U.S. patent number 3,637,357 [Application Number 04/844,195] was granted by the patent office on 1972-01-25 for fuel emulsion with improved stability.
This patent grant is currently assigned to Esso Research and Engineering Company. Invention is credited to Fredrick L. Jonach, James Nixon.
United States Patent |
3,637,357 |
Nixon , et al. |
January 25, 1972 |
FUEL EMULSION WITH IMPROVED STABILITY
Abstract
Stability of viscous liquid hydrocarbon emulsions, wherein the
hydrocarbon is present in a major proportion as the dispersed phase
and emulsifiers do not represent more than 2 wt. percent of the
total emulsion, is improved by the addition of certain dicarboxylic
acid derivatives derived from reaction with amines and
alcohols.
Inventors: |
Nixon; James (Westfield,
NJ), Jonach; Fredrick L. (Short Hills, NJ) |
Assignee: |
Esso Research and Engineering
Company (N/A)
|
Family
ID: |
25292077 |
Appl.
No.: |
04/844,195 |
Filed: |
July 23, 1969 |
Current U.S.
Class: |
44/301;
516/20 |
Current CPC
Class: |
C10L
1/32 (20130101) |
Current International
Class: |
C10L
1/32 (20060101); C10l 001/32 () |
Field of
Search: |
;44/51 ;252/308 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Wyman; Daniel E.
Assistant Examiner: Shine; W. J.
Claims
What is claimed is:
1. In a hydrocarbon emulsion which comprises about 75 to 99 wt.
percent of a liquid hydrocarbon boiling within the range of
70.degree. to 750.degree. F. as a dispersed phase, about 0.5 to 20
wt. percent of a polar organic liquid as the continuous phase, said
organic liquid being immiscible with said hydrocarbon and having a
dielectric constant greater than 25 and a solubility parameter in
excess of 10, and from about 0.25 to about 2 wt. percent of organic
emulsifier, the improvement comprising having in admixture
therewith about 0.25 to about 5 wt. percent of a material useful as
an emulsion stabilizer having the general formula:
wherein X and X' are each selected from the group consisting of
##SPC4## providing that X and X' are not both OR.sub.1 ; Y is a
hydrocarbon radical having one to 42 carbon atoms; R is selected
from the group consisting of C.sub.2 -C.sub.50 straight or branched
chain alkylene radicals, C.sub.5 -C.sub.50 bivalent alicyclic
hydrocarbon radicals and --[R.sub.2 O].sub.e radicals; R.sub.1 is
selected from the group consisting of hydrogen and C.sub.1 to
C.sub.6 alkyl radicals; R.sub.2 is a C.sub.2 -C.sub.3 alkylene
radical; R.sub.3 is a hydrocarbon radical having two to 20 carbon
atoms; R.sub.4 is a hydrocarbon radical having one to 36 carbon
atoms; a is a cardinal number having a value of one to 25; b has a
value of one to 10; c has a value of zero to one; d has a value of
zero to five; e has a value of from one to 50; and the sum of all
the c's and d's is at least one.
2. The composition of claim 1 wherein both X and X' are OROH.
3. The composition of claim 3 wherein R is the hydrocarbon skeleton
of a C.sub.2 -C.sub.8 glycol.
4. The composition of claim 1 wherein X is
X' is selected from the group consisting of OR.sub.1 and
N(R.sub.1).sub.2 ; and R is the hydrocarbon skeleton of a C.sub.2
-C.sub.8 glycol.
5. The composition of claim 4 wherein Y is a C.sub.22 to C.sub.34
group of a C.sub.12 to C.sub.18 dimer acid, R is the hydrocarbon
skeleton of a C.sub.2 -C.sub.5 glycol and R.sub.1 is a C.sub.1
-C.sub.6 alkyl group.
6. The composition of claim 5 wherein Y is a C.sub.34 group of a
C.sub.18 dimer acid; n has a value of about five to about 20; R is
the hydrocarbon skeleton of a C.sub.2 glycol; and R.sub.1 is a
C.sub.1 alkyl group.
7. The composition of claim 1 wherein X is OR.sub.4 ; and
8. The composition of claim 7 wherein R.sub.4 is a hydrocarbon
radical having one to eight carbon atoms and R.sub.2 is a C.sub.2
alkyl group.
9. The composition of claim 8 wherein said emulsion stabilizer is
the amido-ester reaction product formed by reacting di-2-ethylhexyl
sebacate and tetraethylene pentamine.
10. The composition of claim 9 wherein said liquid hydrocarbon is a
jet fuel.
11. The composition of claim 1 wherein X is OR.sub.1 and X' is
selected from the group consisting of NHR.sub.3 OH, ONH.sub.3
R.sub.3 NH.sub.2, NHR.sub.3 NH.sub.2, ONH.sub.2 (R.sub.3 OH).sub.2,
ONH.sub.3 C.sub.3 H.sub.6 [C.sub.2 H.sub.4 O].sub.b OH and
NHC.sub.3 H.sub.6 [C.sub.2 H.sub.4 O].sub.b OH.
