Photocurable and thermosetting resins useful for additive manufacturing processes

Abstract

The resin comprises A) a multifunctional (meth)acrylate, B) an NCO-functional polyurethane, C) a radical initiator, and D) a catalyst, where the multifunctional (meth)acrylate A) has a viscosity at 23° C., determined according to DIN EN ISO 2884-1, of ≦10000 mPa·s, the NCO-functional polyurethane B) has an average NCO group functionality of ≧2 and an equivalent molecular weight for the NCO groups of greater than 300 g / mol, the catalyst D) is an isocyanate trimerization catalyst, and the resin is free of NCO-reactive compounds or, if NCO-reactive compounds are present in the resin, the molar ratio of NCO groups to NCO-reactive groups is ≧5:1.

Description

[Technical field]

[0001] The present invention relates to resins comprising a (meth)acrylate-functional compound, an NCO-functional polyisocyanate, a radical initiator and a catalyst. The present invention also relates to methods of curing such resins, cured resins and articles of manufacture. [Background technology]

[0002] The use of solely acrylate-based additive manufacturing building materials typically results in brittle material properties that are undesirable for the production of functional materials, and therefore there is a strong desire to increase the flexibility of the cured building material resins.

[0003] Patent Document 1 discloses a method for forming a three-dimensional object, comprising: (a) providing a light-transmitting member having a carrier and a fill level, and optionally a structured surface defining the fill level, wherein the carrier and the fill level have a structured region therebetween; (b) mixing a first precursor liquid with a second precursor liquid to produce a polymerizable liquid comprising a mixture of (i) a first component of a photopolymerizable liquid and (ii) a second solidifiable component different from the first component, wherein (i') at least one reactant of the second solidifiable component is included in the first precursor liquid and (ii') at least one reactant or catalyst of the second solidifiable component is included in the second precursor liquid; thereafter, (c) filling the structured region with the polymerizable liquid; and (d) removing any of the reactants (present) in the structured region. (e) optionally washing the three-dimensional intermediate; and (f) simultaneously with or subsequent to the irradiating step, solidifying and / or curing the second solidifiable component in the three-dimensional intermediate to form the three-dimensional object, wherein the second solidifiable component comprises a polymerizable liquid that is solubilized or suspended in the first component.

[0004] Patent document 2 discloses a process for producing an object from a precursor, comprising the steps of depositing a free radical crosslinking resin on a support to obtain a layer of building material bonded to the support corresponding to a first selected cross section of the precursor, depositing a free radical crosslinking resin on the previously applied layer of building material to obtain a further layer of building material corresponding to a further selected cross section of the precursor and bonded to the previously applied layer, and repeating step II) until the precursor is formed, where the deposition of the free radical crosslinking resin at least in step II) is carried out by exposure and / or irradiation of selected areas of the free radical crosslinking resin corresponding to each selected cross section of the object, the free radical crosslinking resin having a viscosity (23°C, DIN EN ISO 2884-1) of 5 mPa·s to 100000 mPa·s. In this process, the free radical crosslinking resin comprises a curable component in which NCO groups and olefinic C=C double bonds are present, and in the curable component the molar ratio of NCO groups to olefinic C=C double bonds is in the range of 1:5 to 5:1.

[0005] Patent document 3 relates to a process for producing an article made of a structural material, the structural material containing free radical crosslinkable groups, NCO groups and groups with Zerewitinoff active H atoms, the article being a three-dimensional article and / or layer. During and / or after the production of the article, the structural material is heated to a temperature of 50° C. or higher, the structural material containing one or more thermally latent tin compounds.

[0006] US Pat. No. 5,399,363 discloses a process for producing an object from a precursor, comprising the steps of I) depositing a free radical cross-linking resin on a support to obtain a layer of building material bonded to the support corresponding to a first selected cross-section of the precursor, II) depositing the free radical cross-linking resin on the previously applied layer of building material to obtain a further layer of building material corresponding to a further selected cross-section of the precursor and bonded to the previously applied layer, and III) repeating step II) until the precursor is formed. The deposition of the free radical cross-linking resin at least in step II) is carried out by introducing energy into selected areas of the free radical cross-linking resin corresponding to the respective selected cross-section of the object. The free radical cross-linking resin has a viscosity (23° C., DIN EN ISO 2884-1) of ≧5 mPa·s to ≦100 000 mPa·s. The free radical crosslinkable resin comprises a curable component comprising an NCO group blocked with a blocking agent, a compound having at least two Zerewitinoff active H atoms, and an olefinic C=C double bond, the blocking agent being an isocyanate or selected such that deblocking of the NCO group is not followed by liberation of the blocking agent as a free molecule or as part of another molecule or moiety. Step III) is followed by a further step IV) in which the precursor obtained after step III) is treated under conditions sufficient to at least partially deblock the NCO groups present in the free radical crosslinkable resin of the obtained precursor, and the functional groups thus obtained are reacted with a compound having at least two Zerewitinoff active H atoms to obtain the target product.

