Abstract: A heat insulating paper cup having an improved seal. The cup can include a body member having an inside surface and an outside surface, and a bottom panel member having a upper surface and a bottom surface. The body member is coated (or in some instances partially coated) on its outside surface with a foamed low density polyethylene, and on its inside surface with an unfoamed modified low density polyethylene. The bottom panel member is coated on its upper surface with a foamed or an unfoamed low density polyethylene or foamed or unfoamed modified low density polyethylene. The body member and bottom panel member are oriented and joined to form a heat seal at an interface between a portion of the unfoamed modified low density polyethylene coated on the inside surface of the body member and a portion of unfoamed low density polyethylene or unfoamed modified low density polyethylene coated on the upper surface of the bottom panel member.

Abstract: Containers are conveyed through an oven on a conveyor to cause a foamable material on each container to foam and become a heat insulative layer. The containers are supported on respective holders of the conveyor, which prevent the containers from contacting one another. Preferably, the holders support the containers loosely, to enable the containers to wobble relative to the holders under the influence of oven air currents and conveyor vibration. The holders thus do not make contact with any given point on their respective containers for a time period that is sufficient to enable the holders to draw enough heat away from the container to adversely affect the foaming operation. The containers are conveyed in single file, along a serpentine path through the oven.