Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2001-03-14
2003-07-15
Nutter, Nathan M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S207000, C525S221000, C525S222000, C525S240000, C044S385000, C044S388000, C044S397000, C044S403000
Reexamination Certificate
active
06593426
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention is described in the German Priority Application No. 10012269.8, filed Mar. 14, 2000, which is hereby incorporated by reference as is fully disclosed herein.
The present invention relates to blends of copolymers, on the one hand containing structural units of derivatives of dibasic carboxylic acids and unsaturated esters 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 their origin, crude oils and middle distillates, such as gas oil, diesel oil and 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 in some cases agglomerate with inclusion of oil. The flow properties of these oils or distillates thus deteriorate, with the result that problems may arise, 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 the 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 fuel is prevented and the supply of fuel or heating medium may be completely stopped.
In addition to the tradiational methods for eliminating the paraffins which have crystallized out (thermal, mechanical 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 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 paraffin crystals. The modified paraffin crystals have less tendency to agglomeration so that the oils into which these additives have been introduced can still be pumped and processed 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 alia, 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-1 1 47 799, oil-soluble copolymers of ethyhlene 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 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 thus paraffin-rich crude oils are being produced and processed. The distillates prepared therefrom contain increasing amounts of n-paraffins, whose distribution is shifting towards increasingly long alkyl chains. Particularly problematic here is a 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 highly 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.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
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 bivale
Krull Matthias
Reimann Werner
Volkmer Thomas
Clariant GmbH
Nutter Nathan M.
Silverman Richard P.
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