RADIATION CURABLE COMPOSITIONS FOR ADDITIVE MANUFACTURING OF TOUGH OBJECTS

Abstract

A liquid, radiation curable composition with a viscosity of 4000 cps or lower comprising component a) 20 to 60 weight percent of one or more oligomer(s), pre-polymer(s) or polymer(s) containing a plurality of ester linkages in the backbone, at least one or more urethane groups and at least two ethylenic unsaturated groups which can form polymeric crosslink networks with the other components in the composition in the presence of radicals, anions, nucleophiles or combination thereof, component b) 30 to 90 weight percent of one or more monomer(s) containing one ethylenic unsaturated group capable of forming polymeric crosslink networks with the other components in the composition in presence of radicals, anions, nucleophiles or combination thereof, component c) 0.01 to 10 weight percent of one or more photoinitiator(s) capable of producing radicals when irradiated with actinic radiation and component d) 0 to 40 weight percent of one or more additive(s) selected from the group consisting of filler(s), pigment(s), thermal stabilizer(s), UV light stabilizer(s), UV light absorber(s), radical inhibitor(s) or oligomer(s) as processing aid, said oligomers are different from the oligomers in component a).

Claims

1-14. (canceled)

15. A liquid radiation curable composition comprising the following components: a) 20 to 60 weight percent of one or more oligomer(s), pre-polymer(s) or polymer(s) containing a plurality of ester linkages in the backbone, at least one urethane group and at least two ethylenic unsaturated groups that can form polymeric crosslink networks with the other components in the composition in the presence of radicals, anions, nucleophiles or combinations thereof; b) 30 to 90 weight percent of one or more monomer(s) comprising one ethylenic unsaturated group capable of forming polymeric crosslink networks with the other components in the composition in the presence of radicals, anions, nucleophiles or combinations thereof; c) 0.01 to 10 weight percent of one or more photoinitiator(s) capable of producing radicals when irradiated with actinic radiation; d) 0 to 40 weight percent of one or more additive(s) selected from the group consisting of: filler(s); pigment(s), thermal stabilizer(s), UV light stabilizer(s), UV light absorber(s), radical inhibitor(s), and oligomer(s) as a processing aid, wherein said oligomers are different from the oligomers in component a); with the provision that component b) is different from the monomers forming the oligomer(s)/pre-polymer(s)/polymer(s) of component a) and the composition has a viscosity of no more than 4000 cps at 25? C.

16. The liquid radiation curable composition of claim 15, wherein the viscosity of the composition is less than 3000 cps at 25? C.

17. The liquid radiation curable composition of claim 15, wherein the ester linkages in the oligomer(s), pre-polymer(s) or polymer(s) of component a) are obtained by reacting aliphatic or aromatic acid(s) or anhydride(s) or mixtures thereof with a mixture of polyol(s) to form polyester polyols.

18. The liquid radiation curable composition of claim 17, wherein the mixture of polyols comprises at least one polyol with at least three hydroxyl moieties in a concentration of at least 3 mol % of the reaction mixture of aliphatic or aromatic acid(s) or anhydride(s) and polyols.

19. The liquid radiation curable composition of claim 17, wherein the aliphatic or aromatic acid(s) or anhydride(s) are selected from the group consisting of: succinic acid, adipic acid, sebacic acid, phthalic acid, terephthalic acid, isophthalic acid, trimellitic acid, pyromellitic acid and their anhydrides or esters, and mixtures thereof.

20. The liquid radiation curable composition of claim 17, wherein the mixture of polyols is selected from the group consisting of: ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2- and 1,3-propylene glycol, dipropylene glycol, polypropylene, 1,4- and 2,3-butylene glycol, 1,6-hexanediol, neopentyl glycol, trimethylolpropane, tris(?-hydroxyethyl)isocyanurate, penta-erythritol, mannitol and sorbitol.

21. The liquid radiation curable composition of claim 17, wherein component a) is obtained by reacting the polyester-polyols with isocyanate-functionalized (meth)acrylates to form polyester-based urethane (meth)acrylate.

22. The liquid radiation curable composition of claim 15, wherein the at least one ethylenic unsaturated group of the monomer in component b) is a (meth)acrylate functional group and the monomer in component b) further comprises a hydrocarbon group selected from a C2-C30 linear, cyclic, branched, aliphatic, aromatic, alicyclic or cycloaliphatic group.

23. The liquid radiation curable composition of claim 22, wherein the one or more monomer(s) in component b) comprise a hydrocarbon group that carries polar functional groups selected from the group consisting of; hydroxy, carboxy, urethane and urea.

