Additive combinations and fuels containing them

Three component additive combinations for improving the flow of distillate fuel oils comprise PA1 (A) a conventional distillate fuel flow improver PA1 (B) a lube oil pour depressant and PA1 (C) a polar compound other than certain specified nitrogen compounds which acts as an anti-agglomerant for wax particles in the fuel oil.

Two component additive systems for treating distillate fuel oil to limit 
the size of wax crystals that form in the fuel oil in cold weather are 
known, as shown by the following patents. 
U.K. Pat. No. 1,469,016 teaches ethylene polymers or copolymers which are 
pour depressants for distillate fuels, in combination with a second 
polymer having alkyl groups of 6 to 18 carbon atoms, which is a polymer of 
an olefin or unsaturated dicarboxylic acid ester, useful in improving the 
cold flow properties of distillate fuel oils. 
U.S. Pat. No. 3,982,909 teaches nitrogen compounds such as amides, 
diamides, ammonium salts or monoesters of dicarboxylic acids, alone or in 
combination with a hydrocarbon microcrystalline wax and/or a pour point 
depressant, particularly an ethylene backbone polymeric pour point 
depressant, are wax crystal modifiers and cold flow improvers for middle 
distillate fuel oils, particularly diesel fuel. 
U.S. Pat. Nos. 3,444,082 and 3,846,093 teach various amides and salts of 
alkenyl succinic anhydride reacted with amines, in combination with 
ethylene copolymer pour point depressants, for distillate fuels. 
The distillate fuel oil, to which flow improvers may be added, is stored in 
various size tanks at refineries, at marketing depots or at final 
distribution terminals. Due to the large volume of the oil in such tanks, 
the bulk oil temperature drops slowly, even though the ambient temperature 
may be considerably below the cloud point (the temperature at which the 
wax begins to crystallize out and becomes visible, i.e., the oil becomes 
cloudy). 
If the winter is particularly cold and prolonged so that bulk oil is stored 
for a long time during very cold weather, the bulk oil may eventually drop 
below its cloud point. These conditions may then result in crystallized 
wax settling to the bottom of the tank and in addition a bottom layer of 
oil forms which has an enriched wax content and a cloud point considerably 
higher than that of the fuel originally pumped into the tank whilst the 
upper layers of the oil are partially dewaxed and have relatively low 
cloud points. The crystal rich bottom layer of oil will therefore exhibit 
a greater tendency towards wax agglomeration than the upper layers and 
such wax agglomeration frequently leads to the plugging of screens and 
other flow constrictions in oil distribution systems. Since the outlets 
from the tanks are near their bottom, if oil is drawn off which has an 
abnormally high amount of wax in the form of relatively large crystallites 
due to said crystal agglomeration, although the agglomerates may pass 
through the filters on the tank, they may block protective screens or 
filters on the truck or clog filters or small diameter fuel lines in the 
customer's storage system. 
We have found that these problems may be reduced by using a three (or more) 
component additive combination for distillate fuel oils, comprising (A) a 
distillate flow improving composition (B) a lube oil pour depressant and 
(C) a polar oil soluble compound different from (A) and (B) and of formula 
RX, where R is an oil solubilizing hydrocarbon group and X is a polar 
group said compound acting as an anti-agglomerant for wax particles in the 
fuel oil. We have found this combination to be particularly useful in 
distillate fuel oils boiling in the range of 120.degree. C. to 500.degree. 
C., especially 160.degree. C. to 400.degree. C., for controlling the size 
of wax crystals that form at low temperatures. 
In general, a three component additive combination of the invention has 
been found effective in not only keeping the initially formed wax crystals 
small, but also in inhibiting the agglomeration of the wax particles that 
are formed. In addition, the additives slow the settling of the wax 
crystals under gravity. 
In a preferred form, the present invention provides a fuel composition 
which comprises distillate fuel oil and from 0.001 to 0.5 wt. %, 
preferably 0.01 to 0.2 wt%, most preferably 0.05 to 0.1 wt. % of a flow 
and filterability improving, multicomponent additive composition 
comprising: (A) one part by weight of a distillate flow improver 
composition (B) 0.1 to 10, preferably 0.5 to 5 most preferably 1 to 2 
parts by weight of a lube oil pour depressant (C) 0.1 to 10, preferably 
0.5 to 5 most preferably 1 to 2, parts by weight of a polar oil soluble 
compound of formula RX as hereinbefore defined which acts as an 
anti-agglomerant for the wax particles. 
For case of handling the additives will generally be supplied as 
concentrates containing 30 to 80 wt. %, a hydrocarbon diluent with 70 to 
20 wt. % of the additive mixture of (A), (B) and (C), dissolved therein. 
The present invention is also concerned with such concentrates. 
The distillate flow improver (A) used in the additive combinations in the 
present invention is a wax crystal growth arrestor and may also contain a 
nucleator for the wax crystals. They are preferably ethylene polymers of 
the type known in the art as wax crystal modifiers, e.g. pour depressants 
and cold flow improvers for distillate fuel oils. These polymers will have 
a polymethylene backbone which is divided into segments by hydrocarbon or 
oxy-hydrocarbon side chains, by alicyclic or heterocyclic structures or by 
chlorine atoms. They may be homopolymers of ethylene as prepared by free 
radical polymerization so as to result in some branching. More usually, 
they will comprise copolymers of above 3 to 40, preferably 4 to 20, molar 
proportions of ethylene per molar proportion of a second ethylenically 
unsaturated monomer which can be a single monomer or a mixture of monomers 
in any proportion. The polymers will generally have a number average 
molecular weight in the range of about 500 to 50,000 preferably about 800 
to about 20,000, e.g., 1000 to 6000, as measured by Vapor Pressure 
Osmometry (VPO), for example by using a Mechrolab Vapor Pressure Osmometer 
Model 302B. 
