Note: Descriptions are shown in the official language in which they were submitted.
- CA 022422F73 1998-08-12
.~ ..
BACKGROUND OF THE INVENTION
The present invention relates to turbine oils, particularly aviation
turbine oils containing additives exhibiting enhanced corrosion resistance.
RELATED ART
While the use of polyol ester base stocks produces turbine lubricat-
ing oils which possess outstanding thermal stability, a satisfactory level of
oxidation stability and corrosion resistance can be achieved only by the use of
additives.
To the end, a wide assortment of different additives have been
proposed and utilized.
U.S. Patent 3,790,478 describes a lubricant for aviation turbines
comprising hindered esters as base stock and containing alkylated diphenyl
amines, and an alkylated phenyl naphthylamine as anti oxidants, a copper
passivator, dispersant polymers and a neutral organic phosphate as load carryingadditive. The lubricant may also contain hydrolytic stabilizers and lead
corrosion inhibitors, e.g., a C l-C20 alkyl gallate, neopentyl glycol disebacate,
sebacic acid or quinizarin.
U.S. Patent 3,790,481 is similar to U.S. Patent 3,790,478 in being
directed to an aviation turbine oil and also recites the presence of lead corrosion
inhibitors selected from the group consisting of C l-C20 alkyl gallate, neopentyl
glycol, disebacate, sebacic acid, and quinizarin.
' CA 022422~3 1998-08-12
U.S. Patent 3,585,137 is directed to a synthetic ester aviation
turbine oil containing an anthranilamide type metal passivator, antioxidants,
phosphate esters, dimer acids. A formulation is disclosed containing
p,p'dioctyldiphenylamine, phenothiazine, sebacic acid, benzotriazole, a mixture
of phosphate esters and, in other examples, various other additive ingredient. In
all cases, however, sebacic acid is indicated as present in the formulation.
U.S. Patent 3,912,640 teaches a gas turbine lubricant comprising a
base stock of a blend of carboxylate ester and low viscosity mineral oil and
- various additives including anti oxidants such as phenothiazines or derivatives
thereof and secondary diaryl amines. Methylene linked hindered bisphenol may
be substituted for a portion of the phenothiazine material. Additional additivespresent in the examples include benzotriazole, sebacic acid, tricresyl phosphate.
Benzotriazole, tolyltriazole, N,N'-disalicylidene dialkyl amines and sebacic acid
are identified as well known metal deactivators. They can be present in the
formulations in amounts of from about 0.005 to about 1.0 wt%. See also GB
1,420,824.
WO 95/29214 discloses a synthetic ester based lubricant for
helicopter tr~n~missions comprising a synthetic ester base stock, an antioxidant,
a neutral organic phosphate, a dicarboxylic acid component, a monocarboxylic
acid component, a triazole and a phosphorus containing extreme pressure
additive.
WO 94/10270 discloses a synthetic ester based aviation turbine oil
containing saturated or unsaturated dicarboxylic acids, e.g., sebacic acid, in
combination with a triazole derivative and specified monocarboxylic acids or an
CA 022422~3 1998-08-12
ester thereof. The combination is reported as being particularly effective in
inhibiting corrosion.
U.S. Patent 5,397,487/U.S. Patent 5,225,094 are directed to
lubricating oils having enhanced rust inhibitor capability containing a minor
synergistic rust inhibiting amount of a combination of two additives, the first
being a material of the Mobilad C 603 type, reported in the '487 patent as beinga succinic anhydride amine derivative of the folmula:
- R1~ H ~
~C C
\O
H~C ICl
o
where Rl and R2 are each independently alkyl or alkenyl of from 1 to 20
carbons, and a second material of the Lubrizol LZ 859 type, reported in
5,397,487 as being a mixture of about 74.5 wt% unreacted tell~ropenyl succinic
acid of the formula
C12H23CI I COOH
CH2 COOH
and about 25.5 wt% of a partially esterified tetrapropenyl succinic acid of the
formula
C12H23CH COOH
CH2 COO(CH2)30H
The patents recite that the lubricant can be natural oil or synthetic
oil based, synthetic oils including synthetic ester. The lubricants are described
CA 022422~3 1998-08-12
as useful in automotive applications, e.g., engine oils, transmission oils, aviation
piston engines, turbines and the like. The lubricant can contain other additiveswhich include dispersants, anti-wear agents, anti-oxidants, corrosion inhibitors,
detergellls, pour point depressants, extreme pressure additives, viscosity indeximprovers, friction modifiers and the like. Specifics of these other additives
were not provided and there were no examples presented employing such other
additives.
