Calcium carbonate is the most widely used pigment in coatings, which plays the role of filling the skeleton and substrate in the paint film, and improves the performance of the coating.
70-80% of putty powder 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 finish paint, calcium carbonate is the ideal matting filler, such as matted cheese rubber wall paint containing heavy calcium carbonate 11.5%;
In metal anti-rust coatings, calcium carbonate has a certain anti-rust effect, and the appropriate dosage is about 30%;
Polyvinyl alcohol 106, 803 and other building interior wall coatings, generally containing light calcium carbonate 16%-20%;
Interior decorative paints, such as polyester vinyl 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, making it delicate, uniform and high whiteness.
Has a certain dry hiding power, the general use of ultra-fine products, when its particle size and titanium dioxide particle size close, can improve the effect of titanium dioxide.
Can improve the film strength, water resistance, dry, scrub resistance.
Reduce costs and use 10%-50%.
For example,ultrafine heavy calcium carbonatePowder materials have significant effects on shortening the dispersion sanding time in the production process of latex paint, increasing the hiding power, improving the viscosity of latex, reducing the amount of titanium dioxide and improving the sanding performance of putty.
In the design of coating formulations, high-performance latex paint using ultrafine calcium carbonate, low-grade latex paint selection of relatively coarse particle size, low oil absorption value of heavy calcium.
At present, the application effect of heavy calcium carbonate powder is better in interior wall latex paint, and its particle size control d97<10μm 、 d50About 1.5 μm, whiteness> 95%, CaCO3≥ 98% 。
2. Calcium carbonate for automobile paint
During the driving of a car, the bottom of the car and the wheel fenders are often washed by the impact of sand, gravel and sewage. Therefore, the paint applied to the surface of the substrate is easily damaged and loses its anti-corrosion ability. The substrate will quickly rust. And cause wear.
In order to solve this problem, it is necessary to apply an underbody coating material having sand impact resistance and corrosion resistance to these parts.PVC plastisol systemIt is a kind of automobile chassis paint, which is mainly composed of PVC paste resin, plasticizer,Filler (calcium carbonate)Stabilizers, tackifiers, solvents and other additives.
The amount of calcium carbonate accounts for nearly 30% of the total component (the specific amount depends on the formula), whilenano calcium carbonateThe addition of calcium carbonate will greatly improve the rheological properties of the system and the impact resistance of the film.
Automobile chassis paint is required to be easy to spray, low viscosity and good fluidity during the construction spraying process, while high viscosity is required after construction to prevent dropping and sagging. This requires the coating at high shear speed, the viscosity is significantly lower, it can be easy to spray leveling; and at low shear speed or static state with high viscosity, can prevent the coating sinking bottom and sagging, the performance of the coating is calledthixotropyNano calcium carbonate products in the construction performance, structural performance can be very good to meet this requirement.
Automobile chassis paint special nano calcium carbonate has the following characteristics:
3. Calcium carbonate for ink
Calcium carbonate is mostly used in printing inks to reduce costs and increase volume filling. General requirementsHigh performance superfine calcium carbonateThe main feature is that the particles are fine, about 0.02-1.0μm, and the specific surface area is large. It has the advantages of large oil absorption, good transparency, good brightness, and good stability.
In practical applications, the usenano light calcium powderornano active light calcium powderThe most appropriate. But the price of nano active light calcium powder is high, so most of them use nano light calcium powder as ink production.
Useactive calcium carbonateThe preparation of ink body bone and viscosity is better, has good printing performance, fast drying, and no side effects. Due to the small particles, used in ink products show excellent dispersion, transparency, excellent gloss and hiding power, as well as excellent ink absorption and drying, so the printing is fine, dot integrity. Especially in the ink widely used resin binder, active calcium carbonate with its excellent stability, almost has replaced other fillers.
At present, most of the domestic high-grade ink filler using superfine calcium carbonate, and must go throughactivation treatment, the crystal form isSpherical or cubic.
4. Calcium carbonate for powder coating
Fillers for powder coatings generally containheavy metal substanceThe content of heavy metals that do not meet international standards, especially in products exported to Europe and the United States, has extremely strict requirements on the content of heavy metals. Calcium carbonate is a cheap and does not contain heavy metal elements of the white filler, in the powder coating can completely replace the commonly usedbarium sulfate filler. mainly usedToys, baby carriages, sporting goods, kitchen utensilsAnd home appliances, such as coating.
