Optimization of Reaction Conditions and Evaluation of the Products for the Reaction of Wood with Vaporous Maleic Anhydride
Yoriko IWAMOTO, Takafumi ITOH, and Kazuya MINATO
Abstract:Chemical modification of wood with maleic anhydride (MA) was carried out in a vapor phase without catalyst. Weight percent gain (WPG), dimensional stability (ASEm), equilibrium moisture content, and weight loss (WL) in the fungal decay tests according to JIS K1571 were discussed from the aspects of optimization of the reaction conditions, analysis of moisture adsorption characteristics, and practical performance of anti-fungal properties. The results are summarized as follows: 1) water leaching of un-reacted and/or weakly bonded MA was notably marked in the reaction at low temperature and in the early stage, and reaction at elevated temperature was necessary for the stable linkages. 2) WPG increased with increasing ratio of reagent to wood sample (R/S ratio), and the R/S ratio was still insufficient within the condition tested (ca. 30% of theoretically required). 3) Competitive reaction of MA with water molecule and hydroxyl group in wood components was expected because larger WPG was observed at lower initial moisture content (IMC). 4) Treatment for about 10 h and 180oC was required for the formation of stable linkage, and satisfactorily high dimensional stability (higher than 50% ASEm) and anti-fungal property (less than 3% WL). Dimensional stabilization efficiency (ASEm per unit WPG) was higher in low R/S ratio, but high R/S ratio was effective for the shortening of the reaction time. On the other hand, the increase of IMC brought the shortened reaction time and high efficiency in dimensional stabilization, although thermal degradation is apprehensive. 5) Formation of cross-linking was suggested from the analysis of moisture adsorption isotherm. Key Words:Maleic anhydride,Vapor phase reaction,Moisture adsorption property,Dimensional stability,Durability