Cyanate esters as monomers in polymerisable compositions

Abstract

The invention relates to the use of cyanate esters as monomers in a polymerisable composition for producing solid products, said composition comprising, as polymerisation initiator, at least one organometallic compound, which can be activated by radiation and / or thermally, and being heated during the polymerisation to a temperature > 70°C, characterised in that a) multi-functional cyanate esters of formula R(OCN)n are used as monomers, in which R is an n-value hydrocarbon group containing up to 50 carbon atoms and n is an integer ≥ 2; b) an organometallic photoinitiator is used as polymerisation initiator; c) a compound comprising at least one acidic hydrogen atom is used as co-catalyst; and d) the polymerisation is performed during the course of a 3D printing method comprising heating and exposure of the photopolymerisable composition, all components first being heated to a temperature > 70°C in order to obtain a homogeneous liquid mixture which is then irradiated at at least the same temperature with a wavelength corresponding to the polymerisation initiator in order to obtain a three-dimensional solid body.

Description

[0001] Cyanate esters as monomers in polymerizable compositions

[0002] The present invention relates to cyanate esters as monomers in polymerizable compositions.

[0003] STATE OF THE ART

[0004] Polycyanate esters are a relatively new class of high-performance thermosets. The monomers used are generally those with at least two cyanate ester groups, sometimes also in oligomeric form. Repeated cyclotrimerization produces cross-linked polymers via triazine rings, i.e., cyanurate groups.

[0005] Among the monomers, both aliphatic and aromatic cyanate esters are found, the latter being preferable with regard to the thermomechanical properties of the polymers, such as glass transition temperature, strength, and dimensional stability. Common aromatic cyanate esters include cyanates of various mono- or polyhydroxy-substituted benzene, biphenyl, or naphthalene derivatives, including bisphenol dicyanates, as well as novolak polycyanates; see, for example, MR Kessler, Wiley Encyclopedia of Composites, John Wiley & Sons, Inc., Hoboken, NJ, USA, pp. 1-15 (2012).

[0006] The cyclotrimerization reactions can be initiated by heating to high temperatures of, for example, 170-200 °C or by the presence of various catalysts and, optionally, co-catalysts. Suitable catalysts include compounds with acidic hydrogen atoms or those with divalent transition metal ions, such as Cu. 2+ , Zn 2+ , Mn2+ , Co 2+ or Ni 2+ , the presence of which causes the formation of complexes of three cyanate ester groups as ligands around the cationic central ion. This complex formation can also be assisted either by heating or by the presence of acidic hydrogen atoms, as shown schematically in Scheme A overleaf for a dicyanate ester N=COROC=N as a monomer, where — ROC=N is a simplified representation of the monomer and R'OH represents the hydrogen donor: Scheme A

[0007] In Kotch et al., Chem. Mater. 7, 801-805 (1995), photopolymerizations of cyanate esters using light-sensitive transition metal complexes of the formula [CpFe(r|6-arene)]X, namely (q6-toluene or -naphthalene)(q5-cyclopentadienyl)iron(II) hexafluorophosphate or antimonate, are also investigated and compared with the results achieved using zinc octoate (zinc 2-ethylhexanoate) as a thermal transition metal catalyst in the polymerization of bisphenol A and E dicyanate monomers. The corresponding polymerizable compositions were coated as films onto a substrate and precured by heating to 393 K (120 °C) for 15 minutes to obtain dry films. These are then irradiated with UV light with a wavelength corresponding to the photoinitiator for 2 minutes and finally cured at 423 K (150 °C).By temporarily exposing the pre-cured compositions to light, the time until the onset of the exothermic peak of thermal curing was significantly shortened and the initial temperature was significantly reduced. While the peak occurred at 267 °C without any catalyst, the temperature was reduced to 111-138 °C when photoinitiators were used. However, when the thermal catalyst zinc octoate was used alone, it was also only 143 °C.

