Removal of color from thermoplastics
Process of decolorizing dyed thermoplastics are provided that includes intermixing a dyed thermoplastic with a decolorization agent solution at a temperature that maintains the crystalline structure of the thermoplastic. The processes for the first time are capable of removing substantial portions of dye from the thermoplastic providing a material that is suitable for recycling processes and use in subsequent recycled articles.
1. A process for forming a decolorized thermoplastic material comprising:
mixing a colored thermoplastic material in solid form with a decolorization agent solution comprising water, diethylene glycol, and 2-butoxyethanol;
said thermoplastic material penetrated with one or more dyes providing color to said thermoplastic material;
heating said colored thermoplastic material to a decolorization temperature that maintains the crystalline structure of said thermoplastic material, said step of heating for a decolorization time subsequent to or simultaneous with said step of mixing; and
decolorizing said thermoplastic material by said mixing step and by said heating step, thereby forming a decolorized thermoplastic material.
2. The process of claim 1 further comprising the step of irradiating said thermoplastic material subsequent to or simultaneous with said step of mixing.
3. The process of claim 1 wherein said decolorization agent solution is substantially free of a dye prior to said step of mixing.
4. The process of claim 1 wherein said thermoplastic material is polyethylene terephthalate.
5. The process of claim 1 wherein said step of heating is by immersing said thermoplastic material in said decolorization agent solution, said decolorization agent solution preheated to said decolorization temperature.
6. The process of claim 1 wherein said decolorization temperature is less than 100 degrees Celsius.
7. The process of claim 1 wherein said decolorization temperature is between 81 and 91 degrees Celsius.
8. The process of claim 1 wherein said dye penetrates said thermoplastic material to less than 1 millimeter prior to said step of mixing.
9. The process of claim 1 wherein said decolorized thermoplastic is clear.
10. The process of claim 1 wherein said decolorized thermoplastic is colorless.
11. The process of claim 1 wherein said dye is a thermolabile dye.
12. The process of claim 1 wherein said dye is an unstable dye.
13. The process of claim 1 wherein said dye is an azo or quinone dye.
14. The process of claim 1 wherein said dye is Disperse Red 1.