NL2034512B1

NL2034512B1 - Multifunctional imidazole esters as epoxy resin accelerators/curing agents

Info

Publication number: NL2034512B1
Application number: NL2034512A
Authority: NL
Inventors: Kumru Baris
Original assignee: Univ Delft Tech
Priority date: 2023-04-06
Filing date: 2023-04-06
Publication date: 2024-10-14
Also published as: WO2024210741A1

Abstract

The present invention is in the ﬁeld of organic macromolecular compounds, their prepara- tion, and compositions based thereon, in particular polycondensates containing more than one epoxy group per molecule, and compositions of epoxy resins. The invention in particular relates to a chemically decomposable thermoset material, in particular a ﬁbre reinforced polymer ther- moset material, a product comprising said material, and a method of degrading said chemically decomposable thermoset material.

Description

P100835NL00

Multifunctional imidazole esters as epoxy resin accelerators/curing agents

FIELD OF THE INVENTION

The present invention is in the field of organic macromolecular compounds, their prepara- tion, and compositions based thereon, in particular polycondensates containing more than one epoxy group per molecule, and compositions of epoxy resins. The invention in particular relates to a chemically decomposable thermoset material, in particular a fibre reinforced polymer ther- moset material, a product comprising said material, and a method of degrading said chemically decomposable thermoset material.

BACKGROUND OF THE INVENTION

In chemistry, a macromolecule is a very large molecule, that is, comprising a very large number of atoms chemically connected to one and another, forming one molecule. Sometimes these macromolecules comprise repeating elements, or combination of repeating elements; these are typically referred to as polymers or copolymers, respectively. Another well-known example is DNA, comprising basic nucleic acids. So it typically relates to a compound with thousands of bonded atoms. Macromolecules have physical properties that are typically different compared to smaller molecules. For instance, their relative insolubility in water and similar solvents.

An example of a polymer is a polycondensate, which is obtained by a polycondensation reaction, that is, monomers are attached to one and another by condensation, that is, release of a water molecule. Polycondensates are a species of plastics, which may have one or more of elas- tomeric, thermoset, vitrimeric, and thermoplastic properties. They can be of natural or synthetic origin. The term fiber refers to a continuous or discontinuous filament of one substance. Fibers are widely used and can be woven into threads and thread ends. They are commonly used to make other materials stronger, especially in terms of tension and torque, by holding together other materials such as polymers and polycondensates, to form composites. An example thereof is the use of such composites in aerospace structures and materials.

Fiber reinforced polymer composites are considered to be important structural materials, with a wide range of industrial application. Therein, fibers constitute lightweight and mechanical properties, whereas a polymer matrix provides structural integrity. In industry, the polymer ma- trix is typically a thermoset (crosslinked, non-re-processable, non-soluble) material, typically based on epoxy resins. Epoxy resins typically require multifunctional epoxy monomers, cured with multifunctional curing agent (typically amine based molecules), such as in an autoclave, in certain temperature-time programs. Addition of curing accelerators can lower the temperature and curing times thereof to provide energy efficiency. Due to their unique nature, composites perform well in structural applications (i.e. aerospace, automotive, marine, wind energy); how- ever, the end-of-life products may form an environmental problem. since thermosets are not sol- uble, fibers can not be separated from polymers, and as a consequence whole composites are be- ing piled up, such as in landfills, since there is no recylability option.

Ideally, recycling would rely on dissolving the polymer matrix to liberate fibers under mild conditions. For this, there have been some attempts, that is to design curing agents with degrada- ble backbones. This is however found to be a very critical design, since by introducing weak bonds as a result of such curing agents the mechanical properties of composites may be jeopard- ized. Recycling can be done by treating composite in special conditions, to break the crosslinks from degradable bonds, hence the polymer becomes soluble, and fiber-polymer separation can be achieved. So far, there is only one industrial product in the market to such an extent, however its synthesis relies on harsh synthetic conditions.

The present invention relates amongst others to a chemically decomposable thermoset ma- terial, and various aspects thereof, which overcomes one or more of the above disadvantages, without jeopardizing functionality and advantages.

