Preparation Of Oxidized Starch By TEMPO Catalyst System And Research Of Its Applications

With TEMPO/NaBr as catalyst, corn starch was oxidized by NaClO. The preparation of glucuronolactone by oxidized starch and the application of oxidized starch at surface sizing were studied. The main work and conclusions are as follows.1) Effect of amount of NaClO, pH, reaction temperature, reaction time on the amount of carboxyl content of the product and yield of oxidized starch were researched. As the results showed, the most important factor was pH, and then were reaction time, oxidant amount and reaction temperature. The optimum reaction conditions were as follows, reaction time 2.5 hours, pH 10.5, temperature 0℃, the amount of NaClO 35% of starch while carboxyl content of oxidized starch reached the highest 5.30% and yield was 88.83%.2) Structure of oxidized starch was characterized by Scanning Electron Microscopy (SEM). Result showed that there was carboxyl group in oxidized starch. From the result of Infrared Spectroscopy (IR) analytic we can find that starch surface damage became severer when oxidation degree increased. Oxidation took place not only on the surface of starch, but also inside the particle.3) Effects of kinds of acid, acid concentration, reaction time on the hydrolysis of oxidized starch were studied. The results showed that the catalytic efficiency of HCl was slightly higher than that of H₂SO₄ in the same conditions. When concentration of HCl was 0.1 mol/L and reaction time was 2 hours, concentration of glucuronic acid in hydrolysate reached the highest .4) Lactonization of hydrolysate occurred in acetic acid after dewater treatment. Effects of temperature, amount of acetic acid on yield of glucuronolactone were investigated. The best conditions of lactonization were as follows, reaction temperature 65℃, amount of acetic acid 0.5mL/g corn starch while yield of glucuronolactone was 17.73%. The purity of the sample was 93.03%, melting point was 176¹79℃, specific rotation at 25℃was +20.25°(H2Osolution).5) Oxidized starch with different carboxyl content were used as surface sizing agent. Relationship between starch oxidation degree and surface sizing effect was studied. Experiment showed that, sizing effect of corrugated medium was the best while carboxyl content of oxidized starch was 0.30%.The best sizing effect of cultural paper was achieved when carboxyl content was 0.75%.