The surface modification technology of calcium carbonate powder is to improve the mechanical properties, chemical properties and mechanical properties of calcium carbonate powder in plastics, rubber and other fields, improve the application performance of calcium carbonate powder, and broaden the application line of the market. The methods for surface modification of calcium carbonate powder are mainly divided into five categories: inorganic surface modification, organic surface modification, polymer surface modification, mechanochemical modification and high-energy surface modification.

 

 

 

Surface modification is an important processing technology necessary to improve the application performance of calcium carbonate, improve applicability, expand the market and dosage. At present, there are mainly inorganic surface treatment, organic surface modification, polymer surface modification, mechanochemical modification and High-energy surface modification.

 

 

 

 

The surface properties of calcium carbonate powder are closely related to the origin of the original ore. Generally speaking, it has the disadvantages of poor acid resistance and high pH, ​​which limits its application scope and usage to a large extent. Treating calcium carbonate with an inorganic surface modifier can produce a double electrostatic layer on the surface of calcium carbonate, thereby reducing the mutual repulsion between particles and reducing the occurrence of accumulation. At the same time, the hydrophilicity of calcium carbonate is increased, so that calcium carbonate can be well wetted in water, thereby increasing the dispersion performance and expanding the scope of application.

 

 

Organic modification mainly refers to the use of chemical or physical methods to wrap the organic modifier on the surface of calcium carbonate to change the surface properties of calcium carbonate, so as to increase interfacial compatibility and reduce mutual agglomeration of powders. It is the most mainstream of calcium carbonate. The surface modification method.

 

 

The commonly used powder modifiers mainly include: fatty acids (salts), phosphate esters, quaternary ammonium salts, silane coupling agents, titanate coupling agents, aluminate coupling agents and composite coupling agents.

 

 

 

Polymer surface modification refers to the formation of a core-shell polymer layer on the surface of calcium carbonate particles. Polymer-modified calcium carbonate has two main situations: one is that monomers on the surface of calcium carbonate are polymerized to form polymer segments; the other is to dissolve the polymer in a suitable solvent to form a polymer solution, and Calcium carbonate is added, and when the polymer gradually adsorbs to the surface of calcium carbonate, the solvent is removed to form a coating. In this way, the polymer can be oriented to adsorb to the surface of calcium carbonate to form an effective adsorption layer, reduce the agglomeration of calcium carbonate particles, improve dispersibility, improve the disadvantages of poor dispersibility of calcium carbonate during use, and achieve the purpose of surface modification

 

 

Mechanochemical modification mainly uses strong mechanical force to activate the surface of calcium carbonate particles, and the crystal structure of the calcium carbonate surface changes, which makes the crystal lattice move to a certain extent, thereby reacting with other substances. Be enhanced.

 

By adopting the method of styrene monomer polymerization and grafting, Wu Wei et al. used mechanochemical methods to promote the polymerization of styrene monomer on the surface of calcium carbonate, reducing the amount of initiators, and improving the high impact resistance of polystyrene (HIPS). ) The mechanical properties increase the compatibility between the filler and the matrix.

 

This method is mainly aimed at calcium carbonate with relatively large particles, but for nano-calcium carbonate, due to its small particle size, mechanical force does not improve it very well, but it can activate some active sites on the surface. And groups can enhance the interaction with the surface modifier of organic powder, so the method of combining mechanochemistry and other modification methods can be used to modify the nanometer calcium carbonate.

 

 

High-energy surface modification mainly uses high-energy rays, plasma and other methods to modify the surface of inorganic powders. This method mainly relies on high-energy rays and plasma sources to bombard and touch the calcium carbonate surface, so that some reactive sites are generated on the calcium carbonate surface, and then unsaturated monomers (such as vinyl groups) are added. Monomer), the unsaturated monomer can react with the active sites on the surface to form a coated organic film on the surface of the inorganic particles.

 

 

In the process of surface modification of calcium carbonate, each type of calcium carbonate surface modification is related to the application process, grinding equipment, powder modifier and other properties.