Papersave Process

The Papersave Process comprises three steps (Pig. 13.5 and 13.7) First, the books, which remain in a dosed treatment chamber during the entire process, need pre-drying. The normal moisture content of 5-7% is temporarily decreased 

Secondly, deacidification follows the pre-drying. The books are impregnated with an alkali solution. The treatment chamber is completely flooded with the treatment chemical. The deacidification chemicals are alcoholates of magnesium and titanium dissolved in hexamethyldisiloxane. Due to the previous drying, the closed books standing in the chamber absorb the solution like a sponge. 

Thirdly, the books are again dried after the treatment solution has been drained. The solvent absorbed during impregnation dries away while the deacidifying chemicals (magnesium and titanium compounds) remain in the paper. 

The entire process takes three days. After the books have been removed from the chamber, they regain lost humidity and return to their normal moisture content. This process is finished after approximately three weeks. During this period the books exude alcohol due to the reaction of the treatment chemicals with water. Therefore, the treated books are stored in a well-ventilated room before being returned to the customer. 

By this treatment the follovdng results are obtained The acids contained in the paper are completely neutralised by the magnesium compounds. The pH of the paper after treatment is raised to between 7 and 9. The pH of some papers can exceed 9 for a short period after treatment. In the following months, the pH of the paper decreases to levels below 9 due to the transformation of magnesium alcoho-lates and magnesium hydroxides in magnesium carbonate. After neutraHsation of the acids, 0.5-2 wt.% of superfluous magnesium carbonate remains in the paper and serves as the alkaline buffer. Thus, acids subsequently formed or introduced into the paper by environmental influences can be neutralised within the paper. 

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Fig. 13.6 Chamber of the Papersave Process mass deacidification plant with a capacity of 60 tons per year.

There are some successful new possibilities in the deaddification of paper up to mass deacidification processes by nonpolar solvents (for example the Papersave Process ) whereas no new achievements have been reached in the strengthening of paper, especially not in nonaqueous treatments. The experiences of paper makers are only of limited use in the strengthening of old papers because the papers cannot be changed in structure and compound during restoration or preservation. 

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