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GCC and Starch modified calcium carbonate2021-01-22 15:17:08

1. Heavy calcium carbonate
Ground calcium carbonate is ground calcium carbonate (GCC). Heavy calcium carbonate is a natural calcium carbonate made by grinding limestone. It has developed from dry grinding to wet grinding. The breakthrough in grinding technology and the application of related additives in the grinding process enable the GCC particle size to reach less than 1.5μm in More than 90%, the average particle size is less than 2μm, which greatly improves the quality and greatly expands the application in the papermaking field. However, as the calcium carbonate filler load increases, the strength, bulk and stiffness of the paper will generally decrease. The filler cuts off the bond between the fiber and the fiber, causing paper damage and limiting the amount of filler added. Therefore, heavy calcium carbonate needs to be modified before adding.
According to research, using starch and modifier compound modification method, the amount of starch is 50% of the weight of heavy calcium carbonate, the amount of modifier stearic acid is 20% of the weight of heavy calcium carbonate, the gelatinization temperature is 65℃, and the gelatinization The time is 120min, and the holding time is 10min. The obtained modified heavy calcium carbonate is added to paper, which greatly improves the physical properties of the paper, and can significantly increase the bonding strength of paper fibers and fibers, and fibers and fillers. When the amount of calcium carbonate is 30% to 40%, compared with unmodified calcium carbonate, modified calcium carbonate can significantly improve the tensile strength, tear strength, and flexural strength of paper; the optical properties of the paper are also changed. The whiteness and opacity of filler paper is lower than that of unmodified filler paper; the particle size of the particles has changed greatly, and the surface area is reduced from 12576.54cm2/g to 4203.79cm2/g.
2. Starch modified calcium carbonate
With the rapid development of alkaline papermaking, the amount of calcium carbonate filler in the papermaking industry has increased sharply, but the problem of low strength and poor retention of calcium carbonate filled paper has not been effectively solved. At present, the research on the modification of calcium carbonate at home and abroad mainly focuses on the coating modification of starch and chitosan polymers, the cationization of calcium carbonate surface and acid-resistant treatments [5-8]. Among them, starch has a low price and has a fiber-reinforcing function. After the calcium carbonate is modified, the strength of the paper filled with it will increase significantly. However, the starch coating process is complicated and difficult to operate, and the starch coating layer is easily soluble in water under papermaking conditions, which affects the application of starch-coated calcium carbonate fillers in papermaking.
 

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