DE1644959B2 - lubricant - Google Patents

Description

Lubricant based on an ester lubricant, which are, for example, very suitable for the lubrication of aircraft gas turbines have good oxidation stability at high temperatures and good extreme pressure properties. Such Lubricants therefore usually contain antioxidants, such as certain substituted phenothiazine 4-, ne and certain secondary aromatic amines and certain extreme pressure additives, such as. B. Triaryl esters of Phosphorothionic acid.

Although these triaryl phosphorothionates give the lubricants very favorable extreme pressure properties, they cause certain metals, especially magnesium, cadmium and p. 82 Steel a corrosion. This type of steel is a quality steel for aircraft gearboxes, which conforms to the provisions of the British Standard ■ -, ■■> Specification EN39B is sufficient. On the other hand, triaryl phosphates are well known extreme pressure additives, however show lubricants containing these additives are insufficient at high temperatures Oxidation instability. bo

From GB-PS 8 23 086 cyclic organic phosphorus compounds are also known, which can also contain sulfur in the molecule and which the corrosion behavior of mineral lubricating oils and synthetic lubricating oils. As a result of the complex structure, these are additives but not easily accessible.

Surprisingly, it has now been found that triarylphosphorothionates and triarylphosphates in Lubricants based on an ester lubricant with regard to anti-corrosion properties and anti-oxidation properties work together in a synergistic manner at high temperatures, especially when these two additives are in certain proportions are present.

The lubricants according to the invention therefore consist of a larger proportion of an ester lubricant and smaller proportions each of a triaryl phosphorothionate and a triaryl phosphate as well optionally other known additives.

Triaryl phosphorothionates suitable for this purpose contain 6 to 10 carbon atoms in each aryl group. Examples are triphenyl, tritolyl, tribenzyl, tixylyl and diphenyltolyl phosphorothionate. Particularly In the context of the invention, preference is given to triphenyl phosphorothionate, hereinafter abbreviated as TPPT.

Suitable triaryl phosphates in the context of the invention are those compounds which are in each Aryl group also contain 6 to 10 carbon atoms, for example triphenyl, tritolyl, tribenzyl, Trixylyl and diphenyltolyl phosphate. However, triphenyl phosphate is preferably used, which hereinafter abbreviated to TPP.

The ratio of triphenyl phosphate to triphenyl phosphorothionate is expediently within the range according to the invention Ester lubricants at about 0.25: 1, but preferably this ratio is no less alsO, 5: l.

Simple esters, complex esters, polyesters can be used as the base oil in the lubricants according to the invention or mixtures of such esters can be used, which also contain thickeners can, depending on the viscometric properties, which are desired for a particular lubricant and for those temperature conditions, under which the lubricant is used. A simple ester is used within the scope of the invention understood an ester of an aliphatic dicarboxylic acid and an aliphatic monovalent Alcohol is derived, it is preferably an ester of an aliphatic dicarboxylic acid with 6 to 10 Carbon atoms in the molecule and a branched monohydric alcohol containing 6 to 12 carbon atoms acts in the molecule. In particular, alcohols are used for this, which are on the beta carbon atom does not contain hydrogen.

Examples of simple esters which are used as the base oil in the ester lubricants according to the invention can be, are

Diisononyl sebacate, di (2-ethylhexyl) sebacate,

Diisooctyl azelate, diisodecyl azelate,

Di (3,5,5-trimethylhexyl) adipate,

2-ethylhexyl 1-3,5,5-trimethylhexyl serbacate

and simple, sterically hindered esters such as 2,2,4-trimethyl pentyl azelate. A complex ester is understood to mean an ester made up of various combinations an aliphatic carboxylic acid, a glycol or polyglycol, an aliphatic monohydric acid Alcohol and / or an aliphatic monocarboxylic acid is obtained. Such esters have z. B. the the following structures, AD (GD) M, A (DG) nM and MG (DG) nM, in which A, D, G and M are used in the Esterification obtained residual groups of an aliphatic monohydric alcohol, an aliphatic dicarboxylic acid, a Giykois or polyglycol as well as one

mean aliphatic monocarboxylic acid and η is an integer from 1 to 6. Examples of typical starting materials for the production of such complex esters are 2-ethylbutyl alcohol, 2-ethylhexyl alcohol, caproic acids, pelargonic acid, capric acid, tertiary acids which do not contain a hydrogen atom, neopentyl glycol, ethylene glycol, propylene glycol, azo glycolic acid, sebumic acid, such as polyethylene glycolic acid glycols, adipaic acid glycols, such as polyethylene glycols and pimelic acid.

