A comparison of two cellulosic thickeners in coating colors at different temperatures: flow behavior and coating performance

摘要

The water-soluble polymer (i.e. the thickener) is a vital component of a coating color and is mainly used to control the flow behavior and the water retention of the color. Variations in these properties may be reflected in the quality of the final dry coating layer. A crucial factor influencing coating color flow and dewatering is the temperature. In this study, the influence of coating color temperature on the rheological properties and on the pilot coating performance of offset-grade coating colors was evaluated. Two types of cellulosic thickener, carboxymethyl cellulose (CMC) and ethyl hydroxyethyl cellulose (EHEC), were compared at two suspension temperatures (23℃ and 43℃). In addition, the coating color formulations were varied with respect to the type of sty-rene-butadiene latex (T 10℃and 22℃) and the solids content (65 and 61 weight-%). In all colors, the amount of thickener was adjusted to give a Brookfield viscosity of 1000 mPas. Coating at 43℃ gave a higher surface roughness accompanied by a lower gloss. When the CMC was replaced by EHEC, static dewatering decreased, but the high-shear viscosity increased, as did the blade load during coating. Lower roughness and higher gloss were obtained using EHEC.