Use of kaolin clay in aqueous barrier coating applications, TAPPI Journal November 2023

Application: This research suggests that cost effective aqueous barrier coatings can be prepared using various kaolin clays to partially substitute for more expensive latex binder components. The barrier properties can be improved using a wide range of kaolin clays, but the use of high aspect ratio clay provides superior performance at reduced coat weight. This research can be utilized to decide a maximum or minimum clay loading to maintain differ-ent types of target barrier performance, as well as blocking and heat seal properties, in a single layer coating system.

Author: Beko Mesic and James H. Johnston

ABSTRACT: The addition of functional coatings to packaging materials is a key requirement for increasing their performance and creating innovative packaging solutions. Flexography, a cost-effective printing method commonly used to print information and graphics directly onto a wide variety of packaging substrates, shows good potential for applying functional coatings. In this study, conventional clay-latex coating formulations containing approximately 1.3 wt% silica nanospheres were applied to a linerboard using a pilot scale flexographic printing web press. The performance of multilayered silica nanosphere-based coatings was compared with conventional coatings containing talc and/or wax dispersion in terms of coating grammage, runnability, and barrier performance. Coating grammage increased with an increased number of coating layers and a significant decrease in both the water vapor transmission rate (WVTR) and the direct water uptake of water (Cobb 120 wettability test) was observed for coatings containing silica nanoparticles. In general, the silica nanosphere-based coatings performed better than talc-based coatings. Talc/wax-based coatings had the highest variation in surface roughness due to an uneven distribution and variations of coating layers.