Method for producing a fibrous material for the manufacturing of preformed parts, in which a binder is added to the fibrous material and it is pressed into a preformed part upon application of heat, characterised in that a portion of particles of plastics and/or fibers from plastics is admixed to a particle or fiber mass of a first group of particles or fibers, the particle size of said particles from plastics and/or fibers from plastics approximately corresponding to the particle size of the particles or fibers of the first group, wherein the particles from plastics and/or fibers from plastics are obtained by crushing and/or defibrating agglomerates of pure or mixed plastics in a disc refiner, and that if necessary water is fed into the disc refiner during the crushing process.