Edge sealing hot melt adhesive is a type of adhesive specifically used for edge sealing of artificial boards. It is a solvent-free thermoplastic adhesive. When hot melt adhesive is heated to a certain temperature, it transforms from a solid state to a molten state. When applied to the surface of artificial board substrates or edge sealing materials, it cools and becomes solid, bonding the edge sealing materials to the substrate.
1. Base material for edge sealing hot melt adhesive
(1) EVA (ethylene vinyl acetate copolymer resin) based hot melt adhesive, which can be divided into two types: with fillers and without fillers. The use of EVA as the base material is a common production technology for edge sealing hot melt adhesive, but its main limitation is poor heat resistance. The environmental temperature for using EVA hot melt adhesive to seal the edges of panel furniture should not exceed 120 ° C;
(2) POL YAMIDE (polyamide) based hot melt adhesive has excellent heat resistance and fast curing characteristics, but its main disadvantage is that it is expensive.
(3) HMPU (polyurethane) based hot melt adhesive is a high-performance type of hot melt adhesive that ensures high-quality board edge sealing. It is expensive and requires special usage methods.
2. Viscosity of edge sealing hot melt adhesive
The viscosity of edge sealing hot melt adhesive cannot directly reflect the performance of the adhesive. In general, the higher the viscosity of edge sealing hot melt adhesive, the better its initial adhesive strength, but the worse its coating performance. Low viscosity hot melt adhesive has a smaller coating amount and better wetting performance. Some hot melt adhesives with low viscosity and fast curing speed may also have high initial adhesive strength. For low-quality particleboard, it is necessary to use high viscosity hot melt adhesive for edge sealing. This is because high viscosity hot melt adhesive has poor flowability and is not as easy to enter the pores at the edges of the particleboard as low viscosity hot melt adhesive during coating, so that the hot melt adhesive can be fully applied to the edges of the board.
3. Density of edge sealing hot melt adhesive
The density of edge sealing hot melt adhesive is generally between 0.95-1.6g/cm3, and its density depends on the amount of filler (the more filler, the higher the density). Due to the requirement of a certain adhesive area for edge sealing of the board, the adhesive amount per unit length of low-density unfilled hot melt adhesive should be smaller than that of filled hot melt adhesive. Moreover, due to the better bonding performance of unfilled hot melt adhesive, achieving the same edge sealing effect, it is possible to use less unfilled hot melt adhesive than filled hot melt adhesive. To reduce the amount of glue applied, the edge banding machine must have a good glue application system.
4. Softening point and operating temperature of edge sealing hot melt adhesive
The softening point is an indicator of the heat resistance of edge sealing hot melt adhesive. The higher the softening point, the less likely the edge sealing hot melt adhesive is to melt. The softening point is also an important aspect of measuring the temperature resistance of panel furniture. In Europe, there is already a set of testing methods for the heat resistance of board edge sealing, and standards have been proposed for the heat resistance of panel furniture. France, Germany, Italy and other countries no longer produce low softening point edge sealing hot melt adhesives on a large scale, but domestic manufacturers (including Taiwanese manufacturers) still produce and provide them to the domestic market. The reason is that domestic furniture manufacturers and consumers currently do not attach enough importance to the heat resistance performance of panel furniture, especially kitchen furniture. The softening point range of EVA hot melt adhesive is generally between 90-135 ℃.
The usage temperature of hot melt adhesive refers to the temperature at which the glue is applied to the glue roller of the edge banding machine. Only at this temperature can the hot melt adhesive achieve optimal adhesive strength. There is a significant discrepancy between the temperature displayed on some edge banding machines and the actual temperature, so it is necessary to regularly calibrate the temperature of the machines. If the temperature of the edge banding machine is too high, it will cause the glue to carbonize and smoke; Too low will also cause a decrease in adhesive strength.
5. Opening time of edge sealing hot melt adhesive and feeding speed of edge sealing machine
The opening time of edge sealing hot melt adhesive refers to the period of time from the beginning of glue application to the time when the edge sealing tape is pressed onto the substrate by the edge sealing machine. The opening time varies depending on the type of glue used. The feeding speed and opening time of the edge banding machine are closely related, and both are very important in the selection and use of hot melt adhesive. The edge banding machine with fast feeding must choose hot melt adhesive with short opening time, otherwise, choose hot melt adhesive with long opening time.
For most manual edge banding machines, due to manual operation by workers, it requires a sufficiently long opening time of the hot melt adhesive used to facilitate edge banding of curved parts. Hot melt adhesive is usually applied to the edge banding tape. In order to ensure the quality of the edge banding, domestic manual edge banding machines also use double-sided adhesive coating. The temperature of the manual edge banding machine's adhesive can is generally controlled below 180 ° C (the German BRANDT manual edge banding machine can be heated to over 200 ° C), so hot melt adhesive with a temperature below 180 ° C should be used. If a thin PVC edge banding strip with a thickness of less than 0.2mm is sealed on a manual edge banding machine, the temperature of the hot melt adhesive used must be around 120 ° C.
