GB2635160A - Phenalkamine curing agents - Google Patents

Abstract

Disclosed is a compound of formula (1), wherein: x is 1-4; n is 1-3; y is 0-3; x + n must be equal to 2-5; R1-R5 are disclosed herein; L is a bond or a hydrocarbyl linker comprising 2-100 carbon atoms and 1-10 amine groups; R5 and L may form a heterocyclic ring; R4 and R5 may form a heterocyclic ring; and the compound must comprise at least one amine group. Preferable compounds are of formulae (1a), (1b), (1c), or (1d). Further disclosed is a method of preparing a Mannich base, comprising the combination of: a phenolic compound; a furaldehyde; and an active amine. This disclosed class of phenalkamine Mannich bases have a high degree of biological based carbon content and may be used as epoxy resin curing agents.

Description

PHENALKAMINE CURING AGENTS

The invention relates to a class of phenalkamine Mannich bases having a high degree of biological based carbon content and useful as epoxy resin curing agents. In particular, the invention is directed to phenolic Mannich base compounds comprising at least one furan derived Mannich base moiety and at least one other substituent, a resin curative composition comprising such compounds, processes for preparing them, and uses thereof.

BACKGROUND OF THE INVENTION

There is an array of curing agents available for epoxy functional materials, but amines and products derived therefrom offer the greatest versatility for curing epoxy resins. Collectively, these materials offer the means for formulating systems that can provide the potential for curing in thin films and/or mass at a broad spectrum of temperatures. Historically, phenolic derived Mannich base curing agents have been used extensively. However, due to regulatory and toxicity issues, the use and availability of these materials is in substantial decline and focus is shifting to more environmentally friendly alternatives.

Many commercial curing agent formulations are based on aliphatic amines, including cyclo-aliphatic and araliphatic amines, as well as to a lesser extent aromatic amines, or a combination thereof. These amines are generally modified in order to enhance their processing and/or performance aspects, as well as to improve the active hydrogen equivalent weight combining ratio with epoxy resins or to reduce the toxicity of the amine curative agent.

Mannich bases are examples of modified amines which offer enhanced properties, especially with regard to improved compatibility with epoxy resins, optimisation of cure speed and degree of cure, as well as resistance to carbamation. Commercially available Mannich bases include phenolic derived compounds that are the reaction product of an aldehyde (generally formaldehyde), a phenolic compound, or a substituted derivative thereof, and an amine. An example structure of a phenolic Mannich base is shown below:

OH

R N NH2

H

Phenolic Mannich Base EP0779311 describes a Mannich base prepared by reacting (i) butyraldehyde, (ii) a phenolic compound, and (iii) a primary or a secondary polyamine. The use of butyraldehyde, rather than formaldehyde or paraformaldehyde, is reported to lower viscosity in the Mannich base products, which can be advantageous when used in epoxy curative applications.

However, the molecular weight, polydispersity and residual free phenol monomer levels has led to the reduction in availability and a decline in popularity of this class of materials. The conventional Mannich base with residual free phenol carries both acute toxicity labelling and a chronic health hazard. The removal of several of the Hazard statements associated with free monomeric phenol is now mandated by some organisations, e.g. REACH [Registration, Evaluation, Authorisation and restriction of Chemicals]. There remains a need for alternative Mannich bases that offer high process performance, broad compatibility with epoxy resins, and avoid the toxicity and environmental issues associated with known amine-derived epoxy resin curatives.

Cardanol is a bio-based phenolic compound derived from cashew nut shell liquid (CNSL) which has been utilised as an alternative to phenol in the preparation of phenalkamine Mannich bases, see F. de Luca Bossa. Et al, "Upgrading Sustainable Polyurethane Foam Based on Greener Polyols: Succinic-Based Polyol and Mannich-Based Polyol", Materials 2020, 13, 3170; and A. Roy. et al, "CNSL, a Promising Building Blocks for Sustainable Molecular Design of Surfactants: A Critical Review", Molecules, 2022, 27(4), 1443.

However, formaldehyde also carries many environmental and health risks. It is classified as a known human carcinogen by international health agencies, such as the International Agency for Research on Cancer (IARC). Long-term exposure has been linked to an increased risk of certain cancers, particularly in occupational settings. To address these problems, regulatory agencies in many countries have established guidelines and standards for formaldehyde emissions in various products. Efforts are also ongoing to develop alternative materials and manufacturing processes with reduced formaldehyde content.

The present invention relates to a class of phenol free phenalkamine Mannich bases derived from substituted phenolic alternatives and furaldehyde, or furaldehyde derivatives, useful as epoxy resin curatives.

SUMMARY OF THE INVENTION

In one aspect, the present invention provides a compound of formula (1):

OH (1)

wherein each R1 is independently selected from: -Ci to Czo alkyl, to Czo haloalkyl, -03 to C20 cycloalkyl, -02 to Czo; alkenyl, -02 to Czo alkynyl, -C, to 020 alkyl-C3 to Clo cycloalkyl, to Czo alkyloxy, -C, to Czo alkylamino, -OH, -0R2, -NHz, -NHR2, -NR22, -C(0)OH, -C(0)0R2, -C(0)NH2, -O(CO)H, -0(CO)R2, -NH(CO)H, -NH(CO)R2, -NR2(CO)H, -NR2(CO)R2, -SH, -SR2, -S021-1, -SO2R2, -SO3R2, -SO3H, -SiR23, -NO2, -CN, F, -CI, -Br, and -I; each R2 is independently selected from: -C, to C20 alkyl, to Czo haloalkyl, -03 to Czo cycloalkyl, -02 to Czo alkenyl, -02 to Czo alkynyl, to Czo alkyl-C3 to Cio cycloalkyl, to C20 alkoxy, and to Czo alkylamino; wherein each R3 is independently selected from: -C, to Czo alkyl, -Ci to Czo haloalkyl, -03 to C20 cycloalkyl, -02 to 020 alkenyl, -02 to C20 alkynyl, -OH, -NH2, -001 to C20 alkyl, -NHCi to Czo alkyl, -N(Ci to Czo alky1)2, -NO2, -CN, -F, -CI, -Br, and -I; wherein each R4 is independently selected from: hydrogen, or a hydrocarbyl group containing 1 to 500 carbon atoms; wherein each L is independently selected from: a direct bond, or a hydrocarbyl linker comprising 2 to 100 carbon atoms and 1 to 10 amine groups; wherein each R5 is independently selected from: hydrogen, or a hydrocarbyl group containing 1 to 50 carbon atoms; optionally wherein R5 is bonded to L such that the -NR5-L-moiety forms a group comprising a -4-to 14-membered heterocycle-; or optionally, wherein L is a direct bond and R4 and R5 are bonded to each other to form a group comprising a -4-to 14-membered heterocycle-; wherein x = 1, 2, 3 or 4; wherein n = 1, 2, or 3; wherein each y = 0, 1, 2 or 3; with the proviso that x + n = 2 to 5; and with the proviso that the compound of formula (1) must comprise at least one amine group.

In a second aspect, the present invention provides a method of preparing a Mannich base, the method comprising performing a Mannich reaction using: i) a phenolic compound substituted with one to four IR1 groups; H) a furaldehyde optionally substituted with one to three R3 groups; and iii) an active amine; wherein R1, R2, and R3 are as defined herein.

In a third aspect, the present invention provides an epoxy resin curative composition comprising a compound of formula (1) or a Mannich base prepared or preparable by the method of the present invention.

In a fourth aspect, the present invention provides a method for preparing a cured epoxy resin, said method comprising: a) contacting an epoxy resin with a compound of formula (1), a Mannich base prepared or preparable by the method of the present invention, or a composition of the present invention; and b) forming a cured epoxy resin.

In a fifth aspect, the present invention provides a cured epoxy resin prepared, or preparable, by the method of the present invention.

In a sixth aspect, the present invention provides the use of a compound of formula (1), a Mannich base prepared or preparable by the method of the present invention, or a composition of the present invention for causing crosslinking in an epoxy resin.

BRIEF DESCRIPTION OF THE FIGURES

Figure 1 demonstrates the viscosity vs temperature of compound A; Figure 2 demonstrates the dry time and the cure time of compound A, at both 5 °C and 25 °C; Figure 3 demonstrates the viscosity vs temperature of compound B; and Figure 4 demonstrates the dry time and the cure time of compound B, at both 5 °C and 25 °C.

DETAILED DESCRIPTION

Definition of Terms For the purposes of the present invention, the following terms as used herein shall, unless otherwise indicated, be understood to have the following meanings. Other terms that are not specifically defined below are to be understood as having their normal meaning in the art.

The term "hydrocarbyl" as used herein, refers to a monovalent, divalent, or multivalent group, comprising hydrogen and carbon atoms, such as a major proportion (i.e., more than 50 %) of hydrogen and carbon atoms, preferably consisting exclusively of hydrogen and carbon atoms. The hydrocarbyl group may be aromatic, saturated aliphatic or unsaturated aliphatic. The hydrocarbyl group may be entirely aliphatic or a combination of aliphatic and aromatic portions. In some examples, the hydrocarbyl group includes a branched aliphatic chain which is substituted by one or more aromatic groups. Examples of hydrocarbyl groups therefore include acyclic groups, as well as groups that combine one or more acyclic portions and one or more cyclic portions, which may be selected from carbocyclic, aryl and heterocyclyl groups. The hydrocarbyl group includes monovalent groups and polyvalent groups as specified and may, for example, include one or more groups selected from alkyl, alkenyl, alkynyl, carbocyclyl (e.g. cycloalkyl or cycloalkenyl), aryl and heterocyclyl. The hydrocarbyl group may contain one or more heteroatoms, such as oxygen, nitrogen, sulphur, silicon or halogen which may be part of a functional group such as an alcohol, ether, carbonyl, ester, carboxylic acid, carbonate, amide, amine, carbamate, urea, thiol, thioether, thioester, thioacid, thioamide, silane organic halide or heterocycle, the hydrocarbyl linker may contain any combination of the above insofar as it is chemically stable. Furthermore, in some embodiments, halogens may entirely replace the hydrogen component of the hydrocarbyl group (i.e. the carbon-bonded hydrogens) to give the corresponding halo-substituted analogue. A monovalent hydrocarbyl group is typically described as a group, whereas a multivalent hydrocarbyl group (such as a divalent or trivalent hydrocarbyl group) is typically described as a linker.

The term "alkyl" as used herein refers to a straight-or branched-chain alkyl moiety. Unless specifically indicated otherwise, the term "alkyl" does not include optional substituents. The term "haloalkyl" as used herein refers to an alkyl group substituted with one or more halogen atoms. The term "halogen" as used herein refers to any of fluorine, chlorine, bromine, or iodine.

The term "alkyloxy" as used herein refers to an alkyl group substituted with one or more hydroxy groups or ether groups. The term "alkylamino" as used herein refers to an alkyl group substituted with one or more primary, secondary, or tertiary amine groups.

The term "cycloalkyl" as used herein refers to a saturated aliphatic hydrocarbyl moiety containing at least one ring, wherein said ring has at least 3 ring carbon atoms. The cycloalkyl groups mentioned herein may optionally have alkyl groups attached thereto. Examples of cycloalkyl groups include groups that are monocyclic, polycyclic (e.g., bicyclic) or bridged ring system. Examples of cycloalkyl groups include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl and the like. The term "heterocycloalkyl" as used herein refers to a cycloalkyl group wherein the ring contains at least one heteroatom selected from oxygen, nitrogen, and sulphur. Examples of heterocycloalkyl groups include morpholine, piperidine, piperazine and the like.

