Dual cure epoxy formulations for 3D printing applications

Abstract

The present invention lies in the field of 3D printing methods. In particular, the invention relates to 3D printing methods for the production of a 3D part in a layer-by-layer manner, wherein the printable composition is a pasty epoxy composition comprising at least one epoxy resin, at least one monomer and/or prepolymer that is polymerizable by exposure to radiation and at least one photoinitiator, wherein the pasty epoxy composition has a viscosity factor (1.5/15) of at least 2 at application temperature.

Claims

1. A method for additive manufacturing a three-dimensional part in a layer-by-layer manner, the method comprising: (i) providing a carrier substrate to support the three-dimensional part and a print head connected to a reservoir of a printable composition; (ii) printing the printable composition with the print head in the form of extrudate strands onto the carrier substrate to form a first layer; (iii) printing the printable composition with the print head in the form of extrudate strands onto the first layer to form a second layer; (iv) optionally repeating step (iii) one or more times to form a third layer or the third layer and subsequent layer(s); (v) exposing the formed layers to radiation directly after forming each layer and/or after forming all of the layers; and (vi) curing the formed layers of the printable composition by heating to obtain the three-dimensional part, wherein the printable composition is a pasty epoxy composition comprising: at least one epoxy resin; at least one monomer and/or prepolymer that is polymerizable by exposure to radiation; at least one photoinitiator; and at least one adhesion promoter, wherein: the pasty epoxy composition has a first viscosity factor (1.5/15) of at least 4 and a second viscosity factor (5/50) at an application temperature, the pasty epoxy composition has a viscosity at a shear rate of 1.5/s of at least 10 Pas, and the first viscosity factor (1.5/15) is greater than the second viscosity factor (5/50).

2. The method of claim 1, wherein the distance of the print head to the carrier substrate or an already formed layer is equal to or greater than the thickness of the printed extrudate strands.

3. The method of claim 1, wherein the second viscosity factor (5/50) at the application temperature is at least 3.

4. The method of claim 1, wherein the application temperature is in a range of from 15 C. to 80 C.

5. The method of claim 1, wherein the viscosity at the shear rate of 1.5/s is at least 20 Pas.

6. The method of claim 1, wherein the at least one epoxy resin comprises an aliphatic epoxy resin.

7. The method of claim 1, wherein the at least one monomer and/or prepolymer that is polymerizable by exposure to radiation is selected from the group consisting of di-acrylates, tri-acrylates and mixtures thereof.

8. The method of claim 1, wherein the printable composition further comprises an epoxy curing catalyst.

9. The method of claim 1, wherein the printable composition further comprises a dual reactive compound.

10. The method of claim 1, wherein the printable composition further comprises at least one compound having at least one oxetane group.

11. The method of claim 1, wherein the pasty epoxy composition further comprises at least one organic hardener co-polymerizable with the at least one epoxy resin.

12. The method of claim 1, wherein the pasty epoxy composition further comprises core-shell particles.

13. The method of claim 1, wherein the radiation is ultraviolet (UV) radiation.

14. The method of claim 5, wherein the viscosity at the shear rate of 1.5/s is at least 30 Pas.

15. The method of claim 1, wherein the at least one epoxy resin is a polyepoxide having an epoxy equivalent of between 110 g/mol and 5000 g/mol.

16. The method of claim 1, wherein the at least one epoxy resin is a polyepoxide having an epoxy equivalent of between 130 g/mol and 2000 g/mol.

17. The method of claim 4, wherein the application temperature is 25 C.

18. The method of claim 4, wherein the application temperature is 55 C.

Description

EXAMPLES

(1) The printable composition has been prepared by the components as mentioned in following table.

(2) The printable composition had a pasty behaviour with a viscosity factor (1.5/15) in the desired range (see table; measured as mentioned in the description).

(3) The printable composition were printed using a standard procedure for application of dual cure formulations using a Loctite 300 application robot and a Loctite UV cure cabinet (UVA Loc 1000) plus standard oven. After printing of each layer the layer has been pre-cured using a UV chamber (UVALOC 1000; 3rd platform, 5 s, 1000 W) or a UV LED. In this manner the layers have been printed on top of each other the gain a three-dimensional structure. After UV-curing the final layer, the printed object was put into an oven at 100 C. for 27 minutes.

