Note: Descriptions are shown in the official language in which they were submitted.
CA 02242474 1998-07-07
Clariant GmbH 1997 DE 401 Dr. KM/sch
Description
Flow improvers for mineral oils
The present invention relates to mixtures of copolymers of ethylene and vinyl
esters
of tertiary carboxylic acids, and their use as flow improvers for mineral
oils.
Crude oils and middle distillates obtained by distillation of crude oils, such
as gas oil,
diesel oil or heating oil, contain, depending on the origin of the crude oils,
various
amounts of n-paraffins, which, when the temperature is reduced, crystallize
out as
platelet-shaped crystals and in some cases agglomerate with inclusion of oil.
This
causes an impairment of the flow properties of these oils or distillates,
which can
result in problems during the recovery, transport, storage and/or use of the
mineral
oils and mineral oil distillates. In the case of mineral oils, this
crystallization
phenomenon can cause deposits on the walls of transportation pipelines,
especially
in winter, and in individual cases, for example during stoppage in a pipeline,
can
even cause complete blocking thereof. Precipitation of paraffins can also
cause
problems during storage and further processing of the mineral oils. In winter,
for
example, it may in some circumstances be necessary to store the mineral oils
in
heated tanks. In the case of mineral oil distillates, the crystallization can
result in
blockage of the filters in diesel engines and furnaces, preventing reliable
metering of
the fuels and in some cases causing complete interruption of the supply of
fuel or
heating medium.
In addition to the classical methods of eliminating the crystallized paraffins
(thermal,
mechanical or using solvents), which merely involve the removal of the
precipitates
which have already formed, recent years have seen the development of chemical
additives (so-called flow improvers or paraffin inhibitors), which, by
interacting
physically with the precipitating paraffin crystals, result in their shape,
size and
adhesion properties being modified. The additives act as additional crystal
nuclei
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and in some cases crystallize with the paraffins, resulting in an increased
number of
relatively small paraffin crystals having a modified crystal shape. Part of
the action of
the additives is also explained by dispersal of the paraffin crystals. The
modified
paraffin crystals have a lower tendency toward agglomeration, so that the oils
to
which these additives have been added can still be pumped and/or processed at
temperatures which are frequently more than 200 lower than in the case of oils
containing no additives.
The flow and low-temperature behavior of mineral oils and mineral oil
distillates is
described by indicating the pour point (determined in accordance with ISO
3016)
and the cold filter plugging point (CFPP, determined in accordance with EN
116).
Both parameters are measured in C.
Typical flow improvers for crude oils and middle distillates are copolymers of
ethylene with carboxylates of vinyl alcohol. Thus, DE-A-1 1 47 799 proposes
adding
oil-soluble copolymers of ethylene and vinyl acetate having a molecular weight
of
between about 1000 and 3000 to petroleum distillate fuels having a boiling
point of
between about 120 and 400 C. Preference is given to copolymers comprising from
about 60 to 99% by weight of ethylene and from about 1 to 40 % by weight of
vinyl
acetate. They are particularly effective when prepared by free-radical
polymerization
in an inert solvent at temperatures of from about 70 to 130 C and pressures of
from
35 to 2100 bar above atmospheric pressure(DE-A-19 14 756).
The prior art also describes mixtures of copolymers as flow improvers.
DE-A-22 06 719 discloses mixtures of ethylene-vinyl acetate copolymers having
various comonomer contents for improving the low-temperature flow behavior of
middle distillates.
DE-A-20 37 673 discloses synergistic mixtures of ethylene-vinyl ester
copolymers of
various molecular weight as flow improvers.
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EP-A-0 254 284 discloses mixtures of ethylene-vinyl acetate copolymers with
ethylene-vinyl acetate-diisobutylene terpolymers as flow improvers for mineral
oils
and mineral oil distillates.
EP-A-0 648 247 discloses mixtures of at least 2 different ethylene-vinyl
acetate
copolymers and their use as flow improvers for mineral oils, where the
copolymers
are firstly hydrolyzed and then re-esterified.
EP-A-0 648 257 discloses mixtures of at least 2 ethylene-vinyl ester
copolymers in
which the vinyl esters are derived from carboxylic acids having 2 to 7 carbon
atoms.
EP-B-0 648 258 discloses ternary mixtures of ethylene-vinyl ester copolymers
in
which one of the mixture components contains between 7.5 and 35 moI% of the
vinyl ester comonomer and another of the mixture components contains less than
10 moI% of the vinyl ester copolymers.
EP-A-0 113 581 discloses mixtures of two ethylene-vinyl ester copolymers in
which
the vinyl ester is derived from a carboxylic acid having 1 to 4 carbon atoms.
