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Application characteristics of mineral fillers in coatings are summarized


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Application characteristics of mineral fillers in coatings are summarized

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Application characteristics of mineral fillers in coatings are summarized


1, an overview of the
Coating is a kind of liquid or liquid solid powder or thick paste state, can be uniformly coated and firmly adhere to the surface of the coated object, and to the coated object decoration, protection and special role, or several functions of a film forming material.
Coating product besides paint, still included to use all sorts of synthetic resin, latex to wait for main raw material production solvent coating, latex coating, water-soluble coating, powdery coating to wait.
The inorganic filler in coating is also called constitution pigment, sometimes also called pigment increment agent, can be divided into non-functional filler and functional filler. The former mainly plays an incremental role in order to reduce the cost of raw materials; The latter has the function of improving some properties of the coating or coating film, such as controlling rheology, improving adhesion, controlling gloss, improving hiding power, preventing corrosion and optimizing pigment concentration.
2. Functions and requirements of fillers in coatings
A filler (pigment) in paint, usually white or slightly colored, having a refractive index of less than 1.7. It has coating with the basic physical and chemical properties of pigment, but as a result of refractive index and film-forming material close, so in the coating is transparent, do not have the coloring power of pigment and hiding ability, paint is an indispensable pigment. Because fill great majority comes from natural ore processing product, its chemical stability, wear-resisting, waterproof wait for a characteristic to be good, and the price is low, have skeleton effect in coating. The filling can increase the thickness of the coating, improve the mechanical properties of the coating, and play the role of durability, corrosion resistance, heat insulation and extinction. On the other hand, it is a way to reduce the cost of paint manufacturing, using its cheap, price is far lower than color pigment, under the premise of meeting the covering power of paint film, appropriately add body pigment to supplement the volume of color pigment due in paint.
The use of fillers in coatings, cost reduction is not the only role. The main functions and functions of fillers are:
1) play the role of skeleton and filling in the paint, increase the thickness of the paint film, make the paint film plump and firm;
2) adjust the rheological property of coating, such as thickening, anti-precipitation, etc.;
3) improve the mechanical strength of the paint film, such as improving the wear resistance and durability;
4) adjust the optical properties of the coating and change the appearance of the coating, such as extinction, etc.;
5) the film-forming material will undergo chemical reaction to form a whole, so that the coating can effectively prevent the penetration of light, improve its water resistance and weather resistance, and extend the service life of the coating;
6) as the filler in the coating, reduce the amount of resin and reduce the production cost;
7) it plays an auxiliary role in the chemical properties of the coating, such as enhancing anti-rust, anti-humidity and flame retardant.
8) different types and grades of coatings have different technical requirements on fillers, but the general requirements on fillers for coatings are as follows.
9) whiteness should be high, especially in the coating color requirements are very high, whiteness requirements in general above 90%.
10) easy dispersion, which is not only conducive to the reduction of coating production grinding dispersion energy consumption and time, more important is conducive to the development of coating performance, because the dispersion of filler and pigment, coating performance (gloss, color, durability, etc.) has a direct impact.
11) should have lower oil absorption, oil absorption value low to improve coating the critical pigment volume concentration (CPVC), save resin binders, and can adapt to meet the requirements of environmental protection requirements of modern high solid coatings, content is higher is prepared beforehand scattered packing pulp, talents and oil absorption value increasingly reduce pigment (especially titanium dioxide) matching.
12) shall be determined with particle size and narrow particle size distribution, sieve residue should be as low as possible, coating requirements packing in many application fields have now ultra-micronization model.the even ultrafine particle size, so as to give play to the role of it in the space in the coating, the coating of the pigment particles were distributed evenly, so as to maximize cover, such as titanium dioxide pigment, coloring, such as color pigments and rust (such as antirust pigment) potential, have the effect of partly replace pigments.
13) can make the coating has good rheology (fluidity, levelling, suspension, thickening, etc.), so that the coating in storage does not precipitate, facilitate the construction of film, forming a smooth smooth coating film.
14) it should have good compatibility with the base materials, pigments and other additives in the coating, but at the same time, it should also have a certain inertia, without chemical reaction with the above-mentioned components.
15) with an appropriate specific surface area, because it affects the coating viscosity, rheology, dispersion stability, sedimentation and oil absorption.
16) with a certain particle shape and crystal form, so that the coating has a certain refractive index and other optical properties and ensure the filler in the coating should function.
3. Types of fillers commonly used in coatings
Commonly used fillers in coatings are calcium carbonate (heavy calcium, light calcium), barite powder (barium sulfate), talc powder, kaolin (porcelain soil), porous powder quartz (silica), white carbon black, precipitated barium sulfate, mica powder, wollastonite, bentonite, etc.
