METHOD FOR PRODUCING AN OBJECT FROM A PRECURSOR, AND USE OF A RADICALLY CROSS-LINKABLE RESIN IN AN ADDITIVE PRODUCTION METHOD

Abstract

The invention relates to a method for producing an object from a precursor, comprising the steps: I) depositing a radically cross-linked resin on a carrier so that a layer of a construction material connected to the carrier is obtained, said layer corresponding to a first selected cross-section of the precursor; II) depositing a radically cross-linked resin on a previously applied layer of the construction material so that an additional layer of the construction material is obtained, which corresponds to a further selected cross-section of the precursor and which is connected to the previously applied layer; III) repeating step II) until the precursor is formed, wherein, at least in step II), the deposition of a radically cross-linked resin is carried out by allowing energy to act on a selected region of a radically cross-linkable resin, corresponding to the respectively selected cross-section of the object, wherein the radically cross-linkable resin has a viscosity (23 C., DIN EN ISO 2884-1) of =5 mPas to =100000 mPas. The radically cross-linkable resin comprises a curable component, in which NCO groups which are blocked with a blocking agent, compounds having at least two Zerewitinoff-active H atoms and olefinic CC double bonds are present, wherein the blocking agent is an isocyanate or the blocking agent is selected in such a manner that, after deblocking of the NCO group, no release of the blocking agent as a free molecule or as a part of other molecules or molecule parts occurs. Following step III), step IV) is carried out: IV) treating the precursor obtained according to step III) under conditions which are sufficient to at least partially deblock NCO groups which are present in the radically cross-linked resin of the obtained precursor, and to react the resulting functional groups with compounds having at least two Zerewitinoff-active H atoms, with the result that the object is obtained.

Claims

1.-15. (canceled)

16. A process for producing an object from a precursor, comprising the steps of: I) depositing a free-radically crosslinked resin atop a carrier to obtain a ply of a construction material joined to the carrier which corresponds to a first selected cross section of the precursor; II) depositing a free-radically crosslinked resin atop a previously applied ply of the construction material to obtain a further ply of the construction material which corresponds to a further selected cross section of the precursor and which is joined to the previously applied ply; III) repeating step II) until the precursor is formed; wherein the depositing of a free-radically crosslinked resin at least in step II) is effected by introducing energy to a selected region of a free-radically crosslinkable resin corresponding to the respectively selected cross section of the object, and wherein the free-radically crosslinkable resin has a viscosity (23 C., DIN EN ISO 2884-1) of 5 mPas to 100 000 mPas, wherein the free-radically crosslinkable resin comprises a curable component comprising NCO groups blocked with a blocking agent, compounds having at least two Zerewitinoff-active H atoms and olefinic CC double bonds, wherein the blocking agent is an isocyanate or the blocking agent is selected such that deblocking of the NCO group is not followed by liberation of the blocking agent as a free molecule or as a part of other molecules or moieties and in that step III) is followed by a further step IV): IV) treating the precursor obtained after step III) under conditions sufficient for at least partially deblocking NCO groups present in the free-radically crosslinked resin of the obtained precursor and reacting the thus obtained functional groups with compounds having at least two Zerewitinoff-active H atoms to obtain the object.

17. The process as claimed in claim 16, wherein the blocking agent is selected from the group consisting of organic isocyanates, lactams, glycerol carbonate, a compound of general formula (I): ##STR00005## in which X is an electron-withdrawing group, R.sup.1 and R.sup.2 independently of one another represent the radicals H, C.sub.1-C.sub.20-(cyclo)alkyl, C.sub.6-C.sub.24-aryl, C.sub.1-C.sub.20-(cyclo)alkyl ester or -amide, C.sub.6-C.sub.24-aryl ester or amide, mixed aliphatic/aromatic radicals having 1 to 24 carbon atoms which may also be part of a 4 to 8-membered ring and n is an integer from 0 to 5 or a combination of at least two of these.

18. The process as claimed in claim 16, wherein the compounds having at least two Zerewitinoff-active H atoms in the curable component are selected from the group consisting of polyamines, polyols or a combination thereof.

19. The process as claimed in claim 16, wherein the curable component comprises a curable compound which comprises NCO groups blocked with the blocking agent and olefinic CC double bonds.

20. The process as claimed in claim 16, wherein the free-radically crosslinkable resin further comprises a free-radical starter.

21. The process as claimed in claim 20, wherein the free-radical starter is selected from the group: -hydroxyphenylketone, benzyldimethylketal, bis(4-methoxybenzoyl)diethylgermanium and/or 2,4,6-trimethylbenzoyldiphenylphosphine oxide.

22. The process as claimed in claim 16, wherein the molar ratio of free NCO groups to Zerewitinoff-active H atoms in the resin is 0.05.

23. The process as claimed in claim 16, wherein in step IV) the treating of the precursor obtained after step III) under conditions sufficient for at least partially deblocking NCO groups present in the free-radically crosslinked resin of the obtained precursor and reacting the thus obtained functional groups with compounds having at least two Zerewitinoff-active H atoms comprises a heating of the body to a temperature of 60 C.

