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Thermoplastic articles

Thermoplastic articles description/claims

This is a continuation of U.S. patent application Ser. No. 09/370,062, filed 24 Aug. 1999, which is a continuation-in-part of co-pending U.S. patent application Ser. No. 09/128,216, filed 3 Aug. 1998, which is a continuation-in-part of co-pending U.S. patent application Ser. No. 08/611,911, filed 6 Mar. 1996, and which is a continuation-in-part of co-pending U.S. patent application Ser. No. 08/843,823, filed 21 Apr. 1997, and which is a continuation-in-part of co-pending U.S. patent application Ser. No. 09/022,226, filed 11 Feb. 1998; this is also continuation-in-part of co-pending International Patent Application No. PCT/US98/16167, filed 3 Aug. 1998; all of these applications are incorporated herein by reference.

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1. Field of the Invention

The present invention relates to processes for manufacturing fertilizers and plastic articles, and more particularly relates to processes for manufacturing phosphorous containing fertilizers and filled plastic articles.

The present invention also relates to froth flotation processes and plastic articles, and more particularly relates to processes for producing mineral filled thermoplastic composites and articles made therefrom.

The present invention also relates to thermoplastic railroad ties and processes for making thereof, and more particularly relates to thermoplastic composite railroad ties and processes for making thereof.

The present invention also relates to protective pilings and processes for making pilings, and more particularly relates to pilings and processes for making pilings.

2. General Background of the Invention

In the fertilizer industry, materials used as sources of calcium and phosphorous are ground in mills and sifted to produce fine particles. For example, phosphate rock is ground to produce phosphate particles to be worked into the soil or for further processing with acids for the manufacture of fertilizers. A conventional process for using phosphate rock in the fertilizer industry involves a wet process wherein the phosphate rock, Ca3(PO4)2, is contacted with sulfuric acid and a byproduct of calcium sulfate is removed as phosphogypsum(CaSO4.2H2O) or hemihydrate (CaSO4.1/2H2O) with residual levels of phosphate in the byproduct. In other words, the wet process waste byproduct typically comprises amounts of calcium sulfate and smaller amounts of di-calcium phosphate. Additionally, the presence of small amounts of fluorine-containing compounds provides a byproduct that is sometimes referred to as fluorogypsum. The byproducts have had limited commercial utility, and accordingly have been at times stock piled as undesired waste product.

Consequently, there is a need and desire to provide processes which solve the problems associated with wet process solid waste byproducts. Also, there is a need and desire to provide useful articles comprising these byproducts. The utilization of two (2) wastes (“Twining”) to produce safe and useful products is referred to as “Beneficial Use” by the United States Environmental Protection Agency (U.S. EPA).

In the mineral industry, mineral ores used as sources of minerals are typically ground in mills near or at the mine site and sifted to produce fine particles which are subjected to froth flotation to produce concentrates of valuable minerals. For example, metallic sulfide ores of copper, lead, zinc, nickel and molybdenum are ground to produce particles which are subjected to froth flotation where the valuable minerals concentrate in the froth leaving an underflow product as waste. A conventional process for concentrating metallic sulfide ores by froth flotation involves (a) grinding the ore to produce particles, (b) treating the particles with a floatation reagent to render the particulates air-avid and water repellant, (c) vigorously agitating and aerating the particles in the presence of water to produce a layer of froth containing air-avid particles and (d) collecting the froth. Valuable concentrations may be either in the froth or in the underflow, but in process involving metallic sulfide ores of copper, lead, zinc, nickel and molybdenum, the valuable minerals concentrate in the froth.

Problems however have been associated with the processes. For example, after the valuable minerals have been removed by the Froth Flotation method, tailings such as calcium carbonate, silica, fluorspar, barium sulfate zinc, lead and molybdenum are stacked or stockpiled. Particularly in the case of lead and molybdenum tailings, there is increasing environmental concerns with the repeated exposure of such tailings to wind and rain resulting in runoffs into rivers, lakes and groundwater.

Consequently, there is an urgent need for safely containing tailings resulting from the Froth Flotation processes and a need to avoid lead and molybdenum contaminated runoff from tailing.

A process is provided for processing ore and for making plastic articles from the solid byproducts therefrom. The process involves (a) providing ore, (b) contacting the ore with reagent in the presence of water to produce coated metallic sulfide particulates, (c) Froth Flotation of the coated particulates, (d) separating at least a portion of the froth from the underflow to produce a flotation product and a tailing byproduct wherein the tailing byproducts typically comprising calcium carbonate, silica, fluorspar, barium sulfate, zinc and lead, (d) drying the tailing byproduct to remove water therefrom, (e) admixing the dried tailing byproduct with thermoplastic and preferably a functionalized compound to produce a filled thermoplastic composition, and (f) melt processing the thermoplastic composition to produce a filled thermoplastic article. The articles are preferably in the form of block shaped articles such as car stops, railroad ties, pilings, poles and timbers suitable for retaining walls and bulkheads. The process avoids the accumulation of undesired tailing byproduct from flotation processes.

In the railroad industry, the railroad tracks comprise metal rails supported on wooden ties. Historically, these wooden ties have exhibited limited useful lives due to their loss of properties upon extended use and extended exposure to environmental elements. The use of composite railroad ties has been disclosed in Neefe U.S. Pat. No. 5,055,350 issued Oct. 8, 1991 which discloses the making of railroad cross-ties from sand and recycled thermoplastic containers by coating the sand with an adhesive substance. The use of sand however can have various problems or disadvantages associated therewith including excessive weight, excessive abrasiveness when used in extrusion processes and when in contact with various processing equipment. Consequently, there is a need and a desire to provide composite railroad ties exhibiting certain enhanced properties.

A composite railroad tie is provided comprising a phosphogypsum filler and a thermoplastic resin. The composite exhibits desirable physical properties for railroad ties. Suitable sources for phospho-gypsum include fertilizer processes involving (a) providing phosphate rock, (b) contacting the phosphate rock with sulfuric acid in the presence of water to produce phosphoric acid and a calcium sulfate, (c) separating at least a portion of the phosphoric acid from the calcium sulfate to produce a phosphoric acid product and a calcium sulfate byproduct, (d) drying the calcium sulfate byproduct to remove water therefrom. The calcium sulfate byproduct (phospho-gypsum) is then admixed with a thermoplastic and a functionalized compound to produce a filled thermoplastic composition. The filled thermoplastic composition is then melt processed (for example injection or compression molded) to produce a filled thermoplastic composite railroad tie. The tie is a useful replacement for wood products having several physical property advantages and being suitably made from recycled plastic and waste byproduct filler.

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