The term "alkenyl" as used herein refers to a straight-or branched-chain alkyl group containing at least one carbon-carbon double bond, of either E or Z configuration unless specified. The term "alkynyl" as used herein refers to a straight-or branched-chain alkyl group containing at least one carbon-carbon triple bond. Examples of alkenyl groups include ethenyl, 2-propenyl, 1-butenyl, 2-butenyl, 3-butenyl, 1-pentenyl, 2-pentenyl, 3-pentenyl, 1-hexenyl, 2-hexenyl, 3-hexenyl and the like.

The term "aryl" as used herein refers to an aromatic carbocyclic ring system. An example of an aryl group includes a group that is a monocyclic aromatic ring system or a polycyclic ring system containing two or more rings, at least one of which is aromatic. Examples of aryl groups include aryl groups that comprise from 1 to 6 exocyclic carbon atoms in addition to ring carbon atoms. Examples of aryl groups include aryl groups that are monovalent or polyvalent as appropriate. Examples of monovalent aryl groups include phenyl, benzyl, naphthyl, fluorenyl, azulenyl, indenyl, anthryl and the like. An example of a divalent aryl group is 1,4-phenylene.

The term "heteroaryl" as used herein refers to an aromatic heterocyclic ring system wherein said ring atoms include at least one ring carbon atom and at least one ring heteroatom selected from nitrogen, oxygen and sulphur. Examples of heteroaryl groups include heteroaryl groups that are a monocyclic ring system or a polycyclic (e.g. bicyclic) ring system, containing two or more rings, at least one of which is aromatic. Examples of heteroaryl groups include those that, in addition to ring carbon atoms, comprise from 1 to 6 exocyclic carbon atoms. Examples of heteroaryl groups include those that are monovalent or polyvalent as appropriate. Examples of heteroaryl groups include pyridyl, pyrimidyl, thiopheneyl, isoxazolyl and benzo[b]furanyl groups.

The term "monoamine" as used herein refers to an organic compound having one amine group. Preferably the monoamine is an organic compound having one amine group having at least one active hydrogen, i.e. a primary amine or secondary amine, also described herein as a "active amine".

The term "polyamine" as used herein refers to an organic compound having a plurality of amine groups. Preferably the polyamine is an organic compound having a plurality of amine groups having active hydrogens, i.e. one or more primary amines and/or secondary amines, also described herein as "active amine(s)". For the avoidance of doubt, in the context of the present invention a diamine' having two amino groups is considered to fall within the scope of a "polyamine", and a monoamine is having one amino group is not considered to fall within the scope of a "polyamine".

The term "active amine" refers to a primary or secondary amine, having at least one amine N-H bond. An active amine may have one or two substituents, which may contain additional amine groups in its substituents, which may be active amines or tertiary amines.

The term "fatty acid" refers to an organic compound having one or more carboxylic acid and one or more carbon chain, which is either saturated or unsaturated. One or more double or triple bonds may be present. One or more carbocyclic sections may also be present.

The term "epoxy resin" as used herein refers to an organic compound having one or more epoxide groups. In the context of the present invention the term "epoxy resin" may be used to refer to a monomeric, or polymeric organic compound, having one or more epoxide groups. An "epoxy resin" may also be referred to in some publications as an "epoxy".

The term "cured epoxy resin" as used herein refers to an organic compound produced by reaction of an "epoxy resin" with a "curing agent", for example by the processes described herein.

The term "curing agent" as used herein refers to any species that is capable of causing crosslinking between molecules of epoxy resin, which may also be referred to as hardening or curing the epoxy resin. Causing crosslinking between molecules of epoxy resin, may for example, occur by nucleophilic reaction of the curing agent with epoxide groups present on the epoxy resin such that the curing agent is incorporated into a cured epoxy resin, or for example, a catalytic process whereby the curing agent catalyses polymerisation of the epoxy resin to a cured epoxy resin.

The term "bio-based", as used herein refers to a material that is derived in whole or in part from biomass resources. Biomass resources are organic materials that are available on a renewable or recurring basis such as crop residues, wood residues, grasses, and aquatic plants. The term "biocarbon" as used herein describes an atom of carbon that is "bio-based", i.e. that the atom of carbon in question is derived from a biomass resource.

The skilled person is able to determine if a material is from a biomass resource, provided that the source of the material is known. Therefore, a skilled person is also able to determine if a material is derived from a from biomass resource, providing they have knowledge of the precursor material from which the material in question is derived. Nevertheless, objective tests may also be used to identify "biocarbon". ASTM D6866 and ISO 16620-2 both provide methods of identifying "biocarbon" based on isotopic analysis. "Biocarbon" has a higher abundance of 14C than, for example, carbon derived from fossil fuels. Thus, the skilled person is also able to objectively test the biocarbon content of a given material.

In the context of the present invention the term "furaldehyde" refers to furan-2-carbaldehyde (CAS 98-01-1). The terms "furfuraldehyde", and "furfural", are also used to refer to furan-2-carbaldehyde in some publications.

The present invention relates to a hitherto unknown class of substituted phenolic Mannich bases derived from furaldehyde or furaldehyde derivatives. The use of furaldehyde in place of formaldehyde which is traditionally used in the preparation of Mannich bases replaces a highly toxic and carcinogenic chemical that is synthesised by energy intensive industrial processes, with an innocuous and naturally derived alternative. The bio-carbon content of the phenalkamine compounds of the present invention is greatly increased by replacing the formaldehyde precursor with furaldehyde. Furaldehyde is an inexpensive, renewable and naturally occurring feedstock derived from the dehydration of sugars, and occurs in a variety of agricultural by-products, including corncobs, oats, wheat bran, and sawdust.

Another advantage provided by the compounds of the present invention is the replacement of phenol as a starting material. As would be appreciated, phenol is a toxic and polluting material. Additionally, residual phenol may be leftover in the end product when phenol is used as a starting material, thus contributing to toxicity of a phenol derived epoxy resin hardener. The present compounds are prepared using substituted phenolic compounds which may be innocuous, as well as naturally occurring, for example, cardanol or guaiacol. The use of naturally occurring substituted phenolic compounds may provide the additional advantage of increasing the bio-based content of the compound formed therefrom.

Thus, the compounds of the present invention offer a significantly improved hazard classification over analogous phenol and/or formaldehyde derived curing agents (and avoids the toxicity issues associated with the production thereof, and epoxy resins obtained therefore), whilst maintaining the useful properties associated with a conventional Mannich base curing agent.

The compounds of formula (1) are useful as curing agents for epoxy resins. The compounds contain amine groups on the side chains which cause cross-linking in epoxy resins. Where the amines are active amines, i.e. primary or secondary amines, the active amines can act as nucleophiles to attack the epoxy groups of an epoxy resin such that the curing agent forms a covalent bond to the epoxy resin and is incorporated into a cured epoxy resin. Tertiary amine groups present on the side chains may act as homopolymerisation catalysts in epoxy systems and as such may also cause cross-linking in epoxy resins. A compound bearing both active and tertiary amines is therefore also especially well-suited to acting as a curing agent. In order to act as a curative, the compound of formula (1) must therefore comprise at least one amine group, and preferably at least one active amine group.

In a first aspect, the present invention provides a compound of formula (1): (1) wherein each R1 is independently selected from: -C, to Czo alkyl, to Czo haloalkyl, -Co to 020 cycloalkyl, -02 to 020; alkenyl, -02 to 020 alkynyl, to C20 alkyl-C3 to Cio cycloalkyl, to 020 alkyloxy, -C, to 020 alkylamino, -OH, -0R2, -NHz, -NHR2, -NR22, -C(0)OH, -C(0)0R2, -C(0)NH2, -O(CO)H, -O(CO)R2, -NH(CO)H, -NH(CO)R2, -NR2(CO)H, -NR2(CO)R2, -SH, -SR2, -S021-1, -SO2R2, -SO3R2, -SO3H, -SiR23, -NO2, -CN, F, -CI, -Br, and -I; each R2 is independently selected from: -Ci to 020 alkyl, to Czo haloalkyl, -C3 to Czo cycloalkyl, -02 to 020 alkenyl, -02 to 020 alkynyl, to 020 alkyl-C3 to 010 cycloalkyl, to Czo alkoxy, and to Czo alkylamino; wherein each R3 is independently selected from: -C, to Czo alkyl, -C, to Czo haloalkyl, -03 to 020 cycloalkyl, -02 to 020 alkenyl, -02 to 020 alkynyl, -OH, -NHz, -001 to 020 alkyl, -NHCi to Czo alkyl, -N(Ci to Czo alky1)2, -NO2, -CN, -F, -CI, -Br, and -I; wherein each R4 is independently selected from: hydrogen, or a hydrocarbyl group containing 1 to 500 carbon atoms; wherein each L is independently selected from: a direct bond, or a hydrocarbyl linker comprising 2 to 100 carbon atoms and 1 to 10 amine groups; wherein each R5 is independently selected from: hydrogen, or a hydrocarbyl group containing 1 to 50 carbon atoms; optionally wherein R5 is bonded to L such that the -NR5-L-moiety forms a group comprising a -4-to 14-membered heterocycle-; or optionally, wherein L is a direct bond and R4 and R5 are bonded to each other to form a group comprising a -4-to 14-membered heterocycle-; wherein x = 1, 2, 3, or 4; wherein n = 1, 2, or 3; wherein each y = 0, 1, 2 or 3; with the proviso that x + n = 2 to 5; and with the proviso that the compound of formula (1) must comprise at least one amine group.

The compound of formula (1) comprises a phenolic core, substituted with 1 to 4 substituents defined as R1. Each R1 group may be the same or different. An R1 group may be present at any one of the 2-, 3-, 4-, 5-and/or 6-positions relative to the phenolic -OH group. The number of R1 groups is defined as x which may be 1, 2, 3, or 4. Preferably x = 1, 2, or 3, more preferably x = 1 or 2, even more preferably x = 1.

It is additionally advantageous that one or more R1 group is an activating group, as this will promote the Mannich reaction. As would be appreciated, the term activating group herein refers to any substituent that increases the reactivity of the ring towards electrophilic aromatic substitution. In this regard, it is also advantageous that R1 groups, preferably activating R1 groups, are present at the 3-, 5-or the 3-and 5-positions relative to the phenolic -OH. This is so that the activating effects of the phenolic -OH and the R1 group(s) are directed towards the same positions and thus have an additive effect.

Preferably each R1 is independently selected from: to Czo alkyl, -03 to Czo cycloalkyl, -02 to Czo alkenyl, -02 to Czo alkynyl, to Czo alkyl-C3 to Clo cycloalkyl, to 020 alkyloxy, to 020 alkylamino, -OH, -OR2, -NHR2, -NR22, -O(CO)H, -O(CO)R2, -NH(CO)H, -NH(CO)R2, -NR2(CO)H, -NR2(CO)R2, -SH, -SR2, and -SiR23; and each R2 is independently selected from: -C, to Czo alkyl, -03 to Czo cycloalkyl, -02 to Czo alkenyl, -02 to 020 alkynyl, -C, to Czo alkyl-C3 to Clo cycloalkyl, -Ci to Czo alkoxy, and to 020 alkylamino.

More preferably each R1 is independently selected from: to Czo alkyl, -03 to Czo cycloalkyl, -02 to 020; alkenyl, -02 to Czo alkynyl, to Czo alkyl-C3 to Clo cycloalkyl, to 020 alkyloxy, to 020 alkylamino, -OH, -OR2, -NHz, -NHR2, and -NR22; and each R2 is independently selected from: to 020 alkyl, -03 to 020 cycloalkyl, -02 to 020 alkenyl, - 02 to Czo alkynyl, -C, to Czo alkyl-C3 to 010 cycloalkyl, to 020 alkoxy, and -C, to 020 alkylamino.

