Electric conductivity of wet recycled paper sheets

为了建立再生纸浆中添加剂的定量测定方法，研究了湿法浆网的电导率和干法纸浆纸页的傅里叶变换衰减全反射红外光谱。对含有聚丙烯酰胺(PAM)干强剂的纸页和进一步回收利用的纸页进行了总结如下：1.湿纸浆纸页的电导率随PAM留留量的增加而降低。PAM中阳离子含量越多，电导率下降幅度越大。2.不含PAM的湿法浆纸板第一次回收时电导率下降，再回收后电导率变化不大。另一方面，对于含有PAM的片材，电导率几乎不受任何回收处理的影响。3.添加PAM的片材与不含PAM的片材的ATR光谱的差异给出了PAM保留在片材中的光谱。无论打浆程度如何，PAM表征谱带的吸光度均随PAM含量的增加而线性增加。因此，提出了一种利用FT-IR-ATR光谱测定PAM保留量的简便方法。此外，通过ATR棱镜和光束角度变化的光谱变化表明，无论打浆程度如何，PAM在纸浆纤维表面的分布都非常接近。4.随着回收次数的增加，残留在纸页中的PAM逐渐被去除。一次回用时，PAM的去除率约为10%。与PAM用量的减少相比，回收对拉伸强度的降低幅度较大。

In order to develope quantitative determination of additives in recycled pulp, electric conductivity of wet pulp web and Fourier transform attenuated total reflection infrared (FT-IR-ATR) spectra of dry pulp sheet were investigated in this study. The concluding remarks for the paper sheets containing polyacrylamide (PAM) dry-strength additives and those further recycled are as followed.1.The electric conductivity of wet pulp sheet decreased with an increase of the PAM amount retained. The more cation amoumt in PAM increased the more the electric conductivity decreased.2.The electric conductivity of wet pulp sheet without PAM decreased on the first recycling and hardly changed by further recycling. On the other hand for the sheet with PAM,the electric conductivity hardly changed by any recycling.3.The difference ATR spectra between those of the sheets with and without PAM gave spectra of the PAM retained in the sheets. The absorbance of PAM characterizing band linearly increased with PAM content of the sheets irrespective of beating degree. Thus, a handy technique using FT-IR-ATR spectroscopy was proposed for determing the amount of PAM retained. Further, spectrum changes through the changes of ATR prism and beam angle indicated that PAM distribution very close to the pulp fiber surfaces irrespective of beating degree.4.The PAM retained in the sheets were gradually removed with an increase of the number of recycling procedures. The ratio of PAM removing was about 10% for a recycling. The decrease of tensile strength by recycling was large comparing with the decrease of PAM amount by recycling.