DE1668988A1 - Oxidation inhibitors for lubricants - Google Patents

Description

DR. FRANZ LEDERER 8 MÖNCHEN 8O

LUCILE-GRAHN-STR. 22 - TEL. C08 I Il 44 08

Munich, 23 "PEBR, 1968 P / Bg

Applicant; Unilever-Emery NoVo ₉ Gonda, Holland Oxidation inhibitors for lubricants

The present invention relates to oxidation inhibitors for lubricant systems and in particular to branched chain ones saturated, aliphatic secondary diamines, which are useful as oxidation inhibitors for lubricants based on synthetic esters »

Oxidation inhibiting furnaces are added to soaking agent liquids in order to reduce oxidative decomposition of the liquid to acidic products, which tend to form sludge and corrode various metal surfaces with which the lubricant comes into contact An increase in the machine temperature places increased demands on the oxygen inhibitor. Therefore, many oxidation inhibitors which ^{offer adequate protection down to temperatures of around 149 0} G essentially do not show any usefulness at higher temperatures. With "Umr C / äöigarrtng üa"'Complete information CtslotnvbmmuxihInen gin /; öLüj ßrhi> liun <i * i «r operating einhet'j mn atwa H ¹ J ⁰ O maximal-'fiii! bt>3X'atur at lan ira tfahra 1955 for ^ lugä ^ tigantrleb Tsr ^: A« iid3isn Gaüfrurbc ^ iaa ^ hiiiäii 'came * a au

1U9044 / 1857

Temperatures of 204 to 232 ⁰ C in modern aircraft gas turbine engines. At temperatures above 149 ^° C., the conventional oxidation inhibitors, such as, for example, alkylated phenols and conventional petroleum lubricating oils, fail.

According to the invention, oxidation inhibitors for lubricants _9, especially lubricants based on synthetic esters; proposed consisting essentially of secondary amines of the general formula

consist, where R ₁ and R «represent branched, saturated aliphatic hydrocarbon groups with 15 to 24 carbon atoms and the hydrocarbon or non-carboxyl part of normally liquid, non-chain, saturated, aliphatic monocarboxylic acids with 16 to 25 carbon atoms and«

Ri.saereioifschmiermitteln saisie in synäieti & heavy echo flohmiöi-aitteln easily the aakuiidären Dlttlky ^ anine acc present invention are capable of oxidizing Sohmiermittelkospositionen with so have to inhibit temperatures such as 232 ⁰ C, you besitsen the further advantages tHe ale in coals? Iöellch lind therefore, two mil! .Artan f- ^ rtrügllcih -Hnd that ai $ die Flllasigküi la », lg $ hti uhüftm iw ¹ , · v ^, ii ^ nUüKji0fc ^: ill: nioir ·; ^^ r? '7.iöh bealnt? iil: ■'; tig ^ u mil \ z% sie i! h ^ aüimi-- · d'y ßlas iossrdlohtungen in lit gzuVf ^ 'Yi'h * -ra ·; laiilmau «lohe augz'aifyn- Llne-t dei ¹ schwie-

BATH

1688988

Rigaten problems with the so far developed oxidation inhibitors, which are able to withstand high temperatures »is hers Tendency to attack rubber or elastomer seals, as a result of which these become hard and brittle and no longer fulfill their task.Some seals such as those made of Yiton -A, a fluorinated polymer »are depolymerized by many of the so-called high-performance oxidation inhibitors.

In the past, aromatic secondary amines such as ZoBo ρ, ρ'-dioctyl-diphenylamine were probably the most popular antioxidants for high temperature machines. While these aromatic secondary amines are able to withstand high temperatures and are generally stable antioxidants, some have suffered from the rough part of being "dirty", that is, forming a sludge that clogs up and causes stunted lubrication when used at high temperatures Temperatures, ie. 232 ^° C. One of the outstanding advantages of the branched-chain aliphatic secondary amines according to the present invention is that they have exceptionally good cleanliness properties, allowing the machines to operate without clogging caused by sludge build-up.