The unsaturated monomers, copolymerizable with ethylene, include 
unsaturated mono and diesters of the general formula: 
##STR1## 
wherein R.sub.1 is hydrogen or methyl; R.sub.2 is a --OOCR.sub.4 group 
wherein R.sub.4 is hydrogen or a C.sub.1 to C.sub.28, more usually C.sub.1 
to C.sub.16, and preferably a C.sub.1 to C.sub.8, straight or branched 
chain alkyl group; or R.sub.2 is a --COOR.sub.4 group wherein R.sub.4 is 
as previously described and R.sub.3 is hydrogen or --COOR.sub.4 as 
previously defined. The monomer, when R.sub.1 and R.sub.3 are hydrogen and 
R.sub.2 is --OOCR.sub.4, includes vinyl alcohol esters of C.sub.1 to 
C.sub.29, more usually C.sub.1 to C.sub.17, monocarboxylic acid, and 
preferably C.sub.2 to C.sub.5 monocarboxylic acid. Examples of such esters 
include vinyl acetate, vinyl isobutyrate, vinyl laurate, vinyl myristate 
and vinyl palmitate, vinyl acetate being the preferred ester. When R.sub.2 
is --COOR.sub.4 and R.sub.3 is hydrogen, such esters include methyl 
acrylate, isobutyl acrylate, methyl methacrylate, lauryl acrylate, 
C.sub.13 Oxo alcohol esters of methacrylic acid, etc. Examples of monomers 
where R.sub.1 is hydrogen and either or both R.sub.2 and R.sub.3 are 
--COOR.sub.4 groups, include mono and diesters of unsaturated dicarboxylic 
acids such as: mono C.sub.13 Oxo fumarate, di-C.sub.13 Oxo fumarate, 
di-isopropyl maleate, di-lauryl fumarate and ethyl methyl fumarate. 
Another class of monomers that can be copolymerized with ethylene include 
C.sub.3 to C.sub.16 alpha monoolefins, which can be either branched or 
unbranched, such as propylene, isobutene, n-octene-1, isooctene-1, 
n-decene-1, dodecene-1, etc. 
Still other monomers include vinyl chloride, although essentially the same 
result can be obtained by chlorinating polyethylene, e.g., to a chlorine 
content of about 10 to 35 wt. %. 
Also included among the distillate flow improvers are the hydrogenated 
polybutadiene flow improvers, having mainly 1,4 addition with some 1,2 
addition such as those of U.S. Pat. No. 3,600,311. 
The preferred ethylene copolymers are ethylene vinyl ester especially vinyl 
acetate copolymers. These may be prepared by high pressure, non solvent 
processes or by our preferred prosess in which solvent, and 5-50 wt. % of 
the total amount of monomer charge other than ethylene are charged to a 
stainless steel pressure vessel which is equipped with a stirrer and a 
heat exchanger. The temperature of the pressure vessel is then brought to 
the desired reaction temperature, e.g., 70.degree. to 200.degree. C. by 
passing steam through the heat exchanger and pressurised to the desired 
pressure with ethylene, e.g., 700 to 25,000 psig, usually 900 to 7,000 
psig. The initiator, usually as a concentrate in a solvent (usually the 
same solvent as used in the reaction) so that it can be pumped, and 
additional amounts of the monomer charge other than ethylene, e.g. the 
vinyl ester, can be added to the vessel continuously, or at least 
periodically, during the reaction time. Also during this reaction time, as 
ethylene is consumed in the polymerization reaction, additional ethylene 
is supplied through a pressure controlling regulator so as to maintain the 
desired reaction pressure fairly constant at all times, the reactor 
temperature is held substantially constant by means of the heat exchanger. 
Following the completion of the reaction, usually a total reaction time of 
1/4 to 10 hours will suffice, the liquid phase is discharged from the 
reactor and solvent and other volatile constituents of the reaction 
mixture are stripped off leaving the copolymer as residue. To facilitate 
handling and blending, the polymer is generally dissolved in a mineral 
oil, preferably an aromatic solvent, such as heavy aromatic naphtha, to 
form a concentrate usually containing 10 to 60 wt. % of copolymer. 
Usually about 50 to 1200, preferably 100 to 600 parts by weight solvent 
based upon 100 parts by weight of copolymer to be produced will be used. A 
hydrocarbon solvent such as benzene, hexane, cyclohexane, t-butyl alcohol, 
etc., and about 0.1 to 5 parts by weight of initiator will generally be 
used. 
The initiator is chosen from a class of compounds which at elevated 
temperatures undergo a breakdown yielding radicals, such as peroxide or 
azo type initiators, including the acyl peroxides of C.sub.2 to C.sub.18 
branched or unbranched carboxylic acids, as well as other common 
initiators. Specific examples of such initiators include dibenzoyl 
peroxide, ditertiary butyl peroxide, t-butyl perbenzoate, t-butyl 
peroctanoate, t-butyl hydroperoxide, alpha, alpha', 
azo-diisobutyronitrile, dilauroyl peroxide, etc. The choice of the 
peroxide is governed primarily by the polymerisation conditions to be 
used, the desired polymer structure and the efficiency of the initiator. 
t-butyl peroctanoate, di-lauroyl peroxide and di-t-butyl peroxide are 
preferred initiators. 
