Coating technology: coating technology and construction operation skills of waterborne coating
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Last Update: 2020-04-03
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Source: Internet
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Author: User
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Key tips: 1 Coating process of waterborne coating (1) furniture coating process Base material grinding → primer application → polishing → puttying (2-3 layers, each layer is dried for 2-3H) → grinding (600-1000 × sandpaper) → primer application → finishing coat (1-3 layers, each layer is separated for 15h, the first 2 layers are dried and then polished with 1000 × sandpaper) → drying (self drying or low-temperature drying) The function of the water-based primer is to improve the wettability of the wood and increase the adhesion; brush or Paint knowledge | precautions for wall paint color selection Recommended introduction: when painting the wall, the owner sometimes has difficulty in choosing what color of the wall paint to paint In fact, there is no ugly color in the wall paint, only the disharmonious color matching The use of wall color contains the knowledge of health Too strong color will stimulate people's perception, make people have a sense of fidgety, affect people's mental health Grasp the basic principles of wall color and paint a colorful space 1、 Wall paint color selection notice 1 Light color is generally used for the top surface Light colors make people feel light, dark colors make people feel heavy Usually, the treatment of rooms is from top to bottom, from shallow to deep For example, the ceiling and walls of rooms are white and Coating home news: 1 Coating process of water-based coating (1) furniture coating process substrate grinding → primer application → grinding → putty scraping (2-3 layers, each layer drying for 2-3H) → grinding (600-1000 × sandpaper) → primer application → finishing coat (1-3 layers, each layer spacing for 15h, the first 2 layers drying and then using 1000 × sandpaper grinding) → drying (self drying or low-temperature drying) The function of the water-based primer is to improve the wettability of the wood and increase the adhesion; the construction of the top coat can be brush or spray, and the coating is filtered through the 200 mesh filter screen; the viscosity is 18-22s (coating - 4 cups) During the furniture coating construction, the coating film shall be thin to prevent sagging, multi-layer thin coating shall be adopted, and the drying time shall be in accordance with the regulations of the manufacturer (2) requirements for environment and base material of building coating process: ensure cement / concrete is maintained for more than 1 month and dried with moisture content less than 10%; all door and window installation works and installation of peripheral fixed facilities are completed; there is no cross operation on the coating surface The ambient temperature is 5-30 ℃, and the humidity is below 75%; there is no gale or rain above level 4 Construction steps: external wall Carry out comprehensive cleaning, remove cement slag, clean the platform; special treatment for local defects, including filling, sealing and polishing; consider covering / sealing the building accessories, peripherals, doors and windows according to the building situation; scrape the first coat of cement polymer putty, polish it with sandpaper after 6-8h; scrape and paint the second coat of cement polymer putty, polish it with sandpaper after 6-8h Level, dry the putty layer for 36-48h; apply one layer of sealing primer, dry it for 4-6h, and polish it with fine sandpaper; apply two layers of finishing paint, with construction interval of 4-8h; clean the construction site During the construction of wall surface finish, the force shall be even and the action shall be fast, so as to avoid repeated brushing and affecting the effect The painting sequence shall be from top to bottom, from roof, eave post, top beam and rafter to wall, door, window and base plate Each part shall also be painted from top to bottom When painting each part, do not stop If you have to stop, you should also choose the connection part of the house structure, such as the joint between the wall and the window frame, so as to avoid unsightly joints Finish coating shall be used up within 2 hours as much as possible after batching, and the 'cross' roller coating method shall be adopted to achieve uniform, no missing coating and sagging It needs to be cured for more than 24 hours The 'cross' spraying method has the best effect in the construction of metal paint for exterior wall, and half gun spraying shall be used to avoid the shadow of interval spraying (3) coating process of plastic products the surface treatment of plastic substrate mainly includes cleaning treatment and surface activation treatment, the purpose of which is to improve the adhesion between film and substrate According to the type