SUMMARY OF THE INVENTION

The present invention relates in a first aspect to a chemically decomposable thermoset material, such as a composite material, in particular a fibre reinforced polymer thermoset mate- rial, comprising 10-90 wt.% of an epoxy resin, 0.1-5 wt.% of an epoxy resin curing agent or epoxy resin accelerator compound C or a reaction product thereof, wherein the compound C comprises a reaction product of at least two of an ester, a thioester, and an ether (E), further com- prising at least two aromatic heterocycle moieties (A), each aromatic heterocycle moiety individ- ually comprising at least two non-adjacent nitrogen atoms, and in between and attached to said at least two of an ester, a thioester, and an ether (E) and said heterocycle moieties (A) an intermedi- ate moiety (R), wherein the intermediate moiety is selected from an alkane, an alkene, an aro- matic compound, and combinations thereof, the compound having a schematic formula of A---E- -R---E---A, in particular with the proviso that no further epoxy resin curing agent or epoxy resin accelerator compound other than compound C is present, and 0-60 wt.% fibres, in particular 1-30 wt.%, more in particular 2-20 wt.%, in particular wherein fibres are selected from carbon fibres, glass fibres, nano-fibres, polymeric fibres, and combinations thereof. Thereto also a straightfor- ward product synthesis is shown (multifunctional imidazole esters). Imidazole ester formation per se is well known in organic chemistry literature, however, in so far as inventors are aware of, never accomplished from a composite perspective. In a one-step room temperature reaction, a library of multifunctional imidazole esters can be formed. These materials have e.g. two possible applications in epoxy systems based on the usage volume: 1) They can be used as curing acceler- ators to provide energy efficiency in curing; 11) when used as curing agent, composites can be re- cycled at room temperature with high efficiencies. The present material comprises various con- stituents, hence a thermoset material. These constituent materials have notably dissimilar chemi- cal or physical properties and are merged to create a material with properties unlike the individ- ual elements. Within the finished structure, the individual elements remain separate and distinct, distinguishing composites from mixtures and solid solutions. Said thermoset material can be de- composed, that is, substantially brought back to its initial constituents, by a chemical action, such as by providing suitable chemicals. One constituent is an epoxy resin, also referred to as poly- epoxide. The resin is typically a (chemical) condensation product of epoxide molecules. In the thermoset material a relatively small amount of compound C is present, or a reaction product thereof, typically acting as a curing agent, and/or an epoxy resin accelerator. The terms “ester”, “thioester”, “ether”, “aromatic”, “heterocycle”, “moiety”, “alkane”, “alkene”, and so on, have their usual chemical meaning. Compound C has a schematic formula of A---E---R---E---A, that is, moiety A is directly or indirectly linked to moiety E, moiety E is directly or indirectly linked to moiety R, moiety R is directly or indirectly linked to (second) moiety E, and (second) moiety

E is directly or indirectly linked to (second) moiety A. A link is typically provided by a chemical bond. In between moieties A—E and so on further moieties may be present, hence an indirect link. The direct or indirect link (chemical bond type typically) is represented by “- - -“. In case of a direct link the representation is equal to the standard chemical bond notation ‘-“; in case of fur- ther moieties M the link represents “-M-(M-};“, wherein p>0, such as pe[ 1-10]. The thermoset material further comprises fibres, in particular synthetic or semi-synthetic fibres. The present fi- bres are significantly longer than wide. The present fibres typically have a length of 1-100 cm, in particular 2-50 cm, such as 5-30 cm, and a width of 1-10000 um, in particular 10-2000 um, more in particular 50-1000 pm, such as 100-500 um. Examples of suitable synthetic fibre material are polyamides, such as nylon, aromatic polyamides, acrylic polyesters, such as PAN, polyesters, such as PET or PBT, polyolefins, in particular polyalkenes, more in particular C;-Cy alkenes, such as PP and PE, poly phenols, such as phenol-formaldehyde (PF), polyurethanes, polyvinyl chlorides (PVC), and PF fibres. In particular reinforcing fibres are considered. For instance, when the present compound is employed as accelerator, at low temperatures (below 70° C) cur- ing kinetics is determined by the curing agent employed. For example, when linear amines are utilized, curing starts at room temperature, which room temperature is provided by the curing agent. At higher temperatures, e.g. starting from 70°C, the present compound shows activity. In this case, compared to reference experiments using e.g. aromatic amines as curing agents, the present compound cures specimens on average at a 30°C lower temperature, which is energy ef- ficient. Alternatively, at same curing temperatures, curing is achieved 1.5 times faster compared to reference. When the present compound is used as curing agent, no curing takes place until 80°C, which is good for resin manufacturing. Starting from 80°C, curing takes place which can be accelerated by employing higher temperatures.

