Calcium content is an important quality and technical index of calcium carbonate. The modified masterbatch has higher requirements on the calcium content of calcium carbonate, generally above 98%. The higher the calcium content, the more stable the processing properties of calcium carbonate. When the calcium content is low, the content of impurities such as heavy metals and other non-metals will increase, which not only affects the use of calcium carbonate, but also affects the processing technology, affecting product quality or causing harm to processing equipment.
The whiteness of calcium carbonate directly affects the whiteness and colorability of the modified masterbatch. Modified masterbatch has very strict requirements on the whiteness of calcium carbonate. At present, the whiteness of 400-mesh calcium carbonate is required to reach more than 95%, and the whiteness of some ore processed calcium carbonate can reach about 97%. In order to improve the whiteness of the products, some manufacturers of modified masterbatches often add fluorescent whitening agents to achieve the effect of increasing the whiteness. However, because the chemical components of the fluorescent whitening agent are prone to decomposition under high temperature and high shear, if the type of fluorescent whitening agent is improperly selected or added in excess, the product will not only decompose and turn yellow, but also cause non-dispersion or non-dispersion. Agglomeration phenomenon. Fluorescent whitening agents are irritating to plastic products that involve hygiene and safety and are in contact with the human body and should not be used.
Hue is also a very important technical indicator of calcium carbonate. The determinants of temperature and hue are the structure and source of the ore. These factors will directly affect the colorability of plastic products, affecting the color and gloss of plastic products. Therefore, the whiteness and hue of calcium carbonate are important technical indicators that cannot be ignored.
The raw materials of calcium carbonate – natural marble, calcite, etc., generally do not contain structural water. After being processed into ultra-fine powder, it is easy to be affected by moisture and absorb moisture during processing, storage and transportation. Calcium carbonate sometimes contains a small amount of volatile substances, if the content of these substances is too high, it will affect the modified masterbatch and plastic products.
The content of moisture and volatile matter in calcium carbonate should generally be controlled at about 0.3%. In practical application, when the moisture content in the product is greater than or equal to 0.3%, it will easily affect the quality of the product, make the surface of the product rough, produce bubbles, burn, decompose, etc. Phenomenon. Therefore, controlling the moisture content is very important to the quality of the modified masterbatch. The commonly used method is to use a high-speed mixer to heat and dry to eliminate moisture.
In the production of high content of calcium carbonate filled and modified masterbatch, the use of water tank infiltration and strand granulation and water ring granulation should be avoided as far as possible. , which can minimize the moisture and volatile content of the modified masterbatch on the premise of increasing the production output, and can ensure the product quality of the modified masterbatch.