Summary:Calcium carbonate is the most widely used extender pigment in coatings. It acts as a leveling effect for the skeleton and substrate in the paint film, and at th
Calcium carbonate is the most widely used extender pigment in coatings. It acts as a leveling effect for the skeleton and substrate in the paint film, and at the same time improves the performance of the coating.
- In the putty powder, 70-80% is heavy calcium;
- In thick paint, the amount of calcium carbonate is generally more than 30%; in water-based paint, the amount of calcium carbonate is 20-60%;
- In the finishing paint, calcium carbonate is an ideal matting filler. For example, the matt white casein wall paint contains heavy calcium carbonate 11.5%;
- In metal anti-rust paint, calcium carbonate has a certain anti-rust effect, and the appropriate amount is about 30%;
- Polyvinyl alcohol 106, 803 and other architectural interior wall coatings generally contain 16%-20% of light calcium carbonate;
- Interior decoration paints, such as polyvinyl acetate emulsion paint, usually contain about 10% calcium carbonate.
Application Of Calcium Carbonate In Coating Industry
1. Calcium Carbonate For Latex Paint
The role of calcium carbonate in latex paint:
As an extender pigment, it has a filling effect to make it fine, uniform and high in whiteness.
It has a certain degree of dry covering power. Generally, ultra-fine products are used. When the particle size is close to that of the titanium dioxide, the covering effect of the titanium dioxide can be improved.
It can improve the strength, water resistance, dryness and scrub resistance of the paint film.
Reduce costs and use 10%-50%.
For example, ultra-fine heavy calcium carbonate powder materials have significant effects on shortening the dispersion and sanding time in the production process of latex paint, increasing hiding power, improving latex viscosity, reducing the amount of titanium dioxide and improving the polishing performance of putty.
When designing paint formulations, high-performance latex paint uses ultrafine calcium carbonate, and low-grade latex paint selects heavy calcium with relatively coarse particle size and low oil absorption.
At present, the application effect of heavy calcium carbonate powder in interior wall latex paint is good, its particle size control d97<10μm, d50 is about 1.5μm, whiteness>95%, CaCO3≥98%.
2. Calcium Carbonate For Car Paint
When a car is driving, the bottom of the car and the wheel fenders are often impacted by sand, gravel, sewage, etc., so the coating on the surface of the substrate is easily damaged and loses its anti-corrosion ability. Quickly rust and wear out.
In order to solve this problem, it is necessary to coat undercarriage paint with sand and gravel resistance and corrosion resistance on these parts. PVC plastisol is a kind of automobile chassis paint, which is mainly composed of PVC paste resin, plasticizer, filler (calcium carbonate), stabilizer, tackifier, solvent and other additives.
The amount of calcium carbonate accounts for nearly 30% of the total components (the specific amount depends on the formula), and the addition of nano-calcium carbonate will greatly improve the rheological properties of the system and the membrane’s performance compared to ordinary calcium carbonate. Impact resistance.
Automobile chassis paint requires easy spraying, low viscosity, and good fluidity during construction and spraying, and high viscosity after construction is required to prevent sticking and sagging. This requires the coating to have a significantly lower viscosity at high shear speeds, so that it can be easily sprayed and leveled; while at low shear speeds or in a static state, it has high viscosity, which can prevent the coating from sinking and sagging. This kind of performance is called thixotropy, and nano-calcium carbonate products can meet this requirement well in terms of construction performance and structural performance.
Nano calcium carbonate special for automotive chassis paint has the following characteristics:
- Has a high degree of activation;
- Has a higher yield stress;
- Has good thixotropy;
3. Calcium Carbonate For Ink
Calcium carbonate is mostly used to reduce costs and increase volume in printing inks. Generally, high-performance ultra-fine calcium carbonate is required. The main feature is that the particles are fine, about 0.02-1.0μm, and the specific surface area is large. It has oil absorption. The advantages of large quantity, good transparency, good brightness, good stability and so on.
In practical applications, it is most suitable to use nano light calcium powder or nano active light calcium powder. However, the price of nano-active light calcium powder is high, so most of them use nano-light calcium powder as printing ink.
The ink prepared with activated calcium carbonate has better body and viscosity, good printing performance, fast drying, and no side effects. Due to the small particles, it exhibits excellent dispersibility, transparency, excellent gloss and hiding power in ink products, as well as excellent ink absorption and drying properties, so the printed products are delicate and the dots are complete. Especially after the extensive use of resin binders in inks, activated calcium carbonate has almost replaced other fillers with its excellent stability.
At present, most domestic high-end ink fillers use ultra-fine calcium carbonate, which must be activated, and the crystal form is spherical or cubic.
4. Calcium Carbonate For Powder Coating
The fillers used in powder coatings generally contain heavy metal substances, and the heavy metal content does not meet international standards. Especially for products exported to Europe and the United States, the requirements for heavy metal content are extremely strict. Calcium carbonate is a cheap white filler that does not contain heavy metal elements. It can completely replace the commonly used barium sulfate filler in powder coatings. Mainly used for painting toys, baby carriages, sporting goods, kitchen utensils and home appliances.
Application of calcium carbonate in powder coatings:
Can be used as a filler for high-gloss coating products;
Semi-gloss paint products can generally be prepared by directly adding calcium carbonate without adding matting agents, which saves costs;
It is a white inorganic pigment that can be used in conjunction with titanium dioxide to reduce costs;
Compared with other fillers, calcium carbonate is most suitable for some environmentally friendly products that require low heavy metal content, such as children's toys, strollers, etc.;
It can increase the powder rate and spray area of the paint, especially when used in mixed powder.
For example, ultrafine activated calcium carbonate has similar oil absorption and light refractive index to barium sulfate, but its density is much lower than that of barium sulfate. With the same amount of filler, the density of powder coatings can be reduced, thereby increasing the spray area. At the same time, due to its good charging performance, the powder coating rate can be improved. In addition, the edge coverage of the powder coating, the hardness of the coating film, and the properties of looseness and anti-caking will also be improved to a certain extent.
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