Coating classification: new dry powder building coating

Core tip: Introduction: In recent years, the construction coatings in our country have developed rapidly, and the research and development of products are also in the direction of water-based, high solid content and low VOC As an important type of waterborne paint, latex paint has an absolute share in the paint market, especially in the home decoration market, because of its convenient use, easy color matching and good water resistance However, because it is a water-based dispersion system, the solid content is mostly 45% - 55%, and the rest are water and volatile substances, which cause great waste for packaging and transportation In addition, taking into account the factors such as emulsion film formation and freezing proof in winter, latex paint will usually be added Paint knowledge how about Akzo Nobel Powder Coating Recommended introduction: powder coating is a kind of coating with different form from general coating, which is in powder form It is a new type of coating, because of its own advantages and more and more known by people Let's introduce Akzo Nobel Powder coating Akzo Nobel Powder coating is a cost-effective coating solution, which can be applied to different kinds of products After the treatment of static electricity and fire baking, a tough and durable coating surface will be formed, with the least impact on the environment Since the introduction of this technology, powder coating has been able to continue to maintain the Introduction: in recent years, architectural coatings in China have developed rapidly, and product research and development are also moving towards water-based, high solid content, low VOC and other directions As an important type of waterborne paint, latex paint has an absolute share in the paint market, especially in the home decoration market, because of its convenient use, easy color matching and good water resistance However, because it is a water-based dispersion system, the solid content is mostly 45% - 55%, and the rest are water and volatile substances, which cause great waste for packaging and transportation In addition, taking into account the factors such as emulsion film formation and anti freezing in winter, additives such as film-forming auxiliaries, ethylene glycol and ammonia can be added into latex paint as the main source of VOC, resulting in environmental pollution Compared with latex paint, dry powder building paint has the advantages of convenient production, zero VOC, convenient packaging and transportation, and has gradually been paid attention to In China, the main film-forming materials of dry powder building coatings are polyol products, mainly including porcelain like coating and interior wall putty The products are generally low-grade, with poor water resistance and weather resistance, which can not meet the requirements of exterior wall decoration In recent years, due to the emergence of redispersible rubber powder and various new building materials additives, the quality of dry powder building coatings has developed greatly Production: like latex paint, the main raw materials of dry building coatings include film forming materials, pigments and fillers and functional aids Among them, the film forming material is mainly redispersible latex powder, which is a powdered thermoplastic resin made of polymer emulsion through spray drying and subsequent treatment At present, the common types of redispersible latex powder on the market are: VAC / E, E / VC / VL, VAC / E / VeoVa At present, acrylic latex powder has also appeared in the market, and its weatherability, water resistance and other properties have been greatly improved As the main film-forming material of dry powder building coating, latex powder should have certain whiteness, good fluidity, good adhesion and good dispersion In addition, it should have good anti caking function during storage to avoid caking with other powder Generally speaking, the greater the amount of redispersible latex powder is, the better the water resistance, scrub resistance, weather resistance and other properties of the coating will be However, considering the cost factor, the amount of redispersible latex powder is generally 10% - 20% There are many kinds of pigments and fillers that can be used in coatings Different pigments and fillers have great influence on the luster and weather resistance of coatings Among them, titanium dioxide is the best white pigment, which has the advantages of strong covering power, high lightness value and easy dispersion Other colored pigments such as iron oxide series have good weather resistance, low oil absorption and easy dispersion The common types of fillers used in coatings are calcium bicarbonate, wollastonite powder, mica, talc powder, kaolin, dolomite, etc Dry powder architectural coatings have higher requirements on the performance of additives, the first requirement is powder materials, in addition, additives are required to be easy to disperse and have certain fluidity Common additives include dispersant, defoamer, wood fiber, cellulose ether, thixotropic lubricant, etc In addition, in order to improve the product performance, special additives such as powder organosilicon hydrophobic agent and antibacterial agent can be added to improve the water resistance and antibacterial property of the coating Dispersant, also known as wetting dispersant, is the key raw material in the production process of dry powder building coating The dispersant itself should have high efficiency dispersion and good fluidity Dispersion efficiency will directly affect many key properties of coatings, such as the amount of water added, viscosity, storage stability, workability, etc Especially in the color system, the efficiency of the dispersant will affect the color development, uniformity and whether the color floats There are many kinds of dispersants, mainly including polyacrylic acid salt and polyphosphate, but most of the products sold in the