1. * GB780034 (A)
Description: GB780034 (A) ? 1957-07-31
Lubricant
Description of GB780034 (A)
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PATENT SPECIFICATION
Inventors: HANS GEORG KIISCHEAI, BENJAMIN THOMAS FO(WLIER and MICHAEL
FREDERIGCK H0ARE 780,034 Date of filing Complete Specification May 27,
1955.
Application Date June 9, 1954.
Complete Specification Published July 31, 1957.
Index at acceptance -Class 91, F2.
International Classification: -C0lOm.
(J MPLETE SPECIFIC(ATION Lubricant We, Esso RESEAICH AND ENGINEBRING
COMPANY, a Corporation duly organized and existing under the laws of
the State of Delaware, United States of America, of Elizabeth, New
Jersey, United States of America, do hereby declare the invention, for
which we pray that a patent may be granted to us, and the method by
which it is to be performed, to be particularly described in and by
the following statement.
This invention relates to compositions particularly adapted to

2. lubricate aviation gas turbine engines.
Broadly speaking, the properties required for an aviation turbine
lubricant are good high temperature stability, good viscosity
temperature characteristics and load carrying ability, and the
coupling of a low viscosity at low temperatures with a low vapour
pressure at high temperatures. It has previously been suggested that
aliplhatic diesters and complex esters form a class of compounds well
suited to fill these needs.
It is the purpose of the present invention to set down composition
limits whereby there may be readily formulated compositions adapted to
meet the needs of turbo jet and turbo prop engines where exceptionally
good viscosity-temperature characteristics are required. These oils,
however, are not restricted in their use and will find application in
aircraft auxiliaries and, for example, the 35 hydraulic fluid field.
The formulations of the present invention have three essential
components, viz. a diester or mixture of diesters, a complex ester or
mixture of complex 40 esters and a soluble polymer or mixture of
polymers.
lhe diesters used are diesters of dicarboxylic acids, preferably acids
having the formula 11OOC (CIH.2)CGOOH, where x is a 45 number from 2
to 10. The particularly preferred acids are adipic, sebacic and
azelaic acids. The alcohol portion of the diester is preferably the
residue of an alcohol of the formula ROH wherein IR is 50 an alkyl
group of from 4 to 12 carbon atoms in branched chain arrangement.
The diester comprises the major proportion/portion by volume of the
lubricant composition and in the particularly 55 preferred
compositions of this invention the choice of diester is very narrow
and comprises a blend of dinonyl sebacate and di-2-ethyl hexyl
sebacate. The reason for this narrow choice is as follows. Sebacic 60
acid and adipic acid are available on a commercial scale at a
reasonable price and the esters dinonyl sebacate and adipate, and
di-2-ethyl hexyl sebacate and adipate. The adipates are eliminated as
a 65 result of their rubber swelling characteristics given in Table I.
TABLE I.
RLUBIBR SWELLING CHIARACTERIISTICS OF ADIP'ATES AND SEB4ACATES.
% change in vol. of rubber when soaked in Itubber Temp. (C. of soaking
Adipate Sebacate A 70 17.1 8.5 B 70' 11.6 5.02 C 100 10.0 2.86 [Frice
3s. 6d.1 r.:
No. 16934/54.
780, 034 :Of the two sebacate esters, dinonyl sebacate has the better
high temperature stability, that is to say at temperatures in 1he
region of 2.50 C. it is less prone to oxidise and form corrosive
oxidation products. However, dinonyl sebacate has a rather high
freezing point (ca -25 C.) but it has been found that the addition of

