.2.

In a preferred embodiment, the ratio of the contents by weight of the amine antioxidant to the phenolic antioxidant is less than 0.9, preferably less than 0.8. In fact, the amine-type antioxidant can represent a toxicological risk, which is why it is advantageous to reduce its share in the antioxidant additive. This reduction is possible by the presence of the supplement tocopherol, which makes it possible to obtain good antioxidant performance while reducing the share of amine-type antioxidant.

In a preferred embodiment of the invention, the base oil is a Group III oil, that is to say it has a sulfur content by weight of less than 0.03% and a viscosity greater than 120.

The lubricating composition according to the invention may also comprise one or more additional products chosen from the group consisting of an anti-wear agent, a detergent, a metal deactivating additive, a phosphite, a lactone, a dispersant, a diluent, a emulsifier, defoamer, corrosion/rust inhibitor, extreme pressure agent, pour point depressant, viscosity index improver and friction modifier.

Example

A composition according to the invention was tested using a group III HC6 oil, to compare its performance with comparative compositions. A thermal aging test at 150°C for 216 hours was carried out according to the CEC (“Coordinating European Council”) L-109-14 procedure.

The evolution of the KV100 viscosity (mm²/s) according to the ASTM D445/446 standard as well as the resistance to oxidation (A/cm) according to the DIN 51453 standard were measured at regular intervals of aging at 150°C : t=0 hours (initial), t= 72 hours, t=144 hours, t=168 hours, t=216 hours.

The antioxidants tested are AO 1135, AO 5057, alpha-tocopherol, and a tocopherol supplement under the reference VB T70.

AO 1135 is a phenolic antioxidant with composition: benzopropanoic acid, 3,5-bis(1,1-dimethyl-1,1-dimethylethyl)-4-hydroxy-, branched alkyl esters in C7-9.

AO 5057 is an amine-type antioxidant, composition: benzenamine, N-phenyl-, reaction products with 2,4,4-trimethylpentene.

VB T70 is a mixture of antioxidants and sunflower oil, of composition:

• 30% sunflower oil
• 70% tocopherols, among which are:
  • 9-20% alpha-tocopherol
  • 1-4% beta-tocopherol
  • 50 to 65% gamma-tocopherol,
  • 20 to 35% delta-tocopherol.

Comparative compositions:

• Membership A:
  • HC6 base oil
• Compound B:
  • 99% HC6 base oil
  • 1% AO 1135
• Component C:
  • 99% HC6 base oil
  • 0.7% AO 1135
  • 0.3% VB170 (which corresponds to approximately 0.21% tocopherol supplement, due to the presence of sunflower oil in VB170)
• Composition D (state of the art):
  • 99% HC-6 base oil
  • 0.5% AO 1135
  • 0.5% AO 5057
• Composition E:
  • 99% HC-6 base oil
  • 0.4% AO 1135
  • 0.4% AO 5057
  • 0.2% alpha-tocopherol

Example of a lubricating composition according to the invention:

Composition F:

• 98.9% HC6 base oil
• 0.45% AO 1135
• 0.45% AO 5057
• 0.2% VB 170 (which corresponds to approximately 0.14% tocopherol supplement)

The test results are shown in Tables 1 and 2 below, as well as in Figures 1 and 2.

• Table 1: KV100 viscosity according to ASTM D445/446 standards (mm²/s)
• Table 2: Oxidation (A/cm) according to DIN 51543

Aging time at 150°C (hours) 0 72 144 168 216 Composition A 6,365 8,258 11.54 13.45 19.87 Composition B 6,348 7,475 9.956 11.14 14.57 Composition C 6,351 7,503 10.04 11.37 15.21 Composition D 6,348 6.962 9,357 10.43 13.59 Composition E 6,358 7,531 10.46 12 17.06 Composition F 6,354 7,198 8,867 9,595 11.4

Aging time at 150°C (hours) 0 72 144 168 216 Composition A 0 79.3 128.6 144.6 173.9 Composition B 0 47.1 104.6 118.5 144.2 Composition C 0 48.2 110.6 126.1 156.9 Composition D 0 29.5 102.4 120.9 157 Composition E 0 50.4 119.3 138.2 174.6 Composition F 0 36.5 87 99.5 123.2

The graph in Figure 1 and Table 1 show the evolution of the viscosity of the oil during its thermal aging, measured according to the ASTM D445/D446 protocols. The ordinate unit is mm ² /s. The unit of time on the abscissa is the duration of thermal aging at 150°C, expressed in hours. This test is particularly relevant for evaluating the performance of a lubricating composition and its behavior over time.