Pieces of aliphatic secondary amines according to the invention have, as already noted, excellent solubility properties and are in all proportions with lubricants the ester type, with and with polyglycol lubricants

109844/1857

petroleum-based miscible without noticeably affecting the liquid range of the basic lubricants »They also bind very stably and can with any of the conventional additives; used in lubricant compositions intended for high temperature application. Furthermore, they remain liquid at extremely low temperatures, i.e. at temperatures as low as minus 73 = 74 ° C and therefore they are suitable for lubricants which have to have an extremely wide range of liquids. Some aliphatic secondary amines (dialkylamines) such as distearylamine, dimyristylamine, and dilaurylamine, and have been used in the past as antioxidants for petroleum lubricants; However, they are generally unsatisfactory for use with itaterschmiermitteln fail because they are solids at room temperature and as a result of crystallization at low temperatures, d.ho temperatures below about minus 29 ⁰ C, from the solution. Furthermore, after they have failed at low temperatures, they are difficult to bring back into solution and are often trapped by filters, which leads to clogging of the lubrication system.

As already mentioned, the hydrocarbon groups H ₁ and R _{2 of} the general formula have about 15 to 24 carbon atoms. The branched-chain monocarboxylic acids with about 16 to 25 carbon atoms which are used in the preparation of the secondary amines according to the invention are liquid at room temperature and are produced synthetically. An acid that is used in the preparation of the inventive se-

109844/1857

Which is particularly suitable for terminating amines is one with 18 carbon atoms, which is formed as a by-product in the polymerization of naturally occurring unsaturated fatty acids according to the processes described in UoSo patent specification 2,812,342. (This patent specification will hereinafter be referred to as the reference patent). The acid in question was identified as isoatearic acid. According to the disclosure of the reference patent, mono- or polyunsaturated fatty acids are thermally treated in the presence of water with or without a catalyst »to produce products» which are commercially known as dlme.re acids o This process automatically delivers a substantial amount of by-product acids »which are a mixture of monomeric acids« The monomeric mixture »which is usually distilled off from the reaction product containing the polymer in vacuo» includes saturated fatty acids »which have not been attacked by the polymerization treatment» probably some unsaturated fatty acids » which the Polymerisatlonsb · - {treatment escaped "and fatty acids" that have been structurally modified by the polymerization in such Weis · that they oppose further polymerization.

Following the process outlined in the reference patent, the monomeric fatty acids are hydrogenated by the iodine number of the mixture to a value below 10 and perhaps down to 3, the natural unsaturations that are roughly present

1098AA / 1857.

Fatty acids negotiated into saturated fatty acids «ground · the hydrogenation treatment also reduces the iodine number of the fatty acids» which have been structurally modified to a certain extent by the polymerisation treatment. Further modifications may take place during the hydrogenation "although it is not known to what extent structural modification of the acids takes place during this stage." The resulting hydrogenated fatty acid mixture is then solvent separated to remove the normal solid fatty acids such as "Bo stearic" and palmitic acid to remove. The residual saturated fatty acid is a modified product "which contains 18 carbon atoms" is a branched chain structure, a linear density below 15 ⁰ C and an iodine value of la substantially 3 bi3 10 has and which is referred to as isostearic acid "The exact structure of isostearic acid is not known; however, nuclear magnetic resonance studies have shown that it is never branched and has an average of at least 3 alkyl groups of 2 carbon atoms or more per molecule, which indicates the presence of at least 2 side chains.

Be the production of the isomeric C ^ -acids for the purpose of producing the secondary ones according to the invention Amines, the procedure described in the reference patent must be practiced very carefully in order to obtain the best possible divorce of the various monomeric acids. When s.fi the hydrogenation program * is not being carried out effectively

101844 / 1IS7,

<=. 7 -

Oleic acid lies dead in the end product as an impurity and she would be “quickly unsaturated! completely unacceptable as " Part of an oxidation inhibitor "Furthermore," if the solvent separation is not carried out effectively, Stearic acid or other solid acids are present, processed to amines by the process according to the invention and used as antioxidants, the lubricant one give unacceptably high stook point · In summary emphasizes again that the process of the reference patent with Sufficient care must be exercised so that structurally modified acids are obtained without the presence of in objectionable amount of undesired impurities

The reference patent describes the branched-chain Cjg-Pett-

acids (isostearic acids) as structurally modified pig ren (what they are in relation to the starting materials). However, these acids are more appropriately referred to as structurally stabilized acids. The acids produced according to the method of the Besugspatenteθ undergo two severe treatments, once a polymerization treatment, which is the To polymerize unsaturated acids as well as to modify structurally is endeavored, on the other hand Hydrogenation treatment which saturates the acids and perhaps further modifies their structure. Hence the structurally modified acids stabilized in the sense, when they have been subjected to such rigorous treatment as to give them their most stable structural form

109844/1857

have developed and are therefore correctly described as "structurally stabilized" «

