Patent ID: 7416779

Claim:
A fiberboard comprising natural fiber and polylactic acid resin mixed in said natural fiber as a binder, said fiberboard (1) having a density of 0.2 g/cm 3 or more, (2) comprising an initial bending strength of 30 MPa or more, said bending strength being calculated in accordance with the following expression bending strength (MPa)=3 PL /2 Wt 2 wherein P is the maximum bending load (N) to a test piece, L is the distance between fulcrums (mm) of the test piece, W is the width of the test piece (mm), and t is the thickness of the test piece (mm), and (3) retaining 20% or more of said initial bending strength after subjecting said fiberboard to a high temperature of 50° C. and a high humidity of 95% RH for 1,200 hours, wherein the polylactic acid resin comprises a carboxyl-terminal quantity of 10 or less equivalent weight/ton and a polycarbodiimide compound which is added to the polylactic acid resin.