Mixtures of ethylene copolymers can also be used. Thus, U.S. Pat. No. 
3,961,916 teaches that improved results can be obtained using an ethylene 
copolymer mixture containing components with different solubilities one of 
which serves primarily as a nucleator to seed the growth of wax crystals, 
while the other more soluble ethylene component serves as a wax crystal 
growth arrestor to inhibit the growth of the wax crystals after they are 
formed. Such a combination of nucleator and wax growth arrestor is the 
preferred distillate flow improver of the compositions of the present 
invention. 
The lube oil pour point depressant is preferably an oil soluble ester 
and/or higher olefin polymer and will generally have a number average 
molecular weight in the range of about 1000 to 200,000, e.g. 1,000 to 
100,000, preferably 1000 to 50,000, as measured, for example, by Vapor 
Pressure Osmometry such as by a Mechrolab Vapor Pressure Osmometer, or by 
Gel Permeation Chromatography. These second polymers include (a) polymers, 
both homopolymers and copolymers of unsaturated alkyl ester, including 
copolymers with other unsaturated monomers, e.g. olefins other than 
ethylene, nitrogen containing monomers, etc. and (b) homopolymers and 
copolymers of olefins, other than ethylene. 
In our preferred lube oil pour depressant at least 10 wt. %, preferably at 
least 25 wt. % and frequently 50 wt. % or more of the polymer will be in 
the form of straight chain C.sub.6 to C.sub.30, e.g., C.sub.8 to C.sub.24, 
e.g., C.sub.8 to C.sub.16 alkyl groups, usually of an alpha olefine or an 
ester, for example, the alkyl portion of an alcohol used to esterify a 
mono or dicarboxylic acid, or anhydride. To illustrate, using a C.sub.16 
straight chain alkyl acrylate as the source of the aforesaid straight 
chain alkyl group, one could have a homopolymer or a copolymer of said 
n-hexadecyl acrylate with a short chain monomer, e.g. a copolymer of 
n-hexadecyl acrylate with methyl acrylate. Or one could have n-hexadecyl 
acrylate copolymerized with docosanyl acrylate. Or, one could have a 
terpolymer of methyl acrylate, n-hexadecyl acrylate, and c.sub.30 branched 
chain alkyl acrylate, alternatively the n-hexadecyl acrylate could be 
copolymerised with an unsaturated ester other than one derived from 
acrylic acid such an ester having its unsaturation in either the acid or 
the alcohol part. 
Among the esters which can be used to make these lube oil pour depressants, 
including homopolymers and copolymers of two or more monomers, are 
ethylenically unsaturated, mono- and diesters represented by the formula: 
##STR2## 
wherein R.sub.1 is hydrogen or C.sub.1 to C.sub.6 hydrocarbyl, preferably 
alkyl, group, e.g. methyl; R.sub.2 is a --OOCR.sub.4 or --COOR.sub.4 group 
wherein R.sub.4 is hydrogen or a C.sub.1 to C.sub.30, e.g. C.sub.1 to 
C.sub.24 straight or branched chain hydrocarbyl, e.g. alkyl group; and 
R.sub.3 is hydrogen or --COOR.sub.4, at least one of R.sub.1, R.sub.2, 
R.sub.3 and R.sub.4 containing a straight chain C.sub.6 to C.sub.30, 
preferably a C.sub.8 -C.sub.24, most preferably a C.sub.8 -C.sub.16 alkyl 
group. The monomer, when R.sub.1 and R.sub.3 are hydrogens and R.sub.2 is 
--OOCR.sub.4 includes vinyl alcohol esters of monocarboxylic acids. 
Examples of such esters include vinyl laurate, vinyl myristate, vinyl 
palmitate, vinyl behenate, vinyl tricosanoate, etc. Examples of esters in 
which R.sub.2 is --COOR.sub.4, include lauryl acrylate, C.sub.13 Oxo 
alcohol esters of methacrylic acid, behenyl acrylate, behenyl 
methacrylate, tricosanyl acrylate, etc. Examples of monomers where R.sub.1 
is hydrogen and R.sub.2 and R.sub.3 are both --COOR.sub.4 groups, include: 
mono and diesters of unsaturated dicarboxylic acids such as mono C.sub.13 
Oxo fumarate, di C.sub.13 Oxo maleate, dieicosyl fumarate, laurylhexyl 
fumarate, didocosyl fumarate, dieicosyl maleate, didocosyl citraconate, 
monodocosyl maleate, dieicosyl citraconate, (di(tricosyl) fumarate, 
dipentacosyl citraconate. Short chain alkyl esters such as vinyl acetate, 
vinyl propionate, methyl acrylate, methyl methacrylate, isobutyl acrylate, 
mono-isopropyl maleate and isopropyl fumarate may be used in copolymers 
with the longer chain alkyl esters. 
