Performance evaluation of acidic, AKD and ASA sizing of straw based writing printing paper

Wheat straw pulp has low values of brightness i.e. 78%-80% GE and pale yellow shade. In acidic sizing system with straw pulp and soap stone filler i.e. magnesium silicate, optical properties can't be enhanced to cope with market accessible imported paper that has very high values of brightness, whiteness, and opacity. By keeping in mind the potential benefits of alkaline sizing system, AKD (Alkene Ketene Dimer) & ASA (Alkenyl Succinic Anhydride) have been tried on wheat straw based writing printing paper with CaCO3 as filler. High values of brightness, whiteness, opacity and porosity 92% GE, 88% CIE, 94% and 350 mL/min respectively have been achieved in alkaline sizing system. Tendency of foam generation has remarkably reduced in alkaline system but slime formation tendency is a bit more. Similarly environmental loads are reduced due to lower values of COD & BOD. High amounts of alkaline sizing chemicals are used due to the presence of fines as compared to wood pulp. In AKD sizing, Curing time is about 24 similar to 36 h while in ASA sizing, on machine-cured product is produced. Due to better compatibility of sizing chemicals, retention aid and fixatives, higher total ash retention and brightness values are achieved in ASA paper as compared to AKD. ASA emulsion hydrolization tendency is more in hot season. In this paper, trial histories of AKD and ASA are presented. In the end, performance of the three sizing systems is evaluated.