THERMOSETTING MATERIAL FOR USE IN A 3D PRINTING PROCESS

Abstract

The present invention relates to a thermosetting material for use in a 3D printing process comprising: a) at least one epoxy resin A, b) at least one elastomer-modified epoxy resin B, c) at least one resin C with a dynamic viscosity of below 4 Pas at 150° C., d) at least one of a curing agent D capable of reacting with A, B and optionally C, e) and optionally additional compounds,
wherein the glass transition temperature of the uncured material is at least 30° C., preferably at least 40° C. as measured with DSC at a heating rate of 20° C./min.

The invention further relates to a method of producing a cured 3D thermoset object and the use of the above-mentioned thermosetting material in a 3D printing process.

Claims

1. A thermosetting material for use in a 3D printing process comprising: a) at least one epoxy resin A, b) at least one elastomer-modified epoxy resin B, c) at least one resin C with a dynamic viscosity of below 4 Pas at 150° C. as determined according to the method given in the description, d) at least one curing agent D capable of reacting with A, B and optionally C, e) and optionally additional compounds, wherein the glass transition temperature of the uncured material is at least 30° C., preferably at least 40° C. as measured with DSC at a heating rate of 20° C./min as determined according to the method given in the description.

2. A material according to the previous claim, characterized in that the material has a minimum viscosity of 50-20000 Pas, preferably 50-10000 Pas, yet preferably 300-5000 Pas, more preferably 500-2000 Pas and most preferably 600-1500 Pas as determined according to the method given in the description.

3. A material according to claim 1, characterized in that gel time of the material is 100-900 seconds, preferably 100-700 seconds, yet preferably 150-400 seconds and most preferably 200-300 seconds at 150° C. as determined according to ISO 8130-6:2011.

4. A material according to claim 1, characterized in that the glass transition temperature of resin C deviates at most 20° C., preferably at most 15° C., more preferably at most 10° C. from the glass transition temperature of epoxy resin A.

5. A material according to claim 1, characterized in that the epoxy resin A is or comprises a bisphenol-based epoxy resin, a phenolic epoxy resin, a Novolac epoxy resin or a mixture thereof.

6. A material according to claim 1, characterized in that elastomer-modified epoxy resin B is or comprises a rubber and/or carboxyl-terminated butadiene-acrylonitrile (CTBN) modified epoxy resin.

7. A material according to claim 1, characterized in that resin C is or comprises an epoxy resin, preferably a(semi)crystalline epoxy resin and/or a polycyclic aromatic ring-based epoxy resin including any partially or fully hydrogenated derivatives thereof, in particular a naphthalene and/or anthracene and/or phenantrene and/or phenaline and/or tetracene based epoxy resin.

8. A material according to claim 1, characterized in that resin C is or comprises a (semi)crystalline polyester resin, preferably an acid-functional (semi)crystalline polyester resin.

9. A material according to claim 1, characterized in that resin C is or comprises a (semi)crystalline, acid functional polyester resin and a polycyclic aromatic ring-based epoxy resin including any partially or fully hydrogenated derivatives thereof, in particular a naphthalene and/or anthracene and/or phenantrene and/or phenaline and/or tetracene based epoxy resin.

10. A material according to claim 1, characterized in that the curing agent D is or comprises an amine-functional compound, in particular an aliphatic amine compound and/or an aromatic amine compound, and/or an amide functional compound, in particular a cyanamide compound, preferably a dicyandiamide-based compound.

11. A material according to claim 1 characterized in that the curing agent D comprises a first compound D1 and a second compound D2 wherein the first compound D1 starts reacting with epoxy resin A at 70-110° C. and the second compound D2 starts reacting with epoxy resin A at a temperature of above 110° C., preferably between 120 and 200° C. and more preferably between 130 and 170° C.

12. A method of producing a cured 3D thermoset object comprising at least the following steps: a. subjecting the material according to any of claims 1-11 to a 3D printing process; b. obtaining a partially cured 3D thermoset object and; c. subjecting the partially cured 3D thermoset object to a post-curing process, comprising a heat treatment, to further cure the 3D thermoset object.

13. A method according to claim 12 characterized in that the heat treatment comprises heating the partially cured 3D thermoset object to a temperature of at least 110° C., preferably 120-300° C., more preferably 130-250° C. and most preferably 140-200° C.

