The next time you’re enjoying a delicious glass of your favorite Merlot, take a moment to think about all of the adhesives that were involved in the process of getting the wine from the vineyard to your table.
The three main types of packaging adhesives are water-based, solvent-based and hot-melt adhesives. Of these, water-based and hot-melt systems are gradually edging out solvent-based systems as adhesive manufacturers strive to reduce volatile organic compound (VOC) emissions and improve air quality.
For packaging applications, water-based adhesives are the most widely used. In addition to air-quality benefits, water-based adhesives offer the advantages of strength, low cost, energy efficiency, ease of use and safety. Water-based adhesives are available in both natural and synthetic variants. Natural ingredients include animal- and vegetable-derived materials like starch and animal glue.
Synthetic water-based adhesives are used—increasingly in place of natural water-based adhesives—to label containers, make composite cans and form and seal cartons and cases.
Use of hot-melt adhesives for packaging applications continues to grow, primarily for automated carton and case sealing. This type of adhesive is 100 percent solid; it contains no solvent or water. On the packaging line, a dispensing system applies the adhesive to a substrate such as paperboard, rigid polyethylene or film-laminated material. The hot-melt adhesive dries quickly after application, forming a strong bond between the joined surfaces.
Because hot-melt adhesives dry so quickly, they are most suitable for high-speed operations. This type of adhesive also can be formulated for use with a range of packaging materials, though any substrate that is sensitive to heat is a poor candidate. Processes that expose the hot-melt bond to high temperatures also are not appropriate, as the heat can cause the adhesive to melt and the bond to fail.