Chemical compositions and their use as fuel additives

Compounds of general formula (I) wherein X and Y are the same or different and are selected from the group consisting of SO.sub.3 (--), --CO--, --C(O)O(--), --R.sup.4 --C(O)O--, --NR.sup.3 C(O)--, --R.sup.4 O--, --R.sup.4 --C(O)O--, --R.sup.4 -- and --NC(O)--, R.sup.4 being --(CH.sub.2).sub.m -- where m is from 0 to 5 and R.sup.3 is defined below; X.sup.1 and Y.sup.1 are the same or different and are selected from the group consisting of (a), R.sup.1 and R.sup.2 being independently selected from the group consisting of alkyl, alkoxy alkyl or polyalkoxyalkyl groups that contain at least 10 carbon atoms in their main chain, and R.sup.3 being a hydrocarbyl group, each R.sup.3 in a compound of formula (I) being the same of different; A is, together with the carbon atoms with which it constitutes the ring structure in formula (I), an aromatic, non-aromatic, or aliphatic group, where any of such groups can be mono- or polycyclic and/or can include one or more hetero atoms selected from nitrogen, sulphur and oxygen; and Z is selected from nitro, hydroxy, alkyl, alkoxy, carboxy acid and carboxy ester, and their use as low temperature flow improvers for distillate fuels.

The invention relates to new chemical compounds which are useful as wax 
crystal modifiers in fuels especially distillate fuels, the use of these 
compounds as distillate fuel additives particularly in combination with 
other additives, and to fuels and concentrates containing the additives 
optionally in combinations with other additives. 
Mineral oils containing paraffin wax have the characteristic of becoming 
less fluid as the temperature of the oil decreases. This loss of fluidity 
is due to the crystallisation of the wax into plate-like crystals which 
eventually form a spongy mass entrapping the oil therein. The temperature 
at which the wax crystals begin to form is known as the Cloud Point and 
the temperature at which the wax prevents the oil from pouring as the Pour 
Point. Between these temperatures the wax crystals can however block 
filters rendering systems such as diesel trucks and domestic heating 
systems inoperable. 
It has long been known that various additives act as wax crystal modifiers 
when blended with waxy mineral oils. These compositions modify the size 
and shape of wax crystals and reduce the cohesive forces between the 
crystals and between the wax and the oil in such a manner as to permit the 
oil to remain fluid at lower temperatures and in some instances to have 
improved filterability at temperatures between the cloud point and the 
pour point. 
Various Pour Point depressants have been described in the literature and 
several of these are in commercial use. For example, U.S. Pat. No. 
3,048,479 describes the use of copolymers of ethylene and C.sub.1 -C.sub.5 
vinyl esters, e.g. vinyl acetate, as pour depressants for fuels, 
specifically heating oils, diesel and jet fuels. Hydrocarbon polymeric 
pour depressants based on ethylene and higher alpha-olefins, e.g. 
propylene, are also known. 
U.S. Pat. No. 3,961,916 describes the use of a mixture of copolymers, to 
control the size of the wax crystals and United Kingdom Patent 1,263,152 
states that the size of the wax crystals may be controlled by using a 
copolymer having a low degree of side chain branching. Both systems 
improve the ability of the fuel to pass through filters as determined by 
the Cold Filter Plugging Point (CFPP) test because, instead of the plate 
like crystals that are formed without the presence of additives, the wax 
crystals produced are needle shaped and will not block the pores of the 
filter rather forming a porous cake on the filter allowing passage of the 
remaining fluid. 
Other additives have also been proposed. For example, United Kingdom Patent 
1,469,016 states that the copolymers of di-n-alkyl fumarate and vinyl 
acetate which have previously been used as pour depressants for 
lubricating oils may be used as co-additives with ethylene/vinyl acetate 
copolymers in the treatment of distillate fuels with high final boiling 
points to improve their low temperature flow properties. 
U.S. Pat. No. 3,252,771 describes the use of polymers of C.sub.16 to 
C.sub.18 alpha-olefins obtained by polymerising olefin mixtures that 
predominate in normal C.sub.16 to C.sub.18 alpha-olefins with aluminium 
trichloride/alkyl halide catalysts as pour depressants in distillate fuels 
of the broad boiling, easy-to-treat types available in the United States 
in the early 1960's. 
It has also been proposed to use additives based on olefin/maleic anhydride 
copolymers. For example, U.S. Pat. No. 2,542,542 describes copolymers of 
olefins such as octadecene with maleic anhydride esterified with an 
alcohol such as lauryl alcohol as pour depressants and United Kingdom 
Patent 1,468,588 describes copolymers of C.sub.22 -C.sub.28 olefins with 
maleic anhydride esterified with behenyl alcohol as coadditives for 
distillate fuels. 