The isoatearic acid described above and in the reference patent

if processed on a secondary amine _{according to the invention s} the preferred Ausfülsrimgsform the invention »

Line other, normally liquid monocarboxylic acids which can be used in the preparation of the secondary amines according to the invention "is one which contains 22 carbon atoms and which can be formed by the polymerization of isobutylene with oleic acid". The product obtained consists essentially after hydrogenation for the purpose of saturation liquid from a mixture of 9- and 10-eekmiäären Butylstearinsäuren »Additional branched acids that can be vei'wendet _s 9 ~ n = - 0etyl <= aargar in acid and 10" MethyXstearinsäure _o As noted earlier, are the acids , which can be used in the production of the secondary amines according to the invention, have 16 Ma 25 carbon atoms 54 ⁰ C be liquid.

The secondary amines according to the invention can be prepared "ground by bringing the saturated liquid aliphatic branched acids for reaction with ammonia, _s them in the nitrile

109844/1857 bad original

to transform the relevant liquid branched acid o Dae NitrA! is recovered and hydrogenated to the amine, the secondary amine is separated off and used as an oxidation inhibitor according to the invention. 33O ⁰ C) and ammonia is kept in constant contact with the acid, whereby the water of reaction is removed o The reaction should take place at a pressure of about 3 »5 -10.5 kg / cm (preferably 6.3 - 7.1 kg / cm) and continued until the reaction product consists essentially of a nitrile. After the nitrile has been recovered, a conventional hydrogenation catalyst such as ZoBo nickel on kieselguhr, Raney nickel _? Palladium or platinum hydrogenated on a suitable support or other known hydrogenation catalyst

The catalyst should stop hydrogenation at pressures of

2 2

3 »5 to 28.1 kg / cm, preferably 21.1 to 26.1 kg / om, and at temperatures of 150 to 25O ⁰ C, preferably from 200 run to 225 ⁰ C "While dee Hydrierungspronesees the nitrile is first converted into a primary amine and then to a substantial extent with elimination of ammonia to a secondary amine. The reaction runs as abs 2 RNH ₂ -> E- | 'ß + m $, where R is the hydrocarbon residue of the liquid branched aliphatic acid «After

109844/1857

the litrile has essentially been converted into the amine, the amine product is cooled, filtered and fractionated to separate the secondary amines from the primary and tertiary amines to separate·

The secondary amines according to the invention can be used as oxidation inhibitors with a large number of lubricating oils, both mineral oils ale oils and synthetic, including diverse kinds of aliphatic Carbonsäureester which have been proposed for use for Schmierζwecke be used "These include dialkyl (Cg-C ₁₈₎ - Esters of aliphatic dicarboxylic acids (Cg - C ₁₂ ), whereby the main diesters are those derived from adipic, azelaic or sebacic acid and a Cg - C ₁₀ alkOhOl »

Speslfisohe examples of Esterschmiermitteln with which the erfindungsgemäSen oxidation inhibitors can be used are _f Diootylazelainat, di-2-äthylhexylsebaeinat, di-2-äthylhexyladipinat, DiZaurylazelainat, Disekundäramylsebazinat, di-2-äthylhexylsuooinat, di-2 '(2' -methoxyäthoxy) äthylsebazinat , Di-2- (2 »-ethylbutoxy) ethyl sebaainate, di» 2-ethylhexylazelainate.

The secondary @ 1κβ oxidation inhibitors according to the invention can be used not only with the above-described aliphatic empty acid esters, but also with polyethersoethers, which soak through reaction . liphatiachar α

108844/1857 bad original

hydric alcohol or an aliphatic monocarboxylic acid 1st, formed in prescribed molar ratios werdenο The present oxidation inhibitors can also be used with koaplexen esters "which is formed by such reactions" ground as that of a mixture * which prescribed amounts of 2-ethyl "-1,3-hexanediol , Sebacic acid and 2 · ethylhexaiiol, or by reacting a mixture containing aöipin · .'dar azelaic acid »diethylene glycol and 2-ethyxcapric acid o By reacting a mono-

carboxylic acid and a glycol ester formed also come to consider the Saurfckomponents is usually an aliphatic acid having at least ifolilenstoffatomen B. The Grlykolkomponente may be a straight GI ^ Iüo.1 such "B _e 1,6-hexane diol, but other glycols * s ie 3" tetraethylene glycol or dipropylene can also be used "Speisifiscbe examples of glycol diesters are: egg oaprinsäureeater of 1 ^ A- butanediol di-2-ethyl-caproic acide8ter of 1 _c 6 ^ hexanediol. _y Mlanrinsäureester of 1 ₉ 4-hexanediol "(Dicaprylaäureester of 1GS-Pentandiolo ester obtained by reaction of Trimethylelelkanen (C ₂ -C) with various monobasic acids ₉ hauptsäehlioli G ^ - O ₁₀ - are formed acids," represent further examples ven esters is that _it's able to be moved with the compounds of base fluid Sehmiermitteln, can be used.

