製紙用パルプから製造したナノセルロースの特徴およびその用途開発事例について

摘要

低炭素社会を実現するためにバイオマスの利用は非常に重要で，地球上に1兆tを超えて蓄積されている植物バイオマスのマテリアル利用に注目が集まっている.植物バイオマスの基本骨格であり，植物繊維をナノオーダーにまで解繊することにより得られるナノセルロース(NC)は，軽量，高強度•高弾性，低線熟膨張，耐熱性，透明性，ガスバリア性などのさまざまな特異的性質を有することから，環境配慮型次世代先端材料として近年世界的に関心が高まっているバイオ系新素材である.%Nanocellulose (NC) is a material which has excellent mechanical properties such as low density, high strength and low thermal expansion. It has attracted a great deal of attention as a plant-based, sustainable and high-performance material. Pulp that is extracted from wood chips and waste paper is environmentally friendly. NC is processed by disintegrating this pulp. Daio Paper has integrated pulp and paper mills where paper production is carried out from the stage of extracting pulp, while using many kinds of fiber sources. Here, we can produce NC from not only chemical pulp but also mechanical and recycled pulp, and each type of resultant NC has different properties. We provide paper with high gas barrier abilities using NC. First, we prepared the base paper coated with NC made by mechanical treatment such as beating and grinding, however, it did not show the gas barrier abilities though the NC film showed high gas barrier abilities. This is because part of NC penetrated into the base paper during coating, therefore NC layer could not be fully formed on the base paper. In order to form the NC layer on it, three-layered sheet was prepared by laminating NC coated film with paper. We successfully prepared the gas barrier paper using NC made by only mechanical treatment. We prepared polypropylene (PP)/ NC composites, using 3 types of NC, and we evaluated mechanical strength and fluidity of the composites. Elastic modulus and strength of each composite increased, and it is highest when using NC made by mechanical pulp. We assume that the lignin, that is hydrophobic component of mechanical pulp, improves the interaction between hydrophilic NC and hydrophobic PP. The fluidity of the PP/ NC composites was not lower than PP. It shows processing suitability of the composites is not reduced by mixing NC. Furthermore we prepared PP/NC composite in different melt-kneading temperature (up to 230℃) and measured mechanical strength. Elastic modulus of the composite kept even by increasing the temperature of the melt-kneading up to 230℃. It indicates that the reinforcing effect of NC is retained until 230℃.