Calcium carbonate
Calcium carbonate is the main filler for coatings (body pigment)
Classification of calcium carbonate for coatings
According to the characteristic classification coating with calcium carbonate according to the characteristic mainly divides light calcium carbonate and heavy calcium carbonate. Light calcium carbonate and heavy calcium carbonate. Light calcium carbonate (precipitated calcium carbonate) can be divided into ordinary precipitated calcium carbonate, fine calcium carbonate, super fine calcium carbonate and active calcium carbonate. Heavy calcium carbonate (natural products) is divided into heavy calcium carbonate, heavy fine calcium carbonate and heavy active calcium carbonate.
According to the classification of crystal morphology, fine calcium carbonate crystals, such as cubic crystal system, needle crystal, spindle crystal and chain crystal, can be obtained by changing the process and controlling the crystal.
According to the size of crystal particles, precipitated calcium carbonate can be divided into: fine calcium carbonate (average particle size 44 ~ 60um). Medium calcium carbonate (mean particle size 15 ~ 44um); Fine calcium carbonate (mean particle size 1 ~ 15um); Superfine calcium carbonate (0.1 ~ 1um); Superfine calcium carbonate (<0.1um).
Heavy calcium carbonate products are divided into single fly powder (200 mesh fine grain size), double fly powder (325 mesh fine grain size) and sifly powder (400 mesh fine grain size). Superfine calcium carbonate (size 1250 mesh).
Application of calcium carbonate in coatings
Calcium carbonate is an important filler in coating production. Calcium carbonate in the paint film skeleton and substrate (steel plate, wood) filling function, enhance the film deposition and permeability. Especially used in metal antirust primer, it forms a hydrogen bond with the metal surface, increasing the adhesion of the paint film, and can absorb hydrogen ions to prevent the metal from forming corrosion tendency of micro battery. In addition, the face of calcium carbonate has a good weather, wear resistance, low electrolyte content, PH value stability effect, can improve corrosion resistance and coating rheology. Coarse calcium carbonate is limited to putty, pore filling compounds, metal primers and other products that require high pigment content, fluidity and a coarse surface. Medium grade calcium carbonate used in building coatings and interior light or semi-gloss paint; Fine - grained calcium carbonate is mainly precipitated calcium carbonate, used in printing inks.
Heavy calcium can be used in a variety of internal, external coating, the most appropriate in waterborne coating applications, because of poor acid resistance, hindered its application in external coating. In general coating, the amount that heavy calcium joins is 10% ~ 35%, the content in coating of all sorts of anaglyph changes is as high as 50%.
In addition to being used for increment, heavy calcium is mainly used to partially replace titanium dioxide (generally 10% ~ 20%, 30% in large quantities) and color pigments, to replace light calcium and precipitated barium sulfate, corrosion resistance and partially replace rust resistance pigments.
When heavy calcium is used as interior building paint, it can be used alone or with talcum powder. Compared with talcum powder, calcium carbonate can reduce the rate of powderization, improve the color retention of light paint and increase the resistance to mold.
Compared with heavy calcium, light calcium has small particle size and narrow particle size distribution range, high oil absorption and brightness. Light calcium can be used in places where the maximum extinction effect is required. Light calcium and heavy calcium are mixed more commonly in semi - smooth, matte paint and matte emulsioni paint.
Talcum powder
Talcum powder is a universal filler in solvent based coatings, which has been introduced into water-based systems due to the advent of finer grade talcum powder. At present, it is used in various primers, intermediate coatings, road signs, industrial coatings and interior and exterior architectural coatings. Due to the soft texture and low abrasion, talcum powder has good suspension and dispersion, so in China's coating industry consumption talcum powder filler proportion is larger.
The talcum powder with flake structure has excellent brushability, fluidity and smoothness of coating film, water resistance and impermeability of enamel bead. It is mainly used for primer and intermediate coating. The amount of oil absorption of fibrous talcum powder is higher, and have good rheological property, can improve a lot of properties of coating, if prevent, deposit when storing and besmear is brushed, flow hangs, improve construction property to wait.
Talc used in the coating industry has many levels of products, such as ordinary size talc (-325 mesh), micro size talc (-20um and -10um), super fine size talc (-5um), chemical pretreatment talc, respectively, are suitable for a variety of specific purposes and purposes.
Coarser grade talcum powder is used in some coating films that require roughness, such as interior wall primer intermediate coat and striped paint; Super fine talcum powder is used to control the gloss, consistency and flow of semi-gloss enamel. In addition to improving the coating performance, micro and micro fine talcum powder also has the ability of space separation, which can partially replace TiO2 and other pigments. Chemically pretreated talc can also replace TiO2 pigments.