[0007] Patent document 5 relates to a method for producing an object from a precursor in an additive manufacturing process, comprising the steps of I) depositing on a carrier a layer of a radically cross-linkable building material corresponding to a first selected cross-section of the precursor, II) depositing on the previously applied layer of radically cross-linkable building material a layer of a radically cross-linkable building material corresponding to a further selected cross-section of the precursor, and III) repeating step II) until a precursor is formed. The radically cross-linkable building material comprises a thermoplastic radically cross-linkable polyurethane with a urethane group content of 5% by weight or more and a photoinitiator. The radically cross-linkable building material is also heated to a processing temperature higher than the melting point of the radically cross-linkable polyurethane. After step III), the precursor having a temperature of 20° C. is defined as the object, or a step IV) is performed in which a chemical reaction is carried out in the precursor obtained after step III), resulting in the object. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] US Patent Application Publication No. 2018 / 264719 [Patent Document 2] US Patent Application Publication No. 2018 / 133953 [Patent Document 3] International Publication No. 2018 / 178025 [Patent Document 4] International Publication No. 2018 / 104223 [Patent Document 5] U.S. Patent Application Publication No. 2020 / 0140707 Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention aims to provide a resin that can be used in additive manufacturing processes, which has greater flexibility after curing than pure acrylate-based resins. [Means for solving the problem]

[0010] There is therefore provided a resin as claimed in claim 1. A method for curing the resin is described in claim 8, a photocurable or obtained resin after method step II) is the subject of claim 13. A thermoset resin as obtained or obtained after method step III) is the subject of claim 14 and an article of manufacture comprising a photocurable and / or thermoset resin is the subject of claim 15.

[0011] The resin comprises A) a multifunctional (meth)acrylate, B) an NCO-functional polyurethane, C) a radical initiator, and D) a catalyst, where the multifunctional (meth)acrylate A) has a viscosity at 23° C., determined according to DIN EN ISO 2884-1, of ≦10000 mPa·s, the NCO-functional polyurethane B) has an average NCO group functionality of ≧2 and an equivalent molecular weight for the NCO groups of greater than 300 g / mol, the catalyst D) is an isocyanate trimerization catalyst, and the resin is free of NCO-reactive compounds or, if NCO-reactive compounds are present in the resin, the molar ratio of NCO groups to NCO-reactive groups is ≧5:1.

[0012] Such resins have two curing pathways: radiation curing of the (meth)acrylate groups and thermally induced trimerization of the NCO groups (leading in particular to isocyanurate formation). Without wishing to be bound by theory, it is believed that after both curing pathways have been taken, a combined network is formed, one network originating from the radiation curing compound A) and the other from the trimerized NCO functional polyurethane B). The versatility of such a combined network lies in the synergistic behavior of the two different networks with regard to mechanical properties.

[0013] In the radiation-cured and heat-cured resins according to the invention, two glass transition temperatures can be observed to overlap. This can result in the appearance of only one glass transition temperature being displayed on the DMA curve. However, the (meth)acrylic network in the double polymer network can have a glass transition temperature of, for example, around 0°C. The second glass transition temperature is due to the trimer network of NCO groups originating from the NCO-functional polyurethane, and can also be, for example, around 0°C. This transition temperature can be adjusted not only by the molecular weight of compound B) but also by the choice of any polyol in B).

[0014] The cured materials based on the resins according to the invention show higher elongation at break than comparable systems based purely on (meth)acrylates. These elongation at break values ​​are understood to be a proxy for the flexibility of the material. Furthermore, the tensile strength is higher for the cured materials obtained from the resins according to the invention than for the pure (meth)acrylate systems. The combination of increased tensile strength and increased elongation increases the toughness. The combination of improved properties allows the material to be used as described as an energy absorber or vibration damper. Furthermore, without wishing to be bound by theory, it is assumed that in at least some embodiments of the combined network, one network takes over the function of the solid filler in the other material. Therefore, the need for solid fillers is eliminated, making the reuse of the combined network material more feasible.

