WO1998027184A1

WO1998027184A1 - Distillate fuels with polyalkylene glycol diacid derivatives as flow improvers

Info

Publication number: WO1998027184A1
Application number: PCT/EP1997/006943
Authority: WO
Inventors: Robert Dryden Tack
Original assignee: Infineum Sa L.P.
Priority date: 1996-12-16
Filing date: 1997-11-27
Publication date: 1998-06-25
Also published as: AU5756598A; GB9626095D0

Abstract

There are disclosed fuel oil compositions having improved low temperature properties which contain an additive being an ester, amide or amine derivative of a polyalkylene glycol diacid or mixtures of this additive with conventional flow improver co-additives.

Description

DISTILLATE FUELS WITH POLYALKYLENE GLYCOL DIACID DERIVATIVES AS FLOW IMPROVERS

This invention relates to fuel oils with improved low temperature properties. More particularly, this invention relates to narrow boiling distillate (NBD) fuels which have a relatively high wax content and which have their flow and filterability properties improved through treatment with a novel additive.

It is known in the art that NBD fuels having a relatively high wax content, i.e., 3-6% by weight at 10°C below cloud point, are difficult to treat effectively with conventional flow improver additives, such as ethylene vinyl acetate copolymers.

An object of this invention is to treat fuels, especially NBD fuels having 3-6%, especially 3-4% by weight, waxy hydrocarbons with an additive system so as to provide the fuel with improved low temperature properties.

For the purpose of this invention NBD fuels are those having a boiling range of from about 200°C (+ or - 50°C) to about 340°C ( + or - 30°C). Thus, such fuel oils have a relatively higher initial boiling point and a relatively lower final boiling point, as compared with middle distillate fuels which have a boiling point range of about 120°C to 500°C, especially 160°C to 400°C.

The use of esters, ethers and ether/esters based on polyoxyalkylene glycols is known in the art and is disclosed in EPA 061895, published October 6, 1982. In this disclosure the esters are those of monocarboxylic fatty acids of 10-30 carbon atoms which are reacted with the glycols to form useful flow improvers, such as the behenate of polyethylene glycol.

The present invention is based on the discovery that polyoxyalkylene glycol dicarboxylic acids when derivatized to form esters, amine salts or amides are useful flow improvers, particularly for use in narrow boiling distillate fuels. Diacids derived from polyalkylene glycols are known in the art and may be prepared by oxidation of the glycol such as disclosed in U.S. Patent No. 3,929,873 (1975), which teaches the oxidation of polyethylene glycol to the corresponding diacid.

In accordance with this invention there have been discovered fuel oil compositions exhibiting improved low temperature properties which contain an effective amount of a flow improver additive being an ester, amine salt or amide derivative, or mixture of derivatives, of a dicarboxylic acid of a polyalkylene glycol, the dicarboxylic acid having the formula:

HOOC-CH₂O(alkylene-O)_nCH₂-COOH

where the alkylene has 2 - 4 carbon atoms, n is an integer and the dicarboxylic acid (diacid) has a molecular weight (Mn, number average) of about 200 to 5,000.

Typically, the additive will be present in the fuel in an amount of about 0.0001 to 0.5 wt. %.

The additives of the invention are useful generally in distillate fuel oils boiling in the range of about 120°C to 500°C, especially 160°C to 400°C, and are particularly useful in NBD fuels having a boiling range of 200°C (+ or - 50°C) to 340°C (+ or - 20°C) and especially such NBD fuels which have a wax content of 3-6% by weight, such as 3-4% by weight.

The additive of this invention is a derivative of the polyalkylene glycol diacid, the derivative being a monoester, diester, monoamine salt of the acid or of the half- ester, diamine salt, diamide or mixed ester/amide amine salts. Ester derivatives are preferably those prepared by reacting the diacid with monohydric aliphatic alcohols having about 6 to 30 carbon atoms, and the amine and amide derivatives are preferably prepared from C₈-C₄₀ primary, secondary, tertiary or quaternary amines or mixtures thereof.