Similarly, Japanese Patent Publication 5,654,037 describes olefin/maleic 
anhydride copolymers which have been reacted with amines as pour point 
depressants and Japanese Patent Publication 5,654,038 describes using 
derivatives of olefin/maleic anhydride copolymers together with 
conventional middle distillate flow improvers such as ethylene vinyl 
acetate copolymers. 
Japanese Patent Publication 5,540,640 describes the use of olefin/maleic 
anhydride copolymers (not esterified) and states that the olefins used 
should contain more than 20 carbon atoms to obtain CFPP activity. 
United Kingdom Patent 2,129,012 describes using mixtures of esterified 
olefin/maleic anhydride copolymers and low molecular weight polyethylene, 
the esterified copolymers being ineffective when used as sole additives. 
The patent specifies that the olefin should contain 10-30 carbon atoms and 
the alcohol 6-28 carbon atoms with the longest chain in the alcohol 
containing 22-40 carbon atoms. 
U.S. Pat. Nos. 3,444,082; 4,211,534; 4,375,973 and 4,402,708 describe the 
use of certain nitrogen containing compounds. 
Long n-alkyl derivatives of difunctional compounds have also been described 
as has their use as wax crystal modifiers for distillate fuels, i.e. 
derivatives, particularly amine derivatives of alkenyl succinic acid (U.S. 
Pat. No. 3,444,082), maleic acid (U.S. Pat. No. 4,211,534) and phthalic 
acid (GB 2923645, U.S. Pat. No. 4,375,973 and U.S. Pat. No. 4,402,708). 
Amine salts of certain alkylated aromatic sulphonic acids are described in 
United Kingdom Patent Specification 1209676 as is their use as antirust 
additives for turbine oils and hydraulic oils. 
The improvement in CFPP activity achieved by the incorporation of the 
additives described in the above-mentioned patent specification is 
achieved by modifying the size and shape of the wax crystals forming to 
produce needle like crystals generally of particle size 10,000 nanometres 
or bigger typically 30,000 to 100,000 nanometres. In operation of diesel 
engines or heating systems at low temperatures, these crystals do not 
generally pass through the filters but form a permeable cake on the filter 
allowing the liquid fuel to pass. The wax crystals will subsequently 
dissolve as the engine and the fuel heats up, which can be by the bulk 
fuel being heated by recycled fuel. This can, however, result in the wax 
crystals blocking the filters, leading to starting problems and problems 
at the start of driving in cold weather or failure of fuel heating 
systems. 
European Patent Publications 0261957, 0261958, 0261959 describe the use as 
additives of compounds having a certain configuration and in particular 
certain novel compounds which make possible a significant reduction in the 
size of the wax crystals formed to below 4,000 nanometres sometimes below 
2,000 nanometres and in some instances below 1,000 nanometres. 
Further compounds have now been devised whose performance in controlling 
the size of wax crystals in distillate fuels is comparable to that of the 
compounds described in EP-A-0261959. 
This invention therefore provides in one aspect a compound of the general 
formula 
##STR2## 
wherein X and Y are the same or different and are selected from the group 
consisting of SO.sub.3.sup.(--), --CO--, --C(O)O.sup.(--), --R.sup.4 
--C(O)O--, --NR.sup.3 C(O)--, --R.sup.4 O--, --R.sup.4 OC(O)--, --R.sup.4 
-- and --NC(O)--, R.sup.4 being --(CH.sub.2).sub.m -- where m is from 0 to 
5 and R.sup.3 is defined as below; 
X.sup.1 and Y.sup.1 are the same or different and are selected from the 
group consisting of 
N.sup.(+) R.sub.3.sup.3 R.sup.2, HN.sup.(+) R.sub.3.sup.3 R.sup.2, H.sub.2 
N.sup.(+) R.sup.3 R.sup.2, H.sub.3 N.sup.(+) R.sup.2, N.sup.(+) R.sup.3 
R.sup.1, N.sup.(+) HR.sub.3.sup.3 R.sup.1, H.sub.2 N.sup.(+) R.sup.3 
R.sup.1, H.sub.3 N.sup.(+) R.sup.1, NR.sup.3 R.sup.2, --R.sup.2, 
--NR.sup.3 R.sup.1 and R.sup.1, 
R.sup.1 and R.sup.2 being independently selected from the group consisting 
of alkyl, typically C.sub.10 to C.sub.40 more preferably C.sub.10 to 
C.sub.30 more preferably C.sub.14 to C.sub.24, alkoxy alkyl or 
polyalkoxyalkyl groups that contain at least 10, typically 10 to 40, 
carbon atoms in their main chain, and R.sup.3 being a hydrocarbyl group, 
preferably alkyl, more preferably C.sub.1 to C.sub.30 most preferably 
C.sub.10 to C.sub.30 straight chain, each R.sup.3 in a compound of formula 
(I) being the same or different; 
A is, together with the carbon atoms with which it constitutes the ring 
stucture in formula (I), an aromatic, non-aromatic, or aliphatic group, 
where any of such grounds can be mono- or poly-cyclic and/or can include 
one or more hetero atoms selected from nitrogen, sulphur and oxygen; and 
Z is selected from nitro, hydroxy, alkyl, alkoxy, carboxy acid and carboxy 
ester, any alkyl groups preferably containing from 1 to 10, more 
preferably 1 to 4, carbon atoms. 
