Study On Compound Modified Starch And Sizing

At present,the development trend of pulp is to research and develop high-performance low-viscosity modified starch slurry.Single modified starch slurry can not fully meet the demand,so it is very meaningful to study high-performance low-viscosity modified starch.In this dissertation,corn starch is used as the raw material for irradiation treatment,and the surface morphology,structure and performance characteristics of the irradiated powder are studied.Then,the irradiated powder is used as the raw material for oxidation and enzymatic treatment to obtain the oxidized starch and the irradiation The surface morphology,structure and properties of the composite modified starch were studied by enzymatic hydrolysis.Finally,the composite modified starch,irradiated powder and raw starch were used to make a slurry,and the slurry and sizing properties were measured.Using carboxyl content as index and irradiated powder as raw material to carry out oxidation experiments,the optimal conditions were obtained: hydrogen peroxide amount 8%,p H = 9,oxidation time t = 3h,oxidation temperature T = 45 ° C,and catalyst amount 0.1%;Using starch viscosity as an index and irradiated powder as raw materials to perform the enzymatic hydrolysis experiment,the optimal conditions were obtained: the enzymatic hydrolysis temperature T = 60 ° C,the enzymatic hydrolysis time t = 60 min,the amount of enzyme was 0.5 ‰,and the p H of the enzyme was 6.Microscopic observation found that the irradiation of small starch particles increased,the surface profile of the starch became more round,and the surface became smoother and smoother;the irradiation of oxidized starch increased the number of irregular particles,the particles appeared broken,and the surface became rough;The particle morphology is similar to that of irradiated powder,and cracks and holes appear on the surface of starch particles.Irradiated starch,the linear content increased,and the branched content decreased.Irradiated powder produces free radicals,reducing molecular weight and degree of polymerization.Each carbon site of the oxidized oxidized starch has an oxidation reaction,which selectively oxidizes the C2,C3,C4 and C6 sites.DSC results show that the initial gelatinization temperature of oxidized starch decreases and thegelatinization enthalpy value decreases;the peak gelatinization temperature and endpoint gelatinization temperature of irradiated enzymatic starch decrease,and the gelatinization enthalpy value increases.The viscosity of irradiated starch decreases,and the viscosity stability first increases and then stabilizes;the viscosity of irradiated oxidized starch further decreases,the viscosity stability continues to increase within 10 k Gy,and the irradiated enzymatic starch is below 10 k Gy,the viscosity decreases,and the viscosity stability continues to increase.The gelatinization temperature of the irradiated starch decreases;the gelatinization temperature of the irradiated powder decreases after oxidation or enzymatic hydrolysis.The transparency of the irradiated powder within 20 k Gy increases,and the settling ability decreases;the transparency of irradiated oxidized starch increases,and the settling ability decreases;when the enzymatic hydrolysis of starch below 20 k Gy,the transparency increases,the radiation dose increases,the transparency changes little,and the set Declining sinking.The sizing test was performed by mixing raw starch,irradiated powder,irradiated oxidized starch,and irradiated enzymatic starch to form a sizing test.The test found that the properties of modified starch sizing and sizing were better than the original starch,and that of oxidized composite modified starch Sizing and sizing are the best.Irradiation,oxidation and enzymolysis will destroy the surface structure of starch.Irradiation will increase amylose content.Oxidation will introduce a large number of carboxyl groups.Irradiated oxidized starch is easier to gelatinize than irradiated enzymatic starch.Below 20 k Gy,Or enzymatic hydrolysis can reduce the viscosity of irradiated powder,and can improve the transparency of starch paste,reduce the settling property,the performance of composite modified starch sizing and sizing is better than single modified starch sizing.A low-viscosity and high-performance slurry was prepared,and the performance of the irradiation-modified composite modified slurry was the best.