[0001] The invention relates to a process for preventing the dissemination of a hydrocarbon
liquid having a free surface into a dispersion of fine liquid droplets under conditions
of shock or stress. It is often desirable to control the extent of misting or dispersion-in-air
of hydrocarbon liquids having rather low flash points. More particularly, hydrocarbon
fuels such as are employed in aircraft are desirably protected from misting under
conditions of shock or stress as produced, for example, during an aircraft crash,
or whenever such fuels are subjected to shock or stress while exposed to an ignition
source. Additionally it is also desirable to control mist formation in hydrocarbon-based
metal cutting fluids employed in metal cutting, grinding and machining operations.
[0002] In U.S. Patent 3,996,023, several polymers suitably employed in preventing the misting
of hydrocarbon fuels are disclosed. Preferred compounds include non-crystalline polymers
substantially devoid of polar groups, especially polymers of ethylenically unsaturated
hydrocarbons such as ethylene, propylene, isobutylene, and butadiene. Polymers formed
by the addition polymerization of alkylene oxides are briefly discussed. In U.S. Patent
3,557,017, ultra high molecular weight oxyalkylene polymers are taught as demulsifiers
and thickeners for hydrocarbon systems used in oil well fracturing. Preferred oxyalkylene
oxide polymers were those derived from propylene oxide.
[0003] Numerous catalyst systems are known for preparation of high molecular weight alkylene
oxides. Illustrative are a combination of ferric halide salts and propylene oxide
disclosed in U.S. Patent 2,706,181, or organoaluminum, organozinc and organomagnesium
compounds taught in U.S. Patent 2,870,100. Improved coordination anionic polymerization
systems include chelated forms of organoaluminum such as disclosed in U.S.Patents
3,219,591; 3,186,958; 3,301,796; and 3,135,705.
[0004] In recent investigations the important contribution of elongation deformation to
polymeric rheological behavior has been identified. It has now been recognized that
various properties of significant commercial application cannot be adequately predicted
by viscometric (shear) flow behavior alone. Often, due to inherent differences in
elongation or tensile deformation versus shear deformation, the corresponding elongational
viscosity and shear viscosity may be related in only the extremely limited case where
the material is Newtonian in both elongation and shear. Because of this recognized
difference between elongational and shear flow, the researcher is not necessarily
able to predict the response to elongational flow of a viscoelastic material based
on knowledge of its shear flow behavior. Such elongational deformation properties
are in fact particularly relevant in imparting improved performance to anti-misting
agents. Because the tensile or elongational viscosity of various materials appears
to be affected by molecular weight considerations, particularly the average molecular
weight and the distribution thereof, as well as by molecular geometry, the elongation
properties of polymeric compounds and therefore the anti-misting properties thereof
are not necessarily predictable on the basis of shear viscosity considerations.
[0005] Another important property of an anti-misting agent is the shear stability of the
material. Application of relatively mild shear should not significantly degrade the
polymer and thereby destroy the polymer's ability to prevent the dispersion of the
hydrocarbon liquid. For example, normal pumping and handling procedures used in transporting
a jet fuel should not cause deterioration of the anti-misting properties of the polymer.
Shear stability is particularly desired in cutting fluids due to repeated use under
conditions of relatively high shear.
[0006] It would be desirable to provide a polymer that is effective in preventing the formation
of hydrocarbon-air dispersions or mists at low levels of concentration, that is highly
soluble in the hydrocarbon liquid, such that even at extremely low temperatures essentially
no precipitate or colloidal state forms, and that is relatively stable and not degraded
by shear forces.
[0007] Accordingly, there is now provided an improved process for preventing the dispersion
of a hydrocarbon liquid having a free surface upon application of shock or stress
comprising adding to the hydrocarbon liquid an effective amount to prevent the dispersion
thereof of a high molecular weight addition polymer comprising polymerized 1,2-epoxybutane.
Also provided is a composition comprising a hydrocarbon liquid and an effective amount
to prevent the formation of a dispersion thereof upon application of shock or stress
thereto of a high molecular weight addition polymer comprising polymerized 1,2-epoxybutane.