14. A 3D object produced from a thermosetting material according to claim 1.

15. Use of a material according to claim 1 in a 3D printing process, preferably in selective laser sintering (SLS), fused filament fabrication (FFF), composite based additive manufacturing (CBAM), fused granular fabrication (FGF) or powder bed 3D printing process and more preferably in selective laser sintering.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0143] FIG. 1 shows typical DSC curves of a material according to the present invention. The Tg of the uncured material is 57° C., whereas the Tg of the fully cured material is 146° C. in the second run and 147° C. in the third run (temperatures at the point of inflection of the respective transition steps). As this shift was less than 2° C., the material before the second run is considered as fully cured. The curing can clearly be observed by the presence of the exothermic reaction starting at temperatures above 100° C. In the second and third DSC-run, no further exothermic reaction is observed, indicating that the material is fully cured.

[0144] FIG. 2 shows typical DSC curves of a material according to the state of the art. The Tg of the uncured material is 57° C., whereas the Tg of the cured material is only 60° C. in the second run and 65° C. in the third run (temperatures at the point of inflection of the respective transition steps). The curing can clearly be observed by the presence of the exothermic reaction starting at temperatures above 110° C. In the second and third DSC-run, no further exothermic reaction is observed, indicating that the material is highly or even fully cured. The slight shift of the Tg from the second to the third run indicates, however, that some residual curing occurred during the second run. As this shift was more than 2° C., the material before the second run is considered as only partially cured.

[0145] FIG. 3 shows curves obtained from a typical viscosity measurement of a material according to the present invention. The black line with the lowest minimum shows the viscosity. The temperature increase is shown by the grey line. As can be seen, the viscosity first decreases, reaches a minimum and then starts to increase as a result of the curing of the material. The minimum viscosity (minimum of (|η*|) of the material is about 706 Pas at about 130° C.

[0146] FIG. 4 shows curves obtained from a typical viscosity measurement of a thermosetting material according to the state of the art and can be interpreted identically to FIG. 3. The minimum viscosity (minimum of |η*|) of the material is 26800 Pas at about 110° C.

[0147] FIG. 5 shows an illustrative example for the determination of the start of the curing reaction between an epoxy resin A with a curing compound D1 by means of a DSC measurement. According to the definition and method given within the present application, the curing reaction between epoxy resin A and curing compound D1 starts at the onset point of the exothermic curing peak, being 141° C.

MEASUREMENT METHODS

[0148] If no measurement method is specified for a certain parameter/property, the measurement shall be performed according to the corresponding ISO standard for the measurement method of the respective parameter/property. If there is no ISO standard, the measurement shall be performed according to corresponding EN standard of the measurement method. If there is no EN standard, the measurement shall be performed according to the corresponding national DIN standard (Germany). If there is no national DIN standard, the measurement shall be performed according to the corresponding national ONORM standard (Austria). If there is also no ONORM standard, the measurement shall be performed by the method that is considered as most appropriate by the skilled person.

[0149] If not specified otherwise herein, the standard to be used for a certain measurement is the one that was published latest before the application date of the present application.

[0150] If a measurement method is given incorrectly or incompletely herein, it is to be replaced or completed by the corresponding standard in accordance with the above ordering.

[0151] [Acid value (AV)] The term acid value or acid number (AV) is defined as the mass of potassium hydroxide (KOH) in milligrams that is required to neutralize one gram of chemical substance. The acid value is a measure of the amount of acid groups in a chemical compound, such as an acid functional polyester, or in a mixture of compounds. Typically, a known amount of sample is dissolved in organic solvent and is then titrated with a solution of potassium hydroxide (KOH) with known concentration and with phenolphthalein as a color indicator. The acid value (AV) is determined analogously to ONORM EN ISO 2114:2002 with the difference that a mixture of 28 parts of acetone and 1 part of pyridine (% w/w) is used as a solvent.

[0152] [Hydroxyl value (HV)] The term hydroxyl value or hydroxyl number (HV) is the value which is defined as the number of milligrams (mg) of potassium hydroxide required to neutralize the acetic acid taken up on acetylation of one gram of a chemical substance that contains free hydroxyl groups. The hydroxyl value is a measure of the content of free hydroxyl groups in a chemical substance, usually expressed in units of the mass of potassium hydroxide (KOH) in milligrams equivalent to the hydroxyl content of one gram of the chemical substance. The analytical method used to determine the hydroxyl value preferably involves acetylation of the free hydroxyl groups of the substance in organic solvent. After completion of the reaction, water is added, and the remaining unreacted acetylation reagent, which is preferably acetic anhydride, is hydrolyzed and measured by titration with potassium hydroxide. The hydroxyl value is determined according to ONORM EN ISO 4629:1998.

