WO2021207777A1 - Curable composition for producing a vitrimer, and vitrimer obtainable therefrom, and method for production of same - Google Patents

Abstract

The invention relates to a curable composition for producing a vitrimer, comprising: a) a crosslinkable monomer, comprising at least one amino group -NR1R2, wherein R1 and R2 represent a glycidyl group, and optionally at least one further functionally crosslinkable group, such as in particular a glycidyl group; b) an anhydride of a carboxylic acid and/or a carboxylic acid as curing agent; c) optionally a catalyst that catalyses a transesterification and/or a curing. The invention also relates to a corresponding cured composition and to a method for producing an epoxy-based thermoset.

Description

Curable composition for producing a vitrimer and vitrimer obtainable therefrom and process for its production

The invention relates to a curable composition for producing a vitrimer.

The invention also relates to a cured composition derived therefrom.

Finally, the invention relates to a method for producing an epoxy-based duromer, in particular a vitrimer.

Vitrimers are among the covalently adaptable networks, the so-called "covalent adaptable networks" (CANs). Vitrimers are polymeric networks, but thermally activated bond exchange reactions can induce topology changes and thus offer the possibility of influencing the shape of a network.

The CANs are divided into two subgroups, the dissociative and associative CANs. In the former, existing connections are first dissolved, which are later formed again with a different spatial molecular shape. With the associative CANs, the total number of bonds remains constant over time, as the chains involved carry out exchange reactions such as transesterification or transamination reactions. Associative CANs also include vitrimers (see: Winne, JM, Leibier, L, Du Prez, F., Dynamic Covalent Chemistry in Polymer Networks: A Mechanistic Perspective, Polym. Chem. 10 (2019) 6091; Montarnal, D. , Capelot, M., Tournilhac, F., Leibier, L, Silica-Like Malleable Materials from Permanent Organic Networks, Science 334 (2011) 965).

Vitrimer systems, to which reference is made below, are particularly capable of transesterification reactions; most of the theoretical background that follows deals with such vitrimer systems.

By rearranging bonds, tensions within a polymer matrix can be relaxed, which can also lead to flow. this makes possible new material properties such as B. Self-healing and recyclability. Activation of these transesterification reactions requires an external stimulus, which can take place thermally or photochemically (see: Capelot, M., Unterlass, MM, Tournilhac, F., Leibier, L., Catalytic control of the vitrimer glass transition, ACS Macro Lett . 1 (2012) 789).

The viscosity of vitrimers changes over the temperature as with strong glass formers and behaves according to the Arrhenius law. If the material exceeds a certain temperature limit, the viscosity drops only slightly. In the case of classical strong glass formers such as silicon oxide and other inorganic compounds, this point is the glass transition temperature T _g and in the case of vitrimers the structural freezing transition temperature Tv (so-called topology freezing transition temperature). According to the definition, this is at the point at which the material has a viscosity of 10 ¹² Pa s (Montarnal, D., Capelot, M., Tournilhac, F., Leibier, L., Silica-Like Malleable Materials from Permanent Organic Networks , Science 334 (2011) 965).

In contrast, classic polymers behave like weak glass formers.

These show a strong reduction in viscosity above the corresponding transition temperature. Such behavior can be described very well using the Williams-Landel-Ferry equation.

Exchange reactions when the temperature rises can take place in a catalyzed or non-catalyzed manner. However, catalyzed vitrimers have a significantly higher exchange rate compared to non-catalyzed systems. In particular, free hydroxyl groups (OH) in the β position to an ester group are essential.

So far, a number of different catalysts have been published which influence the activation energy of a transesterification reaction of a vitrimer. Examples of such catalysts are zinc acetylacetonate Zn (acac) 2, zinc acetate Zn (Oac) and secondary or tertiary amines. In the case of the first-mentioned catalysts, it is assumed that the zinc ion exchanges ligands with two carboxylic acid groups or an anhydride in order to then react with an epoxide. This creates a negatively charged oxygen atom, which leads to transesterification reactions (Demongeot, A., Mougnier, S.-J., Okada, S., Soulie-Ziakovic, C., Tournilhac, F., Coordination and Catalysis of Zn ²⁺ in Epoxy-Based Vitrimers, Polym. Chem. 7 ( 2016) 4486).

