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Depolymerization of Polyesters Using Fully Substituted Amines and Polyamines and Ethylene Glycol Disclosure Number: IPCOM000248170D
Publication Date: 2016-Nov-02
Document File: 4 page(s) / 353K

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Depolymerization of Polyesters Using Fully Substituted Amines and Polyamines and Ethylene Glycol

The chemical depolymerization of polyesters to yield monomers or products that can be used for repolymerization or conversion to other materials has been of interest for some time. Poly(ethylene terephthalate) (PET) can be chemically depolymerized to yield bis(2- hydroxyethyl)terephthalate by reaction with MEG under appropriate conditions or can give dimethylterepthalate by depolymerization with methanol. Chemical depolymerization schemes and technologies have been developed and commercialized in Japan and the United States of America.

The application of acid catalyzed depolymerization technologies to certain classes of polyesters, such as furan containing polyesters, can lead to unwanted chemistry such as loss of the furan moiety by ring opening chemistries. For these sensitive materials, the recovery of the monomers with high purity requires new catalysts that are not acidic in nature. It has been shown recently for PET depolymerization processes certain amines can be used. Particularly, tertiary amines and fully substituted polyamines can be employed. These catalysts are basic in nature and the tertiary amine nature ensures catalytic activity while minimizing losses due to amide formation. These catalysts can used under pressure or at atmospheric pressure with ethylene glycol or higher glycols. Specifically, the pressure needed will be determined by the desired reaction temperature and the boiling point of the glycol and amine catalyst. Suitable catalysts for PET would be triethylene amine, tripropyl amine or higher trialkyl amines. Further, polyamines such as pentamethyl diethylenetriamine or pentaalkyl diethylene triamine or any fully substitute polyamine with two or more amine groups would be suitable. Having the alkyl groups too large or long may inhibit the activity, though, and this needs to be taken into account in deciding the identity of the catalyst. There is no restriction on having all the alkyl groups be the same or similar and mixed alkyl systems can be envisioned and utilized.

The application of pressure or use of a sealed reaction vessel will be determined by the boiling points of the glycol and amine catalyst, as mentioned above. For example, the use of triethylamine, with a boiling point of 89.5 °C would require the application of pressure or a sealed reaction vessel. However, the use of the above mentioned pentamethyl diethylenetriamine, boiling point of 198 °C, can be co-refluxed with ethylene glycol at ambient pressure to effect the desired reaction.

Production of bis(2-hydroxyethyl)furan-2,5-dicarboxylate from Poly(ethylene furan-2,5- dicarboxylate)

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10 grams of PEF was added to a 100 mL RB flask followed by 30 g of ethylene glycol and 0.1 g of pentamethyldiethylenetriamine and equipped with a magnetic stirbar and condenser. The mixture was heated at reflux for two hours and then cooled to ambien...