[0153] [median particle size (d50)] The median particle size d50, also known as the median diameter or the medium value of the particles size distribution (PSD) is to be understood as the particle size at 50% of a cumulative distribution. For example, a d50 value of 60 μm means that 50% of the particles are larger than 60 μm and 50% of the particles are smaller than 60 μm. The d50 value is determined by laser diffraction using a Malvern Mastersizer Scirocco 2000 manufactured by Malvern Panalytical GmbH (Germany). The laser diffraction is a volume-based measurement method, which means that the particle size distribution (PSD) is a volume distribution and the % are to be understood as vol %. The median particle size (d50) was determined according to ISO 8130-13:2019. Terms such as D50, d50, d(50), D(50) and the like are used synonymously herein.

[0154] [Epoxy equivalent weight (EEW)] The epoxy equivalent weight (EEW) is defined as the mass of a compound or a mixture of compounds that contains one (1) mol of epoxy groups. A high EEW means a low content of epoxy groups within the sample. The EEW is determined according to ISO 3001:1999.

[0155] [Weight average molecular weight (Mw)] The weight average molecular weight (Mw) is a statistic number relating to the molecular weight distribution of a chemical sample, typically a resin as defined herein. Mw is determined by gel permeation chromatography (SECurity.sup.2 GPC System, as available from PSS-Polymer (Germany)) against polyacrylate standards. For amorphous compounds, tetrahydrofuran (THF) is employed as eluent; for (semi)crystalline compounds, chloroform is employed as eluent.

[0156] [Reuse percentage (% re)] The reuse percentage (% re) is defined as the mass ratio of recycled powder (e.g. from the powder bed or from overflow containers) to the total powder composition (consisting of fresh and recycled powder) to be used in a 3D printing process. For example, in case a powder composition consists of 30% recycled powder and 70% fresh powder, the reuse percentage is calculated as follows: 30/(70+30)*100%=30% re.

[0157] [Glass transition temperature (Tg)] The glass transition temperature (Tg) is the gradual transition from an amorphous or (semi)crystalline material from a hard and brittle (glassy) state into a rubbery, entropy-elastic state. The glass transition temperature (Tg) of a compound/material is determined by differential scanning calorimetry (DSC) using a NETZSCH (Germany), DSC 204 F1 Phoenix device in accordance to ISO 11357-2:2014 using a heating/cooling rate of 20° C./min (10-15 mg sample weight). The samples were heated/cooled under nitrogen atmosphere. The Tg is determined by evaluating the point of inflection of the endothermal step (only endothermal steps above 0° C. are being considered). The following temperature program is used for the determination of the Tg (see Table 1a):

[0158] Only heating cycle #1 (steps #0 to #6) of the heating/cooling program is applied to determine the Tg of a fresh uncured material or an individual compound (e.g a resin). Only heating cycle #1 is also applied to determine the Tg of an already partially or fully cured material.

[0159] The combination of heating cycles #1 & #2 (steps #0 to #10) of the heating/cooling program is applied as a quick test to determine the Tg of the cured material without performing the additive manufacturing and optional post-curing step (applicable for thermally curable materials only). The material is cured in the course of heating cycle #1 and the Tg of the cured material is then obtained from heating cycle #2. Heating cycle #3 (steps #11 to #13) may additionally be performed afterwards to confirm full curing of the sample.

TABLE-US-00001 TABLE 1a Temperature program for DSC measurements Step Heating Temperature Heating/cooling Time # cycle # Mode [° C.] rate [K/min] [hh:mm] 0 1 Start  25 1 Dynamic  80* 20 00:03 2 Isotherm  80* 00:01 3 Dynamic −25 20 00:05 4 Isotherm −25 00:02 5 Dynamic 250 20 00:14 6 Isotherm 250 00:20 7 2 Dynamic −25 20 00:14 8 Isotherm −25 00:02 9 Dynamic 250 20 00:14 10 Isotherm 250 00:20 11 3 Dynamic −25 20 00:14 12 Isotherm −25 00:02 13 Dynamic 250 20 00:14 *If a curing compound already reacts significantly at a temperature of 80° C., then the sample is heated up to a lower temperature, e.g. 50° C. or 60° C. in steps #1 and #2 depending on the reactivity of the curing compound.

[0160] [Heat deflection temperature (HDT)] The heat deflection temperature, also known as heat distortion temperature, is the temperature at which a polymeric sample deforms under a specified flexural stress. The HDT is determined with a VIC-2450 machine from Zwick Roell (Germany) according to ISO 75-2:2013, wherein method A of said norm is employed and referred to exclusively herein. Said method employs a flexural stress of 1.80 MPa. So any reference to an HDT value is a reference to an HDT-A value.

[0161] [Mechanical properties] The mechanical properties (tensile modulus, stress at break and strain at break) of the 3D objects were measured according to DIN EN ISO 527-1:2019 on a Shimadzu AGS-X (Japan) universal testing machine equipped with a load cell of 10 kN. Tensile type 1A specimens were used and the clamping length was set to 115 mm. The crosshead speed was 5 mm/min for the determination of the tensile modulus, which was obtained by linear regression in the strain range between 0.1 and 0.25%. After reaching 0.25% strain, the crosshead speed was increased to 50 mm/min for the remainder of the test.

