Oil additives and compositions

Details Oil additives and compositions Oil additives and compositions

1994-12-21

1996-02-27

Hamilton, III, Thomas

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Mixing of two or more solid polymers; mixing of solid...

44393, 525 61, C08L 3304, C10L 118

Patent

active

054949670

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 structure 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.
It has been observed that, in many oils, a blend of two different ethylene-vinyl ester copolymers at a given total concentration gives a greater reduction in CFPP than that achieved by the same concentration of either copolymer alone, even when the two copolymers are formed from ethylene and the same vinyl ester, e.g., vinyl acetate, and even when the number average molecular weights and the ester contents of the two copolymers are similar. This effect appears to be different from the effect observed in U.S. Pat. No. 3,961,916, mentioned above, where an improvement results from the combination of copolymers with differing molecular weights and ester contents.
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 further observation that if a first ethylene-vinyl ester copolymer is hydrolysed and re-esterified with the same acid, and the same procedure is adopted with a second ethylene-vinyl ester copolymer, the blend of the two re-esterified copolymers is more effective as a low temperature flow improver than a blend of the original copolymers used at the same concentration. This applies both when the two starting copolymers have similar molecular weights or very diffe

REFERENCES:
patent: 3961916 (1976-06-01), Ilnyckyj et al.
patent: 3985719 (1976-10-01), Hoyt et al.
patent: 4575531 (1986-03-01), Hoyt et al.

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