Description
FIELD OF THE INVENTION
The present invention relates to improving the stability of viscous
liquid hydrocarbon emulsions, wherein the hydrocarbon is present in
a major proportion as the dispersed phase and emulsifiers do not
represent more than 2 wt. percent of the total emulsion. More
particularly, this invention is concerned with the addition to
liquid hydrocarbon emulsion systems using low emulsifier levels
(e.g., 0.5-1.0 wt. percent) of a material useful as an emulsion
stabilizer.
The emulsified systems to which the compounds are added are of the
type in which a normally liquid hydrocarbon fuel is the dispersed
phase and constitutes at least 75 wt. percent of the total
emulsion. Said emulsion has as the continuous phase a minor
proportion of a polar organic liquid, the latter including, but not
being limited to, formamide, ethylene glycol, formamide-urea
mixtures, glycol-formamide mixtures and the like.
DESCRIPTION OF THE PRIOR ART
Viscous emulsions of the type wherein the hydrocarbon fuel is the
dispersed phase have been found to possess certain advantages
particularly in connection with the emulsification of jet fuels for
civilian and military aircraft. It has previously been discovered
that by emulsifying jet fuels to the extent that the fuel dispersed
phase constitutes at least 75 wt. percent of the emulsion while the
continuous phase is largely composed of the remainder of the
emulsion, a certain safety factor is incorporated into such fuels.
Before said discovery, in the crashes of aircraft or in military
operations subject to the impact of enemy projectiles on the
aircraft, the tendency towards sudden ignition of the atomized
and/or vaporized fuel contained in the fuel tanks of such aircraft
was great because of the inherent characteristics of the jet fuels.
However, it was discovered that when such fuel tanks are filled
with stable fuel emulsions which are viscous in nature, the fuel
does not readily vaporize or atomize. Thus, the use of fuel
emulsions practically reduced to a minimum the tendencies for
explosions and burning ordinarily encountered by reason of the
military and civilian punctures or ruptures which apply to fuel
tanks containing liquid fuels, largely because the fuels in
emulsion form have eliminated to substantial degrees the tendency
of the stored fuel to vaporize or atomize. Such emulsions are now
known in the art and have been prepared using the materials set
forth in U.S. Pat. No. 3,429,817, U.S. Pat. No. 3,458,294 and
copending application, Ser. No. 813,271, filed Apr. 3, 1969, which
are incorporated herein by reference. However, it has been found
that at relatively low emulsifier levels (e.g., 0.5-1 wt. percent)
the stability of these emulsions is greatly decreased.
The use of about 0.001 to about 1 wt. percent of the amido-ester
reaction product of a polyamine and a dialkyl ester of a
dicarboxylic acid in fuels as a lubricity additive, and the use of
about 0.001 to about 0.4 wt. percent of the reaction product of a
dicarboxylic acid and a glycol in fuels, also as a lubricity
additive, have been taught in U.S. Pat. No. 3,321,404 and U.S. Pat.
No. 3,429,817, respectively. Similarly, U.S. Pat. Nos. 3,281,358;
3,390,083; 3,180,832 and 3,287,273 disclose the preparation of
antiwear and lubricity additives from dicarboxylic acids and
polyamines; dicarboxylic acids and hydroxy amines; dicarboxylic
acids, glycols and alcohols or amines; and dicarboxylic acids and
glycols. However, it has heretofore not been known that the use of
about 0.25 to about 5 wt. percent of these materials, which are not
recognized in the art as emulsifiers, would improve the emulsion
stability of emulsified fuels at low emulsifier levels thus
permitting the use of lower proportions of high cost
emulsifiers.
SUMMARY OF THE INVENTION
It has now been discovered that the stability of viscous liquid
hydrocarbon emulsions, wherein the hydrocarbon is present in a
major proportion as the dispersed phase and emulsifiers do not
represent more than 2 wt. percent of the total emulsion, is
improved by the addition of a material useful as an emulsion
stabilizer having the general formula:
wherein X and X' are each selected from the group consisting of
##SPC1## providing that X and X' are not both OR.sub.1 ; Y is a
hydrocarbon radical having one to 42 carbon atoms; R is selected
from the group consisting of C.sub.2 -C.sub.50 straight or branched
chain alkylene radicals, C.sub.5 -C.sub.50 bivalent alicyclic
hydrocarbon radicals and --[R.sub.2 O].sub.e radicals; R.sub.1 is
selected from the group consisting of hydrogen and C.sub.1 to
C.sub.6 alkyl radicals; R.sub.2 is a C.sub.2 -C.sub.3 alkylene
radical; R.sub.3 is a hydrocarbon radical having two to 20 carbon
atoms; R.sub.4 is a hydrocarbon radical having one to 36 carbon
atoms; a is a number having a value of one to 25; b has a value of
one to 10; c has a value of zero to one; d has a value of zero to
five; e has a value of from one to 50; and the sum of all the c's
and d's is at least one.
DETAILED DESCRIPTION
In the stabilizing additives of this invention the basic structure
is that of a dicarboxylic acid having the general formula
wherein Y is a hydrocarbon radical having one to 42 carbon atoms.
Starting with these dicarboxylic acids, the additive compounds for
the emulsified fuels are prepared by reacting said acids with
various components. For example, they can be prepared by reacting
said acids with a glycol such as a C.sub.2 -C.sub.50 alkane diol
and/or C.sub.4 -C.sub.100 oxa-alkane diol described in U.S. Pat.
