Synthesis of a novel betaine-type asphalt emulsifier and its investigation by online FTIR spectrophotometry

摘要

A novel betaine-type asphalt emulsifier, 3-(dodecyloxy)-2-hydroxypropan-N-carboxymethyl-N,N-dimethylammonium chloride, has been synthesized in a three-step reaction from lauryl alcohol, epichlorohydrin, dimethylamine, and chloroacetic acid. The optimum reaction conditions were obtained for synthesis of 2-(dodecyloxymethyl)oxirane in the first step. The yield reaches 75.7 % under the optimum conditions of reaction temperature 50 C, reaction time 5 h, feedstock mole ratio of epichlorohydrin to lauryl alcohol 1.4, basicity 33.3 %. The structures of the three products were identified by FTIR. Synthesis of 2-(dodecyloxymethyl)oxirane in the first step was monitored by online FTIR, and an intermediate was detected. On the basis of the experimental data, a plausible reaction mechanism was proposed for the reaction. The critical micelle concentration (CMC) of the final product is low, 8.8 × 10~(-5) mol/L. The surface tension at the CMC is 21.2 mN/m. This product is an excellent emulsifier for asphalt. The prepared bituminous emulsion had high storage stability. The emulsifier is a rapid-set asphalt emulsifier.