Determining the Dynamic Water Retention Contribution of Various Cobinders and Thickeners, 1995 Coating Conference Proceedings

Pekka Salminen

Dow Europe S .A.

John Roper, Mark Pollock & Yohannes Chonde - Dow Chemical Company

A study was made of the static and dynamic water retention properties of various natural and synthetic cobinders or thickeners used in paper coatings. The dynamic water retention was measured on a pilot coater using a modification of the coating scrape-off technique to determine the thickness of the immobilized coating layer at various positions after the blade. The scraping results showed that the dynamic water retention during coating application (i.e. in the flooded nip and under the blade) was similar for the studied systems even though these systems exhibited large differences in the static water retention values measured in the lab. This lack of agreement between the static and dynamic water retention data was attributed to the impact of shear on the wet coating structure during coating application. After the blade, during the time of coating consolidations prior to drying, the choice of cobinder or thickener did affect the rate of dewatering with the results having better agreement with the static dewatering data.