The effect of poly acrylic acid, sodium salt grafted to poly ethylene oxide complex on the physical and optical properties of old newsprint paper deinked pulp

Considering the problems initiated by sodium silicate on reducing the life expectancy of processing equipments and paper strength، recycling of old newspaper using Poly (acrylic acid)، Sodium Salt Grafted to Poly (ethylene oxide) complex were investigated. The organic complex was used at 0. 3، 0. 5، 0. 7، 1، 2 and 3% levels (based on dry weight of waste paper) in deinking. The effect of various charges of the organic complex on the physical and optical properties of deinked pulp was studied and compared with the control (ONP deinked using 0. 5% sodium silicate). The results of physical properties measurements showed that the lowest paper caliper (143. 07 µm) and the highest density (0. 43 g/cm3) were obtained by increasing the complex charge up to 2%. Also، the highest and lowest freeness was observed applying 3% (426. 66 mL CFS) and 2% (350 mL CSF) organic complex respectively. These values were less than the freeness of the control sample. The results of optical properties analysis indicated that the brightness increased to 48. 01% ISO and the yellowness was reduced to 6. 23 % ISO by as the dosage of organic complex was increased up to 1%. The opacity of paper decreased as the organic complex charge increased. In general، the paper with higher density and brightness، lower yellowness and suitable opacity could be produced using 0. 7- 2% Poly Acrylic Acid-Sodium Salt grafted to Polyethylene Oxide complex in deinking of old newspaper.