Food quality polyester recycling
AssigneeWellman, Inc.
InventorsCarl S. Nichols, Tony Clifford Moore
Life of this patent
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Abstract
A method of recycling post-consumer polyester to obtain recycled polyester of sufficiently high purity to meet food packaging requirements is disclosed. The method includes cleaning comminuted pieces of post-consumer polyester to remove surface contaminants; melting the surface-cleaned post-consumer polyester pieces; extruding the post-consumer melt; blending the melt of post-consumer polyester with a melt of virgin polyester prepolymer; solidifying and pelletizing the blended melt while the virgin polyester prepolymer remains as prepolymer; and polymerizing the solid blended pellets in the solid state.
Claims26
A method of recycling post-consumer polyester to obtain recycled polyester with a residual concentration of possible food contaminants of no more than about 215 parts per billion suitable for food contact requirements, the method comprising:
- cleaning comminuted pieces of post-consumer polyester to remove surface contaminants therefrom thereby producing surface-cleaned post-consumer polyester pieces;
- melting the surface-cleaned post-consumer polyester pieces to produce a post-consumer polyester melt;
- extruding the post-consumer polyester melt to reduce the intrinsic viscosity of the post-consumer polyester melt and remove additional contaminants;
- blending the melt of post-consumer polyester with a melt of virgin polyester prepolymer that has an intrinsic viscosity similar to the intrinsic viscosity of the post-consumer polyester melt to produce a blended melt, and blending the melts in a proportion such that one of the melts makes up at least about 25 percent of the blended melt by weight;
- solidifying and pelletizing the blended melt while the virgin polyester prepolymer remains as prepolymer to produce solid blended pellets;
- and
- polymerizing the solid blended pellets in the solid state thereby forming the recycled polyester.
A method of recycling polyester to obtain a recycled polyester with a residual concentration of possible food contaminants of no more than about 215 parts per billion suitable for food contact requirements, the method comprising:
- extruding a melt of cleaned post-consumer polyester to reduce the intrinsic viscosity of the post-consumer polyester and remove additional contaminants;
- solidifying and pelletizing the post-consumer melt to produce post-consumer polyester pellets;
- blending the post-consumer polyester pellets with virgin polyester prepolymer pellets that have an intrinsic viscosity similar to the intrinsic viscosity of the post-consumer pellets to produce a blend of pellets, and blending the pellets in a proportion such that other of the post-consumer or virgin pellets makes up at least about 25 percent of the blend of pellets by weight;
- and
- polymerizing the blend of pellets in the solid state thereby forming the recycled polyester.
Dependencies are inferred from the claim text.