Uses and compositions

Abstract

Use of an ester to treat surfaces, which are not homecare substrates, provides increased water repellency, reduced friction, or improved visual appearance. The ester is a reaction product of a cyclic

Description

Various compounds and compositions are known to impart various properties to substrates, especially the surfaces of substrates, with which they are contacted. Some materials have surfaces (such as rough and / or water absorbent surfaces) that readily accumulate dust and / or dirt and are difficult to clean. This can cause problems such as reducing the cleanliness, robustness, and / or longevity of the material, as well as making the material aesthetically unappealing. It can be desirable to apply suitable compounds and compositions to such materials to provide benefits such as increased water repellency, reduced friction, and improved visual appearance (such as improved visual appearance). Silicone compounds, such as polydimethylsiloxane, functionalised polydimethylsiloxanes, organosilicones, and related compounds are widely used to impart water repelling, low-friction and shine properties to surfaces, including imparting lubrication and / or softening properties. However, there are a number of disadvantages associated with the use of such silicone compounds, including their low biodegradability, which has led to environmental concerns. It is thus an object of the invention to provide an alternative to silicone compounds that can be used in a wide range of applications to provide impart water repelling, low-friction and shine properties to surfaces, including imparting lubrication and / or softening properties. It is another object of the invention to provide alternatives to silicone compounds that are more biodegradable whilst having equal or improved water repelling, low-friction and shine properties to surfaces, including imparting lubrication and / or softening properties. Summary of the Invention According to aspects of the present invention, there is provided a use, method, composition and substrate as set forth in the appended claims. Other features of the invention will be apparent from the dependent claims, and from the description which follows. The inventors have identified that certain ester compounds can provide at least one of increased water repellency, reduced friction, and improved visual appearance to surfaces, which is at least comparable to that provided by known silicone compounds, whilst also being more biodegradable. According to a first aspect of the invention, there is provided a use of an ester compound to treat a surface, wherein the surface is not a surface of a home care substrate and wherein treating the surface provides at least one effect selected from (a) increased water repellency, (b) reduced friction, and (c) improved visual appearance; and wherein the ester compound is the reaction product of reactants comprising one or more first reactants and one or more second reactants, wherein the or each first reactant is a cyclic anhydride and the or each second reactant is a polyol. According to a second aspect of the invention, there is provided a method of treating a surface, wherein the surface is not a surface of a home care substrate and wherein treating the surface provides at least one effect selected from (a) increased water repellency, (b) reduced friction, and (c) improved visual appearance, the method comprising contacting the surface with an ester compound, wherein the ester compound is the reaction product of reactants comprising one or more first reactants and one or more second reactants, wherein the or each first reactant is a cyclic anhydride and the or each second reactant is a polyol. According to a third aspect of the invention, there is provided a composition fortreating a surface that is not a surface of a home care substrate, wherein treating the surface provides at least one effect selected from (a) increased water repellency, (b) reduced friction, and (c) improved visual appearance, and wherein the composition comprises one or more ester compounds, wherein the or each ester compound is the reaction product of reactants comprising one or more first reactants and one or more second reactants, wherein the or each first reactant is a cyclic anhydride and the or each second reactant is a polyol. According to a fourth aspect of the invention, there is a provided a substrate that is not a home care substrate, wherein a surface of the substrate is treated with an ester compound, wherein the ester compound is the reaction product of reactants comprising one or more first reactants and one or more second reactants, wherein the or each first reactant is a cyclic anhydride and the or each second reactant is a polyol. Other features of the invention will be apparent from the dependent claims, and from the description which follows. Features described in relation to the third and fourth aspects may have any of the suitable features and advantages described in relation to the first and second aspects. Detailed Description of the Invention Unless otherwise stated, the following terms used in the specification and claims have the meanings set out below. The terms “alkyl” and “alkylene” include both straight and branched chain alkyl and alkylene groups respectively unless otherwise stated. References to individual alkyl groups such as “propyl” are specific for the straight chain version only and references to individual branched chain alkyl groups such as “isopropyl” are specific for the branched chain version only. For example, “C3-30 alkyl” includes C6-24 alkyl, Ce-s alkyl, propyl, isopropyl and t-butyl. The term “alkenyl” includes both straight and branched chain alkenyl groups. References to individual alkenyl groups such as “propenyl” are specific for the straight chain version only and references to individual branched chain alkenyl groups such as “isopropenyl” are specific for the branched chain version only. For example, “C3-30 alkenyl” includes C6-24 alkenyl, Ce-s alkenyl, propenyl and isopropenyl. Herein C3-30 means a group having from 3 to 30 carbons atoms therein, for example having 3, 4, 5 etc up to 30 carbon atoms. The term "hydrocarbyl" is used in its ordinary sense, which is well-known to those skilled in the art. Specifically, it refers to a group having a carbon atom directly attached to the remainder of the molecule and having predominantly hydrocarbon character. As used in the specification and the appended claims, the singular forms "a", "an," and "the" include both singular and plural referents unless the context clearly dictates otherwise. Throughout this specification, the term “comprising” or “comprises” means including the component(s) specified but not to the exclusion of the presence of other components. The term “consisting essentially of’ or “consists essentially of’ means including the components specified but excluding other components except for components added for a purpose other than achieving the technical effect of the invention. The term “consisting of’ or “consists of’ means including the components specified but excluding other components. Whenever appropriate, depending upon the context, the use of the term “comprises” or “comprising” may also be taken to include the meaning “consists essentially of’ or “consisting essentially of’, and also may also be taken to include the meaning “consists of’ or “consisting of’. As used herein, unless otherwise expressly specified, all numbers such as those expressing values, ranges, amounts of percentages may be read as if prefaced by the word “about”, even if the term does not expressly appear. The recitation of numerical ranges by endpoints includes all integer numbers and, where appropriate, fractions subsumed within that range (e.g. 1 to 5 can include 1,2,3,4 when referring to, for example, a number of elements, and can also include 1.5, 2, 2.70 and 3.80, when referring to, for example, measurements). The recitation of end points also includes the end point values themselves (e.g. from 1.0 to 5.0 includes both 1.0 and 5.0). Any numerical range recited herein is intended to include all sub-ranges subsumed therein. The optional features set out herein may be used either individually or in combination with each other where appropriate and particularly in the combinations as set out in the accompanying claims. The optional features for each exemplary aspect of the invention, as set out herein are also applicable to any other aspects or exemplary aspects of the invention, where appropriate. In other words, the skilled person reading this specification should consider the optional features for each aspect or embodiment of the invention as interchangeable and combinable between different aspects of the invention. As used herein, the term "and / or," when used in a list of two or more items, means that any one of the listed items can be employed by itself or any combination of two or more of the listed items can be employed. For example, if a list is described as comprising group A, B, and / or C, the list can comprise A alone; B alone; C alone; A and B in combination; A and C in combination, B and C in combination; or A, B, and C in combination. The term “reactant” is used herein to refer to a compound comprising at least one reactive functional group. As reported herein, the number average molecular weight was determined by gel permeation chromatography using a polystyrene standard according to ASTM D6579-11 (“Standard Practice for Molecular Weight Averages and Molecular Weight Distribution of Hydrocarbon, Rosin and Terpene Resins by Size Exclusion Chromatography”. UV detector; 254 nm, solvent: unstabilised THF, retention time marker: toluene, sample concentration: 2mg / ml). According to a first aspect of the invention, there is provided a use of an ester compound to treat a surface, wherein the surface is not a surface of a home care substrate and wherein treating the surface provides at least one effect selected from (a) increased water repellency, (b) reduced friction, and (c) improved visual appearance; and wherein the ester compound is the reaction product of reactants comprising one or more first reactants and one or more second reactants, wherein the or each first reactant is a cyclic anhydride and the or each second reactant is a polyol. According to a second aspect of the invention, there is provided a method of treating a surface, wherein the surface is not a surface of a home care substrate and wherein treating the surface provides at least one effect selected from (a) increased water repellency, (b) reduced friction, and (c) improved visual appearance, the method comprising contacting the surface with an ester compound, wherein the ester compound is the reaction product of reactants comprising one or more first reactants and one or more second reactants, wherein the or each first reactant is a cyclic anhydride and the or each second reactant is a polyol. Suitable features of the first and second aspects will now be described. The ester compound as used herein is the reaction product of reactants comprising one or more first reactants and one or more second reactants as defined herein. In other words, the ester compound may be obtainable or obtained by reacting reactants comprising one or more first reactants and one or more second reactants as defined herein. The ester compound as used herein may be the reaction product of reactants consisting essentially of or consisting of one or more first reactants and one or more second reactants as defined herein. In other words, the ester compound may be obtainable or obtained by reacting reactants consisting essentially of or consisting of one or more first reactants and one or more second reactants as defined herein. The first and second reactants may be reacted in any suitable molar ratio to make the ester compound, as would be appreciated by a person skilled in the art. The first and second reactants may be reacted in a molar ratio of from 1:10 to 10:1, preferably from 1:6 to 6:1, for example from 1:3 to 3:1. Suitably, the first and second reactants may be reacted in a molar ratio of from 1.2:1 to 1:1.2. Preferably, the first and second reactants may be reacted in a molar ratio of 1:1. Ratios refer to the total amounts of first reactants or second reactants if more than one first reactant or second reactant is present. The ester compound may be prepared by any suitable method, as would be known to persons skilled in the art. Suitably, the ester compound is not in a solid form. For example, the ester compound is preferably in the form of a liquid or gel, preferably a liquid. In some embodiments, the ester compound does not contain any nitrogen atoms. References herein to a reaction product of reactants comprising the first and second reactants are intended to refer to a product of the reaction of reactants comprising the first and second reactants conducted in any suitable manner. For example, the reaction may occur between the first and second reactants in the absence of other reactant(s) or may occur in the presence of other reactant(s). The or each of the one or more first reactants used to make the ester compound is a cyclic anhydride. Mixtures of two or more different first reactants (i.e. different cyclic anhydrides) may be used to make the ester compound. Any suitable cyclic anhydride may be used to make the ester compound, as would be understood by the person skilled in the art. By the term cyclic anhydride we mean a compound (or reactant) that comprises at least one anhydride group that is contained within a ring structure. For example, the ring structure that contains the anhydride group may comprise from 4 to 8 atoms, which atoms are typically carbon and oxygen. The ring structure that contains the anhydride group may be saturated or partially unsaturated (and is preferably saturated). The cyclic anhydride compound may typically comprise more than 8 atoms. For example, suitable cyclic anhydrides may include one or more of an anhydride of formula (I), of formula (II) and of formula (III): wherein in formula (I) R1 and R2 are each independently selected from hydrogen, an alkyl group and an alkenyl group, or R1 and R2 together with the carbon atoms to which they are attached represent an optionally substituted cyclic group; in formula (II) R3 and R4 are each independently selected from hydrogen, an alkyl group and an alkenyl group, or R3 and R4 together with the carbon atoms to which they are attached represent an optionally substituted cyclic group; and in formula (III) X is CR9R10, O, S, or NR11; R5, R6, R7, R8, R9, R10, and R11 are each independently selected from hydrogen, an alkyl group and an alkenyl group, and / or any of R5, R6, R7, R8, R9, R10, and R11 together with the atoms to which they are attached represent an optionally substituted cyclic group. Cyclic anhydrides of formula (I) are preferred. X may suitably be CR9R10, O, or S. Preferably, X is CR9R10. When any of R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, and R11 represents an alkyl group or an alkenyl group, the or each alkyl or alkenyl group may be branched or unbranched. The or each alkyl group may contain from 1 to 30 carbon atoms and the or each alkenyl group may contain from 2 to 30 carbon atoms. Preferably, the or each alkyl or alkenyl group may contain 6 or more carbon atoms. For example, the or each alkyl or alkenyl group may contain from 6 to 30, such as from 8 to 24, carbon atoms (i.e. may be a Ce-30, such as a Ca-24, alkyl or alkenyl group). When any of R1 and R2, or R3 and R4, orR5, R6, R7, R8, R9, and R10 represents an alkenyl group, the alkenyl group may be a branched alkenyl group, such as a tetrapropenyl group or a polyisobutenyl group. When any of R1 and R2, or R3 and R4, orR5, R6, R7, R8, R9, and R10 represents an alkenyl group, the alkenyl group may be a polyisobutenyl group. The polyisobutenyl group (when present) suitably has a number average molecular weight of from 100 to 2000, preferably from 100 to 1000, for example 260 or 550. The cyclic anhydride may be a polyisobutenyl succinic anhydride, for example wherein the polyisobutenyl group has a number average molecular weight of 260 or 550. When any of R1 and R2, or R3 and R4, orR5, R6, R7, R8, R9, and R10 represents an alkenyl group, the alkenyl group may be derived from a terminal olefin or an internal olefin. For example, the cyclic anhydride monomer may be an alkenyl substituted succinic anhydride prepared by the reaction of an alkene with maleic anhydride, wherein the alkene is a terminal olefin or an internal olefin. In some embodiments the alkenyl group may be derived from a terminal olefin. The term terminal olefin is used to refer to alkene compounds having a predominantly terminal double bond. Such compounds are also commonly described as terminal alkenes. Terminal double bonds terminate in a =CH2 group and may either be at the a-position or may be vinylidene groups. The terminal olefin is preferably an a-olefin. Examples of suitable terminal olefins include C15-18 terminal olefin and Cie terminal olefin. In some preferred embodiments the alkenyl group is derived from an internal olefin. The term internal olefin is used to refer to alkene compounds in which the alkene groups are predominantly not terminal. Examples of suitable internal olefins include C12 internal olefin, C15-18 internal olefin, C16 internal olefin and C18 internal olefin. The internal olefin is a p or higher olefin, such as a p-olefin. Internal olefins are sometimes known as isomerised olefins and may be prepared by isomerisation of an a-olefin. Typically, terminal olefins and internal olefins may be provided as a mixture of isomers. Suitably at least 70 mol%, such as at least 80 mol%, preferably at least 90 mol%, for example at least 95 mol% of the double bonds in terminal olefins are terminal double bonds. Suitably at least 70 mol%, such as at least 80 mol%, preferably at least 90 mol%, for example at least 95 mol% of the terminal double bonds in the terminal olefins are at the a-position (i.e. they are a-alkene groups). Suitably at least 70 mol%, such as at least 80 mol%, preferably at least 90 mol%, for example at least 95 mol% of the double bonds in internal olefins are non-terminal double bonds. Suitably, one of R1 and R2, R3 and R4, orR5, R6, R7, R8, R9, R10, and R11 may be an alkyl group or an alkenyl group (such as an alkenyl group derived from a terminal olefin or an internal olefin, preferably an internal olefin) and the other (or others) may be hydrogen. Examples of cyclic anhydride reactants of the formula (I), (II) or (III) wherein any of R1 and R2, R3 and R4, orR5, R6, R7, R8, R9, R10, and R11 represents hydrogen or a Ce-30, such as a Cs-24, branched or unbranched alkyl or alkenyl group include succinic anhydride, dodecenyl succinic anhydride (such as (2-dodecen-1-yl)succinic anhydride), tetrapropenyl succinic anhydride, octadecenyl succinic anhydride, octenyl succinic anhydride, nonenyl succinic anhydride, C20-24 alkenyl succinic anhydride, C15-18 internal olefin-derived alkenyl succinic anhydride, C16 internal olefin-derived alkenyl succinic anhydride, C16 terminal olefin-derived alkenyl succinic anhydride, maleic anhydride and glutaric anhydride. The cyclic anhydride reactants of the formula (I), (II) or (III) wherein any of R1 and R2, R3 and R4, orR5, R6, R7, R8, R9, R10, and R11 represents hydrogen ora C6-30, such as a Cs-24, branched or unbranched alkyl or alkenyl group may be selected from succinic anhydride, dodecenyl succinic anhydride (such as (2-dodecen-1-yl)succinic anhydride), tetrapropenyl succinic anhydride, octadecenyl succinic anhydride, octenyl succinic anhydride, nonenyl succinic anhydride, C20-24 alkenyl succinic anhydride, maleic anhydride and glutaric anhydride. The cyclic anhydride reactants of the formula (I), (II) or (III) wherein any of R1 and R2, R3 and R4, orR5, R6, R7, R8, R9, R10, and R11 represents hydrogen ora C6-30, such as a Cs-24, branched or unbranched alkyl or alkenyl group may preferably be selected from dodecenyl succinic anhydride (such as (2-dodecen-1-yl)succinic anhydride), tetrapropenyl succinic anhydride, octadecenyl succinic anhydride, octenyl succinic anhydride, nonenyl succinic anhydride, C20-24 alkenyl succinic anhydride, and glutaric anhydride. The cyclic anhydride reactants are preferably selected from C15-18 internal olefin-derived alkenyl succinic anhydride, C16 internal olefin-derived alkenyl succinic anhydride, and C16 terminal olefin-derived alkenyl succinic anhydride. When any of R1 and R2, or R3 and R4, orR5, R6, R7, R8, R9, R10, and R11, together with the atoms to which they are attached represent an optionally substituted cyclic group, the cyclic group so formed may be mono or polycyclic (preferably mono or bicyclic) and may be aromatic or nonaromatic. Examples of aromatic groups that may be so formed include benzene and naphthalene. Examples of non-aromatic groups that may be so formed include cyclopentane, cyclohexane, and cyclooctane. Any of R5, R6, R7, R8, R9, R10, and R11 together with the atoms to which they are attached may represent an optionally substituted cyclic group. Any of R5, R6, R7, R8, R9, R10, and R11 not representing a cyclic group are independently selected from hydrogen, an alkyl group and an alkenyl group as described herein. Two, three, four, five, or six of R5, R6, R7, R8, R9, R10, and R11 together with the atoms to which they are attached may represent an optionally substituted cyclic group. Suitably at least R5 and R7, or R5 and R9, or R5 and R11, or R7 and R9, or R7 and R11, or R5, R7 and R9, or R5, R7 and R11 together with the atoms to which they are attached may represent an optionally substituted cyclic group. For the avoidance of doubt, when any of R5, R6, R7, R8, R9, and R10 together with the atoms to which they are attached represent an optionally substituted cyclic group, one or more of R5, R6, R7, R8, R9, and R10 may contribute to one or more double bonds (for example, aromaticity) in the cyclic group. For example, R8 and R10 may together form a carbon-carbon double bond, which may form part of an aromatic cyclic group. The optionally substituted cyclic group represented by R1 and R2, or R3 and R4, or any of R5, R6, R7, R8, R9, R10, and R11, together with the atoms to which they are attached (when present) may be optionally substituted with any suitable substituent(s), such as for example one or more substituents independently selected from alkyl (for example C1-30, preferably C1-24, such as C1-4 or Ca-24, alkyl), alkenyl (for example C2-30, preferably C2-24, such as C2-4 or Ca-24, alkenyl), alkoxy (for example C1-30, preferably C1-24, such as C1-4 or Ca-24, alkoxy), alkenyloxy (for example C2-30, preferably C2-24, such as C2-4 or Ca-24, alkenyloxy), carboxy, alkoxy-carbonyl (for example C1-30, preferably C1-24, such as C1-4 or Ca-24, alkoxy-carbonyl), alkenyloxy-carbonyl (for example C2-30, preferably C2-24, such as C2-4 or Ca-24, alkenyloxy-carbonyl), hydroxy, halo (for example chloro or fluoro), nitro and cyano groups. The optionally substituted cyclic group represented by R1 and R2, or R3 and R4, or any of R5, R6, R7, R8, R9, R10, and R11, together with the atoms to which they are attached (when present) may alternatively be substituted by groups which form a further cyclic anhydride group. An example of such a cyclic anhydride is pyromellitic dianhydride. However, in some embodiments the cyclic anhydride monomers of the formula (I), (II) or (III) contain a single (i.e. only one) anhydride group. In such embodiments, the optionally substituted cyclic group represented by R1 and R2, or R3 and R4, or any of R5, R6, R7, R8, R9, R10, and R11, together with the atoms to which they are attached (when present) may not be substituted by a further cyclic anhydride group. Examples of suitable cyclic anhydrides of formula (I) in which R1 and R2 together with the carbon atoms to which they are attached represent an optionally substituted cyclic group include optionally substituted 1,2-cyclohexanedicarboxylic anhydride and 1,3-cyclopentanedicarboxylic anhydride. 