Fuel and related compositions – Liquid fuels – Containing organic -c
Reexamination Certificate
2000-06-09
2002-05-21
Howard, Jacqueline V. (Department: 1764)
Fuel and related compositions
Liquid fuels
Containing organic -c
C044S393000
Reexamination Certificate
active
06391071
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to the use of copolymers containing structural units of olefinically unsaturated, hydroxyl-containing compounds and further olefinically unsaturated compounds containing alkyl radicals for improving the lubricity of middle distillates, and to middle distillate fuel oils containing these additives.
Mineral oils and mineral oil distillates which are used as fuel oils generally contain 0.5% by weight or more of sulfur, which causes the formation of sulfur dioxide on combustion. In order to avoid the environmental pollution resulting therefrom, the sulfur content of fuel oils is continually being reduced. The EN 590 standard relating to diesel fuels currently prescribes a maximum sulfur content of 500 ppm in Germany. In Scandinavia, fuel oils containing less than 200 ppm and in exceptional cases containing less than 50 ppm of sulfur are already in use. These fuel oils are generally prepared by hydrorefining the fractions obtained from crude oil by distillation. During the desulfurization, however, other substances which give the fuel oils natural lubricity are also removed. These substances include, inter alia, polyaromatic and polar compounds.
However, it is now been found that the friction- and wear-reducing properties of fuel oils worsen with increasing degree of desulfurization. These properties are frequently so inadequate that signs of corrosion must be expected after only a short time on the materials lubricated by the fuel, for example the distributor injection pumps of diesel engines. The further lowering of the 95% distillation point to below 370° C., in some cases to below 350° C. or below 330° C., which has in the meantime been adopted in Scandinavia intensifies this problem further.
Approaches which claim to be a solution to this problem have therefore been described in the prior art (so-called lubricity additives).
EP-A-0 680 506 discloses esters of carboxylic acids having 2 to 50 carbon atoms as additives for improving the lubricity of low-sulfur middle distillates containing less than 0.5% by weight of S.
DD-126 090 discloses lubricity-improving additives containing copolymers of ethylene and unsaturated carboxylic esters, preferably vinyl acetate, which are added to the fuels in amounts of from 0.01 to 0.5% by weight.
EP-A-0 764 198 discloses additives which improve the lubricity of fuel oils and comprise polar nitrogen compounds based on alkylamines or alkylammonium salts containing alkyl radicals having 8 to 40 carbon atoms.
DE-A-15 94 417 discloses additives for improving the lubricity of oleophilic liquids containing esters of glycols and dicarboxylic acids having at least 11 carbon atoms.
EP-A-0 635 558 discloses diesel oils having sulfur contents of below 0.2% by weight and aromatics contents of below 30% by weight. These diesel oils are mixed with from 100 to 10,000 ppm of C
1
-C
5
-alkyl esters of unsaturated straight-chain C
12
-C
22
-fatty acids derived from oilseed as additives.
EP-A-0 074 208 discloses middle and heavy distillates which have been mixed with copolymers of ethylene and oxyalkylated acrylates or ethylene and vinyl esters of saturated and unsaturated carboxylic acids as additives.
EP-A-0 856 533 discloses copolymers based on vinyl esters of carboxylic acids, vinylaromatic hydrocarbons, hydroxyl-functional unsaturated monomers and further polymerizable polymers. The polymers have OH numbers of 110-170 mg of KOH/g and have molecular weights of 1500-8000 g/mol. However, the polymers are used, according to the disclosure content of the document, for the production of surface coatings for paints. Use in connection with fuel oils is not disclosed.
U.S. Pat. No. 3,915,668 discloses terpolymers of ethylene, 10-25% by weight of C
1
-C
8
-alkylvinyl esters and 10-30% by weight of dialkylvinylcarbinol and their use for improving the cold-flow properties of crude oils and residual oils. The suitability of such terpolymers for improving the lubricity of distillate fuels is not disclosed.
SUMMARY OF THE INVENTION
The object of the present invention was to find additives which result in an improvement in lubricity in middle distillates which have been substantially freed from sulfur and aromatic compounds. At the same time, these additives should also have a favorable effect on the cold-flow properties of these middle distillates.
