Wpływ niektórych środków neutralizujących na własności papieru

The acid reaction of paper, especially when combined with unfavourable conditions of its storage can grow to a cause of hydrolisis of cellulose fibres which in turn becomes the cause of a decreased stability of paper. As one from among several kinds of treatments applied in conservation of papers showing acid reactions may be quoted here their neutralization. The work discussed by the authors within their present publication was aimed at checking the effectiveness and workability of some neutralizing reagents that are usually applied in conservation and at the same time at their confronting with the results achieved with the use of Barrow’s deacidification method. The determinations and tests were carried out on the three following paper grades: (1) Whatman No 4 chromatographic paper, (2) hand-made filter paper manufactured by Jeziorna Paper Mill, and (3) blank newsprint coming from the Paper Mill, Głuchołazy. Properties of papers listed above are presented in Table 1. The papers under test were acidified by their dipping in 10g/l aluminium-potassium sulphate solution (reactions of papers acidified by the use of aluminium-potassium sulphate solution, cf. Table 2). Deacidification of paper samples was carried out by their dipping in solutions of different reagents having appropriate concentrations at 20°C. The time of bath for solutions of barium hydroxide, basic magnesium carbonate and buffer solution was 10 min in each case. While using the Barrow method standard conditions were applied and the combined time of the both baths amounted to 40 min (characteristics of reagents used, see Table 3). The following determinations and tests were carried out with the aim to define the effect of reagents applied on properties exhibited by papers before and after their artificial ageing: (a) paper reaction by contact method, (b) absolute tear resistance tested with the use of the Elmendorf tester, acc. to Polish Standard PN-54-P-04015, (c) number of double folds with the use of the Köhler-Molin tester, acc. to Polish Standard PN-54-P-04012, (d) brightness with the use of the Zeiss leucometer, acc. to Polish Standard PNMLiPD- 56-31033. The artificial ageing was carried out at 105°C within the' period of 72 hrs, acc. to Polish Standard PN-56- P-04030. Resistance to ageing was determined according to changes in strength and has been expressed by В index, i.e. the percentage proportion of properties possessed by the neutralized paper subjected to artificial ageing to those exhibited by the basic paper samples. The alterations in brightness being a result of artificial ageing were expressed with the „loss of brightness” index Z-(1-Rst/Ro)100% where R0 — brightness of basic samples with no ageing treatment applied Rst — brightness of the neutralized paper subjected to ageing treatment. Figures characterizing the above determinations are given in Tables 4, 5 and 6. Through the assessment of results obtained it was possible to come to the following findings: — all the five reagents under investigation allowed to reduce the acidity of paper, — a slightly basic reaction of papers (pH = 7.7 and pH = 8.2) obtained as a result of deacidification with barium hydroxide dissolved in methanol and that carried out with the use of aqueous solution of basic magnesium carbonate had any negative effect on the properties of paper and did not reduce its resistance to artificial ageing, — all the investigated reagents after deacidification caused the increased resistance to artificial ageing when confronted with properties possessed by the basic paper samples, — when compared with Barrow’s method considerably better results of deacidification of both Whatman No 4 chromatographic paper and blank newsprint have been obtained by the use of aqueous solution of buffer, — the results of deacidification achieved with the use of barium hydroxide dissolved in methanol in 1 g to 1 1 proportion are nearing, and, in respect to some properties, even better than those obtained with the Barrow method.