[0008] EP 0,364,073 A1 discloses thermally or radiation-curable compositions based on mono- or polyvalent cyanate esters using organometallic compounds as catalysts, which serve to produce molded articles, coatings, or photoresists. A series of light-sensitive transition metal complexes are also described as organometallic compounds, which were used as catalysts. The cyanate esters used were 2,2-bis(4-cyanatophenyl)propane (bisphenol A dicyanate) and 1,1'-bis(cyanato)biphenyl (presumably referring to the dicyanate of biphenyl-4,4'-diol).For this purpose, DSC ("differential scanning calorimetry") and DPC ("differential photocalorimetry") tests were first conducted with powder mixtures of the respective transition metal complexes and cyanate esters, each heated to 400 °C and irradiated with a 200 W mercury vapor lamp (for DPC). The temperatures of the exotherms caused by polymerization were investigated. The DPC experiments revealed that, in most cases, polymerization of the cyanate esters initiated at a somewhat lower temperature due to irradiation, even without a catalyst. However, the presence of the catalysts caused a temperature decrease of up to 200 °C in DSC (without irradiation) and up to 190 °C in DPC, i.e., below 100 °C. Subsequently, mixtures of cyanate ester, photoinitiator and optionally a solvent were exposed to temperatures between 85 °C and 120 °C, whereby solid bodies were obtained both with and without irradiation.However, nothing is mentioned about their properties.

[0009] And WO 2017 / 040883 A1 discloses a method for producing three-dimensional bodies using a generative manufacturing process, which involves a two-stage curing of a polymerizable composition comprising mono- or polyvalent cyanate esters. For this purpose, a layer-by-layer photopolymerization of various photopolymerizable monomers or prepolymers, such as (meth)acrylates and (meth)acrylamides, as well as various vinyl and other olefinically unsaturated compounds, is first carried out at room temperature to obtain a precured body, which is then subjected to thermal curing by stepwise heating to at least 200 °C and up to 300 °C, during which the polymerization of the cyanate esters also occurs.The latter can be assisted by the optional addition of nucleophilic co-catalysts with acidic hydrogen atoms and / or divalent transition metal ions, and the initial photopolymerization is preferably carried out by Continuous Liquid Interface Production (CLIP). Using bisphenol E dicyanate, polymers, mostly copolymers with various acrylate comonomers, with glass transition temperatures above 200 °C were obtained.

[0010] Against this background, the aim of the invention was to develop a process for producing three-dimensional bodies from cyanate ester monomers by means of a generative manufacturing process, by which polymers with good thermomechanical properties can be obtained without the need for energy-intensive thermal post-treatment.

[0011] SUMMARY OF THE INVENTION

[0012] The present invention achieves this aim by providing the use of cyanate esters as monomers in a polymerizable composition for the production of solid products, wherein the composition further comprises at least one organometallic compound activatable by electromagnetic radiation and / or thermal energy as a polymerization initiator and is heated to a temperature > 70 °C during the polymerization; characterized in that a) multifunctional cyanate esters of the formula R(OCN) nare used as monomers, wherein R is an n-valent hydrocarbon radical having up to 50 carbon atoms and n is an integer > 2; b) an organometallic photoinitiator is used as a polymerization initiator; c) a compound comprising at least one acidic hydrogen atom is used as a co-catalyst; and d) the polymerization is carried out in the course of a 3D printing process comprising heating and irradiating the photopolymerizable composition, wherein all components of the composition are first heated to a temperature > 70 °C in order to obtain a homogeneous liquid mixture, which is then irradiated at at least the same temperature with a wavelength suitable for activating the organometallic compound serving as a polymerization initiator in order to obtain a three-dimensional solid.By combining the process features a) to d) according to the invention, the inventors have succeeded for the first time in producing polymers from multifunctional cyanate ester monomers using a 3D printing process known as hot lithography, which initially heats the polymerizable composition to temperatures above 70 °C and subsequently irradiates the liquid mixture to trigger photopolymerization, which polymers have excellent thermomechanical properties even without complex thermal post-treatment, as the later examples demonstrate.

[0013] What is essential, however, is not only the application of the procedure known as hot lithography according to feature d) to the multifunctional cyanate ester monomers according to feature a), but also the presence of suitable organometallic photoinitiators according to feature b) as well as the presence of co-catalysts with acidic hydrogen atoms according to feature c). As the later comparative examples show, these co-catalysts are indispensable for the process according to the invention, since, with otherwise identical process procedures, no solid polymers are obtainable without co-catalysts.