[0008] Addition polymers comprising polybutylene oxide, e.g., addition polymers of 1,2-epoxybutane,
useful herein may be prepared by any technique suited to the preparation of extremely
high molecular weight polymers. Examples include the anionic polymerization of U.S.
Patents, 2,870,100 and 3,219,591.
[0009] A preferred catalyst for polymerizing 1,2-epoxybutane to extremely high molecular
weight polybutylene oxide comprises a composition prepared by contacting:
Component A, a compound represented by the formula RR'AlX wherein R and R' each independently
represent an alkyl group of 1 to 4 carbon atoms, and X represents hydrogen or an alkyl
or alkoxy group of 1 to 4 carbon atoms;
Component B, an organic nitrogen base compound selected from secondary nitrogen-containing
compounds having basicity about equal to or less than the basicity of dimethylamine
and having no active hydrogen atoms other than those of the secondary nitrogen;
Component C, a S-diketone; and
Component D, water;
in the molar ratios of
B:A - 0.01:1 to 2.5:1
C:A - 0.1:1 to 1.5:1
D:A - 0.01:1 to 1.5:1
provided that when the molar ratio of (C + 2D):A is greater than 3:1, the B:A molar
ratio is at least 1:1.
[0010] The preferred catalyst is more particularly defined as follows. Component A is a
compound represented by the formula RR'AlX wherein R and R' each independently represent
an alkyl group of 1 to 4 carbon atoms, and X represents hydrogen or an alkyl or alkoxy
group of 1 to 4 carbon atoms. In a preferred mode, X represents an alkyl group. In
a more preferred mode, R, R' and X all represent the same alkyl group and most preferably,
the compound is triethylaluminum. Examples of suitable compounds are trimethylaluminum,
triethylaluminum, triisobutylaluminum, tri-n-propylaluminum, tri-n-butylaluminum,
diethylaluminum hydride, dipropyl- aluminum hydride, diisobutylaluminum hydride, diethyl
ethoxy aluminum, and diisobutyl ethoxy aluminum. In practice, Component A is normally
supplied in a solution of a hydrocarbon or other solvent.
[0011] Component B is an organic nitrogen base compound selected from secondary nitrogen-containing
compounds having basicity about equal to or less than the basicity of dimethylamine
and having no active hydrogen atoms other than those of the secondary nitrogen. By
"active hydrogen atoms" are meant Zerewitinoff hydrogen atoms (see J. Am. Chem. Soc.,
49:3181 (1928)) which initiate alkylene oxide polymerization as are found on hydroxyl,
thio or primary and secondary amine functional groups. Such secondary amines are commonly
those bearing electron-withdrawing groups in close proximity to the nitrogen atom
such as carbonyl groups, phenyl rings, cyano groups, halo groups, carboxylic acids
or ester groups, and other such groups that have strong electron-withdrawing effects
on the secondary amine. For example, such compounds are N-alkyl or -aryl amides, arylalkylamines,
diarylamines, and other weak bases. Secondary amines having a pK
b of greater than 4 are suitable and those having pK
b of greater than 6 are preferred. Examples of suitable secondary amines are dimethylamine,
diethylamine, N-methylaniline, N-methyl--p-nitroaniline, N-alkylacetamide, N-arylacetamide,
succinimide, diphenylamine, phenothiazines, and phen- oxazines. Especially preferred
are phenoxazine, phenothiazine and N-acetamide.
[0012] The strengths of organic bases are compiled for a large number of such bases in the
IUPAC work by D. D. Perrin, "Dissociation Constants of Organic Bases in Aqueous Solutions",
Butterworths (London, 1965). For most secondary organic amines not listed therein,
relative base strength may be deduced by examining the value noted for a structurally
related amine then estimating the effect of structural differences on the base strength.
For example, conjugation of the amino group with electron-withdrawing groups lowers
the base strength of the amino group. The effects of structural changes in organic
amines are discussed in great detail in numerous works, for example in "The Chemistry
of the Amino Group", S. Patai, Ed., Chapter 4, "Basicity and Complex Formation" by
J. W. Smith, pp. 161-204, Interscience (New York, 1968).
[0013] One simple method for determining whether a secondary amine is less basic than dimethylamine
is to employ both in side-by-side preparation of the catalyst, use the resulting catalyst
in polymerization of a monomer such as propylene oxide, and then determine the intrinsic
viscosities of the resulting polypropylene oxide products. If the intrinsic viscosity
of the product derived from the catalyst prepared with dimethylamine is lower than
the one from the other amine, then the other amine may be considered less basic than
dimethylamine.
