The present investigation focuses on disintegration kinetics of wet-strength tissue paper in various termo-alkaline and chemical conditions of batch low-consistency repulping process. As chlorine-free repulping aids, we applied sodium persulfate in its original state and in combination with peroxy activator (chemically activated form of sodium persulfate). Based on a first-order kinetic model, we estimated the influence of repulping conditions on the intensity of wet-strength paper defiberization process by the disintegration rate constant kd. The values of kd were found by linear least-squares curve fitting of the experimental data in the t, ln (F'/100) coordinate system, where F' is non-disintegrated or non-defibrated portion of paper, t – repulping time. The results have shown that the termo-alkaline repulping of wet-strength tissue paper (T=60 °C, pH=10.5) compared with mild conditions of repulping (T=40 °C, pH=8.5) leads to an increase of the rate constant of disintegration kd from 5.6·10-3 min-1 to 9.7·10-3 min-1. Addition of 2% persulfate at termo-alkaline repulping increases the rate constant of disintegration kd up to 14,0·10-3 min-1. Application of chemically activated persulfate under the same conditions allows to further increase the kd up to 23.4·10-3 min-1. Raising the temperature and pH of the pulp during persulfate repulping increases the disintegration rate constant kd nonlinearly. Finally, addition of persulfate along with thermo-alkaline pulp treatment lead to decline repulping time and energy by 31% and 29%. It should be noted, that more significant savings of time and energy (57% and 59% respectively) we found at the application of persulfate in a chemically activated form.

The article deals with the actual problem of managing the paper printing properties using factor analysis methods. The analysis of the stone debris method allowed us to prove the combination of data in three ways: the interaction of the ink with the paper surface, which controls the optical density of the print, the value of dot gain; structural properties of the surface, which determine the effusing ability of the paper, printing slip; features of the distribution of the ink layer, which change the parameters of the prints resolution, font resolution threshold, print contrast. The identified factors allowed to simplify the task of rational decision making. As a result of the analysis of a set of technological parameters, i.e. the composition by fiber, filling, surface treatment and mass sizing, production of paper within the improved printing properties was achieved. Changes have been made in the technology of producing uncoated printing paper under the conditions of IUE “Paper Mill” Goznak. The analysis of the quality of management was carried out on the basis of the integral method and made up 92%.

The present investigation focuses on morphological characteristics, tensile and optical properties of secondary fibers obtained in various conditions of batch low-consistency repulping process for wet-strength tissue paper with 100% of bleached softwood kraft pulp. It was found that length-weighted fiber length and fiber width values as well as fiber length and fiber width distributions remained almost unchanged regardless of the repulping time and the presence of persulfates. The shortened repulping cycle due to the use of persulfates lead to an increase in the shape factor from 83.0% to 84.1–84.4%, decrease in the number of fiber kinks from 0.84 to 0.72–0.74 and an increase in zero-span tensile strength of recycled handsheets by 10–12%. At the same time, the shortened repulping cycle resulted in increase in the coarseness of secondary fibers from 190 mg/m to 230–235 mg/m leading to a slight increase in the bulk of the paper and a decrease in its internal bond strength by an average of 8%. The use of persulfates during wet-strength tissue paper repulping improves the color of recycled handsheets and its brightness by up to 3%.