[0162] [Curing degree] The curing degree is defined as the value obtained by dividing the heat released upon reaction of the partially or fully cured material by the heat released upon reaction of the uncured material. The heat released upon reaction is obtained from DSC measurements (NETZSCH, DSC 204 F1 Phoenix, 10-15 mg per sample) of the respective material at a heating rate of 20° C./min by evaluating the area (in J/g) of the exothermic reaction peak(s). Of course, same amounts (by weight) of sample of the uncured and partially cured material have to be used. Only heating cycle #1 (Table 1a) is used for the respective measurement. A partially cured material or 3D thermoset object is defined as having a curing degree of between 0.0001 (0.01%) and 0.9 (90%), whereas a fully cured material or 3D thermoset object is defined as having a curing degree of above 0.9 (90%).

[0163] Alternatively, full curing of a sample can be determined by running two consecutive DSC measurements (NETZSCH, DSC 204 F1 Phoenix, 10-15 mg per sample, 20° C./min heating/cooling rate, −25° C. to 250° C. and observing the shift in Tg. As defined herein, the Tg of a fully cured sample will not significantly shift in two consecutive DSC measurements (|ΔTg|<2° C.). The combination of heating cycle #1 and #2 of the heating/cooling program (see Table 1a) is applied to confirm full curing of the material; for this purpose, the glass transition temperatures of the cured material as determined by the first and second heating cycle are compared. In case |ΔTg|<2° C., the tested material is considered as fully cured.

[0164] [Viscosity]

Material: The viscosity, in particular the minimum viscosity, of the material is measured by using a parallel plate rheometer AR2000ex by TA Instruments (US). For the sample preparation, 1.1 g of the material is pressed into a tablet (diameter=25 mm, height=approximately 1.8 mm) at a pressure of 10 bar by using a manual hydraulic press (Mauthe Maschinenbau, Germany). The tablet is clamped between the two plates of the parallel plate rheometer, the chamber of the rheometer is closed and the measurement is started with the following heating program and parameters: [0165] 20 to 40° C. at a heating rate of 5° C./min [0166] 40 to 60° C. at a heating rate of 10° C./min [0167] 60 to 150° C. at a heating rate of 5° C./min. [0168] the sample is kept at 150° C. for the rest of the measurement (typically 50 minutes in total) [0169] frequency: 1 Hz [0170] amplitude: 0.05%
The storage modulus (G′), the loss modulus (G″), the complex shear modulus (G*) and the complex shear viscosity (η*) are determined. The absolute value of the complex shear viscosity (|η*|) is denoted as the viscosity of the material in Pa*s herein and is provided by the analysis software of the rheometer. Supplementary ISO 6721-10:2015 is being employed. Also, the minimum viscosity (=minimum of the absolute value of the complex shear viscosity=min(|η*|)) may thus be determined by the analysis software of the rheometer.
Resins (e.g.: resins A, B, C)/other compounds: The dynamic viscosity of resins is determined by using a cone-plate viscometer device (Brookfield CAP 2000+ by Brookfield Ametek, US) equipped with spindle 06 (CAP-S-06); depending on the expected dynamic viscosity of the sample, also other spindles might be appropriate (e.g. spindle 02 for dynamic viscosities of below 0.5 Pas at 150° C.). The plate is pre-heated to 150° C. and an appropriate amount of sample (typically about 0.1 g for solid compounds and spindle 06) is applied onto the plate. The sample is heated to 150° C. and the measurement is started by applying a rotational speed of 700 rounds per minute (rpm) for a time period of 115 seconds. The dynamic viscosity at a temperature of 150° C. is then obtained from the display of the device. Supplementary information can be found in the user manual of the device (Manual No. M02-313-I091699 as available from: https://www.brookfieldengineering.com/-/media/ametekbrookfield/manuals/lab%20viscometers/cap2000%20instructions.pdf?la=en [retrieved on 06.05.2021])(e.g.: appropriate choice of spindle, guideline for the appropriate amount of sample, etc.).
[Softening Point] The softening point is determined according to DIN ISO 51920:2012.
[Gel time] The gel time is a measure of the reactivity of a thermosetting material at a given temperature. The shorter the gel time, the faster the curing reaction occurred at the given temperature. The gel time is measured at 150° C. using a Gelnorm Heating System (Gel Instrument AG, Switzerland) with a temperature controller TC-4 (50 to up to 200° C.). The gel time is determined according to ISO 8130-6:2011.

