Process for recycling mixed polymer containing polyethylene terephthalate
First Claim
1. A process for recovering a polyester polymer from a mixed polymer recycle stream, while maintaining the polyester polymer in polymer form, comprising:
- contacting a mixed polymer recycle stream comprising at least 50 weight percent polyester polymer, lesser portions of other polymers, including one or more polyolefins, and impurities, with a chemical wash solvent that dissolves at least a portion of the impurities present in the mixed polymer recycle stream and substantially rejects dissolution of the polyester polymer present in the mixed polymer recycle stream, to form a chemical wash solution containing impurities dissolved in the chemical wash solvent, and a residual mixed polymer recycle stream;
separating the chemical wash solution from the residual mixed polymer recycle stream;
contacting, at an elevated temperature, the residual mixed polymer recycle stream with a selective solvent that selectively dissolves the polyester polymer and substantially rejects dissolution of any other polymer present in the mixed polymer recycle stream, to form a residual waste stream, a separate polyolefin phase, and a selective solvent solution comprising the polyester polymer dissolved in the selective solvent;
separating the selective solvent solution from the separate polyolefin phase, and from the residual waste stream; and
precipitating the polyester polymer from the selective solvent solution, to form a precipitated polyester polymer and a spent selective solvent solution; and
separating the spent selective solvent from the precipitated polyester polymer, to obtain a recovered polyester polymer product having an intrinsic viscosity of from about 0.2 dl/g to about 0.8 dl/g.
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Abstract
The invention described herein provides a process for recycling a mixed polymer recycle stream containing polyester polymers, particularly polyethylene terephthalate (PET) typically in the form of carbonated soft drink or other containers. This novel process includes the steps of: (1) contacting the mixed polymer recycle stream with a solvent which selectively dissolves the PET. (2) separating the selective solvent containing PET from the residual mixed polymer, (3) cooling the selective solvent to precipitate the PET, and (4) removing the selective solvent from the precipitated PET. It is preferable that the mixed polymer recycle stream be prepared for recycling by conventional steps, such as water washing. In a preferred embodiment, the mixed polymer recycle stream is chemically washed subsequent to water washing and prior to contact with the selective solvent. The PET recovered is preferably combined with "virgin" PET and further processed to increase its molecular weight.
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Citations
47 Claims
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1. A process for recovering a polyester polymer from a mixed polymer recycle stream, while maintaining the polyester polymer in polymer form, comprising:
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contacting a mixed polymer recycle stream comprising at least 50 weight percent polyester polymer, lesser portions of other polymers, including one or more polyolefins, and impurities, with a chemical wash solvent that dissolves at least a portion of the impurities present in the mixed polymer recycle stream and substantially rejects dissolution of the polyester polymer present in the mixed polymer recycle stream, to form a chemical wash solution containing impurities dissolved in the chemical wash solvent, and a residual mixed polymer recycle stream; separating the chemical wash solution from the residual mixed polymer recycle stream; contacting, at an elevated temperature, the residual mixed polymer recycle stream with a selective solvent that selectively dissolves the polyester polymer and substantially rejects dissolution of any other polymer present in the mixed polymer recycle stream, to form a residual waste stream, a separate polyolefin phase, and a selective solvent solution comprising the polyester polymer dissolved in the selective solvent; separating the selective solvent solution from the separate polyolefin phase, and from the residual waste stream; and precipitating the polyester polymer from the selective solvent solution, to form a precipitated polyester polymer and a spent selective solvent solution; and separating the spent selective solvent from the precipitated polyester polymer, to obtain a recovered polyester polymer product having an intrinsic viscosity of from about 0.2 dl/g to about 0.8 dl/g. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A process for recovering a polyester polymer from a mixed polymer recycle stream, while maintaining the polyester polymer in polymer form, comprising:
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contacting a mixed polymer recycle stream comprising at least 65 weight percent polyester polymer, lesser portions of other polymers, including one or more polyolefins, and impurities, with a chemical wash solvent selected from the group consisting of methyl ethyl ketone, tetrahydrofuran, and mixtures thereof, to form a chemical wash solution containing impurities dissolved in the chemical wash solvent, and a residual mixed polymer recycle stream; separating the chemical wash solution from the residual mixed polymer recycle stream; contacting, at an elevated temperature, the residual mixed polymer recycle stream with a selective solvent selected from the group consisting of dimethyl terephthalate, dimethyl phthalate, dimethyl isophthalate, dimethyl naphthalate, ethylene carbonate, propylene carbonate, and mixtures thereof, to form a residual waste stream, a separate polyolefin phase, and a selective solvent solution comprising the polyester polymer dissolved in the selective solvent; separating the selective solvent solution from the separate polyolefin phase, and from the residual waste stream; and precipitating the polyester polymer from the selective solvent solution, to form a precipitated polyester polymer and a spent selective solvent solution; separating the spent selective solvent from the precipitated polyester polymer, to obtain a recovered polyester polymer product having an intrinsic viscosity of from about 0.2 dl/g to about 0.8 dl/g; and combining the recovered polyester polymer, in a melt processing operation, with a virgin polyester polymer stream having a comparable molecular weight to produce a recycle-content polyester polymer product containing from about 15 weight percent to about 55 weight percent of the polyester polymer recovered from the mixed polymer recycle stream. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21, 22, 23)