[0014] In preferred embodiments of the invention, multifunctional aromatic cyanate esters, particularly preferably cyanates of bisphenol or novolak derivatives, are used as monomers as multifunctional cyanate esters, since better thermomechanical properties can be achieved with these compared to aliphatic cyanate esters. In further preferred embodiments of the process according to the invention, multifunctional cyanate ester monomers of the formula R(OCN) n where R has not more than 40 carbon atoms and / or where n = 2 to 4, in order to achieve both higher monomer conversion and higher crosslinking densities in a short time than is possible with bulkier or longer-chain monomer units.

[0015] Furthermore, in the 3D printing process d), the composition according to the present invention is preferably first heated to a temperature of 80°C to 100°C, more preferably from 80°C to 90°C, before exposure and / or heated to a temperature of 80°C to 120°C, more preferably from 90°C to 100°C during exposure. The optimal temperatures naturally also depend on the cyanate ester monomers used and their melting point, since in preferred embodiments of the invention, solid monomers and frequently also solid photoinitiators are used at room temperature, whereby the melting points of the organometallic photoinitiators can sometimes be significantly higher than those of the monomers. The reaction temperatures are therefore preferably selected such that a liquid polymerizable composition is provided both before and during the first phase of exposure, which composition has a suitable viscosity (typically below 20 Pa).s) in order to achieve the highest possible monomer conversions, degrees of polymerization and crosslinking densities in a short time without having to add solvents, reactive diluents or the like.

[0016] The choice of the exposure time set for curing a single layer depends, on the one hand, on the layer thickness and, on the other, on all of the factors mentioned above, primarily on the viscosity of the homogeneous solution at the beginning of exposure, but also on the efficiency of the respective photoinitiator, which in turn is influenced by the light transmittance of the liquid solution. For example, for curing compositions that are not 100% transparent, e.g., those containing fillers or colored components, or in which not all components are fully dissolved, the layer thickness can be reduced accordingly in order to achieve the most complete curing possible of the composition of the respective layer in a relatively short time.

[0017] The organometallic photoinitiator b) is not specifically restricted, as long as its cationic central ion is exposed upon exposure to the appropriate wavelength and thus becomes accessible for attachment of the cyanate ester moieties as ligands to enable their trimerization. In preferred embodiments of the invention, an organometallic complex of an Al, Fe, Mn, Ru, Zn, Co, or Cu ion, more preferably an Fe ion, even more preferably a sandwich or half-sandwich compound, in particular a sandwich compound or half-sandwich carbonyl complex, of these metal ions is used, since such photoinitiators have already proven suitable for catalyzing cyanate ester polymerization.

[0018] For example, all organometallic initiators according to the disclosure of EP 0 364 073 A1 cited at the beginning can be used, which can be activated by exposure to suitable wavelengths – and not just thermally. This also includes those corresponding to the disclosed formula [CpFe(r|6-arene)]X, also cited at the beginning ("Kotch et al."; see above), i.e., cyclopentadienyl-arene-iron(II) complexes, as well as similar complexes with other divalent central ions, but also various metal carbonyl complexes. Several representative examples of such organometallic photoinitiators were used in the examples cited later.

[0019] The co-catalyst c) used according to the present invention is also not specifically restricted, as long as it is capable of releasing at least one acidic hydrogen atom under the respective reaction conditions, which supports the trimerization catalyzed by the transition metal ion of the photoinitiator by protonating one of the three cyanate ester groups according to Scheme A above. A wide range of compounds with acidic hydrogen atoms, such as phenols, bisphenols, alcohols, imidazoles, or aromatic amines, is naturally suitable for this purpose. Due to the structural similarity to the aromatic cyanate esters preferably used as monomers according to the present invention, a phenol derivative, more preferably nonylphenol or bisphenol A, is used as the co-catalyst in preferred embodiments of the invention.As the later examples demonstrate, the presence of a co-catalyst c) is an essential feature for the feasibility of the process of the present invention.

[0020] In preferred embodiments of the invention, an oxidizing agent is also mixed into the polymerizable composition in step d). This is also not specifically restricted according to the present invention, but due to its miscibility with the other components of the composition, it is particularly preferably an organic oxidizing agent and, due to its availability, di-tert-butyl peroxide. The presence of the oxidizing agent can significantly shorten the time until the maximum reaction enthalpy (tmax) is reached and thus the polymerization process in the individual layers. Without wishing to be bound by a particular theory, the inventors assume that the oxidizing agent converts the metal ions of the photoinitiator in the polymerizable composition to their highest oxidation state, e.g.from +11 to +111, in which they usually show higher activity for the complex formation reactions with the three cyanate ester groups as ligands.