In addition, minor molar amounts, e.g. 0 to 20 mole %, e.g. 0.1 to 10 mole 
%, nitrogen-containing monomers can be copolymerized into the polymer, 
along with the foregoing monomers. These nitrogen containing monomers 
include those represented by the formula: 
EQU R--CH.dbd.C--H.sub.2 
R is a 5- or 6-membered heterocyclic nitrogen-containing ring which may 
contain one or more substituent hydrocarbon groups in addition to the 
vinyl group. In the above formula, the vinyl radical can be attached to 
the nitrogen or to a carbon atom in the radical R. Examples of such vinyl 
derivatives include 2-vinylpyridine, 4-vinylpyridine, 
2-methyl-2-vinylpyridine, 2-ethyl-5-vinylpyridine, 
4-methyl-5-vinylpyridine, N-vinylpyrrolidone and 4-vinyl-pyrrolidone. 
Other monomers that can be included are the unsaturated amides such as 
those of the formula: 
##STR3## 
wherein R.sub.1 is hydrogen or methyl, and R.sub.2 is hydrogen, an alkyl 
or alkoxy radical, generally having up to about 24 carbon atoms. Such 
amides are obtained by reacting acrylic acid or a low molecular weight 
acrylic ester with an amine such as butylamine, hexylamine, tetrapropylene 
amine, cetylamine, ethanolamine and tertiaryalkyl primary amines. 
As an alternative embodiment of this invention some of the lube oil pour 
depressant may contain polar functions which have an anti-agglomerating 
effect on the wax and thus be component C of the additive combination of 
this invention. Preferred examples are compounds containing esters of the 
type described above in which R.sub.4 is an alkoxy amine. 
Preferred ester polymers for the present purpose, from the point of view of 
availability and cost, are copolymers of vinyl acetate and a dialkyl 
fumarate in about equimolar proportions, and polymers or copolymers of 
acrylic esters or methacrylic esters. The alcohols used to prepare the 
fumarate and said acrylic and methacrylic ester are usually monohydric, 
saturated, straight chain primary aliphatic alcohols containing from 4 to 
30 carbon atoms. These esters need not be pure, but may be prepared from 
technical grade mixtures. 
Any mixtures of two or more polymers of the esters set forth herein can be 
used. These may be simple mixtures of such polymer, or they may be 
copolymers which can be prepared by polymerizing a mixture of two or more 
of the monomeric esters. Mixed esters derived by the reaction of single or 
mixed acids with a mixture of alcohols may also be used. 
The ester polymers are generally prepared by polymerizing a solution of the 
ester in a hydrocarbon solvent such as heptane, benzene, cyclohexane, or 
white oil, at a temperature from 60.degree. C. to 250.degree. C. under a 
blanket of refluxing solvent or an inert gas such as nitrogen or carbon 
dioxide to exclude oxygen. The polymerisation is preferably promoted with 
a peroxide or azo free radical initiator, benzoyl peroxide being 
preferred. 
The unsaturated carboxylic acid ester can be copolymerized with an olefin. 
If a dicarboxylic acid anhydride is used, e.g. maleic anhydride, it can be 
polymerized with the olefin, and then esterified with alcohol. To further 
illustrate, the ethylenically unsaturated carboxylic acid or derivative 
thereof is reacted with an alphaolefin, such as C.sub.8 -C.sub.32, 
preferably a C.sub.10 -C.sub.26, most preferably a C.sub.10 -C.sub.18 
olefin, by mixing the olefin and acid, e.g., maleic anhydride, usually in 
about equimolar amounts, and heating to a temperature of at least 
80.degree. C., preferably at least 125.degree. C., in the presence of a 
free radical polymerization promoter such as benzoyl peroxide or t-butyl 
hydroperoxide or di-t-butyl peroxide. Other examples of copolymers are 
those of maleic anhydride with styrene, or cracked wax olefins, which 
copolymers are then usually completely esterified with alcohol, as are the 
other aforesaid specific examples of the olefin ester polymers. 
Alternatively the lube oil pour depressant used in the compositions of our 
invention may be olefin polymers, which can be either homopolymers and 
copolymers of long chain C.sub.8 to C.sub.32, preferably C.sub.10 to 
C.sub.26, most preferably C.sub.10 -C.sub.18 aliphatic alpha-monoolefins, 
or copolymers of said long chain alpha-monoolefins with shorter C.sub.3 
-C.sub.7 aliphatic alpha-olefins, or with styrene or its derivatives, 
e.g., copolymers comprising 20 to 90 wt. % of said C.sub.8 to C.sub.32 
alpha-olefin and 80 to 10 wt. % of said C.sub.3 to C.sub.7 aliphatic 
monoolefin or styrene-type olefin. 
These olefin polymers may be conveniently prepared by polymerizing the 
monomers under relatively mild conditions of temperature and pressure in 
the presence of a Friedel-Crafts type catalyst, e.g. AlCl.sub.3, which 
will give an irregular polymer, or Ziegler-Natta type of an 
organo-metallic catalyst, i.e., a mixture of a compound derived from a 
Group IV, V or VI metal of the Periodic Table in combination with an 
organometallic compound of a Group I, II or III metal of the Periodic 
Table, wherein the amount of the compound derived from a Group IV-VI metal 
may range from 0.01 to 2.0 moles per mole of the organo-metallic compound. 
Examples of the Ziegler-Natta type catalysts include the following 
combinations: aluminum triisobutyl, aluminum chloride, and vanadium 
trichloride; vanadium tetrachloride and aluminum trihexyl; vanadium 
trichloride and aluminum trihexyl; vanadium triacetyl-acetonate and 
aluminum diethyl chloride; titanium tetrachloride and aluminum trihexyl; 
vanadium trichloride and aluminum trihexyl; titanium trichloride and 
aluminium trihexyl; titanium dichloride and aluminum trihexyl, etc. 
