Aspartic Acid Monomer And Its Polymers

Aspartic acid is one of the twenty kinds of basic aminos which make up the protein, it has been used in biochemical reagents and clinical medicine . Poly(aspartic acid) has been found to be able inhibit scale in water and promote the ability for crops to absorb nutrition. Since it is completely biodegradable it belongs to green chemical. Research on aspartic acid and poly(aspartic acid) has become a central issue abroad while there is few reports about it in China until now. In this article, some novel technologies has been developed for the synthesis of aspartic acid and poly(aspartic acid). These technologies can be described as below: Aspartic acid is synthesized by the reaction of maleic anhydride and ammonia in water in a autoclave and the mother liquid is acidified by maleic acid for reduction the waste. Poly(succinimide) is synthesized by the directly reaction of maleic anhydride and ammonia in water. The hydrolysis kinetics of Poly(succinimide) was investigated. In addition, the performance of the product of poly(aspartic acid) to inhibit scale was investigated.The present aspartic acid synthesis method has many advantages over the traditional technologies. The optimal reaction conditions are: 41.8 g maleic anhydrde, 135 ?, 80 ml H2O, pH=9.5, 1.2 MPa, reaction time 4.5 ~ 5.0 h. acidified by hydrochloric acid, pH=2.5, acidified by maleic acid, pH=3.5 ~ 4.0. Under these conditions, the yield of aspartic acid was above 70% which much higher than those reported in the literature and the purity more than 95%.Poly(aspartic acid) can be obtained from maleic anhydride and ammonia. Poly(succinimide) is synthesized by the directly reaction of maleic anhydride and ammonia in water by controlling the process conditions. The optimal reaction conditions are: the ratio of ammonia and maleic anhydride is 1.1, 165?, reaction time 4 min. After hydrolysis of Poly(succinimide) with base, poly(aspartic acid) is obtained.The performance of poly(aspartic acid) in scale inhibition shows that the scale inhibition efficiency of poly(aspartic acid) can reach to 94.7% when pH value was 8.0.Kinetic studies of poly(succinimide) shows that the hydrolysis of poly(succinimide) obeys the shrinking core model. The active energy of the reaction between poly(succinimide) and NaOH was 75.1 kJ/mol.