[0021] Further, optional components of the polymerizable composition are also not specifically restricted, as long as their presence does not significantly hinder the photopolymerization of the cyanate esters and does not prevent the obtaining of polymers with desired thermomechanical properties. Non-limiting examples of such further components are comonomers that participate in the photopolymerization of the cyanate esters to form corresponding copolymers, such as polyhydric epoxides and maleimides, of which one epoxy or maleimide group reacts with one (epoxide) or two (maleimide) cyanate group(s), respectively. Among the later examples are also those using a representative comonomer. In addition, however, fillers, colorants or dyes, stabilizers, and other conventional additives can also be mixed into the polymerizable compositions in suitable amounts.

[0022] The polymers obtained according to the present invention consistently exhibited good thermomechanical properties.

[0023] EXAMPLES

[0024] The invention is further described below using non-limiting examples which serve only to illustrate the invention and in which the following components were used. Feature a): Cyanate ester monomers

[0025] The following compounds were used as representative aromatic cyanate esters: a1 ) a novolak cyanate (from Lonza, Primaset® PT-30) according to the following formula: , where n = 2-3, melting point: approx. 40 °C; and a2) bisphenol A dicyanate (2,2-bis(4-cyanatophenyl)propane; from TCI) of the following formula: , Melting point: 78-83 °C.

[0026] In one of the examples according to the invention, a combination of the two cyanate esters a1) and a2) was used.

[0027] Feature b): Photoinitiators

[0028] The following compounds were used as representative organometallic photoinitiators: b1 ) (Cumene)(cyclopentadienyl)iron(II) hexafluorophosphate, [CpFeCumeneJPFe- Melting point: 85-87°C; b2) (Methylcyclopentadienyl)manganese(II)-tricarbonyl, Me-CpMn(CO)3 , liquid at room temperature (melting point: 2.2 °C); and b3) Dicyclopentadienyl-bis[2,6-difluoro-3-(1-pyrrolyl)phenyl]titanium (bis(2,6-difluoro-3-(1-hydropyrrol-1-yl)phenyl)titanocene), Cp2Ti(F2Pyr)benzene , Melting point: 160-170 °C.

[0029] Feature c): Co-catalysts

[0030] The following compounds were used as representative co-catalysts with acidic hydrogen atom: c1) Nonylphenol , c3) Bisphenol A , Melting point: 158 °C. e) Co-monomers e1) The only representative co-monomer used, which also served as a crosslinker for the cyanate ester monomer, was 3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexanecarboxylate ("Epoxy"): , liquid at room temperature (melting point: -37 °C). f) Oxidizing agent f1) The only representative oxidizing agent used so far is di-tert-butyl peroxide

[0031] ("DTBP") included in the polymerizable composition: , liquid at room temperature (melting point: -40 °C).

[0032] Examples 1 to 8, Comparison Examples 1 and 2

[0033] Feature d): 3D printing

[0034] Preparation of the polymerizable compositions

[0035] All compositions of the examples and comparative examples were prepared in the same way by simply mixing and heating all components to 80 °C or 90 °C to obtain a liquid mixture, and stirring the mixture until a homogeneous solution was obtained. Polymerization

[0036] The homogeneous solutions were either allowed to cool to room temperature, where they resolidified (in the case of the inventive examples), and then transferred in the solid state into the heatable (or preheated) tank of the 3D printer, or they were quickly poured while still in a hot liquid state into the printer's tank preheated to the respective exposure temperature. In all cases, a Caligma 200UV device from Cubicure was used as the 3D printer, in which one liquid layer of a defined thickness is exposed one after the other on the underside of a movable support platform and thus cured.

[0037] After reaching the exposure temperature of 90 °C or 100 °C – and sometimes simultaneously re-liquefying the solids – the compositions were cured using "hot lithography" 3D printing with layer-by-layer exposure using the printer's laser scanning system with a wavelength of 375 nm. In all cases, a layer thickness of 0.1 mm and a laser scanning system speed of 100 mm / s were selected. In the case of the inventive examples, solid three-dimensional components with a predetermined shape (dimensions: 5 x 4 x 2 cm) were obtained, whereas in the two comparative examples, complete solidification did not occur, but only a formless, highly viscous mass was obtained.

[0038] The type and amount of components (in wt%) as well as the respective temperature before and during exposure are given below for all examples and comparative examples.

