METHOD FOR PRODUCING A THREE-DIMENSIONAL PRINTED ARTICLE

Abstract

The present invention relates to a method for producing a three-dimensional (3D) printed article with a photocurable silicone composition involving a silicone containing as end-group specific (meth)acrylate groups.

Claims

1. A method for producing a three-dimensional printed article comprising (a) for 100 parts by weight of at least one organopolysiloxane polymer CE having the following formula (1):
M*D.sub.xM*  (1) wherein: M* is: R1(R)2SiO.sub.1/2; D is (R)2SiO.sub.2/2; x≥60, preferably 60≤x≤500, and most preferably 90≤x≤400. R is an alkyl group chosen from the group consisting of methyl, ethyl, propyl, trifluoropropyl, and phenyl, and most preferably R is a methyl group, R.sup.1 is a moiety of general formula —C.sub.nH.sub.2nO—CH.sub.2CHR.sup.2(CH.sub.2).sub.m—OCOCH═CHR.sup.3, wherein n is 3 or 4 and m is 0 or 1, preferably m is 1, R.sup.2 is H, OH or —C.sub.zH.sub.2z—CH.sub.2OH, z is 1, 2 or 3 and R.sup.3 is H or —CH.sub.3; (b) from 0 parts to 20 parts by weight, preferably from 1 to 20 parts by weight, and even more preferably from 1 to 10 parts by weight of at least one organopolysiloxane polymer XL having the following formula (2):
M D.sub.v(D.sup.ACR).sub.wM  (2) wherein M is: R.sup.2(R).sub.2SiO.sub.1/2; (R).sub.3SiO.sub.1/2 or R.sup.4(R).sub.2SiO.sub.1/2 D is (R).sub.2SiO.sub.2/2; D.sup.ACR is (R.sup.2)(R)SiO.sub.2/2; y is from 0 to 500, preferably from 10 to 500, and most preferably from 50 to 400, w is from 0 to 50, preferably from 1 to 25, and most preferably from 3 to 20, and when w=0, y is from 1 to 500 and M represents: R.sup.2(R).sub.2SiO.sub.1/2 or R.sup.4(R).sub.2SiO.sub.1/2; R is an alkyl group chosen from the group consisting of methyl, ethyl, propyl, trifluoropropyl, and phenyl, and most preferably R is a methyl group, R.sup.2 is a moiety of the following general formulas: —C.sub.nH.sub.2nO—CH.sub.2CHR.sup.2(CH.sub.2).sub.m—OCOCH═CHR.sup.3, wherein n is 3 or 4 and m is 0 or 1, m is 0 or 1, R.sup.2 is H, OH or —C.sub.zH.sub.2z—CH.sub.2OH, z is 1, 2 or 3 and R.sup.3 is H or —CH.sub.3; or —C.sub.nH.sub.2nO—COCH═CHR.sup.3, wherein n is 3 or 4 and R.sup.3 is H or —CH.sub.3; R.sup.4 is a moiety of formula (3): ##STR00016## (c) from 0.01 to 10 parts by weight of at least one photoinitiator PI, preferably from 0.01 to 3 parts by weight, (d) at least 15 parts by weight, preferably from 20 parts to 100 parts by weight, and even more preferably from 20 parts to 50 parts by weight, of at least one inorganic filler F, (e) from 0 to 10 parts by weight of at least one sensitizer PS, (f) from 0 to 10000 parts by weight of at least one photocurable organic (meth)acrylate-monomer/oligomer M, and (g) from 0 to 10 parts by weight of at least one additive I; 2. exposing the photocurable composition X to actinic radiation to form a cured cross-section on a plate or support, and 3. repeating steps 1) and 2) on the former cured cross section with new layer to build up the three-dimensional printed article.

2. A method according to claim 1 wherein the organopolysiloxane polymer CE according to the invention has an average molecular weight from 4000 g/mol to 40000 g/mol, preferably from 5700 g/mol to 30000 g/mol, and even more preferably from 5700 g/mol to 24000 g/mol.

3. A method according to claim 1 wherein the organopolysiloxane polymer CE comprises as terminal groups meth(acrylate) moieties comprising a hydroxyl group and have the generalized average formula:
M*D.sub.xM* wherein M* is: R.sup.1(R).sub.2SiO.sub.1/2; D is (R).sub.2SiO.sub.2/2; x≥60, preferably 60≤x≤500, and most preferably 90≤x≤400, R is an alkyl group chosen from the group consisting of methyl, ethyl, propyl, trifluoropropyl, and phenyl, and most preferably R is a methyl group, R.sup.1 is a moiety of general formula —C.sub.nH.sub.2nO—CH.sub.2CHR.sup.2(CH.sub.2).sub.m—OCOCH═CHR.sup.3, wherein n is 3 or 4 and m is 0 or 1, m is 0 or 1, R.sup.2 is OH or —C.sub.zH.sub.2z—CH.sub.2OH, z is 1, 2 or 3 and R.sup.3 is H or —CH.sub.3.