24. The liquid radiation curable composition of claim 15, wherein the weight ratio of component a) to component b) ranges from 20:80 to 60:40.

25. The liquid radiation curable composition of claim 18, wherein the aliphatic or aromatic acid(s) or anhydride(s) are selected from the group consisting of: succinic acid, adipic acid, sebacic acid, phthalic acid, terephthalic acid, isophthalic acid, trimellitic acid, pyromellitic acid and their anhydrides or esters, and mixtures thereof.

26. The liquid radiation curable composition of claim 18, wherein the mixture of polyols is selected from the group consisting of: ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2- and 1,3-propylene glycol, dipropylene glycol, polypropylene, 1,4- and 2,3-butylene glycol, 1,6-hexanediol, neopentyl glycol, trimethylolpropane, tris(?-hydroxyethyl)isocyanurate, penta-erythritol, mannitol and sorbitol.

27. The liquid radiation curable composition of claim 26, wherein component a) is obtained by reacting the polyester-polyols with isocyanate-functionalized (meth)acrylates to form polyester-based urethane (meth)acrylate.

28. The liquid radiation curable composition of claim 27, wherein the at least one ethylenic unsaturated group of the monomer in component b) is a (meth)acrylate functional group and the monomer in component b) further comprises a hydrocarbon group selected from a C2-C30 linear, cyclic, branched, aliphatic, aromatic, alicyclic or cycloaliphatic group.

29. The liquid radiation curable composition of claim 28, wherein the one or more monomer(s) in component b) comprise a hydrocarbon group that carries polar functional groups selected from the group consisting of; hydroxy, carboxy, urethane and urea.

30. The liquid radiation curable composition of claim 29, wherein the weight ratio of component a) to component b) ranges from 20:80 to 60:40.

31. An additive manufacturing process comprising the repeated steps of deposition or layering, and irradiating the composition of claim 15 to form a three dimensional object.

32. The additive manufacturing process of claim 31, further comprising the steps of cleaning, washing, sonication, additional dosage of radiation, heating, polishing, coating or combinations thereof.

33. A three-dimensional object formed by an additive manufacturing process of claim 31, wherein the three-dimensional object has a tensile toughness of at least 15 J/m.sup.3 measured according to ASTM D638.

34. The three-dimensional object of claim 33, wherein the tensile strength and elongation at break of the three-dimensional object measured according to ASTM D638 in XY direction and in Z direction differs by not more than 20% from each other.

Description

EXAMPLES

[0061] The subject matter of the present invention is illustrated in more detail in the following examples, without any intention that the subject matter of the present invention be restricted to these examples.

[0062] The liquid radiation curable resin composition is prepared by mixing the ingredients as mentioned in the tables below in a mixing equipment. The polyester-based urethane acrylate oligomer used as component a) in the examples below (termed acrylated polyester oligomer in the table) is prepared according to the procedures described in EP1323758B1. This polyester-based urethane acrylate oligomer has a molecular weight of 6300 g/mol, an acrylate functionality greater than 2.5 and a viscosity of approximately 2800 cps at 40? C. and 39000 cps at 25? C.

[0063] The viscosity is measured using rotational rheometer equipped with cone plate (2?) and reading is obtained at 1 Hz shear rate. Unless otherwise indicated viscosity is measured at a temperature of 25? C.

[0064] The thus prepared resin composition is used to generate the tensile specimens through DLP 3D printing process with an actinic irradiation between 30 and 140 mJ/cm.sup.2.per 100 micron layer thickness.

[0065] The tensile toughness was determined from the area under the stress-strain curve of the specimen measured according to ASTM D638 (see FIG. 1).

[0066] Table 1 summarizes the abbreviations used for the monomers.

[0067] Tables 2 and 3 summarize the resin compositions and properties of the 3D printed specimen.

TABLE-US-00001 TABLE 1 Abbreviation of the monomers Abbreviation Description IBoA Isobornyl acrylate 2-HEA 2-Hydroxyethyl acrylate 2-HEMA 2-Hydroxyethyl methacrylate 2-BACOEA 2-[[(Butylamino)carbonyl]oxy]ethyl acrylate TMCHA 3,3,5-trimethyl cyclohexyl acrylate CTFA Cyclic trimethylolpropane formal acrylate A-LEN-10 Ethoxylated o-phenylphenol acrylate GLYFOMA Glycerol formal acrylate BAPO Phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide TCDDA Tricyclodecane Dimethanol Diacrylate TPGDA Tripropylene Glycol Diacrylate

Example 1

[0068] Compositions 1A, 1B, 1C, 1D and 1E are comparative examples with component a) falling below or exceeding the weight % of the composition range according to the invention. Compositions 1F and 1G comprise component a) in the range according to the invention but composition b) is a mixture of two monomers one monomer having one ethylenic unsaturated group and one monomer having two ethylenic unsaturated groups.