[0015] The polyfunctional (meth)acrylates A) are those which, in the case of monomeric (meth)acrylates, have 2, 3 or more (meth)acrylate groups per molecule, or, in the case of polymeric (meth)acrylates, an average of 1.5 or more, preferably 2 or more (meth)acrylate groups per molecule. Preferred polyfunctional (meth)acrylates A) are 1,4-butanediol di(meth)acrylate, 1,3-butylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, di-trimethylolpropane di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol tri(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, ... di-trimethylolpropane di(meth)acrylate, 1,6-hexanediol di acrylate, tetraethylene glycol di(meth)acrylate, triethylene glycol diacrylate, trimethylolpropane tri(meth)acrylate, tripropylene glycol di(meth)acrylate, polyester diol di(meth)acrylate, polycarbonate diol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polyethylene triol tri(meth)acrylate, polypropylene triol tri(meth)acrylate, polyepoxide diacrylate, and mixtures of at least two of the foregoing materials.

[0016] The NCO-functional polyurethane B) has an average NCO group functionality of 2 or more and an equivalent molecular weight with respect to the NCO group of more than 300 g / mol. Preferably, the average NCO group functionality is 2 to 4, more preferably 2 to 3. The equivalent molecular weight with respect to the NCO group is preferably 400 to 2000 g / mol, more preferably 600 to 1000 g / mol.

[0017] For NCO-functional polyurethanes B), the equivalent molecular weight can be determined, for example, by first titrating a sample to determine the NCO content ("% NCO"), expressed as a percentage by weight based on the total weight of the polyisocyanate, according to DIN EN ISO 14896. The equivalent molecular weight of a polyisocyanate with respect to the NCO groups is calculated by dividing the product of the molecular weight of the NCO group (42 g / mol) and a factor of 100 by the % NCO value.

[0018] NCO-functional polyurethanes B) can be obtained by reacting difunctional polyols with a large excess of diisocyanates. The molar ratio of NCO groups to NCO-reactive groups can be 5:1 or more, or even 10:1 or more.

[0019] Suitable diisocyanates are, for example, those having a molecular weight in the range of 140 g / mol to 400 g / mol and having aliphatically, cycloaliphatically, araliphatically and / or aromatically bound isocyanate groups, such as, for example, 1,4-diisocyanatobutane (BDI), 1,5-diisocyanatopentane (PDI), 1,6-diisocyanatohexane (HDI), 2-methyl-1,5-diisocyanatopentane, 1,5-diisocyanato-2,2-dimethyl Pentane, 2,2,4- or 2,4,4-trimethyl-1,6-diisocyanatohexane, 1,10-diisocyanatodecane, 1,3- and 1,4-diisocyanatocyclohexane, 1,4-diisocyanato-3,3,5-trimethylcyclohexane, 1,3-diisocyanato-2-methylcyclohexane, 1,3-diisocyanato-4-methylcyclohexane, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (isophorone diisocyanate; IPDI), 1-isocyanato-1-methyl-4(3)-isocyanatomethylcyclohexane, 2,4'- and 4,4'-diisocyanatodicyclohexylmethane (H12MDI), 1,3- and 1,4-bis(isocyanatomethyl)cyclohexane, bis(isocyanatomethyl)norbornane (NBDI), 4,4'-diisocyanato-3,3'-dimethyldicyclohexylmethane, 4,4'-diisocyanato-3,3',5,5'-tetramethyldicyclohexylmethane, 4,4 '-Diisocyanato-1,1'-bi(cyclohexyl), 4,4'-diisocyanato-3,3'-dimethyl-1,1'-bi(cyclohexyl), 4,4'-diisocyanato-2,2',5,5'-tetramethyl-1,1'-bi(cyclohexyl), 1,8-diisocyanato-p-menthane, 1,3-diisocyanatoadamantane, 1,3-dimethyl-5,7-diisocyanatoadamantane, 1,3- and 1,4-bis(isocyanatomethyl)benzene (xylylene diisocyanate);Diisocyanates which are preferred are: 1,3- and 1,4-bis(1-isocyanato-1-methylethyl)benzene (TMXDI), bis(4-(1-isocyanato-1-methylethyl)phenyl)carbonate, 2,4- and 2,6-diisocyanatotoluene (TDI), 2,4'- and 4,4'-diisocyanatodiphenylmethane (MDI), 1,5-diisocyanatonaphthalene, and any desired mixtures of such diisocyanates. Non-aromatic diisocyanates are preferred, particularly PDI, IPDI, H12MDI and HDI;

[0020] Suitable polyols are preferably linear polyether polyols, polyester polyols, polyacrylate polyols, polyepoxide polyols or polycarbonate polyols. The molecular weight of the polyols can be from 500 g / mol to 4000 g / mol, preferably from 900 g / mol to 2500 g / mol.

