Diethyl zinc process , paper

With this demonstration that zinc carbonate does not catalyze the photodegradation of paper in the presence of UV light and high humidity, we feel that the diethyl zinc process, as modified by the final carbon dioxide exposure, is now commercially feasible. 

DEZ [Diethyl zinc] A process for preserving books and documents by treatment with diethyl zinc vapor, which neutralizes ary residual acidity from the papermaking process. The articles are placed in a low-pressure chamber and suffused by diethyl zinc vapor. This vapor reacts with the moisture in the paper to yield zinc oxide, which neutralizes the acid. The process was developed by Texas Alkyls (a joint company of Akzo and Hercules) and the U S. Library of Congress. A pilot plant was set up in 1988, capable of treating batches of 300 books, and plans to build two larger plants were announced in 1989. 

Sulfite paper has a relatively short life span, since residual acid will continue to hydrolyze the cellulose and cause embrittlement. Further sources of acid include aluminum sulfate (which is added together with resin to suppress bleeding or feathering of ink into the paper) and S02 and NO from the atmosphere. Much of the world s library collections and archives will soon be lost as the paper crumbles. Various deacidification treatments (e.g., with ammonia, morpholine, cyclohexylamine carbamate, or diethyl-zinc) have been proposed and tried, but at best they can only halt the process of embrittlement and cannot reverse it.14 With the move to kraft pulping, alkaline peroxide bleaching, and increasing use of precipitated calcium carbonate as a filler, the high quality papers produced today are intrinsically acid free and should also resist subsequent acidification by S02-polluted air fairly well. 

A series of papers containing varying amounts of zinc oxide was selected from among those that had been treated with diethyl zinc in the development of the treatment process. The properties of these papers before and after treatment are shown in Table I. All papers were conditioned by TAPPI Method T-402 before testing. Samples of the treated papers and the untreated controls were exposed for 88 h to the light of... 

Thus the ZnO is a nonvolatile base that can be placed in the paper by a gaseous substance. This process seems very promising. However, the major disadvantage of this process (there are always disadvantages) is that diethyl zinc is very flammable and great care must be exercised in its use. This leads to another question Is the treatment effective enough to be worth the risks involved Only through more experiments can this question be answered. 

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