Preparation of thermoplastic polymer particles having controlled geometry and powders obtained therefrom

A process for the preparation of a thermoplastic material P powder comprising particles having controlled geometry and a predetermined mean diameter of less than 1 mm, which comprises the following stages:

• a. forming a melt blend of said thermoplastic material P with at least one additive A to obtain a dispersion of discrete particles of the thermoplastic material P, said additive A comprising a polymeric material having at least a portion of its structure compatible with said thermoplastic material P and at least a portion of its structure incompatible with and insoluble in said thermoplastic material P, to obtain a dispersion of discrete particles of said thermoplastic material P;
• b. cooling said blend to a temperature below the softening temperature of the thermoplastic material P;
• c. treating said cold blend and separating the discrete particles of thermoplastic material P;
• and
• d. introducing at least one compound B which is insoluble in and incompatible with the thermoplastic material P during said stage a) to provide said particles having the desired mean diameter,
• wherein the (weight of additive A +weight of compound B)/(weight of additive A +weight of compound B +weight of material P) ratio by weight R1 ranges from 0.01 to 0.6,
• wherein the concentration by weight of additive A in the blend ranges from 1%to 50%, and
• wherein the additive A comprises a block copolymer D comprising a block of thermoplastic polymer and at least one block of polyalkylene oxide, with the provisos that:
• the block of thermoplastic polymer comprises a star or H macromolecular chain comprising at least one polyfunctional core and at least one branch or one segment of thermoplastic polymer bonded to the core, the core comprising at least three identical reactive functional groups, and
• the block or blocks of polyalkylene oxide are bonded to at least a portion of the free ends of the star or H macromolecular chain selected from the thermoplastic polymer branch or segment ends and the ends of the polyfunctional core.