Fuel and related compositions – Liquid fuels – Containing organic -c
Reexamination Certificate
2000-11-06
2003-07-29
Medley, Margaret (Department: 1714)
Fuel and related compositions
Liquid fuels
Containing organic -c
C044S393000, C208S015000, C208S018000
Reexamination Certificate
active
06599335
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to copolymers of ethylene and vinyl esters of tertiary carboxylic acids and their use as flow improvers for mineral oils.
Crude oils and middle distillates such as gas oil, diesel oil or heating oil, obtained by distillation of crude oils contain, depending on the origin of the crude oils, different amounts of n-paraffins, which crystallize out as lamellar crystals when the temperature is lowered and in some cases agglomerate with inclusion of oil. This results in a deterioration in the flow properties of these oils or distillates, giving rise to problems, for example in 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 lead to deposits on the pipe walls during transport through pipelines, especially in the winter, and in individual cases, for example when the pipeline is shut down, even to complete blockage thereof. The precipitation of paraffin can also cause difficulties in storage and further processing of the mineral oils. Thus, it may be necessary in winter to store the mineral oils in heated tanks. In the case of mineral oil distillates, blockage of the filters in diesel engines and furnaces may occur owing to the crystallization, with the result that reliable metering of the fuels is prevented and complete interruption of the fuel or heating medium feed may occur.
In addition to the traditional methods for eliminating the paraffins which have crystallized out (thermally, mechanically or by means of solvents), which relate only to the removal of the precipitates already formed, recent years have seen the development of chemical additives (so-called flow improvers or paraffin inhibitors) which physically interact with the precipitating paraffin crystals and thus modify their shape, size and adhesion properties. The additives act as additional crystal seeds and partially crystallize out with the paraffins, resulting in a larger number of smaller paraffin crystals with modified crystal shapes. A part of the action of the additives is also explained by dispersing of the paraffin crystals. Modified paraffin crystals have less tendency to agglomerate, so that the oils into which these additives have been introduced can be pumped or processed even at temperatures which are often more than 20° lower than in the case of oils not containing additives.
The flow and low-temperature behavior of mineral oils and mineral oil distillates is described by stating the pour point (determined according to ISO 3016) and the cold filter plugging points (CFPP; determined according to EN 116). Both characteristics are measured in ° C.
Typical flow improvers for crude oils and middle oil distillates are copolymers of ethylene with carboxylic esters of vinyl alcohol. Thus, according to DE-A-11 47 799, oil-soluble copolymers of ethylene and vinyl acetate having a molecular weight between about 1,000 and 3,000 are added to mineral oil distillate, or combustion fuels having a boiling point between about 120 and 400° C. Copolymers which contain from about 60 to 99% by weight of ethylene and from about 1 to 40% by weight of vinyl acetate are preferred. They are particularly effective if they were prepared by free radical polymerization in an inert solvent at temperatures of from about 70 to 130° C. and pressures of from 35 to 2,100 atm (gage pressure) (DE-A-19 14 756).
Other polymers used as flow improvers contain, in addition to ethylene and vinyl acetate, for example 1-hexene (cf. EP-A-0 184 083), diisobutylene (cf. EP-A-0 203 554) or an isoolefin of the formula
in which R and R′ are identical or different and are hydrogen or C
1
-C
4
-alkyl radicals (EP-A-0 099 646). Copolymers of ethylene, alkenecarboxylic esters and/or vinyl esters and vinyl ketone are also used as pour point depressants and for improving the flow behavior of crude oils and middle distillates of crude oils (EP-A-0 111 888).
In addition, copolymers based on &agr;,&bgr;-unsaturated compounds and maleic anhydride are also used as flow improvers. DE-196 45603 describes copolymers of from 60 to 99 mol % of structural units derived from ethylene and from 1 to 40 mol % of structural units which are derived from maleic acid, its anhydride or its imides. The disadvantage of using such compounds is the complicated preparation process, namely high-pressure mass copolymerization of ethylene and maleic anhydride and subsequent imidation of the anhydride groups.
DE-1 162 630 discloses copolymers of ethylene and vinyl esters of straight-chain fatty acids having 4 to 18 carbon atoms as pour point-depressing additive for mineral oil distillates. Neocarboxylic acids are not mentioned.
EP-A-0 217 602 discloses ethylene copolymers with vinyl esters carrying C
1
- to C
18
-alkyl radicals as flow improvers for mineral oil distillates having boiling ranges (90-20%) of less than 100° C.
EP-A-0 648 256 discloses, inter alia, copolymers of ethylene and vinyl esters of C
1
-C
28
-carboxylic acids, but once again no neocarboxylic acids.
EP-A-0 493 769 discloses terpolymers which are prepared from ethylene, vinyl acetate and vinyl neononanoate or neodecanoate and their use as additives for mineral oil distillates.
EP-A-0 584 651 discloses copolymers of ethylene with a tertiary, saturated carboxylic acid for the production of films which have a melt flow index MFI (190/2,16) of from 0.1 to 50 g/10 min. Owing to their high molecular weight and their low solubility, such copolymers are however unsuitable for use as mineral oil additives.
EP-A-0 746 598 discloses copolymers of ethylene and dialkyl fumarates as a mixture with mineral oils which have a cloud point below −10° C.
The efficiency of the known additives for improving the properties of mineral oil fractions is dependent, inter alia, on the origin of the mineral oil from which they were obtained and hence in particular on its composition. Additives which are very suitable for establishing specific properties of fractions of a crude oil can therefore lead to completely unsatisfactory results in distillates of crude oils of another origin.
Additives which have a wide range of use, i.e. which substantially improve the flow properties of mineral oils and mineral oil fractions of different origins at lower temperatures, are now available. Nevertheless, there are cases where they prove to be not very useful or completely useless, for example because they make little contribution to increasing the low-temperature flowability. The reasons for this are varied; the exploitation of raw materials not used to date, the changed processing of the primary products and new market requirements may be mentioned as examples.
In particular, diesel fuels which are distinguished by lower environmental pollution during combustion and are characterized by a very low sulfur content of less than 500 ppm and in particular less than 100 ppm and a low aromatics content can be treated with conventional flow improvers only to an inadequate extent, if at all. Problems are encountered in particular with the winter grades of diesel fuels produced for use under arctic conditions and having extreme low-temperature properties, such as, for example, a cloud point of less than −10° C. and in particular less than −15° C., very narrow distillation cuts having boiling ranges of 20 to 90% by volume less than 100° C., in particular less than 80° C. and in some cases also less than 60° C., and a final boiling point limited to about 360° C. and in particular to about 320° C. The low-temperature properties of such distillates can at present be satisfactorily improved only by adding low-boiling, low-paraffin components, such as, for example, kerosene.
It was therefore the object to develop novel additives for improving the flowability of such mineral oil grades or mineral oil fractions in which the additives of the prior art have only an unsatisfactory action. Furthermore, it was the object to find additives which can be prepared in a process which is less complic
Krull Matthias
Kupetz Markus
Wildfang Raimund
Clariant GmbH
Hanf Scott E.
Jackson Susan S.
Medley Margaret
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