Microfibrillated Cellulose Based Barrier Coatings for Abrasive Paper Products

Paper-based abrasive products are multilayer structures in which the first layer on the paper substrate is usually a latex barrier coating to prevent the migration of adhesive glue into the substrate. The high coat weight (10 g/m2) of latex barrier layers is a cause of environmental concerns. Hence, alternative materials that can provide the barrier function at lower coat weights are desired. In this work, microfibrillated cellulose (MFC) combined with poly(vinyl) alcohol (PVA) were explored as suitable alternatives to the current latex coatings. Barrier coating formulations containing PVA, MFC, and silica (SiO2) were developed and applied to a paper substrate using a rod coating method on a pilot scale. Coating quality and barrier performance were characterized using scanning electron microscope images, air permeance, surface roughness, water contact angle, KIT test, and oil Cobb measurements. The barrier coatings were also studied for adhesion to the subsequent coating layer. An optimal barrier function was achieved with the developed coatings at a low coat weight of ca. 3 g/m2. The adhesion of pure PVA and PVA-MFC barrier coatings to the subsequent coating layer was inadequate; however, silica addition was found to improve the adhesion.