Note: Descriptions are shown in the official language in which they were submitted.
~,o5~859
BACKGROUND OF Tl~ ~NVENTIO~
Field of the Invention:
This invention relates to novel corrosion inhibiting
compositions which have particular utility in preventing
vapor space rust.
It has been observed that steani turbine lubricating
oil systems frequent]y exhibit severe corrosion of the metal
surfaces not normally submerged in the oil. This corrosion
is normally called "vapor space rust". Such corrosion is
observed in the oil sump and oil return lines of many steam
turbines. This vapor space rusting is undesirable because
the rust particles oreak loose from the metal surface
and cause filter plugging and reduce oil flow. Undesirably,
the ~st particles can reach the bearings, reduction gears,
and governors thereby causing extensive damage and costly
down ti~le. The use of vapor space rust inhibitors, which
coat the metal surface and prevent rusting, o~fers a promis-
ing solution to vapor phase rust inhibition proble~s.
DescriPtion of the Prior Art:
~ Some degree of vapor space rust inhibition has
been obtained from suitable members of the following types of
compounds: aliphatic and aromatic acids; primary, secondary
and tertiary amines; amine salts of organic acids; and
alkylolamir.es. U. S. Patent 2,775,560 covers the usa of
aliphatic monocarboxyl-Lc acids containing from 8 to 10 carbon
atoms as vapor space rust inhibitors in turbine oil formula-
tions In the literature, combinations of normal carboxylic
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acids (C8 to C10) with selected low molecular weight aliphatic amines have
been used as vapor space rust inhibitors. Up to now this combination of
acids and amines has not been suggested in the patent literature as vapor
space rust inhibitors.
SUMMARY OF THE INVENTION
In accordance with the invention there is provided a lubricating
oil composition having improved vapor space corrosion properties comprising
from 0.01 to 5.00 weight percent, basis oil of a mixture of at least one
amine salt of a C8 - C10 aliphatic monocarboxylic acid together with at
least one amide of diethanolamine and a fatty acid containing from 12 to
20 carbon atoms, the ratio of amide to acid amine salt being from about
1:1 to about 1:10, the balance, a major amount of a mineral oil. The ratio
of fatty amide to acid-amine salt ranges from 1:1 to 1:10 with the preferred
ratio being 1:2 to 1:6. Uniquely, only unsaturated acids are effective.
Of the acids mentioned above the straight-chain mono or diun-
saturated monocarboxylic acids (C12-C20) are preferred for reacting with
diethanolamine. Suitable amines include normal, branched and cyclic ali-
phatic amines; primary, secondary, tertiary and saturated heterocyclic
amines having twelve carbon atoms or less in the alkyl group or groups.
The acid part of the amine salt can be a C8, Cg or C10 acid.
E~
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DISCLOSURE
SYNTHESIS OF TALL OIL ACID-DIETHANOLAMINE
Equimolar amounts of Tall Oil Acid and diethanol-
amine were cut back with approximately 25% xylene, and the
mixture was heated at reflux until the calculated quantity
of water was recovered from the desired reactions. The
reaction mixture was then stripped to a constant weight
yielding the desired product.
The amide has the following structure:
O CH2-CH2-OH
.. .
R-C-N-CH2-CH2-OH , R=C17 mono and diunsaturated hydro-
carbon.
SYNTHESIS OF DECANOIC ACID-t-BUTYLAMINE SALT
Equimolar amounts of the acid and t-butylamine
were heated together, with 10~ methanol dilution, for 2
hours at 120-130F. The methanol solvent was then removed
by nitrogen stripping at atmospheric pressure, yielding the
decanoic acid-t-butylamine salt. Other decanoic acid-amine
salts were prepared by a similar method. The amine salt
has the following structure:
o
R-C-O H3N-C4Hg, R CgHlg
EXPERIMENTAL RESULTS
Table I shows results obtained with a combina-
tion of a fatty acid amine and a fatty acid amine salt.
Each of the individual additives was first
evaluated as vapor space inhibitors separately and then
compared to combinations of additives. The total concentra-
tion of additive(s) was the same in all cases, either
0.10 or 0.15 wt. ~.
--3--
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The inhibited oil blends were evaluated in a
modified version of the Hot Plate Reflux Rust Testl where
~he hot plate was replaced with a constant temperature cil
bath. Metal specimen were composed of SA~ 1018 mild steel.