Preferred additives of this invention are prepared from a polyethylene glycol dicarboxylic acid having a molecular weight (Mn, number average) of about 200 to 1,000, more preferably about 600. Esters of this acid prepared from C₂₀-C ₂ mixed linear aliphatic alcohols are a preferred derivative additive and these esters may be monoesters, diesters or mixtures thereof such as the mixed esters prepared by reacting the diacid and the mixed C₂₀-C₂₂ alcohols in a 1 to 1.5 molar ratio (diacid:alcohols). Another preferred additive is the ester amine salt prepared by reacting the polyethylene glycol diacid (Mn 600), mixed C₂₀-C₂₂ linear alkanols and dihydrogenated tallow amine in a molar ratio of 1 :1.5:0.5 (acid .alcohols: amine), to form an amine salt of ϊhe ester mixture. A further preferred additive is the amine salt prepared by reacting the above diacid and amine in a molar ratio of 1 :2.

The amines used in forming additives of this invention are preferably long chain C₁₂-C₄₀ secondary amines such as dioctadecyl amine, methyl behenyl amine and the like. Particularly preferred is a secondary hydrogenated tallow amine of the formula HNRιR₂ wherein Rj and R₂ are alkyl groups derived from hydrogenated tallow fat composed of 4% C_H, 31% C_J6 and 59% C₁₈ alkyl groups as the principal alkyl groups.

Another aspect of this invention is the use of the foregoing additives to improve the low temperature properties of fuel oils, especially NBD fuel oils.

The additives of the present invention may conveniently be supplied as concentrates in oil for incorporation into the bulk distillate fuel. Such concentrates, which are further embodiments of this invention, preferably contain 3-75 wt.%, more preferably 3-60 wt.%, most preferably 10-50 wt.% of the additives in solution in oil.

The concentration of the additive in the oil may for example be 10 to 2,000 ppm or to 1,000 ppm of additive (active ingredient) by weight per weight of fuel, preferably 20 to 500 ppm or to 1,000 ppm, more preferably 100 to 500 ppm.

The additive should be soluble the oil to the extent of at least 1,000 ppm by weight per weight of oil at ambient temperature. However, at least some of the additive may come out of solution near the cloud point of the oil in order to modify the wax crystals that form.

CO-ADDITIVES

The additives of the invention may be useful in combination with one or more co-additives for improving the cold flow properties of distillate fuels.

Useful co-additives (i) through (vii) in accordance with the various aspects of this invention are described below.

A further embodiment of this invention comprises fuel oil compositions containing the aforesaid ester, amine and amide derivatives in combination with one or more co-additives selected from the group consisting of comb polymers, polyoxyalkylene compounds, ethylene unsaturated ester copolymers, polar organic nitrogen-containing compounds, hydrocarbon polymers, sulfur carboxy compounds and hydrocarbylated aromatic compounds. Of these co-additives ethylene unsaturated ester copolymers, and as ethylene vinyl acetate copolymers and polar organic nitrogen compounds are particularly preferred. Such co-additives may be present in amounts such that the weight ratio of ester, amine or amide derivative to said co-additive is about 1 :30 to 2:1, and preferably the ratio is about 1:3 to 1 :4 parts by weight of derivative:parts by weight co-additive.

Another aspect of this invention involves use of said combination of ester, amine or amide derivative with said co-additive to improve the low temperature properties of fuel oils, especially NBD fuels.

(i) Comb Polymers

Comb polymers are polymers in which hydrocarbyl groups are pendant from a polymer backbone and are discussed in "Comb-Like Polymers. Structure and Properties", N.A. Plate and V.P. Shibaev, J. Poly. Sci. Macromolecular Revs., 8, p. 117 to 253 (1974).

Advantageously, the comb polymer is a homopolymer having side chains containing at least 6, and preferably at least 10, carbon atoms or a copolymer having at least 25 and preferably at least 40, more preferabl at least 50, molar % of units having side chains containing at least 6, and preferably at least 10, carbon atoms.

