Steel drum environmental protection new coating technology and new equipment

The environment is the space where human beings rely on for survival and development. It is the only source of material and energy. However, the space for the environment is limited, and natural resources are also limited. The existing environment and resources do not allow people to develop, produce and consume without restriction, and they do not allow uncontrolled pollution and destruction. As a major branch of the packaging industry, steel drums have made great progress in recent years, but at the same time they have also brought a lot of environmental pollution, especially the most serious environmental pollution in the steel drum coating production process. The large amount of waste water, waste gas, and waste residue produced by steel drum coating mainly comes from chemical treatment methods such as degreasing, rust removal, phosphating, and passivation on the surface before painting, as well as the scattering of organic solvents and paint mist during the coating process. The solvent during the drying process is evaporated. Modern coating technology is taking various measures in these areas to reduce pollution to the environment and to develop steel barrel coating technology and equipment towards a comprehensive “green” direction. The key is to change the current status of pollution control.

Steel drum environmental protection coating new technology

1, high pressure airless spray technology

High-pressure airless spray coating is used in coating production, which makes traditional air spraying technology a step forward, improves the coating quality and efficiency, reduces the environmental pollution of the air spraying method, and improves the operating conditions. The high-pressure airless spray is to spray the paint with a high pressure through a high-pressure airless sprayer, and the paint is strongly atomized and sprayed onto the surface of the coated steel drum. During the entire spraying process, the atomized spray of the paint is not in contact with the air. The pressure of the sprayed paint is large, the spray rate is fast, and the atomization effect is very good. The possibility of using a high-viscosity, low-solvent, high-slurry paint has resulted in less scattering of atomized paint and solvents, and therefore, environmental pollution and working conditions have been improved.

2, electrostatic spraying technology

Electrostatic spraying technology is based on the traditional air spray technology, applying high-voltage static electricity to spray technology. The negative high-voltage electricity generated by the high-voltage electrostatic generator discharges the negative high-voltage static electricity to the coated steel drum through a sharp-edged cup-shaped spray gun, a disc-type spray gun, and a structure-type high-voltage electrostatic spray gun at the front end. Grounding is the anode coating space. A high-voltage electrostatic field is formed between the two poles, corona discharge by gas ionization, and the paint is sprayed into the high-voltage electrostatic field by a high-voltage electrostatic spray gun, etc., and spray paints such as spin cups, discs, compressed air electrostatic spray guns and the like are rotated. Into the electrostatic field is too finely atomized, and bring it negative. Under the action of the electric field force, atomized and coated negatively charged paint particles, along the tangential direction of rotation of the spray cup and the disk spray gun, and in the same direction as the electric field force, merge and fly to the surface of the coated steel drum (anode). , It is evenly adsorbed on the surface. The electrostatically sprayed coating is dried to form a uniform, glossy, smooth, and smooth, adherent coating. Electrostatic spraying facilitates the production of mechanized and automated flow production. It has high coating efficiency and good quality. The coating utilization rate is 30% to 40% higher than air spray. Being attracted by the electric field force, the atomized paint and organic solvent do not scatter, and automatic spraying can be realized, which significantly improves the environmental pollution and improves the operator's working conditions.

3, powder coating technology

Powder coating technology for the first time achieved solvent-free and non-toxic dry coating production. One-time coating can reach the coating thickness of multi-pass coating for solvent-based coatings. Over-coated powder coatings can be recycled without substantially environmental pollution. The one-time coating production cycle is short, energy and raw materials are saved, the equipment is easy to operate, the construction is safe, the process is simple, and it is easy to realize the production of automated assembly lines. The quality of the coating is high, the output is large, the cost is reduced, and the technical and economic results are significantly improved. At present, the powder coating uses powder electrostatic spraying method and powder electrostatic oscillation coating method. It uses the ground of the painted steel drum as the anode, and the electrode is the cathode in the fixed coating powder chamber and powder container. The external power supply is connected to negative high-voltage static electricity to form a high-voltage electrostatic field between the two poles, and the resulting corona discharge causes the powder particles to be negatively charged. The anode is applied to the surface of the coated steel drum to adsorb powder to form a uniform layer of deposited powder along the direction of the electric field force line. , Dry the film to form a coating.

In recent years, the application of powder coating, especially electrostatic powder coating technology, has been on the rise. The State is also promoting the application of interference-free powder coating technology, which poses a strong challenge to conventional solvent-based coatings and coating technologies. As a revolution in coating technology, powder coating technology has more vitality than advanced coating technologies such as electrophoresis and electrostatic spray solvent coating, which makes coating technology more demanding. Such as: Solvent-free, non-polluting or low-pollution, construction operation is simple, non-toxic, high-quality paint, short cycle, energy saving, fully automated coating production line, continuous improvement in technical and economic benefits. This will inevitably forcefully promote the development of coating technology and promote the thorough reform of coating technology.

