Note: Descriptions are shown in the official language in which they were submitted.
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A-17656/=
Lubricant cornposition
The present invention relates to lubricant compositions which are stabilised against
oxidation-induced degradation. Stabilisation is effected by adding a sterically hindered
amine of specific structure.
It is known and customary to incorporate additives in lubricants based on mineral oils or
synthetic oils to improve the* performance properties. Additives which inhibit
oxidation-induced degradation of the lubricants, so-called antioxidants, are especially
important. Oxidation-induced degradation of lubricants is a particularly important factor in
engine oils on account of the high temperatures prevailing in the combustion chamber of
the engines and of the presence, besides oxygen, of nitrogen oxides (NOX), which act as
oxidation catalysts.
Organic sulfur and phosphorus compounds are used in particular as antioxidants for
lubricants, as are also aromatic amines and phenols, especially sterically hindered phenols
(q.v. Ullmanns Encyclopadie der technischen Chemie, 4th edition, Verlag Chemie, Yol.
20 (1981); pages 541-43). It has also been proposed to use sterically hindered amines for
stabilising lubricants for example in US patent speci~ication 4 069 199 or Japanese Patent
Kokai 85/28496.
European patent application 0 356 677 postulates the use of mixtures of aromatic amines
and sterically hindered amines as antioxidants for lubricating oils, to which mixtures
phenolic antioxidants may also be aaded.
It has now been found that specific sterically hindered amines by themselves, i.e. without
an aromatic amine or a phenolic antioxidant, are particularly suitable for stabilising
lubricants against oxidation-induced degradation.
Specifically, the invention relates to a lubricant composition comprising
(A) a mineral or synthetic oil or a mixture of such oils, and
(B) as antioxidant stabiliser, a sterically hindered amine of formula I
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RCH2 j~R
Pll- Nk~ N(R2)---R3
RCH2 CH3 n
wherein n is 1 or 2,
R is hydro~en or methyl,
Rl is hydrogen, Cl-Cl2alkyl, allyl, benzyl, -CO-R4, -ORs or -O-CO-R6,
R2 is hydrogen, Cl-Cl2alkyl, Cs-Cl2cycloalkyl, C2-CshydroxyaL~cyl or a group of formula
II
R CH3 CH2R
<N--R1 - II
CH3 CH2R
R3, if n is 1, is hydrogen, Cl-Cl~alkyl, Cs-Cl2cycloalkyl, C2-Cshydroxyallcyl,
C3-Cl8alkoxyalkyl or C4-C20dialkylaminoalkyl, and, if n is 2, is C2-Cl2alkylene,2-hydroxy- 1 ,3-propylene or xylylene,
R4 is hydrogen, Cl-Cl2alkyl or phenyl,
Rs is hydrogen, Cl-Cl2alkyl, C5-Cl2cycloaLtcyl or benzyl, and
R6 is Cl-(:~l2alkyl, Cl-Cl2alkoxy or phenyl,
with the proviso that the composition does not contain an axomatic amine and a phenolic
antioxidant.
Rl, R3, R4, Rs or R6 as Cl-Cl2alkyl may be linear or branched aLkyl such as methyl, ethyl,
propyl, isopropyl, butyl, isoamyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl or dodecyl.
R3 as Cl-Cl8alkyl may additionally be tetradecyl, hexadecyl or octadecyl. Rl, R4, Rs or R6
as alkyl are preferably unbranched Cl-C4alkyl.
R2, R3 or Rs as Cs-Cl2cycloalkyl may be cyclopentyl, cyclohexyl, methylcyclohexyi,
cyclooctyl or cyclododecyl. The preferred meaning is cyclohexyl.
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R2 or R3 as C2-Cshydroxyalkyl may be 2-hydroxyethyl, 2-hydroxypropyl,
3-hydroxypropyl or 2-hydroxybutyl. The preferred meaning is 2-hydroxyethyl.
R3 as C3-Cl8alkoxyalkyl may be 2-methoxyethyl, 2-ethoxyethyl, 3-methoxypropyl,
3-ethoxypropyl, 3-isopropoxypropyl, 3-butoxypropyl or 3-dodecyloxypropyl.
R3 as C4-C20dialkylaminoalkyl may be 2-dirnethylaminoethyl, 3-dimethylaminopropyl,
3-di(isopropyl)aminopropyl or 3-di(octyl)aminopropyl.
R6 as Cl-Cl2alkoxy is preferably Cl-C4alkoxy, most preferably methoxy or ethoxy.