In a second aspect the present invention relates to a method of degrading the chemically decomposable thermoset material according to the invention, comprising subjecting the thermo- set material to an aqueous acidic environment with a pH of 2.5-6, in particular with a pH of 3-5, or to an aqueous basic environment with a pH of 8-11,5, in particular with a pH of 9-11, and sep- arating the fibres from the epoxy resin. By carefully selecting the constituents of the present ther- moset material said material can now be decomposed chemically. Therewith the constituents can be separated from one and another, and be reused, such as in a condensation reaction for the more chemical, epoxy, constituents, or by simple application of the fibres. The method of de- grading may be considered as relatively simple, also due to the selection of the constituents of the thermoset material. An acidic or basic environment, typical aqueous, and subjection of the thermoset material therein, during a subjection time, is found to be sufficient for degrading and obtaining the decomposed constituents.

In a third aspect the present invention relates to a use of the compound C or a reaction product thereof, wherein the compound C comprises a reaction product of at least two of an es- ter, a thioester, and an ether (E), further comprising at least two aromatic heterocycle moieties (A), each aromatic heterocycle moiety individually comprising at least two non-adjacent nitro- gen atoms, and in between and attached to said at least two of an ester, a thioester, and an ether (E) and said heterocycle moieties (A) an intermediate moiety (R), wherein the intermediate moi- ety 1s selected from an alkane, an alkene, an aromatic compound, and combinations thereof, the compound having a schematic formula of A---E---R---E---A, for recycling a thermoset material, or for fast curing of an epoxy-resin system, or for energy consumption reduction in an epoxy- resin forming reaction.

In a further aspect the present invention relates to a one step method of forming a com- pound C comprising providing an amount of ketone, the ketone comprising at least two aromatic heterocycle moieties, each aromatic heterocycle moiety individually comprising at least two non- adjacent nitrogen atoms, and in between and attached to said at least two aromatic moieties the ketone moiety, and combinations thereof, reacting the amount of ketone with at least one ester- forming or ether-forming or anhydride-forming compound, wherein the ester-forming or ether- forming or anhydride-forming compound is capable of forming at least two of esters and/or ethers, wherein the ester-forming or ether-forming or anhydride-forming compound is selected from polyols, polyacids, such as poly carboxylic acids, poly alcohols, poly aldehydes, molecules comprising at least one OH-group and one COOH group, and combinations thereof, at a reaction temperature, during a reaction time of at least 10 minutes, therewith forming an at least two of esters and/or ethers comprising compound.

In yet a further aspect the present invention relates to a product comprising compound C, wherein the compound C comprises a reaction product of at least two of an ester, a thioester, and an ether (E), further comprising at least two aromatic heterocycle moieties (A), each aromatic heterocycle moiety individually comprising at least two non-adjacent nitrogen atoms, and in be- tween and attached to said at least two of an ester, a thioester, and an ether (E) and said heterocy- cle moieties (A) an intermediate moiety (R), wherein the intermediate moiety is selected from an alkane, an alkene, an aromatic compound, and combinations thereof, the compound having a schematic formula of A---E---R---E---A, wherein the product is selected from a photo-resist, a transparent material, a thermo-hardened material, a thermoset material, a resin, a coating, a glass-fibre, an adhesive, a curing accelerator for an epoxy resin, a curing agent for an epoxy resin, a fibre reinforce composite, such as a fibre reinforced polymer composite, and a filling, such as a dental filling.

Thereby the present invention provides a solution to one or more of the above mentioned problems.

Advantages of the present description are detailed throughout the description.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates in a first aspect to a chemically decomposable thermo- set material.