As examples of preferred comb polymers there may be mentioned those of the general formula

where D R^π, COOR¹', OCOR¹¹, R^,2COOR^π or OR¹¹ E H, CH₃, D or R¹² G H or D J = H, R¹², R¹²COOR^u, or an aryl or heterocyclic group K H, COOR¹², OCOR¹², OR¹² or COOH L H, R¹², COOR¹², OCOR¹² or aryl R 11 > Cjo hydrocarbyl

R 12

> Ci hydrocarbyl

and m and n represent mole ratios, m being within the range of from 1.0 to 0.4, n being in the range of from 0 to 0.6. R¹¹ advantageously represents a hydrocarbyl 1 group with from 10 to 30 carbon atoms, and R advantageously represents a hydrocarbyl group with from 1 to 30 carbon atoms.

The comb polymer may contain units derived from other monomers if desired or required. It is within the scope of the invention to include two or more different comb copolymers.

These comb polymers may be copolymers of maleic anhydride or fumaric acid and another ethylenically unsaturated monomer, e.g. an α-olefin or an unsaturated ester, for example, vinyl acetate. It is preferred but not essential that equimolar amounts of the comonomers be used although molar proportions in the range of 2 to 1 and 1 to 2 are suitable. Examples of olefins that may be copolymerized with e.g. maleic anhydride, include 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, and 1- octadecene.

The copolymer may be esterified by any suitable technique and although preferred it is not essential that the maleic anhydride or fumaric acid be at least 50% esterified. Examples of alcohols which may be used include n-decan-1-ol, n-dodecan- l-ol, n-tetradecan-1-ol, hexadecan-1-ol, and n-octadecan-1-ol. The alcohols may also include up to one methyl branch per chain, for example, 1-methylpentadecan-l-ol, 2- methyltridecan-1-ol. The alcohol may be a mixture of normal and single methyl branched alcohols. It is preferred to use pure alcohols rather than the commercially available alcohol mixtures but if mixtures are used the R refers to the average number of carbon atoms in the alkyl group; if alcohols that contain a branch at the 1

12 or 2 positions are used R refers to the straight chain backbone segment of the alcohol.

These comb polymers may especially be fumarate or itaconate polymers and copolymers such as, for example, those described in European Patent Applications 153176, 153177 and 225688, and WO 91/16407.

Particularly preferred fumarate comb polymers are copolymers of alkyl fumarates and vinyl acetate, in which the alkyl groups have from 12 to 20 carbon atoms, more especially polymers in which the alkyl groups have 14 carbon atoms or in which the alkyl groups are a mixture of _δ alkyl groups, made, for example, by solution copolymerizing an equimolar mixture of fumaric acid and vinyl acetate and reacting the resulting copolymer with the alcohol or mixture of alcohols, which are preferably straight chain alcohols. When the mixture is used it is advantageously a 1 : 1 by weight mixture of normal C_i and Cι₆ alcohols. Furthermore, mixtures of the C₁₄ ester with the mixed C₁₄/Cι₆ ester may advantageously be used. In such mixtures, the ratio of C₁₄ to C₁₄/C₁₆ is advantageously in the range of from l.T to 4: 1, preferably 2: 1 to 7:2, and most preferably about 3: 1, by weight. The particularly preferred fumarate comb polymers may, for example, have a number average molecular weight in the range of 1,000 to 100,000, preferably 1,000 to 3,000, as measured by Vapour Phase Osmometry (VPO).

Other suitable comb polymers are the polymers and copolymers of α-olefins and esterified copolymers of styrene and maleic anhydride, and esterified copolymers of styrene and fumaric acid; mixtures of two or more comb polymers may be used in accordance with the invention and, as indicated above, such use may be advantageous.

(ii) Polyoxyalkylene Compounds

Examples are polyoxyalkylene esters, ethers, ester/ethers and mixtures thereof, particularly those containing at least one, preferably- at least two C₁₀ to C₃₀ linear saturated alkyl groups and a polyoxyalkylene glycol group of molecular weight up to

5,000 preferably 200 to 5,000, the alkyl group in said polyoxyalkylene glycol containing from 1 to 4 carbon atoms.

