Synthesis And Performance Research Of Polyaspartic Acid Derivative

Polyaspartic acid (PASP) is a kind of biodegradable environmentally friendly scale inhibition dispersing agents. Its performance of dispersion, scale and corrosion inhibition, however, is worse than the other scale inhibition dispersing agents. So it is important to improve its performance of dispersion, scale and corrosion inhibition by research on modified PASP. In this paper, functional groups are introduced in the side chain of PASP in order to develop an environmentally friendly and high-efficient water treatment chemical use in industrial circulating cooling water system.For the purpose of increasing scale inhibition rate, two polyaspartic acid derivatives (PASP-ASP and PASP-SEA-ASP) were prepared from polysuccinimide (PSI) that was thermal condensation polymer of aspartic acid (ASP), taurine (SEA) and ASP. The polyaspartic acid derivatives were separated and purified made use of property of isoelectric point of amino acid and color reaction of amino acid and ninhydrin, and their grafting ratios were mensurated. The structure of polyaspartic acid derivatives were characterized by means of FTIR and elemental analyzer. The effect of the synthesis conditions, such as mole ratio of materials, reaction temperature and reaction time, on the grafting ratios of polyaspartic acid derivatives were studied, and the suitable synthetic reaction conditions were optimized. The mechanism of reaction was nucleophilic addition-elimination reaction. The relationships between the performance of scale inhibition, dispersion, corrosion inhibition and grafting ratios of polyaspartic acid derivatives were studied, Their respective action of different group on process of dispersion, scale and corrosion inhibition were researched. The results showed that the carboxylic acid group was introduced in molecular structure of PASP helped improvement of scale inhibition performance and corrosion inhibition performance, and the sulfonic acid group was introduced helped improvement of dispersive performance, but worsen performance of scale inhibition. In addition, the scale inhibition performance of polyaspartic acid derivatives on calcium carbonate was investigated under the conditions of different dosages, water temperature, water hardness and experiment time, and then the quantitative relationship between the scale and corrosion inhibition rate and the factors above mentioned was determined.The dynamic dirtiness resistance and the dynamic scale inhibition rate of polyaspartic acid derivatives were investigated by dynamic experiments. Both the static and dynamic experiments showed that the dynamic dirtiness resistance of polyaspartic acid derivative that functional groups of possess scale inhibition and dispersion performance were introduced in molecular structure of PASP synchronously was less under less dosage, and the dynamic scale inhibition rate could reach 99.35 % under PASP-SEA-ASP 0.5 mg·L^-1; And the dynamic dirtiness resistance of polyaspartic acid derivative that functional groups of possess scale inhibition performance was introduced in molecular structure of PASP only was less under bigger dosage, and the dynamic scale inhibition rate can reach 96.13 % under PASP -ASP 1.5 mg·L^-1. Because sulfonic acid group take dispersive effect that made the calcium carbonate crystallite not to adhere to heating stick and to disperse in water under less dosage. The proportion of sulfonic acid group was bigger that made function of chelating Ca2+ ion of carboxylic acid group was weaken and then the formed CaCO₃ deposition was more, so overmany CaCO₃ deposition should adhere to heating stick and the dynamic scale inhibition rate could minish when dosage was bigger.The calcium carbonate crystal samples were characterized by SEM and FTIR techniques and the results of the static and dynamic experiments showed that the crystal form of calcium carbonate was global vaterite after polyaspartic acid derivative was added that possessed excellent dispersive performance, and the crystal form of calcium carbonate was similar global vaterite after polyaspartic acid derivative was added that possessed excellent scale inhibition performance. The mechanism of corrosion inhibition was studied by EIS and SEM techniques and the results showed that the face of electrode that absorbed polyaspartic acid derivative was dense and high ordered, and nonpolar group that was–R was directional arranged on the surface of metal and hydrophobe membrane was formed, and that prevent from transfer of charge or matter that was relevant to corrosive reaction. Then that slowed corrosion rate of metal down.