DE1294583B - Biphenols as lubricant additives - Google Patents

Description

1 2

Certain methylene biphenols have proven to be a manufacturing process for the methylene biphenol

An excellent antioxidant for various organic mixtures consists in the implementation of a suitable one niche materials proved, however, for usual mixture appropriately substituted mononuclear Phelich the protective effect of the type of nole to be protected with formaldehyde, also in the form of Paraform material depends. 5 aldehyde or formalin solution, in a lower one

Even minor changes in the structure of an aliphatic alcohol with up to 4 carbon atoms, phenolic antioxidants can be mainly ethanol, in the presence of a basic one Protective effect in relation to one or the other agent, such as potassium or sodium hydroxide. in the Strongly affect material. In general, this means that the reaction will last for a period Manufacturers and consumers of antioxidants an io of about 30 minutes to 6 hours at or near the Considerable inconvenience as different reflux temperatures of the mixture are carried out. Weaving must be produced or stored, it is essential here that the reacting with each other in order for a given material to have the highest aging phenols in ortho- and / or para-position for the hydro-protective effect to reach. xyl group have a hydrogen atom, so that the

In addition, pure, phenolic anti-aging agents are usually solid and can have a number of properties. The best results will be of limited solubility under practically organic media. Therefore obtained anhydrous conditions, ie when the attract consumers often the use of, for example, used as a solvent ethanol mixtures or liquid products as aging has a water content of at most 5 ° / ₀ and protection against, because this more soluble and lighter 20, the reactants are themselves anhydrous, but will be miscible. good results even in the presence of additional water

The object of the present invention is to obtain for deeds.

Lubricants normally in the presence of When using methanol as a solvent

Air, oxygen, ozone or other oxidizing substances occur to a certain extent to form benzyl ethers, Atmosphere tend to oxidative decomposition, anti- 25 the same with the use of higher alcohols Oxidizing agent based on methylene bipheno purpose is less pronounced. A small proportion of len to create, which compared to known, for example such ethers in the inventively used wisely described in British Patent 790 096- reaction products is sometimes beneficial because they are Stabilizers improved solubility- by the solubility is further increased. However, since properties and increased anti-aging effect 30 the anti-aging effect of the ethers is not so great exhibit. is like that of the methylene biphenols, one is recommended

Surprisingly, it was found that when regulating their concentration in the end products. Use of a mixture of symmetrical and symmetrical methylenebiphenols, therefore, when using methanol as the loosymmetrical methylene biphenols in the mixing agent, the desired progression of water, ethanol, isopropanol, dioxane, tetrahydro step is achieved by adding a ratio of 80-50 to 20-50 . In this case satisfies a little extent, furan or other similar polar solvent maximum case 5 ° / ₀ of the protected lubricant medium high phenol and Formaldehydkonzentrabetragende amount of this mixture, in order to maintain the stabilized tion in relation to the methanol, yaw effect to achieve. whereby the ether formation in the desired low

The symmetrical methylenebiphenols of the Mi- 40 scope is kept.

Schung consist of identically substituted phenol Below are some examples for

residues of the general formula methylenebiphenol mixtures described.

A A Example

In a reaction vessel equipped with a reflux condenser, heater, stirrer and nitrogen inlet tube a solution of 470 parts (85 mol percent) of 2-methyl-6-tert.butylph.enol and 103 parts (15 mol-g - g 50 percent) 2,6-di-tert-butylphenol in 1184 parts of pure

Entered ethanol, stirred the reaction mixture, flushed with nitrogen and then initially with about

in the A a tertiary alkyl radical with 4 to 9 carbons- 500 parts of 36% formalin and then with Substance atoms and B hydrogen or alkyl radicals with 264 parts of sodium hydroxide in 500 parts of water Means 4 to 9 carbon atoms. 55 added, with the addition of lye drop by drop

