DE69420736T3 - ADDITIVES AND FUEL COMPOSITIONS - Google Patents

Description

This invention relates to the use of additives for improving the cold flow properties of fuel oil (hereinafter fuel oil, for example distillate petroleum fuel such as middle distillate fuel oil boiling in the range of 110°C to 500°C.

When fuel oils are exposed to low ambient temperatures, paraffin can precipitate from the fuel and affect the flow properties of the oil. For example, middle distillate fuels contain paraffin which precipitates at low temperatures to form large waxy crystals that tend to clog the small pore openings of fuel filters. This problem is particularly acute when the fuel is a diesel fuel because the nominal openings in the fuel filter of diesel engines typically have a diameter between about 5 and 50 µm. Additives to overcome the above problem are known in the art and are referred to as flow improvers.

Such additives can act as wax crystal modifiers when mixed with waxy mineral oil by modifying the shape and size of the crystals of the wax contained therein and reducing the adhesion forces between the crystals and between the wax and the oil to allow the oil to remain flowable at lower temperatures than in the absence of the additive.

Many additives are described in the art for improving the cold flow properties of oils, for example in the form of oil-soluble addition products or condensates, which may be polymeric or monomeric and as described in US-A-3 048 479, GB-A-1 263 152, US-A-3 961 961 and EP-A-0 261 957. Some of the above additives have been used commercially to date as cold flow improvers.

The state of the art also describes that cold flow improvers can be used in combination with other additives. For example, GB-A-1 112 808 describes ethylene/vinyl acetate copolymers in combination with rust inhibitors, anti-emulsifiers, corrosion inhibitors, antioxidants, dispersants, dyes, dye stabilizers, turbidity inhibitors and antistatic additives.

In this invention it has surprisingly been found that the cold flow properties of cold flow improvers such as those described above can be further increased by using coadditives which were not previously known in the art to exhibit cold flow improvement properties.

Thus, a first aspect of the invention is the use of coadditive (A) comprising an oil-soluble lubricity additive comprising a glycerol monoester of unsaturated monocarboxylic acid, wherein the acid has from 2 to 50 carbon atoms, the use being in a composition comprising a major proportion of fuel oil and a minor proportion of component (B) comprising a cold flow improver additive comprising an ethylene/unsaturated ester copolymer having a number average molecular weight, measured by vapor phase osmometry, of from 1000 to 5000 and improving the cold flow properties of the composition.

The improvement of the cold flow performance of component (B) by component (A) of the invention can be applied to the blending of additives into a fuel oil. Thus, a second aspect of the invention is a method of blending additives with fuel oil, comprising (i) injecting component (B) as defined above into the fuel oil, (ii) injecting component (A) as defined above into the fuel oil, (iii) measuring the cold flow properties of the fuel oil after the injections of steps (i) and (ii), and (iv) adjusting the relative injection rate of component (B) and (A) and thereby their relative amounts to take into account the results of step (iii) and to provide the desired cold flow properties in the fuel oil.

The invention also includes a fuel oil composition comprising a major proportion of fuel oil and a combination component (A) comprising an oil-soluble lubricity additive comprising a glycerol monoester of unsaturated monocarboxylic acid, said acid having from 2 to 50 carbon atoms, and component (B) comprising a cold flow improver additive comprising ethylene/unsaturated ester copolymer having a number average molecular weight, as measured by vapor phase osmometry, of from 1000 to 5000, and optionally other additives.

The invention further includes an additive concentrate comprising component (A) and component (B) as defined above and optionally other additives.

Component (A) may additionally comprise (a) oil soluble ashless dispersant/detergent comprising amine acylated with hydrocarbyl carboxy acylating agent or bearing hydrocarbyl groups or hydrocarbyloxy groups, (b) oil soluble nitrate or peroxy cetane improver, and (c) oil soluble petroleum fuel antifoam comprising a silicon based composition or polyamine having at least one primary or secondary amino group acylated with carboxyl acylating agent.

According to the second aspect of this invention, the fuel oil is preferably in the form of a flowing stream, with stage (i) taking place in a first station and stage (ii) in a second station, although the first and second stations may terminate together and injection may be via a common injector. The process may be automated so that a sensor may perform stage (iii), e.g. by measuring the cold filter plugging point (CFPP), and the information may be fed via a control element to control the injection of either or both of components (B) and (A).

The invention surprisingly enables less of component (B) to be used to achieve a desired cold flow improver performance.

The features of the invention will now be discussed in more detail. Patent documents to which reference is made are incorporated herein.

As used in this patent specification, the term "hydrocarbon" refers to a group having a carbon atom directly bonded to the remainder of the molecule and 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 preferably saturated. These groups may contain non-hydrocarbon substituents provided that their presence does not alter the predominantly hydrocarbon character of the group. Examples include keto, halo, hydroxy, nitro, cyano, alkoxy and acyl. When the hydrocarbon group is substituted, a single (mono) substituent is preferred.

