Лако-красочные материалы — производство

Most of the popular coating methods are suitable for pressure-sensitive adhesives. Solvent — based adhesives are usually applied by roller coaters or occasionally by spray applicators. Water-based adhesives also use roller coaters predominantly, with nozzle feed machines the exception. Hot melts may be extruded, applied from slot orifice coaters, or calendared.

Although virtually any type of roll coater may be used, reverse roll coating is the most common. This may incorporate a doctor roll, doctor blade, or Mayer bar to meter the spread rate. With tapes, adhesive is usually applied directly to the tape, which then passes through a drying station incorporating countercurrent air, usually warm. The dried tape is then rolled and slit. With label stock, adhesive is normally applied to the release paper, dried, and then transferred to the label when the label stock is united with the release paper in a nip roll.

Adhesives for reverse roll application will typically have viscosities in the range of 1000 to 10,000 cP. While coating speeds in excess of 200m/min are possible, machine speeds are normally limited by the speed at which the film can be dried. A simple reverse roll coater is shown in Fig. 3.

For low application weights of hot-melt adhesives, slot-orifice coaters are preferred. Variation of slot width and temperature allow a wide range of viscosities and coating weights to be handled. Calendaring is used for high-viscosity adhesives and high coating weights. Extrusion is used for very high viscosity systems and permits both mixing and coating to be performed in a single operation.