As asymmetrical methylene biphenols of the mixture, the formalin is introduced into the reaction vessel and those with different phenol residues are used. After addition of all the reaction components 4 to 9 carbon atoms are substituted, of which the reflux was maintained under constant nitrogen atom at least one of a tertiary alkyl radical with 60 spheres for a further 2 hours. Thereafter 4 to 9 carbon atoms is formed. the reaction mixture was cooled, with 50 ° / ₀ iger

Particularly preferred are the symmetrical acetic acid neutralized and poured into 10,000 parts of water for the purpose of removing the Irish and asymmetrical representatives of alcohol. The compounds in which tertiary alkyl groups in the form of aqueous layer was removed from the organic layer Tertiärbutylgruppen are present, (3,5-di- 65 separated and extracted with hexane-η Then tert.butyl -A- hydroxyphenyl were.) - ( 3 - methyl - 5 - tert.butyl - the organic components combined, washed twice with water (4-hydroxyphenyl) methane under the asymmetrical and dried. The solvent hexane representatives take precedence. was removed at 100 ° C / 2 torr, leaving about 10 parts

3 4

Distillate formed and about 610 parts of a very viscous oil reaction product of viscous, amber-colored oil remained. Up to a concentration of 20% by weight, this oil was found to be completely soluble and miscible in a hydrocarbon lubricating oil from a mixture of 4,4'-methylene-bis- (2,6-di-tert-. It contained as main butylphenol), 4,4'-methylene-bis- (2-methyl-6-tert-5 constituents 4,4'-methylene-bis- (2,6-di-tert-butylphebutylphenol), (3, 5 - di - tert.butyl -4 - hydroxyphenyl) - nol), (3,5-di-tert.butyl-4-hydroxyphenyl) - (3-tert.butyl- (3-methyl-5-tert.butyl- 4-hydroxyphenyl) methane with 2-hydroxyphenyl) methane and (3,5-di-tert-butyl-4-hy-3,5-di-tert-butyl-4-hydroxybenzyl ethyl ether, 3,5-di-hydroxyphenyl ) - (3 - tert.butyl - 4 - hydroxyphenyl) - metert.butyl-4-hydroxybenzyl alcohol, 3-methyl-5-tert-than and various other condensed butyl-4-hydroxybenzylethyl ether and 3-methyl-5-tert. - ionization products of 2,6-di-tert-butylphenol and butyl-4-hydroxybenzyl alcohol as secondary components ortho-tert-butylphenol, such as 4,4'-methylene-b is- (2-tert.-consisted. butylphenol), 2,2'-methylenebis- (6-tert-butylphenol), portions of this viscous liquid were in (3-tert-butyl-2-hydroxyphenyl) - (3-tert-butyl-4-hydroxy-amounts corresponding to a 5-, 10- and 20 weight phenyl) methane, 3-tert-butyl-4-hydroxybenzylethyl percent concentration with heating to 100 ⁰ C 15 ether, S-tert-butyl ^ -hydroxybenzyl ethyl ether, with a neutral hydrocarbon lubricating oil the derivatives of ortho-tert-butylphenol to the dissolved. None of the oil solutions showed any precipitate at room temperature after standing for 3 weeks with the hydroxyl group in ortho- and para-methyl positions; groups have ethyl ether substituents, as well as the reaction described, a polymer of different molecular weight of the pre-highly soluble product was obtained. such existing substituents with open, reactive ones

Ortho and Para positions. Example II

In the vessel described in Example I, an Example IV

Mixture of 187 parts of potassium hydroxide, 76 parts of 25

Paraformaldehyde, 783 parts of an equimolar Mi- 20 parts of potassium hydroxide, 75 parts of paraformaldehyde