[0021] The radical initiator C) can be a thermal initiator and / or a photoinitiator. Examples of thermal initiators C) include azobisisobutyronitrile (AIBN), dibenzoyl peroxide (BPO), tert.-butyl hydroperoxide (TBHP), di-tert.-butyl peroxide (DTBP), cumyl peroxy neodecanoate, 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile) (V-70) and mixtures thereof.

[0022] The photoinitiator C) can be a Norrish type I (cleavage), Norrish type II (abstraction) or cationic photoinitiator. Specific examples are Irgacur™ 500 (a mixture of benzophenone and (1-hydroxycyclohexyl)phenyl ketone), Irgacure™ 819 DW (phenylbis-(2,4,6-trimethylbenzoyl)phosphine oxide), Esacure™ KIP EM (oligo-[2-hydroxy-2-methyl-1-[4-(1-methylvinyl)-phenyl]-propanone]) and Ivocerin™ (bis(4-methoxybenzoyl)diethylgermanium). A preferred photoinitiator is 2-hydroxy-2-methylpropiophenone, available commercially as Omnirad™ 1173. Another preferred photoinitiator system is the mixture available commercially as Omnirad™ BL 750. Mixtures of the aforementioned photoinitiator compounds or systems may also be employed.

[0023] In the resin according to the invention, the radical initiator is generally employed in a concentration of 0.01% to 6.0% by weight, preferably 0.5% to 4.0% by weight, particularly preferably 2.0% to 3.0% by weight, based on the amount of hardenable component employed.

[0024] Isocyanate trimerization catalysts D) are in principle all compounds which promote the addition of isocyanate groups to form isocyanurate groups and thus crosslink the isocyanate-containing molecules present.Specific examples are potassium acetate, potassium acetate in combination with crown ethers, potassium acetate in combination with polyethylene glycol, potassium acetate in combination with polypropylene glycol, tin ethylhexanoate, sodium phenoxide, potassium hydroxide, trioctylphosphine and / or tributyltin oxide.

[0025] In the resins according to the invention, the isocyanate trimerization catalysts can generally be employed in an amount of 0.0005% to 5.0% by weight, preferably 0.1% to 2.0% by weight, particularly preferably 0.5% to 1% by weight, based on the NCO-functional polyurethane B).

[0026] Preferably, the photoinitiator C) is selected from α-hydroxyphenyl ketones, benzil dimethyl ketal, 2,4,6-trimethylbenzoyldiphenyl-phosphine oxide and / or bis(4-methoxy-benzoyl)diethylgermanium and the catalyst D) is selected from potassium acetate, potassium acetate in combination with crown ethers, potassium acetate in combination with polyethylene glycol, potassium acetate in combination with polypropylene glycol, tin ethylhexanoate, sodium phenoxide, potassium hydroxide, trioctylphosphine and / or tributyltin oxide.

[0027] Furthermore, it is provided that the resin is free of NCO reactive compounds, or if NCO reactive compounds are present in the resin, the molar ratio of NCO groups to NCO reactive groups is 5 or more:1. Such NCO reactive compounds to be avoided include monoalcohols, polyols, monoamines, and polyamines. The goal here is to avoid polyurethane or polyurea network formation as much as possible. "Free from" is understood to mean that no intentional addition of such NCO reactive compounds is made, although there are technically unavoidable trace amounts. If NCO reactive compounds must be present in the resin for some reason, the molar ratio of NCO groups to NCO reactive groups is preferably 10 or more:1, more preferably 20 or more:1, and most preferably 100 or more:1.

[0028] In one embodiment, the resin further comprises a monomeric mono(meth)acrylate, which acts as a reactive thinner. Preferred are isobornyl methacrylate (IBOMA), tetrahydrofuryl acrylate (THFA), isobutyl(meth)acrylate, n-butyl(meth)acrylate, isopropyl(meth)acrylate, n-propyl(meth)acrylate, ethyl(meth)acrylate, 2-ethyl-hexyl methacrylate, or a mixture of at least two of the aforementioned substances.

