Oil additives and compositions

Details Oil additives and compositions Oil additives and compositions

1994-12-21

2003-10-28

Medley, Margaret B. (Department: 1714)

Fuel and related compositions

Liquid fuels

Containing organic -c

C044S394000

Reexamination Certificate

active

06638325

ABSTRACT:

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.
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
(a) an oil soluble ethylene copolymer having, in addition to units derived from ethylene, units of the formula
—CH
2
—CRR
1
—  I
and units of the formula
—CH
2
—CRR
2
—  II
the total molar proportion of units of the formulae I and II in the copolymer being less than lot, wherein each R independently represents H or CH
3
, and each R
1
and R
2
independently represents a group of the formula COOR
3
or OOCR
3
, wherein each R
3
independently represents a hydrocarbyl group, provided that the units of the formula I are different from the units of the formula II, or (b) comprising
(i) an oil-soluble ethylene copolymer having, in addition to units derived from ethylene, less than 10 molar per cent of units of the formula
—CH
2
—CRR
1
—  I
and (ii) an oil-soluble ethylene copolymer having, in addition to units derived from ethylene, less than 10 molar per cent of units of the formula
—CH
2
—CRR
2
—  II
wherein R, R
1
, and R
2
have the meanings given above, provided that copolymer (i) differs from copolymer (ii). Advantageously, R represents H.
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 mentioned hydrocarbon groups, including aliphatic, (e.g., alkyl or alkenyl), alicyclic (e.g., cycloalkyl or cycloalkenyl), aromatic, aliphatic and alicyclic-substituted aromatic, and aromatic-substituted aliphatic and alicyclic groups. Aliphatic groups are advantageously saturated. These groups may contain non-hydrocarbon substituents provided their presence does not alter the predominantly hydrocarbon character of the group. Examples include keto, halo, hydroxy, nitro, cyano, alkoxy and acyl. If the hydrocarbyl group is substituted, a single (mono) substituent is preferred. Examples of substituted hydrocarbyl groups include 2-hydroxyethyl, 3-hydroxypropyl, 4-hydroxybutyl, 2-ketopropyl, ethoxyethyl, and propoxypropyl. The groups may also or alternatively contain atoms other than carbon in a chain or ring otherwise composed of carbon atoms. Suitable hetero atoms include, for example, nitrogen, sulfur, and, preferably, oxygen. Advantageously, the hydrocarbyl group contains at most 30, preferably at most 15, more preferably at most 10 and most preferably at most 8, carbon atoms.
Advantageously R
3
represents an alkenyl or as indicated above, preferably, an alkyl group, which is advantageously linear. If the alkyl or alkenyl group is branched, for example, as in the 2-ethylhexyl group, the &agr;-carbon atom is advantageously part of a methylene group. Advantageously, the alkyl or alkenyl group contains up to 30 carbon atoms, preferably from 1 (2 in the case of alkenyy) to 14 carbon atoms, and more preferably from 4 to 10 carbon atoms. As examples of alkyl or alkenyl groups there may be mentioned propyl, n-butyl, iso-butyl, and isomers, preferably the linear isomers, of pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl and icosyl, and their corresponding alkenyl, advantageously alk-omega-enyl, radicals. When R
1
and/or R
2
are of the formula OOCR
3
, R
3
most preferably represents propyl, butyl, or pentyl, and as indicated above, advantageously the linear isomer.
As cycloalkyl, alkaryl and aryl radicals, there may be mentioned, for example, cyclohexyl, benzyl and phenyl.
The copolymer or copolymers may also contain units of formulae other than those mentioned above, for example units of the formula
—CH
2
—CRR
4
—  II
where R
4
represents —OH, or of the formula
—CCH
3
(CH
2
R
5
)—CHR
6
—  IV
where R
5
and R
6
each independently represent hydrogen or an alkyl group with up to 4 carbon atoms, the units IV advantageously being derived from isobutylene, 2-methylbut-2-ene or 2-methylpent-2-ene.
Units of the formula I or II may be terminal units but are advantageously internal units. Advantageously, units of the formula —CRR
1
—CH
2
— and —CRR
2
—CH
2
— represent less than 7.5, preferably from 0.3 to 7.5, and most preferably from 3.5 to 7.0, mole per cent of the polymer.
The copolymer (a) and each of copolymers b(i) and (ii) advantageously have a number average molecular weight, as measured by gel permeation chromatography, of up to 20,000, advantageously up to 15,000, more advantageously in the range of 1,200 to 10,000, preferably 3,000 to 10,000 and most preferably about 5,000. The preferred number average molecular weight will depend to some extent on the number of carbon atoms in R
3
, the higher that number the higher the preferred molecular weight within the range above. Advant

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