LUBRICANT CORROSION INHIBITORS

INHIBITEURS DE CORROSION POUR LUBRIFIANTS

English Abstract

ABSTRACT OF THE DISCLOSURE
A motor oil is provided having enhanced antirusting
qualities imparted by minor amounts of an additive comprising,
in the weight proportions of 1/2 to 2/1, a component A which is
an oil-soluble basic organic nitrogen compound having a total
base member of at least 300 and which is soluble in or hydrolyzed
by water to give an aqueous system of pH at least 9.5, and a
component B which is an alkyl or alkenyl substituted succinic
acid having from about 8 to 30 carbon atoms.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A lubricating oil for internal combustion engines
comprising a major amount of lubricating oil and a minor amount
of a combination of two additives A and B wherein A is an oil-
soluble basic nitrogen compound having a total base number of
at least 300 mg. KOH/g. and which is at least sufficiently
soluble in or hydrolyzed by water to give an aqueous solution
of pH at least 9.5, said nitrogen compound being selected from
the group consisting of (1) compound of the formulae
<IMG> and <IMG>
wherein R15 is alkyl, R4 is an alkylene or cycloalkylene group,
and each of R5, R6, R7 and R8 is hydrogen, lower alkyl or the
group <IMG> wherein R4, R5, and R6 are as defined above,
and said compound contains not more than 20 nitrogen atoms in
the molecule; (2) the reaction product of an aldehyde or a ketone
with a water-soluble primary or secondary aliphatic, cyclo-
aliphatic or heterocyclic amine or hydroxyamine; and (3)
compounds of the formula
<IMG>
wherein R16 is alkyl; R17 is an alkylene group of up to 3
carbon atoms; R16, R19 and R20 are each alkylene; w is 0, 1,
2 or 3, and x, y, and z are each independently an integer of
from 1 to 5; and B is an alkyl or alkenyl succinic acid having
from 10 to 22 carbon atoms, said A and B components having a
weight ratio A/B of from 1/2 to 2/1.
2. A lubricating oil for internal combustion engines
comprising a major amount of lubricating oil and a minor amount
13

of a combination of two additives A and B wherein A is an oil-
soluble basic nitrogen compound having a total base number of
at least 300 mg. KOH/g. and which is at least sufficiently
soluble in or hydrolyzed by water to give an aqueous solution
of pH at least 9.5, said nitrogen compound being a compound of
the formula
<IMG>
wherein R4 is an alkylene or cycloalkylene group, and each of
R5, R6, R7 and R8 is hydrogen, lower alkyl or the group
<IMG> wherein R4, R5, and R6 are as defined above, and
said compound contains not more than 20 nitrogen atoms in
the molecule; and B is an alkyl or alkenyl succinic acid
having from 10 to 22 carbon atoms, said A and B components
having a weight ratio A/B of from 1/2 to 2/1.
3. A composition according to claim 2 characterized in
that A is N,N,N',N'-tetramethyl-1,3-diaminobutane.
4. A composition according to claim 2 characterized in
that A is isophorone diamine.
5. A lubricating oil for internal combustion engines
comprising a major amount of lubricating oil and a minor amount
of a combination of two additives A and B wherein A is an oil-
soluble basic nitrogen compound having a total base number of
at least 300 mg. KOH/g. and which is at least sufficiently
soluble in or hydrolyzed by water to give an aqueous solution
of pH at least 9.5, said nitrogen compound being the reaction
product of an aldehyde or a ketone with a water-soluble primary
or secondary aliphatic, cycloaliphatic or heterocyclic amine
or hydroxyamine; and B is an alkyl or alkenyl succinic acid
having from 10 to 22 carbon atoms, said A and B components
having a weight ratio A/B of from 1/2 to 2/1.
6. A composition according to claim 5 characterized in
that A is a member of the group bis(benzal aminopropyl)piper-
azine, benzal aminopropyl dimethyl amine, and 2-propyl-3-methyl
oxazolidine.
14

