The potential of microfibrillated cellulose in water-laid and foam-laid papers

Dewatering is an essential step in the processing of fibrous materials. The smaller the material size, the more challenging the dewatering process becomes. The dewatering properties of materials containing microfibrillated cellulose (MFC) are known to be especially challenging, particularly at high MFC contents. This study shows that the foam-laid forming technique enables more effective dewatering compared to water-laid forming and enables structures with both high bulk and sufficient strength. In the study, papers were formed using special water-laid and foam-laid sheet formers and MFC dosage was varied up to 15%. Papers containing high amounts of MFC were found to be unsuitable for water-laid forming due to poor dewatering properties resulting from higher fine material, i.e. MFC, content. Foam forming provided good dewatering characteristics even at high MFC contents. In addition to dewatering properties, the mechanical properties of the papers were also studied. According to the strength results, the strength potential of MFC-containing foam-laid papers was found to be greater with respect to z-directional strength than in-plane strength.