[0171] [Reactivity of epoxy resin A with a curing compound (e.g.: D1 or D2] The temperature at which the curing reaction of an epoxy resin A with a curing compound D (e.g.: D1 or D2) starts is determined by preparing a well dispersed mixture (e.g. obtained from extrusion) of the resin A with the respective curing compound (e.g.: D1). The amount of curing compound is chosen so that the epoxy resin A can be fully cured by said curing compound. The mixture is then subjected to a DSC measurement (NETZSCH, DSC 204 F1 Phoenix, 10-15 mg sample weight, only heating cycle #1 according to Table 1a) with a heating rate of 20° C./min. The heat flow is plotted as a function of temperature up to 250° C. (in case the curing reaction occurs at higher temperature or the curing peak is cut off at 250° C., the measurement is performed again up to a higher temperature, e.g.: 300 or 350° C. with a fresh sample). The temperature at which the reaction of the curing compound with the epoxy resin A starts is defined as the so-called onset temperature of the exothermic curing peak. The onset temperature is determined as the temperature at the point of intersection between the baseline of the respective exothermic curing peak and a tangent to the point of inflection of the increasing branch of the exothermic curing peak. This is further illustrated in FIG. 5. This procedure is repeated for each possible combination of one epoxy resin A and one curing compound. For a material comprising one epoxy resin A (R1) and two curing compounds (C1, C2), two model materials with compositions R1C1 and R1C2 need to be prepared and measured as described above to determine the onset temperature of the respective curing reaction. For a material comprising one epoxy resin A (R1) and three curing compounds (C1, C2, C3), the following model materials need to be prepared and measured: R1C1, R1C2, R1C3. In turn, for a material comprising two epoxy resins A (R1, R2) and two curing compounds (C1, C2), the following model materials need to be prepared and measured: R1C1, R1C2, R2C1, R2C2; and so forth.

By this method, suitable compounds to be employed as curing compound D1 and curing compound D2 can be determined by the skilled person in case the temperature dependence of the reactivity of such compound with a respective epoxy resin A is unknown.
[Melting point/range of (semi)crystalline resins] The melting point of (semi)crystalline resins is determined according to ISO 3146:2000

EXAMPLES

Example 1

[0172] The material was composed of D.E.R. 642U (Epoxy Resin A; 54.0 wt %, EEW=500-560 q/eq; viscosity=1.9-3.3 Pas (150° C.), softening point=89-97° C., Dow Chemical Company), Epiclon HP-4710 (naphthalene based epoxy resin C, 5.0 wt %, softening point=96° C., EEW=171 g/eq, viscosity=1.0 Pas (150° C.), DIC Corp.); Kukdo KR-102 (rubber modified Bisphenol-A-type epoxy resin B; 15.0 wt %, EEW=1100-1300, Kukdo Chemical Co, Ltd.); Aradur 835 CH (aliphatic polyamine curing agent, 2.0 wt. %, Huntsman), 2-Ethylimidazole (curing agent, 1.5 wt. %, Donauchem GmbH); Epikure P-108 (accelerated Dicyandiamide curing agent, 1.0 wt %, Hexion Chemicals); Aktifit AM (filler, 10.0 wt. %, Hoffmann Mineral GmbH), Benzoin=Hydroxybenzylphenyl-Ketone (degassing additive, 1.0 wt %, Harke Chemicals GmbH, Germany); Resiflow PL200 (flow additive, 2.5 wt %, Estron Chemical Inc., US), TI-Select TS6200 (pigment additive, 8 wt %, DuPont Titanium Technologies, US). The total quantities of each compound were chosen such that 40 kg of powder was obtained. All compounds were premixed in a high-speed mixer (Thermo PRISM Pilot 3, Thermo Fisher Scientific, US) for 1 min at 25° C. with a rotor speed of 1000 rpm and then extruded in a twin-screw ZSK-18 extruder (Coperion, Germany) at a screw speed of 400 rpm with a temperature gradient from 40 to 100° C. and a cooling device for the feeding area was used. The mixture obtained was then cooled down, granulated and fine ground to obtain a powder having a D50 of less than 80 μm. The Tg of the material was 60° C.

Example 2

[0173] The material was composed identical to Example 1, but Epiclon HP-4710 was exchanged 1:1 with Sirales PE 5900 ((semi)crystalline, carboxy functional polyester, AV=28-36 mgKOH/g, viscosity=1.3 Pas (150° C.), Mp=110° C., melting range of 105-120° C., Sir Industriale, Italy) was employed as resin C. The material was produced in full analogy to Example 1. The Tg of the material was 59° C.