Polyesters are understood as meaning esters which are derived from aliphatic alcohols with at least 3 hydroxyl groups derive in the molecule, for example esters of trimethylolpropane, such as trimethylolpropane tripelargonic acid.

Tetraesters are also suitable for this purpose, for example tetraesters of pentaerythritol or one of them Dimers or trimers of this alcohol and also esters of dipentaerythritol. Such esters are im Commercially available. These are fatty acid esters. Preferably each fatty acid residue contains des Esters 4 to 18 carbon atoms and especially 6 to 14 carbon atoms ^

Polymers of esters can be used as thickeners in the ester lubricants according to the invention Acrylic acid or an alkyl-substituted acrylic acid can be used, for example of lauryl methacrylate. Ethers of a polyoxyalkylene glycol of the general formula are also suitable for this purpose

R ₅ O (R ₇ O) _n R ₆ ,

in which R ₅ denotes an alkyl group, R ₆ denotes a hydrogen atom or an alkyl group and R7 denotes an alkylene group having 2 to 7 carbon atoms, while η is an integer greater than 1. Suitable compounds of this type are commercially available.

Copolymers of propylene oxide and ethylene oxide are also suitable as thickeners, which are also commercially available. Depending on the desired viscometric properties you can these thickeners in concentrations of up to 50% by weight, calculated on the finished lubricant, in the ester lubricants according to the invention are present.

The ester lubricants according to the invention can furthermore contain additional additives, for example Extreme pressure additives, antioxidants, metal deactivators. Anticorrosive agents, antifoam agents, dyes and others for ester lubricants known additives.

Suitable extreme pressure additives are chlorinated di- or polyphenyls and salts of tert-alkyl, primary Amines with monochloromethylphosphonic acid.

Suitable antioxidants are substituted phenothiazines, secondary aromatic amines, alkylated Phenols and bisphenols.

A particularly favorable antioxidant in the context of the invention is a substituted one Phenothiazine of the general formula below

Substituents R 1 _{, R 2} , Ri and R _{4 are} an alkyl or alkoxy radical, while the other substituents are hydrogen atoms.

A secondary aromatic amine is also very suitable as an antioxidant, in which two aromatic groups are attached directly to the nitrogen atom. Examples of such additives are N-benzyl-3,7-dioctylphenothiazine and phenyl-a-naphthylamine.

Triazoles, such as 1,2,3- and 1,2,4-triazoles, are suitable as metal deactivators, especially if these Contain amino and hydrocarbon substituents and acyl or aroyl substituents.

Suitable anti-corrosion agents are carboxylic acids such as sebacic acid, azelaic acid and adipic acid and also metal salts of petroleum sulfonic acids.

Polydimethylsiloxanes with viscosities of 100-100 cSt at 25 ° C. can be used as antifoam agents will.

The invention is explained in more detail by the following examples:

Different amounts of triphenyl phosphate and triphenyl phosphorothionate are used in a basic lubricant A (TPP or TPPT) added. All quantities are given in% by weight.

lubricant A. 64.5% »Hercolube A« *) 31.9% »Hercolube F« **) 1.7% N-Benzyl-3,7-dioctylphenothiazine 1.5% Phenyl - «- naphthylamine 0.02% Azelaic acid 0.0005% Silicone liquid MS 200/12 500 ***) 0.17% JMT / MCMPA - primary Ci ₈ -C ₂₂ Amine salt of monochloromethylphosphonic acid 0.2% Triazole

in which R is an alkyl, aryl, alkaryl, aralkyl or Cvanoalkvlrest and at least one of Lubricant B

A + 0.5% TPPT (for comparison)

Lubricant C

A + 0.5% TPP (for comparison)

Lubricant D

A +1% TPP (for comparison)

Lubricant E.

