United States Patent: 6583217
As everyone should by now be aware, the recycling of polyethylene terephthalate, "PET", plastic, from which the ubiquitous soda pop, and other beverage, containers are made, has become a truly big national deal; with some cities even installing collection bins for items made of the plastic on their street corners.
Reclaimed PET can, in fact, be recycled back into beverage containers; but, the necessary cleaning, purification and clarification steps which are required by mixed batches of reclaimed PET consumer products make it uneconomical to do so; and, virgin material is almost always used for that purpose.
However, discarded PET still remains a valuable thermoplastic resin resource which can be profitably utilized or, more accurately, re-utilized, in less-fastidious applications.
More about all of that, including the fact that there is a lot of it, can be learned via:
Polyethylene terephthalate - Wikipedia, the free encyclopedia; and:
PET bottle recycling - Wikipedia, the free encyclopedia.
However, although PET is a tough and resilient polymer, it is also "flimsy" in the sense that it can't, in and of itself, hold up much weight without flexing and deforming. So, to be re-used in making things that require it to do more while maintaining whatever shape into which it's been molded than hold in the pressure of a carbonated beverage without splitting, it has to be "filled", or reinforced, with some sort of other material.
And, as demonstrated herein by two noted mid-western US institutions of higher learning, Coal Ash can serve as the material which enables the recycling of post-consumer PET into things that are actually strong enough to serve useful purposes.
Comment, concerning one especially important factor, follows excerpts from the initial link to:
"United States Patent 6,583,217 - Composite Material Composed of Fly Ash and Waste PET
Date: June, 2003
Inventors: Yadong Li, et. al., MI, MO and IA
Assignees: Iowa State University and The University of Missouri
Abstract: A composite material and method are described wherein melted waste, chemically unmodified PET material and fly ash particles are mixed in a vessel to disperse fly ash particles in the melted PET material. The resulting mixture then is cooled to solidify the melted PET material to form a composite material having a matrix comprising PET and dispersoids distributed in the matrix and comprising fly ash particles.
(Note the specification of "waste, chemically unmodified PET". The plastic can be recycled chemically in order to produce a more pure plastic resin, as you can learn via the above-cited articles in the Wikipedia. Such chemical recycling, however, as those articles explain, requires costly processing and is considered at this time too expensive for most practical purposes.)
Claims: A method of making a composite material, comprising: mixing melted waste, chemically unmodified PET material and fly ash particles to distribute the fly ash particles in said melted PET material, and solidifying the melted PET material with the fly ash particles therein to provide a composite material having a matrix comprising PET and fly ash particles distributed throughout said matrix.
The method ... wherein solid waste, post-consumer, chemically unmodified PET material and said fly ash particles are mixed together to form a mixture and then the mixture is heated in to a temperature to melt said PET material.
The method ... wherein said solid, waste, post-consumer PET material comprises beverage bottles ... .
The method ... wherein said fly ash particles comprise Class C fly ash (and/or) Class F fly ash.
The method ... wherein said mixture comprises about 50 weight % to about 70 weight % of said fly ash particles.
The method ... including shaping the melted PET material with fly ash particles therein and solidifying said melted PET material.
The material ... wherein (the) matrix comprises chemically unmodified PET material.
The material ... wherein said fly ash particles comprise Class C fly ash (and/or) Class F fly ash (and) wherein said material comprises about 50 weight % to about 70 weight % of said fly ash particles.
A molded body comprising the composite material (and/or a) coating on a substrate wherein said coating comprises the composite material ... .
Background and Field: The present invention is related to composite materials and methods for their manufacture using recycled, post-consumer waste polyethylene terephthalate and fly ash.
Recognizing the environmental benefits, the production and use of waste materials such as fly ash and plastics has been strongly favored by environmental agencies. High-lime fly ash (ASTM Class C fly ash) is a by-product of coal combustion in electric-generating stations that burn low sulfur sub-bituminous and lignite coals. Relatively low lime (ASTM Class F fly ash) is a by-product of coal combustion in electric-generating stations that burn high sulfur anthracite and/or bituminous coals. Millions of tons of fly ash are generated in the United States each year. Currently, the greatest volumes of cementitious (high lime) fly ash are used in engineering applications such as concrete products, roadbase materials, and structural fill materials. The remaining unused fly ash is usually pumped to sluice ponds or transported to landfills as waste, constituting long-term waste management problems.
Waste PET plastic is neither environmentally biodegradable nor compostable, which creates disposal problems. Recycling has emerged as the most practical method to deal with this problem, especially with products such as PET beverage bottles. Currently, a large waste stream is available for recycling applications.
An object of the invention is to provide a composite material from fly ash and recycled, post-consumer waste, (i.e.,) chemically unmodified polyethylene terephthalate (PET).
In addition to environmental incentives for utilization of waste materials, favorable mechanical properties such as low density, minimal water absorption and high compressive strength create several potential uses for the composite material.
The fly ash influences cooling rates and crystallinity of the PET binder matrix during cooling, which allows for an influence of mechanical properties through manufacturing (and) has been found to be economical as filler in the composite material reducing potential manufacturing costs.
The mixture of fly ash and melted PET material can be conventionally molded, extruded or otherwise formed to shaped articles of manufacture, such as building materials including bricks, blocks, and the like, light-weight aggregate for concrete, or may be applied to a substrate as a protective acid resistant coating."
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Note that such Fly Ash-filled PET is so resistant to chemical attack and, almost obviously, the flow of fluid through it, that, the remnants of any chemicals which might be clinging to the largely unmodified and untreated particles of Fly Ash bound in the PET plastic, such as pollutant scrubbing residues, will stay, virtually forever, right where they are; and be, in essence, forever "sequestered".
That, we assert, and as we might later document, would have some significance relative to recent developments concerning MACT issues at the US EPA, and consequent developments relative to the disposition of potential pollutants arising from the combustion of Coal for the generation of genuinely economical and affordable electric power.
But, herein, it's seen that Coal Ash enables the productive and profitable recycling of an ubiquitous waste material that resists biodegradation and, if improperly disposed of, would accumulate in, and increasingly befoul, our natural environment well nigh on into eternity.
Thus, by properly utilizing the solid byproduct Ash arising from our essential use of Coal in the generation of affordable and abundant electricity, we can profitably reclaim and recycle a pernicious environmental contaminant, i.e., post-consumer PET plastic as it's utilized in one form or another, in the manufacture of a reinforced, stronger plastic composite that is needed and can be utilized in a large number of high-strength and/or chemical-resistant, high-performance and value-added, applications.