1,2-Cyclohexanedicarboxylic anhydride is preferred. Examples of suitable anhydrides of formula (II) in which R3 and R4 together with the carbon atoms to which they are attached represent an optionally substituted cyclic group include optionally substituted phthalic anhydride, pyromellitic dianhydride, 1,2-naphthalic anhydride and 2,3-naphthalic anhydride. Examples of a substituted phthalic anhydride may include 1,2,4-benzenetricarboxylic anhydride, and 6-((octadec-9-en-1-yloxy)carbonyl)-1,3-dioxo-1,3-dihydroisobenzofuran-5-carboxylic acid. Examples of suitable anhydrides of formula (III) in which any of R5, R6, R7, R8, R9, R10, and R11 together with the carbon atoms to which they are attached represent an optionally substituted cyclic group include optionally substituted 1,8-naphthalic anhydride and homophthalic anhydride. Preferred cyclic anhydrides include one or more cyclic anhydrides of formula (I) wherein R1 and R2 are each independently selected from hydrogen and a Cs-3o, such as a Cs-24, alkyl or alkenyl group, or wherein R1 and R2 together with the carbon atoms to which they are attached represent an optionally substituted cyclic group; or of formula (II) wherein R3 and R4 are each independently selected from hydrogen and a Cs-3o, such as a Cs-24, alkyl or alkenyl group, or wherein R3 and R4 together with the carbon atoms to which they are attached represent an optionally substituted cyclic group; or of formula (III) wherein X is CR9R10, O, or S and R5, R6, R7, R8, R9, and R10 are each independently selected from hydrogen and a Cs-3o, such as a Cs-24, an alkyl group or alkenyl group, and / or wherein any of R5, R6, R7, R8, R9, and R10 together with the carbon atoms to which they are attached represent an optionally substituted cyclic group. More preferred cyclic anhydrides include one or more cyclic anhydrides of formula (I) wherein R1 and R2 are each independently selected from hydrogen and a Cs-3o, such as a Cs-24, alkenyl group, or wherein R1 and R2 together with the carbon atoms to which they are attached represent an optionally substituted cyclic group; or of formula (II) wherein R3 and R4 are both hydrogen, or wherein R3 and R4 together with the carbon atoms to which they are attached represent an optionally substituted cyclic group; or of formula (III) wherein X is CR9R10, O, or S and R5, R6, R7, R8, R9, and R10are each hydrogen, and / or wherein any of R5, R6, R7, R8, R9, and R10 together with the carbon atoms to which they are attached represent an optionally substituted cyclic group. Preferably, at least one of the first reactants is a cyclic anhydride of formula (I), (II) or (III) wherein at least one of R1 and R2, or at least one of R3 and R4, or at least one of R5, R6, R7, R8, R9, R10, and R11, is a Cs-3o, such as a Cs-24, alkyl or alkenyl (more preferably alkenyl) group (such as an alkenyl group derived from a terminal olefin or an internal olefin, preferably an internal olefin). Preferably, at least one of the first reactants is a cyclic anhydride of formula (I), (II) or (III) wherein at least one of R1 and R2, or at least one of R3 and R4, or at least one of R5, R6, R7, R8, R9, R10, and R11, is a Cs-3o, such as a Cs-24, alkyl or alkenyl (more preferably alkenyl) group (such as an alkenyl group derived from a terminal olefin or an internal olefin, preferably an internal olefin) and the other (or others) is (or are) hydrogen. For example, the cyclic anhydride may be an anhydride of formula (I) wherein R1 and R2 are both hydrogen (i.e. the cyclic anhydride may be succinic anhydride). For example, the cyclic anhydride may be an anhydride of formula (II) wherein R3 and R4 are both hydrogen (i.e. the cyclic anhydride may be maleic anhydride). For example, the cyclic anhydride may be an anhydride of formula (III) in which X is CR9R10 and R5, R6, R7, R8, R9, and R10 each represent hydrogen (i.e. the cyclic anhydride may be glutaric anhydride). For example, the cyclic anhydride may be an anhydride of formula (III) in which X is O and R5, R6, R7, and R8 each represent hydrogen (i.e. the cyclic anhydride may be diglycolic anhydride). For example, the cyclic anhydride may be an anhydride of formula (III) in which X is S and R5, R6, R7, and R8 each represent hydrogen (i.e. the cyclic anhydride may be thiodiglycolic anhydride). For example, the or each cyclic anhydride may be an anhydride of formula (I) wherein R1 and R2 are both hydrogen or wherein one of R1 and R2 is an alkyl or alkenyl group (such as an alkenyl group derived from a terminal olefin or an internal olefin, preferably an internal olefin) and the other of R1 and R2 is hydrogen. For example, the or each cyclic anhydride may be an anhydride of formula (I) wherein R1 and R2 are both hydrogen or wherein one of R1 and R2 is a C6-30, such as a Ca-24, alkyl or alkenyl (more preferably alkenyl) group (such as an alkenyl group derived from a terminal olefin or an internal olefin, preferably an internal olefin) and the other of R1 and R2 is hydrogen. Examples of such cyclic anhydride compounds include succinic anhydride, C20-24 alkenyl succinic anhydride, dodecenyl succinic anhydride (such as (2-dodecen-1-yl)succinic anhydride), nonenyl succinic anhydride, octadecenyl succinic anhydride, octenyl succinic anhydride, C15-18 internal olefin-derived alkenyl succinic anhydride, C16 internal olefin-derived alkenyl succinic anhydride, and C16 terminal olefin-derived alkenyl succinic anhydride. The cyclic anhydride compound may be selected from succinic anhydride, C20-24 alkenyl succinic anhydride, dodecenyl succinic anhydride (such as (2-dodecen-1-yl)succinic anhydride), nonenyl succinic anhydride, octadecenyl succinic anhydride and octenyl succinic anhydride. The cyclic anhydride compound is preferably selected from C15-18 internal olefin-derived alkenyl succinic anhydride, C16 internal olefin-derived alkenyl succinic anhydride, and C16 terminal olefin-derived alkenyl succinic anhydride. Preferably, the or each cyclic anhydride may be an anhydride of formula (I) wherein one of R1 and R2 is an alkenyl group, such as a C6-30 (preferably C8-24) alkenyl group (such as a C6-30 (preferably C8-24) alkenyl group derived from a terminal olefin or an internal olefin, preferably an internal olefin), and the other of R1 and R2 is hydrogen. Examples of such cyclic anhydride compounds include C20-24 alkenyl succinic anhydride, dodecenyl succinic anhydride (such as (2-dodecen-1-yl)succinic anhydride), nonenyl succinic anhydride, octadecenyl succinic anhydride, octenyl succinic anhydride, C15-18 internal olefin-derived alkenyl succinic anhydride, C16 internal olefin-derived alkenyl succinic anhydride, and C16 terminal olefin-derived alkenyl succinic anhydride. The cyclic anhydride compound may be selected from C20-24 alkenyl succinic anhydride, dodecenyl succinic anhydride (such as (2-dodecen-1-yl)succinic anhydride), nonenyl succinic anhydride, octadecenyl succinic anhydride and octenyl succinic anhydride. The cyclic anhydride compound is preferably selected from C15-18 internal olefin-derived alkenyl succinic anhydride, C16 internal olefin-derived alkenyl succinic anhydride, and C16 terminal olefin-derived alkenyl succinic anhydride. Preferably, the or each cyclic anhydride may be dodecenyl succinic anhydride, such as (2-dodecen-1-yl)succinic anhydride. The or each cyclic anhydride may be an anhydride of formula (I) wherein one of R1 and R2 is hydrogen and the other of R1 and R2 is a polyisobutenyl group, for example wherein the polyisobutenyl group suitably has a number average molecular weight of from 100 to 2000, preferably from 100 to 1000, for example 260 or 550. Preferably, the or each cyclic anhydride may be a cyclic anhydride of formula (I) or (II) wherein R1 and R2, or R3 and R4, together with the carbon atoms to which they are attached represent an optionally substituted cyclic group, wherein the cyclic group is an aromatic or a non-aromatic group and is mono or polycyclic. Preferably, the or each cyclic anhydride may be an anhydride of formula (I) wherein R1 and R2 together with the carbon atoms to which they are attached represent an optionally substituted cyclic group, wherein the cyclic group is a non-aromatic (for example saturated) mono or bicyclic group. More preferably, the or each cyclic anhydride may be a cyclic anhydride of formula (I) wherein R1 and R2 together with the carbon atoms to which they are attached represent an optionally substituted cyclic group, wherein the cyclic group is a non-aromatic (for example saturated) monocyclic group, such as a cyclohexane group. Preferably, the or each cyclic anhydride may be an anhydride of formula (II) wherein R3 and R4 together with the carbon atoms to which they are attached represent an optionally substituted cyclic group, wherein the cyclic group is an aromatic mono or bicyclic group, such as a benzene or naphthalene group. More preferably, the or each cyclic anhydride may be a cyclic anhydride of formula (II) wherein R3 and R4 together with the carbon atoms to which they are attached represent an optionally substituted cyclic group, wherein the cyclic group is an aromatic monocyclic group, such as a benzene group. Preferably, the or each cyclic anhydride may be an anhydride of formula (III) wherein X is CR9R10 and R5, R6, R7, R8, R9, and R10 together with the carbon atoms to which they are attached represent an optionally substituted cyclic group, wherein the cyclic group is an aromatic bicyclic group, such as a naphthalene group; or R7 and R8 are hydrogen and R5, R6, R9 and R10 together with the carbon atoms to which they are attached represent an optionally substituted cyclic group, wherein the cyclic group is an aromatic monocyclic group, such as a benzene group. More preferably, the or each cyclic anhydride may be an anhydride of formula (III) wherein X is CR9R10 and R5, R6, R7, R8, R9, and R10 together with the carbon atoms to which they are attached represent an optionally substituted cyclic group, wherein the cyclic group is an aromatic bicyclic group, such as a naphthalene group. When the cyclic anhydride is an anhydride of formula (I) wherein R1 and R2 together with the carbon atoms to which they are attached represent an optionally substituted cyclohexane group, the cyclic anhydride may be of the formula (IA): wherein n is an integer from 0 to 4 and each R12 (when present) is independently selected from alkyl (for example C1-30, preferably C1-24, such as C1-4, alkyl), alkenyl (for example C2-30, preferably C2-24, such as C2-4, alkenyl), alkoxy (for example C1-30, preferably C1-24, such as C1-4, alkoxy), alkenyloxy (for example C2-30, preferably C2-24, such as C2-4, alkenyloxy), carboxy, alkoxy-carbonyl (for example C1-30, preferably C1-24, such as C1-4, alkoxy-carbonyl), alkenyloxycarbonyl (for example C2-30, preferably C2-24, such as C2-4, alkenyloxy-carbonyl), hydroxy, halo (for example chloro or fluoro), nitro and cyano groups, or when n is 2 the two R12 groups may represent a further cyclic anhydride group (such as a further succinic anhydride group). In some embodiments, the cyclic anhydride of formula (IA) contains a single (i.e. only one) anhydride group. In such embodiments, two R12 groups may not represent a further cyclic anhydride group. Examples of suitable succinic anhydrides of formula (IA) include 1,2-cyclohexanedicarboxylic anhydride. When the cyclic anhydride is an anhydride of formula (II) wherein R3 and R4 together with the carbon atoms to which they are attached represent an optionally substituted benzene group, the cyclic anhydride may be of the formula (IIA): wherein n’ is an integer from 0 to 4 and each R13 (when present) is independently selected from alkyl (for example C1-30, preferably C1-24, such as C1-4, alkyl), alkenyl (for example C2-30, preferably C2-24, such as C2-4, alkenyl), alkoxy (for example C1-30, preferably C1-24, such as C1-4, alkoxy), alkenyloxy (for example C2-30, preferably C2-24, such as C2-4, alkenyloxy), carboxy, alkoxy-carbonyl (for example C1-30, preferably C1-24, such as C1-4, alkoxy-carbonyl), alkenyloxycarbonyl (for example C2-30, preferably C2-24, such as C2-4, alkenyloxy-carbonyl), hydroxy, halo (for example chloro or fluoro), nitro and cyano groups, or when n’ is 2 the two R13 groups may represent a further cyclic anhydride group (such as a further succinic anhydride group). When R13 represents a alkoxy-carbonyl (for example C1-30, preferably Ca-24, alkoxy-carbonyl) or alkenyloxy-carbonyl (for example C2-30, preferably Ca-24, alkenyloxy-carbonyl), substituent, the alkoxy-carbonyl or alkenyloxy-carbonyl group may be of the formula -C(O)OR13 wherein R13 is a C1-30, preferably Ca-24, alkyl group or a C2-30, preferably Ca-24, alkenyl group. Suitably R13 may represent an oleyl group. Examples of suitable succinic anhydrides of formula (IIA) include phthalic anhydride, pyromellitic dianhydride, 1,2,4-benzenetricarboxylic anhydride, 1,2-naphthalic anhydride and 2,3-naphthalic anhydride, and 6-((octadec-9-en-1-yloxy)carbonyl)-1,3-dioxo-1,3-dihydroisobenzofuran-5-carboxylic acid. When the cyclic anhydride is an anhydride of formula (III) wherein X is CR9R10 and R5, R6, R7, R8, R9, and R10 together with the carbon atoms to which they are attached representan optionally substituted naphthalene group, the cyclic anhydride may be of the formula (IHA): wherein each of m and m’ is independently an integer from 0 to 3 and each of R14 and R15 (when present) is independently selected from alkyl (for example C1-30, preferably C1-24, such as C1-4, alkyl), alkenyl (for example C2-30, preferably C2-24, such as C2-4, alkenyl), alkoxy (for example Ci-30, preferably C1-24, such as C1-4, alkoxy), alkenyloxy (for example C2-30, preferably C2-24, such as C2-4, alkenyloxy), carboxy, alkoxy-carbonyl (for example C1-30, preferably C1-24, such as C1-4, alkoxy-carbonyl), alkenyloxy-carbonyl (for example C2-30, preferably C2-24, such as C2-4, alkenyloxy-carbonyl), hydroxy, halo (for example chloro or fluoro), nitro and cyano groups. Examples of suitable succinic anhydrides of formula (IIIA) include 1,8-naphthalic anhydride. When the cyclic anhydride is an anhydride of formula (III) wherein X is CR9R10, R7 and R8 are hydrogen and R5, R6, R9 and R10 together with the carbon atoms to which they are attached represent an optionally substituted benzene group, the cyclic anhydride may be of the formula (IIIB): wherein m” is an integer from 0 to 4 and each R16 (when present) is independently selected from alkyl (for example C1-30, preferably C1-24, such as C1-4, alkyl), alkenyl (for example C2-30, preferably C2-24, such as C2-4, alkenyl), alkoxy (for example C1-30, preferably C1-24, such as C1-4, alkoxy), alkenyloxy (for example C2-30, preferably C2-24, such as C2-4, alkenyloxy), carboxy, alkoxy-carbonyl (for example C1-30, preferably C1-24, such as C1-4, alkoxy-carbonyl), alkenyloxycarbonyl (for example C2-30, preferably C2-24, such as C2-4, alkenyloxy-carbonyl), hydroxy, halo (for example chloro or fluoro), nitro and cyano groups. Examples of suitable succinic anhydrides of formula (IIIB) include homophthalic anhydride. Suitably, the or each cyclic anhydride may be selected from one or more of succinic anhydride, maleic anhydride, glutaric anhydride, a Ce-30 alkenyl succinic anhydride such as C20-24 alkenyl succinic anhydride, dodecenyl succinic anhydride (such as (2-dodecen-1-yl)succinic anhydride), nonenyl succinic anhydride, octadecenyl succinic anhydride, octenyl succinic anhydride, octadecyl succinic anhydride, octyl succinic anhydride, C15-18 internal olefin-derived alkenyl succinic anhydride, C16 internal olefin-derived alkenyl succinic anhydride, or C16 terminal olefinderived alkenyl succinic anhydride, a branched alkenyl succinic anhydride such as tetrapropenyl succinic anhydride or polyisobutenyl succinic anhydride, phthalic anhydride, pyromellitic dianhydride, 1,2,4-benzenetricarboxylic anhydride, 1,2-cyclohexanedicarboxylic anhydride, 1,2-naphthalic anhydride, 2,3-naphthalic anhydride, 1,8-naphthalic anhydride and homophthalic anhydride. Suitably, the or each cyclic anhydride may be selected from one or more of succinic anhydride, maleic anhydride, glutaric anhydride, a C6-30 alkenyl succinic anhydride such as C20-24 alkenyl succinic anhydride, dodecenyl succinic anhydride (such as (2-dodecen-1-yl)succinic anhydride), nonenyl succinic anhydride, octadecenyl succinic anhydride, octenyl succinic anhydride, octadecyl succinic anhydride, or octyl succinic anhydride, a branched alkenyl succinic anhydride such as tetrapropenyl succinic anhydride or polyisobutenyl succinic anhydride, phthalic anhydride, pyromellitic dianhydride, 1,2,4-benzenetricarboxylic anhydride, 1,2-cyclohexanedicarboxylic anhydride, 1,2-naphthalic anhydride, 2,3-naphthalic anhydride, 1,8-naphthalic anhydride and homophthalic anhydride. Suitably, the or each cyclic anhydride may be selected from one or more of a C6-30 alkenyl succinic anhydride such as C20-24 alkenyl succinic anhydride, dodecenyl succinic anhydride (such as (2-dodecen-1-yl)succinic anhydride), nonenyl succinic anhydride, octadecenyl succinic anhydride, octenyl succinic anhydride, octadecyl succinic anhydride, or octyl succinic anhydride, a branched alkenyl succinic anhydride such as tetrapropenyl succinic anhydride or polyisobutenyl succinic anhydride, phthalic anhydride, pyromellitic dianhydride, 1,2,4-benzenetricarboxylic anhydride, 1,2-cyclohexanedicarboxylic anhydride, 1,2-naphthalic anhydride, 2,3-naphthalic anhydride, 1,8-naphthalic anhydride and homophthalic anhydride. Suitably, the or each cyclic anhydride may be selected from one or more of succinic anhydride, maleic anhydride, glutaric anhydride, a C6-30 alkenyl succinic anhydride such as C20-24 alkenyl succinic anhydride, dodecenyl succinic anhydride (such as (2-dodecen-1-yl)succinic anhydride), nonenyl succinic anhydride, octadecenyl succinic anhydride, octenyl succinic anhydride, octadecyl succinic anhydride, or octyl succinic anhydride, and a branched alkenyl succinic anhydride such as tetrapropenyl succinic anhydride or polyisobutenyl succinic anhydride. Suitably, the or each cyclic anhydride may be selected from one or more of phthalic anhydride, pyromellitic dianhydride, 1,2,4-benzenetricarboxylic anhydride, 1,2-cyclohexanedicarboxylic anhydride, 1,2-naphthalic anhydride, 2,3-naphthalic anhydride, 1,8-naphthalic anhydride and homophthalic anhydride. More suitably, the or each cyclic anhydride may be selected from one or more of succinic anhydride, maleic anhydride, C20-24 alkenyl succinic anhydride, dodecenyl succinic anhydride (such as (2-dodecen-1-yl)succinic anhydride), nonenyl succinic anhydride, octadecenyl succinic anhydride, octenyl succinic anhydride, phthalic anhydride, pyromellitic dianhydride, 1,2,4-benzenetricarboxylic anhydride, 1,2-cyclohexanedicarboxylic anhydride, 1,2-naphthalic anhydride, 2,3-naphthalic anhydride, 1,8-naphthalic anhydride, homophthalic anhydride and glutaric anhydride. More suitably, the or each cyclic anhydride may be selected from one or more of succinic anhydride, maleic anhydride, C20-24 alkenyl succinic anhydride, dodecenyl succinic anhydride (such as (2-dodecen-1-yl)succinic anhydride), nonenyl succinic anhydride, octadecenyl succinic anhydride, octenyl succinic anhydride, and glutaric anhydride. More suitably, the or each cyclic anhydride may be selected from one or more of C20-24 alkenyl succinic anhydride, dodecenyl succinic anhydride (such as (2-dodecen-1-yl)succinic anhydride), nonenyl succinic anhydride, octadecenyl succinic anhydride, octenyl succinic anhydride, and glutaric anhydride. Preferably, the or each cyclic anhydride may be selected from one or more of succinic anhydride, maleic anhydride, C20-24 alkenyl succinic anhydride, dodecenyl succinic anhydride (such as (2-dodecen-1-yl)succinic anhydride), nonenyl succinic anhydride, octadecenyl succinic anhydride, octenyl succinic anhydride, phthalic anhydride, pyromellitic dianhydride, 1,2,4-benzenetricarboxylic anhydride, 1,2-cyclohexanedicarboxylic anhydride and 1,8-naphthalic anhydride. Preferably, the or each cyclic anhydride may be selected from one or more of succinic anhydride, maleic anhydride, C20-24 alkenyl succinic anhydride, dodecenyl succinic anhydride (such as (2-dodecen-1-yl)succinic anhydride), nonenyl succinic anhydride, octadecenyl succinic anhydride, and octenyl succinic anhydride. Preferably, the or each cyclic anhydride may be selected from one or more of C20-24 alkenyl succinic anhydride, dodecenyl succinic anhydride (such as (2-dodecen-1-yl)succinic anhydride), nonenyl succinic anhydride, octadecenyl succinic anhydride, and octenyl succinic anhydride. Preferably, the or each cyclic anhydride may be selected from one or more of phthalic anhydride, pyromellitic dianhydride, 1,2,4-benzenetricarboxylic anhydride, 1,2-cyclohexanedicarboxylic anhydride and 1,8-naphthalic anhydride. Preferably, the or each cyclic anhydride may be selected from one or more of C15-18 internal olefin-derived alkenyl succinic anhydride, C16 internal olefin-derived alkenyl succinic anhydride, and C16 terminal olefin-derived alkenyl succinic anhydride. The cyclic anhydride compounds discussed herein may be commercially available or may be prepared using procedures well known in the art. For example, alkenyl substituted succinic anhydrides are typically prepared by the reaction of an alkene with maleic anhydride. Preferably, the or each cyclic anhydride may be independently selected from a C6-30 alkyl or alkenyl substituted succinic anhydride, phthalic anhydride and pyromellitic dianhydride. Preferably, the or each cyclic anhydride may be independently selected from a C6-30 alkyl or alkenyl substituted succinic anhydride. Preferably, the or each cyclic anhydride may be independently selected from a C6-30 alkenyl substituted succinic anhydride wherein the alkenyl group is derived from a terminal olefin or an internal olefin, preferably an internal olefin. Preferably, the or each cyclic anhydride may be independently selected from (2-dodecen-1-yl)succinic anhydride, nonenyl succinic anhydride, octadecenyl succinic anhydride, C15-18 internal olefin-derived alkenyl succinic anhydride, C16 internal olefin-derived alkenyl succinic anhydride, C16 terminal olefin-derived alkenyl succinic anhydride, tetrapropenyl succinic anhydride, phthalic anhydride and pyromellitic dianhydride. Preferably, the or each cyclic anhydride may be independently selected from (2-dodecen-1-yl)succinic anhydride, nonenyl succinic anhydride, octadecenyl succinic anhydride, phthalic anhydride and pyromellitic dianhydride. Preferably, the or each cyclic anhydride may be independently selected from (2-dodecen-1-yl)succinic anhydride, nonenyl succinic anhydride, and octadecenyl succinic anhydride. Preferably, the or each cyclic anhydride may be independently selected from phthalic anhydride and pyromellitic dianhydride. The cyclic anhydride compounds discussed herein may be commercially available or may be prepared using procedures well known in the art. The or each of the one or more second reactants used to make the ester compound is a polyol. Mixtures of two or more different second reactants (i.e. different polyols) may be used to make the ester compound. Any suitable polyol may be used to make the ester compound, as would be understood by the person skilled in the art. The term polyol is used to refer to any compound including two or more hydroxy (OH) functional groups. In some embodiments the or each polyol may comprise carbon, hydrogen and oxygen atoms, and optionally additionally nitrogen atoms. In other embodiments, the or each polyol may consist essentially of or consist of carbon, hydrogen and oxygen atoms. Suitable polyols for preparing the ester compound may be compounds having from 2 to 10, preferably from 2 to 6, more preferably 2 or 3, hydroxy groups. In some embodiments the polyol may have only two hydroxy groups (i.e. the polyol may be a diol). Suitable polyols may include one or more of a polyol of formula (IV): H-(OR17)P-OH (IV) wherein each R17 is independently an optionally substituted hydrocarbylene group and p is an integer of at least 1. When p is an integer of greater than 1, the polyol of formula (IV) may comprise groups R17 that are all the same or may comprise groups R17that are different. Suitably, each R17 in the formula (IV) may be the same. Preferably p is an integer from 1 to 140, such as from 1 to 110, from 1 to 40 or from 1 to 10. For example, suitable polyols may include one or more of a polyol of formula (IVA): H-(OR18)q-OH (IVA) wherein each R18 is independently an optionally substituted alkylene group and q is an integer of at least 1. When q is an integer of greater than 1, the polyol of formula (IV) may comprise groups R18 that are all the same or may comprise groups R18 that are different. Suitably, each R18 in the formula (IVA) is the same. Preferably q is an integer from 1 to 140, such as from 1 to 110, from 1 to 40 or from 1 to 10. When the polyol of formula (IV) or (IVA) contains a substituted hydrocarbylene or alkylene group, any suitable substituent may be present, such as for example a carboxy or amido substituent. The polyol of formula (IVA) may have more than 2 hydroxy groups and the group R18 may be a hydroxy substituted alkylene group. Each hydroxy substituted alkylene group R18 may have 1,2 or more hydroxy groups. Each hydroxy substituted alkylene group R18 may preferably have 1 hydroxy group. The polyol of formula (IVA) may have 2 hydroxy groups and the group R18 may be an optionally substituted alkylene group wherein the optional substituent is not hydroxy. The polyol of formula (IV) or of formula (IVA) may be a sugar derived compound in which R17 or R18 includes one or more hydroxy residues. The or each R17 or R18 may represent a cyclic alkylene unit. One or more heteroatoms (for example oxygen atoms) may be present in the cyclic alkylene unit. For example the unit may contain an ether linkage. Suitably the or each R17 or R18 may be one or more saccharide units or may be substituted with one or more saccharide units. Suitably the or each R17 or R18 may be an unsubstituted alkylene group. Preferably the or each R17 or R18 is an optionally substituted alkylene group having from 1 to 50, such as from 1 to 40, preferably from 1 to 30, more preferably from 1 to 20, suitably from 1 to 12 or from 1 to 10, for example