Solvent-based lamination process, also known as dry bond lamination, involves the bonding of two or more multilayer construction of films with a PU adhesive which consists of the solvent content during processing. The solvent content is mixed with the adhesive at a ratio which allows easy application of adhesive to the film. The mixture of adhesive and solvent content is transferred through the mandrel roller by rotation. The mandrel roller is employed for application of the adhesive. This is one of the very hazardous and expensive processing approaches since more heat is required in the machine oven to evaporate the applied solvent content. The SB lamination process is undesirable as it releases a lot of harmful gases into the atmosphere.
Solvent-free lamination, or SF lamination is a process by which multiple roll configurations are utilised to apply two-component PU adhesives between two dissimilar polymers during lamination. During this process, isocyanate-based PU group laminate is processed at a controlled temperature to increase the rate of the reaction.
At atmospheric conditions, the isocyanate will react with the moisture to yield the desired bond strength. After coating the substrate with application weight, the two bonded films are nipped at a pressure between 2~4 bar to improve adhesion and surface wettability. The process is more convenient when compared to other laminating technology since minimum energy is required during the process. Another advantage of this type of adhesive is its ability to enhance the machine to coat at high speed. Although the pot life of SF lamination is limited, this type of lamination is still considered to be environmentally friendly. Solventless lamination is still considered to be environmentally friendly. There is no heat required to evaporate the solvent since this type does not possess solvent.
