Fuel and related compositions – Liquid fuels – Containing organic -c
Reexamination Certificate
1997-07-14
2001-10-23
Medley, Margaret (Department: 1714)
Fuel and related compositions
Liquid fuels
Containing organic -c
C044S395000
Reexamination Certificate
active
06306186
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, to copolymers for use with such fuel oil compositions, and to methods for their manufacture.
Fuel oils, whether derived from petroleum or from vegetable sources, contain components, e.g, alkanes, that at low temperature tend to precipitate as large crystals or spherulites 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. The wax from a diesel fuel, which is primarily an alkane wax, crystallizes as platelets; certain additives inhibit this and cause the wax 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 cold filter plugging point (CFPP) and other operability tests, as well as simulated and field performance) may be achieved by ethylene-vinyl acetate (EVAC) or propionate copolymer-based flow improvers.
In “Wissenschaft und Technik” 42(6), 238 (1989), M. Ratsch & M. Gebauer describe cold flow additives including an EVAC which has been hydrolysed and reesterified with, inter alia, propionic, n-pentanoic and n-hexanoic acids. A preference is expressed for esterifying acids to be straight-chain; a branched chain 3-methyl butanoic acid esterified copolymer gave significantly inferior results to those obtained using n-pentanoic acid esterified material.
In JP-A-58129096, cold flow additives comprising ethylene-vinyl carboxylic acid esters are described, the esterifying acid having a total carbon atom number of from 4 to 8, the additives being especially useful in a narrow boiling middle distillate fuel oil. The degree of branching of the main chain as measured by proton NMR is said to be at least 6 alkyl branches per 100 methylene groups.
British Specification No.1,086,036, EP-A-527,322 and EP-A-518,406 describe terpolymers suitable as latices for coatings, these terpolymers being formed by copolymerising ethylene with a vinyl ester of a tertiary or quaternary aliphatic carboxylic acid and a further ester monomer which may be vinyl acetate.
British Specification No.1,314,855 describes terpolymers of ethylene, vinyl acetate and a vinyl ester of a long-chain carboxylic acid which may be a saturated carboxylic acid having 8 to 30 carbon atoms. The only branched-chain carboxylic acid specifically disclosed is isostearic acid (C
18
). These terpolymers are described as useful in lubricating oils as viscosity index improvers.
British Specification No. 1,244,512 describes terpolymers of ethylene, a vinyl ester of a C
2
to C
4
monocarboxylic acid and an unsaturated ester having a C
10
to C
22
alkyl group, and preferably of the formula.
Wherein X is hydrogen or a methyl group, and Y is a OOCR or —COOR wherein R is preferably a C
10
to C
16
straight chain or branched chain alkyl group. All the specifically disclosed esters wherein Y is OOCR have straight chain alkyl groups.
In WO 94/00536, cold flow additives comprising a terpolymer of ethylene and two different unsaturated esters are disclosed. Terpolymers are also described in EP-A-493769, the starting monomers being ethylene, vinyl acetate, and vinyl neo-nonanoate or -decanoate, and in the references cited in the search report on that application.
The present invention relates to terpolymers showing a surprising improvement in wax crystal modification over those described in the prior art. Being comprised of branched chain unsaturated ester monomer units, the terpolymers useful in the present invention also enable readily available branched chain carboxylic acids to be used in the preparation of additives.
In a first aspect, the present invention provides an oil composition comprising an oil and an oil soluble ethylene terpolymer containing, in addition to units derived from ethylene, units of the formula:
and units of the formula
wherein R
1
and R
2
each independently represent H or methyl; R
3
represents an alkyl group having up to 4 carbon atoms; and R
4
represents a branched chain alkyl group having from 8 to 15 carbon atoms, other than a tertiary alkyl group, or a branched chain alkyl group having at most 7 carbon atoms, R
3
and R
4
being different; the degree of branching of the terpolymer, as measured by proton NMR spectroscopy (as explained in more detail below) being less than 6 CH
3
groups per 100 CH
2
units.
In units of the formula I, R
1
advantageously represents hydrogen, and R
3
advantageously represents ethyl or, especially, methyl. Advantageously R
3
is not t-butyl, but otherwise may be straight-chain or branched, although it is preferred that R
3
is a primary or secondary alkyl group. In units of the formula II, R
2
advantageously represents hydrogen. Advantageously, when R
4
represents a branched chain alkyl group having at most 7 carbon atoms, it is not a tertiary alkyl group.
R
4
preferably represents a secondary alkyl group, such as isopropyl, isobutyl, secbutyl, isopentyl, neo-pentyl, 1- and 2-methyl butyl, 1,2-dimethyl and 1-ethyl propyl, isohexyl, 1-, 2- and 3-methyl pentyl, 1- and 2-ethyl hexyl, 1- and 2-methyl heptyl, 1-ethyl propyl and, especially, 1-ethyl pentyl being preferred.
Terpolymers wherein R
3
represents a primary or secondary alkyl group, and R
4
represents a secondary alkyl group are particularly preferred. In a second aspect, the invention provides an oil-soluble ethylene terpolymer containing, in addition to units derived from ethylene, units of the formula:
and units of the formula
wherein R
1
and R
2
each independently represent H or methyl, R
3
represents a primary or secondary alkyl group having up to 4 carbon atoms, and R
4
represents a secondary alkyl group having up to 15 carbon atoms, R
3
and R
4
being different; the degree of branching of the terpolymer, as measured by proton NMR spectroscopy, being less than 6 CH
3
groups per 100 CH
2
units.
Preferably, R
1
and R
2
each represent hydrogen and R
3
represents a primary alkyl group.
The term “terpolymer”, as used herein in relation to all aspects of the invention, requires the polymer to have at least three different repeat units, i.e., be derivable from at least three different monomers, and includes polymers derivable from four or more monomers. For example, the polymer may contain two or more different units of the formula I or II, and/or may contain units of the formula
wherein R
5
represents a hydrocarbyl group having 5or more carbon atoms other than one as defined by R
4
.
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), alicyclic (e.g., cycloalkyl), 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 hydroc
Bock Jan
Brod Ramah Jessica
Davies Brian William
Ibrahim Tuncel
Exxon Chemical Patents Inc
Medley Margaret
Toomer Cephia D.
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