It is preferred that X.sup.1 and Y.sup.1 together contain at least three 
alkyl, alkoxy alkyl or polyalkoxy alkyl groups. 
In a second aspect of the invention, a distillate fuel composition 
comprises a distillate petroleum fuel boiling in the range of 120.degree. 
C. to 500.degree. C. containing from 0.0001 to 0.5 wt % of a compound of 
formula (I). 
In a third aspect of the invention, a compound of formula (I) is used as an 
additive for improving the low temperature flow properties of a distillate 
petroleum fuel. 
In a fourth aspect of the invention, a concentrate comprises a compound of 
formula (I) in admixture with a solvent therefore, the solvent being 
compatible with a distillate petroleum fuel. 
The cyclic part of the structure of the compound of the present invention 
may be mono-cyclic or polycyclic aromatic or aliphatic, polynuclear 
aromatic, heteroaromatic, and heteroalicyclic. The ring structure may be 
saturated or unsaturated with one or more unsaturations; with at least one 
ring containing 4 or more atoms, and it may be multicyclic, bridged and 
may be substituted. 
Examples of suitable monocyclic ring structures are benzene, cyclohexane, 
cyclohexene, cyclopentane, pyridine and furan. The ring structure may 
contain additional substituents. Suitable polycyclic compounds, that is 
those having two or more ring structures, can take various forms. They can 
be (a) fused aromatic structures, (b) fused partially hydrogenated 
aromatic ring structures where at least one but not all rings are 
aromatic, (c) alicyclic which includes fused alicyclic, bridged alicyclic, 
spiro alicyclic compounds (d) hydrocarbon ring assemblies of like or 
unlike rings which may be aromatic, alicyclic or mixed; (e) any of (a) to 
(d) which contain at least one hetero atom. 
Fused aromatic structures from which the compounds may be derived include 
for example naphthalene, anthracene, phenathrene, fluorene, pyrene and 
indene. Suitable condensed ring structures where none or not all rings are 
benzene include for example azulene, hydronaphthalene, hydroindene, 
hydrofluorene, diphenylene. Suitable bridged alicyclic structures include 
bicycloheptane and bicycloheptene. 
Suitable ring assemblies include biphenyl and cyclohexyl benzene. 
Suitable heteropolycyclic structures include quinuclidine and indole. 
Suitable heterocyclic compounds from which the compounds of this invention 
may be derived include quinoline; indole, 2,3 dihydroindole, benzofuran, 
coumarin and isocoumarin, benzothiophene, carbazole and thiodiphenylamine. 
Suitable non-aromatic or partially saturated ring systems include decalin 
(decahydronaphthalene), d-pinene, cadinene, bornylene. Suitable bridged 
compounds include norbornene, bicycloheptane (norbornane), bicyclo octane 
and bicyclo octene. 
When the cyclic structure is polycyclic, X and Y are preferably attached to 
adjoining ring atoms located completely within a single ring. For example 
if the structure were naphthalene, these substituents would preferably be 
attached to the 1,2-, 2,3-, 3,4-, 5,6-, 6,7- or 7,8- positions rather than 
to the 1,8- or 4,5- positions. 
It has surprisingly been found that the presence of the group Z in the 
position shown in the cyclic structure in formula (I) leads to a 
significant improvement in the ability of the product, when used as an 
additive in distillate fuels, to control the size of the wax crystals that 
form in the fuel as it cools. The group Z is preferably a nitro group for 
use of compounds of formula (I) as distillate additives. For good 
performance as a fuel additive it is preferred that Z be in the 3- 
position on the ring relative to a cationic nitrogen in X.sup.1 and/or 
Y.sup.1 when one is present. Thus for example a compound of the formula 
(II) 
##STR3## 
has considerably greater activity than a compound of the formula (III) 
##STR4## 
A possible factor in the performance of the additive is believed to be due 
to its solubility in the fuel which can depend upon the substituent 
groups. 
The preferred compounds of the present invention are of the formula (VI): 
##STR5## 
more preferably of the formula (VII) 
##STR6## 
R.sup.1 and R.sup.3 being each preferably C.sub.16/18 alkyl or C.sub.17/18 
alkyl. 
It has been found that by using the novel compounds of the present 
invention as additives for distillate fuels the wax crystals which form as 
the fuel cools can be sufficiently small to pass through the filters of 
typical diesel engines and heating systems rather than forming a cake on 
the filter. 
It has also been found that this reduction of wax crystal size according to 
the invention reduces the tendency of the wax crystals to settle in the 
fuel during storage and can also result in a further improvement in the 
CFPP performance of the fuel. 
