著者

牧野 重人

出版者

JAPAN TECHNICAL ASSOCIATION OF THE PULP AND PAPER INDUSTRY

雑誌

紙パ技協誌 (ISSN:0022815X)

巻号頁・発行日

vol.52, no.12, pp.1710-1716, 1998-12-01 (Released:2009-11-19)

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Some applications such as tissue papers or filter papers require strength at wet even though paper orginally has weakness to water. For these applications, wet strength agents that meet such requirement are added to papers at the stage of pulp slurry.Namely, we have polyamide resin or melamine resin for the additives that give paper strength at wet. The main reasons polyamide is suitable for the application are that it can give high wet strength with a little amount of the resin, it can be used in a wide pH range, and it does not contain formaldehyde. Melamine resin is also suitable for the application because of early appearance of wet strength after drying stage in papermaking, dimensional stability, alkali resistance, and ultraviolet-ray resistance.Dry strength of paper largely depends on hydrogen bond among cellulose molecules. Invasion of water among fibers cause the destruction of the hydrogen bond. The wet strength expression mechanism of the polyamide resin apply to the prevention of water infiltration to fiber crossing made by crosslinked resin in drying process of papermaking. On the other hand, that of melamine resin apply to a strong water-resistant bond of methylol group in the resin between hydroxyl groups of the cellulose.For the sake of effective usage of wet strength agents, we should keep the following important points in mind. First, enough heating is necessary for the expression of wet strength as wet strength agents are thermosetting. Secondly, since cation resin electrically interacts with anionic fiber, existence of anionic trash and salts decrease in the resin retention. At last, excessive addition of wet strength agents can cause decrease in the resin retention, pitch trouble, bubbling, increase in drain loading, and etc.