market are liquid, powder dispersants are relatively few, and most of them are imported products Defoamer is also a key raw material, its type and amount of addition will affect the appearance of the film Good defoamer has strong defoaming ability and lasting efficiency The common defoamers are organic modified polysiloxanes, high-grade fatty alcohols, mineral oils, etc In order to obtain better workability and storage stability, appropriate thickener should be added The common thickeners are cellulose ether, bentonite and thixotropic lubricant, which can make the coating have higher viscosity in low shear state, obtain better storage stability, and reduce the sense of sluggish brush and splash in normal construction The addition of wood fiber can prolong the opening time of the coating, improve the workability and prevent the initial cracking of the coating Based on the above factors, the basic formula design is shown in Table 1 Titanium dioxide is used as pigment in white coating The ratio of M (titanium dioxide): m (iron oxide red): 4:1 is used in the colored coating In order to obtain better covering power and stability, two different powder materials are used for packing Before construction, part of the water will be added into the container, and then the powder will be added slowly The mixing speed will be controlled at 750 R / min, and the mixing time will be 15 min then the remaining water will be added to adjust to the appropriate viscosity Performance test method: water resistance: in accordance with GB / T 1733-1993 law a; alkali resistance: in accordance with GB / T 9265; scrub resistance: in accordance with DIN 53778, the coating is exposed to quv-b for 200 h before the test, and sprayed; UV resistance stability: after curing the prepared coating sample for 7 days, put it into the UV light box for irradiation of 100 h After cooling, take out and observe the surface pulverization; viscosity test: use NDJ-1 rotational viscometer to test Performance influencing factors: 1 The basic properties of common pigments and fillers in the selection of pigments and fillers are shown in Table 2 and table 3 In the dry powder building coatings, the pigments and fillers should have lower absorption to ensure better dispersion It can be seen from the above comparison that rutile titanium dioxide in white pigment has lower oil absorption, easier dispersion, better refractive index and strong covering power than anatase titanium dioxide, so it is more suitable for building dry powder building coating Iron oxide red is better than iron oxide yellow in covering power and easier to disperse According to the above principles, the filler is suitable for the selection of heavy calcium carbonate, dolomite and wollastonite Although kaolin and talcum powder can improve the storage stability or leveling of the coating to a certain extent, they are not suitable for the construction of dry powder construction coating In addition, different proportions of pigments and fillers are selected to prepare the coating according to table 4 After a period of outdoor exposure test, the contrast rate, discoloration and differentiation degree are tested The results are shown in Table 4 It can be seen from the above that when the proportion of pigments and fillers is 3:7 or above, the contrast ratio of the coating meets the requirements of the superior product, the color difference changes little, and the degree of pulverization is slight Therefore, pigment: filler = 3:7 or more can be selected in the paint formulation design, and two or more powders with low oil absorption are usually used as filler, such as heavy calcium carbonate, dolomite, wollastonite, etc In order to ensure the fineness and dispersibility of the coating, the fineness of the powder should not be too coarse or too fine, and it is generally selected in the range of 600-1000 meshes 2 The influence of wetting and dispersing agent on the performance of paint is different, and the basic performance is shown in Table 5 In this paper, 500 g dry powder was selected as the building material, and the ratio was m (titanium dioxide): m (heavy calcium carbonate): m (wollastonite): 1:1:1 The wetting dispersant was mixed with the above powder evenly in advance, and added to the water slowly under the condition of high-speed dispersion The slurry with 70% solid content was prepared After 30 minutes of dispersion, the viscosity of the slurry was tested The results are shown in Figure 1 It can be seen from Figure 1 that dispersant a, which was originally applied well in mortar system, is not suitable for use in dry powder building coating system With the increase of the dosage, the viscosity of the slurry decreases slightly at the initial stage, but increases at the later stage When the dispersants B, C and D are added to the pigment paste, the viscosity will drop suddenly when they are added to a certain amount, which can be called the critical point amount The critical point dosage of B is 0.1%, the critical point dosage of C and D is 0.2% According to the experience of coating dispersion, the actual additive dosage of dispersant is generally 1.5-2 times of the critical point dosage The influence of dispersant on the storage stability, foaming and other properties of pigment paste is shown in Table 6 It can be seen from table 6 that different dispersants have different dispersion efficiency, in which a is not suitable for use in dry powder building coatings After adding C, there are many bubbles in the pigment paste, which has a certain odor D efficiency is high, but it is mainly composed of inorganic components, and its later stability is poor In a word, B has good dispersing efficiency, no smell, good foaming and stability, and is a relatively good dispersing agent Home of coatings is specialized in coatings, diatom mud, paint coating, coating technology, fire retardant coating news and coating, diatom mud, paint coating, coating technology, fire 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