Gluing edges using hot melts
For gluing edges using hot melts, a series of values must be taken into account respect to the influence of some fundamental parameters such as:
The temperature of the tail in the tank: an elevated temperature in the tank alters the characteristics of the adhesive in the long term, making the gluing worse.
A low temperature produces a high viscosity of the glue preventing the adequate wettability of the support, with negative results in gluing.
Humidity: high humidity worsens sizing due to the vapor barrier that forms. On the other hand, low humidity always improves it.
Pressure: in the gluing of wood and derivatives, a sufficient pressure must be guaranteed that allows the formation of a continuous, homogeneous and defined thickness gluing line. An efficient sizing resistance can be obtained from a pressure of 5-10kg/ cm2
It’s important to take into account the thickness of the edges that are used to adjust the rollers properly and obtain a homogeneous pressure across the surface.
To avoid problems with the edging, it’s important that the following work instructions be followed in edges:
1. Store the hot melt adhesive in a cool, dry place, protected from sunlight.
2. The application temperature of the hot melt must be adjusted correctly. The temperature measured on the roller should be the same as that recommended in the data sheet. Bearing in mind that the indicated margin will allow adjustment in warm and cold environments.
3. Clean the hot melt application boiler regularly. Products with mineral loads tend to generate a crust that prevents the tail from being properly heated.
4. Roller pressure should be adjusted correctly. Pressure of large rollers approximately 2bar and small ones approximately 4bar for straight edges.
5. Adjust the application weight correctly. The central part of the chipboard (more porous) should be covered with adhesive.
6. The ambient temperature of the materials must be at least 18ºC. In case of lower temperatures, the open time of the adhesive can be drastically reduced and not make a good paste.
7. Avoid air currents near the hot melt application system. It can generate a paste problem, as already mentioned. In PUR applications, this point is vital.
8. The moisture in the wood should be between 8-10%. High humidity could cause poor adhesion and false bonding.
9. Avoid dust. Store the material of the edges in closed plastic containers and open them before each use.