Examples of substituted hydrocarbon 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 heteroatoms include, for example, nitrogen, sulfur and, preferably, oxygen.

The acid, alcohol and ester that characterize the lubricity additive are now discussed in more detail below.

(i) Acid

The acid from which the ester is derived is an unsaturated, straight-chain or branched monocarboxylic acid. For example, the acid can be represented by the formula

R'(COOH)

can be generally described in which R' represents an alkenyl group with 10 (e.g. 12) to 30 carbon atoms. The alkenyl group can have one or more double bonds such as 1, 2 or 3. Examples of unsaturated carboxylic acids are those with 10 to 22 carbon atoms, such as oleic, elaidic, palmitoleic, petroselic, ricinoleic, eleostearic, linoleic, linolenic, gadoleic, erucic or hypogeic acid.

(ii) Alcohol

The alcohol from which the ester is derived is glycerin.

(iii) The Esters

The esters may be used alone or as mixtures of one or more esters and may be composed only of carbon, hydrogen and oxygen. Preferably, the ester has a molecular weight of 200 or more or has at least 10 carbon atoms or both.

Specific examples are esters prepared from one or more of the above-mentioned unsaturated carboxylic acids, such as glycerol monooleate. Such polyhydric esters may be prepared by esterification as described in the art and/or may be commercially available.

The ester has more than one free hydroxy group.

Examples are described in WO-PCT/EP 94/00148.

Additional components are referenced above in lowercase letters:

(a) Ashless dispersants are dispersants designed to improve the detergency of fuel oils and leave little or no metal-containing residue upon combustion. They are described in numerous patents and include the following:

- Polyamines which have been acylated with hydrocarbon polycarboxy acylating agents (e.g. hydrocarbon dicarboxylic anhydride), such as alkenyl succinimide polyamines in which, for example, the alkenyl group Polyisobutylene. Examples are described in EP-A-0 482 253. Also included are cyclized products of such polyamines as described in EP-A-0 525 052.

- Polyamines that have been provided with hydrocarbon groups, e.g. with a polyolefin group such as polyisobutylene. Examples are described in WO-A-91/12302.

- hydrocarbon ether amines such as alkyl ether monoamines, where the hydrocarbon group has, for example, 6 to 26 carbon atoms (e.g. 8 or 10) and is preferably methyl branched alkyl, such as an oxo alcohol derivative. The amine may have, for example, 2 to 8 carbon atoms. Examples are described in US-A- 4,319,987. Other examples are alkoxylated amines as described in US-A-4,409,000.

(b) Examples of cetane improvers are organic nitrates such as nitrate esters containing aliphatic or cycloaliphatic groups of up to 30 carbon atoms, preferably saturated groups and preferably of up to 12 carbon atoms. Examples of such nitrates are methyl, ethyl, propyl, isopropyl, butyl, amyl, hexyl, heptyl, octyl, isooctyl, 2-ethylhexyl, nonyl, decyl, allyl, cyclopentyl, cyclohexyl, methylcyclohexyl, cyclodecyl, 2-ethoxyethyl and 2-(2-ethoxylethoxy)ethyl nitrates. Other examples are fuel-soluble peroxides, hydroperoxides and peroxyesters.

(c) Examples of antifoaming agents include siloxane-polyoxyalkylene copolymers, for example those described in US-A-3,233,986, which comprise at least one siloxane block containing at least two siloxane groups of the formula R₂SiO0.5(4-b) where R is a halogen atom or an optionally halogenated hydrocarbon group and b is 1 to 3, and at least one polyoxyalkylene block containing at least two oxyalkylene groups. In general, the alkylene groups have 2 or 3 carbon atoms. and usually both ethyleneoxy and propyleneoxy groups are present. Advantageously, the copolymer is a polymethylsiloxane-polyoxyalkylene copolymer, preferably having the general formula

(CH3 )3 SiO[CH3 (A)SiO]m[(CH3 )2 SiO]nSi(CH3 )3

in the A

-(CH2 )pO(C2 H4 O)x(C3 H6 O)yZ

in which Z is hydrocarbon, OC(hydrocarbon) or preferably hydrogen and in which the absolute values of m and n and their ratios and the values of p, x and y and their ratios can vary widely, but the total values advantageously give an average molecular weight (weight average) in the range from 600 to 25,000. The ratio of m:n is advantageously in the range from 10:1 to 1:20, or the value of n can be zero, and the ratio of x:y is advantageously in the range from 1:100 to 100:1, preferably 20:80 to 100:1, or one of x or y, but not both, can be zero. Preferred antifoams are those offered under the trade name TEGOPREN by Th. Goldschmidt AG. Preferably, the antifoam agent is present in the fuel in an amount in the range of 0.0001 to 0.2% by weight, preferably 0.005 to 0.02% by weight. Other antifoam agents may be silicon-free, such as those prepared by acylating polyamines as described in WO-A-94/06894.