Nos. 3,180,832; 3,429,817 and 3,287,273. Similarly they can be
prepared by reacting said acids with said glycols to form a partial
ester and then further reacting the resulting partial ester with
ammonia, a C.sub.1 -C.sub.6 alkyl alcohol, a simple primary or
secondary C.sub.1 -C.sub.6 alkyl amine or a polyamine to produce a
blocked polyester in the manner described in U.S. Pat. No.
3,390,083 for reacting ethylene glycol, a C.sub.36 dicarboxylic
acid and an alcohol. They can also be produced by reacting said
acids with C.sub.2 -C.sub.20 polyamines and/or hydroxy amines as
described in U.S. Pat. No. 3,281,358 or by reacting a diester of a
dicarboxylic acid with a hydrocarbon polyamine as described in U.S.
Pat. No. 3,321,404.
It is preferred for some embodiments of the present invention that
the number of carbon atoms between the carboxylic groups of the
dicarboxylic acid be in the range of about eight to about 42.
Especially preferred are the dimers of a C.sub.12 -C.sub.18
unsaturated monocarboxylic acid. Specific examples of these acids
are the dimer of linoleic acid, the dimer of oleic acid, the mixed
dimer of linoleic and oleic acids and the dimer of dodecadienoic
acid. It is also possible to employ dicyclopentadiene dicarboxylic
acid. While the foregoing acids are preferred, similar dicarboxylic
acids such as "VR-1" described in U.S. Pat. No. 2,833,713 and
"D-50" described in U.S. Pat No. 2,470,849 may be used. The dienoic
or trienoic monocarboxylic acid, that is polymerized to give the
dicarboxylic polymer, can have from 12 to 30 carbon atoms.
Extremely suitable dimer acids for use in the present invention are
commercially available from Emery Industries, Inc. under the trade
name of Empol dimer acids. These dimer acids are available in
various grades of dimer acid purity relative to trimer and
monobasic acid content. For example, Empol 1014 dimer acid consists
of 95 percent dimer acid, a minor proportion of trimer acid and a
trace of monobasic acids. Also available are Empol 1018 dimer acid
(containing 16 percent trimer and a trace of monobasic acid), Empol
1022 dimer acid (19 to 22 percent trimer and 2 to 5 percent
monobasic acids) and Empol 1025 dimer acid (containing the same
trimer acid content as Empol 1022 but containing only a trace
amount of monobasic acid). The specifications and typical
compositions of the Empol dimer acids discussed above are given in
table I.
---------------------------------------------------------------------------
TABLE I
Empol Empol Empol Empol 1014 1018 1022 1024
__________________________________________________________________________
Neutralization Equivalent 288-294 287-299 289-301 289-301 Acid
Value 191-195 188-196 186-194 186-194 Saponification Value 195-199
192-198 191-199 191-199 Color, Gardner 1953 max. 8 8 9 9 Monobasic
Acids (Max. Percent) 1.5% 1% 2-5% 1% Dimer Acid 95 83 77 79 Trimer
Acid 4 17 20 21 Monobasic Acids 1 Trace 3 Trace Dimer:Trimer Molar
Ratio 36:1 7:1 6:1 6:1
__________________________________________________________________________
The commercial dimer acids discussed above are generally produced
by polymerization of unsaturated C.sub.18 fatty acids to form
C.sub.36 dibasic dimer acids. Depending on the raw materials used
in the commercial process, the C.sub.18 monomeric acid may be
linoleic acid or oleic acid or mixtures thereof. The resulting
dimer acids can therefore be the dimer of linoleic acid, the dimer
of oleic acid or a mixed dimer of linoleic and oleic acid.
Furthermore as can be seen from the above, table I, these
commercially available "dimer acids" are not necessarily 100
percent pure dimer acids and dimer acids containing minor
proportions of trimer acid and monobasic acids can be utilized in
the practice of the present invention. However, it is essential
that the amount of dimer acid present in the acid composition be at
least 50 percent and preferably above 75 percent, such as 95
percent by weight. It is to be understood that, under certain
circumstances, these dicarboxylic acids can be substituted acids
such as with bromine, fluorine or a hydroxy group.
Specific examples of the foregoing dicarboxylic acids are: dimer
acids (e.g., dilinoleic acid and dioleic acid); straight chain
aliphatic dibasic acids, such as malonic acid; succinic acid,
glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic
acid, sebacic acid and dodecadienoic acid; benzene polycarboxylic
acids, such as phthalic acid, isophthalic acid, terephthalic acid,
hemimellitic acid, trimellitic acid, trimesic acid, prehnitic acid,
mellophanic acid, pyromellitic acid, benzene pentacarboxylic acid
and mellitic acid; and other such as diphenic acid, diglycolic acid
and d-tartaric acid.
As indicated, one embodiment of this invention employs an emulsion
stabilizer formed by reacting a dicarboxylic acid with a C.sub.2
-C.sub.50 alkane diol and/or C.sub.4 -C.sub.100 oxa-alkane diol.
