Preparation Of Calcium Carbonate For Paper Making And The Study Of Its Reaction Kinetic

Rhombohedral and chrysanthemum calcium carbonate can be used as paper filling and coating, it would be advantageous to provide the paper some excellent properties, such as bulk, brightness, opacity, smoothness, writing suitability, printability and other properties. It is worth for us to investigate this item theoretically, and great economical benefits will be achieved. However the studies of this item have not been found in our country.The precipitated calcium carbonate is prepared by a reaction between carbon dioxide gas and a milk of lime obtained from a calciner of lime or the like. This method is popularly used in industries in the world with the reason that it can be controlled easily. In the embodiments, calcium oxide was mixed with water at a certain temperature, then the milk of lime obtained was screened through a mesh sieve to remove grit and heated to a starting carbonation temperature. A certain dosage of crystal-growing controling agent and dispersing agent were added. The slurry was carbonated to precipitate calcium carbonate by introducing a gas mixture of carbon dioxide in air into the slurry. The carbonation was continued until the pH value was less then 8.0. The product was filtered and the filter cake dried at approximately 105℃ for at least two hours to give a PCC product.The dynamics of this reaction was studied to give a guidance for the industrialization, and the reaction kinetic equation including the value of reaction orders, pre-exponential factor and activation energy were received. On the basis of reaction kinetic equation, the excellent technological condition preparation of calcium carbonate for paper making is determined in laboratory, and gained success in the industry. Sodium polyacrylate used as dispersing agent with molecular weight at 4000 was also studied, and a new method was obtained, the operation condition of this technological process is moderate, the properties of products was stable and not sensitive to the temperature,Through experiment, crystal-growing controling agent for rhombic shaped calcium carbonate is determined as A, and crystal-growing controling agent for chrysanthemum shaped calcium carbonate is determined as G The technology for preparation of this shaped product is as following: the carbonate temperature at 10℃-30℃, the concentration of calcium hydroxide is 137-159g/L, the concentration of carbon dioxide is 30% by valume, the dose of crystal-growing controling agent is 0.10-0.15% by weight of dried calciumcarbonate obtained and the dispersing agent is about 0.35% by weight of the dried PCC products, the crystal-growing controling agent and dispersing agent were added before carbon dioxide is introduced in to the slurry. The technology for preparation of sodium polyacrylate with molecular weight at 4000 is as following: the dose of catalyzer is at 8.8%, the concentration of initiator is 5.2%, the concentration of monomer is 38.7% by the total weight of reactant and the reaction temperature can be controlled at 30-40℃.