Powder of spherical crosslinkable polyamide particles, preparation process and use with the selective laser sintering technique

A powder of spherical particles of polyamide (I) functionalized by crosslinking functions Rt rendering it crosslinkable, wherein said crosslinking functions Rt are present at the surface and in the mass of said particles and in that said particles of crosslinkable polyamide (I) have a mean diameter d50 in the range of 20 μm to 100 μm;

• wherein the crosslinking functions Rt are introduced onto a polyamide (II) by grafting, and the crosslinking functions Rt are supplied by grafting, directly onto the amine and/or carboxyl and/or amide functions of the polyamide (II), termed reactive functions Rr, of a crosslinking agent (III) with formula:
• Rg-R1-Si(R2)3-a(R3)a (III)
• in which:
• a=0, 1, or 2;
• Rg is a grafting function that is capable of reacting with Rr;
• R1 is a divalent hydrocarbon group or a covalent bond connecting Si directly to Rg;
• R2 is an alkoxy or acyl group or represents a halogen, the groups R2 being identical or different when a=0 or 1;
• R3 is an alkyl group, the groups R3 being identical or different when a=2;
• and the crosslinking agent (III) is such that a=0, R1 is a divalent hydrocarbon group, R2 is an alkoxy group, Rg is an epoxy group.