The Wax Appearance Temperature (WAT) of the fuel is measured by 
differential scanning calorimetry (DSC). In this test a small sample of 
fuel (25 ) is cooled at 2.degree. C./minute together with a reference 
sample of similar thermal capacity but which will not precipitate wax in 
the temperature range of interest (such as kerosene). An exotherm is 
observed when crystallisation commences in the sample. For example the WAT 
of the fuel may be measured by the extrapolation technique on the Mettler 
TA 2000B. 
The wax content is derived from the DSC trace by integrating the area 
enclosed by the baseline and the exotherm down to the specified 
temperature, the calibration having been previously performed on a known 
amount of crystallizing wax. 
The wax crystal average particle size is measured by analysing a Scanning 
Electron Micrograph of a fuel sample at a magnification of 4000 to 
8000.times. and measuring the longest axis of 50 crystals over a 
predetermined grid. We find that providing the average size is less than 
4000 nanometres the wax will begin to pass through the typical paper 
filters used in diesel engines together with the fuel although we prefer 
that the size be below 3000 nanometres, more preferably below 2000 and 
most preferably below 1000 nanometres, the actual size attainable depends 
upon the original nature of the fuel and the nature and amount of additive 
used but we have found that these sizes and smaller are attainable. 
Fuels containing compounds of formula (I) as additives have outstanding 
benefits when compared with distillate fuels whose cold flow properties 
have been improved by the addition of conventional additives. For example 
the fuels are operable at temperatures approaching the pour point and not 
restricted by the inability to pass the CFPP test. Hence these fuels 
either pass the CFPP test at significantly lower temperatures or obviate 
the need to pass that test. The fuels also have improved coldstart 
performance at low temperatures since they do not rely on recirculation of 
warm fuel to dissolve undesirable wax deposits. The fuels also have a 
reduced tendency for the wax crystals to settle in the fuel during storage 
reducing the tendency for wax to agglomerate at the bottom of storage 
vessels so blocking filters, etc. 
Small crystals may be obtained by adding the compounds of the invention to 
a distillate fuel oil, the amount of the compound added being preferably 
0.0001 to 0.5 wt. %, for example 0.01 to 0.10 wt. %, based on the weight 
of fuel. 
The compounds of the invention may conveniently be dissolved in a suitable 
solvent to form a concentrate of from 20 to 90, e.g. 30 to 80 weight % in 
the solvent. Suitable solvents include kerosene, aromatic naphthas, 
mineral lubricating oils etc. 
When the compounds are used as distillate fuel additives it is preferred 
that R.sup.1, R.sup.2, and R.sup.3 when present contain 10 to 24 carbon 
atoms, for example 14 to 22 preferably 18 to 22 carbon atoms and are 
preferably straight chain or branched at the 1 or 2 position. Suitable 
alkyl groups include decyl, dodecyl, tetradecyl, hexadecyl, octadecyl, 
eicosyl and docosyl (behenyl). Alternatively the groups may be 
polyethylene oxide or polypropylene oxide, the main chain of the groups 
being the longest linear segment. 
The especially preferred compounds defined by formula (I) are the amides or 
amine salts of secondary amines. 
Although three substituents are necessary, as shown in the formulae, it 
should be realised that the compounds can contain one or more further 
substituents attached to ring atoms of the cyclic compounds. 
The compounds of the present invention are preferably prepared from a 
reactant such as that of formula (IV): 
##STR7## 
where X and Y are as defined in respect of formula (I) and additionally 
can together form part of a cyclic anhydride structure wherein an oxy 
group (&gt;O) is common to both X and Y. 
Preferred reactants of formula (IV) are those in which X and Y are selected 
from --C(O)O-- and --SO.sub.3.sup.(--) and particularly preferred 
reactants are compounds of the formula (V): 
##STR8## 
The compounds of the present invention are prepared by reacting both the 
Y-H group and the X-H group of formula (IV) with, for example, amines, 
alcohols, quaternary ammonium salts or mixtures thereof. It has been found 
that the presence of the Z group next to an anhydride ring (as in formula 
(V)) encourages formation of an amide group on the carbon atom adjacent to 
the carbon atom carrying Z thus yielding a product which is predominantly 
the preferred compound although some amounts of the less preferred 
compound, i.e. where the amide group is further from Z, may also be 
obtained. Where the final compounds are the amides or amine salts they are 
preferably of a secondary amine which has a hydrogen and carbon containing 
group containing at least 10 carbon atoms preferably a straight chain 
alkyl group containing from 10 to 30 more preferably 16 to 24 carbon 
atoms. Such amides or salts may be prepared by reacting the acid or 
anhydride with a secondary amine or alternatively by reaction with an 
amine derivative. Removal of water and heating are generally necessary to 
prepare the amides from the acids. Alternatively the Y-H and X-H groups 
may be reacted with an alcohol containing at least 10 carbon atoms or a 
mixture of an alcohol and an amine or sequentially with an amine and an 
alcohol or vice-versa. 
