MULTIPLE RECYCLING IN PILOT-PLANT SCALE

With increasing waste paper utilization rates in gastric papers, recyc ling loops become closer and fibres will be more often recycled. The q uestion arises, to what extent optical, strength and printability prop erties of paper made of recycled fibres will be due to the increased f ibre age. Former investigations focused on laboratory scale and single processes such as deinking or drying. This paper presents results of trials on a pilot plant scale based on six recycling loops comprising sheet formation, drying, calendering, printing and deinking. The lurni sh of the model paper consists of an ash content of 12% and 50 percent bleached kraft ans stone groundwood each. The strength properties wer e impaired insignificantly, although the same fibre material was multi ply reused. Deteriorating optical properties due to repeated printing become evident, taking into account that only a one-stage flotation bu t no dispersion and post flotation have been applied. The runnability and the printability of the paper of all six generations were acceptab le under the given boundary conditions. With this knowledge future dev elopments with reference to fibre age distribution of pulp furnishes a nd quality of newsprint are forecast.