Method and plant for the manufacture of polymer particles

1. A method for the manufacture of foamed or foamable polymer particles comprising the steps of

melting a mass of recycled propellant-containing foamable polymer particles;

removing propellant from the melted mass;

adding a metered amount of additive to the melted mass to form an additive-containing recycled polymer melt;

forming a polymer melt;

adding a metered amount of propellant to said polymer melt to form a propellant-containing polymer melt;

mixing the additive-containing recycled polymer melt and the propellant-containing polymer melt to obtain a homogeneous polymer melt with a homogeneous distribution of propellant and additive;

thereafter cooling the homogeneous polymer melt; and

granulating the cooled homogeneous polymer melt into a plurality of polymer particles.

2. A method as set forth in claim 1 wherein the additive is added to the melted mass of recycled propellant-containing polymer particles after removal of propellant therefrom in one of a liquid form, a solid form and a master batch form.

3. A method as set forth in claim 1 wherein said step of granulating the cooled homogeneous polymer melt occurs under water.

4. A method as set forth in claim 3 wherein said step of granulating the cooled homogeneous polymer melt produces predominantly spherical or ellipsoid particles.

5. A method as set forth in claim 4 wherein the spherical or ellipsoid particles comprise a cutting edge.

6. A method as set forth in claim 4 further comprising the step of thermally treating the produced particles for improving the roundness of the particles.

7. A method as set forth in claim 1 wherein the proportion of recycled polymer melt in the homogeneous polymer melt is between 0.5% and 100%.

8. A method as set forth in claim 1 wherein the additive includes at least one of a flame protection agent, a lubricant, a nucleating agent, a softener, a UV protection agent, an insecticide, a pigment, graphite and/or carbon black particles, metal particles, a master batch and a mixture thereof.

9. A polymer particle made in accordance with the method of claim 1 characterized in having a cutting edge.

10. A method for the manufacture of foamed or foamable polymer particles comprising the steps of

melting a mass of recycled propellant-containing polymer particles in a first step in an extruder;

removing propellant from the melted mass of said first step in a second subsequent step;

adding a metered amount of additive in a third step subsequent to said second step to the melted mass to form an additive-containing recycled polymer melt;

melting polymer particles in a melting apparatus to form a polymer melt in a fourth step occurring in parallel to said first step;

adding a metered amount of propellant in a fifth step subsequent to said fourth step to said polymer melt to form a propellant-containing polymer melt;

mixing the additive-containing recycled polymer melt and the propellant-containing polymer melt in a sixth step subsequent to said fifth step to obtain a homogeneous polymer melt with a homogeneous distribution of propellant and additive;

thereafter cooling the homogeneous polymer melt; and

granulating the cooled homogeneous polymer melt into a plurality of polymer particles.

11. A method as set forth in claim 1 wherein the additive is added to the melted mass of recycled propellant-containing polymer particles after removal of propellant therefrom in one of a liquid form, a solid form and a master batch form.

12. A method as set forth in claim 10 wherein said polymer melt of said fourth step contains at least one additive.