PERMANENCE OF PAPER 1 - PROBLEMS AND PERMANENCY OF ALUM-ROSIN SIZED PAPER SHEETS FROM WOOD PULP

Dry thermal ageing in the presence of air were applied to different al um-rosin sized wood pulp paper sheets. The change in the percentage of alum or adding sodium silicate in the sizing systems was carried out to vary the pH of the sample sheets in the range from 5.65 to 7.0. The changes in chemical composition, mechanical and optical properties, d egree of sizing, in addition to the rate of glycosidic bond cleavage a s a result of thermal ageing were measured. The results obtained show that neutral sized paper sheets have a higher optical and mechanical p ermanence compared with acidic sized papers. The polynominal models wh ich correlate the time of ageing and pH's of sizing system with the me an values of optical changes or quality number of mechanical measureme nts were also proposed.