Epoxide-functionalized monomers having reversible bonds

Abstract

The present invention relates to the field of polymer chemistry, more particularly to new epoxy monomers containing multiple dynamic covalent bonds, to a synthetic process for its preparation. The invention also relates to the uses of the new epoxy monomers.

Description

[0001] Epoxide-functionalized monomers having reversible bonds

[0002] This application claims the benefit of European Patent Application 24383422.3 filed on December 20, 2024.

[0003] The present invention relates to the field of polymer chemistry, more particularly to new epoxy monomers containing multiple dynamic covalent bonds, to a synthetic process for its preparation. The invention also relates to the uses of the new epoxy monomers.

[0004] Background Art

[0005] Thermoset resins are widely utilized in coatings, sealants, adhesives, elastomers, composites, and other advanced materials due to their exceptional mechanical properties, thermal resistance, chemical stability, and adhesion to various substrates. Their versatility has made them indispensable in high-performance applications, such as in the aerospace, automotive, construction, and electronics industries.

[0006] However, one of the fundamental limitations of traditional thermoset resins lies in their irreversible crosslinked network. Once cured, conventional thermoset materials cannot be reshaped, reprocessed, or recycled. This lack of recyclability not only limits the end-of-life management of thermoset-based products but also contributes to growing environmental concerns. Waste from thermoset materials is typically either landfilled or incinerated, leading to resource inefficiency and increased carbon emissions.

[0007] Research into dynamic covalent chemistries has opened pathways for developing fully recyclable thermoset epoxy resins. Dynamic bonds include reversible noncovalent (e.g., hydrogen, TTTT, and metal-ligand bonds and covalent bonds (e.g., transesterification and dynamic disulfide [S-S]). Among these, the incorporation of disulfide bonds into the polymer network has gained significant attention. Disulfide bonds, characterized by the reversible S-S linkage, can undergo dynamic exchange reactions under suitable thermal or chemical conditions, thereby enabling the cleavage and reformation of crosslinks. This dynamic covalent chemistry permits reprocessing and recycling of the material while maintaining its mechanical and thermal properties. Studies have demonstrated that the introduction of disulfide bonds in epoxy resins can lead to networks with self-healing, reprocessability, and recyclability features. On the other hand, transesterification is a classical organic chemistry reaction that has been used on many different substrates for various applications. Transesterification has found great utility in polymer science and it has been employed to dynamic chemistry in sustainable polymers.

[0008] Despite the recent advances, there remains a need for new epoxy monomers that inherently possess multiple dynamic covalent bonds to enable improved material properties. Specifically, such monomers should facilitate enhanced reprocessability, recyclability, and tuneable properties without compromising the excellent performance typically associated with epoxy-based systems.

[0009] Accordingly, there is a need for innovative epoxy monomers that include multiple dynamic covalent bonds to provide versatile epoxy networks while maintaining structural integrity and processability.

[0010] Summary of Invention

[0011] Inventors have provided a new epoxide-functionalized monomer of formula (I) as defined below, having two different cleavable linkages or reversible bonds, a disulfide bond and ester moieties. It is also provided a process for the preparation of the epoxide- functionalized monomer of formula (I), and their uses, such as in the preparation of resins, coatings, adhesives, sealants, elastomers, and composites. Particularly, the inventors have provided a recyclable crosslinked composition which comprises an epoxide- functionalized monomer of formula (I) having two different cleavable linkages or reversible bonds and a crosslinking agent having an epoxide-reactive functional moiety. Particularly, the inventors have provided a recyclable crosslinked composition obtainable by a method that comprises mixing an epoxide-functionalised monomer of formula (I) as defined below, with a crosslinking agent having an epoxide-reactive functional moiety and optionally a catalyst; and curing the mixture thus obtained.

[0012] The inventors have demonstrated that a crosslinked composition obtainable by the process as described herein, has recyclable properties without compromising its physical and chemical properties.

[0013] The presence of two different cleavable linkages or reversible bonds in the epoxide- functionalized monomer compound of formula (I) of the present invention enhances its functionality, processability, and performance, which are critical for various applications. The presence of cleavable linkages or reversible bonds allow the resin to undergo controlled depolymerization or softening during processing. This facilitates better moldability and ease of handling during the manufacturing of prepregs and composites. Thus, according to a first aspect of the invention, it is provided an epoxide-functionalized monomer of formula (I) wherein any R1 and R2 are each independently selected from the group consisting of: -H, C1-C10- alkyl, Cs-Cs-aryl, -OR2, -CO-R3, -O-CO-R4, -SO-Rs, -NH-CO-R6, -COOR7, -NR8R9, - SR10, -NO2, and halogen; each R2, R3, R4, Rs, Re, R7, Rs, R9 and Rware independently selected from H, C1-C10- alkyl, and Cs-Cs-aryl; p and q are each independently an integer selected from 1 , 2, 3 and 4; m and n are each independently an integer selected from 1 , 2, 3 and 4; provided that p+m is 5 and q+n is 5.

[0014] The properties shown by the epoxy monomer of formula (I) of the present invention are based on the presence of two different reversible chemistries in its structure: i) an aromatic disulfide being dynamic by disulfide exchange reactions and ii) an ester being dynamic by transesterification reaction.

[0015] The second aspect of the invention relates to method for the preparation of a compound of formula (I) as defined in in the present invention, the process comprises reacting an epihalohydrin with a compound of formula (II) in the presence of at least one catalyst wherein R1, R2, p, q, m and n are as defined above; the reaction being performed, in any of the alternatives, at a temperature comprised from 10 to 150 °C and wherein the molar ratio between the epihalohydrin and the compound of formula (II) is from 1 to 200. The compound of formula (I) of the invention can also be defined by its preparation process. Thus, in an additional aspect the present invention provides an epoxide- functionalized monomer compound of formula (I) obtainable by the process of the invention described above.

