Solvent-based adhesives for flexible packaging are generally two component polyurethane laminating adhesives. These are designed for use in the dry lamination process, which means solvent acts as carrier for adhesive and applied on primary laminate which is completely dried before bonding to the secondary laminate.
It has such advantages as: (compared to solventless adhesives)
- Higher application weights possible
- Higher molar mass of adhesive structure possible
- Higher amount of polyesters based on aromatic structures possible
- This leads to properties not available by other lamination process: high bond strength, high initial tack, good bearing capacity, high temperature resistance, highly hydrolysis resistant.
2-component solvent-based polyurethane laminating adhesives are supplied in concentrated form and need to be diluted to a viscosity and solid content as per the customer’s requirement.
Running solid percentage of mixed adhesive depends on desired dry adhesive coating weight and cell depth of rotogravure cylinder available. Solid content is critical, in order to obtain the desired dry lamination adhesive coating weight.
