Advantages of Waterborne Adhesives for Flexible Packaging

Since the development of flexible packaging, the reduction and removal of organic solvents in composites has become a common direction for the entire industry. At present, composite methods that can completely eliminate solvents include aqueous compounding and solvent-free compounding. Solvent-free compounding is currently in its infancy due to factors such as cost and technology. The water-based adhesive can be used directly on existing dry laminating machines. Therefore, it is welcomed by domestic soft packaging manufacturers and has been achieved abroad. Great stride development.

Water-based composites are classified into dry composites and wet composites. The wet composites are mainly used in the compounding of paper, plastic, and paper aluminum. White latex is popular in this field. In plastic-plastic composites and plastic aluminum composites, mainly water-based polyurethanes and waterborne acrylic polymers are used.

Waterborne adhesives have the following advantages.

(1) Large composite strength. Water-based adhesives have a large molecular weight, which is several dozen times that of polyurethane adhesives. Its adhesive force is mainly based on van der Waals forces and belongs to physisorption. Therefore, a very small amount of glue can achieve a very high composite strength. For example, compared with two-component polyurethane adhesives, in the composite process of aluminized films, the amount of dry glue that can be coated with 1.8 g/m2 can reach a quantity of dry glue of 2.6 g/m2 of two-component polyurethane adhesive. The composite strength.

(2) It is soft and more suitable for the composite of aluminized films. One-component waterborne adhesives are softer than two-component polyurethane adhesives. When they are completely set, the polyurethane adhesives are very stiff, while the aqueous adhesives are very soft. Therefore, the softness and elasticity of the water-based adhesive are more suitable for the composite of the aluminized film, and it is not easy to cause the transfer of the aluminized film.

(3) It does not need to be cured, and it can be cut after it is unloaded. The one-component waterborne adhesive compound does not need to be matured, and subsequent processing such as slitting and bag making can be performed after the machine is released. This is because the initial adhesive strength of the waterborne adhesive, especially the high shear strength, ensures that the product is compounded. There are no problems such as "tunneling" or wrinkles in the cutting process. In addition, the strength of the composite film using water-based adhesives increased by 50% after 4 hours of storage. This is not the concept of curing, and the colloids themselves are not cross-linked, mainly with the leveling of the adhesive, and the composite strength also increases. The increase.

(4) Thin adhesive layer with good transparency. Due to the small amount of water-based adhesive sizing, and the higher concentration of water-based adhesives than solvent-based adhesives, the amount of water that needs to be dried and discharged is much less than that of solvent-based adhesives. After the water is completely dried, the film becomes very transparent. Because the adhesive layer is thinner, the composite transparency is also better than the solvent-based adhesive.

(5) Environmental protection, harmless to people. After the water-based adhesive is dried, there is no residual solvent. Many manufacturers use water-based adhesives to avoid the residual solvent caused by the compound. Therefore, the use of water-based adhesives is safe and does not harm the health of the operators.

Source: PACK.CN