INFLUENCE OF CLOSURE ON THE WHITE WATER DISSOLVED SOLIDS AND THE PHYSICAL-PROPERTIES OF RECYCLED LINERBOARD

The effect of closing the white water system on the physical propertie s of linerboard produced from recycled fiber under acid rosin sizing c onditions ws investigated. The closing of the system was simulated in a Formette Dynamique and with a British handshet mold. The tensile ind ex showed a slight decrease for the British mold hand-sheets as the wh ite water system closure was simulated by successive recycling of the white water. Zero-span tensile strength, ring crush, tear, and sizing were not affected significantly. Inorganic materials showed an increas e in concentration in the white water with closure and recycling. Ther efore, at high levels of closure (above about 70%), the continuous add ition of alum in this papermaking system should be limited to the leve l of aluminum ion adsorption capacity of the fiber. However, inorganic buildup cannot be avoided for sodium, calcium, chloride, and sulfate because they are not removed well with the fiber but are continuously added with the stock, starch, rosin, and alum. No steady state was rea ched for these inorganics at high closure levels. Therefor, precipitat ion may eventually occur (likely involving low-solubility elements suc h as calcium), and interference wit the physical chemistry of the pape rmaking system can be expected.