7. A lubricating oil for internal combustion engines
comprising a major amount of lubricating oil and a minor amount
of a combination of two additives A and B wherein A is an oil-
soluble basic nitrogen compound having a total base number of
at least 300 mg. KOH/g. and which is at least sufficiently
soluble in or hydrolyzed by water to give an aqueous solution
of pH at least 9.5, said nitrogen compound being a compound
of the formula <IMG> wherein R15 is alkyl; and B is an
alkyl or alkenyl succinic acid having from 10 to 22 carbon atoms,
said A and B components having a weight ratio A/B of from 1/2
to 2/1.
8. A composition according to claim 7 wherein A is N-
ethyl morpholine.
9. A lubricating oil for internal combustion engines
comprising a major amount of lubricating oil and a minor amount
of a combination of two additives A and B wherein A is an oil-
soluble basic nitrogen compound having a total base number of
at least 300 mg. KOH/g. and which is at least sufficiently
soluble in or hydrolyzed by water to give an aqueous solution
of pH at least 9.5, said nitrogen compound being a compound
of the formula
<IMG>
wherein R16 is alkyl; R17 is an alkylene group of up to 3
carbon atoms; R16, R19 and R20 are each alkylene; w is 0, 1,
2 or 3, and x, y, and z are each independently an integer of
from 1 to 5; and B is an alkyl or alkenyl succinic acid
having from 10 to 22 carbon atoms, said A and B components
having a weight ratio A/B of from 1/2 to 2/1.

10. A composition according to claim 9 characterized in
that A is N-n-butyl diethanolamine.
11. A composition according to claim 2, 3 or 4 further
characterized in that B is tetrapropenyl succinic acid.
12. A composition according to claim 5, 6 or 7 further
characterized in that B is tetrapropenyl succinic acid.
13. A composition according to claim 8, 9 or 10 further
characterized in that B is tetrapropenyl succinic acid.
14. An ashless corrosion inhibitor for lubricating oils
for internal combustion engines comprising a blend of a com-
ponent A and a component B both as defined in claim 2, 3 or
4 and the weight proportion of A/B is from 1/2 to 2/1.
15. An ashless corrosion inhibitor for lubricating oils
for internal combustion engines comprising a blend of a com-
ponent A and a component B both as defined in claim 5, 6 or
7 and the weight proportion of A/B is from 1/2 to 2/1.
16. An ashless corrosion inhibitor for lubricating oils
for internal combustion engines comprising a blend of a com-
ponent A and a component B both as defined in claim 8, 9 or
10 and the weight proportion of A/B is from 1/2 to 2/1.
16

Description

10~;~6~7
This invention relates to corrosion inhibitors for
lubricants for internal combustion engines. In particular,
the invention relates to formulations of automotive crankcase
lubricants, especially when low-ash or ashless formulations are
desiredO
Automotive crankcase lubricants generally contain
appreciable amounts of overbased metal compounds, particularly
overbased alkaline earth metal or magnesium petroleum or alkyl
benzene sulphonates. These overbased metal compounds provide
effective rust inhibition by neutralising corrosive acidic
combustion products from the fuel, such as hydrochloric and
hydrobromic acid from the lead scavengers normally present and
low molecular weight organic acids from the oxidation of the fuel
itself. In the absence of overbased additives, as in ashless
oils, or when such additives are present in reduced amounts, as
in "low-ash" oils, rusting becomes a serious problem.
Various commonly known ashless rust-inhibitors have
been tried in ashless automotive crankcase oils with little
success. However, we have now found a combination of additives
providing effective rust-inhibition in ashless oils as well as
in oils which contain ash-producing components.
A need has therefore been shown for a non-ash forming
corrosion or rust inhibitor to which this invention is directed.
According to the invention a composition, effective for a
crankcase lubricating oil for internal combustion engines, is
provided comprising a major amount of lubricating oil, preferably
mineral lubricating oil, and a minor amount of a combination of
two additives A and B, wherein: - A is an oil-soluble basic
organic nitrogen compound having a total base number of at least
300 mg. KOH/g. and which is at least sufficiently soluble in,

1 0~7f~ 7
or hyd~olyzeci by, water to give an aqueous solution o pH at
least 9.S; and B is an alkenyl or alkyl substituted succinic
acid having a total of about lO to about 50, preferably up to 30,
and especially 12 to 22 carbon atoms total. Further, in said
composition, the components.A and B are provided in the weight
ratio A/B of from 1/2 to 2/1.
In accordance with the invention, the basic organic
nitrogen compound or products of hydrolysis thereof must be
capable of providing an aqueous solution having a pH of at least
9.5. The suitability of compounds in this respect can be simply
determined by dissolving 0.05 gms of the compound in lOO mls of
deionized water, previously neutralized to pH 7, and measuring
the pH of the resulting solution.
ph~
.

