1. For exterior wall coatings, the content of SiO2 in ground calcium carbonate should be as low as possible (generally less than 5%), considering the adverse effect of SiO2 on the weatherability of the coating.
2. In anticorrosive coatings, ground calcium carbonate is often used in conjunction with light calcium, and the presence of ground calcium carbonate only assists in adjusting the CPVC value of the coating. Because it is easy to cause the bottom, and the introduction of anti-settling agent generally has some effect on the water resistance.
3. Ground calcium carbonate for paper coating requirements than the general coating to be higher. It is reported that the use of heavy calcium in pulp has better reinforcing effect than light calcium.
As ground calcium is unstable under acidic conditions, it is generally suitable for alkaline papermaking, and when heavy calcium is used, the whiteness, opacity and printability of the paper are significantly improved compared with acid paper containing talcum powder.
From the present situation, alkaline sizing papermaking is the development trend of papermaking industry. As paper coating grade heavy calcium, particle size is generally controlled under 2 micron.
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