Fuel and related compositions – Liquid fuels – Heterocyclic carbon compound containing a hetero ring having...
Reexamination Certificate
2001-03-14
2003-05-20
Woodward, Ana (Department: 1711)
Fuel and related compositions
Liquid fuels
Heterocyclic carbon compound containing a hetero ring having...
C044S340000, C044S341000, C044S346000, C044S393000, C525S203000, C525S207000, C525S222000, C525S225000, C525S227000, C525S228000, C525S229000
Reexamination Certificate
active
06565616
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to blends of copolymers, on the one hand containing structural units of olefins, derivatives of dibasic carboxylic acids and, if required, polyolefins and, on the other hand, containing structural units of ethylene and vinyl esters of tertiary carboxylic acids, and their use as additives to fuel oils for improving their cold flow properties.
Depending on the origin of the crude oils, crude oils and middle distillates, such as gas oil, diesel oil or heating oil, obtained by distillation of crude oils contain different amounts of n-paraffins, which, when the temperature decreases, crystallize out as lamellar crystals and agglomerate, in some cases with inclusion of oil. Consequently, there is a deterioration in the flow properties of these oils or distillates, with the result that problems may occur, for example, in the production, transport, storage and/or use of the mineral oils and mineral oil distillates. When mineral oils are transported through pipelines, this crystallization phenomenon can lead, especially in winter, to deposits on the pipe walls and in individual cases, for example when a pipeline is shut down, even to complete blockage thereof. The precipitation of paraffins can also cause difficulties during the storage and further processing of mineral oils. Under certain circumstances, it may therefore 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 as a consequence of the crystallization, with the result that safe metering of the fuels is prevented and the supply of fuel or heating medium may be completely stopped.
In addition to the traditional methods for eliminating the paraffins which have crystallized out (thermal, mechanical or by means of solvents), which relate only to the removal of the already formed precipitates, recent years have seen the development of chemical additives (so-called flow improvers or paraffin inhibitors) which cooperate physically with the precipitating paraffin crystals and thus modify their shape, size and adhesion properties. The additives act as additional crystal nuclei and partly crystallize out with the paraffins, resulting in a larger number of smaller paraffin crystals having a modified crystal shape. A part of the effect of the additives is also explained by dispersing of the paraffin crystals. The modified paraffin crystals have less tendency to agglomeration, so that the oils into which these additives have been introduced can be pumped and processed even at temperatures which are often more than 20° C. lower than in the case of oils without additives.
The flow behavior and low-temperature behavior of mineral oils and mineral oil distillates is described, inter alit, by stating the cloud point (determined according to ISO 3015), the pour point (determined according to ISO 3016) and the cold filter plugging point (CFPP; determined according to EN 116). These characteristics are measured in ° C.
Typical flow improvers for crude oils and middle 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 of from about 1000 to 3000 are added to power fuels and heating fuels having a boiling point of from about 120 to 400° C. and obtained from mineral oil distillates. 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 are 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 atm (gage pressure) (DE-A-19 14 756).
The prior art furthermore discloses so-called comb polymers which are derived from ethylenically unsaturated monomers having relatively long (e.g. C
8
-C
30
), preferably linear, alkyl radicals. These are used especially in relatively high-boiling paraffin-rich mineral oils, if necessary in combination with ethylene copolymers, for improving the cold flow properties (e.g. GB-A-1 469 016 and EP-A-0 214 786). According to EP-A-0 153 176, comb polymers having C
12
-C
14
-alkyl radicals are also used in narrow-cut distillates having for example (90-20) % distillation ranges of <100° C. and final boiling points of about 340-370° C. According to U.S. Pat. No. 2,542,542 and GB-A-1 468 588, copolymers of maleic anhydride (MAA) and &agr;-olefins, esterified with long-chain fatty alcohols, are used for the treatment of crude oils.
GB-A-14 69 016 describes the use of blends of ethylene copolymers with comb polymers which are derived from C
6
-C
18
-esters of ethylenically unsaturated dicarboxylic acids and olefins and vinyl esters for improving the cold flow properties of middle distillates.
DE-A-35 14 878 describes esterification products of copolymers of maleic anhydride with olefinically unsaturated monomers (olefins, in particular ethylene, and acrylic acid) and primary or secondary alcohols having 16-30 carbon atoms as pour point depressants for paraffin-containing mineral oils. These products have an acid number of less than 20 mg KOH/g.
EP-A-0 214 786 describes middle distillate additives comprising maleic anhydride and straight-chain 1-olefins, which are esterified with fatty alcohols by a polymer-analogous reaction, for improving the cold flow properties of middle distillates.
EP-A-0 320 766 describes polymer blends comprising a copolymer (A1) of 10-60% by weight of vinyl acetate or a copolymer (A2) of 15-50% by weight of vinyl acetate, 0.5-20% by weight of C
6
-C
24
-alpha-olefin and 15.5-70% by weight of ethylene and a copolymer (B) of 10-90% by weight of C
6
-C
24
-alpha-olefin and 10-90% by weight of N-C
6
-C
22
-alkylmaleimide, the mixing ratio of the copolymers (A1) or (A2) to (B) being from 100:1 to 1:1. These polymer blends are used as flow improvers in middle distillates.
EP-A-0 890 589 describes the use of ethylene/vinyl neocarboxylate copolymers for improving the cold flow properties of middle distillates having an extremely low cloud point and a narrow boiling range, it also being possible for comb polymers to be present.
EP-A-0 931 824 describes blends of ethylene/vinyl neocarboxylate copolymers with further ethylene copolymers having a comonomer content of 10-20 mol %. These may furthermore contain comb polymers.
SUMMARY OF THE INVENTION
With increasing depletion of the world's oil reserves, increasingly heavy and hence paraffin-rich crude oils are being produced and processed. The distillates prepared therefrom contain increasing amounts of n-paraffins, whose distribution is shifting to increasingly long alkyl chains. Particularly problematic here is the high content of long-chain n-paraffins having carbon chain lengths of 22 or more. Such oils are also treated using combinations of ethylene-based flow improvers with comb polymers, whose efficiency, however, is often insufficient. There is therefore an increasing need for more efficient additives for the treatment of heavy and paraffin-rich middle distillates.
Surprisingly, it has now been found that blends of at least 2 polymers, which contain copolymers of ethylene and vinyl esters of tertiary carboxylic acids and specific comb polymers, are substantially more suitable for improving the cold flow properties of heavy, paraffin-rich middle distillates than the cold flow improvers of the prior art.
The invention relates to additives for improving the cold flow properties of middle distillates, containing from 10 to 95% by weight of copolymers A), from 5 to 90% by weight of copolymers B) and, if required, from 0 to 70% by weight of copolymers C), which correspond to the following formulae:
A) copolymers of lower olefins and vinyl esters, containing
A1) from 85 to 97 mol % of bivalent structural units of the formula
—CH
2
—CR
1
R
2
— A1
in which R
1
and R
2
, independently of one another, are hydrogen or methyl, and
A2) at lea
Krull Matthias
Reimann Werner
Volkmer Thomas
Clariant GmbH
Silverman Richard P.
Woodward Ana
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