[0014] The amount of Component B to be employed may be expressed in the molar ratio of Component
B per mole of Component A. The lower amount is suitably about 0.01, preferably 0.05
and most preferably 0.1. The upper amount is suitably 2.5, preferably 1 and most preferably
0.5. The optimum molar ratio of B:A for producing very high molecular weight polyethers
is about 0.25:1.
[0015] Component C is selected from β-diketones or the tautomeric enol form thereof. Suitable,
for example, are 2,4-pentanedione, 2,4-hexanedione, 3,5-heptanedione, 1-phenyl-1,3-butanedione,
ethylacetylacetate, and similar materials. Examples of numerous suitable p-diketones
are described in U.S. Patent 2,866,761. Preferred for use as Component C is 2,4-pentanedione
because of its relative availability.
[0016] For the amount of Component C to be employed, expressed as moles of C per mole of
A, a lower amount is suitably 0.1 and preferably 0.2. As an upper amount the ratio
is suitably 1.5 and preferably 0.8. The optimum molar ratio of C:A is about 0.5:1.
[0017] Component D is water and is suitably employed in a lower amount of about 0.1, preferably
0.3 and more preferably 0.4, mole of D per mole of A. The upper amount is suitably
1.5, preferably 1.1 and more preferably 1.0, mole of D per mole of A. The optimum
ratio of D:A is 0.5 to 0.8:1.
[0018] The above components are employed such that when the molar ratio sum of (C + 2D):A
is greater than 3:1, then the B:A molar ratio is at least 1:1. Preferably the components
are combined in the ratio where (B + C + 2D):A is less than or equal to 3:1 and more
preferably less than 2:1. In one embodiment, the following molar ratios are employed
to form a catalyst which when contacted with a vicinal alkylene oxide produces a polyether
of a very high intrinsic viscosity: B:A - about 0.25:1; C:A - about 0.5:1; and D:A
- about 0.6:1. In a second embodiment, a catalyst is prepared which will give moderately
high intrinsic viscosity polyethers when contacted with vicinal alkylene oxides according
to the process described herein. The molar ratios in this second embodiment are: B:A
- about 2.5:1; C:A -about 0.5:1; and D:A - about 0.5:1. The most preferred species
of the catalyst are prepared in the form where B is phenothiazine or N-methylacetamide
or C is 2,4-pentanedione.
[0019] Additional components may be present in the catalyst and certain additives have in
fact been found to provide improved catalytic performance. In particular, a small
but effective amount of a Lewis base such as a tertiary amine or an aliphatic ether
capable of forming a complex with Component A may be added to the catalyst mixture.
Preferred Lewis base compounds are the aliphatic ethers, most suitably cyclic aliphatic
ethers such as tetrahydrofuran or dioxane. These compounds are employed in minor amounts
sufficient to form a complex with Component A in the presence of the remaining components
of the catalyst. Suitably the aliphatic ether is present in molar amounts from 1 to
6 for each mole of Component A.
[0020] Additional components may also be present in the catalyst if desired. For example,
ether alcohols such as 2-methoxyethanol, 2-ethoxyethanol, 2-butoxyethanol, 2-methoxypropanol,
2-ethoxypropanol, and lower alkyl monoethers of diethylene glycol or dipropylene glycol
may be added to the catalyst in purified form as an aid in rendering the catalyst
soluble in various solvents.
[0021] The catalyst formation and polymerization are carried out according to known techniques
such as those of U.S. Patents 3,186,958 and 3,219,591. Suitably the catalyst is prepared
by contacting the components in the desired ratios in any of the common hydrocarbon
or chlorinated hydrocarbon diluents employed for organic reactions so long as they
do not bear Zerewitinoff hydrogen atoms. Suitable diluents, for example, are hexane,
toluene, benzene, styrene, decane, chlorobenzene, trichloroethane, perchloroethylene
and the like. A preferred diluent is the hydrocarbon fluid, e.g., fuel or cutting
oil, to which the polymer will be later added.
