Adhesive testing and application examples of hot melt pressure-sensitive adhesives:
There are various methods for applying hot melt pressure-sensitive adhesives, but regardless of the method used, the adhesive must be preheated to a molten, flowing state in the glue pot. It is then applied directly to the substrate or material to be adhered using suitable application equipment such as rollers or slot-die applicators. The most common labeling devices include roller and slot-die applicators. Generally, hot melt pressure-sensitive adhesives with lower viscosity are easier to coat, and processing temperatures can be moderately reduced, making them suitable for heat-sensitive materials such as PE, PP films, and thermosensitive paper.
Many hot melt pressure-sensitive adhesives with different properties have been successfully applied in various self-adhesive tape and label markets. In the practical application market of hot melt pressure-sensitive adhesive labels, there are roughly five major product categories:
General-purpose
High initial tack
High cold resistance
High heat resistance
Repositionable (removable)
Hot melt pressure-sensitive adhesives for different purposes have different adhesive properties and are generally not interchangeable. However, regardless of the application, hot melt pressure-sensitive adhesives must have good processing performance. Typically, formulators of hot melt pressure-sensitive adhesives will choose the most appropriate raw materials to achieve the best combination of cost and physical properties based on market and customer acceptable pricing, processing characteristics, and final adhesive properties. In theory, as long as the formulation meets market requirements, it is considered an ideal formulation, with no such thing as a universal or secret formula.
Ideal hot melt pressure-sensitive adhesives for labels not only need to meet the processing requirements of coating plants and the adhesive properties for users but also need to provide good post-processing characteristics for printing plants, such as die-cutting, waste removal, and sheet cutting. To achieve proper post-processing characteristics, precise equipment is required, and the conditions between the hot melt pressure-sensitive adhesive and the release paper or film should also meet the following criteria:
(1) When the label is die-cut, the cutting blade must cleanly cut both the substrate and the hot melt pressure-sensitive adhesive layer without sticking.
(2) Regardless of the speed of waste removal, the ideal hot melt pressure-sensitive adhesive should have the right level of tack to adhere to low release force release paper or film without easily peeling off.
(3) Advanced sheet cutting equipment can accurately and quickly perform the sheet cutting and trimming of individual sheets.
