Common knowledge of coatings: application of waterborne coatings in automobile industry

Core tip: due to the increasing call for environmental protection, many products used in automobile coating process are made up of organic solvents During the automobile spraying construction and subsequent drying process, these solvents evaporate to the atmosphere, causing serious pollution, while water-based coatings can reduce the emission of organic solvents to a very low level in the 21st century, Water based coatings will become the mainstream of automotive coatings, and will be used in the automotive bottom, middle and finish The application of water-based coatings in automobile industry is described in the following aspects: electrodeposition primer and secondary paste, water-based metal flash primer and varnish 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 Home of coatings: Due to the increasing call for environmental protection, many products used in automobile coating process are made up of organic solvents During the automobile spraying construction and subsequent drying process, these solvents will volatilize to the atmosphere, causing serious pollution, while the organic solvent emissions of waterborne coatings can be reduced to a very low level In the 21st century, waterborne coatings will become the mainstream of automobile coatings The bottom, middle and top coat of automobile are applied From the aspects of electrodeposition primer and secondary paste, water-based metal flash primer and finishing paint, the application of water-based coatings in automobile industry, as well as the composition and construction process of each water-based coating are described At present, there are three types of cathodic electrophoretic coatings, i.e epoxy resin type, polyurethane type and polyacrylic acid type The most commonly used is epoxy resin, which is based on the modified epoxy resin containing amino group, uses the closed isocyanate as the cross chain agent, neutralizes the amino group through organic acid, and then disperses it in water The pigment is mainly composed of dioxin and physical pigment, and the special lead containing pigment, such as silicate, is used as the anticorrosive agent The lead can also catalyze the curing reaction 2 The control of the electrophoretic process parameters has a great influence on the performance of the paint film It should be noted that deionized water is used for the last cleaning after electrophoretic In order to reduce the secondary flow mark, the drying chamber temperature can be raised to 30 ℃ ~ 40 ℃ and pre dried at 60 ℃ ~ 100 ℃ for 30min, and then dried in 180 ℃ drying chamber for 25min 3 The development trend of cathodic electrophoretic paint is that the automotive primer is cathodic electrophoretic paint, but the research and development work has not stopped Use of lead-free electrophoretic paint The electrophoretic coating technology of will be the main research topic in the next stage It will be developed into ultra thick film type, high weather resistant type, low temperature curing type, edge anti-corrosion type, bottom in one type, composite color type and other aspects The two-layer slurry is often used in automobile body coating Its purpose is to increase corrosion resistance, water resistance, moisture resistance, enhance the adhesion, flexibility of paint film Chemical resistance and mineral oil resistance, so as to improve the protection of the car body The second is to make the paint film more flat and full, improve the gloss and image, and make the car body more beautiful Although the secondary slurry is still in use at present with medium and high solid separation coating, the water-based coating is an inevitable trend 4 The composition of water-based two-way slurry typical water-based two-way slurry is based on polyester, which is cured by amino resin cross chain, and the polyester is dissolved or dispersed in water by neutralization of the contained shuttle group by amine The two-way pulp is a system with high pigment content The treatment of the pigment formula of the water-based two-way pulp is similar to that of the solvent type It is very important for improving the properties of the secondary paste, such as leveling, sanding and moisture resistance, to select the pigment carefully by using Qin dioxide as the coloring pigment, then adding low-cost physical pigment, adding silicate or barium sulfate 5 The construction of water-based two-layer slurry is the most important function to protect the two-layer slurry, that is, to provide a very flat surface, so that the top coat has the best appearance, and the water-based two-layer slurry needs a special construction line Control humidity and temperature for optimum flattening During the actual construction, the temperature of spraying room shall be controlled at ℃ and humidity, and the water-based two-layer slurry shall be sprayed by rotating cup electrostatic spraying, which can be directly or indirectly electrified After spraying, there is a special flash dry area where the water can volatilize slowly at room temperature or blow away the water vapor with low humidity warm air Leave the flash drying area and enter the drying room, where the temperature is heated to the required curing humidity ℃, and the temperature is raised slowly, so as