Particles of polyamide powders and use thereof in powder agglomeration processes
The invention relates to a seeded particle of polyamide (PA) powder consisting of: a polyamide core with a D50 within the range from 15 to 60 μm, and a polyamide shell, characterized in that the shell has an inherent viscosity in solution and a melting temperature which are respectively higher than those of the core.
1 . A seeded particle of polyamide (PA) powder consisting of:
a polyamide core with a volume-median diameter D 50 within the range from 15 to 60 μm, and
a polyamide shell,
wherein the shell has an inherent viscosity in solution and a melting temperature which are respectively higher than those of the core.
2 . The particle as claimed in claim 1 , wherein the shell and the core of the particle are made of polyamide selected from the group consisting of PA 4 , PA 6 , PA 8 , PA 11 , PA 12 , PA 6 / 12 , PA 6 . 12 , PA 6 . 13 , PA 6 . 10 , PA 6 . 6 and PA 10 . 10 .
3 . The particle as claimed in claim 1 , wherein the shell and the core of the particle are of the same nature:
shell and core made of PA 6 , or
shell and core made of PA 12 , or
shell and core made of PA 6 / 12 .
4 . The particle as claimed in claim 1 , wherein the shell and the core of the particle are of different nature:
shell made of PA 6 and a core chosen from PA 8 , PA 11 , PA 12 , PA 6 / 12 , PA 6 . 12 , PA 6 . 10 , PA 10 . 10 ; or
shell made of PA 12 and a core chosen from PA 6 / 12 , PA 6 . 12 ; or
shell made of PA 6 / 12 and a core chosen from PA 11 , PA 12 , PA 6 . 12 , PA 10 . 10 and PA 6 . 10 .
5 . The particle as claimed in claim 1 , wherein the shell has an inherent viscosity in solution within the range from 1.20 to 1.50.
6 . The particle as claimed in claim 1 , wherein the shell has a melting temperature (Tm 1 ) of greater than 180° C.
7 . The particle as claimed in claim 1 , where the shell is obtained by anionic polymerization.
8 . The particle as claimed in claim 1 , wherein the shell is obtained by dissolution and precipitation of polyamide around the core of the particle.
9 . The particle as claimed in claim 1 , wherein the particle has a volume-median diameter D 50 within the range from 17 to 90 μm.
10 . A process for producing the particle as claimed in claim 1 by anionic polymerization in solution in a solvent, comprising the polymerization of the shell from 2-pyrrolidone, from caprolactam, from lauryllactam, from 2-azacyclononanone or from a mixture thereof in the presence of a catalyst, of an activator, of at least one amide chosen from N,N′-alkylenebisamides and of an organic filler for the core of the particle selected from the group consisting of PA 4 , PA 6 , PA 8 , PA 11 , PA 12 , PA 6 / 12 , PA 6 . 12 , PA 6 . 13 , PA 6 . 10 , PA 6 . 6 and PA 10 . 10 .
11 . The process as claimed in claim 10 , wherein the N,N′-alkylenebisamide is chosen from EBS and EBO.
12 . The process as claimed in claim 10 , wherein, in addition to the N,N′-alkylenebisamide, there is a further amide chosen from oleamide, N-stearamide, isostearamide and erucamide.
13 . A process for producing a powder particle as claimed in claim 1 , by dissolution of the polyamide of the shell in an alcohol-based solvent and then precipitation of the polyamide of the shell around the core of the particle.
14 . The process as claimed in claim 13 , wherein the dissolution is carried out under pressure and/or with heating.
15 . The process as claimed in claim 13 , wherein the dissolution is carried out in the presence of the core of the particle in suspension in said solvent.
16 . The process as claimed in claim 13 , wherein the precipitation is carried out by reduction of temperature and/or extraction of solvent.
17 . A process for manufacturing an object by agglomeration of the powder as claimed in claim 1 , during which:
a. a thin layer of powder (layer 1 ) is deposited on a horizontal plate maintained in a chamber heated to a temperature lying between the crystallization temperature (Tc) and the melting temperature (Tm) of said powder,
b. a laser or an input of electromagnetic energy causes the agglomeration of the particles by melting at various points in the powder layer (layer 1 ) according to a geometry corresponding to the object to be manufactured,
c. the horizontal plate is then lowered by a value corresponding to the thickness of one powder layer and then a new powder layer is deposited (layer 2 ),
d. the laser or an input of electromagnetic energy causes the agglomeration of the particles by melting of the powder layer (layer 2 ) according to a geometry corresponding to this new slice of the object to be manufactured,
e. the previous steps are repeated until the object is constructed;
f. an object surrounded by powder is obtained inside the chamber;
g. after complete cooling, the object is separated from the powder, which can be reused for another operation.
18 . The particle as claimed in claim 1 , wherein the shell has a thickness of between 1 and 15 μm.
19 . The particle as claimed in claim 1 , wherein the particle is formed by anionic polymerization in solution in a solvent, comprising the polymerization of the shell from 2 -pyrrolidone, from caprolactam, from lauryllactam, from 2-azacyclononanone or from a mixture thereof in the presence of a catalyst, of an activator, of at least one amide chosen from N,N′-alkylenebisamides and of an organic filler for the core of the particle selected from the group consisting of PA4, PA6, PA8, PA11, PA12, PA6/12, PA6.12, PA6.13, PA6.10, PA6.6 and PA10.10.
20 . The particle as claimed in claim 19 , wherein the N,N′-alkylenebisamide is chosen from EBS and EBO.
21 . The particle as claimed in claim 19 , wherein, in addition to the N,N′-alkylenebisamide, there is a further amide chosen from oleamide, N-stearamide, isostearamide and erucamide.