Method of producing a fiber product having a strength suitable for printing paper and packaging material

A method of producing a modified fiber product selected from printing paper and packaging material, according to which method

• cellulosic pulp is formed into a fiber suspension which consists essentially of, as the fiber component, cellulose pulp fibers,
• components modifying the properties of fibers are added to the fiber suspension and
• the fiber suspension is introduced to a paper machine and formed into a web,
• characterized in that
• alkali soluble carboxymethylcellulose, the DS of which is 0.1 to 0.4 and the polymerization degree of which is about 600–5000, is dissolved in an alkaline solution and then mixed into the fiber suspension at alkaline conditions, and
• at least 10% of the carboxymethylcellulose is bonded to the cellulose pulp fibers prior to the cellulose pulp fibers being formed into a web so that the bonded
• carboxymethylcellulose can not be washed off with water, to produce a modified fiber product having strength suitable for printing paper and packaging material.