Sustainable wood coatings: an innovative pumpable bio-based thixotropic alkyd resine

 
"Thixotropic behavior plays a vital role in ensuring the quality of paints and coatings, helping prevent pigment and filler sedimentation during storage and minimizing sagging during application. Traditional thixotropic alkyd resins are typically hard gels that require high temperatures or significant shear rates for incorporation into final formulations. These requirements pose technological challenges for some coating manufacturers. To address the growing demand for more user-friendly, pumpable thixotropic resins, a new alkyd resin has been developed. This innovative resin is presented in a soft gel form, allowing for easy handling at room temperature without the need for heating, which significantly reduces energy consumption during the paint production process. The resin is dissolved in a dearomatized hydrocarbon solvent with a high flash point, making it both safe for transport and pumpable, which are key characteristics for efficient resin handling. Due to its high flash point, the resin is classified as a safe material and does not require ADR labeling, further simplifying logistics. Moreover, its high solid content aligns with industry requirements for low volatile organic compound (VOC) emissions, making it an environmentally sustainable option for manufacturers. The new resin is bio-based, derived from soybean oil as a renewable resource. It is a polyamide-type long oil alkyd resin, designed to modify the rheological properties of alkyd wood stains and decorative paints. This paper describes the experimental work conducted during the development of this new thixotropic resin. The primary research objective was to achieve a balance between key properties, such as thixotropic efficiency and pumpability, while maintaining a high solid content. A significant part of the experimental work involved rheological measurements to study the resin's flow behavior. Thixotropic efficiency was evaluated using the five-interval thixotropy test (5ITT), a robust method for applying instant shear rate deformation and studying deformation and structural regeneration kinetics. The 5ITT test simulates the effects of pumping and instantaneous stirring during processing and handling of the resin, providing critical data for optimizing the resin's application performance. In the final phase of the experiments, the new resin was tested in combination with a commercially available long-oil alkyd resin, specifically formulated for wood applications. The coating system was subjected to sag resistance testing, a key performance indicator that determines the maximum wet-film thickness at which the coating does not sag on vertical surfaces during the drying process. Poor sag resistance can lead to noticeable defects in the final appearance of coated surfaces, underscoring the importance of this evaluation. Following successful laboratory development, the resin was produced on a pilot plant scale, and it is now commercially available. This new thixotropic resin offers a highly efficient, sustainable, and user-friendly solution to the coatings industry, with advantages including reduced energy consumption, improved handling safety, and compliance with stringent environmental regulations."