Component (B)

Ethylene/unsaturated ester copolymer flow improvers have a polymethylene backbone that is segmented by oxyhydrocarbon side chains.

In particular, the copolymer may comprise ethylene copolymer which, in addition to units derived from ethylene, contains units having the formula

-CR⁵R⁶-CHR⁵-

in which R6 is hydrogen or a methyl group, R5 represents a -OOCR8; or -COOR8; group, where R5 is hydrogen or a straight chain or branched C1 to C28, preferably C1 to C9, alkyl group, provided that R8 does not represent hydrogen when R5 is -COOR8; and R7 represents hydrogen or a -COOR8; group.

These include a copolymer of ethylene with an ethylenically unsaturated ester or derivatives thereof. An example is a copolymer of ethylene with an ester of an unsaturated carboxylic acid, but the ester is preferably one of an unsaturated alcohol with a saturated carboxylic acid. An ethylene/vinyl ester copolymer is advantageous, an ethylene/vinyl acetate, ethylene/vinyl propionate, ethylene/vinyl hexanoate or ethylene/vinyl octanoate copolymer is preferred. Preferably the copolymers contain 1 to 25, e.g. 1 to 20, mole% of the vinyl ester, especially 3 to 17 mole% of the vinyl ester. They can also be in the form of mixtures of two copolymers, such as those described in US-A-3,961,916. The number average molecular weight, measured by vapor phase osmometry, of the copolymer is 1000 to 5000. If desired, the copolymers may be derived from additional comonomers, e.g. they may be terpolymers or tetrapolymers or higher polymers, for example when the additional comonomer is isobutylene or diisobutylene.

The copolymers can be prepared by direct polymerization of comonomers. Such copolymers can also be prepared by transesterification or hydrolysis and reesterification of ethylene/unsaturated ester copolymer to give another ethylene/unsaturated ester copolymer. For example, ethylene/vinyl hexanoate and ethylene/vinyl octanoate copolymers can be prepared in this way, e.g. from ethylene/vinyl acetate copolymer.

Component (B) may be used with cocomponents such as one or more of the following:

Comb polymers

Comb polymers are described in "Comb-Like Polymers. Structure and Properties", N. A. Plate and V. P. Shibaev, J. Poly. Sci. Macromolecular Revs., 8, pages 117 to 253 (1974).

Generally, comb polymers have one or more long chain branches such as hydrocarbon branches, such as oxyhydrocarbon branches, having 10 to 30 carbon atoms pendant from a polymer backbone, with the branch or branches being directly or indirectly bonded to the backbone. Examples of indirect bonding include bonding via interposed atoms or groups, where the bonding can include covalent and/or electrochemical bonding as in a salt.

Advantageously, the comb polymer is a homopolymer having side chains or a copolymer in which at least 25 and preferably at least 40, in particular at least 50 mol.% of the units have side chains containing at least 6 and preferably at least 10 atoms selected from, for example, carbon, nitrogen or oxygen in a linear chain.

Examples of preferred comb polymers are those containing units with the general formula

included, whereby

D = R¹¹, COOR¹¹, OCOR¹¹, R¹²COOR¹¹ or OR¹¹ means,

E = H, CH₃, D or R¹²,

G = H or D means

J = H, R¹², R¹²COOR¹¹, or an aryl or heterocyclic group

K = H, COOR¹², OCOR¹², OR¹² or COOH,

L = H, R¹², COOR¹², OCOR¹² or aryl,

R¹¹ represents a hydrocarbon group having 10 or more carbon atoms and

R¹² represents a hydrocarbon group having 1 or more carbon atoms,

where m and n represent molar ratios, their sum is 1 and m is finite and up to and including 1 and n is zero to less than 1, where m is preferably in the range of 1.0 to 0.4 and n is in the range of 0 to 0.6. R¹¹ advantageously represents a hydrocarbon group having 10 to 30 carbon atoms and R¹² advantageously represents a hydrocarbon group having 1 to 30 carbon atoms.

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

The comb polymers may, for example, be copolymers of maleic anhydride or fumaric acid and another ethylenically unsaturated monomer, e.g. an α-olefin or unsaturated ester, e.g. vinyl acetate. It is preferred, although not necessary, that equimolar amounts of the comonomers are used, although molar proportions in the range of 2:1 to 1:2 are suitable. Examples of olefins which 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-1-ol, n-tetradecan-1-ol, n-hexadecan-1-ol and n-octadecan-1-ol. The alcohols may also include up to one methyl branch per chain, for example 1-methylpentadecan-1-ol, 2-methyltridecan-1-ol. The alcohol may be a mixture of n-alcohols and alcohols with a single methyl branch. It is preferred to use pure alcohols rather than alcohol mixtures which are commercially available. However, if mixtures are used , R¹² refers to the average number of carbon atoms in the alkyl group. When alcohols containing a branch in the 1- or 2-position are used, R¹² refers to the straight chain backbone segment of the alcohol.