[0022] While the catalyst components may be combined in any order desired, because it has
been found most effective to employ polymers of relatively high intrinsic viscosity
in the present invention, it is preferable, particularly where the catalyst consists
essentially of only Components A, B, C and D, that Components B, C and D be first
combined by mixing them well and thereafter adding Component A to the mixture of the
other three components. It is also convenient to prepare the catalyst in situ in the
butylene oxide monomer to be polymerized. This is most preferably done by combining
Components B, C and D in a solvent with the desired quantity of butylene oxide monomer
and thereafter adding Component A to the mixture after which the polymerization is
allowed to proceed. In this fashion, the butylene oxide monomer acts as a cosolvent
for the catalyst prior to initiation of the polymerization. Butylene oxide for polymerization
and use herein may first be purified as by the technique described in U.S. Patent
3,987,065.
[0023] After preparation of the high molecular weight polymer, the catalyst may be "killed"
or deactivated by addition of a reactive hydroxyl compound such as water, alcohols
or organic acids. Where the polymer is prepared in the hydrocarbon fluid, such as
jet fuel, the catalyst may be effectively "killed" by exposure to the atmosphere for
a short time. It is believed that water vapor present in the air is sufficient to
deactivate the catalyst.
[0024] The polymer employed in the instant process comprises polybutylene oxide. Where the
hydrocarbon liquid is a fuel, for example, a jet fuel for gas turbines, it is highly
desirable that the polymeric anti-misting additive not detrimentally form a precipitate
or colloidal state, particularly at low temperatures. The temperature at which such
formation occurs, e.g., the theta temperature of the solution, is desirably less than
-50°C. Further discussion of theta temperature as well as a more detailed description
of suitable components of fuels for gas turbines is contained in U.S. Patent 3,996,023.
[0025] In other applications such as where the hydrocarbon liquid is a cutting fluid, extremely
low theta temperatures are not as necessary. Accordingly, a theta temperature of greater
than -50°C may be suitable. At the same time certain hydrocarbon liquids, especially
cutting fluids, may contain substantial amounts of a non-hydrocarbon component, such
as an alkylene glycol, an alkylene glycol ether or even water. Therefore under conditions
where an extremely low theta temperature is not requisite or the hydrocarbon liquid
additionally comprises non-hydrocarbon components, the polybutylene oxide anti-misting
agent may include comonomers of additional alkylene oxides. Compatibility with fluids
consisting essentially of hydrocarbon liquids is impaired by use of excessive amounts
of lower alkylene oxide comonomers such as propylene oxide and especially ethylene
oxide. Accordingly, only relatively minor amounts of such lower alkylene oxide comonomers
are suitably employed where compatibility with hydrocarbon liquids, particularly a
jet fuel, is desired. Higher vicinal alkylene oxides such as l,2-epoxypentane, 1,2-epoxyhexane,
etc., or glycidyl ethers such as n-butyl glycidyl ether, tertiarybutyl glycidyl ether,
n-octyl glycidyl ether, etc., may be employed as comonomers without as significant
a detrimental effect on compatibility with the hydrocarbon fluid.
[0026] The preferred anti-misting agent for use in hydrocarbon fuels consists essentially
of polymerized 1,2-epoxybutane.
[0027] While in most applications the catalyst residue may be left in the polymer solution
without disadvantageous results, it is also possible to remove catalyst residue. For
example, the aluminum compound which exists as a hydroxide or oxide after deactivation
is only sparingly soluble in hydrocarbon liquids, particularly at low temperatures
and may be removed by filtration. This process may be particularly desired where the
polymer solution is employed as a jet fuel.
[0028] Conventional approaches to molecular weight measure of polyethers employed herein
are often not appropriate. This is usually due to plugging effects because of the
propensity of high molecular weight polyethers to "thicken with shear". It is especially
troublesome with such techniques as gel permeation chromatography for molecular weight
estimation. Nonetheless, dissolved concentrations of less than 0.06 weight percent
of the polyethers generally do not undergo the shear thickening phenomenon.