Thus, the final compounds comprise, depending on the identity of X-X.sup.1, 
and Y-Y.sup.1 for example esters, amides, ethers, primary, secondary or 
tertiary amine salts, amino amides and amino ethers. 
Although the compounds of the invention are useful as sole additives, the 
best effect is usually obtained when they are used in combination with 
other additives known for improving the cold flow properties of distillate 
fuels. 
The compounds are preferably used together with what are known as comb 
polymers of the general formula 
##STR9## 
where 
D=R, C(O).OR, OC(O).R, R'C(O).OR or OR 
E=H or CH.sub.3 or D or R' 
G=H, or D 
m=1.0 (homopolymer) to 0.4 (mole ratio) 
J=R' Aryl or Heterocyclic group, R'CO.OR 
K=H, C(O).OR', OC(O).R', OR', C(O)OH 
L=H, R', C(O).OR', OC(O).R', Aryl, C(O)OH 
n=0.0 to 0.6 (mole ratio) 
R is a hydrocarbyl group containing more than 10 carbon atoms, preferably 
from 10 to 30 carbon atoms 
R' is a C.sub.1 to C.sub.30 hydrocarbyl group. 
Another monomer may be terpolymerized if necessary. 
Examples of suitable comb polymers are the fumarate/vinyl acetate 
particularly those described in our European Patent Publications 0153176 
and 0153177 and esterified olefine/maleic anhydride copolymers and the 
polymers and copolymers of alpha olefines and esterified copolymers of 
styrene and maleic anhydride. 
Examples of other additives with which the compounds of the present 
invention may be used are the polyoxyalkylene esters, ethers, ester/ethers 
and mixtures thereof, particularly those containing at least one, 
preferably at least two C.sub.10 to C.sub.30 linear saturated alkyl groups 
and a polyoxyalkylene glycol group of molecular weight 100 to 5,000 
preferably 200 to 5,000, the alkyl group in said polyoxyalkylene glycol 
containing from 1 to 4 carbon atoms. These materials form the subject of 
European Patent Publication 0,061,895 A2. Other such additives are 
described in U.S. Pat. No. 4,491,455. 
The preferred esters, ethers or ester/ethers which may be used may be 
structurally depicted by the formula: 
EQU R--O(A)--O--R" 
where R and R" are the same or different and may be 
##STR10## 
the alkyl group being linear and saturated and containing 10 to 30 carbon 
atoms, and A represents the polyoxyalkylene segment of the glycol in which 
the alkylene group has 1 to 4 carbon atoms, such as polyoxymethylene, 
polyoxyethylene or polyoxytrimethylene moiety which is substantially 
linear; some degree of branching with lower alkyl side chains (such as in 
polyoxypropylene glycol) may be tolerated but it is preferred the glycol 
should be substantially linear, A may also contain nitrogen. 
Suitable glycols generally are the substantially linear polyethylene 
glycols (PEG) and polypropylene glycols (PPG) having a molecular weight of 
about 100 to 5,000, preferably about 200 to 2,000. Esters are preferred 
and fatty acids containing from 10-30 carbon atoms are useful for reacting 
with the glycols to form the ester additives and it is preferred to use a 
C.sub.18 -C.sub.24 fatty acid, especially behenic acids. The esters may 
also be prepared by esterifying polyethoxylated fatty acids or 
polyethoxylated alcohols. 
Polyoxyalkylene diesters, diethers, ether/esters and mixtures thereof are 
suitable as additives with diesters preferred for use in narrow boiling 
distillates whilst minor amounts of monoethers and monoesters may also be 
present and are often formed in the manufacturing process. It is important 
for additive performance that a major amount of the dialkyl compound is 
present. In particular, stearic or behenic diesters of polyethylene 
glycol, polypropylene glycol or polyethylene/polypropylene glycol mixtures 
are preferred. 
The compounds of this invention may also be used with ethylene unsaturated 
ester copolymer flow improvers. The unsaturated monomers which may be 
copolymerised with ethylene include unsaturated mono and diesters of the 
general formula: 
##STR11## 
wherein R.sub.6 is hydrogen or methyl, R.sub.5 is a --OOCR.sub.8 group 
wherein R.sub.8 is hydrogen formate or a C.sub.1 to C.sub.28, more usually 
C.sub.1 to C.sub.17, and preferably a C.sub.1 to C.sub.8, straight or 
branched chain alkyl group; or R.sub.5 is a --COOR.sub.8 group wherein 
R.sub.8 is as previously described but is not hydrogen and R.sub.7 is 
hydrogen or --COOR.sub.8 as previously defined. 
