Fillers (extender pigments) in paints, usually white or slightly colored, with a refractive index of less
A 1.7 class of pigments.
It has the basic physical and chemical properties of pigments for coatings, but because the refractive index is similar to that of film-forming substances, it is transparent in coatings, and does not have the tinting power and hiding ability of coloring pigments. It is an indispensable pigment in coatings.
Since the vast majority of fillers come from natural ore processing products, their chemical stability, wear resistance, water resistance and other characteristics are good, and the price is low, and they play a skeleton role in the coating. By filling to increase the thickness of the film, improve the mechanical properties of the film, and can play a durable, anti-corrosion, heat insulation, extinction and so on.
On the other hand, it is used as a way to reduce the manufacturing cost of coatings, using its low price, the price is far lower than the color pigment, under the premise of meeting the hiding power of the paint film, the appropriate addition of body pigments to supplement the volume of color pigments in the paint.
1. Play the role of skeleton and filling in the coating, increase the thickness of the paint film, and make the paint film plump and solid;
2. Adjust the rheological properties of the coating, such as thickening, anti-precipitation, etc;
Improve the mechanical strength of the paint film, such as improving wear resistance and durability (e. g. silicon powder);
4. Adjust the optical properties of the coating and change the appearance of the coating film, such as extinction;
5. The film-forming substance chemically reacts to make it into a whole, so that the film can effectively block the penetration of light, improve its water resistance and weather resistance, and extend the service life of the film;
6. As the volume filling in the coating, reduce the amount of resin and reduce the production cost;
7, the chemical properties of the coating plays an auxiliary role, such as enhanced rust, moisture resistance, flame retardancy and so on.
Different coating varieties and grades have different technical requirements for fillers, but the general requirements for fillers for coatings are as follows.
1, high whiteness, especially in the coating film color requirements are very high, whiteness is generally required to be more than 93%.
2, easy to disperse, which not only helps to reduce the energy consumption and time of grinding and dispersion in coating production, but more importantly, it is conducive to the performance of the coating, because the dispersion of fillers and pigments is good or bad, the film performance (gloss, color, durability, etc.) has a direct impact.
3. It is necessary to have lower oil absorption and low oil absorption value to improve the critical pigment volume concentration (CPVC) of the coating, save the resin base material, adapt to the requirements of modern high-solid coatings that meet the requirements of environmental protection, prepare a higher content of pre-dispersed filler slurry, and match the pigments (especially titanium dioxide and whitening powder) with decreasing oil absorption value. Oil absorption value of non-metallic mineral fillers commonly used in coatings.
4, there should be a definite particle size and narrow particle size distribution, sieve residue should be as low as possible, now the coating requires filler in many applications with fine or even ultra-fine particle size, so as to play its role in the space in the coating, so that the pigment particles in the film are evenly distributed, so as to maximize the potential of pigment covering (such as titanium dioxide, whitening powder), coloring (such as color pigments) and rust prevention (such as anti-rust pigments), and play a part of the role of replacing pigments.
5. It can make the coating have good rheological properties (fluidity, leveling, suspension, thickening, etc.), so that the coating does not precipitate during storage, which is convenient for construction to form a smooth and flat coating film.
6. It should have good compatibility with the base material, pigments and other additives in the coating, but at the same time it should be inert and not chemically react with the above ingredients.
7. It has a suitable specific surface area, because it affects the viscosity, rheology, dispersion stability, sedimentation and oil absorption of the coating.
8. It has a definite particle shape and crystal morphology, so that the coating has a definite refractive index and other optical properties and ensures that the filler should have the function in the coating.
The role of each filler in the coating
1. Calcium carbonate
Calcium carbonate has natural and synthetic (precipitation production) two types, a very wide range of particle size, 0.05~44 m can be applied. The amount of natural calcium carbonate is very large, because of its low price, it is quite suitable in some applications.
Coarser varieties are limited to putty, caulking paste, metal primers and other high pigment content, flow and rough surface products. The matting ability of coarse particle size calcium carbonate is very low. Medium particle size varieties are mainly used for internal flat and semi-gloss coatings and housing coatings. Most of the fine particle size varieties are produced by precipitation method and are used for printing inks. Two particle sizes of calcium carbonate are usually used in combination to achieve a balance of properties.