Thus, each mole of the acid is reacted with one or two HOROH groups
wherein R is selected from the group consisting of C.sub.2
-C.sub.50 straight or branched chain alkylene radicals, C.sub.5
-C.sub.50 bivalent alicyclic hydrocarbon radicals and --[R.sub.2
O].sub.e radicals, R.sub.2 is a C.sub.2 -C.sub.3 alkylene radical,
and e has a value of from one to 50. A satisfactory glycol has 16
carbon atoms and the general formula:
wherein the C.sub.6 and C.sub.7 alkyl groups are branched. Other
suitable diols are oxa-alkane diols obtained, for example, by
hydrolysis of ethylene oxide, propylene oxide or other epoxy
compounds. These diols may have molecular weights between 200 and
2,000. An example is 3,6,9-trioxa-1,4,7,10-tetramethyl
undecane-1,11-diol.
The glycols used are preferably oil insoluble. Thus, the glycol
reacted with the dicarboxylic acid may be an alkane diol or an
oxa-alkane diol, straight chain or branched. These alkane diols
will generally have from about two to eight carbon atoms,
preferably two to five carbon atoms in the molecule.
The oxa-alkane diol can have four to 100, preferably four to 40,
carbon atoms with periodically repeating groups of:
wherein R is H or CH.sub.3.
The preferred alkane diol is ethylene glycol and the preferred
oxa-alkane diol is 4-oxa-heptane diol-2,6. Other specific
satisfactory glycols are, for example, propylene glycol,
polypropylene glycol, polyethylene glycol and the like.
The molar quantities of the dicarboxylic acid and glycol reactants
may be adjusted so as to secure either a complete diester or a
partial ester.
The additives of the present invention comprising a reaction
product between a dimerized dicarboxylic acid and a glycol may be
produced by various techniques. Turning now to the embodiment
wherein a diester of a dimeric dicarboxylic acid is used, as
previously indicated, the molar quantities of reactants are
adjusted in this embodiment so as to secure a complete diester. For
example, one process is to reflux an excess of the diol with the
selected dioic acid at 80.degree. C. in the presence of benzene as
diluent and toluene sulfonic acid as catalyst until the theoretical
amount of water has been produced in a water trap in the reflux
condenser. The diluent is then stripped off under vacuum at
40.degree. C. The general reaction equation is as follows:
HOOC--R--COOH+XHO--R'--OH HO--R'OOC--R--COOR'--OH+XH.sub.2 O
wherein R is the radical of a glycol and R' is the hydrocarbon part
of the dimer acid and X is at least two. While either the
dicarboxylic acid or the ester product may be hydrogenated, it is
preferred that the dicarboxylic acid be hydrogenated prior to
esterification when producing the diester. This hydrogenation may
be accomplished by any suitable process known to the art. For
example, the acid may be reduced with hydrogen gas over platinum
catalyst at a temperature in the range from 20.degree. to
100.degree. C. in a steel bomb. The hydrogen pressure in the system
may range from about 10 to 300 pounds. Another method by which
hydrogenation may be accomplished is by the use of lithium hydride
using conventional techniques at ambient temperatures.
Another preferred embodiment of this invention employs an emulsion
stabilizer prepared by reacting said acids with said glycol to form
a partial ester and then further reacting the resulting partial
ester with an alcohol or amine. Generally speaking, the simple
esterification of the dicarboxylic or dimer acid with the glycol is
carried out using equimolar amounts of the two reactants, with the
esterification being continuous, usually under refluxing conditions
until more than 1 but less than 2 moles of water of reaction have
been produced per mole of acid and per mole of glycol employed. By
so controlling the reaction conditions, catalyst concentration, and
the like, the polyesterification reaction results in a partial
ester being formed. The polymeric, partially esterified composition
is believed to have the general formula:
HO--[X--OOC--Y--COO].sub.n X--OOC--Y--COOH
wherein X is the alkylene portion of from two to 50 carbon atoms of
the glycol employed originally and Y is the alkylene portion of the
acid and wherein n is an integer ranging from about 1 to about 25.
Preferably, n is between about 1 and about nine. The desired upper
limit of n depends on the solubility limitation in the particular
hydrocarbon oil in which the additive is to be incorporated.
The above-identified polymeric partial ester is then further
reacted with ammonia, with a primary or secondary amine under
amidation conditions, or with a monohydric alcohol such as methanol
or ethanol is order to block the free carboxyl groups with an amino
group by reacting the OH group of the free carboxyl radicals or by
esterification with the alcohol. In other words, the carboxyl
hydrogens in the above polymerized partial ester are replaced by an
alkyl group of one to six carbon atoms which would be formed if a
monohydric alcohol were employed or the OH of the carboxyl groups
would be replaced by a NR'R" wherein R' would be a C.sub.1 -C.sub.6
alkyl group or hydrogen, and R" would be a C.sub.1 -C.sub.6 alkyl
group or hydrogen, or the R's could be the residue of hexamethylene
tetramine or the like. The blocked ester would have the
formula:
HO[X--OOC--Y--COO].sub.n X--OOC--Y--COZ
wherein Z is an --O alkyl, --NH.sub.2, --NH(alkyl) or
--N(alkyl).sub.2.
In the embodiment of the invention in which said emulsion
stabilizers are the reaction product of said acids with C.sub.2
-C.sub.20 polyamines and/or hydroxy amines, the amine compounds for
use in conjunction with the diacids of the present invention are
selected from the class consisting of polyamines and hydroxy amines
such as amino alcohols, diamines, polyglycol amines, and dialkanol
amines.