24. The process as claimed in claim 16, wherein the surface of the precursor obtained after step III) and/or of the object obtained after step IV) is contacted with a compound comprising Zerewitinoff-active H atoms, wherein water occurring as natural atmospheric humidity in the atmosphere surrounding the precursor and/or the object is excluded.

25. The process as claimed in claim 16, wherein: the carrier is arranged inside a container and is vertically lowerable in the direction of the gravitational force, the container provides the free-radically crosslinkable resin, before each step II) the carrier is lowered by a predetermined distance so that above the uppermost ply of the construction material viewed in the vertical direction a layer of the free-radically crosslinkable resin is formed and in step II) an energy beam exposes and/or irradiates the selected region of the layer of the free-radically crosslinkable resin corresponding to the respectively selected cross section of the object.

26. The process as claimed in claim 16, wherein: the carrier is arranged inside a container and is vertically raisable counter to the direction of the gravitational force, the container provides the free-radically crosslinkable resin, before each step II) the carrier is raised by a predetermined distance so that below the lowermost ply of the construction material viewed in the vertical direction a layer of the free-radically crosslinkable resin is formed and in step II) a plurality of energy beams simultaneously exposes and/or irradiates the selected region of the layer of the free-radically crosslinkable resin corresponding to the respectively selected cross section of the object.

27. The process as claimed in claim 16, wherein step I) comprises applying atop a substrate the free-radically crosslinkable resin corresponding to the first selected cross section of the object and step II) comprises applying atop a previously applied ply of the construction material the free-radically crosslinkable resin corresponding to the further selected cross section of the object and this is followed by introduction of energy to at least the free-radically crosslinkable resin.

28. A method comprising utilizing a free-radically crosslinkable resin having a viscosity (23 C., DIN EN ISO 2884-1) of 5 mPas to 100 000 mPas in an additive manufacturing process, wherein the free-radically crosslinkable resin comprises a curable component comprising NCO groups blocked with a blocking agent, compounds having at least two Zerewitinoff-active H atoms and olefinic CC double bonds, wherein the blocking agent is an isocyanate or the blocking agent is selected such that deblocking of the NCO group is not followed by liberation of the blocking agent as a free molecule or as a part of other molecules or moieties.

29. The method as claimed in claim 28, wherein the additive manufacturing process comprises the exposure and/or irradiation of a previously selected region or applied region of the free-radically crosslinkable resin.

30. A polymer obtainable by the crosslinking of a free-radically crosslinkable resin having a viscosity (23 C., DIN EN ISO 2884-1) of 5 mPas to 100 000 mPas, wherein the free-radically crosslinkable resin comprises a curable component comprising NCO groups blocked with a blocking agent, compounds having at least two Zerewitinoff-active H atoms and olefinic CC double bonds, wherein the blocking agent is an isocyanate or the blocking agent is selected such that deblocking of the NCO group is not followed by liberation of the blocking agent as a free molecule or as a part of other molecules or moieties.

Description

EXAMPLES

Example 1: Production of a Prepolymer Having Blocked Isocyanates and Acylate Functions

[0086] In a glass flask 130.0 g of the linear polypropylene ether polyol Desmophen 1111BD obtained from Covestro Deutschland AG, Germany were initially charged at room temperature. 0.043 g of dibutyltin laurate obtained from Sigma-Aldrich, Germany was initially added to the polyol and 101.9 g of the hexamethylene diisocyanate-based uretdione Desmodur XP 2730 obtained from Covestro Deutschland AG, Germany were subsequently added dropwise over a period of about 30 minutes. The reaction mixture was then heated to 80 C. using a temperature-controlled oil bath until the theoretical residual NCO content of 4.71% was achieved. To this end, samples were withdrawn from the reaction vessel at regular intervals and subjected to titrimetric determination according to DIN EN ISO 11909.

[0087] After achieving the theoretical residual NCO content, 0.20 g of the inhibitor butylhydroxytoluene obtained from Sigma-Aldrich, Germany was added and the mixture was homogenized for 15 minutes. After cooling to 50 C., 33.8 g of hydroxyethyl methacrylate obtained from Sigma-Aldrich, Germany were then added dropwise and the mixture was subjected to further stirring until a residual NCO content of 0% was achieved. 143.2 g of isobornyl acrylate (IBOA) obtained from Sigma-Aldrich, Germany were then added and the mixture was allowed to cool to room temperature. The prepolymer was filled into metal cans and stored at room temperature until further use.

[0088] Without addition of amine as a crosslinking agent the prepolymer according to example 1 was utilized as a comparative example.

[0089] In combination with amines as elucidated in the following examples said prepolymer was used as a basis for inventive resins.

Example 2: Production of a Free-Radically Crosslinkable Resin Comprising 20% IPDA Crosslinker

[0090] 100.0 g of the prepolymer from example 1 and 3.00 g of the photoinitiator Omnirad 1173 from IGM Resins were weighed into a plastic beaker with a lid. These input materials were mixed in a Thinky ARE250 planetary mixer at 2000 revolutions per minute at room temperature for about 2 minutes. 2.17 g of the difunctional crosslinker isophoronediamine (IPDA) obtained from Covestro Deutschland AG, Germany were then added and mixed by hand with a spatula. Stoichiometrically, these amounts resulted in a ratio of amine groups to uretdione groups in the mixture of 1:5.