from 2 to 6, carbon atoms. Preferably the or each R17 or R18 is an unsubstituted alkylene group having from 1 to 50, preferably from 1 to 20, more preferably from 1 to 12 or from 1 to 10, suitably from 2 to 6 carbon atoms. Each R17 or R18 may be straight chained or branched. Suitably the or each R17orR18 may be an ethylene, propylene, butylene, pentylene, hexylene or dodecylene group. When R17 or R18 has more than 2 carbon atoms any isomer may be present. Preferably R17 or R18 is an ethylene or a propylene group, most preferably an ethylene group. When q is 1, R18 may be a group of formula (CH2)x wherein x is from 2 to 12, preferably from 3 to 12. Suitably when q is 1, R18 may be a straight chain or branched optionally substituted alkylene group and the polyol may be selected from ethylene glycol, propylene glycol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,6-hexanediol, 1,12-dodecanediol, trimethylolpropane, 2-ethyl-1,3,-hexanediol, 2,2-diethyl-1,3-propanediol, 2,2-bis(hydroxymethyl)propionic acid, pentaerythritol, sorbitol, xylitol, glycerol and neopentyl glycol. In some embodiments, the polyol may be selected from ethylene glycol, propylene glycol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,6-hexanediol, 1,12-dodecanediol, trimethylolpropane, 2-ethyl-1,3,-hexanediol, 2,2-diethyl-1,3-propanediol, 2,2-bis(hydroxymethyl)propionic acid, pentaerythritol, sorbitol, xylitol, and neopentyl glycol. Suitably when q is 1, R18 may be a straight chain or branched alkylene group having from 2 to 12, preferably from 3 to 12, carbon atoms. Suitable compounds of this type include ethylene glycol, propylene glycol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,6-hexanediol, 1,12-dodecanediol, trimethylolpropane, 2-ethyl-1,3,-hexanediol, 2,2-diethyl-1,3-propanediol, pentaerythritol and neopentyl glycol. Suitably when q is 1, R18 may be a branched alkylene group having from 2 to 12, preferably from 3 to 12, carbon atoms. Suitable compounds of this type include propylene glycol, 1,2-butanediol, 1,3-butanediol, trimethylolpropane, 2-ethyl-1,3,-hexanediol, 2,2-diethyl-1,3-propanediol, pentaerythritol and neopentyl glycol. Suitably when q is 2 or more, the or each R18 may be a straight chain or branched alkylene group and the polyol may, for example, be selected from diglycerol, diethylene glycol, triethylene glycol, dipropylene glycol, tripropylene glycol, polyethylene glycol and polypropylene glycol. Suitably when q is 2 or more, the or each R18 may be a straight chain or branched alkylene group having from 2 to 4, preferably 2 or 3, carbon atoms. Suitable compounds of this type include diethylene glycol, triethylene glycol, di propylene glycol, tripropylene glycol, polyethylene glycol (PEG), for example having a number average molecular weight of from 150 to 6000, and polypropylene glycol (PPG), for example having a number average molecular weight of from 400 to 2000. Polyethylene glycol and polypropylene glycol are preferred. Suitable polyols may include one or more of PEG 6000, PEG 1500, PEG 1000, PEG 600, PEG 400, PEG 200, PPG 2000, PPG 1000 and PPG 425. The or each R17 or R18 may comprise a mixture of isomers. For example when R17 or R18 is propylene, the polyol may include moieties -CH2CH(CH3)- and -CH(CH3)CH2- in any order within the chain. R17 or R18 may comprise a mixture of different groups for example ethylene, propylene or butylene units. The or each R18 may be an ethylene, propylene or butylene group. For example, the or each R18 may be an n-propylene or n-butylene group or an isopropylene or isobutylene group. For example the or each R18 may be -CH2CH2-, -CH2CH(CH3)-, - CH(CH3)CH2-, CH2CH2CH2-, -CH2C(CH3)2-, -CH2CH2CH2CH2-, -CH(CH3)CH(CH3)- or-CH2CH(CH2CH3)-. Preferably R18 is selected from -CH2CH2-, -CH2CH2CH2-, -CH(CH3)CH2- or -CH2CH(OH)CH2, more preferably from -CH2CH2-, and-CH2CH2CH2-. Suitably the polyol of formula (IV) or (IVA) may be a sugar derived alcohol, for example, glucose, fructose, trehalose, sucrose, lactose, maltose or sorbitol, preferably sorbitol. Suitably the polyol of formula (IV) may be selected from one or more of 1,12-dodecanediol, 1,6-hexanediol, trimethylolpropane, neopentyl glycol, polyethylene glycol (such as PEG 6000, PEG 1500, PEG 1000, PEG 600, PEG 400, PEG 200), polypropylene glycol (such as PPG 2000, PPG 1000, PPG 425), sorbitol, trimethylolpropane and xylitol. Suitably, the polyol, for example of formula (IV), may be an ester of glycerol (also known as a glyceride) and a hydroxycarboxylic acid. The ester of glycerol may be a mono-, di- or triglyceride, suitably a tri-glyceride. Suitably, the hydroxycarboxylic acid comprises one or more hydroxyl groups and one or more carboxylic acid groups. The hydroxycarboxylic acid may be a monocarboxylic acid comprising one or more hydroxyl groups. The hydroxycarboxylic acid may be of the formula R19COOH, wherein R19 is a hydroxylsubstituted hydrocarbyl group. R19is suitably a hydroxy-substituted alkyl, alkenyl or alkaryl group, preferably a hydroxy-substituted alkyl or alkenyl group. R19 suitably comprises from 1 to 25 carbon atoms, preferably from 1 to 20 carbon atoms, more preferably from 1 to 17 carbon atoms. Suitably, the hydroxycarboxylic acid may be selected from glycolic acid, lactic acid, hydroxy butyric acid, hydroxyvaleric acid, hydroxycaproic acid, hydroxystearic acid (preferably 12-hydroxystearic acid), 2,2-bis(hydroxymethyl)propionic acid, mandelic acid or ricinoleic acid. Preferably, the hydroxycarboxylic acid or the cyclic ester thereof may be selected from glycolic acid, mandelic acid, ricinoleic acid, malic acid, tartaric acid or citric acid. More preferably, the hydroxycarboxylic acid or the cyclic ester thereof is ricinoleic acid. Preferably, when the polyol is an ester of glycerol, the polyol may be a mono-, di- or tri-glyceride of ricinoleic acid. Most preferably, when the polyol is an ester of glycerol, the polyol may be a tri-glyceride of ricinoleic acid, such as castor oil. Suitable polyols may include one or more of an alkoxylated polyol of formula (IV) or (IVA). These polyols may be the reaction product of a polyol of formula (IV) or (IVA) and one or more alkylene oxides, such as ethylene oxide or propylene oxide. Such alkoxylated polyols may include polyoxyethylene (80) sorbitan monooleate (also known as Tween® 80) and 2,4,7,9-tetramethyl-5-decyne-4,7-diol ethoxylate. Preferably, the or each polyol may be independently selected from castor oil, 1,6-hexanediol, sorbitol, neopentyl glycol and a polyalkylene glycol (such as PEG 200). When the or each polyol comprises carbon, hydrogen, oxygen and nitrogen atoms, the or each polyol may comprise two or more (such as 2 or 3) hydroxy groups and one or more (suitably one) amine groups. The amine groups may suitably be secondary or tertiary amines. Preferably the amine groups are tertiary amines. These polyols may be referred to herein as nitrogen containing polyols. For example, suitable nitrogen containing polyols may include one or more of a polyol of formula (V) or a derivative thereof: NR20R21R22 (V) wherein R20, R21 and R22 are each independently selected from hydrogen, hydroxyalkyl and hydrocarbyl, provided that at least two of R20, R21 and R22 represents a hydroxyalkyl group. Preferably, the at least two of R20, R21 and R22 that represent a hydroxyalkyl group are the same. For example, in the compounds of formula (V), R20 and R21 may each represent hydroxyalkyl and R22 may represent hydrogen, hydroxyalkyl or hydrocarbyl. In the formula (V), the hydroxyalkyl group may contain from 1 to 8, such as from 1 to 4, such as 2 or 3, carbon atoms. For example, each hydroxyalkyl group may be hydroxyethyl or hydroxypropyl, particularly hydroxyethyl. In the formula (V), the hydrocarbyl group (when present) may represent any suitable such group, such as an alkyl group, for example an alkyl group containing from 1 to 10, such as from 1 to 6 or from 1 to 4, carbon atoms. Thus, the hydrocarbyl group may represent a methyl, ethyl, propyl or butyl group (especially butyl or methyl). For example, in the compounds of formula (V), R20 and R21 may each represent hydroxyalkyl and R22 may represent hydrogen, hydroxyalkyl or hydrocarbyl (especially hydrogen or hydrocarbyl, more especially hydrocarbyl). In some embodiments, the R20 and R21 may each represent hydroxyalkyl and R22 may represent hydroxyalkyl or hydrocarbyl. Preferably in the compounds of formula (V), R20 and R21 both represent hydroxyethyl and R22 represents hydrogen or hydrocarbyl, such as a hydrocarbyl group containing from 1 to 6, or from 1 to 4, carbon atoms. Preferably in the compounds of formula (V), R20 and R21 both represent hydroxyethyl and R22 represents hydrogen or an alkyl group containing from 1 to 6, or from 1 to 4, carbon atoms (especially methyl). Examples of suitable nitrogen containing polyols include N-methyl diethanolamine, N-butyl diethanolamine, triethanolamine and diethanolamine, and derivatives thereof. The or each nitrogen containing polyol may be independently selected from N-methyl diethanolamine, N-butyl diethanolamine, and triethanolamine, and derivatives thereof. The or each nitrogen containing polyol may be independently selected from N-methyl diethanolamine, N-butyl diethanolamine, and triethanolamine. References herein to nitrogen containing polyols include derivatives thereof, such as a corresponding quaternary compound. Thus, as example of a suitable derivative of a nitrogen containing polyol is tris(2-hydroxyalkyl)methylammonium compound, for example tris(2-hydroxyethyl)methylammonium methylsulfate, which is a quaternary ammonium salt of triethanolamine. In some preferred embodiments, the nitrogen containing polyols are not derivatised, for example they are not quaternary ammonium salts. Preferably, the or each nitrogen containing polyol may be independently selected from N-butyl diethanolamine, diethanolamine and N-methyl diethanolamine, and derivatives (for example quaternary ammonium salts) thereof. Preferably, the or each nitrogen containing polyol may be independently selected from N-butyl diethanolamine and N-methyl diethanolamine, and derivatives (for example quaternary ammonium salts) thereof. Further examples of suitable nitrogen containing polyols include those formed by reaction of a hydroxy substituted cyclic ester or cyclic carbonate, such as glycerol carbonate or gluconolactone, with a suitable primary or secondary amine compound, such as ethanolamine, dipropylamine, hexylamine, dodecylamine, phenethylamine, dipropylamine, ethylenediamine, or a polyether polyamine. Suitable polyether amines may include polyether monoamines (such as for example Jeffamine M-1000) and polyether polyamines (such as for example Jeffamine ED-600). As the skilled person would appreciate, the reaction of a hydroxy substituted cyclic ester or cyclic carbonate with a suitable primary or secondary amine compound will result in a ring opening reaction to form a compound such as a N-carbamoyl polyol or an amido polyol. The or each polyol may be selected from one or more polyol of the formula (IV) or (IVA) as defined herein (including an ester of glycerol and a hydroxycarboxylic acid (such as castor oil)), one or more of an alkoxylated polyol of formula (IV) or (IVA) as defined herein, one or more nitrogen containing polyol as defined herein (including compounds of the formula (V)) and one or more polyol formed by reaction of a hydroxy substituted cyclic ester or cyclic carbonate with a suitable primary or secondary amine compound. Preferably, the or each polyol may be selected from one or more polyol of the formula (IV) or (IVA) as defined herein (including an ester of glycerol and a hydroxycarboxylic acid (such as castor oil)), one or more of an alkoxylated polyol of formula (IV) or (IVA) as defined herein, one or more nitrogen containing polyol of the formula (V) as defined herein and one or more polyol formed by reaction of a hydroxy substituted cyclic ester or cyclic carbonate with a suitable primary or secondary amine compound. More preferably, the or each polyol may be selected from one or more polyol of the formula (IV) or (IVA) as defined herein (such as an ester of glycerol and a hydroxycarboxylic acid , for example castor oil), and one or more nitrogen containing polyol of the formula (V) as defined herein. In one embodiment, the or each polyol may be selected from one or more polyol of the formula (IV) or (IVA) as defined herein, such as an ester of glycerol and a hydroxycarboxylic acid (for example castor oil). In another embodiment, the or each polyol may be selected from one or more of an alkoxylated polyol of formula (IV) or (IVA) as defined herein. In one embodiment, the or each polyol may be selected from one or more polyol of the formula (IV) or (IVA) as defined herein, such as an ester of glycerol and a hydroxycarboxylic acid (for example castor oil) and from one or more of an alkoxylated polyol of formula (IV) or (IVA) as defined herein. In another embodiment, the or each polyol may be selected from one or more nitrogen containing polyol as defined herein (including compounds of the formula (V)). In another embodiment, the or each polyol may be selected from one or more polyol formed by reaction of a hydroxy substituted cyclic ester or cyclic carbonate with a suitable primary or secondary amine compound. In one embodiment, the ester compound may be the reaction product of reactants comprising one (i.e. a single) cyclic anhydride and one (i.e. a single) polyol. In other embodiments, the ester compound may be the reaction product of reactants comprising two different cyclic anhydrides and one (i.e. a single) polyol, or the ester compound may be the reaction product of reactants comprising one (i.e. a single) cyclic anhydride and two different polyols. The combined amount of the one or more first reactants and the one or more second reactants may be at least 50 mol%, suitably at least 75 mol%, preferably at least 90 mol%, for example at least 95 wt% of the reactants that are reacted to obtain the ester compound. In one embodiment, the ester compound may be the reaction product of reactants consisting essentially of or consisting of one (i.e. a single) cyclic anhydride and one (i.e. a single) polyol. In other embodiments, the ester compound may be the reaction product of reactants consisting essentially of or consisting of two different cyclic anhydrides and one (i.e. a single) polyol, or the ester compound may be the reaction product of reactants consisting essentially of or consisting of one (i.e. a single) cyclic anhydride and two different polyols. The ester compound for use herein may be the reaction product of reactants comprising the one or more first reactants and one or more second reactants as disclosed herein and additionally one or more third reactants. In other words, the ester compound may be the reaction product of reactants comprising one or more first reactants as disclosed herein, one or more second reactants as disclosed herein and one or more third reactants. The one or more third reactants may for example act as end capping groups and / or may introduce additional functional groups to the ester compounds. The one or more third reactants may be selected to impart the desired groups and / or properties to the ester compound by the person skilled in the art. The combined amount of the one or more first reactants, the one or more second reactants, and the one or more third reactants may be at least 50 mol%, suitably at least 75 mol%, preferably at least 90 mol%, for example at least 95 wt% of the reactants that are reacted to obtain the ester compound. The ester compound for use herein may be the reaction product of reactants consisting essentially of or consisting of the one or more first reactants and one or more second reactants as disclosed herein and additionally one or more third reactants. In other words, the ester compound may be the reaction product of reactants consisting essentially of or consisting one or more first reactants as disclosed herein, one or more second reactants as disclosed herein and one or more third reactants. The ester compound for use herein is suitably the reaction product of no more than four different reactants. Preferably, the ester compound is the reaction product of no more than three different reactants. For example, the ester compound may be the reaction product of one first reactant, one second reactant, and one third reactant, or the reaction product of two different first reactants and one second reactant as disclosed herein. In some preferred embodiments, the ester compound is the reaction product of only two different reactants, i.e. one first reactant and one second reactant as disclosed herein (and no further reactants). Examples of suitable third reactants include one or more of the following: (i) polycarboxylic acids or reactive equivalents thereof; (ii) monocarboxylic acids or esters thereof; (iii) hydroxycarboxylic acids or cyclic esters thereof; (iv) epoxide compounds; (v) polyfunctional reactants having a reactive amino group; (vi) monoalcohols; and (vii) monofunctional reactants having a reactive amino group. The third reactant may be (i) a polycarboxylic acid or a reactive equivalent thereof. Suitable polycarboxylic acids comprise two or more carboxylic acid groups, such as two or three carboxylic acid groups. Preferred polycarboxylic acids are dicarboxylic acids. The polycarboxylic acid may be aliphatic or aromatic. The aliphatic polycarboxylic acid may be cycloaliphatic. The aliphatic polycarboxylic acid may be saturated or unsaturated. By the term “unsaturated” we mean that the polycarboxylic acid comprises one or more carbon-carbon double bonds. The polycarboxylic acid may comprise one or more heteroatoms other than in the carboxylic acid groups. By the term “heteroatoms” we mean atoms other than carbon or hydrogen, such as oxygen, nitrogen and sulfur atoms. For example, the polycarboxylic acid may comprise one or more moieties selected from hydroxy groups, amino groups, ether groups, and / or thioether groups. Reactive equivalents of polycarboxylic acids may be used. By the term “reactive equivalent”, we mean a compound that results in the same reaction product as the corresponding polycarboxylic acid. Suitable reactive equivalents include acid chlorides and esters of the polycarboxylic acids described herein. Examples of suitable polycarboxylic acids or reactive equivalents thereof include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, maleic acid, fumaric acid, malic acid, tartaric acid, citric acid, C20-24 alkenyl succinic acid, dodecenyl succinic acid (such as (2-dodecen-1-yl)succinic acid), nonenyl succinic acid, octadecenyl succinic acid, octenyl succinic acid, polyisobutenylsuccinic acid, itaconic acid, 1,2-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, phthalic acid, isophthalic acid, terephthalic acid, homophthalic acid, 1,2,4-benzenetricarboxylic acid, pyromellitic acid, 1,2-naphthalenedicarboxylic acid, 2,3-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, diglycolic acid, thiodiglycolic acid, 3,3’-thiodipropanoic acid, iminodiacetic acid, poly(ethylene glycol)bis(carboxymethyl) ether, a dimer acid, and acid chlorides and esters thereof. Preferably, the polycarboxylic acid is selected from pimelic acid, suberic acid, sebacic acid, dodecanedioic acid, citric acid, diglycolic acid, thiodiglycolic acid, poly(ethylene glycol)bis(carboxymethyl) ether, or a hydrogenated dimer acid. The third reactant may be (ii) a monocarboxylic acid or an ester thereof. Suitable monocarboxylic acids may be aliphatic or aromatic. The aliphatic monocarboxylic acid may be cycloaliphatic. The aliphatic monocarboxylic acid may be saturated or unsaturated. The monocarboxylic acid may contain from 2 to 40 carbon atoms, suitably from 4 to 30 carbon atoms, preferably from 6 to 20 carbon atoms, for example from 8 to 18 carbon atoms. The monocarboxylic acid may be a fatty acid. Examples of suitable monocarboxylic acids or esters thereof include hexanoic acid, octanoic acid, decanoic acid, lauric acid, myristic acid, myristoleic acid, palmitic acid, palmitoleic acid, stearic acid, oleic acid, elaidic acid, linoleic acid, linolelaidic acid, arachidic acid, arachidonic acid, behenic acid, erucic acid, and esters (preferably methyl esters) thereof. Preferably, the monocarboxylic acid is selected from propionic acid, hexanoic acid, lauric acid, stearic acid, oleic acid, or erucic acid. The third reactant may be (iii) a hydroxycarboxylic acid or a cyclic ester thereof. Suitable hydroxycarboxylic acids comprise one or more hydroxy groups and one or more carboxylic acid groups. The hydroxycarboxylic acid may be a monocarboxylic acid comprising one or more hydroxy groups. By the term “cyclic ester” of a hydroxycarboxylic acid we mean a compound comprising a cyclic group, wherein the cyclic group comprises one or more ester groups. The ester may be a cyclic monoester or a cyclic diester. The cyclic ester may correspond to a single cyclised molecule of the hydroxycarboxylic acid. This may, for example, be formed by an intramolecular reaction between the hydroxy group and the carboxylic acid group on one molecule of the hydroxycarboxylic acid. Alternatively, the cyclic ester may correspond to a cyclic dimer of a hydroxycarboxylic acid. This may, for example, be formed by an intermolecular reaction between the hydroxy groups and the carboxylic acid groups on two molecules of the hydroxycarboxylic acid. Examples of suitable hydroxycarboxylic acids or cyclic esters thereof include glycolic acid, lactic acid, hydroxy butyric acid, hydroxyvaleric acid, hydroxycaproic acid, hydroxystearic acid (preferably 12-hydroxystearic acid), dihydroxystearic acid, 2,2-bis(hydroxymethyl)propionic acid, mandelic acid, ricinoleic acid, malic acid, tartaric acid, citric acid, y-butyrolactone, 6-valerolactone, s-caprolactone, menthide, D-lactide, L-lactide, or DL-lactide. Preferably, the hydroxycarboxylic acid is selected from ricinoleic acid or citric acid. The third reactant may be (iv) an epoxide compound. Suitable epoxide compounds may comprise one or more than one epoxide group. For example, suitable epoxide compounds may comprise two epoxide groups. Examples of suitable epoxide compounds include 1,2-epoxydodecane, ethyl glycidyl ether, isopropylglycidyl ether, 2-ethylhexyl glycidyl ether, octyl glycidyl ether, nonyl glycidyl ether, decyl glycidyl ether, butyl glycidyl ether (such as n-butyl glycidyl ether), 1,2-epoxyhexane, epichlorohydrin, glycidyltrimethylammonium chloride, cyclopentene oxide, cyclohexene oxide, poly(ethylene glycol) diglycidyl ether, poly(propylene glycol) diglycidyl ether and poly(butylene glycol) diglycidyl ether. The third reactant may be (v) a polyfunctional reactant having a reactive amino group. By the term “polyfunctional reactant” we mean a reactant with at least two reactive groups. By the term “reactive group” we mean a group that reacts with the first reactant and / or the second reactant. At least one of the reactive groups is a reactive amino group. The other reactive groups in the polyfunctional reactant may be reactive amino groups, or may be reactive groups other than amino groups, such as hydroxy groups or carboxyl groups. Reactive amino groups are suitably primary amino groups or secondary amino groups. The polyfunctional reactant may comprise at least one reactive amino group and at least one hydroxy group. The polyfunctional reactant may be an alkanolamine or an alkoxylated alkanolamine. The polyfunctional reactant may comprise at least two reactive amino groups. The polyfunctional reactant may be an aliphatic diamine, a polyether diamine, ora polyalkylene polyamine. The polyfunctional reactant may comprise at least one reactive amino group and at least one carboxyl group. The polyfunctional reactant may be an amino acid, such as a naturally occurring amino acid. Examples of suitable polyfunctional reactants having at least one reactive amino group include ethanolamine, diethanolamine, ethylene diamine, coco propylene diamine, diethylenetriamine (DETA), triethylenetetramine (TETA), tetraethylenepentamine (TEPA), a polyether diamine (preferably Jeffamine ED-600, Jeffamine ED-900, or Jeffamine ED-2003 which are commercially available), alanine, arginine, asparagine, aspartate, cysteine, glutamine, glutamate, glycine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, proline, serine, threonine, tryptophan, tyrosine, and valine. The third reactant may be (vi) a monoalcohol. Suitable monoalcohols may be aliphatic or aromatic. The aliphatic monoalcohol may be cycloaliphatic. The aliphatic monoalcohol may be saturated or unsaturated. The monoalcohol may contain from 2 to 40 carbon atoms, suitably from 4 to 30 carbon atoms, preferably from 6 to 20 carbon atoms, for example from 8 to 18 carbon atoms. The monoalcohol may be a fatty alcohol. Examples of suitable monoalcohols include hexanol, octanol, 2-ethylhexanol, decanol, dodecanol alcohol, myristyl alcohol, myristoleyl alcohol, palmityl alcohol, palmitoleyl alcohol, stearyl alcohol, oleyl alcohol, elaidyl alcohol, linoleyl alcohol, linolelaidyl alcohol, arachidyl alcohol, arachidonyl alcohol, behenyl alcohol, erucyl