The specimen were polished using 240 grit abrasive and
stored under precipitation naphtha until they were used.
After the test was completed, the specimen were rated
according to the amount and type of rust present. The
following ratings were used:
1. ASTM Publication, 65th. Annual Meeting, Symposium on
Turbine Oils (1962).
NR - No rust
T - Trace Rust, a few isolated pin points of rust
L - Light Rust, several pin points of rust or
small rust spots
M - Moderate Rust, specimen covered with rust
or large rust spots
S - Severe Ru~t, specimen heavily rusted and
pitted
Blends containing the individual additives had
unsatisfactory ratings in the test. However, the blend
containing decanoic acid had a much better rating than blends
containing the other individual additives. The addition of a
small amount of the fatty amide to oil blends containing
decanoic acid combined with either t-butylamine or tributyl-
amine gave synergistic effects in inhibiting vapor space rust
as shown by the explanatory data presented in Table I. It
can be readily seen that the combination of any two of the
three components will not provide equivalent vapor space rust
protection to oil blends. In order to have the noted
improvement in vapor space rust inhibition, an oil blend
must contain the fatty amide, a fatty acid, and an aliphatic
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amine. The acid and amine should be reacted together prior
to being used to form an acid - amine salt.
Further, it can be seen that only fatty amides
prepared from unsaturated acids are effective. Both the
amide prepared from hydrogenated Tall Oil Acid and the
amide prepared from stearic acid had unsatisfactory ratings
when added to oil blends containing octanoic acid combined
with tributylamine. By contrast, the amide prepared from
Tall Oil Acid had improved vapor space rust protection when
added to oil blends containing octanoic acid combined with
tributylamine as shown by the explanatory data presented in
Table I.
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TABLE I
VAPOR SPACE RUST TEST RESULTS OF INHIBITED TURBINE OILS
Additive Wt. ~ Additivel Rusting 2
20 Hrs/210~F
Tall Oil Acid-diethanol 0.10 S
amide (TOA-DEA) 0.15 insoluble
Decampoc acid 0.10 T, L
0.15 2L
t-Butylamine 0.10 3S
0.15 2M,S
Tributylamine 0.10 S
0.15 S
Decanoic acid/t-butylamine Q.10 T, 2L
0.15 T, 2L
Decanoic acid/ 0.10 3S
tributylamine (DATA) 0.15 M, 2S
Decanoic acid/TOA-DEA 0.10 3M
0.15 3L
TQA-DEA/ DA tert BA 0.10 3NR
O.15 3NR
TOA-DEA/DATA 0.10 2T, L
0.15 2T, L
TOA-DEA/octanoic acid/
tributylamine (QATA) 0.15 2T, L
ToA-DEA3/oATA o.l5 L, M, S.
stearic acid-diethanolamide/
DATA 0.15 3S
lIn Turbine Oil qualified agalnst MIL-L-17331F specification.
2NR - No Rust, T-Trace, L-Light, M-Moderate, S-Severe. A
No Rust to trace rating was considered a passing result.
The numbers show the no. of tests run.
3Prepared from hydrogenated Tall Oil Acid.
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Pairs of amides and acid salts which give
substantially equivalent results as the pairs exemplified
~n Table I included the following:
Diethanolamidel Acid Amine Salt
_
Tall Oil Acid-dlethanolamide Decanoic acid-isobutylamine
Palmitic acld-diethanolamide Decanoic acid-n-butylamine
Oleic acid-diethanolamide Decanoic acid-n-pentylamine
Linoleic acid-diethanolamide Decanoic acid-n-hexylamine
Decanoic acid-cyclohexylamine
Decanoic acid-morphollne
Decanoic acid-N-methylmorpholine
A vapor space rust inhibitor composit~Qn can be formed by
combining any one of the diethanolamideæ listed with any
of the acid/amine salts listed.
20ctanoic acid and nonanoic acid may be used in place of
decanoic acid in the cases listed below and combined with
t-butylamine and tributylamine.
Other additives can be used in usual amounts with
the lubricants to which the vapor phase corrosion inhi~itors
of the invention are added. Such additlves lnclude extreme
pressure agents, anti-clogging agents, ant$rust agen s,
oxidation inhib$tors and the like.
The base oil for the addltives of this invention
can be any mineral hydrocarbon oil but usually is a turbine
oil, a hydraulic oil or a draw~ng oil.