Steel drum environmental protection new equipment

1、Air spraying equipment

Air spraying is a traditional coating method. The equipment is still relatively simple after many years of updating. However, the spray gun is constantly updating the structure, and some new types have emerged. Nowadays, domestic and foreign issues such as environmental pollution, health hazards and so on are regarded as national policies and are mentioned in an important position in the form of laws. Therefore, the renewal of the spraying equipment is imminent, and the pace of development needs to be accelerated. Its main equipment such as spray booths, ventilation equipment, pressure feeding equipment, air power and water separators, conveyors and other equipment are updated and modernized. The modern spraying room is more characteristic and conforms to the environment protection: water curtain type, water spin type, spray type, clean spraying room and so on. There are better ventilation devices in modern spraying booths. Most of them are equipped with atomizing scattering paint on the air flow channels. Baffles, mesh filters, or small adsorption devices are widely used.

2, high pressure airless spraying equipment

Domestic high pressure airless spray equipments are pneumatic and electric type. The electric high pressure airless sprayer consists of a diaphragm pump, a single motor and a spray gun. The motor is driven by a plunger pump and an oil pressure control membrane pump. After the absorber sucks the paint, it is pressurized by a high-pressure plunger pump and sprayed at a high pressure (1 800 2 2 200 N/cm2) to reach the coated steel. On the surface of the barrel, the sprayable paint has a viscosity of up to 200 S and is ideal for high-solids coating applications. It saves energy, has a high coating efficiency, and is about 10 times higher than air spray. In recent years, high-voltage electrostatic spraying technology has been applied to high-pressure airless spraying equipment. High-voltage static electricity occurs on the gun body of a high-pressure airless coating gun, so that paints that have a very high pressure are negatively charged. The charge forms a high-voltage electrostatic field between the spray gun and the anode of the coated steel drum, which further atomizes the highly atomized paint particles, generates electrostatic adsorption during spraying, and the paint is uniformly and firmly adsorbed on the surface of the coated steel drum. The formation of excellent coatings reduces the scattering of oversprayed coatings, further increases the efficiency of spraying, saves materials, has good spray quality, reduces environmental pollution, and brings a broader application prospect for high-pressure airless spray technology.

3, electrostatic spraying equipment

Several types of electrostatic coating equipments that are widely used in China, such as high-voltage electrostatic generators, spray booths, spray guns, and feed equipment, are all updated in practice. For example, high-voltage electrostatic generators are becoming small-sized and highly functional. In the development, a constant field circuit was added to the circuit composition to make the electrostatic spray gun inadvertently touch the coated steel drum in the electric field without causing ignition, increasing the operational safety and reducing the risk of fire and the like. The application of the disc electrostatic spraying method has replaced the rotary cup method in the production of many companies. The spraying quality is good, materials are saved, and environmental pollution is significantly reduced.

4, powder coating equipment

The powder coating equipment, especially the electrostatic spraying equipment, is the most up-to-date and has not been widely used in China. However, powder coating has been applied abroad, especially in Europe, North America and other regions. The performance and structure of the coating equipment are more advanced than those in the country and the results are very good. For example, when the electrostatic generator is small-scaled, the supply gun voltage is low when electrostatically sprayed, and it works well when 50 kV is used. The high-voltage generator does not have a cable on the spray gun. Operation is safe and no ignition occurs. One generator for automatic spraying can carry 2 to 4 spray guns. The spray gun adopts an internal charging structure, so that the powder is charged twice inside and outside the spray gun, and has a strong penetration force, less powder scattering, and a high coating quality. Due to continuous upgrading and modernization of equipment, the quality of powder coating production continues to increase. Domestic powder coating is on the rise, and it will soon be widely used in the coating production of steel drums in China.

At present, environmental protection coating technologies at home and abroad have developed rapidly, and various coating methods such as high-pressure airless spray coating, electrostatic spray coating, and powder coating with advanced coating technology features such as mechanization and automated assembly lines have been widely used. New pattern of painting. In these so-called modern advanced painting methods, the latest painting technology of microcomputer program control, automatic CCTV control, and robot operation is introduced. New high-protection, high-decoration, low-toxicity, low-pollution coating and diluent and semi-mechanized, mechanized, and automatic assembly lines for dip coating, shower coating, roll coating, spray coating, and photo-curing, radiation-curing coating, etc. The support constitutes a new coating system for modern paint production that is highly efficient, high-quality, low-cost, energy-efficient, reduces environmental pollution, and improves working conditions. The extensive use of environmental protection facilities has caused the environmental pollution caused by common coating methods to be gradually reduced. The new coating process is rapidly expanding its application and continuous improvement. The coating environmental protection equipment is constantly being developed and put into production. At present, China's coating technology is working hard to catch up with the world's advanced level, people's awareness of environmental protection is also constantly strengthened, the prospects for environmental protection are beautiful. (Liaohe Chemical Plant, Liaozhong County, Liaozhong Liaoning 110200, China)

Source: Surface Engineering Information