The monomer, when R6 and R.sub.7 are hydrogen and R5 is --OOCR.sub.8, 
includes vinyl alcohol esters of C.sub.1 to C.sub.29, more usually C.sub.1 
to C5, monocarboxylic acid, and preferably C.sub.2 to C.sub.29, more 
usually C.sub.1 to C5 monocarboxylic acid, and preferably C.sub.2 to 
C.sub.5 monocarboxylic acid. Examples of vinyl esters which may be 
copolymerised with ethylene include vinyl acetate, vinyl propionate and 
vinyl butyrate or isobutyrate, vinyl acetate being preferred. We prefer 
that the copolymers contain from 5 to 40 wt. % of the vinyl ester, more 
preferably from 10 to 35 wt. % vinyl ester. They may also be mixtures of 
two copolymers such as those described in U.S. Pat. No. 3,961,916. It is 
preferred that these copolymers have a number average molecular weight as 
measured by vapour phase osmometry of 1,000 to 10,000, preferably 1,000 to 
5,000. 
The compounds of the invention may also be used in distillate fuels in 
combination with other polar compounds, either ionic or non-ionic, which 
have the capability in fuels of acting as wax crystal growth inhibitors. 
We have surprisingly found that the use of the compounds of the present 
invention together with these other polar nitrogen compounds can have a 
synergistic effect. Polar nitrogen containing compounds have been found to 
be especially effective when used in combination with the glycol esters, 
ethers or ester/ethers and such three component mixtures are within the 
scope of the present invention. These polar compounds are generally amine 
salts and/or amides formed by reaction of at least one molar proportion of 
hydrocarbyl substituted amines with a molar proportion of hydrocarbyl acid 
having 1 to 4 carboxylic acid groups or their anhydrides; ester/amides may 
also be used containing 30 to 300, preferably 50 to 150 total carbon 
atoms. These nitrogen compounds are described in U.S. Pat. No. 4,211,534. 
Suitable amines are usually long chain C.sub.12 -C.sub.40 primary, 
secondary, tertiary or quaternary amines or mixtures thereof but shorter 
chain amines may be used provided the resulting nitrogen compound is oil 
soluble and therefore normally containing about 30 to 300 total carbon 
atoms. The nitrogen compound preferably contains at least one straight 
chain C.sub.8 to C40, preferably C.sub.14 to C.sub.24 alkyl segment. 
Suitable amines include primary, secondary, tertiary or quaternary, but 
preferably are secondary. Tertiary and quaternary amines can only form 
amine salts. Examples of amines include tetradecyl amine, cocoamine, 
hydrogenated tallow amine and the like. Examples of secondary amines 
include dioctacedyl amine, methyl-behenyl amine and the like. Amine 
mixtures are also suitable and many amines derived from natural materials 
are mixtures. The preferred amine is a secondary hydrogenated tallow amine 
of the formula HNR.sub.1 R.sub.2 where in R.sub.1 and R.sub.2 are alkyl 
groups derived from hydrogenated tallow fat composed of approximately 4% 
C.sub.14, 31% C.sub.16, 59% C.sub.18. 
Examples of suitable carboxylic acids and their anhydrides for preparing 
these nitrogen compounds include cyclohexane, 1,2 dicarboxylic acid, 
cyclohexene, 1,2- dicarboxylic acid, cyclopentane 1,2 dicarboxylic acid, 
naphthalene dicarboxylic acid and the like. Generally, these acids will 
have about 5-13 carbon atoms in the cyclic moiety. Preferred acids useful 
in the present invention are benzene dicarboxylic acids such as phthalic 
acid, isophthalic acid, and terephthalic acid. Phthalic acid or its 
anhydride is particularly preferred. The particularly preferred compound 
is the amide-amine salt formed by reacting 1 molar portion of phthalic 
anhydride with 2 molar portions of di-hydrogenated tallow amine. Another 
preferred compound is the diamide formed by dehydrating this amide-amine 
salt. 
Hydrocarbon polymers may also be used as part of the additive combination 
which may be represented with the following general formula: 
##STR12## 
where 
T=H or R.sup.1 
U=H, T or Aryl 
v=1.0 to 0.0 (mole ratio) 
w=0.0 to 1.0 (mole ratio) 
where R.sup.1 is alkyl. 
These polymers may be made directly from ethylenically unsaturated monomers 
or indirectly by hydrogenating the polymer made from monomers such as 
isoprene, butadiene etc. 
A particularly preferred hydrocarbon polymer is a copolymer of ethylene and 
propylene having an ethylene content preferably between 20 and 60% (w/w) 
and is commonly made via homogeneous catalysis. 
