Influence of Latex Modifications on Viscoelastic Properties of Coating Colours, 1998 Coating Conference Proceedings

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The viscoelasticity of coating colours can have significant influence to the manufacturing of paper and its print properties. The coating speed and coating hold out for example are significantly influenced by the coating rheology. Given the fact that coating colours are complex dispersions with both inorganic and polymer particles, as well as soluble components, a clear understanding of the viscoelasticity is important. The influence of latex surface modification has hardly ever been studied previously. This study examines the viscoelastic properties of a coating colour in which the surface modification of latex particles is systematically varied. The investigation examined a coating colour containing clay, low amounts of carboxymethylcellulose (CMC) and styrene/butadiene latices modified with different levels of carboxylation and different types of ethoxylated comonomers at a constant level. The elastic moduli were highest for the coating colours containing the latices with the highest carboxylation levels in combination with ethoxylated comonomers. The ethoxylate modification is the dominant factor. Increasing only the degree of carboxylation had only a minor effect on viscoelastic properties. The critical strain amplitude was in the same range for all coating colours investigated, independent of the latex modifications.