This invention relates to additive compositions and their use in improving the properties of oil and fuel oil compositions.

It is known that wax separates out from oils and fuel oils at low temperatures thereby impairing certain properties. It is also known to use additives to improve those properties, for example to improve cold flow properties and to inhibit settling of the wax under gravity on standing. Additives for the former are sometimes called Cold Flow Improvers and additives for the latter are sometimes called Wax Anti-settling Additives.

Examples of patent specifications describing such additives and their use are: US Patents 3 048 479; 3 961 916; 3 252 771 ; 2 542 542; 3 444 082; 4 21 1 534; 4 375 973 and 4 402 708; UK Patents 1 263 152; 1 469 016; 1 468 588; 2 129 012; 2 923 645; and 1 209 676; Japanese Patent Publications 56 54 038;

56 54 037; and 55 40 640. Ethylene/unsaturated ester copolymers are a noteworthy class of additives described in one or more of these specifications, and have been used commercially.

EP-A-0 225 688 describes the use of itaconate and citraconate polymers and copolymers for improving the cold flow properties of an oil (crude or lubricating) and fuel oils such as residual fuel, middle distillate fuels and jet fuel or as a dewaxing aid in lubricating oil, which polymers and copolymers can be tailored to suit the particular oil or fuel oil concerned. It describes polymers and copolymers having number average molecular weights as measured by Gel Permeation Chromatography of from 1 ,000 to 500,000 and exemplifies polymers and copolymers of molecular weights of 20,000 and higher.

International Application Number PCT/GB91/00622 (Publication No WO 91/16407) describes the use of polymers embraced within EP-A-0 255 688 of number average molecular weight of 1 ,000 to 20,000 as low temperature flow improvers for distillate fuels, such as in combination with other additives such as ethylene/unsaturated ester copolymers.

However, such combinations are not necessarily as effective as desired in improving the cold flow properties of certain distillate fuels such as, but not necessarily restricted to, waxy fuels.

It has now been found that using hydrocarbylated aromatics in place of at least part of an additive component such as an ethylene/unsaturated ester copolymer significantly improves cold flow performance as will be demonstrated in the examples herein.

Alkylated-aromatics are described in the art for treating fuels. Thus

US-A-3, 245,766 describes the use of chlorinated wax-naphthalene condensation polymers for lowering the pour point of middle distillate petroleum fuel oil; and UK-A- 1 ,436, 793 describes the use of such polymers (and alkylated-aromatics generally) in combination with ethylene-containing polymeric pour point depressants and/or N-aliphatic hydrocarbyl succinamic acid and its amine salts as flow improvers in distillate fuel oils. However, there is no description or suggestion of this use with comb polymers such as itaconate polymers.

US-A-4,255,159 describes a polymeric substance, ie.poly (isomerised C ₁₂ - C ₅₀ mono olefin), alone or as the alkylation derivative of an aromatic compound in combination with a lubricating oil pour depressant having pendant alkyl groups of 6 to 32 carbon atoms as useful in improving the cold flow properties of distillate hydrocarbon oils.

A first aspect of the invention is a crude oil or fuel oil composition comprising a major proportion by weight of a crude oil or a fuel oil and a minor proportion by weight of an additive comprising, in combination,

(i) at least one hydrocarbylated-aromatic pour point depressant other than a poly (isomerised C ₁₂ - C ₅₀ mono olefin) derivative of an aromatic compound; and (ii) at least one comb polymer having pendant oxyhydrocarbyl groups containing 10 or more carbon atoms.

A second aspect of the invention is the use as a flow improver in a crude oil or fuel oil of an additive composition of the first aspect of this invention.

A third aspect of the invention is an additive concentrate comprising an admixture of an additive of the first aspect of this invention dispersed in a liquid medium compatible with a crude oil or fuel oil.

A fourth aspect of the invention is a process for improving the flow properties of a crude oil or fuel oil which comprises incorporating into the oil an additive of the first aspect of this invention.

The individual features of the invention will now be described in further detail.

COMPONENT (i) - Hydrocarbylated-Aromatics

In one form, 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 such as 10 to 30 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.

