To obtain a fire resistant roof substrate material which is light-weight and fire resistant and which can be fixed by wood screws or nails and which is excellent in strength as well by combining plywood and a calcium silicate molding with a low specific gravity and a high strength to constitute the roof substrate material.
This fire resistant roof substrate material 1 has a composite structure that a calcium silicate molding 3 having a low specific gravity and a high strength is laminated on one side face of a structural plywood 2. Water slurry including water and 1-50 pts.wt. solid of a water soluble polymer which is composed of a principal chain and side chains and an amphoteric polymer compound having 50,000-5,000,000 in the total molecular weight against 100 pts.wt. solid content of the water slurry chiefly including calcium silicate hydrate selected from xenotlite and tobermorite, is molded and dried to obtain the low specific gravity and high strength calcium molding 3 having a specific gravity of 0.05-0.3 and a bending strength of 5-60 kg/cm2. This water soluble compound is an amphoteric high-molecular compound having a viscosity of 5-1,000 cP (B type viscometer, 5% aqueous solution, 25°C).
SEGI YASUHIRO
ISHINO SEIJI
TOYO TIRE & RUBBER CO