Abstract: This disclosure is directed to a method for controlling the preheating zone of a tunnel kiln which includes firing and cooling zones. The method comprises forcedly blowing air from the entire ceiling portion of the preheating zone in the downward direction to diffuse hot combustion gas present in the upper portion and to reducing a difference in temperature between the upper and lower portions of the preheating zone. Air may be blown into the preheating zone at a flow rate determined from the quantity of the combustion gas within the preheating zone.

Abstract: According to the process for producing a foam sheet having an embossed pattern of the present invention, a coating containing an aliphatic ketone type solvent as its main ingredient and being incapable by itself of substantially inhibiting decomposition of a blowing agent comprising azodicarbonamide as its main ingredient is printed in the form of a pattern on selected portions of the surface of a foamable polyvinyl chloride resin sheet material containing a specific amine or amines and the blowing agent, and the foamable sheet material subsequently is heated to foam it.