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During the application of a suspension to a porous substrate, some components of the suspension can penetrate the substrate and change the properties of the suspension. During offset printing, a pigmented ink contacts porous paper and absorption of the oil from the ink by the paper influences the final product quality and press operations. Although various models have been presented in the literature to describe these processes, a quantitative comparison of models is lacking. Commercial cyan ink was diluted with mineral oil to generate various pigment and resin concentrations in the oil base. A porous ceramic plate with pores of approximately one micron in the top layer was used to simulate the porous layer of a paper-coating layer. The absorption rate of the ink-oil mixture into the plate was characterized gravimetrically. The viscosity change of the mixture after contact with the ceramic plate was characterized by a controlled stress rheometer. Three different models described in the literature were developed further to predict absorption rates and the rate of increasing viscosity. Next, the predictions of these models were compared to the experiments. A filtercake based model predicts the absorption rate at various concentrations of oil and ink. The increase in viscosity due to absorption is predicted qualitatively using various models. A modified filtercake model is proposed that predicts the absorption rates and viscosity increases of these systems within expected accuracy. [ABSTRACT FROM AUTHOR]

Abstract: Forward roll coating is a common process to deposit thin liquid films onto a continuous web. When the web is porous, some amount of the fluid is forced into the web in the nip. This removal of fluid, along with the deformation of the backing material, influences transfer in the nip as well as operational issues such as misting and coating defects. While much has been reported on forward roll coating for non-porous webs, little has been done when the web is porous. A laboratory roll coating device is used to characterize the pressure profile, the rubber deformation, and the film thickness as the fluid is in contact with a porous web. A pressure transducer is used to record the pressure profile in the nip. The film thickness on the steel roll surface and the gap between the rolls are measured with capacitance probes. Silicone oils, with three different viscosities, are used as test fluids. Three different papers are used in these tests. A model is proposed to describe the pressure profile, rubber deformation, and absorption in a forward roll coating device. The differential equations are solved to describe the nip behavior. A simplified model is also proposed, using an average nip pressure and Darcy''s law, to predict penetration in the nip. The proposed models compare well with the experimental results and predict the dependence on viscosity, nip load, and paper permeability. The experimental results with low viscosity fluids show some speed dependence that is not captured by the model, but the high viscosity fluid behavior agrees well with model predictions. [Copyright &y& Elsevier]

• Natural rubber addition to CNF coating improved water vapor barrier and water holdout • Water-based reactions showed evidence of CNF and natural rubber compatibilization • Compatibilization reactions changed suspension rheology and CNF particle sizes • Reactions improved drainage rates during film formation • Crosslinker reactions showed evidence of dispersing natural rubber in coatings Cellulose nanofibrils (CNF) coatings are excellent grease barriers for biodegradable packaging. However, barrier properties are moisture sensitive, so hydrophobic components such as latexes or polymers are needed to impart moisture resistance, but incompatibility leads to poor dispersion. In this work, CNF modified with norbornenes was reacted with natural rubber (NR) latex in water to improve dispersion, coating formation, and coating moisture resistance by creating hybrid particles. Mixtures and reacted samples were coated through filtration onto paper. The hybrid particles improved NR retention and drainage rate as compared to the CNF/latex mixture. Hybrid particle coatings showed more uniform NR dispersion as compared to the mixtures, which formed NR and CNF layers. NR addition to coatings increased the water contact angle, reduced water absorption, and decreased the water vapor transmission rate. All coatings passed a 12-kit grease test before folding and the mixtures formed a crack-resistant CNF layer on the surface. [ABSTRACT FROM AUTHOR]

Lignocellulose nanofibrils (LCNF) were used as a resin adhesive replacement in fiberboards. The physico-mechanical properties of the panels were affected by the LCNF content and the press temperature. At any given temperature, modulus of rupture (MOR) and internal bond strength (IB) showed a linear relationship with increasing LCNF. A temperature of 180 °C and 20% LCNF content were the optimum processing conditions giving MOR value of 12.1 MPa, close to the minimal recommended for commercial fiberboards. The IB, the thickness swelling, and modulus of elasticity met the standard values. The boards containing thermomechanical pulp (TMP), LCNF and borate minerals showed densities varying between 550 and 610 kg/m 3 . However, the differential density between the core and surface was reduced as LCNF content increased. The three-dimensional LCNF network with an average particle diameter of 12 ± 3 nm promoted fibers bonding and allowed inter-fiber voids filling, as observed in SEM images. Press-temperatures greater than 180 °C could cause material degradation that lowered the mechanical properties of the fiberboards. LCNF displayed a good bonding ability and showed a promising perspective for adhesive replacement in fiberboards. [ABSTRACT FROM AUTHOR]

• Lignin-containing CNF can be produced from old corrugated container (OCC) material. • The effect of increased refining process on CNF is different from that on LCNF. • Density is the major parameter influencing the mechanical properties of nanopapers. • After density, particle size and distribution determine nanopapers properties. A comparative study on the morphology and physico-mechanical properties of cellulose nanofibrils (CNF) and lignocellulose nanofibrils (LCNF) produced using a pilot-scale ultra-refining facility in the form of slurries and films was conducted. Suspensions and films of CNF and LCNF at different fines contents from 50% to 100% were prepared from bleached kraft pulp and old corrugated container (OCC) feedstock, respectively. We showed that the effect of film density on mechanical properties of CNF and LCNF films can outweigh the effect of fines content (or degree of fibrillation) and consequently an equally strong and stiff film can be produced from lower grades of CNF or LCNF at higher densities. After density normalization, particle size was found to be the main determining factor. Finally we conclude that a CNF or LCNF suspension with 70 % fines will yield films as strong and stiff as the materials with 100 % fines providing an opportunity for cost reduction. [ABSTRACT FROM AUTHOR]