Example 3

[0174] D.E.R.™ 6510-HT (epoxy resin A, 41.5 wt %, EEW=400-450 q/eq, viscosity=7.5-9.5 Pas (150° C.), softening point=89-97° C.), Dow Chemical Company); Epiclon® HP-4710 (naphtalene based epoxy resin C, 12.0 wt %, softening point=96° C., EEW=171 g/eq, viscosity=1.0 Pas (150° C.), DIC Corp.); HyPox® RK84L (CTBN-modified epoxy resin B, 10.0 wt %, softening point is not measurable, EEW=1250-1500 g/eq, viscosity=300-500 Pas (100° C.), Huntsman), Aradur 835 CH (aliphatic polyamine curing agent D; 1.5 wt %, Huntsman), 2-Ethylimidazole (curing agent D, 0.5 wt %, Donauchem GmbH); Epikure P-108 (accelerated Dicyandiamide curing agent D, 1 wt %, Hexion Chemicals); Aktifit AM (filler, 9 wt %, Hoffmann Mineral GmbH), Benzoin (Hydroxybenzylphenyl-Ketone degassing additive, 0.5 wt %, Harke Chemicals GmbH); Resiflow PL200 (flow additive, 2.0 wt %, Estron Chemical Inc.); TI-Select TS6200 (pigment filler, 10 wt %, DuPont Titanium Technologies), Exolit® OP1230 (organic phosphinate flame retardant filler, 12 wt %, Clariant Ltd.). The material was produced in full analogy to Example 1. The Tg of the material was 63° C.

Example 4

[0175] D.E.R.™ 6510-HT (epoxy resin A, 44.5 wt %, EEW=400-450 q/eq, viscosity=7.5-9.5 Pas (150° C.), softening point=89-97° C.), Dow Chemical Company); Epiclon® HP-4710 (naphtalene based epoxy resin C, 11.0 wt %, softening point=96° C., EEW=171 g/eq, viscosity=1.0 Pas (150° C.), DIC Corp.); HyPox® RK84L (CTBN modified epoxy resin B, 7.0 wt %, softening point is not measurable, EEW=1250-1500 g/eq, viscosity=300-500 Pas (100° C.), Huntsman); Sirales PE 5900 ((semi)crystalline polyester resin C, 7.0 wt %, acid value=28-36 mgKOH/g, Tg<0° C., viscosity=1.5 Pas (150° C.), Sir Industriale); Aradur 835 CH (aliphatic polyamine curing agent D, 1.5 wt %, Huntsman), 2-Ethylimidazole (curing agent D, 0.5 wt %, Donauchem GmbH); Epikure P-108 (accelerated Dicyandiamide curing agent D, 1 wt %, Hexion Chemicals); Aktifit AM (filler, 8 wt %, Hoffmann Mineral GmbH); Benzoin (Hydroxybenzylphenyl-Ketone degassing additive, 0.5 wt %, Harke Chemicals GmbH); Resiflow PL200 (flow additive, 2.0 wt %, Estron Chemical Inc.); M TI-Select TS6200 (pigment filler, 5 wt %, DuPont Titanium Technologies); Exolit® OP1230 (organic phosphinate flame retardant filler, 12 wt %, Clariant Ldt.). The material was produced in full analogy to Example 1. The Tg of the material was 55° C.

Example 5

[0176] D.E.R.™ 6510-HT (epoxy resin A, 41.5 wt %, EEW=400-450 q/eq, viscosity=7.5-9.5 Pas (150° C.), softening point=89-97° C.), Dow Chemical Company); Epiclon® HP-4710 (naphtalene based epoxy resin C, 12.0 wt %, softening point=96° C., EEW=171 g/eq, viscosity=1.0 Pas (150° C.), DIC Corp.); HyPox® RK84L (CTBN-modified epoxy resin B, 10.0 wt %, softening point is not measurable, EEW=1250-1500 g/eq, viscosity=300-500 Pas (100° C.), Huntsman), Aradur 835 CH (aliphatic polyamine curing agent D; 3.0 wt %, Huntsman), Aktifit AM (filler, 9 wt %, Hoffmann Mineral GmbH), Benzoin (Hydroxybenzylphenyl-Ketone degassing additive, 0.5 wt %, Harke Chemicals GmbH); Resiflow PL200 (flow additive, 2.0 wt %, Estron Chemical Inc.); TI-Select TS6200 (pigment filler, 10 wt %, DuPont Titanium Technologies), Exolit® OP1230 (organic phosphinate flame retardant filler, 12 wt %, Clariant Ltd.). The material was produced in full analogy to Example 1. The Tg of the material was 58° C.

