in the process for manufacturing thermoplastic polymer articles reinforced with long continuous fibers by pultrusion , including impregnating tufts of fibers with thermoplastic resin , circulating an assemblage of said impregnated tufts in a heat assembly so as to melt the resin , and then hot shaping the article in an appropriate die to give it essentially its final shape before passing it through a second cooling die , the improvement including compressing the assemblage of impregnated tufts in the heated assembly consisting essentially of a flat die having an inlet zone and an exit zone , the inlet being wide enough to allow the initial volume of the impregnated tufts to pass through and a horizontal gap adapted to be varied in thickness , and allowing the emerging assembly of impregnated tufts to be brought to the shape of a sheet of minmimium thickness before shaping , and the flat die and rigid polyvinyl chloride article prepared by the process .