A + 1% TPPT (for comparison)

Lubricant F.

A + 0.5% TPP + 1% TPPT

Lubricant G

A + 1% TPP + 1% TPPT

Lubricant H

A + 0.5% TPP + 0.5% TPPT

> ■> Lubricants J

A + 0.3% TPP + 1% TPPT

*) Pentaerythritol esters of saturated fatty acids with an average chain length of 8 carbon atoms in a mixture with a smaller proportion of dipentaerythritol esters.
W) * »j Dipentaerythritol esters of saturated solid acids mixed with smaller amounts of mono- and tripentaerythritol esters.

***) A dimethyl silicone polymer with a viscosity of approx. 12 50OcSt at 25 ° C.

Various tests are carried out on these lubricants, the results obtained being given below are compiled in Tables i to V.

"Bristol Siddeley" Corrosion Test (Table I)

In this test, samples are certain metals long the Esterschmiermittel to be tested 24 hrs. At a temperature of 285 ⁰ C to the action of

Table I.
Corrosion test

exposed. The changes in weight of the metal samples are measured.

Lubricant weight change in mg / cm ²

^mlUel Brass Monel-Alumimetall nium

bronze

S.82 steel

Cast iron silver

SIlOB steel

cadmium

magnesium

nickel

B. -2.0 zero zero -0.14 -19 -2.7 zero -0.24 -11 > -130 zero C. -0.56 zero +0.04 zero -0.19 -0.64 -0.06 +0.07 -2.7 -28 +0.04 D. -0.74 zero zero zero -0.17 -0.46 +0.04 zero -0.69 -29.8 -0.06 E. -0.70 +0.10 -0.03 -0.2 -21.0 -4.03 +0.01 -1.59 -49.0 > -130 +0.03 F. -0.13 zero zero -0.07 -0.37 zero zero zero -3.9 -12 +0.08 G +0.01 zero zero zero zero zero zero zero -2.90 -11.1 +0.07 H zero zero zero zero zero zero zero zero -3.20 -10.4 zero J -0.51 zero zero -0.13 -5.1 -0.81 zero -0.04 -0.51 -100 +0.10

The steel type SIlOB is a corrosion-resistant stainless steel, which is used for Welding is suitable and meets the requirements of the British Standard Specification En58C.

"Rolls-Royce" - Oxidation Blow Test (Table II)

In this test, a Rolls-Royce J3 device is run for 24 hours at a temperature of 250 ° C each used and blowing 50 ml of the ester lubricant to be tested with steam, saturated air at a fixed rate

Table II

Lubricant viscosity increase at 37.8 ⁰ C in%

G
H

663;

320;

155;

343;

From Table I it can be seen that the combined use of triphenylphosphate and Triphenyl phosphorothionate the corrosion is significantly reduced, in comparison to triphenyl phosphorothionate alone, especially with magnesium, cadmium and the S. 82 steel. Although the result for Magnesium is disappointing when using lubricant J, but improved results can be achieved can be achieved by increasing the ratio of TPP to TPPT.

From Table II it can be clearly seen that a favorable antioxidant effect at high temperatures by the synergetic interaction of the two additives is achieved.

»Rolls-Roycew corrosion test, method 1002, Working method A, scheme No. 1 (200 ° C, 192 hours)

After pre-treatment according to the Rolls-Royce 1004, Iss. 1, Sup. 2 for 5 hours at 325 ^C C.

In this corrosion test, the weight change of selected metal sample, it is determined that the subject to be tested are Esterschmiermittels at a temperature of 200 ⁰ C 192 hrs of exposure.. The pretreatment consists in heating about 100 ml of the lubricant to be tested in a stainless steel container at 325 ° C. for 5 hours, the container having a tightly closing cap which is connected to a narrow steel condenser.

The results obtained are summarized in Table III below.