Example 6

[0177] D.E.R.™ 6510-HT (epoxy resin A, 44.5 wt %, EEW=400-450 q/eq, viscosity=7.5-9.5 Pas (150° C.), softening point=89-97° C.), Dow Chemical Company); Epiclon® HP-4710 (naphtalene based epoxy resin C, 11.0 wt %, softening point=96° C., EEW=171 g/eq, viscosity=1.0 Pas (150° C.), DIC Corp.); Kukdo KSR-1000 (Silicone-elastomer Modified Epoxy Resin; 7.0 wt %; Ph-OH EW=1100-1300 g/eq; viscosity=1000-5000 mPa*s (175° C.); Kukdo Chemical Co, Ltd.); Sirales PE 5900 ((semi)crystalline polyester resin C, 7.0 wt %, acid value=28-36 mgKOH/g, Tg<0° C., viscosity=1.5 Pas (150° C.), Sir Industriale); Aradur 835 CH (aliphatic polyamine curing agent D, 3.0 wt %, Huntsman), Aktifit AM (filler, 8 wt %, Hoffmann Mineral GmbH); Benzoin (Hydroxybenzylphenyl-Ketone degassing additive, 0.5 wt %, Harke Chemicals GmbH); Resiflow PL200 (flow additive, 2.0 wt %, Estron Chemical Inc.)M TI-Select TS6200 (pigment filler, 5 wt %, DuPont Titanium Technologies); Exolit® OP1230 (organic phosphinate flame retardant filler, 12 wt %, Clariant Ldt.). The material was produced in full analogy to Example 1. The Tg of the material was 65° C.

Example 7

[0178] D.E.R.™ 6510-HT (epoxy resin A, 50 wt %, EEW=400-450 q/eq, viscosity=7.5-9.5 Pas (150° C.), softening point=89-97° C.), Dow Chemical Company); Kukdo KD 211-H (novolac modified epoxy resin C, 11.0 wt %, softening point=90-98° C., EEW=510-550 g/eq, viscosity=2.5-3.5 Pas (150° C.), DIC Corp.); Kukdo KR-692 (acrylic elastomer Modified Epoxy Resin; 10.0 wt %; EEW=675-775 g/eq; softening point=82-98° C.); Kukdo Chemical Co, Ltd.) Eutomer B31 (curing agent, 1.5 wt %, Eutec Chemical Co. Ltd.), Aktifit AM (filler, 8 wt %, Hoffmann Mineral GmbH); Benzoin (Hydroxybenzylphenyl-Ketone degassing additive, 0.5 wt %, Harke Chemicals GmbH); Resiflow PL200 (flow additive, 2.0 wt %, Estron Chemical Inc.); TI-Select TS6200 (pigment filler, 5 wt %, DuPont Titanium Technologies); Exolit® OP1230 (organic phosphinate flame retardant filler, 12 wt %, Clariant Ltd.). The material was produced in full analogy to Example 1. The Tg of the material was 62° C.

Comparative Example 1 (Example 12 of WO2018167067/Example 15 of WO2018167065)

[0179] The material was composed of “polyester 1” (27.7 wt %); D.E.R 642U (29.3 wt %, Dow Company Company); Sirales PE 5900 ((semi)crystalline polyester, 10.0 wt %, Mp=110° C., melting range of 105-120° C., Sir Industriale); Eutomer B31 (curing agent, 1.2 wt %, Eutec Chemical Co. Ltd.); Aradur 835 (curing agent, 4.0 wt %, Huntsman); Modaflow P6000 (additive, 1.0 wt %, Allnex, Austria); Lanco TF 1778 (additive, 0.8 wt %, Lubizol, US); Ti-select (pigment additive, 13.0 wt %, DuPont); Staphyloid 3832 (core-shell thermoplast filler, 5.0 wt %, AICA, Japan); Tremin VP 939-600 EST (wollastonite filler, 5 wt %, HPF, Quarzwerke, Germany); Omyacarb 1-SV (filler, 3.0 wt %, Omya, Switzerland). The material was produced in full analogy to Example 1. The Tg of the material was 56° C.

[0180] “polyester 1” is a carboxy functional polyester having an acid number of 68-76 mg KOH/g and a viscosity of 2.0 to 3.5 Pas (200° C.), which comprises terephthalic acid, adipic acid, neopentyl glycol, monoethylene glycol and trimellitic anhydride as the essential components and was prepared by melt polymerization at a temperature of up to 240° C.

Comparative Example 2

[0181] Commercially available thermoplastic polyamide 12 (PA12) as available from various suppliers. In here FS3300PA, available from Farsoon Technologies (Hunan Farsoon, China) was employed for comparison purposes. No printing test was performed.

[0182] Before performing any printing tests, the glass transition temperatures of the fully cured materials were measured in order to evaluate the suitability of the respective materials for applications at elevated temperatures. The measured Tg values are listed in Table 1.

