Process for producing an object from a precursor and use of a free-radically crosslinkable resin in an additive manufacturing process

Abstract

A process for producing an object from a precursor comprises the steps of: 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; 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; 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 exposure and/or irradiation of 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 100000 mPas. In the process the free-radically crosslinkable resin comprises a curable component in which NCO groups and olefinic CC double bonds are present, wherein in the curable component the molar ratio of NCO groups to olefinic CC double bonds is in a range from 1:5 to 5:1.

Claims

1. 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; wherein the carrier is arranged inside a container and is vertically raisable counter to the direction of the gravitational force, and the container provides the free-radically crosslinkable resin, 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; wherein 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, 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 exposure and/or irradiation of a selected region of a free-radically crosslinkable resin corresponding to the respectively selected cross section of the precursor and wherein the free-radically crosslinkable resin has a viscosity (23 C., DIN EN ISO 2884-1) of 5 mPas to 100000 mPas, wherein the free-radically crosslinkable resin has a curable component in which NCO groups and olefinic CC double bonds are present, wherein in the curable compound the molar ratio of NCO groups to olefinic CC double bonds is in a range from 1:5 to 5:1, and wherein, after step III), step IV) is further performed: IV) treating the precursor obtained after step III) under conditions sufficient to at least partially trimerize to isocyanurate groups NCO groups present in the free-radically crosslinked resin of the obtained precursor to obtain the object.

2. The process according to claim 1, wherein isocyanurate groups are further present in the curable component, wherein the molar ratio of NCO groups to isocyanurate groups is in a range from 100:1 to 1:2 and in the curable component the molar ratio of olefinic CC double bonds to isocyanurate groups is in a range from 100:1 to 1:5.

3. The process according to claim 1 wherein the curable component comprises a curable compound comprising isocyanurate groups, NCO groups and olefinic CC double bonds, wherein in the curable compound the molar ratio of NCO groups to isocyanurate groups is in a range from 100:1 to 1:2, and in the curable compound the molar ratio of olefinic CC double bonds to isocyanurate groups is in a range from 100:1 to 1:5.

4. The process according to claim 1 wherein the free-radically crosslinkable resin further comprises a free-radical starter and/or an isocyanate trimerization catalyst.

5. The process according to claim 1 wherein at least one free-radical starter is selected from the group: -hydroxyphenylketone, benzyldimethylketal, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis(4-methoxybenzoyl)diethylgermanium and any combination of at least two thereof and/or the isocyanurate trimerization catalyst is selected from: potassium acetate, potassium acetate in combination with a crown ether, potassium acetate in combination with a polyethylene glycol, potassium acetate in combination with a polypropylene glycol, tin octoate, sodium phenoxide, potassium hydroxide, trioctyl phosphine and/or tributyltin oxide.

6. The process according to claim 1 wherein in the resin the molar ratio of NCO groups to Zerewitinoff-active H atoms is 500.

7. The process according to claim 1 wherein the curable component has a number-average molecular weight M.sub.n of 200 g/mol to 5000 g/mol.

8. The process according to claim 1 wherein in step IV) the treating of the precursor obtained after step III) under conditions sufficient to at least partially trimerize to isocyanurate groups NCO groups present in the free-radically crosslinked resin of the obtained precursor comprises a heating of the body to a temperature of 60 C.

9. The process according to claim 1 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.

10. The process according to claim 1 wherein: the carrier is arranged inside a container and is vertically lowerable in the direction of the gravitational force, the container contains the free-radically crosslinkable resin in an amount sufficient to cover at least the carrier and crosslinked resin deposited atop the carrier, 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 precursor.

11. The process according to claim 1 wherein: in step II) a plurality of energy beams simultaneously expose and/or irradiate the selected region of the layer of the free-radically crosslinkable resin corresponding to the respectively selected cross section of the precursor.

12. The process according to claim 1 wherein: in step II) the free-radically crosslinkable resin is applied from one or more printing heads corresponding to the respectively selected cross section of the precursor and is subsequently exposed and/or irradiated.

Description

EXAMPLES

(1) The invention is more particularly elucidated with reference to the examples which follow but without any intention to limit the invention thereto.

