Filler retention in papermaking by polymeric and microparticulate retention aid systems
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Notice bibliographique
Résumé
Mineral pigments are added to paper with the aim of improving its optical and printing properties. The colloidal behavior of calcium carbonate filler shows a dependence on the quality of water used in suspensions, presence of dissolved and colloidal substances and type of polymer used as a retention aid. The role of the retention aids is to attach colloidal particles, such as fines and mineral pigments, to pulp fibers before or during the paper is made. Two very different single-component retention aids were utilized in calcium carbonate fillers destabilization and deposition on fibers. Cationic polyethylenimine destabilized or facilitated deposition of the filler on fibers by a charge neutralization mechanism while cationic polyacrylamide flocculated or deposited the filler on fibers via a bridging mechanism. In the presence of anionic dissolved and colloidal substances, the amount of cationic polyacrylamide had to be increased in order to achieve the same degree of pigment flocculation. The reason for the increase was due to the fact that the cationic polyacrylamide formed a polyelectrolyte complex with the anionic substances, namely sulfonated kraft lignin. The reaction between cationic polyacrylamide and lignin was found to be nearly stoichiometric. Low molecular weight cationic polyacrylamide formed mostly colloidal complexes while high molecular weight cationic polyacrylamide formed predominantly coacervate complexes; this was mainly due to differences in characteristic times of lignin association with the cationic polyacrylamide, clustering of polyacrylamide molecules and reconformation of polymer chains. The performance of two-component retention aid systems consisting of a cationic polyacrylamide and anionic microparticles were evaluated by deposition of calcium carbonate filler on pulp fibers. Kaolin clay and bentonite were used to heteroflocculate polyacrylamide-covered surfaces of the fibers and pigment. Due to their inability to delaminate, kaolin clay and acid-treated montmorillonite showed no effect of calcium carbonate filler deposition. After cation exchange with sodium-rich solutions, which caused the montmorillonite to delaminate, the montmorillonite flocculation efficiency considerably improved. Kaolin clay neither delaminated after the cation exchange nor improved calcium carbonate deposition. Bentonite was found to completely delaminate when using polyacrylamide-treated fibers. When added to a suspension of fibers, filler and cationic polyacrylamide, bentonite was found to be in a form of stacks containing on average four platelets. An alternative way to paper filling with pigment was tested on stationary sheets and on slow and fast Fourdrinier pilot paper machines. Using a secondary headbox on the pilot paper machines, a high degree of loading (above 30%) could be achieved using positive clay or calcium carbonate fillers. However, the fillers lowered the paper strength as they interfered with the fiber-fiber bonding in a similar fashion found in conventionally filled papers.
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Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,001 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,000 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découle