In another form, these materials are alkylated diphenyl ethers such as, for example, described in EP-A-203,812; US-A-4,014,663; US-A-3,999,960, and US- A-5, 102,427. For example, such materials may be alkylated diphenyl ethers wherein the alkyl groups contain from 16 to 44 carbon atoms, such as C20 to C28. and include dialkylated materials. Such materials may be prepared by alkylating diphenyl ether with dimerised or polymerised alpha olefins as described in aforesaid US-A-3,99,960 which is incorporated herein by reference. The diphenyl ether is preferably alkylated with the dimer of an alpha olefin having 16 to 44 carbon atoms, more preferably 18 to 28 carbon atoms.

COMPONENT (ii)

Comb polymers 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).

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

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

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

where D = R , COOR , OCOR ^{1 1} , R ² COOR ^{1 1} or OR ^{1 1}

E = H, CH3, D or R ²

G = H or D

J = H, R ¹² , R ¹² COOR ^{1 1} , or an aryl or heterocyclic group

K = H, COOR ¹² , OCOR ¹² , OR ² or COOH L H, R ¹² , COOR ¹² , OCOR ¹² or aryl

R ^{1 1} Ξ. C10 hydrocarbyl

R ¹² Cl hydrocarbyl

and m and n represent mole ratios, their sum being 1 and m being finite and being up to and including 1 and n being from zero to less than 1 , preferably m being within the range of from 1.0 to 0.4, n being in the range of from 0 to 0.6. R ^{1 1} advantageously represents a hydrocarbyl group with from 10 to 30 carbon atoms, and R ¹² 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 a-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-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-methy_tridecan-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 ¹ refers to the average number of carbon atoms in the alkyl group; if

alcohols that contain a branch at the 1 or 2 positions are used R ¹² refers to the straight chain backbone segment of the alcohol.

These comb polymers may especially be fumarate or itaconate polyme-s and copolymers such as for example those described in European Patent Applications 153 176, 153 177 and 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 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 C14/C16 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 C14 and C-|6 alcohols. Furthermore, mixtures of the C14 ester with the mixed C14/C16 ester may advantageously be used. In such mixtures, the ratio of C14 to C14/C16 is advantageously in the range of from 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 may, 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 Vapour Phase Osmometry (VPO).

Other suitable comb polymers are the polymers and copolymers of alpha-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.

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

Preferably, component (ii) comprises (a) a polymer containing the units:

(III) (II)

where x is an integer and y is 0 or an integer and wherein, in the polymer, the sum of x and y is at least two, the ratio of units (II) to units (I) is between 0 and 2, and the ratio of units (II) to (III) is between 0 and 2 and wherein:

R1 and R2 are the same or different, each representing a C10 to C30 alkyl group,

R3 represents H, -OOCR6, Cι to C30 alkyl, -COOR6, -OR6, or halogen,

R4 represents H or methyl,

R5 represents H, C1 to C30 alkyl, or -COOR6.

R6 represents C1 to C22 alkyl

optionally, each of the groups R1 , R2, R3, R4, R5 and R6 being inertly substituted said polymer preferably being in combination with (b) a comb polymer having, from a polymer backbone, aryl groups and hydrocarbyl groups, which hydrocarbyl groups containing 10 or more carbon atoms.

A fifth aspect of the invention is an additive comprising (a) and (b), as defined above in combination.

Polymer (a) may be a homopolymer of a dialkyl itaconate or citraconate or a copolymer of a dialkyl itaconate or citraconate with an aliphatic olefin, a vinyl ether, a vinyl ester of an alkanoic acid, an alkyl ester of an unsaturated acid, an aromatic olefin, a vinyl halide or a dialkyl fumarate or maleate; or polymer (a) may be a copolymer of dialkyl itaconate or dialkyl citraconate with an aliphatic olefin , a vinyl ester or an alkyl substituted vinyl ester of a C-2 to C31 alkanoic acid.

R1 and R2 are each preferably straight chain although they can be branched. If branched, the branch is preferably a single methyl in the 1 or 2 position. Examples of R1 and R2 are decyl, dodecyl, hexadecyl and eicosyl. Each of R1 and R2 may be a single C10 to C30 alkyl group or a mixture of alkyl groups. Polymers where R1 and R2 are each mixtures of C12 to C20 alkyl groups are particularly useful as flow improvers in middle distillate fuel oils. Polymers where R1 and R2 are each C16 to C22 are particularly useful in heavy fuel oils and crude oils, and polymers where R1 and R2 are each C10 to C18 are particularly useful in lubricating oils. Such particularly useful polymers may be homopolymers or copolymers.

