|
Dow’s c3D solves calender deposit problems Recently installed on The Dow Chemical Company’s pilot coater in Midland, MI, is a new instrument the company has developed—the calender Deposit Detector by Dow (c3D). Dow says the new analytical tool, only available to customers actually at the Midland plant, is designed to help solve why some paper manufacturers encounter deposit build-up on heated calender rolls. It is particularly prevalent amongst papermakers who use high temperature, low pressure calendering for high gloss and high bulk grades. The build-up occurs when the adhesive force between the coatings and the rolls is greater than the cohesive force of the coatings or the adhesive force between coatings and paper. The paper coating becomes tacky as it is heated and begins to stick to the polished steel calender roll. Debris from the paper surface also sticks there. Operating conditions can also lead to build-up which tends to occur over an extended time, say 16 to 24 hours. The c3D instrument can detect build-up before it is visible to the eye. Because it is so sensitive, Dow says, it can tell within minutes whether or not a coating formulation will cause problems. The c3D closely tracks coating behaviour as operating conditions are adjusted permitting identification of the specific factors causing the problem. For one customer, Dow scientists identified a change in the moisture content of the base stock as the cause of problems. In another case, modifying the coating formulation improved performance; further adjustments provided even better over-all performance. Dow says that it is incorporating what it has found out about build-up by using the c3D into new latexes and plastic pigments for better high-temperature calendering performance. PI The Dow Chemical Company, www.dow.com |
|
|