Preparation of cellulose fibers

A method of isolating and preparing cellulose fibers of a desired length-weighted average fiber length lc(l) from cereal straw, the method comprising:

• (i) subjecting the cereal straw to a pretreatment comprising a dry mechanical treatment to remove parts of the cuticular wax from the cereal straw followed by enzymatic pretreatment using one or more protease and/or pectinase enzymes in aqueous suspension to remove remaining cuticular wax from the cereal straw, thus obtaining a solution comprising dewaxed straw material in aqueous suspension,
• (ii) solubilizing hemicellulose and lignin components of the solution in (i) by adjusting the pH and increasing the temperature of the solution to pH 9-11.5 and temperature of 65-95° C. to provide a material,
• (iii) separating the material obtained in (ii) into a solid cellulose fiber fraction and a liquid fraction comprising solubilized hemicellulose and lignin components,
• (iv) suspending the solid cellulose fiber fraction obtained in (iii) in an aqueous liquid, adjusting the temperature and pH of the aqueous liquid to a temperature of 65-95° C. and pH 9-11.5, adding a bleaching agent, and keeping the cellulose fiber fraction in suspension for 60-180 minutes (T1) to provide a bleached material,
• (v) subjecting the bleached material obtained in (iv) to a wet mechanical refining treatment to provide a bleached-refined material,
• (vi) continuing bleaching at a temperature 65-95° C. and a pH 9-11.5 for a duration of 20-90 minutes (T3) without wet mechanical treatment,
• (vii) obtaining a cellulose fiber product by separating the bleached-refined material obtained in (vi) into a bleached-refined solid cellulose fiber fraction and an aqueous bleaching liquor fraction, and
• (viii) optionally washing the bleached-refined cellulose fiber fraction in an aqueous liquid,
• wherein the length-weighted fiber length lc(l) of the cellulose fibers is >0.6 mm.