Plastics separation and recycling methods
First Claim
1. A method of separating raw mixed plastic flakes of high and low densities into heavy and light fractions comprising the steps of washing said raw mixed plastic flakes in a wash liquid and substantially separating said wash liquid from the washed flakes wherein at least one of said washing or said separating of said wash liquid steps includes the use of a liquid containing a surfactant which contacts the flakes, said separation of said wash liquid being effected such that the surfactant is retained on said mixed flakes at the end of said wash liquid separating step, placing said mixed flakes having said retained surfactanat thereon into a flotation liquid having a density intermediate to said heavy and light fractions, and facilitating disengagement of said mixed flakes from one another by maintaining in said flotation liquid a concentration of a surfactant effective to substantially reduce the surface tension of the liquid, said retained surfactant constituting at least a part of said surfactant in said flotation liquid whereby the mixed flakes separate into a light fraction which floats on said flotation liquid and a heavy fraction which does not float on said flotation liquid.
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Accused Products
Abstract
Plastics fragments including polyethylene terephthalate and polyolefins derived from comminution of containers such as beverage bottles are segregated according to specific gravity by flotation. The flotation liquid includes a surfactant to facilitate complete separation of the light and heavy plastic fractions from one another. The surfactant may be a residue of a detergent used to wash the flakes and remove contaminants therefrom. Rinsing prior to flotation separation is controlled so as to leave the desired detergent residue leading to a marked reduction in rinse water requirements.
81 Citations
23 Claims
- 1. A method of separating raw mixed plastic flakes of high and low densities into heavy and light fractions comprising the steps of washing said raw mixed plastic flakes in a wash liquid and substantially separating said wash liquid from the washed flakes wherein at least one of said washing or said separating of said wash liquid steps includes the use of a liquid containing a surfactant which contacts the flakes, said separation of said wash liquid being effected such that the surfactant is retained on said mixed flakes at the end of said wash liquid separating step, placing said mixed flakes having said retained surfactanat thereon into a flotation liquid having a density intermediate to said heavy and light fractions, and facilitating disengagement of said mixed flakes from one another by maintaining in said flotation liquid a concentration of a surfactant effective to substantially reduce the surface tension of the liquid, said retained surfactant constituting at least a part of said surfactant in said flotation liquid whereby the mixed flakes separate into a light fraction which floats on said flotation liquid and a heavy fraction which does not float on said flotation liquid.
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2. A method as claimed in claim I further comprising the step of maintaining said flotation liquid substantially free of foam.
Specification