[0016] The term "obtainable" and "obtained" have the same meaning and are used interchangeably. In any case, the expression "obtainable" encompasses the expression "obtained".

[0017] In a further aspect of the present invention, it is provided the use of an epoxide- functionalized monomer compound of formula (I) as defined herein in the preparation of resins, coatings, adhesives, sealants, elastomers or composites.

[0018] In a further aspect of the present invention, it is provided a crosslinked composition which comprises an epoxide-functionalized monomer compound of formula (I) according to the invention and at least one crosslinking agent having an epoxide-reactive functional moiety.

[0019] An additional aspect of the present invention relates to a process for the preparation of a crosslinked composition, the process comprising:

[0020] (i) mixing an epoxide-functionalized monomer compound of formula (I) of the invention, with a crosslinking agent having an epoxide-reactive functional moiety; and optionally at least one catalyst; and

[0021] (ii) curing the mixture obtained in step (i) at a temperature from 10 °C to 200 °C for a period of time such that the crosslinked epoxide resin composition reaches at least 25% of the maximum Tg value to obtain a crosslinked epoxy resin composition partially or totally cured.

[0022] The crosslinked composition of the invention can also be defined by its preparation process. Thus, in an additional aspect the present invention provides a crosslinked composition obtainable by the process of the invention as described above.

[0023] Depending on the different crosslinking agent having an epoxide-reactive functional moiety used in the preparation of the crosslinked composition, the resulting product may show different properties.

[0024] In another aspect, the invention relates to an article of manufacture made of the compound of formula (I) of the invention.

[0025] In still another aspect, the invention relates to a process for the manufacture of an article as defined above, the process comprising forming the article from the compound of formula (I) of the invention.

[0026] The resin compositions, composites, coatings, adhesives, elastomers or sealants obtained from the epoxide-functionalized monomer compound of formula (I) of the present invention can be designed to meet the specific needs of high-performance industries, including aerospace, automotive, and electronics.

[0027] Detailed description of the invention

[0028] All terms as used herein in this application, unless otherwise stated, shall be understood in their ordinary meaning as known in the art. Other more specific definitions terms as used in the present application are as set forth below and are intended to apply uniformly throughout the specification and claims unless an otherwise expressly set out definition provides a broader definition.

[0029] For the purposes of the invention, the expressions "obtainable", "obtained" and equivalent expressions are used interchangeably, and in any case, the expression "obtainable" encompasses the expression "obtained".

[0030] For the purposes of the present invention, any ranges given include both the lower and the upper endpoints of the range. Ranges given, such as temperatures, times, weights, and the like, should be considered approximate, unless specifically stated. The term "about" or “around” as used herein refers to a range of values ± 10% of a specified value. For example, the expression "about 0.5" or “around 0.5” includes ± 10% of 0.5, i.e. from 0.45 to 0.55.

[0031] The terms “percentage (%) by weight” or “% w / w” have the same meaning and are used interchangeably. The term “percentage by weight” refers to the percentage of an ingredient / component / compound in relation to the total weight of the final mixture / product / resin / composite. For instance, when referred to the crosslinked epoxy resin composition comprised in the matrix phase, is estimated determining the amount of the crosslinked epoxy resin composition with respect to the total weight of the matrix phase and the resulting value is multiplied by 100.

[0032] The term "alkyl" as used herein in the context of the present invention is to be understood as preferably meaning branched and unbranched alkyl, meaning e.g. methyl, ethyl, n- propyl, iso-propyl, n-butyl, iso-butyl, tert-butyl, sec-butyl, pentyl, isopentyl, hexyl, heptyl, octyl, nonyl and decyl and the isomers thereof. The term "halogen" or "halo" (e.g. in epihalohydrin) as used herein is to be understood as meaning fluorine, chlorine, bromine or iodine.

[0033] The term "aryl" as used herein refers to an aromatic, hydrocarbon, ring system, comprising from 5 to 8 carbon atoms, preferably from 5 or 6 carbon atoms. It is further understood that when said aryl group is substituted with one or more substituents, said substituent(s) may be at any positions on said aryl ring(s). Particularly, in the case of aryl being a phenyl group, said substituent(s) may occupy one or both ortho positions, one or both meta positions, or the para position, or any combination of these positions.

[0034] As used herein, the term "C1-C10", e.g. in the context of the definition of "Ci-Cw-alkyl”, is to be understood as meaning an alkyl group having a finite number of carbon atoms of 1 to 6, i.e. 1 , 2, 3, 4, 5, or 6 carbon atoms.

[0035] As it has been stated above, a first aspect of the present invention relates to epoxide- functionalized monomer compounds of formula (I) having two different cleavable linkages or reversible bonds, a disulfide bond and two ester moieties.

[0036] In accordance with some embodiments, p and q are each independently an integer selected from 1 and 2; and Ri and R2 are each independently selected from the group consisting of H, Ci-Ce-alkyl, Cs-Cs-aryl, -OR2, -SO-R5, -NRsRg, -SR10, -NO2, and halogen.

[0037] In some embodiments, p and q are 1 ; and R1 and R2 are H.

[0038] In some embodiments, p and q are 1 ; and the oxiran-2-ylmethyl acetate moieties are in ortho- position with respect to the disulfide.

[0039] In yet another embodiment, the epoxide-functionalized monomer compound is one of formula (la) As it has been stated above, a second aspect of the present invention relates to a process for the preparation of the epoxy-functionalized monomer compounds of formula (I) of the first aspect of the invention.

[0040] In some embodiments, the reaction is performed at a temperature comprising from 10 to 150 °C, preferably 20 to 120°C, more preferably from 50 to 110°C, being particularly preferred from 55 to 95 °C. Preferably, the reaction is performed at 80 °C.

[0041] In another embodiment of the second aspect of the invention, the reaction is performed for a period of time from 1 hours to 100 hours; preferably from 5 to 50 hours; more preferably from 8 to 36 hours; more preferably from 12 to 24 hours. Particularly preferred is about 18 hours.