4. A method according to claim 1 wherein the organopolysiloxane polymer CE (polydimethylsiloxane with 3-acryloxy 2-hydroxypropoxypropyl end-groups) has the following formula (4): ##STR00017## In which n≥60, and preferably 60≤n≤500, and most preferably 80≤n≤400.

5. A method according to claim 1 wherein the organopolysiloxane polymer XL is chosen from the group consisting of polymers (5) to (8): ##STR00018## In which a is from 1 to 20, and preferably a is from 1 to 10, b is from 1 to 500, and preferably b is from 10 to 500. ##STR00019## In which n is from 10 to 400, preferably n is from 50 to 200, and even more preferably n is from 50 to 150. ##STR00020## In which n is from 1 to 500, and preferably n is from 1 to 200. ##STR00021## In which a is from 2 to 50, and preferably a is from 2 to 20; b is from 0 to 500, and preferably b is from 10 to 400.

6. A method according to claim 1 wherein the inorganic filler F is chosen from the group consisting of colloidal silica, fumed silica, precipitated silica or mixtures thereof.

7. A method according to claim 1 wherein the components and the quantities of the components are chosen so as the composition X has a dynamic viscosity below 50 Pa.Math.s at 25° C. and preferentially below 20 Pa.Math.s at 25° C.

8. A method according to claim 1 wherein the photocurable composition X is provided via a 3D printer using a technology chosen from the group consisting of UV-stereolithography (SLA), UV-Digital Light processing (DLP), Continuous Liquid Interface Production (CLIP), Inkjet Deposition and UV extrusion.

Description

EXAMPLES

I) Raw Materials Used in the Examples:

[0101] 1) Polydimethylsiloxane with bis(3-acryloxy2-hydroxypropoxypropyl) end-groups CE:

##STR00011##

Polydimethylsiloxane polymer CE-1 (comparative): n=6; viscosity 170 mPa.Math.s at 25° C. Polydimethylsiloxane polymer CE-2 (comparative) n=45, viscosity 200 mPa.Math.s at 25° C. Polydimethylsiloxane polymer CE-3 (Invention) n is from 250 to 280; viscosity 1200 mPa.Math.s at 25° C. 2) Polydimethylsiloxane with bis(acryloxypropyl) end-groups CE (comparative):

##STR00012##

[0102] Polydimethylsiloxane polymer CE-4 (comparative) n=130, viscosity 430 mPa.Math.s 3) Polydimethylsiloxane with (acryloxy-2-hydroxypropoxypropyl) groups in the chain XL:

##STR00013##

Polydimethylsiloxane polymer XL-1; a is from 3 to 4 and b is around 220. Polydimethylsiloxane polymer XL-2; a is from 7 to 8 and b is around 80.
4) Polymer XL-3: n=95:

##STR00014##

5) Polydimethylsiloxane with (3-acryloxy 2-hydroxypropoxypropyl) end-groups and in the chain XL-4 (with a is from 2 to 3 and b from 140 to 170)

##STR00015##

6) Inorganic filler F1: Pyrogenic Silica surface treated (trimethylsiloxy) sold by Wacker under the tradename HDK® H2000.

7) Photoinitiators PI:

[0103] TPO-L: 2,4,6-trimethylbenzoyldi-phenylphosphinate.
BAPO: Phenylbis (2,4,6-trimethylbenzoyl) phosphine oxide.
TPO: 2,4,6-Trimethylbenzoyldiphenylphosphine oxide.
8) Solvent: IPA=isopropylalcohol.

9) Additives: Kri-Color Trans Pigment (Pigment)

II) Physical Properties

[0104] Viscosity: The viscosity of the sample is measured at 25° C. according to ASTM D445 or ISO3104.
Hardness: The hardness of the cured sample is measured at 25° C. according to ASTM D2240 or ISO868.
Tensile strength and Elongation at break: Tensile strength and elongation at break of the cured sample based on the curable silicone composition are measured at 25° C. according to ASTM D412 or ISO37.
Tear strength: Tear strength of the cured sample is measured at 25° C. according to ASTM D624 or ISO34-1.
II) Formulations (Curing and 3D-Printed with a 3D Printer Asiga)
Formulations were prepared according to Tables 1, 2, 3 or 4.
They were then mixed either manually or with a speed mixer. The resulting mixtures were then poured into the vat of the Asiga 3D printer having a capacity of 1 liter and with a printing plate of XYZ: 119×67×75 mm. An “.stl” file of a H2 specimen (length 40 mm+/−0.5, thickness 2 mm+/−0.2) was then designed. The 2 mm thickness specimens are prepared with an “.stl” file and a building procedure of 27 layers. Each layer has a thickness of 75 micrometers. The first layer is irradiated during 30 s to achieve a good adhesion to the platform, and the following layers are irradiated during 20 s for each layer at 385 nm and 5.8 mW/cm.sup.2 After 3D printing the specimen can be post-cured at 405 nm in an UV box/recto/verso during 180 s.
The physical properties are quoted in the following Tables.

