Features Of Work With Hot Melt Equipment
Peculiarities of Work with Hot-Melt Equipment
If the temperature of the tank is too high, the hot melt adhesive will oxidize and burn, changing its adhesive properties and causing deterioration. At low temperatures, the viscosity of the hot melt adhesive will be too high, which can lead to thread formation, poor flow and mechanical failure of the pump.
Hose and nozzle
If the temperature is too high, this can lead to excess glue application, increasing open time and leading to poor tackiness.
At low temperatures, it is a difficult to supply the adhesive through the nozzle, causing insufficient application.
During the thermal station operation, the accumulation of coked adhesive (scale) forms on the walls of the reservoir and hose, and in subsequent operation it can become detached, which leads to contamination of the filters and nozzle blockage. In this case, the tank, hose and nozzle must be thoroughly cleaned with a special cleaner.
Usually the best results are achieved when the temperature of the bonded surface is above 15 ° C.
When the hot melt comes in contact with a cold surface, its temperature drops rapidly, resulting in a drastic change in viscosity and subsequent wetting difficulties; this can lead to poor gluing.
If the pressure is too low, the glue flow will be severely limited, which may cause insufficient glue application.
At high pressures, an increase in hot melt consumption and faster wear of the pump’s working parts can occur.
If pressing is insufficient, no qualitative gluing will occur. This can lead to seam rupture or poor seam integrity after a period of time.
With excessive pressing, deformation of the package may occur, so that the contact of the glue and surface becomes insufficient, and the joint may break when hardening. This can be especially problematic when the contents of the package are not uniform in shape or the box is not full.
Many modern packaging materials have a coating that has a number of barrier properties to prevent moisture from getting inside or drying out the contents.
Such coatings have low surface energy and can create problems for wetting the substrate with glue.
This leads to weakening of the seam strength and can affect its future integrity.
It is very important that the hot-melt corresponds to the open time of the gluing operation.
If the open time is too short, the surface will not soak, and gluing will not occur or it will dissolve soon after application.
If the open time is too long, the glue will have time to lose its heat and will not gain sufficient adhesion strength.
Open time can change due to adjustments in temperature and pressure, to a certain extent.
Quantity of adhesive
It is important that the optimum amount of hot melt adhesive is applied for quality gluing. If there is too much, it leads to problems with open time and increased flow. The glue can also be pressed outward in the pressing section. The nozzle cut-off may deteriorate; this leads to filament formation and causes equipment contamination: excess glue can detach and adversely affect subsequent line operations (for example, smearing the conveyor rollers).
Quantities that are too small causes rapid solidification and impairs wetting and seam formation during glue application.