Coating flattened thin plastics tube - across entire width by pulling around successive spreader rolls

摘要

In coating thin plastics tube, after it has been flattened, as the flattened tube is continuously pulled forwards, a no. of parallel strips of coating matl. are applied onto one or both sides of it, and then the tube is pulled around at least two successive rolls, each revolving in the contrary direction to the movement of the tube; the pressure exerted by each of these rolls upon the flattened tube is sufficient to spread the strip-like coating matl. uniformly across the entire width. Pref., the applied strips are parallel to the longitudinal direction of the tube and are all applied uniformly. The circumferential speed of the second rolls is pref. greater than that of the first, the prefd. speeds being 0.1-0.6 and 0.3-1.7 times the speed of advance of the tube for the first and second rolls respectively. The strips are pref. applied by a no. of parallel tubes each having an open end sliding along the surface of the moving sheet. Prefd. coating matls. are solns., emulsions and dispersions. Method is useful e.g. for hot-sealing coatings or for providing a gas barrier. A uniform coating is obtd., without the thinned regions occurring at the edges, as is the case when the flattened tube is passed between a pair of rolls.