The recycling of post consumer plastics is a relatively recent phenomenon which is rapidly growing in importance due to growing popular support for recycling and the increased use of plastics in such consumer items as pop bottles and milk bottles. The support is shown in such programs as the widespread "blue box" curbside collection programs, which have been encouraged by greater popular concern for environmental issues, legislation and the increasing cost of waste disposal by land fill. The result is a rapidly growing supply of post consumer plastics for recycling.
The primary criterion for plastic recycling is the purity of the end product. Minute contamination of the recovered plastic can greatly reduce the value of the recovered plastic. Previous plastic recycling technology relies on "float-sink" technology, according to which the target plastic was separated from waste of different specific gravities by grinding the feed material and choosing a liquid of appropriate specific gravity to float off the waste and allow the target plastic to sink, or vice versa. However, this method did not produce an end product of sufficient purity. Recently, hydrocyclones, previously used in mineral separation and other industries, have been applied to plastic separation, and these devices have produced a good improvement over the old technology.
This recycling plastic containers comprising the steps of:
a) grinding said containers into flake-size plastic pieces approximately 3/8-inch or less in maximum dimension.
b) removing light materials from said plastic pieces by air classification
c) introducing said plastic pieces into a wash bin containing turbulent water at ambient temperature and cold water detergent
d) drying said plastic pieces
e) introducing said plastic pieces into a wash bin containing turbulent water at a temperature between 180 and 210 degrees F. and hot water detergent
f) dewatering said plastic pieces
g) separating said plastic pieces from other residue by hydrocylone and
h) drying said separated plastic pieces.