The type and performance of metal aluminum powder powder coating are discussed briefly

1 Introduction With the importance of environmental protection, as an environmental protection, high efficiency, high efficiency and economy of powder coatings, production has increased rapidly in recent years, varieties continue to increase, and applications gradually expand. In terms of decoration, in addition to the ordinary type of different gloss, flat surface of the powder coating varieties, orange, wrinkles, sand, patterns, hammer marks, metal powder powder coating varieties and dosing is also increasing, gradually penetrate into the solvent-based coating applications in various fields. Among these varieties, metallic aluminum powder powder coatings are a major variety of decorative powder coatings, including metallic flash, metal plating, metal patterns, hammer patterns and metallic gloss textured powder coatings. This powder coating is characterized by the appearance of metallic aluminum powder, by changing aluminum powder specifications, coating formulations and manufacturing processes, you can get different properties and coating appearance of the powder coating. The following details the variety of this powder coating, manufacturing process, formulation composition, factors affecting the appearance of coating, application areas and problems.2 varieties of aluminum powder coatingsaluminum powder coatings are the most important varieties of metal powder coatings. Metal aluminum powder powder coating according to the appearance of the coating film is divided into coating flat metal flash, metal coating powder coating; Coating film textured patterns, hammer patterns and metallic glossy textured powder coatings. Can be used for metal aluminum powder powder coating film has epoxy, polyester epoxy, polyester, polyurethane and acrylic resin, the main varieties used in China are polyester epoxy and polyester resin aluminum powder coating.(1) Metal flash powder coating, is a powder coating made by adding non-floating metal flash aluminum powder to the powder coating base powder, and the reflection of the metal flash aluminum powder evenly distributed after the coating has been cured into a film gives the coating a flash effect.(2) Metal coating powder coating, is a powder coating made by adding floating metal aluminum powder to the powder coating base powder, after the coating is cured into film, due to the metal aluminum powder completely covering the coating surface to form a similar "electroplating layer or polished stainless steel" coating appearance.(3) Metal pattern powder coating, is a powder coating made by adding metal aluminum powder and pattern agent to the powder coating base powder, when the coating is cured into a film, due to the influence of the pattern agent on the surface tensor, the appearance of the coating film forms a metallic aluminum powder silver pattern.(4) metal hammer-print powder coating, which is a powder coating made by adding metal aluminum powder and hammer-print agent to the powder coating substrate, which forms a silver hammer pattern when the coating is cured into a film.(5) Metallic gloss texture powder coating, is a powder coating made by adding metallic aluminum powder and texture agent (sand or wrinkle agent) to the powder coating base powder, after the coating is cured into film, due to the effect of aluminum powder and texture agent, the formation of a metallic gloss texture coating appearance.3 Manufacturing process of metal powder coatingsThe main manufacturing process of metallic aluminum powder coatings is similar to that of general powder coatings, including: premixing ofraw materials→ melting extrusion mixing→ cooling and crushing→ fine powder→ →graded sieve→ finished productis manufactured entirely in accordance with the above-mentioned process for the manufacturing process (commonly known as the aluminum powder in-addition process) added during the premixed process, such as hammer patterns, patterns and metal plating powder coatings.For powder coating manufacturing processes that require dry mixing to add metallic aluminum powder (commonly known as aluminum powder plus process), the base powder of unmet aluminum powder is manufactured into a semi-finished product according to the above process, and then added to the metallic aluminum powder according to the formulation quantity, and the product is evenly mixed with the mixer dry mix, such as metal flash, part of the metal coating, pattern and metallic gloss texture powder coating is manufactured in this way.In the manufacturing process (aluminum powder plus process) of adding metal aluminum powder to semi-finished products, in order to prevent the particle size of aluminum powder from being damaged in the mixing process and affect the appearance of the coating, while preventing the powder coating from convergent during the mixing process, generally Mixing is done with a low-speed mixer with no destructive power, very little heat, or even a cooling unit, which includes a V-type mixer, a 3D rotary water cooling mixer, a barrel mixer, a Bonding mixer, and so on.in the dry mixing process of metal aluminum powder, in addition to the Bonding mixer, the powder coating of other mixer mixtures in the metal powder and base powder is in a separate state. Because of the different density and electrical properties of metal powder and powder coating particles, when electrostectrectral powder coating, the two materials have different electrostitive properties, powder rate is also different, resulting in a difference in the content of aluminum powder between powder coating and coating film, but also make the recovery powder and the original powder in the aluminum powder content is different, it is difficult to reuse the recycled powder, will ultimately affect the stability of the appearance quality of the coating product, but also increase the cost of coating.With Bonding mixer or other mixed equipment or manufacturing process that can make aluminum powder glued to powder coating substrate, the content of aluminum powder in the original powder, coating film and recycled powder coating can be consistent, and the recycled powder can be reused, while ensuring the stability of the appearance quality of the coating film. Because Bonding mixer is more expensive, so that the cost of coating manufacturing is relatively high, the use of this equipment manufacturers are relatively small.4 Basic formulation of metal powder coatings and factors affecting coating performance 4.1 Metal flash powder coatings This powder coating is generally composed of base powder and aluminum powder, the main composition of the base powder is the same as ordinary powder coatings, by resin, curing agents, leveling agents, degassing agents, transparent pigments, aluminum powder, aluminum powder special additives, anti-lighting agents or anti-curing agents, etc. In some cases, transparent pigments and fillers are added appropriately for properties such as color tuning and improved film hardness, but the amount of fillers is less than that of ordinary powder coatings. If the amount of addition is large, it will affect the flash effect of aluminum