Research of 2,6-di-tert-butylphenol and 2-methyl-hyd and 568 parts of a mixture of 15 mole percent of 6-tert-butylphenol and 600 parts of 95 ° / _o sodium ethanol 2,6-di-tert-butylphenol and 85 Mole percent 2-methyl entered. The mixture was refluxed in 800 parts of isopropanol under 6-tert-butylphenol for 2 hours, then cooled and dissolved with glacial acetic acid. The mixture was neutralized for 3 hours. The excess alcohol was heated to the reflux temperature, cooled, and then most of it was removed by distillation. The glacial acetic acid was neutralized and the reaction mixture was then poured into 10,000 parts of water with 1,070 parts of ether. After phase separation, the reaction was diluted, washed three times with water, dried, mixed with ether, diluted to three times its volume, and freed from solvents by distillation. 35 then washed three times with water, dried and the resulting liquid mixture of 4,4'-Me- freed from the solvent. The end product consisted of ethylene-bis- (2,6-di-tert-butylphenol), 4,4'-methylene-bis- from a crystalline solid which was dissolved in neutral (2-methyl-6-tert-butylphenol), (3 , 5-di-tert-butyl-4-hy- lubricating oil was soluble. Droxybenzyl) - (3 - methyl - 5 - tert.butyl - 4 - hydroxy-

benzyl) methane and other secondary components 40. .

showed extremely good solubility properties when they were B e 1 s ρ 1 e 1 V

according to the method according to Example I in 5-, 10- and

20 _^0/0 sodium concentration in a neutral, mineralization in 1,250 parts of 95 ° / _o sodium ethanol were 663 parts

lubricating oil has been tested. a mixture of 85 mol percent 2,6-di-tert-butyl-

45 phenol and 15 mole percent 2-methyl-6-tert-butylphenol

Example III dissolved and the solution with 500 parts of a 0.65mo-

added laren, aqueous formaldehyde solution. The Mi

A mixture of 75% 2,6-di-tert-butylphenol and schung was then heated to reflux temperature 15 ° / ₀ ortho-tert-butylphenol with a content of and slowly with 264 parts of sodium hydroxide and 10 ° / o..2.4 , 6-tri-tert-butylphenol was added in the presence of 50,500 parts of water. After addition of the base of ethanol, reacted with paraformaldehyde, the reflux heating being continued for a further 2 hours, the reaction constituents in the following amounts. The mixture was then cooled using: acetic acid and neutralized with about 900 parts of benzene

diluted. The aqueous phase was dissolved in water

724 parts of phenol mixture, _{55 g0S} sen and extracted twice with benzene. The Ver-

20 parts of potassium hydroxide, combined organic solutions were used three times

76 parts of paraformaldehyde, washed with water, dried and distilled

600 parts of 95% ethanol. _{freed from} solvent. The end product is a

Solid matter.

The reaction was continued at reflux for 2 hours

temperature (81 to 83 ⁰ C) carried out and then the B is ρ ie 1 VI

The mixture was ^{cooled to 70 °} C. and neutralized with glacial acetic acid. The alcohol was removed by vacuum distillation 20 parts of potassium hydroxide, 76 parts of paraformaldehyde, starting at 70 ° C. and ending at 35 ° C./10 Torr, and 665 parts of a mixture of 85 mol percent. The residue was then treated with 1400Teilen 65 2,6-di-tert-butylphenol and 15 mole percent 2-methyl-benzene, washed three times in amounts of 6-tert-butylphenol 95 ° / _o sodium parts of water were washed in 600 parts, dried and dissolved by ethanol. The mixture was freed from benzene by vacuum distillation for 2 hours. The heated from reflux temperature, cooled and with ice

vinegar neutralized. Thereafter, the main part of the other than the aging alcohol used according to the invention removed by distillation and the reac-protective agents can also add other lubricants to the lubricating oils tion mixture with 1200 parts of ether as a solvent containing additives to which viscosity index diluted. The product was three times better with proportions, detergents, corrosion inhibitors, Washed from a total of 750 parts of water, getrock- 5 metal deactivators, rust inhibitors, color stabilinet and by vacuum distillation from the solvent sators, pour point depressants, emulsifiers, color-liberated, with 705 parts remaining. fabrics, etc. belong.