The dicarboxylic acid amino alcohol reaction product may be
prepared by reacting 1 mole of dimer acid with 1 mole of an amino
alcohol as follows:
The preferred amino alcohols are those alcohols having from about
two to 20 carbon atoms and R' may be derived from aliphatic,
alicyclic or aromatic hydrocarbons. Specific amino alcohols which
are desirable are monoethanolamine, N-aminoethyl ethanolamine,
p-amino phenol, 4-amino-1-butanol, 5-amino-1-pentanol,
10-amino-1-decanol, and amino isopropanol.
The diacid diamine reaction products in accordance with the present
invention may be made by reacting 1 mole of a dicarboxylic acid
with 1 mole of a diamine as follows:
R may be a bivalent aliphatic, alicyclic or aromatic hydrocarbon
radical containing from nine to 42 carbon atoms. R' may be a
bivalent aliphatic, alicyclic or aromatic hydrocarbon radical
containing from two to 20 carbon atoms. Examples of suitable
diamines are thylene diamine, propylene diamine, 1,4 butane diamine
and 1,6 hexane diamine. In general, the preferred structure for
both the diacids and diamines is .alpha.-.omega..
The polyglycolamines for use in conjunction with the present
invention have the following general structure:
HO--[C.sub.2 H.sub.4 O].sub.n C.sub.3 H.sub.6 NH.sub.2
wherein n has a value of one to 10.
An example of a commercially available product of this type is
polyglycolamine H-163 (n= 2) made by the Union Carbide Chemicals
Company. This may be reacted with a dibasic acid to form an amine
acid addition salt or possibly even a partial ester.
HO--[C.sub.2 H.sub.4 O].sub.2 --C.sub.3 H.sub.6 NH.sub.2 +HOOCRCOOH
HO--[C.sub.2 H.sub.4 O].sub.2 --C.sub.3 H.sub.6 NH.sub.3
OOCRCOOH
The dicarboxylic acid dialkanol amine reaction product for use in
conjunction with the present invention has the following general
formula:
Here again the number of carbon atoms in the dialkanol amine may
vary in the range from about two to 20.
In another preferred embodiment of this invention, the emulsion
stabilizer is the amido-ester reaction product of a hydrocarbon
polyamine and a diester of said acids.
Examples of alcohols which may be used to esterify the dicarboxylic
acids to form said diester intermediates are methanol, ethanol,
propanol, isopropanol, butanol, isobutanol and pentanol. Other
alcohols are benzyl alcohol, cyclohexanol and 2-ethyl hexanol.
These esters may also be mixed esters such as monoethyl monopropyl
ester of the dimer of a dicarboxylic acid such as the dimer of
linoleic acid. Said alcohols will generally contain about one to
about 36 carbon atoms and preferably contain about one to about
eight carbon atoms. Very desirable intermediate esters produced
from said alcohols include the dimethyl ester of dilinoleic acid,
the dimethyl ester of dioleic acid and the dimethyl ester of the
mixed dimer of linoleic and oleic acids. The polyamine is a
compound containing two or more amine groups. Some broad examples
of polyamines are diamines, triamines, tetramines, and pentamines.
Specific examples are dimer diamines made from dilinoleic acid or
dioleic acid, tetraethylene pentamine, propylene diamine,
imino-bis-propyl amine, hexamethylene tetramine, 1,4-bis
(aminomethyl)-cyclohexane, 1,8-p-menthane diamine and fatty acid
1,3 propylene diamine compounds. It is also possible to use hydroxy
amine compounds since these are also difunctional.
The polyamines may contain aliphatic, alicyclic or aromatic groups
or mixed groups such as alkyl-aromatic. The polyamines and
polybasic acid esters may contain alkyl, aryl and alicyclic groups
or mixed alkyl-aryl, etc., groups. Examples of the general types of
polyamine compounds which may be used are shown below:
H.sub.2 n(ch.sub.2).sub.n NH.sub.2 where n has a value of about two
to about 20;
H.sub.2 n(ch.sub.2 ch.sub.2 nj).sub.n CH.sub.2 CH.sub.2 NH.sub.2
where n has a value of zero to about five;
Tallow 1,3 propylene diamines (e.g., Duomeens);
Polyamino benzenes;
Phenylene diamines; and
Dimer diamine.
Thus, in essence, this embodiment of the present invention uses a
reaction product between a dialkyl ester of a dicarboxylic acid and
a polyamine, preferably an oil-insoluble polyamine. A very
desirable reaction product is that obtained between
di-2-ethyl-hexylsebacate and tetraethylene pentamine.
Nonlimiting examples of additives used in other embodiments of this
invention include the mono-beta-hydroxy ethyl ester of C.sub.36
linoleic dimer acid, the bis (beta-hydroxy) ethyl ester of C.sub.36
oleic dimer acid, the reaction product of equal molar amounts of
C.sub.36 linoleic dimer acid and diethanol amine, etc.
As hereinbefore stated, the additives of this invention, which
improve stability and lubricity, are intended for use in viscous
liquid hydrocarbon emulsions containing a high percentage of an
internally dispersed hydrocarbon phase within a continuous phase
and not more than 2 percent emulsifiers. An emulsion containing a
high percentage of an internal dispersed phase exerts a phenomenon
known as "yield stress" (see ASTM D2507 "Tentative Definition of
Terms Relating to Rheological Properties of Gelled Rocket
Propellants.") which might be looked upon as being that force
necessary to overcome the viscosity inertia of the stable emulsion.
