Abstract: A process for forming a mineral wool, resin-bound acoustical insulating fiberboard product is described, which includes steps for mixing mineral wool fibers and powdered thermosetting binder, the introduction of the mixture into an air stream, and the directing of the entrained mixture into a mat-forming zone formed by converging upper and lower forming wires, the exhausting of air through the wires to build up layers of fiber and binder thereon and the consolidation and heating of the layers to form a fiberboard product, the amounts of air exhausted through the forming wires being adjusted so that a resin-enriched layer of predominantly fine fibers is initially deposited on the upper forming wire. A preferred embodiment is disclosed wherein an open mesh glass fabric is positioned between the lower forming wire and the layer of fibers and resins being formed thereover, said fabric acting as a carrier for the board-forming mat.

Abstract: An apparatus for forming a mineral wool fiberboard product is described which includes means for separating mineral wool fibers and means for intimately mixing said fibers with a thermosetting powdered binder, means for entraining said mixture of fibers and binder in an air stream including means for directing said air stream into a mat-forming zone formed by converging upper and lower forming wires, means for exhausting air through said forming wires whereby the fiber and binder mixture is collected as two layers on the forming wires with the two layers becoming consolidated at the nip opening formed between the converging screens, and compacting and heating means whereby the mat of fibers and resins is compacted and cured to form a mineral fiberboard product, said exhaust system behind said screens being adjustable whereby the upper and lower outer layers of fibers and resins initially formed on said screens is comprised of an enriched layer of predominantly fine fibers.