無触媒ホルマール化が紙の物理的, 機械的性質に及ぼす影響

Abstract

濾紙およびクラフト紙を試料として, 無触媒で気相ホルマール化を行い, 得られた結果について触媒を用いた報告例と比較検討した。その結果, 触媒を用いた反応に比べ, 反応時間はかなり長時間を要するが無触媒でも寸法安定化度は80％以上に達した。寸法安定化の速度は反応の初期では, 反応時間の平方根に比例し, 初速度は濾紙の場合, 約130℃以下で温度依存性が強くそれ以上ではほとんど一定となった。一方, クラフト紙では190℃でもなお増加の傾向を示し, みかけの活性化エネルギーは約25kcal/molであった。これは, 濾紙の場合反応温度の上昇とともに拡散が反応の律速段階となり, クラフト紙では実験範囲内で拡散は反応の律速段階でないことを示唆する結果である。機械的強度詰験の結果, 引張り強度は濾紙クラフト紙ともホルマール化により向上し, 耐折強度はP紙の場合, 寸法安定化度60％まで, またクラフト紙では80％でも無処理の値を保った。このような機械的性質の良好な保持は, この処理が無触媒で行われたととが大きく寄与していると考えられる。

A chromatograph filter paper and a kraft paper for electroytic capacitor were treated with vaporous formaldehyde without catalyst, and some of their physical and mechanical properties were determined. Though it needs a longer reaction time compared with the catalyzed reaction, reduction in swelling as high as ca. 80% could be attained without catalyst. In the initial stage of the reaction, the rate of dimensional stabilization was proportional to the square root of reaction time. In the case of filter paper, it depended on the reaction temperature below ca. 130℃, and kept constant above this temperature. On the other hand, for the kraft paper, the initial rate increased even at 190℃, and the apparent activation energy was about 25kcal/mol. These results suggest that for the filter paper, as the reaction temperature was raised, diffusion of the reagent becomes a rate-determining step, and for kraft paper, the diffusion does not control the reaction rate in the temperature range examined. Concerning the mechanical properties, tensile strength increased with reduction in swelling for both filter paper and kraft paper, and their original MIT folding endurance values were maintained until 60 and 80% of reduction in swelling, respectively. This excellent retention of mechanical properties may be characteristic of the uncatalyzed reaction. The fact that the filter paper degradated slightly more than kraft paper can be understood from its decrease in x-ray crystallinity index accompanied by the increase in dimensional stability.