Can the unused flexible packaging polyurethane laminating adhesive be reused?

Flexible packaging polyurethane laminating adhesives are commonly used materials in the lamination processing of food and daily necessities packaging. In many production scenarios, there will be leftover adhesive liquid. Many people wonder if such residual adhesive can be reused. In fact, this type of adhesive is not absolutely un-reusable, but it cannot be used for secondary purposes at will. It needs to be judged strictly based on the state of the adhesive liquid and the preservation method, and the operation should follow industry standards. 

 

Polyurethane laminating adhesives are usually in a two-component formulation. Once opened and mixed, they will react with moisture and oxygen in the air, gradually developing phenomena such as thickening, turbidity, and skining, which significantly reduce the bonding strength and also affect the quality of packaging and compounding. Therefore, the industry generally recommends that the amount of adhesive mixed should be determined on a need basis, and the mixed adhesive should be used up on the same day. Any remaining adhesive should be disposed of as waste first. 

If the remaining glue volume is large and in good condition, without any deterioration issues such as whitening, turbidity, thickening or clumping, it can be processed in a standardized manner and reused to a limited extent. Operators should dilute the remaining glue with a special solvent several times, and then place it in a clean and sealed container. Store it in a cool, dark, dry and well-ventilated place, avoiding high temperatures and moisture. On the next day of operation, use the treated remaining glue as a diluent and add it in small amounts to the newly prepared glue solution. The mixing ratio should be controlled within 20% or less, and it must not be used for high-precision packaging processes such as aluminum foil laminating.