Method Of Manufacturing A Thermoplastic Molding Compound Powder

Abstract

The present invention relates to a method of manufacturing thermoplastic molding compound powder that consists of or comprises spherical or approximately spherical molding compound particles from a suspension of glass-like and/or ceramic and/or metallic substrate particles in a solvent in which a binder is dissolved that has a polymer soluble in the solvent, wherein the binder furthermore has one or more additives soluble in the solvent, with the method comprising the step of spray drying the suspension and with the spray drying being carried out such that the solvent partially or completely transitions into the gas phase.

Claims

1. A method of manufacturing thermoplastic molding compound powder that consists of or comprises spherical or approximately spherical molding compound particles from a suspension of glass-like and/or ceramic and/or metallic substrate particles in a solvent in which a binder is dissolved that has a polymer soluble in the solvent, wherein the binder furthermore has one or more additives soluble in the solvent, with the method comprising the step of spray drying the suspension and with the spray drying being carried out such that the solvent partially or completely transitions into the gas phase.

2. A method in accordance with claim 1, characterized in that the additive or additives is/are molecularly dissolved in the suspension.

3. A method in accordance with claim 1, characterized in that the additive or additives is/are one or more of the substances: plasticizer, mold lubricant, additive that forms an at least binary system with the polymer.

4. A method in accordance with claim 1, characterized in that the polymer is thermoplastic; and/or in that the polymer is selected from one or more of the substances: Polycondensates; polymerizates; or polyadducts.

5. A method in accordance with claim 3, characterized in that the plasticizer is an ester of an aromatic hydroxybenzoic acid.

6. A method in accordance with claim 1, characterized in that the substrate particles each have a maximum dimension B.sub.max and 1 mB.sub.max50 m, that applies to at least 80% of the substrate particles.

7. A method in accordance with claim 1, characterized in that the molding compound particles each have a maximum dimension A.sub.max and 0.005 mmA.sub.max0.3 mm, that applies to at least 80% of the molding compound particles.

8. A method in accordance with claim 1, characterized in that the molding compound particles each have a minimum dimension A.sub.min and a maximum dimension A.sub.max and 0.6A.sub.min/A.sub.max1, that applies to at least 80% of the molding compound particles.

9. A method in accordance with claim 1, characterized in that the solvent is one or more alcohols or one or more alcoholic media.

10. A method in accordance with claim 1, characterized in that the substrate particles consist of one or more of the substances: precious metal, hard metal, glass, ceramics, non-ferrous metal, iron, titanium, their alloys and/or compounds, superalloys and steel or comprise one or more of these substances or metals, alloys or compounds.

11. A method in accordance with claim 1, characterized in that the ceramic and/or metallic and/or glass-like substrate particles are first introduced into the solvent comprising the binder and this suspension is then atomized in a spray system with a partial or complete evaporation of the solvent.

12. A method in accordance with claim 11, characterized in that the introduction of the ceramic and/or metallic and/or glass-like substrate particles takes place at elevated temperature.

13. A method in accordance with claim 1, characterized in that the spray process is carried out at a temperature that is 10 C.-30 C. below the crystallization temperature of the additive polymer.

14. A method in accordance with claim 1, characterized in that the method is carried out such that the suspension is sprayed into a liquid in which the binder is insoluble.

15. A method in accordance with claim 1, characterized in that the binder has a melt viscosity of 10.sup.0 Pa.Math.s to 10.sup.6 Pa.Math.s, at a temperature that is at least 10 C. above a temperature T.sub.s, with the temperature T.sub.s being a glass transition temperature or a crystallite melting temperature of the binder and with a speed drop in particular being selected from the group 1.00 s.sup.1, 2.50 s.sup.1, 5.00 s.sup.1, 10.0 s.sup.1, 25.0 s.sup.1, 50.0 s.sup.1 and 100 s.sup.1.

16. A thermoplastic molding compound powder, characterized in that the molding compound powder is manufactured in accordance with claim 1.