R3 as C2-Cl2alkylene may be linear or branched and is, for example, di- tri-, te~ra-, hexa-,
octa-, deca- or dodecamethylene, 2,2-dimethyl-1,3-propylene or 2,2-dimethyl-4-methyl-
hexamethylene.
Component (B) is preferably a compound of forrnula I, wherein n is 1 or 2, R is hydro~en,
Rl is hydrogen, Cl-C4aLkyl, allyl, benzyl, acetyl or -ORs, R2 is hydrogen, Cl-C4alkyl or a
group of formula II, R3, if n is 1, is hydrogen, Cl-C8alkyl or C3-ClOalkoxyalkyl and, if n is
2, is C2-C8alkylene, and Rs is C6-ClOal}~yl, cyclohexyl or benzyl.
Most preferably, component (B) is a compound of formula I, wherein n is 1 or 2, R is
hydrogen, Rl is hydrogen, methyl or acetyl, R2 is hydrogen and R3, if n is 1, is hydrogen
or C3-C8alkoxyalkyl and, if n is 2, is C2-C6alkylene.
Component (B) is also preferably a sompound of formula I, wherein n is 2 and R3 is
C2-C6alkylene.
The compounds of formula I are known compounds which are disclosed, for e7~ample, in
US patent specifications 3 684 765, 3 904 581 and 4 104 248. They are used as light
stabilisers ~or organic polymers.
Representative examples of individual compounds of formula I are:
2,2,6,6-tetramethyl-4-butylaminopyridine,
2,2,6,6-tetramethyl-4-octylaminopiperidine,
2,2,6,6-tetramethyl-4-cyclohexylaminopiperidine,
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2,2,6,6-tetramethyl-4-(N-hydroxyethylbutylamino)piperidine,
2,2,6,6-tetramethyl-4-(3-methoxypropylamino)piperidine,
2,2,6,6-tetramethyl-4-(3-dimethylaminopropylamino)piperidine,
bis (2,2,6,6-tetramethylpiperidin-4-yl)amine,
2,3 ,6-trimethyl-2,6-diethyl-4-isopropylaminopiperidine,
1 ,2,2,6,6-pentamethyl-4-dodecylarninopiperidine,
1 ,2,2,6,6-pentamethyl-4-(N-methyldodecylamino)piperidine,
1 -acetyl-2,2,6,6-tetramethyl-4-butylaminopiperidine,
1 ,2,3,6-tetramethyl-2,6-diethyl-4-(3-ethoxypropylamino)piperidine,
1 -octyloxy-2,2,6,6-tetramethyl-4-hexylaminopiperidine,
1 -cyclohexyloxy-2,2,G,6-tetramethyl-4-cyclohexylaminopiperidine,
N,N'-bis(2,2,6,6-tetramethylpiperidin-4-yl)- 1 ,2-diaminoethane,
N,N'-bis(2,2,6,6-tetramethylpiperidin-4-yl)-hexamethylenediamine,
N,N '-bis(l ,2,2,6,6-pentamethylpiperidin-4-yl)-hexamethylenediam;ne,
N,N'-bis(l -acetyl-2,2,6,6-tetramethylpiperidin-4-yl)hexamethylenediamine,
N,N'-bis(l-benzyl-2,2,6,6-tetramethylpiperidin-4-yl)-m-xylenediamine,
N,~'-bis(l-octyloxy-2,2,6,6-tetramethylpiperidin-4-yl)-2-hydroxy-1 ,3-diaminopropane.
Component (A) is a mineral or synthetic base oil conventionally used for the preparation
of lubricating oils. Synthetic oils may be, for example, esters of polycarboxylic acids or of
polyols, or they may be aliphatic polyesters or poly-a-olefins, silicones, phosphates or
polyalkylene glycols. The lubricant may also be a fat based on an oil and a thickener. Such
lubricants are described, for example, in D. Klamann "Schmierstoffe und artverwandte
Produkte" (Lubricants and Related Products), Verlag Chemie, Weinheim 1982.
Component (B) is added to the base oil preferably in an amount of 0.05 to 5% by weight,
most preferably 0.1 to 2% by weight, based on said base oil. The addition may be made
direct, or alternatively a concentrated solution of (B) in the oil or in another solvent is f*st
prepared and this solution is added to the oil.
The addition of (B) to the base oil stabilises the oil against oxidation-induced degradation
and reduces sludging in engine oils.
The lubricant composition may additionally contain other additives, for example
phosphorus (III) esters, metal passivators, rl~st inhibitors, viscosity index inlprovers,
pour-point depressants, dispersants. surfactants or antiwear additives.
