PHOTOCURABLE COMPOSITION FOR USE IN 3D PRINTING

Abstract

Described herein are photocurable compositions,

(A) a polyester urethane acrylate, or methacrylate (A),

(B) an acrylamide, or methacrylamide component (B), and

(C) a photoinitiator (C), where the polyester urethane acrylate, or methacrylate (A) is obtained by reacting (A1) a hydroxyalkylacrylate, or hydroxyalkylmethacrylate, (A2) an aliphatic diisocyanate, an aliphatic polyisocyanate, a cycloaliphatic diisocyanate, a cycloaliphatic polyisocyanate, an aromatic diisocyanate, or an aromatic polyisocyanate, or mixtures thereof, (A3) a polyester polyol, and (A4) optionally a second polyol.

The compositions, from which cured three-dimensional shaped articles having high toughness, high E modulus and impact strength can be made, are particularly suitable for the production of three-dimensional articles by stereolithography.

Claims

1. A photocurable composition, comprising (A) a polyester urethane acrylate, or methacrylate (A), (B) an acrylamide, or methacrylamide component (B), and (C) a photoinitiator (C), wherein the amount of component (A) is 30 to 60% by weight and the amount of component (B) is 40 to 70% by weight based on the amount of components (A) and (B), and wherein the polyester urethane acrylate, or methacrylate (A) is obtained by reacting (A1) a hydroxyalkylacrylate, or hydroxyalkylmethacrylate, (A2) an aliphatic diisocyanate, an aliphatic polyisocyanate, a cycloaliphatic diisocyanate, a cycloaliphatic polyisocyanate, an aromatic diisocyanate, or an aromatic polyisocyanate, or mixtures thereof, (A3) a polyester polyol, and (A4) optionally a second polyol.

2. The photocurable composition according to claim 1, wherein component (A1) is selected from the group consisting of 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2- or 3-hydroxypropyl acrylate, 2- or 3-hydroxypropyl methacrylate, 4-hydroxybutyl methacrylate, and 4-hydroxybutyl acrylate.

3. The photocurable composition according to claim 1, wherein component (A2) is selected from the group consisting of 4,4′-, 2,4′- and/or 2,2′-methylenedicyclohexyl diisocyanate (H12MDI), isophorone diisocyanates (IPDI), or tolylene 2,4- and/or 2,6-diisocyanate (TDI).

4. The photocurable composition according to claim 1, wherein the polyester polyol (A3) is derived from aliphatic dicarboxylic acids and aliphatic diols.

5. The photocurable composition according to claim 4, wherein the polyester polyol (A3) is derived from adipic acid and ethylene glycol and 1,4-butanediol.

6. The photocurable composition according to claim 5, wherein the molar ratio of ethylene glycol to 1,4-butanediol in (poly(ethylene 1,4-butylene adipate) diol is from 0.5:1 to 1.5:1.

7. The photocurable composition according to claim 5, wherein the polyester polyol has a number average molecular weight within the range of 4×10.sup.2 to 7.0×10.sup.3.

8. The photocurable composition according to claim 1, wherein the second polyol (A4) is glycerol.

9. The photocurable composition according to claim 1, wherein the acrylamide, or methacrylamide component (B) is acryloylmorpholine.

