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Paper, print media and biomaterials

LGP2, a center of innovative research
LGP2, a center of innovative research

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LGP2 - Polyamideamine epichlorohydrin-based papers: mechanisms of wet strength development and paper repulping

Published on January 25, 2013
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June 5, 2012

Eder Siqueira defended his PhD thesis from the University of Grenoble entitled "Polyamideamine epichlorohydrin-based papers: mechanisms of wet strength development and paper repulping".

Laboratory of Pulp and Paper Science and Graphic Arts (LGP2)This thesis was prepared at the Laboratory of Pulp and Paper Science and Graphic Arts (LGP2) under the supervision of Professor Évelyne Mauret and Professor Naceur Belgacem from Grenoble INP-Pagora.

Polyamideamine epichlorohydrin (PAE) resin is a water soluble wet strength additive used for preparing wet strengthened papers (WSP). Even if PAE is largely used in the papermaking industry, there is still a lack of knowledge concerning the cross-linking reactions, the effect of the operating conditions on the properties of the produced papers as well as the recycling of WSP.

The first part of this work showed that the main PAE cross-linking reaction occurs by a nucleophilic attack of N atoms in the PAE structure forming 2-propanol bridges between PAE macromolecules. A secondary contribution of ester linkages to the PAE cross-linking resulting from the reaction between carboxylic groups and azetidinium rings was also observed. This reaction is important in the presence of carboxylmethyl cellulose (CMC). However, it can be postulated that ester bond formation has a negligible impact on the wet strength of PAE-based papers because the amount of carboxylic groups present in lignocellulosic fibres is considerably less high than in CMC and the resulting formed ester bonds are hydrolysable.

In the second part of this work, the obtained results showed that, when PAE is added to a fibrous suspension (bleached chemical pulp - Eucalyptus), the adsorption, reconformation and/or penetration phenomena reach an apparent equilibrium after 10 min of contact time. An increase of the conductivity of the pulp suspension (from 100 to 3000 S/cm) negatively impacts the strength of the WSP, but for high dosages only (1%).
Finally, the degradation of PAE films and PAE-based papers was studied in order to improve the recycling of WSP. For the tested conditions, sodium persulfate is the most effective reagent but the efficiency of the treatment is decreased when coated papers are used.

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Date of update January 25, 2013

Grenoble INP Institut d'ingénierie Univ. Grenoble Alpes