Polyurethane adhesives have become one of the most important types of adhesives in the field of flexible packaging composite materials due to their outstanding properties, such as high bonding strength, good flexibility, and excellent resistance to media (oil, acid, and chemicals). It is mainly applied in packaging structures that require high-strength composites and special functional requirements.
Its wide application mainly includes the following major categories of flexible packaging:
1. Content resistance packaging: This is the most core application field of polyurethane adhesives. It is widely used to make packaging bags for oily, acidic, spicy or alcoholic contents, etc. For example:
(1)Food packaging: stand-up bags, retard bags, etc. for fried snacks (such as potato chips, puffed foods), meat products (such as ham, cured meat), sauces (such as mayonnaise, chili sauce), cheese, curry, and liquid beverages containing essential oils or alcohol (such as fruit juice, milk beverages). It can effectively prevent the contents from penetrating, avoid delamination between packaging layers, and ensure food safety and shelf life.
(2)Packaging for daily chemical products: packaging bags for liquid cleaning products such as shampoo, body wash, and laundry detergent, as well as cosmetics. The surfactants, fragrances, solvents and other components in these products can easily erode ordinary adhesives, while
Polyurethane Glue can provide reliable barrier and protection.
(3)Retort packaging: Specially developed high-temperature retort
Polyurethane Adhesive, which can be used to produce high-temperature retort bags (such as 121℃ or 135℃ retort). This type of packaging is used for foods such as meat, poultry and soups that require long-term preservation and terminal sterilization. It is required that the adhesive does not decompose, crack or produce any unpleasant odors under high temperature and high pressure.
2. Functional material lamination: When it is necessary to laminate certain high-performance films with substrates, polyurethane adhesives are the first choice. For example:
(1)Aluminum foil (AL) is combined with plastic films (such as BOPP, BOPET, BOPA, CPP, etc.) to create high-barrier packaging materials, which are used for packaging products sensitive to oxygen, moisture and light, such as milk powder, coffee and medicine.
(2)Different types of plastic films (such as BOPET//CPP, BOPA//CPP) are compounded, and the barrier properties, mechanical strength and heat sealability required for packaging are achieved by taking advantage of the characteristics of each material.
In conclusion, for flexible packaging involving oil resistance, acid resistance, chemical corrosion resistance, high-temperature resistance or the need to composite high-barrier materials (such as aluminum foil), the vast majority will choose to use reliable polyurethane adhesives to complete interlayer lamination.
