General knowledge of coating: introduction and application of filler for coating

Core tip: filler pigments (fillers) may be ignored in terms of name But in fact, fillers have a great influence on the properties of most colored coatings There are many types of fillers and great differences in performance Most of the coating formulation personnel have not fully understood their performance and the best application occasions White filling pigment is a kind of mineral material with low refractive index The difference between them lies in composition, particle size and particle shape It has very low covering performance in bright and semi gloss coatings, but it can give the coating a "high dry covering" effect on the basis of low cost in flat gloss coatings（ Shenyang steel structure fireproof coating construction expert punde Building Fire Engineering Co., Ltd Recommended introduction: since its establishment, Shenyang punde Construction Fire Engineering Co., Ltd has cultivated a group of professional construction teams with excellent equipment, rich experience and serious responsibility with advanced and scientific management methods and strict engineering quality assurance and after-sales service system It has undertaken a number of fire system installation projects, which has been praised by customers Every idea and special requirement of you will be fully considered by us and fully realized in the construction technology, which will become the cornerstone of our successful long-term development We are looking forward to your invitation, to provide you with quality services and high-quality technical support! All construction coatings have passed ISO9001 Paint Home News: filler pigments (fillers) from the name may be ignored But in fact, fillers have a great influence on the properties of most colored coatings There are many types of fillers and great differences in performance Most of the coating formulation personnel have not fully understood their performance and the best application occasions White filling pigment is a kind of mineral material with low refractive index The difference between them lies in composition, particle size and particle shape It has very low covering performance in bright and semi gloss coatings, but it can give the coating a "high dry covering" effect (air / Pigment interface) on the basis of low cost in flat gloss coatings Therefore, fillers can be used to adjust the luster, texture, suspension, viscosity, etc the main types of fillers are carbonate, silicate, sulfate and oxide The particle size range of the practical packing is 0.01-44 μ m, and its shape is spherical, acicular, fibrous and flaky The shape of filler particles affects the flexibility and crazing of packaging and coating Particle size and particle size distribution affect covering power, viscosity, film porosity, media and surfactant demand, gloss and fineness The reactivity between the filler and the coating base is very important, which will affect the salt spray resistance, blistering, corrosion resistance and cracking performance of the coating A lot of work has been done to replace one kind of filler with another in order to produce equivalent coating performance It is found that when fillers are replaced with equal weight or equal volume, different coating performance will be produced, such as consistency, durability, permeability, scrub resistance, pollution resistance, light retention, etc The filler is made by grinding natural ore, or by chemical precipitation and then refining and particle size classification The separation process includes wet or dry screening, flotation and centrifugal separation Raw materials and processing technology may affect the pigment performance Calcium carbonate or clay: This is the most commonly used filler in the internal or external coatings of CaCO3, which is used to control the luster, mildew resistance, consistency and reduce the cost of the coatings There are two types of calcium carbonate: natural and synthetic (precipitation production) The particle size range is very wide, and 0.05-44 μ M can be used The amount of natural calcium carbonate is very large Because of its low price, it is quite suitable for some uses The varieties with coarser particle size are limited to putty, caulking paste, metal primer and other products with high pigment content, flow and rough surface The extinction ability of coarse calcium carbonate is very low Medium size products are mainly used for interior flat and semi gloss coatings and house coatings Most of the fine-grained products are produced by precipitation method and are used for printing ink Generally, two kinds of particle size calcium carbonate are used together to achieve performance balance The raw materials of natural calcium carbonate filler include limestone, marble and British calcium carbonate The content of CaCO3 in most varieties was 95% - 99% Some varieties are prepared by dry grinding and flotation The finer ones are wet ground and then graded by precipitation or centrifugation Many brands differ greatly in particle shape, average particle size, particle size distribution and purity Natural calcium carbonate filler is also widely used in outdoor house coatings, which can be used alone or with talcum powder Compared with talc powder, natural calcium carbonate can reduce the pulverization rate, improve the color retention and improve the anti pollution performance The above applications put forward specific requirements for particle size The fine-grained variety, especially the "micro" grade variety, can make the coating crack tendency The results show that the particle size of this kind of calcium carbonate filler should be larger, the demand for medium should be lower, and the activity should also be lower This kind of filler is also suitable for outdoor building latex paint to improve the color retention performance Calcium carbonate is an alkaline substance, which can act as a buffer in water-based coatings, but it can not be used together with alkali sensitive color pigments, such as iron blue and chrome green; it can not be used in situations where water-soluble iron salt or copper salt may be encountered Calcium carbonate can not be used for melamine polyester baking paint with acid catalysis because it will react with catalyst in neutralization As a type of filler, the CaCO3 content of precipitated or synthesized calcium carbonate is 98% - 99%, its particle size is small, its particle size distribution is narrow, its oil absorption is high, and its brightness is higher than that of natural products The particle size range of the better brand is 0.03-8 μ m, which belongs to the colloidal range It has been reported that for the covering