In the production of inventively stabilized

In Example VII mineral lubricating oil, it is often advisable to use the oil

ίο to be heated up to 100 ° C and during the aging

The method according to Example V was repeated to stir the addition of protective agent, and a mixture of 75 ° / ₀ 2,6-di-

tert-butylphenol and 15 ° / ₀ ortho-tert-butylphenol with Example 1

a content of 10% 2,4,6-tri-tert-butylphenol is used. 15 To 10,000 parts from completely distilled off. Mixed base oil sourced, solvent-refined Example VIII Lubricating oil with a density of 28.9 ° API, a Following the procedure of Example V, a viscosity grade of SAE10 W-20 and a Viskosi blend from 85 mole percent 2,6-di-tert-butylphenol rate index of 135.7 100 parts of the product were and 15 mole percent 2- (l, l, 3,3 ~ tetramethylbutyl) -o-kre- ao measured example V was added, sol in the presence of 95% ethanol and aqueous

Formaldehyde implemented. The reaction gave an example 2

Binding mixture with about 25% content of the

substituted methane. 1000 parts from mixed base oil,

. 25 refined lubricating oil made from a light base material with

B e 1 s ρ 1 e 1 IX _an SAE viscosity of 20, an API density of

First the general procedure was according to 30.5 ° and a viscosity index of 107.4 were Example III added during the actual reaction as 0.05% of a stabilizer product that repeated. But then after completion of the reaction according to Example I from an equimolar mixture of the alcohol is distilled off at normal pressure and the 2,6-diisopropylphenol and 2-tert-butyl-6-isopropyl residue with the same volume of a neutral, phenol had been obtained and a considerable amount additive-free, mixed-base lubricating oil diluted Share of (3,5-diisopropyl-4-hydroxyphenyl) - (3-iso- and heated to 85 ° C. In this procedure, propyl-5-tert-butyl-4-hydroxyphenyl) methane was possessed.

the reaction product after complete dissolution

washed three times with water in the lubricating oil and treated

dries. In this way, an end product already dissolved in the oil was obtained, and an oxidatively stable lubricating oil was produced, subsequent solvent separation unnecessary because a base lubricating oil that had been completely distilled off was also involved. an API density of 29.1 °, an SAE number of In the above examples, reaction 40 10 W-30 and a viscosity index of 138.9 with 5% products obtained from a mixture of symmetrical product according to Example X was added, tric and asymmetric methylene biphenols,
Benzyläthern, benzyl alcohols and polymers of different molecular weights exist, which excluded · ^A measurement of the induction period recorded solubility in organic media, beispiels- 45 in the oxidation of lubricating oils, in mineral oils and functional fluids,

own. To determine the antioxidant effect was

By adding the according to the invention used in each case a certain amount of the mixtures described above, lubricating oils and functional examples obtained mixtures in pure, white, liquids such. B. for fluid transmissions and hydraulic 50 refined mineral oil. Ferrihexoate was also added to the blended plants, regardless of whether they were made from natural mineral oil, in order to come from hydrocarbons or to catalyze the oxidation and thereby the test are synthetically produced, except for a storage stability. The iron salt concentration was set at 0.05%, calculated _{on Fe 2} O _{3, to improve the level of oxidation resistance.} 1 ecm speed when used at higher temperatures. 55 of the finished mixture was put into an apparatus, surprisingly, according to the invention, lubricating oils which are stabilized measurement of the oxidative stability of the mineral oil at extremely high temperatures without, which are used from a glass vessel of 12 ecm oxidative decomposition. Invention capacity existed, the decomposition resistance of 60 was seen with an inlet pipe that could be connected to a mixture used in accordance with an increase in the amount of added amount already reduced. The vessel was then flushed with oxygen under atmospheric materials such as hydraulic and other high pressure and connected to the mercury industrial oils and silver pressure gauges from such oils. Thereafter, it was sunk into a thermostat bath of 150 ^° C. obtained by adding metallic soaps, whereby the factory lubricating oils and greases in the presence of oxygen pressure increase indicated by the manometer by air, oxygen or ozone considerably. Another 65 was. The manometer was observed until, according to the invention, a sudden drop in pressure occurred in the vessel to produce a pressure drop. The time greases used organic soaps themselves span from immersion to the start of pressure stabilization, the fall off is considered the induction period of the mineral oil.