alcohol, benzyl alcohol, and choline chloride. Preferably, the monoalcohol is hexanol or oleyl alcohol. The third reactant may be (vii) a monofunctional reactant having a reactive amino group. Suitable monofunctional reactants having a reactive amino group have one reactive amino group and no other reactive groups. The monofunctional reactant may contain other functional groups that are not reactive groups, such as tertiary amino groups or ether groups. The monofunctional reactant may be an aliphatic monoamine (such as a fatty alkyl amine), an N,N-dialkylaminoalkylamine, ora polyether monoamine. The polyether monoamine suitably comprises a polyether backbone selected from polyethylene glycol (PEG), polypropylene glycol (PPG), or a copolymer of polyethylene glycol (PEG) and polypropylene glycol (PPG). The copolymer of PEG and PPG may be a block copolymer or a random copolymer. The polyether backbone is suitably capped at one end with the reactive amino group, and capped at the other end with an alkyl group (preferably a methyl group). The polyether monoamine suitably has a molecular weight of from 150 to 6000, preferably from 400 to 3000, for example from 600 to 2000. The polyether monoamine may have a weight average molecular weight of from 150 to 6000, preferably from 400 to 3000, for example from 600 to 2000. Examples of suitable monofunctional reactants having a reactive amino group include propylamine, dipropylamine, butylamine, hexylamine, octylamine, decylamine, dodecylamine, tetradecylamine, hexadecylamine, octadecylamine, tallow alkyl amine, benzylamine, phenethylamine, 3-dimethylaminopropylamine (DMAPA), or Jeffamine M-1000 (which is commercially available). Preferably, the monofunctional reactant having a reactive amino group is selected from dodecylamine, N,N-dimethylaminopropylamine (DMAPA), or Jeffamine M-1000. The ester compounds may be prepared from the first, second and optionally third reactants by any suitable method, as would be known to the person skilled in the art. The esterification reaction will typically be conducted in the presence of a suitable esterification catalyst, such as tin(ll) ethylhexanoate, tin(ll) oxalate, p-toluenesulfonic acid, methanesulfonic acid, or sulfuric acid. Another suitable catalyst system comprises 1,8-diazabicyclo(5.4.0)undec-7-ene and dicyclohexylurea. The esterification reaction may be carried out for any suitable length of time, such as at least 1 hour, preferably at least 3 hours, for example at least 5 hours. The esterification reaction may be carried out at any suitable temperature, such as from 50 to 300°C, preferably from 100 to 200°C. References herein to a reactant are intended to refer to the compounds that react to form the ester compound and are not intended to include a catalyst used in the reaction. Suitable molar ratios of the first, second and optional third reactants may be used to prepare the ester compounds. Suitably, the ester compound is not further reacted after the reaction of the reactants. When the third reactant is used, the molar ratio of the first reactant to the sum of the second and third reactants is suitably from 1:1 to 1:5, such as from 1:1 to 1:3. Suitably, the ester compound may be the reaction product of reactants consisting essentially of or consisting of one or more first reactants, one or more second reactants, and optionally one or more third reactants, wherein the or each first reactant is a cyclic anhydride; the or each second reactant is a polyol, wherein at least one of the one or more second reactants is a nitrogen containing polyol and / or a polyol of formula (IVA): H-(OR18)q-OH (IVA) wherein each R18 is independently an optionally substituted alkylene group wherein the optional substituent is not hydroxy and q is an integer of at least 1; and the or each third reactant is selected from: (viii) polycarboxylic acids or reactive equivalents thereof; (ix) monocarboxylic acids or esters thereof; (x) hydroxycarboxylic acids or cyclic esters thereof; (xi) epoxide compounds; (xii) polyfunctional reactants having a reactive amino group; (xiii) monoalcohols; and (xiv) monofunctional reactants having a reactive amino group. Suitably, the ester compound may be the reaction product of reactants consisting essentially of or consisting of one or more first reactants, one or more second reactants, and optionally one or more third reactants, wherein the or each first reactant is a cyclic anhydride; the or each second reactant is a polyol, wherein at least one of the one or more second reactants is selected from ethylene glycol, propylene glycol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,6-hexanediol, 1,12-dodecanediol, 2-ethyl-1,3,-hexanediol, 2,2-diethyl-1,3-propanediol, 2,2-bis(hydroxymethyl)propionic acid, neopentyl glycol, diethylene glycol, triethylene glycol, dipropylene glycol, tripropylene glycol, polyethylene glycol, polypropylene glycol, 2,4,7,9-tetramethyl-5-decyne-4,7-diol ethoxylate, N-methyl diethanolamine, N-butyl diethanolamine, diethanolamine, or derivatives (for example quaternary ammonium salts) of N-methyl diethanolamine or N-butyl diethanolamine; and the or each third reactant is selected from: (i) polycarboxylic acids or reactive equivalents thereof; (ii) monocarboxylic acids or esters thereof; (iii) hydroxycarboxylic acids or cyclic esters thereof; (iv) epoxide compounds; (v) polyfunctional reactants having a reactive amino group; (vi) monoalcohols; and (vii) monofunctional reactants having a reactive amino group. Suitably, the ester compound may be the reaction product of reactants consisting essentially of or consisting of one or more first reactants, one or more second reactants, and optionally one or more third reactants, wherein the or each first reactant is a cyclic anhydride; the or each second reactant is a polyol; and the or each third reactant is selected from: (i) polycarboxylic acids or reactive equivalents thereof; (ii) aliphatic monocarboxylic acids or esters thereof; (iii) hydroxycarboxylic acids or cyclic esters thereof; (iv) epoxide compounds; (v) polyfunctional reactants having a reactive amino group; (vi) monoalcohols; and (vii) monofunctional reactants having a reactive amino group. Suitably, the ester compound may be the reaction product of reactants consisting essentially of or consisting of one or more first reactants, one or more second reactants, and optionally one or more third reactants, wherein the or each first reactant is a cyclic anhydride; the or each second reactant is a polyol; and the or each third reactant is selected from: (i) polycarboxylic acids or reactive equivalents thereof; (ii) hydroxycarboxylic acids or cyclic esters thereof; (iii) epoxide compounds; (iv) polyfunctional reactants having a reactive amino group; (v) monoalcohols; and (vi) monofunctional reactants having a reactive amino group. Suitably, the ester compound may be the reaction product of reactants consisting essentially of or consisting of one or more first reactants, one or more second reactants, and optionally one or more third reactants, wherein the or each first reactant is a cyclic anhydride; the or each second reactant is a polyol; and the or each third reactant is selected from: (i) polycarboxylic acids or reactive equivalents thereof; (ii) monocarboxylic acids or esters thereof; (iii) hydroxycarboxylic acids or cyclic esters thereof; (iv) epoxide compounds; (v) polyfunctional reactants having a reactive amino group selected from ethanolamine, diethanolamine, ethylene diamine, coco propylene diamine, diethylenetriamine (DETA), triethylenetetramine (TETA), tetraethylenepentamine (TEPA), a polyether diamine (preferably Jeffamine ED-600, Jeffamine ED-900, or Jeffamine ED-2003 which are commercially available), alanine, arginine, asparagine, aspartate, cysteine, glutamine, glutamate, glycine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, proline, serine, threonine, tryptophan, tyrosine, or valine; (vi) monoalcohols; and (vii) monofunctional reactants having a reactive amino group selected from propylamine, dipropylamine, butylamine, hexylamine, octylamine, decylamine, dodecylamine, tetradecylamine, hexadecylamine, octadecylamine, tallow alkyl amine, benzylamine, phenethylamine, 3-dimethylaminopropylamine (DMAPA), or Jeffamine M-1000. Suitably, the ester compound may be the reaction product of reactants consisting essentially of or consisting of one or more first reactants, one or more second reactants, and optionally one or more third reactants, wherein the or each first reactant is a cyclic anhydride; the or each second reactant is a polyol; and the or each third reactant is selected from: (i) polycarboxylic acids or reactive equivalents thereof; (ii) monocarboxylic acids or esters thereof; (iii) hydroxycarboxylic acids or cyclic esters thereof; (iv) epoxide compounds; and (v) monoalcohols. Suitably, the or each third reactant (when present) is a monocarboxylic acid or an ester thereof selected from hexanoic acid, octanoic acid, decanoic acid, lauric acid, myristic acid, myristoleic acid, palmitic acid, palmitoleic acid, stearic acid, oleic acid, elaidic acid, linoleic acid, linolelaidic acid, arachidic acid, arachidonic acid, behenic acid, erucic acid, and esters (preferably methyl esters) thereof; and the second and third reactants are reacted in a molar ratio of from 1:2 to 2:1, such as from 1:2 to 1:1, preferably 1:1 or 1:1.5. Suitably, the or each third reactant (when present) is a fatty acid and the second and third reactants are reacted in a molar ratio of from 1:2 to 2:1, such as from 1:2 to 1:1, preferably 1:1 or 1:1.5. Ratios refer to the total amounts of second reactants or third reactants if more than one second reactant or third reactant is present. Suitably, at least one of the first reactants may be a cyclic anhydride of formula (I) wherein at least one of R1 and R2 is a Ce-30, such as a Cs-24, alkyl or alkenyl (more preferably alkenyl) group (such as an alkenyl group derived from a terminal olefin or an internal olefin, preferably an internal olefin) and at least one of the second reactants may be castor oil. Suitably, at least one of the first reactants may be a cyclic anhydride of formula (I) wherein R1 is hydrogen and R2 is a Ce-3o, such as a Cs-24, alkyl or alkenyl (more preferably alkenyl) group (such as an alkenyl group derived from a terminal olefin or an internal olefin, preferably an internal olefin) and at least one of the second reactants may be castor oil. Suitably, the first reactant may be a cyclic anhydride of formula (I) wherein R1 is hydrogen and R2 is a Ce-30, such as a Cs-24, alkyl or alkenyl (more preferably alkenyl) group (such as an alkenyl group derived from a terminal olefin or an internal olefin, preferably an internal olefin) and the second reactant may be castor oil. Suitably, the first reactant may be selected from nonenyl succinic anhydride, dodecenyl succinic anhydride. C15-18 internal olefin-derived alkenyl succinic anhydride, C16 internal olefin-derived alkenyl succinic anhydride, and C16 terminal olefin-derived alkenyl succinic anhydride and the second reactant may be castor oil. Suitably, the first reactant may be nonenyl succinic anhydride and the second reactant may be castor oil. Suitably, the first reactant may be selected from C15-18 internal olefin-derived alkenyl succinic anhydride, C16 internal olefin-derived alkenyl succinic anhydride, and C16 terminal olefin-derived alkenyl succinic anhydride and the second reactant may be castor oil. Suitably, the first reactant may be dodecenyl succinic anhydride and the second reactant may be castor oil. The dodecenyl succinic anhydride and the castor oil may be reacted in a molar ratio of from 10:1 to 1:10, such as from 2:1 to 1:2, preferably from 1.5:1 to 1:1.5. The dodecenyl succinic anhydride and the castor oil may be reacted in a molar ratio of from 1:1.2 to 1.2:1. More preferably, the dodecenyl succinic anhydride and the castor oil may be reacted in a 1:1 molar ratio. Suitably, the first reactant may be selected from succinic anhydride, maleic anhydride, glutaric anhydride, C20-24 alkenyl succinic anhydride, nonenyl succinic anhydride, octadecenyl succinic anhydride, octenyl succinic anhydride, octadecyl succinic anhydride, octyl succinic anhydride, C15-18 internal olefin-derived alkenyl succinic anhydride, C16 internal olefin-derived alkenyl succinic anhydride, C16 terminal olefin-derived alkenyl succinic anhydride, a branched alkenyl succinic anhydride such as tetrapropenyl succinic anhydride or polyisobutenyl succinic anhydride, phthalic anhydride, pyromellitic dianhydride, 1,2,4-benzenetricarboxylic anhydride, 1,2-cyclohexanedicarboxylic anhydride, 1,2-naphthalic anhydride, 2,3-naphthalic anhydride, 1,8-naphthalic anhydride or homophthalic anhydride and the second reactant may be castor oil. The first reactant and second reactant may be reacted in a molar ratio of from 1:1.2 to 1.2:1, preferably in a 1:1 molar ratio. Suitably, the first reactant may be selected from succinic anhydride, maleic anhydride, glutaric anhydride, C20-24 alkenyl succinic anhydride, nonenyl succinic anhydride, octadecenyl succinic anhydride, octenyl succinic anhydride, octadecyl succinic anhydride, octyl succinic anhydride, a branched alkenyl succinic anhydride such as tetrapropenyl succinic anhydride or polyisobutenyl succinic anhydride, phthalic anhydride, pyromellitic dianhydride, 1,2,4-benzenetricarboxylic anhydride, 1,2-cyclohexanedicarboxylic anhydride, 1,2-naphthalic anhydride, 2,3-naphthalic anhydride, 1,8-naphthalic anhydride or homophthalic anhydride and the second reactant may be castor oil. The first reactant and second reactant may be reacted in a molar ratio of from 1:1.2 to 1.2:1, preferably in a 1:1 molar ratio. Suitably, the first reactant may be selected from C20-24 alkenyl succinic anhydride, nonenyl succinic anhydride, octadecenyl succinic anhydride, octenyl succinic anhydride, octadecyl succinic anhydride, or octyl succinic anhydride and the second reactant may be castor oil. The first reactant and second reactant may be reacted in a molar ratio of from 1:1.2 to 1.2:1, preferably in a 1:1 molar ratio. Suitably, at least one of the first reactants may be a cyclic anhydride of formula (I) wherein least one of R1 and R2 is a C6-30, such as a Cs-24, alkyl or alkenyl (more preferably alkenyl) group (such as a C6-30, preferably Cs-24, alkenyl group derived from a terminal olefin or an internal olefin, preferably an internal olefin), or at least one of the first reactants may be a cyclic anhydride of formula (II) wherein R3 and R4 are each independently selected from hydrogen, an alkyl group and an alkenyl group, or R3 and R4 together with the carbon atoms to which they are attached represent an optionally substituted cyclic group; and at least one of the second reactants may be selected from N-methyl diethanolamine, N-butyl diethanolamine, castor oil, tris(2- hydroxyethyl)methyl ammonium methylsulfate, PEG 200, PPG 2000, 1,6-hexanediol, sorbitol, or neopentyl glycol. Suitably, at least one of the first reactants may be a cyclic anhydride of formula (I) wherein least one of R1 and R2 is a Ce-3o, such as a Cs-24, alkyl or alkenyl (more preferably alkenyl) group (such as a Ce-30, preferably Cs-24, alkenyl group derived from a terminal olefin or an internal olefin, preferably an internal olefin), or at least one of the first reactants may be a cyclic anhydride of formula (II) wherein R3 and R4 together with the carbon atoms to which they are attached represent an optionally substituted cyclic group; and at least one of the second reactants may be selected from N-methyl diethanolamine, N-butyl diethanolamine, castor oil, tris(2-hydroxyethyl)methyl ammonium methylsulfate, PEG 200, 1,6-hexanediol, or sorbitol. Suitably, at least one of the first reactants may be a cyclic anhydride of formula (I) wherein least one of R1 and R2 is a Cs-3o, such as a Cs-24, alkyl or alkenyl (more preferably alkenyl) group (such as a Ce-30, preferably Cs-24, alkenyl group derived from a terminal olefin or an internal olefin, preferably an internal olefin); and at least one of the second reactants may be selected from N-methyl diethanolamine, N-butyl diethanolamine, castor oil, tris(2-hydroxyethyl)methyl ammonium methylsulfate, PEG 200, 1,6-hexanediol, or sorbitol. Suitably, the ester compound may be the reaction product of reactants comprising, consisting essentially of, or consisting of one or more first reactants and one or more second reactants, wherein the or each first reactant is a cyclic anhydride of formula (I) wherein least one of R1 and R2 is a Ce-30, such as a Cs-24, alkyl or alkenyl (more preferably alkenyl) group, or a cyclic anhydride of formula (II) wherein R3 and R4 are each independently selected from hydrogen, an alkyl group and an alkenyl group, or R3 and R4 together with the carbon atoms to which they are attached represent an optionally substituted cyclic group; and the or each second reactant is a polyol of formula (IVA): H-(OR18)q-OH (IVA) wherein each R18 is independently an unsubstituted alkylene group and q is an integer of at least 1, or a polyol of formula (V): NR20R21R22 (V) wherein R20 and R21 each represent a hydroxyalkyl group and R22 represents a hydrocarbyl group. The molar ratio of one or more first reactants and the one or more second reactants is suitably from 1.2:1 to 1:1.2. Preferably the molar ratio is 1:1. Suitably, the ester compound may be the reaction product of reactants comprising one or more first reactants and one or more second reactants, wherein the or each first reactant is a cyclic anhydride of formula (I) wherein least one of R1 and R2 is a Ce-3o, such as a Cs-24, alkyl or alkenyl (more preferably alkenyl) group, or a cyclic anhydride of formula (II) wherein R3 and R4 together with the carbon atoms to which they are attached represent an optionally substituted cyclic group; and the or each second reactant is a polyol of formula (IVA): H-(OR18)q-OH (IVA) wherein each R18 is independently an unsubstituted alkylene group and q is an integer of at least 1. The molar ratio of one or more first reactants and the one or more second reactants is suitably from 1.2:1 to 1:1.2. Preferably the molar ratio is 1:1. Suitably, the ester compound may be the reaction product of reactants consisting essentially of or consisting of one or more first reactants and one or more second reactants, wherein the or each first reactant is a cyclic anhydride of formula (I) wherein least one of R1 and R2 is a Cs-3o, such as a Cs-24, alkyl or alkenyl (more preferably alkenyl) group, or a cyclic anhydride of formula (II) wherein R3 and R4 together with the carbon atoms to which they are attached represent an optionally substituted cyclic group; and the or each second reactant is a polyol of formula (IVA): H-(OR18)q-OH (IVA) wherein each R18 is independently an unsubstituted alkylene group and q is an integer of at least 1. The molar ratio of one or more first reactants and the one or more second reactants is suitably from 1.2:1 to 1:1.2. Preferably the molar ratio is 1:1. Suitably, the ester compound may be the reaction product of reactants comprising a first reactant and a second reactant, wherein the first reactant is a cyclic anhydride of formula (I) wherein least one of R1 and R2 is a Cs-24 alkyl or alkenyl group; and the second reactant is selected from diethylene glycol, triethylene glycol, dipropylene glycol, tripropylene glycol, polyethylene glycol and polypropylene glycol. The molar ratio of the first reactant and the second reactant is suitably from 1.2:1 to 1:1.2. Preferably the molar ratio is 1:1. Suitably, the ester compound may be the reaction product of reactants consisting essentially of or consisting of a first reactant and a second reactant, wherein the first reactant is a cyclic anhydride of formula (I) wherein least one of R1 and R2 is a Ca-24 alkyl or alkenyl group; and the second reactant is selected from diethylene glycol, triethylene glycol, dipropylene glycol, tripropylene glycol, polyethylene glycol and polypropylene glycol. The molar ratio of the first reactant and the second reactant is suitably from 1.2:1 to 1:1.2. Preferably the molar ratio is 1:1. Suitably, the ester compound may be the reaction product of reactants comprising a first reactant and a second reactant, wherein the first reactant is a cyclic anhydride of formula (I) wherein least one of R1 and R2 is a Ca-24 alkenyl group; and the second reactant is selected from polyethylene glycol and polypropylene glycol. The molar ratio of the first reactant and the second reactant is suitably from 1.2:1 to 1:1.2. Preferably the molar ratio is 1:1. Suitably, the ester compound may be the reaction product of reactants consisting essentially of or consisting of a first reactant and a second reactant, wherein the first reactant is a cyclic anhydride of formula (I) wherein least one of R1 and R2 is a Ca-24 alkenyl group; and the second reactant is selected from polyethylene glycol and polypropylene glycol. The molar ratio of the first reactant and the second reactant is suitably from 1.2:1 to 1:1.2. Preferably the molar ratio is 1:1. Suitably, the ester compound may be the reaction product of reactants comprising, consisting essentially of, or consisting of a first reactant, one or more second reactants, and optionally a third reactant, wherein the first reactant is selected from maleic anhydride, nonenyl succinic anhydride, dodecenyl succinic anhydride, octadecenyl succinic anhydride, phthalic anhydride, or pyromellitic dianhydride; the one or more second reactants are selected from N-methyl diethanolamine, N-butyl diethanolamine, castor oil, tris(2-hydroxyethyl)methyl ammonium methylsulfate, PEG 200, PPG 2000, 1,6-hexanediol, sorbitol, or neopentyl glycol; and the third reactant is oleyl alcohol. The molar ratio of the first reactant and the one or more second reactants is suitably from 1.2:1 to 1:1.2. The molar ratio of the first reactant and the one or more second reactants is preferably 1:1. When the third reactant is used, the molar ratio of the first, second and third reactants is suitably 1:1:1.5. Suitably, the ester compound may be the reaction product of reactants comprising a first reactant, one or more second reactants, and optionally a third reactant, wherein the first reactant is selected from nonenyl succinic anhydride, dodecenyl succinic anhydride, octadecenyl succinic anhydride, or pyromellitic dianhydride; the one or more second reactants are selected from N-methyl diethanolamine, N-butyl diethanolamine, castor oil, tris(2-hydroxyethyl)methyl ammonium methylsulfate, PEG 200, 1,6-hexanediol, or sorbitol; and the third reactant is oleyl alcohol. The molar ratio of the first reactant and the one or more second reactants is suitably from 1.2:1 to 1:1.2. The molar ratio of the first reactant and the one or more second reactants is preferably 1:1. When the third reactant is used, the molar ratio of the first, second and third reactants is suitably 1:1:1.5. Suitably, the ester compound may be the reaction product of reactants consisting essentially of or consisting of a first reactant, one or more second reactants, and optionally a third reactant, wherein the first reactant is selected from nonenyl succinic anhydride, dodecenyl succinic anhydride, octadecenyl succinic anhydride, or pyromellitic dianhydride; the one or more second reactants are selected from N-methyl diethanolamine, N-butyl diethanolamine, castor oil, tris(2-hydroxyethyl)methyl ammonium methylsulfate, PEG 200, 1,6-hexanediol, or sorbitol; and the third reactant is oleyl alcohol. The molar ratio of the first reactant and the one or more second reactants is suitably from 1.2:1 to 1:1.2. The molar ratio of the first reactant and the one or more second reactants is preferably 1:1. When the third reactant is used, the molar ratio of the first reactant, second and third reactants is suitably 1:1:1.5. Suitably, the ester compound may be the reaction product of reactants comprising a first reactant, one or more second reactants, and optionally a third reactant, wherein the first reactant is selected from dodecenyl succinic anhydride, octadecenyl succinic anhydride, or pyromellitic dianhydride; the one or more second reactants are selected from N-methyl diethanolamine, N-butyl diethanolamine, castor oil, tris(2-hydroxyethyl)methyl ammonium methylsulfate, PEG 200, 1,6-hexanediol, or sorbitol; and the third reactant is oleyl alcohol. The molar ratio of the first reactant and the one or more second reactants is suitably from 1.2:1 to 1:1.2. The molar ratio of the first reactant and the one or more second reactants is preferably 1:1. When the third reactant is used, the molar ratio of the first, second and third reactants is suitably 1:1:1.5. Suitably, the ester compound may be the reaction product of reactants consisting essentially of or consisting of a first reactant, one or more second reactants, and optionally a third reactant, wherein the first reactant is selected from dodecenyl succinic anhydride, octadecenyl succinic anhydride, or pyromellitic dianhydride; the one or more second reactants are selected from N-methyl diethanolamine, N-butyl diethanolamine, castor oil, tris(2-hydroxyethyl)methyl ammonium methylsulfate, PEG 