Four factors that affect adhesive migration

1. Raw material surface properties
In the coating process, when the paint mixture is applied to the paper, the water carries the adhesive and penetrates the base paper, that is, the adhesive migrates to the base paper. This permeation can be seen as a capillary flow into the porous system. During the penetration of the coating into the base paper, the pressure generated by the trapped and compressed air in the space of the paper sheet will prevent the coating liquid from entering the paper sheet. This traps air and liquid. The fight between them controls the depth of penetration. The adhesive is carried by the water and migrates to the base paper, so the water permeability of the base paper has an important influence on the degree of migration of the adhesive to the base paper. In general, the effect of the base paper on the migration of the adhesive is mainly reflected in the surface roughness and voidage of the base paper.

2. Coating composition

In coating formulations, the type, morphology, particle size, and charged charge of the pigment have a significant influence on the physical properties of the coating, which also directly affects the migration of the adhesive during the coating process. Fine-grained, irregular-shaped pigments have a large surface area, the number of channels formed by the pigment particles increases, and the flow path of moisture in the wet coating increases, which may increase the migration of the adhesive to the coating surface [1; the form and amount of the adhesive It has obvious influence on the coating structure. Some studies have shown that the latex with strong hydrophilicity, fine particles, and high glass transition temperature has a greater degree of migration to the coating surface after coating and processing; in addition to pigments and adhesives In addition, there are many additives. Studies have shown that if the additive added is a polymer, it will have a limited effect on the migration of the adhesive to the coating surface. This may be due to the viscosity of the coating caused by the addition of the polymer.

3. Apply

In the application process, different configurations of the coating head will produce different forces on the coating, thereby affecting the spread of the coating on the original paper, and also affect the movement of the microscopic components in the coating. This effect is mainly due to the coating head. The effect on the wet coating angle and the resulting linear pressure results in the degree of compression of the base paper and the change in rheological properties of the coating.

4. Drying and drying is an important process in the coating process. During the drying process of the coating, a large amount of water is removed by the heat energy provided by the drying. The rate of dehydration affects the rheology of the coating and the amount of water movement. The direction and direction will strongly influence the migration of the adhesive, and thus the drying conditions will become an important factor affecting the migration of the adhesive. Much of the research on the migration of adhesives has been focused on the drying stage for a long time. Many studies have shown that strong drying will exacerbate the migration of adhesives to the coating surface.

Different drying methods have different effects on the migration of the adhesive. Studies have shown that infrared drying can reduce the migration of the adhesive to the coating surface.




Source: China Paper Additives Network