Deacidification of Acid Paper with Organic Base in Supercritical Carbon Dioxide.

As one of valuable cultural assets, paper materials have been conserved in museums and libraries. However, a solvent, water employed in conventional processes has danger of destroying the paper due to deformation occurred during wet and dry treatments. In this study, supercritical carbon dioxide (scCO₂), that is a fluid beyond critical point of pressure and temperature was used as a new solvent. The scCO₂ can penetrate in micro- and nanospace owing to its extremely low surface tension with carrying substances while it does not adsorb on hydrophilic materials causing no swelling of them. Therefore, the use of scCO₂ is expected to neutralize acid paper without damage. In the experiments, an acid paper without printing was accumulated in multi-layers and treated on batch processing with three organic bases, monoethanolamine, triethanolamine that arc applied in conventional methods and triethylaminc that is relatively dissolved in scCO₂. The pH of paper increased from 5.5 to 7.0 or 7.5 after 1 hr-treatment, suggesting deacidificaiton of the paper by all organic bases in scCO₂ containing methanol. The acid paper handled with triethylamine in scCO₂ methaol was neutralized faster without yellowing as compared with ethanolamines or by a vapor- and liquid phase methods. In addition, the tensile strength of the paper was not significantly influenced by the base treatment in scCO₂. The buffering effect of triethylamine impregnated in the acid paper lasted more than six months. Furthermore, fifty sheets of the acid paper were uniformly neutralized by scCO₂ method using triethylamine. [ABSTRACT FROM AUTHOR]