CA1067687A

CA1067687A - Lubricant corrosion inhibitors

Info

Publication number: CA1067687A
Application number: CA252,996A
Authority: CA
Inventors: Bryan T. Davis; Nicholas W. Moat
Original assignee: ETHYL COOPER Ltd
Current assignee: ETHYL COOPER Ltd
Priority date: 1975-05-23
Filing date: 1976-05-20
Publication date: 1979-12-11
Also published as: JPS5314563B2; DE2622066A1; FR2311839A1; JPS523606A; IT1061566B

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.

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.

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~ class of compounds which has been found useful has the general formula:-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 ~ ~ NH2 II

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 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 \

i.e. N-n-butyl dietha~olamine The B component has the general formula:

21 ~ CH - 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).

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~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.

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~ ~ a~ r o co C~ ~
H

H ~) O .
,1 . ~ ~ U) ~r: m ,, ~ ,, ~ r~
F~ I ~ I ~ r; ~ r;

Z o o o In ~ In ~
m ~ ~ ~ ~ ~ I o E~ I ~D ~O 1` u~ ~ ~r ~r u~
~r er ~ ~r ~ 1-- ~ [~ ~, d~ O O O O O O O O O O ~J
. h ~ ~1 . ,1 O
o r~ rl ~ O ~
~¢ ~ ~ ~1 a) ~1 N ~ IJ O
m ~ Q, ,¢ ~ ~a~
E~ a) a) ~ ~ o ,~ , O O ON Q~ l r-l ~ ~, ~ O
o o I
5~ O O O
OQ~ ,N ~ l N ~ I
~rl ~ O O ~ )a la o E~ o u~ u~ aJ rl " S~ a) E~ I X I I E~ O ,~
¢ Z H H E~ ~ m ~ m 0 ~ o z z ~d z .
~ .

~ l ~
m U~. . . . . . . . . ~ ~
E~ oooo o o ooooo~::
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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.

.. . .. .. . . . . . . . . .
.- . : . , : .

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 and 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 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 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 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 wherein R4 is an alkylene or cycloalkylene group, and each of R5, R6, R7 and R8 is hydrogen, lower alkyl or the group 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.

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 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 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.