[0042] In some embodiments of the second aspect of the invention, the reaction is performed at a temperature from 50 to 110 °C for a period of time from 5 hours to 50 hours. Preferably at a temperature from 55 to 95 °C for a period of time from 8 to 36 hours.

[0043] In a preferred embodiment, the reaction temperature is 80°C, and the period of time is about 18 hours.

[0044] In some embodiments, the reaction is performed in at least two steps, a first step at a temperature T1 for a period of time t1 , and a second step at a temperature T2 for a period of time t2; wherein T1 > T2 and t1 > t2.

[0045] In some embodiments, the reaction is performed in two steps, a first step at a temperature ranging from 55 to 95°C for a period of time of 8 to 36 hours; and a second step at a temperature from 20 to 50 °C for a period of time of 1 minute to 3 hours.

[0046] In a particular embodiment, the reaction is performed in two steps, a first step at a temperature of about 80 °C for a period of time of about 17 hours; and a second step at a room temperature for a period of about 30 minutes.

[0047] The reaction is preferably performed in a basic media.

[0048] Different catalysts are available to the skilled person in order to perform the reaction between the epihalohydrin and the compound of formula (II) as defined above. Illustrative non-limitative examples of catalysts are:

[0049] I. Metal-Based Catalysts

[0050] These catalysts efficiently activate oxidants, such as hydroperoxides, to transfer oxygen to substrates like epichlorohydrin, ensuring high selectivity and yield.

[0051] An illustrative non-limitative example of a metal-based catalyst is Titanium(IV) isopropoxide with tert-butyl hydroperoxide (TBHP).

[0052] II. Organocatalysts

[0053] Organic molecules promote regio- and stereoselective epoxidation, though they are less commonly used with epichlorohydrin.

[0054] An illustrative non-limitative example of an organocatalyst is Proline-derived imidazolidinones.

[0055] III. Enzyme-Based Catalysts

[0056] Enzymes like monooxygenases offer exceptional regio- and stereoselectivity for epoxidation under environmentally friendly conditions.

[0057] An illustrative non-limitative example of an enzyme-based catalyst is Cytochrome P450 monooxygenase.

[0058] IV. Quaternary Ammonium Salts (Phase-Transfer Catalysts)

[0059] These salts facilitate the interaction between aqueous oxidants and organic substrates, enabling efficient epoxidation of compounds like epichlorohydrin.

[0060] An illustrative non-limitative example of a quaternary ammonium salt is TEBAC (Triethylbenzylammonium chloride) with sodium hypochlorite.

[0061] V. Peracid Catalysts

[0062] Peracids act as direct oxygen donors, transferring oxygen efficiently to substrates like epichlorohydrin in a single step.

[0063] An illustrative non-limitative example of a peracid catalyst is MCPBA (meta- Chloroperbenzoic acid).

[0064] VI. Heterogeneous Catalysts

[0065] Solid catalysts, such as zeolites, are highly reusable and provide excellent selectivity in epoxidation reactions.

[0066] An illustrative non-limitative example of a heterogeneous catalyst is TS-1 (Titanium Silicalite-1) with hydrogen peroxide (H2O2).

[0067] VII. Peroxide-Based Catalysts

[0068] These catalysts activate peroxides like H2O2 to generate reactive oxygen species for the epoxidation of alkenes, including epichlorohydrin. An illustrative non-limitative example of a peroxide-based catalyst is Tungsten oxides (WOs) with H2O2.

[0069] VIII. Organic Nitroxyl Radicals

[0070] Nitroxyl radicals provide mild and selective oxidation, though they are less commonly applied to epichlorohydrin epoxidation.

[0071] An illustrative non-limitative example of an organic nitroxyl radical is TEMPO (2,2,6,6-Tetramethylpiperidin-1-oxyl).

[0072] IX. Photocatalysts

[0073] Light-activated catalysts promote green and sustainable epoxidation processes, often using UV or visible light.

[0074] An illustrative non-limitative example of a photocatalyst is Titanium dioxide (TiO2) under UV light.

[0075] X. Hypervalent Iodine Catalysts

[0076] These catalysts selectively transfer oxygen under mild conditions, making them useful for controlled epoxidation.

[0077] An illustrative non-limitative example of a hypervalent iodine catalyst is lodosylbenzene.

[0078] XI. Inorganic and organic bases such as NaOH, KOH, Na2CO3, DBU (2,3,4,6,7,8,9,10-octahydropyrimido[1,2-a]azepine), TBD (1,5,7- T riazabicyclo[4.4.0]dec-5-ene), etc.

[0079] In some embodiments, the catalyst is a quaternary ammonium salt; preferably the catalyst is selected from titanium(IV) isopropoxide with tert-butyl hydroperoxide (TBHP), prolinederived imidazolidinones, cytochrome P450 monooxygenase, TEBAC (triethylbenzylammonium chloride) with sodium hypochlorite, MCPBA (metachloroperbenzoic acid), titanium Silicalite-1) with hydrogen peroxide (H2O2), tungsten oxides (WO3) with H2O2, TEMPO (2,2,6,6-tetramethylpiperidin-1-oxyl), titanium dioxide (TiO2) under UV light, iodosylbenzene, NaOH, KOH, Na2CO3, DBU (2,3,4,6,7,8,9,10- octahydropyrimido[1,2-a]azepine), and TBD (1,5,7-Triazabicyclo[4.4.0]dec-5-ene).

[0080] Preferably, the catalyst is a quaternary ammonium salt catalyst; more preferably the catalyst is TEBAC (triethylbenzylammonium chloride) with sodium hypochlorite.

[0081] The reaction is performed in the presence of a catalytic or stoichiometric or excess amount of a catalyst. The amount of catalyst typically ranges from 0.001 w / w% to 2 w / w% based on the total weight of the reaction media.