powder and the smoothness of the coating film. powder is a dry mixing method added to the end of the powder, the amount of the total amount of base powder 1% to 5%. Depending on the size and brightness of the flash point of the coating appearance, different particle sizes and amounts of aluminum powder are selected. Generally choose the particle size in 15 to 55 m of non-floating aluminum powder, flash point when the choice of large particle size aluminum powder, flash point hour selection particle size small aluminum powder; It is required that the amount of aluminum powder should be used when the film brightness is high, and the amount of aluminum powder should be reduced appropriately when the film brightness is low. 4.2 Metal plating powder coating This powder coating is formulated like a common powder coating and consists of resins, curing agents, leveling agents, degassing agents, pigments, fillers, aluminum powders, aluminum powder additives, detergents or anti-curing agents, etc. In the formulation of aluminum powder dosing is 1% to 5% of the total amount of base powder or formula, according to the appearance of the coating and the brightness of the metal coating to choose different particle size and amount of aluminum powder, the use of particle size in 2.6 to 15 m floating aluminum powder. At present, the main aluminum powder varieties used are dry mixing method plus type floating aluminum powder. Has developed an internal type of aluminum powder, although there are many advantages, but compared to the aluminum powder, its use is large, the cost of coatings is high, the real industrialization of a large number of applications will take some time. 4.3 Metal pattern powder coating This powder coating is formulated from resins, curing agents, patternants, pigments, fillers, aluminum powders, detergents or anti-light curing agents, and is similar to ordinary patterned metal powders. Depending on the variety of aluminum powder, it can be added by adding in or plus two methods. Patterners can also be added by internal or plus methods. In this formulation, there is no leveling agent, and if added, the amount is very small. in the formulation of patternants and aluminum powder is an important factor affecting the appearance of the coating film, with the increase in the amount of patterning agent, the pattern becomes smaller, the coating film becomes flat, the three-dimensional sense of difference; With the increase of aluminum powder, the metal brightness of the coating film is enhanced. The particle size of aluminum powder also has an effect on the appearance of the coating film, and in the case of the same amount, the smaller the particle size of aluminum powder, the brighter the film brightness. In addition, the molten viscosity, reaction activity, pigment variety and dosing of film-forming substances also have some effect on the texture of patterns. 4.4 Metal Hammer Powder Coatings This powder coating is formulated from resins, curing agents, hammers, degassing agents, transparent pigments, small fillers and aluminum powders. In the formulation, the amount of aluminum powder is 0.8% to 1.5% of the total amount of the formula, aluminum powder particle size of less than 20 m floating or non-floating aluminum powder can be used. The dosage of hammer patterning agents will vary according to the variety, if the dosage is 0.1% to 0.2% of the total formulation amount when CAB551-0.2 is used with butyric acid cellulose. Opaque pigments are not suitable for use due to the effect of pigments and fillers on hammer clarity, and the amount of fillers should not exceed 10% of the total formulation, with a clearer hammer texture when fillers are not used. the amount of hammer pattern in the formulation is the main factor to determine the size of hammer texture, with the increase of hammer texture, hammer texture becomes smaller, three-dimensional sense is worse; With the reduction of hammer pattern dosage, hammer texture becomes large, three-dimensional sense is enhanced, and even dew bottom. In addition, the molten viscosity of the film, reaction activity, leveling agent addition and other factors also affect the size of the hammer texture. 4.5 Metallic Glossy Textured Powder Coatings This powder coating is formulated from resins, curing agents, pigments, fillers, texture agents (e.g. wrinkles, sandstones) and aluminum powders. Generally to textured powder coating as a base powder, plus a certain amount of metal aluminum powder dry mix, so that the coating film has a certain metallic luster. The amount of aluminum powder depends on the use, generally 1% to 3% of the total amount of the formula, more suitable for floating aluminum powder with a particle size of less than 20 m. Select aluminum powders of different particle sizes according to the appearance requirements of the coating. 5 Powder coating applications and problems Metallic aluminum powder coatings are decorative powder coatings, mainly used in indoor and outdoor items and products decorative aspects. Outdoor products include street lamps, lamp posts, metal doors and windows, car wheels, etc. Indoor products include ceilings, lighting, toys, fitness equipment, anti-theft doors, building materials, shelves, radiators, electric toys and so on. General polyester, polyurethane powder coatings for outdoor and demanding indoor products; Epoxy and polyester epoxy powder coatings are used in indoor products. the characteristics of powder coatings, aluminum powder coatings will gradually replace some solvent-based coatings, and its use has a growing trend. But powder coating is not a perfect variety, coating film micro-flattening, decorative effect, coating film aluminum powder dispersion and concealment is not as good as solvent-based paint, easy to make a very small amount of aluminum powder particles exposed on the surface of the coating film, long-term exposure to the air when the aluminum powder surface oxidation, so that the coating film darkened, and ultimately affect the decorative effect of the coating film. Coating film coating varnish can overcome this disadvantage, but this increases the material and coating costs, economically less than the application of 2 solvent-based coatings. due to the limitations of powder coatings, aluminum powder coatings are not currently available for the coating of premium car paint, only for decorative requirements are not very high coating. 6 Conclusion Metallic aluminum powder powder coating as an important variety of powder coatings, all powder coatings with thermo-solid resin can be made of this powder coating, so the variety of coatings, a wide range of applications. If the price of "Bonding" equipment used to disperse aluminum powder falls in the future and becomes widespread; Then the in-addition process with metal aluminum powder varieties to be further developed, the cost is reduced, then the quality of various metal aluminum powder coatings will be improved, the price will be reduced, the application area will be further expanded, the use will grow faster, the proportion of alternative solvent-based aluminum powder coatings will be greater.
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