Description
Dimer acid refers to the dimerization of linear unsaturated fatty acid or unsaturated fatty acid ester with linoleic acid of natural oil as the main component, which is self-condensed through Diels-Alder cycloaddition reaction under the catalysis of clay. body. It is a mixture of various isomers, in which the main components are dimers, small amounts of trimers or multimers, and traces of unreacted monomers.
Physical properties
Pure dimer acid is a light yellow transparent viscous liquid with good thermal stability: it does not crystallize at a low temperature of-20 °C, and does not lose its transparent fluidity; it does not evaporate or gel at 250 °C. The color will darken significantly when heated in air. Exposure to metal ions, especially copper and iron ions, can promote color deterioration. Hydrogenated dimer acid is almost colorless and transparent liquid, and the color is not easy to deepen even when heated. Dimer acid is insoluble in water, but soluble in ether, ethanol, acetone, chloroform, benzene, petroleum series solvents.
Chemical properties
Dimer acid is a multifunctional compound, so it can carry out many chemical reactions and has similar reactivity to general unsaturated fatty acids. It can react with alkali metals to form metal salts, and can also be derived into acid chlorides, amides, esters, diisocyanates and other products.
Reaction mechanism
Dimer acid is obtained by heating and polymerizing unsaturated fatty acid under the action of catalyst. The reaction mechanism of dimerization, the current consensus view is the theory of Diels-Alder addition reaction between conjugated and non-conjugated unsaturated fatty acids.
Uses
Dimer acid is an important oleochemical that is widely used in coatings, surfactants, lubricants, printing inks, hot melt adhesives and other industries.
Preparation
Dimer acid is prepared by heating and polymerizing unsaturated fatty acid under the action of catalyst.
References
[1] Maike Unverferth, Michael A. R. Meier. “Selective formation of C36-dimer fatty acids via thiol-ene addition for copolyamide synthesis.” European Journal of Lipid Science and Technology 118 10 (2016): 1470–1474.
[2] Xue Huang. “C36 Dimer Fatty Acid-Based Flexible Unsaturated Polyester Resin: Improvement of Properties by Adjusting the Intermolecular Crosslinking Structure.” Science of Advanced Materials (2021).
