Soft packaging polyurethane adhesives are the core supporting materials in the production of soft packaging composites. Their main functions revolve around interlayer bonding, structural stability, safe compatibility, and durable performance, meeting the usage and safety requirements of soft packaging in fields such as food, cosmetics, and medicine. The specific functions are as follows:
Firstly, the multi-layer substrate is firmly bonded. The flexible packaging is usually composed of various materials such as plastic films, aluminum foils, and paper.
Polyurethane Adhesive can tightly bond heterogeneous materials like PET, NY, PE, CPP, and aluminum foils, forming a high-strength composite film. This solves the problem of significant differences in surface energy between different substrates, making it difficult to bond. It ensures that there is no delamination or edge separation after bonding, and meets the mechanical strength requirements during the bag-making, filling, and transportation processes.
Secondly, enhance the overall barrier and protective performance of the packaging. Through a stable composite structure, in conjunction with the base material, it achieves the blocking of oxygen, water vapor, light, and odors, thereby extending the shelf life of the contents; at the same time, it has good resistance to media, capable of withstanding the erosion of oils, acids, alkalis, alcohols, and seasonings, avoiding packaging delamination, leakage, and swelling, and is particularly suitable for packaging of oily, acidic, and salt-baked foods.
The third aspect is the adaptation of processing and subsequent processes. The adhesive must meet the coating, drying, and curing processes of the high-speed dry composite machine, featuring strong initial adhesion, good leveling properties, and moderate curing speed, which is suitable for high-speed production; at the same time, it must be resistant to friction, folding, and impact, meeting the requirements of bag-making, heat sealing, cutting, handling, and dropping, ensuring that the packaging appearance is flat, without bubbles, and without wrinkles.
The fourth aspect is to ensure hygiene and usage safety. For food and pharmaceutical grade flexible packaging, the adhesive used must have low odor, low residue, no solvent migration or the migration amount must meet the standards. It should comply with national food safety standards. Polyurethane adhesives (especially solvent-free and water-based types) can significantly reduce organic solvent residues, prevent contamination of the contents, and meet the hygiene and safety requirements for direct contact with food and medicine.
Finally, it comes to expanding the application scenarios of packaging. Thanks to its resistance to high and low temperatures, as well as its ability to withstand boiling and freezing, it can be adapted for special packaging such as pasteurization, high-temperature boiling, and cold chain freezing, enabling flexible and stable use of soft packaging in various environments including normal temperature, high temperature, and low temperature. It is an indispensable key material for functional soft packaging.