The secondary amines according to the invention are able to

BAD ORIGINAL 109844/1857

strict oxidation test according to Pratt and Whitney at 232 ⁰ C

2U exist «. Do you exceed dioctyldiphenylsmin at this temperature? one of the most effective oxidation inhibitors developed to date for use in high-performance (high temperature = / machines _{or similar)}

The amount of secondary amine, which is ationslnhibitor apply in a given lubricant than Oxy &, of course, vary with the selected in the particular case antioxidant _v the type of lubricant liquid wedge; and the current machine conditions o In general, good results are achieved “if you set 0 ₉ 1 - 5 _s 0, preferably 0 _? 5 ~ 2.0 Gewo ~ $ secondary amine uses *

The erfinöungsgemäßen Oxydationsinhibitcren can be used together with a number of other lubricant additives and in many cases it is preferred or is it nötigj that find additional materials application ^ An additional atoff- be 4p mitverwenöet must generally "is a metal deactivator such as Z ₀ B ₀ PANA ( Phenyl-alpha-napthyl-amine) _o Other conventional substances, including Eostinhibitors or substances which impart stress properties, auxiliary oxidation inhibitors _P if desired, and viscosity index improvers can be used _e

The present JE. ?: f iriujjg is given by or ".-» the following Beiisp which ii'21 ¹ erlüu * '. <3?' T, ar-er Jrei.iißSMre ^ .i * "■ -ßUiräüksrj f« nliher Yfc ^ &iiiichaii; - .:;. <: ■! · - ■:. ■

'■ 0 9 ¹ CUUI 1 8 δ 1 ⁸ AD ORiq _INal

- 15 example ^

A erfindungsgemäSer Oxydationsinhibitor, Diisoatearylamin, was prepared as follows: 29 * 5 kg isostearic acid were registered in sinen equipped with a stirrer autoclave of 45.4 capacity, the acid was slowly heated to 320 ⁰ C under a constant stream of ammonia and under constant discharge of the reaction Wassere · The Pressure was maintained at about 6.3 to 7 "1 kg / cm". After 7 hours, the reaction products were analyzed and it was found that a considerable amount of the product was still present as an amide. The reaction was therefore continued for a further 7 hours under the conditions given above, after which the product consisted almost exclusively of isostearyl nitrile. The reaction mixture was cooled and the product _{filtered through a full flow filter No. 0} 27 »24.5 kg of isostearyl nitrile were obtained» 1000 g of isostearyl nitrile and 20 g of a 1 ^ nickel catalyst (Harshaw nickel 0104-P, 50 $ active nickel on kieselguhr) were placed in a rocking autoclave registered the system was purged with hydrogen for the purpose of air removal and 'then reacted with hydrogen to a pressure of 21.1 kg / cm was then heated until the temperature reached 200 ⁰ G, and the reaction was stirred at this temperature under a Pressure continued in the 20.4-26.7 kg / cm range. Interim samples were taken to determine the neutralization numbers. As soon as it was found that the product had essentially hydrogenated to the amine (3 1/2 hours) "was there"

109844/1857 BAD OBiGiNAt

System cooled to 150 ^{° C.} The product, approximately 1000 g, was blown from the autoclave and filtered using a filtering agent B (Dicalite). The neutralization number of de-filtered product was 645. The filtered material was then topped at a pressure of 0.3 to

1.2 mm Hg and a temperature up to about 26O ⁰ C to dae entire prieSre amine to remove. The backlog, 83; 2 wt.-3 &,

^ Was then distilled using a short length column at a pressure τοη 0.3-0.4 mm Hg. The first fraction of the product obtained was removed at a pot ^{temperature of 275-280 0} O and a steam temperature of 231 ⁰ C under a pressure of 0.3 mm Hg. This first fraction provided 1.3 parts by weight of the product is Jt, and had a neutralization number of 568. A sweite fraction was Diiflostearylamin was then at a Topfteaperatur 280-300 ⁰ C and a steam tempera door 258-270 ° C located under a 0.35 mm Hg bridge. This faction

"Maohte 72.2 wt -. $ - of the product prepared as described above from, had a neutralization number of 522 and was the one fraction, which was used for the examples cited as Oxydationsinhibitor.

