Flexible packaging polyurethane adhesives are two-component reactive polymer materials, with the core consisting of a main agent containing hydroxyl groups and isocyanate-based curing agents. Through the cross-linking reaction between hydroxyl groups and isocyanate radicals, a gel layer with excellent toughness and adhesion is formed, which is the most mainstream bonding material for dry lamination in flexible packaging such as food and medicine.
Based on product form, they include three types: solvent-based, non-solvent-based, and water-based polyurethane adhesives. Solvent-based polyurethane adhesives have matured, good wetting performance, are suitable for various plastic films and aluminum foil substrates, and have outstanding resistance to boiling and media, and are mostly used in high-demand packaging such as high-temperature boiling bags; the non-solvent system does not contain ethyl acetate, has lower VOC, lower production energy consumption, and is the direction of industry green transformation; water-based polyurethane uses water as the dispersion medium, is safe and low-odor, but has relatively weak water resistance and boiling resistance, and is mostly used in light packaging composite.
Compared with other adhesives, the greatest advantage of polyurethane adhesives is excellent gel layer elasticity, which can be adapted to different thermal expansion and contraction properties of films for composite, and has superior broad-spectrum adhesion performance compared to acrylic adhesives and neoprene adhesives. Acrylic adhesives have lower costs, but are insufficient in moisture resistance and boiling resistance; while polyurethane adhesives can be upgraded from ordinary normal temperature packaging to high-temperature boiling scenarios through molecular structure design.
From the perspective of industry development, environmental protection policies continuously promote the low-VOC transformation. Traditional solvent-based still occupy a large market share, but the industry's research and development focus is constantly shifting towards low-residue, high-weather resistance, and adaptable to degradable substrates polyurethane adhesives. In the future, flexible packaging
Polyurethane Adhesive, in addition to continuously reducing harmful substance residues, also needs to adapt to PLA and other biodegradable film materials, solve the interface bonding problem of degradable substrates, and conform to the development trend of packaging circular economy.