[0082] In some embodiments, the molar ratio between the epihalohydrin and the compound of formula (II) is from 1 to 200; preferably from 1 to 60.

[0083] In accordance with some embodiments, in the compound of formula (II), p and q are each independently an integer selected from 1 and 2; and Ri and R2 are each independently selected from the group consisting of H, Ci-Ce-alkyl, Cs-Cs-aryl, -OR2, -SO-R5, -NRsRg, - SR10, -NO2, and halogen.

[0084] In some embodiments, in the compound of formula (II), p and q are 1 ; and R1 and R2 are H.

[0085] In some embodiments, in the compound of formula (II), p and q are 1 ; and the -COOH moieties are in ortho- position with respect to the disulfide.

[0086] In yet another embodiments, the compound is one of formula (Ila)

[0087] In some embodiments, the epihalohydrin is epichlorohydrin.

[0088] In another embodiment of the second aspect of the invention, the process comprises reacting an epihalohydrin with a compound of formula (Ila), in the presence of at least one catalyst, at a temperature comprised from 10 to 150°C for a period of time from 1 hours to 100 hours.

[0089] In a particular embodiment of the second aspect of the invention, the process comprises reacting epichlorohydrin with the compound of formula (Ila), in the presence of a quaternary ammonium salt catalyst, at a temperature from 55 to 95 °C, preferably of 80°C, for a period of time from 8 to 36 hours, preferably from 12 to 24 hours, more preferably of about 18 hours.

[0090] As it has been stated above, an aspect of the present invention relates to the use of the epoxide-functionalized monomer compound of formula (I) of the invention in the preparation of resins, coatings, adhesives, sealants, elastomers or composites. An example of the multiple applications of the epoxide-functionalized monomer compounds of formula (I) of the present invention is in the preparation of epoxy resin compositions. Thus, as it has been stated above, the present invention provides an epoxy resin composition which comprises an epoxide-functionalized monomer of formula (I), or preferably of formula (la), as defined above, and a crosslinking agent having an epoxidereactive functional moiety.

[0091] The epoxy resin compositions of the present invention are recyclable, reprocessable and reparable. For the purpose of the present invention, the term “reprocessable” is to be understood as that the epoxy resin composition and composites / articles containing it are capable of changing its form, applying pressure and heat. The selection of specific pressure and heat conditions will depend on the specific nature of the material and shape of the final part. Forms part of the routine tasks of the skilled person in the art the selection of appropriate pressure and heat conditions. For the purpose of the present invention, the term “recyclable” is to be understood as that the epoxy resin composition of the present invention is separated and recovered from the reinforcement material of the composites / prepreg / articles containing it without altering its chemical and physical properties and being appropriate for its re-use. For the purpose of the present invention, the term “reparable” is to be understood as that the epoxy resin composition and composites / articles containing it are capable of restoring the initial shape / form after suffering a damage, applying pressure and heat. The selection of specific pressure and heat conditions will depend on the extension and severity of the caused damage, as well as the specific nature of the material and shape of the final part. Forms part of the routine tasks of the skilled person in the art the selection of appropriate pressure and heat conditions.

[0092] In the present invention, the term “resin” means any polymer, oligomer or monomer comprising two or more epoxide groups. In the present invention, the term “polymer” means a molecule of high relative molecular mass, the structure of which essentially comprises the multiple repetition of units derived, actually or conceptually, from molecules of low relative molecular mass. In the present invention, the term “oligomer” means a molecule of intermediate relative molecular mass, the structure of which essentially comprises a small plurality of units derived, actually or conceptually, from molecules of lower relative molecular mass. And, in the present invention, the term “monomer” means a molecule which can undergo polymerization, thereby contributing constitutional units to the essential structure of a macromolecule.

[0093] The term “crosslinks” refers to bonds that link one polymer chain to another or different parts of the same polymer and these bonds can be covalent bonds. As used herein, a “crosslinking agent” refers to a compound containing at least one epoxide-reactive functional moiety, which can participate in curing reactions and form a network structure, thereby improving the characteristics of the prepared material, such as the glass transition temperature (Tg). The person skilled in the art knows suitable crosslinking agents having at least one epoxide-reactive functional moiety.

[0094] Illustrative non-limitative example of epoxy resin’s crosslinkers are: i. Amines

[0095] • Aliphatic Amines: These are fast-curing hardeners used for general-purpose epoxy applications. They provide good strength and chemical resistance but may yellow with UV exposure. o Illustrative non-limitative example of aliphatic amine is Triethylenetetramine (TETA) - Commonly used in adhesives and coatings, offering strong cure and moderate heat resistance.

[0096] • Aromatic Amines: Provide high-temperature resistance and excellent mechanical properties, often used in industrial and structural applications. o Illustrative non-limitative example of aromatic amine are 4,4'- methylenebis(2-isopropyl-6-methylaniline) (MDEA)- and 4,4'- methylenedianiline (MDA). - Known both for them high thermal resistance, ideal for structural applications

[0097] • Cycloaliphatic Amines: Offer a balance between aliphatic and aromatic properties, providing good clarity and UV resistance. o Illustrative non-limitative example of Cycloaliphatic amine is Isophorone diamine (IPDA) - Frequently used in coatings and adhesives for its UV stability and resistance to yellowing. ii. Amides

[0098] • Amides, particularly polyamides, are a recognized type of epoxy hardener (as covered earlier). Beyond polyamides, simple amides or functionalized amides can play specialized roles: o Illustrative non-limitative example of amide is Acrylamide - Occasionally used in UV-curable systems.