10. The photocurable composition according to claim 1, wherein the photoinitiator (C) is a compound of the formula ##STR00037## R.sub.50 is unsubstituted cyclohexyl, cyclopentyl, phenyl, naphthyl or biphenylyl; or is cyclohexyl, cyclopentyl, phenyl, naphthyl or biphenylyl substituted by one or more halogen, C.sub.1-C.sub.12alkyl, C.sub.1-C.sub.12alkoxy, C.sub.1-C.sub.12alkylthio or by NR.sub.53R.sub.54; or R.sub.50 is unsubstituted C.sub.1-C.sub.20alkyl or is C.sub.1-C.sub.20alkyl which is substituted by one or more halogen, C.sub.1-C.sub.12alkoxy, C.sub.1-C.sub.12alkylthio, NR.sub.53R.sub.54 or by —(CO)—O—C.sub.1-C.sub.24alkyl; R.sub.51 is unsubstituted cyclohexyl, cyclopentyl, phenyl, naphthyl or biphenylyl; or is cyclohexyl, cyclopentyl, phenyl, naphthyl or biphenylyl substituted by one or more halogen, C.sub.1-C.sub.12alkyl, C.sub.1-C.sub.12alkoxy, C.sub.1-C.sub.12alkylthio or by NR.sub.53R.sub.54; or R.sub.51 is —(CO)R′.sub.52; or R.sub.51 is C.sub.1-C.sub.12alkyl which is unsubstituted or substituted by one or more halogen, C.sub.1-C.sub.12alkoxy, C.sub.1-C.sub.12alkylthio, or by NR.sub.53R.sub.54; R.sub.52 and R′.sub.52 independently of each other are unsubstituted cyclohexyl, cyclopentyl, phenyl, naphthyl or biphenylyl, or are cyclohexyl, cyclopentyl, phenyl, naphthyl or biphenylyl substituted by one or more halogen, C.sub.1-C.sub.4alkyl or C.sub.1-C.sub.4alkoxy; or R.sub.52 is a 5- or 6-membered heterocyclic ring comprising an S atom or N atom; R.sub.33 and R.sub.34 independently of one another are hydrogen, unsubstituted C.sub.1-C.sub.12alkyl or C.sub.1-C.sub.12alkyl substituted by one or more OH or SH wherein the alkyl chain optionally is interrupted by one to four oxygen atoms; or R.sub.53 and R.sub.54 independently of one another are C.sub.2-C.sub.12-alkenyl, cyclopentyl, cyclohexyl, benzyl or phenyl, or the photoinitiator (C) is a mixture of a compound of the formula (XII) and a compound of the formula ##STR00038## wherein R.sub.29 is hydrogen or C.sub.1-C.sub.18 alkoxy; R.sub.30 is hydrogen, C.sub.1-C.sub.18alkyl, C.sub.1-C.sub.12hydroxyalkyl, C.sub.1-C.sub.18alkoxy, OCH.sub.2CH.sub.2—OR.sub.34, morpholino, S—C.sub.1-C.sub.18alkyl, a group —HC═CH.sub.2, —C(CH.sub.3)═CH.sub.2, ##STR00039## D, E and fare 1-3; c is 2-10; G.sub.1 and G.sub.2 independently of one another are end groups of the polymeric structure; R.sub.34 is hydrogen, ##STR00040## R.sub.31 is hydroxy, C.sub.1-C.sub.16alkoxy, morpholino, dimethylamino or —O(CH.sub.2CH.sub.2O).sub.g—C.sub.1-C.sub.16alkyl; g is 1-20; R.sub.32 and R.sub.33 independently of one another are hydrogen, C.sub.1-C.sub.6alkyl, C.sub.1-C.sub.16alkoxy or —O(CH.sub.2CH.sub.2O).sub.g—C.sub.1-C.sub.16alkyl; or are unsubstituted phenyl or benzyl; or phenyl or benzyl substituted by C.sub.1-C.sub.12-alkyl; or R.sub.32 and R.sub.33 together with the carbon atom to which they are attached form a cyclohexyl ring; R.sub.35 is hydrogen, OR.sub.36 or NR.sub.37R.sub.38; R.sub.36 is hydrogen, C.sub.1-C.sub.12alkyl which optionally is interrupted by one or more non-consecutive O-atoms and which uninterrupted or interrupted C.sub.1-C.sub.12alkyl optionally is substituted by one or more OH, or R.sub.36 is ##STR00041## R.sub.37 and R.sub.38 independently of each other are hydrogen or C.sub.1-C.sub.12alkyl which is unsubstituted or is substituted by one or more OH; R.sub.39 is C.sub.1-C.sub.12alkylene which optionally is interrupted by one or more non-consecutive O, —(CO)—NH—C.sub.1-C.sub.12alkylene-NH—(CO)— or ##STR00042## with the proviso that R.sub.31, R.sub.32 and R.sub.33 not all together are C.sub.1-C.sub.16alkoxy or —O(CH.sub.2CH.sub.2O).sub.g—C.sub.1-C.sub.16alkyl, or the photoinitiator is a mixture of different compounds of the formula (XII), or the photoinitiator is a mixture of compounds of the formula (XII) and (XI).

11. The photocurable composition according to claim 1, wherein components (A) and (B) are the only components of the composition which comprise photopolymerizable groups.

12. A method for producing a three-dimensional article, comprising a) providing the photocurable composition according to claim 1, b) exposing the photocurable composition to actinic radiation to form a cured cross-section, and c) repeating steps (a) and (b) to build up a three-dimensional article.

13. The method according to claim 12, comprising a vat photopolymerization, wherein the photocurable composition in step b) is cured directly onto a translated or rotated substrate, and the irradiation is patterned via stereolithography, holography, or digital light projection (DLP).

14. The method according to claim 12, comprising a) applying a layer of the photocurable curable composition of onto a surface; b) exposing the layer imagewise to actinic radiation to form an imaged cured cross-section; c) applying a second layer of the photocurable composition onto the previously exposed imaged cross-section; d) exposing the layer from step (c) imagewise to actinic radiation to form an additional imaged cross-section, wherein the radiation causes curing of the second layer in the exposed areas and adhesion to the previously exposed cross-section; and e) repeating steps (c) and (d) in order to build up a three-dimensional article.

