Process for processing a material containing fibres, said material containing cellulose, microcrystalline cellulose, pulp, hemicellulose, viscose, chitin, chitosan, alginate, starch, lignin, polyvinyl alcohol, proteins or mixtures thereof, comprising the following steps: a. Providing a mixture comprising (i) at least one polymer selected from the group consisting of cellulose, alpha-cellulose, microcrystalline cellulose, pulp, hemicellulose, viscose, chitin, lignin, chitosan, alginate, starch, silk, natural silk, silk biopolymers, polyvinyl alcohol, polyvinyl acetate, polyurethanes, polyamides, proteins, polymers or copolymers based on acrylic acid and/or its ester and/or amide derivatives, methacrylic acid and/or its ester and/or amide derivatives, vinyl acetate, itaconic acid, maleic acid, fumaric acid, acryloxypropionic acid, methacryloxypropionic acid, styrene sulfonic acid, ethyl methacrylate-2-sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, phosphoethyl methacrylate, cellulose ethers and mixtures thereof, and (ii) a polar aprotic solvent, b. contacting the material to be processed with the mixture provided in step a. to obtain a mixture of the material and the mixture provided in step a, c. treating the mixture obtained in step b. so that at least part of the polymer attaches itself to the fibres of the material, characterized in that the treatment of the mixture in step c. comprises or consists of bringing the mixture into contact with a non-polar solvent. a. Providing a mixture comprising (i) at least one polymer selected from the group consisting of cellulose, alpha-cellulose, microcrystalline cellulose, pulp, hemicellulose, viscose, chitin, lignin, chitosan, alginate, starch, silk, natural silk, silk biopolymers, polyvinyl alcohol, polyvinyl acetate, polyurethanes, polyamides, proteins, polymers or copolymers based on acrylic acid and/or its ester and/or amide derivatives, methacrylic acid and/or its ester and/or amide derivatives, vinyl acetate, itaconic acid, maleic acid, fumaric acid, acryloxypropionic acid, methacryloxypropionic acid, styrene sulfonic acid, ethyl methacrylate-2-sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, phosphoethyl methacrylate, cellulose ethers and mixtures thereof, and (ii) a polar aprotic solvent, (i) at least one polymer selected from the group consisting of cellulose, alpha-cellulose, microcrystalline cellulose, pulp, hemicellulose, viscose, chitin, lignin, chitosan, alginate, starch, silk, natural silk, silk biopolymers, polyvinyl alcohol, polyvinyl acetate, polyurethanes, polyamides, proteins, polymers or copolymers based on acrylic acid and/or its ester and/or amide derivatives, methacrylic acid and/or its ester and/or amide derivatives, vinyl acetate, itaconic acid, maleic acid, fumaric acid, acryloxypropionic acid, methacryloxypropionic acid, styrene sulfonic acid, ethyl methacrylate-2-sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, phosphoethyl methacrylate, cellulose ethers and mixtures thereof, and (ii) a polar aprotic solvent, b. contacting the material to be processed with the mixture provided in step a. to obtain a mixture of the material and the mixture provided in step a, c. treating the mixture obtained in step b. so that at least part of the polymer attaches itself to the fibres of the material,