Coating technology: research and application of epoxy acrylic waterborne primer coating technology

Core tip: with the rapid development of the automobile industry, the car model changes with each passing day and the color changes are colorful At the same time of these changes, the space environment for human survival is also threatened unprecedented, which requires human beings to protect themselves There is only one earth for human beings While enjoying modern means of transportation, we should also think for future generations and benefit the future Based on this, automobile manufacturers all over the world have increased investment in science and technology in environmental protection Automobile coatings are widely used in high solid coatings, water-based coatings and powder coatings to reduce the emission of organic solvents Application scope and advantages of roller ceramic coating Recommended introduction: the surface of ceramic rubber plate used for roller ceramic coating is cast into durable rubber plate by hundreds of independent small ceramic pieces Each ceramic piece has raised characteristics Under general conveyor belt pressure, thousands of unique cast bumps can produce positive traction, prevent slipping and extend the service life of conveyor belt roller At the same time, the bottom layer adopts high-quality rubber, which has strong elasticity and can play a good impact resistance role The scope of application of roller ceramic coating is one three six 83857180 (the same as V) 1 Roller coating in extremely harsh working environment 2 The belt joint is not suitable for fixing with iron buckle; 3 It is suitable for leather Home of coatings news: with the rapid development of the automobile industry, the car model changes with each passing day and the color changes are colorful At the same time of these changes, the space environment for human survival is also under unprecedented threat, which requires human beings to protect themselves There is only one earth for human beings While enjoying modern means of transportation, we should also think for future generations and benefit the future Based on this, automobile manufacturers all over the world have increased investment in science and technology in environmental protection Automobile coatings widely use high solid coatings, water-based coatings and powder coatings to reduce the emission of organic solvents European and American countries have made strict regulations on the emission of organic solvents in the process of automobile coating For example, Germany requires coating 1 *2 area, the emission of organic solvent is less than 35, encourage automobile factories to use low emission organic solvent paint varieties 1 Reasons for using water-based primer Generally speaking, the primer used in automobile is anode electrophoretic primer and cathode electrophoretic primer These two primers have good matching performance and anticorrosive performance with all kinds of finish paint The cavity structure can be evenly coated with paint film However, in the production lines that are not suitable for electrophoretic primer and some production lines without electrophoretic primer (such as: coating lines for refitting car compartment, extra long car compartment and bumper, etc.), a large number of them still make Paint with iron red alkyd primer Because of the large investment in the electrophoretic coating line and the small output of the refitted cars, the production process of spraying primer must be adopted in a large amount in a long time In addition, due to the increasingly high requirements of product quality and environmental protection, a large number of spray primer lines will gradually use water-based primer instead of solvent based primer In this paper, the properties and coating process of epoxy acrylic waterborne primer are investigated with iron red alkyd primer as reference 2 The performance of iron red alkyd primer iron red alkyd primer is widely used, but after practical application and performance test, the anti-corrosion performance of the paint film and the matching performance with the top coat are poor, which can not meet the requirements of automobile coating Test methods for performance items of iron red alkyd primer: the color and appearance of the paint film are flat, matte, and the viscosity of the iron red original paint (coating - 4 cups) / s fineness of the original paint / "* solid content of the original paint / 9 hardness and flexibility / mm impact strength / kg * cm adhesion 4 circle method) / level salt spray resistance / h poor appearance of the top coat with sleeve top coat From table 1, we can see that the mechanical properties of the paint film The performance such as adhesion, impact strength and other indicators are excellent, but its anti-corrosion performance is poor, and the salt spray resistance is only 72h, which is much lower than the technical indicators required by the painting of cars and auto parts When it is used together with amino alkyd finish, the appearance of the finish has many particles, low luster and zero freshness In addition, because of its iron red color, when it is matched with white finish, the color difference of finish is easy to occur (AE is greater than 1.0), which increases the repair amount In view of the shortage of iron red alkyd primer, and on the premise of reducing cost and improving quality, the gray epoxy acrylic waterborne primer was researched and developed with Hunan Hanshou paint company as the substitute of iron red alkyd primer 3 The performance of gray epoxy acrylic water-based primer through the detection of small samples of gray epoxy acrylic water-based primer, it is considered that its technical index is significantly better than that of iron red alkyd primer Test results of gray epoxy acrylic water-based primer performance test method color and appearance of paint film gray, flat, smooth viscosity (coating - 4 cups) / s fineness /! M pH value of the original paint, solid content of the original paint / 6 drying time of the paint film, adhesion (cross cut method) / class flexibility / mm impact strength / kg * cm hardness, film fluidity /! M the paint film without bubbles is allowed to be slightly discolored, acid resistant, alkali resistant and salt fog resistant The 240d paint film is not allowed to be peeled off, and the '2mm original paint along the line is stored for 6 months Note: the plate making condition is low zinc phosphated steel plate Spray epoxy acrylic water-based primer, spray viscosity (coating - 4 cups) is 30 ± 2S, film roughness is 25'30 from table 2, it can be seen that the corrosion resistance, appearance, luster, fineness of gray epoxy acrylic water-based primer are significantly better than iron red alkyd primer 4 The compatibility of primer and finish coat through the performance inspection and detection of iron red alkyd primer and gray epoxy acrylic water-based primer, it is found that the corrosion resistance of the latter is significantly better than the former However, in practical application, how they match with the top coat, and whether they match with the electrophoretic primer and