15. A three-dimensional article, which is a cured product of the photocurable composition according to claim 1.

16. A method of using the photocurable composition according to claim 1, the method comprising using the photocurable composition in a photopolymerization 3D printing process or photopolymer jetting.

17. The photocurable composition according to claim 1, comprising (A) a polyester urethane acrylate, or methacrylate (A), (B) an acrylamide, or methacrylamide component (B), and (C) a photoinitiator (C), wherein the amount of component (A) is 45 to 55% by weight and the amount of component (B) is 45 to 55% by weight based on the amount of components (A) and (B).

18. The photocurable composition according to claim 5, wherein the molar ratio of ethylene glycol to 1,4-butanediol in (poly(ethylene 1,4-butylene adipate) diol is from 0.75:1 to 1.25:1.

19. The photocurable composition according to claim 10, wherein G.sub.1 and G.sub.2 independently of one another are hydrogen or methyl.

20. A three-dimensional article, which is a cured product of the photocurable composition which is produced by the method of claim 12.

Description

EXAMPLES

[0331] General Urethane (Meth)Acrylate Synthesis

[0332] Urethane (meth)acrylates were prepared filling the calculated amount of isocyanate (TDI, HDI, H12MDI, IPDI) in a suitable 3-neck round-bottom flask equipped with temperature element PT100, nitrogen flow, mechanic stirrer and heating hood. The material was heated to 50° C. In some experiments (compare recipes in Table 1), the catalyst 1 was added. Subsequently the polyol 1 was added. Any additional polyol 2, if used, was added afterwards. After addition of all components, the system was flushed with nitrogen and kept under nitrogen atmosphere during the reaction. The mixture was heated to 80° C. and kept at this temperature for 2 h. Then, the mixture was allowed to cool down to 60° C. and the NCO value of the prepolymer was determined. The amount of hydroxyalkyl(meth)acrylate needed to saturate all NCO groups was calculated and added under air at 60° C. The reaction mixture was stirred at this temperature for 1 h what typically led to a decrease in NCO to almost 0. The final urethane acrylate was kept at room temperature (RT) under air in a suitable vial. After 24 h, the viscosity was measured.

[0333] NCO content was determined following DIN EN ISO 11909: primary and secondary amines react with free isocyanate groups to urea groups. This reaction is quantitative under excess of amine. After the complete reaction, the excess amine is determined by back titration with hydrochloric acid.

[0334] Polyol viscosity was determined at 60° C. in accordance with DIN EN ISO 3219 using a cone/plate Brookfield viscometer/CAP 2000+ and a spindle with diameter of 9.53 mm and an angle of 1.8° at a shear rate of 100 s−1.

[0335] Preparation of Inventive Photopolymers and Specimen for Mechanical Testing

[0336] 25 g of the synthesized urethane (meth)acrylates were mixed with acryloylmorpholine at a ratio as specified in Table 2 and 1.5 wt-% photoinitiator TPO by stirring at 70° C. for 30 minutes in a water bath using a 100 ml glass jar which was protected against daylight with aluminum foil. The resulting clear, slightly yellowish mixtures were transferred at 40 to 50° C. into home-made silicone molds (ProtoSil RTV 245, altropol, shore hardness 50) and cured stepwise: Step 1—curing under a low-energy UVA fluorescent lamp (Silvania Blacklight BL368) at 10 cm distance for 60 seconds. Step 2—curing under a 365 nm UV-LED (Hoenle Powerline AC) placed over a conveyor belt (500 mJ/cm.sup.2 per pass) at a total UV dose of 2500 mJ/cm.sup.2 (tensile test, 2 mm specimen thickness) and 5000 mJ/cm.sup.2 (Izod impact strength, 4 mm specimen thickness). The specimens were irradiated on both sides to ensure homogeneous curing. After storage for 24 hours at 50% relative humidity the mechanical properties of the specimen were tested according to DIN EN ISO 527-1 (specimen type 5A) using Zwick Roell 10 kN Pro Line and DIN EN ISO 180 using a Zwick Roell HIT pendulum impact tester B5113.300 (5.5 J pendulum).

[0337] The viscosities of the photopolymers were determined at 50° C. at 100 s.sup.−1 shear rate using a cone/plate (60 mm diameter, 2° cone angle) rheometer (HR-1 Discovery, TA Instruments).

