![]() ![]() Limestone ore mainly consists of CaCO 3 and also contains minerals such as MgO, Fe 2O 3, Al 2O 3, and SiO 2, which are considered as impurities in high quality PCC manufacture. ![]() In general, PCC manufacture processes are divided into the three following steps: (1) quicklime (calcium oxide, CaO) is obtained by the calcination of limestone ore (calcium carbonate, CaCO 3), (2) CaO is turned into slaked lime (calcium hydroxide, Ca(OH) 2) through its reaction with water, which is called “hydraulic process”, and (3) PCC is manufactured by the reaction between Ca(OH) 2 and carbonate ions (CO 3 2−). It is, therefore, necessary to develop manufacturing technology for high quality PCC in Korea to foment a higher value added industry through the effective utilization of limestone. However, PCC is mostly being imported due to the absence of domestic commercial PCC manufacture technology to meet the demand. The demand of high quality PCC in Korea is gradually increasing along with the introduction of the eco-friendly paper process in the paper industry. Accordingly, the alkaline paper making process using PCC is called an “eco-friendly paper process”. Most of all, the process is more environmentally friendly due to following reasons: easier recycling of alkaline paper, less wastewater and by-product production from the process, and less energy consumption due to shorter refining and drying times. It reduces overall manufacture costs and needs fewer corrosive chemicals, thus extending machinery lifetime. Besides that, alkaline paper has several other advantages. This is a critical reason that PCC should be used in paper for library materials. The biggest benefit of alkaline paper made by adding PCC is a much longer life expectancy than that of traditional paper: more than 1,000 years for the best paper and 500 years for average grades. To address all these problems paper has started to be treated with PCC to neutralize the acids formed by the reaction between wood pulp and chemicals. Biological attacks by a variety of species including algae, bacteria, and fungi also shortened the life expectancy of paper. ![]() In addition, the color of acidified paper became yellowish under sunlight, and heat and humidity resulted in the rapid breakdown of the molecules holding the fibers together. In the traditional paper making process based on wood pulp without adding PCC, paper reacted with chemicals such as oxygen, carbon dioxide, and salts in the air, and was finally acidified by natural acid formation. Among those applications, PCC was introduced as a mild base filler in the acid-free paper (alkaline paper) making process in the 1950s, and in particular, PCC addition to paper is currently necessary for library books. Especially, precipitated calcium carbonate (PCC) manufactured from limestone ore is widely used as a raw material in the paper, paint, rubber, and plastic industries. Limestone resources have been introduced to various fields along with industrial developments. ![]()
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