A process and apparatus for coating a surface of an elongated strip article, e.g. aluminum sheet, with a layer of solid polymer material. The process involves heating the polymer to produce a melt having a viscosity of at least 1000 centipoise when measured according to ASTM D4449 at 1 radian per second, extruding the melt onto a moving surface of the strip article through an elongated slot in a coating head having an extended surface adjacent to the slot arranged at an angle to the moving surface to form a coating gap converging in the direction of movement, thereby forming a coating on the strip article, and pushing the coating head towards the surface of the strip article as the melt is extruded as the coating onto the surface from the slot to reduce the coating thickness to a desired range by pressing the extended surface of the coating head onto the coating as the coating is formed. The apparatus includes coating heat, provided with a heater to maintain the viscosity of the melt, and load application device for the coating head, as well as equipment for melting the polymer and supplying the melt under pressure and at the desired temperature to the coating head. The process and apparatus allows strip articles to be coated with thin (1-100 microns) coatings of polymer materials without employing liquids as solvents or the like that cause atmospheric pollution problems.
CROSS-REFERENCE TO RELATED APPLICATION
This is a division of application Ser. No. 344,562, filed Nov. 23, 1994, now abandoned which is a continuation-in-part of application Ser. No. 068,990, filed May 27, 1993.
A process and apparatus, including a separate coating head, for coating a strip article with a coating material. The process involves coating a strip article with a film of coating material by passing the strip article through a coating apparatus having at least one floating coating head provided with a coating face facing and extending laterally across a surface of the strip article to be coated. The coating head exudes a coating material and floats on the coating material as it meters the coating to a film of the desired thickness. The coating face of the coating head has a preferred coating profile between its opposite ends, and wherein distortions of the preferred coating profile during coating of said strip article are substantially prevented by modifying heat flux to or from selected parts of the coating head to compensate for distortions caused by differences of temperature within the coating head. The apparatus provides means of modifying heat flux to prevent such distortions of the coating profile. A removable coating head also includes such means of modifying the heat flux.
A method of applying a multi-layer coating to a surface of an elongated strip article (10) of variable thickness or surface height. The method involves applying at least two layers (12a, 12b,) of different coating materials in the form of solidifiable fluids directly onto the surface (10a, 47, 48) of the elongated metal strip article and reducing the layers to a desired thickness by causing the applied coating materials to encounter at least one coating surface (27) that is movable substantially perpendicularly relative to the strip article and is urged towards the strip article in opposition to hydrodynamic force generated by the coating materials on the at least one coating surface. Differences of thickness or surface height of the strip article are therefore accommodated unduly varying the coating thickness. In the method, one layer (12b) is coated on top of another (12a) in such a way that an outer coating layer is applied on an immediately underlying layer before the immediately underlying layer solidifies. The invention also relates to apparatus for carrying out the method.
