Polyester lubricant additives, their preparation and compositions containing them

Polyesters suitable for use as lubricant additives are prepared by reacting a di-carboxylic acid or anhydride having a branched chain alkyl or alkenyl substituent containing at least 30 carbon atoms with a compound having the formula: ##STR1## wherein R and R.sup.1 are specified substituents which between them possess from 2 to 6 free hydroxyl groups. Lubricating compositions containing these polyester additives are also described.

The present invention relates to lubricant additives, more particularly to 
additives suitable for use as ashless dispersants. 
According to one aspect of the present invention there is provided a 
polyester, prepared by reacting a di-carboxylic acid or anhydride thereof, 
said acid or anhydride having a branched chain alkyl or alkenyl 
substituent containing at least 30 carbon atoms, with a substituted 
carboxypyrrolidone of the following formula A such that the carboxyl 
groups of the acid are substantially completely esterified by hydroxyl 
groups of A, wherein A is: 
##STR2## 
in which: 
(A) R is a hydrogen atom or an alkyl, aryl, aralkyl, hydroxyalkyl, 
(poly)oxyalkylenealkyl or hydroxyalkylaminoalkyl group, an alkyl group 
substituted by one or more heterocyclic rings in which the or each 
heteroatom is preferably a nitrogen atom and which is free from amine 
--N--H groups, for example an imidazoline group or a group of the formula: 
##STR3## 
(b) each R.sup.1 is a group of the formula: 
##STR4## 
and each R.sup.1 is the same as or different from any other group R.sup.1 ; 
(c) R.sup.2 is an alkylene group; 
(D) R.sup.6 is an alkyl, (poly)oxyalkylenealkyl or hydroxyalkyl group, a 
group of the formula: 
##STR5## 
in which the groups R.sup.2 and R may be the same as or different from any 
other group R.sup.2 and R respectively, an alkyl group substituted by one 
or more tertiary amine groups or an alkyl group substituted by one or more 
heterocyclic rings in which the or each heteroatom is preferably a 
nitrogen atom and which is free from amine --N--H groups; 
(E) R.sup.7 is an alkyl, hydroxyalkyl, dialkylaminoalkyl or 
hydroxyalkylaminoalkyl group, or a group of the formula: 
##STR6## 
or a group of the formula: 
##STR7## 
in which the groups R.sup.2 and R may be the same as or different from any 
other group R.sup.2 and R respectively, or is an alkyl group substituted 
by one or more heterocyclic rings in which the or each heteroatom is 
preferably a nitrogen atom and which is free from amine --N--H groups; 
(f) R.sup.8 is a hydrogen atom or as R.sup.7 ; 
(g) provided that there are a total of from 2 to 6, preferably 3 to 6, free 
hydroxyl groups on groups R and/or R.sup.1. 
In accordance with another aspect of the invention there is provided a 
process for preparing a polyester suitable for use as a lubricant additive 
which process comprises reacting a di-carboxylic acid or the anhydride 
thereof, said acid or anhydride having a branched chain alkyl or alkenyl 
substituent containing at least 30 carbon atoms, with a substituted 
carboxypyrrolidone of the foregoing formula A such that the carboxyl 
groups of the acid are substantially completely esterified by hydroxyl 
groups of A. 
The substituted carboxypyrrolidone starting materials of foregoing formula 
A may be obtained using relatively simple variations of well-known 
techniques. Thus, it is well known that itaconic acid, or its esters, will 
condense with a primary amine to form a 2-pyrrolidone having a substituent 
on the nitrogen atom which is the residue of the amine, the 2-keto group 
being derived from one of the carboxyl groups of itaconic acid and having 
a pendant substituent derived from the other carboxyl group of itaconic 
acid on the carbon atom in the 4 position in the pyrrolidone ring. The 
pendant substituent is a carboxyl group in either free or esterified form 
depending on whether itaconic acid or an ester thereof has been used. To 
form the carboxypyrrolidone starting materials of the present invention 
itaconic acid, or an ester thereof, may be condensed with an aminoalcohol 
to yield a carboxypyrrolidone in which the substituent on the nitrogen 
atom has one or more free hydroxyl groups; thus monoethanolamine will 
form: 
##STR8## 
Similarly compounds of the formula: 
##STR9## 
may be prepared from the appropriate aminoalcohol. 
Alternatively an amine other than an aminoalcohol may be used to form 
carboxypyrrolidones in which the substituent on the nitrogen atom does not 
bear a free hydroxyl group, e.g. carboxypyrrolidones of the formula: 
##STR10## 
In yet another alternative di(primary)amines may be used to form bis 
carboxypyrrolidones, e.g. of the formula: 
##STR11## 
The condensation of the primary amine with the itaconic acid, or ester 
thereof, proceeds readily over a wide range of temperatures, e.g. up to 
180.degree. C. However, at relatively high temperatures internal 
esterification may occur between free hydroxyl groups on the substituent 
on the nitrogen atom and the pendant carboxyl group in the 4 position. 
Accordingly, it is preferred to carry out the condensation at a 
temperature of from 80.degree. C. to 120.degree. C. A particularly useful 
technique is to carry out the condensation in refluxing water. 
