Fire Retardant Wood-Fiber Insulating Board

Two types of fire retardant insulating wood-fiber boards have been developed in laboratory and mill scale. Both include treatments which are incorporated in the normal wet process for manufacturing such boards with a concentration of the fire retardant to one side of the board. One type involves addition of a calcium borate mineral, colemanite, to the top fiber layer of the board. Scandinavian class II and British class 1 are achieved. The other type involves addition of a pre-condensate of melamine-dicyandiamide-phosphoric acid mixed with a commercial phosporus-nitrogen compound on the wet lap. Scandinavian class I and British class 1 are achieved. The first type, colemanite, creates no problem in normal board production or in respect to product properties. It is readily suited to full scale application. The second type has a better fire classification but is accompanied by production and product problems, e.g. mildew growth at humid exposure, and needs further development. Both board types have been exposed in ceiling application for 8 years without any reduction in fire classification.