Example 3: Production of a Free-Radically Crosslinkable Resin Comprising 20% Jeffamine T403 Crosslinker

[0091] 100.0 g of the prepolymer from example 1 and 3.00 g of the photoinitiator Omnirad 1173 were weighed into a plastic beaker with a lid and mixed as in example 2. 3.72 g of the trifunctional crosslinker Jeffamine T403 obtained from Sigma-Aldrich, Germany were then added and mixed by hand with a spatula. Stoichiometrically, these amounts resulted in a ratio of amine groups to uretdione groups in the mixture of 1:5.

Example 4: Production of a Free-Radically Crosslinkable Resin Comprising 30% Jeffamine T403 Crosslinker

[0092] 100.0 g of the prepolymer from example 1 and 3.00 g of the photoinitiator Omnirad 1173 were weighed into a plastic beaker with a lid and mixed as in example 2. 5.59 g of the trifunctional crosslinker Jeffamine T403 were then added and mixed by hand with a spatula. Stoichiometrically, these amounts resulted in a ratio of amine groups to uretdione groups in the mixture of 3:10.

Example 5: Curing of a Free-Radically Crosslinkable Resin

[0093] A glass sheet was coated with the free-radically curable resins from the examples 1 to 4 using a knife coater having a 400 m slot. The glass sheet had previously been treated with a 1% solution of soy lecithin in ethyl acetate and dried. The soy lecithin acted as a release agent to allow the cured films to be detached from the substrate again later.

[0094] The coated glass substrates were subsequently cured with mercury and gallium radiation sources in a UV curing plant from Superfici at a belt speed of 5 m/min. The lamp output and belt speed result in a radiation intensity of 1300 mJ/cm.sup.2 being introduced to the coated substrates.

[0095] The UV-cured films on the glass substrates were subsequently post-cured in an air atmosphere in a drying oven at 120 C. for 60 minutes. For some films the curing was carried out at 150 C. instead of at 120 C. to investigate the effect of temperature.

[0096] After cooling to room temperature the cured films were carefully detached from the glass substrates to prepare test specimens for mechanical and thermal characterization.

Example 6: Characterization of a Crosslinked Resin

[0097] For mechanical characterization the self-supporting, cured films from example 5 were prepared as type S2 tensile test specimens according to DIN EN ISO 527 using a punch. 5 test specimens of each film were investigated according to DIN EN ISO 527. The averaged results for breaking elongation, tensile strength and elastic modulus are summarized in table 1.

[0098] For thermal characterization a small sample of about 10 mg of the cured films was investigated using differential scanning calorimetry (DSC) according to DIN EN ISO 11357-1. The glass transition temperatures (T.sub.G) determined from DSC are also summarized in table 1 for all films of the examples. Note: Two glass transition temperatures were determined by DSC for the films.

TABLE-US-00001 TABLE 1 Mechanical and thermal properties of the free-radically cured resins example number Post-curing Elongation Tensile Elastic Amine:uretdione temperature at break strength modulus T.sub.G ratio [ C.] [%] [MPa] [MPa] [ C.] 1 0 room 94 9.6 26 20/+8 (comparative temperature example) 2 1:5 120 80 17.0 143 14/+23 2 1:5 150 78 16.8 141 6.5/+31.5 3 1:5 120 85 13.5 81.4 8/+26 3 1:5 150 72 11.0 98.4 13/+20 4 3:10 120 65 12.0 110 6.5/+30 4 3:10 150 72 12.6 95.6 20/+8

[0099] Compared to the noninventive example 1, inventive examples 2 to 4 show a markedly elevated tensile strength and modulus while breaking elongation remains at a comparable level.

Example 7: Investigation of Uretdione Opening by IR Spectroscopy

[0100] In order to investigate the opening of the uretdione ring and reaction of the deblocked isocyanate groups with the amine groups during oven curing a film according to example 2 was investigated before and after oven curing by means of IR spectroscopy. Analysis was carried out using an FTIR spectrometer (Tensor II) from Bruker. The specimen film was contacted with the platinum ATR unit. The contacted area of the sample was 22 mm. During measurement the IR radiation penetrated 3 to 4 m into the sample depending on wavenumber. An absorption spectrum was then obtained from the sample. In order to compensate for a nonuniform contacting of the samples of different hardnesses a baseline correction and a normalization in the wavenumber range 2600-3200 (CH2, CH3) was performed on all spectra. The interpolation of the uretdione group was performed in the wavenumber range of 1786-1750 cm.sup.1 (CO vibration). The integrated areas under the signals of uretdione groups are summarized in table 2:

TABLE-US-00002 TABLE 2 Uretdione signal area Before oven curing 26.797 After oven curing 15.105

[0101] The reduction in the signal areas corresponding to uretdione can be attributed to a deblocking of the isocyanate groups by ring opening and a crosslinking reaction of the deblocked isocyanate groups with amine.