Development of Technology for Large-Batch Treatment of Paper-Based Information Carriers with Carbon Dioxide Ensuring Their LongTerm Preservation

摘要

A method for nonaqueous neutralization of various brands of paper with alcohol solutions of magnesium methoxide and methoxycarbonate is investigated. The minimum level of alkali reserve (100–150 mg-eq/kg) required for a prolonged preservation of the properties of paper is determined. A method for paper treatment with a neutralizing solution containing Freon, alcohol, and a neutralizing agent and satu- rated with subcritical carbon dioxide is proposed and experimentally tested. It is shown that, under certain conditions, supersaturation with carbon dioxide leads to the recrystallization of neutralizing agent and its deposition in the pores of paper in the form highly dispersed particles. The method makes it possible to adjust the alkali reserve (AR) level by varying the concentration of neutralizing agent and the degree of saturation of the solution with CO_2. The possibility of using supercritical CO_2 as a solvent and transport medium for neu- tralizing agent (magnesium methoxycarbonate) to treat paper-based printings is examined. The optimal regimes of dissolution of neutralizing agent in supercritical CO_2 and of paper treatment were selected, and the working parameters in the reactor and the ratio between the components at which the required level of the AR in paper is achieved are determined. The proposed methods for large-batch neutralization of the acidity of paper provide the minimum required AR level capable of ensuring the preservation of paper for a long period (up to 100 years) under conditions of natural aging with minimum amounts of expensive organic sol- vents, which indicates a high competitiveness of the proposed technologies of large-batch treatment of printed materials.