Polyurea coatings abroad for nearly 10 years, in order to meet the environmental needs and developed a new solvent-free, pollution-free coatings.
It is characterized by: construction process Airless pump is simple, not affected by the construction environment may be below -20 ℃ and 40 ° C above construction, according to the needs of any from the influence of moisture and temperature, the curing time of the coating can be in the range of 10s ~ 30min regulation; solvent evaporation construction is completely green paint; fast curing characteristics, construction on arbitrary surfaces, both vertical and a variety of complex Lotion bottle parts, smooth surface appearance after spraying; water, acid and alkali , radiation-resistant, excellent Cosmetic bottle resistance to oxidation, anti-microbial and other physical and chemical properties.
Another characteristic is that, on various substrates (including steel, iron, aluminum, concrete, wood, etc.), there is very strong adhesion, within a few s to the substrate forming a tough covalent binding force, very difficult to be removed from the substrate. Coating forming, 30min can be used, and has a strong mechanical properties, high heat resistance, water resistance and anticorrosive insulation properties.
Get the rapid popularization and application of this technology in the worldwide oil pipelines corrosion repair. China has also carried out research on this technology.
1 · spray equipment components and operation and maintenance
1.1 the component parts of the spraying equipment
Polyurea coatings A, B (R) two-component reaction fast, the general static mixing spray technology can not be applied to the construction, it is necessary to adopt a two-component high-temperature and high-pressure airless spray equipment. Specialized spray equipment must include: smooth material handling systems, accurate material measurement system, uniform material mixing system, good material atomization system with convenient material cleaning system. Spraying equipment must have heat insulation, pressure, impact mixed functions, polyurea coatings complexity of the strong dependence of the spraying equipment and spraying equipment, spraying equipment and processes dedicated research, investigation and research is ensure the pipeline anticorrosion overhaul polyurea coatings.
Spraying equipment research, selected H20/35Pro automated spray equipment. And its performance, function, and an operation and maintenance of the various components were studied.
Spraying equipment by spraying host, pumping feed pump, gun, gun cleaning cans, spray auxiliary equipment.
1.1.1 spraying host
H20/35Pro host using opposed piston metering pump, uneven load of the work can be eliminated to prolong the life of seals, integral type pump base can ensure the stability of the pressure in the pump cycle, thereby providing a very stable spray Type and perfusion applications coincidence. Meanwhile, H20/35Pro host heating hose and the automatic temperature control system heating capacity, preheating, a temperature sensor in the feed stream is to automatically control the temperature near the gun submerged, can be precise temperature control. Table 1 for the the host system technology H20/35Pro parameters.
Host equipped with a positive displacement metering pumps equipped with a double-acting piston pump. Choose to provide specific ratio range of 1:4 to 4:1. UHMW sealed with hard chrome plated piston rod and cylinder wall to ensure the reliability of the pump system. Have overvoltage protection switches on each pump. Furthermore, GUSMER ® unique metering pump Reply means can automatically isocyanate shaft fully positioned within the cylinder in order to prevent pollution of the humidity, and to extend the service life of the pump seals.
1.1.2 pumping material pump
H20/35Pro Host with the 2:1 pneumatic pumping feed pump, pressure ratio of 2.25:1, the output continuous work 21L/min, while intermittent work 42L/min. The pump can be used both 200L industrial vats, also can be used for the delivery of a variety of packaging materials. The length and thickness of the pipe between the feed pump and pumping the host, there are stringent requirements, otherwise it will lead to lack of feed.
1.1.3 gun
Selected the GX-D71 gun. The GX-D71 gun to the implementation of high-temperature, high-pressure collision impact, in order to achieve uniform mixing of the material A material with R (B).