The comb polymers can in particular be fumarate or itaconate polymers and copolymers, such as those described in EP-A-153 176, EP-A-153 177, EP-A-225 688 and WO 91/16407.

Particularly preferred fumarate comb polymers are copolymers of alkyl fumarates and vinyl acetate in which the alkyl groups have 12 to 20 carbon atoms, especially polymers in which the alkyl groups have 14 carbon atoms or in which the alkyl groups are a mixture of C₁₄/C₁₆ alkyl groups, prepared, 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. If the mixture is used, it is advantageously a 1:1 (w:w) mixture of n-C₁₄ and C₁₆ alcohols. In addition, mixtures of C14 ester with the mixed C14/C16 ester can advantageously be used. In such mixtures, the ratio of C14 to C14/C16 is advantageously in the range of 1:1 to 4:1, preferably 2:1 to 7:2, and most preferably about 3:1, by weight. The particularly preferred fumarate comb polymers can, for example, have a number average molecular weight in the range of 1,000 to 100,000, preferably 1,000 to 30,000, as measured by vapor 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 can be used in accordance with the invention and, as previously stated, this use can be advantageous.

Other examples of comb polymers are hydrocarbon polymers such as copolymers of ethylene and at least one α-olefin, wherein the α-olefin preferably has at most 20 carbon atoms, examples are n-decene-1 and n-dodecene-1. Preferably, the number average molecular weight of this copolymer is at least 30,000. The hydrocarbon polymers can be prepared by methods known in the art, for example using a Ziegler type catalyst.

Compounds with linear group

Such compounds include a compound in which at least one substantially linear alkyl group having from 10 to 30 carbon atoms is linked to a non-polymeric organic radical to provide at least one linear chain of atoms including the carbon atoms of the alkyl groups and one or more non-terminal oxygen atoms.

By "substantially linear" it is meant that the alkyl group is preferably straight chain, but that substantially straight chain alkyl groups with a small degree of branching, such as in the form of a single methyl group branch, can be used.

Preferably, the compound has at least two of these alkyl groups where the linear chain can include the carbon atoms of more than one of the alkyl groups. Where the compound has at least three of the alkyl groups, more than one such linear chain can be present, and the chains can overlap. The linear chain or chains can form part of the linking group between any two alkyl groups in the compound.

The oxygen atom or atoms are preferably inserted directly between carbon atoms in the chain and can be provided, for example, in the linking group in the form of a mono- or polyoxyalkylene group, the oxyalkylene group preferably having 2 to 4 carbon atoms. Examples are oxyethylene and oxypropylene.

As shown, the chain or chains include carbon and oxygen atoms. They may also include other heteroatoms such as nitrogen atoms.

The compound may be an ester in which the alkyl groups are attached to the remainder of the compound as -O-CO-n-alkyl or -CO-O-n-alkyl groups, in the former case the alkyl groups are derived from an acid and the remainder of the compound is derived from a polyhydric alcohol, and in the latter case the alkyl groups are derived from an alcohol and the remainder of the compound is derived from a polycarboxylic acid. The compound may also be an ester in which the alkyl groups are attached to the remainder of the molecule as -O-n-alkyl groups. The compound may be both ester and ether or may contain different ester groups.

Examples include polyoxyalkylene esters, ethers, ester/ethers and mixtures thereof, particularly those containing at least one, preferably at least two linear C10 to C30 alkyl groups and a polyoxyalkylene glycol group having a molecular weight of up to 5000, preferably 200 to 5000, wherein the alkylene group in the polyoxyalkylene glycol contains 1 to 4 carbon atoms, as described in EP-A-61 895 and US-A-4 491 455.

The preferred esters, ethers or ester/ethers that can be used can be represented in their structure by the formula

R²³OBOR²&sup4;

in which R²³ and R²⁴ are the same or different and

(a) n-alkyl,

(b) n-alkyl-CO-,

(c) n-alkyl-OCO-(CH₂)n-

(d) n-Alkyl-OCO-(CH2 )nCO-

where n is, for example, 1 to 34, the alkyl group is linear and contains 10 to 30 carbon atoms and B represents the polyalkylene segment of the glycol in which the alkylene group 1 to 4 carbon atoms, for example a polyoxymethylene, polyoxyethylene or polyoxytrimethylene moiety which is substantially linear, whereby a small degree of branching with lower alkyl side chains (as in polyoxypropylene glycol) can be tolerated, but it is preferred that the glycol is substantially linear. B may also contain nitrogen.

Suitable glycols are generally substantially linear polyethylene glycols (PEG) and propylene glycols (PPG) having a molecular weight of about 100 to 5000, preferably about 200 to 2000. Esters are preferred and fatty acids having 10 to 30 carbon atoms are useful for reacting with the glycols to form the ester additives, it being preferred to use C18 to C24 fatty acids, particularly behenic acid. The esters can also be prepared by esterification of polyethoxylated fatty acids or polyethoxylated alcohols.