Application of calcium carbonate in powder coatings:
Can be used as a filler for high gloss coating products;
Semi-gloss coating products, generally can be directly added to the preparation of calcium carbonate, without adding matting agent, cost savings;
Itself is a white inorganic pigment, can be used with titanium dioxide, 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, baby carriages, etc;
Can improve the coating powder rate and spraying area, especially in the mixed powder is more obvious.
For example,ultrafine activated calcium carbonateIt has a similar oil absorption and light refractive index with barium sulfate, but the density is much smaller than that of barium sulfate. In the case of the same filler dosage, the density of the powder coating can be reduced, thereby increasing the spraying area. At the same time, due to the good charging performance, the powder coating can be improved. In addition, the edge coverage of powder coatings, film hardness, and loose anti-caking properties will also be improved to a certain extent.
Development Trend of Calcium Carbonate for Coating Industry
In the coatings industry,nano calcium carbonateIt has a steric hindrance effect, can play an anti-settling effect in the coating formulation, and can also add whiteness and gloss without affecting the hiding power, which can significantly improve the storage stability of the coating.
The use of "blue shift" phenomenon, added to the latex, can form a shielding effect on the coating, to achieveAnti-ultraviolet aging and anti-thermal agingThe purpose is to increase the thermal insulation of the coating. Nano calcium carbonate as a filler, filled into the coating can greatly improve its flexibility, hardness, leveling, film deposition and permeability.
Exterior wall paint:When nano-calcium carbonate is applied to exterior wall coatings, the coating shows strong "hydrophobicity", and the cracking strength and pollution resistance of the coating are enhanced.
waterborne latex coatings:The general latex paint formula contains a certain amount of rigid particles, and the content in some formulas is quite large. The existence of these rigid particles will lead to excessive stress concentration in the coating film, resulting in cracks in the resin. The introduction of nano calcium carbonate will lead to more contact probability with the resin, more micro cracks and elastic deformation, and more impact energy will be converted into heat energy to absorb, thus improving toughness.
By adding 2%-5% of the amount of pigment filler to the traditional latex paint.Nano calcium carbonate with special polymer surface treatmentIt was found that not only the rheology and opening effect of the coating were improved, but also the water resistance, scrubbing resistance and hardness were greatly improved, and the increase of scrubbing resistance showed a geometric progression.
CurrentlyShashi in Japan, Sim in ItalyThe nano-calcium carbonate produced by other companies is mainly used to modify the performance of water-based latex coatings.
Nano calcium carbonate because of its nano size effect, large specific surface area, surface atoms in a highly activated state and polymer has a high interface interaction, when added to the coating, the coating to obtain a special modification function. Nano calcium carbonate is used in anti-stone coating and topcoat for automobile chassis because of its good thixotropy.
With the continuous improvement of scientific and technological research and quality of life, consumers have higher requirements for product functions, and high performance and multi-function have become the development trend of the coating industry.
Adding in the coating systemNano calcium carbonate, nano ZnO, etc., can make the coating haveAnti-bacterial, anti-mildewAt the same time, it will improve the weather resistance of the coating film and greatly improve the comprehensive quality of the coating.
In recent years, some coating manufacturers and research institutions at home and abroad have begun to study the use of non-metallic minerals and deep-processed products to improve or give coatings new functions. This field has become a new hot spot in the architectural coating industry.
3. Surface modification
In recent years, the application of nano-calcium carbonate in coatings in order to improve coating performance is one of the hot topics in the coating industry,nano calcium carbonateDirectly applied to paint, there are the following defects:
The particles have high surface energy, are in a thermodynamically unstable state, and are easily agglomerated;
The surface of calcium carbonate is hydrophilic and oleophobic, the polarity is very high, it is difficult to disperse in organic media, and the binding force with the base material is poor, which is easy to form interface defects, resulting in the decline of film performance.
The application of nano-calcium carbonate particles in coatings involves the compatibility of nano-materials and binders. The film-forming binders of coatings are obviously different from polymers such as plastics and rubber in terms of the type and quantity of functional groups and relative molecular mass, which leads to differences in the surface polarity of polymers and the interaction modes with pigments and fillers. In order to make nano calcium carbonate successfully applied in coatings, it is necessarySurfacemodification.
In addition, with the development of calcium carbonate industry, there have been many special coating calcium carbonate. Some have a specific crystal shape, some particle size is less than 0.1, some are not easy to settle, some have high gloss, and some are easy to disperse. More and more high-end manufacturers are looking for calcium carbonate for coatings.