[0099] • Polyamides: Derived from dimer acids, they provide excellent flexibility, impact resistance, and moisture resistance. Commonly used in marine and protective coatings. o Illustrative non-limitative example of polyamide is Versamid 140 (by Henkel) - Used in marine coatings and protective applications, providing good moisture resistance and flexibility. iii. Alcohols

[0100] • Alcohols are not the most common primary hardeners but may serve as reactive diluents or co-curing agents in epoxy systems. They react with the epoxy resin to modify its properties. o Illustrative non-limitative example of alcohol is Glycidol - A hydroxylcontaining compound that reacts with epoxy groups. iv. Anhydrides

[0101] • Aliphatic Anhydrides: Offer high chemical resistance and good flexibility, often used in electrical and electronics applications. o Illustrative non-limitative example of aliphatic anhydride is Hexahydrophthalic anhydride (HHPA) - Commonly used in electrical applications for its insulation properties and chemical resistance.

[0102] • Aromatic Anhydrides: Provide high thermal stability and are used in high- temperature applications. o Illustrative non-limitative example of aromatic anhydride is Phthalic anhydride - Used in adhesives and composites that require high thermal stability. v. Thiols (also known as Mercaptans)

[0103] Very fast-curing hardeners, allowing for rapid set times even at low temperatures. Often used for adhesives and coatings where quick curing is needed. o Illustrative non-limitative example of thiols is Ethylhexyl thiol - Known for quick curing, ideal for adhesives and sealants needing rapid roomtemperature set times.

[0104] • Polymercaptans

[0105] Similar to thiols but with multiple reactive thiol groups, used to achieve fast cure rates in applications like sealants and adhesives. o Illustrative non-limitative example of polymercaptans is Capcure 3-800 (by Gabriel Performance Products) - Used for fast-setting adhesives and sealants, particularly in applications where room-temperature curing is required. vi. Phenolic Hardeners

[0106] Provide excellent chemical and heat resistance. Often used in combination with other hardeners to improve chemical resistance and mechanical properties. o Illustrative non-limitative example of phenolic hardeners is Phenolic novolac resin - Common in high-temperature, chemical-resistant coatings and composites. vii. Latent Hardeners These hardeners remain inactive until a specific activation temperature is reached, providing long pot life and stability in storage. Used in applications where delayed curing is advantageous, such as pre-preg composites and adhesives. o Illustrative non-limitative example of latent hardeners is Dicyandiamide (DICY) - Stays inactive at room temperature for long pot life, used in epoxy prepregs and powder coatings until heat-activated. viii. Imidazoles

[0107] Act as accelerators or as primary hardeners in some cases, offering high curing efficiency at elevated temperatures and improving thermal stability. o Illustrative non-limitative example of imidazoles is 2-Methylimidazole - Often used as an accelerator in high-performance coatings for efficient curing at elevated temperatures. ix. Polyetheramine Hardeners

[0108] These are modified amines that provide enhanced flexibility, toughness, and chemical resistance, used in applications like coatings and adhesives that require impact resistance. o Illustrative non-limitative example of polyetheramine is Jeffamine D-230 (by Huntsman) - Provides flexibility and toughness, widely used in impactresistant coatings and adhesives. x. Acid-Activated Hardeners

[0109] Used in applications where low-temperature curing is required, often for industrial coatings and sealants. o Illustrative non-limitative example of acid-activated hardeners is Phenyl phosphonic acid - Common in industrial coatings for low-temperature curing applications.

[0110] Examples of amines suitable as epoxide crosslinking agents are given in the following, without, however, restricting the scope of the invention: 1,2-diaminoethane (ethylenediamine), 1,2-propanediamine, 1,3-propanediamine, 1,4-diaminobutane, 2,2- dimethyl-1 , 3-propanediamine (neopentanediamine), diethylaminopropylamine (DEAPA), 2-methyl-1 , 5-diaminopentane, 1,3-diaminopentane, 2,2,4- or 2,4,4-trimethyl-1 ,6- diaminohexane and mixtures thereof (TMD), 3-aminomethyl-3,5,5-trimethylcyclohexane (isophorone diamine, IPDA), 1,3-bis(aminomethyl)-cyclohexane (1,3-BAC), 1,2- bis(aminomethyl)cyclohexane, hexamethylenediamine (HMD), 1,2- and 1,4- diaminocyclohexane (1,2-DACH and 1,4-DACH), bis(4-aminocyclohexyl)methane (PACM), bis (4-amino-3-)methylcyclohexyl)methane (MACM), bis(4-amino-3,5- dimethylcyclohexyl)methane, diethylenetriamine (DETA), 4-azaheptane-1 , 7-diamine, 1 ,11-diamino-3, 6,9-trioxundecane, 1,8-diamino-3, 6-dioxaoctane, 1,5-diamino-methyl-3- azapentane, 1,10-diamino-4, 7-dioxadecane, bis(3-aminopropyl)amine, 1 ,13-diamino-4,7, 10-trioxatridecane, 4-aminomethyl-1 , 8-diaminooctane, 2-butyl-2-ethyl-1 , 5- diaminopentane, N, N-bis(3-aminopropyl)methylamine, triethylenetetramine (TETA), tetraethylenepentamine (TEPA), pentaethylenehexamine (PEHA), 1,3- benzenedimethanamine (m-xylylenediamine, mXDA), 1,4-benzenedimethanamine (p- xyylenediamine, pXDA), 5-(aminomethyl)bicyclo[[2.2.1]hept-2-yl]methylamine (NBDA, norbornane diamine), dimethyldipropylenetramine, dimethylaminopropylaminopropylamine (DMAPAPA), diethylmethylbenzenediamine (DETDA), 4,4'-diaminodiphenylsulfone (dapsone), mixed polycyclic amines (MPCA) (e.g. Ancamine 2168), dimethyldiaminodicyclohexylmethane (Laromin C260), 2,2-bis(4- aminocyclohexyl)propane, (3 (4),8(9)bis(aminomethyldicyclo[5.2.1.020.6]decane (mixture of isomers, tricyclic primary amines; TCD-diamine), 1,8-diamino-p-menthane, N- aminoethyl-piperazine (N-AEP), N-3-(aminopropyl)piperazine, piperazine, 4-aminophenyl disulfide, 2-aminophenyl disulfide, monoisopropanolamine (MIPA), toluene diamine (DETDA), 4,4'-Methylenedianiline (MDA).

