The Study On Starch Utilization Rate Of Ground Calcium Carbonate Modified By Starch And Its Stability Characterization At High Concentration

As the second raw material in papermaking process,fillers can significantly reduce production costs and improve the optical properties of paper,but the addition of fillers will affect the strength of paper because of different properties and components.As a major modification of inorganic mineral fillers,starch can improve the paper's physical strength on account of its low cost and environmental-friendly properties.Many scholars have studied inorganic mineral filler modified by starch,but utilization ratio and stability of modified starch fillers are urgently to be studied.Based on calcium carbonate and starch as the main raw material,starch-coated GCC was prepared by wet-modified to reach high utilization ratio and utilization rate of raw materials and then applied in the filling experiment to improve paper physical strength.The effect factors on utilization ratio and optical properties and strength properties were studied through single-factor experiment.The four influential factors were concluded in following sequence: stirring rate,dosage of sodium stearate,dosage of calcium chloride,the reaction time.Comprehensive analysis show that the stirring rate was 200 rpm,the reaction time of calcium chloride were 5 minutes,the dosage of calcium chloride was 12.8%(based on the dosage of calcium chloride),the dosage of sodium hexametahposphate was 2.5%.Utilization rate of starch reached 99.60% under this condition.Tensile index and tear index reached 65.25 N?m/g,12.67 mN?m2 /g,and whiteness and opacity reached 87.28% ISO,92.54% respectively.Based on comparison analysis of modified GCC and unmodified GCC,results showed that tensile index had an increase of 28%,tear index had an increase of 42% and burst index had an increase of 45% under the same ash content.Furthmore the ash content can improve 10% under the same paper strength.Relatively speaking,the paper with modified GCC filler has better water resistance than that of unmodified GCC paper.Overall retention rate of paper with modified GCC was higher than that of paper with unmodified GCC.The SEM showed that GCC surface was smooth and had starch-fatty layer on the surface with uneven thickness.It can be seen that the amount of modified GCC were perfectly filled into the pores of the fiber of paper.The stability of modified GCC is characterized by the change of particle size of GCC before and after modification.The modified GCC particle size and its distribution are not obvious at different shear velocity and shear time.All in all,the stability of modified GCC is better.