Patent EP-2248653-A2 (EP)
Inventor: DOHE DIETER
IPC: B29C48/08
Filed: 2010-05-05
Abstract: The method for producing a surface-protective film, which has a high gloss surface on one side without defects, comprises feeding a plastic melt film (2), which is extruded by a slit nozzle (3), to a gap between a cooling roller (4) and a rotating metallic smoothing strip (5) in a melting state, cooling the plastic melt film by contacting to the cooling roller, and subjecting the plastic melt film with a pressure in a wrapping area, in which the smoothing strip acts on the cooling roller, where the pressure is generated by the strip tension of the smoothing strip. The method for producing a surface-protective film, which has a high gloss surface on one side without defects, comprises feeding a plastic melt film (2), which is extruded by a slit nozzle (3), to a gap between a cooling roller (4) and a rotating metallic smoothing strip (5) in a melting state, cooling the plastic melt film by contacting to the cooling roller, and subjecting the plastic melt film with a pressure in a wrapping area, in which the smoothing strip acts on the cooling roller, where the pressure is generated by the strip tension of the smoothing strip. A contact area of the cooling roller and/or the smoothing strip acting on the plastic melt film has a roughness of less than 1 mu m. The contact area of the cooling roller and/or the smoothing strip has a surface improved by a finish treatment or is provided with a coating improving the surface quality. Only the cooling roller or only the smoothing strip has a smooth contact surface acting on the plastic melt film for producing a high-gloss film surface. A counter surface acting on the plastic melt film is formed as rough surface to produce a matt film surface, which does not adhere on the smooth surface. The wrapping area, in which the smoothing strip acts on the cooling roller, is smaller than the cooling area, in which the plastic melt film lies on the cooling roller. The wrapping area corresponds to a wrap angle of 15-90[deg] . The surface-protective film is made of three-layered plastic melt film, which has an outer lying gloss layer made of polymer suited for the production of high gloss surface, a core layer and an outer layer opposite to the gloss layer. The outer layer has the matt film surface, and contains antiblock additive. The surface-protective film has a film thickness of 20-60 mu m, is produced by coextrusion in the compound with a release film, which is removable from the surface-protective film, and is formed in two-layer, where the outer-side layer contacts with the cooling roller or the smoothing strip and the gloss layer forms with high gloss surface. The release film has a partition layer made of a polar polymer and adjacent to the surface-protective film, a polyolefinic supporting layer, and an adhesive-mediator layer bonding the partition layer with the supporting layer, where the adhesion force between the partition layer and an adjacent polyolefinic layer of the surface-protective film is less than the adhesion force between the other layers of the coextrusion combinations. Two surface-protective films are produced by coextrusion in combination with a further partition layer disposed between the surface-protective layers and are subsequently removed from the further partition layer. The further partition layer consists of polar polymer. The surface-protective films made in combination with the partition layer have a film thickness of 20-50 mu m, and have two layers. The first surface-protective film in combination with the partition layer has a further gloss layer with high gloss surface at its outer side, which contacts with the smoothing strip or the cooling roller. The outside outer layer of the second surface-protective film contains antiblock additive. The inner-lying layer of the surface-protective film forms the gloss layer with the high gloss surface after removing the partition layer.