In addition, the choice of the main components (epoxy, hardener and / or catalyst) in the network can have an influence on the reactivity or on the Tv generated. In addition, the choice of the stoichiometry used for the reactants also appears to be important. In the case of an epoxy, with a stoichiometric epoxy: anhydride ratio of 1: 1, fewer hydroxyl groups are naturally formed. If the monomers do not already have hydroxyl groups, transesterification reactions can only take place to a limited extent with this ratio. Reasons why a measurable relaxation still occurs are, on the one hand, that when the resin cures, not all of the hydroxyl groups react with an epoxy ring and, on the other hand, when equimolar resin mixtures are cured, hydroxyl ester groups are formed. In general, OH groups are also formed by the termination of the homopolymerization of the epoxy groups and can arise from side reactions such as the hydrolysis of epoxides or anhydrides by water. Water can be released from the catalyst under the action of heat.

With regard to the mechanical properties of vitrimers, vitrimer systems published to date are mostly soft and have a low hardness, which limits industrial application (Yang, Y., Urban, M. W., Self-healing polymeric materials, Chem.

Soc. Rev. 42 (2013) 7446). In industrial applications, the T _g values of cured epoxy resin materials are often above 100 ° C. in order to meet the requirements of high operating temperatures, especially for applications in the aerospace industry. Previous vitrimer systems usually have a T _g <100 ° C. Reasons for obtaining such soft networks are, on the one hand, the intended incomplete curing of the resin to generate further important hydroxyl groups, which results in a lower network density. On the other hand, using flexible epoxy monomers such as fatty acids leads to softer networks. This is also reflected in the patent reports published to date. Most of the previously published patent applications use glutaric anhydride and Pripol 1040 or bisphenol A diglycidyl ether (DGEBA), which leads to high T _g values, but a slow one in the stoichiometric mixing ratio of 1: 1 Stress relaxation results (US 2017/0044305 A1, US 9,266,292 B2). Most patent applications have a system with Pripol 1040, which is a mixture of different fatty acids and thus belongs to the flexible monomers. To overcome this limitation, different strategies have been developed and implemented. On the one hand, different blends were produced and vitrimer properties were deliberately changed; on the other hand, highly crosslinked systems with a high T _g were produced, which, however, required expensive starting materials. Overall, there are still no satisfactory solutions for economical applications.

The object of the invention is to provide a curable composition for producing a vitrimer which has a high glass transition temperature (T _g ) and high mechanical strength with rapid stress relaxation at the same time and which can be produced from easily available, inexpensive components.

Furthermore, a cured composition derived therefrom is to be specified.

Another aim of the invention is to provide a method of the type mentioned at the outset with which an epoxy-based duromer, in particular a vitrimer, can be produced which has a high glass transition temperature (T _g ) and high mechanical strength with simultaneous rapid stress relaxation and that from simply available, inexpensive components can be produced.

The object relating to a curable composition is achieved by a curable composition for producing a vitrimer, comprising: a) a crosslinkable monomer having at least one amino group -NR ¹ R ² , where R ¹ and R ² stand for a glycidyl group, and optionally at least one further functionally crosslinkable group such as, in particular, a glycidyl group; b) an anhydride of a carboxylic acid and / or a carboxylic acid as hardener; c) optionally a catalyst which catalyzes transesterification and / or curing.

With such a composition according to the invention a starting basis for the production of a vitrimer is created which has a high glass transition temperature (T _g ) and has high mechanical strength with simultaneous rapid stress relaxation and which can be produced from easily available, inexpensive components. The approach according to the invention is conceptually based on epoxy monomers which have tertiary amino groups with the ability to accelerate the transesterification reactions. Despite the basically stoichiometric use of epoxy monomer and hardener (high degree of cure and associated high T _g ), rapid stress relaxation is observed in the vitrimer obtained later. This stress relaxation is an important parameter of vitrimers, since the ability to self-heal, weldability and recyclability usually increases with improved stress relaxation. A catalytic converter can be provided. For some applications, however, it may be preferred that the composition manage entirely without an additional catalyst, since the amino groups of the monomer can at least partially take over the function of the catalyst.