Even more preferably each R1 is independently selected from: -Ci to 020 alkyl, -02 to 020; alkenyl, -OH, -OR2; and each R2 is independently to Czo alkyl.

The nature of the R1 groups will depend on the substituted phenol from which the compound of formula (1) is derived. Preferably, the substituted phenolic compound from which the compound of formula (1) is derived is bio-based. Some examples of suitable substituted phenolic starting materials from which a compound of formula (1) may be derived are shown in Table 1 below.

Table 1: Substituted Phenolic Compounds Name Structure R1 groups Natural Source Cardanol OH 3-(C151-131 -0, 2, 4, orb) CNSL 110, u L.151131 -0, 2. 4, or 6 Cardol OH 3-OH CNSL SO, u 5-(C15H31 -0, 2, 4, or 6) HO u151131 -O. 2, 4, or 6 2-methylcardol OH 2-Me CNSL 0, 3-(C15H31 5-OH -0, 2, 4, or 6) HO L.151.u 31 -O. 2, 4, or 6 Anacardic acid OHO 2-COOH CNSL ®OH 3-(C15H31 -0, 2, 4, or 6) C161-131 -0, 2, 4, or 6 Resorcinol OH 3-OH Rye Ill OH Catechol OH 2-OH Acadia el OH Hydroquinone OH 4-OH Quinic acid

OH

Phloroglucinol OH 3,5-OH Phloretin HO ®OH Guaiacol OH 2-OMe Wood 0 0 The compound of formula (1) comprises 1 to 3 furanyl Mannich base moieties derived from furaldehyde or a substituted furaldehyde, and an active amine. At least one active amine group is required in the active amine precursor from which the compound of formula (1) is derived, in order to take part in the Mannich reaction. In the context of the present invention, the furanyl Mannich base moiety refers to the section of the compound of formula (1) which is shown within the brackets.

The compound of formula (1) must comprise at least one amine group, and preferably at least one active amine group. Although multiple amine groups, and multiple active amine groups are more preferred. More preferably, at least one amine group, which is preferably at least one active amine group, is present in each furanyl Mannich base moiety. Even more preferably, at least two amine groups, which are preferably at least two active amine groups, are present in at least one furanyl Mannich base moiety. Even more preferably still, at least two amine groups, which are preferably at least two active amine groups, are present in each furanyl Mannich base moiety. In other words, the compound of formula (1) may optionally have the proviso that each Mannich base moiety comprises at least one amine group, preferably at least one active amine group. Preferably, the compound of formula (1) has the proviso of comprising at least two amine groups, and preferably at least two active amine groups; and more preferably the proviso that each Mannich base moiety comprises at least two amine groups, preferably at least two active amine groups.

Each furanyl Mannich base moiety may be the same or different. A furanyl Mannich base moiety may be present at any one of the 2-, 3-, 4-, 5-and/or 6-positions relative to the phenolic -OH group. The number of furanyl Mannich base moieties is defined as n which may be 1, 2, or 3. Preferably, the furanyl Mannich base moieties are present at one or more of the 2-, 4-and/or 6-positions relative to the phenolic -OH. More preferably, the furanyl Mannich base moieties are present at each of the 2-, 4-and/or 6-positions relative to the phenolic -OH which are not occupied by R1 groups. The 2-, 4-and 6-positions relative to the phenolic -OH are activated by the activating effect of the phenolic -OH and are thus favoured by the Mannich reaction. The compounds of formulae (la), (1 b), (1 c), and (1d), shown below therefore represent particularly preferable sub-classes of the compound of formula (1).

Preferably, the compound of formula (1) has the formula (1a) (1a) wherein y, R1, R2, R3, R4, R5, and L are as defined herein in relation to the compound of formula (1), including any embodiments described herein in relation thereto: more preferably wherein R1 is -OH, to Czo alkyl, or -C2 to Czo; alkenyl; more preferably wherein R1 is -OH or -Cis alkyl or -015 alkenyl.

Preferably, the compound of formula (1) has the formula (1 b) R4 (1 b) wherein y, R1, R2, R3, R4, R5, and L are as defined herein in relation to the compound of formula (1), including any embodiments described herein in relation thereto; more preferably wherein R1 is -OMe.

--Y(R3)

OH R4 R5 y(R3) R4 0 7

OH R4 y(R3) y(R3)

Preferably, the compound of formula (1) has the formula (1c). R4 R1 (1c)

wherein y, R1, R2, R3, R4, R5, and L are as defined herein in relation to the compound of formula (1), including any embodiments described herein in relation thereto: more preferably wherein R1 is -OH.

Preferably, the compound of formula (1) has the formula (1d) (1d) wherein y, R1, R2, R3, rc n4, R5, and L are as defined herein in relation to the compound of formula (1), including any embodiments described herein in relation thereto: more preferably wherein each R1 is independently selected from -OH, to Czo alkyl, or -C2 to C20; alkenyl; even more preferably wherein either: both R1 groups are -OH; or one R1

L y(R3) R4

NR

OH (R3)y R4

group is -OH and the other is -01 to Czo alkyl, or -02 to Czo; alkenyl, preferably -015 alkyl or -C15 alkenyl.

There are only 5 positions available for substitution on a phenol. Therefore, the total number of x + n cannot be greater than 5. At least one R1 group and at least one furanyl Mannich base moiety must be present in the compound of formula (1). Therefore, the total number of x + n cannot be less than 2. Therefore, the total number of x + n must range from 2 to 5.

The furan moiety may be substituted with 0 to 3 R3 groups. The number of R3 groups on the furan moiety is defined as y, which may thus be 0, 1, 2, or 3. Each furan moiety, in the case of multiple Mannich base moieties, may be the same or different. Preferably, the furan moiety is unsubstituted, i.e. substituted by hydrogen, and thus y = 0.

Typically, all y values are the same, and/or all R3 groups are the same. As would be appreciated a combination of different furan moieties could be achieved by using a mixture of different substituted furaldehyde starting materials.

Typically, wherein one R3 group is present, the R3 group is attached at the available position ortho to the furan oxygen, i.e. the furan 5-position. This is the most common substitution pattern found in naturally derived furaldehyde derivates.

In the case that y is greater than 0, preferably, each R3 is independently selected from: -Ci to C6 alkyl, -Ci to C6 alkoxy, to C6 alkyloxy, and -OH; preferably -CH3, -CH2OH, or -CH2OCH3. These are the most common substituents found in naturally derived furaldehyde derivates. Various bio-based furaldehyde derivates are commercially available, or may be easily prepared by the skilled person from bio-based sources.

The furanyl Mannich base moiety is derived from the optionally substituted furaldehyde and an active amine precursor. The R4, R5, and L groups may also be derived from the active amine precursor (although it is feasible to introduce these groups synthetically at a later stage after the Mannich reaction). As each L is independently either a direct bond or a hydrocarbyl linker comprising 2 to 100 carbon atoms and 1 to 10 amine groups, L when present, will comprise at least one amine group. Therefore, in the case that the active amine precursor taking part in the Mannich reaction is a monoamine, then L will be a direct bond such that the active amine precursor will be directly bonded to R4 and have the formula HNR4R5. In the case that the active amine precursor is a polyamine, L will be a hydrocarbyl linker comprising 2 to 100 carbon atoms and 1 to 10 amine groups, such that the active amine precursor will have the formula HNR5-L-R4 as defined herein. A combination of monoamine and polyamine active amine precursors may also be used to provide differing furanyl Mannich base moieties within a single compound of formula (1).

The scope of monoamines useful as the active amine precursor is not particularly limited. Some examples of suitable monoamines useful as an active amine precursor include dimethylamine, furfurylamine, ethanolamine, anthranilic acid, or amino acids such as tyrosine, tryptamine, or glycine. As would be appreciated, the corresponding furanyl Mannich base moieties are thus described. For example, in the case of dimethylamine, R4 and R5 are both methyl groups. In the case of furfurylamine, either one of R4 or R5 is hydrogen, and the other one of R4 or R5 is -(CH2)-furanyl.

The scope of polyamines useful as the active amine precursor is not particularly limited. Some examples of suitable polyamines useful as an active amine precursor include putrescene, cadaverine, cystamine, lysine, dimethylaminopropylamine, and triethylenetetramine. The L group is derived from the active polyamine precursor which takes part in the Mannich reaction useful for preparing compounds of formula (1). The nature of the L group is thus also not particularly limited, and each L, when present, is independently a hydrocarbyl linker comprising 2 to 100 carbon atoms and 1 to 10 amine groups. For example, when present, each L may be independently selected from: a hydrocarbyl linker comprising 2 to 100 carbon atoms and 1 to 5 amine groups, preferably comprising 2 to 50 carbon atoms and 1 to 5 amine groups, more preferably comprising 2 to 50 carbon atoms and 1 to 2 amine groups, more preferably comprising 2 to 50 carbon atoms and 1 amine group, even more preferably comprising 2 to 20 carbon atoms and 1 amine group, even more preferably comprising 4 to 5 carton atoms and 1 amine group, most preferably wherein each L is independently selected from: a straight chain -C4 alkyl-NH-, -05 alkyl-NH-or -(CH2)2-SS-(CH2)2-NH-. It is preferred that L, when present, is bonded to R4 via an amine.

By way of example, Table 2 below outlines some exemplary precursor active amines useful in the present invention as well as their corresponding furanyl Mannich base moiety and corresponding L, R5, and R4 groups. As would be appreciated, L, R4, and R5 groups of formula (I) may be construed in alternative ways, provided that the groups L, R4, and R5, simultaneously satisfy their respective definitions in formula (I). For example, a substituent on L may constitute either of R4 or R5, or a particular moiety may constitute a part of group L or part of groups R4 or R5.

Table 2: Active Amine Precursors and Corresponding Furanyl Mannich base Moieties Precursor Active Amine Furanyl Mannich Base Moiety L R4 R5 Dimethylamine cj Direct bond -Me -Me

N

C

Ethanolamine o N"...-.........."OH H Direct bond -(CH2)20H -H Furfurylamine o - Direct bond -(CH2)-furanyl -H Ltia, N i)1 H 1 / Tyrosine OH Direct bond -C(CO2H) (CH2- -H C6 H 4-OH) 0 0

OH

tZaZ. 11 Putrescene N."......."..". N H2 -C4 alkyl-NH- -H -H Of ".