The preferred esters, ethers or ester/ethers which may be used may be structurally depicted by the formula

R-O(A)-O-R²

where R and R are the same or different and may be

(a) n-alkyl ff

(b) n-alkyl-C

ft

(c) n-alkyl-O-C-(CH₂)

f? ft

(d) n-alkyl-O-C-(CH ) C- n being, for example, 1 to 30, the alkyl group being linear and saturated and containing 10 to 30 carbon atoms, and A representing the polyalkylene segment of the glycol in which the alkylene group has 1 to 4 carbon atoms, such as a polyoxymethylene, polyoxyethylene or polyoxytrimethylene moiety which is substantially linear; some degree of branching with lower alkyl side chains (such as in polyoxypropylene glycol) may be present but it is preferred that the glycol is substantially linear. A may also contain nitrogen.

Examples of suitable glycols are substantially linear polyethylene glycols (PEG) and polypropylene glycols (PPG) having a molecular weight of about 100 to 5,000, preferably about 200 to 2,000. Esters are preferred and fatty acids containing from 10-30 carbon atoms are useful for reacting with the glycols to form the ester additives, it being preferred to use a C₁₈-C₂₄ fatty acid, especially behenic acid. The esters may also be prepared by esterifying polyethoxylated fatty acids or polyethoxylated alcohols.

Polyoxyalkylene diesters, diethers, ether/esters and mixtures thereof are suitable as additives, diesters being preferred for use in narrow boiling distillates when minor amounts of monoethers and monoesters (which are often formed in the manufacturing process) may also be present. It is important for additive performance that a major amount of the dialkyl compound is present. In particular, stearic or behenic diesters of polyethylene glycol, polypropylene glycol or polyethylene/polypropylene glycol mixtures are preferred.

(iii) Ethylene/Unsaturated Ester Copolymers

Ethylene copolymer flow improvers have a polymethylene backbone divided into segments by oxyhydrocarbon side chains, i.e. ethylene unsaturated ester copolymer flow improvers. The unsaturated monomers copolymerizable with ethylene to form the copolymers include unsaturated mono and diesters of the general formula:

wherein R represents hydrogen or a methyl group; R represents a -OOCR or -COOR group wherein R represents hydrogen or a Ci to C₂₈, preferably C_\ to C_J6, more preferably a to C₈, straight or branched chain alkyl group, provided that R⁴ does not represent hydrogen when R represents -COOR⁴; and

R³ is hydrogen or -COOR⁴.

The monomer, when R and R are hydrogen and R¹ is -OOCR⁴, includes vinyl alcohol esters of Ci to C₂₉, preferably Cj to C₅, monocarboxylic acids, and preferably C to C₂₉, more preferably Ci to C₅ monocarboxylic acids, most preferably

C₂ to C₅ monocarboxylic acids. Examples of vinyl esters which may be copolymerized with ethylene include vinyl acetate, vinyl propionate and vinyl butyrate or isobutyrate, vinyl acetate and vinyl propionate being preferred. Preferably, the copolymers contain from 5 to 40 wt.% of the vinyl ester, more preferably from 10 to

35 wt.% vinyl ester. They may also be in the form of mixtures of two copolymers such as those described in U.S. Patent No. 3,961,916: Preferably, number average molecular weight, as measured by vapour phase osmometry, of the copolymer is

1,000 to 10,000, more preferably 1,000 to 5,000. If desired, the copolymers may be derived from additional comonomers, e.g. they may be terpolymers or tetrapolymers or higher polymers, for example where the additional comonomer is isobutylene or diisobutylene, or a further vinyl ester monomer such as vinyl 2-ethylhexanoate.

Particularly preferred are ethylene-vinyl acetate-vinyl 2-ethylhexanoate terpolymers.

Such copolymers may also be made by transesterification, or by hydrolysis and re-esterification, of an ethylene unsaturated ester copolymer to give a different ethylene unsaturated ester copolymer. For example, ethylene vinyl hexanoate and ethylene vinyl octanoate copolymers may be made in this way, e.g. from an ethylene vinyl acetate copolymer.

(iv) Polar Organic, Nitrogen-containing Compounds

The oil-soluble polar nitrogen compound is either ionic or non-ionic and is capable of acting as a wax crystal growth inhibitor in fuels. It comprises for example one or more of the compounds (a) to (c) as follows: (a) An amine salt and/or amide formed by reacting at least one molar proportion of a hydrocarbyl substituted amine with a molar proportion of a hydrocarbyl acid having 1 to 4 carboxylic acid groups or its anhydride.

