Abstract: The present invention relates to a process for the preparation of discrete particles prepared from a cross-linkable PBT, at least one additive and/or at least one colorant, comprising the steps of mixing together the components, extruding the material, cooling and pelletizing the material, cross-linking the pellets using gamma radiation, electron beam radiation, or heating in an oven, and optionally grinding into particles with an average particle size between 1 and 1000 ?m. The present invention further relates to the use of said cross-linked PBT particles for making a polychromatic article which comprises a transparent or translucent thermoplastic material having said cross-linked PBT particles uniformly dispersed therein.

Abstract: The invention relates to a method for the production of a pigment masterbatch by extrusion, wherein a) a thermoplastic polymer in granular or powder form is metered continuously into a twin-screw extruder; b) the polymer metered in is melted in the extruder; c) a pumpable pigment press cake containing pigment, water and/or organic solvent is metered continuously into the molten polymer through an inlet port of the extruder under elevated pressure, the pressure being sufficiently high that the boiling point of the water and/or organic solvent is higher than the internal temperature of the extruder in the region of this inlet port; d) optionally a flow improver is added; e) the pigment is dispersed into the molten polymer from the press cake by the action of shear forces; f) the water and/or organic solvent are removed through at least one outlet port of the extruder, under elevated pressure, the pressure being sufficiently high that the boiling point of the water and/or organic solvent is higher than the inter