It is measured in dynes per square centimeter and aids in defining
the "viscosity" of the stable emulsion. Under conditions of low
shearing stress, such an emulsion will not flow freely. When a
sufficiently large shearing stress is applied, the "apparent
viscosity" of the emulsion decreases and the material will flow
much more readily. If a critical rate of shear is not exceeded, so
as to break down the emulsion, the material will regain its much
more viscous state once the shear stress is removed.
It is to be noted that the highly viscous, or pseudoplastic,
emulsions which the additives of this invention stabilize are to be
distinguished from gels. A gel consists of a solid
three-dimensional network intertwined with a similar liquid network
wherein neither network is entirely within the other. When a gel is
made to flow under stress, the interconnectivity of the networks is
broken down and must be reestablished in order for the gel to set
again. In contrast, in a pseudoplastic emulsion of the type
involving the present invention, each droplet of the dispersed
phase is actually inside the continuous phase at all times, and
flow under stress merely involves a temporary change of geometric
configuration.
Yield stress values are determined by the need to have a viscosity
that is practical for pumping through a conventional fuel system of
fuel pumps and fuel lines and yet provide a fuel emulsion that will
not flow readily through penetrations of the wall of the fuel tank.
For conventional jet aircraft, both civilian and military, yield
stress values in the range of about 800 to 4,000 are particularly
useful. The most desired yield stress is one that will restrict the
flow out of a punctured, ruptured or split fuel tank or fuel line
to a moderate rate under the existing hydrostatic head so that the
fuel will not spray and form the ball of highly inflammable mist
that usually occurs with an unmodified fuel. The nature of the flow
with the emulsion of the invention is much akin to the flow of
toothpaste from the conventional collapsible tube, forming a mass
or pile instead of a rapidly spreading puddle. Thus, while the
emulsion mass is still capable of catching on fire, it will be
contained within an area that can be much more readily brought
under control than in the case of unthickened fuel.
The dispersed phase of the emulsion can be any liquid which is
substantially immiscible with the liquid employed as the continuous
phase.
The preferred hydrocarbons that form the dispersed phase in the
emulsions of the present invention include those boiling within the
range of about 70.degree. to 750.degree. F., e.g., petroleum
fractions, such as gas oils, kerosene, motor gasoline, aviation
gasoline, aviation turbojet fuels, diesel fuels, Stoddard solvent,
and the like, as well as coal tar hydrocarbons such as coal tar
solvent naphtha, benzene, xylene, hydrocarbon fuels from coal
gasification, shale oil distillates, and the like. Gasoline is
defined as a mixture of liquid hydrocarbons having an initial
boiling point in the range of about 70.degree. to 135.degree. F.
and a final boiling point in the range of about 250.degree. to
450.degree. F. Most usually gasolines are identified as either
motor gasolines or aviation gasolines. Motor gasolines normally
have boiling ranges between about 70.degree. and 450.degree. F.,
while aviation gasolines have narrower boiling ranges between about
100.degree. and 330.degree. F. Gasolines are composed of a mixture
of various types of hydrocarbons, including aromatics, olefins,
paraffins, isoparaffins, and naphthenes. Stoddard solvent generally
has a boiling range of about 300.degree. to 400.degree. F. Diesel
fuels include those defined by ASTM Specification D-975. Jet fuels
generally have boiling ranges within the limits of about
150.degree. to 600.degree. F. Jet fuels are usually designated by
the terms JP-4, JP-5, or JP-6. JP-4 and JP-5 fuels are defined by
U.S. Military Specification MIL-T5624-G. Aviation turbine fuels
boiling in the range of 200.degree. to 550.degree. F. are defined
by ASTM Specification D-1655-59T.
While it is contemplated that the invention is best applicable to
the preparation of hydrocarbon fuels as the dispersed phase, it is
not limited thereto. Such emulsions have been found to be stable at
temperatures ranging from -65.degree. to +140.degree. F. for
periods in excess of 90 days. The dispersed phase may be a
halogenated hydrocarbon such as the perchlorinated or
perfluorinated lower alkanes and alkenes. Tetrafluoroethane,
tetrachloroethylene, hexachloroethane, the perfluoro butanes and
pentanes and the like are examples of liquids that may be
emulsified in water or formamide as the continuous phase. Such
emulsions find utility as drycleaning compositions. Additionally,
oxygen-containing derivatives of hydrocarbons such as methyl
isobutyl ketone, lauryl alcohol, stearyl alcohol, oleic acid,
myristic acid and stearic acid may be the dispersed phase with
water or formamide being the continuous phase. If necessary,
sufficient heat may be applied during emulsification to insure a
liquid phase condition for all the components.
