Application of calcium carbonate in water-based coatings

In recent years, water-based paints have gained favor among consumers due to their advantages such as being "green," "low-carbon," "high-performance," and "widely applicable," and are gradually replacing traditional paints as the dominant choice

Overview of water-based paint

Water-based paint refers to paints that use water as the dissolving medium, with 70% to 90% of its composition being water. It does not contain toxic organic solvents such as benzene, aldehydes, and halogenated hydrocarbons, as well as heavy metal compounds such as formaldehyde, lead, and chromium. It is characterized by being non-toxic, environmentally friendly, containing essentially no volatile substances, having no unpleasant odors, and being stable in nature. It is a safe and pollution-free environmentally friendly paint.

Currently, China's environmentally friendly water-based coatings have formed a four-pronged situation - water-based inorganic zinc-rich coatings, water-based epoxy coatings, water-based acrylic coatings, and water-based polyurethane coatings.

Modification of water-based coatings

In recent years, to address some of the deficiencies of waterborne coatings, research on their modification has emerged one after another. Among them, the most common modification materials include nanoparticles, polyurethane, polyacrylate, silicone, epoxy resin, and nano-oxide modification, etc.

Among them, fillers (extender pigments), as one of the important components of coatings, serve as a crucial implementation approach for inorganic modification technology. Fillers are mostly white or slightly colored powders, lacking tinting strength and hiding power, but they have functions such as increasing the thickness of the paint film, adjusting rheological properties, improving mechanical strength, enhancing the durability of the paint film, and reducing costs. They primarily consist of salts of alkaline earth metals, silicates, and light metal salts such as aluminum and magnesium.

Currently, commonly used fillers in water-based coatings include carbon materials (graphene, carbon nanotubes), calcium carbonate, bentonite, kaolin, silica, mica powder, barium sulfate, talcum powder, etc. Among them, calcium carbonate stands out due to its significant cost advantage, as well as its excellent leveling, suspension, and wear resistance.

Application of water-based paint

Green building materials

The water-based inorganic architectural coatings commonly used in construction projects are primarily composed of alkali metal-modified silicate aqueous solutions and colloidal silica water dispersions as the main film-forming substances, supplemented with pigments, fillers, additives, etc. The resulting coating film is environmentally friendly, non-toxic, fire-resistant, and does not peel or fall off. It exhibits superior weather resistance and color retention properties.

Numerous application experiences and research data have confirmed that adding calcium carbonate to water-based coatings can not only reduce costs but also enhance performance. When combined with pigments such as titanium dioxide, it does not affect the performance of the pigments and can also be used to control fluidity, imparting stability and fastness to the coating.

Woodenware

The main function of calcium carbonate in waterborne wood coatings is to fill gaps. It is not necessary to add it in waterborne wood varnishes, but it is added in small amounts in waterborne wood solid color paints, and in larger amounts in waterborne wood putties.

Car

Currently, countries with relatively developed automotive industries have essentially replaced solvent-based coatings with water-based coatings. In China, research and use of water-based coatings are gradually increasing, and there are already multiple production lines for midcoat and primer coatings. Among them, Shanghai General Motors has taken the lead in building a water-based color paint coating production line. Currently, automotive coatings in China are designed based on water-based coatings, but they are still mainly traditional solvent-based coatings. Currently, water-based coatings are mainly used in automotive primer, midcoat, and topcoat applications.

For example, acrylic anti-chipping underbody coating is mainly composed of acrylic resin obtained through copolymerization of acrylate monomers, formulated with fillers and additives, and is a synthetic resin lotion. Compared to the most widely used PVC plastisol system and polyurethane elastomer underbody coating, styrene-acrylic lotion uses water as the main solvent, with extremely low VOC (volatile organic compound) content, avoiding the defects of flammable and toxic solvents. Moreover, it has good acid and alkali resistance, water resistance, and impact resistance, making it a new type of anti-chipping underbody coating.

In practical applications, there are still some issues with the use of water-based coatings in the automotive industry. Due to the low boiling point of solvent water, which makes evaporation difficult, and its high sensitivity to environmental humidity, as well as its high surface tension, tendency to form bubbles, and low electrical resistance, the coatings are prone to sagging and other defects.