Barite is a sulfate mineral of barium. The main component is BaSO4. It has the characteristics of high density, stable chemical properties, non-magnetic and toxic. It is widely used in petroleum, chemical industry, light industry, metallurgy, medicine, agriculture, atomic energy, and military and other fields.
As an extender pigment, barite powder is widely used in the field of paints and coatings, and plays an important role in improving the thickness, abrasion resistance, water resistance, heat resistance, surface hardness, and impact resistance of the coating film.
The barite powder products used in paints and coatings should not only have high purity, but also have fine particle size. Therefore, in addition to ore beneficiation and purification, ultra-fine crushing processing and surface modification are also required.
(1) Superfine crushing
Barite has low Mohs hardness, high density, good brittleness, and is easy to crush. Therefore, the ultra-fine grinding of barite mostly adopts dry process. Commonly used equipments include jet mill, mechanical impact mill, vibration mill, etc. Among them, the air jet mill can pulverize barite to d97≤5μm. If the ultra-fine pulverization is carried out after the wet beneficiation and purification, the wet ultra-fine pulverization process can also be used, and the equipment can be a stirring mill, a vibration mill, a ball mill, etc.
(2) Surface modification
Because the surface of barite powder is hydrophilic, its application in organic systems is subject to certain restrictions. The purpose of surface modification is to modify its dispersibility in organic systems, prevent precipitation and agglomeration when used in paints, and increase the gloss, toughness, and adhesion of the paint film.
There are many methods for surface modification of barite powder, such as surface chemical coating, precipitation reaction coating, and surface chemistry supplemented by mechanochemistry. Various surface modifiers such as surfactants, coupling agents, inorganic oxides, etc. can be selected according to different application fields.
The experimental research results show that: barite powder modified with a surface modifier containing COOH, OH, SO3 functional groups not only has high activation index, good dispersibility and fluidity, but also has good application effects, which can meet the requirements of red alkyd. Index requirements for blending paint.
In the paint industry, barite powder is required to have sufficient fineness and high whiteness.
Coatings are an important downstream application field of non-metallic mineral powders, and China is the world's largest paint producer. In 2017, the output of coatings reached 20.41 million tons. With the rapid development of the coating industry, the demand for barite powder is increasing, the quality requirements are becoming more and more stringent and diversified, and the market products tend to be functional and refined.