(2) The formulations of free-radically crosslinkable resins reported in the table were produced. The data in the table relate to parts by weight unless otherwise stated.

(3) TABLE-US-00001 1 2 Isocyanate 1 56 70 Isocyanate 2 14 Acrylate 30 30 TPO 0.8 wt % of the acrylate 0.8 wt % of the acrylate BBOT 0.08 wt % of the acrylate 0.08 wt % of the acrylate KOAc 1.5 wt % of isocyanates 1 and 2 1.5 wt % of isocyanate 1 catalyst

(4) Isocyanate 1: reaction product of the 1,6-HDI trimer with hydroxyethyl acrylate and the following idealized structure:

(5) ##STR00001##

(6) Isocyanate 2: NCO-terminated, polyether-modified HDI prepolymer (Desmodur N3100 Covestro Deutschland AG)

(7) Acrylate: 1,6-hexanediol diacrylate (analytical quality obtained from Sigma-Aldrich)

(8) TPO: diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide; photoinitiator (obtained from Sigma-Aldrich)

(9) BBOT: 2,2-(2,5-thiophenediyl)bis(5-(1,1-dimethylethyl))benzoxazole; UV blocker (obtained from Sigma-Aldrich)

(10) KOAc catalyst: potassium acetate+18-crown-6 crown ether in diethylene glycol (components obtained from Sigma-Aldrich and mixed in the ratio: 0.148 g of potassium acetate+0.485 g of 18-crown-6 ether+3.115 g of diethylene glycol.

(11) The resin formulation Autodesk Standard Clear Prototyping Resin PR48 was chosen for a comparative example. This contains about 40 weight % of the aliphatic urethane acrylate EBECRYL 8210, about 40 weight % of the ethoxylated pentaerythritol tetraacrylate SARTOMER SR 494, TPO as a photoinitiator, about 20 weight % of the monofunctional urethane acrylate Rahn Genomer 1122 as a reactive diluent and MAYZO OB+(2,2-(2,5-thiophenediyl)bis(5-tert-butylbenzoxazole)) as a UV blocker.

(12) Formulations 1 and 2 and the formulation of the comparative example were used to produce standard S3 test bars for tensile tests on an Autodesk Ember DLP-based 3D printing apparatus. The wavelength for the exposure was 405 nm. The individual layers of the test bars were arranged parallel to the tensile direction. The layer thickness was 50 m in each case. The exposure time was 5 s/layer.

(13) The precursors produced from formulations 1 and 2 were subsequently heated for 30 minutes at 130 C. in a forced-air drying cabinet.

(14) The thus obtained test bars had the properties reported in the table below.

(15) TABLE-US-00002 comparative 1 2 Modulus of elasticity [GPa], DIN 53504 1 1.3 1.2 Tensile strength [MPa], DIN 53504 34 48 48 Elongation at break [%], DIN 53504 5.4 4.4 5.1 Glass transition temperature [ C.], DSC, 15 70 70 20 K/min

(16) Various aspects of the subject matter described herein are set out in the following numbered clauses:

(17) 1. 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 exposure and/or irradiation of a selected region of a free-radically crosslinkable resin corresponding to the respectively selected cross section of the precursor and
wherein the free-radically crosslinkable resin has a viscosity (23 C., DIN EN ISO 2884-1) of 5 mPas to 100000 mPas,
characterized in that the free-radically crosslinkable resin has a curable component in which NCO groups and olefinic CC double bonds are present, wherein in the curable compound the molar ratio of NCO groups to olefinic CC double bonds is in a range from 1:5 to 5:1,
and in that, after step III), step IV) is further performed: IV) treating the precursor obtained after step III) under conditions sufficient to at least partially trimerize to isocyanurate groups NCO groups present in the free-radically crosslinked resin of the obtained precursor to obtain the object.

(18) 2. Process according to clause 1, characterized in that isocyanurate groups are further present in the curable component, wherein the molar ratio of NCO groups to isocyanurate groups is in a range from 100:1 to 1:2 and in the curable component the molar ratio of olefinic CC double bonds to isocyanurate groups is in a range from 100:1 to 1:5.

