Synthesis and characterization of quaternary ammonium salt tertiary amide type sodium hydroxypropyl phosphate asphalt emulsifier

Abstract

A novel asphalt emulsifier of octadecyl-bis(1-(N,N-dimethyl)propanamide)-(3′-sodium phosphate-2′-hydroxypropyl) ammonium chloride was synthesized in three steps by using octadecylamine, N,N-dimethyl acrylamide, epichlorohydrin, sodium dihydrogen phosphate, and reaction solvent of isopropanol as raw materials. In the first step, octadecyl-bis(1-(N,N-dimethyl)propanamide) tertiary amine was synthesized by the reaction of octadecylamine with N,N-dimethyl acrylamide. The second step is the reaction of epichlorohydrin with sodium dihydrogen phosphate to obtain sodium 3-chloro-2-hydroxypropyl phosphate (intermediate). The third step is the reaction of the first-step product with the intermediates to obtain the asphalt emulsifier product by quaternization reaction. The optimum conditions for the third step were as follows: reaction temperature at 70 °C, reaction time for 5 h, the feedstock mole ratio of epichlorohydrin to octadecylamine at 1.40. Under these conditions, the yield of asphalt emulsifier reaches 95.65%. The structure of asphalt emulsifier was characterized by FTIR, ¹H-NMR and elemental analysis. The results show that the structure of asphalt emulsifier is the same as that of the target product. The critical micelle concentration (CMC) of the asphalt emulsifier at the temperature of 298 K is 1.15 × 10⁻⁶ mol L⁻¹. The surface tension of aqueous solution at critical micelle concentration (γ_CMC) is 27.72 mN m⁻¹. The saturated adsorption amount (Г_CMC) of surfactant aqueous solution is 1.98 × 10⁻³ mmol m⁻². The occupied area per surfactant molecule at the CMC (A_CMC) of surfactant molecules is 0.837 nm² mol⁻¹. The performance test by emulsification with AH-70 asphalt and mixing with aggregate shows that the asphalt emulsifier has good emulsification property, and the prepared asphalt emulsion has good storage stability. The asphalt emulsifier is a rapid-set asphalt emulsifier.