One of
the copolymers is a paraffin crystal nucleating agent, while the other
copolymer is a
growth inhibitor.
EP-A-0 741 181 discloses mixtures of two copolymers, at least one of which
contains a vinyl ester containing alkyl or alkenyl radicals having more than 4
carbon
atoms as comonomer.
The effectiveness of the known additives for improving the properties of
mineral oil
fractions depends, inter alia, on the origin of the mineral oil from which
they have
been obtained and thus, in particular, on its composition. Additives which are
highly
suitable for modifying certain properties of fractions of one crude oil may
therefore
give entirely unsatisfactory results in distillates obtained from crude oils
of another
origin.
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Additives are now available which have a broad range of applications, i.e.
significantly improve the low-temperature flow properties of mineral oils and
mineral
oil fractions having different origins. Nevertheless, there are cases in which
they are
less suitable or even unusable, for example because they contribute only
little
toward increasing the flowability at low temperatures. The causes of this are
many
fold; the tapping of raw materials that have hitherto not been used, the
different
processing of the primary products and new market requirements may be
mentioned
as examples. A further disadvantage of many additives is that they impair the
filterability of mineral oil distillates above the cloud point.
In order to prevent the filtration problems, it is therefore necessary to
observe
special mixing conditions, such as high temperature of mineral oil and/or
additive,
particularly in the case of the ethylene-vinyl acetate copolymers. By
contrast,
terpolymers made from ethylene, vinyl acetate and vinyl esters of
neocarboxylic
acids (Versatic acids) are distinguished by very good solubility, but do not
sufficiently
lower the CFPP, in particular at reiatively high comonomer contents. A further
problem is storage of the additive concentrates. Owing to the limited
solubility in
organic solvents and the comparatively high density of the copolymers,
sedimentation occurs in the storage container, in particular at low storage
temperatures.
The invention provides mineral oil and mineral oil distillate additives which
both result
in very good CFPP lowering and are sufficiently, sofuble, even at low
temperatures,
and which prevent or at least lessen the filtration problems which occur in
the case of
the flow improvers of the prior art. In addition, improved sedimentation
stability of the
concentrates (suspensions) is achieved, even at low temperatures.
Surprisingly, it has been found that this can be achieved by mixtures which
comprise a terpolymer of ethylene, vinyl acetate and a vinyl neocarboxylate
and a
copolymer of ethylene and vinyl acetate. This is also achieved by mixtures of
two of said terpolymers having different comonomer contents and/or molecular
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29374-295
weights, and one of said terpolymers and ethylene-vinyl acetate-olefin
terpolymers.
The invention relates to mixtures comprising
5 A) a copolymer of lower olefins and vinyl esters, comprising
a) from 65 to 94 mol% of divalent structural units of the formula 1
- CH2 - CR'RZ - 1
in which R' and R2, independently of one another, are hydrogen or methyl,
b) from I to 25 mol% of divalent structural units of the formula 2
CHZ CH 2
1 3
OCOR
in which R3 is saturated, branched Cs-C16-alkyl which contains a tertiary
carbon atom, and
c) from 5 to 34 mol% of divalent structural units of the formula 3
CH2 CH 3
I
OCOCH3
where the sum of the molar proportions of comonomers of the formulae 2 and
3 is between 6 and 35 mol%,
and at least one of the following components 131) to B3):
BI) a further copolymer as described under A), or
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B2) an ethylene-vinyl ester copolymer containing from 5 to 35 mol% of
structural
units derived from the vinyl ester, in addition to structural units derived
from
ethylene, or
B3) an ethylene-vinyl ester-olefin terpolymer,
wherein R3 is bonded to the carboxyl function via its tertiary carbon atom.
Preferred vinyl esters for component B2) are vinyl acetate and vinyl
propionate.
Preferred vinyl esters for component B3) are vinyl acetate, vinyl propionate,
vinyl
hexanoate, vinyl laurate and vinyl esters of neocarboxylic acids, here in
particular of
neononanoic, neodecanoic and neoundecanoic acids. Preferred olefins are vinyl
ethers, alkyl acrylates, alkyl methacrylates, isobutylene or higher olefins
having at
least 5 carbon atoms, preferred higher olefins being hexene, 4-methylpentene,
octene and diisobutylene.
The mixing ratio between components A) and B) is preferably from 20:1 to 1:20,
in
particular from 10:1 to 1:10 by weight.
R' and R2 are preferably hydrogen. R3 is preferably a neoalkyl radical having
7 to 11
carbon atoms, in particular a neoalkyl radical having 8, 9 or 10 carbon atoms.