[0029] In another embodiment, the resin further comprises a second polyisocyanate having an average NCO group functionality of 2 or more and an equivalent molecular weight for the NCO groups of less than 300 g / mol. Examples are allophanates, biurets, uretdiones, isocyanurates, iminooxadiazinediones, or a mixture of at least two of the aforementioned polyisocyanates. Particularly preferred second polyisocyanates are allophanates having the following structure, where o and p are, independently of one another, 4, 5 or 6, and R is an alkyl rest having 1 to 6 carbon atoms: [ka]

[0030] In another embodiment, the polyfunctional (meth)acrylate A) has a viscosity at 23° C., determined according to DIN EN ISO 2884-1, of ≧1 mPa·s to ≦1000 mPa·s. A preferred viscosity is ≧5 mPa·s to ≦500 mPa·s.

[0031] In another embodiment, the radical initiator C) is present in an amount of 3 weight percent or less, based on the total weight of the acrylic phase, and the catalyst D) is present in an amount of 1 weight percent or less, based on the weight of the polyisocyanate B).

[0032] In another embodiment, the multifunctional (meth)acrylate A) and the NCO-functional polyurethane B) are present in a weight ratio of from 2:1 to 1:3, based on the total weight of A) and B).

[0033] In another embodiment, the isocyanate trimerization catalyst comprises tin (II) ethylhexanoate.

[0034] Another aspect of the present invention is a method for curing a resin comprising I) providing a resin, II) generating radicals from a radical initiator present in the resin, thereby obtaining a radically cured resin, and III) heating the radically cured resin of step II), thereby obtaining a thermoset resin. In step I), the resin is a resin according to the present invention, in step II), the radicals initiate a reaction between (meth)acrylate groups in the resin, and in step III), the radically cured resin is heated to a temperature of 50° C. or higher, thereby initiating a trimerization reaction of isocyanate groups in the resin, and steps II) and III) can be carried out simultaneously or sequentially.

[0035] Details regarding resins according to the present invention have already been set forth in earlier sections of this specification and will not be repeated here for the sake of brevity.

[0036] The method according to the invention reflects a dual cure approach, whereby irradiation of the resin, thermally or by radiation (e.g. infrared, visible or ultraviolet), solidifies the liquid or plastic starting material under formation of a (meth)acrylate polymer network, and thermal curing builds up an isocyanurate network resulting in a combined network. The temperature in step III) is preferably ≧50° C. to ≦150° C., more preferably ≧90° C. to ≦110° C. If a thermally induced radical curing of the resin is desired in step II), the temperature in step II) is preferably ≧50° C. to ≦150° C., more preferably ≧90° C. to ≦110° C. If it is desired to follow the subsequent performance of step II) as a thermally induced radical curing step with step III), the temperature in step II) is lower than the temperature in step III).

[0037] One embodiment of the method involving photochemical curing in step II) comprises I) providing a resin, II) irradiating the resin, thereby obtaining a photocured resin, and III) heating the photocured resin of step II), thereby obtaining a thermoset resin. In step I), the resin is a resin according to the invention, in which the radical initiator C) is a photoinitiator. In step II), the resin is irradiated to initiate a reaction between (meth)acrylate groups in the resin, and in step III), the photocured resin is heated to a temperature of 50° C. or higher, thereby initiating a trimerization reaction of isocyanate groups in the resin.

[0038] In one embodiment, in step I), the resin is provided as a coating on a substrate. The thermal curing step can serve to harden the shadow areas where light was not sufficiently irradiated.

[0039] In another embodiment, in step II), the resin is selectively irradiated according to a predetermined cross-section of the target article to be manufactured, the selective irradiation is repeated until a predetermined intermediate article comprising a photocured resin is obtained, and in step III), the intermediate article is heated to a temperature of 50° C. or higher, thereby obtaining the target article. This embodiment encompasses additive manufacturing processes such as stereolithography (SLA) and DLP. The thermal curing step III) can be performed outside the SLA or DLP system, thus improving the space-time yield of the finished product relative to the available number of SLA or DLP machines.

[0040] In another embodiment, before step II), resin is selectively applied on a surface according to a predetermined cross-section of the target article to be manufactured, and the selective application and irradiation according to step II) are repeated until a predetermined intermediate article comprising a photocurable resin is obtained, and in step III), the intermediate article is heated to a temperature of 50° C. or higher, thereby obtaining the target article. The surface can be a powder surface. Then, the method according to this embodiment resembles a binder jetting process. Alternatively, the process can be a so-called photopolymer jetting process. Since the application of the resin is selective, the irradiation of step II) does not have to be selective. If so, irradiation of the entire build platform would be sufficient.