The dialkyl itaconate or dialkyl citraconate, when a comonomer, has the formula:

R ⁴

R- C=CH-R ⁵

where R3, R4 and R5 are as defined above. Such a comonomer can be a mixture.

When such a comonomer is an aliphatic olefin, R3 and R5 represent hydrogen or C1 to C30 alkyl groups, preferably n-alkyl groups, that are the same or different.

Thus, when each of R3, R4 and R5 is hydrogen, the olefin is ethylene, and, when R3 is methyl, and R4 and R5 are hydrogen, the olefin is n-propylene. When R3 is an alkyl group, R4 and R5 are preferably hydrogen. Examples of other suitable olefins are butene-1 , butene-2, isobutylene, pentene-1 , hexene-1 , tetradecene-1 , hexadecene-1 and octadecene-1 and mixtures thereof.

Other such comonomers are vinyl esters or alkyl substituted vinyl esters of C-2 to C31 alkanoic acids: in vinyl esters when R3 is R6COO-, R4 is H and R5 is H, and in alkyl substituted vinyl esters when R3 is R6000- and R4 is methyl and/or R5 is Cι to C30 alkyl. Un-substituted vinyl esters are preferred, examples being vinyl acetate, vinyl propionate, vinyl butyrate, vinyl decanoate, vinyl hexadecanoate and vinyl stearate.

Another class of comonomers are the alkyl esters of unsaturated acids, i.e. when R3 is a R600C- and R5 is H or C1 to C30 alkyl. When R4 and R5 are hydrogen, the comonomers are alkyl esters of acrylic acid. When R4 is methyl, the comonomers are esters of methacrylic acid or Cι to C30 alkyl substituted methacrylic acid. Examples of alkyl esters of acrylic acid are methyl acrylate, n-hexyl acrylate, n-decyl acrylate, n-hexadecyl acrylate, n-octadecyl acrylate, and 2-methyl hexadecyl acrylate. Examples of alkyl esters of methacrylic acid are propyl methacrylate, n-butyl methacrylate, n-octyl methacrylate, n-tetradecyl methacrylate, n-hexadecyl methacrylate and n-octadecyl methacrylate. Other examples are the corresponding esters where R5 is alkyl, e.g. methyl, ethyl, n- hexyl, n-decyl, n-tetradecyl and n-hexadecyl.

Another class of comonomers is that where both R3 and R5 are R6000-, i.e. when they are Cι to C22 dialkyl fumarates or maleates and the alkyl groups may be n-alkyl or branched alkyl, e.g. n-octyl, n-decyl, n-tetradecyl, n-hexadecyl or n- octadecyl.

Other examples of comonomer are those where R3 is an aryl group. When R4 and R5 are hydrogen and R3 is phenyl the comonomer is styrene and when one of R4 and R5 is methyl and comonomer is a methyl styrene, e.g. a-methyl styrene. Another example when R3 is aryl is vinyl naphthalene. Other examples when R3 is alkaryl are, for example, substituted styrenes such as vinyl toluene, or 4-methyl styrene.

Another comonomer is that where R3 is halogen, e.g. chlorine, such as vinyl chloride (i.e. R4 and R5 hydrogen).

As stated, some or all of the groups R1, R2, R3, R4, R5 and R6 can be inertly substituted; examples are by one or more halogen atoms such as chlorine or fluorine. For example, the comonomer may be vinyl trichloroacetate. Alternatively, the inert substituent may be an alkyl group, e.g. methyl.

When the ratio of units (II) to units (I) and of units (II) to (III) is 0 the polymer is an itaconate or citraconate homopolymer and when the ratio is 2 the polymer is a copolymer. The ratio is preferably between 0.5 and 1.5. Usually the copolymer consists of units (I) and (II) only, or of units (II) and (III) only, but other units are not excluded. However, the weight percentage of units (I) and (II) or of units (II) and (III) in the copolymer is desirably at least 60%, preferably at least 70%.

The molecular weight of the polymer of component (a), whether a homopolymer or copolymer, may be between 1 ,000 and 500,000, preferably 1 ,000 and 20,000, more preferably between 1 ,000 and 10,000, even more preferably between 2,200 and 5,000, the molecular weights being measured by gel permeation chromatography (GPC) relative to polystyrene standards and being number average molecular weights.