H

Cadaverine / NW N H2 H -05 alkyl-NH- -H -H Cystamine o N.,...---...."..A.,s,..---,NH2 -(CH2)2-SS-(CH2)2-NH- -H -H

H

Dimethylamino propylamine o -C3 alkyl-NMe- -Me -H

NN H

triethylenetetramine 0 -(CHz- -H -H H (CH2-N- "......."..N..,......./1, w*^".........NH2 N H)3H-yDiphenylaniline 0 Direct bond -Ph -Ph 53 N For example, either of R4 and/or R5 may independently be a -01 to C20 alkyl group, a -02 to Czo alkenyl group, a -02 to Czo alkynyl group, -03 to C20 cycloalkyl group, -Cs to C20 cycloalkenyl group, -03 to C20 heterocycloalkyl group, -Cs to Czo heterocycloalkenyl group, a 6-to 14-membered aryl group, a 5-to 14-membered heteroaryl group; and may be further substituted with one or more groups selected from a -01 to Czo alkyl group, a -02 to Czo alkenyl group, a -02 to Czo alkynyl group, -03 to Czo cycloalkyl group, -Cs to C20 cycloalkenyl group, -03 to C20 heterocycloalkyl group, -Cs to C20 heterocycloalkenyl group, a 6-to 14-membered aryl group, a 5-to 14-membered heteroaryl group, to Czo alkyloxy, to Czo alkylamino, -OH,-OR2,oxo, -NH2, -NHR2, -NR22, -C(0)OH, -C(0)0R2, -C(0)NH2, -O(CO)H, -O(CO)R2, -NH(CO)H, NH(CO)R2, -NR2(CO)H, -NR2(CO)R2, -SH, -SR2, -SO2H, -SO2R2, -SO3R2, -S031-1, -SiR23, -NO2, -CN, -F, -CI, -Br, and -I. ;For example, R4 may be a hydrocarbyl linker comprising 2 to 500 carbon atoms, and/or R5 may be a hydrocarbyl linker comprising 2 to 50 carbon atoms. Each L group may be the same or different. ;Various polyamines are used in the preparation of Mannich bases which are also suitable for use in preparing the compound of formula (1). Suitable polyamines may be selected from: 1) an aliphatic primary di-or tri-amine; preferably an ether-groupcontaining aliphatic primary di-or tri-amine; 2) an aliphatic secondary amino-containing tri-amine having two primary aliphatic amino groups; 3) a polyamine having one or two secondary amino groups, preferably products of the reductive alkylation of primary aliphatic polyamines with aldehydes or ketones; or 4) an aromatic polyamine. Specific examples of suitable polyamines include 2,2-dimethyl-1,3-propanediamine, 1,3-pentanediamine (DAMP), 1,5-pentanediamine, 1,5-diamino-2-methylpentane (M PM D), 2-butyl-2-ethyl-1, 5-pentanediamine (C11-nododiamine), 1,6-hexanediamine, 2,5-dimethy1-1,6-hexanediamine, 2,2 (4), 4-trimethylhexamethylenediamine (TM D), 1,7-heptanediamine, 1, 8-octanediamine, 1,9-nonanediamine, 1,10-decanediamine, 1,11-undecandiamine, 1,12-dodecanediamine, 1,2-,1,3-or 1,4-diaminocyclohexane, bis(4-aminocyclohexyl) methane (H12-MDA), bis(4-amino-3-methylcyclohexyl) methane, bis(4-amino-3-ethylcyclohexyl) methane, bis(4-amino-3,5-dimethylcyclohexyl) methane, bis(4-amino-3-ethyl-5-methylcyclohexyl) methane, 1-amino-3-aminomethy1-3,5,5-trimethylcyclohexane (isophoronediamine or IPDA), 2-or 4-methy1-1,3-diaminocyclohexane or mixtures thereof, 1,3-bis(aminomethyl) cyclohexane, 1,4-bis(aminomethyl) cyclohexane, 2,5 (2,6)-bis(aminomethyl) bicyclo [2.2.1] heptane (NBDA), 3(4), 8(9)-Bis(aminomethyl) tricyclo [5.2. 1.02 '6] decane, 1,4-diamino-2,2,6-trimethylcyclohexane (TMCDA), 1,8-Me N-thandiamin, 3,9-bis(3-aminopropyI)-2,4,8,10-tetraoxaspiro [5.5] undecane, 1,3-bis(aminomethyl) benzene (MXDA), 1, 4-bis(aminomethyl) benzene, and combinations thereof; or wherein the polyamine is an aliphatic primary triamine selected from 4-aminomethyl-1,8-octanediamine, 1,3,5-tris(aminomethyl) benzene, 1,3,5-tris(aminomethyl) cyclohexane, tris(2-aminoethyl) amine, tris(2-amino-propyl) amine, tris(3-aminopropyl) amine; or a poly(alkylene oxide) amine, such as a jeffamine (RTM). ;For example, suitable polyamines include secondary amino-containing tri-amines. Suitable aliphatic secondary amino-containing tri-amines having two primary aliphatic amino groups include: 3-(2-aminoethyl) aminopropylamine, bis(hexamethylene) triamine (BHMT), diethylenetriamine (DETA), triethylenetetramine (TETA), tetraethylenepentamine (TEPA), pentaethylenehexamine (PEHA) or higher homologs of linear polyethyleneamines such as polyethylenepolyamine with 5 to 7 ethylenepolyamine units (HEPA), products of the multiple cyanoethylation or cyanobutylation and subsequent hydrogenation of primary polyamines having at least two primary amino groups, such as Dipropylenetriamine (DPTA), N-(2-aminoethyl)-1,3-propanediamine (N3-amine), N,N'-bis(3-aminopropyl) ethylenediamine (N4-amine), N,N'-bis (3-aminopropyI)-1,4-diaminobutane, N5-(3-aminopropy1)-2-methyl-1,5-pentanediamine, N3- (3-aminopentyI)-1,3-pentanediamine, N5-(3-Amino-1-ethyl-propy1)-2-methy1-1,5-pentanediamine, and N,N'-bis (3-amino-1-ethyl-propy1)-2-methyl-1,5-pentanediamine. ;For example, suitable polyamines include polyamines having one or two secondary amino groups. Suitable polyamines having one or two secondary amino groups include: N1-benzy1-1,2-propanediamine, N1-(4-methoxybenzyI)-1,2-propanediamine, N-benzyl1,3-bis (aminomethyl) benzene, N,N1-Dibenzy1-1,3-bis (aminomethyl) benzene, N-2-ethylhexy1-1,3-bis (aminonyl) benzene, N,N'-bis(2-ethylhexyl)-1,3-bis(aminomethyl) benzene, and partially styrenated polyamines, such as partially styrenated 1,3-bis(aminomethyl) benzene (MXDA) (available from Mitsubishi gas Chemical). ;For example, suitable polyamines include aromatic polyamines. Suitable aromatic polyamines include m-and p-phenylenediamine, 4,4'-, 2,4'-and/or 2,2'-diaminodiphenylmethane, 3,3'-dichloro-4,4'-diaminodiphenylmethane (MOCA) diisocyanate, 2,4-and / or 2,6-toluene diamine (available as Ethacure 300 from Albemarle (RTM)), mixtures of 3,5-dimethylthio-2,4-and -2,6-toluene diamine, mixtures of 3,5-diethyl -2,4-and -2,6-toluylenediamine (DETDA), 3,3',5,5'-tetraethy1-4,4'- diaminodiphenylmethane (M-DEA), 3,3',5,5'-tetraethy1-2,2'-dichloro-4,4'- diaminodiphenylmethane (M-CDEA), 3,3'-diisopropy1-5,5'-dimethy1-4,4'- diaminodiphenylmethane (M-MIPA), 3,3',5,5'-tetraisopropy1-4,4'- diaminodiphenylmethane (M-DIPA), 4,4'-diamino diphenylsulfone (DDS), 4-amino-N-(4-aminophenyl) benzenesulfonamide, 5,5'-methylenedianthranilic acid, dimethyl (5,5'- methylenedithethranilate), 1,3-propylenebis(4-aminobenzoate), 1,4-butylenebis(4- aminobenzoate), polytetramethyleneoxide-bis(4-aminobenzoate), 1,2-bis(2-aminophenylthio)ethane, 2-methylpropyl (4-chloro-3,5-diaminobenzoate), t-Butyl (4-chloro-3,5-diaminobenzoate), and combinations thereof. ;For example, suitable polyamines include cyclic secondary amines, 4,4'-bipiperidine being one such example. With respect to the examples above the skilled person would be aware of those moieties in the relevant precursor from which L, R4 and R5 in the compound of formula (1) may derive. As would be appreciated, L, R4 and R5 are derived from the active amine precursor and the L, R4 and R5 groups of the furanyl Mannich base moieties may be constituted in an analogous manner to that represented shown in Table 2. ;Using a bio-based active amine allows for the bio-based content of the compound of formula (1) to be further increased. Preferably, L is derived from a bio-based active amine. Where a bio-based phenolic compound, bio-based furaldehyde, and a biobased active amine are used in the preparation of the compound of formula (1), the compound of formula (1) is 100% bio-based. Preferably the compound of formula (1) is 100% biobased. ;Putrescene (H2N-(CH2)4-N2H) and cadaverine (H2N-(CH2)s-N2H) are examples of biobased active amines useful in the present invention. Therefore, it is preferable that each L is independently selected from: a straight chain -04 alkyl-NH-, -Cs alkyl-NH-,. In these three examples, R4 is hydrogen, although other R4 groups may be introduced synthetically. ;Dimer amines are examples of bio-based active amines useful in the present invention. Dimer amines are diamine compounds derived from dimer acids. Dimer amines thus contain two active amine groups and a carbon chain, and may contain unsaturation and/or cyclisation, such as alkene, cycloalkyl, cycloalkenyl and/or aryl groups as a result of the dimerisation reaction. Dimer amines are commercially available, for example, under the trade name Priamine (RTM). Dimer amines may be easily prepared by the skilled person. Each L group may be derived from a dimer amine. ;A dimer amine may, for example, have the formula H2N-R9-NH2, wherein R9 is a divalent -C16 to 048 hydrocarbyl-group, optionally comprising one or more alkenyl, cycloalkyl, cycloalkenyl, or aryl portion; preferably wherein R9 is a divalent -026 to 040 hydrocarbylgroup, optionally comprising one or more alkenyl, cycloalkyl, cycloalkenyl, or aryl portion; most preferably wherein R9 is a divalent -036 hydrocarbyl-group, optionally comprising one or more alkenyl, cycloalkyl, or cycloalkenyl portion. Where L is derived from such a dimer amine, L is R9-NH-and R4 is hydrogen, although other R4 groups may be introduced synthetically. ;Amino acids are another example of a bio-based source of amines, which may be monoamines, such as glycine, tyrosine, or tryptamine, or may be a polyamine such as lysine. The carboxylic acid groups present on an amino acid are also open to further functionalisation with further active polyamines. ;In this application, the nitrogen atom involved in the Mannich reaction, which is depicted in formula (1) as bonded to IR5 and the CH-furanyl group is described herein as the "Mannich base nitrogen". Any other nitrogen atom which is comprised within L, R4 or R5 is described herein as a "trailing nitrogen". ;Each Mannich base nitrogen is bonded to one R5 group. In the case that this R5 group is hydrogen then the Mannich base nitrogen is a secondary amine. Preferably, this R5 group is hydrogen. Where this R5 group is a hydrocarbyl group, it may be present on the Mannich base nitrogen before the Mannich reaction, or added to the Mannich base nitrogen after the Mannich reaction has taken place. ;Preferably L is bonded to R4 via an amine, or in other words, via a trailing nitrogen. A trailing nitrogen may also be bonded to further substituents which make up part of the L linker. In the case that both of these groups are hydrogen, then the trailing nitrogen is a primary amine. Preferably, R4 is hydrogen, and preferably the other substituent on the amine bonded to R4 is also hydrogen. Where R4 is a hydrocarbyl group, R4 may be present on the relevant trailing nitrogen before the Mannich reaction takes place or may be added to the trailing nitrogen after the Mannich reaction has taken place. ;Certain cyclic functionalities are possible where, for example, L, R4 and/or R5 may be bonded to one another, in addition to the bonds explicitly depicted in formula (1). Various examples of such cyclic functionalities are outlined below. In the context of the present invention, where any L, R4 and/or R5 may be bonded to one another, in addition to the bonds explicitly depicted in formula (1), this would be understood to mean that L, R4 and/or R5 are bonded to a group within the same furanyl Mannich base moiety and not to a different furanyl Mannich base moiety on the same compound of formula (1). ;Optionally R5 may be bonded to L such that the -NR5-L-moiety forms a group comprising a -4-to 14-membered heterocycle-. ;An exemplary furanyl Mannich base moiety, wherein the -NR5-L-moiety forms a group comprising a -4-to 14-membered heterocycle-is shown below. ;Example of -NR5-L-moiety forming a group comprising a -4-to 14-membered heterocycle-In this example, the active amine precursor is 4-aminopiperdine. L can be considered to be a -C3 alkyl-NH-group and R5 can be considered to be a -C2 alkyl-group, wherein the R5 is bonded to L such that the -NR5-L-moiety forms a group comprising a 6-membered heterocycle, i.e. a piperidine. This structure merely serves as an example of the -NR5-Lmoiety forming a group comprising a -4-to 14-membered heterocycle-, many other structures are also possible. In this example R4 is hydrogen and y = 0, although these are not necessarily limitations. ;Additionally or alternatively, L, R4, and/or R5 may comprise cyclic functionality. An example of L comprising cyclic functionality is shown below. ;NH ;Example of L comprising cyclic functionality In this example, the active amine is also a 4-aminopiperdine. L can be considered to be a 6-membered heterocycle group, i.e. a piperidine. This structure merely serves as an example of a cyclic L linker, many other structures are also possible. In this example, R4 and R5 are hydrogen and y = 0, and R4 and R5 are not additionally bonded to L in addition to those bonds explicitly depicted in formula (1), although these are not necessarily limitations. ;NH ;An example of R4 or R5 comprising cyclic functionality is shown below. NH 26 ;Example of R4 or R5 comprising cyclic functionality In this example, the active amine precursor is 1-(3-aminopropyl)pyrrolidine. L is a direct bond, either one of R4 or R5 is hydrogen, and the other one of R4 or R5 is a hydrocarbyl group comprising 7 carbon atoms and including a 5-membered heterocycle, i.e. a pyrrolidine. This structure merely serves as an example of R4 or R5 comprising cyclic functionality, many other structures are also possible. In this example y = 0, although this is not necessarily a limitation. ;It is also possible that R5 is bonded to L such that the -NR5-L-moiety forms a group comprising a -4-to 14-membered heterocycle-, and L comprises one or more further cyclic group as is shown below. ;NO CN H ;Example of -NR5-L-moiety forming a group comprising a -4-to 14-membered heterocycle-and L comprising a further cyclic functionality In this example, the active amine precursor is a 4,4'-bipiperidine. L can be considered to be a -C3 alkyl-group bonded to a 6-membered heterocycloalkyl group and R5 can be considered to be a -02 alkyl-group, wherein R5 is bonded to L such that the -NR5-Lmoiety forms a group comprising a 6-membered heterocycle, i.e. a piperidine. In this example R4 is hydrogen and y = 0, although these are not necessarily limitations. ;Optionally, wherein L is a direct bond, R4 and R5 may be bonded to each other such that the -NR4R5 moiety forms a group comprising a -4-to 14-membered heterocycle-. An exemplary furanyl Mannich base moiety, wherein L is a direct bond and R4 and R5 are bonded to each other such that the -NR4R5 moiety forms a group comprising a -4-to 14-membered heterocycle-is shown below. ;Example of -NR4R5 moiety forming a group comprising a -4-to 14-membered heterocycle-In this example, the active amine precursor is proline. R4 can be considered to be a -CH(CO2H)-group, and R5 can be considered to be a -C3 alkyl-group, or vice versa, wherein R4 and R5 are bonded to each other such that the -NR4R5 moiety forms a group comprising a 5-membered heterocycle, i.e. a pyrrolidine. This structure merely serves as an example of R4 and R5 being bonded to each other such that the -NR4R5 moiety forms a group comprising a -4-to 14-membered heterocycle-, many other structures are also possible. In this example y = 0, although this is not necessarily a limitation. ;As exemplified hereinabove, the furanyl Mannich base moiety may comprise various heterocyclic structures. Some combinations of such heterocyclic moieties are also possible, as are