Ester/amides may be used containing 30 to 300, preferably 50 to 150 total carbon atoms. Suitable amines are usually long chain C₁₂-C ₀ primary, secondary, tertiary or quaternary amines or mixtures thereof but shorter chain amines may be used provided the resulting nitrogen compound is oil soluble and therefore normally contains about 30 to 300 total carbon atoms. The nitrogen compound preferably contains at least one straight chain C₈ to C₄₀, preferably C₁ to C₂₄, alkyl segment.

Suitable amines include primary, secondary, tertiary or quaternary, but preferably are secondary. Tertiary and quaternary amines can only form amine salts. Examples of amines include tetradecyl amine, cocoamine, and hydrogenated tallow amine. Examples of secondary amines include dioctadecyl amine and methyl-behenyl amine. Amine mixtures are also suitable such as those derived from natural materials. A preferred amine is a secondary hydrogenated tallow amine of the formula HNR R wherein R and R are alkyl groups derived from hydrogenated tallow fat composed of approximately 4% C₁₄, 31% C₁₆, 59% Cι₈.

Examples of suitable carboxylic acids and their anhydrides for preparing the nitrogen compounds include cyclohexane 1,2-dicarboxylic acid, cyclohexene 1,2- dicarboxylic acid, cyclopentane 1,2-dicarboxylic acid and naphthalene dicarboxylic acid, and 1 ,4-dicarboxylic acids including dialkyl spirobislactone. Generally, these acids have about 5-13 carbon atoms in the cyclic moiety. Preferred acids useful in the present invention are benzene dicarboxylic acids such as phthalic acid, isophthalic acid, and terephthalic acid. Phthalic acid or its anhydride is particularly preferred. The particularly preferred compound is the amide-amine salt formed by reacting 1 molar portion of phthalic anhydride with 2 molar portions of dihydrogenated tallow amine. Another preferred compound is the diamide formed by dehydrating this amide-amine salt.

Other examples are long chain alkyl or alkylene substituted dicarboxylic acid derivatives such as amine salts of monoamides of substituted succinic acids, examples of which are known in the art. Suitable amines may be those described above.

(b) A chemical compound comprising or including a cyclic ring system, the compound carrying at least two substituents of the general formula (I) below on the ring system. -A-NR*R² (I)

where A is an aliphatic hydrocarbyl group that is optionally interrupted by one ore

1 more hetero atoms and that is straight chain or branched, and R and R are the same or different and each is independently a hydrocarbyl group containing 9 to 40 carbon atoms optionally interrupted by one ore more hetero atoms, the substituents being the same or different and the compound optionally being in the form of a salt thereof.

Preferably, A has from 1 to 20 carbon atoms and is preferably a methylene or polymethylene group.

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. Examples include hydrocarbon groups, including aliphatic (e.g. alkyl or alkenyl), alicyclic (e.g. cycloalkyl or cycloalkenyl), aromatic, 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, sulphur, and preferably, oxygen.

The cyclic ring system may include homocyclic, heterocyclic, or fused polycyclic assemblies, or a system where two or more such cyclic assemblies are joined to one another and in which the cyclic assemblies may be the same or different. Where there are two or more such cyclic assemblies, the substituents of the general formula (I) may be on the same or different assemblies, preferably on the same assembly. Preferably, the or each cyclic assembly is aromatic, more preferably a benzene ring. Most preferably, the cyclic ring system is a single benzene ring when it is preferred that the substituents are in the ortho or meta positions, which benzene ring may be optionally further substituted. The ring atoms in the cyclic assembly or assemblies are preferably carbon atoms but may for example include one or more ring N, S or O atom, in which case or cases the compound is a heterocyclic compound.

Examples of such polycyclic assemblies include:

(I) condensed benzene structures such as naphthalene, anthracene, phenanthrene, and pyrene;

(ii) condensed ring structures where none of or not all of the rings are benzene such as azulene, indene, hydroindene, fluorene, and diphenylene oxide;

(iii) rings joined "end-on" such as diphenyl;

(iv) heterocyclic compounds such as quinoline, indole, 2:3 dihydroindole, benzofuran, coumarin, isocoumarin, benzothiophen, carbazole and thiodiphenylamine;

(v) non-aromatic or partially saturated ring systems such as decalin (i.e. decahydronaphthalene), α-pinene, cardinene, and bornylene; and

(vi) three-dimensional structures such as norbornene, bicycloheptane (i.e. norbornane), bicyclooctane, and bicyclooctene.