The homopolymers and copolymers are generally prepared by polymerising the monomers alone or in solution in a hydrocarbon solvent such as heptane, benzene, cyclohexane, or white oil, at a temperature generally in the range of from 20 ^° C to 150°C and usually promoted by a peroxide or azo type catalyst such as benzoyl peroxide or azodiisobutyronitrile under a blanket of an inert gas such as nitrogen or carbon dioxide in order to exclude oxygen. The polymer may be prepared under pressure in an autoclave or by refluxing.

To prepare copolymers, the polymerisation reaction mixture may contain up to 2 moles of comonomer (e.g. vinyl acetate) per mole of dialkyl itaconate or dialkyl citraconate.

In the practice of the invention, more than one components (a) may be used.

The ratio of component (a) to component (b) when used together may, for example, be in the range of 10:1 to 1 :10 (weight:weight).

Preferably component (b) is of the general formula

wherein D, E, K, m and n are defined as above, and J is an aryl group which may be unsubstituted or substituted.

More specifically, component (b) is preferably a copolymer of the monomers (x) and (y) where

(x) is an ester, being a mono- or di-alkyl fumarate, maleate, itaconate, citraconate, mesaconate, trans- or cis-glutaconate, in which the alkyl group has 8 to 23 carbon atoms, and

(y) is an aromatic substituted olefin having 8 to 40 carbon atoms per molecule, for example of the formula Ar-CH=CH2 where Ar is the aromatic substituent.

(x) is preferably a dialkyl ester, e.g. fumarate, but mono-alkyl esters, e.g. fumarates, are suitable. The alkyl group is preferably straight chain although, if desired, branched chain alkyl groups can be used. Examples of suitable alkyl groups are decyl, dodecyl, tetradecyl, hexadecyl, octadecyl, eicosyl, behenyl or mixtures thereof. Preferably, the alkyl group contains 10 to 18 carbon atoms, such as 10 to 14 carbon atoms. Where the ester is a dialkyl ester such as a dialkyl fumarate the two alkyl groups can be different.

In (y), the aromatic substituent is preferably a phenyl substituent, particularly preferred monomers being styrene, and α- and β-alkyl styrenes such as α-methyl styrene and β-methyl styrene, which may be substituted on the benzene ring, e.g.

with one or more alkyl groups or halogen atoms. Such alkyl substituents may, for example, have 1 to 20 carbon atoms.

The molar proportions of (y) to (x) may, for example, be between 1 :1.5 and 1.5:1 , preferably between 1 :1.2 and 1.2:1 , e.g. about 1 :1. The number average molecular weight of the copolymer of (x) and (y) may be between 2,000 and

100,000, preferably between 5,000 and 50,000, as measured by gel permeation chromatography (GPC) relative to polystyrene standard.

Preferred examples of the component (b) are styrene-maleate copolymers or styrene-fumarate copolymers, it being preferred to use them in this invention in combination with polyitaconates of number average molecular weight between 1 ,000 and 20,000 as component (a).

In the practice of this invention, more than one component (b) may be used.

OTHER COLD FLOW IMPROVERS

The additive composition of the invention may be used in combination with one or more other Cold Flow Improvers as co-additives such as those known in the art. Examples are comb polymers; linear compounds; ethylene unsaturated ester copolymers; polar compounds, either ionic or non-ionic (such as described in EP- A-0 225 688); sulphur carboxy compounds and hydrocarbon polymers.

The other cold flow imDrovers will now be described in further detail as follows:

COMB POLYMERS

Examples include

^* comb polymers having pendant hydrocarbyl groups containing 10 or more carbon atoms such as defined under (i) hereinabove, provided that they are different from the comb polymers (i).

LINEAR COMPOUNDS

Such compounds comprise a compound in which at least one substantially linear alkyl group having 10 to 30 carbon atoms is connected to a non-polymeric organic residue to provide at least one linear chain of atoms that includes the carbon atoms of said alkyl groups and one or more non-terminal oxygen atoms.

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

Preferably, the compound has a least two of said alkyl groups when the linear chain may include the carbon atoms of more than one of said alkyl groups. When the compound has at least three of said alkyl groups, there may be more than one of such linear chains, which chains may overlap. The linear chain or chains may provide part of a linking group between any two such alkyl groups in the compound.