[0111] Examples of imidazole compounds are imidazole, 1 -methylimidazole, 1 -ethylimidazole, 2- methylimidazole, 2-ethylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 2- phenylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenyl-4- methylimidazole, 1-benzyl-2-phenylimidazole, 1-benzyl-2-methylimidazole, 1-(2- aminoethyl)-2-methylimidazole, 1-(2-aminoethyl)-2-ethylimidazole, 1-(3- aminopropyl)imidazole, 1-(3-aminopropyl)-2-methylimidazole, 1-(3-aminopropyl)-2- ethylimidazole, 1 -(3-aminopropyl)-2-phenylimidazole, 1 -(3-aminopropyl)-2- heptadecylimidazole, 1-(3-aminopropyl)-2,4-dimethylimidazole, 1-(3-aminopropyl)-2,5- dimethylimidazole, 1 -(3-aminopropyl)-2-ethyl-4-methylimidazole, 1 -(3-aminopropyl)-2- ethyl-5-methylimidazole, 1-(3-aminopropyl)-4-methyl-2-undecylimidazole, and 1-(3- aminopropyl)-5-methyl-2-undecylimidazole. Among these compounds, particular preference is given to 1-(3-aminopropyl)imidazole (API).

[0112] In accordance with some embodiments, the crosslinking agent having an epoxide-reactive functional moiety is selected from triethylenetetramine (TETA), 4,4'-methylenebis(2- isopropyl-6-methylaniline) (MDEA), 4,4'-Methylenedianiline (MDA), monoisopropanolamine (MIPA), toluene diamine (DETDA), isophorone diamine (IPDA), acrylamide, glycidol, hexahydrophthalic anhydride (HHPA), phthalic anhydride, ethylhexyl thiol, , dicyandiamide (DICY), 2-methylimidazole, phenyl phosphonic acid, 4-aminophenyl disulfide, 2-aminophenyl disulfide. As it has been stated above, an aspect of the present invention relates to a process for the preparation of a crosslinked epoxy resin composition, the process comprising:

[0113] (i) mixing an epoxide-functionalized monomer of formula (I), or preferably of formula (la), as defined herein, with a crosslinking agent having an epoxide-reactive functional moiety; and optionally at least one catalyst; and curing the mixture obtained in step (i) at a temperature from 10 to 200 °C for a period of time such that the crosslinked epoxide resin reaches a glass transition temperature value which is equal to or higher than 40°C but equal to or lower than the maximum glass transition temperature.

[0114] In accordance with some embodiments, the process for the preparation of a crosslinked epoxy resin composition comprises:

[0115] (i) mixing an epoxide-functionalized monomer of formula (I) as defined in the claims, with a crosslinking agent selected from aliphatic amines, aromatic amines, cycloaliphatic amines, amides, alcohols, anhydrides, thiols, polymercaptans, phenolic hardeners, latent hardeners, imidazoles, and acid-activated hardeners; and optionally at least one catalyst; and

[0116] (ii) curing the mixture obtained in step (i) at a temperature from 10 °C to 200 °C for a period of time from 1 minute to 24 hours such that the crosslinked epoxide resin composition reaches the maximum Tg value to obtain a crosslinked epoxy resin composition totally cured.

[0117] As used herein, the term “maximum Tg” refers to the highest glass transition temperature a material can achieve, typically occurring when the material is fully crosslinked.

[0118] In accordance with some embodiments, the process comprises a curing step for a period of time from 1 minute to 24 hours, from 1 minute to 12 hours, from 1 minute to 180 minutes, from 1 minute to 120 minutes, from 1 minute to 100 minutes, from 3 minutes to 90 minutes, from 5 minutes to 60 minutes, from 10 minutes to 45 minutes.

[0119] In accordance with some embodiments, the process for the preparation of a crosslinked epoxy resin composition comprises:

[0120] (i) mixing an epoxide-functionalized monomer of formula (I) as defined in the claims, with a crosslinking agent selected from triethylenetetramine (TETA), 4,4'- methylenebis(2-isopropyl-6-methylaniline) (MDEA), 4,4'-Methylenedianiline (MDA), monoisopropanolamine (MIPA), toluene diamine (DETDA), isophorone diamine (IPDA), acrylamide, glycidol, hexahydrophthalic anhydride (HHPA), phthalic anhydride, ethylhexyl thiol, , dicyandiamide (DICY), 2-methylimidazole, phenyl phosphonic acid, 4-aminophenyl disulfide, 2-aminophenyl disulfide; and optionally at least one catalyst; and

[0121] (ii) curing the mixture obtained in step (i) at a temperature from 10 °C to 200 °C for a period of time from 1 minute to 12 hours such that the crosslinked epoxide resin composition reaches the maximum Tg value to obtain a crosslinked epoxy resin composition totally cured.

[0122] In the present invention, the term "curable" means that the composition is capable of being subjected to conditions which will render the composition to a cured or thermoset state or condition.

[0123] As used herein, the term "cured" or "thermoset" refers to resin or plastic compounds which in their final state as finished articles are substantially infusible and insoluble.

[0124] Thermosetting resins are often liquid at some stage in their manufacture or processing, which are cured by heat, catalysis, or some other chemical means. After being fully cured, thermosets cannot be resoftened by heat. Some plastics which are normally thermoplastic can be made thermosetting by means of crosslinking with other materials.