3. at least 15% of a lonw freezing point diester. particuliarly the
di-2-ethyl hexyl 10 sebacate, to the lhbricant blend reduces the
tendency ot the dinonyl sebacate crystailising on storage at
temperatures in the region of -40W C. Tbis effect is illustrated in
Table II. 15 TABLE II.
CiRYSTALLISATION OF BLENDS CONT.IN1G DIN-ONYL SEBACATE Composition
Effect of storage at -65 F.
Dii.onyl Sebacate DN-S. Soliditication 9-5o, DNS +.5% Dioctyl Sebcate
DOS. Heavy crystallisation 8.5% IDNS + 15 % DOS. No erystallisation
The blend of these two diesters is thin and has limited load-carrying
ability.
This is improved by adding a complex ester. The complex ester
according to this invention may be one of three types.
I. Glycol centred complex ester, i.e.
Alcohol-Dibasic Acid-(Glycol- Dibasic Acid). Alcohol.
II. Dibasic Acid centred complex esters, i.e. 3Monobasic Acid-Glycol
(Dibasic Acid-Glycol)= Monobasic Acid.
III. Alcohol-acid terminated complex esters, i.e. Monobasic
Acid-(Glycol5s Dibasic Acid),, Alcohol, where a; is a number greater
than one;.
may be a non integer in-which case the formula represents the average
of a crude mixture. The complex esters are prepared by a cGmbination
of aicohlols, monobasic acids, dibasic acids and givycols by
esterification in one or more stages. The dibasic acid preferably has
the general formula HOOG(CH2_LC)OOH, where -P is a numiber from 2 to
10. T'he alcohol preferably has the general formula R-Oli, where R is
an alkyl group of 4 to 12 carbon atoms in a branched chain
arrangement, the glycol preferably has the general formula HO(CGH2O)H
- where n and g are numbers from 1 to 6. The monobasic acid preferably
has the general formula RCOOH, where R is an alkyl group of 2 to 22
carbon atoms. Examples of 5S such complex esters are described in
British Patent Specifications Nos. 666 697,
683,803, 743,571, 744-1,816, 758,24:', 740,.5.58, 747,903, 7-.56,95..
British Patent Applications 7.58,522, 758,8-38 and 778,691.
The addition of the complex ester has the advantage of increasing the
viscosity of the blend and improving the high tenmperature
p)erfollranee. However, an upper Jimit has to lbe set for the
proportion of complex ester used since it adversely affects the low
temperature properties. Ii the formulations of the present invention
the proportion of complex ester is from i,--'','3, by volume of the
blend. 70 The third essential ingredient of the lubricant according to
the present invention is a polynmer. 'This must be soluble in blend of
esters and is preferably an oxyg-en coutntining polymer particularly
75 a polymerised unsaturated ester such as a 1-olymerised aclvlate or

4. methacrylate.
Examples of suitable materials are available eomnimereially under the
brand names Acrylloid 710 and Auryloid HF 82.5. Suitable polymerised
acrylate or methacrylate have a molecular weight range within the
range of 5000 to OU0JUUO.
The amount of thle airious ingredients should be such as to giye a
product having 85 a viscosity less thain GUO0 cs. at -40 togethier
with a viscosity of at least 7.. cs. at 210- F. Tihs the preferred
composition ranges for thle lubrieants of this invention are:- 90
i)inonyl Sebacate - 0-75% vol.
Di 2-ethyl-hexyl sebacate- - - More than 1.5% vol.
Complex ester - - - 10-3( 0% vol.
Polymer - - - - 20% wt. 95 It is preferled thlat the compositions
contain in addition an oxidation inhibiting proportion of in
lantioxidant. Suitable anti-oxidani are described in our Application
_No..h098/]. (Patent No. 100 743,571). Examples of preferred
antioxidants are 'atteebol and pheno-thiazine.
Examples of cemapositions according to this invention are given in
Table III, together with their properties:'80,,0.34 TABL0 III.
Complex ester' % by volume - - - 15 20 Dioctyl sebacate % by volume- -
15 15 Dinonyl sebacate % by volume- - 70 65 Acryloid 710 % by weight -
- 4.1 3.7 Catechol- - - - - - - - 1.0 1.0 K.V. at 210 F. cs. - - -
7.49 7.48 100 F. cs.- - - - 31.32 32.33 -40 F. cs.- - - - - 4990 5590
- 40t' F. cs. (after 17 hours at -65' F.) - - 6785 10305 Flash point
F. - - - - - - 420 Pour point F. - - - <-60 < - The complex ester is
one prepared from sebacic acid, polyethylene glycol and
2-ethyl-hexanol.
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* 5.8.23.4; 93p