Producing an item by the selective fusion of polymer powder layers

1. A method for manufacturing an article, the method comprising selectively fusing thermoplastic polymer powder layers, wherein the layers have the following characteristics:

a d50 particle size distribution of between 20 and 100 μm, and also satisfying the following equation: (d90−d10)/d50 between 0.85 and 1.2;

a sphericity factor of between 0.8 and 1; and

an intraparticle porosity lower than 0.05 ml/g;

wherein said article possesses a density having a range of 98.8% to 99.5% of theoretical density.

2. The method as claimed in claim 1 , wherein the powder is manufactured by:

a) mixing a molten thermoplastic polymer with a compound A comprising a polymeric material wherein at least pert of compound A's chemical structure is compatible with the thermoplastic polymer and at least part of compound A's chemical structure is incompatible and insoluble in the thermoplastic polymer, to obtain a mixture comprising a dispersion of discrete particles of thermoplastic polymer;

b) cooling the mixture to a temperature lower than a softening point of the thermoplastic polymer, and

c) treating the cooled mixture to make the particles of thermoplastic polymer disintegrate.

3. The method as claimed in claim 1 , wherein the thermoplastic polymer is a polyolefin.

4. The method as claimed in claim 1 , wherein the thermoplastic polymer is selected from the group consisting of nylon 6, nylon 6-6, mixtures thereof and copolymers thereof.

5. The method as claimed in claim 1 , wherein the powder has a sphericity factor of between 0.9 and 1.

6. The method as claimed in claim 1 , wherein the powder has a d50 particle size distribution of between 30 μm and 70 μm.

7. The method as claimed in claim 1 , wherein the powder has a (d90−d10)/d50 particle size distribution of between 0.9 and 1.2.

8. The method as claimed in claim 1 , wherein the powder has an intraparticle porosity lower than 0.02 ml/g.

9. The method as claimed in claim 1 , wherein the powder has a flowability of between 30 and 60, as determined by standard shear testing technique for particulate solids using a Jenike shear cell.

10. The method as claimed in claim 1 , wherein the powder has an apparent density of between 500 g/l and 700 g/l and a packed density of between 550 g/l and 800 g/l.

11. The method as claimed in claim 1 , wherein the article comprises one or more additives or compounds selected from the group consisting of a mattifier, a heat stabilizer, a light stabilizer, a pigment, a dye, a reinforcing filler, a nucleating agent, and an impact reinforcement agent.

12. The method as claimed in claim 1 , wherein the method for manufacturing the article by selectively fusing layers is a method for rapid prototyping by sintering using a laser.

13. The method as claimed in claim 3 , wherein the polyolefin is selected from the group consisting of a polyethylene, a polypropylene, a polyvinyl chloride, a polyethylene terephthalate, a polystyrene, a polyamide and an acrylic.

14. The method as claimed in claim 11 , wherein the reinforcing filler is an abrasive filler.