to remove the residual moisture in the paint film and prevent pinholes Although the development of waterborne secondary pulps has reached the goal of reducing the emission of organic solvents, only a few production lines in Germany are actually in use Most automobile manufacturers are still evaluating the water-based two-way slurry system Some are in the plan, some are just starting to establish the construction production line of water-based secondary slurry In addition, the problem of paint slag treatment still exists in the water-based secondary slurry In the future, it should be considered that there is no paint slag or it can be recycled The next generation of water-based two-way pulp will have higher resistance, and water-based two-way pulp can also be made into various colors There are two types of water-based metal flash primer, namely, vehicle color paint and metal flash paint In recent years, the development of metallic flash paint series is rapid, pearlescent paint and different color paint with angle emerge in endlessly Spray the same nonvolatile solvent based paint, discharge the solvent, but only the water-based At the same time, the water-based metallic flash paint has a special rheological property It has a better metal effect than solvent based paint by using aluminum powder orientation 1 Composition of waterborne metallic flash paint At present, the water-based basecoat system is made of different resins respectively The products sold on the market include polyurethane vinegar dispersion, polycarbonate, acrylic vinegar, acrylic microgel, or the combination of these resins and appropriate amino resin The purpose of making the shed of metal flash basecoat is to contain amino in the main chain, which can be dissolved or dispersed in water after being neutralized Value to a better, all kinds of base color paint contain a clever cosolvent, the most commonly used for glycol butyl ether Na The colored water-based primer contains pigments with aluminum or mica effect, plus normal transparent or translucent pigments 2 For the construction process, the water-based metal flash paint replaces the solvent based metal flash paint It must have the same constant temperature and humidity conditions as all water-based paints Generally, the construction temperature is 22 ℃ ~ 28 ℃, and the humidity is 60% ~ 80% After the construction of the water-based metal flash paint, there must be a flash drying process Generally, the required temperature and time are about 90 ℃ and 5min Metallic flash primer is usually applied in two coats, with the thickness of the two coats approximately Both coatings can be pneumatically sprayed, or the first electrostatic spraying and the second pneumatic spraying The first layer is constructed with electrostatic high-speed rod, which has high transfer efficiency, about higher than pneumatic spraying Electrostatic high-speed spraying can not be used for spraying the second layer, because of poor atomization, uneven distribution of paint droplet size, and low impact speed of paint droplet on the substrate, so the metal flash effect is greatly reduced, and the appearance is very different from pneumatic spraying In the flash drying area, temperature and humidity are the factors that determine the drying time except the air velocity The degree of drying must be uniform and the coating on the interior of the body must be the same as that on the exterior The specially designed flash dry channel can provide the most suitable hot air flow to reach the coating of all parts of the vehicle body, and evenly raise the humidity, which can be used by infrared heating and air The development of wet paint film rheology is very complex A lot of work on the development of water-based background color focuses on obtaining the best orientation and flattening under metal, preventing sagging, and developing stable aluminum pigment in water We believe that the water-based metal color will have a faster development, and the color will have a high sense of transparency, depth and high color Water based varnish is an important part of the whole process, which plays an important role in improving the durability, scratch resistance, corrosion resistance and other properties of the paint film Many mature varnish are made of isocyanate, silane, fluoropolymer and epoxy acid, but these coatings are harmful to environment and human body However, the success of the development of water-based varnish depends on the further improvement of its corrosion resistance and other properties Although the waterborne Varnish is still in its infancy, it has been sold in the market This coating has a little pseudoplastic property, and its liquid flow regulation can be completed by a high content of additives Like the primer, the water-based varnish also needs to be baked The aqueous paint system can reduce the solvent volatilization in automobile painting construction, and the aqueous metallic flash primer is a milestone in automobile painting Electrophoretic coating has been widely used as automobile primer With the improvement of water-based two-layer slurry and water-based varnish performance, all automobile coatings will be called water-based paint system 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 retardant coating decoration knowledge and decoration renderings,