fused, bridged, or spiro bicycles. However, it is preferable that none of L, R4, and/or R5 are bonded to one another other than the bonds depicted in formula (1). ;Some R4 groups which may be added to the Mannich base nitrogen or a trailing nitrogen comprised within L, after the Mannich reaction has taken place are discussed below. In some cases, the R4 group that is introduced is bio-based, which further increases the bio-based content of the compound of formula (1) and may in some cases be included in a 100% biobased compound of formula (1). ;A fatty acid may be added to one or more Mannich base nitrogen or a trailing nitrogen comprised within L by an amide coupling reaction. In this case the R4 group is a -(CO)-alkyl or -(CO)-alkenyl group. Typically, suitable fatty acids comprise 4 to 28 carbon atoms, and may optionally comprise one or more double bonds. In this case, the resulting R4 group is a -(CO)-C3 to C27 alkyl or alkenyl group, preferably a -(CO)-Cs to C23 alkyl or alkenyl group, more preferably a -(C0)-C, to C19 alkyl or alkenyl group. ;Another example of a group that may be added to one or more trailing nitrogen by an amide coupling reaction is a dimer acid. Dimer acids are dimerised fatty acids which thus contain two carboxylic acid groups, and may contain unsaturation and/or cyclisation, such as alkene, cycloalkyl, cycloalkenyl and/or aryl groups as a result of the dimerisation reaction. Dimer acids, like fatty acids, are derived from natural sources such as tall oil or vegetable oils. Dimer acids are commercially available and may be easily prepared by the skilled person. Each R4 group may be derived from a dimer acid. ;A dimer acid may, for example, have the formula HOOC-R6-000H, wherein R6 is a divalent -014 to 046 hydrocarbyl-group, optionally comprising one or more alkenyl, cycloalkyl, cycloalkenyl, or aryl portion; preferably wherein R6 is a divalent -024 to 038 hydrocarbyl-group, optionally comprising one or more alkenyl, cycloalkyl, cycloalkenyl, or aryl portion; most preferably wherein R6 is a divalent -034 hydrocarbyl-group, optionally comprising one or more alkenyl, cycloalkyl, or cycloalkenyl portion. As would be appreciated, when the carboxylic acid carbons are included, a C8 fatty acid will dimerise to provide an R6 group having a divalent -C14 hydrocarbyl-group, and a C24 fatty acid will dimerise to provide an R6 group having a divalent -046 hydrocarbyl-group. In this way, R6 groups having various numbers of carbon atoms may be provided by dimerisation of lower monomeric fatty acids, or combinations thereof. ;If a dimer acid is reacted with a Mannich base nitrogen or a trailing nitrogen comprised within L, an unreacted carboxylic acid group will be present. This group may then be reacted with a further active amine, such as a polyamine. Any of the above discussed polyamines may be used. An example of a polyamine which is particularly suitable is HR7N-L1-NR7H, wherein L1 is a divalent hydrocarbyl linker comprising 2 to 50 carbon atoms; each R7 is independently selected from hydrogen or a hydrocarbyl group containing 1 to 20 carbon atoms; preferably wherein R7 is hydrogen; optionally wherein one or both R7 groups is/are bonded to L1 such that one or both of the -NR'-L1-and -L1-NR'-moieties form a group comprising a -4-to 14-membered heterocycle-; optionally wherein both R7 groups are bonded to each other such that the -NR'-L1-NR'-moiety forms a group comprising a -5-to 14-membered heterocycle-. ;The nature of L1 is not particularly limited. Each L1 group may be the same or different. The R7 groups on each nitrogen may be the same or different and are preferably hydrogen. Each of the R7 groups on may also be bonded to L1 or to each other to form groups comprising heterocyclic moieties in the same manner as L and R5 as discussed above. For example, each L1 may be independently selected from: -02 to Czo alkyl-, -02 to Czo alkenyl-, or -03 to Czo cycloalkyl-, or a -06 to Czo aryl-, and may optionally comprise 1 to 5 amine groups. Preferably, each L1 is independently selected from: a straight chain -04 alkyl-, -05 alkyl-, or -(CH2)2-SS-(CH2)2-. ;R4 may have the structure: -(00)-R6-(C0)-NR7-1_1-NR7H, where a single dimer acid and a single polyamine are added to the furanyl Mannich base moiety. ;R4 may have the structure: 0 wherein m is from 2 to 7, R° R7 Rim where multiple dimer acids and polyamines are added to the furanyl Mannich base moiety. R4 has a maximum of 500 carbon atoms, therefore the number of carbon atoms in each repeating unit will also impact the maximum value of m. ;Dimer acids are bio-based and may thus be used in conjunction with bio-based polyamines to provide 100% bio-based curing agents. Polyamide side chains derived from dimer acids and polyamines can contribute towards increased flexibility, toughness, and hydrophobic character of the resulting phenalkamine. These properties can be further fine-tuned by adjusting the length, and number of repeating units of the polyamide side chain. ;During the fatty acid dimerisation process, trimer acids are also produced. Most commercially available dimer acids therefore also comprise some degree of trimer acids. Trimer acids are trimeric fatty acids which thus contain three carboxylic acid groups, and may contain unsaturation and/or cyclisation, such as alkene, cycloalkyl, cycloalkenyl and/or aryl groups as a result of the trimerisation reaction. When such a mixture of dimer acids and trimer acids are used to prepare an R4 group as discussed above, trimer acid derived repeating units may also be present. ;For example, a repeating unit comprising a trimer acid and a polyamine may have the structure: wherein R6 is independently a trivalent -021 to 069 hydrocarbyl-group, optionally comprising one or more alkenyl, cycloalkyl, cycloalkenyl, or aryl portion; preferably a trivalent -C36 to C57 hydrocarbyl-group, optionally comprising one or more alkenyl, cycloalkyl, cycloalkenyl, or aryl portion; most preferably a trivalent -Csi hydrocarbyl-group, optionally comprising one or more alkenyl, cycloalkyl, or cycloalkenyl portion; and R7 and L1 may be as defined hereinabove. As would be appreciated, when the carboxylic acid carbons are included, a C8 fatty acid will trimerise to provide an R8 group having a trivalent -021 hydrocarbyl-group, and a C24 fatty acid will dimerise to provide an R8 group having a divalent -069 hydrocarbyl-group. In this way, IR8 groups having various numbers of carbon atoms may be provided by trimerisation of the appropriate monomeric fatty acids, or combinations thereof. ;R4 may have the structure: R7 R' wherein R', R8, and L1 are as defined hereinabove. ;R4 may have a co-oligomeric structure comprising a combined total of m repeating units of; 0 terminated by J.., Li)2.2._, R7 RVand hydrogens, wherein m, R6, R7, R8, and L1 are as defined hereinabove. ;Any combination of the R4 groups described hereinabove, may exist in a single compound of formula (1). For the avoidance of doubt, each represents the attachment point between a repeating unit and the reminder of the compound of formula (1), an adjacent repeating unit, or a terminating hydrogen. ;In a second aspect, the present invention provides a method of preparing a Mannich base, the method comprising performing a Mannich reaction using: i) a phenolic compound substituted with one to four R1 groups; H) a furaldehyde optionally substituted with one to three R3 groups; and iii) an active amine; wherein R1, R2, and R3 are as defined hereinbelow. ;The method of preparing a Mannich base comprises three starting materials. Firstly, the phenolic compound substituted with one to four R1 groups. Each R1 is independently selected from: -Ci to Czo alkyl, to Czo haloalkyl, -03 to Czo cycloalkyl, -02 to C20; alkenyl, -02 to Czo alkynyl, to 020 alkyl-C3 to 010 cycloalkyl, to Czo alkyloxy, -C, to Czo alkylamino, -OH, -0R2, -NHz, -NHR2, -NR22, -C(0)0H, -C(0)0R2, -C(0)NH2, O(CO)H, -0(CO)R2, -NH(CO)H, -NH(CO)R2, -NR2(CO)H, -NR2(CO)R2, -SH, -SR2, S021-1, -SO2R2, -SO3R2, -SO3H, -SiR23, -NO2, -CN, -F, -CI, -Br, and -I; and each R2 is independently selected from: -C, to Czo alkyl, to Czo haloalkyl, -03 to Czo cycloalkyl, - 02 to Czo alkenyl, -02 to Czo alkynyl, -Ci to Czo alkyl-C3 to 010 cycloalkyl, -C, to C20 alkoxy, and to Czo alkylamino. ;This phenolic compound comprises a phenolic core, substituted with 1 to 4 substituents defined as R1. Each R1 group may be the same or different. An R1 group may be present at any one of the 2-, 3-, 4-, 5-and/or 6-positions relative to the phenolic -OH group. Preferably, the phenolic compound is substituted with one to three R1 groups, more preferably one to two R1 groups, even more preferably one R1 group. ;It is additionally advantageous that one or more R1 group is an activating group. It is also advantageous that R1 groups, preferably activating R1 groups, are present at the 3-, 5-or the 3-and 5-position relative to the phenolic -OH. ;Preferably each R1 is independently selected from: to Czo alkyl, -C3 to C20 cycloalkyl, -02 to C20 alkenyl, -02 to Czo alkynyl, to Czo alkyl-C3 to Cio cycloalkyl, to 020 alkyloxy, to C20 alkylamino, -OH, -OR2, -NH2, -NHR2, -NR22, -O(CO)H, -O(CO)R2, -NH(CO)H, -NH(CO)R2, -NR2(CO)H, -NR2(CO)R2, -SH, -SR2, and -SiR23; and each R2 is independently selected from: -Ci to Czo alkyl, -03 to Czo cycloalkyl, -02 to Czo alkenyl, -02 to 020 alkynyl, -C, to Czo alkyl-C3 to Clo cycloalkyl, to Czo alkoxy, and to 020 alkylamino. ;More preferably each R1 is independently selected from: -C1 to Czo alkyl, -03 to 020 cycloalkyl, -02 to Czo; alkenyl, -02 to Czo alkynyl, -C1 to Czo alkyl-C3 to am cycloalkyl, -C1 to 020 alkyloxy, -C1 to 020 alkylamino, -OH, -OR2, -NH2, -NHR2, and -NR22; and each R2 is independently selected from: -C1 to C20 alkyl, -C3 to C20 cycloalkyl, -02 to C20 alkenyl, - 02 to C20 alkynyl, -C, to Czo alkyl-C3 to 010 cycloalkyl, to Czo alkoxy, and -C, to C20 alkylamino. ;Even more preferably each R1 is independently selected from: -Ci to Czo alkyl, -02 to Czo; alkenyl, -OH, -OR2; and each R2 is independently -01 to C20 alkyl. ;Preferably, the phenolic compound substituted with one to four RI groups is bio-based. Some examples of suitable phenolic compound substituted with one to four R1 groups are shown in Table 1 above. ;The second starting material is a furaldehyde optionally substituted with one to three R3 groups. When present, each R3 is independently selected from: -Ci to C20 alkyl, to C20 haloalkyl, -03 to Czo cycloalkyl, -02 to Czo alkenyl, -02 to Czo alkynyl, -OH, -NH2, -001 to 020 alkyl, -NHCi to C20 alkyl, -N(Ci to C20 alky1)2, -NO2, -CN, -F, -CI, -Br, and -I. ;Preferably, each R3 is independently selected from: -Ci to 06 alkyl, to C6 alkoxy, to C6 alkyloxy, and -OH; preferably -CH3, -CH2OH, or -CH2OCH3. ;Preferably, the furaldehyde is not substituted, i.e. is substituted only by hydrogen. Nevertheless, the furaldehyde may be substituted with one to three R3 groups, preferably one to two R3 groups, more preferably one R3 group. Typically, wherein one R3 group is present, the R3 group is attached at the available position ortho to the furan oxygen, i.e. the furan 5-position. ;A combination of furaldehydes optionally substituted with one to three R3 groups may also be used, for example, a combination of substituted and unsubstituted furaldehydes, or a combination of furaldehydes having different substituents. ;The third starting material is an active amine. The active amine must contain at least one primary or secondary amine group (i.e. an active amine group) in order to undergo the Mannich reaction, although it is otherwise not particularly limited in scope. Preferably, the active amine comprises at least two active amine groups. ;Preferably, the active amine has the formula HR5N-L-R4, wherein L, R4, and R5, are as described in relation to the first aspect, or any specific examples described in relation thereto. In such a case, the resulting Mannich base is a Mannich base of formula (1). In such a case, each R4 is independently selected from: hydrogen, or a hydrocarbyl group containing 1 to 500 carbon atoms; each L is independently either a direct bond or a hydrocarbyl linker comprising 2 to 100 carbon atoms, and 1 to 10 amine groups; and each R5 is independently selected from: hydrogen, or a hydrocarbyl group containing 1 to 50 carbon atoms; optionally wherein R5 is bonded to L such that the HNR5-L-moiety forms a group comprising a -4-to 14-membered heterocycle-; and optionally, wherein L is a direct bond, R4 and R5 are be bonded to each other such that the HNR4R5 moiety forms a group comprising a -4-to 14-membered heterocycle-. The active amine preferably has the formula HR5N-L-R4, wherein L, R4, and R5 are as defined in the first aspect and any of the specific examples described in relation thereto. ;Typically, performing the Mannich reaction will involve reacting the starting materials in a stoichiometric ratio. The furaldehyde optionally substituted with one to three R3 groups and the active amine are typically used in a 1:1 molar ratio, although optionally, the ratio may range from 1:1.5 to 1.5:1. The ratio of the phenolic compound substituted with one to four R1 groups to the furaldehyde optionally substituted with one to three R3 groups, and of the phenolic compound substituted with one to four R1 groups to the active amine will depend on the number of furanyl Mannich base moieties that are desired on the Mannich base to be prepared. ;Typically, the ratio of the phenolic compound substituted with one to four R1 groups to the furaldehyde optionally substituted with one to three R3 groups, and of the phenolic compound substituted with one to four R1 groups to the active amine will be 1:(1 x number of furanyl Mannich base moieties). If two furanyl Mannich base moieties are intended then the ratio of the phenolic compound substituted with one to four R1 groups to the furaldehyde optionally substituted with one to three R3 groups, and of the phenolic compound substituted with one to four IR1 groups to the active amine will be 1:2. ;If three furanyl Mannich base moieties are intended then the ratio of the phenolic compound substituted with one to four R' groups to the furaldehyde optionally substituted with one to three R3 groups, and of the phenolic compound substituted with one to four R1 groups to the active amine will be 1:3. However, optionally, the ratio of either the phenolic compound substituted with one to four IR1 groups to the furaldehyde optionally substituted with one to three R3 groups, or of the phenolic compound substituted with one to four IR' groups to the active amine may range from 1.5:(1 x number of furanyl Mannich base moieties) to 1:(2 x number of furanyl Mannich base moieties). Additionally, where it is intended to prepare a Mannich base having differing furanyl Mannich base moieties, different furaldehyde optionally substituted with one to three R3 groups and/or different active amines may be used in the corresponding ratios. ;Typically, the active amine and the furaldehyde optionally substituted with one to three R3 groups are reacted prior to addition of