This process offers simple and safe setup and produces large quantities of alkyd resin, but is inefficient and leads to large material loss.
The water vapor mixes with the solvent, evaporates, and is condensed into a separating vessel. The amount of water extracted can be measured, and the solvent is recycled after separation [ 5 ]. This process results in better color retention, lower product loss, and better temperature control than the fusion process and is therefore the preferred method for large-scale production [ 6 , 7 ].
Classification of Alkyds The three main classifications for alkyds are oxidizing versus nonoxidizing, modified versus unmodified, and oil length. Oxidizing alkyds, often referred to as synthetic drying oils, cross-link in the presence of oxygen in a process known as autoxidation [ 8 ].
Nonoxidizing alkyds are typically used as plasticizers or as hydroxyl-functional resins. These resins require an outside cross-linking mechanism such as melamine-formaldehyde or urea-formaldehyde [ 5 ]. Modified alkyds are resins that contain monomers in addition to polyols, polybasic acids, and fatty acids. This is done to improve certain properties such as water compatibility, durability, and resistance to color change.
Common examples of modified alkyds include styrenated alkyds, silicone alkyds, fluorinated alkyds, and acrylic-alkyd hybrid systems [ 3 , 5 ]. Straight alkyds have good exterior durability, reasonable water resistance when not immersed, and moderate resistance to petroleum solvents. These alkyds are not resistant to concentrated acids, oxidizing acids, or strong organic acids [ 1 , 3 ]. The ratio of monobasic fatty acids to the total weight of the polymer yields the oil length of an alkyd.
Equation 1 describes the formula for determining oil length [ 5 ]. Oil length affects properties such as solubility, dry time, viscosity, gloss, and color retention [ 1 , 6 ]. Solubility in nonpolar aliphatic solvents and drying time increase as oil length increases. Viscosity, gloss, and color retention decrease as oil length increases [ 6 ].
Autoxidation and Driers Alkyd resins naturally cross-link in the presence of oxygen through the process of autoxidation. This relatively slow process can be accelerated with metal salts of alkali earth or heavy metals called driers. The drying process is initiated in an induction period where singlet oxygen forms hydroperoxides that decompose into free radicals.
Primary, or surface, driers catalyze this first step by decomposing hydroperoxides through cycling oxidation states at the surface. While naturally present antioxidants are consumed, the unconsumed free radicals initiate at double bonds of the fatty acid. This free radical can react with oxygen to form peroxy free radicals.
These free radicals react through radical-radical combinations to form cross-links at carbon-carbon, ether, and peroxide bond linkages. Primary driers include cobalt-, manganese-, iron-, cerium-, and vanadium-based compounds. Secondary, or through, driers catalyze drying throughout the film. They include lead-, zirconium-, bismuth-, barium-, aluminum-, and strontium-based metal salts. ACD labs software was used for data analysis. Gel permeation chromatography GPC. Data analysis was performed using Empower GPC software.
Thermogravimetric analysis TGA. The oxidative thermal stability of the resins was determined by using a TA Instruments Q thermogravimetric analyser. TA Universal Analysis software was used for data analysis. Conflicts of interest There are no conflicts to declare. Notes and references F. Maunu, Prog. Sonnati, A. Leclair, A. Romand, O. Choule, W. Coggio and N.
Florent, Paint Coat. Won, H. Sohn, R. Song and S. Santana, G. Ponce and R. Maciel Filho, J. Mialon, A. Pemba and S. Miller, Green Chem. Sousa, C. Vilela, A. Fonseca, M. Matos, C. Freire, G. Gruter, J. Coelho and A. Silvestre, Polym. Sousa, A. Fonseca, A. Serra, C. Freire, A. Silvestre and J. Coelho, Polym. Lammens, M. Franssen, E. Scott and J. Faurie, et al. Kumar, D. Vikramachakravarthi and P.
Pal, Chem. Cavalheiro, J. Dighe, S. Toliwal and R. Khotpal, J. Mare, J. Kumarathasan, A. Rajkumar, N. Hunter and H. Gesser, Prog. Lipid Res. Bouwman and R. Schotten, Eur. Sato and N. Ikekawa, J. Yu, K.These methods allow manufacturers to yield —10, gal of alkyd at a time [ 1 ]. Comparison of resins C and E shows that resins containing N-palmitoylglutamic acid dimethyl ester are slightly more unstable than those containing N-hexadecylglutamic acid dimethyl ester. Schotten, Eur. The primary amine in glutamic acid can be dehydrogenated by the alkyl hydroperoxide, with formation of an imine Scheme 2 , route 1. As air pollution policies in the United States and Europe have become stricter, high solids coatings have been a viable option to meet these regulations. These resins require an outside cross-linking mechanism such as are oxidizing versus nonoxidizing, modified versus unmodified, and oil. This free radical can react with oxygen to form peroxy free radicals. Miller, Green Chem. Gel permeation chromatography GPC. Classification of Alkyds The three main classifications for alkyds the procedure of Yu and co-workers.
Straight alkyds have good exterior durability, reasonable water resistance when not immersed, and moderate resistance to petroleum solvents. Primary, or surface, driers catalyze this first step by decomposing hydroperoxides through cycling oxidation states at the surface. Solubility in nonpolar aliphatic solvents and drying time increase as oil length increases.
Solubility in nonpolar aliphatic solvents and drying time increase as oil length increases.
Free radicals can be generated during the synthesis of alkyd resins at high temperature in the presence of traces of gaseous oxygen. After addition of sodium methoxide base 1 equiv. Vikramachakravarthi and P. The viscosity characteristics are in accordance with the molecular weight values; in general, resins with a higher molecular weight display a higher viscosity.
From this observation it can be deduced that pyroglutamates were incorporated in the polymer matrix as monofunctional chain stoppers Fig. The challenge of mixing immiscible substances has seen breakthroughs in the s and s through the use of surfactants.