Examples 2-5

Comparative oxidation attempts were made with a number commercially available antioxidants that are amines, viz fl-Xtnylanlliil, SIs (I-ethyl-3- »ethylpentyl) aain, p, p · - Dioctyldipbenylamine, and on the other hand with Eiieoitearylaein,

109D44 / 1H7

t * ■

i Λ

an inventive oxidation inhibitor »carried out.

The YorgangBwelse was as follows: 100 g of a lubricant · » Triaethylolpropanedipelargonate monoheptanoate containing a Oxidation inhibitor in the amount given in Table I.

and a weighed copper coupon, were made into an alder aeyerkolben given. The flask was placed in a silicone bath eo immersed so that the surface of the sample is about 25 1/2 mm below the surface of the bath liquid was «In den

Flask was inserted into an air tube and 25 1/2 ma above

held on the surface of the sample. The air speed f was on 4? 5 ,? 1 3rd hour set ο Periodically

»Sample 1 ml was taken with a pipette. The IahalV &*> r pipette was each put through a 200 mesh sieve and under Using a 1 ml Cannon microviscometer (actual Capacity approx. 0.5 ml) a kinematic viscose test was carried out at 37.8 ° C. At the end of the attempt (after 4 days) the remainder of the sample was filtered through a 10 micron Mlliporenfliter * after thorough washing with

the copper coupons were weighed using a solvent (

ρ and the weight losses were calculated in mg per cn exported surface. In the following Table I the results of the tests with the various / iEin «C- * inhibitors are shown.

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Table I.

Viscosities, example 2 Example 5

Example 4 Example 5 ;.

Centlstoke's, at 37.8 <> C

I-ätbyt

aniline,
0.5 * PANA

. . Tuesday - 12

ootyldiphenyl-i ethyl-3-amine, 1.O] C nefchylpentyl) PANA ämin, 0.5%

PANA

2.5 * bioetearylamine. 1, OJf PANA

originally 20.1 22nd ,1 19.4 21.7 1 lay 24.8 24 , 5 25.7 «3.5 2 days 35.9 26th , 9 36.8 25.4 3 days 50.0 30th , 3 51.3 28.8 4 days 72.3 35 ,8th 77.1 33.2 Copper weight
loss. ax / car 0.78 0 , 23 o, 33 0.0

From the above it can be seen that the viscosity of diisoetearylamine, the oxidation inhibitor according to the invention, in the course of at a time less affected than that of any of the other amine oxidation inhibitors tested * N-ethylaniline and Bie (1-ethyl-3-methylpentyl) emin showed increases in viscosity, which go far beyond the tolerable level. One can also found that with plisostearylamine the copper corrosion was significantly less

Examples 6 and 7

In order to further compare the oxidation inhibition properties of dilsostearylaain and p «p'-dioctyldiphenylaain, both were added to the Pratt and Whitney oxidation method (P and W)

1 098AA / 1857

1668986

232 ⁰ C o The following was subjected to τοrgβgangem 200 al test solution containing trlmetbylolpropane dipelargonate monoheptanoate as the lubricant »1.0 wt 1/2 mm by 25 1/2 mm of copper, steel, silver, titanium, magnesium and aluminum were tied together in sequence with wire and suspended in the tea liquid within 6.4 mm from the bottom of the test solution. Above the test liquid was' then an air condenser attached and · the entire device was placed in a heating block constant temperature, which was controlled at 232 ⁰ C plus / minus 0.5 ⁰ C "dry air was then ▼ on at a speed through the inlet tube Introduced 5 liters per hour for 48 hours. At the end of the test period, the samples were cooled to room temperature · The metal coupons were removed, cleaned with solvent to remove soluble deposits, "then weighed to determine the corrosion loss Further, the viscosities at 37.8 and 99 ⁰ C were determined ■ The Viekosltätsveränderungen are in percent listed in Table II. The samples were then gravity filtered through coarse filter paper (Eaton-Dikeman Co., Grade E and D 615), the precipitates washed with acetone, then dried, after which the collected sludge was weighed. The sole weights are expressed in ag per 200 ml sample. The change in the acidity of the tea solution was determined by titrating the lubricant tested and subtracting the original