17. A thermoplastic molding compound powder in accordance with claim 16, characterized in that the binder has a melt viscosity of 10.sup.0 Pa.Math.s to 10.sup.6 Pa.Math.s, at a temperature that is at least 10 C. above a temperature T.sub.s, with the temperature T.sub.s being a glass transition temperature or a crystallite melting temperature of the binder and with a speed drop in particular being selected from the group 1.00 s.sup.1, 2.50 s.sup.1, 5.00 s.sup.1, 10.0 s.sup.1, 25.0 s.sup.1, 50.0 s.sup.1 and 100 s.sup.1.

18. A thermoplastic molding compound powder in accordance with claim 16, characterized in that the molding compound particles of the molding compound powder each have a maximum dimension A.sub.max and 0.005 mmA.sub.max0.3 mm, that applies to at least 80% of the molding compound particles.

19. A thermoplastic molding compound powder in accordance with claim 16, characterized in that the molding compound particles each have a minimum dimension A.sub.min and a maximum dimension A.sub.max and 0.6A.sub.min/A.sub.max1, that applies to at least 80% of the molding compound particles.

20. A thermoplastic molding compound powder in accordance with claim 16, characterized in that the molding compound particles of the molding compound powder are spherical and have a plurality of ceramic and/or metallic and/or glass-like substrate particles.

21. A method for powder-based additive manufacturing comprising printing with a thermoplastic molding compound powder in accordance with claim 16.

Description

[0053] There are shown:

[0054] FIG. 1: a schematic representation of a suspension that is intended for supply into a spray dryer;

[0055] FIG. 2: a schematic representation of the spherical molding compound particles acquired by spray drying the suspension in accordance with FIG. 1; and

[0056] FIG. 3: a schematic representation of a molding compound particle obtained by spray drying an aqueous suspension.

[0057] FIG. 1 shows by reference symbol a metallic substrate particles, e.g. of stainless steel, titanium, etc. that are received in a liquid alcoholic suspension. The alcoholic medium is marked by the reference symbol c. The binder or binder components b is molecularly dissolved in this medium.

[0058] If the suspension shown in FIG. 1 is subjected to a spray drying in that the suspension is directly introduced into a spray dryer at elevated temperature, the alcohol evaporates so that the binder comprising the plasticizer and the metallic particles remain. The binder comprising the plasticizer acts as an adhesion agent between the individual metallic substrate particles and holds them together in a spherical structure that is shown in FIG. 2.

[0059] FIG. 2 thus shows a molding compound particle of which the feedstock compound, i.e. the thermoplastic molding compound powder, consists in accordance with the invention. As can be seen from FIG. 2, the molding compound particle is ball-shaped or substantially ball-shaped.

[0060] It has a diameter of <0.2 mm and can be brought into a melt, preferably into a low-viscosity melt, at a temperature of or from 150 C. without application of pressure, with the melt then being able to be processed into a molding in a 3D printing process.

[0061] The molding compound particles in accordance with FIG. 2 have a good flowability that is in particular significant for coating with a doctor blade as part of a 3D printing process. A further advantage of the molding compound particles in accordance with the invention comprises the fact that they bring about a correspondingly low operating temperature of the 3D printer due to their property of melting at comparatively low temperatures.

[0062] The use of the molding compound particles in accordance with the invention is particularly advantageous with a powder-based, additive production process such as in a 3D SLS method (SLS=selective laser sintering).

[0063] A molding compound particle can be seen from FIG. 3 that was not obtained through the method in accordance with the invention. This particle was obtained by the spray drying of an aqueous suspension that has substrate particles a that are coated by the binder b that was deposited by precipitation on the substrate particle.

[0064] While agglomerates in accordance with FIG. 3 and having a comparatively open porosity between the individual binder-coated substrate particles are obtained in the spray drying of the aqueous suspension, a denser structure of powder and binder results on a spray drying from an alcoholic solution in accordance with the invention, as can be seen from a comparison of FIGS. 2 and 3. This means that the base density of the feedstock particles obtained in accordance with the invention is higher than that of the feedstock particles acquired from the aqueous suspension.

[0065] Higher green densities or bulk densities are of substantial significance for the sintering density later present at the sintered molding on a laser sintering.