power of the inner latex paint and the paper coating, the optimal particle size is about 0.2 μ M Precipitated calcium carbonate is most suitable for situations where the highest dry hiding power is required Some of them have been treated with rosin or fatty acid to further improve their wetting and dispersing properties, and there is no obvious tendency to lose light when they are used in bright coatings In some formulations, the permeability of surface pores can be reduced, so the sealing effect of the first coating can be improved Magnesium silicate or talcum powder: 2MgO · 4sio2 · H2O is a kind of mineral with rich storage capacity, which is mined in many parts of the world Its crystal form and related physical characteristics are different with different producing areas, usually a mixture of various crystal forms The influence of industrial talcum powder on coating performance is controlled by its structure type or mixture type, average particle size and particle size distribution Because most talc products are basically fibrous or flaky, their classification is also based on this The fiber talcum powder has the best outdoor durability, but its fluidity is poor in the coating, and the smoothness of the coating is also insufficient Flake talcum powder can give the coating excellent brushability, leveling, film smoothness and light retention, and also can give the coating or ink a "lubricating" performance The amount of granular talcum powder is small, but it has the best adhesion and grindability, which shows that it is suitable for grindable sealer or surface coating Many brands of talcum powder are specially designed and produced for special purposes The particle size of talcum powder varies from a large particle size with relatively coarse and low oil absorption to a "ultra-fine" grade with high oil absorption The hegman fineness value of the latter can be as high as 7 In the market, there are also talcum powder varieties with surface treatment, very low oil absorption and hegman fineness value of only 6-7, which are suitable for the use of photomagnetic grade The properties of talcum powder vary with different requirements Talcum powder has high brightness and good color in water and oil systems Talcum powder is easy to be wetted and dispersed in all liquid coatings, such as organic solvents, varnishes, alkyd and water-based systems; only moderate agitation is needed in the dispersion process Talcum powder has excellent suspension property in coatings, and it can also help other pigments in the system to maintain suspension state Talcum powder with coarser particle size is suitable for some coatings that require rough coating or "toothed" coating, such as interior wall paint, primer and crepe paint The medium-sized variety (hegman fineness value is about 4) is suitable for house paint and general filler The ultra-fine talcum powder with hegman fineness value of 5-7 is suitable for controlling the gloss, consistency and sagging performance of semi gloss coating Talcum powder is widely used in cement, crack filler and putty According to the different requirements of special products, choose the coarse or fine talc powder Talcum powder can be used in many industrial coatings, especially primer The steel structure primer can use talcum powder in whole or in part, which can improve the precipitability, mechanical force and recoat of coating Talcum powder is preferred for many products, flash primer and transport paint Sheet magnesium silicate, including talc, is suitable for metal primer because it can improve grinding and water resistance The water resistance may be derived from sheet particles extending the way of moisture passing through the coating Aluminum silicate or porcelain clay, kaolin: the composition of Al2O3 · 2SiO2 · 2H2O porcelain clay (kaolin) filler is basically aluminum silicate, which is produced in Carolina, Georgia, England and other places in the United States At first, as a cheap filler, porcelain clay was used in papermaking industry, and it is still widely used In recent years, producers are making porcelain clay suitable for coating industry In the past, air drying and flotation were simply used in the production, but now it has been replaced by water washing, strict particle size control, calcination and surface treatment, so as to improve the grade of products In these reforms, calcination is the most important process, so the scale is very large Most of the particles of porcelain clay are lamellae or hexagonal lamellae The grain size of the most widely used variety is about 10 μ M All kinds of porcelain clay have different degrees of hydrophilicity and are chemically neutral The oil absorption of non calcined porcelain clay is 25-44, and that of calcined porcelain clay is 48-58 The brightness is 80% - 92% reflection value Porcelain clay packing weighs about 21.6 pounds per gallon, about 1 pound less than calcium carbonate Because of its flakiness, it can enhance the mechanical force of the coating, so the porcelain clay can give the coating softness If it is used in house coating, its powdering resistance is stronger than talcum powder Porcelain clay has been widely used in metal primer to improve its grinding performance The amount of calcined porcelain clay is increasing in the indoor flat wall paint and the paint that needs flat coating The particle size of these varieties is very fine, which can reduce floating color and floating tendency when used in color semi gloss and glossy coatings In solvent coating, some kinds of porcelain clay are easy to sink and agglomerate, but after calcination and surface treatment, the above disadvantages can be overcome Because of the hydrophilicity of porcelain clay, it is a good filler for water-based coating They have good suspension performance in water-based coating, are easy to disperse, and give the coating a good brush and leveling Porcelain clay is usually used with other fillers Calcium sulfate: filling pigments such as CaSO4 and CaSO4 · 2H2O exist in two basic forms: anhydrite and gypsum (or gypsum powder) Only the first form is widely used in coating industry Anhydrous gypsum can be made by calcining gypsum Anhydrous gypsum has bright color and good dispersion in the coating It can be used in some bright coatings and other types of products with special properties Anhydrous calcium sulfate is slightly soluble in water and forms gypsum, so when it is used in latex paint for storage, it will form elongated crystal However, due to its water solubility, it can react with some components in latex paint, so the application of anhydrous gypsum powder is very limited Barite or barium sulphate: the practical barium sulphate filling pigments for BaSO4 are