Polymeric Binder
Synthetic emulsion binders are designed to provide high binding strength and pigment compatibility in paper coatings. Carboxylated latex represents a major category of these binders, where carboxylic acid groups are integrated into the polymer chain. This modification increases the colloidal stability of the emulsion and enhances the mechanical stability during high-speed coating processes.
Carboxyl Functionality
Carboxylic acid monomers are typically copolymerized with butadiene and styrene to create a stable polymer structure. By incorporating these functional groups, carboxylated latex achieves strong electrostatic stabilization, which prevents premature coagulation in the presence of shear forces or divalent ions. The localized negative charges on the surface of the latex particles interact with the cationic additives in the coating color.
This specific chemical interaction improves the crosslinking density and increases the water resistance of the finished paper coating. The acidic groups also allow the binder to swell when the pH is adjusted, adjusting the rheology of the coating dispersion.
Coating Performance
High-speed printing papers require binders that maintain pigment adhesion under high mechanical tension. The use of carboxylated latex prevents linting and dusting on the offset press, ensuring clean runs and sharp image reproduction. It also balances the stiffness and elasticity of the dry coating layer.
This prevents cracking at the fold of cartonboard.