[0029] In view of the difficulties in employing gel permeation chromatography to compare
the relative molecular weights of polyethers produced herein, the alternate method
of comparing intrinsic viscosities was instead employed. Intrinsic viscosity [n] is
related to molecular weight by the equation:

wherein K is a constant, M is molecular weight and a is another constant (correlated
to the degree of configurational coiling in the architecture of an involved polymer).
[0030] The value of [q] is determined by plotting the measured specific viscosity divided
by concentration of polymer in solution (η
sp/conc.) vs. conc. and extrapolating to zero concentration. It is dependent upon the
solvent and temperature used during measurements. Toluene is a good solvent for the
purpose. And, 100°F (38°
C) is an apt temperature at which to measure η
sp, per the equation:

wherein t is the efflux time of solution and t is the efflux time of solvent.
[0031] Efflux times are readily measurable in an Ostwald viscometer taking values of solutions
at four different concentrations. Usually 1-2 g of the polymer solution (≅30 percent
solids) is dissolved in toluene overnight with stirring. It is then volumetrically
diluted to =100 ml. Aliquots of 2 ml, 5 ml, and 15 ml from this stock solution are
then further diluted to: 10 ml, 10 ml, and 25 ml, respectively, with more toluene.
Efflux times are then measured on the stock solution, each of the three solutions
and on toluene. With the viscometer employed, toluene had a t
0 of 30.6 seconds, while t for the most concentrated solution being tested is best
kept below 200 seconds by adjusting concentration.
[0032] Concentration for each diluted solution is simply calculable from the concentration
of the stock solution. Three samples of this stock solution are then ordinarily weighed
into aluminum dishes from which they are devolatilized in a vacuum oven at 100°C overnight
(under a normal line vacuum). The aluminum dishes are then reweighed to determine
the weight of pure polymer remaining. Concentration is then calculated as weight percent.
This method of determining concentration is quite convenient since concentration normally
associated with measuring [q] is reported in the literature as "grams/deciliter".
Therefore, values for concentration so determined are higher by a factor corresponding
to the density of toluene (0.8502 g/cc at 38°C). Values forx η
sp/conc. and [η] are correspondingly, therefore, lower by this factor also. Consistent
with this, the herein given [q] values are corrected for the density factor, with
[η] being herein reported in units of dl/g.
[0033] Of particular value in the present invention as anti-misting agents in hydrocarbon
fuels are polymerized 1,2-epoxybutanes having relatively high intrinsic viscosity,
e.g., intrinsic viscosities in toluene at 38°C of at least and preferably 2 and up
to 30. Because of the greater effectiveness toward preventing misting of higher molecular
weight polybutylene oxide polymers, such polymers of higher molecular weight may be
employed in reduced concentrations thereby resulting in more economical operation.
Preferred are concentrations by weight from 0.05 percent to 1 percent, and preferably
from 0.1 percent to 0.5 percent by weight.
[0034] In other applications, such as the prevention of cutting oil misting, polybutylene
oxide polymers of reduced molecular weight and therefore intrinsic viscosity may be
more suitably employed in order to avoid the necessary reduction in polymer effectiveness
due to shear degradation of the polymer under long-life service conditions. At the
same time, increased levels of polymer may be employed in order to offset the loss
in effectiveness due to decreased molecular chain length. Preferred for use in cutting
fluids are amounts of polymer by weight from 0.1 percent to 5.0 percent, most preferably
from 0.2 percent to 1.0 percent.
[0035] In particular regard to hydrocarbon fuels, it should be noted that while the extremely
high molecular weight butylene oxide polymers herein employed are highly shear stable,
they will in fact degrade under application of sufficiently high shear. Accordingly,
it is possible, employing mechanical shearing or other treatment, to degrade the polymer
and thereby render the fuel atomizable or dispersible prior to injection into the
gas turbine.
[0036] The following examples are provided as further illustrations of the invention.