The oxygen atom or atoms are preferably directly interposed between carbon atoms in the chain and may, for example, be provided in the form of a mono- or poly-oxyalkylene group, said oxyalkylene group preferably having 2 to 4 carbon atoms, examples being oxyethylene and oxypropylene.

As indicated the chain or chains include carbon and oxygen atoms. They may also include other hetero-atoms such as nitrogen atoms.

The compound may be an ester where the alkyl groups are connected to the remainder of the compound as -O-CO n alkyl, or -CO-0 n alkyl groups, in the former the alkyl groups being derived from an acid and the remainder of the compound being derived from a polyhydric alcohol and in the latter the alkyl groups being derived from an alcohol and the remainder of the compound being derived from a polycarboxylic acid. Also, the compound may be an ester where the alkyl groups are connected to the remainder of the compound as — O — n — alkyl groups. The compound may be both an ester and an ether or it 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, C-J Q to C30 linear alkyl groups and a polyoxyalkylene glycol group of molecular weight up to 5,000, preferably 200 to 5,000, the alkylene group in said polyoxyalkylene glycol containing from 1 to 4 carbon atoms, as described in EP-A-61 895 and in U.S. Patent No. 4,491 ,455.

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

R ² 3θBOR ²⁴ where R ² ^ and R ²⁴ are the same or different and may be

(a) n-alkyl-

(b) n-alkyl-CO-

(c) n-alkyl-OCO-(CH ₂ )n-

(d) n-alkyl-OCO-(CH ₂ ) _n CO- n being, for example, 1 to 34, the alkyl group being linear and containing from 10 to 30 carbon atoms, and B representing the polyalkylene segment of the glycol in which the alkylene group has from 1 to 4 carbon atoms, for example, 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 tolerated but it is preferred that the glycol should be substantially linear. B may also contain nitrogen.

Suitable glycols generally 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 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 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 when the petroleum based component is a narrow boiling distillate, when minor amounts of monoethers and monoesters (which are often formed in the manufacturing process) may also be present. It is important for active 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.

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 such as described EP-A-356,256.

ETHYLENE COPOLYMER FLOW IMPROVERS

Ethylene copolymer flow improvers have a polymethylene backbone divided into segments by oxyhydrocarbon side chains, i.e. ethylene unsaturated ester copolymer flow improvers.

More especially, the copolymer may comprise an ethylene copolymer having, in addition to units derived from ethylene, units of the formula

-CR R ⁶ -CHR ⁷ - wherein Rβ represents hydrogen or a methyl group;

R5 represents a -OOCR ⁸ or -COOR ⁸ group wherein R ⁸ represents hydrogen or a Cι to Cg, straight or branched chain alkyl group, provided that R ⁸ does not represent hydrogen when R ⁵ represents -COOR ⁴ ; and R ⁷ is hydrogen or -COOR ⁴ .

These may comprise 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 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 US Patent 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.

The copolymers may be made by direct polymerisation of comonomers. 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, eg. from an ethylene vinyl acetate copolymer.

POLAR NITROGEN COMPOUNDS

Such compounds comprise an oil-soluble polar nitrogen compound carrying one or more, preferably two or more, substituents of the formula =NR , where R ¹ represents a hydrocarbyl group containing 8 to 40 atoms, which substituent or one or more of which substituents may be in the form of a cation derived therefrom. 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 (i) to (iii) as follows:

(i) 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, the substituent(s) of formula =NR ¹ being of the formula -NR R ² where R ¹ is defined as above and R ² represents hydrogen or R , provided that R ¹ and R ² may be the same of different, said substituents constituting part of the amine salt and/or amide groups of the compound.

Ester/amides may be used containing 30 to 300, preferably 50 to 150 total carbon atoms. These nitrogen compounds are described in US Patent 4 211 534. Suitable amines are usually long chain C12-C40 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 C-8 to C40, preferably C14 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 dioctacedyl amine and methyl-behenyl amine. Amine mixtures are also suitable such as those derived from natural materials. A preferred amine is a secondary hydrogenated taϋow amine of the formula HNR ¹ R ² wherein R ¹ and R ² are alkyl groups deπved from hydrogenated tallow fat composed of approximately 4% C14, 31 % Ci6, 59% Ci8-

Examples of suitable carboxylic acids and their anhydrides for preparing the nitrogen compounds include cyclohexane 1 ,2 dicarboxyiic acid, cyclohexene 1 ,2 dicarboxylic acid, cyclopentane 1 ,2 dicarboxyiic acid and naphthalene dicarboxyiic 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 dicarboxyiic 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 dicarboxyiic acid derivatives such as amine salts of monoamides of substituted succinic acids, examples of which are known in the art and described in US-A-4 147 520, for example. Suitable amines may be those described above.