In an exemplary embodiment of said chemically decomposable thermoset material 5 the epoxy resin is selected from glycidyl-based epoxy resins, from low molecular weight poly- mers comprising phenols and formaldehydes, such as novolacs, from biobased epoxies such as epoxidized resveratrol, isororbide, vanillin derivatives, cardanol oil, phloroglucinol, petroleum- derived epoxy in particular from tetraglycidyl methylene dianiline, triglycidyl p-aminophenol, and diglycidyl ester of hexahydrophtalic acid Therein, the hydroxy group may be derived from aliphatic diols, polyols (polyether polyols), phenolic compounds or dicarboxylic ac- ids. Phenols can be compounds such as bisphenol A and novolak. Polyols can be com- pounds such as 1,4-butanediol. Di- and polyols lead to glycidyl ethers. Dicarboxylic acids such as hexahydrophthalic acid are used for diglycide ester resins. Instead of a hydroxy group, also the nitrogen atom of an amine or amide can be reacted with epichlorohydrin.

In an exemplary embodiment of said chemically decomposable thermoset material the intermediate moiety (R) each individually is selected from polyols, polyacids, such as poly carboxylic acids, poly alcohols, poly aldehydes, molecules comprising at least one

OH-group and one COOH group, molecules comprising at least one SH-group and one

COOH group, and combinations thereof, in particular wherein the intermediate moiety (R) each individually comprises two OH-groups or two COOH groups.

In an exemplary embodiment of said chemically decomposable thermoset material the aromatic heterocycle moieties (A) is each individually selected from 5-7 ring aromatic moieties, in particular from 5- ring aromatic moieties.

In an exemplary embodiment of said chemically decomposable thermoset material the compound C is selected from in particular from multifunctional imidazole esters, in particular a di-ester of 1,1'-Carbonyldiimidazole (CAS 530-62-1), more in particular

Q O

“, : wl af 1 Tg pe

In an exemplary embodiment the present method of degrading further comprises re- covering the at least two aromatic heterocycle moieties (A), and optionally dissolving the epoxy resin in an organic solvent, in particular wherein the organic solvent is selected from dimethylformamide (DMF), dimethyl sulfoxide (DMSO), and

Dihydrolevoglucosenone (Cyrene)(CAS 53716-82-8).

In an exemplary embodiment of the present method of degrading subjecting is per- formed at a subjecting temperature is in the range of 10-40 °C, in particular at 15-30 °C, more in particular at 20-25 °C.

In an exemplary embodiment of the present method of degrading the subjection time is 1-48 hours, in particular 2-20 hours, such as 4-12 hours.

In an exemplary embodiment of the present one step method the reaction temperature is in the range of 10-40 °C, in particular at 15-30 °C, more in particular at 20-25 °C.

In an exemplary embodiment of the present one step method the reaction time is 1-20 hours, in particular 2-10 hours.

In an exemplary embodiment of the present one step method the reacting is in a solvent, wherein solvent is selected from ketones and aldehydes, in particular from Cz-Cs ketones and al- dehydes, more in particular from acetone, in particular a biobased solvent.

In an exemplary embodiment of the present one step method the ketone moiety is se- lected from C;-Csg ketones, in particular from C1-C3 ketones.

In an exemplary embodiment of the present one step method the ketone and the at least one ester-forming or ether-forming or anhydride-forming compound are provided in a molar ra- tio of 0.5:1 to 2:1, in particular in a molar ratio of 0.8:1 to 1.2:1, more in particular in a molar ra- tio of 0.95:1 to 1.05:1, such as in substantially equal molar amounts.

The invention is further detailed by the accompanying examples, which are exem- plary and explanatory of nature and are not limiting the scope of the invention. To the per- son skilled in the art, it may be clear that many variants, being obvious or not, may be conceivable falling within the scope of protection, defined by the present claims.

Experiments

The following experiments are carried out. 1 mole of 1,4 butanediol is dissolved in 50 mL ethyl acetate in a round bottom flask un-der nitrogen atmosphere. Thereto is added 2,5 moles of CDI in portions. Initially the reaction results in transparent liquid, however the reaction product precipitates as the reac- tion takes place. Following that, the product is filtered and dried under vacuum. 1 mole of sugar based compounds (i.e. isosorbide) is dissolved in 100 mL acetone in a round bottom flask under nitrogen atmosphere. Thereto is added 2,5 moles of CDI in portions. Initially the reaction results in transparent liquid, however the reaction product precipitates as reaction takes place. Following that, the product is filtered and dried under vacuum.