1SSBBSB

The tone of the acid found at the end was determined. Corrosion loss of the metal was shown as a difference (plus or sin ««} the weights of the metal sections before and after the tests

determined and expressed in mg per cm of exposed surface

!Tabel - 2.86 II P uhd W Spec. Example 6 + 0.02 Example 7 max. 50 %
Results Τ3ΑΪ 1 weight ?& p, p -
Dioctyl diphenyl
amine, H PANA + 0.02 TDM ^, 2.5 wt
Diisostearylamine,
1 Ji-PAHA Eeport Viscosity
change,
37.8 ⁰ C (Ji) 229.8 + 0.02 25.6 ——. Acidic sealing
Change 4.44 -11.85 3.69 Total chiama + 0.03 538 + 0.30 ι (mg) 2750 "0.30 Metal corrosion
(mg / oa *) -0.24 • O _t 3O copper +0.15 • 0.30 stole +0.14 "0.30 titanium +0.13 • O _t 3O silver +0.11
• magnesium +0.12 aluminum

$ 1

«Trimethylolpropane dipelargonate aonoheptanoate

The superiority of diisostearylamine as an inhibitor of oxidation is clearly ereiohtlioh according to the above. It can be seen that I> iiiostearylamine forms much less sludge, inhibits the acidic treatment and that at iba the metal corrosion in all

1098U / 1SS7

16689β *

- 19 - "■ ·" ■ '· ■■

Cases within the tolerable limits while using p.p'-diootyldiphenylamine remains excessive Copper and magnesium corrosion occurs

Examples 8 and 9

XM the difference between a erfindungsgemäfien (secondary amine) Oxydationsinhibitor, Biisoetearylamin, einereeita and a linear Dialkylaain comparable molecular weight · Dioctyldecylamin to demonstrate the other hand, were hired comparative tests using these two materials. The experiments went so envisaged that one of two samples Diisodeoylazelainat 1 Gew.Ji Diieoatearylaain and the other sample 1 wt. * Dioctyldeoylaain was added Zusats laughing of the relevant Slawin · the samples were heated to a 'temperature of 100 ⁰ C. . At this temperature, each of the imines was completely mixed into the ester solution in question. The solutions were then allowed to cool in order to check their crouching point and setting point, whereby the deeper results were obtained «

Diisodecylase lainate 99 wt. * 99 wt. * Bilsostearylamine 1 wt. * Dioctyldecylaain - 1 wt. *.

flocculation point -51 »1 ° C +! 5.6 C

Pour point below -56.7 +15.6 ^{0 0} C C

It is easy to see from the above figures that di-alkyl arylamine • 1 «Sohmiermittel-zueats is superior to that with the Eeter ohmic agents over a much wider temperature range Truly ala Uiootyldecjla »in.

108844/1867 ^: ^ ginal inspected

Claims (1)

1Ϊ & 8 & 88 Munich, February 23, 1968 Claims 1. Oxidation inhibitor for lubricants, characterized in that it has the general formula R ₁ R ₂ - - W where R ₁ and R _{2 represent} branched chain saturated aliphatic hydrocarbon groups of 15 to 24 carbon atoms from liquid branched chain saturated aliphatic monocarboxylic acids of 16 to 25 carbon atoms. 2. Oxidation inhibitor according to claim 1, characterized in that the acids mentioned have a liquid range in the lubricant at least down to minus 54 ^° C. 3 · Oxidation inhibitor according to claim 1, characterized in that R ^ and R _{2 are} branched aliphatic hydrocarbon radicals of isostearic acid. 4ο lubricant, characterized in that it contains a predominant proportion of a lubricating oil together with 0.1 to 5 * 0 Contains by weight inte oxidation inhibitors according to claim 1. 5 · Lubricant, characterized in that it contains a predominant portion of a beef oil with 0.1 to 5 * 0 Q «w.-j £ d ·· Oxidation inhibitor according to claim 3 contains · 109844/1857 ° ^RIG ' ^NAL - st- 6. Lubricant according to claim 4, characterized in that that the lubricating oil is a synthetic ester * 7. Lubricant according to claim 5, characterized! that the lubricating oil is a synthetic ■ ester. 8. methods of inhibiting the oxidation of lubricating oils, characterized in that an oxidation inhibitor according to claim 1 is added to them « 9. methods of inhibiting the oxidation of lubricating oils, characterized in that the oxidation inhibitor according to claim 3 is added to them » 109844/185?