In paper coating, a layer of pigment, adhesive and other supplementary materials is applied to the surface of paper. Coating provides whiteness, brightness, gloss and opacity to the paper as well as a smoother and more uniform surface. Pigment is the primary material for coating paper. The most commonly used pigments are clay, calcium carbonate, titanium dioxide and talc.

In paper coating operation, starch is used as an adhesive or binder to bind the pigment particles to each other and to the paper. The same starches used for surface sizing can be used as coating binder too. However, coating starches need to have lower viscosities than starch used in other segments in the paper industry. This is because there is a need for the presence of high amount of starch in coating formula to provide strong binding for the pigment and at the same time the coating should still be leveled and applied as a film on the paper surface. As previously mentioned in surface sizing section, the negative charge of oxidized starch could contribute to the loss of pigment filler if the finished paper is re-pulped; thus, the popularity of oxidized starch as a coating binder has been declined. Hydroxyethylated starch is considered one of the best materials for use as coating binders due to its excellent film forming properties and strong resistance to retro-gradation. We carry several grades of Hydroxyethylated Starch (HES) specifically for the paper coating applications.

If you are looking for specific grade of modified Paper Grade starch for your application, please visit our website iTradeIMEX – a Chicago based Import Export Trading company to get more information and product samples.