Preparation and Its Performance of Rectorite/Poly(Sodium Acrylate-Co-Acrylamide) Superabsorbent Composite

The effect of three different types of purification processes (roasting-magnetic dressing, acid pickling and calcining) on the sulfur content of rectorite clay (pyrite content 4.37%, sulfur content 2.32%) was investigated. By roasting-magnetic dressing, the sulfur content was reduced to 0.52% when roasting at 300 ℃ for 2 h and magnetic dressing twice; By acid pickling, the sulfur content remained 0.57% under the condition of 60 ℃ and acid pickling for 1 h with 60% nitric acid solution; By calcining, 0.78% of sulfur was left if calcined for 0.5 h at 550 ℃. The experimental results indicate there is no obvious inhibition effect (corresponding maximal sulfur content 0.78%) when rectorite/poly (sodium acrylate-Co-acrylamide) is synthesized by in-situ aqueous solution polymerization with the purified rectorite clay as material. At 65-70 ℃, the water absorbencies (WA) of superabsorbent composite (containing 20% purified rectorite clay, 15% acrylamide, 0.25% initiator and 0.08% cross linker, with the neutralization degree of acrylic acid being 80%) in distilled water, tap water and 0.9% NaCl (aq) are 870, 250 and 68 respectively. When the content of rectorite is between 0%-30%, WA of superabsorbent composite is higher than that of superabsorbent resin that contains no rectorite. When WA of superabsorbent composite in distilled water is reduced from 870 g/g to 84 g/g, its gel strength rises from 49 g/cm² to 235 g/cm².