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 towards 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 the application of excess glue, increasing open time and leading to poor tackiness.
At low temperatures, there is a difficult supply of adhesive through the nozzle and insufficient application.
During the operation of the thermal station, the accumulation of coked adhesive (scale) is formed on the walls of the reservoir and hose, and in the subsequent operation, it can become detached, which leads to contamination of the filters and blockage of the nozzle. In this case, the tank, hose and nozzle must be thoroughly cleaned with a special cleaner.
Usually the best results are given by the temperature of the bonded surface 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 consumption of the hot melt and faster wear of working parts of the pump can occur.
If pressing is insufficient, no qualitative gluing will occur. This can lead to rupture of the seam or its poor integrity after a lapse of time.
With excessive pressing, deformation of the package may occur, so that the contact of the glue / surface will become unreliable, 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 the seam strength and can affect its integrity in the future.
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 happen or it will dissolve in the near future.
If the open time is too long, the glue will have time to lose its heat and will not gain sufficient strength.
Open time to a certain extent can change due to adjustments in temperature and pressure.
Quantity of adhesive
It is important that the optimum amount of hot melt adhesive is applied for quality gluing. If it is too much, this leads to problems with the open time and increased flow. The glue can also be pressed outward in the pressing section. The cutoff on the nozzle may deteriorate; this leads to forming filaments and causes contamination of the equipment: excess glue can come off and adversely affect subsequent operations on the line (for example, smearing the conveyor rollers).
Too small quantity causes the effect of rapid solidification and impairs wetting and formation of the seam of the gluing.