The results obtained are shown in Table I below.

Table I.
Antioxidant effect in white mineral oil

additions Conc
tration in
Weight
percent Induk
tion time
in
Minutes 1. without 0 2 to 3 2. 4,4'-methylene-bis-
(2,6-di-tert-butyl-
phenol) 0.496 84 3. Product example I ... 0.496 172 4. Product example II ... 0.496 182 5. Product example IV ... 0.496 195 6. Product example V ... 0.496 125 7. Product example VI ... 0.496 122 8. (3,5-di-tert-butyl-
4-hydroxyphenyl) -
(3-methyl-5-tert-butyl-
4-hydroxyphenyl) -
methane Vioo moles / l

As is seen, the table occurs in staggered with iron hexoate, antioxidants free mineral oil already after 2 to 3 minutes, a pressure drop, a, from which it follows that the mineral oil at 15O ⁰ C against oxidative decomposition is unstable. Even with the addition of pure 4,4'-methylene-bis- (2,6-di-tert-butylphenol), a symmetrical anti-aging agent known to be outstandingly well known, the induction time is only 84 minutes.

In contrast, the mixtures used according to the invention make the mineral oil an excellent one Protection against aging granted. It can also be seen that those mixtures that result from approaches with a lot 2-methyl-6-tert-butylphenol were prepared, especially show outstanding results. But also the mixtures with a considerable content of others Products are effective anti-aging agents and have asymmetric methylene biphenols even the remarkable advantage of better solubility.

B. Polyveriform Oxidation Stability Test

This test, which effectively evaluates the performance of lubricating oil anti-aging agents, was published in in Ind. And Eng. Chem. Anal. Ed., 17, (1945), p. 302 and Anal. Chem., 21, p. 737 (1949) Way done. The equipment and procedure used in the test as well as the relationships between the results and the engine performance are described in the former publication. The apparatus was slightly modified in that the steel sleeve and the copper test piece have been omitted as published.

These testing a neutral mineral engine oil additive-free mixed base oil was used, which to enhance the oxidative ölzer "setting - containing 0.05% ferric oxide in the form of ferric 2-ethylhexoate, and 0.10 ° / ₀ lead bromide as oxidation catalysts - based on oil weight . The most important test conditions consisted of blowing 70 liters of air per hour through the test oil, which is kept at a temperature of 149 ° C., for 20 hours.

Table II Polyveriform test data

additions

concentration acid in
Weight percent number 0 6.0 1.0 5.2 1.0 5.0 1.0 4.8 1.0 4.9 1.0 4.7 1.0 5.0

Percentage
Increase in viscosity (in SUS at
37.8 ⁰ C)

judgement
the visible

Silting up

1. without

2. Product according to Example II.

3. Product according to Example III.

4. Product according to Example V.

5. Product according to Example VI.,

6. Product according to Example VII,

7. Product according to Example VIII

103
62
64
58
56
73
62

A.
A.
A.
A.
A.
A.

Table II clearly shows that excellent results were obtained with samples stabilized according to the invention. In each case a significantly smaller increase in acid number and viscosity was achieved than in the case of the control sample. In addition, it is seen that was favorably influenced by the addition of per 1 ° / ₀ of a mixture according to the invention, the visual Verschlammungsgeechwindigkeit.

