Note: Descriptions are shown in the official language in which they were submitted.
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WAX CRYSTAL MODIFIERS FORMED
FROM DIALKYL PHENYL FUMARATE
FIELD OF THE INVENTION
The invention relates to wax crystal modifier compounds and their
use in improving the flow characteristics of oleagenous fluids especially oils
such as crude oil, lubricating oil, fuel oil and distillate oil.
BACKGROUND OF THE INVENTION
Many oils, especially lubricating oils, fuel oils, distillate oils, and
crude oils, contain straight chain and branched alkanes that crystallize as
their
temperature is lowered. Alkane (wax) crystallization in oleagenous fluids can
affect the fluid's ability to flow. This may result in problems such as
pipeiininig
diffculties in crudes. The temperature at which wax begins to crystallize in
an
oil is called the wax appearance temperature (WAT) of the oil. Polymeric aad
copolymeric additive compounds can be combined with an oil in order to
improve an oil's flow properties. Such additives, known as wax crystal
modifiers, are capable of altering the crystallization properties of waxes
present
in oil. It is believed that wax crystal modifiers improve an oil's flow
properties
by suppressing the WAT or by modifying the growth of wax crystals in the oii
so
that the resulting crystals are small enough so as not to affect the oil's
flow
properties or both. Among these compounds, dialkyl fumarate vinyl acetate
copolymer with C6 to C, 8 aUcyls is particularly popular.
There remains a need, though, for wax crystal modifiers that are
capable of improving the flow properties of oleagenous fluids, especially oils
such as lubricating oils, crude oils, fuel oils, and distillate oils.
C~NFIRRI~Ai lON COPY
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SUMMARY OF THE INVENTION
In one embodiment, the invention is a copolymer of dialkyl phenyl
fwmarate and at least one compound selected from the group consisting of vinyl
acetate, styrene, C3 to C3o a olefin, ethylene, and carbon monoxide.
In another embodiment, the invention is a flow improver for use in
an oleagenous fluid comprising one or more copolymers from dialkyl phenyl
fumarate wherein the alkyl is straight chain or branched and ranges in size
from
C6 to Clso and at least one compound selected from the group consisting of
vinyl
actate, styrene, C3 to C3o a olefin, ethylene, and carbon monoxide.
In another embodiment, the invention is a method for improving
the flow properties in an oleagenous fluid comprising: adding to a major
amount
of the oleagenous fluid a minor amount of at least one copolymer of dialkyl
phenyl fumarate having C6 to Clso straight chain or branched alkyl and at
least
one compound selected from the group consisting of C3 to C3o alpha olefin,
ethylene, styrene, and carbon monoxide.
In another embodiment, the invention is a method for forming a
copolymer comprising combining under free radical polymerization conditions a
C6 to Clso dialkyl phenyl fiunarate in a solvent selected from the group
consisting of hexane, benzene, cyclohexane, and heptane; at least one compound
selected from the group consisting of ethylene and carbon monoxide; and an
initiator selected from the group consisting of t-butyl peroxypivalate,
benzoyl
peroxide, t-butylper benzoate, and t-butyl peroxide, for a time, temperature,
and
pressure sufficient to form the copolymer.
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In another embodiment, the invention is a method for forming a
copolymer comprising:
combining C6 to C,SO dialkyl phenyl fumarate; a compound
selected from the group consisting of vinyl acetate, styrene, and C3 to C3a
alpha
olefin; and an initiator selected from the group consisting of ditertiary-
butyl
peroxide, 2,S-dimethyl-2,5-di-tertiary-butylperoxyhexane, di-cumyl peroxide,
benzoyl peroxide, tertiary-butyl peroxypivalate, tertiary-butyl perbenzoate,
azobisisobutyronitrile, and l, l'-azobis(cyanocyclohexane) under free radical
polymerization conditions for a time and at a temperture sut~cient to form the
copolymer.
DETAILED DESCRIPTION OF THE INVENTION
The invention is based on the discovery that copolymers can be
formed having the formula AB wherein A is formed from dialkyl phenyl
fumarate and B is formed from at least one compound selected from the group
consisting of vinyl acetate, styrene, C3 to C3a a-olefin, ethylene, and carbon
monoxide. The invention is also based on the discovery that such copolymers
are capable, when used in an effective amount, of improving flow properties
like
viscosity in oleagenous fluids, especially lubricating oils, fuel oils,
distillate oils,
and crude oils. While not wishing to be bound by any theory, it is believed
that
the copolymers of the invention improve the flow properties in oleagenous
materials because they function as wax crystal modifiers.