[0125] In the present invention, the term “curing” refers to the hardening of a mixture of an epoxide-functionalized compound and a crosslinking agent by chemical crosslinking. The curing reaction of epoxide is the process by which one or more kinds of reactants, i.e., an epoxide and one or more crosslinking (curing) agents with or without the catalysts are transformed from low-molecular-weight to a highly crosslinked structure. In the curing process, the resin viscosity drops initially upon the application of heat, passes through a region of maximum flow, and begins to increase as the chemical reactions increase the average length and the degree of cross-linking between the constituent resins. This process continues until a continuous 3-dimensional network of polymer chains is created, this stage is termed gelation. In terms of processability of the resin this marks an important watershed: before gelation, the system is relatively mobile, after it the mobility is very limited, the micro-structure of the resin and the composite material is fixed and severe diffusion limitations to further cure are created. Thus, in order to achieve vitrification in the resin, it is usually necessary to increase the process temperature after gelation. For the purpose of the invention, the term “vitrification” is the development of the glassy state of a compound or composition (such as the crosslinked resin composition) as the curing reaction increases and the glass transition temperature (Tg) reaches the curing temperature (Tcure). It means that vitrification occurs when the Tg and the Tcure are equal.

[0126] Furthermore, the present invention covers all possible combinations of particular and preferred groups described hereinabove.

[0127] In another aspect, the present invention provides an article manufactured with the compound of formula (I) of the first aspect of the invention.

[0128] Throughout the description and claims the word "comprise" and variations of the word, are not intended to exclude other technical features, additives, components, or steps. Furthermore, the word “comprise” encompasses the case of “consisting of”. Additional objects, advantages and features of the invention will become apparent to those skilled in the art upon examination of the description or may be learned by practice of the invention. The following examples are provided by way of illustration, and they are not intended to be limiting of the present invention. Furthermore, the present invention covers all possible combinations of particular and preferred embodiments described herein.

[0129] Examples

[0130] Example 1. Synthesis and characterization of the bis(oxiran-2-ylmethyl) 2,2'- disulfanediyldibenzoate (Bipoxy)

[0131] A 1 eq. of 2,2'-disulfanediyldibenzoic acid was dissolved in 10 eq. of epichlorohydrin (ECH). Then, 0.1 eq. of triethylbenzyl ammonium chloride (TEBAC) was added, and the mixture was allowed to react under stirring at 80 °C for 17 hours in air atmosphere. Subsequently, the mixture was cooled to room temperature. 2.7 eq. of NaOH dissolved in deionized distilled water (5M) and 0.1 eq. of TEBAC was added, and the mixture was allowed to continue reacting under stirring for 30 min. Finally, the product was extracted with ethyl acetate and dried with MgSC Then, ECH was removed under reduced pressure using a condenser connected to a vacuum pump, finally, bis(oxiran-2-ylmethyl) 2,2'-disulfanediyldibenzoate was obtained with a 92% yield.

[0132] An NMR spectrometer (TM 600) made by Bruker Ascend, MA was used to perform 1 H- NMR and 13C-NMR studies using CDCI3 as a solvent. The 1H-NMR and 13C-NMR spectra were recorded at 500 MHz and 100 MHz, respectively. 1 H-NMR (500 MHz, CDCI3,b): 8.18 (m,2H, Ar-H), 7.73 (m, 2H, Ar-H), 7.42 (m, 2H, Ar-H), 7.26 (m, 2H, Ar-H), 4.73 (dd, 2H.OCH2), 4.22 (dd, 2H.OCH2), 3.33 (m, 2H, CH in oxirane), 2.84 (dd, 2H.OCH2 in oxirane), 2.71 (dd,2H,OCH2in oxirane). 13C-NMR (100 MHz, CDCI3,b): 168.62 (Ar CO), 131.87 (Ar C), 127.35 (Ar CS), 125.57 (Ar C), 69.13 (OCH2), 49.57 (s, 2C,CHO in oxirane), 43.74 (s, 2C.CH2O in oxirane).

[0133] Example 2. Thermoset epoxy resin

[0134] Bis(oxiran-2-ylmethyl) 2,2'-disulfanediyldibenzoate (Bipoxy) (10 g) and 4,4’- methylenedianiline (MDA) (2.36 g) were fed into a 50 mL flask. The mixture was heated at 80 °C until the MDA was completely dissolved in the resin, while degassing by magnetic stirring under vacuum. Then, the mixture was poured onto a 1 mm thick mold and was allowed to cure at 80 °C for 60 minutes and then another 60 minutes at 130 °C. The obtained thermoset presents a Tg of 128 °C (determined by DSC). The curing process was also characterized by DSC measuring the total enthalpy of the system resulting in 202 J / g.

[0135] Example 3. Thermomechanical properties of epoxy resin

[0136] A TA Instruments DMA Q800 was the instrument utilized for thermomechanical experiments. For both experiments the sample plaques of Example 2 had an average size of 12.5 x 2 x 17.5 mm, and the method of deformation was a film cantilever beam. There was a 25 - 250 °C temperature range. Tracking changes in force and phase angle inside a linear viscoelastic region at a heating rate of 3 °C min-1 at a constant oscillation frequency (1 Hz) and amplitude (15 pm) was necessary to investigate temperaturedependent behavior. Through the temperature ramp the Tg and the modulus were characterized (142 °C and 12 MPa, respectively).

[0137] The same equipment was used for thermomechanical investigations. To perform tensile stress-relaxation experiments the samples were initially preloaded with a force of 1 x 10"3N in order to maintain their straightness. Stretching 1% of the specimens' length resulted in a deformation that lasted the whole test. The temperature used was 200 °C. The stress decrease was recorded, and the stress relaxation modulus was calculated. Using this data and applying the Maxwell's model for viscoelastic fluids, the relaxation times of the thermoset were obtained as the time required to relax 63% of the initial stress. In this case, the relaxation time at 200 °C was only 26 seconds. Mechanical properties of the epoxy resin

[0138] Tensile strength tests were performed according to ASTM 638 and stress vs. elongation curves were monitored.

[0139] The film obtained in Example 2 was laid up and reprocessed in a hot press at 200 °C and 40 bar for 5 minutes. A perfectly compacted film was obtained.

