Fuel and related compositions – Liquid fuels – Containing organic -c
Reexamination Certificate
2001-11-16
2003-07-22
Toomer, Cephia D. (Department: 1714)
Fuel and related compositions
Liquid fuels
Containing organic -c
C044S393000, C044S397000, C044S351000, C044S340000
Reexamination Certificate
active
06596037
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to mixtures of fatty acids and comb polymers of improved low-temperature stability, and to their use for improving the lubricity of middle-distillate fuel oils.
1. Field of the Invention
Mineral oils and mineral-oil distillates which are used as fuel oils generally comprise 0.5% by weight or more of sulfur, which causes the formation of sulfur dioxide on combustion. In order to reduce the resultant environmental pollution, the sulfur content of fuel oils is constantly being reduced further. The EN 590 standard, which relates to diesel fuels, currently prescribes a maximum sulfur content of 350 ppm in Germany. In Scandinavia, fuel oils containing less than 50 ppm and in exception cases less than 10 ppm of sulfur are already in use. These fuel oils are generally produced by subjecting the fractions obtained from crude oil by distillation to reductive refining. During desulfurization, however, other substances are also removed which give the fuel oils a natural lubricity. These substances include, inter alia, polyaromatic and polar compounds.
However, it has now been found that the friction-and wear-reducing properties of fuel oils become worse with increasing degree of desulfurization. These properties are frequently so unsatisfactory that corrosion phenomena must be expected after only a short time on the materials lubricated by the fuel, such as, for example, distributor injection pumps of diesel engines. The maximum value for a 95% distillation point of a maximum of 360° C. which has been prescribed in EN 590 since the year 2000 and the further reduction in the 95% distillation point to below 350° C. and in some cases below 330° C. which has in the meantime been effected in Scandinavia intensify these problems further.
2. Description of the Related Art
The prior art has therefore described approaches which are intended to represent a solution to this problem (so-called lubricity additives).
JP-A-Hei-11-1692 discloses fuel-oil compositions comprising from 0.001 to 0.5% by weight of a C
8
-C
30
-fatty acid mixture which comprises at least 75% by weight of unsaturated fatty acids having one and two double bonds, where the ratio between monounsaturated and diunsaturated fatty acids is from 1:3 to 15:1 by weight, and the fuel-oil composition comprises at most 0.2% by weight of sulfur and at most 40% by weight of aromatic compounds. The oils may comprise further additives, such as antioxidants and flow improvers.
JP-A-Hei-10-110 175 discloses additives for improving the lubricity of fuel oils. The additives comprise a fatty acid selected from straight-chain saturated or unsaturated C
8
-C
28
-fatty acids, and a pour point depressant or a cold-flow improver. The fuel oils have a maximum sulfur content of 0.05% by weight.
The fatty acids used in accordance with the prior art have the disadvantage that they solidify on storage at low temperatures, i.e. often at room temperature, usually at temperatures of from 0° C. to at the latest −5° C., or deposit crystalline fractions and cause problems in handling. This problem can only be partially solved even by dilution with organic solvents, since fractions also crystallize from these solutions or the solution gels and solidifies. For use as lubricity additives, they therefore have to be diluted to a great extent or stored in heated storage containers and dispensed via heated lines. The additive mixtures proposed in JP-A-Hei-10-110 175 have the problem of the high proportions of pour point depressants or cold-flow improvers which are necessary for the preferred fatty acids, and the resultant high viscosity or poor solubility of these additives, which result in clouding or gelling of the concentrates at low storage temperatures.
SUMMARY OF THE INVENTION
The object on which the present invention is based was to find lubricity additives which improve the lubricity of middle distillates at reduced dispensing rates, but remain homogeneous, clear and in particular flowable even at low temperatures.
