Preparation of super durable natural fibers using supecritical carbon dioxide

2007 Fiscal Year Final Research Report Summary

• Project/Area Number: 18550190
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Polymer/Textile materials
• Research Institution: Kyoto Institute of Technology (2007); University of Fukui (2006)
• Principal Investigator: OKUBAYASHI Satoko Kyoto Institute of Technology, Graduate Schoolof Seicnce and Technology, Associate Professor (00284737)
• Co-Investigator(Kenkyū-buntansha): HORI Teruo University of Fukui, Graduate School of Engineering, Professor (90092832)
• Project Period (FY): 2006 – 2007
• Keywords: lvocell / supercritical carbon dioxide / organic alkali / fiber swellinp / fibrillation / WAXD / BET surface area

Research Abstract

The aim of this study is to improve the fibrillation of property of cellulose fibers without damaging fiber structure by controlling micro-fiber structure in supercritical carbon dioxide (sCO_2) that is high diffusible but provides no fiber swelling. The lyocell fiber was treated in scCO_2 containing an organic base, benzyltrimethylammonium hydroxide (BTMAH), water or methanol at 25MPa and over 100 degree Celsius for 1 hr. The diameter of the treated fibers measured in 25 mol/1 NaOH aqueous solution was smaller as compared with untreated fiber. These results indicate the reduction of fiber swelling after BTMAH/solvent/ ScCO_2 treatment. In spite of the decrease in fiber swelling, the fibrillation of the fiber treated in BTMAH/water/scCO_2 was accelerated after adding mechanical abrasion while the fiber treated in BTMAH/methanol/scCO_2 was diminished. In order to clarify the difference, cross section of treated and torn fibers was observed with FE-SEM. The diameter of macro-fibrils of the sample fibers treated in BTMAH/solvent/scCO_2 was smaller and the fibril-fibril structure became unclear in the images. Considering the weight loss of fiber, no changes in BET specific surface area and increase in crystallinity (detected by WAXD) after the treatments, the mechanism of fibril control was suggested as following; The BTMAH/solvent mixture in scCO_2 penetrates in between fibril-fibril space of lyocell fiber and dissolve amorphous cellulose, which enhances the adhesion among finals and decreases fiber swelling and fibrillation. However, the fibrillation is promoted by alkali/scCO_2 containing water that cleavages the hydrogen bonding between cellulose molecules beecause of destroying the cellulose fiber.