Microsphere comprising a polymer core, a shell and an absorber
The present invention relates to Microsphere comprising a core and a shell, in which the core comprises a polymer and at least two laser light absorber. The particle size of the microsphere is for example between 50 nm and 50 micron and preferably between 100 nm and 10 micron. The core comprises a thermoplastic polymer, the shell comprises a compatibilizer. The laser light absorbers are chosen from oxides, hydroxides, sulphides, sulphates and phosphates of metals such as copper, bismuth, tin, aluminum, zinc, silver, titanium, antimony, manganese, iron, nickel, barium, gallium, germanium, arsenic and chromium and combinations of two or more of these metals, laser light absorbing (in)organic dyes or metaloxide coated flakes. The invention further relates to the use of the microsphere as a laser marking additive and to a process for the production of the microsphere by reactive extrusion.
1. A microsphere, comprising a core and a shell, in which the core comprises a polymer, at least two laser light absorbers each, independently, chosen from antimony trioxide, tin dioxide, barium titanate, titanium dioxide, aluminum oxide, copper-hydroxy-phosphate, copper-ortho-phosphate, copper-hydroxide, antimony-tin oxide and bismuthtrioxide, and in which the shell comprises a compatibilizer.
2. A microsphere according to claim 1 , which has a particle size of between 50 nm and 50 micron.
3. A microsphere according to claim 1 , which has a particle size of between 100 nm and 10 micron.
4. A microsphere according to claim 1 , wherein the core comprises a thermoplastic polymer.
5. A microsphere according to claim 1 , wherein the at least two laser light absorbers are antimony-trioxide and antimony-tin oxide.
6. A microsphere according to claim 1 , wherein the thermoplastic polymer is a polyolefine, polyester, polyamide, polysulphone, polycarbonate, polyhydroxide, polyurethane, PVC or styrenic polymer.
7. A microsphere according to claim 1 , wherein the compatibilizer is a grafted thermoplastic polymer.
8. A microsphere according to claim 7 , wherein the grafted thermoplastic polymer is maleic anhydride grafted polyethylene or maleic anhydride grafted polypropylene.
9. A laser marking additive, comprising a microsphere according to claim 1 and one or more carriers suitable for a laser marking additive.
10. A process for preparing a microsphere according to claim 1 , comprising preparing said microsphere by reactive extrusion.
11. A laser writable composition, comprising a matrix polymer and a microsphere according to claim 1 .
12. A method for laser marking a polymer, comprising laser marking said polymer to which a microsphere according to claim 1 has been added.
13. A method for preparing a laser markable polymer, comprising adding a microsphere according to claim 1 to said polymer.