~ class of compounds which has been found
useful has the general formula:-
R7 R5
N ~ R4 N
8 / Rwherein R4 is a straight or branched chain a]kylene group or a
cycloalkylene~group, and R5, R6, R7 and R8 are independently
hydrogen, lower alkyl, preferably methyl or ethyl, or the group
.
- R4 - N wherein R4, R5 and R6 are as defined above,
\R6
provided that not more than 20, preferably not more than 10,
nitrogen atoms are present in the molecule~ Particularly
usçful examples of this class have the formulae:-
jCH3
CH3 CH CH2 C 2 ~
¦ CH3
N
CH3 CH3
CH3 ~ ~ NH2 II
CH3 CH2NH2
-- 4 --
ph~

10~7687
i.e. (I) N,N,N ,N'-te~ramethyl~ diaminobutane and (II)
isophorone diamine.
Further classes of compounds which have been found
useful are the reaction products of aldehydes or ketones with
water-soluble primary or secondary aliphatic, cycloaliphatic or
heterocyclic amines or hydroxy-amines.
Primary mono-amines react with aldehydes or ketones to
give aldimines and ketimines of respective formulae: -
R9CH = N R9 and R9\
/ C = N R9
wherein the R9 group attached to the nitrogen atom may be alkyl,aralkyl or cycloalkyl, optionally containing one or more nitrogen
atoms and wherein the R9 groups attached to carbon may be alkyl,
aralkyl or cycloalkyl provided that when two groups R9 are
attached to the same carbon atom they may jointly form a single
cycloalkyl group, Furthermore, secondary mono-amines give
compounds of formula
~Rl2
Rl N
'~ Rl 3
~ \ ~Rl2
Rll N
~Rl3
wherein Rl is an alkyl or aryl group, Rll is H or an alkyl
or aryl group or Rl and Rl1 may together form part of a ring
structure, and R12 and R13 are lower alkyl or hydroxyalkyl groups,
or may together form part of a heterocyclic ring. When the
amine chosen is a 2-hydroxy substituted primary or secondary
amine, reaction with an aldehyde or a ketone yields an

-- 106768-7
oxa~.o]i~in~ wh~r~ s if th~ amine chosen is s~l~stituted in
thc 2-position by a primary or secondary amino group an
imidazolidine is formed. If the amine is substituted in
the 3-position by a hydroxyl group or a primary or secondary
amino group, the compounds formed are tetrahydro-1,3-
oxazines and tetrahydropyrimidines respectively. Typical
formulae are:-
~14 Rl 4
R I ~ N CH 2 Rl N - CH2
10R ~ o - IH 2 R ~ \ N - ¦H
Rl 4
oxazolidine imidazolidine
~1~ Rl4
Rj N _ CH2 Rl ~ N - CH2
/ C f 2 ~ ~ CH 2
R O - CH Rll N - CH2
Rl 4
tetrahydro-1,3-oxazine tetrahydropyrimidine
~20 where R is H, lower alkyl, hydroxyalkyl or alkylaminoalkyl.
All of these compounds are hydrolyzed by water,
especially in the presence of acids, to the parent aldehyde
or ketone and amine and by this means it is possible to pre-
pare an oil-soluble derivative of an oil-insoluble water-
soluble amine which will release the amine into the a~ueous
phase under engine operating conditions.
The aldehyde or ketone chosen will depend on the
amine selected and the degree of oil solubility which it is
desired to confer. Aldehydes are preferred to ketones since
they react more readily: formaldehyde, acetaldehyde and higher
A

~0~71~S7
aliphatic aldehydes such as n-butyraldehyde and n-heptaldehyde
may be used, but benzaldehyde is particularly preferred.
Examples of suitable ketones are acetone, methyl ethyl ketone,
methyl isobutyl ketone and cyclohexanone.
I'he amine may be a mono-, di- or polyamine or a hydroxy-
substituted amine, such as mono- or di-ethanolamine. Particularly
useful amines are those which contain additional basic nitrogens
in the molecule such as dimethylaminopropylamine and its
homologues and bis aminopropyl piperazine.
Specific examples of compounds which have proved effec-
tive in automotive crankcase lubricants are
bis(benzal aminopropyl)piperazine
benzal aminopropyl dimethylam:ine
2-propyl-~-methyl oxazolidine.
A further class of compounds which has been found
useful as additive A has the general formula: -
Rl 5 13
wherein Rl5 is alkyl e.g. lower alkyl, preferably ethyl. A
particularly useful example of the class has the formula: -
C2H5 ~
i.e. N-ethyl morpholine.
A further class of compounds which has been found
useful has the general formula

