Nano kaolin means that the particle size of kaolin is processed to the nanometer level, and one nanometer is equal to one-thousandth of a micron.
Washed kaolin is to wash the kaolin ore with water to remove coarse sand and impurities. The particle size is usually above 325 mesh. The particle size of 325 mesh is about 43 microns, that is, 43,000 nanometers.
Calcined kaolin is kaolin with sufficient purity, which is fired at high temperatures and then ground. The purpose is to purify and improve whiteness. The firing temperature varies according to the customer's product requirements, ranging from 900 degrees to 1300 degrees.
This difference is huge.
First of all, calcined kaolin is calcined, and the crystal form and original soil have changed; while washed kaolin is only physically treated and will not change the properties of the original soil.
Secondly, the whiteness difference is relatively large. Generally, the whiteness of kaolin will increase after light burning, while water washing will not significantly increase the whiteness.
Third, the uses are different. According to different calcination temperatures, kaolin can be used as a papermaking additive and refractory aggregate. Washed kaolin is generally used as a papermaking filler.
Moreover, calcined kaolin currently mainly refers to hard kaolin (coal-based kaolin). The original soil has no adhesiveness and cannot be directly used as a raw material for papermaking or refractory materials. It needs to be calcined before application; the original soil of washed kaolin has adhesiveness and can be directly used as a refractory binder or papermaking filler.
As a papermaking filler, the whiteness of calcined kaolin is much better, and the cost is also relatively high.