Each hydrocarbyl group constituting R I and R 2 in the invention (Formula I) may for example be an alkyl or alkylene group or a mono- or poly-alkoxyalkyl group.

Preferably, each hydrocarbyl group is a straight chain alkyl group. The number of carbon atoms in each hydrocarbyl group is preferably 16 to 40, more preferably 16 to

24.

Also, it is preferred that the cyclic system is substituted with only two substituents of the general formula (I) and that A is a methylene group.

Examples of salts of the chemical compounds are the acetate and the hydrochloride.

The compounds may conveniently be made by reducing the corresponding amide which may be made by reacting a secondary amine with the appropriate acid chloride; and (c) A condensate of long chain primary or secondary amine with a carboxylic acid-containing polymer.

Specific examples include esters of telemer acid and alkanolamines such as described a long chain epoxide/amine reaction product which may optionally be further reacted with a polycarboxylic acid; and the reaction product of an amine containing a branched carboxylic acid ester, an epoxide and a mono-carboxylic acid polyester.

(v) Hydrocarbon Polymers

Examples are those represented by the following general formula

where T H or R¹ U H, T or aryl R¹ Cι-C₃₀ hydrocarbyl

and v and w represent mole ratios, v being within the range 1.0 to 0.0, w being within the range 0.0 to 1.0.

These polymers may be made directly from ethylenically unsaturated monomers or indirectly by hydrogenating the polymer made from monomers such as isoprene and butadiene.

Preferred hydrocarbon polymers are copolymers of ethylene and at least one α -olefin, having a number average molecular weight of at least 30,000. Preferably the α-olefin has at most 20 carbon atoms. Examples of such olefins are propylene, 1- butene, isobutene, n-octene-1, isooctene-1, n-decene-1, and n-dodecene- 1. The copolymer may also comprise small amounts, e.g. up to 10% by weight of other copolymerizable monomers, for example olefins other than α-olefins, and non- conjugated dienes. The preferred copolymer is an ethylene-propylene copolymer. It is within the scope of the invention to include two or more different ethylene-α-olefin copolymers of this type. The number average molecular weight of the ethylene-α-olefm copolymer is, as indicated above, at least 30,000, as measured by gel permeation chromatography (GPC) relative to polystyrene standards, advantageously at least 60,000 and preferably at least 80,000. Functionally no upper limit arises but difficulties of mixing result from increased viscosity at molecular weights above about 150,000, and preferred molecular weight ranges are from 60,000 and 80,000 to 120,000.

Advantageously, the copolymer has a molar ethylene content between 50 and 85%. More advantageously, the ethylene content is within the range of from 57 to 80%, and preferably it is in the range from 58 to 73%; more preferably from 62 to 71%, and most preferably 65 to 70%.

Preferred ethylene-α-olefin copolymers are ethylene-propylene copolymers with a molar ethylene content of from 62 to 71% and a number average molecular weight in the range 60,000 to 120,000, especially preferred copolymers are ethylene- propylene copolymers with an ethylene content of from 62 to 71% and a molecular weight from 80,000 to 100,000.

The copolymers may be prepared by any of the methods known in the art, for example using a Ziegler type catalyst. Advantageously, the polymers are substantially amorphous, since highly crystalline polymers are relatively insoluble in fuel oil at low temperatures.

The additive composition may also comprise a further ethylene-α-olefin copolymer, advantageously with a number average molecular weight of at most 7,500, advantageously from 1,000 to 6,000, and preferably from 2,000 to 5,000, as measured by vapour phase osmometry. Appropriate α-olefins are as given above, or styrene, with propylene again being preferred. Advantageously the ethylene content is from 60 to 77 molar % although for ethylene-propylene copolymers up to 86 molar % by weight ethylene may be employed with advantage.