the difference are the main indicators reflecting the appearance quality of the car For this reason, blue amino top coat, Pearl White amino top coat and army green semi gloss amino top coat are selected for matching test with three kinds of primers The comparison results are shown in Table 3 It can be seen from table 3 that when iron red alkyd primer is matched with three kinds of top coats, the gloss, freshness and appearance are poor Considering the cathodic electrophoretic primer is the best, followed by gray epoxy acrylic water-based primer, but it can completely meet the requirements of automobiles Appearance quality requirements of car and parts 5 Study on the construction technology of gray epoxy acrylic waterborne primer Water based spraying primer is first applied in the company It is different from solvent based primer Water is used as diluent, and its volatilization speed is much slower than that of organic solvent Therefore, several parameters closely related to construction technology are mainly studied, such as construction viscosity, drying conditions, and the difference between deionized water and tap water as diluent The influence of ambient temperature and humidity on the performance of the paint film Here are 33 kinds of primers and 3 kinds of top coat matching comparison types of gloss / 6 fresh shade color difference ("E) appearance and blue color paint ammonia matching base set iron red alkyd primer is more flat epoxy acrylic waterborne primer cathodic electrophoretic paint flat and smooth and smooth and base iron red alkyd primer is more flat precious surface pearl paint white matching epoxy acrylic waterborne primer flat and smooth ammonia Flat and smooth of cathodic electrophoretic paint and flat iron oxide red alkyd primer; flat and smooth of military green paint with epoxy acrylic waterborne primer; flat and smooth of cathodic electrophoretic paint; 5.1 construction viscosity viscosity is the primary control parameter of spraying process; solvent based paint The viscosity of air spraying is 18'22s (coating - 4 cups), which is slightly adjusted according to the temperature change Sometimes, the viscosity can reach 25s However, water is used as diluent for water-based paint, and the volatilization speed of water is slow If the viscosity control is low, the paint film defects such as sagging will easily occur If the viscosity is high, the orange peel and rough appearance will easily occur Therefore, it is very important to determine the best construction viscosity The corresponding relations of appearance, film thickness, gloss and sagging under different spraying viscosity the appearance of the paint film is smooth, smooth, smooth, smooth and even, smooth and slight orange peel, a small amount of bubbles, a large number of bubbles, film thickness /! M gloss flow hanging /! It is easy to overspray in 36'40s spraying, which results in orange peel and bubbles in the paint film Therefore, it is considered that the construction viscosity is best controlled between 30'32s Because the water volatilization speed is slow and the temperature change has little effect on the water volatilization speed, the construction viscosity does not need to be adjusted frequently in the daily temperature range during the production process 5.2 in drying conditions, the samples obtained at different drying temperature and the same drying time (all 30min) are tested for their salt fog resistance, and the relationship between different drying temperature and salt fog resistance When the drying temperature is lower than 1400, the drying is impervious, resulting in inadequate film curing and poor salt spray resistance; when the temperature is higher than 1400 (such as 1600), salt spray resistance 2001.01 modern coating is the same as coating drying On the premise of quality assurance, in order to save energy and prevent the mechanical properties of the paint film from decreasing due to over drying, the drying temperature is in accordance with the corresponding relationship between the drying temperature in Table 5 and the salt spray resistance of the paint film 5048 * expansion along the fork is more than 2mm, the blister on the board surface is 8080 * expansion along the fork is more than 2mm, the blister on the board surface is more than 2mm for 120120h, there are a few blisters on the board surface 140240 * expansion along the fork is less than 2mm, there is no change on the board surface 160240h expansion along the fork is less than 2mm, there is no change on the board surface, the expansion width and the condition of the board surface are the same as when 140 is dried Study on the phosphating plate and 25 5.3 film thickness diluent as the base material; except for a very small amount of water-soluble solvent, most of the diluents used in water-based paint are water Generally, deionized water is better Using deionized water can reduce the content of impurity ions in paint, improve the chemical resistance and salt spray corrosion resistance of paint film, but the conductivity of deionized water must be controlled at 20! When the electric conductivity of deionized water is qualified, the pH value is weak acid Because the pH value of the original paint of grey epoxy acrylic acid water-based primer is 8.0 ± 0.5, it is weak alkaline If the original paint is diluted with acid-base deionized water, there will be acid-base reaction to generate salt, which will destroy the molecular structure of the film-forming resin and affect the corrosion resistance of the paint film The ionic water and pH are equal to 7, and the conductivity is 170! S / cm of tap water and pH is about 7, conductivity is less than 20! When s / cm pure water is used as the diluent of gray epoxy acrylic waterborne primer, the results of salt spray resistance test are compared Effect of water with different properties as diluent on salt spray resistance of paint film time of salt spray resistance test / * no change of pure water of deionized water, no change, no change, no change, no change, no change, no change, no change, no change, no change, no change, no change, no change, no change, no change, no change, no change, no change, no change, no change, no change, no change, no change, no change, no change, no change, no change, no change, no change, no change, no change, no change, no change, no change, no change, no change, no change! m Salt spray corrosion resistance is the best conductivity in 20! Under S / cm, the pH of pure water is about 7, followed by pH equal to 7, conductivity of 170! When s / cm tap water and pH acid deionized water are used as diluent, the salt spray resistance of the paint film is the worst, so the diluent water used for gray epoxy acrylic waterborne primer shall be neutral, and the pH shall not be less than 7.0, otherwise the anti-corrosion performance of the paint film will be affected 6 Stability test bookmark5 coating quality, stability is one of the key indicators, so simulate the site construction conditions, prepare 1L gray epoxy acrylic water-based primer, under the condition of magnetic stirring, keep it for one month, during the test, add a certain amount of