The
neoalkanoic acids from which the abovementioned neoalkyl radicals can be
derived
are described by the formula 4:
R R, 4
COOH
R' and R" are linear alkyl radicals, together preferably having 5 to 9, in
particular 6 to
8, especially 7 or 8, carbon atoms. Accordingly, the vinyl ester used for the
copolymerization has the formula 5:
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R" R' 5
COO-_~
Preference is given to the vinyl esters of neononanoic, neodecanoic and
neoundecanoic acid. Copolymer A) preferably contains from 1 to 15 mol% of the
structural units of the formula 2.
The sum of the molar proportions of comonomers of the formulae 2 and 3 is
preferably between 6 and 20 mol%.
The copolymers used for the novel mixtures can be prepared by conventional
copolymerization processes, for example suspension polymerization, solution
polymerization, gas-phase polymerization or high-pressure bulk polymerization.
Preference is given to high-pressure bulk polymerization, preferably at
pressures of
from 50 to 400 MPa, in particular from 100 to 300 MPa, and preferably at
temperatures of from 50 to 300 C, in particular from 100 to 250 C. The
reaction of
the monomers is initiated by initiators which form free radicals (free-radical
chained
initiators). This class of substances includes, for example, oxygen,
hydroperoxides,
peroxides and azo compounds, such as cumene hydroperoxide, t-butyl
hydroperoxide, dilauryl peroxide, dibenzoyl peroxide, bis(2-ethylhexyl)
peroxide
carbonate, t-butyl perpivalate, t-butyl permaleate, t-butyl perbenzoate,
dicumyl
peroxide, t-butyl cumyl peroxide, di(t-butyl) peroxide, 2,2'-azobis(2-
methylpropionitrile) and 2,2'-azobis(2-methylbutyronitrile). The initiators
are
employed individually or as a mixture of two or more substances in amounts of
from
0.001 to 20% by weight, preferably 0.01 to 10% by weight, based on the monomer
mixture.
The novel mixtures preferably have melt viscosities at 140 C of from 20 to
10,000 mPas, in particular from 30 to 5000 mPas, especially from 50 to 2000
mPas.
The desired melt viscosity of the mixtures is established by varying the
mixing ratio
of the copolymers.
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The copolymers mentioned under A), B1), B2) and B3) can contain up to 5 mol%,
preferably up to 2 mol%, of further comonomers. Examples of such comonomers
are
vinyl esters, vinyl ethers, alkyl acrylates, alkyl methacrylates having C,- to
C20-alkyl
radicals, isobutylene or higher olefins having at least 5 carbon atoms.
Preferred
higher olefins are hexene, 4-methylpentene, octene and diisobutylene.
The high-pressure bulk polymerization is carried out batchwise or continuously
in
known high-pressure reactors, for example autoclaves or tubular reactors, the
latter
having proved particularly successful. Solvents, such as aliphatic and/or
aromatic
hydrocarbons or hydrocarbon mixtures, benzene or toluene, may be present in
the
reaction mixture. The polymerization is preferably carried out in the absence
of a
solvent. In a preferred embodiment of the polymerization, the mixture of the
monomers, the initiator and, if used, the moderator is fed to a tubular
reactor via the
reactor inlet and via one or more side branches. The monomer streams here can
have different compositions (EP-A-0 271 738).
The novel mixtures are added to mineral oils or mineral oil distillates in the
form of
solutions or dispersions. These solutions or dispersions preferably comprise
from 1
to 90% by weight, in particular from 5 to 80% by weight, of the novel
mixtures.
Suitable solvents or dispersion media are aliphatic and/or aromatic
hydrocarbons or
hydrocarbon mixtures, for example gasoline fractions, kerosine, decane,
pentadecane, toluene, xylene, ethylbenzene or commercial solvent mixtures,
such
as Naphtha, Sheilsoll AB, Solvesso 150, Solvesso 200, Exxsol, ISOPAR and
Shellsol D products. The solvent mixtures mentioned contain various amounts of
aliphatic and/or aromatic hydrocarbons. The aliphatics can be straight-chain
(n-paraffins) or branched (iso-paraffins). Aromatic hydrocarbons can be
monocyclic,
bicyclic, or polycyclic and may contain one or more substituents. Mineral oils
or
mineral oil distillates whose rheological properties have been improved by the
novel
mixtures contain from 0.001 to 2% by weight, preferably from 0.005 to 0.5% by
weight, of the mixtures, based on the distillate.