(vi) Sulphur Carboxy Compounds

Examples are compounds of the general formula

in which -Y-R2 is SO3(") ⁺)NR^ R2, -SOSO HNR^R

-SO₃ (-)(+)H2NR3R2_; -SO3 (-)(+)H NR2,

-X-Rl is -Y-R2 or -CONR3R1,

-R4ORl, -R4OCOR1, -R4, Rl,

-N(COR3)Rl or Z(-)(+)NR^ Rl;

-Z(-) is SO3Θ or -Cθ2(");

1 1

R and R are alkyl, alkoxyalkyl or polyalkoxyalkyl containing at least 10 carbon atoms in the main chain;

R is hydrocarbyl and each R may be the same or different and R is absent or is C] to C₅ alkylene and in

A \ C I C

the carbon-carbon (C-C) bond is either a) ethylenically unsaturated when A and B may be alkyl, alkenyl or substituted hydrocarbyl groups or b) part of a cyclic structure which may be aromatic, polynuclear aromatic or cyclo-aliphatic, it is preferred that X-

1 1

R and Y-R between them contain at least three alkyl, alkoxyalkyl or polyalkoxyalkyl groups.

(vii) Hydrocarbylated-Aromatics

These materials are condensates comprising aromatic and hydrocarbyl parts. The aromatic part is conveniently an aromatic hydrocarbon which may be unsubstituted or substituted with, for example, non-hydrocarbon substituents. Such aromatic hydrocarbon preferably contains a maximum of these substituent groups and/or three condensed rings, and is preferably naphthalene. The hydrocarbyl part is a hydrogen and carbon containing part connected to the rest of the molecule by a carbon atom. It may be saturated or unsaturated, and straight or branched, and may contain one or more hetero-atoms provided they do not substantially affect the hydrocarbyl nature of the part. Preferably the hydrocarbyl part is an alkyl part, conveniently having more than 8 carbon atoms. The molecular weight of such condensates may, for example be in the range of 2,000 to 200,000 such as 2,000 to 20,000, preferably 2,000 to 8,000.

Examples are known in the art, primarily as lube oil pour depressants and as dewaxing aids as mentioned hereinbefore, they may, for example, be made by condensing a halogenated wax with an aromatic hydrocarbon. More specifically, the condensation may be a Friedel-Crafts condensation where the halogenated wax contains 15 to 60, e.g. 16 to 50, carbon atoms, has a melting point of about 200 to 400°C and has been chlorinated to 5 to 25 wt.% chlorine, e.g. 10 to 18 wt.%.

Another way of making similar condensates may be from olefins and the aromatic hydrocarbons.

Multicomponent additive systems may be used and the ratios of additives to be used will depend on the fuel to be treated.

The invention is further illustrated by the following examples which are not to be considered as limitative of its scope.

By one method, the response of the oil to the additives was measured by the

Cold Filter Plugging Point Test (CFPP) which is carried out by the procedure described in detail in "Journal of the Institute of Petroleum", Volume 52, Number 510, June, 1966, pp. 173-285. This test is designed to correlate with the cold flow of a middle distillate in automotive diesels.

In brief, a 40 ml. sample of the oil to be tested is cooled in a bath which is maintained at about -34°C to give non-linear cooling at about l°C/min. Periodically (at each one degree C starting from above the cloud point), the cooled oil is tested for its ability to flow through a fine screen in a prescribed time period using a test device which is a pipette to whose lower end is attached an inverted funnel which is positioned below the surface of the oil to be tested. Stretched across the mouth of the funnel is a 350 mesh screen having an area defined by a 12 millimeter diameter. The periodic tests are each initiated by applying a vacuum to the upper end of the pipette whereby oil is drawn through the screen up into the pipette to a mark indicating 20 ml. of oil. After each successful passage, the oil is returned immediately to the CFPP tube. The test is repeated with each one degree drop in temperature until the oil fails to fill the pipette within 60 seconds. This temperature between the CFPP of an additive free fuel and of the same fuel containing additive is reported as the CFPP depression (dCFPP) by the additive. A more effective flow improver gives a greater CFPP depression at the same concentration of additive.

EXAMPLES

Example 1

An additive of the invention was prepared by reacting a polyethylene glycol dicarboxylic acid (Mn 600) with C_]8-C₂₄ mixture of linear alcohols using a molar ratio of 1:2.0 (acid to alcohol).

