Assembly for adhesive-bonded paper bags/sacks has a radiation unit to deliver electromagnetic and/or near infra red waves at the paper surface to dry and/or cross link the adhesive strip

摘要

To produce an adhesive-bonded paper/cardboard product e.g. where a folded paper section cut from a web is bonded by an adhesive track to give paper bags/sacks, the web or cut section is subjected to a temporary electromagnetic field with a high power density to dry and/or cross-link the adhesive and/or a near infra red radiation especially in a wavelength of 0.8-1.5 mu m. To produce adhesive-bonded paper bags and sacks, the paper surface is irradiated for the adhesive track to be applied directly while the surface is warm. Or the adhesive track is applied to the paper surface, and the paper is irradiated at the reverse side to heat the adhesive through the paper. The radiation directed at the paper surface has a power density of /- 150 kW/m<2> and preferably /- 300 kW/m<2>. The radiation is from an emitter with a radiating temperature of /- 2500 deg K and preferably /- 2900 deg K. The adhesive is a dispersion or starch type. Heat is applied to both the paper surfaces, to be bonded together. The temperature of the paper surface(s) is measured without contact during or directly after radiation, to control the heating action to maintain a paper surface temperature of 70-130 deg C. Heat is applied by radiation over the whole paper surface. Any residual moisture vapor remaining after the heat radiation action is dispersed by a dry gas stream and especially air, during and/or directly after heating. The paper web is moved through the heat radiation zone at a speed of /-2 5 m/sec. and especially /- 50 m/sec. An Independent claim is also included for an assembly (100) to apply an adhesive to a paper web or cut paper sections, with a radiation unit (101) and a main reflector (101b) to generate electromagnetic beams with a high power density and/or in a near infra red range. A glue applicator forms an adhesive track (111) on the paper surface.