The trouble encountered in the processing and finishing of the adhesive tape is closely related to the viscoelasticity of the hot melt adhesive itself and the selected release paper. The following are common problems and solutions for adhesive tape buckles.
(1) when the adhesive is attached to the release paper, the hot melt adhesive can not be closely combined with the release paper. This phenomenon usually occurs in winter, and the temperature is lower in the working environment. In a normal back glue program, the temperature is very high when the pressure sensitive hot melt adhesive is coated on the ribbon. In order to prevent the ribbon from overheating and stretching, it is necessary to cool the hot melt adhesive surface with the fan blower.
However, when the temperature of the working environment is very low, the pressure-sensitive hot melt adhesive will accelerate the cooling after leaving the die. If the gel surface is still blown on the cold air, it may cause the instantaneous phase separation of the composition of the hot melt adhesive, losing the surface viscosity and reducing the bonding force between the hot melt adhesive and the paper.
To solve this problem, we can start from two aspects:
A. when the temperature is low, the fan can be opened and closed. When the temperature is too low, a hot air gun should be added to keep the heat.
B. is converted to hot melt adhesive with better cold resistance. However, we must consider whether other physical properties still meet the market demand.
(2) there are small bubbles in the hot melt adhesive film when the roller is coated with hot melt adhesive. The rollers will naturally bring air into the rubber groove and produce bubbles. After cutting through the blade, large bubbles can be broken up. However, if the consistency is too high, the small bubbles may not be crushed or released, which is transferred to the webbing to form small bubbles and uneven surface. Increasing the operating temperature can reduce the dilute viscosity of the hot melt adhesive to release some bubbles, but it may also cause the deformation of the webbing due to overheating. Providing low consistency hot melt adhesive can improve the problem, but the heat resistance of this kind of hot melt adhesive usually decreases.
In addition, the nylon ribbon and its PU setting fluid have hygroscopicity. When the weaves with high moisture content are used for back gluing, they may also release water vapor at the instant of high heat processing and produce small bubbles between the hot melt adhesive tape and the ribbon interface. The use of the glue on the Die prevents the bubbles introduced from the rubber on the roller wheel in the hot melt adhesive, but the use of a higher moisture content ribbon will still cause the bubble problem.