Talcum powder is a disadvantage of high oil absorption, so in the need for low oil absorption occasions, it must be with low oil absorption filler and barite powder. In addition, talc wear resistance is not high, in need of high wear resistance occasions, to join other filler to make up for. Talcum powder containing other nonmetallic minerals is not suitable for exterior coatings requiring high weatherability due to its easy reaction with acids (such as acid rain). Industrial talc because contain coloured impurity and whiteness to drop, ask very tall to fill lightness consequently occasion, need not talc is packed commonly. Talcum powder has extinction, so it is generally not used in high gloss coating.
Kaolin is one of the fillers widely used in coating industry abroad. In recent years, the amount of kaolin used in the United States is about 300,000 tons per year, among which the amount of calcined kaolin is more than 100,000 tons per year.
Kaolin commonly used in coatings include ultra-fine kaolin, calcined kaolin, active kaolin (surface modification) and so on. Kaolin can be used in a variety of coatings, but water-based building coatings, especially with latex paint, because kaolin in water-based coating has a better hiding power, which can partly replace titanium dioxide pigment. Superfine kaolin can partially replace titanium dioxide, about 10% of the amount of titanium dioxide, can reduce the cost of paint, but has little impact on the gloss, hiding power and storage stability of paint. The refractive index of calcined kaolin was increased from 1.56 to 1.62, which made up for the deficiency of original hiding power and whiteness. In addition, calcined kaolin can improve the opacity of the coating and the firmness of the coating film, which is more resistant to washing and powdering than uncalcined clay. Calcined kaolin instead of some titanium dioxide has been used in road marking paint, powder coating, building external emulsion paint and other applications. Superfine kaolin and calcined kaolin can replace 15% ~ 20% titanium dioxide in exterior wall coating. Some kaolinite shows poor suspension in solvent dilution paint, but calcined kaolinite with surface modification can overcome these shortcomings.
Porous quartz (main component SiO2)
Porous quartz is a kind of pozzolanic sedimentary rock. The product has fine natural particle size (about 0.5 muon), uniform particle distribution, large specific surface area (8.3m2/g), and similar spherical shape without angular shape. In electron microscope images, the surface is all nanoscale mesoporous with an average aperture of about 8.8nm.
The surface of porous quartz contains a certain amount of hydroxyl (-oh) -silanol. As a polar functional group, it can be used in powder coatings to improve the adhesion and adhesion of products. On the other hand, because of the presence of hydroxyl group, it is easier to pass surface treatment of coupling agent, increase its cross-linking and strengthening effect, increase the physical and mechanical properties of the product and improve the tensile strength of the coating.
Porous powder quartz contains Zro2, zirconia property stability, high hardness, plus porous powder quartz porous structure makes the coating has a better hardness performance, and impact resistance.
Porous powder quartz belongs to a kind of of silica system, the safety of using approved, has been widely used in powder coating, building exterior wall coating, thick hair quality coatings, fire retardant coating, waterproof coating, environmental protection coatings, anticorrosive coatings, etc., cheap porous powder quartz can reduce the cost of powder coating, at the same time instead of barium sulfate to reduce soluble barium content in the products, to achieve environmental protection requirement.
Natural porous quartz mainly plays an incremental and semi-reinforcing role in coatings, and can be used in various coatings and architectural coatings, especially primer and intermediate coatings. Fine crystal SiO2 can replace up to 50% TiO2 in epoxy and polyphenol powder coatings.
Natural porous powder quartz because it is the structure of the porous, high porosity, with various particle shape and structure characteristics, and have excellent oil absorption (19 ~ 25 g / 100 g), the combination of irregular structure and oil absorption effect very good matting, high thickening ability and good pigment suspended, coating used it as matting agent. It is mainly used in smooth emulsioni paint and varnish, primer and some concrete paint, and it is also used in the paint to increase the covering pigment covering filler.
Silica (or lightweight silica) due to the large specific surface area, good thermal stability can prevent pigment precipitation, especially in the use of latex paint, adjust the effective viscosity of paint, improve paint film hanging and play the role of extinction, good thermal stability of paint film.
Silica is a kind of multifunctional body pigment and a rheological control agent with excellent properties. In the liquid coating, its rheological control function includes: thickening, thixotropic, anti-flow hanging, covering the edge; In the solid powder coating system, the free flow of powder is enhanced to prevent agglomeration and fluidization.
Barium sulfate
The barium sulfate used as the pigment of paint body has two kinds: natural and synthetic. The natural product weighs the crystal powder and the synthetic product is called precipitated barium sulfate.
The appearance of barium sulfate is a dense white powder, which is an inert substance with a density of 4.5g/cm3. It is the heaviest among the body pigments, with stable chemical properties. It is almost insoluble in water, ethanol and acid, soluble in hot sulfuric acid, alkali resistant and light resistant. The impurity content is little glass luster, cleavage surface is pearl luster. Barite powder has very low oil absorption (6g/100g). Precipitated barium sulfate has superior color and fine particles.