Example 1 - Cutting Oil
[0037] Twenty-five grams of 1,2-butylene oxide, Mobilmet 308® metal cutting and working
oil available commercially from Mobil oil Corporation (225 g), phenothiazine (1.17
g) and 2,4-pentanedione (1.18 g) are combined in a glass reactor. A sample is removed
for water analysis and found to contain 86 ppm water. Additional water (0.19 g) is
added by syringe to produce a total water content of 0.21 g, triethylaluminum (14.8
percent in hexane) (18.0 g) is added under a nitrogen blanket. The reactor is sealed
and placed in a tumbling cage inside a warm water bath at about 86°C for 44 hours.
[0038] After polymerization, cutting oil containing polymerized 1,2-butylene oxide is tested
for mist formation. A solution of Mobilmet 308 cutting oil containing 0.25 percent
by weight of the above polymer is prepared by rapidly stirring a portion of the above
product in the cutting oil. Viscosity of the solution as determined by the cone-plate
method is 0.055 Pa-S (55 cps). Unmodified oil has a viscosity of 0.051 Pa
'S (51 cps).
[0039] Mist control is tested.by comparing mist formation upon injecting air (0.38 MPa;
40 psig) through a drop tube immersed in the fluid to be tested. Mist formation is
noted by visual reference and assigned values of no-mist, low-mist or fail. The fluid
is then exposed to high shear in a laboratory blender for one hour and retested for
anti-mist properties. The cutting oil containing 0.25 weight percent polybutylene
oxide showed no mist formation even after blending for one hour. Untreated Mobilmet
308 produced large amounts of mist under all testing conditions.
Example 2 - Jet Fuel
[0040] An additional quantity of polymerized 1,2-butylene oxide is prepared in hexane solvent.
The catalyst employed is prepared by combining in a dry box under nitrogen atmosphere
at ambient temperature with stirring, hexane solutions of triisobutylaluminum (0.015
mole) and phenothiazine (0.004 mole) (total hexane is about 40 ml). Tetrahydrofuran
(0.090 mole) is added dropwise with stirring over a period of about 10 minutes at
reduced temperature of 0°C-10°C. Next, water (enough to provide 0.006 mole total)
is added dropwise over a period of 10 minutes, followed by acetylacetone (0.006 mole)
which is added dropwise over a period of 5 minutes. The reaction mixture is stirred
for 1 hour and transferred to a Parr bomb reactor and diluted with hexane (100 g)
and toluene (30 g). After aging by heating and stirring under nitrogen for one hour
at 95°C, catalyst preparation is complete.
[0041] The polymer is formed by adding about one mole of 1,2-butylene oxide to the Paar
bomb in increments at 75°C over a one-hour period. The reaction mixture is stirred
at 75°C for 5 hours and then cooled. Evaporation of solvent leaves the desired polymer,
a light amber colored rubbery solid.
[0042] Jet fuel (Jet A) containing 0.2 percent by weight of polymerized 1,2-butylene oxide
prepared employing the catalyst prepared according to the above process is tested
for anti-misting properties by means of the Flammability Comparison Test Apparatus
(FCTA). The testing device consists of a compressed air source connected to a sonic
orifice and a diffuser cone. Fuel is supplied through a metal tube terminating in
the airstream at a point selected to produce high shear to the fuel entering the airstream.
The air fuel mist thereby prepared is passed over a propane torch flame.
[0043] Mist ignition is determined by fuel type (including the presence or absence of an
anti-misting agent), the fuel flow rate and the air velocity.
[0044] Passing, marginal and fail grades are assigned according to visual examination of
the flame propagation. No propagation ahead of the torch constitutes a passing grade.
Propagation ahead of the torch but not to the diffuser cone constitutes a marginal
grade. Propagation ahead of the torch all the way to the diffuser cone constitutes
a failing grade.
[0045] Jet A fuel at 27°C which is not treated with an anti-misting agent consistently fails
under all conditions of air velocity above 40 m/sec at fuel flow rates above 10 ml/sec.
To the contrary, when modified by addition of 0.2 weight percent of polymerized 1,2-butylene
oxide, no consistent failure is observed at fuel flow rates less than 16 ml/sec at
air velocities less than 70 m/sec.
[0046] The above test demonstrates that polymerized 1,2-butylene oxide is an effective anti-misting
agent which demonstrates surprisingly good effectiveness at preventing the formation
of a hydrocarbon fuel/air dispersion even at extremely low concentrations.