the phenolic compound substituted with one to four R1 groups. This is so that the imine/iminium ion is pre-formed before reaction with the phenolic compound. Although alternatively, all three precursors may be reacted simultaneously. ;Typically, the reaction temperature is maintained at 90 °C or lower, preferably 80 °C or lower, more preferably 70 °C or lower, even more preferably 60 °C or lower during addition of the active amine to the furaldehyde optionally substituted with one to three R3 groups, or addition of the furaldehyde optionally substituted with one to three R3 groups to the active amine. This is useful to control the exotherm that is generated upon mixing/reaction/solvation, particularly at a large scale. Preferably, the furaldehyde optionally substituted with one to three R3 groups is added to the active amine over the course of from 20 minutes to 2 hours, although the ideal addition time will vary depending on scale. The active amine may be neat, or may be dissolved in a suitable solvent. The furaldehyde may be added neat or as a solution. ;Typically, active amine and the furaldehyde optionally substituted with one to three R3 groups are reacted at 60 °C or higher once addition is complete. Preferably, this stage is continued for at least 30 minutes, preferably at least 60 minutes, more preferably at least 90 minutes. ;Typically, once reaction of the active amine and the furaldehyde optionally substituted with one to three R3 groups is complete, the reaction mixture is cooled to 60 °C or lower, preferably 50 °C or lower, more preferably 40 °C or lower, before adding the phenolic compound substituted with one to four R1 groups. ;Typically, the temperature is then increased to 100 °C or higher, preferably 110 °C or higher, more preferably 120 °C or higher upon or after addition of the phenolic compound substituted with one to four R1 groups. Typically, the reaction mixture is then maintained 100 °C or higher, preferably 110 °C or higher, more preferably 120 °C or higher for at least 60 minutes, preferably 120 minutes, more preferably 180 minutes, even more preferably 240 minutes, even more preferably 300 minutes, even more preferably 360 minutes, even more preferably 420 minutes. ;As would be appreciated, water is produced as a by-product of the Mannich reaction. Typically, this water will be removed, for example, by atmospheric distillation at 100 °C or higher. Although other methods of water removal are known to the skilled person. ;As would be appreciated, the optimum temperature and timings of the various stages of the reaction would depend on the specific starting materials used, as well as any other reaction conditions such as scale, solvent choice, or catalysis etc. A Lewis acid may be used to catalyse the Mannich reaction. ;It is advantageous that the active amine comprises at least two active amine groups. As would be appreciated, one active amine is required in order to undergo the Mannich reaction, and this active amine may be primary or secondary. A second active amine is useful for further reaction to take place. The further active amine may be useful for reacting with the epoxy groups of epoxy resins, for causing crosslinking in an epoxy resin. Additionally, the further active amine may be useful as a site for further reactivity, for example, for introducing an R4 group. Alternatively, the active amine may comprise one or more additional active amine groups which are protected by a suitable protecting group, which may subsequently be deprotected to provide one or more additional active amine groups on the final product. Such protecting group strategy is within the capability of the skilled person. ;Preferably, the method of the present invention comprises the subsequent step of reacting one or more carboxylic acids with one or more active amine groups present on the Mannich base compound prepared by the method of the present invention, to form one or more amide groups. Preferably wherein the fatty acid is a C4 to C28 fatty acid, more preferably a C6 to C24 fatty acid, even more preferably a C8 to 020 fatty acid. ;Preferably, the method of the present invention comprises the subsequent steps of: i) reacting one or more dimer acids and/or trimer acids with one or more active amine groups present on the Mannich base compound prepared by the method of the present invention, to form one or more amide groups; and ii) reacting one or more polyamines having at least two active amine groups, with one or more carboxylic acid groups derived from the dimer acid and/or trimer acid to form one or more second amide groups. ;More preferably, this method further comprises the subsequent steps of: iii) reacting one or more further dimer acids and/or trimer acids with one or more active amine groups present on the Mannich base compound comprising one or more second amide groups, to form one or more further amide groups; iv) reacting one or more further polyamines having at least two active amine groups, with one or more carboxylic acid groups derived from the further dimer acids and/or trimer acids to form one or more further amide groups; and v) optionally repeating steps iii) and iv) one or more times, preferably from one to five more times. ;Preferably, the one or more dimer acids and further dimer acids independently have the structure HOOC-R6-000H, and the one or more trimer acids and further trimer acids independently have the structure HOOC-R8-(000H)2; wherein each R6 is independently a divalent -Cm to 046 hydrocarbyl-group, optionally comprising one or more alkenyl, cycloalkyl, cycloalkenyl, or aryl portion; preferably a divalent -024 to C38 hydrocarbylgroup, optionally comprising one or more alkenyl, cycloalkyl, cycloalkenyl, or aryl portion; most preferably a divalent -034 hydrocarbyl-group, optionally comprising one or more alkenyl, cycloalkyl, or cycloalkenyl portion; and wherein each R8 is independently a trivalent -021 to 069 hydrocarbyl-group, optionally comprising one or more alkenyl, cycloalkyl, cycloalkenyl, or aryl portion; preferably a trivalent -C36 to 057 hydrocarbylgroup, optionally comprising one or more alkenyl, cycloalkyl, cycloalkenyl, or aryl portion; most preferably a trivalent -051 hydrocarbyl-group, optionally comprising one or more alkenyl, cycloalkyl, or cycloalkenyl portion. Preferably, the one or more polyamines having at least two active amine groups and further polyamines having at least two active amine groups have the structure HNR7-L1-NR7H; wherein each 1_1 is a divalent hydrocarbyl linker comprising 2 to 50 carbon atoms; wherein each R7 is independently selected from hydrogen or a hydrocarbyl group containing 1 to 20 carbon atoms; preferably wherein R7 is hydrogen; optionally wherein one or both R7 groups is/are bonded to L1 such that one or both of the -NR7-L1-and -1_1-NR7-moieties form a group comprising a -4-to 14-membered heterocycle-; optionally wherein both R7 groups are bonded to each other such that the -NR7-L1-NR7-moiety forms a group comprising a -5-to 14-membered heterocycle-. More preferably wherein, any of R6, R7, R8, and L1 are as per any of the definitions used in the first aspect. ;In a third aspect, the present invention provides an epoxy resin curative composition comprising a compound of formula (1) or a Mannich base prepared or preparable by the method of the present invention. ;It has been found that the epoxy resin curative composition may usefully comprise further active amine compounds in order to adjust its properties to adapt the composition to a desired purpose. For example, properties such as the viscosity or active hydrogen equivalent weight may be adjusted by the presence of one or more further active amine compounds. It has also been usefully found that excess active amine can be used in the Mannich reaction during preparation of the compounds of the present invention and then unreacted active amine can be retained to adjust properties of the epoxy resin curative composition without the need for separation. This allows for a more efficient one pot preparation of such compositions. Nevertheless, separation of any excess active amine used in the Mannich reaction could be easily achieved by the skilled person, if desired. ;The epoxy resin curative composition may optionally further comprise any active amine compound described herein as suitable for use as an active amine or polyamine in any of the method steps described herein. ;Any suitable organic solvent may be used as a solvent or diluent in a resin composition of the present invention, for example MeCN, benzene, methanol, ethanol, IPA, butanol, chloroform, DCM, diethyl ether, DMF, dioxane, ethyl acetate, petroleum ether, kerosine, pentane, hexane, heptane, MTBE, NMP, THF, toluene, xylene and mixtures thereof. Toluene is a particularly suitable solvent or diluent for salicylamide Mannich base compounds and resins thereof of the present invention. As would be appreciated, methods of forming and handling a resin composition from a given compound would be known by the skilled person. ;Typically, the epoxy resin curative composition comprises less than 0.1 wt.% of free phenolic compound substituted with one to four R' groups. More preferably, the composition comprises less than 100 ppm, even more preferably less than 50 ppm, of free phenolic compound substituted with one to four R1 groups. The content of free phenolic compound substituted with one to four R1 groups may be reduced, or substantially eliminated, in the curative compositions according to the present invention through the use of an excess of the active amine and/or the furaldehyde optionally substituted with one to three R3 groups and/or through purification techniques, for instance distillation. ;In a fourth aspect, the present invention provides a method for preparing a cured epoxy resin, said method comprising: a) contacting an epoxy resin with a compound of formula (1), a Mannich base prepared or preparable by the method of the present invention; and b) forming a cured epoxy resin. ;Preferably the epoxy resin is selected from epoxidized novolacs and bisphenols (A or F) or halogenated analogues thereof. ;Examples of epoxy-based resins suitable for use in the present invention include polyglycidyl ethers of polyhydric phenols, epoxidised novolacs or similar glycidated polyphenolic resins, glycidated bisphenols, such as glycidated bisphenol A or F, or halogenated (e.g. chlorinated or fluorinated) analogues thereof; polyglycidyl ethers of alcohols, glycols or polyglycols, and polyglycidyl esters of polycarboxylic acids. Preferred examples of epoxy resins are polyglycidyl ethers of a polyhydric phenol. Polyglycidyl ethers of polyhydric phenols can be produced, for example, by reacting an epihalohydrin with a polyhydric phenol in the presence of an alkali. Examples of suitable polyhydric phenols include: 2,2-bis (4-hydroxyphenyl) propane (bisphenol-A); 2,2-bis(4-hydroxy-3-tert-butylphenyl)propane; 1,1-bis(4-hydroxyphenyl) ethane; 1,1- bis(4-hydroxyphenyl) isobutane; bis(2-hydroxy-1-naphthyl) methane; 1,5-dihydroxynaphthalene; 1,1-bis(4-hydroxy-3-alkylphenyl) ethane and the like. Commercial examples of preferred epoxy resins that may be used include EPILOK 60-600 (RTM). ;The epoxy resin to which the curative of the present invention is added may include other additives, such as flow control additives, antifoam agents, or anti-sag agents, as well as other additives such as pigments, reinforcing agents, fillers, elastomers, stabilizers, extenders, plasticizers, or flame retardants depending on the application. ;The epoxy resin can be any epoxy resin which can be cured by the compound of the present invention. Generally, the epoxy resin can be any curable epoxy resin and may have, for instance, a 1,2-epoxy equivalency greater than one and preferably, on average, more than 1.5 epoxide groups per molecule. The epoxy resin can be saturated or unsaturated, linear or branched, aliphatic, cycloaliphatic, aromatic or heterocyclic, and may be substituted, provided such substituents do not interfere with the curing reaction. Such substituents can include bromine. ;In a fifth aspect, the present invention provides a cured epoxy resin prepared, or preparable, by the method of the present invention. ;In a sixth aspect, the present invention provides the use of a compound of formula (1), a Mannich base prepared or preparable by the method of the present invention, or a composition of the present invention for causing crosslinking in an epoxy resin. ;The invention will now be described by reference to the following non-limiting Examples and the Figures. ;EXAMPLES ;Example 1 -Preparation and Analysis of Compound A 306 grams (3 mols) of cadaverine [pentane-1,5-diamine] was added to a 1 litre, round-bottomed flask equipped with a condenser, mechanical stirrer, addition funnel and thermometer. The flask was configured for atmospheric reflux and the agitator started. 288 grams (3 mols) of furaldehyde were added over 30 minutes maintaining the temperature below 90 °C with cooling and addition rate to control the exotherm. After 30 minutes the flask temperature was 87 °C and the contents was heated to 100 °C and held for 60 minutes before being cooled to 50 °C. 300 grams (1 mol) of cardanol was added and the contents heated to 100 °C and then held for 60 minutes. The flask was re-configured for atmospheric distillation and then heated to 135-140 °C over a period of 480 minutes. It was then held at 135-140 °C for 30 minutes before being cooled to <50°C, to provide compound A, shown below, compound A was transferred to a storage container and evaluated as follows. ;H2N N NH2 Compound A Physical test results Property Result Comments Appearance Medium viscosity liquid Very dark Colour [Gardner] 18 ;Viscosity at 25 °C 3.1 Pas Brookfield method ;The ability of compound A to cure an epoxy resin was also tested as set out below. The compound proved to have a rapid gel time with an industry standard epoxy resin. ;C15H31 -0, 2, 4, or 6 H2NWHN Reactivity tests AHEW (compound A) 95 Epoxy resin Bis phenol A diglycidyl ether EEW (epoxy resin) 185-190 g mo1-1 Mix ratio used 100:50 [weight] Mass 150 Grams Gel-time 31.4 minutes The bio-based carbon content of compound A is shown below. As can be seen, each of the cardanol, furaldehyde, and cadaverine starting materials are bio-based, and thus the resulting compound A is 100 % bio-based. ;Bio-based Carbon Content of Compound A Carbon Content Material Wt / g Mwt Formula Total Bio % bio-based Cardanol 300 300 C21H300 C21 21 100 Furaldehyde 288 96 C5H402 C5 5 100 Cadaverine 306 102 C5ki14N2 C5 5 100 Compound A 1:3:3 840 C51 F14204N6 C51 51 100 Figure 1 shows the viscosity (mPa*s) vs temperature (°C) of compound A. Figure 2 shows the dry times and cure times of compound A at 5 °C and 25 °C with an industry standard bisphenol A diglycidyl ether epoxy resin. As can be seen, compound A successfully cured the epoxy resin at both temperatures. After curing at 25 °C, the cured epoxy resin formed had a clear brown non-greasy film. After curing at 5 °C, the cured epoxy resin formed had a greasy surface.