In the curable composition, the monomer has at least two, preferably two to four, amino groups —NR ¹ R ² . Each amino group can carry two glycidyl radicals.

wobei The monomer can have the formula I,

whereby

R ^{4 stands} for a C ₃ -C ₄ o-alkyl, aryl or arylalkyl radical, in particular a C ₅ -C ₁₂ - cycloalkane which is optionally substituted by one or more halogens, for example cyclopentane or cyclohexane, or an aryl radical such as Benzyl, naphthyl, anthracyl, benzylphenyl radicals, diphenylmethanyl or a diclyohexylmethanyl radical and

R ^{5 represents} an amino group, mono- or disubstituted with a glycidyl group, or an ether or sulfide group with a glycidyl radical or a vinyl ester group. Examples of radicals of the type R ⁴ are shown below: The represented radicals R ⁴ can also be substituted, it being possible for individual hydrogens to be substituted by a halogen, in particular fluorine, chlorine or bromine, or by an alkyl radical, in particular by a straight-chain or branched C Ce-alkyl.

Possible radicals R ⁵ are: -H, -CH ₃ , - (CH ₂ ) _n CH ₃ (n = 1 to 9), -CH = CH ₂ , -OH, -OCH ₃ , - - (OCH ₂ ) _n CH ₃ (n = 1 to 9), NH ₂ , SH, COOH, -COOEt, -COOMe, (CH ₂ ) _n -epoxide (n = 1 to 9), -CN, -F, -CI, -Br, in particular the functional groups shown below:

Particularly suitable hardeners are anhydrides of carboxylic acids and / or carboxylic acids.

Replaceable anhydrides are, for example: 5-norbornene-2,3-dicarboxylic anhydride, methyl-5-norbornene-2,3-dicarboxylic anhydride, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, phthalic anhydride, trimellitic anhydride, trimellitic anhydride, triellitic anhydride, maleic anhydride, maleic anhydride, tetracarboxylic acid bis anhydride.

Usable carboxylic acids, in particular dicarboxylic acids, are for example: trimellitic acid, hemimellitic acid, trimesic acid, azelaic acid, sebacic acid, adipic acid, Glutaric acid, pimelic acid, octanedioic acid, cyclohexanedicarboxylic acid, phthalic acid, terephthalic acid, isophthalic acid and / or 5-norbornene-2,3-dicarboxylic acid.

wobei R⁶ für einen geradkettigen oder verzweigten C3-C2o-Alkylrest steht, bevorzugt ein C3-Cio-Alkylen, welches gegebenenfalls substituiert ist, oder R⁶ einen C3-C2o-Aryl- oder einen C3-C2o-Arylalkylrest darstellt. It is particularly preferred if the hardener has the formula II,

where R ^{6 represents} a straight-chain or branched C3-C2o-alkyl radical, preferably a C3-Cio-alkylene, which is optionally substituted, or R ^{6 represents} a C3-C2o-aryl or a C3-C2o-arylalkyl radical.

A molar ratio of monomer to hardener is preferably about 1: 1 to 1: 0.5. This molar ratio relates to the respective total number of functional groups (epoxy groups on the one hand and carboxylic acid groups on the other). Lower ratios down to about 1: 0.5 can prove beneficial for rapid stress relaxation. Overall, by adjusting the molar ratio of monomer to hardener, the properties in the composition that is hardened later can be set or adjusted in a targeted manner. In this way, an optimized range of properties can be achieved for the respective application.

In accordance with the foregoing, it has proven to be advantageous if a cured composition is created from the curable composition explained by curing.

The process-related object of the invention is achieved if a composition according to the invention is cured in a process of the type mentioned at the beginning.

