Fuel and related compositions – Liquid fuels – Containing organic -c
Reexamination Certificate
2000-06-09
2002-04-02
McAvoy, Ellen M. (Department: 1764)
Fuel and related compositions
Liquid fuels
Containing organic -c
C044S389000, C044S393000
Reexamination Certificate
active
06364918
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to amphiphilic copolymers which can be prepared by reacting copolymers of olefinically unsaturated carboxylic acid derivatives and olefinically unsaturated lipophilic monomers with hydroxyl-functional compounds, to their use 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.
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. U.S. Pat. No. 3,520,852 discloses hydroxyimides and a process for their preparation by firstly esterifying styrene-maleic anhydride copolymers using alcohols having 1-5 carbon atoms to give hemiesters. The hemiesters are then reacted with hydroxylamines under imidation conditions to give imides. The products obtained are suitable as coatings and casting compositions, but not as additives for fuel oils.
U.S. Pat. No. 5,064,921 discloses hydroxyl-functional polyacrylates which have been imidated using aminoalcohols. They are used as thickeners together with polyisocyanates in polyurethanes.
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 novel copolymers which can be prepared by reacting copolymers of ethylenically unsaturated carboxylic acids or derivatives thereof and ethylenically unsaturated compounds containing hydrocarbon groups having at least 6 carbon atoms with reagents carrying OH groups 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 oil-soluble copolymers having an OH number of from 10 to 350 and a molecular weight of from 500 to 100,000 g/mol, obtained from the reaction of a copolymer precursor which comprises structural units of
A) from 5 to 95 mol-% of an olefinically unsaturated carboxylic acid or a derivative of such an acid,
B) from 5 to 95 mol-% of an olefinically unsaturated compound having at least one hydrocarbon radical containing at least 6 carbon atoms, and, if desired,
C) from 0 to 40 mol-% of further structural units selected from the group consisting of C
1
-C
6
-alkyl (meth)acrylates, C
1
-C
6
-alkyl vinyl esters and C
2
-C
6
-olefins, with a reagent, which must carry at least one OH group and which, apart from this OH group, has at least one further functional group which is capable of reacting with the carboxylic acid or the derivative of a carboxylic acid as in component A), where the residual acid number is set to a value below 150 mg of KOH/g of copolymer by addition of the reagent.
The invention furthermore relates to middle distillate fuel oils having a sulfur content of less than 0.5% by weight which, besides a relatively large proportion of a fuel oil, contain a relatively small proportion of copolymers of the type defined above.
The invention furthermore relates to the use of the copolymers defined herein for improving the lubricity and cold flow properties of middle distillate fuel oils.
In a preferred embodiment of the invention, the copolymer has an OH number of from 20 to 300 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 60 mol-%. In a further preferred embodiment, the residual acid number is less than 20, in particular less than 10 mg of KOH/g. Preferred copolymers have melt viscosities at 140° C. of from 10 to 5000 mPas, in particular from 15 to 1000 mpas, especially from 20 to 500 mPas.
The carboxylic acids and carboxylic acid derivatives which make up the structural units A) of the copolymer precursor are preferably maleic acid, acrylic acid, methacrylic acid, fumaric acid or itaconic acid, or derivatives thereof.
The derivatives of the carboxylic acids are preferably their anhydrides. Particular preference is given to maleic anhydride. In the case of copolymers of maleic anhydride (MAA) with &agr;-olefins, preference is given to alternating copolymers comprising from about 40 to 60 mol-% of MAA and 60-40 mol-% of &agr;-olefin.
In a further preferred embodiment, the carboxylic acid derivatives are esters with alcohols having 1 to 5 carbon atoms.
Preferred comonomers (B) are olefinically unsaturated compounds carrying hydrocarbon radicals having at least 6 carbon atoms, preferably at least 8 carbon atoms, in particular at least 10 carbon a
Krull Matthias
Nagel Waltraud
Clariant GmbH
Hanf Scott E.
Jackson Susan S.
McAvoy Ellen M.
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