Extrusion coating of viscous materials, mainly materials having viscosities in the range of from about 100,000 to 800,000 centipoises at 350.degree. F. such as tacky industrial grade pressure-sensitive adhesive compositions, certain hot melt adhesive compositions and certain intermediate temperature melting thermoplastic film forming compositions, are usually carried out by operations in which the extrudate issues from a die positioned laterally above the bite or nip formed between a highly polished metal chill roll (sometimes called coating roll) bearing the substrate and a rubber or pressure roll, and falls into the nip to be air drawn to the desired film thickness and then laminated onto the substrate. Sometimes, the die has been positioned above the metal chill roll or the pressure roll but nevertheless at a location sufficiently above the roll so that the film curtain is drawn to reduce its thickness while unattached to the substrate. The extruded film curtain is widest as it leaves the die and narrows during its free fall to the substrate. This phenomenon called draw-down or neck-in is dependent on the composition type, melt temperature and distance of the die above the substrate. The neck-in is accompanied by a thickening of the outside edges of the falling curtain. This thickened edge called an edge bead can be from three to six times thicker than the coating thickness. The edge bead must be removed from the coated or laminated substrate in order to eliminate handling problems. The removal which is carried out by trimming off the edge beads represents a major economic loss since no economical way has been found to recover and reuse this material. Not only the bead material but the substrate also must be eliminated and considered a loss. Although ways have been advised to minimize the loss of materials, additional manipulations are necessary and total loss is not avoided.
Additionally, coatings of manufacturing widths (approximately 5 feet) are difficult to obtain and maintain in uniform thickness. Further, with some substrates, good anchorage of the adhesive is difficult to achieve. It is highly desirable to devise a procedure capable of producing a coated product from a highly viscous coating composition of high quality and uniformity, and with minimum economic waste.