Studies On The Preparation And Properties Of Super Absorbent Resin Made From Starch And Acrylic Acid

The preparation technologies of super absorbent resin from starch and acrylic acidwere studied in the paper. Super absorbent resin was prepared by drying the graftcopolymer, which was formed through grafting acrylic acid onto starch under nitrogenatmosphere, by using ammonium persulfate and N,N,-methylendiacrylamide as initiatorand cross-linking agent, respectively.The preparation process was shortened greatly forleaving out gelatinization of starch and saponification which was necessary to preparesuper absorbent resin through grafting acrylonitrile onto starch. In comparison with otherinitiator,such as [(H₂P₂O₇)₃]³-and Ce⁴⁺,ammonium persulfate was cheaper and moreobtainable .Firstly,graft copolymerization reaction conditions were studied. Effect of theamount of crosslinking agent,monomer and initiator, reaction temperature and time,starch slurry concentration and the neutralization degree of the monomer (pH) on graftcopolymerization reaction and water absorption of the resin was discussed. The optimumgraft copolymerization reaction condition was gotten through orthogonal experiment:starch slurry concentration 6.89%, pH 6.50, mass ratio of monomer and starch 5:1,reaction temperature 55℃, initiator2.50% and crosslinking agent 0.67% on the basis ofthe mass of starch, reaction time 4h, respectively. The distilled water absorption of theresin could reach 975 g/g. In comparison with the same kind of domestic productssynthesized by other researchers,the water absorption of the resin was superior.Secondly, effect of drying technologies on water absorption of the resin was studiedin detail. The influnce of different drying methods and conditions on granular structureof the resin and the starch within it was investigated by electron microscope and scanelectron microscope. The influncing mechanism of drying technologies on waterabsorption of the resin was analized on the basis of the experiment results, drying theoryand water absorption theory of the resin. The conclusion was that effect of dryingtechnologies on water absorption of the resin should be attributed to the changing ofcross-linking density of network structure of the resin. On the basis of analysis of the results, anopinion was presented for the first time, which was that controlling cross-linking density of thestarch-acrylic acid graft copolymers within certain range during graft copolymerization reactionwas favorable to the selection of the drying technologies and improvement of water absorptionof the resin.Then,other properties, such as water absorption speed, salt solution absorption,amount of residual monomer, and improvement of water absorption, water-retention andreabsorption of the soil were studied. The result showed that water absorption speed andsalt solution absorption were both superior. The resin can improve water absorption andwater-retention of the soil greatly, the reabsorption was much better.Finally, the preparation technology was applied to produce on pilot scale, the resultindicated that the distilled water absorption of the SAR could reach 560 g/g, it can makea profit about$ 3600 per ton, the technology could have good prospect on large scaleproduction.