Surprisingly, it is been found that oil-soluble copolymers of ethylenically unsaturated compounds carrying one or more hydroxyl groups and ethylenically unsaturated compounds containing hydrocarbon groups having at least 6 carbon atoms impart the requisite properties to the fuel oils to which they are added as additives.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The invention thus relates to the use of oil-soluble copolymers which comprise
A) from 5 to 80 mol-% of structural units derived from olefinically unsaturated compounds containing at least one free hydroxyl group,
B) from 5 to 95 mol-% of structural units derived from olefinically unsaturated compounds carrying a hydrocarbon radical having at least 6 carbon atoms, and, if desired,
C) from 0 to 40 mol-% of further structural units selected from the group consisting of acrylic acid, acrylates, vinyl esters, vinylethane and alkenes, with the proviso that the structural units mentioned under C) are different from the structural units mentioned under A) and B),
and have a mean molecular weight Mw of from 500 to 100,000 g/mol and an OH number of from 10 to 300 mg of KOH/g, for improving the lubricity and cold flow properties of middle distillates having a sulfur content of less than 0.5% by weight.
The invention furthermore relates to middle distillate fuel oils having a sulfur content of less than 0.5% by weight which contain copolymers of the type defined above.
In a preferred embodiment of the invention, the copolymer has an OH number of from 20 to 250, in particular from 25 to 200, mg of KOH/g. In a further preferred embodiment, the copolymer has a mean molecular weight Mw of from 700 to 10,000 g/mol. In a further preferred embodiment, the proportion of the structural units (A) is from 10 to 70 mol-%, in particular from 15 to 60 mol-%.
The olefinically unsaturated compounds which make up the copolymers (A) are preferably vinyl esters, acrylates, mono- and diesters of ethylenically unsaturated carboxylic acids, methacrylates, alkyl vinyl ethers and/or alkenes carrying hydroxyalkyl, hydroxyalkenyl, hydroxycycloalkyl or hydroxyaryl radicals. These radicals contain at least one hydroxyl group, which can be in any desired position of the radical, but is preferably at the chain end (co-position) or in the para-position in the case of ring systems.
The vinyl esters are preferably those of the formula 1
CH
2
=CH—OCOR
1
(1)
in which R
1
is C
1
-C
30
-hydroxyalkyl, preferably C
1
-C
12
-hydroxyalkyl, especially C
2
-C
6
-hydroxyalkyl, and the corresponding hydroxyoxalkyl radicals. Suitable vinyl esters include 2-hydroxyethyl vinyl ester, &agr;-hydroxypropyl vinyl ester, 3-hydroxypropyl vinyl ester and 4-hydroxybutyl vinyl ester, and diethylene glycol monovinyl ester.
The acrylates are preferably those of the formula 2
CH
2
=CR
2
—COOR
3
(2)
in which R
2
is hydrogen or methyl, and R
3
is C
1
-C
30
-hydroxyalkyl, preferably C
1
-C
12
-hydroxyalkyl, especially C
2
-C
6
-hydroxyalkyl, and the corresponding hydroxyoxalkyl radicals. Suitable acrylates include hydroxyethyl acrylate, hydroxyethyl methacrylate, 2-hydroxy-propyl acrylate, 3-hydroxypropyl acrylate, 3-hydroxypropyl methacrylate, hydroxyisopropyl acrylate, 4-hydroxybutyl acrylate and glycerol monoacrylate. The corresponding esters of methacrylic acid, and esters of ethylenically unsaturated dicarboxylic acids, such as maleic acid, fumaric acid and itaconic acid, with diols are just as suitable.
The alkyl vinyl ethers are preferably compounds of the formula 3
CH
2
=CH—OR
4
(3)
in which R
4
is C
1
-C
30
-hydroxyalkyl, preferably C
1
-C
12
-hydroxyalkyl, especially C
2
-C
6
-hydroxyalkyl, and the corresponding hyd
Krull Matthias
Kupetz Markus
Clariant GmbH
Howard Jacqueline V.
Silverman Richard P.
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