Further features, advantages and effects of the invention emerge from the following exemplary embodiments. In the drawings to which reference is made: 1 conversion of the epoxy groups of different resin systems at 120 ° C. over time; FIG. 2 a comparison of the epoxy band before and after curing in a section of an exemplary FTIR spectrum; FIG.

3 normalized relaxation modulus curves of a DGEBA glutaric anhydride reference system with 5 mol% zinc acetylacetonate hydrate at different temperatures; FIG. 4 Arrhenius diagram for the DGEBA / glutaric anhydride reference system from FIG. 3; FIG.

5 shows stress relaxation for a 1: 1 amintriepoxide / glutaric anhydride system with 5 mol% zinc acetylacetonate hydrate; FIG. 6 Arrhenius diagram for the amine triepoxide / glutaric anhydride system from FIG. 5; FIG. 7 shows a master curve with the reference temperature of 220 ° C .;

8 shows stress relaxation for a 1: 1 diamine tetraepoxide / glutaric anhydride system with 5 mol% zinc acetylacetonate hydrate;

FIG. 9 Arrhenius diagram for the diamine tetraepoxide / glutaric anhydride system from FIG. 8; FIG.

10 shows the temperature-dependent viscosities of the DGEBA reference;

11 shows the temperature-dependent viscosities of the amine triepoxide system; 12 shows the temperature-dependent viscosities of the diamine tetraepoxide system; 13 shows the temperature-dependent complex moduli of elasticity and mechanical loss factors of the DGEBA reference;

14 shows the temperature-dependent complex moduli of elasticity and mechanical loss factors of the amine triepoxide system;

15 shows the temperature-dependent complex moduli of elasticity and mechanical loss factors of the diamine tetraepoxide system;

16 shows thermogravimetric analysis curves of examined vitrimer systems;

17 shows stress relaxation of the 1: 0.5 amintriepoxide system with 5 mol% zinc acetylacetonate hydrate;

18 shows the stress relaxation of the 1: 1 amine triepoxide system without an additional catalyst;

19 shows a comparison of the stress relaxation of the three systems from FIGS. 5, 17 and 18;

20 stress relaxation of the 1: 0.5 diamine tetraepoxide system with 5 mol% zinc acetylacetonate hydrate; 21 stress relaxation of the 1: 1 diamine tetraepoxide system without additional catalyst;

FIG. 22 Comparison of the stress relaxation of the three systems from FIGS. 8, 20 and 21.

Test series 1

Chemicals

Various vitrimer systems were investigated. Some examples are given below. The materials and chemicals used for the production of exemplary vitrimer systems are listed in Table 1 with molecular weights and weight-per-epoxy values (WPE).

Table 1: Chemicals for vitrimer systems

For understanding, the structural formulas of the chemicals are given in Table 2. Table 2: Chemicals for vitrimer systems

Measuring devices Measuring devices which were used to carry out measurements are given in Table 3 below. Table 3: Measuring devices used

Manufacture of vitrimer systems

1: 1 (molar equivalents) epoxy: anhydride vitrimers were made. This means that in the uncured resin, the epoxy and anhydride groups are present in an equimolar ratio. Zinc acetylacetonate hydrate in a concentration of 5 mol% based on the epoxide groups was used as the transesterification and curing catalyst. The following steps were carried out.

- Prepare the mold using silicone tubes with a diameter of 2.5 mm, double-sided adhesive tape and 0.5 mm thick spacer;

- Weighing the respective epoxy and the catalyst into a Teflon beaker;

- Weighing in the glutaric anhydride in a weighing bowl;

- heating and homogenizing the epoxy mixture using a spatula to 100 ° C for 15 to 20 minutes;

- Gradual addition of the anhydride and subsequent homogenization using a spatula;

- Removal of any bubbles and low molecular weight substances from the resin by applying a vacuum by means of a desiccator, if necessary heating the resin to 110 ° C to 120 ° C;

- Pour the resin into the previously prepared mold.

