PRODUCTION OF A PHOTOCURABLE FORMULATION FOR ADDITIVE MANUFACTURING

Abstract

The present invention relates to a method for the production of a photocurable formulation (F) for the use in an additive manufacturing process. In this method a ceramic dispersion (CD) comprising at least one ceramic material, at least one first acrylate and at least one dispersant is mixed with a solution (S) which comprises at least one second acrylate and at least one photoinitiator to obtain the photocurable formulation (F). The present invention furthermore relates to the photocurable formulation (F) obtainable by the inventive method and to a method for the production of a molding in an additive manufacturing process by curing the photocurable formulation (F). Moreover, the present invention relates to the use of the photocurable formulation (F) in an additive manufacturing process.

Claims

1.-15. (canceled)

16. A method for producing a photocurable formulation (F) for the use in an additive manufacturing process, comprising the steps a) providing a ceramic dispersion (CD) comprising the following components (A) at least one ceramic material having a D50 value of at least 2 m, (B1) at least one first acrylate (C) at least one dispersant b) providing a solution (S) comprising the following components (B2) at least one second acrylate (D) at least one photoinitiator c) mixing the ceramic dispersion (CD) provided in step a) and the solution (S) provided in step b) to obtain the photocurable formulation (F).

17. The method according to claim 16, wherein component (A) is selected from the group consisting of SiO.sub.2, ZrO.sub.2, Al.sub.2O.sub.3, ZnO, Fe.sub.2O.sub.3, Fe.sub.3O.sub.4, Y.sub.2O.sub.3, TiO.sub.2, SiC, Si.sub.3N.sub.4, TiB and AlN.

18. The method according to claim 16, wherein component (B1) and component (B2) are independently from one another selected from the group consisting of acrylates and methacrylates.

19. The method according to claim 16, wherein component (C) is selected from the group consisting of ethoxylated fatty alcohols, polyoxyproylene/ethylene block copolymers, ethoxylated nonylphenol, (polyethylene glycol) p-octyl phenyl ether, alkoxylated diamines, sodium lauryl sulfate and cationic dispersants.

20. The method according to claim 16, wherein component (D) is selected from the group consisting of benzophenone, alkylbenzophenones, halomethylatal benzophenones, Michler's ketone, benzoin, benzoin ethers, benzyl ketals, acetophenone derivatives, phenylglyoxylic acid, anthraquinone, methylanthraquinone, acylphosphine oxides and bisacylphosphine oxides.

21. The method according to claim 16, wherein the ceramic dispersion (CD) provided in step a) comprises in the range from 57 to 90% by volume of component (A) in the range from 10 to 42% by volume of component (B1) and in the range from 0.1 to 15% by volume of component (C), based on the sum of the percent by volume of components (A), (B1) and (C).

22. The method according to claim 16, wherein the solution (S) provided in step b) comprises in the range from 75 to 99.9% by weight of component (B2) and in the range from 0.1 to 25% by weight of component (D), based on the sum of the percent by weight of components (B2) and (D).

23. The method according to claim 16, wherein component (B1) and component (B2) have independently from one another a C-C-double bond functionality in the range from 1 to 6.

24. The method according to claim 16, wherein the solution (S) provided in step b) further comprises component (C2) at least one dispersant.

25. The method according to claim 16, wherein in step c) in the range from 75 to 99% by weight of the ceramic dispersion (CD) and in the range from 1 to 25% by weight of the solution (S) are mixed to obtain the photocurable formulation (F), based on the sum of the percent by weight of the ceramic dispersion (CD) and the solution (S).

26. A photocurable formulation (F) obtained by the method according to claim 16.

27. A method for producing a molding in an additive manufacturing process comprising the steps i) providing the photocurable formulation (F) according to claim 26, ii) forming a layer of a first part of the photocurable formulation (F) provided in step i), and curing at least a part of the layer formed using an UV-light source to obtain the molding.

28. The method according to claim 27, wherein step ii) comprises the following steps ii-1) forming a layer of a first part of the photocurable formulation (F) provided in step i), ii-2) curing at least a part of the layer of the first part of the photocurable formulation (F) formed in step ii-1) using an UV-light source to obtain a cured layer, ii-3) forming a second layer of a second part of the photocurable formulation (F) provided in step i) on the cured layer obtained in step ii-2), ii-4) curing at least a part of the second layer of the second part of the photocurable formulation (F) formed in step ii-3) using an UV-light source to obtain the molding.