Nonaqueous, highly polar organic liquids constitute the continuous
phase of the emulsion. All of these liquids are, of course,
immiscible with respect to the hydrocarbon fuel or hydrocarbon
derivative constituting the dispersed phase. These materials are
characterized by having dielectric constants greater than 25 and
solubility parameters greater than 10. Most of them will have
freezing points of 40.degree. F. or lower so that the emulsions
will be stable at relatively low temperatures. Representative
examples of the compounds which may be employed as the continuous
phase are: formamide, dimethyl formamide, dimethyl sulfoxide,
dimethyl acetamide, propylene carbonate, formic acid, glycerol,
glycidol, ethylene glycol, propylene glycol, 2-pyrrolidone, or
mixtures of two or more of such materials. The continuous phase
materials can be still further modified and, in many instances, are
advantageously modified by adding thereto between about 0.5 and
40.0 percent, based upon the weight of the aforementioned
continuous phase material, of a material such as urea, oxamide, and
guanidine, or other solid amide, provided that the nature of the
amide employed and the amount of the amide used are such that when
it is added to the aforementioned continuous phase materials or
mixtures of materials, the mixture still remains liquid under the
emulsification conditions prevailing. A suitable continuous phase
constitutes 80 percent formamide and 20 percent urea. The
properties of the polar organic material, which expression is
intended to include water as compared, for example, with JP-4 jet
fuel, are as follows: ##SPC2##
The emulsification of a hydrocarbon fuel as a dispersed phase in a
continuous phase material, as defined above, is not satisfactorily
accomplished without the presence of one or more organic
emulsifiers, dispersants or surfactants. The materials successfully
used should be essentially nonash forming in nature and if traces
of them are contained in the fuel after demulsification, they
should not form residues in the engines wherein the fuel is
combusted. Hence, the use of nonmetallic emulsifiers is desirable.
The best balance of force of attraction between the hydrocarbon
phase and the continuous phase of the emulsion is obtained by using
a combination of two or more emulsifiers. For most satisfactory
results, the lipophilic portion of the emulsifier must closely
match the particular hydrocarbon or hydrocarbon fraction being
dispersed. To attain the proper balance between lipophilic and
nonlipophilic (i.e., hydrophilic) forces in the emulsifier system,
it is convenient to use the scale of HLB values known to the
emulsifier art. These are discussed by W. C. Griffin in the Journal
of the Society of Cosmetic Chemistry, Dec., 1948, page 419; also in
Kirk-Othmer Encyclopedia of Chemical Technology, Second Edition,
Volume 8, pages 131-133 (1965). Desired HLB values can be obtained
by using two or more emulsifiers in combination. Emulsifiers and
emulsifier combination which give HLB values in the range of 11-16
are satisfactory for producing a stable emulsion in the present
invention when the continuous phase material is formamide.
Formamide gives the greatest latitude in the selection of
emulsifiers that may be used. This is believed to be because of the
optimum combination of strong hydrogen bonding and polarity in
formamide. Mixtures of formamide and solid amides such as urea
appear to give the most satisfactory emulsions when using nonionic
emulsifiers having HLB values in the 11-14 range. With polar
organic liquids within the scope of this invention that are used in
conjunction with amides or with small amounts of water, such as
ethylene glycol, the effective HLB value will depend on the
particular liquid selected and will vary with the proportion of
water or amide to the said organic liquid constituting the
continuous phase.
Among the surfactants or emulsifiers that may be employed in the
present invention are included alkylphenyl, polyethylene glycol
ethers such as Tergitol NPX of Carbide and Carbon Company,
polyethylene polyoxypropylene glycol such as Pluronic L-64 of
Wyandotte Chemical Company, resin acid esters of polyoxyethylene
glycol such as Thofat 242/25 of Armour Industrial Chemical Company,
and alkylphenyl polyethoxy alkanols such as Triton X-102, which is
iso-octyl phenyl polyethoxy ethanol, i.e., the reaction product of
iso-octylphenol and ethylene oxide. The alkyl phenyl polyalkoxy
alkanols are obtained by reacting 5 to 15 molar proportions of a
C.sub.2 to C.sub.3 alkylene oxide with 1 molar proportion of an
alkyl phenol having a C.sub.5 to C.sub.12 alkyl group, e.g., the
reaction product of 6 moles of propylene oxide with 1 mole of
dodecyl phenol, the reaction product of a mixture of 5 moles of
ethylene oxide and 5 moles of propylene oxide with 1 mole of nonyl
phenol, and the reaction product of 8 to 10 moles of ethylene oxide
with 1 mole of iso-octyl phenol. These are included within a
broader class of materials having the formulas:
RA(CH.sub.2 CH.sub.2 O).sub.x CH.sub.2 CH.sub.2 OH
or
RA(CH.sub.2 CH.sub.2 CH.sub.2 O).sub.x CH.sub.2 CH.sub.2 CH.sub.2
OH
where R is a C.sub.8 to C.sub.18 hydrocarbon group, A is oxygen or
sulfur and x is eight to 20.
Other emulsifiers include the fatty acid esters of sorbitan, such
as sorbitan monolaurate, sorbitan monostearate, sorbitan
monopalmitate, sorbitan monooleate, and the alkoxylated fatty acid
esters of sorbitan such as polyoxyethylene sorbitan monostearate,
tristearate or trioleate. The various sorbitan esters of fatty
acids are well known to the art as Spans, and the polyoxyethylene
derivatives of the sorbitan esters of fatty acids are well known as
Tweens. Still other suitable emulsifiers include N-alkyl
trimethylene diamine dioleate of Armour and Company, octakis
(2-hydroxy propyl) sucrose, the condensation products of fatty acid
amides and ethylene oxide, the ethoxylated fatty alcohols,
polyoxyethylene monostearate, polyoxyethylene monolaurate,
propylene glycol mono-oleate, glycerol monostearate, ethanolamine
fatty acid salts, stearyl dimethyl benzene ammonium chloride,
various gums such as gum tragacanth, gum acacia, etc. Where the
presence of metal is not objectionable in the emulsion,
metal-containing emulsifiers can also be used, such as sodium
dioctyl sulfosuccinate (Aerosol OT) or disodium N-octadecyl
sulfosuccinamate (Aerosol 18).