Example 2 -Preparation and Analysis of Compound B 204 grams (2 mols) of cadaverine [pentane-1,5-diamine] was added to a 1 litre, round-bottomed flask equipped with a condenser, mechanical stirrer, addition funnel and thermometer. The flask was configured for atmospheric reflux and the agitator started. 192 grams (2 mols) of furaldehyde were added over 90 minutes maintaining the temperature below 60 °C with cooling and addition rate to control the exotherm. After 90 minutes the flask temperature was 57 °C and the contents was heated to 100 °C for 60 minutes before being cooled to <40 °C. 124 grams (1 mol) of guaiacol was added and the contents heated to 100 °C and then held for 60 minutes. The flask was re-configured for atmospheric distillation and heated to 120 °C over 150 minutes. It was then held at 120 °C for 60 minutes before being cooled to <40 °C, to provide compound B, shown below, compound B was transferred to a storage container and evaluated as follows.

Compound B Physical test results Property Result Comments Appearance Viscous black liquid Colour [Gardner] 18

Viscosity at 25 °C 27 Pas Brookfield method

The ability of compound B to cure an epoxy resin was also tested as set out below. The compound proved to have a rapid gel time with an industry standard epoxy resin.

Reactivity tests AHEW (compound B) 80 Epoxy resin Bis phenol A diglycidyl ether EEW (epoxy resin) 185-190 g mold Mix ratio used 100:42 [weight] Mass 150 Grams Gel-time 26.8 minutes The bio-based carbon content of compound B is shown below. As can be seen, each of the guaiacol, furaldehyde, and cadaverine starting materials are bio-based, and thus the resulting compound B is 100 % bio-based.

Bio-based Carbon Content of Compound B Carbon Content Material Wt / g Mwt Formula Total Bio Guaiacol 124 124 C7H802 C7 7 100 Furfural 192 96 C5H402 C5 5 100 Cadaverine 204 102 C51-114N2 05 5 100 Compound B 1:2:2 484 C27H4004N4 C27 27 100 Figure 3 shows the viscosity vs temperature of compound B. Figure 4 shows the dry times and cure times of compound B at 5 °C and 25 °C with an industry standard bisphenol A diglycidyl ether epoxy resin. As can be seen, compound B successfully cured the epoxy resin at both temperatures. After curing at 25 °C, the cured epoxy resin formed had a clear brown non-greasy film. After curing at 5 °C, the cured epoxy resin formed had a greasy surface.