The resin was then allowed to cure in an oven at 120 ° C. for 18 hours. The degree of cure was then measured by means of FTIR spectroscopy. Characterization of the vitrimer systems

FT-IR spectroscopy:

The following steps were carried out for IR spectroscopy.

- Dissolve the resin formulation in a few milliliters of chloroform and homogenize the sample by shaking the sealed sample bottle by hand;

- Application of the mixture in the middle of a silicon wafer;

- Production of a thin layer by means of a centrifugal spin coating process;

- Covering the layer with a calcium fluoride plate;

- measuring the background;

- Clamping the silicon wafer in the measuring device;

- measuring the sample in a wave number range from 4500 cm ^-1 to 750 cm ^-1 ;

- Hardening of the sample at 120 ° C and measurement of the cooled sample at periodic intervals.

Shear stress relaxation test:

For the relaxation test, the MCR 501 rheometer was heated to the respective measuring temperature. Based on this, the maximum measurement duration had to be estimated. The measuring chamber was flooded with nitrogen at a constant volume flow of 1 m ^{3 / h.} Rectangular samples were tested for the measurement. The samples were 5 mm wide, 30 mm high, and approximately 1.5 mm thick. The following steps were also carried out.

- Measuring the sample geometry and entering these values into a computer program;

- Clamping the sample in a solid fixture;

- Wait until the test chamber temperature reaches the set value;

- Repeated loosening and clamping of the specimen in order to compensate for the thermal expansion and thus to reduce stresses;

- Start the measurement after the temperature has stabilized again for 20 minutes;

- Applying a deformation of 1% and measuring the torque over time; - Comparing the initial thrust module calculated by the computer and the changed thrust module;

- Stopping the measurement at a relaxation of 36.78%, as this indicates the relaxation time with a value of 1 / e.

Further characterization methods:

The other measurement methods were carried out as follows:

- Dynamic mechanical analyzes were carried out in the linear viscoelastic range. The test frequency was 1 Hz and the complex modulus of elasticity as well as the mechanical loss modulus were calculated from the measurement data.

- Thermogravimetric analyzes were carried out under a nitrogen atmosphere, at a heating rate of 10 K / min and an approximate sample weight of 10 mg.

Results and interpretation

Curing of the vitrimers systems

The curing behavior of two resin systems in comparison to a standard system from the literature, namely bisphenol A diglycidyl ether, DGEBA crosslinked with glutaric anhydride, was investigated using IR spectroscopy (for the compositions, see Tables 1 and 2).

The results of the FTIR spectroscopy are shown in FIG. For this purpose, the height of the peaks was analyzed, compared with the initial values and standardized. For this purpose, only the epoxy bands at a wave number of 913 cm ^{−1 were} analyzed (see FIG. 2). The two anhydride peaks are superimposed in the course of the reaction by the carbonyl peak of the ester group formed, which was taken into account in the evaluation. As can be seen in FIG. 1, the epoxy groups react quickly in all systems and are only present in small amounts after 100 minutes. If the gel point is reached more quickly, the diamine tetraepoxide system could transition to diffusion-controlled curing earlier and thus slow down the rate of reaction. Since the IR samples as well as the resin plates for the relaxation measurements were stored at 120 ° C. for 18 h, it can be assumed that the vitrimer plates also contain the Epoxides and anhydrides have reacted completely. Such an exemplary comparison of the epoxy band before and after curing is shown in FIG.

Evaluation of vitrimer properties on the basis of relaxation tests FIG. 3 shows the normalized relaxation module of the DGEBA reference vitrimer. It can be seen here that the modules drop faster at higher temperatures. This trend is consistent with relaxation curves in the literature. Steps that can be seen in the illustration of the measurement at 220 ° C can be explained by slipping of the sample or by shaking the measurement setup, but this does not affect the validity of the measurement results due to the insignificance.

The relaxation times from FIG. 3 made it possible to create an Arrhenius diagram which is shown in FIG. 4. The activation energy was calculated and is 119.5 kJ / mol. A similar system has been described in the literature, but with a significantly higher epoxide: anhydride ratio of 1: 0.5. In this latter system, the material has more hydroxyl groups due to the stoichiometry and transesterification reactions can therefore take place more frequently, which lowers the activation energy.