29. The method according to claim 28, wherein steps ii-1) and ii-2) are repeated at least once.

30. An additive in a manufacturing process comprising the photocurable formulation (F) according to claim 26 in an additive manufacturing process.

Description

EXAMPLES

[0185] Ceramic dispersion (CD)

[0186] The ceramic dispersion was prepared by mixing 86.7% by weight of a silica (SiO.sub.2) powder with a D50 value of 9 m as component (A) with 1.73% by weight of a polypropoxy quaternary ammonium chloride (trade name: Variquat CC NS 42 by Evonik) as component (C) in hexanediol diacrylate (trade name: Laromer HDDA by BASF SE) as component (B1), using a double helix mixer (helix pitch 1:1, agitator diameter 12.5 inches) at agitator speeds up to 100 rpm as high-shear dispersion equipment.

[0187] The mixing procedure was carried out in a 10 gallon reactor. Component (B1) and component (C) were poured into a vessel and mixed at minimum speed (15-20 rpm). Component (A) was then added stepwise while mixing at minimum speeds. Temperature control was used to keep the batch temperature below 35 C. After addition of component (A) the mixture was stirred for 2 hours at a speed determined based on torque. It was desired to keep the torque below 90 ft-lb.

[0188] The obtained ceramic dispersion (CD) had a viscosity of 21 Pas measured with a Brookfield viscosimeter (spindle type 64 at 6 rpm) at a temperature of 25 C.

[0189] No sediment formation on the bottom of the holding jar filled to a height of 10 cm was obtained, no agglomerates were visible in light-microscopic observations of material drawn-downs and no significant change of viscosity with age was obtained. The ceramic dispersion (CD) was stable for at least twelve weeks while submitted to cyclic temperature changes (cycle: 6 hours holding at 20 C., 6 hours ramp-up to 50 C., 6 hours holding at 50 C., 6 hours ramp-down to 20 C.).

[0190] In FIG. 1 the viscosity of the obtained ceramic dispersion (CD) over twelve weeks is shown. It can be seen that the viscosity is constant over the time within the standard deviation.

[0191] Photocurable Formulation (F)

[0192] The obtained ceramic dispersion (CD) was mixed with a solution (S) comprising hexanediol diacrylate (trade name: Laromer HDDA by Evonik) and ethoxylated trimethylolpropane triacrylate (trade name: Laromer LR 8863 by Evonik) as component (B2), hydroxycyclohexyl phenyl ketone (trade name: Irgacure 184 by BASF SE) as component (D), polypropoxy quaternary ammonium chloride (trade name: Variquat CC NS 42 by Evonik) as dispersant and 2-(2H-benzotriazol-2-yl)-4-methyl-phenol (trade name: Tinuvin 171 by BASF SE) as UV absorber to obtain the photocurable formulation (F). The obtained photocurable formulation (F) had the following composition: 80% by weight of the ceramic powder, 1.6% by weight of polypropoxy quaternary ammonium chloride, 15.5% by weight of hexanediol diacrylcate, 1.94% by weight of ethoxylated trimethylolpropane triacrylate, 1.05% by weight of hydroxycyclohexyl phenyl ketone and 0.04% by weight of 2-(2H-benzotriazol-2-yl)-4-methyl-phenol. The mixing of the ceramic dispersion (CD) and the solution (S) was performed using a dispersion disk (diameter: 4 cm) at 800 rpm for 30 minutes.

[0193] The obtained photocurable formulation (F) had a viscosity of 2.1 Pas measured with a Brookfield viscosimeter (spindle type 62 at 12 rpm) at 25 C.

[0194] The photocurable formulation's (F) stability was defined as the start time of sediment formation at room temperature (20 C.). The sediment formation was tested by scratching the bottom of a holding jar that was filled to a height of 10 cm with photocurable formulations (F) with a spatula. The photocurable formulation (F) was stable for twelve hours.

[0195] The photocurable formulation (F) was used in a stereolithography apparatus (Raplas RPS450) to obtain a molding. The molding was then cleaned of unreacted material by rinsing and gentle brushing with tripropylene glycol methyl ether (TPM), followed by a rinse with water. The obtained molding showed high precision and low curl distortion.