Life cycle assessment of multi-step versus one-step coating processes using oil or bio-based resins

Nowadays, before setting up an industrial process, special attention has to be paid to its environmental footprint. This new way of thinking allows evaluating the hotspots so as to propose solutions to conceive more eco-friendly processes. Thus, the coating industry is increasingly preoccupied by the environmental impacts of newly designed paints. That is why innovation tries to take into consideration both the formulation composition and the application and drying methods. Following a Life Cycle Assessment (LCA) approach, the present study aims to compare the environmental impacts of self-stratifying coatings (with three process steps), either oil-based or bio-based, to those of an oil-based multilayered coating (with six process steps). The concept of the self-stratifying coating is to bring the primer, the intermediate and the top coat properties together in a one-pot formulation to produce a multi-functional coating through a less laborious process. The total environmental impact of each process can be characterized by four main categories of impacts: Climate Change Human Health (CCHH), Human Toxicity (HT), Climate Change Ecosystem (CCE) and Fossil Depletion (FD), which together represent approximately 86% of the global impact for each system. The results obtained show that the self-stratifying oil-based coating process is more energy efficient compared to the currently used multilayered oil-based coating process, with a 15% decrease of CCHH, HT and CCE indicators and a 14% decrease of FD indicator, corresponding to a 13.6% decrease of the total environmental impact. However, as this decrease was lower than expected, particular attention was then paid to the chemicals used (resins, solvents) and to the process conditions. The substitution of the oil-based epoxy resin by a bio-based one and the use of less harmful solvents allow reducing the total environmental impact by 32.4% compared to the multilayered oil-based system (with 30% decrease of CCHH indicator, 50% of HT indicator, 31% of CCE indicator and 34% of FD indicator). In a global way, electricity consumption control and the nature of chemicals used were reported to contribute in a significant way to the improvement of the process environmental impact. (c) 2019 Elsevier Ltd. All rights reserved.