Effect of TiO2@CaCO3 Waterborne Primer on the Coloring Performance of Inkjet-Printed Wood Product Coatings

Abstract

Calcium carbonate (CaCO3) is a widely used inorganic filling pigment used in coatings, and it is known for its nontoxicity, odorlessness, and environmental friendliness. The application of CaCO3 as a filler can effectively reduce raw material costs, and optimization of the filler formula enhances the coating film performance. In this study, oak planks were prepared as substrates for water-based inkjet printing. Three composite water-based primers with different TiO2-to-CaCO3 ratios and a polyurethane resin primer were used to prepare the substrate for the printing surface. The properties of the water-based primer coating and the water-based inkjet printing coating were characterized and analyzed via Fourier-transform infrared spectroscopy, video-based contact angle analysis, and environmental scanning electron microscopy. The aim was to investigate the effects of the composite waterborne primer coatings on the ink absorption and coloring properties of the interface between wood substrates and waterborne inkjet coatings. Sample WDCC-3#, with a TiO2-to-CaCO3 ratio of 15:35, exhibited the most comprehensive characteristics. The wood surface coated with 15 g/m2 of the polyurethane resin primer and 15 g/m2 of WDCC-3# exhibited a 5.8° contact angle of the water-based ink, first-grade adhesion, 4 H hardness, 70.52 whiteness value, and a roughness of ~2.33. The surface of the printed water-based inkjet-coated substrate was uniform and smooth, featuring rounded and transparent edges of the water-based ink droplets and a small CMYK color difference value. Therefore, the composite waterborne primer, incorporating TiO2 and CaCO3 in specific ratios, can be effectively combined with waterborne polyurethane primer coatings. This combination significantly improves the interfacial compatibility between the oak surface and waterborne inkjet coatings, leading to enhanced ink absorption on the oak plank surface during printing. This results in a high degree of color reproduction and clearer printed images. Overall, this study provides valuable insights for the development of primer programs for the industrial application of waterborne digital inkjet technology on wood products.