The compounds may also be used together with compounds similar to those 
described in our European Patent Application 0261959 as having the general 
formula 
##STR13## 
where 
A and B may be the same or different and may be alkyl, alkenyl or aryl; 
L is selected from the group consisting of 
EQU &gt;CH--CH&lt; and &gt;C=C &lt; 
and A, B and L together can constitute part of a cyclic structure which can 
be aromatic, alicyclic or mixed aromatic/alicyclic, and with the proviso 
that the groups --X--X.sup.1 and Y--Y.sup.1 are located on different 
carbon atoms constituting L and in that when A, B and L do not constitute 
part of a cyclic structure one of A or B may be hydrogen and in that when 
L is non-cyclic ethylenic, said X--X.sup.1 and Y--Y.sup.1 groupings are 
present in a cis configuration; 
X is selected from the group consisting of 
SO.sub.3.sup.(--), --C(O)--, --C(O)O.sup.(--), --R.sup.4 --C(O)O--, 
--NR.sup.3 C(O)-- --R.sup.4 O--, --R.sup.4 OC(O)--, --R.sup.4 -- and 
--NC(O)--; 
X.sup.1 is selected from the group consisting of 
N.sup.(+) R.sub.3.sup.3 R.sup.2, HN.sup.(+) R.sub.2.sup.3 R.sup.2, H.sub.2 
N.sup.(+) R.sup.3 R.sup.2, H.sub.3 N.sup.(+) R.sup.2, N.sup.(+) 
R.sub.3.sup.3 R.sup.1, N.sup.+ HR.sub.2.sup.3 R.sup.1, H.sub.2 N.sup.(+) 
R.sub.3.sup.3 R.sup.1, H.sub.3 N.sup.(+) R.sup.1, NR.sup.3 R.sup.2, 
--R.sup.2, --NR.sup.3 R.sup.1, and R.sup.1 ; 
Y is --SO.sub.3.sup.(--) or --SO.sub.2 ; 
when Y is SO.sub.3.sup.(--) Y.sup.1 is selected from the group consisting 
of N.sup.(+) R.sub.3.sup.3 R.sup.2, HN.sup.(+) R.sub.2.sup.3 R.sup.2, 
H.sub.2 N.sup.(+) R.sup.3 R.sup.2 and H.sub.3 N.sup.(+) R.sup.2 
and when Y is --SO.sub.2 --Y.sup.1 is --OR.sup.2, --NR.sup.3 R.sup.2 or 
--R.sup.2 
and wherein R.sup.1 and R.sup.2 are independently selected from the group 
consisting of alkyl, alkoxy alkyl or polyalkoxyalkyl groups containing at 
least 10 carbon atoms in their main chain; 
R.sup.3 is hydrocarbyl and each R.sup.3 may be the same or different; and 
R.sup.4 is --(CH.sub.2).sub.n -- where n is from 0 to 5. 
The invention is illustrated by the following Examples in which reference 
will be made to the accompanying figures wherein 
FIG. 1 is an IR trace of Additive A; 
FIG. 2 is a proton NMR trace of Additive A; 
FIG. 3 is a proton NMR trace of Additive H. 
FIGS. 4-7 are each proton NMR traces of compounds of the present invention. 
The following additives were prepared as described. 
Additives coded A and H are compounds of the invention. 
Additive A 
3-nitro phthalic anhydride (commercially available) was reacted with two 
moles of dihydrogenated tallow amine in a toluene solvent at 50% (w/w) 
concentration. The reaction mixture was stirred at 60.degree. C. for 15 
mins and the solvent removed by evaporation under reduced pressure at 
50.degree. C. to form a half amide/half amino salt whose structure, 
represented by formula (IX) below: 
##STR14## 
where R is C.sub.16/18 alkyl, was confirmed by Infra red and proton NMR 
spectroscopy, the traces being FIGS. 1 and 2 hereof. 
This product was coded Additive A when tested in distillate fuels and was 
tested together with certain of the following other additives in indicated 
hereinafter. 
Additive B 
A 1:1 molar styrene-maleic anhydride copolymer was esterified with 2 moles 
of C.sub.14 H.sub.29 OH per mole of anhydride groups, the alcohol being 
used in a slight excess of approximately 5% alcohol. The esterification 
was catalysed by p-toluene sulphonic acid (1/10 mole) in xylene solvent. 
The product (coded additive B) had a number average molecular weight (Mn) 
of 50,000 and contained 3% (w/w) untreated alcohol. 
Additive C 
Additive C was made in a similar way to Additive B but using 2 moles of a 
1:1 molar mixture of C.sub.12 H.sub.25 OH and C.sub.14 H.sub.29 OH to 
esterify the styrene maleic anhydride copolymer. This too gave a copolymer 
of number average molecular weight of 50,000 and contained 3.3% (w/w) free 
alcohol. 
Additive D 
An ethylene vinyl acetate copolymer having a number average molecular 
weight of 3,500 a vinyl acetate content of 13% and a side chain branching 
of 8 methyls/100 methylenes. 
Additive E 
The reaction product of phthalic anhydride and two moles of dihydrogenated 
tallow amine to form a half amide/half amine salt. 
Additive F 
The reaction product of pyromellitic dianhydride and four moles of 
dihydrogenated tallow amine to form the di(half amide/half amine salt). 
