Effect of water-resistant agent on properties of coating and coated paper

With the rapid development of paper industry, especially coated paper has been developed rapidly, the printing industry on coated paper quality requirements are getting higher and higher. In order to ensure the printing quality, the surface of coated paper must have the ability to resist wet friction. Wet friction resistance refers to the degree of damage to the surface of the paper after a certain area of paper and cardboard is subjected to wet friction under a certain pressure, which reflects the ability of the surface of the paper not to be destroyed by wet friction.

And for the waterproof coated paper with special requirements, in order to make it obtain the ability of surface waterproof and water resistance, in the paper production process, in addition to the sizing process in the sizing agent and surface sizing agent, the fastest effect is to add water resistance additives in the coating preparation process, so that the coating layer to obtain good water repellent performance.

At the same time, based on the considerations of safety and environmental protection, the national quality requirements for food wrapping paper and household paper are becoming more and more stringent, and now more is the use of polyamide polyurea formaldehyde resin (PAPU) water repellent. PAPU is widely used, because it does not contain free formaldehyde, and it is fast, it works when it gets off the machine, and it can also effectively improve the adaptability of coated paper in the printing process.

PAPU has a strong application to pH value, and the viscosity of PAPU added to the paint is stable and the curing speed is fast. PAPU molecular chain contains chloroethanol group and polyamine group two active functional groups, of which chloroethanol group and paint adhesive produce chemical bonding bond, polyamine group and paint adhesive combination to form ionic bond, cross-linked curing to form a network of curing film, which is the main source of PAPU water resistance, but also as a coating water resistant agent working principle.

In actual use, PAPU can not only form chemical bonds with coated starch, but also form ionic bonds with styrene butadiene latex, and the wet friction resistance of the coating is increased. In addition, the weak cationic properties of PAPU water resistant agent can also produce micro-flocculation with anions in the coating, improve the puffiness, porosity and permeability of the coating layer, and improve the printing performance of the finished paper.

Rheological property is an important indicator of the paint, PAPU type water resistant agent can increase the viscosity of the paint, adding PAPU type water resistant agent after the water loss value of the paint is reduced, water retention is better. PAPU type water resistant agent is suitable for the preparation of high viscosity paint, and the water retention performance of the paint is better.