[0039] Example 1

[0040] Cyanate ester: a1 ) Novolac cyanate Primaset® PT-30 94

[0041] Photoinitiator: b1 ) [CpFeCumoljPFe- 1

[0042] Co-catalyst: d) nonylphenol 5

[0043] 100 wt.% Mixing temperature 90 °C, exposure temperature 100 °C Example 2

[0044] Cyanate ester: a1) Novolac cyanate Primaset® PT-30 94

[0045] Photoinitiator: b2) Me-CpMn(CO)3 1

[0046] Co-catalyst: d) Nonylphenol 5 >

[0047] 100% by weight

[0048] Mixing temperature 80 °C, exposure temperature 90 °C

[0049] Example 3 Cyanate ester: a1 ) Novolak cyanate Primaset® PT-30 94

[0050] Photoinitiator: b3) Cp2Ti(F2Pyr)benzene 1

[0051] Co-catalyst: c1) Nonylphenol 5

[0052] >

[0053] 100 wt.% Mixing temperature 100 °C, exposure temperature 120 °C

[0054] Example 4

[0055] Cyanate ester: a1) Novolac cyanate Primaset® PT-30 94

[0056] Photoinitiator: b1) [CpFeCumolJPFe- 1 Co-catalyst: c2) Trimethylolpropane 5

[0057] >

[0058] 100% by weight

[0059] Mixing temperature 90 °C, exposure temperature 100 °C Example 5

[0060] Cyanate ester: a1) Novolac cyanate Primaset® PT-30 84

[0061] Photoinitiator: b1) [CpFeCumolJPFe- 1

[0062] Co-catalyst: c3) Bisphenol A 5

[0063] Co-monomer: e1 ) Epoxy 10 >

[0064] 100% by weight

[0065] Mixing temperature 100 °C, exposure temperature 110 °C Example 6

[0066] Cyanate ester: a1 ) Novolac cyanate Primaset® PT-30 94

[0067] Photoinitiator: b1) [CpFeCumolJPFe- 1

[0068] Co-catalyst: c3) Bisphenol A 5

[0069] 100% by weight

[0070] Mixing temperature 100 °C, exposure temperature 110 °C

[0071] Example 7

[0072] Cyanate ester: a2) Bisphenol A dicyanate 94

[0073] Photoinitiator: b1) [CpFeCumolJPFe- 1

[0074] Co-catalyst: d) Nonylphenol 5

[0075] 100% by weight

[0076] Mixing temperature 100 °C, exposure temperature 110 °C

[0077] Example 8

[0078] Cyanate ester: a1) Novolac cyanate Primaset® PT-30 47 a2) Bisphenol A dicyanate 47

[0079] Photoinitiator: b1) [CpFeCumolJPFe- 1

[0080] Co-catalyst: d) Nonylphenol 5

[0081] 100% by weight

[0082] Mixing temperature 90 °C, exposure temperature 100 °C

[0083] Example 9

[0084] Cyanate ester: a1) Novolac cyanate Primaset® PT-30 93

[0085] Photoinitiator: b1) [CpFeCumolJPFe- 1

[0086] Co-catalyst: d) Nonylphenol 5

[0087] Oxidizing agent f1 ) Di-tert-butyl peroxide 1

[0088] 100% by weight

[0089] Mixing temperature 90 °C, exposure temperature 100 °C Comparison example 1

[0090] Cyanate ester: a1) Novolac cyanate Primaset® PT-30 99

[0091] Photoinitiator: b1 ) [CpFeCumoljPFe- 1

[0092] Co-catalyst: - 0

[0093] 100% by weight

[0094] Mixing temperature 90 °C, exposure temperature 100 °C

[0095] Comparison example 2

[0096] Cyanate ester: a1) Novolac cyanate Primaset® PT-30 95

[0097] Photoinitiator: - 0

[0098] Co-catalyst: c1) nonylphenol 5

[0099] 100 wt.% Mixing temperature 80 °C, exposure temperature 100 °C

[0100] As previously mentioned, the compositions of the two comparative examples did not produce solids, but only dimensionally unstable, highly viscous masses, whereas in all nine examples of the present invention the desired shaped bodies were obtained.

