Water-based paint construction process
Water-based paint construction process Text / water paint assistant With the promulgation and implementation of increasingly stringent national environmental regulations, the requirements for painting are also increasing. Painting should not only ensure good corrosion resistance, high decorative performance, high construction performance, but also use good performance materials and processes to reduce volatile organic compounds (VOC) emissions. In recent years, water-based paints have become the main force of coatings because of their environmentally friendly ingredients. First, what is water-based paint? Water-based paint is water-based thinner, organic solvent-free paint, free of benzene, toluene, xylene, formaldehyde, free TDI toxic heavy metals, non-toxic and non-irritating odor, harmless to the human body, does not pollute the environment, full of paint film It is crystal clear, flexible and has the characteristics of water resistance, abrasion resistance, aging resistance, yellowing resistance, fast drying and convenient use. Can be used in a variety of materials such as wood, metal, plastic, glass, building surfaces. The water-based paint is a water-soluble resin as a film-forming material, and is represented by polyvinyl alcohol and various modified products thereof, in addition to water-soluble alkyd resin, water-soluble epoxy resin, and inorganic polymer water-based resin. 1. The biggest advantage of water-based paint - environmental protection Conventional oil paints contain more than 85% organic solvents, while water-based paints contain only 10% organic solvents, so VOC emissions are lower. At the same time, water-based paint also has good paint properties, good permeability and gloss. Other advantages are shown in Table 1. 2, the shortcomings of water-based paint - longer evaporation time Compared with solvent-based paints, water-based paints have low volatilization rate, high surface tension, high conductivity, corrosiveness and bubble generation, resulting in water-based paints that differ from solvent-based paints in equipment and construction processes. Second, the technical characteristics of water-based paint spraying The volatilization of water in the water-based paint is mainly controlled by adjusting the temperature and humidity of the spray booth, while the solvent-based paint can adjust the solid content by adjusting the evaporation rate of the diluent. The coating color of the water-based paint is usually 20% to 30%, and the solid content of the solvent-based paint is as high as 60% to 70%, so the smoothness of the water-based paint is good, but at the same time, it needs to be heated and dried. Otherwise, quality problems such as sag and air bubbles are prone to occur, so the control technology of coating rheology is the key to the design of water-based paint. 1. Equipment technical characteristics (1) Painting room and drying room First of all, because the corrosiveness of water is larger than that of the solvent, the circulating water treatment system of the spray booth needs to be made of stainless steel. Secondly, the air flow condition of the spray booth is good, and the wind speed is controlled between 0.2 and 0.6 m/s. Or the air flow rate reaches 28000m3/h (normal paint booth can meet this condition). In the same drying room, the moisture content in the air will cause corrosion to the equipment. Therefore, the interior wall of the drying room should also be made of anti-corrosion material. . (2) Automatic spraying system The optimum temperature for spraying the water-based paint spray booth is 20 ° C ~ 26 ° C, and the optimum relative humidity is 60% ~ 75%. The allowable temperature is 20 to 32 ° C, and the relative humidity is allowed to be 50% to 80%. Therefore, the paint booth must have an appropriate temperature and humidity control device. Domestic car painting spray booths can be adjusted in temperature and humidity in winter, but there is very little temperature regulation and humidity adjustment in summer, because the required cooling capacity is too large, so there is very little cold air. (3) Other equipment Air gun. Use mechanical methods to help speed up the drying of the paint layer, such as a dedicated blow gun. The control layer does not require mechanical methods to accelerate drying. spray gun. Whenever possible, use a special spray gun with a barometer to ensure that the spray pattern is consistent with the final repair results. Make sure the spray gun is completely clean and dry with clean, dry air before use. This procedure is important for storing solvent-cleaned spray guns. Washing machine. A dedicated water-based washing machine is used to ensure that the oily and water-based paint wastes are treated separately, and the paint containers and paint sticks can also be cleaned in the washing machine. Tap water can corrode the gun body and should not be used to wash the gun. 2. Spraying and flashing of water-based paint 2.1 Spraying of water-based paint Two spray methods (dry and wet spray) were used using a gravity spray gun (shoring SART HVLP 1.3 or RP 1.3 mm). The relevant parameters are shown in Table 2. 2.2 Water-based paint flash Since water-based paints and clear varnishes are “wet-on-wet†construction, water-based paints have the problem of pre-baking, which is to volatilize most of the water and co-solvent in the paint. Tests have shown that the solvent content (mainly water) of the waterborne paint coating should be reduced to less than 10%, and the sprayed clear varnish does not dissolve the color paint layer to produce blisters, which affects the appearance quality. If it is flashed under normal temperature conditions, the solvent content of the water-based paint cannot reach 10% or less. Therefore, proper forced drying must be carried out before spraying the clear varnish on the water-based paint. A common forced drying device is a blow gun, which should be blown in the same direction as the airflow in the paint booth. The air gun cannot be perpendicular to the paint surface, otherwise it will cause paint defects. After the paint layer is sufficiently dried, it can be sprayed with varnish. First, a mixed varnish (for example, P190-68505P190-6060 is formulated according to the ratio of varnish: curing agent: thinner 2:1: 5% to 10%). The medium-concentration varnish is sprayed in two layers, and the drying time is about 5 to 7 minutes per layer. Spray a layer of half of a high-concentration varnish (spray a layer of mist cover and spray a layer of wet spray). The drying time is about 10 to 15 minutes. to sum up In recent years, the global automobile manufacturing industry has been affected by the financial crisis, production has fallen sharply, and China's automobile manufacturing industry has entered a period of rapid development. In 2009, China's automobile production and sales exceeded 13 million, surpassing the United States five years ahead of schedule. However, compared with industrial developed countries, there is still a big gap in automotive coatings and coating technology. The development of water-based coatings has been restricted by equipment investment and strict operating environment requirements. The automotive coating lines built in the last century have not been designed for water-based processes and are difficult to be retrofitted. Fortunately, in recent years, China's automobile manufacturing industry has built nearly 20 water-based paint coating lines. It is reported that there are many water-based paint coating lines of Shanghai GM, Shenyang Beisheng, FAW-Volkswagen, Shanghai Automobile and other units to be built. The automotive industry is the first to create water-based coatings, which can play a demonstration role for other industries. The development of water-based coatings is conducive to saving resources, reducing environmental pollution, implementing cleaner production, and achieving effective social and economic benefits. It is foreseeable that with the continuous advancement and innovation of coatings and coating technology, there will be new breakthroughs in the price, performance, construction process and equipment investment of water-based coatings, and there will be more in promoting and expanding the application of water-based coatings. Great development space. Plastic Bottle,Plastic Bamboo Bottle,Plastic Sports Bottle,Plastic Bottle For Drinks Ningbo Auland International Co.,Ltd. , https://www.everwaterbottle.com