[0041] In another embodiment, step III) is carried out at a temperature of ≧80° C. to ≦120° C. for a period of ≧4 hours to ≦24 hours.

[0042] Furthermore, the present invention relates to a photocurable resin obtainable or obtainable after step II) of the process according to the invention and to a thermocurable resin obtainable or obtainable after step III) of the process according to the invention.

[0043] A further aspect of the invention is an article of manufacture comprising a photocured resin according to the invention and / or a thermoset resin according to the invention. Examples of such articles of manufacture include medical devices, personalized medical articles, replicated medical implants, dental articles, sterilization containers, and footwear components. [Brief description of the drawings]

[0044] [Figure 1] 1 shows the E′ and tan δ curves for the material obtained in Example 19. [Diagram 2] 4 shows the corresponding tensile curves measured at 23° C. [Diagram 3] 1 is a diagram showing flexibility. [Figure 4] 1 shows DMA curves of samples (Examples 14 to 17) prepared with ISO-3. [Diagram 5] 1 is a diagram showing a tensile curve. [Figure 6] FIG. 13 shows the effect of additional polyisocyanate compared to Example 15 vs. Example 15a, which increases crosslink density, resulting in a stable plateau modulus. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS EXAMPLES

[0045] The present invention will now be further illustrated, without intending to be limited thereto, with reference to the following examples and figures. Comparative examples are referred to as "(Comp.)".

[0046] material Hexamethylene diisocyanate (HDI, NCO content: 50%) and isophorone diisocyanate (IPDI, NCO content: 37.62%), as well as polyether carbonate polyol (Polyol-1) were supplied by Covestro Deutschland AG.

[0047] The isocyanate Allo-1 was a low viscosity allophanate based on HDI with an isocyanate content of approximately 20.0% according to ISO 11909, a viscosity of approximately 500 mPa·s at 23° C. according to ISO 3219 / A.3, and an isocyanate group functionality of approximately 2.5. The equivalent weight with respect to NCO groups was 210 g / mol.

[0048] Allo-1 was supplied by Covestro Deutschland AG and used as received. Polytetrahydrofuran (Polyol-2) was purchased from BASF. Photoinitiators Omnirad BL750 and Omnirad 1173 were supplied by IGM Resins. The inhibitor 2,5-bis(5-tert-butyl-2-benzoxazolyl)thiophene was purchased from sigma Aldrich and used as received. The (meth)acrylates mentioned below (IBOMA, DPGDA, THFA, PEGDA 700 g / mol) were purchased from sigma Aldrich and used as received.

[0049] The polyols used were as follows:

[0050] TIFF2024524577000003.tif28170

[0051] The acrylates used were as follows:

[0052] TIFF2024524577000004.tif60170

[0053] method Gel permeation chromatography (GPC) was performed on four PSS SDV Analytical columns according to DIN 55672-1:2016-03 using an Agilent 1100 series pump and an Agilent 1200 series UV detector (230 nm) at 40° C. and 1 mL / min with tetrahydrofuran as eluting solvent.

[0054] Total energy input is 1300mJ / cm 2 Thin films were prepared on a Superfici Modulo UVM Plus machine equipped with gallium and mercury radiation sources.

[0055] FTIR spectra were measured on a Bruker FTIR Spectrometer Tensor II equipped with an ATR crystal.

[0056] Dynamic mechanical analysis of the cured thin films was performed according to ISO 6721 on a Seiko Instruments Exstar 6100 DMS at an oscillation frequency of 1 Hz. The experiments were carried out from -150°C to 250°C at a heating rate of 2 K / min. The glass transition temperature was determined by evaluation of the maximum peak of the loss factor curve tan δ.

[0057] Tensile tests were carried out on a Zwick Retro with a 2 kN load cell at a test speed of 200 mm / min and a preload of 0.5 N according to DIN EN ISO 527. The elastic modulus (E-modulus) was determined between 0.05% and 0.025% elongation at a test speed of 1 mm / min.

[0058] Printing was performed with an ANYCUBIC PhotonS equipped with a 405 nm UV-LED light source. STL files were created using an ANYCUBI Photon slicer. The layer thickness was 100 μm and printing parameters were selected for each formulation (see Table 5).