The polymerization is usually carried out by mixing the catalyst components 
in an inert diluent such as a hydrocarbon solvent, e.g, hexane, benzene, 
toluene, xylene, heptane, etc., and then adding the monomers into the 
catalyst mixture at atmospheric or superatmospheric pressures and 
temperatures within the range between about 50.degree. and 180.degree. F. 
Usually atmospheric pressure is employed when polymerizing monomers 
containing more than 4 carbon atoms in the molecule and elevated pressures 
are used if the more volatile C.sub.3 or C.sub.4 alpha-olefins are 
present. The time of reaction will depend upon, and is interrelated to, 
the temperature of the reaction, the choice of catalyst, and the pressure 
employed. In general, however, 1/2 to 5 hours will complete the reaction. 
The polar compound, which is component (C), is different from the 
distillate flow improver and the lube oil pour depressant, and is 
generally monomeric and may be ionic or non-ionic. The compound which 
inhibits agglomeration of wax particles in the oil should not be an oil 
soluble nitrogen compound containing about 30 to 300 carbon atoms and 
having at least one straight chain alkyl segment of 8 to 40 carbons and 
selected from the class consisting of amine salts and/or amides of 
hydrocarbyl carboxylic acids or anhydrides having 1 to 4 carboxyl groups. 
Examples of suitable ionic compounds are those in which the anion is the 
oil soluble group 
EQU R.sub.5 Y 
Where Y is the polar end group and R.sub.5 is an oil solubilising group 
which may be one or more substituted or unsubstituted, unsaturated or 
saturated hydrocarbon groups which may be aliphatic, cycloaliphatic or 
aromatic, R.sub.5 is preferably alkyl, alkaryl or alkenyl. R.sub.5 should 
preferably contain a total of from 8 to 150 carbon atoms. Where the 
compound is non-ionic we prefer that R.sub.5 contain from 8 to 30, more 
preferably 12 to 24, most preferably 12 to 18 carbon atoms. Where the 
compound is ionic we prefer that it contains from 8 to 150 carbon atoms, 
preferably 50 to 120 carbon atoms most preferably 70 to 100 carbon atoms 
and we particularly prefer that these be derived from alkyl groups 
containing from 1 to 30, preferably 12 to 30 carbon atoms. It is preferred 
that when R.sub.5 is composed of alkyl groups that they be straight chain. 
Alternatively R.sub.5 may be an alkoxylated chain. 
Examples of suitable polar end groups Y include the sulphonate 
SO.sup.-.sub.3 group, the sulphate OSO.sup.-.sub.3 group, the phosphate, 
PO.sup.-.sub.2 group, the phenate PhO.sup.- group and the borate BO.sup.- 
group. Thus our preferred anions include R.sub.5 SO.sup.-.sub.3, R.sub.5 
OSO.sup.-.sub.3 ; (R.sub.5 O).sub.2 PO.sup.-.sub.2 ; R.sub.5 PHO-- and 
(R.sub.5 O).sub.2 BO with R.sub.5 being the oil solubilizing hydrocarbon 
group. 
Where the anion is a sulphonate, we prefer to use an alkaryl sulphonate 
which may be any of the well known neutral or basic sulphonates. 
Where the anion is phenate, we prefer it be derived from alkyl phenol, or 
bridged phenols, including those of the general formula 
##STR4## 
where M is a linking group of one or more, e.g. 1 to 4, carbon or sulphur 
atoms, and R.sub.5 is as defined above. Here again, the phenate used may 
be any of the well known neutral or basic compounds. 
When the anion is borate, sulphate or phosphate, R.sub.5 may altenatively 
be alkoxylated chains. Examples of such compounds in the case of sulphates 
include the (R.sub.6 --(OCH.sub.2 CH.sub.2)--O).sup.- group and in the 
case of phosphates and borates the (R.sub.6 --(OCH.sub.2 CH.sub.2).sub.n 
--O).sup.-.sub.2 group, wherein R.sub.6 is as defined above. 
The cation for these salts is preferably a mono-, di-, tri or tetra alkyl 
ammonium or phosphonium ion of formula 
EQU R.sub.7 ZH.sup.+.sub.3 ; (R.sub.7).sub.2 ZH.sup.+.sub.2 ; (R.sub.7).sub.3 
ZH.sup.+ ; (R.sub.7).sub.4 Z.sup.+ 
where R.sub.7 is hydrocarbyl, preferably alkyl. When the cation contains 
more than one such group they may be the same or different, and Z is 
nitrogen or phosphorus. R.sub.7 preferably has a carbon content within the 
definition given above for R.sub.5. 
Examples of suitable alkyl groups include methyl, ethyl, propyl, n-octyl, 
n-dodecyl, n-tridecyl, C.sub.13 Oxo, coco, tallow behenyl, lauryl, 
dodecyl-octyl, coco-methyl, tallow-methyl, methyl-n-octyl, 
methyl-n-dodecyl, methyl-behenyl, tallow. 
The group R.sub.7 may be substituted by, for example, hydroxy or amino 
groups (as for example in the polyamine). As an alternative embodiment the 
hydrocarbyl group of the cation can provide the oil-solubility, as for 
example in the salts of fatty amines such as tallow amine. 
