Study On Superabsorbent Resin Of Buckwheat Starch Graft

The starch content in buckwheat was 70%, so it was a special starch resource. The construct of buckwheat starch particles was close, the rate of straight chain starch was pretty high, and also the branched-chain starch had more long-chains. At the same time, the water-holding of starch was so strong, the starch paste's peak viscosity, heat viscosity and final cold viscosity were all excellent. Starch super absorbent resins had many advantages such as available raw materials, lower production cost, good environment compatibility, convenient usefulness, etc. Thus, they were widely applied in numerous fields. In order to make super absorbent polymer that had high absorbent speed and certain salt tolerance, the preparation techniques of BSGAAA(buckwheat starch graft acrylic acid and acrylamide) and BSGAAAA(buckwheat starch graft acrylic acid,acrylamide and acrylate) was optimized with buckwheat as raw material, acrylic acid and acrylamide as monomer, ammonium persulfate as initiator, N,N′-methylene-bis-acrylamide as cross-linker under condition of protection by nitrogen. Synchronously, their construction,water-absorbing and water-holding capability were compared, the results as follow:(1)During the production process of BSGAAA, effects of initiator and cross-linker amount on absorbent rate were terrifically remarkable, effects of all factors on absorbent rate of BSGAAA appeared in turn as follow: initiator>cross-linker>starch> acrylamide, while fairish interaction existed between starch and initiator amount, initiator and acrylamide amount.The feasible condition for preparation of super absorbent polymer with BSGAAA was that: starch, initiator, cross-linker and acrylamide quantity were 20%, 0.96%, 0.12% and 10% of monomer amount, the reaction temperature was 60℃and neutralization value of acrylic acid was 85%. Under the condition, the absorbent rate of polymer produced was 640g/g.(2)The mathematical model of BSGAAAA preparation was:Y=524.121-14.112X₁-75.952 X₂ -73.832X₁²-26.102X₃²+47.500X₁X₂-25.000X₁X₃-17.500X₂X₃。Effects of all factors on absorbent rate of BSGAAAA showed in turn as follow: cross-linker ratio>starch ratio>neutralization value of acrylic acid. Thereinto, effects of cross-linker on polymer absorbent rate were wondrously notable, while prominent interaction happened among starch ratio,neutralization value of acrylic acid and initiator ratio. The optimum reaction condition of BSGAAAA preparation was: starch, initiator, cross-linker amount were 6.08%, 0.48%, 0.025‰of acrylic acid, the neutralization value of acrylic acid was 81.5%, the reaction temperature was 60℃. Under the condition, the absorbent rate of polymer produced was 680g/g.(3) The absorbent speed of BSGAAA was swift, and the best rate is 640g/g; the water-losing percentage of resin gel was 60% after one week's time; the absorbent multiple gradually declined when repeat absorbent test times increased; the absorbent rates of NaCl,CaCl2,MgSO4,KBr under the thickness of 0.1% were respectively 100,20,65 and 140g/g. comparing to each other, BSGAAAA had higher absorbent rate, salt tolerance, repeat absorption and the absorbent gel had better high temperature-resistance.(4) The absorbent ratios of polymer were seriously influenced by different drying processes. Under the same production conditions, the absorbent ratio of BSGAAA, produced with vacuum freeze drying method, was 640g/g, while with electric oven drying method, the ratio was just 400g/g. The absorbent ratio of BSGAAAA could even reach high to about 680g/g with electric oven drying method; by comparison, the absorbent ratio of BSGAAAA was remarkably higher than that of BSGAAA.