Polyoxyalkylene diesters, diethers, ether/esters and mixtures thereof are suitable as additives, with diesters being preferred when the petroleum-based component is a narrow boiling distillate, where small amounts of monoethers and monoesters (often formed during the manufacturing process) may be present. It is important for active performance that a larger amount of the dialkyl compound be present. In particular, stearic or behenic diesters of polyethylene glycol, polypropylene glycol or polyethylene/polypropylene glycol mixtures are preferred.

Examples of other compounds in this general category are those described in Japanese Patent Publication Nos. 2-51477 and 3-34790 and EP-A-117 108 and EP-A-326 356, and cyclic esterified ethoxylates described in EP-A-356 256.

Hydrocarbon polymers

Examples are those with the following general formula:

, in the

T = H or R¹

U = H, T or Aryl

R¹ = C₁- to C₃₀-hydrocarbon,

and v and w represent molar ratios, where v is in the range of 1.0 to 0.0 and w is in the range of 0.0 to 1.0.

These polymers can be prepared directly from ethylenically unsaturated monomers or indirectly by hydrogenating the polymer prepared 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 contain 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-olefin copolymer is, as shown 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 there is no upper limit, but mixing problems result due to increased viscosity at molecular weights above about 150,000, and preferred molecular weight ranges are 60,000 and 80,000 to 120,000.

The copolymer advantageously has a molar ethylene content between 50 and 85%. The ethylene content is particularly advantageous in the range of 57 to 80% and preferably in the range of 58 to 73%, especially 62 to 71% and most preferably 65 to 70%.

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

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

The additive composition may also comprise a further ethylene/alpha-olefin copolymer, advantageously having a number average molecular weight of at most 7500, advantageously 1000 to 6000 and preferably 2000 to 5000, measured by vapor phase osmometry. Suitable alpha-olefins are as indicated above or styrene, with propylene again being preferred. Advantageously the ethylene content is 60 to 77 mole percent, although with ethylene/propylene copolymers up to 86 mole percent ethylene can advantageously be used.

Examples of hydrocarbon polymers are described in WO-A-9 111 488.

Polar compounds

Such compounds comprise an oil-soluble polar nitrogen compound bearing one or more, preferably two or more substituents having the formula =NR¹, where R¹ is a hydrocarbon group having 8 to 40 carbon atoms, the substituent or one or more of the substituents optionally being in the form of a cation derived therefrom. The oil-soluble polar nitrogen compound is either ionic or non-ionic and is capable of being used in fuels to act as a paraffin crystal growth modifier. It comprises, for example, one or more of the compounds (i) to (iii) as follows:

(i) An amine salt and/or amide formed by reacting at least a molar proportion of hydrocarbyl-substituted amine with a molar proportion of hydrocarbyl acid having 1 to 4 carboxylic acid groups or its anhydride, wherein the substituent(s) having the formula =NR¹ has the formula -NR¹R², wherein R¹ is as defined above and R represents hydrogen or R¹, provided that R¹ and R² may be the same or different, the substituents representing part of the amine salt and/or amide groups of the compound.

Esters/amides having a total of 30 to 300, preferably 50 to 150 carbon atoms may be used. These nitrogen compounds are described in US-A-4,211,534. Suitable amines are usually long chain primary, secondary, tertiary or quaternary C₁₂ to C₄₀ amines or mixtures thereof, but shorter chain amines may be used provided that the resulting nitrogen compound is oil soluble and therefore normally contains a total of about 30 to 300 carbon atoms. The nitrogen compound preferably contains at least one straight chain C₈ to C₄₀, preferably C₁₄ to C₂₄ alkyl segment.

Suitable amines include primary, secondary, tertiary or quaternary, but preferably secondary. Tertiary and quaternary amines can only form amine salts. Examples of amines include tetradecylamine, coco-amine and hydrogenated tallow amine. Examples of secondary amines include dioctadecylamine and methylbehenylamine. Amine mixtures are also suitable, such as those derived from natural materials. A preferred amine is a secondary hydrogenated tallow amine having the formula HNR¹R², in which R¹ and R² are alkyl groups derived from hydrogenated tallow fat and composed of approximately 4 wt% C₁₄, 31 wt% C₁₆ and 59 wt% C₁₈.

Examples of suitable carboxylic acids and their anhydrides for the preparation of the nitrogen compounds include cyclohexane- 1,2-dicarboxylic acid, cyclohexene-1,2-dicarboxylic acid, cyclopentane-1,2-dicarboxylic acid and naphthalenedicarboxylic acid and 1,4-dicarboxylic acids including dialkyl spirobislactone. Generally, these acids have about 5 to 13 carbon atoms in the cyclic portion. Preferred acids useful in the present invention are benzenedicarboxylic acids such as phthalic acid, isophthalic acid and terephthalic acid. Phthalic acid or its anhydride is particularly preferred. The most preferred compound is the amide/amine salt prepared by reacting one molar portion of phthalic anhydride with 2 molar portions of di(hydrogenated tallow)amine. Another preferred compound is the diamide prepared 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 and described, for example, in US-A-4,147,520. Suitable amines may be those described above.