of plastic, the oil stains on the surface can be selected as low-grade alcohol, aromatic hydrocarbon and ketone solvent The methods of surface activation include oxidation treatment, chromic acid treatment, corona treatment and plasma treatment In addition, due to the residual stress or local crystallization of plastic products after pressing, cracks or fine lines will occur during coating, which is not conducive to coating wetting, and can be eliminated by annealing or air blowing This is particularly important in the development and application of waterborne coatings And the surface functionalization is to give the substrate conductive, vacuum spraying metal, UV protective layer and other special functions In recent years, the main varieties of water-based coatings for plastics include one-component water-based acrylic alkyd coating, water-based acrylic polyester coating, one-component and two-component water-based polyurethane coating, water-based epoxy ester coating, etc The common coating processes of ABS and PC plastic products are as follows: Grinding or finishing of substrate (applicable to parts with burr or surface defect) → pretreatment (annealing treatment, alcohol solvent cleaning or activation treatment) → elimination of static electricity (electrostatic precipitator) → application of primer → drying → drying → electrostatic precipitator → application of finish paint → drying, leveling → drying → cooling → inspection of coating construction, generally spray 1-2 layers, each layer of film thickness of 10-15 μ M If the film is too thin, it will affect the leveling; if the film is too thick, it will cause sagging, edge shrinkage and other phenomena 2、 Construction points of water-based coating construction method of water-based coating is not too different from the conventional construction method Brush coating, dip coating, roller coating, spray coating, etc shall be selected in combination with the specific conditions of workpiece shape, anti-corrosion requirements, appearance decoration, etc For castings, dip coating shall be adopted, and the groove shall be fully leveled, but the coating formed by dip coating shall be uneven The expected coating film can be obtained by roller coating on the thin piece and curing at 230 ℃ for 3-4 min The spraying methods of water-based coating are as follows: ① Air spraying is applicable to the coating with viscosity less than 30s (coating - 4 cups, the same below); ② air assisted airless spraying (or air mixing method) is applicable to the coating with viscosity greater than 30s, which has been widely used in wood furniture industry; ③ electrostatic spraying, due to the high conductivity of the water-based coating, should select the special electrostatic spray gun for the water-based coating, such as Wagner of Germany, nuoxin of America, etc All companies can provide For example, the construction conditions of waterborne alkyd enamel: the viscosity of the coating is 20-24s; the DC voltage is 45-60kv; the curing conditions are surface drying for 30min and then drying at 80 ℃ for 20-30min Although the construction requirements of water-based coating are basically the same as solvent based coating, it still has its particularity Therefore, the following items should be paid attention to in the construction (1) after cleaning treatment, the surface shall be free of residue and burr of film remover, and surface activation or functional treatment shall be conducted according to different types of plastic materials; metal parts shall be subject to conversion film treatment on degreased base materials, and sand blasted surface shall be up to sa1-2, with roughness of 50 μ M (2) the surface of the base course of mortar, concrete and brick masonry shall be hard, flat, rough, clean and wet, with certain strength If there is any unevenness, it shall be leveled; if there is any floating ash layer, dust, etc., it shall be removed by wire brush, oil stain, sliding grease, etc by solvent; the vulnerable hollow part shall be removed until the hard base is exposed, it shall be leveled by cement mortar; for each part Cracks, cracks, cold joints and other parts should be chiseled into V shaped grooves and repaired by cement or latex mortar The cement mortar is used to fill the gray joints of the brick masonry The pipes, iron parts and power outlets around the base should be cut into circular grooves and pressed with emulsion modified mortar The dry base, especially brick masonry, should be treated with water spray and humid treatment Wipe off the free water with cloth to improve the adhesion with the base layer (3) during the construction of waterproof layer, add 40% - 50% water to dilute and mix the waterborne acrylate waterproof coating, and brush 1-2 layers on the treated base, so as to speed up the penetration of the coating into the base and increase its adhesion strength to the base The construction temperature shall be greater than 5 ℃, and construction cannot be carried out in rainy days After