As Table II shows, the anti-aging agents used according to the invention are exceptionally effective even at greatly increased temperatures; however, it was found that many known compounds which show Alterurtgsschutzeigenschaften at 138 ⁰ C, fail to 149 ° C Polyveriformtest. Thus, the transition from 138 to 149 ° C represents a critical test for the usefulness of an anti-aging agent in a lubricating oil.

To demonstrate the technical superiority of the mixtures of symmetrical mixtures used according to the invention and asymmetric methylene biphenols versus pure asymmetric products in the

δο Oxidation stabilization of lubricants, the polyveriform test was also carried out on (3,5-di-tert-butyl-4-hydroxyphenyl) - (3 - methyl - 5 - tert-butyl - 4 - hydroxyphenyl) methane ("compound 203") was used. Further 4,4'-isopropylidene-bis- (2,6-di-tert-butylphenol) ("Compound 34"), a compound similar to that in British Patent 790 096 described 2- (4-methoxy-3,5-di-tert-butylphenyl) - 2 - (4 - hydroxy - 3,5 - di - tert-butylphenyl) -

909 519 / 5Π

is structurally related to propane. The two comparison compounds were each used in two different base oils tested, whose behavior in the additive-free state is also determined as a reference basis became. The results obtained are - along with the data for the products for comparison purposes according to Examples III and VII from Table II - compiled in Table III.

Table III Polyveriform test data

additions

Without

Product according to
Example III

Product according to
Example VII

Without

Compound 203

Without

Compound 203

Without

Connection 34.

Without

Connection 34

Conc
tration in
Weight
percent acid
number 0 6.0 1.0 5.0 1.0 4.7 0 5.2 1.0 3.8 0 5.8 1.0 3.7 0 7.4 1.0 6.9 0 5.1 1.0 4.2

Percentage increase in viscosity

103 64

73

98

61

87

66

144

132

110

96

Table III makes it clear that the increase in the acid number with the aid of the mixtures used according to the invention was reduced by 1.0 or 1.3, but with the aid of compound 34 only by 0.5 or 0.9. Similarly, the viscosity increase was achieved according to / _0, but reduced by 30 and 39 ° with the joint 34 by only 12 or 14%. Since the tests were carried out with the rather low additional concentration of only 1%, there were no extremely different results in comparison with compound 203. After all, the reduction in the acid number with stabilization according to the invention was in the range of the values achieved with compound 203, while the relative numbers 39 and 30% with stabilization according to the invention show a clear improvement compared to 37 and 21% with compound 203 with regard to suppressing the increase in viscosity .

C. Motor test

This test was used to demonstrate reduced engine wear properties, greatly improved Oxidation stability of the oil and greatly reduced bearing corrosion properties when used according to the invention stabilized lubricant. On the one hand, pure, additive-free mineral oil was used as test products the SAE viscosity 20 and on the other hand the same mineral oil with an addition of 0.5 percent by weight of the mixture obtained according to Example III is used.

A preferred set of tests was performed using slightly modified CRC test protocol L-38 of a 1-cylinder CLR oil test engine. The-

This L-38 test is described in detail in a publication issued by the Motor Oil Oxidation Test Group pi the Motor Vehicle, Fuel, Lubricant and Equipment Research Committee of the Coordinating Research Council Inc. It consists of at least 40 hours of continuous operation of the engine under constant speed, air-fuel ratio and fuel flow conditions after a break-in period of 4 ¹ Iz hours. Before each test run, the engine is carefully cleaned, certain machine parts are measured and a new set of piston rings and new copper-lead inserts are used for the connecting rod test bearings. The performance of the test oil is determined on the basis of a visual examination of the engine for precipitation, the weight loss of the copper-lead test bearing and a comparison of the test data obtained from used oil samples taken from time to time with the corresponding fresh oil data. The test data relate to the viscosity at 37.8 ° C, the acid number and a visual oil assessment.