[0140] Example 6. Thermoset epoxy resin

[0141] Bis(oxiran-2-ylmethyl) 2,2'-disulfanediyldibenzoate (Bipoxy) (10 g) and 4,4’- methylenedianiline (MDA) (2.36 g) were fed into a 50 mL flask. The mixture was heated at 80 °C until the MDA was completely dissolved in the resin, while degassing by magnetic stirring under vacuum. Then, the mixture was poured onto a 1 mm thick mold and was allowed to cure at 150 °C for 20 minutes. The obtained thermoset presents a Tg of 128 °C (determined by DSC). The curing process was also characterized by DSC measuring the total enthalpy of the system resulting in 202 J / g.

[0142] Citation List

[0143] 1. Mat. Horiz. 2016, 3(3), 241-247

[0144] 2. Polymer 2016, 82, 319-326

[0145] 3. EP2949679

[0146] 4. W02024008671

[0147] 5. ISO 11357-2 standard

[0148] 6. ASTM D3171

[0149] 7. ASTM D2584

[0150] 8. ASTM 638

Claims

Claims1 . A compound of formula (I)wherein any R1 and R2 are each independently selected from the group consisting of: -H, C1-C10- alkyl, Cs-Cs-aryl, -OR2, -CO-R3, -O-CO-R4, -SO-Rs, -NH-CO-R6, -COOR7, -NR8R9, - SR10, -NO2, and halogen; each R2, R3, R4, Rs, Re, R7, Rs, R9 and Rware independently selected from H, C1-C10- alkyl, and Cs-Cs-aryl; p and q are each independently an integer selected from 1 , 2, 3 and 4; m and n are each independently an integer selected from 1 , 2, 3 and 4; provided that p+m is 5 and q+n is 5.

2. The compound of formula (I) according to claim 1 , wherein p and q are each independently an integer selected from 1 and 2; and R1 and R2 are each independently selected from the group consisting of H, Ci-Ce-alkyl, Cs-Cs-aryl, -OR2, -SO-Rs, -NR8Rg, - SR10, -NO2, and halogen; wherein R2, Rs, Rs, R9 and Rware as defined in claim 1.

3. The compound according to any of the claims 1-2 wherein p and q are 1 ; and R1 and R2 are H.

4. The compound according to any of the claims 1-3, wherein p and q are 1 ; and the oxiran-2-ylmethyl acetate moieties are in ortho- position with respect to the disulfide.

5. The compound according to any of the claims 1-3, which is one of formula (la)6. A process for the preparation of a compound of formula (I) as defined in any of the claims 1-5, the process comprises reacting an epihalohydrin with a compound of formula (II) in the presence of at least one catalystwherein Ri, R2, p, q, m and n are as defined in claim 1 ; the reaction being performed, in any of the alternatives, at a temperature comprised from 10 to 150 °C and wherein the molar ration between the epihalohydrin and the compound of formula (II) is from 1 to 200.

7. The process according to claim 6 wherein the catalyst is selected from quaternary ammonium salts8. The process according to any of the claims 6-7, which comprises reacting epichlorohydrin with a compound of formula (Ila)in the presence of at least one quaternary ammonium salt catalyst, at a temperature of 80°C for a period of time from 1 to 100 hours.

9. Use of an epoxide-functionalized monomer of formula (I) as defined in any of the claims 1-5 in the preparation of resins, coatings, adhesives, sealants, elastomers or composites.

10. A crosslinked composition comprising a compound according to any of the claims 1-4 and at least one crosslinking agent selected from aliphatic amines, aromatic amines, cycloaliphatic amines, amides, alcohols, anhydrides, thiols, polymercaptans, phenolic hardeners, latent hardeners, imidazoles, and acid-activated hardeners.

11. The thermoset composition according to any of the claims 8-9, wherein the crosslinking agent is selected from triethylenetetramine (TETA), 4,4'-methylenebis(2-isopropyl- 6-methylaniline) (MDEA), 4,4'-Methylenedianiline (MDA), monoisopropanolamine (MIPA), toluene diamine (DETDA), isophorone diamine (IPDA), acrylamide, glycidol, hexahydrophthalic anhydride (HHPA), phthalic anhydride, ethylhexyl thiol, , dicyandiamide (DICY), 2-methylimidazole, phenyl phosphonic acid, 4-aminophenyl disulfide, 2- aminophenyl disulfide.

12. A process for the preparation of a crosslinked epoxy resin composition, the process comprising:(i) mixing an epoxide-functionalized monomer of formula (I) as defined in any of the claims 1-5, with a crosslinking agent selected from aliphatic amines, aromatic amines, cycloaliphatic amines, amides, alcohols, anhydrides, thiols, polymercaptans, phenolic hardeners, latent hardeners, imidazoles, and acid-activated hardeners; and optionally at least one catalyst; and(ii) curing the mixture obtained in step (i) at a temperature from 10 °C to 200 °C for a period of time from 1 minutes to 24 hours such that the crosslinked epoxide resin composition reaches the maximum Tg value to obtain a crosslinked epoxy resin composition totally cured.

13. The process according to claim 12, wherein the crosslinking agent is selected from triethylenetetramine (TETA), 4,4'-methylenebis(2-isopropyl-6-methylaniline) (MDEA), 4,4'- Methylenedianiline (MDA), monoisopropanolamine (MIPA), toluene diamine (DETDA), isophorone diamine (IPDA), acrylamide, glycidol, hexahydrophthalic anhydride (HHPA), phthalic anhydride, ethylhexyl thiol, , dicyandiamide (DICY), 2-methylimidazole, phenyl phosphonic acid, 4-aminophenyl disulfide, 2-aminophenyl disulfide; and the curing step is for a period of time from 1 minute to 12 hours such that the crosslinked epoxide resin composition reaches the maximum Tg value to obtain a crosslinked epoxy resin composition totally cured.

14. An article of manufacture made of the compound of formula (I) as defined in any of the claims 1-5.

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