The main varieties of fillers used in coatings are: calcite powder (heavy calcium), talcum powder, calcined kaolin, washed kaolin, wollastonite, mica powder, barium sulfate, quartz powder, dolomite, attapulgite, synthetic aluminum silicate, etc.
Calcite powder (heavy calcium) Density: 2.6 Oil absorption: 25-50 Features: high whiteness, low cost, stable performance. Uses: Too wide. In the coating industry, a large number of fillers are used. Used in primer, it can enhance the precipitation and permeability of primer to the surface of base layer. Used in thick paint, it can thicken, thicken, fill and level up. In semi-gloss paint or matte paint, it is an ideal matting filler. In metal antirust coating, hydrolysis can generate calcium hydroxide, which can form hydrogen bond with iron surface to enhance the adhesion of coating film and can also absorb H; Used in architectural coatings, low oil absorption, the low demand for emulsion can not only reduce the cost of latex paint, but also play a skeletal role, increase the thickness of the coating film, improve mechanical strength, wear resistance, etc., so it has become the most commonly used filler in latex paint. Compared with the advantages and disadvantages of light calcium, light calcium has a large oil absorption capacity and requires a large amount of emulsion, thus increasing the cost. Light calcium is not very stable and is easy to agglomerate, resulting in unstable storage of latex paint. Light calcium reaches a certain fineness, and dry cover is slightly better.
Talcum powder layered structure density: 2.7-2.8 Mohs hardness: 1 features: smooth feeling. With coating: extensive. Used in interior wall coatings, can improve the scrub resistance and construction; used in anticorrosive coatings, due to the extension of the diffusion path of corrosive substances, can improve the protective effect; similar to precipitated silicate, talc can also act as a pigment isolation agent, improve the coloring effect of the pigment. Disadvantages: easy to powder, the recommended dosage is appropriate.
Calcined kaolin flake structure density: 2.50-2.63 Mohs hardness: 3-4 Oil absorption: 50-95 Specific surface area: 8-16 Features: It can improve the thixotropy and precipitation resistance of the coating, has no effect on rheology, and has a matting effect, Increase whiteness and cover. Disadvantages: large water absorption, not suitable for improving the thixotropy of the coating, not suitable for the preparation of hydrophobic coating.
Wollastonite acicular or fibrous structure density: 2.8 refractive index: 1.62 Mohs hardness: 4.5-5.0 has a strengthening effect, reduce crack sensitivity, a certain thickening and thixotropic effect. In the paint industry: can be used as a system pigment and extender practical, it can increase the bright color of white paint, without reducing the whiteness and hiding power of the paint, can replace part of the titanium white, and can maintain this color for a long time. Wollastonite has low oil absorption and good filling amount, which can reduce coating cost. Wollastonite needle-like crystal makes it a good suspending agent for coatings, making the precipitation of colored paint soft and easy to redisperse. Wollastonite has high alkalinity and is very suitable for polyvinyl acetate coatings, which can make colored pigments disperse evenly. Wollastonite also has the ability to improve the corrosion resistance of metal coatings and is used as a reinforcing agent in self-cleaning coatings. Apart from water-based coatings, it can also be used for primer, intermediate coating, oily coating, road sign coating, etc. Replacing asbestos in asphalt coating; Wollastonite is used in coating, which can improve the abrasion resistance and weather resistance of coating. The reason lies in its acicular and fibrous structure, which is superimposed in coating. Besides increasing the shielding property of coating film, it also has strong ability to reflect ultraviolet rays, thus improving the aging resistance of coating film. According to the data: using it to replace 20% titanium white will not change the opacity and other properties of the coating film; silicate and silica opacity, because the particle surface is hydrophilic. Water diffuses into these pigment particles much more easily than into the latex particles, and after drying forms a fine air/silica interface within the fused emulsion coating film, increasing the opacity of the coating film.
Barium sulfate (barite powder) density: 4.3-4.5 refractive index: 1.63-1.65 oil absorption: 9 barium sulfate acid, alkali, light, heat, melting point as high as 1500 ℃, insoluble in water, low oil absorption. Disadvantages: high density, easy to precipitate, appropriate selection of higher fineness, do a good job of thickening system. In the paint industry is mainly used in the primer, the use of its low oil absorption, less paint consumption, can be made of thick film primer, good filling, good leveling, good impermeability, increase the hardness and wear resistance of the coating. Barium sulfate has a high refractive index and is mainly used in color paints, which can save a lot of expensive color paste costs.
Sericite Sericite is a kind of fine-grained muscovite, which is a layered silicate. The structure is composed of two layers of silicon oxide tetrahedron sandwiched by a layer of aluminum oxide octahedron. The crystals are scaly, elastic and bendable. Density: 2.8 oil absorption: 20-50 sericite has good acid resistance, alkali resistance, good chemical stability, medium dry hiding power and good suspension. Used in coatings can improve the weather resistance of coatings, prevent water vapor penetration, prevent cracking, delay pulverization. By adding mica to the formulation containing talc, the corrosion resistance of the coating is improved, the surface hardness is increased, the scrub resistance is improved, and the pigment efficiency is improved.
Synthetic aluminum silicate Synthetic aluminum silicate is actually a sodium aluminum silicate, which is an amorphous and highly dispersed system pigment. Density: 2.0-2.1 Average particle size: 1.5μm Oil absorption: 75-150 Small particle size, narrow particle size distribution, no precipitation and stratification phenomenon, greatly improving the suspension of the coating, pure color of the coating, strong coloring power, improved hiding power, can improve the dispersibility and fineness index of the coating, and has good effects on the appearance, gloss, fullness and hardness of the coating. Synthetic aluminum silicate does not interact with phosphate dispersants, but latex paints have good dispersion stability. The ultra-fine properties and high dispersion of synthetic aluminum silicate can make the latex paint slightly thicker to prevent pigment precipitation and surface stratification. In addition, the scrub resistance and weather resistance of the coating film of latex paint will not be reduced by the addition of ultra-fine aluminum silicate, instead of 10-20% of the amount of titanium dioxide, the hiding power of the paint will not be weakened. The reasonable use of aluminum silicate to replace part of the latex paint produced by titanium dioxide will have the following characteristics: due to the small particle size, narrow particle size distribution, no precipitation stratification phenomenon, the suspension of the filler is greatly improved, and the opening effect is good. The color of the coating is pure, the coloring power is strong, and the hiding power is improved. Due to the improvement of the dispersion and fineness index of the coating, the appearance, gloss, fullness, hardness and dispersion of the coating have a good effect. As a result of saving 10-20% of titanium dioxide, thereby significantly reducing the production cost of coatings. In addition, the synthetic aluminum silicate is alkaline, which plays a buffering role in the acid and alkali of the coating, especially in the vinyl acetate latex paint system, which can prevent the pH value of the latex paint from dropping due to the hydrolysis of vinyl acetate during storage. Disadvantages: Because of its large specific surface area, high oil absorption, and must be thoroughly dispersed to play its synergistic effect, otherwise it is easy to cause post-thickening. In addition, it has a matting effect and is not suitable for high-gloss paint.