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Abstract: “Stickies” are tacky species, present in recycled paper and coated broke, derived from coating formulations, adhesives etc. They impact negatively on paper quality and cause web runnability problems by deposit build-up. To sustain recycling, stickies are controlled by adsorbing them onto minerals added to the recycled stock. We report isotherms for a fatty acid ester defoamer and an acrylic acid ester copolymer adsorbing from colloidal suspension onto various talcs and modified calcium carbonates. We used commercial preparations of the fatty acid ester defoamer and acrylic acid ester copolymer to provide a simple analogue to the industrial process. The modified calcium carbonates are hydrophilic with anionic and cationic sites present. Adsorption isotherms for low surface area modified calcium carbonate conform to the Langmuir model, while those for high surface area modified calcium carbonate reflect a two stage process involving the formation of a monolayer over the mineral surface and subsequent partial aggregation. Talc platelets display hydrophilic edges and hydrophobic surfaces. Adsorption onto them appears to involve three stages; specifically, a hydrophilic interaction between hydrophilic groups on the molecules and the talc edges, followed by hydrophobic interactions between the molecules and the talc surfaces, and finally by formation of multilayers. [ABSTRACT FROM AUTHOR]

Abstract: A range of calcium carbonate-based tablets and paper coating layers, with latex or starch as binder, were prepared. Their dry porous structures were analysed by mercury porosimetry. Some of these samples were also examined by electron microscopy. The porous space of these structures has been simulated using a network model named Pore-Cor, which creates network structures with percolation behaviour and porosity matching those of the experimental sample. Representative particles were grown between the cubic pores and cylindrical throats of the void network model until they touched up to four of the adjacent void features. The sizes of these representative particles, or skeletal elements, have been previously shown to be realistic for the case of unconsolidated sand and glass beads. The size distributions of these skeletal elements were compared with each other and with experiment using a Mann–Whitney test. The sizes of the skeletal elements were found to increase with the particle size of the calcium carbonate powder. The properties of the binders, used in the paper coating formulations, were found to have a major influence on the sizes of the skeletal elements, whose sizes also increased with coating thickness. These findings give insights into the wet structure and the drying process of paper coatings. [Copyright &y& Elsevier]