For an amine triepoxide vitrimer according to Tables 1 and 2, corresponding measurement curves and a master curve are shown in FIGS. 5 to 7.

As can be seen, the reference sample relaxes strongly, which can be explained by the catalytic activity of the tertiary amines which are in the structure of the epoxide. This second type of catalyst means that the activation energy of the samples is correspondingly low. The master curve of this system in FIG. 7 shows that only the 200 ° C. and 220 ° C. curves are on top of one another; deviations can be seen from a temperature of 250 ° C. and above. This could be caused by a greater deviation of the deformation from the linear viscoelastic range or by the second reaction path (transesterification catalysis by amines).

The results for the corresponding diamine tetraepoxide system are shown in FIGS. 8 and 9. As can be seen, the relaxation is slower than with the amine triepoxide system. In addition, the reference sample relaxes faster than the sample at 200 ° C, but this does not occur with the other systems.

Viscosities can be calculated on the basis of the relaxation times and shear modulus obtained from the relaxation tests. Using an exponential extrapolation, the viscosities of 10 ¹² Pa s could be calculated, as shown in Fig.

10 to 12 is shown. It can be seen here that in the DGEBA reference system and the diamine tetraepoxide system, the calculated T _{v is} above a temperature at which relaxation was observed. This contradicts the literature, according to which no sufficient transesterification reactions can take place below the structural freezing transition temperature to observe relaxation. Such freezing has also been observed in many elastomeric systems. These have a significantly lower shear modulus, which lowers _{the viscosity and thus lowers the T v.} In the case of thermoset-like systems, the definition of the structural freezing transition temperature should therefore require a revision; this change would be possible because the viscosity ^{limit of 10 12} Pa s is a purely arbitrary limit. Another possibility would be to use a different material law than that used in the literature in order to obtain a better calculation of the viscosities. Here, the Maxwell model can also be replaced by the more complex, general Maxwell model.

Evaluation of the mechanical analysis The dynamic mechanical analysis made it possible to determine the complex moduli of elasticity and the mechanical loss factors as a function of the temperature of the vitrimer systems. These are shown in FIGS. 13 to 15. The glass transition temperatures could be determined with the aid of the mechanical loss maxima. The high glass transition temperatures of the amine triepoxide and the di am i ntetrae poxi d system are noticeable.

Evaluation of the thermogravimetric analyzes FIG. 16 shows the TGA curves of vitrimers. The onset of decomposition is indicated by vertical lines. It can be seen that the two amine systems begin to decompose at 340 ° C and the DGEBA system at 380 ° C. Since the relaxation measurements were carried out at these temperatures, it can be assumed that no significant degradation has taken place under these conditions. This testifies to the accuracy of the data obtained during the relaxation measurement, as no material degradation took place during the measurement.

Test series 2

The above test series 1 was based on stoichiometric resin formulations (ratio of epoxy and anhydride groups of 1: 1) with Zn (acac) 2 as the catalyst. In a supplementary further test series 2, resin formulations with a non-stoichiometric ratio between epoxide and anhydride (1: 0.5) and Zn (acac) 2 as a catalyst were produced. The excess of epoxy groups leads to a higher number of OH groups and, associated with this, to a higher activity in stress relaxation. In addition, stoichiometric resin formulations (ratio of epoxy and anhydride groups of 1: 1) were produced without the addition of a catalyst. The aim here was to show that the tertiary amino groups in the structure of the epoxy crosslinkers are capable of catalyzing the transesterification reactions.

The compositions for this test series 2 are given in Tables 3 to 5.

Tabelle 4: Einwaagen weitere Diamintetraepoxid-Systeme

Table 3: Weighing in of further amine triepoxide systems

Table 4: Weighing in of further diamine tetraepoxide systems

Table 5: Weights for the reference system

Investigations on stress relaxation in the amine triepoxide system

As can be seen in FIGS. 5, 17 to 19, all systems have a temperature-dependent stress relaxation which is rapid for highly networked vitrimer networks. This becomes clear when the three systems are compared with one another (FIG. 19).