USP 5,599,779 is directed to a synergistic rust inhibiting composi-
tion consisting of (a) N-acylsarcosine compound, (b) dicarboxylic acid having 6
to 48 carbon atoms and (c) an amine selected from primary, secondary or tertiaryamines or imidazoline compounds. The primaly, secondary, or tertiary amine is
described as being one selected from the group of compounds of the formula:
R2
R1- I R3
wherein Rl, R2, R3 are independently selected from hydrogen, alkyl having up to
14 carbons, hydroxyalkyl, cycloalkyl, or polyalkyleneoxy groups.
It would be highly desirable if the corrosion inhibiting performance
of synthetic ester based aviation turbine oils could be improved employing a
combination of readily available additives.
DESCRIPTION OF THE INVENTION
The present invention is a synthetic ester based turbine oil of
enhanced corrosion inhibiting capacity comprising a major amount of a synthetic
ester oil base stock and a minor amount of a corrosion inhibiting additive
selected from the group consisting of ( I) N acyl derivatives of C,0 to C20 linear
CA 022422~3 1998-08-12
_ S _
or branched alkyl or alkenyl mono carboxylic acid as a first component and a
dicarboxylic acid as a second component in the absence of aliphatic primary,
secondary, or tertiary amines or imidazolines, (2) a combination of as a first
component one or more dicarboxylic acids such as sebacic acid, azelaic acid,
dioleic acid (known as dimer acids) and a second component selected from (a)
linear or branched alkyl or alkenyl succinic acid/anhydride ester or hemi ester or
hydroxylated derivatives of such esters or hemi esters, and (b) linear or branched
alkyl or alkenyl substituted succinimides or amino substituted succinimides, (3)longer chain dicarboxylic acids containing 36 to 54 carbons as the first
component and hydrocarbyl substituted imidazolines as the second component.
The diesters that can be used as base oils for the improved turbo oil
of the present invention are formed by esterification of linear or branched C6-CI5
aliphatic alcohols with one of such dibasic acids as adipic, sebacic, or azelaicacids. Examples of diesters are di-2-ethylhexyl sebacate and dioctyl adipate.
The synthetic polyol ester which can be used as the base oil is
formed by the esterification of an aliphatic polyol with carboxylic acid. The
aliphatic polyol contains from 4 to 15 carbon atoms and has from 2 to 8
esterifiable hydroxyl groups. Examples of polyol are trimethylolpropane,
pentaerythritol, dipentaerythritol, neopentyl glycol, tripentaerythritol and
mixtures thereof.
The carboxylic acid reactant used to produce the synthetic polyol
ester base oil is selected from aliphatic monocarboxylic acid or a mixture of
aliphatic monocarboxylic acid and aliphatic dicarboxylic acid. The carboxylic
acid contains fiom 4 to 12 carl)on atoms and includes the straight and branched
chain aliphatic acids, and mixtures of monocarboxylic acids may be used.
CA 022422~3 1998-08-12
The preferred polyol ester base oil is one prepared from technical
pentaerythritol and a mixture of C4-C12 carboxylic acids. Technical penta-
ery~ritol is a mixture which includes about 85 to 92% monopentaerythritol and
8 to 15% dipentaerythritol. A typical commercial technical pentaerythritol
contains about 88% monopentaerythritol having the formula
C H20H
HoH2c--c--c H2oH
C H20H
and about 12% of dipentaerythritol having the formula
CH20H CH20H
HOH 2C C--C--O C C CH20H
H2 H2
II cH2oH cH2oH
The technical pentaerythritol may also contain some tri and tetra pentaerythritol
that is normally formed as by-products duling the manufacture of technical
pentaerythritol .
The preparation of esters from alcohols and carboxylic acids can
be accomplished using conventional methods and techniques known and f~mili~r
to those skilled in the art. In general, technical pentaerythritol is heated with the
desired carboxylic acid mixture optionally in the presence of a catalyst.
Generally, a slight excess of acid is employed to force the reaction to comple-
tion. Water is removed during the reaction and any excess acid is then stripped
fiom the reaction mixture. The esters of technical pentaerythritol may be used
CA 022422~3 1998-08-12
without further purification or may be fulther purified using conventional
techniques such as distillation.
For the purposes of this specification and the following claims, the
term "technical pentaerythritol ester" is understood as meaning the polyol esterbase oil prepared from technical pentaerythritol and a mixture of C4-C,2
carboxylic acids.