Surprisingly, it has been found that mixtures of fatty acids with comb polymers remain flowable and clear for an extended time even at significantly reduced temperatures, in some cases down to below −20° C., in particular cases down to below −30° C. and in special cases down to below −40° C., and in addition improve the lubricity of middle distillates more efficiently than pure fatty acids of the prior art.
DETAILED DESCRIPTION OF THE INVENTION
The invention thus relates to low-temperature-stabilized fatty acid mixtures comprising from 10 to 99.99% by weight of fatty acid mixtures comprising
A1) from 1 to 99% by weight of at least one saturated mono- or dicarboxylic acid having 6 to 50 carbon atoms,
A2) from 1 to 99% by weight of at least one unsaturated mono- or dicarboxylic acid having 6 to 50 carbon atoms, and from 0.01 to 90% by weight of copolymers comprising
B1) from 40 to 60 mol % of bivalent structural units of the formula
where X═O or N—R
1
,
in which a and b=0 or 1 and a+b=1, and
B2) from 60 to 40 mol % of bivalent structural units of the formula
—H
2
C−CR
2
R
3
—B2
and, if desired,
B3) from 0 to 20 mol % of bivalent structural units derived from polyolefins, where the polyolefins can be derived from monoolefins having 3 to 5 carbon atoms, and in which
R
1
is an alkyl or alkenyl radical having from 10 to 40 carbon atoms or an alkoxyalkyl radical having from 1 to 100 alkoxy units and from 1 to 30 carbon atoms in the alkyl radical, and
R
3
is a radical of the formula OCOR
4
or COOR
4
, in which R
4
is C
1
-C
24
-alkyl, and the number of carbon atoms in the polyolefin molecules on which the structural units B3) are based is from 35 to 350, and
R
2
is hydrogen or methyl.
The invention also relates to low-temperature-stabilized solutions of the fatty acid mixtures according to the invention in solvents, such as, for example, aliphatic and/or aromatic hydrocarbons or hydrocarbon mixtures, and oxygen-containing hydrocarbons, or mixtures thereof. The fatty acid mixtures according to the invention preferably comprise 1-80%, especially 10-70%, in particular 25-60%, of solvent.
The invention furthermore relates to fuel oils comprising, in addition to a relatively large proportion of middle distillate having a sulfur content of up to 0.05% by weight, a relatively small proportion of a low-temperature-stabilized fatty acid mixture as defined above.
The invention furthermore relates to the use of said fatty acid mixtures comprising constituents A and B for improving the lubrication properties of low-sulfur middle distillates having a sulfur content of up to 0.05% by weight.
Preferred fatty acids (constituent A) are those having 8-40 carbon atoms, in particular 12-22 carbon atoms. The alkyl radicals in the fatty acids essentially consist of carbon and hydrogen. However, they may carry further substituents, such as, for example, hydroxyl, halogen, amino or nitro groups, so long as these do not impair the predominant hydrocarbon character.
Constituent A2) may contain one or more double bonds and be of natural or synthetic origin. In the case of polyunsaturated carboxylic acids, their double bonds may be isolated or conjugated. The proportion of saturated fatty acids A1) in the mixture of A1) and A2) is preferably less than 20% by weight, in particular less than 10% by weight, especially less than 5% by weight. In preferred fatty acid mixtures, which is taken to mean the combination of A1) and A2) here, at least 50% by weight, in particular at least 75% by weight, especially at least 90% by weight, of the constituents contain one or more double bonds. These preferred fatty acid (mixtures) have iodine numbers of at least 40 g of l/100 g, preferably at least 80 g of l/100 g, in particular at least 125 g of l/100 g.
Examples of suitable fatty acids are lauric, tridecanoic, myristic, pentadecanoic, palmitic, margaric, stearic, isostearic, arachic and behenic acid, oleic and erucic acid, palmitoleic, myristoleic, linoleic, linolenic, elaeosteric and
Krull Matthias
Reimann Werner
Clariant GmbH
Silverman Richard P.
Toomer Cephia D.
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