Effect of Water Retention of Coating on Sheet Properties Part III

Okomori Koji, Morii Hirokazu, Fujiwara Hideki

doi:10.2524/jtappij.54.977

Water retention of a coating color on base paper influences final properties of the coated paper and the blade coating operation. However, there is not any standard method to evaluate water retention of a coating color even though several have been suggested. We separated “Water Retention” into static water retention and dynamic water retention. Coating runnability was evaluated by the two kinds of water retention. Water loss rate at short dwell time influenced coating runnability under a blade. Binder in a coating color also penetrated into base paper with water when the coating color was applied. We measured water loss rate of actual coatings and dilute latex emulsions to evaluate a trend of binder penetration. Binder went through a membrane filter and penetrates into filter papers when water loss ratio was measured under pressure. This binder penetration was measured by ultraviolet absorption in refection. We suggested two new concepts “Total Latex Loss” and “Penetrating Latex Loss”, both calculated from these signals and the depth of latex penetration. Binder penetration, high shear rate viscosity and water loss rate should be combined well to have a good coating runnability and to produce high quality papers.<BR>In this study, the effects of blade response and binder penetration on the latex concentration of coated paper surfaces were investigated. The blade response depended on water retention and high shear rate viscosity. The binder penetration depends on water loss ratio, total latex loss, and penetrating latex loss. Our results showed that latex concentration of coated paper surface depended on blade response and the type of binder penetration.

Effect of Water Retention of Coating on Sheet Properties Part III

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