200, 1,6-hexanediol, or sorbitol; and the third reactant is oleyl alcohol. The molar ratio of the first reactant and the one or more second reactants is suitably from 1.2:1 to 1:1.2. The molar ratio of the first reactant and the one or more second reactants is preferably 1:1. When the third reactant is used, the molar ratio of the first reactant, second and third reactants is suitably 1:1:1.5. Suitably, the ester compound may be the reaction product of reactants comprising, consisting essentially of, or consisting of a first reactant and one or more second reactants, wherein the first reactant is selected from maleic anhydride, nonenyl succinic anhydride, dodecenyl succinic anhydride, or phthalic anhydride; and the one or more second reactants are selected from N-methyl diethanolamine, N-butyl diethanolamine, castor oil, PEG 200, PPG 2000, or neopentyl glycol. The molar ratio of the first reactant and the one or more second reactants is suitably from 1.2:1 to 1:1.2. The molar ratio of the first reactant and the one or more second reactants is preferably 1:1. Preferably, the ester compound is the reaction product of reactants comprising: (i) dodecenyl succinic anhydride and N-methyl diethanolamine, preferably in a molar ratio of 1:1; (ii) dodecenyl succinic anhydride, castor oil, and tris(2-hydroxyethyl)methyl ammonium methylsulfate, preferably in a molar ratio of 1:0.6:0.4; (iii) dodecenyl succinic anhydride and N-butyl diethanolamine, preferably in a molar ratio of 1:1; (iv) octadecenyl succinic anhydride and N-butyl diethanolamine, preferably in a molar ratio of 1:1; (v) dodecenyl succinic anhydride, N-methyl diethanolamine, and castor oil, preferably in a molar ratio of 1:0.5:0.5; (vi) dodecenyl succinic anhydride and castor oil, preferably in a molar ratio of 1:1; (vii) dodecenyl succinic anhydride, N-butyl diethanolamine, and PEG 200, preferably in a molar ratio of 1:0.5:0.5; (viii) pyromellitic dianhydride, PEG 200 and oleyl alcohol, preferably in a molar ratio of 1:1:1.5; (ix) dodecenyl succinic anhydride, N-butyl diethanolamine, and 1,6-hexanediol, preferably in a molar ratio of 1:0.8:0.2; (x) octadecenyl succinic anhydride and N-methyl diethanolamine, preferably in a molar ratio of 1:1; (xi) dodecenyl succinic anhydride, sorbitol, and 1,6-hexanediol, preferably in a molar ratio of 1:0.2:0.8; or (xii) nonenyl succinic anhydride and PEG 200, preferably in a molar ratio of 1:1. Preferably, the ester compound is the reaction product of reactants consisting essentially of or consisting of: (i) dodecenyl succinic anhydride and N-methyl diethanolamine, preferably in a molar ratio of 1:1; (ii) dodecenyl succinic anhydride, castor oil, and tris(2-hydroxyethyl)methyl ammonium methylsulfate, preferably in a molar ratio of 1:0.6:0.4; (iii) dodecenyl succinic anhydride and N-butyl diethanolamine, preferably in a molar ratio of 1:1; (iv) octadecenyl succinic anhydride and N-butyl diethanolamine, preferably in a molar ratio of 1:1; (v) dodecenyl succinic anhydride, N-methyl diethanolamine, and castor oil, preferably in a molar ratio of 1:0.5:0.5; (vi) dodecenyl succinic anhydride and castor oil, preferably in a molar ratio of 1:1; (vii) dodecenyl succinic anhydride, N-butyl diethanolamine, and PEG 200, preferably in a molar ratio of 1:0.5:0.5; (viii) pyromellitic dianhydride, PEG 200 and oleyl alcohol, preferably in a molar ratio of 1:1:1.5; (ix) dodecenyl succinic anhydride, N-butyl diethanolamine, and 1,6-hexanediol, preferably in a molar ratio of 1:0.8:0.2; (x) octadecenyl succinic anhydride and N-methyl diethanolamine, preferably in a molar ratio of 1:1; (xi) dodecenyl succinic anhydride, sorbitol, and 1,6-hexanediol, preferably in a molar ratio of 1:0.2:0.8; or (xii) nonenyl succinic anhydride and PEG 200, preferably in a molar ratio of 1:1. Preferably, the ester compound is the reaction product of reactants comprising: (i) dodecenyl succinic anhydride and N-methyl diethanolamine, preferably in a molar ratio of 1:1; (ii) dodecenyl succinic anhydride, castor oil, and tris(2-hydroxyethyl)methyl ammonium methylsulfate, preferably in a molar ratio of 1:0.6:0.4; (iii) dodecenyl succinic anhydride and N-butyl diethanolamine, preferably in a molar ratio of 1:1; (iv) octadecenyl succinic anhydride and N-butyl diethanolamine, preferably in a molar ratio of 1:1; (v) dodecenyl succinic anhydride, N-methyl diethanolamine, and castor oil, preferably in a molar ratio of 1:0.5:0.5; (vi) dodecenyl succinic anhydride and castor oil, preferably in a molar ratio of 1:1; (vii) dodecenyl succinic anhydride, N-butyl diethanolamine, and PEG 200, preferably in a molar ratio of 1:0.5:0.5; (viii) pyromellitic dianhydride, PEG 200 and oleyl alcohol, preferably in a molar ratio of 1:1:1.5; (ix) dodecenyl succinic anhydride, N-butyl diethanolamine, and 1,6-hexanediol, preferably in a molar ratio of 1:0.8:0.2: (x) octadecenyl succinic anhydride and N-methyl diethanolamine, preferably in a molar ratio of 1:1; or (xi) dodecenyl succinic anhydride, sorbitol, and 1,6-hexanediol, preferably in a molar ratio of 1:0.2:0.8. Preferably, the ester compound is the reaction product of reactants consisting essentially of or consisting of: (i) dodecenyl succinic anhydride and N-methyl diethanolamine, preferably in a molar ratio of 1:1; (ii) dodecenyl succinic anhydride, castor oil, and tris(2-hydroxyethyl)methyl ammonium methylsulfate, preferably in a molar ratio of 1:0.6:0.4; (iii) dodecenyl succinic anhydride and N-butyl diethanolamine, preferably in a molar ratio of 1:1; (iv) octadecenyl succinic anhydride and N-butyl diethanolamine, preferably in a molar ratio of 1:1; (v) dodecenyl succinic anhydride, N-methyl diethanolamine, and castor oil, preferably in a molar ratio of 1:0.5:0.5; (vi) dodecenyl succinic anhydride and castor oil, preferably in a molar ratio of 1:1; (vii) dodecenyl succinic anhydride, N-butyl diethanolamine, and PEG 200, preferably in a molar ratio of 1:0.5:0.5; (viii) pyromellitic dianhydride, PEG 200 and oleyl alcohol, preferably in a molar ratio of 1:1:1.5; (ix) dodecenyl succinic anhydride, N-butyl diethanolamine, and 1,6-hexanediol, preferably in a molar ratio of 1:0.8:0.2; (x) octadecenyl succinic anhydride and N-methyl diethanolamine, preferably in a molar ratio of 1:1; or (xi) dodecenyl succinic anhydride, sorbitol, and 1,6-hexanediol, preferably in a molar ratio of 1:0.2:0.8. Preferably, the ester compound is the reaction product of reactants comprising: (i) dodecenyl succinic anhydride and N-methyl diethanolamine, preferably in a molar ratio of 1:1; (ii) dodecenyl succinic anhydride and N-butyl diethanolamine, preferably in a molar ratio of 1:1; (iii) dodecenyl succinic anhydride and castor oil, preferably in a molar ratio of 1:1; (iv) dodecenyl succinic anhydride, N-butyl diethanolamine, and PEG 200, preferably in a molar ratio of 1:0.5:0.5; (v) phthalic anhydride and PPG 2000, preferably in a molar ratio of 1:1; (vi) dodecenyl succinic anhydride, N-butyl diethanolamine, and neopentyl glycol, preferably in a molar ratio of 1:0.5:0.5; (vii) maleic anhydride and castor oil, preferably in a molar ratio of 1:1; (viii) dodecenyl succinic anhydride, N-butyl diethanolamine, and PPG 2000, preferably in a molar ratio of 1:0.5:0.5; (ix) nonenyl succinic anhydride and castor oil, preferably in a molar ratio of 1:1; (x) nonenyl succinic anhydride and PEG 200, preferably in a molar ratio of 1:1; or (xi) phthalic anhydride and PEG 200, preferably in a molar ratio of 1:1. Preferably, the ester compound is the reaction product of reactants consisting essentially of or consisting of: (i) dodecenyl succinic anhydride and N-methyl diethanolamine, preferably in a molar ratio of 1:1; (ii) dodecenyl succinic anhydride and N-butyl diethanolamine, preferably in a molar ratio of 1:1; (iii) dodecenyl succinic anhydride and castor oil, preferably in a molar ratio of 1:1; (iv) dodecenyl succinic anhydride, N-butyl diethanolamine, and PEG 200, preferably in a molar ratio of 1:0.5:0.5; (v) phthalic anhydride and PPG 2000, preferably in a molar ratio of 1:1; (vi) dodecenyl succinic anhydride, N-butyl diethanolamine, and neopentyl glycol, preferably in a molar ratio of 1:0.5:0.5; (vii) maleic anhydride and castor oil, preferably in a molar ratio of 1:1; (viii) dodecenyl succinic anhydride, N-butyl diethanolamine, and PPG 2000, preferably in a molar ratio of 1:0.5:0.5; (ix) nonenyl succinic anhydride and castor oil, preferably in a molar ratio of 1:1; (x) nonenyl succinic anhydride and PEG 200, preferably in a molar ratio of 1:1; or (xi) phthalic anhydride and PEG 200, preferably in a molar ratio of 1:1. Preferably, the ester compound is the reaction product of reactants comprising, or of reactants consisting essentially of or consisting of, dodecenyl succinic anhydride and castor oil, suitably in a molar ratio of from 1:1.2 to 1.2:1, preferably in a molar ratio of 1:1, and wherein the ester compound has a number average molecular weight of from 2,000 to 3,000 Daltons and / or a polydispersity index of from 1 to 4, such as from 1.1 to 2, preferably from 1.5 to 1.6. Preferably, the ester compound is the reaction product of reactants comprising, or of reactants consisting essentially of or consisting of, nonenyl succinic anhydride and PEG 200, suitably in a molar ratio of from 1:1.2 to 1.2:1, preferably in a molar ratio of 1:1. The ester compound may be a polymer. The reactants used to prepare the ester compound may be monomers. The first reactant may be a first monomer, the second reactant may be a second monomer, and the third reactant (when present) may be a third monomer. Thus, the ester compound may be a polymer comprising, consisting essentially of, or consisting of repeat units derived from the one or more first reactants, repeat units derived from the one or more second reactants, and optionally repeat units derived from one or more third reactants as defined herein. Typically, the polymer is a polyester. The polymer may be a random copolymer or a block copolymer, in particular when there is more than one first reactant or more than one second reactant. Preferably, the polymer is a random copolymer. The polymer formed from the first, second and optional third reactants may comprise a suitable number of total monomer units (i.e. repeat units). For example, the polymer may comprise at least 4 monomer units. In other words, the polymer may comprise a total of at least 4 monomer units including the first, second and optional third monomers. Suitably, the polymer may comprise from 4 to 50 monomer units, preferably from 4 to 30 monomer units. Suitably, the polymer herein that is the reaction product of monomers comprising one or more first monomers and one or more second monomers is substantially free or free of cross-linking. Suitably, the ester compound has a number average molecular weight of from 1,000 to 150,000 Daltons, preferably from 1,000 to 15,000 Daltons (for example from 2,000 to 7,000 or from 2,000 to 3,000 Daltons). Suitably, the ester compound has a polydispersity index of from 1 to 4, such as from 1.1 to 2, preferably from 1.5 to 1.6. The polydispersity index of an ester compound is given by the ratio of Mwto Mn (Mw / Mn), wherein Mw is the weight-average molecular weight and Mn is the number average molecular weight. Preferably, the ester compound is substantially free of silicon atoms. By substantially free of silicon atoms we mean that the ester compound contains less than 1 wt% of silicon in the ester compound, preferably less than 0.5 wt% of silicon in the ester compound. More preferably, the ester compound is free of silicon atoms, by which we mean that it is not possible to detect silicon in the ester compound. Suitable methods of measuring the amount of silicon in an ester compound are well known to those skilled in art and include elemental analysis and inductively coupled plasma (ICP) spectroscopy. Preferably, the ester compound is substantially free of fluorine atoms. The ester compound may be substantially free of halogen atoms. By substantially free of fluorine or halogen atoms we mean that the ester compound contains less than 1 wt% of fluorine or halogen in the ester compound, preferably less than 0.5 wt% of fluorine or halogen in the ester compound. More preferably, the ester compound is free of fluorine atoms. The ester compound may be free of halogen atoms. By free of fluorine or halogen atoms we mean that it is not possible to detect fluorine or halogen in the ester compound. Suitable methods of measuring the amount of fluorine or halogen in a compound are well known to those skilled in art and include elemental analysis and inductively coupled plasma (ICP) spectroscopy. Preferably, the ester compound is substantially free of quaternary ammonium moieties. By substantially free of quaternary ammonium moieties we mean that the ester compound contains less than 1 wt% of quaternary nitrogen atoms in the ester compound, preferably less than 0.5 wt% of quaternary nitrogen atoms in the ester compound. More preferably, the ester compound is free of quaternary ammonium moieties, by which we mean that it is not possible to detect quaternary ammonium moieties in the ester compound. The use of the ester compound according to the first aspect is to treat a surface to provide at least one effect (i.e. to the substrate) selected from (a) increased water repellency, (b) reduced friction, and (c) improved visual appearance. The method according to the second aspect treats a surface to provide at least one effect (i.e. to the substrate) selected from (a) increased water repellency, (b) reduced friction, and (c) improved visual appearance. The use of the first aspect and method of the second aspect is to treat a surface. The surface is any surface that is not a surface of a home care substrate. The surface may be a surface of any suitable substrate, provided that it is not a home care substrate. References herein to treating and contacting a surface are intended to refer to treating or contacting the entire surface or a portion thereof. References to herein to (a) increased water repellency, (b) reduced friction, and (c) improved visual appearance of a surface are intended to mean as compared to an otherwise identical surface that has not been treated with the ester compound or composition as disclosed herein. The use of the first aspect and the method of the second aspect treat a surface, wherein treating the surface provides at least one effect selected from: (a) increased water repellency, (b) reduced friction, and (c) improved visual appearance. Treating the surface may provide at least one effect selected from: (a) increased water repellency, and (b) reduced friction. Treating the surface may provide: (a) increased water repellency, and (b) reduced friction. Treating the surface may provide at least two effects selected from: (a) increased water repellency, (b) reduced friction, and (c) improved visual appearance. Treating the surface may provide: (a) increased water repellency, (b) reduced friction, and (c) improved visual appearance. Treating the surface may provide (a) increased water repellency, i.e. to the surface. A surface with increased water repellency may have decreased water wettability. Wettability can be determined by measuring the contact angle between a liquid droplet and a solid surface, and a decrease in wettability may be demonstrated by measuring a greater contact angle following treatment of the surface with the ester compound defined herein. Methods and equipment for the measurement of contact angle are well known to the skilled person. An example is ISO / TS 14778:2021 which is concerned with the measurement of contact angle on paper and board substrates. Water is less likely to adhere to water repellent surfaces, and water droplets may simply roll off the surface. In doing so, water droplets may carry undesirable particles, such as foulants, pollution, food waste, oils, dust or dirt away from the surface. Treating the surface may therefore provide an enhanced cleaning effect or self-cleaning effect, and / or increased resistance to undesirable particles such as foulants, pollution, food waste, oils, dust or dirt. Treating the surface may repel undesirable particles, such as foulants, pollution, food waste, oils, dust or dirt, and / or may prevent deep soiling. By repel undesirable particles we mean that treating the surface may reduce or prevent deposition of the undesirable particles on the surface. A surface with increased water repellency may dry more quickly. A surface with increased water repellency may substantially or completely prevent water from penetrating the surface, providing long-lasting protection against moisture, stains, and potential water damage. Methods and equipment for the measurement of water repellency are well known to the skilled person. An example is the test procedure TM22-2017e which may be used to measure the water repellency of a fabric. The water repellency of the surface of a substrate may be measured by weighing the substrate, immersing the substrate in water (for example, for 5 minutes), removing the substrate from the water and allowing excess water to drain off (for example, for 1 minute), then weighing the substrate again. The weight of the water in the substrate compared to the weight of the dry substrate (i.e. before immersion in water) corresponds to the water uptake of the substrate. A lower water uptake (i.e. relative to a control experiment in which the ester compound is absent) corresponds to increased water repellency. A surface with increased water repellency may be especially useful for applications where surfaces require cleaning. For example, it is advantageous to provide a surface with increased water repellency, such that the surface may be readily and / or more effectively cleaned. Treating the surface may provide (b) reduced friction, i.e. to the surface. By providing reduced friction we mean that the surface has an increased smoothness and / or a reduced resistive force or coefficient of friction when an object is slid over the surface. A surface with reduced friction may be useful for applications where surfaces move against one another. Thus, when the effect is to provide reduced friction, this may advantageously provide improved lubrication. Thus, the use of the first aspect and the method of the second aspect may provide improved lubrication of a surface thereof. The use of the first aspect may therefore provide the use of an ester compound as defined herein as a lubricant for a surface. The method of the second aspect may provide a method of lubricating a surface, the method comprising contacting the surface with an ester compound as defined herein. The use of the first aspect may be the use of the ester compound as defined herein as a lubricating agent. Friction between two surfaces may be determined by sliding the surfaces against one another and measuring the resistive force or coefficient of friction. The coefficient of friction of plastic films may be measured by the test procedure ASTM D1894. A surface with reduced friction may reduce the build up of static on the surface. Thus, treating the surface may provide (b) reduced friction and thereby provide an antistatic effect. A surface with an antistatic effect may advantageously reduce the buildup of dust and reduce electric discharges when the surface contacts another surface. Treating the surface may provide (c) improved visual appearance, i.e. to the surface. For example, improved visual appearance may provide increased shine. By “shine” we mean the perceived reflectiveness of a surface. As used herein, shine, gloss and reflectiveness are considered interchangeable. A surface with increased shine may be desirable from an aesthetic standpoint. Increased shine can also be a visual indicator of the surface having other properties provided by treatment with the ester compound as defined herein, such as increased water repellency and / or reduced friction. When the shine of the surface decreases, this can be used to prompt a user to retreat the surface with the ester compound. The gloss or shine of surfaces can be measured by reflectance methods, for example DIN 67530. A surface with improved visual appearance (such as increased shine) may be useful for applications where surfaces are required to look appealing visually. The use of the first aspect and the method of the second aspect suitably involve coating at least a portion of the surface with the ester compound as defined herein. The ester compound may be coated onto the surface by spreading, such as by a blade, brush, cloth or sponge. The ester compound may be applied onto the surface by spraying, for example from a pressurised can. The ester compound may be applied to the surface as a foam, for example by spraying the ester compound through a foam-forming nozzle. The use of the first aspect and the method of the second aspect may involve distributing the ester compound as defined herein in the substrate. When the substrate is a solid substrate, the solid substrate may be formed from a liquid precursor (such as a melt) into which the ester compound is admixed. Typically, the ester compound will migrate to the surface of the liquid precursor and thereby the surface of the solid substrate. For example, the ester compound may be admixed into an extruded product prior to extrusion. The use and method according to the first and second aspects may treat any suitable surface that is not a surface of a home care substrate and that would benefit from one or more of (a) increased water repellency, (b) reduced friction, and (c) improved visual appearance (especially (a) increased water repellency and (b) reduced friction). The surface is not a surface of a home care substrate. In other words, the surfaces that are referred to in this specification are non-home care surfaces. By a home care substrate we mean any substrate of the home or household contents. Home care substrate preferably includes a fabric or a hard surface. “Fabric” includes clothing, linens and other household textiles, such as upholstery, curtains, blinds etc. In the context of fabrics, the term “linen” is used to describe certain types of laundry items including bed sheets and bed covers, pillow cases, towels, tablecloths, table napkins, uniforms and the like, but also washable household items such as curtains and blinds, washable upholstery items such as cushion covers and the like. The term “ household textiles” can include woven fabrics, non-woven fabrics, and knitted fabrics and fabrics can include natural or synthetic fibres such as silk fibres, linen fibres, cotton fibres, polyester fibres, polyamide fibres such as nylon, rayon, acrylic fibres, acetate fibres, and blends thereof including cotton and polyester blends, fabrics which are elastic and / or contain elastane, and also viscose, modal and lyocell. “Hard surface” includes surfaces of dishes and other household surfaces. “Dishes” is meant generically and encompasses essentially any items which may be found in a dishwashing (manual or automatic machine) load, including crockery, chinaware, glassware, plasticware, siliconeware, silverware, hollowware and cutlery and any of these may comprise a hard surface; and “household surface” means any surface found in and around houses as in kitchens, bathrooms, e.g., floors, walls, tiles, windows, cupboards, sinks, showers, shower plastified curtains, wash basins, WCs, fixtures and fittings, and furniture. Hard surfaces may be made of different materials like ceramic, vinyl, no-wax vinyl, linoleum, melamine, glass, Inox®, Formica®, vitroceramic, any plastics, plastified wood, metal or any painted or varnished or sealed surface and the like; as well as household appliances including, but not limited to refrigerators, freezers, washing machines, automatic dryers, ovens, microwave ovens, dishwashers and so on. The surface is suitably an industrial surface. By industrial surface we mean any surface in an industrial setting and scale. The industrial surface may undergo a treatment as defined herein during an industrial process, such as an industrial process of the manufacturing industry, the packaging industry, construction industry, the automotive industry, the aviation industry, the agricultural industry, or the mining industry. An industrial process does not, for example, include a consumer-related activity. Thus, the industrial surface is found in an industrial setting not, for example, the home. The industrial surface may be a surface of an industrial product. By an industrial product we mean a product in an industrial setting and scale, which may undergo a treatment as defined herein during an industrial process. The industrial surface may be a surface of industrial equipment. By industrial equipment we mean equipment that is used in an industrial setting and scale, for example that is used in large scale manufacturing, storage, extraction, processing, treatment and / ortransportation. Examples of industrial equipment will be well known to persons skilled in the art and include machinery and engines (including components thereof). The industrial surface may treated by an industrial process in the manufacturing industry. For example, the industrial surface may be