An extensive list of emulsifiers together with their HLB values is
given in Kirk-Othmer Encyclopedia of Chemical Technology, Second
Edition, Volume 8, pages 128-130 (1965). From this list it is
possible to select those that either alone or in admixture will
give an HLB value suitable for use in the present invention.
The liquid hydrocarbon emulsions of the present invention using
formamide, formamide-solid amide mixtures, formamide-glycol
mixtures and the like, as the continuous phase will generally
contain the following broad and preferred ranges of components:
Wt. % Concentration
__________________________________________________________________________
Component Broad Preferred
__________________________________________________________________________
Dispersed Phase 75-99 85-98.5 Continuous Phase 0.5-20 0.5-8
Emulsifier 0.25-2 0.5-1 Stabilizing Additive 0.25-5 0.5-1
__________________________________________________________________________
The above ranges are not necessarily attainable without regard to
the specific types of substances selected for use as the initial
components of the emulsion. Thus, where JP-4 jet fuel is the
dispersed phase component and a mixture of formamide containing 20
percent urea constitutes the continuous phase component, the ranges
may be over the entire range above stated; whereas, if JP-4 fuel is
the dispersed phase and formamide containing 35-50 percent urea is
the continuous phase, the selection of the relative amounts of
dispersed phase would require that in producing a stable emulsion,
said emulsion would contain a final concentration of the dispersed
phase toward the lower end of the above-stated ranges while the
continuous phase would be correspondingly toward the higher end of
the amounts specified in the above ranges.
The components of the emulsion can be added in any order desired or
all of them can be added simultaneously as an admixture. Thus, it
is possible to combine the stability additive of this invention
with the hydrocarbon phase and the emulsifiers with the continuous
phase material or to add the stability additive along with the
emulsifier to the continuous phase, and then to add the hydrocarbon
fuel mixture to the continuous phase. Alternatively, with two
emulsifiers, one of which is lipophilic and the other hydrophilic,
the lipophilic emulsifier can be added to the hydrocarbon phase and
the hydrophilic emulsifier added to the continuous phase and then
the two phases can be combined. It is preferred that only a portion
of the hydrocarbon fuel ultimately to become the dispersed phase be
added in the initial emulsification operation, although all of the
continuous phase ultimately to be incorporated into the final
emulsion can be added in the first stage of emulsification. For
example, in producing a gallon (2,500 cc.) of emulsion, the
hydrocarbon fuel can be added to about 60 cc. of the continuous
phase at a rate of about 10 cc. per minute and after the first
minute or two the input of hydrocarbon fuel can be increased by
increments of 10 cc. per minute until a rate of 40 cc. per minute
is reached. The additional rate can then be held at 40 cc. per
minute for about 50 minutes until the emulsion is completed.
Similarly, the methods described in U.S. Pat. No. 3,416,320 or U.S.
Pat. No. 3,458,294 could be used.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The nature of the invention will be further understood when
reference is made to the following examples which include preferred
embodiments which are not to be construed as a limitation of the
invention.
Examples
In all of the following comparative emulsions (all percentages are
weight percent), the base emulsion was composed of JP-4 jet fuel,
as the dispersed phase, 0.4 percent of urea and 1.6 percent of
formamide as the continuous phase, and various percentages of
emulsifiers and stabilizing additives as indicated. All emulsions
were prepared and their characteristics measured at room
temperature, unless otherwise noted. In preparing these emulsions
the amine-ester adduct was added to the continuous phase along with
the emulsifiers while the polyester adduct was added to the
hydrocarbon phase. ##SPC3##
Table II serves to demonstrate that while fuel emulsions tend to be
unstable at low emulsifier levels, this unstability is eliminated
by the emulsion stabilizers of this invention. As can be seen from
comparative emulsions A and B, stability increases with increased
emulsifier concentration. However, emulsifiers are expensive and
even 1 percent of emulsifier A does not stabilize the emulsion. On
the other hand, 0.5 percent of emulsifier A and 0.5 percent of a
less expensive amine ester adduct produces a completely stable
emulsion. This unexpected stabilizing effect is achieved despite
the fact that said stabilizers are not recognized in the art as
emulsifiers and in fact are not effective by themselves as
emulsifiers for the present system.
Example 2 serves to illustrate the use of these additives in other
emulsifier systems and examples 3, 4 and 5 illustrate their use in
conjunction with different concentrations of dispersed fuel.
While particular embodiments of this invention are shown in the
examples, it will be understood that the invention is obviously
subject to the variations and modifications disclosed above without
departing from its broader aspects and, therefore, it is not
intended that the invention be limited to the specific
modifications which have been given above for the sake of
illustration, but only by the appended claims.
* * * * *