For the epoxy formulation, a commercial epoxy Epikote 828 and hardener Epikote hardener 651 are mixed in the ratio suggested by supplier, LAS Aerospace . Thereto present compound C is added in an amount of 1 wt.% and all components are mixed and de-gassed, until obtaining a clear solution at room temperature. Following that, the clear solution is placed in a Teflon mold and cured in an oven. In this case compound C accelerates curing process compared to original recipe. For composite formation, based on viscosity and curing kinetics, suitable manufacturing methods are applied to obtain fibre reinforced composites.

For an epoxy formulation, a commercial epoxy, Epikote 828, a monofunctional epoxy monomer as reactive diluent (5 wt.%), present compound C (20 wt.%), and in partic- ular imidazole are mixed in epoxy equivalent ratios. All components are mixed and degassed until obtaining a clear solution, at room temperature (heating may be considered for some resins). Following that, the solution is placed in a Teflon mold and cured in an oven. In this case compound C acts as a curing agent. For composite formation, based on viscosity and curing kinetics, suitable manufacturing methods are applied to obtain fibre reinforced com- posites.

For degradation experiments, present compound C cured epoxy thermoset resin are immersed in a basic or an acidic aqueous solution, respectively, at room temperature for 12- 24 hours, wherein the resin forms granulates. So-formed granulates are dissolved in an or- ganic solvent, in particular DMF, or are hot-pressed to form a thermoset. In case of compo- sites, fibres are separated at that stage.

The invention although described in detailed explanatory context may be best under- stood in conjunction with the accompanying figures.

It should be appreciated that for commercial application it may be preferable to use one or more variations of the present system, which would similar be to the ones disclosed in the pre- sent application and are within the spirit of the invention.

SUMMARY OF THE FIGURES

Figs. 1-4 show FT-IR spectra.

DETAILED DESCRIPTION OF THE FIGURES

Figure 1. FT-IR spectra of butanediol derived bisfunctional imidazole ester.

Figure 2. FT-IR spectra of isosorbide derived bisfunctional imidazole ester.

Figure 3. FT-IR spectra of epoxy resin cured with butanediol derived bisfunctional imidaz- ole ester.

Figure 4. FT-IR spectra of polymer obtained via degradation of epoxy resin.

Th figures show the various esters are actually formed and can be degraded accordingly.

For the purpose of searching the following section is added, of which the subsequent sec- tion represents a translation into Dutch. 1. A chemically decomposable thermoset material, in particular a fibre reinforced polymer ther- moset material, comprising 10-90 wt.% of an epoxy resin, 0.1-5 wt.% of an epoxy resin curing agent or epoxy resin accelerator compound C or a re- action product thereof, wherein the compound C comprises a reaction product of at least two of an ester, a thioester, and an ether (E), further comprising at least two aromatic heterocycle moie- ties (A), each aromatic heterocycle moiety individually comprising at least two non-adjacent ni- trogen atoms, and in between and attached to said at least two of an ester, a thioester, and an ether (E) and said heterocycle moieties (A) an intermediate moiety (R), wherein the intermediate moiety is selected from an alkane, an alkene, an aromatic compound, and combinations thereof, the compound having a schematic formula of A---E---R---E---A, in particular with the proviso that no further epoxy resin curing agent or epoxy resin accelerator compound other than com- pound C is present, and 0-60 wt.% fibres, in particular 1-30 wt.%, more in particular 2-20 wt.%, in particular wherein fibres are selected from carbon fibres, glass fibres, nano-fibres, polymeric fibres, and combinations thereof. 2. The chemically decomposable thermoset material according to embodiment 1, wherein the epoxy resin is selected from glycidyl-based epoxy resins, from low molecular weight polymers comprising phenols and for- maldehydes, such as novolacs, from biobased epoxies such as epoxidized resveratrol, isororbide, vanillin derivatives, cardanol oil, phloroglucinol, petroleum-derived epoxy in particular from tetraglycidyl methylene dianiline, triglycidyl p-aminophenol, and diglycidyl ester of hexahy- drophtalic acid. 3. The chemically decomposable thermoset material according to any of embodiments 1-2, wherein the intermediate moiety (R) each individually 1s selected from polyols, polyacids, such as poly carboxylic acids, poly alcohols, poly aldehydes, molecules comprising at least one OH- group and one COOH group, molecules comprising at least one SH-group and one COOH group, and combinations thereof, in particular wherein the intermediate moiety (R) each individually comprises two OH-groups or two COOH groups. 4. The chemically decomposable thermoset material according to any of embodiments 1-3, wherein the aromatic heterocycle moieties (A) is each individually selected from 5-7 ring aro- matic moieties, in particular from 5- ring aromatic moieties. 5. The chemically decomposable thermoset material according to any of embodiments 1-4, wherein the compound C is selected from multifunctional imidazole esters, in particular a di-es- ter of 1,1'-Carbonyldiimidazole (CAS 530-62-1), more in particular 0 0 : Jmol