[0101] These were subjected to dynamic mechanical thermal analysis (DMTA) for their thermomechanical properties as well as tensile tests, with all nine samples delivering excellent values, including glass transition temperatures (Tg) of over 300 °C and tensile stresses (oz) of well over 45 N / mm 2 Specifically, the following values ​​were measured for the molded bodies obtained by 3D printing (rounded averages of three determinations each):

[0102] Such high values ​​have never been achieved for molded articles produced by additive manufacturing using cyanate esters as monomers. Furthermore, in analogous experiments, the polymerizable compositions of inventive examples 1 and 9, which differ only in the presence of the oxidizing agent, as well as of examples 7 and 8, were prepared as described above by mixing and heating to 90 °C. However, instead of transferring these compositions to the 3D printer's tank, a sample of each was transferred to a DSC crucible. They were then placed in the measurement chamber of a Netzsch photo-DSC device, preheated to 100 °C, and exposed to wavelengths of 320–500 nm. The maximum reaction enthalpy, ΔH, and the time to reach it, tmax, were measured in each case. The following values ​​were obtained (rounded averages of three determinations):

[0103] Apparently, the presence of only 1 wt.% of the oxidizing agent (instead of 1 wt.% of the cyanate ester) in Example 9 reduced the tmax by about one-third compared to the otherwise identical composition of Example 1 with novolak cyanate a1) as photoinitiator. The same applies to the comparison between Example 9 and Example 8 with a 50:50 mixture of novolak cyanate a1) and bisphenol A dicyanate a2), and compared to Example 7, which only contained bisphenol A dicyanate a2), tmax was even reduced by more than two-thirds.

[0104] The use according to the invention of cyanate esters as monomers in a process for producing three-dimensional solid products therefore obviously offers significant and unexpected advantages over the prior art.

Claims

PATENT CLAIMS 1. Use of cyanate esters as monomers in a polymerizable composition for the production of solid products, wherein the composition further comprises at least one organometallic compound activatable by electromagnetic radiation and / or thermal energy as a polymerization initiator and is heated to a temperature > 70 °C during the polymerization, characterized in that a) multifunctional cyanate esters of the formula R(OCN) na) monomers are used, wherein R is an n-valent hydrocarbon residue with up to 50 carbon atoms and n is an integer > 2; b) a metal-organic photoinitiator is used as a polymerization initiator; c) a compound comprising at least one acidic hydrogen atom is used as a co-catalyst; and d) the polymerization is carried out in the course of a 3D printing process comprising heating and irradiation of the photopolymerizable composition, wherein all components of the composition are first heated to a temperature > 70 °C to obtain a homogeneous liquid mixture, which is then irradiated at at least the same temperature with a wavelength suitable for activating the organometallic compound serving as the polymerization initiator to obtain a three-dimensional solid.

2. Use according to claim 1, characterized in that multifunctional aromatic cyanate esters, preferably cyanates of bisphenol or novolac derivatives, are used as monomers.

3. Use according to claim 1 or 2, characterized in that in the formula R(OCN) n R has up to 40 carbon atoms; and / or n = 2 to 4; 4. Use according to one of claims 1 to 3, characterized in that the composition is produced using a 3D printing process. - is first heated to a temperature of 80 °C to 100 °C, preferably 80 °C to 90 °C, before exposure; and / or - is heated to a temperature of 80 °C to 120 °C, preferably 90 °C to 100 °C, during exposure.

5. Use according to one of claims 1 to 4, characterized in that a metal-organic complex of an Al, Fe, Mn, Ru, Zn, Co or Cu ion, preferably an Fe ion, is used as the metal-organic photoinitiator.

6. Use according to claim 5, characterized in that a sandwich or half-sandwich compound, preferably a sandwich compound or a half-sandwich carbonyl complex, is used as the organometallic complex.

7. Use according to any one of claims 1 to 6, characterized in that a phenol derivative, preferably nonylphenol or bisphenol A, is used as a co-catalyst.

8. Use according to any one of claims 1 to 7, characterized in that in step d) an oxidizing agent, preferably an organic oxidizing agent, is also mixed into the polymerizable composition.

9. Use according to claim 8, characterized in that di-tert-butyl peroxide is mixed in as an organic oxidizing agent.

10. Use according to any one of claims 1 to 9, characterized in that after completion of the 3D printing process, a thermal post-curing is carried out, preferably by heating for several hours to a temperature > 200 °C and / or by heating for several days to a temperature < 200 °C.

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