Alkyl substituted dicarboxylic acids or their anhydrides or the derivatives 
thereof may also be used as the polar compound. For example, succinic acid 
derivatives of the general formula 
##STR5## 
where at least one of R.sub.8 or R.sub.9 is a long chain (e.g. 30 to 150) 
carbon atoms alkyl group preferably polyisobutylene or polypropylene. The 
other of R.sub.8 or R.sub.9 may be similar or be hydrogen. P and O may be 
the same or different, they may be carboxylic acid groups, esters or may 
together form an anhydride ring. 
As a less preferred alternative the cation may be metallic and if so the 
metal is preferably an alkali metal such as sodium or potassium or an 
alkaline earth metal such as barium, calcium or magnesium. 
Whilst the ionic type compounds described above are our preferred polar oil 
soluble compounds we have found that polar, non-ionic compounds are also 
effective. For example primary amines of formula R.sub.10 NH.sub.2, 
secondary amines R.sub.10 NH.sub.2 and primary alcohols R.sub.10 -OH may 
be used providing they are oil soluble and for this reason R.sub.10 
preferably contain at least 8 carbon atoms and preferably has the carbon 
content specified above for R.sub.5 in the case of non-ionic compounds. 
We have found that although these polar compounds have little effect on wax 
formation or crystal growth, when they are the sole additive in a fuel 
they significantly reduce the extent to which already formed wax crystals 
agglomerate. A less important effect of these compounds is that many of 
them reduce the rate at which wax settles from fuels containing nucleating 
and/or growth arresting additives. We find that the presence of these 
polar compounds is effective in common fuel storage conditions, even when 
fuel is stored for an extended period at low temperatures and when its 
temperature is reduced very slowly (i.e. around 0.3.degree. C./hour. 
The distillate fuel oils in which the additive combinations of the present 
invention are especially useful generally boil within the range of 
120.degree. C. to 500.degree. C., e.g. 150.degree. to 400.degree. C. The 
fuel oil can comprise atmospheric distillate or vacuum distillate, or 
cracked gas oil or a blend in any proportion of straight run and thermally 
and/or catalytically cracked distillates. The most common petroleum 
distillate fuels are kerosene, jet fuels, diesel fuels and heating oils. 
The heating oil may be either a straight run distillate or a cracked gas 
oil or a combination of the two. The low temperature flow problem 
alleviated by using the additive combinations of the present invention is 
most usually encountered with diesel fuels and with heating oils. 
There has been a tendency recently to increase the final boiling point 
(FBP) of distillates so as to maximise the yield of fuels. These fuels 
however include longer chain paraffins in the fuel and therefore generally 
have higher cloud points. This in turn aggravates the difficulties 
encountered in handling these fuels in cold weather and increases the need 
to include flow improving additives. 
In measuring the boiling characteristics of these high end point fuels, 
ASTM-1160 distillation (a distillation under vacuum) can be used and the 
resulting boiling points are then corrected to boiling points at 
atmospheric pressure. Alternatively, ASTM Method D-86, which is an 
atmospheric distillation can be used, but usually some thermal cracking 
will occur so that the results of the D-86 distillation are less accurate. 
Oil soluble, as used herein, means that the additive is soluble in the fuel 
at ambient temperatures, e.g. at least to the extent of 0.1 wt.% additive 
in the fuel oil at 25.degree. C., although at least some of the additive 
comes out of solution near the cloud point in order to modify the wax 
crystals that form. 
The invention is illustrated but in no way limited by reference to the 
following Examples. 
In these Examples, the distillate flow improver A used was a concentrate in 
an aromatic diluent of about 50 wt.% of a mixture of two ethylene-vinyl 
acetate copolymers, having different oil solubilities, so that one 
functions primarily as a wax growth arrestor and the other as a nucleator, 
in accord with the teachings of U.S. Pat. No. 3,961,916. More 
specifically, the polymer is a polymer mixture of about 75 wt.% of wax 
growth arrestor and about 25 wt.% of nucleator. The wax growth arrestor 
consists of ethylene and about 38 wt.% vinyl acetate, and has a molecular 
weight of about 1800 (VPO). It is identified in said U.S. Pat. No. 
3,961,916 as Copolymer B of Example 1 (column 8, lines 25-35). The 
nucleator consists of ethylene and about 16 wt.% vinyl acetate and has a 
molecular weight of about 3000 (VPO). It is identified in said U.S. Pat. 
No. 3,961,916 as Copolymer H (See Table I, columns 7-8). 
The lube oil pour depressant B was an oil concentrate of about 50 wt.% of 
mineral lubricating oil and about 50 wt.% of a copolymer of dialkyl 
fumarate and vinyl acetate in about equimolar proportions, having a number 
average molecular weight (VPO) of about 15,000 prepared in conventional 
manner using a peroxide initiator and solvent. The fumarate was prepared 
by esterifying fumaric acid with a mixture of straight chain alcohols 
averaging about C.sub.12. A typical analysis of the alcohol mixture is as 
follows: 0.7 wt.% C.sub.6, 10 wt.% C.sub.8, 7 wt.% C.sub.10, 47 wt.% 
C.sub.12, 17 wt.% C.sub.14, 8 wt.% C.sub.16, 10 wt.% C.sub.18. 
The fuels in which the Additives were tested are described in the following 
table: 
______________________________________ 
Fuel 1 2 3 4 
______________________________________ 
Cloud Point, .degree.C. 
+2.0 +3.0 +2.0 0.0 
(as measured by ASTM D-3117) 
Wax Appearance Point, .degree.C. 