NNT OORO ON

\l ln 6. A method of degrading the chemically decomposable thermoset material according to any of embodiments 1-5, comprising subjecting the thermoset material to an aqueous acidic environment with a pH of 2.5-6, in particular with a pH of 3-5, or to an aqueous basic environment with a pH of 8-11,5, in particular with a pH of 9-11, and separating the fibres from the epoxy resin. 7. The method of degrading according to embodiment 6, further comprising recovering the at least two aromatic heterocycle moieties (A), and optionally dissolving the epoxy resin in an organic solvent, in particular wherein the organic sol- vent is selected from dimethylformamide (DMF), dimethyl sulfoxide (DMSO), and Dihy- drolevoglucosenone (Cyrene)(CAS 53716-82-8). 8. The method of degrading according to any of embodiments 6-7, wherein subjecting is per- formed at a subjecting temperature is in the range of 10-40 °C, in particular at 15-30 °C, more in particular at 20-25 °C, and/or wherein the subjection time 1s 1-48 hours, in particular 2-20 hours, such as 4-12 hours. 9. Use of the compound C or a reaction product thereof, wherein the compound C comprises a reaction product of at least two of an ester, a thioester, and an ether (E), further comprising at least two aromatic heterocycle moieties (A), each aromatic heterocycle moiety individually com- prising at least two non-adjacent nitrogen atoms, and in between and attached to said at least two of an ester, a thioester, and an ether (E) and said heterocycle moieties (A) an intermediate moiety (R), wherein the intermediate moiety is selected from an alkane, an alkene, an aromatic com- pound, and combinations thereof, the compound having a schematic formula of A---E---R---E---

A, for recycling a thermoset material, or for fast curing of an epoxy-resin system, or for energy consumption reduction in an epoxy-resin forming reaction. 10. A one step method of forming a compound C comprising providing an amount of ketone, the ketone comprising at least two aromatic heterocycle moieties, each aromatic heterocycle moiety individually comprising at least two non-ad- jacent nitrogen atoms, and in between and attached to said at least two aromatic moieties the ketone moiety, and combinations thereof, reacting the amount of ketone with at least one ester-forming or ether-forming or anhy- dride-forming compound, wherein the ester-forming or ether-forming or anhydride-form- ing compound is capable of forming at least two of esters and/or ethers, wherein the es- ter-forming or ether-forming or anhydride-forming compound is selected from polyols, polyacids, such as poly carboxylic acids, poly alcohols, poly aldehydes, molecules com- prising at least one OH-group and one COOH group, molecules comprising at least one

SH-group and one COOH group, and combinations thereof, at a reaction temperature, during a reaction time of at least 10 minutes, therewith forming an at least two of esters and/or ethers comprising compound. 11. The one step method according to embodiment 10, wherein the reaction temperature is in the range of 10-40 °C, in particular at 15-30 °C, more in particular at 20-25 °C, and/or wherein the reaction time is 1-20 hours, in particular 2-10 hours. 12. The one step method according to any of embodiments 10-11, wherein the reacting is in a solvent, wherein solvent is selected from ketones and aldehydes, in particular from C3-Cs ke- tones and aldehydes, more in particular from acetone, in particular a biobased solvent.