[0059] The NCO content was determined by titration. Approximately 2.0 g of a sample not containing isocyanate groups (blank sample) was added to 5.0 mL of a 0.1 M dibutylamine solution in xylene, followed by 50.0 mL of acetone and 3 drops of phenol red solution (0.1 g in 80 g of a mixture of 20% ethanol in water). This solution was then titrated with a 0.1 M hydrochloric acid solution to produce a color change and the amount consumed was recorded. The NCO group containing samples were treated accordingly. The NCO content "% NCO" was calculated in the following way: %NCO = 4.2 × M × (V ブランク -V 試料 ) / m (where M is the molar concentration of hydrochloric acid (e.g., 0.1 mol / L), m is the sample weight (g), and V ブランク is the consumption of hydrochloric acid in the blank sample in mL, and V 試料 is the amount of hydrochloric acid consumed in the sample in mL).

[0060] NCO-terminated polyurethanes were prepared according to the literature with minor modifications (Driest, PJ; Dijkstra, DJ; Stamatialis, D.; Grijpma, DW, The Trimerization of Isocyanate-Functionalized Prepolymers: An Effective Method for Synthesizing Well-Defined Polymer Networks. Macromolecular Rapid Communications 2019, 40 (9), 1800867).

[0061] Typically, HDI or IPDI was heated to 100° C. under nitrogen in a three-neck flask equipped with a stirrer, condenser, and thermometer. 100 g of polymeric diol, buffered with 0.1 g of dibutyl phosphate, was added dropwise to the HDI / IPDI in a molar ratio of 10:1 / 10:1 (NCO:OH). This was allowed to react for 3 hours or until the desired isocyanate content was obtained (determined by titration). The product was then transferred to a thin-film evaporator and evaporated at 140° C. or 150° C., respectively, under reduced pressure (typically 10 -2 Excess HDI or IPDI was removed at 100 psi (mbar). The HDI / IPDI monomer content was determined by GC.

[0062] The NCO-functional polyurethanes were obtained as transparent, viscous resins. All polyurethanes were analyzed by GPC. Table 1 below shows the data of the synthesized NCO-terminated polyurethanes ("ISO") and their corresponding viscosities measured according to DIN EN ISO 2884-1.

[0063] TIFF2024524577000005.tif61170

[0064] Curing results of the formulations of the invention: Cured products based on acrylic and isocyanate-terminated precursors were prepared by mixing different amounts of NCO-terminated polyurethane and low viscosity (meth)acrylate, photoinitiator (Omnirad 1173) and tin(II) ethylhexanoate as trimerization catalyst. All samples were prepared by mixing the substances for 2 min. Afterwards, thin films were applied with a 400 μm doctor blade onto a glass substrate that had been pretreated with soy lecithin solution to facilitate removal. Afterwards, the cured products were applied with a total energy input of 1300 mJ cm. -2 The films were cured under a gallium and mercury radiation source at 100° C. for 12 hours for thermal post-curing, until all isocyanate groups were converted as determined by FTIR spectroscopy. The presence of isocyanates was confirmed by IR spectroscopy (2265 cm -1 For printing, the photoinitiator was Omnirad BL 750, and an additional inhibitor (<0.1 wt%) was added to avoid dark curing and to increase the structure resolution.

[0065] 3D printing was performed on an ANYCUBIC PhotonS equipped with a 405 nm UV-LED light source. STL files were created using an ANYCUBI Photon slicer. The layer thickness was 100 μm and printing parameters were selected for each formulation (see Table 5).

[0066] Tables 1a and 1b show the results for hardened formulations 1 to 4 of the present invention.

[0067] Tables 2 and 3 show the results for the formulations of the present invention and the comparative examples.

[0068] Table 4 shows three examples printed on a conventional DLP printer.

[0069] Table 5 shows examples containing high molecular weight acrylates for comparison.

[0070] Table 6 shows more comparative examples highlighting the effect of the pure acrylic polymer network.

[0071] In all tables, the "elongation [%]" value is understood to be the elongation value until break. "nd" stands for undetermined and "na" stands for not applicable, for example when the sample was not suitable for measuring a certain parameter.

[0072] TIFF2024524577000006.tif62170

[0073] TIFF2024524577000007.tif58170

[0074] TIFF2024524577000008.tif52170

[0075] TIFF2024524577000009.tif56170

[0076] FIG. 1 shows the E′ and tan δ curves for the material obtained in Example 19.

[0077] TIFF2024524577000010.tif84170

[0078] TIFF2024524577000011.tif53170

[0079] TIFF2024524577000012.tif47170

[0080] In Examples 26 and 27, the samples broke during the measurement.