-2.5 -4.4 -2.0 -3.3 
(See ASTM D-3117) 
Distillation, .degree.C. 
(ASTM-D-1160) 
Initial Boiling Point .degree.C. 
184 185 162 179 
20% Boiling Point 249 230 203 224 
90% Boiling Point 351 345 337 340 
Final Boiling Point 
383 376 340 377 
______________________________________ 
The following Polar compounds (C) were used in the examples: 
##STR6## 
##STR7## 
##STR8## 
##STR9## 
5. CH.sub.3 (CH.sub.2).sub.15-17 NH.sub.2 
6. (CH.sub.3 (CH.sub.2).sub.15- 17).sub.2 NH 
7. C.sub.18 H.sub.37 OH 
8. C.sub.14 H.sub.29 OH 
In each instance the hydrocarbyl groups were straight chain. 
The polymeric additives A and B were added in the form of the aforesaid oil 
concentrates while the polar compound was added to the oil directly. 
The initial response of the oils to the additives was measured by the Cold 
Filter Plugging Point Test (CFPPT) which is carried out by the procedure 
described in detail in "Journal of the Institute of Petroleum", Volume 52, 
Number 510, June 1966 pp. 173-185. In brief, a 40 ml. sample of the oil to 
be tested is cooled in a bath to about -34.degree. C. Periodically (at 
each one degree Centigrade drop in temperature starting from at least 
2.degree. C. 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 of about 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. The test is repeated with each one degree drop in temperature 
until the oil fails to fill the pipette within 60 seconds. The results of 
the test are reported as the temperature (the plugging point) in 
.degree.C. at which the oils fail to fill the pipette in 1 minute. 
The behaviour of the oils at sustained low temperatures was assessed by 
subjecting the oils to a cold soak test in which separate 500 ml samples 
of each test blend in an addition glass funnel were first cooled at 
1.degree. C. and 0.3.degree. C. per hour from room temperature of about 
20.degree. C. to -8.degree. C. The test blend was thereafter held at 
-8.degree. C. for the indicated period. A 50 ml portion of this cooled 
test fuel blend was drawn off from the bottom of the funnel and 
transferred to another container and subjected to a modified Cold Filter 
Plugging Point Test (CFPPT). In this test a sample at the cold soak 
temperature is sucked by 200 mm water vacuum pressure through a filter 
screen and the minimum mesh through which it would pass measured. The 
portion was then allowed to return to room temperature (about 20.degree. 
C.) after which it was subjected to the ASTM cloud point determination.

EXAMPLE 1 
Visual wax settling of Fuel 1 treated with the ethylene backbone copolymer, 
the lube oil pour depressant and certain of the polar compounds (2) was 
observed and the following table shows the advantage of the three 
component mixtures in inhibiting wax settling. 
______________________________________ 
Additive Waxy Layer (Vol %) 
concentration (ppm) 
25 hrs soak 
37 hrs soak 
61 hrs soak 
A B C (No.) at -8.degree. C. 
at -8.degree. C. 
at -8.degree. C. 
______________________________________ 
100 -- -- 15 15 14 
300 -- -- 15 15 13 
500 -- -- 15 13 12 
100 100 50 of (1) 
88 86 77 
100 100 50 of (2) 
87 86 79 
100 100 50 of (3) 
89 86 79 
100 100 50 of (4) 
89 88 85 
100 100 50 of (5) 
89 87 83 
100 100 50 of (6) 
91 89 87 
100 100 50 of (7) 
88 89 86 
______________________________________ 
EXAMPLE 2 
Wax settling is quantitatively determined by the wax enrichment of the 
bottom layers of the cold soaked fuel. The greater the correlation of the 
wax appearance points (WAP) of the top and bottom 10% with the WAP of the 
original fuel the less wax settling has occurred. The following table 
shows the reduced wax settling when the three-component mixture is used in 
Fuel 2. 
______________________________________ 
Additive conc. (ppm) 
Wax Appearance Point .degree.C. 
A B C No (3) Top 10% Bottom 10% 
______________________________________ 
-- -- -- - 4.4 -4.4 
300 -- -- -11.0 +5.5 
400 -- -- -11.5 +5.0 
600 -- -- -12.0 +4.0 
200 200 100 - 4.5 -4.4 
______________________________________ 
In this test the fuel is cooled at 0.3.degree. C./hr down to -8.degree. C. 
and held at this temperature for 70 hours. 
EXAMPLE 3 
The polar compounds (C) were tested on their own in Fuel 3 using the 
standard CFPP test. The results show that these compounds do not possess, 
on their own, any significant wax crystal modifying properties. The 
results for the tests using the conventional flow improver (A) are added 
for comparison. 
______________________________________ 
Additive Concentration (ppm) 
CFPP (.degree.C.) 
______________________________________ 
None -- -2 
C1 100 -3 
C1 300 -3 
C2 100 -4 
C2 300 -3 
C3 100 -3 
C3 300 -3 
A 100 -11 
A 300 -15 
______________________________________ 
EXAMPLE 4 
Samples of Fuel 4 treated with certain quantities of the distillate flow 
improver (A), the lube oil pour depressant (B), and the polar compound (C) 
were cooled down to 5 degrees below its wax appearance point at 
0.3.degree. C./hr and held at this temperature for 35 hours. The following 
table shows the advantage of the three-component mixture over the 
conventional flow improver (A) in preventing wax settling and giving 
improved filterability as shown the modified CFPP test. 