Collision mixed by precision machining having a longer service life of the hybrid module inside the mixing chamber to achieve, there are a variety of different models are available, when the mode control block to be used in combination, to provide optimum mixing and mode works. At the outlet of the gun, with a different form of the mode control panel (PatternControlDisc, referred to as PCD). , Can be realized by changing the models of the PCD round, fan spray and pouring and different output volume, to provide a more efficient mixing and mode works. Collaboration with the completion of the stem and the front and rear seals and gas cap gun shot / off gun mechanical self-cleaning process, all mixed raw materials can be cleaned after each sprinkler from the mixing chamber cleaning, reduce expensive, Environmental harmful solvent cleaning program. Stop gun for the longer period of time (such as troubleshooting, overnight, etc.) use the special wash the the gun cans and organic solvent to be thoroughly cleaned without dismantling the gun.
1.1.4 gun cleaning tank
The internal structure of the gun is very fine and A, R material and easily cured ordinary cleaning method has been unable to conduct a thorough cleaning of the spray gun, you must use a specially equipped with high-pressure spray gun cleaning tank cleaning.
GX-D71 gun is a mechanical self-cleaning spray gun, is the combination of impact-type, gas atomized spray gun mixing chamber and the valve stem. From the gun the characteristics of the GX-D71: This design does not require a traditional gun as in pause spraying must use organic solvents or high-pressure air to clean the pipette tip, greatly reduce the maintenance and upkeep of the workload. However, in longer stopping gun (such as weekends, overnight, etc.), the cleaning tank with a special gun must be thoroughly cleaned with a small amount of organic solvent, but do not have to disassemble the gun body. Continuous construction in the actual use of the GX-D71 gun week only need to dismantle the gun cleaned once a sufficient, demolition, installation is relatively simple.
1.1.5 spraying auxiliary equipment
Spraying equipment, auxiliary equipment, including air compressors and oil-water separator. The air compressor is the entire spray system necessary equipment to host the proportion of the spray gun, pneumatic pump powered pump for pumping material. Common air compressor on the market there are two kinds of piston and screw. Piston air compressor noise, but its less mass, the volume is also smaller. The final selection of a piston compressor. The oil-water separator for removing moisture in the air, oil and minor impurities. Without the various components of the pneumatic mechanism of the dried compressed air purification will cause serious damage; more importantly, the oil entrained in the compressed air, moisture, the impurities cause polyurea paint coatings defects such as shrinkage, bubbling destroy the coating appearance quality and intrinsic quality.
1.2 spraying equipment operation and maintenance
1.2.1 spraying equipment connection
In the spraying site, a spray the apparatus comprising H20/35Pro host, GX-D71 gun, mention the feed pump, the feed tube, the many components of the A component, R component, and heated hoses must be reasonable to connect, in order to ensure spraying operations smoothly completed.
The air from the air compressor, must go through the air dryer. The 2 mention feed pump are respectively inserted industrial vat equipped with the A component and the R component, the material from the Uploader feed pump with the feed tube into the host, the host through accurate metering pumps to control a volume ratio of 1:1, while receiving the heating and pressurization of the host. Subsequently, the material outflow host insulation hose, to reach the gun, and pull the trigger, from the respective directions through filter high pressure impingement mixing in the mixing chamber, and then high-speed spray to receive compressed air at the nozzle to form a uniform fan or round material surface, spraying onto the tube stereolithography.
1.2.2 spraying equipment on-site operation
The complex structure of spray equipment, the connection is complex, many steps, and any step in the whole spraying process errors are likely to lead to the device directly to end-of-life, so steps throughout the spraying process equipment must be standardized to determine. After a after repeated spraying test fumble, field steps of spraying equipment, and operate in strict accordance with the procedure set spray test.
Maintenance of 1.2.3 spraying equipment
The device long-term in a non-operating state, in order to prevent the moist air of the contact A, R feed vat and pumping feed pump crystallized, solidified, deterioration needs to be A, R Balloting feed pump is removed from 200L vats, and insert equipped with a cleaning agent protective sleeve, A, R material drums filled nitrogen sealed. Turn off the host, but not off the air compressor and A material, R ball valve material feed.