The dibasic carboxylic acid comprising one component of the
combination additive added to the base stock to enhance the corrosion inhibitingperformance of the lublicant is a C8 to C40 total carbon number dicarboxylic acid
or mixture of such acids, preferably a Cg to C36 dicarboxylic acid or mixture
thereof. The dicarboxylic acids can be any n-alkyl, branched alkyl, aryl, or alkyl
substituted aryl dicarboxylic acid or mixture thereof having a total number of
carbons within the above recited ranges. Preferred dicarboxylic acids are
selected from the group consisting of the commercially available di-oleic acids
known as "dimer acids", sebacic acid, azelaic acid and mixtures thereof. These
acids are added to the turbo oil formulations in an amount in the range of 100 to
1000 ppm, preferably 200 to 500 ppm, more preferably 200 to 400 ppm.
The second component of the corrosion inhibiting additive
combination is selected from the group consisting of (a) N-acyl delivatives of
C1o-C20 linear or branched chain alkyl or alkenyl mono carboxylic acids, said
material having the structural formula:
C H2 C
H02 C I R2 III
R1
CA 022422~3 1998-08-12
-8-
where R1 is linear or branched C1-C6 alkyl and R2 is Clo-C20 linear or
branched alkyl or alkenyl group; preferably R~ is CH3 and R2 is oleic (a
comrnercial material called Sarkosyl O, available from Ciba Geigy Corporation,
which is the N-acyl derivative of the amine acid sarcosine is an example of one
such suitable material); (b) linear or branched alkyl or alkenyl succinic
acid/anhydride ester or hemi ester or hydroxylated derivatives of such esters orhemi-ester, said material having the structural formula:
~ o Rs
R3 Cl H IV
CH2 ICI O R4
wherein R3 is a Cg-C 16 linear or branched alkyl or alkenyl, R4 and Rs are the
same or different and are hydrogen, C l-C4 alkyl or C2-C4 alkenyl or
(CH2)n Cl H CH3
OH
where n can be an integer from zero to 5, preferably R3 is C10 12 branched
alkenyl, R~ is H and R5 is
C H2 f H C H3
OH
and n and m are each 1, (commercial materials such as Lubrizol 859 from the
Lubrizol Corporation or Parabar 302 from Exxon Chemical Company being
representative of such materials) and (c) reaction product of linear or branchedalkyl or alkenyl substituted succinic anhydride with substituted amino-
imidazolines resulting in what are believed to be linear or branched alkyl or
CA 02242253 1998-08-12
alkenyl substituted succinimide or amine substituted succinimides, which are
believed to be of the structural formula:
R ~C N (C H2)X~N--(C H2)~ ~N
~ ~ R7
R6 C--OH
and
RR8~C C\
N--(CH2)X~N--(CH2)X3~N\
R6 ' R7
o
and mixtures thereof, wherein R~" R8, R9 and Rlo are the same Ol different and
are H or a Cl-CI6, linear or branched alkyl or alkenyl wherein at least one of R6,
R8, Rg or Rlo is hydrocarbyl, preferably at least one of R~" R8, R9 or Rlo is a
C10-C~4 hydrocarbyl, more preferably a C~2 hydrocarbyl, e.g., tetra propenyl, and
R7 is C8-C20, preferably C~ C~8, linear or branched alkyl or alkenyl and x is 2 to
10, preferably 2 and y is 0 or 1~ preferably 0. Commercially available material
known as Mobilad C-603 fiom Mobil Chemical Company and Hitec H 536 from
Ethyl are believed to be examples of such materials.
CA 022422~3 1998-08-12
- 10-
This second component is added to the turbo oil formulation in an
amount in the range 100 to 1000 ppm, preferably 300 to 1000 ppm, more
preferably 300 to 500 ppm.
When the combination which is employed is the combination of
dibasic carboxylic acid and the N acyl derivative of Cl0-C20 linear or branched
chain alkyl or alkenyl monocarboxylic acid, the combination is employed in the
turbine oil formulation in the absence of any aliphatic primary, secondary, or
tertiary amines or imidazolines.
In an altelnate embodiment, longer chain dicarboxylic acids such
as dimers and trimers of Cl8 dicarboxylic acids, e.g., C36-Cs4 poly carboxylic
acids, exemplifled by EMPOL 1022 can be used in combination with hydro-
carbyl substituted imidazole, such as 2-(heptadecenyl)-4,5-dihydro-lH-
imidazole-1-ethanol, represented by the formula
CH3(CH2h6~
C H2C H20H
and available commercially from Ciba Geigy as Amine O. In this embodiment,
the acid is employed in an amount in the range of about 100 to 300 ppm and the
imidazole is employed in an amount in the range of about 100 to 500 ppm.
