Process for recycling polyester materials
First Claim
1. A method for removing colorants from colored polyester waste wherein the method comprises the following sequential steps:
- a. depolymerizing said colored polyester by adding a glycol to said polyester at a temperature in the range of from 180°
C. to 280°
C. for a period of from one to five hours to produce a glycolyzed monomer;
b. optionally filtering specific contaminants from said glycolyzed monomer;
c. feeding said glycolyzed monomer through a bed of activated carbon to remove some colorant;
d. extracting the remaining colorant from said glycolyzed monomer by introducing said glycolyzed monomer to a stirred reactor along with an extraction solvent at a temperature that is below the temperature of the glycolyzed monomer, said extraction solvent being selected from water, methanol, or a glycol whereby the glycolyzed monomer precipitates out and the remaining colorant transfers to the extraction solvent; and
e. separating said glycolyzed monomer from the extraction solvent.
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Abstract
The present invention is a process for recycling colored polyester. More specifically, colored polyester for recycling is depolymerized by the addition of glycol to form the monomer BHET. The BHET is contacted with activated carbon to remove some colorant. The remaining colorant is extracted with water, alcohol, or glycol to produce white, purified BHET. The white, purified BHET is separated from the extraction solvent (water, alcohol, or glycol) by filtering, decanting, or centrifuging, for example. The purified BHET monomer can be polymerized to polyethylene terephthalate meeting food contact specifications, using known polymerization processes.
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Citations
13 Claims
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1. A method for removing colorants from colored polyester waste wherein the method comprises the following sequential steps:
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a. depolymerizing said colored polyester by adding a glycol to said polyester at a temperature in the range of from 180°
C. to 280°
C. for a period of from one to five hours to produce a glycolyzed monomer;b. optionally filtering specific contaminants from said glycolyzed monomer; c. feeding said glycolyzed monomer through a bed of activated carbon to remove some colorant; d. extracting the remaining colorant from said glycolyzed monomer by introducing said glycolyzed monomer to a stirred reactor along with an extraction solvent at a temperature that is below the temperature of the glycolyzed monomer, said extraction solvent being selected from water, methanol, or a glycol whereby the glycolyzed monomer precipitates out and the remaining colorant transfers to the extraction solvent; and e. separating said glycolyzed monomer from the extraction solvent. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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Specification