The graph in Figure 2 and Table 2 show the development of oxidation, measured according to the DIN 51453 protocol. The ordinate unit is A/cm. The unit of time on the abscissa is the duration of thermal aging at 150°C, expressed in hours.

In Figs. 1 and 2, it can be seen that the performances are the lowest for composition A, which does not contain any antioxidant additive.

Composition D, which is the benchmark antioxidant formulation used on a large scale on the lubricants market, is the state-of-the-art composition which obtains the best performance in terms of viscosity (fig. 1). Composition F, produced according to the invention, is similar to composition D with part of the antioxidants replaced by a mixture of tocopherols of the alpha, beta, gamma and delta types.

The results of composition F are better in terms of viscosity (fig. 1) and oxidation (fig. 2) than those of composition D. The comparison of compositions D and F makes it possible to conclude that there is an improvement in performance obtained by the presence of tocopherols.

Composition E is also similar to composition D, but this time with the presence of exclusively alpha-type tocopherols.

The performances of composition E represented in FIGS. 1 and 2 are less good than composition F, and even less good than composition D. The performance-enhancing effect observed previously is therefore not present with exclusively alpha-type tocopherols, which shows the importance beta, gamma and delta tocopherols.

Composition B includes only a phenolic antioxidant, and Composition C is similar to Composition B with some of the phenolic antioxidant replaced with the mixture of alpha, beta, gamma and delta tocopherols.

The performances of composition C represented in FIGS. 1 and 2 are less good than composition B. The performance-enhancing effect observed previously thanks to the tocopherols is therefore not present in the absence of an antioxidant of the amine type. This reveals an effect of regeneration of the amine-type antioxidant by tocopherols, explaining that tocopherols make it possible to improve performance in composition F.

Consequently, in the compositions according to the invention it is possible to reduce the quantity of antioxidant of the amine type compared to the state of the art by adding a little tocopherol of the beta, gamma or delta type, which is a advantage due to the toxicity of amine-type antioxidants. One can for example provide an antioxidant with 50% phenol antioxidant, 40% amine antioxidant, and 10% tocopherol supplement, or 45% phenol antioxidant, 40% amine antioxidant, and 15% supplement tocopherol.

Although the above description is based on particular embodiments, it is in no way limiting the scope of the invention, and modifications may be made, in particular by substitution of technical equivalents or by different combination of any or part of the characteristics developed above.

Claims (8)

A lubricating composition comprising a base oil and an antioxidant additive, in which:

• the content by weight of antioxidant additive is between 0.5 and 1.5%,
• said antioxidant additive comprises a phenolic antioxidant, an amine-type antioxidant, and a tocopherol supplement,
• the antioxidant additive has a tocopherol supplement content by weight of between 5 and 30%,
• the tocopherol supplement includes at least one element from the list consisting of: beta-tocopherol, delta-tocopherol and gamma-tocopherol,
• the sum of the contents by weight of beta-tocopherol, delta-tocopherol and gamma-tocopherol in the tocopherol supplement is more than 50%.

A lubricating composition according to claim 1, wherein the sum of the contents by weight of beta-tocopherol, delta-tocopherol and gamma-tocopherol in the tocopherol supplement is greater than 70%. Lubricating composition according to the preceding claim, in which the tocopherol supplement consists of a mixture of several types of tocopherols, in the proportion of 0 to 20% alpha-tocopherol, 0 to 5% beta-tocopherol, 50 to 65% gamma-tocopherol and 20-35% delta-tocopherol. Lubricating composition according to one of Claims 1 to 2, in which the tocopherol supplement comprises delta-tocopherol. A lubricating composition according to claim 4, wherein the tocopherol supplement has a delta-tocopherol content by weight greater than 50%. Lubricating composition according to one of the preceding claims, in which the antioxidant additive has a ratio of the contents by weight of the antioxidant of the amine type to the phenolic antioxidant of less than 0.9, preferably less than 0.8. Lubricating composition according to one of the preceding claims, in which the base oil has a sulfur content by weight of less than 0.03% and a viscosity index greater than 120. Use of a lubricating composition according to one of the preceding claims, in a heat engine.