Claims (24)

1. CLAIMS1. A compound of formula (1): (1) wherein each R1 is independently selected from: -C, to Czo alkyl, -Ci to Czo haloalkyl, -03 to 020 cycloalkyl, -02 to 020; alkenyl, -02 to 020 alkynyl, to 020 alkyl-C3 to Clo cycloalkyl, to 020 alkyloxy, -C, to 020 alkylamino, -OH, -0R2, -NH2, -NHR2, -NR22, -C(O)OH, -C(0)0R2, -C(0)NH2, -0(CO)H, -0(CO)R2, -NH(CO)H, -NH(CO)R2, -NR2(CO)H, -NR2(CO)R2, -SH, -SR2, -302H, -SO2R2, -SO3R2, -SO3H, -SiR23, -NO2, -CN, F, -CI, -Br, and -I; each R2 is independently selected from: -C, to Czo alkyl, to Czo haloalkyl, -03 to 020 cycloalkyl, -02 to Czo alkenyl, -02 to Czo alkynyl, to Czo alkyl-C3 to 010 cycloalkyl, to 020 alkoxy, and to Czo alkylamino; wherein each R3 is independently selected from: -Ci to Czo alkyl, to Czo haloalkyl, -03 to 020 cycloalkyl, -02 to 020 alkenyl, -02 to 020 alkynyl, -OH, -NH2, -001 to 020 alkyl, -NHCi to Czo alkyl, -N(Ci to Czo alky1)2, -NO2, -CN, -F, -CI, -Br, and -I; wherein each R4 is independently selected from: hydrogen, or a hydrocarbyl group containing 1 to 500 carbon atoms; wherein each L is independently selected from: a direct bond, or a hydrocarbyl linker comprising 2 to 100 carbon atoms and 1 to 10 amine groups; wherein each R5 is independently selected from: hydrogen, or a hydrocarbyl group containing 1 to 50 carbon atoms; optionally wherein R5 is bonded to L such that the -NR5-L-moiety forms a group comprising a -4-to 14-membered heterocycle-; or optionally, wherein L is a direct bond and R4 and R5 are bonded to each other to form a group comprising a -4-to 14-membered heterocycle-; wherein x = 1, 2, 3, or 4; wherein n = 1, 2, or 3; wherein each y = 0, 1, 2 or 3; with the proviso that x + n = 2 to 5; and with the proviso that the compound of formula (1) must comprise at least one amine group.
2. 2. The compound of Claim 1, wherein each R' is independently selected from: -C1 to Czo alkyl, -03 to 020 cycloalkyl, -02 to 020 alkenyl, -02 to 020 alkynyl, to 020 alkyl-C3 to Clo cycloalkyl, -C1 to Czo alkyloxy, -C1 to Czo alkylamino, -OH, -OR2, -NH2, -NHR2, -NR22, O(CO)H, -O(CO)R2, -NH(CO)H, -NH(CO)R2, -NR2(CO)H, -NR2(CO)R2, -SH, -SR2, and -SiR23; and each R2 is independently selected from: -C1 to Czo alkyl, -C3 to Czo cycloalkyl, -02 to C20 alkenyl, -02 to Czo alkynyl, to 020 alkyl-C3 to Clo cycloalkyl, -C1 to Czo alkoxy, and to 020 alkylamino.
3. 3. The compound of Claim 1 or Claim 2, wherein each R1 is independently selected from: -C1 to Czo alkyl, -03 to C20 cycloalkyl, -C2 to Czo; alkenyl, -C2 to Czo alkynyl, -C1 to C20 alkyl-C3 to C10 cycloalkyl, -C1 to 020 alkyloxy, to C20 alkylamino, -OH, -OR2, -NHz, -NHR2, and -NR22; and each R2 is independently selected from: 3-C1 to Czo alkyl, -C3 to Czo cycloalkyl, -02 to 020 alkenyl, -02 to Czo alkynyl, -C1 to 020 alkyl-C3 to Clo cycloalkyl, -C1 to Czo alkoxy, and -C1 to C20 alkylamino.
4. 4. The compound of any one of the preceding claims, wherein each R1 is independently selected from: -C, to Czo alkyl, -02 to Czo; alkenyl, -OH, -OR2; and each R2 is independently -C1 to 020 alkyl.
5. 5. The compound of any one of the preceding claims, wherein each R3 is independently selected from: to C6 alkyl, to C6 alkoxy, to C6 alkyloxy, and -OH; preferably -CH3, -CH2OH, or -CH2OCH3.
6. 6. The compound of any one of the preceding claims, wherein y = 0 or 1; preferably wherein y = 0.
7. 7. The compound of any one of the preceding claims, wherein x = 1, 2 or 3; preferably wherein x = 1 or 2, more preferably wherein x = 1.
8. 8. The compound of any one of the preceding claims, wherein the compound has the formula (1 a): R4 (1a) wherein y, R1, R2, R3, R4, R5, and L are as defined in any one of the preceding claims: preferably wherein R1 is -OH, -Ci to Czo alkyl, or -C2 to Czo, alkenyl; more preferably wherein R1 is -OH or -Cis alkyl or -Cm alkenyl.
9. 9. The compound of any one of Claims 1 to 7, wherein the compound has the formula (1 b): R4 (1 b) wherein y, R1, R2, R3, R4, R5, and L are as defined in any one of the preceding claims; preferably wherein R1 is -OMe.
10. 10. The compound of any one of Claims 1 to 7, wherein the compound has the formula (1c): R4OH/ \ (R3) (R3)y R4 R1 (1c) wherein y, R1, R2, R3, R4, R5, and L are as defined in any one of the preceding claims: preferably wherein R1 is -OH.
11. 11. The compound of any one of the preceding claims, wherein the compound has the formula (1d): (R3)y R4 (1d) wherein y, R1, R2, R3, R4, R5, and L are as defined in any one of the preceding claims: preferably wherein each R1 is independently selected from -OH, -Ci to Czo alkyl, or -C2 to C20; alkenyl; more preferably wherein either: both R1 groups are -OH; or one R1 group is -OH and the other is -C, to Czo alkyl, or -02 to 020; alkenyl, preferably -015 alkyl or -C15 alkenyl.
12. 12. The compound of any one of the preceding claims, wherein each L is a direct bond.
13. 13. The compound of any one of Claims 1 to 11, wherein each L is independently selected from: a hydrocarbyl linker comprising 2 to 50 carbon atoms and 1 to 5 amine groups, preferably wherein L is bonded to R4 via an amine; more preferably wherein each L is independently selected from: a straight chain -(CH2)2-SS-(CH2)2-NH-, -04 alkyl-NH-or -Cs alkyl-NH-, wherein the -NH-moiety is bonded to the R4 group.
14. 14. The compound of any one of the preceding claims, wherein each R4 is either hydrogen or a Ci to C500 hydrocarbyl group having one of the following structures: a) a -(CO)-C3 to 027 alkyl or alkenyl group, preferably a -(C0)-Cs to 023 alkyl or alkenyl group, more preferably a -(CO)-C7 to Cig alkyl or alkenyl group; b) -(C0)-R6-(C0)-NR'-L'-NR7H; d) a co-oligomeric structure comprising a combined total of m repeating units of; and, terminated by hydrogens: wherein each R6 is independently a divalent -C14 to 046 hydrocarbyl-group, optionally comprising one or more alkenyl, cycloalkyl, cycloalkenyl, or aryl portion; preferably a divalent -024 to 038 hydrocarbyl-group, optionally comprising one or more alkenyl, cycloalkyl, cycloalkenyl, or aryl portion; most preferably a divalent -034 hydrocarbylgroup, optionally comprising one or more alkenyl, cycloalkyl, or cycloalkenyl portion: wherein each L1 is a divalent hydrocarbyl linker comprising 2 to 50 carbon atoms; wherein each R7 is independently selected from hydrogen or a hydrocarbyl group containing 1 to 20 carbon atoms; preferably wherein R7 is hydrogen; optionally wherein one or both R7 groups is/are bonded to L1 such that one or both of the -NR'-L1-and -1_1-N R7-moieties form a group comprising a -4-to 14-membered heterocycle-; optionally wherein both R7 groups are bonded to each other such that the -NR'-L1-NR'-moiety forms a group comprising a -5-to 14-membered heterocycle-; wherein each R8 is independently a trivalent -C21 to C69 hydrocarbyl-group, optionally comprising one or more alkenyl, cycloalkyl, cycloalkenyl, or aryl portion; preferably a trivalent -C36 to Cs7 hydrocarbyl-group, optionally comprising one or more alkenyl, cycloalkyl, cycloalkenyl, or aryl portion; most preferably a trivalent -051 hydrocarbylgroup, optionally comprising one or more alkenyl, cycloalkyl, or cycloalkenyl portion; wherein each,AAAJ", represents the attachment point between a repeating unit and the reminder of the compound of formula (1), an adjacent repeating unit, or a terminating hydrogen; and wherein m is from 2 to 7.
15. 15. The compound of any one of the preceding claims, wherein each R5 is hydrogen.
16. 16. A method of preparing a Mannich base, the method comprising performing a Mannich reaction using: i) a phenolic compound substituted with one to four R1 groups; ii) a furaldehyde optionally substituted with one to three R3 groups; and Hi) an active amine; wherein R1, R2, and R3 are as defined in any one of Claims 1 to 15.
17. 17. The method of Claim 16, wherein the active amine and the furaldehyde optionally substituted with one to three R3 groups are reacted prior to addition of the phenolic compound substituted with one to four R1 groups.
18. 18. The method of Claim 17, wherein the active amine and the furaldehyde optionally substituted with one to three R3 groups are reacted at 60 °C or higher; and/or wherein the temperature is increased to 100 °C or higher upon or after addition of the phenolic compound substituted with one to four R1 groups.
19. 19. The method of any one of Claims 16 to 18, wherein the method comprises the subsequent steps of: i) reacting one or more dimer acids and/or trimer acids with one or more active amine groups present on the Mannich base compound prepared by the method of any one of Claims 16 to 18, to form one or more amide groups; and ii) reacting one or more polyamines having at least two active amine groups, with one or more carboxylic acid groups derived from the dimer acid and/or trimer acid to form one or more second amide groups.
20. 20. The method of Claim 19, further comprising the subsequent steps of: iii) reacting one or more further dimer acids and/or trimer acids with one or more active amine groups present on the Mannich base compound comprising one or more second amide groups, to form one or more further amide groups; iv) reacting one or more further polyamines having at least two active amine groups, with one or more carboxylic acid groups derived from the further dimer acids and/or trimer acids to form one or more further amide groups; and v) optionally repeating steps iii) and iv) one or more times.
21. 21. An epoxy resin curative composition comprising a compound of any one of Claims 1 to 15 or a Mannich base prepared or preparable by the method of any one of Claims 16 to 20.
22. 22. A method for preparing a cured epoxy resin, said method comprising: a) contacting an epoxy resin with a compound of any one of Claims 1 to 15, a Mannich base prepared or preparable by the method of any one of Claims 16 to 20, or a composition of Claim 21; and b) forming a cured epoxy resin, preferably wherein the epoxy resin is selected from epoxidized novolacs and bisphenols (A or F) or halogenated analogues thereof.
23. 23. A cured epoxy resin prepared, or preparable, by the method of Claim 22.
24. 24. Use of a compound of any one of Claims 1 to 15, a Mannich base prepared or preparable by the method of any one of Claims 16 to 20, or a composition of Claim 21 for causing crosslinking in an epoxy resin.