Example 2

An additive of the invention was prepared by reacting the same acid of Example 1 with a dihydrogenated tallow amine in a molar ratio of 1:2.0 (acid:amine)

Example 3

An additive was prepared from behenyl alcohol (2 moles) and Mn 600 polyethylene glycol diacid ( 1 mole) to provide a diester.

Example 4

An additive was prepared by reacting the same diacid of Example 1 with a di- C₂o-C ₂ alkylamine in a molar ratio of 1 :2 acid: amine,

Properties of Test Fuels

IBP Initial boiling point, °C FBP = Final boiling point, °C

WAT = Wax appearance temperature

Cloud Point is °C CFPP is °C

In the Table below:

"Comparison" is polyethylene glycol dibehenate.

Co-additive 3 is the reaction product of dihydrogenated tallow amine and phthalic anhydride, a polar nitrogen compound.

Co-additive 4 is ethylene vinyl acetate, containing 35% by weight vinyl acetate and having a molecular weight of about 4500.

In the table below, the Compounds of Examples 1 to 4 were mixed with co- additive 3 in a weight ratio of 1/3 and the same compounds were mixed with co- additive 4 in a weight ratio of 1/4. "None" refers to either the fuel alone or the fuel with only the co-additives and not the compounds of the invention. Examples 2 and 4 were only tested in Fuel C.

Table

CFPP Results on Treating the Test Fuels with combination of the Example 1 and 3 Additives and Co-Additives 3 and 4 and Comparison Additive

Claims

1. A fuel oil composition exhibiting improved low temperature properties which contains an effective amount of an additive being an ester, amine salt or amide derivative, or mixture of derivatives, of a polyalkylene glycol dicarboxylic acid of the formula

HOOC-CH₂O(alkylene-O)_nCH₂COOH

where the alkylene has 2-4 carbon atoms and n is an integer and the dicarboxylic acid has a molecular weight of 200 to 5,000.

2. The composition of claim 1, wherein the additive is a monoester or diester derivative, or mixture thereof, prepared from an alcohol having about 6 to 30 carbon atoms and the alkylene is ethylene.

3. The composition of claim 1 wherein- the additive is a mixture of monoesters and diesters prepared by reacting the dicarboxylic acid with a C₆-C₃₀ alcohol in the molar ratio of 1 to 1.5 acid to alcohol or the amine salt thereof and the alkylene is ethylene.

4. The composition of claim 3 wherein the alcohol is a mixture C₂₀-C₂₂ mixed linear alkanols.

5. The composition of claim 4 wherein the additive is an amine salt of the partially esterified mixture prepared by reacting the diacid, alcohol and amine in a molar ratio of 1 :1.5:0.5 diacid to alcohol to amine.

6. The composition of claim 5 wherein the amine is a dihydrogenated tallow amine.

7. The composition of claim 1 wherein the dicarboxylic acid has a molecular weight of about 600.

8. The composition of claims 4 or 5 wherein the dicarboxylic acid has a molecular weight of about 600 and the alkylene is ethylene.

9. The composition of claim 1 wherein the additive is an amide or diamide derivative.

10. The composition of claim 1 wherein the additive is a monoamine or diamine salt derivative.

11. The composition of claim 1 wherein the additive is a mixture of an ester, an amine salt and an amide of said dicarboxylic acid.

12. The composition of claim 1 wherein the alkylene is propylene.

13. The composition of claim 1 wherein there is present a co-additive selected from the group consisting of comb polymers, polyoxyalkylene compounds, ethylene unsaturated ester copolymers, polar organic nitrogen-containing compounds, hydrocarbon polymers, sulfur carboxyl compounds and hydrocarbylated aromatic compounds.

14. The composition of claim 13 wherein the co-additive is an ethylene vinyl acetate copolymer.

15. The composition of claim 13 wherein the co-additive is a polar organic nitrogen-containing compound.

16. The composition of claim 13 wherein the weight ratio of the ester, amine or amide derivative to the co-additive is from 1 :30 to 2:1.

17. The composition of claim 16 wherein the ratio is 1:3 to 1:4.