The turbine oil of the present invention may also contain any of the
other, typical additives which are usually or preferably present in such fully
formulated products. Thus, a fully formulated turbine oil may contain one or
more of the following classes of additives: antioxidants, antiwear agents,
extreme pressure additives, antifoamants, detergents, hydrolytic stabilizers, metal
CA 022422~3 1998-08-12
deactivators, other rust inhibitors, etc. Total amounts of such other additives can
be in the range 0.5 to 15 wt% preferably 2 to 10 wt%, most preferably 3 to
8 wt%
Antioxidants which can be used include aryl amines, e.g. phenyl-
naphtylamines and dialkyl diphenyl amines and mixtures thereof, hindered
phenols, phenothiazines, and their derivatives.
The antioxidants are typically used in an amount in the range 1 to
5 wt%.
Antiwear/exbreme pressure additives include hydrocarbyl
phosphate esters, particularly brihydrocarbyl phosphate esters in which the
hydrocarbyl radical is an aryl or alkaryl radical or mixture thereof. Particularantiwear/extreme pressure additives include tricresyl phosphate, triaryl
phosphate and mixtures thereof. Other or additional anti wear/extreme pressure
additives may also be used.
The antiwear/exbreme pressure additives are typically used in an
amount in the range 0 to 4 wt%, preferably I to 3 wt%.
Industry standard corrosive inhibitors may also be included in the
turbo oil. Such known corrosion inhibitors include the various b iazols, for
example, tolylbiazol, 1,2,4 benzobriazol, 1,2,3 benzobriazol, carboxy benzo-
triazole, alkylated benzobiazol.
The standard corrosion inhibitor additive can be used in an amount
in the range 0.02 to .5 wt%, preferably 0.05 to 0.25 wt%.
CA 022422~3 1998-08-12
-12-
Other rust inhibitors common to the industry include the various
hydrocarbyl amine phosphates and/or amine phosphates.
As previously indicated, other additives can also be employed
including hydrolytic stabilizers pour point depressants, anti foaming agents,
viscosity and viscosity index improver, etc.
The invention is fulther described by reference to the following
non-limiting examples and comparative examples.
Base Folmulation I is a Tech-PE polyol ester additized with
tricresylphosphate, arylamine antioxidants, benzotriazole derivative copper
deactivator, an amine phosphate extreme pressure agent. To this base
formulation individual corrosion inhibitors were added and D665A rust results
were obtained as shown in Table 1. Values reported are percent rust in the
D665A rust test. A passing result requires that no rust be present.
Additive combination of sebacic acid with alternatively Hitec 536,
Mobilad-C603, Parabar 302 or Sarkosyl-0 are reported in Table 2. At lower
concentrations the additive combinations show improvement over the base case
in Table 1. With the combination of 200 ppm sebacic acid and 300 ppm of the
other corrosion inhibitor, passing results are obtained which are not achievablevia a single corrosion inhibitor. It is desirable to limit the concentration of
dicarboxylic acid component because higher levels of acidity can catalyze polyolester hydrolysis. By using the combination of corrosion inhibitors total acidity is
reduced while anti-corrosion pel~ormance equal to or exceeding that achieved
with high concentrations of acid are obtained.
CA 022422~3 1998-08-12
-13-
Table 3 shows additive combinations in Base Formulation 2. Base
Formulabion 2 differs from Base Formulation I only in that the antioxidant breatrate is somewhat higher. Again combination of corrosion inhibitors at certain
concenbrations are more effective than either inhibitor used alone.
Table 4 gives the base line results for single corrosion inhibitors in
base Formulation 3. Base Formulation 3 is similar to Base Formulation 2 except
that an alternate antioxidant is substituted at the same hreat rate. Several
observations can be made. Only Amine-0 is capable of yielding passing results
when used alone. Sebacic acid is much more efficient alone than the longer
chain dicarboxylic acid Empol 1022, a mixture of dimers and bimers of Cl8
unsaturated dicarboxylic fatty acids.
Table 5 provides results for Base Folmulation 3 with a combina-
bion of corrosion inhibitors. Passing results are achieved for 400 ppm sebacic
acid with 1000 ppm of the second corrosion inhibitor.
Table 6 repolts the results with Empol 1022 and Amine O showing
that for the apparently severe Base Folmulation 3 the combination achieves
passing results at concenbation of as low as 100 ppm of each of Empol 1022 and
Amine O.
