Oil additives and compositions

Details Oil additives and compositions Oil additives and compositions

1994-12-21

1996-09-10

Howard, Jacqueline V.

Fuel and related compositions

Liquid fuels

Containing organic -c

44395, 508467, 508472, C10L 118, C10M14508

Patent

active

055542000

DESCRIPTION:

BRIEF SUMMARY
This invention relates to oil compositions, primarily to fuel oil compositions, and more especially to fuel oil compositions susceptible to wax formation at low temperatures, and to additive compositions for such fuel oil compositions.
Heating oils and other distillate petroleum fuels, for example, diesel fuels, contain alkanes that at low temperature tend to precipitate as large crystals of wax in such a way as to form a gel stricture which causes the fuel to lose its ability to flow. The lowest temperature at which the fuel will still flow is known as the pour point.
As the temperature of the fuel falls and approaches the pour point, difficulties arise in transporting the fuel through lines and pumps. Further, the wax crystals tend to plug fuel lines, screens, and filters at temperatures above the pour point. These problems are well recognized in the art, and various additives have been proposed, many of which are in commercial use, for depressing the pour point of fuel oils. Similarly, other additives have been proposed, and are in commercial use for reducing the size and changing the shape of the wax crystals that do form. Smaller size crystals are desirable since they are less likely to clog a filter; certain additives inhibit the wax from crystallizing as platelets and cause it to adopt an acicular habit, the resulting needles being more likely to pass through a filter than are platelets. The additives may also have the effect of retaining in suspension in the fuel the crystals that have formed, the resulting reduced settling also assisting in prevention of blockages.
Effective wax crystal modification (as measured by CFPP and other operability tests, as well as simulated and field performance) may be achieved by ethylene-vinyl acetate or propionate copolymer (EVAC or EVPC)-based flow improvers.
In EP-A-45342 is described a cold flow additive, based on an EVAC modified by esterification with 2-ethylhexanoic, acrylic, and phthalic acids.
In "Wissenschaft und Technik" 42(6), 238 (1989), M. Ratsch & M. Gebauer describe cold flow additives including an EVAC esterified with, inter alia, n-hexanoic acid.
In U.S. Pat. No. 3,961,916, middle distillate flow improvers are described which comprise a wax growth arrestor and a nucleating agent, the former being preferably a lower molecular weight ethylene-vinyl ester copolymer with a higher ester content, the latter preferably a higher molecular weight copolymer with a lower ester content, the esters preferably, but not necessarily, both being vinyl acetate.
In DE-AS-2407158, middle distillate flow improvers are described, comprising a mixture of low molecular weight ethylene-vinyl ester and ethylene-acrylic acid ester copolymers, both containing at least 40 mole per cent of the ester component.
The present invention is concerned to provide an oil, especially a fuel oil, additive effective to improve low temperature flow of the oil, and is based on the observation that a composition comprising at least two different copolymers of ethylene with an unsaturated ester, or a composition comprising a copolymer of ethylene with at least two different types of unsaturated ester-derivable units, is an effective cold flow improver having advantages over previously proposed compositions.
In a first aspect, the present invention provides a composition comprising: from ethylene, from 7.5 to 35 molar per cent of units of the formula from ethylenes up to 10 molar per cent of units of the formula and R.sup.2 independently represents a group of the formula COOR.sup.3 or OOCR.sup.4, wherein R.sup.3 and R.sup.4 independently represent a hydrocarbyl group, provided that R.sup.1 and R.sup.2 do not both represent the acetate group, the proportion of units I in polymer (i) being at least 2 molar percent greater than the proportion of units II in polymer (ii).
As used in this specification the term "hydrocarbyl" refers to a group having a carbon atom directly attached to the rest of the molecule and having a hydrocarbon or predominantly hydrocarbon character. Among these, there may be m

REFERENCES:
patent: 4661121 (1987-04-01), Lewtas
patent: 4802892 (1989-02-01), Shimada et al.
patent: 5205839 (1993-04-01), Reimann
patent: 5256166 (1993-10-01), Fischer
patent: 5330545 (1994-07-01), Lewtas et al.

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