Application of water-based adhesive materials to soft packaging industry
Waterborne composite is divided into dry process and wet process. Wet compound is mainly used in the combination of paper and plastic, paper and aluminum, and white latex is popular in this field. Waterborne polyurethane and waterborne acrylic polymers are mainly used in plastic composite and plastic aluminum composites. Water adhesives have the following advantages:
(1) the composite strength is large. The molecular weight of water-based adhesives is a few times as many times as polyurethane adhesives, and its cohesive force is mainly by the van Edward force, which belongs to physical adsorption, so a very small amount of glue can reach a fairly high composite strength. For example, compared with two component polyurethane adhesives, the amount of dry glue coated with 1.8g / m2 can reach the composite strength of double component polyurethane adhesive 2.6g / m2 in the process of aluminum coating.
(2) softer and more suitable for aluminum coating. The single component water adhesive is softer than the two component polyurethane adhesive. When they are completely solidified, the polyurethane adhesive is very rigid, while the water adhesive is very soft. Therefore, the softness and elasticity of water-based adhesives are more suitable for the composite coating of aluminum plating, which does not lead to the transfer of aluminized film easily.
(3) do not need to be cured, the machine can be cut after the machine. The single component waterborne adhesive compound does not need to be ripened, and the subsequent process of cutting and bag making can be carried out after the machine is removed. This is because the initial adhesive strength of the water adhesive, especially the shear strength, ensures that the product will not produce "tunnel" and folds in the process of compound and cutting. Moreover, the strength of the composite membrane can be increased by 50% after putting it in 4 hours. This is not the concept of ripening. The colloid itself does not cross link, mainly with the leveling of the glue, and the composite strength will also increase.
(4) thin film and good transparency. Because the sizing of water adhesive is small, and the concentration of the adhesive is higher than that of the solvent based adhesive, the moisture of drying and discharging is much less than that of the solvent type adhesive. After the water is completely dried, the film will become very transparent. Because the adhesive layer is thinner, the transparency of the composite will be better than that of the solvent adhesive.
(5) environmental protection, harmless to people. There is no residual solvent after water adhesives are dried. Many manufacturers use water-based adhesives to avoid the residual solvents brought by the compound, so it is safe to use water-based adhesives, and no harm to the health of the operators.
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