DE1148684B - Ester-based lubricating oil - Google Patents

Description

When using lubricating oils at high temperatures, for example in modern aircraft gas turbines and in hydraulic systems, particular difficulties arise as a result Oxidation forms acidic products which are deposited as deposits and sludge.

It has now been found that ester-based lubricating oils are thereby made particularly resistant to oxidation by adding two different types of additives to them. Accordingly, refers the invention on ester lubricating oils, which by the addition of small amounts of

a) a triazine and from

b) characterized a complex of such an amine with a copper salt of a fatty acid are, wherein the molar ratio of a total amount of free and bound amine to the Copper is between 2 and 75.

Each of these additives is preferably used in an amount of from 0.05 to 10 ^fl / o, in particular from 0.1 to 4 percent by weight, calculated on the total mixture.

Aliphatic esters, from z. B. dicarboxylic acids and monohydric alcohols as well Esters of pentaerythritol or its dimers or trimers with monobasic acids and so-called "Complex esters", which are various combinations of dibasic acids, glycols and alcohols or from dibasic acids, glycols and monobasic acids. Table A shows the various structures known as “complex esters” and typical starting materials for the formation of such esters.

35 Table A

Complex esters

1. Alcohol - (dibasic acid - glycol) _n - monobasic acid

R ₁ - (OOCR ₂ COO-Rg) _n -OOCR ₄
(See U.S. Patent 2575195). Ester-based lubricating oil

Applicant:

Shell

International Research Maatschappij N.V., The Hague

Representative: Dr. K. Schwarzhans

and Dipl.-Chem. Dr. phil. E. Jung, patent attorneys,

Munich 19, Romanplatz

Claimed priority: V. St. v. America 6 June 1960 (No. 33 952)

Hans Low, William Walter Reynolds,

East Alton, 111., and Donald William Schmulling, St. Louis, Mo.

(V. St. A.) have been named as inventors

Monohydric alcohols 2-ethylbutyl alcohols, 2-ethylhexyl alcohols.

Monobasic acids caproic acid, pelargonic acid, capric acid

2. Alcohol — dibasic acid— (glycol — two-glycols

basic acid) "- alcohol

R ₁ -0OCR ₂ COO (R ₃ -0OR ₄ COO) _n -R ₅

(See U.S. Patent 2703,811).

3. Glycol monobasic (dibasic acid - glycol) “- monobasic acid
R ₁ COO-R ₂ - (OOCR ₃ COO-R ₄ ) _{n -0OCR 5} (see U.S. Patent 2,575,196). 2,2-dimethylpropanediol-1,3, ethylene glycol, propylene glycol.

Dibasic acids 50

Sebacic acid, azelaic acid.

309 580/391

One or more compounds with the formula can also be used as diesters

ROOC-Z-COOR

can be used in which Z represents an alkylene chain having 4 to 8 carbon atoms and R represents a Means an alkyl group of 4 to 14 carbon atoms which is the remainder of an aliphatic monovalent Alcohol from the range of butyl to tetradecyl alcohol is equivalent to. Suitable dibasic acids for the formation of such esters are adipic, Pimellic, suberic, acellic and sebacic acids. Provide alcohols with branched hydrocarbon chains Diesters with particularly desirable properties. Typical examples of these alcohols are isobutyl, 2-ethylbutyl-, 2-ethylhexyl-, 1-methylhexyl-, 1-methylheptyl-, l-methyl-4-ethyloctyl-, 2,2,4-trimethylhexyl-, 2-isopropyl-3,3-dimethylbutyl-, 1,4-dimethylbutyl- and 1-isobutyl-4-ethyloctyl alcohol.

Ester lubricants of the formula ROOC — Z — COOR

Bis (2-ethylhexyl) sebacate,

Bis (isononyl) sebacate,

Bis (2-ethylhexyl) adipate,

Bis (l-methylheptyl) azelate, bis (2,2,4-trimethylhexyl) pimelate, Bis (1,4-diethylhexyl) adipate, bis (1,4-dimethyloctyl) adipate, bis (2-ethylbutyl) suberate,

(2-ethylhexyl) - (isononyl) sebacate, (l-methylhexyl) - (2-ethylbutyl) sebacate.

Alkyltriazines,

2,4-diethyltriazine,

2,4,6-trimethyltriazine,

2-methyl-4,6-diethyl-triazine, 2-methyl-4-aminotriazine.

Aryl triazines,

2,4-diphenyl-triazine,

2-phenyl-4-aminotriazine,

2-benzyl-triazine,

2-Benzyl-4-0 ^{s (} i-benzylamino) triazine.

Triazinylamines,

(Triazinyl) - (2-pyridyl) amine, di (triazinyl) amine.

