Thermoplastic article having a metallic flake appearance

Abstract

The transparent articles described herein have interspersed small particles with a metallic glint. This appearance is achieved by dispersing metal oxide-coated glass platelets within a thermoplastic matrix. It is desirable to take steps to avoid breaking the glass platelets during the process of preparing these materials.

What is claimed is:  
     
       1. A transparent article having a metallic flake appearance, which article comprises an amount of metal oxide-coated glass platelets effective to provide a metallic flake appearance, wherein said platelets are dispersed within a transparent polymer matrix. 
     
     
       2. The transparent article according to claim  1 , wherein the transparent polymer matrix further contains a dye or pigment. 
     
     
       3. The transparent article according to claim  1 , wherein the transparent polymer matrix is natural. 
     
     
       4. The transparent article according to claim  1 , wherein the transparent polymer matrix is polycarbonate with dispersed spheres of polymethyl methacrylate. 
     
     
       5. The transparent article according to claim  1 , wherein the platelets are present in an amount of 0.01 to 2 percent by weight. 
     
     
       6. The transparent article according to claim  5 , wherein the transparent polymer matrix is selected from the group consisting of polycarbonate homopolymers, polycarbonate copolymers, copolyester carbonates, polymethyl methacrylate, polyetherimides, transparent polyimides, halo olefin polymers, transparent polyamides, polyesters, transparent polycarbonate-polyester blends, polysulfones, polyether and polyphenyl sulfones, transparent acrylonitrile butadiene styrene, styrene acrylonitrile, polystyrene, cellulosics, miscible transparent polystyrene-polyphenylene oxide (PS-PPO) blends, acrylics, polycarbonate-polysiloxanes, polyetherimide-polysiloxanes, polyarylates, polyethylene terephthalate, and blends and copolymers of all of the above. 
     
     
       7. The transparent article according to claim  6 , wherein the transparent polymer matrix is selected from the group consisting of polymethyl methacrylate, polycarbonate homopolymers, polycarbonate copolymers, copolyester carbonates, polyethylene terephthalate, styrene acrylonitrile polystyrene, transparent acrylonitrile butadiene styrene and cellulosics. 
     
     
       8. The transparent article according to claim  7 , wherein the transparent polymer matrix comprises a polycarbonate homopolymer. 
     
     
       9. The transparent article according to claim  7 , wherein the transparent polymer matrix comprises copolyester carbonate. 
     
     
       10. The transparent article according to claim  7 , wherein the transparent polymer matrix consists essentially of a polycarbonate homopolymer and copolyester carbonate. 
     
     
       11. The transparent article according to claim  1 , wherein the platelets have an average particle size of greater than 30 microns. 
     
     
       12. A method for making a transparent article which comprises melt extruding a transparent polymer matrix together with an amount of metal oxide-coated glass platelets effective to provide a metallic flake appearance, thereby dispersing the metal oxide-coated glass platelets within a transparent polymer matrix. 
     
     
       13. The method according to claim  12 , wherein the transparent polymer matrix comprises a polymer selected from the group consisting of a polycarbonate homopolymer and copolyester carbonate. 
     
     
       14. The method according to claim  13 , wherein the melt extrusion is performed under conditions which avoid exposing the platelets to sufficient shear to increase in the yellowness index of the transparent article. 
     
     
       15. The method according to claim  14 , wherein the platelets are introduced into molten polymer matrix downstream in an extruder. 
     
     
       16. The method according to claim  15 , wherein a concentrate of high platelet content pellets are introduced into an extruder together with an additional matrix material which does not contain the platelets. 
     
     
       17. The method according to claim  16 , wherein the matrix of the concentrate pellets differs from the additional matrix material. 
     
     
       18. A transparent article having a metallic flake appearance, wherein said article is prepared by melt extruding a transparent polymer matrix together with an amount of metal oxide-coated glass platelets effective to provide a metallic flake appearance, thereby dispersing the metal oxide-coated glass platelets within a transparent polymer matrix.