Influence of pulp temperature and convective drying on wet tensile strength of towel papers with poly(amidoamine epichlorohydrin) additive

The influence of the temperature of the paper pulp and drying of towel papers containing polyamidoamine-epichlorohydrin (PAE – 3.5 mg/g ADM) on their wet tensile strength was investigated. The paper was produced from pulp containing 40% pine fibers and 60% eucalyptus bleached kraft fibers, heated to 25 °C, 40 °C, and 50 °C, after which the paper was dried with hot air in the temperature range of 190 to 330 °C. The aim of the research was to determine the influence of the temperature of the paper pulp and drying of the paper formed from it on the degree of PAE bonding with fibers and its self-crosslinking ability. The sheets obtained were tested for wet strength in both the machine direction (MD) and cross direction (CD). The results indicated that the paper drying temperature had a key influence on the increase in its wet strength, while heating the pulp before forming the sheets had a relatively minor effect. The increase in drying temperature to 330 °C allowed the wet tensile index (WTI) to be improved over 100% compared to drying at ambient temperature, with the highest strength demonstrated by samples formed from pulp heated to 50 °C and dried at 330 °C. Paper samples with PAE, tested wet for CD, showed strength at a level of 36 to 44% of the values obtained for MD. The obtained results contribute to the deepening of knowledge on the mechanism of increase in wet strength of PAE-modified towel papers, depending on the temperature conditions used during their production.