The copolymers of the present invention are represented by the
formula AB wherein A is formed from dialkyl phenyl fumarate (DAPhF). As
such, these copolymers have the structure:
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H H
C I ~ B-~
C=O C=O
O O
/ ~ /
\ \
R R
Comonomer B is formed from at least one compound selected from
the group consisting of vinyl acetate, styrene, C3 to C3o a-olefin, ethylene,
and
carbon monoxide. The term copolymer is thus used in accordance with its more
general meaning where the polymer comprises two or more different monomers.
R represents independently selected straight chain or branched
alkyl groups of from about Cg to about C,so carbon atoms. Preferred alkyls
range
from about Cg to about C4o.
Copolymers of the present invention are prepared from dialkyl
phenyl fumarate esters. Such esters may be prepared by reacting fumaric
chloride with an alkyl phenol in the presence of triethylamine.
The copolymers of this invention can be synthesized using free-
radical polymerization. In case of copolymers of dialkyl phenyl fumarate with
monomers like vinyl acetate, styrene or a-olefins, polymerizaton can be
carried
out in a standard glass reactor. Typically, inhibitors from the monomers such
as
vinyl acetate or styrene are removed via an inhibitor remover column. The
purified monomers are then placed in tubes with the DAPhF ester monomers.
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The tubes are capped with septa and flushed with nitrogen for one to four
hours
before polymerization. The relative amounts of monomer A: monomer B in the
copolymer can be varied from 5:95 to 95:5 mole percent.
The reactions can be carried out in solvent or neat. Whenever a
solvent is used, solvent should be nonreactive or noninterfering in free
radical
polymerization can be used. Such solvents include benezene, cyclohexane,
hexane, heptane, etc. Solvents like xyiene or oil can also be used. The
solvent
may be flushed with argon or nitrogen and then added to the monomers.
The polymerization reactions can be carried out from 40 to 100°C
depending on reactivity of monomers, half life of the initiator used, or the
boiling point of the solvent. The reactions are carried out under inert
atmosphere. The solvents are brought to the reaction temperatures, and the
initiator (dissolved in the appropriate solvents) is added to the solution.
Typical
free radical initiators includes dialkyl peroxides such as ditertiary-butyl
peroxide, 2,5-dimethl-2,5-di-tertiary-butylperoxyhexane, di-cumyl peroxide;
alkyl peroxides such as benzoyl peroxide; peroxy esters such as tertiary-butyl
peroxypivalate, tertiary-butyl perbenzoate; and also compounds such as azo-bis-
isobutyronitrile. A free radical initiator with an appropriate half life at
reaction
temperature of from about 60°C to about 140°C can be used. For
the reactions
done neat (without solvent), both monomers and initiator are loaded together,
flushed with nitrogen, and then brought to reaction temperature. The mixture
is
stirred for a time sufficient to ensure that a substantially homogeneous
mixture is
obtained. The time and temperature if the reactions can be varied. Reactions
can be stopped after 1 hour to 48 hours. The resulting copolymer can be
isolated
by precipitating the polymer in non-solvent (solvent in which polymer is not
soluble). The product is then dried in vacuum oven.
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When using monomers that are gases at room temperature, such as
ethylene or carbon monoxide, the reactions are generally carried out in high
pressure reactors such as autoclave reactors. In such copolymerizations, the
reactor is initially charged with monomers like dialkyl phenyl fumarate
dissolved
in solvent like hexane, and initiator is added. Typical initiators include t-
butyl
peroxypivalate, benzoyl peroxide, t-butylper benzoate, t-butyl peroxide. The
reactor is sealed and purged with purified nitrogen. The reactor is then
pressurized with carbon monoxide and/or ethylene monomer to appropriate
pressure. The pressure can range from about 100 to about 3000 psig. The
preferred polymerization pressure ranges from about 500 to about 1200 psig.
Reaction temperature can range from about 40 to about 200°C,
depending on
solvent and the initiator half life. The pressure of the reaction can be
maintained
for few hours to 48 hours depending on monomer reactivity, solvent, and the
initiator half life. The reactor is allowed to cool to room temperature and is
then
depressurized. The solvent is removed on rotary evaporator to obtain the
product.
The products are generally characterized by standard techniques
like FTIR, NMR, and GPC.
According to the present invention, wax crystal modifiers are
added to the oleagenous fluid in a concentration ranging from about IO to
about
50,000 ppm based on the weight of the oleagenous fluid. The preferred
concentration is about 500 ppm. Non-limiting examples of oleagenous fluids
containing paraffinic (alkane) species that benefit from the addition of the
compounds of the invention include crude oils, i.e., oils as obtained from
drilling
and before refining or separating, fuel oils such as middle distillate fuel
oil, and
oils of lubricating viscosity ("lubricating oils").