Other examples are condensates as described in EP-A-327 423.

(ii) A chemical compound comprising or including a cyclic ring system, wherein the compound has at least two substituents having the following general formula (I)

-A-NR¹R² (I)

on the ring system, in which A is an aliphatic hydrocarbon group which is optionally interrupted by one or more heteroatoms and is straight-chain or branched, and R¹ and R² are the same or different and each independently is a hydrocarbon group having 9 to 40 carbon atoms and is optionally interrupted by one or more heteroatoms, where the substituents are the same or different and the compound is optionally in the form of its salt.

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

The term "hydrocarbon" as used in the specification refers to a group having a carbon atom directly attached to the remainder of the molecule and having 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 preferably saturated. These groups may contain non-hydrocarbon substituents provided that their presence does not alter the predominantly hydrocarbon character of the group. Examples include keto, halogen, hydroxy, nitro, cyano, alkoxy and acyl. When the hydrocarbon group is substituted, a single (mono) substituent is preferred.

Examples of substituted hydrocarbon 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 heteroatoms include, for example, nitrogen, sulfur and, preferably, oxygen.

The cyclic ring system may include homocyclic, heterocyclic or fused polycyclic structures or a system in which two or more such cyclic structures are linked together and in which the cyclic structures may be the same or different. When two or more such cyclic structures are present, the substituents of general formula (I) may be on the same or different structures, preferably on the same structure. Preferably, the or each cyclic structure is aromatic, in particular a benzene ring. Most preferably, the cyclic ring system is a single benzene ring, wherein It is preferred that the substituents are in ortho or meta positions, whereby the benzene ring may optionally be further substituted.

The ring atoms in the cyclic structure or structures are preferably carbon atoms, but may include, for example, one or more N, S or O atoms in the ring, in which case or cases the compound is a heterocyclic compound.

Examples of such multinuclear structures include:

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

(b) fused ring structures in which none or not all of the rings are benzene, such as azulene, indene, hydroindene, fluorene and diphenylene oxides,

(c) End-to-end connected rings such as diphenyl,

(d) heterocyclic compounds such as quinoline, indole, 2,3-dihydroindole, benzofuran, coumarin, isocoumarin, benzothiophene, carbazole and thiodiphenylamine,

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

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

Each hydrocarbon group representing R¹ and R² in the invention (formula I) may be, for example, an alkyl or alkylene group or mono- or polyalkoxyalkyl group. Preferably, each hydrocarbon group is a straight-chain alkyl group. The number of carbon atoms in each hydrocarbon group is preferably 16 to 40, especially 16 to 24.

It is also preferred that the cyclic system is substituted with only two substituents having the general formula (I) and that A is a methylene group.

Examples of salts of chemical compounds are acetate and hydrochloride.

The compounds may be conveniently prepared by reducing the corresponding amide, which is prepared by reacting a secondary amine with the corresponding acid chloride, and

(iii) A condensate of long chain primary or secondary amine with carboxylic acid containing polymer.

Specific examples include polymers as described in GB-A- 2 121 807, FR-A-2 592 387 and DE-A-39 41 561, and also esters of telomer acid and alkanolamines as described in US-A- 4 639 256 and the reaction product of amine containing branched carboxylic acid ester, epoxy and monocarboxylic acid polyester as described in US-A-4 631 071.

Sulfur carboxy compounds

Examples are those described in EP-A-0 261 957.

Fuel oil

The fuel oil is suitably a middle distillate fuel oil. Such distillate fuel oils generally boil in the range of about 110°C to about 500°C, e.g. 150°C to about 400°C. The fuel oil may comprise atmospheric distillate or vacuum distillate or cracked gas oil, or a mixture in any proportion of direct distilled and thermally and/or catalytically cracked distillates. The most common petroleum distillate fuels are kerosene, jet fuel, diesel fuels, heating oil and heavy fuel oils. The heating oil may be a direct atmospheric distillate or may contain small amounts, e.g. up to 35% by weight, of vacuum gas oil or cracked gas oils, or both.

The fuel oil can be animal, vegetable or mineral oil and can also be synthetic. It can also contain other additives than those mentioned above.

The concentration of the additive combination in the oil may, for example, be in the range of 1 to 5000 ppm by weight of additive (active ingredient) per weight of fuel, such as 10 to 2000 ppm by weight. ppm active ingredient per weight of fuel, preferably 25 to 500 ppm, in particular 100 to 200 ppm.

The additive should be soluble in the oil to the extent of at least 1000 ppm by weight of the oil at moderate temperature. However, near the cloud point of the oil, at least a portion of the additive may separate from the solution to modify the wax crystals that form.