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With the same result of optimizing the effectiveness as flow improvers for
certain
substrates, the novel mixtures can also be employed together with one or more
oil-
soluble coadditives which even alone improve the low-temperature flow
properties of
crude oils, lubricating oils or fuel oils. Examples of such coadditives are
polar
compounds which effect paraffin dispersal (paraffin dispersants) and comb
polymers.
Paraffin dispersants reduce the size of the paraffin crystals and have the
effect that
the paraffin particles do not deposit, but instead remain colloidally
dispersed with a
significantly reduced tendency to sediment. Paraffin dispersants which have
proven
successful are oil-soluble polar compounds containing ionic or polar groups,
for
example amine salts and/or amides, which are obtained by reacting aliphatic or
aromatic amines, preferably long-chain aliphatic amines, with aliphatic or
aromatic
mono-, di-, tri- or tetracarboxylic acids or anhydrides thereof (US-
4,211,534). Other
paraffin dispersants are copolymers of maleic anhydride and a,R-unsaturated
compounds, which can, if desired, be reacted with primary monoalkylamines
and/or
aliphatic alcohols (EP-A-0 154 177), the products of the reaction of
alkenylspirobislactones and amines (EP-A-0 413 279) and, as described in
EP-A-0 606 055, products of the reaction of terpolymers based on a,R-
unsaturated
dicarboxylic anhydrides, a,R-unsaturated compounds and polyoxyalkenyl ethers
of
lower unsaturated alcohols. Alkylphenol-formaldehyde resins are also suitable
as
paraffin dispersants.
The term comb polymers is taken to mean polymers in which hydrocarbon radicals
having at least 8, in particular at least 10, carbon atoms are bonded to a
polymer
backbone. Preference is given to homopolymers whose alkyl side chains contain
at
least 8 and in particular at least 10 carbon atoms. In the case of copolymers,
at least
20%, preferably at least 30%, of the monomers have side chains (c.f. Comb-like
Polymers - Structure and Properties; N.A. Plate and V.P. Shibaev, J. Polym.
Sci.
Macromolecular Revs. 1974, 8, 117 ff). Examples of suitable comb polymers are
fumarate-vinyl acetate copolymers (c.f. EP-A-O 153 176), copolymers of a C6
C24-a-
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olefin and an N-C6- to C22-alkylmaleimide (c.f. EP-A-0 320 766), furthermore
esterified olefin-maleic anhydride copolymers, polymers and copolymers of a-
olefins
and esterified copolymers of styrene and maleic anhydride.
5 The mixing ratio (in parts by weight) of the novel mixtures with paraffin
dispersants
or comb polymers is in each case from 1:10 to 20:1, preferably from 1:1 to
10:1.
The novel mixtures are suitable for improving the low-temperature flow
properties of
animal, vegetable or mineral oils. They are particularly suitable for use with
middle
10 distillates. The term middle distillates is taken to mean, in particular,
mineral oils
which have been obtained by distillation of crude oil and boil in the range
from 120
to 400 C, for example kerosine, jet fuel, diesel and heating oil. Advantages
of the
novel mixtures are their CFPP synergism compared with the individual
components
and good filterability above the cloud point of the oils containing additives,
although
individual components are not filterable. The concentrates have a
significantly
improved shelf life at low temperatures.
The novel mixtures can be used alone or together with other additives, for
example
dewaxing auxiliaries, corrosion inhibitors, antioxidants, lubricity additives
or sludge
inhibitors.
Examples
The following polymers were employed, in each case in the form of a 50%
suspension in kerosine (the abbreviations are as follows:
E = ethylene, VA = vinyl acetate, VeoVa = vinyl neodecanoate,
V140 = melt viscosity at 140 C, measured in accordance with ISO 3219):
A) E-VA copolymer containing 32% by weight of VA, V140 = 125 mPas
B) E-VA copolymer containing 28% by weight of VA, V140 = 300 mPas
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C) E-VA-diisobutylene terpolymer containing 25% by weight of VA and 5% by
weight of diisobutylene, V140 = 280 mPas
D) E-VA-VeoVa terpolymer containing 25% by weight of VA and 9.5% by weight
of VeoVa, V140 = 850 mPas in accordance with EP 493769
E) E-VA-VeoVa terpolymer containing 31% by weight of VA and 8% by weight of
vinyl neodecanoate, V140 = 110 mPas in accordance with EP 493769
F) E-VA-VeoVa terpolymer containing 32% by weight of VA and 11 % by weight
of vinyl neodecanoate, V140 = 260 mPas in accordance with EP 493769
G) E-VA-VeoVa terpolymer containing 31 % by weight of VA and 9% by weight of
vinyl neodecanoate, V140 = 230 mPas
Table 1: Characterization of the test oils (data in C)
Test oil 1 Test oil 2 Test oil 3 Test oil 4 Test oil 5
Start of boiling 174 166 180 166 165
20% of boiling point 204 209 268 214 109
50% of boiling point 239 252 307 282 243
90% of boiling point 328 315 350 356 327
End of boiling 367 337 336 376 357
Cloud Point -8 -12 0 +4.2 -7.2
CFPP -10 -16 -3 +3 -9
Solubility of the polymer mixtures
The solubility of the polymers and their mixtures was determined in a
filtration test as
follows: 130 ml of test oil 1 were mixed at room temperature with, unless
stated
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otherwise, 500 ppm of the additive conditioned at 40 C. After the vessel had
been
swirled around 20 times, a visual check was made as to whether additive
residues
were visible, the mixture was then filtered through a 0.8 pm cellulose nitrate
filter
(diameter 25 mm) under a vacuum of 200 mbar. A filtration time of less than
five
minutes for the entire volume of oil indicates good solubility of the
additive. For a
filtration time of more than five minutes, the volume filtered in this time
was noted.
