Study On Synthesis Of Polyaspartic Acid And Its Scale Corrosion Inhibition Performance

Polyaspartic acid is a kind of nontoxic, total-biodegradable, invironmental-frendly water treatment agent. In this paper, the synthesis of polyaspartic acid and its scale corrosion inhibition performance are researched.Firstly, polysuccinimide as intermediate is synthezed by using maleic, urea as materials. Then, polysuccinimide is hydrolyzed to product polyaspartic acid. The influence of factors such as the molar ratio of reaction materials, reaction temperature, reaction time, the amount of sodium hydroxide for hydrolyzing, the temperature for hydrolyzing, and the time for hydrolyzing on the yield of polyaspartic acid are investigated. The reaction conditions are optimized for evry step. The optimized conditions for the synthesis of polyaspartic acid are: the molar ratio of maleic to urea is 1/0.95, the reaction temperature is 95℃, the reaction time is 3.75h; the optimized conditions for the synthezing of polysuccinimide are: the quality ratio of maleic ammonium to phosphate is 1/0.55, the reaction temperature is 190℃, the reaction time is 40min; the optimized conditions for the hydrolyzing of polysuucinimide are: the dosage of 2mol/L sodium hydroxide is 7.5mL, the hydrolyzing temperature is 45℃,the hydrolyzing time is 55min. The yield of polyaspartic acid is up to 83.0% under these optimized conditions. The IR and DT-TGA test are carried out for the product. The results show that the product is polyaspartic, and it has good thermal stability.Secondly, the influence of factors such as scale inhibitor concentration, calcium concentration, constant temperature, constant time on the scale inhibition of polyaspartic acid and its combination with polyacrylic acid or hydrolytic polymaleic anhydride are investigated. The results show that polyaspartic acid and its combination with polyacrylic acid or hydrolytic polymaleic anhydride have good scale inhibition. When the concentration of polyaspartic is 10mg/L, the scale inhibition rate is 93.64%; the concentration of polyaspartic acid and polyacrylic acid is 10mg/L, the scale inhibition rate is 95.81%; the concentration of polyaspartic acid and hydrolytic polymaleic anhydride is 10mg/L, the scale inhibition rate is 95.51%.Finally, the influence of factors such as corrosion inhibitor concentration, pH value, constant temperature, constant time on the corrosion inhibition of polyaspartic acid and its combination with zinc sulfate or sodium tungstate are investigated. The results show that polyaspartic acid and its combination with zinc sulfate or sodium tungstate have good corrosion inhibition.When the concentration of polyaspartic acid is 20mg/L, the corrosion inhibition rate is 77.93%; the concentration of polyaspartic acid and zinc sulfate is 20mg/L, the corrosion inhibition rate is 82.83%; the concentration of polyaspartic acid and sodium tungstate is 20mg/L, the corrosion inhibition rate is 83.50%.