Polyurethane adhesives will dominate the field of flexible packaging for pharmaceuticals

     Due to the wide variety of materials in composite pharmaceutical packaging, enterprises have turned to two-component polyurethane adhesives for the compounding of polar plastics and non-polar materials.

      At present, pressure-sensitive adhesives used in flexible packaging composite materials for pharmaceuticals have been replaced by polyurethane adhesives, and ester-soluble polyurethane adhesives are mainly used. This type of adhesive is a two-component ester-soluble adhesive. Its main agent is a polyurethane polyol containing hydroxyl groups modified from polyether or polyester polyol aromatic isocyanate, and the curing agent is a synthesis of aromatic isocyanate and trimethylolpropane. This type of adhesive has excellent performance, mature technology and a wide variety, but it is highly toxic and costly. The large amount of solvents it emits pollutes the environment. Composite materials may undergo hydrolysis over time, releasing a carcinogenic substance that seriously affects the health of operators. With the enhancement of environmental awareness, the usage of this type of adhesive has been continuously decreasing.

     The application of alcohol-soluble polyurethane adhesives: It uses industrial alcohol as the solvent, has low production costs, good hygiene performance, is harmless to humans and causes no pollution to the environment. The disadvantages are that it cannot withstand a temperature of 100℃ and cannot be used to package highly corrosive products. Another type of adhesive is water-based Polyurethane Adhesive mainly composed of water-soluble or water-dispersible solvents. Its advantages include using water instead of organic solvents, eliminating the risk of combustion, and having a low cost. However, its bonding performance is poor.

     At present, adhesives for composite flexible packaging materials are developing towards solvent-free types. Solvent-free adhesives are basically composed of two-component polyurethane adhesives. The main agent and curing agent have high viscosity and fluidity at room temperature. During lamination, the main agent and curing agent are mixed in proportion, and after heating, they are roller-coated onto the substrate. Since no organic solvents are used, the cost is reduced. There is no pollution to the environment caused by the evaporation of organic solvents. It eliminates the need for large-scale drying, heating, ventilation and exhaust gas emission devices, reducing energy consumption. The product has no residual solvent damage, the production speed is increased, the maintenance cost is low, and the benefits are significant. It is the future development direction in the field of pharmaceutical flexible packaging.