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The oleagenous compositions and additive compounds of the
present invention may be used in combination with other co-additives such as
ethylene-vinyl acetate copolymers, fumarate-vinyl acetate copolymers, and
mixtures thereof.
It is believed that copolymer flow improvers of this invention when
present in an effective amount are capable of inhibiting the nucleation and
growth of wax crystals in oleagenous fluids such as oils. While not wishing to
be bound by any theory, it is believed that the presence of an effective
amount of
copolymer results in a lowering the oil's wax appearance temperature because
the copolymer molecules are sufficiently similar to the paraffinic crude
species
to incorporate themselves into growing wax crystals. Once incorporated, it is
believed that the polymeric nature of the flow improver, i.e., its
"branchiness"
and high molecular weight, prevent the further addition of the crude's
paraffinic
species to the crystal. The presence of the copolymer in the growing wax
crystal
is also believed to alter the crystals' morphology by inhibiting growth that
naturally tends towards undesirable large flat platelets. Such platelets are
believed to result from the interlocking, intergrowth, and agglomeration of
nucleated wax crystallites. Such changes in crystal shape resulting from
copolymer incorporation greatly diminish the wax crystals' ability to
interlock,
intergrow, and agglomerate.
In the practice of the invention, it is desirable to first deterniine the
molecular weight distribution of the paraffinic species present in the
oleagenous
fluid. It is believed that the compounds of the present invention are most
effective when the molecular weight distribtuion of the alkyls present in the
fumaric species of the copolymer is approximately the same as the molecular
weight distribution of the oil's paraffinic species.
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.g.
While the compounds of the present invention are useful in all
olegenous fluids containing paraffmic species, the preferred compound will
depend on the type of fluid used.
For lubricating oils, for example, flow improvement is needed at
temperatures much lower than are ordinarily required for crude oil
transportation. Consequently, copolymers with alkyls in the fumarate species
ranging from about C12 to about C,4 and molecular weights ranging from about
2000 to about 100,000 are preferred. In crude oils, compounds of reduced
solubility are required, and the preferred compounds contain alkyls ranging
from
about Cis to about Cao and molecular weights ranging from about 2,000 to about
50,000. For distillate oils, preferred copolymers contain alkyls ranging from
about C,o to about C22 and have molecular weights ranging from about 2,000 to
about 20,000.
The invention is further described in the following non-limiting
examples. In these examples, alkyl chain lengths are sometimes represented by
a
range of carbon and hydrogen atoms, such as C24-2aHa9-57~ ~ such cases, the
alkyl groups present in the fumaric species of the inventions monomers,
polymers, and copolymers are random mixtures of alkyl groups ranging in size,
approximately, over the entire range.
EXAMPLES
Example 1 ~ Reaction of fumaric chloride and dodecyl phenol.
Into a round bottom flask, 16.95g (0.065 mole) of dodecyl phenol
was placed with 325 mL toluene. Into this solution was added 30 mL of triethyl-
amine. 5.2g (0.034 mole) of fumaryl chloride diluted with 25 mL of toluene was
then slowly added over a period of 1 hour at room temperature. The mixture
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was heated to 80°C for 4 h, cooled to room temperature, and poured into
200 mL
5% HC 1. The solution was extracted with ether and dried with NaHC03. The
solvents, ether and toluene, were removed on a rotary evaporator to obtain
18.4
of the product. An IR spectrum of the product showed the absorption peak due
to ester carbonyl at 1741 cm ~ and the double bond peak at 1647 crri' . The
product also showed peaks at 1604 and 1593 cm ~ due to aromatic rings. 13C
NMR of the product showed the double bond absorption peak at 134.0 ppm
(-HC=CH-, carbon) and the carbonyl ester peak at 163 ppm.
R
C1 O
H C=O H C~
Triethylamine
-C + R ~ ~ OH ----; C C
C-O H ~-O H
O
C1
R
Example 2' The synthesis of dialkvl phenyl fumarate monomer (C~oPhF
C3o+ olefin alkylated phenol was synthesized by reaction of phenol
with C3o+ alpha olefin using a strongly acidic resin (obtained from Aldrich,
Inc.,
Milwaukee, WI under the tradename AMBERLYST 15TM) comprising divinyl
benzene-crosslinked polystyrene, to which sulfonic groups are attached, as a
catalyst. C3a+ phenol fumarate ester was synthesized using a procedure similar
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to that used to synthesize dodecyl phenol fumarate. An IRspectrum of the
product showed absorption peaks due to ester carbonyl at 1757 and 1710 clri t
and the double bond peak at 1641 cm t. The product also showed a peak at 1606
cm ~ due to an aromatic ring. The 13C NMR spectrum of product showed the
double bond absorption peak at 134.0 ppm (-HC=CH-, carbon) and the carbonyl
ester peak at 163 ppm. The aliphatic region of the spectrum suggests that
alkyl
chains are substantially linear.
