Coated air duct insulation sheets and the like and the method of coating such sheets

An on-line method of forming a multilayered coating on an insulation sheet, comprising:

• providing an insulation sheet, the insulation sheet having first and second major surfaces, lateral edges and end edges;
• applying a first coating layer of a first foamed or frothed coating composition directly to the first major surface of the insulation sheet with the concentration of the coating composition being applied substantially uniformly over the first major surface;
• heating an exposed major surface of the first coating layer to stabilize the first coating composition at the exposed major surface of the first coating layer so that the first coating layer remains an essentially discrete layer when a second coating layer is applied to the exposed major surface of the first coating layer and to only partially cure the first coating composition at the exposed major surface of the first coating layer so that the exposed major surface of the first coating layer remains tacky and a second coating layer applied to the exposed major surface of the first coating layer will readily bond to the first coating layer;
• applying a second coating layer of a second foamed or frothed coating composition directly to the exposed major surface of the first coating layer subsequent to heating the exposed major surface of the first coating layer with the concentration of the second coating composition being applied substantially uniformly over the exposed major surface of the first coating layer;
• and
• heating the insulation sheet and the first and second coating layers, subsequent to the application of the second coating layer, until the first and second coating layers are substantially dried and cured.