Polymer Solubility
Carboxylated polymer dispersions dissolve or swell in alkaline aqueous solutions to provide controlled viscosity and adhesion in paper coatings. These specialized polymer systems contain acrylic or maleic acid monomers that remain insoluble under acidic conditions but activate at a higher pH. Utilizing an alkali-soluble binder allows formulators to prepare stable, water-resistant coatings that remain susceptible to chemical removal.
Coating Application
Formulation rheology under high shear depends on the neutralization state of the polymer chains. When the pH of a coating color containing an alkali-soluble binder is adjusted with ammonia or sodium hydroxide, the acid groups ionize and cause the polymer chains to extend. This conformational transition increases the viscosity and water retention of the coating, preventing premature drainage into the paperboard substrate during blade coating.
Recycling Removal
Packaging boards designed for circular recovery rely on the rapid release of coatings during repulping. Because the process water in recycling plants is maintained at a pH above eight, the alkali-soluble binder dissolves completely and releases the mineral pigments from the wood fibers. This rapid dissolution prevents the formation of insoluble micro-stickies that could otherwise deposit on the paper machine wires, making the recovered fiber slurry cleaner and easier to reprocess into high-quality recycled paperboard.