40

The preferred aliphatic polyesters in the new lubricating oils are tetraesters, such as the pentaerythritol esters or the dimers or trimers thereof are used. Preferably each contains remainder 4 to 18 carbon atoms and preferably 6 to 14 carbon atoms. Typical examples are pentaerythritol tetracaproate, Dipentaerythrite xavalerate, pentaerythritol tetraheptoate, pentaerythritol dicaproate divalerate, Pentaerythritol tricaproate heptoate and mixtures of these compounds.

From the group of the triazines, derivatives of 2,4-diamino-triazine are particularly suitable. The following Table B shows typical examples of compounds suitable for this purpose:

Table B.
Triazines

Diaminotriazines,

2,4-diamino-6-benzyl-triazine, 2,4-diamino-6-methyl-triazine, 2,4-diamino-6-propyl-triazine, 2,4-diamino-triazine,

2,4-diamino-6-phenyl-triazine.

Monoaminotriazines,
2- (N-methylamino) triazine,
2- (N-phenylamino) -triazine,
2-amino-triazine.

The oxidation-preventing effect of the present combination is surprising in itself, since copper is known per se as an effective accelerator for oxidations. The present invention is based on the discovery that there is an optimum ratio of the excess of free amine to ^a 5 of that amount bound in the copper complex and that within this range a marked stabilization of the oxidizing properties of the ester-based lubricating oil is observed.

For the preparation of the complexes according to the invention, such copper salts are preferably used which are derived from divalent copper, while the fatty acid radical from any Fatty acid with 2 to 24 carbon atoms can be derived. Suitable fatty acids are e.g. vinegar, Propionic, butyric, hexanoic, octanoic, dodecanoic, caproic, caprylic, capric, stearic, oleic, linoleic acid, etc. The acid should preferably be saturated and have 2 to 12 carbon atoms per molecule.

The copper complexes can be formed in situ in the lubricating oil, or they can already have been made separately beforehand. The complexes are immediately carried out in the latter Mixing the appropriate solutions, such as the alcohol solutions of the amine and the copper salt, and then evaporating to dryness.

The formation of the metal complex is an equilibrium reaction. Hence an excess of free amine serves primarily two purposes; first, it reduces the amount of the freely soluble Copper ion, which would act as an oxidizing agent, and secondly, it provides the formation the largest possible amount of active inhibitor safely by balancing in favor of the complex is moved. If, on the other hand, there is an excess of the free copper compound, predominates the oxidative effect of copper. On the other hand, if too large amounts of free amine are present, the inhibition of oxidation is also reduced, since the free amines appear to be are not very effective inhibitors. So was z. B. found by comparative tests, that the maximum inhibition of oxidation was achieved when the molar ratio of total amine to copper was between 2 and 75, preferably between 5 and 35.

The course of oxidation as derived from the rate of oxygen absorption in the

Mixtures according to the present invention can be derived, shows that the amine in the form of Copper complex is oxidized before it performs its intended function as an antioxidant. Oxidation of the amine can take place before or after the amine is incorporated into the lubricating oil. The exact structure of the oxidation products has not yet been established, but is for that Fraction of the oxidized product which is most effective in preventing the oxidation of the Ester lubricating oil, a nitrogen to copper molar ratio on the order of about 20 to 30 while the less effective fractions of the oxidized product have a nitrogen-to-copper molar ratio on the order of 3 to 6.

Further unexpected reductions in the tendency of the lubricating oil to oxidize are achieved by the additional presence of small amounts (e.g. 0.05 to 10%, preferably 0.1 to 4 percent by weight) of certain, phenolic compounds known as lubricating oil additives, in particular alkylene bisphenols. Typical connections of this type are:

4,4'-methylene-bis- (2,6-di-tert-butylphenol), 4,4'-methylenebis (2- (2-ethylhexyl) phenol),

2,2'-methylene-bis (4-isopropylphenol).

The numerical values contained in the examples show the advantages that result from the use of such Bisphenols in addition to the combination of the copper complex and the free amine can be achieved. the The following examples explain the invention in more detail: For the preparation of the described below Amine-copper complex is not claimed in the context of the invention.

An alcoholic solution of copper (II) caprylate is in stoichiometric ratio with an alcoholic Mixed solution of 2,4-diamino-6-phenyl-1,3,5-triazine.

The green precipitate has a melting point of 210 to 214 ° C, and elemental analysis shows that it contains 55.5 percent by weight carbon, 7.42 percent hydrogen, 13.3 percent nitrogen and 14.0 percent copper. This agrees with the theoretically assumed formula

Formula, and this fact indicates the likelihood of dimerization. This is also probably because the copper (II) can then form a complex of a rectangular type.

example 1

The lubricant based on a pentaerythritol ester from a mixture of fatty acids with an average 8 to 10 carbon atoms per ester bond is modified with 0.025 mol of 2,4-diamino-6-phenyl-triazine per liter of solution. The following table shows the effect of adding copper caprylate to this mixture in terms of oxidation prevention, copper caprylate added in this way forms a complex with part of the amine in situ. The mixtures are made up by heating 204 ° C tested, with oxygen passed through at a rate of 1 1 per hour in the form of bubbles will.