TABLE-US-00002 TABLE 2 Compositions for liquid radiation curable resin for 3D printing Composition 1A 1B 1C 1D 1E 1F 1G Component a) Acrylated 8.3% 8.3% 8.3% 66.6% 66.6% 50.0% 50.0% Polyester Oligomer Component b) IBoA 2.8% 2.8% 2.8% 22.2% 22.2% 16.7% 16.7% Component b) TMCHA 88.9% 11.1% Component b) 2-HEMA 88.9% 11.1% Component b) CTFA 88.9% Component b) TCDDA 33.3% Component b) TPGDA 33.3% Component b) 2-HEA Component b) 2-BACOEA Component b) A-LEN-10 Component b) GLYFOMA Component c) Photoinitiator 1.0 1.0 1.0 1.0 1.0 1.0 1.0 [BAPO] PHR PHR PHR PHR PHR PHR PHR Viscosity [cps] 7 17 46 47400 21600 18000 3820 Tensile Toughness [J/m.sup.3] 0.52 0.42 6.91 Not Printable 6.8 9.1

[0069] Example 1A, 1B, 1C demonstrated low viscosity resin <50 cps and printability, however, the tensile toughness of these samples was below 15 J/m.sup.3.

[0070] Example 1D and 1E showed the composition leads to a viscosity of 47400 and 21600 cps, far exceeding the viscosity of 4000 cps at 25? C. Tensile properties of example 1D and 1E could not be measured as composition given in example 1D and 1E was unable to be printed by DLP 3D printer. Going beyond the weight range given for component a) according to the invention affects either the tensile toughness or viscosity of the composition significantly.

[0071] Example 1F and 1G demonstrate the effect of using monomers for component b) with two ethylenic unsaturated groups instead of just one according to the invention. Even if the formulation also contains component b) with one ethylenic unsaturated group, adding monomers with two ethylenic unsaturated groups leads to a tensile toughness below 15 J/m.sup.3.

Example 2

[0072]

TABLE-US-00003 TABLE 3 Compositions for liquid radiation curable resin for 3D printing Composition 2F 2G 2H 2I 2J 2K Component a) Acrylated 50.0% 50.0% 50.0% 50.0% 50.0% 50.0% Polyester Oligomer Component b) IBoA 50.0% 16.7% 16.7% 16.7% 16.7% 16.7% Component b) TMCHA 33.3% Component b) 2-HEMA Component b) CTFA Component b) 2-HEA 33.3% Component b) 2-BACOEA 33.3% Component b) A-LEN-10 33.3% Component b) GLYFOMA 33.3% Component c) Photoinitiator 1.0 1.0 1.0 1.0 1.0 1.0 [BAPO] PHR PHR PHR PHR PHR PHR Viscosity [cps] 3870 812 2140 2680 1690 1490 Tensile Toughness [J/m.sup.3] 25.9 25.3 15.9 17.89 18.41 23.5

[0073] Compositions 2F, 2G, 2H, 2I, 2J and 2K according to the invention all show a tensile toughness exceeding 15 J/m.sup.3. The viscosity of these samples is below 4000 cps.

Example 3

[0074] For a three-dimensional object formed by an additive manufacturing process using a liquid radiation curable composition according to invention the tensile strength, elongation at break and tensile toughness in XY direction (parallel to the build platform) and in Z direction (perpendicular to the build platform) as determined by ASTM D638 method should differ not more than 20% from each other.

TABLE-US-00004 TABLE 4 Composition for a printed three-dimensional object demonstrating isotropic behavior Composition 3L Methacrylated Polyester Oligomer 50.0% IBoA 16.7% TMCHA 33.3% TPO 2.0 PHR Carbon Black 0.07 PHR Print Direction XY Z ? Ultimate Tensile Strength [MPa] 24.0 21.3 ?11.25% Elongation at Break [%] 127.0 121.0 ?4.7% Tensile Toughness [J/m.sup.3] 21.1 17.3 ?17.9%

[0075] The results shown in Table 4 describe the isotropic behavior of the printed three-dimensional object using a liquid radiation curable composition according to the invention. As can be seen from Table 4, tensile strength, elongation at break and tensile toughness of the printed specimen in XY direction and in Z direction all differ less than 20%.