Abstract
New vanadium-based drier, stabilized with macrocyclic chelating ligand, is described. Its drying activity was established on solvent-borne alkyd resins of different oil-length modified by soybean oil. The test coatings were characterized by standardized mechanical tests as well as spectroscopic methods. Time-resolved infrared spectroscopy was used for determination of kinetic parameters of the autoxidation process while the EPR (electron paramagnetic resonance) spectroscopy enabled confirmation of stability of oxovanadium(IV) species in the cured films. The obtained experimental data revealed promising catalytic activity of the oxovanadium(IV) compound stabilized with N,N,N,N-chelating ligand at low concentration. At 0.03 wt % of metal in dry matter content, it shows short total dry times not exceeding 12 h while commercial cobalt(II) 2-ethylhexanoate is, at the same concentration, considerably lower active with total dry times 15.4 h (alkyd of short oil-length) and >24 h (alkyd of medium oil-length).
Highlights
Alkyds became a preeminent binder for coatings since the 1950s and they are still one of the most widespread in the paint production industry [1]
Oxovanadium compound VO was prepared according to literature procedure [28]
Paramagnetic nature of the title compound enables the use of EPR spectroscopy for characterization
Summary
Alkyds became a preeminent binder for coatings since the 1950s and they are still one of the most widespread in the paint production industry [1]. Curing of alkyd resins is based on oxo-polymerization of fatty acids chains containing sensitive C–H bonds on bis-allylic moiety [4]. This process, known as autoxidation, includes a series of radical reactions within termination step 3-dimensional crosslinked film (Figure 1) [5]. The autoxidation is very slow, and the use of catalysts, so-called driers, is necessary in common alkyd-based paint systems. Primary driers are redox-active transition metal compounds accelerating the autoxidation process of air-drying paints. Their ability to change oxidation state can enforce the alkyl radical formation through hydrogen abstraction [10]. Due to limited air-oxygen diffusion, the coatings are cured from top surface down to the substrate which is why they are often
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