Continuous production of transparent polyester using waste

C - Chemistry – Metallurgy – 08 – J

Patent

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Details

C08J 11/04 (2006.01) C08L 67/00 (2006.01)

Patent

CA 2464646

The present invention concerns a process for making polyester containing up to 50 percent by weight transparent recycled waste polyester by a novel equilibrium depolymerization process. The equilibrium depolymerization process of the present invention for making polyester containing transparent waste polyester comprises the steps of: 1) continuously providing a stream containing oligomers having a DP of at least about 1.5; 2) continuously feeding transparent polyester waste to an extruder; 3) continuously melting in said extruder said waste polyester; 4) continuously extruding said molten polyester into said stream containing oligomers; and 5) continuously completing the esterification creating a prepolymer mixture; and 6) continuously polymerizing said prepolymer mixture thereby producing polyester containing waste transparent polyester suitable for food grade applications. The present invention meets or exceeds the Food and Drug Administration (FDA) requirements for food contact with polyester and is thus useful in food contact applications, for example beverage containers and polyester film wrap.

L'invention concerne un procédé relatif à la production de polyester contenant jusqu'à 50 %, en poids, de déchets recyclés de polyester transparent. On utilise à cet effet un procédé de dépolymérisation à l'équilibre. Ledit procédé, qui permet d'élaborer ce polyester à partir de déchets recyclés de polyester transparent, comprend les étapes suivantes: 1) fourniture en continu d'un flux qui contient des oligomères à degré de polymérisation au moins égal à environ 1,5; 2) injection en continu de déchets de polyester transparent dans une extrudeuse; 3) fusion en continu des déchets considérés dans l'extrudeuse; 4) extrusion en continu du polyester fondu donnant un flux qui contient des oligomères; 5) estérification en continu visant à établir un mélange de prépolymère; et 6) polymérisation en continu de ce mélange donnant un polyester qui contient des déchets recyclés de polyester transparent, approprié aux applications de catégorie alimentaire. Pour les besoins de l'invention, les normes du Secrétariat américain aux produits alimentaires et pharmaceutiques (Food and Drug Administration, FDA) sont atteintes, voire confortablement respectées, s'agissant du contact entre les produits alimentaires et le polyester. L'invention se prête donc aux applications qui font intervenir ce type de contact, par exemple dans le cas des contenants pour boissons et des emballages sous film en polyester.

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