Barite powder packing is mainly used for industrial primers and automotive intermediate coatings that require high film strength, high filling force and high chemical inertness. It is also used in topcoats that require high gloss. In emulsioni paint, because barite refractive index is high (1.637), fine barite powder can have the function of translucency white pigment, can replace partial titanium dioxide powder in coating.
Wollastonite is mainly composed of calcium metasilicate (CaSiO3), with a needle like structure, good brightness, refractive index (1.62) and relatively low oil absorption (20 ~ 26g/100g).
Wollastonite can be used as a body pigment and a part of the white pigment in the paint to cover up and increase the cost of paint. Keep the white paint a long, bright hue.
Acicular wollastonite (l/d ratio 10:1 ~ 20:1) ACTS as a smoothing agent in coatings, improves the mechanical strength of coatings, and sometimes replaces harmful asbestos in reinforced coatings. Coating is generally used in the finer grade (such as 325 mesh) and fine grade (10um) wollastonite powder, because it is conducive to the development of coating hiding power. Can be used for oil building paint, sound absorption (sound insulation) paint, road paint, polyvinyl acetate emulsion paint. The surface treated wollastonite can be used in industrial alkyd, epoxy and other anticorrosive coatings to improve the corrosion resistance of the metal primer and partially replace the active antirust pigment.
Mica powder
White mica is mainly used in coating, but also a small amount of gold mica. It is mainly used as filler in anticorrosive coatings and functional coatings for its sheet structure with high diameter to thickness ratio, good heat resistance, weather resistance, transparency, chemical resistance, uv shielding and other properties. In the coating formula is mainly used for some special oil and water based coatings, the amount of about 20 percent from industrial coatings to about 40 percent embossed architectural coatings.
Wet ground mica powder is an important application field. It is used as carrier material of titanium pearlescent pigment. Coating, ink, plastic and other industries need different specifications series of mica titanium pearlescent pigment.
Natural graphite can be used in steel structure maintenance coatings because of its flake structure and good hiding rate. Its good electrical conductivity and black color make it suitable for use in electrical shielding coatings for electronic computers, which can contain up to 75% graphite. Another use is antistatic floor paint. It can be used in heat resistant coatings, primer, closed coatings and water-resistant coatings, due to good light resistance, can be used in automotive paint, as an effect pigment.
Aluminum hydroxide
In the category of inorganic flame retardant additives, aluminum hydroxide is the largest amount and the most widely used, it is not only good flame retardant performance, but also can prevent smoke, do not produce drops, do not produce toxic gas, therefore, to obtain a wider range of applications, the amount of use is also increasing year by year. Scope of use: thermosetting plastics, thermoplastics, synthetic rubber, coatings and building materials and other industries.
Aluminum hydroxide as an inorganic flame retardant, although has a good flame retardant effect, but its filling capacity has a certain high standard, such a high filling capacity is bound to affect the compatibility and mechanical properties of high polymer and inorganic filler, resulting in a serious impact on the performance of flame retardant products. For these reasons, an increasing number of individuals or research institutions have modified the surface of aluminum hydroxide (we call it activation) to produce activated aluminum hydroxide. The molecular formula of activated aluminum hydroxide is AL(OH)3 or AL2O3·3H2O, the molecular weight is 78, white powder, mainly containing aluminum hydroxide, coupling agent and so on.
Using high quality raw materials by ultrafine airflow comminution and classification, activated aluminum hydroxide - activated aluminum hydroxide on the surface of coupling agent solves the defects of traditional aluminum hydroxide in essence. 1. As an additive halogen-free smoke suppressant and flame retardant, activated aluminum hydroxide is characterized by large amount of addition, good flame retardant effect and low cost, which can improve the material's arc-resistance, impact strength and bending strength. 2. The surface area is increased to some extent, increasing the fluidity, uniform particle size distribution, good stability, no corrosive gas. Dispersive sex is good in resin, join amount more, produce not easily bend hair white phenomenon. Used in plastics, not volatile, not exudate, can be retained in plastics for a long time. It has good compatibility with many other substances.
Application range of activated aluminum hydroxide
Active aluminum hydroxide in the production of products in the range of application have been greatly extended, especially in these years, the active aluminum hydroxide in the application of wire and cable made substantial breakthrough, applied in the electric wire electric cable aluminum hydroxide as fire retardant filler, more efficient to improve the electrical performance of wire and cable, but also increase the flame retardant ability of the wire and cable, and realize the low pollution. In addition, activated aluminum hydroxide is used in insulating materials, flame-retardant rubber hose, rubber belt, duct cloth, electrical materials, etc.