As an adhesive, hot melt glue is widely used in the disposable sanitary products industry. This paper briefly introduces several process parameters that affect the bonding effect of hot melt pressure sensitive adhesive.
The opening time of the machine is the time from the glue head to the composite area of hot melt glue, usually in seconds. It will affect its temperature and the wetting of the second substrate. In theory, the shorter the better. However, in practice, it is also necessary to consider the limitations of the placement position of the rubber head or the production speed. Its opening time refers to the time that it maintains its initial viscosity after coating. The opening time of the machine must be much lower than its opening time, otherwise the bonding effect will become worse if it has been cooled and cured before compounding.
The gluing temperature refers to the temperature of hot melt glue in the glue head, which will affect its wetting of the substrate. Theoretically, the higher the temperature, the better, but considering its thermal stability, the heat resistance of the substrate and other factors, such as "glue infiltration". In some applications, the temperature higher than 180 ℃ will affect the performance of the adhesive and the gluing process. In general, due to the partial heat loss before compounding, the longer opening time and the glue spraying process need to set a higher temperature. When adding glue, it should be a few times, otherwise the temperature of the glue box will fluctuate greatly.
The amount of glue applied will affect the cooling rate of hot melt glue, thus affecting the wetting of the second substrate. Theoretically, the less the amount of glue, the better, but we must consider the final bonding force requirements and opening time. Usually, if the machine is open for a long time, the amount of glue will be larger. Generally speaking, the amount of adhesive on the back of sanitary napkins or paper diapers is 25~35g/ m2, the amount of adhesive on the wing guard of sanitary napkins is 30~40g/ m2, the amount of adhesive on structural adhesive is about 3~4g/ m2, the amount of structural adhesive for bottom membrane composite is 1~2g/ m2, and the amount of rubber band adhesive is 15~25g/ m2.
Composite refers to the bonding of two substrates under pressure. The composite pressure is the pressure given by the machine during the composite bonding of two layers of substrate. The composite pressure will affect the wetting ability of hot melt glue to the substrate, making it penetrate into the two substrates respectively, determining the surface form of the bonding area. It should be allowed to enter the composite roller as soon as possible. Theoretically, the higher the composite pressure is, the better. However, the bearing capacity of the mechanical properties of the substrate, the wear of the roller and the glue penetration need to be considered.
Hot melt glue is widely used in the disposable sanitary products industry because it does not contain organic solvents, has fast coating speed, and is safe and hygienic. Understanding the process parameters that affect the bonding effect of hot melt pressure sensitive adhesive will help people further understand this material.