13. The one step method according to any of embodiments 10-12, wherein the ketone moiety is selected from C1-Cs ketones, in particular from C1-C: ketones. 14. The one step method according to any of embodiments 10-13, wherein the ketone and the at least one ester-forming or ether-forming or anhydride-forming compound are provided in a mo- lar ratio of 0.5:1 to 2:1, in particular in a molar ratio of 0.8:1 to 1.2:1, more in particular in a mo- lar ratio of 0.95:1 to 1.05:1, such as in substantially equal molar amounts. 15. A product comprising compound C, wherein the compound C comprises a reaction product of at least two of an ester, a thioester, and an ether (E), further comprising at least two aromatic heterocycle moieties (A), each aromatic heterocycle moiety individually comprising at least two non-adjacent nitrogen atoms, and in between and attached to said at least two of an ester, a thioe- ster, and an ether (E) and said heterocycle moieties (A) an intermediate moiety (R), wherein the intermediate moiety is selected from an alkane, an alkene, an aromatic compound, and combina- tions thereof, the compound having a schematic formula of A---E---R---E---A, wherein the prod- uct is selected from a photo-resist, a transparent material, a thermo-hardened material, a thermo- set material, a resin, a coating, a glass-fibre, an adhesive, a curing accelerator for an epoxy resin, a curing agent for an epoxy resin, a fibre reinforce composite, such as a fibre reinforced polymer composite, and a filling, such as a dental filling.

Claims

Conclusions

1. A chemically degradable thermosetting material, in particular a fibre reinforced polymer thermosetting material, comprising 10-90 wt.% epoxy resin, 0.1-5 wt. % of an epoxy resin curing agent or epoxy resin accelerator compound C or a reaction product thereof, wherein compound C is a reaction product of at least two of an ester, a thioester, and an ether (E), further comprising at least two aromatic heterocycle groups (A), each aromatic heterocycle group separately comprising at least two non-adjacent nitrogen atoms, and therebetween and attached to said at least two of an ester, a thioester, and an ether (E) and said heterocycle groups (A) an intervening group (R), the intervening group being selected from an alkane, an alkene, an aromatic compound, and combinations thereof, having the schematic formula A---E---R--- E---A, in particular with the proviso that no other epoxy resin curing agent or epoxy resin accelerator is present other than compound C, and 0-60 weight percent of fibers, in particular 1-30 weight percent, more particularly 2-20 weight percent, wherein the fibers are selected from carbon fibers, glass fibers, nanofibers, polymeric fibers, and combinations thereof.

2. The chemically degradable thermosetting material according to claim 1, wherein the epoxy resin is selected from glycidyl-based epoxy resins, from low molecular weight polymers comprising phenols and formaldehydes, such as novolacs, from bio-based epoxies such as epoxidized resveratrol, isorobide, vanillin derivatives, cardanol oil, phloroglucinol, petroleum-derived epoxy, in particular from tetraglycidylmethylenedianiline, triglycidyl p-aminophenol, and diglycidyl ester of hexahydrophthalic acid.

3. The chemically degradable thermosetting material according to any one of claims 1 to 2, wherein the intermediate portion (R) is each individually selected from polyols, polyacids, such as polycarboxylic acids, polyalcohols, polyaldehydes, molecules having at least one OH group and one COOH group, molecules having at least one SH group and one COOH group, and combinations thereof, in particular wherein the intermediate portion (R) each individually comprises two OH groups or two COOH groups.

4. The chemically degradable thermosetting material according to any one of claims 1 to 3, wherein the aromatic heterocycle groups (A) are each individually selected from aromatic 5-7-ring groups, in particular from aromatic 5-ring groups.

5. The chemically degradable thermosetting material according to any one of claims 1 to 4, wherein the compound C is selected from multifunctional imidazole esters, in particular a diester of 1,1'-carbonyldiimidazole (CAS 530-62-1), more in particular O O \==/ read

6. A method for the degradation of the chemically degradable thermosetting material according to any one of claims 1 to 5, comprising subjecting the thermosetting material to an aqueous acidic medium with a pH of 2.5 to 6, in particular with a pH of 3 to 5, or to an aqueous basic medium with a pH of 8 to 11.5, in particular with a pH of 9 to 11, and separating the fibres from the epoxy resin.