The homopolymerization of the epoxy groups generates OH groups, especially in the 1: 0.5 system, which contribute to even faster stress relaxation. This effect is known per se from the relevant specialist literature. When Zn (acac) 2 is added, the stress relaxation is increased, since the transesterification reactions are accelerated in the presence of the catalyst at an elevated temperature. Without the addition of the

Although the network exhibits a less pronounced stress relaxation due to the catalyst, this can evidently still be achieved to an entirely satisfactory extent even without a catalyst. Investigations on stress relaxation in the amine triepoxide system In comparison to the amine triepoxide system, the uncatalyzed diamine tetrate epoxide system shows a very high stress relaxation at 220 ° C, which is of a similar magnitude to that of the catalyzed resin formulation. This becomes clear when the two 1: 1 systems are compared at 220 ° C. (see FIGS. 8 and 20 to 22). It can be concluded from this that the tertiary amino groups in the epoxy monomers, with a suitable network structure, have a sufficiently high reactivity to catalyze transesterification to a high degree at elevated temperature.

Based on the available stress relaxation data, the Tv values and activation energies given in Tables 6 and 7 were determined for the vitrimer systems. Table 6: Tv values and activation energy E _a for the amine triepoxide system

Table 7: Tv values and activation energy E _a for the diamine tetraepoxide system

The glass transition temperatures of the networks were determined in the course of DMA investigations (determined from the maximum of the tan (δ) curve) and are summarized in Table 8 below. Table 8: T _g values of the networks

Recycle of the Vitrimers The cured networks were comminuted with a ball mill for 90 seconds and 30 Hz. The resulting powder was pressed with a press (Dr. Collins) for 40 min at a maximum of 250 ° C and 5 bar pressure or a PVT 100 press (SWO Polymertechnik) with 500 bar at 250 ° C. The highly crosslinked vitrimer powders can be easily compressed and thus also recycled, whereby, naturally at higher pressures, pellets of better quality can be produced.

Vitrimers according to the invention are generally distinguished by a high T _v value, which can be higher than 180 ° C., preferably 190 ° C. or more. At the _{same time, T g} values are higher than 110.degree. C., preferably higher than 120.degree.

Claims

Claims 1. A curable composition for the production of a vitrimer, comprising a) a crosslinkable monomer having at least one amino group -NR ¹ R ² , where R ¹ and R ² stand for a glycidyl group, and optionally at least one further functionally crosslinkable group such as, in particular, a glycidyl group; b) an anhydride of a carboxylic acid and / or a carboxylic acid as hardener; c) optionally a catalyst which catalyzes transesterification and / or curing. 2. Curable composition according to claim 1, wherein the monomer has at least two, preferably two to four, amino groups -NR ¹ R ² . 3. Curable composition according to claim 1 or 2, wherein the monomer has the formula I,

where R ^{4 is} a C3-C4o-alkyl, aryl or arylalkyl radical and where R ^{5 represents} an amino group, mono- or disubstituted with a glycidyl group, or an ether or sulfide group with a glycidyl radical or a vinyl ester group. 4. Curable composition according to one of claims 1 to 3, wherein the hardener has the formula II,

where R ^{6 stands} for a straight-chain or branched C3-C2o-alkyl radical, preferably a C ₃ -Cio-alkylene, which is optionally substituted, or a C ₃ -C ₂ o-aryl or a C3-C2o-arylalkyl radical. 5. Curable composition according to one of claims 1 to 4, wherein a molar ratio of monomer to hardener is about 1: 1 to 1: 0, 5 is. 6. Cured composition formed by curing a curable composition according to any one of claims 1 to 5. 7. A method for producing an epoxy-based thermoset, in particular a vitrimer, comprising the steps of providing a curable composition according to one of claims 1 to 5 and subsequent curing of the composition.