TABLE-US-00001 TABLE 1 Formulations and physical properties (% by weight). Examples 1-Comp. 2-Comp. 3-Invention Polymer CE-1 75.00%  0.00%  0.00% Polymer CE-2  0.00% 75.00%  0.00% Polymer CE-3  0.00%  0.00% 75.00% Polydimethylsiloxane polymer XL-1  4.00%  4.00%  4.00% Inorganic filler F1 30.00% 30.00% 30.00% Photoinitiator TPO-L  1.00%  1.00%  1.00% Mechanical Properties Tensile (psi) Too Brittle Too Brittle 366 Tensile (MPa) to Test to Test 2.52 Elongation (%) 182 Tear (lb/inch) 26 Tear (N/mm) 4.55 Hardness (Shore A) 90 72 28.2

TABLE-US-00002 TABLE 2 Formulations and physical properties (% by weight). Examples 4-Comp. 5-Inv. 6-Inv. 7-Inv. 8-Inv. Polymer CE-3 100.00% 100.00% 100.00% 100.00% 100.00% Polydimethylsiloxane polymer  5.09%  5.33%  5.04%  5.11%  5.11% XL-1 Inorganic filler F1  11.83%  26.67%  45.80%  51.26%  57.66% Pigment  0.24%  0.00%  0.00%  1.58%  0.00% Photoinitiator TPO-L  0.24%  0.27%  0.31%  0.32%  0.33% Tensile (psi) 278 306 384 458 588 Tensile (MPa) 1.92 2.11 2.65 3.16 4.05 Elongation (%) 108 214 196 200 252 Tear (lb/in) 11 15.1 59 67 90 Tear (N/mm) 1.93 2.64 10.33 11.73 15.76 Hardness (Shore A) 27 28.5 25.9 32.9 34.5

[0105] The comparison of Example 4 (comparative) versus examples 5 to 8 (according to the invention) shows that by using a specific acrylated end-capped silicones (acryloxypropoxypropyl end-groups according to the invention in combination with at least 15 parts by weight (for 100 parts by weight of the acrylated end-capped silicones) of an inorganic filler it was possible to obtain via 3D-UV photoprinting a cured material which has higher elongation-in-break properties well above 140% described in the prior art, and with very good tensile strength and tear properties when the filler is present above.

TABLE-US-00003 TABLE 3 Formulations and physical properties (% by weight) at 5 mW/cm.sup.2 Examples 9 10 11 Polymer CE-3 100.00% 0 0 Polydimethylsiloxane polymer 0 100.00% 0 CE-4 (comparative) Polydimethylsiloxane with (methacryloxy- 0 0 100.00% propyl)end-groups XL-3 Photoinitiator TPO-L  0.40%  0.40%  0.40% Elongation (%) 108 70 50

[0106] A comparison between examples 9 and 10 shows that polydimethylsiloxane with (acryloxypropoxypropyl) end-groups CE as used in the invention is already showing a superior properties (even with no inorganic filler) in terms of elongation in break properties (+30%) compared to the standard polydimethylsiloxane with acryloxypropyl end-groups CE-4 used in the prior art.

TABLE-US-00004 TABLE 4 Formulations and physical properties (% by weight). Examples 10-Inv. 11-Inv. 12-Inv. Polymer CE-3 75% 75% 75% Polydimethylsiloxane with (acryloxyhydroxy-  4% 0 0 propoxypropyl) groups in the chain XL-1 Polydimethylsiloxane with (acryloxyhydroxy- 0  4% 0 propoxypropyl) groups in the chain XL-2 Polydimethylsiloxane with (acryloxyhydroxy- 0 0  4% propoxypropyl) end-groups and in the chain XL-4 Inorganic filler F1 20% 20% 20% Photoinitiator TPO-L  1%  1%  1% Tensile (psi) 306 340 305 Tensile (MPa) 2.11 2.34 2.10 Elongation (%) 214 150 150 Tear (lb/in) 15.1 10.19 13.95 Tear (N/mm) 2.64 1.78 2.44 Hardness (Shore A) 28.5 26.8 32
In Table 4, it was possible to attain excellent elongation-in-break properties with a wide variety of polydimethylsiloxanes with acrylates groups (crosslinkers).