Carboxyl Group of Pulp Cellulose and Retention of PAE Resins

Abstract

In this paper a relationship between PAE resins retention and pulp carboxy group content was studied.By heat-curing after absorption on the pulp cellulose, PAE resins are chemically bonded to it. It is, therefore, recognized that in spite of acid treatment which is usually used for the determination of carboxyl group PAE resins remaining on pulps do not desorbed by ion exchange for hydrogen ion. We might expect that the rest of the carboxyl group of pulps after absorbing are directly measured. It was found that the retention of PAE resins depends upon carboxyl group content in pulps, and the isotherms is apparently in agreement with the Langmuir adsorption equation. The correspondence between cellulose carboxyl groups and basic groups due to nitrogen amine in the PAE resins, was in the ratio of 1 : 1.0 to 1 : 2.4. The authours consider that both groups play a role as adsorption sites. Pitch in three kinds of pulps were removed with ethanol-benzene (1 : 1) mixture following alkali-treatment (mercelization), or the reverse operation was made. The results showed that a considerable number of carboxyl groups present in the amorphous regions containing such materials as β-cellulose, pitch and other water soluble portions. Pulps are said to be fibriled in the amorphous region during the beating process. Hence it is expected that the beating operation causes the retention of PAE resins to increase with increasing the carboxyl group content. The increase of PAE resins retention was not observed, and also the increase of the carboxyl group content. These facts implied that PAE resins penetrate positively into the amorphous regions independing of beating. We consider that the amorphous region plays an important role in the retention of reagents generally used for papers.