the surface of a product of the manufacturing industry or the surface of equipment used in the manufacturing industry. The industrial surface may be treated by an industrial process in the packaging industry. For example, the industrial surface may be the surface of a product of the packaging industry or the surface of equipment used in the packaging industry. The industrial surface may be treated by an industrial process in the construction industry. For example, the industrial surface may be the surface of a product of the construction industry or the surface of equipment used in the construction industry. The industrial surface may be treated by an industrial process in the automotive industry. For example, the industrial surface may be the surface of a product of the automotive industry or the surface of equipment used in the automotive industry. The industrial surface may be treated by an industrial process in the aviation industry. For example, the industrial surface may be the surface of a product of the aviation industry or the surface of equipment used in the aviation industry. The industrial surface may be treated by an industrial process in the agricultural industry. For example, the industrial surface may be the surface of a product of the agricultural industry or the surface of equipment used in the agricultural industry. The industrial surface may be treated by an industrial process in the mining industry. For example, the industrial surface may be the surface of a product of the mining industry or the surface of equipment used in the mining industry. The surface is suitably a solid surface. The solid surface may be a hard surface or a soft surface. The surface may be formed from any suitable material such as one or more materials selected from metal, glass, ceramic, glass-ceramic, stone, concrete, gypsum, stucco, plastic, rubber, wood, paper-based materials (such as paper or cardboard) and leather (including combinations thereof, such as a laminate for example). Examples of suitable surfaces include the surfaces of extruded products (such as pellets, granules, or films), moulds, non-household buildings (such as walls, windows, floors, or ceilings), paper-based packaging, construction materials (such as plasterboard, gypsum, stucco, or concrete), vehicles (such as windows, tyres, vehicle bodies, or vehicle interiors), plants (such as seeds), solid agrochemical compositions, and non-household fibrous substrates. The surface may be selected from the surface of an extruded product (such as a pellet, granule, or film), a mould, paper packaging, a construction material (such as plasterboard, gypsum, stucco, or concrete), a vehicle (such as a window, tyre, vehicle body, or vehicle interior), a plant (such as a seed), a solid agrochemical composition, ora non-household fibrous substrate. The surface may be selected from the surface of an extruded product (such as a pellet, granule, or film), a mould, paper packaging, a construction material (such as plasterboard, gypsum, stucco, or concrete), a plant (such as a seed), or a solid agrochemical composition. The use of the first aspect and the method of the second aspect may provide a surface of an extruded product or a precursor thereof with reduced friction. The extruded product or the precursor thereof may be treated with the ester compound defined herein during manufacture of the extruded product. By “precursor” of the extruded product, we mean the extruded product prior to extrusion. Suitably, the precursor of the extruded product is treated with the ester compound defined herein prior to extrusion of the precursor. The reduced friction of the surface of the precursor may facilitate the extrusion process, for example by providing better handling and better cleaning due to reduced residue on the extrusion equipment. The extruded product may be a pellet, a granule, or a film. The extruded product may be a plastic film. The plastic film may form part of, or be suitable for manufacturing, plastic bags or packaging. The surface of the plastic film may be treated with the ester compound defined herein during manufacture of the plastic film, and / or manufacture of plastic bags or packaging from the plastic film. By “manufacture of packaging” we mean to refer to the formation of the components of the packaging or the assembly of the packaging. The reduced friction of the surface of the plastic film reduces friction between the surface of the plastic film and other surfaces of the plastic film, between the surface of the plastic film and surfaces of other plastic films, and / or between the surface of the plastic film and manufacturing equipment. This may advantageously improve the movement of the plastic film through a manufacturing line (for example an extrusion line) or a packaging line, by causing the plastic film to slide more easily. The use of the first aspect may be the use of the ester compound as defined herein as a slip additive. The plastic film may comprise any suitable polymeric material, such as polyethylene or polypropylene. The polyethylene may be selected from very low density polyethylene, linear low density polyethylene, low density polyethylene, medium density polyethylene, high density polyethylene, or ultra-high molecular weight polyethylene. Preferably, the polymeric material is prepared from vinyl monomers, especially alpha olefins such as ethylene or propylene. The use of the first aspect and the method of the second aspect may provide a surface of a mould with reduced friction. The mould may be for the manufacture of moulded objects. An internal surface of the mould (preferably, a surface that will be in contact with a moulded object) is treated with the ester compound defined herein. The reduced friction of the surface of the mould may advantageously prevent sticking of a moulded object in the mould and facilitate removal of the moulded object from the mould. The use of the first aspect and the method of the second aspect may provide a surface of a nonhousehold building with increased water repellency, reduced friction, and / or improved visual appearance. By non-household building we mean a building that is not a home. Examples of suitable non-household buildings include commercial buildings (such as offices, shops, restaurants, and hotels), institutional buildings (such as schools and hospitals), and industrial buildings (such as factories and warehouses). The surface may be an exterior surface or an interior surface of the building. The surface of the building may be selected from a surface of a wall, a window, a floor, or a ceiling. The use of the first aspect and the method of the second aspect may provide a surface of a wall, floor, or ceiling of a non-household building with increased water repellency, reduced friction, and / or improved visual appearance. Increasing the water repellency and / or reducing the friction of the surface of the wall, floor, or ceiling may prevent dust or dirt from adhering to the surface, facilitate cleaning of the surface, and / or reduce the formation of streaks on the surface. When the wall, floor, or ceiling is painted, the colour intensity of wall, floor, or ceiling may be increased. When the wall, floor, or ceiling is treated with the ester compound as disclosed herein, paint may be more easily and / or evenly applied to the treated wall, floor or ceiling. The use of the first aspect and the method of the second aspect may provide a surface of a window of a non-household building with increased water repellency and / or reduced friction. Increasing the water repellency and / or reducing the friction of the surface of the window may prevent dust or dirt from adhering to the window, facilitate cleaning of the window, shorten drying times, reduce the formation of streaks on the window, provide the window with an anti-fingerprint effect, and / or provide the window with an antifogging effect. The use of the first aspect and the method of the second aspect may provide a surface of a paper-based material with increased water repellency. Examples suitable of paper-based materials include paper and cardboard. Paper-based materials are typically vulnerable to damage from exposure to water or moisture. Therefore, increasing the water repellency of a surface of a paper-based material may advantageously increase the lifetime of the underlying paper-based material. The surface of the paper-based material may be the surface of paperbased packaging (for example packaging comprising paper or cardboard). The use of the first aspect and the method of the second aspect may provide a surface of a construction material with increased water repellency. The construction material may be plasterboard, gypsum, stucco, or concrete. The construction material is preferably plasterboard, gypsum, or stucco, further preferably plasterboard or gypsum. Plasterboard is typically a panel of gypsum between two sheets of paper, and may be prepared by feeding a foamed slurry of stucco (calcined gypsum) and water between two sheets of paper. Both paper and gypsum are typically vulnerable to damage from exposure to water (including recycled water) or moisture. Therefore, increasing the water repellency of the paper sheets and / or the gypsum in plasterboard may increase the lifespan of the plasterboard and allow the use of recycled water. The ester compound as defined herein may be coated on a surface of plasterboard or gypsum. Alternatively, the ester compound may be admixed into a slurry of stucco and water as an additive during the production of plasterboard or gypsum. For example, the method of the second aspect may comprise admixing the ester compound into a slurry comprising water and stucco or gypsum. The method may further comprise drying the slurry to form gypsum. The ester compound may be present in the bulk of the gypsum and / or at the surface of the gypsum produced in this way. The ester compound is suitably present at the surface of the gypsum. The method may provide a construction material (and not just a surface thereof) with increased water repellency. The ester compound used to treat (for example, the surface of) the construction material (for example, by admixing into a slurry of water and stucco or gypsum) is preferably the reaction product of reactants comprising, consisting essentially of, or consisting of a first reactant and a second reactant, wherein the first reactant is a cyclic anhydride of formula (I) wherein least one of R1 and R2 is a Ca-24 alkenyl group; and the second reactant is selected from polyethylene glycol and polypropylene glycol. The molar ratio of the first reactant and the second reactant is suitably from 1.2:1 to 1:1.2. Preferably the molar ratio is 1:1. The use of the first aspect and the method of the second aspect may provide a surface of a vehicle with increased water repellency, reduced friction, and / or improved visual appearance. The surface may be an exterior surface or an interior surface of the vehicle. The vehicle may be selected from a road vehicle, a water vehicle, or an air vehicle. Preferably the vehicle is a road vehicle, such as a car. The surface of the vehicle may be selected from a surface of a window, a tyre, a vehicle body, or a vehicle interior. The use of the first aspect and the method of the second aspect may provide a surface of a vehicle window with increased water repellency and / or reduced friction. Increasing the water repellency and / or reducing the friction of the surface of the window may prevent dust or dirt from adhering to the window, facilitate cleaning of the window, shorten drying times, reduce the formation of streaks on the window, provide the window with an anti-fingerprint effect, and / or provide the window with an antifogging effect. The use of the first aspect and the method of the second aspect may provide a surface of a tyre with increased water repellency and / or improved visual appearance. The tyre is suitably the tyre of a road vehicle such as a car. Increasing the water repellency and / or shine of the surface of the tyre may improve the appearance of the tyre, increase the durability of the tyre, reduce build up of undesirable particles (such as dirt) on the tyre, and / or reduce degradation of other components of the vehicle, such as wear brakes. The use of the first aspect and the method of the second aspect may provide a surface of a vehicle body with increased water repellency, reduced friction, and / or improved visual appearance. The surface of the vehicle body is suitably an exterior surface of the vehicle body. The vehicle body suitably comprises coated metal. The vehicle body may be a car body. Increasing the water repellency and / or reducing the friction of the surface of the vehicle body may prevent dust or dirt from adhering to the body, facilitate cleaning of the body, shorten drying times, reduce the formation of streaks on the body, facilitate water sheeting and beading, and / or provide the body with rain resistance. The use of the first aspect and the method of the second aspect may provide a surface of a vehicle interior with increased water repellency, reduced friction, improved visual appearance, and / or an antistatic effect. The vehicle interior may be interior plastic trim or leather. Increasing the water repellency and / or reducing the friction of the surface of the vehicle interior may improve the dirt resistance and facilitate cleaning of the surface. Reducing the friction of a leather surface in the vehicle interior may increase the softness thereof. The use of the first aspect and the method of the second aspect may provide leather (or a surface thereof) with increased softness and / or flexibility. This may be the result of reduced friction. The use of the first aspect and the method of the second aspect may provide a surface of a seed with increased water repellency and / or reduced friction. By “seed” we mean a plant seed. Increasing the water repellency of the surface of a seed may increase the length of time the seed may be stored before planting. Reducing the friction of the surface of a seed may improve the flow characteristics of the seed during plantation, in particular when a plurality of such seeds are being planted. The ester compound used to treat the surface of the seed is preferably the reaction product of reactants comprising, consisting essentially of, or consisting of one or more first reactants and one or more second reactants, wherein the or each first reactant is a cyclic anhydride of formula (I) wherein least one of R1 and R2 is a Ce-30, such as a Cs-24, alkyl or alkenyl (more preferably alkenyl) group, or a cyclic anhydride of formula (II) wherein R3 and R4 are each independently selected from hydrogen, an alkyl group and an alkenyl group, or R3 and R4 together with the carbon atoms to which they are attached represent an optionally substituted cyclic group; and the or each second reactant is a polyol of formula (IVA): H-(OR18)q-OH (IVA) wherein each R18 is independently an unsubstituted alkylene group and q is an integer of at least 1, or a polyol of formula (V): NR20R21R22 (V) wherein R20 and R21 each represent a hydroxyalkyl group and R22 represents a hydrocarbyl group. The molar ratio of one or more first reactants and the one or more second reactants is suitably from 1.2:1 to 1:1.2. Preferably the molar ratio is 1:1. The use of the first aspect and the method of the second aspect may provide a surface of a solid agrochemical composition with increased water repellency. The solid agrochemical composition may be in the form of pellets or granules. The solid agrochemical composition may be applied to the surface of a crop, such as a leaf, stem or root. The solid agrochemical composition may be a pesticide composition. Increasing the water repellency the surface of the solid agrochemical composition may advantageously slow the release of active ingredients (such as pesticides) from the solid agrochemical composition into soil, allowing the agrochemical composition to be effective for a longer period of time. The ester compound used to treat the surface of a solid agrochemical composition is preferably the reaction product of reactants comprising, consisting essentially of, or consisting of one or more first reactants and one or more second reactants, wherein the or each first reactant is a cyclic anhydride of formula (I) wherein least one of R1 and R2 is a Ce-30, such as a Cs-24, alkyl or alkenyl (more preferably alkenyl) group, or a cyclic anhydride of formula (II) wherein R3 and R4 are each independently selected from hydrogen, an alkyl group and an alkenyl group, or R3 and R4 together with the carbon atoms to which they are attached represent an optionally substituted cyclic group; and the or each second reactant is a polyol of formula (IVA): H-(OR18)q-OH (IVA) wherein each R18 is independently an unsubstituted alkylene group and q is an integer of at least 1, or a polyol of formula (V): NR20R21R22 (V) wherein R20 and R21 each represent a hydroxyalkyl group and R22 represents a hydrocarbyl group. The molar ratio of one or more first reactants and the one or more second reactants is suitably from 1.2:1 to 1:1.2. Preferably the molar ratio is 1:1. The use of the first aspect and the method of the second aspect may provide a surface of a nonhousehold fibrous substrate with reduced friction. By non-household fibrous substrate we mean a fibrous substrate that is not in the home. In other words, the fibrous substrate is treated with an ester compound as defined herein outside of a household setting. The fibrous substrate is preferably treated with the ester compound in an industrial setting. Suitably, the fibrous substrate is a thread. The thread may be formed from a natural fibre, such as cotton, or a synthetic fibre, such as polyester. The thread may be a cotton, denim or polyester thread (preferably a cotton or denim thread). The use of the first aspect and the method of the second aspect may provide improved lubrication of the thread outside of a household setting, for example in textile manufacturing. The use of the first aspect may therefore provide the use of an ester compound as defined herein as a lubricant for a thread in textile manufacturing. Lubrication of threads in textile manufacturing may advantageously reduce damage to the threads and reduce wear and tear to industrial textile manufacturing equipment in contact with the threads. Suitably, the ester compound defined herein may be coated on a surface of the thread and / or on a surface of industrial textile manufacturing equipment in contact with the thread. The ester compound as used herein may be formulated as a component of a composition. In other words, the ester compound may be comprised in a composition. Thus, in the use or method of the first or second aspect, the ester compound may be comprised in a composition. Suitably, the ester compound may be comprised in a composition, wherein the composition additionally comprises at least one solvent and optionally one or more surfactants. In the use or method of the first or second aspect, the ester compound may be comprised in a composition, wherein the composition additionally comprises at least one solvent and one or more surfactants. The one or more surfactants may be selected from anionic surfactants, cationic surfactants, non-ionic surfactants, and amphoteric or zwitterionic surfactants. Preferably, the one or more surfactants may be independently selected from one or more of a fatty alkyl amphoacetate, an alkyl (poly)glycoside, an acyl glycinate, a sulfosuccinate, an amphodiacetate and a fatty alcohol ether carboxylate. The composition may comprise at least 0.1 wt%, at least 0.5 wt%, at least 1 wt%, at least 2 wt%, at least 5 wt%, or at least 10 wt% of the ester compound. The composition may comprise 80 wt% or less, such as 20 wt% or less, for example 10 wt% or less of the ester compound. The composition may comprise from 0.1 to 20 wt%, preferably from 0.1 to 10 wt%, for example from 0.5 to 5 wt% of the ester compound. The composition may comprise at least 20 wt%, such as at least 30 wt%, at least 40 wt%, at least 50 wt%, at least 60 wt%, at least 70 wt%, or at least 80 wt% of the ester compound. The composition may comprise 100 wt% or less, 99 wt% or less, such as 95 wt% or less, for example 90 wt% or less of the ester compound. The composition may comprise from 10 to 100 wt%, such as from 10 to 99 wt%, preferably from 20 to 95 wt%, for example from 50 to 90 wt% of the ester compound. References herein to the amount of ester compound in the composition are intended to refer to the total of the or each ester compound as defined herein that is included in the composition. According to a third aspect of the invention, there is provided a composition for treating a surface that is not a surface of a home care substrate, wherein treating the surface provides at least one effect selected from (a) increased water repellency, (b) reduced friction, and (c) improved visual appearance, and wherein the composition comprises one or more ester compounds, wherein the or each ester compound is the reaction product of reactants comprising one or more first reactants and one or more second reactants, wherein the or each first reactant is a cyclic anhydride and the or each second reactant is a polyol. The composition is suitable for treating a surface that is not a surface of a home care substrate to provide at least one effect selected from (a) increased water repellency, (b) reduced friction, and (c) improved visual appearance of the surface. The ester compound referred to in relation to the third aspect may comprise the reaction product of reactants comprising one or more first reactants, one or more second reactants and optionally one or more third reactants as defined herein. The ester compound referred to in relation to the third aspect may be the reaction product of reactants consisting of one or more first reactants, one or more second reactants and optionally one or more third reactants as defined herein. Features of the ester compound, and of the first and second reactants (and the third reactants when present), in relation to the third aspect of the invention are as set out herein in relation to the first and second aspects of the invention. The composition of the third aspect may comprise at least 0.1 wt%, at least 0.5 wt%, at least 1 wt%, at least 2 wt%, or at least 5 wt% of the one or more ester compounds. The composition may comprise 80 wt% or less, such as 20 wt% or less, for example 10 wt% or less of the one or more ester compounds. The composition may comprise from 0.1 to 20 wt%, preferably from 0.1 to 10 wt%, for example from 0.5 to 5 wt% of the one or more ester compounds. The composition of the third aspect may comprise at least 20 wt%, such as at least 30 wt%, at least 40 wt%, at least 50 wt%, at least 60 wt%, at least 70 wt%, or at least 80 wt% of one or more ester compounds. The composition of the third aspect may comprise 100 wt% or less, such as 99 wt% or less, such as 95 wt% or less, for example 90 wt% or less of the one or more ester compounds. The composition of the third aspect may comprise from 10 to 100 wt%, such as from 10 to 99 wt%, preferably from 20 to 95 wt%, for example from 50 to 90 wt% of the one or more ester compounds. The composition of the third aspect may comprise any suitable solvent, such as for example a polar solvent, such as a polar protic solvent. The solvent may be an aqueous solvent. Thus, the composition may be an aqueous composition. The term “aqueous solvent” herein is considered to mean water or mixtures of water and at least one water miscible solvent. Water miscible solvents may include alcohols and substantially water-miscible organic solvents. The solvent may be a non-aqueous solvent. The non-aqueous solvent suitably comprises an organic solvent, such as an alcohol. The non-aqueous solvent preferably does not comprise any surfactant. Suitable such alcohols for use in the solvent include monohydric alcohols, polyhydric alcohols, alkoxy alcohols and aryloxy alcohol. Suitable alcohols are monohydric alcohols, polyhydric alcohols and alkoxy alcohols. Preferred alcohols are miscible with water. Suitable simple monohydric alcohols include methanol, ethanol, isopropanol and butanol. The solvent may comprise a polyhydric alcohol or an alkoxyalcohol. Suitable alkoxy alcohols include diethylene glycol monobutyl ether, 3-methoxy-3-methyl-1-butanol and 2-butoxyethanol. Suitable aryloxy alcohols include 2-phenoxyethanol. Suitable polyhydric alcohols include glycerol, ethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol and 2-methylpentanediol. Suitable polyhydric alcohols include glycerol, ethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol and polypropylene glycol. Preferably, the non-aqueous solvent comprises a monohydric alcohol such as isopropanol. The composition of the third aspect may additionally comprise one or more surfactants (in particular when the solvent is an aqueous solvent). Any suitable surfactant(s) may be included, such as for example one or more surfactants selected from anionic surfactants, cationic surfactants, non-ionic surfactants, and amphoteric or zwitterionic