construction, it must be ensured that there is no rain (snow), etc within 8 hours, otherwise the paint film is easy to blister and peel off, the technical indicators such as waterproof and pollution resistance cannot be guaranteed, and the rainwater pollution on the wall cannot be cleaned Wall paint construction can not be diluted with water, should be fully mixed evenly, otherwise it is easy to produce color difference, affecting its quality The exterior wall primer must be applied once for the construction of exterior wall paint, and the exterior wall primer cannot be mixed with the top coat for construction, otherwise the wall is prone to the phenomenon of "map drawing" such as alkali, salt, white and color The wall paint produced in the same batch shall be used for the construction of the whole wall If there is a small amount of surplus in the previous batch of wall paint, which is not enough for the roll coating construction of the whole wall, the remaining wall paint in the previous batch shall be used as the first finishing coat construction The second finishing coat of the whole wall shall be used in the second batch of finishing coat construction to ensure that the color of the whole wall is relatively consistent The grey cement for new wall painting must be dried for more than 15 days, and the wall paint shall be used up within 2 hours as much as possible to avoid being polluted by organic solvent The unused wall paint shall be covered with the barrel cover for preservation The quality acceptance of construction wall shall be carried out 10 days after the completion of construction 3、 Spraying operation skill of water-based coating spraying method is one of the most important methods of water-based coating construction When the surface of the object is painted by spraying method, thin and uniform coating film can be obtained For different geometry, there are holes, gaps, unevenness, and the coating can be evenly distributed; for large surface, spraying is faster and more effective than brushing However, some operation skills must be mastered in the construction by spraying method Adjust the coating with clean water to the viscosity suitable for spraying (20-30s) If there is no viscometer for a while, visual inspection method can be used: stir up the paint with iron bar or wood bar and stop at 20cm for observation If the paint liquid keeps on line for a short time (several seconds), it is too thick; if the paint liquid is cut off immediately from the upper edge of the barrel, it is too thin; if the paint liquid just stops at 20cm, it will be cut off immediately and drop down This viscosity is more appropriate The air pressure is best controlled at 0.3-0.4mpa If the pressure is too small, the paint liquid will not atomize well, and the surface will form pockmarks; if the pressure is too large, it is easy to flow and hang, and the paint mist is too large, which wastes materials and affects the health of the operator The distance between nozzle and object surface is generally 300-400mm Too close is easy to flow and hang; too far is uneven, prone to pitting, and the nozzle is far from the surface, causing waste of paint fog on the way The distance shall be adjusted according to the type, viscosity and air pressure of the paint: the spraying distance of slow drying paint can be farther, the spraying distance of quick drying paint can be closer; when the viscosity is thick, it can be closer, when the viscosity is thin, it can be farther; when the air pressure is high, it can be farther, and the pressure hour can be closer The so-called near point and far point refers to the adjustment within 10-50mm If it exceeds this range, it is difficult to obtain an ideal paint film The spray gun can move up and down, left and right It is better to move evenly at the speed of 10-12m / min the spray nozzle shall be straight on the surface of the object for spraying, and oblique spraying shall be minimized When spraying to both ends of the object surface, the hand that pulls the trigger of the spray gun should be loosened quickly to reduce the paint mist Because the two ends of the object surface often need to receive more than two times of spraying, which is the most likely place to cause sagging When spraying, the next layer shall be pressed to 1 / 3 or 1 / 4 of the previous layer, so as to avoid leakage When spraying quick drying paint, it is necessary to finish spraying in sequence at one time, and the effect of re spraying is not ideal When spraying in the open outdoor place, pay attention to the wind direction (it is not suitable for operation in case of strong wind) The operator shall stand in the downwind direction to prevent the paint mist from being blown to the sprayed paint film and causing unsightly granular surface The spraying sequence is: first difficult, then easy, first inside and then outside, first high and then low, first small area and then large area This will not cause
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