Abstract: Fiber boards of high strength which are highly water- and flame-resistant are disclosed, as well as a method for making such boards and an inorganic binder composition for bonding wood fibers. The boards comprise a lignin-containing fiber material, a binder derived from a binder composition comprising an alkali silicate solution, sulphur and/or an inorganic sulphur compound, and a calcium and/or magnesium compound and, optionally, fillers and/or hydrophobing agents.The fiber boards are manufactured by mixing the lignin-containing fiber material with the binder composition and optional further additives, whereupon the mix is compressed at a high pressure and at a temperature of 130.degree.-230.degree. C.

Abstract: A fibre board having improved strength, water-resistance and flame resistance comprises a lignin-containing fibre material and a binder. The binder is formed from a binder solution containing an alkali silicate solution, a sulphur component, and an metal component. The solution may also include hydro-foaming agents, fillers and other materials. The preferred binder solution includes 50-90 parts by weight alkai silicate solution, 0.5-10 parts by weight sulphur component and 10-40 parts by weight of the metal component. A method is also presented for the formation of an improved fibre board through utilization of a preferred mixture of a lignin-containing fibre material and a preferred binder solution under pressure, at a temperature of about 130.degree. to 230.degree. centigrade.