Concentrates are convenient as a means of incorporating the additive into bulk oil such as distillate fuel, which incorporation may be carried out by methods known in the art. The concentrates may also contain other additives as required and preferably contain from 3 to 75%, more preferably from 3 to 60%, most preferably from 10 to 50% by weight of the additive, preferably in solution in oil. Examples of carrier liquids are organic solvents including hydrocarbon solvents, for example petroleum fractions such as naphtha, kerosene and fuel oil, aromatic hydrocarbon-containing aromatic fractions (e.g. Solvesso (trade name)) and paraffinic hydrocarbons such as hexane, pentane and isoparaffins, and includes mixtures of the above. The carrier liquid must of course be selected for its compatibility with the additive and with the fuel.

The additives of the invention can be incorporated into bulk oil by other methods as known in the art. If other additives are required, they can be incorporated into the bulk oil at the same time as the additives of the invention or at another time. Examples of other additives include antioxidants, corrosion inhibitors, deflocculants, metal deactivators, cosolvents, additive package compatibilizers, odor improvers, antistatic additives (conductivity improvers), biocides, dyes, smoke reducers, catalyst life enhancers, performance multipliers, fuel economy additives, demulsifiers and spray modifiers.

The following compounds can be used in the invention.

Additive

B1 Ethylene/vinyl acetate copolymer having a number average molecular weight of 3300 as measured by gel permeation chromatography (GPC) and containing about 36 wt% vinyl acetate.

B2 Ethylene/vinyl acetate copolymer having a number average molecular weight of 5000 as measured by gel permeation chromatography (GPC) and containing about 13.5 wt% vinyl acetate.

B3 Mixture of additives B1 and B2 in weight : weight ratio (B1 : B2) of 3 : 1

C N,N-dialkylanunonium salt of 2-N',N'-dialkylamidobenzoate which is the reaction product of reacting 1 mole of phthalic anhydride with 2 moles of di(hydrogenated tallow)amine to form half amide/half amine salt.

Testing

The following tests evaluate the effectiveness of the tested additives as filterability improvers in distillate fuels.

Simulated filter plugging point (SFPP)

The test was carried out according to the procedure essentially as described in EP-A-0 403 097 and is a variant of the CFPP test.

Cold filter plugging point (CFPP test)

The test, which was carried out according to the procedure described in detail in the "Journal of the Institute of Petroleum", Volume 52, Number 510, June 1966, pages 173 to 285, was designed to correlate with the cold flow behavior of middle distillate in automotive diesel engines.

Briefly, a sample of the oil to be tested (40 ml) is cooled in a bath maintained at about -34ºC to give non-linear cooling at about 1ºC/minute. Periodically (at each degree Celsius, starting from above the cloud point) the cooled oil is tested for its ability to pass through a fine sieve in a prescribed period of time, using a test device which is a pipette with an inverted funnel attached to the lower end and placed below the surface of the oil to be tested. Stretched across the mouth of the funnel is a 350 mesh sieve (mesh number 350) having an area given by a diameter of 12 mm. The periodic tests are each initiated by applying a vacuum to the upper end of the pipette, thereby drawing oil through the sieve into the pipette upwards to a mark indicating 20 ml of oil. After each successful pass, the oil is immediately returned to the CFPP test tube. The test is repeated with each degree decrease in temperature until the oil can no longer fill the pipette within 60 seconds. The temperature at which failure occurs is reported as the CFPP temperature.

The additive combinations of the invention may also be effective to reduce the tendency of the wax to settle in the fuel (i.e., they may be anti-wax settling additives) and may exhibit activity in slow cooling tests such as the extended programmed cooling test (XPCT) known in the art.

Components BX and BY

BX: B2 (56 ppm), B1 (169 ppm), 7 (75 ppm), C (75 ppm)

BY: B2 (50ppm), 3 (100ppm), 6 (100ppm), C (100ppm), 5 (200ppm)

The concentrations of the constituents of components BX and BY in the fuels are given in brackets as a percentage by weight of the fuel. The constituents indicated with reference numbers 3 and 5 to 7 above are as follows (in addition to the constituents already defined here):

3 Ethylene/vinyl acetate copolymer having a number average molecular weight of 3300 as measured by GPC, containing 36 wt% vinyl acetate

5 Itaconate polymer having a number average molecular weight of about 4000 as measured by GPC prepared by polymerizing monomer in cyclohexane solvent using free radical catalyst, wherein the monomer contained linear alkyl groups having 18 carbon atoms.

6 Copolymer of styrene and esterified fumaric acid, wherein the alkyl groups had 14 carbon atoms, the copolymer had a number average molecular weight of 15,000, measured by GPC, and contained proportions of styrene and esterified fumaric acid in a ratio of 1:1 (mol:mol)

7 A fumarate ester/vinyl acetate copolymer having a number average molecular weight of about 20,000 as measured by GPC, wherein the fumarate ester contains linear alkyl groups having 12 to 14 carbon atoms.