III 7th Ti / C and Cu / Ni / Si I-iuUstuhl 16 44 959 Ph-
Brass 8th Fast
arhcitsslahl Cu Tabel zero -1.2 1-8.9 -2.1 -0.03 -1.5 Lubricant Weight change in mg / cm zero -1.8 -36 -6.4 -6.3 -2.0 middle ΛΙ zero -0.94 -6.1 l'h-liron / c Steel with
high ge
stop in
C and Cr -1.8 Ni / Cr-on
sat / hardened
stole -0.23 -1.5 D. zero -1.2 -3.7 -0.27 E. zero -4.3 -16 -21 G zero -0.86 -2.9 -2.6

From this table it can be seen that the corrosion caused by triphenyl phosphorothionate is significantly reduced at high temperatures by the addition of triphenyl phosphate.

A danger with the use of triphenyl phosphate in an ester is that the phosphate too an acidic phosphate can be hydrolyzed, which in turn causes partial hydrolytic decomposition of the ester catalyzed to the half ester. This half ester has a corrosive effect while at the same time alcohol formed lowers the flash point. This behavior was determined using two well-known tests tested, namely by means of the Rolls-Royce hydrolysis stability test and by means of the S.O.D. lead corrosion storage stability test.

In the Rolls-Royce test, 250 ml of the to

Table IV

^{The lubricant to be tested is heated to 90 °} C. together with 25 ml of distilled water until the acid value has risen by 1.5 mg KOH / g. In the SOD test, a test piece made of lead is placed on a stirrer together with a copper piece acting as a catalyst, and this stirrer is immersed in the lubricant mixture to be tested and rotated at a predetermined speed. At the same time, air is blown through the lubricant at a rate that is set for one hour at a temperature of 166.8 ° C.

These measures will be carried out both at the fresh lubricant and after a 7tätigen storage at 110 ⁰ C. The results obtained are summarized in Table IV.

lubricant
D.

“Rolls-Roycew hydrolytic stability test
(Number of hours until the Siurc value rises by 1.5 mg KOH / g) 134 124 126

Weight loss of the lead sample after 1 hour at 162.8 C in mg / 6.45 cm ²

Before storage -0.19 -0.67 zero

After 7 days of storage at 110 C -1.86 -0.56 -0.49

These results confirm that the triphenyl phosphate does not appear in the lubricants of the present invention has an adverse hydrolytic effect on the ester lubricant.

Finally, the action of triphenyl phosphate on common esters, such as di-isooctyl azelate, has been determined.

The results summarized in Table V confirm that a lubricant containing only 1% Contains triphenyl phosphate but no triphenyl phosphorothionate, gives rise to higher lead corrosion, i. H., that there is more hydrolysis than when the same ester contains both 1% of the phosphate and 1% of PhosDhorlhionates contains.

Table V

lubricant Hster Ester + 1% TPP + 1% TPP + I% TPPT Weight loss of lead sample after 7 days of storage tion at 110 C and 1 hour treatment at 0.19 162.8 C 5.45

Claims (7)

Patent claims: 1. Lubricant, consisting of a larger proportion of an ester lubricant and smaller> Portions of a triarylphosphorothionate and a triarylphosphate as well as possibly others known additives. 2. Lubricant according to claim 1, characterized characterized in that it is a triaryl phosphorothionate having 6 to 10 carbon atoms in each aryl group, in particular contains triphenyl phosphorothionate. 3. Lubricant according to claims 1 and 2, characterized in that it is a triaryl phosphate with 6 to 10 carbon atoms in each aryl group, ι> especially triphenyl phosphate. 4. Lubricant according to Claims 1 to 3, characterized in that it is the triaryl phosphate and the triaryl phosphorothionate in a ratio of 0.25: 1. jo 5. Lubricant according to claims 1 to 3, characterized in that it is the triaryl phosphate and the triaryl phosphorothionate in a ratio of 0.5: 1. 6. Lubricant according to claims 1 to 5, >> characterized in that it is a simple ester, a complex ester and / or as a lubricating oil base contains a polyester. 7. Lubricant according to claims 1 to 6, characterized in that there is also a jo Contains thickener, preferably in concentrations of up to 50 percent by weight, based on the finished lubricant.