Yellowing of Newspaper after Deacidification with Methyl Magnesium Carbonate
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| Format: | Article |
| Language: | English Slovak |
| ISSN: | ISSN 0034-5806 |
| Online Access: | http://www.viks.sk/chk/res_1_97_25_38.doc |
| Abstract: | SUMMARIES. Deacidification of newspaper with methyl magnesium carbonate results in decreasing brightness. Yellowing is caused by the linkage of magnesium to phenolic OH groups of lignin. If de-acidified paper is exposed to sunlight without the UV component, significandy slower oxidation of lignin occurs, which results in slower yellowing. After long-term ageing die degree of yellowing of deacidified newspaper becomes identical with that of untreated papers. We expect that in the course of long-term storage brightness of deacidified papers will not change substantially. CONCLUSION. The exposure of wood pulp newspaper to daylight resulted in increased yellowing of paper, this effect occurring most intensively during the first 50 days and reflecting photochemical oxidation reactions of lignin. The yellowing process progressed more slowly during storage under favourable conditions with no light access. Additional yellowing occurring after deacidification of newspaper with methyl magnesium carbonate was caused by a magnesium reaction or by the linkage of magnesium methanolates with phenolic hydroxy groups of lignin. After de-acidification the yellowing of newspaper in light is slower, and gradually the difference in brightness between deacidified and non-treated newspapers disappears. The lignin-free papers did not suffer substantial changes. The presence of magnesium either in linkage with lignin or in the form of magnesium ions significantly retarded degradation caused by oxidation and photooxidation reactions. Natural ageing of newspaper deacidified with methyl magnesium carbonate demonstrated that this deacidification procedure can be used for newspaper preservation. |
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| ISSN: | ISSN 0034-5806 |