Claims (23)

1. Use of coadditive (A) comprising an oil-soluble lubricity additive comprising a glycerol monoester of an unsaturated monocarboxylic acid, wherein the acid has 2 to 50 carbon atoms, wherein the use is in a composition comprising a major proportion of fuel oil and a minor proportion of component (B) comprising a cold flow improver additive comprising an ethylene/unsaturated ester copolymer having a number average molecular weight, as measured by vapor phase osmometry, of 1000 to 5000 and improving the cold flow properties of the composition. 2. Use according to claim 1, wherein the lubricity additive is the ester of a monocarboxylic acid having the formula R'(COOH) in which R' represents an alkenyl group having 10 to 30 carbon atoms. 3. Use according to claim 2, wherein the alkenyl group has 1, 2 or 3 double bonds. 4. Use according to any one of the preceding claims, wherein the acid is oleic, elaidic, palmitoleic, petroselic, ricinoleic, eleostearic, linoleic, linolenic, gadoleic, erucic or hypogeic acid. 5. Use according to any one of the preceding claims, wherein the glycerol monoester is glycerol monooleate. 6. Use according to any one of the preceding claims, wherein component (B) comprises an ethylene/unsaturated ester copolymer. 7. Use according to claim 6, wherein the unsaturated ester is of unsaturated alcohol with saturated carboxylic acid. 8. Use according to any one of the preceding claims, which additionally comprises as a co-additive an oil-soluble polar nitrogen compound having one or more substituents of the formula -NR¹-, in which R¹ is a hydrocarbon group having 8 to 40 carbon atoms, the substituents or one or more of the substituents optionally being in the form of a cation derived therefrom. 9. Use according to one of the preceding claims, in which the fuel oil is middle distillate fuel oil. 10. Use according to one of the preceding claims, in which the total concentration of components (A) and (B) in the fuel oil is in the range from 25 to 500 ppm by weight of active ingredient per part by weight of fuel oil. 11. A fuel oil composition comprising a major proportion of fuel or propellant oil and a combination of component (A) comprising an oil-soluble lubricity additive comprising a glycerol monoester of unsaturated monocarboxylic acid, said acid having 2 to 50 carbon atoms, and Component (B) comprising a cold flow improver additive comprising ethylene/unsaturated ester copolymer having a number average molecular weight, measured by vapor phase osmometry, from 1000 to 5000, and optionally other additives. 12. Additive concentrate, which Component (A) comprising an oil-soluble lubricity additive comprising a glycerol monoester of unsaturated monocarboxylic acid, said acid having 2 to 50 carbon atoms, and Component (B) comprising a cold flow improver additive comprising ethylene/unsaturated ester copolymer having a number average molecular weight measured by vapor phase osmometry of 1000 to 5000, and may contain other additives. 13. A composition according to claim 11 or claim 12, wherein the lubricity additive comprises the ester of a monocarboxylic acid having the formula R'(COOH) in which R' represents an alkenyl group having 10 to 30 carbon atoms. 14. A composition according to claim 13, wherein the alkenyl group has 1, 2 or 3 double bonds. 15. A composition according to any one of claims 11 to 14, wherein the acid is oleic, elaidic, palmitoleic, petroselic, ricinoleic, eleostearic, linoleic, linolenic, gadoleic, erucic or hypogeic acid. 16. A composition according to any one of claims 11 to 15, wherein the glycerol monoester is glycerol monooleate. 17. A composition according to any one of claims 11 to 16, wherein component (B) comprises an ethylene/unsaturated ester copolymer in which the unsaturated ester is of unsaturated alcohol with saturated carboxylic acid. 18. A composition according to any one of claims 11 to 17, which additionally comprises as a co-additive an oil-soluble polar nitrogen compound having one or more substituents of the formula -NR¹-, in which R¹ represents a hydrocarbon group having 8 to 40 carbon atoms, the substituents or one or more of the substituents optionally being in the form of a cation derived therefrom. 19. A composition according to claim 11 or any one of claims 13 to 18 when dependent on claim 11, wherein the fuel oil is middle distillate fuel oil. 20. A composition according to claim 11 or any one of claims 13 to 19 when dependent on claim 11, wherein the total concentration of components (A) and (B) in the fuel oil is in the range of 25 to 500 ppm by weight of active ingredient per part by weight of fuel oil. 21. Process for mixing additives with fuel oil, in which (i) component (B) as defined in claim 1 is injected into the fuel oil, (ii) component (A) as defined in claim 1 is injected into the fuel oil, (iii) the cold flow properties of the fuel oil are measured after the injections of steps (i) and (ii), and (iv) the relative injection rates of components (B) and (A) and thereby their relative amounts are adjusted to take into account the results of step (iii) and to provide the desired cold flow properties in the fuel oil. 22. A process according to claim 21, wherein the fuel oil comprises a flowing stream thereof, step (i) takes place in a first station and step (ii) takes place in a second station. 23. A method according to claim 21 or 22, wherein a sensor performs the step (iii) and the information is fed via a control unit to control the injection of one or both components (B) and (A).