Reinforcement fibers and/or process fibers based on plant fibers

Reinforcement fibers and/or process fibers based on plant fibers obtained by removing wood components and other undesired components from fiber-containing parts of the plant fibers, treating the plant fibers from which the wood components have been removed with an aqueous solution of at least one metal compound selected from a group consisting of metal oxides, metal hydroxides, metal carbonates, metal sulfates, metal thiosulfates, metal sulfites, metal silicates, metal phosphates and mixtures thereof, and thereafter washing and treating said fibers with an inorganic or organic binding agent;

• or neutralizing said fibers with a mineral acid after said fibers have been treated with said at least one metal compound and have not been washed, such that a product is obtained in which said at least one metal compound is distributed between said fibers in an unreacted form;
• or oxidizing said fibers from which the wood components have been removed by treating said fibers with an oxidation agent;
• or carbonizing said non-pretreated plant fibers by heating said fibers to a temperature from about 250.degree. C. to about 350.degree. C. with the controlled addition of air such that carbonization of said fibers takes place.