|
Nanocellulose is a term referring to nano-structured cellulose. This may be either cellulose nanofibers (CNF) also called microfibrillated cellulose (MFC), nanocrystalline cellulose (NCC), or bacterial nanocellulose, which refers to nano-structured cellulose produced by bacteria. CNF is a material composed of nanosized cellulose fibrils with a high aspect ratio (length to width ratio). Typical lateral dimensions are 5–20 nanometers and longitudinal dimension is in a wide range, typically several micrometers. It is pseudo-plastic and exhibits the property of certain gels or fluids that are thick (viscous) under normal conditions, but flow (become thin, less viscous) over time when shaken, agitated, or otherwise stressed. This property is known as thixotropy. When the shearing forces are removed the gel regains much of its original state. The fibrils are isolated from any cellulose containing source including wood-based fibers (pulp fibers) through high-pressure, high temperature and high velocity impact homogenization, grinding or microfluidization (see manufacture below). Nanocellulose can also be obtained from native fibers by an acid hydrolysis, giving rise to highly crystalline and rigid nanoparticles (often referred to as CNC or nanowhiskers) which are shorter (100s to 1000 nanometers) than the nanofibrils obtained through the homogenization, microfluiodization or grinding routes. The resulting material is known as nanocrystalline cellulose (NCC). ==History and terminology== The terminology microfibrillated/nanocellulose or (MFC) was first used by Turbak, Snyder and Sandberg in the late 1970s at the ITT Rayonier labs in Whippany, New Jersey, USA to describe a product prepared as a gel type material by passing wood pulp through a Gaulin type milk homogenizer at high temperatures and high pressures followed by ejection impact against a hard surface. The terminology (MFC) first appeared publicly in the early 1980s when a number of patents and publications were issued to ITT Rayonier on this totally new nanocellulose composition of matter.〔 In later work Herrick at Rayonier also published work on making a dry powder form of the gel.〔 Since Rayonier is one of the world's premier producers of purified pulps their business interests have always been 1) to create new uses and new markets for pulps and 2) never to compete with new or potentially new customers. Thus, as the patents issued,〔 Rayonier gave free license to whoever wanted to pursue this new use for cellulose. Rayonier,as a company, never pursued scale-up. Rather, Turbak et al. pursued 1) finding new uses for the MFC/nanocellulose. These included using MFC as a thickener and binder in foods, cosmetics, paper formation, textiles, nonwovens, etc. and 2) evaluate swelling and other techniques for lowering the energy requirements for MFC/Nanocellulose production.〔Turbak, A.F., F.W. Snyder, and K.R. Sandberg "Microfibrillated Cellulose—A New Composition of Commercial Significance," 1984 Nonwovens Symposium, Myrtle Beach, SC, Apr. 16–19, 1984, pages 115–124./publisher = TAPPI Press, Atlanta, GA〕 ITT closed the Rayonier Whippany Labs in 1983–84 and further work on making a dry powder form of MFC was done by Herric at the Rayonier labs in Shelton, Washington, USA〔 The field was later taken up in Japan in the mid 1990s by the group of Taniguchi and co-workers and later by Yano and co-workers.〔 and a host of major companies (see numerous U.S. patents issued to P&G, J&J, 3M, McNeil, etc. using U.S. patent search under inventor name Turbak search base). Today, there are still extensive research and development efforts around the world in this field. As of August 2012, NCC was produced in a factory operated by CelluForce, producing one ton per day, and by a just-opened facility operated by the US Forest Service.〔(【引用サイトリンク】title=Why wood pulp is world's new wonder material - tech - 23 August 2012 )〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「nanocellulose」の詳細全文を読む スポンサード リンク
|