Example 3' The synthesis of dialk r~l phenyl fumarate monomer C24-2RPhF
CZa-ZS+ olefin allrylated phenol was synthesized by reaction of
phenol with C24_2g+ alpha olefin using a strongly acidic resin (obtained from
Aldrich, Inc., Milwaukee, WI under the tradename AMBERLYST 15TM)
comprising divinyl benzene-crosslinked polystyrene, to which sulfonic groups
are attached, as a catalyst. C2a-so+ phenol fumarate ester synthesized using a
procedure similar to that used to synthesize dodecyl phenol fumarate. An IR
spectrum of the product showed absorption peaks due to ester carbonyl at 1746
and 1710 crri' and the double bond peak at 1645 crri'. 'The product also
showed
a peak at 1605 cm 1 due to an aromatic ring. The 13C NMR spectrum of product
showed the double bond absorption peak at 134.0 ppm (-HC=CH-, carbon) and
the carbonyl ester peak at 163 ppm. The aliphatic region of the spectrum
suggests that alkyl chains are substantially linear.
Example 4~ The synthesis of dialk~ phenyl fumarate/carbon monoxide copolymer
A 300 mL autoclave engineer's reactor was charged with 2.5 g of
dialkyl phenyl fumarate (C3oPhF) dissolved in 150 mL n-hexane and 0.606 g of a
75% solution of t-butyl peroxypivalate in mineral spirits. [t-Butyl peroxy-
pivalate has a 10-hour half life 55°C in a 0.2 M benzene solution
(Swern,
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.. Organic Peroxides, John Wiley and Sons, 1970, Vol. 1 pp 82, 87)]. The
reactor
was sealed and purged with purified nitrogen. The reactor was then pressurized
with carbon monoxide to 700 psig. The temperature was raised to 66°C
while
stirring, and the pressure was maintained for 24 hours. The reactor was
allowed
to cool to room temperature and was then depressurized. 'Then hexane was
removed on a rotary evaporator leaving 3.65g of product. An IR spectrum of the
product showed the ester carbonyl peak at 1757 cm 1. 13C NMR of the product
was recorded in CDC13 using chromium {III) acetylacetonate ("Cr(acac)3") as a
relaxation agent, following quantification of the spectrum. ~3C NMR of this
product showed the disappearance of the double bond peak at 134 ppm and the
monomer carbonyl peak at 163 ppm. The product contained two types of
carbonyls (multiple peaks around 210 ppm and 172 ppm). The relative
integration of the carbonyls is in the product suggested that there was 3.4
mole
CO incorporation from carbon monoxide in the copolymer. GPC of the
product was recorded in THF using polystyrene standards. GPC of the product
showed that the polymer had a peak molecular weight of 4300.
Examples 5 through 9' Synthesis of Dialkyl Fumarate with Vinyl Acetate
Copolymers of dialkyl phenyl fumarate with vinyl acetate were
synthesized with R groups of C~2H25, CZa-28, Ha9-57~ C3oW . Such copolymers
have the structure
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( I I I
C---C C- C
I__ I_ ~ I
I I i
0 o c~
I
/ / CH3
I I
\ \
R R
R = C 12H25, C30H61 ~ Or C24-28H49-57
Copolymers were formed using free-radical polymerization
techniques as follows:
Hydroquinone inhibitor was removed from the vinyl acetate by
passing it through an inhibitor remover column. The purified vinyl acetate was
placed in tubes with the dialkyl phenyl fumarate ester monomers. The tubes
were capped with septa and flushed with nitrogen for one hour. The solvent was
flushed with nitrogen and added to the tubes containing the monomers. The
solutions were brought to their reaction temperatures, and the initiator
(dissolved
in the appropriate solvents) was added to each monomer solution. For the runs
done neat (without solvent), both monomers and initiator were loaded together,
flushed with nitrogen, and then brought to reaction temperature. The mixtures
were stirred overnight. The next day, the polymer solutions were precipitated
in
methanol and vacuum dried.
