| With the global plant fiber resources shortage and price rise,more and more of the inorganic fillers were added to the paper in order to reduce the cost and improve the optical properties and printability of paper.But the strength of paper with high content fillers would be reduced greatly.Starch as a reinforcing agent for paper was widely to improve the strength of paper.However,the retention rate of starch in paper was low,and the pollution of white water was large by starch,which resulted in a low level of starch consumption.GCC was modified by starch to prepare starch-GCC composites,which could improve the strength of paper with high content fillers,but also could increase the amount of starch in paper and decrease on water pollution by starch.This paper had put forward a new insight into the structure and model of starch-GCC composites.Adding compound sulfate and polymerization aluminum chloride to reduce the solubility of starch in the system of starch-GCC composites.The properties of the starch-GCC composites and the application in paper were also carried out.The actual structure and the possibility of the formation of starch-GCC composites were studied through the aspects of morphological changes,particle size and distribution,analysis of surface elemental in the preparation of starch-GCC composites.The results showed that GCC with small filler particles was precipitated/absorbed on the larger starch granules,forming an irregular network,instead of an ideal core-shell structure.The effect of GCC system on the solubility of starch and the reduction of starch solubility in the starch-GCC composites system were investigated.Comparing with the distilled water system,the initial gelatinization temperature of starch decreased by 3.88℃ under the GCC system.When the gelatinization temperature was 95℃,the solubility of starch increased by about 53.17%.The single factor experiment was carried out to find that the ratio of GCC with starch,the place GCC addition,the amount of compound sulfate,the dosage of PAC played the important role on the solubility of starch in the starch-GCC composites system.The optimum conditions were found out through orthogonal experiments: the mass ratio of GCC with starch was 10:1,added for GCC after adding starch insulation,compound sulfate concentration was 3%,the amount of PAC was 0.6%,the solubility of starch decreased from 20.31% to 6.21%,reduced by 69.42%.The properties of the starch-GCC composites were characterized.Starch-GCC composites had good shear resistance.Comparing with GCC suspension,starch-GCC composites had better dispersibility and was not easy to settle.The sedimentation rate of the suspension of starch-GCC composites was only 1/3 of GCC suspension.The starch-GCC composites made the pulp performance of water filtration better.Under the same conditions,the water filtration rate of the pulp could be increased by about 10.51%,and the retention rate of starch was increased by about 64.46%.By using compound sulfate and PAC to reduce the solubility of starch in the starch-GCC composite system,both the retention rate of starch and the drainage performance of the pulp were improved,which made the filtration rate increase by approximately 14.37%,and the starch retention rate increase by approximately 21.85%.Under the same ash content,the tensile strength,bursting strength,stiffness,surface strength and tearing strength of starch-GCC composite filled paper were better than those of GCC and starch filled paper and GCC filled paper,and the strength performance was increased by 16% at least.After the compound sulfate and PAC were used to reduce the solubility of starch in the starch-GCC composite system,the tensile strength,burst strength,stiffness,surface strength and tearing strength of the paper filled with starch-GCC composite were further improved by 15%.In terms of optical properties,under the same content of GCC,the paper filled with starch-GCC composites wass slightly worse than the paper filled with GCC,the whiteness of the paper was reduced by 2.63%,and the opacity was reduced by about 6.01%. |