The pendant carboxyl group on the 4 position of the carboxypyrrolidone ring 
may have one of a number of different forms according to the polyester 
final product desired. This can be achieved in a number of cases by 
forming the carboxypyrrolidone from an appropriately substituted ester of 
itaconic acid. However, it is preferred to carry out the condensation with 
itaconic acid or an alkyl ester thereof in which the alkyl group contains 
from 1 to 8, more preferably 1 to 4 carbon atoms and thereafter to convert 
the pendant carboxyl group to the desired form. Thus esterification of a 
free carboxyl group with an alcohol can be used to convert the acid form 
to an alkyl ester. Alternatively a carboxyl group in alkyl ester form can 
be transesterified to form a different alkyl ester. Similarly 
esterification or transesterification with a diol or polyol can be used to 
form a hydroxylalkyl ester of the pendant carboxyl group. Such conversion 
can be carried out using conventional esterification and 
transesterification techniques. 
Alternatively, the pendant carboxyl group can be reacted with various 
amines to introduce nitrogen-containing substituents. For example, 
amidation of the pendant carboxyl group (in either free or ester form) can 
be used to form compounds of the formula: 
##STR12## 
Amidation can usually be readily carried out by heating together the amine 
and carboxypyrrolidone at a temperature of from 100.degree. to 200.degree. 
C. preferably distilling out water or alcohol formed in the reaction. In 
most cases a temperature of from 140.degree. to 180.degree. C. has been 
found to be most suitable. 
When the substituent on the pendant carboxyl group is difunctional larger 
quantities or carboxypyrrolidone may be used to form a bis compound, e.g. 
of the formula: 
##STR13## 
The esterification of the chosen carboxypyrrolidone starting material with 
the long-chain substituted carboxylic acid or anhydride in accordance with 
the present invention can be carried out using any of the well-known 
long-chain substituted dicarboxylic acids or anhydrides thereof. The 
long-chain substituent is preferably derived from a polyolefin, e.g. 
polypropylene or polybutylene, and will commonly have a molecular weight 
of from 700 to 3,000. The long-chain substituent confers oil solubility on 
the final product and the optimum size for the substituents will depend, 
inter alia, on the total number of substituents present in the product. 
Accordingly, the size of the substituent can vary widely, but normally 
substituents having a molecular weight of from 900 to 1500 are most 
preferred. It is particularly preferred to use the long-chain succinic 
acids derived from the reaction of a polyolefin with maleic anhydride. 
The long-chain substituted acid may be reacted with the carboxypyrrolidone 
in an amount according to the number of free hydroxyl groups to be 
present. In one form of the invention a long-chain substituted 
dicarboxylic acid is reacted with a carboxypyrrolidone in which the 
substituent on the nitrogen atom has one free hydroxyl group, e.g. derived 
from an aminoalcohol, and the substituent on the pendant carboxyl group 
likewise has one free hydroxyl group to form a linear polyester comprising 
alternating pyrrolidone rings and long-chain substituted esterified 
dicarboxylic acid groups. 
In another form of the invention a long-chain substituted di-carboxylic 
acid or anhydride is reacted with a carboxypyrrolidone in which the 
substituents on the nitrogen atom and on the pendant carboxyl group have a 
total of from 3 to 6 hydroxyl groups in such proportions that the 
resultant polyester contains from 1 to 4 free hydroxyl groups per long 
chain substituted di-carboxylic acid unit. 
In a particularly preferred form of the invention a polybutenyl succinic 
anhydride of molecular weight from 900 to 1500 is reacted with a 
carboxypyrrolidone of formula A in which R is a hydroxyalkyl or 
hydroxyalkylaminoalkyl group, R.sup.1 is --NHR.sup.7 and R.sup.7 is 
hydroxyalkyl or hydroxyalkylaminoalkyl. 
The esterification may be carried out using well-known techniques. An 
esterification catalyst, such as p-toluene sulfonic acid is preferably 
used. The esterification is preferably carried out in the absence of a 
solvent but an inert organic solvent, particularly, a water-entraining 
solvent such as toluene or xylene optionally with a polar solvent such as 
dimethyl formamide, or mineral oil, may be used if desired. 
After formation of the final products they may be purified using the usual 
techniques. A very useful technique is to dissolve the product in an 
organic solvent such as toluene or petroleum ether, water wash, filter and 
finally strip off the organic solvent. 
The present invention, in a further aspect, also includes lubricating 
compositions comprising a major proportion of a lubricating oil, 
especially a mineral oil, having dissolved therein a minor proportion of 
the additives of the present invention, for example 0.1% to 10%, more 
preferably 0.5% to 5%, by weight based on the total weight of the 
composition. 
The additives may also be formed into concentrates of the type commonly 
used by manufacturers in the blending of oil and such concentrates are 
also included within the scope of the present invention. In accordance 
with a further aspect of the invention there is provided a lubricating oil 
concentrate comprising a major proportion of a polyester additive of the 
invention and a minor proportion of a lubricating oil. 
Furthermore, the additives may also be used in conjunction with additives 
conventionally used in lubricants, such as antioxidants, anti-wear 
additives, corrosion inhibitors, detergents, thickeners, load carrying 
agents, pour point depressants, and viscosity index improvers. They may 
also be formed into concentrated additive packages, of the type commonly 
used in oil blending, with such conventional additives. Accordingly, such 
additive packages and lubricants which contain such conventional additives 
in addition to the additives of the present invention are also within the 
scope of the present invention. 
In accordance with a further aspect of the invention there is provided an 
additive package containing a minor amount of a lubricating oil and a 
major amount of an additive consisting of one or more polyesters of the 
invention in combination with one or more, conventional additives.