Powder comprising polymer-coated inorganic particles

1. A powder, comprising composite particles:

wherein the composite particles, comprise:

an inorganic core particle having a d 50 median diameter of from 1 to 70 μm; and

at least a partial coating of a precipitated polymer on the core;

wherein the d 50 median diameter of the composite particles is from 20 to 150 μm,

a ratio of a d 50 median diameter of the composite particles to the d 50 median diameter of the core particles is from 1.15 to 30,

a thickness of the at least partial precipitated polymer coating of the composite particle is 1.5 μm or greater,

the melting point of the polymer in a first heating procedure is greater than in a second heating procedure, as measured by differential scanning calorimetry (DSC),

the inorganic core particle is at least one material selected from the group consisting of a polyphosphate, a phosphinate, boron carbide and a ceramic, the precipitated polymer of the coating comprises at least one polymer selected from the group consisting of a polyolefin, a polyethylene, a polypropylene, a polyvinyl chloride, a polyacetal, a polystyrene, a polyimide, a polysulphone, a poly(N-methylmethacrylimide) (PMMI), a polymethyl methacrylate (PMMA), a polyvinylidene fluoride (PVDF), an ionomer, a polyether ketone, a poly aryl ether ketone, a polyamide, and a copolyamide,

the inorganic core particle material does not include titanium dioxide, and

a melting point of the coating polymer is obtainable when the polymer is exposed to an electromagnetic energy.

2. The powder according to claim 1 , wherein the d 50 median diameter of the core particles is from 1 to 60 μm.

3. The powder according to claim 1 , wherein the ratio of the d 50 median diameter of the composite particles to the d 50 median diameter of the core particles is from 1.5 to 15.

4. The powder according to claim 1 , wherein a number average weight ratio of the at least partial precipitated polymer coating to the core particle, is from 0.1 to 30.

5. The powder according to claim 1 , wherein a BET specific surface area of the composite particle is from 1 to 60 m 2 /g.

6. The powder according to claim 1 , wherein the precipitated polymer of the at least partial coating is a polyamide having at least 8 carbons per carbonamide group.

7. The powder according to claim 6 , wherein the polyamide is at least one selected from the group consisting of nylon-6,12, nylon-11 and nylon-12.

8. The powder according to claim 1 , wherein an enthalpy of fusion of the polymer in the first heating procedure is at least 50% greater than in the second heating procedure, as measured by differential scanning calorimetry (DSC).

9. The powder according to claim 1 , which further comprises at least one selected from the group consisting of a powder flow-aid, a pigment and a heat stabilizer.

10. The powder according to claim 9 , wherein a content of the composite particles in the powder is at least 50% by weight.

11. A process for producing the composite particles according to claim 1 , the process comprising:

at least partially dissolving a polymer for the coating in a medium comprising a solvent which at least partially dissolves the polymer;

adding the inorganic core particles to the medium, before, during or after at least partially dissolving the polymer;

suspending the core particles in the medium; and then

precipitating the polymer from the at least partial solution onto the core particles to obtain the composite particles;

wherein

the d 50 median diameter of the core particles is from 1 to 70 μm.

12. The process according to claim 11 , wherein a density of the core particles is greater or not more than 20% smaller than the density of the solvent used for the precipitation of the polymer.

13. The process according to claim 11 , wherein the solvent for the polymer is ethanol and a density of the core particles is greater or not more than 20% smaller than the density of ethanol.

14. A process for producing a moulded article, the process comprising:

applying a layer of the composite powder according to claim 1 ;

selectively melting at least one region of the layer by introduction of electromagnetic energy;

allowing the melted region to solidify;

applying another layer of composite powder and repeating the melting and solidification to perform a layer-by-layer process in which a molding having a structure according to the selective treatment is obtained;

wherein the melting selectivity is achieved by applying susceptors, inhibitors, or absorbers to each applied layer or by applying a mask to the applied layer.

15. A moulded article obtained according to the process of claim 14 .