surfactants. The composition may comprise an anionic surfactant. Suitable anionic surfactants may include sulfate surfactants (such as mono- or di-alkyl sulfates or alkyl ether sulfates), sulfonate surfactants, alkyl ether carboxylate surfactants, sarcosinate surfactants, phosphate surfactants, succinate surfactants, sulfosuccinate surfactants, sulfoacetate surfactants, isethionate surfactants, taurate surfactants, amino acid surfactants such as glutamates and glycinates, lactylate surfactants, and fatty acid salts. Particularly exemplary salts of the above, where applicable, are the sodium, potassium, ammonium, magnesium and triethanolamine salts. The composition may comprise a cationic surfactant. The cationic surfactant may be an ammonium salt such as an alkyl trimethyl ammonium salt, a dialkyl dimethyl ammonium salt, an alkyl-(N-hydroxyethyl)-dimethyl ammonium salt, or an alkyldimethylbenzylammonium salt (i.e. a benzalkonium salt). The salt may be a halide, hydroxide, sulfate, hydrogensulfate, phosphate, or carboxylate salt. The salt is suitably a halide salt, such as a fluoride, chloride, or bromide salt. The salt may be a carboxylate salt, such as formate or acetate salt. Preferably, the salt is chloride. The composition may comprise a non-ionic surfactant. Suitable non-ionic surfactants for use herein include alcohol alkoxylates (such as alcohol ethoxylates, alcohol propoxylates, and ethylene oxide / propylene oxide copolymer derived surfactants), aliphatic esters, aromatic esters, sugar esters (such as sorbitan esters), alkyl (poly)glycosides, fatty acid alkoxylates (such as fatty acid ethoxylates and fatty acid propoxylates), or polyethylene glycol esters (including partial esters), glycerol esters (including glycerol partial esters and glycerol triesters), fatty alcohols (such as cetearyl alcohol, lauryl alcohol, stearyl alcohol, behenyl alcohol), and alkanolamides. The composition may comprise an amphoteric or zwitterionic surfactant. The amphoteric or zwitterionic surfactant may be selected from betaines (such as alkyl betaines and alkylamidopropyl betaines), amphoacetates, diamphoacetates, and amine oxides (such as alkylamine oxides and alkylamidopropyl amine oxides). Suitable amphoteric or zwitterionic surfactants include lauryl betaine, cocamidopropyl betaine, sodium lauroamphoacetate, sodium cocoamphoacetate, disodium cocoamphodiacetate, lauramine oxide, C12-18 alkyldimethylamine oxide, myristamine oxide, and cocamidopropyl amine oxide. The one or more surfactants may be selected from a fatty alkyl amphoacetate (for example cocoyl amphoacetate, lauryl amphoacetate), an alkyl (poly)glycoside (for example lauryl glycoside), an acyl glycinate (for example cocoyl glycinate), a sulfosuccinate, an amphodiacetate and a fatty alcohol ether carboxylate (for example C8-12 alkyl ether (6-11 moles EO) carboxylate). The composition of the third aspect may comprise the one or more surfactants in an amount of from 1 to 100 wt%, suitably from 5 to 50 wt%, preferably from 10 to 25 wt% based on the total weight of the one or more ester compounds. The composition may comprise the one or more surfactants in an amount of from 0.1 to 99 wt%, suitably from 1 to 50 wt%, for example from 10 to 25 wt% or from 0.1 to 20 wt% based on the total weight of the composition. The composition referred to in relation to the first and second aspects of the invention may be a composition according to the third aspect of the invention. Suitably the composition of the third aspect is substantially free of silicon atoms. By substantially free of silicon atoms we mean that the composition contains less than 1 wt%, preferably less than 0.5 wt%, of silicon in the composition. More preferably, the composition is free of silicon atoms, by which we mean that it is not possible to detect silicon in the composition. Suitable methods of measuring the amount of silicon in a composition are well known to those skilled in art and include elemental analysis and inductively coupled plasma (ICP) spectroscopy. According to a fourth aspect of the invention, there is a provided a substrate that is not a home care substrate, wherein a surface of the substrate is treated with an ester compound, wherein the ester compound is the reaction product of reactants comprising one or more first reactants and one or more second reactants, wherein the or each first reactant is a cyclic anhydride and the or each second reactant is a polyol. The substrate that has been treated with the ester compound is suitably provided with at least one effect selected from (a) increased water repellency, (b) reduced friction, and (c) improved visual appearance of the surface, compared to a substrate that has not been treated with the ester compound. The ester compound referred to in relation to the fourth aspect may comprise the reaction product of reactants comprising one or more first reactants, one or more second reactants and optionally one or more third reactants as defined herein. The ester compound referred to in relation to the fourth aspect may be the reaction product of reactants consisting of one or more first reactants, one or more second reactants and optionally one or more third reactants as defined herein. Features of the substrate, the ester compound, and of the first and second reactants (and the third reactants when present), in relation to the fourth aspect of the invention are as set out herein in relation to the first and second aspects of the invention. The ester compound as used in the fourth aspect may be formulated as a component of a composition. In other words, the substrate of the fourth aspect may be treated with a composition comprising the ester compound. Suitably, the ester compound may be comprised in a composition, wherein the composition additionally comprises at least one solvent and optionally one or more surfactants. The composition referred to in relation to the fourth aspect of the invention may be a composition according to the third aspect of the invention. The substrate may be selected from a construction material or a seed. The substrate may be a construction material. The construction material may be plasterboard, gypsum, stucco, or concrete. Preferably, the construction material is gypsum or plasterboard, further preferably plasterboard. Plasterboard typically comprises a gypsum core disposed between two sheets of paper. The ester compound as defined herein may be present at a surface of the gypsum core and / or the sheets of paper. The ester compound may further be present within the gypsum core. This may be achieved by admixing the ester compound into a slurry of stucco and water as an additive during the production of the plasterboard. The ester compound with which (for example, the surface of) the construction material is treated (for example, by admixing into a slurry of water and stucco or gypsum) is preferably the reaction product of reactants comprising, consisting essentially of, or consisting of a first reactant and a second reactant, wherein the first reactant is a cyclic anhydride of formula (I) wherein least one of R1 and R2 is a Ca-24 alkenyl group; and the second reactant is selected from polyethylene glycol and polypropylene glycol. The molar ratio of the first reactant and the second reactant is suitably from 1.2:1 to 1:1.2. Preferably the molar ratio is 1:1. The substrate may be a seed. By “seed” we mean a plant seed. A surface of the seed is suitably treated with the ester compound as defined herein. Examples The invention will now be further described with reference to the following non-limiting examples. Example 1 - synthesis of polyol reactant from gluconolactone and amine Gluconolactone and an amine (1 eq) were combined in methanol (100 mL, for 70 mmol of gluconolactone) and heated at 65°C for 2 hours. The reaction mass was concentrated in vacuo to provide a polyol, which was used in subsequent reactions without further purification. In cases where a diamine was used (for example ethylenediamine or Jeffamine ED-600) the mole equivalents of diamine were reduced (0.5 eq). Example 2 - synthesis of polyol reactant from glycerol carbonate and amine Glycerol carbonate and an amine (1 eq) were combined and heated at 70°C for two hours. The reaction mass was cooled to provide a polyol, which was used in subsequent reactions without further purification. In cases where a diamine was used (for example ethylenediamine or Jeffamine ED-600) the mole equivalents of diamine were reduced (0.5 eq). Example 3 - general method for synthesis of ester compounds The cyclic anhydride reactant(s) were combined with the polyol(s) and optional further third reactants. Tin(ll) ethylhexanoate (0.5 wt% relative to the total weight of reactants) was added. The reaction mass was heated at 160°C for 6 hours. The resulting ester compound was 5 decanted from the reaction flask, and no further purification was carried out. Ester compounds 1 to 76 were prepared according to Example 3, using the reactants and reaction stoichiometries as set out in Table 1. Tablei Ester compound Cyclic anhydride 1 Cyclic anhydride 2 (when present) Polyol 1 Polyol 2 (when present) Further reactant (when present) Molar ratio of reactants 1 Dodecenyl succinic anhydride N-methyl diethanolamine 1:1 2 Dodecenyl succinic anhydride Castor oil Tris(2-hydroxy ethyl)methyl ammonium methylsulfate 1:0.6:0.4 3 Dodecenyl succinic anhydride N-butyl diethanolamine 1:1 4 Octadecenyl succinic anhydride N-butyl diethanolamine 1:1 5 Dodecenyl succinic anhydride N-Methyl diethanolamine Castor oil 1:0.5:0.5 6 Dodecenyl succinic anhydride Castor oil 1:1 7 Dodecenyl succinic anhydride N-butyl diethanolamine PEG 200 1:0.5:0.5 8 Pyromellitic dianhydride PEG 200 Oleyl alcohol 1:1:1.5 9 Dodecenyl succinic anhydride N-butyl diethanolamine 1,6-Hexanediol 1:0.8:0.2 10 Octadecenyl succinic anhydride N-methyl diethanolamine 1:1 11 Dodecenyl succinic anhydride Sorbitol 1,6-Hexanediol 1:0.2:0.8 12 Dodecenyl succinic anhydride 1,12-Dodecanediol 1:1 13 Phthalic anhydride PPG 2000 1:1 14 Dodecenyl succinic anhydride N-butyl diethanolamine 1,6-Hexanediol 1:0.5:0.5 15 Dodecenyl succinic anhydride N-butyl diethanolamine PEG 400 1:0.5:0.5 16 Dodecenyl succinic anhydride N-butyl diethanolamine Neopentyl glycol 1:0.5:0.5 17 Maleic anhydride Castor oil 1:1 18 Dodecenyl succinic anhydride N-butyl diethanolamine PPG 2000 1:0.5:0.5 19 Dodecenyl succinic anhydride Trimethylol propane 1:1 20 C20-24ASA PEG 6000 1:1 21 Dodecenyl succinic anhydride N-butyl diethanolamine PEG 1000 1:0.5:0.5 22 C20-24ASA PEG 1000 Citric acid 1:0.9:0.1 23 Dodecenyl succinic anhydride N-butyl diethanolamine Diglycolic acid 1:0.5:0.5 24 Succinic anhydride Sucrose 1:0.5 25 Pyromellitic dianhydride PEG 200 Oleyl alcohol 1:1:2 26 Dodecenyl succinic anhydride N-butyl diethanolamine PPG 1000 1:0.5:0.5 27 Octenyl succinic anhydride Castor oil 1:1 28 Nonenyl succinic anhydride 1,6-Hexanediol 1:1 29 Dodecenyl succinic anhydride N-butyl diethanolamine Oleyl alcohol 1:0.9:0.1 30 Dodecenyl succinic anhydride N-butyl diethanolamine PEG 600 1:0.5:0.5 31 C20-24ASA PEG 1000 1:1 32 Dodecenyl succinic anhydride Trimethylol propane Erucic acid 1:1:1 33 Nonenyl succinic anhydride Castor oil 1:1 34 C20-24ASA Reaction product of gluconolactone and dodecylamine, prepared according to Ex 1 1:1 35 Dodecenyl succinic anhydride N-butyl diethanolamine PPG 2000 1:0.9:0.1 36 C20-24ASA PEG 1500 1:1 37 Pyromellitic dianhydride PEG 1000 Oleyl alcohol 1:1:1 38 Octadecenyl succinic anhydride 2,4,7,9- Tetramethyl-5-decyne-4,7-diol ethoxylate 1:1 39 Phthalic anhydride Trimethylol propane Erucic acid 1:1:1 40 Nonenyl succinic anhydride Neopentyl glycol 1:1 41 C20-24ASA Succinic anhydride Neopentyl glycol 0.25:0.75:1 42 C20-24ASA 2,4,7,9-Tetramethyl-5-decyne-4,7-diol ethoxylate 1:1 43 Dodecenyl succinic anhydride N-butyl diethanolamine 1,2-Propanediol 1:0.5:0.5 44 Pyromellitic dianhydride PEG 300 Oleyl alcohol 1:1:1.5 45 Dodecenyl succinic anhydride N-butyl diethanolamine Jeffamine M-1000 1:0.9:0.1 46 Dodecenyl succinic anhydride N-butyl diethanolamine Duomeen CD 1:0.9:0.1 47 Nonenyl succinic anhydride PEG 6000 1:1 48 C20-24ASA PEG 1000 Citric acid 0.5:1:0.5 49 Nonenyl succinic anhydride PEG 200 1:1 50 Pyromellitic dianhydride PPG 425 Oleyl alcohol 1:1:1.5 51 Nonenyl succinic anhydride 1,12- Dodecanediol 1:1 52 Dodecenyl succinic anhydride Xylitol 1,6-Hexanediol 1:0.25:0.75 53 Dodecenyl succinic anhydride N-butyl diethanolamine PPG 425 1:0.5:0.5 54 1,2-Cyclohexane-dicarboxylic anhydride PPG 2000 1:1 55 Octadecenyl succinic anhydride Neopentyl glycol 1:1 56 Dodecenyl succinic anhydride N-butyl diethanolamine 3-Dimethyl-amino propyl-amine 1:0.9:0.1 57 C20-24ASA PPG 425 1:1 58 Phthalic anhydride PEG 200 1:1 59 Dodecenyl succinic anhydride Castor oil PEG 200 1:0.75:0.25 60 Dodecenyl succinic anhydride N-butyl diethanolamine Trimethylolpropane 1:0.9:0.1 61 Dodecenyl succinic anhydride N-butyl diethanolamine Oleic acid 0.9:1:0.1 62 Dodecenyl succinic anhydride N-butyl diethanolamine Castor oil 1:0.9:0.1 63 Pyromellitic dianhydride PPG 425 Oleyl alcohol 1:1:2 64 Dodecenyl succinic anhydride N-butyl diethanolamine 2-Ethyl-1,3-hexanediol 1:0.5:0.5 65 Dodecenyl succinic anhydride PPG 2000 1:1 66 Dodecenyl succinic anhydride N-butyl diethanolamine PEG 600 1:0.2:0.8 67 Nonenyl succinic anhydride Trimethylol propane Erucic acid 1:1:1 68 Dodecenyl succinic anhydride Succinic anhydride Neopentyl glycol 0.1:0.9:1 69 C20-24ASA Reaction product of glycerol carbonate and Jeffamine M-1000, prepared according to Ex 2 1:1 70 C20-24ASA 1,12- Dodecanediol 1:1 71 Phthalic anhydride N-methyl diethanolamine 1:1 72 Octadecenyl succinic anhydride Diethanolamine 1:1 73 Pyromellitic dianhydride PEG 400 Oleyl alcohol 1:1:1.5 74 C20-24ASA Succinic anhydride Tris(2-hydroxy ethyl)methyl ammonium methylsulfate 0.25:0.75:1 75 C20-24ASA Trimethylol propane Erucic acid 1:1:1 76 Dodecenyl succinic anhydride Tris(2-hydroxy ethyl)methyl ammonium methylsulfate 1:1 Table 2 - abbreviations and chemical names PEG Poly(ethylene glycol) PPG Poly(propylene glycol) Duomeen CD N-cocoyl propylene diamine, commercially available from Nouryon Specialty Chemicals (Amsterdam, Netherlands) Jeffamine M-1000 Polyether monoamine comprising ethylene oxide and propylene oxide derived repeat units and having Mn ~ 1,000. Commercially available from Huntsman Corporation (Texas, United States) C20-24 ASA Commercially available alkenyl succinic anhydride including a mixture of C20 to C24 alkenyl groups Example 4 - Preparation of gypsum cubes A series of gypsum slurry compositions were prepared by admixing 438.25 grams of commercial gypsum for plaster, 318.95 grams of water, and 21.91 grams of an ester compound as shown in Table 3. Each slurry composition was poured into separate cube moulds, which were then left at room temperature to solidify. The gypsum cubes were demoulded on the next day and kept at 60°C overnight to dry. Each composition was sufficient to provide three moulded gypsum cubes. Table 3 Composition Ester compound 1 Ester compound 49 A blank composition was prepared by following the process of Example 4, but without any ester compound. Example 5 - Performance test Each of the gypsum cubes prepared in Example 4 were weighed and then immersed in water for 5 minutes. The gypsum cubes were removed from the water and were suspended in air for 1 minute to let excess water drip. Each cube was then weighed, and the water uptake (%) was calculated using the following formula : (weight after immersion) — (weight before immersion) Water uptake (%) =----------------—■— ----------------------- weight before immersion Table 4 shows the average results from three repetitions (cubes) for each composition. Table 4 Composition Water uptake (%) Difference compared to blank (%) Blank 37 N / A 1 14 -23 Composition 1 has a water uptake that is lower than that of the blank, demonstrating the hydrophobic effect imparted to the gypsum composition when the ester compound is used. Example 6 - Coefficient of friction test The dynamic coefficient of friction (COF dn) measures the resistance to movement between two surfaces. It is the force needed to maintain the movement after it has begun. Dynamic coefficient of friction (COF dn) was measured for three different substrates (cotton, denim and polyester) using a COF-21 Friction and Peel Tester (Regmed, Brazil) with the following parameters: Test Unit: N Sled mass: 200.0 g Test Speed: 150.0 Dynamic distance: 130mm Statistic: yes Chart Scale: 2.5 N The ester compounds were dissolved in ethanol at a concentration of 20 wt%. 5 mL of each ethanol solution was applied to the fibrous substrate using a hand roller. The substrates were allowed to dry overnight at ambient temperature before measuring COF dn. The measurements were compared to control samples where the fibrous substrate had not been treated with the ester compound, and the percentage change in COF dn was calculated. The results are shown in Table 5. A negative percentage value indicates a reduction in COF dn due to the presence of the ester compound on the fibrous substrate. Table 5 Ester compound Change in COF dn compared to control (%) Cotton Denim Polyester 6 -27 -14 -10 Example 7 - Seed flow test Seed treatment slurry A was prepared having the following composition: Seed Treatment slurry A Component Amount (wt%) Comment Pesticide 0 Pigment 12.5 Pigment was Red 48:2 (35 wt% dispersion in water) Coating 37.5 Carnauba wax-based emulsion Ester compound 2.5 Water to 100 Commercial corn seeds (Viking 99-00 hybrid, 100 g) were mixed with seed treatment slurry A (1 mL) and stood at ambient temperature and relative humidity (RH) 50 % for 5 minutes. The treated seeds were transferred to a stainless steel funnel with an opening of 30 mm diameter and a stoppered outlet. The stopper was removed and the time taken for the funnel contents to empty was recorded. The control for each test was a seed treatment slurry equivalent to A but without the ester compound. Where the time taken for the funnel to empty was lower when using the additized seed treatment slurry, compared to the control, this was considered to be a “pass”. In other words, the ester compound was providing a lubricating effect to the treated seeds and enabling faster flow. The results are shown in Table 6 below. Table 6 Ester compound Performance in seed flow test 7 Pass 13 Pass 17 Pass 58 Pass Example 8 - Simulated Rain Fastness Test This test simulates the interaction of a rain droplet with a substrate (e.g. a leaf) that has been coated with a pesticide formulation. A precleaned glass slide was treated with a drop of solution A (~ 0.3 mL) dispensed using a disposable pipette, to form a wet film on the slide. Solution A contained the following components : Component Amount (wt%) Comment Polyvinylpyrrolidone) 20 Agrimer 90 (MW 1,000,000 - 1,700,000 a product of Ashland Inc, Delaware, US) Rhodamine 6B dye 0.1 Ester compound 10 Water to 100 The slide was oven dried overnight (54 °C) and allowed to cool to ambient temperature. The dried PVP film was further secured to the glass slide using 3M Scotch Magic™ tape but leaving a square central region of the dried PVP film exposed. A droplet of deionized water (3 pL) was added to exposed area of the dried PVP film. After standing for 90 seconds, excess water was removed by gently dabbing with a laboratory wipe. The exposed area was visually inspected to determine the extent of dissolution or disintegration of the PVP film. The control sample for the experiment was Solution A without the ester compound. The ester compounds under test were considered to “pass” when the extent of dissolution or disintegration of the PVP film formed using Solution A (containing the ester compound) was less than when using the control sample without ester compound. The results are shown in Table 7 below. Table 7 Ester compound Performance in Simulated Rain Fastness Test 1 Pass 3 Pass 6 Pass 7 Pass 17 Pass 33 Pass 58 Pass Example 9 - Preparation of substrates and compositions for use in evaluation of improvement of shine, friction reduction and water repellency (Examples 10 to 12) Prior to treatment with ester compounds and evaluation of the resulting properties (reduced friction, water repellency, improved visual appearance) the substrates used in the experiments were prepared as shown in Table 8. Table 8 Substrate Preparation method Exterior car panel (painted metal) UV - ozone cleaning, 10 minutes Interior car panel (plastic) Cotton calico Used as obtained Denim Boiled wool Black card (smooth, 250GSM) Leather The ester compounds were deposited on the test substrates as composition types as shown in Table 9. Table 9 Composition type Description X Emulsion containing ester compound (1wt%), sodium lauroamphoacetate (0.2wt%)*, ethanol (5wt%)** and water to 100wt% Y Solution of ester compound (1wt%) in ethanol * of a 25 wt% aqueous solution ** ethanol was only added if the ester compound was not miscible in a solution of sodium lauroamphoacetate (0.2 wt%) in water The prepared substrates and composition types were used in Examples 10 to 12. Example 10 - Shine improvement test Shine improvement was determined by spraying a 1 wt% active solution of the ester compound (composition type X) onto the substrate (leather) and visually observing the surface of the substrate after drying. The visual observation was compared to the untreated substrate. A “pass” result indicates that a visual improvement in shine was observed for the ester compound -treated substrate. The results are shown in Table 10. Table 10 Substrate Ester compound Result Leather 6 Pass Leather 16 Pass Example 11 - Friction reduction test Substrates, which were initially prepared according to Table 8 prior to treatment, were treated by applying a liquid composition containing 1wt% of the ester compound. For denim substrates, these were treated by soaking for 1 hour (composition type X). Excess liquid was removed. The substrates were dried (60°C) then cooled to ambient temperature before running the friction test. For the friction test, a weighted block (250g) having baize fabric attached to its surface was then rubbed across the treated substrate. The results were observed relative to an untreated substrate. Each test was repeated twice, with two different (independent) operators. A “pass” result indicates that both operators recorded lower friction for the treated substrate, compared to the untreated substrate. The results are shown in Table 11. Table 11 Substrate Ester compound Result Denim 18 Pass Example 12 - Water repellency test Substrates, which were initially prepared according to Table 8 prior to treatment, were treated by applying a liquid composition of type X or Y. For exterior car panel (painted metal) and interior car panel (plastic rim) substrates a 1wt% solution of the ester compound was sprayed onto the surface (composition type X) and the surface was buffed using a Car Buffer Polisher with a microfibre cloth attachment before carrying out the droplet test. For cotton and boiled wool substrates, these were treated by soaking for 1 hour (composition type X). Excess liquid was removed. The substrates were dried (60°C) then cooled to ambient temperature before carrying out the droplet test. For black card, this was sprayed with the ester compound composition (composition type Y) and left to dry at ambient temperature before carrying out the droplet test. For the droplet test, after drying, the initial shape and absorption time of a de-ionized water droplet dropped on the treated surface was visually inspected. The results were observed relative to a substrate treated with an identical composition other than the ester compound being absent. A “pass” result indicates that the water droplet did not absorb into the substrate or was absorbed at a much lower speed than the comparative tests. For non absorbent substrates the spreading behaviour of the water droplet was visually compared to that on an identically treated surface, other than the ester compound being absent. A “pass” result indicated less droplet spreading on the ester compound treated surface relative to the comparative tests. Other substrate types were treated as already described above in Examples 10 and 11. The results are shown in Table 12. Table 12 Substrate Ester compound Result Exterior Car Panel (painted metal) 49 Pass Exterior Car Panel (painted metal) 33 Pass Interior Car Panel (Plastic) 49 Pass Interior Car Panel (Plastic) 33 Pass Cotton calico 33 Pass Boiled wool 33 Pass Black Card 49 Pass Black Card 33 Pass Unless otherwise stated herein, the reference to “liquid”, “gel” and “solid” refer to a state at 25 °C and standard pressure (101,325 Pa). Attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference. All of the features disclosed in this specification (including any accompanying claims, and 5 drawings), and / or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and / or steps are mutually exclusive. Each feature disclosed in this specification (including any accompanying claims, and drawings) 10 may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features. The invention is not restricted to the details of the foregoing embodiment(s). The invention 15 extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