Natural calcium carbonate fillers are also widely used in outdoor housing coatings, can be used alone, can also be used with talcum powder. Compared with talcum powder, natural calcium carbonate can reduce the pulverization rate, improve color retention and improve anti-pollution performance.
2. Talcum powder
The main component of talc is talc containing water.
The molecular formula is Mg3[Si4O10](OH)2. Talc
. The crystals are pseudo-hexagonal or rhombohedral flakes, occasionally. Usually dense lumpy, leaf-like, radioactive
like, fibrous aggregates. Colorless transparent or white, but with a small amount of impurities and light green, light yellow, light brown or even light red; cleavage surface was pearl luster.
It has excellent physical and chemical properties such as lubricity, fire resistance, acid resistance, insulation, high melting point, chemical inactivity, good hiding power, soft, good luster, strong adsorption force, etc., because the crystal structure of talc is layered, so it has the tendency of easy to split into scales and special lubricity.
Talc powder has good suspension and easy dispersion, and low corrosion, in the coating, talcum powder as a filler can play a skeleton role, reduce manufacturing costs and improve the film hardness of the coating. It also has the characteristics of improving the stability of product shape, increasing tensile strength, shear strength, pressure strength, reducing deformation, elongation, thermal expansion coefficient, high whiteness, uniform particle size and strong dispersion. The talcum powder with flake particle structure can make the coating film have high water resistance and impermeability of enamel. The talcum powder with fibrous particle structure can improve the rheological property and leveling property of the coating, and improve the weather resistance of the coating.
Talc powder is mainly used in primers and intermediate coatings, many products and flash primer and transport paint preferred talc powder. The primer for steel structure can be used in whole or in part with talc powder to improve the precipitation of the coating, the mechanical force of the coating film and the recoatability.
3. Wollastonite powder
Wollastonite chemical formula for CaSiO3, theoretical chemical composition: CaO48.25%, SiO251.75%. Pure wollastonite is rare in nature. In the process of its formation, Ca is sometimes partially replaced by Fe, Mn, Ti and Sr plasma to be homoplasmic, mixed with a small amount of Al and trace K and Na.
In the coating industry, wollastonite powder as paint, coating filler, can improve the physical and chemical properties of the product, durability, reduce the gloss of the paint, enhance the expansion ability of the coating, reduce cracks, but also can reduce the oil absorption, enhance corrosion resistance. Wollastonite bright color, high reflectivity, suitable for the production of high quality white paint and clear transparent colored paint. The acicular wollastonite powder has good flatness, high color coverage and uniform distribution, and has the characteristics of anti-ultraviolet. It is widely used in interior wall coatings, exterior wall coatings, special coatings and latex paint. Ultrafine particle size, whiteness, PH value is higher, the paint color and coating is better, and the paint is alkaline can be used as steel and other metal equipment anti-corrosion coating.
4. Mica powder
Mica powder is a non-metallic mineral, containing a variety of components, including SiO2, the content is generally about 49%, Al2O3 content in about 30%. Mica powder has good elasticity and toughness. Insulation, high temperature resistance, acid and alkali resistance, corrosion resistance, strong adhesion and other characteristics, is an excellent additive.
The application of mica powder in coatings is mainly reflected in the following aspects:
1), barrier effect: flake filler in the film to form a basic parallel orientation arrangement, water and other corrosive substances on the film penetration is strongly blocked, in the case of the use of high quality sericite powder (wafer diameter thickness ratio of at least 50 times, preferably more than 70 times), water and other corrosive substances through the film penetration time is generally extended by 3 times. Because sericite powder filler is much cheaper than seed resin, it has very high technical and economic value. The use of high-quality sericite powder is an important means to improve the quality and performance of anti-corrosion coatings and exterior wall coatings. During the coating process, the sericite wafer is subjected to surface tension before the paint film is cured and lies down, automatically forming a structure parallel to each other and parallel to the surface of the paint film. Such a layer-by-layer arrangement, its orientation is just perpendicular to the direction in which corrosive substances penetrate the paint film, and the barrier effect is most fully exerted.