(4) Objects printed with the inventive compositions by using the inventive method show a high resolution with a smooth surface and at the same time have a good interlayer adhesion and strong mechanical properties. Objects printed with the composition according to the comparative examples 1 and 2 show a lower resolution and rough surfaces, in case 3D printing was possible at all.

(5) TABLE-US-00001 E1 E2 E3 E4 E5 E6 E7 E8 E9 Aliph. Epoxy Resin 1 13.67 16.57 16.16 16.16 13.67 Aliph. Epoxy Resin 2 23.67 13.50 Arom. Epoxy Resin 24.62 Oxetane 10.00 11.82 11.82 10.00 10.00 CSR 1 39.59 14.11 14.11 14.11 16.68 16.68 14.11 14.11 CSR 2 8.32 CSR 3 33.53 Polyol 1 8.32 8.32 9.83 9.83 8.32 8.32 Polyol 2 10.42 Adhesion promoter 1.57 8.32 1.57 1.86 1.86 1.57 1.57 2.56 GLYMO 0.24 0.24 0.24 0.28 0.28 0.24 0.24 Epoxy Acrylate 1 10.00 11.82 11.82 10.00 10.00 Epoxy Acrylate 2 10.00 10.00 10.00 Triacrylate 3.00 3.00 3.00 3.00 3.55 3.55 3.00 3.00 3.00 Diacrylate 6.20 6.20 6.20 6.20 7.33 7.33 6.20 6.20 6.00 Surfactant 2.65 2.65 2.65 2.65 3.13 3.13 2.65 2.65 Amorphous fumed silica 7.88 Pigment 0.15 0.03 Fumed silica 5.49 1.49 5.49 5.49 7.88 9.49 9.49 Calcium Oxide 2.80 Boron Nitride 1.18 1.18 1.18 1.18 1.18 1.18 Calcium metasicate 8.90 wollastonite Bariumsulftat 19.59 23.59 19.59 19.59 4.93 4.93 15.59 15.59 Cationic curing catalyst 1.00 1.00 1.00 1.00 1.18 1.18 1.00 1.00 Fenuron 0.50 Dicyandiamide 4.64 Hydrophob fumed silica 2.00 Photoinitiator 1 3.00 3.00 3.00 3.00 3.55 3.55 3.00 3.00 Photoinitiator 2 1.00 Sum (1.5/s) at 25 C. [Pas] 116 3.8 38 42 563 1218 116 178 163* (15/s) at 25 C. [Pas] 70 8 8 9 74 116 25 41 32* Viscosity factor (1.5/15) 1.66 0.48 4.7 4.7 7.6 10.5 4.6 4.3 5* *at 55 C.

(6) TABLE-US-00002 Aliph. Epoxy (3,4-Epoxycyclohexane)methyl-3,4- Resin 1 epoxycyclohexylcarboxylate, liquid, Epoxy Equivalent 130 g/eq Aliph. Epoxy (3,4-Epoxycyclohexane)methyl-3,4- Resin 2 epoxycyclohexylcarboxylate modified epsilon-caprolactone, liquid Arom. Epoxy Epoxy resin based on bisphenol A Resin and epichorohydrin, liquid, Epoxy Equivalent 187 g/eq Oxetane Bis(3-ethyl-3-oxethanyl)methoxymethyl)biphenyl CSR 1 30% CSR (vinyl acrylic copolymer) in liquid cycloaliphatic epoxy resin CSR 2 methacrylate-butadiene-styrene core-shell CSR 3 40% CSR in unmodified liquid epoxy resin based on bisphenol A Polyol 1 Polyethylene glycol, molecular weight 400 g/mol Polyol 2 Polyol, OH value 1-1.15 eq/kg GLYMO 3-Glycidyloxypropyltrimethoxysilan Epoxy Liquid epoxy methacrylate resin based Acrylate 1 on bisphenol A diglycidylether Epoxy Liquid EPOXY ACRYLATE OLIGOMER Acrylate 2 Triacrylate TRIMETHYLOLPROPANE TRIACRYLATE (TMPTA) Diacrylate ETHOXYLATED BISPHENOL A DIACRYLATE Cationic curing Catalyst based on hexafluoroantimonate catalyst Photoinitiator 1 Mixture of Oxyphenyl-acetic acid 2-(2-oxo-2-phenyl-acetoxy-ethoxy)- and Oxyphenyl-acetic acid 2-[2-hydroxy-ethoxy]-ethyl ester Photoinitiator 2 Bis(2,4,6-Trimethylbenzoyl)phenylphosphine oxide