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

(ii) 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 ¹ R ² (I)

where A is an aliphatic hydrocarbyl group that is optionally interrupted by one or more hetero atoms and that is straight chain or branched, and R ¹ and R ² are the same or different and each is independently a hydrocarbyl group containing 9 to 40 carbon atoms optionally interrupted by one or 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

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

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

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

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

(e) non-aromatic or partially saturated ring systems such as decalin

(i.e. decahydronaphthalene), a-pinene, cardinene, and bornylene; and

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

Each hydrocarbyl group constituting R 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

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

Specific examples include polymers such as described in GB-A-2,121 ,807, FR-A-2,592,387 and DE-A-3,941 ,561 ; and also esters of telemer acid and alkanoloamines such as described in US-A-4,639,256; and the reaction product of an amine containing a branched carboxylic acid ester, an episode and a mono- carboxylic acid polyester such as described in US-A4,631 ,071.

HYDROCARBON POLYMERS

Examples are those represented by the following general formula

where T = H or R

U = H, T or aryl

R = C1- C9 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 a- olefin, having a number average molecular weight of at least 30,000. Examples of such olefins are propylene, 1-butene, isobutene, n-octene-1 and isooctene-1. The copolymer may also comprise small amounts, e.g. up to 10% by weight of other copolymerizable monomers, for example olefins other than a-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-a-olefin copolymers of this type.

The number average molecular weight of the ethylene-a-olefin 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 per cent. 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-a-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-alpha-olefin copolymer, advantageously with a number average molecular weight of at most 7500, advantageously from 1 ,000 to 6,000, and preferably from 2,000 to 5,000, as measured by vapour phase osmometry. Appropriate a-olefins are as given above, or styrene, with propylene again being preferred. Advantageously the ethylene content is from 60 to 77 molar per cent although for ethylene-propylene copolymers up to 86 molar per cent by weight ethylene may be employed with advantage.

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

SULPHURCARBOXYCOMPOUNDS

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

OIL AND FUEL OIL

The oil may be a crude oil, i.e. an oil as obtained from drilling and before refining, when the inventive composition may be used as a flow improver or dewaxing aid.

Examples of fuel oils are petroleum-based fuel oils such as middle distillate fuel oils, i.e. fuels obtained in refining crude oil as the fraction between the lighter kerosene and jet fuels fraction and the heavy fuel oil fraction. Examples are diesel fuel, aviation fuel, kerosene, fuel oil, jet fuel and heating oil etc. Generally, suitable distillate fuels are those boiling in the range of 100 to 500 ^° C (ASTM D1160), preferably those boiling in the range 150 to 400 ^° C, for example those having a relatively high Final Boiling Point (FBP) of above 360 ^° C. The fuel oil may be a biofuel used alone or in combination with a petroleum fuel oil.

The invention may be particularly applicable to those middle distillate fuel oils having a relatively high wax content, eg. 1.5 or more such as 2% or greater, eg. greater than 2.5%, advantageously greater than 3%, preferably greater than 4%, for example up to 10% all figures being by weight measured at 10°C below the Wax Appearance Temperature (sometimes abbreviated to WAT) of the fuel.

Biofuels, i.e. fuels from animal or vegetable sources, are believed to be less damaging to the environment on combustion, and are obtained from a renewable source. It has been reported that on combustion less carbon dioxide is formed than is formed by the equivalent quantity of petroleum distillate fuel, e.g. diesel fuel, and very little sulphur dioxide is formed. Certain derivatives of vegetable oil, for example rapeseed oil, e.g. those obtained by saponification and re- esterification with a monohydric alcohol, may be used as a substitute for diesel fuel. It has recently been reported that mixtures of a rapeseed ester, for example, rapeseed methyl ester (RME), with petroleum distillate fuels in ratios of, for example, 10:90 by volume are likely to be commercially available in the near future.

Thus, a biofuel is a vegetable or animal oil or both or a derivative thereof.