The additives indicated were employed as 50% dispersions in kerosine.
Table 2: Solubility of the polymer mixtures (test oil 1)
Pure copolymer Filtration time Volume
Blank value (= no additive) 36 sec -
A) - 90 ml
B) Additive insoluble
C) Additive insoluble
D) Additive insoluble
E) 65 sec -
F) 43 sec -
Mixtures
A + E (1:1) 72 sec -
D + F (8:1) 55 sec -
A + F 58 sec -
B+ E(1:1) 52 sec -
B+ E(1:1), 1000 ppm 54 sec -
C + E (1:4) 175 sec -
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Solubility of the polymers and mixtures (test oil 5):
Pure copolymers and Filtration time Volume
mixtures
A) 300 sec 230 ml
B) Additive insoluble -
E) 32 sec -
G) 33 sec -
A + G (1:1) 73 sec -
B+ E(1:3) 125 sec -
Blank value 31 sec -
Sedimentation stability
In order to assess the sedimentation behavior of dilute suspensions of flow
improvers, 50% solutions of the copolymer waxes in kerosine were prepared at
from
80 to 100 C and diluted with a further 9 parts of kerosine (room temperature),
forming suspensions which were cloudy at room temperature. Their sedimentation
behavior was assessed over a period of two weeks from the amount of sediment.
In
order to quantify the sedimentation behavior, the WDI (wax dispersion index)
was
determined.
volume of sediment
WDI = -------------------------- = 100%
total volume
A high WDI indicates low sedimentation and thus good stability of the
suspension.
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Table 3
Wax Dispersion Index (WDI, %)
Product Appearance 3 Days 6 Days 10 Days 14 Days
RT
A sign. cloudy 92 92 2 3
D sign. cloudy 95 20 2 1
E clear 100 100 100 100
D + F sign. cloudy 97 97 91 1
E + D + F slightly cloudy 100 100 100 100
A + F slightly cloudy 100 100 100 100
A + E slightly cloudy 100 100 100 100
CFPP Synergism
Tables 4 to 6 show the superior effectiveness of the novel polymer mixtures
compared with the individual components as additives for mineral oils and
mineral oil
distillates with reference to the CFPP test (cold filter plugging test in
accordance with
EN 116). The additives are employed as 50% suspensions in kerosine. Data in
C.
Table 4: CFPP synergism in test oil 2
400 ppm 600 ppm
A -17 -21
E -18 -22
A+E -21 -24
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Table 5: CFPP synergism in test oil 3
600 ppm 800 ppm 1000 ppm
A -6 -11 -14
5 E -6 -10 -14
F -5 -8 -9
A+F -7 -14 -16
E+F -6 -13 -17
10 Table 6: CFPP synergism in test oil 4
200 ppm 300 ppm 400 ppm
A 0 0 -1
B 0 -3 -4
15 E +2 0 +1
G +1 -2 -4
A + G (1:1) -1 -6 -7
B + E (1:3) -1 -5 -6
List of trade names used
Solvent Naphtha aromatic solvent mixtures having a boiling range of from
Shellsol AB 180 to 210 C
Solvesso 150
Solvesso 200 aromatic solvent mixture having a boiling range of from
230 to 287 C
Exxsol Dearomatized solvent in various boiling ranges, for
example Exxsol D60: 187 to 215 C
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ISOPAR (Exxon) isoparaffinic solvent mixture in various boiling ranges,
for example ISOPAR L: 190 to 210 C
Shellsol D mainly aliphatic solvent mixture in various boiling ranges.
