Polyurethane adhesives are widely used in the field of flexible packaging due to their excellent performance, almost covering the vast majority of common composite packaging bags in daily life. The following are the main usage scenarios and packaging types:
1. Packaging with high requirements for resistance to contents
This is the most core application field of polyurethane adhesives. Many food and daily chemical products themselves are corrosive or contain easily permeable components, which require adhesives that can effectively resist them.
(1)Boiling packaging bags: They are used for packaging cooked food, meat, bean products and other foods that need to be sterilized by boiling in water below 100℃. Polyurethane adhesives can withstand high-temperature and high-humidity environments, ensuring that there is no delamination between packaging layers. For instance, common vacuum packaging bags for chicken legs and sausages.
(2)Retort packaging bags: Higher requirements, used for high-temperature retort sterilization at 121℃ or even 135℃. This type of packaging is used for sauces, meat sauces, dishes, etc. The
Polyurethane Adhesive can still maintain a strong adhesive force and flexibility under such extreme conditions. For example, the packaging of some soft canned foods.
(3)Packaging for oily foods: such as puffed foods, nuts, fried foods, hams, etc. Grease is prone to penetrate and dissolve common adhesives, causing delamination of the packaging. Polyurethane adhesives have excellent oil resistance and can effectively prevent the penetration of grease.
(4)Acidic food packaging: such as fruit juice, yogurt, pickles, vinegar, etc. Acidic substances can corrode certain adhesives, while polyurethane adhesives can provide stable protection.
(5j)Packaging for daily chemical products: such as packaging bags for laundry detergent, shampoo, cosmetics, etc. These products often contain complex components such as surfactants, fragrances, and organic solvents. Polyurethane adhesives can provide reliable chemical stability, preventing leakage and deterioration.
2. Packaging of Common Material Combinations
Polyurethane adhesives have excellent bonding effects on various film materials and can achieve a "strong alliance".
(1)Aluminum-plastic composite bags: This is the most typical application. Combining aluminum foil (with excellent barrier properties) with plastic film (with good heat sealability and strength) is often used in products such as milk powder, coffee, and medicines that have extremely high requirements for moisture-proofing and light-proofing. Polyurethane adhesive is the key to achieving this strong composite.
(2)Transparent high-barrier packaging bags: Made by combining transparent high-barrier materials (such as aluminum-coated film, silicon-coated film) with polyethylene, etc., they are used for foods that need to display contents and require long-term preservation, such as snacks, tea, pet food, etc.
(3)Plastic-plastic composite bags: Even for the lamination of ordinary plastic films, such as polyester/polyethylene, nylon/cast polypropylene, etc., polyurethane adhesives are widely used to meet the packaging requirements of regular goods, such as biscuits, noodles, candies, etc.
In summary, as long as the packaging bags need to withstand certain temperatures (boiling in water, steaming), come into contact with oils, acidic substances or chemical components, or require the firm bonding of high-performance materials with different properties (such as aluminum foil, high-barrier plastics), polyurethane adhesives are usually the preferred solution. It provides a crucial technical guarantee for the long-term preservation of food and the safe storage of daily chemical products.