Vegetable oils are mainly triglycerides of monocarboxylic acids, e.g. acids containing 10-25 carbon atoms and listed below

where R is an aliphatic radical of 10-25 carbon atoms which may be saturated or unsaturated.

Generally, such oils contain glycerides of a number of acids, the number and kind varying with the source vegetable of the oil.

Examples of oils are rapeseed oil, coriander oil, soyabean oil, cottonseed oil, sunflower oil, castor oil, olive oil, peanut oil, maize oil, almond oil, palm kernel oil, coconut oil, mustard seed oil, beef tallow and fish oils. Rapeseed oil, which is a mixture of fatty acids partially esterified with glycerol, is preferred as it is available in large quantities and can be obtained in a simple way by pressing from rapeseed.

Examples of derivatives thereof are alkyl esters, such as methyl esters, of fatty acids of the vegetable or animal oils. Such esters can be made by transesterification.

As lower alkyl esters of fatty acids, consideration may be given to the following, for example as commercial mixtures: the ethyl, propyl, butyl and especially methyl esters of fatty acids with 12 to 22 carbon atoms, for example of lauric acid, myristic acid, palmitic acid, palmitoleic acid, stearic acid, oleic acid, elaidic acid, petroselic acid, ricinoleic acid, elaeostearic acid, linoleic acid, linolenic acid, eicosanoic acid, gadoleic acid, docosanoic acid or erucic acid, which have an iodine number from 50 to 150, especially 90 to 125. Mixtures with particularly advantageous properties are those which contain mainly, i.e. to at least 50 wt%

methyl esters of fatty acids with 16 to 22 carbon atoms and 1 , 2 or 3 double bonds. The preferred lower alkyl esters of fatty acids are the methyl esters of oleic acid, linoleic acid, linolenic acid and erucic acid.

Commercial mixtures of the stated kind are obtained for example by cleavage and esterification of natural fats and oils by their transesterification with lower aliphatic alcohols. For production of lower alkyl esters of fatty acids it is advantageous to start from fats and oils with high iodine number, such as, for example, sunflower oil, rapeseed oil, coriander oil, castor oil, soyabean oil, cottonseed oil, peanut oil or beef tallow. Lower alkyl esters of fatty acids based on a new variety of rapeseed oil, the fatty acid component of which is derived to more than 80 wt% from unsaturated fatty acids with 18 carbon atoms, are preferred.

The fuel oil may also contain other additives such as stabilisers, dispersants, antioxidants, corrosion inhibitors, demulsifiers, antifoams, cetane improvers, lubricity additives, and/or anti-static additives.

Also the invention may be applicable to a fuel oil having a sulphur concentration of 0.2% by weight of less based on the weight of the fuel. Preferably, the sulphur concentration is 0.05% by weight or less, more preferably 0.01 % by weight or less. The art describes methods for reducing the sulphur concentration of hydrocarbon middle distillate fuels, such methods including for example solvent extraction, sulphuric acid treatment and hydrodesulphurisation.

Heating oils may be made of a blend of virgin distillate, e.g. gas oil, naphtha, etc and cracked distillates, e.g. catalytic cycle stock. A representative specification for a diesel fuel includes a minimum flash point of 38 ^° C and a 90% distillation point between 282 and 380 ^° C.

The total amount of additive composition provided in the oil in this invention is preferably 0.0001 to 5.0 wt%, for example 0.001 to 0.5 wt% (active matter), based on the weight of fuel.

Where the invention is a concentrate, the additive composition may form from 20 to 90, e.g. 30 to 80 wt% thereof. Examples of liquid carriers for use in a concentrate are solvents such as kerosene, aromatic naphthas and mineral lubricating oils.

EXAMPLES

The invention will now be particularly described, by way of example only, as follows. The examples include comparative examples in addition to examples of the invention as will be indicated. Mn means number average molecular weight as measured by GPC relative to polystyrene standards.

ADDITIVES

The additives used were as follows, designated by the indicated code letters.

A: a mixture of two ethylene/vinyl acetate copolymers comprising an approximately 13:1 (wt:wt) mixture of a first copolymer of M _n 2500 containing 36.5 wt % vinyl acetate and a second copolymer of M _n 5000 containing 13.5 wt % vinyl acetate;

B1 : a wax-naphthalene condensate prepared as described herein;

B2: an alkylated diphenyl ether, dialkylated with C20 to C24 alkyl groups; being the reaction product of diphenyl ether and a C20 to C24 olefin cut and prepared as described in US-A-5, 102,427.