Additive G 
One mole of ortho-sulphobenzoic acid cyclic anhydride was reacted with 2 
moles of di-(hydrogenated) tallow amine in a xylene solvent at 50% (w/w) 
concentration. The reaction mixture was stirred at between 100.degree. C. 
and the refluxing temperature. The solvent and chemicals were kept as dry 
as possible to prevent the anhydride from being hydrolysed. 
The product, coded Additive G, was shown by 500 MHz Nuclear Magnetic 
Resonance Spectroscopy to be the N,N-dialkyl ammonium salt of 
2-dialkylamido benzene sulphonate where the alkyl groups are nC.sub.16-18 
H.sub.33-37, i.e. to have the formula (X) below: 
##STR15## 
Additive H 
Additive H, another compound of the invention, was prepared as follows: 
3-carboxymethyl phthalic anhydride was treated with two moles of 
dihydrogenated tallow amine in a xylene solvent at 50% (w/w) 
concentration. The reaction mixture was stirred at 60.degree. C. to form a 
half amide/half amino salt whose formula, (XI) below 
##STR16## 
where R is C.sub.16/18 alkyl, was confirmed by proton NMR spectroscopy and 
the traces being FIG. 3 hereof. 
Further Compounds 
Further compounds according to this invention and having the formulae XII, 
XIII, XIV and XV were made by methods analogous to those described herein. 
##STR17## 
In each of the formulae, R is C.sub.16/18 alkyl. The structures shown are 
confirmed by the traces of FIG. 4-7 respectively. 
Testing 
The effectiveness of Additive A, and additive systems containing it as 
filterability improvers in distillate fuels were determined by the 
following methods. 
By one method, the response of the oil to the additives was measured by the 
Cold Filter Plugging Point Test (CFPP) which is carried out by the 
procedure described in detail in "Journal of the Institute of Petroleum", 
Volume 52, Number 510, June 1966, pp. 173-285. This test is designed to 
correlate with the cold flow of a middle distillate in automotive diesels. 
In brief, a 40 ml. sample of the oil to be tested is cooled in a bath which 
is maintained at about -34.degree. C. to give non-linear cooling at about 
1.degree. C./min. Periodically (at each one degree C starting from above 
the cloud point), the cooled oil is tested for its ability to flow through 
a fine screen in a prescribed time period using a test device which is a 
pipette to whose lower end is attached an inverted funnel which is 
positioned below the surface of the oil to be tested. Stretched across the 
mouth of the funnel is a 350 mesh screen having an area defined by a 12 
millimeter diameter. The periodic tests are each initiated by applying a 
vacuum to the upper end of the pipette whereby oil is drawn through the 
screen up into the pipette to a mark indicating 20 ml. of oil. After each 
successful passage, the oil is returned immediately to the CFPP tube. The 
test is repeated with each one degree drop in temperature until the oil 
fails to fill the pipette within 60 seconds. This temperature is reported 
as the CFPP temperature. The difference between the CFPP of an additive 
free fuel and of the same fuel containing additive is reported as the CFPP 
depression by the additive. A more effective flow improver gives a greater 
CFPP depression at the same concentration of additive. 
Another determination of flow improver effectiveness is made under 
conditions of the flow improver Programmed Cooling Test (PCT) which is a 
slow cooling test designed to indicate whether the wax in the fuel will 
pass through filters such as are found in heating oil distribution system. 
In the test, the cold flow properties of the described fuels containing the 
additives were determined as follows. 300 ml. of fuel are cooled linearly 
at 1.degree. C./hour to the test temperature and the temperature then held 
constant. Wax which has settled in the bottle is dispersed by gentle 
stirring, then a CFPP filter assembly is inserted. The tap is opened to 
apply a vacuum of 500 mm. of mercury and closed when 200 ml. of fuel have 
passed through the filter into the graduated receiver. A PASS is recorded 
if the 200 ml. are collected within two minutes through a given mesh size 
of a FAIL if the flow rate is too slow indicating that the filter has 
become blocked. CFPP filter assemblies with filter screens of 20, 30, 40, 
60, 80, 100, 120, 150, 200, 250, 350 and 500 mesh number also 25&lt;m, 20&lt;m, 
15&lt;m and 10&lt;m hole size in filter are used, plus a volkswagen tank screen 
mesh (referred to as VW) and an LTFT filter are used to determine the 
finest mesh (largest mesh number) the fuel will pass. The larger the mesh 
number that a wax containing fuel will pass, the smaller are the wax 
crystals and the greater the effectiveness of the additive flow improver. 
It should be noted that no two fuels will give exactly the same test 
results at the same treatment level for the same flow improver additive. 
The order of the filters used, in increasing pore size is as follows: 
10 .mu.m, 15 .mu.m, 20 .mu.m, 25 .mu.m, 500, LTFT, VW, 350, 250, 200, 150, 
120, 100, 80, 60, 40, 30, 20 
where numbers alone indicate mesh numbers.