In-line lamination describes the application of a clear plastic film to the top and/or bottom of a base material creating a multi-layered product that is done on a continuous web. In in-line laminating operations, adhesives are applied to the web by the last printing station of a press, before being combined with a second web to form the multi-layered product. Laminates are typically composed of different plastic films layered over other plastic films, paper, and/or aluminum foil. The finished laminations can be used for a variety of end-use applications, although food packaging consumes the largest portion of these laminations.
Best Management Practices & Pollution Prevention
The flexographic film and paper laminating industry is rapidly changing from solvent-based adhesives to water-based polyurethane adhesives and acrylic emulsions for dry-bond laminating. Very low residual monomer 100 percent solids systems (hot melts) are rapidly gaining acceptance as an alternative technology to traditional dry-bond laminating techniques.
Water-based and hot-melt adhesives help reduce VOC or HAP emissions compared to traditional solvent products. Additionally, any waste material generated from cleanup is typically not hazardous wastes, as compared to solvent-based adhesives, which are considered hazardous waste and a source of VOC or HAP emissions.
Using 100% solids (i.e., solventless) adhesives eliminates solvent emissions and drying requirements and consequently reduces the VOC or HAP emissions and energy consumption.
Greater printing and laminating speeds can be obtained since the problem of insufficient drying, or trapped solvents, is eliminated. The size of equipment is minimized, compared to solvent lamination equipment, as well.
For access to vendors who may supply alternative materials and equipment, see the PNEAC Vendor Directory.
Solvent-based adhesives are subject to Clean Air Act and RCRA regulations because they can release VOCs and HAPs. Once a facility emits VOCs and HAPs above a certain level, then they are subject to permit and control requirements. Waste disposal is also a concern as certain adhesives can be classified as hazardous wastes, which require special handling and disposal.
When utilizing water based adhesive systems, generally the glue waste and wastewater must be treated before being discharged into a sanitary sewer or must be shipped off site for disposal. This is due to the biological oxygen demand (BOD) of the starches and other organic materials in the waste.
Health & Safety
Formaldehyde and vinyl acetate are hazardous materials and, if possible, should be eliminated from the adhesive formulation. If the formaldehyde and vinyl acetate cannot be eliminated from the glue formulation, employees should be monitored for exposure to excessive levels of formaldehyde and vinyl acetate, especially since these materials can lead to long term health affects.