Construction pretreatment technology of flexible packaging material polyurethane laminated adhesive

Pre-treatment of flexible packaging films, aluminum foils and other substrates must be done well before coating polyurethane laminating adhesive, which is the core process to ensure the composite bonding effect and prevent quality problems such as delamination, foaming and weak bonding, which directly determines the stability of flexible packaging products.

 

The first process is cleaning and degreasing the substrate. Dust, oil stain, release agent and water vapor are easily attached to the surface of flexible packaging substrate, which will form an isolation layer and hinder the combination of polyurethane laminating adhesive and substrate. At the same time, water will react with the composition of the adhesive and destroy the structure of the adhesive layer. Before construction, special organic solvent or neutral cleaning agent can be used to wipe and clean the surface of the substrate to completely remove stains and impurities, and then hot air drying can be used to ensure that the surface of the substrate is clean and dry. The metal aluminum foil substrate also needs to clean up the oxidized impurities on the surface.

 

Secondly, surface activation treatment is carried out. The surface polarity of some plastic films is weak and the adhesion is poor, so it is difficult to make the adhesive evenly wet and spread. Conventional corona treatment is used to change the molecular structure of the substrate surface through high-voltage discharge, so as to improve the surface activity and wettability of the substrate, so that the polyurethane laminating adhesive can closely adhere to the substrate surface and greatly improve the bonding strength.

 

Finally, do a good job in environmental and substrate state control. After pretreatment, the substrate should be protected from secondary moisture and impurities, and the construction environment should be kept dry and ventilated. At the same time, check the surface state of the substrate to ensure that there are no oil stains, water stains and wrinkles, and the surface activation effect is uniform. After the state is confirmed to be qualified, the coating operation of polyurethane laminating adhesive can be carried out to ensure the quality of composite production.