A process is provided for making
thermoplastic-composites from recycled thermoplastics (polyolefins) together with
phosphogypsum waste by-product from the
phosphate fertilizer wet process or, in an equally preferred embodiment with fluorogypsum waste by-product from
fluorine production wet process to produce lumber profiles. The process involves (a) admixing
phosphogypsum (
calcium sulfate) and / or fluorogypsum (
calcium fluoride) waste byproduct and / or
Flue Gas Desulfurization (FGD)
gypsum and / or crude
gypsum and / or calcined
gypsum with thermoplastics and a functionalized compound with or without
coupling agents to produce a filled
thermoplastic-composite composition, and (b) melt
processing the composition to produce a filled
thermoplastic-composite article. The articles are preferably in the form of railroad cross ties or construction articles such as common lumber profiles, panels, tiles, poles, utility poles, crossarms for utility poles, roofing tiles, pipeline skids, pilings, marine
fender-piles (including light emitting piles), bulkheads, revetments, and are useful for constructing various structures, such as oilfield board roads and equipment mats. The process avoids the accumulation of undesired
phosphogypsum / fluorogypsum “stacks” and provides
environmentally friendly useful products which require no
chemical preservatives to prevent
insect infestation or decay from the elements.
Tailings from ore
processing can also be used as a filler.