(19) 3. Process according to clauses 1 or 2, characterized in that the curable component comprises a curable compound which comprises NCO groups and olefinic CC double bonds, wherein in the curable compound the molar ratio of NCO groups to olefinic CC double bonds is in a range from 1:5 to 5:1.

(20) 4. Process according to clause 3, characterized in that the curable component comprises a curable compound comprising isocyanurate groups, NCO groups and olefinic CC double bonds, wherein in the curable compound the molar ratio of NCO groups to olefinic CC double bonds is in a range from 1:5 to 5:1, in the curable compound the molar ratio of NCO groups to isocyanurate groups is in a range from 100:1 to 1:2, and in the curable compound the molar ratio of olefinic CC double bonds to isocyanurate groups is in a range from 100:1 to 1:5.

(21) 5. Process according to any of clauses 1 to 4, characterized in that the free-radically crosslinkable resin further comprises a free-radical starter and/or an isocyanate trimerization catalyst.

(22) 6. Process according to clause 5, characterized in that at least one free-radical starter is selected from the group: -hydroxyphenylketone, benzyldimethylketal, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis(4-methoxybenzoyl)diethylgermanium and any combination of at least two thereof

(23) and/or

(24) the isocyanurate trimerization catalyst is selected from: potassium acetate, potassium acetate in combination with a crown ether, potassium acetate in combination with a polyethylene glycol, potassium acetate in combination with a polypropylene glycol, tin octoate, sodium phenoxide, potassium hydroxide, trioctyl phosphine and/or tributyltin oxide.

(25) 7. Process according to any of clauses 1 to 6, characterized in that in the resin the molar ratio of NCO groups to Zerewitinoff-active H atoms is 500.

(26) 8. Process according to any of clauses 1 to 7, characterized in that the curable component has a number-average molecular weight M.sub.n of 200 g/mol to 5000 g/mol.

(27) 9. Process according to any of clauses 1 to 8, characterized in that in step IV) the treating of the precursor obtained after step III) under conditions sufficient to at least partially trimerize to isocyanurate groups NCO groups present in the free-radically crosslinked resin of the obtained precursor comprises a heating of the body to a temperature of 60 C.

(28) 10. Process according to any of clauses 1 to 9, characterized in that 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.

(29) 11. Process according to any of clauses 1 to 10, characterized in that: the carrier is arranged inside a container and is vertically lowerable in the direction of the gravitational force, the container contains the free-radically crosslinkable resin in an amount sufficient to cover at least the carrier and crosslinked resin deposited atop the carrier, 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 precursor.

(30) 12. Process according to any of clauses 1 to 10, characterized in that: 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 expose and/or irradiate the selected region of the layer of the free-radically crosslinkable resin corresponding to the respectively selected cross section of the precursor.

(31) 13. Process according to any of clauses 1 to 10, characterized in that: in step II) the free-radically crosslinkable resin is applied from one or more printing heads corresponding to the respectively selected cross section of the precursor and is subsequently exposed and/or irradiated.

(32) 14. Use of a free-radically crosslinkable resin having a viscosity (23 C., DIN EN ISO 2884-1) of 5 mPas to 100000 mPas in an additive manufacturing process,

(33) characterized in that

(34) the resin has a curable compound which comprises isocyanurate groups, NCO groups and olefinic CC double bonds,

(35) wherein the molar ratio of NCO groups to olefinic CC double bonds is in a range from 1:5 to 5:1, in the curable compound the molar ratio of NCO groups to isocyanurate groups is in a range from 100:1 to 1:2, and in the curable compound the molar ratio of olefinic CC double bonds to isocyanurate groups is in a range from 100:1 to 1:5.

(36) 15. Polymer obtainable by crosslinking of a resin having a viscosity (23 C., DIN EN ISO 2884-1) of 5 mPas to 100000 mPas,

(37) characterized in that

(38) the resin comprises a curable component comprising NCO groups and olefinic CC double bonds, wherein the molar ratio of NCO groups to olefinic CC double bonds is in a range from 1:5 to 5:1.