Feed pump is working, construction (experimental) with DOP lotion top tube material, continue to use the DOP circulating cleaning after cleaning residual liquid sealed in conveying tube. Cleaning cycle, lotion 20kg, pressure 3 ~ 5MPa Cleaning 30min, three times. Covered with machine guarding mesh cover, store fixed the Treasury.
2 · spraying process determine
Polyurea coating with high temperature, high pressure, hedge percussive mixing process, so the spray process is complete reaction, whether excellent performance largely depends on the correct determination of the spraying process. The determination of the spraying process, including the determination of the two key parameters: the spraying temperature and spray pressure.
2.1 spraying temperature determine
In the polyurea coating of the spraying process, the elevated temperature to improve the spray effect is very favorable. Meanwhile, the temperature sensitivity of the of polyurea coatings reaction temperature constant is low, therefore the elevated temperatures will not cause the sharp acceleration of the reaction rate, it will due to the significant decrease of the viscosity of the material so that the material mixture of the A, R and fluidity is improved, but the reaction from the apparent point of view seems to heat up more gentle the. The actual temperature is controlled at 70 to 75 ° C. The pair of hose is heated in order to ensure that in the transmission process of the material, A, R the temperature of the material will not be the extension of the transmission distance reduces, thereby increasing the system viscosity, resulting in poor mixing effect. Therefore, the heating temperature of the hose should be consistent with the temperature of the main heater basic or slightly higher, generally set at 75 ° C. In addition, the temperature of the hose than the main heater temperature rise is slow, it is generally open hose heating to facilitate the operation.
2.2 Determination of spray pressure
Polyurea coatings is in the high pressure impingement mixing the reaction, thus increasing the pressure on the performance of the entire system has obvious benefits. Better atomization pressure increase, the coating surface roughness, the cellulite phenomenon apparently disappeared; However, the disadvantage is that the pressure is increased, spraying anti-splash phenomenon heavier, need to further strengthen the visor of the spray area and construction workers protection, which bring greater security risk to the entire construction process. After the experiment, that the polyurea coatings, the spray pressure is between 2000 ~ 3500psi.
Poor regulation of 2.3 Spray Pressure
Of polyurea coatings, ideal mixing effects are: A, R material of uniform density, the heating temperature, spray pressure, and polyurea coatings equivalent so as to ensure reaction. But in practice, due to the various physical properties often different in the A, R material density, viscosity, etc., so it is difficult to achieve the desired mixing. Reflected in the operation is the spraying, A, R material spray pressure difference is difficult to adjust to 0.
Spraying should pay special attention to the pressure difference of the A component and the R component, when a pressure difference ≤ 500psi, can ensure uniform mixing of the two kinds of materials; when the differential pressure is greater than 500psi, the material must be readjusted to ensure that the materials were mixed uniformly and to ensure that the curing is not in the gun.
Therefore, in the actual spraying process, based on different polyurea coating formulations, A, R feed pressure differential field adjustment is an important step in preparing high performance polyurea coatings.
2 in preparation for spraying, the first trial spray polyurea board observed A, R discharging pressure gauge material calculated differential pressure between the two, in the process of spray test. If both of the differential pressure is greater than 500 psi, it should immediately stop the spraying, and to adjust the pressure.
Adjusting pressure approach is to adjust the A, R feed heating temperature. A material generally elevated heating temperature, to reduce the heating temperature of the R materials, and then re-spraying operations, re-observed pressure difference, until both pressure of 500psi, preferably within 200psi. It is worth noting that, regardless of increased or decreased temperature should not exceed a temperature in the range of 70 ~ 75 ℃.
3 Conclusion
Existing polyurea spray equipment typical equipment, a detailed understanding of the performance and the role of the important parts of the polyurea coating spray equipment, connection, operation, maintenance, and maintenance of a method developed equipment. The spray temperature, the spray pressure, and other parameters of the spraying process is determined by experiments.