[0081] Figure 1 shows the DMA curve of Example 19. The material has a glass transition temperature at about 0°C and a storage modulus of 7x10 6 The sample has a stable plateau modulus at higher temperatures of 100 MPa. Figure 2 shows the corresponding tensile curve measured at 23°C. The sample exhibits high flexibility with an elongation of over 70%. The flexibility is further illustrated in Figure 3. The hysteresis reveals a permanent deformation of only 5%, illustrating the elastic behavior of the sample.

[0082] Figure 4 shows the DMA curves of the samples prepared with ISO-3 (Examples 14-17). When in the glass transition region at 23°C, the material exhibits high flexibility as evidenced in the tensile curves shown in Figure 5. Finally, Figure 6 shows the effect of additional polyisocyanate compared to Example 15 vs. Example 15a, which increases the crosslink density, resulting in a stable plateau modulus.

Claims

1. A) a polyfunctional (meth)acrylate, B) an NCO-functional polyurethane, C) a radical initiator, D) a catalyst, A resin comprising: wherein the polyfunctional (meth)acrylate A) has a viscosity at 23°C of 10,000 mPa·s or less as determined according to DIN EN ISO 2884-1, the NCO-functional polyurethane B) has an average NCO group functionality of 2 or more and an equivalent molecular weight greater than 300 g / mol with respect to the NCO group, the catalyst D) is an isocyanate trimerization catalyst, the resin does not contain an NCO-reactive compound, or when an NCO-reactive compound is present in the resin, the molar ratio of the NCO group to the NCO-reactive group is 5 or more:1, characterized resin.

2. The resin according to claim 1, further comprising a monomer mono(meth)acrylate.

3. The resin according to claim 1, further comprising a second polyisocyanate having an average NCO group functionality of 2 or more and an equivalent molecular weight less than 300 g / mol with respect to the NCO group.

4. The resin according to any one of claims 1 to 3, wherein the polyfunctional (meth)acrylate A) has a viscosity at 23°C of 1 mPa·s or more and 1000 mPa·s or less as determined according to DIN EN ISO 2884-1.

5. The resin according to any one of claims 1 to 3, wherein the radical initiator C) is present in an amount of 3% by weight or less based on the total weight of the acrylic phase, and the catalyst D) is present in an amount of 1% by weight or less based on the weight of the polyisocyanate B).

6. The resin according to any one of claims 1 to 3, wherein the polyfunctional (meth)acrylate A) and the NCO-functional polyurethane B) are present in a weight ratio of 2:1 to 1:3 based on the total weight of A) and B).

7. The resin according to any one of claims 1 to 3, wherein the isocyanate trimerization catalyst contains tin(II) 2-ethylhexanoate.

8. I) preparing a resin, II) generating radicals from a radical initiator present in the resin, thereby obtaining a radical-cured resin, III) heating the radical-cured resin of step II), thereby obtaining a thermoset resin, A method for curing a resin, comprising: In step I), the resin is the resin according to any one of claims 1 to 3, In step II), the radical initiates the reaction between (meth)acrylate groups in the resin. In step III), the radically cured resin is heated to a temperature of 50 °C or higher, thereby initiating the trimerization reaction of the isocyanate groups in the resin. A method, characterized in that steps II) and III) can be carried out simultaneously or sequentially.

9. The method according to claim 8, wherein in step I), the resin is provided as a coating on a substrate.

10. In step II), the resin is selectively irradiated according to a predetermined cross-section of the article to be manufactured, and the selective irradiation is repeated until a predetermined intermediate article containing the photocurable resin is obtained. The method according to claim 8, wherein in step III), the intermediate article is heated to a temperature of 50 °C or higher, thereby obtaining the article to be manufactured.

11. Before step II), the resin is selectively applied onto the surface according to a predetermined cross-section of the article to be manufactured, and the selective application and irradiation in step II) are repeated until a predetermined intermediate article containing the photocurable resin is obtained. The method according to claim 8, wherein in step III), the intermediate article is heated to a temperature of 50 °C or higher, thereby obtaining the article to be manufactured.

12. The method according to claim 8, wherein step III) is carried out at a temperature of 80 °C or higher and 120 °C or lower for a time of 4 hours or longer and 24 hours or shorter.

13. A photocurable resin that can be obtained or is obtained after step II) of the method according to claim 8.

14. A thermosetting resin that can be obtained or is obtained after step III) of the method according to claim 8.

15. A manufactured product containing the photocurable resin according to claim 13.

16. A manufactured product containing the thermosetting resin according to claim 14.

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