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24. A process for recovering a polyester polymer from a mixed polymer recycle stream, while maintaining the polyester polymer in polymer form, comprising:
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contacting, at a first elevated temperature, a mixed polymer recycle stream comprising at least 50 weight percent polyester polymer, lesser portions of other polymers, including one or more polyolefins, and impurities, with a chemical wash solvent that dissolves any polyolefins present, and at least a portion of the impurities present in the mixed polymer recycle stream, and substantially rejects dissolution of the polyester polymer present in the mixed polymer recycle stream, to form a residual polymer recycle stream and a chemical wash solution comprising polyolefin polymer and impurities dissolved in the chemical wash solvent; separating the chemical wash solution from the residual polymer recycle stream; contacting, at a second elevated temperature, the residual polymer recycle stream with a selective solvent that selectively dissolves the polyester polymer and substantially rejects dissolution of other polymers present in the mixed polymer recycle stream, to form a selective solvent solution containing the polyester polymer dissolved in the selective solvent, and a residual waste stream; separating the selective solvent solution from the residual waste stream; precipitating the polyester polymer from the selective solvent solution, to form a precipitated polyester polymer and a spent selective solvent solution; and separating the spent selective solvent from the precipitated polyester polymer, to obtain a recovered polyester polymer product having an intrinsic viscosity of from about 0.2 dl/g to about 0.8 dl/g. - View Dependent Claims (25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35)
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36. A process for recovering a polyester polymer from a mixed polymer recycle stream, while maintaining the polyester polymer in polymer form, comprising:
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contacting, at a first elevated temperature, a mixed polymer recycle stream comprising at least 50 weight percent polyester polymer, lesser portions of other polymers, including one or more polyolefins, and impurities, with a chemical wash solvent selected from the group consisting of cyclohexanone, alkyl-substituted cyclohexanones, diol diacetates, dibutyl phthalate, and mixtures thereof, to form a residual polymer recycle stream and a chemical wash solution comprising polyolefin polymer and impurities dissolved in the chemical wash solvent; separating the chemical wash solution from the residual polymer recycle stream; contacting, at a second elevated temperature, the residual polymer recycle stream with a selective solvent selected from the group consisting of dialkyl terephthalates, dimethyl phthalate, dialkyl isophthalates, dialkyl naphthalates, alkylene carbonates, and mixtures thereof, to form a selective solvent solution containing the polyester polymer dissolved in the selective solvent, and a residual waste stream; separating the selective solvent solution from the residual waste stream; precipitating the polyester polymer from the selective solvent solution, to form a precipitated polyester polymer and a spent selective solvent solution; separating the spent selective solvent from the precipitated polyester polymer, to obtain a recovered polyester polymer product having an intrinsic viscosity of from about 0.2 dl/g to about 0.8 dl/g; and combining the recovered polyester polymer, in a melt processing operation, with a virgin polyester polymer stream having a comparable molecular weight to produce a recycle-content polyester polymer product containing from about 15 weight percent to about 55 weight percent of the polyester polymer recovered from the mixed polymer recycle stream. - View Dependent Claims (37, 38, 39, 40, 41, 42, 43, 44, 45, 46)
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47. A process for recovering a polyester polymer from a mixed polymer recycle stream, while maintaining the polyester polymer in polymer form, comprising:
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contacting, at an elevated temperature, a mixed polymer recycle stream comprising at least 50 weight percent polyester polymer, lesser portions of other polymers, including one or more polyolefins, and impurities, with a selective solvent that selectively dissolves the polyester polymer and substantially rejects dissolution of the other polymers and impurities present in the mixed polymer recycle stream, to form a residual waste stream, a separate polyolefin phase, and a selective solvent solution comprising the polyester polymer dissolved in the selective solvent; separating the selective solvent solution from the separate polyolefin phase, and from the residual waste stream; precipitating the polyester polymer from the selective solvent solution, to form a precipitated polyester polymer and a spent selective solvent solution; separating the spent selective solvent and the precipitated polyester polymer, to obtain a recovered polyester polymer product having an intrinsic viscosity of from about 0.2 dl/g to about 0.6 dl/g; and combining, in a melt processing operation, the recovered polyester polymer product with a virgin polyester polymer product having a comparable intrinsic viscosity, to produce a recycle-content polyester polymer product containing at least 15 weight percent of the polyester polymer recovered from the mixed polymer recycle stream.
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Specification