抄録
The authors found that the wet strength of paper is increased only by the heat treatment, and the strength obtained is almost as much as those of the melamine or urea resin treated papers. The fundamental mechanism of the development of the wet strength is discussed, and influences of imbibed water, oxidations, acids and salts are investigated as reported in a series of previous papers.
Influences of the lignin content and the morphological factors of the fiber on the heat treatment of paper are treated in the present paper. Being subjected to heat treatments, the wet strength development is interfered by the presence of lignin. But the strength development decreases with lesser lignin content. This seems to be caused by change of the other effective components or parts. The beating of the fiber is not so much effective to the wet strength development as to the dry strength development. It is not the case that finer fibers are more susceptible to the effects of the heat treatment. Papers made from cotton and viscose rayon as well as from wood pulp show the wet strength development at the heat treatment, but their strengths and ratios of the wet strength to the dry strength are markedly different from each other. These differences seem to owe to. the morphological factors, but to be more related to the other microscopic factors, for instances, the accesibility of the original fibers or the hemicellulose content. The lower D. P. cellulose molecules are not so sensitive to the heat treatment as low as 130°C, but more sensitive to the higher temperature treatment of 190°C than the higher D. P. cellulose molecules.