7. The degradation method according to claim 6, further comprising recovering the at least two aromatic heterocycle groups (A), and optionally dissolving the epoxy resin in an organic solvent, the organic solvent being selected in particular from dimethylformamide (DMF), dimethylsulfoxide (DMSO) and dihydrolevoglucosenone (Cyrene) (CAS 53716-82-8).

8. The degradation method according to any one of claims 6 to 7, wherein the subjecting is carried out at a subjecting temperature of 10-40 °C, in particular at 15-30 °C, more in particular at 20-25 °C, and/or wherein the subjecting time is 1-48 hours, in particular 2-20 hours, for example 4-12 hours.

9. Use of the compound C or a reaction product thereof, wherein the compound C comprises a reaction product of at least two of an ester, a thioester, and an ether (E), further comprising at least two aromatic heterocycle groups (A), each aromatic heterocycle group separately comprising at least two non-adjacent nitrogen atoms, and between and attached to said at least two of an ester, a thioester, and an ether (E) and said heterocycle groups (A) an intervening group (R), wherein the intervening group is selected from an alkane, an alkene, an aromatic compound, and combinations thereof, wherein the compound has a schematic formula of A---E---R---E---A, for recycling a thermosetting material, or for rapid curing of an epoxy resin system, or for reducing energy consumption in an epoxy resin forming reaction.

10. A one-step process for forming a compound C, comprising: Providing an amount of ketone, wherein the ketone comprises at least two aromatic heterocycle groups, wherein each aromatic heterocycle group separately comprises at least two non-adjacent nitrogen atoms, and between said at least two aromatic groups the ketone group, Reacting the amount of ketone with at least one ester-forming, ether-forming, or anhydride-forming compound, wherein the ester-forming, ether-forming, or anhydride-forming compound is capable of forming at least two esters and/or ethers, wherein the ester-forming, ether-forming, or anhydride-forming compound is selected from polyols, polyacids, such as polycarboxylic acids, polyalcohols, polyaldehydes, molecules having at least one OH group and one COOH group, molecules having at least one SH group and one COOH group, and combinations thereof, at a reaction temperature, for a reaction time of at least 10 minutes, forming a compound comprising at least two esters and/or ethers.

11. The one-step process according to claim 10, wherein the reaction temperature is in the range of 10-40 °C, in particular 15-30 °C, more in particular 20-25 °C, and/or wherein the reaction time is 1-20 hours, in particular 2-10 hours.

12. The one-step process according to any one of claims 10 to 11, wherein the reaction takes place in a solvent, the solvent being selected from ketones and aldehydes, in particular from C3-C8 ketones and aldehydes, more in particular from acetone, in particular a biologically based solvent.

The one-step process according to any one of claims 10 to 12, wherein the ketone moiety is selected from C1-C8 ketones, in particular from C1-C3 ketones.

The one-step process according to any one of claims 10 to 13, wherein the ketone and at least one ester-forming, ether-forming or anhydride-forming compound are provided in a molar ratio of 0.5:1 to 2:1, in particular in a molar ratio of 0.8:1 to 1.2:1, more in particular in a molar ratio of 0.95:1 to 1.05:1, such as in substantially equal molar amounts.

15. A product comprising compound C, wherein said compound C comprises a reaction product of at least two of an ester, a thioester, and an ether (E), further comprising at least two aromatic heterocycle groups (A), each aromatic heterocycle group separately comprising at least two non-adjacent nitrogen atoms, and between and attached to said at least two of an ester, a thioester, and an ether (E) and said heterocycle groups (A) an intervening group (R), said intervening group being selected from an alkane, an alkene, an aromatic compound, and combinations thereof, said compound having a schematic formula of A---E---R---E---A, said product being selected from a photoresin, a transparent material, a thermosetting material, a thermoset material, a resin, a coating, a glass fiber, an adhesive, an epoxy resin curing accelerator, an epoxy resin curing agent, a fiber-reinforced composite, such as a fiber-reinforced polymer composite, and a filling, such as a dental filling.