Certain changes were made to the L-38 test procedure described for the tests below. The oil sump was kept at 138 ° C. and the speed was kept constant at 3075 rpm. Instead of the required aluminum camshaft thrust washer, a bronze one was used. The fuel used in the test consisted of 60% alkylate and 40% commercially available base material with 0.79 cm ³ / liter tetraethyl lead. The exhaust gas, namely the total amount of the blow-by gas and the air escaping into the crankcase, was not measured. The test results obtained are shown in Table IV.

Table IV
L-38 test results

additive

Without

Product of
Example III

concentration
Weight percent

0.5

Bearing weight loss

mg

1828
139

Oil after 40 hours of testing

Acid number

3.1 2.0

Viscosity increase,%

10.9 6.4

The mixtures used according to the invention are also anti-aging agents for steam turbine oil. This was done using the American Society for Testing Materials Bearing's standard testing procedure ASTM designation D-943-54 proven. According to this test procedure, 300 ecm are suitable test oil brought into contact with 60 ecm of water and the resulting oil-water system at a temperature of 95 ° C held while at the same time oxygen at a rate of 3 1 / hour. blown through will. The oxidation is catalyzed by the use of iron and copper wire. Periodically the acid number of the test oil is determined and a failure of the anti-aging agent is determined by a Acid number above 2.0 displayed. It has been found that by adding small amounts of the various according to the invention mixtures used to make steam turbine oil have considerable resistance to oxidative decomposition is achieved.

The effectiveness of the mixtures used as anti-aging agents for fats was determined by means of the Norma Hoffman Grease Oxidation Stability Test,

ASTM Test Procedure D-942-50. It has been found that even small proportions according to the invention Mixtures used in common fats strongly suppress their oxidative decomposition. For example, a lithium-based grease that was originally free of anti-aging agents was used 0.5 percent by weight of the product according to Example IX mixed and the aforementioned oxidation stability test subject. It was found that the absorption of oxygen by the fat was greatly delayed was.

The mixtures used according to the invention are also anti-aging agents for synthetic oils and in particular diester oils of the in Ind. and Eng. Chem., 39 (1947), pp. 481 to 491. she can be used, for example, by the esterification of straight-chain, dibasic acids having 4 to about 16 carbon atoms with monohydric, saturated, aliphatic alcohols having 1 to about 10 carbon atoms formed diester very effectively to stabilize ao sam. These are made from branched-chain Alcohol derived diester lubricants having molecular weights between about 300 and about 600 especially powerful lubricants which are very effective as a result of the mixtures used according to the invention be stabilized sam.

In order to demonstrate the effectiveness of the mixtures used according to the invention in the case of diester lubricants, a series of panel coking tests was performed. Those in the magazine "Lubrication", 40, (1954), No. 4, described panel coking apparatus is used to assess the usability of synthetic Jet engine lubricants. The method is to put a lubricant on one heated aluminum sheet kept at a controlled temperature is sprayed on. The weight of the on The precipitate formed on the sheet serves as a measure of the oxidation stability of the lubricant. A strict one The test consists of keeping the panel in operation for 10 hours at 316 ° C and the spray device Operate every minute for 5 seconds. In such attempts, diester lubricants stabilized according to the invention have been found an unusually low weight of precipitation on the sheet metal.

The mixtures used according to the invention can also be used as additives to transmission fluids.

Claims (3)

Patent claims: 1. Use of a mixture of symmetrical and asymmetrical methylene biphenols, where their ratio is 80-50 to 20-50, as antioxidants for lubricants. 2. Use of symmetrical methylenebiphenols with identically substituted phenol radicals the general formula -OH in which A is a tertiary alkyl radical having 4 to 9 carbon atoms and B is hydrogen or alkyl radicals with 4 to 9 carbon atoms, according to claim 1. 3. Use of asymmetric methylenebiphenols with different phenol residues, the are each substituted by one to two alkyl radicals each having 4 to 9 carbon atoms, of which at least one of a tertiary alkyl radical having 4 to 9 carbon atoms is formed according to claim 1.