C1 : a homopolymer of a dialkyl ester of itaconic acid whose alkyl groups are linear and have 18 carbon atoms made by polymerising the monomer using a free radical catalyst, the homopolymer having an M _n of 3,500;

C2: a homopolymer of a dialkyl ester of itaconic acid whose alkyl groups are linear and have 16 carbon atoms made by polymerising the monomer using a free radical catalyst, the homopolymer having an M _n of 3,500;

D: a styrene/dialkyl fumarate copolymer whose alkyl groups have 14 carbon atoms, the copolymer having an M _n of 15,000 to 30,000;

E: an N,N-dialkylammonium salt of 2-N ¹ , N ¹ - dialkylamidobenzoate, being the reaction product of reacting one mole of phthalic anhydride with two moles of dihyrogenated tallow amine to form a half amide/half amine salt.

FUEL

The test fuel were middle distillate fuels characterised as follows, all temperatures being in ^° C.

FUELS

1 2 3

Wax Appearance Temperature +12 - 5 - 8 (WAT):

(measured by Differential Scanning Calorimetry)

Density (g/m I) 0.8561 0.8496 0.8281

Wax Content at 10°C below 4.25 4.2 2.0 WAT (wt%)

D 86 Distillation Characteristics: IBP 215 167 145

229 194

249 204

283 231

330 326

345 346

360 361

GENERAL PROCEDURE

An additive (which includes a combination of individual additive components as identified by juxtaposition of additive code letters in the results hereinafter) was added to the test diesel fuel by standard methods. One or more of the following tests were then carried out on the so-treated fuel.

THE COLD FILTER PLUGGING POINT TEST (OR CFPP TEST)

The test 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, 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 1 ^° C/min. Periodically (at each one degree centigrade starting from above the cloud point), the cooled oil 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 millimetre 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, the temperature at which failure occurs being reported as the CFPP temperature.

WAX ANTI-SETTLING (WAS) TEST

The extent of the settled layer (WAS) was visually measured as a percentage of the total fuel volume by leaving the treated fuel in a measuring flask. Extensive wax settling would be indicated by a low number whilst an unsettled fluid fuel would be indicated by 100%.

LOW TEMPERATURE FILTERABILITY TEST (LTFT)

The test was carried out according to ASTM Designation D 4539-91 entitled "Standard Test Method for Filterabiiity of Diesel Fuels by Low-Temperature Flow Test (LTFT)".

RESULTS

Example 1

This was carried out using Fuel 1. The results were are follows:

Additive concentrations in parts per million by weight of active ingredient are indicated in parentheses.

The results show that substituting B1 for part of the A content of the additive significantly improves both CFPP and WAS performance.

The CFPP of the base fuel was +8°C.

Additives C2 and D were added jointly as a concentrate comprising 34% by weight of C2, 11 % by weight of D and 55% by weight of a heavy aromatic solvent.

In Example 1 (comp), A was added as a concentrate comprising 59% by weight of the first copolymer, 4.5% by weight of the second copolymer and 36.5% by weight of a heavy aromatic solvent.

In Example 1 (invention), A and B1 were added jointly as a concentrate comprising 55.5% by weight of the first copolymer of A, 4.5% by weight of the second copolymer of B, 1.5% by weight of B1 , and 38.5% by weight of a heavy aromatic solvent.

Example 2

This was carried out using Fuel 2. The results were as follows:

Example Additive Combination Lowest Temperature Passing LTFT (°C)

2 (comp 1) A (100) -12

E (300)

C1 (200)

D (200)

2 (comp 2) A (100) ^■ 12 E (300) D (400)

2 (comp 3) A (100) -14 E (300) C1 (400)

2 (comp 4) A (100) -13 E (300) B2 (400)

2 (invention) ( A (100) -17

( E (300)

( C1 (200)

( B2 (200)

Additive concentrations in parts per million by weight of active ingredient are indicated in parentheses.

Thus, the inventive combination gives the best results. In particular, comparison with Example 2 (comp 3) shows that substituting B2 for part of the C1 content improves performance.

Example 3

This was carried out using Fuel 3. The results were as follows:

Additive concentrations in parts per million by weight of active ingredient are indicated in parentheses.

The results show that substituting B2 for D improves performance.