1. A use of an ester compound to treat a surface, wherein the surface is not a surface of a home care substrate and wherein treating the surface provides at least one effect selected from (a) increased water repellency, (b) reduced friction, and (c) improved visual appearance; and wherein the ester compound is the reaction product of reactants comprising one or more first reactants and one or more second reactants, wherein the or each first reactant is a cyclic anhydride and the or each second reactant is a polyol.

2. A method of treating a surface, wherein the surface is not a surface of a home care substrate and wherein treating the surface provides at least one effect selected from (a) increased water repellency, (b) reduced friction, and (c) improved visual appearance, the method comprising contacting the surface with an ester compound, wherein the ester compound is the reaction product of reactants comprising one or more first reactants and one or more second reactants, wherein the or each first reactant is a cyclic anhydride and the or each second reactant is a polyol.

3. The use or method according to claim 1 or 2, wherein the ester compound is a polymer.

4. The use or method according to claim 3, wherein the polymer comprises at least 4monomer units.

5. The use or method according to any preceding claim, wherein the or each cyclic anhydride is one or more of an anhydride of formula (I), of formula (II) or of formula (III):wherein in formula (I) R1 and R2 are each independently selected from hydrogen, an alkyl group and an alkenyl group, or R1 and R2 together with the carbon atoms to which they are attached represent an optionally substituted cyclic group;in formula (II) R3 and R4 are each independently selected from hydrogen, an alkyl group and an alkenyl group, or R3 and R4 together with the carbon atoms to which they are attached represent an optionally substituted cyclic group; andin formula (III) X is CR9R10, O, S, or NR11; R5, R6, R7, R8, R9, R10, and R11 are each independently selected from hydrogen, an alkyl group and an alkenyl group, and / or any of R5, R6, R7, R8, R9, R10, and R11 together with the atoms to which they are attached represent an optionally substituted cyclic group.

6. The use or method according to claim 5, wherein the or each first reactant is a cyclic anhydride selected from one or more of succinic anhydride, maleic anhydride, glutaric anhydride, a Ce-30 alkenyl succinic anhydride such as C20-24 alkenyl succinic anhydride, dodecenyl succinic anhydride (such as (2-dodecen-1-yl)succinic anhydride), nonenyl succinic anhydride, octadecenyl succinic anhydride, octenyl succinic anhydride, octadecyl succinic anhydride, or octyl succinic anhydride, a branched alkenyl succinic anhydride such as tetrapropenyl succinic anhydride or polyisobutenyl succinic anhydride, phthalic anhydride, pyromellitic dianhydride, 1,2,4-benzenetricarboxylic anhydride, 1,2-cyclohexanedicarboxylic anhydride, 1,2-naphthalic anhydride, 2,3-naphthalic anhydride, 1,8-naphthalic anhydride and homophthalic anhydride..

7. The use or method according to claim 5 or 6, wherein the or each first reactant is a cyclic anhydride selected from one or more of succinic anhydride, maleic anhydride, C20-24 alkenyl succinic anhydride, dodecenyl succinic anhydride (such as (2-dodecen-1-yl)succinic anhydride), nonenyl succinic anhydride, octadecenyl succinic anhydride, octenyl succinic anhydride, phthalic anhydride, pyromellitic dianhydride, 1,2,4-benzenetricarboxylic anhydride, 1,2-cyclohexanedicarboxylic anhydride and 1,8-naphthalic anhydride..

8. The use or method according to any preceding claim, wherein the or each second reactant is a polyol having from 2 to 10, preferably from 2 to 6, more preferably 2 or 3, hydroxy groups.

9. The use or method according to claim 8, wherein the or each polyol is selected from one or more polyol of the formula (IV), one or more of an alkoxylated polyol of formula (IV), one or more nitrogen containing polyol, and one or more polyol formed by reaction of a hydroxy substituted cyclic ester or cyclic carbonate with a suitable primary or secondary amine compound, wherein the polyol of formula (IV) is of the formula H-(OR17)P-OH, wherein each R17 is independently an optionally substituted hydrocarbylene group and p is an integer of at least 1.

10. The use or method according to claim 8 or 9, wherein the or each second reactant is a polyol independently selected from castor oil, 1,6-hexanediol, sorbitol, neopentyl glycol and a polyalkylene glycol (such as PEG 200).

11. The use or method according to any of claims 1 to 5, 8, or 9, wherein the ester compound is the reaction product of reactants comprising one or more first reactants and one or more second reactants, wherein the or each first reactant is a cyclic anhydride of formula (I)wherein least one of R1 and R2 is a Ce-30, such as a Cs-24, alkyl or alkenyl (more preferably alkenyl) group, or a cyclic anhydride of formula (II) wherein R3 and R4 together with the carbon atoms to which they are attached represent an optionally substituted cyclic group; and the or each second reactant is a polyol of formula (IVA):H-(OR18)q-OH (IVA)wherein each R18 is independently an unsubstituted alkylene group and q is an integer of at least 1.

12. The use or method according to any preceding claim, wherein the ester compound has a number average molecular weight of from 1,000 to 150,000 Daltons, preferably from 1,000 to 15,000 Daltons (for example from 2,000 to 7,000 Daltons).

13. The use or method according to any preceding claim, wherein the ester compound is substantially free of silicon atoms.

14. The use or method according to any preceding claim, wherein the surface is an industrialsurface.

15. The use or method according to claim 14, wherein the industrial surface is a surface that is found in the manufacturing industry, the packaging industry, construction industry, the automotive industry, the aviation industry, the agricultural industry, or the mining industry.

16. The use or methodaccording to claim 15, wherein theindustrial surfaceis foundin themanufacturing industry.

17. The use or methodaccording to claim 15, wherein theindustrial surfaceis foundin thepackaging industry.

18. The use or methodaccording to claim 15, wherein theindustrial surfaceis foundin theconstruction industry.

19. The use or methodaccording to claim 15, wherein theindustrial surfaceis foundin theautomotive industry.

20. The use or methodaccording to claim 15, wherein theindustrial surfaceis foundin theaviation industry.

21. The use or methodaccording to claim 15, wherein theindustrial surfaceis foundin theagricultural industry.

22. The use or methodaccording to claim 15, wherein theindustrial surfaceis foundin themining industry.

23. The use or method according to any preceding claim, wherein surface is selected from the surface of an extruded product (such as a pellet, granule, or film), a mould, paper packaging, a construction material (such as plasterboard, gypsum, stucco, or concrete), a vehicle (such as a window, tyre, vehicle body, or vehicle interior), a plant (such as a seed), a solid agrochemical composition, ora non-household fibrous substrate.

24. The use or method according to any preceding claim, which provides a surface of plasterboard, gypsum or stucco with increased water repellency.

25. The use or method according to any preceding claim, wherein the ester compound is comprised in a composition, wherein the composition additionally comprises at least one solvent and optionally one or more surfactants.

26. The use or method according to claim 25, wherein the composition comprises one or more surfactants selected from anionic surfactants, cationic surfactants, non-ionic surfactants, and amphoteric or zwitterionic surfactants.

27. The use or method according to claim 26, wherein the one or more surfactants are independently selected from one or more of a fatty alkyl amphoacetate, an alkyl (poly)glycoside, an acyl glycinate, a sulfosuccinate, an amphodiacetate and a fatty alcohol ether carboxylate.

28. The use or method according to any of claims 25 to 27, wherein the composition comprises from 0.1 to 20 wt%, preferably from 0.1 to 10 wt%, for example from 0.5 to 5 wt% of the ester compound.

29. A composition fortreating a surface that is not a surface of a home care substrate, wherein treating the surface provides at least one effect selected from (a) increased water repellency, (b) reduced friction, and (c) improved visual appearance, and wherein the composition comprises one or more ester compounds, wherein the or each ester compound is the reaction product of reactants comprising one or more first reactants and one or more second reactants, wherein the or each first reactant is a cyclic anhydride and the or each second reactant is a polyol.

30. The composition according to claim 29, wherein the composition comprises at least 0.1 wt%, such as from 0.1 to 20 wt%, preferably from 0.1 to 10 wt%, for example from 0.5 to 5 wt% of the one or more ester compounds.

31. The composition according to claim 29 or 30, wherein the composition additionally comprises one or more surfactants.

32. The composition according to claim 31, wherein the one or more surfactants are independently selected from anionic surfactants, cationic surfactants, non-ionic surfactants, and amphoteric or zwitterionic surfactants.

33. The composition according to claim 32, wherein the one or more surfactants are independently selected from one or more of a fatty alkyl amphoacetate, an alkyl (poly)glycoside, an acyl glycinate, a sulfosuccinate, an amphodiacetate and a fatty alcohol ether carboxylate.

34. A substrate that is not a home care substrate, wherein a surface of the substrate is treated with an ester compound, wherein the ester compound is the reaction product of reactants comprising one or more first reactants and one or more second reactants, wherein the or each first reactant is a cyclic anhydride and the or each second reactant is a polyol.A