Micro- and Nanofibrillated Cellulose as a Rheology Modifier Additive in CMC-Containing Pigment-Coating Formulations

Abstract

Suspension rheology of aqueous coatings influences the coating application performance at high speeds and during high rates of change of the shear rate, as well as the quality of the coated end product determined by the relationship between dewatering, immobilization, and coating coverage. In the case of paper coatings, the end-use printing can be significantly affected by the coating uniformity, pore structure, and surface chemistry. Nanocellulose-containing materials, such as microfibrillated (MFC) and nanofibrillated (NFC) cellulose, are potential additives that could at least partly substitute other natural and synthetic cobinders, including viscoelasticity-inducing starch, carboxymethyl cellulose (CMC), and polyacrylic thickeners, in paper-coating color formulations. Work is reported here in which a systematic comparison of dewatering and rheological characteristics of coating colors, based on three different pigments and mixtures thereof, is illustrated using CMC as the cobinder and incorporated with MFC/NFC as the partial cobinder replacement. All colors are shown to exhibit viscoelasticity, but the MFC/NFC additives are seen to operate as water-binding gel-forming components rather than with the flocculating thickening action of CMC. Immobilization of the color in the presence of nanofibrillar material is identified as the point of gel–water entrapment rather than the traditional stick–slip particle–particle interlocking mechanism predominating in traditional flocculant thickener formulations.

Forming and Dewatering of a Microfibrillated Cellulose Composite Paper

“…Initially, samples were subjected to low shear rate (0.1 s -1 ), then subsequently high shear rate (500 s -1 ), and finally once again low shear rate, the recovery stage (0.1 s -1 ). Structure recovery was traced in respect to recovery of dynamic transient viscosity (η + ) in the third interval, expressed as percentage (%) of ratio η + / η0 after 300 s of measurements, where η0 is the low shear viscosity at the beginning of first interval (Dimic-Misic et al 2013a).…”

Cellulose nanofibrils for one-step stabilization of multiple emulsions (W/O/W) based on soybean oil

“…CNF is commonly prepared via mechanical disintegration of wood fibers, leading to fibril diameter as small as few nanometers and several micrometers in length [13]. They have been extensively suggested as strength promoters [14][15][16][17] and rheology modifiers [18]. CNF is also considered as an excellent shape anisotropic nanomaterial that is able to stabilize surfactant-free emulsions, also known as Pickering emulsions, via particle assembling and network formation at the interface [19,45].…”

The Influence of Nano-Fibrillated Cellulose as a Coating Component in Paper Coating

“…It is believed the pseudoplasticity and shear thinning behavior of NFC suspensions may improve the rheological properties of the coating material; as a result, the properties of coated paper may improve as well (Koepenick 2004(Koepenick , 2005. Researchers have used NFC as a rheology modifier additive in CMC-containing pigment coating formulations and found that NFC additives operated as a water-binding, gelforming component (Dimic-Misic et al 2013). In this work, it was also discovered that the substitution of CMC with NFC makes the introduction of new types of rheology modifiers in coating colors possible, which could lead to improved strength of coated paper.…”