Table 1 sets forth copolymerization reaction details. 3%
azobisisobutyronitrile is available from Aldrich, Inc., Milwaukee, WI under
the
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tradename AIBNTM, and 3% [ 1,1'-azobis(cyanocyclohexane)] is an available
from DuPont Chemicals, Wilmington, DE under the tradename V-88TM.
TABLE 1
Example Monomer Reaction Wt% Reaction
Number Monomers Ratio Solvent InitiatorTem . C
C~zPhF/VA 50/50 wt% Neat 3% AIBN 65
6 CizPhF/VA 50/50 wt% Chloroform3% AIBN 65
7 C3oPhF/VA 7/93 wt% Neat 3% V-88 76
8 CzzsPhF/VA 50/50 wt% Chloroform5% AIBN 62
9 CzzsPhF/VA 50/50 wt% Neat 5% AIBN 76
CiZPhF = Didodecylphenol fumarate
C~PhF = Di[p-alkyl (C3o) phenyl] fumarate
C~.2sPhF = Di[p-alkyl (CZa-28)phenyl] fumarate
Table 2 sets forth characterization results for these copolymers.
TABLE 2
Example Mole Ratio GP C
Number b NMR Peak MW Mn Mw Mw/Mn
4,660 4,500 7,370 1.6
6 1,?90 1,570 2,020 1.3
7 31/69 22,634 19,387 57,222 2.95
8 40/60 4,976 4,346 6,185 1.42
9 14,390 10,100 23,700 2.35
Examples 10 throu;~h 12' Synthesis of Di p-alk~,phenyll Fumarate with Styrene
Dialkyl phenyl fumarate - styrene copolymer having the structure:
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C---C C- C
I I I~ I
C=O C=0
I I
O O
i I
\ \
R R
R = C30H61 Or C24-28~'i49-57
Copolymers were synthesized according to the polymerization conditions set
forth in Examples 5 through 9. Tables 3 and 4 show the polymerization condi-
dons and characterization results, respectively.
TABLE 3
Example Mole Reaction Wt % Reaction
Number Monomers Ratio Solvent Initiator Tem .
C
C3oPhF/St ene 9/91 wt% Neat 3% V-88 76
11 C2a.2aP~-St 50/50 Chloroform5% AIBN 62
rene wt%
12 Czs-ZSP1~-S 50/50 Neat 5% AIBN 76
ene wt%
C~PhF: Di[p-allryl(C3p)phenyl] fumarate
C24-28P~~ Di[p-alkyl(Cz4-zs)phenyl] fumarate
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TABLE 4
Example Mole Ratio GPC
Number B NMR Peak MW Mn Mw Mw/Mn
10/90 86,455 50,308 23,3020 4.63
11 14/86 14,700 5,498 14,653 2.67
12 28,040 14,700 44,650 3.00
Example 13 ~ Wax Crystallization Studies
Seven samples of Alaska North Slope crude oil were prepared.
The samples were studied using differential scanning calorimetry at a cooling
rate of 10°C per minute. The results are set forth in Table 5.
TABLE 5
Additive Additive Treat Level, WAT OWAT
ppm
Alaskan North Slo a - 14.5 -
Crude
Example 4 500 13.3 1.2
2,500 12.4 2.1
Exam le 8 5,000 13.8 0.7
Exam le 9 5,000 11.0 3.5
Exam le 11 500 13.6 0.9
Exam le 12 500 13.5 1.0
These differential scanning colormetry ("DSC") studies are used to
study the thermodynamics and kinetics of oleagenous fluids containing some of
the additives of the present invention. DSC is used herein to reveal phase
transition in oleagenous fluids containing the additives of the present
invention
in order to study interactions between the fluid and the additives.
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DSC measurements were conducted over a temperature ranging
from -140°C to 100°C, in both heating and cooling, at a rate of
10°C per minute.
A nitrogen purge of 50 cm3 per minute was used, and all samples were warmed
to about 60°C before sampling. In each sample, the additives were
completely
dissolved in the fluid, and care was taken to prevent loss of any low
volatility
species present.
WAT is a measure of the thermodynamic barrier for the formation
of a stable nucleus for further crystal growth. It is the temperature at which
stable wax crystals first begin to appear. For wax crystallization to take
place,
solutions have to be supercooled to cross this thermodynamic free energy
barrier
to nucleation. A lowering of the WAT is desirable, because it indicates a
larger
thermodynamic barrier for further wax crystal growth. Additives that interfere
with the nucleation stage of wax formation increase the free energy barrier
and,
thereby, decrease the WAT. Larger decrease in WAT indicate better
performance of the wax crystal modifier additive.
Table 5 shows that the additives of the present invention are
effective wax crystal modifiers.