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Representative examples of phosphorus (III) esters are:
triphenylphosphite, decyl triphenylphosphite, phenyl didecylphosphite,
tris(nonylphenyl)phosp}lite, trilauryl phosphite, trioctyldecyl phosphite, distearylpentaery-
thritol diphosphite, tris(2,4-di-tert-butylphenyl)phosphite, diisodecylpentaerythritol
diphosphite, bis(2,4-di-tert-butylphenyl)pentaerythritoldiphosphite, tris(stearylsorbitol)tri-
phosphite, tetrakis(2,4-di-tert-butylphenyl)-4,4'-biphenylene diphosphonite,
bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphite.
Typical examples of metal deactivators, for example for copper, are: triazoles,
benztriazoles and derivatives thereof, tolutriazoles and derivatives thereof, 2-mercapto-
benzothiazole, 2-mercaptobenzotriazole, 2,4-dimercaptobenzotriazole, 2,5-dimercapto-
benzothiadiazole, 5,5'-methylenebisbenzotriazole, 4,5,6,7-tetrahydrobenzotriazole,
salicylidene propylenediamine, salicylaminoguanidine and the salts thereof.
Examples of rust inhibitors are:
a) Organic acids, the esters, metal salts and anhydrides thereof, e.g.: N-oleylsarcosine,
sorbitan monooleate, lead naphthenate, alkenylsuccinic anhydride such as dodecenyl-
succinic anhydride, monoesters and monoamides of alkenylsuccinic acid, 4-nonyl-
phenoxyacetic acid.
b) Nitrogen-containing compounds, for example:
I. Primary, secondary or tertiary aliphatic or cycloaliphatic amines and amine saLlts of
organic and inorganic acids, for example oil-soluble alkylammonium carboxylates.II. Heterocyclic compounds, e.g. substituted imidazolines and oxazolines.
c) Phosphorus-containing compounds, for example: amine salts of phosphoric or phos-
phonic acid monoesters, zinc dialkyldithiophosphates.
d) Sulfur-containing compounds, for example: barium dinonyl-naphthalenesulfonates,
calcium petroleum sulfonates.
Examples of viscosity index improvers are:
polyacrylates, polymethylacrylates, vinyl pyrrolidone/methacrylate copolymers, poly-
vinylpyrrolidones, polybutene, olefin copolymers, styrene/acrylate copolymers,
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polyethers.
Examples of pour-point depressors aue:
polymethacrylates, alkylated naphthalene derivatives.
Examples of dispersants/surfactants are:
polybutenylsuccinan ides or polybutenylsuccinimides, polybutenylphosphonic acid
derivatives, basic magnesium, calcium and barium sulfonates and phenolates.
Examples of anti-wear additives are:
compounds which contain sulfur and/or pho~sphorus and/or halogen, such as sulfurised
vegetable oils, zinc dialkyldithiophosphates, tritolylphosphate, chlorinated paraffins, alkyl
disulfides and aryl disulfides, aLIcyl trisulfides and aryltrisulfides, triphenylphosphoro-
thionates, diethanolaminomethyltolyltriazole, bis(2-ethylhexyl)aminomethyltolyltriazole.
The lubricant composition may also contain solid lubricants such as graphite or
molybdenum sulfide.
The following Examples illustrate the invention in more detail. Parts and percentages are
by weight.
Example 1: The induction time of the oxidation of oil samples by air containing 400 ppm
of NO2 is measured under isothermic conditions using a differential scanning calorimeter
(Thermoanalyzer 1090, DuPont). The measurement is made at 170(~ under a pressure of
8 bar. The base oil used is a standard mineral oil (Aral(~ 136), to which 1 vol.% of
1-decene is added to promote oxygen sensitivity. The following amine stabilisers are
added to the oil:
A-1: 2,2,6,6-tetramethyl-4-~3-methoxypropylamino)piperidine
A-2: N,N'-bis(2,2,6,6-tetramethylpiperidin-4-yl)pentamethyldiamine
A-3: N,N'-bis(2,2,6,6-tetramethylpiperidin-4-yl)hexamethylenediamine
A-4: bis(2,2,6,6-tetramethylpiperidin-4-yl)amine
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A-5: 2,2,6,6-tetramethyl-4-butylaminopiperidine.
The induction times are given in Table 1. The longer the incluction time, the greater the
antioxidising effect of the test stabiliser.
Table 1
Stabiliser nduction time (min)
0.55% of A-1 72
0.55% of A-2 132
0.55% of A-3 107
0.55% of A-4 115
0.55% of A-5 77
without 35
