Surface modification of calcium carbonate powder mainly addresses three issues: ① Dispersion of calcium carbonate; ② Interface bonding with organic polymer materials; ③ Functionalization and specialization after surface modification.

Surface modification of calcium carbonate powder mainly solves three problems: ① Dispersion of calcium carbonate; ② Combination with organic polymer materials interface; ③ Functionalization and specialization after surface modification.

　　Therefore, when selecting a surface modifier, the above points should be considered comprehensively, and the structure, properties, and mechanism of action of the surface modifier with calcium carbonate powder should be considered. The properties of the base material, formula, process technology requirements, and physicochemical properties of calcium carbonate of organic polymer products should also be considered for correct and targeted selection.

　　In addition, in the selection of modifiers, do not only use coupling agents for surface modification, but also add a certain amount of other modifying agents and auxiliaries according to the properties of calcium carbonate powder, the formula and process technology requirements of organic polymer products, etc., to cooperate with coupling agents for more effective surface modification, so that the performance and quality of modified calcium carbonate powder products meet higher requirements and reduce the cost of products.

　　Calcium carbonate powder modified with coupling agents will produce a small amount of agglomerated particles, which will affect the quality of the product. Therefore, effective classification must be carried out to ensure the quality of the product.

　　Commonly used surface modifiers for calcium carbonate include stearic acid (salt), titanate coupling agent, and aluminate coupling agent.

　　1. Stearic acid (salt)

　　Stearic acid (salt) is the most commonly used surface modifier for calcium carbonate. In the dry process, stearic acid can be added directly. In the wet process, stearic acid should be saponified first or stearic acid salts, such as sodium stearate, should be used.

　　In order to make stearic acid better dispersed and uniformly interact with calcium carbonate particles, stearic acid can also be diluted with a solvent (such as anhydrous ethanol) in advance, and other auxiliaries can also be added appropriately during modification.

 

 

 

　　The activated calcium carbonate modified with stearic acid (salt) is mainly used in filling polyvinyl chloride plastics, cable materials, adhesives, inks, and coatings.

　　2. Titanate coupling agent

　　The molecular structure of the titanate coupling agent is divided into six functional areas, each with its own characteristics. After understanding its characteristics, you can flexibly select a titanate coupling agent that meets various requirements according to the characteristics of the powder to be treated and the application field.

　　Titanate coupling agents are divided into monoalkoxy type, chelating type, and coordination type:

　　(1) The characteristic of the monoalkoxy type is that it has multiple functions and a wide range of applications, mainly suitable for treating dry calcium carbonate powder.

　　(2) The chelating type contains ethylene glycol chelating groups and is suitable for surface modification of calcium carbonate powder with a certain water content.

　　(3) The coordination type has good water resistance, most of which are insoluble in water and do not undergo transesterification reactions, suitable for surface modification of various powders.

　　Calcium carbonate treated with titanate coupling agent has good compatibility with polymer molecules. At the same time, because the titanate coupling agent can form molecular bridges between calcium carbonate molecules and polymer molecules, it enhances the interaction between organic polymers or resins and calcium carbonate, and can improve the mechanical properties of thermoplastic filled composites, such as impact strength, tensile strength, bending strength, and elongation. Compared with untreated calcium carbonate filler or stearic acid (salt)-treated calcium carbonate, the performance of calcium carbonate surface-coated modified with titanate coupling agent has been significantly improved.

　　3. Aluminate coupling agent

　　Aluminate coupling agents were rarely used in the past because they were easily hydrolyzed. In recent years, the aluminate coupling agents produced by manufacturers have adopted a special structure that partially satisfies the coordination number of the central aluminum atom, which has greatly improved the quality of their products. Aluminate coupling agents are light in color, have high thermal stability coordination effects and lubrication plasticizing effects, and have a wide range of applications.