Synthesis And Characterization Of Modified-Attapulgite/ Polyspartic Acid Compound Absorbent Resin

Ploy(aspartic acid) (PAsp) is a novel low cross-linked functional polymer material with strongly hydrophilic functional groups, such as carboxyl group and hydroxyl et al. PAsp can absorb much water without being dissolved in it. However, the application fields of pure PAsp are limited due to its various defects, such as poor salt resistance, arising from the uni-structure of PAsp. Thus in this paper, modified-attapulgite/poly(aspartic acid) (MATP/PAsp) compound absorbent resin was prepared by using PSI synthesized from the thermal polycondensation of L-aspartic acid as well as attapulgite having been modified by silane coupling agent y-aminopropyl triethoxysilane (KH-550) as raw material, N, N-dimethyl formamide (DMF) as benign organic solvent, 1,6-hexamethylenediamine as crosslinking agent, respectively. Influence factors of capabilities of MATP/PAsp composite resin were investigated, and the synthesis conditions were optimized. In addition, characterizations for resin were also accomplished.Firstly, in the process of the preparation of PAsp water absorbent resin, the affect elements, including concentration of PSI, additional amount of crosslinking agent 1,6-hexamethylenediamine as well as reaction temperature, for its absorbent properties were discussed. Consequently, optimization criterias for synthesis of PAsp were obtained. Moreover, effect of dispersant on the absorbent performances of PAsp was also investigated. In this paper, In the process of synthesis of PAsp superabsorbent polymer, de-ionized water, methanol, ethanol and n-butanol were added into the solution of PSI(viscosity-average molecular weight:94647), respectively, and a homogeneous system was achieved. After that,1,6-hexamethylene diamine acted as cross-linking agent was added. Finally, biodegradable superabsorbent resin with three-dimensional structure was prepared. For further identification of microstructures of this resin, transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and thermo-gravimetry analyses (TG) had been used. In this paper, by comparing the influence of these four kinds of dispersants on the water absorption performances of PAsp resin, it was concluded as follows:whichever dispersant, when added moderately, could markedly improve the water-swelling ratio of PASP resin, whereby, water was prefer. The PAsp polymer using water as dispersant had a 945 g·g-1 water-swelling ratio in de-ionized water and 94 g·g-1 in a 0.9% sodium chloride solution; While n-butyl alcohol was served as dispersant, there was a higher fluid absorption rate for the PAsp resin, which could reach swelling equilibrium in 7 hours. In addition, when mixed solvent composed of deionized water and n-butanol, the mass ratio of which was 7:3, was used as dispersant, the water absorption performance of resin was superior to pure water and pure butanol. The resin could reach swelling equilibrium in 6 hours, and its water-swelling ratio in deionized water was up to 1004 g.g-1.The absorbent properties for PAsp resin would gradually decrease with the increasing of drying times. After 5 times, the swelling ratio of PAsp could still achieve 400 g.g-1, indicating that the resin had a good repeated bibulous performance.Water-superabsorbent resin presents excellent absorption performances in distilled water but poor tolerance in salt solution. While inorganic hedrogels (especially clay hrdorgels) were proved to display good salt tolerance in spite of bad stability. It was assumed that the properties of water-absorbent resin, especially salt tolerance, could be improved by the introduction of clays, such as kaoline, montmorillonite, attapulgite and so on. What’s more, another benefit of introduction of org-clay was to reduce the production cost of water absorbent resin.In this work, MATP/PAsp composite superabsorbent resin with 3-D network structure was prepared by the method of solution polymerization, wherein we used polysuccinimide(PSI, viscosity-average molecular weight: 78979) and attapulgite(ATP) as raw material, y-aminopropyl triethoxysilane (KH550) as the modifier, and 1,6-hexamethylenediamine as the crosslinking agent.For further identification of microstructures of this resin, transform infrared spectroscopy(FTIR) and scanning electron microscopy(SEM) were adopted. Influences of the particle size, addition, and Modification time.on the absorption performances of resin were investigated respectively. It was found that there is a significant improvement in micro structure with the introduction of MATP, and the water absorption and retention performance were also increased. The optimum MATP/PAsp composite resin was obtained under condition of particle size range of 0.047mm-0.054mm, addition dopant of 2 wt%, modification time of 6.5h. The bibulous multiple of composite resin in distilled water and normal saline were 892g/g and 95g/g, respectively, which were better than uncomposite resin samples obviously. The water holding ratio for composite resin was measured to be 66.12%after 6h’s constant temperature drying at 50℃, which is higher by 7.72% than none-composite resin.