Table I.

IVl Ol V CHI alinia
Total amine Oxidation time Copper caprylate to copper in hours in percent by weight
Copper, based on for absorption of
1 mole of O ₂ Lubricating oil mixture _ per gram of oil 73.0 (without catalyst) 0 29.1 15th 0.0020 13.2 44 0.0050 7.65 62 0.0110 3.82 83 0.0190 1.91 85 0.0380 0.96 89 0.0760 47 0.1520 33

C ₉ H ₉ N ₅

Cu (C ₈ H ₁₅ O ₂ ) ₂ .

However, the experimentally determined molecular weight is 945, i.e. H. almost double the empirical

Example 2

The following Table II shows the advantages obtained by using a combination of 2,4-diamino-6-phenyl-triazine can be achieved with varying amounts of copper catalyst in the lubricating oil base according to Example 1. It is important that within of the claimed molar ratio, the acid number of the oxidized oil is at a minimum. this indicates that the peroxide formation is also reduced to a minimum by the combination of additives became.

Table II

2,4-diamino-6-phenyl-triazine metal Molar ratio
Amine to copper Oxidation time
in hours Acid number 0 moles per liter
0 moles per liter
0.025 moles per liter
0.025 moles per liter Solid copper
0.005 percent by weight copper + ^{2 a} >
0.019 weight percent copper + ²
0.0760 weight percent copper + ² 7.6
1.9 14th
16
85
47 5.1
5.9
4.2
5.1

Ό Added as copper caprylate.

Example 3 (2,6-di-tert-butylphenol). From the following " 65 given numbers it can be seen that an unexpected similar mixture, which were prepared with a synergetic effect, is obtained through the application the same lubricating oil base as in the essence of this bisphenol in addition to the copper grain 1, were modified with 4,4'-methylene-bis-plex and an excess of free amine.

Table III

additive Oxidation time Oxidation time (Oxidation time —14) 0.025 moles per liter in hours -14 a) combined ■ \ τ_ . JNr. 14th minus
(Oxidation time -14) W (2,4-diamino-6-bhenyl-triazine) 15th 1 simple 1 4,4'-methylene-bis- (2,6-di-tert-butylphenol) 27 13th 2 Copper caprylate, ^
0.005 weight percent copper + ² 16 2 - 3 (2) + (4) 62 48 - 4th (3) + (4) 24 10 - 5 (2) + (3) + (4) 91 • 77 + 45 6th C. 7th + 61

^a ) Pure oxidation time based on the additive alone, ie after subtracting the oxidation time in hours, which is observed for the starting material alone (14 hours).

b) Difference between the hours determined experimentally (e.g. 48 for mixture No. 5) and the sum the hours in the same column that were achieved with the individual inhibitors (e.g. 1 and 2 for the mixtures No. 2 and 4).

Claims (11)

PATENT CLAIMS: 1. Ester-based lubricating oil, in particular an aliphatic ester, characterized by the addition of small amounts of a) a triazine and from b) a complex of such an amine with a copper salt of a fatty acid, wherein the molar ratio of the total amount of free bound amine to the copper is between 2 and 75. 2. Lubricating oil according spoke 1, characterized in that it is an ester of pentaerythritol or its dimer or trimer with a monocarboxylic acid, preferably with a fatty acid with 4 to 18 carbon atoms. 3. Lubricating oil according to spoke 1, characterized in that it is an ester of the formula ROOC-Z-COOR contains, in which Z is an alkylene chain with 4 to 8 carbon atoms and R is an alkyl group with Is 4 to 14 carbon atoms. 4. Lubricating oil according to claim 1 to 3, characterized in that it is a substituted triazine, in particular a 2,4-diamino-triazine, such as 2,4-diamino-6-phenyl-triazine, contains. 5. Lubricating oil according spoke 1 to 4, characterized in that the complex is divalent Contains copper. 6. Lubricating oil according spoke 1 to 5, characterized in that the copper complex of derived from a fatty acid having 2 to 24 carbon atoms and in particular 2 to 12 carbon atoms is. 7. Lubricating oil according spoke 1 to 6, characterized in that the copper complex of caprylic acid is derived. 8. lubricating oil according spoke 1 to 7, characterized in that the molar ratio of total amine to copper is between 5 and 35. 9. Lubricating oil according spoke 1 to 8, characterized in that it is the amine in oxidized Contains shape. 10. Lubricating oil according to claim 1 to 9, characterized in that it also has a low Amount of a phenolic compound known as a lubricating oil additive, such as an alkylene bisphenol and in particular 4,4'-methylene - bis - (2,4 - ditert.butylphenol) contains. 11. Lubricating oil according spoke 1 to 10, characterized in that there is every single additive in an amount from 0.05 to 10 percent by weight, in particular from 0.1 to 4 percent by weight, calculated on the total mixture. © 309 580/391 5.63