2) Improve the physical and mechanical properties of the paint film: the use of sericite powder can improve a series of physical and mechanical properties of the paint film. The key is the morphological characteristics of the filler, that is, the diameter-thickness ratio of the flake filler and the length-diameter ratio of the fibrous filler. The particle-packed filler is like sand and gravel in the concrete, which plays a reinforcing role in the reinforcement.
3), improve the wear resistance of the paint film: the hardness of the resin itself is limited, and the strength of many fillers is not high (such as talcum powder). On the contrary, sericite is one of the components of granite, and its hardness and mechanical strength are great. Therefore, the anti-wear performance can be significantly improved by adding sericite powder as filler in the coating. Most of the automotive coatings, pavement coatings, mechanical anti-corrosion coatings and wall coatings use sericite powder.
4), insulation performance: sericite has a very high resistance, itself is the most excellent insulation material. With silicone resin or silicone boron resin to form a compound, encountered high temperature into a ceramic material with good mechanical strength and insulation performance, so the wire and cable made of this kind of insulating material, even after burning in a fire, still maintain the original insulation state. It is very important for mines, tunnels, special buildings, special facilities, etc.
5), flame retardant: sericite powder is a very valuable flame retardant filler, if combined with organic halogen flame retardant, can be made of flame retardant and fire retardant coatings.
6), anti ultraviolet, infrared performance: sericite has excellent shielding ultraviolet and infrared properties. Therefore, adding wet sericite powder to outdoor coatings can greatly improve the anti-ultraviolet performance of the paint film and delay the aging of the paint film. Its infrared shielding properties are used in the preparation of thermal insulation materials (such as paint).
7), heat radiation and high temperature coating: sericite has good infrared radiation ability, such as with iron oxide, can cause excellent heat radiation effect.
8), sound insulation shock absorption effect: sericite can significantly change the material of a series of physical modulus, the formation or change the material's viscoelasticity. Such materials efficiently absorb vibrational energy and attenuate vibration and sound waves. In addition, vibration waves and sound waves form repeated reflections between mica wafers, which also weakens their energy. Sericite powder is also used to formulate noise reduction, sound insulation, shock absorption coatings.
5. Calcined kaolin
Calcined kaolin has the characteristics of high whiteness, strong covering power, bright luster, fine particle size, fast adsorption speed, excellent acid and alkali resistance, moderate oil absorption, and stable physical and chemical properties. It is a new type of plasticity additive, Non-toxic and tasteless are environmentally friendly functional fillers, It can replace part of titanium dioxide and all replace lide powder, etc. directly reduce product costs. Performance: plasticity, adhesion, dispersion, insulation, sintering, flame retardant, fire resistance, adsorption, weather resistance, chemical stability.
6. Barium sulfate (barite powder)
Barium sulfate (barite powder) is a kind of environmentally friendly material with strong chemical inertness, good stability, acid and alkali resistance, moderate hardness, high specific gravity, high whiteness, and can absorb harmful rays. It is widely used in various coatings, medium and high-grade inks,Rubber, paper, ceramics, cosmetics and other fields.
Refined barium sulfate is widely used in various coatings (water, oil and powder coatings), ink, paper, engineering plastics, high-grade electrical insulation plastic, rubber products, etc. Barium sulfate can be used as a white coating, can also be used as a filler for rubber and paper, can increase its weight and smoothness. Precipitated barium sulfate is used as filler, brightening agent and weighting agent in rubber, plastic, paper making, paint, ink, coating and other industries.
7. Silica powder
Silicon powder is a non-toxic, tasteless, non-polluting inorganic non-metallic material, mainly through natural quartz (SiO2) or fused quartz (amorphous SiO2 after high temperature melting and cooling of natural quartz) is micropowder processed by crushing, ball milling (or vibration, air flow milling), flotation, pickling purification, high purity water treatment and other processes. Because silicon powder has good temperature resistance, acid and alkali corrosion resistance, high insulation, low expansion, chemical stability, high hardness and other excellent properties, it is widely used in chemical industry, electronics, integrated circuits (IC), electrical appliances, plastics, coatings, Advanced paint, rubber, national defense and other fields. In the paint industry, silicon powder has the characteristics of fine particle size, high hardness, good suspension and dispersion, low oil absorption and high resistivity. Based on these characteristics, the addition of silicon powder in the paint is helpful to improve the corrosion resistance, wear resistance, insulation and high temperature resistance of the paint.