[0338] All UV doses were measured with a UV-Control 3CT, UV-technik meyer gmbh. [0339] TDI: is a mixture of 2,4-Toluene diisocyanate (2,4-TDI, 80%) and 2,6-TDI (20%) with a NCO content of 48%. Trade name BASF: Lupranat T 80 A [0340] HDI: is 1,6-Hexane diisocyanate with a NCO content of 50%. Trade name BASF: Basonat H [0341] H12MDI: is Dicyclohexylmethane-4,4′-diisocyanate with a NCO content of 32%. Trade name Evonik: Vestanat H12MDI [0342] IPID: is Isophorondiisocyanate with a NCO content of 38%. Trade name Evonik: Vestanat IPDI [0343] Polyol 1: is a Polyester polyol based on adipic acid, ethylene glycol and 1,4-butanediol; OH value=55 mg KOH/g, functionality=2. Trade name BASF: Lupraphen 6601/3 [0344] Polyol 2: is Propane-1,2,3-triol from BASF. [0345] Catalyst 1: is a tin based catalyst. Trade name BASF: Fomrez UL 28. [0346] HEA: is Hydroxyethylacrylate purchased from Sigma Aldrich (96%, contains 200-650 ppm monomethyl ether hydroquinone as inhibitor) [0347] HEMA: is Hydroxyethylmethacrylate purchased from Sigma Aldrich (97%, contains ≤250 ppm monomethyl ether hydroquinone as inhibitor)

[0348] The examples in Table 2 show that by using the inventive compositions, a combination of mechanical properties (E modulus, elongation at break and impact strength) can be achieved which was not possible so far. While by changing the Laromer® UA 9089: acryloylmorpholine ratio, E modulus can be increased or decreased in the comparative examples, the corresponding impact strength values obtained by the compositions of the comparative examples are significantly lower compared to the impact strength values obtained by the compositions of examples 1 to 5. In addition, elongation at break is substantially higher for the inventive compositions confirming their superior mechanical properties.

TABLE-US-00001 TABLE 1 Polyester urethane Polyester urethane Polyester urethane Polyester urethane Polyester urethane acrylate 1 methacrylate 1 acrylate 2 acrylate 3 acrylate 4 TDI [g] 19.5 19.5 — — — HDI [g] — — 20.7 — — H12MDI [g] — — — 20.1 — IPDI [g] — — — — 20.0 Polyol 1 [g] 80.5 80.5 79.3 79.9 80.0 Polyol 2 [g] 0.5 — — — — Catalyst 1 — 0.01 HEA [g] 14.7 — 19.8 7.9 10.2 HEMA [g] — 19 — — —

TABLE-US-00002 TABLE 2 Comparative Comparative Comparative Example 1 Example 2 Example 3 Example 4 Example 5 example 1 example 2 example 3 Component Wt-% Wt-% Wt-% Wt-% Wt-% Wt-% Wt-% Wt-% Acryloylmorpholine.sup.1 49.25 49.25 59.25 49.25 49.25 49.25 59.10 39.40 Polyester urethane acrylate 1 49.25 — — — — — — — Polyester urethane methacrylate — 49.25 — — — — — — 1 Polyester urethane acrylate 2 — — 39.25 — — — — — Polyester urethane acrylate 3 — — — 49.25 — — — — Polyester urethane acrylate 4 — — — — 49.25 — — — Laromer ® UA 9089.sup.2 — — — — — 49.25 39.40 59.1 Omnirad ® TPO.sup.3 1.50 1.50 1.50 1.50 1.50 1.50 1.50 1.50 Total 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 Viscosity [mPas] at 50° C./100 413 356 182 772 428 49 46 85 s.sup.−1 E modulus [MPa] 1280 ± 57  1460 ± 116  1322 ± 160  749 ± 33  1010 ± 24  1662 ± 325  1706 ± 214  1347 ± 178  Tensile strength at break [MPa]  46 ± 0.3  46 ± 3.5  40 ± 2.7  29 ± 6.8  36 ± 3.6 56.1 ± 5.9  58.0 ± 9.2  45.7 ± 7.1  Elongation at break [%] 150 ± 37  99 ± 34  30 ± 7.3 180 ± 71  174 ± 11  7.6 ± 1.9 3.1 ± 0.6 11.2 ± 4.8  Izod impact strength (unnotched) >135.sup.4 >135.sup.4 132 >135.sup.4 >135.sup.4  49 ± 1.9 35 ± 20 55 ± 15 [kJ/m.sup.2] Izod impact strength (notched) 29.3 ± 1.3  24.9 ± 1.3  — — — 18.8 ± 1.1  21.1 ± 1.9  20.3 ± 1.1  [J/m] .sup.1Rahn AG, .sup.2BASF, .sup.3IGM Resins, .sup.4limit of impact strength testing equipment (5.5 J pendulum)