Water-barrier coating based on lignin oil found on the principle of an O/W Pickering emulsion stabilized by different nanocelluloses together with or without pectin, TAPPICon25

In the first part of this work, Pickering emulsions were prepared using enzymatically pretreated CNF (CNF-Gen1), carboxymethylated CNF (CNF-Gen2) or cellulose nanocrystals (CNC) as stabilizers. 10:90 oil-in-water (O/W) Pickering model emulsions were prepared with an oil fraction consisting of soybean oil or epoxidized soybean oil. Emulsions were evaluated for optimum coating formulation stability at 0.5, 1.0 and 1.5 wt.% CNF-Gen1, CNF-Gen2 and CNC.

The most promising formulation from the first part of this work was selected for continuation in part two. The soybean oil and epoxidized soybean oil were replaced by a proprietary lignin oil. The lignin ester component in the lignin oil contributes to the formation of a water barrier functionality in the coating layer. The subsequent water barrier formulations could be divided into two categories. In the first category, the O/W ratio was kept constant at 10:90, but the lignin content varied between 5 wt.% and 40 wt.% in the oil fraction. In the second category, the lignin content was kept constant at 40 wt.%, but the O/W ratio varied between 10:90 and 40:60. The aim of this approach was to improve the water barrier by maximizing the lignin content in the Pickering emulsion coating layer, while keeping the formulation viscosity within a favorable process window for industrially relevant future coating needs.

At higher O/W ratios, these Pickering emulsions showed a very steep increase in viscosity, making them difficult to coat. The use of pectin in combination with CNF-Gen1 resulted in a co-stabilized Pickering emulsion that was both coatable and provided a water barrier layer with a Cobb60 value of 1-4 g/m2 at a dry coating weight of 6-8 g/m2 on board.

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