Patent ID: 7157138

Claim:
A fiber board manufactured by bonding kenaf fibers obtained by fiber-opening kenaf with a thermosetting adhesive agent, wherein the kenaf fibers having an average length of 10 to 200 mm with an average diameter being set in a range of 10 to 300 μm are used, and a fiber mat formed by aggregating the kenaf fibers is impregnated with the thermosetting adhesive agent so that the fiber board is formed so as to have a density of 600 to 900 kg/m 3 , the thermosetting adhesive agent is a phenolic resin having an average molecular weight of 400 to 700, which contains 10 to 40% by weight of a monomer and 60 to 90% by weight of a polymer having a molecular weight of 200 to 2,000, and the pH of the thermosetting adhesive agent is set to not more than 10.