Surface modification is an important means necessary to improve the application performance, applicability, market and dosage of calcium carbonate. Its effect is mainly manifested in the following aspects:
Improve calcium carbonate dispersibility
Ultra-refinement is an important way to improve the quality of calcium carbonate, but the smaller the particle size of calcium carbonate, the higher the surface energy, the stronger the adsorption, and the more serious the agglomeration phenomenon.
Select the appropriate surface treatment agent and the corresponding activation method to improve the dispersibility of the product and prevent secondary agglomeration. Otherwise, if the particles are agglomerated, the actual particle size of the calcium carbonate product is much larger than the particle size of the primary particle, and the mixing shear force is limited during plastic processing, and the agglomeration is not easy to break up, which is bound to cause local defects, and its application effect is on the contrary. Not as good as ordinary activated calcium carbonate.
Improve calcium carbonate compatibility
Through surface modification, the interfacial compatibility and affinity of calcium carbonate with organisms can be increased, thereby improving the product performance of composite materials such as rubber or plastic.
When using stearic acid and coupling agent for surface treatment of nano-calcium carbonate powder, from the practical application point of view, this type of surface activation can only improve the compatibility of powder particles in the polymer, and further Dispersion during rubber blending into vulcanization still requires strong mechanical action. New nano-calcium carbonate surface treatment agents and dispersants should be synthesized according to the principles of polymer science.
Gives calcium carbonate functionality
Through surface modification, calcium carbonate can be transformed from a common filler material into a multifunctional modifier, such as:
In plastics, it can improve the dimensional stability, hardness and rigidity of plastic products, improve the processing performance of plastics and the heat resistance and astigmatism of products;
As filler in rubber, it can increase volume, reduce cost, improve processing performance and vulcanization performance;
In papermaking, it can be used as filler of paper, white pigment of coated paper, filler of calcium plastic paper, etc.;
As a filler in coatings, it can play a skeleton role, so it is called “extender pigment”; in oil-based coatings, the filling amount can reach 10-50%, and in water-based coatings, the filling amount can reach 10-20%.
Decrease the oil absorption value of calcium carbonate
The lower the oil absorption value, the better. If the oil absorption value is too high, the product will absorb too much plasticizer during mixing, which will increase the viscosity of the system, affect the processing performance of the resin, and increase the amount of plasticizer, thereby increasing the product. cost. Therefore, reducing the oil absorption value has become the key to improving its application performance. At present, calcium carbonate products with low oil absorption value have obvious advantages in the market. Surface modification is an important means to reduce the oil absorption value of powder. After the surface modification of calcium carbonate, its surface polarity is weakened, the friction force between particles becomes smaller, and the lubricity becomes better, so the accumulation is more compact, the bulk density increases, and the oil absorption value decreases.
Increase the added value of calcium carbonate
At present, my country’s ordinary calcium carbonate is overcapacity, and low-price competition is fierce. The surface-modified calcium carbonate has a significantly improved use effect, a good user experience, and a natural increase in value. Of course, the price of calcium carbonate modified with different meshes is also different.