| Calcium carbide residue is a by-product of acetylene production process that can pollute the environment. So far, there is not a good way to handle the carbide slag and the value-added of products is not high. Calcium carbonate is low-cost filler and white pigment, which is widely used in plastics, rubber, paper and daily necessities, especially ultra-fine calcium carbonate that is compatible with polymer and improve polymer physical properties. So using carbide slag as raw materials produce high demand ultra-fine calcium carbonate, which is undoubtedly the best way to deal with carbide slag. The main research contents and conclusions are illustrated as follow:1. Using carbide slag as raw material and propionic acid as the leaching agent that could remove the impurities of carbide slag. In this process, the leaching agent mechanism was studied and the effect of the amount of leaching agent for leaching rate of Ca2+. Preparation of ultra-fine calcium carbonate was coated propionic acid by liquid-liquid continuous reaction. Studing on the Ca2+concentration, the amount of Na2CO3, dropwise and the stirring rate affected product purity, particle size, particle size distribution and the best process conditions were determined by single factor variable method and L16(44) orthogonal experiment method. In addition, the FT-IR, XRD and SEM were used to characterize the product. The results showed that calcium carbonate was spherical particles, the particle size between about2μm to4μm. The surface of calcium carbonate was coated with a certain amount of organic matter and the polymorph of calcium carbonate was calcite crystal form.2. The calcium carbonate obtained by the above liquid phase method (Z-CaCO3), Zhejiang linghua activity of precipitated calcium carbonate (L-CaCO3) and Zhejiang linghua nano calcium carbonate (N-CaCO3) according to10%,20%,30%and40%of the amount of filler filled polyvinyl chloride (PVC). The PVC/CaCO3was prepared GB/T1040-2006standard tensile spline by two-roll mill and tablet rheometer and then the mechanical and rheological properties of standard tensile spline were tested. The results showed that10%Z-CaCO3filling PVC had highest tensile strength (20MPa) much better than the other two types of calcium carbonate filling. The elongation at break and rheological properties had not significant difference.3. Using carbide slag as raw material and ammonium chloride as the leaching agent that could remove the impurities of carbide slag. In this process, the leaching agent mechanism was studied and the effect of the amount of leaching agent for leaching rate of Ca2+. Preparation of ultra-fine calcium carbonate was coated oleic acid by microemulsion method. Studing on Ca2+concentration, the concentration of ammonium carbonate, W (molar ratio of oil and surfactant), the ultrasonic power and the amount of n-butanol affected product purity, particle size, brightness, oil absorption, hydrochloric acid insoluble matter content and the content of iron by L16(45) orthogonal experiment method. According to the results of L16(45) orthogonal experiment, the best process conditions were determined. In addition, the FT-IR, XRD, SEM and TG were used to characterize the product. The results showed that the morphology of calcium carbonate was pinecone shape, the particle size between about800-1200nm and the polymorph was vaterite crystal form. The surface organic content of calcium carbonate was3.5%and the mechanism of organic coated was elaborated.4. The calcium carbonate obtained by the above liquid phase method (Z-CaCO3), Zhejiang linghua activity of precipitated calcium carbonate (L-CaCO3) and Zhejiang linghua nano calcium carbonate (N-CaCO3) according to10%,20%,30%and40%of the amount of filler filled polypropylene (PP). The standard tensile, bending and impact spline were prepared through the extruder melt blending and injection molding machine. Then, the mechanical and rheological properties of standard tensile spline were tested. The results showed that regardless of the filling amount was high or low filling amount, Z-CaCO3filling PP could have the greatest tensile and flexural strength much better than L-CaCO3and N-CaCO3filling PP, the maximum tensile strength could be achieved34.5MPa and the maximum bending strength could be achieved42.8MPa. The rheological properties indicated the melt viscosity of PP/CaCO3composite which filled by Z-CaCO3and L-CaCO3decreased with the increase of calcium carbonate content. These maybe the surface of Z-CaCO3and L-CaCO3were coated by organic matter. However, PP/N-CaCO3emerged the opposite result because of the surface of N-CaCO3having little coated by organic matter. Further, the PP matrix compatibility with the CaCO3could be observed by SEM. The results showed that the three kinds of calcium carbonate compatibility with PP matrix were relatively good in low fill. At30%and40%loading, L-CaCO3and N-CaCO3appeared aggregates in the PP matrix. However the Z-CaCO3in the PP matrix remained well dispersion. |
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