TABLE-US-00002 TABLE 1 Tg values of the uncured and fully cured materials Tg [° C.] Tg [° C.] # uncured fully cured Example 1 60 130 Example 2 59 120 Example 3 63 154 Example 4 55 135 Example 5 58 144 Example 6 65 125 Example 7 62 120 Comparative Example 1 56 63 Comparative Example 2 48.8* 48.8* *Tg values are identical because thermoplastic PA12 is not curable.

[0183] Printing Tests

[0184] In order to assess the suitability of the material according to the present invention to be used in a 3D printing process, 3D printing tests were performed. An SLS 3D printing process was chosen, as the materials according to the present invention are particularly suitable to be provided in powder form. Further, the closest state of the art also used an SLS process, which allowed easy comparison of the materials and obtainable 3D thermoset objects according to the present invention with the state of the art. However, the materials according to the present invention may be used for various 3D printing processes other than SLS.

[0185] [SLS printing process] A PRODWAYS ProMaker P1000 SLS 3D Printer (Prodways, France) was used for all the SLS 3D printing tests. Tensile bars (type 1A) according to DIN EN ISO 527-1:2019 were printed. The parameter settings of the SLS 3D printer are listed in Table 2.

TABLE-US-00003 TABLE 2 SLS 3D printer parameter settings for the printing tests hatch layer powder bed feeder laser distance scan speed thickness temperature temperature power [W] [mm] [mm/sec] [mm] [° C.] [° C.] 16 0.13 3500 0.10 65 45

[0186] After the 3D printing process, the objects (partially cured 3D thermoset objects) were unpacked from the powder bed by hand and sandblasted by using a Guyson Formula 1200 blast cabinet.

[0187] [Post-Curing]

[0188] The printed objects were post-cured in a convection oven (Thermo Fisher Scientific (US), Heraeus OVEN 199L) using the following temperature program: start at 25° C.-printed object is put in the oven; heating 1° C./min; holding for 30 minutes at 100° C.; heating: 1° C./min; holding 15 minutes at 150° C.; heating 1° C./min and further holding 15 minutes at 200° C. Then the post-cured objects (fully cured 3D thermoset objects) were cooled to ambient temperature (25° C.). Finally, full curing of the 3D thermoset objects was confirmed by DSC (the shift in Tg was below 0.5° C. in two consecutive DSC measurements according to the method as described above).

Characterization of the Fully Cured 3D Thermoset Objects

[0189] [Mechanical properties] The mechanical characterization of the printed objects was carried out using a commercially available tensile tester (DIN EN ISO 527-1:2019) facility (Shimadzu (Japan) AGS-X (Japan) universal testing machine). A clamping length of 115 mm and a crosshead speed of 5 mm/min were applied. The following Table 3 shows the determined mechanical properties of fully cured tensile bars (type 1A). Based on the tensile test, the tensile modulus, the stress at break and the strain at break were determined according to DIN EN ISO 527-1:2019.

TABLE-US-00004 TABLE 3 Mechanical properties of the fully cured tensile bars Tensile modulus Stress at Strain at # [GPa] break [MPa] break [%] Example 1 2.51 46.8 2.45 Example 2 2.7 31 1.5 Example 3 2.5 46 2.4 Example 4 2.6 38 1.7 Comparative 1.85 32.0 5.03 Example 1 Comparative 1.6 46 36 Example 2

[0190] The heat deflection temperature (HDT) and the glass transition temperature (Tg) of the fully cured, inventive and comparative, 3D thermoset objects were determined and are listed in Table 4.

TABLE-US-00005 TABLE 4 HDT and Tg of the fully cured 3D objects # HDT-A [° C.] Tg [° C.] Example 1 100 130 Example 2 98 120 Example 3 132 154 Example 4 110 135 Example 5 125 144 Example 6 102 125 Example 7 90 120 Comparative 49 63 Example 1 Comparative 84 49 Example 2

[0191] [Chemical test] In order to assess the chemical stability, in particular towards swelling and dissolution, fully cured printed objects with a length of 30 mm, width of 9.75 mm and height of 4 mm were stored in different solvents for two weeks at 25° C. The dimensions (length, width, height) of the objects were re-measured after two weeks storage in the respective solvent. The fully cured printed objects of Example 1 neither dissolved nor showed any changes in dimension after two weeks.

TABLE-US-00006 TABLE 5 Chemical stability of fully cured printed parts made of a material according to Example 1 Percentage variance [%] Solvent length width height Toluene 0 0 0 Isopropanol 0 0 0 Water 0 0 0 Acetic acid 0 0 0

[0192] The printed parts of Comparative Example 1 were swelling very strongly after 24 hours storage in all solvents. Therefore, the measurement was stopped after 24 hours.