______________________________________ 
Waxy WAP of Minimum 
Additive conc. (ppm) 
Layer Bottom Mesh 
A B C (No.) (Vol %) 10% (.degree.C.) 
Passed 
______________________________________ 
-- -- -- -- -3.0 
100 -- -- 10 -10.0 100 
200 -- -- 10 -- 100 
400 -- -- 10 -- 150 
100 200 100 (3) 100.sup.1 
-4.0 250 
100 200 100 (8) 100.sup.1 
-4.0 150 
100 200 100 (5) 100.sup.1 
-4.5 250 
100 200 100 (6) 100.sup.1 
-4.0 250 
______________________________________ 
.sup.1 Three component mixtures produced a totally cloudy sample with a 
small denser waxy layer at the bottom whereas the fuel treated with A 
above had a clean supernatent above the settled wax showing less wax 
settling using the three component mixture. 
EXAMPLE 5 
Fuel 2 was treated with A alone and with the mixture of A, B and C. The 
table shows the advantage of the 3-component mixture over the conventional 
flow improver (A) in reducing wax settling and improving filterability. 
The fuel was cooled down to -8.degree. C. (4.degree. C. below its normal 
Wax Appearance Point of -4.degree. C.) and held at this temperature for 20 
hrs. The filterability was tested by the modified CFPP test at -8.degree. 
C. 
______________________________________ 
Waxy Wax Appearance 
Minimum 
Additive conc. (ppm) 
Layer Point of bottom 
Mesh 
A B C (No.) (Vol %) 
10% (.degree.C.) 
Passed 
______________________________________ 
-- -- -- -4.0 
400 -- -- 9 5.5 60 
600 -- -- 10 7.5 60 
200 200 100 (1) 100.sup.1 
-- 150 
200 200 100 (3) 100.sup.1 
-- 120 
200 200 100 (4) 100.sup.1 
-4.0 150 
200 200 100 (7) 100.sup.1 
-- 120 
200 200 100 (5) 100.sup.1 
3.0 250 
200 200 100 (6) 100.sup.1 
3.0 150 
______________________________________ 
.sup.1 As in the Table of Example 4. 
EXAMPLE 6 
Comparative tests were made on Fuel 1 using the polar compound C6 to 
demonstrate the advantages of using the three component mixture rather 
than combinations of the two of the components. 
The fuel samples were cooled at 0.3.degree. C./hour down to -8.degree. C. 
and held at this temperature for 72 hours and the results are shown in 
Table 6. 
TABLE 6 
______________________________________ 
Waxy Minimum 
Additive conc. (ppm) 
Layer Mesh 
A B C6 Vol % Passed 
______________________________________ 
100 10 
100 A Gel formed 
100 A Gel formed 
100 100 10 20 
100 100 A Gel formed 
100 100 11 20 
100 200 100 100.sup.1 40 
______________________________________ 
.sup.1 As in Table of Example 4. 
EXAMPLE 7 
In this Example, the fuel used had a cloud point of -3.degree. C., a WAP of 
-6.degree. C., an initial boiling point of 180.degree. C. and a final 
boiling point of 365.degree. C. and a CFPP of -7.degree. C. The distillate 
flow improver used was A and the lube oil pour depressant was B whilst the 
polar compound C9 was polyisobutylene succinic anhydride, the 
polyisobutylene chain being of about 1000 molecular weight. 
The treated fuel was cooled at 1.degree. C./hour to -11.degree. C., held at 
-11.degree. C. for 55 hours and then warmed up to 0.degree. C., held at 
0.degree. C. for 8 hours, again cooled at 1.degree. C./hour to -11.degree. 
C. and held at -11.degree. C. for a further 9 hours. A sample of the cold 
soaked fuel is then sucked through a filter under a pressure of 200 
millimeters of water and the minimum mesh through which the material would 
pass was determined and the results are shown in the following Table 7. 
TABLE 7 
______________________________________ 
Minimum Mesh 
Blend Passed 
______________________________________ 
43 150 ppm A 85 
150 ppm B 
100 ppm C9 
44 150 ppm A 100 
150 ppm B 
150 ppm C9 
______________________________________ 
EXAMPLE 8 
In this Example, the fuel used had a cloud point of +2.degree. C., a wax 
appearance point of -4.degree. C., an initial boiling point of 185.degree. 
C. and a final boiling point of 376.degree. C. The CFPP temperature for 
the untreated fuel was -5.degree. C. The polar compounds were C9, and C10 
which was the diamide of the polyisobutylene succinic anhydride C9 of 
Example 7 and di-normal butyl amine. 
The treated fuel was cooled at 1.degree. C./hour to -8.degree. C., held at 
-8.degree. C. for 30 hours, warmed to +2.degree. C. in 2 hours, held at 
+2.degree. C. for 5 hours, cooled again to -8.degree. C. at 1.degree. 
C./hour and held again at -8.degree. C. for a further 10 hours. 
20 mls of the bottom 10% of the sample was sucked through a filter under 
200 mm of water pressure and the minimum mesh passed is given in the 
following Table. 
______________________________________ 
Additive Conc Minimum Mesh 
Blend ppm Passed 
______________________________________ 
45 150 ppm A 60 
150 ppm B 
75 ppm C9 
46 150 ppm A 250 
150 ppm B 
75 ppm C10 
______________________________________