While Amine O can be an effective corrosion inhibitor when used
alone, in combination with other acidic components typically present in
formulated turbine oils, incompatibilities can be observed, especially at higherconcentrations. For this reason, therefore, Amine O is not a preferred corrosioninhibitor for formulated turbine oils.
CA 02242253 1998-08-12
-14-
TABLE 1
BASE FORMULATION #l
PLUS ONE CORROSION ~NHIBITOR
AVERAGE - - - - - - - - - - - - CONCENTRATION, ppm - - - - - - - - - - - - - -
D665 - % RustSebacic AcidHitec 536Mobilad-C603 PAR-302 SAR-0
73
16 100
18 200
2 500
100
100
100
100
200
200
200
200
500
500
500
500
CA 022422~3 1998-08-12
- 15 -
TABLE 2
BASE FORMULATION #l
PLUS COMBINATION OF CORROSION INHIBITORS
AVERAGE - - - - - - - - - - - - CONCENTRATION, ppm - - - - - - - - - - - - - -
D665 - % Rust Sebacic AcidHitec 536 Mobilad-C603 PAR-302 SAR-0
100 100
100 100
100 100
100 100
200 100 50
200 200
200 300
Pass 200 300
Pass 200 300
3 200 300
7 300 100
300 200
3 300 300
13 100 200
100 300
200 200
100 100
12 150 150
CA 02242253 1998-08-12
-16-
TABLE 3
BASE FORMULATION #2
PLUS COMBINATION OF CORROSION lNHIBITORS
AVERAGE - - - - - - CONCENTRATION, ppm - - - - - -
D665 - % Rust Sebacic Acid Hitec 536 Mobilad-C603
100
6 50 200
- Pass 50 300
Pass 50 500
Pass 400 300
Pass 400 500
200 300
400 300
CA 02242253 1998-08-12
TABLE 4
BASE FORMULATION #3
PLUS ONE CORROSION INHIBITOR
AVERAGE -- - - - - - - - - - - CONCENTRATION, ppm - - - - - - - - - - - - -
SebacicEmpol Mobilad
D665 - % Rust Acid 1022 H-536 C603 SAR-0 Amine-0
(None)
100
200
500
1000
100
3 200
500
1000
300
500
300
7 500
300
500
Pass 300
Pass 500
1 000
1 000
1000
Pass 1000
CA 022422~3 1998-08-12
TABLE 5
BASE FORMULATION #3
PLUS COMBINATION OF CORROSION INHIBITORS
AVERAGE - - - - - - - - - - - - CONCENTRATION, ppm - - - - - - - - - - - - -
D65 - % RustSebacic Acid H-536Mobilad C603 PAR-302 SAR-0
200 100
200 500
400 500
7 200 300
2 400 300
400 100
200 500
400 500
200 100
2 200 300
200 500
400 100
2 400 300
400 500
200 100
200 300
200 soo
400 100
400 300
400 500
200 300
7 400 500
600 So0
CA 02242253 1998-08-12
- 19-
TABLE 5
BASE FORMULATION #3
PLUS COMBINATION OF CORROSION lNHIBITORS
(continu~)
AVERAGE --- - -- - - - - - - CONCENTRATION, ppm -- - - -- - - -- - - - -
D65 - % RustSebacic Acid H-536Mobilad C603 PAR-302 SAR-0
B/L 600 1000
Pass 400 1000
600 500
Pass 600 1000
3 400 500
Pass 400 1000
B/L 600 500
600 1000
3 400 500
B/L 400 1000
CA 022422~73 1998-08-12
- 20 -
TABLE 6
BASE FORMULATION #3
PLUS COMBINATION OF CORROSION INHIBITORS
AVERAGE - - - - - - - - - - - CONCENTRATION, ppm -- - - - -- - - - - - -
D665 -%RustEmpol 1022 H-536Mobilad C603 SAR-0 Amine-0
200 300
200 300
200 300
200 300
200 500
200 500
200 500
Pass 200 500
Pass 100 100
Pass 200 300
Pass 200 500
400 100
Pass 400 300
When considering the data in these Tables, one needs to bear
several factors in mind. Rust tests are highly variable. Thus, for those skilled in
the art, it is the trend in rust results with increasing additive concentration which
is most important. When all of the data are examined, it is clear that none of the
additives alone (except for Amine O, which has its own unique drawbacks
associated with it), are able to provide passing results. Combinations of rust
inhibitors, however, are able to achieve passing results at concentration levelswhich do not have harmful secondary effects.
Even when the test results are not a pass, the combination of rust
inhibitors provides an improved rust rating than either additive alone. This trend
clearly indicates a synergistic interaction of the combined corrosion inhibitors.