106761~7
R16 _ _ N -R17 (R190) H
~ 80)xH \ ~R2~o)zH
w
wherein R~'6 is alkyl, preferably lower alkyl; R17 is lower
alkyler.e preferably ethylene or propylene; R18, Rl9 and R20
are the same or different and are alkylene, preferably ethylene
or propylene; w is 0, 1, 2 or 3; and x, y and z are the same or
different and each is an integer of from 1 to 5, preferably
1 or 2. A particularly preferred member o thls class, which
has been found useful, has the formula -
/ CH2 CH~OH
C4Hg N \
CH2 CH20H
i.e. N-n-butyl dietha~olamine
The B component has the general formula:
21 ~ CH - CO2 H
CH2 - CO2 H
wherein R21 is a straight or branched chain alkyl or alkenyl
group containing 8 to 30 carbon atoms. For reasons of better
oil solubility R21 is preferably an alkenyl group or a branched
chain alkyl group. A member of this class which has been shown
to be particularly useful is tetraprop,enyl succinic acid (TPSA).
-- 8 --
ph :b" `

~067~87
Component A of the lubricating compositions of the
present invention will normally be present in an amount of from
0 1% to 10~ by weight, more preferably 0.2~ to 2.0~ by weight,
based on the total weight of the composition. Component B will
normally be present in an amount of from 0.1~ to 10~ by, more
preferably 0.2~ to 2.0~ by weight, based on the total weight of
the com~osition. An essential requirement of this invention is
the use of the basic organic nitrogen compound and the carboxylic
acid compound together. Without the organic nitrogen compound,
the tetrapropenyl succinic acid was found to have only limited
rust-inhibiting properties in automotive crankcase oilsO Without
the carboxylic acid, the basic nitrogen compounds exhibited no
rust-inhibiting properties when used at chemically equivalent
concentrations, Better results have been obtained than would
have been expected using either the acid or the amine component
above, Still better results have been obtained by using
proportions of amine to acid such that an excess of amine over
that required to form the neutral salt of the acid was present.
The use of excess amine over that required to neutralize the
carboxylic acid is therefore highly preferred.
The combination of components A and B in accordance
with the present invention effectively reduces corrosion, as
measured by the ASTM Sequence IIC engine test, and also reduces
the formation of lead-containing deposits which occur in the
hydraulic valve lifters. It is believed that the formation
of such deposits may be enhanced by the use of ashless sulfur-
containing antioxidantsO me use of a combination of components
A and B in accordance with the present invention is therefore

~0~7687
highly desirable in oil formations which also contain such
sulphur-containing antioxidants. However, the compositions of the
present invention may also contain, if desired, other known
lubricant additives. For example, compositions according to the
present inven;tion may contain commonly used ashless dispersants
or detergents such as derivatives of polyisobutenyl succinic
acid, e.g. PIB succinimides or PIB succinic acid esters or
mono-carboxylic acid amides or esters derived from polyiso-
butylene or polypropylene formed by reacting the chlorinated
hydrocarbon with acrylic acid.
Ashless antioxidants which may be used in the present
invention include hindered phenols, i.e. phenols having at
least one alkyl group, usually t-butyl, on the ring and adjacent
to the OH group. Other antioxidants include sulphurized
hydrocarbons, dithiocarbamates, phenothiazine derivatives and
arylamines such as phenyl a-naphthylamine and its derivatives.
Zinc dialkyl dithiophosphate antioxidants may also
be used provided any product of its interaction with component
A is oil-soluble.
The following Table summarizes data which demonstrate
the preferred embodiments of the invention9 when used as additives
for spark-ignition internal combustion engine lubricants. The
evaluation procedure used was the ASTM Sequence IIC engine-
test according to the method described in ASTM Special Technical
Publication 315F.
10 .

10f~7~87
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10~'7~87
Blends A~ ~and C were all ashless blends containing
succinimide or ester type ashless dispersantsJ ashless, sulphur-
containing antioxidants and another corrosion inhibitor of the
surface-active type.
Without limiting their invention to one mode of operation
applicants believe that component A acts not as a surface-active
rust inhibitor but in the body of the oil, by a process of pH
modification, in much the same manner as the overbased sulphonates
hereinbefore referred to. In this connection laboratory tests
have shown that the pH of acidic aqueous solutions in contact
with a lubricating oil containing A is modified, whereas no
modification occurs in the absence of component A.
It has also been noted that the most effective species
of component A are freely soluble in both oil and water. This
is deemed to be an important factor since water is one of the
principal components of combustion gases and it tends to condense
to form aqueous acids. Consequently, in a highly preferred
embodiment of the present invention component A is soluble in
mineral oil in amounts of at least up to 2~ and is also soluble,
or hydrolyzed by, water. Additional desirable characteristics
of component A are a high boiling point and low volatility.
.. . .. .. . . . . . . . . .
.- . : . ,
: .